Assessment of the mesopore wall catalytic activities of MFI zeolite with mesoporous/microporous hierarchical structures

MFI zeolite with a mesoporous/microporous hierarchical structure (MeMFI zeolite) was hydrothermally synthesized with an organosilane surfactant. The acid catalytic activities of the mesopore walls were evaluated for various reactions involving bulky molecules, such as the protection of benzaldehyde with pentaerythritol, the condensation of benzaldehyde with 2-hydroxyacetophenone, the esterification of benzylalcohol with hexanoic acid, and the cracking of branched polyethylene. The catalytic activities of pristine MeMFI zeolite were very high compared with those of a conventional MFI catalyst. The catalytic activities of MeMFI were lost almost completely after selective dealumination of the surface Al on the mesopore walls using tartaric acid. For small molecular reactions, however, the mesoporous zeolite still exhibited high catalytic activities even after the dealumination process. This indicates that bulky molecular reactions occurred due to Al sites located at the surface of the mesopore walls.