Catalytic fast pyrolysis is a method for converting lignocellulosic biomass into renewable aromatics and olefins. Water is a byproduct of this reaction and is also present in the biomass feed. As the water partial pressure is increased from 0 to 212 Torr (0 to 28 kPa), there is an increase in furan conversion from 43.8 to 84.8 % over ZSM-5. The CO 2 and propylene yields also increase from 0.7 to 16.4 % and 2.9 to 44.9 %, respectively, as the water partial pressure increases. Water partial pressures in an industrial catalytic fast pyrolysis reactor should be within the range of water partial pressures used in this study. These results demonstrate that the presence of water promotes hydrolysis reactions in the gas-phase conversion of furanic pyrolysis vapors over zeolite catalysts.Lignocellulosic biomass is an inexpensive and renewable feedstock that can be used to produce renewable fuels and chemicals.[1] Several processes for biomass conversion are currently under development.[1a] One approach is catalytic fast pyrolysis (CFP), which converts lignocellulosic biomass into aromatics in a single-step reaction that uses zeolite catalysts [2] and a fluidized bed reactor.[2c,e,f] Previously, it has been reported [2a,b, 3] that during CFP the biomass first undergoes pyrolysis reactions to produce anhydrosugars (such as levoglucosan), followed by dehydration, decarbonylation, and decarboxylation reactions, which produce furanic intermediate species that are further converted into aromatic species through acid-catalyzed reactions. The conversion of furans over HZSM-5 has been used as a model reaction for the CFP of real biomass [2c, 4] in an attempt to elucidate the reaction chemistry. Water is a byproduct of the CFP process produced in the dehydration reactions. In addition, water is present with the biomass and therefore fed into the process with the biomass. The objective of this paper is to study the effect of water on the CFP chemistry.There are a few studies in the literature that have reported on the role of water in conversion of pyrolysis vapors over zeolite catalysts. Horne et al. [5] examined the effect of co-feeding water [at a partial pressure of 74 Torr (1 Torr = 0.13 kPa)] with biomass during pyrolysis, and then upgrading the pyrolytic vapors over a bed of ZSM-5. The water was found to double the yields of all gaseous product species (CO, CO 2 , H 2 , methane, and C 2 and C 3 alkanes and olefins) at all temperatures investigated (400-550 8C). The addition of steam to the catalytic pyrolysis of lipids produced by the algae Chlorella pyrenoidosa (the main fatty acids contained in this algae are oleic acid, linoleic acid, and palmitic acid) over ZSM-5 has been shown to shift product selectivity towards CO, CO 2 , and C 2 -C 4 olefins, as well as decreasing selectivity towards alkanes and coke.[6] Table 1 and Figure 1 a-c show the effect of increasing the water partial pressure for furan conversion over ZSM-5 at 600 8C. These experiments were done by co-feeding water and furan over a ZSM-5 catalyst (H-form, ...
