A METHOD FOR ISOMERIZING ALKYLBENZENES, IN PARTICULAR XYLENES

Abstract: The method is based on the application of a catalyst which comprises an inorganic oxide support containing at least one mixed oxide compound of SiO2 and Al2O3 in any proportion, and performing the isomerization at a temperature between 150 and 300<o> C under a pressure ranging from about atmospheric to a few atmospheres in the presence of a catalyst having been produced by reaction of the support with an aluminium alkyl compound of the type AlRyX3-y, wherein R = CH3, C2H5 or C3H7, y = 1 or 2 and X = Cl, preferably Al(C2H5)Cl2. The support may be impregnated with platinum and/or rhenium. Characteristic features of this method are that the isomerization process can be run without any promotor, and that isomerization of xylene under moderate conditions yields a high degree of conversion and high selectivity. It has been shown by means of examples that the process can be run within the temperature range 150 to 300<o> C and under a pressure of about atmospheric to a few atmospheres, with from 0 to 30% ethylbenzene in the feed stock and with or without dilution of the feed with toluene. The method is particularly well applicable to converting meta-xylene to ortho- and para-xylene. Also examples of production of the catalyst have been given.

Description: A method for isomerizing al ylbenzenes, in particular xylenes. The present invention relates to a process for isomerizing •alkylbenzenes, in particular xylenes, in the presence of a * κ solid (heterogeneous) catalyst. -* Aromatic Cg__f ra +j_ons from petrochemical industrial plants and petroleum refineries will as a rule contain the three xylene iso ers in proportions which approximately are IS per cent ortho-xylene, 58 per cant meta-xylene and 24 per cent para-xylene. Meta-xylene is a substantially less demanded product than ortho- and para-xylene which i.a. σonsi ' tute basic materials for important products such as phtaliσ acid anhydride and terephthalic acid. Consequently, conversion of meta-xylene to ortho- and para-xylene represents an important industrial process. A previously well known and applied process for isomerization of xylenes relates to the use of a catalyst which is based on platinum deposited on the mixed oxide compound 3iO-,/_ι_Q The process runs at temperatures from 420 to 480° C and at pressures from 10 to 20 atm. The feed has a hydrogen/hydrocarbon ratio of approximately 10, and may contain up to 45 per cent ethylbenzene. In another previously known and applied xylene isomerization process a catalyst with platinum on AI-Q is used. The conditions in this process are appro imately as given above, except for a somewhat lower hydrogen consumption, and the feed may contain from 10 to 15 per cent ethylbenzene. More processes of similar types are utilized for isomerizing xylene. A common feature of these industrial processes is that they concern application of catalysts which comprise metal on supports, often platinum on Al^ or plati„um on S i0 2 /Al 2 0 3 . SUBSTITUTE SHEET In still another applied process for isomerizing xylene a zeolite catalyst containing rare earth metals is used. The process is a liquid phase process that runs at temperatures from 200 to 500° c and at a pressure of 22 at . , and with 20 ■per cent toluene in the feed. In the patent literature isomerization of xylene by means of catalyst systems with platinum deposited on A1,0 3 has been described, U.S. Patent Speci ication No. 4,179,581, and systems with fluorided l 2 o 3 , U.S. Patent Specif cation No. 3,898,297. -Catalyst systems with nickel deposited on AI2Q3 and other oxide supports have also been described. Additionally, there are patent speci ications relating to isomerization of xylene in the presence of different synthetic zeolite catalysts, as well as special liquid phase systems as for instance with HF/3F,, Conversion of meta-xylene to ortho-xylene and para-xylene is a monomoleσular reaction which is assumed to go via 1,2 - shifts of methyl groups. This reaction is independent of the pressure. On the contrary, bireaσtions, like e.g. disproportionation of xylene, are bimolec lar reactions and are promoted by high pressure. These reactions consume more energy, and are more predominant at higher temperatures. Previously known processes applied industrially for isomerizing xylene are encumbered with the drawback that they are operated at relatively high pressures and temperatures, and thus yield unwanted biproduσts. An object of the present invention is to provide a catalytic process for isomerizing alkylbenzenes at moderate pressures and temperatures in order to enhance the selectivity. This object has been obtained by the method according to the invention, which method is based on the application of a heterogeneous catalyst which comprises an inorganic oxide support containing at least one mixed oxide compound of SiO_ . lώ-ϊ? . ,1 _i _ £ ' . 9f -<____-. _ and I2O- in any proportion, and which is characterized in that the isomerization is performed at a temperature between 150 and 300° C and under a pressure ranging from about atmospheric to a few atmospheres in the presence of a catalyst •having been produced by reaction of the support with an aluminium alkyl compound of the type AIR X 3 , wherein R - CH 3 , C 2 H 5 or C 3 H 7 , y = 1 or 2 and X = Cl. The improved effect of the catalyst containing a mixed oxide compound of SiO_ and I2O- 3 has been illustrated in table 1, page 6. A catalyst with such an aluminium alkyl compound is known previously from DE Patent Application No. 2,62S,195, but the catalyst described therein comprises a support consisting of aluminium oxide and boron oxide for qui-σe another process, namely alkylation of aromatic hydrocarbons. Further, another catalyst with such an aluminium alkyl compound is known previously from FR Patent Specification No. 2,264,725, but the catalyst described in some detail in this specification and as exemplified consists of aluminium oxide with noble metals and is applied for trans alkylation of toluene with polymethyibenzenes to produce xylenes. Still further, patent specifications and other publications have been issued on aliphat-isomerization in the presence of aluminium sesqui-chloride deposited on 1 2 Q_. impregnated with platinum, FR Patent Specification No. 2,206,124. To complete, research results on isomerization of the aliphatiσs butane and hexane in the presence of catalyses produced by depositing Al ( CHgjcig on aluminium oxide have been reported by A. Krzywiσki, M. Marczewski, J.C.S. Faraday I, 1980, 7,6, 1311 - 1322. The new catalyst given above and also the production of this catalyst is of decisive importance for practical working of the invention, and partly for the understanding of the invention as well. Thus, the following description of the invention will also comprise a description of the catalyst and of the production thereof. One characterizing feature of this production is that unreacted Al reagent can be removed after the reaction of the support with the aluminium alkyl compound by washing the product with a polar solvent, for instance σhlorobenzene. This feature implies a considerable advantage over known processes because aluminium alkyl compounds under given circumstances may be present as strongly adsorbed dimer-like compounds on the surface of the catalyst, and it is of importance to the stability of the catalyst that adsorbed species be removed. The materials composition of the support which were found to be well applicable for the production of the catalyst according to the invention is e.g. Si0 i-. i3?j i«_£0_f and i 2 0 3 /55ϊSi<_ 2 . The oxides were subjected to heat treatment (calcination) in the temperature range from 200 to 600° C, preferably 300 to 450° C, and reached under inert conditions with aluminum alkyl compounds as given above, preferably with aluminiu -ethy -dichloride, A1{C 2 H 5 )C1 2 « The reaction can take place in a seperate reaction vessel or in the isomerization reactor to be used, in an atmosphere free from air or moisture, for instance under nitrogen or argon. A hydrocarbon solvent, preferably of -one type C H 2 J . 2 , wherein n = 5, 6 or 7, is used as a reaction medium and/or solvent for the Alcompound. Most expediently the conversion takes place at room temperature, and the product is dried in vacuum for several hours. Al- and Cl-analyses suggest that reactions are taking place between the aluminum alkyl compound and hydroxyl groups on the surface of the support, such reactions being of the type.* C:. '? I ^»» Str¬ and: !3i - OH + AlEt 2CI- StH £.t wherein Ξt = 2 H S> The amount of chlorine in the catalyst can be from O.i to 1- wt. per cent, and_ pref ably 3 tp 12 wt. per cent. The catalyst can be subjected to heat treatment under inert conditions, separately or- in the reactor, at temperatures in the range from 200 to 500° C, or if desired be calcined in an atmosphere with a controlled content of H' 2 o. Prior to the reaction given above materials for the support can be impregnated with a metal compound, for instance an aquous solution of K j ptClg and/or H 4 «β0 4 . In succession to such impregnation the impregnated product is reduced in hydrogen atmosphere at temperatures in the range from 200 to 400° C An impregnated support can contain from O.i to 2 per cent Pt and/or Re, preferably 0.2 to 1 per cent. The isomerization process according to the invention is particularly well applicable to conversion of meta-xylene to ortho-xylene and para-xylene. This isomerization process can be performed in gas or liquid phase, and as mentioned above in the temperature range from 150 to 300° C and at a pressure of about atmospheric to a few atmospheres. The feed can consist of met -Ey-Leae or a mixture of Cg-arσmatiσs where the ratio between the xylene isomers is different from that of an equilibrium mixture, and where the content of ethyl benzene can range from 0 to 30 per cent. Thus it has been found that xylene can be isomer zed under moderate conditions with a high degree of conversion and with very high selectivity. One characterizing feature of this isomerization process is that it can be run without addition of a promotor, contrary to the previously -known processes wherein catalysts based on aluminium alkyl are applied, which processes seem to be conditioned by the use of a promotor in the feed stock, for instance use of the corrosive HC1. The feed can be diluted with a solvent, and it has been found that dilution with up to 50 per cent toluene gave a substantially improved selectivity, so that the selectivity in several cases amounted to approximately 100 per cent. The effect on the degree of conversion as well was favourable in a number of occasions, and in no case negative. The isomerization process has been run with or without hydrogen. When run with hydrogen the ratio hydroσarbαn/H 2 - _ t In liquid phase tests in an autoclave at a pressure of a few atmospheres and at a moderate temperature of 175° C and with a meta-xylene/ oluene ratio equalling 1 a maximum conversion and selectivity was obtained, i.e. conversion until the equilibrium ratio between the xylenes was achieved, and without formation of undesired biproduσts. An advantage of being able to operate at such mild conditions as set forth herein is that bireaσtions, as for instance disproportionation of xylene, are less pronounced. One of the disproportionation products is toluene, and industrial application of toluene as a solvent will also reduce this bireaction and contribute to high selectivity. Gas phase tests in a fixed bed integral reactor showed that variants of catalysts as given above possessed a good -stability after a certain initial phase, and that the stability was improved by introducing metal - in particular platinum - in the support. Presence of ethyl benzene in the feed had a low influence on the degree of isomerization and gave a small decrease in the selectivity. Hydrogen in the feed gave increased stability, and with hydrogen the selectivity was very high. Table 1 below shows results from some examples of isomerization tests performed in accordance with the invention, with different feed compositions and with catalysts produced by reacting AlEtCl 2 with different types of supports. All catalysts were subjected to heat treatment at 250° C prior to testing. To present a survey, results have been given in table 2 below, which results show how low the conversion is in isomerization tests with AlEtCl2 in homogeneous solution, and with pure, not chemically modified supports. As mentioned above, mixed oxide compounds of the type Al 2 0 3 /Si0 2 are applied as catalysts in commercial isomerization processes, but where the pressures and temperatures are substantially higher than those given by the invention. The test results show that the high selectivity and conversion which have been obtained in the isomerization process described herein, explicitly can be referred to the solid catalyst preparation, and not to soluted aluminium alkyl species, neither to effects of the support. SUBST-TUTE SHEET O PΓ 1 P Table 1. Isomerization of meta-xylene in autoclave at 175° C for 20 hours over solid catalysts based on AlEtCl 2 . Feed Type of Conver¬ Relative Seleσ- Meta- Toluene Ethyl- support sion σonver- tivity xylene ben- sion zene % % mol!« olH molH olH Si0 2 14.4- 32.7 80.- 100.- A1 2 Q 3 23.7 53.9 82.4 100.- 0.3HPt/Al 2 o 3 11.3 25.7 80.3 100.- 0.35SRe/Al 2 0 3 11.3 25.7 81.6 100.- 0.3?S?t/0.2HRe/ I 2 0 3 12.- 27.3 84.- 100,- Al-0-/6?JSiO, 26.7 70.7 73.7 100.- Si Q 2 /13S«Al 2 0 3 31.4 71.4 82.4 100.- 33.7 75.6 r-J 100.- 50,- 50.- 38.2 86.8 92.1 75.- 25.- 35.2 80.- 90.4 30.- 10.- Si0 2 /125*Ai 2 O 3 38.3 87.- 81.7 100.- u 41.1 93.4 92.3 50.- 50.- 34.9 73.3 77.4 99.- 1.- ir 40,- 90.9 65. — 95.- 5.- 42.2 95.9 55.1 90.- 10.- 0.3?ϊPt/SiO 2 / 12?«A1 2 0 3 35.- 79.5 80.5 100.- 0. *± 42.2 95.9 75.9 100.- 0.3 β 4Re/SiO 2 / 12HAl 2 o 3 34.3 79.3 31.6 100.- 0.3?«Pt/0.2?«Re/ 12 # 4A1 2 0 3 35.2 80.- 84.1 100.- OMPI Conversion ■= converted meta-xylene in per cent (5s). Relative conversion = conversion in relation to maximum obtainable conversion (44%) under equilibrium conditions at 175° C. Selectivit = per cent ( % ) (ortho-xylene - para-xylene) in the product formed. Table 2. Isomerization of meta-xylene in autoclave at 175° C/20 hours. Catalyst Conversion Relative Selec- component conversion tivity % % % AlEtCl 2 (solution) 1.5 4.- 38.- Si0 2 /400° <-.< 0 ru 0 - Al 2 O 3 /400° C 1.0 2.5 85.- Al 2 O 3 /65.SiO 2 /400° C 0.9 2.5 84.- Si0 2 /i35«Al 2 O 3 /400 O 1.5 4.- 53.- The invention is now to be explained by means of the following examples of performance, wherein Et = , Production of catalyst: Example 1. Reaction of Si0 2 /i35$Ai 2 0 3 (calcined at 400° C) with AiEtCl 2< 15 g of a water-treated, calcined support Si0 2 /i2 % l 2 θ /400° c were weighed out and transferred to an argon filled 250 ml two-necked flask connected to an inert gas line. 40 ml of - U E mm,.,,« ^ .-_ ! -««r«β- 1 ? *sw?S2" OMPI absolute (abε. ) normal (n-) hexane was added, and then a hexane solution of 15 mi 50 % AIEtCl 2 was added-. Hea't and gas developed- on adding AlEtCl 2 ; -ohe reaction was rather vigorous the first 10 to 15 in. , then the reaction subsided rapidly. After a respite for two hours at room temperature the mixture was transferred to a filter and the liquid was sucked off. The solid material was then washed with 2 x 25 ml of heptane and thereafter with chlorobenzene for 2 hours (6 x 25 ml), and finally with heptane (5 x 25 ml) for 1 hour. The solid material was dried 1 hour in vacuum (approx. 1 mm Hg) , and thereafter 20 hours in high vacuum (approx. 1Q~* mm Hg) . The preparation was preserved under argon in a sσhlenk-tube. Al analyses on the catalyst showed! 10.55 % Al. Al analyses on the support: 5.73 % Al. This corresponds to 1.76 mmoles of deposited Al per g of catalyst. Cl analysis: 12.6 % = 3.55 mmoles Cl/g of catalyst. Molar ratio Cl : Al = 3.56 : 1.75 = 2.02. Example 2. Reaction of Si0 2 /ι 3 5« I 2 0 3 (calcined at 400° C) with aluminum-diethyl-chloride, AlΞt 2 ci. The catalyst was produced by reaction of 19 g of Siθ2 13SsA1 2 0 3 /400 ° C with 5 ' 5 l of A12fe 2 Ci in 50 abs * n-heptane in accordance with the method described in Example Results of analyses: Al! <A1 cat. * A1 support ) = 2 ' S5 * = ° ' S S mmoles of Al/g Cls 5.42 % = 1.53 mmoles of Cl/g C ! C σat. ~ c support** * 3 - 40 s 2 « 33 mmoles of C/g H ! (K cat. ~ consumed 0K)= 0.53 % = 6.78 mmoles of H/g Al j Cl : C 2 : H 5 = 1 : 1.5 : 1.9 j 1.4 (moles). Approx. 10 g of the catalyst were weighed out in a quartz - OMPJ Wfa IPO 44 vessel , in a drybox and transferred inertly to an oven wherein the catalyst was dried at 250° C under N 2 for 4 hours, cooled and transferred to a schlenk-tube. Results of analyses: Al 2.66 % = 0.99 mmoles of Al/g Cl 5.54 % - 1.55 mmoles of Cl/g C 2.30 % = 1.92 mmoles of C/g H 0.45 % = 4.55 mmoles of H/g Al : Cl : C 2 Hm. = 1 ■ 1.6 : 0.94 (moles). Example 3. Reaction of ?t-Si0 2 i255Al 2 0 3 with AlEtCl 2 . 30 g of SiO./Al-Q-q were placed in a beaker and admixed with 0.24 g of K 2 ?tCl-.5H 2 0 dissolved in 50 ml of destilled water. After 2 hours the solution was evaporated to dryness on evaporation apparatus (RQTAVAPOR) at 100° C and dried for 2 hours at 150° C (drying chamber) and thereafter for 23 hours at 400° C under N 2 . Analysis: 0.27 % Pt. The material was reduced with H 2 f 0r hours at 200° C. The Pt-impregnated support was transferred to a 2-neσked flask under inert conditions and admixed with 50 ml abs. n-heptane, and further treated as described in Example 1. Chlorine analysis: 7.69 % Cl . Example 4. Reaction of Re-Al 2 o 3 (calcined at 350° C) with AiEtCi 2 , rl 50 g of Al 2 o_ were impregnated with 220 mg of NH 4 Reθ dissolved in 35 mi of water. After 24 hours the water was evaporated on ROT VAPOR, and the sample was reduced with hydrogen. During the reaction the temperature was increased 1° C/min. to 350° C, and then kept at 350° C for 2 hours. Re-analysiss 0.34 % Re. The preparation was reacted with AlΞtCi 2 under inert conditions as described in Example 1. Cl-anaiysis: 5.3 . Ci. Example 5. Reaction of Pt,Re-Al 2 o 3 with AiΞtCi 2 . 50 g of» i 2 o 3 were placed in a beaker and admixed with a solution of 0.5 g of H 2 P Ci s .SH 2 0 and 0.11 g of H 4 Re0 4 in 36 ml of destilled water. After preservation at room temperature (without stirring) for 24 hours the water was evaporated on ROTAVAPOR at 50 to 60° C. Analyses: 0.26 % Pt 0.17 Re The material was reduced as described in the preceding example. Then 30.5 g of the impregnated support was reacted with AlEtCl 2 s described in Example 1. Analysis: 5.71 % Cl. Example 6. Reaction of Si0 2 (calcined at 500° C) with AlΞt-c . 2.5 g of Si0 2 wer e treated with 1.3 ml of AlEt 2 Ci in 25 mi oi n-hexane under inert conditions as described in. E ample 1. Analyses: 4.1 % Al, 5.25 % Cl, 4.05 % C zH (ethane was liberated by treatment with a concentrated alkaline solution). Al Cl C 2 H 5 = 0.93 1.02 Isomerization: Example 7. Isomerization of meta-xylene in liquid phase (1 at .). 2 g of the catalyst as produced in accordance with Example i ( 3iO 2 /i33 4 Al 2 O 3 /400° C/AiStCi 2 ) * were admixed with 30 mi of meta-xylene and transferred inertly to a 100 mi 2-necked flask with reflux condenser. The mixture was refiuxed (at approx. 150° C) for 31 hours and samples were taken out with a syringe for gas σhromatography (GO analyses, at first taken every hour for 5 hours, then after a period of 23 hours, after another period of 25 hours and after a final one of 31 hours. On completing the test the catalyst was filtered off (inertly), washed with benzene and heptane, dried in vacuum and analysed for Cl. 5 mi of the filtrate were evaporated in air. The residue from the evaporation was diluted with acid and analysed for Al. Results of analyses: Catalyst before application: 3.4 mmoles of Cl/g Catalyst after application : 3.4 mmoles of Cl/g Reaction mixture (liquid) : Al was not detected, i.e. maximum 0.001 mmoles of Ai/g was removed from the catalyst. \ Product compositions: Reaction ' Products, mol % time hours toluene benzene p-X* m-K* o-X* trimethyl benzene 1 0.299 0.024 7.503 86.464 5.483 0.222 2 0.565 — 11.491 79.041 3.256 0.543 3 1.252 0.021 13.353 73.536 10.079 1.199 4 1.547 0.019 14.755 71.052 10.864 1.551 5 2.207 0.026 15.526 58.543 11.534 2.053 6 2.346 0.021 15.741 67.836 11.715 2.292 23 5.253 0.027 17,382 53.720 13.525 5.034 25 5.253 0.019 17.451 58.363 13.613 5.275 31 5.599 0.030 17.313 57.395 13.193 4.355 » * p = para, m = meta. o = ortho. X * = xylene. (As well as in the following description. ) Example 8. Isomerization of o-xylene and m-xylene in mixture in liquid phase (autoclave, 175° C) . a) 1 g of the catalyst produced in accordance with Example 1 ( Si0 2 /i3?jAl 2 0 3 400 o C/AlΞtCl 2 > was admixed with 15 mi of a mixture of xylenes (o-xylene : m-xylene = 1 : 9), transferred inertly to a Parr autoclave and kept heated at 175° C for 20 hours. On completing the test the mixture was filtrated inertly. The composition of products in the liquid was analysed on a GO When it is mentioned in this example, and in successive examples, that the isomerization was cerformed in an autoclave OMP /fa IP it is to be understood in this connection that the isomerization was performed at a pressure of from about atmospheric to a few atmospheres. The catalyst was dried in vacuum and analysed for Cl. 5 ml of the filtrate were transferred to a round flask and cooled with liquid 2 . Then 2 to 3 ml of water were added, and the flask was kept at room temperature until warmed. The mixture was shaken, well admixed with 2.5 ml of IN H,so 4 and transferred to a 50 ml flask. The organic layer was removed by means of a pipette, the flask was filled with destilled water, and the solution was analysed for Cl and Al. Analyses: Catalyst before application: 3.4 mmoles of Cl/g Catalyst after application t 2.3 mmoles of Cl/g Filtered reaction mixture . No detectable amounts of Al and Cl, i.e. < 0.001 mmoles of Cl/g and < 0.001 mmoles of Al/g of catalyst dissolved in the liquid Conversion : 45.75 % Selectivity . ' 51.45 X Yield i 28.15 % (Maximum obtainable yield: 40 % ) o-xylene : m-xylene : p-xylene = 20.9 : 53.0 : 24.2 (Thermodyna iσ equilibrium ratio: 20.0 : 55,3 : 24.2) b) An isomerization test under such conditions and with such a mixture of xylenes as described in a), but with 1 g of a catalyst having been produced by reaction of Si0 2 (calcined at 400° C ) with AiEtCi 2 . followed by drying in vacuum (5i0 2 /400° C/AlEtCl 2 ) . Conversion : 14.4 '4 Selectivity : 80.0 % ,-_- B Yield : 11 . 5 % σ) An isomerization test as described in a) , but with 1 g of a catalyst having been produced by reaction of 1 2 Q ( calcined at 400° C) with AlStCl 2 , followed by drying in vacuum. Conversion : 39.1 % Selectivity : 63.3 % Yield : 25,7 % Example 9. An isomerization test as described in Example 8 with 1 g of a catalyst having been produced in accordance with Example 4 ( Re Al 2 Q 3 3 5o° C/AlΞtCl 2 dried at 250° and with 15 xi of m-xyiene in a Parr autoclave for 20 hours at 250° O Example 10. (A preferred example of performance. ) Isomerization of m-xylene diluted with toluene in liquid phase (175° C, autoclave) . An isomerization test as described in Example 3 with 1 g of a catalyst Si0 2 /i3S4 A i 2 0 3 / 0 o C/AiEtCl 2 , dried at 250° produced in accordance with Example i, the feed consisting of 15 ml of m-xyiene and 15 ml of toluene. The process was run for 20 hours at 175° O Conversion : 33.7 5s Selectivity : OJ 100 % Example 11. Isomerization of m-xyiene in liquid phase with ethylbenzene and toluene in the feed stock (175° C, autoclave). The isomerization test was performed as described in Example 3, in which test 1 g of Si Q 2 / 2J$ l2θ 3 (calcined at 400° C ) having been reacted with AlEtCl- and calcined at 250° C was added to 30 ml of a feed consisting of 45 % m-xylene, 45 % toluene and 10 % ethylbenzene, Conversion : 49.5 % Selectivity : 63.4 % Converted ethylbenzene : 74.4 % Example 12. Isomerization of m-xyiene in liquid phase with ethylbenzene in the feed stock (250° C, autoclave), The isomerization test was performed as described in Example 8 with 1 g of Si0 2 /12*A1 Z 0 3 calcined at 400° reacted with AlEtCl 2 and dried at 500° C. The catalyst was supplied with 15 mi of m-xylene admixed with 5 % ethylbenzene, and the process was run at 250° C for 20 hours. Conversion : 35.1 % Selectivity : 62.7 % Converted ethylbenzene : 49.5 % Example 13. Isomerization of m-xyiene in liquid phase in the presence of toluene and hydrogen. a) Reaction conditions: KSV (Weight hourly : 0.42 g of xylene/g of catalyst per space velocity) hour •_ _ _<-' _! Z"n I * Temperature : 180° C Amount of catalyst : 10 g of Pt/3i 2 /i25s i2θ 3 calcined at 400° C, reacted with AlΞtCl 2 and dried at 250° C Hydrogen : 20 ml/min. Feed mixture : 0.05 moles % of benzene 55.29 moles % of toluene 0.11 moles % of p-xyiene 44.33 moles % of m-xylene 0.19 moles % of o-xylene The catalyst was weighed inertly, commingled with an equal amount in volume of 1 ml gias beads and transferred to the reactor under N 2 . After heating to 180° C the test was started, and a mixture of hydrogen, toluene and m-xylene was pumped in. The product was analysed on a gas chromatograph with an automatic gas sampling system. Samples were taken every hour, initially, later every two hours and then every four hours. The conversion decreased slowly from approx, 50 % in the initial phase to approx. 25 % after 72 hours, and the selectivity increased from approx. 7 % to approx. 90 . b) An isomerization test with conditions and feed stock as described in a), but with 10 g of a catalyst having been produced by reacting Re/Si0 2 / 12 ?j l 2 O 3 (hydrogenated at 350° by means of the method described in Example 4. The conversion decreased from 42 % at start to 15 . after 80 hours, and the selectivity increased in the same period of time from 70 '4 to 86 '4. c) An isomerization test as described in a) , but with 10 g of a catalyst having been produced by reacting Pt,Re/Si0 2 / i2 . 4AI , 2θ3 (hydrogenated at 350° C with AiStCi 2 followed by drying at 250° C as described in Example 5. The conversion decreased from 48 X at start to 23 X after 75 hours, and the selectivity increased in the same period of time from 72 . to 83 '4. - d) An isomerization test as described in a), but with 10 g of a catalyst having been produced in accordance with Example i (Si0 2 /i25.Ai 2 0 3 /400° C/AiEtCl 2 ) and dried at 250° C. The conversion decreased from 40 % at start to approx. 10 % after 75 hours, and the selectivity increased in the same period of time from 78 i. to 95 '4. Example 14. Isomerization of m-xyiene in gas phase. An isomerization test performed as described in Example 13, Catalyst : 10 g of 3i0 2 12 ?jAi 2 0 3 calcined at 400° C, reacted with AlΞtCi, and dried at 250° C Feed m-xyiene (93.23 X ) Reaction temperature 190° C WHSV 0.21 Sampling every 30 min. Conversion 43.5 hours 25.2 "4 (35.3 X selectivity) X Cl X C X H Analysis of catalyst before test: 5.27 0.50 0.42 Analysis of catalyst after test : 4.93 3.92 0.53 Example 15. An isomerization test performed as described in Example 13, Catalyst : 10 g of Al 2 o 3 /6*Siθ 2 calcined at 400 ,o ' rC., reacted with AlZtCi '2- and calcined at 250° C " Feed m-xyiene Reaction temperature s 183° C WHSV J 0.21 Sampling : every 30 min, Maximum obtainable conversion : 75.3 X after hour Conversion after 22 hrs: 5.1 X Selectivity : 34.1 X Example IS, Isomerization of m-xyiene in gas phase with ethylbenzene in the feed. An isomerization test as described in Example 13. KSV 0.42 Temperature 190° c Catalyst 10 g of S 0 2 /i2ϋAi 2 3 calcined at 400° C, reacted with AiEtCi 2 , and dried at 250° C Feeα mixture 0.06 moles X of benzene 0.68 moles X of toluene 0.23 moles X of p-xylene 3.54 moles X of m-xyiene 0.62 moles X of o-xyiene 4.59 moles X of ethylbenzene Conversion after 20 hours : 14.9 X Selectivity after 20 hours: 86.3 X Example 17 . Isomerization of m-xyiene in gas phase. An isomerization test performed as described in Example 13, WHSV 0.23 Temperature 190° C Catalyst 10 g of 5i0 2 calcined at 400° reacted with AlΞtCl 2 and dried in vacuum at 20 C Feed m-xylene Conversion after 5 hours 13. 2 X Selectivity after 5 hours i 82 . 2 X

Claims: CLAIMS: 1. A method for isomerization of alkylbenzenes, in particular -xylenes, in the presence of a heterogenous catalyst comprising an inorganic oxide support containing at least one mixed oxide compound of S 0 2 and A1 2 0 3 in any proportion, c h a r a c t ¬ e r i z d in that the isomerization is performed at a temperature from 150 to 300° c and under a pressure ranging from about atmospheric to a few atmospheres in the presence of a catalyst having been produced by reaction of the support with an aluminium alkyi compound of the type AIR x- wherein R - c "3, C2H5 or C 3 H-* 7 , y = 1 or 2 and X = Cl. 2. A method as claimed in claim 1, c h a r a c t e r i z e d in that the isomerization is performed in the presence of a catalyst where the support has been impregnated with at least one of the metal comtounds H,,ptCi,- and "NH» eθ . 3. A method as claimed in claim 1 or 2, c h a r a c t e r ¬ z e d in that the xylenes are subjected to isomerization conditions in the presence of a catalyst having been produced by reaction of the support with the aluminium alkyl compound Al.C 2 κ 5 )Cl 2 . 4. A method as claimed in claim 1 or 3, c h a r a c t e r ¬ i z e d in that a feed comprising meta-xylene and toluene in the ratio 1 : 1 is subjected to isomerization conditions for conversion of meta-xylene to ortho-xylene and para-xylene. 5. A method as claimed in claim 4, c h a r a c t e r i z e d in that the feed contains from 0 to 30 X ethylbenzene. 6. A method as claimed in claim 4 or 5, c h a r a c t e r ¬ i z e d in that hydrogen is supplied to the feed, so that the ratio hydrocarbon : hydrogen = 1 : 1. 7. A method as claimed in one or more of the claims 1 to 5, c h a r a c t e r i z e d in that the isomerization is performed in the absence of a promotor. Izs i mil-mi ITUTs . _ •_ .._..___ -

Inventors: BLINDHEIM ULF, HAEGH GERD SYNNOEVE, NILSEN BJOERN PETTER, BLINDHEIM, ULF, HAEGH, GERD, SYNNOEVE, NILSEN, BJOERN, PETTER
Applicants: SENTRALINST FOR IND FORSKNING, SENTRALINSTITUTT FOR INDUSTRIELL FORSKNING
Application year: 1983
Main classification: C07C5
IPC codes: C07C5