Catalytic Combustion for Ultra-Low Emissions

Abstract

Catalytic combustion is an emerging technology in which fuels can be combusted homogeneously supported by a catalyst. The catalyst allows non-flammable mixtures of fuel and air to be oxidized with the resulting heat generated used to initiate thermal or homogeneous combustion. With the proper catalysts the fuel can be combusted with efficiencies so high that unburned CO or HC emissions are less than 10 ppm. Furthermore, because the fuel-air mixtures are relatively lean compared to conventional processes the adiabatic temperatures are below that required for the formation of NOx i.e. > 1500°C. The success of this technology would eliminate the need for expensive after-treatment of emissions from gas fired power plants and boilers.This is a very demanding application, especially for natural gas fueled combustors, since the catalyst will have to initiate reaction between 400 and 500°C, at linear velocities exceeding 50 ft/sec, and retain its activity after experiencing temperatures up to 1400°C. Furthermore, the monolithic ceramic or metallic support upon which the catalyst is deposited must also retain structural integrity after experiencing high temperatures and severe thermal shock.This paper will describe the fundamental concepts of this new technology, the major technical problems being addressed and the progress being made.

Influence of the addition of H2 upon the behavior and properties of a Pd(2wt.%)/γ-Al2O3 catalyst and a comparison with the case of the Pt-based catalyst

“…However, a better knowledge of the surface phenomena governing the catalytic behavior is still necessary for a more widespread use of catalytic combustion. It is well known that the oxidation state of palladium is one of the key parameters governing the combustion process efficiency [9][10][11]. Recently, we have proposed a reaction scheme for CCM on Pd/g-alumina catalyst [12], mainly based on operando Raman [13] and operando DRIFTS [12,14] experiments.…”

The Activation of a Pd/γ-alumina Catalyst During Methane Combustion: Investigation of the Phenomenon and of Potential Causes

“…Actually, this technology emerged in the beginning of the 1970s [2,8], but its large-scale application is still limited by some problems that have to be solved like a better activity of the catalyst at low temperature and the improvement of its stability at high temperature [5,6,9,10]. For CCM at low temperature, Pd-supported catalysts are largely recognized as the best catalytic systems [2][3][4][5]9,11,12].…”

Investigation of the physico-chemical implications of the hydrogen presence during H2-assisted catalytic combustion of methane using Pd(10wt.%)/γ-Al2O3 catalyst

“…It has been proposed that two distinct palladium phases coexist during CCM, namely an oxide phase (PdO) and a metallic phase (Pd) [1,14,18,21]. Given that H 2 is a highly reductant gas, the potential reduction of the palladium phase has to be taken into account.…”

“…[5,6,[8][9][10][11][12]). Furthermore, most of them have been made on Pt-based catalysts [5,6,8], whereas Pdbased catalysts are considered as the most active systems for CCM [1,[13][14][15][16][17][18][19][20][21][22]. Unfortunately, information is scarce concerning the effective influence of the hydrogen presence in the CCM feed on the physico-chemical properties of the catalyst.…”