Zeolites are the most common catalysts used for atmospheric deoxygenation of biomass pyrolysis derived feedstocks. The catalytic performance of the zeolite and the yield of deoxygenation greatly depend on the nature of the feedstock. Lignin is the most difficult part of biomass to be deoxygenated and lignin derived phenolic compounds cause rapid deactivation of zeolites. The main purpose of this research was to study the origin of zeolite deactivation in atmospheric deoxygenation of phenolic compounds. Phenol and m-cresol were selected as model compounds for lignin. In order to investigate their effect on zeolite deactivation, catalytic conversion of a mixture of methanol with m-cresol or phenol and a mixture of m-cresol with phenol were carried out over HBeta and Fe/HBeta, respectively. Co-feeding phenol or m-cresol with methanol caused high deactivation of HBeta and significant reduction in the aromatics yield. Meanwhile, these phenols had low reactivity over HBeta. Catalytic performance was enhanced by iron impregnation on zeolite, and Fe/HBeta could considerably convert m-cresol into aromatic hydrocarbons through hydrogenolysis. However, this catalyst was not efficient for deoxygenation of phenol. Strong adsorption of phenol molecules on zeolite acid sites resulting in high formation of coke was the main source of zeolite deactivation which was attenuated by an increase in reaction temperature.