Condensation of 1, 2, 4-Trimethylbenzene with Acetaldehyde and Catalytic Cracking of Condensation Products

Abstract

The condensation of C₉ aromatic hydrocarbons (C₉) with CH₃CHO in the presence of H₂SO₄ and the catalytic cracking of the condensation products over a SiO₂-Al₂O₃ catalyst were investigated. The isomer distribution of 1, 1-diarylethanes (DAE), the condensates formed, were measured. DAE formed from n- and i-PB (Abbreviation of each C₉ isomer is noted in Table 1), and 1, 3, 5- and 1, 2, 4-TMB consisted of a single isomer, while three DAE isomers were formed from o-, m-, and p-ET, 1, 2, 3-TMB, and indane, respectively. The reactivity of C₉ in the condensation was expressed in the increasing order as follows: 1, 2, 4-TMB>1, 2, 3-TMB>m-ET>indane>1, 3, 5-TMB>o-ET>p-ET>i-PB>n-PB.
When C₉ reformate was used as an aromatic feed, the concentrations of n-PB and ET in unchanged C₉ increased 1.5 times after the condensation reaction, and the concentration of 1, 2, 4-TMB in C₉ obtained by the catalytic cracking of DAE increased 2 times.
About 80% of 2, 4, 5-TMPE (1, 1-bis (2, 4, 5-trimethylphenyl) ethane) formed from 1, 2, 4-TMB was obtained by chilling the crude condensation products. About 90% of alkylstyrenes obtained by the catalytic cracking of the condensate were composed of o-substituted isomers.