Preparation Of Fe-based Spinel Catalyst And Catalytic Combustion Of Toluene

As we all know,the method to control the volatile organic compounds?VOCs?has been an important topic in the environmental field.Moreover,the catalytic combustion is one of the most efficient methods to control the VOCs.The key of the catalytic combustion technology is the research of high efficiency catalysts.Spinel and other metal composite oxide,with low cost and strong anti-toxicity,is the hotspot in the field of catalytic combustion.In this thesis,Fe-based spinel catalysts were prepared by sol-gel auto-combustion method.The catalysts were characterized by TG-DTA,FT-IR,XRD,N₂adsorption-desorption,TEM,SEM H₂-TPR and XPS.The effects of A-side cation,calcination temperature and Ce-dopeing on the catalytic combustion activity of Fe-based spinel catalyst were investigated.AFe₂O₄ catalysts had appeared the lamellar spinel crystals and the multilevel pore structure with prevalence to mesoporou.Are the catalytic combustion activity of the catalyst with different A-side cation were quite different.The catalytic combustion activity of CuFe₂O₄ was best.When the concentration of toluene was 300±50mg·m^-3 and the gas hourly space velocity?GHSV?was 6000h^-1,the T50 and T90 were188?and 239?,respectively.CuFe₂O₄ catalyst had a unique trans-spinel structure with a lattice volume of only 294.02?³.This could greatly improve its catalytic combustion activity.At the same time,CuO and?-Fe₂O₃ crystals existed in the system,and its'synergistic effected with the spinel structure greatly increased the surface activity of the catalyst,which promoted the formation of oxygen vacancy and active sites,and the O_ele/O_1S was 35.76%.The metal ions replaced the H⁺of the–COOH in the citric acid complex,which ensured that the metal particles were combined with each other to form a spinel structure,when CuFe₂O₄ was prepared by sol-gel auto-combustion method.When the CuFe₂O₄ dry-gel burnd at 200-230?,the formal CuFe₂O₄ spinel crystal was produced.It could form a more stable flaky Fe?CuFe?O₄ spinel,when the product was calcined at different temperature.When the product was calcined at 500?,a more stable flaky trans-spinel Fe?CuFe?O₄ was formed.The CuFe₂O₄ expressed the best catalytic activity,the spinel crystal lattice size was 32.9nm and the specific surface area was 10.4cm²·g^-1.When the calcined temperature was continuously raised to 700?,the specific surface area was reduced to 7.2cm²·g^-1,and the surface activity of the catalyst was reduced at the same time.The doping of Ce in CuFe₂O₄ could improve the catalytic activity of the catalyst.There was a flaky trans-spinel CuFe₂O₄ in the Cu_0.8Ce_0.2Fe₂O₄,and the lattice size was 24.4nm.At the same time,Cu and Fe were into the CeO₂ crystal,which could increase the oxygen storage capacity of the catalyst,so that Cu and Fe were easier to be reduced.The presence of Ce³⁺could provide more oxygen vacancy for the catalyst,and Ce³⁺/Ce⁴⁺was 31.09%in this system.The O_ele/O_1S was 52.38%,which greatly improved the catalytic combustion activity.When the concentration of toluene was 300±50mg·m^-3 and the gas hourly space velocity?GHSV?was 6000h^-1,the T50 and T90 were 180?and 215?,respectively.