NO138932B - PROCEDURE FOR THE PREPARATION OF A CATALYST SPECIALLY FOR ISOMERIZATION OF HYDROCARBONS - Google Patents

Description

It is known that aluminum oxide catalysts containing

containing a metal from the platinum group, most often platinum, are useful for the isomerization of paraffinic hydrocarbons. Its-

worse, none of these catalysts has had sufficient activity at low temperature. Catalysts for isomerization at low temperature are desired in order to take advantage of the more favorable isomer distribution at low temperature.

It has long been assumed that a better halogenation of the catalyst would allow catalysts that were both active and stable at low temperature. However, a rather simple increase in the halogen content of the catalyst by adding a halogen to the catalyst carrier in the form of an impregnation solution did not lead to the desired activity at low temperature.

A significant step forward in the area of isomerization catalysts with improved activity was taken when researchers in the petroleum area discovered that when a metal from the platinum group on

an aluminum oxide catalyst was treated with a metal halide

of the Friedel Crafts type, increased the isomerization activity of the catalyst at low temp.

Other researchers discovered that treatment with a polyhalogen compound of a platinum group metal on an aluminum oxide catalyst led to a catalyst with good isomerization activity at low temperature.

Unfortunately, even these very active catalysts did not

the necessary activity for the processes for which they were used to become economic.

It has now been found that a greatly improved isomerization catalyst for low temperature use is obtained when the aluminum oxide containing a platinum group metal and optionally promoter metals is treated sequentially with a Friedel Crafts metal halide consisting of AlCl^ and then with a polyhalide compound .

The invention therefore provides a method for the production of a catalyst, where a composite aluminum oxide material containing 0.1-5 wt$ metal from the platinum group and optionally 0.01-2 wt$ of a promoter consisting of Re, Ge, Sn or mixtures thereof, is reduced and then treated with a Friedel Crafts metal halide consisting of AlCl^,

and the method is characterized by the fact that the treatment with A1C1- is carried out at a temperature of 100-600 C, preferably in a reducing atmosphere, so that the composite aluminum oxide material has a content of 2-15% by weight of bound halogen, after which the thus treated composite aluminum oxide material is treated in a non-reducing atmosphere at a temperature of 100-600°C with a polyhalogen compound consisting of compounds containing at least 2 halogen atoms on the same carbon or sulfur atom, to add an additional amount of bound halogen to the composite aluminum oxide material.

According to the invention, the aluminum oxide used can be any of the various hydrated aluminum oxides or aluminum oxide gels, such as boehmite, gibbsite or bayerite etc. Activated aluminum oxide qualities, i.e., aluminum oxide be-

acted at a temperature above approx. <1>+00°C to remove at least part of the chemically and/or physically bound water and hydroxyl groups which are commonly found in connection with aluminum oxide, are particularly suitable. The aluminum oxide is preferably made of an activated aluminum oxide which is characterized by having a superior

surface area of o . 100-. 500 m2/g. Particularly preferred aluminum oxide grades are γ-aluminum oxide and γ-aluminum oxide produced by heat treatment at a temperature of 300 - 850°C.

The aluminum oxide component also serves as carrier material for the other catalyst components and should preferably be substantially free of sodium, e.g. have a sodium content of less than approx. 0.5 weight$. The aluminum oxide is most often used in a form that determines the shape of the finished catalyst, e.g. in the form of balls, pills, granules, extrudates or as a powder. The catalyst is preferably produced in the form of balls. Sodium-free aluminum oxide balls can be easily and advantageously produced using the well-known oil drop method. In short, this entails that an aluminum oxide sol, such as an aluminum oxide sol obtained by dissolving aluminum in hydrochloric acid under controlled conditions, is dispersed in the form of small droplets in a hot oil bath. The drops gel to form spherical particles. The aluminum oxide is chemically hardened with ammonia as a neutralizing agent or hardening agent. The ammonia is usually added using an ammonia-producing compound, such as hexamethylenetetramine, which is mixed into the sun. Only part of the ammonia-yielding compound is split into ammonia in the course of the relatively short time during which the initial gelation occurs. During subsequent ageing, the remaining ammonia-yielding compound is split so that a further polymerization of the aluminum oxide and desired pore properties are obtained. After aging for 10-2^ hours at 50-105°C, the aluminum oxide balls are washed, dried and calcined or activated at 500-850°C.

Although the invention relates to the production of a catalyst containing a metal from the platinum group, i.e. platinum, palladium, rhodium, ruthenium, osmium and iridium, platinum constitutes a preferred catalyst component. The platinum group metal can be added to the aluminum oxide by any known technique. It is preferred to add the metal from the platinum group by impregnation, whereby the aluminum oxide particles are suspended, immersed in, blotted with or otherwise held down in an aqueous solution of a soluble compound of the metal from the platinum group. Examples of suitable compounds include platinum chloride, chloroplatinic acid, ammonium chloroplatinate, dinitrodiaminoplatinum, palladium chloride and chloropalladium acid, etc. A very good impregnation is obtained when the aluminum oxide is impregnated with an aqueous solution of chloroplatinic acid that has been acidified with hydrochloric acid to facilitate an even distribution of platinum on the aluminum oxide. The obtained composite material will inevitably contain bound halogen, even though the bound halogen will most often amount to less than approx. 1.5 wt$ of the composite material. The aluminum oxide is preferably kept in contact with the impregnation solution for at least approx. 30 minutes at room temperature, and the impregnation solution is then evaporated to dryness. Thus, e.g. a volume-wise amount of aluminum oxide particles is immersed in an essentially equivalent volume of impregnation solution in a rotary steam dryer equipped with a steam jacket and tumbled in this for a short time at room temperature. Water vapor is then supplied to the dryer jacket to promote evaporation of the solution and recovery of substantially dry, impregnated aluminum oxide particles.

The dried composite material is generally calcined at 375°-600°C in air to convert the platinum group metal substantially to oxide. According to the present method, the composite material of aluminum oxide and the metal from the platinum group, which is used as starting material, is produced in a reduced form. It is then advantageous to treat the composite material in an essentially anhydrous hydrogen atmosphere at <I>f25-650°C to ensure that a uniform and finely divided dispersion of the metal from the platinum group on the aluminum oxide is achieved.

According to the present method, the starting material of aluminum oxide and the metal from the platinum group is first treated with a Friedel Graft s metal halide consisting of AICT^ to react AICT^ with the aluminum oxide to form a composite material containing 2-15% by weight of bound halogen. A suitable known way of reacting the two components is to evaporate AlCl^ and sublimate it on the composite material of aluminum oxide and the metal from the platinum group. The AlCl^ vapors can be diluted with hydrogen, nitrogen or another inert dilution gas. It is preferred to use a reducing gas, such as hydrogen. The reaction of AlCl^ with the aluminum oxide will occur, at least to some extent, during the sublimation process. However, it is preferred to subject the Friedel Kraft aluminum chloride to a subsequent heat treatment in contact with the aluminum oxide at a temperature somewhat higher than the vaporization temperature of the aluminum chloride. The subsequent heat treatment, which is usually carried out at a temperature of 300-600°C, serves to promote the reaction of the aluminum chloride with the aluminum oxide at the same time as unreacted aluminum chloride is vaporized and separated so that the finished composite catalyst is essentially free of aluminum chloride. Aluminum chloride sublimes at approx. 178°C, and a suitable evaporation temperature is 180-550°C. It appears that the aluminum chloride at least partially reacts with the aluminum oxide, giving off hydrogen chloride. The composite materials will, however, at this stage in any case contain 2-15% by weight of bound halogen, presumably, but not necessarily, in the form of an aluminum oxychloride, and will be essentially free of unreacted AlCl^.

This composite material is then treated with a polyhalogen compound containing at least 2 halogen atoms on the

the same carbon or sulfur atom. A generic term for these compounds is "gem dihalogens". Of other suitable polyhalogen compounds, mention can be made of any organic compound containing a /CXj group, in which X denotes a halogen atom. Methyl halide, haloform, methylhaloform, carbon tetrahalide, sulfur dihalide, sulfuryl halide, thionyl halide, carbonyl halide and thiocarbonyltetrahalide are preferred compounds. In particular, it is preferred to use methylene chloride, chloroform, ethylchloroform, carbon tetrachloride, sulfuryl chloride, thionyl chloride, carbonyl chloride or thiocarbonyl tetrachloride.

It is also possible, although not preferred, to use a mixture of halogen and other compounds which will react to form a suitable dihalogen compound. Carbonyl chloride, C0C12, is a suitable polyhalogen compound which can be prepared by reacting CO and C^. The aluminum oxide is thus still treated with a polyhalogen compound even if separate streams of Clp and CO are supplied to a carrier gas on the upstream side of the aluminum oxide.

Of the polyhalogen compounds, it is preferred to use carbon tetrachloride.

The treatment of the composite material of aluminum oxide

and the metal from the platinum group with AlCl^ is preferably carried out in a reducing atmosphere. If the composite material is not reduced at this step of the present process, it will be reduced when the finished catalyst finally enters a reducing atmosphere, such as the atmosphere present in an isomerization reactor. For each water molecule that is formed in the reactor, one active site on the catalyst is lost, and it is therefore highly desirable that the reduction take place for the halogenation steps. The treatment with the polyhalogen compound requires a non-reducing atmosphere in order to obtain an active catalyst. The composite material of aluminum oxide and the metal from the platinum group can be treated with the polyhalogen compound as such, but this is preferably diluted with an ikkrf-reducing gas, such as Ng, air or Og, etc. Nitrogen is preferred. The composite material can be treated at 100-600°C with the polyhalogen compound for 0.2-5 hours, so that it occupies at least approx. 0.1% by weight further bound halogen. Bonded halogen obtained by treatment with AICT^ is not the same as bonded halogen obtained by treatment with a polyhalogen compound. Catalyst activity deteriorates when the amount of bound

halogen is provided by the treatment with AlCl₂ alone or by the treatment with a polyhalogen compound alone. Moreover, the sequence of treatment is also of significant importance, i.e. that when the composite material is first treated with a polyhalogen compound and then with AlCl 2 , a poorer catalyst is obtained.

Catalysts prepared using the present method are useful for use in a number of different hydrocarbon conversions where the reactor temperatures are 25-760°C. These catalysts are e.g. useful for the hydrocracking of heavy oils which can be hydrotreated to remove pollutants Sg, Og and Ng during the formation of petroleum products of gasoline and light gases, i.e. LPG. For this method, temperatures need never exceed 300°C, and pressures of 5-70 atmospheres are used. The catalysts produced by the present process are particularly useful for the isomerization of paraffinic hydrocarbons, such as n-butane to n-octane, or mixtures thereof, and also for the isomerization of weakly branched saturated hydrocarbons to more highly branched saturated hydrocarbons, such as for the isomerization of 2- or 3-methylpentane to 2,2- and 2,3-dimethylbutane, and also for the isomerization of naphthenes, e.g. for the isomerization of dimethylcyclopentane to methylcyclohexane and methylcyclopentane to cyclohexane etc. The catalysts are particularly advantageous for isomerization at low temperature of straight-chain hydrocarbons containing h- 6 carbon atoms.

Paraffinic hydrocarbons can be isomerized with these catalysts at low temperatures of . 65-235°C. The feed material is mixed with hydrogen so that a molar ratio between hydrogen and hydrocarbon of 0.25:1 - 20:1 is obtained at a pressure from atmospheric pressure to 1^-0 atmospheres. For a continuous process, it is advantageous to use a floating space velocity per hour (LHSV) or volume of additional material per hour at 15°C per volume of catalyst of 0*5-10.

According to a preferred embodiment of the invention, a catalyst is produced by γ-aluminum oxide containing Ojl-2.0 wt% platinum, treated in a hydrogen atmosphere in contact with aluminum chloride and reacted with the aluminum oxide to form a composite material containing 2.0-6 .0% by weight of chloride, after which the composite material is treated in a nitrogen atmosphere at 150-350°C with CCl^ to add 0.1-5% by weight of bound chloride to the composite material.

Further investigations have shown that in some cases the same beneficial effects are obtained from the distinctive double halogenation treatment according to the invention when the catalyst contains a promoter metal consisting of Ge, Sn or Re. Ge and Sn are better promoters than Re. Pb seems to adversely affect the isomerization activity and is therefore not used.

The promoter metal is placed in each case until the composite material for the double halogenation treatment is carried out.

The most favorable effects of a promoter metal are generally obtained when the platinum group metal is made of platinum, although palladium is also favorably affected by a promoter metal. If other metals from the platinum group are used, beneficial effects are very difficult to demonstrate with the simplified laboratory test method used.

Tin and germanium are both preferred promoters. Tin is the most preferred promoter metal, not only because it is cheap, but also because it is a somewhat better promoter metal than germanium.

The tin which constitutes the preferred promoter metal <1> can be lined with the aluminum oxide in any conventional manner. The aluminum oxide can be impregnated or subjected to ion exchange before, after or simultaneously with the metal from the platinum group. Other suitable methods include simultaneous precipitation or simultaneous gelation of the tin component and the aluminum oxide with subsequent impregnation or ion exchange of the tin-aluminium oxide material with a compound of a metal from the platinum group. If the tin is precipitated at the same time as the aluminum oxide, a soluble tin compound, such as divalent or tetravalent tin chloride, can be mixed with an aluminum oxide sol for the sol and dripped into a hot oil bath. After calcination, an aluminum oxide carrier material is obtained which comprises tetravalent tin oxide intimately bound to the aluminum oxide. If impregnation is used for the supply of the tin component, it is preferable to use a solution of chloroplatinic acid, hydrochloric acid and divalent or tetravalent tin chloride as the impregnation solution. Oxalic acid can be used instead of HC1 with approximately the same effect.

When the promoter metal is made of germanium, the germanium component can be added to the support material in any suitable manner, before, after or simultaneously with the platinum group metal. It is possible to add the germanium component to the composite material by adding a soluble germanium compound, e.g. germanium tetrachloride, to an aluminum oxide sol, then simultaneously gelling the mixture in a hot oil bath to obtain a spherical gel product. This is not preferred because a subsequent treatment of the gelled product will without exception lead to a loss of the expensive germanium component. It is therefore preferred to impregnate the aluminum oxide with the germanium component. When impregnation is resorted to, a solution of a cleavable germanium compound is most often used, e.g. an acidic germanium tetrachloride solution or germanium monoxide in chlorine water. A particularly preferred impregnation solution is a solution of chloroplatinic acid together with germanium monoxide in chlorine water.

When the promoter metal is made of rhenium, this component can be added to the aluminum oxide in any usual way, before, after or simultaneously with the component from the platinum group. It is preferred to carry out a simultaneous impregnation, and a solution of perrhenic acid, chloroplatinic acid and hydrochloric acid is a particularly preferred impregnation solution.

The finished composite material should contain 0.01-2% by weight of promoter metal and 0.01-2% by weight of platinum.

Example 1

Sodium-free Y aluminum oxide balls with a diameter of approx. 1.6 mm and containing 0.3% by weight bound chloride was prepared using the oil drop method. The spheres were impregnated with 0.<*>+ wt% platinum by immersing the spheres in an aqueous solution of chloroplatinic acid, after which the solution was evaporated to dryness in contact with the spheres in a rotary water vapor evaporator. The broken impregnated balls were then calcined at 500-550°C, first in air for 2 hours and then in hydrogen for 1 hour. About. 50 g Al Cl-, was slowly evaporated into 750-1000 cm<J> hydrogen carrier gas per minute which was passed over 125 g of reduced, platinum-impregnated spheres. It used A1C1-. was added in the amount of approx. 1.5 hours at a temperature of 55'0 C. The spheres were then flushed with H2 for approx. 1 hour at 600°C. 60 g of CCl^ was then slowly added to 2000 cm^ of nitrogen carrier gas per minute which was directed over the balls. The CCl 2 used was added in a volume of approx. 1.5 hours at a temperature of 275°C. The catalyst was flushed with N 2 for 1 hour at 300°C to remove unreacted CCl 2 . The finished catalyst contained 0.5 wt% platinum and 5.9 wt% bound chloride.

The thus produced catalyst was examined in connection with the isomerisation of n-pentane and n-hexane to isopentane or 2,2-dimethylbutane. 50 cm 2 of catalyst was placed in the form of a static bed in a reactor. The feed material of 50 mol% n-pentane and 50 mol% n-hexane and mixed with hydrogen so that a hydrogen:hydrocarbon molar ratio of approx. 8:1, was brought into contact with the catalyst at a liquid space velocity per hour of 2-.0. The reactor temperature was 10°C and the pressure 69 atmospheres. The data for the investigations are reproduced in Table I.

As indicated above, the order of the treatments is with AlCl^ and

CCl^ of decisive importance. The treatment with 'AlCl^ must be carried out before the treatment with CCl^. This is explained in more detail in the example below where the sequence was reversed.

Example 2 (not according to the invention)

About. 60 g of CC1^_ was passed over 125 g of reduced, platinum-impregnated aluminum oxide beads using Ng as carrier gas. It was necessary to carry out the treatment with CCl^ for approx. 1.5 hours at 300°C. The spheres were then flushed with Ng at a temperature of 300°C. Then 50 g of AlCl₂ was vaporized and passed over the spheres using Hg as carrier gas. It was necessary to carry out the treatment with AlCl^

for 1.5 hours at a temperature of 550°C. The spheres were then purged with Hg for 1 hour at 600°C. The finished catalyst contained 0.5 wt% of platinum and 5.71 wt% of bound chloride.

The catalyst was examined as in Example 1. The examination data are reproduced in Table I.

In examples 3 and 'f, it has been shown that no improved activity can be established if the chloride content is provided by treatment with AlCl₂ or CCl₂ alone.

Example 3 (not according to the invention)

50 g of AlCl^ ^le vaporized into a carrier gas of Hg and passed over 125 g of reduced, platinum-impregnated aluminum oxide spheres. The AlCl₂ used was added over the course of 1.5 hours at 550°C. The spheres were then flushed with Hg for 1 hour at 600°C. The finished catalyst contained 0.<*>+ wt% platinum and 5.56 wt% bound chloride. Survey data are reproduced in Table I,

Example h - (not according to the invention)

hh g of CCl^ was passed over 130 g of reduced platinum-impregnated spheres using Ng as carrier gas. The treatment with CCl^ was carried out over the course of approx. 1.5 hours at 300°C.. The finished catalyst was flushed with Ng for 1 hour at 300°C to remove unreacted CCl 2 . The catalyst contained 0.<!>+ wt$ of platinum and 5.66 wt$ of bound chloride. Survey data are reproduced in Table I.

Example 5

)f -aluminum oxide spheres with a diameter of 1.6 mm and containing 0.3 wt% chlorine were impregnated in an aqueous solution of chloroplatinic acid, hydrochloric acid and tetravalent stannous chloride so that they obtained a content of 0.6 wt% Pt and 0.5 wt% Sn. Drying, calcination and halogenation were carried out as in example 1. The finished catalyst contained 8.78% by weight of bound chlorine. The catalyst was examined as indicated in Example 1. Examination data are reproduced in Table II. In this table, the data obtained according to example 1 is also reproduced for the sake of comparison.

Example 6

Y aluminum oxide balls with a diameter of 1.6 mm and containing 0.3 wt% of bound chlorine were impregnated in an aqueous solution of chloroplatinic acid, germanium tetrachloride and hydrochloric acid until they obtained a content of 0.375 wt% Pt and 0.5 wt% Ge. This composite material was processed and examined as in Example 1. Examination data is reproduced in Table II. The catalyst contained 5.53 wt% of bound chlorine

Example 7

γ-aluminum oxide spheres with a diameter of 1.6 mm and containing 0.3% by weight of bound chlorine and 0.6% by weight of co-precipitated tin were impregnated in an aqueous solution of chloroplatinic acid and hydrochloric acid. The composite material contained 0.6 wt% Pt and 0.6 wt% Sn. The composite material obtained was dried, calcined and halogenated as in Example 1. The catalyst" contained 6.35% by weight of bound chlorine. This catalyst was examined as in Example 10. Examination data are

reproduced in Table II.

Example 8

Investigations were also carried out using platinum group metals other than Pt. A Pd-Sn catalyst was prepared by conventional impregnation of Pd on an aluminum oxide which had been co-precipitated with a tin component, to produce a composite material with 0.5<*>f wt$ Pd, 0.5 wt$ Sn and 5.25 wt% Cl on aluminum oxide. This material was then dried, calcined and halogenated as in Example 1. Examination data are reproduced in Table

II.

Example 9 (comparison example)

A composite Ni material was prepared by a conventional impregnation technique and then dried, calcined, and halogenated as in Example 1. The catalyst contained 1.0 wt% Ni and was examined to determine its activity in the isomerization of butane, and it was found that the activity was excellent. The isomerization of butane was carried out at very low ratios H^hydrocarbon of typically 0.5:1 or less so that the reaction conditions used were very different from those used in examples 1-8„ It surprisingly turned out that when the Ni catalyst was examined to determine its activity in the isomerization of n-C 2 , it was an unsatisfactory catalyst. It has not been unequivocally clarified why the Ni catalyst is excellent for the isomerization of C 2 , but not satisfactory for the isomerization of C 2 .

Example m

Balls of Y-aluminum oxide with a diameter of 1.6 mm and containing 0.4% by weight of platinum and 0.3% by weight of bound chloride were produced by the method described in the above examples. AlCl₂ was sublimed on the composite material at a temperature of 550°C during 1.5 hours and then flushed with H₂ ~ for 3 hours at a temperature of 600°C, as described above. 250 cm of the catalyst was treated (A) at a temperature of 350°C with 50 ml of sulfur dioxydichloride (SO2CI2) and (B) at a temperature of 255°C with 50 ml of sulfur oxychloride (S0C12) • In each treatment, a carrier gas consisting of of dry nitrogenous vapors of the sulfur oxychloride derivative passed through the catalyst. After the treatment, the finished catalyst had a higher chloride content as follows: (A) 4.7 6% by weight bound chloride and (B)

5.5% by weight bound chloride.

Example 31

Catalysts containing tin as a promoter were prepared by a similar method as described above, and activated with sulfur oxychloride. A spherical catalyst containing γ-aluminum oxide was impregnated with 0.6% by weight of platinum and 0.5% by weight of co-precipitated tin. The catalyst contained 0.3% by weight of bound chloride. AlCl-j was sublimed on the catalyst at a temperature of 550°C and then flushed for one hour with H A ~ at a temperature of 6003°C. To increase the bound chloride content of the catalyst, 250 cm of the catalyst was treated with (C) 50 ml of sulfur dioxydichloride (SO 2 Cl 2 ) at 350°C using a stream of dry nitrogen which was passed through the used SO 2 Cl 2 to effect the treatment. The resulting catalyst (C) contained 6.13% by weight of bound chloride.

Example -\ ?

Another 250 cm 3 sample of the catalyst of Example 11 containing tin as a promoter was treated with 50 ml of sulfur oxychloride (SOCl 2 ) using a stream of dry nitrogen at a temperature of 260°C. This catalyst sample (D) had a final bound chloride content of 7.14% by weight.

The isomerization activity of the catalysts was investigated in an activity test in connection with n-C^ and n-Cg paraffins under similar test conditions as used according to Table I, and the test results are given in Table III below.

The results obtained using a sulfur compound containing at least two halogen atoms on the same sulfur atom suggest their effectiveness in adding additional halogen to achieve a higher isomerization activity when the catalyst has been pretreated with AlCl.J.

Example 13

Composites were prepared using the usual Pt-Sn-Re impregnation technique and then dried, calcined and halogenated as in Example 1. Research data suggested that Sn+Re as promoter metals led to a slightly improved catalyst.

Claims (3)

1. Process for the production of a catalyst, where a composite aluminum oxide material containing 0.1-5 wt% metal from the platinum group and optionally 0.01-2 wt% of a promoter consisting of Re, Ge, Sn or mixtures thereof, is reduced and then treated with a Friedel Crafts metal halide consisting of AlClg, characterized in that the treatment with A1C1.J is carried out at a temperature of 100-600°C, preferably in a reducing atmosphere, so that the composite aluminum oxide material has a content of 2-15 wt. % bound halogen, after which the thus treated composite aluminum oxide material is treated in a non-reducing atmosphere at a temperature of 100-600°C with a polyhalogen compound consisting of compounds containing at least 2 halogen atoms on the same carbon or sulfur atom, to add a further amount of bound halogen to the composite aluminum oxide material. 2. Method according to claim 1, characterized in that an aluminum oxide is used which is essentially free of sodium. 3. Method according to claim 1 or 2, characterized in that during the treatment with the polyhalogen compound, at least 0.1% by weight of further bound halogen is added to the composite aluminum oxide material.