PROCESS FOR THE PRODUCTION OF FATTY ALCOHOLS

摘要

A process is described for producing fatty alcohols. A fatty acid or fatty acid mixture is esterified in a column reactor in which there is a plurality of esterification trays each having a predetermined liquid hold-up and containing a charge of a solid esterification catalyst thereon, e.g. an ion exchange resin containing -SO3H and/or -COOH groups. A liquid phase containing the fatty acid or fatty acid mixture flows down the column reactor from one esterification tray to the next downward one against an upflowing lower alkanol vapour stream, e.g. methanol vapour. Relatively dry lower alkanol vapour (water content not more than 5 mole %) is injected into the bottom of the column reactor. Water of esterification is removed from the top of the column reactor in the vapour stream, whilst ester product is recovered from the sump of the reactor. As the liquid flows down the trays it encounters progressively drier lower alkanol. The ester product recovered from the bottom of the reactor has an ester content of at least 99 mole % (calculated on a lower alkanol free basis). This ester product is then subjected to vapour phase hydrogenation, using typically a reduced copper oxide-zinc oxide catalyst. The resulting mixture contains, in addition to at least about 0.5 mole % up to about 5 mole % of unreacted ester, product fatty alcohol or alcohols and lower alkanol, there being no need to separate the lower alkanol from the ester if the lower alkanol is methanol. This is distilled to yield a fatty alcohol fraction which contains a minor amount of a lower alkyl (e.g. methyl) fatty acid ester or esters. The fatty alcohol fraction is subjected to transesterification to convert substantially all of any lower alkyl ester present to wax ester or esters. The resulting lower alkanol (e.g. methanol) is partially evaporated. Then the intermediate transesterification mixture is distilled to recover fatty alcohols. The residue from this distillation step is mixed with excess lower alkanol and again transesterified to reconvert wax ester or esters to lower alkyl esters. This mixture is re-distilled and the recovered mixture of lower alkanol, methyl fatty acid esters, and fatty alcohol or alcohols can be recycled. If an alkyl titanate is used as transesterification catalyst then both distillation steps can be effected without prior separation of the catalyst and the non volatile residue from the second distillation step can be recycled to the first transesterification step.