Fig. 1: Schematic representation of additive-intensified isobutane alkylation.

A multiscale framework is proposed for additive-mediated alkylation, coupling microscopic interfacial parameters with a mesoscopic mass-transfer model to quantify the interfacial mass-transfer flux. The detailed interfacial properties of interfacial tension (γ), diffusion coefficients (D), and interfacial isobutane concentration difference (∆c_isobutane^*) for the H₂SO₄-catalyzed isobutane alkylation system without and with additive at various interface coverage and temperature are investigated using MD simulations. By incorporating key microscopic interfacial parameters (D, γ, ∆c_isobutane^*) into the mesoscopic liquid–liquid mass transfer model, the simulated hydrocarbon droplet diameter (d_p), specific surface area (a), mass transfer parameters (k_L, k_La), and N_isobutane for the corresponding system are determined. A dimensionless parameter, the interfacial enhancement factor, representing the tunability degree in the N_isobutane induced by the additive, is constructed. By decoupling N_isobutane from the apparent kinetic model, a mass transfer-free kinetic model for the instantaneous H₂SO₄-catalyzed alkylation is developed.