| 摘要 |
Tert.-butyl-hydroquinone is prepared by reacting hydroquinone with isobutylene or tert-butyl alcohol in the presence of an aromatic hydrocarbon containing 6-8 carbon atoms and phosphoric acid at an elevated temperature with agitation. The amount of phosphoric acid used is preferably from about 1 to about 6 times the weight of hydroquinone employed. The hydroquinone and tert.-butyl alcohol or isobutylene are preferably used in approximately equimolecular amounts. The aromatic hydrocarbon, usually toluene or xylene, serves to remove the mono-tert.-butyl derivative from the hydroquinone-catalyst phase and thus protect it from further alkylation. The reaction is generally conducted at reflux temperature and the water formed in the reaction when tert.-butyl alcohol is used is removed by azeotropic distillation. Tert.-butyl-hydroquinone is used for the stabilization of oils and fats. In examples, the process of the invention is carried out batchwise, in successive batches or continuously. In the batchwise process: (1) hydroquinone, toluene or xylene and phosphoric acid are mixed and heated while tert.-butyl-alcohol is added slowly, the aromatic hydrocarbon layer is separated from the acid layer (which may be re-used) and the tert.-butyl-hydroquinone obtained therefrom; (2) as in (1) but using isobutylene and xylene. In the successive batch process hydroquinone, phosphoric acid and toluene, are mixed and refluxed, tert.-butyl alcohol is added slowly (further hydroquinone being added at intervals during this addition), the toluene and acid layers are separated, the toluene layer is cooled to crystallize tert.-butyl hydroquinone and then filtered, the filtrate and the phosphoric acid being used in successive batches. In the continuous process, equal volumes of toluene and phosphoric acid are heated to boiling point in a cylindrical reactor and well stirred at the bottom (i.e. the acid layer) only, a mixture of tert.-butyl alcohol, toluene and hydroquinone is fed in at the bottom of the reactor, the toluene solution of the product being drawn off at the top of the reactor, the tert.-butyl hydroquinone separated and the toluene recycled.
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