Porous carbon support loaded catalyst, method for preparing the same, and use thereof

Abstract

The application discloses a porous carbon carrier loaded catalyst, a preparation method and application thereof. In the catalyst, the content of active metal components distributed in the pores of the porous carbon carrier accounts for more than 50% of the total content of all active metal components in the catalyst. The catalyst is stable in the system, and the active center is not easy to flow out, thereby solving the problems of easy flow-out of the active components of the heterogeneous catalyst and short service life of the catalyst in the prior art. In addition, when the catalyst is used for preparing a dialkyl carbonate, the catalyst has excellent conversion rate and selectivity.

Description

Technical Field

[0001] This invention provides a supported catalyst, and more specifically relates to a catalyst in which an active metal component is mainly supported in the pores of a porous carbon support, a method for preparing the catalyst, and the application of the catalyst in the preparation of dialkyl carbonates. Background Technology

[0002] Dimethyl carbonate (DMC) is a chemically active and physically excellent raw material that is non-toxic and readily biodegradable. It is a novel, low-pollution, environmentally friendly, and green basic chemical raw material, widely used in the chemical industry as a solvent, gasoline additive, lithium-ion battery electrolyte, and reagent for carbonylation, methylation, and carbonyl methoxylation. Currently, countries worldwide are actively researching green chemical processes based on DMC, an environmentally friendly raw material. Among these methods, transesterification is superior due to its milder reaction conditions, higher yield, and the co-production of ethylene glycol or propylene glycol, making it a highly promising industrial approach.

[0003] Generally, alkali metal hydroxides, alkali metal carbonates, and alkali metal alcohols (US2011040117A1; WO2010063780A1) are used as catalysts in transesterification reactions. However, because these are homogeneous catalysts, they are difficult to separate from the products and reuse. Commonly used heterogeneous catalysts include alkali metals or alkali metal salts supported on supports, metal oxide catalysts, zeolite or clay materials for alkali (earth) metal exchange, and ion exchange resins. Alkali metals or alkali metal salts supported on a carrier, such as KF / Al2O3, NaOH / chitosan, and Cs2CO3 / SiO2-Al2O3 (CN101249452A; CN101121147A; WO2001056971A1), have the disadvantage of being easily affected by water and CO2 in the air and being prone to loss during the reaction, resulting in decreased activity. Metal oxide catalysts, such as Al2O3 and MgO (US2005080287A1; US6207850B1), and zeolite or clay materials for alkali (earth) metal exchange, such as Cs-ZSM-5 and Mg-smectite (WO2000073256A1), have the disadvantage of generally low activity or selectivity. Ion exchange resins, such as quaternary ammonium or tertiary amine resins, are generally not heat-resistant or swelling-resistant, and their activity decreases rapidly over time.

[0004] Therefore, finding a catalyst with high stability and high conversion rate for the preparation of dialkyl carbonates remains an urgent need in this field. Summary of the Invention

[0005] In response to the above situation, the inventors of this invention conducted in-depth research and surprisingly discovered that by loading the active metal component onto a modified resin support and then calcining the resin support, a catalyst in which the active metal component is mainly distributed within the pores of a porous carbon support can be obtained. This catalyst exhibits excellent stability and high catalytic activity, thus completing this invention.

[0006] Specifically, a first aspect of the present invention provides a porous carbon-supported catalyst, characterized in that it comprises a porous carbon support, an active metal component, and at least one heteroatom selected from nitrogen, sulfur, and phosphorus, wherein, relative to the total mass of the catalyst, the content of the porous carbon support is 50% to 99%, the content of the active metal component, calculated as an active metal oxide, is 0.1% to 50%, and the content of the heteroatom, calculated as an element, is 0.1% to 5%; the active metal is at least one selected from magnesium, aluminum, and calcium, and the content of the active metal component distributed in the pores of the porous carbon support, calculated as an active metal oxide, is more than 50% of the total content of all active metal components in the catalyst.

[0007] A second aspect of the present invention provides a method for preparing a catalyst, comprising the following steps:

[0008] (1) The modification step of contacting the halogenated alkyl resin with a modifier to modify it and obtain the modified halogenated alkyl resin.

[0009] (2) A contacting step in which the modified haloalkylated resin is contacted with a metal precursor of an active metal to obtain a contact product; and

[0010] (3) A roasting step in which the contact product is optionally dried and then roasted in an inactive gas atmosphere.

[0011] A third aspect of the present invention provides a method for preparing dialkyl carbonate, wherein a carbonate and a lower alcohol are reacted in the presence of the catalyst described above or the catalyst prepared by the method of the present invention to obtain dialkyl carbonate.

[0012] Technical effect

[0013] In the catalyst of this invention, the content of active metal components distributed within the pores of the porous carbon support is higher than that of active metal components distributed on the surface of the porous carbon support. The proportion of active metal components distributed within the pores exceeds 50% relative to the total content of all active metal components in the catalyst. Therefore, the catalyst of this invention exhibits excellent conversion and selectivity in the preparation of dialkyl carbonates, and has a long catalyst lifetime, making it suitable for industrial use. Furthermore, this carbon-supported catalyst exhibits stable catalyst system properties and minimal loss of active centers during the preparation of dialkyl carbonates, solving the problems of easy loss of active components and short catalyst lifetime inherent in heterogeneous catalysts of previous technologies.

[0014] In the preparation method of the catalyst of the present invention, by using a spherical porous resin support, the utilization rate of the support and the density of active centers can be effectively improved, solving the problem of low activity of heterogeneous catalysts in the prior art; by modifying the resin and then loading the precursor of the active metal, and then calcining it, more of the active metal component can enter the pores of the carbon support, thereby efficiently preparing the catalyst of the present invention.

[0015] In the method for preparing dialkyl carbonate of the present invention, the catalyst of the present invention or the catalyst prepared by the method of the present invention is used to prepare dialkyl carbonate from carbonates and lower alcohols with high conversion rate and high selectivity. Attached Figure Description

[0016] Figure 1 This is a scanning electron microscope image of catalyst C1 prepared in Example 1 of the present invention;

[0017] Figure 2 This is a scanning electron microscope image of catalyst S1 prepared in Comparative Example 1 of the present invention;

[0018] Figure 3 Transmission electron microscopy image of catalyst C1 prepared in Example 1 of this invention;

[0019] Figure 4 Transmission electron microscopy image of catalyst S1 prepared in Comparative Example 1 of this invention.

[0020] Figure 5 (a) Scanning electron microscope image of catalyst C1 prepared in Example 1 of the present invention under a 100-micrometer scale; (b) Scanning electron microscope image of the interior of catalyst prepared in Example 1 of the present invention under a 10-micrometer scale.

[0021] Figure 6 (a) Scanning electron microscope (SEM) image of the interior of catalyst C1 prepared in Example 1 of the present invention under a 200 nm scale; (b) Scanning electron microscope (SEM) image of the interior of catalyst C1 prepared in Example 1 of the present invention under a 100 nm scale.

[0022] Figure 7 Energy dispersive X-ray spectroscopy (EDX) and surface scan (SSD) spectra of catalyst C1 prepared in Example 1 of the present invention; (a) Selected area surface scan (SSD) spectrum; (b) Carbon elemental distribution map; (c) Oxygen elemental distribution map; (d) Magnesium elemental distribution map; (e) EDX spectrum.

[0023] Figure 8 (a) Scanning electron microscope image of catalyst S1 prepared in Comparative Example 1 of the present invention under a 100-micrometer scale; (b) Scanning electron microscope image of the interior of catalyst S1 prepared in Comparative Example 1 of the present invention under a 20-micrometer scale.

[0024] Figure 9 (a) Scanning electron microscope image of the interior of catalyst S1 prepared in Comparative Example 1 of the present invention under a 200 nm scale; (b) Scanning electron microscope image of the interior of catalyst S1 prepared in Comparative Example 1 of the present invention under a 100 nm scale.

[0025] Figure 10 Energy dispersive X-ray spectroscopy (EDX) and surface scan (SDS) spectra of catalyst S1 prepared in Comparative Example 1 of the present invention; (a) Selected area surface scan (SDS) spectrum; (b) Carbon elemental distribution map; (c) EDX spectrum. Detailed Implementation

[0026] The present invention is described in detail below with reference to specific embodiments. However, it should be noted that the scope of protection of the present invention is not limited by these specific embodiments and principle explanations, but is determined by the claims.

[0027] In this invention, except where expressly stated, any matters or issues not mentioned herein are directly applicable to what is known in the art without any changes. Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or concepts are considered part of the original disclosure or record of this invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination clearly unreasonable.

[0028] All features disclosed in this invention can be combined arbitrarily, and such combinations should be understood as the content disclosed or recorded in this invention. Unless those skilled in the art consider such combinations to be obviously unreasonable, they should all be regarded as specifically disclosed and recorded in this invention. The numerical points disclosed in this specification, unless otherwise specified, include not only the numerical points specifically disclosed in the embodiments, but also the endpoints of each numerical range in the specification. Any combination of these numerical points should be regarded as the range disclosed or recorded in this invention.

[0029] In this invention, the technical and scientific terms that are given a definition shall be used as defined thereon, and those that are not given a definition shall be understood according to their common meaning in the art.

[0030] [Carbon-supported catalyst]

[0031] This invention provides a porous carbon-supported catalyst, comprising a porous carbon support, an active metal component, and at least one heteroatom selected from nitrogen, sulfur, and phosphorus. The porous carbon support comprises 50%–99% of the total mass of the catalyst, the active metal component comprises 0.1%–50% (based on active metal oxide), and the heteroatom comprises 0.1%–5% (based on elemental composition). The active metal is at least one selected from magnesium, aluminum, and calcium. The active metal component, based on active metal oxide, accounts for more than 50% of the total active metal component content in the catalyst, distributed within the pores of the porous carbon support.

[0032] In the catalyst of this invention, the porous carbon support is derived from the calcination of porous resin materials in an inert gas.

[0033] In the catalyst of the present invention, the particle size of the porous carbon support is not particularly limited, and the particle size can be 0.1 mm to 3 mm, preferably 0.3 mm to 2 mm. The pore size of the porous carbon support of the present invention is not particularly limited, for example, it can be 5 to 500 nm, preferably 50 to 300 nm.

[0034] In one embodiment of the present invention, the content of porous carbon support relative to the total mass of the catalyst is 50% to 99%, preferably 55% to 90%, and more preferably 60% to 85%.

[0035] In this invention, at least one heteroatom selected from nitrogen, sulfur, and phosphorus comes from the modifier used in the preparation of the catalyst. During the calcination step, the modifier is calcined, leaving at least one heteroatom from nitrogen, sulfur, and phosphorus.

[0036] In one embodiment of the invention, the content of at least one heteroatom selected from nitrogen, sulfur and phosphorus, on an elemental basis, is 0.1% to 5% relative to the total mass of the catalyst; preferably 0.3% to 4.5%, more preferably 0.5% to 4%.

[0037] In this invention, the catalyst also contains oxygen; however, this invention does not intend to limit the oxygen content. Generally, the oxygen content is included in the oxides of this invention.

[0038] In one embodiment of the present invention, the catalyst may also contain halogen elements derived from halogenated alkylating resins. Typically, halogen elements are removed during calcination; however, some halogen elements may still remain as impurities. The present invention does not intend to limit the content of halogen elements.

[0039] In this invention, the content of active metal components (calculated as oxides), heteroatom content (calculated as elements), and optionally halogen atom content (calculated as elements) in the catalyst can be determined using methods known in the art, such as elemental analysis. The remaining content after deducting the active metal oxide content, heteroatom content, and optionally halogen atom content is recorded as the content of the porous carbon support of this invention. In this invention, the active metal oxide is derived from the calcination product of the active metal precursor introduced during catalyst preparation.

[0040] In one embodiment of the present invention, the content of the active metal component, calculated as active metal oxide, is 0.1% to 50% relative to the total mass of the catalyst, preferably 5% to 45%, and more preferably 10% to 40%.

[0041] In one embodiment of the present invention, the active metal is at least one selected from magnesium, aluminum, and calcium, preferably at least one selected from magnesium and calcium.

[0042] In the catalyst of the present invention, the active metal component includes any valence state and any oxidation state of the active metal. Typically, in the catalyst of the present invention, the active metal component usually exists in the form of a metal oxide, which is the product of calcining the precursor of the active metal.

[0043] In this invention, unless otherwise specified, the active metal component is typically measured in the form of an active metal oxide.

[0044] In the catalyst of the present invention, the content of active metal components distributed within the pores of the porous carbon support (sometimes referred to as the inner surface or interior in the present invention) is greater than that of active metal components distributed on the surface of the porous carbon support (sometimes referred to as the outer surface or exterior in the present invention).

[0045] In one embodiment of the present invention, the content of the active metal component distributed in the pores of the porous carbon support, based on the active metal oxide, accounts for more than 50% of the content of the active metal component contained in the catalyst, preferably more than 55%, more preferably more than 60%, further preferably more than 65%, and most preferably more than 75%. The upper limit of the percentage of the content of the active metal component distributed in the pores of the porous carbon support relative to the content of the active metal component contained in the catalyst is not particularly limited, but is preferably 100%. However, from the perspective of actual production costs, the upper limit can be 99%, 98%, 96%, 96%, or 95%.

[0046] In one embodiment of the present invention, the content of the active metal component distributed on the surface (outer surface or exterior) of the porous carbon support, based on the active metal oxide, is less than 50% relative to the content of the active metal component contained in the catalyst, preferably less than 45%, more preferably less than 40%, further preferably less than 35%, and most preferably less than 30%. The lower the lower limit of the content of the active metal component distributed on the surface (outer surface or exterior) of the porous carbon support relative to the content of the active metal component contained in the catalyst, the better; preferably 0. However, from the perspective of actual production costs, the lower limit can be 5%, 4%, 3%, 2%, or 1%.

[0047] In this invention, the content of active metal components distributed on the surface (outer surface or exterior) of the porous carbon support can be determined using XPS. That is, in this invention, the content of active metals on the porous carbon support determined by XPS is taken as the content of active metals on the surface (outer surface or exterior) of the porous carbon support.

[0048] It should be noted that, in this invention, the content of active metal components within the pores (inner surface or interior) of the porous carbon support can be obtained by subtracting the content of active metal components distributed on the surface (outer surface or exterior) of the porous carbon support from the total content of active metal components in the porous carbon support. Here, the total content of active metal components in the catalyst can be determined by elemental analysis or the like; on the other hand, in this invention, the content of active metal components in the porous carbon support determined by XPS is taken as the content of active metal components on the surface (outer surface or exterior) of the porous carbon support. Therefore, based on these two measurements, the content of active metal components distributed within the pores (inner surface or interior) of the porous carbon support can be calculated: Content of active metal components within the pores (inner surface or interior) = Total content of active metal components in the porous carbon support - Content of active metal components distributed on the surface (outer surface or exterior) of the porous carbon support determined by XPS.

[0049] In this invention, by distributing the active metal component mainly (e.g., more than 50%) within the pores of the porous carbon support, and more preferably distributing the majority (e.g., more than 55%, more preferably more than 60%, further preferably more than 65%, and most preferably more than 70%) within the pores of the porous carbon support, the catalyst exhibits excellent conversion rate, high selectivity, and a significantly extended catalyst lifetime.

[0050] One embodiment of the present invention provides a catalyst for preparing dimethyl carbonate, comprising a support and an active component, characterized in that the mass percentages of the support and the active component in the catalyst are respectively: 50% to 99.9% for the support and 0.1% to 50% for the active component; the support is carbon, and the active component is selected from at least one of magnesium, calcium, and aluminum; the carbon is obtained by carbonization of modified chloromethyl resin;

[0051] The active components are distributed on the surface of the carrier and within the carrier pores, and the content of active components within the carrier pores is greater than the content of active components on the carrier surface.

[0052] Catalyst preparation methods

[0053] A second aspect of the present invention provides a method for preparing a catalyst, comprising the following steps:

[0054] (1) The modification step of contacting the halogenated alkyl resin with a modifier to modify it and obtain the modified halogenated alkyl resin.

[0055] (2) A contacting step in which the modified haloalkylated resin is contacted with a metal precursor of an active metal to obtain a contact product; and

[0056] (3) A calcination step in which the contact product is optionally dried and then calcined in an inert gas atmosphere.

[0057] The modifier is at least one compound selected from nitrogen-containing compounds, sulfur-containing compounds, and phosphorus-containing compounds.

[0058] The inventors of this invention have discovered that by modifying a halogenated alkylated resin with a modifier, and then allowing the modified resin to interact with an active metal precursor and calcining it, a catalyst in which the active metal component is mainly distributed within the pores of a porous carbon support can be obtained.

[0059] In this invention, halogenated or halogenated substances can include fluorine, chlorine, bromine and iodine, preferably chlorine or iodine, and more preferably chlorine.

[0060] In this invention, the alkyl group in alkylation can be C1-C6 alkyl groups, preferably C1-C4 alkyl groups, and more preferably methyl, ethyl, propyl, or isopropyl.

[0061] In one embodiment of the present invention, halogenation is preferably halogenation, and more preferably chloromethylation.

[0062] In this invention, the halogenated alkylated resin can be obtained by halogenating and modifying a conventional resin (preferably by halogenation and methylation, more preferably by chloromethylation), or a commercially available halogenated alkylated resin can be used, as long as the resin has a porous structure.

[0063] In this invention, halogenated alkylated resins can be listed as halogenated styrene resins, such as chloromethyl resins, and especially chloromethylstyrene resins.

[0064] As a halogenated alkylated styrene resin, it can be a commercially available product and can also be prepared by methods known in the art, including but not limited to the following methods: alkylating polystyrene with a halogenated olefin (C2-C6 halogenated olefin) to produce halogenated alkylated polystyrene (CN1137788A). Additionally, as a chloromethylstyrene resin, it can be a commercially available product and can also be prepared by methods known in the art, including but not limited to the following methods: preparing polystyrene microsphere resin by suspension polymerization and reacting it with chloromethyl ether to obtain chloromethylstyrene resin (CN103864973A). Furthermore, halogenated alkylated styrene resin or chloromethylstyrene resin can also be prepared by methods described in CN103709278A, CN104788592A, etc.

[0065] In one embodiment of the present invention, the particle size of the halogenated alkyl resin is 0.1 mm to 3 mm, preferably 0.3 mm to 2 mm.

[0066] In one embodiment of the present invention, the pore size of the halogenated alkylating resin is 5-500 nm, preferably 50-300 nm.

[0067] In one embodiment of the present invention, the halogenated alkylated resin is spherical.

[0068] In step (1) of this invention, the modifier is contacted with the haloalkylated resin to modify it, thereby obtaining the modified haloalkylated resin (hereinafter sometimes also referred to as the modified product or modified resin). This invention does not intend to limit the description of the reaction occurring at this stage; it is speculated that this may be due to the interaction between the nitrogen, phosphorus, or sulfur heteroatoms contained in the modifier and the haloalkyl group. Furthermore, the introduced heteroatoms can promote the dispersion of the subsequent active metal precursor within the support, improve the dispersion of the metal active component, promote alkalinity, and facilitate the deposition of the active metal component within the pores of the porous carbon support after calcination.

[0069] Therefore, in this invention, the modifier is at least one compound selected from nitrogen-containing compounds, sulfur-containing compounds, and phosphorus-containing compounds.

[0070] In one embodiment of the present invention, the nitrogen-containing compound is a nitrogen-containing organic compound.

[0071] In one embodiment of the present invention, the nitrogen-containing organic compound is any organic compound containing a nitrogen atom, without particular limitation, and may be an alkylamine or a 5- or 6-membered nitrogen-containing heterocyclic aromatic compound. Examples of alkylamines include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, cyclohexylamine, octylamine, decylamine, dimethylamine, diethylamine, dibutylamine, trimethylamine, triethylamine, and tributylamine. Examples of 5- or 6-membered nitrogen-containing heterocyclic aromatic compounds include at least one of the following 5- or 6-membered nitrogen-containing heterocyclic aromatic compounds optionally substituted with C1-C6 alkyl groups. Examples of 5- or 6-membered nitrogen-containing heterocyclic aromatic compounds include at least one of piperazine, pyridine, imidazole, 1-methylimidazolium, quinoline, pyrrole, indole, carbazole, isoindole, and thiazole. These nitrogen-containing heterocyclic aromatic compounds may optionally be substituted with C1-C6 alkyl groups. In this invention, the C1-C6 alkyl group is preferably a C1-C4 alkyl group, more preferably methyl, ethyl, propyl, or isopropyl. In one embodiment of this invention, the number of substituents "substituted by C1-C6 alkyl groups" can be 1, 2, 3, 4, or 5, preferably 1, 2, or 3, more preferably 1 or 2.

[0072] In one embodiment of the present invention, the sulfur-containing compound is a sulfur-containing organic compound.

[0073] In one embodiment of the present invention, the sulfur-containing organic compound is any organic compound containing sulfur atoms and is not particularly limited. Examples include sulfides such as dimethyl sulfide, diethyl sulfide, dipropyl sulfide, dihexyl sulfide, dicyclohexyl sulfide, and diphenyl sulfide; dialkyl disulfide compounds such as dimethyl disulfide, diethyl disulfide, dipropyl disulfide, dibutyl disulfide, dihexyl disulfide, dicyclohexyl disulfide, and ethylmethyl disulfide; thiophenes optionally substituted with C1-C6 alkyl groups such as thiophene, 2-methylthiophene, 3-methylthiophene, 2,3-dimethylthiophene, 2-ethylthiophene, and benzothiophene; heterocyclic sulfur compounds such as tetrahydrothiophene and thiopyran; aromatic sulfur compounds such as diphenyl sulfide, diphenyl disulfide, methylphenyl disulfide, and methylphenyl sulfide; thiourea; and sulfides such as methyl sulfide, ethyl sulfide, and butyl sulfide.

[0074] In one embodiment of the present invention, the phosphorus-containing compound is a phosphorus-containing organic compound.

[0075] In one embodiment of the present invention, the phosphorus-containing organic compound is any organic compound containing phosphorus atoms, without particular limitation. Examples include triphenylphosphine, triethylphosphine, tributylphosphine, tripropylphosphine, trioctylphosphine, and tricyclohexylphosphine.

[0076] In one embodiment of the present invention, the modifier is preferably selected from at least one of imidazole optionally substituted with C1-C6 alkyl, pyridine optionally substituted with C1-C6 alkyl, thiophene optionally substituted with C1-C6 alkyl, thiazole optionally substituted with C1-C6 alkyl, piperazine optionally substituted with C1-C6 alkyl, and triphenylphosphine, more preferably at least one of imidazole, 1-methylimidazolium, pyridine, piperazine, and thiophene.

[0077] In one embodiment of the present invention, the mass ratio of the halogenated alkyl resin to the modifier is 1:(0.1 to 1.2), preferably 1:(0.15 to 1), for example 1:1, 1:0.8, or 1:0.6.

[0078] In one embodiment of the present invention, the modification step can be carried out in a solvent, which may be at least one selected from toluene, methanol, ethanol, n-propanol, n-butanol, isobutanol, tert-butanol, tetrahydrofuran, dichloromethane, chloroform, N,N-dimethylformamide, ether, and water.

[0079] In one embodiment of the present invention, the mass ratio of the halogenated alkylating resin to the solvent is 1:(1-10), preferably 1:(2-8), for example 1:3.792 or 1:5.688.

[0080] In one embodiment of the present invention, the modification step can be carried out at a temperature of 30°C to 150°C, preferably 40°C to 120°C, for example, 70°C, 80°C, or 90°C. The solution containing the resin raw material can be heated before the resin raw material comes into contact with the modifier, or the solution can be heated during the contact between the resin raw material and the modifier.

[0081] In this invention, there is no particular limitation on the modification time of the modification step. In one embodiment of this invention, the modification time of the modification step is 1h to 24h, preferably 2h to 18h, for example 12h or 15h.

[0082] In one embodiment of the present invention, the solution containing the resin raw material and the modifier may be mixed and stirred during the modification process. The mixing and stirring rate is 50 rpm to 1000 rpm, preferably 100 rpm to 800 rpm, for example, 500 rpm or 800 rpm. The stirring time is not particularly limited, for example, it can be 2 hours.

[0083] In one embodiment of the present invention, in step (1), the modified product may be washed and dried as needed. In this case, the solvent described above may be used for washing, followed by drying. The drying conditions may include a drying temperature of 80°C to 180°C, for example, 100°C or 120°C; and a drying time of 1 hour to 48 hours, for example, 24 hours.

[0084] In step (2) of the present invention, the modified haloalkylated resin (modified product) is contacted with the metal precursor of the active metal to obtain a contact product.

[0085] In this invention, step (2) loads the active metal precursor onto the modified haloalkylated resin.

[0086] In this invention, the active metal is at least one selected from magnesium, calcium, and aluminum, preferably at least one selected from magnesium and calcium.

[0087] In one embodiment of the present invention, the metal precursor of the active metal is at least one of the nitrate, chloride, and sulfate forms of the active metal.

[0088] In one embodiment of the present invention, the mass ratio of the modified halogenated alkyl resin to the metal precursor of the active metal is 1:0.1 to 3, preferably 1:0.2 to 2.

[0089] In one embodiment of the present invention, the metal precursor of the active metal exists in the form of a solution, and the solvent can be selected from the solvents mentioned above, preferably water. In summary, in one embodiment of the present invention, the mass concentration of the metal precursor solution of the active metal is 5% to 50%, for example 6.5%, 7%, 8%, 8.8%, 17.6%, 26.4%, and 35.2%.

[0090] In one embodiment of the present invention, the mass ratio of the modified haloalkylated resin to the solution of the metal precursor containing the active metal is 1:(1-10), preferably 1:(2-6).

[0091] In one embodiment of the present invention, the contacting step is carried out in the presence of a solvent, which may be at least one selected from toluene, methanol, ethanol, n-propanol, n-butanol, isobutanol, tert-butanol, tetrahydrofuran, dichloromethane, chloroform, N,N-dimethylformamide, ether, and water.

[0092] In one embodiment of the present invention, a solution containing a modified resin and an active metal precursor is mixed and stirred. The mixing and stirring conditions are not particularly limited. For example, the mixing and stirring rate is 100 rpm to 800 rpm, preferably 200 rpm to 600 rpm; the stirring temperature is 30°C to 100°C, preferably 50°C to 80°C, for example 50°C or 80°C; and the stirring time is 1 h to 10 h, preferably 2 h to 8 h, for example 2 h, 6 h, or 8 h.

[0093] In step (3) of the present invention, the product obtained in the contact step is calcined in an inactive gas atmosphere to obtain the catalyst of the present invention.

[0094] In one embodiment of the present invention, in step (3), the product obtained in the contact step is first dried and then calcined. The drying conditions are not particularly limited, for example, the temperature is 80℃~180℃, preferably 90℃~150℃, for example 100℃, and the time is 1h~48h, preferably 2h~36h, for example 14h, 24h.

[0095] In this invention, modified resin particles loaded with active metal precursors are calcined. During the calcination process, the resin particles are carbonized and transformed into a porous carbon support. This porous carbon support serves as the porous carbon support for the catalyst of this invention. The active metal component is mainly enriched in the pores (inner surface or interior) of the porous carbon support. At the same time, the modifier is removed, leaving at least one heteroatom selected from nitrogen, sulfur, and phosphorus in the carbon support.

[0096] In this invention, there is no limitation on the inert gas; any inert gas known in the art is acceptable. In one embodiment of this invention, the inert gas may include nitrogen, rare gases selected from argon, etc.

[0097] In one embodiment of the present invention, the calcination temperature is 200℃~1000℃, preferably 250℃~600℃, for example 400℃, 500℃, 600℃, and the calcination time is 1h~48h, preferably 2h~24h, for example 4h, 5h, 8h.

[0098] One embodiment of the present invention provides a method for preparing a catalyst for preparing dimethyl carbonate, wherein, in the preparation of modified chloromethyl resin, chloromethyl resin is mixed with a solvent, a modifier is added, and modified to obtain modified chloromethyl resin; preferably, the modifier is a nitrogen-containing five- or six-membered heterocyclic aromatic compound, the modified chloromethyl resin is a modified chloromethyl styrene resin, and the solvent is at least one of toluene, methanol, ethanol, n-propanol, n-butanol, isobutanol, tert-butanol, tetrahydrofuran, dichloromethane, chloroform, N,N-dimethylformamide, ether, and water; more preferably, the chloromethyl resin is styrene-based, and the modifier is at least one of piperazine, imidazole, and pyridine; even more preferably, the particle size of the chloromethyl resin is 0.1 mm to 3 mm, preferably 0.3 mm to 2 mm; and the chloromethyl resin is spherical;

[0099] And / or, the mass ratio of the chloromethyl resin to the solvent is 1:(1-10), preferably 1:(2-8);

[0100] And / or, the mass ratio of the chloromethyl resin to the modifier is 1:(0.1-1.2), preferably 1:(0.15-1);

[0101] And / or, before adding the modifier, a heating step is further included; the temperature after heating is 30℃~150℃, preferably 40℃~120℃;

[0102] And / or, the mixing speed is 50 rpm to 1000 rpm, preferably 100 rpm to 800 rpm; the mixing time is 2 hours;

[0103] And / or, the modification time is 1h to 24h, preferably 2h to 18h; preferably, after modification, the product is further cooled, separated, washed and dried; more preferably, the drying temperature is 80 to 180℃ and the drying time is 1h to 48h.

[0104] And / or, the preparation method includes the step of loading the active component onto a carrier.

[0105] In one embodiment of the present invention, when the active component is loaded onto a support, the support is mixed and stirred with a metal precursor solution containing the active component, dried, and then calcined in an inactive gas atmosphere to obtain the catalyst.

[0106] In one embodiment of the present invention, the metal precursor solution containing the active component is at least one of magnesium, calcium, aluminum nitrate solution, chloride solution, and sulfate solution, and the mass concentration of the metal precursor solution containing the active component is 5% to 50%.

[0107] In one embodiment of the present invention, when the active component is loaded onto a carrier, the mass ratio of the carrier to the metal precursor solution containing the active component is 1:(1-10), preferably 1:(2-6).

[0108] And / or, the stirring rate is 100 rpm to 800 rpm, the stirring temperature is 50°C to 80°C, and the stirring time is 2 h to 8 h;

[0109] Or, the drying temperature is 80℃~180℃, and the time is 1h~48h;

[0110] And / or, the inactive gas is nitrogen or argon;

[0111] And / or, the roasting temperature is 200℃~1000℃ and the time is 1h~48h, preferably, the roasting temperature is 250℃~600℃ and the time is 2h~24h.

[0112] [Preparation method of dialkyl carbonate]

[0113] A third aspect of the present invention provides a method for preparing a dialkyl carbonate of general formula (I), comprising the step of reacting a carbonate of general formula (II) and a lower alcohol of general formula (III) in the presence of a catalyst to obtain a dialkyl carbonate of general formula (I); wherein the catalyst is the catalyst of the present invention described above or a catalyst prepared by the catalyst preparation method of the present invention described above.

[0114] R1-OCOO-R1(I)

[0115] In formula (I), each R1 is independently selected from C1-C6 alkyl groups;

[0116] R2-OCOO-R2(II)

[0117] In formula (II), each R2 is independently selected from C1-C6 alkyl groups, and at least one R2 is different from at least one R1; or two R2s are bonded to each other to form a C2-C6 alkylene group;

[0118] R1-OH(III)

[0119] In formula (III), R1 is selected from C1-C6 alkyl groups.

[0120] In one embodiment of the present invention, the reaction temperature for preparing the dialkyl carbonate represented by general formula (I) is 40°C to 130°C, preferably 50°C to 120°C. For example, 70°C, 80°C, 90°C, 110°C, and 120°C.

[0121] In one embodiment of the present invention, the reaction time for preparing the dialkyl carbonate represented by general formula (I) is 1h to 15h, preferably 2h to 12h, for example 4h, 6h, 8h, 10h.

[0122] In one embodiment of the present invention, in the preparation of the dialkyl carbonate represented by general formula (I), the molar ratio of the lower alcohol represented by general formula (III) to the carbonate represented by general formula (II) is (0.5 to 15):1, preferably (1 to 12):1, for example 4:1, 6:1, 8:1.

[0123] In one embodiment of the present invention, in the preparation of the dialkyl carbonate represented by general formula (I), the mass ratio of the catalyst to the carbonate represented by general formula (II) is (0.001 to 0.5):1, preferably (0.05 to 0.5):1. For example, 0.2:1, 0.3:1, 0.4:1.

[0124] In one embodiment of the present invention, in the dialkyl carbonate represented by general formula (I), the two R1s can be the same or different. When the two R1s are the same, the dialkyl carbonate is a symmetrical dialkyl carbonate; when the two R1s are different, the dialkyl carbonate is an asymmetrical dialkyl carbonate. In the present invention, R1 can include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and sec-butyl. Therefore, in the present invention, the dialkyl carbonate represented by general formula (I) can include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, dibutyl carbonate, etc.

[0125] In one embodiment of the present invention, in the carbonate represented by general formula (II), each R2 is independently selected from C1-C6 alkyl groups, and at least one R2 is different from at least one R1. In the present invention, R2 may include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, sec-butyl, pentyl, and hexyl.

[0126] In one embodiment of the present invention, in the carbonate of general formula (II), the two R2 atoms are linked together to form a C2-C6 alkylene group. In this case, the carbonate of general formula (II) is a cyclic carbonate, such as ethylene carbonate or propylene carbonate.

[0127] In this invention, one or more lower alcohols represented by general formula (III) may be used. Examples of lower alcohols in this invention include methanol, ethanol, propanol, isopropanol, butanol, and their isomers.

[0128] In this invention, at least one of the two R1s in the lower alcohol represented by general formula (III) is the same as that in the dialkyl carbonate represented by general formula (I).

[0129] In this invention, R2 and R1 can be the same, but at least one R2 is different from at least one R1.

[0130] In other words, in this invention, the carbonate represented by general formula (II) and the lower alcohol represented by general formula (III) undergo an ester exchange reaction, such that R1 in the lower alcohol represented by general formula (III) becomes at least one end of the dialkyl carbonate represented by general formula (I).

[0131] In one embodiment of the present invention, a method for preparing dimethyl carbonate is provided, characterized in that it includes a step of reacting alkylene carbonate and methanol in the presence of a catalyst to obtain dimethyl carbonate; wherein the catalyst is the catalyst of the present invention.

[0132] And / or, the reaction temperature is 40℃~130℃, preferably 50℃~120℃;

[0133] And / or, the reaction time is 1 hour to 15 hours, preferably 2 hours to 12 hours.

[0134] And / or, the molar ratio of methanol to alkylene carbonate is (2-15):1, preferably (3-12):1;

[0135] And / or, the mass ratio of the catalyst to the alkylene carbonate is (0.001–0.5):1, preferably (0.05–0.5):1;

[0136] And / or, the alkylene carbonate is one or more of ethylene carbonate or propylene carbonate.

[0137] The catalyst of the present invention, or the catalyst prepared by the catalyst preparation method of the present invention described above, is used in the transesterification reaction of carbonates of general formula (II) and lower alcohols of general formula (III) to prepare dialkyl carbonates. Even when repeatedly used (e.g., more than 10 times), the activity decreases by less than 5%, achieving good technical results.

[0138] As an example of the reaction conditions for preparing dialkyl carbonate, the following can be cited: The reaction is carried out at a temperature of 80°C, with a molar ratio of lower alcohol to cyclic carbonate of 8:1 and a mass ratio of catalyst to cyclic carbonate of 0.3:1, for 10 hours. Under these conditions, the conversion rate of cyclic carbonate is 80.4%, and the selectivity of dialkyl carbonate is 99.9%.

[0139] Example

[0140] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to these embodiments.

[0141] The gas chromatograph used in this invention is an Agilent 7890 chromatograph. The analytical conditions are as follows: HP-FFAP column, injection port temperature 280℃, FID detector, programmed column temperature ramping, maintaining 50℃ for 3 minutes, then increasing to 230℃ at 10℃ / min and maintaining for 10 minutes, split ratio 50:1, and component content analysis using the correction-normalization method.

[0142] The elemental analysis of heteroatom content was performed using a Therm2000 instrument.

[0143] XPS testing was performed on an X-ray photoelectron spectrometer (XPS, AXIS ULTRA DLD) from Kratos Corporation in Japan.

[0144] Metal elemental analysis was performed using ICP-OES, with the instrument being a Varian 725ES.

[0145] SEM was performed using a scanning electron microscope (SEM, Merlin) from ZEISS GmbH, Germany.

[0146] TEM images were obtained using a Tecnai 20S-TWIN transmission electron microscope at an operating voltage of 200 kV.

[0147] The conversion rate of raw materials in the example is calculated as follows: (mass of raw materials input - mass of product after reaction * content of raw materials) / mass of raw materials input * 100%.

[0148] In the examples, the selectivity of carbonates was calculated as follows: (yield of carbonate product after reaction / theoretical carbonate yield of raw materials consumed) * 100%.

[0149] The method for calculating the proportion of active metal components distributed in the pores of porous carbon supports is: (content of active metal components in the catalyst as active metal oxides - content of active metal components as active metal oxides detected by XPS) / content of active metal components in the catalyst as active metal oxides.

[0150] Example 1

[0151] This embodiment provides a method for preparing dimethyl carbonate:

[0152] Preparation of the catalyst for the preparation of dimethyl carbonate: In a 500 ml three-necked flask, 50 g of chloromethylstyrene resin and 200 ml (189.6 g) of N,N-dimethylformamide were added, and the mixture was stirred at 500 rpm for 2 h. The temperature was raised to 90 °C, and 50 g of imidazole was added. The reaction was maintained at this temperature for 12 h. After cooling, the product was separated, washed with deionized water, and dried at 100 °C for 24 h to obtain the modified resin. Then, in another... In a 500ml three-necked flask, 20g of modified resin and 100g of 8.8g magnesium nitrate were added and dissolved in water. The mixture was stirred at 500 rpm for 6 hours at 80℃, then dried in an oven at 100℃ for 14 hours. Finally, it was transferred to a muffle furnace and calcined at 500℃ for 5 hours under a nitrogen atmosphere to obtain catalyst C1. Catalyst C1 contained 10% magnesium oxide by mass. The scanning electron microscope image of catalyst C1 is shown below. Figure 1 As shown, the transmission electron microscope (TEM) image of catalyst C1 is as follows: Figure 3 As shown, the catalyst has a nitrogen content of 2.6%, a pore size of 150 nm, and a magnesium oxide content of 86.7% within the pores.

[0153] In the above catalyst preparation process, the chloromethylstyrene resin is spherical with a particle size of 0.5 mm.

[0154] Preparation of dimethyl carbonate: 22.0 g (0.25 mol) of ethylene carbonate, 64.0 g (2 mol) of methanol and 4.4 g of catalyst C1 were placed in a 100 mL autoclave and reacted at 120 °C for 4 h. The molar ratio of methanol to ethylene carbonate was 8:1 and the mass ratio of catalyst C1 to ethylene carbonate was 0.2:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene carbonate was calculated to be 80.4%, and the selectivity of dimethyl carbonate was 99.9%.

[0155] Furthermore, after the reaction was completed, the particulate catalyst in the reaction solution was filtered and recovered, washed with deionized water, and then dried in an oven at 100°C for 24 hours before being reused, under the same conditions as the dimethyl carbonate preparation process described above. After the reaction, the liquid product was analyzed by gas chromatography to calculate the ethylene carbonate conversion rate.

[0156] The catalyst was recycled 10 times, and the conversion rate of ethylene carbonate was greater than 80% in each case, while the selectivity of dimethyl carbonate remained at 99.9%.

[0157] Figure 5In the image, (a) shows a scanning electron microscope (SEM) image of the catalyst C1 prepared in Example 1 of the present invention at a 100-micrometer scale; (b) shows a scanning electron microscope image of the interior of the catalyst prepared in Example 1 of the present invention at a 10-micrometer scale. It can be seen that the outer surface of the carbon support is smooth, and magnesium oxide is mainly distributed on the inner surface of the carbon support.

[0158] Figure 6 In the image, (a) shows a scanning electron microscope (SEM) image of the interior of catalyst C1 prepared in Example 1 of the present invention at a 200 nm scale; (b) shows a scanning electron microscope (SEM) image of the interior of catalyst C1 prepared in Example 1 of the present invention at a 100 nm scale. It can be seen that the pores are partially filled, indicating that magnesium oxide is deposited inside.

[0159] Figure 7 The energy dispersive X-ray spectroscopy (EDX) spectrum and EDX spectrum of catalyst C1 prepared in Example 1 of this invention are shown; (a) Selected area scan spectrum; (b) Carbon elemental distribution map; (c) Oxygen elemental distribution map; (d) Magnesium elemental distribution map; (e) EDX spectrum. It can be seen that magnesium oxide is mainly distributed inside the carbon support, and the EDX abundance is relatively high.

[0160] Example 2

[0161] This embodiment provides a method for preparing dimethyl carbonate:

[0162] Preparation of the catalyst for the preparation of dimethyl carbonate: In a 500ml three-necked flask, 50g of chloromethylstyrene resin and 200ml (189.6g) of N,N-dimethylformamide were added and stirred at 500 rpm for 2 hours. The temperature was raised to 90℃, and 50g of imidazole was added. The reaction was maintained at this temperature for 12 hours. After cooling, the product was separated, washed with deionized water, and dried at 100℃ for 24 hours to obtain the modified resin. Then, in another 500ml three-necked flask, 20g of the modified resin and 17.6g of magnesium nitrate were added and dissolved in water to prepare a 100g solution. The mixture was stirred at 600 rpm for 8 hours at 50℃, dried in an oven at 100℃ for 24 hours, and then transferred to a muffle furnace and calcined at 400℃ for 8 hours under a nitrogen atmosphere to obtain catalyst C2. The mass percentage of magnesium oxide in catalyst C2 was 20%. The catalyst has a nitrogen content of 2.2%, a pore size of 200 nm, and a magnesium oxide content of 71.1% inside the pores.

[0163] In the above catalyst preparation process, the chloromethylstyrene resin is spherical with a particle size of 0.9 mm.

[0164] Preparation of dimethyl carbonate: 22.0 g (0.25 mol) of ethylene carbonate, 48.0 g (1.5 mol) of methanol and 4.4 g of catalyst C2 were placed in a 100 mL autoclave and reacted at 110 °C for 6 h. The molar ratio of methanol to ethylene carbonate was 6:1, and the mass ratio of catalyst C2 to ethylene carbonate was 0.2:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene carbonate was calculated to be 74.5%, and the selectivity of dimethyl carbonate was 99.9%.

[0165] Furthermore, after the reaction was completed, the particulate catalyst in the reaction solution was filtered and recovered, washed with deionized water, and then dried in an oven at 100°C for 24 hours before being reused, under the same conditions as the dimethyl carbonate preparation process described above. After the reaction, the liquid product was analyzed by gas chromatography to calculate the ethylene carbonate conversion rate.

[0166] The catalyst was recycled 10 times, and the conversion rate of ethylene carbonate was greater than 74% and the selectivity of dimethyl carbonate remained at 99.9%.

[0167] Example 3

[0168] This embodiment provides a method for preparing dimethyl carbonate:

[0169] Preparation of the catalyst for the preparation of dimethyl carbonate: In a 500ml three-necked flask, 50g of chloromethylstyrene resin and 300ml (284.4g) of N,N-dimethylformamide were added and stirred at 800 rpm for 2 hours. The temperature was raised to 80℃, and 40g of imidazole was added. The reaction was maintained at this temperature for 12 hours. After cooling, the product was separated, washed with deionized water, and dried at 120℃ for 24 hours to obtain the modified resin. Then, in another 500ml three-necked flask, 20g of the modified resin and 26.4g of magnesium nitrate were added and dissolved in water to prepare a 100g solution. The mixture was stirred at 300 rpm for 8 hours at 50℃, dried in an oven at 100℃ for 24 hours, and then transferred to a muffle furnace and calcined at 500℃ for 4 hours under a nitrogen atmosphere to obtain catalyst C3, which has a magnesium oxide content of 30%. The catalyst has a nitrogen content of 1.7%, a pore size of 250 nm, and a magnesium oxide content of 63.3% inside the pores.

[0170] In the above catalyst preparation process, the chloromethylstyrene resin is spherical with a particle size of 0.7 mm.

[0171] Preparation of dimethyl carbonate: 22.0 g (0.25 mol) of ethylene carbonate, 32.0 g (1.0 mol) of methanol and 4.4 g of catalyst C3 were placed in a 100 mL autoclave and reacted at 110 °C for 10 h. The molar ratio of methanol to ethylene carbonate was 4:1, and the mass ratio of catalyst C3 to ethylene carbonate was 0.2:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene carbonate was calculated to be 61.4%, and the selectivity of dimethyl carbonate was 99.9%.

[0172] Furthermore, after the reaction was completed, the particulate catalyst in the reaction solution was filtered and recovered, washed with deionized water, and then dried in an oven at 100°C for 24 hours before being reused, under the same conditions as the dimethyl carbonate preparation process described above. After the reaction, the liquid product was analyzed by gas chromatography to calculate the ethylene carbonate conversion rate.

[0173] The catalyst was recycled 10 times, and the conversion rate of ethylene carbonate was greater than 60% in each case, while the selectivity of dimethyl carbonate remained at 99.9%.

[0174] Example 4

[0175] This embodiment provides a method for preparing dimethyl carbonate:

[0176] Preparation of the catalyst for the preparation of dimethyl carbonate: In a 500ml three-necked flask, 50g of chloromethylstyrene resin and 300ml (284.4g) of N,N-dimethylformamide were added and stirred at 800 rpm for 2 hours. The temperature was raised to 70℃, and 30g of imidazole was added. The reaction was maintained at this temperature for 15 hours. After cooling, the product was separated, washed with deionized water, and dried at 120℃ for 24 hours to obtain the modified resin. Then, in another 500ml three-necked flask, 20g of the modified resin and 100g of 35.2g magnesium nitrate were added and dissolved in water. The mixture was stirred at 400 rpm for 2 hours at 50℃, dried in an oven at 100℃ for 24 hours, and then transferred to a muffle furnace and calcined at 500℃ for 4 hours under a nitrogen atmosphere to obtain catalyst C4, which has a magnesium oxide content of 40%. The catalyst has a nitrogen content of 1.8%, a pore size of 300 nm, and a magnesium oxide content of 63.3% inside the pores.

[0177] In the above catalyst preparation process, the chloromethylstyrene resin is spherical with a particle size of 1.0 mm.

[0178] Preparation of dimethyl carbonate: 22.0 g (0.25 mol) of ethylene carbonate, 64.0 g (2 mol) of methanol and 8.8 g of catalyst C4 were placed in a 100 mL autoclave and reacted at 90 °C for 8 h. The molar ratio of methanol to ethylene carbonate was 8:1 and the mass ratio of catalyst C4 to ethylene carbonate was 0.4:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene carbonate was calculated to be 80.9% and the selectivity of dimethyl carbonate was 99.9%.

[0179] Furthermore, after the reaction was completed, the particulate catalyst in the reaction solution was filtered and recovered, washed with deionized water, and then dried in an oven at 100°C for 24 hours before being reused, under the same conditions as the dimethyl carbonate preparation process described above. After the reaction, the liquid product was analyzed by gas chromatography to calculate the ethylene carbonate conversion rate.

[0180] The catalyst was recycled 10 times, and the conversion rate of ethylene carbonate was greater than 80% in each case, while the selectivity of dimethyl carbonate remained at 99.9%.

[0181] Example 5

[0182] This embodiment provides a method for preparing dimethyl carbonate:

[0183] Preparation of the catalyst for the preparation of dimethyl carbonate: In a 500ml three-necked flask, 50g of chloromethylstyrene resin and 300ml (284.4g) of N,N-dimethylformamide were added and stirred at 800 rpm for 2 hours. The temperature was raised to 70℃, and 30g of imidazole was added. The reaction was maintained at this temperature for 15 hours. After cooling, the product was separated, washed with deionized water, and dried at 120℃ for 24 hours to obtain the modified resin. Then, in another 500ml three-necked flask, 20g of the modified resin and 26.4g of magnesium nitrate were added and dissolved in water to prepare a 100g solution. The mixture was stirred at 400 rpm for 2 hours at 50℃, dried in an oven at 100℃ for 24 hours, and then transferred to a muffle furnace and calcined at 500℃ for 4 hours under a nitrogen atmosphere to obtain catalyst C5, which contains 30% magnesium oxide. The catalyst has a nitrogen content of 1.8%, a pore size of 180 nm, and a magnesium oxide content of 64.4% inside the pores.

[0184] In the above catalyst preparation process, the chloromethylstyrene resin is spherical with a particle size of 1.0 mm.

[0185] Preparation of dimethyl carbonate: 22.0 g (0.25 mol) of ethylene carbonate, 64.0 g (2 mol) of methanol and 6.6 g of catalyst C5 were placed in a 100 mL autoclave and reacted at 80 °C for 10 h. The molar ratio of methanol to ethylene carbonate was 8:1 and the mass ratio of catalyst C5 to ethylene carbonate was 0.3:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene carbonate was calculated to be 80.5%, and the selectivity of dimethyl carbonate was 99.9%.

[0186] Furthermore, after the reaction was completed, the particulate catalyst in the reaction solution was filtered and recovered, washed with deionized water, and then dried in an oven at 100°C for 24 hours before being reused, under the same conditions as the dimethyl carbonate preparation process described above. After the reaction, the liquid product was analyzed by gas chromatography to calculate the ethylene carbonate conversion rate.

[0187] The catalyst was recycled 10 times, and the conversion rate of ethylene carbonate was greater than 80% in each case, while the selectivity of dimethyl carbonate remained at 99.9%.

[0188] Example 6

[0189] This embodiment provides a method for preparing dimethyl carbonate:

[0190] Preparation of the catalyst for the preparation of dimethyl carbonate: In a 500ml three-necked flask, 50g of chloromethylstyrene resin and 300ml (284.4g) of N,N-dimethylformamide were added and stirred at 800 rpm for 2 hours. The temperature was raised to 70℃, and 30g of thiophene was added. The reaction was maintained at this temperature for 15 hours. After cooling, the product was separated, washed with deionized water, and dried at 120℃ for 24 hours to obtain the modified resin. Then, in another 500ml three-necked flask, 20g of the modified resin and 26.4g of magnesium nitrate were added and dissolved in water to prepare a 100g solution. The mixture was stirred at 400 rpm for 2 hours at 50℃, dried in an oven at 100℃ for 24 hours, and then transferred to a muffle furnace and calcined at 500℃ for 4 hours under a nitrogen atmosphere to obtain catalyst C6, which has a magnesium oxide content of 30%. The catalyst has a sulfur content of 2.7%, a pore size of 100 nm, and a magnesium oxide content of 66.4% inside the pores.

[0191] In the above catalyst preparation process, the chloromethylstyrene resin is spherical with a particle size of 1 mm.

[0192] Preparation of dimethyl carbonate: 22.0 g (0.25 mol) of ethylene carbonate, 64.0 g (2 mol) of methanol and 8.8 g of catalyst C6 were placed in a 100 mL autoclave and reacted at 70 °C for 8 h. The molar ratio of methanol to ethylene carbonate was 8:1 and the mass ratio of catalyst C6 to ethylene carbonate was 0.4:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene carbonate was calculated to be 80.2%, and the selectivity of dimethyl carbonate was 99.9%.

[0193] Furthermore, after the reaction was completed, the particulate catalyst in the reaction solution was filtered and recovered, washed with deionized water, and then dried in an oven at 100°C for 24 hours before being reused, under the same conditions as the dimethyl carbonate preparation process described above. After the reaction, the liquid product was analyzed by gas chromatography to calculate the ethylene carbonate conversion rate.

[0194] The catalyst was recycled 10 times, and the conversion rate of ethylene carbonate was greater than 80% in each case, while the selectivity of dimethyl carbonate remained at 99.9%.

[0195] Example 7

[0196] This embodiment provides a method for preparing dimethyl carbonate:

[0197] Preparation of the catalyst for the preparation of dimethyl carbonate: In a 500ml three-necked flask, 50g of chloromethylstyrene resin and 300ml (284.4g) of N,N-dimethylformamide were added and stirred at 800 rpm for 2 hours. The temperature was raised to 70℃, and 30g of imidazole was added. The reaction was maintained at this temperature for 15 hours. After cooling, the product was separated, washed with deionized water, and dried at 120℃ for 24 hours to obtain the modified resin. Then, in another 500ml three-necked flask, 20g of the modified resin and 8g of calcium nitrate were added and dissolved in water to prepare a 100g solution. The mixture was stirred at 300 rpm for 2 hours at 50℃, dried in an oven at 100℃ for 24 hours, and then transferred to a muffle furnace and calcined at 500℃ for 4 hours under a nitrogen atmosphere to obtain catalyst C7, which has a calcium oxide content of 20%. The catalyst has a nitrogen content of 2.2%, a pore size of 120 nm, and a calcium oxide content of 68.8% inside the pores.

[0198] In the above catalyst preparation process, the chloromethylstyrene resin is spherical with a particle size of 1.0 mm.

[0199] Preparation of dimethyl carbonate: 22.0 g (0.25 mol) of ethylene carbonate, 64.0 g (2 mol) of methanol and 8.8 g of catalyst C7 were placed in a 100 mL autoclave and reacted at 70 °C for 8 h. The molar ratio of methanol to ethylene carbonate was 8:1 and the mass ratio of catalyst C7 to ethylene carbonate was 0.4:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene carbonate was calculated to be 80.4%, and the selectivity of dimethyl carbonate was 99.9%.

[0200] Furthermore, after the reaction was completed, the particulate catalyst in the reaction solution was filtered and recovered, washed with deionized water, and then dried in an oven at 100°C for 24 hours before being reused, under the same conditions as the dimethyl carbonate preparation process described above. After the reaction, the liquid product was analyzed by gas chromatography to calculate the ethylene carbonate conversion rate.

[0201] The catalyst was recycled 10 times, and the conversion rate of ethylene carbonate was greater than 80% in each case, while the selectivity of dimethyl carbonate remained at 99.9%.

[0202] Example 8

[0203] This embodiment provides a method for preparing dimethyl carbonate:

[0204] Preparation of the catalyst for the preparation of dimethyl carbonate: In a 500ml three-necked flask, 50g of chloromethylstyrene resin and 300ml (284.4g) of N,N-dimethylformamide were added and stirred at 800 rpm for 2 hours. The temperature was raised to 70℃, and 30g of triphenylphosphine was added. The reaction was maintained at this temperature for 15 hours. After cooling, the product was separated, washed with deionized water, and dried at 120℃ for 24 hours to obtain the modified resin. Then, in another 500ml three-necked flask, 20g of the modified resin and 17.6g of magnesium nitrate were added and dissolved in water to prepare 80g of solution. The mixture was stirred at 500 rpm for 2 hours at 50℃, dried in an oven at 100℃ for 24 hours, and then transferred to a muffle furnace and calcined at 500℃ for 4 hours under a nitrogen atmosphere to obtain catalyst C8, which has a magnesium oxide content of 20%. The catalyst has a phosphorus content of 2.2%, a pore size of 150 nm, and a magnesium oxide content of 71.6% inside the pores.

[0205] In the above catalyst preparation process, the chloromethylstyrene resin is spherical with a particle size of 1.0 mm.

[0206] Preparation of dimethyl carbonate: 22.0 g (0.25 mol) of ethylene carbonate, 64.0 g (2 mol) of methanol and 8.8 g of catalyst C8 were placed in a 100 mL autoclave and reacted at 90 °C for 8 h. The molar ratio of methanol to ethylene carbonate was 8:1 and the mass ratio of catalyst C8 to ethylene carbonate was 0.4:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene carbonate was calculated to be 80.3%, and the selectivity of dimethyl carbonate was 99.9%.

[0207] Furthermore, after the reaction was completed, the particulate catalyst in the reaction solution was filtered and recovered, washed with deionized water, and then dried in an oven at 100°C for 24 hours before being reused, under the same conditions as the dimethyl carbonate preparation process described above. After the reaction, the liquid product was analyzed by gas chromatography to calculate the ethylene carbonate conversion rate.

[0208] The catalyst was recycled 10 times, and the conversion rate of ethylene carbonate was greater than 80% in each case, while the selectivity of dimethyl carbonate remained at 99.9%.

[0209] Example 9

[0210] This embodiment provides a method for preparing dimethyl carbonate:

[0211] Preparation of the catalyst for the preparation of dimethyl carbonate: In a 500ml three-necked flask, 50g of chloromethylstyrene resin and 300ml (284.4g) of N,N-dimethylformamide were added and stirred at 800 rpm for 2 hours. The temperature was raised to 70℃, and 30g of piperazine was added. After reacting at this temperature for 15 hours, the product was cooled and separated. The product was then washed with deionized water and dried at 120℃ for 24 hours to obtain the modified resin. Then, in another 500ml three-necked flask, 20g of the modified resin and 11.4g of aluminum nitrate were added and dissolved in water to make a solution of 100g. The mixture was stirred at 500 rpm for 2 hours at 50℃. After drying in an oven at 100℃ for 24 hours, the mixture was transferred to a muffle furnace and calcined at 600℃ for 4 hours under a nitrogen atmosphere to obtain catalyst C9, which has an alumina content of 20%. The catalyst has a nitrogen content of 0.8%, a pore size of 100 nm, and an alumina content of 67.6% inside the pores.

[0212] In the above catalyst preparation process, the chloromethylstyrene resin is spherical with a particle size of 1.2 mm.

[0213] Preparation of dimethyl carbonate: 22.0 g (0.25 mol) of ethylene carbonate, 64.0 g (2 mol) of methanol and 8.8 g of catalyst C9 were placed in a 100 mL autoclave and reacted at 90 °C for 8 h. The molar ratio of methanol to ethylene carbonate was 8:1 and the mass ratio of catalyst C9 to ethylene carbonate was 0.4:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene carbonate was calculated to be 80.6%, and the selectivity of dimethyl carbonate was 99.9%.

[0214] Furthermore, after the reaction was completed, the particulate catalyst in the reaction solution was filtered and recovered, washed with deionized water, and then dried in an oven at 100°C for 24 hours before being reused, under the same conditions as the dimethyl carbonate preparation process described above. After the reaction, the liquid product was analyzed by gas chromatography to calculate the ethylene carbonate conversion rate.

[0215] The catalyst was recycled 10 times, and the conversion rate of ethylene carbonate was greater than 80% in each case, while the selectivity of dimethyl carbonate remained at 99.9%.

[0216] Example 10

[0217] This embodiment provides a method for preparing dimethyl carbonate:

[0218] Preparation of the catalyst for the preparation of dimethyl carbonate: In a 500ml three-necked flask, 50g of chloromethylstyrene resin and 300ml (284.4g) of N,N-dimethylformamide were added and stirred at 800 rpm for 2 hours. The temperature was raised to 70℃, and 30g of 1-methylimidazole was added. The reaction was maintained at this temperature for 15 hours. After cooling, the product was separated, washed with deionized water, and dried at 120℃ for 24 hours to obtain the modified resin. Then, in another 500ml three-necked flask, 20g of the modified resin and 26.4g of magnesium nitrate were added and dissolved in water to prepare a 100g solution. The mixture was stirred at 500 rpm for 2 hours at 50℃, dried in an oven at 100℃ for 24 hours, and then transferred to a muffle furnace and calcined at 500℃ for 4 hours under a nitrogen atmosphere to obtain catalyst C10, which contains 30% magnesium oxide. The catalyst has a nitrogen content of 1.6%, a pore size of 150 nm, and a magnesium oxide content of 66.5% inside the pores.

[0219] In the above catalyst preparation process, the chloromethylstyrene resin is spherical with a particle size of 1.0 mm.

[0220] Preparation of dimethyl carbonate: 22.0 g (0.25 mol) of ethylene carbonate, 64.0 g (2 mol) of methanol and 6.6 g of catalyst C10 were placed in a 100 mL autoclave and reacted at 80 °C for 10 h. The molar ratio of methanol to ethylene carbonate was 8:1, and the mass ratio of catalyst C10 to ethylene carbonate was 0.3:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene carbonate was calculated to be 80.5%, and the selectivity of dimethyl carbonate was 99.9%.

[0221] Furthermore, after the reaction was completed, the particulate catalyst in the reaction solution was filtered and recovered, washed with deionized water, and then dried in an oven at 100°C for 24 hours before being reused, under the same conditions as the dimethyl carbonate preparation process described above. After the reaction, the liquid product was analyzed by gas chromatography to calculate the ethylene carbonate conversion rate.

[0222] The catalyst was recycled 10 times, and the conversion rate of ethylene carbonate was greater than 80% in each case, while the selectivity of dimethyl carbonate remained at 99.9%.

[0223] Example 11

[0224] This embodiment provides a method for preparing methyl ethyl carbonate:

[0225] Preparation of methyl ethyl carbonate: 22.5 g (0.25 mol) dimethyl carbonate, 46.0 g (1 mol) ethanol and 6.75 g catalyst C10 were placed in a 100 mL autoclave and reacted at 100 °C for 10 h. The molar ratio of ethanol to dimethyl carbonate was 4:1, and the mass ratio of catalyst C10 to dimethyl carbonate was 0.3:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of dimethyl carbonate was calculated to be 91.6%, and the selectivity of methyl ethyl carbonate was 92.4%.

[0226] Example 12

[0227] This embodiment provides a method for preparing methyl ethyl carbonate:

[0228] Preparation of methyl ethyl carbonate: 22.5 g (0.25 mol) dimethyl carbonate, 11.5 g (0.25 mol) ethanol and 4.5 g catalyst C10 were placed in a 100 mL autoclave and reacted at 100 °C for 10 h. The molar ratio of ethanol to dimethyl carbonate was 1:1, and the mass ratio of catalyst C10 to dimethyl carbonate was 0.2:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of dimethyl carbonate was calculated to be 64.5%, and the selectivity of methyl ethyl carbonate was 73.1%.

[0229] Comparative Example 1

[0230] This comparative example provides a method for preparing dimethyl carbonate:

[0231] Preparation of the catalyst for the preparation of dimethyl carbonate: In a 500ml three-necked flask, 20g of chloromethylstyrene resin and 8.8g of magnesium nitrate were added and dissolved in water to prepare a solution of 100g. The solution was stirred at 80℃ for 6 hours, then dried in an oven at 100℃ for 14 hours. Finally, it was transferred to a muffle furnace and calcined at 500℃ for 5 hours under a nitrogen atmosphere to obtain catalyst S1. The mass percentage of magnesium oxide in catalyst S1 was 10%. The scanning electron microscope image of catalyst S1 is shown below. Figure 2 As shown, the transmission electron microscope image of catalyst S1 is as follows: Figure 4 As shown in the figure. Measurements and calculations indicate that there are almost no active metal components within the pores.

[0232] In the above catalyst preparation process, the chloromethylstyrene resin is spherical with a particle size of 0.5 mm.

[0233] Preparation of dimethyl carbonate: 22.0 g (0.25 mol) of ethylene carbonate, 64.0 g (2 mol) of methanol and 4.4 g of catalyst S1 were placed in a 100 mL autoclave and reacted at 120 °C for 4 h. The molar ratio of methanol to ethylene carbonate was 8:1 and the mass ratio of catalyst S1 to ethylene carbonate was 0.2:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene carbonate was calculated to be 59.6%, and the selectivity of dimethyl carbonate was 99.8%.

[0234] Figure 8 In the image, (a) shows a scanning electron microscope (SEM) image of catalyst S1 prepared in Comparative Example 1 of the present invention at a 100-micrometer scale; (b) shows a scanning electron microscope (SEM) image of the interior of catalyst S1 prepared in Comparative Example 1 of the present invention at a 20-micrometer scale. It can be seen that the outer surface of the carbon support is rough, with magnesium oxide adhering thereto, while almost no magnesium oxide is observed on the inner surface of the carbon support.

[0235] Figure 9 In the image, (a) shows a scanning electron microscope (SEM) image of the interior of catalyst S1 prepared in Comparative Example 1 of the present invention at a 200 nm scale; (b) shows a scanning electron microscope (SEM) image of the interior of catalyst S1 prepared in Comparative Example 1 of the present invention at a 100 nm scale. It can be seen that the interior of the carbon support maintains its pore structure, and no magnesium oxide has entered.

[0236] Figure 10 The following are the energy dispersive spectroscopy (EDS) surface scan and EDX spectra of catalyst S1 prepared in Comparative Example 1 of the present invention; (a) shows the selected area surface scan spectrum; (b) shows the carbon elemental distribution map; and (c) shows the EDX spectrum. It can be seen that there is essentially no magnesium oxide distribution in the internal pores of the carbon support, and magnesium is barely detectable in the EDX results.

[0237] Comparative Example 2

[0238] This comparative example provides a method for preparing dimethyl carbonate:

[0239] Preparation of catalyst for dimethyl carbonate: 20g of magnesium nitrate was transferred into a muffle furnace and calcined at 500℃ for 5h under a nitrogen atmosphere to obtain powdered catalyst S2.

[0240] Preparation of dimethyl carbonate: 22.0 g (0.25 mol) of ethylene carbonate, 64.0 g (2 mol) of methanol and 4.4 g of catalyst S2 were placed in a 100 mL autoclave and reacted at 120 °C for 4 hours. The molar ratio of methanol to ethylene carbonate was 8:1, and the mass ratio of catalyst S2 to ethylene carbonate was 0.2:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene carbonate was calculated to be 32.7%, and the selectivity of dimethyl carbonate was 99.9%.

[0241] Comparative Example 3

[0242] This comparative example provides a method for preparing dimethyl carbonate:

[0243] Preparation of the catalyst for dimethyl carbonate: 20g of styrene resin and 8.8g of magnesium nitrate were added to a 500ml three-necked flask and dissolved in water to prepare a 100g solution. The solution was stirred at 80℃ for 6 hours, then dried in an oven at 100℃ for 14 hours. Finally, it was transferred to a muffle furnace and calcined at 500℃ for 5 hours under a nitrogen atmosphere to obtain catalyst S3. The mass percentage of magnesium oxide in catalyst S3 was 6.5%. Measurements and calculations showed that there was almost no active metal component within the pores.

[0244] In the above catalyst preparation process, the chloromethylstyrene resin is spherical with a particle size of 0.5 mm.

[0245] Preparation of dimethyl carbonate: 22.0 g (0.25 mol) of ethylene carbonate, 64.0 g (2 mol) of methanol and 4.4 g of catalyst S3 were placed in a 100 mL autoclave and reacted at 120 °C for 4 h. The molar ratio of methanol to ethylene carbonate was 8:1 and the mass ratio of catalyst S3 to ethylene carbonate was 0.2:1. After the reaction was completed, the autoclave was cooled to room temperature and vented. The liquid product was analyzed by gas chromatography, and the conversion rate of ethylene carbonate was calculated to be 39.4%, and the selectivity of dimethyl carbonate was 99.9%.

[0246] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A porous carbon-supported catalyst for the preparation of dialkyl carbonates, characterized in that, It comprises a porous carbon support, an active metal component, and at least one heteroatom selected from nitrogen, sulfur, and phosphorus. The porous carbon support content is 50% to 99% relative to the total mass of the catalyst, the active metal component content is 0.1% to 50% based on active metal oxides, and the heteroatom content is 0.1% to 5% based on elements. The active metal is at least one selected from magnesium, aluminum, and calcium. The active metal component, based on active metal oxides, accounts for more than 50% of the total active metal component content in the catalyst and is distributed in the pores of the porous carbon support. The active metal exists in the form of metal oxides.

2. The catalyst according to claim 1, characterized in that, The porous carbon support has a particle size of 0.1 mm to 3 mm and a pore size of 5 to 500 nm.

3. The catalyst according to claim 1 or 2, characterized in that, It satisfies at least one of the following conditions: Based on active metal oxides, the content of active metal components distributed in the pores of the porous carbon support accounts for more than 55% of the total content of active metal components in the catalyst. The porous carbon support content is 55-90% relative to the total mass of the catalyst, and the active metal component content, calculated as active metal oxides, is 5-45%; and The content of heteroatoms, calculated by element, is 0.3% to 4.5%.

4. The catalyst according to claim 1 or 2, characterized in that, Based on active metal oxides, the content of active metal components distributed on the outer surface of the porous carbon support, as determined by XPS, is less than 45% relative to the total content of all active metal components in the catalyst.

5. The catalyst according to claim 1 or 2, characterized in that, It satisfies at least one of the following conditions: The porous carbon support has a particle size of 0.3 mm to 2 mm and a pore size of 50 to 300 nm. Based on active metal oxides, the content of active metal components distributed in the pores of the porous carbon support accounts for more than 70% of the total content of active metal components in the catalyst. The content of porous carbon support relative to the total mass of the catalyst is 60-85%, and the content of active metal component, calculated as active metal oxide, is 10-40%. The heteroatom content, calculated by element, is 0.5%–4%; and Based on active metal oxides, the content of active metal components distributed on the outer surface of the porous carbon support, as determined by XPS, is less than 30% relative to the total content of all active metal components in the catalyst.

6. A method for preparing a porous carbon-supported catalyst according to any one of claims 1-5, comprising the following steps: (1) A modification step of contacting the halogenated alkylated resin with a modifier to modify it and obtain the modified halogenated alkylated resin. (2) A contacting step in which the modified haloalkylated resin is contacted with a metal precursor of an active metal to obtain a contact product; and (3) A calcination step in which the contact product is optionally dried and then calcined in an inert gas atmosphere. The modifier is at least one compound selected from nitrogen-containing compounds, sulfur-containing compounds, and phosphorus-containing compounds, and the active metal is at least one selected from magnesium, aluminum, and calcium.

7. The method for preparing the catalyst according to claim 6, wherein, Step (1) satisfies at least one of the following conditions: Halogenated alkylated resins are halogenated methylated resins; The modifier is at least one of alkylamines, 5- or 6-membered nitrogen-containing heterocyclic aromatic compounds, thiophenes, and triphenylphosphine. The mass ratio of the halogenated alkylated resin to the modifier is 1:(0.1-1.2); The modification step is carried out in a solvent, which is selected from at least one of toluene, methanol, ethanol, n-propanol, n-butanol, isobutanol, tert-butanol, tetrahydrofuran, dichloromethane, chloroform, N,N-dimethylformamide, ether, and water, and the mass ratio of the halogenated alkylating resin to the solvent is 1:(1-10). The temperature of the modification step is 30℃~150℃; The modification time for the modification step is 1 hour to 24 hours; The modification step is carried out under mixing and stirring at a speed of 50 rpm to 1000 rpm. In the modification step, the obtained modified halogenated alkyl resin is washed and dried. The drying conditions are: drying temperature 80℃~180℃ and drying time 1h~48h.

8. The method for preparing the catalyst according to claim 6, wherein, Step (2) satisfies at least one of the following conditions: The metal precursor of the active metal is at least one of the nitrate, chloride, and sulfate forms of the active metal. The mass ratio of the modified haloalkylated resin to the metal precursor of the active metal is 1:0.1-3; The metal precursor of the active metal is contacted in solution with the modified haloalkylated resin obtained in step (1), and the solvent for the contacting step is at least one selected from toluene, methanol, ethanol, n-propanol, n-butanol, isobutanol, tert-butanol, tetrahydrofuran, dichloromethane, chloroform, N,N-dimethylformamide, ether, and water. Step (2) is carried out under mixing and stirring conditions, wherein the mixing and stirring rate is 100 rpm to 800 rpm; the mixing and stirring temperature is 30℃ to 100℃; and the mixing and stirring time is 1h to 10h.

9. The method for preparing the catalyst according to claim 6, wherein, Step (3) satisfies at least one of the following conditions: The contact product obtained in step (2) is dried under the following conditions: temperature 80℃~180℃, time 1h~48h. The inactive gas is at least one of nitrogen and rare gases; The roasting temperature is 200℃~1000℃, and the roasting time is 1h~48h.

10. The method for preparing the catalyst according to claim 6, wherein at least one of the following conditions is satisfied: In step (1), the halogenated alkylating resin is chloromethylated styrene resin; In step (1), the modifier is at least one of methylamine, ethylamine, hexylamine, propylamine, dimethylamine, diethylamine, piperazine substituted with C1-C6 alkyl, pyridine substituted with C1-C6 alkyl, imidazole substituted with C1-C6 alkyl, quinoline substituted with C1-C6 alkyl, pyrrole substituted with C1-C6 alkyl, indole substituted with C1-C6 alkyl, carbazole substituted with C1-C6 alkyl, isoindole substituted with C1-C6 alkyl, thiazole substituted with C1-C6 alkyl, thiophene substituted with C1-C6 alkyl, and triphenylphosphine. In step (1), the mass ratio of the halogenated alkylated resin to the modifier is 1:(0.15-1); In step (1), the modification step is carried out in a solvent, and the mass ratio of the halogenated alkylating resin to the solvent is 1:(2-8); In step (1), the temperature of the modification step is 40℃~120℃; In step (1), the modification time of the modification step is 2h to 18h; In step (1), the modification step is carried out under mixing and stirring, and the mixing and stirring rate is 100 rpm to 800 rpm; In step (2), the mass ratio of the modified haloalkylated resin to the metal precursor of the active metal is 1:0.2 to 2; Step (2) is carried out under mixing and stirring conditions, wherein the mixing and stirring rate is 200 rpm to 600 rpm; the mixing and stirring temperature is 50℃ to 80℃; and the mixing and stirring time is 2h to 8h. In step (3), the contact product obtained in step (2) is dried under the following conditions: temperature 90℃~150℃, time 2h~36h; and In step (3), the roasting temperature is 250℃~900℃ and the roasting time is 2h~24h.

11. A method for preparing dialkyl carbonates represented by the following general formula (I), characterized in that, Under the action of the catalyst described in any one of claims 1-5 or the catalyst prepared by the preparation method according to any one of claims 6-10, the carbonate represented by general formula (II) and the lower alcohol represented by general formula (III) are reacted to obtain the dialkyl carbonate represented by general formula (I). R1-OCOO-R1 (I) In formula (I), each R1 is independently selected from C1-C6 alkyl groups; R2-OCOO-R2 (II) In formula (II), each R2 is independently selected from C1-C6 alkyl groups, and at least one R2 is different from at least one R1; or two R2s are bonded to each other to form a C2-C6 alkylene group; R1-OH (III) In formula (III), R1 is selected from C1-C6 alkyl groups.

12. The preparation method according to claim 11, characterized in that, At least one of the following conditions must be met: The reaction temperature is 40℃~130℃; The reaction time is 1 hour to 15 hours.

13. The preparation method according to claim 11 or 12, characterized in that, At least one of the following conditions must be met: The molar ratio of the lower alcohol represented by general formula (III) to the carbonate represented by general formula (II) is (0.5-15):1; The mass ratio of the catalyst to the carbonate represented by general formula (II) is (0.05-0.5):1; In equation (I), the two R1s are identical; and In formula (II), the two R2s are bonded to each other to form a C2-C6 alkylene group.

14. The preparation method according to claim 11, characterized in that, At least one of the following conditions must be met: The carbonate represented by general formula (II) is at least one of ethylene carbonate and propylene carbonate. The lower alcohol is selected from at least one of methanol, ethanol, propanol, isopropanol, and butanol; The dialkyl carbonate represented by general formula (I) is at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, and dibutyl carbonate.

15. The preparation method according to claim 11, characterized in that, At least one of the following conditions must be met: The reaction temperature is 50℃~120℃; The reaction time is 2 hours to 12 hours. The molar ratio of the lower alcohol represented by general formula (III) to the carbonate represented by general formula (II) is (1-12):1; and The mass ratio of the catalyst to the carbonate represented by general formula (II) is (0.05-0.5):1.

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