阅读说明：本技术 一种六氟异丙基甲醚的气相制备方法 (Gas phase preparation method of hexafluoroisopropyl methyl ether ) 是由 李伟 胡江平 于 2020-05-28 设计创作，主要内容包括：本发明公开了一种六氟异丙基甲醚的气相制备方法,所述气相制备方法包括：在催化剂作用下,六氟异丙醇和碳酸二甲酯反应得到所述六氟异丙基甲醚,所述催化剂具有50％～95％中等强度酸性中心和50％～95％中等强度碱性中心。本发明具有原料转化率高、产品选择性高、工艺简单、适于工业化生产等优点。(The invention discloses a gas-phase preparation method of hexafluoroisopropyl methyl ether, which comprises the following steps: under the action of a catalyst, reacting hexafluoroisopropanol with dimethyl carbonate to obtain hexafluoroisopropyl methyl ether, wherein the catalyst has 50-95% of medium-strength acid centers and 50-95% of medium-strength alkaline centers. The invention has the advantages of high conversion rate of raw materials, high product selectivity, simple process, suitability for industrial production and the like.)

1. A gas phase preparation method of hexafluoroisopropyl methyl ether is characterized in that: under the action of a catalyst, reacting hexafluoroisopropanol with dimethyl carbonate to obtain hexafluoroisopropyl methyl ether, wherein the catalyst has 50-95% of medium-strength acid centers and 50-95% of medium-strength alkaline centers.

2. The gas-phase production method of hexafluoroisopropyl methyl ether according to claim 1, characterized in that: the catalyst has 55% to 90% medium strength acid sites and 50% to 75% medium strength basic sites.

3. The gas-phase production method of hexafluoroisopropyl methyl ether as claimed in claim 1 or 2, characterized in that: the catalyst is selected from at least one of metal oxide, metal fluoride or molecular sieve, the metal oxide is single-component metal oxide or combination of at least two-component metal oxide, and the metal fluoride is single-component metal fluoride or combination of at least two-component metal fluoride.

4. The gas-phase production method of hexafluoroisopropyl methyl ether as claimed in claim 3, characterized in that: the metal oxide is selected from at least one of magnesium oxide, aluminum oxide, calcium oxide, strontium oxide, barium oxide, zinc oxide, iron oxide and lanthanum oxide; the metal fluoride is at least one selected from magnesium fluoride, aluminum fluoride, zinc fluoride, calcium fluoride, strontium fluoride, barium fluoride, iron fluoride and antimony fluoride.

5. The gas-phase production method of hexafluoroisopropyl methyl ether according to claim 4, wherein: the catalyst is a combination of two metal oxides.

6. The gas-phase production method of hexafluoroisopropyl methyl ether as claimed in claim 5, characterized in that: the catalyst is a mixture of magnesium oxide and aluminum oxide, and the molar ratio of the magnesium oxide to the aluminum oxide is as follows: 5% -95%: 95 to 5 percent.

7. The gas-phase production method of hexafluoroisopropyl methyl ether as claimed in claim 3, characterized in that: the metal oxide catalyst is prepared by adopting a coprecipitation method, and comprises the following steps:

A1. dissolving soluble metal salt in water, adding a proper amount of ammonia water while stirring, adjusting the pH to 8-10, then stirring and aging at room temperature, carrying out suction filtration, washing with water, and drying to obtain a catalyst precursor;

A2. and roasting the catalyst precursor in a muffle furnace at 450-600 ℃ for 2-10 h, and then cooling, crushing and molding to obtain the metal oxide catalyst.

8. The gas-phase production method of hexafluoroisopropyl methyl ether according to claim 7, wherein: the soluble metal salt is selected from at least one of nitrate, phosphate, trifluoroacetate or acetate.

9. The gas-phase production method of hexafluoroisopropyl methyl ether according to claim 1, characterized in that: the molar ratio of the hexafluoroisopropanol to the dimethyl carbonate is 1: 1-1: 5, the reaction temperature is 150-300 ℃, the reaction pressure is 0.1-1.0 MPa, and the contact time of the catalyst is 0.1-100 s.

10. The gas-phase production method of hexafluoroisopropyl methyl ether according to claim 1, characterized in that: the gas phase preparation reaction is carried out in a tubular reactor, a fluidized bed reactor, an adiabatic reactor or an isothermal reactor.

Technical Field

The invention relates to preparation of hydrofluoroether, in particular to a method for preparing hexafluoroisopropyl methyl ether from hexafluoroisopropanol and dimethyl carbonate as raw materials in a gas phase under the action of a medium-strength acidic and medium-strength alkaline catalyst.

Background

The hydrofluoroether is an important fluorine-containing compound, has excellent environmental protection performance, has zero ODP (ozone depletion potential), low GWP (global warming potential), and short atmospheric residence time, and is considered to be one of ideal substitutes for CFCs (carbon fiber reinforced composites). The hydrofluoroether also has the advantages of low toxicity, non-corrosiveness, non-flammability, no smoke generation, and easy storage and transportation, and is expected to be applied to a plurality of fields.

For the synthesis of hexafluoroisopropyl methyl ether, the following are reported in the prior art:

U.S. Pat. No. 4, 3346448A and German patent GB1250928A disclose the preparation of hexafluoroisopropyl methyl ether from hexafluoroisopropanol and dimethyl sulfate as starting materials by liquid phase reaction under the action of a base, but the process presents a great safety risk in industrial applications due to the extreme toxicity of dimethyl sulfate.

Chinese patent CN101544547A discloses a method for obtaining hexafluoroisopropyl methyl ether by using hexafluoroisopropanol and dimethyl carbonate as raw materials and performing a liquid phase methylation reaction under the action of an alkaline oxide, but the yield of the method is only 89% when potassium carbonate is used as a catalyst, and high-temperature and high-pressure reaction conditions are required, so that the method has high energy consumption and high cost in industrial application.

Therefore, there is a need to develop a method for preparing hexafluoroisopropyl methyl ether, which has high product yield, low production cost, safety and environmental protection, and is suitable for industrial production.

Disclosure of Invention

In order to solve the technical problems, the invention provides a gas phase preparation method of hexafluoroisopropyl methyl ether, which has the advantages of high conversion rate of raw materials, high product selectivity, simple process and suitability for industrial production.

The catalyst of the invention adopts NH as the acid center with different strength₃TPD curve determination and determination of the distribution of the different intensity acid centers by integration of the TPD profile, in particular:

the desorption peak appears at 80-150 ℃, and the acidity is weak;

the medium acidity is obtained when a desorption peak appears at 150-300 ℃;

when the desorption peak appears at 300-450 ℃, the acidity is strong.

The catalyst of the invention adopts CO as basic center with different strengths₂Determination of the TPD curve and determination of the distribution of the different intensity basic centres by integration of the TPD profile, in particular：

The desorption peak appears at 80-150 ℃, and the pH value is weak alkalinity;

the medium alkalinity appears when the desorption peak appears at 150-300 ℃;

when the temperature is higher than 300 ℃, the desorption peak appears, and the strong basicity is obtained.

The purpose of the invention is realized by the following technical scheme:

a gas phase production process of hexafluoroisopropyl methyl ether, comprising: under the action of a catalyst, reacting hexafluoroisopropanol with dimethyl carbonate to obtain hexafluoroisopropyl methyl ether, wherein the catalyst has 50-95% of medium-strength acid centers and 50-95% of medium-strength alkaline centers. The reaction equation is as follows:

the catalyst of the invention comprises, in addition to the medium-strength acid sites: weak acidity and strong acidity acid centers, the distribution of which is such that the overall performance of the catalyst according to the invention is moderately strong.

The catalyst of the invention comprises, in addition to the medium-strength basic centers: the catalyst comprises weak alkalinity centers and strong alkalinity centers, wherein the distribution of the weak alkalinity centers and the strong alkalinity centers is only required to meet the condition that the whole catalyst of the invention shows medium-strength alkalinity.

Preferably, the catalyst has 55% to 90% medium strength acid centers, 0% to 20% weak acid centers and 0% to 25% strong acid centers; further preferably, the catalyst has 75% to 90% medium strength acid sites, 5% to 15% weak acid sites and 2% to 15% strong acid sites.

Preferably, the catalyst has 50% to 75% medium strength basic centers, 10% to 40% weak basic centers and 0% to 30% strong basic centers; further preferably, the catalyst has 55% to 70% medium strength basic centers, 15% to 40% weak basic centers and 3% to 15% strong basic centers.

The catalyst of the present invention is selected from at least one of a metal oxide, a metal fluoride, which may be a single component metal oxide or a combination of at least two component metal oxides, or a molecular sieve, which may be a single component metal fluoride or a combination of at least two component metal fluorides, including but not limited to ZSM-5, mordenite, 13X molecular sieves, so long as the catalyst has a distribution of medium strength acid centers and medium strength basic centers that satisfies the aforementioned ranges.

Further preferably, the metal oxide is selected from at least one of magnesium oxide, aluminum oxide, zinc oxide, ferric oxide, calcium fluoride; the metal fluoride is at least one of magnesium fluoride, zinc fluoride and calcium fluoride.

More preferably, the catalyst is a combination of two metal oxides, or a combination of two metal fluorides, or a combination of one metal oxide and one metal fluoride. Most preferably, the catalyst is a combination of two metal oxides. The metal fluoride catalyst is not used, so that the preparation of the catalyst does not need hydrofluoride, and the reaction is safer, cleaner and more environment-friendly.

In one embodiment, the catalyst is a mixture of magnesium oxide and aluminum oxide, wherein the molar ratio of magnesium oxide to aluminum oxide is: 5% -95%: 95 to 5 percent. Preferably, the molar ratio of magnesium oxide to aluminum oxide is: 45% -75%: 55 to 25 percent.

The invention adopts magnesium oxide and aluminum oxide catalysts with 55-90% of medium-strength acid centers and 50-75% of medium-strength alkaline centers, can greatly improve the selectivity of hexafluoroisopropyl methyl ether, and has the following reaction mechanism:

the catalyst of the invention is prepared by adopting a conventional method, such as a blending grinding method, a coprecipitation method, a hydrothermal synthesis method, a sol-gel method and the like, and the catalyst with the distributed medium-strength acid centers and medium-strength alkaline centers is prepared.

Preferably, the metal oxide catalyst of the present invention is prepared by a coprecipitation method, comprising the steps of:

A1. dissolving soluble metal salt in water, adding a proper amount of ammonia water while stirring, adjusting the pH to 8-10, then stirring and aging at room temperature, carrying out suction filtration, washing with water, and drying to obtain a catalyst precursor;

A2. and roasting the catalyst precursor in a muffle furnace at 450-600 ℃ for 2-10 h, and then cooling, crushing and molding to obtain the metal oxide catalyst.

The metal fluoride catalyst can be prepared by introducing anhydrous hydrogen fluoride or hydrofluoric acid for fluorination to obtain the corresponding metal fluoride catalyst.

Further, the soluble metal salt is selected from at least one of nitrate, phosphate, trifluoroacetate or acetate. When the catalyst is single-component metal oxide or metal fluoride, the soluble metal salt is one; when the catalyst is a combination of metal oxides and/or metal fluorides, the soluble metal salt employs a plurality of metal salts.

Under the action of the catalyst, in the process for preparing hexafluoroisopropyl methyl ether from hexafluoroisopropanol and dimethyl carbonate in a gas phase, the reaction temperature can be properly reduced. Preferably, the molar ratio of the hexafluoroisopropanol to the dimethyl carbonate is 1: 1-1: 5, the reaction temperature is 150-300 ℃, the reaction pressure is 0.1-1.0 MPa, and the catalyst contact time is 0.1-100 s. More preferably, the molar ratio of the hexafluoroisopropanol to the dimethyl carbonate is 1: 1-1: 4, the reaction temperature is 200-260 ℃, the reaction pressure is 0.1-0.5 MPa, and the catalyst contact time is 1-50 s.

According to the aforementioned gas phase production method of hexafluoroisopropyl methyl ether, the gas phase production reaction may be carried out in a tubular reactor, a fluidized bed reactor, an adiabatic reactor, or an isothermal reactor.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention adopts the catalysts of medium-strength acid centers and medium-strength alkaline centers, improves the reaction activity of the gas phase preparation process of hexafluoroisopropyl methyl ether, and further improves the selectivity of the product and the conversion rate of raw materials.

2. The catalyst of the invention has good catalytic activity and stability, can stably operate for a long time, and is suitable for industrial production.

The gas phase preparation method of the invention can realize continuous production and has high production efficiency.

Detailed Description

The present invention is further illustrated by the following examples, which are not intended to limit the invention to these embodiments. It will be appreciated by those skilled in the art that the present invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.

In the embodiment of the invention, the reaction product is tested by adopting a gas chromatography, and the analysis step comprises the following steps: condensing and collecting reaction products, taking condensate liquid for gas chromatography analysis, taking high-purity nitrogen as carrier gas, and detecting conditions as follows: the temperature of the gasification chamber is 220 ℃, the temperature of the detector is 220 ℃, the initial temperature of the column temperature is 35 ℃, the temperature is kept for 5min, the heating rate is 20 ℃/min, the final temperature is 200 ℃, and the temperature is kept for 3 min.

Preparation example 1

Soluble metal salts (magnesium nitrate hexahydrate (0.2mol, 51.3g), aluminum nitrate nonahydrate (1.2mol,450.2g)) were dissolved in 1000ml of distilled water, ammonia was slowly added dropwise with stirring until the PH became about 9.5, and the mixture was stirred at room temperature for 5 hours, then filtered, washed with water, dried, and then calcined at 500 ℃ for 6 hours, cooled, pulverized, and molded to obtain a magnesium oxide/aluminum oxide catalyst designated as LW-1. The molar ratio of magnesium oxide to aluminum oxide in the magnesium oxide/aluminum oxide catalyst is calculated according to the dosage of soluble salt, ICP-OES is adopted to carry out quantitative determination on metal elements, and distribution of different strength acid centers is carried out through NH₃Calculation of the TPD curve, the different intensity basic centers passing through the CO₂-TThe PD curve was calculated and the specific results are shown in table 1 below.

Preparation example 2

The procedure of this preparation is the same as that of preparation 1 except that: the molar ratio of the soluble salt magnesium nitrate hexahydrate to the aluminum nitrate nonahydrate (the specific ratio is shown in table 1) is changed, and catalysts LW-2-LW-10 are respectively prepared.

Preparation example 3

The procedure of this preparation is the same as that of preparation 1 except that: the soluble metal salt was prepared using zinc acetate (0.1mol,18.3g) and ferric nitrate nonahydrate (0.2mol,80.8g) to provide catalyst LW-11.

Preparation example 4

The procedure of this preparation is the same as that of preparation 1 except that: the soluble metal salt was prepared using only magnesium nitrate hexahydrate (1.0mol, 256.5g) to provide catalyst LW-12.

Preparation example 5

The procedure of this preparation is the same as that of preparation 1 except that: the soluble metal salt was prepared using aluminum nitrate nonahydrate (0.6mol,225.1g) to provide catalyst LW-13.

Preparation example 6

The procedure of this preparation is the same as that of preparation 1 except that: the fluorination step of adding the catalyst is specifically as follows: catalyst LW-12 is fluorinated with anhydrous hydrogen fluoride to provide catalyst LW-14.

TABLE 1 catalyst composition and distribution of different strength acid/base active sites

Example 1

20ml of a solid catalyst LW-1 was charged in a tubular reactor made of monel having an inner diameter of 1/2 inches and a length of 40cm, the reactor was heated to 250 ℃ and the molar ratio of hexafluoroisopropanol to dimethyl carbonate was controlled at 1:2, a liquid raw material mixture was introduced into a mixing chamber using a sample pump, the liquid raw material was vaporized in the mixing chamber and passed through the reactor filled with the catalyst for 8 seconds, the reaction product was cooled and collected in a cold trap, and the composition of the reaction product was analyzed by gas chromatography, to obtain the raw material conversion rate and the product selectivity as shown in Table 2 below.

Example 2

Example 2 was performed as in example 1, except that: the catalysts LW-2 to LW-14 in the preparation examples were used in place of the catalyst LW-1, and the results of the reaction by gas chromatography analysis are shown in Table 2 below.

Example 3

The operation of this example is the same as example 1 except that: the reaction temperature was reduced to 240 ℃ while using catalyst LW-7.

Example 4

The operation of this example is the same as example 3, except that: the molar ratio of hexafluoroisopropanol to dimethyl carbonate was controlled to 1: 1.5.

Example 5

The operation of this example is the same as example 3, except that: the reaction contact time was increased to 10 seconds.

Example 6

A tubular reactor made of Monel alloy with the inner diameter of 1/2 inches and the length of 40cm is filled with 20ml of solid catalyst LW-7, the temperature of the reactor is raised to 240 ℃, the molar ratio of hexafluoroisopropanol to dimethyl carbonate is controlled to be 1:2, a liquid raw material mixture is introduced into a mixing cavity by using a sample injection pump, the liquid raw material is gasified in the mixing cavity and passes through the reactor filled with the catalyst, the contact time is 8 seconds, the stability of the catalyst under the continuous reaction condition of 500 hours is examined, and the chromatographic analysis result after the catalyst reacts for 500 hours shows that the conversion rate of the raw material is kept above 84%, and the selectivity of the product is kept above 99%, and the result is shown in Table 2.

Table 2, reaction results Table