Autothermal Oxidative Pyrolysis of Alternative Hydrocarbon Feedstocks

Thursday, November 11, 2010: 10:10 AM
251 A Room (Salt Palace Convention Center)
Christine M. Balonek, Joshua L. Colby and Lanny D. Schmidt, Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN

Traditional pyrolysis units are heated externally, requiring large energy inputs, and produce gases, solid chars, and complex liquid mixtures. We have developed and demonstrated an oxidative pyrolysis reactor able to run autothermally with negligible solid char formation. The heat necessary for pyrolysis is generated internally, eliminating the heat transfer issues associated with external heating. This process can produce both synthesis gas and hydrocarbon products from alternative feedstock models of biomass and plastic wastes. Solid cellulose and polyethylene (PE) particles were fed individually with air to a Rh-Ce/γ-Al2O3 catalytic fixed-bed reactor. Catalyst temperature and product species were studied as a function of the inlet C/O ratio, the ratio of carbon moles in the solid feed to oxygen moles in the O2 feed. At all C/O ratios reported, the solid feed was completely converted with negligible coke formation at millisecond time scales. Cellulose and PE pyrolysis produced large amounts of synthesis gas at low C/O ratios (0.5 to 1.0). Cellulose pyrolysis produced up to 20 % carbon selectivity to C3+ hydrocarbons at C/O of 1.3 (autothermal operation was unsustainable at higher C/O ratios). At similar conditions, PE pyrolysis had 50 % selectivity to C3+, and selectivity continued to increase with increasing C/O ratio to 90 % at C/O = 3.4. This high initial yield of C3+ hydrocarbons from cellulose and PE pyrolysis demonstrates the potential for autothermal oxidative pyrolysis to utilize alternative hydrocarbon feedstocks in a fast, clean, and efficient way.

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