Methanol plant retrofit for manufacture of acetic acid

<u>FIELD OF THE INVENTION</u>

The present invention is directed generally to a process for making synthesis gas from which streams of carbon monoxide and methanol can be obtained for the manufacture of acetic acid, and more particularly to the retrofit of a methanol plant to divert all or a portion of the syngas from the existing methanol synthesis loop to a carbon monoxide separator and to react the methanol from the methanol synthesis loop with the carbon monoxide from the separator in approximately stoichiometric proportions to directly or indirectly make acetic acid.

<u>BACKGROUND OF THE INVENTION</u>

The manufacture of acetic acid from carbon monoxide and methanol using a carbonylation catalyst is well known in the art. Representative references disclosing this and similar processes include <patcit id="pcit0001" dnum="US1961736A"><text>U.S. patents 1,961,736 to Carlin</text></patcit> et al (Tennessee Products); <patcit id="pcit0002" dnum="US3769329A"><text>3,769,329 to Paulik</text></patcit> et al (Monsanto); <patcit id="pcit0003" dnum="US4081253A"><text>4,081,253 to Marion</text></patcit> (Texaco Development Corporation); <patcit id="pcit0004" dnum="US5155261A"><text>5,155,261 to Marston</text></patcit> et al (Reilly Industries); <patcit id="pcit0005" dnum="US5672743A"><text>5,672,743 to Garland</text></patcit> et al (PB Chemicals); <patcit id="pcit0006" dnum="US5728871A"><text>5,728,871 to Joensen</text></patcit> et al (Haldor Topsoe); <patcit id="pcit0007" dnum="US5773642289A"><text>5,773,642 289 to Denis</text></patcit> et al (Acetex Chimie); <patcit id="pcit0008" dnum="US5817869A"><text>5,817,869</text></patcit> to Hinnenkamp et al (Quantum Chemical Corporation); <patcit id="pcit0009" dnum="US5877347A"><text>5,877,347</text></patcit> and <patcit id="pcit0010" dnum="US5877348A"><text>5,877,348 to Ditzel</text></patcit> et al (BP Chemicals); <patcit id="pcit0011" dnum="US5883289A"><text>5,883,289 to Denis </text></patcit>et al (Acetex Chimie); and <patcit id="pcit0012" dnum="US5883295A"><text>5,883,295 to Sunley </text></patcit>et al (BP Chemicals); and <patcit id="pcit0013" dnum="EP845452A"><text>EP 845,452-A</text></patcit> (Topsoe Haldor AS) and <patcit id="pcit0014" dnum="DE3712008A"><text>DE 3712008-A</text></patcit> (Linde AG).

The primary raw materials for acetic acid manufacture are, of course, carbon monoxide and methanol. In the typical acetic acid plant, methanol is imported and carbon monoxide, because of difficulties associated with the transport and storage thereof, is generated in situ, usually by reforming natural gas or another hydrocarbon with steam and/or carbon dioxide. A significant expense for new acetic acid production capacity is the capital cost of the equipment necessary for the carbon monoxide generation. It would be extremely desirable if this capital cost could be largely eliminated or significantly reduced.

Market conditions, from time to time in various localities, can result in relatively low methanol prices (an oversupply) and/or high natural gas prices (a shortage) that can make methanol manufacture unprofitable. Operators of existing methanol manufacturing facilities can be faced with the decision of whether or not to continue the unprofitable manufacture of methanol in the hope that product prices will eventually rebound and/or raw material prices will drop to profitable levels. The present invention addresses a way of modifying an existing unprofitable methanol plant to make it more profitable when methanol prices are low and/or gas prices are high.

As far as applicant is aware, there is no disclosure in the prior art for modifying existing methanol plants, including methanol/ammonia plants, to supply stoichiometric MeOH and CO for manufacturing acetic acid, for example, that can be a more valuable product than MeOH.

<u>SUMMARY OF THE INVENTION</u>

The present invention involves the discovery that the large capital costs associated with CO generation for a new acetic acid plant can be significantly reduced or largely eliminated by retrofitting an existing methanol or methanol/ammonia plant to make acetic acid. All or part of the syngas is diverted from the MeOH synthesis loop and supplied instead to a separator unit to recover CO₂, CO and hydrogen, which are advantageously used in various novel ways to produce acetic acid. The recovered CO₂ can be supplied to the reformer to enhance CO production, or to the MeOH synthesis loop to make methanol. The recovered CO is usually supplied to the acetic acid reactor with the methanol to make the acetic acid. The recovered hydrogen can be supplied to the MeOH loop for methanol production, used for the manufacture of ammonia or other products, burned as a fuel, or exported, since the hydrogen is normally produced in excess of the requirements for methanol synthesis in the present invention.

The carbon dioxide can be fed into a reformer to which natural gas and steam (water) are fed. Syngas is formed in the reformer wherein both the natural gas and the carbon dioxide are reformed to produce syngas with a large proportion of carbon monoxide relative to reforming without added carbon dioxide. Alternatively or additionally, the CO₂ can be supplied to the MeOH loop, with additional CO from the synthesis gas and/or additional imported CO₂, for catalytic reaction with hydrogen to make methanol.

The syngas can be split into a first part and a second part. The first syngas part is converted to methanol in a conventional methanol synthesis loop that is operated at half of the design capacity of the original plant since less syngas is supplied to it. The second syngas part can be processed to separate out carbon dioxide and carbon monoxide, and the separated carbon dioxide can be fed back into the feed to the reformer to enhance carbon monoxide formation, and/or fed to the MeOH synthesis loop to make methanol. The separated carbon monoxide can then be reacted with the methanol to produce acetic acid or an acetic acid precursor by a conventional process.

Separated hydrogen, which is generally produced in excess beyond that required for methanol synthesis in the present process, can also be reacted with nitrogen, in a conventional manner, to produce ammonia. Also, a portion of acetic acid that is produced can be reacted in a conventional manner with oxygen and ethylene to form vinyl acetate monomer. The nitrogen for the ammonia process (especially for any added ammonia capacity in a retrofit of an original methanol plant comprising an ammonia synthesis loop) and the oxygen for the vinyl acetate monomer process, can be obtained from a conventional air separation unit.

Broadly, the present invention provides, in one aspect, a method for retrofitting an original methanol plant which has at least one steam reformer for converting a hydrocarbon to a syngas stream containing hydrogen and carbon monoxide, a heat recovery section for cooling the syngas stream, a compression unit for compressing the syngas stream, and a methanol synthesis loop for converting at least a portion of the hydrogen and carbon monoxide in the syngas stream to methanol. The method converts the methanol plant into a retrofitted plant for manufacturing a product from carbon monoxide and methanol selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof. The method comprises the steps of: (a) diverting a portion of the syngas stream from at least one reformer to a separation unit; (b) operating the methanol synthesis loop with a feed comprising the remaining syngas stream to produce less methanol than the original methanol plant; (c) operating the separation unit to separate the diverted syngas into at least a carbon monoxide-rich stream and a hydrogen-rich stream, wherein the quantity of hydrogen in the hydrogen-rich stream is greater than any net hydrogen production of the original methanol plant; and (d) reacting the carbon monoxide-rich stream from the separation unit with the methanol from the methanol synthesis loop to form the product, wherein the diversion of the syngas stream is balanced for production of the methanol from the methanol synthesis loop and the carbon monoxide-rich stream from the separation unit for stoichiometric conversion to the product.

Preferably, at least one steam reformer is modified to increase carbon monoxide production in the syngas stream. The syngas stream preferably comprises carbon dioxide, and the separation unit produces a carbon dioxide-rich stream that is preferably recycled to at least one reformer to increase the carbon monoxide production.

The reaction step can include the direct catalytic reaction of methanol and carbon monoxide to form acetic acid as in the Mosanto-BP process, for example, or alternatively can comprise the intermediate formation of methyl formate and isomerization of the methyl formate to acetic acid, the intermediate reaction of CO and two moles of methyl alcohol to form methyl acetate and hydrolysis of the methyl acetate to acetic acid and methanol, or the carbonylation of the methyl acetate to form acetic anhydride.

In one preferred embodiment of the retrofitting method, the present invention provides a method for retrofitting an original methanol plant that has at least one steam reformer for converting a hydrocarbon/steam feed to a syngas stream containing hydrogen and carbon monoxide, a heat recovery section for cooling the syngas stream, a compression unit for compressing the syngas stream, and a methanol synthesis loop for converting at least a portion of the hydrogen and carbon monoxide in the syngas stream to methanol. The retrofitted plant can manufacture a product from carbon monoxide and methanol selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof. The retrofitting method comprises the steps of: (a) modifying at least one steam reformer for operation with a feed comprising a relatively increased carbon dioxide content; (b) diverting a portion of the syngas stream from at least one steam reformer to a separation unit; (c) operating the methanol synthesis loop with a feed comprising the remaining syngas stream to produce less methanol than the original methanol plant; (d) operating the separation unit to separate the diverted syngas into a carbon dioxide-rich stream, a carbon monoxide-rich stream and a hydrogen-rich stream; (e) recycling the carbon dioxide-rich stream from the separation unit to at least one modified steam reformer to increase the carbon monoxide formation relative to the original methanol plant and increase the molar ratio of carbon monoxide to hydrogen; (f) reacting the carbon monoxide-rich stream from the separation unit with the methanol from the methanol synthesis loop to form the product, wherein the diversion of the syngas stream is balanced for the production of the methanol from the methanol synthesis loop and the carbon monoxide-rich stream from the separation unit for stoichiometric conversion to the product.

The modified steam reformer is preferably modified to operate at a higher temperature to enhance the carbon conversion to carbon monoxide. The separation unit can include a solvent absorber and stripper for carbon dioxide recovery, and a cryogenic distillation unit for carbon monoxide and hydrogen recovery.

The compression unit preferably has a three-stage compressor, and the syngas stream diversion preferably occurs between the second and third compression stages. The third compressor stage is preferably modified for operation at a lower throughput than the original methanol plant. Where the methanol synthesis loop of the original methanol plant includes a recycle loop compressor, the recycle loop compressor can also be modified for operation at a lower throughput.

The method can also comprise importing a stream of mixed CO/carbon dioxide stream, for example in a 1:2 to 2:1 molar ratio. The imported stream can be supplied to the methanol synthesis loop or to the separation unit, but is preferably supplied to the reformer wherein the carbon dioxide therein is converted to CO.

The method can further comprise the step of reacting the hydrogen in the hydrogen-rich stream with nitrogen to make ammonia. Where the original methanol plant produces a hydrogen-rich stream comprising a loop purge from the methanol synthesis loop that was reacted with nitrogen to make ammonia, the retrofitted plant can use the hydrogen-rich stream from the separation unit as a primary hydrogen source for the ammonia production. With the additional hydrogen available from the syngas, additional ammonia can be produced in the retrofitted plant relative to the original methanol plant.

The method can further comprise installing a vinyl acetate monomer unit for reacting a portion of the acetic acid with ethylene and oxygen to make vinyl acetate monomer. An air separation unit can be installed to make the oxygen for the vinyl acetate monomer unit, and the nitrogen produced from the air separation unit preferably matches the nitrogen required for the additional ammonia production.

In another aspect, the present invention provides a process for making hydrogen and a product selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof, from a hydrocarbon via methanol and carbon monoxide which can be effected by construction of a new plant or retrofit of an existing plant. The process comprises the steps of: (a) reforming the hydrocarbon with steam in the presence of a minor proportion of carbon dioxide to form a syngas containing hydrogen, carbon monoxide, and carbon dioxide having a molar ratio of R ((H₂-CO₂)/(CO+CO₂)) from 2.0 to 2.9; (b) recovering heat from the syngas to form a cooled syngas stream; (c) compressing the cooled syngas stream to a separation pressure; (d) diverting a major portion of the compressed syngas to a separation unit; (e) separating the syngas diverted to the separation unit into a carbon-dioxide-rich stream, a carbon monoxide-rich stream and a hydrogen-rich stream; (f) recycling the carbon dioxide-rich stream to the reforming step; (g) further compressing the remaining minor portion of the syngas to a methanol synthesis pressure higher than the separation pressure; (h) operating a methanol synthesis loop to convert the hydrogen and carbon monoxide in the further compressed syngas into a methanol stream; and (i) reacting the carbon monoxide-rich stream from the separation unit with the methanol stream from the methanol synthesis loop to make the product. The diversion step is preferably balanced to obtain stoichiometric amounts of carbon monoxide and methanol.

The process preferably has a molar ratio of carbon dioxide to hydrocarbon comprising natural gas in feed to the reforming step from 0.1 to 0.5 and a ratio of steam to natural gas from 2 to 6. The methanol synthesis loop can be operated below a total maximum combined design throughput of all methanol synthesis reactor(s) in the loop. The process can further comprise the step of reacting the hydrogen in the hydrogen-rich stream with nitrogen in an ammonia synthesis reactor to make ammonia. The process can also comprise the step of separating air into a nitrogen stream and an oxygen stream and supplying the nitrogen stream to the ammonia synthesis reactor. Where the product comprises acetic acid or an acetic acid precursor which is converted to acetic acid, the process can further comprise the step of supplying the oxygen stream from the air separation unit to a vinyl acetate synthesis reactor, along with a portion of the acetic acid from the carbon monoxide-methanol reaction step, and ethylene, to produce a vinyl acetate monomer stream.

In a further aspect the present invention provides a method for retrofitting an original methanol plant, comprising at least one steam reformer for converting a hydrocarbon to a syngas stream containing hydrogen, carbon monoxide, and carbon dioxide, and a methanol synthesis loop for converting hydrogen and carbon monoxide from the syngas stream to methanol, into a retrofitted plant for manufacturing a product from carbon monoxide and methanol selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof. The method includes (1) separating all or part of the syngas stream in a separation unit into respective streams rich in carbon dioxide, carbon monoxide and hydrogen; (2) operating the methanol synthesis loop with a feed comprising (a) carbon dioxide and (b) a portion of the hydrogen-rich stream; and (3) reacting at least a portion of the carbon monoxide-rich stream from the separation unit with methanol from the methanol synthesis loop to form the product. The feed to the methanol synthesis loop can include imported carbon dioxide and/or a portion of the synthesis gas. Preferably, all of the syngas stream is supplied to the separation step. The amount of the hydrogen-rich stream is generally in excess of the stoichiometric hydrogen required by the methanol synthesis loop. Preferably, all of the carbon dioxide-rich stream is supplied to the synthesis loop, and all of the carbon monoxide-rich stream to the reaction step.

In a preferred embodiment, the retrofitting method comprises (1) supplying a major portion of the syngas stream to a separation unit for separating the syngas stream into respective streams rich in carbon dioxide, carbon monoxide and hydrogen, (2) operating the methanol synthesis loop with a feed comprising the carbon-dioxide-rich stream from the separation unit, a minor portion of the syngas stream, and an additional source of carbon dioxide to produce a methanol stream, and (3) reacting the carbon monoxide-rich stream from the separation unit with the methanol stream from the methanol synthesis loop to form the product.

In another preferred embodiment, the retrofitting method comprises (1) supplying the syngas stream to a separation unit for separating the syngas stream into respective streams rich in carbon dioxide, carbon monoxide and hydrogen, (2) operating the methanol synthesis loop with a feed comprising the carbon-dioxide-rich stream from the separation unit, a portion of the hydrogen-rich stream from the separation unit, a minor portion of the syngas stream, and carbon dioxide from an additional source, to produce a methanol stream, and (3) reacting the carbon monoxide-rich stream from the separation unit with the methanol stream from the methanol synthesis loop in stoichiometric proportions to form the product.

In a further preferred embodiment, the retrofitting method comprises importing a stream of mixed CO/carbon dioxide stream, for example in a 1:2 to 2:1 molar ratio. The imported stream can be supplied to the methanol synthesis loop or to the separation unit, but is preferably supplied to the reformer for conversion of the carbon dioxide to CO.

In yet another aspect, the present invention provides a process for making hydrogen and a product selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof, from a hydrocarbon via intermediate methanol, carbon monoxide, and carbon dioxide. The process includes (1) reforming the hydrocarbon with steam to form a syngas containing hydrogen, carbon monoxide, and carbon dioxide, (2) recovering heat from the syngas to form a cooled syngas stream, (3) compressing the cooled syngas stream to a separation pressure, (4) processing the syngas in a separation unit to separate a carbon monoxide-rich stream from the hydrogen and carbon dioxide, (5) operating a methanol synthesis loop to react a first portion of the hydrogen from the separation unit with the carbon dioxide from the separation unit, and additional carbon dioxide from another source, to obtain a methanol stream, (6) reacting the carbon monoxide-rich stream from the separation unit with the methanol stream from the methanol synthesis loop in stoichiometric proportions to form a product selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof.

Regardless of whether the plant is a retrofit or a new plant, where the product comprises acetic acid, the reaction step preferably comprises reacting methanol, methyl formate, or a combination thereof in the presence of a reaction mixture comprising carbon monoxide, water, a solvent and a catalyst system comprising at least one halogenated promoter and at least one compound of rhodium, iridium or a combination thereof. The reaction mixture preferably has a water content up to 20 weight percent. Where the reaction step comprises simple carbonylation, the water content in the reaction mixture is more preferably from 14 to 15 weight percent. Where the reaction step comprises low-water carbonylation, the water content in the reaction mixture is more preferably from 2 to 8 weight percent. Where the reaction step comprises methyl formate isomerization or a combination of isomerization and methanol carbonylation, the reaction mixture more preferably contains a nonzero quantity of water up to 2 weight percent. The reaction step is preferably continuous.

<u>BRIEF DESCRIPTION OF THE DRAWINGS</u>

<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig. 1</figref> (prior art) is an overall block flow diagram of a typical methanol/ammonia plant using hydrogen from the methanol synthesis loop purge to make ammonia, which can be retrofitted according to the present invention for acetic acid manufacture.</li><li><figref idref="f0002">Fig. 2</figref> is an overall block flow diagram of the plant of <figref idref="f0001">Fig. 1</figref> after it has been retrofitted according to the present invention to make acetic acid, vinyl acetate monomer and additional ammonia.</li><li><figref idref="f0003">Fig. 3</figref> is a simplified schematic process flow diagram of the front end of the plant of <figref idref="f0002">Fig. 2</figref> showing the synthesis gas production and CO₂ recycle in the retrofitted plant wherein existing equipment is shown as a solid line, new equipment as a dash-dot-dash line, and modified equipment as a dotted line.</li><li><figref idref="f0004">Fig. 4</figref> is a simplified schematic process flow diagram of a portion of the plant of <figref idref="f0002">Fig. 2</figref> showing the CO/H₂ separation and the methanol synthesis in the retrofitted plant wherein existing equipment is shown as a solid line, new equipment as a dash-dot-dash line, and modified equipment as a dotted line.</li><li><figref idref="f0005">Fig. 5</figref> is an overall block flow diagram of the plant of <figref idref="f0001">Fig. 1</figref> after it has been retrofitted according to an alternate embodiment of the present invention wherein a portion of the syngas stream is diverted to separation and the MeOH synthesis loop is supplied with hydrogen and CO₂ recovered from the separation, a remaining portion of the syngas and additional imported CO₂.</li><li><figref idref="f0006">Fig. 6</figref> is an overall block flow diagram of the plant of <figref idref="f0001">Fig. 1</figref> after it has been retrofitted according to another alternate embodiment of the present invention wherein all of the syngas stream is diverted to separation and the MeOH synthesis loop is supplied with hydrogen and CO₂ recovered from the separation and additional imported CO₂.</li></ul>

<u>DETAILED DESCRIPTION OF THE INVENTION</u>

With reference to <figref idref="f0001">Fig. 1</figref>, an original plant which can be retrofitted according to one embodiment of the present invention has an existing conventional steam reformer unit <b>10,</b> methanol (MeOH) synthesis unit <b>12</b> and preferably ammonia synthesis unit <b>14</b> wherein hydrogen for the ammonia synthesis unit <b>14</b> is taken as purge stream <b>16</b> from the methanol synthesis loop. The retrofit of the present invention is generally applicable to any plant that generates and uses synthesis gas to make methanol. As used in the present specification and claims, reference to "original plant" shall mean the plant as built and including any intervening modifications prior to the retrofit of the present invention.

The reformer unit <b>10</b> is typically a fired furnace containing parallel tube banks filled with conventional reforming catalyst such as alumina-supported nickel oxide, for example. The feed to the reformer(s) is any conventional reformer feed such as a lower hydrocarbon, typically naphtha or natural gas. The reformer can be a single-pass reformer or a two-stage reformer, or any other commercially available reformer, such as, for example, a KRES unit available from Kellogg, Brown &amp; Root, as is known to those skilled in the art. The reformer effluent of the original methanol plant can contain any conventional H₂:CO ratio, but is normally close to 2.0 in plants making solely methanol, and higher, e.g. 3.0 and above, in plants producing a separate hydrogen product or intermediate hydrogen-containing stream, e.g. for ammonia synthesis. The hydrogen-containing stream is typically obtained as purge stream <b>16</b> from the methanol synthesis unit <b>12</b> loop which is necessary to keep the level of hydrogen and inerts from building up in the synthesis gas recirculated through the methanol synthesis unit <b>12.</b>

According to the present invention, the original plant of <figref idref="f0001">Fig. 1</figref> is retrofitted to produce acetic acid (HAC) using the existing reformer <b>10</b> and methanol synthesis unit <b>12,</b> and keeping any ammonia synthesis unit <b>14,</b> as shown in <figref idref="f0002">Fig. 2</figref>. A portion of the effluent <b>18</b> from the reformer <b>10</b> is diverted from the methanol synthesis unit <b>12</b> via line <b>20</b> to a new CO₂ removal unit <b>22.</b> The CO₂ removal unit <b>22</b> separates the stream from line <b>20</b> into a CO₂-rich stream <b>24</b> and a CO₂-lean stream <b>26</b> using conventional CO₂ separation equipment and methodology such as, for example, absorption-stripping with a solvent such as water, methanol, generally aqueous alkanolamines such as ethanolamine, diethanolamine, methyldiethanolamine and the like, aqueous alkali carbonates such as sodium and potassium carbonates, and the like. Such CO₂ absorption-stripping processes are commercially available under the trade designations Girbotol, Sulfinol, Rectisol, Purisol, Fluor, BASF (aMDEA) and the like.

The CO₂ recovered from the CO₂ removal unit <b>22</b> or from another source can be supplied to the reformer <b>10.</b> Increasing the CO₂ in the feed to the reformer <b>10</b> increases the CO content of the effluent <b>18.</b> Analogous to steam reforming where a hydrocarbon reacts with steam to form synthesis gas, the reaction of the hydrocarbon with carbon dioxide is often called CO₂ reforming. As the carbon dioxide content of the reformer feed is increased, the share of the carbon in the carbon monoxide in the product synthesis gas <b>18</b> that is supplied from the carbon dioxide increases in relative proportion and the share originating from the hydrocarbon decreases. So, for a given CO production rate, the hydrocarbon feed gas requirement is reduced. During the early stage of reforming, heavier hydrocarbons are converted to methane:         HC + H₂O =&gt; CH₄ + CO₂ The main steam and CO₂ reforming reactions convert methane to hydrogen and carbon monoxide:         CH₄ + H₂O ⇔ 3 H₂ + CO         CH₄ + CO₂ ⇔ H₂ + 2 CO The shift reaction converts carbon monoxide to carbon dioxide and more hydrogen:         CO + H₂O ⇔ CO₂ + H₂ The conversion of the heavier hydrocarbons goes to completion. The steam reforming, CO₂ reforming, and shift reaction are equilibrium-restricted. The overall reaction is strongly endothermic. The reformer <b>10</b> can, if desired, be modified for additional heat input for supplemental CO₂ reforming and additional heat recovery. The effluent <b>18</b> from the modified reformer <b>10</b> has a molar ratio of hydrogen minus CO₂ to CO plus CO₂ (referred to in the present specification and claims as the "R ratio" (H₂ - CO₂)/(CO + CO₂)), which can be optimized for methanol synthesis, preferably within the range from 2.0 to 2.9. The possibility of optimizing the R ratio arises from the discovery that the hydrogen for the ammonia synthesis no longer needs to be obtained as the methanol purge stream <b>16,</b> but can instead be recovered from the syngas diverted via line <b>20</b> as discussed in more detail below.

The CO₂-lean stream <b>26</b> contains primarily CO and hydrogen and can be separated in CO separation unit <b>28</b> into a CO-rich stream <b>30</b> and a hydrogen-rich stream <b>32.</b> The separation unit <b>28</b> can comprise any equipment and/or methodologies for separating the CO/hydrogen mixture into relatively pure CO and hydrogen streams, such as, for example, semi-permeable membranes, cryogenic fractionation, or the like. Cryogenic fractional distillation is preferred, and can include simple partial condensation without any columns, partial condensation with columns, optionally with a pressure swing absorption (PSA) unit and a hydrogen recycle compressor, or methane wash. Normally, partial condensation with columns is sufficient for obtaining CO and hydrogen of sufficient purity for acetic acid and ammonia production, respectively, keeping equipment and operating costs to a minimum, although the PSA unit and hydrogen recycle compressor can be added for increasing the hydrogen purity and CO production rate. For acetic acid manufacture, the CO stream <b>30</b> preferably contains less than 1000 ppm hydrogen and less than 2 mole percent nitrogen plus methane. For ammonia production, the hydrogen stream <b>32</b> which is sent to a nitrogen wash unit (not shown) preferably contains at least 80 mol% hydrogen, more preferably at least 95 mol% hydrogen.

A portion of the hydrogen stream <b>32</b> is supplied to the existing ammonia synthesis unit <b>14</b> in place of the methanol loop purge stream <b>16.</b> The quantity of hydrogen produced in the stream <b>32</b> is generally much larger than the amount previously supplied via line <b>16.</b> This is due in large part to the fact that less methanol is made in the retrofitted plant, and thus less hydrogen is consumed for methanol synthesis. The additional hydrogen capacity can be used as a fuel supply, or as a raw hydrogen source for another process, such as, for example, increased ammonia conversion. Additional ammonia can be made by supplying a portion of the additional hydrogen to the existing ammonia synthesis reactor <b>14</b> where the ammonia conversion capacity can be increased, and/or by installing additional ammonia synthesis unit <b>33.</b> The increased ammonia capacity can be complemented by the presence of existing ammonia handling, storage and transport facilities which may be able to accommodate the additional ammonia capacity with little or no modification.

The methanol synthesis unit <b>12</b> is a conventional methanol conversion unit such as, for example, an lCl reactor. The methanol synthesis unit <b>12</b> of the retrofitted plant shown in <figref idref="f0002">Fig. 2</figref> is essentially the same as in the original plant prior to the retrofit, except that the quantity of methanol produced is lower, preferably half of that of the original plant. Concomitantly, the loop recycle compressor (not shown) is operated at a lower capacity and the purge stream <b>16</b> is considerably reduced in quantity. As mentioned above, the purge stream <b>16</b> is no longer needed for supplying the hydrogen to the ammonia converter <b>14,</b> since this is now supplied in the retrofitted plant from the hydrogen stream <b>32</b> separated directly from the portion of the reformer <b>10</b> effluent <b>18</b> diverted from the feed to the methanol synthesis unit <b>12</b> via line <b>20.</b> If desired, the purge stream <b>16</b> can now be used for fuel and/or as a hydrogen source for hydrodesulfurization of the feed to the reformer <b>10.</b> Since there is no longer any need to pass the excess hydrogen through the methanol synthesis unit <b>12</b> for use in the ammonia unit <b>14,</b> the feed to the methanol synthesis unit <b>12,</b> i.e. the effluent <b>18,</b> can be compositionally optimized for more efficient methanol conversion, as described above. It can also be desirable to modify the methanol synthesis unit <b>12,</b> if desired during the retrofit, to include any other modifications which are not present in the original plant but have become conventional and have been developed for methanol synthesis loops since the construction of the original plant and have not previously been incorporated therein.

The amount of syngas in the effluent <b>18</b> from the reformer <b>10</b> which is diverted to CO₂/CO/H₂ separation is preferably balanced to provide a stoichiometric ratio of methanol and CO to produce acetic acid therefrom in acetic acid synthesis unit <b>34.</b> Preferably, the ratio of CO in line <b>30</b> and methanol in line <b>36</b> is equal or the methanol is produced at a 10-20% molar excess, e.g. a molar ratio from 1.0 to 1.2. To produce this ratio of methanol and CO, a relatively larger quantity (total kg/hr) of the effluent <b>18</b> is diverted into line <b>20,</b> and the remaining minor portion is fed in line <b>38</b> to the methanol synthesis unit <b>12.</b>

The acetic acid synthesis unit <b>34</b> employs conventional acetic acid manufacturing equipment and methodology well known and/or commercially available to those skilled in the art, such as, for example, from one or more of the acetic acid manufacturing patents mentioned above. For example, a conventional BP/Monsanto process can be employed, or an improved BP/Monsanto process employing BP-Cativa technology (iridium catalyst), Celanese low water technology (rhodium-lithium acetate catalyst), Millenium low water technology (rhodium-phosphor oxides catalyst), Acetex technology (rhodium-iridium catalyst) and/or dual process methanol carbonylation-methyl formate isomerization. The reaction generally comprises reacting methanol, methyl formate, or a combination thereof in the presence of a reaction mixture comprising carbon monoxide, water, a solvent and a catalyst system comprising at least one halogenated promoter and at least one compound of rhodium, iridium or a combination thereof. The reaction mixture preferably has a water content up to 20 weight percent. Where the reaction comprises simple carbonylation, the water content in the reaction mixture is preferably from 14 to 15 weight percent. Where the reaction comprises low-water carbonylation, the water content in the reaction mixture is preferably from 2 to 8 weight percent. Where the reaction comprises methyl formate isomerization or a combination of isomerization and methanol carbonylation, the reaction mixture preferably contains a nonzero quantity of water up to 2 weight percent. The reaction is typically continuous. An acetic acid product is obtained via line <b>40.</b>

If desired, a portion of the acetic acid from line <b>40</b> can be fed to a conventional vinyl acetate monomer synthesis unit <b>42</b> where it is reacted with ethylene via line <b>44</b> and oxygen via line <b>46</b> to obtain monomer product stream <b>48.</b> The oxygen in line <b>46</b> can be obtained, for example, using a conventional (preferably cryogenic) air separation unit <b>50</b> which also produces a nitrogen stream <b>52</b> corresponding to the amount of air from line <b>54</b> needed for the oxygen in line <b>46.</b> The amount of air separated can be matched to produce the nitrogen required via line <b>52</b> for the additional ammonia capacity added by ammonia synthesis unit <b>33</b> as mentioned above.

In the alternate embodiment shown in <figref idref="f0005">Fig. 5</figref>, the CO available for acetic acid manufacture is increased by diverting a much larger portion of the syngas from line <b>18</b> via line <b>20</b> to the CO₂ removal unit <b>22,</b> than in the embodiment of <figref idref="f0002">Fig. 2</figref>. This increases the requirement for CO needed for the methanol synthesis unit <b>12.</b> However, the CO requirement for the methanol synthesis unit <b>12</b> can also be met by supplying CO₂, although the hydrogen required for methanol synthesis with CO₂ is higher. The CO₂ stream <b>24</b> from the CO₂ removal unit <b>22</b> is thus supplied to methanol synthesis unit 12 instead of reformer <b>10</b> as in the <figref idref="f0002">Fig. 2</figref> embodiment. Additional CO or CO₂, or a mixture of CO/ CO₂, as needed for the methanol synthesis <b>12</b> can be supplied from another source (not shown) via line <b>25.</b> It is preferred to import CO₂ instead of CO because CO₂ is usually easier to produce and transport than CO, and it is also less toxic. Some of the hydrogen obtained in line <b>32</b> from the CO separation unit <b>28</b> can be supplied via line <b>35</b> to the methanol synthesis unit <b>12.</b> Since the amount of hydrogen in line <b>32</b> is generally greater than the amount of hydrogen required for methanol synthesis unit <b>12,</b> even when using CO₂ as a feedstock in place of CO, the excess hydrogen via line <b>37</b> can be exported for another use, such as, for example, ammonia synthesis or combustion as a fuel gas.

The embodiment of <figref idref="f0005">Fig. 5</figref> can have advantages over that of <figref idref="f0002">Fig. 2</figref> in that the retrofit does not require modification of the reformers <b>10,</b> and the methanol synthesis unit <b>12</b> can be operated at essentially design capacity without significantly changing any stream compositions in the methanol synthesis unit <b>12.</b> Furthermore, the embodiment of <figref idref="f0005">Fig. 5</figref> can be operated without excess methanol production, while at the same time producing hydrogen via line <b>37</b> for export.

The embodiment of <figref idref="f0006">Fig. 6</figref> is similar to <figref idref="f0005">Fig. 5</figref> except that there is no syngas supplied to the methanol synthesis unit <b>12,</b> and it is instead supplied in its entirety to the CO₂ removal unit <b>22.</b> This has the further advantage of maximizing CO and acetic acid production with slightly higher CO₂ import requirements and slightly less hydrogen production via line <b>37.</b>

<u>Example 1</u>

The retrofit of an existing methanol plant includes its reconfiguration to produce methanol and CO in stoichiometric ratio for acetic acid manufacture while still producing hydrogen at least sufficient for existing ammonia synthesis. The original plant converts 760 MTPD of natural gas in a single-pass reformer with a steam:carbon molar ratio of 2.8 to form 1760 MTPD synthesis gas containing 74.1 mol% hydrogen, 15.5 mol% CO, 7.1 mol% CO₂, 3.1 mol% methane, 0.2 mol% nitrogen, dry basis, which is added to the methanol synthesis loop. The feed to the methanol synthesis reactor in the original plant (recycle plus makeup synthesis gas) is 5600 MTPD of a feed gas comprising 82.2 mol% hydrogen, 9 mol% methane, 4.8 mol% CO, 3 mol% CO₂, 0.6 mol% nitrogen, and 0.4 mol% MeOH and other constituents, dry basis. The synthesis gas is converted in the original plant to 1560 MTPD crude methanol which is refined by distillation to give 1335 MTPD of refined product. The net loop purge gas (raw hydrogen gas for ammonia synthesis) in the original plant comprises 84.3 mol% hydrogen, 10.5 mol% methane, 2.2 mol% CO, 2 mol% CO₂, 0.7 mol% nitrogen, 0.4 mol% MeOH and other constituents, dry basis, and is sufficient for ammonia production in the original plant of 500 MTPD.

The original plant is retrofitted in accordance with <figref idref="f0003">Figs. 3</figref> and <figref idref="f0004">4</figref> to produce 760 MTPD methanol and 606 MTPD CO which can make 1208 MTPD acetic acid, and 331 MTPD hydrogen which can make 1085 MTPD ammonia. The existing reformer <b>106</b> is modified to add a new induced draft fan (not shown) and larger steam superheat, mixed feed and feed coils (not shown). The existing third stage synthesis gas compressor <b>122</b> is modified for a lower throughput by replacing the inner bundle including rotor and diaphragms. The existing synthesis gas recirculation compressor <b>126</b> is similarly modified for a lower flow rate by replacing the inner bundle including rotor and diaphragms. A new aMDEA CO₂ removal unit <b>128,</b> a new package refrigeration unit <b>138,</b> a new cold box unit <b>142</b> including driers and CO compressor, a new CO₂ compressor <b>134</b> to recycle CO₂ to the reformer <b>106</b> and new hydrogen compressors <b>148</b> to supply hydrogen to the existing ammonia plant (not shown) and a new 600 MTPD ammonia plant (not shown) are added. Prior to and/or during the retrofit (at least while the existing equipment is operational, before shutdown construction), the methanol plant can be operated at a reduced rate, bypassing approximately 27% of the synthesis gas from the discharge of the synthesis gas compressor <b>122</b> directly to the existing ammonia plant.

Advantages of the retrofit compared to a completely new CO/MeOH plant are the use of existing units and equipment, such as desulfurization, reforming including waste heat recovery, synthesis gas compressor and circulator, etc. Additional advantage is provided by the use of the existing offsite and infrastructure such as steam generation, water treatment, cooling water system, control room and product loading facilities.

With reference to <figref idref="f0003">Fig. 3</figref> which shows a block flow diagram for the retrofitted plant, natural gas is supplied in line <b>100</b> to desulfurizer/saturator unit <b>102.</b> The existing sulfur removal system is used to remove any H₂S and organic sulfur from the process feed gas. This gas is mixed with a recycle stream <b>104</b> of hydrogen-rich synthesis gas to provide a hydrogen content of 2.4 mol%, and is heated in the desulfurizer heat exchanger (not shown) and in the convection section <b>116</b> of the reformer <b>106</b> to a temperature of 330°C. The heated gas enters the desulfurizer unit <b>102</b> where organic sulfur compounds are first hydrogenated to hydrogen sulfide over a bed of nickel/molybdenum catalyst (not shown). Below the NiMo catalyst is a bed of zinc oxide adsorbent (not shown) in which the hydrogen sulfide is reacted to form zinc sulfide.

The desulfurized feed is passed through the existing saturator where the gas is saturated with water from line <b>108</b> to reduce the process steam requirement. The gas exiting the saturator in line <b>110</b> is mixed with recycle carbon dioxide in line <b>112</b> and medium-pressure steam from line <b>114</b> so that the mixed gas has 3 moles of equivalent steam per mole of carbon, where equivalent steam is calculated as moles of steam plus 0.6 times moles of carbon dioxide.

Addition of CO₂ to the feed gas is a modification of the existing operation of the reformer <b>106.</b> This produces more CO and balances the synthesis gas composition in effluent stream <b>115</b> for more efficient methanol production as described above. The mixed feed is preheated in the modified mixed feed coils (not shown) in the reformer <b>106</b> to 515°C.

The hot mixed feed is distributed to the reformer <b>106</b> catalyst tubes (not shown), passes down through the nickel reforming catalyst, and reacts to form hydrogen, CO and CO₂. Pressure and temperature at the outlet of the catalyst tubes is 19 bars (absolute) and 880°C. The heat recovery unit <b>116</b> is a convection section of the reformer <b>106</b> and includes coils for the high pressure steam boiler, high pressure steam superheating (modified in the retrofitted plant), mixed feed preheating (modified in the retrofitted plant), feed gas preheating (modified in the retrofitted plant), and combustion air preheating. As mentioned above, modified coils are provided for steam superheating, mixed feed preheating and feed gas preheating services. The reformer <b>106</b> includes a new induced draft fan. The old induced draft fan is used as the forced draft fan in the retrofitted plant. The reformer effluent <b>115</b> is used to generate steam, preheat boiler feed water, and provide heat in the reboilers for the topping and refining columns in the existing exchangers (not shown).

The synthesis gas in line <b>118</b> is compressed from 17.3 bars (absolute) to 41.7 bars (absolute) in the first casing of the existing synthesis compressor (first and second stages <b>120</b>) without modification. The gas in discharge line <b>121</b> is then split so that 62% goes to the CO/H₂ production via line <b>130</b> and the rest is sent via line <b>123</b> to the second casing (third stage compressor <b>122</b> supplying syngas to line <b>125</b> for MeOH synthesis). The third compressor stage <b>122</b> of the synthesis gas compressor handles only 40% of the flow of the original plant. This casing is modified with a new inner bundle including rotor and diaphragms. The gas is then cooled in the original third inter-stage cooler (not shown) and water is separated in the original inter-stage separator (not shown). The make-up gas in line <b>125</b> is then mixed with recycle gas from line <b>124</b> (see <figref idref="f0004">Fig. 4</figref>) and compressed in recycle circulator <b>126</b> to 80 bars (absolute). The circulator <b>126</b> will also handle only 61% of the original flow and therefore requires a new inner bundle including rotor and diaphragms.

Sixty-two percent of the gas from the second stage of the synthesis gas compressor <b>120</b> is sent via line <b>130</b> to a new aMDEA CO₂ removal system <b>128.</b> This is a single-stage aMDEA system licensed from BASF in which the circulating solution is 40 wt% aMDEA, designed to reduce the carbon dioxide content in the gas stream <b>130</b> from 9.7 vol% to 100 ppmv, on a dry basis, in line <b>132.</b> The absorber (not shown) is operated at 35° to 40°C and 39.5 bars (absolute). The absorber overhead gas (not shown) enters a knockout drum (not shown) for separation of any entrained solution. The rich solution from the absorber bottom passes through a hydraulic turbine (not shown) for power recovery. The turbine produces power to help drive one of the lean solution pumps (not shown). The solution then enters a stripper (not shown) designed in three sections: a contact cooler on top, a low-pressure (LP) flash section in the middle, and a stripper section in the bottom. The rich solution from the hydraulic turbine enters the LP flash section which promotes CO₂ flashing by pressure reduction. A semi-lean solution pump (not shown) pumps the solution from the bottom of the LP flash section through the lean/semi-lean solution exchanger (not shown) to the top of the stripper section. The exchanger recovers heat from the lean solution leaving the stripper section. The solution leaving the stripper section is reboiled by low-pressure steam in a CO₂ stripper steam reboiler (not shown). The carbon dioxide and steam from the LP flash section is cooled to 35°C in the contact cooler section. This is accomplished by contact with cooling water. Cooled carbon dioxide having a purity of at least 99 vol% on a dry basis is sent via line <b>133</b> to new CO₂ compressor <b>134,</b> a four-stage, motor-driven, integrally geared turbo compressor which discharges the CO₂ into line <b>112</b> at 26 bars (absolute) for recycle to the reformer <b>106</b> upstream from the mixed feed coil as mentioned previously. The regenerated lean solution is cooled in the lean/semi-lean solution exchanger and then by cooling water. The cooled lean solution is pumped to the top section of the absorber, and a slipstream can be filtered to remove solids. Make-up water is added to the system via line <b>136.</b>

The synthesis gas in line <b>132</b> is cooled to 4.4°C in new package refrigeration unit <b>138</b> (see <figref idref="f0004">Fig. 4</figref>) which uses a screw compressor and ammonia as refrigerant. The chilled synthesis gas from the unit <b>138</b> is then passed via line <b>140</b> into driers/cold box unit <b>142</b> where it is dried and separated cryogenically into noncondensed hydrogen stream <b>144</b> and CO stream <b>146.</b> The driers (not shown) are parallel beds packed with molecular sieve, one of which is on line while the other is being regenerated. In the driers, the moisture content of the gas is reduced below 0.5 ppmv and the carbon dioxide content is reduced below 1 ppmv. Each drier can normally operate 12 hours and regeneration with hot (288°C) reject gas from the CO/H₂ plant and cooling takes 6 hours, allowing 6 hours of stand-by.

The separation of CO and H₂ in the cold box employs a partial condensation process using two columns (not shown). The dried gas from the driers is cooled and partially liquefied in feed/effluent exchangers (not shown). The liquid is separated out, while the hydrogen product is superheated and expanded in a hydrogen expansion turbine (not shown). Cold gas from the turbine at 19.5 bars (absolute) is re-heated in the feed/effluent exchangers and leaves the cryogenic unit at 19.0 bars (absolute) and 10°C via line <b>144.</b> The liquid that was separated out, rich in CO, is flashed into a hydrogen reject column (not shown). Flash gas containing mostly hydrogen is taken from the top of the column, and re-heated in the feed/effluent exchangers to the same temperature and pressure as the gas from the turbine with which it is mixed in line <b>144</b> for supply to the hydrogen compressor <b>148.</b>

Reboil for the hydrogen reject column is provided by condensing high pressure CO in a reboiler (not shown). The bottom product from the hydrogen reject column, now lean in hydrogen but containing excess methane, is flashed into a CO/CH₄ column (not shown) where CH₄ is separated from the CO and exits the column as a liquid bottoms product. The liquid methane is evaporated and heated to ambient in the feed/effluent exchangers and exits the unit <b>142</b> at 3.15 bars (absolute) as fuel gas via line <b>150.</b> The CO from the top of the CO/CH₄ column is heated in the feed/effluent exchangers and compressed in a CO compressor (not shown) into line <b>146.</b> The CO compressor is also utilized in the heat pump cycle by cooling CO in one of the feed/effluent exchangers, condensing in the reboilers for the hydrogen reject and CO/CH₄ columns and subcooling in another one of the feed/effluent exchangers. Subcooled liquid CO is used as reflux in the CO/CH₄ column and as refrigerant in the feed/effluent exchangers. The evaporated CO is reheated in one of the feed/effluent exchangers before recompression in the CO compressor.

The hydrogen compressor unit <b>148</b> comprises three parallel reciprocating, non-lubricated compressors which can each compress 50% of the hydrogen produced to 80 bars (absolute) into line <b>152.</b> Normally two compressors are on line and the third is a spare. The quantity of hydrogen produced in line <b>152</b> is sufficient to produce 1084 MTPD ammonia. The existing ammonia plant (not shown) requires just enough hydrogen to make 500 MTPD ammonia, so the rest of the hydrogen product is used to make 584 MTPD ammonia in a new ammonia plant (not shown). The pressure of the hydrogen required for the new ammonia plant can be more or less than 80 bars, so the hydrogen compressor pressure can be adjusted accordingly.

The make-up syngas in line <b>123</b> (see <figref idref="f0004">Fig. 4</figref>) is more balanced for MeOH synthesis and has a lower R ratio of 2.1 relative to the original plant. The lower R value is due to CO₂ reforming and results in lower circulation in recycle line <b>124</b> and in very little purge from the MeOH loop via line <b>160.</b> Gas from the discharge of the recycle stage <b>126</b> flows through line <b>162</b> to original methanol converter <b>164</b> and process flows essentially follow the original process flow scheme in line <b>166,</b> heat recovery and cooling unit <b>168,</b> line <b>170,</b> methanol separator <b>172,</b> recycle line <b>124,</b> letdown vessel <b>174,</b> and fuel gas stream <b>176,</b> at 61-65% of original operating flows. The operation of the MeOH converter <b>164</b> was simulated by Kellogg, Brown &amp; Root to estimate the performance of the converter <b>164</b> at the new operating conditions and lower capacity. The MeOH product stream <b>178</b> from the letdown vessel <b>176</b> is 760 MTPD.

Flow rates, compositions and properties of selected streams in the retrofitted plant are listed in Table 1 below: <tables id="tabl0001" num="0001"><table frame="all"><title>Table 1</title><tgroup cols="16"><colspec colnum="1" colname="col1" colwidth="24mm" /><colspec colnum="2" colname="col2" colwidth="14mm" /><colspec colnum="3" colname="col3" colwidth="13mm" /><colspec colnum="4" colname="col4" colwidth="16mm" /><colspec colnum="5" colname="col5" colwidth="14mm" /><colspec colnum="6" colname="col6" colwidth="16mm" /><colspec colnum="7" colname="col7" colwidth="16mm" /><colspec colnum="8" colname="col8" colwidth="14mm" /><colspec colnum="9" colname="col9" colwidth="16mm" /><colspec colnum="10" colname="col10" colwidth="14mm" /><colspec colnum="11" colname="col11" colwidth="14mm" /><colspec colnum="12" colname="col12" colwidth="14mm" /><colspec colnum="13" colname="col13" colwidth="14mm" /><colspec colnum="14" colname="col14" colwidth="16mm" /><colspec colnum="15" colname="col15" colwidth="16mm" /><colspec colnum="16" colname="col16" colwidth="15mm" /><thead><row><entry valign="top">Stream ID</entry><entry align="center" valign="top">100</entry><entry align="center" valign="top">104</entry><entry align="center" valign="top">110</entry><entry align="center" valign="top">112</entry><entry align="center" valign="top">115</entry><entry align="center" valign="top">121</entry><entry align="center" valign="top">123</entry><entry align="center" valign="top">124</entry><entry align="center" valign="top">130</entry><entry align="center" valign="top">132</entry><entry align="center" valign="top">144</entry><entry align="center" valign="top">146</entry><entry align="center" valign="top">162</entry><entry align="center" valign="top">166</entry><entry align="center" valign="top">178</entry></row><row><entry valign="top">Dry Mole %</entry><entry namest="col2" nameend="col16" align="left" valign="top" /></row></thead><tbody><row><entry>H₂</entry><entry align="right">--</entry><entry align="right">61.27</entry><entry align="right">2.40</entry><entry align="right">0.62</entry><entry align="right">68.79</entry><entry align="right">68.82</entry><entry align="right">68.82</entry><entry align="right">61.26</entry><entry align="right">68.82</entry><entry align="right">76.20</entry><entry align="right">95.30</entry><entry align="right">0.09</entry><entry align="right">62.44</entry><entry align="right">58.36</entry><entry align="right">0.02</entry></row><row><entry>N₂</entry><entry align="right">0.70</entry><entry align="right">2.01</entry><entry align="right">0.60</entry><entry align="right">--</entry><entry align="right">0.18</entry><entry align="right">0.18</entry><entry align="right">0.18</entry><entry align="right">2.01</entry><entry align="right">0.18</entry><entry align="right">0.20</entry><entry align="right">0.09</entry><entry align="right">0.83</entry><entry align="right">1.73</entry><entry align="right">1.91</entry><entry align="right">--</entry></row><row><entry>CH₄</entry><entry align="right">93.95</entry><entry align="right">30.53</entry><entry align="right">72.86</entry><entry align="right">0.01</entry><entry align="right">2.90</entry><entry align="right">2.90</entry><entry align="right">2.90</entry><entry align="right">30.54</entry><entry align="right">2.90</entry><entry align="right">3.21</entry><entry align="right">0.06</entry><entry align="right">0.08</entry><entry align="right">26.25</entry><entry align="right">29.11</entry><entry align="right">0.10</entry></row><row><entry>CO</entry><entry align="right">--</entry><entry align="right">2.28</entry><entry align="right">0.10</entry><entry align="right">0.16</entry><entry align="right">18.40</entry><entry align="right">18.40</entry><entry align="right">18.40</entry><entry align="right">2.28</entry><entry align="right">18.40</entry><entry align="right">20.38</entry><entry align="right">4.55</entry><entry align="right">99.00</entry><entry align="right">4.78</entry><entry align="right">2.17</entry><entry align="right">--</entry></row><row><entry>CO₂</entry><entry align="right">0.15</entry><entry align="right">3.49</entry><entry align="right">20.04</entry><entry align="right">99.20</entry><entry align="right">9.73</entry><entry align="right">9.70</entry><entry align="right">9.70</entry><entry align="right">3.49</entry><entry align="right">9.70</entry><entry align="right">0.01</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">4.45</entry><entry align="right">3.37</entry><entry align="right">0.70</entry></row><row><entry>C₂H₆</entry><entry align="right">3.60</entry><entry align="right">--</entry><entry align="right">2.76</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry></row><row><entry>C₃H₈</entry><entry align="right">1.14</entry><entry align="right">--</entry><entry align="right">0.87</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry></row><row><entry>i-C₄</entry><entry align="right">0.14</entry><entry align="right">--</entry><entry align="right">0.11</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry></row><row><entry>n-C₄</entry><entry align="right">0.24</entry><entry align="right">--</entry><entry align="right">0.18</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry></row><row><entry>n-C₅</entry><entry align="right">0.08</entry><entry align="right">--</entry><entry align="right">0.06</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry></row><row><entry>MeOH</entry><entry align="right">--</entry><entry align="right">0.42</entry><entry align="right">0.01</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">0.42</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">0.36</entry><entry align="right">5.08</entry><entry align="right">99.18</entry></row><row><entry>Dry Flow, KMOUHR</entry><entry align="right">2215</entry><entry align="right">91</entry><entry align="right">2894</entry><entry align="right">579</entry><entry align="right">9569</entry><entry align="right">9565</entry><entry align="right">3641</entry><entry align="right">19839</entry><entry align="right">5924</entry><entry align="right">5345</entry><entry align="right">4273</entry><entry align="right">903</entry><entry align="right">23480</entry><entry align="right">21174</entry><entry align="right">998</entry></row><row><entry>Dry Flow, KG/HR</entry><entry align="right">38088</entry><entry align="right">817</entry><entry align="right">64192</entry><entry align="right">25290</entry><entry align="right">108480</entry><entry align="right">108330</entry><entry align="right">41235</entry><entry align="right">178660</entry><entry align="right">67095</entry><entry align="right">41802</entry><entry align="right">13802</entry><entry align="right">25272</entry><entry align="right">219890</entry><entry align="right">213940</entry><entry align="right">32048</entry></row><row><entry>H₂O, KMOL/HR</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">6820</entry><entry align="right">4.0</entry><entry align="right">4360</entry><entry align="right">15.1</entry><entry align="right">5.7</entry><entry align="right">6.8</entry><entry align="right">9.4</entry><entry align="right">11.0</entry><entry align="right">--</entry><entry align="right">--</entry><entry align="right">10.2</entry><entry align="right">340</entry><entry align="right">333</entry></row></tbody></tgroup><tgroup cols="16"><colspec colnum="1" colname="col1" colwidth="24mm" /><colspec colnum="2" colname="col2" colwidth="14mm" /><colspec colnum="3" colname="col3" colwidth="13mm" /><colspec colnum="4" colname="col4" colwidth="16mm" /><colspec colnum="5" colname="col5" colwidth="14mm" /><colspec colnum="6" colname="col6" colwidth="16mm" /><colspec colnum="7" colname="col7" colwidth="16mm" /><colspec colnum="8" colname="col8" colwidth="14mm" /><colspec colnum="9" colname="col9" colwidth="16mm" /><colspec colnum="10" colname="col10" colwidth="14mm" /><colspec colnum="11" colname="col11" colwidth="14mm" /><colspec colnum="12" colname="col12" colwidth="14mm" /><colspec colnum="13" colname="col13" colwidth="14mm" /><colspec colnum="14" colname="col14" colwidth="16mm" /><colspec colnum="15" colname="col15" colwidth="16mm" /><colspec colnum="16" colname="col16" colwidth="15mm" /><thead><row><entry valign="top">Total Flow</entry><entry namest="col2" nameend="col16" align="right" valign="top" /></row></thead><tbody><row><entry>KMOL/HR</entry><entry align="right">2215</entry><entry align="right">91</entry><entry align="right">9713</entry><entry align="right">582</entry><entry align="right">13929</entry><entry align="right">9580</entry><entry align="right">3647</entry><entry align="right">19846</entry><entry align="right">5933</entry><entry align="right">5356</entry><entry align="right">4273</entry><entry align="right">903</entry><entry align="right">23490</entry><entry align="right">21514</entry><entry align="right">1331</entry></row><row><entry>KGIHR</entry><entry align="right">38088</entry><entry align="right">817</entry><entry align="right">187047</entry><entry align="right">25362</entry><entry align="right">187047</entry><entry align="right">108600</entry><entry align="right">41338</entry><entry align="right">178780</entry><entry align="right">67262</entry><entry align="right">42001</entry><entry align="right">13802</entry><entry align="right">25272</entry><entry align="right">220070</entry><entry align="right">220070</entry><entry align="right">38047</entry></row><row><entry>Temperature, °C</entry><entry align="right">10.0</entry><entry align="right">35.0</entry><entry align="right">515.0</entry><entry align="right">146.3</entry><entry align="right">880.0</entry><entry align="right">35.0</entry><entry align="right">35.0</entry><entry align="right">35.0</entry><entry align="right">35.0</entry><entry align="right">40.0</entry><entry align="right">10.0</entry><entry align="right">35.0</entry><entry align="right">41.8</entry><entry align="right">270.0</entry><entry align="right">35.0</entry></row><row><entry>Pressure, bar(a)</entry><entry align="right">62.0</entry><entry align="right">25.0</entry><entry align="right">22.3</entry><entry align="right">26.0</entry><entry align="right">19.0</entry><entry align="right">41.2</entry><entry align="right">41.2</entry><entry align="right">79.3</entry><entry align="right">41.2</entry><entry align="right">39.5</entry><entry align="right">19.0</entry><entry align="right">35.0</entry><entry align="right">84.2</entry><entry align="right">78.0</entry><entry align="right">6.0</entry></row><row><entry>Density, KG/M³</entry><entry align="right">52.54</entry><entry align="right">7.87</entry><entry align="right">6.58</entry><entry align="right">33.64</entry><entry align="right">2.65</entry><entry align="right">17.96</entry><entry align="right">17.96</entry><entry align="right">27.29</entry><entry align="right">17.96</entry><entry align="right">11.67</entry><entry align="right" /><entry align="right" /><entry align="right">29.35</entry><entry align="right">17.05</entry><entry align="right">823.60</entry></row><row><entry>Average MW</entry><entry align="right">17.20</entry><entry align="right">9.00</entry><entry align="right">19.26</entry><entry align="right">43.54</entry><entry align="right">13.43</entry><entry align="right">11.34</entry><entry align="right">11.34</entry><entry align="right">9.01</entry><entry align="right">11.34</entry><entry align="right">7.84</entry><entry align="right">3.23</entry><entry align="right">27.98</entry><entry align="right">9.37</entry><entry align="right">10.23</entry><entry align="right">28.58</entry></row></tbody></tgroup></table></tables>

<u>Example 2</u>

An existing methanol plant is reconfigured to produce methanol and CO in a stoichiometric ratio for the manufacture of 1,000,000 metric tons/year of acetic acid in accordance with the embodiment of <figref idref="f0005">Fig. 5</figref>. Assuming 340 days/year of production, this is 2040 kmol/h of acetic acid, which requires 2040 kmol/h MeOH and 2040 kmol/h CO.

Assume the original plant converts natural gas in two single-pass reformers <b>10</b> to form synthesis gas containing 11,660 kmol/h hydrogen, 2180 kmol/hr CO, and 1290 kmol/h CO₂. To produce the desired quantity of acetic acid, enough syngas to obtain 2040 kmol/h of CO from the new CO separation unit <b>28</b> has to be diverted from the feed to the existing methanol synthesis unit <b>12</b> to the new CO₂ removal unit <b>22.</b> This leaves 140 kmol/h CO in the remaining syngas for feed to the methanol synthesis unit <b>12.</b> To make 2040 kmol/h MeOH, there is needed a total of 2040 kmol/h of any combination of CO and/or CO₂. With the 140 kmol/h CO from the remaining syngas in line <b>38,</b> and 1290 kmol/h CO₂ from the remaining syngas in line <b>38,</b> as well as the CO₂ from the CO₂ removal unit <b>22</b> via line <b>24,</b> an additional 610 kmol/h CO₂ is needed. This CO₂ is imported via new line <b>25.</b>

To produce the methanol in methanol synthesis unit <b>12,</b> there are needed two moles of hydrogen for each mole of CO feed, as well as three moles of hydrogen for each mole of CO₂ feed, or (2)(140) + (3)(1290+610) = 5980 kmol/h H₂. The two existing reformers <b>10</b> produce 11,660 kmol/h, leaving 5680 kmol/h hydrogen for export.

<u>Example 3</u>

The existing methanol plant of Example 2 is reconfigured to produce methanol and CO in a stoichiometric ratio for the manufacture of the maximum quantity of acetic acid in accordance with the embodiment of <figref idref="f0006">Fig. 6</figref>, i.e. by supplying all of the syngas from the reformers <b>10</b> to the new CO₂ removal unit <b>22.</b> By converting all of the available CO (2180 kmol/hr) to acetic acid, the acetic acid production is 2180 kmol/h or 1.07 x 10⁶ metric tons/year.

To make 2180 kmol/h MeOH, there is needed a total of 2180 kmol/h of any combination of CO and/or CO₂. With no CO from the syngas, and 1290 kmol/h CO₂ from the CO₂ removal unit <b>22</b> via line <b>24,</b> an additional 890 kmol/h CO₂ is needed. This CO₂ is imported via line <b>25.</b>

To produce the methanol in methanol synthesis unit <b>12,</b> there are needed three moles of hydrogen for each mole of CO₂ feed, or (3)(2180) = 6540 kmol/h H₂. The two reformers produce 11,660 kmol/h, leaving 5120 kmol/h hydrogen for export.

In various embodiments as follows, the invention relates to: <ul id="ul0002" list-style="none" compact="compact"><li>A. A method for modifying an original methanol plant for manufacturing a product from carbon monoxide and methanol selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof, wherein the original methanol plant comprises at least one reformer, preferably a steam reformer, for converting a hydrocarbon to a syngas stream containing hydrogen, carbon monoxide, and carbon dioxide, and a methanol synthesis loop for converting hydrogen and carbon monoxide from the syngas stream to methanol, wherein, the method comprises the steps of: installing a separation unit for separating all or part of the syngas stream into respective streams rich in carbon dioxide, carbon monoxide and hydrogen; supplying at least a portion of the carbon-dioxide-rich stream to the steam reformer, to the methanol synthesis loop, or to a combination thereof; and reacting at least a portion of the carbon monoxide-rich stream from the separation unit with methanol from the methanol synthesis loop to form the product.</li><li>B. A method for retrofitting an original methanol plant for manufacture of a product from carbon monoxide and methanol selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof, wherein the original plant comprises at least one steam reformer for converting a hydrocarbon to a syngas stream containing hydrogen, carbon monoxide, and carbon dioxide, and a methanol synthesis loop for converting hydrogen and carbon monoxide from the syngas stream to methanol, wherein the method comprises the steps of: separating all or part of the syngas stream in a separation unit into respective streams rich in carbon dioxide, carbon monoxide and hydrogen; operating the methanol synthesis loop with a feed comprising (1) carbon dioxide and (2) a portion of the hydrogen-rich stream; reacting at least a portion of the carbon monoxide-rich stream from the separation unit with methanol from the methanol synthesis loop to form the product.</li><li>C. The method of embodiment B wherein the feed to the methanol synthesis loop comprises imported carbon dioxide.</li><li>D. The method of embodiment B or C wherein the feed to the methanol synthesis loop includes a portion of the synthesis gas.</li><li>E. The method of embodiment B or C wherein all of the syngas stream is supplied to the separation step.</li><li>F. The method of embodiment B or C wherein the amount of the hydrogen-rich stream is in excess of the stoichiometric hydrogen required by the methanol synthesis loop.</li><li>G. The method of embodiment B or C wherein all of the carbon dioxide-rich stream is supplied to the synthesis loop.</li><li>H. The method of embodiment B or C wherein all of the carbon monoxide-rich stream is supplied to the reaction step.</li><li>I. A method for retrofitting an original methanol plant for manufacture of a product from carbon monoxide and methanol selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof, wherein the original plant comprises at least one steam reformer for converting a hydrocarbon to a syngas stream containing hydrogen, carbon monoxide, and carbon dioxide, and a methanol synthesis loop for converting hydrogen and carbon monoxide from the syngas stream to methanol, the method comprising the steps of: supplying a major portion comprising at least half of the syngas stream to a separation unit for separating the syngas stream into respective streams rich in carbon dioxide, carbon monoxide and hydrogen; operating the methanol synthesis loop with a feed comprising the carbon-dioxide-rich stream from the separation unit, a minor portion comprising less than half of the syngas stream, and an additional source of carbon dioxide to produce a methanol stream; reacting the carbon monoxide-rich stream from the separation unit with the methanol stream from the methanol synthesis loop to form the product.</li><li>J. A method for retrofitting an original methanol plant for manufacture of a product from carbon monoxide and methanol selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof, wherein the original plant comprises at least one steam reformer for converting a hydrocarbon to a syngas stream containing hydrogen, carbon monoxide, and carbon dioxide, and a methanol synthesis loop for converting hydrogen and carbon monoxide from the syngas stream to methanol, the method comprising the steps of: supplying the syngas stream to a separation unit for separating the syngas stream into respective streams rich in carbon dioxide, carbon monoxide and hydrogen; operating the methanol synthesis loop with a feed comprising the carbon-dioxide-rich stream from the separation unit, a portion of the hydrogen-rich stream from the separation unit, a minor portion comprising less than half of the syngas stream, and carbon dioxide from an additional source, to produce a methanol stream; reacting the carbon monoxide-rich stream from the separation unit with the methanol stream from the methanol synthesis loop in stoichiometric proportions to form the product.</li><li>K. A process for making hydrogen and a product selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof, from a hydrocarbon via intermediate methanol, carbon monoxide, and carbon dioxide, comprising the steps of: reforming the hydrocarbon with steam to form a syngas containing hydrogen, carbon monoxide, and carbon dioxide; recovering heat from the syngas to form a cooled syngas stream; compressing the cooled syngas stream to a separation pressure; processing the syngas in a separation unit to separate a carbon monoxide-rich stream from the hydrogen and carbon dioxide; operating a methanol synthesis loop to react a first portion of the hydrogen from the separation unit with the carbon dioxide from the separation unit and additional carbon dioxide from another source to obtain a methanol stream; reacting the carbon monoxide-rich stream from the separation unit with the methanol stream from the methanol synthesis loop in essentially stoichiometric proportions to form a product selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof.</li><li>L. A method for retrofitting an original methanol plant, wherein the original methanol plant comprises (1) at least one steam reformer for converting a hydrocarbon to a syngas stream containing hydrogen and carbon monoxide, (2) a heat recovery section for cooling the syngas stream, (3) a compression unit for compressing the syngas stream, and (4) a methanol synthesis loop for converting at least a portion of the hydrogen and carbon monoxide in the syngas stream to methanol, into a retrofitted plant for manufacturing a product from carbon monoxide and methanol selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof, comprising the steps of: diverting a portion of the syngas stream from at least one reformer to a separation unit; operating the methanol synthesis loop with a feed comprising the remaining syngas stream to produce less methanol than the original methanol plant; operating the separation unit to separate the diverted syngas into at least a carbon monoxide-rich stream and a hydrogen-rich stream, wherein the quantity of hydrogen in the hydrogen-rich stream is greater than any net hydrogen production of the original methanol plant; reacting the carbon monoxide-rich stream from the separation unit with the methanol from the methanol synthesis loop to form the product, wherein the diversion of the syngas stream is balanced for the approximately stoichiometric production of the methanol from the methanol synthesis loop and the carbon monoxide-rich stream from the separation unit for conversion to the product.</li><li>M. The method of embodiment L further comprising modifying at least one steam reformer to increase carbon monoxide production in the syngas stream.</li><li>N. The method of embodiment M wherein the syngas stream comprises carbon dioxide and the separation unit produces a carbon dioxide-rich stream that is recycled to at least one reformer to increase the carbon monoxide production.</li><li>O. The method of embodiment N wherein the syngas stream in the original plant has a molar ratio R ((H₂-CO₂)/(CO+CO₂)) less than about 2.0 or greater than about 2.9 and wherein the retrofitted plant has an R ratio from about 2.0 to about 2.9.</li><li>P. A method for retrofitting an original methanol plant, having at least one steam reformer for converting a feed comprising hydrocarbon and steam essentially free of carbon dioxide into a syngas stream containing hydrogen and carbon monoxide, a heat recovery section for cooling the syngas stream, a compression unit for compressing the syngas stream, and a methanol synthesis loop for converting at least a portion of the hydrogen and carbon monoxide in the syngas stream to methanol, into a retrofitted plant for manufacturing a product from carbon monoxide and methanol selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof, comprising the steps of: modifying at least one steam reformer for operation with a feed comprising carbon dioxide; diverting a portion of the syngas stream from at least one steam reformer to a separation unit; operating the methanol synthesis loop with a feed comprising the remaining syngas stream to produce less methanol than the original methanol plant; operating the separation unit to separate the diverted syngas into a carbon dioxide-rich stream, a carbon monoxide-rich stream and a hydrogen-rich stream; recycling the carbon dioxide-rich stream from the separation unit to at least one modified steam reformer to increase the carbon monoxide formation relative to the original methanol plant and increase the molar ratio of carbon monoxide to hydrogen; reacting the carbon monoxide-rich stream from the separation unit with the methanol from the methanol synthesis loop to form the product, wherein the diversion of the syngas stream is balanced for the stoichiometric production of the methanol from the methanol synthesis loop and the carbon monoxide-rich stream from the separation unit for conversion to the product.</li><li>Q. The method of embodiment P wherein the modified steam reformer is modified to operate at a higher temperature.</li><li>R. The invention of any one of embodiments A through Q wherein the separation unit comprises a solvent absorber and stripper for carbon dioxide recovery and a cryogenic distillation unit for carbon monoxide and hydrogen recovery.</li><li>S. The method of embodiment P or Q wherein the compression unit comprises a three-stage compressor and the syngas stream diversion occurs between the second and third compression stages.</li><li>T. The method of embodiment S further comprising modifying the third compressor stage for operation at a lower throughput than the original methanol plant.</li><li>U. The method of embodiment P wherein the methanol synthesis loop of the original methanol plant comprises a recycle loop compressor, wherein the recycle loop compressor is modified for operation at a lower throughput.</li><li>V. The invention of any one of embodiments A through U further comprising the step of reacting the hydrogen in the hydrogen-rich stream with nitrogen to make ammonia.</li><li>W. The invention of any of embodiments A through J and L through V wherein in the original methanol plant a hydrogen-rich stream comprising a loop purge from the methanol synthesis loop was reacted with nitrogen to make ammonia, and in the retrofitted plant the hydrogen-rich stream from the separation unit is used as a primary hydrogen source for the ammonia production.</li><li>X. The invention of embodiment W wherein additional ammonia is made in the retrofitted plant relative to the original methanol plant.</li><li>Y. The invention of embodiment X wherein the product comprises acetic acid and the method further comprises the step of installing a vinyl acetate monomer unit for reacting a portion of the acetic acid with ethylene and oxygen to make vinyl acetate monomer.</li><li>Z. The invention of embodiment Y further comprising installing an air separation unit to make the oxygen for the vinyl acetate monomer unit and wherein nitrogen produced from the air separation unit matches the nitrogen required for the additional ammonia production.</li><li>AA. A process for making hydrogen and a product selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof, from a hydrocarbon via methanol and carbon monoxide, comprising the steps of: reforming the hydrocarbon with steam in the presence of a minor proportion of carbon dioxide to form a syngas containing hydrogen, carbon monoxide, and carbon dioxide, wherein the syngas has a molar R ratio ((H₂-CO₂)/(CO+CO₂)) from about 2.0 to about 2.9; recovering heat from the syngas to form a cooled syngas stream; compressing the cooled syngas stream to a separation pressure; diverting a major portion of the compressed syngas to a separation unit; separating the syngas diverted to the separation unit into a carbon dioxide-rich stream, a carbon monoxide-rich stream and a hydrogen-rich stream; recycling the carbon dioxide-rich stream to the reforming step; further compressing the remaining minor portion of the syngas to a methanol synthesis pressure higher than the separation pressure; operating a methanol synthesis loop to convert the hydrogen, carbon monoxide and carbon dioxide in the further compressed syngas into a methanol stream; reacting the carbon monoxide-rich stream from the separation unit with the methanol stream from the methanol synthesis loop to form a product selected from the group consisting of acetic acid, acetic anhydride, methyl formate, methyl acetate and combinations thereof, wherein the diversion step is balanced to obtain approximately stoichiometric amounts of carbon monoxide and methanol.</li><li>BB. The process of embodiment AA wherein the methanol synthesis loop is operated substantially below a total maximum combined design throughput of all methanol synthesis reactor(s) in said loop.</li><li>CC. The process of embodiment AA or BB further comprising the step of reacting the hydrogen in the hydrogen-rich stream with nitrogen in an ammonia synthesis reactor to make ammonia.</li><li>DD. The process of embodiment CC further comprising the step of separating air into a nitrogen stream and an oxygen stream and supplying the nitrogen stream to the ammonia synthesis reactor.</li><li>EE. The process of embodiment DD wherein the product comprises acetic acid or an acetic acid precursor which is converted to acetic acid, and further comprising the step of supplying the oxygen stream from the air separation unit to a vinyl acetate synthesis reactor, along with a portion of the acetic acid from the carbon monoxide-methanol reaction step, and ethylene, to produce a vinyl acetate monomer stream.</li><li>FF. The process of embodiment AA wherein a molar ratio of carbon dioxide to hydrocarbon comprising natural gas in feed to the reforming step is from about 0.1 to about 0.5.</li><li>GG. The invention of any one of embodiments A through FF wherein the product comprises acetic acid and the reaction step comprises reacting methanol, methyl formate, or a combination thereof in the presence of a reaction mixture comprising carbon monoxide, water, a solvent and a catalyst system comprising at least one halogenated promoter and at least one compound of rhodium, iridium or a combination thereof.</li><li>HH. The invention of embodiment GG wherein the reaction mixture has a water content up to 20 weight percent.</li><li>II. The invention of embodiment HH wherein the reaction step comprises simple carbonylation and the water content in the reaction mixture is from about 14 to about 15 weight percent.</li><li>JJ. The invention of embodiment HH wherein the reaction step comprises low-water carbonylation and the water content in the reaction mixture is from about 2 to about 8 weight percent.</li><li>KK. The invention of embodiment HH wherein the reaction step comprises methyl formate isomerization or a combination of said isomerization and methanol carbonylation and the reaction mixture contains a nonzero quantity of water up to 2 weight percent.</li><li>LL. The invention of embodiment HH wherein the reaction step is continuous.</li><li>MM. The invention of any of embodiments A through FF wherein the reaction step comprises the intermediate formation of methyl formate and isomerization of the methyl formate to acetic acid.</li><li>NN. The invention of any of embodiments A through FF wherein the reaction step comprises the intermediate reaction of CO and two moles of methanol to form methyl acetate and hydrolysis of the methyl acetate to acetic acid and methanol.</li></ul>