Catalyst for co-production of dimethyl carbonate and monomethyl malonate, its preparation and use

Abstract

The application discloses a catalyst for co-production of dimethyl carbonate and monomethyl malonate, and a preparation method and application thereof. The catalyst comprises rhodium nanoparticles and grafted ionic liquid coupling agents. When the catalyst is used in a coupling reaction of dimethyl oxalate decarbonylation for preparing dimethyl carbonate and methyl glycolate carbonylation for preparing monomethyl malonate, the modified rhodium nanoparticles can be uniformly dispersed in liquid-phase reaction raw materials, quasi-homogeneous catalysis is realized, CO generated by decarbonylation can be supplied to the carbonylation reaction, atomic utilization is improved, in-situ generated CO can reduce the activation energy required by the carbonylation reaction, the reaction temperature is lower, the selectivity is higher, and the catalytic life of the decarbonylation reaction is prolonged.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials, and particularly to a catalyst for a coupled decarbonylation and carbonylation reaction, its preparation method, and its application in the co-production of dimethyl carbonate and dimethyl malonate in the coal-to-ethylene glycol route. Background Technology

[0002] Dimethyl malonate (DMM) is an important raw material for the production of the pharmaceutical drug pipemidic acid. In China, the production process for DMM primarily uses the cyanidation esterification method. Chloroacetic acid is neutralized with sodium carbonate to produce sodium chloroacetate, which is then cyanided with sodium cyanide to obtain sodium cyanoacetate. Sodium cyanoacetate is hydrolyzed to sodium malonate, which is then esterified with methanol under sulfuric acid catalysis to obtain DMM. This process suffers from significant pollution and complexity. CN112239408A proposes a technical route for obtaining DMM via the carbonylation of methyl acetal, but this route uses a homogeneous catalyst, which suffers from catalyst loss and ligand decomposition. New processes developed abroad mainly utilize catalytic carbonylation, using chloroacetate, carbon monoxide, and methanol as raw materials, and synthesizing DMM in a one-step reaction in the presence of a catalyst. In comparison, the catalytic carbonylation method is technologically advanced, but it is complex, requires harsh reaction conditions, and faces challenges in industrialization.

[0003] Dimethyl carbonate (DMC) is a low-toxicity, environmentally friendly, and widely used chemical raw material. It is also an important intermediate in organic synthesis. Its molecular structure contains functional groups such as carbonyl, methyl, and methoxy groups, giving it various reactivity properties. In production, it is safe, convenient, low-polluting, and easy to transport. The rapid development of lithium-ion batteries, in particular, has led to a continuous increase in the demand for DMC. Furthermore, with the expansion of coal-to-ethylene glycol production capacity, the decarbonylation of dimethyl oxalate (DMO) to produce high-value-added DMC offers certain economic benefits, along with environmental and cost advantages.

[0004] The co-production of dimethyl carbonate and monomethyl malonic acid is a new product chain extending from dimethyl oxalate, which is of great significance for the development of clean coal utilization. Furthermore, no method for the co-production of dimethyl carbonate and monomethyl malonic acid has been reported in existing technologies. Summary of the Invention

[0005] This invention provides a catalyst for the co-production of dimethyl carbonate and monomethyl malonate, its preparation method, and its application. The catalyst of this invention can achieve pseudo-homogeneous catalysis; the CO generated from decarbonylation can supply the carbonylation reaction, improving atom utilization. Furthermore, the in-situ generated CO can lower the activation energy required for the carbonylation reaction, resulting in a lower reaction temperature, higher selectivity, higher stability, and extended catalytic lifetime of the decarbonylation reaction.

[0006] The first aspect of the present invention provides a catalyst for the co-production of dimethyl carbonate and monomethyl malonate, wherein the catalyst comprises rhodium nanoparticles and a grafted ionic liquid coupling agent.

[0007] Furthermore, the ionic liquid coupling agent is a product of the reaction between an iodosilane coupling agent and a nitrogen heterocyclic compound, wherein the molar ratio of the nitrogen heterocyclic compound to the iodosilane coupling agent is 1 to 1.5:1.

[0008] Furthermore, the iodosilane coupling agent is selected from at least one of (3-iodopropyl)tris(1-methylethoxy)-silane, 3-iodopropyltrimethoxysilane, 4-iodobutyltrimethoxysilane, (4-iodobenzyloxy)trimethoxysilane, iodophenyltrimethoxysilane, and m-(trimethylsiloxy)iodobenzene.

[0009] Further, the nitrogen heterocyclic compound is selected from at least one of N-methoxyethyl-2-pyrrolidone, 1-methyl-3-pyrrolidone, N-methylpyrrolidone, 2-mercapto-1-methylimidazolium, 1-ethylimidazolium, N-triphenylmethylimidazolium, N,N-diimidazolylmethane, pyridine, 4-dimethylaminopyridine, N-methylpyrrole, 4-methylpyridine, and N-methylindole.

[0010] Furthermore, in the catalyst, the average size of the rhodium nanoparticles is 4–16 nm, preferably 4–8 nm.

[0011] Furthermore, in the catalyst, the content of rhodium nanoparticles is 50% to 65% based on the weight of the catalyst, and the content of ionic liquid coupling agent is 35% to 50%.

[0012] A second aspect of the present invention provides a method for preparing a catalyst for the co-production of dimethyl carbonate and monomethyl malonate, comprising:

[0013] (1) Mix the rhodium salt, reducing agent and solvent, and react under an inert atmosphere;

[0014] (2) After solid-liquid separation, the product obtained in step (1) is modified by adding iodosilane coupling agent, water and organic solvent to the obtained solid to obtain a solid.

[0015] (3) The solid obtained in step (2) is dispersed in a dispersion medium, and a nitrogen heterocyclic compound is added to react and the catalyst is obtained.

[0016] Further, in step (1), the rhodium salt is selected from at least one of ammonium rhodium chloride, rhodium acetylacetonate, rhodium dicarbonyl acetylacetonate, rhodium dimer acetate, rhodium chloride, and rhodium iodide.

[0017] Further, in step (1), the reducing agent is selected from at least one of oleylamine, octadecylamine, aniline, ethylene glycol, diethylene glycol, and triethylene glycol.

[0018] Further, in step (1), the solvent is selected from at least one of oleylamine, oleic acid, octadecylamine, octadecene, ethylene glycol, diethylene glycol, and triethylene glycol. The solvent may be the same as the reducing agent or a different substance.

[0019] Furthermore, when the solvent used in step (1) is at least one of oleylamine, octadecylamine, ethylene glycol, diethylene glycol, and triethylene glycol, other reducing agents may or may not be added to the reaction system. The amount of reducing agent used is determined to reduce high-valence rhodium to zero-valence rhodium. Those skilled in the art can determine the amount of reducing agent and solvent based on the actual situation.

[0020] Furthermore, in step (1), the concentration of rhodium salt in the resulting mixture is 10–80 mmol / L.

[0021] Further, in step (1), the reaction is carried out under heating conditions, and the heating rate is 4–7 °C / min. The reaction temperature is 120–160 °C, the reaction time is 1–4 h, and the reaction is carried out under normal pressure.

[0022] Further, in step (2), the iodosilane coupling agent is selected from at least one of (3-iodopropyl)tris(1-methylethoxy)-silane, 3-iodopropyltrimethoxysilane, 4-iodobutyltrimethoxysilane, (4-iodobenzyloxy)trimethoxysilane, iodophenyltrimethoxysilane, and m-(trimethylsiloxy)iodobenzene.

[0023] Further, in step (2), the organic solvent is selected from at least one of cyclohexane, n-hexane, n-heptane, octane, and nonane, preferably cyclohexane.

[0024] Further, in step (2), the mass ratio of the amount of iodosilane coupling agent added to the theoretical rhodium (rhodium obtained by complete reduction of rhodium salt) is 1.5 to 3:1, the molar ratio of the amount of water added to the iodosilane coupling agent is 3 to 12:1, and the mass ratio of the amount of organic solvent added to the theoretical rhodium is 7 to 15:1.

[0025] Furthermore, in step (2), the modification temperature is 50-70℃ and the modification time is 1-3h.

[0026] Further, in step (2), after the modification is completed, the solvent is evaporated to dryness, and the product is washed to obtain a solid. The washing is performed with ethanol, and the washing is performed 3 to 5 times.

[0027] Further, in step (3), the dispersion medium is selected from at least one of toluene, ethylbenzene, and p-xylene ethyl acetate, preferably toluene.

[0028] Further, in step (3), the nitrogen heterocyclic compound is selected from at least one of N-methoxyethyl-2-pyrrolidone, 1-methyl-3-pyrrolidone, N-methylpyrrolidone, 2-mercapto-1-methylimidazolium, 1-ethylimidazolium, N-triphenylmethylimidazolium, N,N-diimidazolylmethane, pyridine, 4-dimethylaminopyridine, N-methylpyrrole, 4-methylpyridine, and N-methylindole.

[0029] Further, in step (3), the molar ratio of the amount of nitrogen heterocyclic compound added to the iodosilane coupling agent is 1 to 1.5:1, and the mass ratio of the dispersion medium to the nitrogen heterocyclic compound is 4 to 18:1.

[0030] Furthermore, in step (3), the reaction temperature is 50–70°C and the reaction time is 4–40 h.

[0031] Further, in step (3), after the reaction is complete, the lower layer product is taken, washed, and dried to obtain the catalyst. The washing uses at least one of toluene, ethylbenzene, p-xylene, and ethyl acetate, and the washing is performed 3 to 5 times. The drying is vacuum drying, and the vacuum drying temperature is 60 to 90°C, and the vacuum drying time is 2 to 8 hours.

[0032] The third aspect of the present invention provides a method for co-producing dimethyl carbonate and monomethyl malonic acid, wherein the method comprises: using dimethyl oxalate and methyl glycolate as reactants, and carrying out a decarbonylation and carbonylation coupled reaction under a CO atmosphere and the action of the above-mentioned catalyst to prepare dimethyl carbonate and monomethyl malonic acid.

[0033] Furthermore, in the method described, a mixture of dimethyl oxalate and methyl glycolate is uniformly mixed with a catalyst in a high-pressure reactor and reacted at a certain temperature to generate dimethyl carbonate monomethyl malonate.

[0034] Furthermore, in the method described, the molar ratio of dimethyl oxalate to methyl glycolate is 1 to 3:1.

[0035] Furthermore, the reaction conditions of the method are as follows: catalyst concentration of 2-10 wt%, initial CO pressure of 1-4 MPa, reaction temperature of 140-200℃, preferably 160-180℃, and reaction time of 30-150 min.

[0036] Furthermore, the reaction of the method is shown in equations (1) and (2):

[0037]

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] 1. The catalyst of this invention is a novel bifunctional catalyst, comprising rhodium nanoparticles and a grafted ionic liquid coupling agent. Rhodium serves as the main catalyst for the carbonylation reaction, while the iodide anion contained in the ionic liquid coupling agent acts as both a co-catalyst for the carbonylation reaction and the main catalyst for the decarbonylation reaction. The grafted ionic liquid coupling agent on the surface of the rhodium nanoparticles aggregates a high concentration of iodide ions, increasing the local concentration of the co-catalyst in the reaction solution and enhancing the catalyst activity. Thanks to the immobilization effect of the rhodium nanoparticle grafting, the stability of the ionic liquid coupling agent is improved, extending the catalytic lifetime of the decarbonylation reaction. Furthermore, the high concentration of iodide ions increases the concentration of catalytically active centers for the decarbonylation reaction in the reaction solution, further enhancing the catalyst activity.

[0040] 2. The method for co-producing dimethyl carbonate and monomethyl malonic acid provided by this invention specifically involves directly supplying the CO generated from the dimethyl oxalate to dimethyl carbonate reaction to the carbonylation reaction of methyl glycolate to produce monomethyl malonic acid, achieving self-production and self-use of CO and improving atom utilization. The CO generated in situ from the decarbonylation of dimethyl oxalate can lower the activation energy required for the carbonylation reaction of methyl glycolate, resulting in a lower reaction temperature and higher selectivity. Attached Figure Description

[0041] Figure 1 This is a transmission electron microscope image of the rhodium nanoparticles obtained in Example 1 of the present invention. Detailed Implementation

[0042] To more clearly illustrate the present invention, the following description, in conjunction with embodiments and accompanying drawings, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0043] In this invention, a Hitachi HT7700 transmission electron microscope (TEM) was used to observe the size and dispersibility of rhodium nanoparticles. For nanoparticle observation, the prepared catalyst was dispersed in dimethyl carbonate, diluted to a suitable concentration, dropped onto a carbon film, and allowed to air dry before being injected for observation. One hundred particles were selected from a local area, and their average diameter was measured and calculated using ImageJ software.

[0044] In this invention, the conversion rate of dimethyl oxalate (%) = (mass of dimethyl oxalate in the raw material - mass of dimethyl oxalate in the product) / mass of dimethyl oxalate in the raw material × 100%;

[0045] Methyl glycolate conversion rate (%) = (mass of methyl glycolate in raw material - mass of methyl glycolate in product) / mass of methyl glycolate in raw material × 100%;

[0046] Dimethyl carbonate selectivity (%) = molar amount of dimethyl carbonate in the product / (molar amount of dimethyl oxalate in the feed - molar amount of dimethyl oxalate in the product) × 100%;

[0047] Selectivity of monomethyl malonate (%) = molar amount of monomethyl malonate in the product / (molar amount of methyl glycolate in the feed - molar amount of methyl glycolate in the product) × 100%.

[0048] Catalyst lifetime is defined as the number of cycles required for the conversion of dimethyl oxalate to decrease to 90% of its initial value in the decarbonylation reaction.

[0049] Example 1

[0050] Catalyst preparation: 5 mmol of rhodium acetylacetone was dissolved in 100 ml of oleylamine. Under a nitrogen atmosphere, the temperature was increased to 150 °C at 4 °C / min, and the reaction was stirred for 2 h. The product was centrifuged, and the precipitate was added with 1 g (3 mmol) of iodophenyltrimethoxysilane, 0.45 g of water, and 6 g of cyclohexane. The mixture was stirred and refluxed at 60 °C for 2 h. After the solvent was evaporated by rotary evaporation, the product was washed three times with ethanol. 0.57 g (4 mmol) of N-methoxyethyl-2-pyrrolidone and 6 g of toluene were added, and the mixture was reacted at 70 °C for 28 h. The lower layer was washed three times with toluene and dried under vacuum at 70 °C for 6 h to obtain the catalyst. By weight, the content of rhodium nanoparticles was 53 wt%, and the content of ionic liquid coupling agent was 47 wt%, with an average size of 4.8 nm for the rhodium nanoparticles.

[0051] Catalyst evaluation: 1g catalyst, 20g dimethyl oxalate and 10g methyl glycolate were added to a high-pressure reactor, purged with nitrogen and then charged with 2MPa CO. The temperature was raised to 160℃ and the reaction was carried out for 80min. The results are shown in Table 1.

[0052] Examples 2-4

[0053] Compared with Example 1, Examples 2-4 differ only in the catalyst evaluation reaction temperature.

[0054] The catalyst was prepared using the same method as in Example 1, and the results are shown in Table 1.

[0055] Table 1 Evaluation results for each case

[0056]

[0057]

[0058] Examples 5-8

[0059] Compared with Example 1, Examples 5-8 differ in the reduction time of the rhodium precursor.

[0060] The catalyst evaluation method was the same as in Example 1, and the results are shown in Table 2.

[0061] Table 2 Evaluation Results for Each Case

[0062]

[0063] Example 9

[0064] Catalyst preparation: 6 mmol of rhodium chloride was dissolved in 110 mL of diethylene glycol. Under a nitrogen atmosphere, the temperature was increased to 160 °C at 5 °C / min, and the reaction was stirred for 1.5 h. The product was centrifuged, and the precipitate was added to 1.3 g (4.2 mmol) of 4-iodobutyltrimethoxysilane, 0.6 g of water, and 7.4 g of cyclohexane. The mixture was stirred and refluxed at 65 °C for 2.5 h. After the solvent was evaporated by rotary evaporation, the product was washed three times with ethanol. Then, 0.82 g (6.25 mmol) of N-methylindole and 5 g of toluene were added, and the mixture was reacted at 70 °C for 28 h. The lower layer was washed three times with toluene and dried under vacuum at 80 °C for 6 h to obtain the catalyst. By weight, the content of rhodium nanoparticles was 64 wt%, and the content of ionic liquid coupling agent was 36 wt%, with an average size of 5.1 nm for the rhodium nanoparticles.

[0065] Catalyst evaluation: 1g catalyst, 24g dimethyl oxalate and 15g methyl glycolate were added to a high-pressure reactor, purged with nitrogen and then charged with 1.9MPa CO. The temperature was raised to 170℃ and the reaction was carried out for 70min. The results are shown in Table 3.

[0066] Example 10

[0067] Catalyst preparation: 7 mmol of rhodium dicarbonyl acetylacetone was dissolved in 120 mL of ethylene glycol. Under a nitrogen atmosphere, the temperature was increased to 160 °C at 5 °C / min, and the reaction was stirred for 1.5 h. The product was centrifuged, and the precipitate was added to 1.3 g (4 mmol) m-(trimethylsiloxy)iodobenzene, 0.6 g of water, and 8.3 g of cyclohexane. The mixture was stirred and refluxed at 65 °C for 2.5 h. After the solvent was evaporated by rotary evaporation, the product was washed three times with ethanol. 0.82 g (6.7 mmol) of 4-dimethylaminopyridine and 9 g of toluene were added, and the reaction was carried out at 70 °C for 28 h. The lower layer was washed three times with toluene and dried under vacuum at 80 °C for 6 h to obtain the catalyst. The content of rhodium nanoparticles was 54 wt% and the content of ionic liquid coupling agent was 46 wt%, with an average size of 4.4 nm for the rhodium nanoparticles.

[0068] Catalyst evaluation: 1g catalyst, 24g dimethyl oxalate and 15g methyl glycolate were added to a high-pressure reactor, purged with nitrogen and then charged with 2MPa CO. The temperature was raised to 170℃ and the reaction was carried out for 70min. The results are shown in Table 3.

[0069] Example 11

[0070] Catalyst preparation: 6 mmol of rhodium dimer acetate was dissolved in 150 mL of octadecylamine. Under a nitrogen atmosphere, the temperature was increased to 160 °C at 5 °C / min, and the reaction was stirred for 1.5 h. The product was centrifuged, and the precipitate was added to 1.2 g (3.2 mmol) of (3-iodopropyl)tris(1-methylethoxy)silane, 0.3 g of water, and 5.6 g of cyclohexane. The mixture was stirred and refluxed at 65 °C for 2.5 h. After the solvent was evaporated by rotary evaporation, the product was washed three times with ethanol. Then, 1.15 g (3.7 mmol) of N-triphenylmethylimidazolium and 5 g of toluene were added, and the reaction was carried out at 70 °C for 28 h. The lower layer was washed three times with toluene and dried under vacuum at 80 °C for 6 h to obtain the catalyst. The content of rhodium nanoparticles was 59 wt% and the content of ionic liquid coupling agent was 41 wt%, with an average size of 4.7 nm for the rhodium nanoparticles.

[0071] Catalyst evaluation: 1g catalyst, 24g dimethyl oxalate and 15g methyl glycolate were added to a high-pressure reactor, purged with nitrogen and then charged with 2MPa CO. The temperature was raised to 170℃ and the reaction was carried out for 70min. The results are shown in Table 3.

[0072] Example 12

[0073] Catalyst preparation: 4 mmol of ammonium chlororhodium was dissolved in 100 mL of triethylene glycol. Under a nitrogen atmosphere, the temperature was increased to 160 °C at 5 °C / min, and the reaction was stirred for 1.5 h. The product was centrifuged, and the precipitate was added to 0.88 g (2.6 mmol) of (4-iodobenzyloxy)trimethoxysilane, 0.36 g of water, and 5.4 g of cyclohexane. The mixture was stirred and refluxed at 65 °C for 2.5 h. After the solvent was evaporated by rotary evaporation, the product was washed three times with ethanol. Then, 0.37 g (3.2 mmol) of 2-mercapto-1-methylimidazolium and 5 g of toluene were added, and the reaction was carried out at 70 °C for 28 h. The lower layer was washed three times with toluene and dried under vacuum at 80 °C for 6 h to obtain the catalyst. The content of rhodium nanoparticles was 61 wt% and the content of ionic liquid coupling agent was 39 wt%, with an average size of 4.9 nm for the rhodium nanoparticles.

[0074] Catalyst evaluation: 1g catalyst, 24g dimethyl oxalate and 15g methyl glycolate were added to a high-pressure reactor, purged with nitrogen and then charged with 2MPa CO. The temperature was raised to 170℃ and the reaction was carried out for 70min. The results are shown in Table 3.

[0075] Table 3 Evaluation Results for Each Case

[0076]

[0077]

[0078] Comparative Example 1

[0079] Catalyst preparation: 5 mmol of rhodium acetylacetone was dissolved in 100 ml of oleylamine. Under a nitrogen atmosphere, the temperature was increased to 150 °C at 4 °C / min, and the reaction was stirred for 2 h. The product was centrifuged, dried, and washed to obtain rhodium nanoparticles. The average size of the rhodium nanoparticles was 4.8 nm.

[0080] 1 g of iodophenyltrimethoxysilane, 0.45 g of water, and 6 g of cyclohexane were stirred and refluxed at 60 °C for 2 h. After the solvent was evaporated by rotary evaporation, 0.57 g of N-methoxyethyl-2-pyrrolidone and 6 g of toluene were added, and the mixture was reacted at 70 °C for 28 h. The lower layer was washed three times with toluene and dried under vacuum at 70 °C for 6 h to obtain the ionic liquid coupling agent.

[0081] Catalyst evaluation: The rhodium nanoparticles and ionic liquid coupling agent (total 1 g) obtained from Comparative Example 1 were added to a high-pressure reactor along with 20 g of dimethyl oxalate and 10 g of methyl glycolate. After nitrogen purging, CO was introduced at 2 MPa, and the temperature was raised to 160 °C. The reaction was carried out for 80 min. The results are shown in Table 4. By catalyst weight, the content of rhodium nanoparticles was 53 wt%, and the content of ionic liquid coupling agent was 47 wt%.

[0082] Comparative Example 2

[0083] Compared to Example 1, Comparative Example 2 used rhodium particles with an average size of 20 nm.

[0084] Catalyst preparation: 5 mmol of rhodium acetylacetone was dissolved in 60 mL of oleylamine. Under a nitrogen atmosphere, the temperature was increased to 170 °C at 2 °C / min, and the reaction was stirred for 6 h. The product was centrifuged, and the precipitate was added with 1 g (3 mmol) of iodophenyltrimethoxysilane, 0.45 g of water, and 6 g of cyclohexane. The mixture was stirred and refluxed at 60 °C for 2 h. After the solvent was evaporated by rotary evaporation, the product was washed three times with ethanol. Then, 0.57 g (4 mmol) of N-methoxyethyl-2-pyrrolidone and 6 g of toluene were added, and the mixture was reacted at 70 °C for 28 h. The lower layer was washed three times with toluene and dried under vacuum at 70 °C for 6 h to obtain the catalyst. The content of rhodium nanoparticles was 74 wt%, and the content of ionic liquid coupling agent was 26 wt%.

[0085] The catalyst evaluation method was the same as in Example 1, and the results are shown in Table 4.

[0086] Comparative Example 3

[0087] Compared with Example 1, Comparative Example 3 omits the rhodium reduction process and directly uses rhodium acetylacetone and an ionic liquid coupling agent as catalysts.

[0088] Catalyst preparation: 5 mmol of rhodium acetylacetonate was added to 1 g (3 mmol) of iodophenyltrimethoxysilane, 0.45 g of water, and 6 g of cyclohexane. The mixture was stirred and refluxed at 60 °C for 2 h. After rotary evaporation to remove the solvent, the product was washed three times with ethanol. Then, 0.57 g (4 mmol) of N-methoxyethyl-2-pyrrolidone and 6 g of toluene were added, and the mixture was reacted at 70 °C for 28 h. The lower layer was washed three times with toluene and dried under vacuum at 70 °C for 6 h to obtain the catalyst. The coupling agent content was 33.3% and the rhodium acetylacetonate content was 66.7 wt% by weight of the catalyst.

[0089] The catalyst evaluation method was the same as in Example 1, and the results are shown in Table 4.

[0090] Comparative Example 4

[0091] Compared to Example 1, the ionic liquid in Comparative Example 4 was 1-butyl-3-methylimidazolium tetrafluoroborate.

[0092] Catalyst preparation: 5 mmol of rhodium acetylacetone was dissolved in 100 ml of oleylamine. Under a nitrogen atmosphere, the temperature was increased to 150 °C at 4 °C / min, and the reaction was stirred for 2 h. The product was centrifuged, dried, and washed to obtain rhodium nanoparticles.

[0093] Rhodium nanoparticles were mixed with a certain amount of 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid. The content of rhodium nanoparticles was 53 wt% by weight of the catalyst, and the content of ionic liquid was 47 wt%. The average diameter of the rhodium nanoparticles was 4.8 nm.

[0094] The catalyst evaluation method was the same as in Example 1, and the results are shown in Table 4.

[0095] Comparative Example 5

[0096] Catalyst preparation: 1 g (3 mmol) of iodophenyltrimethoxysilane was added to 0.57 g (4 mmol) of N-methoxyethyl-2-pyrrolidone and 6 g of toluene, and the mixture was reacted at 70 °C for 28 h. The lower layer was washed three times with toluene and dried under vacuum at 70 °C for 6 h to obtain the ionic liquid coupling agent.

[0097] 5 mmol of rhodium acetylacetone was dissolved in 100 ml of oleylamine. Under a nitrogen atmosphere, the temperature was increased to 150 °C at 4 °C / min, and the reaction was stirred for 2 h. The product was centrifuged, and the precipitate was added with the above-mentioned ionic liquid coupling agent, 0.45 g of water, and 6 g of cyclohexane. The mixture was stirred and refluxed at 60 °C for 2 h. The product was evaporated to dryness and then washed three times with ethanol to obtain the catalyst. The content of rhodium nanoparticles was 82 wt% by weight of the catalyst, and the content of the coupling agent was 18 wt%. The average size of the rhodium nanoparticles was 4.8 nm.

[0098] The catalyst evaluation method was the same as in Example 1, and the results are shown in Table 4.

[0099] Table 4

[0100]

[0101] The specific embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A catalyst for the co-production of dimethyl carbonate and monomethyl malonate, characterized in that, The catalyst comprises rhodium nanoparticles and a grafted ionic liquid coupling agent; the average size of the rhodium nanoparticles is 4-16 nm; in the catalyst, based on the catalyst weight, the content of rhodium nanoparticles is 50 wt%-65 wt%, and the content of the ionic liquid coupling agent is 35 wt%-50 wt%; the ionic liquid coupling agent is a product of the reaction between an iodosilane coupling agent and a nitrogen heterocyclic compound, and the molar ratio of the nitrogen heterocyclic compound to the iodosilane coupling agent is 1-1.5:1; the iodosilane coupling agent is selected from (3-iodopropyl)tris(1-methylethoxy)- The nitrogen heterocyclic compound is selected from at least one of silane, 3-iodopropyltrimethoxysilane, 4-iodobutyltrimethoxysilane, (4-iodobenzyloxy)trimethoxysilane, iodophenyltrimethoxysilane, and m-(trimethylsiloxy)iodobenzene; the nitrogen heterocyclic compound is selected from at least one of N-methoxyethyl-2-pyrrolidone, 1-methyl-3-pyrrolidone, N-methylpyrrolidone, 2-mercapto-1-methylimidazolium, 1-ethylimidazolium, N-triphenylmethylimidazolium, N,N-diimidazolylmethane, pyridine, 4-dimethylaminopyridine, N-methylpyrrole, 4-methylpyridine, and N-methylindole.

2. The catalyst according to claim 1, characterized in that, The average size of the rhodium nanoparticles is 4~8 nm.

3. A method for preparing the catalyst for the co-production of dimethyl carbonate and monomethyl malonate as described in any one of claims 1-2, comprising: (1) Mix the rhodium salt, reducing agent and solvent, and carry out the reaction under an inert atmosphere; (2) After solid-liquid separation, the product obtained in step (1) is modified by adding iodosilane coupling agent, water and organic solvent to the obtained solid to obtain a solid. (3) The solid obtained in step (2) is dispersed in a dispersion medium, and a nitrogen heterocyclic compound is added to react and the catalyst is obtained.

4. The preparation method according to claim 3, characterized in that, In step (1), the rhodium salt is selected from at least one of ammonium rhodium chloride, rhodium acetylacetonate, rhodium acetylacetonate dicarbonyl, rhodium dimer acetate, rhodium chloride, and rhodium iodide; And / or, the reducing agent is selected from at least one of oleylamine, octadecylamine, aniline, ethylene glycol, diethylene glycol, and triethylene glycol; And / or, the solvent is selected from at least one of oleylamine, oleic acid, octadecylamine, octadecene, ethylene glycol, diethylene glycol, and triethylene glycol.

5. The preparation method according to claim 3, characterized in that, In step (1), the concentration of rhodium salt in the resulting mixture is 10~80 mmol / L.

6. The preparation method according to claim 3, characterized in that, In step (1), the reaction temperature is 120~160℃, the reaction time is 1~4h, and the reaction is carried out under normal pressure; And / or, in step (2), the modification temperature is 50~70℃ and the modification time is 1~3h; And / or, in step (3), the reaction temperature is 50~70℃ and the reaction time is 4~40h.

7. The preparation method according to claim 3, characterized in that, In step (2), the mass ratio of the amount of iodosilane coupling agent added to the theoretical rhodium is 1.5~3:1, the molar ratio of the amount of water added to the iodosilane coupling agent is 3~12:1, and the mass ratio of the amount of organic solvent added to the theoretical rhodium is 7~15:

1. And / or, in step (3), the molar ratio of the amount of nitrogen heterocyclic compound added to the iodosilane coupling agent is 1~1.5:1, and the mass ratio of the dispersion medium to the nitrogen heterocyclic compound is 4~18:

1.

8. A method for co-producing dimethyl carbonate and monomethyl malonic acid, the method comprising: using dimethyl oxalate and methyl glycolate as reactants, and under a CO atmosphere, carrying out a decarbonylation and carbonylation coupling reaction in the presence of any one of the catalysts described in claims 1-2 or the catalysts obtained by any one of the preparation methods described in claims 3-7, to prepare dimethyl carbonate and monomethyl malonic acid.

9. The method according to claim 8, characterized in that, In the method described, the molar ratio of dimethyl oxalate to methyl glycolate is 1 to 3:

1.

10. The method according to claim 8, characterized in that, The reaction conditions for the method are as follows: catalyst concentration of 2-10 wt%, initial CO pressure of 1-4 MPa, reaction temperature of 140-200℃, and reaction time of 30-150 min.

11. The method according to claim 10, characterized in that, The reaction temperature is 160~180℃.

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