A method for preparing long-chain carboxylic acids from long-chain alpha-olefins using a metal-organic framework material as catalyst
Patent Information
- Application Number
- CN202611224501.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-13
- Publication Date
- 2026-10-13
AI Technical Summary
[0007]为解决现有催化体系催化剂难分离回收、生产成本高以及对长链α-烯烃活性低等难题，本发明提供一种金属有机框架材料催化长链α-烯烃制备长链羧酸的方法
[0023]（1）本发明采用MIL-101（Cr）作为非均相催化剂，催化剂制备方法简单，反应结束后可通过离心直接实现催化剂与产物分离，便于循环使用，降低了后处理成本。
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of heterogeneous catalysis technology, specifically relating to a method for preparing long-chain carboxylic acids from long-chain α-olefins using metal-organic framework materials. Background Technology
[0002] Long-chain aliphatic carboxylic acids, usually referring to those with ≥ C carbons. 12 Fatty acid compounds are important basic raw materials for fine chemicals, widely used in surfactants, plasticizers, rubber, lubricant additives, fragrances, cosmetics, synthetic waxes, pharmaceutical intermediates, and polymer modifiers. Traditional methods for preparing long-chain fatty carboxylic acids mainly involve the addition of petroleum-based even-carbon olefins to syngas followed by oxidation, or the high-temperature hydrolysis of natural oils to obtain corresponding aldehydes followed by oxidation. However, traditional methods suffer from low yields, demanding reaction conditions, and high equipment requirements. Given the important uses and demand for long-chain fatty carboxylic acids, and the limitations of traditional sources due to raw material production constraints, large-scale application of these compounds is directly limited. High-temperature Fischer-Tropsch synthesis often produces large quantities of long-chain linear α-olefins as byproducts, accounting for up to 70% of hydrocarbon products, but their relative value is low. Therefore, if the terminal carbon-carbon double bonds (C=C) of long-chain α-olefins can be directionally converted to carboxyl groups (COOH) through catalytic oxidation, a new process route for preparing coal-based long-chain fatty carboxylic acids can be constructed, possessing extremely broad market prospects and industrial application potential.
[0003] The oxidative cracking of olefins to carboxylic acids is an important reaction in organic synthesis and industrial production, and a great deal of work has been done on this topic. The oxidation of the C=C double bond in olefins requires the synergistic effect of both an oxidant and a catalyst. In early stages, researchers used stoichiometric inorganic compounds as oxidants, such as KMnO4 and CrO2. x RuO4, OsO4+NaIO4, etc., are all oxidants, but these oxidants are toxic and easily produce many byproducts. Ruthenium and osmium are both precious metals, which limits the application of these systems on an industrial scale. The use of Oxone or Phl(OAc)2 is also widely adopted, but these oxidants are expensive and difficult to separate. Tert-butyl hydroperoxide has also been successfully used as an oxidant. In the presence of a suitable catalyst (Mn-MIL-101, indium trichloride, gold nanoparticles), it can only achieve the oxidative cracking of C=C bonds in aromatic olefins, but it is difficult to achieve the oxidation reaction of long-chain α-olefins with more than C8.
[0004] Considering both oxidation efficiency and environmental friendliness, hydrogen peroxide (H2O2) has gradually become a common choice for the cleavage of aliphatic C=C bonds. However, it usually needs to be used in conjunction with metal catalysts such as palladium, rhenium, ruthenium, and tungsten to promote the oxidative cleavage of C=C bonds to prepare carboxylic acids. Among these, W compounds can react with most olefin substrates, but when using hydrogen peroxide, a "water-oil" two-phase reaction is formed. Since long-chain α-olefins have poor solubility in water, expensive phase transfer catalysts (PTCs) such as quaternary ammonium salts and phosphonium salts are required. Furthermore, the reaction is difficult to separate and has poor recycling capacity.
[0005] Although existing olefin oxidative cracking to carboxylic acid systems have made some progress, problems such as difficult catalyst recovery, the need for phase transfer catalysts, low selectivity and yield of target carboxylic acids, and insufficient greenness of the process are still common for long-chain α-olefin substrates, making it difficult to meet the needs of industrial applications. Therefore, developing a novel catalytic system that can efficiently catalyze the oxidative cracking of long-chain α-olefins in a two-phase system, while possessing high catalytic activity, easy catalyst separation and recovery, and a green and environmentally friendly process, is of significant research importance and application value.
[0006] Over the past two decades, metal-organic frameworks (MOFs) have attracted widespread attention as heterogeneous catalysts. MOFs are porous crystalline materials with periodic network structures formed by the self-assembly of organic ligands and transition metal ions. MOFs possess advantages such as large specific surface area, regular channels, tunable pore size, and diverse topologies. Among them, MIL-101(Cr) not only combines the advantages of traditional MOF materials but also boasts a simple synthesis method and higher thermal and chemical stability than other MOF materials. Furthermore, the structure of MIL-101(Cr) contains unsaturated chromium metal sites, which can chelate with most electronic functional groups, demonstrating excellent application potential in catalysis. Therefore, applying MIL-101(Cr) as a heterogeneous catalyst to the oxidative cracking reaction of long-chain α-olefins is expected to overcome the problems of difficult catalyst separation and strong dependence on phase transfer catalysts in traditional catalytic systems, providing a new technical approach for the green and efficient preparation of long-chain carboxylic acids. Summary of the Invention
[0007] To address the challenges of existing catalytic systems, such as difficult catalyst separation and recovery, high production costs, and low activity towards long-chain α-olefins, this invention provides a method for preparing long-chain carboxylic acids from long-chain α-olefins using metal-organic framework materials. This method offers advantages such as low production costs, easy catalyst separation, high catalytic activity, and an overall environmentally friendly process.
[0008] To achieve the above objectives, the present invention employs the following technical solution:
[0009] This invention provides a method for preparing long-chain carboxylic acids from long-chain α-olefins catalyzed by metal-organic framework materials, comprising the following steps:
[0010] Using long-chain α-olefins as raw materials, the metal-organic framework material MIL-101(Cr) was used as a heterogeneous catalyst, a 30% H2O2 solution was used as an oxidant, and an organic solvent was used to construct the reaction system. Under mild conditions, the C=C double bond of long-chain α-olefins was efficiently and selectively oxidized and cracked to directionally generate long-chain carboxylic acids with one less carbon atom than the raw olefins.
[0011] Furthermore, the long-chain α-olefin is one of 1-tetrideene, 1-heptadecene, and 1-nonadene, the molar ratio of H2O2 to substrate is 8~18:1, and 0.02g~0.11g of heterogeneous catalyst is used for every 2.1mmol of substrate.
[0012] Furthermore, the mild conditions are: a reaction temperature of 50~70℃ and a reaction time of 4~12h.
[0013] Furthermore, the preparation method of the metal-organic framework material MIL-101(Cr) is as follows:
[0014] Step 1: Mix chromium nitrate nonahydrate, terephthalic acid, and mineralizing agent, and then dissolve them by ultrasonic stirring;
[0015] Step 2: The mixture obtained in Step 1 is subjected to a crystallization reaction. After the reaction is completed, it is naturally cooled to room temperature and then centrifuged at 4500 r / min for 10 min to collect the product.
[0016] Step 3: N,N-dimethylformamide, deionized water and hot ethanol are added sequentially to the separated product, and the mixture is washed with sonication.
[0017] Step 4: Vacuum dry the washed product to obtain the metal-organic framework material MIL-101(Cr).
[0018] Furthermore, the mineralizing agent in step 1 is one of hydrofluoric acid, concentrated hydrochloric acid, and acetic acid.
[0019] Furthermore, in step 1, the molar ratio of the raw materials is: chromium nitrate nonahydrate: terephthalic acid: mineralizer = 1:1:1.
[0020] Furthermore, in step 2, the crystallization reaction is carried out at a temperature of 220°C for 8 hours.
[0021] Furthermore, in step 4, the vacuum drying temperature is 80°C and the time is 12 hours.
[0022] Compared with the prior art, the present invention has the following advantages:
[0023] (1) The present invention uses MIL-101 (Cr) as a heterogeneous catalyst. The catalyst preparation method is simple. After the reaction, the catalyst and product can be directly separated by centrifugation, which is convenient for recycling and reduces the post-processing cost.
[0024] (2) The present invention uses hydrogen peroxide as an oxidant, and the main byproduct during the oxidation process is water, which has the characteristics of being environmentally friendly and green.
[0025] (3) The present invention can realize the oxidative cracking of long-chain α-olefins under normal pressure and 50-70℃ conditions, without the need for high temperature and high pressure reaction conditions. The process conditions are mild and the equipment requirements are low, which has good prospects for industrial application.
[0026] (4) This invention can achieve efficient oxidative cracking of C=C double bonds in long-chain α-olefins. It has good substrate applicability to long-chain α-olefins with carbon chain length ≥ C12, and can obtain high substrate conversion rate and target long-chain carboxylic acid selectivity, providing a new technical route for the high-value utilization of coal-based long-chain α-olefins. Attached Figure Description
[0027] Figure 1 This is an X-ray powder diffraction pattern of the catalyst MIL-101(Cr) synthesized with different mineralizers in this invention.
[0028] Figure 2 This is a schematic diagram illustrating the effect of different mineralizers on the oxidation of olefins in this invention.
[0029] Figure 3 This is a schematic diagram illustrating the effect of the molar ratio of H2O2 to olefins on olefin oxidation in this invention.
[0030] Figure 4 This is a schematic diagram illustrating the effect of reaction temperature on olefin oxidation in this invention.
[0031] Figure 5 This is a schematic diagram illustrating the effect of reaction time on olefin oxidation in this invention.
[0032] Figure 6 This is a schematic diagram illustrating the effect of catalyst dosage on olefin oxidation in this invention. Detailed Implementation
[0033] To further illustrate the technical solution of the present invention, the present invention will be further described below through embodiments.
[0034] Product analysis was performed using an Agilent 7820A gas chromatograph. The analytical conditions were as follows: Agilent DB-FFAP column; column temperature 100℃ for 5 min; ramped to 200℃ at 20℃ / min and held for 15 min; injection port temperature 300℃; detection temperature 280℃; split injection, split ratio 20:1; injection volume 0.2 μL. The positions of each component were determined using GC-MS, and the conversion of long-chain α-olefins and the selectivity of the target long-chain carboxylic acids were calculated using the internal standard method.
[0035] Example 1: Synthesis of MIL-101(Cr)-HF using hydrofluoric acid as a mineralizing agent
[0036] Step 1: Mix 4.8g of chromium nitrate nonahydrate, 1.98g of terephthalic acid, 0.5mL of hydrofluoric acid, and 60mL of deionized water, and sonicate for 30 minutes to dissolve completely.
[0037] Step 2: Transfer the mixture obtained in Step 1 to a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene, crystallize at 220 °C for 8 h, and after the reaction is completed, allow it to cool naturally to room temperature before centrifugation.
[0038] Step 3: Add N,N-dimethylformamide (DMF), deionized water, and hot ethanol to the separated product in sequence, and wash in sonication for 30 min.
[0039] Step 4: Place the washed product in an 80℃ vacuum drying oven and dry for 12 hours to obtain the desired product MIL-101(Cr)-HF.
[0040] Using long-chain α-olefins as raw materials, the metal-organic framework material MIL-101(Cr) was used as a heterogeneous catalyst, a 30% H2O2 solution was used as an oxidant, and acetonitrile was used as an organic solvent to construct the reaction system. Under mild conditions, the C=C double bond of long-chain α-olefins was oxidized and selectively cracked to generate long-chain carboxylic acids with one less carbon atom than the raw olefins. The catalytic activity of the obtained products was then tested.
[0041] Taking 1-tridecene as an example, the specific performance evaluation procedure was as follows: In a 50 mL round-bottom flask equipped with a magnetic stirrer and a condenser, 2.1 mmol of 1-tridecene, 15 mL of acetonitrile, 0.05 g of catalyst, and 31.5 mmol of 30% H₂O₂ were added sequentially. The reaction mixture was refluxed and stirred at 70 °C for 8 h. After the reaction was complete, 0.1 g of biphenyl (internal standard) was added to the solution. After thorough mixing, the catalyst was centrifuged, and the supernatant was subjected to chromatographic quantitative analysis. The positions of each component were determined using GC-MS, and the conversion rate of 1-tridecene and the selectivity of lauric acid were calculated using the internal standard method. The results are shown below. Figure 2 .
[0042] Example 2: Synthesis of MIL-101(Cr)-HCl using concentrated hydrochloric acid as a mineralizing agent
[0043] The preparation method in this embodiment is the same as in Example 1, except that hydrofluoric acid (0.5 mL) is replaced with concentrated hydrochloric acid (1 mL), yielding the product MIL-101(Cr)-HCl. The evaluation results are shown below. Figure 2 .
[0044] Example 3: Synthesis of MIL-101(Cr)-HAc using acetic acid as a mineralizing agent
[0045] The preparation method in this embodiment is the same as in Example 1, except that hydrofluoric acid (0.5 ml) is replaced with acetic acid (0.6 ml), yielding the product MIL-101(Cr)-HAc. Evaluation results are shown below. Figure 2 .
[0046] according to Figure 1 and Figure 2 It can be seen that different mineralizers can synthesize MIL-101(Cr), among which the MIL-101(Cr) synthesized by hydrofluoric acid has the best catalytic performance. Subsequently, the effects of H2O2 dosage, reaction time, reaction temperature and catalyst dosage on the oxidative cracking reaction of 1-tetracene will be further investigated using the MIL-101(Cr) synthesized by HF acid as a catalyst.
[0047] The effect of the molar ratio of H₂O₂ to 1-tetracene was investigated: n(1-tetracene) = 2.1 mmol, T = 70 °C, t = 8 h, and catalyst dosage was 0.05 g. The results are as follows: Figure 3 As shown, as the molar ratio of H2O2 to 1-tetracene gradually increased from 8:1 to 12:1, the olefin conversion rate continuously increased from 64.37% to 82.4%, while the carboxylic acid selectivity only increased to 41.1%. Within this range, the carboxylic acid selectivity was low, possibly due to insufficient oxidant causing residual intermediates such as epoxides, making it difficult to deeply oxidize to carboxylic acids. Further increasing the H2O2 dosage to 15:1 resulted in a 1.43% increase in olefin conversion, but the selectivity increased from 41.1% to 62.4%. When the H2O2 dosage was greater than 15:1, neither the olefin conversion rate nor the selectivity changed significantly. Therefore, the optimal molar ratio of H2O2 to 1-tetracene is 15:1.
[0048] The effect of reaction temperature on olefin oxidation was investigated: n(1-tridecene) = 2.1 mmol, H₂O₂:1-tridecene = 15:1, t = 8 h, catalyst dosage was 0.05 g. The results are as follows: Figure 4As shown, the reaction hardly occurs at 50℃. With increasing temperature, the catalyst's activation efficiency for H2O2 increases, the conversion of 1-tridecene rises from 36% to 83%, and the selectivity for lauric acid increases from 31% to 62%. Therefore, the optimal reaction temperature is 70℃.
[0049] The effect of reaction time on olefin oxidation was investigated: n(1-tridecene) = 2.1 mmol, H₂O₂:1-tridecene = 15:1, T = 70 °C. Figure 5 As shown, with the reaction time increasing from 4 h to 8 h, the conversion rate of 1-tridecene continuously increased and gradually stabilized, while the selectivity of lauric acid first increased to a peak at 8 h and then gradually decreased. At a reaction time of 8 h, the conversion rate of 1-tridecene was 83%, and the selectivity of lauric acid was 62%. Therefore, the optimal reaction time is 8 h.
[0050] The effect of catalyst dosage on olefin oxidation was investigated: n(1-tridecene) = 2.1 mmol, H₂O₂:1-tridecene = 15:1, T = 70 °C, t = 8 h. Figure 6 As shown, when the catalyst dosage is 0.02 g, the number of active sites provided by the catalyst to activate H2O2 is limited, resulting in low selectivity for lauric acid. When the catalyst dosage is greater than 0.05 g, the selectivity for lauric acid shows a decreasing trend, possibly because excessive catalyst is prone to agglomeration, causing active sites to be encapsulated and pores to be blocked. Therefore, the optimal catalyst dosage is 0.05 g.
[0051] Example 4: The catalyst MIL-101(Cr)-HF prepared by the method of Example 1 was used for the oxidative cracking reaction of 1-heptadecene. The reaction products were analyzed by gas chromatography. The results showed that the conversion rate of 1-heptadecene was 65% and the selectivity of palmitic acid was 69%.
[0052] Example 5: The catalyst MIL-101(Cr)-HF prepared by the method of Example 1 was used for the oxidative cracking reaction of 1-nonadene. The reaction products were analyzed by gas chromatography. The results showed that the conversion rate of 1-nonadene was 49% and the selectivity of stearic acid was 58%.
[0053] The foregoing has shown and described the main features and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.
[0054] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A method for preparing long-chain carboxylic acids from long-chain α-olefins catalyzed by metal-organic framework materials, characterized in that, Includes the following steps: Using long-chain α-olefins as raw materials, the metal-organic framework material MIL-101(Cr) was used as a heterogeneous catalyst, a 30% H2O2 solution was used as an oxidant, and an organic solvent was used to construct the reaction system. Under mild conditions, the C=C double bond of long-chain α-olefins was efficiently and selectively oxidized and cracked to directionally generate long-chain carboxylic acids with one less carbon atom than the raw olefins.
2. The method for preparing long-chain carboxylic acids from long-chain α-olefins catalyzed by metal-organic framework materials according to claim 1, characterized in that, The long-chain α-olefin is one of 1-tetratene, 1-heptadecene, and 1-nonadene. The molar ratio of H2O2 to substrate is 8~18:1, and 0.02g~0.11g of heterogeneous catalyst is used for every 2.1mmol of substrate.
3. The method for preparing long-chain carboxylic acids from long-chain α-olefins catalyzed by metal-organic framework materials according to claim 1, characterized in that, The organic solvent is acetonitrile.
4. The method for preparing long-chain carboxylic acids from long-chain α-olefins catalyzed by metal-organic framework materials according to claim 1, characterized in that, The mild conditions are: reaction temperature of 50~70℃ and reaction time of 4~12h.
5. The method for preparing long-chain carboxylic acids from long-chain α-olefins catalyzed by metal-organic framework materials according to claim 1, characterized in that, The preparation method of the metal-organic framework material MIL-101(Cr) is as follows: Step 1: Mix chromium nitrate nonahydrate, terephthalic acid, and mineralizing agent, and then dissolve them by ultrasonic stirring; Step 2: The mixture obtained in Step 1 is subjected to a crystallization reaction. After the reaction is completed, it is naturally cooled to room temperature and then centrifuged at 4500 r / min for 10 min to collect the product. Step 3: N,N-dimethylformamide, deionized water and hot ethanol are added sequentially to the separated product, and the mixture is washed with sonication. Step 4: Vacuum dry the washed product to obtain the metal-organic framework material MIL-101(Cr).
6. The method for preparing long-chain carboxylic acids from long-chain α-olefins catalyzed by metal-organic framework materials according to claim 5, characterized in that, The mineralizing agent in step 1 is one of hydrofluoric acid, concentrated hydrochloric acid, and acetic acid.
7. The method for preparing long-chain carboxylic acids from long-chain α-olefins catalyzed by metal-organic framework materials according to claim 5, characterized in that, The raw material molar ratio in step 1 is: chromium nitrate nonahydrate: terephthalic acid: mineralizer = 1:1:
1.
8. The method for preparing long-chain carboxylic acids from long-chain α-olefins catalyzed by metal-organic framework materials according to claim 5, characterized in that, The crystallization reaction in step 2 is carried out at a temperature of 220°C for 8 hours.
9. The method for preparing long-chain carboxylic acids from long-chain α-olefins catalyzed by metal-organic framework materials according to claim 5, characterized in that, In step 4, the vacuum drying temperature is 80℃ and the time is 12h.