TiO₂ Nanowires Decorated With Nano-Pd Particles And Its Application In Benzyl Alcohol Oxidation Reaction

Benzaldehyde is the simplest and most important aromatic aldehyde in industry.It is widely used in medicine,dyes,spices,resin and other industries.At present,the main method of producing benzaldehyde is benzyl chloride hydrolysis in industry which exists a severe drawback of containing chloride in the products.This limits its application in the industry of medicine and spices severely.The most popular methods of producing benzaldehyde without chlorine include direct oxidation of toluene,direct oxidation of benzyl alcohol and hydrogenation reduction presently.The method of direct oxidation of toluene owns disadvantages of low selectivity of benzaldehyde and low efficiency of products separating.While the method of hydrogenation reduction costs excessive which makes it hard to be used in industry.The method of liquid-phase oxidation of benzyl alcohol proves to be more promising due to its advantages of simple technology,environment friendly,but it usually needs high temperature and high pressure.So it is crucial to improve its performance at lower reaction pressure and temperature so as to be applied in industrial production.TiO₂ nanowires with different crystals act as the carriers in this paper.Zero state Pd nanoparticles were successfully loaded on the carriers by the method of biological reduction and sol loading obtaining a series of catalysts with different crystal.TEM,XRD,UV-vis DRS,BET and XPS techniques were applied to character morphology,crystal structure,absorption ability of light,specific surface area,pore structure and surface element valence in the catalysts.By using benzyl alcohol as the target reactant,we studied the influence of loading capacity of Pd,carrier material,crystal type of TiO₂ nanowires,reaction temperature and reaction time on catalytic performance of benzene methanol liquid phase oxidation reaction as well as the stability of the catalysts.Results showed that the conversion rate of benzyl alcohol reached 84.5%and the selectivity of benzaldehyde reached 88.8%when TNWs-450/Pd was used as the catalyst.The initial conditions were listed as follows:the mass of catalyst was 0.2 g,the volume of benzyl alcohol was 20 mL,the volume flow rate of O₂ was 90 mL/min,the reaction temperature was 90?and the reaction time was 6h.This showed that the problem of high temperature and high pressure needed in the reaction was solved effectively.Conversion rate of benzene methanol changed a little and selectivity of benzaldehyde rose slightly after 6 circles'reuse of TNWs-450/Pd catalyst.All these showed that the TNWs-450/Pd catalyst was long-term stable and presented a big potential for industrial application.