A method for efficiently dehalogenating aliphatic hydrocarbon halides

Abstract

The present invention relates to a method for efficiently dehalogenating aliphatic hydrocarbon halides. The method uses aliphatic hydrocarbon halides as raw materials, performs catalytic dehalogenation in an organic-water two-phase system under the action of a hydrodehalogenation catalyst, a co-catalyst, and an acid-binding agent, and yields the corresponding low-toxic, easy-to-handle, or non-toxic, reusable aliphatic hydrocarbons. The method achieves a single-pass halogen removal rate exceeding 80% and an aliphatic hydrocarbon selectivity exceeding 99%.

Description

Technical Field

[0001] The present invention relates to a method for catalytic hydrodehalogenation of aliphatic hydrocarbon halides. Background Art

[0002] Heterogeneous catalytic hydrodehalogenation, as an organic synthesis method, has long been used in the production of fine chemicals and has gained increasing attention in environmental protection in recent years. It can convert highly toxic or severely environmentally polluting halogenated hydrocarbons, which are difficult to treat by conventional methods, into less toxic, easily treatable or non-toxic and recyclable compounds. For example, through catalytic hydrodehalogenation, halogenated alkanes, halobenzenes, polyhalogenated biphenyls, halogenated phenols, etc. can be converted into the corresponding alkanes, benzene, biphenyls and phenols. Commonly used catalysts are Group VIII metals (supported on inorganic carriers) or complexes, and alcohols, organic acid salts or hydrogen are used as hydrogen sources for catalytic hydrodehalogenation reactions. The most commonly used ones are Pd / C, Raney nickel catalysts, etc.

[0003] Generally speaking, from the perspective of catalytic reaction substrates, the reactivity of bond cleavage of chemical bonds depends on the bond dissociation energy of the chemical bonds. The bond dissociation energy of the C-X bond is as follows: C-I (222 kJ / mol) < C-Br (280 kJ / mol) < C-Cl (339 kJ / mol) < C-F (456 kJ / mol). Based on the bond dissociation energy of the C-X bond, the reactivity of the C-X bond cleavage in the hydrodehalogenation reaction should be C-I > C-Br > C-Cl > C-F. Since the C-F bond is quite stable, it is very difficult to achieve the reductive elimination of fluorine in organic fluorides under mild conditions. For organic halogenated compounds containing the same halogen atom but having different molecular skeletons, the rule of the speed of C-X bond cleavage is: benzyl halides > olefin halides > aromatic halides > aliphatic hydrocarbon halides. Moreover, the spatial / stereochemical environment around the halogen atom has an important influence on the elimination of the halogen atom, and dehalogenation is more difficult under a large steric hindrance spatial stereochemical environment.

[0004] Therefore, for aliphatic alkane halides, especially aliphatic alkane halides with branched chains and large steric hindrance, the reaction conditions for catalytic hydrodehalogenation are more severe. Currently, there is a lack of reports on efficient dehalogenation methods for aliphatic hydrocarbon halides, and a method for efficient dehalogenation of aliphatic hydrocarbon halides needs to be developed to meet the needs of dehalogenation of aliphatic hydrocarbon halides. Summary of the Invention

[0005] The object of the present invention is to provide a method for efficient hydrodehalogenation of aliphatic hydrocarbon halides.

[0006] In order to achieve the above object of the invention, the technical scheme adopted by the present invention is as follows:

[0007] The invention discloses a method for efficiently dehalogenating aliphatic hydrocarbon halides, which uses aliphatic hydrocarbon halides as raw materials, an organic-water two-phase system as the reaction solvent, and adds a hydrodehalogenation catalyst, a co-catalyst and an acid binding agent to react, thereby realizing liquid-phase hydrodehalogenation of the halogenated aliphatic hydrocarbons.

[0008] In the method of the present invention, the aliphatic hydrocarbon halide is a monohalide or polyhalide of a C4-C20 straight-chain or branched aliphatic hydrocarbon; wherein the halides include chlorides, bromides, and iodides, and aliphatic hydrocarbon chlorides and bromides are preferred.

[0009] In the method of the present invention, the hydrodehalogenation catalyst is a metal palladium coordination catalyst, and its addition amount is 0.01-0.1wt% of the aliphatic hydrocarbon halide.

[0010] The preparation method of the present invention comprises the following steps: dissolving a certain amount of palladium acetate and triphenylphosphine in trifluoroacetic acid, evaporating the mixture on a steam bath, adding trifluoroacetic acid after evaporation to dryness, and evaporating the mixture again; and drying the residue at 50-60° C. under vacuum to obtain a powdered palladium coordination catalyst.

[0011] The molar ratio of palladium acetate to triphenylphosphine is 1:(1.8-2.2); the molar ratio of palladium acetate to the total amount of trifluoroacetic acid is 1:(2.2-2.6).

[0012] In the preparation method of the present invention, the co-catalyst is NaBH4, and the added amount thereof is 1.0 to 10.0 wt% of the aliphatic hydrocarbon halide.

[0013] The preparation method of the present invention comprises an organic-aqueous two-phase reaction solvent, wherein the organic solvent is selected from one or more of methanol, ethanol, isopropanol, tert-butanol, tetraethylethylenediamine, and tetrahydrofuran, preferably one or more of tetraethylethylenediamine and tetrahydrofuran. The mass ratio of the organic solvent to water is 1 to 5:1. The mass ratio of the total reaction solvent to the aliphatic hydrocarbon halide is 0.2 to 1.0:1.

[0014] In the preparation method of the present invention, the acid-binding agent is NaOH, and the amount of NaOH added is such that the molar ratio of the halogen atoms of the aliphatic hydrocarbon halide to NaOH is 1:(1.0-1.5).

[0015] The preparation method of the present invention comprises the following steps: the reaction temperature is 30-150° C., preferably 60-120° C.; the reaction hydrogen pressure is 0.5-5.0 MPaA, preferably 1-4.0 MPaA; and the reaction time is 2-10 h, preferably 3-8 h.

[0016] Taking monochloroisododecane as an example, the reaction for preparing isododecane by efficient dechlorination of the present invention is as follows:

[0017]

[0018] The present invention has the following advantages:

[0019] 1. The solution of the present invention has high activity and high selectivity for aliphatic hydrocarbon halides that are difficult to dehalogenate by hydrodehalogenation, with a single-pass halogen removal rate of more than 80% and an aliphatic hydrocarbon selectivity of more than 99%.

[0020] 2. The application range of aliphatic hydrocarbon halides is wide, and monohalides or polyhalides of C4 to C20 straight-chain or branched aliphatic hydrocarbons are applicable. DETAILED DESCRIPTION

[0021] The method provided by the present invention is described in detail below with reference to examples. It should be noted that the scope of the present invention includes but is not limited to such examples.

[0022] Sources of reagents in the examples:

[0023] Aliphatic hydrocarbon halides (such as monochloroisooctane, monochlorododecane, etc.), produced by Wanhua Chemical

[0024] Methanol, ethanol, isopropanol, tert-butanol, NaOH, tetramethylethylenediamine, tetrahydrofuran, palladium acetate, triphenylphosphine, trifluoroacetic acid, industrial grade, Aladdin

[0025] The analytical instruments and methods used are as follows:

[0026] NMR: Varian-NMR 300;

[0027] Gas chromatograph: Agilent-7820;

[0028] Gas chromatography column: 0.25 mm × 30 m DB-5 capillary column, FID detector, vaporizer temperature 280°C, column oven temperature 280°C, FID detector temperature 300°C, argon carrier flow 2.1 mL / min, hydrogen flow 30 mL / min, air flow 400 mL / min, injection volume 1.0 μL. Olefin conversion and product selectivity were calculated using the area normalization method. Temperature program: preheat to 40°C, hold for 5 min, then ramp from 40°C to 280°C at a rate of 15°C / min, hold for 2 min.

[0029] Example 1: Preparation of Metal Palladium Coordination Catalyst

[0030] Weigh 100g of palladium acetate and 230g of triphenylphosphine into a three-necked flask, add 55mL of trifluoroacetic acid, stir evenly with a glass rod, and evaporate on a steam bath at 70°C. After evaporation to dryness, add 28mL of trifluoroacetic acid and evaporate again. The residue after evaporation is dried under vacuum at 50°C to obtain a powdered metal palladium coordination catalyst.

[0031] Example 2: Efficient Hydrodechlorination of Monochlorododecane to Prepare Dodecane

[0032] 20.0g of deionized water was weighed and added to a beaker. 23.0g of NaOH was added and stirred to dissolve. 30.0g of tetramethylethylenediamine, 100.0g of monochlorododecane, 0.05g of the metal palladium coordination catalyst prepared in Example 1 and 5.0g of NaBH4 were then added. After stirring, the mixture was transferred to a reactor using a self-priming paddle stirring method. The reaction was sealed and nitrogen purged three times. The reaction was carried out for 4h at a reaction temperature of 100°C, a hydrogen pressure of 2.0MPaA and a stirring speed of 1000r / min. After the reaction was completed, the reaction was cooled, purged with nitrogen and depressurized. The gas chromatographic analysis of the reaction results showed that the hydrodechlorination conversion of monochlorododecane was 96% and the selectivity of dodecane was 99.6%.

[0033] Example 3: Efficient Hydrodechlorination of Monochloroisooctane to Prepare Isooctane

[0034] Weigh 47.0g of deionized water into a beaker, add 32.0g of NaOH and stir to dissolve. Add 53.0g of tetrahydrofuran, 100.0g of monochloroisooctane, 0.1g of the metal palladium coordination catalyst prepared in Example 1 and 8.0g of NaBH4, stir evenly and transfer to a reactor, which adopts a self-priming paddle stirring form. After sealing, nitrogen is replaced three times, and the reaction is carried out for 6h under the conditions of reaction temperature of 120°C, hydrogen pressure of 4.0MPaA and stirring speed of 1000r / min. After the reaction is completed, the temperature is lowered, nitrogen is replaced, and the pressure is released. The sample is analyzed by gas chromatography. The reaction result is a monochloroisooctane hydrodechlorination conversion rate of 88% and an isooctane selectivity of 99.8%.

[0035] Example 4: Efficient Hydrodechlorination of Dichloroisododecane to Prepare Isododecane

[0036] Weigh 36.0g of deionized water into a beaker, add 34g of NaOH and stir to dissolve. Add 41.0g of tetrahydrofuran, 80.0g of dichloroisododecane, 0.08g of the metal palladium coordination catalyst prepared in Example 1 and 6.0g of NaBH4, stir evenly and transfer to a reactor, which adopts a self-priming paddle stirring form. After sealing, nitrogen is replaced three times, and the reaction is carried out for 8h under the conditions of reaction temperature of 120°C, hydrogen pressure of 4.0MPaA and stirring speed of 1000r / min. After the reaction is completed, the temperature is lowered, nitrogen is replaced, and the pressure is released. The sample is analyzed by gas chromatography. The reaction results are as follows: a dichloroisododecane hydrodechlorination conversion rate of 81% and an isododecane selectivity of 99.3%.

[0037] Comparative Example 1: Preparation of isododecane by hydrodechlorination of dichloroisododecane

[0038] Weigh 36.0g of deionized water into a beaker, add 34g of NaOH and stir to dissolve. Add 41.0g of tetrahydrofuran, 80.0g of dichloroisododecane, 0.08g of palladium acetate catalyst and 6.0g of NaBH4, stir evenly and transfer to a reactor with self-priming paddle stirring. After sealing, replace with nitrogen three times and react for 8h at a reaction temperature of 120°C, a hydrogen pressure of 4.0MPaA and a stirring speed of 1000r / min. After the reaction is completed, cool down, replace with nitrogen, release the pressure, take samples for gas chromatography analysis, and the reaction results are a dichloroisododecane hydrodechlorination conversion rate of 13% and an isododecane selectivity of 98.9%.

[0039] Comparative Example 2: Efficient Hydrodechlorination of Monochloroisooctane to Prepare Isooctane

[0040] Weigh 47.0g of deionized water into a beaker, add 32.0g of NaOH and stir to dissolve. Add 53.0g of tetrahydrofuran, 100.0g of monochloroisooctane, and 0.1g of the metal palladium coordination catalyst prepared in Example 1, stir evenly and transfer to a reactor, which adopts a self-priming paddle stirring form. After sealing, nitrogen is replaced three times, and the reaction is carried out for 6h under the conditions of reaction temperature of 120°C, hydrogen pressure of 4.0MPaA, and stirring speed of 1000r / min. After the reaction is completed, the temperature is lowered, nitrogen is replaced, and the pressure is released. The sample is analyzed by gas chromatography. The reaction results are a monochloroisooctane hydrodechlorination conversion rate of 35% and an isooctane selectivity of 99.1%.

[0041] Comparative Example 3: Preparation of isododecane by hydrodechlorination of dichloroisododecane

[0042] Weigh 36.0g of deionized water into a beaker, add 34g of NaOH and stir to dissolve. Add 41.0g of tetrahydrofuran, 80.0g of dichloroisododecane, and 3g of Raney nickel catalyst, stir evenly and transfer to a reactor with self-priming paddle stirring. After sealing, replace with nitrogen three times and react for 8h at a reaction temperature of 120°C, a hydrogen pressure of 4.0MPaA, and a stirring speed of 1000r / min. After the reaction is completed, cool down, replace with nitrogen, release the pressure, and take samples for gas chromatography analysis. The reaction results show that the conversion rate of dichloroisododecane hydrodechlorination is only 8%, and the selectivity of isododecane is 99.2%.

Claims

1. A method for dehalogenating aliphatic hydrocarbon halides, characterized in that: In a reaction solvent, aliphatic hydrocarbon halides are used as raw materials and react under the action of a hydrodehalogenation catalyst, a co-catalyst and an acid binding agent to achieve liquid phase hydrodehalogenation of aliphatic hydrocarbon halides; the reaction temperature is 30-150°C, and the reaction hydrogen pressure is 0.5-5.0MPaA; The aliphatic hydrocarbon halide is a monohalide or polyhalide of a C4-C20 straight-chain or branched aliphatic hydrocarbon, the hydrodehalogenation catalyst is bis(trifluoroacetic acid)bis(triphenylphosphine)palladium, the co-catalyst is NaBH4, and the acid-binding agent is NaOH.

2. The method according to claim 1, characterized in that The halogenated compound includes at least one of chlorine, bromide, and iodide.

3. The method according to claim 1 or 2, characterized in that The amount of the hydrodehalogenation catalyst added is 0.01 to 0.1 wt% of the aliphatic hydrocarbon halide.

4. The method according to claim 1, wherein The preparation method of the hydrodehalogenation catalyst comprises: dissolving a certain amount of palladium acetate and triphenylphosphine in trifluoroacetic acid, evaporating on a steam bath, evaporating to dryness, adding trifluoroacetic acid and evaporating again, and drying the residue to obtain a powdered metal palladium coordination catalyst; The molar ratio of palladium acetate to triphenylphosphine is 1:(1.8-2.2); the molar ratio of palladium acetate to trifluoroacetic acid is 1:(2.2-2.6).

5. The method according to claim 1, wherein The amount of the co-catalyst added is 1.0 to 10.0 wt% of the aliphatic hydrocarbon halide.

6. The method according to claim 1, characterized in that The reaction solvent is an organic-water two-phase system, and the organic solvent is selected from one or more of methanol, ethanol, isopropanol, tert-butanol, tetraethylethylenediamine, and tetrahydrofuran.

7. The method according to claim 6, characterized in that The mass ratio of the organic solvent to water is (1-5):1, and the mass ratio of the total reaction solvent to the aliphatic hydrocarbon halide is (0.2-1.0):

1.

8. The method according to claim 1, characterized in that The molar ratio of the halogen atom of the aliphatic hydrocarbon halide to NaOH is 1:(1.0-1.5).

9. The method according to claim 1, characterized in that The reaction temperature is 60-120°C; the reaction hydrogen pressure is 1-4.0 MPaA; and the reaction time is 2-10 hours.

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