Submitted to: Journal of Analytical & Applied Pyrolysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 29, 2008
Publication Date: May 5, 2009
Citation: Jackson, M.A., Compton, D.L., Boateng, A.A. 2009. Screening heterogenous catalysts for the pyrolysis of lignin. Journal of Analytical and Applied Pyrolysis. 85:226-230. Interpretive Summary: Declining supplies of petroleum have led to increasing demands for biofuels. Ethanol and biodiesel are the commonly encountered biofuels with ethanol blended with gasoline and biodiesel blended with petroleum diesel. Currently, about six billion gallons a year of ethanol and 450 million gallons per year for biodiesel are used for transportation. The third leg of the biofuels triad is known as “py-oil,” shorthand for pyrolysis oil. Pyrolysis is heating material to high temperatures in the absence of oxygen. The resulting py-oil is similar to crude oil and needs to be refined in order to be used as a fuel. We are searching for solids (catalysts) to mix with biomass that will result in better py-oil. So far, we have shown that we can remove the oxygen from the oil with one catalyst or produce hydrogen gas from another. The high level of oxygen in py-oil is one of the difficulties it presents. Being able to make hydrogen is attractive since it, too, is a good fuel.
Technical Abstract: The pyrolytic conversion of pure lignin at 600°C in flowing helium over five catalysts is described and compared to the control bed material, sand. Product distribution as char, liquid and gas are described as well as the composition of the liquid and gas fractions. The catalysts examined were HZSM-5, KZSM-5, Al-MCM-41, solid phosphoric acid, and a hydrotreating catalyst. The sand yields a liquid phase that is 97% oxygenated aromatics and a gas phase that is CH4 (18 vol%), CO2 (16 vol%) and CO (12 vol%). HZSM-5 is the best catalyst for producing a deoxygenated liquid fraction yielding almost equal amounts of simple aromatics (46.7%) and naphthalenic ring compounds (46.2%). The gas phase over this catalyst consists of CH4 (22 vol%), CO2 (14 vol%), H2 (12 vol%), and CO (10 vol%). The Co/Mo/Al2O3 hydrotreating catalyst yielded a liquid consisting of 21% aromatics, 4% naphthalenics, 75% oxygenated aromatics, and a gas phase that is rich in hydrogen: H2 (18 vol%), CO2 (16 vol%), CH4 (12 vol%), and CO (8 vol%).