Effect of the support acidity in methane reforming with CO2 over nickel-zeolites catalysts

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Microcalorimetric studies and methane reforming by CO2 on Ni-based zeolite catalysts

A series of catalysts contg. nickel, based on HZSM-5 and USY zeolites, have been prepd. by ionic exchange; a Ni/gamma-Al2O3 catalyst has been prepd. by impregnation, for comparison. Ammonia and CO adsorption microcalorimetry and temp. programmed redn. expts. have shown that NiZSM-5 is the most acidic and the most reducible catalyst. The study of the reaction of methane reforming by carbon dioxide in presence of these catalysts has shown that the catalytic performance depends simultaneously on the acidity, reducibility, and structure of the zeolite. Globally, it appears that the catalytic properties of NiUSY are superior to those of NiZSM-5 and Ni/gamma-Al2O3

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

In-situ hydrogasification/regeneration of NiAl-hydrotalcite derived catalyst in the reaction of CO2 reforming of methane: A versatile approach to catalyst recycling

A novel approach describing the in-situ regeneration of NiAl hydroalcite derived catalyst between two cycle reaction systems of CO reforming of methane, also known as dry reforming of methane (DRM) is described herein. The catalyst was initially prepared by co-precipitation method at pH = 11 and calcined at 450°C for 6 h. The obtained material was characterized using X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET), atomic absorption spectroscopy (AAS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry (TG/ATD) and temperature programmed reduction (TPR-H) techniques. Following treatment of our catalyst under DRM conditions, the catalyst was subjected to in-situ hydrogasification conditions to promote regeneration followed by a second DRM cycle. An increase of 15.7% in the conversion of CH and 17.3% in the conversion of CO was attained, while the ratio of resulting H/CO augmented by 14%. The ratio of H consumed over the course of two hours hydrogasification, to that generated over ten hours of DRM, was 9.6%. The small particle sizes of resulting Ni°species as well as their high stability were both key factors contributing to the increase in the amount of H/CO produced prior to and after regeneration.The authors of this paper would like to thank the General Directorate for Scientific Research and Technological Development (DGRSDT), under the umbrella of the Algerian Ministry of Higher Education and Scientific Research for their generous funding to support this work

Hydrogen production via methane dry reforming process over CoAl and CoMgAl-Hydrotalcite derived catalysts

Co0.67Al0.31 and Co0.14Mg0.54Al0.31 hydrotalcite based catalysts were prepared by a coprecipitation method at a fixed pH=11, exhibiting a suitable hydrotalcite structure to be used as a catalyst in the reaction of the dry reforming of methane (DRM). Calcination at 450 °C provides the best conditions to prepare the most adapted structure and morphology to be later used in the DRM reaction. The samples were characterised by XRD, FTIR, SEM and it was shown that they exhibit a specific surface in the 30-70 g/cm² and a crystallite size of approximately 20 nm. The results of the TPR analysis showed clearly that CoAl-HT has better catalytic performances than CoMgAl-HT. This result can be explained by the presence of the Co0 for the catalyst CoAl-HTc-R and the total absence in the sample CoMgAl-HTc-R. The solid CoMgAl- HTc-R requires high reduction temperature compared to CoAl- HTc-R due to the strong CoO-MgO interactionsPeer reviewe