三氯化铝-金属氯化物复合物催化苯的甲基化反应

METHYLATION OF BENZENE WITH METHANE CATALYZED BY ALUMINUM CHLORIDE-METAL CHLORIDE COMPLEXES

1.前言 苯与甲烷通常是惰性很强的物质,尤其是在苯与甲烷之间,一般不容易发生化学反应。Olah曾报导,以HF-SbF3为催化剂,苯可与甲烷直接发生甲基化反应而生成甲苯。但甲苯的收率仅为0.1％,且催化剂本身也有强烈的腐蚀性。Loffler等人以Ni/SiO2为催化剂,在300℃下发现甲烷可与苯反应,但甲苯收率也只有约7％。 最近我们发现,无水三氯化铝及某些金属氯化物以适当的方式处理后所得到的复合物,可有效地催化苯与甲烷的反应,主要产物有甲苯和二甲苯等。实验结果表明。

It was found that benzene and methane, catalyzed by aluminum chloride-metal chloride complexes, could undergo chemical reaction giving methylation products of benzene. Products of lower molecular weight, analyzed by gas chromatography and mass spectrometry, are mainly composed of toluene and xylene. It was found that the order of catalytic activity of these complexes for the methylation of benzene could be described as: AlCl3-CoCl2>AlCl3-CuCl2>AlCl3-NiCl2>AlCl3-FeCl2>AlCl3-CuCl Such reaction conditions, as reaction time, temperature, were also considered in the study. It was shown that the yields of toluene and xylene, the main methylation products in the process, increased with increasing reaction temperature and time. For example, when A1C13-CoCl2 was used, yield of toluene increased from 3 % to 30% with increasing temperature from 100℃ to 250℃ under methane 4 MPa after 12 h. At the same time, the change for xylene is from 5% to 30%. The yield of toluene obtained in this way is much higher than that of reported in the literature for the same reaction. However, the yield tends to decrease if reaction temperature is too high and time is too long, because these condions are in favour of some side reactions. There is a slight difference between the tendency of yield curves of toluene and xylene. This indicated that some more complex reactions took place in the process.