GB628686A - Production of butadiene - Google Patents

Abstract

2 (iii) Butadiene is produced by catalytically de hydrogenating n-butane to n-butene and buta diene in a first reaction zone, the yield of buta diene being about 10-30 per cent by volume of the n-butane, separating n-butene from the products, catalytically dehydrogenating it to butadiene in a second reaction zone, and recovering butadiene formed in both zones. Catalysts such as Cr, V or Mo oxide on alumina, desirably with Mg or Zn oxide, are suitable. For the second stage, alumina with minor amounts of Ba and K oxides or magnesia with minor amounts of Fe, Cu, and K oxides are effective, especially when steam is added to the charge. Temperatures of 565-675 DEG C., abso lute pressures of 0.05-0.5 atmos., and space velocities of 200-1000 vols./vol./hour in the first stage, or 200-2000 in the second, are suitable. Products of the first stage pass to a separation zone where light gases, butenes, and butadiene are separated from unconverted butane as by fractionation, solvent extraction and azeotropic distillation. Butane is re cycled, butenes passed to the second dehydro genation zone, and butadiene, together with that formed in said second zone, collected. Steam may be added to the second zone to give a total pressure of 0.25-3.5 atmos. above atmospheric. If the original charge is olefinic, it may be introduced into the separation zone. Iso-hydrocarbons formed are separated in this zone and removed. Fluid, fixed or moving catalyst type of operation may be used, and carbon deposits burnt off as necessary. p