Catalytic Reaction of 1, 2, 4-Trimethylbenzene with Formaldehyde in Vapor Phase

Abstract

For the preparation of 1, 2, 4, 5-tetramethylbenzene (1, 2, 4, 5-TeMB) by the one step process, the catalytic reaction of 1, 2, 4-trimethylbenzene (1, 2, 4-TMB) with formaldehyde in the presence of hydrogen was studied under the vapor phase at atmospheric pressure.
Among catalysts examined, phosphotungstic acid-SiO₂, NiO-MoO₃-Al₂O₃ and CoO-MoO₃-Al₂O₃ were relatively active. Especially in the catalytic reaction by CoO-MoO₃-Al₂O₃ undesirable reactions such as isomerization, demethylation and disproportionation took place only to a small extent.
Optimum conditions with the CoO-MoO₃-Al₂O₃ catalyst were; reaction temperature 350°C, molar ratio 1, 2, 4-TMB/HCHO; 5, H₂/1, 2, 4-TMB; 1-2, and contact time 0.9sec. Under these conditions, the yield of TeMB's was 10.5% and the purity of 1, 2, 4, 5-TeMB in TeMB's was 80%.
It is considered that TeMB's were formed chiefly by the hydrogenolysis of trimethylbenzylalcohols which are the intermediate products of 1, 2, 4-TMB with formaldehyde.