A method for preparing industrial-grade mixed oil by enzymatic glycerin esterification of waste oil

Abstract

The present invention relates to the field of biochemical engineering technology, and in particular to a method for preparing industrial-grade mixed oil by enzymatic glycerization of waste oil. The method of the present invention is used to treat low-quality waste oil, and can catalyze the free fatty acids and glycerol therein to generate glyceride under mild conditions, and is energy-saving and environmentally friendly, has no chemical pollution, and can achieve the effect of reducing acid and increasing ester in waste low-quality oil, which is of great significance to promoting the production of industrial-grade mixed oil, promoting environmental protection and economic sustainable development.

Description

Technical Field

[0001] The invention relates to the technical field of biochemical engineering, and in particular to a method for preparing industrial-grade mixed oil by catalyzing the acid reduction of high-acid-value oils and fats using a bio-enzyme method. Background Art

[0002] Industrial-grade mixed oil refers to non-compliant waste animal and vegetable oils and fats produced in the catering service industry, food processing industry and household cooking, including waste oil, frying oil and other inedible oils and fats. After processing, it can be used to produce biodiesel, plasticizers, lubricants and other chemical raw materials. The production and export of industrial-grade mixed oil by enterprises is conducive to improving the recycling of waste resources, achieving export and foreign exchange earnings, and at the same time avoiding the return of waste oil to the table, ensuring food hygiene and safety.

[0003] However, waste oils and fats must be processed in advance before they can be traded as commodity industrial-grade mixed oils. High-quality waste oils and fats, such as sewage oil and frying oil, can be separated into qualified industrial mixed oils through simple precipitation, heating, three-phase separation and other processes. For low-quality oils and fats, their fatty acid content is high, and the saponification value, iodine value, phosphorus content and other indicators are far from meeting the export standards of industrial-grade mixed oils.

[0004] Glycerol esterification refers to the process of generating glycerol ester and water from free fatty acid and glycerol under certain conditions. At present, chemical catalysis is mainly used. Chinese patent CN108330001B discloses a method of realizing a multi-reactor series continuous glycerol esterification reaction in a reaction tank by setting a baffle and combining the use of a circulating pump, and using the principle of a communicating vessel, thereby achieving the purpose of reducing the acidity of the product. Chinese patent CN111471529B discloses a method for glycerol esterification of high acid value oils and fats. Under vacuum conditions, the reaction temperature is 200°C, and by adding a chemical targeting inducer, the acid value of high acid value oils and fats can be reduced under the synergistic effect of monoglyceride and glycerol. Chinese patent CN118272164A discloses a method for preparing industrial-grade mixed oil by glycerol esterification. Under the conditions of reaction temperature of 90-245°C and vacuum residual pressure of 4000Pa-15000Pa, high acid value oils and fats are treated for 270min-540min, and the acid value can be reduced to below 1mg KOH / g. The chemical method has a high reaction temperature, usually above 200°C, lacks selectivity, and produces many reaction by-products, making it easy for unsaturated fatty acids to be oxidized.

[0005] In recent years, the esterification reaction between fatty acids and glycerol catalyzed by microbial lipase has gradually emerged. Lipase, also known as triacylglycerol acyl hydrolase, has a very wide substrate spectrum and high stereoselectivity and regioselectivity. Therefore, it is a class of enzymes with multiple catalytic abilities, which can catalyze the hydrolysis, alcoholysis, esterification, transesterification and reverse synthesis of glycerides and other water-insoluble esters. It is widely used in food, beverage, washing, medicine, biochemical and other industries. Chinese patent CN101294170B discloses a method for producing fatty acids by hydrolyzing animal and vegetable oils or waste animal and vegetable oils using lipase, which uses lipase to carry out hydrolysis reaction in the presence of an emulsifier, and the hydrolysis rate reaches more than 90%. Chinese patent CN119040406A provides a high-content OPO oil mixture and a preparation method thereof. The OPO structure ester prepared by ester exchange reaction using specific raw materials increases the content of OPO and SN-2 palmitic acid, and significantly reduces the content of palmitic acid glyceride.

[0006] The lipase-catalyzed glycerol esterification method is used to treat inferior waste oils. The esterification reaction has strong specificity, mild reaction conditions, no need for high temperature conditions, few by-products, and is environmentally friendly and pollution-free. It can achieve the effect of reducing acid and increasing ester, thereby broadening the application scope of industrial-grade mixed oil production raw materials, reducing production costs, and helping to achieve the "dual carbon" goals. It plays a vital role in promoting environmental protection and promoting sustainable economic development. Summary of the invention

[0007] In order to solve the problems of the prior art, the present invention provides a method for preparing industrial-grade mixed oil by enzymatic glycerin esterification of waste oil, comprising the following steps:

[0008] (1) adding hot water to the inferior waste oil raw material for washing to remove phospholipids, inorganic salts and inorganic acids, filtering to remove lower layer water and impurities, and adjusting the pH of the raw material with potassium hydroxide solution;

[0009] (2) mixing the processed oil raw material, glycerol and lipase according to a certain proportion, and shearing them with a high-speed shearing machine;

[0010] (3) The mixed raw materials are introduced into a reactor for preheating, the esterification reaction is started under continuous stirring, and the free water generated by the reaction is removed by vacuum extraction.

[0011] Preferably, in step (1), the temperature of the hot water is 60-80° C., the concentration of the potassium hydroxide solution is 32%, the oil raw material is one of waste oil, acidified oil, kitchen waste oil, and deodorized distillate, and the pH of the raw material is adjusted to 5-8.

[0012] Preferably, in step (2), the mass ratio of the oil raw material, glycerol and lipase is 100:5-10:0.3-1, and the lipase is lipase FM-10, lipase 5000MM, Transform 2.0, TL100L, 20000L, the high-speed shearing time is 3-10min, and the rotating speed is 10000r / min.

[0013] Preferably, the preheating temperature in step (3) is 40-60°C, the stirring speed is 200r / min, and the vacuum degree is -0.8-1kPa.

[0014] The method of the present invention is used to treat inferior waste oils and fats, and can catalyze free fatty acids and glycerol therein to generate glyceride under mild conditions. The method is energy-saving and environmentally friendly, has no chemical pollution, requires a small number of equipment, and has low heat loss. The method can achieve the effect of reducing the acid and increasing the ester content of the waste inferior oils and fats, is conducive to industrial expansion, and is of great significance for promoting the production of industrial-grade mixed oils, and promoting environmental protection and economic sustainable development. DETAILED DESCRIPTION

[0015] The present invention is further described in conjunction with specific implementation cases, and those skilled in the art can better understand and grasp the present invention by this, rather than limiting the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0016] The acid value determination method described in the embodiment of the present invention is as follows:

[0017] Referring to GB 5009.229-2016, take a clean 250mL conical flask and weigh 5g of the prepared oil sample with a balance, and its mass m is in grams. Take another clean 250mL conical flask, add 50mL of 95% ethanol, and then add 0.5mL of phenolphthalein indicator. Then, put this conical flask in a 100℃ water bath and heat until the ethanol is slightly boiling. Take out the conical flask, and while the temperature of the ethanol is still above 70℃, immediately titrate the ethanol with a 0.5mol / L potassium hydroxide solution containing a standard titration solution. When the ethanol initially turns slightly red and there is no obvious fading within 15s, stop the titration immediately, and the acidity of the ethanol is neutralized. Pour this neutralized ethanol solution into the conical flask containing the sample while it is hot, and then put it in a 100℃ water bath and heat until the ethanol is slightly boiling, and shake the conical flask vigorously to form a suspension. Finally, take out the conical flask and immediately titrate the hot ethanol suspension of the sample with 0.5 mol / L potassium hydroxide solution containing standard titration solution while it is still hot. When the sample solution begins to turn slightly red and there is no obvious fading within 15 seconds, it is the endpoint of the titration. Stop the titration immediately and record the milliliters of standard titration solution consumed in this titration. This value is V.

[0018] Acid value calculation formula:

[0019]

[0020] Where X AV is the acid value of the sample, V is the volume of the standard titration solution consumed in the sample determination, in mL;

[0021] V0 is the volume of the standard titration solution consumed in the corresponding blank determination, in mL; c is the molar concentration of the standard titration solution, in mol / L; 56.1 is the molar mass of potassium hydroxide, in g / mol; m is the weight of the oil sample, in g.

[0022] The determination method of the glyceride content described in the embodiment of the present invention is as follows:

[0023] The glyceride content in the product was determined by high performance liquid chromatography. 25 mg of sample was dissolved in 1 mL of mobile phase, mixed evenly, and then passed through the membrane and loaded.

[0024] Chromatographic conditions: chromatographic column Sepax HP-Silica (4.6 mm × 250 mm × 5 μm),

[0025] Detector: Evaporative light scattering detector;

[0026] Column temperature: 30°C;

[0027] Sample concentration: 25 mg / mL,

[0028] Injection volume: 15 μL;

[0029] The ratio of mobile phase hexane:isopropanol:formic acid was 15:1:0.03 (v / v / v);

[0030] Flow rate: 1 mL / min.

[0031] Example 1 Enzymatic glycerin esterification of high-acid waste oil

[0032] Weigh 200g of waste cooking oil into a beaker, add 40mL of 80℃ hot water, stir at 80℃ for 30min using a water bath magnetic stirrer, let stand and settle for 2h, take the upper oil layer, adjust the pH to 6.2 with 32% NaOH solution, the oil sample is brown-red after pretreatment, take a sample to determine the initial acid value and glyceride content.

[0033] Weigh 100g of the pretreated waste oil sample in a beaker, add 8g of glycerol, 0.8g of lipase 5000MM, use a high-speed shearing machine at a speed of 10000r / min, shear and mix for 10min, and then pour it into the reactor. The reactor temperature is set to 50℃, the vacuum degree is minus 0.8kpa, the stirring speed is 300r / mim, and the acid value and glyceride content are measured after 24h of reaction. The test results are shown in Table 1.

[0034] Table 1 Acid value and glyceride determination results

[0035]

[0036] It can be seen from Table 1 that the acid value of the high-acid waste oil raw material after enzymatic glycerol esterification was greatly reduced from 110.4KOH / (mg / g) to 3.2KOH / (mg / g), and the triglyceride content was increased from 38.2% to 80.5%, indicating that the enzymatic high-acid waste oil glycerol esterification method has a better effect of reducing acid and increasing ester.

[0037] Example 2 Rapeseed Acidification Oil Enzymatic Glyceride

[0038] Weigh 200g of rapeseed acidified oil into a beaker, add 40mL of 80℃ hot water, stir at 80℃ for 30min using a water bath magnetic stirrer, let stand and settle for 2h, take the upper oil layer, adjust the pH to 5.8 with 32% NaOH solution, the oil sample is brown-red after pretreatment, take a sample to determine the initial acid value and glyceride content.

[0039] Weigh 100g of pretreated rapeseed acidified oil in a beaker, add 12g of glycerol and 0.3g of lipase FM-10, use a high-speed shearing machine at a speed of 10000r / min, shear and mix for 10min, and then pour it into the reactor. The reactor temperature is set to 60℃, the vacuum degree is minus 1kpa, the stirring speed is 400r / mim, and after reacting for 24h, samples are taken to determine the acid value and glyceride content. The test results are shown in Table 2.

[0040] Table 2 Acid value and glyceride determination results

[0041]

[0042] It can be seen from Table 2 that the acid value of the rapeseed acidified oil raw material after enzymatic glycerol esterification reaction was greatly reduced from 128.5KOH / (mg / g) to 2.1KOH / (mg / g), and the triglyceride content was increased from 4.3% to 86.2%, indicating that the enzymatic high-acid rapeseed acidified oil glycerol esterification method has a better effect of reducing acid and increasing ester.

[0043] Example 3 Enzymatic glyceridification of palm fatty acid distillate

[0044] Weigh 200 g of palm fatty acid distillate into a beaker, add 40 mL of 90°C hot water, stir at 80°C for 30 min using a water bath magnetic stirrer, let stand for 2 h, take the upper oil layer, adjust the pH to 6.0 with 32% NaOH solution, the oil sample is light yellow after pretreatment, and take a sample to determine the initial acid value and glyceride content.

[0045] Weigh 100g of pretreated palm fatty acid distillate into a beaker, add 12g of glycerol, 0.4g of lipase Transform 2.0, use a high-speed shearing machine at a speed of 10000r / min, shear and mix for 10 minutes, and then pour into the reactor. The reactor temperature is set to 60°C, the vacuum degree is minus 0.8kpa, the stirring speed is 400r / mim, and after reacting for 24 hours, samples are taken to determine the acid value and glyceride content. The test results are shown in Table 3.

[0046] Table 3 Acid value and glyceride determination results

[0047]

[0048] It can be seen from Table 3 that the acid value of the palm fatty acid distillate raw material after enzymatic glycerol esterification was greatly reduced from 182.2KOH / (mg / g) to 2.6KOH / (mg / g), and the triglyceride content was increased from 2.1% to 90.5%, indicating that the enzymatic palm fatty acid distillate glycerol esterification method has a good effect of reducing acid and increasing ester.

[0049] Example 4 Enzymatic glyceryl esterification of high-acid crude rice bran oil

[0050] Weigh 200g of high-acid rice bran crude oil into a beaker, add 40mL of 90℃ hot water, stir at 80℃ for 30min using a water bath magnetic stirrer, let stand and settle for 2h, take the upper oil layer, adjust the pH to 6.0 with 32% NaOH solution, the oil sample is light yellow after pretreatment, and take a sample to determine the initial acid value and glyceride content.

[0051] Weigh 100g of pretreated high-acid rice bran crude oil in a beaker, add 6g of glycerol and 0.8g of lipase FM-10, use a high-speed shearing machine at a speed of 10000r / min, shear and mix for 10min, and then pour it into a reactor. The reactor temperature is set to 60°C, the vacuum degree is minus 0.8kpa, the stirring speed is 400r / mim, and the acid value and glyceride content are measured after 24h of reaction. The test results are shown in Table 4.

[0052] Table 4 Acid value and glyceride determination results

[0053]

[0054] As can be seen from Table 4, the acid value of the high-acid crude rice bran oil raw material after enzymatic glycerol esterification was greatly reduced from 57.2KOH / (mg / g) to 1.6KOH / (mg / g), and the triglyceride content was increased from 4.3% to 8.1%, indicating that the enzymatic high-acid crude rice bran oil glycerol esterification method has a better effect of reducing acid and increasing ester.

[0055] Example 5 Enzymatic glycerinization of soybean oil refining byproducts

[0056] Weigh 200g of soybean oil refining by-product into a beaker, add 40mL of 80℃ hot water, stir at 80℃ for 30min using a water bath magnetic stirrer, let stand and settle for 2h, take the upper oil layer, adjust the pH to 5.5 with 32% NaOH solution, the oil sample is light yellow after pretreatment, and take samples to determine the initial acid value and glyceride content.

[0057] Weigh 100g of pretreated soybean oil refining byproduct into a beaker, add 10g glycerol, 0.3g lipase Transform 2.0, use a high-speed shearing machine at a speed of 10000r / min, shear and mix for 10 minutes, and then pour into the reactor. The reactor temperature is set to 50°C, the vacuum degree is minus 0.8kpa, the stirring speed is 400r / mim, and after reacting for 24 hours, samples are taken to determine the acid value and glyceride content. The test results are shown in Table 5.

[0058] Table 5 Acid value and glyceride determination results

[0059]

[0060] It can be seen from Table 5 that the acid value of the soybean oil refining by-product raw material after the enzymatic glycerol esterification reaction was greatly reduced from 95KOH / (mg / g) to 2.2KOH / (mg / g), and the triglyceride content was increased from 22.5% to 78.5%, indicating that the enzymatic soybean oil refining by-product glycerol esterification method has a better effect of reducing acid and increasing ester.

[0061] Comparative Example 6 Chemical Catalytic Glyceride Esterification of High Acid Waste Oil

[0062] Weigh 200 g of high-acid waste oil, add 40 mL of 80°C hot water, stir at 80°C for 30 min using a water bath magnetic stirrer, let stand and settle for 2 h, and then take the upper oil layer to determine the acid value and glyceride content.

[0063] 100 g of the pretreated waste oil was weighed and added to the reactor, 150 g of glycerol and 5 g of sulfuric acid were added, the reaction temperature was set to 240°C, the nitrogen flux was 200 mL / min, the stirring blade speed was set to 600 r / min to start the reaction, and the acid value and glyceride content were measured after 12 hours of reaction. The results are shown in Table 6.

[0064] Table 6 Acid value and glyceride determination results

[0065]

[0066] It can be seen from Table 6 that although the acid value of the high-acid waste oil raw material after the chemical glycerol esterification reaction is greatly reduced from 110.4KOH / (mg / g) to 1.5KOH / (mg / g), the triglyceride esterification rate is not high, and the fatty acids react more to generate diglycerides and monoglycerides. In the subsequent production of biodiesel as an industrial-grade mixed oil raw material, it is easy to cause poor emulsification and stratification. Therefore, compared with chemical glycerol esterification enzymes, enzyme-catalyzed glycerol esterification of high-acid oils has obvious advantages.

[0067] The method of the present invention is used to treat low-quality waste oils and fats, and can catalyze the free fatty acids and glycerol therein to generate glyceride under mild conditions. It is energy-saving and environmentally friendly, has no chemical pollution, and can achieve the effect of reducing the acid and increasing the ester in the waste low-quality oils and fats. It is of great significance to promote the production of industrial-grade mixed oils, promote environmental protection and promote economic sustainable development.

Claims

1. A method for preparing industrial-grade mixed oil by enzymatic glycerol esterification of waste oil, characterized in that: The steps include: (1) Add hot water at a temperature of 60-80°C to the waste oil raw material for washing, remove the lower layer of water and impurities by sedimentation filtration, and adjust the pH value of the raw material with potassium hydroxide solution; (2) mixing the processed oil raw material, glycerin and lipase, and shearing them using a high-speed shearing machine; (3) The mixed raw materials are introduced into a reactor for preheating, the esterification reaction is started under continuous stirring, and the free water generated by the reaction is removed by vacuum extraction.

2. The method according to claim 1, characterized in that The waste oil raw material in step (1) is any one of gutter oil, acidified oil, kitchen waste oil and deodorized distillate.

3. The method according to claim 1 or 2, characterized in that The concentration of potassium hydroxide solution in step (1) is 32%.

4. The method according to claim 3, characterized in that In step (1), the pH value is adjusted to 5-8.

5. The method according to claim 4, characterized in that The mass ratio of the waste oil raw material, glycerol and lipase in step (2) is 100:5-10:0.3-1.

6. The method according to claim 5, characterized in that The high-speed shearing time in step (2) is 3-10 min, and the rotation speed is 10000 r / min.

7. The method according to claim 6, characterized in that The preheating temperature in step (3) is 40-60°C, the stirring speed is 200 r / min, and the vacuum degree is -0.8-1 kPa.

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