Fabrication of Zeolite Beta With Hydrophobic Pore for Synthesis of Lactide From Lactic Acid

Lactide, a key raw material for polylactic acid, is prone to hydrolysis during synthesis from lactic acid using zeolite beta, reducing yield. To address this issue, zeolite beta with hydrophobic pores was synthesized by template-free method with in situ silicon source modification by tetraethoxyfluorosilane (TEFS). The effect of TEFS addition on the morphology, acidity, and wettability of the synthesized zeolite beta was investigated. The modification with F groups increases the total acid amount and the strength of strong acid sites, especially the Brønsted acid sites; simultaneously, the hydrophobicity of pores was also improved. F group–modified zeolite beta achieved a lactide yield of 84%, significantly higher than the 70% yield of unmodified zeolite beta. This enhancement could be attributed to the increase in Brønsted acid sites and the improvement of the hydrophobic pore microenvironment. This could improve the catalytic reaction activity; additionally, the rapid removal of water from near acid sites could promote the forward movement of the reaction equilibrium and inhibit the hydrolysis of lactide. This work provides a new approach to improve the hydrophobicity of the pores of zeolites as solid acid catalysts, which is beneficial to the efficient production of lactide.