J. Cserényi

Conversion of methane to benzene over Mo2C and Mo2C/ZSM-5 catalysts

The activation and dehydrogenation of CH2 on Mo2C and MO2C/ZSM-5 have been investigated under non-oxidizing conditions. Unsupported Mo2C exhibited very little activity towards methane decomposition at 973 K. The main reaction pathway was the decomposition of methane to give hydrogen and carbon with a trace amount of ethane. Mixing Mo2C with ZSM-5 support somewhat enhanced its catalytic activity, but did not change the products of the reaction. A dramatic change in the product formation occurred on partially oxidized Mo2C/ZSM-5 catalyst; besides some hydrocarbons benzene was produced with a selectivity of 70–80% at a conversion of 5–7%. Carburization of highly dispersed MoO3 on ZSM-5 also led to a very active catalyst: the conversion of methane at the steady state was 5–6% and the selectivity of benzene formation was 85%.

Catalytic reaction of methane with carbon dioxide over supported palladium

The reforming of methane with carbon dioxide has been investigated at 673–773 K on supported palladium catalysts in a fixed-bed continuous-flow reactor. In addition, the dissociation of carbon dioxide and methane, and the reactivity of the surface carbon formed have also been examined. The dissociation of carbon dioxide, detected by infrared spectroscopy, occurred at the lowest temperature, 373 K, on Pd/TiO2. It was greatly promoted by the presence of methane. The decomposition of methane at the temperature of the CH4 + CO2 reaction (ca. 773 K) proceeded initially at a high rate yielding hydrogen and small amounts of ethane and ethene. The deposition of surface carbon was also observed, which was hydrogenated only above 720 K. The reaction between carbon dioxide and methane occurred rapidly above 673 K to give carbon monoxide and hydrogen with a ratio of 1.3–1.7. Very little carbon was deposited during the reaction of a stoichiometric gas mixture. Kinetic parameters of the reaction were determined and a possible reaction mechanism is proposed. kw|carbon dioxide hydrogenation; kinetics; methane reforming; palladium

A comparative study on the activation and reactions of CH4 on supported metals

The catalytic effects of silica-supported Pt metals were tested and compared in the decomposition of methane and its conversion into higher hydrocarbons. The dissociation of methane is readily measurable at 473–673 K. The rate of initial decomposition at 523 K was the highest on Rh, but it dropped to a low value within a short contact time. The gaseous products were hydrogen and ethane in small, variable amounts. Hydrogen of the carbonaceous species formed in the decomposition led to the production of aliphatic hydrocarbons.

A comparative study of the complete oxidation of dimethyl ether on supported group VIII metals

In the study of the interaction of dimethyl ether with alumina-supported platinum metals by means of infrared spectroscopy, methoxy species bonded to the alumina and CO adsorbed on the metals have been detected. The complete oxidation of dimethyl ether in a flow system sets in above 400 K and proceeded to 100% conversion at ~673 K. No or only very slight deactivation was observed in 5 h. The specific activity order of the catalysts is: Ru>Pt>Ir>Pd>Rh.

Adsorption and reactions of CH3Cl on Mo2C based catalyst

Abstract The adsorption of CH3Cl on ZSM-5, Mo2C/ZSM-5 and Mo2C/SiO2 was investigated by temperature-programmed desorption (TPD) and Fourier transform infrared spectroscopy (FTIR). The formation of methoxy species was clearly identified on all the three catalysts. Three elementary steps were considered to explain the absorption bands observed in the IR spectra and to describe the reaction products found at higher temperatures: (i) the interaction of CH3Cl with the OH groups of ZSM-5, (ii) dissociation of CH3Cl yielding CH3, and (iii) the elimination of HCl from the adsorbed CH3Cl to give CH2 species. A new finding was the identification of the alkenyl carbocation formed on the Lewis acidic sites of ZSM-5. The decomposition of CH3Cl on ZSM-5 proceeded at 673 K with a high conversion yielding propylene, ethylene, butane, methane and benzene in decreasing selectivities. Deposition of Mo2C on ZSM only slightly modified the catalytic behavior of ZSM-5. Its promoter effect came into prominence on silica surface.