The deactivation of nickel catalysts used in Arak and Razi petrochemical complexes followed by catalyst regeneration was evalu-ated. The characterization of the different structures was made by powder X-ray diffractio...The deactivation of nickel catalysts used in Arak and Razi petrochemical complexes followed by catalyst regeneration was evalu-ated. The characterization of the different structures was made by powder X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),transmission electron microscopy(TEM),and carbon & sulfur analyzer. The Ni particle size was estimated from XRD patterns and TEM graphs. The agglomeration of nickel particle and the poison by sulfur components were recognized as the main reasons in deactivation of Arak and Razi catalysts,respectively. The activity of the used catalysts before and after regeneration was measured on methane steam reforming at a CH4:H2O ratio of 1:3 at 850 oC. The regeneration processes for Arak and Razi samples were performed with CO2 as an oxidative atmosphere and steam as a regenerating agent,respectively. The results show that,(1) no residual sulfur components were on the regenerated Razi catalyst surface without changing the structure of the catalyst and the regenerated catalyst has gained 80% of its catalytic activity,and that(2) the nickel particle size of regenerated Arak specimen decreased remarkably as measured by Debye-Scherrer equation from XRD patterns. TEM images were in agreement with the XRD results and indicated a decrease in nickel particle size of regenerated catalyst. Additionally,in both regenerated catalysts all the coke on the surface of the support was eliminated after regeneration.展开更多
LaMn1-xCuxO3±δ perovskite oxides (x = 0, 0.2, 0.4, 0.6, 0.8, 1) were prepared by two different methods, the Pechini and sol-gel methods. The catalysts were characterized by Fourier transform infrared spectroscop...LaMn1-xCuxO3±δ perovskite oxides (x = 0, 0.2, 0.4, 0.6, 0.8, 1) were prepared by two different methods, the Pechini and sol-gel methods. The catalysts were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray fluorescence spectroscopy, N2 adsorption, and temperature-programmed reduction. Their catalytic activity in the oxidation of methane and CO was evaluated. EDS and SEM results showed that the Pechini samples had more homogeneity and smaller particles (higher specific surface area). The catalytic activity for methane combustion was highest for x = 0.2. In CO oxidation, the oxides with x = 0.2 and x = 0.4 were the most active. The Pechini samples had higher activity and stability than the sol-gel samples.展开更多
In this study, mixed metal oxides developed with a perovskite-type structure that show great potential for use in catalysis. Perovskite oxide catalysts with the composition LaMoxV1-xOn （x = 0.1, 0.3, 0.5, 0.7, and 0....In this study, mixed metal oxides developed with a perovskite-type structure that show great potential for use in catalysis. Perovskite oxide catalysts with the composition LaMoxV1-xOn （x = 0.1, 0.3, 0.5, 0.7, and 0.9） have been synthesized by the sol-gel method and then used in the ethane dry reforming reaction for the direct synthesis of acetic acid. The influence of the nature of the metallic source （metal, nitrate, acetylacetonate, and ammonium） on gel formation has been studied by Fourier-transform infrared spectroscopy （FT-IR） and thermogravimetric analysis （TGA-DTA）. After calcination, the obtained perovskites were characterized by X-ray diffraction （XRD） and energy-dispersive X-ray spectrometry （EDS） coupled with scanning electron microscopy （SEM）. The catalysts were then subjected to thermo-programmed reduction （TPR）. The surface area （BET） was found to increase from 2.6 m^2/g （x = 0.1） to 5.1 m2/g （x = 1.0） with increasing molybdenum content following calcinations at 750 °C, and pure LaMoxV1-xOn perovskite was obtained with good homogeneity. The catalysts have been characterized by XRD, SEM, EDS, and carbon analysis （CA）. The results indicate that through this synthesis it is possible to obtain highly crystalline, homogeneous and pure solids, with well-defined structures. The direct synthesis of acetic acid from ethane over the perovskite catalysts was studied at temperatures between 450 and 850 °C and elevated pressures between 1 and 8 bar. It was found that the yield of acetic acid and the selectivity of its formation could be increased by incorporating more molybdenum into the perovskite structure. The experimental studies have shown that the calcination temperature and the molybdenum content have a significant influence on the catalytic activity. Amongst the catalysts tested, LaMo0.7V0.3O4.2 exhibited the best activity and stability.展开更多
文摘The deactivation of nickel catalysts used in Arak and Razi petrochemical complexes followed by catalyst regeneration was evalu-ated. The characterization of the different structures was made by powder X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),transmission electron microscopy(TEM),and carbon & sulfur analyzer. The Ni particle size was estimated from XRD patterns and TEM graphs. The agglomeration of nickel particle and the poison by sulfur components were recognized as the main reasons in deactivation of Arak and Razi catalysts,respectively. The activity of the used catalysts before and after regeneration was measured on methane steam reforming at a CH4:H2O ratio of 1:3 at 850 oC. The regeneration processes for Arak and Razi samples were performed with CO2 as an oxidative atmosphere and steam as a regenerating agent,respectively. The results show that,(1) no residual sulfur components were on the regenerated Razi catalyst surface without changing the structure of the catalyst and the regenerated catalyst has gained 80% of its catalytic activity,and that(2) the nickel particle size of regenerated Arak specimen decreased remarkably as measured by Debye-Scherrer equation from XRD patterns. TEM images were in agreement with the XRD results and indicated a decrease in nickel particle size of regenerated catalyst. Additionally,in both regenerated catalysts all the coke on the surface of the support was eliminated after regeneration.
文摘LaMn1-xCuxO3±δ perovskite oxides (x = 0, 0.2, 0.4, 0.6, 0.8, 1) were prepared by two different methods, the Pechini and sol-gel methods. The catalysts were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray fluorescence spectroscopy, N2 adsorption, and temperature-programmed reduction. Their catalytic activity in the oxidation of methane and CO was evaluated. EDS and SEM results showed that the Pechini samples had more homogeneity and smaller particles (higher specific surface area). The catalytic activity for methane combustion was highest for x = 0.2. In CO oxidation, the oxides with x = 0.2 and x = 0.4 were the most active. The Pechini samples had higher activity and stability than the sol-gel samples.
文摘In this study, mixed metal oxides developed with a perovskite-type structure that show great potential for use in catalysis. Perovskite oxide catalysts with the composition LaMoxV1-xOn （x = 0.1, 0.3, 0.5, 0.7, and 0.9） have been synthesized by the sol-gel method and then used in the ethane dry reforming reaction for the direct synthesis of acetic acid. The influence of the nature of the metallic source （metal, nitrate, acetylacetonate, and ammonium） on gel formation has been studied by Fourier-transform infrared spectroscopy （FT-IR） and thermogravimetric analysis （TGA-DTA）. After calcination, the obtained perovskites were characterized by X-ray diffraction （XRD） and energy-dispersive X-ray spectrometry （EDS） coupled with scanning electron microscopy （SEM）. The catalysts were then subjected to thermo-programmed reduction （TPR）. The surface area （BET） was found to increase from 2.6 m^2/g （x = 0.1） to 5.1 m2/g （x = 1.0） with increasing molybdenum content following calcinations at 750 °C, and pure LaMoxV1-xOn perovskite was obtained with good homogeneity. The catalysts have been characterized by XRD, SEM, EDS, and carbon analysis （CA）. The results indicate that through this synthesis it is possible to obtain highly crystalline, homogeneous and pure solids, with well-defined structures. The direct synthesis of acetic acid from ethane over the perovskite catalysts was studied at temperatures between 450 and 850 °C and elevated pressures between 1 and 8 bar. It was found that the yield of acetic acid and the selectivity of its formation could be increased by incorporating more molybdenum into the perovskite structure. The experimental studies have shown that the calcination temperature and the molybdenum content have a significant influence on the catalytic activity. Amongst the catalysts tested, LaMo0.7V0.3O4.2 exhibited the best activity and stability.
