| 摘要 |
1,150,849. Methanol, purification by distillation. ALLIED CHEMICAL CORP. 5 Oct., 1967 [6 Oct., 1966], No. 45565/67. Heading BIB. Methanol, contaminated with dimethyl ether, ethanol and higher alcohols, is purified by distillation in a system of three fractionating columns 19, 39, 46, each operated with major reflux; the crude methanol is submitted to extractive distillation with a countercurrent of hot water in column 19, dimethyl ether and other readily volatile impurities being eliminated through vent-cooler 35 and in non-reflexed condensate 36, the bottoms from column 19 are distilled in column 39 wherein all the methanol is vapourised and the bulk of the water flows to the base, the vapours are partially condensed in condenser 43 and the non-condensed part of the distillate is rectified in column 46, yielding methanol as condensate the major part of which is refluxed to column 46, and the required purified methanol (99.95%) product being withdrawn through valve 74 or valve 76. If the distillate from column 46 contains residual low-boiling impurities, the required purified methanol is withdrawn as a liquid side-stream through valve 76; and the non-refluxed part of the overhead condensate is passed through line 77 to column 19. Crude methanol from a catalytic synthesis flows from line 11 into tank 12 where dissolved gases and some methanol flash off. The gases are scrubbed with recycle water in scrubber 14 in order to remove methanol, the scrubbed gases being vented through line 15, and the dilute aqueous solution being supplied through line 16 and heat-exchanger 18 to the upper section of column 19. The de-gassed crude methanol withdrawn from the base of tank 12 is neutralized with caustic alkali in line 23, and then fed through heat-exchanger 25 and line 26 into column 19. A liquid side-stream containing higher alcohols is withdrawn from the lower section of column 39 and is passed through cooler 57 to decanter 58, from which the separated aqueous layer is returned to column 39 through line 59. A fraction which contains ethanol is discharged from the base of column 46 and through line 62. The water withdrawn from the base of column 39 is recycled through line 49 and heat-exchanger 25 or 18 for use as solvent water in column 19 and as wash water in scrubber 14, part of the water being discharged through line 51. The portion of the recycle water for use in scrubber 14 is pre-cooled in cooler 54. The upper section of column 19 may have 20 plates, the lower section being packed with ceramic Berl saddles equivalent to 17 plates; and column 39 may be of similar type. The purified methanol withdrawn from the system may be treated with a cation type ion exchange resin to remove trace impurities.
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