The Control of Regio- and Chemo-Selectivity in the Gas-phase, Acid-Catalyzed Methylation of 1,2-Diphenol (Catechol)

摘要

The catalytic properties of materials having either (i) Bronsted-type acidity (H-mordenite and Al phosphate), or (ii) Lewis-type acidity (Al trifluoride), were investigated in the reaction of gas-phase catechol methylation with methanol. H-mordenite and A1F3 gave high selectivity to guaiacol (the product of O-methylation) only under mild reaction conditions, that is for very low catechol conversion. In fact, the increase of temperature led to the transformation of guaiacol to phenol and cresols, and to considerable catalyst deactivation. The use of a mildly acidic catalyst, A1P04, instead made it possible to obtain a stable catalytic performance, with high selectivity to guaiacol at 42% catechol conversion.