FI79522B - FOERFARANDE FOER SEPARERING AV FETTSYROR. - Google Patents

Description

1 79522

Method for the separation of fatty acids

The field of application of this invention is solid state absorbent separation of fatty acids. More specifically, this invention relates to a process for the separation of fatty acids which uses an adsorbent consisting of certain polymers which selectively adsorb one fatty acid from a feed mixture containing more than one fatty acid.

It is known in the art of separation that certain crystalline aluminosilicates can be used to separate certain fatty acid esters from their mixtures. For example, U.S. Patents 4,048,205, 4,049,688 and 4,066,677 disclose methods for separating fatty acid esters of varying degrees of unsaturation from mixtures of saturated and unsaturated fatty acid esters. These methods use adsorbents consisting of X or Y zeolites containing the selected cation at interchangeable cationic sites.

In contrast, this invention relates to the separation of certain fatty acids and not fatty acid esters. It has now been found that absorbents consisting of nonionic hydrophobic insoluble, crosslinked polystyrene polymers have adsorption selectivity over one fatty acid over another fatty acid, which makes it possible to separate such fatty acids by selective adsorption of a solid layer. In a specific embodiment, the invention relates to a method for separating stearic acid from palmitic acid. In another specific embodiment, the invention relates to a method for separating oleic acid from linoleic acid. Fatty acids have considerable use in the field of plasticizers and surfactants. Fatty acid derivatives have value in the blending of lubricating oils, as a lubricant in the textile and casting industries in specialty varnishes, as water-resistant agents, 2,795,22 in the cosmetics and pharmaceutical industries, and as biodegradable detergents.

Briefly, in one embodiment, the invention is a method of separating a first fatty acid selected from the group consisting of stearic acid and oleic acid from a mixture of a first fatty acid and a second fatty acid selected from the group consisting of palmitic acid and linoleic acid. contacting the mixture with an adsorbent consisting of a nonionic hydrophobic, insoluble, crosslinked polystyrene polymer having adsorption selectivity for the first fatty acid, wherein the first fatty acid is selectively adsorbed on the oil when the first acid is acidic acid, the first acid is stearic acid, , the second acid is linoleic acid.

In yet another embodiment, the invention relates to a process for separating a first fatty acid selected from the group consisting of stearic acid and oleic acid from a mixture comprising a first fatty acid and a second fatty acid selected from the group consisting of palmitic acid and linoleic acid, wherein the first acid is stearic acid. the second acid being palmitic acid and wherein when the first acid is oleic acid, the second acid is linoleic acid, and wherein the method uses an adsorbent consisting of a nonionic, hydrophobic, insoluble, crosslinked polystyrene polymer comprising the steps of: (a) maintaining a net flow of adsorption in the direction in which the column contains at least three zones in which separate functional functions take place and which are connected in series with the end zones of said column which are connected to provide a continuous connection of the zones? (b) maintaining in the column an adsorption zone, a zone defined by an adsorbent located between the feed inlet stream at the upstream boundary of the zone and the raffinate effluent at the downstream boundary of the zone; (c) maintaining a purge zone immediately upstream of the adsorption zone, the purge zone of which is defined by an adsorbent located between the extract effluent at the upstream boundary of the purge zone and the feed inlet stream at the downstream boundary of the purge zone; (d) maintaining a desorption zone immediately upstream of the purification zone, the desorption zone of which is defined by an adsorbent located between the feed stream of the desorbent at the upstream boundary of the zone and the extract effluent at the downstream boundary of the zone; (e) introducing the feed mixture into the adsorption zone under adsorption conditions to effect selective adsorption of the first fatty acid by the adsorbent in the adsorption zone and removing the raffinate effluent consisting of the second fatty acid from the adsorption zone; (f) passing the desorption material to the desorption zone under pre-sorption conditions to effect displacement of the first fatty acid from the adsorbent in the desorption zone; (g) removing the extract effluent consisting of the first fatty acid and the desorption material from the desorption zone; (h) passing at least a portion of the extract effluent to a separation device and separating at least a portion of the desorption material therein under separation conditions; and (i) periodically advancing through the adsorbent column downstream of the liquid flow in the adsorption zone, feed inlet stream, raffinate effluent, desorbent inlet stream and extract effluent to perform zone transfer through the adsorbent and extract effluent and extract effluent.

Other embodiments of the present invention comprise details of the feed, adsorbents, desorbent, desorbent materials and operating conditions, all of which will be described below on each side of the present invention in the following description.

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Initially, the definitions of the various terms used throughout the patent specification are useful in explaining the operation, purposes, and advantages of the method.

A "feed mixture" is a mixture containing one or more extraction components and one or more raffinate components to be separated by this method. The phrase "feed stream" means the stream of the feed mixture that enters the adsorbent used in the process.

An "extract component" is a compound or type of compound that is more selectively adsorbed by an adsorbent, while a "raffinate component" is a compound or type of compound that is less selectively adsorbed. In this method, the first fatty acid is an extract component and the second fatty acid is a raffinate component. The phrase "desorbent material" generally means a material capable of desorbing an extract component. The phrase "desorbent stream" or "desorbent inlet stream" means the stream with which the desorbent material enters the adsorbent. The phrase "raffinate stream" or "raffinate effluent" means a stream with which the raffinate component is removed from the adsorbent.

The composition of the raffinate stream can range from substantially 100% desorbent material to substantially 100% raffinate components. The phrase "extract stream" or "extract effluent stream" means a stream in which an extract material desorbed with a desorbent material is removed from an adsorbent. The composition of the extract stream can also vary from substantially 100% desorbent material to substantially 100% extract components. At least a portion of the extract stream, and preferably at least a portion of the raffinate stream from the separation process, is passed to a separation plant, typically fractional distillation equipment, in which at least a portion of the desorbent material is separated to produce an extract product and a raffinate product. The terms "extract product" and "raffinate product" refer to products produced by the process that contain, in that order, the extract component and the raffinate component in higher concentrations than those found in the extract stream and the raffinate stream. Although the process of this invention makes it possible to produce a high purity first acid product or a second fatty acid product (or both) in high yields, it should be noted that the adsorbent never completely adsorbs the extract component and the adsorbent is not completely adsorbed to the raffinate component. Therefore, varying amounts of raffinate component may be present in the extract stream and also varying amounts of extract component may be present in the raffinate stream. The extract and raffinate streams are then further separated from each other and from the feed mixture based on the ratio of the extract component to the raffinate component concentrations present in each stream. Most specifically, the ratio of the concentration of the first fatty acid to the concentration of the less selectively adsorbed second fatty acid is lowest in the raffinate stream, next highest in the feed mixture and highest in the extract stream. Likewise, the ratio of the concentration of the less selectively adsorbed first fatty acid to the concentration of the more selectively adsorbed second fatty acid is highest in the raffinate stream, followed by the highest in the feed mixture and lowest in the extract stream.

The phrase "selective pore volume" of an adsorbent is defined as the volume of adsorbent that selectively adsorbs the extract component from the feed mixture. The phrase "non-selective pore volume" of the adsorbent is the volume of the adsorbent that does not selectively retain the extract component from the feed mixture. This volume comprises cavities of the adsorbent which do not contain adsorbent sites and pore spaces between the adsorbent particles. Selective pore volume and non-selective cavity volume are generally expressed in volumetric amounts and are important in determining the appropriate fluid flow rates required to be introduced into the operating zone in order for efficient operations to occur with a given amount of adsorbent. When the adsorbent "enters" the operating zone (defined and described below) used in one embodiment of this method, its non-selective pore volume, together with its selective pore volume, transports the liquid to that zone. The non-selective pore volume is used to determine the amount of liquid that should enter the zone directly upstream of the adsorbent to replace the liquid in the non-selective pore volume. If the amount of liquid entering the zone is less than that. non-selective pore volume of the adsorbent material entering the zone, a net liquid effluent to the zone by the adsorbent. Because this net effluent is liquid / present in the non-selective pore volume of the adsorbent, it contains in most cases less selectively retained feed components. The selective pore volume of the adsorbent may in certain cases adsorb portions of the raffinate material from the liquid surrounding the adsorbent, as in certain cases there is competition between the extract material and the raffinate material for adsorbing sites in the selective pore volume. If a large amount of raffinate material relative to the extract material surrounds the adsorbent, the raffinate material may be competitive enough to adsorb to the adsorbent.

Before considering feed mixtures that can be fed into the process of this invention, reference will first be made briefly to the terminology and general production of fatty acids. Fatty acids are a large group of aliphatic monocarboxylic acids, many of which are present as glycerides (glycerol esters) in natural fats and oils. Although some have limited the term "fatty acids" to a series of acetic acids for both normal and branched chain saturated acids, it is now widely used, and also used herein, to include closely related unsaturated acids, certain substituted acids, and even aliphatic acids containing alicyclic substituents and substituents. are a few exceptions, with the exception of acids containing an even number of 7 79522 carbon atoms. Unsaturated fatty acids can be divided into monoethanoid, diethanoid, trietanoid, etc. (or monoethylene, etc.) based on the number of double bonds in the hydrocarbon chain. for a fatty acid having at least one double bond and the phrase "polyethanoid fatty acid" means a fatty acid having more than one double bond per molecule. Fatty acids are typically prepared from glyceride fats or oils by one of several "cleavage" or hydrolytic methods. In all cases, the hydrolysis reaction can be concentrated to a reaction of a fat or oil with water, which produces fatty acids plus glycerol. In modern fatty acid plants, this process is performed by continuous high pressure and high temperature hydrolysis of fat. The most commonly used feedstocks for the production of fatty acids are coconut oil, palm oil, inedible animal fats and commonly used vegetable oils, soybean oil, cottonseed oil and corn oil. The composition of the fatty acids obtained from the "cleavage" depends on the fat or oil from which it is made.

As detailed information on the fatty acid composition of fats has accumulated over a wide range of materials, it has become increasingly apparent that the component acids of natural fats tend to group them according to their biological origin. Moreover, it has been found that the fats of the simplest and most primitive organisms are usually composed of a very complex mixture of fatty acids, while as biological development progresses, the major component acids of the fats of higher organisms have become fewer in number. In the animal kingdom, this type change is remarkably consistent and culminates in fats from higher terrestrial animals to fats in which oleic, palmitic, and stearic acids are the only major components. All fats from aquatic animals contain a large number of combined fatty acids, which are mainly unsaturated series. The transition from aquatic to terrestrial fats also results in a significant simplification of the composition of mixed fatty acids; most unsaturated acids except oleic acid disappear.

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As a result, in most higher terrestrial animals, the major component acids of fats are limited to oleic, palmitic, and stearic acids, and in addition, about 60-65% of the acids belong to the C 1-4 series, saturated or unsaturated. Thus, the composition of the fatty acids obtained from the "cleaver" can vary widely depending on the fat or oil fed to the "cleaver". Rarely, the composition of the fatty acid mixture obtained from the "cleaver" is ideal or even satisfactory for most uses. Therefore, fractionation is used almost universally to produce products that are more desirable for certain end uses than "splitter" mixtures. Molecular weight fractionation is usually carried out by fractional distillation. There is some difference in the volatility of any two fatty acids of different chain lengths and in practice the usefulness of fractional distillation is enhanced by the absence of odd acids from natural fats so that 2 carbon atoms is almost always the minimum difference in chain length of fatty acids in the mixture. In such an operation, fractionation columns are sometimes capable of producing fatty acids with a purity of 95% or better in terms of chain length, depending on the chain length in question. However, it is not possible to separate unsaturated fatty acids or saturated fatty acids by commercial fractional distillation when all have the same chain length or a very small difference in chain length.

The invention relates to the separation of certain mixtures of these fatty acids; more specifically, it is directed to separating the first fatty acid from a mixture comprising a first fatty acid and a second fatty acid, wherein when the first fatty acid is stearic acid the second fatty acid is palmitic acid and wherein when the first fatty acid is oleic acid the second fatty acid is linoleic acid. An example of a typical feed mixture is known as "tall oil fatty acids" and contains about 1% by volume of palmitic acid, 2% by volume of stearic acid, 51% by volume of oleic acid, 45% by volume of linoleic acid and 4% by volume of 9,79522 others. The feed mixtures that can be fed to the process may contain, in addition to fatty acids, a diluent material which is not adsorbed by the adsorbent and which is preferably separable from the extract and raffinate effluents by fractional distillation. When a diluent is used, the diluted concentration in the mixture of diluted and fatty acids can be from a few% by volume up to about 90% by volume.

The desorbent materials used in various prior adsorption separation processes in the art will vary depending on such factors as the type of operation used. In fluidized bed systems where the selectively adsorbed feed component is removed from the adsorbent by a cleaning stream, the choice of desorbent is less critical and desorbent materials consisting of gaseous hydrocarbons such as methane, ethane, etc. or other types of gases such as nitrogen or hydrogen may be used. pressures or both to effectively purify the adsorbed feed component from the adsorbent. However, in adsorption separation processes, which are generally used continuously at substantially constant pressures and temperatures to ensure the liquid phase, the desorbent material must be chosen judiciously to satisfy many criteria. First, the desorbent material should displace the extract component from the adsorbent at reasonable mass flow rates without being strongly adsorbed by itself so as not to unduly prevent the extract component from displacing the desorbent material in the next adsorption cycle. Expressed as selectivity (described in more detail below), it is preferred that the adsorbent be more selective for all extract components compared to the raffinate component than it is for the desorbent material compared to the raffinate component. Second, the desorbent materials must be compatible with the particular adsorbent and feed mixture. More specifically, they must not reduce or destroy the critical selectivity of the adsorbent for the extract component over the raffinate component. In addition, the desorbent materials should be substances that are easily separable from the feed mixture introduced into the process. Both the raffinate stream and the extract stream are removed from the adsorbent as a mixture with the desorbent material and without a method of separating at least a portion of the desorbent material, the purity of the extract product and the raffinate product would not be very high and the desorbent material would not be reusable in the process. Therefore, it has been considered that any desorbent material used in this process has the advantage of having a substantially different average boiling point than the feed mixture to allow at least some of the desorbent material to be separated from the feed components in the extract and raffinate streams by simple fractional distillation. The phrase "substantially different" as used herein means that the difference between the average boiling points of the desorbent material and the feed mixture is at least about 5 ° C. The boiling range of the desorbent material may be higher or lower than that of the feed mixture. Finally, desorbent materials should also be materials that are readily available and therefore affordable. In the preferred isothermal, isobaric liquid phase operation of the process of the invention, desorbent materials consisting of a mixture belonging to the mixture group of acetonitrile and methanol have been found to be particularly effective; acetonitrile, tetrahydrofuran and water; dimethylacetamide and water; methanol and water; dimethylformamide and water; quaternary methylammonium hydroxide, water and methanol; and quaternary propylammonium hydroxide.

It has also been found in the art in the past that certain properties of adsorbents are highly desirable, if not absolutely necessary for the successful operation of a selective adsorption process. These features are equally important to this process. Such properties include: adsorption capacity for a volume of extract component per volume of adsorbent; selective adsorption of extract component 11 79522 compared to raffinate campaign and desorbent material? and sufficiently high adsorption and desorption rates of the extract component to and from the adsorbent. The ability of the adsorbent to adsorb a given volume of extract component is, of course, a necessity; without such ability, the adsorbent is useless for adsorption separation. In addition, the higher the capacity of the adsorbent with respect to the extract component, the better the adsorbent. The increased capacity of a given adsorbent makes it possible to reduce the amount of adsorbent required to separate the extract component of known concentration contained in a given feed mixture. Reducing the amount of adsorbent required for a given adsorption separation lowers the cost of the separation process. It is important that a good initial capacity of the adsorbent is maintained during the actual use of the separation process for some economically desirable lifetime. Another necessary property of the adsorbent is the ability of the adsorbent to separate the components of the feed from each other, or in other words that the adsorbent has an adsorbent selectivity (B) for one component over the other. Relative selectivity can be expressed not only for one feed component relative to another, but can also be expressed between any component of the feed mixture and the desorbent material. Selectivity (B) as used throughout this specification is defined as the ratio of the two components of the adsorbed phase to the ratio of the same two components in the non-adsorbed phase under equilibrium conditions. Relative selectivity is shown as Equation 1 below:

Equation 1 (volume% C / volume% D). Selectivity = (B) = --— (volume% C / volume% D) ö where C and D are the two components of the feed expressed as volume percentages and the abbreviations A and U represent the adsorbed and non-adsorbed phases, respectively. Equilibrium conditions of 12,79522 were determined when the feed mixture passing over the adsorbent layer did not change its composition after contact with the adsorbent layer. That is, no net material transition occurred between the adsorbed and the adsorbed phase. When the selectivity of the two components approaches 1.0, the adsorbent does not primarily adsorb one component over the other; they both adsorb (or do not adsorb) to approximately the same extent relative to each other. When (B) changes below or above 1.0, the adsorbent primarily adsorbs one component over the other. Comparing the selectivity of the adsorbent with respect to one component C over component D, (B) greater than 1.0, indicates the primary adsorption of component C to the adsorbent. (B) less than 1.0 would indicate that component D is adsorbed primarily, leaving the non-adsorbed phase enriched for component C and the adsorbed phase enriched for component D. Ideally, desorbent materials should have a selectivity value of about 1 or slightly less than 1 relative to all extract components so that all extract components can be desorbed as one class at reasonable desorbent material flow rates and so that extract components can displace the desorbent material in the next adsorption step. Although it is theoretically possible to separate the extract component from the raffinate component when the selectivity of the adsorbent for the extract component relative to the raffinate component is greater than 1, it is preferred that this selectivity approach 2. As with relative volatility, the higher the selectivity, the easier the separation. Higher selectivities allow the use of a smaller amount of adsorbent. A third important property is the rate of exchange of the extract component of the feed mixture material, or in other words, the relative rate of desorption of the extract component. This property is directly proportional to the amount of desorbent material that must be used in the process to recover the extract component from the adsorbent; higher exchange rates reduce the amount of desorbent material, i3 79522, required to remove the extract component and therefore make it possible to reduce the operating costs of the process. At higher exchange rates, less desorbent material must be pumped through the process and separated from the extract stream for reuse in the process.

A dynamic tester is used to test different adsorbents with a given feed mixture and desorbent material to measure the adsorption capacity, selectivity, and exchange rate properties of the adsorbent. The apparatus consists of an adsorbent chamber (comprising a helical column with a volume of approximately 70 cm) / with feed outlets at opposite ends of the chamber. The chamber is included in the temperature control means, and in addition, a pressure control device is used to operate the chamber at a predetermined constant pressure. A quantitative and qualitative analytical device / such as a refractometer, polarimeter and chromatograph can be connected to the outlet line of the chamber and used to quantify or qualitatively determine one or more components of the adsorbent in the outlet stream leaving the chamber. The pulse test / performed using this apparatus and the following general procedure is used to determine selectivities and other data for different adsorbent systems. The adsorbent is filled to equilibrium with the respective desorbent material by passing the desorbent material through the adsorbent chamber. At the appropriate time, a feed pulse containing a tracer of known concentration and the respective extract component or raffinate component, or both, all diluted in a desorbent, is injected for a period of several minutes. The desorbent stream is returned and the tracer and extract component or raffinate component (or both) are eluted, for example, in a liquid and solid chromatographic operation. The effluent can be analyzed in operation or, alternatively, effluent samples can be collected from time to time and later analyzed separately with analytical equipment and traces of corresponding component peak covers are generated.

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From the test data, the performance of the adsorbent can be determined in terms of pore volume, retention volume of the extract or raffinate component, selectivity of one component over another, and desorption rate of the extract component under the influence of the desorbent. The retention volume of the extract or raffinate component can be described as the distance between the center of the peak cover of the extract or raffinate component and the peak cover of the tracer component or some other known reference point. It is expressed as the volume of desorbent in cubic centimeters pumped during this time interval, represented by the distance between the spike covers. The selectivity (B) of the extract component over the raffinate component can be described as the ratio of the distance between the peak component of the extract component and the center of the tracer peak cover (or other checkpoint) to the corresponding distance between the peak area of the raffinate component peak and the center of the tracer peak cover. The rate of exchange of the extract component with the desorbent can generally be described by the width of the spike covers in the middle of the intensity. The smaller the peak width, the higher the desorption rate. The rate of desorption can also be described by the distance between the center of the tracer peak cover and the disappearance of the freshly desorbed extract component. This distance is again the volume of desorbent pumped during this time interval.

A more accurate evaluation of promising adsorbent systems and the transformation of this type of information into practical separation processes requires actual testing of the best system in a continuous liquid-solid countercurrent contactor. The general principles of operation of such a device have been previously described and can be found in U.S. Patent 2,985,589. Specific laboratory test equipment utilizing these principles is described in U.S. Patent 3,706,812. The equipment includes a plurality of adsorbent mixtures having a plurality of inlet tubes attached to layered manifolds and which terminate in a rotary distribution valve. At a given valve position, the feed and desorbent is 79522 is fed through two tubes and a raffinate and extract stream and discharged through the other two. All remaining inlet pipes are inactive and when the distribution valve position moves forward in one step, all active positions move one layer forward. This simulates a situation where the adsorbent physically moves countercurrent to the liquid flow. Further details of the above-mentioned nonionic adsorbent testing apparatus and adsorbent evaluation technique can be found in the presentation "Separation of Cg Aromatics by Adsorption" by A.J. de Rosset, R.W. Neuzil, D.J. Korous and D.H. Rosback have held the association at the American Chemical Society Conference in Los Angeles, California, March 28-April 2, 1971.

The adsorbents used in the process of this invention include nonionic, hydrophobic, insoluble, crosslinked polystyrene polymers, preferably those manufactured and sold by Rohm & Haas Company under the tradename "Amberlite". The types of Amberlite polymers known to be effective for use in this invention are referred to in the literature by Rohm & Haas as Amberlite XAD-2 and Amberlite XAD-4 and are described in the literature as "hard, insoluble large-surface area, porous polymer spheres." The different types of polymeric Amberlite adsorbents differ in physical properties such as pore volume, surface area, average pore diameter, rank density, and nominal screen size classes. Applications of polymeric Amberlite adsorbents that have been proposed in the Rohm & Haas literature include decolorization of the pulp mill bleaching stream, decolorization of dye waste, and removal of pesticide from sewage waste. There is, of course, no clue in the literature to the surprising finding that polymeric Amberlite Adsorbents are effective in separating monoethanoid fatty acids from diethanoid fatty acids.

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The essential advantage of polymeric Amberlite adsorbents over crystalline aluminosilicates is that the former, in contrast to the latter, can be used for the direct separation of fatty acids without first converting the fatty acids to their corresponding esters. The aforementioned prior art patents are applicable only to fatty acid esters because the free carboxyl group of the fatty acid reacts chemically with the crystalline aluminosilicates used in these processes. The adsorbent of the present invention does not have such reactivity and therefore the process of the present invention is uniquely suited for the separation of fatty acids.

The adsorbent can be used in the form of a dense, dense solid layer which is contacted alternately with the feed mixture and the desorbent materials. In the simplest embodiment of the invention, the adsorbent is used in the form of a single static layer, in which case the process is only semi-continuous. In another embodiment, a series of two or more static layers may be used as a solid layer in contact with a suitable valve system so that the feed mixture is passed through one or more adsorbent layers while desorbent materials may be passed through one or more other layers in the series. The flow of the feed mixture and desorbent materials can take place either upwards or downwards through the desorbent. Any conventional equipment used for liquid-solid contact of the static layer can be used.

Countercurrent moving bed or simulated moving bed countercurrent systems have a much higher separation efficiency than solid adsorbent bed systems and are therefore preferred. In the moving bed or simulated moving bed processes, adsorption and desorption operations take place continuously, which enables both the continuous production of the extract and raffinate stream and the continuous utilization of the feedstock 79522 desorbent streams. In a preferred embodiment of this process, a method known in the art as a simulated moving bed countercurrent system is used. The principles and order of operation of this flow system are described in U.S. Patent 2,985,589, which is incorporated herein by reference. In such a system, the gradual movement of several liquid inlets down the adsorbent chamber simulates the upward movement of the adsorbent contained in the chamber. Only four of the inlet pipes are active at any given time; feed inlet stream, de-sorbent inlet stream, raffinate effluent and extract effluent tubes. Simultaneously with the simulated upward movement of this solid adsorbent, a liquid filling the pore volume of the packed layer of adsorbent takes place. In order to maintain the countercurrent contact, the flow of liquid down the adsorbent chamber can be provided by a pump. As the active fluid inlet moves through the circulation cycle, i.e., from the top of the chamber to the bottom, the chamber circulation pump moves through different zones that require different flow rates. A programmed flow controller can be used to set and control these flow rates.

The active liquid inlets efficiently divide the adsorbent chamber into separate zones, each with a separate function. In an embodiment of this process, it is generally necessary to have three separate operating zones present for the process to occur, although in some cases an optional fourth zone may be used.

The adsorption zone, zone 1, is defined as the adsorbent located between the feed inlet stream and the raffinate outlet stream. In this zone, the feedstock is contacted with the adsorbent, the extract component is adsorbed and the raffinate stream is removed. Since the general flow through zone 1 occurs from the feed stream entering the zone to the raffinate stream leaving the zone, the flow in this zone is considered to be downstream as it proceeds from the feed inlet stream to the raffinate effluent stream.

ie 79522 Immediately upstream of the liquid stream in zone 1 is the purification zone, zone 2. The purification zone is defined as the adsorbent between the extract effluent and the feed inlet stream. The basic functions in zone 2 are the displacement of all the raffinate material transferred to zone 2 from the non-selective pore volume of the adsorbent by transferring the adsorbent to this zone and desorbing all of the raffinate material adsorbed on the adsorbent or selectively adsorbed on the adsorbent. Purification is achieved by directing a portion of the extract stream leaving zone 3 to zone 2 at the upstream boundary of zone 2, i.e., the extract effluent to cause displacement of the raffinate material. The flow of material in zone 2 takes place downstream from the extract discharge stream to the feed inlet stream.

Immediately upstream of zone 2 in zone 2 with respect to the flowing liquid, there is a desorption zone or zone 3. A desorption zone is defined as an adsorbent between the desorbent inlet stream and the extract outlet stream. The purpose of the desorption zone is to allow the desorbent material entering this zone to displace the extract component / which was adsorbed on the adsorbent in previous contact with the feed in zone 1 in the previous stage of the operation. The flow of liquid in zone 3 takes place in substantially the same direction as in zones 1 and 2.

In some cases, an optional buffer zone / zone 4 may be used. If this zone, defined as the adsorbent between the raffinate effluent and the desorbent inlet stream, is used, it is located immediately upstream of the liquid stream to zone 3. Zone 4 would be used to maintain the amount of desorbent used in the desorption step, as part of the raffinate stream removed from zone 1 can be led to zone 4. displacement of desorbent material in the zone from this zone to the desorption zone. Zone 4 contains enough adsorbent so that the raffinate material present in the raffinate stream from zone 1 to zone 4 can be prevented from entering zone 3 and thus contaminating the extract stream removed from zone 3. In cases where the fourth operating zone is not used, the raffinate flow from zone 1 to zone 4 must be carefully monitored so that the flow directly from zone 1 to zone 3 can be stopped when a significant amount of raffinate material is present in the zone 3 from zone 1 to zone 3. .

The circulating propagation of the supply and discharge streams through the solid bed of adsorbent can be accomplished by using a manifold system in which valves in the manifold are used sequentially to cause the supply and discharge streams to shift, allowing liquid to flow countercurrent to the adsorbent. Another mode of operation for countercurrent flow of solid adsorbent to liquid involves the use of a rotary poppet valve in which the inlet and outlet streams are connected to the valve and the pipes through which the inlet, extract outlet, desorbent inlet and raffinate outlet streams pass in the same direction. . Both the extension tube device and the poppet valve are known in the art. In particular, rotary poppet valves that can be used in this operation can be found in U.S. Patents 3,040,777 and 3,422,848. Both of the aforementioned patents disclose a rotary type connecting valve in which suitable propagation of different supply and discharge flows from fixed sources can be achieved without difficulty.

In many cases, one zone of action contains a much larger amount of adsorbent than another zone of action. For example, in some operations, the buffer zone may contain a smaller amount of adsorbent compared to the adsorbent required for the adsorption and purification zones.

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It can also be seen that in cases where a desorbent is used which can easily desorb the extract material from the adsorbent material, a relatively small amount of adsorbent is required in the desorption zone compared to the adsorbent required in the buffer zone or adsorption zone or purification zone. Since it is not required that the adsorbent be located in a single column, the use of multiple chambers or a series of columns is within the scope of the invention.

It is not necessary that all feed and discharge streams be used simultaneously and, in fact, in many cases, one of the streams may be cut off while the others carry out the material feed and discharge. The device which can be used to carry out the process of the present invention may also comprise a series of individual layers connected to each other by connecting pipes 11a in which supply or discharge taps are arranged, to which different supply or discharge streams can be attached and moved alternately and from time to time for continuous operation. . In some cases, the connecting pipes may be connected to transfer taps which, during normal operation, do not act as a pipe through which the material passes into and out of the process.

It has been contemplated that at least a portion of the extract effluent passes to a separation device where at least a portion of the desorption material can be separated to produce an extract product containing a reduced concentration desorbent material. Preferably, but not necessarily for process operation, at least a portion of the raffinate effluent is also passed to a separation device where at least a portion of the desorbent material can be separated to produce a desorbent stream that can be reused in the process and a raffinate product containing reduced concentration desorbent material. The separation device is typically a fractionation column, the design and operation of which are well known in the separation field.

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Reference may be made to U.S. Patent 2,985,589 and D.B.

Broughton's presentation entitled "Continuous Adsorptive Processing - A New Separation Technique" held at the 34th Annual Meeting of the Society of Chemical Engineers in Tokyo, Japan on April 2, 1969, both of which are incorporated herein by reference, to further illustrate the flow diagram of the simulated moving bed countercurrent process .

Although both liquid and vapor phase operations can be used in many adsorption separation processes, a liquid phase operation is preferred for this process due to the lower temperature requirements and higher yields of extract product that can be obtained by the liquid phase operation compared to those obtained by the vapor phase operation. Adsorption conditions include a temperature range of about 20-200 ° C, with a range of about 20-100 ° C being more preferred, and a pressure range of about normal pressure to about 3450 kPa, with a range of about 1725 kPa being more preferred to provide a liquid phase. Desorption conditions include the same temperature and pressure ranges as used for adsorption conditions.

The size of the units in which the process of this invention can be utilized can range from pilot plant scale (see, e.g., U.S. Patent 3,706,812, which is incorporated herein by reference) to commercial scale, and their flow rates can range from just a few hours per hour to many thousands of liters per hour. .

The following examples are presented to illustrate the selectivity ratio that enables the process of the invention. The example is not intended to unduly limit the scope and spirit of the appended claims.

Example I

This example shows the selectivities of two polymeric Amberlite adsorbents, Amberlite XAD-2 and Amberlite XAD-4, for oleic acid over linoleic acid.

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The feed mixture contained the desorbent and tallow fatty acids used in that pulse experiment in a 90:10 ratio of desorbent to tallow fatty acids. Tallow oil fatty acids had the following composition:

Fatty acids

Palmitin (C160) 1

Stearin (CH 2 O 2) 2 oil (C 18 I) 51

Linoleum (C182) 45

All others 4

Retention volumes and selectivities were obtained using the pulse tester and the procedure described above. In particular, the adsorbents were tested on a 70 cm 2 twisted column using the following sequence of operations for each pulse experiment. The desorbent material was continuously passed through a column containing an adsorbent at a nominal liquid volume flow rate per hour (LHSV) of about 1.0. The pore volume was determined by determining the volume of desorbent required to fill the packed dry column. At the appropriate time, the flow of desorbent material was stopped and a 3 10 cm sample of the feed mixture was injected onto the column through the sample loop and the flow of desorbent material was restored. Samples from the effluent were automatically collected in an automated sampler and subsequently analyzed by chromatographic analysis. From the analysis of these samples, peak cover concentrations were developed for the components of the feed mixture. The fatty acid retention volume was calculated by measuring the distances from the checkpoint moment to zero to the corresponding fatty acid centers and subtracting the distance representing the pore volume of the adsorbent. The selectivities of the adsorbent with respect to oleic acid over linoleic acid in the presence of a desorbent material are in quotients obtained by dividing the retention volume with respect to oleic acid by the retention volume with respect to linoleic acid. The results of these pulse experiments are shown in Table 1.

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Figure 1 is an example of a graphical representation of the results of a pulse experiment, the data of which are also shown in Table 1.

This pulse test was performed at 90 ° C with Amberlite XAD-2 adsorbent and a mixture of 85% dimethylformamide and 15% water as desorbent. As shown in Figure 1, linoleic acid eluted first and then oleic acid.

Table 1 and Figure 1 show that oleic acid is more strongly adsorbed than linoleic acid, especially with certain combinations of desorbent mixture when used to separate fatty acids containing 18 carbon atoms per molecule. Moreover, the differences achieved with many of these combinations are significant, as in Figure 1, for example, and clearly have commercial productivity.

Example II

This example shows the results of using Amberlite XAD-2 adsorbent to separate stearic acid from a mixture of about 50-50 stearic and palmitic acids diluted in desorbent in a ratio of 90:10 between desorbent and acid mixture. The desorbent used contained 85% by weight of dimethylformamide and 15% by weight of water.

Data were obtained using the pulse tester and procedure described above at 90 ° C. More specifically, the adsorbent was placed in a 70 cm helical column and the following procedure was used. The desorbent material was continuously passed countercurrently through the column containing the adsorbent at a flow rate of 1.2 ml / min. At the appropriate time 3, the flow of desorbent material was stopped and a 10 cm sample of the feed mixture was injected onto the column through the sample loop and the flow of desorbent material was restored. Outflow samples were automatically collected in an automated sampler and later analyzed by chromatographic analysis.

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Figure 2 is a graphical representation of the results of the pulse experiments. Figure 2 shows that stearic acid is adsorbed more strongly than palmitic acid, especially with the desorbent mixture used. Moreover, the difference achieved with this combination was significant and clearly had commercial feasibility.

Claims (5)

26 79522 A process for separating a first fatty acid selected from the group consisting of stearic acid and oleic acid from a mixture of said first fatty acid and a second fatty acid selected from the group consisting of palmitic acid and linoleic acid, characterized in that said mixture is contacted with an adsorbent consisting of a nonionic, hydrophobic, insoluble, crosslinked polystyrene polymer under adsorption conditions selected to selectively adsorb said first acid rather than said second acid, wherein said first acid is said stearic acid, said second acid being stearic acid, the first acid is oleic acid, said second acid is linoleic acid. A method according to claim 1, characterized in that said first fatty acid is recovered by desorption with a desorbent under desorption conditions. Process according to claim 2, characterized in that said adsorption and desorption conditions include a temperature between about 20-200 ° C and a pressure between approximately normal pressure and about 3450 kPa. Process according to Claim 3, characterized in that it is carried out in the liquid phase. A method according to claim 1, characterized in that said desorbent consists of a mixture of a mixture group comprising acetonitrile and methanol; acetonitrile, tetrahydrofuran and water; acetone and water; dimethylacetamide and water; methanol and water; dimethylformamide and water; quaternary methylammonium hydroxide, water and methanol; and quaternary propylammonium hydroxide, water and methanol.