Fast lightoff of millisecond catalytic partial oxidation reactors

This research investigates the fast lightoff of catalysts for partial oxidation of alkane fuels to produce synthesis gas, a combination of hydrogen and carbon monoxide, at millisecond contact times. This work focuses on studying the transient behavior of this reaction system specifically for the production of hydrogen for fuel cells, combustion engines, and diesel engines. The hydrogen can be used in three ways: as a direct fuel for a fuel cell, as a fuel or fuel additive in combustion engines, and to light off a catalytic converter in combustion and diesel engines.; In this research, the lightoff of the partial oxidation system running on methane, i-butane, and i-octane is investigated. Lightoff of the catalyst is achieved by feeding fuel and air at combustion stoichiometry, igniting with a spark, and heating the catalyst with a flame stabilized 1–2 centimeters from the catalyst front face. After seconds of heating with combustion, the feed stoichiometry is switched from combustion to partial oxidation, i.e. the fuel feed is increased with no change in oxygen feed. At this switching time, flames in the reactor extinguish and surface reactions begin to dominate over gas phase reactions. A thermocouple monitors the back face temperature of the catalyst. Mass spectroscopy is used to monitor product gas composition in real time to capture the transient that occurs in the first 30 seconds of the system start-up. Lightoff temperatures are achieved in less than 5 seconds as well as steady state hydrogen production.; Transient kinetic reactor simulations are carried out to describe the time evolution of product formation. The simulations are based on three assumptions: (1) pseudo-steady state, (2) plug flow, and (3) a defined temperature profile. These three assumptions greatly simplify the 3-dimesional partial differential equations that completely describe the system. A reaction mechanism consisting of 20 reactions with 16 surface species and 4 gas phase species is used to describe the catalytic system. The simulations accurately predict the hydrogen species profiles over time based on a temperature profile that has a front face 100°C higher than the back face.