Study On FeAl(PO₄)₂ Catalysts For 1,2-Dichloropropane To Form Propylene Oxide In Membrane Reactor

A series of phosphate catalysts and Kieselguhr-Mullite ceramic supported SiO2-Fe2O3 membrane tubes have been prepared and used as catalyst and membrane reactor for 1,2-dichloropropane dechloroxidation forming to propylene oxide, in order to increase the conversion of 1,2-dichloropropane and the selectivity to propylene oxide. This work mainly focuses on:(1)A series of phosphate catalysts have been prepared by precipitation method and sol-gel method respectively. The effects of preparing method, materials, conditions of drying and calcination on the properties of the catalysts have been investigated. Under a proper preparing conditions, an amorphous FeAl(PO4)2 catalyst with the specific area more than 90m2/g and the particle size about 10 nm was obtained.(2)H2O adsorbs　on phosphate M of Lewis acid sites M－O bond and oxygen of Lewis base sites P=O bond in molecular state and dissociative state, with M representing Fe or Al. H2O adsorbs on AlPO4 catalyst in molecular state, but H2O adsorbs on FePO4 and FeAl(PO4)2 catalysts in molecular state and dissociative state. 1,2-dichloropropane adsorbs on phosphate M of Lewis acid sites M－O bond in molecular state. The acidity of Lewis acid sites and the basicity of Lewis base sites　influence the intensity between water, 1,2-dichloropropane and catalyst. The specific area of catalyst influences the capacity of adsorption.(3)H2O adsorbs　on FeAl(PO4)2 at the synergistic action of Lewis acid sites and Lewis base sites in dissociative state and forms P－OH and Fe－O－, then 1,2-dichloropropane absorbs on P－OH and forms HCl and intermediate product propene after action. Propene acts with Fe－O－ and forms propylene oxide. Using amorphous FeAl(PO4)2 as catalyst, 1,2-dichloropropane convention rate and propylene oxide selectivity are 86.3% and 87.9% respectively under a proper reaction condition.(4)Kieselguhr-Mullite membrane supports,with uniform microstructure, better strength character and permeability, have been successfully prepared by extrusion. Its pore-size concentrates around 2.01(m, stacking density is about 1.58 g/cm3, the interspace ratios is 47.0% and the side compressive strength is 13.40Mpa. Effects of original particle size of kieselguhr, plasiticizer and extrusion mould on the processing have been studied. Effects of dry conditions and sintering systems to the properties of supports have also been analyzed. Based on the discussion, preparation conditions and methodology have been proposed.(5)Kieselguhr-Mullite supported SiO2 intermediate membrane and SiO2-Fe2O3 separation membrane have been prepared by sol-gel method and sol-gel-template technique respectively. Perfect SiO2 membrane　and SiO2-Fe2O3 membrane, with good micromorphology, uniform pore size distribution around 45 nm and 4nm and thickness about 2(m and 0.5(m respectively, have been prepared by treating impregnation-drying-calcination three times. SiO2-Fe2O3 membrane, SiO2 membrane and Kieselguhr-Mullite membrane support are tightly and stably linked together by Fe-O-Si-O-Si bond. HCl can be separated selectively by Kieselguhr-Mullite supported SiO2-Fe2O3 membrane because of surface diffusion.(6)Membrane catalytic reactivity of 1,2-dichloropropane dechloroxidation to propylene oxide has been investigated, with Kieselguhr-Mullite supported SiO2-Fe2O3 membrane tube as membrane reactor and amorphous FeAl(PO4)2 as catalyst. It is showed that 1,2-dichloropropane convention rate and propylene oxide selectivity of membrane catalytic reactions are always better than convention catalytic reaction　under the same reaction conditions. 1,2-dichloropropane convention rate and propylene oxide selectivity are 90.9% and 88.3% respectively under a proper reaction condition.