Catalytic reduction of nitrogen oxides on carbonaceous systems and carbon dioxide gasification at elevated pressures

The reduction of NO_x species over catalytically—promoted carbonaceous systems can be an effective approach for the removal of these species from effluent gases from stationary and non-stationary combustion sources. One of the major objectives of the current work is to improve the understanding of catalytic NO and N₂O reduction on carbons, as well as the role of carbon monoxide in these systems.; The experimental work in the current study was conducted principally in a packed bed reactor/gas flow system that was constructed for this purpose. The analytical techniques employed were quadrupole mass spectrometry, NO _x chemiluminescence, and gas chromatography. Both uncatalyzed and catalyzed (potassium-promoted) phenolic resin char and Wyodak coal char samples were investigated, as well as the catalytic effect of additional CO introduced in the reactor feed gas.; The apparent activation energy is 161 ± 3.8 kJ/mol for the uncatalyzed resin char, which decreases to 80–90 ± 4.3 kJ/mol for the potassium-promoted resin char. The apparent activation energies are even less for the Wyodak coal char, and the reactivities exhibit a “two regime” behavior, whereby the apparent activation energy in the high temperature regime is greater than that in the low temperature regime. The location of this “break” is dependent on the nature of the carbon, as well as additives/impurities, but it is typically observed in the range of 850–1075K.; The principal effects of potassium in the current work are to significantly increase the reactivity both by increasing the number of active sites via the catalyst dispersion, and reducing the apparent activation energy. Additional CO can increase the reactivity further, but this effect is decidedly secondary to metal catalysis and is only evident at lower temperatures. In the case of the Wyodak coal char, however, the effect of potassium seems to primarily increase the turn-over rate on active sites.; N₂O reduction on the potassium-promoted chars exhibit a lower apparent activation energy than NO reduction over the same materials and produces primarily CO₂. Additional CO in the reactor feed gas had no discernible effect on the N₂O reduction rate for the phenolic resin char, but it did increase the reactivity of the promoted, demineralized Wyodak coal char. The latter is attributed to residual mineral matter impurities that are not removed by the demineralization procedure that was used.; In addition to the preceding, some work was done on the carbon-CO ₂ reaction at elevated pressures in a high pressure thermobalance. For the phenolic resin char it is shown that the apparent activation energy decreases with increasing CO₂ pressure. As a result of this behavior, increasing pressure causes the reactivity to increase significantly at low temperatures, but since the reactivity curves merge at high temperature, this effect diminishes significantly with increasing temperature. This behavior was not observed for the Wyodak coal char; that is, the reactivity was practically unaffected by increasing the total pressure up to 15 atm. Reactivity was found to increase monotonically with CO₂ partial pressure for both chars, and the presence of additional CO in the feed gas was found to have a significant inhibiting effect on the reaction rate. (Abstract shortened by UMI.)...