Study On Catalytic Decomposition Of A And Ethyl Mercaptan By Cerium Zirconium Solid Solution And Rare Earth Modified ? Zeolite Molecular Sieve

Low carbons levels mercaptan difficultly removed are extensively present in natural gas and petroleum products,mainly including methyl mercaptan(CH3SH)and ethyl mercaptan(C2H5SH).Low carbons levels mercaptan will hinder the processing and utilization of natural gas and petroleum products.In addition,low carbon mercaptan is also a kind of malodorous contaminated gas,which is harmful to human health and atmospheric environment quality.Therefore,a low waste,the efficient method called catalytic decomposition method had been given much attention in the present work.The product of catalytic decomposition could be used for the regeneration and recycling as industrial raw materials.Urea grind combustion method was employed to rapidly synthesize ceria-zirconia nanoparticles for ethyl mercaptan and ethyl mercaptan catalytic decomposition.The effect of different calcination temperatures on the catalytic activity of Ce0.8Zr0.2O2 was investigated at atmospheric pressure.The physical and chemical properties,and surface structure of materials were characterized by XRD,TEM,BET,H2-TPR,XPS and Raman.In addition,several studies were carried out to explore the catalytic activity of H-Beta zeolite,H-Y zeolite and a series of modified H-Beta zeolites.The main results are summarized as follows:(1)The urea grind combustion method was employed to rapidly synthesize ceria-zirconia nanoparticles with high-performance for CH3SH catalytic decomposition.Compared with classical surfactant-assisted method,the method offered advantages of easy operation and time-saving.An improvement of catalytic activity for CH3SH decomposition was observed for Ce0.8Zr0.2O2 nanoparticles prepared by this method.CH3SCH3 is an intermediate product during CH3SH decomposition,and CH4 and H2S could be identified as the principal products under the condition of high temperature.The urea grind combustion method is beneficial to the incorporation of more Zr4+ into CeO2 lattice,resulting in the number of oxygen vacancies increased.Combined with those results,it was found that better CH3SH catalytic decomposition activity was attributed to the formation of more oxygen vacancy,increased amount of surface chemisorbed oxygen and better reducibility.(2)The effect of different calcination temperatures on the catalytic activity of Ce0.8Zr0.2O2 was investigated at atmospheric pressure.The physical and chemical properties,and surface structure of materials were characterized by XRD,TEM,BET,H2-TPR,XPS and Raman.Results showed that Ce0.8Zr0.2O2 solid solution prepared by urea grind combustion method exhibited excellent catalytic activity for CH3CH2SH decomposition.More Zr4+ entered into the CeO2 lattice by raising temperature at a certain range,leading to the increase in concentration of oxygen vacancies and enhancing the oxygen mobility.However,when the temperature was too high,the specific surface area of catalyst decrease and the concentration of surface adsorbed oxygen declines.The Ce0.8Zr0.2O2 solid solution calcined at 600? exhibited the best catalytic activity for decomposition of CH3CH2SH,which was attributed to the synergic effects among the Ce3+ concentration of catalyst surface,the increased concentration of oxygen vacancies and the larger specific surface area.Increasing the Ce3+concentration of catalyst surface and concentration of oxygen vacancies is beneficial to the migration of oxygen and catalytic decomposition.Moreover,increasing specific surface area of catalyst can improve adsorption properties,exposing more active sites,and the catalytic activity is enhanced accordingly.(3)Compared with H-Y zeolite,H-Beta zeolites has better catalytic activity for CH3CH2SH decomposition and high C2H4 selectivity.The active evaluation of modified H-Beta zeolites with the different rare earth(La,Ce,Pr,Nd,Sm,Eu,Gd,Er,Y)was carried out,and the order of catalytic activity:9%Er/H-Beta>9%Gd/H-Beta>9%Nd/H-Beta>9%Eu/H-beta>9%Y/H-Beta>9%La/H-Beta>9%Sm/H-Beta>9%Ce/H-Beta>H-Beta>9%Pr/H-Beta.The catalytic activity of modified H-Beta zeolites for decomposition of methyl mercaptan was greatly enhanced except 9%Pr/H-Beta.Er and Gd modified H-Beta zeolites show the better catalytic activity.The modification of rare earth could improve the catalytic stability of H-Beta zeolites.