| 摘要 |
Conjugated diolefins contaminated with relatively high levels of acetylenic impurities in a hydrocarbon feedstream are purified by a cyclic, vapor phase, predominantly catalytic cracking process which selectively removes alpha-cetylenes in a single pass. A feedstream containing about equal weights of isoprene and mixed monoolefins and alkanes contaminated with alpha-acetylenes including isopropenyl acetylene inter alia, up to about 5.0 percent by weight (% by wt) of the feedstream, and a larger amount of cyclopentadiene, is contacted in the vapor phase with a supported Group I B metal oxide catalyst in the absence of hydrogen, at a temperature in the range from about 300 DEG F. to about 360 DEG F. In this narrow temperature range, the loss of diolefin is less than 1% by weight. Essentially all the cyclopentadiene (CPD) is left unconverted. Isopropenyl acetylene content of the effluent is generally less than about 25 ppm in the single pass process which is carried out in a fixed bed reactor operating at substantially atmospheric pressure. In an analogous process, from a crude butadiene feedstream containing less than about 1.0 percent by weight of vinyl acetylene and methyl acetylene, inter alia, a butadiene effluent is recovered having less than about 200 ppm alpha-acetylenes. The butadiene effluent, substantially free from poisons for a cis-polybutadiene polymerization catalyst, except CPD, if it is present in the feed, minimizes the loss of this catalyst and provides better yields.
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