Study On Catalysts And Membrane Reactor Of Isobutane Partial Oxidation With Carbon Dioxide Couple 'Catalysis-separation' Reaction

In this paper, Pd/VSiO and Pd/MgO/VSiO catalysts were prepared by the methods of surface modification and incipient impregnation. Their structures, valence states, chemisorption properties of isobutane and carbon dioxide and catalytic behavior for isobutane partial oxidation with CO₂ were characterized by BET, XRD, TEM, XPS, TPD, IR and micro-reactor techniques. The results showed that the lattice oxygen of V=O is the active site on the Pd/VSO catalyst, and the valence of vanadium in the V=O is positive 5. Isobutane was chemisorbed on the lattice oxygen of V=O through the H atoms in -CH3 and–CH. and carbon dioxide was chemisorbed horizontally on the Pd metallic and V4+ through their synergetic effect. The V5+-V4+ couple plays a key role in the redox mechanism of the catalytic reaction. MgO introduced promoted the dispersion of V2O5 and Pd metallic on the surface of silica. The addition of MgO could improve conversation of i-C4H10 and selectivity of i-C4H8 because electrophobic effect of MgO to lattice oxygen of V=O could promote the chemisorption and activation of the H atoms in -CH3 and–CH.A new kind of soluble polyimide with plenty of carboxyl along the polyimide backbone was solution imidized employing 4, 4'-hexafluoroisopropylidenediphthalic anhydride, 2, 4, 6-trimethyl-1, 3-phenylenediamine and 3, 5-diaminobenzoic acid. The different kinds of membrane reactors of polyimide/-inorganic, SiO₂, TiO₂ and SnO₂ supported on TiO₂/kieselguhr-mullite were prepared. Their morphologies, chemical structures, thermal performances, pore distribution and gas permeability were characterized by methods of SEM, FTIR, XPS, TG/DTA, DSC, BET and gas permeability measurement. The results showed that the morphology of the supported membranes was quite homogeneous and the layers of each membrane were coupled tightly and naturally. The hybrid membranes possess higher thermal stability and compatibility between the organic and inorganic components. The hybrid membranes possess the space networks with regular pores formed by the connection between the polyimide and inorganic phases via the carboxyls along the polyimide backbone. The pure polyimide and each hybrid membrane showed separation properties for CO₂ and H2O. The polyimide-SnO₂ hybrid membranes have fine separation properties for CO, and the separation function was increased with the increasing of SnO₂ contents.The conversional catalytic reaction and membrane catalytic reaction for i-C4H10 partial oxidation with CO₂ were studied over Pd/MgO/VSiO catalyst in the polyimide-inorganic, SiO2, TiO2 and SnO2, hybrid membranes reactors. Under the conditions of 400°C, 0.1MPa, mixed gas space velocity of 1200h-1 and CO2 / i-C4H10 ratio of 1, the isobutane conversion of 9.32%, 9.83%, 10.45% and isobutene selectivity of 96.44%, 96.78%, 97.14% are achieved. However, under the same conditions, the isobutane conversion and isobutene selectivity of the conversional catalytic reaction were 7.54% and 95.71%, respectivly.