Process for recovering anisole from a diphenyl carbonate light component waste liquid

Abstract

This invention proposes a process for recovering anisole from the light component waste liquid of diphenyl carbonate, specifically comprising: passing the light component waste liquid of diphenyl carbonate into an adsorption column packed with adsorbent to remove strongly polar and non-polar impurities, obtaining a pretreated waste liquid; passing the pretreated waste liquid into a light component removal tower to remove the light component impurities, with crude anisole as the bottom product; and passing the crude anisole into a product tower to remove the heavy component impurities, with commercial-grade anisole as the top product. This invention solves the technical problem of the need to improve the purity and yield of recovered anisole in the prior art, while further reducing heat loss during the recovery process.

Description

Technical Field

[0001] This invention relates to the field of chemical separation and recovery technology, and in particular to a process for recovering anisole from light component waste liquid of diphenyl carbonate. Background Technology

[0002] During the transesterification process to synthesize diphenyl carbonate, anisole is generated as a side reaction and is present in the light component waste liquid. It has both recycling value and separation difficulty. As an important organic intermediate and solvent, anisole is widely used in the fields of fragrance, medicine and pesticide. The purity requirements of the product are strict. However, the polar impurities such as phenol contained in the waste liquid can easily form an azeotropic system with anisole, which has become the core bottleneck restricting its efficient recovery.

[0003] Currently, the recovery of anisole mostly adopts single distillation or conventional molecular sieve adsorption coupled distillation processes. Conventional molecular sieves rely solely on physical adsorption through basic pores and lack targeted polar adsorption sites, resulting in insufficient removal capacity for highly polar impurities such as phenol. When a large amount of impurities enter the distillation system, it not only exacerbates the azeotropic phenomenon leading to the loss of anisole, but also reduces the purity of the final product. At the same time, traditional processes do not achieve effective heat circulation within the system, and the distillation process relies on a large amount of external heat sources, resulting in high energy consumption, which is difficult to meet the energy-saving and cost control requirements of industrial production.

[0004] Furthermore, while some processes can reduce material retention in the adsorption stage by eliminating adsorption pretreatment and directly proceeding to distillation, the direct introduction of impurities still cannot guarantee the purity of anisole, and does not fundamentally solve the problems of azeotropic loss and excessive energy consumption. Therefore, developing anisole recovery process that combines high-selectivity impurity removal, high-yield recovery, and low-energy operation, achieving synergistic optimization of the structure and composition of modified adsorption materials, and organically coupling it with the distillation system and heat cycle has become an urgent technical challenge to be solved in current industrial applications. Summary of the Invention

[0005] Based on the technical problems existing in the background art, the present invention proposes a process for recovering anisole from the light component waste liquid of diphenyl carbonate, which solves the technical problem that the purity and yield of the recovered anisole need to be improved in the prior art, and further reduces the heat loss in the recovery process.

[0006] The present invention proposes a process for recovering anisole from the light component waste liquid of diphenyl carbonate, comprising the following steps: S1. Pass the light component waste liquid of diphenyl carbonate into an adsorption column filled with adsorbent to remove the strongly polar impurities and non-polar impurities, and obtain the pretreated waste liquid. S2. Pass the pretreated waste liquid into the light component removal tower to remove the light component impurities, and the crude anisole is obtained from the bottom of the tower. S3. Pass the crude anisole into the product tower to remove the heavy component impurities, and the product is discharged from the top of the tower to obtain commercial grade anisole.

[0007] In this invention, the purity and yield of anisole recovery from light component waste liquid of diphenyl carbonate are further improved by combining adsorption separation pretreatment and multi-tower distillation.

[0008] Preferably, in step S2, before the pretreated waste liquid is fed into the light residue removal tower, the pretreated waste liquid is also fed into the feed preheater for preheating. The preheating temperature is 120-130℃, and the time is 1-2 hours.

[0009] Preferably, in step S3, before the light component from the top of the column is condensed, the light component from the top of the column is further passed into the feed preheater for heat exchange.

[0010] In this invention, the light components discharged from the top of the tower and the pretreatment waste liquid flow independently in different heat exchange channels of the feed preheater. The two transfer heat only through the heat exchange wall. The light components discharged from the top of the tower and the pretreatment waste liquid do not come into direct contact and do not mix, so as to achieve heat recovery and utilization while ensuring that the purity of the materials is not affected.

[0011] In this invention, by transferring the heat from the top of the product tower to the feed preheater of the light-weight product tower as a heat source for heat exchange, heat self-circulation within the process system is achieved, solving the technical problem that heat loss during the recovery process needs to be further reduced.

[0012] Preferably, in step S1, the adsorbent packed in the adsorption column is a phosphorus-modified molecular sieve, which is prepared by the following method: After the molecular sieve undergoes an ion exchange reaction with an ammonium salt, it is calcined once to obtain an H-type molecular sieve; after the H-type molecular sieve undergoes an impregnation reaction with trimethyl phosphate, it is calcined a second time to obtain the phosphorus-modified molecular sieve.

[0013] In this invention, the ion exchange reaction is carried out under hydrothermal conditions, and the NH4 in the ammonium salt (ammonium chloride) aqueous solution... + It diffuses into the pores of molecular sieves (such as Beta molecular sieves) and interacts with the negatively charged Na+ on the molecular sieve framework. + K + After a reversible ion exchange reaction involving alkali metal cations, and repeated washing to neutrality, the generated metal chlorides and unreacted free ammonium chloride can be removed, and the NH4+ after ion exchange can be... + - The molecular sieve is calcined, and the NH4+ inside the molecular sieve pores... + A thermal decomposition reaction occurs, and the NH3 produced by the decomposition escapes in gaseous form. + Then it will replace the original NH4 +The position of H balances the negative charge of the molecular sieve framework, ultimately forming a structure with H + H-type molecular sieves with cation exchange sites; After the H-type molecular sieve is fully dispersed in deionized water, trimethyl phosphate is added and adsorbed onto the surface of the molecular sieve through physical impregnation and diffuses into the pores. It forms hydrogen bonds with the silanol and aluminol hydroxyl groups on the molecular sieve framework. After evaporation to remove water, the binding sites of trimethyl phosphate and the hydroxyl groups of the molecular sieve are fixed. Subsequently, after calcination, trimethyl phosphate undergoes a demethylation reaction, and the P=O group in its molecule undergoes dehydration condensation with the silanol / aluminol hydroxyl groups of the molecular sieve to form stable Si-OP and Al-OP covalent bonds, successfully grafting phosphorooxy groups onto the surface and pore openings of the molecular sieve. At the same time, calcination removes unbound trimethyl phosphate decomposition products, and finally obtains a phosphorus-modified Beta molecular sieve adsorbent with a surface rich in polar phosphorooxy functional groups and a well-preserved pore structure.

[0014] In this invention, trimethyl phosphate cannot be replaced by other phosphorus-containing compounds. The core reason is its unique molecular structure and reaction characteristics, which allow it to precisely cooperate with H-type molecular sieves to achieve directional grafting of phosphorus and oxygen functional groups, forming stable Si-OP and Al-OP covalent bonds. The resulting adsorbent can efficiently remove highly polar impurities such as phenol and non-polar light components from waste liquids by virtue of its pore shape selectivity and the synergistic effect of polar phosphorus and oxygen functional groups, thus avoiding azeotropic formation at the source and improving the purity and yield of anisole recovery. Other phosphorus-containing compounds, due to differences in steric hindrance, functional group type, and reactivity, cannot achieve this precise grafting and may also damage the molecular sieve pore structure, failing to form suitable polar adsorption sites. They may even cause anisole loss and reaction product residues that block the pores. If other phosphorus-containing compounds are used instead, the resulting adsorbent will lose its high selective removal ability for waste liquid impurities, leading to anisole azeotropic loss during subsequent distillation and a significant decrease in purity and yield.

[0015] Preferably, the molecular sieve is a Beta molecular sieve, and the ammonium salt is ammonium chloride and / or ammonium nitrate; The mass ratio of the molecular sieve to the ammonium salt is 1:2.5-3.5, and the mass ratio of the H-type molecular sieve to trimethyl phosphate is 1:1.5-2.

[0016] Preferably, the ion exchange reaction temperature is 70-80℃ and the time is 7-8h; the impregnation reaction temperature is 20-30℃ and the time is 1-1.5h; the first calcination temperature is 500-600℃ and the time is 4-5h; and the second calcination temperature is 500-600℃ and the time is 4-5h.

[0017] Preferably, the adsorption column is obtained by filling the adsorbent into the inner cavity of an adsorption column with filter screens at both ends; The filter screen has a mesh size of 60-100, and the adsorbent loading is 0.8-0.9 g / cm³. 3 .

[0018] Preferably, in step S1, the volumetric flow rate of the diphenyl carbonate light component waste liquid passed into the adsorption column is 1-2 m³ / s. 3 ·h -1 .

[0019] Preferably, in step S2, the flow rate of the pretreated waste liquid into the light-light ...

[0020] Preferably, in step S3, the working pressure of the product tower is -(50-60) kPa, and the temperature at the top of the tower is 125-145℃.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In this invention, the phosphorus-modified molecular sieve is formed by first exchanging the molecular sieve with ammonium salt ions and calcining it to form an H-type molecular sieve, with H in the framework. + To provide cation exchange sites, the pore structure and surface adsorption sites were optimized. Subsequently, after impregnation with trimethyl phosphate and calcination, phosphorus and oxygen functional groups were successfully grafted onto the surface and pore openings of the molecular sieve, forming Si-OP and Al-OP covalent bond structures. The pore shape selectivity of the H-type molecular sieve and the polar phosphorus and oxygen functional groups of the adsorbent work synergistically to selectively adsorb and remove strongly polar impurities such as phenol and non-polar light component impurities from the light component waste liquid of diphenyl carbonate. This significantly reduces the impurity content entering the distillation system, avoids the problem of impurities forming azeotropes with anisole that are difficult to separate, and significantly improves the mass fraction of the recovered anisole.

[0022] (2) In this invention, after the modified molecular sieve is calcined by ion exchange, the pore structure is more regular and the mass transfer efficiency is improved. When combined with an adsorbent with phosphorus and oxygen functional groups on the surface, the synergistic effect formed by the two in terms of elemental composition and spatial structure makes the adsorption column filled with the adsorbent have a significantly improved adsorption selectivity and removal efficiency for impurities in waste liquid. This avoids the decrease in material flow efficiency caused by impurities clogging the adsorption column and the packing of the distillation column, and also reduces the loss of anisole due to azeotropy of impurities during the distillation process, ensuring the effective amount of anisole participating in the distillation, while improving the collection efficiency of anisole fraction in the distillation column, thereby increasing the yield of anisole.

[0023] (3) In this invention, the process of pretreatment by adsorption column coupled with double-tower distillation is adopted. The structure and composition of modified molecular sieve and adsorbent work synergistically to achieve efficient removal of impurities from waste liquid, laying a high-quality material foundation for subsequent distillation process and reducing the difficulty of distillation separation. At the same time, the heat generated at the top of the anisole product tower can be transported to the feed preheater of the anisole light removal tower as a heat source, realizing the heat self-circulation in the process system and replacing the supply of external heat source. This not only further improves the mass fraction and yield of anisole in conjunction with adsorption pretreatment, but also reduces the heat loss in the process preparation process, achieving energy saving and high efficiency in the anisole recovery process. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the process for recovering anisole from the light component waste liquid of diphenyl carbonate according to the present invention; in the figure: 1, preheater for feed to the anisole light component removal tower; 2, anisole light component removal tower; 3, condenser for the anisole light component removal tower; 4, anisole product tower; 5, heat source; 6, commercial grade anisole. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In this application, the Beta molecular sieve is selected from Shandong Hefeng Environmental Protection Technology Co., Ltd., CAS No. 69912-79-4, with a silica-alumina ratio of 25.

[0027] Example 1

[0028] Reference Figure 1 This embodiment proposes a process for recovering anisole from the light component waste liquid of diphenyl carbonate, specifically including: (1) The adsorbent was prepared at a concentration of 0.8 g / cm³. 3 The filler material is packed into the inner cavity of an adsorption column sealed with 80-mesh filters at both ends to form an adsorption column, allowing the light component waste liquid of diphenyl carbonate to pass through a 1m³ flow path. 3 ·h -1 The volumetric flow rate passes through the adsorption column; The above-mentioned adsorbent is a phosphorus-modified molecular sieve, which is prepared by the following method: 100g of Beta molecular sieve was added to a reaction vessel containing 5000mL of 5.3wt% ammonium chloride aqueous solution. After stirring at 70℃ for 7h, the mixture was filtered, and the filter cake was washed with deionized water until the washing liquid was neutral. The cake was then transferred to an oven and dried at 80℃ to constant weight. It was then removed, ground, passed through an 80-mesh sieve, and placed in a muffle furnace for calcination at 500℃ for 4h to obtain H-type Beta molecular sieve. 30g of the above-mentioned H-type Beta molecular sieve was added to a reaction vessel containing 900mL of deionized water and stirred at 20℃ for 60min. Then, 50g of trimethyl phosphate was added and stirring was continued for 3h. After the reaction was completed, the temperature was raised to 70℃ and the solvent water was evaporated by stirring at a constant temperature. The mixture was then transferred to an oven and dried at 80℃ to constant weight. The mixture was then removed, ground, passed through an 80-mesh sieve, and then placed in a muffle furnace and calcined at 500℃ for 4h. The phosphate-modified molecular sieve was then obtained. (2) The pretreated waste liquid flowing out of the adsorption column is fed into the anisole light removal tower preheater 1, and its flow rate is controlled to be 15% of the packing volume of the anisole light removal tower 2. It is preheated at 120°C for 1 hour to obtain the preheated pretreated waste liquid. (3) The preheated and pretreated waste liquid is fed into the anisole light component removal tower 2. The pressure of the light component removal tower is controlled at 0.1 MPa, the temperature at 165℃, and the heating rate at 5℃ / min. The bottom product including anisole and phenol and the light component at the top of the tower are obtained. After the bottom product is discharged, crude anisole is obtained. The light component at the top of the tower is condensed by the anisole light component removal tower condenser 3 and the waste liquid is recovered and treated. (4) Crude anisole is fed into the anisole product tower 4. The working pressure of the anisole product tower 4 is controlled at -50 kPa. When the temperature at the top of the anisole product tower rises to 125°C, the heat outlet switch at the top of the anisole product tower is opened, so that the light component 5 at the top of the tower enters the anisole light component removal tower preheater 1 and is then condensed. The anisole product tower continues to produce commercial grade anisole 6.

[0029] Example 2

[0030] This embodiment proposes a process for recovering anisole from light component waste liquid of diphenyl carbonate, specifically including: (1) The adsorbent was prepared at a concentration of 0.85 g / cm³. 3 The filler material is packed into the inner cavity of an adsorption column sealed with 80-mesh filters at both ends to form an adsorption column, allowing the light component waste liquid of diphenyl carbonate to pass through at a flow rate of 1.5m. 3 ·h -1 The volumetric flow rate passes through the adsorption column; The above-mentioned adsorbent is a phosphorus-modified molecular sieve, which is prepared by the following method: 100g of Beta molecular sieve was added to a reaction vessel containing 5500mL of 5.3wt% ammonium chloride aqueous solution. After stirring at 75℃ for 7.5h, the mixture was filtered, and the filter cake was washed with deionized water until the washing liquid was neutral. The cake was then transferred to an oven and dried at 80℃ to constant weight. It was then removed, ground, passed through a 60-mesh sieve, and placed in a muffle furnace for calcination at 550℃ for 4.5h to obtain H-type Beta molecular sieve. 30g of the above-mentioned H-type Beta molecular sieve was added to a reaction vessel containing 950mL of deionized water and stirred at 25°C for 60min. Then, 55g of trimethyl phosphate was added and stirring was continued for 3.5h. After the reaction was completed, the temperature was raised to 75°C and the solvent water was evaporated by stirring at a constant temperature. The mixture was then transferred to an oven and dried at 80°C to constant weight. After drying, the mixture was ground and passed through an 80-mesh sieve. Finally, it was placed in a muffle furnace and calcined at 550°C for 4.5h. The phosphorus-modified molecular sieve was then obtained. (2) The pretreated waste liquid flowing out of the adsorption column is fed into the feed preheater of the anisole light removal tower, and its flow rate is controlled to be 15% of the packing volume of the anisole light removal tower. It is preheated at 125°C for 1.5 hours to obtain the preheated pretreated waste liquid. (3) The preheated and pretreated waste liquid is fed into the anisole removal tower. The pressure of the removal tower is controlled at 0.1 MPa, the temperature at 165°C, and the heating rate at 5°C / min. The bottom product containing anisole and phenol is obtained. After discharge, crude anisole is obtained. (4) Crude anisole is fed into the anisole product tower. The working pressure of the anisole product tower is controlled at -55 kPa. When the temperature at the top of the anisole product tower rises to 135°C, the heat outlet switch at the top of the anisole product tower is opened so that the light components at the top of the tower enter the anisole light component removal tower preheater and are then condensed. The anisole product tower continues to produce commercial grade anisole.

[0031] Example 3

[0032] This embodiment proposes a process for recovering anisole from light component waste liquid of diphenyl carbonate, specifically including: (1) The adsorbent was prepared at a concentration of 0.9 g / cm³. 3 The filler material is packed into the inner cavity of an adsorption column sealed with 100-mesh filters at both ends to form an adsorption column, allowing the light component waste liquid of diphenyl carbonate to pass through a 2m... 3 ·h -1 The volumetric flow rate passes through the adsorption column; The above-mentioned adsorbent is a phosphorus-modified molecular sieve, which is prepared by the following method: 100g of Beta molecular sieve was added to a reaction vessel containing 6000mL of 5.3wt% ammonium chloride aqueous solution. After stirring at 80℃ for 8 hours, the mixture was filtered. The filter cake was washed with deionized water until the washing liquid was neutral. It was then transferred to an oven and dried at 80℃ to constant weight. The cake was then removed, ground, passed through an 80-mesh sieve, and placed in a muffle furnace for calcination at 600℃ for 5 hours to obtain H-type Beta molecular sieve. 30g of the above-mentioned H-type Beta molecular sieve was added to a reaction vessel containing 1000mL of deionized water and stirred at 30℃ for 70min. Then, 60g of trimethyl phosphate was added and stirring was continued for 4h. After the reaction was completed, the temperature was raised to 80℃ and the solvent water was evaporated by stirring at a constant temperature. The mixture was then transferred to an oven and dried at 80℃ to constant weight. The mixture was then removed, ground, passed through an 80-mesh sieve, and then placed in a muffle furnace and calcined at 600℃ for 5h. The phosphate-modified molecular sieve was then obtained. (2) The pretreated waste liquid flowing out of the adsorption column is fed into the feed preheater of the anisole light removal tower, and its flow rate is controlled to be 15% of the packing volume of the anisole light removal tower. It is preheated at 130°C for 2 hours to obtain the preheated pretreated waste liquid. (3) The preheated and pretreated waste liquid is fed into the anisole removal tower. The pressure of the removal tower is controlled at 0.1 MPa, the temperature at 165°C, and the heating rate at 5°C / min. The bottom product containing anisole and phenol is obtained. After discharge, crude anisole is obtained. (4) The crude anisole is fed into the anisole product tower. The working pressure of the anisole product tower is controlled at -60 kPa. When the temperature at the top of the anisole product tower rises to 145°C, the heat outlet switch at the top of the anisole product tower is opened so that the light components at the top of the tower enter the anisole light component removal tower preheater and are then condensed. The anisole product tower continues to produce commercial grade anisole.

[0033] Comparative Example 1 This comparative example proposes a process for recovering anisole from the light component waste liquid of diphenyl carbonate. The difference from Example 3 is that in step (1), H-type Beta molecular sieve is used as an adsorbent.

[0034] Comparative Example 2 This comparative example proposes a process for recovering anisole from diphenyl carbonate light component waste liquid. The difference from Example 3 is that in step (1), Beta molecular sieve is used as an adsorbent.

[0035] Comparative Example 3 This comparative example presents a process for recovering anisole from diphenyl carbonate light component waste liquid. The difference from Example 3 is that the adsorbent loading is omitted in step (1).

[0036] Comparative Example 4 This comparative example proposes a process for recovering anisole from diphenyl carbonate light component waste liquid. The difference from Example 3 is that in step (1), orthophosphoric acid is used instead of trimethyl phosphate, and the resulting modified molecular sieve is used as an adsorbent.

[0037] Performance testing: The mass fraction of commercial-grade anisole recovered from Examples 1-3 and Comparative Examples 1-2 was determined according to the standard GB / T 9722-2023 "General Rules for Gas Chromatography of Chemical Reagents" to represent the purity of the recovered commercial-grade anisole. The specific test results are shown in Table 1 below. The yields of commercial-grade anisole recovered from Examples 1-3 and Comparative Examples 1-2 were calculated using the following formula;

[0038] in: M: Total mass of commercial-grade anisole recovered; ω: Mass fraction of anisole; m1: Total mass of diphenyl carbonate light component waste liquid added.

[0039] Reference Figure 1 Process simulation was conducted, and the material balance simulation results and heat balance results during the experimental process were obtained by directional analysis and calculation of energy flow within the process system. The specific test results are shown in Table 2 below. Table 1 Performance test data of the recovered samples

[0040] Table 2. Heat balance calculation results during the experiment

[0041] Note: The thermal balance here is based on... Figure 1 The given process flow of the Lihuayi ANS recovery unit model was obtained through directional analysis and calculation of the energy flow within the system. The heat balance calculation results are based on... Figure 1 The process flow simulation shown is obtained through directional analysis and calculation of the energy flow within the system. The system uses the latent heat of distillation carried by the high-purity gaseous anisole (heat source 5) produced at the top of the anisole product tower as a directional heat flow (Q) to be transported to the feed preheater of the anisole light-weight removal tower for heat exchange. The heat load (Q value, unit kcal / h) of T101 (light-weight removal tower system) and T102 (product tower system) is determined by calculating the enthalpy difference between their input and output streams (i.e., enthalpy change multiplied by flow rate), thereby obtaining the heat consumption of each unit during the experiment.

[0042] As shown in Table 1 above, Comparative Example 1 lacks the calcination grafting process of trimethyl phosphate and H-type molecular sieve. Therefore, no Si-OP, Al-OP covalent bonds or polar phosphorus-oxygen functional groups are formed in the adsorbent. The adsorbent relies solely on the pore shape selectivity of the modified molecular sieve and the H-type molecular sieve. + The removal of highly polar impurities such as phenol from waste liquid by cation exchange sites significantly reduces the ability of these impurities to be removed. A large amount of these highly polar impurities enter the distillation system and form azeotropes with anisole, resulting in a significant loss of anisole during distillation and making it impossible to effectively separate the impurities. This factor directly leads to a decrease in the anisole yield of Comparative Example 1 to 65.3% and a decrease in the mass fraction of anisole to 85.3%. The original Beta molecular sieve used in Comparative Example 2 had not undergone ammonium chloride ion exchange and trimethyl phosphate modification, its pore structure was not optimized, and it contained no H₂. + The cation exchange sites and polar phosphorus and oxygen functional groups only possess basic pore physical adsorption capabilities, and can only retain a small amount of heavy impurities. The removal effect on light component impurities and polar impurities in waste liquid is extremely poor, and a large amount of impurities still enter the distillation system, causing azeotropic loss of anisole and a decrease in product purity. However, the original Beta molecular sieve still has a certain physical adsorption effect, and the impurity removal effect is better than that of Comparative Example 3 without adsorbent. Therefore, the anisole production yield of Comparative Example 2 is 73.5%, and the anisole mass fraction is 90.5%. In Comparative Example 3, the light component waste liquid of diphenyl carbonate was directly introduced into the distillation system without any adsorption pretreatment. Various impurities in the waste liquid directly participated in the distillation process. Although the amount of anisole participating in the distillation was more sufficient due to the absence of material retention and pore blockage issues caused by the absence of an adsorption column, and the absence of non-specific adsorption of anisole by the adsorbent reduced material loss in the adsorption stage, resulting in an anisole yield of 79.8%, the absence of any impurity removal step led to a large amount of impurities entering the distillation system, which affected the purity of the anisole, with a mass fraction of 94.7%.

[0043] In Comparative Example 4, a modified molecular sieve obtained by impregnating H-type Beta molecular sieve with a phosphorus-containing compound other than trimethyl phosphate was used as an adsorbent. Although trimethyl phosphate and H-type Beta molecular sieve achieved effective loading and directional binding of polar phosphorus and oxygen functional groups through impregnation, other phosphorus-containing compounds, such as phosphoric acid, could not form stable bonds with the hydroxyl groups on the surface of the molecular sieve under impregnation conditions due to differences in molecular structure, functional group characteristics and reactivity. It was difficult to construct targeted and highly polar adsorption sites, and the removal effect on impurities such as phenol was significantly worse. This directly led to a decrease in the yield of anisole formation in Comparative Example 4 to 69.4% and a decrease in the mass fraction of anisole to 88.2%.

[0044] In summary, Comparative Example 1 only used modified Beta molecular sieves with ammonium chloride ion exchange, lacking trimethyl phosphate modification, while Comparative Example 2 directly used the original Beta molecular sieve. Neither of them had polar adsorption sites for phenol, so they could not remove the core impurities and solve the azeotropic problem between anisole and phenol. Moreover, their pores would cause non-specific adsorption-desorption of impurities, resulting in local enrichment of impurities and exacerbating the azeotropic phenomenon. At the same time, the adsorbent pores were easily blocked by heavy impurities, and they would also non-specifically retain materials, resulting in uneven feed flow rate in the distillation column, disruption of gas-liquid balance, and decreased mass and heat transfer efficiency, further reducing the distillation separation effect. In contrast, Comparative Example 3 had no adsorption column, and the waste liquid directly entered the distillation system. This avoided the problems of local enrichment of impurities and reduced distillation efficiency caused by inferior adsorbents, and there was no material retention by the adsorbent. The distillation column could operate under stable conditions, with only a small amount of impurities remaining due to the formation of azeotropes from the original impurities in the waste liquid. Therefore, its anisole purification effect was better than that of Comparative Examples 1 and 2, which were affected by ineffective impurity removal and the superposition of double negative effects.

[0045] As shown in Table 2, in this invention, commercial-grade anisole is used as heat source 5, and its carrier is high-purity gaseous anisole at the top of the anisole product tower. Under the high temperature and negative pressure of the anisole product tower, the high-purity anisole that has undergone deep separation in the tower rises to the top of the tower in gaseous form. This gaseous anisole is not only the raw material for commercial-grade anisole, but also carries a large amount of latent heat generated during the distillation process, becoming a heat source carrier that can be recycled within the process system.

[0046] Heat source 5 and commercial-grade anisole 6 are separated through phase change condensation separation and directional heat transfer. Essentially, they represent the separation of the energy and material properties of the same material, not the separation of different substances. When the anisole product tower reaches the specified process conditions, the heat outlet switch at the top of the tower is opened. The gaseous anisole, which serves as the carrier of heat source 5, is directed to the anisole delight tower preheater through the heat outlet. During this process, the gaseous anisole only releases a portion of the heat and remains in a gaseous state, thus fulfilling the heat supply function of heat source 5. After heat exchange and heat release, the gaseous anisole enters the matching condensation system. After being cooled, it undergoes a gas-liquid phase change and transforms into a liquid phase. This portion of liquid anisole has undergone deep impurity removal and its purity meets the commercial-grade standard, which is the commercial-grade anisole 6, and is collected and output.

[0047] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A process for recovering anisole from diphenyl carbonate light component waste liquid, characterized in that, Includes the following steps: S1. Pass the light component waste liquid of diphenyl carbonate into an adsorption column to remove the strongly polar impurities and non-polar impurities to obtain pretreated waste liquid. S2. Pass the pretreated waste liquid into the light component removal tower to remove the light component impurities. After the product is discharged from the bottom of the tower, crude anisole is obtained. S3. The crude anisole is passed into the product tower to remove the heavy component impurities. The light component discharged from the top of the tower is condensed to obtain commercial grade anisole.

2. The process for recovering anisole from the light component waste liquid of diphenyl carbonate according to claim 1, characterized in that, In step S2, before the pretreated waste liquid is fed into the light residue removal tower, the pretreated waste liquid is also fed into the feed preheater for preheating. The preheating temperature is 120-130℃, and the time is 1-2 hours.

3. The process for recovering anisole from the light component waste liquid of diphenyl carbonate according to claim 2, characterized in that, In step S3, before the light components discharged from the top of the column are condensed, the light components discharged from the top of the column are also sent to the feed preheater for heat exchange.

4. The process for recovering anisole from the light component waste liquid of diphenyl carbonate according to any one of claims 1-3, characterized in that, In step S1, the adsorbent packed in the adsorption column is a phosphorus-modified molecular sieve, which is prepared by the following method: After the molecular sieve undergoes an ion exchange reaction with an ammonium salt, it is calcined once to obtain an H-type molecular sieve; after the H-type molecular sieve undergoes an impregnation reaction with trimethyl phosphate, it is calcined a second time to obtain the phosphorus-modified molecular sieve.

5. The process for recovering anisole from the light component waste liquid of diphenyl carbonate according to claim 4, characterized in that, The molecular sieve is a Beta molecular sieve, and the ammonium salt is ammonium chloride and / or ammonium nitrate; The mass ratio of the molecular sieve to the ammonium salt is 1:2.5-3.5, and the mass ratio of the H-type molecular sieve to trimethyl phosphate is 1:1.5-2.

6. The process for recovering anisole from the light component waste liquid of diphenyl carbonate according to claim 4, characterized in that, The ion exchange reaction temperature is 70-80℃ and the time is 7-8h; the impregnation reaction temperature is 20-30℃ and the time is 1-1.5h; the first calcination temperature is 500-600℃ and the time is 4-5h; the second calcination temperature is 500-600℃ and the time is 4-5h.

7. The process for recovering anisole from the light component waste liquid of diphenyl carbonate according to claim 4, characterized in that, The adsorption column is obtained by filling the adsorbent into the inner cavity of a column shell sealed with filter screens at both ends; The filter screen has a mesh size of 60-100, and the adsorbent loading is 0.8-0.9 g / cm³. 3 .

8. The process for recovering anisole from the light component waste liquid of diphenyl carbonate according to any one of claims 1-3, characterized in that, In step S1, the volumetric flow rate of the diphenyl carbonate light component waste liquid passed into the adsorption column is 1-2 m³ / s. 3 ·h -1 .

9. The process for recovering anisole from the light component waste liquid of diphenyl carbonate according to any one of claims 1-3, characterized in that, In step S2, the flow rate of the pretreated waste liquid into the light-light ...

10. The process for recovering anisole from the light component waste liquid of diphenyl carbonate according to any one of claims 1-3, characterized in that, In step S3, the working pressure of the product tower is -(50-60) kPa, and the temperature at the top of the tower is 125-145℃.

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