Method for recovering tert-butyl alcohol from waste liquid containing methylbenzene and tert-butyl alcohol

Abstract

The invention relates to the technical field of multi-component separation, and discloses a method for recovering tert-butyl alcohol from waste liquid containing toluene and tert-butyl alcohol, which comprises the following steps: (1) carrying out first rectification on the waste liquid containing toluene and tert-butyl alcohol to obtain a first gas-phase material and water; (2) condensing the first gas-phase material and then carrying out second rectification to obtain a second gas-phase material; the tower top operation temperature of the first rectification is 3-5 DEG C higher than the tower top operation temperature of the second rectification; the tower kettle operation temperature of the first rectification is 14-20 DEG C higher than the tower kettle operation temperature of the second rectification; (3) condensing the second gas-phase material, carrying out oil-water separation to obtain an oil phase and a water phase, and returning the oil phase to the step (2) for secondary rectification; and returning the water phase to the step (1), and carrying out first rectification again. The method can separate waste liquids containing different concentrations of tert-butyl alcohol, does not need to introduce new components, and has the advantages of high separation recovery rate, high product purity and simple steps.

Description

Technical Field

[0001] This invention relates to the field of multi-component separation technology, and more specifically to a method for recovering tert-butanol from waste liquid containing toluene and tert-butanol. Background Technology

[0002] tert-Butanol is a colorless crystalline solid, a weakly polar small-molecule organic compound. In the presence of a small amount of water, it is a colorless volatile liquid with a camphor-like odor. It has a wide range of applications, primarily as a gasoline additive, solvent, and raw material for organic synthesis. Under normal pressure, tert-butanol forms an azeotropic system with water. However, methods for the separation and purification of this azeotropic system have been reported, including azeotropic distillation, extractive distillation, adsorption distillation, pervaporation, and adsorption. Each method has its advantages and disadvantages, and the appropriate method must be selected based on factors such as separation requirements, energy costs, and environmental standards in practical applications.

[0003] Currently, the upstream feedstock for conventional azeotropic distillation processes is mostly a high-concentration tert-butanol aqueous solution prepared by isobutylene hydration. Its feed composition is already close to the tert-butanol-water azeotropic composition, making the process directly applicable. However, for industrial wastewater containing toluene and tert-butanol, this process has significant limitations: Firstly, existing processes require the introduction of cyclohexane as an entrainer to disrupt the azeotropic equilibrium. This process not only introduces new foreign components, leading to poor treatment of the target wastewater, but also introduces additional impurities, increasing the burden on subsequent treatment. Secondly, if this process is used to separate tert-butanol-water mixtures, the concentration of tert-butanol must first be pre-raised to near the azeotropic composition using a dehydration tower, followed by multiple steps including the addition of the entrainer (cyclohexane), separation in an azeotropic distillation tower, and purification in a recovery tower. The entire process involves high equipment investment costs and large energy consumption, making it neither economically viable nor practically ideal. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of cumbersome separation methods and poor separation effect of existing technologies for separating waste liquid containing toluene and tert-butanol, and to provide a method for recovering tert-butanol from waste liquid containing toluene and tert-butanol. This method has the characteristics of high purity of the separated product, high separation recovery rate and simple separation steps.

[0005] To achieve the above objectives, the present invention provides a method for recovering tert-butanol from waste liquid containing toluene and tert-butanol, the method comprising: (1) The waste liquid containing toluene and tert-butanol is subjected to a first distillation to obtain a first gaseous material and a first product; the mass fraction of tert-butanol in the waste liquid is 2.5wt%-86wt% based on the total mass of the waste liquid; (2) The first gaseous material is condensed and then subjected to a second distillation to obtain a second gaseous material; the top operating temperature of the first distillation column is 2-5℃ higher than the top operating temperature of the second distillation column; the bottom operating temperature of the first distillation column is 14-20℃ higher than the bottom operating temperature of the second distillation column. (3) After the second gas phase material is condensed, oil and water are separated to obtain an oil phase and a water phase. The oil phase is returned to step (2) for a second distillation to obtain tert-butanol; the water phase is returned to step (1) for a first distillation.

[0006] Through the above technical solution, the present invention has the following advantages: (1) The method of the present invention can efficiently separate mixtures containing different concentrations of tert-butanol (the feed concentration of tert-butanol can be as low as 2.5wt%), and the separation recovery rate is between 94% and 99.99%.

[0007] (2) The method of the present invention can separate tert-butanol, toluene and water without introducing new components (impurities), and the separated product has high purity, with the mass fraction of tert-butanol reaching more than 90 wt%.

[0008] (3) The method of the present invention only requires two distillation columns to complete the separation, the steps are simple, and the equipment investment and energy consumption are low. Detailed Implementation

[0009] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0010] This invention provides a method for recovering tert-butanol from waste liquid containing toluene and tert-butanol, the method comprising: (1) The waste liquid containing toluene and tert-butanol is subjected to a first distillation to obtain a first gaseous material and a first product; the mass fraction of tert-butanol in the waste liquid is 2.5wt%-86wt% based on the total mass of the waste liquid; (2) The first gaseous material is condensed and then subjected to a second distillation to obtain a second gaseous material; the top operating temperature of the first distillation column is 2-5℃ higher than the top operating temperature of the second distillation column; the bottom operating temperature of the first distillation column is 14-20℃ higher than the bottom operating temperature of the second distillation column. (3) After the second gas phase material is condensed, oil and water are separated to obtain an oil phase and a water phase. The oil phase is returned to step (2) for a second distillation to obtain tert-butanol; the water phase is returned to step (1) for a first distillation.

[0011] In this invention, the top operating temperature of the first distillation column is 2-5°C higher than the top operating temperature of the second distillation column; the bottom operating temperature of the first distillation column is 14-20°C higher than the bottom operating temperature of the second distillation column. In this invention, the bottom and top temperatures are directly related to the composition of the extracted material. By controlling the difference in operating temperatures between the first and second distillation columns within the above range, it is convenient to establish a dual-column azeotropic distillation system, which can effectively control the relative changes in the components of the two columns, thereby improving the purity and recovery rate of tert-butanol.

[0012] In this invention, preferably, the top operating temperature of the first distillation column is 3.5-4.5°C higher than the top operating temperature of the second distillation column, such as 3.5°C, 3.6°C, 3.7°C, 3.8°C, 3.9°C, 4°C, 4.1°C, 4.2°C, 4.3°C, 4.4°C, 4.5°C, or any value or range between the above values; the bottom operating temperature of the first distillation column is 14-17°C higher than the top operating temperature of the second distillation column, such as 14°C, 14.5°C, 15°C, 15.2°C, 15.4°C, 15.8°C, 16°C, 16.1°C, 16.2°C, 16.5°C, 16.7°C, 16.9°C, 17°C, or any value or range between the above values.

[0013] The inventors of this invention have discovered that the method of this invention can not only efficiently treat waste liquid containing high concentrations of tert-butanol, but also specifically solve the technical pain points of difficult separation and low treatment efficiency of waste liquid containing low concentrations of tert-butanol (mass fraction of tert-butanol below 16wt%), and can achieve effective treatment of waste liquid containing tert-butanol at different concentration gradients.

[0014] In this invention, preferably, the mass fraction of tert-butanol in the waste liquid is 4.5wt%-16wt%, such as 4.5wt%, 5wt%, 8wt%, 10wt%, 12wt%, 14wt%, 15wt%, 15.1wt%, 15.5wt%, 15.8wt%, 16wt%, or any value or range between the above values, based on the total mass of the waste liquid.

[0015] In this invention, preferably, the mass ratio of tert-butanol to toluene in the waste liquid is greater than 12:1.

[0016] More preferably, the mass ratio of tert-butanol to toluene in the waste liquid is greater than 50:1, more preferably (55-1510):1, such as 55:1, 80:1, 100:1, 200:1, 300:1, 500:1, 560:1, 600:1, 800:1, 1000:1, 1100:1, 1200:1, 1300:1, 1400:1, 1500:1, 1510:1 or any value or range between the above values.

[0017] In this invention, no particular type of distillation column is specified. Any distillation column conventionally defined in the art can be applied to this invention, and those skilled in the art can choose according to actual needs.

[0018] In this invention, the feed inlet of the first distillation column is located in the upper middle part of the first distillation column. The upper middle part refers to the position of the feed inlet on the plate based on the total number of plates in the first distillation column (denoted as N, where N is a positive integer). The position of the plate is such that the plate number counted from the top of the column is within the range of (N / 4) to (N / 2) (if it is a non-integer, the adjacent integer plate is taken, and the plate closest to the middle is preferred).

[0019] In this invention, preferably, in step (1), the first distillation is carried out in a first distillation column, the feed inlet of the first distillation column is located in the upper part of the first distillation column, the theoretical number of the first distillation column is 10-60, the reflux ratio is 1-15, the operating pressure of the first distillation column is 0.09-0.2MPa, the operating temperature at the top of the column is 76-85℃, and the operating temperature at the bottom of the column is 95-100℃.

[0020] According to some preferred embodiments of the present invention, in step (1), the theoretical number of plates of the first distillation column is 15-30, the reflux ratio is 1.5-5, the operating pressure of the first distillation column is 0.1MPa (atmospheric pressure), the operating temperature at the top of the column is 78-80℃, and the operating temperature at the bottom of the column is 97-99℃.

[0021] According to a preferred embodiment of the present invention, in step (1), the water mass fraction in the first product is ≥99wt%. This first product can be treated using advanced treatment processes for reuse, or it can be directly discharged provided that relevant emission regulations and standards are met.

[0022] In this invention, the feed inlet of the second distillation column is located in the upper middle part of the second distillation column. The upper middle part refers to the position of the feed inlet on the tray based on the total number of trays of the first distillation column (denoted as N, where N is a positive integer). The position of the tray is such that the tray number counted from the top of the column is within the range of (N / 4) to (N / 2) (if it is a non-integer, the adjacent integer tray is taken, and the tray closest to the middle is preferred).

[0023] In this invention, preferably, in step (2), after the first gaseous material is condensed, the solution is fed into the second distillation column for distillation.

[0024] In this invention, preferably, in step (2), the distillation is carried out in a second distillation column, the feed inlet of the second distillation column is located in the upper part of the second distillation column, the theoretical number of the second distillation column is 10-60, the reflux ratio is 1-15, the operating pressure of the second distillation column is 0.09-0.2MPa, the operating temperature at the top of the column is 72-80℃, and the operating temperature at the bottom of the column is 78-85℃.

[0025] According to some preferred embodiments of the present invention, in step (2), the theoretical number of plates of the second distillation column is 15-30, the reflux ratio is 1.5-5, the operating pressure of the second distillation column is 0.1 MPa (atmospheric pressure), the operating temperature at the top of the column is 75-76°C, and the operating pressure at the top of the column is 0.1 MPa (atmospheric pressure).

[0026] According to some preferred embodiments of the present invention, in step (2), the mass fraction of tert-butanol is ≥90wt%.

[0027] In this invention, preferably, in step (3), the second gaseous material is condensed and then the solution is fed into an oil-water separator for separation.

[0028] In this invention, preferably, in step (3), the oil-water separation is carried out in an oil-water separator, the operating temperature of which is 40-60℃, the operating pressure is 0.09-0.2MPa, and the separation time is 5-120 minutes.

[0029] More preferably, in step (3), the oil-water separation is carried out in an oil-water separator, the operating temperature of which is 45-55℃, the operating pressure is 0.1MPa (atmospheric pressure), and the separation time is 30-60 minutes.

[0030] According to a preferred embodiment of the present invention, in step (3), the mass fraction of toluene in the oil phase is 43wt%-46wt% based on the total mass of the oil phase.

[0031] According to a preferred embodiment of the present invention, the oil phase obtained from the liquid-liquid separation process is returned to step (2) for a second distillation; the aqueous phase is returned to step (1) for a first distillation. This operation can achieve cross-distillation boundaries through phase separation, thereby obtaining a tert-butanol product with higher purity than the tert-butanol-water azeotrope. By selectively refluxing the product into the corresponding distillation step, the separation and extraction rate of tert-butanol can be significantly improved, reducing material waste. At the same time, by using stepwise circulating distillation, the residual amount of impurities in the system can be further reduced, optimizing the purity of tert-butanol.

[0032] In this invention, preferably, the oil phase inlet is located above the first and second plates.

[0033] The present invention will be described in detail below through examples. Unless otherwise specified, all examples and comparative examples are conventional methods. Unless otherwise specified, all reagents and materials are commercially available. The mass fractions of tert-butanol and toluene were determined by an Agilent GC-MS gas chromatograph, and the mass fraction of water was determined by an Agilent GC-MS gas chromatograph. Recovery rate of tert-butanol = (mass of tert-butanol in the product ÷ mass of tert-butanol in the feed) × 100%.

[0034] Example 1 (1) A feed containing 76.81 wt% tert-butanol and 0.136 wt% toluene (the remainder being water) is introduced into the first distillation column. The operating pressure of the first distillation column is controlled at atmospheric pressure, the operating temperature at the top of the column is 79.90 °C, the operating temperature at the bottom of the column is 98.79 °C, the theoretical number of plates is 20, the feed inlet is located at the 8th plate, and the reflux ratio is 3.5. The first gaseous material is obtained at the top of the column, and the first product is obtained at the bottom of the column. The first gaseous material is a mixture of tert-butanol, toluene, and water, and the mass fraction of water in the first product is 99.72 wt%.

[0035] (2) The first gaseous material obtained in step (1) is condensed and introduced into the second distillation column. The operating pressure of the second distillation column is controlled to be atmospheric pressure, the operating temperature at the top of the column is 75.72℃, the operating temperature at the bottom of the column is 82.07℃, the number of trays is 25, the feed inlet of the first gaseous material condensate is located above the 8th tray, the reflux ratio is 3.5, and the second gaseous material is obtained at the top of the column.

[0036] (3) The second gaseous material obtained in step (2) is condensed and introduced into an oil-water separator for oil-water separation. The operating temperature of the oil-water separator is controlled at 50°C and the operating pressure is 0.1 MPa. After separation for 30 minutes, an oil phase and a water phase are obtained. The mass fraction of toluene in the oil phase is 44.1%. Subsequently, the oil phase is returned to step (2) for re-distillation. The oil phase inlet is located above the first plate. The obtained water phase is returned to the first distillation column in step (1) for re-distillation.

[0037] (4) In the above steps, 1 ton of the tert-butanol-containing raw material is introduced into the first distillation column, and the stable operation time of the equipment is controlled to be 2 hours (starting from when the raw material has completely entered the equipment and the system reaches the preset process parameters); after the operation cycle is completed, 770.6 kg of the target product is collected in the bottom of the second distillation column, of which the mass fraction of tert-butanol is 99.6 wt%, the mass fraction of water is 0.1 wt%, the mass fraction of toluene is 0.3 wt%, and the recovery rate of tert-butanol is calculated to be 99.92%.

[0038] Example 2 (1) A feed containing 15.1 wt% tert-butanol and 0.01 wt% toluene (the remaining components are water) is introduced into the first distillation column. The operating pressure of the first distillation column is controlled at atmospheric pressure, the operating temperature at the top of the column is 79.93℃, the operating temperature at the bottom of the column is 97.98℃, the theoretical number of plates is 20, the feed inlet is located at the 8th plate, and the reflux ratio is 3.5. The first gaseous material is obtained at the top of the column, and the first product is obtained at the bottom of the column. The first gaseous material is a mixture of tert-butanol, toluene and water, and the mass fraction of water in the first product is 99.41 wt%.

[0039] (2) The first gaseous material obtained in step (1) is condensed and introduced into the second distillation column. The operating pressure of the second distillation column is controlled to be atmospheric pressure, the operating temperature at the top of the column is 75.72℃, the operating temperature at the bottom of the column is 81.89℃, the number of trays is 25, the feed inlet of the first gaseous material condensate is located above the 8th tray, the reflux ratio is 3.5, and the second gaseous material is obtained at the top of the column.

[0040] (3) The second gaseous material obtained in step (2) is condensed and introduced into an oil-water separator for oil-water separation. The operating temperature of the oil-water separator is controlled at 50°C and the operating pressure is 0.1 MPa. After separation for 30 minutes, an oil phase and a water phase are obtained. The mass fraction of toluene in the oil phase is 44.14 wt%. Subsequently, the oil phase is returned to step (2) for re-distillation. The oil phase inlet is located above the first plate. The obtained water phase is returned to the first distillation column in step (1) for re-distillation.

[0041] (4) In the above steps, 1 ton of the tert-butanol-containing raw material is introduced into the first distillation column, and the stable operation time of the equipment is controlled to be 1 hour (starting from when the raw material has completely entered the equipment and the system reaches the preset process parameters); after the operation cycle is completed, 147.73 kg of the target product is collected in the bottom of the second distillation column, of which the mass fraction of tert-butanol is 99 wt%, the mass fraction of water is 0.41 wt%, the mass fraction of toluene is 0.59 wt%, and the recovery rate of tert-butanol is calculated to be 96.85 wt%.

[0042] Example 3 (1) A feed containing 4.5 wt% tert-butanol and 0.08 wt% toluene (the remaining components are water) is introduced into the first distillation column. The operating pressure of the first distillation column is controlled at atmospheric pressure, the operating temperature at the top of the column is 79.5℃, the operating temperature at the bottom of the column is 98.79℃, the theoretical number of plates is 20, the feed inlet is located at the 8th plate, and the reflux ratio is 3.5. The first gaseous material is obtained at the top of the column, and the first product is obtained at the bottom of the column. The first gaseous material is a mixture of tert-butanol, toluene and water, and the mass fraction of water in the first product is 99.70 wt%.

[0043] (2) The first gaseous material obtained in step (1) is condensed and introduced into the second distillation column. The operating pressure of the second distillation column is controlled to be atmospheric pressure, the operating temperature at the top of the column is 75.72℃, the operating temperature at the bottom of the column is 82.03℃, the number of trays is 25, the feed inlet of the first gaseous material condensate is located above the 8th tray, the reflux ratio is 3.5, and the second gaseous material is obtained at the top of the column.

[0044] (3) The second gaseous material obtained in step (2) is condensed and introduced into an oil-water separator for oil-water separation. The operating temperature of the oil-water separator is controlled at 50°C and the operating pressure is 0.1 MPa. After separation for 30 minutes, an oil phase and a water phase are obtained. The mass fraction of toluene in the oil phase is 44.09 wt%. Subsequently, the oil phase is returned to step (2) for re-distillation. The oil phase inlet is located above the first plate. The obtained water phase is returned to the first distillation column in step (1) for re-distillation.

[0045] (4) In the above steps, 1 ton of the tert-butanol-containing raw material is introduced into the first distillation column, and the stable operation time of the equipment is controlled to be 3 hours (starting from when the raw material has completely entered the equipment and the system reaches the preset process parameters); after the operation cycle is completed, 43.156 kg of the target product is collected in the bottom of the second distillation column, of which the mass fraction of tert-butanol is 98.144 wt%, the mass fraction of water is 0.016 wt%, the mass fraction of toluene is 1.84 wt%, and the recovery rate of tert-butanol is calculated to be 94.12%.

[0046] Example 4 (1) A feed containing 30 wt% tert-butanol and 1.06 wt% toluene (the remainder being water) is introduced into the first distillation column. The operating pressure of the first distillation column is controlled at atmospheric pressure, the operating temperature at the top of the column is 79.14℃, the operating temperature at the bottom of the column is 97.31℃, the theoretical number of plates is 20, the feed inlet is located at the 8th plate, and the reflux ratio is 3.5. The first gaseous material is obtained at the top of the column, and the first product is obtained at the bottom of the column. The first gaseous material is a mixture of tert-butanol, toluene, and water, and the mass fraction of water in the first product is 99.2 wt%.

[0047] (2) The first gaseous material obtained in step (1) is condensed and introduced into the second distillation column. The operating pressure of the second distillation column is controlled to be atmospheric pressure, the operating temperature at the top of the column is 75.72℃, the operating temperature at the bottom of the column is 81.94℃, the number of trays is 25, the inlet of the condensate of the first gaseous material is located above the 8th tray, the return oil phase inlet of the oil-water separator is located above the 1st tray, the reflux ratio is 3.5, and the second gaseous material is obtained at the top of the column.

[0048] (3) The second gas phase material obtained in step (2) is condensed and introduced into an oil-water separator for oil-water separation. The operating temperature of the oil-water separator is controlled at 50°C and the operating pressure is 0.1 MPa. After separation for 30 minutes, an oil phase and a water phase are obtained. The mass fraction of toluene in the oil phase is 44.1 wt%. Subsequently, the oil phase is returned to step (2) for re-distillation. The obtained water phase is returned to the first distillation column in step (1) for re-distillation.

[0049] (4) In the above steps, 1 ton of the tert-butanol-containing raw material is introduced into the first distillation column, and the stable operation time of the equipment is controlled to be 3 hours (starting from when the raw material has completely entered the equipment and the system reaches the preset process parameters); after the operation cycle is completed, 305.42 kg of the target product is collected in the bottom of the second distillation column, of which the mass fraction of tert-butanol is 96.4 wt%, the mass fraction of water is 0.002 wt%, the mass fraction of toluene is 3.58 wt%, and the recovery rate of tert-butanol is calculated to be 98.14%.

[0050] Example 5 (1) A feed containing 50 wt% tert-butanol and 0.033 wt% toluene (the remaining components are water) is introduced into the first distillation column. The operating pressure of the first distillation column is controlled at atmospheric pressure, the operating temperature at the top of the column is 79.96℃, the operating temperature at the bottom of the column is 97.59℃, the theoretical number of plates is 10, the feed inlet is located at the 4th plate, and the reflux ratio is 1. The first gaseous material is obtained at the top of the column, and the first product is obtained at the bottom of the column. The first gaseous material is a mixture of tert-butanol, toluene and water, and the mass fraction of water in the first product is 99.3 wt%.

[0051] (2) The first gaseous material obtained in step (1) is condensed and introduced into the second distillation column. The operating pressure of the second distillation column is controlled to be atmospheric pressure, the operating temperature at the top of the column is 75.72℃, the operating temperature at the bottom of the column is 80.89℃, the number of trays is 25, the feed inlet of the first gaseous material condensate is located above the 8th tray, the reflux ratio is 3.5, and the second gaseous material is obtained at the top of the column.

[0052] (3) The second gaseous material obtained in step (2) is condensed and introduced into an oil-water separator for oil-water separation. The operating temperature of the oil-water separator is controlled at 50°C and the operating pressure is 0.1 MPa. After separation for 30 minutes, an oil phase and a water phase are obtained. The mass fraction of toluene in the oil phase is 44.55%. Subsequently, the oil phase is returned to step (2) for re-distillation. The oil phase inlet is located above the first plate. The obtained water phase is returned to the first distillation column in step (1) for re-distillation to recover toluene and tert-butanol.

[0053] (4) In the above steps, 1 ton of the tert-butanol-containing raw material is introduced into the first distillation column, and the stable operation time of the equipment is controlled to be 1 hour (starting from when the raw material has completely entered the equipment and the system reaches the preset process parameters); after the operation cycle is completed, 514.095 kg of the target product is collected in the bottom of the second distillation column, of which the mass fraction of tert-butanol is 96.6 wt%, the mass fraction of water is 3.2 wt%, the mass fraction of toluene is 0.2 wt%, and the recovery rate of tert-butanol is calculated to be 99.32%.

[0054] Example 6 (1) A feed containing 15 wt% tert-butanol and 0.25 wt% toluene (the remaining components are water) is introduced into the first distillation column. The operating pressure of the first distillation column is controlled at atmospheric pressure, the operating temperature at the top of the column is 79.93℃, the operating temperature at the bottom of the column is 97.98℃, the theoretical number of plates is 20, the feed inlet is located at the 8th plate, and the reflux ratio is 3.5. The first gaseous material is obtained at the top of the column, and the first product is obtained at the bottom of the column. The first gaseous material is a mixture of tert-butanol, toluene and water, and the mass fraction of water in the first product is 99.40 wt%.

[0055] (2) The first gaseous material obtained in step (1) is condensed and introduced into the second distillation column. The operating pressure of the second distillation column is controlled at atmospheric pressure, the top operating temperature is 75.72℃, the bottom operating temperature is 79.78℃, the number of trays is 10, the feed inlet of the first gaseous material condensate is located above the third tray, the reflux ratio is 1, and the second gaseous material is obtained at the top of the column. Among them, the mass fraction of tert-butanol is 90wt%, the mass fraction of water is 4.9wt%, and the mass fraction of toluene is 5.1wt%.

[0056] (3) The second gaseous material obtained in step (2) is condensed and introduced into an oil-water separator for oil-water separation. The operating temperature of the oil-water separator is controlled at 50°C and the operating pressure is 0.1 MPa. After separation for 30 minutes, an oil phase and a water phase are obtained. The mass fraction of toluene in the oil phase is 44.75%. Subsequently, the oil phase is returned to step (2) for re-distillation. The oil phase inlet is located above the first plate. The obtained water phase is returned to the first distillation column in step (1) for re-distillation to recover toluene and tert-butanol.

[0057] (4) In the above steps, 1 ton of the tert-butanol-containing raw material is introduced into the first distillation column, and the stable operation time of the equipment is controlled to be 1 hour (starting from when the raw material has completely entered the equipment and the system reaches the preset process parameters); after the operation cycle is completed, 162.81 kg of the target product is collected in the bottom of the second distillation column, wherein the mass fraction of tert-butanol is 90 wt%, the mass fraction of water is 4.9 wt%, the mass fraction of toluene is 5.1 wt%, and the recovery rate of tert-butanol is calculated to be 97.7%.

[0058] Example 7 (1) A feed containing 15 wt% tert-butanol and 1.25 wt% toluene (the remaining component is water) is introduced into the first distillation column. The operating pressure of the first distillation column is controlled at atmospheric pressure, the operating temperature at the top of the column is 78.24℃, the operating temperature at the bottom of the column is 97.98℃, the theoretical number of plates is 20, the feed inlet is located at the 8th plate, and the reflux ratio is 3.5. The first gaseous material is obtained at the top of the column, and the first product is obtained at the bottom of the column. The first gaseous material is a mixture of tert-butanol, toluene and water, and the mass fraction of water in the first product is 99.44 wt%.

[0059] (2) The first gaseous material obtained in step (1) is condensed and introduced into the second distillation column. The operating pressure of the second distillation column is controlled to be atmospheric pressure, the operating temperature at the top of the column is 75.72℃, the operating temperature at the bottom of the column is 79.78℃, the number of trays is 25, the feed inlet of the first gaseous material condensate is located above the 8th tray, the reflux ratio is 1, and the second gaseous material is obtained at the top of the column.

[0060] (3) The second gaseous material obtained in step (2) is condensed and introduced into an oil-water separator for oil-water separation. The operating temperature of the oil-water separator is controlled at 50°C and the operating pressure is 0.1 MPa. After separation for 30 minutes, an oil phase and a water phase are obtained. The mass fraction of toluene in the oil phase is 44.75 wt%. Subsequently, the oil phase is returned to step (2) for re-distillation. The oil phase inlet is located above the first plate. The obtained water phase is returned to the first distillation column in step (1) for re-distillation.

[0061] (4) In the above steps, 1 ton of the tert-butanol-containing raw material is introduced into the first distillation column, and the stable operation time of the equipment is controlled to be 1 hour (starting from when the raw material has completely entered the equipment and the system reaches the preset process parameters); after the operation cycle is completed, 159.71 kg of the target product is collected in the bottom of the second distillation column, of which the mass fraction of tert-butanol is 90.97 wt%, the mass fraction of water is 0.97 wt%, the mass fraction of toluene is 8.06 wt%, and the recovery rate of tert-butanol is calculated to be 96.86%.

[0062] Example 8 (1) A feed containing 85.5 wt% tert-butanol and 1.22 wt% toluene (the remainder being water) is introduced into the first distillation column. The operating pressure of the first distillation column is controlled at atmospheric pressure, the operating temperature at the top of the column is 79.61 °C, the operating temperature at the bottom of the column is 98.79 °C, the theoretical number of plates is 20, the feed inlet is located at the 8th plate, and the reflux ratio is 3.5. The first gaseous material is obtained at the top of the column, and the first product is obtained at the bottom of the column. The first gaseous material is a mixture of tert-butanol, toluene, and water, and the mass fraction of water in the first product is 99.72 wt%.

[0063] (2) The first gaseous material obtained in step (1) is condensed and introduced into the second distillation column. The operating pressure of the second distillation column is controlled to be atmospheric pressure, the operating temperature at the top of the column is 75.72℃, the operating temperature at the bottom of the column is 81.89℃, the number of trays is 30, the feed inlet of the first gaseous material condensate is located above the 8th tray, and the reflux ratio is 3.5; the second gaseous material is obtained at the top of the column.

[0064] (3) The second gaseous material obtained in step (2) is condensed and introduced into an oil-water separator for oil-water separation. The operating temperature of the oil-water separator is controlled at 50°C and the operating pressure is 0.1 MPa. After separation for 30 minutes, an oil phase and a water phase are obtained. The mass fraction of toluene in the oil phase is 44.1 wt%. Subsequently, the oil phase is returned to step (2) for re-distillation. The oil phase feed is above the first plate. The obtained water phase is returned to the first distillation column in step (1) for re-distillation.

[0065] (4) In the above steps, 1 ton of the tert-butanol-containing raw material is introduced into the first distillation column, and the stable operation time of the equipment is controlled to be 0.2 hours (starting from when the raw material has completely entered the equipment and the system reaches the preset process parameters); after the operation cycle is completed, 870.258 kg of the target product is collected in the bottom of the second distillation column, of which the mass fraction of tert-butanol is 98.2 wt%, the mass fraction of water is 0.3 wt%, the mass fraction of toluene is 1.5 wt%, and the recovery rate of tert-butanol is calculated to be 99.95%.

[0066] Comparative Example 1 (1) A feed containing 4.5 wt% tert-butanol and 0.08 wt% toluene (the remaining components are water) is introduced into the first distillation column. The operating pressure of the first distillation column is controlled at atmospheric pressure, the operating temperature at the top of the column is 79.03℃, the temperature at the bottom of the column is 93.1℃, the theoretical number of plates is 20, the feed inlet is located at the 8th plate, and the reflux ratio is 3.5. The first gaseous material is obtained at the top of the column, and the first product is obtained at the bottom of the column. The first gaseous material is a mixture of tert-butanol, toluene and water, and the mass fraction of water in the first product is 95.42 wt%.

[0067] (2) The first gaseous material obtained in step (1) is condensed and introduced into the second distillation column. The operating pressure of the second distillation column is controlled to be atmospheric pressure, the operating temperature at the top of the column is 75.72℃, the temperature at the bottom of the column is 81.75℃, the number of trays is 25, the feed inlet is located at the 8th tray, the reflux ratio is 3.5, and the second gaseous material is obtained at the top of the column.

[0068] (3) The second gaseous material obtained in step (2) is condensed and introduced into an oil-water separator for oil-water separation. The operating temperature of the oil-water separator is controlled at 50°C and the operating pressure is 0.1 MPa. After separation for 30 minutes, an oil phase and a water phase are obtained. The mass fraction of toluene in the oil phase is 44.29 wt%. Subsequently, the oil phase is returned to step (2) for re-distillation. The oil phase feed is above the first plate. The obtained water phase is returned to the first distillation column in step (1) for re-distillation.

[0069] (4) In the above steps, 1 ton of the tert-butanol-containing raw material is introduced into the first distillation column, and the stable operation time of the equipment is controlled to be 3 hours (starting from when the raw material has completely entered the equipment and the system reaches the preset process parameters); after the operation cycle is completed, 20.58 kg of the target product is collected in the bottom of the second distillation column, of which the mass fraction of tert-butanol is 93.91 wt%, the mass fraction of water is 0.19 wt%, the mass fraction of toluene is 5.9 wt%, and the recovery rate of tert-butanol is calculated to be 42.95%.

[0070] Comparative Example 2 (1) A feed containing 15 wt% tert-butanol and 0.25 wt% toluene (the remaining components are water) is introduced into the first distillation column. The operating pressure of the first distillation column is controlled at atmospheric pressure, the operating temperature at the top of the column is 79.93℃, the temperature at the bottom of the column is 97.98℃, the theoretical number of plates is 20, the feed inlet is located at the 8th plate, and the reflux ratio is 3.5. The first gaseous material is obtained at the top of the column, and the first product is obtained at the bottom of the column. The first gaseous material is a mixture of tert-butanol, toluene and water, and the mass fraction of water in the first product is 99 wt%.

[0071] (2) The first gaseous material obtained in step (1) is condensed and introduced into the second distillation column, and 0.6 wt% cyclohexane is added for distillation. The operating pressure of the second distillation column is controlled at atmospheric pressure, the operating temperature at the top of the column is 64.95℃, the temperature at the bottom of the column is 80.17℃, the number of trays is 25, the feed port is located at the 8th tray, the reflux ratio is 3.5, and the second gaseous material is obtained at the top of the column.

[0072] (3) The second gas phase material obtained in step (2) is condensed and introduced into an oil-water separator for oil-water separation. The operating temperature of the oil-water separator is controlled at 50°C and the operating pressure is 0.1 MPa. After separation for 30 minutes, an oil phase and a water phase are obtained. The mass fraction of toluene in the oil phase is 0.0001 wt%, and the mass fraction of cyclohexane is 75.37 wt%. Subsequently, the oil phase is returned to step (2) for re-distillation. The oil phase feed is above the first plate. The obtained water phase is returned to the first distillation column in step (1) for re-distillation.

[0073] (4) In the above steps, 1 ton of the tert-butanol-containing raw material is introduced into the first distillation column, and the stable operation time of the equipment is controlled to be 1 hour (starting from when the raw material has completely entered the equipment and the system reaches the preset process parameters); after the operation cycle is completed, 154.816 kg of the target product is collected in the bottom of the second distillation column, of which the mass fraction of tert-butanol is 94.5 wt%, the mass fraction of water is 4.75 wt%, the mass fraction of toluene is 0.07 wt%, and the mass fraction of cyclohexane is 0.68 wt%, and the recovery rate of tert-butanol is calculated to be 97.53%.

[0074] Although Comparative Example 2 can achieve better separation results, its process introduces cyclohexane as an external component. The coexistence of multiple impurities will interfere with the quality detection of tert-butanol, and the increase in the types of impurities may affect the downstream application of tert-butanol and limit the applicable scenarios of the product.

[0075] Comparative Example 3 (1) A feed containing 15 wt% tert-butanol and 0.25 wt% toluene (the remaining components are water) is introduced into the first distillation column. The operating pressure of the first distillation column is controlled at atmospheric pressure, the operating temperature at the top of the column is 79.93℃, the temperature at the bottom of the column is 97.98℃, the theoretical number of plates is 20, the feed inlet is located at the 8th plate, and the reflux ratio is 3.5. The first gaseous material is obtained at the top of the column, and the first product is obtained at the bottom of the column. The first gaseous material is a mixture of tert-butanol, toluene and water, and the mass fraction of water in the first product is 99.44 wt%.

[0076] (2) The first gaseous material obtained in step (1) is condensed and introduced into the second distillation column. The operating pressure of the second distillation column is controlled to be atmospheric pressure, the operating temperature at the top of the column is 75.72℃, the operating temperature at the bottom of the column is 81.89℃, the number of trays is 25, the feed inlet is located at the 8th tray, and the reflux ratio is 3.5. The second gaseous material is obtained at the top of the column.

[0077] (3) In the above steps, 1 ton of the tert-butanol-containing raw material is introduced into the first distillation column, and the stable operation time of the equipment is controlled to be 1 hour (starting from when the raw material has completely entered the equipment and the system reaches the preset process parameters); after the operation cycle is completed, 168.35 kg of the target product is collected, of which the mass fraction of tert-butanol is 86.95 wt%, the mass fraction of water is 12.99 wt%, the mass fraction of toluene is 0.06 wt%, and the recovery rate of tert-butanol is calculated to be 96.9%.

[0078] The results above show that, using the method provided by this invention to recover tert-butanol from waste liquid containing toluene and tert-butanol, the recovery rate of tert-butanol obtained by the embodiments of this invention is over 94%, and the mass fraction of tert-butanol is over 90 wt%, without the need to introduce new components. At the same time, the separation steps of this method are simple, and the equipment investment and energy consumption are low.

[0079] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for recovering tert-butanol from waste liquid containing toluene and tert-butanol, characterized in that, The method includes: (1) The waste liquid containing toluene and tert-butanol is subjected to a first distillation to obtain a first gaseous material and a first product; the mass fraction of tert-butanol in the waste liquid is 2.5wt%-86wt% based on the total mass of the waste liquid; (2) The first gaseous material is condensed and then subjected to a second distillation to obtain a second gaseous material; the top operating temperature of the first distillation column is 2-5℃ higher than the top operating temperature of the second distillation column; the bottom operating temperature of the first distillation column is 14-20℃ higher than the bottom operating temperature of the second distillation column. (3) After the second gas phase material is condensed, oil and water are separated to obtain an oil phase and a water phase. The oil phase is returned to step (2) for a second distillation to obtain tert-butanol; the water phase is returned to step (1) for a first distillation.

2. The method according to claim 1, wherein, The mass fraction of tert-butanol in the waste liquid is 4.5wt%-16wt% based on the total mass of the waste liquid.

3. The method according to claim 1, wherein, The mass ratio of tert-butanol to toluene in the waste liquid is greater than 12:

1.

4. The method according to claim 3, wherein, The mass ratio of tert-butanol to toluene in the waste liquid is greater than 50:

1.

5. The method according to claim 1, wherein, In step (1), the first distillation is carried out in a first distillation column. The feed inlet of the first distillation column is located in the upper part of the first distillation column. The theoretical number of plates of the first distillation column is 10-60, the reflux ratio is 1-15, the operating pressure of the first distillation column is 0.09-0.2MPa, the operating temperature at the top of the column is 76-85℃, and the operating temperature at the bottom of the column is 95-100℃.

6. The method according to claim 5, wherein, In step (1), the theoretical number of plates in the first distillation column is 15-30, and the reflux ratio is 1.5-5.

7. The method according to claim 1, wherein, In step (2), the distillation is carried out in a second distillation column. The feed inlet of the second distillation column is located in the upper part of the second distillation column. The theoretical number of plates of the second distillation column is 10-60, the reflux ratio is 1-15, the operating pressure of the second distillation column is 0.09-0.2MPa, the operating temperature at the top of the column is 72-80℃, and the operating temperature at the bottom of the column is 78-85℃.

8. The method according to claim 7, wherein, In step (2), the theoretical number of plates in the second distillation column is 15-30, and the reflux ratio is 1.5-5.

9. The method according to claim 1, wherein, In step (3), the oil-water separation is carried out in an oil-water separator. The operating temperature of the oil-water separator is 40-60℃, the operating pressure is 0.09-0.2MPa, and the separation time is 5-120 minutes.

10. The method according to claim 9, wherein, In step (3), the oil-water separation is carried out in an oil-water separator. The operating temperature of the oil-water separator is 45-55℃, the operating pressure is 0.1MPa, and the separation time is 30-60 minutes.