Energy Fuels 2009, 23, 6181–6188 Published on Web 10/07/2009
: DOI:10.1021/ef900663a
Supercritical CO2 Fractionation of Bio-oil Produced from Mixed Biomass of Wheat and Wood Sawdust P. K. Rout,† M. K. Naik,† S. N. Naik,‡ Vaibhav V. Goud,§ L. M. Das,^ and Ajay K. Dalai*,† †
Catalysis and Chemical Engineering Laboratories, Department of Chemical Engineering, University of Saskatchewan, Saskatoon, SK, Canada S7N5C5, ‡Center for Rural Development and Technology, Indian Institute of Technology, Delhi, §Department of Chemical Engineering, Indian Institute of Technology Guwahati, Assam, and ^Center for Energy Studies, Indian Institute of Technology, Delhi Received June 29, 2009. Revised Manuscript Received September 7, 2009
Interest in the biomass as a source of fuel, chemicals, and materials is growing fast. The bio-oil derived from biomass is attractive due to its renewability and the fact that it is CO2 balanced and sulfur free. The physical and chemical characteristics of biomass (i.e. wheat-wood sawdust) were estimated using proximate analysis, calorific value, crystallinity, devolatalization behavior, and ultimate analysis. Inductively coupled plasma mass spectroscopy (ICP-MS) of ash, X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and composition of water-soluble sugars of mixed biomass (wheat-wood sawdust) were also carried out. For commercial purposes, the same biomass was used for conversion to bio-oil by fast pyrolysis process. In order to investigate its properties, bio-oil was systematically characterized using different measurements such as proximate analysis and calorific value, whereas the chemical composition of bio-oil was estimated using CHNS, 1H nuclear magnetic resonance (NMR), gas chromatography flame ionization detection (GC-FID), and GC/MS. The bio-oil obtained was a mixture of hydrocarbons, pyranoids, furanoids, benzenoids, and fatty acids/alcohols along with 45% of water. The high amount of water present in bio-oil forms an azeotrope with organic polar compounds. The organic fraction of the biooil was isolated by supercritical carbon dioxide (SC-CO2), and it was observed that the first fraction of SC-CO2 extraction collected at 25 MPa was enriched with furanoids (9.9%), pyranoids (9.0%), and bezenoids (44.8%). The organic fraction present in the bio-oil was extracted by organic solvents, and the yields and chemical compositions of products were compared with those obtained from SC-CO2 fractions.
renewable source of raw feedstock for conversion into biofuels and chemicals.2 The availability of biomass in the world is 220 billion ovendry ton (odt) per year or 4500 EJ (1018 J).3 It is world’s largest and most sustainable energy resource. Due to the high energy content of biomass, its utilization will lead to reduction of fossil fuel consumption and greenhouse gas emissions and partially solve the dependence on fossil fuels in many countries.4 Biomass consists of cellulose, hemicellulose, and lignin. The use of renewable resources for fuel, such as bio-oil derived from lignocellulosic biomass, has great potential to partially replace petroleum fuel. The characterization of lignocelluosic biomass is important to determine its feasibility for the biofuel production. Selected biomasses such as wheat straw and wood sawdust are abundant in Canada. For example, Saskatchewan produces 7.6 million ton of wheat annually based on the average taken over the production of the past 10 years.4 In Canada, the average annual wood cut has been estimated at 167.5 million m3 creating over 60 million ton of residue.3,5 These were used
1. Introduction Bio-oil produced from biomass is a potentially promising alternative fuel for the transport sectors owing its ecological advantage. These renewable energy resources become quickly popularized due to their lack of environmental risks and pollution. However, some of the inefficient conversion processes such as wood furnaces release more pollutants than natural gas furnaces. Biomass materials are natural high molecular substances composed of carbon, hydrogen, oxygen, and nitrogen. Biomass such as wood waste, sawdust, and agriculture waste can be easily acquired. Biomass is seen as one of the best options for providing a renewable fuel and also has the added advantage of begin CO2 neutral. This is due to CO2 intake by plants from atmosphere due to photosynthesis and subsequent release of this CO2 during the biomass conversion process. In addition to their sustainable favorability, they are, in general, more evenly distributed over earth’s surface than fossil fuels and may be exploited using less capital-intensive technologies. Hence, they increase the scope for diversification and decentralization of energy supplies and the achievement of energy self-sufficiency at a local, regional, and national level.1 Lignocelluloses biomass represents a
(2) Sanderson, M. A.; Agblevor, F.; Collins, M.; Johnson, D. K. Biomass Bioeng. 1996, 11, 365–370. (3) World energy council. Survey of energy resources, 20th ed.; Elsevier Ltd: Oxford, 2004; p 267. (4) Agricultural statistics. Information of Government of Saskatchewan website. (5) Mohan, D.; Pittman, C. U., Jr; Steele, P. H. Energy Fuels 2006, 20, 848–889.
*Corresponding author. E-mail:
[email protected]. Phone no.: 1 (306) 966 4771. Fax no.: 1 (306) 966 4777. (1) Jones, M. R. Biomass for energy. In Biomass handbook; Kitani, O., Hall, C. W., Eds.; section 1.2.2. r 2009 American Chemical Society
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Energy Fuels 2009, 23, 6181–6188
: DOI:10.1021/ef900663a
Rout et al.
heating value that is about half that of conventional fuel oil.12 Fast pyrolysis processes produce 60-75 wt % of liquid biooil, 15-25 wt % of solid char, and 10-20 wt % of noncondensable gases, depending on the feedstock used. No waste is generated, because the bio-oil and solid char can each be used as a fuel and the gas can be recycled back into the process.13 Fast pyrolysis uses much faster heating rates than traditional pyrolysis. Advanced processes are carefully controlled to give high liquid yields. Pyrolysis was the thermochemical process applying high heat to lignocellulosic materials in the absence of air or in reduced air that converts organic materials into usable fuels.14 There are four essential features of a fast pyrolysis process.15 First, very high heating and heat transfer rates are used, which usually requires a finely ground biomass feed. Second, a carefully controlled pyrolysis reaction temperature is used, often in the range of 500-550 C. Third, short vapor residence times are used (
