Shu Ronglu,Du Yifan,Cao Liping,Zhao Hui,Luo Xiaoying,Wang Wei
Cerium samarium oxides catalysts with K + doping on the wall surface of cordierite honeycomb ceramics were preparation by sol–gel and dipping processes. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and Fourier transform-infrared spectroscopy were used to characterize the structural morphology and phase compositions. Through XPS analysis and H 2 -TPR measurement of monolithic catalyst, it is found that potassium ions improve the oxygen mobility in CeO 2 lattice and form surface active oxygen, increase the amount of oxygen adsorbed on the surface and improve the oxidation–reduction capacity. The catalytic combustion research demonstrates that T 10 , T 50 and T m in samples (Ce/Sm-0 K, Ce/Sm-0.3 K, Ce/Sm-0.5 K and Ce/Sm-0.7 K) decrease significantly compared with the blank reference (Cordierite). And the optimized sample Ce/Sm-0.5 K possess the lowest T 10 (389.6 °C), the lowest T 50 (425.5 °C), and the lowest T m (419 °C) in comparison with other samples. The cycle stability investigation reveals that sample Ce/Sm-0.5 K has excellent structural stability and stable catalytic performance, which has potential application in soot catalytic combustion field.
Ordered double-perovskite oxides of Sr 2− x K x FeMoO 6 (0.00 ⩽ x ⩽ 0.10) are synthesized via sol–gel method. X-ray powder diffraction analysis shows that all the samples have a single phase and exhibit I4/m symmetry. The cation order of Sr 2− x K x FeMoO 6 decreases from 94.4(2)% to 50.4(2)%, indicating that Fe/Mo is in nearly complete disorder. The magnetic property of Sr 2− x K x FeMoO 6 samples depends on temperature under zero-field-cooling (ZFC) and field-cooling (FC) processes at an applied magnetic field of 100 Oe. The thermal irreversibility behavior in the FC and ZFC curves indicates a typical cluster glass behavior in this system. The H / M versus M 2 curves indicate a second-order magnetic transition, resulting in a small variation in magnetic entropy. Antisite defect is the primary reason for the effective paramagnetic moment.
Yang Du,Shi-Qi Yang,Yun-Jie Li,Zhi-Bin Wang,Xing-Bao Wang,Zhen-Yi Du,Wen-Ying Li
Nickel-based catalysts have been broadly studied for the steam reforming of coal/biomass tar due to their inexpensiveness and good activity. Nevertheless, their industrial application has long been restricted by the deactivation induced by carbon deposition and Ni sintering in the reforming process. Herein, ordered mesoporous nickel-alumina catalysts with varying K contents were prepared. Their performance in steam reforming of toluene as a model compound of tar was evaluated to reveal the effects of K doping. Among them, the catalyst with 2 wt% K loading displayed the best catalytic activity and stability. Experimental and theoretical calculation results suggested that K doping enhances the water adsorption capability of the catalysts, which thereby reduces the amount and graphitization degree of carbon deposits. Moreover, the K doping reduces the acid amount of the support and thereby inhibits the formation of carbon deposits as well. However, K doping does not affect the reaction pathway of the catalysts in toluene steam reforming, and the main reaction intermediates detected with in-situ DRIFTS remain the carbonate groups. Furthermore, the confinement effects of the ordered mesoporous structures inhibit the sintering of Ni particles and the formation of carbon deposits. In addition, the influence of different spatial positions of K on the catalysts was explored. It was found that the K introduction via the one-pot solvent evaporation induced self-assembly method can suppress the loss of K from the catalysts.
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