Critical Technologies: The Role of Chemistry

Critical Technologies The Role of Chemistry and Chemical Engineering, National Research Council, National Academy Press, Washington, D.C., 1992. 

This review is focused on the science and technology of framework metal-containing zeotype materials, a critical and increasingly important class of catalyst. In the following paragraphs, first the structural characteristics of zeo-Htes, which are close and well investigated relatives of zeotype materials, will be briefly summarized. Then the role of the framework metal for the structural and surface chemistry of zeolite and zeotype materials will be introduced. 

Moreover, the described phenomena will bear relevance for the metal-promoter interaction in promoted supported transition or noble metal catalysts. Unless spillover effects play a decisive role, promotion can occur only if the active metal and promoter oxide are in contact. Obviously, in such complex systems the surface- and interface-free energies and the mobilities of individual components under preparation conditions critically will determine their morphology and distribution. For a deeper understanding of the detailed mechanisms of wetting and spreading in such complex systems as supported catalysts, additional fundamental studies are required, in which our basic knowledge in surface chemistry, surface spectroscopy, colloid and solid-state chemistry, and powder technology must be combined. 

Mass spectrometry has been, and will continue to be, a critical tool for the discovery of new lead chemistries from nature. It continues to play a central role in several phases of the natural products discovery processes that include source selection, screening, dereplication, and identification. Mass spectrometry will likely remain a key technology that should contribute to the success of natural product lead generation programs in both the pharmaceutical and agrochemical industries. 

Many food processes, which affect food quality and stability, are diffusion controlled (Karel et al., 1994 Roos, 1995). Transport of key penetrants such as water into or out of a polymeric food matrix can play a critical role in food quality and stability. Water is one of the major components and a very good plasticizer in foods. The quality and stability of dehydrated products, multi-domain foods, and the performance of biofilms and encapsulation and controlled release technologies are affected by moisture transport. The rates of molecular mobility and diffusion-limited reactions strongly depend on the factors surrounding the food. Temperature and water activity (fl ) pl y significant roles in penetrant diffusion. The physical state of the carrier matrix, chemistry, size, and structure of diffusing molecule and specific... 

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