Propene and CO oxidation on Pt/Ce-Zr-SO 4 2– diesel oxidation catalysts: Effect of sulfate on activity and stability

Hydrothermal-treated Pt/Al2O3 as an excellent catalyst for toluene total oxidation

The preparation of highly active supported noble metal catalysts with a low noble metal loading has always been the ultimate goal of researchers working on catalysis. Hydrothermally treated Pt/Al₂O₃ (Pt/Al₂O₃-H) exhibits better catalytic activity than that (Pt/Al₂O₃-C) treated via the conventional calcination approach. At the high space velocity of 100,000 mL/(g∙hr), the temperature that correspond to 50% toluene conversion (T₅₀) of Pt/Al₂O₃-H is 115°C lower than that of Pt/Al₂O₃-C, and the turnover frequency (TOF) value can reach 0.0756 sec^-1. The mechanism by which the hydrothermal approach enhances Pt/Al₂O₃ activity has been investigated. The structure associated with the high catalytic activity of Pt nanoparticles (NPs) can be retained via hydrothermal treatment. Furthermore, the support is transformed to AlO(OH) with numerous surface hydroxyl groups, which in turn can facilitate the adsorption of toluene. And the synergistic effects of Pt NPs and AlO(OH) increases the contents of Pt in oxidation state and active oxygen, which are beneficial for toluene oxidation.

Stabilization of Pt in SiO2–Al2O3 Microspheres at High Mechanical Resistance, Promoted with W Oxides for the Combustion of CO

This study shows the development of a combustion promoter for the oil-refining process called fluid catalytic cracking (FCC). The investigation of a catalyst prepared for the combustion of CO composed of 0.05 wt% Pt supported on SiO2–Al2O3–0.5 wt% W microspheres with high mechanical resistance, promoted with tungsten oxides (WOx) that can inhibit the sintering of Pt, is reported. The addition of WOx in SiO2–Al2O3 inhibited the decrease in the specific area when calcined from 550 °C to 950 °C. SiO2–Al2O3 support in the form of calcined microspheres with average diameters between 70–105 µm were produced by spray drying, using two atomization discs with vanes of different geometry: a straight rectangular blade disc (DAR) and a curved rectangular vanes disc (DAC). The DAR disk produced whole microspheres, while the DAC had hollow and broken microspheres. The microspheres were characterized by XRD, SEM, optical microscopy, N2 physisorption (BET area) and fracture resistance tests. The Pt catalysts were evaluated by TPR, H2 chemisorption and CO combustion. The catalyst of 0.05 wt% Pt/SiO2–Al2O3–0.5 wt% turned out to be the most stable. A thermal stabilization effect was observed at contents lower than 1 wt% W that allowed it to inhibit the sintering of the Pt catalyst.

Tuning the degradation activity and pathways of chlorinated organic pollutants over CeO2 catalyst with acid sites: synergistic effect of Lewis and Brønsted acid sites

The synergistic effect of Lewis and Brønsted acid sites can promote the effective degradation of chlorobenzene following the hydrolysis pathway of producing less toxic by-products.

In situ sulfation of Cu/TiO2 catalysts for catalytic combustion of dichloromethane

Herein, a facile in situ sulfation strategy was employed for modifying Cu/TiO₂ catalysts using CuSO₄ as the precursor to enhance the performance of dichloromethane (DCM) catalytic combustion.

A Novel One-Step Hydrothermal Preparation of Ru/SnxTi1-xO2 Diesel Oxidation Catalysts and its Low-Temperature Performance

The rutile Sn_xTi_1-xO₂ (x = 0, 0.33, 0.5, 0.67, 1) solid solution was synthesized by a one-step hydrothermal method, in which tetrabutyl titanate and Tin (IV) chloride pentahydrate were used as raw materials. A series of Ru/Sn_xTi_1-xO₂ were then prepared by the impregnation process in RuCl₃ to investigate the performance and stability of CO and C₃H₈ oxidation. These catalysts were characterized through XRD, N₂ adsorption-desorption, FT-IR, TEM, XPS, H₂-TPR, and O₂-TPD techniques. The effect of Sn/Ti molar ratio and hydrothermal condition on the low-temperature catalytic oxidized performance and stability of Ru/Sn_xTi_1-xO₂ were investigated. The results indicated that Ru/Sn_0.67Ti_0.33O₂ catalyst showed an excellent activity and stability at low temperatures. The CO conversion reached 50% at 180 °C and 90% at 240 °C. Besides, the C₃H₈ conversion reached 50% at 320 °C, the complete conversion of C₃H₈ realized at 500 °C, and no deactivation occurs after 12 h of catalytic reaction. The excellent low-temperature activity and stability of the Ru/Sn_0.67Ti_0.33O₂ were attributed to the following factors. Firstly, XRD results showed that Sn⁴⁺ was successfully introduced into the lattice of TiO₂ to replace Ti⁴⁺ forming a homogeneous solid solution (containing -Sn⁴⁺-O-Ti⁴⁺- species), which was consistent with TEM and N₂ adsorption-desorption results. The introduction of Sn could suppress the growth of anatase crystal and promote the formation of rutile phase, and this phase transition was helpful to improve the low-temperature activity of the catalysts. Secondly, TEM images showed that ultrafine Ru nanoparticles (~ 5 nm) were dispersed on Sn_0.67Ti_0.33O₂ support, suggesting that the formation of Sn_xTi_1-xO₂ solid solution was beneficial to the dispersion of Ru particles.

In Situ Investigations on the Facile Synthesis and Catalytic Performance of CeO2-Pt/Al2O3 Catalyst

Ceria-modified Pt/Al2O3 catalyst has been commonly prepared by the impregnation of platinum on ceria-modified alumina and widely applied in the chemical industry and automotive industry. The in situ diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS), and thermogravimetric (TG) analysis techniques were employed to investigate the typical mechanisms of the bis(ethanolammonium)hexahydroxyplatinate(IV) and cerium nitrate decomposition catalyzed by Ptδ+ species for the facile synthesis of CeO2-Pt/Al2O3 catalyst. It was found that Pt4+-catalyzed decomposition of cerium nitrate leads to the higher dispersity of ceria and forming more active oxygen species, on the basis of X-ray diffraction (XRD) and H2 temperature-programmed reduction (H2-TPR) results. The in situ activity measurements were also performed to investigate the reaction mechanisms and the specific activities for the catalytic CO, NO, C3H6 and C3H8 co-oxidation. The results indicate that undesirable N2O by-product is formed by the selective catalytic reduction (SCR) of NO by C3H6 below 350 °C. The cerium addition effectively improves the activity of catalytic oxidation, but exhibits an increased N2O yield, due to the increased reducibility.

The promotion effect of tungsten on monolith Pt/Ce0.65Zr0.35O2 catalysts for the catalytic oxidation of toluene

The temperature for the complete conversion of toluene on the monolith Pt-WO₃/Ce_0.65Zr_0.35O₂ catalyst decreases by about 30 °C compared to that on Pt/Ce_0.65Zr_0.35O₂.