Microwave-assisted pyrolysis of biomass: Catalysts to improve product selectivity

Yiqin Wan, Paul Chen, Bo Zhang, Changyang Yang, Yuhuan Liu, Xiangyang Lin, Roger Ruan

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223 Scopus citations

Abstract

This study was intended to evaluate the effects of catalysts on product selectivity of microwave-assisted pyrolysis of corn stover and aspen wood. Metal oxides, salts, and acids including K2Cr2O7, Al2O3, KAc, H3BO3, Na2HPO4, MgCl2, AlCl3, CoCl2, and ZnCl2 were pre-mixed with corn stover or aspen wood pellets prior to pyrolysis using microwave heating. The thermal process produced three product fractions, namely bio-oil, gas, and charcoal. The effects of the catalysts on the fractional yields were studied. KAc, Al2O3, MgCl2, H3BO3, and Na2HPO4 were found to increase the bio-oil yield by either suppressing charcoal yield or gas yield or both. These catalysts may function as a microwave absorbent to speed up heating or participate in so-called "in situ upgrading" of pyrolytic vapors during the microwave-assisted pyrolysis of biomass. GC-MS analysis of the bio-oils found that chloride salts promoted a few reactions while suppressing most of the other reactions observed for the control samples. At 8 g MgCl2/100 biomass level, the GC-MS total ion chromatograms of the bio-oils from the treated corn stover or aspen show only one major furfural peak accounting for about 80% of the area under the spectrum. We conclude that some catalysts improve bio-oil yields, and chloride salts in particular simplify the chemical compositions of the resultant bio-oils and therefore improve the product selectivity of the pyrolysis process.

Original languageEnglish (US)
Pages (from-to)161-167
Number of pages7
JournalJournal of Analytical and Applied Pyrolysis
Volume86
Issue number1
DOIs
StatePublished - Sep 2009

Bibliographical note

Funding Information:
This work was supported by the Open Foundation of the State Key Laboratory of Food Science, Nanchang University, China Ministry of Education PCSIRT Program (IRT0540), and by US Department of Energy and US Department of Agriculture and University of Minnesota Initiative for Renewable Energy and the Environment grants.

Keywords

  • Aspen
  • Bio-oils
  • Biofuels
  • Catalysis
  • Catalysts
  • Corn stover
  • Microwave
  • Pyrolysis

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