アミン被毒SiO₂-Al₂O₃触媒によるキシレンの選択メチル化

抄録

Xylenes were methylated with methanol on base-modified SiO₂-Al₂O₃ catalyst at 250° by the use of a gas-phase heterogeneous flow method. On commercially obtained SiO₂-Al₂O₃ trimethylbenzenes reached equillibrium composition at the reaction temperature among pseudocumene, hemimellitene, and mesitylene. In contrast, on ethylenediamine-modified SiO₂-al₂O₃, mesitylene was not observed in the methylation products. Pseudocumene and hemimellitene produced from ο-and m-xylene were in a molar ratio of 6 : 4, and pseudocumene was obtained exclusively from p-xylene. The selectivity on these catalysts was examined by acidic properties of the catalyst and the distribution of trimethylbenzene isomers. The acid site of H₀≤0.8 disappeared from the NH₃-modified catalyst which showed selective methylation.