Method for synthesizing methyl 1, 6-hexamethylene dicarbamate under catalysis of bismuth metal salt

Abstract

The invention relates to a method for synthesizing methyl 1, 6-hexamethylene dicarbamate under the catalysis of bismuth metal salt. The method comprises the following steps: adding 1, 6-hexamethylenediamine, dimethyl carbonate and a catalyst into a reactor, and carrying out stirring reaction for 6-9 hours at 60-100 DEG C and normal pressure to obtain 1, 6-hexamethylene dicarbamate; the catalyst is metal salt bismuth acetate or supported bismuth acetate. The catalyst is simple in preparation process and can be recycled for multiple times, the cost loss is reduced, and the product yield is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of organic chemical industry, and in particular relates to a method for preparing 1,6-hexamethylenediaminomethyl ester by catalysis of bismuth metal salt. Background Art

[0002] 1,6-Hexamethylenedicarbamate (HDC) is an intermediate for the production of 1,6-hexamethylene diisocyanate. 1,6-Hexamethylene diisocyanate is an aliphatic isocyanate widely used in the polyurethane industry. It has outstanding chemical stability and excellent oil resistance, wear resistance, anti-powdering, gloss retention, color retention and other advantages. It is widely used in plastics, coatings, textiles, rubber and other industries. In industry, 1,6-hexamethylene diisocyanate is mainly prepared by the phosgene method. The raw material phosgene in this method is highly toxic, the environment is seriously polluted, and the production cost is expensive. Therefore, it is urgent to develop a green and environmentally friendly non-phosgene production process. Among them, the carbamate thermal decomposition method has attracted widespread attention from researchers. This method uses dimethyl carbonate instead of highly toxic phosgene, and mainly includes the synthesis of the intermediate HDC and its thermal decomposition. The above reaction process has mild conditions and low raw material toxicity, which meets the development requirements of green chemical industry.

[0003] As an environmentally friendly chemical raw material, dimethyl carbonate is widely used in carbonylation, methylation, methoxycarbonylation and other synthetic processes due to its pollution-free and highly active characteristics. In recent years, the process of catalytic synthesis of HDC by methoxycarbonylation of dimethyl carbonate and 1,6-hexanediamine has made breakthrough progress. This method has mild conditions and is easy to control. The byproduct methanol can be recovered as a raw material to produce dimethyl carbonate. At present, the methoxycarbonylation reaction of dimethyl carbonate and 1,6-hexanediamine mostly uses homogeneous catalysts, such as Mn(OAc)2, NaOCH3, NaOAC, Zn(OAC)2, Bi(NO3)3, etc. Although they have high conversion rates and selectivity when applied to the process, they all have the disadvantages of easy deactivation, difficult separation and recovery, and inability to be recycled.

[0004] For example, Wang Yue et al. (CN101565389A) used a variety of metal oxides to synthesize HDC by heterogeneous catalysis. The metal oxides used were directly calcined from metal precursors or prepared from metal precursors after sol-gel or precipitation. This method requires the addition of excess dimethyl carbonate, and the raw material conversion rate and product selectivity are low; Xiao Fukui et al. (CN105126804A) used an impregnation method to prepare an X / SiO2 heterogeneous catalyst, wherein X is a metal salt NaOCH3, Bi(NO3)2, NaOAc, Pb(OAc)2, Zn(OAc)2, Sc(OTf)3, NaCF3SO3, Na2C2O4, C6H5ONa, NaNO3 or C7H5NaO2, but the reaction time is as long as 36h, the efficiency is low, and the product yield is generally low. In short, heterogeneous catalysts can solve the problem of separation and recovery, but the reaction efficiency is low. Therefore, it is very important to develop a HDC synthesis method with low cost loss, easy catalyst recovery and recycling, and high reaction efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide a method for synthesizing 1,6-hexamethylenediaminomethyl formate with bismuth metal salt catalysis, for the current 1,6-hexamethylenediaminomethyl formate synthesis method, which has the problems of high cost loss, complicated operation process, non-recyclable catalyst and low product yield. The method adopts metal salt bismuth acetate or supported bismuth acetate as a catalyst, wherein supported bismuth acetate is supported by any one of silica gel, activated carbon and molecular sieve, and the active component bismuth acetate is impregnated. The catalyst preparation process is simple and can be recycled many times. Compared with the previous catalyst, the present invention does not require excessive dimethyl carbonate, reduces cost loss and improves product yield.

[0006] The technical solution adopted by the present invention is: A method for synthesizing 1,6-hexamethylenediaminomethyl formate using a bismuth-based metal salt as catalyst, the method comprising the following steps: Add 1,6-hexanediamine, dimethyl carbonate and a catalyst into a reactor, stir and react at 60-100° C. and normal pressure for 6-9 hours to obtain 1,6-hexamethylenediaminomethyl ester; The catalyst is a metal salt bismuth acetate or a supported bismuth acetate, and the added amount is 5% to 20% of the mass of 1,6-hexanediamine; the molar ratio of dimethyl carbonate to 1,6-hexanediamine is 2 to 6:1 The method also includes the following steps: adding a solvent to dissolve the reaction mixture after the reaction is completed, removing the solid catalyst by centrifugal filtration, and performing gas chromatography analysis after diluting the filtrate.

[0007] The solvent is methanol or ethanol.

[0008] The preparation method of the metal salt bismuth acetate catalyst comprises the following steps: (1) Weigh Bi2O3, acetic acid and acetic anhydride into a reactor and condense and reflux at 140-160°C for 1-3 hours; wherein, 1-10 g of Bi2O3 and 1-5 mL of acetic anhydride are added for every 30 mL of acetic acid; (2) filtering the filtrate obtained in the previous step, and evaporating it at 60-70° C. to obtain crystals; (3) dissolving the crystals obtained in step (2) in acetic acid at 70-100° C., and then cooling to room temperature to obtain crystals; wherein 0.5-2.0 g of crystals are added to every 15 mL of acetic acid; (4) The solid obtained in step (3) is filtered and dried under vacuum at 50° C. for 8 to 12 hours to obtain the metal salt bismuth acetate.

[0009] The preparation method of the supported bismuth acetate catalyst comprises the following steps: (1) Dissolve bismuth acetate in acetic acid and stir continuously at 70-100°C until completely dissolved; add 0.2-1.0 g of bismuth acetate and 1-3 g of carrier per 15 mL of acetic acid; (2) adding the carrier to the salt solution of step (1) and stirring for 12 to 36 hours; (3) The liquid in step (2) is filtered off, and the solid is dried at 50° C. in vacuum for 8 to 12 hours to obtain supported bismuth acetate.

[0010] Preferably, the carrier comprises silica gel, activated carbon or molecular sieve, and the metal salt loading is 10 to 40 wt%.

[0011] The essential features of the present invention are: The present invention uses bismuth acetate as the active component of the catalyst. 3+ It coordinates with the carbonyl oxygen in dimethyl carbonate to enhance the positive charge of the carbonyl carbon, thereby promoting the nucleophilic attack of the nitrogen anion in 1,6-hexanediamine on the carbonyl carbon of dimethyl carbonate; and unlike other acetates, bismuth acetate is insoluble in the reaction solution and insoluble in methyl alcohol. Like supported bismuth acetate, it is heterogeneous and can be directly separated by centrifugation.

[0012] The present invention has the following beneficial effects: (1) The present invention uses dimethyl carbonate instead of toxic phosgene, which is environmentally friendly, and the reaction is carried out at normal pressure and low temperature, with mild conditions and little safety hazard; (2) The present invention uses bismuth metal salt as the active component for the first time, has a simple preparation process, good catalytic performance, and a conversion rate of up to 100%; (3) The bismuth-based catalyst prepared by the present invention is a heterogeneous catalyst and can be recycled and reused multiple times. In addition, no excessive dimethyl carbonate is required during the reaction process, thereby reducing cost losses. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0014] Example 1 Take 4gBi2O3, 30ml acetic acid and 3ml acetic anhydride in a 100ml three-necked flask, condense and reflux at 150℃ for 2h, filter and obtain the filtrate after dissolution, evaporate the filtrate at 60℃ to obtain crystals, then take 1g solid and redissolve it in 15ml acetic acid at 70℃ and cool to room temperature for crystallization, finally dry it at 50℃ in vacuum for 10h to obtain the metal salt bismuth acetate catalyst.

[0015] 5.81g (i.e. 0.05mol) of 1,6-hexanediamine, 17ml (i.e. 0.2mol) of dimethyl carbonate and 0.872g of the metal salt bismuth acetate catalyst obtained above were weighed and placed in a three-necked flask equipped with a condenser and stirring device, and reacted at 80°C for 8h, then 50ml of ethanol was added to fully dissolve the reaction mixture, and the solid catalyst was separated by centrifugation. The filtrate was diluted and analyzed by gas chromatography. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 78%.

[0016] Example 2 Take 0.5g of bismuth acetate and dissolve it in 15ml of acetic acid, stir it in a water bath at 70℃, add 2g of HY molecular sieve after dissolution and continue to stir and immerse for 12h, then centrifuge and separate the solid. Dry it at 50℃ in vacuum for 10h to obtain 20wt%Bi(C2H3O2)3 / HY catalyst.

[0017] 0.05 mol of 1,6-hexanediamine, 0.2 mol of dimethyl carbonate and 0.872 g of 20 wt% Bi(C2H3O2)3 / HY were weighed and placed in a three-necked flask equipped with a condenser and agitator. After reacting at 80°C for 8 hours, 50 ml of ethanol was added to fully dissolve the reaction mixture, and the solid catalyst was separated by centrifugation. The filtrate was diluted and analyzed by gas chromatography. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 71%.

[0018] Example 3 The other steps were the same as those in Example 2, except that the added catalyst was 0.872 g of 20 wt% Bi(C2H3O2)3 / MCM-41. The reaction results showed that the conversion rate of 1,6-hexanediamine was 99% and the yield of the product HDC was 66%.

[0019] Example 4 The other steps were the same as those in Example 2, except that the added catalyst was 0.872 g of 20 wt% Bi(C2H3O2)3 / TS. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 62%.

[0020] Example 5 The other steps were the same as those in Example 2, except that the added catalyst was 0.872 g of 20 wt% Bi(C2H3O2)3 / ZSM-5. The reaction conditions were the same as those in Example 1, and the reaction results showed that the conversion rate of 1,6-hexanediamine was 99%, and the yield of the product HDC was 67%.

[0021] Example 6 The other steps were the same as those in Example 2, except that the added catalyst was 0.872 g of 20 wt% Bi(C2H3O2)3 / SiO2. The reaction results showed that the conversion rate of 1,6-hexanediamine was 99% and the yield of the product HDC was 65%.

[0022] Example 7 The other steps were the same as those in Example 2, except that the added catalyst was 0.872 g of 20 wt % Bi(C2H3O2)3 / AC. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 69%.

[0023] Example 8 The other steps were the same as those in Example 2, except that the catalyst added was 0.291 g of 20 wt% Bi(C2H3O2)3 / HY. The reaction conditions were the same as those in Example 1, and the reaction results showed that the conversion rate of 1,6-hexanediamine was 99%, and the yield of the product HDC was 57%.

[0024] Example 9 The other steps were the same as those in Example 2, except that the catalyst added was 0.581 g of 20 wt% Bi(C2H3O2)3 / HY. The reaction conditions were the same as those in Example 1, and the reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 67%.

[0025] Example 10 The other steps were the same as those in Example 2, except that the catalyst added was 1.162 g of 20 wt% Bi(C2H3O2)3 / HY. The reaction conditions were the same as those in Example 1, and the reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 69%.

[0026] Embodiment 11 The other steps were the same as those in Example 2, except that the catalyst added was 0.872 g of 10 wt% Bi(C2H3O2)3 / HY. The reaction conditions were the same as those in Example 1, and the reaction results showed that the conversion rate of 1,6-hexanediamine was 98%, and the yield of the product HDC was 61%.

[0027] Example 12 The other steps were the same as those in Example 2, except that the catalyst added was 0.872 g of 30 wt% Bi(C2H3O2)3 / HY. The reaction conditions were the same as those in Example 1, and the reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 68%.

[0028] Embodiment 13 The other steps were the same as those in Example 2, except that the catalyst added was 0.872 g of 40 wt% Bi(C2H3O2)3 / HY. The reaction conditions were the same as those in Example 1, and the reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 66%.

[0029] Embodiment 14 The other steps were the same as those in Example 2, except that the reaction time was 6 h. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 62%.

[0030] Embodiment 15 The other steps were the same as those in Example 2, except that the reaction time was 7 h. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 67%.

[0031] Example 16 The other steps were the same as those in Example 2, except that the reaction time was 9 h. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 64%.

[0032] Embodiment 17 The other steps were the same as those in Example 2, except that the reaction temperature was 60° C. The reaction results showed that the conversion rate of 1,6-hexanediamine was 94%, and the yield of the product HDC was 58%.

[0033] Embodiment 18 The other steps were the same as those in Example 2, except that the reaction temperature was 70° C. The reaction results showed that the conversion rate of 1,6-hexanediamine was 96%, and the yield of the product HDC was 62%.

[0034] Embodiment 19 The other steps were the same as those in Example 2, except that the reaction temperature was 90° C. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 67%.

[0035] Embodiment 20 The other steps were the same as those in Example 2, except that the reaction temperature was 100° C. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 56%.

[0036] Embodiment 21 The other steps were the same as those in Example 2, except that 0.1 mol of dimethyl carbonate was added. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 61%.

[0037] Embodiment 22 The other steps were the same as those in Example 2, except that 0.15 mol of dimethyl carbonate was added. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 64%.

[0038] Embodiment 23 The other steps were the same as those in Example 2, except that 0.25 mol of dimethyl carbonate was added. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 69%.

[0039] Embodiment 24 The other steps were the same as those in Example 2, except that 0.3 mol of dimethyl carbonate was added. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 59%.

[0040] Embodiment 25 The other steps were the same as those in Example 1, except that the added catalyst was the metal salt bismuth acetate recycled and reused for the second time. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 75%.

[0041] Embodiment 26 The other steps were the same as those in Example 1, except that the added catalyst was the metal salt bismuth acetate recycled and reused for the third time. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 74%.

[0042] Embodiment 27 The other steps were the same as those in Example 1, except that the added catalyst was the metal salt bismuth acetate recycled and reused for the fourth time. The reaction results showed that the conversion rate of 1,6-hexanediamine was 100%, and the yield of the product HDC was 71%.

[0043] It can be seen from the above examples that the method for preparing 1,6-hexamethylenediaminomethyl ester of the present invention has mild reaction conditions, a simple operation process, and the prepared bismuth metal salt has good activity and is easy to separate from the reaction system, and has good industrial prospects.

[0044] The above descriptions are only some specific examples of the present invention, but the protection scope of the present invention is not limited thereto, nor is any limitation imposed on the present invention by the order of the embodiments. Any modification, improvement or equivalent substitution made by any technician familiar with the technical field of the present invention within the technical scope reported in the present invention shall be covered within the protection scope of the present invention.

[0045] Matters not covered by the present invention are known technologies.

Claims

1. A method for synthesizing 1,6-hexamethylenediaminomethyl ester using a bismuth-based metal salt as catalyst, characterized in that the method comprises the following steps: Add 1,6-hexanediamine, dimethyl carbonate and a catalyst into a reactor, stir and react at 60-100° C. and normal pressure for 6-9 hours to obtain 1,6-hexamethylenediaminomethyl ester; in, The catalyst is a metal salt bismuth acetate or a supported bismuth acetate, and the added amount is 5% to 20% of the mass of 1,6-hexanediamine; the molar ratio of dimethyl carbonate to 1,6-hexanediamine is 2 to 6:

1.

2. The method for synthesizing 1,6-hexamethylenediaminomethyl ester by catalysis of bismuth metal salt as claimed in claim 1, characterized in that: In the supported bismuth acetate, the bismuth acetate loading is 10 to 40 wt %.

3. The method for synthesizing 1,6-hexamethylenediaminomethyl ester catalyzed by bismuth metal salts as claimed in claim 1, characterized in that it also comprises the following steps: adding a solvent to dissolve the reaction mixture after the reaction is completed, and centrifugally filtering to remove the solid catalyst; The solvent is methanol or ethanol.

4. The method for synthesizing 1,6-hexamethylenediaminomethyl ester using a bismuth-based metal salt as catalyzed by claim 1, characterized in that the preparation method of the metal salt bismuth acetate catalyst comprises the following steps: (1) Weigh Bi2O3, acetic acid and acetic anhydride into a reactor and condense and reflux at 140-160°C for 1-3 hours; Add 1-10 g Bi2O3 and 1-5 mL acetic anhydride to every 30 mL acetic acid; (2) filtering the filtrate obtained in the previous step, and evaporating it at 60-70° C. to obtain crystals; (3) dissolving the crystals obtained in step (2) in acetic acid at 70-100° C., and then cooling to room temperature to obtain crystals; wherein 0.5-2.0 g of crystals are added to every 15 mL of acetic acid; (4) The solid obtained in step (3) is filtered and dried under vacuum at 50° C. for 8 to 12 hours to obtain the metal salt bismuth acetate.

5. The method for synthesizing 1,6-hexamethylenediaminomethylformate catalyzed by bismuth-based metal salts as claimed in claim 1, characterized in that the preparation method of the supported bismuth acetate catalyst comprises the following steps: (1) Dissolve bismuth acetate in acetic acid and stir continuously at 70-100°C until completely dissolved; add 0.2-1.0 g of bismuth acetate and 1-3 g of carrier per 15 mL of acetic acid; (2) adding the carrier to the salt solution of step (1) and stirring for 12 to 36 hours; (3) The liquid in step (2) is filtered off, and the solid is dried at 50° C. in vacuum for 8 to 12 hours to obtain supported bismuth acetate.

6. The method for synthesizing 1,6-hexamethylenediaminomethyl ester using bismuth-based metal salt as catalyzed by claim 5, wherein the carrier comprises silica gel, activated carbon or molecular sieve.