| 摘要 |
Method of maintaining activity of self-regenerating dehydrogenation catalysts used for converting alkyl aromatic hydrocarbons (1-2 rings and 1-2 2-3 c alkyl groups) into corresponding alkenyl groups by passing mixt. of steam and feed over catalyst at 600-700 degrees C. Comprises intermittent (7-30 mins in each 24-48 hrs) stopping of hydrocarbon feed and maintaining flow of steam: little or no carbon oxides are made during the activation period. The cycles are then repeated. After treatment flow of hydrocarbon is resumed. The catalyst compsns. are known (US 3205179 and 3703593) and activation procedure is applicable to those catalysts contg. major amts. of at least one oxide of Fe, Zn, Cr or Mg, various amts. of alkali metal (pref. K) oxide, hydroxide carbonate, and Cr cpds. as promoter. Typical catalyst compsns. are (a) 62.5-87.9% wt. Fe2O3, 2-2.5% wt. Cr2O3 and 9.6-35.3% wt. K2O or K2CO3 and opt. about 3.5% wt. V2O5, (b) 24.8-30% wt. each of Fe2O3 and ZnO, 5-30% wt. K oxide, hydroxide or carbonate, 5-10% wt. Cu, Cd, Ag or Th oxide, 5-10% wt. alkali metal chromate and 1-5% wt. refratocry cement, and (c) 23.6% wt. ferric oxide hydrate, 35.3% anhydrous ferric oxide, 16.7% K2CO3, 2.5% K2Cr2O7, 2.5% V2O5, 2.8% cement, 8.3% methyl cellulose and 8.3% graphite. Typically process is applied to dehydrogenation of ethyl benzene with feed contg. 0.4-1 pt. steam per part hydrocarbon and to dehydrogenation of diethylbenzene with feed contg. 1.5-6 pts. steam per pt. hydrocarbon. |
