•Nd-containing mesoporous silica support xNdMS were prepared by sol–gel method.•Positive effect of Nd on structural properties of Ni/xNdMS was investigated.•Ni/xNdMS catalysts exhibited high catalytic performance in OCRM and DRM reactions.•The oxidation state and the nickel particle size affected the activity.Ordered mesoporous silica materials based on nickel and other elements have been extensively studied because controlling the size of metal nanoparticles is an effective method to tune the superficial physicochemical process. Neodymium (Nd)-promoted mesoporous silica xNdMS (x: molar ratio of Nd/Si = 0.01, 0.02, 0.04, 0.06) were prepared through a sol–gel strategy. Nickel-based catalysts with high dispersion by using xNdMS as supports were investigated for methane reforming with carbon dioxide and/or oxygen to produce syngas. xNdMS supports and nickel catalysts were examined by combining textural, structural, local and surface information. The characterization results showed that Nd was successfully incorporated into the mesoporous framework of MS and Nd was beneficial to improve the metal dispersion. All Nd-promoted Ni/MS catalysts were effective for the methane reforming reaction. Ni/0.04NdMS catalyst exhibited the highest initial catalytic activity during 12 h time on stream, which was attributed to its high metal dispersion, more basic sites and the strengthened nickel-support interaction. The readily deactivation and poorest catalytic activity of Ni/MS catalyst were due to the serious oxidation of metallic nickel under reaction medium.Download high-res image (254KB)Download full-size image

The adsorption capacities of a heterometallic metal–organic framework (CPM-200-In/Mg) to VOCs (HCHO, C2H4, CH4, C2H2, C3H8, C2H6, C2H3Cl, C2H2Cl2, CH2Cl2 and CHCl3) and some inorganic gas molecules (HCN, SO2, NO, CO2, CO, H2S and NH3), as well as its selectivity in ternary mixture systems of natural gas and post-combustion flue gas are theoretically explored at the grand canonical Monte Carlo (GCMC) and density functional theory (DFT) levels. It is shown that CPM-200-In/Mg is suitable for the adsorption of VOCs, particularly for HCHO (up to 0.39 g g−1 at 298 K and 1 bar), and the adsorption capacities of some inorganic gas molecules such as SO2, H2S and CO2 match well with the sequence of their polarizability (SO2 > H2S > CO2). The large adsorption capacities of HCN and HCHO in the framework result from the strong interaction between adsorbates and metal centers, based on analyzing the radial distribution functions (RDF). Comparing C2H4 and CH4 molecules interacting with CPM-200-In/Mg by VDW interaction, we speculate that the high adsorption capacities of their chlorine derivatives in the framework could be due to the existence of halogen bonding or strong electrostatic and VDW interactions. It is found that the basic groups, including –NH2, –N and –OH, can effectively improve both the adsorption capacities and selectivity of CPM-200-In/Mg for harmful gases. Note that the adsorption capacity of CPM-200-In/Mg–NH2 (site 2) (245 cm3 g−1) for CO2 exceeded that of MOF-74-Mg (228 cm3 g−1) at 273 K and 1 bar and that for HCHO can reach 0.41 g g−1, which is almost twice that of 438-MOF and nearly 45 times of that in active carbon. Moreover, for natural gas mixtures, the decarburization and desulfurization abilities of CPM-200-In/Mg–NH2 (site 2) have exceeded those of the MOF-74 series, while for post-combustion flue gas mixtures, the desulfurization ability of CPM-200-In/Mg–NH2 (site 2) is still comparable to those of the MOF-74 series at 303 K and 4 MPa. We hope that the current theoretical study could guide experimental research in the future.

•Impregnation strategy of Y2O3 addition on Ni/Al2O3 and Co/Al2O3 catalysts.•Positive effect of Y2O3 on Ni/Al2O3 and negative effect of Y2O3 on Co/Al2O3.•Ni/YAl2O3 exhibited better activity and stability compared to Ni + Y/Al2O3.•Co/YAl2O3 showed the largest amount of carbon deposit and metal sintering.The overall purpose of this study was to develop an effective catalyst with high carbon resistance in the conversion of methane to synthesis gas via dry reforming. The catalytic performances of α-Al2O3 supported nickel- and cobalt-based catalysts modified with Y2O3 were investigated in this process. Sequential impregnation and co-impregnation of Y2O3 addition were employed during the catalyst preparation. The modification effect of Y2O3 and the preparation strategies on the surface structure, physico-chemical properties and coke deposition were revealed. For nickel catalysts, two impregnation methods of yttrium addition both greatly increased the activity and stability compared with counterpart Ni catalyst. Furthermore, the best performance over Ni/YAl2O3 catalyst prepared by sequential impregnation was related to smaller metallic nickel particle and more basic sites, while its remarkable stability was due to the small degree of graphitization and the less amount of carbon deposit. This sintering-resistant and higher carbon-resistant nickel catalyst is potentially useful for methane conversion in high reaction temperature. On the contrary, the negative effect of Y2O3 was clearly found for Co/Al2O3 catalyst. The introduction of Y2O3 led to inadequate reduction and metal sintering in reduced and spent catalysts. Co/YAl2O3 prepared by sequential impregnation exhibited steep deactivation during the methane reforming reaction because of the obvious cobalt sintering and serious carbon deposition.

•Synergic modification by EG and CA favored better distribution of Ni particles.•Synergic modification prevented Ni aggregation in high reaction temperature.•EG showed better alcohol property for pretreating silica support.•EG improved the supported metal species to interact with the isolated SiOH.•Adding appropriate CA into the impregnation solution favored Ni dispersion.This study targeted the novel silica-supported nickel-based catalyst (Ni/SiO2) modified by organic agents. The synergic modification effect of ethylene glycol (EG) and citric acid (CA) on the nickel catalyst was investigated. EG was used to pretreat the silica support and CA was used in the impregnation solution to synthesize the nickel based catalysts with different CA loadings. NiCA-x/SiO2-EG (x: molar ratio of CA/Ni ranging from 0.25 to 1.5) catalysts achieved an excellent stability and higher catalytic activity than the catalysts without EG in oxidative CO2 reforming of methane (CH4/CO2/O2 = 40/20/10, total flow rate = 60 ml/min, reaction temperature = 750 °C, and reaction pressure = 1 atm). EG addition modified the surface properties of silica support. The use of CA in the impregnation solution had a clear effect on the dispersion of NiO and Ni in the silica matrix. For the catalysts with the same content of CA, the catalysts with EG modification showed the synergic effect of EG and CA by improving the chemical interaction between Ni and support, resulting in higher dispersion of nickel. The temperature programmed reduction revealed that the reduction peak shifted to higher temperature with increasing CA loading, which was attributed to the smaller metallic Ni size of the reduced catalysts. The transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy confirmed that the addition of organic additive modified the silica surface and retained the metallic Ni species, and thus preventing the metal aggregation at high reaction temperature. The NiCA-1.5/SiO2-EG catalyst exhibited the highest activity, which was due to the small metallic metal size (4 nm) and the strong interaction between silica support and metal species.