Iron-Containing Graphite as a Friedel-Crafts Alkylation Catalyst

The activity of iron-containing graphites for the Friedel-Crafts reaction of phenol with tert-butyl halides was studied. Graphites were characterized by XRD and XPS. The reaction of phenol with either various tert-butyl halides or tert-butyl alcohol on iron-containing graphite was performed in a benzene solvent for 4 h at 50°C. The conversion and yield of the reaction on iron-containing graphite decreased in the order, tert-butyl iodide, tert-butyl bromide, and tert-butyl chloride, whereas for AlCl3, tert-butyl chloride was the most reactive while tert-butyl iodide was the least. Activated charcoal was not reactive. The presence of iron accelerated the reaction of phenol with the tert-butyl halide on graphite to yield p-tert-butylphenol as the main product. The presence of both tert-butyl bromide and iron increased the distance between the layers of graphite but not in the presence of either the iron or tert-butyl bromide. tert-Butyl halide was first adsorbed on graphite and then dissociated to form tert-butyl and halogen ions. The peak was observed at d=11.9 Å in the XRD pattern of the graphite after the reaction in which the high purity graphite was treated with tert-butyl halide and iron in phenol. This is probably due to the mixture of phenol with tert-butyl ion and iron inserted into the layers of graphite to form a two-stage structure.