Amphiphilic Zeolite Beta-Stabilized Pickering Emulsion as a High-Efficiency Interfacial Catalysis Platform for Lactide Synthesis from Lactic Acid

The depletion of fossil fuels and environmental pollution over petroleum-based plastics have driven the demand for sustainable biopolymers such as polylactic acid (PLA). Lactide (LD) is the key monomer for synthesis of high-molecular-weight PLA. Herein, we propose amphiphilic zeolite beta-stabilized Pickering emulsion as a high-efficiency interfacial catalytic platform for LD synthesis. Amphiphilic zeolite beta is fabricated by the surface modification of dimethyldiethoxysilane, enabling the formation of stable water-in-oil Pickering emulsions. The microstructure of the emulsion, catalytic performances, and process intensification mechanism are systematically investigated. Under optimized conditions (100 mg zeolite beta, 3 mL of p-xylene, 0.05 mL of H2O, and 140 °C, 2 h), lactic acid (LA) conversion and LD yield reaches 98.3% and 95.78%, respectively. The superior performance arises from three synergistic effects in Pickering emulsion: (1) Enhanced mass transfer via a large oil–water interface; (2) By precisely matching Brønsted acidic sites with the reaction microenvironment, the coupling of LA esterification to LD and hydrolysis of lactate oligomers to regenerate LA is achieved, contributing to effective conversion of LA; (3) Rapid spatial isolation of oil-soluble LD in the oil phase to inhibit hydrolysis. This work offers a low-energy and high-efficiency synthesis route for LD, advancing sustainable PLA production.