Andrzej Machocki

Methane oxidative coupling in an undiluted reaction mixture in a reactor-adsorber system with gas recirculation

Abstract Results of the oxidative coupling of methane obtained in a reactor-adsorber system with gas recirculation, with a continuous supply on the methane-oxygen reaction mixture without a diluent gas ( p (CH 4 + O 2 ) = 1 atm, CH 4 :O 2 = 20:1), are described. At total methane conversion equal to 94%, the C 2+ hydrocarbon selectivity of the process was 70%, while ethylene contents was 92% in the obtained hydrocarbons.

Single-Layer Graphene as an Effective Mediator of the Metal-Support Interaction.

Single-layer chemical vapor deposition (CVD)-grown graphene was transferred onto a ZnO (0001) substrate forming a large-area, low-defect density, protective layer. The quality of the graphene layer and its effect on the interaction between the ZnO support and vapor-deposited cobalt particles was investigated by spectroscopic and microscopic techniques. We demonstrate that the in-between graphene layer influences both the oxidation state and the morphology of cobalt upon annealing in vacuum. In particular, cobalt strongly interacts with the bare ZnO substrate forming flat particles, which are readily oxidized and redispersed upon annealing in ultrahigh vacuum conditions. In contrast, in the presence of the graphene interlayer, cobalt forms highly dispersed nanoparticles, which are resistant to oxidation, but prone to surface diffusion and agglomeration. The graphene layer exhibits remarkable stability upon cobalt deposition and vacuum annealing, while interaction with reactive gases can facilitate the formation of defects.

Complete Oxidation of Methane over Palladium Supported on Alumina Modified with Calcium, Lanthanum, and Cerium Ions

Abstract The activity and thermal stability of Pd/Al 2 O 3 and Pd/(Al 2 O 3 +MO x ) (M=Ca, La, Ce) palladium catalysts in the reaction of complete oxidation of methane are presented in this study. The catalyst supports were prepared by sol-gel method and they were dried either conventionally or with supercritical carbon dioxide. Then they were impregnated with palladium nitrate solution. The catalysts with unmodified alumina had a high surface area. The activity and thermal stability of the alumina- supported catalyst was also very high. The introduction of calcium, lanthanum, or cerium oxide into alumina support caused a decrease of the surface area in the way dependent on the support precursor drying method. These modifiers decreased the activity of palladium catalysts, and they required higher temperatures for the complete oxidation of methane than unmodified Pd/Al 2 O 3 . The improvement of the palladium activity by lanthanum and cerium support modifier was observed only at low temperatures of the reaction.

Surface State and Catalytic Performance of Ceria‐Supported Cobalt Catalysts in the Steam Reforming of Ethanol

The effect of the particle size and the addition of a K promoter on the oxidation state of Co/CeO2 was investigated and correlated with selectivity for ethanol steam reforming performed with various H2O/EtOH molar ratios. Spectroscopic studies showed that the oxidation state of the catalyst components depends on the H2O/EtOH molar ratio. Surface oxygen‐containing species (OH and Kδ+−Oδ−) are necessary to achieve a good catalyst selectivity, to decrease the amount of coke deposited and to change the nature of the product from fully dehydrogenated C=C to CHx. Besides the surface concentration of oxygen‐containing species, the catalyst morphology and the location at which oxygen‐containing species are chemisorbed may be equally important to their abundance; the selective ceria‐supported Co catalyst should have well‐dispersed Co particles deposited on a well‐dispersed support.

Catalysts for the utilization of methane from the coal mine ventilation air

Catalysts for the utilization of methane from the coal mine ventilation air The paper indicates coal mines as the source of permanent emission of low-concentrated gases, which have increased the greenhouse effect. This paper proposes the catalytic oxidation of methane as the solution to the problem of methane utilization when its concentration in the air is insufficient for flame combustion. The studies which have been conducted for many years enabled finding the active oxide and metallic catalytic systems for the reaction of methane oxidation. For the utilization of gases with low-concentrated methane, using the low-temperature catalysts, especially palladium catalysts, seems to be economically well-justified. Depending on technological solutions it can be considered as the method for methane utilization or as an environmentally friendly way for the generation of electric and thermal energy.

INFLUENCE OF THE ANION OF PROMOTING SODIUM COMPOUNDS ON THE ACTIVITY AND SELECTIVITY IN OXIDATIVE COUPLING OF METHANE

The influence of the sodium compound anion-the promoter of the CaO/magnesiumaluminium spinel system-on the activity and selectivity in oxidative coupling of methane has been studied. It is found that the catalysts show optimal properties when the sodium compound of a weak acid is used.

Oxidative coupling of methane at moderate (600–650°C) temperatures

The presented results of methane oxidative coupling indicate that the lowering of the reaction temperature below 700°C, without any loss of its effectiveness, requires a much longer contact time than the times applied in a great majority of studies reported so far.