Propane Ammoxidation to Acrylonitrile over Vanadia-Based Xerogel/Aerogel Catalysts
Dong Jin Suh1, Jinsoon Choi2, and Chee Burm Shin2. (1) Clean Technology Research Center, Korea Institute of Science and Technology, P,O.Box 131, Cheongryang, Seoul, 136-791, South Korea, (2) Department of Chemical Engineering, Ajou University, San5, Wonchon, Paldal, Suwon, 442-749, South Korea
Vanadia-based xerogels/aerogels were prepared by modified sol-gel methods using either alkoxide or non-alkoxide precursors and studied as catalysts for propane ammoxidation to acrylonitrile. The cogelation of an appropriate vanadium precursor with aluminum, titanium, niobium, silicon, or zirconium precursors led to highly dispersed composite catalysts. For vanadia-alumina aerogels, XRD peaks corresponding to bulk V2O5 did not appear up to 40 wt.% vanadia content. Catalytic reactions were carried out in a fixed-bed flow reactor with a stoichiometric ratio (1:1:2) of propane, ammonia, and oxygen and in a temperature range of 673-833 K. Interactions between vanadia and supports or the electron density of desorption sites accounted for the product selectivities to acetonitrile (paraffin), propylene (olefin), and acrylonitrile (olefin). Among 10 wt.% vanadia-loaded aerogels, vanadia-niobia aerogels showed the highest acrylonitrile/acetonitrile ratio and acrylonitrile yield, while 15 wt% vanadia-alumina xerogel exhibited the highest acrylonitrile yield of 20 %. Yields and selectivities were also affected by the kinds of vanadium precursor and the antimony addition as well as reactant ratio.