Ganesh Chandra Dhal

Preparation and application of effective different catalysts for simultaneous control of diesel soot and NOX emissions: An overview

Soot particulates and nitrogen oxides (NOX) from diesel engine exhaust have been causing serious problems to human health and the global environment. NO contributes not only to the production of acid rain but also to the production of photochemical smog in a reaction with hydrocarbons while under the influence of sunlight. Fine soot particulates (C8H to C10H), which contain mutagenic hydrocarbons, can easily reach far down into lung tissues when inhaled and therefore have a detrimental impact on human health. Diesel engines are the primary power source of vehicles used in heavy duty applications. These include two wheelers, buses, large trucks, and inside-highway construction and mining equipment. Furthermore, diesel engines are becoming an increasing part of the light duty vehicle market worldwide. In India, 100% of heavy duty vehicles, 60% of light-duty commercial vehicles and 20% of passenger cars are diesel powered. Diesel exhaust is inherently low in the concentration of CO and unburned HC, for NO and particulate matter are being objectionable to be removed from the exhaust. Since the reduction of both NO and soot particulate emissions to the allowed level cannot be accomplished by engine modifications alone, after-treatment activity for the simultaneous reduction of emissions should be developed.

Simultaneous abatement of diesel soot and NOX emissions by effective catalysts at low temperature: An overview

ABSTRACT The diesel engine generally achieves the highest fuel, energy, and thermal efficiency due to its very high compression/expansion ratio (14:1 to 25:1). Diesel engines can have a thermal efficiency that exceeds 50%. The main problem is that they emit more pollution like fine black soot particulates (C8H to C10H) and nitrogen oxides (NOX). These pollutants have been causing serious problems for human health and the global environment and also impacts on the engine. There are many types of catalysts investigated for simultaneous control of these two pollutants, i.e., platinum group metals (PGM; Pt, Pd, Rh, and Ir) based, spinel-type oxides, hydrotalcite, rare earth metal oxides, mixed transient metal oxides, etc. The high raw material cost of PGM catalysts has become a significant issue, so developing non-PGM catalysts are one of the promising challenges. There are no extra reductants required because soot catalytically oxidizes itself in the presence of NOX at a faster rate than molecular oxygen and simultaneously NOX is reduced to nitrogen. The order of oxidation potential of NOX to oxidized soot in comparison to molecular oxygen is as follows: NO2 > NO > O2. To meet the very strict EPA US 2010 and Euro VI regulations of particulate matter (PM) and NOX for heavy-duty and light-duty vehicular stringent emission, it is very important to apply the integrated catalytic systems to significantly remove PM and NOX simultaneously. Many papers related to simultaneous control of soot and NOX over different catalysts have been published but till now some of effective catalysts showing high conversion at low temperatures (possibly within the range typical of diesel exhaust: 150–450°C) have not been reviewed. Thus, this article provides a summary of published information regarding the effective catalysts, their preparation methods, properties, and application for simultaneous control of diesel soot and NOX.

The choice of precursors in the synthesizing of CuMnOx catalysts for maximizing CO oxidation

The hopcalite (CuMnOx) catalyst is a well-known catalyst for CO oxidation at a low temperature and it is synthesized by the co-precipitation method with different types of precursors. Activity of the CuMnOx catalysts for CO oxidation is strongly dependent upon the combination of precursors, ranking in order {Mn(Ac)2 + Cu(NO3)2} > {Mn(Ac)2 + Cu(Ac)2} > {Mn(NO3)2 + Cu(NO3)2} > {Mn(NO3)2 + Cu(AC)2}. All the precursors were precipitated by KMnO4 solution and the precursors mostly comprised of MnO2, Mn2O3 and CuO phases. Keeping the same precipitant while changing the precursors caused a change in the lattice oxygen mobility which influenced the CO oxidation activity. The calcination strategy of the precursors has great influence on the activity of resulting catalysts. The reactive calcination (RC) conditions produce multifarious phenomena of CO oxidation and the precursor decomposition in a single-step process. The activity order of the catalysts for CO oxidation was as follows: reactive calcination (RC) > flowing air > stagnant air. Therefore, we recommended that the RC route was the more appropriate calcination route for the production of highly active CuMnOx catalysts. All the catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller analysis, X-ray photoelectron spectroscopy and scanning electron microscopy technique. The influence of precursors on the structural properties and the catalytic activity of co-precipitation derived binary CuMnOx catalysts for CO oxidation has been investigated.