FI73460C - Process for separating fatty acids from resin acids. - Google Patents

Description

73460

Method for separating fatty acids from rosin acids

The present invention relates to the separation of fatty acids by means of a molecular sieve in a solid layer. More specifically, the invention relates to a process for separating fatty acids from rosin acids, which process comprises using a molecular sieve comprising silicalite. The fatty acids are selectively retained and the rosin acids are removed from the molecular sieve containing fatty acids. Fatty acids are removed from the molecular sieve by displacement with a displacement fluid under displacement conditions.

It is well known that certain crystalline aluminosilicates can be used to separate hydrocarbons from their mixtures. For example, the separation methods disclosed in U.S. Patents 7,985,589 and 3,201,491 use zeolite A to separate normal paraffins from branched chain paraffins, and the methods described in U.S. Patents 3,265,750 and 3,510,423 use type X and Y zeolites to separate olefinic hydrocarbons from paraffinic hydrocarbons. X- and Y-type zeolites have been used not only for the separation of different hydrocarbon species but also for methods of separating separate hydrocarbon isomers. As some examples, adsorbents comprising X and Y zeolites have been used in the process of U.S. Patent 3,114,782 to separate alkyl trisubstituted benzene isomers, in the process of U.S. Patent 3,864,416 to monocyclic alkyl tetrasubstituted monocyclic substituents. and in the process of U.S. Patent 3,668,267 to separate certain alkyl substituted naphthalenes. Due to the commercial importance of paraxylene, possibly the best known and most widely used methods for the separation of hydrocarbon isomers are those used to separate paraxylene from a mixture of C8 aromatics. For example, the methods described in U.S. Patents 3,558,730, 3,558,732, 3,626,020, 3,663,638 i, 2,73460 f, and 3,734,974 use certain zeolite-containing adsorbents to separate paraxylene from raw material mixtures containing paraxylene. and at least one other xylene isomer, by selectively adsorbing paraxylene over other xylene isomers.

The present invention, in turn, relates to the separation of non-hydrocarbons and more particularly fatty acids. Fatty acids are mainly used in plasticizers and surfactants. Fatty acid derivatives are valuable in the manufacture of lubricating oils, such as for the textile and plastics industries, in various varnishes and as a water-resistant agent in cosmetics and pharmaceuticals, as well as in naturally degradable detergents.

It is known from U.S. Pat. No. 4,048,205 to use zeolites of types X and Y to separate esters of unsaturated fatty acids from saturated fatty acid esters. However, zeolites of types X and Y do not distinguish esters of rosin acids in tall oil from fatty acid esters or free acids, apparently because the pore size (greater than 7 Angstroms) of such zeolites is large enough to receive and retain relatively large diameter esters. as well as the corresponding free acids). The type A zeolite, on the other hand, has a pore size (about 5 Angstroms) such that it is unable to receive either of the above-mentioned esters (or free acids) and is therefore unable to distinguish between them. An additional problem when using zeolite to separate free acids is the reaction between the zeolite and the free acids.

It has now been found that silicalite, which is a non-zeolite, hydrophobic, crystalline silica molecular sieve, is excellently suitable for use in the separation process of the invention because of its ability to retain fatty acids, but not resin acids, especially when used in combination with a specific displacement fluid. reacts with free acids.

Briefly, one embodiment of the invention comprises a method for separating a fatty acid from a raw material mixture containing a fatty and rosin acid. The raw material mixture is contacted with a molecular sieve containing silicalite under separation conditions, whereby the fatty acid is selectively retained. The resin acid is then removed from the molecular sieve containing the fatty acid. The fatty acid is then removed from the molecular sieve by displacement with a displacement liquid under displacement conditions.

According to another embodiment of the invention, it comprises a method for removing fatty acid from a mixture of fatty acid and rosin acid, the method comprising the steps of: (a) maintaining a net fluid flow through a molecular sieve column in one direction, the column containing at least three zones of different processing operations connected in series with the end zones of the statue and connected so as to provide a continuous connection of the zones; (b) maintaining a retention zone in the column, wherein the zone is formed by a molecular sieve located between the feed stream of the upstream boundary of the zone and the raffinate effluent of the downstream of the zones; (c) maintaining the purification zone immediately upstream of the retention zone, the purification zone being formed by a molecular sieve located at the upstream extraction outlet of the purification zone and at the feedstock feed stream downstream of the purification zone; (d) maintaining the displacement zone immediately upstream of the purification zone, wherein the displacement zone is bounded by a molecular sieve located between the displacement flow at the upstream boundary of the zone and the extraction stream downstream of the zone; providing selective retention of the fatty acid by a molecular sieve in the retention zone and removal of the raffinate effluent from the retention zone; (f) introducing the displacement liquid into the displacement zone under displacement conditions to effect displacement of the fatty acid from the adsorbent in the displacement zone; (g) removing an extract stream comprising a fatty acid and a displacement fluid from the displacement zone; (h) periodically passing the feed stream, the raffinate effluent, the displacement liquid inlet stream, and the extract effluent stream and the raffinate effluent stream downstream of the molecular sieve column with respect to the liquid flow in the retention zone.

Other embodiments of the invention include details of raw material mixtures, molecular sieves, displacement fluids, and processing conditions, all of which are discussed in more detail below in the detailed description of the invention.

In the accompanying drawings: Fig. 1 schematically shows an embodiment of the invention, which is a simulated moving bed with an adsorption column 1, a piping system 3 and various connecting lines described below, Figs. 2 and 3 graphically show the values obtained in the examples below.

The various terms used in this specification to explain the operation, objects and advantages of the method according to the invention are defined below.

A "feedstock mixture" is a mixture containing one or more extract components and one or more raffinate components that are separated in the process of the invention. The term "feed stream" means the stream of the raw material mixture that is passed to the process screen used in the process.

5,73460 An "extract component" is a compound or species of a compound that is retained by a molecular sieve, while a "raffinate component" is a compound or species of a compound that is not retained. In this method, the fatty acid is the extract component and the linolenic acid is the raffinate component. "Displacement fluid" generally means a fluid capable of displacing an extract component. "Displacement fluid stream" or "displacement fluid inlet stream" means a stream through which a displacement fluid passes through a molecular sieve. "Diluent" or "diluent stream" means a stream through which a diluent enters a molecular sieve. "Raffinate stream" or "raffinate effluent" means a stream by which a raffinate component is removed from a molecular sieve. The composition of the raffinate stream can range from substantially 100% displacement fluid to substantially 100% raffinate components. "Extract stream" or "extract effluent" means a stream by which an extract material displaced by a displacement liquid is removed from a molecular sieve. The composition of the extract stream can also range from substantially 100% displacement liquid to substantially 100% extract components. At least a portion of the extract stream from the separation treatment, and preferably a portion of the raffinate stream, is passed to separation equipment, usually fractionation equipment, in which at least a portion of the displacement liquid and diluent are separated to obtain an extract product and a raffinate product. The terms "extract product" and "raffinate product" refer to products prepared in this process and containing the extract component and the raffinate component at a higher concentration than in the extract stream and the raffinate stream, respectively. Although the process of the invention makes it possible to prepare a high purity fatty acid product and a rosin acid product (or both) in high yield, it should be noted that the molecular sieve never completely retains the extract component nor the raffinate component. As a result, the raffinate component may be present in varying amounts in the extract stream, and similarly, the new component may be present in varying amounts in the raffinate stream. The extract and raffinate streams are then further separated from each other and from the feedstock mixture based on the concentration ratio present in the particular stream between the extract component and the raffinate component. More specifically, the ratio of fatty acid concentration to non-retained rosin acid is lowest in the raffinate stream, followed by the highest in the feedstock mixture and highest in the extract stream. Similarly, the ratio of rosin acid concentration to retained fatty acid is highest in the raffinate stream, next highest in the feedstock mixture and lowest in the extract stream.

By "selective pore volume" of a molecular sieve is meant the volume of the molecular sieve that selectively retains the extract component from the raw material mixture. The "non-selective pore volume" of a molecular sieve is the volume of the molecular sieve that does not selectively retain the extract component from the raw material mixture. This volume includes those pores of the molecular sieve that receive the raffinate components and the spaces between the particles of the molecular sieve. Selective pore volume and non-selective pore volume are generally expressed in units of volume and are important in determining the correct flow rates of the liquid that must be introduced into the treatment zone to perform efficient treatment using a given amount of molecular sieves. When a molecular sieve "enters" a treatment zone (described in more detail below) in accordance with one embodiment of the invention, its non-selective pore volume, together with its selective pore volume, transports fluid to that zone. The non-selective pore volume is used to determine the amount of liquid that must be introduced into the same zone upstream of the molecular sieve to displace the liquid present in the non-selective pore volume. If the flow rate of the liquid passing into a given zone is less than the non-selective pore volume of the molecular sieve entering that zone, the molecular sieve will cause additional fluid retention in that zone. Because this additional retention consists of a liquid present in the non-selective pore volume of the molecular sieve, in most cases it contains unrestrained components of the raw material.

7 73460

Before considering the raw material mixtures that can be derived from the treatment according to the invention, the terminology and the preparation of fatty acids in general will be briefly discussed first. Fatty acids are a large group of aliphatic monocarboxylic acids, several of which are present as glycerides (glycerol esters) in natural fats and oils. Although the term "fatty acids" is limited to a few saturated acids of the acetic acid series, both straight and branched chain, it is commonly used herein to include similar unsaturated acids, certain substituted acids, and even aliphatic acids containing alicyclic substituents. with the exception of higher straight-chain, unsubstituted acids having an even number of carbon atoms. fatty acids having at least one double bond, and the term "polyethanoid fatty acids" means fatty acids having more than one double bond in a molecule. iras fats or oils using any of a number of "cleavage" or hydrolytic methods. In all cases, the hydrolysis reaction can be considered as a reaction of a fat or oil with water to give fatty acids plus glycerol. In modern fatty acid production plants, this method is carried out by continuously carrying out the hydrolysis of fat at high pressure and high temperature. Examples of starting materials commonly used in the preparation of fatty acids include coconut oil, palm oil, non-edible animal fats and commonly used vegetable oils, soybean oil, cottonseed oil and corn oil.

73460

The source of fatty acids which is the main subject of the present invention is tall oil, a by-product of the pulp industry which is usually recovered from black liquor in the production of pine pulp by the sulphate or power pulp process. Tall oil contains about 50-60% fatty acids and about 34-40% resin acids. Fatty acids include oleic, linolenic, palmitic and stearic acids. Resin acids, such as abietic acid, are monocarboxylic acids with a molecular structure containing carbon, hydrogen, and oxygen, and have three fused 6-membered carbon rings that result in a much larger molecular diameter of resin acids compared to fatty acids.

The raw material mixtures fed to the process according to the invention may contain, in addition to the tall oil components, a diluent which is not adsorbed by the adsorbent and which can advantageously be separated from the extract and raffinate by fractional distillation. When a diluent is used, its concentration in the mixture of diluent and acids is preferably from a few volume percent to about 75 volume percent, with the remainder being fatty and rosin acids. Although in the past e.g. U.S. Patent No. 4,329,280 discloses that silica lithium is effective in separating fatty and rosin acid esters, and separation of free acids using silica lithite has not previously been accomplished.

The displacement fluids previously used in various adsorbent and molecular sieve separation treatments vary depending on such factors as the quality of the treatment. In various separation treatments that operate continuously at substantially constant pressures and temperatures to ensure a liquid phase and that use a molecular sieve, the displacement material must be carefully selected to meet a number of requirements. First, the displacing agent should displace the extract component from the Mole sieve using reasonable mass flow rates, but still allow the extract component to enter the molecular sieve so as not to adversely prevent the extract component 9 73460 from displacing the displacement material in the next separation step. In addition, the displacement fluids must be substances that are easily separable from the raw material mixture fed to the treatment. Both the raffinate stream and the extract stream are removed from the molecular sieve in admixture with the displacement fluid, and unless a method is used to separate at least a portion of the displacement fluid, the purity of the extract product and the raffinate product is not very high and the displacement fluid cannot be reprocessed. Consequently, it has been found that the displacement liquid used in the treatment should be such that it preferably has a significantly different average boiling point compared to the feedstock so that at least part of the feedstock is separated from the feedstock components in extract and raffinate streams by simple fractional distillation. which allows displacement fluid to be reused in handling.

As used herein, the term "substantially different" means that the difference in average boiling point between the displacement fluid and the raw material mixture should be at least about 5 ° C. The boiling range of the displacement liquid may be higher or lower compared to the raw material mixture. Finally, displacement fluids should be those that are readily available and therefore reasonably priced. In the isothermal, isobaric liquid phase treatment of the invention, it has been found that displacement fluids comprising organic acids are effective, and short chain organic acids having 2 to 5 carbon atoms are most preferred, especially when using a diluent as below. are shown. However, it has been found that the optimal displacement fluid is a solution of a light ketone (diethyl ketone or lighter) and water.

It has been found that silicate can also be ineffective in separating fatty and rosin acids when using a Mole kiln screen layer in redistribution after the displacement step. When a displacement fluid is present in the bed, no selective retention of the fatty acid occurs. It is assumed that the displacement fluid, especially the organic acid, participates in or even catalyzes 10,73460 hydrogen-bound dimerization reactions because of the similarity between the fatty and resin acid molecules and possibly the displacement fluid molecules. The dimerization reaction can be represented by the formulas: FA + FA ^ ------ Λ (FAFA) RA + RA v - (RARA) FA + RA s ·· (FARA) in which FA and RA are fatty and resin acids, respectively. Organic acid displacement fluid molecules may also need to be considered as reactants and product components in the above equations. The dimers prevent the separation of fatty and rosin acids from each other by preventing the former from entering the pores of the molecular sieve. Inhibition of separation by the presence of dimers does not appear to be a major problem in the above process for the separation of fatty acid esters.

It has been found that the above dimerization reactions can be reduced at least to the extent necessary to allow the separation of resin and / or fatty acids by first rinsing the molecular sieve with a suitable diluent. This diluent removes the displacement fluid from at least the non-selective pore volume of the molecular sieve. Adequate separation requires, first, that the components of the feedstock stream be dissolved in the diluent, as well as easy separation of the diluent in a conventional manner, such as by means of a displacement liquid.

It has also been found that the above-mentioned pre-rinsing can also be avoided if the displacement liquid is formed by an organic acid in solution with a suitable diluent capable of reducing dimerization. The measure of this property is the polarity index of the liquid. The polarity index is described in the article "Classification of the Solvent Properties of Common Liquids";

II

11 73460

Syfider L., J. Chromatography, 92, 223 (1974), which is incorporated herein by reference. The minimum value of the polarity index of the displacement liquid diluent, which is necessary in the process according to the invention to avoid pre-rinsing, is 3.5, especially if the displacement liquid is the above-mentioned short-chain organic acid. The diluent should comprise about 50-95% by volume of the amount of displacement fluid. The polarity indices of certain selected diluents are as follows:

Solvent Polarity Index

Iso-octane -0.4 n-hexane 0.0

Toluene 2,3 p-xylene 2,4

Benzene 3.0

Methyl ethyl ketone 4.5

Acetone 5.4

It has recently been found that the optimal displacement liquid which makes pre-rinsing unnecessary is a solution containing a water-soluble substance with a high polarity index, i. a light ketone selected from the group consisting of acetone, methyl ethyl ketone and diethyl ketone, and water. It should be noted that the polarity index of water is 9.0, and as a result, a mixture of water and e.g. acetone has a very high polarity index, since the polarity indices of the components of such a mixture must be added together, i. the polarity index of the 50/50 mixture of acetone and water is: 0.5 x 5.4 + 0.5 x 9.0 = 7.2. The ketone is important, of course, not only because it increases the polarity index, but also to obtain a displacement fluid that is soluble in the tall oil feedstock. The mixture of water and ketone further improves the separation of tall oil by silicate due to its very high polarity index and because the water it contains is assumed to bind double-bonded oxygen (donor atom) fatty and resin acid carboxyl groups, preventing such oxygen from binding to active hydrogen and other carboxyl groups. from forming dimers.

73460

An acid-free, aqueous displacement fluid also has other advantages. One advantage is that the corrosive effect of short-chain organic acids is eliminated. Another advantage is that the water in the displacement liquid prevents the deactivation of the molecular sieve due to highly polar compounds, such as mineral salts, especially sodium sulphate present in crude tall oil, by dissolving such compounds and transporting them away. The presence of water also reduces ester formation from alcohols in crude tall oil by reversing the reaction equilibrium to the left, where acid plus alcohol form esters plus water.

The molecular sieve used in the process of the invention is silicalite. As mentioned above, silica is a hydrophobic, crystalline silica molecular sieve. Silicalite is described in U.S. Patent Nos. 4,061,724 and 4,104,294, which are incorporated herein by reference. Due to its aluminum-free structure, silkalite has no ion exchange properties and is hydrophobic and organophilic. Silicalite thus forms a molecular sieve, but is not a zeolite. Silicalite is uniquely suitable for use in the separation treatment according to the invention due to the fact that its pore size and shape are such that this allows the silicalite to function as a molecular sieve, i. it receives fatty acid molecules in its pores, i.e. its internal structure, but does not receive resin acid molecules. Silicite is described in detail in the article "Silicalite, A New Hydrophobic Crystalline Silica Molecular Sieve"; Nature, Vol. 271, February 9, 1973, to which reference is made herein.

Silicalite, in the same way as previously known adsorbents or molecular sieves, is most preferably used in combination with a suitable binder. The binder promotes the formation or agglomeration of the crystalline parts of the silicalite, otherwise it is formed by a fine powder. Not all binders previously used are suitable for use in 73460 in separating tall oil components due to the reactivity of the binder or the effect on the separation treatment. A binder has now been invented which, in combination with silicalite, provides a new molecular sieve which is uniquely suitable for separating tall oil constituents. Silicalite is bound by silica, i. the silicalite is combined with a silica matrix. The silicalite is combined with silica by dispersing the silicalite powder in colloidal, amorphous silica to give a precursor, this precursor is gelled, and this gel is then treated to provide substantially complete removal of hydroxyl groups from the silicalite and silica matrix. Colloidal amorphous silica comprises an aqueous colloidal dispersion of amorphous silica particles, and gelation is preferably accomplished by removing water from this dispersion, although other gelation methods may be used, such as changing the pH or adding salt or a water-miscible organic solvent. The silicalite should be present in the silica matrix in amounts of about 75-98% by weight of the silicalite based on the mixture of non-volatile substances. Prior to treatment of the gel, it is extruded to remove hydroxyl groups, preferably still in a plastic state, and then broken up into separate particles. The plastic state occurs for at least a portion of the time that water is removed to effect gelation. After treatment, the particles can be further ground to be more physically suitable for use in a particular separation treatment, usually to a fineness of 16-60 (Standard U.S. Mesh).

The colloidal amorphous silica most preferred for use in accordance with the invention is that described by Du Pont Co. markets under the trademark "Ludox". Colloidal silica "Ludox" is silica formed by discrete, homogeneous spheres with no internal surface area or detectable crystallinity, dispersed in an alkaline medium that reacts with the surface of the silica to form 14 73460 and forms a negative charge. The stabilizing cations in this alkaline medium may be sodium or ammonium ions, and the concentration of silica in the colloidal dispersion may be about 30-50% by weight based on SiO 2.

The literature of Du Pont Co describing the colloidal silica "Ludox" shows that during drying, the hydroxyl groups on the surfaces of the silica particles condense to cleave water to form siloxane bonds (Si - O - Si), causing fusion, bonding of the particles to each other. and particles that are chemically inert and heat resistant. However, it has been found that further drying of silica-bonded silica under the conditions used in this art to effect drying, i. heating in an air furnace at a temperature slightly above 100 ° C provides a molecular sieve that is not suitable for separating the constituents of tall oil. Such a molecular sieve reacts with fatty and rosin acids, and the separation obtained is very poor, since the fatty acid components leave considerably waste of rosin acid components. The reason which is presumed to cause such behavior is that what is stated in Du Pont Co's literature on the formation of siloxane bonds during normal drying is essentially true, but a very small amount of hydroxyl groups (or ammonium groups remain if these stabilizing cations are present). ammonium ions), which are irrelevant for most practical purposes, but which make the adsorbent completely unsuitable for use in the process according to the invention. In this context, it should be noted that other silicalite binders have also been tried, but with equally poor results. Organic binders, such as polyvinyl alcohol, are unsuitable, probably due to the presence of hydroxyl groups. Binders formed from natural clay have selectivity for certain constituents of tall oil and thus affect the effectiveness of silicalite.

tl 73460 It is therefore necessary to treat the gelled silica-bound silicalite in the above-mentioned manner in order to remove the hydroxyl groups and replace them with siloxane bonds. The obtained silicalite in the obtained silica-dimatrix molecular sieve is very suitable for separating tall oil components from each other because it provides an excellent separating effect of pure silicalite and at the same time a physically strong and stable molecular sieve suitable for factory-scale separation.

There are several ways to treat gelled silica-bound silicate to achieve substantially complete removal of hydroxyl groups. One way is to heat treat at a temperature in the range of about 450-1000 ° C, with a minimum treatment time of about 3-48 h, which can occur under oxygen, nitrogen and / or hydrogen. acid. Another way is to first contact the molecular sieve with an alcohol such as ethanol and then heat treat the molecular sieve at an elevated temperature (above about 350 ° C) in the presence of oxygen. A third way to eliminate hydroxyl groups is to chlorinate the molecular sieve at an elevated temperature, as disclosed in, e.g., U.S. Patent No. 4,308,172, wherein the molecular sieve is contacted at an elevated temperature with a chlorinating agent (e.g., CCl 2, COCl 2,

Cl 2, Cl 2 Cl 2, SO 2 Cl 2 or SO 2), the resulting chlorinated molecular sieve is dechlorinated at elevated temperature and the dechlorinated molecular sieve is oxidized at elevated temperature.

Another way to effect the removal of hydroxyl groups by chlorination is to contact the molecular sieve at an elevated temperature with a mixture of oxygen and silicon tetrachloride.

The molecular sieve can be used in the form of a dense, uniform, solid layer which is contacted alternately with the raw material mixture and the displacement liquid. According to the simplest embodiment of the invention, a molecular sieve is used in the form of a single static layer, in which case, in the case of 16,73460, the treatment is only semi-continuous. In another embodiment, a series of two or more static layers may be used in a solid layer having a suitable valve arrangement so that the feedstock mixture is passed through one or more molecular sieve layers, while the displacement fluid may be passed through one or more other layers in the series. The flow of the raw material mixture and the displacement liquid through the molecular sieve can take place either upwards or downwards. Any conventional equipment used in the static layer to bring the liquid and solid into contact can be used.

However, a countercurrent moving bed system or a simulated countercurrent moving bed system has a much higher separation efficiency than fixed bed based systems and is therefore the most preferred. In systems based on a moving bed or a simulated moving bed, retention and displacement treatments take place continuously, which enables both the continuous production of extract and raffinate streams and the continuous use of feed and displacement liquid streams and possibly the necessary rinsing stream. In a preferred embodiment of this method, the so-called a simulated moving bed countercurrent system. The principles and steps of handling such a flow system are set forth in U.S. Patent No. 2,985,589, which is incorporated herein by reference. In such a system, the successive downward movement of multiple fluid inlets in the molecular sieve chamber simulates the upward movement of the molecular sieve in the chamber. Only five inlet lines operate at any one time, namely raw material feed flow, displacement liquid feed flow, rinsing liquid feed flow, raffinate effluent, and extract effluent. Simultaneously with the simulated upward flow of this solid molecular sieve, the movement of the liquid that fills the pore volume of the dense layer of the molecular sieve takes place. In order to maintain countercurrent contact, a downward flow of liquid in the molecular sieve chamber 17 73460 can be provided by a pump. When the active fluid inlet moves through the cycle, i.e. from the top of the chamber to its bottom, the chamber circulation pump moves through different zones where different flow rates are required. A programmed flow control device can be used to achieve and control these flow rates.

The active fluid inlets efficiently divide the molecular sieve chamber into separate zones, each with a different function. In this embodiment of the treatment, it is generally necessary to have three separate treatment zones in order for the treatment to take place, although in a few cases four zones may be used.

The positive net flow of fluid occurs through all parts of the column in the same direction, although the composition and velocity of the fluid flow will naturally vary from point to point. Figure 1 shows zones I, II, III and IV, as well as piping system 3, pump 2, which provides a positive net flow of liquid, and line 4, which is connected to pump 2. Figure also shows treatment supply and discharge lines, which provide flow through piping system 3.

The retention zone, zone I, is the part of the molecular sieve located between the feedstock input stream 5 and the raffinate effluent stream 7. In this zone, the raw material comes into contact with the molecular sieve, the extract component is retained and the raffinate stream is removed. Since the general flow through zone I takes place from the feedstock stream, which in this zone becomes the raffinate stream leaving the zone, it is considered that the flow in this zone occurs downstream from the feedstock feed point to the raffinate outlet. The liquid rinsing stream (diluent) can be directed to zone I at a point somewhat downstream of the raw material inlet. If a diluent is used, it is added at a rate sufficient to displace the displacement liquid in the simulated motion of at least the non-selective pore volume of the dense layer of the molecular sieve in zone I, which promotes fatty acid retention.

Immediately downstream of the liquid flow, there is a purification zone II in zone I. The purification zone is formed by a molecular sieve between the extract effluent and the feed stream 5. The basic treatments that take place in zone II are displacement from the non-selective pore volume of the molecular sieve by the circulating stream of raffinate material that enters this zone II when the molecular sieve is changed to this zone. Purification is accomplished by directing a portion of the extract stream exiting Zone III to Zone II at the upstream boundary of Zone II, i.e., a portion of the extract effluent stream, so as to effect displacement of the raffinate material. The material flow in zone II takes place upstream of the extract effluent to the feedstock feed stream.

Immediately upstream in zone II, with respect to the flow of liquid in this zone, is a displacement zone, i.e. zone III. This displacement zone is formed by the molecular sieve located between the displacement liquid inlet 13 and the extract outlet 11. The purpose of the displacement zone is to allow the displacement fluid entering this zone to displace the extract component left in the Mole sieve during previous contact with the raw material in zone I during the previous cycle of treatment. The fluid flow in zone III takes place substantially in parallel with that in zones I and II.

In a few cases, an optional buffer zone, zone IV, may be used. This zone, bounded by a molecular sieve between the raffinate effluent stream 7 and the displacement liquid feed stream 13, is located, if used, immediately upstream of the liquid stream in zone II: 19 73460. Zone IV can be used to retain the displacement fluid used in the displacement step because part of the raffinate stream removed from Zone I can be directed to Zone IV to displace the molecular sieve in that zone from the displacement zone. Zone IV contains sufficient molecular sieves so that the raffinate material in the raffinate stream passing from zone I to zone IV can be prevented from entering zone III and thus contaminating the product stream leaving zone III. In cases where the fourth treatment zone is not used, the raffinate stream that would have flowed from zone I to zone IV must be carefully treated so that the flow directly from zone I to zone III can be stopped when there is sufficient raffia from zone I to zone III. that the extract effluent does not become dirty.

In a preferred embodiment of the invention, zone IV is used and the rinse-diluent stream, if used, can be led not only to zone I but also to zone IV; to zone IV at the upstream boundary of zone IV. In this way, the displacement fluid that would otherwise enter Zone IV from Zone III as part of the simulated moving bed is maintained in Zone II, assuming that an appropriate amount of rinsing fluid is used. This also reduces the need for displacement fluid. Thus, when the molecular sieve enters zone I, it has a suitable minimum displacement fluid content.

Cyclic conduction of feed and discharge streams through the solid bed of the molecular sieve can be accomplished by using a tubing system in which the valves in the piping operate sequentially to provide variation in feed and discharge streams allowing fluid flow in countercurrent to the fixed slot molecular sieve. Another treatment that provides a countercurrent flow of solid molecular sieve to the liquid involves the use of a rotary poppet valve, in which the feed and discharge streams are connected to this valve, and the lines through which the feed, extract, feed and raffinate take place are shifted. direction through the molecular sieve layer. Both said piping arrangement and the poppet valve are already known. Rotary poppet valves that can be utilized in this discussion are disclosed in U.S. Patent Nos. 3,040,777 and 3,422,848. Both said patents disclose a rotary connecting valve in which proper conduction of various feed and discharge flows from solid feedstocks can be achieved without difficulty.

In many cases, one functional zone contains a much larger number of molecular sieves than another functional zone. For example, in a few treatments, the buffer zone may contain a smaller amount of molecular sieve compared to the amount of molecular sieve required in the retention and purification zones. It can also be seen that in cases where a displacement fluid that can easily displace the extract material from the molecular sieve is used, a relatively small amount of molecular sieve is required in the displacement zone compared to the amount of molecular sieve required in the buffer zone or retention zone or purification zone. Since it is not necessary for the molecular sieve to be located in a single statue, several chambers or sets of statues can be used according to the invention.

It is not necessary that all feed and discharge streams be used simultaneously, and in reality, in many cases, multiple streams may be shut off simultaneously while others provide material feed and discharge. The equipment that can be used to carry out the method according to the invention may also comprise a series of separate layers connected to each other by connecting lines fitted with pipe connections for supply and discharge, to which different supply and discharge flows can be attached and alternated alternately and periodically. 73460 van to provide processing. In a few cases, the connecting lines can be connected to these pipe connections, which during normal processing do not act as a line through which the material passes into and out of the processing.

It should be noted that at least a portion of the extract effluent can be passed to separation devices in which at least a portion of the displacement liquid, including the diluent, can be separated to obtain an extract product containing the displacement liquid at a lower concentration. Preferably, but not necessarily, for process operation, at least a portion of the raffinate removal stream is also passed to separation devices in which at least a portion of the diluent can be separated to provide a diluent stream that can be used for reprocessing and to produce a raffinate product containing less diluent. Separation devices usually consist of a fractionation column, the structure and operation of which are well known in the art.

Reference may be made in this connection to U.S. Patent 2,985,589 and D.B. To Broughton's paper "Continuous Adsorptive Processing - A New Separation Technique" presented at the 34th Annual Meeting of the Society of Chemical Engineers in Tokyo, Japan on April 2, 1969, both of which present a more detailed countercurrent treatment based on a simulated moving bed.

As for the separation conditions, although both liquid and vapor phases can be used in several adsorbent separation treatments, the liquid phase is most preferable due to the lower required temperature and because the extracted product can be obtained in higher yield in liquid phase treatment compared to vapor phase treatment. When the displacement liquid is formed by an organic acid, the separation conditions comprise a temperature range of about 20-200 ° C, with a range of about 20-100 ° C being most preferred. When the displacement liquid comprises a solution of light ketones and water, the separation is carried out in the temperature range of 22,73460 at about 90-140 ° C, with 120 ° C being most preferred. In any case, the separation conditions must be such that the pressure is sufficient to maintain the liquid phase. The displacement conditions include the same temperature and pressure ranges as when performing the separation.

The size of these units that can be used in the process of the invention can vary on an experimental scale (see, for example, U.S. Patent 3,706,812) to a factory scale, and flow rates can range from a few ml per hour to several thousand liters per hour.

A dynamic test apparatus is used to test different molecular sieves using some specific raw material mixture and displacement fluid to determine the molecular sieve retention capacity and exchange rate. The apparatus comprises a helical molecular sieve chamber with a volume of approximately 70 ml and with inlet and outlet points at opposite ends. The chamber has temperature control devices, and in addition, a pressure control device is used to control the operation of the chamber at a predetermined constant speed. Apparatus for performing quantitative and qualitative analysis, such as reflectometers, polarimeters, and chromatographic devices, can be fitted to the outlet line of the chamber and used to quantitatively or qualitatively determine one or more components of the substance exiting the molecular sieve chamber. The pulse test performed using this equipment and the following general method is used to determine the values of various molecular sieve systems. The molecular sieve is filled to equilibrium with a given displacement fluid by passing this displacement fluid through a molecular sieve chamber. At a suitable time, a dose of raw material containing a tracer of known concentration and a specified extract component or raffinate component, or both, all diluted with displacement fluid, is injected over several minutes. The displacement fluid flow is stopped and the tracer and extract component or raffinate component (or both) are eluted by liquid-solid chromatography 23,73460. The effluent may be analyzed from the flow or, alternatively, the effluent may be sampled periodically and analyzed separately at a later time with analytical equipment to develop peak envelopes or similar component peaks.

Based on the data obtained from the experiments, the performance of the molecular sieve can be evaluated in terms of pore volume, amount of retention of the extract or raffinate component, and the rate of displacement of the extract component from the molecular sieve. The amount of retention of the extract or raffinate component can be determined by the distance between the peak of the tracer component, the center of the sheath, and some other known reference point. It is expressed as the volume in the displacement fluid pumped during this period, represented by the distance between the peaks of the jacket. Exchange rate of an extract component with the displacement fluid can generally be characterized by the width of the peak of the shells of half-intensity means. The narrower the top jacket, the higher the displacement rate. The displacement rate can also be characterized by the distance between the peak of the tracer shell and the point of disappearance of the extract component, the latter being just displaced. This distance is also the volume of the displacement fluid pumped during said time.

The following non-limiting examples illustrate the method of the invention but do not limit the scope of the invention.

Example I

The experimental equipment described above was used to obtain the values of this example. The liquid temperature was 60 ° C and the liquid flow was upwards in the column at a rate of 1.2 ml / min. The raw material stream comprised 20% by weight of distilled tall oil and 80% by weight of displacement liquid. The statue was filled with 23% by weight of bound "Ludox" silicalite) prepared according to a preferred embodiment of the invention, which involved gel immersion by removing water (drying) followed by treatment to remove hydroxyl groups, which in this case was heating in air at 1000 ° C for 48 h. The resulting molecular sieve was ground and screened to a particle size of 20-50 (mesh). The displacement liquid used consisted of 89% by volume of methyl ethyl ketones and 20% by volume of acetic acid.

The results of this example are shown in the attached Figure 2. As can be seen from Figure 2, the difference obtained is quite good. The separation of resin acids from fatty acids is clear and unambiguous, although there is a moderate overlap (waste) between the resin acid and linolenic acid curves and the linolenic acid and oleic acid curves.

The curves also show the absence of the above-mentioned reactivity between the adsorbent and the components of the raw material mixture, which has previously been found to occur with silicalite and an organic binder or silica and silica binder not heat-treated according to the invention.

Additional experiments with experimental equipment were performed according to the invention, but using various displacement fluids, such as a mixture of propionic acid and heptane and pentanoic acid. The results varied to some extent, as did the quality of the separation, but in all cases a clear separation was obtained. Efficient and well-practiced separation of tall oil constituents is thus achieved. However, it is possible, as the following example shows, to achieve an even better separation.

Example II

The experiment of Example I was repeated except that the displacement liquid was a solution of 90% by volume of acetone and 10% by volume of water and the column temperature was 120 ° C. The temperature was raised to prevent the formation of liquid phases in the column, but it was not expected to otherwise affect the quality of the separation in any other way.

The results of this example are shown in the attached Figure 3. The separation provided by this improvement of the invention is clearly seen. Resin acid residues in fatty acids are virtually non-existent. In addition, the overlap between the curves of linolenic acid and oleic acid is considerably reduced, indicating that the two acids can be separated in the second treatment following the separation of the resin acids in the first treatment.

Claims (11)

1. A process for separating fatty acid from a mixture of precursor material containing fatty acid and resin acid, characterized in that the process comprises contacting this mixture of precursor material in separation conditions with a selective silicite containing silicite. quenching the fatty acid, removing the resin acid from the molecular sieve containing the fatty acid and then removing this fatty acid from the molecular sieve by displacement by displacement fluid at displacement conditions. 2. A process according to claim 1, characterized in that the displacing liquid comprises an organic acid, that the process is cyclic and that the molecular sieve is flushed in the rinsing conditions with a diluent before contacting each mixture of precursor material with the separating, rinsing and rinsing intermediate. The states are conditioned by a temperature in the range of 20-200 C and a pressure sufficient to maintain a liquid phase. Process according to claim 1, characterized in that the displacing liquid comprises a soluble organic acid in a diluent, the diluent being soluble in the mixture of the starting material and its polarity index is at least 3.5. 4. A process according to claim 3, characterized in that the organic acid is a compound of 2-5 carbon atoms in the molecule and said diluent is selected from a group consisting of acetone, methyl ethyl ketone or diethyl ketone, wherein said separation and displacement conditions - oo is heated by a temperature within the range of 20-200 C and a pressure sufficient to maintain a liquid phase. Il 3i 73460 Process according to Claim 1, characterized in that the displacing liquid comprises a solution of ketone in water, the ketone being selected from a group consisting of acetone, methyl ethyl ketone and diethyl ketone. 6. A process according to claim 5, characterized in that the displacement liquid contains about 5-30% by volume of water and that the separation and displacement conditions operate under a temperature of about 90-140 ° C and a pressure sufficient to maintain a liquid phase. Process according to claim 1, characterized in that the molecular sieve comprises silicalite dispersed in a silica matrix, that a precursor to this molecular sieve consists of silicalite powder dispersed in colloidal, amorphous silica, whereby this preliminary product is gelatinized and then treated. in a manner which provides a substantially complete elimination of the hydroxyl groups from the molecular sieve. A molecular sieve according to claim 7, characterized in that the pre-product comprises an aqueous content, colloidal dispersion of amorphous silica particles and a silica powder, and that the gelation is effected by removing water from this dispersion. A process for removing fatty acid from a mixture of fatty and resin acid, in which a molecular sieve containing silicalite method is used, characterized in that it comprises the following steps, wherein (a) a net flow of liquid is maintained in a direction through the column of the molecule. , which contains At least three zones, where different processing functions take place and which are connected in series with the end zones of the column and united so that a continuous connection between the zones is achieved; ; (b) an embankment zone is maintained in the column, said zone being a molecular sieve arranged between a supply stream 32 7 3 4 6 0 at an upstream boundary of the zone and a refinery outlet stream at a downstream boundary of the zone; (c) a purification zone is maintained immediately upstream from the damming zone, said purification zone being a molecular sieve between an extract outlet stream at an upstream boundary of the purification zone and the stream for supply of starting material at a downstream boundary; (d) an displacement zone is maintained immediately upstream of the purification zone, said displacement zone being defined by a molecular sieve while an inlet fluid flow stream at an upstream boundary of the zone and an outlet stream downstream of the extract stream; (e) the stream of starting material is led into the dam zone at separation conditions, such that a selective damming of the fatty acid is effected by the molecule screen located in the dam zone and a refinery outlet stream is removed from the dam zone; (f) the displacement liquid is introduced into the displacement zone in the displacement condition to effect displacement of the fatty acid from the adsorbent in the displacement zone; (g) the extract stream comprising the fatty acid and the displacement fluid is removed from the displacement zone; (h) to the feed stream, the refiner outlet stream, the displacement inlet stream and the outlet stream of the extract as well as the refinerate are periodically passed through the molecular sieve column downstream to the liquid stream in the dam zone. Method according to claim 9, characterized in that as a step it comprises maintaining a buffer zone immediately upstream relative to the displacement zone, said buffer zone being defined by a molecular sieve between the inlet stream of the buffer fluid at a downstream fluid at the buffer zone. refiner outlet stream at an upstream boundary of the buffer zone.