they used to make acetic anhydride from oil. with the rise in oil prices in the early seventies, the company began looking for alternative inexpensive materials. coal was the obvious choice. first, it is gasified, producing hydrogen and carbon monoxide. at a later stage, carbon monoxide is reacted with methyl acetate to produce acetic anhydride. it is this crucial step which requires the rhodium. a rhodium compound acts as the catalyst. catalysts are substances which increase the rate of reaction without being consumed by the reaction. catalysts do this by lowering the activation energy. here again is our activation energy hill. with a catalyst, a new activated complex forms with a lower activation energy. more colliding molecules now have sufficient energy to overcome the hill, so the reaction rate is increased. the reaction to produce acetic anhydride has a very high activation energy. without a catalyst present, the reaction would not be feasible. rhodium is an extremely expensive and rare metal. it costs nearly $50,000 a pou