GB1499067A - Process for the preparation of tetrahydroanthraquinone - Google Patents

Abstract

1499067 Preparation of tetrahydroanthraquinone BAYER AG 16 July 1976 [19 July 1975] 29722/76 Heading C2C Tetrahydroanthraquinone is prepared by reacting naphthoquinone and butadiene in the presence of naphthalene and phthalic anhydride in the liquid phase, the butadiene being added in an amount of at least 3 mols per mol of naphthoquinone either in a pure or commercially available form (i.e. possibly containing other hydrocarbons such as butane and/or butene) at below 100‹ C. or as a solution (particularly in naphthalene or phthalic anhydride) at below 150‹ C., the reaction being effected at 60- 200‹ C. and 3-120 bars pressure in a tube reactor providing residence times of 0À1-5 hours and laminar flow of the reaction mixture, and in the presence of a polymerization inhibitor (which may be naphthoquinone and/or tetrahydroanthraquinone themselves), the heat of reaction being removed by means of a coolant having a temperature difference between feed and discharge of at most 20‹ C. The excess butadiene can be isolated from the reaction mixture obtained and can be re-cycled. The residual mixture may be employed directly, or after separation of the naphthalene, in the preparation of anthraquinone.