Highly chemoselective esterification for the synthesis of monobutyl itaconate catalyzed by hierarchical porous zeolites

Monobutyl itaconate (MBI) are commercially prepared by using freshly distilled acetyl chloride as catalysts, which, however, always results in complicated purification processes due to the usage of water-carrying agents. Here, we report the highly selective production of MBI by using zeolite-based hierarchical porous materials as catalysts in the esterification between itaconic acid and n-butyl alcohol. Two typical hierarchically porous-structured catalysts, namely hierarchical mesoporous zeolites (HMZ) and hierarchical nanozeolite assembly (HNZ), with distinctive meso- or nano-porosities and highly crystallized ZSM-5 framework, were prepared, and both of them exhibited high catalytic activity and reusability in the selective esterification between itaconic acid and n-butyl alcohol. The extraordinarily high selectivity to MBI was achieved and attributed to the decreased diffusion restriction in the meso- or nano-porous network and shortened diffusion path in the zeolite framework or zeolites nanocrystals of HMZ and HNZ, respectively, which prevented further esterification of monoesters into diesters.

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► Hierarchical mesoporous zeolites (HMZ) and nanozeolite assembly (HNZ) were prepared.
► HMZ were synthesized by using CTAB and F127 as co-mesoporogens.
► HNZ were prepared in a self-assembly process without secondary porogens.
► Both of them could selectively esterify the nonconjugated carboxyl groups.
► The mesoporosity and shortened diffusion path were found to be the main reasons.