Reaction pathways in the liquid phase alkylation of biomass‐derived phenolic compounds

Abstract

Alkylation is a promising reaction for the upgrading of bio‐oil because it maximizes the retention of carbon in the liquid product. The alkylation of m‐cresol with isopropanol and HY zeolite was studied in a liquid phase system. The experimental results were fitted with two conventional surface kinetic models, Langmuir–Hinshelwood and Eley–Rideal, from which adsorption and rate constants were estimated. Two types of alkylation reactions were observed: C‐alkylation with formation of a CC bond with the ring and O‐alkylation with formation of an ether bond with the hydroxyl group. It was concluded that O‐alkylation products do not undergo intramolecular rearrangement but first decompose into the corresponding phenolic. Alkylation occurs from both isopropanol and propylene, both of them yielding O‐and C‐alkylation to different extents. Isopropanol favors O‐alkylation while propylene favors C‐alkylation. Rate constants for multiple alkylation steps were progressively lower, suggesting the presence of steric hindrance during incorporation of additional isopropyl groups. © 2014 American Institute of Chemical Engineers AIChE J , 61: 598–609, 2015