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The bulk-phase Cu-Ce-Zr catalyst BP-gel was prepared by the sol-gel method and investigated for the oxidation of toluene in a fixed-bed reactor. For comparison, other bulk-phase catalysts (thermal decomposition (BP-td), solid-state reaction (BP-sr)) and supported catalysts (incipient wetness impregnation (S-iwi), saturated impregnation (S-si)) were tested. The results showed that the catalytic activities were in the following order: BP-gel>S-si>S-iwi>BP-td>BP-sr. The BP-gel catalyst, which has a mesoporous structure, is beneficial for the mass transfer of reactant molecules. The thermal stability of the BP-gel catalyst was improved by the introduction of ZrO2. Bulk CuO in the catalysts reduced their activity because the synergetic effect between CuO and CeO2 decreased. The low-temperature reducibility, large pore sizes, rich oxygen vacancies, and active oxygen species contributed to the highest activity of the BP-gel, with a T90 as low as 219°C, and no deactivation was observed during the 72 h stability test at the set temperature. [ABSTRACT FROM AUTHOR]

The development of non-noble metal catalyst is essential for VOCs controlling. Cu-Ce based catalyst is a promising catalyst, and the oxygen vacancies dominants the catalytic oxidation process but the traditional calcination is not conducive to its generation. Herein a series of CuO/CeO 2 nanorod catalysts for toluene oxidation were prepared with non-equilibrium plasma comparing with traditional calcination. It is found that the treatment of non-equilibrium plasma after calcination can significantly enhance the synergism between CuO active phase and CeO 2 support leading to high dispersion of CuO. And the non-equilibrium plasma is favorable to increase Cu+/Cu2+ and Ce3+/Ce4+ ratios generating more oxygen vacancies in the catalyst. In the process of toluene oxidation, the rich oxygen vacancy can accelerate adsorption and activation of gaseous oxygen which consequently improve the catalytic activity for toluene oxidation. [Display omitted] • Oxygen vacancy (O v) in Cu-Ce catalyst dominants VOCs oxidation. • Traditional calcination is not conducive to O v generation. • Non-equilibrium plasma (NEP) was used to prepare CuO/CeO 2. • NEP treatment after calcination enhances synergy between CuO and CeO 2. • Enhanced synergy improves O v and gaseous oxygen activation for activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Utilizing Bacterial Cellulose as a Pore-Forming Agent to Synthesize Multi-Layered, Multi-Porous Composite Metal Oxide Catalysts. • Bacterial Cellulose Mitigates Environmental Risks and Cost in Catalyst Preparation. • In-Depth Analysis Reveals How the Pore Structure Created by Cellulose Pore-Forming Agent Enhances Catalytic Activity. Utilizing environmentally-friendly bacterial cellulose as a scaffold, a highly porous, layered OA-BC catalyst was synthesized through an enhanced sol-gel process. This catalyst demonstrated exceptional performance in the oxidation of toluene, outperforming conventional alternatives that utilize chemical porogens. The OA-BC catalyst efficiently degrades toluene at 220℃ with high stability and hydrophobicity, indicating resistance to deactivation. Its superior activity is due to increased oxygen vacancies, enhanced metal oxide cooperation, and a layered porous structure, which together enhance active oxygen species and oxygen diffusion. Calcination of the OA-BC catalyst results in molecular cleavage and formation of small aggregates, increasing hydroxyl groups that stabilize Cu and Ce centers, enhancing toluene-oxygen reactions. In-situ infrared and X-ray photoelectron spectroscopy confirm stable monodentate Cu+ ligands, contributing to its high catalytic activity. This study introduces a novel approach by employing bacterial cellulose as a template for synthesizing a porous stratified OA-BC catalyst, demonstrating superior performance in toluene oxidation. The efficacy of catalyst results from a tripartite synergy involving the stratified porous architecture, the stabilizing effect of Cu+-coordinating ligands and hydroxyl groups, and the interplay of hydroxyl electron donors and acceptors, shedding light on environmentally benign catalyst development. [ABSTRACT FROM AUTHOR]

[Display omitted] • The typical intermediates in the oxidation process of toluene were obtainned by experiments and the formation paths were predicted. • The transition states of possible intermediates were searched and compared for the reaction energy and activation energy for every step. • The optimum formation path of benzaldehyde and benzoic acid was determined. Catalytic oxidation technology is still the mainstream technology of VOCs treatment at present, and it is of great significance to study the main active components of catalysts and clarify the evolution and transformation process of intermediate products in the catalytic process for clarifying the reaction mechanism and guiding the catalyst design. Pd was identified as the main active component in catalytic oxidation of toluene, and the important intermediate products in the degradation of toluene, i.e., benzaldehyde and benzoic acid, were obtained through experiment and In-situ DRIFT spectra. However, the specific evolution process of intermediates is difficult to observe experimentally. The conversion of toluene on Pd (1 1 1) surface was studied by DFT calculation. Benzaldehyde was the most stable intermediate and benzoic acid was the most stable energy state of the reaction products. Then the activation energies and reaction energies of all possible reaction paths from toluene to benzaldehyde or benzoic acid were calculated, and the only transition state was obtained. Two pathways for the formation of benzaldehyde and benzoic acid were identified, in which the oxidation reaction after dehydrogenation may be the common rate-determining step of the two pathways, with a maximum energy barrier of 0.80 eV. [ABSTRACT FROM AUTHOR]

Catalytic oxidation technology is a promising strategy to eliminate carbon monoxide (CO), volatile organic compounds (VOC) and other emissions from industrial boilers and to address ammonia (NH 3) escape. Herein, we demonstrate the potential of copper-cerium-zirconium mixed oxides or those supported on TiO 2 or ZSM-5 substrates for the simultaneous catalytic removal of CO, toluene and NH 3. Among them, CuCeZr/ZSM-5 exhibits the best co-processing ability for mixed gases. In situ infrared spectroscopy analyses suggest that there is a competitive adsorption among CO, toluene and NH 3 , and the inhibition is in descending order of toluene＞CO＞NH 3. Based on the physical-chemical characterizations, the Cu-Ce interfacial structure plays an important role in CO ignition at low temperatures. More importantly, the abundant acidic sites on the ZSM-5 support can improve the stability of adsorbed NH 3 at high temperatures, resulting in the best NH 3 catalytic oxidation performance of CuCeZr/ZSM-5 with no secondary pollutants of NO x. This study provides a strategy for the catalyst design to eliminate multiple pollutants targeting the properties of pollutants. [Display omitted] • Simultaneous removal of CO, toluene and NH 3 was achieved by CuCeZr based catalyst. • The best mixed gas treatment was observed for CuCeZr/ZSM-5 catalyst. • Cu-Ce interfacial structure allows preferential ignition of CO at low temperature. • The acidic sites on the ZSM-5 promoted the adsorption and oxidation of NH 3. [ABSTRACT FROM AUTHOR]