Method of dehydrogenation of hydrocarbon capable of dehydrogenation

Yo

MINISTRY OF INDUSTRY

INDUSTRIAL PROPERTY REGISTRY

IS

NUMBER

459.044

Θ A2

DATE OF PRESENTATION

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SPAIN

ADDITION CERTIFICATE

25-5-1977

<td>(3^ PRIORITIES; (countless</td><td>θ DATE</td><td>θ COUNTRY</td>

<td> 689.517</td><td> 24-5-76</td><td>USA</td>

θDATE OF PUBLICITY @ PATENT TO WHICH IT IS ADDED

4A2.289 ^^INTERNATIONAL CLASSIFICATION θ TITLE ΟΕ THE INVENTION

IMPROVEMENTS MADE TO THE SUBJECT OF MAIN PATENT No. 442,289 applied for on November 5, 1975, for: “Process for converting a hydrocarbon.”

|(tj)'applicant (S>

UOP INC η

(Case 1755)

APPLICANT'S ADDRESS

Ten UOP Plaza, Algor.quin &amp;. I/'t. Progpect Roads-, Des Plaines, Illinois, United States of America (72) INVENTOR(S)

John Chandler Hayes and Ernest Leo Pollitzer

<td>θ HOLDER (esi '</td>

<td>^4) REPRESENTATIVE DON FERRANDO DE ELZABURU MARQUEZ ' (P-65.987)</td>

UNE A - 4

MOD 3107

USE AS FIRST PAGE OF MEMORY

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TGG.

14067

P.- 65.987

The present application is for a Certificate of Addition to earlier Spanish patent application N442289, filed November 3, 1975. Said earlier patent application claimed an acid catalytic composition comprising a porous support material containing, on an elemental basis, 0.01 to 2% by weight_sof platinum group metal, 0.5 to 5% by weight of cobalt, 0.01 to 5% by weight of tin, and 0.1 to 3.5¾% by weight of halogen, where the platinum group metal, cobalt and tin are uniformly dispersed throughout the porous support material,_or where substantially all of the platinum group metal is present in the elemental metallic state, where substantially all of the tin is present in an oxidation state higher than that of the elemental metal, and where substantially all of the cobalt is present in the elemental metallic state or in a state reducible to the elemental metallic state under hydrocarbon conversion conditions, and also a process for converting hydrocarbons by subjecting them to contact with said catalyst, under hydrocarbon conversion conditions.

The subject of the present invention is an improved method for dehydrogenating a dehydrogenable hydrocarbon to produce a hydrocarbon product containing the same number of carbon atoms but fewer hydrogen atoms. In another aspect, the present invention involves a method for dehydrogenating normal paraffin hydrocarbons containing 4 to 30 carbon atoms per molecule to the corresponding normal monoolefin with minimal production of byproducts. In yet another aspect, the present invention relates to a novel catalytic composition

I Ioj» . -3num.

14067

2b non-acidic multi-metallic comprising a combination of catalytically effective amounts of a platinum group component, a cobalt component, a tin component, and an alkali or alkaline earth component, with a porous support material. This non-acidic composition has very beneficial characteristics of activity, selectivity and stability when used in the dehydrogenation of hydrocarbons susceptible to dehydrogenation, such as aliphatic hydrocarbons, naphthenic hydrocarbons and alkyl aromatic hydrocarbons.

In the earlier application it was disclosed that a combination of cobalt and tin can be used, under certain conditions, to beneficially interact with the platinum group component of a dual-function catalyst, with a resulting marked improvement in the performance of such catalyst. It has now been established that a catalyst composition comprising a platinum group component, a cobalt component and a tin component, with a porous support material, can have superior activity, selectivity and stability characteristics when used in a hydrocarbon dehydrogenation process, if these components are uniformly dispersed in the porous support material in specified amounts. and if the oxidation state of the metallic ingredients is controlled so that substantially all of the platinum group component is present in the elemental metallic state, substantially all of the tin component is present in the positive oxidation state, and substantially all of the catalytically available cobalt component is present in the elemental metallic state.

I lojit num. — —

1UO67 or in a state that can be reduced to the elemental metallic state.

such under dehydrogenation conditions, or in a mixture of these states. Furthermore, it has been found that a particularly preferred multi-metal catalyst composition of this type contains not only a platinum group component, a cobalt component and a tin component, but also an alkaline or alkaline earth component, in an amount that ensures that the resulting catalyst is not acidic.

Hydrocarbon dehydrogenation is an important commercial process due to the demand for dehydrogenated hydrocarbons for use in the manufacture of various chemical products such as detergents, plastics, synthetic rubbers, pharmaceuticals, high-octane gasoline, perfumes, drying oils, and ion-exchange resins. Examples of this demand include the manufacture of high-octane gasoline using Cg monoolefins and the alkylation of isobutane. Another example is the dehydrogenation of normal paraffinic hydrocarbons to produce normal monoolefins, which have 30 carbon atoms per molecule. These normal monoolefins can be used in the synthesis of a number of other chemical products. For example, derivatives of normal monoolefins have become of substantial importance to the detergent industry, where they are used to produce biodegradable alkylarylsulfonate and oxyalkylated phenol alkylsulfonate detergents. These monoolefins can also be hydrated to produce alcohols for plasticizers and/or synthetic lubricating oils.

Products prepared by dehydrogenation of alkyl aromatic hydrocarbons find application in the in30

Sheet No. — 5~

14067 petroleum, petrochemical, pharmaceutical, detergent, and plastics industries. For example, ethylbenzene dehydrogenates to produce styrene, while isopropylbenzene dehydrogenates to form alpha-methylstyrene.

The primary measure of a dehydrogenation catalyst's effectiveness involves its ability to perform its intended function with minimal interference from side reactions over extended periods of time. The terms used to measure how well a particular catalyst performs its intended functions in a particular hydrocarbon conversion reaction are activity, selectivity, and stability. These terms are generally defined as follows: (1) activity is a measure of the ability of the catalyst to convert the hydrocarbon reactant into products, at a specified level of severity, where severity level means the specific reaction conditions used, i.e., temperature, pressure, contact time, and the presence of diluents such as Hj;

(2) selectivity usually refers to the amount of desired product or products obtained, relative to the amount of reactant charged or converted; (3) stability refers to the rate of change with time of the parameters activity and selectivity, the lower rate evidently implying the more stable catalyst.

Particularly good results are obtained with the catalyst of the invention by virtue of the presence of a sufficient amount of alkaline or alkaline earth component to ensure that the resulting catalyst is not acidic.

Therefore, the present invention is directed to a method for dehydrogenating a dehydrogenable hydrocarbon.

The hydrogenation comprising contacting the hydrocarbon, under dehydrogenation conditions, with a catalytic composition comprising a porous support material containing, on an elemental basis, about 0.01 to about 2% by weight of platinum group metal, about 0.1 to about 5.5% by weight of cobalt, about 0.01 to about 5% by weight of tin, and about 0.1 to about 5.5% by weight of alkali metal or alkaline earth metal; wherein the platinum group metal, catalytically available cobalt, tin, and alkali metal or alkaline earth metal are uniformly dispersed throughout the porous support material; wherein the average crystallite size of the catalytically available tin and cobalt is less than 100 angstroms in greatest dimension; where substantially all of the platinum group metal is present in the elemental metallic state; where substantially all of the tin is present in an oxidation state higher than that of the elemental metal; and where substantially all of the catalytically available cobalt is present in the elemental metallic state or in a state that is susceptible to reduction to the elemental metallic state under dehydrogenation conditions, or in a mixture of these states.

The catalyst and process of the invention are particularly suitable for the dehydrogenation of aliphatic hydrocarbons containing 2 to 30 carbon atoms per molecule,

The invention is also directed to a composition of matter, namely a non-acidic dehydrogenation catalyst, comprising a porous support material that 30 llojii ηιΊηι.

-71UO67

1O contains, on an element basis, about 0.01 to about 2% by weight of platinum group metal, about 0.1 to about 5% by weight of cobalt, about 0.1 to about 5% by weight of alkali metal or alkaline earth metal, and about 0.01 to about 5¾% by weight of tin; wherein the platinum group metal, catalytically available cobalt, tin and alkali metal or alkaline earth metal are uniformly dispersed throughout the porous support material; wherein the average crystallite size of the catalytically available tin and cobalt is less than 100 angstroms in maximum dimension; where substantially all of the catalytically available cobalt is present in the elemental metallic state, or in a state that is susceptible to reduction to the elemental metallic state, under dehydrogenation conditions, or in a mixture of these states; and where substantially all of the tin and alkali metal or alkaline earth metal are present in an oxidation state greater than that of the elemental metal.

Regarding the terms used here: (1) the term non-acidic means that the catalyst produces less than 10% conversion of 1-butene to isobutylene when tested under dehydrogenation conditions, and preferably less than 1%, and C2) the term uniformly dispersed throughout a support material is intended to mean that the amount of the component in question, expressed on a weight percent basis, is approximately the same in any reasonably divisible portion of the .

support material that as a whole,

They are hydrocarbons particularly suitable for

Ilojll ilútli. -8 —

14067.

10' feedstock in the present process: aliphatic compounds containing 2 to 30 carbon atoms per molecule, alkyl aromatic hydrocarbons in which the alkyl group contains 2 to 6 carbon atoms, and naphthenes or alkyl substituted naphthenes. Specific examples are: (1) alkanes such as ethane, propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, n-heptane, 2-methylhexane, 2,2,3-trimethylbutane, and the like; (2) naphthenes such as cyclopentane, cyclohexane, methylcyclopentane, ethylcyclopentane, n-propylcyclopentane, 1,3-dimethylcyclohexane.

no, and similar compounds; and (3) alkyl aromatics such as ethylbenzene, n-butylbenzene, 1,3,5-triethylbenzene, isopropylbenzene, isobutylbenzene, ethylnaphthalene, and similar compounds.

In a preferred embodiment, the hydrocarbon susceptible to dehydrogenation is a normal paraffinic hydrocarbon having about 4 to 30 carbon atoms per molecule. For example, normal paraffinic hydrocarbons containing about 10 to 18 carbon atoms per molecule are particularly suitable for the production of alkylbenzenesulfonate detergents, while n-alkanes having 6 to 10 carbon atoms can be dehydrogenated to monoolefins which can be dehydrated to produce alcohols. Preferred feed streams for the manufacture of detergent intermediates contain a mixture of 4 or 5 adjacent normal paraffin homologs, such as C^_Q to C₁₃, C_1;t to C₁₁₍, to C₁₅, and similar mixtures.

It is preferred that the support material for the

-914067

Ilojn núiu.

catalyst is a large surface area porous adsorbent support, having a surface area of about 25 to about 500 m /g. The support material must be relatively refractory to the conditions used in the dehydrogenation process, and therefore may be (1) activated carbon, coke, charcoal; (2) silica or silica gel, silicon carbide, clays, and salicylic acids, including those synthetically prepared and those occurring in nature, which may or may not have been acid treated, e.g., attapulgite clay, kaolin clay, diatomaceous earth, fuller's earth, kaolin, kieselguhr, etc.; (3) ceramic materials, porcelain, crushed brick, bauxite; (4) Refractory inorganic oxides such as alumina, titanium dioxide, zirconium dioxide, chromium oxide, zinc oxide, oxide of. magnesium, thorium oxide, boron oxide, silica-alumina, silica-magnesium oxide, chromium oxide-alumina, alumina-boron oxide, silica-zirconia, etc.; (5) crystalline zeolitic aluminosilicates such as mordenite and/or faujasite occurring naturally or prepared synthetically, either in the hydrogen form or in a form which has been treated with multi-cations. valent; (6) spinels such as MgAlgO^, FeA^O^, ZnA^O^ MnAlgO^, CaAljO^ and other similar compounds having the formula MO-AljOg^ where M is a metal having a valency of 2; and (7) combinations of elements from one or more of these groups. Refractory inorganic oxides are preferred, including the crystalline aluminas known as gamma, eta and gamma or eta alumina.

zeta, giving the best results alumina

Alumina may contain small proportions of other refractory inorganic oxides such as silica,

-1014067

Jloju nttm.

zirconium oxide and magnesium oxide; however, the preferred support is gamma alumina or substantially pure eta.

Preferred support materials have an apparent bulk density of about 0.2 to about 0.7 g/cc, a mean pore diameter of about 20 to about 30 angstroms, a pore volume of about 0.1 to about 1 cc/g, and a surface area of about 100 to about 500 m/g. The best results are obtained with gamma alumina in the form of spherical particles which have: a relatively small diameter (i.e. approximately 1.6 mm), an overall density apparent bulk density of about 0.2 to about 0.1 (more preferably about 0.3) g/cc, a pore volume of about 0.4 cc/g, and a surface area of about 150 to about 200 m/g. The preferred alumina support material may be prepared in any suitable manner (see, e.g., U.S. Patent 2,620,314).

The term catalytically available cobalt, as used herein, is intended to mean that portion of the cobalt component that is available for use in accelerating the dehydrogenation reaction of interest.

For certain types of support materials it has been observed that a portion of the cobalt incorporated into them is bound in a way that makes it unavailable catalytically. Specific examples are observed where a portion of the cobalt in their crystal structure is catalytically unavailable.

of this effect when the support material can form a spinel-like structure with a portion of the cobalt component, and/or when a refractory cobalt oxide or aluminate is formed by reaction of the support material (or preci:

r

Hajit πότη.

-1114067 '25 (or thereof) with a portion of the cobalt. When this happens, it is only with great difficulty that the portion of the cobalt bound to the support can be reduced to a catalytically active state, and the conditions required to do so are beyond the levels of severity normally associated with dehydrogenation conditions, and in fact are likely to seriously damage the necessary porous characteristics of the support. The concept of the present invention simply requires that the amount of cobalt added to the catalyst in question be adjusted to meet the support requirements as well as the catalytically available cobalt requirements of the present invention. Thus, the specifications for oxidation state, particle size, and dispersion of the cobalt component are to be construed as directed toward a description of the catalytically available cobalt. Furthermore, the specifications for the amount of cobalt used are to be interpreted as including all cobalt contained in the catalyst, in any form.

An essential feature of the present invention is that substantially all of the tin component of the composition is in a higher oxidation state than the elemental metal, preferably in the +2 or +4 oxidation state, such as the oxide, halide, oxyhalide or the like, or in chemical combination with the support material such that the tin is in a positive oxidation state. Experiments have established that the tin component of these catalysts is not reduced by contact with hydrogen at temperatures between 538 and 539°C.²C and 649^toC. Therefore, in the preparation and use of this catalyst, it should not be f

Na*tt leaf.

-1214067.

subjected to a reducing atmosphere at temperatures above 6492-0. The tin must be uniformly dispersed; if it is not properly dispersed in the support, it can be reduced in the pre-reduction stage, resulting in an inferior catalyst. The best results are obtained when the tin component is present in the catalyst as tin oxide. The term tin oxide, as used herein, refers to a tin-oxygen coordination complex that is not necessarily stoichiometric. The tin co-constituent may be incorporated into the catalyst composition in any manner that effectively disperses this component throughout the support material.

- *- V.

in the required particle size, as described in the previous Spanish patent application n^to 442289, by the same authors.

When the tin is added by impregnating the support with a strongly acidic aqueous tin solution, the acid used in the impregnation solution may be an organic or inorganic acid that is capable of maintaining the pH of the impregnation solution between about -1 or less and about 3, and preferably less than 1, during the impregnation step, and that does not contaminate the resulting catalyst. A particularly preferred impregnating solution comprises stannous chloride dissolved in a nitric acid solution containing nitric acid in an amount corresponding to at least about 2 to about 5% by weight of the support material to be impregnated. Another useful impregnating solution is stannous chloride dissolved in an alcohol.

IIoJh Π&lt;ιπι -1314067 anhydrous, such as ethanol.

. The amount of the tin component contained

Yo

I in the present composition is preferably sufficient to constitute about 0.01 to about 5% in .

• weight of the final composition, calculated on an element-by-element basis, although in some cases substantially larger amounts of tin can be used. Best results are typically obtained with approximately 0.05 to approximately 2.5% by weight of tin.

An essential feature of the present invention is that substantially all of the platinum group component exists in the final catalyst composition in the elemental metallic state. This component will generally constitute about 0.01 to about 2% by weight of the final catalyst composition, calculated on an elemental basis. Excellent results are obtained when the catalyst contains about 0.05 to about 1% by weight. weight of platinum, iridium, rhodium or palladium metal. Particularly preferred mixtures of these metals are platinum and iridium, and platinum and rhodium.

This component can be added to the support by grinding it with an aqueous solution of the platinum group metal. Typically, the preferred method is a compound of platinum, iridium, rhodium, or palladium chloride, such as chloroplatinic, chloroiridic, or chloropalladic acid, or hydrated rhodium trichloride. Hydrogen chloride or nitric acid is preferably added to the impregnation solution to further facilitate the uniform distribution of the metallic components throughout the support material. It is preferable to impregnate the support material after having

lltijii No. -14- 14067

It has been calcined, to minimize the risk of removing valuable platinum or palladium compounds.

The addition of the essential cobalt component is described in the previous Spanish patent application n² 442.289. As stated there, although this component may initially be incorporated into the composition in many different decomposition-susceptible forms, it appears that the catalytically active state for hydrocarbon conversion with this component is the elemental metallic state. In other words, substantially all of the catalytically available cobalt component must exist, in the catalytic composition, either in the elemental metallic state or in a state that is susceptible to reduction to the elemental metallic state under dehydrogenation conditions, or in a mixture of these states. The preferred preparation method, specifically described in Example I, results in a catalyst having the cobalt component catalytically available in a mixture of the reducible oxide form and the elemental metal form. Based on the behavior of such a catalyst, it is believed that substantially all of the oxide form^- The reduction phase of the cobalt component is reduced to the elemental metallic state when a dehydrogenation process using this catalyst is initiated and brought to hydrocarbon dehydrogenation conditions. The cobalt component may be present in an amount of about 0.1 to about 5% by weight thereof, calculated on the basis of elemental cobalt. Best results are obtained with about 0.5 to about 2% by weight of cobalt. It is also preferred to choose the quantity es_

HoJh nnni — 15 —

140.67..

specific cobalt, from this wide range of weight, depending on the amount of platinum group component, on an atomic basis, as explained below.

The best results are obtained when the catalytically available cobalt component is relatively evenly distributed throughout the material - a relatively small particle or crystallite with a maximum dimension less than 100 angstroms. The cobalt impregnating solution is small in size and has a maximum dimension of less than 100 angstroms.

Preferably, an aqueous solution of cobalt acetate or cobalt nitrate. The cobalt component may be added to the support material either before, at the same time as, or after the other metallic components are combined with it. The best addition results are usually achieved when this component is impregnated with an aqueous impregnating solution after the platinum group compound has been applied to a support material containing tin.

In fact, excellent results are obtained, as shown in the examples, with a two-stage impregnation method using a second aqueous impregnation solution, containing cobalt acetate or nitrate and nitric acid.

An essential ingredient of the catalyst used in the present invention is the alkaline or alkaline earth component. This component exists in the catalyst composition in an oxidation state higher than that of the elemental metal, such as the oxide or hydroxide, or in combination with one or more of the other components of the composition, or in combination with the support material, for example as alkali or alkaline earth metal alumina. Since the composition

It is always calcined or oxidized in an air atmosphere before use in llojn no. -1614067

1O dehydrogenation of hydrocarbons, the most likely state in which this component exists during use in the dehydrogenation reaction is the corresponding metal oxide, such as lithium oxide, potassium oxide, or sodium oxide. The amount of this component is chosen so as to provide a non-acidic composition containing about 0.1 to about 5% by weight of the alkali metal or alkaline earth metal, and more preferably about 0.25 to about 3.5% by weight. The best enhancements are obtained with lithium or potassium. The function of this component is to neutralize any acidic material, such as halogen, that may have been used in the preparation of the catalyst.

This alkaline or alkaline earth component can be combined with the porous support material in any manner that results in a relatively uniform dispersion of this component throughout the support material, with consequent neutralization of any acid sites that may be present. Good results are obtained by impregnation, coprecipitation, or ion exchange. Impregnation before, during, or after calcination, or before, during, or after the addition of the other metallic ingredients, is preferred. Best results are obtained when this component is added after the addition of the platinum and tin group components, because the alkali or alkaline earth metal acts to neutralize the acidic materials used in the preferred impregnation method for these metallic components. In fact, it is preferred to add the components of the pia group tin and tin to the support material, then oxidize in loose co30 ηύηι. —17

14067 stream of high temperature humid air (i.e., typically about 316 to 538°C), then treating with steam or a mixture of air and steam, at about 427 to about 566°C, to remove at least a portion of any residual acidity, and then adding the cobalt and alkali or alkaline earth metal components. Typically, the addition of this component is accomplished by contacting the support material with a solution of a suitable, decomposable compound or salt of the desired alkali or alkaline earth metal, such as the hydride, sulfate, nitrate, acetate, carbonate, or phosphate. Excellent results are obtained with an aqueous solution of lithium nitrate or potassium nitrate and cobalt acetate or nitrate.

The preferred amounts of the various catalyst components may also be expressed in terms of the amount of platinum group component, expressed on an atomic basis. Thus, the cobalt is preferably sufficient to provide an atomic ratio of cobalt to platinum group metal of about 0.15:1 to about 66:1, with best results obtained at an atomic ratio of about 1.6:1 to about 18:1. Similarly, the atomic ratio of tin to platinum group metal contained in the composition is about 0.1:1 to about 13:1, with the preferred range being about 0.3:1 to about 5:1. Likewise, the atomic ratio of alkali metal or alkaline earth metal to platinum group metal is preferably from about 5:1 to about 100:1 or more, with the best range being about 10:1 to about 75:1.

ltojn no. — 18 —

14067 •Another significant parameter for the catalyst is the total metal content, which is defined as the sum of the platinum group component, cobalt component, tin component, and alkaline or alkaline earth component, calculated on an elemental metal basis. Good results are ordinarily obtained with the catalyst in question when this parameter is set at a value of about 0.2 to about 5% by weight, with the best results ordinarily being achieved at a metal loading of about 0.4 to about 4% by weight.

After the catalyst components have been combined with the support material, the composition will generally be dried at a temperature of approximately 93°C.²C aa approximadamente 316²C,-for a period of about 2 ºC, about 24 hours or more, and will finally calcine or oxidize at a temperature of about 316²C to approximately 593²C, preferably approximately 427²C to approx. approximately 510²C, in an air atmosphere, for a period of about 0.5 to 10 hours, preferably about 1 to about 5 hours, to convert substantially all of the metallic components to the corresponding oxide form. When acidic components are present, it is good practice to subject the composition to a high-temperature treatment, with water vapor or a mixture of water vapor and air, after the acid incorporation step, to remove as much of the acid component as possible. For example, after impregnating the support material with chloroplatinic acid, it is preferred to treat the composition with water vapor or a mixture of water vapor and air, at approximately 316°C.²C to 593²C, to eliminate chloride.

Ilojn n Cun. -1914067

1O • The previous Spanish patent application n^fi

442289 It also describes the preferred waterless reduction step to which the catalyst is subjected prior to use, to selectively reduce the platinum group component to the corresponding metal, while maintaining the tin component in a positive oxidation state, and to ensure a uniform and finely divided dispersion of the metallic components throughout the support material. It is best to dry the oxidized catalyst prior to this reduction step by passing a stream of dry air or nitrogen through it at a temperature of about 260°C to 593°C and a VEHG of about 100 to 300 hr until the effluent stream contains less than 1000 ppm HgO, and preferably less than 500 ppm. The reducing agent may be contacted with the oxidized catalyst at a temperature of about 427°C.^toC at approximately 649^toC (preferably about 454-C to about 51092) and VEHG of about 300 to 1000 hr^-^.

Although maintaining the catalyst in question in a substantially sulfur-free state is a particularly preferred mode of operation of the present invention (as explained in the earlier Spanish patent application no.^to 442289), the reduced catalyst composition may in some circumstances be beneficially subjected to a presulfiding operation designed to incorporate into the catalyst composition from about 0.01 to about 0.5% by weight of sulfur, calculated on an elemental basis. Preferably, this presulfiding treatment takes place in the presence of hydrogen and a suitable sulfurizing reagent, such as hydrogen sulfide, mercaptans, or sulfur.

30.

I laja niutt.

-2014067

10 organic compounds of lower molecular weight. A mixture of hydrogen and hydrogen sulfide having about 10 moles of hydrogen per mole of hydrogen sulfide, for example, can be used at a temperature between about 10^toC and approximately 593^toC or ma.s. It is also within the scope of the invention to carry out the sulfidation during the use of the catalyst, by adding the sulfur compound to the reactor containing the catalyst, in an amount that provides approximately 500 ppm by weight, preferably 1 to 20 ppm by weight, of sulfur, based on the hydrocarbon load.

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The dehydrocarbon susceptible to dehydrogenation may be brought into contact with the catalyst in a fixed bed system, a moving bed system, a fluidized bed system, or in a batch type operation, but the fixed bed system is preferred. The hydrocarbon feed stream is preheated to the desired reaction temperature and then passed to a dehydrogenation zone, which may comprise one or more separate reactors, with suitable heating means between them to ensure that the desired conversion temperature is maintained at the inlet to each reactor. The reactants can be contacted with the catalyst bed in an upward, downward or radial flow manner, the latter being preferred, and the reactants can be in liquid phase, mixed liquid-vapor phase, or preferably vapor phase.

Hydrogen is the preferred diluent for use in the present dehydrogenation method because it performs the dual function of lowering the partial pressure of the i

.1 Unjo -21- 14067 i

hydrocarbon susceptible to dehydrogenation and suppressing the formation of carbonaceous deposits on the catalyst.

i | Hydrogen should be used in quantities that ensure a hydrogen to hydrocarbon molar ratio of approximately

J ' *_· t ♦ ! 1:1 to approximately 20:1, preferably approximately !

1.5:1 to approximately 10:1. The hydrogen charged to the dehydrogenation zone will typically be recycled hydrogen obtained from the effluent stream from this zone, following suitable hydrogen separation. Although the dehydrogenation zone must generally be in a water-free state, improved results can be obtained under certain circumstances when hydrogen is used as a diluent if water or a water-yielding substance (such as an alcohol, ketone, ether, or aldehyde) is added to the dehydrogenation zone in an amount (calculated on a water equivalent basis) corresponding to about 1 to about 5,000 ppm by weight of the hydrocarbon feedstock.

*.^;_v · ·»» -· r ro, and preferably: approximately 1 to 1000 ppm by weight.

Regarding the conditions used in the method of the present invention, the conversion temperatures are chosen from the range of approximately 371²C a approximately'649^toC, choosing a lower portion value from this interval for hydrocarbons that dehydrogenate more easily, such as normal paraffins.

-long chain, and the upper portion of this interval is more difficult for hydrocarbons that dehydrogenate such as propane, butane and the like. For example, for normal paraffins Oθ to C^q the two approximately 427 are obtained.²C to approximately 510-C. The pressure used should ordinarily be as low as possible for best results. — 22 —

14067..

10 which is consistent with maintaining catalyst stability, and is usually from about 0.1 to about 10 atmospheres, preferably from about 0.5 to about 13 atmospheres. The liquid hourly space velocity (volume of liquid hydrocarbon loaded per hour per unit volume of catalyst) is chosen

-1 from the range of about 1 to about 40 hr, preferably (for normal targa chain paraffins) about 25 to 35 hr.

The effluent stream withdrawn from the dehydrogenation zone will contain unconverted dehydrogenable hydrocarbons, hydrogen, and dehydrogenation reaction products. Typically, this stream is cooled and passed to a separation zone where a hydrogen-rich vapor phase is separated from a hydrocarbon-rich liquid phase. Unreacted dehydrogenable hydrocarbon is recovered from this hydrocarbon-rich liquid phase. This recovery may be carried out in any suitable manner, such as by passing the liquid phase through a bed of adsorbent material capable of selectively retaining the dehydrogenated hydrocarbons contained therein, or by contacting it with a solvent having high selectivity for the dehydrogenated hydrocarbon, or by a suitable fractionation scheme when feasible. If the dehydrogenated hydrocarbon is a monoolefin, suitable adsorbents having this capability are activated silica gel, activated carbon, activated alumina, and various types of specially prepared zeolite crystalline aluminosilicates, molecular sieves, or the dehydrogenated hydrocarbons can be

I lojn num. — 23“·

14067.

den separate from unconverted dehydrocarbons susceptible to dehydrogenation by utilizing the former's ability to take part in any of several well-known chemical reactions, such as alkylation> oligomerization, halogenation, sulfonation, hydration, oxidation, and the like. In any case, a stream containing the unreacted dehydrogenation-susceptible hydrocarbons will typically be recovered and recycled to the dehydrogenation stage. Similarly, a hydrogen stream will be withdrawn from the hydrogen separation zone, a portion of which will be expelled from the system to remove the net hydrogen production, and the remaining portion will be recycled by suitable compression means, to the dehydrogenation stage, to provide the diluent hydrogen for the same.

In a preferred embodiment of the present invention, in which long chain normal paraffinic hydrocarbons are dehydrogenated to the corresponding normal fine monooles, a preferred mode of operation of this hydrocarbon recovery step involves an alkylation reaction. In this mode, the hydrocarbon-rich liquid phase withdrawn from the hydrogen separation zone is combined with a stream containing an alkylating aromatic, and the resulting mixture is passed to an alkylation zone containing a suitable highly acidic catalyst, such as an anhydrous hydrogen fluoride solution. In the alkylation zone, the monoolefins react with the alkylating aromatic, while the unconverted normal paraffins remain substantially unchanged. The effluent stream from the alkylation zone is HoJm ním». “24- . 3Lθθ7.

Ί .

í i

li ¡

I i

I i

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The alkylation process can then be easily divided, typically by a suitable fractionation system, so!

to allow the recovery of unreacted normal paraffins. The resulting stream of unconverted normal paraffins is then usually recycled to the dehydrogenation stage of the present invention.

The following examples are presented to further illustrate the mode of operation, utility and benefits associated with the dehydrogenation method and the non-acidic multimetallic catalyst composition of the present invention. . .

All of these examples are carried out in a laboratory-scale dehydrogenation facility, comprising a reactor, hydrogen separation zone, heating means, cooling means, pumping means, compression means, and similar conventional equipment. In this installation, the feed stream containing the hydrocarbon susceptible to dehydrogenation is combined with a hydrogen-containing recycle gas stream, which contains water in an amount corresponding to approximately 100 ppm by weight of the hydrocarbon feed, and the resulting mixture is heated to the desired conversion temperature, which here refers to the temperature maintained at the reactor inlet. The heated mixture is then passed into contact with the multimetal catalyst, which is maintained as a 100 cc fixed bed of catalyst particles in the reactor. The pressures reported here are recorded at the reactor outlet. An effluent stream is withdrawn from the reactor, cooled, and passed to the separation zone where a hydrogen gas phase is separated from a linjtA niüii.

-2514067 hydrocarbon-rich liquid phase, containing dehydrogenated hydrocarbons, unconverted dehydrocarbons susceptible to dehydrogenation, and a small amount of dehydrogenation reaction by-products. A portion of the hydrogen-rich gas phase is recovered as excess recycle gas, the remaining portion being continuously recycled by suitable compression means to the heating zone as described above. The hydrocarbon-rich liquid phase, withdrawn from the separation zone, is subjected to analysis to determine the conversion and selectivity to the desired dehydrogenated hydrocarbon. All percent conversions of dehydrocarbon susceptible to dehydrogenation presented here are calculated on the basis of the disappearance of dehydrocarbon susceptible to dehydrogenation and are expressed in percent moles. Similarly, selectivities are presented on the basis of moles of desired hydrocarbon produced per 100 moles of dehydrocarbon converted.

All catalysts used in these examples are prepared according to the following preferred method, with appropriate modification of the stoichiometry to achieve the compositions presented in each example. A support material, of tin-containing alumina, consisting of 1.6 mm spheres having an apparent overall density of about 0.3 g/cc, is first prepared as follows: forming an aluminum hydroxychloride sol by dissolving granules of substantially pure aluminum in a hydrochloric acid solution, adding stannic chloride to the resulting sol, mixing hexamethylenetetramine with the resulting sol

14067.

'20

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I of tin-containing alumina, gelling the resulting solution by dropping it into an oil bath, to form i

i spherical particles of alumina hydrogel containing tin, aging and washing the resulting particles with an ammoniacal solution, and finally drying, calcining and steaming the aged and washed particles to form spherical particles of gammi-alumina containing the desired amount of tin in the form of tin oxide, and substantially less than 0.1¾ by weight of combined chloride.

The resulting tin-containing gamma alumina articles are then contacted, in a first impregnation step, under suitable impregnation conditions, with an aqueous impregnating solution containing chloroplatinic acid in an amount that produces a final multimetallic catalytic composition containing a uniform dispersion of the below specified amounts of platinum and nitric acid. Nitric acid is used in an amount of approximately 5¾ of the weight of the alumina particles. To ensure uniform dispersion of the metallic components in the support material, the impregnating solution is kept in contact with the support material particles for approximately 1/2 hour at a temperature of approximately 21 °C.^toC, with constant stirring. The impregnated spheres are then dried at a temperature of about 107°C for about one hour, and then calcined or oxidized in an air atmosphere containing about 5 to 25% by vol. of 1^0, at a temperature of about 260°C to about 538°C, for about 2 to 10 hours.

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140.67.

which is effective in converting all metallic components to the corresponding oxide forms. The resulting oxide particles are treated with a stream of water containing about 10% of water, at a temperature of about

30% of- steam

427^toC a approximately 538^toC, for a further period of about 1 to about 5 hours, to reduce any residual combined chloride contained in the catalyst to less than 0.5% by weight, and preferably less than 0.2% by weight.

The cobalt component and the alkaline or alkaline earth component are then added to this oxidized catalyst and subjected to steam stripping, in a second impregnation stage. In this step, the multimetallic catalyst, oxidized and treated with water vapor, is brought into contact with an aqueous solution of a suitable cobalt salt, soluble and susceptible to decomposition, and of the alkaline or alkaline earth component, under conditions that give a uniform dispersion of these components in the support material. For the catalysts used in the present examples, the salts are cobalt nitrate or acetate, and lithium nitrate or potassium nitrate. The quantities of cobalt and alkali metal salts used are chosen to produce a final catalyst containing the required amount of cobalt and having the desired non-acidic characteristics. The resulting particles, impregnated with cobalt and alkali or alkaline earth metal, are then dried and oxidized in an air atmosphere, in much the same manner as described above after the first impregnation stage.

The resulting oxidized catalyst is dried by

Sheet ntiiiii. “28“

140 Gj contact of the oxidized particles with a stream of dry air, at a temperature of approximately 499²C, VEHG ! -1 j of 300 hr , for approximately 10 hours..The dried catalyst is purged with dry nitrogen, and then reduced

I • selectively by contact with a stream of dry hydrogen i ' ' ' j, at a temperature of approximately 499²C, pressure

Atmospheric and hourly space velocity of gas of about 500 hr, and for a period of between 1 and 10 hours, which substantially reduces the entire platinum group component to the corresponding elemental metal, while maintaining the alkaline or alkaline earth components, and tin, in a positive oxidation state, EXAMPLE I

The catalyst contains, on an elemental basis, 0.375% by weight platinum, 0.5% by weight cobalt, 0.1% by weight tin, 0.6% by weight lithium, and less than 0.15% by weight combined chloride. These amounts correspond to the following atomic ratios: (1) Sn/Pt of 0.44:1, (2) Co/Pt of 4.4:1, and (3) Li/Pt of 45:1. The feed stream is commercial grade normal dodecane. The dehydrogenation reactor is operated at a temperature of 454²C, pressure of 0.68 atm manom, hourly space velocity of liquid of 32 hr, and molar ratio between recirculation gas and hydrocarbon of 5:1, After a stabilization period, a test period of 20 hours is carried out during which the average conversion of normal dodecane is maintained at a high level, with a selectivity of approximately 90% to normal dodecane,

EXAMPLE II

The catalyst is the same one used in the

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14067.

Example I. The feed stream is tetradecane. The conditions used are a temperature of 4382C, pressure of 1.36 atm. manom., liquid space velocity of '32 hr , and molar ratio of gas to molar ratio of

5:1 recirculation and hydrocarbon ratio. After a stabilization period, a 20-hour test shows an average conversion of approximately 12%, and a selectivity of approximately

90% to normal tetradecene.

EXAMPLE III

The catalyst contains, on an elemental basis,

0.3% by weight of platinum, 1.0% by weight of cobalt, 0.2% by weight of tin and 0.6% by weight of lithium, with the combined chloride being less by weight. The atom ratios (2) Co/Pt of 11:1,

0.2% The relevant cases are: (1) Sn/Pt of 1.09:1, and (3) Li/Pt of 56.2:1. The feed stream is substantially pure cyclohexane. The conditions are a temperature of 482 kJ/cm, a pressure of 6.8 atm, a liquid hourly space temperature of 3.0 hr, and a recycle gas to hydrocarbon mole ratio of 4:1. After a stabilization period, a 20-hour test is run with almost quantitative conversion of cyclohexane to benzene and hydrogen.

EXAMPLE IV

The catalyst contains, on an elemental basis,

0.375% by weight of platinum, 1.0% by weight of cobalt, 0.25% by weight of tin, by weight of chloride

1.5% by weight of potassium, and less than 0.2% combined. The governing atomic ratios are: (1)

Sn/Pt of 1.09:1, (2) Co/Pt of 8.83:1, .

and (3) K/Pt of 20:1. The feed stream is commercial grade ethylbenzene. The conditions used

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They are subjected to a pressure of 1.02 atm manom, hourly gas space velocity of 32 hr, temperature of 543^C and molar ratio between recirculation gas and hydrocarbon of 4:1. During a test period of 20 hours, 85% or more of i is observed.

i equilibrium conversion of ethylbenzene. The selectivity to styrene is approximately 95%.

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