Catalytic Oxidative Dehydrogenation of Butane and/or Butene to produce 1,3-Butadiene

Abstract

Commercial availability and low price of light alkane/alkenes make them very attractive in many branches of industry. Potentially interesting is their use in the process of oxidative dehydrogenation leading to production of dienes. In particular Oxidative dehydrogenation of n-butene has attracted much attention as a promising process for on-purpose 1,3-butadiene production. This study was undertaken to carry out oxidative dehydrogenation of butane/butenes to 1,3-butadiene (important substrate in production of synthetic rubber and polyamides) taking place over the zinc-ferrite catalysts prepared by co-precipitation method. A series of zinc ferrite (ZnFe2O4) catalysts was prepared by a co-precipitation method and applied to the oxidative dehydrogenation of 1-butene to 1,3-butadiene. Different parameters were studied for the synthesis of zinc ferrite catalyst like Fe:Zn atomic ratio, e ect of pH in the preparation, crystallinity, surface acidity, washing of the precipitate. NH3-TPD experiments were conducted to correlate the acid property with the catalytic performance of zinc ferrite catalysts. The acid property of zinc ferrite catalyst plays an important role in abstracting an a-hydrogen atom from n-butene to form P-allyl intermediate. It was revealed that the yield for 1,3-butadiene increased with increasing surface acidity of the catalyst. Selective partial oxidation including the oxidative dehydrogenation of n-butene proceeds by Mars-Van Krevelen Redox mechanism. It was observed that the catalytic activity is signi cantly dependent upon not only on the crystallinity but also the composition of ferrite catalyst. If crystallinity of a catalyst is too high, the oxygen spill over through the lattice is severely suppressed and the redox mechanism is no longer e ective and results in low catalytic activity. Solid state studies using X-ray di raction and FT-IR spectroscopy indicated that the zinc ferrite phase was formed on the synthesized catalyst. Catalyst Testing Unit was developed to test the activity of the synthesized catalyst. Catalytic test were performed in a continuous xed bed catalytic reactor at temperatures around 350-650°C. It was revealed that at low reaction temperatures, around 300 to 370°C conversion of n-butene and selectivity for 1,3-butadiene was low. Selectivity for 1,3-butadiene was high at temperatures around 400-480°C. At very high temperatures around 500-600°C side reactions were maximum. Among the various catalyst prepared, ZnFe2O4 prepared at pH 9 (binded with alumina) showed the best catalytic performance in the oxidative dehydrogenation of 1-butene with 70% conversion of 1-butene and 90% selectivity for 1,3-butadiene.