| People gradually realize that developing cleaner energy to replace oil fuel has become the primary problem of the energy development strategy because of environmental pollution and the energy crisis. Starting from the strategy of sustainable development, ethanol fuel with its high cleaning properties and reproducibility, will undoubtedly become new clearn energy. The emission of alcohol fuel cars such as hydrocarbons, nitrogen, sulfur oxide will be much lower comparing with gasoline vehicles. However unburned alcohol fuel and some intermediate products such as aldehydes will also cause certain harm on the environment and human health, so the emission purification of alcohol fuel car will be necessary. The purpose of purifying is converting alcohol aldehyde mid-products entirely to CO2 and H2O, which requires catalysts with well low-temperature catalytic performance and good depth oxidation selectivity.In this paper, the total oxidation of ethanol and acetadehyde has been investigated on the new device in order to make up the deficiency of praphase work which ignored the selectivities of oxidation intermediate products and the completely oxidation products. The effect of catalytic oxidation for alcohol and aldehyde on Pd/Al2O3-TiO2 catalysts added different contences of vanadium oxidation were investigated, Pd catalyst is optimized by adding different content of vanadium oxide activity, finally the optimal proportion of Pd and V was found.The changes of characters on catalysts surface structure were researched by various characterization methods such as XRD, N2 adsorption, TPD, TPR infrared, and find some relationship between catalytic mechanism and surface properties and various metal oxide components. In order to facilitate comparative study, single palladium catalyst and single vanadium catalysts were also part of the research, to contrast research. The experimental results have specific get the following several:(1) In the single palladium catalyst series, Pd oxide component is the subject of catalytic for alcohol aldehyde conversion.The conversion of ethanol increases and the middle product acetaldehyde decreases with the increase of the vanadium content. The catalytic oxidation of acetaldehyde show more prominent advantage on the catalyst with high levels of active components. The ethanol and Acetaldehyde can be completely transformed on 5Wt% palladium catalyst in 200 centigrade degree. This indicated that the Pd catalyst for alcohol and aldehyde catalytic mainly is completely oxidation.(2) In the single V catalyst series, Vanadium oxide is the subject of catalytic components, with its increase of quality percentage, the ethanol conversion in 200 centigrade degree also showed a higher catalytic performance,but produce more intermediate products. The catalytic for the acetaldehyde is low, the completely transformation of acetaldehyde was at centigrade degree. This indicated that V catalyst for alcohol aldehyde oxidation is mainly part of oxidation.(3) Add V activity in single palladium catalyst for the second plasma-assisted of catalyst have a obvious of influence, when the adding quantity is few (3%),there is a synergistic effect between Pd components and V components and that makes the complete oxidation activity of catalysts improved.In 200 centigrade degree the transformation of alcohol and aldehyde completely achieved. The lower amount V (5-8%) the activity of catalyst decreased due to vanadium covered the carrier surface,and the role of Pd can not be played.(4) The investigation of catalyst carrier by comparison, composite carrier catalyst can combine the advantages of aluminum oxide and titanium oxide in a suit, likely between two carriers there is a part of ion mutual embedded, and that changed crystal defect and oxygen storage capacity, or formed some crystallology structure and shows prominent advantage of catalytic oxidation to alcohol.(5) The activity of catalyst changes a lot because of adding acid additives in single V catalyst series and bi-component series in preparation of catalysts, overall activity of catalyst have promote role when add acid additives such as nitric acid and acetic acid,while alkali additives play an inhibition role in oxidation of ethanol. This may be due to different additives and roles caused by different ways.(6) The catalytic performance of Pd/Al2O3-TiO2 with vanadium pentoxide has been improved for the complete oxidation of ethanol and acetaldehyde.The strong interaction among various components is conformed by characterizations of the surface properties.The result shows that the catalyst surface properties has changed a lot after adding vanadium such as the lattice oxygen and absorption of oxygen and changes the valence of metal ions which changes the activity and selectivity of catalysts.That demonstrates that there are strong interaction and mutual infiltration between the two activity components and carrier.(7) XRD results showed that compound carrier with sharp over-mining type titanium dioxide as the main body, aluminium exists among them in the form of single-layer scattered. A small amount of vanadium pentoxide did good to palladium component deposition on the carrier, or proper V may enter in grid of TiO2 and caused lattice defects,then change the lattice oxygen and adsorption oxygen quantity, affecting catalytic activity. (8) Nitrogen adsorption result shows that single palladium catalyst added with different quality percentage of vanadium pentoxide made different effects on specific surface area, pore size distribution. when adding proper (1～3%) can make specific surface area, pore size distribution of catalysts be in an appropriate state for adsorption and generate species species spread, thus showing the of the best catalytic activity. When add too much to make it gathered in carrier, covering the surface jams plasma-assisted duct, then activity of catalyst reduced.(9) NH3-TPD shows that moderate vanadium can change the catalyst surface acidity, namely to increase appropriately weak acidic sites and weakening the strong acidic bits.furthermore, while adding a larger V components (1-5#, 1-8#) will lead to strong acidic bits,which cause activity of catalyst reduced.This result indicates that only weakly acidic sites plays an important advantage role in catalytic reaction.(10) H2-TPR results show that in a single vanadium catalysts, the reduction temperature was reduced on the compound carrier with V2O5 loading, which indicated that there was a interaction occuring between vanadium pentoxide and carrier. The existence of carrier improved its redox performance,while the vanadium pentoxide of aggregation was harder than the single scattered, and restore species increased. Add vanadium pentoxide in single palladium catalyst inhibit its redox performance, but interaction between each other increased number of PdO, and this helps to improve the activity of catalysts. |
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