WO2000075096A1

WO2000075096A1 - Process for the reduction of glycerin in transesterification operations

Info

Publication number: WO2000075096A1
Application number: PCT/US2000/014912
Authority: WO
Inventors: Marty A. Cronin
Original assignee: Cognis Corporation
Priority date: 1999-06-09
Filing date: 2000-05-31
Publication date: 2000-12-14
Also published as: AU5048700A

Abstract

The present invention is an improvement in the process for the production of fatty acid esters. It has been surprisingly discovered that adding steam to the reaction product stream of a transesterification process at a point in the production of fatty acid esters following the transesterification reaction of an oil improves the separation of the free glycerin from the fatty acid esters.

Description

PROCESS FOR THE REDUCTION OF GLYCERIN IN TRANSESTERIFICATION OPERATIONS

BACKGROUND OF THE INVENTION

Numerous esters are synthesized from carboxylic acids and alcohols,

and are known to be useful in various fields. In addition, esters derived from

natural products are used as, for example, oil, fats or flavor.

The preparation of fatty acid esters by base-catalyzed

transesterification has long been known. A survey of known processes may

be found in J.A.O.C. Soc. 61 (1984), page 343ff., the entire contents of which

are herein incorporated by reference, and in Ullmann, Enzyklopadie d. techno

Chemie [Ullmann's Encyclopedia of Chemical Engineering], Fourth Edition,

Vol. 11 , page 432, the entire contents of which are herein incorporated by

reference. United States patent 5,434,279 describes a process for preparing

fatty acid esters of short chain monohydric alcohols, the entire contents of

which are herein incorporated by reference. In all these processes, the

preparation is done by mixing fatty acid glycerides, and in particular animal or

vegetable oils and fats, with an excess of the short-chain alcohols, with the

addition of a basic catalyst and separation of the subsequently forming

heavier glycerin phase, under reaction conditions that vary depending on the

quality of the starting materials.

Following the transesterification reaction the mixture of fatty acid esters

and glycerin is processed through a series of separation steps to separate the

fatty acid esters from the free glycerin. Many down stream uses of fatty acid esters are effected by the amount

of free glycerin remaining in the fatty acid ester product.

Ways to improve the separation of the glycerin from the ester product

are always sought. It is therefore desirable to improve the efficiency of the

process of separating the glycerin from the fatty acid ester. It would be

desirable to have a method that results in the reduction of the amount of free

glycerin in the final ester product.

SUMMARY OF THE INVENTION

The present invention is an improvement in the process for the

production of fatty acid esters. It has been surprisingly discovered that

adding steam to the reaction product stream of a transesterification process

at a point in the process following the conversion of the oil to ester, improves

the separation of the free glycerin from the fatty acid esters.

Another aspect of the invention is the fatty acid ester made with

reduced free glycerin.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic of one embodiment of the invention.

Figure 2 is a process flow diagram of one embodiment of the invention.

DESCRIPTION OF THE INVENTION

Except in the claims and the operating examples, or where otherwise

expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood

as modified by the word "about" in describing the broadest scope of the

invention. Practice within the numerical limits stated is generally preferred.

Also, throughout this description, unless expressly stated to the contrary:

percent, "parts" of, and ratio values are by weight; the description of a group

or class of materials as suitable or preferred for a given purpose in connection

with the invention implies that mixtures of any two or more of the members of

the group or class are equally suitable or preferred; description of constituents

in chemical terms refers to the constituents at the time of addition to any

combination specified in the description or of generation in situ by chemical

reactions specified in the description, and does not necessarily preclude other

chemical interactions among the constituents of a mixture once mixed.

The present invention provides a process for transesterification of an

oil and the subsequent glycerin removal from the resulting ester. The

invention comprises adding steam to the product stream of a

transesterification process. This novel step enhances the separation of

glycerin from the fatty acid ester product. Utilizing the invention can improve

the product purity by reducing the amount of free glycerin in the fatty acid

ester product. The invention results in a more pure product, with little

investment. The change to the process is simple and inexpensive yet results

in a product that has reduced the free glycerin remaining in the fatty acid

ester product by more then 60% then when conducted without the added steam. Using a steam feed stream as a method to enhance free glycerin

removal has advantages over using a liquid water feed stream. First, with

steam there is little if any extra equipment, such as pumps or holding tanks,

necessary to inject the steam into the process stream. Extra equipment is

costly in building floor space as well as in capital investment. By choosing

steam with enough pressure, the steam pressure itself will be sufficient to

move the steam into the process stream. The steam flow helps to mix the

steam with the process fluids as it condenses providing contact between the

condensed steam and the free glycerin in the process stream.

Examples of oils which can be used in the process according to the

invention include but are not limited to coconut oil, canola oil, tall oil, tallow oil,

corn oil, soybean oil.

Any alcohol can be used. Examples of alcohols that can be used

include, but are not limited to monohydric aliphatic alcohols having from 1 to 5

carbon atoms, such as methanol, ethanol, butanols, neopentyl alcohol.

The invention in its simplest form comprises a transesterification

process of an oil with an alcohol in the presence of a catalyst at a suitable

pressure and temperature. A suitable pressure and temperature are those

that are sufficient to effect the transesterification of the oil by the alcohol. The

resulting fatty acid ester product is then recovered and purified. What is

meant by purified is that the unreacted raw materials and side products of the

reaction such as the glycerin are removed to give a product consisting

substantially of fatty acid ester. The process according to the invention

consists of the above reaction followed by a purification process wherein, after some initial removal of unreacted raw materials and side products, the

stream containing the reaction product, the fatty acid ester, is mixed with

steam. The reaction product/steam mixture is processed through a

separation process, such as a cooler and a coalescer where the free glycerin

separates from the reaction product leaving a more pure product.

The ratio of steam added to reaction product is from about 1 part

steam to about 100 parts reaction product to about 5 parts steam to about

100 parts reaction product and preferably from about 1 :100 to about 4:100.

In a preferred embodiment, the transesterification process comprises

reacting an oil with an alcohol in the presence of a catalyst at temperature

and pressure sufficient to effect the transesterification of the oil by the

alcohol. The preferred temperature range is from about 175 F to about

200 F. The preferred pressure range is from about 30 psig to about 75 psig.

The preferred catalyst is sodium methylate. The preferred alcohol is

methanol. The product of the reaction is separated, producing two streams.

The preferred method of separation is in a decanter. The lighter weight

stream contains the fatty acid esters with excess alcohol and some minor

amount of glycerin. The heavier weight stream contains primarily glycerin and

excess alcohol. The glycerin in the process fluids can be in either a free form

or in the form of unreacted raw material such as the initial oil fed to the reactor.

The lighter stream containing the reaction product is optionally

processed through a second reactor and then followed by a second

separation step. The preferred temperature range is from about 170 F to about 195 F. The preferred pressure range is from about 30 psig to about 75

psig. The preferred method of separation is using a decanter. The lighter

stream taken off the second separation step contains primarily fatty acid

esters and alcohol with some minor amount of glycerin. The heavier stream

contains primarily glycerin and alcohol. Following the transesterification

reaction, the lighter weight stream containing the fatty acid esters is

processed through an evaporator, preferably a falling film evaporator. This

evaporation step separates the unreacted alcohol from the fatty acid ester.

The stream coming off the evaporator that contains the fatty acid ester is

combined with a stream of steam and then processed through a cooler and

coalescer to separate the water/glycerin from the crude fatty acid ester

product. The added steam condenses when mixed with the reaction product

providing intimate mixing of condensed steam with the ester phase.

Typically, the crude fatty acid ester product is about 0.3% or greater by weight

glycerin. With the steam injection into the process stream after the oil has

been converted to fatty acid ester, the crude product is preferably less than

0.2 % by weight glycerin, more preferably less than 0.1% by weight glycerin

and most preferably less than 0.05% by weight glycerin.

Claims

What is claimed is:

1. A process for making a fatty acid ester comprising:

(a) providing a fatty acid;

(b) providing an alcohol;

(c) providing a catalyst;

(d) reacting the carboxylic acid with the alcohol, in the presence of the

catalyst, to form a primary reaction product containing a fatty acid ester and

glycerin;

(e) providing a steam feed stream;

(f) introducing the steam feed stream into the primary reaction product

to form a secondary reaction product containing a fatty acid ester product,

glycerin and water; and

(g) separating the fatty acid ester product from the glycerin and water.

2. The process of claim 1 wherein the alcohol is a C1.5 alcohol.

3. The process of claim 1 wherein the alcohol is methanol.

4. The process of claim 1 wherein the catalyst is sodium methylate.

5. The process of claim 1 wherein the steam feed stream is introduced

into the reaction product in an amount of from about 1 part steam to about

100 parts reaction product.

6. The process of claim 1 wherein the steam feed stream is introduced

into the reaction product in an amount of from about 4 parts steam to about

100 parts reaction product.

7. The process of claim 1 further comprising separating glycerin and

alcohol from the reaction product of (d) to form a purified reaction product,

prior to introducing the steam feed stream.

8. The process of claim 7 wherein the fatty acid ester product contains

less than about 0.2% by weight glycerin, based on the weight of the fatty acid

ester product.

9. The process of claim 7 wherein the fatty acid ester product contains

less than about 0.1% by weight glycerin, based on the weight of the fatty acid

ester product.

10. The process of claim 7 wherein the fatty acid ester product contains

less than about 0.05% by weight glycerin, based on the weight of the fatty

acid ester product.

11. The product of the process of claim 1.

12. The product of the process of claim 2.

13. The product of the process of claim 3.

14. The product of the process of claim 4.

15. The product of the process of claim 5.

16. The product of the process of claim 6.

17. The product of the process of claim 7.

18. The product of the process of claim 8.

19. The product of the process of claim 9.

20. The product of the process of claim 10.