Jiang Guiyuan

Effects of Light Rare Earth on Acidity and Catalytic Performance of HZSM-5 Zeolite for Catalytic Cracking of Butane to Light Olefins

Abstract The effects of rare earth (RE) on the structure, acidity, and catalytic performance of HZSM-5 zeolite were investigated. A series of RE/HZSM-5 catalysts, containing 7.54% RE (RE = La, Ce, Pr, Nd, Sm, Eu or Gd), were prepared by the impregnation of the ZSM-5 type zeolites (Si/Al =64:1) with the corresponding RE nitrate aqueous solutions. The catalysts were characterized by means of FT-IR, UV-Vis, NH 3 -TPD, and IR spectroscopy of adsorbed pyridine. The catalytic performances of the RE/HZSM-5 for the catalytic cracking of mixed butane to light olefins were also measured with a fixed bed microreactor. The results revealed that the addition of light rare earth metal on the HZSM-5 catalyst greatly enhanced the selectivity to olefins, especially to propylene, thus increasing the total yield of olefins in the catalytic cracking of butane. Among the RE-modified HZSM-5 samples, Ce/HZSM-5 gave the highest yield of total olefins, and Nd/HZSM-5 gave the highest yield of propene at a reaction temperature of 600°C. The presence of rare earth metal on the HZSM-5 sample, not only modified the acidic properties of HZSM-5 including the amount of acid sites and acid type, that is, the ratio of L/B (Lewis acid/Bronsted acid), but also altered the basic properties of it, which in turn promoted the catalytic performance of HZSM-5 for the catalytic cracking of butane.

Selective Oxidation Performance of Propane over Supported Vanadium Oxide Catalysts

A series of SBA-15 supported vanadium oxide catalysts with different active components were prepared by the method of incipient-wet impregnation. The structures of the catalysts were characterized by N2 adsorption, X-ray diffraction (XRD), ultraviolet (UV)-Raman, Fourier transform infrared (FTIR), and ultraviolet-visble diffuse reflectance spectroscopy (UV-Vis DRS) techniques, and their catalytic performances for the selective oxidation of propane were investigated. The results showed that SBA-15 was a better support in the catalyst system than SiO2 for the selective oxidation of propane to aldehydes. The SBA-15 supported low loading catalyst is a highly dispersed catalyst system and the SBA-15 supported vanadium oxide samples with low loading (n(V)/n(Si)<2.5%) have ordered hexagonal mesostructures. For the VOx/SBA-15 catalysts, isolated vanadyl species with tetrahedral coordination are the active sites for aldehyde formation at very low loadings of vanadium (n(V)/n(Si)<0.1%). The polymeric vanadyl species with octahedral coordination and microcrystalline vanadium oxide are active sites for the oxidative dehydrogenation or deep oxidation of propane when the loading of vanadium (n(V)/n(Si)) is higher than 2.5%.

The Selective Catalytic Reduction of NOx Over Cd-Ce-Ti Metal Oxide Catalysts

The transition metal oxide Cd-Ce-TiO2 catalysts were prepared by the method of coprecipitation. The catalysts were characterized by means of XRD, BET, SEM, TEM, Raman and UV-Vis DRS. And the catalytic activities of the catalysts for deNOx were evaluated by NH3-SCR reaction. The nanoparticles will be formed for Cd-Ce0.2-TiOx catalysts with the different metal Cd contents. The catalysts possess the irregular, mesoporous structure. XRD and Raman data demonstrated that at the low content of Cd, anatase structure disappeared in the catalyst, but the amorphous oxide was formed. And BET pore size distribution shows the formation of the mesoporous structure in the mixed-oxide. Among all the catalysts, 2% Cd-Ce0.2-TiOx catalyst exhibits the best NH3-SCR performance with a wide temperature window from 225 to 525°C for NO conversion above 90%.