CN105237336A - Method for synthesizing dimethyl carbonate and ethylene glycol by catalyzing transesterification through load type ion liquid - Google Patents

Abstract

The invention belongs to the technical field of industrial catalysis and provides a method for synthesizing dimethyl carbonate and co-producing ethylene glycol by catalyzing transesterification with a loaded ionic liquid. The supported ionic liquid is based on chlorine-containing resin particles as a carrier, and an ionic liquid in which a hydroxyl anion structural unit and an imidazolium cation structural unit are paired as a catalytic active center, and is supported by a chemical bond to prepare a functionalized supported ionic liquid catalyst. It is used to catalyze the transesterification reaction of ethylene carbonate and methanol, and simultaneously synthesize two chemical products of dimethyl carbonate and ethylene glycol. The catalyst preparation process is simple and easy to operate, and the catalyst can be recovered by simple filtration, which is very beneficial to solve the problem of difficult separation of the product and the catalyst. It will have great application potential and market prospect.

Description

Method for synthesizing dimethyl carbonate and co-producing ethylene glycol through transesterification reaction catalyzed by a loaded ionic liquid

technical field

The invention belongs to the technical field of industrial catalysis, and relates to a method for catalytically synthesizing dimethyl carbonate and co-producing ethylene glycol with a loaded ionic liquid, specifically referring to a method that uses ethylene carbonate and methanol as raw materials, and is catalyzed by a loaded ionic liquid. A method for synthesizing dimethyl carbonate and co-producing ethylene glycol by exchange reaction.

Background technique

Dimethyl carbonate is a green chemical basic raw material with low toxicity and high activity. Using the multifunctional organic synthesis research platform of dimethyl carbonate [ZhangSJ, ChenYH, _{LiFWetal.FixationandconversionofCO2usingionicliquids.CatalysisToday} , 2006,115:61-69.], through transesterification [KimWB, LeeJS.Anewprocessforthesynthesisofdiphenylcarbonatefromdimethylcarbonate.phenolovercathetery ., 1999,59(1):83-88.], Methylation reaction [SelvaM, PerosaA, TundoP, MemoliS. .] and methoxycarbonylation reaction [NagarajuN, KuriakoseG.AnewcatalystforsynthesisofN,N-biphenylureafromanilineanddimethylcarbonate.GreenChem.,2002,269-271.], etc., can synthesize polycarbonate, isocyanate, polycarbonate glycol and urethane, etc. A variety of important chemical materials have huge market value and application potential. In addition, ethylene glycol is not only one of the main raw materials for synthetic polyester materials, but also an important additive for the preparation of antifreeze. The production and market of this product directly affect the development and growth of the polyester and automobile industries. Through transesterification, ethylene carbonate is used as the reaction substrate to develop a new technology for the co-production of ethylene glycol from dimethyl carbonate, which is conducive to the construction of an industrial chain with low cost and high added value, and can enhance the market competitiveness of products.

At present, there are two kinds of catalysts for transesterification that have been reported: one is alkali metal or alkali metal salt [BuyschHJ, KrimmH, RudolphH.USPat4181676 (1980).] and traditional ionic liquid [DharmanMM, JuHY, ShimHL, LeeMK, KimKH, ParkDW.Significantinfluenceofmicrowavedielectriceatingonionicliquidcatalyzedtransesterificationofethylenecarbonatewithmethanol.J.Mol.Catal.A:Chem.,2009,303:96-101.] etc., the catalytic activity shown is generally not high, the separation of product and catalyst is difficult, and the subsequent product purification process is complicated; Yes, heterogeneous catalysts include metal oxides such as CaO, MgO, ZnO, Fe ₂ O ₃ or their mixtures [UranoY, KirishikikM, OndaY, TsunekiH. US Pat 5430170 (1995).] and amorphous inorganic materials, SBA-15 , MCM-41 and other supported quaternary ammonium or quaternary phosphine supported ionic liquid catalysts [ChoHJ, KwonHM, TharunJ, ParkDW. , KohJC, ParkDW.Synthesisofdimethylcarbonatefromethylenecarbonateandmethanolusingimmobilizedionicliquidonamporphoussilica.J.Ind.Eng.Chem.,2010,16:474-478], although this can solve the separation problem of the catalyst, but due to the lack of good compatibility between the substrate and the catalyst, the shown The catalytic activity is generally not high, and it generally needs to be inert gas CO ₂ under pressure (0.51-1.34MPa) to proceed smoothly.

High molecular polymer is a kind of carrier material with good compatibility with the reaction substrate. The reaction substrate can be better dispersed around the active center, which is beneficial to reduce the mass transfer resistance and promote the forward reaction. Since the key to the process ^of transesterification reaction is that RO nucleophile attacks the carbonyl carbon atom, the acetal intermediate formed enters the catalytic cycle mechanism process, and the catalytic reaction is easier to proceed smoothly with the enhancement of the proton-absorbing ability of the active center of the catalyst. In view of this, the present invention uses the organic polymer material as the carrier and the imidazole-type ionic liquid containing the hydroxyl anion structural unit as the catalytic active center to catalyze the transesterification reaction to synthesize dimethyl carbonate and co-produce ethylene glycol, so as to solve the problem of difficult separation of the product and the catalyst The problem is to establish a high value-added, environment-friendly and efficient transesterification reaction with a supported ionic liquid catalytic system.

Contents of the invention

The object of the present invention is to propose a kind of method that uses load-type ionic liquid as catalyst, catalyzes the transesterification reaction of ethylene carbonate and methanol, and efficiently synthesizes dimethyl carbonate and co-produces ethylene glycol. The supported ionic liquid catalyst involved uses an organic polymer material as a carrier, uses imidazole and its compounds to chemically modify the halogen-containing resin particles through a substitution reaction, and then uses an alkali metal hydroxide to perform ion exchange for anion structural units. Realize the chemical loading of functionalized ionic liquids, and the prepared catalysts are used in the transesterification reaction with ethylene carbonate and methanol as the reaction substrate, and catalyze the synthesis of dimethyl carbonate and co-production of ethylene glycol with high activity and high selectivity. Chemical products and catalysts can be recycled and reused after simple filtration.

Technical scheme of the present invention is as follows:

1. Synthesis of supported ionic liquid catalysts

Halogen-containing resin particles are used as the carrier, and imidazole compounds and their derivatives are supported by chemical bonds through substitution reactions; then, alkali metal hydroxides are used to obtain supported ionic liquid catalysts modified by hydroxyl anion structural units through ion exchange reactions , see formula (1).

Among them, X=Cl, Br, I; R=—C _n H _2n+1 , n=0, 1, 2, 3, 4… and other natural numbers; high molecular polymers are polystyrene and its derivatives, resin particles etc., the particle size range of resin particles is 0.1-2000 μm; solvent 1 is any one of toluene, acetonitrile, benzene, methylene chloride, DMSO, dioxane, N,N-dimethylformamide and chloroform; The reaction time is 0-48h; the solvent 2 is any one of deionized water, tetrahydrofuran and ether; the alkali is any one of sodium hydroxide, potassium hydroxide and lithium hydroxide, and the mass concentration of alkali metal hydroxide is 0.01~1.2g/mL, the anion pairing temperature is 25~90℃, and the reaction time is 0.5~48h.

2. Transesterification reaction

Put the 100mL round-bottomed flask equipped with magnetic stirring and condenser tube into the oil bath heated to the reaction temperature in advance; then, add ethylene carbonate, catalyst and methanol in sequence, and cool to room temperature after the reaction is completed (see formula (2)), through simple filtration or centrifugation, the recovery and reuse of the catalyst is realized, and the filtrate is quantitatively analyzed by a gas chromatograph, and the conversion rate of the reaction substrate and the selectivity of the product are calculated. For the specific calculation method, see Appendix I.

The mass ratio of methanol to ethylene carbonate is 2:1-20:1, the amount of catalyst is 0.5-20wt% of the amount of ethylene carbonate, the reaction temperature is 30-85°C, and the reaction time is 0.5-32h.

The supported ionic liquid catalyst provided by the invention is used for transesterification to synthesize dimethyl carbonate and co-produce two chemical products of ethylene glycol, and has the following effects and benefits:

1. With the halogenated polymer polymer material as the carrier, through the substitution reaction, the imidazole and its derivatives are chemically loaded, treated with alkali metal hydroxide, and the anionic structural unit ion exchange reaction occurs, and the functionalized loaded type can be obtained The ionic liquid catalyst has a simple preparation process, is easy to operate, has high added value, and is beneficial to industrial scale-up production.

2. The substrate has good compatibility with the catalyst, and can be well dispersed around the catalytic active center, which is beneficial to reduce the diffusion and mass transfer resistance of the substrate, increase the catalytic reaction rate, and promote the smooth progress of the reaction.

3. The imidazole-type ionic liquid is paired with the anion structural unit by ion exchange through the alkali metal hydroxide, and the prepared hydroxyl anion structural unit chemically modified supported ionic liquid catalyst helps to enhance the nucleophilic attack on the carbonyl carbon atom ^of RO , thereby accelerating the catalytic reaction process and promoting the positive movement of the reaction balance, which is very beneficial to improving the yield of dimethyl carbonate co-production ethylene glycol products.

4. After the reaction, the catalyst can be recovered and reused by simple filtration or centrifugal separation. The separation process is simple and easy to operate. It has important theoretical research significance and significance for improving the utilization efficiency of the catalyst and building an environmentally friendly green catalytic system. scientific value.

detailed description

The supported ionic liquid catalyst used in the present invention is used in the following examples, so as to understand the contents of the present invention, but without departing from the stated purpose of the present invention, it does not represent or limit the scope of protection of the present invention, and does not Limit the content of this invention in any way.

The synthesis of embodiment 1 catalyst

Add 8.36g of polystyrene resin particles containing 18-19wt% chlorine, two equivalents of methylimidazole and 50mL of toluene to a 100mL three-neck flask equipped with a magnet, and heat to reflux for 24 hours, stop the reaction, and cool to room temperature. After the mixed solution is simply filtered and vacuum-dried, resin particles functionalized with imidazolium cations are obtained. Then, using KOH aqueous solution with a mass percentage of 20%, after ion exchange reaction for 24h, the crude catalyst was obtained, washed with deionized water (3×100mL), ethanol (3×50mL) successively, and dried in vacuo. A supported ionic liquid catalyst chemically modified by the hydroxyl anion structural unit was obtained, and the elements were quantitatively analyzed by an elemental analyzer: the contents of C, H, N, and O were 131.25wt%, 12.29wt%, 25.61wt% and 5.99wt% respectively %, so it is speculated that the loading of hydroxyl anion is 6.36wt%.

Embodiment 2 transesterification reaction

In the 250mL three-necked round-bottom flask that spherical reflux condenser is housed, add 10g ethylene carbonate, 80g methyl alcohol and the embodiment 1 catalyst that accounts for ethylene carbonate mass percentage composition 8.0wt% successively, after mixing uniformly, insert 80 ℃ in an oil bath, magnetically stirred for 8 hours, cooled to room temperature, and the catalyst was filtered and separated, and the filtrate was quantitatively analyzed by a gas chromatograph, calculated according to Appendix I: the conversion rate of ethylene carbonate reached 99.4%, and dimethyl carbonate was generated. Both ester and glycol selectivities were 99.9%.

Example 3

In the 250mL three-necked round bottom flask, add 10g ethylene carbonate, 80g methyl alcohol and account for the catalyzer of embodiment 1 of 5.0wt% in ethylene carbonate mass percentage composition successively, other steps are with embodiment 2, and the transformation rate of ethylene carbonate is 68.4%, the selectivity of forming dimethyl carbonate is 73.1%, and the selectivity of ethylene glycol is 99.9%.

Example 4

In the 250mL three-necked round bottom flask, add 10g ethylene carbonate, 100g methyl alcohol and account for ethylene carbonate mass percentage composition successively and be the embodiment 1 catalyst of 8.0wt%; %, the selectivity of generating dimethyl carbonate is 97.4%, and the selectivity of ethylene glycol is 97.1%.

Example 5

In a 250mL three-necked round-bottomed flask, add 10g ethylene carbonate, 80g methanol and the catalyst of Example 1, which is 8.0wt% by weight of ethylene carbonate, in turn, mix well, put it in an oil bath at 70°C, and react 8h, the others are the same as in Example 2, the conversion rate of ethylene carbonate is 64.1%, the selectivity to dimethyl carbonate is 67.4%, and the selectivity to ethylene glycol is 82.3%.

Example 6

In the 250mL three-necked round-bottomed flask, the ratio of raw materials added successively is the same as in Example 5, and the operating conditions are the same as in Example 2. After mixing uniformly, react for 5h to obtain a conversion rate of 77.1% for ethylene carbonate and generate dimethyl carbonate. The selectivity is 98.7%, and the selectivity of ethylene glycol is 99.9%. Embodiment 7 Catalyst recycling situation

After the transesterification reaction, the mixed solution was simply filtered, and the filter cake was rinsed with absolute ethanol (3×100 mL), and then vacuum-dried to recover the catalyst. Then, the catalyst that will reclaim is joined in the three-necked round-bottomed flask, is used again for catalyzing the transesterification reaction, and other is with embodiment 2, and the transformation rate that obtains ethylene carbonate is 86.3%, generates the selection of dimethyl carbonate and ethylene glycol The sex is 99.9%. Subsequently, the catalyst was recycled and reused again, and the catalytic activity remained basically unchanged for at least five times. The specific results are shown in Table 1.

Table 1 Catalyst recycling ^a

Cycles 1 2 3 4 5 6 EC conversion rate (%) 89.4 86.3 83.4 84.0 84.6 84.0 Selectivity of generating DMC (%) 99.9 99.9 99.9 99.9 97.8 80.5 Selectivity of generating EG (%) 99.9 99.9 99.9 99.9 96.5 86.0

^a See Appendix I for the calculation method.

Although the above content has described the present invention in detail with general descriptions and specific embodiments, on the basis of the present invention, some modifications or improvements that those skilled in the art can make to it will be obvious to those skilled in the art of. Therefore, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Appendix I

Claims (9)

1. the method for a load-type ion liquid catalyzed transesterification Synthesis of dimethyl carbonate coproduction ethylene glycol, it is characterized in that: pass through substitution reaction, in organic solvent environment, utilize imidazolium compounds and derivative thereof, through reflux, chemically modified is carried out to halogen-containing resin particle, recycle certain density oxyhydroxide and the ion-exchange of anion structure unit is carried out to it, the functionalization load-type ion liquid catalyst that obtained hydroxyl anion structure unit and glyoxaline cation structural unit match, for the transesterification reaction that NSC 11801 and methyl alcohol participate in, at normal pressure, under optimal temperature and condition of no solvent, catalytic synthesizing dimethyl carbonate coproduction ethylene glycol product, after reaction terminates, catalyzer is through simple separation means, realize recovery and the cycling and reutilization of catalyzer.

2. the method for load-type ion liquid catalyzed transesterification Synthesis of dimethyl carbonate coproduction ethylene glycol according to claim 1, is characterized in that: the structure of described load-type ion liquid catalyst is:

r refers to-C _nh _2n+1, n=0, the natural numbers such as 1,2,3....

3. the method for load-type ion liquid catalyzed transesterification Synthesis of dimethyl carbonate coproduction ethylene glycol according to claim 1 or 2, it is characterized in that: the carrier of described load-type ion liquid catalyst is halogen-containing resin particle, and indication resin particle particle size range is 0.1 ~ 2000 μm.

4. the method for load-type ion liquid catalyzed transesterification Synthesis of dimethyl carbonate coproduction ethylene glycol according to claim 3, it is characterized in that: described resin particle refers to the particulate matter of halogen-containing polystyrene and derivative thereof, described halogen refers to Cl, Br and I.

5. the method for load-type ion liquid catalyzed transesterification Synthesis of dimethyl carbonate coproduction ethylene glycol according to claim 1, it is characterized in that: described organic solvent refers to toluene, acetonitrile, benzene, methylene dichloride, DMSO, diox, N, any one in N-dimethyl formamide and chloroform, temperature of reaction is reflux temperature, and the reaction times is 0 ~ 48h.

6. the method for load-type ion liquid catalytic synthesizing dimethyl carbonate coproduction ethylene glycol according to claim 1, it is characterized in that: described strong alkali hydroxides refers to sodium hydroxide, potassium hydroxide and lithium hydroxide etc., solvent environment is any one in deionized water, tetrahydrofuran (THF) and ether, the mass concentration of alkali metal hydroxide is 0.01 ~ 1.2g/mL, negatively charged ion pairing temperature is 25 ~ 90 DEG C, and its reaction times is 0.5 ~ 48h.

7. the method for load-type ion liquid catalyzed transesterification Synthesis of dimethyl carbonate coproduction ethylene glycol according to claim 1, is characterized in that: the catalyst levels of described transesterification reaction load-type ion liquid accounts for 0.5 ~ 20wt% of NSC 11801 quality.

8. the method for load-type ion liquid catalyzed transesterification Synthesis of dimethyl carbonate coproduction ethylene glycol according to claim 1, it is characterized in that: the temperature of described transesterification reaction is 30 ~ 85 DEG C, reaction times is 0.5 ~ 32h, and the mass ratio of methyl alcohol and NSC 11801 is 2:1 ~ 20:1.

9. the method for load-type ion liquid catalyzed transesterification Synthesis of dimethyl carbonate coproduction ethylene glycol according to claim 1, is characterized in that: the simple separation means of described catalyzer refer to simple filtration or centrifugation.