The Study Of Catalyst For Selective Synthesis Of Acrylonitrile From Acetonitrile And Methanol

Acrylonitrile is one of the most important chemicals in chemical industries, especially in polymer industries . Generally, it is synthesized by the ammoxidation of propylene over multicomponent bismuth molybdate catalysts . The main by-product during the production of acrylonitrile is acetonitrile. Although acetonitrile can be used as a solvent, more of it is burned because the worldwide demand is much lower than the supply. Hence, the use of acetonitrile for the production of more valuable chemicals and products will be a very important technological achievement.Through adding a carbon atom at the α-position, acetonitrile can be transformed to acrylonitrile which is used far-rangingly. Formaldehyde, methanol and methane have been utilized as methylating agents. 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.The M (M=Mn, Cr, Fe) supported on BaCO₃ catalysts were prepared by impregnation of BaCO3 with an aqueous solution of Mn(NO₃)₂ and Cr(NO₃)₃, and their catalytic performance for the synthesisof acrylonitrile from acetonitrile and methanol was studied. As a result, the performance of the Mn/BaC03 catalyst is better than the others, and the optimum temperature for the catalyst for the conversion of acetonitrile and selectivity to acrylonitrile appeared at 400 °C. At this temperature, the selectivity of acrylonitrile is 92.7% and the conversion of acetonitrile is 19.9%. The NH3-TPD and CO2-TPD results indicate that the activity of the catalysts is close contact with the surface acid sites and basic sites of the catalysts. After the addition of CeC>2 or KC1 , the surface acid sites and basic sites of the catalysts decreased as well as the activity of the catalysts.Due to the molding of BaCO3 powder is more difficult than the support SiO2 during the preparation, a series of Mn-Mg/SiO2 catalysts with different Mn or Mg loadings were prepared by an impregnation method. The phase and the surface acidity and basicity of catalysts were investigated by using of XRD, Raman and TPD techniques. The presence of Mn enhanced the distribution of MgO on the surface of SiC>2. The strong basicity of the catalysts is contributed to the synthesis of acrylonitrile from acetonitrile and methanol. As a result, the effect of the Mno.8-Mgo.2/Si02 catalyst was better than any other catalysts in this experiment, and the selectivity to acrylonitrile was 88.6%, the conversion of acetonitrile was 31.5% at 480 °C.According to the studies of the texture and structural property of the...