Yankang Duan

Enhancement of N2O catalytic decomposition over Ca modified Co3O4 catalyst

A series of Ca modified Co3O4 catalysts with different Ca/Co molar ratios were synthesized by the co-precipitation method and applied to N2O catalytic decomposition. The experimental results showed that the performance of N2O catalytic decomposition was obviously enhanced by the addition of Ca into the Co3O4 catalyst. The Ca modified Co3O4 catalyst with Ca/Co molar ratio of 1:2 exhibited the highest catalytic performance and almost 100% N2O conversion was achieved at 400 °C. The characterization results showed that the addition of suitable calcium composition could promote the growth of the 111 crystal plane of Co3O4 and provide abundant surface oxygen on the surface of the catalyst. The kinetics studies confirmed that the activation energy of the Ca modified Co3O4 catalyst with Ca/Co molar ratio of 1:2 (Ea = 17.84 kJ mol−1) was lower than that of pure Co3O4 (Ea = 43.21 kJ mol−1), implying that the addition of Ca into the Co3O4 was beneficial to the catalytic decomposition of N2O.

Catalytic hydrolysis of HCN on ZSM-5 modified by Fe or Nb for HCN removal: surface species and performance

The catalytic hydrolysis of HCN was systematically investigated using Fe/ZSM-5, Nb/ZSM-5 and Fe–Nb/ZSM-5 catalysts. Fe–Nb/ZSM-5 exhibited the highest HCN hydrolysis activity and the reaction products were NH3 and CO. However, no NH3 was detected due to the large ammonia storage capacity of the catalysts. The interaction between the Fe and Nb species resulted in increased amounts of isolated Fe3+, Nb5+, oligomeric FexOy and NbxOy clusters, which could contribute to improving HCN hydrolysis. Furthermore, the excellent redox properties, favored pore structure and abundance of surface acid sites were responsible for the superior catalytic hydrolysis of HCN. Furthermore, the reaction pathway was speculated as follows: HCN and H2O reacted to produce methanamide. Methanamide further reacted with H2O to generate ammonium formate, which decomposed to formic acid and NH3. Formic acid was then converted into CO and H2O via pyrolysis.

Effect of WO3 content on the catalytic activity of CeO2-ZrO2-WO3 for selective catalytic reduction of NO with NH3

Abstract A series of CeO2-ZrO2-WO3 catalysts (CZW) was prepared by the hydrothermal method. The effect of WO3 content on their catalytic properties for selective reduction of NOx with NH3 was investigated. The catalysts were characterized by X-ray diffraction, N2 sorption, H2 temperature-programmed reduction, NH3 temperature-programmed desorption and NO temperature-programmed desorption techniques. It was shown that WO3 existed as amorphous species in the CZW. Introduction of WO3 in the CZW dramatically enhanced its surface acidity and gave rise to strongly adsorbed NO species, consequently increasing the catalytic activity. In addition, appropriate amounts of WO3 also increased the surface area and improved the reduction behavior of the catalyst. Compared to the CeO2-ZrO2, the CZW with 20% WO3 not only exhibited high resistivity to SO2, but also had a wider reaction temperature window. It showed a NOx conversion of > 90% at the space velocity of 60000 h−1 in the temperature range of 200–463°C.

Performance and characterisation of CeO2–TiO2–WO3 catalysts for selective catalytic reduction of NO with NH3

Ce-Ti-W-Ox catalysts were prepared and applied to the NH3-selective catalytic reduction (SCR) reaction. The experimental results showed that the Ce-Ti-W-Ox catalyst prepared by the hydrothermal method exhibited higher NO conversion than those synthesised via the sol-gel and impregnating methods, while the optimal content of WO3 and molar ratio of Ce/Ti were 20 mass % and 4: 6, respectively. Under these conditions, the catalyst exhibited the highest level of catalytic activity (the NO conversion reached values higher than 90 %) across a wide temperature range of 225–450°C, with a range of gas hourly space velocity (GHSV) of 40000–140000 h−1. The catalyst also exhibited good resistance to H2O and SO2. The influences of morphology, phase structure, and surface properties on the catalytic performance were investigated by N2 adsorption-desorption measurement, XRD, XPS, H2-TPR, and SEM. It was found that the high efficiency of NO removal was due to the large BET surface area, the amorphous surface species, the change to element valence states, and the strong interaction between Ce, Ti, and W.

Effect of preparation methods on the catalytic activity of Co 3 O 4 for the decomposition of N 2 O

A number of Co3O4 catalysts with various structures and exposed crystal planes were prepared by different methods. The effects of the structures and exposed crystal planes on the catalytic activity of Co3O4 catalysts were investigated for the catalytic decomposition of N2O. The Co3O4 with nanorod structure was enclosed by (220) planes; Co3O4 with irregular shape crystallites predominantly exposed (111) and (040) lattice planes; Co3O4 with bulk particles only showed the single exposure of (040) planes; the spherical particles of Co3O4 presented the (220) and (311) planes. The results indicated that Co3O4 with irregular shape crystallites showed the best catalytic activity and over 80% of N2O conversion was obtained at 384–450°C. The bulk particles of Co3O4 showed inferior performance. In addition, the exposed crystal planes of Co3O4 prepared by different methods can affect the catalytic decomposition of N2O.

Probing the thermal-enhanced catalytic activity of CO oxidation over Pd/OMS-2 catalysts

The present research has probed the effect of different thermal-treatment temperatures on the catalytic activity of CO oxidation and the physio-chemical properties of an OMS-2 supported palladium catalyst. The catalytic activity of Pd/OMS-2 increased with an increase in the thermal-treatment temperature from 300 to 500 °C. The optimal Pd/OMS-2 catalyst exhibited over 99% CO conversion at 35 °C. An elevated thermal-treatment temperature up to 500 °C led to a decrease in OMS-2 crystallinity and surface chemisorbed oxygen (–OH), while the surface atomic ratios of oxygen/Mn and palladium increased with the calcination temperature. A high thermal-treatment temperature above 500 °C led to the phase transformation of OMS-2 into Mn2O3, and an abrupt alteration in the Pd–support interaction and deactivation of the Pd/OMS-2 catalyst.