C4 fraction of the cracked petroleum hydrocarbons was catalytically oxidized by air. Butenebutadiene fraction and spent-butane (B-B fraction from which butadiene has been extracted) were used for the feeds. The reactor tube was of steel pipe with inner diameter of 22mm. and length of 2, 300mm., provided with a nitre bath. The volume of catalyst in the reactor tube was varied from 200 to 250cc. V2O5-MoO3 catalyst was supported on pumice of 4-6mesh/in2.
The effect of factors, such as concentration of C4 fraction, reaction temperature, and flow rate of gas were examined. The optimum conditions were as follows:
reaction temperature 340-400°C
concentration of C4 fraction nearly 0.4mol%
space velocity 4, 000-8, 000cc./hr.cc.
Under these conditions, the yield of maleic anhydride was 35mol% of the used B-B fraction, and 15mol% of the used spent-butane. The yield was affected by the content of butadiene in the feed.