Preparation And Characterization Of New Nanostructured Catalysts For Oxidative Dehydrogenation Of Propane To Propene

The research drive to develop an oxidation dehydrogenation (ODH) process for propane comes from the facts that the chemical industry depends heavily on the propene and other alkenes feedstock. The major source of propene currently is steam cracking and FCC, the steam cracking maximizes ethene yield and in the FCC plant propene is produced as a by-product, so propene production from these sources will barely match the consumption. Thermal dehydrogenation suffers from several drawbacks, such as thermodynamics limited, rapid coking and high reaction temperature, from the industrial standpoint. ODH can be a viable route for production alkenes as the presence of oxygen counteracts the thermodynamic limitation and prevent coking. While this has been recognized for a long time, an industrially applicable process has not been developed, because secondary oxidation of alkanes to carbon oxides is very significant on most materials. Thus the yield of alkenes remained under 30%, far from satisfactory for commercial application. So it is necessary to develop other new efficient catalysis materials for the ODH of propane. Recently considerable interest has been focused on the catalytic properties of the mixed oxide materials containing cerium due to their improved redox properties and their ability to store and release oxygen under the reaction conditions, which is related to the occurrence of bulk reduction at a moderate temperature. So it is possible to prepare catalyst with high performance under lower temperature for the ODH of propane for propene. Besides the nanocomposite materials, the potential applications porous solid of ordered mesoporous silica with pore walls of uniform width in the range 1-5 nm and controlled uniform pore diameters in the range 2.5-25 nm as periodic hosts for the preparation of mesoporous catalysts with chemically functionalized surfaces have been widely investigated in the past decade. SB A- 15 is a newly discovered mesoporous silica molecular sieve with larger pore diameters, tunable uniform hexagonal channels and thick framework walls, which improve itsAbstractthermal stability, so it is a promising new type of porous support for fabrication the catalyst for ODH of propane.Generally, there are two commonly accepted reaction mechanisms for describing the molecular process of the ODH of propane. One is the redox mechanism and the other is the radical mechanism. For the former reaction mechanism, we have investigated the mixed oxides containing cerium with high performance under lower temperature as well as the vanadium-based catalysts. For the radical mechanism, the boron oxide-based catalysts were studied. Through the preparation, characterization and activity test, we have systematically investigated the reaction nature of the ODH propane over different catalysts.1 . Preparation, Characterization of Ce-Ni-O Mixed Oxide Catalysts and Application in the Oxidative Dehydrogenation of PropaneCewNinO catalysts (m/n denotes the molar ratio of Ce to Ni) with well-defined doughnut-like macrostructures, were prepared by alcoholic coprecipitation of oxalate precursor. For comparison, the pure CeO2 and NiO were prepared by the same method, the reference samples denoted as CemNiwO-OC, CeOTNinO-KC and CeOTNinO-imp were prepared by aqueous oxalate coprecipitation, KOH coprecipitation and conventional wet-impregnation methods, respectively. The SEM image reveals that the CehfoO-OG sample consists of well-defined doughnut-like macrostructures with uniform size of ca. 14 um, which is totally different from the ones prepared by other techniques. The TEM result reveal that there are strong interaction between cerim and ruckle in the CeNi2O-OG, but there are much weaker interaction between cerim and nickle in the CeNi2O-OC, which is consited of single NiO and CeOi. On the other hand, the combined XRD, Laser-Raman, H2-TPR and XPS results reveal that: (1) There are three types nickle phase in the CemNinO-OG samples- aggregated NiO on the support CeO2, high dispersed NiO with strong interaction with CeO2...