A process for the preparation of alkylphenols by phenol alkylation

Abstract

The present application relates to a kind of by phenol alkylation reaction preparation alkyl phenol method.The method uses anatase titanium dioxide as catalyst, phenol as reaction substrate, alcohol as alkylating agent, under nitrogen atmosphere, phenol alkylated product is obtained in one-step process.The reaction process is as follows:phenol, alcohol and solvent are mixed with catalyst, then put into pressure vessel, seal, and fill in protective gas, reaction temperature is higher than 280 DEG C, reaction time is longer than 4 hours, phenol is reacted into ortho α-C alkylated product.The method has simple reaction process, can be synthesized with high selectivity ortho straight-chain alkyl phenol product, catalyst is stable, easy to separate from reaction system and can be repeatedly used, with good industrial application prospect.

Description

Technical Field

[0001] This invention relates to a method for preparing alkylphenols via phenol alkylation reaction, specifically involving the alkylation reaction of phenol and alcohols catalyzed by anatase titanium dioxide, to synthesize ortho-substituted linear alkylphenols with high selectivity, belonging to the field of organic synthesis applications. Background Technology

[0002] Alkylation is a mainstream C–C bond formation technology widely used in the production of chemical raw materials and fuels. Phenolic compounds are important organic chemical raw materials widely used in the national economy, with many downstream products spanning numerous fields. Alkylphenol chemicals include nonylphenol, octylphenol, dodecylphenol, tert-butylphenol, and many other products, widely used in the production of antioxidants, surfactants, lubricant additives, rubber additives, and insulating materials, with end-use applications in pharmaceuticals, pesticides, fragrances, plastics, coatings, and many other industries. Globally, approximately 540,000 tons of long-chain alkylphenols are synthesized annually, playing an irreplaceable role in the production of pesticides and surfactants due to their unique properties.

[0003] Currently, the production of alkylphenol chemicals mainly uses petroleum-based chemicals as raw materials, employing Lewis or... Acids serve as catalysts, including inorganic acids and acidic oxides such as alumina and molecular sieves. Acid-catalyzed alkylation reactions typically proceed via electrophilic substitution of carbocations on the carbon atom of the benzene ring. However, due to the rearrangement mechanism of carbocations, primary carbocations readily rearrange into more stable secondary carbocations. Therefore, when using long-chain (3 or more carbon atoms) alkenes or primary alcohols as alkylating agents, a mixture of multiple branched alkyl products is usually formed on the benzene ring, with straight-chain alkyl products rarely obtained. Thus, the selective preparation of long-chain alkylphenols remains a persistent challenge in organic synthesis applications. Furthermore, due to the electron-donating effect of alkyl groups as substituents on the benzene ring, products from a single alkylation step, if not promptly separated from the reaction system, are more likely to undergo further alkylation reactions, thus further affecting the selectivity of the target product.

[0004] Current routes for preparing long-chain alkylphenols involve Friedel-Crafts acylation followed by Clemmensen reduction to obtain the alkylated product. This multi-step process is not yet feasible for large-scale industrial applications. Reports indicate that selective alkylation of phenols with alcohols to produce long-chain alkylphenols can be achieved using supported noble metal catalysts such as Pd / C or Ru–H complex catalysts in the presence of additives such as BuOLi bases. However, the use of noble metal catalysts and equivalent additives in these systems limits the further widespread application of this technology due to cost constraints.

[0005] The reported technologies for preparing alkyl phenol by phenol alkylation reaction have the following problems: for the classic acid-catalyzed alkylation system, due to the limitation of carbonium ion mechanism, it is difficult to obtain a single alkyl phenol product with high selectivity, especially when the target product is a long-chain alkyl phenol. For the existing noble metal-catalyzed alkylation system, the cost of noble metal catalyst and the necessity of additives limit the development and application of the technology. Based on the research results of the literature, there is no report on the high-selectivity preparation of long-chain alkyl phenol by alkylation reaction of phenol and alcohol using noble metal-free anatase titanium dioxide (TiO2-A) as catalyst. SUMMARY

[0006] The significance of the present application is to use noble metal-free anatase TiO2 (TiO2-A) as catalyst to synthesize long-chain alkyl phenol by alkylation reaction of phenol and alcohol with high selectivity, effectively solving the problem of direct synthesis of long-chain alkyl phenol with high selectivity in alkylation reaction.

[0007] To achieve the above-mentioned purpose, the present application realizes the technical scheme as follows: a TiO2-A catalyzed alkylation method of phenol and alcohol, phenol or its derivative, alcohol and reaction solvent are mixed with catalyst, then put into a pressure vessel, sealed and filled with reaction gas, the reaction temperature is higher than 280℃, and the reaction time is longer than 4 hours. After the reaction is completed, the reaction kettle is naturally cooled, depressurized and opened, and the obtained liquid is subjected to rotary evaporation to remove the solvent, thereby obtaining the mixture of alkylation product and unreacted raw materials phenol and alcohol.

[0008] The phenol substrate includes phenol or substituted phenol, and the substituent group includes one or more of methyl, chlorine, amino, nitro, methoxy and the like, which is located at ortho, para or meta position. The alcohol includes primary alcohol and secondary alcohol in monohydric alcohol, and the carbon chain in alkyl alcohol is ≥2 without specific limitation, and both low-carbon alkyl alcohol and high-carbon alkyl alcohol are suitable for the reaction of the present application.

[0009] (1) The reaction solvent is one of n-decane, benzene, toluene and o-xylene;

[0010] (2) The reaction gas is nitrogen or argon, and the gas pressure at the beginning of the reaction is 0.1-4 MPa, preferably 1-2 MPa;

[0011] (3) The reaction temperature is 280-320℃, preferably 300-310℃, and the reaction time is 60-1440 min, preferably 720-960 min;

[0012] (4) The molar ratio of phenol and alcohol is not particularly limited, and both can be reacted. When the molar ratio of phenol and alcohol is less than 1, the unreacted phenol is contained in the product, and can be removed by post-treatment. When the molar ratio of phenol and alcohol is greater than or equal to 1, the phenol is fully reacted by using an excess of alcohol. The amount of catalyst used is not particularly limited, and the reaction can be carried out by selecting the amount of catalyst according to the actual situation. The amount of the reaction solvent is not particularly limited, and the amount of the reaction solvent known to those skilled in the art can be used.

[0013] (5) The catalyst is anatase titanium dioxide (TiO2-A). The TiO2-A can be prepared by a known method or purchased on the market.

[0014] The alkylation reaction always occurs on the α-C in the alcohol molecule and the carbon adjacent to the phenolic hydroxyl group, which is called ortho-α-C alkylation reaction. When applied to the synthesis reaction of alkyl phenol, the alkylation product with a long straight chain at the ortho position of phenol can be obtained with high selectivity.

[0015] Compared with the existing phenol alkylation technology, the present application has the following advantages:

[0016] (1) In the present application, the alkylation reaction has the following unique selectivity: the alkylation reaction always occurs on the α-C in the alcohol molecule, and the alkylation process does not cause isomerization of the alkyl chain, and a straight chain alkylation product can be obtained; the alkylation reaction selectively occurs at the ortho position of the phenol; the alkylation reaction can still obtain a monoalkyl chain product with high selectivity under the condition of high yield; in general, under the optimized reaction conditions, the conversion rate of phenol in a single alkylation reaction is higher than 84%, and the selectivity of ortho-α-C alkylation product is greater than 80%;

[0017] (2) The TiO2-A catalyst used in the present application is simple to prepare and stable in nature. After the reaction, the crystal structure and dispersion degree of the catalyst do not change significantly, and the catalyst can be used for the next reaction without treatment. After three reactions, the catalytic activity and product selectivity do not decrease significantly;

[0018] (3) The present application has a wide range of application for different alcohol alkylating agents. In the present application, primary alcohols or secondary alcohols can be used as alkylating agents for the reaction, and have good reactivity. The configuration of the alkyl chain is maintained during the reaction, thereby high-selectivity synthesizing the target alkylation product. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The gas chromatogram after the reaction of Example 5.

[0020] Figure 2 The XRD pattern of the catalyst before and after the reaction of Example 1. DETAILED DESCRIPTION

[0021] In order to further illustrate the present application, several specific implementation cases are given below, but the present application is not limited to these examples.

[0022] The TiO2-A catalyst is applied to the alkylation reaction of phenol, after the reaction is completed, the reaction system is cooled to room temperature, qualitative and quantitative analysis and measurement are performed by using gas chromatography-mass spectrometry and gas chromatography, the internal standard method is used for quantitative method, and n-hexadecane is used as the internal standard.

[0023] The conversion rate of phenol and the yield of the alkylation product are calculated by using the following formula:

[0024]

[0025]

[0026] Wherein, n(phenol) and n(alkylated product) represent the molar amount of phenol and the alkylation product respectively.

[0027] Example 1

[0028] (1) Preparation of TiO2-A catalyst: in a round bottom flask with a volume of 500 mL, 100 mL of anhydrous ethanol and 20 mL of tetrabutyl titanate are added, and after being fully dissolved, a solution is obtained. Another 20 mL of ultrapure water, 20 mL of anhydrous ethanol and 12 mL of acetic acid are fully mixed and then added dropwise into the tetrabutyl titanate ethanol solution. At the same time of dropping, strong mechanical stirring is used to ensure uniform mixing of the solution. After the dropping is completed, the sol is allowed to stand for 12 h. Then, ultrapure water is used for cleaning, and a centrifuge is used for separation. The separated solid sample is dried at 110℃ overnight. Finally, the dried sample is calcined in a muffle furnace, the temperature is raised to 400℃ at a rate of 2℃ / min, and then kept for 4 h to obtain the TiO2-A sample.

[0029] (2) Catalytic alkylation reaction: The alkylation reaction was carried out in a Hastelloy C276 material reactor with a volume of 50 ml, which was purchased from Beijing Century Sylon Instrument and Equipment Co., Ltd., model E50, equipped with a temperature sensor, stirring, a pressure gauge and a programmed temperature device. Before each reaction, 0.2 g of TiO2-A catalyst, 2.5 mmol of phenol, 10 mmol of 1-propanol substrate and 25 ml of toluene as solvent were weighed and added to the reactor, and then the reactor was sealed. The reactor was purged with N2 for 10 min, and then the air in the reactor was exhausted and pressurized to 1 MPa. Then the reactor was heated to 300°C, and the stirring was kept at 500 rpm. After 16 h of reaction, the reactor was cooled to room temperature, 40.2 mg of n-hexadecane was added as an internal standard, and then filtered with a polytetrafluoroethylene filter. The substrate and product were analyzed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography (GC-FID). The conversion of phenol and the yield of alkylation product are shown in Table 1.

[0030]

[0031] Example 2

[0032] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that only the amount of phenol was adjusted to 3.3 mmol, and the other conditions in the catalyst preparation process and the catalytic reaction process were unchanged. The conversion of phenol and the yield of alkylation product are shown in Table 1.

[0033] Example 3

[0034] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that only the amount of phenol was adjusted to 5 mmol, and the other conditions in the catalyst preparation process and the catalytic reaction process were unchanged. The conversion of phenol and the yield of alkylation product are shown in Table 1.

[0035] Example 4

[0036] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that only the amount of phenol was adjusted to 10 mmol, and the other conditions in the catalyst preparation process and the catalytic reaction process were unchanged. The conversion of phenol and the yield of alkylation product are shown in Table 1.

[0037] Example 5

[0038] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that only the reaction time was adjusted to 4 h, and the other conditions in the catalyst preparation process and the catalytic reaction process were unchanged. The conversion of phenol and the yield of alkylation product are shown in Table 1.

[0039] Example 6

[0040] The catalyst preparation and catalytic conversion reaction conditions are the same as those in Example 1, except that only the reaction time is adjusted to 8 h, and other conditions in the catalyst preparation process and catalytic reaction process remain unchanged. The conversion rate of phenol and the yield of the alkylation product are shown in Table 1.

[0041] Example 7

[0042] The catalyst preparation and catalytic conversion reaction conditions are the same as those in Example 1, except that only the reaction time is adjusted to 12 h, and other conditions in the catalyst preparation process and catalytic reaction process remain unchanged. The conversion rate of phenol and the yield of the alkylation product are shown in Table 1.

[0043] Example 8

[0044] The catalyst preparation and catalytic conversion reaction conditions are the same as those in Example 5, except that only the reaction solvent is changed to n-decane, and other conditions in the catalyst preparation process and catalytic reaction process remain unchanged. The conversion rate of phenol and the yield of the alkylation product are shown in Table 1.

[0045] Example 9

[0046] The catalyst preparation and catalytic conversion reaction conditions are the same as those in Example 5, except that only the reaction solvent is changed to benzene, and other conditions in the catalyst preparation process and catalytic reaction process remain unchanged. The conversion rate of phenol and the yield of the alkylation product are shown in Table 1.

[0047] Example 10

[0048] The catalyst preparation and catalytic conversion reaction conditions are the same as those in Example 5, except that only the reaction solvent is changed to o-xylene, and other conditions in the catalyst preparation process and catalytic reaction process remain unchanged. The conversion rate of phenol and the yield of the alkylation product are shown in Table 1.

[0049] Example 11

[0050] The catalyst preparation and catalytic conversion reaction conditions are the same as those in Example 5, except that only the reaction temperature is changed to 280℃, and other conditions in the catalyst preparation process and catalytic reaction process remain unchanged. The conversion rate of phenol and the yield of the alkylation product are shown in Table 1.

[0051] Example 12

[0052] The catalyst preparation and catalytic conversion reaction conditions are the same as those in Example 5, except that only the reaction temperature is changed to 290℃, and other conditions in the catalyst preparation process and catalytic reaction process remain unchanged. The conversion rate of phenol and the yield of the alkylation product are shown in Table 1.

[0053] Example 13

[0054] The catalyst preparation and catalytic conversion reaction conditions are the same as those in Example 1, except that only the type of the alkylation reagent alcohol is changed to 1-dodecanol, and other conditions in the catalyst preparation process and the catalytic reaction process remain unchanged. The conversion rate of phenol and the yield of the alkylation product are shown in Table 1.

[0055] Example 14

[0056] The catalyst preparation and catalytic conversion reaction conditions are the same as those in Example 1, except that only the type of the alkylation reagent alcohol is changed to 1-dodecanol, and other conditions in the catalyst preparation process and the catalytic reaction process remain unchanged. The conversion rate of phenol and the yield of the alkylation product are shown in Table 1.

[0057]

[0058] Example 15

[0059] The catalyst preparation and catalytic conversion reaction conditions are the same as those in Example 1, except that only the type of the alkylation reagent alcohol is changed to 1-dodecanol, and other conditions in the catalyst preparation process and the catalytic reaction process remain unchanged. The conversion rate of phenol and the yield of the alkylation product are shown in Table 1.

[0060]

[0061] Example 16

[0062] The catalyst preparation and catalytic conversion reaction conditions are the same as those in Example 1, except that only the type of the alkylation reagent alcohol is changed to 1-dodecanol, and other conditions in the catalyst preparation process and the catalytic reaction process remain unchanged. The conversion rate of phenol and the yield of the alkylation product are shown in Table 1.

[0063]

[0064] Example 17

[0065] The catalyst preparation and catalytic conversion reaction conditions are the same as those in Example 14, except that the reaction time is adjusted to 24 h, and other conditions in the catalyst preparation process and the catalytic reaction process remain unchanged. The conversion rate of phenol and the yield of the alkylation product are shown in Table 1.

[0066] Example 18

[0067] The catalyst preparation and catalytic conversion reaction conditions are the same as those in Example 17, except that the used catalyst after the first reaction is used instead of fresh catalyst for the reaction to verify the cycle stability of the catalyst, and other conditions in the catalytic reaction process remain unchanged. The conversion rate of phenol and the yield of the alkylation product are shown in Table 1.

[0068] Example 19

[0069] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 17, except that the catalyst after two reactions was used instead of fresh catalyst to verify the recycling stability of the catalyst, and other conditions during the catalytic reaction were unchanged. The conversion of phenol and the yield of the alkylated product are shown in Table 1.

[0070] Example 20

[0071] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 17, except that the catalyst after two reactions was used instead of fresh catalyst to verify the recycling stability of the catalyst, and other conditions during the catalytic reaction were unchanged. The conversion of phenol and the yield of the alkylated product are shown in Table 1.

[0072] Comparative Example 1

[0073] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that only the type of catalyst was changed to γ-Al2O3, and other conditions during the catalytic reaction were unchanged. The conversion of phenol and the yield of the alkylated product are shown in Table 1.

[0074] Comparative Example 2

[0075] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that only the type of catalyst was changed to H-ZSM-5, and other conditions during the catalytic reaction were unchanged. The conversion of phenol and the yield of the alkylated product are shown in Table 1.

[0076] Comparative Example 3

[0077] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that only the type of catalyst was changed to rutile titanium oxide (TiO2-R), and other conditions during the catalytic reaction were unchanged. The conversion of phenol and the yield of the alkylated product are shown in Table 1.

[0078] Comparative Example 4

[0079] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that only the type of catalyst was changed to P25 TiO2, and other conditions during the catalyst preparation and catalytic reaction were unchanged. The conversion of phenol and the yield of the alkylated product are shown in Table 1.

[0080] Comparative Example 5

[0081] The catalyst preparation and catalytic conversion reaction conditions were the same as in Example 1, except that no catalyst was added, and other conditions during the catalytic reaction were unchanged. The conversion of phenol and the yield of the alkylated product are shown in Table 1.

[0082] Table 1. Evaluation results of the alkylation reaction of phenol

[0083]

[0084]

[0085]

[0086] Example 21

[0087] The alkylation reaction of substituted phenol with 1-propanol was carried out, with the same catalyst and reaction conditions as in Example 1, except that the structure of the phenol was different. The specific structure and reaction yield are shown in Table 2.

[0088] Table 2. Alkylation reaction of substituted phenol with 1-propanol

[0089]

Claims

1. A method for preparing alkylphenols by alkylation reaction of phenol, characterized in that: Anatase titanium dioxide is used as a catalyst for the alkylation reaction of phenolic compounds with alcohols; the alcohols are one or more of primary and secondary monohydric alcohols, and the alcohols are alkyl alcohols; the alkyl alcohols have a carbon chain >2; the alkylation reaction occurs on the carbon adjacent to the α-carbon and the phenolic hydroxyl group in the alcohol molecule, yielding a product with alkylation at the ortho position of the phenol; the alkylation reaction uses an organic solvent as the reaction medium, and the organic solvent is toluene.

2. The method for preparing alkylphenols by phenol alkylation reaction according to claim 1, characterized in that: Using anatase titanium dioxide as a catalyst, phenolic compounds as reaction substrates, alcoholic compounds as alkylating agents, and organic solvents as reaction media, alkylated products of phenol are prepared under the protection of a chemically inert gas.

3. The method for preparing alkylphenols by phenol alkylation reaction according to claim 1, characterized in that: Phenolic compounds are one or more of phenol and phenols containing mono- or poly-substituted groups.

4. The method for preparing alkylphenols by phenol alkylation reaction according to claim 1, characterized in that: The reaction pressure is 0.1-4 MPa, the reaction temperature is 280-320 ℃, and the reaction time is 60-1440 min.

5. The method for preparing alkylphenols by phenol alkylation reaction according to claim 4, characterized in that: The reaction pressure is 1-2 MPa; the reaction temperature is 300-310 ℃; and the reaction time is 720-1440 min.

6. The method for preparing alkylphenols by phenol alkylation reaction according to claim 2, characterized in that: The chemically inert gas is selected from one or a mixture of nitrogen and argon.

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