CN106866370B - Method for removing lipid in crude glycerol - Google Patents
Method for removing lipid in crude glycerol Download PDFInfo
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- CN106866370B CN106866370B CN201611268706.1A CN201611268706A CN106866370B CN 106866370 B CN106866370 B CN 106866370B CN 201611268706 A CN201611268706 A CN 201611268706A CN 106866370 B CN106866370 B CN 106866370B
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- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/88—Separation; Purification; Use of additives, e.g. for stabilisation by treatment giving rise to a chemical modification of at least one compound
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- C07C29/09—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by hydrolysis
- C07C29/095—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by hydrolysis of esters of organic acids
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
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- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
- C07C29/80—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation
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Abstract
A method for removing lipids from glycerol, the method comprising the steps of: (1) primary treatment: putting a glycerol raw material containing lipids into a reaction kettle, heating, adding hydrochloric acid, stirring, and separating to obtain an upper layer containing fatty acids and a lower layer containing crude glycerol; (2) saponification: putting the crude glycerol into a reaction kettle, heating, adding sodium hydroxide or potassium hydroxide, and adjusting the pH value to obtain a glycerol mixture containing sodium soap or potassium soap; (3) double decomposition reaction: adding metal chloride salt into glycerol mixture containing sodium soap or potassium soap for reaction, and stirring to obtain glycerol, fatty acid metal soap, and sodium chloride or potassium chloride mixture; (4) separation: and (4) standing the mixture obtained in the step (3), and separating to obtain an upper layer which is a mixture of fatty acid metal soap, sodium chloride or potassium chloride and a lower layer which is glycerol. The method of the invention can effectively remove lipid impurities in the raw material of the crude glycerol, reduce the saponification equivalent of the glycerol and improve the purity of the glycerol.
Description
Technical Field
The invention relates to a method for refining glycerol, in particular to a method for removing lipid (impurities) in glycerol, belonging to the technical field of chemical industry.
Background
Glycerol, known by the scientific name "glycerol", is a colorless, sweet, clear, viscous liquid that can absorb moisture from the air, as well as hydrogen sulfide and sulfur dioxide. Insoluble in benzene, chloroform, carbon tetrachloride, carbon disulfide, petroleum ether and oils. Glycerol has a relative density of 1.26362, a melting point of 17.8 ℃, a boiling point of 290.0 ℃ (decomposition), a refractive index of 1.4746, a flash point (open cup) of 176 ℃, and is known as glycerol by national standards.
Glycerol is a commodity with a wide range of applications, and its preparation methods include saponification, hydrolysis and alcoholysis of fats and oils, as well as synthesis and fermentation. But at present, the oil is mostly prepared by finely processing glycerol which is a byproduct in oil hydrolysis (fatty acid production) and alcoholysis (biodiesel production). Crude glycerol is a raw material for producing refined glycerol products. It is mainly derived from the by-products of the processes of hydrolysis (fatty acid production) and alcoholysis (biodiesel production) of fats and oils, thus entraining more or less lipid impurities (fatty acids, fatty acid methyl esters, glycerides, fatty acid soaps, etc.).
The current technological measures for treating the lipid impurities by refined glycerol manufacturers at home are as follows: 1. adding hydrochloric acid to hydrolyze fatty acid soap, and standing for layering to remove most lipid impurities by utilizing the insolubility of fatty acid and fatty acid ester in glycerol; 2. and adding sodium hydroxide to adjust the pH value to 8-9 so as to saponify the residual lipid in the crude glycerol to generate fatty acid sodium soap, thereby preventing fatty acid from being gasified in a distillation process and entering a glycerol product. Such methods have the following disadvantages: 1) firstly, adding acid to acidolyze fatty acid soap, standing and layering to separate fatty acid; adding alkali to neutralize residual fatty acid to generate sodium soap, wherein the sodium soap is not vaporized under the condition of a glycerin distillation process, and the salt content in the raw material of the crude glycerin is increased in the processes of adding the acid and the alkali; 2) crude glycerin is distilled in an alkaline state, and glycerin polymerization or decomposition side reaction is easy to occur, so that glycerin raw materials are lost, and the yield is reduced; 3) the residual lipid in the crude glycerin raw material exists in the distillation process in the form of sodium soap, and the sodium soap is more accumulated along with the prolonging of the production time, so that the consistency of the material in a distillation kettle is increased, the pH value is increased, the polymerization side reaction is aggravated, excessive distillation residues are formed, and the product yield is further lost; 4) the sodium soap is gradually increased in the distillation kettle, so that a filter screen of the continuous desalting device is gradually blocked in the distillation process, the working efficiency of the desalting device is seriously influenced, and the production cost is increased.
In addition, the domestic refined glycerol manufacturers also have a technological measure for treating the lipid impurities, which is as follows: 1. adding hydrochloric acid to hydrolyze fatty acid soap, and standing for layering to remove most lipid impurities by utilizing the insolubility of fatty acid and fatty acid ester in glycerol; 2. adding calcium hydroxide to adjust the pH value to 8-9 so as to saponify the residual lipid in the crude glycerol to generate calcium soap; 3. adding lime water, filtering, and separating to obtain glycerol. Such methods have the following disadvantages: 1) because calcium hydroxide is only slightly soluble in water, the content of the calcium hydroxide in the lime water is not high, so that the moisture content of the crude glycerin raw material is increased too much, and the moisture is required to be evaporated in the subsequent process, so that the processing cost is increased; 2) because calcium hydroxide does not belong to strong base and is difficult to saponify grease and methyl ester under general conditions, grease, methyl ester and other lipid impurities in crude glycerol are difficult to remove by using lime water, and the impurity removal effect cannot be achieved; 3) lime water is adopted, calcium hydroxide has certain solubility in glycerin, and new calcium hydroxide impurity is introduced while impurities are removed; 4) the lime water is adopted, sodium hydroxide is generated finally after the reaction, and the solubility of the sodium hydroxide in the glycerol is higher due to the principle of 'similarity and compatibility', so that the purity of the glycerol is influenced.
Disclosure of Invention
Aiming at the defect of removing lipid from crude glycerol raw materials of domestic glycerol manufacturers at present, a process method for removing lipid impurities from crude glycerol raw materials is provided so as to eliminate or reduce the defect of the prior process of domestic manufacturers at present. The method can effectively remove lipid impurities in the crude glycerol raw material, reduce the saponification equivalent of the glycerol and improve the purity of the glycerol; in addition, the method can reduce the subsequent distillation cost, simplify the process and improve the efficiency.
The invention discloses a treatment method for removing lipid impurities in a crude glycerin raw material. The method is characterized in that lipids (fatty acid, fatty acid methyl ester, monoglyceride, diglyceride, sodium fatty acid and the like) in crude glycerol are firstly reacted with acid to primarily remove fatty acid soaps so as to eliminate the emulsifying property of the soaps in crude glycerol raw materials, standing is carried out to remove most of the lipids, sodium hydroxide is added to react residual lipids in the raw materials to generate fatty acid sodium soap, metal chloride is added to react to generate fatty acid metal salt which is insoluble in glycerol, and standing precipitation (or centrifugal separation) is carried out to realize separation and removal by utilizing density difference.
According to a first embodiment of the present invention, there is provided a method for removing lipids (impurities) from glycerol, the method comprising the steps of:
(1) primary treatment (or pretreatment): placing crude glycerin material containing lipids in a reaction kettle, heating, adding hydrochloric acid, performing acidolysis under stirring, and separating the reaction mixture to obtain fatty acids and crude glycerin containing (a small amount, e.g. 0.1 wt% to 15 wt%, such as 0.5 wt% to 10 wt%, 1 wt% to 6 wt%) fatty acids;
(2) saponification: placing crude glycerol containing fatty acids in a reaction kettle, heating, adding sodium hydroxide or potassium hydroxide for saponification to obtain glycerol mixture containing sodium soap or potassium soap;
(3) double decomposition reaction: adding calcium chloride, magnesium chloride or aluminum trichloride into a glycerin mixture containing sodium soap or potassium soap for precipitation reaction, and stirring to obtain a mixture containing glycerin, fatty acid metal soap and sodium chloride or potassium chloride;
(4) separation: and (4) separating the mixture obtained in the step (3) to respectively obtain a mixture of fatty acid metal soap, sodium chloride or potassium chloride and obtain primarily purified glycerol.
Preferably, the method further comprises:
(5) and (3) distillation: and (4) distilling the glycerol obtained in the step (4) to obtain refined glycerol.
For crude glycerol feedstocks containing lipids, the lipids include one or more selected from the group consisting of fatty acids, fatty acid methyl esters, monoglycerides, diglycerides, and sodium fatty acids.
According to a second embodiment of the present invention, there is provided a process for purifying crude glycerol containing fatty acids (impurities) (free or almost free of the above lipids), which comprises the steps of:
(I) saponification: placing crude glycerol containing fatty acids in a reaction kettle, heating, adding sodium hydroxide or potassium hydroxide for saponification to obtain glycerol mixture containing sodium soap or potassium soap;
(II) metathesis reaction: adding calcium chloride, magnesium chloride or aluminum trichloride into a glycerin mixture containing sodium soap or potassium soap for precipitation reaction, and stirring to obtain a mixture containing glycerin, fatty acid metal soap and sodium chloride or potassium chloride;
(III) separation: and (3) separating the mixture obtained in the step (II) to respectively obtain a mixture of fatty acid metal soap, sodium chloride or potassium chloride and obtain primarily purified glycerin.
Preferably, the method further comprises:
(IV) distillation: and (3) distilling the glycerol obtained in the step (III) to obtain refined glycerol.
In the application, step 1 is carried out as follows: putting a glycerol raw material containing lipids into a reaction kettle, heating, adding hydrochloric acid, stirring, and separating to obtain an upper layer containing fatty acids and a lower layer containing crude glycerol containing (a small amount of) fatty acids. Wherein hydrochloric acid is added in an amount such that the pH in the reaction vessel is 2-4, for example 2-3. After the acid hydrolysis is completed, the pH is brought to 3 to 6, preferably 3.5 to 5.5, more preferably 4 to 5. The heating temperature is 60 to 95 ℃, preferably 70 to 90 ℃, and more preferably 75 to 85 ℃. The stirring time is 0.2 to 2 hours, preferably 0.5 to 1.5 hours, and more preferably 0.6 to 1 hour.
In the application, step 2 or step I is carried out as follows: putting the crude glycerol into a reaction kettle, heating, adding sodium hydroxide or potassium hydroxide, adjusting the pH, and stirring to obtain a glycerol mixture containing sodium soap or potassium soap. Wherein sodium hydroxide or potassium hydroxide is added in an amount such that the pH of the reaction mixture in the reaction vessel is 6.8 to 8.5, preferably 6.9 to 8, more preferably 7 to 7.5. The heating temperature is 70 to 95 ℃, preferably 80 to 92 ℃, and more preferably 85 to 90 ℃. The stirring time is 0.2 to 2 hours, preferably 0.5 to 1.5 hours, more preferably 0.6 to 1 hour.
In the application, step 3 or step II is carried out as follows: adding metal chloride salt calcium chloride, magnesium chloride or aluminum trichloride (generally in the form of aqueous solution) into glycerol mixture containing sodium soap or potassium soap, and stirring to obtain glycerol, fatty acid metal soap, sodium chloride or potassium chloride mixture. Wherein the molar ratio of metal chloride salt to sodium or potassium soap added is 0.4-0.7:1, preferably 0.5-0.65:1, more preferably 0.55-0.6:1, e.g. 0.5: 1. The stirring time is 0.1-1h, preferably 0.2-0.8h, more preferably 0.3-0.6 h.
In the application, step 4 or step III is carried out as follows: separating the mixture obtained in the step (3) or the step II to obtain a mixture of fatty acid metal soap, sodium chloride or potassium chloride, and obtaining glycerol. Preferably, the separation described herein is one of filtration, suction filtration, sedimentation or centrifugation.
In the present invention, the distillation in the step (5) is a distillation under reduced pressure, and it is preferable to employ a batch or semi-continuous distillation.
In the present invention, the glycerin obtained in step (4) has a saponification equivalent of less than 0.8 and a glycerin content of more than 75%.
In the present invention, the saponification equivalent of the refined glycerin obtained in step (5) is lower than the detection limit, and the glycerin content is higher than 95%. The balance of water.
The invention relates to a method for removing lipid in glycerin, and impurities comprise fatty acid, fatty acid methyl ester and grease.
Taking the example of adding sodium hydroxide and calcium chloride, the fatty acid is added with sodium hydroxide to react to generate sodium fatty acid (sodium soap) and water, and the reaction formula is as follows:
the methyl ester is added with sodium hydroxide to react to generate sodium fatty acid (sodium soap) and methanol, and the reaction formula is as follows:
the method comprises the following steps of (1) saponifying grease by adding sodium hydroxide to generate sodium fatty acid (sodium soap) and glycerol, wherein the reaction formula is as follows:
wherein: r includes R1、R2、R3。
The lipid components in the crude glycerin are reacted to generate sodium soap, and then calcium chloride solution is added to react with the sodium soap to generate insoluble fatty acid calcium (calcium soap) so as to separate the insoluble fatty acid calcium from the crude glycerin, wherein the reaction formula is as follows:
the method finally obtains fatty acid calcium, sodium chloride, methanol, water and glycerin, wherein the fatty acid calcium, the sodium chloride and the water are not compatible with the glycerin, the density of the fatty acid calcium is about 1.07, the density of the glycerin is 1.264, the densities of the water and the sodium chloride are all smaller than the density of the glycerin, the fatty acid calcium, the sodium chloride and the water can be automatically layered after standing for a period of time, the upper layer is impurities, and the lower layer is the glycerin. Meanwhile, the boiling point of methanol is 64.7 ℃, while the saponification reaction temperature of the present invention is 70-95 ℃, that is, as long as methanol is generated by the reaction, methanol is automatically volatilized, and thus, only glycerin is contained in the final product.
The lipid impurity components in the crude glycerin material are not limited to fatty acid, methyl ester, grease and sodium aliphatate. From the above-mentioned several steps of reactions (ionic reactions), it is seen that sodium hydroxide can react fatty acid, methyl ester and fat to produce sodium fatty acid (sodium soap), and the produced sodium soap, together with sodium soap possibly present in the crude glycerin material, undergoes double decomposition reaction with calcium chloride to produce calcium soap which is hardly soluble, and is separated. Thus, lipid impurities in the crude glycerin material can be removed very effectively.
Compared with the method for treating crude glyceride impurities by lime water, the method adopts metal chloride (taking calcium chloride as an example) and has the following differences and effects: 1) the invention firstly uses strong alkali (sodium hydroxide or potassium hydroxide) to convert all lipid components in crude glycerin into sodium soap, and then uses calcium chloride solution (30-60% content, preferably 40-45% content) to carry out double decomposition reaction with the sodium soap to generate calcium soap for separation, thus thoroughly removing lipid impurities; calcium hydroxide is not strong alkali and has low concentration, the reaction on fatty acid components cannot be thorough, and because the calcium hydroxide does not belong to strong alkali, grease and methyl ester are difficult to saponify under common conditions, grease, methyl ester and other lipid impurities in crude glycerol are difficult to remove by lime water, and the impurity removal effect cannot be achieved; 2) the calcium chloride is easy to dissolve in water, and the concentration of the water solution of the calcium chloride is many times higher than that of calcium hydroxide of lime water, so that the influence of the water quantity on the glycerol content of the crude glycerol raw material is not large, and the energy consumption of the subsequent process cannot be increased; calcium hydroxide is slightly soluble in water, so that the calcium hydroxide content in the lime water is low, the water content of the crude glycerin raw material is increased too much due to low calcium hydroxide content in the lime water, and the water needs to be evaporated in the subsequent process, so that the processing cost is increased; 3) the purity of the commercial calcium chloride is better than that of the commercial calcium hydroxide, the effective utilization rate is much higher, and the operation is more convenient than that of lime, so the production cost is much lower than that of the calcium hydroxide; 4) the final product of the method can be well separated from the glycerin, the fatty acid calcium is insoluble in the glycerin, the sodium chloride can be separated out in the production process, and the water can be evaporated. After separation, glycerin with higher purity can be obtained; by adopting the lime water, the calcium hydroxide has certain solubility in the glycerol, and the impurities are removed while new impurities of the calcium hydroxide are introduced; the lime water is adopted, sodium hydroxide is generated finally after the reaction, and the solubility of the sodium hydroxide in the glycerol is higher due to the principle of 'similarity and compatibility', so that the purity of the glycerol is influenced.
Purpose of removing lipid impurities in crude glycerol: lipid impurities in the raw material of the crude glycerol are removed without entering a distillation process, so that the distillation process effect in the process of producing the refined glycerol from the crude glycerol is optimized. The treatment method can reduce the saponification equivalent of the crude glycerol to a value close to the national standard of industrial refined glycerol, can realize neutral distillation, avoids or reduces adverse side reactions such as polymerization, decomposition, thickening and the like of the glycerol in the distillation process, relatively improves the product yield and the yield in unit time, namely optimizes the distillation process efficiency and reduces the production cost.
The by-product of hydrolysis or alcoholysis of natural oils and fats, crude glycerol, contains lipid impurities, and the raw materials of crude glycerol are generally from fatty acid manufacturers and biodiesel manufacturers. Due to the difference of equipment and technology of various manufacturers, the by-product crude glycerin has different pH values. The pH value is approximately between 4 and 9. The raw material PH value of the byproduct crude glycerine of the biodiesel is liquid at normal temperature and is less than 7, which indicates that biodiesel manufacturers add acid to the raw material of the byproduct crude glycerine to treat the raw material of the byproduct crude glycerine and recover most lipid components; the raw material PH value of the biodiesel byproduct crude glycerine is more than 8, and the raw material is in a paste state (mainly the byproduct crude glycerine of the biodiesel produced by palm oil in southeast Asia countries) at normal temperature, which indicates that biodiesel manufacturers do not add acid to treat and recover lipid components. If the raw material is in paste state, acidolysis treatment is carried out to separate out fatty acid components.
In the invention, the method comprises the steps of firstly carrying out primary treatment by using hydrochloric acid to separate out fatty acid components; then add intoAnd (2) adjusting the pH value of a sodium hydroxide solution to 7-7.5, converting lipid substances in the glycerol into sodium soap, adding a calcium chloride solution (or other suitable metal chlorides), and reacting all the sodium soap to generate fatty acid metal soap which is insoluble in the glycerol and has density lower than that of the glycerol and sodium chloride. The emulsifying property of the sodium soap in the system is eliminated, so that lipid substances in the system can be separated out more easily.At the same timeNeutral distillation is realized, and adverse side reactions in the distillation process are avoided. (because crude glycerin is distilled in an alkaline state, glycerin polymerization or decomposition side reaction is easy to occur, so that glycerin raw material is lost, and the yield of glycerin is reduced.) if sodium soap exists in a material system according to the domestic current process method, the sodium soap cannot be vaporized under the glycerin distillation process condition, and lipid remained in the crude glycerin raw material exists in the distillation process in the form of the sodium soap, the sodium soap is accumulated more along with the extension of the production time, so that the consistency of the material in a distillation kettle is increased, the pH value is increased, the polymerization side reaction of glycerin is aggravated, excessive distillation residue is formed, and the product yield is further lost.
More specifically, the method of the invention comprises the following steps:
firstly, discharging the pasty raw materials into a heating ground tank, melting the pasty raw materials, pumping the melted raw materials into an acid-resistant stirring reaction kettle, slowly adding hydrochloric acid solution, stirring (the temperature is controlled to be 75-85 ℃) and reacting until the pH value is 5-4, wherein the reaction time is 30 minutes. Then pumping into a settling tank for standing for 6 hours, separating out lower-layer crude glycerol, pumping into a crude glycerol raw material storage tank, and pumping upper-layer fatty acids into a fatty acid storage tank;
secondly, heating the crude glycerin raw material to 85-90 ℃, adding liquid caustic soda with the pH value lower than 7.5 of the raw material to the pH value of 8-8.5, and stirring for reacting for 40 minutes until the pH value end point is 7.5, so as to react the lipid substances to generate sodium soap;
and thirdly, adding a calcium chloride solution (or other suitable metal chlorides) at the original temperature of the previous step, and calculating the addition amount of the calcium chloride solution according to the soap content in the raw materials, wherein the addition amount of the calcium chloride is 1.1 times of the theoretical calculation amount. The reaction was stirred for 20 minutes. The aim is to react sodium soap to produce fatty acid metal soap which is insoluble in glycerin and has density lower than that of glycerin and sodium chloride;
and fourthly, keeping the temperature of the crude glycerin raw material reacted in the last two steps, standing for more than 12 hours, precipitating and layering. The upper layer is fatty acid or lipid metal soap and absorbs some other impurities which are insoluble in glycerol and have density lower than that of glycerol, and the lower layer is pure crude glycerol.
Optionally, distilling the clean crude glycerol obtained in the fourth step to obtain refined glycerol.
In the invention, the method comprises the steps of firstly carrying out primary treatment by using hydrochloric acid to separate out fatty acid components; then using strong alkali to saponify, the impurity in glycerol is converted into sodium soap or potassium soap, then adding calcium chloride solution (or other suitable metal chloride), the calcium chloride itself is not dissolved in glycerol, reacting the sodium soap or potassium soap to generate fatty acid metal soap which is not dissolved in glycerol and has density less than that of glycerol and sodium chloride (or potassium chloride). The problem that calcium chloride and sodium hydroxide are dissolved in glycerol in the prior art is avoided, and the purity of the glycerol is improved. If calcium chloride and sodium chloride exist in the glycerol, crude glycerol is distilled in an alkaline state, and side reaction of polymerization or decomposition of glycerol easily occurs, so that the glycerol raw material is lost, and the yield of the glycerol is reduced. Meanwhile, if the double decomposition reaction is incomplete, sodium soap (or potassium soap) exists, the sodium soap cannot be vaporized under the condition of the glycerin distillation process, and the residual lipid in the crude glycerin raw material exists in the distillation process in the form of the sodium soap, so that the sodium soap accumulates more along with the extension of the production time, the consistency of the material in the distillation kettle is increased, the pH value is increased, the polymerization side reaction of the glycerin is aggravated, excessive distillation residues are formed, and the product yield is further lost.
Compared with the prior art, the invention has the following beneficial technical effects:
(1) the invention can completely convert lipid substances in the raw material of the crude glycerine into sodium soap by using strong alkali (sodium hydroxide), and then calcium chloride is added to generate calcium soap for removal;
(2) the calcium chloride is easy to dissolve in water, and the concentration of the water solution of the calcium chloride is many times higher than that of calcium hydroxide of lime water, so that the influence of the water quantity on the glycerol content of the crude glycerol raw material is not large, and the energy consumption of the subsequent process cannot be increased; the process for removing lipid impurities reduces the consumption of hydrochloric acid and liquid caustic soda, thereby reducing the increase of inorganic salt in the raw materials and optimizing the effect of the subsequent distillation process;
(3) the purity of the commercial calcium chloride is better than that of the commercial calcium hydroxide, the effective utilization rate is much higher, and the operation is more convenient than that of lime, so the production cost is much lower than that of the calcium hydroxide;
(4) the final product of the method can be well separated from the glycerin, and the fatty acid calcium, the sodium chloride and the water can be effectively and cleanly separated in the production process, so that the glycerin with higher purity can be obtained. The invention firstly reacts the residual lipid impurities in the raw material of the crude glycerin to generate sodium soap, then adds calcium chloride (or other suitable metal chlorides) solution to react to generate metal soap which is insoluble in the glycerin and adsorbs other micro-solid impurities to be separated out, and does not enter a distillation process, thereby ensuring the product quality and further optimizing the efficacy of the distillation process.
(5) The former step completely removes impurities causing adverse reactions in the subsequent heating distillation step, and obviously improves the distillation process effect.
Drawings
FIG. 1 is a process flow diagram of a process for removing lipids from glycerol according to the present invention.
Detailed Description
The raw materials used in the following examples are all commercially available raw materials.
For the raw glycerol feedstock, one can choose:
1) and the by-product of hydrolysis or alcoholysis of natural oil and fat, namely crude glycerin, contains lipid impurities, and the raw materials of the crude glycerin generally come from fatty acid manufacturers and biodiesel manufacturers. Due to the difference of equipment and technology of various manufacturers, the by-product crude glycerin has different pH values. The pH value is approximately between 4 and 9.
2) The pH value of the by-product crude glycerol raw material of the biodiesel is less than 7, and the raw material is in a liquid state at normal temperature, which indicates that a biodiesel manufacturer adds acid to the by-product crude glycerol raw material for treatment, and most lipid components are recovered;
3) and if the pH value of the biodiesel byproduct crude glycerin raw material is greater than 8, the raw material is in a paste state at normal temperature, which indicates that the biodiesel manufacturer does not add acid to treat and recover lipid components. Such crude glycerol feedstocks are produced in southeast Asia countries using palm oil.
If the raw material is in paste state, acidolysis treatment is carried out to separate out fatty acid components.
Embodiments of the present invention are described in more detail below.
1. Experiment of
1 kg of crude glycerol raw material comprehensive sample (taking a storage tank as a detection unit) is taken by a laboratory, and is sent to a laboratory for detecting the following items:
glycerol content 78.5%, pH 5.0 saponification equivalent 2.5mmol/100g
Calculating the amount of calcium chloride solution added (liter/ton raw material) according to the saponification equivalent value
The method for processing the raw material sample before the test saponification equivalent project comprises the following steps:
firstly, 100g (sensing quantity is 0.001g) of a sample is accurately weighed and placed in an Erlenmeyer flask, the PH value is adjusted to 3-2 by hydrochloric acid (the number of milliliters of hydrochloric acid is accurately recorded), and the sample is stirred and heated to 85-90 ℃ for reaction for 20 minutes. The aim is to hydrolyse possible soaps present in the raw material sample to fatty acids.
And adding a KOH solution with the concentration of 0.1mol/L to adjust the pH value to 6.8-7.0. The reaction was stirred in order to neutralize the mineral acid in the starting material sample.
The reaction formula is as follows: HCl + KOH → KCl + H2O
And thirdly, measuring the saponification equivalent of the sample according to a standard method. The calculated calcium chloride addition can be determined by the saponification equivalent value.
In this case, the lipid impurities are present in the starting material in the form of potassium soaps of fatty acids, and 1 molecule of calcium chloride is required for the metathesis reaction to form 2 molecules of potassium soaps into calcium soaps. I.e. one molecule of calcium chloride corresponds to two molecules of potassium hydroxide. The ratio is: 111/2: 56.1-0.99
The amount of 30% calcium chloride solution (density 1.28) added to the production was calculated by the laboratory staff from the saponification equivalent weight determined for the batch as follows:
adding pure calcium chloride (g) 2.5X 56.1X 1000/100X 0.99X 1388.5(g) to each ton of raw material
Converted into the amount of calcium chloride solution (L) ═ 1388.5 ÷ 30% ÷ 1000 ÷ 1.28 ÷ 3.62(L)
To ensure complete metathesis reaction, the amount of calcium chloride solution is multiplied by 1.2 coefficient
In actual production, the calcium chloride solution added into each ton of raw materials of the batch is 3.62 multiplied by 1.2 which is 4.344 (L).
2. Production on an industrial scale:
preparing industrial hydrochloric acid (content: 30%), liquid caustic soda (NaCH content: 30%), CaCl2Solution (content 30%).
2.1) pumping raw materials into a reaction kettle from a raw glycerol raw material pump according to the specified scale (15 tons), stirring and heating to 75-80 ℃, and measuring the pH value to be 5.2. Adding liquid alkali to adjust the pH value to 7.8-8.2, stirring and reacting for 20 minutes, wherein the pH value at the end point of the reaction is 7.3-7.5;
2.2)15 tons of raw materials need to be added with 65L of calcium chloride solution, the calcium chloride solution is accurately added in a stirring state, and the mixture is pumped into a precipitation tank after reacting for 20 minutes.
2.3) standing and precipitating for 12 hours, pumping the lower layer crude glycerol into a clean crude glycerol storage tank (observing a solution layering interface in a sight glass), taking 500g of a clean crude glycerol comprehensive sample by an inspector, detecting the saponification equivalent weight of the clean crude glycerol comprehensive sample to be reduced to 0.68mmol/100g, wherein the glycerol content is 77.6 percent, and continuing processing by a distillation process after the clean crude glycerol is qualified.
The upper lipid is pumped into a lipid storage tank and is sold as a byproduct to fatty acid manufacturers or lubricating grease manufacturers as a raw material.
3. Sample test example
Raw material quality indexes of crude glycerol are as follows: glycerol content 78.5%;
pH 5.2
Saponification equivalent 2.5(mmol/100g)
The test data are as follows:
number of specimens 300g
Stirring and heating to 85 DEG C
Adding a small amount of liquid alkali (1mol/L) to the pH value of 8.0
Stirring and reacting for 40min
2.2ml of calcium chloride solution (30%) is added
Standing for 4 hours under the condition of heat preservation (70-80 ℃)
As a result:
lipid impurities and crude glycerin are clearly layered;
the saponification equivalent was reduced to 0.57(mmol/100 g);
the content of glycerin is 75.5 percent
The clean crude glycerol is clear and transparent, and the color is brownish yellow;
achieving the purpose of removing lipid impurities.
Example 1
A method for removing lipids from glycerol, the method comprising the steps of:
(1) primary treatment: accurately weighing 15 tons of glycerin raw materials, placing the raw materials into a reaction kettle, adding hydrochloric acid, adjusting the pH to 2.5, stirring for 30 minutes, heating to 85 ℃, filtering, settling, wherein the upper layer is fatty acids, and the lower layer is crude glycerin containing a small amount of fatty acids;
(2) saponification: putting the crude glycerol into a reaction kettle, heating to 85 ℃, adding sodium hydroxide with the concentration of 0.1mol/L, adjusting the pH to 7.5, and stirring for 40 minutes to obtain a glycerol mixture containing sodium soap;
(3) double decomposition reaction: adding calcium chloride into the glycerin mixture containing the sodium soap for reaction, and stirring for 20 minutes to obtain a mixture of glycerin, fatty acid metal soap and sodium chloride;
in this case, the lipid impurities are present in the starting material in the form of sodium soaps of fatty acids, and 1 molecule of calcium chloride is required for the metathesis reaction to form 2 molecules of sodium soaps into calcium soaps. I.e. one molecule of calcium chloride corresponds to two molecules of sodium hydroxide. The ratio is: 111/2: 56.1-0.99;
the amount of 30% calcium chloride solution (density 1.28) added to the production was calculated by the laboratory staff from the saponification equivalent weight determined for the batch as follows:
adding pure calcium chloride (g) 2.5X 56.1X 1000/100X 0.99X 1388.5(g) to each ton of raw material
Converted into the amount of calcium chloride solution (L) ═ 1388.5 ÷ 30% ÷ 1000 ÷ 1.28 ÷ 3.62(L)
To ensure complete metathesis reaction, the amount of calcium chloride solution is multiplied by 1.2 coefficient
In actual production, the calcium chloride solution added into each ton of raw materials of the batch is 3.62 multiplied by 1.2 which is 4.344 (L);
(4) separation: and (4) standing the mixture obtained in the step (3) for 12 hours, filtering, standing and separating, wherein the upper layer is a mixture of fatty acid metal soap and sodium chloride, and the lower layer is glycerol.
The experimental results are as follows: lipid impurities and crude glycerin are clearly layered; the lower layer is taken out by an inspector for detection, the saponification equivalent weight is reduced to 0.68mmol/100g through detection, and the glycerol content is 77.6%.
Example 2
Example 1 is repeated except that the method further comprises:
(5) and (3) distillation: and (3) carrying out reduced pressure distillation on the glycerol obtained in the step (4) at the temperature of 70-80 ℃ to obtain refined glycerol. The glycerol purity was 95.8%. The content of fatty acids and glycerol dimers and trimers is less than 0.1 wt.%. The fatty acid content is below the detection limit.
Example 3
Example 1 was repeated except that potassium hydroxide was used instead of sodium hydroxide in step (2) and magnesium chloride was used instead of calcium chloride in step (3).
The experimental results are as follows: lipid impurities and crude glycerin are clearly layered; the saponification equivalent is reduced to 0.57(mmol/100g), the glycerol content is 75.5%, and the pure crude glycerol is clear and transparent and has brownish yellow color.
Example 4
(1) Primary treatment: accurately weighing 300g of glycerol raw material, placing the glycerol raw material in a triangular flask, adding hydrochloric acid, adjusting the pH to 4, stirring for 30 minutes, heating to 85 ℃, and filtering, wherein the upper layer is fatty acid, and the lower layer is crude glycerol;
(2) saponification: putting the crude glycerol into a reaction kettle, heating to 85 ℃, adding sodium hydroxide with the concentration of 0.1mol/L, adjusting the pH to 7.5, and stirring for 40 minutes to obtain a glycerol mixture containing sodium soap;
(3) double decomposition reaction: adding calcium chloride into the glycerin mixture containing the sodium soap for reaction, and stirring for 20 minutes to obtain a mixture of glycerin, fatty acid metal soap and sodium chloride; the amount of calcium chloride added was 2.2 ml.
(4) Separation: and (4) standing the mixture obtained in the step (3) for 4 hours, and filtering to obtain a mixture of fatty acid metal soap and sodium chloride at the upper layer and glycerin at the lower layer.
The experimental results are as follows: lipid impurities and crude glycerin are clearly layered; the saponification equivalent is reduced to 0.69(mmol/100g), the glycerol content is 78.0 percent, and the pure crude glycerol is clear and transparent and has brownish yellow color.
Comparative example 1
A method for removing lipids from glycerol, the method comprising the steps of:
(1) primary treatment: accurately weighing 100g of glycerol raw material, placing in a triangular flask, adding hydrochloric acid, adjusting pH to 4, stirring for 30 minutes, heating to 85 ℃, and filtering, wherein the upper layer is fatty acids, and the lower layer is crude glycerol;
(2) saponification: putting crude glycerol into a reaction kettle, heating to 85 ℃, adding calcium hydroxide with the concentration of 0.02mol/L, adjusting the pH to 8, and stirring for 40 minutes to obtain glycerol and fatty acid metal soap; the amount of the added calcium chloride is 15 ml;
(3) separation: and (3) standing the mixture obtained in the step (2) for 12 hours, and filtering to obtain a mixture of fatty acid metal soap and sodium chloride at the upper layer and glycerin at the lower layer.
(4) And (3) distillation: and (4) carrying out reduced pressure distillation on the glycerol obtained in the step (3) at the temperature of 70-80 ℃ to obtain refined glycerol. The glycerol purity was 72.8%. Glycerol dimer and trimer content was 4.5 wt%. The residual fatty acid content was 0.5 wt%.
Comparative example 2
A method for removing lipids from glycerol, the method comprising the steps of:
(1) primary treatment: accurately weighing 100g of glycerol raw material, placing in a triangular flask, adding hydrochloric acid, adjusting pH to 3, stirring for 30 minutes, heating to 85 ℃, and filtering, wherein the upper layer is fatty acids, and the lower layer is crude glycerol;
(2) saponification: putting the crude glycerol into a reaction kettle, heating to 85 ℃, adding sodium hydroxide with the concentration of 0.1mol/L, adjusting the pH to 7.5, and stirring for 40 minutes to obtain a glycerol mixture containing sodium soap;
(3) double decomposition reaction: adding calcium hydroxide with the concentration of 0.02mol/L into a glycerin mixture containing sodium soap for reaction, and stirring for 20 minutes to obtain a mixture of glycerin, fatty acid metal soap and sodium chloride; the amount of calcium chloride added is 11 ml;
(4) separation: and (4) standing the mixture obtained in the step (3) for 12 hours, and filtering to obtain a mixture of fatty acid metal soap and sodium hydroxide as an upper layer and glycerin as a lower layer.
(5) And (3) distillation: and (3) carrying out reduced pressure distillation on the glycerol obtained in the step (4) at the temperature of 70-80 ℃ to obtain refined glycerol. The glycerol purity was 71.2%. Glycerol dimer and trimer content 5.2 wt%. The residual fatty acid content was 0.6 wt%.
Claims (11)
1. A method for removing lipids from glycerol, the method comprising the steps of:
(1) primary treatment: placing a crude glycerin raw material containing lipids in a reaction kettle, heating, adding hydrochloric acid, carrying out acidolysis reaction under stirring, and separating the reaction mixture to obtain fatty acids and crude glycerin containing the fatty acids;
(2) saponification: placing crude glycerol containing fatty acids in a reaction kettle, heating, adding sodium hydroxide or potassium hydroxide for saponification to obtain glycerol mixture containing sodium soap or potassium soap;
(3) double decomposition reaction: adding calcium chloride, magnesium chloride or aluminum trichloride into a glycerin mixture containing sodium soap or potassium soap for precipitation reaction, and stirring to obtain a mixture containing glycerin, fatty acid metal soap and sodium chloride or potassium chloride;
(4) separation: and (4) separating the mixture obtained in the step (3) to respectively obtain a mixture of the fatty acid metal soap and sodium chloride or potassium chloride and obtain primarily purified glycerin.
2. The method of claim 1, further comprising:
(5) and (3) distillation: and (4) distilling the glycerol obtained in the step (4) to obtain refined glycerol.
3. The method of claim 2, wherein the lipid comprises one or more selected from the group consisting of fatty acids, fatty acid methyl esters, monoglycerides, diglycerides, and sodium fatty acids.
4. The method of claim 3, wherein: the distillation in the step (5) is reduced pressure distillation.
5. The method of claim 4, wherein: the distillation in the step (5) is batch or semi-continuous distillation.
6. The method according to any one of claims 1-5, wherein: the separation in the step (4) is one of filtration, suction filtration, sedimentation or centrifugal separation.
7. A method for purifying crude glycerin containing fatty acids, the method comprising the steps of:
(I) saponification: placing crude glycerol containing fatty acids in a reaction kettle, heating, adding sodium hydroxide or potassium hydroxide for saponification to obtain glycerol mixture containing sodium soap or potassium soap;
(II) metathesis reaction: adding calcium chloride, magnesium chloride or aluminum trichloride into a glycerin mixture containing sodium soap or potassium soap for precipitation reaction, and stirring to obtain a mixture containing glycerin, fatty acid metal soap and sodium chloride or potassium chloride; and
(III) separation: and (3) separating the mixture obtained in the step (II) to respectively obtain a mixture of the fatty acid metal soap and sodium chloride or potassium chloride and obtain primarily purified glycerin.
8. The method of claim 7, further comprising:
(IV) distillation: and (3) distilling the glycerol obtained in the step (III) to obtain refined glycerol.
9. The method of claim 8, wherein: the distillation in the step (IV) is reduced pressure distillation.
10. The method of claim 9, wherein: the distillation in step (IV) is a batch or semi-continuous distillation.
11. The method according to any one of claims 7-10, wherein: the separation in step (III) is one of filtration, suction filtration, sedimentation or centrifugal separation.
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| CN110437035A (en) * | 2019-08-27 | 2019-11-12 | 如皋市涤诺皂业有限公司 | A kind of glycerine water solution treatment process generated for grease hydrolysis |
| CN112159306A (en) * | 2020-09-09 | 2021-01-01 | 湖北天基生物能源科技发展有限公司 | Method for purifying by-product crude glycerol of biodiesel prepared from waste oil |
| WO2022155776A1 (en) * | 2021-01-19 | 2022-07-28 | 汇智工程科技股份有限公司 | Acidification and hydrolysis air flotation apparatus for glycerol refinement production process |
| CN115404129A (en) * | 2022-09-16 | 2022-11-29 | 临沂明英工贸有限公司 | Production process for producing acidified oil from mixed oil leftover material |
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