Synthetic natural gas from biomass by catalytic conversion in supercritical water

Biomass can be effectively converted to synthetic natural gas (Bio-SNG) in water near or above its critical point (374 degrees C, 22.1 MPa). If an active and selective catalyst is used, no tars or char are formed. The onset of the gasification reaction was visualized in sealed quartz capillaries as high pressure batch reactors, by using an optical microscope. By pressure differential analysis of batch experiments, the onset temperature was found around 250 degrees C, which is much lower than conventional atmospheric gasification processes operating at 800-900 degrees C. The temporal evolution of the gaseous products in the batch experiments was consistent with a sequential gasificationmethanation mechanism, where methane is formed from CO2 and H-2. A Ru on carbon catalyst exhibiting excellent long-term stability was tested at 400-500 degrees C and space velocities up to 33 g(HC) g(cat).(-1) h(-1) in a continuous test rig at 30 MPa.