Apparatus and method for separating a mixture of methanol, ethanol, toluene and water

Abstract

This invention belongs to the field of chemical separation technology, specifically relating to an apparatus and method for separating mixtures of methanol, ethanol, toluene, and water. The apparatus includes a distillation kettle, a distillation column, a column reboiler, a reboiler, a condenser, a reflux tank, a phase separation tank, and a receiving tank. The method specifically involves the formation of binary or ternary azeotropes between toluene and methanol, ethanol, and water in the material. Due to the positive deviation of Raoult's law from the binary azeotropic systems (toluene-methanol, toluene-ethanol, toluene-water) and the ternary azeotropic systems (toluene-ethanol-water), resulting in a minimum azeotropic point, the separation is achieved by increasing or decreasing the amount of water in the system, utilizing the differences in the binary and ternary azeotropic components and the liquid stratification characteristics. This invention can separate methanol, ethanol, and toluene products with a purity greater than 99.5%. The process of this invention is short, requires less equipment investment, is easy to operate, and provides thorough product separation, making it suitable for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of chemical separation technology, specifically relating to an apparatus and method for separating a mixture of methanol, ethanol, toluene and water. Background Technology

[0002] Methanol, also known as hydroxymethane, is the simplest saturated monohydric alcohol with the chemical formula CH3OH. It has a molecular weight of 32.04, a relative density of 0.792 (20 / 4℃), a melting point of -97.8℃, and a boiling point of 64.7℃. It is miscible with water, ethanol, diethyl ether, benzene, ketones, nitriles, halogenated hydrocarbons, and many other organic solvents. Methanol has a wide range of applications, serving as a basic organic chemical raw material and a high-quality fuel. It is mainly used in fine chemicals and plastics, and is one of the important basic organic raw materials for pesticides, pharmaceuticals, and materials. After further processing, methanol can be used as a novel alcohol-based fuel or blended into gasoline. It can also be used to manufacture various organic products such as acetic acid, chloromethane, methylamine, and dimethyl sulfate. Toluene (Methyl Benzene) is an organic compound with the chemical formula C7H8, a molecular weight of 92.14, a relative density of 0.872 (20 / 4℃), a melting point of -94.9℃, and a boiling point of 110.6℃. It is a colorless, volatile liquid with a characteristic aromatic odor, miscible with ethanol, ether, acetone, chloroform, carbon disulfide, and glacial acetic acid, and very slightly soluble in water. Toluene is mainly produced from crude oil through petrochemical processes. As a solvent, it is used in oils, resins, natural and synthetic rubber, coal tar, asphalt, and cellulose acetate. It is also used as a solvent in cellulose paints and varnishes, and as a solvent in photographic plates and inks. Toluene is also a major raw material in organic synthesis, especially in the synthesis of benzoyl chloride and phenyl, saccharin, trinitrotoluene, and many dyes. It is also a component of aviation and automotive gasoline. Toluene is widely used as a solvent and is an important raw material in organic chemicals. It is extensively used in the production of dyes, pharmaceuticals, pesticides, explosives, auxiliaries, fragrances, and other fine chemicals, as well as in the synthetic materials industry. Its most important applications are in polyurethane products, dyes and organic pigments, rubber additives, pharmaceuticals, and explosives. Ethanol (ET), commonly known as alcohol, is an organic compound with the structural formula CH3CH2OH or C2H5OH, molecular formula C2H6O, molecular weight 40.07, melting point -114.0℃, boiling point 78.3℃, and relative density 0.7893 (20 / 4℃). Ethanol is miscible with water in any proportion and is miscible with chloroform, diethyl ether, methanol, acetone, and most other organic solvents. Ethanol has wide applications in the electronics industry, chemical industry, medical and health care, food industry, and agricultural production.

[0003] The manufacturing processes of pesticides, pharmaceuticals, and electronic materials often produce byproducts of methanol-ethanol-toluene-water mixtures. These materials require distillation separation; otherwise, they are considered hazardous solid waste. However, methanol, ethanol, and toluene in these mixtures are common solvents. Distillation can separate these solvents into substances with high concentrations, turning waste into valuable resources. Distillation separation of mixtures relies on the relative volatility of the components; the greater the difference in relative volatility, the easier the separation. However, for some mixtures, the relative volatility of the components is close to or equal to 1, making ordinary distillation methods insufficient for separation, necessitating the use of special distillation techniques.

[0004] Currently, commonly used special distillation methods include azeotropic distillation, extractive distillation, membrane separation, pressure swing distillation, and adsorption distillation. Methanol and toluene are commonly used organic solvents in the fine chemical and pharmaceutical fields. Under normal pressure, they deviate positively from Raoult's law, forming a minimum azeotrope with an azeotropic temperature of 63.8℃. The mass fraction of methanol in the azeotrope is 69%, and the mass fraction of toluene is 31%. Conventional distillation methods are difficult to effectively separate them. In actual production, to solve the problem of separating methanol and toluene azeotropes, if a continuous azeotropic distillation process is used, two distillation columns and one water extraction column are required for methanol and toluene distillation separation. However, the continuous three-column process has a large throughput, complex equipment, high automation requirements, and high investment. If a continuous extractive distillation process is used, two distillation columns are required: an extraction column and a solvent recovery column. There are many extraction solvents that can be selected for extractive distillation. Due to the large extraction solvent ratio, the regeneration of the extraction solvent requires negative pressure distillation, resulting in high energy consumption and a relatively complex process. To address the separation of ethanol, toluene, and water mixtures, several challenges exist. Toluene and ethanol form a homogeneous azeotrope (azeotropic temperature 76.7℃, azeotropic composition containing 68% ethanol), while toluene and water form a heterogeneous water azeotrope (azeotropic temperature 84.1℃, azeotropic composition containing 13.5% water). Furthermore, toluene, ethanol, and water also form a ternary heterogeneous azeotrope (azeotropic temperature 74.4℃, azeotropic composition toluene-ethanol-water = 51-37-12). A continuous azeotropic distillation process requires three distillation columns: an ethanol azeotropic column, a toluene distillation column, and an ethanol recovery column, along with a phase separator. This three-column combination process has a large throughput, complex equipment, high automation requirements, and high investment costs. A continuous extractive distillation process requires two distillation columns: an extraction column and a solvent recovery column. Extractive distillation offers a wide range of solvent options, but due to the high solvent ratio, solvent regeneration requires negative pressure distillation, resulting in high energy consumption and a relatively complex process. Azeotropic pressure distillation utilizes the differences in azeotropic temperature and component content of azeotropes under different pressure conditions to separate methanol, ethanol, and toluene. The relative volatility of components decreases during the pressure process, energy consumption increases, high and low heat sources need to be thermally integrated, the process is complex, and the temperature and pressure of the pressure distillation column are relatively high, resulting in a high level of safety defects. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention provides an apparatus and method for separating a mixture of methanol, ethanol, toluene and water. The purpose is to solve the technical problems that existing special distillation methods cannot meet the requirements for efficient separation of a mixture of methanol, ethanol, toluene and water, and that have defects such as complex separation equipment and insufficient safety.

[0006] The first technical solution provided by this invention is a method for separating a mixture of methanol, ethanol, toluene, and water, the specific technical solution of which is as follows:

[0007] A method for separating a mixture of methanol, ethanol, toluene, and water includes the following steps:

[0008] S1, the material to be separated is distilled and then fractionally distilled to obtain a methanol-toluene mixed fraction, and an ethanol-toluene-water mixed fraction is obtained at the bottom of the column;

[0009] S2, the methanol-toluene mixed fraction in step S1 is distilled and cooled to separate phases to obtain an upper oil phase and a lower water phase. The separated oil and water phases are then distilled separately to obtain toluene and methanol products respectively.

[0010] S3, the ethanol-toluene-water mixture fraction from step S1 is distilled, and the ethanol-toluene-water ternary azeotrope is collected from the top of the column and cooled and separated to obtain an upper oil phase and a lower water phase. The separated oil and water phases are then distilled separately to obtain toluene and ethanol products respectively.

[0011] In some embodiments, step S1 includes the following steps:

[0012] S11, the material to be separated is distilled to obtain a gaseous material, wherein the gaseous material is a mixture of methanol-ethanol-toluene-water.

[0013] S12, after the gaseous material in step S11 is distilled, the bottom of the column yields an ethanol-toluene-water mixture fraction, and the top of the column is condensed to obtain a methanol-toluene azeotrope fraction.

[0014] Further, in step S11, the operating pressure of distillation is 105-110 kPa and the temperature is 65-110℃; in step S12, the bottom pressure of distillation column is 105-110 kPa; the top temperature of distillation column is 66-110℃ and the bottom temperature of distillation column is 70-115℃; the operating reflux ratio of distillation is 0.1-15.

[0015] In some implementations, step S2 includes the following steps:

[0016] S21, the methanol-toluene mixed fraction in step S1 is distilled to obtain a methanol-toluene azeotrope at the top of the column;

[0017] S22, add deionized water to the methanol-toluene azeotrope in step S21 for cooling and phase separation to obtain an upper oil phase and a lower water phase, wherein the upper oil phase is crude toluene;

[0018] S23, the crude toluene in step S22 is distilled, and the methanol-toluene azeotrope obtained at the top of the column is added to deionized water for cooling and phase separation to obtain an upper oil phase and a lower water phase. The upper oil phase is distilled again to collect the finished toluene.

[0019] In step S24, the lower aqueous phase in both step S22 and step S23 is distilled to remove the toluene-methanol transition fraction. The distillation is then carried out again with a reflux ratio of 5-10, and the finished methanol product is collected with a reflux ratio of 1-3.

[0020] Furthermore, in step S21, the reflux ratio of the methanol-toluene azeotrope collected by distillation is 1-5; in step S22, the water addition ratio is top distillate:water = 0.1-3; in step S23, the operating conditions for collecting the finished toluene are as follows: top temperature 110.6℃, bottom temperature 115-120℃.

[0021] In some embodiments, step S3 includes the following steps:

[0022] S31, the ethanol-toluene-water mixture fraction in step S1 is subjected to distillation and dehydration treatment to obtain an ethanol-toluene-water mixture fraction with a concentration of less than 50,000 ppm, and then subjected to distillation to obtain an ethanol-toluene-water ternary azeotrope.

[0023] S32, the ethanol-toluene-water ternary azeotrope in step S31 is separated into an upper oil phase and a lower water phase;

[0024] S33, the upper oil phase in step S32 is subjected to multiple distillation phase separations until the ethanol and water are completely removed, and the finished product toluene is collected.

[0025] S34, after dehydrating the lower aqueous phase from step S32 and the lower aqueous phase from the multiple distillation phases in step S33, perform distillation to collect ethanol, water and toluene transition fractions, and collect the finished ethanol from the aqueous phase after separation.

[0026] Furthermore, in step S31, the reflux ratio for obtaining the ethanol-toluene-water ternary azeotrope by distillation is 1-3; in step S33, the operating reflux ratio for distillation is 1-5; and in step S34, the operating reflux ratio for distillation is 1-10.

[0027] The second technical solution provided by this invention is an apparatus for separating a mixture of methanol, ethanol, toluene, and water, adapted to the method described in the first technical solution. The specific technical solution is as follows:

[0028] The system includes a distillation kettle, a rectification unit, a phase separator, a reflux tank, an aqueous phase receiving tank, a crude toluene receiving tank, a transition fraction tank, and a product tank. The distillation kettle is connected to the rectification unit. The rectification unit is connected to the phase separator sequentially through a primary condenser and a secondary condenser. The phase separator is also connected to the top of the reflux tank, the top of the aqueous phase receiving tank, and the crude toluene receiving tank. The bottom of the reflux tank is connected to the rectification unit and to the top of the transition fraction tank via a reflux cooler. The top of the aqueous phase receiving tank is connected to the top of the rectification unit, the top of the crude toluene receiving tank, the top of the transition fraction tank, and the top of the product tank, respectively. The bottoms of the aqueous phase receiving tank, the crude toluene receiving tank, and the transition fraction tank are all connected to the rectification unit.

[0029] In some embodiments, the distillation unit includes a distillation column and a reboiler. The distillation column has 50-80 theoretical plates, with 25-40 theoretical plates in the rectification section and 25-40 theoretical plates in the stripping section. The top of the distillation column is connected to the bottom of the primary condenser and the reflux tank, respectively.

[0030] The reboiler is located at the bottom of the distillation column, and a reboiler is provided in the reboiler. The distillation column and the reboiler are both connected to the distillation vessel. The bottom of the aqueous phase receiving tank, the bottom of the crude toluene receiving tank, and the bottom of the transition fraction tank are all connected to the reboiler. A bottom condenser is connected to the bottom of the reboiler.

[0031] In some embodiments, the phase separator includes a phase separation cooler and a phase separation tank connected in communication. The phase separation cooler is connected to the secondary cooler. The upper part of the phase separation tank is connected to the middle part of the distillation column, the top of the reflux tank, and the top of the crude toluene receiving tank, respectively. The bottom of the phase separation tank is connected to the top of the aqueous phase receiving tank.

[0032] This invention has the following beneficial effects: The raw materials contain solvents methanol, ethanol, toluene, water, and other small amounts of inorganic salts and high-boiling impurities, which are byproducts or solid wastes of related factories. The quantity and composition of the raw materials vary greatly. The raw materials are simply distilled to remove high-boiling residues. Through rectification, a toluene-methanol binary azeotrope is obtained at the top of the column, and an ethanol-toluene-water triadic mixture is obtained at the bottom. The toluene-methanol binary azeotrope is further extracted by adding deionized water, using water as an extractant, to extract methanol and water from the azeotrope. After rectification, methanol and toluene products are obtained. The ethanol-toluene-water triadic mixture utilizes the cooling and phase separation characteristics of the ethanol-toluene-water triadic azeotrope, i.e., after phase separation, the oil phase toluene has a low water content, while the water phase has a high water content. This separates the water and toluene from the system, and combines with ethanol and toluene to form a binary azeotrope, maximizing the yield of ethanol products. After phase separation, the upper layer is rectified to obtain the product toluene, and the lower layer is rectified to obtain the ethanol-toluene-water fraction, which can be reused to improve the yield. The method and apparatus of this invention provide mild separation conditions, avoiding adverse factors such as high temperature and high pressure, thus improving safety. The separation process of this invention is simple, the objective is clear, the quality of the separated product is stable, the process is safe and reliable, the manufacturing cost is low, and its implementation can bring considerable economic benefits. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the apparatus provided by the present invention for separating a mixture of methanol, ethanol, toluene and water;

[0034] The markings in the diagram are as follows: R1, distillation kettle; T1, distillation column; V1, column bottom; V2, phase separation tank; V3, reflux tank; V4, aqueous phase receiving tank; V5, crude toluene receiving tank; V6, transition fraction tank; V7, product tank; E1, reboiler; E2, primary condenser; E3, secondary condenser; E4, phase separation cooler; E5, reflux cooler; E6, bottom condenser; 1, feed inlet; 2, fraction inlet; 3, deionized water inlet; 4, product outlet; 5, top fraction outlet; 6, bottom fraction outlet; 7, high-boiling feed outlet. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0036] like Figure 1 As shown, the raw materials or distillate fractions enter the distillation kettle or column reboiler via a raw material pump, employing batch or semi-continuous operation, as detailed below:

[0037] (1) The material in the distillation vessel R1 is heated by steam; the material is vaporized, the operating pressure is 105-110 kPa, and the temperature is 65-110℃; the gaseous material in the column bottom V1 enters the distillation column T1, and the gaseous material is a mixture of methanol-ethanol-toluene-water; the non-volatile salts and high-boiling organic substances obtained at the bottom of the distillation vessel R1 are discharged from the system while hot through the high-boiling material outlet 7;

[0038] (2) The methanol-ethanol-toluene-water mixture is a binary and multi-component azeotropic system. By adding or subtracting water, the homogeneous or heterogeneous azeotropic material composition is eliminated, and then the distillation separation is carried out to finally obtain a qualified product.

[0039] (3) The reboiler V1 is a horizontal reboiler. The material is heated by the reboiler E1 for distillation. The operating pressure at the top of the column is atmospheric pressure, and the pressure at the bottom of the column is 105-10 kPa. The temperature at the top of the column is 66-110℃, and the temperature at the bottom of the distillation column T1 is 70-115℃. The gaseous material at the top of the column enters the primary condenser E2 and the secondary condenser E3 in sequence. The refrigerant for the two condensers is circulating water. The condensate enters the reflux tank V3 or the phase separator according to the process requirements. The condensate in reflux tank V3 is divided into two streams by a reflux pump. One stream enters the feed inlet at the top of distillation column T1, and the other stream is cooled by reflux cooler E5 before entering aqueous phase receiving tank V4, crude toluene receiving tank V5, transition fraction tank V6, and product tank V7. The operating reflux ratio of distillation column T1 is 0.1-15. The theoretical number of plates in distillation column T1 is 50-80, of which 25-40 are in the rectification section and 25-40 are in the stripping section.

[0040] (4) The phase separator is composed of a phase separation tank V2 and an operating temperature of 20-30℃, with a residence time of 0.5-3h. The phase separator has two material sources: condensate from the top of the column and effluent from the reflux cooler E5. If the phase separator directly receives the condensate from the top of the column, the phase separation cooler E4 is connected to the deionized water inlet 3. The condensate can be mixed with water. After cooling and phase separation, the upper oil phase (crude toluene) enters the reflux tank V3, and the lower aqueous phase (containing water, alcohols, and a small amount of toluene) enters the aqueous phase receiving tank V4. The dehydration method is as follows: In the total reflux dehydration process, the toluene phase is pumped into the top of distillation column T1, and the theoretical reflux ratio of distillation column T1 is 0. If the phase separator receives the liquid from the reflux cooler E5, after the material is cooled and separated, the upper oil phase containing toluene is fed into the crude toluene receiving tank V5 or returned to the feed inlet in the middle of distillation column T1, and the lower aqueous phase containing water, alcohols and a small amount of toluene is returned to the feed inlet in the middle of distillation column T1 or connected to the aqueous phase receiving tank V4. The dehydration method is toluene-ethanol-water ternary azeotropic dehydration, and the reflux ratio of distillation column T1 is 1-10.

[0041] (5) The distillation products and fractions are collected by effectively combining the phase separator and the reflux tank V3 to obtain methanol, ethanol and toluene intermediate fractions, and finally obtain methanol, ethanol and toluene products with a content of >99.5% through distillation.

[0042] Specifically, the raw material (entering the system through raw material inlet 1) consists of 5-15% methanol, 20-60% ethanol, 20-60% toluene, 0.5-20% water, and 0.5-3% other inorganic salts and high-boiling-point substances. To separate the methanol-ethanol-toluene-water mixture, firstly, a distillation vessel R1 is used to remove heavy components from the raw material to prevent clogging of the packing and bottom V1 of the distillation column T1 if the raw material directly enters it. Furthermore, the ethanol-toluene-water mixture fraction and the methanol-toluene azeotrope fraction can be directly pumped into the middle of distillation column T1 or into the bottom V1. These two fractions do not contain inorganic salts, and since they are generated during the distillation separation process, their composition varies greatly depending on the process conditions.

[0043] First, the gaseous solvent in the raw material in distillation vessel R1 is separated by continuous distillation. The condensate from the top of distillation column T1 enters reflux tank V3, and part of it is refluxed back to the top of the column by the reflux pump, while the rest is cooled and collected into the receiving tank, resulting in a methanol-toluene mixed fraction discharged through the top fraction outlet 5, with a composition of 69% methanol and 31% toluene. The bottom material of distillation column T1 is cooled by the bottom condenser E6, and the bottom pump outputs an ethanol-toluene-water mixed fraction through the bottom fraction outlet 6, with a composition of 20-55% ethanol, 20-50% toluene, and 1-20% water. The reflux ratio for the distillation operation is 2-5.

[0044] The methanol-toluene mixed fraction, composed of a methanol-toluene binary azeotrope, contains no ethanol or water. This fraction can be directly fed into the bottom of the distillation column V1 via a pump or the bottom valve of the receiving tank from fraction inlet 2. A batch distillation method is used to separate the methanol and toluene azeotrope. The reflux ratio of the toluene azeotrope collected from the batch distillation column T1 is controlled at 1-5. Water is added to the collected azeotrope at a ratio of top distillate:water = 0.1-3. After mixing and cooling, the azeotrope is separated in a phase separator. The upper toluene phase enters the crude toluene receiving tank V5, while the lower aqueous phase returns to the middle of the distillation column T1. This process continues until the toluene phase separation is complete. A small amount of the toluene-methanol transition fraction is collected into the aqueous phase receiving tank V4 at a reflux ratio of 5-10. Then, finished methanol is collected from the top of the column at a reflux ratio of 1-3 and fed into the product receiving tank. The product is then pumped out as methanol with a purity >99.5%. Water is obtained at the bottom of the column.

[0045] The crude toluene from crude toluene receiving tank V5 enters the bottom of column V1; the methanol-toluene mixture and transition fraction collected from the top of distillation column T1 enter either the aqueous phase receiving tank V4 or the crude toluene receiving tank V5, and the finished toluene is collected under the following operating conditions: top temperature 110.6℃, bottom temperature 115-120℃, reflux ratio 1-10; the collected finished toluene enters the receiving tank and is pumped out as finished toluene with a purity greater than 99.5%;

[0046] The bottom product of distillation column T1, after being pumped out by the bottom pump to obtain an ethanol-toluene-water mixed fraction, enters the reboiler V1. A batch distillation process is used to separate the ethanol-m-benzene-water ternary azeotrope. The reflux ratio of the toluene ternary azeotrope collected from batch distillation column T1 is controlled at 1-5. The destination of the material in the phase separator is determined based on the toluene and water content in the product. The collected ternary azeotrope is further cooled by reflux cooler E5 and the phase separator, separating into two layers. The upper toluene phase can be returned to distillation column T1 or sent to the crude toluene receiving tank V5, while the lower aqueous phase can be received in tank V4 or returned to distillation column T1. If the material contains... With low moisture content, ethanol content >80%, and toluene 5-15%, total reflux dehydration can be used. This means the condensate at the top of the column directly enters the phase separator for cooling and phase separation. The upper oil phase (toluene) enters the reflux tank V3 and is pumped back to the top of the column by the reflux pump, while the lower water phase enters the water phase receiving tank V4. Total reflux dehydration stops when the phase separation interface in the phase separator V2 disappears, and normal distillation operation resumes with a reflux ratio of 1-10. The distillation yields ethanol, water, and a toluene-ethanol transition fraction, which enters the transition fraction receiving tank. Finally, the finished ethanol product is collected and enters the product tank V7, from which a product pump outputs ethanol with a purity >99.5%.

[0047] The material in the aqueous ethanol receiving tank (aqueous phase receiving tank V4) is the lower aqueous phase after phase separation of the ternary azeotrope, with a composition of 53% ethanol, 11% toluene, and 36% water. The material is fed into the bottom of the column V1 for batch distillation via a feed pump or directly. The ethanol-toluene-water ternary azeotrope is collected from the top of the column and fed into the reflux tank V3. The ethanol-toluene-water mixture is collected by the reflux pump and fed into the transition fraction tank V6. The material composition is 78% ethanol, 15% toluene, and 3-7% water. Water is obtained at the bottom of the column, with a solvent content (ethanol + toluene) of <0.05%, and is discharged from the system via the bottom pump.

[0048] The material in the crude product receiving tank (crude toluene tank) is the upper oil phase of the ternary azeotrope after phase separation, with a composition of 15% ethanol, 84% toluene, and 1% water. The material is pumped into the bottom of the column V1 directly or via a feed pump. Ionized water is added to the bottom of column V1 at a ratio of 10-15% of the feed. Through intermittent distillation, the azeotrope is collected from the top of the column and fed into the reflux tank V3. After being cooled by the reflux pump and cooler, it is fed into the phase separator. The lower aqueous phase is fed into the aqueous phase receiving tank V4. The material composition is 53% ethanol, 11% toluene, and 36% water. The upper toluene is returned to the distillation column T1 until the ethanol and water are completely removed. A small amount of toluene transition fraction is fed into the toluene-ethanol transition fraction tank V6. Finally, the finished toluene is collected into the product tank V7 and pumped out with a toluene content >99.5%.

[0049] Example 1

[0050] The raw material used in this embodiment is No. 1 raw material. After pretreatment and distillation to remove impurities, the toluene-methanol azeotrope is obtained from the top of the distillation column T1 and the ethanol-toluene-water mixed fraction is obtained from the bottom of the column. The crude distillation process is as follows:

[0051] The raw material or distillate fraction is pumped into distillation vessel R1 or column reboiler V1, using batch or semi-continuous operation. The material in distillation vessel R1 is heated by steam; the material vaporizes at an operating pressure of 105-110 kPa and a temperature of 65-110℃. The vaporous material in the vessel enters the feed inlet in the middle of distillation column T1; the vaporous material is a mixture of methanol-ethanol-toluene-water. Non-volatile salts and high-boiling organic compounds are obtained at the bottom of distillation vessel R1 and discharged from the system while hot. The material in column reboiler V1 is heated by reboiler E1 for distillation; the operating pressure at the top of the column is atmospheric pressure, and the pressure at the bottom is 105-110 kPa. The top temperature... The temperature is 64℃, and the bottom temperature of distillation column T1 is 70-80℃. The gaseous material at the top of the column sequentially enters the primary condenser E2 and the secondary condenser E3. The refrigerant for both condensers is circulating water, and the condensate enters the reflux tank V3. After being pumped out, one path enters the feed inlet at the top of distillation column T1, and the other path is cooled by reflux cooler E5 and then enters the aqueous phase receiving tank V4. The operating reflux ratio of distillation column T1 is 2-3, and the theoretical number of plates is 60, of which 30 are in the rectification section and 30 are in the stripping section. Through distillation, the methanol-toluene azeotrope is obtained at the top of the column, and the ethanol-toluene-water mixture is obtained at the bottom of the column.

[0052] The composition of the No. 1 raw material is shown in Table 1, and the composition of the distillate obtained from the crude distillate of the No. 1 raw material is shown in Table 2.

[0053] 2. Separation of the methanol-toluene azeotrope fraction:

[0054] The methanol-toluene azeotrope fraction is separated by two distillations using the T1 distillation system of this unit.

[0055] First, the methanol-toluene azeotrope enters the bottom of column V1 at a reflux ratio of 1-5. The azeotrope obtained at the top of the column is mixed with deionized water and separated by a phase separator. The upper oil phase (crude toluene) enters the crude toluene receiving tank V5; the lower aqueous phase enters the feed inlet in the middle of distillation column T1 at a water ratio of 1 / 0.5-2 (collected fraction / water). After separation, a small amount of transition fraction is collected and enters the aqueous phase receiving tank V4. Then, the finished methanol is collected at a reflux ratio of 1-3 and enters the product tank V7, which is then pumped out via product pump P4. The methanol content is >99.5%, and the moisture content is <0.05%.

[0056] The crude toluene fraction enters the bottom of column V1, with an operating reflux ratio of 1-5. The azeotrope obtained at the top of the column is added to deionized water and separated by a phase separator. The upper oil phase toluene enters the middle feed inlet of distillation column T1, while the lower methanol-containing aqueous phase enters the aqueous phase receiving tank V4. The water addition ratio is: collected fraction / water = 1 / 0.1-1. After separation, a small amount of transition fraction is collected and enters the crude toluene receiving tank V5. Then, with a reflux ratio of 1-3, the finished toluene is collected and enters the product tank V7, which is then pumped out. The toluene content is >99.5%, and the moisture content is <0.05%.

[0057] 3. Separation of ethanol-toluene-water mixed fractions:

[0058] (1) If the ethanol-toluene-water mixed fraction after crude distillation has a high water content, it can be processed by a rectification unit. After rectification, the top of the column will have an ethanol-toluene-water mixed fraction with less water content, and the bottom of the column will have water.

[0059] (2) The ethanol-toluene-water mixed fraction with low water content is fed into the rectification unit for processing. In the early stage, toluene is collected. The ternary azeotrope collected from the top of the column is cooled and fed into the phase separator. The upper oil phase toluene is separated and fed into the crude toluene receiving tank V5. The lower water phase is separated and returned to the feed inlet in the middle of the rectification column T1. The reflux ratio is 1-3. In the middle stage, dehydration is performed. The ternary azeotrope collected from the top of the column is cooled and fed into the phase separator. The upper oil phase toluene is separated and returned to the feed inlet in the middle of the rectification column T1. The lower water phase is separated and fed into the water phase receiving tank V4. The reflux ratio is 1-3. In the later stage, the product is collected. The ethanol-toluene intermediate fraction collected from the top of the column is fed into the crude toluene receiving tank V5. Then the ethanol product is received into the product tank V7 and output through the product pump. The ethanol content is >99.5% and the water content is <0.05%.

[0060] (3) The oil phase toluene fraction after separation enters the rectification unit for processing. During the rectification process, water can be added for separation and water and ethanol can be removed from the system by total reflux. Alternatively, a ternary azeotrope can be used for cooling separation to remove water and ethanol from the system. The operating reflux ratio is 1-5. The ethanol-toluene intermediate fraction is collected from the top of the column and enters the transition fraction receiving tank. Finally, the finished toluene is collected into the product tank V7 with an operating reflux ratio of 0-1 and output through the product pump. The toluene content is >99.5% and the moisture content is <0.05%.

[0061] Example 2

[0062] In this embodiment, raw material #2 is used. After pretreatment and distillation to remove impurities, a toluene-methanol azeotrope is obtained at the top of distillation column T1, and a mixed ethanol-toluene-water fraction is obtained at the bottom of the column. The process method is the same as in Example 1 and will not be repeated here.

[0063] The composition of the No. 2 raw material is shown in Table 1, and the composition of the fraction obtained from the crude distillation of the No. 2 raw material is shown in Table 2.

[0064] The separation process for the methanol-toluene azeotrope was the same as in Example 1 and will not be repeated here.

[0065] After the raw material #2 is coarsely distilled, a mixed fraction of ethanol-toluene-water is obtained at the bottom of the column. The separation process is the same as the distillation method of the mixed fraction of ethanol-toluene-water in Example 1. Due to the low water content, an appropriate amount of water can be added to the ternary azeotrope at the top of the column to promote stratification. Finally, ethanol and toluene products with a content of more than 99.5% are obtained, with the ethanol product having a larger content than the toluene product.

[0066] Example 3

[0067] In this embodiment, raw material #3 is used. After pretreatment and distillation to remove impurities, a toluene-methanol azeotrope is obtained at the top of distillation column T1, and a mixed ethanol-toluene-water fraction is obtained at the bottom of the column. The process method is the same as in Example 1.

[0068] The composition of the No. 3 raw material is shown in Table 1, and the composition of the distillate obtained from the crude distillate of the No. 3 raw material is shown in Table 2.

[0069] The separation process for the methanol-toluene azeotrope was the same as in Example 1 and will not be repeated here.

[0070] After the raw material #3 is coarsely distilled, a mixed fraction of ethanol-toluene-water is obtained at the bottom of the column. The separation process is the same as the distillation method of the mixed fraction of ethanol-toluene-water in Example 1. Due to the high water content, the mixed fraction can be dehydrated by coarse distillation to obtain a ternary mixture with a water content of 3-5%. Then, distillation separation is carried out. At this time, the ternary azeotrope at the top of the column enters the phase separator and directly separates into layers. The dehydration time is shortened and the energy consumption is low. Finally, ethanol and toluene products with a content of more than 99.5% are obtained.

[0071] Example 4

[0072] In this embodiment, raw material #4 is used. After pretreatment and distillation to remove impurities, a toluene-methanol azeotrope is obtained from the top of distillation column T1, and an ethanol-toluene-water mixed fraction is obtained from the bottom of the column. The process method is the same as in Example 1.

[0073] The composition of the No. 4 raw material is shown in Table 1, and the composition of the distillate obtained from the crude distillate of the No. 4 raw material is shown in Table 2.

[0074] The separation process of methanol-toluene azeotrope from the top crude feed and the separation process of ethanol-toluene-water mixed fraction from the bottom feed are the same as in Example 1. The final product obtained is methanol, ethanol and toluene with a content of more than 99.5%, which will not be described in detail here.

[0075] Example 5

[0076] In this embodiment, raw material #5 is used. After pretreatment and distillation to remove impurities, a toluene-methanol azeotrope is obtained from the top of distillation column T1, and an ethanol-toluene-water mixed fraction is obtained from the bottom of the column. The process method is the same as in Example 1.

[0077] The composition of the No. 5 raw material is shown in Table 1, and the composition of the distillate obtained from the crude distillate of the No. 5 raw material is shown in Table 2.

[0078] The separation process for the methanol-toluene azeotrope was the same as in Example 1 and will not be repeated here.

[0079] After the No. 5 feed is coarsely distilled, the bottom of the column yields an ethanol-toluene-water mixed fraction. The separation process is the same as the ethanol-toluene-water mixed fraction rectification method in Example 3. Due to the high water content, the mixed fraction can be dehydrated by coarse distillation to obtain a ternary mixture with a water content of 3-5%. Then, rectification separation is carried out. At this time, the ternary azeotrope at the top of the column enters the phase separator and directly separates into layers. The dehydration time is shortened and the energy consumption is low. Finally, ethanol and toluene products with a content of more than 99.5% are obtained.

[0080] Example 6

[0081] In this embodiment, raw material #6 is used. After pretreatment and distillation to remove impurities, a toluene-methanol azeotrope is obtained from the top of distillation column T1, and an ethanol-toluene-water mixed fraction is obtained from the bottom of the column. The process method is the same as in Example 1.

[0082] The composition of the No. 6 raw material is shown in Table 1, and the composition of the fraction obtained from the crude distillation of the No. 6 raw material is shown in Table 2.

[0083] The separation process of the methanol-toluene azeotrope from the top of the column and the separation process of the ethanol-toluene-water mixed fraction from the bottom of the column are the same as in Example 4. The final product obtained is methanol, ethanol and toluene with a content of more than 99.5%, which will not be described again.

[0084] Example 7

[0085] In this embodiment, raw material #7 is used. After pretreatment and distillation to remove impurities, a toluene-methanol azeotrope is obtained from the top of distillation column T1, and an ethanol-toluene-water mixed fraction is obtained from the bottom of the column. The process method is the same as in Example 1.

[0086] The composition of the No. 7 raw material is shown in Table 1, and the composition of the distillate obtained from the crude distillate of No. 7 raw material is shown in Table 2.

[0087] The separation process for the methanol-toluene azeotrope was the same as in Example 1 and will not be repeated here.

[0088] After the 7# feed is coarsely distilled, the bottom of the column yields an ethanol-toluene-water mixed fraction. The separation process is the same as the ethanol-toluene-water mixed fraction rectification method in Example 1. Due to the high water content, the mixed fraction can be dehydrated by coarse distillation to obtain a ternary mixture with a water content of 3-5%. Then, rectification separation is carried out. At this time, the ternary azeotrope at the top of the column enters the phase separator and directly separates into layers. The dehydration time is shortened and the energy consumption is low. Finally, ethanol and toluene products with a content of more than 99.5% are obtained.

[0089] Example 8

[0090] In this embodiment, No. 8 raw material is used. After pretreatment and distillation to remove impurities, a toluene-methanol azeotrope is obtained from the top of the distillation column T1, and an ethanol-toluene-water mixed fraction is obtained from the bottom of the column. The process method is the same as in Example 1.

[0091] The composition of the No. 8 raw material is shown in Table 1, and the composition of the distillate obtained from the crude distillate of No. 8 raw material is shown in Table 2.

[0092] The separation process for the methanol-toluene azeotrope was the same as in Example 1 and will not be repeated here.

[0093] After the coarse distillation of feed #8, a mixed fraction of ethanol-toluene-water is obtained at the bottom of the column. The separation process is the same as the rectification method of the mixed fraction of ethanol-toluene-water in Example 1. Since the water content is close to the ternary azeotropic composition, rectification separation is carried out directly. At this time, the ternary azeotrope at the top of the column enters the phase separator and directly separates into layers. The dehydration time is longer than that in Example 7, and the overall energy consumption is basically the same as that in Example 7. Finally, ethanol and toluene products with a content of more than 99.5% are obtained.

[0094] Table 1 Raw Material Composition Table

[0095]

[0096] Table 2 Composition of Crude Distillate

[0097]

[0098]

[0099] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. The present invention is not limited to the examples described above. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for separating a mixture of methanol, ethanol, toluene, and water, characterized in that, Includes the following steps: S1, the material to be separated is distilled and then fractionally distilled to obtain a methanol-toluene mixed fraction, and an ethanol-toluene-water mixed fraction is obtained at the bottom of the column; S2, the methanol-toluene mixed fraction in step S1 is distilled and cooled to separate phases to obtain an upper oil phase and a lower water phase. The separated oil and water phases are then distilled separately to obtain toluene and methanol products respectively. S3, the ethanol-toluene-water mixture fraction from step S1 is distilled, and the ethanol-toluene-water ternary azeotrope is collected from the top of the column and cooled and separated to obtain an upper oil phase and a lower water phase. The separated oil and water phases are then distilled separately to obtain toluene and ethanol products respectively.

2. The method for separating a mixture of methanol, ethanol, toluene, and water according to claim 1, characterized in that, Step S1 includes the following steps: S11, the material to be separated is distilled to obtain a gaseous material, wherein the gaseous material is a mixture of methanol-ethanol-toluene-water. S12, after the gaseous material in step S11 is distilled, the bottom of the column yields an ethanol-toluene-water mixture fraction, and the top of the column is condensed to obtain a methanol-toluene azeotrope fraction.

3. The method for separating a mixture of methanol, ethanol, toluene, and water according to claim 2, characterized in that, In step S11, the operating pressure of distillation is 105-110 kPa and the temperature is 65-110℃; in step S12, the bottom pressure of distillation column is 105-110 kPa; the top temperature of distillation column is 66-110℃ and the bottom temperature of distillation column is 70-115℃; the operating reflux ratio of distillation is 0.1-15.

4. The method for separating a mixture of methanol, ethanol, toluene, and water according to claim 1, characterized in that, Step S2 includes the following steps: S21, the methanol-toluene mixed fraction in step S1 is distilled to obtain a methanol-toluene azeotrope at the top of the column; S22, Deionized water is added to the methanol-toluene azeotrope in step S21 for cooling and phase separation to obtain an upper oil phase and a lower water phase, wherein the upper oil phase is crude toluene; S23, the crude toluene in step S22 is distilled, and the methanol-toluene azeotrope obtained at the top of the column is added to deionized water for cooling and phase separation to obtain an upper oil phase and a lower water phase. The upper oil phase is distilled again to collect the finished toluene. In step S24, the lower aqueous phase in both step S22 and step S23 is distilled to remove the toluene-methanol transition fraction. The distillation is then carried out again with a reflux ratio of 5-10, and the finished methanol product is collected with a reflux ratio of 1-3.

5. The method for separating a mixture of methanol, ethanol, toluene, and water according to claim 4, characterized in that, In step S21, the reflux ratio of the methanol-toluene azeotrope collected by distillation is 1-5; in step S22, the water addition ratio is top distillate:water = 0.1-3; in step S23, the operating conditions for collecting the finished toluene are as follows: top temperature 110.6℃, bottom temperature 115-120℃.

6. The method for separating a mixture of methanol, ethanol, toluene, and water according to claim 1, characterized in that, Step S3 includes the following steps: S31, the ethanol-toluene-water mixture fraction in step S1 is subjected to distillation and dehydration treatment to obtain an ethanol-toluene-water mixture fraction with a concentration of less than 50,000 ppm, and then subjected to distillation to obtain an ethanol-toluene-water ternary azeotrope. S32, the ethanol-toluene-water ternary azeotrope in step S31 is separated into an upper oil phase and a lower water phase; S33, the upper oil phase in step S32 is subjected to multiple distillation phase separations until the ethanol and water are completely removed, and the finished product toluene is collected. S34, after dehydrating the lower aqueous phase from step S32 and the lower aqueous phase from the multiple distillation phases in step S33, perform distillation to collect ethanol, water and toluene transition fractions, and collect the finished ethanol from the aqueous phase after separation.

7. The method for separating a mixture of methanol, ethanol, toluene, and water according to claim 6, characterized in that, In step S31, the reflux ratio for obtaining the ethanol-toluene-water ternary azeotrope by distillation is 1-3; in step S33, the operating reflux ratio for distillation is 1-5; and in step S34, the operating reflux ratio for distillation is 1-10.

8. An apparatus for separating a mixture of methanol, ethanol, toluene, and water, based on the method of any one of claims 1-7, characterized in that, The system includes a distillation kettle (R1), a rectification unit, a phase separator, a reflux tank (V3), an aqueous phase receiving tank (V4), a crude toluene receiving tank (V5), a transition fraction tank (V6), and a product tank (V7). The distillation kettle (R1) is connected to the rectification unit, which is connected to the phase separator via a primary condenser (E2) and a secondary condenser. The phase separator is also connected to the top of the reflux tank (V3), the top of the aqueous phase receiving tank (V4), and the crude toluene receiving tank (V5). The bottom of the reflux tank (V3) is connected to the distillation unit and to the top of the transition fraction tank (V6) via the reflux cooler (E5). The top of the aqueous phase receiving tank (V4) is connected to the top of the distillation unit, the top of the crude toluene receiving tank (V5), the top of the transition fraction tank (V6), and the top of the product tank (V7). The bottoms of the aqueous phase receiving tank (V4), the crude toluene receiving tank (V5), and the transition fraction tank (V6) are all connected to the distillation unit.

9. The apparatus for separating a mixture of methanol, ethanol, toluene, and water according to claim 8, characterized in that, The distillation unit includes a distillation column (T1) and a reboiler (V1). The distillation column (T1) has 50-80 theoretical plates, with 25-40 theoretical plates in the rectification section and 25-40 theoretical plates in the stripping section. The top of the distillation column (T1) is connected to the bottom of the primary condenser (E2) and the reflux tank (V3), respectively. The reboiler (V1) is located at the bottom of the distillation column (T1). A reboiler (E1) is provided in the reboiler (V1). The distillation column (T1) and the reboiler (V1) are both connected to the distillation vessel (R1). The bottom of the aqueous phase receiving tank (V4), the bottom of the crude toluene receiving tank (V5), and the bottom of the transition fraction tank (V6) are all connected to the reboiler (V1). A bottom condenser (E6) is connected to the bottom of the reboiler (V1).

10. The apparatus for separating a mixture of methanol, ethanol, toluene, and water according to claim 8, characterized in that, The phase separator includes a phase separation cooler (E4) and a phase separation tank (V2) connected together. The phase separation cooler (E4) is connected to the secondary condenser. The upper part of the phase separation tank (V2) is connected to the middle part of the distillation column (T1), the top of the reflux tank (V3), and the top of the crude toluene receiving tank (V5). The bottom of the phase separation tank (V2) is connected to the top of the aqueous phase receiving tank (V4).

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