Ni-Al hydrotalcite derived catalyst （Ni-Al2O3-HT） exhibited a narrow Ni particle-size distribution with an average particle size of 4.0 nm. Methanation of CO2 over this catalyst initiated at 225℃ and reached 82.5% ...Ni-Al hydrotalcite derived catalyst （Ni-Al2O3-HT） exhibited a narrow Ni particle-size distribution with an average particle size of 4.0 nm. Methanation of CO2 over this catalyst initiated at 225℃ and reached 82.5% CO2 conversion with 99.5% CH4 selectivity at 350℃, which was much better than its impregnated counterpart. Characterizations by means of CO2 microcalorimetry and 27 Al NMR indicated that large amount of strong basic sites existed on Ni-Al2O3-HT, originated from the formation of Ni-O-Al structure. The existence of strong basic sites facilitated the activation of CO2 and consequently promoted the activity. The combination of highly dispersed Ni with strong basic support led to its unique and high efficiency for this reaction. Keywords展开更多
Trace amounts of noble metal-doped Ni/Mg（AI）O catalysts were pre- pared starting from Mg-Al hydrotalcites （HTs） and tested in daily start-up and shut-down （DSS） operation of steam reforming （SR） of methane or ...Trace amounts of noble metal-doped Ni/Mg（AI）O catalysts were pre- pared starting from Mg-Al hydrotalcites （HTs） and tested in daily start-up and shut-down （DSS） operation of steam reforming （SR） of methane or partial oxidation （PO） of propane. Although Ni/Mg（Al）O catalysts prepared from Mg（Ni）-Al HT exhibited high and stable activity in stationary SR, PO and dry reforming of methane and propane, the Ni/Mg（Al）O catalysts were drastically deactivated due to Ni oxidation by steam as purge gas when they were applied in DSS SR of methane. Such deactivation was effectively suppressed by doping trace amounts of noble metal on the catalysts by using a ＂memory effect＂ of HTs. Moreover, the noble metal-doped Ni/Mg（Al）O catalysts exhibited ＂intelligent＂ catalytic behaviors, i.e., self-activation and self-regenerative activity, leading to high and sustainable activity during DSS operation. Pt was the most effective among noble metals tested. The self-activation occurred by the reduction of Ni2＋ in Mg（Ni,Al）O periclase to Ni^0 assisted by hydrogen spillover from Pt （or Pt-Ni alloy）. The self-regenerative activity was accomplished by self-redispersion of active Ni^0 particles due to a reversible reductionoxidation movement of Ni between the outside and the inside of the Mg（Al）O periclase crystal; surface Ni^0 was oxidized to Ni2＋ by steam and incorporated into Mg（Ni2＋,Al）O periclase, whereas the Ni2＋ in the periclase was reduced to Ni^0 by the hydrogen spillover and appeared as the fine Ni^0 particles on the catalyst surface. Further a ＂green＂ preparation of the Pt/Ni/[Mg3.sAl]O catalysts was accomplished starting from commercial Mg3.5-AI HT by calcination, followed by sequential impregnation of Ni and Pt.展开更多
基金supported by the National Natural Science Foundation of China(21103173)
文摘Ni-Al hydrotalcite derived catalyst （Ni-Al2O3-HT） exhibited a narrow Ni particle-size distribution with an average particle size of 4.0 nm. Methanation of CO2 over this catalyst initiated at 225℃ and reached 82.5% CO2 conversion with 99.5% CH4 selectivity at 350℃, which was much better than its impregnated counterpart. Characterizations by means of CO2 microcalorimetry and 27 Al NMR indicated that large amount of strong basic sites existed on Ni-Al2O3-HT, originated from the formation of Ni-O-Al structure. The existence of strong basic sites facilitated the activation of CO2 and consequently promoted the activity. The combination of highly dispersed Ni with strong basic support led to its unique and high efficiency for this reaction. Keywords
基金supported by the New Energy and Industrial Technology Development Organization (NEDO),Japan
文摘Trace amounts of noble metal-doped Ni/Mg（AI）O catalysts were pre- pared starting from Mg-Al hydrotalcites （HTs） and tested in daily start-up and shut-down （DSS） operation of steam reforming （SR） of methane or partial oxidation （PO） of propane. Although Ni/Mg（Al）O catalysts prepared from Mg（Ni）-Al HT exhibited high and stable activity in stationary SR, PO and dry reforming of methane and propane, the Ni/Mg（Al）O catalysts were drastically deactivated due to Ni oxidation by steam as purge gas when they were applied in DSS SR of methane. Such deactivation was effectively suppressed by doping trace amounts of noble metal on the catalysts by using a ＂memory effect＂ of HTs. Moreover, the noble metal-doped Ni/Mg（Al）O catalysts exhibited ＂intelligent＂ catalytic behaviors, i.e., self-activation and self-regenerative activity, leading to high and sustainable activity during DSS operation. Pt was the most effective among noble metals tested. The self-activation occurred by the reduction of Ni2＋ in Mg（Ni,Al）O periclase to Ni^0 assisted by hydrogen spillover from Pt （or Pt-Ni alloy）. The self-regenerative activity was accomplished by self-redispersion of active Ni^0 particles due to a reversible reductionoxidation movement of Ni between the outside and the inside of the Mg（Al）O periclase crystal; surface Ni^0 was oxidized to Ni2＋ by steam and incorporated into Mg（Ni2＋,Al）O periclase, whereas the Ni2＋ in the periclase was reduced to Ni^0 by the hydrogen spillover and appeared as the fine Ni^0 particles on the catalyst surface. Further a ＂green＂ preparation of the Pt/Ni/[Mg3.sAl]O catalysts was accomplished starting from commercial Mg3.5-AI HT by calcination, followed by sequential impregnation of Ni and Pt.
