Study On Different Pt/MO_x Catalyst For Catalytic Oxidation Of CO And VOCs

Volatile organic compounds(VOCs) and carbon monoxide were the main source of atmospheric pollutants, which could lead to the increase of PM 2.5 and the haze weather. Catalytic oxidation was considered one of the most promising and effective methods to eliminate VOCs and CO. Studying the catalysts was the core technology of catalytic VOCs and CO oxidation. There were three main factors effects on the oxidation performance of Pt-based catalyst. Namely, metal oxide and platinum’s species, platinum particles’ size, the interaction between platinum particles and supporter. Howere, these factors were closely related to the preparation methods of catalysts. In this article, we prepared a serice of catalysts with four different methods. Namely, being reduced by KBH4, decomposing of platinum coordination compounds, being reduced by H2 in gas phase, being reduced by H2 in liquid phase. we studied the catalysts’ activity about VOCs and CO. The properties of the synthesized catalysts were characterized using X-ray diffraction(XRD), N2 adsorption-desorption(Brunauer-Emmett-Teller(BET) method), transmission electron microscopy(TEM), X- ray photoelectron spectroscopy(XPS) and temperature-programmed reduction of H2(H2-TPR). The main research contents and results are as follows:Using four different methods which had been mentioned above to prepare Pt/MOx(MOx=TiO2, CeO2, Zr O2, Al2O3 and C), and studying those catalysts’ activity of CO oxidation. The active supports(TiO2、CeO2) had higher activity than the inert support(Al2O3、ZrO2、C). Especially, TiO2 was the best support for CO oxidation. Because active supports could be reduced when took part in the reaction, the reduced supports would produce many oxygen vacancies which had advantage for the adsorption of oxygen. Four kind Pt/TiO2 catalysts: being reduced by KBH4, decomposing of platinum coordination compounds, being reduced by H2 in gas phase, being reduced by H2 in liquid phase. They ignition temperature of CO oxidation was 103、127、115 and 180℃, respectively. Then studying the other factors such as gaseous hourly ace velocity, the concentration of CO, the loading of platinum, it showed that the higher platinum load, lower concentration of CO, lower gaseous hourly ace velocity had advantage for reaction.Due to the TiO2 had a excellent activity for CO oxidation, so we rearch the Pt/ TiO2 deeply. The catalytic properties of titanium dioxide supported platinum catalysts, prepared by four different methods were investigated for the catalytic oxidation of volatile organic compounds(VOCs) such as toluene, acetone, and ethyl acetate. As a result, toluene present in the incoming feed stream(GHSV of 18000 ml·g-1·h-1) could be completely removed at temperatures below 130, 154, 180 and 243?C, respectively. Ethyl acetate could be completely removed at temperatures below 218, 230, 245 and 268?C, respectively. Acetone could be completely removed at temperatures below 138, 145, 167 and 187?C, respectively. Then fresh catalyst and deactivity catalyst were characterized by many kinds of instruments,we found that agglomeration of platinum particles was the main reason for it deactived.The properties of the synthesized catalysts were characterized by all kinds of machines, and it had results were as follows: ①Pt/TiO2 prepared by KBH4, it had better low temperature reduction performance; the content of Pt0 was 79.9% on the surface of catalyst; particles dispersion were very good but the particles’ size distribution was wide, about 2-5 nm; the channel structure of catalyst was destroyed, nanoparticles and support had strong interaction force. ②Pt/TiO2 prepared by decomposing of platinum coordination compounds, it had better low temperature reduction performance; the content of Pt0 was 72.8% on the surface of catalyst; particles dispersion were very good and the particles’ size distribution was narrow, about 3 nm; the channel structure of catalyst was intactness, nanoparticles and support had little interaction force. ③being reduced by H2 in gas phase, it had not low temperature reduction performance; the content of Pt0 was 72.8% on the surface of catalyst; particles dispersion were very bad; the channel structure of catalyst was destoried, nanoparticles and support had strong interaction force. ④being reduced by H2 in liquid phase, it had better low temperature reduction performance; the content of Pt0 was 52.8% on the surface of catalyst; particles dispersion were very good; the channel structure of catalyst was intactness, nanoparticles and support had little interaction force.Pt/TiO2 prepared by KBH4 had best activity for CO and VOCs oxidation. There were four reason for it: the first, it had best low temperature reduction performance; the second, it had a large number Pt0 which was the active site of adsorbing carbon monoxide. The third, partial reduced titanium dioxide produce the oxygen vacancy on the surface of supporter. It appeared a new active site—Pt-Vo-Ti3+, which has a strong oxygen adsorption ability. moreover, oxidation of carbon monoxide is a structure sensitivity reaction, and partial reduced titanium dioxide has larger crystal lattice defect, so it has advantage for oxidation of carbon monoxide. The last, Pt nanoparticles disperse within the carrier surface and hole, so it has the best dispersity. H2PtCl6 been reduced by H2 in liquid phase had the worst activity for CO and VOCs oxidation, because it had little Pt0. Decomposing of platinum coordination compounds had advantage for VOCs oxidation, however, H2PtCl6 been reduced by H2 in gas phase had advantage for CO oxidation, because molecular diffusion had a bigger effect on reaction.