CN112574067B - Method for preparing high-purity m-xylylene diisocyanate without phosgene - Google Patents

Method for preparing high-purity m-xylylene diisocyanate without phosgene Download PDF

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CN112574067B
CN112574067B CN202110202259.4A CN202110202259A CN112574067B CN 112574067 B CN112574067 B CN 112574067B CN 202110202259 A CN202110202259 A CN 202110202259A CN 112574067 B CN112574067 B CN 112574067B
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oac
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xylylene diisocyanate
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黄森彪
王敏
廖广明
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Fuhai Dongying New Material Technology Co ltd
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    • C07C263/00—Preparation of derivatives of isocyanic acid
    • C07C263/04—Preparation of derivatives of isocyanic acid from or via carbamates or carbamoyl halides
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
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    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/26—Catalysts comprising hydrides, coordination complexes or organic compounds containing in addition, inorganic metal compounds not provided for in groups B01J31/02 - B01J31/24
    • B01J31/38—Catalysts comprising hydrides, coordination complexes or organic compounds containing in addition, inorganic metal compounds not provided for in groups B01J31/02 - B01J31/24 of titanium, zirconium or hafnium
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    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
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    • C07C269/04—Preparation of derivatives of carbamic acid, i.e. compounds containing any of the groups, the nitrogen atom not being part of nitro or nitroso groups from amines with formation of carbamate groups
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    • B01J2231/00—Catalytic reactions performed with catalysts classified in B01J31/00
    • B01J2231/40—Substitution reactions at carbon centres, e.g. C-C or C-X, i.e. carbon-hetero atom, cross-coupling, C-H activation or ring-opening reactions
    • B01J2231/42—Catalytic cross-coupling, i.e. connection of previously not connected C-atoms or C- and X-atoms without rearrangement
    • B01J2231/4277—C-X Cross-coupling, e.g. nucleophilic aromatic amination, alkoxylation or analogues
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Abstract

The invention relates to the technical field of isocyanate preparation, in particular to a method for preparing high-purity m-xylylene diisocyanate without phosgene. The method for preparing the high-purity m-xylylene diisocyanate without phosgene comprises the steps of reacting m-xylylenediamine with dimethyl carbonate under the action of a catalyst A to obtain m-xylylene dicarbamate; carrying out decomposition reaction on m-xylylene dicarbamate under the action of a catalyst B, emptying methanol by nitrogen replacement in the reaction process, and carrying out reduced pressure distillation after the reaction is finished to obtain m-xylylene diisocyanate; the catalyst A takes Lewis acid as an active component and takes nano SiO2Or TiO2The catalyst B is superfine composite oxide as carrier supported catalyst. The preparation method disclosed by the invention has the advantages of good product selectivity, high yield, high purity and no catalyst residue, improves the product quality, and meets the requirements of high-end fields.

Description

Method for preparing high-purity m-xylylene diisocyanate without phosgene
Technical Field
The invention relates to the technical field of isocyanate preparation, in particular to a method for preparing high-purity m-xylylene diisocyanate without phosgene.
Background
M-xylylene diisocyanate (M-XDI) with molecular formula C10H8N2O2Molecular weight of 188.06, and its chemical formula is as follows:
Figure DEST_PATH_IMAGE001
。
the isocyanate group is connected with methylene, so that the polyurethane belongs to aliphatic isocyanate, has the advantages of fast reaction, short drying time, no yellowing and the like compared with polyurethane generated by common aromatic isocyanate-diphenylmethane diisocyanate (MDI), can obtain a paint film with high hardness and good stability, and is mainly used for high-grade spectacle lenses, high-grade polyurethane paint, flexible packages, outdoor sealants, elastomers, leather, adhesives and the like.
The existing phosgene method technology is mainly divided into a gas phase phosgene method and a liquid phase phosgene method. The gas phase phosgene method needs high temperature and high pressure, has large technical difficulty and is less in development and application. The liquid phase phosgene method is divided into a direct phosgene method and a salt-forming phosgene method, the direct phosgene method is to directly react primary amine and phosgene to prepare corresponding isocyanate, and urea byproducts are easily generated in the reaction process; the reaction process of the salt-forming phosgene method is not easy to generate urea byproducts, so the salt-forming phosgene method is usually adopted when aliphatic and alicyclic isocyanate is prepared. British patents GB1162155A and GB1146664A and Chinese patents CN101203488A, CN1045578A, CN102070491A and CN105218422A all disclose methods for preparing corresponding isocyanate by a salt-forming phosgene method.
Although the phosgene method is generally adopted in the existing industry, the process type uses the highly toxic phosgene, so that the process has great danger in the processes of use, transportation and storage, and various strict safety measures are required to be adopted; a large amount of hydrogen chloride gas is generated in the reaction process, so that the method has strong corrosivity on equipment, the requirement on the equipment in the production process is particularly high, the service life of the equipment is short, and various defects or hidden dangers exist; in addition, chlorine residue in the product also seriously affects the product quality. With the enhancement of environmental awareness, the search for safer, more efficient and green manufacturing methods to replace phosgene methods is a necessary trend in the development of isonitrile acid ester preparation technology.
The reports of isocyanate preparation by a non-phosgene method are also more, and Chinese patent CN1590369A discloses that the isocyanate is prepared in a corresponding solvent by taking m-xylylenediamine, carbon dioxide, alkali and a dehydrating agent as reactants, the yield is 65-87%, and the selectivity is 98%. However, the method needs to be carried out under high pressure, and an acid binding agent, a dehydrating agent and a large amount of solvent are also needed to be added, so that the cost is high, and the industrial feasibility is not high.
Chinese patents CN103351313A, CN102827035A, and CN102659632A all disclose synthesis processes for preparing corresponding isocyanates by triphosgene method, and use triphosgene and corresponding amine or hydrochloride of amine to prepare isocyanates under the condition of catalyst. However, triphosgene still releases a large amount of corrosive hydrogen chloride gas in the reaction process, so that equipment is corroded, the environment is polluted, and meanwhile, chlorine remains in the product to seriously affect the product quality.
Dimethyl carbonate (DMC) is a chemical raw material with low toxicity, environmental protection and wide application, and the preparation of isocyanate by using dimethyl carbonate to replace phosgene is a non-phosgene process route with environmental protection and industrial prospect. Dimethyl carbonate and aliphatic (aromatic) primary amine directly react to synthesize carbamate under the action of a catalyst, then the carbamate is thermally decomposed into isocyanate under the action of the catalyst, and a byproduct generated in the reaction process is methanol instead of hydrochloric acid, so that the problems of corrosion, safety, product quality and the like of equipment are fundamentally solved. If the method is combined with a methanol gas phase oxidation carbonylation preparation process, a 'zero-emission' green synthesis process can be formed. The process routes are reported in patents US4307029, US4547322, WO8805430A1, CN101195590A, CN101011657A, CN105143177A, CN200510021147 and the like, however, the problems of poor product selectivity, low yield, low purity, catalyst residue and the like generally exist in the existing reported processes.
Disclosure of Invention
The invention aims to solve the problems that no chlorine element is involved in the reaction process, the problem of chloride ion residue does not exist in the product, the product has good selectivity, high yield and high purity, no catalyst residue exists, the product quality is improved, and the requirements of high-end fields are met.
The method for preparing the high-purity m-xylylene diisocyanate without phosgene comprises the following steps:
(1) m-xylylenediamine (M-XDA) and dimethyl carbonate (DMC) react under the action of a catalyst A to obtain M-xylylene dicarbamate (M-XDC);
(2) adding M-xylylene dicarbamate (M-XDC) into an organic solvent, carrying out decomposition reaction under the action of a catalyst B, emptying a byproduct methanol by nitrogen displacement in the reaction process, and carrying out reduced pressure distillation after the reaction is finished to obtain M-xylylene diisocyanate (M-XDI).
In the step (1), the reaction is carried out under the protection of nitrogen, the reaction temperature is 100-250 ℃, the reaction pressure is 0.1-3 MPa, and the reaction time is 0.5-10 h.
In the step (1), the molar ratio of m-xylylenediamine to dimethyl carbonate is 1 (2-10).
In the step (1), the addition amount of the catalyst A is 0.1-5% of the molar amount of m-xylylenediamine.
Wherein the catalyst A takes Lewis acid as an active component and takes nano SiO2Or TiO2The supported catalyst is used as a carrier, wherein the mass ratio of the active component to the carrier is (0.1-5) to 1;
the Lewis acid is Zn (NO)3)2、Zn(OAc)2、Pb(OAc)2、Mn(OAc)2、Co(OAc)2、Bi(OAc)2One or more of;
nano SiO2The carrier has an average primary particle diameter of 5 to 100nm and a specific surface area (BET method) of 100 to 500m2/g；
Nano TiO 22The carrier has an average primary particle diameter of 50 to 500nm and a specific surface area (BET method) of 20 to 200m2/g。
Preferably, the preparation method of the catalyst A is as follows:
dissolving Lewis acid into deionized water, stirring and mixing, and thenImpregnation into nanosilicon dioxide (SiO)2) Or nano titanium dioxide (TiO)2) On a carrier, after the impregnation is finished, filtering, vacuum drying, and then N in a tube furnace2Roasting at high temperature under protection to obtain corresponding nano SiO2Or TiO2A supported catalyst.
In the step (1), after the reaction is finished, the reaction solution is post-treated, and the method comprises the following steps:
1) carrying out solid-liquid separation and filtration on the reaction liquid to obtain a catalyst A and a filtrate containing M-XDC, washing and drying the catalyst A with ethanol, then repeatedly recycling the catalyst A, washing the filtrate with a dilute hydrochloric acid solution, then separating a water phase, carrying out reduced pressure concentration on the obtained solution phase, and removing excessive dimethyl carbonate and generated solvents such as methanol and the like to obtain a crude product of M-XDC;
2) recrystallizing the M-XDC crude product with absolute ethyl alcohol, filtering and drying to obtain a white crystallized high-purity M-XDC product.
And (3) dissolving the M-XDC obtained after the reaction and purification in the step (1) in a high-temperature solvent, and using the M-XDC in the high-temperature thermal cracking reaction in the step (2) under the action of a catalyst.
In the step (2), the reaction is carried out under the protection of nitrogen, the reaction temperature is 100-300 ℃, the reaction pressure is 0.1-3 MPa, the temperature is kept for 20-40min after the pressure in the reactor is not obviously increased any more, and the reaction is finished.
In the step (2), the organic solvent is a high-temperature solvent, preferably one or more of dimethyl phthalate, dibutyl phthalate, dioctyl phthalate, o-dichlorobenzene, n-pentadecane, dioctyl sebacate and diisooctyl sebacate; the mass ratio of the organic solvent to the M-XDC is (2-10) to 1.
In the step (2), the addition amount of the catalyst B is 0.01-5% of the molar weight of M-XDC.
The catalyst B has a particle size of 100 to 200nm and a specific surface area (BET method) of 50 to 200m2A superfine composite oxide per gram.
The superfine composite oxide is one or more of zinc oxide-silicon dioxide, lead oxide-silicon dioxide, manganese oxide-silicon dioxide, zinc oxide-titanium dioxide, lead oxide-titanium dioxide, manganese oxide-titanium dioxide, zinc oxide-aluminum oxide, copper oxide-aluminum oxide and copper oxide-silicon dioxide; the composite molar ratio is (0.1-10): 1. An ultrafine composite oxide having a double transition metal structure is preferable.
Preferably, catalyst B is prepared as follows:
dissolving one or more metal salt solutions and a surfactant in deionized water, stirring, simultaneously dropwise adding a NaOH solution until the pH value is more than or equal to 10, and continuously stirring to obtain a precipitate; and refluxing the generated precipitate at the temperature of more than or equal to 100 ℃ for 12-48 h, performing suction filtration and washing for several times, drying at the temperature of 70-100 ℃ for 12-24 h, placing in a muffle furnace, and roasting at the temperature of 300-800 ℃ for 1-10 h in the air atmosphere to obtain the superfine composite oxide catalyst.
Wherein the salt solution is Zn (NO)3)2、Zn(OAc)2、Pb(OAc)2、Mn(OAc)2、Co(OAc)2、Ti(OAc)2、Cu(OAc)2、Si(OCH2CH3)4And AlCl3One or more of (a).
In the step (2), after each reaction is carried out for 20min or when the pressure is more than 0.5MPa in the reaction process, the byproduct methanol is discharged by nitrogen replacement.
In the step (2), after the reaction is finished, post-treatment is carried out on the reaction solution, and the method comprises the following steps:
and (2) carrying out solid-liquid separation and filtration on the reaction liquid to obtain a catalyst B and a filtrate containing M-xylylene diisocyanate (M-XDI), washing the catalyst B with ethanol for a plurality of times, drying in vacuum, repeatedly recycling, carrying out reduced pressure distillation on the filtrate, carrying out reduced pressure distillation under a lower vacuum degree to remove a high-temperature solvent, then reducing the vacuum degree to a high vacuum degree, and further rectifying to obtain the high-purity M-XDI.
The reduced pressure distillation comprises the following processes: distilling the high-temperature solvent under the conditions of vacuum degree of 1000-2000 Pa and temperature of 100-150 ℃; further reducing the vacuum degree to 50-500 Pa, and rectifying at 100-150 ℃ to obtain the high-purity M-XDI.
The reaction route for preparing m-xylylene diisocyanate is as follows:
(1) m-xylylene dicarbamate (M-XDC):
Figure DEST_PATH_IMAGE003
；
(2) preparation of M-xylylene diisocyanate (M-XDI):
Figure DEST_PATH_IMAGE005
。
the invention adopts nano SiO in the step (1)2Or TiO2As a catalyst carrier, the catalyst carrier makes full use of the high specific surface area: firstly, the active ingredient, namely Lewis acid, is fully adsorbed and uniformly distributed on a carrier, and the adsorption quantity and the adsorption tightness can be improved; secondly, the nano-carrier can fully adsorb the reaction liquid to ensure that the active ingredients, namely Lewis acid, are closely contacted with the reaction components (m-xylylenediamine and dimethyl carbonate). Further, the nano SiO in the step (1)2Or TiO2The supported catalyst is a heterogeneous catalyst, and compared with a Lewis acid homogeneous catalyst, the supported catalyst has the remarkable advantages of easy separation, no catalyst residue, repeated recycling, high raw material conversion rate, high product yield and the like.
The reaction of M-xylylenediamine (M-XDA) with dimethyl carbonate (DMC) usually results in less formation of di-substituted methyl dicarbamate, with more formation of substantially mono-substituted methyl monocarbamate. However, in the present invention, the conversion of M-XDA into disubstituted M-XDC can be greatly promoted by using a Lewis acid supported catalyst, and the product is mainly disubstituted M-XDC. With Zn (OAc)2For example, the possible reaction mechanism is shown below:
Figure DEST_PATH_IMAGE006
。
first, Zn (OAc)2Zn in (1)2+With carbonyl oxygen in DMCThe atoms coordinate to form a Zn-O coordination bond, Zn (OAc)2Conversion to a bidentate complex allows the carbonyl carbon atom in the DMC to be activated. One amino group in M-XDA is taken as a nucleophilic reagent to perform nucleophilic reaction (methoxycarbonylation) with activated carbonyl carbon atoms in the complex to generate intermediate products, namely methyl monocarbamate and methanol. Finally, another unreacted amino group in the methyl monocarbamate re-nucleophilically attacks another activated carbonyl carbon atom in the DMC to form the M-XDC final product.
The method adopts the superfine composite oxide as the heterogeneous catalyst in the step (2), and has the advantages of simple operation, easy separation, no catalyst residue, repeated recycling, high raw material conversion rate, high product yield and the like.
In the reaction process of the step (2), the problem that the final product M-XDI is easy to recombine with the byproduct methanol in the thermal cracking process also exists, which is one of the difficult problems of the thermal cracking process, and the generated methanol needs to be removed in time. The invention can be emptied in time by setting the interval time or the pressure limit value in the reaction process to remove the byproduct methanol generated in the reaction, thereby solving the process problem.
Compared with the prior art, the invention has the following beneficial effects:
(1) the method adopts low-toxicity, green and environment-friendly dimethyl carbonate to replace highly-toxic phosgene or triphosgene to prepare m-xylylene diisocyanate, accords with the green chemical development concept, changes the main by-product of the reaction process from highly-corrosive hydrochloric acid into methanol, reduces the requirement on equipment to a great extent, prolongs the service life of the equipment, reduces the production cost, does not relate to chlorine element in the reaction process, does not have the problem of chlorine ion residue in the product, improves the product quality, and has wider application field;
(2) in the preparation stage of an intermediate product, namely M-xylylene dicarbamate (M-XDC), and in the preparation stage of a final product, namely M-xylylene diisocyanato ester (M-XDI), supported Lewis acid (Lewis acid) and superfine composite oxide with high specific surface area are respectively adopted as catalysts, the two catalysts are heterogeneous catalysts, and the preparation method has the advantages of simplicity in operation, easiness in separation, no catalyst residue, reusability, high raw material conversion rate, high product yield and the like, and the finally prepared M-xylylene diisocyanate (M-XDI) has high purity and high yield by screening the high-efficiency supported Lewis acid catalyst and the superfine composite oxide catalyst and assisting a purification process and a reduced pressure rectification process under high vacuum degree;
(3) when M-xylylene diisocyanate (M-XDI) is prepared, the air is discharged in time by setting interval time or pressure limit value to remove a byproduct methanol generated in the reaction, the problem that M-xylylene diisocyanate is easy to recombine with the byproduct methanol in a thermal cracking process in the preparation process is solved, and high-purity M-xylylene diisocyanate is obtained by vacuum rectification under high vacuum degree.
Detailed Description
The invention is further illustrated by the following examples, which are given by way of illustration, but do not restrict the scope of the invention.
Example 1
23.9g of Zn (OAc)2·2H2Dissolving O in 500ml deionized water, stirring at room temperature, and gradually adding 80g of nano SiO2Support (average primary particle size 12nm, specific surface area (BET method) 200. + -.25 m2(ii)/g; drying at 120 deg.C for 12h before use), stirring at room temperature, soaking for 12h, filtering, vacuum drying at 60 deg.C for 12h, and N in a tube furnace2Roasting for 3h at 300 ℃ under protection to obtain a supported catalyst Zn (OAc)2/SiO2，Zn(OAc)2/SiO2Mass ratio = 20/80.
Into a 1L autoclave, M-xylylenediamine (M-XDA, 136.1g, 1.0 mol), dimethyl carbonate (DMC, 450.4g, 5.0 mol), and the supported catalyst Zn (OAc) prepared in the above-mentioned step were charged2/SiO2(9.2 g, wherein Zn (OAc)2The amount of substance/M-XDA amounting to about 1%) with N2Replacing air in the reaction kettle, and then filling N2To 0.3 MPa. Starting the mechanical stirring device to stir the mixture,heating to 180 ℃, reacting for 6 hours under the reaction pressure of 1.5MPa, cooling to room temperature, exhausting gas in a reaction kettle, taking out reaction solution, filtering and separating to obtain a solid catalyst and filtrate, washing the obtained filtrate with 50ml of 1mol/L diluted hydrochloric acid solution, separating a water phase, concentrating the obtained solution phase under reduced pressure to obtain a m-xylylene dicarbamate crude product, recrystallizing and drying with absolute ethyl alcohol to obtain a white crystalline solid product, and using the white crystalline solid product for the next thermal cracking reaction. 217.3g of M-xylylene dicarbamate (M-XDC) was obtained in 86.2% yield, 99.2% purity and 102.8-103.5 ℃ melting point.
Example 2
23.3g of Pb (OAc)2·3H2O and 80g of nano SiO2(average primary particle size 12nm, specific surface area (BET method) 200. + -. 25m2Preparation of the Supported catalyst Pb (OAc) according to the procedure described in example 12/SiO2，Pb(OAc)2/SiO2Mass ratio = 20/80.
M-xylylenediamine (136.1 g, 1.0 mol), dimethyl carbonate (450.4 g, 5.0 mol), and the supported catalyst Pb (OAc) prepared in the above step2/ SiO2（16.3g，Pb(OAc)2Mole ratio of M-XDA of about 1%), according to the procedure of example 1, 233.5g of M-xylylene dicarbamate was obtained in a yield of 92.6% and a purity of 99.4%.
Example 3
28.3g of Mn (OAc)2·4H2O and 80g of nano SiO2(average primary particle size 12nm, specific surface area (BET method) 200. + -. 25m2Preparation of the Supported catalyst Mn (OAc) according to the procedure of example 12/SiO2，Mn(OAc)2/SiO2Mass ratio = 20/80.
M-xylylenediamine (136.1 g, 1.0 mol), dimethyl carbonate (450.4 g, 5.0 mol), and the supported catalyst Mn (OAc) prepared in the above step2/ SiO2（8.7g，Mn(OAc)2Molar ratio of M-XDA of about 1%), prepared according to the procedure of example 1 to give M-xylylene229.9g of diamino methyl formate, 91.2% yield and 99.2% purity.
Example 4
12.0g of Zn (OAc)2·2H2O、11.7g Pb(OAc)2·3H2O and 80g of nano SiO2(average primary particle size 12nm, specific surface area (BET method) 200. + -. 25m2Preparation of Supported Complex catalyst Zn (OAc) according to the procedure of example 12/Pb(OAc)2/SiO2，Zn(OAc)2/Pb(OAc)2/SiO2Mass ratio = 10/10/80.
M-xylylenediamine (136.1 g, 1.0 mol), dimethyl carbonate (450.4 g, 5.0 mol), and the supported catalyst Zn (OAc) prepared in the above step2/Pb(OAc)2/SiO2（12.7g，Zn(OAc)2+Pb(OAc)2Mole ratio of M-XDA of about 1%), according to the procedure of example 1, M-xylylene dicarbamate was obtained in 232.4g, yield 92.2% and purity 99.4%.
Example 5
12.0g of Zn (OAc)2·2H2O 、14.2g Mn(OAc)2。4H2O and 80g of nano SiO2(average primary particle size 12nm, specific surface area (BET method) 200. + -. 25m2Preparation of Supported Complex catalyst Zn (OAc) according to the procedure of example 12/Mn(OAc)2/SiO2，Zn(OAc)2/Mn(OAc)2/SiO2Mass ratio = 10/10/80.
M-xylylenediamine (136.1 g, 1.0 mol), dimethyl carbonate (450.4 g, 5.0 mol), and the supported catalyst Zn (OAc) prepared in the above step2/Mn(OAc)2/SiO2（8.9g，Zn(OAc)2+Mn(OAc)2Mole ratio of M-XDA of about 1%), according to the procedure of example 1, there was obtained 228.4g of M-xylylene dicarbamate with a yield of 90.6% and a purity of 99.2%.
Example 6
Mixing 11.7g of Pb (OAc)2·3H2O 、14.2g Mn(OAc)2·4H2O and 80g nmSiO2(average primary particle size 12nm, specific surface area (BET method) 200. + -. 25m2/g) preparation of the Supported Complex catalyst Pb (OAc) according to the procedure of example 12/ Mn(OAc)2/SiO2，Pb(OAc)2/ Mn(OAc)2/SiO2Mass ratio = 10/10/80.
M-xylylenediamine (136.1 g, 1.0 mol), dimethyl carbonate (450.4 g, 5.0 mol), and the supported catalyst Pb (OAc) prepared in the above step2/Mn(OAc)2/SiO2（12.5g，Pb(OAc)2+Mn(OAc)2Mole ratio of M-XDA of about 1%), according to the procedure of example 1, 230.9g of M-xylylene dicarbamate was obtained in a yield of 91.6% and a purity of 99.2%.
Example 7
23.9g of Zn (OAc)2·2H2Dissolving O in 600ml deionized water, stirring at room temperature, and gradually adding 80g of nano TiO2(average primary particle diameter 150nm, specific surface area (BET method) 100. + -.10 m)2(ii)/g; drying at 120 deg.C for 12h before use), stirring at room temperature, soaking for 12h, filtering, vacuum drying at 60 deg.C for 12h, and N in a tube furnace2Roasting for 3h at 300 ℃ under protection to obtain a supported catalyst Zn (OAc)2/TiO2，Zn(OAc)2/TiO2Mass ratio = 20/80.
M-xylylenediamine (136.1 g, 1.0 mol), dimethyl carbonate (450.4 g, 5.0 mol), and the supported catalyst Zn (OAc) prepared in the above step2/TiO2（9.2g，Zn(OAc)2Mole ratio of M-XDA of about 1%), according to the procedure of example 1, M-xylylene dicarbamate 240.0g was obtained in a yield of 95.2% and a purity of 99.4%.
Example 8
23.3g of Pb (OAc)2·3H2O and 80g of nano TiO2(average primary particle diameter 150nm, specific surface area (BET method) 100. + -.10 m)2Preparation of the Supported catalyst Pb (OAc) following the procedure described in example 72/TiO2，Pb(OAc)2/TiO2Mass ratio = 20/80.
M-xylylenediamine (136.1 g, 1.0 mol), dimethyl carbonate (450.4 g, 5.0 mol), and the supported catalyst Pb (OAc) prepared in the above step2/TiO2（16.3g，Pb(OAc)2Mole ratio of M-XDA of about 1%), according to the procedure of example 1, M-xylylene dicarbamate 243.5g was obtained in a yield of 96.6% and a purity of 99.5%.
Example 9
28.3g of Mn (OAc)2·4H2O and 80g of nano TiO2(average primary particle diameter 150nm, specific surface area (BET method) 100. + -.10 m)2Preparation of the Supported catalyst Mn (OAc) according to the procedure in example 72/TiO2，Mn(OAc)2/TiO2Mass ratio = 20/80.
M-xylylenediamine (136.1 g, 1.0 mol), dimethyl carbonate (450.4 g, 5.0 mol), and the supported catalyst Mn (OAc) prepared in the above step2/TiO2（8.7g，Mn(OAc)2Mole ratio of M-XDA of about 1%), according to the procedure of example 1, M-xylylene dicarbamate of 241.5g was obtained in 95.8% yield and 99.5% purity.
Example 10
12.0g of Zn (OAc)2·2H2O、11.7g Pb(OAc)2·3H2O and 80g of nano TiO2(average primary particle diameter 150nm, specific surface area (BET method) 100. + -.10 m)2Preparation of Supported Complex catalyst Zn (OAc) according to the procedure of example 72/Pb(OAc)2/TiO2，Zn(OAc)2/Pb(OAc)2/TiO2Mass ratio = 10/10/80.
M-xylylenediamine (136.1 g, 1.0 mol), dimethyl carbonate (450.4 g, 5.0 mol), and the supported catalyst Zn (OAc) prepared in the above step2/Pb(OAc)2/TiO2（12.7g，Zn(OAc)2+Pb(OAc)2Molar ratio of M-XDA of about 1%), prepared according to the procedure of example 1 to give M-xylylenediamine247.6g of methyl formate, 98.2% yield and 99.6% purity.
Example 11
12.0g of Zn (OAc)2·2H2O 、14.2g Mn(OAc)2·4H2O and 80g of nano TiO2(average primary particle diameter 150nm, specific surface area (BET method) 100. + -.10 m)2Preparation of Supported Complex catalyst Zn (OAc) according to the procedure of example 72/Mn(OAc)2/TiO2，Zn(OAc)2/Mn(OAc)2/TiO2Mass ratio = 10/10/80.
M-xylylenediamine (136.1 g, 1.0 mol), dimethyl carbonate (450.4 g, 5.0 mol), and the supported catalyst Zn (OAc) prepared in the above step2/Mn(OAc)2/TiO2（8.9g，Zn(OAc)2+Mn(OAc)2Mole ratio of M-XDA of about 1%), according to the procedure of example 1, M-xylylene dicarbamate was obtained in 245.1g, yield 97.2% and purity 99.6%.
Example 12
Mixing 11.7g of Pb (OAc)2·3H2O、14.2g Mn(OAc)2·4H2O and 80g of nano SiO2(average primary particle diameter 150nm, specific surface area (BET method) 100. + -.10 m)2/g) preparation of the Supported Complex catalyst Pb (OAc) according to the procedure in example 72/ Mn(OAc)2/TiO2，Pb(OAc)2/Mn(OAc)2/TiO2Mass ratio = 10/10/80.
M-xylylenediamine (136.1 g, 1.0 mol), dimethyl carbonate (450.4 g, 5.0 mol), and the supported catalyst Pb (OAc) prepared in the above step2/Mn(OAc)2/SiO2（12.5g，Pb(OAc)2+Mn(OAc)2Mole ratio of M-XDA of about 1%), according to the procedure of example 1, M-xylylene dicarbamate 242.8g was obtained in a yield of 96.3% and a purity of 99.5%.
The reaction conditions and the reaction results of examples 1 to 12 are shown in Table 1 below:
TABLE 1 reaction conditions and reaction results of examples 1 to 12
Figure DEST_PATH_IMAGE008
As can be seen from Table 1, the product yields in examples 1-6 are generally lower than the corresponding product yields in examples 7-12 under the same reaction conditions, indicating that TiO is used2The catalyst carrier has better reaction effect. This may be combined with Ti as the transition metal, TiO2Besides the uniform dispersion of Lewis acid active center, the carrier can make the reaction activity higher, and also has a certain catalytic action. Furthermore, as can be seen from Table 1, the catalysts having a mixture of various Lewis acids have a better catalytic effect, particularly, those containing Pb (OAc)2The catalyst of (1).
The catalysts in the embodiments 1 to 12 are all load-type heterogeneous catalysts, and have the advantages of easy separation and repeated recycling. Based on the best working example 10, the catalyst Zn (OAc)2/Pb(OAc)2/TiO2After filtration and separation, the mixture is washed for 3 times by absolute ethyl alcohol, dried in vacuum at 100 ℃ and recycled. The catalyst was examined for its recycling performance in examples 13 to 17 under the operating conditions of example 1. The reaction conditions and the reaction results are shown in table 2:
table 2 reaction conditions and results of examples 13 to 17
Figure DEST_PATH_IMAGE010
As can be seen from Table 2, the catalysts Zn (OAc)2/Pb(OAc)2/TiO2After 5 times of recycling, the yield and purity of XDC are hardly reduced, which shows that the supported catalyst has good recycling performance.
Example 18
2.0g of sodium dodecylbenzenesulfonate surfactant was dissolved in 200 mL of distilled water, and 11.0g of Zn (OAc) was added2。2H2O (0.05 mol) and 10.4g Si (OCH)2CH3)4(tetraethyl orthosilicate, 0.05 mol), stirred in a 50 ℃ water bath while adding a NaOH solution (2mol/L) dropwise to a solution pH =11, then stirred vigorously for 30 min. Refluxing the generated precipitate at 110 deg.C for 48 hr, filtering, washing several times, drying at 80 deg.C for 24 hr, and calcining at 600 deg.C in muffle furnace for 6 hr to obtain superfine composite oxide ZnO/SiO2A catalyst; superfine oxide ZnO/SiO2Specification: the particle size distribution is 20-50 nm, and the specific surface area (BET method) is 100 +/-20 m2/g，ZnO/SiO2The ratio of the amounts of substances = 50/50.
M-xylylene dicarbamate (126.1 g, 0.5 mol), dimethyl phthalate (440.4 g) and catalyst superfine composite oxide ZnO/SiO2（0.7g，ZnO+SiO2The ratio of the amount of substance/M-XDC was about 2%). Under the protection of nitrogen, starting stirring, heating to 250 ℃, discharging methanol generated by the reaction after each reaction is carried out for 20min or the pressure is more than 0.5MPa, and simultaneously replacing nitrogen for protection. After the reaction is finished (after the pressure is not obviously increased any more, the temperature is kept for 30 min), the temperature is reduced to room temperature, and the filtration is carried out to obtain the filtrate of the catalyst and the m-xylylene diisocyanate. And (3) under the condition that the vacuum degree of the obtained filtrate is 1000-2000 Pa, the temperature of the reaction kettle is 100-150 ℃, and the distilled fraction is dimethyl phthalate serving as a solvent. And after the solvent is completely distilled off, continuously reducing the vacuum degree to 50-500 Pa, keeping the temperature of the reaction kettle between 100 ℃ and 150 ℃, and rectifying to obtain 88.9g of m-xylylene diisocyanate with the purity of 99.5% and the yield of 94.5%.
Example 19
2.0g of sodium dodecylbenzenesulfonate surfactant, 19.0g of Pb (OAc)2。3H2O (0.05 mol) and 10.4g Si (OCH)2CH3)4(tetraethyl orthosilicate, 0.05 mol) was prepared by the procedure of example 18 to obtain ultrafine composite oxide PbO/SiO2A catalyst; superfine composite oxide PbO/SiO2Specification: the particle size distribution is 20-50 nm, and the specific surface area (BET method) is 80 +/-20 m2/g，PbO/SiO2The ratio of the amounts of substances = 50/50.
M-xylylene dicarbamate (A) and (B)126.1g, 0.5 mol), dimethyl phthalate (440.4 g), catalyst superfine composite oxide PbO/SiO2（1.4g，PbO+SiO2The amount of substance/M-XDC was about 2%), and prepared according to the procedure of example 18, to give 87.6g of M-xylylene diisocyanate with a purity of 99.5% and a yield of 93.2%.
Example 20
2.0g of sodium dodecylbenzenesulfonate surfactant, 12.3g of Mn (OAc)2。4H2O (0.05 mol) and 10.4g Si (OCH)2CH3)4(tetraethyl orthosilicate, 0.05 mol) was prepared by the procedure of example 18 to obtain a superfine composite oxide MnO/SiO2A catalyst; superfine composite oxide MnO/SiO2Specification: the particle size distribution is 20-50 nm, and the specific surface area (BET method) is 80 +/-20 m2/g，MnO/SiO2The ratio of the amounts of substances = 50/50.
M-xylylene dicarbamate (126.1 g, 0.5 mol), dimethyl phthalate (440.4 g) and catalyst superfine composite oxide MnO/SiO2（0.7g，MnO+SiO2The amount of substance/M-XDC was about 2%), and prepared according to the procedure of example 18, to give 88.2g of M-xylylene diisocyanate with a purity of 99.5% and a yield of 93.8%.
Example 21
2.0g of sodium dodecylbenzenesulfonate surfactant, 11.0g of Zn (OAc)2。2H2O (0.05 mol) and 17.0g Ti (OC)4H9)4(0.05 mol) was prepared by the procedure of example 18 to obtain a superfine composite oxide ZnO/TiO2A catalyst; superfine oxide ZnO/TiO2Specification: the particle size distribution is 20-50 nm, and the specific surface area (BET method) is 100 +/-20 m2/g，ZnO/TiO2The ratio of the amounts of substances = 50/50.
M-xylylene diamino methyl formate (126.1 g, 0.5 mol), dimethyl phthalate (440.4 g) and catalyst superfine composite oxide ZnO/TiO2（0.8g，ZnO+TiO2The amount of substance/M-XDC was about 2%), prepared according to the procedure of example 18 to give isophthalodine92.7g of methyl diisocyanate, the purity is 99.5 percent, and the yield is 98.6 percent.
Example 22
2.0g of sodium dodecylbenzenesulfonate surfactant, 19.0g of Pb (OAc)2。2H2O (0.05 mol) and 17.0g Ti (OC)4H9)4(0.05 mol) was prepared by the procedure of example 18 to obtain ultrafine composite oxide PbO/TiO2A catalyst; superfine oxide PbO/TiO2Specification: the particle size distribution is 20-50 nm, and the specific surface area (BET method) is 80 +/-20 m2/g，PbO/TiO2The ratio of the amounts of substances = 50/50.
M-xylylene dicarbamate (126.1 g, 0.5 mol), dimethyl phthalate (440.4 g) and catalyst superfine composite oxide PbO/TiO2（1.5g，PbO+TiO2The amount of substance/M-XDC was about 2%), and prepared according to the procedure of example 18, to give 91.2g of M-xylylene diisocyanate with a purity of 99.5% and a yield of 97.0%.
Example 23
2.0g of sodium dodecylbenzenesulfonate surfactant, 12.3g of Mn (OAc)2。4H2O (0.05 mol) and 17.0g Ti (OC)4H9)4(0.05 mol) was prepared by the procedure of example 18 to obtain ultrafine composite oxide MnO/TiO2A catalyst; ultrafine oxide MnO/TiO2Specification: the particle size distribution is 20-50 nm, and the specific surface area (BET method) is 80 +/-20 m2/g，MnO/TiO2The ratio of the amounts of substances = 50/50.
M-xylylene dicarbamate (126.1 g, 0.5 mol), dimethyl phthalate (440.4 g) and catalyst superfine composite oxide MnO/TiO2（0.8g，MnO+TiO2The amount of substance/M-XDC was about 2%), and prepared according to the procedure of example 18, to give 91.7g of M-xylylene diisocyanate with a purity of 99.5% and a yield of 97.5%.
In the above examples 18 to 23, the reaction conditions and the reaction results are shown in the following table 3:
table 3 reaction conditions and results of examples 18 to 23
Figure DEST_PATH_IMAGE012
As can be seen from Table 3, under the same reaction conditions, based on TiO2Superfine composite oxide ZnO/TiO2、PbO/TiO2、MnO/TiO2Compared with SiO-based2The ultrafine composite oxides of (a) have more excellent catalytic effects, which may be associated with Ti, Zn, Pb and Mn as transition metals, which differ in acidity from one another, resulting in different catalytic activities. As a composite oxide catalyst, different metal ions are tightly connected, and can play a synergistic role in catalyzing the thermal decomposition process of M-XDC, so that the catalyst has a better catalytic effect.
As can be seen from Table 3 above, the ultrafine composite oxide ZnO/TiO in example 212Has the best catalytic effect, and simultaneously has the advantages of easy separation and repeated recycling when being used as a load type heterogeneous catalyst. Based on example 21, an ultrafine composite oxide ZnO/TiO was added2After the catalyst is filtered and separated, the catalyst is washed for 3 times by absolute ethyl alcohol, and then is dried in vacuum at 100 ℃ for repeated recycling. The catalyst was examined for its cyclability in examples 24 to 28 under the operating conditions of example 18. The reaction conditions and the reaction results are shown in table 4:
TABLE 4 reaction conditions and results of examples 24 to 28
Figure DEST_PATH_IMAGE014
As can be seen from Table 4, the ultrafine composite oxide ZnO/TiO2After the catalyst is recycled for 5 times, the yield and the purity of M-XDI are hardly reduced, which shows that the supported catalyst has good recycling performance.
In the reaction step (1), nano SiO2Or TiO2The supported catalyst is a heterogeneous catalyst, and has the advantages of being compared with a Lewis acid homogeneous catalystHas the obvious advantages of easy separation, no catalyst residue, repeated and cyclic use, high raw material conversion rate, high product yield and the like. In comparative examples 1 to 3, Lewis acid homogeneous catalysts, such as anhydrous Zn (OAc), were used2Anhydrous Pb (OAc)2And anhydrous Mn (OAc)2The reaction process and effect are as follows:
comparative example 1
In a 1L autoclave, M-xylylenediamine (M-XDA, 136.1g, 1.0 mol), dimethyl carbonate (DMC, 450.4g, 5.0 mol) and a catalyst, anhydrous zinc acetate (Zn (OAc)21.8g, of which Zn (OAc)2The amount of substance/M-XDA amounting to about 1%) with N2Replacing air in the reaction kettle, and then filling N2To 0.3 MPa. Starting a machine to stir, heating to 180 ℃, reacting for 6 hours under the reaction pressure of 1.5MPa, cooling to room temperature, exhausting gas in a reaction kettle, taking out the reaction solution, washing the obtained reaction solution by using 50ml of dilute hydrochloric acid solution with the concentration of 1mol/L, then separating a water phase, adding 50ml of deionized water to repeat the washing and separation of the water phase, concentrating the obtained solution phase under reduced pressure to obtain a m-xylylene dicarbamate crude product, then recrystallizing and drying by using absolute ethyl alcohol to obtain a white crystalline solid product, and using the white crystalline solid product for the next thermal cracking reaction. 164.4g of M-xylylene dicarbamate (M-XDC) was obtained in a yield of 65.2% and a purity of 96.5%.
Comparative example 2
M-xylylenediamine (136.1 g, 1.0 mol), dimethyl carbonate (450.4 g, 5.0 mol) and lead acetate anhydrous as a catalyst (Pb (OAc)2 3.3g，Pb(OAc)2Mole ratio of M-XDA of about 1%), according to the procedure of comparative example 1, M-xylylene dicarbamate was obtained in an amount of 193.6g, yield of 76.8% and purity of 98.6%.
Comparative example 3
M-xylylenediamine (136.1 g, 1.0 mol), dimethyl carbonate (450.4 g, 5.0 mol) and manganese acetate anhydrous as a catalyst (Mn (OAc)2 1.7g，Mn(OAc)2Molar ratio of M-XDA of about 1%), according to the procedure of comparative example 1 to give 178.0g of M-xylylene dicarbamate in yield70.6 percent and the purity is 98.0 percent.
In the above comparative examples 1 to 3, the reaction conditions and the reaction results are shown in the following table 5:
TABLE 5 reaction conditions and reaction results for comparative examples 1 to 3
Figure DEST_PATH_IMAGE016
Comparing the M-XDC yield data in tables 1 and 5, using a Lewis acid homogeneous catalyst such as anhydrous Zn (OAc)2Anhydrous Pb (OAc)2And anhydrous Mn (OAc)2The catalytic effect is obviously inferior to that of corresponding nano SiO2Or TiO2Supported catalysts, especially nano TiO2A supported catalyst. By using nano SiO2Or TiO2As a catalyst carrier, the catalyst fully utilizes the high specific surface area, uniformly disperses the Lewis acid active center and ensures that the reaction activity is higher. In addition, in order to wash out the residual Lewis acid homogeneous catalyst in the product, deionized water needs to be added for washing in the post-treatment process, which results in increased wastewater amount and incapability of recycling the Lewis acid homogeneous catalyst.
In the reaction step (2), the superfine composite oxide adopted in the embodiments 18 to 23 has a good catalytic effect, and is especially based on TiO2Superfine composite oxide ZnO/TiO2、PbO/ TiO2、MnO/TiO2The catalytic effect is more excellent, which may be associated with Ti, Zn, Pb and Mn as transition metals, which are different in acidity from each other, so that they have different catalytic activities. In comparative examples 4 to 8, the ultrafine single-component oxide was prepared as a catalyst according to the same method, and the reaction process and effects thereof were as follows:
comparative example 4
2.0g of sodium dodecylbenzenesulfonate surfactant was dissolved in 200 mL of distilled water, and 20.8g of Si (OCH) was added2CH3)4(tetraethyl orthosilicate, 0.1 mol), stirred in a 50 ℃ water bath while adding NaOH solution (2mol/L) dropwise to a solution pH =11, then stirred vigorously for 30 min. Refluxing the generated precipitate at 110 deg.C for 48h, and filteringWashing for several times, drying at 80 ℃ for 24h, and roasting in a muffle furnace at 600 ℃ for 6h to obtain the superfine oxide SiO2A catalyst; superfine oxide SiO2Specification: the particle size distribution is 20-50 nm, and the specific surface area (BET method) is 120 +/-20 m2/g。
M-xylylene dicarbamate (M-XDC, 126.1g, 0.5 mol), dimethyl phthalate (440.4 g) and catalyst ultrafine oxide SiO (molecular sieve catalyst) were added into a 1L autoclave2（0.6g，SiO2The ratio of the amount of substance/M-XDC was about 2%). Under the protection of nitrogen, starting stirring, heating to 250 ℃, discharging methanol generated by the reaction after each reaction is carried out for 20min or the pressure is more than 0.5MPa, and simultaneously replacing nitrogen for protection. After the reaction is finished (after the pressure is not obviously increased any more, the temperature is kept for 30 min), the temperature is reduced to room temperature, and the filtration is carried out to obtain the filtrate of the catalyst and the m-xylylene diisocyanate. And (3) under the condition that the vacuum degree of the obtained filtrate is 1000-2000 Pa, the temperature of the reaction kettle is 100-150 ℃, and the distilled fraction is dimethyl phthalate serving as a solvent. And after the solvent is completely distilled off, continuously reducing the vacuum degree to 50-500 Pa, keeping the temperature of the reaction kettle between 100 ℃ and 150 ℃, and rectifying to obtain 70.7g of m-xylylene diisocyanate with the purity of 99.5% and the yield of 75.2%.
Comparative example 5
2.0g of sodium dodecylbenzenesulfonate surfactant, 34.0g of Ti (OC)4H9)4(0.1 mol) is prepared according to the operation steps in the comparative example 4, and the superfine TiO oxide is obtained2A catalyst; ultrafine oxide TiO2Specification: the particle size distribution is 20-50 nm, and the specific surface area (BET method) is 120 +/-20 m2/g。
M-xylylene dicarbamate (126.1 g, 0.5 mol), dimethyl phthalate (440.4 g) and catalyst ultrafine oxide TiO2（0.8g，TiO2The amount of substance/M-XDC was about 2%), according to the procedure of comparative example 4, M-xylylene diisocyanate 80.5g was obtained with a purity of 99.5% and a yield of 85.6%.
Comparative example 6
2.0g of sodium dodecyl benzene sulfonate surfactant,22.0g Zn(OAc)2。2H2O (0.1 mol) is prepared according to the operation steps in the comparative example 4, and the superfine oxide ZnO catalyst is obtained; specification of superfine oxide ZnO: the particle size distribution is 20-50 nm, and the specific surface area (BET method) is 100 +/-20 m2/g。
Methylbenzenedimethylenedicarbamate (126.1 g, 0.5 mol), dimethyl phthalate (440.4 g), and a catalyst ultrafine oxide ZnO (0.8 g, the amount ratio of ZnO/M-XDC substance was about 2%), were prepared according to the procedure of comparative example 4 to obtain 77.6g of xylylene diisocyanate with a purity of 99.5% and a yield of 82.5%.
Comparative example 7
2.0g of sodium dodecylbenzenesulfonate surfactant, 37.9g of Pb (OAc)2。3H2O (0.1 mol) is prepared according to the operation steps in the comparative example 4, and the superfine oxide PbO catalyst is obtained; specification of superfine oxide PbO: the particle size distribution is 20-50 nm, and the specific surface area (BET method) is 80 +/-20 m2/g。
Methylbenzenedimethylenedicarbamate (126.1 g, 0.5 mol), dimethyl phthalate (440.4 g), catalyst ultrafine oxide PbO (2.2 g, amount ratio of PbO/M-XDC substance about 2%), was prepared according to the procedure of comparative example 4 to obtain 74.1g of xylylene diisocyanate with purity of 99.5% and yield of 78.8%.
Comparative example 8
2.0g of sodium dodecylbenzenesulfonate surfactant, 24.5g of Mn (OAc)2。4H2O (0.1 mol) is prepared according to the operation steps in the comparative example 4, and the superfine oxide MnO catalyst is obtained; specification of superfine oxide MnO: the particle size distribution is 20-50 nm, and the specific surface area (BET method) is 80 +/-20 m2/g。
Methylbenzenedimethylenedicarbamate (126.1 g, 0.5 mol), dimethyl phthalate (440.4 g), catalyst ultrafine oxide MnO (0.7 g, MnO/M-XDC content ratio of about 2%), was prepared according to the procedure of comparative example 4 to obtain 75.5g of isophthalenedimethylene diisocyanate with a purity of 99.5% and a yield of 80.3%.
In the comparative examples 4 to 8, the reaction conditions and the reaction results are shown in the following Table 6:
TABLE 6 reaction conditions and reaction results for comparative examples 4 to 8
Figure DEST_PATH_IMAGE018
Comparing the M-XDI yield data in tables 3 and 6, the catalytic effect of the catalyst using the ultra-fine single-component oxide catalyst was significantly inferior to that of the ultra-fine composite oxide catalyst.
In addition, as can be seen from the foregoing description, in the step (2), there is a problem that the final product M-XDI is easily recombined with the byproduct methanol of the thermal cracking process, which is also one of the problems of the thermal cracking process, and it is necessary to remove the generated methanol in time. The invention can be emptied in time by setting the interval time or the pressure limit value in the reaction process to remove the byproduct methanol generated in the reaction, thereby solving the process problem. Superfine composite oxide ZnO/TiO with best catalytic effect2As a catalyst, in comparative example 9, the reaction was carried out in such a manner that methanol as a by-product was not excluded, and the reaction process and effects were as follows:
comparative example 9
Adding M-xylylene diamino methyl formate (M-XDC, 126.1g, 0.5 mol), dimethyl phthalate (440.4 g) and catalyst superfine composite oxide ZnO/TiO into a 1L high-pressure reaction kettle2（0.8g，ZnO+TiO2The ratio of the amount of substance/M-XDC was about 2%). Under the protection of nitrogen, stirring is started, the temperature is raised to 250 ℃ for reaction, and a by-product methanol generated in the reaction is not discharged in the reaction process. After the reaction is finished (after the pressure is not obviously increased any more, the temperature is kept for 30 min), the temperature is reduced to room temperature, and the filtration is carried out to obtain the filtrate of the catalyst and the m-xylylene diisocyanate. And (3) under the condition that the vacuum degree of the obtained filtrate is 1000-2000 Pa, the temperature of the reaction kettle is 100-150 ℃, and the distilled fraction is dimethyl phthalate serving as a solvent. After the solvent is completely distilled off, the vacuum degree is continuously reduced to 50-500 Pa, the temperature of the reaction kettle is kept between 100 ℃ and 150 ℃, and the mixture is rectified to obtain 56.6g of m-xylylene diisocyanate with the purity of 99.5 percentThe yield thereof was found to be 60.2%.
The reaction conditions and the catalyst were the same in example 21 and comparative example 9, and the difference between them was whether methanol produced as a by-product during the reaction was timely removed. By comparing the M-XDI yield of the two, the method can be seen that the byproduct methanol generated in the reaction process is removed in time, and the recombination of the byproduct methanol and M-XDI is prevented, thereby having very important function for improving the M-XDI yield.

Claims (7)

1. A method for preparing high-purity m-xylylene diisocyanate without phosgene is characterized by comprising the following steps: the method comprises the following steps:
(1) m-xylylenediamine and dimethyl carbonate react under the action of a catalyst A, after the reaction is finished, solid-liquid separation and filtration are carried out on reaction liquid to obtain a catalyst A and a filtrate containing M-XDC, the catalyst A is washed by ethanol and dried and then repeatedly recycled, the filtrate is washed by a dilute hydrochloric acid solution and then separated into a water phase, and after the obtained solution phase is subjected to reduced pressure concentration, excessive dimethyl carbonate and generated solvents such as methanol are removed to obtain a crude product of M-XDC; recrystallizing the M-XDC crude product with absolute ethyl alcohol, filtering and drying to obtain M-xylylene diamino methyl formate;
(2) adding m-xylylene dicarbamate into an organic solvent, carrying out decomposition reaction under the action of a catalyst B, emptying a byproduct methanol through nitrogen displacement in the reaction process, distilling the organic solvent under the conditions of a vacuum degree of 1000-2000 Pa and a temperature of 100-150 ℃ after the reaction is finished, further reducing the vacuum degree to 50-500 Pa, and rectifying at the temperature of 100-150 ℃ to obtain m-xylylene diisocyanate;
the catalyst A takes Lewis acid as an active component and takes nano TiO2The supported catalyst is used as a carrier, wherein the mass ratio of the active component to the carrier is 0.1-5: 1;
lewis acids being Zn (OAc)2And Pb (OAc)2Mixed, or Zn (OAc)2And Mn (OAc)2Mixing;
nano TiO 22Average origin of vectorA primary particle diameter of 50 to 500nm and a BET specific surface area of 20 to 200m2/g；
The catalyst B has a particle size of 100-200 nm and a BET specific surface area of 50-200 m2The superfine composite oxide is one or more of zinc oxide-silicon dioxide, lead oxide-silicon dioxide, manganese oxide-silicon dioxide, zinc oxide-titanium dioxide, lead oxide-titanium dioxide, manganese oxide-titanium dioxide, zinc oxide-aluminum oxide, copper oxide-aluminum oxide and copper oxide-silicon dioxide, and the composite molar ratio is 0.1-10: 1.
2. The method for preparing high-purity m-xylylene diisocyanate without phosgene according to claim 1, wherein: in the step (1), the reaction is carried out under the protection of nitrogen, the reaction temperature is 100-250 ℃, the reaction pressure is 0.1-3 MPa, and the reaction time is 0.5-10 h.
3. The method for preparing high-purity m-xylylene diisocyanate without phosgene according to claim 1, wherein: in the step (1), the molar ratio of m-xylylenediamine to dimethyl carbonate is 1: 2-10.
4. The method for preparing high-purity m-xylylene diisocyanate without phosgene according to claim 1, wherein: in the step (1), the addition amount of the catalyst A is 0.1-5% of the molar amount of m-xylylenediamine.
5. The method for preparing high-purity m-xylylene diisocyanate without phosgene according to claim 1, wherein: in the step (2), the reaction is carried out under the protection of nitrogen, the reaction temperature is 100-300 ℃, and the reaction pressure is 0.1-3 MPa.
6. The method for preparing high-purity m-xylylene diisocyanate without phosgene according to claim 1, wherein: in the step (2), the organic solvent is one or more of dimethyl phthalate, dibutyl phthalate, dioctyl phthalate, o-dichlorobenzene, n-pentadecane, dioctyl sebacate and diisooctyl sebacate; the mass ratio of the organic solvent to the m-xylylene dicarbamate is 2-10: 1.
7. The method for preparing high-purity m-xylylene diisocyanate without phosgene according to claim 1, wherein: in the step (2), the addition amount of the catalyst B is 0.01-5% of the molar weight of the m-xylylene dicarbamate.
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