A Structural Study by Transmission Electron Microscopy of the Reactions of Some Graphite Intercalation Compounds

The intercalation compounds potassium graphite, graphite ferric chloride, graphite copper sulphide and graphite iron have been prepared. The structures of these compounds, examined by transmission electron microscopy and electron diffraction exhibit similar features, the most common being dark areas with bright discs and ring moire patterns. Electron diffraction patterns from areas of ring moire patterns are distorted indicating uneven intercalation. Potassium graphite, prepared and examined in situ at 573K, appears to contain a mixture of Stage I and higher compounds. Graphite ferric chloride is evenly intercalated and is a stage I compound while graphite copper sulphide appears to be a stage II or higher compound. Graphite iron contains iron in three forms, namely, a graphite iron intercalation complex, iron crystallites and some finely dispersed iron. The areas of iron crystallites also contain THF which causes exfoliation of the graphite as a result of the heating effect of the electron beam. Graphite ferrous chloride formed by reduction of graphite ferric chloride exhibits aggregations of FeCl2 within the graphite layers. Some expulsion of FeCl3 also occurs on heating graphite ferric chloride. The catalytic activity of potassium graphite, graphite ferric chloride, graphite copper sulphide and graphite ferrous chloride for ammonia synthesis from N2/H2 was studied in the range 483-723K and the structures of the intercalation compounds examined after reaction by transmission electron microscopy and electron diffraction. Gaseous products were analysed by mass spectrometry, infra-red analysis, and wet chemical methods and in no case was free ammonia observed. Reaction was observed above 483K after 1 hour in a flow system over potassium graphite. Reaction occurs within the graphite layers and decomposition of the potassium graphite to KNH2 at 573K was observed possibly via a ternary intermediate. Reduction of graphite ferric chloride and graphite copper sulphide takes place on reaction with nitrogen and hydrogen in the range 523-723K. The graphite ferrous chloride formed, exhibited some activity for ammonia synthesis with formation of aggregates within the layers which were provisionally identified as NH4Cl. The catalytic activity of graphite ferrous chloride and graphite iron for the hydrogenation of butadiene was also studied. At 573K graphite ferrous chloride catalysed the polymerisation of butadiene in a similar manner to free ferrous chloride. Electron diffraction indicated that a small amount of iron was formed which could be responsible for the minor hydrogenation reaction observed. Graphite iron exhibited low catalytic activity for the hydrogenation of butadiene compared to iron. Heating graphite iron causes the decomposition of the compound with agglomeration and expulsion of iron particles from the lattice. These iron particles exhibited high catalytic activity for carbon deposition in the butadiene, hydrogen system