磷钼酸催化下甲苯的区域选择性硝化

为解决硝硫混酸硝化生产对硝基甲苯过程中,因甲苯硝化的低选择性和大量废酸对环境的危害,研究了磷钼酸对甲苯硝化反应的催化活性。通过气相色谱,研究了催化剂用量、硝化反应时间、硝化反应温度、催化剂的重复使用等因素对甲苯硝酸硝化区域选择性的影响。结果表明,在醋酐存在条件下,以CCl4为溶剂,以质量分数为95%的硝酸为硝化剂,反应温度控制在50℃,反应进行60 min,0.8 g经400℃焙烧1.5 h后的磷钼酸为催化剂,对甲苯表现出了强的区域选择性,甲苯硝化产物邻对位摩尔比达0.88,较硝硫混酸的1.67显著降低,产物得率达82.5%。该催化剂可循环使用5次,催化活性变化很小。

Regioselective Nitration of Toluene with Nitric Acid in the Presence of Phosphomolybdic Acid Catalysts

Catalytic activities of phosphomolybdic acid for regioselective nitration of toluene to synthesize p-nitrotoluene were investigated with the aid of gas chromatography.The results showed that,when the nitration temperature was controlled at 50 ℃ and the reaction time was 60 min,nitration of toluene by using 95% nitric acid as nitrating agent in the presence of acetic anhydride and 0.8 g phosphomolybdic acid catalyst(calcinated at 400 ℃ for 1.5 h) showed high regioselectivity,formed mononitrotoluene with ortho-para isomer mol ratio of 0.88,far below 1.67 by using mixed nitric and sulfuric acids,and gave a yield of 82.5%.The catalyst could be reutilized up to five times with little decrease in activity.