| 摘要 |
1,137,268. Recovering isoprene; isopentane. JAPAN GAS-CHEMICAL CO. Inc. 2 Nov., 1966 [17 Nov., 1965; 2 May, 1966], No. 49221/66. Heading C5E. A C 5 hydrocarbon fraction containing C 5 paraffins, mono-olefins, di-olefins and acetylenes, and possibly a fraction boiling above C 5 (e.g. a C 5 cut from a naphtha thermal cracking process), is treated to recover polymerization grade isoprene by a process comprising the following steps:- (a) Heating to dimerize cyclopentadiene; (b) Distilling to remove components boiling higher than 55‹ C., including cyclopentadiene dimer; (c) Distilling the fraction remaining from (b) to remove components boiling below isoprene (mainly isopentane and including acetylenic impurities) ; (d) Extractively distilling the residue from (c) to obtain a diolefin fraction, suitable solvents being #-methoxypropionitrile (preferred), acetonitrile (which may contain a small amount of water), dimethyl formamide, and dimethyl acetamide; (e) Boiling off the selective solvent from the diolefin extract, and optionally washing the diolefin mixture obtained with water; and (f) Separating isoprene from the diolefin mixture by rectification. The process may be carried out at atmospheric or superatmospheric pressure. Isoprene of at least 99.8% purity may be recovered.
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