Preparation, Structure, And Properties Of Ultrafine Rare Earth W-based Complex Oxides La-Fe-W-O Catalysts

In present, partial oxidation of Toluene and substituted Toluene in vapor phase is one of the programs that had been extensively studied in the field of heterogeneous catalysis and surface scientific research. Since long-term, great efforts have been made in improving the catalytic selectivity by altering the composition and structure of catalysts and adopting the optimum catalytic reaction conditions. But, the lack of selectivity is always the baffling problem. In this dissertation, recent developments and prospects in the various catalysts of partial oxidation of Toluene and substituted Toluene are reviewed. In this work, the ultrafine rare earth W-based complex oxides La-Fe-W-O particles have been successfully synthesized for the first time by the polymerized complex method. The catalytic properties of the ultrafine W-based complex oxides La-Fe-W-O particles and their correlation to the particle size, crystal structure, surface properties, reducibility have been investigated by using TEM, ED, DTA-TG, IR, XRD, Rietveld analysis, XPS, Mossbauer spectroscopy, TPD, TPR, BET surface area measurement, and fixed-bed microreactor tests.La-Fe-W gels can be prepared by the polymerized complex method using citric acid and ethylene glycol (CA-EG) under the appropriate experimental conditions, which can be converted to the corresponding complex oxides with particle size in the range of ultrafine scale. The synthetic temperature of the ultrafine W-based complex oxides La-Fe-W-0 particles is 550 ℃(for x=0.0, La₂W₃O₁₂) and lower than 450 ℃(for others) respectively. The gel preparation conditions such as the molar ratio of citric acid(CA) to total metal ions, pH value of the solution, and the temperature for the pretreatment of the gels, exert great influence on the structure and morphology of the W-based complex oxides.