Papers by Keyword: Methane Conversion

Abstract: Pr-Zr mixed oxides prepared by co-precipitation were used as oxygen carriers for converting methane into synthesis gas through gas-solid reactions. The structural evolution and reducibility of Pr-Zr oxygen carriers with calcination temperatures from 600 to 1200°C were investigated by XRD and TPR techniques and correlated to their activity for methane selective oxidation. The Pr-Zr mixed oxides calcined at 600-800°C show outstanding thermostability, and higher calcination temperatures result in phase segregation. Pr0.7Zr0.3O2-δ possesses high temperature stability(<900 °C) and the best appropriate calcination temperature is 800°C for methane gas-solid reaction.

Abstract: The two-step steam methane reforming for production syngas and hydrogen was investigated by using Ce-based oxygen carriers (CeO2, CeO2-ZrO2，CeO2-Fe2O3) which were prepared by co-precipitation method and characterized by means of X-ray diffractometer and Raman spectroscopy. CH4 temperature programmed and isothermal reactions were adopted to test syngas production reactivity, and redox properties were evaluated by a successive redox cycle. The results showed that the incorporation of ZrO2 into CeO2 was found to be an effective approach for enhancing the reducibility of CeO2 in methane conversion reaction and redox performance, and the addition of Fe2O3 into CeO2 could obviously increase the amount of reactive oxygen species in CeO2-Fe2O3 and the yields of syngas and hydrogen reached maximum in the 3rd cycle, but the redox stability of CeO2-Fe2O3 needs to be enhanced.

Abstract: In this study, mathematical modelling of oxidative coupling of methane (OCM) to C₂ hydrocarbons (C₂H₆ and C₂H₄) over La2O3/CaO catalyst in a fixed-bed reactor operated under isothermal and non-isothermal conditions was investigated using the MATLAB program. In this process, methane and acetylene were the inputted feed and ethane, ethylene, propylene, propane, i-butane and n-butane were the output products. The amount of methane conversion obtained was 12.7% for the former feed however; if pure methane was inputted this conversion rose to 13.8%. Furthermore, the plasma process would enhance the conversion, selectivity towards desired product and process yield. A comparison between the thermal and the plasma process showed that the methane conversion and production yield in the plasma were higher than in the thermal process under the same operating conditions. Finally, the results of the catalytic OCM and methane conversion processes in the plasma phase were compared with one another.

Abstract: Pure CeO₂ and a series of (x %) K-CeO₂ (x=1, 2, 3, 4) catalysts were respectively prepared by the precipitation and incipient wetness impregnation methods, and characterized by means of XRD, BET and H₂-TPR techniques. The catalytic activity was investigated by the gas-solid reaction with methane in the absence of gaseous oxidant in a fixed bed reactor at 800 °C. The XRD measurement showed that doping of K₂CO₃ did not change the structure of CeO₂ with the addition of K₂CO3 without formation of Ce-K-O solid solution in these materials. Surface area of catalysts was _{Subscript text}decreased with the impregnation amount of K₂CO₃. Reducibility of catalysts was obviously enhanced by the addition of K₂CO₃ as shown in H₂-TPR tests. The catalysts activity tests indicated that adding K₂CO₃ to CeO₂ could promote the oxygen storage capacity of catalysts. K species in CeO₂ could affect the CO formation in methane oxidation.

Abstract: In the general framework of studies on nanomaterials for micro-sensors, cerium dioxide nanopowders (CeO2-z) and nanocomposites systems of copper doped ceria (CuOx-CeO2-z) were prepared and characterized. The aim of this specific study is to try to connect catalytic activity of such nanopowders with microstructure, additional phases and/or doping effect. The nanopowders of pure and doped cerium oxide were elaborated from various “Sol-Gel” chemical routes. Microstructural analysis was first carried out by X-ray diffraction (XRD). The specific areas were determined from BET adsorption techniques and the results were correlated to the size determinations obtained from XRD. The catalytic activity of such nanopowders in presence of methane gas CH4 was analyzed making use of FTIR spectrometry and a homemade device. For a better understanding of such catalytic responses, we proposed a modeling approach of solid gas interactions that takes into account a typical temperature dependent Avrami's model.