Thermodynamics and the other chemical engineering sciences: old models for new chemical products and processes

Much recent academic research in molecular thermodynamics has been directed toward ever-more-complex theories without adequate attention to how such theories may be used in contemporary chemical technology; too often, researchers develop theories for their own sake, delegating to others (who?) to figure out how to use them. For new chemical product design, it is typically necessary to inter-relate thermodynamics with other sciences (notably mass transfer); for chemical process design, it is desirable to direct molecular-thermodynamic ideas toward evolving industries (e.g., biotechnology). Toward those ends, conventional models can often provide helpful information. To illustrate, three examples are briefly discussed: first, design of a drug-delivery system and second, design of polymer blends to achieve desired mechanical properties. In both examples, the key to success is not the conventional molecular model but its combination with Fickian diffusion. The third example concerns precipitation of proteins from aqueous salt solutions; a remarkably simple model shows how equilibria in protein solutions are qualitatively different from those in conventional solutions. Calculations show that, for protein solutions, on a plot of temperature vs, concentration, the freezing line (for liquid-solid equilibria) lies above the liquid-liquid coexistence curve, as verified by experiment. (C) 1999 Elsevier Science B.V. All rights reserved.