A method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene

Abstract

The present invention belongs to the technical field of fluorine chemical industry, and specifically relates to a method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene. The method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene comprises the following steps: preheating trans-2-ethoxy-1,1,1,4,4,4-hexafluoro-2-butene, mixing with hydrogen, and reacting to obtain trans-1,1,1,4,4,4-hexafluoro-2-butene under the action of a catalyst; the catalyst is composed of aluminum-magnesium composite oxide and a transition metal of Group VIII. The selectivity of trans-1,1,1,4,4,4-hexafluoro-2-butene obtained by the preparation method of the present invention can reach 99%, and the reaction temperature of the preparation method is moderate, the three wastes are small, and the obtained trans-1,1,1,4,4,4-hexafluoro-2-butene has important application value in industries such as electricity, electrical appliances and electronics.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine chemical industry, and particularly relates to a method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene. Background Art

[0002] 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz), including cis and trans configurations, trans (E-HFO-1336mzz) has a boiling point of 7.5℃ and is a colorless, odorless, non-flammable gas at room temperature and pressure. It has good environmental properties (ODP=0, GWP=18, atmospheric life of only 22 days), high safety, non-toxicity, flame retardancy, oil solubility and good material compatibility, and has good application prospects in insulation, heat pumps, refrigeration and other fields.

[0003] Application in electrical insulation: Studies have shown that E-HFO-1336mzz, as a new type of gas developed, has similar excellent performance in electrical insulation and arc extinguishing medium, and has a low GWP value, which meets environmental protection requirements. Siemens once stated that the relative dielectric strength of E-HFO-1336mzz is higher than that of SF6, and it can be used as an insulating gas / arc extinguishing medium in electrical devices greater than 1kV. The HFO-1336mzz molecule carries six fluorine atoms on the two terminal methyl groups, which can correspondingly form precursor dielectric breakdown by gas discharge through dissociative attachment (such as forming negatively charged fluoride ions). At the same time, compared with other new insulating gases (mainly fluorinated ketones and fluorinated nitriles), E-HFO-1336mzz has a low atmospheric lifetime and low toxicity.

[0004] Application in heat pump working fluid: E-HFO-1336mzz can realize waste heat recovery in high-temperature heat pump and low-temperature heat pump as heat pump working fluid, and has high economic value. Jason et al. proved that E-HFO-1336mzz has a higher condensation temperature than HFC-134a, HFO-1234yf or HFO-1234ze, and its GWP value is at an extremely low level, while the COPH value is significantly higher, which is conducive to its economic use in heat pump applications. Specific application areas include low-pressure steam sterilization, central heating, high-temperature drying, process heating, food manufacturing, drying / dehydration, etc.

[0005] The preparation method of E-HFO-1336mzz was reported as early as 1952 (Journal of Chemical Society 19522504). 2-iodo-hexafluorobutane was synthesized by reacting trifluoroiodomethane with trifluoropropylene, and then E-HFO-1336mzz was prepared by dehydroiodination under alkaline conditions. In recent years, with the discovery of various excellent properties of E-HFO-1336mzz, more and more related patent reports have been published. However, the existing methods have defects such as poor selectivity for trans products and the need to use chemical amounts of metal elements or bases. For example, using R123 as a raw material, coupling synthesis of E-HFO-1336mzz (WO2015142981, WO2009117458) requires the use of a chemical amount of copper powder as a coupling reagent and the selectivity for trans products is only about 50%. E-HFO-1336mzz can also be prepared by hydrogenation of hexafluorobutyne (WO2017027323, WO2015059500, WO2019243704). Since the saponification method is required in the preparation process, this method produces a lot of waste alkali, and the cis selectivity of the product is obviously due to the trans selectivity. In addition, WO2016014348 and WO2001007384 respectively use R1233xf and R1233zd to prepare E-HFO-1336mzz. Due to the high temperature cracking process, the reaction temperature reaches 600-725°C, and the energy consumption is very high. Fluorination is also one of the important methods for preparing E-HFO-1336mzz. It uses polyhalogenated alkanes and anhydrous hydrogen fluoride under the action of a catalyst, but the cis- and trans-selectivity of the product is greatly related to temperature (WO2015142981, WO2016078225, WO2020206335, WO2019051389). Summary of the invention

[0006] In view of the shortcomings and defects of the prior art, the present invention aims to provide a method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene. The selectivity of the trans-1,1,1,4,4,4-hexafluoro-2-butene prepared by the preparation method can reach 99%, and the reaction temperature of the preparation method is moderate, the three wastes are small, and the prepared trans-1,1,1,4,4,4-hexafluoro-2-butene has important application value in the power, electrical appliances and electronics industries.

[0007] In order to achieve the above object, the present invention adopts the following technical scheme: a method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene, comprising the following steps:

[0008] Preheating trans-2-ethoxy-1,1,1,4,4,4-hexafluoro-2-butene, mixing with hydrogen, and reacting under the action of a catalyst to obtain trans-1,1,1,4,4,4-hexafluoro-2-butene;

[0009] The catalyst includes an aluminum-magnesium composite oxide and a Group VIII transition metal.

[0010] Preferably, the aluminum-magnesium composite oxide has a molecular sieve-like structure and a microporous structure.

[0011] Preferably, the molar ratio of the 2-ethoxy-1,1,1,4,4,4-hexafluoro-2-butene to hydrogen is 1:(1-5). More preferably, the molar ratio of the 2-ethoxy-1,1,1,4,4,4-hexafluoro-2-butene to hydrogen is 1:(2-4).

[0012] Preferably, the BET surface area of ​​the aluminum-magnesium composite oxide is between 200 and 500 m 2 / g.

[0013] Preferably, the Group VIII transition metal is one or two of Ru, Ni or Co.

[0014] Preferably, the mass content of the Group VIII transition metal is 0.5 to 10.0 wt % of the total mass of the catalyst.

[0015] Preferably, the preparation method of the aluminum-magnesium composite oxide comprises the following steps:

[0016] The aluminum-containing compound and the magnesium-containing compound are used as raw materials, polyethylene glycol or organic amine is added as a template agent, and the synthesis is carried out by a hydrothermal method, a solvent thermal method or a dry gel method. The hydrothermal method, the solvent thermal method or the dry gel method are conventional techniques in the art.

[0017] Preferably, the method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene comprises at least one of the following (1) to (2):

[0018] (1) The aluminum-containing compound includes aluminum hydroxide, pseudo-boehmite, hydrated aluminum oxide, and aluminum isopropoxide;

[0019] (2) The magnesium-containing compounds include magnesium oxide, magnesium nitrate, magnesium acetate, and metallic magnesium.

[0020] Preferably, the method for preparing the catalyst comprises the following steps:

[0021] The aluminum-magnesium composite oxide is immersed in a Group VIII transition metal solution, dried, and sintered at a constant temperature of 500-600° C. in a muffle furnace to obtain a catalyst.

[0022] Preferably, the method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene comprises at least one of the following (1) to (3):

[0023] (1) The reaction temperature is 150-250° C.;

[0024] (2) The reaction space velocity is 1.0 to 5.0 h -1 ;

[0025] (3) The reaction pressure is 0.2 to 2.0 MPa.

[0026] More preferably, the method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene comprises at least one of the following (1) to (3):

[0027] (1) The reaction temperature is 180-225° C.;

[0028] (2) The reaction space velocity is 1.5 to 2.5 h -1 ;

[0029] (3) The reaction pressure is 0.4-1.0 MPa.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The invention uses a supported catalyst to prepare trans-1,1,1,4,4,4-hexafluoro-2-butene in a fixed bed reactor in one step. The reaction temperature is moderate and the product trans selectivity is high, which can reach up to 99%. Meanwhile, the invention uses 2-ethoxy-1,1,1,4,4,4-hexafluoro-2-butene as a raw material, which not only enables the active components of the catalyst to have better oxygen affinity, but also the alkoxy removed by the catalyst during the reaction will not cause catalyst poisoning, thereby further improving the catalytic activity of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the hydrogen spectrum of trans-1,1,1,4,4,4-hexafluoro-2-butene prepared in Example 1 of the present invention.

[0033] Figure 2 This is the carbon spectrum of trans-1,1,1,4,4,4-hexafluoro-2-butene prepared in Example 1 of the present invention.

[0034] Figure 3 This is the fluorine spectrum of trans-1,1,1,4,4,4-hexafluoro-2-butene prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] In the embodiments and comparative examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0037] Example 1. Preparation method of trans-1,1,1,4,4,4-hexafluoro-2-butene

[0038] (1) Preparation of carrier

[0039] Pseudo-boehmite and magnesium oxide were mixed in a weight ratio of 45:55, diluted nitric acid was added to dissolve, and then a template agent polyethylene glycol 10000 was added, dried at 100°C, and then calcined in a muffle furnace at 500°C for 8 hours to obtain a catalyst carrier;

[0040] (2) Preparation of Catalyst

[0041] The obtained catalyst carrier was immersed in a mixed solution of 5g / 1000mL ruthenium nitrate and 5g / 1000mL nickel nitrate, with a solid-liquid ratio of 1:1. After drying at 100℃, it was sintered at 500℃ in a muffle furnace for 6 hours to obtain a 0.5% finished catalyst, recorded as 0.5Ru / 0.5Ni / Al x Mg y O z ;

[0042] (3) Evaluation of catalyst reaction effect

[0043] The reaction was carried out in a continuous fixed bed reactor. The catalyst loading was 10 mL, the carrier gas was hydrogen, the reactant was 2-ethoxy-1,1,1,4,4,4-hexafluoro-2-butene, the reactant was fed by a liquid micro pump, the molar ratio of 2-ethoxy-1,1,1,4,4,4-hexafluoro-2-butene to hydrogen was 1:2, and the space velocity was controlled at 2.5 h -1 The reaction pressure was 1.0 MPa, the reaction temperature was 225°C, and after 6 hours of reaction, the gas phase composition was analyzed by gas chromatography. The conversion rate was 97% and the selectivity was 99%.

[0044] The NMR data of the product are as attached. Figures 1 to 3 shown.

[0045] Embodiments 2 to 4

[0046] The difference between Examples 2 to 4 and Example 1 is that the reaction temperatures are different, and the other steps refer to Example 1.

[0047] The specific parameters, conversion rate and selectivity results are shown in Table 1.

[0048] Table 1

[0049] Example Reaction temperature / ℃ Conversion rate (%) Selectivity (%) 2 150 80 88 3 180 93 97 4 250 97 63

[0050] Embodiments 5 to 7

[0051] The difference between Examples 5 to 7 and Example 1 is that the reaction pressure parameters are different, and the other steps refer to Example 1.

[0052] The specific parameters and conversion rate and selectivity results are shown in Table 2.

[0053] Table 2

[0054]

[0055]

[0056] Embodiments 8 to 10

[0057] The difference between Examples 8 to 10 and Example 1 is the effect of changing the space velocity on the reaction. The other steps refer to Example 1.

[0058] The specific parameters, conversion rate and selectivity results are shown in Table 3.

[0059] Table 3

[0060] Example <![CDATA[Air speed / h -1 > Conversion rate (%) Selectivity (%) 8 1.0 75 82 9 1.5 95 95 10 5.0 82 64

[0061] Examples 11 to 13

[0062] The difference between Examples 11 to 13 and Example 1 is the effect of changing the hydrogen molar ratio on the reaction. The other steps refer to Example 1.

[0063] The specific parameters and conversion rate and selectivity results are shown in Table 4.

[0064] Table 4

[0065] Example Hydrogen molar ratio Conversion rate (%) Selectivity (%) 11 1：1 78 79 12 1：4 95 96 13 1：5 89 88

[0066] Embodiments 14 to 20

[0067] The difference between Examples 14 to 20 and Example 1 is that changing the catalyst components and the mass content of the Group VIII transition metal affects the reaction. The other steps refer to Example 1.

[0068] The specific parameters, conversion rate and selectivity results are shown in Table 5.

[0069] Table 5

[0070] Example Catalyst components Conversion rate (%) Selectivity (%) 14 <![CDATA[0.5Ru / Al x Mg y O z ]]> 73 75 15 <![CDATA[2.0Ru / Al x Mg y O z ]]> 88 91 16 <![CDATA[5.0Ru / Al x Mg y O z ]]> 92 90 17 <![CDATA[5.0Ru / 2.5Ni / Al x Mg y O z ]]> 91 93 18 <![CDATA[5.0Ru / 5.0Ni / Al x Mg y O z ]]> 93 97 19 <![CDATA[5.0Ru / 2.5Co / Al x Mg y O z ]]> 78 98 20 <![CDATA[5.0Ru / 5.0Co / Al x Mg y O z ]]> 89 99

[0071] Comparative Example 1

[0072] Compared with Example 1, the difference of this comparative example is that the reaction temperature is 100°C.

[0073] For other steps, refer to Example 1.

[0074] The conversion was 32% and the selectivity was 78%.

[0075] Comparative Example 2

[0076] Compared with Example 1, the difference of this comparative example is that the reaction pressure is 2.5 MPa.

[0077] For other steps, refer to Example 1.

[0078] The conversion was 80% and the selectivity was 35%.

[0079] Comparative Example 3

[0080] Compared with Example 1, the difference of this comparative example is that the reaction space velocity is 0.5h -1 .

[0081] For other steps, refer to Example 1.

[0082] The conversion was 72% and the selectivity was 54%.

[0083] Comparative Examples 4-5

[0084] Compared with Example 1, the difference between Comparative Examples 4 and 5 is that the hydrogen molar ratio of the reaction is different. The specific parameters and conversion rate and selectivity results are shown in Table 6.

[0085] For other steps, refer to Example 1.

[0086] Table 6

[0087]

[0088]

[0089] Comparative Examples 6 to 8

[0090] Compared with Example 1, the difference between Comparative Examples 6 to 8 is that different catalyst components are used. Specific parameters and conversion rate and selectivity results are shown in Table 7.

[0091] For other steps, refer to Example 1.

[0092] Table 7

[0093] Comparative Example Catalyst components Conversion rate (%) Selectivity (%) 6 0.5Pd / 0.5Cu / AlxMgyOz 15 48 7 0.5Pt / 0.5La / AlxMgyOz 39 76 8 0.5Ru / 0.5Ni / AlxMgyOz 32 85

[0094] Comparative Examples 9 to 10

[0095] Compared with Example 1, the difference between Comparative Examples 9 and 10 is that different raw material components are selected. Specific parameters and conversion rate and selectivity results are shown in Table 8.

[0096] For other steps, refer to Example 1.

[0097] Table 8

[0098] Comparative Example raw material Conversion rate (%) Selectivity (%) 9 <![CDATA[CF3CH=CClCF3]]> 21 33 10 <![CDATA[CF3CH=CFCF3]]> 29 42

[0099] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene, characterized in that: The following steps are involved: Preheating trans-2-ethoxy-1,1,1,4,4,4-hexafluoro-2-butene, mixing with hydrogen, and reacting under the action of a catalyst to obtain trans-1,1,1,4,4,4-hexafluoro-2-butene; The catalyst is composed of aluminum-magnesium composite oxide and group VIII transition metal, and the group VIII transition metal is one or two of Ru, Ni or Co.

2. The method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene as claimed in claim 1, characterized in that: The molar ratio of the 2-ethoxy-1,1,1,4,4,4-hexafluoro-2-butene to hydrogen is 1:(1-5).

3. The method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene as claimed in claim 1, characterized in that: The BET surface area of ​​the aluminum-magnesium composite oxide is 200-500 m 2 / g.

4. The method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene as claimed in claim 1, characterized in that: The mass content of the Group VIII transition metal is 0.5-10.0 wt % of the total mass of the catalyst.

5. The method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene as claimed in claim 1, characterized in that: The preparation method of the aluminum-magnesium composite oxide comprises the following steps: The aluminum-containing compound and the magnesium-containing compound are used as raw materials, polyethylene glycol or organic amine is added as a template agent, and the synthesis is carried out through a hydrothermal method, a solvent thermal method or a dry glue method.

6. The method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene as claimed in claim 5, characterized in that: At least one of the following (1) to (2): (1) The aluminum-containing compound is at least one of aluminum hydroxide, pseudo-boehmite, hydrated aluminum oxide, and aluminum isopropoxide; (2) The magnesium-containing compound is at least one of magnesium oxide, magnesium nitrate and magnesium acetate.

7. The method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene as claimed in claim 1, characterized in that: At least one of the following (1) to (3): (1) The reaction temperature is 150-250°C; (2) The reaction space velocity is 1.0~5.0 h -1 ; (3) The reaction pressure is 0.2~2.0 MPa.

8. The method for preparing trans-1,1,1,4,4,4-hexafluoro-2-butene as claimed in claim 7, characterized in that: At least one of the following (1) to (3): (1) The reaction temperature is 180-225°C; (2) The reaction space velocity is 1.5~2.5 h -1 ; (3) The reaction pressure is 0.4~1.0 MPa.

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