The generation of synthesis gas (hydrogen and carbon monoxide mixture) from two global warming gases of carbon dioxide and methane via dry reforming is environmentally crucial and for the chemical industry as well. Herein, magnesium-promoted NiO supported on mesoporous zirconia, 5Ni/xMg-ZrO 2 (x = 0, 3, 5, 7 wt%) were prepared by wet impregnation method and then were tested for syngas production via dry reforming of methane. The reaction temperature at 800 °C was found more catalytically active than that at 700 °C due to the endothermic feature of reaction which promotes efficient CH 4 catalytic decomposition over Ni and Ni-Zr interface as confirmed by CH 4-TSPR experiment. NiO-MgO solid solution interacted with ZrO 2 support was found crucial and the reason for high CH 4 and co 2 conversions. The highest catalyst stability of the 5Ni/3Mg-ZrO 2 catalyst was explained by the ability of CO 2 to partially oxidize the carbon deposit over the surface of the catalyst. A mole ratio of hydrogen to carbon monoxide near unity (H 2 /CO ~ 1) was obtained over 5Ni/ZrO 2 and 5Ni/5Mg-ZrO 2 , implying the important role of basic sites. Our approach opens doors for designing cheap and stable dry reforming catalysts from two potent greenhouse gases which could be of great interest for many industrial applications, including syngas production and other value-added chemicals. The production of syngas (a mixture of H 2 and CO) through dry reforming of methane is an excellent strategy to reduce the global warming effects of carbon dioxide (CO 2) and methane (CH 4). Noble metals such as palladium (Pd), platinum (Pt), and ruthenium (Ru) have been used for this purpose, but costly precursors and instability of catalyst, at high reaction temperature around 800 °C, have limited their application 1. On the other hand, costeffective nickel (Ni) metal, supported on an appropriate supports such as alumina 2 , mesoporous silicates 3-7 , and zirconia 8-10 , has been found to withstand at this reaction temperature (800 °C). In this context, many researchers have followed the surface modification methodology to optimise the catalyst performance because Ni-based catalyst is also prone to deactivation. The first series of modifications were carried out over alumina supports

Nickel catalysts supported on zirconium oxide and modified by various amounts of lanthanum with 10, 15, and 20 wt.% were synthesized for CO2 reforming of methane. The effect of La2O3 as a promoter on the stability of the catalyst, the amount of carbon formed, and the ratio of H2 to CO were investigated. In this study, we observed that promoting the catalyst with La2O3 enhanced catalyst activities. The conversions of the feed, i.e., methane and carbon dioxide, were in the order 10La2O3 > 15La2O3 > 20La2O3 > 0La2O3, with the highest conversions being about 60% and 70% for both CH4 and CO2 respectively. Brunauer–Emmett–Teller (BET) analysis showed that the surface area of the catalysts decreased slightly with increasing La2O3 doping. We observed that 10% La2O3 doping had the highest specific surface area (21.6 m2/g) and the least for the un-promoted sample. The higher surface areas of the promoted samples relative to the reference catalyst is an indication of the concentration of the metals at the mouths of the pores of the support. XRD analysis identified the different phases available, which ranged from NiO species to the monoclinic and tetragonal phases of ZrO2. Temperature programmed reduction (TPR) analysis showed that the addition of La2O3 lowered the activation temperature needed for the promoted catalysts. The structural changes in the morphology of the fresh catalyst were revealed by microscopic analysis. The elemental compositions of the catalyst, synthesized through energy dispersive X-ray analysis, were virtually the same as the calculated amount used for the synthesis. The thermogravimetric analysis (TGA) of spent catalysts showed that the La2O3 loading of 10 wt.% contributed to the gasification of carbon deposits and hence gave about 1% weight-loss after a reaction time of 7.5 h at 700 °C.

Dry reforming of CH4 was conducted over promoted Ni catalysts, supported on mesoporous gamma-alumina. The Ni catalysts were promoted by various metal oxides (CuO, ZnO, Ga2O3, or Gd2O3) and were synthesized by the incipient wetness impregnation method. The influence of the promoters on the catalyst stability, coke deposition, and H2/CO mole ratio was investigated. Stability tests were carried out for 460 min. The H2 yield was 87% over 5Ni+1Gd/Al, while the CH4 and CO2 conversions were found to decrease in the following order: 5Ni+1Gd/Al > 5Ni+1Ga/Al > 5Ni+1Zn/Al > 5Ni/Al > 5Ni+1Cu/Al. The high catalytic performance of 5Ni+1Gd/Al, 5Ni+1Ga/Al, and 5Ni+1Zn/Al was found to be closely related to their contents of NiO species, which interacted moderately and strongly with the support, whereas free NiO in 5Ni+1Cu/Al made it catalytically inactive, even than 5Ni/Al. The 5Ni+1Gd/Al catalyst showed the highest CH4 conversion of 83% with H2/CO mole ratio of ~1.0.

Metrics & MoreArticle Recommendations * sı Supporting Information ABSTRACT: 0.1−3 wt % Ce-promoted MCM-41-supported nickel catalysts were prepared for dry reforming of CH 4 (DRM) and characterized by surface area and pore analyses, powder X-ray diffraction , temperature-programed reduction with H 2 , temperature-programed CO 2 desorption, X-ray photoelectron spectroscopy, thermogravimetric analysis, and scanning transmission electron microscopy using a high-angle annular dark field. Notably, 5Ni0.5Ce/MCM-41 has a bimodal distribution of NiO crystallites inside and outside the pores of MCM-41, the highest number of basic sites inducing profound CO 2 interactions with the surface, and metallic nickel particles interacting with the support for facilitating CH 4 dissociation. In addition, a thin surface layer of ceria provides surface oxygen species for carbon deposit oxidation. All these physiochemical properties ensured >90% conversion (H 2 /CO ∼ 1) over 330 min on stream and >80% conversion over 75 h of time on stream (H 2 /CO = 0.98) over the 5Ni0.5Ce/MCM-41 catalyst. A higher ceria loading than 0.5 wt % masked the active Ni sites with a ceria layer, which diminished the number of basic sites and deteriorated the catalytic performance.

No abstract