Co Selective Methanation Performance Of Nickel-Based Catalysts Over Titanium Modified SBA Molecular Sieve

At present,the fuel cell electric vehicle that use proton exchange membrane fuel cells?PEMFCs?as the power source must solve the problem of high neat hydrogen acquisition.The bottleneck that needs to be broken through is the deep purification of a small amount of CO in the hydrogen-rich feed gas to avoid irreversible poisoning of PEMFCs platinum electrode.CO selective methanation is one of the effective methods that can be used to deeply purify CO in hydrogen-rich gas.The key lies in the development of a metal-supported catalyst with high catalytic activity,high selectivity and stability at low temperatures.In this paper,isopropyl titanate was used as titanium source to modify SBA-16 and SBA-15 mesoporous molecular sieves by grafting synthesis.The supported Ni-based catalyst was prepared by impregnation and CO selective methanation was used as a probe reaction to evaluate its catalytic performance and stability.XRD,N₂adsorption-desorption,SEM,TEM,FT-IR,XPS,H₂-TPR characterization methods were used to characterize and analyze the catalyst.The effect of Ti on the surface properties and structural characteristics of the catalyst was explored,and the effects of Ti loading,Ni loading,calcination temperature and reduction temperature on the performance of the catalyst were discussed.The main research contents are as follows:?1?The Ni/Ti-SBA-16 catalyst still maintained an ordered mesoporous structure with a large specific surface area.Ti was mainly dispersed in the pore channel or surface in the form of anatase Ti O₂ Crystal.The appropriate Ti loading can enhance the interaction between the active component and the support,help to form more uniform active particles,promote the dispersion of active component,and effectively inhibit the sintering and agglomerating of active metals.When the Ti loading was 15 wt%,Ni loading was 20 wt%,calcination temperature was350?,and reduction temperature was 500?,the 20Ni/15Ti-SBA-16 catalyst showed better catalytic performance in the lower reaction temperature range of 170-205?.A small amount of CO in the hydrogen-rich gas can be deeply removed(<10×10^-6),while maintaining the reaction selectivity higher than 50%.The catalyst also had good catalytic stability.The CO conversion and selectivity were close to 100%when tested at 180?for 120 hours.?2?The Ti introduced by the Ni/Ti-SBA-15 catalyst was successfully doped into the mesoporous framework mainly in the form of Si-O-Ti bonds.Isopropyl alcohol was used as a solvent to disperse isopropyl titanate,which was beneficial to slow down the hydrolysis rate of Ti source,inhibiting the crystal growth of Ti O₂ particles,and avoiding a large number of Ti O₂blocking mesoporous channels.When the Ti loading was 5.9wt%,Ni loading was 15 wt%,calcination temperature was 400?,and reduction temperature was 500?,the 15Ni/5.9Ti-SBA-15 catalyst showed ideal CO selective methanation catalytic performance.It can reduce the CO outlet concentration in hydrogen-rich gas to less than 10×10^-6 within a wide low-temperature reaction range of 160-220?,while maintaining the reaction selectivity higher than50%and maintaining good catalytic stability.