Preparation Of Highly Dispersed Pt/Hβ Catalysts By Supercritical Deposition And Their Catalytic Combustion Performance

The pollution of volatile organic compounds（VOCs）caused serious atmospheric environmental problems and harmed human health.At present,catalytic combustion is the most promising technology in the treatment of VOCs.Noble metal catalyst supported on zeolite is of the mainstream catalytic systems,which combinaed the high efficient active centers of noble metal and the adsorption capacity of zeolite,and has a good application prospect.However,the noble metal components are expensive,which limited its practical application.In this work,highly dispersed Pt/Hβcatalysts were prepared by supercritical fluid deposition（SFD）withβzeolite as carrier,which could improve the utilization of noble metals and the low temperature activity of the catalyst.In this paper,the effects of Pt metal precursor and co-solvent on the physicochemical properties of the Pt/Hβcatalyst during SFD were systematically investigated.The catalyst with Na₂Pt Cl₆ as Pt metal precursors and ethanol as co-solvent was the best method to prepare 1.6 nm Pt particles supported on theβzeolite.On this basis,the effect of reduction temperature on the structure and catalytic performance of the catalyst was further investigated.It was found that the appropriate reduction temperature was 450℃.Under this condition,the proportion of metal Pt⁰of the catalyst was high,and the sintering of Pt could be prevented,and the catalytic combustion performance of toluene was the best.By comparing the physicochemical properties and toluene catalytic combustion performance of Pt/Hβcatalyst prepared by SFD and impregnation,it was found that the Pt particles prepared by SFD method had smaller size and higher dispersion.The temperature of 90%toluene conversion(T₉₀)of the catalyst prepared by SFD method was 25℃lower than that of the catalyst prepared by impregnation method,which showed obvious size effect in this process.And when the catalyst prepared by SFD had the same activity,the Pt loading is only 50%of that of the impregnation catalyst,showing obvious reducing the amount of used noble metal effect.The stability of the catalyst was good.During the long-term evaluation at 190℃for 72 h,the conversion of toluene remained above 98%,and and no obvious sintering growth of Pt nanoparticles.