Preparation Of V-W-Mn/Ti Honeycomb Catalysts And Ce-Mn-Ti Catalysts And Research Of Their Nature In The Catalytic Combustion Of Chlorobenzene

Dioxins is a persistent organic pollutants, they can harm the health ofbody of human beings and environment seriously, For reducing this toxicpollutants, people has been developing many correlative technologies,and catalytic oxidation is a effective approach, in this process, theV-W-Mn/Ti honeycomb catalysts were broadly used presently, but Vspecies of this catalysts is toxic, so there are many people begin to creategreen catalyst, rare earth and its oxides combining transition metal oxidesis a important developmental direction.In the first part of this paper, we prepared a series of V-W-Mn/Tihoneycomb catalysts via a process contain mix/pug milling/extrusion/drying and calcination, the precursors of active species is ammoniummetavanadate, ammonium metatungstate, manganic sulfate andmanganese nitrate, respectively. The V-W-Mn/Ti honeycomb catalystsbefore drying and calcination were characterized by Thermogravimetry,according to data of thermogravimetry, approprite protocols of drying andcalcination were constituted. For investigate the effect of calcination onthe nature of catalysts, the honeycomb catalysts prepared under differentcalcination temperatures were characterized by Raman spectroscopy. Theresults show that it can observe characteristic peaks of anatase TiO₂obviously, furthermore, the intensity of these peaks would rise firstly andthen decline as the calcination temperture changed from300℃to550℃and reach maxmium when the calcination temperature is400℃, in goodagreement with the change of the content of support in the bulk ofhoneycomb catalysts. Additionally, it can observe the patterns of Vspecies and Mn species and the intensity of it is very low, the patterns ofW species were probbaly covered by the peaks of anatase TiO₂, thisresults show that active species were dispersed on the support possibly.The second chapter of this paper reports the preparation of powdered Ce/Ti, Mn/Ti and Ce-Mn/Ti catalysts, in this process, cerium nitrate,manganese nitrate and titanium sulfate used as the precursors of twoactive species and support, respectively. These catalysts were tested forcatalytic oxidation of chlorobenzene, as a model of dioxin. The resultsshow that the activity of Ce-Mn/Ti catalysts is higher than that of Ce/Tiand Mn/Ti catalysts, and the performance of Ce-Mn/Ti catalysts preparedunder different calcination temperatures is disparate and would decline asrising of calcination temperature, correlative activity order isCe-Mn/Ti（400℃）> Ce-Mn/Ti（500℃）> Ce-Mn/Ti（600℃）>Ce-Mn/Ti（700℃）. In order to understand the effect of calcinationtemperature on the performance of Ce-Mn/Ti catalysts, a series ofcharacterization contain scanning electron microscope（SEM）,transmission electron microscope（TEM）, N2adsorption-desorption, X-raydiffractometer（XRD）, Raman spectroscopy（Raman） and H2-temperatureprogrammed reduction（H₂-TPR） has been conducted. The characterizedresults were summarized as below, as rising of calcination temperature,the particles of catalysts would enlarge and get together gradually, thischange would result in declining of micropores, specific surface area andpore volume, finally, the adsorption of chlorobenzene on the surface ofcatalyst would be influence. Furthermore, the active species disperseduniformly on the support firstly, as heightening of calcination temperature,these active species would form bigger crystals and oxidability ofcatalysts ascend, all of this would bring the activity of catalysts on thecombustion of chlorobenzene down.