Effect of Re Addition on the Water–Gas Shift Activity of Ni Catalyst Supported by Mixed Oxide Materials for H₂ Production

Water–gas shift (WGS) reaction was performed over 5% Ni/CeO2, 5% Ni/Ce-5% Sm-O, 5% Ni/Ce-5% Gd-O, 1% Re 4% Ni/Ce-5% Sm-O and 1% Re 4% Ni/Ce-5% Gd-O catalysts to reduce CO concentration and produce extra hydrogen. CeO2 and M-doped ceria (M = Sm and Gd) were prepared using a combustion method, and then nickel and rhenium were added onto the mixed oxide supports using an impregnation method. The influence of rhenium, samarium and gadolinium on the structural and redox properties of materials that have an effect on their water–gas shift activities was investigated. It was found that the addition of samarium and gadolinium into Ni/CeO2 enhances the surface area, reduces the crystallite size of CeO2, increases oxygen vacancy concentration and improves Ni dispersion on the CeO2 surface. Moreover, the addition of rhenium leads to an increase in the WGS activity of Ni/CeMO (M = Sm and Gd) catalysts. The results indicate that 1% Re 4% Ni/Ce-5% Sm-O presents the greatest WGS activity, with the maximum of 97% carbon monoxide conversion at 350 °C. An increase in the dispersion and surface area of metallic nickel in this catalyst results in the facilitation of the reactant CO adsorption. The result of X-ray absorption near-edge structure (XANES) analysis suggests that Sm and Re in 1% Re 4% Ni/Ce-5% Sm-O catalyst donate some electrons to CeO2, resulting in a decrease in the oxidation state of cerium. The occurrence of more Ce3+ at the CeO2 surface leads to higher oxygen vacancy, which alerts the redox process at the surface, thereby increasing the efficiency of the WGS reaction

Numerical simulation of porous media combustion for high temperature heat exchanger

The purpose of this work is developing the numerical 1D model of porous media combustion for investigating porous media burner systems. The software is used to solve energy, mass transfer and chemical reaction equation of the combustion. The operating condition and property parameters, which mainly affect the functions and quality of the industrial burner design, such as the inlet velocity of the reactants, the equivalence ratio, the extinction coefficient and the thermal conductivity of porous media, will be investigated and validated with experimental data. For developing the procedure of experiment, three diameter sizes of porous media materials (5 mm, 10 mm, and 15 mm.) were used. As a result, the developed model will be used as a tool to explore temperature distribution of heat exchange to improve thermal performance and overall efficiency system. Moreover, this knowledge can be applied to design porous media burner systems for uniform temperature distribution operation