Gradient porous Co–Cu–Mn mixed oxides modified ZSM-5 membranes as high efficiency catalyst for the catalytic oxidation of isopropanol

Structure and molecular-level transformation for oxidation of effluent organic matters by manganese oxides

As important organic components in water environments, effluent organic matters (EfOMs) from wastewater treatment plants are widely present in Mn-rich environments or engineered treatment systems. The redox interaction between manganese oxides (MnOx) and EfOMs can lead to their structural changes, which are crucial for ensuring the safety of water environments. Herein, the reactivities of MnOx with EfOMs were evaluated, and it was found that MnOx with high specific surface area, active high-valent manganese content and lattice oxygen content (i.e., amorphous MnO2) possessed stronger oxidizing ability towards EfOMs. Accompanying by EfOMs oxidation, Mn(IV) and Mn(III) were reduced into Mn(II), with Mn(III) as the significant active species. Through molecular-level transformation analysis by ultrahigh mass spectrometry (FT-ICR MS), the highly reactive compounds in EfOMs were clearly determined to be that with more aromatic and unsaturated structures, especially lignin-like compounds (the highest content in EfOMs (over 60 %)). EfOMs were oxidized by amorphous MnO2 into products with lower humification index (0.60 vs. 0.46), smaller apparent molecular weight (386.94 Da vs. 368.68 Da), and higher biodegradability (BOD5/COD: 0.12 vs. 0.78). This finding suggested that redox reactions between MnOx and EfOMs might alter their abiotic and biotic behaviors in receiving water environments.

Enhanced catalytic performance of CuCr/ZSM-5 catalyst by chemical vapour deposition for trichloroethylene oxidation

The CuCr mixed oxides catalysts supported on ZSM-5 zeolite (CuCr/ZSM-5) were synthesized via metal organic chemical vapour deposition (MOCVD) method for catalytic oxidation of trichloroethylene (TCE). SEM, XRD, BET, H2-TPR, NH3-TPD and XPS were tested. The active components were dispersed uniformly over the surface of ZSM-5 zeolite. The catalytic experimental results exhibited that the CuCr/ZSM-5 exhibited the best catalytic performance for TCE oxidation with 90% of TCE at 338°C and the concentration of C2Cl4 decreased compared with Cu/ZSM-5 and Cr/ZSM-5. The possible reason is that CuCr/ZSM-5 has superior reducibility, higher Cu2+ surface concentration as well as more surface oxygen.

Porous stainless-steel fibers supported CuCeFeOx/Zeolite catalysts for the enhanced CO oxidation: Experimental and kinetic studies

To develop novel catalysts of high-performance and cost-effectiveness, and to investigate the reaction kinetics of CO oxidation, ternary CuCeFeO_x catalysts supported on zeolite/PSF (porous stainless-steel fibers) were synthesized for the first time. Effects of different Ce/Fe ratios, loading amounts, calcination temperatures, and reaction kinetics were investigated. Remarkably improved catalytic performance was achieved in the PSF-supported catalysts compared to the granular ones, owing to the increased mass/heat transfer efficiency and the high dispersion of active metal oxide species anchored on the zeolite layer. The Cu₃Ce₁₂Fe₄-400 sample exhibited the best catalytic activity with a temperature difference in T₉₀ of almost 40 °C lower than the worst one. Characterization results from XRD, FTIR, TEM, XPS, H₂-TPR, etc. revealed that the promoted reducibility of metal oxides and formation of more oxygen vacancies significantly contributed to the enhanced catalytic activity. Furthermore, a generalized rate expression was derived from intrinsic and macro kinetic studies by assuming the conversion of CO to CO₂ as the rate-determining step, in which CO oxidation over the PSF-supported catalysts followed the pseudo-first-order kinetic established by the Langmuir-Hinshelwood type mechanism.

Total Oxidation of Isopropanol in Its Liquid Phase, at a Low Temperature in the Presence of Prepared and Characterized Zinc Oxide

The complete oxidation of isopropanol in its liquid phase at a low temperature was studied in the presence of zinc oxide (ZnO). This solid was prepared with the precipitation method. Structural analysis (infrared in Fourier transform and diffraction of X-rays) and textured (adsorption/desorption of N2) were conducted for the wurtzite structure results, an IV type isotherm with a type H3 hysteresis. This solid presents a good catalytic activity against the complete oxidation of isopropanol, a constant of selectivity equal to 1; however, the studied temperatures were 40, 60, and 80°C. In addition, a kinetic study of the oxidation was performed and showed that the reaction follows a successive mechanism isopropanol-acetone-carbon dioxide. The low value of the apparent energy of the activation of this solid confirms the high value of the initial rate of the catalytic oxidation reaction of isopropanol in the temperature range studied.

Influence of oxalate ligand functionalization on Co/ZSM-5 activity in Fischer Tropsch synthesis and hydrodeoxygenation of oleic acid into hydrocarbon fuels

Achieving high degree of active metal dispersions at the highest possible metal loading and high reducibility of the metal remains a challenge in Fischer Tropsch synthesis (FTS) as well as in hydrogeoxygenation (HDO).This study therefore reports the influence of oxalic acid (OxA) functionalization on the metal dispersion, reducibility and activity of Co supported ZSM-5 catalyst in FTS and HDO of oleic acid into paraffin biofuel. The Brunauer–Emmett–Teller (BET) results showed that cobalt oxalate supported ZSM-5 catalyst (CoOx/ZSM-5) synthesized from the incorporation of freshly prepared cobalt oxalate complex into ZSM-5 displayed increase in surface area, pore volume and average pore size while the nonfunctionalized cobalt supported on ZSM-5 (Co/ZSM-5) catalyst showed reduction in those properties. Furthermore, both XRD and XPS confirmed the presence of Co° formed from the decomposition of CoOx during calcination of CoOx/ZSM-5 under inert atmosphere. The HRTEM showed that Co species average particle sizes were smaller in CoOx/ZSM-5 than in Co/ZSM-5, and in addition, CoOx/ZSM-5 shows a clear higher degree of active metal dispersion. The FTS result showed that at CO conversion over Co/ZSM-5 and CoOx/ZSM-5 catalysts were 74.28% and 94.23% and their selectivity to C₅₊ HC production were 63.15% and 75.4%, respectively at 4 h TOS. The HDO result also showed that the CoOx/ZSM-5 has higher OA conversion of 92% compared to 59% over Co/ZSM-5. In addition CoOx/ZSM-5 showed higher HDO and isomerization activities compared to Co/ZSM-5.

Sintered metal fibers@carbon molecular sieve membrane (SMFs@CMSM) composites for the adsorptive removal of low concentration isopropanol

Structured fixed-bed adsorber based on SMF@CMSM adsorbents show enhanced mass transfer and 3 bed utilization efficiency.

Synthesis of 5A zeolite coating/PSSF composites and the application for adsorption of methane from air

We fabricated 5A zeolite/PSSF composites and applied it in the end of the fixed bed to improve the bed utilization and to reduce the bed pressure drop.

Preparation and characterization of novel porous zeolite beta coating/PSSF composite in fluoride media

A novel porous zeolite beta coating/PSSF composite was prepared by secondary growth method in fluoride media.

Catalytic activity and stability of porous Co–Cu–Mn mixed oxide modified microfibrous-structured ZSM-5 membrane/PSSF catalyst for VOCs oxidation

Porous microfibrous-structured ZSM-5 membrane catalyst possesses excellent catalytic activity and stability.