Commercial catalysts, including zeolites (HZSM-5), fluid catalytic cracking (FCC) catalysts, transition metal catalysts (Fe/Cr), and aluminas, were successfully evaluated in a fixed bed catalytic reactor using a mixture of model compounds to simulate biomass flash pyrolysis vapors. Successful criteria including the stability index (SI), the water generation (WG), and the loss of organics (LO) were introduced to monitor the effect of catalysts and ascertain major changes in the obtained liquid product composition. SI being a measure of the effective carbonyls reduction after catalytic cracking reached 100% in the case of HZSM-5 catalysts, leading to the selective production of aromatic hydrocarbons. Transition metal catalysts (Fe/Cr) lead to the selective production of phenol and light phenolics. Comparable trends were obtained using solid biomass in the catalytic fixed bed reactor.