Limitations for improving selectivity in chemical reactors

The design of chemical plants involves many engineering tradeoffs that balance capital cost, energy cost, operability, efficiency, safety, reliability, complexity, environmental impact and sustainability, to name a few. The classical tradeoff between reactor costs and separation costs dominates many decisions particularly when material and energy recycles are incorporated in the plant topology. Chemical reactors have several size and operating variables that must be selected to achieve an efficient and profitable system: size, temperature, pressure and reactant recycle. All of these parameters impact selectivity if undesirable byproducts are formed. The purpose of this paper is to quantitatively explores how reactor design variables can be adjusted to achieve very high selectivity in those cases in which the suppression of the production of the undesired product is critical because of safety, toxicity, environmental or sequestration issues. • Improving selectivity in the cumene process is studied • Recycle flowrate, reactor size and pressure increase selectivity but increase energy and capital costs • The economics do not look attractive for the cumene process