| Chlorinated organic compounds have been widely used in chemical industry,pesticides and medicines,but most chlorinated organic compounds are recalcitrant to biodegradation and have strong biotoxicity and carcinogenicity,which will cause long-term environmental and health risks.Therefore,exploring effective method for the removal of chlorinated organic pollutants is of significant importance and environmental implication.Liquid-phase catalytic hydrogenation provides a green,simple and cost-effective method for the removal of chlorinated organic compounds.To achieve efficiently removal of chlorinated organics,the catalyst is the key,supported Pd are commonly used as active catalyst because of its strong capability for H2activation under ambient conditions.It is worth noting that the structure and properties of supported Pd catalysts are variable,while there are many types of chlorinated organic pollutants,each of which is quite different.The activity of liquid-phase catalytic hydrodechlorination could be affected by a number of factors.Adjusting the structure of the supported Pd catalyst?electronic properties and geometric configuration?and selecting chlorinated organic pollutants with different size and properties to study the correlation effect of the catalyst structure and hydrodechlorination,in this way we can clarify the influence of catalyst and the structure of chlorinated organic to the activity of catalytic hydrodechlorination,which has great significance on removing chlorinated organic pollutants in water efficiently.In this thesis,through selecting different supports?ordinary Ti O2,Ce O2,MCN and Ce O2 with different morphologies?,comparing preparation methods?different reduction methods and reduction temperatures?and adjusting the size of catalyst,to obtain different supported Pd catalyst.At the same time,different properties?4-chlorophenol,chloraceacid?and different molecular sizes?4-chlorophenol,2,4-dipchlorophenol and 2,4-chlorobenzene acetate?were selected as target pollutants The structural properties of the catalysts were analyzed by transmission electron microscope?TEM?,X-ray photoelectron spectroscopy?XPS?,X-ray diffraction?XRD?,in situ infrared spectroscopy of CO adsorption?In-situ CO-IR?and other characterization methods to investigate the relationship between catalyst structures and catalytic properties,exploring the association between catalytic activity and the structural properties of catalysts and chlorinated organic compounds,The main research results are as follows:?1?Using different materials with different type?Ti O2,MCN and Ce O2?and different morphology?rod Ce O2,cube Ce O2,octoplastul Ce O2?as carriers,and changing the preparation method of catalyst?hydrogen reduction and sodium borideal reduction?to adjust the structure of Pd particles on the surface of the catalyst,while selecting 4-chlorophenol and chloroacetic acid of different properties as reactants,the study shows that the proportion of Pd?+is higher in the catalyst which reduced by sodium boron hydride,the catalyst shows higher hydrodeprecation activity on MCAA.While the proportion of Pd0 is higher in the catalyst which reduced by hydrogen,the catalyst shows higher hydrodeprecation activity on 4-CP.Besides,we found the high activity of the catalyst is associated with the Pd collection with a three-tooth structure.?2?Using precipitation deposition and adjusting Pd load,the catalysts with Pd particle sizes of 1.0 nm,2.2 nm and 2.5 nm were prepared,and choosing three different molecular sizes of chlor-chloride organisms as target pollutants?4-chlorophenol,2,4-dipchlorophenol and 2,4-dipchloropreol and 2,4-dipchlorobenzeyacid?,to study the best size of the Pd catalyst for chlorinated organic compounds with different molecular size.It is found that the catalytic activity of Pd/Ti O2 is affected by the combined effect of Pd particle size effect and pollutant molecular blocking effect,when the reaction size is larger,the smaller the catalyst size is conducive to catalytic hydrogenation dechlorination,and when the reaction material size is larger,the catalyst with a small particle size is not conducive to catalytic hydrogenation dechlorination.According to the kinetic fitting,we found that under the catalysis of small size?Pd/Ti O2-0.05?,hydrodechlorination of 2,4-D was mainly in the gradual dechlorination mode,with the increase in size of the catalyst,the ratio of 2,4-D synchronous dechlorination increased.And under all catalysis,the hydrodechlorination of 2,4-DCP was mainly in the synchronous dechlorination mode.The effect of the preparation method on catalytic hydrogenation dechlorination is further explored by changing the reduction mode and temperature.The results show that the aggregate state Pd is more conducive to catalytic hydrogenation dechlorination than the separation state Pd,wherein the large collection Pd of the three-tooth structure is more conducive to catalytic hydrogenation dechlorination than the small collection Pd of the two-tooth structure. |
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