Transition metals-incorporated zeolites as environmental catalysts for indoor air ozone decomposition

Green synthesis of solketal from glycerol using metal-modified ZSM-5 zeolite catalysts: process optimization

This study investigates the production of solketal (2,2-dimethyl-1,3-dioxolane-4-methanol) from glycerol via ketalization reaction using M-ZSM-5 catalysts (M = Fe, Co, Ni, Cu, and Zn). The wet impregnation method ensured precise metal loading and versatility in catalyst preparation. We present a novel approach by employing a suite of characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), Thermogravimetric analysis (TGA), and Field-emission scanning electron microscopy (FE-SEM), to elucidate the catalyst's structure, bonding, surface area, thermal stability, and morphology, ultimately linking these properties to their performance. Solketal synthesis was optimized in a reactor, with parameters like temperature, glycerol:acetone molar ratio, catalyst amount, reaction time, and stirring speed. Optimal conditions were identified as 60 °C, 1:4, 0.2 g, 60 min, and 1200 rpm, respectively. Gas chromatography-mass spectrometry (GC-MS) analysis confirmed successful solketal formation. Among M-ZSM-5 catalysts tested, Cu-ZSM-5 emerged the most efficient, achieving an impressive 99% glycerol conversion and 96% solketal selectivity. Notably, Cu-ZSM-5 catalyst displayed exceptional reusability, regaining its initial activity through calcination, thus minimizing waste generation. This research unveils Cu-ZSM-5 as a highly efficient catalyst and promotes sustainability by utilizing a renewable glycerol feedstock to produce valuable solketal with applications in fuel additives, solvents, and pharmaceuticals. This work paves the way for developing environmentally friendly processes for waste valorization and producing valuable bio-based chemicals.

One-Pot Synthesis of Ultra-Small Pt Dispersed on Hierarchical Zeolite Nanosheet Surfaces for Mild Hydrodeoxygenation of 4-Propylphenol

The rational design of ultra-small metal clusters dispersed on a solid is of crucial importance in modern nanotechnology and catalysis. In this contribution, the concept of catalyst fabrication with a very ultra-small size of platinum nanoparticles supported on a hierarchical zeolite surface via a one-pot hydrothermal system was demonstrated. Combining the zeolite gel with ethylenediaminetetraacetic acid (EDTA) as a ligand precursor during the crystallization process, it allows significant improvement of the metal dispersion on a zeolite support. To illustrate the beneficial effect of ultra-small metal nanoparticles on a hierarchical zeolite surface as a bifunctional catalyst, a very high catalytic performance of almost 100% of cycloalkane product yield can be achieved in the consecutive mild hydrodeoxygenation of 4-propylphenol, which is a lignin-derived model molecule. This instance opens up perspectives to improve the efficiency of a catalyst for the sustainable conversion of biomass-derived compounds to fuels.

Effect of copper ion-exchange on catalytic wet peroxide oxidation of phenol over ZSM-5 membrane

Cu-ZSM-5 zeolite membrane catalysts prepared by ion exchange method were synthesized on paper-like sintered stainless fibers (PSSFs) with three-dimensional net structure for the catalytic wet peroxide oxidation (CWPO) of phenol in structured fixed bed reactor. The experimental results exhibited that the BET of optimal catalyst was 165 m²/g with the ion exchange concentration of 0.1 M and time of 24 h, respectively, at temperature of 40 °C and one time ion exchange. The FT-IR results illustrated that band intensity was the lowest, and original Cu⁺ species and lattice oxygen were predominant in optimal catalyst according to the XPS results. Then, the effects of ion exchange concentration, time, temperature and times on catalytic performance of phenol were also investigated in structured fixed bed. It was found that the phenol was completely removed, TOC conversion (around 76.6%), high CO₂ selectivity (about 78%) and low copper leaching rate (about 30%) were achieved with only 1.91 wt% copper loading over the optimal catalyst. Finally, a reasonable reaction mechanism occurring in the presence of H₂O₂ for CWPO of phenol was proposed by analyzing the HPLC results, which indicated Fenton-like reactions were mainly based on the HO· production by catalytic decomposition of hydrogen peroxide with Cu⁺ species.

Recent advances in catalytic decomposition of ozone

Ozone (O₃), as a harmful air pollutant, has been of wide concern. Safe, efficient, and economical O₃ removal methods urgently need to be developed. Catalytic decomposition is the most promising method for O₃ removal, especially at room temperature or even subzero temperatures. Great efforts have been made to develop high-efficiency catalysts for O₃ decomposition that can operate at low temperatures, high space velocity and high humidity. First, this review describes the general reaction mechanism of O₃ decomposition on noble metal and transition metal oxide catalysts. Then, progress on the O₃ decomposition performance of various catalysts in the past 30 years is summarized in detail. The main focus is the O₃ decomposition performance of manganese oxides, which are divided into supported manganese oxides and non-supported manganese oxides. Methods to improve the activity, stability, and humidity resistance of manganese oxide catalysts for O₃ decomposition are also summarized. The deactivation mechanisms of manganese oxides under dry and humid conditions are discussed. The O₃ decomposition performance of monolithic catalysts is also summarized from the perspective of industrial applications. Finally, the future development directions and prospects of O₃ catalytic decomposition technology are put forward.

Co/Fe and Co/Al layered double oxides ozone catalyst for the deep degradation of aniline: Preparation, characterization and kinetic model

In this work, Co/Fe and Co/Al layered double oxides (Co/Fe-LDO and Co/Al- LDO)ozone catalysts were obtained from Co/Fe and Co/Al layered double hydroxides intermediates (Co/Fe-LDH and Co/Al-LDH). Firstly, the optimal preparation parameters of the two intermediates were determined, then the morphology and mineralogy microstructure of the derived Co/Fe-LDO and Co/Al- LDO ozone catalysts were systematically studied. Finally, the reaction kinetics of the two ozone catalysts for the deep degradation of aniline wastewater in catalysts/ozone systems were established. The results showed that the optimal preparation conditions were set as pH 12, temperature 60 °C, cobalt‑iron ratio 3:1 for Co/Fe-LDH intermediate, and pH 12, temperature 70 °C, cobalt‑aluminum ratio 3:1 for Co/Al-LDH intermediate. During calcination treatment, the dehydration and recrystallization effect impelled LDH intermediate to form LDO catalyst. The derived ozone catalysts Co/Fe-LDO and Co/Al-LDO possess layered structure, and Co species was mainly based on Co₃O₄ as the main mineral phase of the two ozone catalysts. The addition of catalyst can realize the deep ozonation catalysis of aniline wastewater. The kinetic models established on the aniline oxidized by ozone or catalyst/ozone systems were both fitted the first-order reactions, and the reaction activation energy for COD_Cr and TOC degradation were significantly reduced in catalyst/ozone system.