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Microstructures of the Sulfonic Acid-Functionalized Ionic Liquid/Sulfuric Acid and Their Interactions: A Perspective from the Isobutane Alkylation
journal contribution
posted on 2018-01-08, 00:00 authored by Weizhong Zheng, Chizhou Huang, Weizhen Sun, Ling ZhaoThe all-atom force
field for concentrated sulfuric acid (98.30
wt %) was developed in this work based on ab initio calculations.
The structural and dynamical properties of sulfuric acid and the mixing
behaviors of sulfuric acid with ionic liquids (ILs), i.e., SFIL (1-methyl-3-(propyl-3-sulfonate)
imidazolium bisulfate ([PSMim][HSO4])) and non-SFIL (1-methyl-3-propyl
imidazolium bisulfate ([PMim][HSO4])), were investigated
using a molecular dynamics simulation. For sulfuric acid, most H3O+ ions were found beside HSO4– ions, forming a contact ion pair with the HSO4– ions, and three-dimensional hydrogen-bonding networks existed in
the sulfuric acid. Analyses indicate that both ILs could be miscible
with sulfuric acid with a strong exothermic character. The new strong
interaction site between the sulfonic acid group of SFIL and an H2SO4 molecule through a strong hydrogen-bonding
interaction was observed, which was beneficial to the catalytic activity
and stability of the sulfuric acid. This observation is in good agreement
with the experimental results that indicate SFILs could enhance the
reusability of sulfuric acid for the isobutane alkylation about 4-fold
compared to that of non-SFILs. Hopefully this work will provide insights
into the screening and designing of new isobutane alkylation catalysts
based on sulfuric acid and SFILs.