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.