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Dehydrocyclodimerization of conjugated dienes catalyzed by solid bases

1990; Science Press; Volume: 63; Issue: 3 Linguagem: Inglês

10.1016/0304-5102(90)85129-6

1873-3131

Hiroyasu Suzuka, Hideshi Hattori,

Carbon dioxide utilization in catalysis

1,3-Butadiene and 2-methyl-1,3-butadiene undergo dehydrocyclodimerization to form aromatics over solid base catalysts such as ZrO2, MgO, CaO, SrO, La2O3, and Nd2O3 below 473 K. Among the catalysts examined, ZrO2 exhibited the highest activity. In the reaction of 1,3-butadiene, the main products were ethylbenzene, o- and p-xylenes. Over MgO catalyst, o-xylene was most selectively formed, while over the other catalysts ethylbenzene was selectively formed. In the reaction of 2-methyl-1,3-butadiene, which is more reactive than 1,3-butadiene, the main products were m- and p-cymenes. Over MgO and CaO catalysts, m-cytnene was predominant, while over ZrO2 catalyst, p-cymene was primarily formed. On the basis of product distributions and poisoning experiments with carbon dioxide, water, pyridine and ammonia, it is suggested that basic sites on the catalysts participate in the reaction, and the reaction mechanisms are discussed. Over MgO, it is proposed that the main reaction involves anionic intermediates for dehydrocyclodimerization of both 1,3-butadiene and 2-methyl-1,3-butadiene. Over ZrO2, base-catalyzed Diels-Alder reaction followed by double bond isomerization and dehydrogenation are proposed.