Preparation Of Highly Dispersed Ru/C Catalyst Via Supercritical Fluid Deposition And Its Catalytic Performance

The supported noble metal catalysts show good catalytic activity inhydrogenations and some oxidation reactions, which have attracted wide attractions.For the noble metal catalysts, the main factors influencing their catalytic activity aremetal dispersion and particle size. Some prepararion methods，effectively controllingthe dispersion and metal particle size, usually use some poisonous or highly volatilereagents. Therefore, the main object of this work is preparation of carbonaceousmaterial supported ruthenium catalysts by mean of the supercritical fluid deposition(SFD) technology taking advantage of the special advanced performances ofsupercritical fluids (SCF). In order to control the metal particle size and improve thedispersion effectively, some preparation raw materials, such as organic metalprecursors, co-solvents and supports, are carefully selected; the pretreatmentmethods of supports and the process conditions of SFD are optimized; the possiblemechanism for ethanol in SFD process is briefly suggested. Moreover, the catalyticactivity for butanone hydrogenation of the as-prepared Ru/C catalysts is alsoinvestigated systematically.The optimum deposition system Ru3(CO)12-ethanol-CNTs was selectedsuccessfully. For the Ru/CNTs catalysts prepared using different co-solvents, the Ruparticles tend to aggregate with the increase of surface tension and polarity ofco-solvents. After optimizing the pretreatment conditions of supports, there exist theoptimal ultrasound treatment time of20min and the optimal ratio1/14of CNTs toHNO3. The longer deposition time is beneficial to the deposition of metal Ru oncarriers, but could result in the aggregation of metal particles. According to theparticle size and real Ru loading, the optimal deposition and therotical Ru loading is4h and0.5%, respectively.It is found from the catalytic activity investigation that the catalytic activity isapparently increased with the decrease of metal particle size. Compared with thecommercial Ru/AC catalyst, the catalytic butanone hydrogenation activity and theutilization of Ru metal for the Ru/CNTs catalyst prepared by SFD process are bothenhanced. The stability tests indicate that the catalytic activity of Ru/CNTs catalystafter multiple usage times can remain nearly the same, the Ru metal particles would not drop from the carrier surface, and the Ru nano-particles would not seriouslyaggregate after the recycle applications of catalyst. Thus the Ru/CNTs catalystprepared by SFD process could show ideal stability.