Facile Preparation And Modification Of Spherical Activated Carbon And Their Performance For Isobutane Dehydrogenation

In this work,the spherical activated carbon derived from phenolic resin were synthesized by ammonium alginate assisted sol-gel method,characterized by X-ray diffraction（XRD）,transmission electron microscopy（TEM）,infrared spectroscopy（IR）,X-ray photoelectron spectroscopy（XPS）,thermogravimetry（TG）and BET and used as catalyst in the reaction of isobutane direct dehydrogenation.The effects of different preparation conditions,including preparation temperature and time of phenolic resin,calcination temperature and time as well as the effect of adding content of nonmetallic elements in the spherical activated carbon on catalytic performance for the dehydrogenation of isobutane were also investigated.The results show that the carbon spheres prepared by this method have higher mechanical strength and spherical degree,larger specific surface area and pore volume.In the process of preparation,the reaction time and reaction temperature of phenolic resin are the direct factors that affect the formation and specific surface area of carbon spheres.The preparation conditions of the phenolic resol with reaction time 2 h and reaction temperature368 K are the best,for this spherical activated carbon has good mechanical strength（50N/beads）and larger surface area（394.7 m²/g）.In addition,using CaCO₃ as pore-enlarging agent during the process of preparation can not only increase the surface area（584.3 m²/g）,but also improve the dehydrogenation activity of carbon spheres.At the same time,a small amount of non metallic elements are introduced into carbon spheres during the preparation process,the reaction activity and the selectivity of the isobutene are improved obviously.The experimental results show that the spherical activated carbon prepared by using calcium carbonate as a pore-enlarging agent and calcined at the temperature of 923 K showed the best isobutane dehydrogenation performance.At 848 K,H₂/C₄H₁₀=1,SV=1600h^-1,the conversion of isobutane can reach up to 28%,and the selectivity of isobutene can reach up to 95%.In addition,in the modified process,we found that the best ratio of the non metal elements（N,P）is about 1%respectively.For N,P doped carbon spheres,the conversion of isobutane up to 37%and 35%,the selectivity of isobutene is up to 93%and95%can be obtained,respectively.