Weiming Lin

Selective catalytic methanation of CO in hydrogen-rich gases over Ni/ZrO2 catalyst

Ni/ZrO2 catalysts were prepared by the incipient-wetness impregnation method and were investigated in activity and selectivity for the selective catalytic methanation of CO in hydrogen-rich gases with more than 20 vol% CO2. The result showed that Ni loadings significantly influenced the performance of Ni/ZrO2 catalyst. The 1.6 wt% Ni loading catalyst exhibited the highest catalytic activity among all the catalysts in the selective methanation of CO in hydrogen-rich gas. The outlet concentration of CO was less than 20 ppm with the hydrogen consumption below 7%, at a gas-hourly-space velocity as high as 10000 h−1 and a temperature range of 260 °C to 280 °C. The X-ray diffraction (XRD) and temperature programmed reduction (TPR) measurements showed that NiO was dispersed thoroughly on the surface of ZrO2 support if Ni loading was under 1.6 wt%. When Ni loading was increased to 3 wt% or above, the free bulk NiO species began to assemble, which was not favorable to increase the selectivity of the catalyst.

Effect of CeO2 on the catalytic performance of Ni/Al2O3 for autothermal reforming of methane

Abstract The effect of promoter Ce on the catalytic performance of Ni/Al 2 O 3 catalyst for autothermal reforming of methane to hydrogen was investigated. The catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The results indicated that the catalytic performance of the catalysts was improved with the addition of Ce. Ni/Ce 30 Al 70 O δ showed the highest CH 4 conversion in operation temperatures ranging from 650 °C to 850 °C. At the same time, the decrease in H 2 /CO ratio with increasing reaction temperature was consistent with the fact that water-gas shift reaction was thermodynamically unfavorable at higher temperatures. The XRD result indicated that adding Ce to Ni/Al 2 O 3 catalyst prevented the formation of NiAl 2 O 4 and facilitated the formation of NiO. The formation of NiO increased the number of active sites, resulting in higher activity. Comparing the TPR profiles of Ni/Ce 30 Al 70 O δ with Ni/Al 2 O 3 , it could be clearly observed that with the addition of Ce, the total reduction peak areas in the middle and low temperatures increased. It was most probably that the addition of Ce inhibited the stronger interaction between Ni and Al 2 O 3 to form the phase of NiAl 2 O 4 , and favored the formation of the strong interaction between NiO species and CeO 2 . Therefore, the addition of Ce to the Ni/Al 2 O 3 catalyst increased the active surface that promoted the activity of the catalyst.

Autothermal reforming of methane over Ni catalysts supported over ZrO2-CeO2-Al2O3

Abstract Ni catalysts supported on Al2O3, ZrO2-Al2O3, CeO2-Al2O3 and ZrO2-CeO2-Al2O3 were prepared by coprecipitation method, and their catalytic performances for autothermal reforming of methane to hydrogen were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS. The relationship between the structures and catalytic activities of the catalysts was discussed. The results showed that the catalytic activity and stability of the Ni/ZrO2-CeO2-Al2O3 catalyst was better than those of other catalysts with the highest CH4 conversion, H2/CO and H2/COx ratio at 750° C. The catalyst showed a little deactivation along the reaction time during its 72 h on stream with the mean deactivation rate of 0.08%/h. The catalytic performance of the Ni/ZrO2-CeO2-Al2O3 catalyst was also affected by reaction temperature, nO2:nCH4 molar ratio and nH2O : nCH4 molar ratio. TPR, XRD and XPS measurements indicated that the formation of ZrO2-CeO2 solid solution could improve the dispersion of NiO, and inhibit the formation of NiAl2O4, and thus significantly promoted the catalytic activity of the Ni/ZrO2-CeO2-Al2O3 catalyst.

Autothermal Reforming of Methane over Ni Catalysts Supported on CuO-ZrO2-CeO2-Al2O3

Abstract Ni catalysts supported on various mixed oxides of Al 2 O 3 with rare earth oxide and transitional metal oxides were synthesized. The studies focused on the measurement of the autothermal reforming of methane to hydrogen over Ni catalysts supported on the mixed oxide Zr x Ce 30- x Al 70 O δ ( x =5, 10, 15). The catalytic performance of Ni/Zr 10 Ce 20 Al 70 O δ was better than that of other catalysts. XRD results showed that the addition of Zr to Ni/Ce 30 Al 70 O δ prevented the formation of NiAl 2 O 4 and facilitated the dispersion of NiO. Effects of CuO addition to Zr 10 Ce 20 Al 70 O δ were also investigated. The activity of Ni catalyst supported on CuO-ZrO 2 -CeO 2 -Al 2 O 3 was somewhat affected and the Ni/Cu 5 Zr 10 Ce 20 Al 65 O δ showed the best catalytic performance with the highest CH 4 conversion, yield of H 2 , selectivity for H 2 and H 2 /CO production ratio in operation temperatures ranging from 650 to 750 °C.

Selective Oxidation of CO in Excess H2 over Ru/Al2O3 Catalysts Modified with Metal Oxide

Abstract The Ru/Al2O3 catalysts modified with metal oxide (K2OandLa2O3) were prepared via incipient wetness impregnation method from RuCl3·nH2O mixed with nitrate loading on Al2O3 support. The activity of catalysts was evaluated under simulative conditions for the preferential oxidation of CO (CO-PROX) from the hydrogen-rich gas streams produced by reforming gas, and the performances of catalysts were investigated by XRD and TPR. The results showed that the activity temperature of the modified catalysts Ru-K2O/Al2O3 and Ru-La2O3/Al2O3 were lowered approximately 30 °C compared with pure Ru/Al2O3, and the activity temperature range was widened. The conversion of CO on Ru-K2O/Al2O3 and Ru-La2O3/Al2O3 was above 99% at 140–160 °C, suitable to remove CO in a hydrogen-rich gas and the selectivity of Ru-La2O3/Al2O3 was higher than that of Ru-K2O/Al2O3 in the active temperature range. Slight methanation reaction was detected at 220 °C and above.

Removal of CO from reformed fuels by selective methanation over Ni-B-Zr-Oδ catalysts

The Ni-B-Oδ and Ni-B-Zr-Oδ catalysts were prepared by the method of chemical reduction, and the deep removal of CO by selective methanation from the reformed fuels was performed over the as-prepared catalysts. The results showed that zirconium strongly influenced the activity and selectivity of the Ni-B-Zr-Oδ catalysts. Over the Ni-B-Oδ catalyst, the highest CO conversion obtained was only 24.32% under the experimental conditions studied. However, over the Ni-B-Zr-Oδ catalysts, the CO methanation conversion was higher than 90% when the temperature was increased to 220 °C. Additionally, it was found that the Ni/B mole ratio also affected the performance of the Ni-B-Zr-Oδ catalysts. With the increase of the Ni/B mole ratio from 1.8 to 2.2, the CO methanation activity of the catalyst was improved. But when the Ni/B mole ratio was higher than 2.2, the performance of the catalyst for CO selective methanation decreased instead. Among all the catalysts, the Ni29B13Zr58Oδ catalyst investigated here exhibited the highest catalytic performance for the CO selective methanation, which was capable of reducing the CO outlet concentration to less than 40 ppm from the feed gases stream in the temperature range of 230–250 °C, while the CO2 conversion was kept below 8% all along. Characterization of the Ni-B-Oδ and Ni-B-Zr-Oδ catalysts was provided by XRD, SEM, DSC, and XPS.

Effect of Transition Metals (Cu, Co and Fe) on the Autothermal Reforming of Methane over Ni/Ce0.2Zr0.1 Al0.7 Oδ Catalyst

Abstract The transition metals (Cu, Co, and Fe) were applied to modify Ni/Ce 0.2 Zr 0.1 Al 0.7 O δ catalyst. The effects of transition metals on the catalytic properties of Ni/Ce 0.2 Zr 0.1 Al 0.7 O δ autothermal reforming of methane were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS. Tests in autothermal reforming of methane to hydrogen showed that the addition of transition metals (Cu and Co) significantly increased the activity of catalyst under the conditions of lower reaction temperature, and Ni/Cu 0.05 Ce 0.2 Zr 0.1 Al 0.65 O δ was found to have the highest conversion of CH 4 among all catalysts in the operation temperatures ranging from 923 K to 1023 K. TPR, XRD and XPS measurements indicated that the cubic phases of Ce x Zr 1− x O 2 solid solution were formed in the preparation process of catalysts. Strong interaction was found to exist between NiO and Ce x Zr 1− x O 2 solid solution. The addition of Cu improved the dispersion of NiO, inhibited the formation of NiAl 2 O 4 , and thus significantly promoted the activity of the catalyst Ni/Cu 0.05 Ce 0.2 Zr 0.1 Al 0.65 O δ .

Carbon nanotubes supported Pt-Ru-Ni as methanol electro-oxidation catalyst for direct methanol fuel cells

Abstract Carbon nanotubes (CNTs) supported Pt-Ru and Pt-Ru-Ni catalysts were prepared by chemical reduction of metal precursors with sodium borohydride at room temperature. The crystallographic properties and composition of the catalysts were characterized by X-ray diffraction (XR, D) and energy dispersive X-ray (EDX) analysis, and the catalytic activity and stability for methanol electro-oxidation were measured by electrochemical impedance spectroscopy (EIS), linear sweep voltammetries (LSV), and chronoamperometry (CA). The results show that the catalysts exhibit face-centered cubic (fee) structure. The particle size of Pt-R.u-Ni/CNTs catalyst is about 4.8 nm. The catalytic activity and stability of the Pt-Ru-Ni/CNTs catalyst are higher than those of Pt-Ru/CNTs catalyst.

Carbon nanotubes-Nafion composites as Pt-Ru catalyst support for methanol electro-oxidation in acid media

Carbon nanotubes-Nafion (CNTs-Nafion) composites were prepared by impregnated CNTs with Nafion in ethanol solution and characterized by FT-IR. Pt-Ru catalysts supported on CNTs-Nafion composites were synthesized by microwave-assisted polyol process. The physical and electrochemical properties of the catalysts were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), CO stripping voltammetry, cyclic voltammetry (CV) and chronoamperometry (CA). The results showed that the Nafion incorporation in CNTs-Nafion composites did not significantly alter the oxygen-containing groups on the CNTs surface. The Pt-Ru catalyst supported on CNTs-Nafion composites with 2 wt% Nafion showed good dispersion and the best CO oxidation and methanol electro-oxidation activities.

Preparation and oxygen permeation properties of SrFe(Cu)O3−δ dense ceramic membranes

Abstract Mixed oxygen-ionic and electronic conducting membranes of SrFe(Cu)O 3–δ were prepared by solid-state reaction method. The crystal structure, oxygen nonstoichiometry, and phase stability of the materials were studied by TGA and XRD. Oxygen permeation fluxes through these membranes were studied at operating temperature ranging from 750 to 950 °C. Results showed that doping Cu in SrFeO 3–δ compound had a significant effect on the formation of single-phased perovskite structure. For SrFe 1–x Cu x O 3–δ series materials, the oxygen nonstoichiometry and the oxygen permeation flux increased considerably with the increase of Cu-doping content (x = 0.1–0.3). The sintering property of the membrane decreased significantly when the Cu substitution amount reached 40%. SrFe 0.7 Cu 0.3 O 3–δ showed high oxygen permeation flux, but SrCuO 2 and Sr 2 Fe 2 O 5 phases formed in the compound after oxygen permeation test induced cracks in the membrane.