Cordierite monoliths coated with Pd-Fe/a- Al2O3 catalysts were prepared at various calcination temperatures and characterized by thermogravimetry, temperature-programmed reduction, transmission electron microscopy, di...Cordierite monoliths coated with Pd-Fe/a- Al2O3 catalysts were prepared at various calcination temperatures and characterized by thermogravimetry, temperature-programmed reduction, transmission electron microscopy, diffuse reflectance infrared Fourier transfor- mation spectroscopy and X-ray diffraction. The performance of the catalytic monoliths for the synthesis of dimethyl oxalate (DMO) through a CO coupling reaction was evaluated. Monolithic catalysts with calcination temperatures ranging from 473 K to 673 K exhibited excellent dispersion of Pd, good CO adsorption properties, and excellent performance for the coupling reaction. The optimized monolithic catalyst exhibited a much higher Pd efficiency (denoted as DMO (g).Pd (g)-1 h 1) (733h-1) than that of the granular catalyst (60.2 h-1), which can be attributed to its honeycomb structure and the large pore sizes in the a-Al2O3 washcoat which was accompanied with an even distribution of the active component in the coating layer along the monoliths channels.展开更多
Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane. Adjusting the s...Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane. Adjusting the surface acid-base properties of catalysts by introduction of alkali metal (Na, K) oxides inhibits the carbonization and as a result, improves the operational stability of these catalysts. An effect of promotion of nickel-alumina based composite doped by lanthanum oxide is found. This effect, caused by an additional route for the CO2 activation on Ni-La2O3/Al2O3/cordierite catalyst, is displayed in increase of methane conversion under conditions of an oxidant excess.展开更多
Binary oxide systems(Cu Cr2O4, Cu Co2O4), deposited onto cordierite monoliths of honeycomb structure with a second support(finely dispersed Al2O3), were prepared as filters for catalytic combustion of diesel soot ...Binary oxide systems(Cu Cr2O4, Cu Co2O4), deposited onto cordierite monoliths of honeycomb structure with a second support(finely dispersed Al2O3), were prepared as filters for catalytic combustion of diesel soot using internal combustion engine’s gas exhausts(O2, NOx, H2 O, CO2) and O3 as oxidizing agents. It is shown that the second support increases soot capacity of aforementioned filters, and causes dispersion of the particles of spinel phases as active components enhancing thereby catalyst activity and selectivity of soot combustion to CO2. Oxidants used can be arranged with reference to decreasing their activity in a following series: O3 NO2〉 H2 O 〉 NO 〉 O2〉 CO2. Ozone proved to be the most efficient oxidizing agent: the diesel soot combustion by O3 occurs intensively(in the presence of copper chromite based catalyst) even at closing to ambient temperatures.Results obtained give a basis for the conclusion that using a catalytic coating on soot filters in the form of aforementioned binary oxide systems and ozone as the initiator of the oxidation processes is a promising approach in solving the problem of comprehensive purification of automotive exhaust gases at relatively low temperatures, known as the "cold start" problem.展开更多
文摘Cordierite monoliths coated with Pd-Fe/a- Al2O3 catalysts were prepared at various calcination temperatures and characterized by thermogravimetry, temperature-programmed reduction, transmission electron microscopy, diffuse reflectance infrared Fourier transfor- mation spectroscopy and X-ray diffraction. The performance of the catalytic monoliths for the synthesis of dimethyl oxalate (DMO) through a CO coupling reaction was evaluated. Monolithic catalysts with calcination temperatures ranging from 473 K to 673 K exhibited excellent dispersion of Pd, good CO adsorption properties, and excellent performance for the coupling reaction. The optimized monolithic catalyst exhibited a much higher Pd efficiency (denoted as DMO (g).Pd (g)-1 h 1) (733h-1) than that of the granular catalyst (60.2 h-1), which can be attributed to its honeycomb structure and the large pore sizes in the a-Al2O3 washcoat which was accompanied with an even distribution of the active component in the coating layer along the monoliths channels.
文摘Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane. Adjusting the surface acid-base properties of catalysts by introduction of alkali metal (Na, K) oxides inhibits the carbonization and as a result, improves the operational stability of these catalysts. An effect of promotion of nickel-alumina based composite doped by lanthanum oxide is found. This effect, caused by an additional route for the CO2 activation on Ni-La2O3/Al2O3/cordierite catalyst, is displayed in increase of methane conversion under conditions of an oxidant excess.
文摘Binary oxide systems(Cu Cr2O4, Cu Co2O4), deposited onto cordierite monoliths of honeycomb structure with a second support(finely dispersed Al2O3), were prepared as filters for catalytic combustion of diesel soot using internal combustion engine’s gas exhausts(O2, NOx, H2 O, CO2) and O3 as oxidizing agents. It is shown that the second support increases soot capacity of aforementioned filters, and causes dispersion of the particles of spinel phases as active components enhancing thereby catalyst activity and selectivity of soot combustion to CO2. Oxidants used can be arranged with reference to decreasing their activity in a following series: O3 NO2〉 H2 O 〉 NO 〉 O2〉 CO2. Ozone proved to be the most efficient oxidizing agent: the diesel soot combustion by O3 occurs intensively(in the presence of copper chromite based catalyst) even at closing to ambient temperatures.Results obtained give a basis for the conclusion that using a catalytic coating on soot filters in the form of aforementioned binary oxide systems and ozone as the initiator of the oxidation processes is a promising approach in solving the problem of comprehensive purification of automotive exhaust gases at relatively low temperatures, known as the "cold start" problem.