Catalyst precursors, catalysts for the preparation of dialkyl carbonates, and processes for their preparation and use

Abstract

The application provides a catalyst precursor for preparing dialkyl carbonate, a catalyst and a preparation method and application thereof. The catalyst precursor comprises alkali metal carbonate nanoparticles and coupling agents grafted on surfaces of the alkali metal carbonate nanoparticles, the content of the alkali metal carbonate nanoparticles is 60wt%-90wt% based on the weight of the catalyst precursor, and the content of the coupling agents is 10wt%-40wt%. The catalyst comprises alkali metal carbonate nanoparticles and quaternary ammonium salt ionic liquids grafted on surfaces of the alkali metal carbonate nanoparticles. The application of the catalyst for preparing dialkyl carbonate can improve the selectivity of the target product, prolong the service life of the catalyst and effectively reduce the generation of side reactions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalysts, and particularly relates to a catalyst precursor for preparing dialkyl carbonate, a catalyst and a preparation method and application thereof. BACKGROUND

[0002] Dimethyl carbonate is a low-toxicity, environmentally friendly, and widely used chemical raw material, which contains CH3O-, CH3O-CO-, -CO-, and other functional groups, and is widely used as an intermediate for organic synthesis, and is known as a "new cornerstone" of today's organic synthesis. A variety of high-value fine special chemicals such as lithium battery electrolyte, pharmaceuticals, pesticides, synthetic materials, and lubricating oil additives can be prepared from dimethyl carbonate.

[0003] There are many reports on the synthesis method of carbonate, mainly including phosgene method, ester exchange method, oxidative carbonylation method, CO low-pressure gas phase synthesis method, etc. The phosgene method for preparing dimethyl carbonate has harsh process conditions, complex process, serious equipment corrosion, and pollution of toxic substance phosgene, and belongs to the process on the verge of elimination. CN105251496A discloses a supported catalyst for preparing dimethyl carbonate by ester exchange, which has mild reaction conditions and easy separation of the catalyst, but has the problem of loss of active components, and the raw material of ester exchange process, ethylene oxide, is derived from petroleum, and the raw material cost fluctuates greatly. CN114031500A adopts the oxidative carbonylation method to directly synthesize dimethyl carbonate from CO2 and methanol, which is easy to obtain and more safe and environmentally friendly, but the conversion rate is relatively low, and the application is limited. CN108144603A discloses a catalyst for synthesizing dimethyl carbonate by CO low-pressure gas phase method, which has high activity and good stability, but the selectivity is low, and the development of the catalyst requires higher requirements, and in addition, the cost of Pd-based catalyst is high.

[0004] The production capacity of coal-to-ethylene glycol is excessive, and it is urgent to plan more economically valuable products by utilizing the excessive production capacity. It is advantageous to produce dimethyl carbonate with high added value from oxalic acid dimethyl ester based on the existing coal-to-ethylene glycol device in terms of stable raw material source, small investment, and large operation flexibility. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a catalyst precursor for preparing dialkyl carbonate, a catalyst and a preparation method and application thereof. The catalyst of the present application can be used to prepare dialkyl carbonate, the selectivity of the target product is high, the service life of the catalyst is long, and the generation of side reactions can be effectively reduced.

[0006] The first aspect of the present application provides a catalyst precursor for preparing dialkyl carbonate, which comprises alkali metal carbonate nanoparticles and coupling agents grafted on the surface of the nanoparticles, wherein the content of the alkali metal carbonate nanoparticles is 60wt%-90wt% and the content of the coupling agents is 10wt%-40wt% based on the weight of the catalyst precursor.

[0007] Further, the alkali metal carbonate is selected from at least one of potassium carbonate, rubidium carbonate and cesium carbonate.

[0008] Further, the diameter of the alkali metal carbonate nanoparticles is 15-32nm.

[0009] Further, the coupling agents are tertiary amine coupling agents, preferably at least one of 2-(2-pyridyl)ethyltrimethoxysilane, N,N-bis[(diphenylphosphino)methyl]-3-(triethoxysilyl)-1-propanamine, N-[beta-(N,N-diacetoxy)aminoethyl]-gamma-(N-acetoxy)aminopropyltrimethoxysilane, bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-dimethyl-1-(trimethoxysilyl)methylamine, N,N-bis[(diphenylphosphino)methyl]-3-(triethoxysilyl)-1-propanamine, (N,N-dimethyl-3-aminopropyl)trimethoxysilane, diethylaminomethyltriethoxysilane, N-methyl-N-(tributoxysilyl)cyclohexylamine, N-benzylidene-3-(trimethoxysilyl)propylamine, N,N-bis(triethoxysilylmethyl)cyclohexylamine, N,N-dimethyl-4-(triethoxysilyl)aniline, and N,N-bis[(triethoxysilyl)methyl]allylamine.

[0010] The second aspect of the present application provides a preparation method of the catalyst precursor, which comprises:

[0011] (1) mixing an alkali metal precursor with ethanol, heating to a reaction temperature, and then introducing a mixed gas containing carbon dioxide to perform a reaction;

[0012] (2) adding coupling agents to the reaction material obtained in step (1) and continuing the reaction to obtain the catalyst precursor.

[0013] Further, in step (1), the alkali metal precursor is selected from at least one of potassium hydroxide, rubidium hydroxide and cesium hydroxide.

[0014] Further, in step (1), the concentration of the solution obtained after mixing the alkali metal precursor with ethanol is 0.3-1.2 mol / L. The volume concentration of carbon dioxide in the mixed gas is 50%-90%, and the rest is at least one of nitrogen, helium and neon. The flow rate of the mixed gas per liter of ethanol solution is 2.4-5.4 L / h. The total amount of carbon dioxide added is 0.5-0.8 moles per mole of alkali metal precursor.

[0015] Further, in step (1), the reaction temperature is 45-75℃, and the reaction continues for 2-10 min after the mixed gas is passed through.

[0016] Further, in step (2), the coupling agent is a tertiary amine coupling agent selected from at least one of 2-(2-pyridyl)ethyltrimethoxysilane, N,N-bis[(diphenylphosphino)methyl]-3-(triethoxysilyl)-1-propanamine, N-[β-(N,N-diacetoxy)aminoethyl]-γ-(N-acetoxy)aminopropyltrimethoxysilane, bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-dimethyl-1-(trimethoxysilyl)methylamine, N,N-bis[(diphenylphosphino)methyl]-3-(triethoxysilyl)-1-propanamine, (N,N-dimethyl-3-aminopropyl)trimethoxysilane, diethylaminomethyltriethoxysilane, N-methyl-N-(tributoxysilyl)cyclohexylamine, N-benzylidene-3-(trimethoxysilyl)propylamine, N,N-bis(triethoxysilylmethyl)cyclohexylamine, N,N-dimethyl-4-(triethoxysilyl)aniline and N,N-bis(triethoxysilylmethyl)allylamine.

[0017] Further, in step (2), the amount of the coupling agent added is 25wt%-55wt% of the mass of the alkali metal precursor.

[0018] Further, in step (2), the reaction time is 30-120 min, and the reaction temperature is 50-70℃.

[0019] Further, in step (2), after the reaction is completed, the obtained product is filtered, washed and dried to obtain the catalyst precursor. The washing can use at least one of ethanol, ethylene glycol, glycerol and diethylene glycol. The drying temperature is 60-120℃, and the drying time is 2-8 h.

[0020] The third aspect of the present application provides a catalyst for preparing dialkyl carbonate, which comprises: alkali metal carbonate nanoparticles and quaternary ammonium salt ionic liquid grafted on the surface of the nanoparticles.

[0021] The quaternary ammonium salt ionic liquid is the product of the reaction of the coupling agent in the catalyst precursor with dialkyl oxalate.

[0022] The fourth aspect of the present application provides a preparation method of the catalyst, comprising: reacting the catalyst precursor with a dialkyl oxalate to obtain the catalyst.

[0023] Further, the mass ratio of the catalyst precursor to the dialkyl oxalate is 1:1-1.5.

[0024] Further, the reaction temperature is 80-150℃, and the reaction time is 1-3h.

[0025] Further, in the preparation of the catalyst, the dialkyl oxalate used is preferably the same as the type of the reaction raw material catalyzed by the catalyst. For example, if the catalyst is used for the catalytic reaction of dimethyl oxalate, the catalyst precursor is preferably reacted with dimethyl oxalate to prepare the catalyst.

[0026] Further, the preparation of the catalyst can be carried out in a catalytic reaction device or outside the catalytic reaction device.

[0027] The fifth aspect of the present application provides an application of the catalyst, which is: using a dialkyl oxalate as a reaction raw material, and carrying out a decarbonylation reaction under the action of the catalyst to prepare a dialkyl carbonate.

[0028] Further, the dialkyl oxalate is preferably at least one of dimethyl oxalate, diethyl oxalate, and methyl ethyl oxalate.

[0029] Further, the decarbonylation reaction is carried out in a distillation column. The reaction raw material and the catalyst are fed from the bottom of the distillation column, mixed, reacted, and the light components (including dialkyl carbonate and CO, etc.) generated by the reaction are taken out from the top of the column by distillation, separated, and the dialkyl carbonate is obtained.

[0030] Further, the reaction conditions include: the reaction temperature is 150-210℃, preferably 170-190℃; the reaction pressure is 0.1-0.8MPa, preferably 0.2-0.5MPa; the mass ratio of the reaction raw material to the catalyst is 5-20:1, preferably 3-6:1; the weight hourly space velocity of the reaction raw material is 2-10h -1 , preferably 4-8h -1 ; the column temperature is 90-150℃, preferably 100-130℃.

[0031] Reaction mechanism: as shown in formula (1), taking dimethyl oxalate as an example, the carbonyl group is removed under the catalytic action to generate the product dimethyl carbonate. Dimethyl carbonate can further be decarbonylated and oxygenated under the catalytic action to generate dimethyl ether by a side reaction.

[0032]

[0033] Compared with the prior art, the present application has the following advantages:

[0034] 1、 The catalyst precursor of the present application uses the insolubility of carbonate in ethanol to obtain nano-carbonate particles, increases the specific surface area and active center of the catalyst, and improves the catalytic efficiency. The catalyst precursor surface is grafted with a tertiary amine-containing coupling agent, which can subsequently react with oxalic acid dialkyl ester to graft quaternary ammonium salt ionic liquid on the surface of the obtained catalyst.

[0035] 2、 The quaternary ammonium salt ionic liquid grafted on the surface of the catalyst of the present application can be uniformly dispersed into oxalic acid dialkyl ester through phase transfer, thereby converting the liquid-solid heterogeneous reaction into a liquid-liquid homogeneous reaction, promoting the efficient catalysis of alkali metal ions on the decarbonylation reaction of oxalic acid dialkyl ester, greatly reducing the required reaction temperature, and reducing the generation of side reactions.

[0036] 3、 The present application can reduce the required reaction temperature, reduce the generation of side reactions, and greatly prolong the service life of the catalyst.

[0037] 4、 Compared with traditional fixed bed reactors and tank reactors, the reaction device of the present application can timely remove the target product carbonic acid dialkyl ester generated by the reaction to prevent further reaction and improve the selectivity of the target product. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 Process schematic diagram for producing carbonic acid dialkyl ester according to the present application;

[0039] Among them, 1-reaction raw material (oxalic acid dialkyl ester); 2-catalyst; 3-product light component (including carbonic acid dialkyl ester); 4-product heavy component. DETAILED DESCRIPTION

[0040] In order to more clearly illustrate the present application, the present application will be further described below in conjunction with examples and drawings. Those skilled in the art should understand that the specific description below is illustrative rather than limiting, and should not limit the protection scope of the present application.

[0041] In the present application, the catalyst life is defined as the number of hours required when the carbonic acid dialkyl ester discharge rate is reduced to 90% of the initial value.

[0042] In the present application, the higher the discharge rate represents the higher activity of the catalyst;

[0043] Carbonic acid dialkyl ester selectivity (%) = (discharged carbonic acid dialkyl ester discharge mass flow rate / 90) / (oxalic acid dialkyl ester feed mass flow rate / 118) x 100%.

[0044] Combination Figure 1Further, the process for producing dialkyl carbonate according to the present application is described with oxymethyl oxalate as raw material. The raw material oxymethyl oxalate 1 and catalyst 2 are put into a distillation column reactor, and the reaction is carried out. The light component 3 of the product obtained from the reaction is taken out from the top of the column, and further separated to obtain oxymethyl carbonate. The heavy component 4 of the product is discharged from the bottom of the column.

[0045] Example 1

[0046] Preparation of catalyst precursor: 0.4 mol KOH is dissolved in 1 L ethanol, and heated to 60°C. A mixture of 70 vol% carbon dioxide and 30 vol% nitrogen gas is slowly introduced into the solution at a rate of 3 L / h, and the total amount of carbon dioxide is 0.3 mol. The reaction is continued for 4 min to obtain potassium carbonate. 9 g of 2-(2-pyridyl)ethyl trimethoxysilane is slowly added dropwise, and the reaction is continued for 60 min. The product is filtered, washed with ethanol, and dried at 90°C for 3 h to obtain a white solid catalyst precursor. The content of potassium carbonate nanoparticles is 72 wt% based on the weight of the catalyst precursor, and the content of coupling agent is 28 wt%. The diameter of the potassium carbonate nanoparticles is 23 nm.

[0047] Preparation and application of catalyst: 30 g of the catalyst precursor is taken at the bottom of a distillation column, and 300 g of oxymethyl oxalate is pre-mixed at 90°C for 2 h to obtain a catalyst. The generated catalyst is fully dispersed in the remaining oxymethyl oxalate. Nitrogen gas is introduced to replace the column, and the pressure is controlled at 0.25 MPa. The oil bath at the bottom of the column is heated to 180°C, and the reaction is carried out under stirring. Oxymethyl oxalate is continuously fed at the bottom of the column, and the weight hourly space velocity of oxymethyl oxalate is 5 h -1 The space velocity is adjusted according to the liquid level to keep the liquid level unchanged. The temperature of the column body is 105°C, and oxymethyl carbonate is taken out from the top of the column. After the device is stabilized, the product is analyzed, and the results are shown in Table 1.

[0048] Example 2-3

[0049] Compared with Example 1, the only difference in the preparation of the catalyst precursor in Example 2-3 is that different kinds of alkali metal precursors are used (see Table 1 for details).

[0050] The catalyst evaluation method is the same as that in Example 1, and the results are shown in Table 1.

[0051] Table 1: Catalysts and evaluation results of each example

[0052]

[0053] Example 4-6

[0054] Compared with Example 1, the difference between Example 4-6 is the temperature of the oil bath at the bottom of the column during the application of the catalyst.

[0055] The catalyst evaluation method is the same as that in Example 1, and the results are shown in Table 2.

[0056] Table 2 Catalysts and evaluation results of each example

[0057]

[0058] Examples 7-8

[0059] The difference between Examples 7-8 and Example 1 is that different reaction pressures are used when the catalyst is applied.

[0060] The catalyst evaluation method is the same as Example 1, and the results are shown in Table 3.

[0061] Table 3 Catalysts and evaluation results of each example

[0062]

[0063] Example 9

[0064] Preparation of catalyst precursor and catalyst: 0.3 mol of KOH is dissolved in 1 L of ethanol and heated to 65°C. A mixture of 80 vol% carbon dioxide and 20 vol% helium gas is slowly introduced into the solution at a rate of 5 L / h, with a total amount of carbon dioxide being 0.2 mol, and the reaction is continued for 5 min to obtain potassium carbonate. 6 g of N,N-dimethyl-4-(triethoxysilyl)aniline is slowly added dropwise, and the reaction is continued for 45 min. The obtained product is filtered, washed with ethanol, and dried at 85°C for 4 h to obtain a white solid catalyst precursor. The content of potassium carbonate nanoparticles is 79 wt%, and the content of coupling agent is 21 wt%, based on the weight of the catalyst precursor, and the potassium carbonate nanoparticles are directly 30 nm.

[0065] 30 g of the catalyst precursor is added to 30 g of dimethyl oxalate, and pre-mixed at 100°C for 1.5 h to obtain the catalyst.

[0066] Catalyst evaluation: the obtained catalyst is added to the bottom of a distillation column, and 320 g of dimethyl oxalate is added. Nitrogen gas is introduced to replace the column, and the pressure is controlled at 0.2 MPa. The oil bath at the bottom is heated to 180°C, and the reaction is stirred. Dimethyl oxalate is continuously fed to the column, and the space velocity is 3 h -1 The space velocity is adjusted according to the liquid level to keep the liquid level unchanged, and the temperature of the column body is 105°C. Dimethyl oxalate is collected at the top, and the products are analyzed after the device is stabilized, as shown in Table 4.

[0067] Examples 10-12

[0068] The difference between Examples 10-12 and Example 9 is that different coupling agents are used in the preparation of the catalyst precursor.

[0069] The catalyst evaluation method is the same as Example 9, and the results are shown in Table 4.

[0070] Table 4 Catalysts and evaluation results of each example

[0071]

[0072] Comparative Examples 1-3

[0073] Comparative Examples 1-3 are ordinary K2CO3, unmodified nano-K2CO3 and other coupling agent modified nano-K2CO3 (the preparation method of the catalyst of Comparative Example 3 is the same as that of Example 1, except that the type of coupling agent is different from that of Example 1).

[0074] The catalyst evaluation method is the same as that of Example 1, and the results are shown in Table 5.

[0075] Table 5 Evaluation results of catalysts of Comparative Examples 1-3

[0076]

[0077] Comparative Example 4

[0078] Comparative Example 4 differs from Example 1 in that the catalyst and dimethyl oxalate are reacted in a closed high-pressure stirred tank to prepare dimethyl carbonate. 30 g of catalyst and 300 g of dimethyl oxalate are added to the high-pressure tank, stirred and mixed, nitrogen is introduced to replace, the heating jacket is heated to 180°C, and the reaction is stirred. After 1 h of reaction, the product is analyzed after cooling, as shown in Table 6.

[0079] Table 6 Evaluation results of catalysts of Comparative Example 4

[0080] Example number Reactor Dimethyl carbonate selectivity (%) Example 1 Distillation column 98 Comparative example 4 Autoclave 64

[0081] The above detailed description of the specific embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A catalyst precursor for the production of a dialkyl carbonate, characterized in that, The catalyst precursor comprises alkali metal carbonate nanoparticles and coupling agents grafted on the surface of the nanoparticles, the content of the alkali metal carbonate nanoparticles is 60wt%-90wt% and the content of the coupling agents is 10wt%-40wt% based on the weight of the catalyst precursor; The alkali metal carbonate is selected from at least one of potassium carbonate, rubidium carbonate and cesium carbonate, and the diameter of the alkali metal carbonate nanoparticles is 15-32nm; The coupling agent is selected from at least one of 2-(2-pyridyl)ethyltrimethoxysilane, N,N-bis[(diphenylphosphino)methyl]-3-(triethoxysilyl)-1-propanamine, N-[beta-(N,N-diacetoxy)aminoethyl]-gamma-(N-acetoxy)aminopropyltrimethoxysilane, bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-dimethyl-1-(trimethoxysilyl)methylamine, N,N-bis[(diphenylphosphino)methyl]-3-(triethoxysilyl)-1-propanamine, (N,N-dimethyl-3-aminopropyl)trimethoxysilane, diethylaminomethyltriethoxysilane, N-methyl-N-(tributoxysilyl)cyclohexylamine, N-benzylidene-3-(trimethoxysilyl)propylamine, N,N-bis(triethoxysilylmethyl)cyclohexylamine, N,N-dimethyl-4-(triethoxysilyl)aniline and N,N-bis[(triethoxysilyl)methyl]allylamine.

2. A process for the preparation of the catalyst precursor of claim 1, characterized in that, The method comprises: (1) mixing an alkali metal precursor with ethanol, heating to a reaction temperature, and then introducing a mixed gas containing carbon dioxide to perform a reaction; (2) adding a coupling agent to the reaction material obtained in step (1) to continue the reaction to obtain a catalyst precursor; In step (1), the volume concentration of carbon dioxide in the mixed gas is 50%-90%, and the rest is at least one of nitrogen, helium and neon; In step (1), the reaction temperature is 45-75℃.

3. The method of claim 2, wherein, In step (1), after the alkali metal precursor is mixed with ethanol, the concentration of the obtained solution is 0.3-1.2mol / L.

4. The method of claim 2, wherein, In step (1), the flow rate of the mixed gas introduced per liter of ethanol solution is 2.4-5.4L / h, and the total amount of carbon dioxide added is in a molar ratio of 0.5-0.8:1 to the alkali metal precursor.

5. The method of claim 2, wherein, In step (2), the amount of the coupling agent added is 30wt%-55wt% of the mass of the alkali metal precursor.

6. The method of claim 2, wherein, In step (1), after the mixed gas is introduced, the time for continuing the reaction is 2-10min; and / or, in step (2), the reaction time is 30-120min, and the reaction temperature is 50-70℃.

7. A catalyst for the production of a dialkyl carbonate, characterized by, The catalyst comprises alkali metal carbonate nanoparticles and quaternary ammonium salt ionic liquids grafted on the surface of the nanoparticles, and the catalyst is prepared by reacting the catalyst precursor of claim 1 with a dialkyl oxalate.

8. The catalyst according to claim 7, characterized in that: The mass ratio of the catalyst precursor to the dialkyl oxalate is 1:1-1.5; and / or, the reaction temperature is 80-150℃, and the reaction time is 1-3h.

9. Use of a catalyst as claimed in claim 7, characterized in that The application is: using oxalic acid dialkyl ester as a reaction raw material, and performing decarbonylation reaction under the action of the catalyst to prepare dialkyl carbonate.

10. Use according to claim 9, characterized in that, The oxalic acid dialkyl ester is at least one of dimethyl oxalate, diethyl oxalate and methyl ethyl oxalate.

11. Use according to claim 9, characterized in that, The decarbonylation reaction is performed in a distillation column, the reaction raw material and the catalyst are fed from the bottom of the distillation column, mixed, and reacted, light components generated in the reaction are taken out from the top of the distillation column through distillation, separated, and dialkyl carbonate is obtained.

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