Combined treatment method for mixed alcohol waste and heavy alcohol waste

Abstract

The present invention relates to a combined treatment method for a mixed alcohol waste and a heavy alcohol waste. The combined treatment method is characterized by comprising the following reaction steps: step 1, optionally, subjecting the mixed alcohol waste mainly comprising C1-C4 saturated monohydric alcohols to preliminary separation treatment, so as to at least partially remove water and acids contained therein, and optionally, at least partially separating a heavy component mainly comprising esters, so as to obtain a preliminary purified product of the mixed alcohol waste; step 2, in the presence of an optional catalyst, mixing the mixed alcohol waste that has optionally undergone the preliminary separation treatment, the heavy alcohol waste and an optionally added alcohol, and reacting same to obtain a product containing a glycolate and ethylene glycol; and optionally, step 3, separating a material containing the glycolate and ethylene glycol from the product obtained in step 2 and the heavy component which is optionally obtained in step 1, wherein the heavy alcohol waste comprises at least one of ethylene glycol, glycolic acid and methyl glycolate, and a polymer generated from at least one of the compounds by a polymerization reaction. The present invention also relates to a system for implementing the method according to the present invention.

Description

Combined treatment method for mixed alcohol waste and heavy alcohol waste Technical Field

[0001] The present invention relates to the field of chemical waste treatment, and in particular to a method for jointly treating mixed alcohol waste and heavy alcohol waste. Background Art

[0002] Polyglycolic acid is the fastest biodegradable polymer among aliphatic thermoplastic linear polyesters. Due to its high heat resistance, high strength, rapid degradation rate, strong oxygen barrier and solvent resistance, it has excellent performance. It also has certain processability and can be extruded, injection molded, spun, and blow molded using general equipment. Therefore, it is widely used in many fields such as medicine, agriculture, forestry, and packaging. It is a new field that developed countries such as Japan and the United States are focusing on.

[0003] In recent years, with breakthroughs in coal-to-ethylene glycol technology in my country, the industrialization of PGA is imminent. The production capacity of polyglycolic acid plants under construction and planned in China is approximately 1.13 million tons. This production route produces a large amount of fusel oil as a byproduct, with organic matter accounting for over 50% of the waste, primarily monohydric and dihydric alcohols. Because these fusel alcohol wastes contain numerous impurities with similar boiling points, and some exist as azeotropes, direct separation of the components is challenging. Therefore, these byproducts are currently sold as waste at prices of 500-800 yuan per ton. These high-value-added alcohols are treated as waste and sold at low prices, resulting in a significant waste of corporate resources and incompatible with national circular economy policies. Furthermore, many small enterprises only perform simple separation of these waste products, resulting in low utilization rates and high energy consumption, with the remaining fraction being discharged as wastewater, causing environmental pollution. However, no method for the simple and effective recycling and treatment of these fusel alcohol wastes has been disclosed.

[0004] CN108250481A discloses a method for catalytic alcoholysis of waste PET, using homogeneous catalysts such as tungstate and zinc acetate and a diol as a solvent. The residual catalyst after alcoholysis makes the product not sufficiently pure, resulting in a low hydroxyl value of the depolymerized product. Furthermore, excessive heavy metal ion content in the catalyst will adversely affect the product's repolymerization and subsequent processing applications.

[0005] CN111203202A discloses a polymer catalyst degradation method for treating polymer materials such as polyether, polyester, polysiloxane, polyurethane, and polyamide. However, a metal compound containing active hydroxyl groups on the surface is also used as a homogeneous catalyst, and the impact of subsequent processing needs to be considered.

[0006] CN114031600A discloses a method for recovering caprolactone from poly-ε-caprolactone waste. The method can be carried out under solvent-free conditions, but requires vacuum conditions, which are more stringent.

[0007] Therefore, there is an urgent need for a method for treating fusel oil (including mixed alcohol waste and heavy alcohol waste) produced as a by-product from a polyglycolic acid production device or from a process for producing ethylene glycol or methyl glycolate by an oxalate process to recover high-value-added components such as methyl glycolate and ethylene glycol. The method has simple steps, a fast reaction rate, and does not generate other complex by-products.

[0008] Summary of the Invention

[0009] The present invention aims to overcome the problems in the prior art of processing fusel oil (including mixed alcohol waste and heavy alcohol waste) as a by-product from a polyglycolic acid production plant, such as the complexity of the process steps and the impact of the generated by-products on the subsequent processing of the desired product. The present invention provides a combined processing method for the mixed alcohol waste and the heavy alcohol waste. The method can fully utilize the mixed alcohol waste and the heavy alcohol waste to recover high-value-added components such as methyl glycolate without generating complex by-products and without affecting the quality of subsequent products.

[0010] To achieve the above objectives, the inventors, after in-depth research, surprisingly discovered that if mixed alcohol waste and heavy alcohol waste from a polyglycolic acid production process or other processes are jointly treated to react the main components contained therein (e.g., by alcoholysis), high-value target compounds, primarily glycolate and ethylene glycol, can be simply and effectively recovered. This reaction system has low requirements for alcohol purity, and the alcohol can contain low-boiling point lipid impurities at a content of less than or equal to 20 wt %, without this impurity affecting the yield and purity of glycolate. Furthermore, the inventors surprisingly discovered that, compared with methods that separately treat mixed alcohol waste and heavy alcohol waste, the method of the present invention can also significantly increase the yield of these high-value target compounds and reduce separation and purification operations.

[0011] Therefore, according to a first aspect of the present invention, the present invention provides a combined treatment method for mixed alcohol waste and heavy alcohol waste, characterized in that the combined treatment method comprises the following reaction steps:

[0012] Step 1. Optionally, subjecting a mixed alcohol waste material mainly comprising C1-C4 saturated monohydric alcohols to a preliminary separation treatment to at least partially remove the water and acid contained therein, and optionally at least partially separate a heavy component mainly comprising esters (e.g., glycolate and polymers thereof), to obtain a preliminarily purified product of the mixed alcohol waste material;

[0013] Step 2. In the presence of an optional catalyst, the mixed alcohol waste material that has been subjected to the optional preliminary separation treatment, the heavy alcohol waste material, and the optional added alcohol are mixed and reacted to obtain a product containing glycolate and ethylene glycol, and optionally

[0014] Step 3. A step of separating a material containing glycolate and ethylene glycol from the product obtained in step 2 and optionally the heavy component obtained in step 1;

[0015] The heavy alcohol waste contains at least one of ethylene glycol, glycolic acid and methyl glycolate and a polymer produced by polymerization reaction of at least one of these compounds.

[0016] According to a second aspect of the present invention, the present invention provides a system for implementing a method for jointly treating mixed alcohol waste and heavy alcohol waste according to the first aspect above, comprising: an optional preliminary separation unit, a reaction unit and a product separation unit, wherein the preliminary separation unit is used to at least partially remove water and acid contained in the mixed alcohol waste and optionally separate a heavy component mainly containing esters to obtain a preliminary purified product of the mixed alcohol waste; the reaction unit is used to mix and react heavy alcohol waste, added alcohol, the preliminary purified product of the mixed alcohol waste and the optional heavy component mainly containing esters in the presence of an optional catalyst; and the product separation unit is used to separate a material containing glycolate and ethylene glycol from the reaction product from the reaction unit.

[0017] The combined processing method and the system for implementing the combined processing method according to the present invention have at least the following beneficial effects:

[0018] The combined treatment method for mixed alcohol waste and heavy alcohol waste according to the present invention has simple process steps, fast reaction rate, no complex by-products are generated, does not affect the quality of the desired product, is economical and practical, can fully utilize the main components in the mixed alcohol waste and heavy alcohol waste, significantly improve the yield of useful products, save the separation steps of the mixed alcohol waste and heavy alcohol waste respectively, thereby reducing energy consumption, recovering high-value-added components such as materials containing glycolate, and achieving quality improvement and efficiency enhancement of the mixed alcohol waste and heavy alcohol waste.

[0019] In the method according to the present invention, organic matter from fusel oil (including mixed alcohol waste and / or heavy alcohol waste) generated during the production of polyglycolic acid is recovered to obtain high-value-added components such as methyl glycolate and ethylene glycol, turning waste into treasure and improving the quality and efficiency of PGA byproducts, thereby maximizing the economic benefits of the enterprise while ensuring green production. Furthermore, by selecting appropriate methods and conditions for the initial separation of mixed alcohol waste, the appropriate type of added alcohol, the introduction of an appropriate type and amount of catalyst, and the appropriate ratio of reaction raw materials, reaction conditions, and separation conditions, the yield and purity of the glycolate-containing material can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 shows a flow chart of a method for jointly treating mixed alcohol waste and heavy alcohol waste according to one embodiment of the present invention;

[0021] FIG2 shows a flow chart of a method for jointly treating mixed alcohol waste and heavy alcohol waste according to another embodiment of the present invention. DETAILED DESCRIPTION

[0022] The specific embodiments of the present application are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0023] Any specific numerical value disclosed in this specification (including the endpoints of a numerical range) is not limited to the exact value of the numerical value, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within the range of ±5% of the exact value. Moreover, for a disclosed numerical range, the values ​​between the endpoints of the range, between the endpoints and the specific points in the range, and between the specific points can be arbitrarily combined to form one or more new numerical ranges, and these new numerical ranges should also be considered to be specifically disclosed in this specification.

[0024] Unless otherwise specified, the terms used in this specification have the same meanings as commonly understood by those skilled in the art. If a term is defined in this specification and its definition is different from the common understanding in the art, the definition in this specification shall prevail.

[0025] In this specification, except for matters explicitly described, any matters or issues not mentioned are directly applicable to those known in the art without any changes. Moreover, any embodiment described in this specification can be freely combined with one or more other embodiments described in this specification, and the technical solutions or technical ideas formed thereby are considered part of the original disclosure or original description of the present invention, and should not be regarded as new content not disclosed or anticipated in this specification, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0026] Unless explicitly stated otherwise, throughout the specification and claims, the term "comprise" or variations such as "include" or "comprising", etc., will be understood to include the stated elements or components but not to exclude other elements or other components.

[0027] In this specification, the terms "first," "second," etc. are used to distinguish between two different elements or components and are not intended to define a specific position or relative relationship. In other words, in some embodiments, the terms "first," "second," etc. may be used interchangeably. The expression "primarily comprising" indicates that the component accounts for a higher proportion by weight or molar amount of the composition than the other components account for. In this specification, the term "alcohol" generally refers to monoalcohols and does not include diols, unless otherwise specified.

[0028] According to a first aspect of the present invention, the present invention provides a combined treatment method for mixed alcohol waste and heavy alcohol waste, characterized in that the combined treatment method comprises the following reaction steps:

[0029] Step 1. Optionally, subjecting a mixed alcohol waste material mainly comprising C1-C4 saturated monohydric alcohols to a preliminary separation treatment to at least partially remove the water and acid contained therein, and optionally at least partially separate a heavy component mainly comprising esters (e.g., glycolate and polymers thereof), to obtain a preliminarily purified product of the mixed alcohol waste material;

[0030] Step 2. In the presence of an optional catalyst, the mixed alcohol waste material that has been subjected to the optional preliminary separation treatment, the heavy alcohol waste material, and the optional added alcohol are mixed and reacted to obtain a product containing glycolate and ethylene glycol, and optionally

[0031] Step 3. A step of separating a material containing glycolate and ethylene glycol from the product obtained in step 2 and optionally the heavy component obtained in step 1;

[0032] The heavy alcohol waste contains at least one of ethylene glycol, glycolic acid and methyl glycolate and a polymer produced by polymerization reaction of at least one of these compounds.

[0033] In the above reaction step 2, other possible substances may also be added, as long as the substances do not negatively affect the reaction occurring in the reaction step and the properties and subsequent treatment of the desired product.

[0034] According to a specific embodiment of the first aspect of the present invention, as shown in FIG1 , the present invention provides a combined treatment method for mixed alcohol waste and heavy alcohol waste, the combined treatment method comprising the following steps:

[0035] S1. Optionally, performing preliminary separation on the mixed alcohol waste to at least partially separate a heavy component mainly comprising esters, referred to as a "first heavy component," and at least partially remove water and acid contained in the mixed alcohol waste, referred to as a "first intermediate component," to obtain a preliminary purified product of the mixed alcohol waste, referred to as a "first light component."

[0036] S2. In the presence of an optional catalyst, the heavy alcohol waste, the optional added alcohol, and the mixed alcohol waste that has not been subjected to preliminary separation treatment (if step S1 is not performed) or the preliminary purified product of the mixed alcohol waste obtained in step S1 (if step S1 is performed) are mixed to react; and

[0037] S3. The reaction product obtained in step S2 and the first heavy component obtained in step S1 are combined, and a material containing glycolate and ethylene glycol is separated therefrom.

[0038] According to another specific embodiment of the first aspect of the present invention, as shown in FIG2 , the present invention provides a combined treatment method for mixed alcohol waste and heavy alcohol waste, the combined treatment method comprising the following steps:

[0039] S1. Optionally, subjecting the mixed alcohol waste to a preliminary separation treatment to at least partially separate a heavy component primarily comprising esters, referred to as a "first heavy component," and at least partially remove water and acid contained therein, referred to as a "first intermediate component," to obtain a preliminary purified product of the mixed alcohol waste, referred to as a "first light component."

[0040] S2. In the presence of an optional catalyst, the heavy alcohol waste, the optionally added alcohol, the mixed alcohol waste that has not been subjected to preliminary separation treatment (if step S1 is not performed) or the preliminary purified product of the mixed alcohol waste obtained in step S1 and the first heavy component (if step S1 is performed) are mixed to react; and

[0041] S3. Separating the material containing glycolate and ethylene glycol from the reaction product obtained in step S2.

[0042] In the combined treatment method according to the first aspect of the present invention, whether or not to perform a preliminary separation step on the mixed alcohol waste material depends primarily on the amounts of water and acid contained in the mixed alcohol waste material. Because water and acid contained in the mixed alcohol waste material can corrode or poison the catalyst used in the reaction step, affecting its active sites and easily deactivating it, the water content in the mixed alcohol waste material is advantageously kept below 4%, advantageously below 3%, or even below 1%, before participating in the reaction step. Simultaneously, the acid content in the mixed alcohol waste material participating in the reaction step is below 3%, advantageously below 2%, or even below 1%. Most preferably, the mixed alcohol waste material participating in the reaction step contains virtually no water or acid. If the mixed alcohol waste material participating in the reaction step already contains sufficiently low levels of water and acid, for example, less than 1% water and less than 0.5% acid, the preliminary separation step or step S1 of the mixed alcohol waste material may be omitted, provided that this does not significantly affect catalyst activity. Another advantage of performing preliminary separation on the mixed alcohol waste is that it can remove low-boiling point esters, ketones and ethers contained in the mixed alcohol waste, as these impurities may interfere with subsequent reaction steps.

[0043] In the combined treatment method according to the first aspect of the present invention, the mixed alcohol waste is initially separated to obtain a first light component, a first intermediate component, and a first heavy component. The first light component, as a preliminary purification product of the mixed alcohol waste, mainly comprises light alcohols, such as C1-C4 alcohols, and is fed into the reaction step as a solvent or reaction reagent to participate in the reaction. The first intermediate component mainly contains impurities such as water, acid, ketone, and ether and is discarded. The first heavy component mainly comprises ester compounds, especially propylene glycol ester compounds and / or polymers thereof, which are fed into the reaction unit (step) to participate in the reaction or directly fed into the separation unit (step) to be combined with the reaction product obtained in the reaction unit and separated together. The separated material containing glycolate and optionally ethylene glycol is recovered as a product.

[0044] According to one embodiment of the first aspect above, the mixed alcohol waste may be a by-product of a device for producing polyglycolic acid. Preferably, the mixed alcohol waste comprises: C1-C4 saturated monohydric alcohol and water, and at least one of a low-boiling point ester with a boiling point of 50-90°C, acetic acid and methyl glycolate, and at least one of their polymers.

[0045] The C1-C4 saturated monohydric alcohol may be, for example, methanol and ethanol; the low-boiling-point ester with a boiling point of 50-90° C. may be, for example, methyl acetate and ethyl acetate.

[0046] Furthermore, the mixed alcohol waste may further include: one or more of esters, ethers and ketones with a boiling point of 100-150° C. The esters with a boiling point of 100-150° C. do not include methyl glycolate.

[0047] According to one embodiment of the first aspect above, the mixed alcohol waste can be a by-product from a process for producing polyglycolate; in the mixed alcohol waste, the content of C1-C4 saturated monohydric alcohol is 30-70wt%, preferably 40-69wt%, for example 45wt%, 50wt%, 55wt% and 60wt%; the content of low-boiling point esters with a boiling point of 50-90°C is 1-9wt%, preferably 1-7wt%; the content of water is 4-35wt%, preferably 4-30wt%; the content of acetic acid is 1-15wt%, preferably 1-10wt%, the total content of esters, ethers and ketones with a boiling point of 100-150°C is 1-30wt%, preferably 1-20wt%, and the content of methyl glycolate is 1-41wt%, preferably 10-40wt%.

[0048] According to one embodiment of the first aspect, the high-temperature treatment process that the mixed alcohol waste material may undergo before use may result in the formation of some polymers. Therefore, the mixed alcohol waste material may include polymers generated by polymerization reactions of at least one of C1-C4 saturated monohydric alcohols, low-boiling esters with a boiling point of 50-90°C, acetic acid, methyl glycolate, and esters, ethers, and ketones with a boiling point of 100-150°C. Preferably, the polymer content in the mixed alcohol waste material is 0-10 wt%, and preferably, the mixed alcohol waste material contains no polymers.

[0049] According to one embodiment of the first aspect, the heavy alcohol waste material may be a byproduct from a dimethyl oxalate hydrogenation unit or production process. Preferably, the heavy alcohol waste material comprises at least one of ethylene glycol, glycolic acid, and methyl glycolate, and a polymer formed by a polymerization reaction of at least one of ethylene glycol, glycolic acid, and methyl glycolate. The ethylene glycol can be separated as a product along with the glycolate product for recovery.

[0050] According to an embodiment of the first aspect above, the heavy alcohol waste may also include: monohydric alcohols such as methanol, ethanol, and butanol, dihydric alcohols such as propylene glycol and butylene glycol, ethers such as dimethyl ether and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, and one or more ketones such as 1,4-dioxane-2,5-dione.

[0051] According to one embodiment of the first aspect above, based on the total weight of the mixed alcohol waste and the heavy alcohol waste, the content of polymer from the heavy alcohol waste is greater than or equal to 5wt%, preferably 10-80wt%, more preferably 20-70wt%, for example 30wt%, 40wt%, 50wt% or 60%.

[0052] According to one embodiment of the first aspect above, in the heavy alcohol waste, the content of ethylene glycol is 15-75wt%, preferably 30-70wt%, for example, 40wt% and 50wt%; the content of methyl glycolate is 0-30wt%, for example, 10-29wt%; and the content of glycolic acid is 0-10wt%, for example, 5-10wt%, based on the total weight of the heavy alcohol waste.

[0053] According to one embodiment of the first aspect above, the methods used for the preliminary separation include but are not limited to: distillation, distillation concentration, adsorption and extraction; preferably, distillation is used; more preferably, distillation is carried out at a temperature not higher than 165°C.

[0054] According to one embodiment of the first aspect above, in the preliminary separation step or in step S1, the preliminary separation method is performed by distillation, which includes:

[0055] a. The mixed alcohol waste is subjected to a first distillation at a top pressure of 20-201 kPa, for example, 20-101 kPa or 101-201 kPa, and at a temperature of 40-120 ° C. The number of plates of the first distillation is controlled to be 5-38, and the reflux ratio is 0.1-12 to obtain the first light component and the undistilled material;

[0056] b. The undistilled material obtained from the first distillation is subjected to a second distillation at a top pressure of 20-121 kPa, for example, at a top pressure of 20-101 kPa or 101-121 kPa and a temperature of 60-162 ° C, wherein the number of plates of the second distillation is controlled to be 5-38 and the reflux ratio is 0.1-12 to obtain the first intermediate component and the first heavy component.

[0057] The above-described preliminary separation method can be performed in one or two distillation towers. If the preliminary separation method is performed in one distillation tower, the undistilled material from the first distillation does not need to be removed, and the process can be continued intermittently or continuously by adjusting the top pressure and temperature of the distillation tower. If the preliminary separation method is performed in two distillation towers, the undistilled material from the first distillation needs to be removed and then transferred to the second distillation tower for a second distillation.

[0058] In the above-mentioned preliminary separation method, the obtained first light component mainly contains low-quality alcohols, such as C1-C4 alcohols, such as methanol. Preferably, the methanol content in the first light component is 80-100wt%, and more preferably, the methanol content in the first light component is 85-100wt%. Since the first light component contains a relatively high content of methanol, it can be used as a solvent in reaction step 2 (or step S2) and participate in the reaction; the first intermediate component mainly contains impurities such as water, acids, esters, ketones, and ethers, which are distilled out and then treated as waste; the first heavy component obtained as the bottom product mainly contains glycolate compounds, which are fed to the reaction unit to participate in the reaction or fed to the separation unit to be combined with the reaction product obtained in the reaction unit and separated together.

[0059] According to one embodiment of the first aspect, in the reaction step 2 or in step S2, the optional added alcohol is selected from a saturated monohydric alcohol; preferably a C1-C4 saturated monohydric alcohol, such as methanol and ethanol. The glycolate in the recovered glycolate-containing material is the glycolate of the corresponding alcohol, such as methyl glycolate and ethyl glycolate. The added alcohol can be fresh alcohol or a light component (hereinafter referred to as "second light component") from the product separation step 3 (or step S3) of the method according to the present invention.

[0060] Preferably, the added fresh alcohol is methanol, and therefore the glycolate in the corresponding glycolate-containing material recovered is mainly methyl glycolate.

[0061] In order to further increase the reaction rate, preferably, in reaction step 2 or in step S2, the reaction is carried out in the presence of a catalyst for catalyzing the alcoholysis reaction. Preferably, the catalyst is selected from a material containing a metal oxide, and the metal oxide is preferably selected from one or more of calcium oxide, zinc oxide, copper oxide, aluminum oxide, and rare earth oxides (such as cerium oxide), preferably a material containing zinc oxide. According to a preferred embodiment, based on the total weight of the catalyst, the catalyst comprises: 20-80wt% of zinc oxide, 5-45wt% of copper oxide and 1-30wt% of aluminum oxide; preferably, the catalyst further comprises 0.1-10wt% of rare earth element oxide, preferably, the rare earth element is selected from at least one of lanthanum, cerium, zirconium and neodymium; preferably, based on the total weight of the catalyst, the catalyst comprises: 40-70wt% of zinc oxide, 10-40wt% of copper oxide, 5-25wt% of aluminum oxide and 1-8wt% of rare earth element oxide, for example, the catalyst comprises the following components: 67wt% of calcium oxide, 20wt% of copper oxide, 10wt% of aluminum oxide and 3wt% of cerium oxide; or comprises the following components: 67wt% of zinc oxide, 20wt% of copper oxide, 10wt% of aluminum oxide and 3wt% of cerium oxide. More preferably, in reaction step 2 or in step S2, the amount of the catalyst is 1-100 g based on 100 g of the heavy alcohol waste, that is, the ratio of the amount of the catalyst to the amount of the heavy alcohol waste is 1-100:100.

[0062] According to one embodiment of the first aspect above, in the above-mentioned reaction step 2 or in the S2 step, depending on whether the preliminary separation step or the S1 step of the mixed alcohol waste is performed, and depending on the difference between the viscosity of the reaction mixture and the desired viscosity, the reaction mixture may include heavy alcohol waste, mixed alcohol waste (if the preliminary separation step or the S1 step is not performed) and / or the first light component from the preliminary separation step or the S1 step, optionally added fresh alcohol and optionally a light component from the reaction product separation step or the S3 step; wherein the optionally added alcohol mainly acts as a solvent to reduce the viscosity of the reaction mixture containing the mixed alcohol waste and the heavy alcohol waste; that is, if the viscosity of the reaction mixture is too large, it is necessary to additionally add an alcohol solvent; if the viscosity of the reaction mixture is appropriate, it is not necessary to additionally add an alcohol solvent, and the additionally added alcohol may come from fresh alcohol or from the light component mainly containing light alcohol (hereinafter also referred to as the second light component) from the reaction product separation step 3 or the S3 step. Therefore, according to a preferred embodiment, in the above-mentioned reaction step 2 or in the S2 step, the reaction mixture comprises heavy alcohol waste, the first light component from the S1 step, added fresh alcohol and optionally a light component from the reaction product separation step 3 or the S3 step; or, in the above-mentioned reaction step 2 or in the S2 step, the reaction mixture comprises heavy alcohol waste, the first light component and the first heavy component from the S1 step, added alcohol and optionally a light component from the reaction product separation step 3 or the S3 step.

[0063] When the heavy alcohol waste, the added fresh alcohol, the first light component obtained in the preliminary separation step 1 (or S1 step) and the optional light component from the reaction product separation step 3 or S3 step are mixed and reacted, the amounts of the heavy alcohol waste, the added alcohol, the first light component and the light component from the reaction product separation step 3 or S3 step are such that the ratio of the weight of the heavy alcohol waste in the obtained mixture to the total weight of the first light component and the added alcohol is 1:(1-7), preferably 1:(2-5).

[0064] According to one embodiment of the first aspect above, in reaction step 2 or in step S2, when the heavy alcohol waste, the added alcohol, the first light component obtained in the preliminary separation step 1 (or step S1) and the first heavy component are mixed and reacted, the amounts of the heavy alcohol waste, the added alcohol, the first light component and the first heavy component are such that the ratio of the weight of the heavy alcohol waste, the total weight of the added alcohol and the first light component, and the weight of the first heavy component is 1:(1-7):(0.01-0.5), preferably 1:(2-5):(0.1-0.4).

[0065] According to one embodiment of the first aspect above, preferably, in the reaction step or in step S2, the reaction pressure is 0.1-6 MPa; the reaction temperature is not higher than the boiling point of each component and their azeotrope in the mixed alcohol waste and heavy alcohol waste under the same pressure conditions, preferably 130-230°C, preferably 160-220°C; the reaction time is 10 minutes to 4 hours, preferably 0.5 hours to 3 hours.

[0066] According to one embodiment of the first aspect above, in the product separation step 3 or in step S3, the method for separating the glycolate-containing material includes but is not limited to: vacuum distillation, atmospheric distillation, atmospheric distillation, vacuum distillation and pressure distillation, etc.; preferably, vacuum distillation or atmospheric distillation is used; more preferably, vacuum distillation or atmospheric distillation is performed at a temperature not higher than 160°C.

[0067] According to one embodiment of the first aspect above, in the product separation step or in step S3, the separation method includes the following steps:

[0068] A. subjecting the reaction product obtained in the reaction step or in step S2 to a third distillation at a tower top pressure of 20-201 kPa, for example, 20-101 kPa or 101-201 kPa, and at a tower top temperature of 50-160° C., preferably 70-140° C., wherein the number of plates in the third distillation is controlled to be 5-42 and the reflux ratio is controlled to be 1-15, to separate the second light component;

[0069] B. The undistilled material obtained from the third distillation is subjected to a fourth distillation under conditions of a top pressure of 5 Pa to 101 kPa and a top temperature of 70° C. to 170° C., with the number of plates in the fourth distillation controlled to be 5 to 42 and the reflux ratio to be 1 to 15, to separate a material containing glycolate, referred to as the "second intermediate component". The material remaining in the bottom of the column mainly contains undecomposed polymer, referred to as the "second heavy component".

[0070] The above-described reaction product separation method can be implemented in a single distillation tower or in two distillation towers. If the initial separation method is implemented in a single distillation tower, the undistilled material from the first distillation does not need to be removed and can be directly separated intermittently or continuously by adjusting the top pressure and temperature of the distillation tower. If the reaction product separation method is implemented in two distillation towers, the undistilled material from the third distillation needs to be removed and then transferred to the second distillation tower for the fourth distillation.

[0071] Typically, parameters such as the top temperature and bottom temperature, top pressure, etc. of the distillation tower are adjusted and selected by technicians within the above range according to actual conditions; however, according to one embodiment, the top temperature difference ΔT between the second distillation and the first distillation may be greater than 15°C, for example, 20-50°C; the top temperature difference ΔT between the fourth distillation and the third distillation may be greater than 30°C, for example, 40-90°C; and / or, the bottom temperature difference ΔT between the second distillation and the first distillation may be greater than 15°C, for example, 20-50°C; the bottom temperature difference ΔT between the fourth distillation and the third distillation may be greater than 30°C, for example, 40-90°C; and / or, the top pressure difference ΔP between the first distillation and the second distillation may be greater than 5kPa, for example, 10-80kPa; the top pressure difference ΔP between the third distillation and the fourth distillation may be greater than 10kPa, for example, 15-90kPa.

[0072] In the above-mentioned preliminary separation method, the second light component mainly comprises low-quality alcohols, such as C1-C4 alcohols, such as methanol. Since the second light component contains a relatively high content of alcohol, it can be returned to reaction step 2 or step S2 as a solvent together with the added fresh alcohol and participate in the reaction.

[0073] According to one embodiment of the first aspect above, the combined treatment method further includes: returning at least a portion of the remaining material after separating the glycolate-containing material to reaction step 2 or step S2 for reaction; and, at least a portion of the second light component distilled out after the third distillation is returned to the reaction step 2 or step S2 as one of the sources of alcohol and participates in the reaction, and at least a portion of the heavy component mainly comprising residual polymer (referred to as the "second heavy component") that is not distilled out after the fourth distillation is further converted as waste to be treated.

[0074] 1 is used to illustrate a preferred embodiment of the combined treatment method for mixed alcohol waste and heavy alcohol waste according to the present invention, wherein the combined treatment method comprises the following steps: introducing the mixed alcohol waste into a preliminary separation unit for preliminary purification and separation, and obtaining a first light component mainly containing light alcohol, a first intermediate component containing water, acid and low-boiling esters, ketones, and ether impurities, and a first heavy component containing high-boiling esters (mainly glycolate and possible polymers of the esters); wherein the first light component is fed into the reaction unit as a solvent, the first intermediate component is discarded as waste, and the first heavy component is fed into the product separation unit. The heavy alcohol waste and the added alcohol (including fresh methanol and the second light component from the product separation unit) are fed into the reaction unit, mixed with the first light component in the reaction unit and reacted, and the obtained reaction product is combined with the first heavy component and then fed into the product separation unit for separation to obtain a second light component mainly containing lower alcohols, a second intermediate component (a material mainly containing glycolate and / or ethylene glycol) and a second heavy component (mainly containing unreacted polymer), respectively. The second intermediate component is recovered as a product, and at least a portion of the second light component and at least a portion of the second heavy component are returned to the reaction unit to participate in the reaction.

[0075] FIG2 is an example of another preferred embodiment of the combined treatment method for mixed alcohol waste and heavy alcohol waste according to the present invention, wherein the combined treatment method comprises the following steps: introducing the mixed alcohol waste into a preliminary separation unit for preliminary separation to obtain a first light component mainly comprising light alcohol, a first intermediate component containing water, acid and low-boiling esters, ketones, and ethers, and a first heavy component containing high-boiling esters (mainly glycolates and possible polymers of the esters); wherein the first light component and the first heavy component are fed into a reaction unit, and the first intermediate component is discarded as waste. The heavy alcohol waste, added alcohol (including fresh methanol and the second light component from the product separation unit), the first light component, and the first heavy component are mixed and reacted in the reaction unit, and the resulting reaction product is fed into the product separation unit for separation to obtain a second light component containing lower alcohol, a second intermediate component (a material containing glycolates and / or ethylene glycol), and a second heavy component (mainly containing unreacted polymers), respectively. The second intermediate component is recovered as a product, and at least a portion of the second light component and at least a portion of the second heavy component are returned to the reaction unit to participate in the reaction.

[0076] According to the second aspect of the present invention, the present invention also provides a system for implementing the combined treatment method according to the first aspect of the present invention, which comprises: an optional preliminary separation unit, a reaction unit and a product separation unit, wherein the preliminary separation unit is used to remove water and acid in the mixed alcohol waste, and optionally separate a first heavy component mainly containing high-boiling point esters to obtain a preliminary purified product; the reaction unit is used to mix and react the heavy alcohol waste, the preliminary purified product and the optional added alcohol; and the product separation unit is used to separate a material containing glycolate and / or ethylene glycol from the reaction product.

[0077] According to one embodiment of the second aspect of the present invention, the preliminary separation unit includes one or more distillation towers, the reaction unit includes one or more reaction kettles, and the product separation unit includes one or more distillation towers.

[0078] According to one embodiment of the second aspect of the present invention, the preliminary separation unit includes two distillation towers connected in series, namely, a first distillation tower and a second distillation tower, the reaction unit includes a reactor, and the product separation unit includes two distillation towers connected in series, namely, a third distillation tower and a fourth distillation tower.

[0079] Example

[0080] The following examples and comparative examples illustrate the technical solutions and the technical effects of the present invention. In the following examples and comparative examples, unless otherwise specified, the operating methods and parameter measurement methods involved are conventional methods in the art, and the reagents and materials or raw materials used are all commercially available.

[0081] The following two catalysts were used in the examples:

[0082] Catalyst 1: zinc oxide 40wt%, copper oxide 40wt%, aluminum oxide 19wt%, cerium oxide 1wt%;

[0083] Catalyst 2: zinc oxide 70wt%, copper oxide 10wt%, aluminum oxide 15wt%, lanthanum oxide 5wt%.

[0084] The composition of the material or product is measured and calculated using a gas chromatograph according to the normalization method. The type and content of each component are determined by the chromatographic peak. Among them, although it is difficult to determine the specific molecular structure of some esters, ketones, ether impurities, polymers, and some components with higher boiling points in the heavy components, their retention time in the spectrum is fixed, and the content of the polymer will change significantly after the reaction, while the content of other substances whose molecular structure is difficult to determine does not change before and after the reaction, thereby determining the type and content of each component. In the following examples, various reaction parameters are calculated as follows:

[0085] Product (i.e., glycolate and ethylene glycol) yield (%) = total weight of glycolate and ethylene glycol in the recovered product containing glycolate and ethylene glycol / (total weight of methyl glycolate and ethylene glycol in the heavy alcohol waste + weight of methyl glycolate in the mixed alcohol waste) × 100%.

[0086] Conversion rate of polymer (%) = (weight of polymer in heavy alcohol waste and mixed alcohol waste - weight of polymer in reaction product) ÷ weight of polymer in heavy alcohol waste and mixed alcohol waste × 100%;

[0087] Selectivity of glycolate (%) = (weight of glycolate in the reaction product - weight of glycolate in the heavy alcohol waste and mixed alcohol waste) ÷ (weight of polymer in the heavy alcohol waste and mixed alcohol waste - weight of polymer in the reaction product) × 100%;

[0088] Selectivity of ethylene glycol (%) = (weight of ethylene glycol in the reaction product - weight of ethylene glycol in the heavy alcohol waste and mixed alcohol waste) ÷ (weight of polymer in the heavy alcohol waste and mixed alcohol waste - weight of polymer in the reaction product) × 100%.

[0089] Example 1

[0090] A mixed alcohol waste stream at a mass flow rate of 975 kg / h was fed into the first distillation column of the preliminary separation unit. The mixed alcohol waste stream contained 1.45 wt% ethanol, 36 wt% methanol, 10 wt% water, 40.76 wt% methyl glycolate, 3.12 wt% acetic acid, 2.15 wt% methyl acetate, and 6.52 wt% ester, ether, and ketone impurities. The first distillation column had a top temperature of 71.8°C, a bottom temperature of 110°C, a top pressure of 35 kPa, a plate number of 20, and a top reflux ratio of 5. A first light fraction, comprising 91.2 wt% methanol, 3.3 wt% ethanol, and 5.5 wt% methyl acetate, was extracted from the top of the column at a mass flow rate of 375 kg / h. This first light fraction was fed into the reaction unit as a solvent. The bottoms of the first distillation column are fed into the second distillation column of the preliminary separation unit. The second distillation column has a top temperature of 98.2°C, a bottom temperature of 159.8°C, a top pressure of 25 kPa, a plate count of 20, and a top reflux ratio of 3. A first intermediate component containing water, acid, ester, ketone, and ether impurities is withdrawn from the top at a mass flow rate of 200 kg / h. A first heavy component rich in methyl glycolate is withdrawn from the bottoms of the second distillation column at a mass flow rate of 400 kg / h and fed to the product separation unit.

[0091] A heavy alcohol waste stream at a mass flow rate of 5,650 kg / h, methanol at 2,665 kg / h, and a first light fraction from the primary separation unit and a second light fraction from the product separation unit at a total mass flow rate of 26,950 kg / h were fed into a reactor in a reaction unit. The reactor contained a catalyst having the following composition: 40 wt% zinc oxide, 40 wt% copper oxide, 19 wt% aluminum oxide, and 1 wt% cerium oxide. The heavy alcohol waste stream contained 2.5 wt% methyl glycolate, 20.54 wt% ethylene glycol, and 76.96 wt% of a polymer-rich component. The temperature of the reactor is 180°C, the pressure is 2 MPa, the residence time of the reaction materials is 1 hour, and a liquid product with a mass flow rate of 35,650 kg / h is obtained, which contains: 76.26 wt% of methanol, 10.03 wt% of methyl glycolate, 11.18 wt% of ethylene glycol, and 2.53 wt% of heavy components (including unreacted polymers and substances with unidentified molecular structures but with a boiling point greater than or equal to 200°C and remaining in the distillation tower kettle of the product separation unit).

[0092] The liquid product was combined with the first heavy component from the second distillation column and fed to the third distillation column of the product separation unit. The third distillation column had a top temperature of 72.1°C, a bottom temperature of 138.1°C, a pressure of 35 kPa, a plate number of 20, and a top reflux ratio of 2. A second light component, methanol with a mass purity of 98.7 wt%, was withdrawn from the top at a mass flow rate of 27,000 kg / h. Of this, 26,950 kg / h was returned to the reaction unit as a circulating solvent, and 50 kg / h was withdrawn from the system. A liquid phase material with a mass flow rate of 9,050 kg / h was withdrawn from the bottom of the third distillation tower and fed into the fourth distillation tower of the product separation unit. The fourth distillation tower had a top temperature of 121.2°C, a bottom temperature of 159°C, a pressure of 10 kPa, a plate number of 20, and a top reflux ratio of 3. A second intermediate component containing 46.2 wt% methyl glycolate and 45.5 wt% ethylene glycol was withdrawn from the top of the fourth distillation tower at a mass flow rate of 8,600 kg / h. The second intermediate component was recovered as a product, wherein the combined mass purity of these two compounds was 91.7 wt%. The product yield of this embodiment was calculated to be approximately 464%, with a polymer conversion rate (%) of 93.5%, a glycolate selectivity (%) of 106.9%, and an ethylene glycol selectivity (%) of 88.9%. Simultaneously, 450 kg / h of heavy components was obtained in the bottom of the fourth distillation tower.

[0093] Example 2

[0094] A mixed alcohol waste stream at a mass flow rate of 975 kg / h was fed into the first distillation column of the preliminary separation unit. The mixed alcohol waste stream contained 3.2 wt% ethanol, 37 wt% methanol, 19 wt% water, 27.13 wt% methyl glycolate, 3.12 wt% acetic acid, 2.2 wt% methyl acetate, and 8.35 wt% ester, ketone, and ether impurities. The first distillation column had a top temperature of 72°C, a bottom temperature of 95.2°C, a top pressure of 35 kPa, a plate number of 20, and a top reflux ratio of 5. A first light fraction was extracted from the top of the column at a mass flow rate of 380 kg / h. The first light fraction contained 92.5 wt% methanol, 1.6 wt% ethanol, and 5.9 wt% methyl acetate. This first light fraction was fed into the reaction unit as a solvent. The bottoms from the first distillation column are fed into the second distillation column of the preliminary separation unit. The second distillation column has a top temperature of 104°C, a bottom temperature of 161.6°C, a top pressure of 25 kPa, a plate count of 20, and a top reflux ratio of 3. A first intermediate component containing water, acid, ester, ketone, and ether impurities is withdrawn from the top at a mass flow rate of 270 kg / h. A first heavy component rich in methyl glycolate is withdrawn from the bottoms of the second distillation column at a mass flow rate of 325 kg / h and fed to the product separation unit.

[0095] A mass flow rate of 5650 kg / h of heavy alcohol waste having the same composition as that of the heavy alcohol waste in Example 1, 2680 kg / h of methanol, and a total mass flow rate of 26650 kg / h of the first light fraction from the preliminary separation unit and the second light fraction from the product separation unit were fed into a reactor containing a catalyst in a reaction unit. The catalyst had the following composition: 70 wt% zinc oxide, 10 wt% copper oxide, 15 wt% aluminum oxide, and 5 wt% lanthanum oxide. The reactor was heated to 200° C., pressure was 2 MPa, and the residence time of the reaction mass was 2 hours. A liquid product having a mass flow rate of 35350 kg / h was obtained, which comprised 75.3 wt% methanol, 10.53 wt% methyl glycolate, 11.68 wt% ethylene glycol, and 2.49 wt% heavy components (including unreacted polymers and substances whose molecular structure was not identified but whose boiling point was greater than or equal to 200° C. and remained in the distillation reactor of the product separation unit).

[0096] The liquid product was combined with the first heavy component from the second distillation column and fed to the third distillation column of the product separation unit. The third distillation column had a top temperature of 72.1°C, a bottom temperature of 147.1°C, a pressure of 35 kPa, a plate number of 20, and a top reflux ratio of 2. A second light component was withdrawn from the top at a mass flow rate of 26,700 kg / h, consisting of methanol with a mass purity of 98.7 wt%. 26,650 kg / h of this second light component was returned to the reaction unit as a circulating solvent, and 50 kg / h was withdrawn from the system. A liquid phase material at a mass flow rate of 8,975 kg / h was withdrawn from the bottom of the third distillation tower and fed to a fourth distillation tower of the product separation unit. The fourth distillation tower had a top temperature of 121.2° C., a bottom temperature of 158° C., a top pressure of 10 kPa, a plate number of 20, and a top reflux ratio of 3. A second intermediate component comprising 46.4 wt% methyl glycolate and 48.1 wt% ethylene glycol was withdrawn from the top of the fourth distillation tower at a mass flow rate of 8,550 kg / h. The second intermediate component was recovered as a product, wherein the combined mass purity of these two compounds was 94.5 wt%. The selectivity (%) of glycolate was calculated to be 110.3%, and the selectivity (%) of ethylene glycol was calculated to be 92.3%. The product yield of this embodiment was approximately 515.8%. Simultaneously, 425 kg / h of heavy components was obtained in the bottom of the fourth distillation tower.

[0097] Example 3

[0098] A mixed alcohol waste stream at a mass flow rate of 975 kg / h was fed into the first distillation column of the preliminary separation unit. The mixed alcohol waste stream contained 1 wt% ethanol, 42 wt% methanol, 10 wt% water, 34.76 wt% methyl glycolate, 3.12 wt% acetic acid, 2.6 wt% methyl acetate, and 6.52 wt% ester, ketone, and ether impurities. The first distillation column had a top temperature of 71°C, a bottom temperature of 104°C, a top pressure of 35 kPa, a plate number of 20, and a top reflux ratio of 5. A first light fraction, comprising 93.1 wt% methanol, 1.0 wt% ethanol, and 5.9 wt% methyl acetate, was extracted from the top of the column at a mass flow rate of 435 kg / h. This first light fraction was fed into the reaction unit as a solvent. The bottoms from the first distillation column are fed into the second distillation column of the preliminary separation unit. The second distillation column has a top temperature of 102°C, a bottom temperature of 159°C, a top pressure of 25 kPa, a plate count of 20, and a top reflux ratio of 3. A first intermediate component containing water, acids, esters, ketones, and ethers is withdrawn from the top at a mass flow rate of 200 kg / h. A first heavy component rich in methyl glycolate is withdrawn from the bottoms of the second distillation column at a mass flow rate of 340 kg / h and fed to the reaction unit.

[0099] A heavy alcohol waste stream at a mass flow rate of 5,650 kg / h, methanol at 3,200 kg / h, a first heavy component rich in methyl glycolate at 340 kg / h, and a first light component from a preliminary separation unit and a second light component from a product separation unit at a total mass flow rate of 26,450 kg / h were fed into a reactor in a reaction unit. The heavy alcohol waste stream comprised 10.2 wt% methyl glycolate, 14 wt% ethylene glycol, and 75.8 wt% of a polymer-rich component. The reactor contained 2 kg of a catalyst having the following composition: 40 wt% zinc oxide, 40 wt% copper oxide, 19 wt% aluminum oxide, and 1 wt% cerium oxide. The temperature of the reactor is 190°C, the pressure is 2.2 MPa, the residence time of the reaction materials is 1 hour, and a liquid product with a mass flow rate of 35735 kg / h is obtained, which contains: 72 wt% of methanol, 14.29 wt% of methyl glycolate, 11.18 wt% of ethylene glycol, and 2.53 wt% of heavy components (including unreacted polymers and substances with unidentified molecular structures but with a boiling point greater than or equal to 200°C and remaining in the distillation tower kettle of the product separation unit).

[0100] The liquid product was fed into the third distillation column of the product separation unit. The third distillation column had a top temperature of 71°C, a bottom temperature of 153°C, a top pressure of 80 kPa, a plate number of 20, and a top reflux ratio of 2. A second light component, 97 wt% pure methanol, was withdrawn from the top at a mass flow rate of 26,500 kg / h. 26,450 kg / h of this second light component was returned to the reaction unit as a circulating solvent, and 50 kg / h was removed from the system. A mass flow rate of 9575 kg / h of liquid material was extracted from the bottom of the third distillation tower and fed into the fourth distillation tower of the product separation unit. The top temperature of the fourth distillation tower was 123°C, the bottom temperature was 149°C, the pressure was 10 kPa, the number of plates was 20, and the top reflux ratio was 3. A mass flow rate of 9188 kg / h of a second intermediate component was extracted from the top of the fourth distillation tower. The second intermediate component contained 55.4 wt% of methyl glycolate and 43.1 wt% of ethylene glycol. The second intermediate component was recovered as a product, and the combined purity of the two compounds was 98.5 wt%. Calculated results show that the product yield of this embodiment is approximately 531.4%, and the conversion rate (%) of the polymer is 95.9%. The selectivities of methyl glycolate and ethylene glycol in the products obtained are approximately 116.0% and 88.7%, respectively. Simultaneously, 387 kg / h of heavy components were obtained in the bottom of the fourth distillation tower.

[0101] Example 4

[0102] This example was operated in the same manner as Example 1, except that the reaction steps were carried out in a reactor without a catalyst. Measurement and analysis of the final product revealed that the product yield in this example was approximately 274%, the polymer conversion was approximately 67.6%, and the selectivities for methyl glycolate and ethylene glycol in the resulting product were approximately 78.4% and 38.3%, respectively.

[0103] Comparative Example 1

[0104] In this comparative example, the process was carried out in the same manner as in Example 3, except that the mixed alcohol waste and the heavy alcohol waste were reacted separately, and the total yield of the product was calculated.

[0105] A mixed alcohol waste stream at a mass flow rate of 975 kg / h is fed into the first distillation column of the preliminary separation unit. The mixed alcohol waste stream comprises: 1 wt% ethanol, 42 wt% methanol, 10 wt% water, 34.76 wt% methyl glycolate, 3.12 wt% acetic acid, 2.6 wt% methyl acetate, and 6.52 wt% ester, ketone, and ether impurities. The first distillation column has a top temperature of 71°C, a bottom temperature of 104°C, a pressure of 35 kPa, 20 plates, and a top reflux ratio of 5. A first light fraction is extracted from the top of the column at a mass flow rate of 435 kg / h. The first light fraction comprises 93.1 wt% methanol, 1.0 wt% ethanol, and 5.9 wt% methyl acetate. This first light fraction is fed into the reaction unit as a solvent. The bottoms from the first distillation column were fed to the second distillation column of the preliminary separation unit. The second distillation column had a top temperature of 102°C, a bottom temperature of 159°C, a pressure of 25 kPa, 20 plates, and an overhead reflux ratio of 3. A first intermediate component containing water, acid, ester, ketone, and ether impurities was withdrawn from the top at a mass flow rate of 200 kg / h. A first heavy component rich in methyl glycolate was withdrawn from the bottoms of the second distillation column at a mass flow rate of 340 kg / h.

[0106] The first light fraction and the first heavy fraction rich in methyl glycolate were then mixed and fed into a reactor containing a catalyst composed of 40 wt% zinc oxide, 40 wt% copper oxide, 19 wt% aluminum oxide, and 1 wt% cerium oxide. A first liquid product was produced at a rate of 775 kg / h, containing approximately 33.77 wt% methyl glycolate.

[0107] A mass flow rate of 5,650 kg / h of heavy alcohol waste with the same composition as in Example 1, 3,500 kg / h of methanol, and a total mass flow rate of 27,950 kg / h of a second light fraction from the product separation unit were fed into a reactor in a reaction unit containing a catalyst comprising 40 wt% zinc oxide, 40 wt% copper oxide, 19 wt% aluminum oxide, and 1 wt% cerium oxide. The heavy alcohol waste contained 2.5 wt% methyl glycolate, 20.54 wt% ethylene glycol, and 76.96 wt% of a polymer-rich component. The reactor was maintained at a temperature of 180°C, a pressure of 2 MPa, and a residence time of 1 hour. A second liquid product having a mass flow rate of 37,100 kg / h was obtained, comprising approximately 9.70 wt% methyl glycolate, approximately 10.24 wt% ethylene glycol, and the remainder primarily methanol.

[0108] The first liquid phase product is mixed with the second liquid phase product and fed into the third distillation column of the product separation unit. The third distillation column has a top temperature of 72.1°C, a bottom temperature of 140.2°C, a pressure of 35 kPa, a plate number of 20, and a top reflux ratio of 2. A second light component having a mass flow rate of 28,000 kg / h of methanol with a mass purity of 99.4 wt% is withdrawn from the top of the column, of which 27,950 kg / h is returned to the reaction unit as a circulating solvent, and 200 kg / h is withdrawn from the system. The tower bottom extraction mass flow rate is 9875kg / h of liquid phase material and is sent into the fourth distillation tower of described product separation unit from the tower reactor of the 3rd rectifying tower. The tower top temperature of this fourth rectifying tower is 121.2 ℃, tower bottom temperature is 159 ℃, pressure is 10kPa, tower plate number is 20, tower top reflux ratio is 3, the tower top extraction mass flow rate is 8700kg / h of the second intermediate component from the tower top of the 4th rectifying tower, it comprises 44.2wt% methyl glycolate and 39.3wt% ethylene glycol, the second intermediate component is recovered as product, and wherein the combined mass purity of these two compounds is 83.5wt%. According to calculation, the product yield of this embodiment is about 443%, and the conversion rate (%) of polymer is about 90%. In the products therefrom, the selectivities of methyl glycolate and ethylene glycol are about 100.9% and 85.3% respectively.

[0109] The schemes and results of the above examples are listed in Table 1.

[0110] Table 1.

[0111] As can be seen from the results of the above embodiments, Examples 1 and 2 of the present invention use the method shown in Figure 1 (combined treatment scheme 1) to treat mixed alcohol waste and heavy alcohol waste. The first heavy component obtained by the preliminary separation of the mixed alcohol waste does not participate in the reaction, but is combined with the reaction product from the reaction step and then separated; Example 3 uses the method shown in Figure 2 (combined treatment scheme 2) to treat mixed alcohol waste and heavy alcohol waste. The first heavy component obtained by the preliminary separation of the mixed alcohol waste participates in the reaction in the reaction step, and then the reaction product is separated. Both treatment methods can achieve very high product yields and achieve efficient recovery of mixed alcohol waste and heavy alcohol waste. In addition, compared with Example 1, Example 2 uses a different catalyst and increases the reaction temperature to achieve a higher polymer conversion rate and better product yield. In addition, compared to Examples 1 and 2 of Combined Treatment Method 1, Example 3 using Combined Treatment Method 2 can achieve a higher product yield using Combined Treatment Method 2. This may be because the bottoms (methyl glycolate-rich stream) left after the mixed alcohol waste is distilled twice contain a portion of glycolate polymers. By entering the reaction unit for reaction, this portion of polymers can be converted, thereby achieving a higher product yield. In the embodiments of the present invention, the product (including ethylene glycol and glycolate) yield is much higher than 100%. This is because the polymers (mainly glycolate polymers) and other components in the mixed alcohol waste and heavy alcohol waste generate ethylene glycol and glycolate through alcoholysis and depolymerization reactions, resulting in the ethylene glycol and glycolate content in the product stream being much higher than the ethylene glycol and glycolate content contained in the initial mixed alcohol waste and heavy alcohol waste.

[0112] By comparing Examples 1-3 with Example 4, it can be seen that in the reaction steps of the method of the present invention, the conversion and alcoholysis reaction of the polymer in the mixture of mixed alcohol waste and heavy alcohol waste can be achieved without the use of a catalyst. However, the polymer conversion rate (%) and product yield (%) are significantly lower, and the selectivity for methyl glycolate (%) and ethylene glycol (%) are also significantly lower. Therefore, it is preferred to use the catalyst according to the present invention in the reaction process of the mixture of mixed alcohol waste and heavy alcohol waste.

[0113] By comparing Example 3 and Comparative Example 1, it can be seen that when the mixed alcohol waste and the heavy alcohol waste are jointly treated, the polymers contained in the two wastes have a significantly higher conversion rate than when they are treated separately, and more methyl glycolate and ethylene glycol are produced, thereby significantly improving the product yield. Moreover, the separate treatment of the mixed alcohol waste and the heavy alcohol waste requires more fresh alcohol than their joint treatment to dissolve and alcoholyze the heavy alcohol waste; in addition, both products produced by the reaction of the mixed alcohol waste and the reaction of the heavy alcohol waste need to be separated by distillation, which consumes more energy than the joint treatment method and involves more separation steps, resulting in higher production costs.

[0114] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A combined treatment method for mixed alcohol waste and heavy alcohol waste, characterized in that: The combined treatment method comprises the following steps: Step 1. Optionally, subjecting a mixed alcohol waste material mainly comprising C1-C4 saturated monohydric alcohols to a preliminary separation treatment to at least partially remove the water and acid contained therein, and optionally at least partially separate a heavy component mainly comprising esters, to obtain a preliminary purified product of the mixed alcohol waste material; Step 2. In the presence of an optional catalyst, the mixed alcohol waste material that is optionally subjected to preliminary separation treatment, the heavy alcohol waste material and the optional added alcohol are mixed and reacted to obtain a product containing glycolate and ethylene glycol, and, optionally Step 3. A step of separating a material containing glycolate and ethylene glycol from the product obtained in step 2 and optionally the heavy component obtained in step 1; The heavy alcohol waste contains at least one of ethylene glycol, glycolic acid and methyl glycolate and a polymer produced by a polymerization reaction of at least one of these compounds.

2. The combined processing method according to claim 1, characterized in that: The combined treatment method comprises the following steps: S1. Optionally, the mixed alcohol waste is subjected to preliminary separation to at least partially separate a heavy component mainly comprising esters, referred to as a "first heavy component", and at least partially remove water and acid contained in the mixed alcohol waste, referred to as a "first intermediate component", to obtain a preliminary purified product of the mixed alcohol waste, referred to as a "first light component"; S2. In the presence of an optional catalyst, the heavy alcohol waste, the optional added alcohol, and the mixed alcohol waste that has not been subjected to preliminary separation treatment or the preliminary purified product of the mixed alcohol waste obtained in step S1 are mixed to react; and S3. The reaction product obtained in step S2 and the first heavy component obtained in step S1 are combined, and the material containing glycolic acid ester and ethylene glycol is separated therefrom.

3. The combined processing method according to claim 1, characterized in that: The combined treatment method comprises the following steps: S1. Optionally, the mixed alcohol waste is subjected to a preliminary separation treatment to at least partially separate a heavy component mainly comprising esters, referred to as a "first heavy component", and at least partially remove water and acid contained therein, referred to as a "first intermediate component", to obtain a preliminary purified product of the mixed alcohol waste, referred to as a "first light component"; S2. in the presence of an optional catalyst, the heavy alcohol waste, the optional added alcohol, Mixing with the mixed alcohol waste that has not been subjected to preliminary separation treatment or the preliminary purified product of the mixed alcohol waste obtained in step S1 and the first heavy component to react; and S3. Separating the material containing glycolic acid ester and ethylene glycol from the reaction product obtained in step S2.

4. The combined treatment method according to any one of claims 1 to 3, characterized in that: The mixed alcohol waste comprises: C1-C4 saturated monohydric alcohol, water, and at least one of low-boiling esters, acetic acid and methyl glycolate with a boiling point of 50-90°C, and optionally at least one of esters, ethers and ketones with a boiling point of 100-150°C; preferably, in the mixed alcohol waste, the content of C1-C4 saturated monohydric alcohol is 30-70wt%, the content of low-boiling esters with a boiling point of 50-90°C is 1-9wt%, the content of water is 5-35wt%, the content of acetic acid is 1-15wt%, the total content of esters, ethers and ketones with a boiling point of 100-150°C is 1-30wt%, and the content of methyl glycolate is 1-41wt%.

5. The combined treatment method according to any one of claims 1 to 4, characterized in that: Based on the total weight of the mixed alcohol waste and the heavy alcohol waste, the content of polymer from the heavy alcohol waste is greater than or equal to 5wt%, preferably 10-80wt%; and / or, based on the weight of the heavy alcohol waste, the content of ethylene glycol in the heavy alcohol waste is 15-75wt%, the content of methyl glycolate is 0-30wt%, and the content of glycolic acid is 0-10wt%.

6. The combined treatment method according to any one of claims 1 to 5, characterized in that: The step 1 or step S1 comprises: a. The mixed alcohol waste is subjected to a first distillation at a top pressure of 101-201 kPa and a top temperature of 40-120 ° C; or, the mixed alcohol waste is subjected to a first distillation at a top pressure of 20-101 kPa and a top temperature of 40-110 ° C, the number of plates of the first distillation is controlled to be 5-38, the reflux ratio is 0.1-12, and the first light component and the undistilled material are obtained; b. subjecting the undistilled material obtained from the first distillation to a second distillation at a tower top pressure of 101-121 kPa and a tower top temperature of 60-160° C.; or, subjecting the undistilled material obtained from the first distillation to a second distillation at a tower top pressure of 20-101 kPa and a tower top temperature of 50-162° C., controlling the number of plates of the second distillation to 5-38 and the reflux ratio to 0.1-12, to obtain the first intermediate component and the first heavy component.

7. The combined treatment method according to any one of claims 1 to 6, characterized in that: The alcohol added in the reaction step is selected from saturated monohydric alcohols, preferably C1-C4 saturated monohydric alcohols, and more preferably methanol.

8. The combined treatment method according to any one of claims 1 to 7, characterized in that: In the reaction step, the reaction is carried out in the presence of a catalyst; the catalyst is selected from a material containing zinc oxide and / or a material containing copper oxide, preferably the catalyst contains 20-80wt% of zinc oxide, 5-45wt% of copper oxide and 1-30wt% of aluminum oxide; preferably, the weight ratio of the amount of the catalyst to the amount of the heavy alcohol waste is 1-100:

100.

9. The combined treatment method according to any one of claims 2 and 4-8, characterized in that: In the S2 reaction step, the amounts of the heavy alcohol waste, the added alcohol and the preliminary purified product obtained in S1 are such that the ratio of the weight of the heavy alcohol waste to the total weight of all alcohols is 1:(1-7); and / or, in the S2 reaction step, the reaction conditions include: pressure of 0.1-6MPa, temperature of 160-220°C, and time of 10 minutes to 4 hours.

10. The combined treatment method according to any one of claims 3 to 8, characterized in that: In the reaction step S2, the amounts of the heavy alcohol waste, the added alcohol, the preliminary purified product obtained in S1 and the first heavy component are such that the ratio of the weight of the heavy alcohol waste: the total weight of all alcohols: the weight of the heavy component is 1:(1-7):(0.01-0.5); and / or, in the S2 reaction step, the reaction conditions include: a pressure of 0.1-6 MPa, a temperature of 160-220°C, and a time of 10 minutes to 4 hours.

11. The combined treatment method according to any one of claims 1 to 8, characterized in that: In step 3 or step S3, the separation method comprises: A. subjecting the reaction product obtained in step 2 or in step S2 to a third distillation at a tower top pressure of 20-201 kPa and a tower top temperature of 50-160° C., controlling the number of plates of the third distillation to be 5-42 and the reflux ratio to be 1-15, to separate the second light component, B. The undistilled material obtained from the third distillation is subjected to a fourth distillation under the conditions of a tower top pressure of 5Pa-101kPa and a tower top temperature of 70-170°C, the number of plates of the fourth distillation is controlled to be 5-42, and the reflux ratio is controlled to be 1-15, to separate the material containing glycolate.

12. The combined treatment method according to any one of claims 1 to 11, characterized in that: The combined treatment method further comprises: returning at least a portion of the remaining material after separating the glycolate-containing material to the reaction step for reaction.

13. The combined processing method according to claim 8, characterized in that: The catalyst also includes 0.1-10wt% of rare earth element oxides; preferably, based on the total weight of the catalyst, the catalyst includes: 40-70wt% of zinc oxide, 10-40wt% of copper oxide, 5-25wt% of aluminum oxide and 1-8wt% of rare earth element oxides; preferably, the rare earth element is selected from at least one of lanthanum, cerium, zirconium and neodymium.

14. A system for implementing the combined treatment method according to any one of claims 1 to 13, comprising: an optional preliminary separation unit, a reaction unit and an optional product separation unit, wherein the preliminary separation unit is used to at least partially remove water and acid contained in the mixed alcohol waste and optionally separate a heavy component mainly comprising esters to obtain a preliminary purified product of the mixed alcohol waste; the reaction unit is used to react a mixture comprising heavy alcohol waste, added alcohol, the preliminary purified product of the mixed alcohol waste and an optional heavy component mainly comprising esters in the presence of an optional catalyst; and the product separation unit is used to separate a material containing glycolic acid ester from the reaction product from the reaction unit.

15. The system according to claim 14, characterized in that The preliminary separation unit includes a first distillation column and a second distillation column which are connected in series, the reaction unit includes one or more reaction tanks, and the product separation unit includes a third distillation column and a fourth distillation column which are connected in series.

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