Anthraquinone vapor phase

In the dyestuff industry, anthraquinone still ranks high as an intermediate for the production of dyes and pigments having properties unattainable by any other class of dyes or pigments. Its cost is relatively high and will remain so because of the equipment and operations involved in its manufacture. As of May 1991, anthraquinone sold for 4.4/kg in ton quantities. In the United States and abroad, anthraquinone is manufactured by a few large chemical companies (62). At present, only two processes for its production come into consideration manufacture by the Friedel-Crafts reaction utilizing benzene, phthahc anhydride, and anhydrous aluminum chloride, and by the vapor-phase catalytic oxidation of anthracene the latter method is preferred. 

The vapor-phase oxidation (VPO) of butadiene with air at 200—500°C produces maleic anhydride [108-31-6]. Catalysts used are based on vanadium and molybdenum oxides (89,90). Alternatively, when using a catalyst containing Al, Mo, and Ti, butadiene undergoes a complex series of condensations and oxidations to form anthraquinone at 250°C (91). 

Vapor phase oxidation. The first claims to be made public for the vapor pliase oxidation of anthracene to anthraquinone appeared in a patent issued to Walter.28 As catalysts, the oxides of the metals of the fifth and sixth groups of the periodic system were used. The oxidation of various substances in the vapor phase was claimed but the importance of the new process was not recognized until the war caused a revival in interest. Although the original process was not directly applicable to large scale production because of limitations in catalyst activity, temperature control, and heat removal, it did furnish a basis for the subsequent development of the general vapor phase oxidation processes. 

As indicated by available data the major product obtained in the catalytic vapor phase oxidation of anthracene aside from total combustion products obtained in some cases, is anthraquinone. Operating conditions are designed and controlled in such a way that this is the main product, obtained in as pure a form as possible. 

---