A method for preparing nitrile by oxidative cleavage of alcohol

Abstract

A method for preparing nitriles by oxidative cleavage of alcohols. The present invention provides a novel method for oxidative cleavage of alcohols into nitriles, specifically a method using a manganese oxide compound synthesized by potassium permanganate and manganese sulfate in an alkaline solution as a catalyst for the continuous oxidative cleavage of alcohols into nitriles. This method facilitates the synthesis of aromatic nitriles, heteroatom aromatic nitriles, and aliphatic nitrile compounds under mild reaction conditions, using air or oxygen as the oxygen source without the addition of any additives. The method is characterized by simple operation, a highly adaptable catalytic system, and high yield and selectivity.

Description

Technical Field

[0001] The present invention relates to the field of chemistry and chemical engineering, and in particular to a method for preparing nitrile by oxidative cracking of alcohol. Technical Background

[0002] Nitriles are a very important class of compounds in chemistry and biology, and are also used as pharmaceuticals, agricultural chemicals, and fine chemicals. Traditional methods for preparing aromatic nitrile compounds include the Sanderman reaction, transition-metal-catalyzed cross-coupling of aromatic halides, or direct aromatic carbon-hydrogen bond activation. However, these methods typically require highly toxic hydrocyanic acid and metal cyanides and produce large amounts of inorganic salts, which is inconsistent with the development of green chemistry. Therefore, methods for preparing nitriles by oxidative cleavage using readily available, renewable alcohols as starting materials in the presence of oxygen have attracted increasing attention. Furthermore, from economic and environmental perspectives, oxygen is an ideal oxidant: it is not only inexpensive and abundant, but also produces only water as a byproduct after oxidation.

[0003] In recent years, methods for oxidative cleavage of alcohols to produce nitriles have been reported. However, most involve homogeneous noble metal complexes. From an economic perspective, heterogeneous catalysts offer greater industrial value due to their recyclability. Currently, few heterogeneous systems have been reported for catalyzing the oxidative cleavage of alcohols to produce nitriles.

[0004] Therefore, it is very necessary to develop new highly active heterogeneous catalyst systems to achieve efficient oxidative cleavage of alcohols to produce nitriles. Summary of the Invention

[0005] The present invention provides a novel method for synthesizing nitriles. The method uses a cheap and easily prepared manganese oxide as a catalyst to catalyze the oxidation and cleavage of alcohols into nitrile compounds under mild conditions.

[0006] The substrate is an alcohol compound, and the reaction is carried out at 110-130° C. for 8-12 hours. The reaction product is treated to obtain the nitrile compound;

[0007] The preparation method of the manganese oxide compound is as follows: using potassium permanganate and manganese nitrate as raw materials in a mass ratio of 0.2:1-0.5:1, stirring at room temperature for 12-24 hours in an alkaline solution, filtering, washing with a large amount of deionized water to obtain a solid, and drying the obtained solid at 60-80°C before use.

[0008] The alkaline solution is one or more of lithium hydroxide solution, potassium hydroxide solution, sodium hydroxide solution, sodium carbonate solution or potassium carbonate solution, and ammonia water, and the volume molar concentration of the solution is 0.1-0.2 mol / L.

[0009] In the above scheme, the ammonium source used is ammonia gas with a pressure of 0.1-0.5 MPa (preferably 0.3-0.5), and the oxygen source is one or both of air and oxygen with a pressure of 0.1-1 MPa (preferably 0.4-0.8).

[0010] In the above reaction, the reaction temperature is preferably 110-130° C., and the reaction time is preferably 8-10 h.

[0011] In the above scheme, the molar ratio of the amount of catalyst to the substrate is 1:10.

[0012] In the above scheme, the substituent on the alcohol is selected from C 6-12 Aryl, C 6-12 Arylmethyl, or C l-6 One or more than two alkyl groups; wherein, C 6-12 Aryl or C 6-12 The aryl group of the arylmethyl group has no substituent or has 1-5 substituents, and the substituents are halogen, C l-4 Alkyl, C 1-4 Alkoxy, C 2-5 One or more of alkoxy carbonyl, nitro or -CN; C l-6 The alkyl group has no substituent or has 1 to 6 substituents, and the substituents are one or more of halogen, nitro, hydroxyl or -CN.

[0013] Due to the application of the above scheme, the present invention has the following advantages compared with the existing technology:

[0014] 1. The raw materials required for the catalyst used in the present invention can be directly purchased.

[0015] 2. Compared with the reported literature, the by-product of the present invention is only water.

[0016] 3. The catalyst of the present invention is a heterogeneous catalyst, which is different from the homogeneous catalytic system reported in the past and can be recycled.

[0017] 4. The catalytic system of the present invention efficiently and selectively catalyzes the oxidation and breakdown of alcohols into nitriles without the generation of other by-products

[0018] Therefore, this method is simple to operate and has potential application prospects. DETAILED DESCRIPTION

[0019] The following embodiments will help to understand the present invention, but are not intended to limit the present invention.

[0020] The following examples use a method for preparing a manganese oxide compound as follows: potassium permanganate and manganese nitrate are prepared in a 0.5:1 mass ratio (5 g) in 100 ml of an alkaline solution (0.2 mol / L sodium hydroxide solution). The mixture is stirred at room temperature for 24 hours, filtered, and washed with water to obtain a solid. The resulting solid is dried at 80°C to obtain the desired manganese oxide MnOx, where x = 1.5.

[0021] Example 1 Oxidative Cleavage of Phenylethanol to Prepare Nitrile

[0022]

[0023] 40 mg of MnOx and 0.5 mmol of phenylethanol were placed in a reaction flask, followed by 2 mL of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was stirred in a 110°C oil bath for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed a 90% yield of benzonitrile.

[0024] Comparative Example 1: Preparation of Nitrile by Oxidative Fractionation of Phenylethanol

[0025]

[0026] 40 mg of MnOx and 0.5 mmol of phenylethanol were added to a reaction flask, followed by 2 mL of 1,4-dioxane as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was stirred in a 110°C oil bath for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed a 30% yield of benzonitrile.

[0027] Comparative Example 2: Oxidative Fractionation of Phenylethanol to Prepare Nitrile

[0028]

[0029] 40 mg of MnOx and 0.5 mmol of phenylethanol were added to a reaction flask, followed by 2 mL of methanol as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was stirred in a 110°C oil bath for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed a 25% yield of benzonitrile.

[0030] Comparative Example 3: Oxidative cleavage of phenylethanol to produce nitrile

[0031]

[0032] 40 mg of MnOx and 0.5 mmol of phenylethanol were added to a reaction flask, followed by 2 mL of toluene as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was stirred in a 110°C oil bath for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed a 26% yield of benzonitrile.

[0033] Comparative Example 4: Preparation of Nitrile by Oxidative Fractionation of Phenylethanol

[0034]

[0035] 40 mg of MnOx and 0.5 mmol of phenylethanol were added to a reaction flask, followed by 0.5 mL of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was stirred in a 90°C oil bath for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed a 40% yield of benzonitrile.

[0036] Example 2 Oxidative Cleavage of Phenylethanol to Prepare Nitrile

[0037]

[0038] 40 mg of MnOx and 0.5 mmol of phenylethanol were added to a reaction flask, followed by 3 mL of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was stirred in a 90°C oil bath for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed an 80% yield of benzonitrile.

[0039] Example 3 Oxidative Cleavage of Phenylethanol to Prepare Nitrile

[0040]

[0041] 40 mg of MnOx and 0.5 mmol of phenylethanol were added to a reaction flask, followed by 2 mL of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.3 MPa, followed by oxygen gas to 1 MPa. The reactor was stirred in a 110°C oil bath for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed a 70% yield of benzonitrile.

[0042] Example 4 Oxidative Cleavage of 4-Methylphenylethanol to Prepare Nitrile

[0043]

[0044] 40 mg of MnOx and 0.5 mmol of 4-methylphenylethanol were added to a reaction flask, followed by 2 mL of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was placed in a 120°C oil bath and stirred for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed a 92% yield of 4-methylbenzonitrile.

[0045] Example 5 Oxidative cleavage of 4-methoxyphenylethanol to produce nitrile

[0046]

[0047] 40 mg of MnOx and 0.5 mmol of 4-methoxyphenylethanol were added to a reaction flask, followed by 2 mL of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was placed in a 110°C oil bath and stirred for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed a 92% yield of 4-methoxybenzonitrile.

[0048] Example 6 Oxidative Cleavage of 2-Methoxyphenylethanol to Nitrile

[0049]

[0050] 40 mg of MnOx and 0.5 mmol of 2-methoxyphenylethanol were added to a reaction flask, followed by 2 mL of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was placed in a 110°C oil bath and stirred for 10 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed an 88% yield of 4-methoxybenzonitrile.

[0051] Example 7 Oxidative Cleavage of 4-Fluorophenylethanol to Prepare Nitrile

[0052]

[0053] 40 mg of MnOx and 0.5 mmol of 4-fluorophenylethanol were added to a reaction flask, followed by 2 ml of acetonitrile as solvent. The mixture was transferred to a reactor, which was then filled with ammonia gas to 0.5 MPa and then with oxygen gas to 1 MPa. The reactor was placed in a 110°C oil bath and the reaction progress was monitored by GC-MS. After the reaction was complete, naphthalene was added as an internal standard. The yield of 4-fluorobenzonitrile was quantitatively analyzed by GC. After a 9-hour reaction, the yield of 4-fluorobenzonitrile was 85%.

[0054] Example 8 Oxidative Cleavage of 4-Chlorophenylethanol to Prepare Nitrile

[0055]

[0056] 40 mg of MnOx and 0.5 mmol of 4-chlorophenylethanol were added to a reaction flask, followed by 2 mL of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was placed in a 130°C oil bath and stirred for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed an 85% yield of 4-chlorobenzonitrile.

[0057] Example 9 Oxidative Cleavage of 4-Chlorophenylethanol to Nitrile

[0058]

[0059] 40 mg of MnOx and 0.5 mmol of 4-bromophenethanol were added to a reaction flask, followed by 2 mL of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was placed in a 130°C oil bath and stirred for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed an 80% yield of 4-bromobenzonitrile.

[0060] Example 10 Oxidative cleavage of 2-pyridineethanol to prepare nitrile

[0061]

[0062] 40 mg of MnOx and 0.5 mmol of 2-pyridineethanol were added to a reaction flask, followed by 2 mL of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was placed in a 130°C oil bath and stirred for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed an 80% yield of 2-pyridinecarbonitrile.

[0063] Example 11 Oxidative Cleavage of 2-Phenylphenethanol to Prepare Nitrile

[0064]

[0065] 40 mg of MnOx and 0.5 mmol of 2-phenylphenylethanol were placed in a reaction flask, followed by 2 mL of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was placed in a 130°C oil bath and stirred for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. GC analysis revealed an 80% yield of 2-phenylbenzonitrile.

[0066] Example 12 Oxidative Cleavage of 1-Phenylethanol to Prepare Nitrile

[0067]

[0068] 40 mg of MnOx and 0.5 mmol of 1-phenylethanol were placed in a reaction flask, followed by 2 ml of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was placed in a 110°C oil bath and stirred for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed a 90% yield of benzonitrile.

[0069] Example 13 Oxidative Cleavage of Phenyl Ethylene Glycol to Prepare Nitrile

[0070]

[0071] 40 mg of MnOx and 0.5 mmol of phenyl glycol were placed in a reaction flask, followed by 2 ml of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was placed in a 110°C oil bath and stirred for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed a 90% yield of benzonitrile.

[0072] Example 14 Oxidative Cleavage of 3(±)-Hydrobenzoic Acid to Prepare Nitrile

[0073]

[0074] 40 mg of MnOx and 0.5 mmol of (±)-hydrobenzoylmethane were added to a reaction flask, followed by 2 ml of acetonitrile as solvent. The mixture was transferred to a reactor. Ammonia gas was first introduced to 0.5 MPa, followed by oxygen gas to 1 MPa. The reactor was placed in a 110°C oil bath and stirred for 8 hours. After the reaction was complete, the mixture was cooled to room temperature and naphthalene, the internal standard, was added. Quantitative analysis by GC revealed a 90% yield of benzonitrile.

Claims

1. A method for preparing nitrile by oxidative cracking of alcohol, characterized in that: Using manganese oxide as a catalyst, in acetonitrile solvent, with an alcohol compound as the substrate, the reaction is carried out at 90-130 ° C for 8-12 h to obtain the nitrile compound; The reaction formula is: ; For every 0.5 mmol of substrate, the amount of solvent used is 2-3 mL, The structural formula of alcohol compounds is , wherein R is selected from C 6-12 The aryl group, substituted by halogen, C l-4 Alkyl, C 1-4 Alkoxy, n=2-6; The ammonium source used is ammonia gas at a pressure of 0.3-0.5 MPa, and the oxygen source is one or both of air and oxygen at a pressure of 0.4-0.8 MPa. The preparation method of the manganese oxide compound is as follows: potassium permanganate and manganese nitrate are used as raw materials in a mass ratio of 0.2:1-0.5:1, stirred at room temperature for 12-24 hours in an alkaline solution, filtered, washed with water to obtain a solid, and dried at 60-80 ° C to obtain the desired manganese oxide MnO x , x is 1.

5.

2. The method according to claim 1, characterized in that The reaction temperature is 110-130 °C and the reaction time is 8-10 h.

3. The method according to claim 1, characterized in that The alkaline solution is one or more of lithium hydroxide solution, potassium hydroxide solution, sodium hydroxide solution, sodium carbonate solution or potassium carbonate solution, and ammonia water, and the concentration of the solution is 0.1-0.2 mol / L.

4. The method according to claim 1, characterized in that The structural formula of alcohols is , n= 2-4.

5. The method according to claim 1, wherein For every 0.5 mmol of substrate, the amount of catalyst used is 30-60 mg and the amount of solvent used is 2 mL.

6. The method according to claim 1, characterized in that The amount of catalyst used was 40 mg for every 0.5 mmol of substrate.

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