Process for dry synthesis and continuous separation of a...

Organic compounds -- part of the class 532-570 series – Organic compounds – Fatty compounds having an acid moiety which contains the...

Reexamination Certificate

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C554S216000

Reexamination Certificate

active

06262285

ABSTRACT:

TECHNICAL FIELD
This invention relates to an improved process for the low pressure transesterification of triglycerides using excess methanol and an alkali catalyst, and in particular the continuous separation of fatty acid methyl esters (FAME) from glycerol and the recovery of excess methanol from the reaction products using a dry vacuum system.
BACKGROUND OF INVENTION
Prior processes for producing FAME by transesterification of triglycerides (i.e., natural oils) with excess methanol and alkali catalysts used batch decantation of the reaction products followed by a water wash of the FAME fraction to remove by-product glycerol therefrom. Where transesterification processes are practiced on a semi-continuous or continuous basis, water washing of glycerol, and often times methanol, from the FAME has been regularly practiced. Water washing produces an enriched FAME fraction, and a glycerol fraction containing excess methanol and water. In this type of process, excess methanol is ultimately rectified from the wash water via an expensive distillation step.
It would be desirable to provide a continuous low pressure transesterification process having low soap production and high conversion of triglycerides which does not include the introduction of water for washing glycerol from the FAME fraction.
SUMMARY OF THE INVENTION
The present invention provides a dry transesterification process to produce FAME from triglycerides. This dry transesterification process combines a feed solution of excess methanol and alkali catalysts with a triglyceride (e.g., vegetable oil) feed, and continuously separates the resulting FAME and glycerol fractions by a continuous decantation process, thus obviating the required practice of a water wash step, or steps, for FAME purification (i.e., glycerol removal). This selectively continuous process of separating the reaction products eliminates the costly washing step, and those further steps associated with such processing, because continuous separation is more efficient than batch decantation, yielding reaction products of greater purity. No additional water is introduced into the system since water washing has been eliminated in the present invention and because the vacuum system used to recover the methanol from the FAME and glycerol products is also dry. This permits the use of a molecular sieve column to eliminate the minute amounts of water present in the excess methanol, whether the water comes from air leaks into the system or from moisture in the natural oil feed etc., rather than rectification of the excess methanol from the wash water using distillation as in the batch approach. Desiccant columns equipped with molecular sieves are used to dry the recovered excess methanol.
The improved process begins with the combination and agitation of stored and recovered (i.e., recycled) excess methanol, with an alkali catalyst in a methanol/catalyst mixing tank to form a feed solution. Triglycerides from storage are added to the methanol/catalyst solution, with the combination then heated and pumped to a low pressure agitated reactor where the transesterification reaction occurs under appropriate process conditions. The reaction produces FAME and glycerol fractions, each of which contains a methanol component. The reaction fractions are delivered to a decanter for continuous separation.
The FAME fraction is pumped to a methanol stripping column which removes the included methanol therefrom while the FAME product is ultimately sent to storage. The other continuously separated output, namely, the glycerol fraction, is pumped to a separate methanol stripping column which removes the included methanol therefrom while the glycerine product is ultimately sent to storage. The excess methanol recovered from both the FAME and glycerol fractions is thereafter compressed, condensed and dried for recycling (i.e., feed for the methanol/catalyst solution).


REFERENCES:
patent: 5424467 (1995-06-01), Bam et al.

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