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A series of spinel type CoCr 2 O 4 catalysts calcined at different temperatures were prepared and tested for oxidation of dichloromethane (CH 2 Cl 2 ). These catalysts were active for this reaction. The final products in the reaction were CO x , HCl and Cl 2 , without the formation of Cl-containing organics. The best performance was obtained on a catalyst calcined at 400 °C (CoCr 2 O 4 -4), with a T 50 of 218 °C and a T 90 of 257 °C, which was mainly due to the highest surface area of this catalyst (91.3 m 2 g −1 ). Detailed quantitative analyses revealed that the catalytic behavior was synergistically governed by surface acidity and reducibility of the catalyst, as evidenced by ammonia temperature-programmed desorption and hydrogen temperature-programmed reduction results, respectively. Kinetic studies revealed similar activation energies (124.5–155.5 kJ mol −1 ) on these catalysts, implying the reaction might follow the same pathways on these catalysts. More importantly, in situ Fourier transform infrared spectroscopic investigation of the reaction revealed that formate species were the main reaction intermediates, which could be further oxidized to CO and CO 2 . [ABSTRACT FROM AUTHOR]

Three Ti-containing porous materials − a mesoporous Ti-MCM-41 with distorted tetrahedral framework Ti sites (denoted as Ti-MCM-41-C), a microporous titanium silicate (TS-1) with tetrahedral framework Ti sites and a hybrid Ti-MCM-41 containing TS-1 microstructure (denoted as Ti-MCM-41-H) were used to prepare supported Au catalysts for gas phase propylene epoxidation in the presence of H 2 and O 2 . Both catalyst structures and catalytic reaction kinetics were investigated in detail. The kinetic results show that the apparent activation energies for both PO and CO 2 formation follow the order of Au/Ti-MCM-41-C < Au/Ti-MCM-41-H < Au/TS-1. Besides, the adsorption behaviors of propylene on the catalysts were strongly affected by the chemical environment of the framework Ti sites and pore structure in the supports. The adsorption capacity follows the order of Au/Ti-MCM-41-H > Au/TS–1 > Au/Ti-MCM-41-C, in consistence with the order of propylene conversion rate, and the adsorption stability follows the order of Au/TS–1 > Au/Ti-MCM-41-H > Au/Ti-MCM-41-C, in consistence with the order of apparent activation energy. These results demonstrated that the adsorption strength of propylene on the titanosilicates supports strongly affected the catalytic behavior, and implied that the support with balanced defective Ti sites and mesoporous/microporous structure may be a promising approach in the preparation of high-performance supported Au catalysts. [ABSTRACT FROM AUTHOR]

It was found that a series of spinel CoCr 2 O 4 oxides were very active and selective for dichloromethane combustion, and the best performance was obtained on a catalyst calcined at 600 °C (with a areal specific reaction rate of 3.41 × 10 −8 mol CH2Cl2 s −1 m −2 at 220 °C). Quantitative analyses revealed that Cr 3+ /Cr 6+ cations could partially substitute Co 3+ cations in the octahedral sites of the spinel oxide at high-temperature calcination and thus to enhanced reducibility and surface acidity of the oxide, which synergistically governed the observed catalytic behaviors. Moreover, it was found that high valent Cr species (Cr 6+ ) played very important role in the reaction, with a much higher turnover frequency (2.2 × 10 −3 s −1 ) than that of the Cr 3+ (0.56 × 10 −3 s −1 ). [ABSTRACT FROM AUTHOR]

A series of Pt/CeO 2 catalysts with different Pt contents were prepared using an incipient wetness impregnation method and tested for CO oxidation. Kinetic study on the catalysts indicated that the reaction rate was independent of the partial pressures of CO and O 2 ( r = k app [CO] 0 [O 2 ] 0 ). The derived reaction pathways involved chemisorption of CO on surface Pt atoms and reacting with lattice oxygen provided by the CeO 2 support at the Pt–CeO 2 interface, suggesting a Mars van-Krevelen type reaction on these catalysts and the interfacial Pt–O–Ce ensembles being the active sites. Also, turnover frequencies (TOFs) calculated based on Pt dispersion and periphery Pt atoms were found to be proportional to the Pt particle size, with the large Pt particles possessing higher TOF than the small ones. Such a trend was interpreted by the important role of the oxygen vacancies via the formation of Pt–Ce–O solid solution, which could accelerate the mobility of lattice oxygen and consequently the activity. [ABSTRACT FROM AUTHOR]

A Pt catalyst supported on CuO-CrO x composite oxide (Pt/CuCrO x ) was prepared and tested for CO oxidation in the presence of CO 2 and H 2 O. It was found that the catalyst was stable in the realistic reaction conditions and the catalytic activity was improved in the presence of CO 2 and H 2 O compared to that in dry condition. Kinetic investigation and temperature – programmed desorption of CO results revealed that the addition of CO 2 in the feed resulted in the competitive adsorption of CO/CO 2 and the formation of surface carbonate species, which consequently deactivated the catalyst. In contrast, although the presence of H 2 O also inhibited the adsorption of CO, the possible formation of surface hydroxyl groups may trigger a new and more facile reaction route for CO oxidation, which could explain the promoting effect of H 2 O. Therefore, the current findings makes the catalyst promising in CO oxidation under realistic reaction conditions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Kinetic study of CO oxidation was conducted on CuO/MO2 catalysts (M=Si, Ti, Ce). [•] Langmuir–Hinshelwood mechanism was proposed for CO oxidation over CuO/SiO2 catalyst. [•] Interfacial reaction was proposed over CuO/TiO2 and CuO/CeO2 catalysts. [•] Cu atoms located on CuO–support interface of large CuO particles were more active. [•] Enhanced activity was due to higher CO chemisorption density on large CuO particles. [Copyright &y& Elsevier]