Enhancement of Ni-NiO-CeO2 Interaction on Ni-CeO2/Al2O3-MgO Catalyst by Ammonia Vapor Diffusion Impregnation for CO2 Reforming of CH4.

Ni-based catalysts have been widely used for the CO2 reforming of methane (CRM) process, but deactivation is their main problem. This study created an alternative electronic Ni-NiO-CeO2 interaction on the surface of 5 wt% Ni-5 wt% CeO2/Al2O3-MgO (5Ni5Ce(xh)/MA) catalysts to enhance catalytic potential simultaneously with coke resistance for the CRM process. The Ni-NiO-CeO2 network was developed on Al2O3-MgO through layered double hydroxide synthesis via our ammonia vapor diffusion impregnation method. The physical properties of the fresh catalysts were analyzed employing FESEM, N2 physisorption, and XRD. The chemical properties on the catalyst surface were analyzed employing H2-TPR, XPS, H2-TPD, CO2-TPD, and O2-TPD. The CRM performances of reduced catalysts were evaluated at 600 °C under ambient pressure. Carbon deposits on spent catalysts were determined quantitatively and qualitatively by TPO, FESEM, and XRD. Compared to 5 wt% Ni-5 wt% CeO2/Al2O3-MgO prepared by the traditional impregnation method, the electronic interaction of the Ni-NiO-CeO2 network with the Al2O3-MgO support was constructed along the time of ammonia diffusion treatment. The electronic interaction in the Ni-NiO-CeO2 nanostructure of the treated catalyst develops surface hydroxyl sites with an efficient pathway of OH* and O* transfer that improves catalytic activities and coke oxidation.

Combined Steam and CO2 Reforming of Methane over the Hierarchical Ni-ZrO2 Nanosheets/Al2O3 Catalysts at Ultralow Temperature and under Low Steam.

This research developed hierarchical 10 wt % Ni-1 wt % ZrO2/Al2O3 catalysts for combined steam and CO2 reforming of methane (CSCRM) reaction to produce syngas for gas-to-liquid (GTL) application under the ultralow temperature and low steam condition. The hierarchical nanosheet catalysts were prepared via a novel impregnation technique assisted by ammonia vapor diffusion with various times (1, 6, and 12 h) to develop the different magnitude of hierarchical nanosheets on the surface. Then, CSCRM at 600 °C was performed on the catalysts for 6 h. The results evidenced the improvement of H2 selectivity, reaching an appropriate H2/CO ratio (1.9-2.0) in FT subunits in the GTL process when nanosheets existed on the surface due to the increase in H2O adsorption-dissociation sites. The good dispersion of hierarchical nanosheets accompanied by the ZrO2 promoter successfully enhanced the CH4 conversion and the coke prevention through the spread nanosheets because of the increase in the number of active sites and the surface interaction. The interaction of hierarchical nanosheets created the H2O activation-dissociation sites that allowed CO2 to be selective on the oxygen vacancy sites, producing more OH* and OH* on the catalyst surface to resist the carbon deposition during CSCRM operation.