CN114605288A

CN114605288A - High-efficiency separation and recovery process and device for isocyanate polymer

Info

Publication number: CN114605288A
Application number: CN202011404529.1A
Authority: CN
Inventors: 李建峰; 尚永华; 朱付林; 王鹏飞; 吴谦; 王鹏; 曹吉祥; 贾峥瑞; 黎源
Original assignee: Wanhua Chemical Group Co Ltd; Wanhua Chemical Ningbo Co Ltd
Current assignee: Wanhua Chemical Group Co Ltd; Wanhua Chemical Ningbo Co Ltd
Priority date: 2020-12-03
Filing date: 2020-12-03
Publication date: 2022-06-10
Anticipated expiration: 2040-12-03
Also published as: CN114605288B

Abstract

The invention discloses a high-efficiency separation and recovery process and a device of isocyanate polymer, wherein uretdione in the isocyanate polymer is heated in a decomposer to decompose and generate methyl isocyanate monomer, and a large amount of isocyanate polymer is recovered after impurity adsorption. The invention has the advantages of less investment of process equipment, simple operation, reduction of the generation rate of the polymer by more than 50 percent, improvement of the preparation yield and quality of the isocyanate, reduction of solid waste, reduction of the production cost and very high economic benefit and environmental benefit.

Description

High-efficiency separation and recovery process and device for isocyanate polymer

Technical Field

The invention belongs to the technical field of isocyanate production, and particularly relates to an isocyanate separation treatment process for improving the product yield.

Background

An important reaction characteristic of the isocyanate component is its tendency to self-polymerize, which is also a self-sealing of the isocyanate. Under the action of nucleophilic reagent, the isocyanate can shift the lone pair of electrons of isocyanate group carbon atom to nitrogen atom to form complex, and then they are added to other isocyanate to generate self-assembly structure. Particularly, for isocyanate containing benzene ring, because of the influence of electron withdrawing of aromatic ring, NCO group has stronger reactivity, and isocyanate containing benzene ring is polymerized more easily.

In the isocyanate manufacturing process, partial isocyanate is subjected to self polymerization in the heating process to generate various polymeric isocyanates, and the isocyanate monomer can obtain structures such as uretdione, tripolymer, pentamer, carbodiimide, uretonimine and the like through polymerization, so that the content of NCO groups is reduced, and the performance of the product is influenced.

For example, a uretidione ring forming a four-membered heterocyclic structure, such as the following structural formula (I):

wherein R, R' in formula (I) are each independently selected from aliphatic, alicyclic or aromatic hydrocarbon groups having 4 to 15 carbon atoms (e.g., 4 to 5, 7, 8, 10, 13, 15, and the like, each having a single point number of carbon atoms).

Generally, in the isocyanate XDI production process, due to its higher reactivity, about 200 or more kilograms of polymer can be produced per ton of XDI isocyanate produced, and polymer solid waste is difficult to handle.

In order to solve the above problems in the prior art, EP0699659 describes a process and an apparatus for separating a solid residue from a residue solution, wherein up to 20% of a high-boiling hydrocarbon which is inert under the evaporation conditions is added, and the mixture is heated under vacuum to the evaporation temperature, at which point the valuable substances evaporate and condense. The disadvantage of this process is the additional use of high-boiling solvents, which have to be worked up in a further process.

Hydrolysis of the isocyanate distillation residue with water for recovery, especially in the preparation of toluene diisocyanate, has been studied for a relatively long time, for example in US3331876, GB795639, DE2703313 and EP1935877, where the isocyanate distillation residue is hydrolyzed with water at elevated temperature and pressure. In this way, part of the residue is converted into an amine, which, after suitable work-up purification, is recirculated to the phosgenation process again taking part in the photochemical preparation of isocyanates. Wherein, after the TDI residue and water are rapidly converted into solid state, re-liquefaction gradually occurs along with the hydrolysis process. But the solid material prevents the process from continuing. And the valuable isocyanates are in turn hydrolyzed to the starting substances and must be phosgenated again. The method takes isocyanic acid contained in the fluid residue rich in free isocyanate as a raw material, so that the conversion of TDI generated by the action of phosgene to toluenediamine reduces economic benefit and has higher recovery cost.

In actual industrial processes, these polymers are usually subjected to forced drying evaporation using a dryer. The dryer is imported complete equipment, is high in price, can only be used for treating isocyanate TDI solid tar at present, and improves the overall manufacturing cost and the occupied area. Secondly, in the process of treatment, as the substance to be treated moves in the upper and lower spaces in the whole separator, the whole space requiring the separator needs to maintain a higher reaction temperature, thereby causing higher energy consumption and great operation difficulty.

Because the products are provided with motor and other moving equipment, strict sealing is needed when materials enter the cracking device for safety, a large number of sealing devices are needed, and production accidents are easy to occur once sealing elements are damaged.

In the production process, various operation conditions are required to be adjusted according to the physical properties of raw materials, so that the device can be stably operated, the consumption of the raw materials and energy is reduced, and the production cost is reduced, which is a difficult problem for enterprises.

Another way of disposing of the heavy isocyanate components is to discharge them directly as waste in one operation. Because the waste isocyanate belongs to dangerous solid waste, a special unit is required to carry out incineration and other treatments, a large amount of nitrogen-containing tail gas is generated, and valuable product isocyanate is burnt away. Thus not only increasing the production cost, but also polluting the environment.

In addition, some hydrolysis chlorine is inevitably generated during the preparation of isocyanate due to the use of high-activity phosgene during the preparation. The index of the hydrolysis chlorine is an important index for controlling the quality of isocyanate in the isocyanate manufacturing industry. The hydrolysis chlorine contains tar, ureas, unreacted phosgene, hydrogen chloride and other compounds containing chlorine components (e.g., carbamoyl chloride, ureido-formyl chloride, etc.). In particular, the type and content of chlorine-containing impurities can directly cause the isocyanate activity to fluctuate, thereby affecting the repeatability and stability of the product. All after recovery of the highly hydrolysable chlorine polymer components, how to match the respective processes is critical.

Most of the chlorine-containing impurities are removed by inert gas purging and distillation, as reported in EP482490, CN1064074A, US3912600, US3219678, etc., while the remaining part is relatively stable and can remain in the isocyanate product. These chlorine-containing impurities occur both in aromatic isocyanates (e.g., MDI, TDI, etc.) and in aliphatic and cycloaliphatic isocyanates (e.g., HDI, HMDI, etc.). Thus, the fundamental removal of the hydrolyzed chlorine impurities from isocyanates is also a problem to be solved. At present, the final removal of this type of species seems to be the most difficult step for the purification of isocyanate monomers by distillation, since the major impurities to be removed, whose vapour pressure is close to that of isocyanate monomers, make the removal of these chlorine-containing impurities particularly difficult.

In addition, for treating heavy isocyanate components, a crude product of a separation system has high content of hydrolysable chloride compounds and huge content after pyrolysis, and is difficult to directly recover to obtain a qualified product.

Therefore, in view of the stability of the cracking production process and the economical efficiency of production, there is still a need for a process and an apparatus for separating and recovering isocyanate polymer efficiently to improve the economic and environmental benefits.

Disclosure of Invention

In order to solve the problems, the invention provides an efficient separation and recovery process of an isocyanate polymer, which depolymerizes an industrial byproduct polymer, can effectively reduce the content of uretdione to improve the yield, and simultaneously performs adsorption treatment on impurities to obtain a product meeting the quality requirements in the fields of coatings, adhesives, optics and the like.

It is a further aspect of the present invention to provide apparatus for such an efficient separation and recovery process.

In order to achieve the above purpose, the invention adopts the following technical scheme:

a high-efficiency separation and recovery process of isocyanate polymer comprises the following steps:

1) feeding the isocyanate material with high polymer content into a depolymerizer for high-temperature depolymerization to obtain a micromolecule isocyanate crude product;

2) condensing the micromolecule isocyanate crude product through a heat exchanger, then feeding the micromolecule isocyanate crude product into a high-speed rotary adsorption reactor, and adsorbing to reduce the impurity content to obtain an intermediate product;

3) and (3) after the intermediate product exchanges heat with the crude product of the micromolecule isocyanate in the step 2) through a heat exchanger, sending the intermediate product to a rectification process for refining, and obtaining the high-quality diisocyanate monomer.

In a specific embodiment, the depolymerization temperature in the depolymerizer in the step 1) is 150-280 ℃, preferably 170-250 ℃; the pressure in the depolymerizer is negative pressure, preferably 0.1-10 kpa, more preferably 1-5 kpa; the retention time of the isocyanate material with high polymer content is 0.5-10 min, preferably 1-5 min.

In a specific embodiment, the isocyanate material in the step 1) is dispersed and atomized by inert gas flow through a nozzle to form liquid drops, and the given particle size of the liquid drops is less than or equal to 500 microns, preferably less than or equal to 50 microns; preferably, the inert gas is selected from one or more of nitrogen, carbon dioxide, argon, preferably nitrogen; the introduction amount of the inert gas is 1-10 times, preferably 3-5 times of the mole number of the isocyanate material.

In a specific embodiment, the content of the small molecule isocyanate monomer obtained after depolymerization in step 1) is 30 to 90 wt%, preferably 50 to 80 wt%, based on the total mass of the isocyanate.

In a specific embodiment, the temperature in the high-speed rotary adsorption reactor in the step 2) is 25-85 ℃; the rotating speed of a high-speed rotating adsorption disc of the high-speed rotating adsorption reactor is 100-1000 rpm, preferably 300-800 rpm; the flow velocity of the micromolecule isocyanate crude product entering the high-speed rotary adsorption device is 0.1-1 m/s.

In a specific embodiment, a solid adsorbent is arranged in a selected high-speed rotating adsorption disc, and a layer of inert porcelain pills is placed on the inner layer and the outer layer of the solid adsorbent; preferably, the solid adsorbent is selected from any one or more of metal oxides, such as copper oxide, iron oxide, boron oxide, magnesium oxide, barium oxide, calcium oxide and silicates, aluminosilicates, borosilicates, zeolites, ion exchangers, activated carbon, silica gel.

In a particular embodiment, the diisocyanate is selected from aliphatic or aromatic diisocyanates; preferably, the aliphatic diisocyanate is one or more of hexamethylene diisocyanate, methylcyclohexyl diisocyanate, dimethylcyclohexyl diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornane diisocyanate or cyclohexyldimethylene diisocyanate; the aromatic isocyanate is one or more of toluene diisocyanate, p-phenylene diisocyanate or xylylene diisocyanate; more preferably, the diisocyanate is cyclohexyl dimethylene diisocyanate or xylylene diisocyanate.

On the other hand, the device for the high-efficiency separation and recovery process of the isocyanate polymer comprises a depolymerizer, a heat exchanger and a high-speed rotary adsorption reactor, wherein an outlet of the depolymerizer is connected with a heat medium inlet of the heat exchanger, a heat medium outlet of the heat exchanger is connected with an inlet of the high-speed rotary adsorption reactor, an outlet of the high-speed rotary adsorption reactor is connected with a refrigerant inlet of the heat exchanger, and a refrigerant outlet of the heat exchanger is connected with an intermediate product tank.

In a specific embodiment, the depolymerizer is a tubular reactor, the top of the depolymerizer is provided with a vaporization spray head, a baffle plate is arranged in an inner tube of the depolymerizer, and the outlet of the depolymerizer is provided with a wire mesh demister; preferably, the baffle plate is a sector baffle plate with a cross section of 1/3-1/4, the sector baffle plate is spirally arranged from an inlet position to an outlet position, the sector baffle plate has a downward inclination angle of 10-30 degrees, and the baffle plate is provided with at least one round hole of 1-20 mm, preferably 3-10 mm.

In a specific embodiment, the high-speed rotary adsorption reactor comprises a tank body and a rotary adsorption rotary disc arranged in the middle of the tank body, wherein the tank body is of a jacket structure; 2-10 rotary adsorption rotary tables are arranged, the upper layer and the lower layer are distributed in the inner cavity of the device, and each adsorption rotary table is provided with a solid adsorbent; and a layer of inert porcelain pills is placed on the inner layer and the outer layer of the solid adsorbent and is used for protecting the adsorbent.

By adopting the technical scheme, the invention has the following beneficial effects:

(1) the process of the invention adds the vaporizing spray head in the depolymerizer, utilizes the liquid atomization technology to better vaporize the feed liquid and depolymerize at high temperature, and compared with the distillation method of the traditional process, the process can greatly accelerate the processing speed and realize the recovery of more than 50 percent of isocyanate monomers in isocyanate polymers. The depolymerizer and the high-speed rotary adsorption reactor have the advantages of large treatment capacity, high separation efficiency, small equipment volume, short retention time and small liquid holdup, thereby realizing large separation treatment capacity and obvious treatment effect.

(2) The process of the invention adopts a high-speed rotary adsorption reactor, and utilizes a dechlorination technology to effectively reduce the content of chlorine impurities in the product to 300ppm, thereby meeting the quality requirement of the diisocyanate product. Meanwhile, the pyrolysis steam is subjected to heat exchange through the heat exchange device, and energy is efficiently utilized. The method can prepare the isocyanate with qualified performance at lower cost and higher yield.

(3) The process method and the device have the advantages of high automation degree, easy operation and control of the process, low cost, no need of hydrolysis treatment, reduction of environmental hazard, improvement of operation environment, realization of environment-friendly and operation-friendly synthesis process, high product yield, low production cost, easy realization of industrial production, and great implementation value and social, economic and environmental benefits.

Drawings

FIG. 1 is a schematic view of the recycling apparatus of the present invention.

FIG. 2 is a schematic cross-sectional view of the inner depolymerization tube of the decomposer according to the present invention.

FIG. 3 is a schematic view of a fan baffle in a depolymerization tube provided in accordance with the present invention.

Fig. 4 is a schematic cross-sectional view of a rotary adsorption disk provided by the present invention.

The device comprises a raw material tank 1, a raw material delivery pump 2, a depolymerizer 3, a crude product tank 4, a demister 5 (gas phase outlet), a condenser 6, a crude product delivery pump 7, an absorber 8 inlet, a high-speed rotary adsorption reactor 9, an adsorption turntable 10, an intermediate product collecting tank 11, an intermediate product delivery pump 12, an intermediate product tank 13, a baffle plate fixing rod 14, a depolymerizer 15 pipe wall, a fan-shaped baffle plate 16, a baffle plate hole 17, a jacket 18, a distributor 19, a collector 20, an adsorbent 21, inert ceramic balls 22 and an adsorption disc supporting plate 23.

Detailed Description

The following examples will further illustrate the method provided by the present invention in order to better understand the technical solution of the present invention, but the present invention is not limited to the listed examples, and should also include any other known modifications within the scope of the claims of the present invention.

As shown in figure 1, a device for high-efficiency separation and recovery process of isocyanate polymer, isocyanate polymer raw material in a raw material tank 1 is sent to a top inlet of a depolymerizer 3 through a raw material conveying pump 2, tiny liquid drops formed by atomization of a vaporizing spray nozzle at the top are sent to a tube pass of the depolymerizer 3 to be depolymerized at high temperature to form small molecular isocyanate monomer, part of the isocyanate polymer which is not depolymerized flows into a crude product tank 4 from a bottom outlet of the depolymerizer 3, the formed small molecular isocyanate monomer gas phase material is sent to a condenser 6 through a foam remover (gas phase outlet) 5, the gas phase material is changed into liquid phase after heat exchange and condensation, the liquid phase is sent to an absorber inlet 8 of a high-speed rotary adsorption reactor 9 through a crude product conveying pump 7, the liquid phase flows into an adsorption rotary disc 10 through a distributor 19, and the liquid phase is uniformly distributed and contacted with an adsorbent layer arranged on the adsorption rotary disc 10 under the drive of the high-speed rotary adsorption rotary disc 10, chlorine-containing impurities and the like in the liquid phase are adsorbed, the liquid phase is gradually thrown out under the action of centrifugal force, is collected by a collector 20 and flows into an intermediate product collecting tank 11, and is sent to a condenser 6 through an intermediate product conveying pump 12 to exchange heat with the gas phase extracted from a gas phase outlet of a depolymerizer 3 so as to condense the gas phase material, and the intermediate product material flow enters an intermediate product tank 13 after being heated and optionally enters a rectification process to be refined to obtain a pure diisocyanate.

The device for the high-efficiency separation and recovery process of the isocyanate polymer is mainly formed by sequentially connecting a raw material tank 1, a depolymerizer 3, a condenser 6 and a high-speed rotary adsorption reactor 9, wherein the connection can be directly realized by pipelines, and a corresponding storage tank (buffer tank), a motor, a delivery pump, related auxiliary pipelines, valve instruments and the like can also be arranged in the middle according to needs. These general chemical tanks, pumps, valves, meters, etc. are the common auxiliary facilities in the chemical field.

In the invention, the top of the depolymerizer 3 is provided with a vaporizing spray head, the depolymerizer is a tubular reactor, the pyrolysis liquid gas (isocyanate polymer raw material) of the depolymerizer passes through a tube pass, and the high-temperature medium passes through a shell pass. The depolymerization temperature is generally controlled to be between 150 and 280 ℃. When the depolymerizer is in operation, the isocyanate polymer raw material in the raw material tank 1 is pressurized and fed to the vaporization nozzle by the raw material feed pump 2. In the depolymerizer, atomized small droplets are heated by a high-temperature depolymerizing tube, then the macromolecular raw materials are pyrolyzed and polymerized into micromolecular isocyanate under the condition of high temperature and no oxygen, gaseous micromolecular isocyanate monomers enter a heat exchanger and are condensed into liquid, and the non-depolymerized uretdione and the macromolecular polymer are enriched in a residue tank 4.

In particular, the vaporization nozzle is located in the center of the concentric rings of the depolymerizer; the spray head is at least one of air atomization, a solid cone and a spiral spray head; the isocyanate polymer raw material is dispersed and atomized by inert gas flow through a spray head. The inert gas is selected from one or more of nitrogen, carbon dioxide and argon, and is preferably nitrogen. The introduction amount of the inert gas is 1 to 10 times, preferably 3 to 5 times of the mole number of the raw material. In the specific working process, inert carrier gas is firstly introduced to enable the decomposer to reach the set pressure, then raw materials are introduced, and the flow is adjusted to achieve the vaporization effect.

Specifically, the isocyanate polymer raw material is pressurized to 0.3-1.5 MPa by a raw material delivery pump and delivered to a wide-angle solid cone nozzle, the spraying angle of the nozzle is 50-90 degrees, and the given particle size of atomized liquid drops is less than or equal to 500 microns, preferably less than or equal to 50 microns. Generally, smaller droplets are more effective at high temperature depolymerization decomposition.

Wherein, the vaporization shower nozzle can be detachable construction, according to the inlet pressure condition that rises, judges whether the spout blocks up to regularly clear up the shower nozzle. The temperature at which the depolymerization device is heated varies depending on the isocyanate material, for example, xylylene diisocyanate is heated to about 190 ℃ and dicyclohexylmethane diisocyanate is heated to about 220 ℃. However, in view of preventing thermal deterioration, the depolymerization temperature is preferably 150 to 280 ℃, more preferably 170 to 250 ℃, the residence time is 0.5 to 10min, more preferably 1 to 5min, and the pressure in the depolymerization unit is kept at a negative pressure, preferably 0.1 to 10kpa, more preferably 1 to 5kpa, under an oxygen-free condition.

As shown in fig. 2 and 3, a baffle plate is arranged in the inner tube of the depolymerizer, the baffle plate can be of a fan-shaped structure, a plurality of fan-shaped baffle plates 16 are spirally arranged from an inlet position to an outlet position and are fixed through a baffle plate fixing rod 14, the arc-shaped edge of each fan-shaped baffle plate 16 is abutted against the pipe wall 15 of the depolymerizer to play a certain supporting role, a plurality of baffle plate holes 17 are formed in each baffle plate, liquid drops sprayed by a vaporization spray head flow through each baffle plate from top to bottom, so that gas-liquid materials spirally downwards layer by layer, raw materials are subjected to sufficient heating reaction, and polymers are sufficiently depolymerized and decomposed. The baffle plate is formed by a plurality of fan-shaped baffle plates with 1/3-1/4 tube body cross sections and is spiral from an inlet position to an outlet position. The fan-shaped baffle plate has a downward inclination angle of 10-30 degrees, and a circular hole of 1-20 mm, preferably 3-10 mm, is arranged on the baffle plate.

As a wire mesh demister arranged at the outlet of the depolymerizer, for example, a 5-50-mesh stainless steel wire mesh is selected, isocyanate monomer gas with liquid foam is prevented from being carried with macromolecular polymers by the demister.

The content of the micromolecule isocyanate monomer obtained after depolymerization is 30-90 wt% of the total amount, preferably 50-80 wt%. Correspondingly, the content of residual liquid obtained by depolymerization is 5-70 wt%, preferably 10-50 wt% based on the total amount.

Next, the small molecule isocyanate monomer obtained by depolymerization passes through a condenser 6, and is condensed from a gaseous state to a liquid state. The crude product is conveyed to a high-speed rotary adsorption reactor 9 by a crude product conveying pump 7, and impurities are adsorbed by an adsorbent to improve the product quality. In the invention, the temperature of the micromolecule isocyanate monomer gas phase material entering the condenser 6 is 100-200 ℃, the temperature after the micromolecule isocyanate monomer gas phase material is condensed into liquid phase is 30-90 ℃, and the micromolecule isocyanate monomer gas phase material is sent into a high-speed rotary adsorption reactor; meanwhile, the temperature of the intermediate product conveyed to the condenser 6 from the intermediate product conveying pump 12 is 25-85 ℃, and the outlet temperature after heat exchange is 35-130 ℃.

In the method of the invention, the high-speed rotary adsorber 9 is a novel equipment technology capable of greatly enhancing the transfer and micro-mixing processes, and the basic principle is to accelerate the mass transfer speed between liquid and liquid molecules by using the rotary shearing action. Under the condition of high-speed rotation, the molecular diffusion and interphase mass transfer processes among different small molecules are much faster than those under the ordinary condition, and the liquid polymer rapidly flows to the edge under the action of centrifugal force, so that the liquid polymer flows through the baffle ring. The liquid is in flowing contact with the adsorbent, and huge shearing force enables the liquid to be broken into films, filaments and drops, so that a huge and rapidly updated phase interface is generated, the diffusion distance between different phase materials is greatly shortened, and the phase mass transfer rate is greatly enhanced compared with that of the traditional tower phase mass transfer process.

The filtration of the crude product by the adsorbent in the high-speed rotary adsorption reactor of the present invention can be carried out in a continuous or batch manner. The shell of the high-speed rotary adsorption reactor for adsorption is welded with a jacket, or the high-speed rotary adsorption reactor is of a jacket structure and is provided with a heat exchange jacket 18, and a heat exchange medium is introduced into the jacket 18, so that the temperature of the high-speed rotary adsorption reactor is controlled to be 25-85 ℃. The equipment also comprises a motor and a transmission mechanism, 2 or more than 2 adsorption turntables, and a plurality of adsorption turntables are distributed in the inner cavity of the device in an up-and-down layer manner.

In the invention, the high-speed rotating adsorption reactor comprises a tank body and an adsorption rotary disc arranged in the middle of the tank body, wherein an adsorbent layer is arranged on the adsorption rotary disc. A plurality of inert porcelain pills are respectively placed on the inner layer and the outer layer of the adsorbent layer, for example, a layer of inert porcelain pill is placed on the inner layer and the outer layer of the adsorbent layer, and the inert porcelain pills are used for protecting the adsorbent and preventing the adsorbent from being quickly pulverized and lost due to physical impact.

The high-speed rotary adsorption reactor 9 drives the adsorption turntable 10 to rotate at a high speed through an electrode, and the motor is a variable frequency motor, and mainly has the functions of providing different speeds to drive the adsorption turntable to rotate, realizing the change of the turbulent motion strength of liquid, and adjusting the diffusion distance and the retention time of materials. The rotating speed of an adsorption rotating disc of the high-speed rotary adsorption reactor is 100-1000 rpm, preferably 300-800 rpm, and the flow speed of materials entering the adsorption rotating disc is 0.1-1 m/s.

Particularly, a distributor 19 and a collector 20 are also arranged in the tank body of the high-speed rotary adsorption reactor; the top of the tank body is provided with an inlet 8, and the inlet of the tank body is provided with a distributor 19 for uniformly distributing micromolecule isocyanate liquid phase fluid; the bottom of the tank is provided with a collector 20, for example a drip pan, for collecting the intermediate product.

When the device is used, process liquid enters the tank body from the inlet 8 at the upper part of the tank body of the high-speed rotary adsorption reactor, is uniformly distributed to the ceramic pill part of the first inner layer through the distributor 19 in the tank body, the liquid is diffused to the outer layer under the action of centrifugal force, and the uniform gap of the ceramic pill also plays a role in distributing the process liquid. The adsorbent filled in the adsorbent layer generates adsorption reaction, and the liquid after the reaction flows through the outer layer ceramic pill of the adsorbent layer to the collector 20 and enters the product storage tank 11 through the outlet of the high-speed rotary adsorption reactor.

In the present invention, as shown in fig. 4, each adsorption turntable is provided with an adsorbent 21 therein and a support plate 23 therein, and in the adsorption process of the decomposition liquid, one adsorption turntable and the other adsorption turntable are connected in series and operate, and the turntables are detachable. And replacing the adsorbent of the absorption turntable in time according to the quality of the intermediate product of the effluent. If need change, at first change first order absorption carousel, shift the lower floor and adsorb the carousel and use to the upper strata, realize make full use of adsorbent activity to effectively prolong adsorbent life. Through the arrangement of the distributor, the liquid flow entering the adsorber tool is ensured to be uniformly distributed, so that the adsorbent can exert a good adsorption effect and is not easy to locally penetrate.

Furthermore, inert alumina porcelain pill layers 22 are arranged on the inner layer and the outer layer of the adsorbent, the alumina porcelain pills are uniformly placed, gaps of the alumina porcelain pills can play a role in effectively distributing chlorine-containing liquid flow, and meanwhile, the porcelain pills positioned at the lower part of the adsorbent have supporting and protecting roles, so that the chlorine-containing liquid flow is promoted to uniformly pass through the adsorbent layer, and the adsorbent is prevented from being pulverized. The solid adsorbent selected is a metal oxide such as copper oxide, iron oxide, boron oxide, magnesium oxide, barium oxide, calcium oxide and silicates, aluminosilicates, borosilicates, zeolites, ion exchangers, activated carbon and silica gel or mixtures of these substances.

The activity of the adsorbent decreases with increasing duration of operation, and the adsorbent needs to be replaced after a certain duration of operation. In the invention, the treatment capacity of the adsorbent is more than or equal to 150g/g, namely, each gram of the adsorbent can treat more than 100g of micromolecular isocyanate material. The particle size of the adsorbent used is preferably 1 to 10mm, particularly preferably 2 to 6 mm. The adsorbent particles are preferably cylindrical in shape because oversized particles have a small specific surface area, while undersized particles are susceptible to dusting and loss of adsorbent.

Furthermore, the adsorption turntable is provided with a 316L stainless steel wire net for filling an adsorbent and inert ceramic balls, and the 316L stainless steel wire net is a 3-5-layer 50-mesh stainless steel wire net.

By arranging the jacket heat exchanger, the temperature of the adsorption reaction is controlled, and the adsorption reaction is usually carried out at a temperature of less than 120 ℃, preferably less than 90 ℃, and particularly preferably 40-80 ℃.

The adsorbed product enters a heat exchanger 6 to exchange heat with a depolymerizer gas-phase crude product, after the heat exchange with the product, the cracking monomer is condensed into a liquid state from a gas state, the temperature is reduced to 30-90 ℃, the product utilizes the waste heat of the depolymerizer and is raised to 35-130 ℃, the product enters rectification for purification after being buffered in an intermediate product tank, a rectification feeding preheater is omitted, a qualified product is obtained, preheating steam is saved, and therefore energy consumption is saved.

The invention provides a high-efficiency separation and recovery process of an isocyanate polymer, which is characterized by comprising the following steps:

1) the polymer, especially isocyanate material with high content of uretdione, is sent into a depolymerizer for high-temperature depolymerization to obtain a micromolecule isocyanate crude product.

Wherein the depolymerization temperature in the depolymerizer is 150-280 ℃, and preferably 170-250 ℃; the pressure in the depolymerizer is negative pressure, preferably 0.1-10 kpa, and more preferably 1-5 kpa; the retention time is 0.5-10 min, preferably 1-5 min.

Wherein, the isocyanate material is dispersed and atomized by inert gas flow through a nozzle to form liquid drops, and the given particle size of the liquid drops is less than or equal to 500 mu m, preferably less than or equal to 50 mu m; preferably, the inert gas is selected from one or more of nitrogen, carbon dioxide, argon, preferably nitrogen; the introduction amount of the inert gas is 1-10 times, preferably 3-5 times of the mole number of the isocyanate material.

The content of the micromolecular isocyanate monomer obtained after depolymerization is 30-90 wt%, preferably 50-80 wt% based on the total mass of the isocyanate.

2) And condensing the micromolecule isocyanate crude product through a heat exchanger, then feeding the micromolecule isocyanate crude product into a high-speed rotary adsorption reactor, and adsorbing to reduce the impurity content to obtain an intermediate product.

Wherein the temperature in the high-speed rotary adsorption reactor is 25-85 ℃; the rotating speed of a high-speed rotating adsorption disc of the high-speed rotating adsorption reactor is 100-1000 rpm, preferably 300-800 rpm; the flow velocity of the micromolecule isocyanate crude product entering the high-speed rotary adsorption device is 0.1-1 m/s.

Wherein, a solid adsorbent is arranged in the selected high-speed rotating adsorption disc, and a layer of inert porcelain pills is placed on the inner layer and the outer layer of the solid adsorbent; preferably, the solid adsorbent is selected from any one or more of metal oxides, such as copper oxide, iron oxide, boron oxide, magnesium oxide, barium oxide, calcium oxide and silicates, aluminosilicates, borosilicates, zeolites, ion exchangers, activated carbon, silica gel.

Wherein the diisocyanate is selected from aliphatic or aromatic diisocyanates; preferably, the aliphatic diisocyanate is one or more of hexamethylene diisocyanate, methylcyclohexyl diisocyanate, dimethylcyclohexyl diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornane diisocyanate or cyclohexyldimethylene diisocyanate; the aromatic isocyanate is one or more of toluene diisocyanate, p-phenylene diisocyanate or xylylene diisocyanate; more preferably, the diisocyanate is cyclohexyldimethylene diisocyanate or xylylene diisocyanate.

The invention also provides a method for improving the yield of the industrial production of isocyanate and maximizing the value of the isocyanate product produced by depolymerization, wherein the method comprises the following steps:

in the course of separating the pure isocyanate, the isocyanate is self-polymerized and concentrated at the separation temperature to give a crude product having a high uretdione content, by separation methods known in the isocyanate preparation art.

The first step is as follows: and (4) feeding the material to be treated into a depolymerizer, and controlling related parameters to obtain a coarse decomposition liquid.

The second step is that: and (4) enabling the decomposition liquid to enter a high-speed rotary adsorption reactor, controlling related parameters, reducing the content of impurities, and obtaining an intermediate product.

As a preferable scheme, the invention also comprises a third step of rectifying and refining the components separated and collected in the second step to obtain the high-quality diisocyanate monomer with the content of more than 99.50 percent.

The term "uretdione" as used herein means, unless otherwise specified, uretdione of isocyanate.

The following experimental examples of the invention were analyzed using the following instruments:

the content of isocyanate monomer, uretdione and polymer is determined by Gel Permeation Chromatography (GPC), and the analysis conditions are as follows: agilent1260 (1260 ALS autosampler, 1260TCC column oven, 1260RID differential detector).

The hydrolysis chloride is that after the reflux alcoholysis of a sample, water is added for hydrolysis, and two substances of carbamoyl chloride and hydrogen chloride in the product react with alcohol and water to generate urea, carbamate, carbon dioxide and chloride ions. After acidification with nitric acid, the chloride ions in the sample were titrated with a silver nitrate standard solution. The chlorine hydrolysis method is referred to as "GB/T12009.4-2016 aromatic isocyanate part 2 for plastic polyurethane production: the method is suitable for measuring the content of the isocyanate in isocyanate series samples such as crude products, tar and the content of the isocyanate.

The equipment used in the invention is a general chemical reactor, a heat exchanger, a storage tank, a pump and the like, and the material is a stainless steel 316L material which is resistant to isocyanate corrosion. The used equipment is manufactured by Wanhua Mucun chemical mechanical processing company, the diameter of the rotating disk is 500mm, the rotating disk is double-layer, the volume of the separating cylinder is 1000L, and the power of the motor is about 3 kilowatts. The atomizing spray head used spray J series air atomizing nozzle 1/4J from Sprey, USA.

Example 1

In the separation of XDI (xylylene diisocyanate), a large amount of XDI polymer was produced, and the mass percentage was such that the monomer content was 25.9%, the uretdione content was 61.8%, the other high polymer was 12.3%, the uretdione content was high, the solid content was at room temperature, and the hydrolysis chlorine was 3508 ppm.

An XDI polymer raw material was taken and thermally depolymerized by adding it to the reaction tube of the present invention. Feedstock was sprayed into the depolymerizer using a Spray air atomization nozzle 1/4J. Nitrogen is selected for atomization, and the introduction amount is 3 times of the mole number of the raw materials. Pressurizing the raw materials to 0.5MPa by a delivery pump, spraying the raw materials into a depolymerizer, and regulating the pressure and temperature conditions of depolymerizer equipment to depolymerize. Gaseous XDI monomer enters a condenser to be condensed to be within 90 ℃, the obtained reaction liquid is subjected to statistics of hydrolytic chlorine and monomer content, and specific experimental results are shown in Table 1.

Examples 2 to 10 and comparative examples 1 to 3

The same procedure as in example 1 was repeated except that the starting materials used were the same as in example 1, the XDI polymer depolymerization reactions under different process conditions were continuously carried out, and the obtained reaction solution was subjected to statistics of the contents of hydrolysis chlorine and monomer except that the XDI depolymerization conditions were different. The results are shown in table 1.

TABLE 1

Example 11

The preferable separation conditions were selected and the adsorption reaction was examined using an intermediate xylylenediisocyanate having a hydrolysis chlorine of 7320 ppm.

The depolymerized material is sent to a high-speed rotary adsorption device at the flow rate of 0.5m/s, the rotating speed of an adsorption disc is controlled at 500rpm, and impurity adsorption reaction is carried out.

The self-synthesized alkali metal oxide supported adsorbent is adopted, the granularity of the adsorbent is 2 x 10mm, the bulk density is 0.8kg/L, the radial crushing strength is more than or equal to 60N/cm, the abrasion is less than or equal to 3%, the thickness of a filling disc is 50mm, and the filling volume of a single absorption disc is 10L.

The preparation of the adsorbent comprises the following steps:

1) modification of activated carbon: weighing the dehydrated specific surface area of 1000m²(g), a bulk weight of 0.51kg/L, a particle size of 200 meshAnd (3) placing the activated carbon powder into a potassium hydroxide solution with the mass concentration of 18% according to the solid-to-liquid ratio of 1:5, and soaking at 60 ℃ for 10 h. And after the reaction is finished, filtering, separating, washing with deionized water until the pH value is 6-7, and finally drying at 80 ℃.

2) Molding: weighing the following raw materials in percentage by mass: 60 parts of activated carbon, 10 parts of sodium carbonate, 15 parts of copper oxide, 2 parts of propyl cellulose, 3 parts of ammonium bicarbonate and 10 parts of sodium bicarbonate. And then adding deionized water to adjust the humidity, extruding and molding by a phi 2 x 10mm mold, and finally drying in a blast oven at 60 ℃ for 10 hours to obtain a semi-finished product of the activated carbon-based adsorbent.

3) And (3) activation: and roasting and activating the semi-finished product of the activated carbon-based adsorbent at the absolute pressure of 20kpa and the temperature of 350 ℃ for 10 hours to obtain the metal oxide carbon-loaded adsorbent.

An excessively high temperature leads to a further polymerization of the monomers, the operating temperature of the adsorption being 25 ℃ and the operating pressure being atmospheric. After heat exchange by the condenser, the crude product and the intermediate product are compared and analyzed. And (4) feeding the separated monomer into a rectifying tower to obtain a product.

Examples 12 to 20 and comparative examples 4 to 5

The same procedure as in example 11 was carried out except that the starting materials used were the same as in example 11, the XDI polymer adsorption reaction under different process conditions was continuously carried out, and the obtained reaction liquid was subjected to statistics of hydrolysis chlorine, except that the XDI adsorption conditions were different, and the results are shown in Table 2.

TABLE 2

And continuously analyzing the extracted intermediate product, and evaluating the penetration condition of the adsorbent according to the condition of the chlorine content of the intermediate product. As can be seen from Table 2, when the treatment capacity of the adsorbent reaches 150g/g, the hydrolyzed chlorine is still less than or equal to 500ppm, and then the qualified isocyanate monomer can be obtained through the subsequent rectification, and the index is still acceptable.

And (3) carrying out vacuum rectification on the treated monomer under the rectification pressure of 330pa and the distillation temperature of 138 ℃ to obtain the substance, namely the XDI product.

Example 21

In the separation of H₆XDI (cyclohexyldimethylene diisocyanate) which generates a large amount of H₆The XDI polymer had a composition containing 73.9% of monomer, 22.8% of uretdione and 3.3% of other high polymer, a high uretdione content, a viscous liquid at room temperature, and 1908ppm of hydrolytic chlorine.

Get H₆XDI polymer feed, by feeding into the depolymerizer of the present invention, is thermally depolymerized. Feedstock was sprayed into the depolymerizer using a Spray air atomization nozzle 1/4J. Nitrogen is selected for atomization, and the introduction amount is 2 times of the mole number of the raw materials. Pressurizing the raw materials to 0.4MPa by a delivery pump, spraying the raw materials into a depolymerizer, and regulating the pressure and temperature conditions of depolymerizer equipment to depolymerize. Gaseous H₆XDI monomer enters a condenser to be condensed to 110 ℃, the obtained reaction liquid is subjected to statistics of hydrolytic chlorine and monomer content, and specific experimental results are shown in Table 3.

Examples 22 to 31 and comparative examples 6 to 8

The starting materials used were the same as in example 21, and H was carried out continuously under different process conditions₆XDI polymer depolymerization reaction, the obtained reaction solution was subjected to statistics of content of hydrolysis chlorine and monomer, except that H therein₆The same procedure as in example 21 was carried out in this comparative example except that the XDI depolymerization conditions were different. The results are shown in table 3.

TABLE 3

Example 32

The preferable separation conditions were selected and the adsorption reaction was examined using an intermediate product of cyclohexyldimethylene diisocyanate having a hydrolytic chlorine of 1560 ppm.

The material is sent to a high-speed rotary adsorption device at the flow rate of 0.5m/s, the rotating speed of an adsorption disc is controlled at 600rpm, and impurity adsorption reaction is carried out. The self-synthesized alkali metal oxide supported adsorbent is adopted, the granularity of the adsorbent is 2 x 10mm, the bulk density is 0.8kg/L, the radial crushing strength is more than or equal to 60N/cm, the abrasion is less than or equal to 3%, the thickness of a filling disc is 50mm, and the filling volume of a single absorption disc is 10L.

The preparation of the adsorbent comprises the following steps:

1) modification of activated carbon: prepared by the same procedure as example 11.

2) Molding: weighing the following raw materials in percentage by mass: 60 parts of activated carbon, 10 parts of sodium carbonate, 15 parts of zinc oxide, 2 parts of ethyl cellulose, 3 parts of ammonium bicarbonate and 10 parts of sodium bicarbonate. And then adding deionized water to adjust the humidity, extruding and molding by a phi 2 x 10mm mold, and finally drying in a blast oven at 60 ℃ for 10 hours to obtain a semi-finished product of the activated carbon-based adsorbent.

3) And (3) activation: prepared by the same procedure as example 11.

The treated monomer is vacuum rectified under the rectification pressure of 190pa and the distillation temperature of 115 ℃ to obtain a substance H₆XDI products.

Continuously carrying out H under different process conditions₆XDI adsorption reaction, and the obtained reaction liquid is subjected to hydrolysis chlorine statistics, and specific experimental results are shown in Table 4.

Examples 33 to 41 and comparative examples 9 to 10

The starting materials used were the same as in example 32, and H was carried out continuously under different process conditions₆XDI polymer adsorption reaction, and subjecting the obtained reaction solution to statistics of hydrolysis chlorine, wherein H is different from H₆The comparative example was carried out in the same manner as in example 32 except that the XDI adsorption conditions were different, and the results are shown in Table 4.

TABLE 4

Serial number	Adsorbent handling capacity g/g	Adsorption temperature/. degree.C	Adsorption disc rotation speed/rpm	Hydrolyzed chlorine/ppm
					Example 32	10	25	600	195
Example 33	10	50	600	158
					Example 34	10	60	600	116
Example 35	10	85	600	105
					Example 36	1	60	600	89
Example 37	50	60	600	125
					Example 38	100	60	600	157
Example 39	150	60	600	170
					Example 40	10	60	300	166
EXAMPLE 41	10	60	1000	193
					Comparative example 9	200	60	600	245
Comparative example 10	10	60	1500	402

And continuously analyzing the extracted intermediate product, and evaluating the penetration condition of the adsorbent according to the condition of the chlorine content of the intermediate product. As can be seen from Table 4, when the treatment capacity of the adsorbent reaches 150g/g, the hydrolytic chlorine is still less than or equal to 200ppm, and the index is still acceptable.

The experimental data show that the process is stable, the depolymerization of the polymer is enhanced at high temperature, and the full contact between the isocyanate and the adsorbent is ensured by the design of the high-speed rotary adsorption device. The process of the invention is used for XDI and H₆The yield of isocyanate such as XDI and the like is obviously improved, a large amount of polymers can be recycled, proper technological parameter conditions are controlled, the recovery rate is over 50 percent, the content of hydrolytic chlorine of the recycled micromolecule isocyanate product is lower than 500ppm, H is higher than H, and the like₆The hydrolytic chlorine content of XDI is lower than 200ppm, the index of obtaining qualified isocyanate monomer by rectification again is met, the waste liquid discharge is reduced, the economy is improved, meanwhile, the environmental hazard can be reduced, the operation environment is improved, and the environment-friendly and operation-friendly synthesis process is realized.

While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. It will be appreciated by those skilled in the art that modifications or adaptations to the invention may be made in light of the teachings of the present specification. Such modifications or adaptations are intended to be within the scope of the present invention as defined in the claims.

Claims

1. An efficient separation and recovery process of isocyanate polymer is characterized by comprising the following steps:

2. The process for efficiently separating and recovering an isocyanate polymer according to claim 1, wherein the depolymerization temperature in the depolymerizer in the step 1) is 150 to 280 ℃, preferably 170 to 250 ℃; the pressure in the depolymerizer is negative pressure, preferably 0.1-10 kpa, more preferably 1-5 kpa; the retention time of the isocyanate material with high polymer content is 0.5-10 min, preferably 1-5 min.

3. The process for separating and recovering isocyanate polymer according to claim 2, wherein the isocyanate material in step 1) is atomized by the inert gas flow through a nozzle to form liquid droplets, and the given particle size of the liquid droplets is less than or equal to 500 μm, preferably less than or equal to 50 μm; preferably, the inert gas is selected from one or more of nitrogen, carbon dioxide, argon, preferably nitrogen; the introduction amount of the inert gas is 1-10 times, preferably 3-5 times of the mole number of the isocyanate material.

4. The high-efficiency separation and recovery process of isocyanate polymer according to claim 3, wherein the content of the small molecule isocyanate monomer obtained after depolymerization in step 1) is 30-90 wt%, preferably 50-80 wt%, based on the total mass of isocyanate.

5. The efficient separation and recovery process of isocyanate polymer according to claim 1, wherein the temperature in the high-speed rotary adsorption reactor in the step 2) is 25-85 ℃; the rotating speed of a high-speed rotating adsorption disc of the high-speed rotating adsorption reactor is 100-1000 rpm, preferably 300-800 rpm; the flow velocity of the micromolecule isocyanate crude product entering the high-speed rotary adsorption device is 0.1-1 m/s.

6. The process for separating and recovering isocyanate polymer according to claim 1 or 5, wherein a solid adsorbent is arranged in the selected high-speed rotating adsorption disc, and a layer of inert porcelain pellets is placed on the inner layer and the outer layer of the solid adsorbent; preferably, the solid adsorbent is selected from any one or more of metal oxides, such as copper oxide, iron oxide, boron oxide, magnesium oxide, barium oxide, calcium oxide and silicates, aluminosilicates, borosilicates, zeolites, ion exchangers, activated carbon, silica gel.

7. The process for the high efficiency separation and recovery of isocyanate polymer according to claim 1, wherein the diisocyanate is selected from the group consisting of aliphatic or aromatic diisocyanates; preferably, the aliphatic diisocyanate is one or more of hexamethylene diisocyanate, methylcyclohexyl diisocyanate, dimethylcyclohexyl diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornane diisocyanate or cyclohexyldimethylene diisocyanate; the aromatic isocyanate is one or more of toluene diisocyanate, p-phenylene diisocyanate or xylylene diisocyanate; more preferably, the diisocyanate is cyclohexyl dimethylene diisocyanate or xylylene diisocyanate.

8. The device for the high-efficiency separation and recovery process of the isocyanate polymer according to any one of claims 1 to 7, which is characterized by comprising a depolymerizer, a heat exchanger and a high-speed rotary adsorption reactor, wherein an outlet of the depolymerizer is connected with a heat exchanger heat medium inlet, a heat exchanger heat medium outlet is connected with the high-speed rotary adsorption reactor inlet, a high-speed rotary adsorption reactor outlet is connected with a heat exchanger refrigerant inlet, and a heat exchanger refrigerant outlet is connected with an intermediate tank.

9. The device of claim 8, wherein the depolymerizer is a tubular reactor, a vaporizing spray head is arranged at the top of the depolymerizer, a baffle plate is arranged in an inner tube of the depolymerizer, and a wire mesh demister is arranged at an outlet of the depolymerizer; preferably, the baffle plate is a sector baffle plate with a cross section of 1/3-1/4, the sector baffle plate is spirally arranged from an inlet position to an outlet position, the sector baffle plate has a downward inclination angle of 10-30 degrees, and the baffle plate is provided with at least one round hole of 1-20 mm, preferably 3-10 mm.

10. The device according to claim 8, wherein the high-speed rotary adsorption reactor comprises a tank body and a rotary adsorption rotary disc arranged in the middle of the tank body, and the tank body is of a jacket structure; 2-10 rotary adsorption rotary tables are arranged, the upper layer and the lower layer are distributed in the inner cavity of the device, and each adsorption rotary table is provided with a solid adsorbent; and a layer of inert porcelain pills is placed on the inner layer and the outer layer of the solid adsorbent and is used for protecting the adsorbent.