The prefered method for the manufacture of anthraquinone in small scale production is the reaction of phthalic anhydride with benzene in the presense of aluminum chloride to give o-benzoyl benzoic acid in a ball mill reactor followed by acid cyclization.
The two reaction paths are thoroughly investigated to give optimum operation conditions of ball mill reactor, and to find out relation between the acid concentration, temperature, reaction time and conversion in acid reactor, respectively.
The results shows that the optimum operation conditions in ball mill reactor are as follows : rotation speed 50-65% critical speed, fractional ball filling 30-35%, material to void ratio 1.5 and 20% excess benzene feed based upon theoretical.
In acid reactor the cyclization reaction rate is continuously catalyzed by additional sulfuric acid. A sulfuric acid concentration and temperature combinations are measured to give expected conversion in time.
The economic aspects of this process is also considered by scale up design based on pilot plant experiment.
With a projected production of 100 tons/year anthraquinone and 50 tons/year o-benzoyl-benzoic acid simultaneously, the total investment is 370 million wons with the rate of return on investment of 10.19% after tax.