Until World War I, the major chemical route to acetone was the thermal conversion of "grey acetate of lime," i. e., calcium acetate derived from neutralizing pyroligneous acid (wood distillate) with lime (14). An excellent early kinetic study of this reaction was performed by Ardagh et al. (15) although the reaction is difficult (16).

The thermal conversion of calcium acetate, propionate, and butyrate to 2-propanone (acetone), 3-pentanone, and 4-heptanone, respectively, is a first-order reaction (17). The rate constants follow an Arrhenius dependence on temperature with the constants shown in Table IV. The Arrhenius constants for each species are similar except for calcium propionate below 398°C. The reactions are very rapid; at 440°C, it takes less than one minute to achieve 90% conversion.

The thermal decomposition is quite selective to liquid products with theoretical yields over 93% for calcium acetate and butyrate, and over 87% for calcium propionate. Gaseous products account for the remaining material. In the liquid product, over 90% is the primary product (2-propanone, 3-pentanone, 4-heptanone) with other ketones being the dominant by-products. These by-products will also contribute to the value of the final fuel. The composition of the liquid product was remarkably independent of the temperature, even at very high temperatures, indicating that the products are stable at the reaction conditions.