Studies On The Preparation And Performances Of TiO₂ Supports

Laden catalyst is one of the most important catalysts in the chemical industry. Supports take important roles in catalysis as the footstone of laden catalyst. TiO₂ support is a newfashioned catalyst carrier in recent years. TiO₂ support became the studying focus since researchers of Exxon Company found the SMSI on titanic supported noble metal catalyst in 1978. Preparation and performances of TiO₂ support were studied in this thesis.TiO₂ supports were prepared by using nanometer TiO₂ powder and metatitanic acid as materials. In the preparation process, a small quantity of additive and water were firstly added to the mixture of the materials. Then the mixture was mixed round, extruded to be a form of strip which was dehydrated for twelve hours in atmosphere. At last the supports undergo drying at 80 ℃ for two hours then at 120 ℃ for three hours in the oven and calcining at 350 ℃ in the muffle for four hours. Relations were studied between strength, surface area and ratios of two materials, the temperature of calcining, the types and quantities of additives. Microstructure, heat stability and pore distribution of the TiO₂ supports were studied by scanning electron microscopy(SEM), TG, X-ray powder diffraction(XRD) and automated mercury porosimeters. And the results were discussed in theory.Noble metal load and SMSI (strong metal-support interaction) of the supports were studied for farther research. Incipient wetness impregnation is especially significant for noble metal load for its high efficiency and low cost. Three ways of incipient wetness impregnation for noble load were adopted in experiments. Pd distributions in the supports were detected by energy dispersive X-ray spectroscopy microanalyzer (EDS). The better method was selected by compare. Some special phenomena resulted from SMSI were studied by TPR and TG-DSC. The SMSI effect between noble metal and titanic supports was farther confirmed. The mechanisms of inducing the SMSI effect were also discussed.The final purpose of TiO₂ support preparation is to obtain the high active catalystfor hydrogenation. The catalytic activity and stability of Pd/TiO2 were studied by using catalytic hydrogenation o-nitrotoluene as probe reaction. The hydrogenation products were analyzed by gas chromatography (GC). Pd/TiC>2 catalysts exhibited especially good activity for the reaction in atmosphere pressure. The mechanisms of Pd/TiCh catalysts for hydrogenation were investigated according to the results of experiments.