Method for the directed preparation of 2-methyl-1-butanol from methanol and n-butanol
By leveraging the synergistic effect of gallium-doped carbon-coated nickel-based catalysts and alkaline additives, the reaction conditions of methanol and n-butanol were controlled, solving the problem of insufficient selectivity of the target product in the direct coupling of methanol and n-butanol. This enabled the highly selective directional synthesis of 2-methyl-1-butanol, simplifying the process and improving product stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGDONG UNIV OF TECH
- Filing Date
- 2026-05-09
- Publication Date
- 2026-08-04
AI Technical Summary
In existing technologies, the direct coupling of methanol and n-butanol results in insufficient selectivity of the target product, numerous side reactions, and reliance on the extraction of fusel oil alcohols or subsequent complex separation, leading to long processes, high energy consumption, and unstable product composition.
By employing a gallium-doped carbon-coated nickel-based catalyst and a basic promoter, the relative rates between dehydrogenation, condensation, dehydration, and hydrogenation steps can be controlled by adjusting the mass ratio of methanol to n-butanol, reaction temperature, and time, thereby promoting the formation of 2-methyl-1-butanol.
The highly selective directional synthesis of 2-methyl-1-butanol was achieved, which simplified the process, reduced the complexity of subsequent separation, improved the stability of product composition, and featured a simple process that is easy to scale up and repeat.
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Figure CN122502248A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of alcohol catalytic conversion technology, specifically relating to a method for the directional cross-coupling of methanol and n-butanol to prepare 2-methyl-1-butanol (active pentanol). Background Technology
[0002] With the adjustment of the global energy structure and the continuous development of renewable carbon resource utilization technologies, the construction of high-value-added chemicals and fuel molecules based on biomass and carbon dioxide conversion products has become an important research direction in the energy and chemical industry. The continuous expansion of the fermentation ethanol industry not only provides large-scale renewable alcohol feedstocks, but also generates a certain proportion of by-product streams, among which fuse oil is one of the typical by-products in the fuel ethanol distillation process.
[0003] Fusel oil alcohols are typically multi-component mixtures, mainly containing 3-methyl-1-butanol (isoamyl alcohol), 2-methyl-1-butanol (active pentanol), isobutanol, water, and small amounts of other alcohols, esters, and aldehydes. These mixtures exhibit multi-component thermodynamic coupling and azeotropic behavior. Separating and purifying single pentanol isomers often requires complex fractionation processes and high energy consumption, leading to significant fluctuations in product costs and difficulty in achieving a stable supply. In particular, existing separation patents explicitly state that conventional distillation separation of 2-methyl-1-butanol and 3-methyl-1-butanol is difficult, requiring methods such as extractive distillation to increase relative volatility. Other disclosed processes specifically target fermented fusel oil alcohols through liquid-liquid extraction or coupled separation to recover pentanol components. This indicates that the existing route of "first obtaining mixed pentanols, then separating the target isomer" is not the simplest and most economical technical path. Therefore, directly constructing the 2-methyl-1-butanol molecular skeleton from structurally well-defined and stably sourced low-carbon alcohol feedstocks has significant technological appeal. Therefore, starting from a more controllable raw material system, directly preparing the target branched pentanol isomer through directed catalytic reaction has become an important technical approach to replace the separation and extraction route.
[0004] 2-Methyl-1-butanol is a C5 branched primary alcohol with significant applications. This compound can be used as an organic solvent, a chemical reaction medium, and in liquid-liquid extraction processes. As an oxygen-containing organic intermediate, 2-methyl-1-butanol can also be used as a raw material in organic synthesis. It can be further used in esterification and other conversion processes to prepare pentanol ester flavor compounds and other fine chemicals. Its good solubility and moderate boiling point make it suitable as a solvent in industries such as coatings, inks, and resins. More importantly, it is a useful synthetic raw material in reactions such as alkylation, oxidation, and esterification. For example, it can be used as a pharmaceutical intermediate to introduce specific pentyl groups; it is also a key precursor in the synthesis of certain fragrances (such as methyl 2-methylbutyrate, the capitol component of magnolia). Its chiral isomers (such as the S-type) are even more valuable in the synthesis of chiral fine chemicals and pharmaceuticals due to their optical activity. Existing literature also indicates that 2-methyl-1-butanol, as a pentanol isomer, is receiving continued attention due to its potential application as a component of biofuels or advanced fuels. Pentanol isomers are considered commercially attractive biofuel candidates. Compared to lower alcohols such as ethanol, higher alcohols typically have higher energy density, lower hygroscopicity, and are more compatible with gasoline in terms of fuel infrastructure, thus showing good prospects for fuel blending applications. Furthermore, it can serve as a precursor for the synthesis of chiral liquid crystal materials and as a natural equivalent flavoring agent for blending food flavorings with notes of banana, whiskey, and apple.
[0005] From a reaction pathway perspective, β-methylation or cross-coupling of alcohols typically involves hydrogen cycling steps such as "dehydrogenation to form a carbonyl intermediate—condensation to form a C–C bond—dehydration—hydrogenation reduction." Methanol can serve as a C1 unit source in the β-methylation process of substrate molecules. However, existing research has largely focused on ethanol self-condensation or methanol-ethanol cross-coupling systems, with relatively limited reports on the directed synthesis of 2-methyl-1-butanol from the cross-reaction of methanol and n-butanol. Achieving highly selective directed synthesis, especially in non-noble metal heterogeneous catalytic systems, remains a significant challenge.
[0006] Under heterogeneous catalytic conditions, published literature indicates that methanol as a C1 source for alcohol β-methylation is a known route. However, existing representative studies focus more on general alcohol β-methylation under homogeneous Ir and Mn catalytic systems, or on adjacent reactions such as isobutanol and isobutyraldehyde in methanol / ethanol systems. While homogeneous systems can achieve reactions under milder conditions, they also face challenges related to water tolerance, recycling, and industrial scale-up. Heterogeneous processes related to methanol / ethanol mainly revolve around isobutanol or other higher alcohols. Furthermore, regarding the methanol and n-butanol system of interest in this application, the goal is not general carbon enrichment, but rather the targeted generation of 2-methyl-1-butanol. In this system, methanol is prone to side reactions such as reforming and cracking, reducing the effective utilization of the C1 unit; n-butanol or its intermediate butyraldehyde may undergo self-condensation, excessive carbon enrichment, or other parallel reactions, leading to a more complex product profile.
[0007] Therefore, how to suppress side reactions and promote the target β-methylation pathway using methanol and n-butanol as raw materials without relying on complex separation routes, and by rationally controlling catalytic conditions such as reactant ratios, alkali dosage, reaction medium, temperature, and time, remains a technical problem to be solved in this field. Based on this background, it is necessary to develop a synthetic method capable of precisely controlling the reaction pathway in a methanol and n-butanol system to achieve highly selective and directional synthesis of 2-methyl-1-butanol, thereby providing a new technical solution for the high-value utilization of renewable platform alcohols. Summary of the Invention
[0008] The purpose of this invention is to provide a method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol, in order to solve the problems of long process, high energy consumption, unstable product composition, insufficient selectivity of target product and many side reactions in the process of direct coupling of methanol and n-butanol when relying on the extraction of fusel oil alcohol or subsequent complex separation to obtain 2-methyl-1-butanol.
[0009] The above-mentioned objective of the present invention is achieved through the following technical solution:
[0010] Therefore, the first technical solution provided by this invention is as follows:
[0011] A method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol, comprising the following steps in sequence:
[0012] S1. Add the metal-doped carbon-coated nickel-based catalyst, methanol, n-butanol, water and alkaline additive to the reaction vessel, mix them evenly to obtain a reaction mixture system;
[0013] S2. The reaction mixture obtained in step S1 is reacted at 160~200℃ for 18~24h under closed conditions. After the reaction is completed, the liquid phase product is separated to obtain a product containing 2-methyl-1-butanol.
[0014] The mass ratio of methanol, butanol, water, alkaline additive to gallium-doped carbon-coated nickel catalyst is 4:1:5:1.3:0.15-4.5:0.5:5:1.3:0.15.
[0015] Furthermore, in the above-mentioned method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol, the metal-doped carbon-coated nickel-based catalyst is a gallium-doped carbon-coated nickel-based catalyst.
[0016] Furthermore, in the above-described method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol, the alkaline auxiliary agent is an alkali metal hydroxide.
[0017] Furthermore, in the above-described method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol, the alkali metal hydroxide is potassium hydroxide.
[0018] Furthermore, in the above-described method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol, the gallium-doped carbon-coated nickel-based catalyst is prepared through the following steps:
[0019] 1) Dissolve 10.4 mmol nickel nitrate and 20.8 mmol citric acid in deionized water, then add 0.12 g anhydrous gallium chloride into the solution and stir until homogeneous. First, heat the solution on an 80 ℃ hot plate until it becomes gel-like, then transfer it to a 100 ℃ oven and dry for 24 h to obtain a completely dried precursor.
[0020] 2) The precursor obtained in step 1) is heated to 500 °C for 2 h in a nitrogen atmosphere at a heating rate of 5 °C / min, then cooled to room temperature naturally, and then O2 / Ar gas is introduced for 2 h to obtain a gallium-doped carbon-coated nickel-based catalyst.
[0021] This invention uses methanol and n-butanol as raw materials. Under the synergistic effect of a catalyst and an alkaline auxiliary agent, methanol is used as a C1 donor to participate in the directional β-methylation reaction of n-butanol, thereby obtaining a reaction system with 2-methyl-1-butanol as the target product.
[0022] This invention achieves the goal of increasing the production ratio and selectivity of 2-methyl-1-butanol by synergistically controlling the mass ratio of methanol to n-butanol, the reaction temperature, and the reaction time, thereby adjusting the relative rates between the series steps of dehydrogenation, condensation, dehydration, and hydrogenation.
[0023] Specifically, the ratio of methanol to n-butanol affects the effective concentration of C1 donors in the reaction system and the competition between cross-coupling and side reactions; the reaction temperature affects alcohol dehydrogenation activation, intermediate condensation conversion, and the extent of side reactions; and the reaction time further affects the degree of conversion of intermediates to the target product and the tendency for subsequent deep reactions. By controlling these parameters within an appropriate range, it is beneficial to promote the cross-coupling pathway of methanol and n-butanol and reduce the adverse effects of side reactions such as deep methanol decomposition, n-butanol self-condensation, and excessive carbonization on the selectivity of the target product.
[0024] Compared with the prior art, the present invention has the following beneficial effects:
[0025] This invention uses methanol and n-butanol as direct raw materials. By synergistically controlling the mass ratio of methanol to n-butanol, reaction temperature, and reaction time, it achieves targeted promotion of the 2-methyl-1-butanol formation pathway. Compared with routes that rely on fusel oil alcohols to separate and extract target isomers, this invention can directly construct the target molecular skeleton from a well-defined raw material system, which helps reduce the complexity of subsequent separation and improve the stability of product composition.
[0026] Meanwhile, this invention focuses on process parameter control, which can improve the selectivity of the target product by adjusting the reaction conditions under fixed catalytic system conditions. It features simple process, clear control, easy scale-up and reproducibility, and provides a feasible technical route for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol. Attached Figure Description
[0027] Figure 1 The image shows the X-ray powder diffraction (XRD) pattern of the gallium-doped carbon-coated nickel catalyst prepared in Example 1 of this invention.
[0028] Figure 2 This is a carbon number distribution diagram of the reaction solution after gas chromatography analysis and data processing following the completion of the reaction in Example 1 of the present invention.
[0029] Figure 3 This is a carbon number distribution diagram of the reaction solution after gas chromatography analysis and data processing following the reaction in Example 2 of the present invention.
[0030] Figure 4 This is a carbon number distribution diagram of the reaction solution after gas chromatography analysis and data processing, as shown in Example 3 of the present invention.
[0031] Figure 5 This is a carbon number distribution diagram of the reaction solution after gas chromatography analysis and data processing following the completion of the reaction in Example 4 of the present invention.
[0032] Figure 6 This is the original chromatogram obtained by gas chromatography analysis of the reaction solution after the reaction in Example 2 of the present invention.
[0033] Figure 7 This is the original chromatogram of the reaction solution obtained by gas chromatography after the reaction in Example 3 of the present invention.
[0034] Figure 8 This is the original chromatogram obtained by gas chromatography analysis of the reaction solution after the reaction in Example 4 of this invention. Detailed Implementation
[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.
[0036] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.
[0037] Example 1
[0038] This embodiment provides a method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol. Gallium-doped carbon-coated nickel-based catalyst, methanol, n-butanol, deionized water and potassium hydroxide are added to a reaction vessel in sequence, mixed evenly, and then the reaction vessel is sealed and reacted at 160°C for 18 hours.
[0039] After the reaction was completed, the product was naturally cooled to room temperature. The liquid product was collected, and after centrifugation or filtration to remove the solid catalyst, it was analyzed by gas chromatography to calculate the selectivity and carbon yield of 2-methyl-1-butanol.
[0040] The mass ratio of methanol, butanol, water, potassium hydroxide, and gallium-doped carbon-coated nickel catalyst is 4:1:5:1.3:0.15. Example 2
[0041] This embodiment provides a method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol, which differs from Example 1 in that the mass ratio of methanol, butanol, water, potassium hydroxide and gallium-doped carbon-coated nickel catalyst is 4.5:0.5:5:1.3:0.15.
[0042] Example 3
[0043] This embodiment provides a method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol. The difference between this embodiment and Example 2 is that the reaction temperature in this embodiment is 180°C, while the conditions and reagents for the remaining steps are the same as in Example 2.
[0044] Example 4
[0045] This embodiment provides a method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol. The difference between this embodiment and Example 2 is that the reaction temperature in this embodiment is 200°C, while the conditions and reagents for the remaining steps are the same as in Example 2.
[0046] Example 5
[0047] This embodiment provides a method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol. The difference between this embodiment and Example 1 is that the reaction time in this embodiment is 24 hours, while the conditions and reagents for the remaining steps are the same as in Example 1.
[0048] Comparative Example 1
[0049] The method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol provided in this comparative example differs from that in Example 1 in that the mass ratio of methanol, butanol, water, potassium hydroxide and gallium-doped carbon-coated nickel catalyst is 1.5:3.5:5:1.3:0.15.
[0050] Comparative Example 2
[0051] The method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol provided in this comparative example differs from that in Example 1 in that the mass ratio of methanol, butanol, water, potassium hydroxide and gallium-doped carbon-coated nickel catalyst is 3.5:1.5:5:1.3:0.15.
[0052] Comparative Example 3
[0053] The method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol provided in this comparative example differs from Example 1 in that: in step S2, the reaction time in this example is 6 hours, while the conditions and reagents for the remaining steps are the same as in Example 1.
[0054] Comparative Example 4
[0055] The method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol provided in this comparative example differs from Example 1 in that: in step S2, the reaction time in this example is 12 hours, while the conditions and reagents for the remaining steps are the same as in Example 1.
[0056] The gallium-doped carbon-coated nickel-based catalyst described in this application is prepared by the following steps:
[0057] 1) Dissolve 10.4 mmol nickel nitrate and 20.8 mmol citric acid in 50 ml deionized water, then add 0.12 g anhydrous gallium chloride, stir well, heat on an 80 ℃ hot plate until gel-like, then transfer to a 100 ℃ oven to dry for 24 h to obtain a completely dried precursor.
[0058] 2) The precursor obtained in step 1) is heated to 500 °C for 2 h in a nitrogen atmosphere at a heating rate of 5 °C / min, then cooled to room temperature naturally, and then O2 / Ar gas is introduced for 2 h to obtain a gallium-doped carbon-coated nickel-based catalyst.
[0059] X-ray powder diffraction test: The catalyst used in this application was subjected to X-ray powder diffraction (XRD) test. The results are as follows: Figure 1 As shown, the catalyst used has typical metallic Ni diffraction peaks, indicating that a corresponding nickel-based active phase has been formed in the catalyst.
[0060] After the reactions of Examples 1-5 and Comparative Examples 1-4 were completed, the liquid products were separated by centrifugation and analyzed by gas chromatography. The results are shown in Table 1.
[0061] Table 1
[0062] Example 1 20.9 54.3 16.1 87.7 Example 2 13.1 50.2 9.3 92.7 Example 3 21.0 77.5 14.1 96.1 Example 4 22.7 74.5 12.8 94.7 Example 5 21.6 57.7 17.6 89.8 Comparative Example 1 33.0 41.5 34.6 22.4 Comparative Example 2 25.3 55.9 22.2 73.5 Comparative Example 3 16.6 30.5 12.4 69.2 Comparative Example 4 21.9 50.8 16.6 82.4
[0063] Note: The carbon yield of alcohol products is the yield of liquid phase products;
[0064] The selectivity of 2-methyl-1-butanol is the percentage of 2-methyl-1-butanol in the total yield of all alcohol products.
[0065] C-mol% is expressed in moles of carbon.
[0066] As can be seen from Table 1, the mass ratio of methanol to n-butanol, the reaction temperature, and the reaction time have a significant impact on the formation of 2-methyl-1-butanol.
[0067] Under the conditions of reaction temperature of 160℃ and reaction time of 18h, as the mass ratio of methanol to n-butanol increased, the selectivity of 2-methyl-1-butanol increased from 22.4% to 73.5%, 87.7% and 92.7%, respectively. This indicates that increasing the proportion of methanol is beneficial to promoting methanol as a C1 donor to participate in the directional coupling reaction of n-butanol, thereby increasing the production ratio of 2-methyl-1-butanol.
[0068] It should be noted that the higher carbon yield of the liquid-phase alcohol products in Comparative Example 1 is mainly due to the formation of more non-target high-carbon byproducts, such as C8 isomeric alcohols. Therefore, although the total carbon yield of alcohol products is higher under these conditions, it is not conducive to the targeted formation of the target product, 2-methyl-1-butanol. In this invention, the selectivity of 2-methyl-1-butanol should be used as the primary evaluation criterion.
[0069] Under the conditions of a methanol to n-butanol mass ratio of 4.5:0.5 and a reaction time of 18 h, increasing the reaction temperature further improves the formation of 2-methyl-1-butanol. When the temperature is increased from 160℃ to 180℃, the selectivity of 2-methyl-1-butanol increases from 92.7% to 96.1%, the carbon yield of the liquid-phase alcohol product increases from 9.3% to 14.1%, and the butanol conversion rate increases significantly, indicating that appropriately increasing the reaction temperature is beneficial to the target reaction. When the reaction temperature is further increased to 200℃, the selectivity of 2-methyl-1-butanol decreases to 94.7%, and the carbon yield of the liquid-phase alcohol product decreases to 12.8%, indicating that excessively high temperatures may lead to an increase in side reactions, thus hindering the further selective formation of 2-methyl-1-butanol.
[0070] Under the conditions of a methanol to n-butanol mass ratio of 4:1 and a reaction temperature of 160℃, the reaction time also affects the formation of 2-methyl-1-butanol. When the reaction time was extended from 6 h to 12 h, 18 h, and 24 h, the selectivity of 2-methyl-1-butanol was 69.2%, 82.4%, 87.7%, and 89.8%, respectively, and the carbon yields of the liquid-phase alcohol products were 12.4%, 16.6%, 16.1%, and 17.6%, respectively. The results indicate that within the time range investigated in this application, extending the reaction time is beneficial to improving the selectivity of 2-methyl-1-butanol.
[0071] In summary, this invention effectively improves the selectivity of 2-methyl-1-butanol by controlling the mass ratio of methanol to n-butanol, the reaction temperature, and the reaction time. Specifically, under the conditions investigated in this application, the highest selectivity of 2-methyl-1-butanol, reaching 96.1%, was achieved when the mass ratio of methanol to n-butanol was 4.5:0.5, the reaction temperature was 180°C, and the reaction time was 18 h. Furthermore, extending the reaction time to 24 h at a methanol to n-butanol mass ratio of 4:1 and a reaction temperature of 160°C further enhances the formation of 2-methyl-1-butanol.
[0072] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
Claims
1. A method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol, characterized in that, The steps are as follows: S1. Add the metal-doped carbon-coated nickel-based catalyst, methanol, n-butanol, water and alkaline additive to the reaction vessel, mix them evenly to obtain a reaction mixture system; S2. The reaction mixture obtained in step S1 is reacted under closed conditions at 160~200℃ for 6~24h. After the reaction is completed, the liquid phase product is separated to obtain a product containing 2-methyl-1-butanol. The mass ratio of methanol, butanol, water, alkaline additive to gallium-doped carbon-coated nickel catalyst is 4:1:5:1.3:0.15-4.5:0.5:5:1.3:0.
15.
2. The method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol according to claim 1, characterized in that, The metal-doped carbon-coated nickel-based catalyst is a gallium-doped carbon-coated nickel-based catalyst.
3. The method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol according to claim 1, characterized in that, The alkaline additive is an alkali metal hydroxide.
4. The method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol according to claim 1, characterized in that, The alkali metal hydroxide mentioned is potassium hydroxide.
5. The method for the directional preparation of 2-methyl-1-butanol from methanol and n-butanol according to claim 1, characterized in that, The gallium-doped carbon-coated nickel-based catalyst is prepared by the following steps: 1) Dissolve 10.4 mmol nickel nitrate and 20.8 mmol citric acid in deionized water, then add 0.12 g anhydrous gallium chloride into the solution and stir until homogeneous. First, heat the solution on an 80 ℃ hot plate until it becomes gel-like, then transfer it to a 100 ℃ oven and dry for 24 h to obtain a completely dried precursor. 2) The precursor obtained in step 1) is heated to 500 °C for 2 hours under nitrogen atmosphere at a heating rate of 5 °C / min, then cooled to room temperature naturally, and then O2 / Ar gas is introduced for 2 hours to obtain gallium-doped carbon-coated nickel-based catalyst.