A series of heterogeneous catalysts with tunable superacidity, namely 12-tungstophosphoric acid (HPW) immobilized on imidazolium chloride ionic liquid (IL)-modified mesoporous SBA-15 silica (denoted as z-HPW-IL/ SBA; z = HPW/IL molar ratio), were prepared. The physicochemical properties of these synthesized catalysts were characterized by various analytical and spectroscopic techniques such as EA, ICP-MS, XRD, FT-IR, N-2 adsorption/desorption isotherm measurements, and multinuclei NMR. In particular, their acid properties were characterized by solid-state P-31 NMR of adsorbed trimethylphosphine oxide (TMPO) as the probe molecule. The HPW-IL/SBA catalysts were exploited for catalytic alkylation of benzene with 1-dodecene, and relevant effects of their acid features (i.e., amount, strength, and distribution of acid sites) on catalytic performances and yields of linear alkylbenzenes (LABs) were investigated. It was found that the acidity of the z-HPW-IL/SBA catalyst may readily be controlled by varying the molar ratio (z) of the incorporated HPW-IL composite. Moreover, superior 1-dodecene conversion and LAB selectivity were simultaneously achieved with z = 1.16, revealing an optimal preservation of superacidic Bronsted acid sites.