H2SO4-catalyzed isobutane alkylation under low temperatures promoted by long-alkyl-chain surfactant additives

To deeply understand the role of surfactants on the acid/C4 hydrocarbon miscibility, the catalytic activity and molecular-level interfacial properties of long-alkyl-chain cationic surfactants (hexadecyltrimethylammonium bromide, CATB and dihexadecyldimethylammoniumchloride, DDAB) and anionic one (sodium dodecyl benzene sulfonate, SDBS) were studied as additives for H2SO4 alkylation using experiments and molecular dynamics simulations. Surfactant additives are found to efficiently decrease by-products and promote higher selectivity of trimethylpentanes (TMPs) and higher research octane number (RON), which is attributed to the improvement of acid/hydrocarbons interface, including better interfacial dispersion, higher I/O ratio, and lower interfacial tension. Surfactant additives show an interfacial intensification, quite different from intrinsic reaction intensification by low temperature. Combination of SDBS additive and lower temperature contributes to significantly higher TMP selectivity and higher RON up to 84.20 wt% and 99.07 at 269.2 K from 60.21 wt% and 94.34 at 281.2 K, respectively. The information provides good reference for the industrial H2SO4 alkylation.

Automated summary

Through experiments and simulations, it was found that surfactant additives can efficiently reduce by-products and promote higher selectivity of target products in H2SO4 alkylation reaction by improving the acid/hydrocarbons interface properties. The combination of SDBS additive and lower temperature significantly enhances the selectivity of TMP and RON.