James J. Spivey

Catalytic oxidation of methane over hexaaluminates and hexaaluminate-supported Pd catalysts

Abstract An aqueous (NH4)2CO3 coprecipitation method, based on that of Groppi et al. [Appl. Catal. A 104 (1993) 101–108] was used to synthesize Sr1−xLaxMnAl11O19−α hexaaluminates. These materials were first synthesized by alkoxide hydrolysis. This synthesis route requires special handling of the starting materials and is not likely to be commercially practical. The materials prepared by (NH4)2CO3 coprecipitation have similar surface areas as those prepared by the alkoxide hydrolysis method. Their CH4 oxidation activity, measured as the temperature needed for 10% conversion of methane, is higher than those prepared by alkoxide hydrolysis. The La-substantiated material, LaMnAl11O19−α, shows high surface area with 19.3xa0m2/g after calcination at 1400°C for 2xa0h. It is active for CH4 oxidation with T10% at 450°C using 1% CH4 in air and 70u2008000xa0cm3/hxa0g space velocity. The stability and activity of LaMnAl11O19−α prepared by (NH4)2CO3 coprecipitation method is a simple and important step forward for the application of CH4 catalytic combustion for gas turbines.

Novel technologies for SO{sub x}/NO{sub x} removal from flue gas

The goal of this project is to develop a cost-effective low temperature deNO{sub x} process. NO{sub x} removal at temperatures between 120C--150C was investigated using the approaches of (1) selective reduction of NO{sub x} by alcohol or acetone (2) adsorption of NO{sub x} with an effective sorbent. The chief problem encountered in low temperature reduction of NO was catalyst deactivation due to coke formation. In this quarter, a possible solution explored was increasing the loading of precious metals (Pd and Ag) on oxide supports, as precious metals are known to be effective in the oxidation of hydrocarbons at low temperatures. However, no improvement was observed. Another solution was the replacement of NO by NO{sub 2} in the feed for the carbon-based catalyst tested, as NO{sub 2} was observed to slow down the deactivation rate over Cu-ZrO{sub 2} catalyst. However, rapid reduction of NO{sub 2} to NO by the carbon support occurred, making this approach impractical. As part of this approach, search for better NO oxidation catalysts continued this quarter. It was found that on different carbon catalysts at 30C and a W/F of 0.01g.min/cc, NO conversion to NO{sub 2} between 82--90% can be achieved. This activity, however, decreased with increasing temperature. SO{sub 2} also poisoned the oxidation activity of the activated carbon. Au dispersed on lanthanum oxide was another catalyst tested and had an NO conversion to NO{sub 2} of 17% at 250C. The catalytic performance of this catalyst could be improved by increasing its surface area. Finally, the adsorption capacity of NO{sub x} of a carbon sample provided by ISGS and an inorganic sorbent were tested. The capacity of the inorganic sorbent was found to be much higher.