Vapor-Phase Hydrodeoxygenation of Guaiacol to Aromatics over Pt/HBeta: Identification of the Role of Acid Sites and Metal Sites on the Reaction Pathway

摘要

A comparative study of the hydrodeoxygenation of guaiacol, a phenolic compound derived from the lignin fraction of biomass with both hydroxyl and methoxyl functional groups, was performed on HBeta, Pt/SiO2, and Pt/HBeta at 350 degrees C and atmospheric pressure. The reaction pathway and the roles of the acid and metal sites were studied. Acid sites catalyze transalkylation and dehydroxylation reactions to produce monohydroxyl phenolics (phenol, cresols, and xylenols) as the major final products. Pt sites catalyze demethylation to result in catechol as the primary product, which can either be deoxygenated to phenol followed by phenol to benzene, or decarbonylated to cyclopentanone and further to butane. The close proximity of Pt and acid sites in bifunctional Pt/HBeta improves transalkylation and deoxygenation (or dehydroxylation) reactions and inhibits demethylation and decarbonylation reactions significantly, which leads to aromatics as the major final products with a total yield 85%. Both the activity and stability of bifunctional Pt/HBeta during the hydrodeoxygenation of guaiacol are improved compared to those of HBeta and Pt/SiO2. The addition of water to the feed further improves the activity and stability through the hydrolysis of the O-CH3 bond of guaiacol on acid sites and the removal of coke around Pt.