Chu Wei

Effects of Promoter on NiMgAl Catalyst Structure and Performance for Carbon Dioxide Reforming of Methane

Catalysts were prepared by adding different types of promoter (Co, Ir, or Pt) to the supported nickel catalyst NiMgAl samples. These catalysts were characterized by H2 temperature-programmed reduction (H2- TPR), CO2/CH4 temperature-programmed surface reactions (CO2/CH4-TPSR), and CO2 temperature- programmed desorption (CO2-TPD). The effects of the catalyst structure on catalytic performance in the methane dry reforming reaction with carbon dioxide were investigated. The addition of a small amount of promoter (Pt or Ir) can lower the reduction temperature of the nickel active component, and enhance performance in the methane dry reforming reaction. The catalysts with Co or Ir promoter feature lower activation energies than the unmodified NiMgAl catalyst. The activation energy was 51.8 kJ∙mol - 1 for the NiMgAl sample, decreasing to 26.4 kJ∙mol - 1 for the NiPtMgAl catalyst, which showed overall better catalytic performance. Results of CH4-TPSR and CO2-TPSR demonstrate that the NiPtMgAl catalyst can generate more active carbon species on the catalyst surface. The CO2-TPD results show that adding a promoter can increase the CO2 adsorbed/desorbed amount compared with the unmodified NiMgAl catalyst over the same reaction temperature range.

Effect of Silver Content on Catalytic Performances of SiO 2 -Supported Silver Tungstophoric Acid for the Synthesis of Polytetrahydrofuran

A series of supported silver salts of heteropolyacid AgxH3-xPW/SiO2 (x=0.5, 1.0, 1.5, 2.0, 2.5, 3.0) were synthesized and showed high reactivity and stability in tetrahydrofuran polymerization, which were due to the saltsʹ insolubility in polar solvent. The amount of Ag ion replaced in the salt and the amount of the salt loaded on the silica significantly influenced the catalytic performance. Change in the Ag content of the supported silver salt altered the crystal phase composition of the silver tungstophoric acid and catalystʹs acid strength. The AgxH3-xPW/SiO2 catalyst had the highest acid strength and the highest polymerization activity when x=2.0. When the Ag2HPW loading was 30% (mass fraction), the catalyst exhibited the best dispersion and highest activity for the polymerization of tetrahydrofuran. Compared with the conventional silica supported heteropolyacid (HPW/SiO2) catalyst, the present 30%Ag2HPW/SiO2 displayed excellent reusability, with its reactivity only slightly declining after 4 reuses. Through the introduction of the Ag ion, the stability of the novel supported 30%Ag2HPW/SiO2 was significantly improved and the obtained polymer product, polytetrahydrofuran, had a stable average molecular weight.