The Dechlorination Of Chlorinated Organic Pollutant Over The Pd-based Catalysts

Recently, removing the chlorinated disinfection by-products of drinking water efficiently have become one of the research hotspot in the environment engineering field. However the method of catalytic hydrogenation to activate C-Cl bond is best. If H2 as hydrogen source to degrade TCE, there are some disadvantages that hard to apply largely and the need high pressure. If factories use H2 as hydrogen source to activate the C-Cl bond which is hard to carry out in the large scale water supply system. It also need large consumption and difficult engineer. However formic acid as model compound to storage hydrogen which is less by-products, high selectivity to target products, and easy to apply is very important in industry. Pd based catalyst were selected as catalyst to degrade chlorinated organic compound have been investigated. So we select formic acid as hydrogenation reactant,trichloroethylene(TCE) as the chlorinated disinfection by-products, Pd/MCM-41 and Pd-Au/Al2O3 as catalyst to degrade the TCE.The different component Pd/MCM-41, Pd-Au/MCM-41 catalysts were prepared though impregnation. This study investigated the the effect of the loading amount of Pd and Au content, temperature and the initial concentration of formic acid and TCE to the reaction activity though headspace and GC analysis method.We selected MCM-41 and Al2O3 as the optimal supports for Pd and Pd-Au bimetilic catalyst though activity test. Then 1.5% is the optimal loading amount for Pd and Au. We screen out the optimal reaction condition though test the effect of reaction temperature, catalyst initial concentration, TCE initial concentration, formic acid initial concentration on reaction rate. In room temperature, TCE can be degraded 100% in half hour for 1.5%Pd/Al2O3 TCE can be degraded 98.3% in ten minutes for 1.5%Pd-1.5%Au/Al2O3. TCE reaction rate and formic acid reaction rate will be increased with increasing the temperature; TCE reaction rate will decrease with increase the formic acid concentration; TCE and formic acid reaction rate increased with increased catalyst concentration. TCE and formic acid reaction rate reduced with increased the TCE initial concentration.The catalyst characterization result indicates that TOF can be increased with increased the Pd loading amount. But TOF of catalyst have no large change when the Pd loading amount were more than 1.5%; The XRD image of 1.5%Pd-1.5%Au/Al2O3, there are no characteristric peak of Pd and Au, so we can deduce that the particle size is less than 5nm. So it has large special area that is apt to adsorb formic acid to dissociate.