Gasification of biomass model compounds in supercritical water

Model compounds for lignin and protein were gasified in supercritical water (SCW). Experiments were conducted in quartz batch reactors to eliminate unintentional catalytic effects of metal reactor materials.; We examined the effect of nickel metal on the gasification of methanol in supercritical water at 500°C and 550°C. In the absence of nickel, conversions up to 20% were reached after 2 hours. The pseudo-first-order rate constant for homogeneous gasification is 3.2 (+/- 0.4) x 10-5 s-1 at 550°C. In the presence of a Ni wire conversions of up to 90% were reached in less than 5 minutes. The pseudo-first-order rate constants for Ni-catalyzed gasification are 0.0018 +/- 0.0007 cm/s and 0.0027 +/- 0.0006 cm/s at 500 and 550°C. Hydrogen, carbon monoxide and carbon dioxide were the major products detected. Hydrogen was always the most abundant. With multiple uses, the Ni wire showed deactivation as a catalyst for methanol gasification.; We examined the gasification of glycine in supercritical water at 500°C and 600°C with a water density of 0.079 g/mL. The gasification efficiency for glycine in SCW was low. Large amounts (20%--90%) of the carbon were detected in the aqueous phase after 1 hour of reaction for both homogeneous and Ni-catalyzed reactions. Solid char was also produced. Of the gases that were formed, CO was most abundant from the homogeneous reactions, while hydrogen was the most abundant in the presence of a nickel catalyst. The Ni helped gasify the carbon, as less carbon was found in the aqueous phase, as well as increased the gas yields.; This work also examined the gasification of guaiacol and phenol in supercritical water at 400--700°C. Guaiacol is mainly gasified into hydrogen, carbon dioxide, carbon monoxide and methane. The rest of the guaiacol decomposes to phenol and o-cresol or reacts to form char. Nickel does not affect the conversion of guaiacol to phenol and ocresol, but it significantly changes the gas product compositions.; Phenol is mainly gasified into hydrogen, carbon dioxide and methane. Hydrogen was the most abundant product at high phenol conversions. The gas compositions measured experimentally at high phenol conversions were largely consistent with those anticipated from chemical equilibrium calculations. In the absence of nickel, phenol conversions up to 68% were reached after 1 hour at 600°C. In the presence of Ni wire, complete conversion was obtained within 10 minutes. The pseudo-first-order rate constant at 600°C for homogeneous gasification of phenol is 3.0 (+/- 0.4) x 10-4 s -1, and the rate constant for Ni-catalyzed gasification is 1.1 (+/- 0.1) x 10-3 cm/s.; The concentrations of both water and phenol were varied to determine their effects. For Ni-catalyzed reactions, increasing the water density at a constant phenol loading lowered the phenol conversion. Increasing the phenol loading at a fixed water density increased the conversion and gas yield. A detailed kinetic analysis was performed to determine global rate equations for phenol disappearance.