C4 Alkylation Catalyzed By Cocatalysts/Sulfuric Acid

Ionic liquids have outstanding co-catalytic performance in sulfuric acid-catalyzed C4 alkylation,while the high cost of ILs is believed to be the major problem for the extensive industrial application.In this work,six kinds of ILs were synthesized,including[Gly][HSO4],[Pro][HSO4],[C16H33(CH3)3N][HSO4],[OPSIm][HSO4],[BPSIm][HSO4]and[PS2Im][HSO4]and they were characterized by 1H-NMR 13C-NMR,IR,and the water content and Hammett acidity were determined by Karl Fischer Moisture Analyzer and Hammett indicator-UV spectrum method,respectively.Then,six ILs and six commercial auxiliaries with amphiphilic functions were used as cocatalysts for alkylation experiments.The effects of the type of co-catalyst,ionic alkyl chain length,reaction time,temperature,and additive amount on the composition and octane number(RON)of the alkylated product were investigated.The result shows that the[OPSIm][HSO4]and the amphiphilic auxiliaries CTAB have the most significant promoting on the quality of alkylated oil.There is a good linear relationship between the contents of alkylation products and the RON and the alkyl chain length of the amphiphilic auxiliary.The optimal process conditions for the C4 alkylation catalyzed by amphiphilic auxiliary-H2SO4 system were obtained.Finally,the molecular dynamics simulation(MD)was used to study the effect of amphiphilic auxiliaries on the two-phase interface of the alkylation reaction.The result shows that CTAB and SDS molecules tend to aggregate at the interface.Compared with SDS,long alkyl chains of CTAB tend to extend vertically into the interface of the two phases,which is conducive to the dispersion of acid and hydrocarbon in heterogeneous phases.With the increased amount of CTAB,the interface thickness increases gradually,while much more CTAB would lead to the decrease of the molar fraction of C4 hydrocarbon at interface that is not favorable to alkylation reaction,consistent with experimental results.The relevant research results in this paper are helpful for in-depth understanding of the catalysis of ionic liquids and amphiphilic auxiliaries in the C4 alkylation reaction,and are expected to provide a theoretical basis for the industrial application of the cocatalyst/H2SO4-catalyzed C4 alkylation process.