<p>Understanding and correlation of the multiscale interfacial mass transport behaviors mediated by the additive for liquid/liquid dispersion system is challenging. Here, we propose interfacial mass transfer flux through the quantitative coupling between microscopic interfacial parameters and mesoscopic droplet mass transfer model for H₂SO₄-catalyzed isobutane alkylation with emphasis on additive molecular design to industrial process intensification. Microscopic interfacial parameters are incorporated into CFD-PBM model to determine interfacial mass transfer flux of isobutane (<i>N</i>_{<i>isobutane</i>}). Based on the ratio of <i>N</i>_{<i>isobutane</i>} in the system with and without the additives, the interfacial enhancement factor <i>E</i> is proposed and validated as an indicator for optimal additive screening. Decoupled <i>N</i>_{<i>isobutane</i>} from apparent kinetic model, mass transfer-free kinetic parameters of isobutane alkylation are determined, quantitatively confirming the reaction is mass transfer controlled. Additive-mediated process intensification reveals PPG400 additive increases alkylate capacity by 24.85% up to 99.83 kt/a from 79.96 kt/a in additive-free system.</p>