PAA-derived carbon-based metal Lewis acid catalysts for polyol ester synthesis

A carbon-based metal-functionalized catalyst (PAA-M) supported on sodium polyacrylate (PAA-Na) was developed for the esterification of neopentyl glycol with acetic acid to produce neopentyl glycol monoacetate and diacetate. Using an ion-crosslinking/carbonization strategy, Sn 4+ , Zr 4+ , Al 3+ , and Fe 3+ ions not only served as catalytic metal centers but also modified the evolution of the polyacrylate network during pyrolysis, generating metal-containing carbon composites with distinct surface acidity, thermal stability, and hierarchical pore structures. The results demonstrate that product distribution was governed by the coupled effects of metal species, acid-site density and strength, pore structure, and mass transfer, rather than by Lewis acidity alone. Under an acid/alcohol molar ratio of 3:1 at 110 °C, Sn-PAA and Zr-PAA provided relatively high activity and favored diester formation, with diester selectivities of 67% and 66%, respectively. In contrast, Al-PAA and Fe-PAA promoted monoester accumulation, showing diester selectivities of only 57–58%. Sn-PAA exhibited a controllable monoester- production window, with the monoester yield reaching 46–49% within 0.5–2 h before further conversion to diester. Zr-PAA maintained nearly constant conversion and product distribution over five reuse cycles, while Sn-PAA showed only a minor decrease in conversion from 80.0 to 78.7%. These findings establish a structure-performance relationship for PAA-derived metal–carbon catalysts and demonstrate that the catalyst composition and carbonized network can be used to regulate the monoester/diester distribution in polyol esterification.