Effect of CH4 Co-Feeding On Biomass Catalytic Pyrolysis

Effect of CH₄ Co-feeding on Biomass Catalytic Pyrolysis

Shoucheng Du, Ari Fischer, George M. Bollas

Department of Chemical and Biomolecular Engineering, University of Connecticut, Storrs, CT

During biomass (catalytic) pyrolysis, a large portion of oxygen atoms are removed from biomass in the form of H₂O, which means that the remaining hydrocarbons are poor in H atoms. This problem can be addressed by co-feeding of biomass with hydrogen-rich feedstocks, such as CH₄.  Similar concepts have been explored in literature with co-feeding alcohols in biomass pyrolysis.  Zhang et al. [1] studied the fast catalytic pyrolysis of wood with alcohols (methanol, 1-propanol, 1-butanol and 2-butanol) co-feeding in a fluidized bed reactor. The experimental result showed that the co-feeding of biomass with alcohols significantly increased carbon yield (aromatics + olefins + C₅ compounds), especially aromatics yield (from 5.9% to 21.4%). Based on the H/C_eff ratio hypothesis proposed by Zhang et al. [2], introduction of a hydrogen richer compound (methane) compared with methanol is preferable.

CH₄ dehydroaromatization over ZSM-5 is a well-studied process. Mo/ZSM-5  is  arguably  the  best  catalyst  for  methane aromatization [3¨C5],  while  comparison  of  the  efficiency  of  the  process  in  fixed  and  fluidized bed  reactors [3] shows  that  high  conversions  are  obtained  at  400-500°C  and WHSVs  in  the range 1.4-2hr^-1. Co-feeding biomass pyrolysis with CH₄ using ZSM-5 with small fractions of Mo additive has the potential to overcome biomass pyrolysis limitations, resulting in high-quality biofuels.  The objective of this presentation is to explore the feasibility of improving bio-oil quality by biomass/CH₄ co-pyrolysis using bifunctional catalysts. Mo supported ZSM-5 catalysts, were formulated using commercial ZSM-5 and the wet impregnation method.  Experiments were performed in the spouted bed reactor using biomass model compounds (D-glucose) and pine sawdust. The experimental results including gas, liquid, and solid analysis for biomass/ZSM-5, biomass/CH₄/ZSM-5, biomass/Mo/ZSM-5 and biomass/CH₄/Mo/ZSM-5 will be presented. Different biomass/CH₄ co-feeding ratios will also be investigated and presented. 

References:

[1]      H. Zhang, T.R. Carlson, R. Xiao, G.W. Huber, Green Chemistry 14 (2012) 98.

[2]      H. Zhang, Y.-T. Cheng, T.P. Vispute, R. Xiao, G.W. Huber, Energy & Environmental Science 4 (2011) 2297.

[3]      B. Cook, D. Mousko, W. Hoelderich, R. Zennaro, Applied Catalysis A: General 365 (2009) 34.

[4]      A. Smieškov¨˘, P. Hudec, N. Kumar, T. Salmi, D.Y. Murzin, V. Jor¨Şk, Applied Catalysis A: General 377 (2010) 83.

[5]      C. Xu, H. Liu, M. Jia, J. Guan, S. Wu, T. Wu, Q. Kan, Applied Surface Science 257 (2011) 2448.