Liquid Phase Reaction of Acetaldehyde over Various ZSM-5 Zeolites

Article abstract of DOI:10.1246/bcsj.66.2498

Acetaldehyde reacted over various ion-exchanged ZSM-5 zeolites at 15+/-0.5 deg C under a nitrogen pressure of 1x10⁵ Pa.The main products of the reaction were 2α,4α,6α-trimethyl-1,3,5-trioxane (cis-paraldehyde) and its isomer, 2α,4α,6β-trimethyl-1,3,5-trioxane (trans-paraldehyde).Several rare earth ZSM-5 (REZSM-5) and M/HZSM-5 (partially proton exchanged ZSM-5) catalysts exhibited high activities for trans-paraldehyde formation.The reaction appeared to proceed by the following scheme: cis-paraldehyde <*> acetaldehyde <*> trans-paraldehyde.A comparison of the catalytic activity with the IR intensity of acidic OH groups over the catalyst suggested that the active site for cis-paraldehyde formation was the Broensted acidic site, while the active site for trans-paraldehyde formation was a Broensted acid site in the neighborhood of an Mⁿ⁺ site in the ZSM-5 zeolite pore.