(17a) Reactive Flash Volatilization Of Nonvolatile Carbohydrates For Synthesis Gas

Carbohydrates such as cellulose and starch constitute a major fraction of biomass available as agricultural residue, grasses, and trees. Using RhCe/Al₂O₃ catalysts at residence times less than 70 milliseconds, these biopolymers can be directly converted to synthesis gas products near equilibrium. The effect of steam addition, N₂/O₂ feed ratio, and air preheat conditions were examined to maximize selectivity to synthesis gas at all considered fuel/air ratios. With the addition of the steam, ~80% of the hydrogen in glycerol can be converted directly to H₂. Selectivity to H₂ and CO from cellulose was observed ~50% near equilibrium maintaining 2/3 of the carbohydrate fuel value. Autothermal conversion is likely to occur by coupling the endothermic biomass decomposition process with highly exothermic catalytic partial oxidation. By directly contacting carbohydrate particles with a hot catalytic surface capable of providing high heating rates, the solid particle forms volatile organics which flow into a porous catalyst and reform with oxygen to form synthesis gas. Deactivation over 20 hrs of operation was not detected, possibly because the formation of char is limited by high particle heating rates.