催化氨氧化法制备2-氰基吡嗪的研究

开发了一种由VMoOP四元素组成的氨氧化催化剂(V-II型)，用该催化剂在固定床反应器内由2-甲基吡嗪为原料进行气固相接触氨氧化反应制备了2-氰基吡嗪。V-II型催化剂组分中矾、磷的比例是影响催化剂反应活性及选择性的主要因素，矾磷比为1．9时，催化活性最好。探讨了氨氧化反应机理，认为2-甲基吡嗪经过氧化、脱水分别生成了吡嗪羧酸和吡嗪酰胺中间体后最终生成2-氰基吡嗪。正交实验确定了反应的影响因素和最佳条件，结果表明：反应温度是影响产品收率的最主要因素，当2-甲基吡嗪、氨气、空气的投料量分别为0．05mL．min-1，200mL．min-1,1000mL．min-1，反应温度430℃时，2-氰基吡嗪选择性大于90％，单程收率大于87％，产品纯度大于99％。按小试工艺条件放大l00倍中试，结果与小试吻合。

Synthesis of 2-Cyanopyrazine by Catalytic Ammoxidation

A new V-II ammoxidation catalyst comprising VMoOP four elements was developed. 2-cyanopyrazine was prepared from 2-methylpyrazine with above catalyst by vapor phase catalytic ammoxidation in a fixed-bed reactor. The ratio of V to P in the catalyst is the main factor influencing the catalytic activity. When the ratio is 1.9, the activity is the highest. The ammoxidation mechanism was also studied. It could be seen that 2-methylpyrazine was oxidated and dehydrated to form intermediates pyrazinyl carboxylic acid and pyrazinamide, which then changed into 2-cyanopyrazine. The factors influencing the reaction and the optimized condition were determined by orthogonal experiments. Results show that the reaction temperature is the key factor influencing the product yield. When the flow rates of 2- methylpyrazine, ammonia and air are 0.05mLmin -1, 200mLmin -1 and 1000mLmin -1, respectively, and the temperature in 430C, the 2-cyanopyrazine yield is 87%, and its purity is above 99%. A pilot-scale production was carried out, which scaled-up the laboratory-scale one hundred fold. The result of the pilot-scale production was in accordance with that of the laboratorial experiments.