MXPA97009834A - Method of transesterification to prepare polyol polyester - Google Patents

Abstract

A transesterification method for preparing polyol polyesters is described. The transesterification reaction of fatty acid esters of alkyl and polyols to make polyol polyesters can be coupled with a process for making a lower alkyl, esters of fatty acids. An inert gas is used to remove the alcohols. The gaseous alcohols derived from the transesterification reaction are used as the source of alcohol in the synthesis of lower alkyl esters and the inert gas of the alcohol stream can be recirculated. The process comprises preparing methyl esters of fatty acid, recovering the methyl esters and then transesterifying a polyol in a solvent-free two-step process, with methyl esters of fatty acid.

Description

METHOD OF TRANSESTERIFICATION TO PREPARE POLYOLES POLYESTERS TECHNICAL FIELD The present is a continuous process for preparing polyol polyesters using a transesterification reaction. The transesterification polyester formation reaction can be coupled with a process for making a lower alkyl, for example, methyl, fatty acid esters, which use the gaseous alcohols derived from the transesterification reaction as a source of the alkyl alcohols lower.

BACKGROUND OF THE INVENTION Polyol fatty acid polyesters have been suggested as low calorie or reduced calorie substitutes for triglyceride and oil fats used in foods. For example, the sugar fatty acid esters, non-digestible, nonabsorbable or fatty acid esters of sugar alcohol having at least 4 fatty acid ester groups with each fatty acid having from 8 to 22 carbon atoms, They have been used as replacements, partial or total fat in food compositions with a low calorie content. See Mattson and Volpenhein; United States Patent 3,600,186; Issued on August 17, 1971. Likewise, certain intermediate fusion polyol polyesters have been developed and provide a passive oil loss control, while at the same time exhibiting a reduction in the waxy appearance in the mouth. See, Bernhardt; European Patent Application Nos. 236,288 and 233,856; published on September 9, and August 26, 1987, respectively. Mixtures of completely liquid polyol polyesters with fully solid polyol polyester materials, preferably esterified with saturated fatty acids of C10 to C2 »(for example, sucrose octastearate) have also been proposed. Other mixtures of liquid polyol polyesters and solid nondigestible fats are also known. See, for example, Elsen et al, U.S. Patent 5,422,131, 1995, Jandacek; U.S. Patent 4,005,195; and Kandacek / Mattson; U.S. Patent 4,005,196; Both issued on January 25, 1977. A number of different procedures in the art have been described for preparing these highly esterified polyol fatty acid polyesters, in particular, sucrose polyesters. One such method involves a solvent-free transesterification, essentially two steps of the polyol (eg, sucrose) with the fatty acid esters of an easily removable alcohol (eg, methyl esters of fatty acid). In the first step, a mixture of sucrose, methyl esters, alkali metal fatty acid soap and a basic esterification catalyst are heated to form a melt bath. The amount of methyl esters used is such that the melt forms mainly partial fatty acid esters of sucrose, for example, mono-di and sucrose triesters. In the second step, an excess of methyl esters is added to this melting bath, which is then heated to convert the partial sucrose esters to more highly esterified sucrose polyesters, for example, hexa-, hepta and particularly octa esters of saccharose. See, for example, U.S. Patent 3,963,699 (Rizzi et al.), Issued June 15, 1976; Patent of the United States 4,517,360 (Volpenhein), issued on May 14, 1985; and U.S. Patent 4,518,772 (volpenhein), issued May 21, 1985; which describe two-step, solvent-free transesterification processes for preparing polyol esters of highly esterified fatty acid, in particular, highly esterified polyesters of sucrose. In some processes for preparing highly esterified polyesters of polyol fatty acid, all fatty acid methyl esters are added to the polyol (eg, sucrose) at the beginning of the reaction, that is, in a single stage addition process. See, for example, U.S. Patent 4,611,055 (Yamamoto et al.) Issued September 9, 1986. As the two-step processes, sucrose partial fatty acid esters are first formed and then converted to polyesters. of sucrose more highly esterified. Accordingly, these single-stage and two-stage procedures are collectively referred to hereafter as transesterifications of "two stages" where the "first stage" involves the formation of partial esters and where the "second stage" involves the conversion of partial esters to more highly esterified polyesters. Alternatively, highly esterified polyol polyesters can be prepared through two-step solvent-based processes (see for example, U.S. Patent 4,954,621 issued to Masaoka et al.), Or solvent-based or solvent-free processes. of a stage, see for example, U.S. Patent 4,968,791, (Van Der Plank), issued November 6, 1990; U.S. Patent 5,079,355 (Meszaros Grechke et al.), issued January 7, 1992; or U.S. Patent 5,071,975 (see der Plank et al.), issued December 10, 1991. The methyl esters used to prepare polyol polyesters can be prepared through the transesterification of triglyceride oils and fats with methanol in the presence of of an alkaline catalyst. After the transesterification reaction, a layer of crude glycerin, comprising glycerin formed in the transesterification reaction, soap formed through the catalyst, catalyst, some methyl esters and methanol, is prepared from the acid methyl ester layer fatty. The methyl ester layer is purified by any suitable recovery method, such as, for example, distillation. Processes of this type have been described in U.S. Patents 2,383,596, 2,383,579, 2,383,580, 2,383,596, 2,383,599, 2,383,601, 2,383,602, 2,383,614, 2,383,632 and 2,383,633 and in European Patent 0 164 643. An extra stage of esterification before recovery, but after separation of the fatty acid methyl ester layer from the glycerol layer may optionally be used to produce high yields of the highly pure fatty acid methyl esters. See European Patent 391 485. Methyl esters are a source of carboxylic acid, less expensive than hydrochlorides or anhydrides, and are sufficiently reactive to provide a good source of fatty acids for complex esterification reactions. The economy of the reactions is such that the relatively lower cost of methyl esters is more important than any of the aggregate processing costs. The lower alkyl alcohol group is chosen since the alcohol can be easily removed in the subsequent transesterification reaction by vacuum distillation or reducing the partial pressure of the alcohol using a nitrogen or inert gas spray, forcing the transesterification reaction to reach the end. Typically, methyl esters of fatty acids are prepared from sources of naturally occurring fatty acids, usually triglycerides from vegetable or animal sources. Methyl alcohol replaces glycerin. The resulting mixture of methyl esters is easily separated, providing a purified source of fatty acids. In a normal polyester polyol synthesis of this type, the polyol is reacted with a lower alkyl fatty acid ester in the presence of a catalyst and under an inert atmosphere. The inert gas stream from this transesterification reaction contains the liberated lower alkyl alcohol, which is continuously removed from the reaction to activate the polyester polyol synthesis at the end. The transesterification reaction can be coupled with another transesterification process to make a lower alkyl, for example, methyl esters of fatty acids, through a reaction of gaseous alcohols derived from the synthesis reaction of polyol polyester as a source of the alcohols lower alkyl. It has been found that the alcohol, diluted with nitrogen or other inert gas vehicle, can be reacted with a fatty acid ester, preferably a triglyceride, to form the corresponding methyl or fatty acid alkyl ester in a very efficient process. Preferably, the reaction is carried out in an absorption column, but can be carried out in an intermittent process. The inert gas spray recovered from the polyol polyester synthesis is used to make the starting methyl esters for the synthesis. At the same time, more than 90% and up to 99.7% of the methanol is removed from the inert gas stream. The free alcohol or reduced alcohol nitrogen (inert gas) can then be continuously recirculated to the polyester polyol synthesis. This ability to recirculate nitrogen significantly improves the economics of these reactions. A key economic activator for this procedure is the activation or close coupling of methyl ester synthesis and transesterification reactions, which use these esters as a source of fatty acid or carboxylic acid. Traditionally, methanol can be recovered from the source of inert gas through condensation, absorption into organic solvents (eg, triethylene glycol) or adsorption onto activated carbon. This reaction when coupled with a polyester polyol synthesis, removes a methanol recovery system separately, eliminates methanol handling and partially reduces methanol discharge to the environment. It is an object of this invention to provide an improved method for making polyol polyesters. It is further an object of this invention to provide an object for making methyl esters of fatty acids through a transesterification reaction, using gaseous methanol in a reactive adsorption column, which is coupled with a synthesis of polyol polyester.BRIEF DESCRIPTION OF THE INVENTION A process for preparing polyester polyol is claimed, wherein the synthesis of alkyl ester and the synthesis of polyol polyester are coupled. The reaction comprises the steps of making a triglyceride or other source of fatty acid with a gaseous mixture of an inert gas and lower alkyl alcohol at a temperature of between about 20 ° C to about 100 ° C, at a pressure of about 0.9842 to about 10.54 kg / cm2 (14 to approximately 150 psia) (kilograms per square centimeter absolute) in the presence of a catalyst. The molar ratio of methanol to triglyceride is in the range of 0.1: 1 to about 15: 1. Alkyl esters are prepared from glycerin through centrifugation or other separation technique, and from mono and diglycerides through fractionation, as is conventionally practiced in the art. The purified stream of the inert gas is recovered, which is used as the spray gas in a polyester polyol synthesis, where a polyol is reacted with the methyl ester recovered from the first step in a solvent-free two-stage process , which comprises forming partial polyol fatty acid esters from a reaction mixture containing fatty acid esters of an easily removable alcohol in the presence of an effective amount of a basic catalyst and optionally an effective amount of a soap emulsifier , and wherein the second step comprises polyol forming highly esterified fatty acid polyesters from a mixture containing the partial polyol fatty acid polyesters, a portion of the fatty acid esters and an effective amount of a basic catalyst. The polyol can also be an alkoxylated polyol having three or more hydroxy groups.

DESCRIPTION OF THE DRAWINGS Figure 1 shows a typical reactive adsorption column and the flow of materials to the reactor. A variety of column inmates can be used. The illustrated column uses interstage deflectors (11) to control the triglyceride flow, and agitation (15) to produce intimate contact of the gas and liquid phases. Figure 2 is a block diagram of the procedure. All percentages herein are by weight unless otherwise indicated.

DETAILED DESCRIPTION OF THE INVENTION The process is described in detail with reference to methyl esters and methyl alcohol, since these are the most commonly used lower alkyl group. However, it should be readily understood that any lower alkyl alcohol can be used. By lower alkyl alcohols is meant the Cj-Cg alcohol including all its isomers. Only monoalcohols are used. The process is used with triglycerides as the source of fatty acid, but any natural or synthetic source of fatty acid esters can be used in place of the triglyceride. For example, diglycerides, glycol esters, waxes or other sources can be used. Triglyceride is the preferred source, since it is a renewable resource, readily available and relatively inexpensive. Marine and fish oils are good sources of polyunsaturated fatty acids, vegetable oils and animal fats and oils are sources of saturated and unsaturated fatty acids. These fats and oils can be divided and selectively hydrogenated to produce the desired fatty acids for the formation of methyl or alkyl esters. Suitable preferred saturated fatty acids include, for example, acetic, butyric, caproic, caprylic, capric, lauric, myristic, palmitic, stearic, arachidic, behenic, isomiristic, isomargaric, hydroxystearate, and anteisoararacic acids. Suitable preferred unsaturated fatty acids include, for example, myristoleic, palmitoleic, ricinoleic, linoleic, oleic acids, elaidic, linolenic, eleosteric, arachidonic, erucic, and erythrogenic. The fatty acids can be used "as such" and / or after hydrogenation and / or isomerization and / or purification. The preferred sources of fatty acids are vegetable oils, hydrogenated vegetable oils, marine and fatty oils and animal oils. Preferred vegetable oils include corn oil, canola oil, olive oil, cottonseed oil, soybean oil, sunflower seed oil, rapeseed oil with a high content of erucic acid, partially or completely soybean oil hydrogenated, canola oil, partially or completely hydrogenated, partially or completely hydrogenated sunflower seed oil, rapeseed oil with a high content of partially or completely hydrogenated erucic acid and cottonseed oil, partially or completely hydrogenated. As used herein, the term "gas stream" means that it encompasses the mixture of alcohol and inert gas that is used in the reaction. This stream is a by-product of the polyol polyester synthesis step below. It can be used in this reaction, nitrogen, carbon dioxide, helium or other inert gas. Nitrogen is preferred due to its easy availability and cost. The stream or water is not acceptable since the water will neutralize the catalyst and can hydrolyze both the triglycerides and the methyl esters that are formed.

SYNTHESIS OF POLYOL POLYESTER The second step of the process of the present invention comprises the transesterification of a fatty acid methyl ester and a polyol. This transesterification reaction can occur in a one-step or two-step process, which can be solvent-based or solvent-free (See, for example, U.S. Patent 4,954,621 (Masaoka et al.); of the United States 4,968,791 (Van Der Plank), issued November 6, 1990; United States Patent 5,079,355 (Meszaros Grechke et al.) issued January 7, 1992; or United States Patent 5,071,975 (US Pat. See der Plank et al.) Issued December 10, 1991, incorporated herein by reference). Preferably, the transesterification reaction is a solvent-free two-step transesterification reaction, wherein polyol polyesters of fatty acid are present. When an esterification reaction, free of two-stage solvent, is used, the polyol partial polyesters of fatty acid are first formed from a heterogeneous mixture containing a polyol, at least a portion of the required quantity of the methyl esters of acid fatty, an effective amount of a basic catalyst and optionally, but, preferably, an emulsifier to improve the contact between the polyol (sucrose) and the methyl esters such as partial soap and / or sucrose esters. The starting materials, which are substantially free of glycerin and monoglyceride, are preferably selected for use herein. As used herein, the term "polyol" is intended to include any linear, cyclic or aromatic compound containing at least four free esterifiable hydroxyl groups, or a linear, cyclic or aromatic compound having at least three, esterifiable hydroxyl groups , free. Suitable polyols include monosaccharides such as mannose, galactose, arabinose, xylose, ribose, apiose, rhamnose, psychose, fructose, sorbose, tagitose, ribulose, xylulose, and erythrulose; the oligosaccharides such as maltose, kokibiosa, nigerose, cellobiose, lactose, melibiose, gentibiose, turanosa, rutinose, trehalose, sucrose and raffinose, and polysaccharides of amylose, glycogen, cellulose, chitin, inulin, agarose, zylan, mannan and galactans in the process of the present invention. The sugar alcohols most highly distributed in nature and suitable for use herein are sorbitol, mannitol and galactitol. The alkoxylated polyols include ethoxylated glycerin having an average of 3 to 15 propoxylated ethoxy and glycerin groups (See U.S. Patent 5,389,932, issued February 14, 1995, and 4,861,613, issued August 29, 1989 for examples of Suitable alkoxylated compounds Particularly preferred classes of materials suitable for use herein include monosaccharides, disaccharides and sugar alcohols.Preferred carbohydrates and sugar alcohols include xylitol, sorbitol and sucrose.The most preferred is sucrose. polyol with a small particle size, for example, sucrose in the esterification reactions to form polyol polyesters is highly desirable to improve the speed of the reaction.An improved reaction can be achieved without the use of a solvent, either in one step preliminary or in the same reaction, if the particle size of the solid polyol is less than about 100 microns, preferably less than about 50 microns, more preferably less than about 10 microns. These particle sizes can be varied, for example, through a combination of milling, shredding and / or screening. Alkaline metal soaps are typically and preferably used as emulsifiers in this process herein. For solid polyols, such as sucrose, it is believed that such soaps are essential. As used herein, the term, "alkali metal fatty acid soap" includes the alkali metal salts of saturated and unsaturated fatty acids having from about 8 to about 22 carbon atoms, preferably from about 8 to 18 carbon atoms. Accordingly, suitable alkali metal fatty acid soaps include, for example, the lithium, sodium, potassium, rubidium and cesium salts of the fatty acids described above. Mixtures of fatty acids derived from soybean oil, sunflower oil, safflower oil and corn oil are preferred. Accordingly, preferred alkali metal fatty acid soaps include potassium soap made from fatty acids of soybean oil. Although a certain level of soap is typically necessary for optimum performance, especially with solid polyols (eg, sucrose), the absolute level of the soap remains desirably low, even when there is another emulsifier present. The level of soap must be at least sufficient to dissolve the polyol at an affected rate. Therefore, the level of soap can be reduced as a result of a smaller particle polyol, for example, sucrose and / or reaction conditions that favor solubilization of the polyol. Too much soap can cause excessive foam formation. The level of soap in the first stage of the reaction, desirably is 0.001 of about 0.75, preferably about 0.1 to about 0.4 moles of soap per mole of polyol. The soap is preferably used in combination with another emulsifier preferably with the lower esters of the polyol and the fatty acid which are present either being added as part of the initial reaction mixture, or by mixing. Also, the soap preferably is potassium soap of hydrogenated fatty acids containing from about 8 to about 22 carbon atoms. As the fatty acid ester actives, it is also highly desirable that the soap contain little or no digrase ketones and / or β-ketoesters. These byproducts can be formed in. soap as a result of contact with basic reagents, such as potassium hydroxide, used during saponification. Preferably, the soap contains about 10 ppm or less of difatty ketones and / or β-ketoesters. Suitable basic catalysts for use in the preparation of the polyol fatty acid polyesters described in the present invention include alkali metals, such as sodium, lithium and potassium, alloys of two or more alkali metals, such as sodium-lithium alloys and sodium potassium; alkali metal hydrides, such as sodium, lithium and potassium hydride; alkali metal lower alkyls (C ^ C ^) such as butyllithium and alkali metal (C1-C4) alkoxides of lower alcohols, such as lithium methoxide, potassium t-butoxide, potassium methoxide, and / or methoxide of Sodium Potassium methoxide is preferred, especially when used with potassium soap Certain basic catalysts, such as sodium and potassium hydride, are particularly prone to generate digrase ketones and / or keto esters Another particularly preferred class of catalyst basic includes potassium carbonate, sodium carbonate, barium carbonate or mixtures of these compounds having particle sizes that are less than about 100 microns, of less than about 50 microns, as discussed in more detail below. It has been found that when these specific compounds are used as catalysts, improved yields of the higher color polyol polyesters are obtained. igero, when compared to essentially identical reactions performed using more conventional catalysts, such as sodium hydride, potassium hydride, soap or sodium methoxide. These preferred catalysts also prefer to be used in admixture with the more conventional basic catalysts, described above. The most preferred catalysts for use herein are potassium carbonate and / or potassium methoxide. The use of these catalysts are further described in U.S. Pat. No. 4,571,360 (Volpenhein), issued May 14, 1985, which is incorporated herein by reference. More reactive catalysts such as potassium or sodium methoxide can be protected until added to the reaction mixture. Preferably, the catalyst must be suspended in, or very preferably encapsulated with, a material that will be present in the reaction mixture or easily separated from the reaction mixture. Suitable encapsulating agents include alkyl esters of, for example, ci6 ~ c22- fatty acids (As described below, these catalysts can also be protected when prepared from, and stored in a lower alcohol (C ^ - C ^), such as methanol, under anhydrous conditions). The addition of these reactive catalysts plus alkanes in the second step of the reaction after the polyol has an average degree of esterification of greater than about 60%, preferably more than about 85%, provides an improved reaction kinetics and gives as resulting in a higher degree of esterification of the polyol that does not create the level of the color / odor materials that could be created if such catalysts were present from the start of the reaction. The catalyst level is kept as low as possible, particularly in the second stage of the reaction, as fully discussed below, typically in the range of from about 0.01 to about 0.5, preferably from about 0.01 to about 0.1, more preferably from about 0.02 to about 0.05, moles of catalyst per mole of polyol. The level of catalyst can be reduced to the smallest amount that is effective to give a reasonable rate of reaction. It is possible to have very rapid reactions, using only the residual base in, for example, the soap emulsifier commonly used in such reactions. It is desirable to keep the level of the base as low as possible to minimize the formation of colored bodies and / or odor and / or excess soap and / or by-products. It is also desirable to effect the removal of the oversized catalyst after the first reaction step and / or the destruction and removal of the catalyst after the reaction has reached the desired end point. Typically, the molar ratio of the fatty acid methyl esters to the polyol varies from about 8: 1 to about 13.5: 1. If soap is used as an emulsifier, the molar ratio of the soap to the polyol typically ranges from about 0.08: 1 to about 0.75: 1. If partial sucrose esters are used as an emulsifier, these may be added to the starting mixture at a level of 1% to 50% by weight, preferably 5% to 30%, more preferably 10% to 20%. It is advantageous to use combinations of fatty esters and soap. The ratio of the catalyst to the polyol typically ranges from about 0.02: 1 to about 0.2: 1. The precise relationship of these reagents can be freely selected within the previously described guide lines. However, some routine experimentation may be necessary in order to establish the optimal relationships for a given group of reagents. The first stage reaction mixture can be formed in a solvent-free form or by using a solvent such as water to dissolve one or more of the reactants (eg, sucrose), followed by removal of the solvent prior to carrying out the first stage reaction. This first stage reaction mixture is then heated to an appropriate temperature to provide a melt bath, in which the polyol and the fatty acid methyl esters react to form partial polyol fatty acid esters. As used herein, the term "polyol fatty acid partial esters" are those polyol esters wherein up to about 50% of the hydroxy groups of the polyol have been esterified.

In the case of sucrose, the primary sucrose fatty acid partial esters are the mono-, di and / or triesters. The end of the first stage of the reaction is usually determined by measuring the level of unreacted polyol in the reaction mixture. In the case of sucrose, the end of the first stage typically occurs when the level of unreacted sucrose is less than 1%. The reaction mixture of the first stage is typically heated to temperatures from about 129.4 ° to about 140.6 ° C (265 ° to about 285 ° F), preferably from about 132.2 ° C to about 135 ° C (270 ° to about 275 ° C) F). These reaction temperatures typically obtain a rapid initial esterification of the polyol to form the partial polyester polyols of the fatty acid without excessive degradation of the polyol. The first stage reaction is also desirably performed with a spray of the inert gas, such as the methane partial pressure which is from about 1 to about 100 mm Hg, preferably from about 5 to about 50 mm Hg. If the soap is the emulsifier, then the average degree of esterification reaches approximately 60%, the soap emulsifier is no longer needed to facilitate the reaction and, therefore, can be removed. The soap emulsifier is not essential after the polyol has reacted once and there is enough partial ester to maintain the homogeneity of the reaction mixture. The removal of the soap can be achieved for example, through filtration, centrifugation, etc., since the soap is relatively insoluble in the reaction mixture at high degrees of esterification. The filtered reaction mixture typically has a soap level of less than about 0.5, preferably less than about 0.1 moles of soap per mole of polyol, more preferably less than about 0.05 moles of soap per mole of polyol. The filtrate of the reaction can be used as a reagent in the first stage reaction mixture. However, since the composition of this material may vary, it is usually best not to recirculate it. Also, the unreacted polyol and / or the large particle catalyst are desirably removed from the reaction mixture through filtration and / or centrifugation. In the second step of the solvent-free transesterification reaction, highly esterified fatty acid polyester polyol is formed from a reaction mixture containing the partial polyol fatty acid esters. The remaining portion of the methyl esters of fatty acid has an effective amount of a basic catalyst. This remaining portion of the fatty acid methyl esters can be obtained by including an excess thereof in the first stage reaction mixture, ie, an amount beyond that required to form the partial polyol fatty acid esters ("addition"). one-stage "). However, the remaining portion of the fatty acid methyl esters required to obtain highly esterified polyol fatty acid polyesters is typically added to the reaction mixture resulting from the first stage of the reaction ("two step" addition). The reaction mixture resulting from the first stage of the reaction may contain sufficient basic catalyst for the purposes of the second stage of the reaction. However, more basic catalyst could be added if necessary. This additional basic catalyst may be the same as the basic catalyst used in the first stage of the reaction, or it may be a different basic catalyst. During the second stage of the reaction, the lower fatty acid polyol esters and the remaining portion of the fatty acid esters react to provide polyol polyesters of highly esterified fatty acid. As used herein, the term "polyol ester of highly esterified fatty acid" refers to a polyol wherein at least about 50%, preferably at least about 70% and more preferably at least about 96%, of the hydroxy groups, are esterified. In the case of highly esterified sucrose polyesters, this typically refers to hexa, hepta and particularly octa esters. For example, if at least about 96% of the sucrose hydroxy groups are esterified, at least about 70% of the sucrose esters are sucrose octaesters. During both stages, an inert gas spray is used to remove the lower alkyl alcohols as they are formed and to avoid the oxidation reactions that occur. This stream of inert gas / lower alkyl alcohol is converted into a feed stream for the synthesis of methyl ester described below.

SYNTHESIS OF METALLIC ESTER The triglyceride is converted to the methyl ester or lower alkyl ester by the following procedure: the triglyceride is contacted with a gaseous stream of nitrogen or other inert gas and lower alkyl alcohol in an intermittent reactor or preferably in a continuous reactive absorption column . Methanol contains 1 to 10% of the gas stream. The partial pressure of the alcohol in the gas stream affects the solubility of the alcohol and activates the reaction. Therefore, the concentration of the alcohol in the inert gas as well as the temperature and pressure of the inlet gas stream / alcohol are important. The gas / ethanol stream enters the column in (1) and disperses through the spray ring (13). The flow velocity of the gas stream, i.e. the nitrogen-alcohol mixture, as the column enters, is from about 0.1: 1 to about 7.5: 1 (basis by weight) relative to the triglyceride flow. The exact shape and structure of the spray devices are not critical to the reaction, and their configuration is easily determined by one skilled in the art. What is important is that the inert gas / alcohol stream is dispersed in the triglyceride in a form that comes in contact with the triglyceride, effectively allowing the alcohol to be absorbed and reacted with the triglyceride, and in this way convert the acids fatty to esters of alcohol. For a maximum conversion of the triglyceride to the alkyl ester, a molar excess of alcohol is used; in the range of 3 moles of alcohol to one mole of triglyceride up to a ratio of approximately 15: 1. This represents a ratio of 1 to 5 times of alcohol to fatty acid group. For the maximum removal of methanol from the nitrogen stream an excess of triglyceride is used. In this case, the ratio of alcohol to triglyceride is from 0.1: 1 to approximately 3: 1. Under preferred conditions, both the high methyl ester conversion and the alcohol removal are obtained. The triglyceride or other source of fatty acid is mixed with an esterification catalyst and added to the reactor. In a countercurrent column reactor, enter 3 and flow down the column. The column contains a material that disperses nitrogen and inert gas and methanol in the triglyceride. Packing or agitated steps 15 are preferred as shown in Figure 1. Other columns may be used such as tray columns, perforated disk columns and bubble columns. The exact type of column that is used is not critical and depends on a number of factors, which will be readily apparent to those skilled in the art. Nitrogen and methyl alcohol can be contacted with the triglyceride in a variety of ways including countercurrent, concurrent or intermittent systems. The countercurrent is the preferred method. Basic catalysts suitable for use in preparing methyl esters used in the process of the present invention include alkali metals such as sodium, lithium and potassium; alloys of two or more alkali metals, such as sodium-lithium and sodium-potassium alloys; alkali metal hydrides, such as sodium, lithium and potassium hydride, lower alkali metal alkyl, (C1-C4) such as butyl lithium; and (C 1 -C 4) alkali metal alkoxides of alcohols, such as lithium methoxide, potassium t-butoxide, potassium methoxide and / or sodium methoxide, The preferred catalyst is a basic catalyst, eg, a hydroxide, alkoxide or alkali metal or alkaline earth metal carbonate. Preferably, the reaction is catalyzed by potassium or sodium alkoxide, corresponding to the lower alkyl alcohol. When methanol is lower alkyl alcohol, sodium or potassium methoxide is used. Alkali metal alkoxides are readily available in commercial form or can be prepared through the reaction of potassium or sodium with an excess of alcohol. The most preferred catalysts are sodium or potassium methoxide or potassium carbonate. Acid catalysts such as p-toluenesulfdnico acid can also be used, phosphonic acid, sodium potassium mono or diphosphate, hydrochloric acid or sulfuric acid. The catalyst is typically used at a level of from about 0.1% to about 1.0% of the triglyceride (base in weight). As the mono and diglycerides are formed, they facilitate the reaction and create a foam. The reaction time may vary from 5 minutes to 5 hours, preferably from 1/2 hour to 2 hours. The exact time depends on the size of the reaction vessel, as well as the material flow velocity, temperatures and pressure. In a reaction column, the triglyceride is added to the reaction vessel, together with the catalyst. Nitrogen and methyl alcohol are passed from a transesterification of polyol polyester, through the column and brought into contact with the triglyceride. A preferred source of this gas stream is the transesterification synthesis reaction of the polyester polyol, using methyl esters as the source of the fatty acid. The gas stream is mixed with triglyceride in a ratio of about 15 moles of alcohol per mole of triglyceride to about 3 moles of lower alkyl alcohol per mole of triglyceride. This causes the reaction to proceed so that most of the triglyceride (from 80% to 95%) is converted to methyl esters. When this reaction is used to clean the inert gas stream, the molar ratio of alcohol to triglyceride is from 0.1: 1 to about 3: 1. The reaction temperature is between about 20 ° C and about 100 ° C. The pressure of preference is atmospheric or above atmospheric. Generally, the reaction is performed between 0.9482 kg / cm2a at approximately 10.54 kg / cm2. The preferred pressure level for introducing methanol is in the range of 1053 kg / cm2 to 8.7875 kg / cm2 and more preferably 2.4605 kg / cm2 to 7.03 kg / cm2. The glycerin esters and any monoglyceride and diglyceride are recovered from the bottom of the column as a mixture with any unreacted triglyceride. In the countercurrent column reactor, these salts are through 3. The mixture is first separated by sedimentation or centrifugation, wherein the glycerin is also separated from the mixture. Optionally, additional methanol or alcohol can be added to activate the reaction that comes to term. In this case, a separation step of glycerin is referred to. The remaining catalyst and glycerin are removed by washing with water of the crude reaction mixture. The catalyst and glycerin dissolve in the water and the esters are removed by sedimentation or centrifugation. Cleaning of the crude reaction mixture is achieved through conventional processing. The methyl esters are then separated or purified by distillation or other conventional means. The methyl esters can be further purified through fractionation, including molecular distillation, if desired.

The inert gas used in this reaction preferably is recovered from the transesterification reaction of polyol polyester. The nitrogen leaving this reaction is typically less than 2000 ppm methanol or alcohol and can be as low as 50 ppm alcohol. The lower levels of methanol or residual alcohol in the nitrogen are reacted with excess triglycerides. The nitrogen exhaust is then used to spray the polyester polyol process. The following examples illustrate this invention, but are not intended to limit the same. Examples 1 to 3 are intended to show what lower levels of residual alcohol can be achieved in nitrogen (50 ppm at 520 ppm) at a broader range of pressures (1.0545 to 5.9755 kg / cm2) (15 psig or 85 psig) with a stoichiometric excess of triglyceride. The conversion of methyl esters was low in each case (approximately 20%).

Example 1 INGREDIENTS AMOUNT soybean oil stoichiometric excess (23.61 kg / h) sodium methoxide 0.05 mol / mol nitrogen oil 14.5 kg / h methanol 4.0 g / min (16% N2) In a continuous multistage stirred column was fed triglyceride (refined, decolorized and deodorized soybean oil) containing sodium methoxide, continuously in the upper part of the reactor. The reactor has a diameter of 15.24 cm (6 inches) and a height of 121.9 cm (48 inches) and has 10 agitated stages. The agitator was operated at approximately 1500 rpm. The column was configured as in Figure 1. The triglyceride was passed countercurrent to a methanol / nitrogen stream fed from the bottom of the reactor. The reactor was maintained at 38 ° C and 4.54 kg / cm2 (64.7 psia) to (3.51 kg / cm2m) (50 psig). The nitrogen / methanol flow is 14.5 kg / h (32 lb / h). The nitrogen stream of the product contains 40 ppm of methanol. This nitrogen stream was used in the polyester polyol synthesis described in Example 6.

EXAMPLE 2 In a reaction similar to Example 1, the nitrogen gas stream containing 1.6% methanol derived from a polyol polyester synthesis, and passed through the column at 23.6 kg / hour (52 pounds / hour). The triglyceride containing 0.05 moles of solid sodium methoxide per mole of triglyceride was fed to the top of the column at 23.6 kg / hour (52 pounds / hour). The temperature is 43 ° C and the pressure is 7,008 kg / cm2a (99.7 psia). The nitrogen outlet has 80 ppm of methanol therein.

EXAMPLE 3 Reactive absorption was performed in a multi-stage countercurrent stirred column. The triglyceride was continuously fed to the top of the reactor and the product was expelled to the bottom. The nitrogen / methanol was fed to the bottom of the reactor and discharged at the top. A stoichiometric excess of triglyceride was used.

Terms ? Liquid feed - 23.6 kg / hour (52 lb / h) catalyzed triglyceride (0.05 moles of solid NaOCH3 per mole of triglyceride) Gas feed - 14.5 kg / hour (32 lb / h) nitrogen, 4.0 grams / minute, methanol ( 16% MeOH) Temperature 37 ° C (98 ° F) Pressure - 1.0545 kg / cm2a (15 psig) Results: 520 ppm (0.52%) of methanol in nitrogen output.

EXAMPLE 4 Reactive absorption was carried out in a multistage, countercurrent stirred column, as in the previous example. The triglyceride was continuously fed to the top of the reactor and the product was expelled to the bottom. Nitrogen / methanol was fed to the bottom of the reactor and discharged at the top. Approximately a stoichiometric amount of triglyceride and methanol was used.

Conditions: Liquid feed - 36.28 kg / h (80 lb / h) of catalyzed triglyceride (0.15 mol of solid NaOCH3 per mol of triglyceride) Gas feed - 90.71 kg / h (200 lb / h) of nitrogen, 3.538 kg / h (7.8 lbs / h) of methanol Temperature 54 ° C (130 ° F) Pressure - 4.569 kg / cm2 (65 psig) Rebulls: 2000 ppm (0.20%) of methanol in nitrogen output 81% conversion of triglyceride to methyl esters.

EXAMPLE 5 Reactive absorption conversion of triglyceride to methyl esters was analyzed in an intermittent stirred reactor of 1.5 liters. A stoichiometric excess of methanol was bubbled through catalyzed triglyceride. Conditions,; Liquid - 883 grams of triglyceride, 3.05 of sodium methoxide catalyst Gas - 1.6 liters / minute, nitrogen, 2.1 grams / minute, methanol Temperature -90 ° C (194 ° F) Pressure - atmospheric (14.7 psia) Results: 55% of conversion of triglyceride to methyl esters in 30 minutes. 80% conversion to methyl esters in 75 minutes. The reaction mixture at 80% conversion was allowed to settle giving as a result of two phases. The heavier phase (mainly glycerin) was removed. The remaining mixture was further reacted under conditions similar to those described above for 75 minutes, leading to 96% methyl esters in the final product. These methyl esters were purified and then used in a synthesis as described in Example 6.

EXAMPLE 6 Methyl ester 597.9 kg (1,317 pounds) was mixed with 90.8 kg (200 pounds) of potassium stearate, 13.2 kg (300 pounds) of granulated sucrose and 5.4 kg (12 pounds) of granulated potassium carbonate in a 2835 liter reactor (750 gallons) for 7.5 hours at a temperature of 135 ° C with a nitrogen spray to maintain the partial pressure of methanol below 10 mm Hg. Additional 951.1 kg (2.095 pounds) and 5.4 kg (12 pounds) granulated carbonate were added to the reactor and mixed for an additional 5 hours at 135 ° C while maintaining a methanol partial pressure of less than 4 mm Hg until the composition of polyester polyol is 74.9% octaester, 24.8% heptaester and 0.25% hexaester and lower. The nitrogen gas with methanol was sent to a reactive absorption vessel as described in Example 1. The soap was removed by adding 95.7 kg (211 pounds), if the deionized water is at 77 ° C, in a stirred tank reactor of 2835 liters (750 gallons) and centrifuged. Color levels and lower soap levels were removed by washing with water with 285.5 kg (629 pounds) of deionized water at 77 ° C in a stirred tank reactor for 10 minutes at a low rpm. The water was sedimented for an hour through gravity and then drained from the bottom of the reactor. The product was dried by reducing the pressure to < 10 mm Hg and maintaining the temperature at 65 ° -80 ° C. 15.8 kg (35 pounds) silica gel was mixed with a dry product at 77 ° C for 30 minutes. The silica gel was removed at a filter pressure and the product was then evaporated at a temperature of 235 ° C (455 ° F) at a pressure of 1.0 mm Hg and finally the vapor was separated with 10% steam in a column Packed at a temperature of 235 ° C (455 ° F) and a pressure of 2 mm Hg.

Example 7 Approximately 200 g / min of feed composed of 9% sucrose, 85.0% methyl esters, 1% potassium methoxide catalyst and 5% potassium stearate was fed to a continuous reactor. Approximately 400 g / min of nitrogen was fed to the bottom of the reactor. The temperature remained absolutely at 275 ° F and the pressure was absolutely atmospheric. The reaction proceeded to approximately 97% sucrose to sucrose polyester. The nitrogen stream effluent approximately 3% methanol. This nitrogen stream was compressed at 4.56 kg / cm2m (65 psig), cooled below 37.77 ° C (100 ° F) and fed to the bottom of the reagent absorption column. Then, 140 g / min. Of triglyceride was fed with 1 g / min. of NaOCH3 from the catalyst to the top of this column and reacted to form methyl esters as described in EXAMPLE 4. The reactive absorption column was maintained at approximately 37.77 ° C (100 ° F). The triglyceride was converted to approximately 80% methyl esters while the methanol was simultaneously removed from the nitrogen stream. The nitrogen stream that exited contained approximately 2000 ppm methanol. The nitrogen stream was then recirculated to the first reactor. The methyl esters produced in the second reaction were additionally made with an excess of methanol, achieving approximately 99% conversion. These esters were then washed 3 times with 10% by weight of water and divided into a rubbed film evaporator. The divided methyl esters were made part of the feed material to the first continuous reactor.

Claims (10)

1. A process for preparing polyol polyesters of fatty acid, the process is characterized in that it comprises the steps of: (A) preparing methyl esters of fatty acid, through (i) reacting a source of fatty acid with an intimate mixture of a gas inert and a lower alkyl alcohol at a temperature between 200 ° C to 100 ° C at a pressure of 14 to 150 psia in the presence of a catalyst; and (ii) recovering the methyl esters and thereafter; (B) transesterifying the methyl esters of fatty acid and a polyol in a solvent-free two-step process, which comprises forming partial polyol fatty acid esters from a polyol-containing reaction mixture and at least a portion of the fatty acid esters of the easily removable alcohol in the presence of an effective amount of a basic catalyst and optionally an effective amount of soap emulsifier and wherein the second stage comprises polyol highly esterified fatty acid polyesters from a reaction mixture containing the polyol polyesters of fatty acid, the remaining portion of the fatty acid esters and an effective amount of a basic catalyst, both steps are conducted in the presence of an inert gas, wherein the inert gas is recirculated between the step (A ) and step (B).

2. The process according to claim 1, characterized in that the catalyst in both steps is selected from the group consisting of sodium methoxide, sodium or potassium alkoxide, sodium or potassium carbonate, and mixtures thereof.

3. The process according to claim 1 or 2, characterized in that the lower alkyl alcohol is methanol and the inert gas is nitrogen.

4. The process according to claims 1, 2 or 3, characterized in that the source of fatty acid is a triglyceride selected from the group consisting of vegetable oils, hydrogenated vegetable oils, marine oils and animal fats and oils.

5. The process according to claims 1, 2, 3 or 4, characterized in that the molar ratio of the lower alkyl alcohol to triglyceride is from 0.: 1 to 15: 1.

6. The process according to claims 1, 2, 3, 4 or 5 characterized in that the methyl ester reaction of step (A) is conducted in a reaction column.

7. The method according to claim 6, characterized in that the column is selected from the group consisting of packed columns, tray columns, perforated disk columns, bubble columns and agitated columns.

8. The process according to claims 1, 2, 3, 4, 5, 6, 7 or 8, characterized in that the polyol is a sugar or a sugar alcohol, and wherein the level of soap in step (B) is from 0.01 to 0.75 moles per mole of polyol.

9. The process according to claims 1, 2, 3, 4, 5, 6, 7 or 8, characterized in that the inert gas is recirculated nitrogen from step (A).

10. The process according to claims 1, 2, 3, 4, 5, 6, 7, 8 or 9 characterized in that the molar ratio of fatty acid esters to polyol is from 8: 1 to 13.5: 1, wherein the temperature from step (B) is from 129.4 ° C to 132 ° C, and where the partial pressure of the methanol in step (B) is from 1 to about 100 mm Hg.