Search

Monometallic and bimetallic Cu:Ni catalysts with different Cu:Ni molar ratios (3:1, 2:1, 1:1, 1:2, 1:3) were synthesized by wetness impregnation on activated carbon and characterized by TPR (temperature programmed reduction), XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy). The synthesized catalysts were evaluated in the gas phase production of diethyl carbonate from ethanol and carbon dioxide. The largest catalytic activity was obtained over the bimetallic catalyst with a Cu:Ni molar ratio of 3:1. Its improved activity was attributed to the formation of a Cu-Ni alloy on the surface of the catalyst, evidenced by XPS and in agreement with a previous assignment based on Vegard law and TPR analysis. During the reaction rate experiments, it observed the presence of a maximum of the reaction rate as a function of temperature, a tendency also reported for other carbon dioxide-alcohol reactions. It showed that the reaction rate-temperature data can be adjusted with a reversible rate equation. The initial rate as a function of reactant partial pressure data was satisfactorily adjusted using the forward power law rate equation and it was found that the reaction rate is first order in CO 2 and second order in ethanol., (© 2024. The Author(s).)

The adsorptive removal of acetaldehyde is more compatible for real-world applications. However, it must be upgraded from simple adsorption to a high efficiency process with value added products. This study develops a modified zeolite with Mg 2+ ions that possesses acid-base sites for the removal of acetaldehyde at room temperature. Through a modified procedure, MgO is coated on commercial zeolite (13x), achieving a porosity of 501 m 2  g -1 with MgO particles of 100 nm and pore diameter of 2.6 nm, and high breakthrough capacity of 50.00 mg/g. The initial pH and concentration of Mg 2+ ion 12.5 and 0.2 M, respectively, with a maximum breakthrough capacity of 12.72 mg/g at 10% humidity. Significant variations in breakthrough capacity with respect to humidity in the presence of H 2 S and NH 3 demonstrate the effects of water and gases on adsorption efficiency. Desorptive oxidation of adsorbed acetaldehyde at 250 °C yielded a high molecular weight intermediate ethylene oxide formation. The oxidation is followed by aldol condensation and hydrogenation. The higher breakthrough capacity and the intermediate product yielded using the developed MgO-zeolite proves the acid-base reaction sites involved in acetaldehyde removal follows chemisorption and possible process scale-up., (Copyright © 2021 Elsevier Ltd. All rights reserved.)