Catalytic combustion of hydrocarbons over perovskites

Abstract

The advantages and disadvantages of the catalysts so far employed or proposed for the low-temperature catalytic combustion of hydrocarbons, in both static and mobile energy production devices, are discussed. Furthermore, a La0.9Ce0.1CoO3 perovskite has been prepared by a recently proposed new flame-hydrolysis method. This proved a high surface area, thermally highly resistant catalyst. The partial substitution of Ce for La in such a cobaltite led to a relatively low suprafacial activity, but to a high bulk oxygen mobility, leading to high intrafacial activity for the catalytic flameless combustion of methane. The best operating conditions have been also found, for supporting the so prepared active phase, by dip-coating of a cordieritic honeycomb support, after deposition of an alumina primer. A very active and durable catalyst was so obtained, useful for practical application in the environmentally friendly low-temperature combustion of methane.

Catalytic combustion of methane over mixed oxides derived from Co–Mg/Al ternary hydrotalcites

“…The methane light-off temperatures on the catalysts are well consistent with the specific combustion rates ( Table 2). The calculated Ea for methane combustion over xCoMAO-800 catalysts are in the range from 90 kJ/mol to 120 kJ/mol, suggesting the materials are suitable for catalytic combustion [1,16]. However, the catalytic activity on xCoMAO-800 is not linear relevant to cobalt loading amounts, which can be attributed to the different SSAs and interactions existing in various compositions as shown by porosity, TPR and TG-DSC: the higher porosity and oxidation power, the better access of reactant to the catalysts surface.…”

“…Generally, supported noble metal oxides, particularly palladium oxide, are excellent catalysts for lower temperature combustion, but noble metals are expensive and prone to deactivation owing to sintering, decomposition and undesirable interaction with supports under hydrothermal situations encountered in combustion [3,6,[8][9][10]. A variety of inexpensive transition metal oxide catalysts, such as solid solution oxides [11][12][13], perovskites [14][15][16], pyrochlores [17][18][19] and hexaaluminates [7,[20][21][22] have been explored for catalytic combustion of methane. Unfortunately, no single catalyst, so far, can tolerate the stringent hydrothermal conditions existing in methane combustion.…”

“…Extensive efforts have been made to develop Co-based oxide combustion catalysts with the solid solution, perovskite, pyrochlore and hexaaluminate structures [11,14,[16][17][18]24,25]. However, perovskites and pyrochlores and solid solution oxide catalysts suffer from gas diffusion limitation in combustion due to their low specific surface areas (SSAs) [15,[17][18][19]24].…”

Chemical reaction engineering, process design and scale-up issues at the frontier of synthesis: Flow chemistry

“…An organic solution of the precursors is fed to a burner together with a flow of oxygen. By calibrating the residence time into the flame and the combustion enthalpy of the solvent, the particle size and, more in general, catalyst properties such as thermal resistance, can be finely tuned [96][97][98][99][100][101].…”

Effects of Cobalt and Nickel Substitution οn Physical Properties of Perovskite Type Oxides Prepared by the Sol-Gel Citrate Method

“…There is a growing interest in perovskite-type oxides with the general formula ABO 3 , where A is lanthanum and B is a first-row transition metal (Cr, Mn, Fe, Ni, or Co) for use as catalysts or catalyst precursors for internal reforming of methane in solid oxide fuel cell systems and for CO 2 reforming of CH 4 . As catalysts, the B-site cation is considered to be responsible for the catalytic activity while the A-site cation is considered to be responsible for thermal stability [1].…”