Patent ID: 7193121
Filing Date: 2007-03-20
Classification: C07C

Abstract:
1. A process for preparing 4-vinylcyclohexene, which comprises the steps (A) providing an n-butane-containing feed gas stream, (B) feeding the n-butane-containing feed gas stream into at least one dehydrogenation zone and dehydrogenating n-butane to butadiene to give a product stream comprising butadiene, n-butane, possibly 1-butene and 2-butene and possibly water vapor and other secondary constituents, said product stream not containing any significant amounts of acetylenically unsaturated hydrocarbons or allenes, (C) feeding the product stream from dehydrogenation, without prior partial hydrogenation of said product stream, and if appropriate after separating off water vapor and secondary constituents, into a dimerization zone and catalytically dimerizing butadiene to give a product stream comprising 4-vinylcyclohexene, n-butane and possibly 1-butene, 2-butene and unreacted butadiene, and (D) separating off 4-vinylcyclohexene from the product stream from the dimerization and recirculating n-butane and possibly 1-butene, 2-butene and unreacted butadiene to the dehydrogenation zone wherein the dehydrogenation of n-butane to butadiene comprises the steps (B1) feeding oxygen and the n-butane-containing feed gas stream into a first dehydrogenation zone and, in the presence of a dehydrogenation catalyst, nonoxidatively dehydrogenating n-butane to 1-butene, 2-butene and possibly butadiene to give a product gas stream comprising butadiene, n-butane, 1-butene, 2-butene and possibly secondary constituents, (B2) feeding the product gas stream comprising n-butane, 1-butene, 2-butene, possibly butadiene and possibly secondary constituents into a second dehydrogenation zone and oxidatively dehydrogenating 1-butene and 2-butene to butadiene to give a product gas stream comprising butadiene, n-butane, water vapor and possibly secondary constituents, wherein the catalytic, nonoxidative dehydrogenation of n-butane to 1-butene, 2-butene and butadiene is carried out as an autothermal dehydrogenation, and wherein the dehydrogenation catalyst in step (B1), comprises platinum and/or palladium.