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

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 K 2 Cr 2 O 7 , Al 2 O 3 , KAc, H 3 BO 3 , Na 2 HPO 4 , MgCl 2 , AlCl 3 , CoCl 2 , and ZnCl 2 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, Al 2 O 3 , MgCl 2 , H 3 BO 3 , and Na 2 HPO 4 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 MgCl 2 /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.

[1]  J. I. Seeman,et al.  A model that distinguishes the pyrolysis of d-glucose, d-fructose, and sucrose from that of cellulose. Application to the understanding of cigarette smoke formation , 2003 .

[2]  A. Pütün,et al.  Catalytic pyrolysis of biomass in inert and steam atmospheres , 2008 .

[3]  Asri Gani,et al.  Effect of cellulose and lignin content on pyrolysis and combustion characteristics for several types of biomass. , 2007 .

[4]  N. Bakhshi,et al.  Catalytic upgrading of fast pyrolysis oil over hzsm-5 , 1993 .

[5]  Paul Chen,et al.  Physical and chemical properties of bio-oils from microwave pyrolysis of corn stover , 2007, Applied biochemistry and biotechnology.

[6]  N. Bakhshi,et al.  Catalytic upgrading of pyrolysis oil , 1993 .

[7]  S. Saka,et al.  Influence of neutral inorganic chlorides on primary and secondary char formation from cellulose , 2008, Journal of Wood Science.

[8]  M. Gray,et al.  Pyrolysis of a wood-derived material. Effects of moisture and ash content , 1985 .

[9]  Z. Qi,et al.  Review of biomass pyrolysis oil properties and upgrading research , 2007 .

[10]  W. McWhinnie,et al.  Rapid microwave pyrolysis of coal: Methodology and examination of the residual and volatile phases , 1995 .

[11]  Johnathan E. Holladay,et al.  Metal Chlorides in Ionic Liquid Solvents Convert Sugars to 5-Hydroxymethylfurfural , 2007, Science.

[12]  Paul T. Williams,et al.  Comparison of products from the pyrolysis and catalytic pyrolysis of rice husks , 2000 .

[13]  Paul T. Williams,et al.  Analysis of aromatic hydrocarbons in pyrolytic oil derived from biomass , 1995 .

[14]  J. J. Pis,et al.  Investigations into the characteristics of oils produced from microwave pyrolysis of sewage sludge , 2005 .

[15]  Suping Zhang,et al.  Upgrading of liquid fuel from the pyrolysis of biomass. , 2005, Bioresource technology.

[16]  Angelos A. Lappas,et al.  Evaluation of various types of Al-MCM-41 materials as catalysts in biomass pyrolysis for the production of bio-fuels and chemicals , 2006 .

[17]  B. Babu,et al.  Modeling, simulation and estimation of optimum parameters in pyrolysis of biomass , 2003 .

[18]  Giovanni Camino,et al.  Origin of furanic compounds in thermal degradation of cellulosic insulating paper , 1998 .

[19]  S. Saka,et al.  Catalytic pyrolysis of cellulose in sulfolane with some acidic catalysts , 2007, Journal of Wood Science.

[20]  K. Khilar,et al.  Influence of mineral matter on biomass pyrolysis characteristics , 1995 .

[21]  D. Klass Biomass for Renewable Energy, Fuels, and Chemicals , 1998 .

[22]  Johan E. Hustad,et al.  In situ catalytic upgrading of biomass derived fast pyrolysis vapours in a fixed bed reactor using mesoporous materials , 2006 .

[23]  R. Furneaux,et al.  The products of the zinc chloride-promoted decomposition of cellulose in aqueous phenol at 350°C , 1992 .

[24]  C. Gong,et al.  Cellulose hydrolysis using zinc chloride as a solvent and catalyst , 1994 .