Staged Catalytic Gasification/Steam Reforming of Pyrolysis Oil Guus van Rossum,* Sascha R. A. Kersten, and Wim P. M. van Swaaij Faculty of Science and Technology, Research Institute IMPACT, Thermo-Chemical ConVersion of Biomass, UniVersity of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands Gasification/steam reforming of pyrolysis oil was studied in a staged reactor concept, which consisted of an inert fluidized bed and a catalytic fixed bed. Methane and C 2 -C 3 free syngas is produced at a single temperature around 800 °C at atmospheric pressure. By lowering the temperature of the fluidized bed (432-500 °C), its function is changed from a gasifier to an evaporator, and in this way the subsequent catalyst bed actually sees vaporized pyrolysis oil compounds (instead of a fuel gas), which it can more readily convert to syngas. However, the temperature of the fixed bed cannot be too low (min 700 °C) to avoid excessive carbon deposition. System calculations show that when pressurized (30 bar) pyrolysis oil gasification/reforming is considered, the catalytic exit bed temperature should be high (900-1000 °C) to reach sufficient enough methane conversion when syngas is the desired product. When only steam is added at elevated pressure, the H 2 /CO ratio readily increases, which is desired for hydrogen production. For other applications (e.g., Fischer-Tropsch), carbon dioxide probably has to be recycled to keep the H 2 /CO ratio around 2-3. The lower heating value efficiency of pyrolysis oil gasification/reforming is comparable to the lower end of the reported range of commercial methane steam reforming. 1. Introduction Pyrolysis oil is an interesting intermediate biobased energy carrier because of its high volumetric energetic density and low ash content as compared to the original biomass source. However, due to the type of components present in pyrolysis oil, its high oxygen and water content direct applications of pyrolysis oil are, at present, limited to heat and power production besides niche applications like food flavoring and extraction of specialty chemicals. 1 To upgrade the pyrolysis oil to chemicals and transportation fuels, three major routes can be identified: (i) direct improvement of the pyrolysis oil during production (e.g., catalytic pyrolysis 2 and staged condensation 3 ), (ii) py- rolysis oil upgrading via decarboxylation and/or hydrogenation, 4 and (iii) upgrading via syngas (hydrogen and carbon monoxide) production. In the present Article, gasification (reforming) of pyrolysis oil to syngas is considered. Syngas 5 is widely used for the production of heat and power (∼4%), ammonia (∼53%), methanol (∼11%), hydrogen for refineries (∼24%), and transportation fuels (∼8%) with a worldwide production of 6 TJ/year in 2003. 6 The most straightforward method to produce synthesis gas from biomass is via high temperature entrained flow gasifica- tion. 7 However, this gasification technology has a few disadvantages. Because of the severity of the process and the pure oxygen that is needed, high temperature gasification can only be applied economically on a very large scale (500 MW or higher). For stand-alone biobased syngas production, such high capacities are logistically cumbersome when raw biomass from the fields is considered. Biomass densification techniques (pyrolysis, hydrothermal liquefaction, and pelletization with or without torrefaction) are a solution for the mismatch between the locations where the biomass is available and where the products are required. The minerals and metals that are present in the biomass are converted to slag when solid or slurry biomass entrained flow gasification is being applied. While the slag can be used in the current industry infrastructure as a construction material, up- scaling of biomass utilization will lead to land depletion because the mineral and metal balances are not closed. Low temperature conversion processes result in ash, which in principle can be recycled back to the ground. Operating at very high temperatures lowers the energetic efficiency, especially for biomass with its low heating value of maximally 20 MJ/kg (wet basis). To produce a clean syngas (low in tar and in methane) at moderate process temperatures (<950 °C), various research groups have studied the application of catalysts for biomass gasification. 8 Lowering the temperature and refraining from the need for pure oxygen for the gasifier reduces equipment costs and allows for gasification at smaller scale. Up until now, syngas production in catalytic gasifiers taking in solid biomass has always needed downstream catalytic gas/vapor conversion steps. 9 Advantages of converting biomass derived liquids rather than biomass itself are that a liquid is easier to handle, store, and transport, its volumetric energy density is much higher, and it contains lower level of catalysts poisoning species as compared to the biomass source it is derived from. Czernick and co-workers 10 have shown that the fraction of pyrolysis oil that dissolves in water can be gasified with a nickel catalyst to hydrogen-rich gas at around 850 °C. The steam over carbon ratio used (∼7) was, however, high. Van Rossum et al. 11 have started research on low temperature gasification (500-900 °C) of the whole pyrolysis oil in a fluidized bed both catalytically and noncatalytically. Noncata- lytically, a fuel gas (H 2 , CO, CO 2 ,H 2 O, CH 4 ,C 2 -C 3 , and tars) is produced because, besides thermal cracking, other reactions hardly occur. The catalytic fluidized bed suffers from severe irreversible deactivation, leading after a short period also to fuel gas instead of the desired synthesis gas. Pursuing a single reactor conversion has the advantage that it is a simple and compact process. However, application of a catalytic fluidized bed for gasification of bioliquids has up until now not yet been successful due to activity loss of the catalyst. 10,11 Recently, 12,13 * To whom correspondence should be addressed. Tel.: +31 534893902. Fax: +31 534894738. E-mail: g.vanrossum@utwente.nl. Ind. Eng. Chem. Res. 2009, 48, 5857–5866 5857 10.1021/ie900194j CCC: $40.75  2009 American Chemical Society Published on Web 05/21/2009