Preparation And Isomerization Performance Of Metal Modified Largepore Structure Solid Superacid Catalyst

Isomerization of light alkanes is an important way to produce high-octane gasoline.Solid superacid catalysts have received extensive attention because of their advantages such as no environmental pollution and high low temperature isomerization activity.In this paper,S2O8^2-/Zr O2-Al2O3（SZA_c,where c represents spherical Al₂O₃）type solid superacid catalyst was synthesized from spherical Al₂O₃ with strong acidity and large pore diameter,and through different transition metals（M=Ni,Mn,Fe,Zn）Modified and prepared M–SZA_c–R catalysts;Ni（x）–SZAγ–R with different Ni contents and La（x）–Ni–SZAγ–R（x with different La contents）were prepared fromγ-Al2O3 and spherical Al2O3,respectively Represents metal content,c andγrepresent spherical andγ-type Al₂O₃)catalysts,respectively.XRD,FTIR,SEM,EDS,BET,C-S analysis and other methods were used to characterize the prepared catalyst.Using n-pentane isomerization reaction as a probe,the effects of transition metal and Al₂O₃ types,as well as Ni and La metal content on the isomerization performance of solid superacid catalyst were studied,and the following conclusions were obtained:（1）Among the M-SZA_c-R catalysts modified by different transition metals M（Ni,Fe,Mn,Zn）,the Ni-SZA_c-R catalyst has a large specific surface area,suitable acidity,and can expose more activity center.The order of isomerization activity of each catalyst is Ni–SZA_c–R>Zn–SZA_c–R>Fe–SZA_c–R>Mn–SZA_c–R.（2）In Ni（x）–SZAγ–R prepared with different Ni contents,when the Ni content is 1 wt.%,The Ni（x）–SZAγ–R catalyst has the best isomerization activity in hydrogen/positive At a molar ratio of pentane of 4.0,a reaction pressure of 2.0 MPa,and a reaction temperature of 200 ^oC,the isopentane yields of Ni（1.0）–SZAγ–R and Ni（1.0）–SZA_c–R catalysts were 65.3%and 63.7%,respectively.For the catalyst prepared by spherical Al₂O₃,the order of activity is Ni（1.0）–SZA_c–R>Ni（0.5）–SZA_c–R>Ni（2.0）–SZA_c–R>Ni（5.0）–SZA_c–R,while forγ-Al₂O₃ prepared catalyst,the activity size order is Ni（1.0）-SZAγ-R>Ni（2.0）-SZAγ-R>Ni（0.5）-SZAγ-R>Ni（5.0）-SZAγ-R.（3）In the study of La（x）–Ni–SZAγ–R catalysts with different La contents,it was found that the rare earth metal La can disperse the metal Ni well on the catalyst surface,inhibit the growth of the tetragonal phase Zr O₂ grains The catalyst has a larger specific surface area and an appropriate amount of acid,thereby improving the low temperature isomerization performance of the catalyst.Compared with Ni–SZA_c–R,the optimal reaction temperature of La（1.0）–Ni–SZA_c–R catalyst with a La content of 1 wt.%Was reduced by 40 ^oC,and the isopentane yield was increased by 5%.For the catalyst prepared by spherical Al₂O₃,the activity order is La（1.0）–Ni–SZA_c–R>La（1.2）–Ni–SZA_c–R>La（0.8）–Ni–SZA_c–R>La（2.0）–Ni–SZA_c–R,and for the catalyst prepared byγ-Al₂O₃,the activity sequence is La（1.0）–Ni–SZAγ–R>La（1.2）–Ni–SZAγ–R>La（0.8）–Ni–SZAγ–R>La（2.0）–Ni–SZA_c–R.（5）The stability of the Ni（1.0）–SZAγ–R catalyst was investigated,and it was found that the isopentane yield could be maintained above 62.6%in the initial 2000 min of the reaction,indicating that the solid superacid catalyst prepared by the large pore carrier has good stability.