Insights into the Kinetics of the Guaiacol Alkylation with Cyclohexanol in a One-Pot Process

Abstract

The kinetics of the one-pot liquid-phase alkylation of guaiacol (G) with cyclohexanol (CHOL) at 383 K, 1 atm and over Amberlyst 36 (a catalyst containing Brønsted acid sites) was studied using Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetic models. Initially, CHOL dehydrates into cyclohexene, which by O-alkylation with G forms cyclohexyl-2-methoxyphenyl ether (CHMPE) and by C-alkylation leads to cyclohexyl-2-methoxy phenol isomers (CHMP), valuable intermediates in Fine Chemistry. An appropriate model, with physical and statistical meaning, was successfully found for dimensioning a batch industrial reactor for producing valuable CHMP. The selected model indicates that the rate limiting step of the dehydration of CHOL into cyclohexene (CH) is the surface chemical reaction involving a single acid site whereas the rate limiting step for the O-alkylation (considered reversible) and for the C-alkylation (assumed irreversible) is the surface chemical reaction between adsorbed G and CH. Additional experiments at different reactants ratio were performed to validate the kinetic expression in other experimental conditions and the catalytic results confirm the mechanism proposed.