2.3 Experimental process
For the typical alkylation process, the reaction took place in a batch reactor with 1 L volume equipped with a cooling system. At first, the 180 ml DESs/H2SO4 mixture was put into the reactor, in which the ratio of DESs to H2SO4 was set to be 0.5, 1.0, 3.0, 5.0 and 8.0 wt%, respectively. Subsequently, the N2 gas was added to purge the reactor by three times to remove the air, after which the cooling system turned on to keep reaction temperature at the given temperature. The pressure in the reactor was controlled at 0.5 MPa to maintain the C4 reactants as liquid phase. Then, 120 mL of isobutane/2-butene mixture with a given ratio were quickly injected into the reactor and the agitation started to work at the stirring rate of 3000 rpm to achieve a well-distributed dispersion between C4 reactants phase and acid phase. After the reaction stopped, the products were collected and analyzed by GC after being extracted and separated from acid phase using carbon tetrachloride. The details of the analysis of the products displayed on our previous work18.