Basic Research On The Application Of Pt-SO₄^2-/ZrO₂-Al₂O₃ To Catalyze The Isomerization Of Alkanes

The light alkanes isomerization is the transformation of low octane n-paraffins into high octane isoparaffins,and isoparaffins are important components of high octane clean gasoline.With the stringency of the environmental protection requirements,the isomerization process attracts more and more attention.SO42-/ZrO2(SZ)solid superacid catalyst has many advantages,such as super acidity,excellent low temperature isomerization activity and environmental friendliness and so on.Thus,the isomerization over SZ-based catalyst possesses good prospect.In this paper,the effects of material sources of the catalyst such as zirconium oxychloride and pseudoboehmite,the agitation during sulfation process,the sulfation sequence and the micro-amplification preparation of Zr(OH)4 on the isomerization performance of Pt-SO42-/ZrO2-Al2O3(PSZA)catalyst were investigated.On this basis,the deactivation behavior of the PSZA catalyst was studied.The physicochemical properties of the catalyst before and after deactivation were studied by means of XRD,TQ FT-IR and Py-IR.The results showed that the elemental compositions and crystal structure of Zr(OH)4 prepared by industrial and analytically pure zirconium oxychloride were almost the same,and the prepared catalysts had similar properties;the high crystallinity of the pseudoboehmite resulted in the low sulfur content,high isomerization activity and high mechanical strength of PSZA;during the sulfation process,the catalyst prepared by stirring impregnation had higher isomerization activity than the catalyst prepared by static impregnation;calcining of Zr(OH)4 after immersing sulfuric acid gave catalyst with higher isomerization activity than calcining of Zr(OH)4 before immersing sulfuric acid;after Zr(OH)4 was micro-amplified from 25g to 250g,the isomerization activity of catalyst did not change significantly;the catalyst deactivation rate was slightly slowed down as the reaction temperature increased;there existed a suitable matching relationship between alumina content and calcination temperature.PSZA 10-700 had the highest isomerization activity,and its mechanical strength was up to 200N/cm;both pretreatment of carrier gas and pretreatment of reaction feed significantly improved the isomerization activity of PSZA.The analytical pure n-hexane and the reforming topped oil from the refinery were respectively used as reaction feed,and the isomerization stability of the catalyst obviously increased with the increase in the number of pretreatments of the reaction feed;the activity of PSZA10-700 was higher in 460h isomerization reaction when n-hexane was pretreated for 3 times,and n-hexane stable conversion rate decreased slightly from 87%to 84%.Moreover,the sulfur species and the ratio of Br(?)nsted acid to Lewis acid of the spent catalyst changed to some extent after the 460h isomerization reaction.