Enhanced catalytic performance of Nb doping Ce supported on ordered mesoporous TiO2-SiO2 catalysts for catalytic elimination of 1,2-dichlorobenzene

The Design of Sulfated Ce/HZSM-5 for Catalytic Decomposition of CF4

CF₄ has a global warming potential of 6500 and possesses a lifetime of 50,000 years. In this study, we modified the HZSM-5 catalyst with Ce and sulfuric acid treatment. The S/Ce/HZSM-5 catalyst achieves 41% of CF₄ conversion at 500 °C, which is four times higher than that over Ce/HZSM-5, while the HZSM-5 exhibits no catalytic activity. The effects of modification were studied by using NH₃-TPD, FT-IR of pyridine adsorption, and XPS methods. The results indicated that the modification, especially the sulfuric acid treatment, strongly increased the Lewis acidic sites, strong acidic sites, and moderate acidic sites on catalysts, which are the main active centers for CF₄ decomposition. The mechanism of acidic sites increases by modification and CF₄ decomposition is clarified. The results of this work will help the development of more effective catalysts for CF₄ decomposition.

Ordered mesoporous TiO2/SBA-15 confined CexWy catalysts for selective catalytic reduction of NO using NH3

The ordered mesoporous structure could improve the dispersion of nanoparticles, promote effective collision, and enhance redox capacity and surface acidity.

Construction of Superhydrophobic Ru/TiCeOx Catalysts for the Enhanced Water Resistance of o-Dichlorobenzene Catalytic Combustion

In this paper, a simple method to enhance the H₂O resistance of Ru/TiCeO_x catalysts for o-DCB catalytic combustion by constructing superhydrophobic coating of phenyltriethoxysilane (PhTES) was proposed. The effect of PhTES content on the pore structure, specific surface area, H₂O resistance, contact angle (CA) value, and catalytic activity of the catalyst was studied. When water was added, the pristine Ru/TiCeO_x catalytic activity decreased by about 26%, while the Ru/TiCeO_x-16Ph activity hardly decreased. According to the analysis results of XRD, FT-IR, SEM, and CA, PhTES was closely coated on the surface of Ru/TiCeO_x to produce a more hydrophobic surface. The Ru/TiCeO_x-16Ph catalyst had strong hydrophobicity, and the contact angle was 159.8°, which not only significantly enhanced the water resistance and self-cleaning activity but also showed a good elimination temperature (T₉₀ = 341 °C) for the o-DCB. The enhanced water resistance of Ru/TiCeO_x-XPh catalysts resulted from the reduction of the active centers consumed (water occupying oxygen vacancy sites). The reaction mechanism of the Ru/TiCeO_x-16Ph catalyst based on surface oxygen species and the Deacon reaction was proposed. This method provided new idea for the design of a new water-resistant composite catalyst and promoted the practical application of the composite catalyst in the catalytic oxidation of o-DCB.

Mechanistic insights into the contribution of Lewis acidity to brominated VOCs combustion over titanium oxide supported Ru catalyst

CH₃Br catalytic oxidation as the probe reaction was investigated over Ru supported on TiO₂ with different crystalline phases. 1% Ru/anatase TiO₂ (a-TiO₂) exhibited superior stability at 240 °C after a 180 h time-on-stream run. And there was an induced activation for 1% Ru/a-TiO₂ during the initial 60 h reaction. Then the activity sustained stable. To elucidate the intrinsic mechanism, a series of characterizations were performed such as XRD, CO-Pulse, H₂-TPR, XPS and NH₃-TPD etc. Results showed that the Ru particle size increased and the Ru⁰ content decreased as the reaction proceeded, which were not conductive to the reaction. It was assumed that the catalytic activity was strongly dependent on other factors. In combination with NH₃-TPD and Py-FTIR measurements, it was confirmed that the enhanced activity and stability was strongly associated with the surface acidity, especially moderate strong Lewis acid (L acid). The increase of the acid amount and acidity strength was led by the generation and adsorption of HBr, Br₂ and RuO_xBr_y during the reaction, among which HBr and Br₂ was easier to desorb at 250 °C. While moderate strong L acid was sourced from the formation of RuO_xBr_y. The addition of transition metal (Ce, Co, Mn, Nb and Ni) further validated that the moderate strong L acid played a decisive role in the CH₃Br catalytic oxidation.