Catalytic Autothermal Reforming of Renewable Fuels at Millisecond Times
L. D. Schmidt
Department of chemical Engineering and Materials Science
University of Minnesota
We compare the reforming of different types of biofuels by autothermal reforming at millisecond contact times to produce synthesis gas, hydrogen, and chemicals. Fuels examined are alcohols, esters, carbohydrates, biodiesel, vegetable oil, and solid biomass.
Biofuels generally have higher conversions than fossil fuels because the hydroxyl and ester linkages in these fuels produce higher sticking coefficients than for saturated alkanes. Consequently, conversions of all biofuels in these processes are nearly 100%. Highly oxygenated feedstocks tend to produce mostly syngas with little olefins or oxygenated products because surface reactions dominate, and these larger products are formed predominantly by homogeneous reaction processes after all oxygen is consumed.
Recent results on production of syngas by reactive flash volatilization of nonvolatile liquids and solids will also be described. We show that, by impinging cold liquid drops or small solid particles onto the hot catalyst surface, the process can be operated in steady state with no carbon formation for many hours. This occurs because, while pyrolysis of vegetable oils and carbohydrates at low temperatures produces carbon, above ~600oC the equilibrium shifts to produce syngas rather than solid carbon.
Recent results using fast photography at 1000 frames per second will be shown that examine the time dependence of solid and liquid particle decomposition and disappearance. Spatial profiles of temperature and species concentrations within the working catalyst will also be described.
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