Rafiqul Gani

Group-contribution based estimation of pure component properties

A new method for the estimation of properties of pure organic compounds is presented. Estimation is performed at three levels. The primary level uses contributions from simple groups that allow describing a wide variety of organic compounds, while the higher levels involve polyfunctional and structural groups that provide more information about molecular fragments whose description through first-order groups is not possible. The presented method allows estimations of the following properties: normal boiling point, critical temperature, critical pressure, critical volume, standard enthalpy of formation, standard enthalpy of vaporization, standard Gibbs energy, normal melting point and standard enthalpy of fusion. The group-contribution tables have been developed from regression using a data set of more than 2000 compounds ranging from C=3–60, including large and complex polycyclic compounds. Compared to the currently used group-contribution methods, the new method makes significant improvements both in accuracy and applicability.

Chemical product design: challenges and opportunities

Abstract This paper highlights for a class of chemical products, the design process, their design with respect to the important issues, the need for appropriate tools and finally, lists some of the challenges and opportunities for the process systems engineering (PSE)/computer-aided process engineering (CAPE) community. The chemical products considered belong to the following types: chemical/biochemical/agrochemical products, coatings and solvents, food (nutraceuticals), HI&I (household, industrial and institutional), personal care, pharmaceuticals and drugs. The challenges and opportunities are highlighted in terms of the needs for multi-level modeling with emphasis on property models that are suitable for computer-aided applications, flexible solution strategies that are able to solve a large range of chemical product design problems and finally, a systems chemical product design framework with the overall objective to reduce the time and cost to market a new or improved product.

Estimation of the acentric factor and the liquid molar volume at 298 K using a new group contribution method

Abstract The method of Constantinou and Gani [Constantinou, L. and Gani, R., 1994. A new group contribution method for the estimation of properties of pure compounds. AIChE J., 40(10): 1697–1710] is extended to the estimation of the acentric factor and the liquid molar volume at 298 K. Thus, it now allows reliable prediction of all the common corresponding-state physical properties. In addition to the accurate estimation of liquid molar volumes at 298 K for low-molecular-weight compounds, the technique can be used for amorphous polymers.

A multi-step and multi-level approach for computer aided molecular design

Abstract A general multi-step approach for setting up, solving and solution analysis of computer aided molecular design (CAMD) problems is presented. The approach differs from previous work within the field of CAMD since it also addresses the need for a computer aided problem formulation and result analysis. The problem formulation step incorporates a knowledge base for the identification and setup of the design criteria. Candidate compounds are identified using a multi-level generate and test CAMD solution algorithm capable of designing molecules having a high level of molecular detail. A post solution step for result analysis and verification is included in the methodology.

Design of environmentally benign processes: integration of solvent design and separation process synthesis

Abstract This paper presents a hybrid method for design of environmentally benign processes. The hybrid method integrates mathematical modelling with heuristic approaches to solving the optimisation problems related to separation process synthesis and solvent design and selection. A structured method of solution, which employs thermodynamic insights to reduce the complexity and size of the mathematical problem by eliminating redundant alternatives, has been developed for the hybrid method. Separation process synthesis and design problems related to the removal of a chemical species from process streams because of environmental constraints are particularly suited for solution with the hybrid method. Application of the hybrid method is highlighted through two illustrative examples. The first example involves the determination of an optimal flowsheet for the removal of a chemical species from an azeotropic mixture and the second example involves the determination of environmentally benign substitute solvents for removal of a chemical species from wastewater.

Separation process design and synthesis based on thermodynamic insights

Abstract This paper presents a new methodology which employs physicochemical properties and their relationships to separation techniques for design and synthesis of separation processes. The methodology covers a wide range of separation problems and consists of selection and identification of separation techniques (and the corresponding separation tasks), the sequencing of the separation tasks and the determination of appropriate and consistent conditions of operation. For a specified multicomponent separation problem, subsets of feasible separation techniques are first identified for every binary and user-specified separation tasks. The number of alternatives for each separation task is reduced by systematically analyzing the relationships between properties, separation technique and conditions of operation. After the final step, an estimate of the final process flowsheet is produced with a list of possible alternatives for the separation tasks. Application of the methodology is demonstrated through examples highlighting the different steps of the methodology.

MOLECULAR DESIGN OF SOLVENTS FOR LIQUID EXTRACTION BASED ON UNIFAC

Abstract On the basis of the UNIFAC group contribution method, it is proposed to synthesize molecular structures with specific solvent properties for the separation of aromatic and paraffinic hydrocarbons. The potential solvents were studied with regard to their solvent power, selectivity and binodal curve on the basis of UNIFAC predictions. In this way good potential solvents were found. In general the number of molecular structures that can be obtained from the various groups is very large. An efficient computerized synthesis of compounds for the molecular design of solvents was developed.

Method for selection of solvents for promotion of organic reactions

A method to select appropriate green solvents for the promotion of a class of organic reactions has been developed. The method combines knowledge from industrial practice and physical insights with computer-aided property estimation tools for selection/design of solvents. In particular, it employs estimates of thermodynamic properties to generate a knowledge base of reaction, solvent and environment related properties that directly or indirectly influence the rate and/or conversion of a given reaction. Solvents are selected using a rules-based procedure where the estimated reaction-solvent properties and the solvent-environmental properties guide the decision making process. The current method is applicable only to organic reactions occurring in the liquid phase. Another gas or solid phase, which may or may not be at equilibrium with the reacting liquid phase, may also be present. The objective of this method is to produce, for a given reaction, a short list of chemicals that could be considered as potential solvents, to evaluate their performance in the reacting system, and, based on this, to rank them according to a scoring system. Several examples of application are given to illustrate the main features and steps of the method.

Computer aided molecular design with combined molecular modeling and group contribution

Computer-aided molecular design (CAMD) provides a means for determining molecules or mixtures of molecules (CAMMD) having a desirable set of physicochemical properties. The application range of CAMD is restricted due to limitations on the complexity of the generated molecular structures and on the availability of suitable models for property prediction. A new CAMD methodology that addresses this issue by combining molecular modeling techniques with a traditional CAMD approach is presented. The new method includes a new molecular/atomic structure generation algorithm, a large collection of property estimation methods, and, a link to molecular modelling tools. Application of the new CAMD method is highlighted through two industrial examples.

Correlation and Prediction of Thermal Properties and Phase Behaviour for a Class of Aqueous Electrolyte Systems

Abstract An extended UNIQUAC model is used to describe phase behaviour (VLE, SLE) and thermal properties (heat of mixing, heat capacity) for aqueous solutions containing ions like (Na + , K + , H + ) (Cl − , NO 3 − , SO 4 2− , OH − , CO 3 2− , HCO 3 − ). A linear temperature dependence of the binary interaction parameters allows good agreement with experimental data in the temperature range 0–110°C.