Separation of trimethyl borate and methanol by extractive distillation was investigated first using dimethyl sulfoxide as the solvent. The performance of six commonly used strong polar solvents was theoretically calculated and experimentally determined. Dimethyl sulfoxide was selected due to its outstanding separation efficiency. A flowsheet was proposed with optimized facility sizings and operation conditions. Stability and controllability of the process were evaluated by imposing disturbances. It was found difficult to cope with feed variations using pure temperature control structures due to a large solvent/feed ratio. So, an improved reflux-to-feed ratios (improved R/F) scheme with a composition controller was put forward to address large fluctuations. Supervision of products' purity confirmed that this control structure worked effectively.