Study On Synthesizing Acetonitrile By Propane Ammoxidation

This paper preliminzrily investigated the catalysts for synthesizing acetonitrile by propane ammoxidation and characterized the catalysts.Firstly industrial production and direct synthesis of acetonitrile were overviewed. The new technology of Synthesizing Acetonitrile by propane ammoxidation was adopted. Its technical key is research and exploitation of catalysts. In order to prepare better catalysts, effects of Mo-V catalyst system and Sb-Nb catalyst system on yield to acetonitrile, selectivity to acetonitrile and propane conversion were investigated,respectively. Mo-V Catalyst system was then selected. Effects of molar ratio of Mo to V and weight ratio of support on catalyst properties were also investigated. Several assisting components were screened and proportions of assisting components were optimized. Composition of the catalysts was determined. The experiments were carried out on a mico-fixed-bed reactor. Effects of temperature, contact time, oxygen to propane ratio and ammonia to propane ratio on catalyst properties were also investigated. The specific surface, pore volume, pore diameter distribution and surface shape of the catalysts were characterized by-using mercury intrusion method and SEM. The results showed that Mo and V were suitable active components and when their molar ratio was 1 to 0.6 and weight ratio of support was 50%, the activity of the catalyst was the highest. The addition of Mg to catalysts improved the activity and selectivity of the catalysts. Molar ratio of primary active component and assisting active component was 1/0.6/0.3. A catalyst was made having the empirical composition, MoV0.6 Mg0.3/r -A12O3.The optimum process conditions were that the reaction temperature was 520℃, the contact time was 1.8s and the molar feed ratios were 1 propane./1.6 oxygen/1.4 ammonia. Under this optimum condition, analysis of the reactor effluent showed that the propane conversion was 42%; yield and selectivity of propane to acetonitrile were 13.1% and 30.9 %, respectively.Characteristic of the catalysts showed that MoV0.6Mg0.3/r -A12O3 was the better catalyst in the experiment, which accorded with the result of the experiment.