PREPARATION OF 1-(2-METHYLBUTYL)-4-METHYLBENZENE

Abstract: The invention concerns a preparation process for 1-(2-methylbutyl)-4-methylbenzene, in which p-xylene is alkylated with 1-butene using a basic catalyst, which is a zeolite impregnated with an alkali metal, a hydrotalcite on a carrier or CsOH on a carrier. The method is suitable for a continuous process, and a solid bed catalyst can be used. The selectivity of the method is good.

Description: PREPARATION OF 1- (2-METHYLBUTYLV4-METHYLBENZENE FIELD OF THE TECHNOLOGY The invention concerns a preparation process for 1- (2-methylbutyl)-4-methyl- benzene, in which p-xylene is alkylated with l-butene using a basic catalyst. The invention is especially focusing on the use of some special catalysts. BACKGROUND OF THE TECHNOLOGY 1- (2-methylbutyl)-4-methylbenzene can be used as a raw-material in chemical synthesis. For instance in the petrochemical industry it can be used as a raw- material for the preparation of 2,6-dimethyl-naphthalene. One possibility for preparing 1- (2-methylbutyl)-4-methylbenzene or l-(p-toluyl)-2- methylbenzene is to alkylate one of the methyl groups in p-xylene with l-butene. In this reaction basic catalysts, especially alkali metals, are the most suitable ones. In most cases the catalyst is supported on a solid carrier. Especially potassium carbonate has been used as a carrier. A common catalyst system has been solid sodium dispersed on the surface of potassium carbonate. However, the problem has been a rather poor selectivity. Different alkylbenzenes are obtained and they are difficult to separate from each other. Furthermore, l-butene easily dimerizes. Many different alkali metal catalyst systems have been proposed in order to improve the selectivity of the alkyiation of p-xylene. The alkali metals (for instance Na, K, their combinations), the metal compounds (for instance elementary, oxide, hydr¬ oxide), the carriers (for instance K2CO3, AI2O3, silica), as well as the preparation procedures of the catalyst systems (for instance dispersion of a molten metal, and thermal decomposition of a metal compound) have been varied. Furthermore, the selectivity can be improved by different types of promotors (for instance organo- metal compounds). For instance in the publication JP-A-50093925 one has proposed a catalyst system in which potassium has been dispersed on γ-Al2θ3. DESCRIPTION OF THE INVENTION General description Now a process according to patent claim 1 has been invented. Advantageous applications of the invention are presented in the other claims. In the process according to the invention, a selective heterogeneous catalyst is used, which catalyst is a zeolite impregnated with an alkali metal like sodium, a supported hydrotalcite or a supported CsOH. The process can be continuous, and a solid bed catalyst can be used. The selectivity of the process is good. The zeolite which is impregnated with an alkali metal can for instance be X or Y faujasite. The support for hydrotalcite or CsOH can be for instance Siθ2, AI2O3 or a zeolite. The reaction can take place for instance at a temperature of 100-350°C and a pressure of 1-3 bar. When the catalyst is a zeolite which has been impregnated with an alkali metal, the temperature can preferably be 150-350°C and the pressure is preferably 1-3 bar. When the catalyst is hydrotalcite or CsOH the temperature can preferably be 100-300°C. A zeolite which has been impregnated with an alkali metal can preferably be prepared so that - The zeolite is impregnated with an alkali metal azide after which it is heated to about 450°C - The zeolite is impregnated with the vapour of an alkali metal or - The zeolite is impregnated with an alkali metal solution like a solution with ammo¬ nia or a solution with tetrahydrofurane which contains naphthalene. Specific description In a base catalyzed alkyiation reaction between an alkyl-aromatic hydrocarbon and an alkene, an intermediate product, usually a carbanion, is obtained in the alkyl chain and in this way the side chain is alkylated. According to the invention, a selective heterogeneous alkylating catalyst is used which catalyst is a zeolite that has been impregnated with alkali metal, hydrotalsite or CsOH. In the zeolite active alkali metal clusters can be created for instance in the following ways: - Impregnation with a metal vapour - Treatment with a solution of an organometal compound (for instance n-butyl¬ lithium in hexane) - Treatment with a solution of a metal in a primary amine or ammonia - Treatment of precipitated zeolite and metal in an organic solvent - Radiation in vacuum with γ- or X-rays - Impregnation with an alkali metal azide and its thermal decomposition. The formation of metal clusters can already be seen from the change in colour, and this observation can be confirmed by using ESR-spectroscopy. The form and position of the clusters in the zeolite structure can be studied by using diffractometric techniques. Alkali metal clusters on the surface of a zeolite can be considered as Brønstedt- bases, and they act as active centers in base catalyzed reactions of hydrocarbons. A most useful preparation process for a zeolite catalyst is azide impregnation and thermal decomposition. It has been observed that both steps are rather complicated. Part of the azide is enclosed into the pores of the zeolite and obtains a significant thermal stability. As a result a system with many different kinds of chemical compounds is obtained. Example 1 Preparation of the NaN3/pow NaY catalyst A 30% solution was made by dissolving 0.384 mol NaN3 in water. 100 g LZ-Y52 zeolite powder was added under efficient agitation. The water was evaporated at 80°C and the solid material obtained was stored in the vessel. Example 2 Preparation of the NaN3/gran/NaY catalyst 100 g granulated NaY zeolite (Si/Al=3.2) which had been made in the laboratory was mixed with a 30% NaN3 solution. After about 24 h the temperature was increased to 80°C and the water was evaporated. The solid material obtained was stored in air in the vessel. Example 3 Preparation of the NaN3/gran/NaX catalyst A 13 X zeolite powder made in Hungary was saturated with a NaN3 solution so that materials were obtained which contained 4 or 10% NaN3/zeolite-g. The saturation was carried out in a water solution. Example 4 Preparation of the CsOH/CsY catalyst 31.82 g LZ-Y52 zeolite powder (UOP) was ion exchanged in three steps: (i) the ion exchange was done in 600 ml of a 0.1 mol/1 CsCl solution at 80°C for 2 h, after which it was filtrated and dried at 80°C, (ii) the ion exchange was done in 500 ml of a 0.1 mol/1 CsCl solution at 80°C for 2 h, and (iii) the second steps was repeated, and it was washed and dried at 80°C. The material was homogenized in a 0.1 mol/1 CsOH solution. The suspension was mixed efficiently and the water was evaporated during mixing. The catalyst was stored in a desiccator. Example 5 Preparation of the CsOH/CsX catalyst 35.49 g granulated 13 zeolite (UC) was ion exchanged according to Example 4 using 700 and 600 ml 0.1 mol 1 CsCl solution. CsOH was precipitated onto the ion exchanged material according to Example 4. Example 6 Preparation of the HT/Siθ2 catalyst Hydrotalcite was made by co-precipitating Al and Mg hydroxide. In order to synthesize 3.1 [Mg-Al-Cθ3] one prepared two solutions: 14.07 g A1(N03) 3*9H2θ and 28.85 g Mg(N03) 2*6H2θ was dissolved in 250 ml distilled water (solution A) and 10.59 g Na2Cθ3 and 13.5g NaOH was dissolved in 250 ml distilled water (solution B). Solutions A and B were combined by dropping at a speed of 100 ml/min under continuous agitation. At the same time pH was controlled to 8.5+0.05. The agitation was continued for 48 h after which the gel was treated under hydrothermal conditions at 180°C. The crystalline material obtained was filtrated and washed. From the water containing material obtained a suspension with a solids content of 50% was made, and 100 g of a silica gel with large pores was added to this suspension. The water was evaporated and the solid material was dried. Example 7 Preparation of the Na/amm NaY catalyst About 100 ml ammonia was condensed by cooling with a carbon dioxide/acetone- condenser and 3 g sodium metal was added to the liquid. (When sodium is added the cooling must be very carefully controlled). When the temperature had stabilized, 10 g of preheated NaY zeolite was added very slowly. (One must above all make sure that the zeolite is totally dehydratized. Otherwise a very exothermal reaction with the water will take place and the product obtained will not be homogeneous). After this the ammonia was evaporated which took place by itself when the cooling was stopped. In order to prevent contamination with air and humidity a slow nitrogen purge was used. After the ammonia had been removed, the solid material was carefully transferred in to a closed vessel. By this method sodium can be nearly homogeneously dispersed on zeolite. Example 8 Preparation of the Na/vap/NaY catalyst In the upper part of a reactor composed of two parts 10 g NaY zeolite was pretreated in vacuum at 500°C. 3 g of sodium was put onto a glass filter in the lower part of the reactor. After the pretreatment of the zeolite had been made the heater of the lower part was set at 700 C and nitrogen was pumped through. The flow rate of the nitrogen was 1 ml/min so that the oven would not cool rapidly. The sodium evaporated slowly and the vapour went trough the zeolite layer. After some time a mirror of solidified sodium appeared on the walls of the cold pipes. This was considered to represent the time when one half had gone through. When this treatment was continued for five times as long a grayish colour appeared and the treatment was finished. The product made in this way was stored in a dry desiccator under vacuum. Example 9 Preparation of the Na naph NaY catalyst Absolute tetrahydrofurane was made by drying with NaA zeolite and distilling it from sodium in an argon phase. Finally the tetrahydrofurane treated in this way was distilled from ketene in an argon phase and the product was used immediately. In order to make the catalyst the following steps were done under dry conditions. 10 g of naphthalene dried in a desiccator was dissolved in the absolute tetrahydrofurane mentioned above. 2 g of purified elementary sodium was transferred to a bottle containing the naphthalene solution. After some time a blue colour was formed. In this stage 10 g of NaY zeolite, which had been pretreated in vacuum at 500°C, was poured into the solution. The solvent was evaporated and the solid material obtained was protected from contamination with air or humidity. Example 10 Alkyiation in a continuous reactor The reaction between p-xylene and l-butene was performed in a medium pressure continuous reactor at a temperature of 100-350°C and a pressure of 1-10 bar, most preferably 3-8 bar. The volume flow rates of the reactants were between 1500- 4000h " 1 , most preferably 1000-2000h " ] , for l-butene and 3000-3500h _ 1 for p- xylene. In most experiments l-butene and p-xylene were fed at a rate of 2000 and 3000h " . The results are presented as a summary in the table below. Temperature [°C] Catalyst Yield [%] l-(2-Methyl-butyl) n-Pentyltoluene 4-methyl-benzene 150 Na/gran/NaY 0.12 0.45 200 Na/gran/NaY 0.34 0.73 250 Na/gran/NaY 0.56 0.98 300 Na/gran/NaY 0.23 0.78 150 HT/Si0 2 0.04 0.15 100 CsOH/CsX 0.12 0.62 150 CsOH/CsX 0.15 0.55 200 CsOH/CsX 0.10 0.62 250 CsOH/CsX 0.12 0.60 300 CsOH/CsX 0.15 0.55 100 CsOH/CsY 0.35 0.85 200 CsOH/CsY 0.45 0.80 300 CsOH/CsY 0.25 0.55 Example 11 Alkyiation in a Berty-reactor The reaction between p-xylene and 1 -butene was performed in a Berty-type reactor, in which a longer contact time can be used. The volume flow rate of l-butene was 100-300h " most preferably 200-250h " and the volume flow rate of p-xylene was 300-500h " , most preferably 450-500h " . The pressure was kept between 1-3 bar. The results are presented in the table below. Temperature [°C] Catalyst Yield [%] l-(2-Methyl-butyl)- n-Pentyltoluene 4-methyl-benzene 200 Na/gran/NaX 0.21 2.35 250 Na/gran/NaX 0.23 2.80 300 Na/gran/NaX 0.49 3.92 350 Na/gran/NaX 0.53 3.67 100 Na/gran/NaY 0.12 0.44 150 Na/gran/NaY 0.45 0.98 200 Na/gran/NaY 0.58 1.32 250 Na/gran/NaY 0.33 1.45 300 Na/gran/NaY 0.34 1.34 250 Na/gran/NaY 0.82 1.13 250 Na/amm/NaY 0.75 1.18 250 Na/naph/THF/NaY 0.59 0.88 150 HT/Si0 2 0.16 0.53 250 HT/Si0 2 0.04 0.15 150 HT/AI9O3 0.07 0.16 250 HT/A1 2 0 3 0.08 0.31 150 CsOH/CsX 0.35 0.91 250 CsOH/CsX 0.33 0.98 150 CsOH/CsY 0.15 1.12 250 CsOH/CsY 0.22 1.25 The best results were obtained for the NaN3/gran/NaX catalyst at 300 C. In this case the life time of the catalyst was 3 h, after which the catalyst was poisoned by the humidity. It must be noted that water decreases the life time of the catalyst considerably so that water free chemicals for instance must necessarily be used.

Claims: Claims 1. Process for preparing l-(2-methylbutyl)-4-methylbenzene, in which process p- xylene is alkylated with l-butene using a basic catalyst, wherein the catalyst is a selective heterogeneous catalyst, which catalyst is a zeolite impregnated with alkali metal, a supported hydrotalcite or a supported CsOH. 2. Process according to claim 1, wherein the reaction is carried out at a tempera¬ ture of 100-350°C and a pressure of 1-3 bar. 3. Process according to claim 1 or 2, wherein the catalyst is a zeolite impregnated with an alkali metal. 4. Process according to claim 3, wherein the catalyst is a zeolite impregnated with sodium. 5. Process according to claim 3 or 4, wherein the zeolite is X or Y faujasite. 6. Process according to any of claims 3-5, wherein the catalyst is prepared by impregnating a zeolite with sodium azide and after that heating it at 450°C. 7. Process according to any of claims 3-5, wherein the reaction is carried out at a temperature of 150-35O°C. 8. Process according to claim 1 or 2, wherein the catalyst is a supported hydrotalcite or a supported CsOH. 9. Process according to claim 8, wherein the reaction is carried out at a tempera¬ ture of 100-300°C. 10. Process according to claim 8 or 9, wherein the catalyst support is Si0 2 , AI2O3 or a zeolite.

Inventors: CSICSERY SIGMUND M, KIRICSI IMRE, KOSKIMIES SALME, CSICSERY, SIGMUND, M., KIRICSI, IMRE, KOSKIMIES, SALME
Applicants: CSICSERY SIGMUND M, KIRICSI IMRE, KOSKIMIES SALME, OPTATECH OY, CSICSERY, SIGMUND, M., KIRICSI, IMRE, KOSKIMIES, SALME
Application year: 1996
Main classification: C07C2
IPC codes: B01J21, B01J29, C07B61, C07C2, C07C15