NUCLEAR-MAGNETIC-RESONANCE IN CHEMICAL-ENGINEERING - PRINCIPLES AND APPLICATIONS

In recent years chemical engineers have shown an increasing interest i n non-invasive measurement techniques; Nuclear Magnetic Resonance (NMR ) is perhaps the ultimate technique of this kind. Over the past 10 yea rs notable developments have been made in both spectrometer hardware a nd our ability to understand and manipulate nuclear spin interactions, and it is now possible to address research areas in catalysis, materi als science, mass transfer and flow visualisation which are of real in terest to chemical engineers. This review is divided into two sections . Part I identifies three broad categories of magnetic resonance measu rements: Spectroscopy, diffusion measurement and imaging and outlines the basic principles underlying these experiments. A summary of the va rious nuclear spin interactions and the chemical information they yiel d is given. In progressing to the introduction of diffusion measuremen ts, the application of magnetic field gradients is discussed and the b asic Pulsed Gradient Spin Echo (PGSE) and related measurement techniqu es are presented. The principles of NMR imaging are then described in the context of the two popular experimental schemes: projection-recons truction and spin-warp imaging. The principles and application of para meter-selective imaging experiments are outlined and limitations on at tainable resolution are noted. Extension of NMR imaging to the study o f flow phenomena is also discussed. Part II of the review reports a nu mber of examples of NMR methods applied to problems of direct relevanc e to chemical engineers. This literature survey starts with an overvie w of applications of NMR spectroscopy in the fields of catalysis, adso rption, measurement of phase equilibria and the consideration of NMR a s a quality control technique. The use of PGSE methods to study diffus ion phenomena is discussed, with particular emphasis being placed on h ow theoretical models in combination with NMR experiments are being us ed to gain insight into transport processes occurring within porous me dia. Recent developments in NMR imaging and their application to the s tudy of ceramics processing, polymers, porous media, catalysis, food p rocessing, filtration processes, and transport within reactors and pac ked columns are also presented. Finally, the state-of-the-art in NMR d ow imaging studies is discussed and the ability of NMR to study two-ph ase how phenomena is highlighted.