PROCESS FOR SELECTIVELY ALKYLATING BIPHENYL

Abstract: The para-isomer of an alkylbiphenyl is selectively synthesised by the alkylation of biphenyl with propylene or butene employing, as a catalyst, a zeolite having a molar ratio of SiO₂:Al₂O₃ of not less than 10.

Description: The present invention relates to a process for producing a p-monoalkylbiphenyl and a p,p'-dialkylbiphenyl. Many aromatic alkyl compounds are useful in various fields, and those having a substituent at a para-position are especially important. Among such compounds are para-isopropylbiphenyl, which is useful as a solvent for a dye for pressure-sensitive recording paper, and 4,4'-di-isopropylbiphenyl, which is convertible to 4,4'-biphenyl dicarboxylic acid or 4,4'-dihydroxybiphenyl by oxidation of its side chains. As a process for producing an alkylbiphenyl, (1) a method of reacting biphenyl with an olefin or an alkyl halide in the presence of a Friedel-Crafts catalyst such as aluminum chloride and (2) a method of reacting biphenyl with an olefin or an alcohol by using a solid acid catalyst such as silica alumina and zeolite are known. These methods, however, have a low selectivity for para-isomers. JP-A-56-156,222 (1981) discloses a method of producing an alkylbiphenyl which is rich in meta- and para-isomers by reacting biphenyl with an olefin while applying silica alumina or zeolite as a catalyst. However, the ratio of para-isomer to meta-isomer in the alkylbiphenyl obtained by this method is not always high enough. This reference does not disclose any process for producing a 4,4'-dialkyl compound. The following methods are known as a process for producing 4,4'-dialkylbiphenyl: (1) Synthesis,(11)822,(1978) A method of reacting the iodonium salt of diaryl with CH₃MgS in the presence of NiCl₂ as a catalyst. Since the raw material is difficult to obtain, this method cannot be industrially practicable. (2) Japanese Patent Publication No.47-10,705(1972), US Patent 3,539,622. A method of producing 4,4'-dialkylbiphenyl from an aromatic mercury compound using CuCl₂, PdCl₂ or LiCl as a catalyst. This reference also discloses a process for producing p,p,-bicumyl (4,4'-di-isopropylbiphenyl). However, a method using a mercury compound is unfavorable in view of influence on a human body. (3) Azerb.Khim.Zh(1)21-6(1971). A method of producing dialkylbiphenyl by reacting an aromatic halide with metallic sodium is described. This method, however, includes many side reactions such as dehalogenation etc., and the yield of the aimed product is rather low. The use of metallic sodium cannot be an industrial method. On the other hand, many patents have been presented mainly by Mobil Oil for a process about selective alkylation of an aromatic group by using zeolite. Many of these patents are directed to producing a p-dialkylbenzene and no process to produce an alkylbiphenyl is found except one disclosed in the above Japanese Patent Application Laid-Open (KOKAI)NO.56-156,222(1981). Biphenyl derivatives having a substituent at a para-position includes not only p-phenylphenol, 4,4'-dihydroxybiphenyl, which are already under commercial production, but also many useful derivatives such as p-isopropylbiphenyl, p-isopropenylbiphenyl and 4,4'-biphenyl dicarboxylic acid. However, processes for producing these derivatives have not reached a sufficient level, and development of an economical process has been desired. The present invention provides a process for the preparation of a p-monoalkylbiphenyl and a p,p'-dialkylbiphenyl which process comprises alkylating biphenyl with propylene or butene at a temperature of from 200°C to 320°C until not more than 49.4 mol % biphenyl remains unalkylated using a Mordenite type zeolite catalyst having a molar ratio of SiO₂:Al₂O₃ of not less than 10.2:1. It is thus possible to provide a process for producing, with good selectivity, a p-monoalkylbiphenyl and a p,p'-dialkylbiphenyl. An alkylation process for selectively obtaining a p-monoalkylbiphenyl and a p,p'-dialkylbiphenyl from propylene or butene can be provided by applying, as a catalyst, a zeolite in which the molar ratio of SiO₂ to Al₂O₃ is not less than 10.2:1. An alkylation process for selectively obtaining a para isomer of an alkylbiphenyl by using a Mordenite type zeolite as a catalyst is therefore possible. A zeolite in which the ions are exchanged with H⁺ is preferable because of its strong activity, but it is not necessary that the ions are completely exchanged by H⁺. However, zeolites substituted largely, for instance, by NH4⁺ or alkali metals are impractical because of their low activity. Among silica alumina catalysts other than a zeolite, there are some which have an excellent alkylation activity, but they have a low selectivity for para-isomers. Y-, L- and A-type zeolites, in other words zeolites having the molar ratio of SiO₂ to Al₂O₃ is less than 10:1, do not exhibit good selectivity for para-isomers, either. Since the isomer selectivity of these zeolites is poor, they are unsuitable as a catalyst for achieving the object of the present invention. The molar ratio of SiO₂ to Al₂O₃ of the zeolite catalyst for the present invention is not less than 10.2:1. However, when this ratio is too large, the reaction activity itself is apt to become lower, so that the ratio is preferably not to be more than 50:1. The preferred molar ratio of SiO₂:Al₂O₃ is from 10.2:1 to 50:1 as a consequence. A suitable molar ratio of SiO₂:Al₂O₃ is 19.0:1. The preferable molar ratio of an olefin to biphenyl in the raw materials is generally 0.5:1 to 2.2:1. The molar ratio is appropriately determined depending upon whether the intended product is a monoalkylated compound, dialkylated compound or both of them. However, when the molar ratio of the olefin to biphenyl is less than 0.5:1, the amount of unreacted biphenyl becomes impractically large. On the other hand, if the molar ratio is 2.2:1 or more, an unnecessarily large amount of trialkylated compound is unfavourably produced. When the alkylation is conducted with propylene, the para-isopropylbiphenyl thus produced or the 4,4'-di-isopropylbiphenyl thus produced can be recovered. When the alkylation is conducted with butene, the para-sec-butylbiphenyl thus produced or the 4,4'-di-sec-butylbiphenyl thus produced can be recovered. The reaction temperature is 200 to 320°C, preferably 220 to 300°C. The temperature is determined within this range depending on the activity of the catalyst and the degree of reaction (alkylation degree). The alkylation degree is obtained from the following formula, wherein each component of the reaction mixture is expressed by molar fraction: Alkylation degree = (monoalkylated compound) + [2 x (dialkylated compound)] + [3 x (trialkylated compound)] + [4 x (tetra-alkylated compound)] When the reaction temperature is lower than 200°C, the reaction rate is impractically low, while the reaction temperature higher than 320°C unfavorably brings about the production of heavy compound, which lead to deterioration of the catalyst and increases the by-products due to decomposition alkylation reactions. The para-alkylbiphenyl produced by the process according to the present invention can be separated from other products and purified by conventional distillation and/or crystallization. Other by-products, for example, a meta-alkylbiphenyl is convertible to a para-alkylbiphenyl by a known trans-alkylation method or the like. The para-alkylbiphenyl obtained, which is useful by itself, can be converted to another useful para-substituted biphenyl by oxidizing side chains. Example 1 Into an 1 liter autoclave made of stainless steel, 616 g of biphenyl and 30 g of TSZ-640 HOA (Mordenite type zeolite produced by Toyo Soda Co., Ltd., molar ratio of SiO₂ to Al₂O₃ is 19.0) were charged, and the temperature was raised to about 250°C. Propylene was supplied under stirring while maintaining the pressure at 1 kg/cm²G, thereby bringing the mixture into reaction at 250°C for 5 hours. The composition of reaction product and other data are shown in Table 1. Example 2 The reaction was carried out at 250°C for 3 hours by using TSZ-640 HOA in the same way as in Example 1. The results are shown in Table 1. Example 3 The reaction was carried out at 270°C for 15 hours by using TSZ-640 HOA in the same way as in Example 1. The results are shown in Table 1. Example 4 The reaction was carried out at 200°C for 5 hours in the same way as in Example 1 except that 60 g of TSZ-640 HOA was used as the catalyst. The results are shown in Table 1. Example 5 The propylation reaction was carried out at 230°C for 15 hours in the same way as in Example 1 except that 30 g of TSZ-600 HOA (Mordenite type zeolite produced by Toyo Soda Co., Ltd., molar ratio of SiO₂/to Al₂O₃ is 10.2) was used as the catalyst. The results are shown in Table 1. The alkyl biphenyls were analyzed by gas chromatography. The operating conditions were as follows: Column: SUS Golay column (0.25 mmΦ x 45 m) Temperature: 150°C Carrier gas: helium Detector: FID The selectivity for the para-isomer was calculated with the following formula by using the analyzed values of the reaction mixture (containing unreacted biphenyl): wherein MIPB represents monoisopropylbiphenyl, and DIPB di-isopropylbiphenyl. Comparative Example 1; Reaction using a silica alumina catalyst: The propylation reaction was carried out at 240°C for 2 hours in the same way as in Example 1 except that 60 g of silica alumina X-630 HN (produced by Nikki Chemical Co., Ltd., containing 27% of Al₂O₃) was used as the catalyst. The results are shown in Table 2. Comparative Example 2; Reaction using a Y-type zeolite: The propylation reaction was carried out at 200°C for 2 hours in the same way as in Example 1 except that 30 g of Y-type zeolite TSZ-330 HUA (produced by Toyo Soda Co., Ltd., molar ratio of SiO₂/to Al₂O₃ is 6) was used as the catalyst. The results are shown in Table 2. Comparative Example 3; Reaction using an L-type zeolite: The propylation reaction was carried out at 200°C for 1 hour in the same way as in Example 1 except that 30 g of L-type zeolite TSZ-500 HOA (produced by Toyo Soda Co., Ltd., molar ratio of SiO₂ to Al₂O₃ is 6) was used as the catalyst. The results are shown in Table 2. Example 6; Butylation reaction: Butylation reaction was carried out at 260°C for 4 hours by using 2-butene in place of propylene and 30 g of TSZ-640 HOA as the catalyst in the same way as in Example 1. The composition of the reaction product and other data are shown in Table 3. Example 7; Butylation reaction: The butylation reaction was carried for 6 hours in the same way as in Example 6 except for using 60 g of TSZ-640 HOA. The composition of the reaction product and other date are shown in Table 3.

Claims: A process for the preparation of a p-monoalkylbiphenyl and a p,p'-dialkylbiphenyl which process comprises alkylating biphenyl with propylene or butene at a temperature of from 200°C to 320°C until not more than 49.4 mol % biphenyl remains unalkylated using a Mordenite type zeolite catalyst having a molar ratio of SiO₂:Al₂O₃ of not less than 10.2:1. A process according to claim 1, wherein the starting molar ratio of olefin:biphenyl is from 0.5:1 to 2.2:1. A process according to claim 1 or 2, wherein said molar ratio of SiO₂:Al₂O₃ is from 10.2:1 to 50:1. A process according to any one of the preceding claims, wherein said molar ratio of SiO₂:Al₂O₃ is 19.0:1. A process according to any one of the preceding claims, wherein the alkylation is conducted with propylene and the para-isopropylbiphenyl thus produced is recovered. A process according to any one of claims 1 to 4, wherein the alkylation is conducted with propylene and the 4,4'-di-isopropylbiphenyl thus produced is recovered. A process according to any one of claims 1 to 4, wherein the alkylation is conducted with butene and the para-sec-butylbiphenyl thus produced is recovered. A process according to any one of claims 1 to 4, wherein the alkylation is conducted with butene and the 4,4'-di-sec-butylbiphenyl thus produced is recovered.

Inventors: HOSHI, SHOUICHI, NAKAMURA, TADASHI, OKADA, YOSHIO
Applicants: KUREHA KAGAKU KOGYO KABUSHIKI KAISHA
Application year: 1988
Main classification: C07C15
IPC codes: B01J29, C07B61, C07C2, C07C1, C07C67, C07C15