Molten-salt Derived Iron Oxide Catalysts And Their Performance For The Removal Of Volatile Organic Compounds

In recent years,with the increase of industrialization in China,the problem of air pollution is becoming more and more serious,which has caused a fatal blow to the ecological environment.To solve this problem,the government has introduced relevant policies to control the emission of volatile organic compounds（VOCs）.Among the many methods,catalytic oxidation is considered to be one of the most effective methods,duing to its simple process and high purification efficiency.The key is fabricating highly efficient and cheap catalysts.On the basis of the pre-laboratory work,we have prepared a batch of low-load precious metal nano-catalysts using the in-situ molten salt method,we use this catalyst to test catalytic activity for different VOCs（toluene,xylene）,and the main results are as follows:（1）By using molten salt method,by adjusting the composition of molten salt,the precursor,the quality ratio of molten salt and the precursor,the roasting temperature and the time of the heat preservation,etc,a number of FeO_y types with different morphology were prepared.These works were laid the foundation for the subsequent sample preparation.（2）The catalysts for low-load platinum noble metal were prepared by in-situ molten salt.The x Pt/Fe₂O₃ catalysts（x=0,0.034,0.063,0.22,or 0.30 wt%）were fabricated by using a mixture of NaNO₃ and NaF as molten salt and Fe（NO₃）₃ and Pt（NH₃）₄（NO₃）₂ as metal precursors.Compared catalytic activity of different loading Pt over Fe₂O₃ catalysts,0.22 wt%Pt/Fe₂O₃ was shown the best catalytic activity,the T_10%,T_50%,and T_90%（temperatures required for achieving O-xylene oxidation of 10%,50%,and 90%,respectively）was 163,209 and 229 ℃ at space velocity of 40,000mL/（g h）.Moreover,it was found that this catalyst exhibited a high thermal stability and anti-catalyst deactivation.It is concluded that the excellent catalytic activity of0.22 wt%Pt/Fe₂O₃ was due to its high dispersion of the Pt nanoparticles on the surface of Fe₂O₃ and good low-temperature reducibility.In consideration of the nice performance,low cost,fine stability,and simple produced,0.22 wt%Pt/Fe₂O₃ sample can serve as a classic catalyst for the complete oxidation of typical VOCs.（3）The catalysts for low-load palladium noble metal were prepared by in-situ molten salt.Using a mixture of NaNO₃ and NaCl as molten salt and Fe（NO₃）₃ and PdCl₂ as metal precursors,x Pd/Fe₂O₃ catalysts（x=0,0.066,0.16,0.22,or 0.38 wt%）were fabricated after calcinations.Compared catalytic activity of different loading Pd over Fe₂O₃ catalysts,0.38 wt%Pd/Fe₂O₃ was shown the best catalytic activity for toluene oxidation at space velocity of 40,000 mL/（g h）.The T_10%,T_50%,and T_90%for toluene oxidation was 163,209 and 229 ℃.This similar to Pt/Fe₂O₃ catalysts,precious metals,improve the catalytic activity,we can think of in situ molten salt method is a simple and easy to operate effective methods for the preparation of supported noble metal catalysts.