Highly Active Amino-Modified MCM-41-Supported Zinc Catalyst for Acetylene Hydration to Acetaldehyde

Selectivity adsorption of sulfate by amino-modified activated carbon during capacitive deionization

ABSTRACTCapacitive deionization (CDI) is an environmentally friendly desalination technique with low energy consumption. However, unmodified carbon electrode materials have poor sulfate selectivity and adsorption capacity. In this work, to improve sulfate selectivity, we prepared activated carbon materials loaded with different amino contents by grafting amino groups via acid treatment for different times. In the competitive ion adsorption experiments, the sulfate selectivity of AC was only 0.64 and the amino-modified AC increased by 1.98-2.52 times due to the formation of stronger hydrogen bonds between the amino group and sulfate. AC-NH₂-4 had the best selectivity and the sulfate selective coefficient was 2.25. The desorption of sulfate was 92.46% within one hour. In addition, the surface of the amino-modified activated carbon showed significantly improved electrochemical properties and better capacitance. The specific capacitance of amino-modified AC in different electrolyte solutions was consistent with the competitive adsorption results. The specific capacitance of amino-modified AC in Na₂SO₄ electrolyte solution was the highest. The modified electrode material also had the advantages of a higher adsorption capacity and excellent regeneration performance after continuous electric adsorption-desorption cycles. Therefore, it may have development potential to selectively adsorb sulfate in practical applications.

A density functional theory exploration on the Zn catalyst for acetylene hydration

The acetylene hydration method to produce acetaldehyde has been widely used for over 130 years; however, a detailed molecular-level understanding of the reaction mechanism is still lacking. In the present work, we systematically investigated the mechanisms of such reactions on ZnCl₂, Zn(OH) Cl, and Zn(OH)₂ catalysts through density functional theory (DFT) methods. The Fukui function, condensed Fukui function, and Hirshfeld charges enabled us to predict the active sites of the catalysts and acquire electron transfer information. From these data, we found that catalysts bearing hydroxyl groups exhibited relatively low adsorption performances compared with catalysts without this functionality. The calculations demonstrated that the three studied catalysts had three distinct reaction paths. For the Zn(OH)Cl and Zn(OH)₂ catalysts, the reaction took place through a one-shift H₂O molecule transfer route, avoiding higher energy barrier pathways. Interestingly, we found that the energy required for breaking the O-H bond in water determined the activation energy of the studied catalytic reactions. The activation barrier increased in the order Zn(OH)Cl ≈ Zn(OH)₂ < ZnCl₂. This trend suggests that Zn(OH)Cl and Zn(OH)₂ are promising catalysts for the hydration of acetylene. Graphical abstract.