摘要: A 12-phosphotungstic acid (PTA)-based esterification catalyst was prepared by modifying PTA with 1, 2, 3-trizaole-4, 5-dicarboxylic acid (TDA). The obtained TDA-PTA sample was characterized with XRD, FT-IR, SEM, TG and potentiometric titration techniques, and its catalytic properties for esterification of oleic acid with methanol were studied. In addition, the effects of reaction conditions, including catalyst amount, oleic acid/alcohol molar ratio, reaction time and reaction temperature, on its catalytic performance were investigated. After modification with TDA, although the Keggin structure of PTA is kep and the sample shows strong acidity, the particle morphology changes to regular spheres. In particular, the sample exhibits high catalytic activity and stability in esterification of oleic acid with methanol. The modification of PTA by TDA effectively prevents PTA from dissolving in the reaction mixture, and thus, the TDA-PTA can be recycled at least six runs without severe loss of catalytic activity, showing that it is a good heterogeneous catalyst for esterification.
摘要: The sulfated zirconia was prepared by directly impregnating ammonium persulphate on the crystalline zirconia and followed by the calcination temperatures of 300-500℃. The structural properties of the catalysts were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, ammonia temperature programmed desorption (NH3-TPD), Fourier transform infrared spectroscopy (FT-IR) and a scanning electron microscope (SEM) equipped with an energy dispersive spectroscope (EDS). The experiment results demonstrated that the catalysts presented the tetragonal structure of zirconia and high crystallinity. The catalyst calcined at 500℃ possessed the highest sulfur content and acidic sites in the catalysts. The catalyst exhibited high catalytic activity in transesterification of soybean oil with methanol. The yield of biodiesel achieved 84.6% because of the preferable super-acid sites on the surface of the catalyst.
摘要: CuO-CeO2 monolithic catalysts supported on SiO2-Al2O3 modified glass-fiber honeycomb were prepared via co-impregnation method and their performance in the oxidation of volatile organic compounds (VOCs) such as ethyl acetate, isopropanol and toluene was evaluated. Various techniques such as N2 sorption, X-ray powder diffraction (XRD), hydrogen-temperature programmed reduction (H2-TPR), ammonia-temperature programmed desorption (NH3-TPD) and chemisorption of VOCs were employed to characterize the catalysts. The results show that the copper oxide species are highly dispersed on the CuO-CeO2 based catalysts; moreover, the size of CeO2 nanoparticles increases with the decrease of copper/ceria molar ratio. The addition of ceria oxide can evidently increase the amount of total acid sites, especially the Lewis ones, which can enhance the adsorption capacity of ethyl acetate and isopropanaol and promote the oxidation of ethyl acetate and isopropanaol. In the case of toluene combustion, the addition of large amount of CeO2 may decrease the reducibility and oxygen activation capability; as a result, it contributes little to the adsorption of toluene, resulting in a low activity in the oxidation of toluene. The catalytic activity is related both to the reactivity of surface oxygen and to the adsorption capacity of the catalyst towards VOC molecules, which are determined by the complex interactions among copper, cerium oxide and the support.
