Developing　catalysts　enabling　reactive　separation　is　a　promising　strategy　to　enhance　reaction　and　separation　efficiency　of　esterification　processes.　Herein,　we　designed　a　class　of　hybrid　catalysts　with　p-toluenesulfonic　acid　(PTSA)　as　main　catalyst,　and　hydrogensulfate　ILs　as　support　catalyst　and　extractant.　Using　the　designed　catalysts　for　methyl　esterification　of　long-chain　fatty　acids,　phase　splitting　can　occur,　resulting　in　ester-rich　and　catalyst-rich　phases.　Under　optimal　conditions,　the　conversion　of　palmitic　acid　(PA)　gives　methyl　palmitate　(MP)　yield　of　98.2　%　in　3　h　at　348.2　K.　The　catalysts　are　also　applicable　for　effective　conversion　of　other　long-chain　fatty　acids　and　can　be　facilely　recycled　through　liquid–liquid　separation　without　loss　of　activity.　COSMOtherm　and　Gaussian　calculations　were　performed　to　rationalize　the　reactive　separation　behavior　of　the　designed　catalysts.　The　kinetic　and　thermodynamic　properties　of　the　esterification　reaction　were　also　examined　using　pseudo-homogeneous　(PH)　model　with　non-ideality　corrections.　©　2025　Elsevier　Ltd