Tracer cross-correlation techniques

Cross Correlation. Considerable research has been devoted to correlation techniques where a tracer is not used. In these methods, some characteristic pattern in the flow, either natural or induced, is computer-identified at some point or plane in the flow. It is detected again at a measurable time later at a position slightly downstream. The correlation signal can be electrical, optical, or acoustical. This technique is used commercially to measure paper pulp flow and pneumatically conveyed soHds. 

In Chapter 1, Fyfe, Mueller, and Kokotailo describe the applications of solid-state NMR to the study of zeolite molecular sieve catalysts and related systems. Zeolites provide an apt arena in which to demonstrate the capabilities of modern techniques such as sample spinning, cross-polarization, and multidimensional correlation spectroscopy. In Chapter 2, Karger, and Pfeifer consider the question of molecular diffusion in catalyst systems. Applications of NMR techniques such as imaging, lineshape analysis, relaxation, pulsed field gradient echo spectroscopy, and NMR tracer exchange are described and compared with other, more traditional techniques such as radioactive tracing. In Chapter 3, Haw discusses the use of NMR to probe catalytic processes, showing how the combination of temperature control with novel NMR probes makes it possible to elucidate reaction mechanisms in situ. 

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