Methane to methanol in supercritical water

Abstract

We examined the feasibility of producing methanol from the partial oxidation of methane in nearcritical and supercritical water. Oxygen was always the limiting reactant. The parameter space investigated experimentally included temperatures between 349 and 481 "C, batch holding times between 1 and 9 min, water densities between 0.15 and 0.35 g mL-I, initial methane to water molar ratios between 0.05 and 0.27, and initial methane to oxygen molar ratios between 10 and 26. Experiments within this parameter space led to methane conversions up to 6%, and oxygen conversions up to 100%. Methanol, carbon monoxide, and carbon dioxide were the major products. The methanol selectivities ranged from 0.04 to 0.75, with the highest selectivities occurring at the lower conversions. The highest methanol yield was 0.7%. Reactions performed in glass-lined reactors proceeded to higher conversions than did reactions in stainless-steel reactors under otherwise identical conditions. A detailed chemical kinetics model showed that the methanol selectivity increased with temperature and with the methane to oxygen molar ratio, but decreased with increasing oxygen conversion. The methanol yield showed the same trends with temperature and the methane to oxygen ratio, but the yield increased with oxygen conversion.

Evaluating reaction pathways of hydrothermal abiotic organic synthesis at elevated temperatures and pressures using carbon isotopes

“…While the dearth of experimental studies under similar physical and chemical conditions precludes direct comparison, compounds of both organic classes do exist as products of organic reactions with supercritical water in elevated temperature and pressure environments (Savage et al, 1994). Formation of alcohols and carboxylic acids has been confirmed unambiguously in this study by repetitive experiments and high-resolution mass spectrometry.…”

Reactions at supercritical conditions: Applications and fundamentals

“…The authors also reported a reaction network and pseudo-first-order rate constants that were consistent with their experimental data. Savage et al (1994b) also reported experimental results for the conversion of methane to methanol near the critical point of water. Unlike Dixon and Abraham, this group did not use a catalyst.…”

Experimental measurements and kinetic modeling of CH4/O2 and CH4/C2H6/O2 conversion at high pressure

“…[7,12], are often limited to pressures below 20 bar, whereas studies of homogeneous partial oxidation of CH 4 to CH 3 OH [43][44][45][46][47][48][49][50][51][52] typically operate in the 20-100 bar and 600-900 K range, similar to the present study but limited to very reducing conditions. Finally, data are available on oxidation of CH 4 in supercritical water (663-923 K, 35-350 bar) [53][54][55][56][57][58].…”