Catalytic Reforming of Methane by Carbon Dioxide over Nickel-Exchanged Zeolite Catalysts

International audienceA series of nickel-exchanged catalysts based on ZSM-5, USY, and Mordenite zeolites has been prepared by the ionic exchange method. The NiZeol catalysts have been characterized by XRD and BET. The exchange levels and nickel contents of the catalysts have been determined by chemical analysis. The acidity of the zeolite supports has been investigated using NH3 adsorption microcalorimetry. The number of acidic sites was found to decrease according to the following sequence: HUSY > HZSM-5 > HMOR. The temperature programmed reduction studies showed that the most reducible catalyst is NiZSM-5. The Ni-exchanged zeolites presented good catalytic performance in the methane reforming by CO2. At a temperature of 650°C, CH4 conversions of 71 and 54% were achieved on NiUSY and NiZSM-5 respectively. At 400°C, CO2 FTIR adsorption has shown that CO2 decomposes into CO and oxygen on NiZSM-5 which explains its reactivity at such a low temperature, while no decomposition of this probe molecule was observed on the NiUSY catalyst. The catalytic performance was found to vary in the following sequence at 650° C: NiUSY > NiZSM-5 > NiMOR. Moreover, the catalytic performances were found to depend strongly on the CO2/CH4 ratio in the feed and were markedly improved for CO2/CH4 greater than 1

Studies on MeAPSO-5: An investigation of physicochemical and acidic properties

Oliveira, Alcineia C. Essayem, Nadine Tuel, Alain Clacens, Jean-Marc Ben Taarit, Younes 20th Ibero American Catalysis Symposium SEP 17-22, 2006 Gramado, BRAZILThis work reports physicochemical and acidic properties of MeAPSO-5 (Me = chromium or iron), regardless their performance in the production of isobutane. Chromium and iron were partially introduced in SAPO-5 by direct hydrothermal synthesis. The solids were characterized by XRD, chemical analysis, N-2 adsorption isotherms, EPR, XPS, and calorimetry of ammonia adsorption. Their activity was also evaluated in the isomerization of n-butane. The purity of hydrothermally synthesized SAPO-5 was identified in all solids. EPR and XPS showed that chromium and iron exist as Cr2O3 and Fe2O3, respectively, mostly distributed on the solid surface. However, no reflections characteristic of these oxides were found in the XRD patterns. The chromium and iron cause different effects on the acidity: chromium increases the solid acidity whereas iron reduces drastically the acidic features. While distinct activity were observed between CrSAPO-5 and the FeSAPO-5 in n-butane isomerization, it is noteworthy that the pure SAPO-5 is not active in the reaction due to the too low strength of its acid sites. Results suggest that the n-C-4 isomerization activity of CrSAPO-5 may be ascribed to its enhanced acidity while, contrary to what was observed in the case of mordenite or sulfated zirconia, Iron addition to SAPO-5 did not enhance the catalytic activity via a possible participation of redox steps. (c) 2007 Elsevier B.V. All rights reserved

Xylene production over sulphated modified mordenite

International audienc

Structural, acidic and catalytic features of transition metal-containing molecular sieves in the transformation of C-4 hydrocarbon

MATERIAUX+ATU:NESNon

Preparation of Co 2+ /ZSM5 Catalysts by Solid-State Reaction: Influence of the Precursor on Cobalt Speciation

International audienc

The effect of support morphology on the activity of HZSM-5-supported molybdenum catalysts for the aromatization of methane

International audienceThe aromatization of methane was investigated over Mo2C supported on several HZSM-5 zeolites with different morphologies and Si/Al ratios. X-ray diffraction, elemental analyses, X-ray photoelectron spectroscopy, 27Al NMR spectroscopy, nitrogen adsorption, and scanning electron microscopy were used to characterize the supports. Support morphology was observed to play a crucial role in this reaction, which was studied under conditions in which actual rates could be compared. Although rates did not vary linearly either with the total number of the acid sites or with the external surface area, turnover frequencies of the surface acid sites, calculated using the Si/Al ratios determined from XPS measurements, were observed to vary linearly with the external surface area