Preparation Of Pt Supported Catalysts And Their Catalytic Properties

Chlorinated organic compounds have been widely used in the industry, but theiraccidental release into the environment cause an environmental hazard. Catalytichydrogenation of chlorinated organic contaminants is a promising non-destructivetechnology with low energy demands, by which chlorinated organic contaminantscan be converted into products of commercial value. Nano-catalysts have fascinatingcatalytic properties compared with traditional catalysts, so they are used to catalyzethe hydrogenation of chlorinated organic compounds. In this paper we chosechloronitrobenzene and chlorobenzene as the text object. The thesis focused on thefollowing aspects:Firstly, supported Pt nanocatalysts with controlled particle size and sizedistribution were prepared by immobilizing Pt colloids on different oxide supports(γ-Fe2O3, Fe2O3, Fe3O4, Al2O3) via physical adsorption. These catalysts were used tocatalyze the hydrogenation of o-chloronitrobenzene (o-CNB) to o-chloroaniline(o-CAN) under mild reaction conditions (25C,0.1MPa). The results showed thatthe supports had a great effect on the catalytic property, the hydrodechlorination ofthe product o-CAN was completely suppressed over iron oxide support catalyst. ThePt/γ-Fe2O3exhibited higher catalytic selectivity and activity than other similar works(activity=0.20molo-CNB/(molPt·s)). The stability of the Pt/γ-Fe2O3was investigated,the results showed that by elevating the drying temperature(50C、80C、150C)could increase the stability of the catalyst.Secondly, a series of layered double hydroxide (LDH) were prepared byco-precipitation method. Relatively well-formed crystalline layered structure wasverified by XRD characterization. The functional groups of organic vibration modes can be observed in the FT-IR spectra. The “unprotected” Pt nanoparticles (stabilizedby simple ions and ethylene glycol) were immobilized on these supports, and used inthe hydrodechlorination of chlorobenzene under ambient conditions (298K,0.1MPa). The Pt/Mg2Al-CO3-LDH catalysts exhibited an excellent activity comparedwith other catalysts. The Fe in the layered double hydroxide poisoned the catalystscompletely, no conversion of chlorobenzene at the same reaction conditions.Meanwhile the addition of Zr、Cu、La into the support also makes a decrease in thecatalytic activity.Finally, PVP-protected Pt colloids and “unprotected” Pt nanoparticles wereprepared. Then the two types of colloids were immobilized on ZrO2、SiO2、CeO2,respectivively. The Pt-supported catalysts were used to catalyze the liquid phasehydrogenation of chlorobenzene. The results showed that the property of metalcolloids and supports had an effect on the catalytic activity and selectivity. ThePt/ZrO2catalysts exhibited best catalytic properties compared with other catalysts.The effect of the concentration of chlorobenzene and different additives on thehydrogenation reaction over Pt/ZrO2was studied. The reaction was verified to befirst order to the concentration of chlorobenzene. The additives showed differenteffect on the catalytic properties of Pt/ZrO2.