(604q) Investigating the Impact of HZSM-5 Silica-to-Alumina Ratio on the Performance of Duckweed Catalytic Fast Pyrolysis

Authors: 
Wright, M. M., Iowa State University
Brown, R. C., Iowa State University

There is growing interest in the use of duckweed for biofuel applications due to its high growth rate and biomass productivity. Experiments have shown that duckweed could be converted into biofuels through thermochemical processes such as fast pyrolysis. Duckweed fast pyrolysis yields a refinery intermediate feedstock known as bio-oil that could be upgraded into gasoline- and diesel-range fuels. However, raw bio-oil contains oxygen and nitrogen in concentrations that are incompatible existing refinery infrastructure. Bio-oil properties can be improved with the use of catalytic pyrolysis to remove impurities and enhance the product distribution. Many researchers have conducted catalytic fast pyrolysis (CFP) of different biomass such as lignocellulose and microalgae. Previous results indicate that HZSM-5 is an efficient catalyst for producing aromatic hydrocarbons. In this study, we conducted CFP of duckweed (lemna sp.) in a micro-furnace pyrolyzer (PY-2020iS, Frontier Laboratories, Japan) and compared the performance of different zeolite catalysts. Four HZSM-5 catalysts with silica-to-alumina ratios (SAR) of 23, 30, 50 and 80 were tested to investigate the effect of catalyst composition on the yield and product distribution of aromatic hydrocarbons. All these four catalysts significantly increased the yield of aromatic hydrocarbons from duckweed CFP compared to non-catalytic trials. Among the four HZSM-5 catalysts, the catalyst with a SAR of 30 provided the highest aromatic yield while catalyst with SAR of 80 provided the lowest yield. These results indicate that moderate SARs are favorable for aromatic production during duckweed CFP. By comparing the aromatic hydrocarbon distributions between duckweed CFPs with different catalysts, the results show that catalyst with SAR of 80 achieved the highest C9 aromatic hydrocarbons selectivity. This result is partially due to the largest mesopore volume (around 0.077 cm3/g) of the SAR 80 catalyst among the catalysts tested. The catalysts with SAR of 30 and 50, which have similar mesopore volume, achieved similar aromatic product distributions. In summary, these results suggest that the SAR of HZSM-5 catalyst has a significant influence on the total aromatic yield, and the mesopore volume has greater influence on the aromatic product distribution. Further study of duckweed CFP with HZSM-5 catalyst could improve our understanding of the underlying mechanisms that lead to higher aromatic yields and select product distributions.
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