(375j) Integrated Process and Molecular Design for Reactive Systems
The reverse problem formulation is a technique used to design a process to obtain the optimum performance. Using the integrated process and product design techniques, the optimum solutions for process and product design problems can be obtained without committing to any specific components in the solution step. The property targets to be satisfied by the product have been estimated in the process design stage based on the specifications of the final product. The property clustering techniques have been employed to represent the property target region in the form of algebraic equations. However, the existing techniques for solving such problems are limited to non-reactive systems. In this work, we are introducing an algorithm that can be used for solving integrated process and molecular design problems for reactive systems on a property based platform. The property clustering technique will be extended into identifying a set of target properties for the components in the system that provides the optimum process performance. Once the property targets have been identified, a molecular design problem can be formulated to identify the potential candidate molecules that meet the targets identified in the previous problem. The molecular design involves the identification of potential molecules possible from the specific types of reactions in the process. To design the molecules, a recently introduced concept known as molecular signature descriptors has been used. The signature is a systematic coding system of atom types and the signature of a molecule can be obtained as a linear combination of its atomic signatures (Visco et al 2002). The molecular signatures can be tailored to track the change in molecular groups in a molecule resulting from different types of chemical reactions. The changes in the chemical structure can be correlated with the changes in the properties of the molecule. Therefore, the changes in the molecular structure due to reactions can be represented as a function of the property. The developed algorithm applies different QSAR/QSPR expressions that make use of different topological indices. It has been proven that a number of topological indices of molecules can be represented in terms of molecular signatures and it is possible to correlate the topological indices to the actual properties and biological activities (Faulon et al 2003). Here, the new algorithm utilizes molecular property operators based on signatures for solving the inverse problem of obtaining the molecular structures that satisfy the property targets estimated in the process design step. A new set of equations will be employed to ensure that the molecules meet the safety and environmental constraints as well. The principles in graph theory are incorporated to track signatures and to avoid the generation of infeasible molecular structures. This contribution will illustrate the developed methods and highlight their use through a case study.