Catalytic Performance And Sulfur Dioxide Resistance Of Zirconia-supported Platinum-palladium Nanoparticles For Methane Combustion

With the development of human society,the consumption of oil reserves is getting faster and faster,and the use scope of natural gas is becoming more and more extensive,such as new energy vehicles and etc.At the same time,there are still the use of biogas digesters in many rural areas in China.All of the above activities will cause the emission of methane to increase.Considering that the treatment of methane gas requires the use of catalytic combustion,it is important to choose a high-performance catalyst.The toxic effect of the catalyst in catalytic combustion cannot be ignored,and the sulfur-containing gas inactivates the catalyst is relatively difficultIn this Master Degree thesis,PtPd_x（x is the Pd/Ptmolar ratio,and equal to 0.48,0.90,2.20,and 2.40）bimetallic nanoparticles（NPs）were synthesized using PdCl₂ and H₂PtCl₆ aqueous solutions as precursor solution,polyvinal alcohol（PVA）as protecting agent,and Na BH₄ as reducing agent,and the as-obtained metal NPs were supported on the surface of ZrO₂,thus preparing the yPtPd_x/ZrO₂（y is the weight loading of the noble metal（s）,and equal to 0.54,0.61,and 0.44 wt%）,yPt/ZrO₂（y=0.65 wt%）,and yPd/ZrO₂（y=0.55 wt%）catalysts,which are denoted as0.44PtPd_2.20/ZrO₂,0.54PtPd_0.90/ZrO₂,0.61PtPd_0.48/ZrO₂,0.55Pd/ZrO₂,and0.65Pt/ZrO₂,respectively.A variety of instruments were used to characterize the physicochemical properties of the catalyst itself,evaluate the catalytic activity of the catalyst on methane combustion,and investigate its sulfur dioxide resistance.The main findings of this Master Degree thesis are as follows:（1）The PtPd_x NPs with an average size of 2.4-3.6 nm were synthesized,which were loaded on the surface of ZrO₂,thus preparing the 0.44PtPd_2.20/ZrO₂,0.54PtPd_0.90/ZrO₂,0.61PtPd_0.48/ZrO₂,0.55Pd/ZrO₂,and 0.65Pt/ZrO₂ catalysts.The results show that the catalyst is a monoclinic ZrO₂ crystal phase,and the supported precious metals are highly dispersed on ZrO₂.（2）The 0.44PtPd_2.20/ZrO₂ catalyst has excellent thermal stability,water resistance and sulfur resistance.That is,at airspeed（SV）=20,000 m L/（g h）,the catalyst oxidation to methane T_50%=345 ℃,T_90%=408 ℃,apparent activation energy（E_a）=59 k J/mol,turnover frequency(TOF_Pd)and specific reaction rate at 350℃ is 466.6μmol/(g_Pd s)and 0.61μmol/(g_cat s),respectively.（3）The 0.44PtPd_2.20/ZrO₂ catalyst also exhibited excellent thermal stability,water resistance,and sulfur dioxide resistance.After addition of 100 ppm SO₂,methane conversion over the 0.55Pd/ZrO₂ and 0.44PtPd_2.20/ZrO₂ catalysts decreased from about 90 to 45 and 76%,respectively.Methane conversion over the 0.55Pd/ZrO₂catalyst was recovered to 57%after SO₂ was cut off,but that over the0.44PtPd_2.20/ZrO₂ catalyst was almost restored to its initial level.According to the results of SO₂-TPD,XPS,FT-IR and in situ DRIFTS characterization,we can conclude that the introduction of the second metal Ptmade the SO₂ originally adsorbed at the PdO active sites be more adsorbed on the surface of Pt,thereby protecting the PdO active sites from being poisoned by SO₂.Hence,the0.44PtPd_2.20/ZrO₂ catalyst possessed the excellent sulfur dioxide resistance.