Clean Diesel Power via Microwave Susceptible Oxidation Catalysts

Abstract

The problem of soot emissions from diesel engines is introduced and the possible solution of combining doped perovskites and microwave (mw) irradiation to "clean up" diesel soot filters is outlined. Eighteen doped perovskite catalysts are synthesized and tested for propane and CO oxidation, which are taken as model components for soot. The activity, selectivity, and SO2 tolerance are compared under conventional heating and mw irradiation. By combining mw irradiation and doped perovskites, one can create "hot spots" on the catalyst, resulting in efficient and selective heating of the active site, as well as less poisoning. Sr-doped and Ce-doped manganese perovskites show the highest activity. These catalysts are also the most selective, and have a high mw susceptibility. Optimal SO2 tolerance is displayed by Cr perovskites, from which the La0.8Ca0.2CrO3 combination uniquely converts propane before CO, and therefore can be used to remove >C2 hydrocarbons from a mix with CO. Possible mechanistic scenarios are presented and discussed.

Selective Hydrogen Oxidation in the Presence of C3 Hydrocarbons Using Perovskite Oxygen Reservoirs

“…[18,19] By coating a low-loss ceramic monolith with a microwave-susceptible perovskite catalyst, fast and efficient heating is achieved, since all the energy is supplied where it is needed, that is, on the combustion catalyst itself. [20][21][22][23] Perovskite-type oxides, ABO 3 , can be successfully applied as solid "oxygen reservoirs" in redox reactions such as selective hydrogen combustion. This reaction is part of a novel process for propane oxidative dehydrogenation, wherein the lattice oxygen of the perovskite is used to combust hydrogen selectively from the dehydrogenation mixture at 550 8C.…”

Microwaves in Heterogeneous Gas‐Phase Catalysis: Experimental and Numerical Approaches

“…Very small differences in conversion and selectivity were observed between experiments under microwave and classical conditions. Contrary to the above, Beckers et al [73] showed that propane oxidation was greatly enhanced by microwave irradiation. On the La 0.9 Sr 0.1 MnO 3 catalyst, the same conversion was reached at a ∼200°C lower temperature when microwave heating was applied.…”

“…Higher rate Imprecise temperature measurement [30] No effects n/a [61,62] Propane oxidation Negligible effect n/a [71,72] Higher conversion, reduction of reaction temperature Hot-spot formation [73] Ethane/propane/n-butane dehydrogenation…”

Total oxidation of lean propane over α-Fe2O3 using microwaves as an energy source

“…Will et al [7] investigated LaCoO 3 , LaMnO 3 and La x Sr 1-x MnO 3 catalysts and found small differences in propane conversion and CO 2 selectivity between experiments under microwave and classical conditions. Contrary to them, Beckers et al [8] showed that propane oxidation was greatly enhanced by microwave irradiation over catalysts with perovskite structure.…”

“…But there are only few reports concerning propane total oxidation under microwave radiation using mixed oxides as catalysts. Beckers et al [8,29] revealed that most of studied doped perovskites give higher propane conversion rates and suggests the hypothesis that MW heating creates ''hot spots'' on the catalysts active sites depending on the nature of occupied B site atom in the perovskite structure and its number of unpaired d-electrons. The most active La 0.9 Sr 0.1 MnO 3 enables full propane conversion at 350°C i.e.…”