CN116655470A - Method for synthesizing dimethyl carbonate by full-cycle catalysis - Google Patents

Method for synthesizing dimethyl carbonate by full-cycle catalysis Download PDF

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Publication number
CN116655470A
CN116655470A CN202310154278.3A CN202310154278A CN116655470A CN 116655470 A CN116655470 A CN 116655470A CN 202310154278 A CN202310154278 A CN 202310154278A CN 116655470 A CN116655470 A CN 116655470A
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reaction
ionic liquid
catalyst
methanol
carbonate
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王玉鑫
侯家祥
阎子祯
魏文胜
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Shenghua New Energy Technology Wuhan Co ltd
Shenyang University of Chemical Technology
Shinghwa Advanced Material Group Co Ltd
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Shenghua New Energy Technology Wuhan Co ltd
Shenyang University of Chemical Technology
Shinghwa Advanced Material Group Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C68/00—Preparation of esters of carbonic or haloformic acids
    • C07C68/04—Preparation of esters of carbonic or haloformic acids from carbon dioxide or inorganic carbonates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
    • B01J31/0277—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
    • B01J31/0278—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
    • B01J31/0279—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 cationic portion being acyclic or nitrogen being a substituent on a ring
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C68/00—Preparation of esters of carbonic or haloformic acids
    • C07C68/08—Purification; Separation; Stabilisation

Abstract

The application discloses a method for synthesizing dimethyl carbonate by full-cycle catalysis, which comprises an ionic liquid catalyst, propylene Oxide (PO) and carbon dioxide (CO) 2 ) Synthesizing Propylene Carbonate (PC) in a high-pressure reaction kettle, enabling raw materials of the synthesized PC and methanol (MeOH) to flow into a rectifying tower without separating a catalyst, obtaining high-purity dimethyl carbonate (DMC) and byproduct 1, 2-Propylene Glycol (PG) products through series reactions, simultaneously utilizing reaction system products of tetraethyl 1, 2-propylene glycol ammonium oxide (PG-TEA) as cycloaddition reaction and transesterification reaction catalysts, realizing the whole process flow without introducing other impurities, only consuming hydrogen bromide and alkali to generate water and metal bromide, realizing the total circulation reflux of the catalyst and the MeOH, and preparing the catalyst from the catalystThe DMC synthesis has important industrial application value in the field of DMC synthesis.

Description

Method for synthesizing dimethyl carbonate by full-cycle catalysis
Technical Field
The application relates to a method for synthesizing dimethyl carbonate by full-cycle catalysis, belongs to the field of chemistry and chemical industry, and particularly belongs to the technical field of dimethyl carbonate production.
Background
Excessive consumption of fossil energy and CO 2 The continuous increase in emissions causes environmental deterioration problems such as global warming and sea level elevation. Building green manufacturing system, improving resource energy utilization efficiency and reasonably utilizing CO 2 The production of versatile high value chemicals is a current research hotspot. CO 2 Cycloaddition product of Ethylene Carbonate (EC) and methanol (MeOH) transesterification DMC (dimethyl carbonate) is a more environment-friendly and efficient synthetic route compared with other DMC synthetic routes, and realizes CO 2 The indirect utilization of the synthetic polyester fiber, the polyester resin and the glycol which is a large amount of raw materials of the antifreeze are also one of the most main methods for DMC industrial production worldwide. Catalysts reported for the transesterification of EC with MeOH to synthesize DMC are alkoxide-based catalysts, acid-based catalysts, ion-exchange resin-based catalysts [8 ]]Montmorillonite-based catalysts, metal oxide-based catalysts, hydrotalcite-based catalysts, and the like. In recent years, ionic Liquids (ILs) have been widely used as a green and environmentally friendly solvent, catalyst and additive in gas adsorption, organic synthesis, batteries and the like, and have attracted attention in the transesterification of EC and MeOH to DMC and EG.
The Ionic Liquids (ILs) have special properties of good thermal stability, solubility, negligible vapor pressure, controllable polarity, adjustable structure and the like, so that the Ionic Liquids (ILs) maintain excellent mass transfer performance in the reaction. The ionic liquid catalysts commonly used in transesterification reactions are mainly classified into homogeneous catalysts and heterogeneous catalysts, wherein the heterogeneous catalysts comprise heterogeneous ionic liquid catalysts, and specifically comprise polyionic liquid catalysts and ionic liquid supported or supported catalysts. The heterogeneous ionic liquid catalyst has the problems of overhigh reaction temperature, longer reaction time, overhigh catalyst content and the like, and the intrinsic reasons are low transesterification efficiency of heterogeneous catalysis. Although the catalytic activity of the homogeneous ionic liquid is far higher than that of the heterogeneous ionic liquid catalyst, the homogeneous ionic liquid catalyst has the problems of difficult separation, high separation energy consumption, initiation of product polymerization, introduction of impurities and the like.
Disclosure of Invention
According to one aspect of the application, a full-cycle catalytic dimethyl carbonate synthesis method is provided, which is to perform cycloaddition reaction on a strong alkaline ionic liquid homogeneous catalyst based on hydroxyethoxy anions, propylene oxide and carbon dioxide in a high-pressure reaction kettle to synthesize alkyl carbonate, then the catalyst is not separated, the synthesized alkyl carbonate and methanol are mixed and then are put into a tower kettle of a reaction-rectifying tower to react, a dimethyl carbonate-methanol azeotrope is extracted from the tower top, the tower kettle is dihydric alcohol, high-yield synthesis of DMC and byproduct dihydric alcohol is realized, recycling of the catalyst is realized, new impurities are not introduced at all, and the method has important industrial application value in the field of carbonate chemical synthesis.
The application adopts the following technical scheme:
a method for synthesizing dimethyl carbonate by full cycle catalysis comprises the following steps:
s1, flowing a raw material containing an ionic liquid catalyst, alkyl carbonate and methanol into a rectifying tower, and reacting I to obtain a tower bottom product and a tower top product;
the tower kettle product comprises dihydric alcohol, methanol and an ionic liquid catalyst;
the top product is an azeotrope of dimethyl carbonate and methanol;
s2, flash evaporating the tower kettle product, separating to obtain a mixture of methanol and liquid, heating and decomposing the liquid mixture, and separating to obtain triethylamine, ethylene and dihydric alcohol products;
s3, adding hydrogen bromide into the ethylene, reacting II to obtain vinyl bromide, mixing with triethylamine, and reacting III to obtain tetraethyl ammonium bromide;
s4, rectifying and purifying part of the dihydric alcohol product, then adding alkali into the dihydric alcohol product, and reacting IV to obtain metal dihydric alcohol salt;
s5, mixing the metal dibasic alkoxide with the tetraethylammonium bromide, reacting V to obtain an ionic liquid catalyst, and circularly refluxing the ionic liquid catalyst into the raw materials;
s6, separating the tower top product to obtain methanol and dimethyl carbonate.
Optionally, in the step S1, the alkyl carbonate is prepared by the following steps:
and (3) carrying out cycloaddition reaction on a material containing an ionic liquid catalyst, propylene oxide and carbon dioxide to obtain the alkyl carbonate.
Alternatively, the cycloaddition reaction conditions are: the reaction temperature is 115-130 ℃, the reaction time is 1-6 h, and CO 2 The initial pressure was 2.6MPa.
Optionally, the molar ratio of the propylene oxide to the carbon dioxide is 1:1-2.8; the molar ratio of the epoxypropane to the ionic liquid catalyst is 1:0.001-0.0025.
Optionally, in the step S1, the conditions of the reaction I are: the reaction temperature is 20-110 ℃, and the reaction pressure is 10-50 KPa.
Optionally, in the step S1, the conditions of the reaction I are: the reaction temperature is 20-68 ℃ and the reaction pressure is 10-50 KPa.
Optionally, in the step S1, the molar ratio of the alkyl carbonate to the methanol is 1:6-15; the molar ratio of the alkyl carbonate to the ionic liquid catalyst is 1:0.001-0.0025.
Optionally, the alkyl carbonate is selected from at least one of ethylene carbonate and propylene carbonate.
Optionally, the ionic liquid catalyst is selected from at least one of tetraethyl glycol ammonium oxide and tetraethyl 1, 2-propylene glycol ammonium oxide.
Optionally, in the step S2, the temperature of the flash evaporation is 100-110 ℃.
Optionally, in the step S2, the temperature of the thermal decomposition is 120-140 ℃.
Optionally, in the step S3, the conditions of the reaction II are: the reaction temperature is 25-60 ℃ and the reaction pressure is 10-50K Pa.
Optionally, in the step S3, the weight ratio of the ethylene to the hydrogen bromide is 1:0.9-1.5.
Optionally, in the step S3, the condition of the reaction III is: the reaction temperature is 25-60 ℃, and the reaction pressure is 10-50 KPa.
Optionally, in the step S3, the weight ratio of the bromoethylene to the triethylamine is 1:0.9-1.5.
Optionally, in the step S4, the conditions of the reaction IV are: the reaction temperature is 50-135 ℃, the reaction pressure is-0.1 to-0.08 Pa, and the rotary evaporation is carried out;
optionally, in the step S4, the molar ratio of the ethylene glycol to the alkali is 1:0.5-1.
Optionally, in the step S1, the molar ratio of the ethylene glycol to the base is selected from any value of 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:0.7, 1:0.75, 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, or a range value therebetween.
Optionally, in the step S1, the molar ratio of the ethylene glycol to the alkali is 1:0.5-0.53.
Optionally, in the step S4, the base is at least one selected from sodium hydroxide, potassium hydroxide, cesium hydroxide and lithium hydroxide.
Optionally, the dihydric alcohol is at least one selected from ethylene glycol and 1, 2-propylene glycol.
Optionally, in the step S5, the condition of the reaction V is: the reaction temperature is 50-70 ℃, and the reaction is rotary steaming.
Optionally, in the step S5, the molar ratio of the glycol salt to the tetraethylammonium bromide is 1:0.8-1.2.
Optionally, in step S1, the overhead product comprises 49 to 50wt% dimethyl carbonate and 49 to 50wt% methanol.
Optionally, the methanol obtained in the step S2 and the methanol obtained in the step S6 are recycled back into the raw material.
Optionally, in the step S4, water is also separated during the reaction IV.
Optionally, in the step S5, a byproduct metal bromide is also separated during the reaction V.
The application has the beneficial effects that:
the method for synthesizing the full-cycle catalytic dimethyl carbonate provided by the application adopts the reaction product in the synthesis method of the used dimethyl carbonate as an ionic liquid catalyst, does not introduce additional impurities, has high thermal stability, strong alkalinity and high-efficiency transesterification reaction catalyzing capacity, uses tetrabutyl glycol ammonium oxide with the molar content of 0.18% of alkyl carbonate as a catalyst, ensures that the DMC yield is 42.8%, and ensures that the TOF value is up to 2853.6h -1 Has important industrial application value in the field of carbonic ester chemical synthesis.
Drawings
FIG. 1 is a schematic flow chart of a method for synthesizing dimethyl carbonate in example 1 of the present application;
FIG. 2 shows EGK, TEAB and [ TEAB ] during the preparation of example 1 of the present application]OCH 2 CH 2 FT-IR spectrum of OH;
FIG. 3 is a chart showing the FT-IR spectrum of PG-TEA prepared in example 2 of the present application and the FT-IR spectrum derived from the synthesis of PG-TBA and PG-CH by the product;
FIG. 4 is a block diagram of [ TEAB ] prepared in application example 1]OCH 2 CH 2 OH and results from product Synthesis [ TBAB]OCH 2 CH 2 OH、[Emim]The OCH2CH2OH catalyst is used for the reaction influence contrast diagram of the transesterification synthetic DMC;
FIG. 5 is a graph showing the comparison of PG-TEA prepared in example 2 of the present application and PG-TBA and PG-CH catalysts derived from product synthesis for catalyzing cycloaddition;
FIG. 6 is a graph showing the comparative effect of PG-TEA prepared in example 2 of the present application and PG-TBA and PG-CH catalysts derived from product synthesis on transesterification DMC synthesis.
Detailed Description
The present application is described in detail below with reference to examples, but the present application is not limited to these examples.
The starting materials and catalysts in the examples of the present application were purchased commercially, unless otherwise specified.
In the examples of the present application, the characterization analysis of mid-infrared spectrum (IRTracer-100 Fourier infrared spectrometer, shimadzu corporation, japan) was performed as a routine operation, and those skilled in the art would be able to perform the operation according to the instructions of the instrument.
In the present application, "EGK" refers to potassium ethylene glycol.
In the present application, "PGK" means potassium 1, 2-propanediol.
In the present application, "[ TEAB ] OCH2CH2OH" means tetraethyl glycol oxyammonium.
In the present application, "[ TBAB ] OCH2CH2OH" means tetrabutylammonium glycolate.
In the present application, "[ Emim ] OCH2CH2OH" means 1-ethyl-3-methylimidazole ethyleneglycol oxy salt.
In the present application, "PG-TEA" refers to tetraethyl 1, 2-propanediol monoammonium.
In the present application, "PG-TBA" means tetrabutyl 1, 2-propanediol ammonium oxide.
In the present application, "PG-CH" refers to choline 1, 2-propanediol oxyammonium.
In the present application, "PO" refers to cyclopropane.
In the present application, "PC" means propylene carbonate.
In the present application, "EC" refers to ethylene carbonate.
In the present application, "MeOH" refers to methanol.
In the present application, "DMC" refers to dimethyl carbonate.
In the present application, "EG" is ethylene glycol.
In the present application, "PG" is 1, 2-propanediol.
Conversion selectivity and yield calculated for PO and PC in the examples of the application mode of calculation:
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; x is X PO Conversion of propylene oxide,%; s is S PC Selectivity for propylene carbonate,%; s is S DMC Selectivity for dimethyl carbonate,%; s is S PM1 Selectivity for 1-methoxy-2-propanol,%; s is S PM2 Selectivity for 2-methoxy-1-propanol,%; y is Y DMC Yield of dimethyl carbonate,%; y is Y PM1 Yield of 1-methoxy-2-propanol,%; y is Y PM2 Yield,%; n is the mol quantity and mol of the target product; n is n PO Is the molar quantity of propylene oxide, mol; nPC is the molar amount of propylene carbonate,%; n is n PM1 Molar amount,%; n is n PM2 Is the molar quantity, mol, of 2-methoxy-1-propanol; n is n DMC Is the molar quantity, mol, of dimethyl carbonate; n is n Cat The molar quantity of the active site of the catalyst and the mol; s is S Target object Selectivity for the target product,%.
The EC conversion, product selectivity and DMC yield calculations are shown below:
Y/％＝100×X×S a
wherein: x is the conversion rate of ethylene carbonate; s is S a Selectivity for dimethyl carbonate; s is S b Selectivity for hydroxyethyl methyl carbonate; s is S c Is dihydroxyethyl carbonate selectivity; y is the yield of the dimethyl carbonate; n is n a An amount of dimethyl carbonate material; n is n b Is of hydroxyethyl methyl carbonate material; n is n c An amount of a dihydroxyethyl carbonate material; n is n d Is the amount of unreacted ethylene carbonate material. t is the reaction time, h; n is n EC Molar amount of DMC; n is n cat Is the molar quantity of the active site of the catalyst and mol.
Example 1
The scheme shown in FIG. 1 was followed by EC, meOH, [ TEAB ]]OCH 2 CH 2 Adding an OH catalyst into a reaction-rectification tower according to the mol ratio of 1:10:0.0018, wherein the reaction temperature is 68 ℃, the tower top temperature is 63.6 ℃, the components are MeOH and DMC azeotrope, the tower bottom temperature is about 70 ℃, the components are about 50% MeOH, 50% EG and trace catalyst, and the flash at 105 DEG CAfter steaming MeOH, crude EG and catalyst were obtained, which was continuously heated to 130℃and maintained for 2h to decompose the catalyst into triethylamine (Et 3 N), ethylene (C) 2 H 4 ) And EG, and separating crude EG from the product, [ TEAB ]]OCH 2 CH 2 EG after OH decomposition is the product. Decomposed C 2 H 4 The molar ratio of the catalyst to HBr is 1:1 mixing and generating addition reaction to generate C 2 H 3 Br (step 1), C 2 H 3 Br and Et again 3 N is in mole ratio of 1:1.5 mixing and quaternizing to generate TEAB (step 3 in the reaction process); EG and KOH in a weight ratio of 1:0.5, mixing and dehydrating to generate EGK (step 2) and mixing EGK and TEAB according to a weight ratio of 1:1 mixing to give catalyst [ TEAB]OCH 2 CH 2 OH (step 4) and KBr with high added value. The catalyst does not introduce extra impurities in the reaction process, and the whole recycling process of the catalyst is only equivalent to the consumption of HBr and KOH to generate KBr and H 2 O。
Wherein, the liquid crystal display device comprises a liquid crystal display device,
reaction procedure step1: c (C) 2 H 4 +HBr→C 2 H 5 Br
Reaction procedure step2: EG+KOH→EGK+H 2 O
Reaction procedure step3: c (C) 2 H 5 Br+Et 3 N→TEAB
Reaction procedure step4: TEAB+EGK- [ TEAB ]]OC 2 H 2 OH+KBr
Example 2
The PG-TBA catalyst, PO and CO were prepared as shown in the scheme of FIG. 1 2 Adding the catalyst into an autoclave according to the molar ratio of 1:1.6:0.0013 for cycloaddition reaction, adding MeOH into the catalyst without separation, feeding the catalyst into a reaction-rectification tower according to the molar ratio of PC, meOH and PG-TBA catalyst of 1:10:0.0013, wherein the reaction temperature is 68 ℃, the tower top temperature is 63.6 ℃, the composition is an azeotrope of MeOH and DMC, the tower bottom temperature is about 70 ℃, the composition is about 50% MeOH, 50% EG and a trace amount of catalyst, flash evaporating the MeOH at 105 ℃ to obtain crude EG and the catalyst, continuously heating to 130 ℃ and keeping for 2 hours, and decomposing the catalyst into triethylamine (Et 3 N), ethylene (C) 2 H 4 ) The light of the volume of the PG and the volume of the PG,and separating the crude PG from the product, wherein PG after PG-TEA decomposition is the product. Decomposed C 2 H 4 The molar ratio of the catalyst to HBr is 1:1.1 mixing and generating addition reaction to generate C 2 H 3 Br (step 1), C 2 H 3 Br and Et again 3 N is in mole ratio of 1:1.5, mixing and quaternizing to generate TEBA (step 3 in the reaction process); PG and KOH in a molar ratio of 1:0.5, mixing and dehydrating to generate PGK (step 2), wherein the molar ratio of PGK to TEAB is 1:1 to produce the ionic liquid catalyst PG-TEA (step 4 in the reaction process) and KBr with high added value. The catalyst does not introduce extra impurities in the reaction process, and the whole recycling process of the catalyst is only equivalent to the consumption of HBr and KOH to generate KBr and H 2 O。
Wherein, the liquid crystal display device comprises a liquid crystal display device,
reaction procedure step1: c (C) 2 H 4 +HBr→C 2 H 5 Br
Reaction procedure step2: PG+KOH- & gtPGK+H 2 O
Reaction procedure step3: c (C) 2 H 5 Br+Et 3 N→TEAB
Reaction procedure step4: TEAB+PGK→PG-TEA+KBr
Example 3
As in the case of step2 to step4 of example 1, 62g of EG (1 mol) originating in example 1 was taken and placed in a 500ml beaker, and 28.0g of KOH (0.5 mol) was then slowly added to the solution and stirred in an ultrasonic apparatus for 2 hours to completely dissolve the KOH. Treating with a rotary evaporator at 135 ℃ for 3h, enabling KOH and EG to react to generate water, and simultaneously generating EG and 1, 2-propylene glycol potassium salt (EGK), wherein the alkali content of EGK is 4.9mmol/g through titration analysis; 32.24g tetrabutylammonium bromide (0.1 mol) was weighed into a 50g methanol solution, and equimolar EGK (18.73 g) was added thereto; stirring at room temperature for 24h, and filtering; rotary evaporating the filtrate at 60deg.C for 3 hr to obtain ionic liquid catalyst [ TBAB ]]OCH 2 CH 2 OH。
Example 4
As in the case of the reaction procedures step2 to step4 of example 1, 62g of EG (1 mol) originating in example 1 were taken and placed in a 500ml beaker, and then28.0g KOH (0.5 mol) was slowly added to the solution and stirred in an ultrasonic apparatus for 2 hours to completely dissolve the KOH. Treating with a rotary evaporator at 135 ℃ for 3h, enabling KOH and EG to react to generate water, and simultaneously generating EG and 1, 2-propylene glycol potassium salt (EGK), wherein the alkali content of EGK is 4.9mmol/g through titration analysis; weigh 19.1g [ Emim ]]Br (0.1 mol) was dissolved in 50g of methanol solution, to which was added equimolar EGK (18.73 g); stirring at room temperature for 24h, and filtering; rotary evaporating the filtrate at 60deg.C for 3 hr to obtain ionic liquid catalyst [ Emim ]]OCH 2 CH 2 OH。
Example 5
As in the case of step2 to step4 of example 2, 76.1g of PG (1 mol) obtained in example 2 was placed in a 500ml beaker, 28.0g of KOH (0.5 mol) was then slowly added to the solution, and the solution was stirred in an ultrasonic apparatus for 2 hours to completely dissolve the KOH. Then, the mixture was treated with a rotary evaporator at 135℃for 3 hours, KOH and PG were reacted to produce water, and PG and 1, 2-propanediol potassium salt (PGK) were simultaneously produced, and the alkali content of PGK was 4.9mmol/g by titration analysis, and the above PGK (0.1 mol) and anhydrous methanol (200 mL) were added to a 500mL beaker and stirred at room temperature. 32.24g of tetrabutylammonium bromide TBAB (0.1 mol) were slowly added to the resulting mixture, stirred at room temperature for 24 hours, and filtered; the filtrate is rotary evaporated for 3h at 60 ℃ to obtain the ionic liquid catalyst PG-TBA.
Example 6
As in the case of step2 to step4 of example 2, 76.1g of PG (1 mol) obtained in example 2 was placed in a 500ml beaker, 28.0g of KOH (0.5 mol) was then slowly added to the solution, and the solution was stirred in an ultrasonic apparatus for 2 hours to completely dissolve the KOH. Then, the mixture was treated with a rotary evaporator at 135℃for 3 hours, KOH and PG were reacted to produce water, and PG and 1, 2-propanediol potassium salt (PGK) were simultaneously produced, and the alkali content of PGK was 4.9mmol/g by titration analysis, and the above PGK (0.1 mol) and anhydrous methanol (200 mL) were added to a 500mL beaker and stirred at room temperature. 13.9g of choline chloride CH (0.1 mol) was then slowly added to the resulting mixture, stirred at room temperature for 24h, and filtered; the filtrate was rotary evaporated at 60℃for 3h to give the ionic liquid catalyst PG-CH. And filtering to remove the byproduct KBr. 1, 2-propanediol ammonium oxide.
Test example 1
Determination of ionic liquid PG-TEA base Strength Range of 15.0 Using Hammett indicator method<H-<18.4, PG-TBA, PG-CH base Strength Range 18.4<H-<22.3 Hammett indicators used in this process are phenolphthalein, 2, 4-dinitroaniline, p-nitroaniline, diphenylamine and aniline. Compared with common strong alkali such as sodium hydroxide, sodium methoxide and sodium tert-butoxide, the ionic liquid PG-TEA alkali strength is equivalent to that of potassium hydroxide, and the PG-TBA and PG-CH alkali strength are equivalent to that of sodium tert-butoxide and higher than that of sodium methoxide. The alkali amounts of the PG-TEA, PG-TBA and PG-CH ionic liquids measured by adopting a benzoic acid titration method are respectively 1.81, 2.45 and 2.98mmol/g, and [ TEAB ] is measured]OCH 2 CH 2 The alkali strength of the OH catalyst ranges from 9.8 to 15.0, which is equivalent to that of sodium methoxide, and the alkali amount results are 2.27 respectively.
Test example 2
For EGK, TEAB, [ TEAB ] derived from product Synthesis in example 1]OCH 2 CH 2 OH was subjected to FT-IR spectroscopy and the results are shown in FIG. 2, comparing potassium Ethylene Glycol (EGK), tetrabutylammonium bromide (TEAB), tetrabutylammonium ethyleneglycol oxy ([ TEAB)]OCH 2 CH 2 OH) characteristic functional group spectra. FIG. 2 (a) is a FT-IR diagram of EGK at 3358, 1653, 1380, 1296, 1091, 1043 and 885cm -1 There are distinct characteristic peaks, the wavenumbers of which lie at 3358 and 1296cm -1 Is the stretching vibration and in-plane bending vibration peak of O-H bond in EGK; 1653cm -1 The absorption peak at this point is the bending vibration peak of the H-O-H bond of water, which is confirmed by TG-DTA plot; 1380cm -1 The absorption peak at the position is attributed to the symmetrical bending vibration peak of the C-H bond in the methylene; 1091 and 1043cm -1 The absorption peak at the position is attributed to two C-O bond stretching vibration peaks in EGK; 885cm -1 The absorption peak is assigned to the C-C bond skeleton vibration peak. FIG. 2 (b) is a FT-IR chart of TEAB at 2958, 2874 and 1473cm -1 There are distinct functional group characteristic peaks of 2958 and 2874cm -1 Wavenumber belongs to symmetrical and asymmetrical stretching vibration of C-H bonds; 1473cm -1 The C-H bond asymmetric bending vibration peak attributed to methyl in TEAB. FIG. 2 (c) simultaneously observes the characteristic functional group peaks shown in FIG. 2 (a) and FIG. 2 (b),it was demonstrated that ethylenedioxy anions have successfully replaced bromoanions and are ionically bound to quaternary ammonium salts.
Test example 3
As shown in FIG. 3, the 3 ionic liquids PG-TBA, PG-TEA and PG-CH obtained in examples 2, 5 and 6 and derived from the synthesis of the product PG were tested for characterization of the functional groups, respectively, with the absorption peak at 3400cm-1 being the stretching vibration of the-OH group and 2968cm-1 being the-CH 3 Stretching vibration of the base, 2866cm -1 is-CH 2 Is characterized in that 1648cm-1 is C-N stretching vibration, 1384cm -1 Is C-H symmetrical bending vibration of 1289cm -1 C-O stretching vibration 1139cm -1 Is the stretching vibration peak of the single bond of C-C. The synthetic ionic liquid is shown to have typical cationic and 1, 2-propanediol anionic functional groups.
Test example 4
FIG. 4 shows that the reaction temperature was 50℃and the reaction time was 30min at a reaction condition of EC/MeOH molar ratio of 1/10. According to the alkali measurement result of the acid-base titration method on the ethylene glycol oxo-anion liquid, the catalyst addition amount is adjusted, the consistent number of active centers (alkali concentration) in the process of carbonate transesterification is ensured, the influence on the synthesized catalyst caused by incomplete EGK and bromate reaction in the process of catalyst preparation is eliminated, and the catalyst addition amount is 0.18% of EC molar amount. When the ionic liquid catalyst is [ TBAB ] obtained in example 1]OCH 2 CH 2 At OH, EC conversion was 75.3%, DMC yield 73.5%, TOF 816.7h-1. When the ionic liquid catalyst was [ TEAB ] obtained in example 3]OCH 2 CH 2 At OH, EC conversion was 74.4%, DMC yield 72.6%, TOF 800.0h-1. When the ionic liquid catalyst is [ Emim ] obtained in example 4]When OCH2CH2OH is adopted, the EC conversion rate is 74.8%, the DMC yield is 74.0%, and TOF is 820.0h-1. Under the condition that the anion structure of the synthesized ionic liquid is unchanged, when the cation structure is changed, the EC conversion rate, DMC yield and TOF value of the synthesized ionic liquid are not obviously different. From the experimental result, the ionic liquid of which the anions are ethylene glycol oxyanions has equivalent capability of catalyzing the conversion of the EC into DMC, and the structure of the cations in the catalyst has no influence on the conversion of the EC into DMC. Catalyst only [ TEAB]OCH 2 CH 2 OH can be recycled in the production process of the present application.
Test example 5
As shown in FIG. 5, 3 ionic liquid catalysts (PG-TBA, PG-TEA and PG-CH) obtained in examples 2, 5 and 6 and derived from the synthesis of the product PG were tested for the effect of catalyzing cycloaddition reaction, and the epoxidation reaction was carried out under conditions of 8.00g (0.14 mol) PO and CO, respectively 2 The initial pressure was 2.6MPa and the catalyst amounts were all equimolar (1.13X10 -3 mol), reaction temperature 130℃and reaction time 6h. The calculated PO conversions were 98.48%, 99.03% and 79.85%, respectively, and TON was 118.84, 119.51 and 96.36, respectively. Description of PG-TEA and PG-TBA catalyzing CO 2 Is equivalent to the PO catalytic cycloaddition reaction capability and is superior to PG-CH. The selectivity of the product PC is over 99 percent, which indicates that no other side reactions occur. Because the ionic bond of the 1, 2-propylene glycol oxyanion and the tetrabutylammonium cation is weaker, free anions and cations are easier to form in the solution, so that the catalytic activity of the solution is enhanced, the optimal reaction effect is achieved, but the decomposition substance of PG-TBA has high boiling point and cannot be circulated in the production process of the application.
Test example 6
As shown in figure 6, after cycloaddition reaction is carried out on 3 ionic liquid catalysts (PG-TBA, PG-TEA and PG-CH) obtained in examples 2, 5 and 6 and derived from the synthesis of the product PG, the catalyst is directly added into MeOH with 10 times of the molar weight of the generated PC without separation, the reaction temperature is 68 ℃, the difference of PC transesterification capability catalyzed by three catalysts of a reaction-rectifying tower is obvious, DMC selectivity of the 3 catalysts is more than 99%, PG-CH activity is worst, and conversion balance is achieved in 360 min; the PG-TEA catalytic activity is improved, and the conversion balance is achieved in the reaction for 180 min; PG-TBA has excellent transesterification catalytic ability of PC and MeOH, and the DMC yield reaches 71.22% after only 120min of reaction to reach the reaction balance. The excellent catalytic activity of the ionic liquid is attributed to the strong nucleophilicity of anions, the 1, 2-propanediol oxyanion can be reversibly exchanged with hydrogen protons in MeOH to activate the MeOH to generate methoxy anions, then the methoxy anions attack carbon atoms on carbonyl groups to complete nucleophilic reaction, the catalytic efficiency of PG-TBA and PG-TEA is better than that of PG-CH, the catalytic effect of PG-TBA is slightly better than that of PG-TEA, and the fact that in quaternary ammonium salts with the same anion substituent, the ionic bond of 1, 2-propanediol anion and tetrabutylammonium cation is weaker, free anions are easier to form in solution, so that the catalytic activity of the ionic liquid is enhanced, but the decomposition substances of PG-TBA have high boiling points and cannot be circulated in the production process of the application.
While the application 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 application, and it is intended that the application is not limited to the specific embodiments disclosed.

Claims (10)

1. The full-cycle catalytic dimethyl carbonate synthesis method is characterized by comprising the following steps of:
s1, flowing a raw material containing an ionic liquid catalyst, alkyl carbonate and methanol into a rectifying tower, and reacting I to obtain a tower bottom product and a tower top product;
the tower kettle product comprises dihydric alcohol, methanol and an ionic liquid catalyst;
the top product is an azeotrope of dimethyl carbonate and methanol;
s2, flash evaporating the tower kettle product, separating to obtain a mixture of methanol and liquid, heating and decomposing the liquid mixture, and separating to obtain triethylamine, ethylene and dihydric alcohol products;
s3, adding hydrogen bromide into the ethylene, reacting II to obtain vinyl bromide, mixing with triethylamine, and reacting III to obtain tetraethyl ammonium bromide;
s4, rectifying and purifying part of the dihydric alcohol product, then adding alkali into the dihydric alcohol product, and reacting IV to obtain metal dihydric alcohol salt;
s5, mixing the metal dibasic alkoxide with the tetraethylammonium bromide, reacting V to obtain an ionic liquid catalyst, and circularly refluxing the ionic liquid catalyst into the raw materials;
s6, separating the tower top product to obtain methanol and dimethyl carbonate.
2. The method according to claim 1, wherein in the step S1, the alkyl carbonate is prepared by the steps of:
carrying out cycloaddition reaction on a material containing an ionic liquid catalyst, propylene oxide and carbon dioxide to obtain alkyl carbonate;
preferably, the cycloaddition reaction conditions are: the reaction temperature is 115-130 ℃, the reaction time is 1-6 h, and CO 2 The initial pressure is 2.6MPa;
preferably, the molar ratio of the propylene oxide to the carbon dioxide is 1:1-2.8; the molar ratio of the epoxypropane to the ionic liquid catalyst is 1:0.001-0.0025;
preferably, in the step S1, the conditions of the reaction I are: the reaction temperature is 20-110 ℃, and the reaction pressure is 10-50 KPa;
preferably, in the step S1, the molar ratio of the alkyl carbonate to the methanol is 1:6-15; the molar ratio of the alkyl carbonate to the ionic liquid catalyst is 1:0.001-0.0025;
preferably, the alkyl carbonate is selected from at least one of ethylene carbonate and propylene carbonate;
the ionic liquid catalyst is selected from at least one of tetraethyl glycol ammonium oxide and tetraethyl 1, 2-propylene glycol ammonium oxide.
3. The method according to claim 1, wherein in the step S2, the flash evaporation temperature is 100 to 110 ℃;
preferably, in the step S2, the thermal decomposition temperature is 120 to 140 ℃.
4. The method according to claim 1, wherein in the step S3, the conditions of the reaction II are: the reaction temperature is 25-60 ℃, and the reaction pressure is 10-50 KPa;
preferably, in the step S3, the weight ratio of the ethylene to the hydrogen bromide is 1:0.9-1.5.
5. The method according to claim 1, wherein in the step S3, the condition of the reaction III is: the reaction temperature is 25-60 ℃, and the reaction pressure is 10-50 KPa;
preferably, in the step S3, the weight ratio of the bromoethylene to the triethylamine is 1:0.9-1.5.
6. The method according to claim 1, wherein in the step S4, the conditions of the reaction IV are: the reaction temperature is 50-135 ℃, the reaction pressure is-0.1 to-0.08 Pa, and the rotary evaporation is carried out;
preferably, in the step S4, the molar ratio of the dihydric alcohol to the alkali is 1:0.5-1;
preferably, in the step S4, the base is at least one selected from sodium hydroxide, potassium hydroxide, cesium hydroxide and lithium hydroxide;
preferably, the dihydric alcohol is at least one selected from ethylene glycol and 1, 2-propylene glycol.
7. The method according to claim 1, wherein in the step S5, the condition of the reaction V is: the reaction temperature is 25-50 ℃, and the mixture is steamed in a rotary way;
preferably, in the step S5, the molar ratio of the metal dialkoxide to the tetraethylammonium bromide is 1:0.8-1.2.
8. The method according to claim 1, wherein in step S1, the overhead product comprises 49-50 wt% dimethyl carbonate and 49-50 wt% methanol.
9. The method according to claim 1, wherein the methanol obtained in step S2 and the methanol obtained in step S6 are recycled back to the feedstock.
10. The method according to claim 1, wherein in step S4, water is also separated during the reaction IV;
preferably, in the step S5, a byproduct metal bromide is also separated during the reaction V.
CN202310154278.3A 2023-02-22 2023-02-22 Method for synthesizing dimethyl carbonate by full-cycle catalysis Pending CN116655470A (en)

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