Palladium Base Preparation Of Modified Aluminum Anodic Oxidation Catalyst And Toluene Catalytic Combustion Performance Study

Volatile organic compounds (VOCs, volatile organic compounds) is refers to the boiling point range in50～100℃to240～260℃between compounds, is also a important atmospheric pollutants, the ecological environment and human there is a serious health risk. Catalytic combustion purification method is the most effective treatment method of VOCs. This method has high combustion efficiency, low temperature light-off sex good, won’t produce secondary pollution, combustion from organic pollutants concentration limit etc, and in the treatment of VOCs in the purification treatment has obvious advantages.Catalytic combustion method is the most direct, economic VOCs processing, high efficiency, wide range, and its center is the research and development of catalysts, therefore preparation has a low temperature high activity, stability good catalyst is the catalytic combustion process of VOCs key.This thesis mainly with aluminum screen for matrix, the anode oxidation for preparation of coating, reoccupy chemical plating technology in a alumina coating of aluminum screen load on precious metal Pd preparation monolithic catalyst, and with toluene catalytic combustion purification as probe reaction, on the catalytic combustion performance, the main research contents and results are as follows:First of all, catalyst carrier coating preparation. Metal carrier and traditional ceramic carrier, compared to geometric ratio area more, be helpful for catalytic activity physical adsorption, and reduce exhaust resistance; Heat conduction coefficient is higher, can rapid heat transfer, thus avoid carrier local overheating structure thermal damage; Specific heat more low, can shorten to catalytic reaction temperature time, fast ignition. Metal carrier become a most development potential of the tail gas purification catalyst carrier form. However, the existence of high temperature oxidation resistance of metal carrier sex is bad, the carrier material forming process of complex, carrier material and the adhesion strength of the coating is of some shortcomings, especially coating load difficulties and in the process of using disbonding problem, is the metal carrier failed so far to to large-scale use of one of the main factors. Based on the anodic oxidation technology, makes the metal aluminium screen surface generating a layer of highly ordered many pass membrane, the inspection, the anode oxidation time, current density and reaction temperature on the porous membrane formation of influence, through the contrast surface area, XRD, SEM. etc characterization analysis. The results show that metal aluminum screen matrix on anode oxidation modification of the optimal technological conditions for reaction temperature25℃, current density1.5A/dm2and reaction time120min, generated anode oxidation membrane most law; Compared with traditional coating preparation methods, and the anode oxidation coating preparation of coated rate high, fall off rate is low, the coating firm degree better, coating more even, the basal specific surface area higher advantages.Then, choose Pd for active component, the chemical plating technology preparation Pd/Al2O3/Al screen overall is a catalyst, and optimize the preparation technology of the catalyst, with toluene as reaction gas stability of catalyst were examined catalytic performance. The experimental results show that:after anodic oxidation of aluminum screen,0.4wt%Pd/Al2O3/Al wire under the action of catalyst and toluene190℃is completely catalytic conversion, and direct electroless plating catalyst carrier, compared to the anode oxidation modified metal aluminum sheet matrix is a kind of excellent properties, development prospect of functional materials, and at the same time draw, chemical plating temperature of60℃, solution concentration is0.2g/L, catalyst best roasting temperature of600℃. The corresponding representation also show that, with the temperature, the high dispersion PdO and crystallization type PdO as the main active ingredient, in the temperature600℃～700℃, PdO mass sintering, resulting in catalyst deactivation. From the catalytic performance and economic factors,0.4wt%of Pd/AlO3/Al whole is catalyst cost-effective, the catalyst light-off temperature T10and complete combustion temperature T99respectively for165℃and190℃.Finally, the catalyst performance, structure and characterization are analyzed.0.4wt%Pd/Al2O3/Al screen catalyst in toluene sample gas concentration for1～8g m-3·airspeed in5000～20000h-1range all can show good catalytic performance,100h life experiments catalyst activity basic remain unchanged. From the thermal shock, firm degree, XRD, UV diffuse. H2-TPR、02-TPD analysis results also show that the catalyst depends on the Pd- PdO synergy complete catalytic combustion reaction, in metal Pd and PdO phase interface adsorption oxygen into lattice oxygen rate balance, catalyst activity to achieve stability; Chemical plating for preparation of d/A12O3/Al screen the whole is catalyst active component in the substrate load firm, and the load is low, PdO with small particle monolayer uniform distribution, but capacity greater than0.60wt%, the PdO carrier in starting the reunion, leading to the catalytic activity is reduced, but also caused a certain waste; Through the SEM to carrier and the morphology of catalyst are characterized, and the results showed that the anodic oxidation process of the catalyst, the catalytic activity and the formation of surface oxide film on state.