Catalytic oxidation of ethyl acetate over CuO/ZSM-5 catalysts: Effect of preparation method

A tailored and rapid approach for ozonation catalyst design

Catalytic ozonation is widely employed in advanced wastewater treatment owing to its high mineralization of refractory organics. The key to high mineralization is the compatibility between catalyst formulation and wastewater quality. Machine learning can greatly improve experimental efficiency, while fluorescence data can provide additional wastewater quality information on the composition and concentration of organics, which is conducive to optimizing catalyst formulation. In this study, machine learning combined with fluorescence spectroscopy was applied to develop ozonation catalysts (Mn/γ-Al₂O₃ catalyst was used as an example). Based on the data collected from 52 different catalysts, a machine-learning model was established to predict catalyst performance. The correlation coefficient between the experimental and model-predicted values was 0.9659, demonstrating the robustness and good generalization ability of the model. The range of the catalyst formulations was preliminarily screened by fluorescence spectroscopy. When the wastewater was dominated by tryptophan-like and soluble microbial products, the impregnation concentration and time of Mn(NO₃)₂ were less than 0.3 mol L^-1 and 10 h, respectively. Furthermore, the optimized Mn/γ-Al₂O₃ formulation obtained by the model was impregnation with 0.155 mol L^-1 Mn(NO₃)₂ solution for 8.5 h and calcination at 600 °C for 3.5 h. The model-predicted and experimental values for total organic carbon removal were 54.48% and 53.96%, respectively. Finally, the improved catalytic performance was attributed to the synergistic effect of oxidation (•OH and ¹O₂) and the Mn/γ-Al₂O₃ catalyst. This study provides a rapid approach to catalyst design based on the characteristics of wastewater quality using machine learning combined with fluorescence spectroscopy.

Silica-Supported Copper (II) Oxide Cluster via Ball Milling Method for Catalytic Combustion of Ethyl Acetate

Highly dispersed CuO/SiO2 catalysts were successfully synthesized by a green process of ball milling (BM) under solvent-free and room temperature conditions. The structural evolution of CuO/SiO2 catalysts prepared by BM was elucidated by TG-DSC, XRD, FT-IR, and XPS characterizations. We found that the copper acetate precursor was dispersed over the layer of copper phyllosilicate which was formed by reacting between the copper acetate precursor and the silica support during the BM process. The copper phyllosilicate layer over the support might play an important role in the stabilization of the CuO cluster (<2 nm) during thermal pretreatment. The 15% CuO/SiO2 catalyst exhibited the best catalytic activity for the catalytic combustion of ethyl acetate as it owned a highest active surface area of CuO among the CuO/SiO2 catalysts with different copper loadings.

Catalytic ozone oxidation toluene over supported manganese cobalt composite: influence of catalyst support

In this study, the manganese cobalt composite (Mn-Co)-loaded SiO₂, MgO, TiO₂, γ-Al₂O₃ and silicalite-1 were prepared by ultrasonic complexation method. The catalysts were characterized by XRD, BET, SEM, TEM, H₂-TPR and XPS, and the activity of catalytic oxidation of toluene was evaluated. It was found that Mn-Co loaded γ-Al₂O₃ (Mn₂CoO_x/γ-Al₂O₃) exhibited excellent catalytic activity. When the gas hour space velocity (GHSV) was 45,000 h^-1, the removal rate of toluene reached 91.2% within 5.5 h, and the selectivity of CO₂ was 71.10% at ambient temperature. The operation of Mn₂CoO_x/γ-Al₂O₃ at different temperatures was investigated, and the better toluene removal efficiency more than 80% after reacting 9h was obtained at 50 °C. The characterization results showed that better catalytic activity is related to smaller grain size, higher Mn³⁺/Mn⁴⁺ values and the relative content of active oxygen species (O_II + O_III). Increased amounts of low state species easily led to the imbalance of the catalyst surface charge and promoted the formation of more oxygen vacancies.

Recovery of cathode materials from spent lithium-ion batteries and their application in preparing multi-metal oxides for the removal of oxygenated VOCs: Effect of synthetic methods

Due to the sustainable use of wastes, cathode materials of spent lithium-ion batteries are recovered and used as transition metal precursors to prepare metal oxides catalysts for the oxidation of VOCs. In this work, a series of manganese-based and cobalt-based metal oxides are synthesized via different preparation methods. Catalytic activities of the catalysts prepared are investigated through complete oxidation of oxygenated VOCs and the physicochemical properties of optimum samples are characterized. Evaluation results indicate that MnOx (SY) (HT) sample prepared via hydrothermal method and CoOx (GS) (CP) synthesized via co-precipitation method had better performance, because they have higher specific surface area, higher concentration of active oxygen species and high-valence metal ion, as well as better low-temperature reducibility compared to the other multi-metal oxides used in the study. In addition, TD/GC-MS results imply that further oxidation of by-products requires high reaction temperature during VOCs oxidation.

Promotional removal of oxygenated VOC over manganese-based multi oxides from spent lithium-ions manganate batteries: Modification with Fe, Bi and Ce dopants

In this work, cathode materials of spent lithium-ions manganate batteries are recovered as the precursor of manganese-based oxides catalysts and furthermore, different amount of Fe, Bi, Ce are introduced to modify their properties. A series of MnOx(MS)-X Fe, MnOx(MS)-X Bi and MnOx(MS)-X Ce samples with crystal phase of Mn₅O₈ are synthesized using combustion method and then the catalytic behavior and physicochemical properties of prepared catalysts are investigated. Compared to binary MnOx-5% Fe, MnOx-15% Bi and MnOx-10% Ce samples, multi MnOx(MS)-5% Fe, MnOx(MS)-15 Bi and MnOx(MS)-10% Ce catalysts display enhanced catalytic performance significantly in the removal of oxygenated VOC, which could be attributed to larger specific surface area, higher concentration of surface active oxygen species and Mn⁴⁺ ions and better reducibility at low temperature. In-situ DRIFTS results imply that main oxygen-containing functional groups such as carbonyl (-C=O), carboxyl (-COO), hydroxyl (-OH) can be observed during VOC oxidation and by comparison, it can be found that gas-phase O₂ plays a crucial role in facilitating the further oxidation of by-products into CO₂. In addition, TD/GC-MS results point out that the main by-products are formaldehyde; 2-propanol, 1-methoxy-; ethanol, 2-methoxy-, acetate; 2-ethoxyethyl acetate; acetic acid during VOC oxidation.

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.

Enhanced catalytic performance for volatile organic compound oxidation over in-situ growth of MnOx on Co3O4 nanowire

Hierarchical Co₃O₄@MnOx material has been synthesized by in-suit growth of MnOx on the Co₃O₄ and applied in catalytic oxidation of volatile organic compounds (VOCs). Results revealed that T₉₀ of acetone on the Co₃O₄@MnOx was 195 °C, which was 36 °C and 32 °C lower than that on the Co₃O₄ and MnOx/Co₃O₄, respectively. The universality experiments demonstrated that T₉₀ of ethyl acetate and toluene on the Co₃O₄@MnOx were 200 °C and 222 °C, respectively. The above results indicated that Co₃O₄@MnOx catalyst presented a robust catalytic performance. Characterization results showed that high catalytic activity of the Co₃O₄@MnOx catalyst could be attributed to the improvement of low temperature reducibility, the enhancement of Co³⁺ and adsorbed oxygen species resulted from the sufficient reaction between MnO₄^- and Co²⁺ during secondary hydrothermal process. Furthermore, stability and water-resistance experiments showed the Co₃O₄@MnOx catalyst with high cycle and long-term stability, satisfied endurability to 5.5-10 vol. % water vapor at 210 °C.

Creation of CuOx/ZSM-5 zeolite complex: healing defect sites and boosting acidic stability and catalytic activity

CuO_x/ZSM-5 was achieved by hydrothermally disintegrating CuO nanoparticle into zeolite. Further studies proved that stable clusters formed and connected with internal silanol, which leads to optimal acidity and high stability in hexane cracking.

Catalytic oxidation of ethyl acetate over LaBO3 (B = Co, Mn, Ni, Fe) perovskites supported silver catalysts

A series of silver catalysts supported on lanthanum based perovskites LaBO₃ (B = Co, Mn, Ni, Fe) were synthesized and evaluated in the catalytic oxidation of ethyl acetate. XRD, BET, TEM/HRTEM, HAADF-STEM, XPS and H₂-TPR were conducted, and the results indicate that redox activity of the catalysts is of great importance to the oxidation reaction. Activity tests demonstrated that Ag/LaCoO₃ was more active than the other samples in ethyl acetate oxidation. Moreover, the CO₂ selectivity, CO_x yields and byproduct distributions for all catalysts were studied, and Ag/LaCoO₃ showed the best catalytic performance. Besides, Ag/LaCoO₃ also showed excellent catalytic activity for other OVOCs.

Ag/LaBO₃ (B = Co, Mn, Ni, Fe) were investigated for the catalytic oxidation of ethyl acetate, and Ag/LaCoO₃ showed the best catalytic performance.