4. Conclusions
The effect of several DESs on the quality of alkylate and the acid/hydrocarbons interfacial properties were investigated via experiments and MD simulations. It is found that the introduction of DESs almost has no impact on the reaction time. ChCl-Pho (1:2) displays the most outstanding catalytic performance with RON up to 97.37 and the C8 selectivity up to 83.64%. The most suitable addition ratio for ChCl-Pho (1:2) and ChCl-TsOH (1:1) to H2SO4 is about 1.0 wt% with the improvement of C8 contents from 74.50 wt% in pure H2SO4 system at 281.2 K to 83.64 wt% and 80.71 wt% as well as the increase in RON from 95.80 to 97.37 and 96.93, respectively. However, the excessive addition of DESs leads to the decrease in reaction enhancement, which is attributed to reduction of the H2SO4 acidity. ChCl-Pho (1:2) and ChCl-TsOH (1:1) have a little influence on 2,3,4-TMPs and DMHs, including 2,5-DMH, 2,4-DMH, and 2,3-DMH with lower RON. However, both of them have a great effect on the conversion of LEs and HEs to TMPs. With the addition of ChCl-Pho (1:2), the targeted C8components and the RON increase obviously from 83.77% at 281.2 K to 86.07% at 274.2 K, 97.39 at 281.2 K to 98.27 at 274.2 K, respectively, which is mainly contributed to low reaction temperature. The addition of ChCl-Pho (1:2) and ChCl-TsOH (1:1) show the effective catalytic performance, but both of them can not improve the catalytic lifetime of H2SO4 catalyst.
From MD simulations, the phenyl molecules, such as Pho, TsOH, and BOA molecules, is found to aggregate close to the interface with a higher density peak in the interfacial regions, which plays the essentially important role in the tunability of acid/hydrocarbons interface. The addition of DESs can significantly increase the interfacial thickness, promote the solubility and diffusion of isobutane with respect to butene in comparison to the pure H2SO4 system, thus making positively contributions to the quality of alkylate.