WO2022047681A1 - 制备mdi的方法和光气制备方法 - Google Patents

制备mdi的方法和光气制备方法 Download PDF

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WO2022047681A1
WO2022047681A1 PCT/CN2020/113112 CN2020113112W WO2022047681A1 WO 2022047681 A1 WO2022047681 A1 WO 2022047681A1 CN 2020113112 W CN2020113112 W CN 2020113112W WO 2022047681 A1 WO2022047681 A1 WO 2022047681A1
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catalyst
phosgene
packing section
activated carbon
mass
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PCT/CN2020/113112
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English (en)
French (fr)
Inventor
文放
王振有
赵东科
陈良进
徐丹
董超
张宏科
吴雪峰
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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 PCT/CN2020/113112 priority Critical patent/WO2022047681A1/zh
Publication of WO2022047681A1 publication Critical patent/WO2022047681A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/18—Carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/20—Carbon compounds
    • B01J27/22—Carbides
    • B01J27/224—Silicon carbide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/80—Phosgene
    • 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
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C265/00—Derivatives of isocyanic acid
    • C07C265/14—Derivatives of isocyanic acid containing at least two isocyanate groups bound to the same carbon skeleton

Definitions

  • the invention relates to the technical fields of phosgene preparation and MDI preparation, in particular to a phosgene preparation method capable of reducing trace impurities in phosgene and an MDI preparation method capable of improving the stability of MDI production process.
  • Phosgene is an important raw material in the production process of MDI. Phosgene is obtained by the phosgene synthesis reaction between CO and chlorine under the catalytic reaction of activated carbon.
  • Chinese published patent CN105916810A describes the control method of free chlorine in phosgene and the operation scheme of starting and stopping, but this patent only focuses on the control of free chlorine, and does not involve the control of high-boiling chlorinated hydrocarbons.
  • Chinese patent CN1156393C introduces a method for preparing phosgene with a carbon tetrachloride content of less than 150 ppm, and describes the scheme of the preparation process. Likewise, this document does not recognize the effect of high-boiling substances in chlorides on the reaction yield during the phosgenation reaction.
  • the present invention provides a method for preparing phosgene capable of reducing the impurity content of high-boiling chlorinated hydrocarbons in phosgene and a method for preparing MDI with improved process stability.
  • One aspect of the present invention provides a method for preparing MDI (diphenylmethylene diisocyanate), the method comprising: in the presence of a solvent, phosgene raw material and MDA (diphenylmethylene diamine) are prepared in light
  • a phosgenation reaction is carried out in the gasification reactor to generate a reaction product comprising the MDI and hydrogen chloride, and the hydrogen chloride is discharged from the phosgenation reactor as an external exhaust phase, and all the phosgenation reaction will be used to participate in the phosgenation reaction.
  • the mass content of the chlorinated hydrocarbon impurities contained in the phosgene raw material is controlled to be less than 1000 ppm; the chlorinated hydrocarbon impurities are saturated and/or unsaturated chlorinated hydrocarbons with 2 carbon atoms.
  • the mass content of the above-mentioned chlorinated hydrocarbon impurities contained in the phosgene raw material is, for example, less than 1000 ppm, less than 900 ppm, less than 800 ppm, less than 600 ppm, less than 500 ppm, less than 400 ppm, less than 100 ppm, less than 50 ppm, less than 20 ppm, less than 15 ppm, etc., such as greater than 0.1 ppm and less than 1000 ppm, eg greater than 1.5 ppm and less than 400 ppm.
  • the chlorinated hydrocarbon impurities refer to saturated and/or unsaturated chlorinated hydrocarbons with 2 carbon atoms, and are specifically composed of one or more of the following compounds: ethylene monochloride, ethylene dichloride , trichloroethane, tetrachloroethane, monochloroethylene, dichloroethylene, trichloroethylene, tetrachloroethylene, monochloroacetylene, dichloroacetylene, these impurities are also referred to herein as high boiling point chlorinated hydrocarbon impurities.
  • the above-mentioned chlorinated hydrocarbon impurities contained in phosgene may be constituted by one or more of the specific chlorinated hydrocarbon compounds listed above.
  • the solvent includes one or more of chlorobenzene, dichlorobenzene, and toluene, preferably, the solvent is chlorobenzene.
  • the phosgene is prepared by performing a phosgene synthesis reaction with carbon monoxide and chlorine in the presence of a catalyst in a phosgene synthesis reactor, and a catalyst and an inert filler are loaded in the catalyst loading zone of the phosgene synthesis reactor.
  • the catalyst is composite activated carbon with high thermal conductivity, and the catalyst loading area is divided into a first loading section, a second loading section and a third loading section from bottom to top; based on the catalyst and inert packing in each loading section The total mass of the catalyst in the second packing section is greater than that in the first packing section, and the catalyst mass percentage in the third packing section is greater than that in the second packing section. percentage;
  • the preparation of the high thermal conductivity composite activated carbon includes the following steps: mixing the activated carbon powder, the granular additives and the adhesive with water to make a paste, drying and molding, and then heating the activated carbon powder at 600-800° C. (for example, 600° C., 650° C., 700°C, 750°C, 800°C, etc.) for constant temperature carbonization (for example, the constant temperature carbonization time is more than 2h, such as 2-72h, such as 2h, 4h, 8h, 24h, 48h, 72h, etc.) to obtain the high thermal conductivity composite activated carbon;
  • the mass ratio of the granular additive and the activated carbon powder is (1-10):100 (for example, 1:100, 3:100, 5:100, 7:100, 10:100, etc.), and the granular additive is selected from One or more of alumina ceramic balls, silicon carbide, graphite, and boron carbide.
  • the drying conditions for the drying molding include placing the paste in a constant temperature
  • the above-mentioned high thermal conductivity composite activated carbon is used as a catalyst, and the catalyst is loaded in the catalyst loading area of the phosgene synthesis reactor according to a specific loading method.
  • the reactivity between carbon and chlorine is greatly reduced,
  • the generation of high-boiling chlorinated hydrocarbons (saturated and/or unsaturated chlorinated hydrocarbons with 2 carbon atoms) is reduced, thereby effectively reducing the impurity content of high-boiling chlorinated hydrocarbons in the phosgene synthesis process, and high-boiling chlorinated hydrocarbons can be obtained
  • the phosgene raw material with low impurity content, specifically, the mass content of high-boiling point chlorinated hydrocarbon impurities in the obtained phosgene is less than 1000ppm, such as more than 0.1ppm and less than 1000ppm, such as less than 400ppm, such as more than 1.5ppm and
  • the mass percentage of the catalyst in the first packing section is 0%-50% (for example, 0%, 10%, 20%, 30%, 40%, 50%, etc.)
  • the mass percentage of the catalyst in the second packing section is 20%-80% (for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, etc.)
  • the mass percentage of the catalyst in the third packing section is 40%-100% (for example, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc.
  • the catalyst mass percentage in the second packing section is greater than the catalyst mass percentage in the first packing section, and the catalyst in the third packing section The mass percentage is greater than the catalyst mass percentage in the second packing section;
  • the height ratio of the first packing section is 10%-40% (for example, 10%, 20%, 30%, 40%, etc.), and the height ratio of the second packing section 10%-80% (such as 10%, 30%, 50%, 80%, etc.), the height ratio of the third filling section is 10-80% (such as 10%, 30%, 50%, 80%, etc.) ).
  • the activated carbon powder and granular additives are mixed in advance to form a paste.
  • a paste is formed by adding an appropriate amount of adhesive and water.
  • the mass ratio of the powder is (3-20):100 (for example, 3:100, 5:100, 10:100, 15:100, 20:100, etc.)
  • the mass ratio of the activated carbon powder to the water is (20 -50):100 (for example, 20:100, 30:100, 40:100, etc.)
  • the adhesive used can be, for example, emulsified phenolic resin, activated clay, emulsified coal tar, carboxymethyl cellulose and the like.
  • the inert filler loaded in the catalyst loading zone is one or more of alumina ceramic balls, spherical silicon carbide, and graphite.
  • the above-mentioned phosgene preparation process is specifically a technical scheme formed on the basis of the existing technology for preparing phosgene by phosgene synthesis reaction under the catalysis of activated carbon based on carbon monoxide and chlorine, mainly in that the existing catalyst is improved and Combined with the specific packing method of the catalyst, the impurity content of high-boiling point chlorinated hydrocarbons in the existing phosgene synthesis reaction can be reduced, and phosgene with a high-boiling point chlorinated hydrocarbon content of less than 1000 ppm can be obtained.
  • other process conditions for the preparation of phosgene corresponding conventional process conditions in the art can be adopted.
  • the pressure is 1 barg-7 barg, preferably 2.5 barg-3.5 barg
  • the phosgene synthesis reactor that is, the phosgene synthesis reaction tower
  • the phosgene synthesis reactor that is, the phosgene synthesis reaction tower
  • the phosgene synthesis reactor that is, the phosgene synthesis reaction tower
  • the volume flow ratio of carbon monoxide and chlorine gas is 100:(85-98).
  • the mass content of the high-boiling chlorinated hydrocarbon impurities in the external exhaust gas phase is less than 800 ppm, such as greater than 0.5 ppm and less than 800 ppm, such as less than 350 ppm , such as greater than 2ppm and less than 350ppm;
  • the mass content of the high-boiling point chlorinated hydrocarbons in the solvent of the reaction system is less than 4%, such as greater than 50 ppm and less than 4%, such as less than 2.5%, For example, more than 100 ppm and less than 2.5%.
  • the method for preparing MDI provided by the present invention is specifically a technical scheme formed by improving the existing technology based on phosgene and MDA for preparing MDI through phosgenation reaction, mainly in that the high boiling point chlorine in the phosgene raw material is treated Substitute hydrocarbon impurity content control, so as to achieve technical effects such as improving the stability of the process.
  • other process conditions of the method for preparing MDI corresponding conventional process conditions in the art can be adopted.
  • the reaction conditions for the phosgenation reaction include: the pressure of the phosgenation reaction is 1 barg-7 barg, preferably 2.5 barg-3.5 barg, and the maximum temperature of the phosgenation reactor is 110 ° C-180 ° C, preferably 125°C-145°C, the mass ratio of pure phosgene participating in the reaction (referring to the phosgene in phosgene solution) to MDA is 1.5-3.0, preferably 2.0-2.5; the MDA and the phosgene are respectively used
  • the solvent is prepared into MDA solution and phosgene solution and put into the reaction system.
  • the MDA mass concentration of the MDA solution is 20%-45%, preferably 30%-40%; the phosgene mass concentration of the phosgene solution is 40%-40%- 90%, preferably 60%-75%.
  • the present invention also provides a method for preparing phosgene capable of reducing the impurity content of chlorinated hydrocarbons in phosgene.
  • the phosgene is prepared by performing a phosgene synthesis reaction with carbon monoxide and chlorine in a phosgene synthesis reactor in the presence of a catalyst,
  • the high thermal conductivity composite activated carbon is used as the catalyst in the phosgene synthesis reactor, the catalyst loading zone of the phosgene synthesis reactor is loaded with a mixture of catalyst and inert filler, and the catalyst loading zone of the phosgene synthesis reactor consists of the following It is divided into a first packing section, a second packing section and a third packing section in sequence; based on the total mass of the catalyst and inert packing in each packing section, the mass percentage of the catalyst in the second packing section is greater than that in all the packing sections.
  • the catalyst mass percentage in the first packing section, the catalyst mass percentage in the third packing section is greater than the catalyst mass
  • the preparation of the high thermal conductivity composite activated carbon includes the following steps: mixing the activated carbon powder, the granular additives and the adhesive with water to make a paste, drying and molding, and then heating the activated carbon powder at 600-800° C. (for example, 600° C., 650° C., 700°C, 750°C, 800°C, etc.) for constant temperature carbonization (for example, the constant temperature carbonization time is more than 2h, such as 2-72h, such as 2h, 4h, 8h, 24h, 48h, 72h, etc.) to obtain the high thermal conductivity composite activated carbon;
  • the mass ratio of the granular additive and the activated carbon powder is (1-10):100 (for example, 1:100, 3:100, 5:100, 7:100, 10:100, etc.), and the granular additive is selected from One or more of alumina ceramic balls, silicon carbide, graphite, and boron carbide; preferably, the drying conditions for the drying molding include placing the paste in a constant
  • the chlorinated hydrocarbon impurities are saturated and/or unsaturated chlorinated hydrocarbons with a carbon number of 2, and such impurities are also referred to herein as high boiling point chlorinated hydrocarbon impurities.
  • the content of the chlorinated hydrocarbon impurities is less than 1000ppm, such as less than 1000ppm, less than 900ppm, less than 800ppm, less than 600ppm, less than 500ppm, less than 400ppm, less than 100ppm, less than 50ppm, less than 20ppm, less than 15ppm, etc. , eg greater than 0.1 ppm and less than 1000 ppm, eg less than 400 ppm, eg greater than 1.5 ppm and less than 400 ppm.
  • the mass percentage of the catalyst in the first packing section is 0%-50% (eg 0%, 10%, 20%, 30%) , 40%, 50%, etc.)
  • the mass percentage of the catalyst in the second packing section is 20%-80% (for example, 20%, 30%, 40%, 50%, 60%, 70%, 80% etc.)
  • the mass percentage of the catalyst in the third packing section is 40%-100% (eg 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc.); and based on each The total mass of the catalyst and the inert filler in the packing section, the mass percentage of the catalyst in the second packing section is greater than the mass percentage of the catalyst in the first packing section, and the mass percentage of the catalyst in the third packing section is greater than the The mass percentage of catalyst in the second packing section; based on the total height of the catalyst packing section, the height ratio of the first packing section is 10%-40% (eg 10%, 20%, 30%, 40%, etc.) , the height ratio of the second fill
  • the mass ratio of the adhesive to the activated carbon powder is (3-20):100 (for example, 3:100, 5:100, 10:100, 15:100, 20:100, etc.), and the The mass ratio of activated carbon powder to the water is (20-50):100 (for example, 20:100, 30:100, 40:100, etc.).
  • the inert filler loaded in the catalyst loading zone is one or more of alumina ceramic balls, spherical silicon carbide, and graphite;
  • the chlorinated hydrocarbon impurities are specifically one or more of the following compounds: a Ethyl chloride, dichloroethane, trichloroethane, tetrachloroethane, monochloroethylene, dichloroethylene, trichloroethylene, tetrachloroethylene, monochloroacetylene, dichloroacetylene.
  • a Ethyl chloride dichloroethane, trichloroethane, tetrachloroethane, monochloroethylene, dichloroethylene, trichloroethylene, tetrachloroethylene, monochloroacetylene, dichloroacetylene.
  • the pressure is controlled to be 1barg-7barg, preferably 2.5barg-3.5barg
  • the phosgene synthesis reactor (phosgene synthesis tower) ) outlet temperature is 30 °C-270 °C, preferably 190 °C-220 °C, and the volume flow ratio of carbon monoxide and chlorine is 100:(85-98).
  • HCS substances high-boiling point chlorinated hydrocarbon impurities
  • the inventors of the present application have found through research that in the process for preparing MDI by using phosgene and MDA through phosgenation reaction, when the high-boiling chlorinated hydrocarbons (saturated and/or non-carbon atoms with 2 carbon atoms) in the raw material phosgene When the content of saturated chlorinated hydrocarbons) is high, the effluent hydrogen chloride cannot bring out the high-boiling point chlorinated hydrocarbons in time, which will cause the high-boiling point chlorinated hydrocarbons to be enriched in the process system, resulting in the composition of the solvent in the reaction system.
  • the inventors of the present application have surprisingly found that in the process of preparing MDI, by using a phosgene raw material whose mass content of high-boiling point chlorinated hydrocarbon impurities is controlled to be less than 1000 ppm to prepare MDI, it is possible to avoid the boiling point of the solvent in the reaction system being at the same level as that of MDI. Large fluctuations occur in the preparation process, thereby helping to ensure a relatively stable product yield, improving the stability of the process production, and extending the process cycle.
  • the mass content of the high-boiling point chlorinated hydrocarbon impurities contained in the phosgene raw material is, for example, greater than 0.1 ppm and less than 1000 ppm; in some embodiments, the mass content of the high-boiling point chlorinated hydrocarbon impurities contained in the phosgene raw material is The mass content is eg less than 400 ppm, eg greater than 1.5 ppm and less than 400 ppm.
  • the lower the mass content of the high-boiling point chlorinated hydrocarbon impurities contained in the phosgene raw material the better.
  • phosgene with low impurity content of high-boiling point chlorinated hydrocarbons can be obtained.
  • the quality of high-boiling point chlorinated hydrocarbon impurities can be obtained.
  • the phosgene raw material with a content of less than 1000 ppm can provide a phosgene raw material with a mass content of high-boiling chlorinated hydrocarbon impurities less than 1000 ppm for the downstream MDI preparation, and improve the process stability of MDI preparation.
  • the yield of the chemical reaction process is affected.
  • the inventors have determined that the content of high-boiling point chlorinated hydrocarbons in phosgene is controlled to be less than 1000 ppm, which can ensure that the boiling point of the solvent will not rise significantly during the production process of phosgene, thereby realizing phosgene.
  • the yield of the chemical reaction process is stable and reaches the expected target.
  • the present invention optimizes, improves and prepares the types of catalysts involved in phosgene synthesis, and obtains a high thermal conductivity composite activated carbon, which is used in the synthesis reaction of phosgene in combination with a specific filling method, which greatly reduces the interaction between carbon and chlorine. Reactive, reducing the formation of high-boiling chlorinated hydrocarbons.
  • the content of the present invention is further described below in conjunction with the examples, but the content of the present invention is not limited to the following examples.
  • the test method of specific conditions is not indicated, and it is generally in accordance with conventional conditions.
  • the “content” involved in the text refers to the mass content unless otherwise specified.
  • Silicon carbide Shanghai Baitu, domestic silicon carbide
  • Emulsified phenolic resin Shanghai Latex Factory, HX30;
  • Activated clay Qingdao Wanhong Mining Co., Ltd.;
  • Activated carbon powder Tsurumi, Japan, 4GV-K.
  • HCS substance saturated/unsaturated chlorinated hydrocarbon impurities with a carbon number of 2, denoted as HCS substance
  • the content of various high-boiling point chlorinated hydrocarbon impurities is obtained by gas chromatography, and the sum of the contents of each high-boiling point chlorinated hydrocarbon impurity is the total content of high-boiling point chlorinated hydrocarbon impurities.
  • phosgene is prepared by using a phosgene synthesis device.
  • the content of hydrocarbons (such as ethane, ethylene, acetylene, etc.) in the introduced CO is less than 1 ppm, and the volume flow ratio of CO to chlorine is 100:93.
  • the operating temperature of the phosgene synthesis (ie the outlet temperature of the phosgene synthesis reactor) is 200°C, the operating pressure is 3.0 barg, the activated carbon is packed in the tube, the diameter of the tube is DN50 (that is, the diameter of the tube is 50mm), and the length of the tube is 5000mm, the catalyst used is 4GV type activated carbon from Tsurumi, Japan, and the inert agent is alumina ceramic balls; the catalyst loading area is divided into three sections from bottom to top, and the loading method is that the height of the first section is 1.0m, mixed with 80wt% oxidation Aluminum ceramic balls, 20wt% activated carbon, the height of the second section is 1.0m, mixed with 40wt% alumina ceramic balls, 60wt% activated carbon, and the third section height is 3.0m, all of which are activated carbon.
  • the content of high-boiling point chlorinated hydrocarbons (HCS substances) in the phosgene produced by phosgene synthesis is detected to be 6520 ppm, and it is continuously sent to the phosgenation reactor to react with MDA to generate MDI.
  • the solvent used in the phosgenation reaction is chlorobenzene.
  • the pressure of the gasification reaction is 3.2 barg
  • the maximum temperature of the phosgenation reactor is 135°C
  • the mass ratio of pure phosgene and MDA participating in the reaction is 2.5
  • the MDA mass of the MDA solution (solvent is chlorobenzene) put into the reaction system The concentration was 30%, and the phosgene concentration in the phosgene solution (the solvent was chlorobenzene) put into the reaction system was 70%.
  • the total amount of HCS in chlorobenzene, the solvent used in the phosgenation reaction reached 4%, which caused the boiling point of the solvent to rise from 132 °C to 144 °C, and the phosgenation reaction yield decreased from 99.5%.
  • the system began to show obvious blockage. After 8 months of operation, it had to stop to drain, replace the solvent, and remove the HCS substance in the solvent.
  • This comparative example uses a phosgene synthesis device with by-product steam.
  • the activated carbon is different from that of Comparative Example 1, and the catalyst loading method is the same as that of Comparative Example 1.
  • the content of high-boiling chlorinated hydrocarbons (marked as HCS substances) exceeds the standard.
  • phosgene is prepared by using a phosgene synthesis device.
  • the hydrocarbons in the introduced CO are less than 1 ppm, the volume flow ratio of CO and chlorine is 100:93, and the phosgene synthesis operating temperature (that is, the phosgene synthesis reaction
  • the outlet temperature of the device) is 205 °C, the operating pressure is 3.0 barg, the activated carbon is packed in the tube, the diameter of the tube is DN50, the length of the tube is 5000mm, and the catalyst used is Norit-B type activated carbon from Norit, the Netherlands , the inert agent uses alumina ceramic balls; the catalyst loading area is divided into three sections from bottom to top, the filling method is that the height of the first section is 1.0m, mixed with 80wt% alumina ceramic balls and 20wt% activated carbon, and the height of the second section is 1.0 m. m, mixed with 40wt% alumina ceramic balls and 60wt% activated carbon, the height of the
  • HCS substances high-boiling point chlorinated hydrocarbons
  • the content of high-boiling point chlorinated hydrocarbons (HCS substances) in the phosgene produced by phosgene synthesis is detected to be 7710 ppm, and is continuously sent to the phosgenation reactor to react with MDA to generate MDI.
  • the solvent used in the phosgenation reaction is chlorobenzene.
  • the pressure of the gasification reaction is 3.2 barg
  • the maximum temperature of the phosgenation reactor is 135°C
  • the mass ratio of pure phosgene and MDA participating in the reaction is 2.5
  • the MDA mass of the MDA solution (solvent is chlorobenzene) put into the reaction system The concentration was 30%, and the phosgene concentration in the phosgene solution (the solvent was chlorobenzene) put into the reaction system was 70%.
  • the total amount of HCS in chlorobenzene, the solvent used in the phosgenation reaction reached 5.2%, which caused the boiling point of the solvent to rise from 132 °C to 141 °C, and the phosgenation reaction yield decreased from 99.5%.
  • the system began to show obvious blockage. After 7.5 months of operation, the system had to be stopped to drain and replace the solvent to remove the HCS substance in the solvent.
  • This comparative example uses a phosgene synthesis device with by-product steam.
  • the activated carbon is the same as that of Comparative Example 1, and the filling method is different from that of Comparative Example 1.
  • the content of high-boiling chlorinated hydrocarbons (marked as HCS substances) exceeds the standard.
  • phosgene is prepared by using a phosgene synthesis device.
  • the content of hydrocarbons in the introduced CO is less than 1 ppm
  • the volume flow ratio of CO and chlorine is 100:93
  • the phosgene synthesis operating temperature (that is, phosgene synthesis
  • the outlet temperature of the reactor) is 205 ° C
  • the operating pressure is 3.0 barg
  • the activated carbon is packed in the tube
  • the diameter of the tube is DN38
  • the length of the tube is 5000mm
  • the catalyst used is Japan Tsurumi 4GV type activated carbon, inert
  • the catalyst is made of alumina ceramic balls; the catalyst loading area is divided into three sections from bottom to top.
  • the filling method is that the height of the first section is 1.5m, which is mixed with 75wt% alumina ceramic balls and 25wt% activated carbon, and the height of the second section is 1.0m. Mixed with 40wt% alumina ceramic balls and 60wt% activated carbon, the height of the third section is 2.5m, all of which are activated carbon.
  • the content of high-boiling point chlorinated hydrocarbons (HCS substances) in the phosgene produced by phosgene synthesis is detected to be 5500 ppm, and is continuously sent to the phosgenation reactor to react with MDA to generate MDI.
  • the solvent used in the phosgenation reaction is chlorobenzene.
  • the pressure of the gasification reaction is 3.2 barg
  • the maximum temperature of the phosgenation reactor is 135°C
  • the mass ratio of pure phosgene and MDA participating in the reaction is 2.5
  • the MDA mass of the MDA solution (solvent is chlorobenzene) put into the reaction system The concentration was 30%, and the phosgene concentration in the phosgene solution (the solvent was chlorobenzene) put into the reaction system was 70%.
  • the total amount of HCS in chlorobenzene, the solvent used in the phosgenation reaction reached 4.9%, which caused the boiling point of the solvent to rise from 132 °C to 143 °C, and the phosgenation reaction yield decreased from 99.5%.
  • the system began to show obvious blockage. After 9.5 months of operation, the system had to be stopped to discharge and replace the solvent, and the HCS substance in the solvent was removed.
  • This comparative example uses a phosgene synthesis device with by-product steam, uses high thermal conductivity composite activated carbon, and the filling method is not appropriate, and the content of high boiling point chlorinated hydrocarbons (referred to as HCS substances) slightly exceeds the standard.
  • HCS substances high boiling point chlorinated hydrocarbons
  • the high thermal conductivity composite activated carbon used in this example is prepared according to the following steps: mixing activated carbon powder, granular additives and adhesives in water to make a paste, drying and molding, and the drying conditions are placed under constant temperature and humidity conditions, and the temperature is 28 ° C. , humidity 5%, stand for 12h, and then carbonize with water vapor at 660°C for 6h to obtain the high thermal conductivity composite activated carbon; wherein the mass ratio of the granular additive and the activated carbon powder is 5:100, and the adhesive and The mass ratio of activated carbon powder is 10:100, the mass ratio of the activated carbon powder to water is 50:100, the adhesive is emulsified phenolic resin, and the granular additive is silicon carbide.
  • phosgene is prepared by using a phosgene synthesis device.
  • the hydrocarbons in the introduced CO are less than 1 ppm, the volume flow ratio of CO and chlorine is 100:94, and the phosgene synthesis operating temperature (that is, the phosgene synthesis reaction
  • the outlet temperature of the device) is 210 °C, the operating pressure is 3.1 barg, the high thermal conductivity composite activated carbon is filled in the tube, the diameter of the tube is DN38, the length of the tube is 5000mm, and the catalyst used is the high thermal conductivity composite activated carbon prepared above. ;
  • the catalyst loading area is divided into three sections from bottom to top.
  • the loading method is that the height of the first section is 1.0m, and 100wt% is filled with high thermal conductivity composite activated carbon.
  • the second section is 1.0m high, and 100wt% is filled with high thermal conductivity composite activated carbon. m, 100wt% loading of high thermal conductivity composite activated carbon.
  • the content of high-boiling point chlorinated hydrocarbons (HCS substances) in the phosgene produced by phosgene synthesis is detected to be 1100 ppm, and is continuously sent to the phosgenation reactor to react with MDA to generate MDI.
  • the solvent used in the phosgenation reaction is chlorobenzene.
  • the pressure of the gasification reaction is 3.2 barg
  • the maximum temperature of the phosgenation reactor is 135°C
  • the mass ratio of pure phosgene and MDA participating in the reaction is 2.5
  • the MDA mass of the MDA solution (solvent is chlorobenzene) put into the reaction system The concentration was 30%, and the phosgene concentration in the phosgene solution (the solvent was chlorobenzene) put into the reaction system was 70%.
  • high thermal conductivity composite activated carbon is used, and the filling method is the same as that of Comparative Example 1, and there is no phenomenon that the content of high-boiling point chlorinated hydrocarbons (referred to as HCS substances) exceeds the standard.
  • HCS substances high-boiling point chlorinated hydrocarbons
  • the high thermal conductivity composite activated carbon used in this example is prepared according to the following steps: mixing activated carbon powder, granular additives and adhesive in water to make a paste, drying and molding, and the drying conditions are placed under constant temperature and humidity conditions, and the temperature is 25°C. , humidity 8%, stand for 18h, and then carry out constant temperature carbonization with water vapor at 650°C for 4h to obtain the high thermal conductivity composite activated carbon; wherein the mass ratio of the granular additive and the activated carbon powder is 5:100, and the adhesive and The mass ratio of activated carbon powder is 10:100, the mass ratio of the activated carbon powder to water is 50:100, the adhesive is emulsified phenolic resin, and the granular additive is silicon carbide.
  • phosgene is prepared by using a phosgene synthesis device.
  • the hydrocarbons in the introduced CO are less than 1 ppm, the volume flow ratio of CO and chlorine is 100:93, and the phosgene synthesis operating temperature (that is, the phosgene synthesis reaction
  • the outlet temperature of the device) is 205 °C, the operating pressure is 3.0 barg, the high thermal conductivity composite activated carbon is filled in the tube, the diameter of the tube is DN38, the length of the tube is 5000mm, and the catalyst used is the high thermal conductivity composite activated carbon prepared above , the inert agent uses alumina ceramic balls; the catalyst loading area is divided into three sections from bottom to top, the filling method is that the height of the first section is 1.5m, mixed with 75wt% alumina ceramic balls, 25wt% high thermal conductivity composite activated carbon, and the second section is 1.5m high.
  • the height of the section is 1.0m, mixed with 40wt% alumina ceramic balls and 60
  • the content of high-boiling point chlorinated hydrocarbons (HCS substances) in the phosgene produced by phosgene synthesis is detected to be 800 ppm, and it is continuously sent to the phosgenation reactor to react with MDA to generate MDI.
  • the solvent used in the phosgenation reaction is chlorobenzene.
  • the pressure of the gasification reaction is 3.2 barg
  • the maximum temperature of the phosgenation reactor is 135°C
  • the mass ratio of pure phosgene and MDA participating in the reaction is 2.5
  • the MDA mass of the MDA solution (solvent is chlorobenzene) put into the reaction system The concentration was 30%, and the phosgene concentration in the phosgene solution (the solvent was chlorobenzene) put into the reaction system was 70%.
  • a high thermal conductivity composite activated carbon device is used, and the filling method is different from that of Example 1, and there is no phenomenon that the content of high boiling point chlorinated hydrocarbons (marked as HCS substances) exceeds the standard.
  • the high thermal conductivity composite activated carbon used in this example is prepared according to the following steps: mixing activated carbon powder, granular additives and adhesive in water to make a paste, drying and molding, and the drying conditions are placed under constant temperature and humidity conditions, and the temperature is 25°C. , humidity 8%, stand for 18h, and then carry out constant temperature carbonization with water vapor at 650°C for 6h to obtain the high thermal conductivity composite activated carbon; wherein the mass ratio of the granular additive and the activated carbon powder is 10:100, and the adhesive and The mass ratio of activated carbon powder is 10:100, the mass ratio of the activated carbon powder to water is 50:100, the adhesive is emulsified phenolic resin, and the particle additive is graphite.
  • phosgene is prepared by using a phosgene synthesis device.
  • the hydrocarbons in the CO introduced are less than 1 ppm, the volume flow ratio of CO and chlorine is 100:93, and the phosgene synthesis operating temperature is 200 °C (that is, light The outlet temperature of the gas synthesis reactor), the operating pressure is 3.0 barg, the activated carbon is packed in the tube, the diameter of the tube is DN50, the length of the tube is 5000mm, the catalyst used is the high thermal conductivity composite activated carbon prepared above, the inert agent Spherical silicon carbide is used; the catalyst loading area is divided into three sections from bottom to top, the filling method is that the height of the first section is 0.5m, mixed with 80wt% spherical silicon carbide and 20wt% high thermal conductivity composite activated carbon, and the height of the second section is 1.0m. Mixed with 40wt% spherical silicon carbide and 60wt% high thermal conductivity composite activated carbon, the height of
  • HCS substances high-boiling point chlorinated hydrocarbons
  • the solvent used in the phosgenation reaction is dichlorobenzene
  • the pressure of the phosgenation reaction is 5.1 barg
  • the maximum temperature of the phosgenation reactor is 145°C
  • the mass ratio of the pure phosgene and MDA participating in the reaction is 2.5
  • the MDA of the MDA solution put into the reaction system
  • the mass concentration was 30%
  • the phosgene concentration in the phosgene solution (the solvent was chlorobenzene) put into the reaction system was 70%.
  • a high thermal conductivity composite activated carbon device is used, and the filling method is different from that of Example 1, and there is no phenomenon that the content of high boiling point chlorinated hydrocarbons (marked as HCS substances) exceeds the standard.
  • the high thermal conductivity composite activated carbon used in this example is prepared according to the following steps: mixing activated carbon powder, granular additives and adhesive in water to make a paste, drying and molding, and the drying conditions are placed under constant temperature and humidity conditions, and the temperature is 26 ° C. , humidity 5%, stand for 23h, and then carbonize with water vapor at 680°C for 4h to obtain the high thermal conductivity composite activated carbon; wherein the mass ratio of the granular additive and the activated carbon powder is 7:100, and the adhesive and The mass ratio of activated carbon powder is 10:100, the mass ratio of the activated carbon powder to water is 45:100, the adhesive is activated clay, and the granular additive is alumina ceramic balls.
  • phosgene is prepared by using a phosgene synthesis device.
  • the hydrocarbons in the CO introduced are less than 1 ppm, the volume flow ratio of CO and chlorine is 100:94, and the phosgene synthesis operating temperature is 210 °C (that is, light The outlet temperature of the gas synthesis reactor), the operating pressure is 2.9barg, the activated carbon is packed in the tube, the diameter of the tube is DN25, the length of the tube is 5000mm, the catalyst used is the high thermal conductivity composite activated carbon prepared above, the inert Spherical silicon carbide is used; the catalyst loading area is divided into three sections from bottom to top.
  • the filling method is that the height of the first section is 1.0m, which is mixed with 80wt% spherical silicon carbide and 20wt% high thermal conductivity composite activated carbon, and the height of the second section is 2.0m. Mixed 60wt% spherical silicon carbide, 40wt% high thermal conductivity composite activated carbon, the height of the third section is 2.0m, all of which are high thermal conductivity composite activated carbon.
  • HCS substances high-boiling point chlorinated hydrocarbons
  • the solvent used in the phosgenation reaction is dichlorobenzene
  • the pressure of phosgenation reaction is 5.1barg
  • the maximum temperature of phosgenation reactor is 145 °C
  • the mass ratio of pure phosgene and MDA participating in the reaction is 2.5
  • the MDA solution (solvent is dichlorobenzene) put into the reaction system is The mass concentration of MDA is 30%
  • the concentration of phosgene in the phosgene solution (solvent is dichlorobenzene) put into the reaction system is 70%.
  • a high thermal conductivity composite activated carbon device is used, and the preparation formula of the high thermal conductivity activated carbon is different from that of Example 1, and there is no phenomenon that the content of high boiling point chlorinated hydrocarbons (marked as HCS substances) exceeds the standard.
  • the high thermal conductivity composite activated carbon used in this example is prepared according to the following steps: mixing activated carbon powder, granular additives and adhesive in water to make a paste, drying and molding, and the drying conditions are placed under constant temperature and humidity conditions, and the temperature is 21 ° C. , humidity 3%, stand for 24 hours, and then carbonize with water vapor at 800°C for 2 hours to obtain the high thermal conductivity composite activated carbon; wherein the mass ratio of the granular additive and the activated carbon powder is 1.5:100, and the adhesive and The mass ratio of activated carbon powder is 10:100, the mass ratio of the activated carbon powder to water is 30:100, the adhesive is activated clay, and the granular additive is alumina ceramic balls.
  • phosgene is prepared by using a phosgene synthesis device, the hydrocarbons in the introduced CO are less than 1 ppm, the volume flow ratio of CO to chlorine is 100:95, and the phosgene synthesis operating temperature (that is, the phosgene synthesis reaction
  • the outlet temperature of the device) is 215°C, the operating pressure is 3.0barg, the activated carbon is filled in the tube, the diameter of the tube is DN25, the length of the tube is 5000mm, the catalyst used is the high thermal conductivity composite activated carbon prepared above, the inert agent Spherical silicon carbide is used; the catalyst loading area is divided into three sections from bottom to top, the filling method is that the height of the first section is 2.0m, mixed with 80wt% spherical silicon carbide and 20wt% high thermal conductivity composite activated carbon, and the height of the second section is 2.0m. 60wt% spherical silicon carbide and 40wt% high thermal conductivity composite activated carbon are mixed
  • HCS substances high-boiling point chlorinated hydrocarbons
  • the solvent used in the phosgenation reaction is dichlorobenzene
  • the pressure of phosgenation reaction is 5.1barg
  • the maximum temperature of phosgenation reactor is 145 °C
  • the mass ratio of pure phosgene and MDA participating in the reaction is 2.5
  • the MDA (solvent is dichlorobenzene) of the MDA solution put into the reaction system ) mass concentration is 30%
  • the phosgene concentration in the phosgene solution (solvent is dichlorobenzene) put into the reaction system is 70%.

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Abstract

本发明提供制备MDI的方法和光气制备方法，本发明提供的制备MDI的方法，包括：在溶剂存在下，将光气原料和MDA在光气化反应器中进行光气化反应生成包含所述MDI和氯化氢的反应产物，所述氯化氢作为外排气相排出所述光气化反应器，将用于参与所述光气化反应的所述光气原料中含有的高沸点氯代烃杂质的质量含量控制为小于1000ppm；所述高沸点氯代烃杂质为碳原子数为2的饱和和/或不饱和氯代烃。本发明提供的MDI制备方法具有改善的工艺稳定性。

Description

制备MDI的方法和光气制备方法 技术领域
本发明涉及光气制备技术领域和MDI制备技术领域，特别涉及一种能降低光气中微量杂质的光气制备方法以及一种能改善MDI生产工艺稳定性的MDI制备方法。
背景技术
光气是MDI生产过程中的一个重要原料，光气是通过CO与氯气在活性炭催化反应条件下，发生光气合成反应得到的。
根据公开的专利文献报道，目前解决光气中的杂质含量偏高有以下几种方法：
中国公开专利CN105916810A描述了光气中的游离氯的控制方法和开停车的操作方案，但是该专利仅关注游离氯的控制，没有涉及对高沸点氯代烃类物质进行控制。
中国公开专利CN102092713A描述了高温下，氯气与活性炭表面对象长时间的接触会引发四氯化碳的形成，并认识到了四氯化碳是一种严重影响聚碳酸酯产量的有害副产品，且四氯化碳一致被认为与臭氧层损耗和全球变暖有关。该文献经关注四氯化碳的形成所造成的的影响，并且对四氯化碳的影响的认识局限于臭氧层损耗以及全球变暖，没有认识到对工艺过程本身的影响。该专利也没有认识到其他氯化烃类物质将在该过程中生成以及可能带来的影响。
中国公开专利CN104415770A、中国专利CN110655078A认识到光气化反应过程中通过壳程将移热介质移出，尾气通过固定床反应器出口进入保护塔中进一步反应，保证保护塔出口尾气中游离氯含量<50ppm，四氯化碳含量<50ppm。这些文献认识到了四氯化碳物质对于产品质量色号的影响，但是均 没有对氯代物中的高沸点物质在光气化反应过程中对反应收率的影响进行认识。
中国专利CN1156393C介绍了一种四氯化碳含量小于150ppm的光气制备方法，并对制备过程的方案进行了描述。同样的，该文献也并没有认识到对氯代物中的高沸点物质在光气化反应过程中对反应收率的影响。
发明内容
本发明提供一种能够降低光气中高沸点氯代烃杂质含量的光气制备方法以及一种具有改善的工艺稳定性的制备MDI的方法。
本发明为达到其目的，提供如下技术方案：
本发明一方面提供一种制备MDI(二苯基亚甲基二异氰酸酯)的方法，所述方法包括：在溶剂存在下，将光气原料和MDA(二苯基亚甲基二胺)在光气化反应器中进行光气化反应生成包含所述MDI和氯化氢的反应产物，所述氯化氢作为外排气相排出所述光气化反应器，将用于参与所述光气化反应的所述光气原料中含有的氯代烃杂质的质量含量控制为小于1000ppm；所述氯代烃杂质为碳原子数为2的饱和和/或不饱和氯代烃。
所述光气原料中含有的上述氯代烃杂质的质量含量例如小于1000ppm、小于900ppm、小于800ppm、小于600ppm、小于500ppm、小于400ppm、小于100ppm、小于50ppm、小于20ppm，小于15ppm等，例如大于0.1ppm且小于1000ppm，例如大于1.5ppm且小于400ppm。
本发明中，所述氯代烃杂质是指碳原子数为2的饱和和/或不饱和氯代烃，具体为以下化合物中的一种或多种构成：一氯乙烷、二氯乙烷、三氯乙烷、四氯乙烷、一氯乙烯、二氯乙烯、三氯乙烯、四氯乙烯、一氯乙炔、二氯乙炔，本文中这些杂质也称为高沸点氯代烃杂质。在实际生产过程中，光气中所含有的上述氯代烃杂质可能为上述所列具体氯代烃化合物中的一种或多种构成。
一些实施方式中，所述溶剂包括氯苯、二氯苯、甲苯中的一种或多种，优选所述溶剂为氯苯。
优选实施方式中，所述光气通过将一氧化碳和氯气在催化剂存在下于光气合成反应器中进行光气合成反应制得，所述光气合成反应器的催化剂装填区中装填催化剂和惰性填料的混合物，所述催化剂为高导热复合活性炭，且所述催化剂装填区由下到上依次分为第一装填段、第二装填段和第三装填段；基于各装填段中的催化剂和惰性填料的总质量，所述第二装填段中的催化剂质量百分比大于所述第一装填段中的催化剂质量百分比，所述第三装填段中的催化剂质量百分比大于所述第二装填段中的催化剂质量百分比；
所述高导热复合活性炭的制备包括如下步骤：将活性炭粉、颗粒添加剂和胶黏剂用水混匀制成膏状物，干燥成型，之后用水蒸气在600-800℃(例如600℃、650℃、700℃、750℃、800℃等)进行恒温碳化(恒温碳化时间例如为2h以上，例如2-72h，例如2h、4h、8h、24h、48h、72h等)，得到所述高导热复合活性炭；其中所述颗粒添加剂和所述活性炭粉的质量比为(1-10):100(例如1:100、3:100、5:100、7:100、10:100等)，所述颗粒添加剂选自氧化铝瓷球、碳化硅、石墨、碳化硼中的一种或多种。优选的，所述干燥成型的干燥条件包括将所述膏状物放置在恒温恒湿环境中静置12-24h，其中温度为20-30℃，湿度为0-10％。
采用上述优选方案，以上述高导热复合活性炭为催化剂，并按照特定装填方式装填于光气合成反应器的催化剂装填区，在光气合成过程中，大大减少了碳与氯之间的反应活性，减少了高沸点氯代烃(碳原子数为2的饱和和/或不饱和氯代烃)的生成，从而有效降低了光气合成过程中高沸点氯代烃杂质含量，可以获得高沸点氯代烃杂质含量低的光气原料，具体的，使获得的光气中高沸点氯代烃杂质的质量含量小于1000ppm，例如大于0.1ppm且小于1000ppm，例如小于400ppm，例如大于1.5ppm且小于400ppm。
优选实施方式中，基于各装填段中的所述催化剂和惰性填料的混合物的总质量，所述第一装填段中所述催化剂的质量百分比为0％-50％(例如0％、 10％、20％、30％、40％、50％等)，所述第二装填段中所述催化剂的质量百分比为20％-80％(例如20％、30％、40％、50％、60％、70％、80％等)，所述第三装填段中所述催化剂的质量百分比为40％-100％(例如40％、50％、60％、70％、80％、90％、100％等)；并且基于各装填段中的催化剂和惰性填料的总质量，所述第二装填段中的催化剂质量百分比大于所述第一装填段中的催化剂质量百分比，所述第三装填段中的催化剂质量百分比大于所述第二装填段中的催化剂质量百分比；
基于所述催化剂装填区的总高度，所述第一装填段的高度比例为10％-40％(例如10％、20％、30％、40％等)，所述第二装填段的高度比例为10％-80％(例如10％、30％、50％、80％等)，所述第三装填段的高度比例为10-80％(例如10％、30％、50％、80％等)。
在制备高导热复合活性炭催化剂时，预先将活性炭粉和颗粒添加剂混匀制成膏状物，具体而言，在加入适量胶黏剂和水混匀形成膏状物，所述胶黏剂与活性炭粉的质量比为(3-20):100(例如3:100、5:100、10:100、15:100、20:100等),所述活性炭粉与所述水的质量比为(20-50):100(例如20:100、30:100、40:100等)，所用的胶黏剂例如可以是：乳化酚醛树脂、活性黏土、乳化煤焦油、羧甲基纤维素等。
一些实施方式中，所述催化剂装填区中装填的所述惰性填料为氧化铝瓷球、球状碳化硅、石墨中的一种或多种。
上述光气制备工艺，具体为在现有的基于一氧化碳和氯气在活性炭催化下通过光气合成反应制备光气的工艺基础上进行改进而形成的技术方案，主要在于对现有的催化剂进行改进并结合催化剂的特定装填方式，从而实现降低现有光气合成反应中高沸点氯代烃杂质含量，获得高沸点氯代烃含量低于1000ppm的光气。关于光气制备的其他工艺条件，可以采用本领域相应的常规工艺条件。一些实施方式中，在所述光气合成反应器中进行所述光气合成反应过程中，压力为1barg-7barg，优选2.5barg-3.5barg，光气合成反应器(即，光气合成反应塔)的出口温度为30℃-270℃，优选190℃-220℃，一氧化碳与 氯气的体积流量比例为100:(85-98)。
一些实施方式中，基于本发明的MDI制备方法制备MDI过程中，所述外排气相中所述高沸点氯代烃杂质的质量含量为小于800ppm，例如大于0.5ppm且小于800ppm，例如小于350ppm，例如大于2ppm且小于350ppm；
一些实施方式中，通过光气化反应生产所述MDI过程中，反应体系的溶剂中的所述高沸点氯代烃质量含量为小于4％，例如大于50ppm且小于4％，例如小于2.5％，例如大于100ppm且小于2.5％。
本发明提供的制备MDI的方法，具体为在现有的基于光气和MDA通过光气化反应制备MDI的工艺基础上进行改进而形成的技术方案，主要在于对光气原料中的高沸点氯代烃杂质含量的控制，从而达到改善工艺的稳定性等技术效果。关于制备MDI的方法的其他工艺条件，可以采用本领域相应的常规工艺条件。一些实施方式中，所述光气化反应的反应条件包括：光气化反应的压力为1barg-7barg，优选2.5barg-3.5barg，光气化反应器的最高温度为110℃-180℃，优选125℃-145℃，参与反应的纯光气(即指以光气溶液中的光气计)与MDA的质量比为1.5-3.0，优选2.0-2.5；所述MDA和所述光气分别用所述溶剂配成MDA溶液和光气溶液后投入反应体系中，所述MDA溶液的MDA质量浓度为20％-45％，优选30％-40％；光气溶液的光气质量浓度为40％-90％，优选60％-75％。
本发明还提供一种能够降低光气中氯代烃杂质含量的光气制备方法，通过将一氧化碳和氯气在催化剂存在下于光气合成反应器中进行光气合成反应制得所述光气，在所述光气合成反应器中采用高导热复合活性炭作为催化剂，所述光气合成反应器的催化剂装填区中装填催化剂和惰性填料的混合物，所述光气合成反应器的催化剂装填区由下到上依次分为第一装填段、第二装填段和第三装填段；基于各装填段中的所述催化剂和惰性填料的总质量，所述第二装填段中的催化剂质量百分比大于在所述第一装填段中的催化剂质量百分比，所述第三装填段中的催化剂质量百分比大于在所述第二装填段中的催化剂质量百分比。
所述高导热复合活性炭的制备包括如下步骤：将活性炭粉、颗粒添加剂和胶黏剂用水混匀制成膏状物，干燥成型，之后用水蒸气在600-800℃(例如600℃、650℃、700℃、750℃、800℃等)进行恒温碳化(恒温碳化时间例如为2h以上，例如2-72h，例如2h、4h、8h、24h、48h、72h等)，得到所述高导热复合活性炭；其中所述颗粒添加剂和所述活性炭粉的质量比为(1-10):100(例如1:100、3:100、5:100、7:100、10:100等)，所述颗粒添加剂选自氧化铝瓷球、碳化硅、石墨、碳化硼中的一种或多种；优选的，所述干燥成型的干燥条件包括将所述膏状物放置在恒温恒湿环境中静置12-24h，其中温度为20-30℃，湿度为0-10％。
所述氯代烃杂质为碳原子数为2的饱和和/或不饱和氯代烃，本文中这类杂质也称为高沸点氯代烃杂质。
所制得的光气中，所述氯代烃杂质的含量小于1000ppm，例如小于1000ppm、小于900ppm、小于800ppm、小于600ppm、小于500ppm、小于400ppm、小于100ppm、小于50ppm、小于20ppm，小于15ppm等，例如大于0.1ppm且小于1000ppm，例如小于400ppm，例如大于1.5ppm且小于400ppm。
基于各装填段中的所述催化剂和惰性填料的混合物的总质量，所述第一装填段中所述催化剂的质量百分比为0％-50％(例如0％、10％、20％、30％、40％、50％等)，所述第二装填段中所述催化剂的质量百分比为20％-80％(例如20％、30％、40％、50％、60％、70％、80％等)，所述第三装填段中所述催化剂的质量百分比为40％-100％(例如40％、50％、60％、70％、80％、90％、100％等)；并且基于各装填段中的催化剂和惰性填料的总质量，所述第二装填段中的催化剂质量百分比大于所述第一装填段中的催化剂质量百分比，所述第三装填段中的催化剂质量百分比大于所述第二装填段中的催化剂质量百分比；基于所述催化剂装填区的总高度，所述第一装填段的高度比例为10％-40％(例如10％、20％、30％、40％等)，所述第二装填段的高度比例为10％-80％(例如10％、30％、50％、80％等)，所述第三装填段的高度比例为10-80％(例如10％、30％、50％、80％等)。
一些实施方式中，所述胶黏剂与活性炭粉的质量比为(3-20):100(例如3:100、5:100、10:100、15:100、20:100等),所述活性炭粉与所述水的质量比为(20-50):100(例如20:100、30:100、40:100等)。
一些实施方式中，所述催化剂装填区中装填的所述惰性填料为氧化铝瓷球、球状碳化硅、石墨中的一种或多种；
所述氯代烃杂质(即碳原子数为2的饱和和/或不饱和氯代烃，本文中也称为高沸点氯代烃杂质)具体为以下化合物中的一种或多种构成：一氯乙烷、二氯乙烷、三氯乙烷、四氯乙烷、一氯乙烯、二氯乙烯、三氯乙烯、四氯乙烯、一氯乙炔、二氯乙炔。在实际生产过程中，光气中所含有的上述氯代烃杂质可能为上述所列具体氯代烃化合物中的一种或多种构成。
一些实施方式中，在所述光气合成反应器中进行所述光气合成反应过程中，压力控制为1barg-7barg，优选2.5barg-3.5barg，所述光气合成反应器(光气合成塔)的出口温度为30℃-270℃，优选190℃-220℃，，一氧化碳与氯气的体积流量比例为100:(85-98)。
本申请发明人发现，光气合成过程中，由于催化剂表面出现高温热点等因素，容易导致光气合成产生微量的高沸点氯代烃类杂质(记为HCS物质)。本申请发明人经研究发现，在利用光气和MDA通过光气化反应制备MDI的工艺中，当原料光气中的高沸点氯代烃类物质(碳原子数为2的饱和和/或不饱和氯代烃)含量偏高时，外排氯化氢无法及时将高沸点氯代烃类物质带出，会导致高沸点氯代烃类物质在工艺系统内形成富集，造成反应体系内的溶剂组成逐渐发生变化，存在工艺运行参数偏差增大、稳定性下降、设备能力偏离设计条件、装置无法正常运行下去等问题，更严重的，在偏低正常工艺运行参数的条件下，会导致反应条件变化、反应失控等问题，引发MDI及聚合MDI发生自聚、产生大量气体、进而燃烧爆炸的风险。本申请发明人令人惊讶地发现，在制备MDI的过程中，通过使用高沸点氯代烃杂质的质量含量控制为小于1000ppm的光气原料来制备MDI，可以避免反应体系中的溶剂沸点在 MDI制备过程中发生大幅波动，从而利于确保获得较为稳定的产物收率，提高工艺生产的稳定性，利于延长工艺周期。
一些实施方式中，所述光气原料中含有的高沸点氯代烃杂质的质量含量例如大于0.1ppm且小于1000ppm；一些实施方式中，所述光气原料中含有的高沸点氯代烃杂质的质量含量例如小于400ppm，例如大于1.5ppm且小于400ppm。较佳的，所述光气原料中含有的高沸点氯代烃杂质的质量含量越低越好。
基于本发明提供的上述能够降低光气中高沸点氯代烃杂质含量的光气制备方法，可以获得高沸点氯代烃杂质含量低的光气，具体的，可以得到高沸点氯代烃杂质的质量含量小于1000ppm的光气原料，从而为下游的MDI制备提供高沸点氯代烃杂质的质量含量小于1000ppm的光气原料，改善制备MDI的工艺稳定性等。
本发明提供的技术方案具有如下有益效果：
1.本发明人令人惊讶地发现光气中高沸点氯代烃物质含量偏高的情况下，会造成光气化反应的溶剂中出现HCS物质含量升高，进一步影响溶剂的沸点，造成光气化反应过程的收率受到影响。本发明人通过大量的装置试验，确定了光气中的高沸点氯代烃物质含量控制为低于1000ppm，可以保证光气化生产过程中溶剂的沸点不会出现明显的上升，从而实现光气化反应过程的收率稳定达到预期目标。
2.本发明对光气合成涉及到的催化剂种类进行优化改进及制备，得到一种高导热复合活性炭，结合特定的装填方式用于光气的合成反应中，大大减少了碳与氯之间的反应活性，减少了高沸点氯代烃物质的生成。
具体实施方式
为了更好的理解本发明的技术方案，下面结合实施例进一步阐述本发明 的内容，但本发明的内容并不仅仅局限于以下实施例。下列实施例中未表明具体条件的试验方法，通常按照常规条件。
文中涉及的“含量”，若未特别说明，均指质量含量。
原料说明：
碳化硅：上海百图，国产碳化硅；
乳化酚醛树脂：上海乳胶厂，HX30；
活性黏土：青岛万鸿矿业有限公司；
氧化铝瓷球：上海百图；
石墨：武汉卡诺斯科技有限公司，石墨LZ295；
MDA：万华化学；
活性炭粉：日本鹤见，4GV-K。
各实施例和对比例中，涉及到以下的测定方法：
1.溶剂中高沸点氯代烃杂质(即碳原子数为2的饱和/不饱和氯代烃杂质，记为HCS物质)测定：使用甲醇稀释溶剂100倍体积后，通过气相色谱，ECD检测器测定高沸点氯代烃杂质总量；
气相色谱条件：柱箱温度在35℃下保持8min，以5℃/min速率升温到100℃，再以10℃/min升温到200℃保持5min；柱流量：1.5ml/min；进样口温度：220℃；检测器温度：320℃；分流比：5:1；尾吹气流量：60ml/min；
通过气相色谱检测得到各种高沸点氯代烃杂质的含量，将各个高沸点氯代烃杂质的含量求和，即为高沸点氯代烃杂质总含量。
2.光气中高沸点氯代烃杂质(记为HCS物质)测定：光气通入过量NaOH的水溶液(氢氧化钠浓度为5wt％)中吸收光气，尾气再以氯苯吸收；吸收尾 气后的氯苯与吸收光气的NaOH水溶液按照体积比1:1混合萃取，取氯苯相以甲醇稀释100倍体积后，通过气相色谱，ECD检测器测定高沸点氯代烃杂质总量，气相色谱条件和高沸点氯代烃杂质总量的测定参见上文的“溶剂中高沸点氯代烃杂质测定”；
3.光气化反应收率测定：使用甲苯溶解反应液，加入二正丁基胺水溶液(1mol/L)将反应液中的NCO基团完全反应，使用盐酸标准液(1mol/L)滴定，最终确定反应液中的NCO％含量(方法参见GB/T 12009.4-201)；使用甲苯溶解MDA，使用盐酸标准液(1mol/L)滴定，最终确定MDA液中的AN％(AN即-NH 2基团)含量(方法参见GB 11889-89)。光气化反应收率＝8*NCO％/21/AN％。
对比例1
本对比例使用副产蒸汽的光气合成装置，出现了高沸点氯代烃(记为HCS物质)含量超标现象。
本案例中通过使用光气合成装置制备光气，所通入的CO中的烃类物质(如乙烷、乙烯、乙炔等)含量小于1ppm,CO与氯气的体积流量之比为100:93，光气合成操作温度(即光气合成反应器的出口温度)为200℃，操作压力为3.0barg，活性炭装填于列管之中，列管的直径为DN50(即直径50mm)，列管长度为5000mm，使用的催化剂为日本鹤见的4GV型活性炭，惰性剂使用的是氧化铝瓷球；催化剂装填区由下至上分为三段，装填方式为第一段高度1.0m，混合了80wt％氧化铝瓷球、20wt％活性炭，第二段高度1.0m，混合了40wt％氧化铝瓷球、60wt％活性炭，第三段高度3.0m，全部为活性炭。
光气合成生产的光气中高沸点氯代烃(HCS物质)含量经检测为6520ppm，并持续送入光气化反应器，与MDA反应生成MDI，光气化反应使用的溶剂为氯苯，光气化反应的压力为3.2barg，光气化反应器的最高温度为135℃，参与 反应的纯光气与MDA的质量比为2.5，投入反应体系的MDA溶液(溶剂为氯苯)的MDA质量浓度为30％，投入反应体系的光气溶液(溶剂为氯苯)中的光气浓度为70％。运行至8个月时，光气化反应使用的溶剂氯苯中的HCS物质总量达到了4％，并导致溶剂的沸点从132℃上升至144℃，光气化反应收率从99.5％下降到98.2％，系统开始出现明显的堵塞现象，运行8个月后不得不停车外排、置换溶剂，将溶剂中的HCS物质除去。
对比例2
本对比例使用副产蒸汽的光气合成装置，其活性炭差别于对比例1，催化剂装填方式与对比例1一致，同样出现了高沸点氯代烃(记为HCS物质)含量超标现象。
本案例中通过使用光气合成装置制备光气，所通入的CO中的烃类物质小于1ppm,CO与氯气的体积流量之比为100:93，光气合成操作温度(即光气合成反应器的出口温度)为205℃，操作压力为3.0barg，活性炭装填于列管之中，列管的直径为DN50，列管长度为5000mm，使用的催化剂为荷兰诺瑞特的Norit-B型活性炭，惰性剂使用的是氧化铝瓷球；催化剂装填区由下至上分为三段，装填方式为第一段高度1.0m，混合了80wt％氧化铝瓷球、20wt％活性炭，第二段高度1.0m，混合了40wt％氧化铝瓷球、60wt％活性炭，第三段高度3.0m，全部为活性炭。
光气合成生产的光气中高沸点氯代烃(HCS物质)含量经检测为7710ppm，并持续送入光气化反应器，与MDA反应生成MDI，光气化反应使用的溶剂为氯苯，光气化反应的压力为3.2barg，光气化反应器的最高温度为135℃，参与反应的纯光气与MDA的质量比为2.5，投入反应体系的MDA溶液(溶剂为氯苯)的MDA质量浓度为30％，投入反应体系的光气溶液(溶剂为氯苯) 中的光气浓度为70％。运行至7.5个月时，光气化反应使用的溶剂氯苯中的HCS物质总量达到了5.2％，并导致溶剂的沸点从132℃上升至141℃，光气化反应收率从99.5％下降到98.3％，系统开始出现明显的堵塞现象，运行7.5个月后不得不停车外排、置换溶剂，将溶剂中的HCS物质除去。
对比例3
本对比例使用副产蒸汽的光气合成装置，其活性炭与对比例1一致，装填方式差别于对比例1，同样出现了高沸点氯代烃(记为HCS物质)含量超标现象。
本案例中通过使用光气合成装置制备光气，所通入的CO中的烃类物质含量小于1ppm,CO与氯气的体积流量之比为100:93，光气合成操作温度(即光气合成反应器的出口温度)为205℃，操作压力为3.0barg，活性炭装填于列管之中，列管的直径为DN38，列管长度为5000mm，使用的催化剂为日本鹤见的4GV型活性炭，惰性剂使用的是氧化铝瓷球；催化剂装填区由下至上分为三段，装填方式为第一段高度1.5m，混合了75wt％氧化铝瓷球、25wt％活性炭，第二段高度1.0m，混合了40wt％氧化铝瓷球、60wt％活性炭，第三段高度2.5m，全部为活性炭。
光气合成生产的光气中高沸点氯代烃(HCS物质)含量经检测为5500ppm，并持续送入光气化反应器，与MDA反应生成MDI，光气化反应使用的溶剂为氯苯，光气化反应的压力为3.2barg，光气化反应器的最高温度为135℃，参与反应的纯光气与MDA的质量比为2.5，投入反应体系的MDA溶液(溶剂为氯苯)的MDA质量浓度为30％，投入反应体系的光气溶液(溶剂为氯苯)中的光气浓度为70％。运行至9.5个月时，光气化反应使用的溶剂氯苯中的HCS物质总量达到了4.9％，并导致溶剂的沸点从132℃上升至143℃，光气化 反应收率从99.5％下降到98.1％，系统开始出现明显的堵塞现象，运行9.5个月后不得不停车外排、置换溶剂，将溶剂中的HCS物质除去。
对比例4
本对比例使用副产蒸汽的光气合成装置，使用高导热复合活性炭，装填方式不恰当，出现了高沸点氯代烃(记为HCS物质)含量小幅度超标现象。
本实施例所用的高导热复合活性炭按如下步骤制备：将活性炭粉、颗粒添加剂和胶黏剂在水中混匀制成膏状，干燥成型，干燥条件为放置在恒温恒湿条件下，温度28℃，湿度5％，静置12h，之后用水蒸气在660℃进行恒温碳化6h，得到所述高导热复合活性炭；其中所述颗粒添加剂和所述活性炭粉的质量比为5:100，胶黏剂与活性炭粉的质量比为10:100,所述活性炭粉与水的质量比为50:100，胶黏剂为乳化酚醛树脂，所述颗粒添加剂为碳化硅。
本案例中通过使用光气合成装置制备光气，所通入的CO中的烃类物质小于1ppm,CO与氯气的体积流量之比为100:94，光气合成操作温度(即光气合成反应器的出口温度)为210℃，操作压力为3.1barg，高导热复合活性炭装填于列管之中，列管的直径为DN38，列管长度为5000mm，使用的催化剂为上述制备的高导热复合活性炭；催化剂装填区由下至上分为三段，装填方式为第一段高度1.0m，100wt％装填高导热复合活性炭，第二段高度1.0m，100wt％装填高导热复合活性炭，第三段高度2.5m，100wt％装填高导热复合活性炭。
光气合成生产的光气中高沸点氯代烃(HCS物质)含量经检测为1100ppm，并持续送入光气化反应器，与MDA反应生成MDI，光气化反应使用的溶剂为氯苯，光气化反应的压力为3.2barg，光气化反应器的最高温度为135℃，参与反应的纯光气与MDA的质量比为2.5，投入反应体系的MDA溶液(溶剂为 氯苯)的MDA质量浓度为30％，投入反应体系的光气溶液(溶剂为氯苯)中的光气浓度为70％。连续运行至11个月，光气化反应使用的溶剂氯苯中的HCS物质总量为3.7％，并导致溶剂的沸点从132℃上升至139℃，光气化反应收率从99.5％下降到98.4％，系统未出现明显堵塞的问题。
实施例1
本例使用高导热复合活性炭，装填方式与对比例1一致，未出现了高沸点氯代烃(记为HCS物质)含量超标现象。
本实施例所用的高导热复合活性炭按如下步骤制备：将活性炭粉、颗粒添加剂和胶黏剂在水中混匀制成膏状，干燥成型，干燥条件为放置在恒温恒湿条件下，温度25℃，湿度8％，静置18h，之后用水蒸气在650℃进行恒温碳化4h，得到所述高导热复合活性炭；其中所述颗粒添加剂和所述活性炭粉的质量比为5:100，胶黏剂与活性炭粉的质量比为10:100,所述活性炭粉与水的质量比为50:100，胶黏剂为乳化酚醛树脂，所述颗粒添加剂为碳化硅。
本案例中通过使用光气合成装置制备光气，所通入的CO中的烃类物质小于1ppm,CO与氯气的体积流量之比为100:93，光气合成操作温度(即光气合成反应器的出口温度)为205℃，操作压力为3.0barg，高导热复合活性炭装填于列管之中，列管的直径为DN38，列管长度为5000mm，使用的催化剂为上述制备的高导热复合活性炭，惰性剂使用的是氧化铝瓷球；催化剂装填区由下至上分为三段，装填方式为第一段高度1.5m，混合了75wt％氧化铝瓷球、25wt％高导热复合活性炭，第二段高度1.0m，混合了40wt％氧化铝瓷球、60wt％高导热复合活性炭，第三段高度2.5m，全部为高导热复合活性炭。
光气合成生产的光气中高沸点氯代烃(HCS物质)含量经检测为800ppm，并持续送入光气化反应器，与MDA反应生成MDI，光气化反应使用的溶剂为氯 苯，光气化反应的压力为3.2barg，光气化反应器的最高温度为135℃，参与反应的纯光气与MDA的质量比为2.5，投入反应体系的MDA溶液(溶剂为氯苯)的MDA质量浓度为30％，投入反应体系的光气溶液(溶剂为氯苯)中的光气浓度为70％。连续运行至18个月，光气化反应使用的溶剂氯苯中的HCS物质总量为0.5％，并导致溶剂的沸点从132℃上升至134℃，光气化反应收率从99.5％下降到99.3％，系统未出现明显堵塞的问题。
实施例2
本例使用高导热复合活性炭装置，装填方式区别于实施例1，未出现了高沸点氯代烃(记为HCS物质)含量超标现象。
本实施例所用的高导热复合活性炭按如下步骤制备：将活性炭粉、颗粒添加剂和胶黏剂在水中混匀制成膏状，干燥成型，干燥条件为放置在恒温恒湿条件下，温度25℃，湿度8％，静置18h，之后用水蒸气在650℃进行恒温碳化6h，得到所述高导热复合活性炭；其中所述颗粒添加剂和所述活性炭粉的质量比为10:100，胶黏剂与活性炭粉的质量比为10:100,所述活性炭粉与水的质量比为50:100，胶黏剂为乳化酚醛树脂，所述颗粒添加剂为石墨。
本案例中通过使用光气合成装置制备光气，所通入的CO中的烃类物质小于1ppm,CO与氯气的体积流量之比为100:93，光气合成操作温度为200℃(即光气合成反应器的出口温度)，操作压力为3.0barg，活性炭装填于列管之中，列管的直径为DN50，列管长度为5000mm，使用的催化剂为上述制备的高导热复合活性炭，惰性剂使用的是球状碳化硅；催化剂装填区由下至上分为三段，装填方式为第一段高度0.5m，混合了80wt％球状碳化硅、20wt％高导热复合活 性炭，第二段高度1.0m，混合了40wt％球状碳化硅、60wt％高导热复合活性炭，第三段高度2.5m，全部为高导热复合活性炭。
光气合成生产的光气中高沸点氯代烃(HCS物质)含量经检测为380ppm，并持续送入光气化反应器，与MDA反应生成MDI，光气化反应使用的溶剂为二氯苯，光气化反应的压力为5.1barg，光气化反应器的最高温度为145℃，参与反应的纯光气与MDA的质量比为2.5，投入反应体系的MDA溶液(溶剂为氯苯)的MDA质量浓度为30％，投入反应体系的光气溶液(溶剂为氯苯)中的光气浓度为70％。连续运行至18个月，光气化反应使用的溶剂氯苯中的HCS物质总量为0.6％，并导致溶剂的沸点从132℃上升至134.5℃，光气化反应收率从99.5％下降到99.46％，系统未出现明显堵塞的问题。
实施例3
本例使用高导热复合活性炭装置，装填方式区别于实施例1，未出现了高沸点氯代烃(记为HCS物质)含量超标现象。
本实施例所用的高导热复合活性炭按如下步骤制备：将活性炭粉、颗粒添加剂和胶黏剂在水中混匀制成膏状，干燥成型，干燥条件为放置在恒温恒湿条件下，温度26℃，湿度5％，静置23h，之后用水蒸气在680℃进行恒温碳化4h，得到所述高导热复合活性炭；其中所述颗粒添加剂和所述活性炭粉的质量比为7:100，胶黏剂与活性炭粉的质量比为10:100,所述活性炭粉与水的质量比为45:100，胶黏剂为活性黏土，所述颗粒添加剂为氧化铝瓷球。
本案例中通过使用光气合成装置制备光气，所通入的CO中的烃类物质小于1ppm,CO与氯气的体积流量之比为100:94，光气合成操作温度为210℃(即光气合成反应器的出口温度)，操作压力为2.9barg，活性炭装填于列管之中， 列管的直径为DN25，列管长度为5000mm，使用的催化剂为上述制备的高导热复合活性炭，惰性剂使用的是球状碳化硅；催化剂装填区由下至上分为三段，装填方式为第一段高度1.0m，混合了80wt％球状碳化硅、20wt％高导热复合活性炭，第二段高度2.0m，混合了60wt％球状碳化硅、40wt％高导热复合活性炭，第三段高度2.0m，全部为高导热复合活性炭。
光气合成生产的光气中高沸点氯代烃(HCS物质)含量经检测为15ppm，并持续送入光气化反应器，与MDA反应生成MDI，光气化反应使用的溶剂为二氯苯，光气化反应的压力为5.1barg，光气化反应器的最高温度为145℃，参与反应的纯光气与MDA的质量比为2.5，投入反应体系的MDA溶液(溶剂为二氯苯)的MDA质量浓度为30％，投入反应体系的光气溶液(溶剂为二氯苯)中的光气浓度为70％。连续运行至24个月，光气化反应使用的溶剂氯苯中的HCS物质总量为0.1％，并导致溶剂的沸点从132℃上升至132.5℃，光气化反应收率为99.6％，未明显下降，系统未出现明显堵塞的问题。
实施例4
本例使用高导热复合活性炭装置，高导热活性炭的制作配方区别于实施例1，未出现高沸点氯代烃(记为HCS物质)含量超标现象。
本实施例所用的高导热复合活性炭按如下步骤制备：将活性炭粉、颗粒添加剂和胶黏剂在水中混匀制成膏状，干燥成型，干燥条件为放置在恒温恒湿条件下，温度21℃，湿度3％，静置24h，之后用水蒸气在800℃进行恒温碳化2h，得到所述高导热复合活性炭；其中所述颗粒添加剂和所述活性炭粉的质量比为1.5:100，胶黏剂与活性炭粉的质量比为10:100,所述活性炭粉与水的质量比为30:100，胶黏剂为活性黏土，所述颗粒添加剂为氧化铝瓷球。
本案例中通过使用光气合成装置制备光气，所通入的CO中的烃类物质小于1ppm,CO与氯气的体积流量之比为100:95，光气合成操作温度(即光气合成反应器的出口温度)为215℃，操作压力为3.0barg，活性炭装填于列管之中，列管的直径为DN25，列管长度为5000mm，使用的催化剂为上述制备的高导热复合活性炭，惰性剂使用的是球状碳化硅；催化剂装填区由下至上分为三段，装填方式为第一段高度2.0m，混合了80wt％球状碳化硅、20wt％高导热复合活性炭，第二段高度2.0m，混合了60wt％球状碳化硅、40wt％高导热复合活性炭，第三段高度1.0m，全部为高导热复合活性炭。
光气合成生产的光气中高沸点氯代烃(HCS物质)含量经检测为11ppm，并持续送入光气化反应器，与MDA反应生成MDI，光气化反应使用的溶剂为二氯苯，光气化反应的压力为5.1barg，光气化反应器的最高温度为145℃，参与反应的纯光气与MDA的质量比为2.5，投入反应体系的MDA溶液的MDA(溶剂为二氯苯)质量浓度为30％，投入反应体系的光气溶液(溶剂为二氯苯)中的光气浓度为70％。连续运行至24个月，光气化反应使用的溶剂氯苯中的HCS物质总量为0.095％，并导致溶剂的沸点从132℃上升至132.5℃，光气化反应收率为99.62％，未明显下降，系统未出现明显堵塞的问题。
表1：实施例和对比例实验结果
Figure PCTCN2020113112-appb-000001
Figure PCTCN2020113112-appb-000002
从运行情况对比可以看到，通过使用高导热复合活性炭并配合在三个装填段中催化剂浓度呈增加趋势的装填方式，可以获得HCS物质含量低于1000ppm的光气，将其应用于MD I制备工艺中，反应体系的溶剂中HCS物质含量可以控制在0.6％以内，光气化反应收率均稳定在99％以上，光气化反应系统消除了堵塞问题，运行周期长，可以满足18个月的要求。
本领域技术人员可以理解，在本说明书的教导之下，可对本发明做出一些修改或调整。这些修改或调整也应当在本发明权利要求所限定的范围之内。

Claims (11)

  1. 一种制备MDI的方法，所述方法包括：在溶剂存在下，将光气原料和MDA在光气化反应器中进行光气化反应生成包含所述MDI和氯化氢的反应产物，所述氯化氢作为外排气相排出所述光气化反应器，其特征在于，将用于参与所述光气化反应的所述光气原料中含有的氯代烃杂质的质量含量控制为小于1000ppm；所述氯代烃杂质为碳原子数为2的饱和和/或不饱和氯代烃；
    所述光气原料中含有的氯代烃杂质的质量含量例如大于0.1ppm且小于1000ppm，例如小于400ppm，例如大于1.5ppm且小于400ppm。
  2. 根据权利要求1所述的制备MDI的方法，其特征在于，所述氯代烃杂质选自以下化合物中的一种或多种：一氯乙烷、二氯乙烷、三氯乙烷、四氯乙烷、一氯乙烯、二氯乙烯、三氯乙烯、四氯乙烯、一氯乙炔、二氯乙炔；
    和/或，所述溶剂包括氯苯、二氯苯、甲苯中的一种或多种，优选所述溶剂为氯苯。
  3. 根据权利要求1所述的制备MDI的方法，其特征在于，所述光气通过将一氧化碳和氯气在催化剂存在下于光气合成反应器中进行光气合成反应制得，所述光气合成反应器的催化剂装填区中装填催化剂和惰性填料的混合物，所述催化剂为高导热复合活性炭，所述催化剂装填区由下到上依次分为第一装填段、第二装填段和第三装填段；基于各装填段中的催化剂和惰性填料的总质量，所述第二装填段中的催化剂质量百分比大于所述第一装填段中的催化剂质量百分比，所述第三装填段中的催化剂质量百分比大于所述第二装填段中的催化剂质量百分比；
    所述高导热复合活性炭的制备包括如下步骤：将活性炭粉、颗粒添加剂和胶黏剂用水混匀制成膏状物，干燥成型，之后用水蒸气在600-800℃进行恒 温碳化，得到所述高导热复合活性炭；其中所述颗粒添加剂和所述活性炭粉的质量比为(1-10):100，所述颗粒添加剂选自氧化铝瓷球、碳化硅、石墨、碳化硼中的一种或多种；优选的，所述干燥成型的干燥条件包括将所述膏状物放置在恒温恒湿环境中静置12-24h，其中温度为20-30℃，湿度为0-10％。
  4. 根据权利要求3所述的制备MDI的方法，其特征在于，基于各装填段中的所述催化剂和惰性填料的总质量，所述第一装填段中所述催化剂的质量百分比为0％-50％，所述第二装填段中所述催化剂的质量百分比为20％-80％，所述第三装填段中所述催化剂的质量百分比为40％-100％；并且基于各装填段中的催化剂和惰性填料的总质量，所述第二装填段中的催化剂质量百分比大于所述第一装填段中的催化剂质量百分比，所述第三装填段中的催化剂质量百分比大于所述第二装填段中的催化剂质量百分比；
    基于所述催化剂装填区的总高度，所述第一装填段的高度比例为10％-40％，所述第二装填段的高度比例为10％-80％，所述第三装填段的高度比例为10-80％。
  5. 根据权利要求3或4所述的制备方法，其特征在于，所述胶黏剂与活性炭粉的质量比为(3-20):100,所述活性炭粉与所述水的质量比为(20-50):100；
    和/或，所述催化剂装填区中装填的所述惰性填料为氧化铝瓷球、球状碳化硅、石墨中的一种或多种。
  6. 根据权利要求3-5任一项所述的制备方法，其特征在于，在所述光气合成反应器中进行所述光气合成反应过程中的压力控制为1barg-7barg，优选2.5barg-3.5barg，所述光气合成反应器的出口温度为30℃-270℃，优选190℃-220℃，一氧化碳与氯气的体积流量比例为100:(85-98)。
  7. 根据权利要求1-6任一项所述的制备MDI的方法，其特征在于，
    所述光气化反应的反应条件包括：光气化反应的压力为1barg-7barg，优选2.5barg-3.5barg；光气化反应器的最高温度为110℃-180℃，优选125℃-145℃；参与反应的纯光气与MDA的质量比为1.5-3.0，优选2.0-2.5；所述 MDA和所述光气分别用所述溶剂配成MDA溶液和光气溶液后投入反应体系中，所述MDA溶液的MDA质量浓度为20％-45％，优选30％-40％，所述光气溶液的光气质量浓度为40％-90％，优选60％-75％。
  8. 一种能够降低光气中氯代烃杂质含量的光气制备方法，通过将一氧化碳和氯气在催化剂存在下于光气合成反应器中进行光气合成反应制得所述光气，其特征在于，在所述光气合成反应器中，采用高导热复合活性炭作为催化剂，所述光气合成反应器的催化剂装填区中装填催化剂和惰性填料的混合物，所述光气合成反应器的催化剂装填区由下到上依次分为第一装填段、第二装填段和第三装填段；基于各装填段中的所述催化剂和惰性填料的总质量，所述第二装填段中的催化剂质量百分比大于在所述第一装填段中的催化剂质量百分比，所述第三装填段中的催化剂质量百分比大于在所述第二装填段中的催化剂质量百分比；
    所述高导热复合活性炭的制备包括如下步骤：将活性炭粉、颗粒添加剂和胶黏剂用水混匀制成膏状物，干燥成型；之后用水蒸气在600-800℃进行恒温碳化，得到所述高导热复合活性炭；其中所述颗粒添加剂和所述活性炭粉的质量比为(1-10):100，所述颗粒添加剂选自氧化铝瓷球、碳化硅、石墨、碳化硼中的一种或多种；优选的，所述干燥成型的干燥条件包括将所述膏状物放置在恒温恒湿环境中静置12-24h，其中温度为20-30℃，湿度为0-10％；
    所述氯代烃杂质为碳原子数为2的饱和和/或不饱和氯代烃。
  9. 根据权利要求8所述的光气制备方法，其特征在于，所制得的光气中，所述氯代烃杂质的含量小于1000ppm，例如大于0.1ppm且小于1000ppm，例如小于400ppm，例如大于1.5ppm且小于400ppm。
  10. 根据权利要求8所述的制备方法，其特征在于，基于各装填段中的所述催化剂和惰性填料的混合物的总质量，所述第一装填段中所述催化剂的质量百分比为0％-50％，所述第二装填段中所述催化剂的质量百分比为20％-80％，所述第三装填段中所述催化剂的质量百分比为40％-100％；并且基于各装填段中的催化剂和惰性填料的总质量，所述第二装填段中的催化剂质 量百分比大于所述第一装填段中的催化剂质量百分比，所述第三装填段中的催化剂质量百分比大于所述第二装填段中的催化剂质量百分比；
    基于所述催化剂装填区的总高度，所述第一装填段的高度比例为10％-40％，所述第二装填段的高度比例为10％-80％，所述第三装填段的高度比例为10-80％。
  11. 根据权利要求8-10任一项所述的制备方法，所述胶黏剂与活性炭粉的质量比为(3-20):100,所述活性炭粉与所述水的质量比为(20-50):100；
    和/或，所述催化剂装填区中装填的所述惰性填料为氧化铝瓷球、球状碳化硅、石墨中的一种或多种；
    和/或，所述氯代烃杂质选自以下化合物中的一种或多种：一氯乙烷、二氯乙烷、三氯乙烷、四氯乙烷、一氯乙烯、二氯乙烯、三氯乙烯、四氯乙烯、一氯乙炔、二氯乙炔。
    和/或，在所述光气合成反应器中进行所述光气合成反应过程中的压力控制为1barg-7barg，优选2.5barg-3.5barg，所述光气合成反应器的出口温度为30℃-270℃，优选190℃-220℃，一氧化碳与氯气的体积流量比例为100:(85-98)。
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