WO2015149381A1 - 一种光气法制异氰酸酯的溶剂精制方法及所使用的装置 - Google Patents

一种光气法制异氰酸酯的溶剂精制方法及所使用的装置 Download PDF

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WO2015149381A1
WO2015149381A1 PCT/CN2014/075169 CN2014075169W WO2015149381A1 WO 2015149381 A1 WO2015149381 A1 WO 2015149381A1 CN 2014075169 W CN2014075169 W CN 2014075169W WO 2015149381 A1 WO2015149381 A1 WO 2015149381A1
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solvent
desiccant
absorption
layer
adsorbent
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PCT/CN2014/075169
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English (en)
French (fr)
Inventor
张宏科
姚雨
赵东科
华卫琦
陈斌
石德凯
陈青龙
徐丹
王阳
史其乐
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万华化学集团股份有限公司
万华化学（宁波）有限公司
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Priority to US15/301,132 priority Critical patent/US9840462B2/en
Publication of WO2015149381A1 publication Critical patent/WO2015149381A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C263/00—Preparation of derivatives of isocyanic acid
    • C07C263/18—Separation; Purification; Stabilisation; Use of additives
    • C07C263/20—Separation; Purification
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
    • B01D15/08—Selective adsorption, e.g. chromatography
    • B01D15/10—Selective adsorption, e.g. chromatography characterised by constructional or operational features
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C263/00—Preparation of derivatives of isocyanic acid
    • C07C263/10—Preparation of derivatives of isocyanic acid by reaction of amines with carbonyl halides, e.g. with phosgene

Definitions

  • the invention belongs to the field of chemical industry, and particularly relates to a method for purifying a solvent of a phosgene process isocyanate and a device used in the method, in particular to a method for rapidly removing moisture and iron in a solvent used for the production of an isocyanate phosgene method. , phosgene and hydrogen chloride, and methods to reduce the solvent color.
  • isocyanate is mainly prepared by phosgene method at home and abroad, including MDI (diphenylmethane diisocyanate), TDI (toluene diisocyanate), HDI (hexamethylene diisocyanate) and the like.
  • the method comprises the steps of: mixing a corresponding polyamine such as diphenylnonanediamine and polyarylene polyphenyl polyamine or toluenediamine with a solvent, and then fully mixing with phosgene for phosgenation reaction, after the reaction is completed.
  • a corresponding photochemical reaction solution is obtained, and the photochemical reaction solution is desorbed with phosgene and a solvent to obtain a crude product.
  • chlorobenzene, o-dichlorobenzene, toluene or the like is mainly used as a solvent.
  • the requirements for moisture, iron content, phosgene, hydrogen chloride content and platinum cobalt color are very high.
  • the moisture content is less than 100 ppm
  • the iron content is less than 5 ppm
  • the phosgene and hydrogen chloride content are required.
  • the platinum cobalt color is below 30. If the moisture content of the solvent is too high, the corrosion of the equipment will be accelerated in the presence of phosgene on the one hand, and the urea will react with the isocyanate to form urea on the other hand, which seriously affects the quality of the product.
  • Excessive iron content in the solvent leads to an increase in the iron content of the isocyanate product, which affects the foaming quality of the product.
  • Excessive levels of phosgene and hydrogen chloride in the solvent will accelerate the corrosion of the equipment.
  • the polyamine reacts with phosgene to form isocyanate, and then reacts with the polyamine to form urea, which also affects product quality.
  • the solvent has a higher color number, it directly affects the color of the product isocyanate.
  • waste solvent with high color number and high water content, and some parts will be generated during the abnormal opening and stopping of the device.
  • a waste solvent for phosgene and hydrogen chloride are directly discharged, which not only produces a large amount of waste liquid but also wastes resources. Therefore, for economic and environmental reasons, it is necessary to study the recycling and recycling of waste solvents.
  • the solvent will be depleted, and it is necessary to replenish the reaction system with fresh solvent.
  • Patent document CN103073412A discloses a PTA (fine terephthalic acid) solvent dehydration system and a dehydration process thereof. This document describes the removal of water from PTA solvents by extraction and azeotropic distillation, which reduces the load and steam usage of subsequent azeotropic distillation, but for the treatment of low moisture solvents (less than 100 ppm) and iron content. The effect of the solvent is one, and the entrainer affects the quality of the isocyanate product.
  • PTA fine terephthalic acid
  • Patent document CN101955426A discloses a method for optimizing the dehydration process of azeotropic indigo solvent in an industrial p-benzoic acid plant, providing a basis for reforming the production process, saving energy and reducing consumption, but for treating simultaneous moisture, phosgene and HC1. Solvent applications are limited.
  • Patent Document CN101326495A describes a method of dehydrating an organic solvent molecular sieve.
  • the organic solvent removes moisture from the ethanol through the molecular sieve bed.
  • the molecular sieve regeneration cost is high, and the phosgene, HC1, and iron fraction cannot be removed at the same time, and the color number of the solvent cannot be effectively reduced.
  • Patent Document CN1903990A describes an oil deacidification adsorbent and a preparation method thereof, wherein the activated clay and the inorganic alkaline substance are mixed and used for deacidification of the oil.
  • the adsorbent is directly used for removing water in the organic solvent, which has local overheating, high pressure drop and channeling phenomenon, and has limited effect on the removal of phosgene and hydrogen chloride, and has limited effect on the removal of colored substances in the solvent.
  • the solvent refining method described in the above literature mainly removes the water in the solvent by azeotropic fine grazing, molecular sieve treatment and inorganic alkaline substances, and the treatment cost is high, and the solvent water content is high (required content is less than 100). Ppm), while reducing the color of the solvent, the treatment effect is poor and there is local overheating and channeling effect.
  • the process of simultaneously treating the moisture, iron, phosgene and hydrogen chloride in the isocyanate production solvent and reducing the solvent color number has not been disclosed. .
  • a first aspect of the present invention provides an apparatus for purifying a solvent of a phosgene process isocyanate.
  • the device is a multi-stage absorption tower comprising a bottom support packing section, an intermediate packing absorption section and a top supporting packing section from bottom to top; the intermediate packing absorption section comprises an N-stage absorption layer and N is 3- An integer of 8, preferably N is an integer of 4-6, the first to the Nth absorption layers are arranged from bottom to top; the first to N-1th absorption layers are each connected to the upper portion of the external feed tube
  • the liquid distribution device and the lower absorption filler layer are composed, and the Nth absorption layer only contains the absorption filler layer; the absorption filler layer of each absorption layer is uniformly mixed by the desiccant and the adsorbent; the solvent to be purified enters from the external feed tube.
  • the absorption tower is purified from the top outlet, and the waste liquid is a desiccant solution that absorbs moisture, iron, phos
  • the liquid distribution device of the present invention can use any liquid distributor known to those skilled in the art to uniformly distribute the solvent to be purified in the absorption filler layer of the corresponding absorption layer, and strengthen the solvent to be purified and the desiccant and the adsorbent.
  • the contact improves the treatment effect while preventing the generation of channel flow.
  • the liquid distributor includes, but is not limited to, a nozzle type, a trough type, a two-layer tube type liquid distributor.
  • the mass ratio of the desiccant to the adsorbent of the absorbing filler layer of the first-stage absorption layer of the present invention is 1:1-5:1, preferably 2:1-4:1, and the desiccant accounts for all the drying in the multi-stage absorption tower.
  • the mass ratio of the desiccant to the adsorbent of the absorbing filler layer of the N-stage absorbing layer is 5:1-12:1, preferably 6:1-10:1,
  • the desiccant accounts for 4-15%, preferably 5-10% of the mass of all the desiccant in the multistage absorption tower; the mass ratio of the desiccant to the adsorbent of each of the absorption filler layers of the second to N-1th absorbent layer 5:1-15:1, preferably 6:1-10:1, the desiccant of each level of the absorbent layer occupies 15-92%, preferably 20-45%, of the mass of all desiccants in the multistage absorption tower.
  • the desiccant of the present invention is an alkaline desiccant selected from one or two or more of calcium oxide, sodium hydroxide and potassium hydroxide, preferably sodium hydroxide; the BET specific surface area of the desiccant is 1500-4500 m 2 /g, preferably 2500-4000 m 2 /g, to ensure sufficient contact with the solvent to be purified; average particle size is 0.5-10 ⁇ , preferably 1-5 ⁇ ; mechanical strength is 85-99% Preferably, it is 90-98% to ensure that the service life of the desiccant is sufficiently long during the refining process.
  • the adsorbent of the invention adopts a macroporous resin adsorbent or activated carbon capable of adsorbing a colored substance in a solvent to be purified, and the macroporous resin adsorbent is selected from a non-polar macroporous adsorption resin of a styrene polymer and a divinylbenzene polymer.
  • a non-polar macroporous adsorption resin of a styrene polymer and a divinylbenzene polymer preferably D101 (for example, commercially available from Xi'an Lanxiao Technology Co., Ltd.), LX-60 (for example, commercially available from Xi'an Lanxiao Technology) Ltd.
  • activated carbon is preferably coconut shell activated carbon (for example, commercially available from Chengde Jingda activated carbon) Manufacturing Co., Ltd.;
  • the adsorbent has a BET specific surface area of 2500-5000 m 2 /g, preferably 3000-4500 rn 2 /g; a mesopore pore diameter of 2-10 nm, preferably 2-5 nm; mechanical strength It is 85-98%, preferably 90-95%.
  • the macroporous resin adsorbent or activated carbon according to the present invention can form a van der Waals force with iron ions in a solvent to be purified, and effectively adsorb iron in the solvent to be purified.
  • the support filler of the top support filler section and the bottom support filler section of the present invention is selected from one or two or more of crushed stone, molecular sieve and activated carbon, preferably molecular sieves, such as 3A molecular sieve, 5A molecular sieve and/or 10A.
  • molecular sieves such as 3A molecular sieve, 5A molecular sieve and/or 10A.
  • a molecular sieve of a type more preferably a molecular sieve of type 3A.
  • the top support filler of the present invention has the same mass as the bottom support filler, and the mass ratio of the top support filler to all the desiccants in the multistage absorption tower is 1:20-1:3, preferably 1:15-1:5.
  • the volume flow rate of the total feed amount of the solvent to be purified and the total mass of all the desiccant and the adsorbent in the multistage absorption tower is 1:200-1:600 m 3 /kg/h, preferably 1:300-1:500 m 3 /kg/h.
  • the feeding mode of the refining solvent in the multi-stage absorption tower is selected to be a multi-stage feeding mode, wherein the volume of the external feeding tube of the first-stage absorption layer is occupied by the volume 1/15-1/3 of the total volume of the purified solvent, preferably 1/10-1/5, the amount of the external feed tube of the N-1th absorption layer accounts for the total volume of the solvent to be refined. 1/15-1/3, preferably 1/10-1/5, the amount of the external feed tube of the absorption layers of the second to N-2 stages is the total amount of the solvent to be refined. 1/15-4/5, preferably 1/10-7/10.
  • the solvent to be purified enters the multi-stage absorption tower through a plurality of streams, and the desiccant can be effectively dispersed by water absorption, phosgene and exothermic heat of hydrogen chloride, while absorbing water, phosgene and hydrogen chloride.
  • the desiccant solution is discharged through the bottom of the multi-stage absorption tower, which can quickly take out the heat and prevent the desiccant from sucking. Local overheating caused by water, phosgene and hydrogen chloride exotherm.
  • the solvent to be purified enters the multi-stage absorption tower through a plurality of streams, and the flow caused by the single stream entering the absorption tower is prevented from being excessively large, the initial channel flow is reduced, and the solvent to be purified is uniformly distributed by the liquid distribution device.
  • the absorbing filler layer of each primary absorption layer effectively prevents the generation of channel flow.
  • the solvent to be purified is introduced into the absorption tower through a plurality of streams, thereby avoiding the low water absorption of the top desiccant after the single stream enters the absorption tower, and the tower
  • the bottom desiccant is saturated with water and causes the problem of uneven water absorption of the desiccant.
  • the flow rate of the bottom layer is large, the residence time is long, and the drying dose is large, which is beneficial to remove moisture, phosgene, hydrogen chloride, iron and colored substances in the solvent.
  • the adsorbent which exists in a specific mass ratio in the present invention also serves as a drier for the desiccant, and reduces the contact adhesion between the desiccant after water absorption, and at the same time, the drying after the water absorption
  • the agent solution is discharged through the bottom of the multistage absorption tower, which can effectively prevent the desiccant from being knotted.
  • the residence time of the solvent to be purified in the multistage absorption tower of the present invention is 0.25-8 h, preferably 2-4 h.
  • a part of the purified solvent of the present invention is refluxed and mixed with the solvent to be purified to enter a multistage absorption column, and the reflux ratio is 0.5-4, preferably 1-3.
  • the pressure drop between the outer feed tube of the first stage absorbent layer and the top outlet of the multistage absorption tower of the present invention is 5-40 kPa, preferably 10-25 kPa.
  • the solvent to be purified is a waste solvent containing impurities generated by the phosgene method for preparing an isocyanate or a solvent, which is required to be added to the reaction system, such as water, iron content, and a fresh solvent whose color number is not up to standard. It is selected from one or two or more of o-dichlorobenzene, chlorobenzene and toluene.
  • the solvent to be purified has a moisture content of 150-600 ppm, preferably 200-300 ppm; an iron content of 40-300 ppm, preferably 50-200 ppm; and a phosgene and a hydrogen chloride content of 0-10000 ppm, preferably 0-5000 ppm; platinum-cobalt color number is 30-100, preferably 40-80; refined solvent has water content ⁇ 50 ppm, iron content ⁇ 5 ppm, phosgene and hydrogen chloride content ⁇ 20ppm, platinum-cobalt color No. ⁇ 20.
  • the purified waste solvent of the present invention is preferably reused as a solvent for the preparation of isocyanate by phosgene.
  • the iron content of the present invention is calculated based on the iron atom content.
  • the adsorbent and the desiccant are uniformly mixed to effectively prevent the desiccant from absorbing the water after the water absorption, the desiccant absorbs moisture, Local overheating caused by phosgene and hydrogen chloride exotherm and the generation of channel flow, while effectively reducing the pressure drop.
  • Figure 1 is a schematic view of a multistage absorption tower apparatus according to the present invention used in Examples 1-5. detailed description
  • the L color of the isocyanate is determined by the L, a, b values of the CIE color system known to those skilled in the art;
  • the iron content in the solvent is the iron atom content measured at 248.33 nm by atomic absorption emission. ;
  • the water in the solvent is determined by a fully automatic Karl Fischer moisture meter
  • the phosgene and hydrogen chloride content in the solvent are reacted with sodium hydroxide and phosgene and hydrogen chloride, and then silver nitrate is added, and the residual silver ion content is measured by an automatic potentiometric titrator, and then converted into a phosgene and a hydrogen chloride content in the solvent;
  • the coconut shell activated carbon used was purchased from Chengde Jingda Activated Carbon Manufacturing Co.; the macroporous resin D101 used was purchased from Xi'an Lanxiao Technology Co., Ltd.
  • Example 1 The coconut shell activated carbon used was purchased from Chengde Jingda Activated Carbon Manufacturing Co.; the macroporous resin D101 used was purchased from Xi'an Lanxiao Technology Co., Ltd.
  • the desiccant is sodium hydroxide, the total amount of desiccant in the absorption tower is 500 kg, and the desiccant has a BET specific surface area of 2500 m 2 /g, an average particle diameter of 1 ⁇ , and a mechanical strength of 90%.
  • the adsorbent is coconut shell activated carbon, The BET specific surface area is 3000 m 2 /g, the mesopore diameter is 2 nm, and the mechanical strength is 90%.
  • the top and bottom support packings of the absorption tower are type 3A molecular sieves, and the total amount is 50 kg.
  • the absorption layer N is 4 layers, and the first to third absorption layers are respectively composed of an upper liquid distribution device and a lower absorption filler layer connected to the external feed pipe, and the desiccant and the adsorbent of the absorption filler layer of the first absorption layer are
  • the mass ratio is 2:1
  • the desiccant accounts for 5% of the mass of all desiccant in the multistage absorption tower
  • the mass ratio of the desiccant to the adsorbent of the second and third stages of the absorbent layer of each absorption layer is 10 :1
  • the desiccant of the absorbing filler layer of each of the second and third stages of the absorption layer accounts for 45% of the mass of all the desiccant in the multistage absorption tower
  • the mass ratio is 10:1, and the desiccant accounts for 5% of the mass of all desiccants in the multistage absorption tower.
  • the desiccant of the absorbing filler layer of each absorption layer is mixed and filled with the adsorbent, and the pressure drop between the external feed pipe of the first-stage absorption layer of the multi-stage absorption tower and the outlet of the column top is 10 kPa.
  • the solvent to be purified is the waste chlorobenzene solvent generated by the abnormal opening and stopping of the MDI production device, and the volume flow rate of the total feed amount and the total mass of all the desiccant and the adsorbent in the multistage absorption tower are 1:300 m 3 /kg/ h, the feed amount of the external feed pipe of the first-stage absorption layer accounts for 1/5 of the volume of the total feed amount of the solvent to be refined, and the feed amount of the external feed pipe of the second-stage absorption layer accounts for the total solvent to be purified 7/10 of the volume of the feed amount, the feed amount of the external feed pipe of the third-stage absorption layer accounts for 1/10 of the total feed amount of the solvent to be purified.
  • the residence time of the solvent to be purified in the multistage absorption tower is 2 h, and the reflux ratio of the solvent after purification to the solvent to be purified is 1.
  • the solvent to be purified has a water content of 300 ppm, an iron content of 50 ppm, a phosgene and a hydrogen chloride content of 5000 ppm, and a platinum-cobalt color number of 40.
  • the solvent analysis results after purification are shown in Table 1.
  • the purified solvent is reused as a solvent for MDI production, and the production method is as described in Table 1 with reference to the method for producing MDI described in Patent Document CN1254724A.
  • the desiccant is potassium hydroxide, the total amount of desiccant in the absorption tower is 1000 kg, and the desiccant has a BET specific surface area of 3000 m 2 /g, an average particle diameter of 3 ⁇ , and a mechanical strength of 95%.
  • the adsorbent is coconut shell activated carbon with a BET specific surface area of 3500 m 2 /g, a mesoporous pore size of 4 nm and a mechanical strength of 93%.
  • the top and bottom support packings of the absorption tower are type 5A molecular sieves, and the total amount is 80 kg.
  • the absorption layer N is 5 layers, and the first to fourth absorption layers are respectively composed of an upper liquid distribution device and a lower absorption filler layer connected to the external feed pipe, and the desiccant and the adsorbent of the absorption filler layer of the first absorption layer are
  • the mass ratio is 3:1, the desiccant accounts for 7% of the mass of all desiccant in the multistage absorption tower, and the mass ratio of desiccant to adsorbent of the absorption filler layer of each of the second to fourth stages of the absorption layer is 9 :1 , desiccant of the absorption packing layer of each stage of the second to fourth stage absorption house It accounts for 29% of the mass of all desiccant in the multi-stage absorption tower, and the mass ratio of the desiccant to the adsorbent of the absorption filler layer of the fifth-stage absorption layer is 6:1, and the desiccant accounts for all the desiccant mass in the multi-stage absorption tower.
  • the desiccant of the absorbing filler layer of each absorption layer is uniformly mixed and filled with the adsorbent.
  • the pressure drop between the outer feed tube and the top outlet of the first stage absorber of the multistage absorber is 16 kPa.
  • the solvent to be purified is the waste dichlorobenzene solvent produced during the overhaul of the TDI production unit.
  • the volumetric flow rate of the total feed amount and the total mass of all desiccant and adsorbent in the multistage absorption tower are 1:400 m 3 /kg/ h
  • the amount of the external feed tube of the first-stage absorption layer is 1/8 of the volume of the total feed amount of the solvent to be refined
  • the amount is 3/8 of the volume of the total amount of the solvent to be refined, respectively
  • the amount of the external feed tube of the fourth-stage absorption layer is 1/8 of the total amount of the solvent to be purified.
  • the residence time of the solvent to be purified in the multistage absorption tower is 3 h
  • the reflux ratio of the solvent after purification to the solvent to be purified is 1.5.
  • the solvent to be purified has a water content of 200 ppm, an iron content of 150 ppm, a phosgene and a hydrogen chloride content of 4000 ppm, and a platinum-cobalt color number of 60.
  • the solvent analysis results after purification are shown in Table 1.
  • the purified solvent was reused as a solvent for TDI production, and the production method was as described in the method for producing TDI described in Patent Document CN101205199A.
  • the analysis results of the obtained product TDI are shown in Table 1.
  • the desiccant is sodium hydroxide, the total amount of desiccant in the absorption tower is 800 kg, and the desiccant has a BET specific surface area of 4000 m 2 /g, an average particle diameter of 5 ⁇ , and a mechanical strength of 98%.
  • the adsorbent is a divinylbenzene polymer-based nonpolar macroporous resin D101 having a BET specific surface area of 4500 m 2 /g, a mesoporous pore diameter of 5 nm, and a mechanical strength of 95%.
  • the top and bottom support packings of the absorption tower are 10A molecules with a total amount of 90 kg.
  • the absorption layer N is 6 layers, and the first to fifth absorption layers are respectively composed of an upper liquid distribution device and a lower absorption filler layer connected to the external feed pipe, and the desiccant and the adsorbent of the absorption filler layer of the first absorption layer are
  • the ratio of the desiccant to the mass of all the desiccant in the absorption tower is 4%, and the mass ratio of the desiccant to the adsorbent of the absorption filler layer of each of the second to fifth stages of the absorption layer is 5: 1.
  • the desiccant of the absorbing filler layer of each of the second to fifth stages of the absorption layer accounts for 20.5% of the mass of all the desiccant in the multistage absorption tower, and the desiccant and the adsorbent of the absorbing filler layer of the sixth-stage absorption layer
  • the mass ratio is 5:1
  • the desiccant accounts for 8% of the mass of all desiccants in the multistage absorption tower.
  • the desiccant of the absorbing filler layer of each absorption layer is mixed and filled with the adsorbent, and the pressure drop between the external feed tube of the first-stage absorption layer of the multi-stage absorption tower and the outlet of the column is 25 kPa.
  • the solvent to be purified is the fresh chlorobenzene solvent to be added to the HDI production unit, and the volume flow rate of the total feed amount
  • the ratio of the total mass of the desiccant to the adsorbent in the multistage absorption tower is 1:500 m 3 /kg/h, and the amount of the external feed tube of the first-stage absorption layer accounts for the total amount of the solvent to be refined. 1/5 of the volume, the external feed tube of the second-stage absorption layer to the fourth-stage absorption layer accounts for 1/5 of the volume of the total feed amount of the solvent to be refined, and the external feed of the fifth-stage absorption layer
  • the amount of the tube fed is 1/5 of the volume of the total amount of solvent to be refined.
  • the residence time of the solvent to be purified in the multistage absorption tower was 4 h, and the reflux ratio of the solvent after purification to the solvent to be purified was 3.
  • the solvent to be purified has a moisture content of 150 ppm, an iron content of 200 ppm, a phosgene and hydrogen chloride content of 0 ppm, and a platinum-cobalt color number of 80.
  • the results of the solvent analysis after purification are shown in Table 1, and the purified solvent is used as a solvent for HDI production.
  • the production method is as described in the patent document CN101429139A.
  • the analysis results of the obtained product HDI are shown in Table 1. .
  • the desiccant is calcium oxide, the total amount of the desiccant in the absorption tower is 1200 kg, and the desiccant has a BET specific surface area of 4200 m 2 /g, an average particle diameter of 4.5 ⁇ m, and a mechanical strength of 95%.
  • the non-polar macroporous adsorption resin LX-60 which is a styrene polymer, has a BET specific surface area of 4,800 m 2 /g, a mesopore diameter of 4.5 nm, and a mechanical strength of 93%.
  • the top and bottom support packings of the absorption tower are type 5A molecular sieves, and the total amount is 120 kg.
  • the absorption layer N is 6 layers, and the first to fifth absorption layers are respectively composed of an upper liquid distribution device and a lower absorption filler layer connected to the external feed pipe, and the desiccant and the adsorbent of the absorption filler layer of the first absorption layer are
  • the mass ratio is 4:1, the desiccant accounts for 10% of the mass of all the desiccant in the absorption tower, and the mass ratio of the desiccant to the adsorbent of the absorption filler layer of each of the second to fifth stages of the absorption layer is 5: 1.
  • the desiccant of the absorbing filler layer of each of the second to fifth stages of the absorption layer accounts for 20.5% of the mass of all the desiccant in the multistage absorption tower, and the desiccant and adsorbent of the absorbing layer of the sixth-stage absorption layer
  • the mass ratio is 5:1
  • the desiccant accounts for 8% of the mass of all desiccants in the multistage absorption tower.
  • the desiccant of the absorbing filler layer of each absorption layer is uniformly mixed with the adsorbent, and the pressure drop between the external feed pipe and the top outlet of the first-stage absorption layer of the multi-stage absorption tower is 25 kPa.
  • the solvent to be purified is the fresh benzene solvent to be added to the MDI production unit, and the ratio of the volumetric flow rate of the total feed amount to the total mass of the desiccant and the adsorbent in the multistage absorption tower is 1:400 m 3 /kg/h,
  • the feed amount of the external feed pipe of the primary absorption layer accounts for 1/5 of the volume of the total feed amount of the solvent to be refined, and the feed amount of the external feed pipe of the second-stage absorption layer to the fourth-stage absorption layer is occupied.
  • the amount of the total amount of the refined solvent is 1/5
  • the amount of the external feed tube of the fifth-stage absorption layer is 1/5 of the volume of the total amount of the solvent to be purified.
  • the residence time of the solvent to be purified in the multistage absorption tower was 3.5 h, and the reflux ratio of the solvent after purification to the solvent to be purified was 2.
  • the solvent to be purified has a moisture content of 250 ppm and an iron content of 120 ppm.
  • Phosgene and hydrogen chloride contain The amount is O ppm and the platinum-cobalt color number is 60.
  • the refined solvent analysis is as shown in Table 1, and the purified solvent is used as a solvent for MDI production.
  • the production method is as described in the patent document CN1254724A.
  • the analysis of the obtained product MDI is shown in Table 1. Shown. Example 5
  • the desiccant is potassium hydroxide, the total amount of desiccant in the absorption tower is 900 kg, and the desiccant has a BET specific surface area of 3200 m 2 /g, an average particle diameter of 5 ⁇ , and a mechanical strength of 95%.
  • the non-polar macroporous adsorption resin LX-20 which is a styrene polymer, has a BET specific surface enthalpy of 5000 m 2 /g, a mesoporous pore diameter of 4 nm, and a mechanical strength of 95%.
  • the top and bottom support packings of the absorption tower are type 3A molecular sieves, and the total amount is 90 kg.
  • the absorption layer N is 5 layers, and the first to fourth absorption layers are respectively composed of an upper liquid distribution device and a lower absorption filler layer connected to the external feed pipe, and the desiccant and the adsorbent of the absorption filler layer of the first absorption layer are
  • the mass ratio is 3:1, the desiccant accounts for 7% of the mass of all desiccant in the multistage absorption tower, and the mass ratio of the desiccant to the adsorbent of the absorbent layer of the second to fourth stage of each absorption layer is 9 :1, the desiccant of the absorbing filler layer of each of the second to fourth stages of the absorption layer accounts for 29% of the mass of all the desiccant in the multistage absorption tower, and the desiccant and adsorbent of the absorbing filler layer of the fifth-stage absorption layer
  • the mass ratio is 6:1, and the desiccant accounts for 6% of the mass of all desiccants in the multistage absorption tower.
  • the desiccant of the absorbing filler layer of each absorption layer is uniformly mixed and filled with the adsorbent.
  • the pressure drop between the outer feed tube and the top outlet of the first stage absorption layer of the multistage absorption tower is 20 kPa.
  • the solvent to be purified is the waste chlorobenzene solvent generated during the overhaul of the TDI production equipment.
  • the volume flow rate of the total feed amount is the ratio of all the desiccant to the total amount of the adsorbent in the multistage absorption tower: 1:420 m 3 /kg/ h
  • the amount of the external feed tube of the first-stage absorption layer is 1/8 of the volume of the total feed amount of the solvent to be refined
  • the feed of the external feed tube of the second-stage absorption layer and the third-stage absorption layer The amount is 3/8 of the volume of the total amount of the solvent to be refined, respectively
  • the amount of the external feed tube of the fourth-stage absorption layer is 1/8 of the total amount of the solvent to be purified.
  • the residence time of the solvent to be purified in the multistage absorption tower was 4 h
  • the reflux ratio of the solvent after purification to the solvent to be purified was 1.5.
  • the solvent to be purified has a moisture content of 260 ppm, a bismuth content of 180 ppm, a phosgene and a hydrogen chloride content of 3000 ppm, and a platinum-cobalt color number of 50.
  • the solvent analysis results after purification are shown in Table 1.
  • the purified solvent was reused as a solvent for TDI production, and the production method was determined by referring to the method for producing TDI described in the patent document CN101205199A.
  • the analysis of the obtained product TDI is shown in Table 1.
  • Comparative example 1 The waste chlorobenzene solvent is treated by a vacuum decompression tower.
  • the operating pressure of the vacuum distillation column is 40 kpa, the reflux ratio is 2:1, the temperature at the bottom of the column is controlled at 100-105 °C, and the temperature at the top of the column is controlled at 60-65 °C.
  • the solvent to be purified is the waste chlorobenzene solvent produced by the abnormal opening and stopping of the MDI production equipment, wherein the water content is 300 pm, the iron content is 50 ppm, the phosgene and hydrogen chloride content is 5000 ppm, and the platinum-cobalt color number is 60.
  • the solvent analysis results are shown in Table 1.
  • the purified solvent is reused as a solvent for MDI production, and the production method is as described in Table 1 with reference to the method for producing MDI described in Patent Document CN1254724A. Comparative example 2
  • the waste dichlorobenzene solvent is treated by an azeotropic distillation column, the entraining agent is tetrahydrofuran, and the entraining agent is added to the azeotropic distillation tower with the solvent to be purified, and the mass ratio of the entraining agent to the solvent to be purified is 10:i. , operating reflux ratio of 2, an azeotropic distillation column operating pressure is 101.3 kPa, column top temperature was controlled at 65-69 ° C, column bottom temperature is controlled at 138-140 ° C 0
  • the solvent to be purified is the waste dichlorobenzene solvent produced during the solvent operation of the TDI production unit after overhaul, wherein the water content is 280 ppm, the iron content is 45 ppm, the phosgene and hydrogen chloride content is 4800 ppm, and the platinum-drill color number is 55.
  • the solvent analysis results after purification are shown in Table 1.
  • the purified solvent was reused as a solvent for TDI production, and the production method was as described in Patent Document CN101205199A.
  • the analysis results of the obtained product TDI are shown in Table 1. Table 1 Analysis results

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Abstract

本发明公开了一种光气法制备异氰酸酯的溶剂的精制方法以及该方法所采用多级吸收塔。通过本发明的方法和多级吸收塔处理含有水分、铁分、和/或光气、氯化氢、以及其它带色物质的待精制溶剂，能有效防止干燥剂吸水板结，塔内局部过热以及沟流的产生，同时有效降低压降；此外，精制后的溶剂中水分≤50ppm，铁分含量≤5ppm，光气和氯化氢含量≤20ppm，铂-钴色号≤20，可作为光气法制备异氰酸酯的溶剂使用，能够明显提高异氰酸酯的L色。采用本发明的方法，通过对溶剂的精制和循环利用，能大大减少溶剂损耗，降低生产成本，工艺可操作性强，连续性与稳定性好。

Description

一种光气法制异氰酸酯的溶剂精制方法及所使用的装置
技术领域
本发明属于化工领域， 具体涉及一种光气法制异氰酸酯的溶剂的精制方法 以及该方法所使用的装置， 尤其是涉及一种快速脱除异氰酸酯光气法生产所使用 的溶剂中的水分、 铁分、 光气及氯化氢以及降低溶剂色号的方法。 技术背景
目前， 国内外主要采用光气法制备异氰酸酯， 包括 MDI (二苯基甲烷二异氰 酸酯)、 TDI(甲苯二异氰酸酯)、 HDI (六亚曱基二异氰酸酯)等。 该方法是将相应的 多胺如二苯基曱烷二胺及多亚曱基多苯基多胺或甲苯二胺与溶剂混合后再与光 气进行充分混合进行光气化反应， 反应结束后得到相应的光化反应液， 光化反应 液脱除光气、 溶剂后得到粗产品。 该反应中， 主要使用氯苯、 邻二氯苯、 甲苯等 作为溶剂。
作为异氰酸酯生产过程中的溶剂对水分、 铁分、 光气、 氯化氢含量及铂钴色 号质量要求很高， 一般要求水分含量低于 100 ppm， 铁分含量低于 5 ppm, 光气 及氯化氢含量低于 50 ppm, 铂钴色号低于 30。 如果溶剂中水分含量过高， 一方 面会在光气存在下加快设备腐蚀， 另一方面水分会与异氰酸酯反应生成脲， 严重 影响产品质量。 溶剂中铁分含量过高则会导致异氰酸酯产品中铁分含量升高， 影 响产品发泡质量。 溶剂中光气及氯化氢含量过高， 则会加快设备腐蚀， 同时溶剂 与多胺混合过程中， 多胺与光气反应生成异氰酸酯， 然后与多胺反应生成脲， 也 会影响产品质量。 此外， 如果溶剂的色号较高， 则会直接影响产品异氰酸酯的颜 色。
在异氰酸酯的工业化生产中，装置大修开车时需要首先用溶剂运转系统将系 统中水分带出， 同时会产生色号高及含水量高的废溶剂， 在装置异常开停车过程 中也会产生一部分含光气及氯化氢的废溶剂。 这些废溶剂如杲直接排掉， 不但会 产生大量废液同时会造成浪费资源。 因此， 出于经济和环保的原因， 需要研究废 溶剂的回收再利用问题。 此外， 在异氰酸酯的生产过程中， 溶剂会有损耗， 需要 向反应系统中补充新鲜溶剂， 而市场采购的溶剂往往含有较高的水分、 铁分等对 于异氰酸酯生产不利的成分或色号较高，因此，也需要研究新鲜溶剂的处理问题。 专利文献 CN103073412A公开了一种 PTA (精对苯二曱酸)溶剂脱水系统及其 脱水工艺。 该文献中描述通过萃取及共沸精餾的方法脱除 PTA溶剂中水分， 能 够减少后续共沸精餾的负荷及蒸汽用量，但是对于处理低水分溶剂 (低于 100 ppm) 及含铁分的溶剂的效果一 ， 且共沸剂会影响异氰酸酯产品质量。
专利文献 CN101955426A公开了一种工业精对苯二曱酸装置共沸精愤溶剂 脱水过程优化的方法， 为生产工艺的改造、 节能降耗提供依据， 但对于处理同时 含水分、 光气及 HC1的溶剂应用有限。
专利文献 CN101326495A描述了一种有机溶剂分子筛脱水的方法。有机溶剂 通过分子筛床层脱除乙醇中水分。 读方法中分子筛再生成本高， 不能同时脱除光 气、 HC1、 铁分， 且不能有效降低溶剂的色号。
专利文献 CN1903990A描述了一种油品脱酸吸附剂及制备方法， 其中， 活性 白土和无机碱性物质混合后用于油品脱酸。该吸附剂直接用于脱除有机溶剂中水 分存在局部过热、 压降高及沟流现象， 对于光气及氯化氢的脱除效果有限， 且对 于溶剂中有色物质脱除效果有限。
上述文献中所描述的溶剂精制的方法主要是通过共沸精榴、分子筛处理及无 机碱性物质脱除溶剂中的水分， 存在处理成本较高， 对于溶剂水含量要求高 (要 求含量低于 100 ppm),同时降低溶剂颜色的处理效果较差且存在局部过热及沟流 效应， 报道中尚未披露能够同时处理异氰酸酯生产溶剂中水分、 铁分、 光气及氯 化氢， 并降低溶剂色号的工艺方法。 因此， 针对光气法制备异氰酸酯过程中的体 系特点， 需要开发能够快速处理高水分、 高铁分和高色号的新鲜溶剂以及装置大 修开停车过程中产生的高氷分、 高铁分、 高光气、 高氯化氢和高色号的溶剂的方 法。
现有技术中采用食盐或单纯碱性干燥剂处理异氰酸酯生产过程中产生的高 水分、 高铁分、 高光气、 高氯化氢及高色号的溶剂的技术不能将溶剂中全部杂质 除去， 且溶剂中水分仅能处理至 150 ppm左右， 对溶剂中铁分及带色物质没有脱 除效果， 溶剂中光气及氯化氢仅能处理至 500 ppm左右， 处理后的溶剂不能再用 于异氰酸酯的生产过程中的溶剂。 发明内容
本发明目的是提供一种用于精制光气法制异氰酸酯溶剂的装置， 以及使用该 装置精制光气法制异氰酸酯的溶剂的方法。 通过采用本发明的装置和方法， 能够 快速脱除待精制溶剂中的水分、 铁分、 光气及、 氯化氢以及其他带色物质， 工艺 流程简单， 能有效降低生产成本， 条低污染排放及溶剂损耗。
为了达到以上目的，本发明的第一方面提供了一种用于精制光气法制异氰酸 酯的溶剂的装置。 所述装置为多级吸收塔， 该多级吸收塔从下而上包括底部支撑填料段、 中间 填料吸收段和顶部支撑填料段； 所述中间填料吸收段包括 N级吸收层并且 N为 3-8的整数，优选 N为 4-6的整数，第一级吸收层至第 N级吸收层从下而上排列； 第一级至第 N-1级吸收层均由连接外部进料管的上部液体分布装置和下部吸收填 料层组成， 第 N级吸收层仅含有吸收填料层；每级吸收层的吸收填料层由干燥剂 和吸附剂均匀混合而成； 待精制溶剂由外部进料管进入多级吸收塔， 精制后的溶 剂由塔顶出口采出， 废液为吸收了水分、 铁分、 光气及氯化氢的干燥剂溶液， 由 塔底采出。
本发明所述的液体分布装置可以采用本领域技术人员公知的任意液体分布 器， 将待精制溶剂均匀分布在相应各级吸收层的吸收填料层， 强化待精制溶剂与 干燥剂、 吸附剂之间的接触， 提高处理效果， 同时可以防止沟流的产生。 例如， 所述液体分布器包括但不限于喷嘴式、 槽式、 双层排管式液体分布器。 本发明所述第一级吸收层的吸收填料层的干燥剂与吸附剂的质量比为 1:1-5:1 , 优选 2:1-4:1 , 干燥剂占多级吸收塔内所有干燥剂质量的 4-15%, 优选 5-10%; 第 N級吸收层的吸收填料层的干燥剂与吸附剂的质量比为 5:1-12:1 , 优 选 6:1-10:1 , 干燥剂占多级吸收塔内所有干燥剂质量的 4- 15%, 优选 5-10%; 第 二级至第 N-1 级吸收层的每级吸收填料层的干燥剂与吸附剂的质量比为 5:1-15:1 , 优选 6:1-10:1 , 每级吸收填料层的干燥剂占多级吸收塔内所有干燥剂质 量的 15-92%, 优选 20-45%。
本发明所述干燥剂为碱性干燥剂， 选自氧化钙、 氢氧化钠和氢氧化钾中的一 种或两种或多种， 优选为氢氧化钠； 所述干燥剂的 BET 比表面积为 1500-4500 m2/g,优选为 2500- 4000 m2/g, 以保证与待精制溶剂充分接触； 平均粒径为 0.5-10 μηι,优选为 1-5 μπι;机械强度为 85-99%,优选为 90-98%, 以保证在精制过程中， 干燥剂的使用寿命足够长。 本发明所述吸附剂采用能够吸附待精制溶剂中带色物质的大孔树脂吸附剂 或活性炭， 大孔树脂吸附剂选自苯乙烯聚合物的非极性大孔吸附树脂和二乙烯苯 聚合物的非极性大孔吸附树脂中的一种或两种或多种， 优选 D101 (例如， 可商购 自西安蓝晓科技有限公司）、 LX-60(例如， 可商购自西安蓝晓科技有限公司）和 LX-20(例如， 可商购自西安蓝晓科技有限公司）中的一种或两种或多种； 活性炭 优选为椰壳质活性炭 (例如， 可商购自承德净达活性炭制造有限公司）； 所述吸附 剂的 BET比表面积为 2500-5000 m2/g, 优选为 3000-4500 rn2/g; 中孔孔径为 2-10 nm, 优选为 2-5 nm; 机械强度为 85-98%, 优选为 90-95%。
本发明所述的大孔树脂吸附剂或活性炭能够与待精制溶剂中的铁离子形成 范德华力， 有效吸附待精制溶剂中的铁分。
本发明所述顶部支撑填料段和底部支撑填料段的支撑填料选自碎石、分子筛 和活性炭中的一种或两种或多种， 优选分子筛， 如 3A型分子筛、 5A型分子筛和 /或 10A型分子筛， 更优选 3A型分子筛。
本发明所述顶部支撑填料与底部支撑填料质量相同， 顶部支撑填料与多級吸 收塔内所有干燥剂的质量比 1:20-1:3， 优选为 1:15-1:5。
根据本发明的另一方面，本发明提供了一种光气法制异氰酸酯的溶剂的精制 方法， 该方法通过使用如上所述的、 根据本发明第一方面所提供的多级吸收塔来 实现。
进一步的， 根据本发明的方法， 在使用所述多级吸收塔处理待精制溶剂时， 所述待精制溶剂总进料量的体积流速与多级吸收塔内所有干燥剂与吸附剂总质 量的比为 1:200-1:600 m3/kg/h， 优选 1:300-1:500 m3 /kg/h。
优选地， 在本发明的方法中， 多级吸收塔中精制溶剂的进料方式选择为多级 进料方式， 其中， 所述第一级吸收层的外部进料管的进料量体积占待精制溶剂总 进料量体积的 1/15-1/3, 优选 1/10-1/5, 第 N-1 级吸收层的外部进料管的进料量 占待精制溶剂总进料量体积的 1/15-1/3, 优选 1/10- 1/5, 第二级至第 N-2级的各 级吸收层的外部进料管的进料量占待精制溶剂总进料量的 1/15-4/5 , 优选 1/10-7/10。
在这种多级进料方式中， 待精制溶剂通过多个流股进入多级吸收塔， 能够将 干燥剂吸水、 光气及氯化氢后的放热进行有效分散， 同时吸水、 光气及氯化氢后 的干燥剂溶液通过多级吸收塔塔底排放， 能迅速将这些热量带出， 避免干燥剂吸 收水、 光气及氯化氢放热导致的局部过热。 此外， 待精制溶剂通过多个流股进入 多级吸收塔中， 也避免了单一流股进入吸收塔造成的流量过大， 降低初始沟流, 并通过液体分布装置使得待精制溶剂均勾分布在每一级吸收层的吸收填料层，有 效防止沟流的产生。
根据本发明的方法， 由于所述多级吸收塔采用多层设计， 配合待精制溶剂通 过多个流股进入吸收塔， 因此避免了单一流股进入吸收塔后顶部干燥剂吸水量 低，而塔底干燥剂吸水饱和而造成干燥剂吸水不均匀问题，同时底层流股流量大， 停留时间长， 干燥剂量多， 有利于脱除溶剂中水分、 光气、 氯化氢、 铁分及带色 物质。
根据本发明的方法，本发明中所述以特定的质量比存在的吸附剂同时也作为 干燥剂的稀幹剂， 降低吸水后的干燥剂之间的接触粘结力， 同时吸水后的千燥剂 溶液通过多级吸收塔塔底排出， 能有效防止干燥剂的板结。
优选地， 根椐本发明的方法， 本发明所述待精制溶剂在多级吸收塔内的停留 时间为 0.25-8 h, 优选 2-4 h。
优选地， 根据本发明的方法， 本发明所述精制后的溶剂一部分回流与待精制 溶剂混合后进入多级吸收塔， 回流比为 0.5-4， 优选为 1-3。
优选地， 根据本发明的方法， 本发明所述多级吸收塔第一级吸收层外部进料 管与塔顶出口之间的压降为 5-40 kPa, 优选为 10-25 kPa。
根据本发明， 所述待精制溶剂为光气法制备异氰酸酯所产生的含有杂质的废 溶剂或者因溶剂损耗， 需要在制备中补充入反应体系的水、 铁含量及色号不达标 的新鲜溶剂， 其选自邻二氯苯、 氯苯和曱苯中的一种或两种或多种。 所述待精制 溶剂中水分含量为 150-600 ppm, 优选为 200-300 ppm; 铁分含量为 40- 300 ppm, 优选为 50-200 ppm; 光气及氯化氢含量为 0-10000 ppm, 优选为 0-5000 ppm; 铂 -钴色号为 30-100,优选为 40-80;精制后的溶剂中水分≤50 ppm，铁分含量≤5 ppm, 光气和氯化氢含量≤20ppm, 铂-钴色号≤20。
本发明所述的精制后的废溶剂优选重新作为光气法制备异氰酸酯的溶剂循 环使用。
本发明所述的铁分含量均按照铁原子含量计算。
与现有的技术相比， 使用本发明的方法和装置能获得如下优势：
(1)吸附剂和干燥剂均匀混合，有效防止干燥剂吸水后板结、干燥剂吸收水分、 光气和氯化氢放热导致的局部过热以及沟流的产生， 同时有效降低压降。
(2)能够快速将待精制溶剂中水分脱除至很低水平 (≤50 ppm), 铁分含量降至 很低水平(≤5 ppm) , 同时脱除溶剂中夹带的光气及氯化氢含量至很低水平 (<20ppm), 降低溶剂的铂 -钴色号(≤20), 提高异氰酸酯的 L色， 处理效杲明显， 实现资源回收利用， 减少设备腐蚀。
(3)解决了目前光气化法制备异氰酸酯过程中采用精馏工艺脱除溶剂中微量 水、 光气及氯化氢需要蒸汽量较多， 能耗较高的问题。 具有生产工艺流程简单， 成本低， 能够大大减少溶剂损耗， 以年产 80 万吨粗 MDI计算可以减少溶剂损耗 100吨 /年， 降低生产成本。 附图说明
图 1是实施例 1-5中使用的根据本发明的多级吸收塔装置示意图。 具体实施方式
以下实施例用于进一步说明本发明， 但本发明不受其限制。 下列实施例中未 注明具体条件的实验方法， 通常按照常规条件。
在以下实施例中：
异氰酸酯的 L色通过本领域技术人员已知的 CIE表色系统的 L、a、b值测定； 溶剂中的铁分含量是通过原子吸收发射光 i昝仪在 248.33 nm处测得的铁原子 含量；
溶剂中水分采用全自动卡尔费休水分测定仪测定；
溶剂中光气及氯化氢含量通过氢氧化钠和光气及氯化氢反应 , 然后加入硝酸 银， 通过自动电位滴定仪测定剩余银离子含量， 然后转化为溶剂中光气与氯化氢 含量；
所使用的椰壳质活性炭商购自承德净达活性炭制造公司； 所使用的大孔树脂 D101商购自西安蓝晓科技有限公司。 实施例 1
干燥剂为氫氧化钠， 吸收塔内干燥剂总量为 500kg, 干燥剂的 BET比表面积 为 2500 m2/g, 平均粒径为 1 μηι, 机械强度为 90%。 吸附剂为椰壳质活性炭， BET比表面积为 3000 m2/g， 中孔孔径为 2 nm,机械强度为 90%。 吸收塔顶部及 底部支撑填料为 3A型分子筛， 总量均为 50 kg。 吸收层 N为 4层， 第一级至第 三级吸收层均由连接外部进料管的上部液体分布装置和下部吸收填料层组成， 第一级吸收层的吸收填料层的干燥剂与吸附剂的质量比为 2:1 , 干燥剂占多级吸 收塔内所有干燥剂质量的 5%, 第二级和第三级每级吸收层的吸收填料层的干燥 剂与吸附剂的质量比为 10:1 , 第二级和第三级每级吸收层的吸收填料层的干燥 剂占多級吸收塔内所有干燥剂质量的 45%, 第四级吸收层的吸收填料层的干燥 剂与吸附剂的质量比为 10:1， 干燥剂占多级吸收塔内所有干燥剂质量的 5%。 每 级吸收层的吸收填料层的干燥剂与吸附剂均勾混合填充， 多级吸收塔第一级吸 收层外部进料管与塔顶出口之间的压降为 10 kPa。
待精制溶剂为 MDI生产装置异常开停车产生的废氯苯溶剂， 其总进料量的 体积流速与多级吸收塔内所有干燥剂与吸附剂总质量的比为 1:300 m3 /kg/h, 第 一级吸收层的外部进料管的进料量占待精制溶剂总进料量的体积的 1/5, 第二级 吸收层的外部进料管的进料量占待精制溶剂总进料量的体积的 7/10, 第三级吸 收层的外部进料管的进料量占待精制溶剂总进料量的 1/10。 待精制溶剂在多级 吸收塔内的停留时间为 2 h， 精制后的溶剂与待精制溶剂的回流比为 1。
待精制溶剂中水分含量为 300 ppm, 铁分含量为 50 ppm, 光气及氯化氢含量 为 5000 ppm, 铂-鈷色号为 40,精制后的溶剂分析结果如表 1所示。将精制后的 溶剂重新作为 MDI生产的溶剂， 生产方法参照专利文献 CN1254724A中所述生 产 MDI的方法， 所得到的产品 MDI的分析结杲如表 1所示。 实施例 2
干燥剂为氢氧化钾， 吸收塔内干燥剂总量为 1000 kg, 干燥剂的 BET比表面 积为 3000 m2/g, 平均粒径为 3 μηι, 机械强度为 95%。 吸附剂为椰壳质活性炭， BET比表面积为 3500 m2/g, 中孔孔径为 4 nm，机械强度为 93%。 吸收塔顶部及 底部支撑填料为 5A型分子筛， 总量均为 80 kg。 吸收层 N为 5层， 第一级至第 四级吸收层均由连接外部进料管的上部液体分布装置和下部吸收填料层组成， 第一级吸收层的吸收填料层的干燥剂与吸附剂的质量比为 3:1 , 干燥剂占多级吸 收塔内所有干燥剂质量的 7%，第二级至第四级每级吸收层的吸收填料层的干燥 剂与吸附剂的质量比为 9:1 , 第二级至第四级每级吸收屋的吸收填料层的干燥剂 占多级吸收塔内所有干燥剂质量的 29%, 第五级吸收层的吸收填料层的干燥剂 与吸附剂的质量比为 6:1 , 干燥剂占多级吸收塔内所有干燥剂质量的 6%。 每级 吸收层的吸收填料层的干燥剂与吸附剂均匀混合填充。 多级吸收塔第一级吸收 层外部进料管与塔顶出口之间的压降为 16 kPa。
待精制溶剂为 TDI生产装置大修时产生的废二氯苯溶剂，其总进料量的体积 流速与多級吸收塔内所有干燥剂与吸附剂总质量的比为 1:400 m3/kg/h, 第一级 吸收层的外部进料管的进料量占待精制溶剂总进料量的体积的 1/8, 第二级吸收 层及第三级吸收层的外部进料管的进料量分别占待精制溶剂总进料量的体积的 3/8, 第四级吸收层的外部进料管的进料量占待精制溶剂总进料量的 1/8。待精制 溶剂在多级吸收塔内的停留时间为 3h， 精制后的溶剂与待精制溶剂的回流比为 1.5.
待精制溶剂中水分含量为 200 ppm, 铁分含量为 150 ppm, 光气及氯化氢含 量为 4000 ppm, 铂-钴色号为 60，精制后的溶剂分析结果如表 1所示。 将精制后 的溶剂重新作为 TDI生产的溶剂， 生产方法参照专利文献 CN101205199A中所 述生产 TDI的方法， 所得到的产品 TDI的分析结果如表 1所示。 实施例 3
干燥剂为氢氧化钠， 吸收塔内干燥剂总量为 800 kg, 干燥剂的 BET比表面 积为 4000 m2/g, 平均粒径为 5 μηι, 机械强度为 98%。 吸附剂为二乙烯苯聚合物 基的非极性大孔树脂 D101 , BET比表面积为 4500 m2/g, 中孔孔径为 5 nm, 机 械强度为 95%。 吸收塔顶部及底部支撑填料为 10A型分子 ， 总量均为 90 kg。 吸收层 N为 6层， 第一级至第五级吸收层均由连接外部进料管的上部液体分布 装置和下部吸收填料层组成， 第一级吸收层的吸收填料层的干燥剂与吸附剂的 ^量比为 4:1， 干燥剂占吸收塔内所有干燥剂质量的 10%, 第二级至第五级每级 吸收层的吸收填料层的干燥剂与吸附剂的质量比为 5:1， 第二级至第五级每级吸 收层的吸收填料层的干燥剂占多级吸收塔内所有干燥剂质量的 20.5%，第六級吸 收层的吸收填料层的干燥剂与吸附剂的质量比为 5:1， 干燥剂占多級吸收塔内所 有干燥剂质量的 8%。 每级吸收层的吸收填料层的干燥剂与吸附剂均勾混合填 充， 多级吸收塔第一級吸收层外部进料管与塔顶出口之间的压降为 25 kPa。
待精制溶剂为欲加入 HDI生产装置的新鲜氯苯溶剂，其总进料量的体积流速 与多级吸收塔内千燥剂与吸附剂总质量的比为 1:500 m3/kg/h, 第一级吸收层的 外部进料管的进料量占待精制溶剂总进料量的体积的 1/5, 第二级吸收层至第四 级吸收层的外部进料管的进料量占待精制溶剂总进料量的体积的 1/5, 第五级吸 收层的外部进料管的进料量占待精制溶剂总进料量的体积的 1/5。待精制溶剂在 多级吸收塔内的停留时间为 4 h, 精制后的溶剂与待精制溶剂的回流比为 3。
待精制溶剂中水分含量为 150 ppm, 铁分含量为 200 ppm, 光气及氯化氢含 量为 0 ppm， 铂-钴色号为 80。 精制后的溶剂分析结果如表 1所示， 将精制后的 溶剂作为 HDI生产的溶剂， 生产方法参照专利文献 CN101429139A中所述生产 HDI的方法， 所得到的产品 HDI的分析结果如表 1所示。 实施例 4
干燥剂为氧化钙， 吸收塔内千燥剂总量为 1200 kg, 干燥剂的 BET比表面积 为 4200 m2/g, 平均粒径为 4.5 μιη, 机械强度为 95%。 吸附剂为苯乙烯聚合物的 非极性大孔吸附树脂 LX-60, BET比表面积为 4800 m2/g, 中孔孔径为 4.5 nm, 机械强度为 93%。吸收塔顶部及底部支撑填料为 5A型分子筛，总量均为 120 kg。 吸收层 N为 6层， 第一级至第五级吸收层均由连接外部进料管的上部液体分布 装置和下部吸收填料层組成， 第一级吸收层的吸收填料层的干燥剂与吸附剂的 质量比为 4:1 , 干燥剂占吸收塔内所有千燥剂质量的 10%, 第二級至第五级每级 吸收层的吸收填料层的干燥剂与吸附剂的质量比为 5:1 , 第二级至第五级每级吸 收层的吸收填料层的干燥剂占多级吸收塔内所有干燥剂质量的 20.5%，第六级吸 收层的吸收填料层的干燥剂与吸附剂的质量比为 5:1 , 干燥剂占多级吸收塔内所 有干燥剂质量的 8%。 每级吸收层的吸收填料层的干燥剂与吸附剂均句混合填 充， 多级吸收塔第一级吸收层外部进料管与塔顶出口之间的压降为 25 kPa。
待精制溶剂为欲加入 MDI生产装置的新鲜曱苯溶剂， 其总进料量的体积流 速与多级吸收塔内干燥剂与吸附剂总质量的比为 1:400 m3/kg/h, 第一级吸收层 的外部进料管的进料量占待精制溶剂总进料量的体积的 1/5, 第二级吸收层至第 四級吸收层的外部进料管的进料量占待精制溶剂总进料量的体积的 1/5, 第五级 吸收层的外部进料管的进料量占待精制溶剂总进料量的体积的 1/5。待精制溶剂 在多级吸收塔内的停留时间为 3.5 h, 精制后的溶剂与待精制溶剂的回流比为 2。
待精制溶剂中水分含量为 250 ppm, 铁分含量为 120 ppm, 光气及氯化氢含 量为 O ppm, 铂-钴色号为 60。 精制后的溶剂分析结杲如表 1所示， 将精制后的 溶剂作为 MDI生产的溶剂， 生产方法参照专利文献 CN1254724A 中所述生产 MDI的方法， 所得到的产品 MDI的分析结杲如表 1所示。 实施例 5
干燥剂为氢氧化钾， 吸收塔内干燥剂总量为 900 kg, 干燥剂的 BET比表面 积为 3200 m2/g, 平均粒径为 5 μπι， 机械强度为 95%。 吸附剂为苯乙烯聚合物的 非极性大孔吸附树脂 LX-20, BET比表面轵为 5000 m2/g, 中孔孔径为 4 nm, 机 械强度为 95%。 吸收塔顶部及底部支撑填料为 3A型分子筛， 总量均为 90 kg。 吸收层 N为 5层， 第一级至第四级吸收层均由连接外部进料管的上部液体分布 装置和下部吸收填料层组成， 第一级吸收层的吸收填料层的干燥剂与吸附剂的 质量比为 3:1 , 干燥剂占多级吸收塔内所有干燥剂质量的 7%, 第二级至第四级 每级吸收层的吸收填料层的干燥剂与吸附剂的质量比为 9:1， 第二级至第四级每 级吸收层的吸收填料层的干燥剂占多级吸收塔内所有干燥剂质量的 29%， 第五 级吸收层的吸收填料层的干燥剂与吸附剂的质量比为 6:1 , 干燥剂占多级吸收塔 内所有干燥剂质量的 6%。每级吸收层的吸收填料层的干燥剂与吸附剂均匀混合 填充。 多级吸收塔第一级吸收层外部进料管与塔顶出口之间的压降为 20 kPa。
待精制溶剂为 TDI生产装置大修时产生的废氯苯溶剂，其总进料量的体积流 速与多级吸收塔内所有干燥剂与吸附剂总 ^量的比为 1:420 m3/kg/h, 第一级吸 收层的外部进料管的进料量占待精制溶剂总进料量的体积的 1/8, 第二级吸收层 及第三级吸收层的外部进料管的进料量分别占待精制溶剂总进料量的体积的 3/8, 第四级吸收层的外部进料管的进料量占待精制溶剂总进料量的 1/8。待精制 溶剂在多级吸收塔内的停留时间为 4h, 精制后的溶剂与待精制溶剂的回流比为 1.5。
待精制溶剂中水分含量为 260 ppm, 鉄分含量为 180 ppm, 光气及氯化氢含 量为 3000 ppm, 铂-钴色号为 50,精制后的溶剂分析结果如表 1所示。将精制后 的溶剂重新作为 TDI生产的溶剂， 生产方法参照专利文献 CN101205199A中所 述生产 TDI的方法， 所得到的产品 TDI的分析结杲如表 1所示。 对比例 1 通过减压精德塔处理废氯苯溶剂。 减压精馏塔的操作压力为 40 kpa, 回流比 为 2:1 , 塔底温度控制在 100- 105 °C , 塔顶温度控制在 60-65°C。
待精制溶剂为 MDI生产装置异常开停车产生的废氯苯溶剂， 其中含水量为 300 pm, 铁分含量为 50 ppm, 光气及氯化氢含量为 5000 ppm, 铂-钴色号为 60, 精制后的溶剂分析结果如表 1所示。 将精制后的溶剂重新作为 MDI生产的溶剂， 生产方法参照专利文献 CN1254724A中所述生产 MDI的方法，所得到的产品 MDI 的分析结果如表 1所示。 对比例 2
通过共沸精馏塔处理废二氯苯溶剂， 共沸剂为四氢呋喃， 将共沸剂与待精制 溶剂一起加入共沸精馏塔塔釜， 共沸剂与待精制溶剂质量比为 10:i， 操作回流比 为 2, 共沸精馏塔的操作压力为 101.3kpa,塔顶温度控制在 65-69 °C , 塔底温度控 制在 138-140 °C 0
待精制溶剂为 TDI生产装置大修后溶剂运转期间产生的废二氯苯溶剂，其中 含水量为 280 ppm, 铁分含量为 45 ppm, 光气及氯化氢含量为 4800 ppm， 铂-钻 色号为 55, 精制后的溶剂分析结果如表 1 所示。 将精制后的溶剂重新作为 TDI 生产的溶剂，生产方法参照专利文献 CN101205199A中所述生产 TDI的方法，所 得到的产品 TDI的分析结果如表 1所示。 表 1 分析结果
Figure imgf000012_0001

Claims

权利要求
1、 一种光气法制异氰酸酯的溶剂的精制方法， 其特征在于， 待精制溶剂采 用多级吸收塔处理， 该多级吸收塔从下而上包括底部支撑填料段、 中间填料吸收 段和顶部支撑填料段；所述中间填料吸收段包括 N级吸收层并且 N为 3-8的整数， 优选 N为 4-6的整数， 第一级吸收层至第 N级吸收层从下而上排列； 其中， 第一 级至第 N-1级吸收层均由连接外部进料管的上部液体分布装置和下部吸收填料层 组成， 每级吸收层的吸收填料层由干燥剂和吸附剂均匀混合而成。
2、 根据权利要求 1 所述的方法， 其特征在于， 所述第一级吸收层的吸收填 料层的干燥剂与吸附剂的质量比为 1:1-5:1 ,优选 2:1-4:1 ,干燥剂占多级吸收塔内 所有干燥剂质量的 4- 15%, 优选 5-10%; 第 N级吸收层的吸收填料层的干燥剂与 吸附剂的质量比为 5:1-12:1 ,优选 6:1-10:1，千燥剂占多级吸收塔内所有干燥剂质 量的 4-15%， 优选 5-10%; 第二级至第 N-1级吸收层的每级吸收填料层的干燥剂 与吸附剂的质量比为 5:1-15:1，优选 6:1-10:1 ,每级吸收填料层的干燥剂占多级吸 收塔内所有干燥剂质量的 15-92%, 优选 20-45%。
3、 根据权利要求 1或 2所述的方法， 其特征在于， 所述干燥剂为减性干燥 剂，选自氧化钙、氢氧化钠和氢氧化钾中的一种或两种或多种，优选为氢氧化钠； 所述干燥剂的 BET比表面积为 1500-4500 m2/g, 优选为 2500-4000 m2/g; 平均粒 径为 0.5-10 μιη, 优选为 1-5 μηι; 机械强度为 85-99%, 优选为 90-98%。
4、 根据权利要求 1-3 任一项所述的方法， 其特征在于， 所述吸附剂为大孔 树脂吸附剂或活性炭， 其中大孔树脂吸附剂选自苯乙烯聚合物的非极性大孔吸附 树脂和二乙烯苯聚合物的非极性大孔吸附树脂中的一种或两种或多种 ,优选选自 D101、 LX-60和 LX-20中的一种或两种或多种； 活性炭优选为椰壳质活性炭； 所 述吸附剂的 BET比表面积为 2500-5000 m2/g, 优选为 3000-4500 m2/g; 中孔孔径 为 0.5-10 nm, 优选为 1-5 nm; 机械强度为 85-98%, 优选为 90-95%。
5、 根据权利要求 1所迷的方法， 其特征在于， 所述顶部支撑填料段和底部 支撑填料段的支撑填料选自碎石、 分子筛和活性炭中的一种或两种或多种， 优选 分子筛， 更优选 3A型分子筛； 顶部支撑填料与底部支撑填料质量相同， 顶部支 撑填料与多级吸收塔内所有干燥剂的质量比为 1 :20-1 :3 , 优选为 1 :15-1:5。
6、 才艮据权利要求 1-5任一项所述的方法， 其特征在于， 所述待精制溶剂总 进料量的体积流速与多级吸收塔内所有干燥剂与吸附剂总质量的比为
1 :200-1 :600m3/kg/h, 优选 1 :300-1 :500 m3/kg/h。
7、 根据权利要求 6所述的方法， 其特征在于， 所述第一级吸收层的外部进 料管的进料量体积占待精制溶剂总进料量体积的 1/15-1/3 , 优选 1/10- 1/5 , 第 N- 1 级吸收层的外部进料管的进料量占待精制溶剂总进料量的 1/15-1/3 , 优选 1/10-1/5, 第二级至笫 N-2级的各级吸收层的外部进料管的进料量占待精制溶剂 总进料量的 1/15-4/5, 优选 1/10-7/10。
8、 根据权利要求 7所述的方法， 其特征在于， 所述待精制溶剂在多级吸收 塔内的停留时间为 0.25-8 h, 优选为 2-4 h。
9、 根据权利要求 6-8任一项所述的方法， 其特征在于， 所述精制后的溶剂 一部分回流与待精制溶剂混合后进入多级吸收塔， 回流比为 0.5-4， 优选为 1-3; 所述多级吸收塔第一级吸收层外部进料管与塔顶出口之间的压降为 5-40 kPa, 优 选为 10-25 kPa。
10、 根据权利要求 1-9任一项所述的方法， 其特征在于， 所述待精制溶剂为 光气法制备异氰酸酯所产生的含有杂庸的废溶剂或者因溶剂损耗， 需要在制备中 补充入反应体系的水、 铁含量及色号不达标的新鲜溶剂， 其选自邻二氯苯、 氯苯 和甲苯中的一种或两种或多种； 所述待精制溶剂中水分含量为 150-600 ppm， 优 选为 200- 300 ppm; 铁分含量为 40-300 ppm, 优选为 50- 200 ppm; 光气及氯化氢 含量为 0-10000 ppm, 优选为 0-5000 ppm; 铂-钴色号为 30-100, 优选为 40-80; 精制后的溶剂中水分≤50 ppm, 铁分含量≤5 111, 光气和氯化氢含量≤20ppm, 铂 -钴色号≤20。
11、 一种用于精制光气法制异氰酸酯的溶剂的多级吸收塔， 其特征在于， 所 述多级吸收塔从下而上包括底部支撑填料段、 中间填料吸收段和顶部支撑填料 段； 所述中间填料吸收段包括 N级吸收层并且 N为 3-8的整数， 优选 N为 4-6 的整数， 第一级吸收层至第 N级吸收屋从下而上排列； 其中， 第一级至第 N-1 级吸收层均由连接外部进料管的上部液体分布装置和下部吸收填料层组成，每级 吸收层的吸收填料层由干燥剂和吸附剂均匀混合而成。
12、 根据权利要求 11 所述的多级吸收塔， 其特征在于， 所述第一级吸收层 的吸收填料层的干燥剂与吸附剂的质量比为 1:1-5:1 ,优选 2:1-4:1 ,干燥剂占多级 吸收塔内所有干燥剂质量的 4-15%, 优选 5-10%; 第 N级吸收层的吸收填料层的 干燥剂与吸附剂的质量比为 5:1-12:1 ,优选 6:1-10:1，干燥剂占多级吸收塔内所有 干燥剂质量的 4-15%, 优选 5- 10%; 第二级至第 N-1级吸收层的每级吸收填料层 的干燥剂与吸附剂的质量比为 5:1-15:1 ,优选 6:1-10:1 ,每级吸收填料层的干燥剂 占多级吸收塔内所有千燥剂质量的 15-92%, 优选 20-45%。
13、 根据权利要求 U或 12所述的多级吸收塔， 其特征在于， 所述干燥剂为 碱性干燥剂， 选自氧化钙、 氢氧化钠和氢氧化钾中的一种或两种或多种， 优选为 氢氧化钠； 所述干燥剂的 BET 比表面积为 1500-4500 m2/g， 优选为 2500-4000 m2/g;平均粒径为 0.5-10 μηι,优选为 1-5 μπι;机械强度为 85-99%,优选为 90-98%。
14、 根据权利要求 11-13任一项所述的多级吸收塔， 其特征在于， 所述吸附 剂为大孔树脂吸附剂或活性炭，其中大孔树脂吸附剂选自苯乙烯聚合物的非极性 大孔吸附树脂和二乙烯苯聚合物的非极性大孔吸附树脂中的一种或两种或多种， 优选选自 D101、 LX-60和 LX-20中的一种或两种或多种； 活性炭优选为椰壳质 活性炭；所述吸附剂的 BET比表面积为 2500-5000 m2/g，优选为 3000-4500 m2/g; 中孔孔径为 0.5-10 nm, 优选为 1-5 nm; 机械强度为 85-98%， 优选为 90- 95%。
15、 ^据权利要求 11 所述的多级吸收塔， 其特征在于， 所述顶部支撑填料 段和底部支撑填料段的支撑填料选自碎石、分子筛和活性炭中的一种或两种或多 种， 优选分子篩， 更优选 3A型分子筛； 顶部支撑填料与底部支撑填料质量相同， 顶部支撑填料与多级吸收塔内所有干燥剂的质量比为 1 :20-1:3 , 优选为 1 :15-1 :5。
16、 权利要求 11-15任一项所述的多级吸收塔在光气法制备异氰酸酯中的应 用。
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