(68e) Effect of CH3Cl Impurity On Reforming CH4/CO2 Mixtures On Rh/γAl2O3 Catalysts

Municipal Solid Waste decomposition in landfills produces a gas mixture (LFG) of approximately 50% carbon dioxide and 50% methane that has an average energy value of 500 btu ft^-3.  Methane emissions from waste management constituted 27% of the total anthropogenic methane emissions in 2007 according to the Energy Information Administration’s Emissions of Greenhouse Gases Report.  Currently LFG is vented, collected and flared or collected and converted to energy.   Since land filling will continue to be used in the foreseeable future, it makes sense to design landfills that capture the maximum possible amount of methane for use in generating power. However, because of the low heating value of LFG, most engines need to be modified considerably and require a consistent composition of the fuel. LFG variation leads to higher pollutant emissions, such as NO_X, CO and unburned hydrocarbons (UHC) and emissions waiver are often required before LFG thermal energy projects are permitted. One solution is to catalytically reform the LFG to syngas to produce more robust combustion or a more consistent feedstock for liquid fuel production.

This research investigates the viability of a Rh/γ-Al₂O₃ catalyst to reform LFG, and explores auto-thermal reforming (ATR) as a way to eliminate the need for external heat transfer by generating it internally in a monolithic reactor.  The impurities in LFG include higher order hydrocarbons, sulfur compounds, and chlorinated hydrocarbons.  The impact of chlorinated compounds on GHG reforming performance is not well understood.  The impact of 10-50 ppm CH₃Cl addition to CH₄/CO₂ mixtures has been investigated on a 4% Rh/γ-Al₂O₃ catalyst for dry and auto thermal reforming conditions.  Experimental findings indicate that the impact on performance is more pronounced at moderate operating temperatures of 400°C with a change in H₂/CO selectivity from 1.4 to 0.85.  Using a combination of flow-through reactor pulse testing and various characterization methods it was found that chloride deposition primarily replaces OH sites on the alumina support and poisons the reverse water gas shift reaction.