Molecular distillation decolorization method of long-chain fatty acid

Abstract

The invention belongs to the technical field of chemical engineering, and discloses a molecular distillation decolorization method of long-chain fatty acid. According to the scheme, gas and solid impurities in long-chain fatty acid raw materials are removed through melting and filtering, and colorless or light-colored fatty acid products are separated from mixed materials through molecular distillation by means of free path differences among the fatty acid products, colored polymers and discolored metamorphic products. The method has the advantages that no adsorbent is used, so that the residue of the waste adsorbent and the post-treatment process are avoided; molecular distillation is adopted for direct separation, the heating time is short, the vacuum degree is high, and deterioration and coking of materials at high temperature for a long time are avoided; no solvent is needed; a pump can be used for continuous feeding and discharging, and continuous operation is facilitated; the method is safe, efficient and stable in decolorization effect.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a molecular distillation decolorization method for long-chain fatty acids. Background Technology

[0002] Fatty acid products are widely used in the food, pharmaceutical, and industrial sectors. With market development, the demand for different types of light-colored fatty acids is increasing across various industries. Low-color palmitic acid, oleic acid, stearic acid (isostearic acid), and their derivatives are widely used in the cosmetics industry as emulsifiers, detergents, light-colored soap bases, and base oils. In high-end manufacturing, low-color fatty acids and their derivatives are required as raw materials for precision component cleaning agents and lubricants. The ink and coating industries require light-colored oleic acid and linoleic acid as production raw materials.

[0003] Fatty acid products are often decolorized using distillation or adsorption processes. Distillation or rectification processes require maintaining high vacuum and temperature levels, making equipment operation difficult and costly. Unsaturated fatty acid products or impurities (such as oleic acid and linoleic acid) are prone to polymerization or deterioration at high temperatures, affecting product quality and posing safety hazards during production. Adsorption processes, while producing light-colored products, generate large amounts of waste adsorbent, requiring additional hazardous waste treatment.

[0004] Chinese patent application 201010189076.5 discloses a method for preparing light-colored linseed oil fatty acids. The method involves flash evaporation of dehydrated and degassed fatty acids to obtain a light-colored linseed oil fatty acid product. Although this process avoids the problem of oil deterioration caused by prolonged exposure to high temperatures, the iron-cobalt color of the decolorized product ranges from 1 to 6, indicating an unstable decolorization effect.

[0005] Chinese patent application 201610996758.4 discloses a method for decolorizing and deodorizing fatty acids from gutter oil. The method involves melting and hydrolyzing the gutter oil to obtain fatty acids, and then removing the color and odor from the fatty acids using an adsorbent. However, the decolorized product is pale yellow to white, and the decolorization effect is unstable, failing to meet the color requirements of some industries.

[0006] Therefore, there is an urgent need for a safe, efficient, and stable decolorization process to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a molecular distillation decolorization method for long-chain fatty acids, which solves many defects in existing decolorization processes.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for molecular distillation decolorization of long-chain fatty acids, comprising the following steps: (1) The long-chain fatty acid raw material is heated and melted, and the liquid that is immiscible with the long-chain fatty acid is removed to obtain liquid long-chain fatty acid. (2) The liquid long-chain fatty acids are filtered to remove impurities; (3) Set the preheating temperature, heating temperature, vacuum pressure and condensation temperature of the molecular distillation apparatus; after the vacuum pressure and temperature reach the set conditions, adjust the scraper speed, open the feeding valve, control the feeding speed to feed, and perform molecular distillation on the filtered and impurity-removed liquid long-chain fatty acids. Collect the decolorized long-chain fatty acids at the outlet of the light component and collect the colored impurities at the outlet of the heavy component. In step (3), the preheating temperature is 25~250℃, the heating temperature is 50~250℃, the vacuum pressure is 0.1~300Pa, the condensation temperature is -5~80℃, the scraper rotation speed is 30~500rpm, and the feeding speed is 1.5~50kg / (m²). 2 ·h).

[0009] Furthermore, in the molecular distillation decolorization method, the long-chain fatty acid raw material in step (1) includes a monocarboxylic acid and colored impurities with a molecular weight greater than that of the target monocarboxylic acid.

[0010] Furthermore, in the molecular distillation decolorization method, the monocarboxylic acid is selected from at least one of (a), (b), (c), and (d): (a) Straight-chain monocarboxylic acids with 16 to 20 carbon atoms (b) Branched monocarboxylic acids with 16 to 20 carbon atoms (c) Straight-chain or branched monocarboxylic acids with 16 to 20 carbon atoms and a methyl terminus replaced by a phenyl group. (d) Straight-chain or branched monocarboxylic acids with 16 to 20 carbon atoms and methyl terminus replaced by cycloalkyl groups.

[0011] Furthermore, in the molecular distillation decolorization method, the heating and melting temperature in step (1) is ≤120℃.

[0012] Furthermore, in the molecular distillation decolorization method, the filtration accuracy of the filtration and impurity removal in step (2) is 0.1~50μm.

[0013] Furthermore, in the molecular distillation decolorization method, the porous filter medium used for filtration and impurity removal in step (2) includes at least one of organic polymers and inorganic materials. The organic polymers include one or more of nylon, aramid, spandex, polyester, polytetrafluoroethylene, polyvinylidene fluoride, polyethersulfone, and cellulose. The inorganic materials include metal filters and / or ceramics.

[0014] Furthermore, in the molecular distillation decolorization method, in step (3), the preheating temperature is lower than the heating temperature, and the condensation temperature is lower than the preheating temperature.

[0015] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: The present invention first removes gaseous and solid impurities from long-chain fatty acid raw materials through melting and filtration, and then separates colorless or light-colored fatty acid products from the mixture by molecular distillation, utilizing the difference in the free path between fatty acid products and colored polymers and discolored deteriorated products. The advantages of this invention are: no adsorbent is used, avoiding the residue and post-treatment of waste adsorbent; direct separation by molecular distillation, with short heating time and high vacuum, avoids material deterioration and coking at high temperatures for extended periods; no solvent is required; continuous feeding and discharging can be achieved using a pump, facilitating continuous operation; it is safe, efficient, and provides stable decolorization. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0017] Figure 1 This is a schematic diagram of the process route for the molecular distillation decolorization method of long-chain fatty acids. Detailed Implementation

[0018] This invention provides a molecular distillation decolorization method for long-chain fatty acids, the process flow diagram of which is shown below. Figure 1 As shown, it includes the following steps: (1) The long-chain fatty acid raw material is heated and melted, and the liquid that is immiscible with the long-chain fatty acid is removed to obtain liquid long-chain fatty acid. (2) The liquid long-chain fatty acids are filtered to remove impurities; (3) Set the preheating temperature, heating temperature, vacuum pressure and condensation temperature of the molecular distillation apparatus; after the vacuum pressure and temperature reach the set conditions, adjust the scraper speed, open the feeding valve, control the feeding speed to feed, and perform molecular distillation on the filtered and impurity-removed liquid long-chain fatty acids. Collect the decolorized long-chain fatty acids at the outlet of the light component and collect the colored impurities at the outlet of the heavy component. In step (3), the preheating temperature is 25~250℃, the heating temperature is 50~250℃, the vacuum pressure is 0.1~300Pa, the condensation temperature is -5~80℃, the scraper rotation speed is 30~500rpm, and the feeding speed is 1.5~50kg / (m²). 2 ·h).

[0019] In this invention, the long-chain fatty acid raw material in step (1) preferably includes a monocarboxylic acid and colored impurities with a molecular weight greater than that of the target monocarboxylic acid.

[0020] In this invention, the mass fraction of the monocarboxylic acid in the long-chain fatty acid raw material is not limited, and the actual test results of different long-chain fatty acid raw materials shall prevail.

[0021] In this invention, the monocarboxylic acid is selected from at least one of (a), (b), (c), and (d): (a) Straight-chain monocarboxylic acids with 16 to 20 carbon atoms (b) Branched monocarboxylic acids with 16 to 20 carbon atoms (c) Straight-chain or branched monocarboxylic acids with 16 to 20 carbon atoms and a methyl terminus replaced by a phenyl group. (d) Straight-chain or branched monocarboxylic acids with 16 to 20 carbon atoms and methyl terminus replaced by cycloalkyl groups.

[0022] In this invention, the monocarboxylic acid is selected from one or more of palmitic acid, octadecanoic / polyunsaturated acids, linoleic acid, stearic acid, isostearic acid, arachidic acid, methyl-terminated phenyl-substituted octadecanoic fatty acids, and methyl-terminated cycloalkyl-substituted octadecanoic fatty acids.

[0023] In this invention, when the monocarboxylic acid is selected from multiple sources, the proportion of each substance is not limited, and any scheme known to those skilled in the art can be used.

[0024] In this invention, the colored substance preferably includes dimer fatty acids, polyfatty acids and / or other substances that change color upon heating, such as carbon black and asphalt-like colloids, produced by the thermal or oxidative decomposition of fatty acids.

[0025] In this invention, the long-chain fatty acid raw material in step (1) is preferably in solid, semi-solid or liquid state.

[0026] In this invention, the heating and melting atmosphere in step (1) is preferably atmospheric pressure, nitrogen protection, or vacuum conditions.

[0027] In this invention, the heating and melting temperature in step (1) is preferably ≤120℃, more preferably ≤100℃, and even more preferably ≤85℃. The heating and melting temperature is determined based on the carbon chain length, molecular structure, and number of unsaturated bonds of the raw material. The heating and melting time is not limited; the long-chain fatty acid raw material only needs to be melted into a liquid state.

[0028] In this invention, the purpose of heating and melting in step (1) is to retain the fatty acid phase after the liquid is completely melted and the immiscible liquids are separated into layers, so as to separate the immiscible liquids and bubbles in the raw material and reduce the load of subsequent molecular distillation.

[0029] In this invention, the filtration accuracy of the impurity removal process in step (2) is preferably 0.1~50μm, more preferably 0.22~30μm, and even more preferably 23μm.

[0030] In this invention, the porous filter medium for filtering and removing impurities in step (2) preferably includes at least one of organic polymers and inorganic substances, and is more preferably an organic polymer.

[0031] In this invention, the organic polymer preferably includes one or more of nylon, aramid, spandex, polyester, polytetrafluoroethylene, polyvinylidene fluoride, polyethersulfone, and cellulose, more preferably one of nylon, aramid, spandex, and polyester, and more preferably nylon.

[0032] In this invention, the inorganic material preferably includes a metal filter and / or ceramic, and more preferably a metal filter.

[0033] In this invention, the purpose of the filtration and impurity removal in step (2) is to remove suspended or settled solid mechanical impurities from fatty acids.

[0034] In this invention, the molecular distillation apparatus in step (3) is preferably the Gongyi Yuhua YHMD-60(B) molecular distillation apparatus.

[0035] In this invention, in step (3), the preheating temperature is preferably 50~200℃, more preferably 60~120℃, and even more preferably 80℃; The heating temperature is preferably 150~200℃, more preferably 150~190℃, and even more preferably 150℃; The vacuum pressure is preferably 0.5~100Pa, more preferably 30~70Pa, and even more preferably 50Pa; The condensation temperature is preferably 0~25℃, more preferably 5~20℃, and even more preferably 10℃; The scraper rotation speed is preferably 100~300 rpm, more preferably 150~200 rpm, and even more preferably 150 rpm; The preferred feeding rate is 2~20 kg / (m²). 2 ·h), further preferably 5~15kg / (m 2 ·h), more preferably 10kg / (m 2 ·h).

[0036] In this invention, in step (3), the preheating temperature is preferably lower than the heating temperature, and the condensation temperature is preferably lower than the preheating temperature.

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] In the embodiments, the qualitative and quantitative analysis methods for long-chain fatty acids in raw materials and products were gas chromatography (AOCS Ce 1b-89), and the colorimetric analysis method was the platinum-cobalt colorimetric method (ISO2211).

[0039] Example 1

[0040] This embodiment provides a molecular distillation decolorization method for long-chain fatty acids, including the following steps: (1) The raw material to be processed (long-chain fatty acids account for 98 wt% of the total raw material, and the normalized composition of fatty acid types and gas phase analysis is: palmitic acid 15 wt%, octadecanoic mono / polyunsaturated acid 20 wt%, stearic acid 55 wt%, methyl-terminated phenyl-substituted octadecanoic fatty acid 10 wt%) is placed at 100°C until the material is completely melted, and the water layer of the melted material is discarded. (2) The fatty acid layer was filtered with a 600-mesh nylon filter bag (pore size about 23 μm) to remove suspended and precipitated mechanical impurities, and a clear brown liquid long-chain fatty acid filtrate was obtained (platinum cobalt color greater than the detection limit of 500 degrees). (3) Set the molecular distillation apparatus (Gongyi Yuhua YHMD-60(B) molecular distillation apparatus) to a vacuum pressure of 0.5 Pa, a preheating temperature of 60 °C, a heating temperature of 150 °C, and a built-in condenser temperature of 5 °C. After the temperature and pressure reach the preset conditions, set the scraper speed to 100 rpm and open the discharge valve to discharge 2 kg / (m³) of water. 2 Feed at a rate of h) to begin molecular distillation; collect the light components as a decolorized product, test the product's platinum-cobalt color at 230 Hazen, and the product yield is 91 wt%.

[0041] Example 2

[0042] This embodiment provides a molecular distillation decolorization method for long-chain fatty acids, including the following steps: (1) The raw material to be treated (long-chain fatty acids account for 97.5 wt% of the total raw material, and the normalized composition of fatty acid types and gas phase analysis is: palmitic acid 70 wt% and stearic acid 30 wt%) is placed at 80°C until the material is completely melted, and the water layer of the melted material is discarded. (2) The fatty acid layer was filtered with a 600-mesh nylon filter bag (pore size about 23 μm) to remove suspended and precipitated mechanical impurities, resulting in a clear brown liquid long-chain fatty acid filtrate (platinum cobalt color value of 270 degrees). (3) Set the molecular distillation apparatus (manufacturer: Gongyi Yuhua, model: YHMD-60(B)) to a vacuum pressure of 30Pa, a preheating temperature of 80℃, a heating temperature of 150℃, and a built-in condenser temperature of 10℃. After the temperature and pressure reach the preset conditions, set the scraper speed to 100rpm and open the discharge valve to discharge 2kg / (m³) of material. 2 Feed at a rate of h) to begin molecular distillation; collect the light components as a decolorized product, test the product's platinum-cobalt color at 25 Hazen, and the product yield is 85 wt%.

[0043] Example 3

[0044] This embodiment provides a molecular distillation decolorization method for long-chain fatty acids, including the following steps: (1) The raw material to be processed (long-chain fatty acids account for 98.5 wt% of the total raw material, and the normalized composition of fatty acid types and gas phase analysis is: palmitic acid 20 wt%, stearic acid 75 wt%, methyl terminal cycloalkyl substituted octadecane fatty acids 5 wt%) is placed at 80°C until the material is completely melted, and the water layer of the melted material is discarded. (2) The fatty acid layer was filtered with a 600-mesh nylon filter bag (pore size about 23 μm) to remove suspended and precipitated mechanical impurities, and a clear brown liquid long-chain fatty acid filtrate was obtained (platinum cobalt color greater than the detection limit of 500 degrees). (3) Set the molecular distillation apparatus (manufacturer: Gongyi Yuhua, model: YHMD-60(B)) to a vacuum pressure of 70Pa, a preheating temperature of 120℃, a heating temperature of 200℃, and a built-in condenser temperature of 25℃. After the temperature and pressure reach the preset conditions, set the scraper speed to 150rpm and open the discharge valve to discharge 5kg / (m³) of material. 2 Feed at a rate of h) to begin molecular distillation; collect the light components as a decolorized product, test the product's platinum-cobalt color to be 20 Hazen, and the product yield to be 88 wt%.

[0045] Example 4

[0046] This embodiment provides a molecular distillation decolorization method for long-chain fatty acids, including the following steps: (1) The raw material to be processed (long-chain fatty acids account for 99.5 wt% of the total raw material, and the normalized composition of fatty acid types and gas phase analysis is: palmitic acid 80 wt%, stearic acid 8 wt%, methyl terminal cycloalkyl substituted octadecanoic fatty acid 10 wt%, arachidic acid 2 wt%) is placed at 85°C until the material is completely melted, and the water layer of the melted material is discarded. (2) The fatty acid layer was filtered through a 0.22 μm nylon filter membrane to remove suspended and precipitated mechanical impurities, resulting in a clear brown liquid long-chain fatty acid filtrate (platinum-cobalt color value of 350 degrees). (3) Set the molecular distillation apparatus (manufacturer: Gongyi Yuhua, model: YHMD-60(B)) to a vacuum pressure of 50Pa, a preheating temperature of 50℃, a heating temperature of 190℃, and a built-in condenser temperature of 0℃. After the temperature and pressure reach the preset conditions, set the scraper speed to 200rpm and open the discharge valve to discharge at a rate of 10kg / (m³). 2 Feed at a rate of h) to begin molecular distillation; collect the light components as a decolorized product, test the product's platinum-cobalt color at 15 Hazen, and the product yield is 93 wt%.

[0047] In summary, the long-chain fatty acid decolorization method provided by this invention uses molecular distillation for direct separation of materials, achieving high vacuum and short heating time. This effectively avoids product quality degradation caused by long-term heating and deterioration or coking of fatty acids. Furthermore, it does not use adsorbents or other solvents, offering advantages such as safety, high efficiency, stability, and environmental friendliness. The process flow of this invention is simple, safe, and efficient; it eliminates the need for decolorizing agents or adsorbents, reducing reagent usage; and the short heating time avoids material denaturation caused by prolonged heating.

[0048] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for molecular distillation decolorization of long-chain fatty acids, characterized in that, Includes the following steps: (1) The long-chain fatty acid raw material is heated and melted, and the liquid that is immiscible with the long-chain fatty acid is removed to obtain liquid long-chain fatty acid. (2) The liquid long-chain fatty acids are filtered to remove impurities; (3) Set the preheating temperature, heating temperature, vacuum pressure and condensation temperature of the molecular distillation apparatus; after the vacuum pressure and temperature reach the set conditions, adjust the scraper speed, open the feeding valve, control the feeding speed to feed, and perform molecular distillation on the filtered and impurity-removed liquid long-chain fatty acids. Collect the decolorized long-chain fatty acids at the outlet of the light component and collect the colored impurities at the outlet of the heavy component. In step (3), the preheating temperature is 25~250℃, the heating temperature is 50~250℃, the vacuum pressure is 0.1~300Pa, the condensation temperature is -5~80℃, the scraper rotation speed is 30~500rpm, and the feeding speed is 1.5~50kg / (m²). 2 ·h).

2. The molecular distillation decolorization method according to claim 1, characterized in that, The long-chain fatty acid raw material in step (1) includes monocarboxylic acids and colored impurities with a molecular weight greater than that of the target monocarboxylic acid.

3. The molecular distillation decolorization method according to claim 2, characterized in that, The monocarboxylic acid is selected from at least one of (a), (b), (c), and (d): (a) Straight-chain monocarboxylic acids with 16 to 20 carbon atoms (b) Branched monocarboxylic acids with 16 to 20 carbon atoms (c) Straight-chain or branched monocarboxylic acids with 16 to 20 carbon atoms and a methyl terminus replaced by a phenyl group. (d) Straight-chain or branched monocarboxylic acids with 16 to 20 carbon atoms and methyl terminus replaced by cycloalkyl groups.

4. The molecular distillation decolorization method according to any one of claims 1 to 3, characterized in that, The heating and melting temperature in step (1) is ≤120℃.

5. The molecular distillation decolorization method according to claim 1, characterized in that, The filtration accuracy of the impurity removal process in step (2) is 0.1~50μm.

6. The molecular distillation decolorization method according to claim 1 or 5, characterized in that, The porous filter medium used for filtration and impurity removal in step (2) includes at least one of organic polymers and inorganic materials. The organic polymers include one or more of nylon, aramid, spandex, polyester, polytetrafluoroethylene, polyvinylidene fluoride, polyethersulfone, and cellulose. The inorganic materials include metal filters and / or ceramics.

7. The molecular distillation decolorization method according to claim 1, characterized in that, In step (3), the preheating temperature is lower than the heating temperature, and the condensation temperature is lower than the preheating temperature.

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