| 摘要 |
The thermal dehydrogenation of hydrocarbons, especially aliphatic mono-olefines having four or more carbon atoms/molecule and in particular normal butylenes to butadiene, is accomplished in the presence of a calcium nickel phosphate catalyst, preferably containing a minor amount of chromium oxide, activated by contact with steam and/or oxygen and/or air at 650-800 DEG C. In examples, butadiene is produced in catalysis-regeneration cycles in which mixtures of 20 parts of steam and 1 part of mixed n-butylenes are dehydrogenated at 575 DEG or 650 DEG C. Specifications 634,391 and 634,580 are referred to.ALSO:A calcium nickel phosphate catalyst containing from 6.5-12 atoms of calcium/atom of nickel and substantially free from carbonaceous material is heated at 650-800 DEG C. in contact with steam and/or oxygen and/or air for at least 1 hour to increase its selective activity for the thermal dehydragenation of a n-butylene to butadiene in preferance to side reactions. The preferred catalyst comprises a minor amount of chromium oxide and contains 7.5-9.2 atoms of calcium/atom of nickel; activation may be at 675-750 DEG C. for at least 5 hrs., e.g. 5-50 hrs. The gas is preferably passed through a bed of the catalyst. Prior to the activation, carbonaceous deposits, if present on the catalyst must be removed, e.g. by a conventional burning-off step. Calcium nickel phosphate may be prepared by mixing suitable proportions of water-soluble calcium and nickel salts and a water-soluble orthophosphate in a neutral to alkaline aqueous medium, removing, washing and drying the precipitate, which may then if desired be mixed with a suitable binder such as graphite or mineral oil, pelleted or granulated, and the binder removed by oxidation, e.g. by heating in air or air and steam. In the examples, in which both freshly prepared and used catalysts are employed, comparative results are given for the production of butadiene in catalysis-regeneration cycles, activation according to the invention being generally performed after 10 cycles. Specifications 634,391 and 634,580 are referred to. |
