Method for efficiently preparing arachidic acid and behenic acid by adsorbing and removing impurities from raw materials through bio-based calcium oxide

Abstract

The invention discloses a method for efficiently preparing arachidic acid and behenic acid by adsorbing and decontaminating raw materials through bio-based calcium oxide, and relates to the field of grease chemical engineering, the method comprises the following steps: S1, high-erucic acid rapeseed oil raw materials are subjected to decontaminating treatment through an adsorption column filled with bio-based calcium oxide, and the bio-based calcium oxide is prepared by calcining aquatic organism shells; s2, carrying out acidic hydrolysis on the impurity-removed raw material to obtain mixed fatty acid; according to the method for efficiently preparing the arachidic acid and the behenic acid by adsorbing and removing impurities from the raw materials through the bio-based calcium oxide, the bio-based calcium oxide is prepared from waste shells, high-value utilization of waste is achieved, and the cost is low. The material has a high specific surface area and abundant mesopores, and shows a selective adsorption capacity far higher than that of common calcium oxide on polar impurities such as thioglycoside and colloid, the removal rate can reach 88% or above, and the purity of the raw materials is guaranteed from the source.

Description

TECHNICAL FIELD

[0001] The present application relates to oil and fat chemical technology, in particular to a method for efficiently preparing arachidic acid and behenic acid by adsorbing and removing impurities from raw materials with bio-based calcium oxide. BACKGROUND

[0002] Arachidic acid (eicosanoic acid) and behenic acid (docosanoic acid) are two important long-chain saturated fatty acids, which are widely used in cosmetics, food, medicine and chemical industry. At present, its production is highly dependent on imports, the market supply is tight, and the price is high.

[0003] The traditional production process mainly adopts phosphoric acid acidification method to pre-remove sulfur from rapeseed oil, and then carries out hydrogenation and hydrolysis. This process has obvious defects: the desulfurization efficiency is low, and the impurities such as glucosinolate are not completely removed; the residual impurities are easy to cause the poisoning and deactivation of the subsequent hydrogenation catalyst, and the hydrogenation reaction is difficult; the quality of the final product is unstable, and the purity is difficult to meet the requirements of high-end applications. Therefore, developing an efficient and complete raw material purification technology is the key to stably producing high-purity arachidic acid and behenic acid.

[0004] Calcium oxide is often used for oil deacidification, but its conventional source (mineral calcination) has limited specific surface area and general adsorption performance. It is of great significance to seek a calcium oxide material with wide source, low cost and excellent adsorption performance, and apply it to the removal and purification of high-erucic acid oil, in order to improve the economy and product competitiveness of the overall process. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a method for efficiently preparing arachidic acid and behenic acid by adsorbing and removing impurities from raw materials with bio-based calcium oxide. The core of the present application is to use a bio-based calcium oxide prepared from waste aquatic organism shells as a special adsorbent. This adsorbent has a unique porous structure and high specific surface area, and can efficiently and selectively adsorb and remove harmful impurities such as glucosinolate and gum in high-erucic acid rapeseed oil, thereby providing pure raw materials for subsequent hydrogenation reaction, and significantly improving the efficiency of the catalyst and the quality of the product.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme: a method for efficiently preparing arachidic acid and behenic acid by adsorbing and removing impurities from raw materials with bio-based calcium oxide, comprising the following steps:

[0007] S1, passing high-erucic acid rapeseed oil raw material through an adsorption column filled with bio-based calcium oxide for impurity removal treatment, wherein the bio-based calcium oxide is prepared by calcining aquatic organism shells;

[0008] S2, acid hydrolysis of the impurity-removed raw material to obtain mixed fatty acids;

[0009] S3, hydrogenation reaction of the mixed fatty acids in the presence of a hydrogenation catalyst;

[0010] S4, the hydrogenated product is subjected to molecular distillation to separate peanut acid fraction and behenic acid fraction.

[0011] Through the synergistic effect of the four steps, high-purity peanut acid and behenic acid are efficiently prepared from high erucic rapeseed oil. The core is to use the biological calcium oxide made from calcination of aquatic organism shells as an adsorbent. First, in step S1, the high erucic rapeseed oil raw material is passed through an adsorption column filled with the biological calcium oxide. The microporous structure and surface basic sites of the biological calcium oxide can selectively adsorb polar impurities such as phospholipids, pigments, and free fatty acids in the raw material, thereby achieving pretreatment and purification of the raw material. Then, in step S2, the de-impurity raw material is subjected to acid hydrolysis. Under the conditions of acid and heat, the ester bond of triglyceride in oil and fat is broken, and mixed fatty acids are released. Next, in step S3, the mixed fatty acids are subjected to hydrogenation reaction in the presence of a hydrogenation catalyst. The catalyst activates hydrogen, and the carbon-carbon double bonds in the unsaturated fatty acids, especially erucic acid, in the mixed fatty acids are hydrogenated and saturated, thereby converting all fatty acids into saturated C20 and C22 fatty acids, which are precursors of peanut acid and behenic acid. Finally, in step S4, the product mainly composed of saturated fatty acids after hydrogenation is subjected to molecular distillation. Under high vacuum and controlled temperature, the small boiling point difference between peanut acid and behenic acid is utilized to separate them on the surface of the evaporator, and they are respectively condensed and collected, thereby obtaining high-purity peanut acid fraction and behenic acid fraction.

[0012] Further, the aquatic organism shell is oyster shell or clam shell.

[0013] The aquatic organism shell is oyster shell or clam shell, which is widely sourced and is a common aquaculture waste. Its main component is calcium carbonate, which can be efficiently converted into biological calcium oxide after calcination, and its naturally formed porous microstructure is retained or enhanced, which provides ideal specific surface area and active sites for adsorption and de-impurity, and realizes recycling of resources.

[0014] Further, the preparation method of the biological calcium oxide comprises: making the cleaned shell into powder, calcining at 800-950℃ for 2-6 hours, and grinding to a particle size of 150-250 mesh.

[0015] By making the cleaned shell into powder and calcining at a temperature of 800 to 950 degrees Celsius for 2 to 6 hours, the calcium carbonate in the shell can be completely decomposed into calcium oxide and the organic residues can be removed, forming a highly active adsorbent material. Subsequently, grinding to a particle size of 150 to 250 mesh is to obtain a powder with uniform and appropriate particle size, so as to ensure that it has a suitable stacking density and fluid channel when filling the adsorption column, thereby realizing full and effective contact with the raw material oil in step S1 and maximizing the efficiency of adsorption and de-impurity.

[0016] Further, in step S1, the operating pressure of the adsorption column is 0.1-0.3 MPa, and the flow rate of the raw oil is 5-15 mL / min for a chromatographic column with a diameter of 50 mm.

[0017] The operating conditions of the adsorption column in step S1 are controlled to have an operating pressure in the range of 0.1 to 0.3 MPa, so as to provide sufficient driving force to make the viscous raw oil pass through the packed bed of bio-based calcium oxide smoothly without crushing the adsorbent structure; and the flow rate of the raw oil is controlled to be 5 to 15 mL per minute for a chromatographic column with a diameter of 50 mm, so as to ensure sufficient contact residence time of the raw oil with the bio-based calcium oxide particles, so that the impurities can be fully adsorbed, thereby achieving high-efficiency impurity removal effect and providing pure raw material for the subsequent steps.

[0018] Further, in step S2, the acid hydrolysis conditions are as follows: sulfuric acid or hydrochloric acid is used as the hydrolysis agent, the reaction temperature is 70-90℃, the acid concentration is 10-30%, and the reaction time is 3-5 hours.

[0019] Sulfuric acid or hydrochloric acid is used as the hydrolysis agent because they are both strong acids and can provide high concentration of hydrogen ions to catalyze the hydrolysis reaction of ester bonds; the reaction temperature is controlled to be 70 to 90 degrees Celsius, the acid concentration is controlled to be 10 to 30 percent, and the reaction time is controlled to be 3 to 5 hours, and the synergistic effect of these conditions is to ensure that triglycerides are completely hydrolyzed into mixed fatty acids while avoiding excessive temperature or acid concentration that can cause side reactions of fatty acids or accelerate equipment corrosion, thereby efficiently obtaining the mixed fatty acid product.

[0020] Further, in step S3, the hydrogenation reaction conditions are as follows: Pd / C or Raney Ni is used as the catalyst, the reaction temperature is 160-200℃, the hydrogen pressure is 2.0-4.0 MPa, and the reaction time is 4-8 hours.

[0021] Palladium on carbon catalyst or Raney nickel catalyst is used because they have high activity and selectivity for hydrogenation of fatty acids; the reaction temperature is controlled to be 160 to 200 degrees Celsius, the hydrogen pressure is controlled to be 2.0 to 4.0 MPa, and the reaction time is controlled to be 4 to 8 hours, so as to provide sufficient energy and reactant concentration for the hydrogenation reaction under the joint action of the catalysts, to ensure that the unsaturated bonds in the mixed fatty acids, especially the double bonds in erucic acid, are completely hydrogenated and saturated, thereby converting the fatty acid composition to be mainly saturated arachidic acid and behenic acid, which is convenient for subsequent separation.

[0022] Further, in step S4, the molecular distillation conditions are as follows: the evaporator temperature is 210-230℃, and the system vacuum degree is ≤0.5 Pa.

[0023] The evaporator temperature is set at 210 to 230 degrees Celsius to give the target components arachidic acid and behenic acid sufficient kinetic energy to evaporate from the liquid film surface while avoiding substantial evaporation of higher carbon number or heat sensitive substances; the system vacuum is controlled at less than or equal to 0.5 Pa to significantly lower the boiling point of the material, enabling distillation at a temperature far below the normal pressure boiling point, thereby minimizing thermal decomposition or polymerization of the fatty acids, achieving efficient and mild separation based on the difference in mean free path of molecular motion, and ultimately obtaining high purity arachidic acid and behenic acid fractions.

[0024] An arachidic acid prepared by the method has a purity of ≥98%.

[0025] The purity of the arachidic acid product is greater than or equal to 98%, and this high purity result is directly due to the synergy of the entire method, especially the step S1 of removing a large amount of impurities by adsorption of biobased calcium oxide, the step S3 of unifying the saturation degree of fatty acids by hydrogenation reaction, and the step S4 of high-precision separation by molecular distillation, which together guarantee that the final arachidic acid product has extremely high chemical purity.

[0026] A behenic acid prepared by the method has a purity of ≥98%.

[0027] The purity of the behenic acid product is greater than or equal to 98%, and the high-purity behenic acid is obtained due to the optimization and contribution of each step in the method, from the adsorption pretreatment of the raw material, complete hydrolysis and hydrogenation conversion, to the final efficient molecular distillation separation, the entire process chain is designed to maximize the yield and purity of the target product behenic acid.

[0028] Compared with the prior art, the method for efficiently preparing arachidic acid and behenic acid by adsorbing and removing impurities from raw materials by biobased calcium oxide provided by the application has the following beneficial effects:

[0029] 1. Biobased calcium oxide is prepared from waste shells, achieving high-value utilization of waste and being low in cost. The material has a high specific surface area and abundant mesopores, and shows a selective adsorption capacity for polar impurities such as glucosinolates and gums that is much higher than that of ordinary calcium oxide, with a removal rate of more than 88%, thereby ensuring the purity of the raw material from the source.

[0030] 2. The impurity removal step significantly reduces the risk of deactivation of the subsequent hydrogenation catalyst, stabilizes the hydrogenation conversion rate at more than 99.5%, and improves the reaction efficiency and service life of the catalyst.

[0031] 3. Through precise control of molecular distillation, arachidic acid and behenic acid with a purity of ≥98% can be simultaneously separated from the same batch of raw materials, the process has high atom economy, and the product value is maximized.

[0032] 4. The whole process uses biomass waste as adsorbent raw material, is clean and meets the development direction of green chemical industry. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art according to these drawings.

[0034] Figure 1 Process flow diagram provided for the embodiments of the present application;

[0035] Figure 2 Nitrogen adsorption-desorption isotherm and pore size distribution diagram of the prepared bio-based calcium oxide provided for the embodiments of the present application;

[0036] Figure 3 Gas chromatogram comparison diagram of the final products of Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0037] In order to make those skilled in the art better understand the technical solutions of the present application, the present application will be further described in detail below with reference to the drawings.

[0038] Raw materials used in the embodiments: high erucic rapeseed oil, erucic acid content ≥45%, purchased from Heda Xisipu Chemical Co., Ltd. Sichuan. Unless otherwise specified, the reagents used are commercially available analytical pure.

[0039] As shown in the accompanying Figure 1 to the accompanying Figure 3 :

[0040] Example 1:

[0041] S1, preparation and impurity removal of bio-based calcium oxide:

[0042] Take 1 kg of raw oyster shells, wash and dry, and then use a crusher to preliminarily crush. Then use a ball mill (QM-3SP2) to grind to pass through a 100-mesh sieve. Soak in 0.5 mol / L HCl solution for 2 hours, and then wash with deionized water until the filtrate is neutral. Place the powder in a muffle furnace (SX2-4-10) and heat at a rate of 5℃ / min to 900℃, and keep the temperature for 4 hours. After natural cooling, grind again to pass through a 200-mesh sieve to obtain white bio-based calcium oxide powder. The specific surface area is 58.3 m² / g and the average pore size is 5.2 nm by BET test.

[0043] The 200 g of the bio-based calcium oxide wet packing was filled in a chromatographic column (Φ50 mm x 800 mm. 1.0 L of high erucic rapeseed oil was taken, and a laminar pump was used to pump into the top of the column at a flow rate of 10 mL / min, and the system pressure was maintained at 0.2 MPa. The effluent oil was collected. The test showed that the glucosinolate content was reduced from 45 μmol / g to 4.2 μmol / g, and the removal rate was 90.7%.

[0044] S2, acid hydrolysis:

[0045] 500 g of the oil was taken, 100 g of 20% (w / w) sulfuric acid solution was added, and it was placed in a 1000 mL three-necked flask, heated in a 80°C water bath, and reacted at a stirring speed of 500 rpm for 4 hours. After the reaction was completed, it was allowed to stand and separate into layers, the upper oil phase was taken and washed with hot water until it was neutral, and the hydrolyzed mixed fatty acid was obtained.

[0046] S3, hydrogenation reaction:

[0047] All the hydrolyzed fatty acids were added to a 500 mL high-pressure reaction kettle, and 5 g of 5% Pd / C catalyst was added. After sealing, the air in the kettle was replaced with hydrogen three times. Then the temperature was raised to 180°C, hydrogen was introduced to stabilize the pressure at 3.0 MPa, and the stirring was started (800 rpm and the timer was started, and the reaction was carried out for 6 hours. After the reaction was completed, the temperature was lowered and the pressure was released, the catalyst was recovered by filtration, and the hydrogenated fatty acid was obtained. Gas chromatography analysis showed that the hydrogenation conversion rate of erucic acid was 99.6%.

[0048] S4, molecular distillation:

[0049] The hydrogenated fatty acid was added to the feed tank of a short-path molecular distillation device (KDL-5. The evaporator temperature was set to 220°C, the condenser temperature was set to 50°C, and the system vacuum degree was maintained to 0.1 Pa by a diffusion pump. The feed pump was started, and the feed rate was controlled at 2 mL / min. Light fraction, main fraction and heavy fraction were collected respectively.

[0050] S5, product analysis:

[0051] Gas chromatography (GC-2010 Plus, FID detector and mass spectrometry (GC-MS analysis:

[0052] Light fraction: mainly C16:0 and C18:0 fatty acids (stearic acid, etc., purity 95.3%.

[0053] Main fraction 1 (arachidic acid fraction: arachidic acid (C20:0 content 98.5%, yield (calculated from C20 unsaturated acid in raw material oil) 41.8%.

[0054] Main fraction 2 (behenic acid fraction: behenic acid (C22:0 content 98.8%, yield (calculated based on C22 unsaturated acid in raw material oil) 48.1%.

[0055] Example 2:

[0056] Change the calcination condition of the bio-based calcium oxide: the calcination temperature is 800℃, the holding time is 5 hours, and the remaining steps are completely same as those in Example 1. The specific surface area of the obtained adsorbent is 65.1 m² / g, and the glucosinolate removal rate is 85.5%. Finally, the purity of arachidic acid is 97.9%, and the purity of behenic acid is 98.1%.

[0057] Example 3:

[0058] Change the hydrogenation reaction condition: 2% Raney Ni catalyst (amount 1.5%, reaction temperature 190℃, hydrogen pressure 2.5 MPa, reaction time 7 hours, and the remaining steps are same as those in Example 1. Finally, the purity of arachidic acid is 98.0%, and the purity of behenic acid is 98.3%.

[0059] Comparative Example 1:

[0060] The commercially available analytical pure calcium oxide (National Pharmaceutical Group, the specific surface area is 8.7 m² / g by BET test) is used to replace the bio-based calcium oxide in Example 1 to carry out adsorption and impurity removal, and the addition amount is same as 200 g. After the impurity removal, the glucosinolate content in the oil is 29.3 μmol / g, and the removal rate is only 34.9%. The subsequent steps are same as those in Example 1. After the hydrogenation, the conversion rate is 92.1%. After the molecular distillation, the purity of arachidic acid is only 94.5%, the purity of behenic acid is only 94.8%, and the product color is yellowish.

[0061] Comparative Example 2:

[0062] Without carrying out the adsorption and impurity removal treatment, the high erucic rapeseed oil is directly subjected to acid hydrolysis, hydrogenation and molecular distillation, and all the subsequent step parameters are same as those in Example 1. After the hydrogenation reaction is carried out for 2 hours, the pressure no longer decreases, and the conversion rate is stalled at about 85%. After the product is subjected to the molecular distillation, the impurity peaks in the arachidic acid and behenic acid fractions obviously increase, and the purity is less than 90%.

[0063] Table 1: Comparison of experimental results:

[0064] Item Example 1 Example 2 Comparative Example 1 Comparative Example 2 Adsorbent specific surface area, (m2 / g) 58.3 65.1 8.7 - Sulphosin removal, (%) 90.7 85.5 34.9 0 Erdic acid hydrogenation conversion, (%) 99.6 99.3 92.1 ~85 Arachidic acid purity, (%) 98.5 97.9 94.5 ＜90 Behenic acid purity, (%) 98.8 98.1 94.8 ＜90

[0065] As known from the above examples and comparative examples, the adsorption and impurity removal using the specific bio-based calcium oxide is a key step to ensure the efficient operation of the whole process and obtain high-purity co-production products. The effect is significantly better than that of the conventional material, and is also much better than that of the process route without impurity removal.

[0066] The foregoing merely illustrates some exemplary embodiments of the application, and it will be appreciated that those skilled in the art will be able to devise various modifications without departing from the spirit and scope of the application. The appended drawings and description are illustrative only, and are not intended to be limiting.

Claims

1. A method for efficiently preparing arachidic acid and behenic acid from raw materials by adsorption and deimpurification using bio-based calcium oxide, characterized in that, Includes the following steps: S1. The high-erucic acid rapeseed oil raw material is subjected to impurity removal treatment by passing it through an adsorption column filled with bio-based calcium oxide, wherein the bio-based calcium oxide is prepared by calcining the shell of an aquatic organism. S2. The purified raw material is subjected to acidic hydrolysis to obtain mixed fatty acids; S3. The mixed fatty acids are subjected to a hydrogenation reaction in the presence of a hydrogenation catalyst; S4. The hydrogenated product is subjected to molecular distillation to separate the arachidic acid fraction and the behenic acid fraction.

2. The method for efficiently preparing arachidic acid and behenic acid by adsorption and deimpurification of raw materials using bio-based calcium oxide according to claim 1, characterized in that, The shell of the aquatic organism is an oyster shell or a raw oyster shell.

3. The method for efficiently preparing arachidic acid and behenic acid by adsorption and deimpurification of raw materials using bio-based calcium oxide according to claim 1, characterized in that, The preparation method of the bio-based calcium oxide includes: making the cleaned shell into powder, calcining it at 800-950℃ for 2-6 hours, and grinding it until the particle size passes through a 150-250 mesh sieve.

4. The method for efficiently preparing arachidic acid and behenic acid by adsorption and deimpurification of raw materials using bio-based calcium oxide according to claim 1, characterized in that, In step S1, the operating pressure of the adsorption column is 0.1-0.3 MPa, and the flow rate of the feed oil is 5-15 mL / min for a 50 mm diameter chromatography column.

5. The method for efficiently preparing arachidic acid and behenic acid by adsorption and deimpurification of raw materials using bio-based calcium oxide according to claim 1, characterized in that, In step S2, the conditions for acid hydrolysis are: using sulfuric acid or hydrochloric acid as the hydrolysing agent, a reaction temperature of 70-90℃, an acid concentration of 10-30%, and a reaction time of 3-5 hours.

6. The method for efficiently preparing arachidic acid and behenic acid by adsorption and deimpurification of raw materials using bio-based calcium oxide according to claim 1, characterized in that, In step S3, the conditions for the hydrogenation reaction are as follows: using Pd / C or Raney Ni as a catalyst, reaction temperature 160-200℃, hydrogen pressure 2.0-4.0 MPa, and reaction time 4-8 hours.

7. The method for efficiently preparing arachidic acid and behenic acid by adsorption and deimpurification of raw materials using bio-based calcium oxide according to claim 1, characterized in that, In step S4, the conditions for molecular distillation are: evaporator temperature 210-230℃, system vacuum degree ≤0.5 Pa.

8. Arachidic acid prepared by the method according to any one of claims 1-7, characterized in that, Its purity is ≥98%.

9. A behenic acid prepared by the method according to any one of claims 1-7, characterized in that, Its purity is ≥98%.

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