Carbon-Catalyzed Gasification of Organic Feedstocks in Supercritical Water

TLDR

Carbon catalysts such as spruce wood charcoal, macadamia shell charcoal, coal activated carbon, and coconut shell activated carbon enable gasification of organic feedstocks in supercritical water. The study examined glycerol, glucose, cellobiose, whole biomass extracts, and DoD waste liquids, assessing how temperature, pressure, reactant concentration, WHSV, and catalyst type influence glucose gasification. Complete conversion of glucose to a hydrogen‑rich synthesis gas was achieved at 600 °C, 34.5 MPa, WHSV 22.2 h⁻¹, and similar conditions yielded full conversion of biomass and high destruction efficiencies for DoD wastes; catalyst deactivation after 4 h without swirl was mitigated by a swirl generator, maintaining near‑100 % efficiency for over 6 h.

Abstract

Spruce wood charcoal, macadamia shell charcoal, coal activated carbon, and coconut shell activated carbon catalyze the gasification of organic compounds in supercritical water. Feedstocks studied in this paper include glycerol, glucose, cellobiose, whole biomass feedstocks (depithed bagasse liquid extract and sewage sludge), and representative Department of Defense (DoD) wastes (methanol, methyl ethyl ketone, ethylene glycol, acetic acid, and phenol). The effects of temperature, pressure, reactant concentration, weight hourly space velocity, and the type of catalyst on the gasification of glucose are reported. Complete conversion of glucose (22% by weight in water) to a hydrogen-rich synthesis gas was realized at a weight hourly space velocity (WHSV) of 22.2 h-1 in supercritical water at 600 °C, 34.5 MPa. Complete conversions of the whole biomass feeds were also achieved at the same temperature and pressure. The destruction efficiencies for the representative DoD wastes were also high. Deactivation of the carbon catalyst was observed after 4 h of operation without swirl in the entrance region of the reactor, but the carbon gasification efficiency remained near 100% for more than 6 h when a swirl generator was employed in the entrance of the reactor.