甲苯甲醇侧链烷基化反应中甲酸盐的形成及其作用

将碱金属碳酸盐修饰的KX和NaY沸石用于催化甲苯甲醇侧链烷基化反应,并结合甲醇吸附的红外光谱以及异丙醇和甲醇催化分解反应结果,剖析了甲酸盐的形成及其作用.结果表明,碱金属碳酸盐的负载能提高碱金属离子交换八面沸石的催化活性.在反应过程中催化剂表面形成了不同数量的甲酸盐,尤其是K2CO3修饰的KX上;甲酸盐主要来源于碳酸盐与甲醇分解产物甲醛的反应,它的形成对催化剂甲苯甲醇侧链烷基化活性的影响较大,类似于碱金属硼酸盐的修饰,改善了催化剂的表面酸碱性,形成了更为有效的活性中心.

Formation and Function of Formate in the Side-Chain Alkylation of Toluene with Methanol

KX and NaY zeolites were promoted with alkali carbonates and used in the side-chain alkylation of toluene with methanol.The formation and function of formate were investigated by the infrared spectra of methanol adsorbed on the samples and the catalytic decomposition of isopropanol and methanol.Loading alkali carbonates could improve the catalytic performance of alkali-exchanged faujasite zeolites.During the side-chain alkylation process,various amounts of formate were formed on the surface of the catalysts,especially for K2CO3 promoted KX.These formate species derived from the reaction of carbonates with formaldehyde,the dehydrogenation product of methanol.The formation of formate was closely related to the activity of catalysts in the side-chain alkylation of toluene with methanol.Similar to the promotion of alkali borate,the surface acid/base property of the catalysts was modified by these formate species,and thus generated more effective active sites.