Preparation Of Zinc Oxide Based Desulfurizer By Melt Infiltration And Its Performance For Hydrogen Sulfide Removal At Ambient Temperature

With increasing depletion of global fossil fuels and serious environmental problems,the development of novel technologies with high efficiency,energy saving and environmentally friendly features has been imminent.Proton exchange membrane fuel cell?FEMFC?is regarded as the most potential and promising energy device in 21st century,because it has the advantages of green,high efficiency and reliability.In order to meet the requirement of FEMFC,it is necessary to carry out the ultra-fine desulfurization for the hydrogen-rich gas that supplied for FEMFC.Zinc oxide is a widely used metal oxide desulfurizer,because it has the advantages of high desulfurization efficiency and large equilibrium constant and stable sulfide products.However,the activity of zinc oxide is very low at ambient temperature,which leads to poor breakthrough capacity and low utilization.How to improve its activity at ambient temperature has always been a research hotspot.Loading zinc oxide on porous carriers can effectively improve its activity by increasing the specific surface area and porosity,and then greatly increasing the accessible active sites.The performance of desulfurizer usually depends on the dispersion,grain size and loading amount of active components,which are easily affected by loading method.Therefore,exploring a proper loading method is essential for zinc oxide supported desulfurizer.In this paper,melt infiltration was used to prepare zinc oxide-based desulfurizers with molecular sieve?MCM-41,SBA-15 and MCM-48?as carriers.The structural characteristics and the desulfurization-regeneration performance of the as-prepared zinc oxide-based desulfurizer are explored and compared with the desulfurizer prepared by impregnation method.Further modification of desulfurizer by doping nickel oxide was also studied.The obtained conclusions are as follows:The results of DSC,FT-IR,XRD,nitrogen adsorption,TEM indicate that zinc oxide can be loaded in the pores of carriers by melt infiltration method;the optimum preparation condition of desulfurizer is aging at 42? for 24h in hydrothermal reactor then calcining at 400? for 4 h in air atmosphere.Compared with the impregnation method,melt infiltration method has the advantages that the dispersion of zinc oxide is more uniform and the grains are smaller.The experimental results of breakthrough test in fixed bed show that the best zinc oxide loading contents are 20 wt%for carriers of MCM-41 and SBA-15,and 30 wt%for MCM-48.The corresponding utilization is 69.8%,52.2%,and 45.1%,respectively.With the same loading,the utilization of zinc oxide of desulfurizers prepared by impregnation method is only 26.8%,38.2%and 28.3%,respectively.Obviously,melt infiltration is superior to impregnation for preparation of zinc oxide supported desulfurizer.The study also found that the desulfurizers with characteristics of large specific surface area,big pore size and high strength are favorable.However,carrier with a small pore size,large specific surface area and high strength can benefit much more from the melt infiltration method.The results of XPS,NH₃-TPD,H₂-TPR,py-IR and evaluation indicate that a proper amount of nickel oxide may enhance the Lewis acidity on the surface of zinc oxide and makes the grains more uniform.As a result,its performance will be greatly improved.