(674c) Control of C2-Hydrocarbon Formation in the Supercritical Water Reformation of Jet Fuel

Jet fuel may be reformed non-catalytically into hydrogen-rich synthesis gas by a novel process utilizing supercritical water which acts synergistically as a solvent and as a reformant. This novel process produces little carbon build-up inside the reactor even after days of continuous operation. The complex process chemistry may be modeled using two principal chemical reactions: (1) reformation of jet fuel hydrocarbon molecules into hydrogen and carbon oxides and (2) pyrolysis of jet fuel hydrocarbons into unsaturated lighter hydrocarbons. The pyrolysis reactions are competing reactions with the reformation reaction. Lighter, unsaturated hydrocarbons produced as intermediates by pyrolysis may be either reformed, undergo further pyrolysis, or be saturated by reacting with the desired product, hydrogen. Of particular interest in this paper is the undesirable hydrogenation of ethylene to ethane, which both may be resulted in from the process in measureable concentrations. A series of supercritical water reformation of jet fuel experiments were conducted using a 1-liter Inconel 625 Grade 1 tubular reactor at 24 MPa between 800 K and 975 K. It is found that ethylene undergoes concurrent hydrogenation with the ultimate product of the process, hydrogen, producing ethane. Formation of ethane in the reformation reactor is detrimental to the overall process effectiveness, due to its depletive consumption of the product hydrogen as well as reduction of the reformation efficiency. The effects of temperature and water-to-hydrocarbon ratio upon molar concentrations of ethylene and ethane in the gaseous products are examined. The optimal process conditions that minimize unwanted ethane and ethylene formation are found and experimentally demonstrated.