The synthesis of novel reactor designs is still left to experimentation and coincidence rather than systematic design procedures. industrial practice often applies textbook knowledge originally developed for simple and trivial systems, to complex reaction processes involving multiple phases and complicated kinetics and economic tradeoffs. This work outlines important developments for the design and optimization of multiphase reaction systems under isothermal conditions with strong and consistent evidence of novelty in the design structures. The reactor designs are screened with a systematic methodology based on a novel representation and a reliable optimization approach. The work significantly extends previous efforts in homogeneous systems and the optimization is able to handle all typical complexities. The method is laking up applications in industry and is illustrated here for a gas-liquid chlorination example.