Process for purifying caprolactam
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United States of America Patent
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Apr 29, 2008
Grant Date -
Mar 15, 2007
app pub date -
Jul 16, 2004
filing date -
Jul 25, 2003
priority date (Note) -
Expired
status (Latency Note)
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Abstract
The invention relates to a process for purifying caprolactam, said process comprising (a) subjecting the caprolactam to a hydrogenation by treating the caprolactam with hydrogen in the presence of a heterogeneous nickel containing hydrogenation catalyst, (b) distilling at least a portion of the hydrogenated caprolactam in a distillation column containing nickel in an amount sufficiently low such that .DELTA.PAN.sub.Ni.ltoreq.3, wherein .DELTA.PAN.sub.Ni=.DELTA.PAN-.DELTA.PAN.sub.Ni=0, .DELTA.PAN=increase of the PAN number of caprolactam during distilling, .DELTA.PAN.sub.Ni=0 increase of the PAN number of caprolactam during distilling under the same conditions in a distillation column free of nickel. Nickel is removed from the caprolactam solution prior to the distillation step.
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