CN110642674B - Method for co-producing acrolein in refining process of biodiesel byproduct crude glycerol - Google Patents
Method for co-producing acrolein in refining process of biodiesel byproduct crude glycerol Download PDFInfo
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Abstract
The invention relates to a method for co-producing acrolein in the refining process of biodiesel byproduct crude glycerol, which comprises the steps of crude glycerol separation, crude glycerol refining, acrolein separation and the like. The co-production of acrolein is realized in the refining process of the crude glycerol, and the additional value of the carbon three chemicals is effectively improved. The method for co-producing acrolein has the advantages of simple and convenient process flow, simple operation, easy realization of industrial implementation and extremely great popularization and application values.
Description
[ technical field ] A method for producing a semiconductor device
The invention belongs to the technical field of efficient resource development and comprehensive utilization. More particularly, the invention relates to a method for co-producing acrolein in the refining process of biodiesel byproduct crude glycerol.
[ background of the invention ]
Glycerol is known as eight major industrial raw materials, and is a main source of economic benefit in oil chemical production, so that the glycerol is always concerned by operators. Glycerol is a main raw material for producing epichlorohydrin; acrolein is an intermediate in the production of 1, 3-propanediol, a high-value carbon three product.
In recent years, with the increasing depletion and demand of petroleum resources, the world faces a crisis of energy shortage. With respect to national energy safety, countries around the world compete for renewable energy to alleviate the oil stress problem.
Biodiesel is a product with great development prospect as a renewable energy source, is a typical 'green energy source', and has the characteristics of good environmental protection performance, good engine starting performance, good combustion performance, wide raw material source, renewability and the like. The biodiesel oil is fatty acid methyl ester or ethyl ester prepared by ester-converting vegetable oil (such as oleum Rapae, soybean oil, peanut oil, corn oil, cottonseed oil, etc.), animal oil (such as fish oil, lard, beef tallow, mutton fat, etc.), waste oil or microbial oil with methanol or ethanol. Vegetable oils and animal fats having fatty acid glycerides (i.e., triglycerides) of a certain structural symbol are generally used as raw materials for biodiesel. Thus, a large amount of glycerol is produced during biodiesel production, which can yield about 100kg of glycerol per 1 ton of biodiesel produced.
Glycerol is an attractive and renewable green chemical basic raw material. In recent years, the market of glycerin in China is very active, and as one of eight basic chemical raw materials, the glycerin is widely applied to nearly 2000 products in the industries of medicines, foods, tobaccos, cosmetics, printing ink, national defense, leather, printing and dyeing, coatings, synthetic resins, pesticides, toothpaste and the like.
Acrolein is the simplest unsaturated aldehyde, is an important chemical raw material, is used for synthesizing various organic intermediates such as acrylic acid, methionine, 3-methylpyridine, 1, 3-propanediol and the like, and is widely applied to the aspects of materials, pesticides, feeds and the like. The prior industrial production method of the acrolein takes propylene as a raw material, and is prepared by oxidation with Bi-Mo-O composite metal oxide as a catalyst under the condition of a fixed bed, and the conversion rate of the propylene and the selectivity of the acrolein can reach 95 percent and 85 percent.
A large number of researches on acrolein preparation by glycerol dehydration have been reported, for example, CN101070276A discloses that an acidic molecular sieve is used as a catalyst, the temperature is 200-500 ℃, the pressure is 0.001-3.0 MPa, and the liquid space velocity is 0.1-100 h-1Under the condition, the yield of the acrylic acid can reach 70-80%. However, the molecular sieve catalyst has the problem of poor high-temperature hydrothermal performance; CN102936190A, CN102936189A and CN102942462A adopt pyridine, imidazole and quaternary ammonium salt ionic liquid as catalystsAnd a reagent for preparing acrolein by liquid phase dehydration of glycerol at a reaction temperature of 250-350 ℃ and a molar ratio of the ionic liquid to the glycerol of 0.1: 100-1.5: 100, wherein the conversion rate of the glycerol is 100% and the yield of the product acrolein is 30.5-68.2%. However, the ionic liquid catalyst has the problems of high cost, low production efficiency and the like compared with a fixed bed reactor. CN 105498845A adopts supercritical CO2The CsPW/Zr-MCM-41 catalyst prepared in the environment has the glycerol conversion rate of 65.2-100% and the acrolein selectivity of 56.8-85.4%, but the supercritical condition has high requirements on equipment and large investment.
The inventor optimizes the catalytic route for preparing the acrolein by the glycerol in CN 108554453A, makes up for the defects of the prior art, enables the conversion rate of raw materials and the selectivity of products to reach a higher level, and is an important breakthrough for realizing industrialization of the technical route for preparing the acrolein by dehydrating the glycerol. In recent years, the present inventors have intensively studied the process of refining crude glycerin of this company, and found that a small amount of glycerin is dehydrated to form acrolein in the process of refining crude glycerin, and that the acrolein is produced and introduced into the refined glycerin product to affect the quality of glycerin, and that the method of removing acrolein by deodorization of glycerin can improve the quality of the refined glycerin product, but since the amount of acrolein is small, there is no value in recycling.
At present, the most effective preparation method of the biodiesel is a chemical catalytic transesterification method, wherein the acid catalysis method has the widest applicability, and hydrochloric acid and sulfuric acid are common homogeneous acid catalysts. The sulfuric acid is used as a catalyst, so that the high acid value grease is favorably esterified. In addition, during the process of decomposing a small amount of soap in the methyl ester to recover fatty acid and recovering a small amount of glycerin, diluted acid is required, the diluted acid is usually hydrochloric acid or sulfuric acid, and the sulfuric acid has high soap decomposition performance. The sulfuric acid is used as a homogeneous acid catalyst and a soap decomposer, so that high quality of the biodiesel can be obtained in the production process of the biodiesel, but the refining process of the byproduct glycerol is not favorable. This is because the solubility of sodium sulfate in crude glycerin is low, and the crude glycerin refining distillation apparatus is likely to cause scarring. For example, it has been thought that the sulfate-containing crude glycerol purification process does not substantially maintain normal production. Therefore, the sulfate group-containing crude glycerin has a low market price.
Therefore, the present inventors propose that co-production of acrolein can be achieved by pretreatment in the course of refining crude glycerin. The present inventors have finally completed the present invention through a large number of experiments and studies.
[ summary of the invention ]
[ problem to be solved ]
The invention aims to provide a method for co-producing acrolein in the refining process of biodiesel byproduct crude glycerol.
[ solution ]
The invention is realized by the following technical scheme.
The invention relates to a method for co-producing acrolein in the refining process of biodiesel byproduct crude glycerol. The method comprises the following steps:
A. separation of crude glycerol
Separating sulfate radical-containing crude glycerol produced in the production process of biodiesel in a liquid separation tank 1 to remove a surface oil layer, respectively sending the rest crude glycerol to an acid processor 3 through a pump 2 and a pipeline and an acid treating agent for acid treatment, then adding a flocculating agent to control the pH value of the crude glycerol to be 3.5-4.5 to generate fatty acid metal salt precipitates, separating, and respectively sending the crude glycerol and an alkali treating agent on the upper layer to an alkali processor 4 through pipelines for alkali treatment to obtain pretreated crude glycerol;
B. crude glycerol purification
The pretreated crude glycerol obtained in the step A is sent to a light component removal tower 5 through a pipeline to remove light components in the pretreated crude glycerol, and the light components are sent to a biochemical treatment system through a pipeline to be treated; the crude glycerol with light components removed is conveyed into a reaction rectifying tower 7 through a pipeline by a crude glycerol pump 6, and is refined in the presence of potassium bisulfate, so that a part of glycerol is dehydrated to generate acrolein, a mixture containing the acrolein, water and a small amount of glycerol is discharged from the top of the reaction rectifying tower 7, and is condensed by a heat exchanger 10 to obtain crude acrolein; the obtained refined glycerol is sent to a storage tank 8 from the lateral line of the reaction rectifying tower 7 through a pipeline, wherein a part of the refined glycerol is discharged through a refined glycerol pump 9, and the rest part of the refined glycerol returns to the upper part of the reaction rectifying tower 7; a crude glycerol distillation residue is obtained at the bottom of the reaction rectifying tower 7 and is sent to a glycerol residue treatment system through a pipeline;
C. acrolein separation
The crude acrolein enters from the top of the short-path distiller 11, and is subjected to distillation separation to obtain a light component and a heavy component, and the light component acrolein is condensed and discharged from the bottom of the short-path distiller 11 to an acrolein storage tank 12 for storage; the heavy component of the yellow glycerin is discharged from the side line of the short-path distiller 11 and returns to the lightness-removing tower 5 to recover the glycerin.
According to a preferred embodiment of the present invention, in step A, the crude glycerin comprises 75-85% by weight of glycerin, 8-12% by weight of water, and 3-6% by weight of SO4 2+With the balance to 100% non-glycerol organics.
According to another preferred embodiment of the present invention, in step A, the remaining crude glycerin is subjected to acid treatment with an acid treatment agent at a temperature of 50 to 60 ℃ and a pH of 3.0 to 4.0 in an acid treatment device 3.
According to another preferred embodiment of the present invention, in the step a, the acid treatment agent is an aqueous solution of sulfuric acid having a concentration of 18 to 25% by weight; the usage amount of the glycerol is that the pH value of the residual crude glycerol reaches 3.0-4.0.
According to another preferred embodiment of the present invention, in the step a, the flocculant is an aqueous solution of aluminum sulfate having a concentration of 1 to 3% by weight.
According to another preferred embodiment of the present invention, in the step A, in the alkali treatment device 4, the upper layer crude glycerin is subjected to alkali treatment with an alkali treatment agent at a temperature of 80 to 90 ℃ and a pH of 7.0 to 8.0.
According to another preferred embodiment of the present invention, in the step a, the alkali treatment agent is an aqueous solution of potassium hydroxide having a concentration of 8 to 12% by weight, and is used in an amount to bring the pH of the upper crude glycerin to 7.0 to 8.0.
According to another preferred embodiment of the present invention, in step B, the pretreated crude glycerol is subjected to light component removal in the light component removal tower 5 under the conditions of temperature of 120-150 ℃ and pressure of 3-10 KPa.
According to another preferred embodiment of the present invention, in step B, the crude glycerol from which the light components are removed is refined in the reactive distillation column 7 at a temperature of 165 to 170 ℃ and a pressure of 1.5 to 3.0KPa to obtain crude acrolein and refined glycerol.
According to another preferred embodiment of the present invention, in step C, the crude acrolein is distilled in the short path distiller 11 under the conditions of pressure of 7 to 10KPa, heating surface temperature of 60 to 80 ℃ and built-in condenser temperature of-13 to-15 ℃.
The present invention will be described in more detail below.
The invention relates to a method for co-producing acrolein in the refining process of biodiesel byproduct crude glycerol. The method comprises the following steps:
A. separation of crude glycerol
Crude glycerol produced during biodiesel production contains lipids. The oil and fat are insoluble in the glycerol solution, the density of the oil and fat is lower than that of crude glycerol, and the oil and fat can be separated into oil and fat in a light phase and crude glycerol in a heavy phase in a liquid separating tank, and the light phase is cut and separated.
Separating sulfate radical-containing crude glycerol produced in the production process of biodiesel in a liquid separation tank 1 to remove a surface oil layer, respectively sending the rest crude glycerol to an acid processor 3 through a pump 2 and a pipeline and an acid treating agent for acid treatment, then adding a flocculating agent to control the pH value of the crude glycerol to be 3.5-4.5 to generate fatty acid metal salt precipitates, separating, and respectively sending the crude glycerol and an alkali treating agent on the upper layer to an alkali processor 4 through pipelines for alkali treatment to obtain pretreated crude glycerol; the specific process is shown in figure 1.
The biodiesel is fatty acid methyl ester obtained by esterifying and transesterifying animal and vegetable oil with short-chain alcohol such as methanol, and refining. The main component of the animal and vegetable oil is saturated or unsaturated fatty acid glyceride, which is esterified and transesterified under the acid-base catalysis condition to produce a great amount of acid or base and salt-containing glycerol, commonly called crude glycerol.
The crude glycerin used in the invention contains 75-85% of glycerin, 8-12% of water and 3-6% of SO by weight4 2+And the rest to 100 percent of non-glycerol organic matter is called MONG for short.
Crude glycerol must be refined for use. Crude glycerol typically requires acid-base pretreatment prior to refining in order to maximize glycerol recovery.
First, crude glycerin containing sulfate radicals is subjected to liquid separation in a liquid separation tank 1 to remove an oil layer on the surface thereof, and the remaining crude glycerin is sent to an acid treatment apparatus 3 through a pump 2 and a pipe and an acid treatment agent, respectively, and subjected to acid treatment.
In the present invention, crude glycerin is allowed to settle and separate into an oil layer and a crude glycerin layer in a liquid separation tank 1 in a natural standing state. The separation operation can be terminated as judged by a densitometer and then its superficial oil layer removed by a conventional method using a cut-out with an overflow.
The liquid separating tank 1 used by the invention is a flat-bottom tank container, and is non-standard chemical equipment.
The remaining crude glycerin is sent to an acid processor 3 through a pump 2 and a pipeline and an acid treatment agent respectively for acid treatment. In the present invention, the main purpose of the acid treatment is to convert fatty acid salts contained in crude glycerin into fatty acids.
According to the invention, the remaining raw glycerol is subjected to an acid treatment in an acid treatment unit 3 at a temperature of 50 to 60 ℃ and a pH of 3.0 to 4.0 with an acid treatment agent. The acid treatment agent is a sulfuric acid aqueous solution with the concentration of 18-25% by weight; the usage amount of the glycerol is that the pH value of the residual crude glycerol reaches 3.0-4.0.
During acid treatment, the temperature is controlled at a lower temperature of 50-60 ℃, so that a good flocculation effect can be obtained in the following process. If the temperature is lower than 50 ℃, the crude glycerin has high viscosity and is not beneficial to floc settling separation; if the temperature is higher than 60 ℃, the formed flocs are fine and are not beneficial to flocculation, so that the acid treatment temperature is suitably controlled to be 50-60 ℃.
In the invention, the pH value of the residual crude glycerol is controlled to be 3.0-4.0. If this pH is less than 3.0, subsequent fatty acid flocculation is not favoured; if the pH is more than 4.0, it is not preferable to completely convert the fatty acid salts contained in the crude glycerin into fatty acids during the acid treatment, and the acid treatment effect is deteriorated, so that it is necessary to control the pH of the remaining crude glycerin to 3.0 to 4.0.
The sulfuric acid used in the present invention is a product currently marketed, for example, by huafeng chemical limited, nji county, under the trade name sulfuric acid.
The acid treatment is followed by the addition of a flocculant. The main function of the flocculant is to promote the flocculating settling of fatty acids so that their fatty acids can be sufficiently removed. The flocculant used in the invention is an aluminum sulfate aqueous solution with the concentration of 1-3% by weight, and is a product sold in the current market, for example, a product sold by Zibo positive aluminum salt chemical company Limited under the trade name of industrial-grade aluminum sulfate. The fatty acid flocculation precipitation separation is carried out by using a filtering device which is generally used in the technical field of chemical industry.
Then, the crude glycerin from which the fatty acid is removed and the alkali treatment agent are respectively sent to an alkali processor 4 through pipelines to be subjected to alkali treatment, so that pretreated crude glycerin is obtained. The main purpose of the alkali treatment is to form a soap by reacting fatty acids contained in crude glycerin with an alkali treatment agent.
In the alkali processor 4, the upper layer crude glycerine is subjected to alkali treatment by an alkali treatment agent under the conditions that the temperature is 80-90 ℃ and the pH is 7.0-8.0. The alkali treatment agent is a potassium hydroxide aqueous solution with the concentration of 8-12% by weight, and the use amount of the alkali treatment agent is that the pH value of the upper layer crude glycerol reaches 7.0-8.0. The potassium hydroxide used in the present invention is a product currently marketed, for example, by Shandong Fei Shuo chemical science and technology Co., Ltd.
In fact, the alkali treatment temperature does not significantly affect the alkali treatment effect, but an appropriate increase in the alkali treatment temperature is advantageous for the alkali treatment agent dispersion. At this temperature, if the pH of the upper crude glycerin is less than 7.0, the fatty acids contained in the crude glycerin are not sufficiently neutralized; if this pH is more than 8.0, the crude glycerin is strongly foamed upon evaporation to remove water, resulting in glycerin loss, and therefore, it is reasonable that the pH of the upper crude glycerin is 7.0 to 8.0.
In the invention, in the alkali treatment process, sulfate radicals in the crude glycerol are treated and reacted by potassium hydroxide to obtain potassium bisulfate.
In the present invention, the acid treater 3 and the alkali treater 4 are reaction vessels having a conical bottom structure with a stirrer, and are apparatuses well known to those skilled in the art of chemical engineering, such as an apparatus sold under the trade name of stirred tank by auspicious mechanical science and technology ltd, and an apparatus sold under the trade name of stirred tank by wuximin Yao chemical plant ltd.
B. Crude glycerol purification
The pretreated crude glycerol obtained in the step A is sent to a light component removal tower 5 through a pipeline to remove light components in the pretreated crude glycerol, and the light components are sent to a biochemical treatment system through a pipeline to be treated; the crude glycerol with light components removed is conveyed into a reaction rectifying tower 7 through a pipeline by a crude glycerol pump 6, and is refined in the presence of potassium bisulfate, so that a part of glycerol is dehydrated to generate acrolein, a mixture containing the acrolein, water and a small amount of glycerol is discharged from the top of the reaction rectifying tower 7, and is condensed by a heat exchanger 10 to obtain crude acrolein; the obtained refined glycerol is sent to a storage tank 8 from the lateral line of the reaction rectifying tower 7 through a pipeline, wherein a part of the refined glycerol is discharged through a refined glycerol pump 9, and the rest part of the refined glycerol returns to the upper part of the reaction rectifying tower 7; a crude glycerol distillation residue is obtained at the bottom of the reaction rectifying tower 7 and is sent to a glycerol residue treatment system through a pipeline; the specific processing flow is shown in figure 2.
The boiling point of glycerol at atmospheric pressure is 290 ℃ and at 204 ℃ it starts to decompose and the polymerization takes place. Therefore, in the present invention, the steps of refining the pretreated raw glycerin are all performed under reduced pressure.
According to the invention, the crude glycerol is pretreated in a lightness-removing tower 5 at the temperature of 120-150 ℃ and the pressure of 3-10 KPa to remove light components containing water and methanol.
In the invention, the crude glycerol with light components removed is refined in a reactive distillation tower 7 at the temperature of 165-170 ℃ and the pressure of 1.5-3.0 KPa, namely, a part of glycerol is dehydrated to generate acrolein in the presence of potassium hydrogen sulfate. The basic function of potassium bisulfate in the refining process is to accelerate the dehydration of glycerol to acrolein.
When refining is carried out, the refining pressure is 1.5-3.0 KPa, and if the refining temperature is lower than 165 ℃, the reaction conversion rate of acrolein generated by glycerin dehydration is low; if the refining temperature is higher than 170 ℃, a small amount of glycerin is polymerized to generate polyglycerol; therefore, the purification temperature is preferably 165 to 170 ℃;
similarly, when the refining temperature is 165-170 ℃, if the refining pressure is lower than 1.5KPa, the materials in the reactive distillation tower will be boiled suddenly, and the temperature will be reduced; if the refining pressure is higher than 3.0KPa, the materials in the reactive distillation tower cannot be gasified, so that the required refining temperature is high; therefore, the refining pressure is preferably 1.5 to 3.0 KPa;
according to the standard GB/T13216-.
In the present invention, the light component removal column 5 and the reactive distillation column 7 are both a packed column-type separation and purification column apparatus having a distillation function, and are also common apparatuses well known to those skilled in the art, such as a product sold under the trade name of rectification column by Jiangsu and energy technology Co., Ltd, and a product sold under the trade name of rectification column by Qingdao Jienenghuo high tech, Ltd.
The crude glycerin pump 6, the refined glycerin pump 9, and the heat exchanger 10 used in the present invention are all currently commercially available devices, such as those sold under the trade name horizontal multistage centrifugal pump by south pump industry gmbh, and those sold under the trade name plate heat exchanger by jiang yin daniel cooler gmbh.
The storage tank 8 used in the invention is a tank storage of a non-standard chemical container. The refined glycerol in the storage tank 8 is determined by analyzing and determining by a sodium periodate titration method in a standard GB/T13216-2008 glycerol test method, and the purity of the refined glycerol is calculated to be 95-96% by weight.
C. Acrolein separation
The crude acrolein enters from the top of the short-path distiller 11, and is subjected to distillation separation to obtain a light component and a heavy component, and the light component acrolein is condensed and discharged from the bottom of the short-path distiller 11 to an acrolein storage tank 12 for storage; the heavy component of the yellow glycerin is discharged from the side line of the short-path distiller 11 and returns to the lightness-removing tower 5 to recover the glycerin. The specific processing flow is shown in figure 2.
The short-path distillation is a special liquid-liquid separation technology operated under vacuum, which is different from the traditional distillation and relies on the bubbling mass transfer separation principle under the bubble point and the dew point temperature, but relies on the free escape on the surface of a liquid layer, and utilizes the difference of the moving mean free paths of different substance molecules to realize the separation. Specifically, the liquid mixture containing acrolein light component flows along the heating plate and is heated, the light and heavy molecules escape from the liquid surface and enter the gas phase, the moving distance of the light and heavy molecules after escaping from the liquid surface is different due to different free paths of the light and heavy molecules, the light molecular acrolein can reach the built-in condensing coil to be condensed and discharged, and the heavy molecular glycerin can reach the condensing coil to be discharged along with the mixed liquid, so that the light molecular acrolein and the heavy molecular glycerin are separated. The temperature difference between the heating surface and the condensing surface of the short-range distiller is 73-95 ℃. When the temperature of the heating surface is too high, the escape of heavy components is accelerated, the separation efficiency is reduced, and the polymerization of materials is accelerated; and its temperature is too low, which lowers the productivity. When the temperature of the condenser is too high, the acrolein content of the tail gas is high, and when the temperature is too low, the requirement on a refrigerant is severe.
The short path distiller used in the present invention is a well known apparatus to those skilled in the art, such as a product sold under the trade name short path distiller by Wuxi horse chemical machinery, Inc., and a product sold under the trade name molecular distiller by Jiangsu Mike chemical machinery, Inc.
According to the invention, the crude acrolein is distilled in a short-path distiller 11 under the conditions of pressure of 7-10 KPa, heating surface temperature of 60-80 ℃ and built-in condenser temperature of-13-15 ℃. The obtained light component acrolein can be sold as a chemical intermediate product after 0.02 percent of polymerization inhibitor hydroquinone is added into the light component acrolein by weight, or can also be used for producing 1, 3-propylene glycol.
In the invention, the molar yield of the refined glycerol is calculated according to the following formula:
the molar yield of the refined glycerol is equal to the actual molar number of the refined glycerol produced and the molar number of the refined glycerol contained in the crude glycerol raw material;
the molar yield of acrolein is calculated as follows:
the molar yield of acrolein is the actual mole of acrolein produced divided by the theoretical total conversion of glycerol to acrolein in the crude glycerol feed.
[ advantageous effects ]
The invention has the beneficial effects that: the co-production of acrolein is realized in the refining process of the crude glycerol, and the additional value of the carbon three chemicals is effectively improved. The method for co-producing acrolein has the advantages of simple and convenient process flow, simple operation, easy realization of industrial implementation and extremely great popularization and application values.
[ description of the drawings ]
FIG. 1 is a flow chart of the pretreatment of biodiesel by-product crude glycerol according to the present invention;
FIG. 2 is a flow diagram of the pre-treatment crude glycerol purification;
in the figure:
1-liquid separation tank; 2-a pump; 3-an acid processor; 4-alkali treatment; 5-a light component removal tower; 6-crude glycerol pump; 7-a rectifying tower; 8-a storage tank; 9-refined glycerol pump; 10-a heat exchanger; 11-short path distiller; 12-acrolein tank.
[ detailed description ] embodiments
Example 1: the method for co-producing acrolein in the refining process of biodiesel byproduct crude glycerol comprises the following implementation steps:
A. separation of crude glycerol
This example uses 2000g of a composition containing 80% by weight glycerol, 9% by weight moisture, 5% SO4 2+With the balance to 100% sulfate group-containing crude glycerin of non-glycerin organic matter.
Separating the sulfate-containing crude glycerol in a separating tank 1 to remove the surface oil layer, respectively sending the rest crude glycerol to an acid treatment device 3 through a pump 2 and a pipeline and an acid treatment agent through a pipeline, and performing acid treatment for 20min by using the acid treatment agent under the conditions of 50 ℃ and pH 3.0, wherein the acid treatment agent is a sulfuric acid aqueous solution with the concentration of 25% by weight; the usage amount is that the pH value of the rest crude glycerin reaches 3.0;
adding aluminum sulfate aqueous solution flocculant with the concentration of 2% by weight, controlling the pH value of the aluminum sulfate aqueous solution flocculant to be 3.5 to generate fatty acid metal salt precipitate, separating, respectively sending the crude glycerol and the alkali treatment agent on the upper layer to an alkali processor 4 through pipelines, and performing alkali treatment on the crude glycerol and the alkali treatment agent under the conditions that the temperature is 80 ℃ and the pH value is 7.0 to obtain pretreated crude glycerol; the alkali treatment agent is a 10% by weight aqueous solution of potassium hydroxide used in an amount to bring the pH of the upper crude glycerin to 7.0;
B. crude glycerol purification
The pretreated crude glycerol obtained in the step A is sent to a light component removal tower 5 through a pipeline to remove light components in the pretreated crude glycerol, and the light components are sent to a biochemical treatment system through a pipeline to be treated; the crude glycerol with light components removed is conveyed into a reaction rectifying tower 7 through a pipeline by a crude glycerol pump 6, and is refined under the conditions of 165 ℃ and 2.0KPa pressure and in the presence of potassium bisulfate, so that a part of glycerol is dehydrated to generate acrolein, a mixture containing the acrolein, water and a small amount of glycerol is discharged from the top of the reaction rectifying tower 7, and is condensed by a heat exchanger 10 to obtain crude acrolein; the obtained refined glycerol is sent to a storage tank 8 from the lateral line of the reaction rectifying tower 7 through a pipeline, wherein a part of the refined glycerol is discharged through a refined glycerol pump 9, and the rest part of the refined glycerol returns to the upper part of the reaction rectifying tower 7; a crude glycerol distillation residue is obtained at the bottom of the reaction rectifying tower 7 and is sent to a glycerol residue treatment system through a pipeline;
C. acrolein separation
The crude acrolein enters from the top of the short-path distiller 11, and is distilled under the conditions of pressure of 7KPa, heating surface temperature of 70 ℃ and built-in condenser temperature of-14 ℃ to obtain a light component and a heavy component through separation, and the light component acrolein is condensed and discharged to an acrolein storage tank 12 from the bottom of the short-path distiller 11 to be stored; the heavy component of the yellow glycerin is discharged from the side line of the short-path distiller 11 and returns to the lightness-removing tower 5 to recover the glycerin.
The results of the tests for the refined glycerol and acrolein products according to the methods described in the specification are shown in Table 1.
Table 1: results of this example
According to the calculation method described in the specification of the application, the molar yield of the refined glycerol under the working condition is 75.0% and the molar yield of the acrolein is 19.0% according to the calculation result of the example 1.
Example 2: the method for co-producing acrolein in the refining process of biodiesel byproduct crude glycerol comprises the following implementation steps:
A. separation of crude glycerol
This example uses 2000g of a composition containing by weight 85% glycerol, 8% moisture, 3% SO4 2+With the balance to 100% sulfate group-containing crude glycerin of non-glycerin organic matter.
Separating the sulfate-containing crude glycerol in a separating tank 1 to remove the surface oil layer, delivering the rest crude glycerol to an acid treatment device 3 through a pump 2 and a pipeline and an acid treatment agent respectively through pipelines, and performing acid treatment for 2020 min at 55 ℃ and pH 3.5 with the acid treatment agent which is a sulfuric acid aqueous solution with the concentration of 20% by weight; it is used in such an amount that the remaining crude glycerol has a pH of 3.5,
adding aluminum sulfate aqueous solution flocculant with the concentration of 2% by weight, controlling the pH value of the aluminum sulfate aqueous solution flocculant to be 4.5 to generate fatty acid metal salt precipitate, separating, respectively sending the crude glycerol and the alkali treatment agent on the upper layer to an alkali processor 4 through pipelines, and performing alkali treatment on the crude glycerol and the alkali treatment agent under the conditions that the temperature is 85 ℃ and the pH value is 7.5 to obtain pretreated crude glycerol; the alkali treatment agent is a 10% by weight aqueous solution of potassium hydroxide used in an amount to bring the pH of the upper crude glycerin to 7.5;
B. crude glycerol purification
The pretreated crude glycerol obtained in the step A is sent to a light component removal tower 5 through a pipeline to remove light components in the pretreated crude glycerol, and the light components are sent to a biochemical treatment system through a pipeline to be treated; the crude glycerol with light components removed is conveyed into a reaction rectifying tower 7 through a pipeline by a crude glycerol pump 6, and is refined under the conditions of 168 ℃ and 1.5KPa pressure and in the presence of potassium bisulfate, so that a part of glycerol is dehydrated to generate acrolein, a mixture containing the acrolein, water and a small amount of glycerol is discharged from the top of the reaction rectifying tower 7, and is condensed by a heat exchanger 10 to obtain crude acrolein; the obtained refined glycerol is sent to a storage tank 8 from the lateral line of the reaction rectifying tower 7 through a pipeline, wherein a part of the refined glycerol is discharged through a refined glycerol pump 9, and the rest part of the refined glycerol returns to the upper part of the reaction rectifying tower 7; a crude glycerol distillation residue is obtained at the bottom of the reaction rectifying tower 7 and is sent to a glycerol residue treatment system through a pipeline;
C. acrolein separation
The crude acrolein enters from the top of the short-path distiller 11, and is distilled under the conditions of pressure of 8KPa, heating surface temperature of 60 ℃ and built-in condenser temperature of-13 ℃ to obtain a light component and a heavy component through separation, and the light component acrolein is condensed and discharged to an acrolein storage tank 12 from the bottom of the short-path distiller 11 to be stored; the heavy component of the yellow glycerin is discharged from the side line of the short-path distiller 11 and returns to the lightness-removing tower 5 to recover the glycerin.
The results of the detection of the refined glycerol and acrolein products according to the methods described in the specification are shown in Table 2.
Table 2: results of this example
According to the calculation method described in the specification of the application, the molar yield of the refined glycerol under the working condition is 65.7% and the molar yield of the acrolein is 26.0% according to the calculation result of the example 2.
Example 3: the method for co-producing acrolein in the refining process of biodiesel byproduct crude glycerol comprises the following implementation steps:
A. separation of crude glycerol
This example uses 2000g of a composition containing 75% by weight of glycerol, 12% by weight of moisture, 6% by weight of SO4 2+With the balance to 100% sulfate group-containing crude glycerin of non-glycerin organic matter.
Separating the sulfate-containing crude glycerol in a separating tank 1 to remove the surface oil layer, delivering the rest crude glycerol to an acid treatment device 3 through a pump 2 and a pipeline and an acid treatment agent respectively through pipelines, and performing acid treatment for 20min at the temperature of 60 ℃ and the pH value of 4.0 by using the acid treatment agent which is an aqueous solution of sulfuric acid with the concentration of 18 percent by weight; it is used in such an amount that the remaining crude glycerin reaches a pH of 4.0,
adding aluminum sulfate aqueous solution flocculant with the concentration of 2% by weight, controlling the pH value of the aluminum sulfate aqueous solution flocculant to be 4.0 to generate fatty acid metal salt precipitate, separating, respectively sending the crude glycerol and the alkali treatment agent on the upper layer to an alkali processor 4 through pipelines, and performing alkali treatment on the crude glycerol and the alkali treatment agent under the conditions that the temperature is 90 ℃ and the pH value is 8.0 to obtain pretreated crude glycerol; the alkali treatment agent is a 10% by weight aqueous solution of potassium hydroxide used in an amount to bring the pH of the upper crude glycerin to 8.0;
B. crude glycerol purification
The pretreated crude glycerol obtained in the step A is sent to a light component removal tower 5 through a pipeline to remove light components in the pretreated crude glycerol, and the light components are sent to a biochemical treatment system through a pipeline to be treated; the crude glycerol with light components removed is conveyed into a reaction rectifying tower 7 through a pipeline by a crude glycerol pump 6, and is refined under the conditions of 170 ℃ and 3.0KPa pressure and in the presence of potassium hydrogen sulfate, so that a part of glycerol is dehydrated to generate acrolein, a mixture containing the acrolein, water and a small amount of glycerol is discharged from the top of the reaction rectifying tower 7, and is condensed by a heat exchanger 10 to obtain crude acrolein; the obtained refined glycerol is sent to a storage tank 8 from the lateral line of the reaction rectifying tower 7 through a pipeline, wherein a part of the refined glycerol is discharged through a refined glycerol pump 9, and the rest part of the refined glycerol returns to the upper part of the reaction rectifying tower 7; a crude glycerol distillation residue is obtained at the bottom of the reaction rectifying tower 7 and is sent to a glycerol residue treatment system through a pipeline;
C. acrolein separation
The crude acrolein enters from the top of the short-path distiller 11, and is distilled under the conditions of the pressure of 10KPa, the temperature of a heating surface of 80 ℃ and the temperature of a built-in condenser of-15 ℃ to obtain a light component and a heavy component by separation, and the light component acrolein is condensed and discharged to an acrolein storage tank 12 from the bottom of the short-path distiller 11 to be stored; the heavy component of the yellow glycerin is discharged from the side line of the short-path distiller 11 and returns to the lightness-removing tower 5 to recover the glycerin.
The results of the detection of the refined glycerol and acrolein products according to the methods described in the specification are shown in Table 3.
Table 3: results of this example
According to the calculation method described in the specification of the application, the molar yield of the refined glycerol in the working condition is 56.4% and the molar yield of the acrolein is 31.5%, which is calculated according to the result of the example 3.
In examples 1-3, the glycerol content was determined according to the sodium periodate titration method specified in GB/T13216-; the glycerol color number was determined according to the platinum-cobalt colorimetric method specified in GB/T13216-. Acrolein content was determined using a GC9790 gas chromatograph using conventional methods; the moisture content was measured according to the Karl Fischer method defined in GB/T6283-2008.
Claims (4)
1. A method for co-producing acrolein in the refining process of biodiesel byproduct crude glycerol is characterized by comprising the following steps:
A. separation of crude glycerol
Separating crude glycerin containing sulfate radicals generated in the production process of biodiesel in a liquid separating tank (1) to remove an oil layer on the surface of the crude glycerin, respectively sending the rest crude glycerin to an acid processor (3) through a pump (2) and a pipeline and an acid treating agent through pipelines for acid treatment, then adding a flocculating agent to control the pH value of the crude glycerin to be 3.5-4.5 to generate fatty acid metal salt precipitates, separating, and respectively sending the crude glycerin on the upper layer and the alkali treating agent to an alkali processor (4) through pipelines for alkali treatment to obtain pretreated crude glycerin;
the crude glycerol comprises 75-85% of glycerol, 8-12% of water and 3-6% of SO by weight4 2+With the balance to 100% of non-glycerol organics;
the acid treatment agent is a sulfuric acid aqueous solution with the concentration of 18-25% by weight; the usage amount of the glycerol is that the pH value of the rest crude glycerol reaches 3.0-4.0;
the flocculating agent is an aluminum sulfate aqueous solution with the concentration of 1-3% by weight;
the alkali treatment agent is a potassium hydroxide aqueous solution with the concentration of 8-12% by weight, and the use amount of the alkali treatment agent is that the pH value of the upper layer crude glycerol reaches 7.0-8.0;
B. crude glycerol purification
The pretreated crude glycerol obtained in the step A is sent to a light component removal tower (5) through a pipeline to remove light components in the pretreated crude glycerol, and the light components are sent to a biochemical treatment system through a pipeline to be treated; the crude glycerol with light components removed is conveyed into a reaction rectifying tower (7) through a pipeline by a crude glycerol pump (6), and is refined in the presence of potassium bisulfate, so that a part of glycerol is dehydrated to generate acrolein, a mixture containing the acrolein, water and a small amount of glycerol is discharged from the top of the reaction rectifying tower (7), and is condensed by a heat exchanger (10) to obtain crude acrolein; the obtained refined glycerol is sent to a storage tank (8) from the lateral line of the reaction rectifying tower (7) through a pipeline, wherein a part of the refined glycerol is discharged through a refined glycerol pump (9), and the rest part of the refined glycerol returns to the upper part of the reaction rectifying tower (7); a crude glycerol distillation residue is obtained at the bottom of the reaction rectifying tower (7) and is sent to a glycerol residue treatment system through a pipeline;
removing light components in the pretreated crude glycerol in a light component removal tower (5) under the conditions of temperature of 120-150 ℃ and pressure of 3-10 KPa;
C. acrolein separation
The crude acrolein enters from the top of the short-path distiller (11), and is subjected to distillation separation to obtain a light component and a heavy component, and the light component acrolein is condensed and discharged from the bottom of the short-path distiller (11) to an acrolein storage tank (12) for storage; the heavy component yellow glycerol is discharged from the side line of the short-path distiller (11) and returns to the lightness-removing tower (5) to recycle the glycerol;
the crude acrolein is distilled in a short-path distiller (11) under the conditions of pressure of 7-10 KPa, heating surface temperature of 60-80 ℃ and built-in condenser temperature of-13-15 ℃.
2. The method according to claim 1, wherein in step A, the remaining crude glycerin is subjected to acid treatment with an acid treatment agent at a temperature of 50 to 60 ℃ and a pH of 3.0 to 4.0 in an acid treatment device (3).
3. The method according to claim 1, wherein in step A, the upper layer crude glycerol is subjected to alkali treatment with an alkali treatment agent at a temperature of 80 to 90 ℃ and a pH of 7.0 to 8.0 in an alkali treatment device (4) to obtain pretreated crude glycerol.
4. The method according to claim 1, wherein in the step B, the crude glycerin from which light components are removed is refined in a reactive distillation column (7) at a temperature of 165-170 ℃ and a pressure of 1.5-3.0 KPa to obtain crude acrolein and refined glycerin.
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| CN101367711A (en) * | 2007-08-15 | 2009-02-18 | 罗门哈斯公司 | Method for purification of glycerol from biodiesel production |
| CN102245551A (en) * | 2008-12-09 | 2011-11-16 | 赢创斯托豪森有限公司 | Method for producing acrolein comprising the regeneration of a raw glycerin phase |
| CN103209947A (en) * | 2010-11-11 | 2013-07-17 | 株式会社日立工业设备技术 | Glycerin purification method |
| CN104387249A (en) * | 2014-10-30 | 2015-03-04 | 清华大学 | Preparation method of acraldehyde |
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| CN101367711A (en) * | 2007-08-15 | 2009-02-18 | 罗门哈斯公司 | Method for purification of glycerol from biodiesel production |
| CN102245551A (en) * | 2008-12-09 | 2011-11-16 | 赢创斯托豪森有限公司 | Method for producing acrolein comprising the regeneration of a raw glycerin phase |
| CN103209947A (en) * | 2010-11-11 | 2013-07-17 | 株式会社日立工业设备技术 | Glycerin purification method |
| CN104387249A (en) * | 2014-10-30 | 2015-03-04 | 清华大学 | Preparation method of acraldehyde |
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