Hydrophobic SnO/Al2O3@PDVB solid acid catalyst enables high-efficiency esterification of pentaerythritol

The solid acid-catalyzed esterification of pentaerythritol with isomeric carboxylic acids，(2-ethylhexanoic acid and isononanoic acid) constitutes a green and sustainable synthetic route. However, the intrinsic hydrophilicity of conventional solid acid catalysts impedes the desorption of water generated during esterification, thereby promoting the reverse hydrolysis reaction and substantially limiting catalytic efficiency. Herein, a hydrophobic porous poly(divinylbenzene) (PDVB) layer was integrated with the solid acid SnO/Al 2 O 3 via a hydrothermal in-situ growth approach to fabricate a series of SnO/Al 2 O 3 @PDVB composite catalysts. By tuning the mass ratio of SnO/Al 2 O 3 to PDVB, the hydrophobicity, pore structure parameters, and surface acidic sites of the composite catalyst SnO/Al 2 O 3 @PDVB can be effectively modulated. Characterization results indicate that when the mass ratio of SnO/Al 2 O 3 to PDVB is 1:7, the water contact angle of SnO/Al 2 O 3 @PDVB catalyst increases markedly from 14.0° (pristine SnO/Al 2 O 3 ) to 121.8°. Esterification experiments demonstrate that the presence of SnO/Al 2 O 3 @PDVB enhances the pentaerythritol conversion from 61.5% to 99.2% under optimized conditions (200 °C, 6 h). Furthermore, the catalyst retained high activity over four consecutive cycles, maintaining a pentaerythritol conversion of 96.0%. The performance improvement is ascribed to the hydrophobic PDVB component, which facilitates rapid water removal from the catalyst surface, drives the equilibrium toward ester formation, and increases the accessibility of active acid sites. This work not only boosts the esterification efficiency of pentaerythritol but also offers a rational design strategy for developing high-performance, water-tolerant solid acid catalysts.