Acetonitrile And Methanol Selective Synthesis Of Acrylonitrile In Alkaline Earth Catalyst

As one of the most important basic chemicals in the chemical industries, acrylonitrile (AN) can be used to produce a large variety of everyday products. Today more than 95% of the world's acrylonitrile is produced using the Sohio ammoxidation processs of propylene. Acetonitrile (ACN) is the main by-product during the production of acrylonitrile. Although acetonitrile can be used as a solvent, more of it is burned because the worldwide demand is much lower than the supply. Therefore, how to convert it to other useful chemicals is an efficient way to enhance economic benefit and social benefit.Through adding a carbon atom at the -position, acetonitrile can be transformed to acrylonitrile which is used far-rangingly. Methane, methanol and formaldehyde are good candidates for methylating agent. Because acetonitrile can been synthesized from the reaction of ammonia and syngas, and the latter can made from methane reforming, if the processs of the oxidative methylation of acetonitrile succeeds in the future, then acrylonitrile can been produced from the resource of natural gas which is abundant in our country instead of from the resource of petroleum which is decreasing more and more.Series of X/MgO(X=Fe, Cr, Mn, Ag) catalysts have been prepared and characterized by means of XRD, MOssbauer spectroscopy, TG-DTA, BET, t^-TPR, TPD and Laman spectroscopy. The effect of some factors on the oxidative methylation of acetonitrile to acrylonitrile with methanol over these catalysts have been studied respectively, which includes reaction temperature, reaction time, loading of active component, calcination temperature and time of catalysts. The results j show] the addition of these transition elements except Ag to MgO can improve the catalytic performance greatly.Fe/MgO catalysts prepared by impregnation method show better catalytic performance than Fe/MgO catalysts prepared by precipitation method. As for the series of Fe/MgO catalysts prepared by impregnation method, the optimum condition is 5% of Fe loading and 400 C of reaction temperature with 22.6% of acetonitrile conversion and 81.9% of selectivity to acrylonitrile. XRD and MBssbauer spectroscopy experiments show Fe species finely disperses on the catalyst surface in the form of tiny super-paramagnetic grain of -Fe2O3, and the crystallite size is lower than 10nm. TPR profiles of Fe/MgO have two reduction peaks a, p. The low temperature reduction peak a is attributed to the reduction of Fe2O3 to Fe3O4 and the high temperature reduction peak p is attributed to the reduction of Fe3O4 to Fe. CO2-TPD profiles show more of moderately strong base sites on the catalysts surface are favorable for the reaction.CH3OH-TPD profiles show CHaOH dissociating more easily is one of the reasons for catalytic performance improvement.As to the series of Cr/MgO catalysts, the optimum condition is 0.5~5% of Cr loading, 600"C of calcination temperature and 400 of reaction temperature. It is also found that the introduction of Na or K to Cr/MgO is favorable for the improvement of acetonitrile conversion, but there is a decrease on selectivity to acrylonitrile. The effect of introduction of Na is larger than introduction of K. For the series of Mn/MgO catalysts, when Mn loading is 5%, the catalyst has best catalytic performance at 420'C. Ag/MgO catalysts have low catalytic activity for the reaction. The reason is that inside of Ag atom have stronger metal bonds and cohesion, and chemical valence of Ag is zero, so Ag reacts with MgO weakly and Ag disperses on the surface of MgO difficultly.