(207e) Model Compound Study of Phenolic Compounds Conversion Over Acidic Zeolites During Bio-Oil up Grading
Phenolics compounds are a family of compounds derived from lignin biomass via fast pyrolysis (and/or liquefaction and/or solvolysis). The major functional groups of phenolics are hydroxy group (?OH) and methoxy group (?OCH3). Methoxybenzene (anisole) was selected as a model compound to represent the ?OCH3 group of phenolic compounds conversion during bio-upgrading over acidic zeolites. Conversion of anisole was studied over an HZSM-5 zeolite at varying space times (W/F), reaction temperatures, type of carrier gas, and concentration of water in the feed. Several bimolecular and unimolecular reactions are proposed to take place. The bimolecular reactions include the following transalkylation reactions: a) anisoles to phenol and methylanisole; b) phenol and methylanisole to cresols; c) phenol and anisole to cresol and phenol; d) methylanisole and cresol to phenol and xylenol. A pseudo first-order kinetic model based on these bimolecular reactions was found to describe well the observed product distribution as a function of W/F. Shape selectivity effects prevail over electrophilic substitution and thermodynamic equilibrium effects in the formation of methylanisole isomers. However, the opposite is true for the distribution of cresol isomers. The kinetic analysis indicates that the contribution of unimolecular reactions such as isomerization is much lower than that of bimolecular reactions. When H2 was used as a carrier, catalyst stability showed slighly improvement in comparison to the runs under He. Remarkably, addition of water was found to increase catalytic activity significantly.