Convertion process of hydrocarbon raw material

The present invention relates to a process for catalytic conversion of hydrocarbons, using a polymetallic, acidic catalyst.

A polymetallic catalytic compound, acid with dual functionality, having high activity, selectivity and high stability, used in hydrocarbon conversion processes, such as isomerization, hydroisomerization, dehydrogenation, desulfurization, denitrogenation, hydrogenation, alkylation, is known. decalcylation, disproportionation, polymerization, hydro-disalkylation, transalkylation, cyclization, dehydrocyclization, cracking, hydrocracking, halogenation, reforming. This acid catalyst, containing a platinum group component, a cobalt component, a tin component and a halogen, on a refractory porous support material, can greatly improve the efficiency of the hydrocarbon conversion process if the metal components are dispersed. uniformly in the support material and if their oxidation states are adjusted to the optimum values,

The activity of known multimetallic catalysts, used in hydrocarbon conversion processes, irreversibly decreases due to sulfur compounds and

The Holder;

UOP, Inc., Des Plaines, Illinois,

United States of America presence of water in raw materials used.

The process, according to the invention, removes these disadvantages, in that, in order to avoid deactivation of the catalyst, by removing from the reaction system of sulfur and water, up to a content less than 1 ppm., It performs the pretreatment of the raw materials, respectively, of the hydrocarbons and hydrogen, each separately or in the mixture, before entering the zone, by reaction, by passing them through a bed containing an adsorbent material, selective for the roll! and water, consisting of a finely divided reactive metal with a large specific surface, selected from: potassium, sodium, magnesium, aluminum, zinc, iron, nickel, cobalt, copper, a metal oxide, or a mixture of a metal oxide, which reacts with sulfur with a dehydrating material.

The following is an example of an embodiment of the invention. In order to demonstrate the improvements, as well as the particular purity conditions of the process according to the present invention, two separate hydrocarbon conversion tests are performed using separate portions of the known catalyst (a sulfur-free catalyst containing 0.3¼ weight platinum, 1, 0¼ by weight LIBRARY

LEI PRICE 3.50 balt, 0.2% by weight tin and 1.1% by weight chlorine). In the first sample only the usual hydrofinishing is used for the purification of the raw material. In the second sample, after the usual hydrofinishing of the raw material, a protective bed, consisting of finely divided particles of metallic sodium, with a large specific surface, is used to remove traces of sulfur and water, according to the present invention. From all other points of view, the samples are run under identical conditions.

The hydrocarbon conversion sample used for comparison is an accelerated, high-load, catalytic reforming sample to determine in a relatively short period of time of the oil 1

Raw material analysis

<td>Density at 15 ° C</td><td> 0,7421</td>

<td>Distillation curve, ®C</td><td></td>

<td>Initially boiling point, ° C</td><td> 103</td>

<td>Boiling point 5%</td><td> 103</td>

<td>Boiling point 10%</td><td> 121</td>

<td>Boiling point 30%</td><td> 130</td>

<td>Boiling point 50%</td><td> 147</td>

<td>Boiling point 70%</td><td> 161</td>

<td>Spell 90%</td><td> 168</td>

<td>Boiling point 95%</td><td> 194</td>

<td>Nitrogen, ppm by weight</td><td> 0,1</td>

<td>Sulfur, ppm by weight</td><td> 0,2</td>

<td>Water, ppm by weight</td><td> 14...18</td>

<td>Octane figure, clean Fl</td><td> 37,6 |</td>

<td>Paraffin,% volume</td><td> 68,85 '</td>

<td>Naftene,% volume</td><td> 21.72</td>

<td>Aromatic,% volume</td><td> 9,02,</td>

the relative activity, selectivity and stability characteristics of the catalyst under different conditions. In both tests the same raw material was used, its main characteristics being given in table 1. As shown above, in the second sample the raw material is treated with a protective bed, consisting of adsorbent sodium with a large specific surface, under such conditions. chosen, it is able to remove practically all the miners - sulfur and water contained in the raw material4. This stage of treatment is performed in the liquid phase, before entering the raw material into the reaction area containing the catalyst.

The accelerated reforming sample aims to determine in a very short period of time whether the catalyst and the evaluated working conditions have superior characteristics, to be used in, the reforming operation under severe conditions. Each sample consists of a series of 24-hour measurement periods, each · of these periods comprising 12 hours of operation, followed by 12 hours of testing, during which time the product C₅⁺ refurbished from the plant is collected and analyzed. Both samples are conducted under identical conditions, ie at an hourly spatial speed of 3.0 h.^—1, a pressure of 21 at, a gas-hydrocarbon ratio of 10: 1 and a temperature at the inlet of the reactor continuously adjusted during the sample, to reach and maintain the octane value of C_s⁺ at 100 F — 1 clean.

Both samples are executed in a pilot scale reforming installation, comprising a reaction area with a fixed bed of catalyst subjected to measurement, a hydrogen separation zone, a debranching column, the necessary heating, pumping and condensing systems. , compression and other ordinary equipment. The technology used in this installation comprises the entry of a recirculated hydrogen stream and the raw material and heating the resulting mixture to the desired conversion temperature. The heated mixture is then passed, circulating down, into a reactor containing the catalyst subjected to measurements, in the form of a stationary bed. An effluent stream is discharged to the bottom of the reactor, cooled to 13'C and passed into a gas-liquid separation zone, in which the hydrogen-rich gas phase is separated from the liquid phase consisting of hydrocarbons. A portion of the gas phase is then passed continuously through a scrubber containing sodium with a large specific surface. The resulting hydrogen stream, practically free of water and sulfur, is fed back into the reactor. The excess gas in the separation zone, which contains hydrogen, is recovered and recirculated. The liquid phase in the separation zone is evacuated and passed into a debonding column, where the light ends (for example, C, to C)₄) are extracted as debutanization gas at the top of the column, and the hydrocarbon current C₅⁺ reformat is obtained at the base of the column as the main product.

The results of the separate samples performed with and without adsorption bed for the raw material are presented for each period in table 2 in the form of the inlet temperature in the reactor in ° C, necessary to obtain the value o f the octane number and the quantity of hydrocarbons C₅⁺ recovered reformats, expressed as «/ o in volume of raw material.

Table 2

<td colspan="5">Results of accelerated reformation tests</td>

<td>peri-</td><td colspan="2">No table protectors</td><td colspan="2">With protective table</td>

<td>oacla</td><td>T, ° c</td><td>C₅+ A / " a).</td><td>T, ° C</td><td>c₅+% you.</td>

<td> 1</td><td> 516</td><td> 68,48</td><td> 514</td><td> 69,02</td>

<td> 2 \</td><td> 519</td><td> 70,25</td><td> 510</td><td> 70,40</td>

<td> 3 .·</td><td> 523</td><td></td><td> 512</td><td> _</td>

<td> 4</td><td> 526</td><td> 72,11</td><td> 511</td><td> 70,71</td>

<td> 5</td><td> 529</td><td> —</td><td> 513</td><td></td>

<td> 6</td><td> 531</td><td> 73,19</td><td> 513</td><td> 70,61</td>

<td> 7</td><td> 533</td><td> ,—</td><td> 514</td><td></td>

<td> 8</td><td> 538</td><td> 72,25</td><td> 514</td><td> 69.93</td>

<td> 9,</td><td> —</td><td> __</td><td> 511</td><td></td>

<td> 10</td><td> —</td><td></td><td> 512</td><td> 70,81</td>

<td> 11</td><td> —</td><td> .—</td><td> 511</td><td> _</td>

<td>takes</td><td> —.</td><td> _</td><td> ! 511</td><td> 70,16</td>

<td> 13</td><td> —</td><td> —</td><td> 512</td><td></td>

From the analysis of the results of the comparative tests from table 2, it follows that the main effect of using the protective bed for the raw material is that of the substantial improvement of the catalyst performances, in particular, in the field of activity and of the activity-selectivity characteristic. A good measure of activity for a reforming catalyst is the temperature at the inlet to the reactor, which is required to reach the desired octane value. The data presented in table 2 on this variable cl early show that, when using the protective bed, the catalyst is much more active and more stable than the catalyst that was used without a protective bed. The increase of activity, as a result of the present invention, is equal to or greater than that corresponding to 15 ° C, the temperature of entry into the reactor. The reaction rate is practically doubled or tripled for every 10 ° C increase in the reactor temperature. A6997 (1 means that the process according to the invention is practically 4 or 5 times more active than the process taken as a control. A specific example of this increase in activity can be obtained by following the data of the 8th period of the trial (ie 192 hours in the sample). At this point, the process according to the invention requires an inlet temperature of 514 ° C to give oc10 tan, as opposed to the usual process which requires a temperature of 538 ° C at the same point of the sample. This difference of 24 ° C at the temperature required to obtain the oc15 tan is the proof of the ability of the process according to the invention to greatly accelerate the rate of the reforming reaction, without practically altering the yield in C₅⁺. Thus, the data clearly show that the process according to the invention is more active and more stable than the known process.

The main element of the invention is the use of the catalyst in a reaction zone, which is maintained continuously in the absence of sulfur and water. The expression "practically free of sulfur and water" means: 1) that the total quantity of contaminated sulfur, regardless of form (elemental sulfur, hydrogen sulfide, com30 organic or inorganic wells containing sulfur) and regardless of source, is continuously maintained at a value of less than 1 ppm by weight, based on the material a premium containing hydrocarbons, and 2) that the total amount of water or contaminants that water releases (such as, for example, oxygen or organic or inorganic compounds containing oxygen) that enter the reaction area, is continuously maintained at a value of less than 1 ppm by weight of the feedstock containing hydrocarbons supplied. The very pure atmosphere must be maintained for the entire duration of the hydrocarbon conversion from the catalyst priming and after the hydrocarbon conversion conditions are reached. During the start-up period, some deviations from these conditions are allowed, in terms of water content; However, the lack of sulfur must also be ensured during the start-up period, in order to achieve all the advantages provided by the process, according to the invention.

The sources of sulfur and water contaminants, in the case of the typical process of conversion of hydrocarbons, are: the raw material containing hydrocarbons, the hydrogen current, the catalyst and the conversion plant itself. Of these, the main source is the raw material containing hydrocarbons, the other sources gaining greater importance only under special conditions, which will be described⁶⁵ in the following.

'Since any raw material, containing hydrocarbons, which can be used in the process according to the invention contains quantities of sulfur and water above the quantities specified above, it is necessary to pretreat the raw material, in order to remove contaminants. If the concentration of these contaminants is not more than 10 up to 100 times above the specified permissible value, the raw material can be treated directly in an adsorption stage of the contaminants. In the usual cases, however, these contaminants are present in larger quantities, by weight or more by weight of the raw material, so a two-step treatment is required, consisting of a first stage of coarse removal, followed by a second stage of adsorption of contaminants,

The coarse purification step generally comprises a catalytic treatment with hydrogen, at elevated raw material temperature, such as, for example, hydrofining, hydrotreating, hydrodesulfurization or other similar methods, to remove most of the contaminants producing sulfur, nitrogen or water. Typically, this is accomplished by bringing the stream of raw material, containing contaminants in contact with a sulfur-resistant hydrofining catalyst, in the presence of hydrogen, under such conversion conditions, so as to decompose the contaminants based on sulfur, nitrogen and oxygen. , to form hydrogen sulfide, water and ammonia. The usual hydrofinishing catalyst comprises one or more oxides or sulfides of the transition metals in groups VI or VIII of the periodic table of the elements. A preferred hydrofinishing catalyst comprises a mixture of a metal component in Group VIII of the iron and a metal component in Group VI of the transition metals, on a suitable refractory porous substrate. Particularly good results are obtained when the metal in the iron group is cobalt. and / or nickel, and the group VI transition metal is molybdenum or tungsten. The preferred support for this type of catalyst is a refractory inorganic oxide. For example, good results are obtained with a hydrofinishing catalyst, containing cobalt oxide and molybdenum oxide on an aluminum and silica substrate. The conditions used in this hydrofinishing step are chosen from the following values: a temperature from 316 ° C to 510 ° C, a pressure from 35 to 341 at, an hourly spatial velocity of the liquid from 1 to 24 h ~¹ and a circulation speed of hi, 3 of the drug from 89 to 1783 volumes of hydrogen per volume of charge. After the hydrofinishing step, most of the hydrogen sulphide, ammonia and water formed are easily removed from the raw material by a stripping operation. The appropriate hydrofining conditions are chosen from the ones listed above, depending on the quantities and the form of presentation of sulfur, oxygen and nitrogen. The raw material thus treated is then passed into the second step, adsorption purification, according to the invention. It should be noted that, in some cases, when a readily available raw material is available, the desired sulfur and water contents, according to the invention, can be reached in this stage of hydrogen treatment, without the need for further adsorption, · However, this mode of work is not recommended, due to the danger of disturbances in the hydrogen treatment step, which can lead to improper release of contaminants into the reaction area containing the catalyst, with the consequence of its inevitable destruction.

The adsorption stage of the contaminants is performed either on the partial current, previously treated with hydrogen, or directly on the raw material containing hydrocarbons, when coarse purification is not required, as shown above. The first thing that is done in this stage of adsorption of contaminants is the removal of traces of sulfur and water, which cannot be economically removed by the usual methods of hydrogen treatment or which cannot be treated under hydrofining conditions, or have not been completely separated by stripping performed after the hydrogenation step. Even when the raw material to be introduced to the adsorption stage is within the permissible limits of purity, it is preferred to treat it in this way, in order to prevent any disturbances in the continuation of the technological process, as a result of variations in the composition of the raw material, 'of the working errors, the power interruption. This last possibility is the reason why the adsorption step is carried out in an area called "protective bed.

According to the invention, the hydrocarbon-containing feedstock is contacted with a selective adsorbent for sulfur and water, under adsorption conditions so chosen, to ensure that a well-treated feedstock is obtained, containing less than 1 ppm by weight of sulfur and less than 1 ppm by weight of water. The adsorption stage is performed immediately prior to the introduction of the raw material to the hydrocarbon conversion stage and generally consists of the passage of the raw material through a protective bed, containing the adsorbent as a dense and compact bed, fixed or mobile, the operation in fixed bed being preferred. The size of the adsorbent particles is chosen so as to ensure a good contact between it and the raw material, without producing an excessive drop of pressure when passing through the bed.

The adsorbent used in the protective bed is selected from the following categories ·. (1) reactive metal particles with large specific surface area_; (2) metallic oxide particles. Reactive sulfur acceptor, with large specific surface (3) clay that selectively absorbs sulfur and water or other clay materials; (4) for the case when sulfur and water are found only in the form of H_ZS and H₂O, partially dehydrated crystalline aluminum-silicate zeolites, having practically uniform pores, with a diameter between 4 and 13 Å and (5) mixtures of these adsorbents.

Reactive metals suitable as adsorbents are potassium, sodium, magnesium, aluminum, zinc, copper, iron, nickel, cobalt and other electropositive metals which, in finely divided form, have high affinity for sulfur and water. In addition, a mixture of metals can be used. Reactive metals can be used in the form of grit, scrap, powders or can be deposited on a suitable porous support material such as activated alumina, porous clays, silica, bauxite.

The reactive metal oxides that can be used are those that have the ability to accept sulfur and form the corresponding metal sulfides. Suitable metal oxides are alumina, zinc oxide, copper oxide, magnesium oxide, iron oxide, cobalt oxide, nickel oxide, manganese oxide and other acceptor reactive metal oxides! of sulfur. Mixtures of these reactive metal oxides may also be used.

Because, in general, these metal oxides form water when they absorb sulfur-containing contaminants and because they have low selectivity for water, it is preferable to use them in combination with a suitable desiccant. The desiccant may be used in admixture with the metal or the metal oxide particle bed may be followed by a desiccant particle bed or the metal oxide may be deposited on a support material having dehydrating properties such as, for example, aluminum-silicate zeolite dehydrated crystalline, activated alumina, silica gel, bauxite, alumina impregnated with calcium chloride, magnesium oxide. Sulfur acceptor metal oxide may be used in the form of spheres, powders, axes, pellets, or may be deposited on a porous support material, as in the case of reactive metal.

As an adsorbent, adsorbent clays can be used, if sulfur and water are easily retained. Suitable clays, selective for the adsorption of sulfur and water, are the bleaching soil, attapulgite, kaolin, hectorite, montmorillonite and other materials that can be activated before use, by treating, if necessary, with a suitable acid.

Considering all the adsorbents mentioned so far, it was found that the best results are obtained when the protective bed contains finely divided particles of sodium with high specific surface area. It is understood, of course, that the adsorbent can be used until the adsorption power is exhausted, after which it is replaced or in some cases regenerated, by known methods, such as, for example, hydrogen treatment at high temperatures.

The adsorption conditions are chosen according to the characteristics of the adsorbent and of the raw material, in order to achieve the desired degree of purification. In general, temperatures between -18 and 427 ° C and pressures from 1 to 35 at are used. The contact time is of the order of 0.1 up to 100 min, depending on the specific conditions. In general, the pressure and temperature used have the minimum value required to reach the desired degree of decontamination. Thus, the adsorption step can be executed in the liquid phase or in the vapor phase, the liquid phase work being preferred to the use of adsorbents consisting of highly reactive metals, and the vapor phase work for the rest of the adsorbents. When working in the vapor phase, the adsorption pressure and temperature are preferably close to the values ​​used in the hydrocarbon conversion stage.

A second possible source of sulfur and water is the current of hydrogen that enters the reaction zone. Generally, the hydrogen stream can be treated, prior to its entry into the reaction zone, in a protective bed containing no selective adsorbent for sulfur and water, under adsorption conditions so chosen, to produce a treated hydrogen stream containing more less than 1 ppm by volume of sulfur and less than 1 ppm by volume of water. Because the contaminants present in the hydrogen stream are predominantly H₂O and H₂S, tra69970 its strength is easier than that of the raw material; more than that, all the adsorbents mentioned above can also be used in this operation. The adsorption conditions used in the hydrogen current treatment step are chosen as shown above for the purification of the raw material.

In general, it is preferred to separate treatment of the hydrogen stream and the raw material containing hydrocarbons, in different adsorbent beds, which can be made according to the specific characteristics of each effluent.

However, it is possible to use a single adsorbent bed to treat the mixture of hydrogen and raw materials containing hydrocarbons, prior to its entry into the reaction zone, in the particular case, when practically all the hydrogen used is produced autogenously in the conversion step. hydrocarbons and recirculated in the reaction zone (the production of pure hydrogen takes place in the reaction zone), after the process is started and its entry into the regime, only the hydrocarbon feedstock is treated for the removal of contaminants, because the hydrogen stream is pure if the feedstock has been well treated. For example, in the usual catalytic reforming process, where most hydrogen is autogenous, the main source of sulfur and water in the reaction area is the raw material containing hydrocarbons. Maintaining sulfur and water-free raw material is usually sufficient to ensure that the catalyst is disposed of in a free environment of sulfur and water. Furthermore, because hydrogen is an auxiliary product of the catalytic reforming process, the hydrogen stream to be introduced into the process is usually obtained by recycling a portion of the hydrogen rich stream recovered from the effluent discharged from the reforming area. In this particular situation, the recirculated hydrogen stream is practically free of sulfur and water if the raw material is kept free of these contaminants.

The only other possible sources of sulfur and water, other than those mentioned above, that can influence the performance of the catalyst, are the contaminants initially combined with the catalyst and / or the contaminants present in the installation. As shown above, an essential feature of the useful acid polymetallic catalyst12 is that it is practically free of sulfur. As a result, the sulfur released by the catalyst cannot be a problem in the process. The water released from the catalyst during the process start-up period can be eliminated by passing the recirculated hydrogen current over a protective bed, as shown above, or by drying the installation and the catalyst, before starting the process, using a gas stream. suitable drying. Sulfur from the plant is usually not present in the case of new plants, it becomes a problem only when the process is carried out in a plant that has been supplied with a raw material with sulfur content, in the latter case. , the present invention recommends an initial pretreatment of the plant in order to remove all the decomposed sulfur. This is easily achieved by any known method of stripping sulfur from plants; for example, through the circulation of a sulfur-free hydrogen stream through the plant, at a relatively high temperature, from 427 to 650 ° C, until the HjS content of the exhaust gas decreases to a very small value, practically until May. less than 5 ppm in volumes and preferably less than 2 ppm in volumes.

The process of conversion of hydrocarbons, according to the present invention, has the advantage that it ensures the improvement of the performance of acid polymetallic catalysts, while eliminating the possibility of deactivating them during use.