Catalyst for co-production of dimethyl carbonate and monomethyl malonate as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst for co-production of dimethyl carbonate and monomethyl malonate as well as a preparation method and application of the catalyst. The catalyst comprises rhodium nanoparticles and a grafted ionic liquid coupling agent. When the catalyst is used for a coupling reaction of preparing dimethyl carbonate by decarbonylation of dimethyl oxalate and preparing monomethyl malonate by carbonylation of methyl glycolate, the modified rhodium nanoparticles can be uniformly dispersed in a liquid-phase reaction raw material, so that quasi-homogeneous catalysis is realized, CO generated by decarbonylation can be supplied to carbonylation reaction, the atom utilization rate is increased, and the cost is reduced. And the CO generated in situ can reduce the activation energy required by the carbonylation reaction, so that the reaction temperature is lower, the selectivity is higher, and the catalytic life of the decarbonylation reaction is prolonged.

Description

Technical Field

[0001] The invention relates to the field of catalytic materials, and in particular to a catalyst for decarbonylation and carbonylation coupling reaction and a preparation method thereof, as well as application in the co-production of dimethyl carbonate and dimethyl malonate in a coal-to-ethylene glycol route. Background Art

[0002] Dimethyl malonate (DMM) is an important raw material for producing medicine pipemidic acid. The production process of dimethyl malonate is mainly based on cyanide esterification. Chloroacetic acid and sodium carbonate are neutralized to generate sodium chloroacetate, which is then cyanated with sodium cyanide to obtain sodium cyanoacetate. Sodium cyanoacetate is hydrolyzed into sodium malonate, and then esterified with methanol under sulfuric acid catalysis to obtain dimethyl malonate. This process has the problems of large pollution and complex process. CN112239408A proposes a technical route for obtaining dimethyl malonate by carbonylation reaction of methylal, but this route uses a homogeneous catalyst, and there are problems such as easy loss of catalyst and decomposition of ligand. The new process developed abroad is mainly based on catalytic carbonylation, that is, chloroacetate, carbon monoxide, and methanol are used as raw materials, and dimethyl malonate is synthesized by one-step reaction in the presence of a catalyst. In contrast, the catalytic carbonylation process is advanced in technology, but the process is complex, the reaction conditions are harsh, and industrialization is difficult to achieve.

[0003] Dimethyl carbonate (DMC) is a chemical raw material with low toxicity, excellent environmental performance and wide application. It is also an important organic synthesis intermediate. Its molecular structure contains functional groups such as carbonyl, methyl and methoxy groups, and has multiple reaction properties. It is safe, convenient, less polluting and easy to transport in production. In particular, the rapid development of lithium-ion batteries has continuously increased the demand for dimethyl carbonate. In addition, with the expansion of the production capacity of coal-to-ethylene glycol, the preparation of high-value-added dimethyl carbonate by decarbonylation of dimethyl oxalate (DMO) has certain economic benefits, and has environmental and cost advantages.

[0004] The co-production of dimethyl carbonate and monomethyl malonate is a new product chain extended from dimethyl oxalate as raw material, which is of great significance to the development of clean utilization of coal. In addition, there is no method for co-production of dimethyl carbonate and monomethyl malonate reported in the prior art. Summary of the invention

[0005] The present invention provides a catalyst for co-producing dimethyl carbonate and monomethyl malonate, and a preparation method and application thereof. The catalyst of the present invention can realize pseudo-homogeneous catalysis, CO generated by decarbonylation can be supplied to carbonylation reaction, thus improving the atomic utilization rate, and CO generated in situ can reduce the activation energy required for carbonylation reaction, thus making the reaction temperature lower, the selectivity higher, the stability higher, and prolonging the catalytic life of decarbonylation reaction.

[0006] A 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 of 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 to 1.5:1.

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

[0009] Furthermore, the nitrogen heterocyclic compound is selected from at least one of N-methoxyethyl-2-pyrrolidone, 1-methyl-3-pyrrolidone, N-methylpyrrolidone, 2-mercapto-1-methylimidazole, 1-ethylimidazole, N-tritylimidazole, N,N-diimidazole methane, pyridine, 4-dimethylaminopyridine, N-methylpyrrole, 4-methylpyridine, and N-methylindole.

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

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

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

[0013] (1) mixing a rhodium salt, a reducing agent and a solvent, and reacting them under an inert atmosphere;

[0014] (2) After solid-liquid separation of the product obtained in step (1), an iodosilane coupling agent, water and an organic solvent are added to the obtained solid for modification to obtain a solid;

[0015] (3) dispersing the solid obtained in step (2) in a dispersion medium, adding a nitrogen heterocyclic compound to react, and obtaining the catalyst.

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

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

[0018] Furthermore, 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 different from the reducing agent.

[0019] Furthermore, when the solvent in step (1) is at least one of oleylamine, octadecylamine, ethylene glycol, diethylene glycol, and triethylene glycol, no other reducing agent may be added to the reaction system, or other reducing agents may be added. The amount of reducing agent is such that high-valent rhodium is reduced to zero-valent rhodium. Those skilled in the art may determine the amount of reducing agent and solvent according to actual conditions.

[0020] Furthermore, in step (1), the concentration of rhodium salt in the mixed solution obtained after mixing is 10 to 80 mmol / L.

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

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

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

[0024] Furthermore, 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 to 70° C., and the modification time is 1 to 3 hours.

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

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

[0028] Furthermore, 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-methylimidazole, 1-ethylimidazole, N-tritylimidazole, N,N-diimidazole methane, pyridine, 4-dimethylaminopyridine, N-methylpyrrole, 4-methylpyridine, and N-methylindole.

[0029] Furthermore, in step (3), the molar ratio of the nitrogen heterocyclic compound added to the iodinated silane 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 to 70° C., and the reaction time is 4 to 40 hours.

[0031] Furthermore, in step (3), after the reaction is completed, the lower layer of the product is washed and dried to obtain the catalyst. The washing is performed using at least one of toluene, ethylbenzene, and ethyl acetate of p-xylene, and the number of washings is 3 to 5 times. The drying is vacuum drying, 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 malonate, wherein the method comprises: using dimethyl oxalate and methyl glycolate as reaction raw materials, carrying out decarbonylation and carbonylation coupling reaction under the action of the above catalyst in a CO atmosphere to prepare dimethyl carbonate and monomethyl malonate.

[0033] Furthermore, in the method described above, a mixed solution of dimethyl oxalate and methyl glycolate is uniformly mixed with a catalyst in an autoclave, and reacts at a certain temperature to generate dimethyl carbonate and monomethyl malonate.

[0034] Furthermore, in the method described above, 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 is 2-10wt%, CO initial pressure is 1-4MPa, reaction temperature is 140-200°C, preferably 160-180°C, and reaction time is 30-150min.

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

[0037]

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The catalyst of the present invention is a novel bifunctional catalyst, comprising rhodium nanoparticles and a grafted ionic liquid coupling agent. Rhodium is the main catalyst of the carbonylation reaction, and the iodide anion contained in the ionic liquid coupling agent is both a co-catalyst of the carbonylation reaction and a main catalyst of the decarbonylation reaction. The ionic liquid coupling agent grafted on the surface of the rhodium nanoparticles gathers a high concentration of iodine ions, increases the local co-catalyst concentration in the reaction solution, and enhances the catalyst activity. Thanks to the grafting and fixing effect of the rhodium nanoparticles, the stability of the ionic liquid coupling agent is improved, the catalytic life of the decarbonylation reaction is extended, and the high concentration of iodine ions increases the concentration of the catalytic active centers of the decarbonylation reaction in the reaction solution, enhancing the catalyst activity.

[0040] 2. The method for co-producing dimethyl carbonate and monomethyl malonate provided by the present invention, specifically, the CO generated by the reaction of preparing dimethyl carbonate from dimethyl oxalate is directly supplied to the carbonylation reaction of methyl glycolate to prepare monomethyl malonate, thereby achieving self-production and self-use of CO and improving the atomic utilization rate. The CO generated in situ by the decarbonylation of dimethyl oxalate can reduce the activation energy required for the carbonylation reaction of methyl glycolate, making the reaction temperature lower and the selectivity higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a transmission electron micrograph of the rhodium nanoparticles obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0042] In order to explain the present invention more clearly, the present invention is further described below in conjunction with embodiments and drawings. It should be understood by those skilled in the art that the content described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0043] In the present invention, the size and dispersibility of rhodium nanoparticles are observed using a transmission electron microscope HT7700 of Hitachi, Japan. When observing the nanoparticles, the prepared catalyst is dispersed in dimethyl carbonate, diluted to a suitable concentration, and dripped onto the carbon film. After natural air drying, the sample is injected for observation. 100 local particles are selected and their average diameter is measured and calculated using ImageJ software.

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

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

[0046] Dimethyl carbonate selectivity (%) = molar amount of dimethyl carbonate in the product / (molar amount of dimethyl oxalate in the raw material - 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 raw material - molar amount of methyl glycolate in the product) × 100%.

[0048] The catalyst life is defined as the number of cycles required for the conversion of dimethyl oxalate in the decarbonylation reaction to decrease to 90% of the initial conversion.

[0049] Example 1

[0050] Catalyst preparation: 5mmol of acetylacetonate rhodium was dissolved in 100ml of oleylamine, heated to 150℃ at 4℃ / min under nitrogen atmosphere, and stirred for 2h. The product was centrifuged, and the precipitate was added with 1g (3mmol) of iodophenyltrimethoxysilane, 0.45g of water and 6g of cyclohexane, and stirred and refluxed at 60℃ for 2h. The product was evaporated to dryness and washed with ethanol three times, and 0.57g (4mmol) of N-methoxyethyl-2-pyrrolidone and 6g of toluene were added and reacted at 70℃ for 28h. The lower layer was washed with toluene three times, and vacuum dried at 70℃ for 6h to obtain the catalyst. Based on the weight of the catalyst, the content of rhodium nanoparticles was 53wt%, and the content of ionic liquid coupling agent was 47wt%, wherein the average size of the rhodium nanoparticles was 4.8nm.

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

[0052] Embodiments 2 to 4

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

[0054] The catalyst preparation method is the same as in Example 1. The results are shown in Table 1.

[0055] Table 1 Evaluation results of each case

[0056]

[0057]

[0058] Embodiments 5 to 8

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

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

[0061] Table 2 Evaluation results of each case

[0062]

[0063] Example 9

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

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

[0066] Example 10

[0067] Catalyst preparation: 7 mmol of acetylacetonato dicarbonyl rhodium was dissolved in 120 ml of ethylene glycol, heated to 160°C at 5°C / min under nitrogen atmosphere, and stirred for 1.5 hours. The product was centrifuged, and the precipitate was added with 1.3 g (4 mmol) of m-(trimethylsilyloxy)iodobenzene, 0.6 g of water and 8.3 g of cyclohexane, and stirred and refluxed at 65°C for 2.5 hours. The product was evaporated to dryness and washed with ethanol three times, and 0.82 g (6.7 mmol) of 4-dimethylaminopyridine and 9 g of toluene were added and reacted at 70°C for 28 hours. The lower layer was washed with toluene three times, and vacuum dried at 80°C for 6 hours to obtain the catalyst. Based on the weight of the catalyst, the content of rhodium nanoparticles was 54 wt%, and the content of the ionic liquid coupling agent was 46 wt%, wherein the average size of the rhodium nanoparticles was 4.4 nm.

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

[0069] Embodiment 11

[0070] Catalyst preparation: 6 mmol of dimerized rhodium acetate was dissolved in 150 ml of octadecylamine, and the temperature was raised to 160°C at 5°C / min under a nitrogen atmosphere, and the reaction was stirred for 1.5 hours. The product was centrifuged, and the precipitate was added with 1.2 g (3.2 mmol) (3-iodopropyl) tris (1-methylethoxy) -silane, 0.3 g of water and 5.6 g of cyclohexane, and the reaction was stirred and refluxed at 65°C for 2.5 hours. The product was evaporated to dryness and washed with ethanol three times, and 1.15 g (3.7 mmol) of N-trityl imidazole and 5 g of toluene were added and reacted at 70°C for 28 hours. The lower layer was washed with toluene three times, and vacuum dried at 80°C for 6 hours to obtain the catalyst. Based on the weight of the catalyst, the content of rhodium nanoparticles was 59 wt%, and the content of the ionic liquid coupling agent was 41 wt%, wherein the average size of the rhodium nanoparticles was 4.7 nm.

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

[0072] Example 12

[0073] Catalyst preparation: 4mmol ammonium chlororhodate was dissolved in 100ml triethylene glycol, heated to 160℃ at 5℃ / min under nitrogen atmosphere, and stirred for 1.5h. The product was centrifuged, and the precipitate was added with 0.88g (2.6mmol) (4-iodobenzyloxy) trimethoxysilane, 0.36g water and 5.4g cyclohexane, and stirred at 65℃ for 2.5h. The product was evaporated to dryness and washed with ethanol three times, and 0.37g (3.2mmol) 2-mercapto-1-methylimidazole and 5g toluene were added and reacted at 70℃ for 28h. The lower layer was washed with toluene three times, and vacuum dried at 80℃ for 6h to obtain the catalyst. Based on the weight of the catalyst, the content of rhodium nanoparticles was 61wt%, and the content of ionic liquid coupling agent was 39wt%, wherein the average size of the rhodium nanoparticles was 4.9nm.

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

[0075] Table 3 Evaluation results of each case

[0076]

[0077]

[0078] Comparative Example 1

[0079] Catalyst preparation: 5 mmol of rhodium acetylacetonate was dissolved in 100 ml of oleylamine, heated to 150°C at 4°C / min under nitrogen atmosphere, stirred for 2 hours, and the product was centrifuged, dried, and washed to obtain rhodium nanoparticles, wherein the average size of the rhodium nanoparticles was 4.8 nm.

[0080] 1g iodophenyltrimethoxysilane, 0.45g water and 6g cyclohexane were stirred and refluxed at 60°C for 2h. The product was evaporated to dryness and then 0.57g N-methoxyethyl-2-pyrrolidone and 6g toluene were added and reacted at 70°C for 28h. The lower layer was washed three times with toluene and vacuum dried at 70°C for 6h to obtain an ionic liquid coupling agent.

[0081] Catalyst evaluation: The rhodium nanoparticles and ionic liquid coupling agent (1 g in total) obtained in Comparative Example 1 were added to an autoclave with 20 g of dimethyl oxalate and 10 g of methyl glycolate, and 2 MPa of CO was charged after nitrogen replacement. The temperature was raised to 160° C. and the reaction was carried out for 80 min. The results are shown in Table 4. Based on the weight of the catalyst, the content of the rhodium nanoparticles was 53 wt%, and the content of the ionic liquid coupling agent was 47 wt%.

[0082] Comparative Example 2

[0083] Compared with Example 1, the average size of the rhodium particles used in Comparative Example 2 is 20 nm.

[0084] Catalyst preparation: 5mmol of acetylacetonato rhodium was dissolved in 60ml of oleylamine, and the temperature was raised to 170℃ at 2℃ / min under nitrogen atmosphere, and the reaction was stirred for 6h. The product was centrifuged, and the precipitate was added with 1g (3mmol) of iodophenyltrimethoxysilane, 0.45g of water and 6g of cyclohexane, and the reaction was stirred and refluxed at 60℃ for 2h. The product was evaporated to dryness of the solvent and washed with ethanol three times, and 0.57g (4mmol) of N-methoxyethyl-2-pyrrolidone and 6g of toluene were added and reacted at 70℃ for 28h. The lower layer was washed with toluene three times, and vacuum dried at 70℃ for 6h to obtain the catalyst. Based on the weight of the catalyst, the content of rhodium nanoparticles was 74wt%, and the content of the ionic liquid coupling agent was 26wt%.

[0085] The catalyst evaluation method is 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 acetylacetonate and an ionic liquid coupling agent as a catalyst.

[0088] Catalyst preparation: Take 5mmol of rhodium acetylacetonate, add 1g (3mmol) of iodophenyltrimethoxysilane, 0.45g of water and 6g of cyclohexane, and stir and reflux at 60°C for 2h. After the product is evaporated to dryness, wash it three times with ethanol, add 0.57g (4mmol) of N-methoxyethyl-2-pyrrolidone and 6g of toluene, and react at 70°C for 28h. Take the lower layer, wash it three times with toluene, and vacuum dry it at 70°C for 6h to obtain the catalyst. Based on the weight of the catalyst, the content of the coupling agent is 33.3%, and the content of the rhodium acetylacetonate is 66.7wt%.

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

[0090] Comparative Example 4

[0091] Compared with Example 1, the ionic liquid of Comparative Example 4 is 1-butyl-3-methylimidazolium tetrafluoroborate.

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

[0093] The rhodium nanoparticles and a certain amount of 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid are mixed. Based on the weight of the catalyst, the content of the rhodium nanoparticles is 53wt%, the content of the ionic liquid is 47wt%, and the average diameter of the rhodium nanoparticles is 4.8nm.

[0094] The catalyst evaluation method is 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 with 0.57 g (4 mmol) of N-methoxyethyl-2-pyrrolidone and 6 g of toluene and 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 an ionic liquid coupling agent.

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

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

[0099] Table 4

[0100]

[0101] The specific implementation modes of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A catalyst for co-producing dimethyl carbonate and monomethyl malonate, characterized in that: The catalyst comprises rhodium nanoparticles and a grafted ionic liquid coupling agent.

2. The catalyst according to claim 1, characterized in that The ionic liquid coupling agent is a product of the reaction of 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 to 1.5:

1.

3. The catalyst according to claim 2, characterized in that The iodosilane coupling agent is selected from at least one of (3-iodopropyl)tri(1-methylethoxy)-silane, 3-iodopropyltrimethoxysilane, 4-iodobutyltrimethoxysilane, (4-iodobenzyloxy)trimethoxysilane, iodophenyltrimethoxysilane, and m-(trimethylsiloxy)iodobenzene; And / or, the nitrogen heterocyclic compound is selected from at least one of N-methoxyethyl-2-pyrrolidone, 1-methyl-3-pyrrolidone, N-methylpyrrolidone, 2-mercapto-1-methylimidazole, 1-ethylimidazole, N-tritylimidazole, N,N-diimidazole methane, pyridine, 4-dimethylaminopyridine, N-methylpyrrole, 4-methylpyridine, and N-methylindole.

4. The catalyst according to claim 1, characterized in that The average size of the rhodium nanoparticles is 4 to 16 nm, preferably 4 to 8 nm.

5. The catalyst according to claim 1, characterized in that In the catalyst, based on the weight of the catalyst, the content of rhodium nanoparticles is 50wt% to 65wt%, and the content of the ionic liquid coupling agent is 35wt% to 50wt%.

6. A method for preparing a catalyst for co-producing dimethyl carbonate and monomethyl malonate, comprising: (1) mixing a rhodium salt, a reducing agent and a solvent, and reacting them under an inert atmosphere; (2) After solid-liquid separation of the product obtained in step (1), an iodosilane coupling agent, water and an organic solvent are added to the obtained solid for modification to obtain a solid; (3) dispersing the solid obtained in step (2) in a dispersion medium, adding a nitrogen heterocyclic compound to react, and obtaining the catalyst.

7. The preparation method according to claim 6, characterized in that: In step (1), the rhodium salt is selected from at least one of ammonium chlororhodate, rhodium acetylacetonate, rhodium dicarbonyl acetylacetonate, 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.

8. The preparation method according to claim 6, characterized in that: In step (1), the concentration of rhodium salt in the mixed solution obtained after mixing is 10 to 80 mmol / L.

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

10. The preparation method according to claim 6, characterized in that: In step (2), the iodosilane coupling agent is selected from at least one of (3-iodopropyl)tri(1-methylethoxy)-silane, 3-iodopropyltrimethoxysilane, 4-iodobutyltrimethoxysilane, (4-iodobenzyloxy)trimethoxysilane, iodophenyltrimethoxysilane, and m-(trimethylsiloxy)iodobenzene; And / or, 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-methylimidazole, 1-ethylimidazole, N-tritylimidazole, N,N-diimidazole methane, pyridine, 4-dimethylaminopyridine, N-methylpyrrole, 4-methylpyridine, and N-methylindole.

11. The preparation method according to claim 6, characterized in that: In step (2), the mass ratio of the amount of iodosilane coupling agent added to the theoretical rhodium 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; And / or, in step (3), the molar ratio of the 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.

12. A method for co-producing dimethyl carbonate and monomethyl malonate, the method comprising: using dimethyl oxalate and methyl glycolate as reaction raw materials, carrying out decarbonylation and carbonylation coupling reaction under a CO atmosphere in the presence of a catalyst according to any one of claims 1 to 5 or a catalyst obtained by the preparation method according to any one of claims 6 to 11, to prepare dimethyl carbonate and monomethyl malonate.

13. The method according to claim 12, characterized in that In the method, the molar ratio of dimethyl oxalate to methyl glycolate is 1 to 3:

1.

14. The method according to claim 12, characterized in that The reaction conditions of the method are as follows: catalyst concentration is 2-10wt%, CO initial pressure is 1-4MPa, reaction temperature is 140-200°C, preferably 160-180°C, and reaction time is 30-150min.

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