Process for producing highly pure terephthalic acid
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United States of America Patent
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Nov 4, 1997
Grant Date -
N/A
app pub date -
Apr 29, 1996
filing date -
May 17, 1995
priority date (Note) -
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status (Latency Note)
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Abstract
There is disclosed a process for producing highly pure terephthalic acid by converting a slurry of terephthalic acid crystals in acetic acid solvent which crystals are obtained by liquid-phase oxidation of p-alkylbenzene, into a slurry thereof in water solvent by mother liquor replacement and then subjecting the latter slurry to a catalytic hydrogenation treatment which process comprises the steps of introducing the slurry of terephthalic acid crystals in acetic acid into a mother liquor replacement column at the top portion; forming an accumulation layer of the terephthalic acid crystals at the bottom portion by the sedimentation of the crystals; feeding replacing water sufficient for the formation of upward rising stream of water to the inside of the column at the bottom portion; and withdrawing the accumulation layer of the crystals from the bottom portion of the column. The accumulation layer is kept at a slightly fluidized stable state and is smoothly withdrawn from the bottom of the column by slowly rotating an arm-type agitation blade placed in the layer or by feeding the replacing water dividedly into two trains.
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