Catalytic Reactions of Guaiacol: Reaction Network and Evidence of Oxygen Removal in Reactions with Hydrogen
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Catalytic Reactions of Guaiacol: Reaction Network and Evidence of Oxygen Removal in Reactions with Hydrogen Tarit Nimmanwudipong • Ron C. Runnebaum David E. Block • Bruce C. Gates
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Received: 17 December 2010 / Accepted: 2 March 2011 / Published online: 30 March 2011 Ó The Author(s) 2011. This article is published with open access at Springerlink.com
Abstract The conversion of guaiacol, a prototypical compound representative of lignin-derived pyrolysis biooils, was catalyzed by Pt/Al2O3 in the presence of H2 at 573 K. The conversion took place with a high selectivity for aromatic carbon–oxygen bond cleavage relative to the accompanying methyl group transfer reactions. This oxygen removal was not observed in the absence of H2 as a coreactant. Products that were formed by methyl-group transfer match those produced in the conversion catalyzed by zeolite HY, which was not active for oxygen removal reactions. Keywords Guaiacol Supported platinum Zeolite Y Transalkylation Hydrodeoxygenation
from these liquids to minimize the instability and corrosion issues. In comparison with the widely investigated cellulose-derived components of bio-oils (including carbohydrates) [8–10], the lignin-derived components have lacked attention, and there is limited understanding of the reaction networks and kinetics [11–13]. Our approach was to begin investigating the reaction network for a characteristic lignin-derived compound found in pyrolysis bio-oils—guaiacol. A specific goal was to elucidate the oxygen-removal reactions in the conversion in the presence of an important class of catalysts: a metal dispersed on an acidic support (Pt/Al2O3). Data were also collected with a solid acid catalyst (zeolite HY) to identify the reactions catalyzed by an acidic function (such as the Al2O3 support) and distinguish them from the reactions catalyzed by the metal.
1 Introduction 2 Experimental Lignin constitutes as much as 30 wt% of lignocellulosic biomass [1, 2] and offers excellent potential as a feedstock for conversion to fuels and chemicals by pyrolysis, giving ‘‘bio-oils.’’ The results of earlier investigations [3–7] show that catalytic upgrading can be used to remove oxygen
T. Nimmanwudipong R. C. Runnebaum D. E. Block B. C. Gates (&) Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616, USA e-mail: [email protected] D. E. Block Department of Viticulture and Enology, University of California, Davis, CA 95616, USA
Powders of Pt/Al2O3 (1 wt% Pt, Sigma-Aldrich) and zeolite HY (Zeolyst CBV 720) were pre-treated in flowing streams of H2/N2 and N2, respectively, at 573 K. Catalytic reactions were conducted in a once-through packed-bed flow reactor under the following conditions, with liquid reactant (99.5 wt% guaiacol) vaporized into a flowing gas stream (30% H2/70% N2 in experiments with Pt/Al2O3 and N2 in experiments with HY zeolite): catalyst mass, 0.010–0.100 g (catalyst diluted with particles of inert, nonporous a-Al2O3); temperature, 573 K; pressure, 140 kPa; liquid reactan
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