A series of Ni/SBA-15 catalysts with Ni contents ranging from 5 wt% to 15 wt%, as well as another series of 10%Ni/MgO/SBA-15 catalysts, in which the range of the MgO content was from 1 wt% to 7 wt%, were prepared, and...A series of Ni/SBA-15 catalysts with Ni contents ranging from 5 wt% to 15 wt%, as well as another series of 10%Ni/MgO/SBA-15 catalysts, in which the range of the MgO content was from 1 wt% to 7 wt%, were prepared, and their catalytic performances for the reaction of combined steam and carbon dioxide reforming of methane were investigated in a continuous flow microreactor. The structures of the catalysts were characterized using the XRD, H2-TPR and CO2-TPD techniques. The results indicated that the CO selectivity for this reaction was very close to 100%, and the H2/CO ratio of the product gas could be controlled by changing the H2O/CO2 molar ratio of the feed gas. The simultaneous and plentiful existing of steam and CO2 had a significant influence on the catalytic performance of the 10%Ni/SBA-15 catalyst without modification. After reacting at 850 °C for 120 h over this catalyst, the CH4 conversion dropped from 98% to 85%, and the CO2 conversion decreased from 86% to 53%. However, the 10%Ni/3%MgO/SBA-15 catalyst exhibited a much better catalytic performance, and after reacting for 620 h, the CO2 conversion over this catalyst dropped from 92% to around 77%, while the CH4 conversion was not decreased. Oxidation of the Ni0 species as well as carbon deposition during the reaction were the main reasons for the deactivation of the catalyst without modification. On the other hand, modification by the MgO promoter improved the dispersion of the Ni0 species, and enhanced the CO2 adsorption affinity which in turn depressed the occurring of carbon deposition, and thus retarded the deactivation process.展开更多
Novel Mg O–SBA-15 supported catalysts were prepared for oxidative esterification of methacrolein(MAL) with methanol to methyl methacrylate(MMA). The Mg O–SBA-15 supports were synthesized with different magnesia load...Novel Mg O–SBA-15 supported catalysts were prepared for oxidative esterification of methacrolein(MAL) with methanol to methyl methacrylate(MMA). The Mg O–SBA-15 supports were synthesized with different magnesia loadings from different magnesium precursors and hydrochloric acid molar concentrations. The Mg O–SBA-15 supports and Pd–Pb/Mg O–SBA-15 catalysts were characterized by several analysis methods. The results revealed that the addition of Mg O improved the ordered structure of SBA-15 supports and provided surface alkalinity of SBA-15 supports. The average size of the Pd3 Pb particles on magnesia-modified Pd–Pb/Mg O–SBA-15 catalysts was smaller than that on the pure silica-based Pd–Pb/SBA-15 catalysts. The experiments on catalyst performance showed that the magnesia-modified Pd–Pb/Mg O–SBA-15 catalysts had higher activity than pure silica-based Pd–Pb/SBA-15 catalysts, showing the strong dependence of catalytic activity on the average size of active particles. The difference of activity between Pd–Pb/SBA-15 catalysts and Pd–Pb/Mg O–SBA-15 catalysts was due to the discrepant structural properties and surface alkalinity provided by Mg O, which led to the different Pd3 Pb particle sizes and then resulted in the different number of active sites. Besides magnesia loadings, other factors, such as hydrochloric acid molar concentration and magnesium precursors, had considerable influences on the catalytic activity.展开更多
基金the National Basic Research Program ofChina (Project No. 2005CB221405)the National "863" Project ofChina (No. 2006AA10Z425)the Beijing Natural Science Foun-dation (Project No: 8062023)
文摘A series of Ni/SBA-15 catalysts with Ni contents ranging from 5 wt% to 15 wt%, as well as another series of 10%Ni/MgO/SBA-15 catalysts, in which the range of the MgO content was from 1 wt% to 7 wt%, were prepared, and their catalytic performances for the reaction of combined steam and carbon dioxide reforming of methane were investigated in a continuous flow microreactor. The structures of the catalysts were characterized using the XRD, H2-TPR and CO2-TPD techniques. The results indicated that the CO selectivity for this reaction was very close to 100%, and the H2/CO ratio of the product gas could be controlled by changing the H2O/CO2 molar ratio of the feed gas. The simultaneous and plentiful existing of steam and CO2 had a significant influence on the catalytic performance of the 10%Ni/SBA-15 catalyst without modification. After reacting at 850 °C for 120 h over this catalyst, the CH4 conversion dropped from 98% to 85%, and the CO2 conversion decreased from 86% to 53%. However, the 10%Ni/3%MgO/SBA-15 catalyst exhibited a much better catalytic performance, and after reacting for 620 h, the CO2 conversion over this catalyst dropped from 92% to around 77%, while the CH4 conversion was not decreased. Oxidation of the Ni0 species as well as carbon deposition during the reaction were the main reasons for the deactivation of the catalyst without modification. On the other hand, modification by the MgO promoter improved the dispersion of the Ni0 species, and enhanced the CO2 adsorption affinity which in turn depressed the occurring of carbon deposition, and thus retarded the deactivation process.
基金Supported by the Key Program of the National Natural Science Foundation of China(21036007)the National High-Tech Project of China(2012AA062903)
文摘Novel Mg O–SBA-15 supported catalysts were prepared for oxidative esterification of methacrolein(MAL) with methanol to methyl methacrylate(MMA). The Mg O–SBA-15 supports were synthesized with different magnesia loadings from different magnesium precursors and hydrochloric acid molar concentrations. The Mg O–SBA-15 supports and Pd–Pb/Mg O–SBA-15 catalysts were characterized by several analysis methods. The results revealed that the addition of Mg O improved the ordered structure of SBA-15 supports and provided surface alkalinity of SBA-15 supports. The average size of the Pd3 Pb particles on magnesia-modified Pd–Pb/Mg O–SBA-15 catalysts was smaller than that on the pure silica-based Pd–Pb/SBA-15 catalysts. The experiments on catalyst performance showed that the magnesia-modified Pd–Pb/Mg O–SBA-15 catalysts had higher activity than pure silica-based Pd–Pb/SBA-15 catalysts, showing the strong dependence of catalytic activity on the average size of active particles. The difference of activity between Pd–Pb/SBA-15 catalysts and Pd–Pb/Mg O–SBA-15 catalysts was due to the discrepant structural properties and surface alkalinity provided by Mg O, which led to the different Pd3 Pb particle sizes and then resulted in the different number of active sites. Besides magnesia loadings, other factors, such as hydrochloric acid molar concentration and magnesium precursors, had considerable influences on the catalytic activity.
