A molecular design methodology by the simultaneous optimisation of performance, safety and health aspects

Computer aided molecular design (CAMD) techniques have been implemented to design molecules or mixtures that satisfy a set of desirable target properties as specified by the customers. Molecular physical and thermodynamic properties are often selected as the target properties during the design stage. However, the incorporation of safety and health aspects into CAMD is not strongly emphasised in many design problems. Because of this, many chemical substances available in the market may lead to adverse health impacts following prolonged and repeated exposure. Therefore, the integration of safety and health aspects as design criteria in the existing CAMD methods is of paramount importance. This is to ensure that the synthesised product does not bring harm and health-related hazards to the consumers. In this work, a novel chemical product design methodology has been developed to integrate both safety and health aspects, as well as the target physicochemical properties into a single-stage CAMD framework. The assessment of safety and health parameters are based on the molecular properties that have significant impact on both aspects. Each property is introduced with an index value depending on the degree of potential hazards. Disjunctive programming algorithm is employed to assist in allocating index scores to the molecules depending on their property values. Fuzzy optimisation is applied to optimise two principal design criteria in this work: product target properties and its safety and health performance. A case study on solvent design for gas sweetening process has been carried out to determine the optimal molecule with reasonably low safety and health hazards level, and at the same time, achieves the target properties.