Solid layer crystallization benefits

With some of the other layer-lattice solid lubricants, the natural electronic structure does not provide the same benefit but a favourable structure can be brought about by intercalation of metallic atoms into their crystal structures, and this is described in more detail in Chapter 14. 

While the acid strength of HPAs is high, they have a limitation in their use in catalysis, and this is due to their low surface area in the solid state (SlOm g- ), which corresponds to the external surface area of the crystal. When the reactants have a polar character, however, HPAs can take up polar molecules in amounts that correspond to more than 100 surface layer, and in this case their catalytic behaviour has been called bulk type catalysis [31"). Therefore, in the case of catalytic reactions involving polar molecules, they occur not only at the surface but also in the bulk solid of certain HPAs. The practical effect is that the catalytic system behaves like a highly concentrated solution, and this explains why these solids have been named pseudoliquids [31 j. Under the pseudoliquid conditions all acid sites are accessible to reactants, and the benefits of the system have been used commercially for reactions such as the hydration of propylene and n-butenc, separation of isobutene, and polymerization of tetrahydrofuran 20, 31". ... 

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