Development of wet environmental TEM (wet-ETEM) for studies of liquid-catalyst reactions on the nanoscale
Understanding reacting materials at the atomic level is important for the design and development of new generation catalytic materials, new routes for polymers and green technological processes (Gai, 1992). To probe dynamic gas molecule-catalyst interactions directly at the atomic level, we have pioneered the development of in-situ environmental high resolution transmission electron microscopy (EHRTEM) with atomic resolution (Gai et al, 199598; Boyes and Gai, 1997), which was highlighted by the American Chemical Society (Haggin, 1995). Heterogeneous routes for hydrogenation and polymerization are of considerable interest in the chemical technology, because they offer economical alternatives and are environmentally beneficial. An example is the hydrogenation of aliphatic dintriles used in the chemical industry to produce diamines (Bellefon et al, 1994). These are subsequently reacted with adipic acid and polymerized to produce the polyamide, nylon 6,6. Of particular commercial importance is the hydrogenation of adiponitrile (ADN, NC(CH2)4CN) to hexamethylene diamine (HMD, Η2Ν(ΟΗ2)όΝΗ2), an important intermediate in the manufacture of the polyamide. Many commercial polymerization processes are derived from solutions and the associated chemical reactions occur on the nanoscale. Probing reactions in solutions is therefore of great importance in the development of advanced process technologies. Thus far, liquid-solid reactions have been studied with limited resolution at room temperature, and the results tend to be averaged over large areas.