Discovering the key role of MnO2 and CeO2 particles in the Fe2O3 catalysts for enhancing the catalytic oxidation of VOC: Synergistic effect of the lattice oxygen species and surface-adsorbed oxygen

Acid etching post-treatment enhanced fungal sterilization performance of copper-manganese-cerium oxide in liquid and aerosol: Materials and molecular biological mechanisms

Bioaerosol is one of the main ways to spread respiratory infectious diseases. In order to further improve the sterilization efficiency of copper-manganese-cerium oxide (CuMnCeOx), the post-treatment method based on acid etching was adopted. The results showed that sterilization efficiency of the treated CuMnCeOx could reach 99% in aerosol with space velocity of 1400 h-1. L(+)-ascorbic acid successfully promoted the formation of Cu+, oxygen vacancies and the generation of reactive oxygen species (ROS) on the surface of the treated CuMnCeOx. During sterilization in liquid system, the transcriptome identified 316 differentially expressed genes, including 270 up-regulated genes and 46 down-regulated genes. Differentially expressed genes were significantly enriched in cell wall (GO:0005618) and external encapsulating structure (GO:0030312). Up-regulated genes were shown in regulation of reactive oxygen species biosynthetic processes (GO:1903409, GO:1903426, GO:1903428) and positive regulation all of reactive oxygen species metabolic process (GO:2000379), indicating that ROS induced cell death by destroying cell wall.

Toluene catalytic oxidation over gold catalysts supported on cerium-based high-entropy oxides

A series of cerium-based high-entropy oxide catalysts (the ratio of CeO2 and HEO is 1:1) was prepared by a solid-state reaction method, which exploit their unique structural and performance advantages. The Ce-HEO-T samples can achieve 100% toluene conversion rate above 328°C when they were used as catalysts directly. Subsequently, the Ce-HEO-500 exhibited the lowest temperature for toluene oxidation was used as a support to deposit different amounts of Au for a further performance improvement. Among all of prepared samples, Au/Ce-HEO-500 with a moderate content of Au (0.5 wt%) exhibited the lowest temperature for complete combustion of toluene (260°C), which decreased nearly 70°C compared with Ce-HEO-500 support. Moreover, it also showed excellent stability for 60 h with 98% toluene conversion rate. Most importantly, under the condition of 5 vol.% H2O vapour, the toluene conversion rate remained unchanged and even increased slightly compared with that in dry air, exhibiting excellent water resistance. Combined with the characterizations of XRD, SEM, TEM, BET, Raman, H2-TPR and XPS, it was found that the high dispersion of active Au NPs, the special high-entropy structure and the synergistic effect between Au and Ce, Co, Cu are the key factors when improving the catalytic performance in the Au/Ce-HEO-500 catalyst.

Establishing efficient toluene elimination over cobalt-manganese bimetallic oxides via constructing strong Co-Mn interaction

Doping proves to be an efficacious method of establishing intermetallic interactions for enhancing toluene oxidation performance of bimetallic oxides. However, conventional bimetallic oxide catalysts are yet to overcome their inadequacy in establishing intermetallic interactions. In this work, the dispersion of Mn-Co bimetallic sites was improved by hydrolytic co-precipitation, strengthening the intermetallic interactions which improved the structural and physicochemical properties of the catalysts, thus significantly enhancing its catalytic behavior. MnCo-H catalysts fabricated by the hydrolytic co-precipitation method showed promising catalytic performance (T50 = 223 °C, T90 = 229 °C), robust stability (at least 100 h) and impressive water resistance (under 10 vol.% of water) for toluene elimination. Hydrolytic co-precipitation has been found to improve dispersion of MnCo elements and to enhance interaction between Co and Mn ions (Mn4+ + Co2+ = Mn3+ + Co3+), resulting in a lower reduction temperature (215 °C) and a weaker Mn-O bond strength, creating more lattice defects and oxygen vacancies, which are responsible for superior catalytic properties of MnCo-H samples. Furthermore, in situ DRIFTs showed that gaseous toluene molecules adsorbed on the surface of MnCo-H were continuously oxidized to benzyl alcohol → benzaldehyde → benzoate, followed by a ring-opening reaction with surface-activated oxygen to convert to maleic anhydride as the final intermediate, which further generates water and carbon dioxide. It was also revealed that the ring-opening reaction for the conversion of benzoic acid to maleic anhydride is the rate-controlling step. This study reveals that optimizing active sites and improving reactive oxygen species by altering the dispersion of bimetals to enhance bimetallic interactions is an effective strategy for the improvement of catalytic behavior, while the hydrolytic co-precipitation method fits well with this corollary.

Study on the Catalytic Oxidation of Toluene Using CeO2@S-AZMB Prepared from Spent Zn-Mn Batteries

The recycling and utilization of waste alkaline zinc manganese batteries (S-AZMB) has always been a focus of attention in the fields of environment and energy. However, current research mostly focuses on the recycling of purified materials, while neglecting the direct reuse of waste batteries. Here, we propose a new concept of preparing thermal catalysts by combining unpurified S-AZMB with CeO2 by means of ball milling. A series of characterizations and experiments have confirmed that the combination with S-AZMB not only enhances the thermal catalytic activity of CeO2 but also significantly enhances the concentration of surface oxygen vacancies. In the toluene removal experiment, the temperature (T90) at 90% toluene conversions of CeO2@S-AZMB was 180 °C, lower than the 220 °C for CeO2. More noteworthy is that this S-AZMB-based thermal catalyst can maintain a good structure and thermal catalytic stability in cyclic catalysis.

Synthesis of cordierite using municipal solid waste incineration fly ash as one additive for enhanced catalytic oxidation of volatile organic compounds

Municipal solid waste incineration (MSWI) fly ash is a hazardous waste, which needs various recycling in order to reach "net-zero waste". This work aimed to synthesize cordierite using MSWI fly ash as one additive and investigate influence of the additive on properties of the cordierite. As a result, the cordierite was successfully synthesized when the additive weight ratio was <15 % and the synthesis strategy was universally feasible for 14 kinds of different MSWI fly ashes. As a heat accumulator, the cordierite attained compressive strength of 42.1 MPa, water absorption of 26 %, bulk density of 1.87 g·cm-3, and open porosity of 47 %. After five cycles of thermal impact at 1200 °C, the strength was only decreased by 15 %. These properties were comparable to a commercial cordierite. As a catalyst carrier, after loading Mn and Cu species, the cordierite removed 100 % of toluene at 250 °C. In comparison, a commercial cordierite only got a removal of 34.4 %. The enhanced activity was attributed to co-existing spinel and bytownite as well as imbedded Zn and Cu in the MSWI fly ash-added cordierite. Therefore, this work devotes to hazardous recycling, green development, and cycled economy.

Insights into the underpinning effect of graphene in Cu1Mn10 on enhancing the low-temperature catalytic activity for CO oxidation

CO emission is a critical issue of industrial processes such as steel-smelting, cement manufacturing, and waste incineration. Catalytic oxidation based on Cu-Mn binary catalysts shows great potential for efficient removal of CO, whereas their practical applicability is limited by the inferior low-temperature catalytic activity and the high catalyst cost owing to a substantial quantity of Cu. In this study, doping graphene is designed to adjust the electron transfer capability to improve the low-temperature catalytic activity as well as reduce the amount of Cu, and thereby Cu1Mn10 catalysts doped with slight amounts of graphene (x%G-Cu1Mn10, x is 1∼5) were fabricated. It was found that the introduction of graphene could form effective electron transport channels to enhance the intermetallic interaction and oxygen vacancy generation, thus improving the low-temperature catalytic performance of the Cu1Mn10 catalyst. Among all the catalysts, 4%G-Cu1Mn10 exhibited the highest activity, achieving CO conversion of 92% at 110 °C at a weight hourly space velocity of 120,000 mL/(g∙h). The introduction of graphene also enabled the catalyst with excellent catalytic activity and stability at a relative humidity of 70%. Attractively, 4%G-Cu1Mn10 can be further loaded into the polyester fabric, presenting great application potentials in the effective elimination of CO during the dust removal process since the flue gas temperature in the dust collector is just around the T90% and the catalyst that is inside of fabric fiber rather than on the fabric surface can be rarely influenced by the dust. In general, doping graphene provides a facile method to enhance the low-temperature activities of the Cu-Mn binary catalysts and cut down the use of valuable Cu, showing great application potential.

Hydrocarbon Synthesis from CO2 and H2 Using the Ultrafine Iron-Containing Catalytic Systems Based on Carbonized Cellulose

Carbon materials were formed by the hydrothermal carbonization of cellulose, which were used as support for carbon dioxide hydrogenation catalysts (Fe/C and Fe-Mn/C). In the presence of these catalytic systems, CO2 conversion reached 50%. It is shown that the manganese introduction into the Fe-containing catalytic system significantly affects the distribution of gaseous С1-С4 products and liquid С5+ hydrocarbons. Promotion leads to the suppression of methane formation and an increase in the proportion of C2-C4 light olefins in gaseous products, as well as to intensification of secondary processes with the formation of a significant amount of iso-structures in liquid products. The different distribution of С1-С6 alcohols in the oxygen-containing products on the Fe/C and Fe-Mn/C catalysts indicates the manganese effect on the routes of their formation.

Reduced graphene oxide as an effective promoter to the layered manganese oxide-supported Ag catalysts for the oxidation of ethyl acetate and carbon monoxide

The layered manganese oxide (δ-MnO₂)-supported reduced graphene oxide (rGO)-promoted silver catalysts (xAg- yrGO/δ-MnO₂; x and y are the Ag and rGO contents (wt%), respectively) were prepared via a polyvinyl alcohol-protected reduction route. Physicochemical properties of these materials were determined using the numerous techniques, and their catalytic activities were evaluated for the oxidation of CO and ethyl acetate. It is found that the loading of rGO as an electron transfer promoter could significantly strengthen the metal-support interaction (SMSI) between Ag and δ-MnO₂ and increase specific surface area of the sample, hence improving catalytic performance of the sample. Activity evaluation reveals that 1Ag- 1.0rGO/δ-MnO₂ showed the best catalytic activity and the lowest apparent activation energy (E_a), giving a T_90% of 140 °C and an E_a of 42.7 kJ/mol for CO oxidation, and a T_90% of 160 °C and an E_a of 39.8 kJ/mol for ethyl acetate oxidation at space velocity (SV) = 60,000 mL/(g h). The good performance of 1Ag- 1.0rGO/δ-MnO₂ was associated with its high Mn³⁺/Mn⁴⁺ or O_ads/O_latt molar ratio, good low-temperature reducibility, and strong SMSI between Ag and δ-MnO₂. The in situ DRIFTS characterization demonstrates that the carbonate and acetate species were the main intermediate products in CO and ethyl acetate oxidation over 1Ag- 1.0rGO/δ-MnO₂, respectively. The 1Ag- 1.0rGO/δ-MnO₂ sample was not significantly altered in physicochemical property after 55 h of stability test, but its activity decreased in the presence of water vapor, especially such an effect on ethyl acetate oxidation was more obvious, which was possibly due to the competitive adsorption of water and reactants on the catalyst surface.

Dimethyl Ether Oxidation over Copper Ferrite Catalysts

The depletion of fossil energy sources and the legislation regarding emission control demand the use of alternative fuels and rapid progression of aftertreatment technologies. The study of dimethyl ether (DME) catalytic oxidation is important in this respect, as DME is a promising clean fuel and at the same time a VOC pollutant present in the tail gases of industrial processes. In the present work, copper ferrite catalysts synthesized via the citrate complexation method have been evaluated in DME oxidation. N2-physisorption, XRD, H2-TPR, and XPS were employed for the characterization of the mixed oxide catalysts. The copper ferrite spinel phase was detected in all samples accompanied by a gradual decrease in the bulk CuO phase upon increase in iron content, with the latter never vanishing completely. The Fe0.67Cu0.33 catalyst exhibited the highest catalytic activity in DME oxidation, attaining approximately a 4-fold higher oxidation rate compared to the respective pure copper and iron oxides. The enhanced catalytic performance was attributed to the higher specific surface area of the catalyst and its enhanced redox properties. Highly dispersed copper species were developed owing to the formation of the spinel phase. DME-TPD/TPSR experiments showed that the surface lattice oxygen of the Fe0.67Cu0.33 catalyst can oxidize preadsorbed DME at a lower temperature than all other catalysts which is in agreement with the H2-TPR findings.