CN113563189B - One-step method for efficiently catalyzing CO 2 Method for converting dimethyl carbonate catalyst - Google Patents
One-step method for efficiently catalyzing CO 2 Method for converting dimethyl carbonate catalyst Download PDFInfo
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- B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
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- B01J31/0281—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature containing nitrogen as cationic centre the nitrogen being a ring member
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- B01J31/0298—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature the ionic liquids being characterised by the counter-anions
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Abstract
One-step method for efficiently catalyzing CO 2 A method for converting dimethyl carbonate catalyst relates to a method for preparing catalyst, which synthesizes ionic liquid 1-ethyl-3-methylimidazolium salt ([ Emim) with high thermal stability and strong alkalinity and new structure]IM), alkali strength 18.4<H ‑ <22.3, equivalent to sodium tert-butoxide, alkali content of 2.83 mmol/g and decomposition temperature higher than 144 ℃. The catalyst realizes PO and CO 2 And MeOH starting material high yield (36.27%) dimethyl carbonate (DMC) was synthesized in one step and the TON value was 37.04. A new process route for synthesizing DMC by a two-stage linkage method without catalyst separation is developed: first catalyze PO and CO 2 Cycloaddition reaction is carried out, the conversion rate of 97.40% PO and the PC yield close to 97.40% are achieved under mild conditions, and TON value is 99.49; then MeOH is introduced for transesterification, [ Emim ]]The IM synthesis process is simple and environment-friendly, has strong alkalinity, high thermal stability and excellent catalytic activity, and has important industrial application value in the field of carbonate synthesis.
Description
Technical Field
The invention relates to a method for preparing a catalyst, in particular to a one-step method for efficiently catalyzing CO 2 A method for converting dimethyl carbonate catalyst.
Belongs to the field of chemistry and chemical engineering, and the industry of synthesizing carbonic ester. In particular, to a catalytic CO 2 A novel synthesis method of high-efficiency strong alkaline ionic liquid for efficiently converting into dimethyl carbonate in one step and a two-stage fixed bed series reaction process based on the catalyst.
Background
The transitional consumption of fossil energy causes CO in the atmosphere 2 、CH 4 The gas content of the isothermal chamber exceeds the standard, so that global warming, extreme weather and sea level are continuously increased, and the human living environment is continuously deteriorated. From the aspects of carbon neutralization and environmental protection, the energy end product CO 2 As a nontoxic and cheapThe conversion of valuable and renewable carbon resources with low energy consumption into valuable chemicals has important academic value and application prospect, and is the optimal strategy for sustainable development of human beings.
By CO 2 And the coal chemical industry platform compound methanol (MeOH) direct or indirect synthesis of dimethyl carbonate (DMC) are of great interest. DMC has faint scent, is a non-toxic, readily biodegradable and environmentally friendly commodity chemical. The number of oxygen atoms in the molecule is more than 53%, and the molecule contains rich functional groups, so that various chemical reactions can be performed. DMC has wide application, and can be used as monomer for synthesizing five engineering plastic polycarbonate, synthesized pesticide and medical intermediate, green solvent, lithium ion battery solvent, etc. Can also be added into gasoline to improve the octane number of the gasoline, enhance shock resistance and obviously reduce PM2.5 and NOx emission.
DMC synthesis methods include direct synthesis, urea alcoholysis, direct/indirect oxidative carbonylation of methanol, and transesterification. Wherein CO is 2 Direct synthesis of DMC with MeOH is simple, intrinsically safe, but limited by thermodynamic constraints (DeltarH2= -27.9 kJ/mol, deltarGθ= 32.6 kJ/mol), exothermic and not spontaneously occurring, while CO 2 The chemical inertness and the by-product water can not remove the reaction system in time, so that the balance limit and other factors are caused, and the DMC yield is lower. The urea alcoholysis route has the advantages of low cost, easy obtaining of raw materials and relatively low production cost, and benefits from the scale effect of the synthetic ammonia. However, the intermediate methyl carbamate is easy to decompose into byproducts such as isocyanic acid, and the like, so that the reaction equipment is blocked, and the continuous operation stability of the device in the demonstration process is poor, and the DMC yield is low. The CO gas phase/liquid phase oxidative carbonylation method has cheap and easily obtained raw materials, mainly generates DMC and water, and has few byproducts. The indirect oxidative carbonylation process is the oxo-synthesis of DMC from MeOH via the intermediate methyl nitrite. The cost of raw materials is low, the process is simple, and the DMC yield is high; however, the Cl-containing catalyst and NOx are used as oxidizing agents to circulate, so that a large amount of acid-containing wastewater is generated, and various byproducts of oxygen-containing compounds such as dimethyl oxalate, methyl formate and the like are generated. Direct oxidative carbonylation of methanol process O 2 Directly participate in, the accessory substances are more, and potential safety hazards exist. Starting from Propylene Oxide (PO) or Ethylene Oxide (EO) with CO 2 After Propylene Carbonate (PC) and Ethylene Carbonate (EC) are obtained by cycloaddition, DMC is obtained by transesterification of MeOH and by-product 1, 2-propanediol or ethylene glycol is obtained, and the process has the advantages of mild reaction condition, good catalytic activity, relatively simple process, high product yield, high purity and the like. Compared with other DMC synthetic routes, the transesterification method is a more environment-friendly and efficient synthetic route and is a main DMC industrial production method in China.
Wen et al have first studied on KHCO 3 As catalyst, high temperature (140 ℃) and high pressure (CO 2 Pressure 12 MPa) PO, CO 2 DMC was synthesized in one step from MeOH reactant. The reaction was carried out for 6 hours, the PO conversion rate reached 96.87%, but the DMC yield was only 16.84%. Chun et al reacted with choline chloride/MgO as catalyst at 120℃and 2.5 MPa for 6 h with DMC yields up to 65.4% and after 4 repeated uses the DMC yields down to 12.58%. Chen et al uses a 1-butyl-3-methylimidazole tetrafluoroborate and sodium methoxide composite catalyst, and realizes that the conversion rate of PO reaches 95% and the DMC yield reaches 67.5% at a high temperature of 150 ℃. However, the ionic liquid is incompatible with sodium methoxide powder and cannot be separated from the reaction system, so that the ionic liquid is difficult to reuse. Tia et al uses tetrabutylammonium bromide and tertiary amine composite catalyst at high temperature 150 ℃ and higher CO 2 The reaction is carried out under the initial pressure of 15 MPa, the conversion rate of PO reaches 98 percent, and the yield of DMC reaches 84 percent. In summary, the existing one-step synthesis of DMC by taking PO as a reaction raw material has the defects of overhigh reaction temperature and higher CO 2 The initial pressure is that the composite catalyst with more than two components of quaternary ammonium salt or halogen and strong alkali salt is adopted, so that the catalyst is difficult to reuse.
Disclosure of Invention
The invention aims to provide a one-step method for efficiently catalyzing CO 2 The invention provides a method for converting methyl carbonate into methyl carbonate by catalyzing CO2 by a strong alkaline ionic liquid with single component, novel structure, high temperature resistance and high stability, and provides a novel process for synthesizing methyl carbonate by one step by using a fixed bed at two ends of the catalyst without separation based on the developed homogeneous ionic liquid catalyst.
The invention aims at realizing the following technical scheme:
one-step method for efficiently catalyzing CO 2 A process for converting a dimethyl carbonate catalyst, the process comprising the steps of:
propylene oxide, CO 2 And reacting with methanol as a raw material, and obtaining the dimethyl carbonate by using the homogeneous ionic liquid catalyst with high yield.
New two-stage chain reaction process without separation of catalyst, first stage fixed bed reactor, catalyst first catalyzed epoxypropane and CO 2 Synthesizing propylene carbonate; then, the catalyst is mixed with methanol and cooled, and then enters a second-stage reaction-rectifying tower, dimethyl carbonate-methanol azeotrope is extracted from the tower top, and the tower bottom is 1, 2-propanediol to realize CO 2 And propylene oxide is synthesized into dimethyl carbonate in one step with high yield;
the catalyst is an ionic liquid;
the ionic liquid comprises cations and anions;
both the anions and cations contain nitrogen-containing heterocycles.
The one-step method is used for efficiently catalyzing CO 2 Method for converting dimethyl carbonate catalyst, wherein the reaction temperature is 100-130 ℃, the reaction time is 2-9 h, and CO 2 The initial pressure is 1.8-3.8 MPa, and the catalyst dosage is 0.5-10% of the mass of the raw material PO; the reaction temperature in the transesterification process is 68 ℃;
preferably, the reaction temperature is 120 ℃;
preferably, the reaction time is 9 h;
preferably, the CO 2 The initial pressure is 2.6 MPa;
preferably, the catalyst is used in an amount of 3% by mass of the raw material PO;
preferably, the transesterification temperature is 68 ℃;
preferably, the cation has the formulaOr->The structure shown;
the anions have the formula[ MEANS FOR SOLVING PROBLEMS ]>Or->The structure shown;
wherein R is 1 Independently selected from one of C1-C6 alkyl, C2-C6 alkenyl and C3-C6 aryl;
preferably, the molar ratio of the epoxypropane to the carbon dioxide to the methanol in the raw material containing the epoxypropane to the carbon dioxide to the methanol is 1:1:10-1:2.8:15;
preferably, the molar ratio of the propylene oxide to the carbon dioxide in the raw material containing the propylene oxide to the carbon dioxide is 1:1-1:2.8;
preferably, the molar ratio of propylene carbonate to methanol in the raw material containing propylene carbonate to methanol is 1:10;
preferably, the reaction time is 2-9 hours;
preferably, a chemical equilibrium is reached within reaction 9h at 120 ℃;
preferably, the reaction is carried out at 68 ℃ for 30 min to reach chemical equilibrium;
preferably, R 1 、R 2 Independently selected from-CH 3 、-CH 2 CH 3 、-(CH 2 ) 2 CH 3 、-(CH 2 ) 3 CH 3 One of them.
The one-step method is used for efficiently catalyzing CO 2 A method for converting a dimethyl carbonate catalyst, wherein the catalyst is an ionic liquid.
The one-step method is used for efficiently catalyzing CO 2 A method for converting dimethyl carbonate catalyst, the preparation of the ionic liquid comprising the steps of:
a1 Adding alkali into the solution I containing the ionic liquid anion source, and reacting to obtain ionic liquid anion metal salt;
a2 Dissolving the ionic liquid anion metal salt in a solvent, adding the ionic liquid cation salt, and reacting to obtain the ionic liquid.
The one-step method is used for efficiently catalyzing CO 2 A method for converting dimethyl carbonate catalyst, in the step a 1), the solvent in the solution I is at least one selected from ethanol, benzene, toluene and xylene;
the alkali is organic alkali or inorganic alkali;
the organic base comprises sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium methoxide, potassium ethoxide or potassium tert-butoxide;
the inorganic base includes lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide;
the ionic liquid anion metal salt is at least one selected from ionic liquid anion Li salt, anion Na salt, anion K salt and ionic liquid anion Cs salt;
preferably, in the step a 1), in the solution I, the concentration of the ionic liquid anion source is 0.05-0.8 g/mL;
the molar ratio of the ionic liquid anion source to the alkali is 0.9-1.1;
preferably, in step a 1), the ionic liquid anion source comprises imidazole, pyrrole or morpholine;
preferably, in step a 1), the reaction conditions are: reacting for 24 hours in ice bath;
preferably, step a 1) further comprises: after the reaction is finished, removing the solvent to obtain imidazole anion salt, pyrrole anion salt or morpholine anion salt;
preferably, in step a 2), the solvent comprises a water-carrying agent;
the water carrying agent is at least one selected from methanol, ethanol, benzene, toluene and xylene;
the ionic liquid cation salt is selected from 1-R 1 -3-methyl-imidazole bromide, 1-R 1 -3-methyl-imidazole iodonium salt, N-methyl-N-R 2 Morpholine bromide, N-methyl-N-
R 2 -at least one of morpholinodinium salts;
preferably, in step a 2), the ratio of the ionic liquid anionic metal salt to the solvent is 0.1-0.9: 0.05-1.2 g/mL;
preferably, in step a 2), the reaction conditions are: reaction 24 h at room temperature;
preferably, step a 2) further comprises: and after the reaction is finished, removing the solvent to obtain the high-purity ionic liquid.
The one-step method is used for efficiently catalyzing CO 2 A method for converting a dimethyl carbonate catalyst, wherein the method comprises a two-stage chain reaction process without separating the catalyst; first stage fixed bed reactor, catalyst first catalyzes epoxypropane and CO 2 Synthesizing propylene carbonate; then, the catalyst is directly fed into a second-stage reaction-rectifying tower after being mixed with methanol for cooling without separation, dimethyl carbonate-methanol azeotrope is extracted from the tower top, and the tower bottom is 1, 2-propylene glycol to realize CO 2 And propylene oxide is used for synthesizing dimethyl carbonate in one step and high yield.
The invention has the advantages and positive effects that:
1. the invention provides a high-efficiency one-step catalytic CO 2 The synthesized ionic liquid with a new structure has the characteristics of high temperature resistance, high stability and strong alkalinity, and can efficiently catalyze cycloaddition and transesterification.
2. The catalyst provided by the invention does not need a separated two-stage chain reaction process, so that the reaction flow can be obviously shortened, and the production energy consumption can be reduced.
Drawings
FIG. 1 (A) is a photograph of imidazole potassium synthesized in example 1 of the present invention;
FIG. 1 (B) is a photograph of a [ Emim ] Im ionic liquid synthesized in example 1 of the present invention;
FIG. 2 is a nuclear magnetic H spectrum of [ Emim ] Im ionic liquid synthesized in example 1 of the present invention;
FIG. 3 is a nuclear magnetic C spectrum of [ Emim ] Im ionic liquid synthesized in example 1 of the present invention;
FIG. 4 is an infrared plot of [ Emim ] Im ionic liquid synthesized in example 3 of the present invention;
FIG. 5 is a thermal gravimetric-differential plot of [ Emim ] Im ionic liquids synthesized in example 4 of the present invention;
FIG. 6 is a single component ionic liquid catalyzed CO of example 5 of the present invention 2 Synthesizing DMC reaction effect in one step;
FIG. 7 shows the effect of the PO cycloaddition reaction catalyzed by the [ Emim ] IM in example 6 KI, TBAB of the present invention;
FIG. 8 shows the effect of the invention on the transesterification reaction of carbonate catalyzed by example 6 KI, TBAB and [ Emim ] IM;
FIG. 9 is a graph showing the effect of reaction temperature on cycloaddition reaction in example 7 of the present invention;
FIG. 10 is a graph showing the effect of reaction time on cycloaddition in example 8 of the present invention;
FIG. 11 is a diagram of example 9 CO of the present invention 2 Influence of initial pressure on cycloaddition reaction;
FIG. 12 is a graph showing the effect of catalyst content on cycloaddition reaction in example 10 of the present invention;
FIG. 13 is a graph showing the effect of reaction time on DMC yield at various temperatures for example 11 according to the present invention;
FIG. 14 shows the recycling effect of the catalyst of example 12 of the present invention;
FIG. 15 shows the mechanism of the cycloaddition and transesterification reaction presumed in example 13 of the present invention.
Detailed Description
The present invention will be described in detail below with reference to the embodiments shown in the drawings, but the present invention is not limited to these embodiments.
Emim synthesized in the first-stage fixed bed reactor of the present invention]IM ionic liquids first catalyze PO and CO 2 And synthesizing PC. WhileThen, the catalyst is not separated, mixed with MeOH and cooled, and then enters a second-stage reaction-rectifying tower, DMC-MeOH azeotrope is extracted from the tower top, and the tower bottom is 1, 2-propanediol, so as to realize CO 2 And PO are not separated, DMC and co-product 1, 2-propanediol are synthesized in one step with high yield.
The first section of fixed bed reactor screens out the optimal cycloaddition reaction condition: the mass of the catalyst is 3% of the mass of PO, the reaction temperature is 120 ℃, and the CO is 2 The initial pressure is 2.6 MPa, the reaction time is 9 hours, the PO conversion rate is up to 97.40%, and the PC selectivity is more than 99%. And then, the reaction product enters a second-stage reaction-rectifying tower to react, meOH with 10 times of the molar weight of the theoretical generated PC is added for transesterification, the DMC yield reaches 83.63 percent and the selectivity reaches 99 percent under the condition of the reaction temperature of 68 ℃, and the catalyst reaches the fact of synthesizing DMC by ultra-high catalysis. The catalyst was reused seven times without significant deactivation. The prepared novel strong alkaline ionic liquid is directly used for replacing potassium iodide, tetrabutylammonium bromide, potassium methoxide, sodium methoxide and conventional imidazole ionic liquid. [ Emim ]]The IM synthesis process is simple and environment-friendly, has strong alkalinity, high thermal stability and excellent catalytic activity, and has important industrial application prospect in the field of carbonate synthesis.
The preparation method of the dimethyl carbonate is characterized by comprising the following steps of:
propylene oxide, CO 2 And reacting with methanol as a raw material, and obtaining the dimethyl carbonate by using the homogeneous ionic liquid catalyst with high yield.
New two-stage chain reaction process without separation of catalyst, first stage fixed bed reactor, catalyst first catalyzed epoxypropane and CO 2 Synthesizing propylene carbonate. Then, the catalyst is mixed with methanol and cooled, and then enters a second-stage reaction-rectifying tower, dimethyl carbonate-methanol azeotrope is extracted from the tower top, and the tower bottom is 1, 2-propanediol to realize CO 2 And propylene oxide is used for synthesizing dimethyl carbonate in one step and high yield.
The catalyst is an ionic liquid;
the ionic liquid comprises cations and anions;
both the anions and cations contain nitrogen-containing heterocycles.
The reaction temperature is 100-130 ℃, the reaction time is 2-9 h, and CO 2 The initial pressure is 1.8-3.8 MPa, and the catalyst dosage is 0.5-10% of the mass of the raw material PO; the reaction temperature in the transesterification process is 68 ℃;
preferably, the reaction temperature is 120 ℃;
preferably, the reaction time is 9 h;
preferably, the CO 2 The initial pressure is 2.6 MPa;
preferably, the catalyst is used in an amount of 3% by mass of the raw material PO;
preferably, the transesterification temperature is 68 DEG C
Preferably, the cation has the formulaOr->The structure shown;
the anions have the formula[ MEANS FOR SOLVING PROBLEMS ]>Or->The structure shown;
wherein R is 1 Independently selected from one of C1-C6 alkyl, C2-C6 alkenyl and C3-C6 aryl;
preferably, the molar ratio of the epoxypropane to the carbon dioxide to the methanol in the raw material containing the epoxypropane to the carbon dioxide to the methanol is 1:1:10-1:2.8:15;
preferably, the molar ratio of the propylene oxide to the carbon dioxide in the raw material containing the propylene oxide to the carbon dioxide is 1:1-1:2.8;
preferably, the molar ratio of propylene carbonate to methanol in the raw material containing propylene carbonate to methanol is 1:10;
preferably, the reaction time is 2-9 hours;
preferably, a chemical equilibrium is reached within reaction 9h at 120 ℃;
preferably, the reaction is carried out at 68 ℃ for 30 min to reach chemical equilibrium;
preferably, R 1 、R 2 Independently selected from-CH 3 、-CH 2 CH 3 、-(CH 2 ) 2 CH 3 、-(CH 2 ) 3 CH 3 One of them.
The catalyst is an ionic liquid; the preparation method of the ionic liquid comprises the following steps:
a1 Adding alkali into the solution I containing the ionic liquid anion source, and reacting to obtain ionic liquid anion metal salt;
a2 Dissolving the ionic liquid anion metal salt in a solvent, adding the ionic liquid cation salt, and reacting to obtain the ionic liquid.
The solvent in the solution I is at least one selected from ethanol, benzene, toluene and xylene;
the alkali is organic alkali or inorganic alkali;
the organic base comprises sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium methoxide, potassium ethoxide or potassium tert-butoxide;
the inorganic base includes lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide;
the ionic liquid anion metal salt is at least one selected from ionic liquid anion Li salt, anion Na salt, anion K salt and ionic liquid anion Cs salt;
preferably, in the step a 1), in the solution I, the concentration of the ionic liquid anion source is 0.05-0.8 g/mL;
the molar ratio of the ionic liquid anion source to the alkali is 0.9-1.1;
preferably, in step a 1), the ionic liquid anion source comprises imidazole, pyrrole or morpholine;
preferably, in step a 1), the reaction conditions are: reacting for 24 hours in ice bath;
preferably, step a 1) further comprises: after the reaction is finished, removing the solvent to obtain imidazole anion salt, pyrrole anion salt or morpholine anion salt;
preferably, in step a 2), the solvent comprises a water-carrying agent;
the water carrying agent is at least one selected from methanol, ethanol, benzene, toluene and xylene;
the ionic liquid cation salt is selected from 1-R 1 -3-methyl-imidazole bromide, 1-R 1 -3-methyl-imidazole iodonium salt, N-methyl-N-R 2 Morpholine bromide, N-methyl-N-
R 2 -at least one of morpholinodinium salts;
preferably, in step a 2), the ratio of the ionic liquid anionic metal salt to the solvent is 0.1-0.9: 0.05-1.2 g/mL;
preferably, in step a 2), the reaction conditions are: reaction 24 h at room temperature;
preferably, step a 2) further comprises: and after the reaction is finished, removing the solvent to obtain the high-purity ionic liquid.
The catalyst does not need a new process of separated two-stage chain reaction, the first stage of fixed bed reactor, and the catalyst firstly catalyzes epoxypropane and CO 2 Synthesizing propylene carbonate. Then, the catalyst is directly fed into a second-stage reaction-rectifying tower after being mixed with methanol for cooling without separation, dimethyl carbonate-methanol azeotrope is extracted from the tower top, and the tower bottom is 1, 2-propylene glycol to realize CO 2 And propylene oxide is used for synthesizing dimethyl carbonate in one step and high yield.
As one embodiment, the catalyst is a homogeneous strong base ionic liquid.
The preparation method of the homogeneous phase strong alkaline ionic liquid catalyst comprises the following steps:
(1) Imidazole potassium salt synthesis: 34 Dissolving g (0.5 mol) imidazole in 500 mL absolute ethyl alcohol at room temperature, slowly adding 28 g (0.5 mol) KOH powder under ice bath condition, continuously stirring for 24 h until the mixture is completely dissolved, filtering the mixed product, carrying out reduced pressure rotary distillation on the filtrate at 80 ℃ for 1h, separating generated water and ethanol solvent, and cooling to room temperature to obtain brown solid imidazole potassium salt, wherein the yield of imidazole potassium reaches 96.62 percent through calculation.
(2) 1-ethyl-3-methyl-imidazole salt [ Emim ] IM synthesis: taking 57.3 g (0.23 mol) of methanol solution containing 75% of 1-ethyl-3-methylimidazole bromine salt by mass, adding 200 mL of absolute ethyl alcohol, and stirring at room temperature for 20 min. 23.85 g (0.23 mol) of potassium imidazole was slowly added and the temperature was controlled to around 25℃to give a large amount of KBr as a white precipitate, which was stirred continuously for 24. 24 h and then filtered. Rotary distillation at 65 deg.c under-0.1 MPa pressure of 2.2 h to obtain viscous yellow liquid 38.92-g, 1-ethyl-3-methyl-imidazole salt [ Emim ] IM, with a calculated yield of 95.07%.
The imidazole ionic liquid has the following reaction formula
The homogeneous catalyst is high-purity active ionic liquid, and the purity is more than 99%.
In the present invention, "[ Emim ] Im" means 1-ethyl-3-methylimidazole salt.
In the present invention, "PO" refers to cyclopropane.
In the present invention, "MeOH" refers to methanol.
In the present invention, "PC" means propylene carbonate.
In the present invention, "DMC" refers to dimethyl carbonate.
In the present invention, "PG" is 1, 2-propanediol.
In the present invention, "PM1" is 1-methoxy-2-propanol.
In the present invention, "PM2" is 2-methoxy-1-propanol.
In the present invention, "HPMC" is 1-hydroxy-2-propylmethyl carbonate.
In the present invention, "HMC" is 2-hydroxypropyl methyl carbonate.
In the present invention, C1 to C6 refer to the number of carbon atoms contained. The term "C1-C6 alkyl" refers to an alkyl group having 1-6 carbon atoms.
In the present invention, the "alkanyl" is a group formed by losing any one of the hydrogen atoms on the molecule of the alkane compound. The alkane compound comprises straight-chain alkane, branched alkane, cycloparaffin and cycloparaffin with branched chains.
In the present invention, the "alkylene group" is a group formed by losing any one of hydrogen atoms on an olefin compound molecule.
In the present invention, the "aromatic hydrocarbon group" is a group formed by removing one hydrogen atom on an aromatic ring from an aromatic compound molecule; such as p-tolyl formed by the loss of a hydrogen atom para to the methyl group on the phenyl ring by toluene.
The specific embodiment of the invention is as follows:
the starting materials and catalysts in the examples of the present invention were purchased commercially, unless otherwise specified.
In the embodiment of the invention, the density analysis, the viscosity analysis, the alkali intensity analysis, the alkali amount analysis, the nuclear magnetic H spectrum analysis, the nuclear magnetic C spectrum analysis, the infrared spectrum analysis and the thermogravimetric-differential thermal (TG-DTA) characterization analysis are all conventional operations, and can be operated according to instrument instructions by a person skilled in the art.
In the embodiment of the invention, the conversion rate and selectivity are calculated as follows:
in the examples of the present invention, conversion, selectivity and yield calculations:
X PO /%=(n PC +n DMC +n PM1 +n PM2 )×100/(n PC +n DMC +n PM1 +n PM2 +n unreacted PO )
S PC /%= n PC ×100/(n PC +n DMC +n PM1 +n PM2 )
S DMC /%=n DMC ×100/(n DMC +n PC +n PM1 +n PM2 )
S PM1 /%=n PM1 ×100/(n PC +n DMC +n PM2 )
S PM2 /%=n PM2 ×100/(n PC +n DMC +n PM1 )
Y DMC /% =X PO ×S DMC
Y PM1 /% =X PO ×S PM1
Y PM2 /% =X PO ×S PM2
TON=n Target object /n Cat =(n PO ×X PO ×S Target object )/ (n Cat )
Wherein: PM1 is 1-methoxy-2-propanol, PM2 is 2-methoxy-1-propanol; XPO is the conversion of propylene oxide,%; SPC is propylene carbonate selectivity,%; SDMC is the selectivity of dimethyl carbonate,%; SPM1 is the selectivity,%; SPM2 is the selectivity,%; YMC is the yield of dimethyl carbonate,%; YPM1 is the yield,%; YPM2 is the yield,%; n is the mol quantity and mol of the target product; nPO is the molar amount, mol, of propylene oxide; nPC is the molar amount of propylene carbonate,%; nPM1 the mole percent of 1-methoxy-2-propanol; nPM2 the mole amount and mole of 2-methoxy-1-propanol; nDMC is the molar amount of dimethyl carbonate, mol; nCat is the molar quantity of the active site of the catalyst and mol; s is the selectivity of the target product,%.
Example 1
Imidazole potassium salt synthesis: 34 g (0.5 mol) imidazole is dissolved in 500 mL absolute ethanol at room temperature, 28 g (0.5 mol) KOH powder is slowly added under ice bath condition, stirring is continued for 24 h until the mixture is completely dissolved, the mixed product is filtered, the filtrate is distilled under reduced pressure and rotation at 80 ℃ for 1h, the generated water and ethanol solvent are separated, and the temperature is reduced to room temperature to obtain brown solid (as shown in fig. 1 (A)), and the yield of imidazole potassium reaches 96.62 percent through calculation.
1-ethyl-3-methyl-imidazole salt [ Emim ]]IM synthesis: taking 57.3 g (0.23 mol) of methanol solution containing 75% of 1-ethyl-3-methylimidazole bromine salt by mass, adding 200 mL of absolute ethyl alcohol, and stirring at room temperature for 20 min. 23.85 g (0.23 mol) of potassium imidazole was slowly added and the temperature was controlled to around 25℃to give a large amount of KBr as a white precipitate, which was stirred continuously for 24. 24 h and then filtered. Rotary distillation at 65℃under-0.1 MPa for 2.2 h gave 38.92 g as a viscous yellow liquid as shown in FIG. 1 (B) in a calculated yield of 95.07%. The nuclear magnetic spectrum is shown in fig. 2 and 3. FIG. 2 Synthesis of [ Emim]Im ionic liquid nuclear magnetic H-spectrum: 1 h NMR (500 MHz, DMSO-d 6) delta 7.75 (s, 1H), 7.66 (s, 1H), 7.21 (s, 1H), 6.73 (s, 3H), 4.14 (q, j=7.3 Hz, 2H), 3.80 (s, 3H), 1.37 (t, j=7.3 Hz, 3H); FIG. 3 synthetic [ EmIm]Im ionic liquid nuclear magnetism C spectrum: 13 C NMR (126 MHz, DMSO) δ 136.99, 136.18, 123.97, 122.31, 44.51, 36.06, 15。
example 2
The physical parameters of the 1-ethyl-3-methyl-imidazole ionic liquid ([ Emim ] IM) are measured, the density is about 1.1 g/mL, the viscosity is 45.6 mpa.s, the Hammett indicator method is used for measuring the alkali strength of the ionic liquid [ Emim ] IM to 18.4 < H- < 22.3, and the Hammett indicator used in the process is as follows: phenolphthalein (9.8), 2, 4-dinitroaniline (15.0), p-nitroaniline (18.4), diphenylamine (22.3) and aniline (27.0), the alkali intensity interval of which is determined from the color change of the indicator. The results show that the alkali strength is equivalent to that of industrial sodium tert-butoxide and is higher than that of sodium methoxide. The amount of base in the ionic liquid was 2.83 mmol/g based on the amount of benzoic acid added at 0.1 mol/L.
Example 3
Synthesis of Ionic liquid 1-ethyl-3-methylimidazole [ Emim ]]The results of the characterization of the IM functionality are shown in fig. 4, 3142, 3074 and 2976 cm -1 The absorption peak at the position is the telescopic vibration peak of each substituted alkyl C-H on the imidazole ring. 1668 and 1570 cm -1 The absorption peak at the position is attributed to a C=N telescopic vibration peak in the imidazole ring, 1448 and 1448 cm -1 The telescopic vibration peak of C=C double bond in imidazole ring, 1172 and 1172 cm -1 Is C-N key surface inward bend in imidazole ringQu Zhendong peaks, 829 and 763 cm -1 The absorption peaks at the positions are respectively attributed to in-plane and out-of-plane bending vibrations of the C-H bonds on the imidazole ring.
Example 4
The analysis of the thermal stability of the synthesized ionic liquid 1-ethyl-3-methylimidazole [ Emim ] IM under nitrogen atmosphere is shown in figure 5, and the ionic liquid has three-stage weight loss process, wherein 2% weight loss from room temperature to 144 ℃ is methanol solvent remained in the process of preparing the ionic liquid; obvious weight loss occurs at 144-262 ℃, the weight loss is 68.02 percent, and the imidazole ring begins to be mostly decomposed along with strong heat absorption; 262 to 356 ℃ is complete decomposition of imidazole ring, the weight loss rate is 26.69 percent and the phenomenon of heat absorption is accompanied; heating to 500 deg.c to maintain the residual 2 wt% unchanged, and decomposing to form [ Emim ] IM. The physical properties, functional group characteristics, nuclear magnetic characterization and other results of the ionic liquid prepared in the examples 1-4 can prove that the prepared catalyst is 1-ethyl-3 methylimidazolium salt, hammett titration, alkali measurement and thermogravimetric analysis prove that the catalyst has high alkali strength (18.4 < H- < 22.3), alkali content of 2.83 mmol/g and high thermal stability.
Example 5
Respectively with KI, tetrabutylammonium bromide (TBAB) and 1-ethyl-3-methylimidazole ([ Emim)]IM) was used as a catalyst for the synthesis reaction under the reaction conditions shown in the catalyst evaluation method described above, and the reaction results are shown in fig. 6.KI and TBAB have catalytic CO only 2 The cycloaddition reaction capacity occurs, the PO conversion rate is 43.88% and 31.53% respectively at reaction 2 and h, and 98.79% and 98.35% respectively at reaction 9 and h; there is substantially no effect of catalyzing transesterification of PC and MeOH and alcoholysis of PO and MeOH, so both catalysts have a PC selectivity greater than 99%, a DMC selectivity and yield less than 1%, and a TON value of approximately zero.
By using [ Emim ]]IM catalyst, reactions 2 and 9h, PO conversion 86.90% and 98.57%, PC selectivity 55.35% and 43.66%, DMC selectivity 23.63% and 36.79%, DMC yield 20.34% and 36.27%, corresponding to TON values of 20.77 and 37.04. [ Emim ] compared to KI and TBAB]IM exhibits good DMC yields but still does not meet expectations. The reason for this is: [ Emim ]]IM has strong alkalinity and not only catalyzes CO 2 The cycloaddition reaction occursThe alcoholysis reaction should be catalyzed simultaneously by PO and MeOH. GC-MS analysis of the products showed that there was indeed alcoholysis of the products 1-methoxy-2-propanol (PM 1) and 2-methoxy-1-propanol (PM 2), and PM1 selectivities at reactions 2 and 9h had reached 12.63% and 15.59%, respectively, and PM2 selectivities reached 8.39% and 3.96%.
Example 6
The DMC selectivity and yield should be improved by completing the PO addition cyclization reaction in the absence of MeOH, followed by PC and MeOH transesterification. Therefore, we designed a new process for synthesizing DMC by one-step catalytic cycloaddition and transesterification two-stage chain reaction method. The two-stage chain reaction process for synthesizing DMC in one step includes such steps as reaction in fixed-bed reactor in the first stage and without MeOH addition]IM catalysis of PO and CO 2 Synthesizing PC; adding necessary amount of MeOH into the system, mixing and cooling to make the MeOH enter a reaction-rectifying tower of the second section for further reaction and separation, overflowing DMC-MeOH azeotrope from the top of the tower, and obtaining 1, 2-propylene glycol from the tower bottom, thereby realizing CO 2 And DMC synthesis of PO without isolation in high yield.
Specific validation experiments used KI, TBAB and [ Emim ]]The IM catalyst catalyzes, under the condition of not adding any solvent and auxiliary agent, the CO is catalyzed first 2 And PC, which is generated in situ by PO cycloaddition at low temperature, is transesterified with MeOH. Epoxidation reaction conditions: the mass of the catalyst is 3% of the mass of PO, the reaction temperature is 120 ℃, and the CO is 2 The initial pressure was 2.6 MPa. The results of gas chromatography analysis of the products after reactions 2h and 9h are shown in FIG. 5. PO conversions for the three catalysts at reaction 2h were 37.49%, 46.37% and 64.90%, respectively, indicating [ Emim ]]IM-catalyzed CO 2 And PO epoxidation ability is significantly better than KI and TBAB. The PC selectivity of the 3 catalysts is up to 99%, which indicates that no other side reactions occur under the reaction conditions. The PO conversion for the three catalysts at reaction 9h was 98.28%, 97.95% and 97.40%, respectively, with the corresponding PC selectivity still maintained above 99%, indicating that the reaction time of 9h was sufficient to evaluate the maximum catalytic performance of the 3 catalysts used in this study.
Then, meOH with 10 times of the molar weight of PC is directly added into the reactor, and the reaction temperature is 68 ℃ so as to fix the samplingThe reaction products were collected and analyzed at intervals ranging from 1 to 120 min, the results of which are shown in FIG. 7. Obviously, the difference of PC transesterification capability catalyzed by the three catalysts is obvious, the TBAB activity is the worst, and the PC conversion rate, DMC selectivity and yield at 120 min of reaction are only 33.67%,34.67% and 11.68%; KI has higher DMC selectivity, the DMC yield gradually increases with the reaction time, and the PC conversion, DMC selectivity and yield at 120 min of reaction are only 26.63%, 67.41% and 17.96%; [ Emim ]]IM has excellent PC transesterification catalytic capacity, and the PC conversion, DMC selectivity and yield are as high as 72.87%, 97.36% and 70.94% only for 5 min, with a reaction equilibrium being reached in 30 min, when the DMC yield is 83.63%. The MeOH content was increased to 20 times the PC molar content, and DMC selectivity and yield at 120 min of reaction were 99.84% and 87.81%, respectively. The DMC yield of the process is mainly limited by the reaction equilibrium (raw material composition) and, if coupled with the reaction-rectification process, DMC yield (in CO 2 Calculated) can reach more than 98 percent.
Example 7
Reaction temperature vs PO and CO 2 The effect of the cycloaddition reaction is shown in FIG. 9. Catalyst [ Emim]IM mass 3% of PO mass, initial CO 2 The pressure is 2.6 MPa, CO 2 The molar ratio of/PO was 1.6:1, reaction time 9h. Under all reaction temperature conditions, the PC selectivity of the target product is more than 99 percent, which indicates the synthesis [ Emim ]]IM has excellent ability to directionally catalyze PO cycloaddition. 100. When the temperature is lower than the DEG C, the PC yield reaches 80.69 percent, and the TON value reaches 82.42; with continued increases in reaction temperature to 110 and 120 ℃, PC yields increased further to 89.36% and 97.40%, TON increased to 91.28 and 99.49; the temperature was raised to 130℃and the PC yield was 97.75% and TON was 99.85, all without significant changes. Taking into account PO and CO 2 The cycloaddition reaction is a strong exothermic reaction with reduced volume, and the reduction of the reaction temperature is beneficial to promoting the reaction to proceed in the forward direction and improving the PO equilibrium conversion rate. Therefore, subsequent experiments preferably use 120℃reaction conditions.
Example 8
FIG. 10 shows the reaction time vs. PO and CO 2 The effect of cycloaddition reactions. Catalyst [ Emim]IM mass is 3% of PO mass, reaction temperature is 120 ℃, CO 2 Initial pressure2.6 MPa. The PC selectivity of the target product is more than 99% in all reaction times. When the reaction time is 2h, the PC yield is 64.90%; increasing the reaction time to 4 and 6 hours, the yield of PC to 88.77% and 96.20%; the time is increased to 9h, and the yield of PC reaches 97.40 percent. Since PC selectivity was over 99% in the sampling time interval, TON showed a similar trend with increasing reaction as yield, increasing from 63.23 of 2h to 99.49 of 9h.
Example 9
CO 2 The effect of initial pressure on the cycloaddition reaction is shown in FIG. 11. Catalyst [ Emim]The IM content is 3% of PO mass, the reaction temperature is 120 ℃, and the reaction time is 9h. CO 2 At different initial pressures, PC selectivity was greater than 99%. When CO 2 The initial pressure is 1.8 MPa, namely CO 2 When the molar ratio of the PC to the PO raw material is 1:1, the PC yield is 87.61 percent, and TON is 89.49; CO 2 At an initial pressure of 2.0 MPa (CO 2/PO molar ratio=1.2:1), the yield of PC is 90.94% and TON is 92.89; when CO 2 At an initial pressure of 2.4 MPa (CO 2/PO molar ratio=1.4:1), the yield of PC is 97.03% and TON is 99.11; continuous CO enhancement 2 The initial pressure was 2.6 MPa (CO) 2 The PC yield increased significantly to 97.40% and TON value increased to 99.49 at a molar ratio of/po=1.6:1); continuing to lift CO 2 Pressure to 3.2 (CO) 2 Molar ratio of/po=2.2:1) and 3.8 MPa (CO 2 The PC yield was instead reduced to 93.96% and 93.25% and TON was also reduced to 95.98 and 95.25 at/PO molar ratio = 2.8:1). This is consistent with the results reported in many literature, PC yields with CO during low pressure processes 2 Pressure is increased to increase, CO 2 When the partial pressure exceeds a certain pressure, the PC yield is dependent on the CO 2 The pressure increases and slowly decreases. Too high an initial pressure can lead to CO 2 Liquefying and dissolving in the reaction raw material PO, diluting the catalyst concentration, weakening the action between PO and the catalyst active site, reducing the catalytic efficiency of the catalyst, and being unfavorable for the reaction to proceed in the forward direction. Therefore, the subsequent experimental work is preferably CO 2 The initial pressure was 2.6 MPa.
Example 10
FIG. 12 shows catalyst usage versus PO and CO 2 The effect of cycloaddition reactions. CO 2 Initial pressureThe reaction temperature is 120 ℃ and the reaction time is 9h at 2.6 MPa. The PC selectivity is more than 99% with different catalyst dosage. When the catalyst [ Emim]When the IM mass is 0.5% of the PO mass, the yield of PC is 66.34%, and the TON value is as high as 406.59; with the continuous increase of the catalyst dosage to 1% and 3% of PO mass, the PC yield is obviously increased to 73.49% and 97.40%, and the TON value is reduced to 225.21 and 99.49; the catalyst dosage is continuously increased to 5% and 10% of PO mass, the PC yield reaches 98.58% and 98.95%, and the improvement is not obvious. The TON value can still reach 30.32 even if the catalyst content is 10%. The catalyst amount was 3% of the mass of PO in view of economical factors.
Example 11
FIG. 13 is a graph depicting the effect of [ Emim ] IM catalyst on the efficiency of transesterification of PC with MeOH at various reaction temperatures and times. The catalyst amount was 0.4. 0.4 wt% by weight of the total mass of the reaction materials, and the PC/MeOH molar ratio was 1/10. The DMC selectivity reaches over 99% under all temperature conditions, and no intermediate product is generated basically, so that the DMC yield is similar to PC selectivity. The reaction temperature is 0, 25, 50 and 68 ℃ for 10 min, and DMC yields are 7.95%, 10.21%, 21.33% and 38.01% respectively; when the reaction time was 60 min, DMC yields increased to 18.57%, 27.27%, 58.74% and 71.99%, respectively. 25. At the temperature of 200 min, the reaction equilibrium is reached; 50. at the temperature of 120 min, the reaction equilibrium is reached; 68. the reaction is carried out at the temperature of 60 min to reach equilibrium. When the reaction temperature was increased from 0 to 68℃and the reaction time was 30 min, the TON value and DMC yield were significantly increased from 12.96 to 70.15 and from 12.81 to 68.98%, respectively. The experimental results fully show that the transesterification reaction rate of PC and MeOH has obvious dependence on the reaction temperature, and the [ Emim ] IM also shows extremely high catalytic activity even under extremely low temperature conditions, can complete the transesterification reaction within extremely short time after PC ring opening, and has ultra-strong transesterification catalytic capability.
Example 12
Study [ Emim]IM ionic liquid catalyst for continuous 7 times of high temperature catalysis of CO 2 And PO epoxidation reaction and low-temperature catalysis in-situ to generate transesterification reaction effect of PC and MeOH. Epoxidation reaction conditions: [ Emim ]]IM content is 3% of PO mass, epoxidation reaction temperature is 12%0 ℃， CO 2 Initial pressure 2.6 MPa (CO) 2 Molar ratio of/po=1.6:1), reaction time 9h, sample analysis time point 9h. Then, to the system added the theoretical formation of PC molar 10 times MeOH, at 68 degrees, reaction for 30 minutes after sampling analysis. No solvent or auxiliary agent is added in the whole reaction process, and only the ionic liquid [ Emim ] with the same mass is added at the beginning of the reaction]IM continuously catalyzes both epoxidation and transesterification reactions. After single two-step reaction, the MeOH, PC, DMC and 1, 2-propylene glycol and other raw materials and products are separated under reduced pressure at 140-145 ℃, and the rest ionic liquid is recovered and directly used for the next two-stage reaction cycle until the 6 th cycle is finished.
The relationship between PO and PC conversions and DMC yields and the number of ionic liquid [ Emim ] IM reuses is shown in FIG. 14 below. [ Emim ] IM was used for the first time with a PO conversion of 97.40%, a PC conversion of 85.07%, and a DMC yield of 83.63%. When the catalyst is repeatedly used once, the PO conversion rate is not reduced to 98.05 percent, and the reason is that the product 1, 2-propanediol is slightly remained in the ionic liquid, and the PO ring opening is promoted through the hydrogen bond action. At this time, the PC conversion and DMC yield were respectively 84.25% and almost similar to the DMC yield at the first use, and no decrease in the DMC yield was observed. When the number of repeated use was increased to the fourth time, the PO conversion was decreased to 97.34% and the DMC yield was decreased to 83.82%, but the decrease was not significant. When the catalyst was used repeatedly for 5 times, the PO conversion rate was reduced to 96.68%, the DMC yield was 80.96%, the PO conversion rate was reduced by 0.72% and the DMC yield was reduced by about 4% compared to the first time. It should be emphasized here that the chromatographic analysis of the product taken twice per cycle yields approximately a 1% mass loss of the ionic liquid, which in turn is estimated to be about 96% of the actual mass of the ionic liquid of the system at the 5 th reuse. Therefore, after being recycled for 6 times, the novel ionic liquid is additionally supplemented with 0.024, 0.024 g. Thus, the PO conversion, PC conversion and DMC yield were both increased at reaction 7, and restored to 97.48%,84.58%, and 83.74%, respectively, with comparable catalytic effect to the fresh catalyst used for the first time. The results prove that the [ Emim ] IM new structure ionic liquid synthesized by the research has good thermal stability and catalytic stability, can always maintain higher cycloaddition and transesterification reaction efficiency in the repeated use process, and has no obvious reduction of activity.
Example 13
The reaction mechanism is presumed to be as shown in FIG. 15 [ Emim]IM exists in a state of anions and cations, and imidazole cations electrophilically attack oxygen atoms of propylene oxide to elongate and deform C-O bonds; the imidazole anion nucleophilic attacks the less sterically hindered C atom in propylene oxide, breaking the C-O bond, forming intermediate a. The anions and cations act together to activate propylene oxide to open the ring, forming an oxyanion-containing intermediate species b. Subsequent nucleophilic attack of oxyanions in intermediate species b on CO 2 The positively charged C atom in the molecule generates carbonate intermediate C; then the carbonate intermediate C is subjected to intramolecular substitution under the action of imidazole anions to generate a new C-O bond, so as to obtain propylene carbonate d, and release 1-ethyl-3-methylimidazole cations and imidazole anions.
Ionic liquids [ Emim ] in transesterification]The imidazole anions in IM capture hydrogen on the hydroxyl groups of methanol through hydrogen bonding, thereby activating the methanol to form CH 3 An O-group; CH (CH) 3 O-nucleophilic attack on the carbonyl group in PC (d) to cleave the c=o bond to form intermediate e; since intermediate e is unstable, at least one of the four C-O bonds attached to C is broken, which is a typical nucleophilic addition-elimination reaction. The C-O bond in the 1-position cannot be broken under the alkali catalysis system because of C + And O − Is not stable in the form of free radicals; cleavage of the C-O bond at the 2-position results in the formation of PC and CH 3 O − The groups, C-O bonds in the 3 and 4 positions, are broken to give intermediates f and g. The electronegativity of f and g is weaker than CH due to the electron withdrawing effect of O linked to C=O in the structures of f and g 3 O − Electronegativity and easier generation; f and g abstract or combine with H+ in the system to produce H intermediate 1-hydroxy-2-propyl methyl carbonate (HPMC) and i intermediate 2-Hydroxypropyl Methyl Carbonate (HMC); CH 3O-nucleophilic attack of carbonyl groups in intermediates HPMC and HMC to form intermediates j and k; because j and k are unstable, 4-bit C-O bond is broken to form target product DMC and intermediate product PG negative ions l and m; l and m abstract or combine with H+ in the system to generate final product PG; PG anions l and m may also attack carbonyl groups in intermediate HPMC and HMC, breaking the c=o bond to formIntermediates n and o; cleavage of the C-O bond in intermediate 3 yields intermediates p and q.
Example 14
According to the mechanism of cycloaddition and transesterification presumed in example 13, the active center of the synthesized ionic liquid with a new structure is imidazole anions with strong affinity, and anions such as imidazole, pyrrole, thiophene and the like with various branched structures are in the protection scope of the patent.
While the invention has been described in terms of preferred embodiments, it will be understood by those skilled in the art that various changes and modifications can be made without departing from the scope of the invention, and it is intended that the invention is not limited to the specific embodiments disclosed.
Claims (2)
1. One-step method for catalyzing CO 2 A process for converting dimethyl carbonate, said process comprising the steps of:
propylene oxide, CO 2 Reacting with methanol as a raw material, and obtaining the dimethyl carbonate by using a homogeneous ionic liquid catalyst with high yield;
new two-stage chain reaction process without separation of catalyst, first stage fixed bed reactor, catalyst first catalyzed epoxypropane and CO 2 Synthesizing propylene carbonate; then, the catalyst is mixed with methanol and cooled, and then enters a second-stage reaction-rectifying tower, dimethyl carbonate-methanol azeotrope is extracted from the tower top, and the tower bottom is 1, 2-propanediol to realize CO 2 And propylene oxide is synthesized into dimethyl carbonate in one step with high yield;
the catalyst is 1-ethyl-3-methyl-imidazole salt [ Emim ] IM.
2. A one-step catalytic CO according to claim 1 2 The method for converting the dimethyl carbonate is characterized in that the reaction temperature is 100-130 ℃, the reaction time is 2-9 h, and CO 2 The initial pressure is 1.8-3.8 MPa, and the catalyst dosage is used as raw materialPO is 0.5-10% by mass; the reaction temperature during transesterification was 68 ℃.
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| CN113563189A (en) | 2021-10-29 |
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