A method for preparing 1-methoxy-2,7-octadiene

Abstract

The present invention discloses a method for preparing 1-methoxy-2,7-octadiene, belongs to the field of chemical technology, and solves the problem that the reaction efficiency of the corresponding preparation reaction in the prior art is not ideal. The method includes the following steps: in an oxygen-free environment, a palladium source and a palladium source ligand are dissolved in methanol, and acetic acid is added as a stabilizer and stirred at room temperature to obtain a catalyst prefabricated liquid; methanol, a catalyst and 1,3-butadiene are sequentially added to the catalyst prefabricated liquid, and a telomerization reaction is carried out under oxygen-free conditions. After the reaction is completed, the pressure is released after cooling to room temperature to obtain the 1-methoxy-2,7-octadiene. The palladium catalytic system 1,3-butadiene conversion rate obtained by the preparation method of the present invention is high, the selectivity of the ligand is better and the catalyst concentration is lower, and it can be used for industrial production of 1-MOD.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industry, and more particularly to a method for preparing 1-methoxy-2,7-octadiene. Background Art

[0002] The telomerization of 1,3-butadiene with methanol is a key step in the commercially available route to 1-octene. The telomerization product, 1-methoxyoctadiene (1-MOD), is fully hydrogenated to 1-methoxyoctane, which is then thermally cracked to yield the desired oct-1-ene and recyclable methanol. In addition to 1-MOD, two major byproducts are formed: 3-methoxyoctadiene (3-MOD) and 1,3,7-octatriene (OCT).

[0003] The palladium-catalyzed reaction of 1,3-butadiene with methanol to form 1-MOD is considered a key step in the synthesis of 1-octene. Although a three-step process for preparing 1-octene using 1,3-butadiene and methanol as raw materials has been developed using a Pd / PPh3 catalytic system and put into production in 2008, research and development of palladium catalysts with higher activity and regioselectivity under milder conditions is ongoing in both industry and academic laboratories. n-Heterocyclic carbenes and triarylphosphines are the two primary ligands for palladium catalysts.

[0004] Compared with the excellent performance of the (NHC)Pd catalyst developed by Beller et al., the catalytic performance of Pd-phosphine complexes was relatively poor until the synthesis of bukly-type phosphine ligands by van Leeuwen et al. in 2010, which made a huge leap in catalyst efficiency. Since phosphine ligands have more stable performance than NHC ligands under commercially relevant production conditions when using industrial raw materials, the development of more efficient phosphine ligands for the polymerization reaction of 1,3-butadiene with methanol still has great prospects. Summary of the Invention

[0005] The present invention provides a method for preparing 1-methoxy-2,7-octadiene, which is used to solve the problem that the reaction efficiency of the corresponding preparation reaction in the prior art is not ideal.

[0006] In a first aspect, the present invention provides a method for preparing 1-methoxy-2,7-octadiene, comprising the following steps: dissolving a palladium source and a palladium source ligand in methanol in an oxygen-free environment, adding acetic acid as a stabilizer, and stirring at room temperature to obtain a catalyst prefabricated liquid; sequentially adding methanol, a sodium methoxide catalyst, and 1,3-butadiene to the catalyst prefabricated liquid, and performing a telomerization reaction under oxygen-free conditions; after the reaction is completed, cooling to room temperature and releasing the pressure to obtain the 1-methoxy-2,7-octadiene, wherein the palladium source ligand is any one of formula (1), formula (2), formula (3), formula (4), formula (5), and formula (6).

[0007]

[0008] As a possible implementation, the palladium source is any one of bis(acetylacetonate)palladium, palladium chloride, tetrakis(triphenylphosphine)palladium, tris(dibenzylideneacetone)dipalladium and bis(dibenzylideneacetone)palladium.

[0009] As a possible implementation method, the reaction conditions of the telomerization reaction are: temperature 50-90° C., initial pressure ≥0.80 MPa, and duration 1-48 h.

[0010] As a possible implementation manner, the palladium source concentration is 0.00065 mol% to 0.0025 mol%; and / or the methanol water content is 0 to 240 ppm.

[0011] As a possible implementation manner, the palladium source ligand is twice the equivalent of the palladium source; and / or the acetic acid is one times the equivalent of the palladium source.

[0012] As a possible implementation manner, the conversion rate of 1,3-butadiene is 60% to 95%; the selectivity of 1-methoxy-2,7-octadiene is 89% to 95%.

[0013] In a second aspect, the present invention provides 1-methoxy-2,7-octadiene prepared by the method described in any possible implementation of the first aspect.

[0014] In a third aspect, the present invention provides a use of 1-methoxy-2,7-octadiene according to any possible implementation of the second aspect in the preparation of 1-octene.

[0015] The primary objective of the present invention is to provide a highly efficient catalyst system for the telomerization of 1,3-butadiene and methanol. The palladium-catalyzed system obtained by the present invention exhibits high 1,3-butadiene conversion, improved ligand selectivity, and lower catalyst concentration, making it suitable for the industrial production of 1-MOD. To achieve this objective, the present invention synthesizes a series of ligands. The precursor xanthene is obtained by reacting p-tert-butylphenol with acetone under the catalysis of trifluoromethanesulfonic acid. The precursor xanthene is then further brominated and lithiated to form different diarylphosphines to yield the final series of ligands. Furthermore, the present invention provides a series of ligands that exhibit high butadiene conversion (60% to 95%) and high 1-MOD selectivity (89% to 95%) at low concentrations (5 to 50 ppm) in this reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 Schematic diagram of the mass spectrum of 1-methoxy-2,7-octadiene provided in an embodiment of the present invention.

[0018] Figure 2 Schematic diagram of the hydrogen nuclear magnetic resonance spectrum of 1-methoxy-2,7-octadiene provided in an embodiment of the present invention.

[0019] Figure 3 Schematic diagram of gas chromatography of the product of Experiment III provided in an embodiment of the present invention.

[0020] Figure 4 Schematic diagram of gas chromatography of the product of Experiment IX provided in an embodiment of the present invention.

[0021] Figure 5 Schematic diagram of gas chromatography of the product of Experiment X provided in an embodiment of the present invention.

[0022] Figure 6 Schematic diagram of gas chromatography of the product of Experiment XIII provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 efforts are within the scope of protection of the present invention.

[0024] To address the problem of unsatisfactory reaction efficiency of the corresponding preparation reaction in the prior art, this example provides a preparation experiment of 1-methoxy-2,7-octadiene and statistics on the conversion rate of butadiene and the selectivity of 1-MOD.

[0025] It can be seen that the palladium catalytic system obtained by the preparation method of the present invention has a high 1,3-butadiene conversion rate, better ligand selectivity, and lower catalyst concentration, and can be used for the industrial production of 1-MOD. The present invention synthesizes this series of ligands and obtains xanthenes by reacting p-tert-butylphenol with acetone under the catalysis of trifluoromethanesulfonic acid. The present invention provides a series of ligands that have high butadiene conversion rates (70% to 95%) and high 1-MOD selectivity (89% to 95%) in this reaction at low concentrations (5 to 50 ppm).

[0026] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0027] Example 1

[0028] This example provides an experiment for preparing 1-methoxy-2,7-octadiene.

[0029] The preparation experiment provided in this embodiment includes the following steps: after two gas exchanges with low-pressure high-purity nitrogen, the autoclave is evacuated to negative pressure (-0.09 MPa); sodium methoxide (0.01-0.5 mol%) is dissolved in methanol (1-10 wt%) (sodium methoxide serves as a promoter to provide an alkaline environment for the reaction, and methanol serves as both a solvent and a reactant) and introduced into the autoclave under negative pressure. In this embodiment, the methanol is dried over a 3A molecular sieve to a water content of 10-200 ppm; the reaction kettle is heated to 400 ℃ for 2 hours. The temperature is lowered to -20 to 0°C, 1,3-butadiene (30 to 300 g) is frozen into a liquid in a -40°C cold bath, and introduced into the autoclave under negative pressure; a catalyst prefabricated liquid [the preparation method comprises the steps of dissolving a palladium source (0.0001 to 0.01 mol%) and two equivalents of a ligand in approximately 50 g of methanol, adding one equivalent of acetic acid as a stabilizer, and stirring at room temperature for half an hour] is added under negative pressure; the temperature is gradually increased, and timing is started after reaching the temperature; the temperature is lowered after the reaction time is reached, and the reaction is terminated.

[0030]

[0031] Experiment I: Pd(acac)2 (0.0025 mol%, 20 mg) was used as the palladium source and Formula (1) (0.005 mol%) was used as the ligand. When the reaction reached 90°C, the reaction pressure was increased to 0.64 MPa by nitrogen. The reaction was carried out for 2.5 hours, and the temperature was lowered after the time was reached. When the temperature dropped to 25°C, the pressure was released to normal pressure. The product was analyzed by mass spectrometry to obtain the following: Figure 1 The results shown in the figure were analyzed by nuclear magnetic resonance hydrogen spectrum of the product, and the results were as follows Figure 2 From the results shown, it can be seen that 1-methoxy-2,7-octadiene was successfully prepared.

[0032] Experiment II: Pd(acac)2 (0.0025 mol%, 20 mg) was used as the palladium source, and formula (1) (0.005 mol%) was used as the ligand; when the reaction reached 90°C, the reaction pressure was increased to 0.88 MPa by nitrogen, and the reaction was carried out for 2.5 h. During the reaction, the pressure decreased with time to 0.67 MPa, and the temperature was cooled after the time was reached; when the temperature dropped to 25°C, the pressure was released to normal pressure.

[0033] Experiment III: Pd(acac)2 (0.0025 mol%, 20 mg) was used as the palladium source and Formula (1) (0.005 mol%) was used as the ligand. When the reaction reached 90°C, the reaction pressure was increased to 1.03 MPa by nitrogen. The reaction was carried out for 2.5 h. During the reaction, the pressure gradually decreased to 0.82 MPa. After the reaction time was reached, the temperature was lowered. When the temperature dropped to 25°C, the pressure was released to normal pressure. The product was analyzed by gas chromatography to obtain the following: Figure 3 The results shown.

[0034] Experiment IV: Pd(OAc)2 (0.0025 mol%, 15 mg) was used as the palladium source, and formula (1) (0.005 mol%, 52 mg) was used as the ligand; when the reaction reached 90°C, the reaction pressure was increased to 0.96 MPa by nitrogen, and the reaction was carried out for 2.5 h. After the reaction time was reached, the temperature was lowered; when the temperature dropped to 25°C, the pressure was released to normal pressure.

[0035]

[0036] Experiment V: Pd(acac)2 (0.0025 mol%, 20 mg) was used as the palladium source, and formula (1a) (0.005 mol%, 90 mg) was used as the ligand; when the reaction reached 90°C, the reaction pressure was increased to 1.00 MPa by nitrogen, and the reaction was carried out for 4 hours. After the time was reached, the temperature was cooled; when the temperature dropped to 25°C, the pressure was released to normal pressure.

[0037] Experiment VI: Pd(acac)2 (0.0025 mol%, 20 mg) was used as the palladium source, and formula (2a) (0.005 mol%, 52 mg) was used as the ligand; when the reaction reached 90°C, the reaction pressure was increased to 1.00 MPa by nitrogen, and the reaction was carried out for 4 hours. After the time was reached, the temperature was cooled; when the temperature was cooled to 25°C, the pressure was released to normal pressure.

[0038] Experiment VII: Pd(acac)2 (0.0025 mol%, 20 mg) was used as the palladium source, and formula (3a) (0.005 mol%, 52 mg) was used as the ligand; when the reaction reached 90°C, the reaction pressure was increased to 1.13 MPa by nitrogen, and the reaction was carried out for 2.5 hours. After the reaction time was reached, the temperature was lowered; when the temperature dropped to 25°C, the pressure was released to normal pressure.

[0039] Experiment VIII: Pd(acac)2 (0.0025 mol%, 20 mg) was used as the palladium source, and formula (1) (0.005 mol%) was used as the ligand; when the reaction reached 80°C, the reaction pressure was increased to 1.03 MPa by nitrogen, and the reaction was carried out for 2.5 h. During the reaction, the pressure decreased to 0.75 MPa over time, and the temperature was lowered after the time was reached; when the temperature dropped to 25°C, the pressure was released to normal pressure.

[0040] Experiment IX: Pd(acac)2 (0.0025 mol%, 20 mg) was used as the palladium source and Formula (1) (0.005 mol%, 67 mg) was used as the ligand. When the reaction reached 70°C, the reaction pressure was increased to 1.01 MPa by nitrogen. The reaction was carried out for 2.5 hours. During the reaction, the pressure gradually decreased to 0.71 MPa. After the reaction time was reached, the temperature was lowered. When the temperature dropped to 25°C, the pressure was released to normal pressure. The product was analyzed by gas chromatography to obtain the following: Figure 4 The results shown.

[0041] Experiment X: Pd(acac)2 (0.0025 mol%, 20 mg) was used as the palladium source and Formula (1) (0.005 mol%, 67 mg) was used as the ligand. When the reaction reached 60°C, the reaction pressure was increased to 0.89 MPa by nitrogen. The reaction was carried out for 2.5 hours. During the reaction, the pressure gradually decreased to 0.78 MPa. After the reaction time was reached, the temperature was lowered. When the temperature dropped to 25°C, the pressure was released to normal pressure. The product was analyzed by gas chromatography to obtain the following: Figure 5 The results shown.

[0042] Experiment XⅠ: Pd(acac)2 (0.00125 mol%, 10 mg) was used as the palladium source, and formula (1) (0.0025 mol%) was used as the ligand; when the reaction reached 90°C, the reaction pressure was increased to 1.20 MPa by nitrogen, and the reaction was carried out for 2.5 h. During the reaction, the pressure decreased with time to 0.97 MPa, and the temperature was cooled after the time was reached; when the temperature dropped to 25°C, the pressure was released to normal pressure.

[0043] Experiment XII: Pd(acac)2 (0.000625 mol%, 10 mg) was used as the palladium source, formula (1a) (0.00125 mol%) was used as the ligand, and butadiene (5.32 mol, 288 g) was used; when the reaction reached 90°C, the reaction pressure was increased to 1.36 MPa by nitrogen, and the reaction was carried out for 5 h. During the reaction, the pressure decreased over time to 1.22 MPa, and the temperature was cooled after the time was reached; when the temperature dropped to 25°C, the pressure was released to normal pressure.

[0044] Experiment XIII: Pd(acac)2 (0.000625 mol%, 10 mg) was used as the palladium source, formula (1) (0.00125 mol%) was used as the ligand, and butadiene (5.32 mol, 288 g) was used; when the reaction reached 70°C, the reaction pressure was increased to 1.13 MPa by nitrogen, and the reaction was carried out for 16 hours. During the reaction, the pressure gradually decreased to 0.85 MPa, and after the reaction time was reached, the temperature was lowered; when the temperature dropped to 25°C, the pressure was released to normal pressure. The product was analyzed by gas chromatography, and the following was obtained: Figure 6 The results shown.

[0045] Experiment XIV: Pd(acac)2 (0.0008 mol%, 13 mg) was used as the palladium source, formula (1) (0.00125 mol%) was used as the ligand, and butadiene (5.32 mol, 288 g) was used; when the reaction reached 70°C, the reaction pressure was increased to 1.06 MPa by nitrogen, and the reaction was carried out for 16 h. During the reaction, the pressure decreased over time to 0.73 MPa, and the temperature was cooled after the time was reached; when the temperature dropped to 25°C, the pressure was released to normal pressure.

[0046] Experiment XV: Pd(acac)2 (0.00125 mol%, 10 mg) was used as the palladium source, formula (1) (0.0025 mol%) was used as the ligand, and methanol was used to dry it through a 4A molecular sieve, with a water content of 170 ppm; when the reaction reached 90°C, the reaction pressure was increased to 1.20 MPa by nitrogen, and the reaction was carried out for 2.5 h. During the reaction, the pressure decreased over time to 1.07 MPa, and the temperature was cooled after the time was reached; when the temperature dropped to 25°C, the pressure was released to normal pressure.

[0047] Experiment XVI: Pd(acac)2 (0.00125 mol%, 10 mg) was used as the palladium source, formula (1) (0.0025 mol%) was used as the ligand, and undried methanol (water content of 210-240 ppm) was used; when the reaction reached 90°C, the reaction pressure was increased to 1.30 MPa by nitrogen, and the reaction was carried out for 2.5 h. During the reaction, the pressure decreased over time to 1.15 MPa, and the temperature was cooled after the time was reached; when the temperature dropped to 25°C, the pressure was released to normal pressure.

[0048] The target product peak was identified by GC-MS fitting, selectivity was determined by comparing the integrated areas of the GC peaks, and butadiene conversion was calculated by weight gain of the reaction solution. Calculations were performed for each of the three experimental groups, yielding the results shown in Table 1.

[0049] Table 1 Parameters and statistical results of each group of experiments

[0050]

[0051] A comparison of Experiment I (pressure 0.64 MPa), Experiment II (pressure 0.88-0.67 MPa), and Experiment III (pressure 1.03-0.82 MPa) in Table 1 shows that, within a certain range, the conversion of butadiene is positively correlated with the reaction pressure. A comparison of Experiment III (palladium source Pd(acac)2) and Experiment IV (palladium source Pd(OAc)2) in Table 1 shows that, within a certain range, the conversion of butadiene is related to the choice of palladium source. From the comparison of Experiment III [ligand formula (1)], Experiment V [ligand formula (1a)], Experiment VI [ligand formula (2a)] and Experiment VII [ligand formula (3a)] in Table 1, it can be seen that within a certain range, the conversion rate of butadiene is related to the selection of ligand; from Experiment V, it can be seen that although ligand formula (1a) has excellent performance in conversion rate, it is not conducive to the selectivity of 1-MOD; from Experiment VI, it can be seen that although ligand formula (2a) has excellent performance in 1-MOD selectivity, it is not conducive to conversion rate; from Experiment VII, it can be seen that ligand formula (3a) performs poorly in both conversion rate and 1-MOD selectivity. A comparison of Experiment III (90°C), Experiment VIII (80°C), Experiment IX (70°C), and Experiment X (60°C) in Table 1 shows that within a certain range, the selectivity of 1-MOD is negatively correlated with temperature; when the temperature is below 70°C, the conversion rate decreases significantly. A comparison of Experiment III (0.0025 mol% palladium source concentration), Experiment XI (0.00125 mol% palladium source concentration), Experiment XII (0.000625 mol% palladium source concentration), Experiment XIII (0.000625 mol% palladium source concentration), and Experiment XIV (0.0008 mol% palladium source concentration) in Table 1 shows that within a certain range, the conversion rate of butadiene is related to the palladium source concentration; when the palladium source concentration is below 0.0008 mol%, the conversion rate of butadiene decreases significantly. From the comparison of Experiment XⅠ (methanol water content 0), Experiment XV (methanol water content 170 ppm) and Experiment XVI (methanol water content 210-240 ppm) in Table 1, it can be seen that within a certain range, the conversion rate of butadiene is related to the methanol water content. When the methanol water content is higher than 170 ppm, the conversion rate of butadiene is significantly reduced.

[0052] As can be seen, increasing reaction pressure (initial pressure ≥ 0.80Mpa) helps improve the butadiene conversion, selecting a reasonable reaction temperature range (70-90°C) helps improve reaction selectivity and conversion, selecting a reasonable palladium source concentration range (0.0008mol%-0.0025mol%) helps improve the conversion, and reducing the water content of methanol (<170ppm) helps improve the conversion. The present invention combines the above-mentioned factors and, by regulating the concentration of palladium to reduce process costs, can achieve a butadiene conversion of 87.1% and a selectivity of 93.0% at 70°C using only 8ppm of palladium.

[0053] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0054] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing 1-methoxy-2,7-octadiene, characterized in that: The following steps are involved: In an oxygen-free environment, a palladium source and a palladium source ligand are dissolved in methanol, and acetic acid is added as a stabilizer and stirred at room temperature to obtain a catalyst preformed liquid; Methanol, sodium methoxide catalyst and 1,3-butadiene are sequentially added to the catalyst prefabricated liquid, and a telomerization reaction is carried out under anaerobic conditions. After the reaction is completed, the temperature is lowered to room temperature and the pressure is released to obtain the 1-methoxy-2,7-octadiene. Wherein, the palladium source is Pd(acac)2, and the palladium source ligand is of formula (1), ； The water content of the methanol is less than 170 ppm.

2. The method according to claim 1, characterized in that The reaction conditions of the telomerization reaction are: temperature 50-90° C., initial pressure ≥0.80 MPa, and duration 1-48 h.

3. The method according to claim 1, characterized in that The palladium source concentration is 0.00065 mol% to 0.0025 mol%.

4. The method according to claim 1, wherein The palladium source ligand is twice the equivalent of the palladium source; And / or, the acetic acid is one equivalent of the palladium source.

5. The method according to any one of claims 1 to 4, characterized in that The conversion rate of 1,3-butadiene is 60% to 95%; The selectivity of the 1-methoxy-2,7-octadiene is 89% to 95%.

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