Method for preparing high-carbon alcohol through low-temperature water-phase coupling of ethanol and catalyst thereof
By using dual -carbon -source HCP phase NI base nano -catalysts, the HCP phase of metal nickel is induced to optimize the electronic configuration and control environment of the catalyst, solve the problem of being difficult to catalyze biomass fermentation ethanol under low temperature water phase. Catalytic upgrades below ℃ and effective preparation of high carbon alcohol.
Patent Information
- Application Number
- CN202411454995.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-17
- Publication Date
- 2025-01-24
AI Technical Summary
The prior art is difficult to effectively catalyze the aqueous solution of biomass fermentation of ethanol under low temperature aqueous phase, prepare high-carbon alcohols, and the reaction conditions are harsh.
Dual carbon source HCP phase Ni-based nanocatalyst is used to induce the HCP phase of metallic nickel through polyethyleneimine and polyvinylpyrrolidone, optimizing the electronic configuration and coordination environment of the catalyst to achieve catalytic upgrade below 100°C.
The catalytic upgrade of biomass fermentation ethanol aqueous solution is achieved below 100 ° C, reducing the generation of by -products and increasing the yield of C4+alcohol.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of catalysts, and in particular relates to a dual-carbon source HCP phase Ni-based nanocatalyst. The invention also relates to a preparation method and application of the dual-carbon source HCP phase Ni-based nanocatalyst. Background Art
[0002] Biomass fermentation ethanol can be used as a sustainable biofuel and a raw material for the future chemical industry. Currently, an increasing amount is produced from renewable biomass resources. However, the crude bioethanol obtained after fermentation is mainly a dilute aqueous solution. The polar nature of ethanol makes it difficult to separate from water, so the subsequent purification is a very expensive process. As with the production of first-generation fuel ethanol, usually more than half of the energy is consumed in the distillation and dehydration steps. Therefore, it is of great significance to directly upgrade the aqueous solution of biomass fermentation ethanol under mild conditions. The alcohol condensation reaction, also known as the Guerbet reaction, is an important method for producing higher alcohols. High-carbon alcohols have great application potential in plasticizers, surfactants, clean mixed fuels, etc. The condensation of bio-fermentation ethanol with a small number of carbon atoms has attracted widespread attention from industry and academia, and it can be used to make improved higher alcohol biofuels or other useful chemicals from renewable resources.
[0003] On the other hand, the use of water as a reaction medium has attracted great attention due to its many advantages from economic, environmental and safety perspectives. Various effective catalytic systems in water have been developed, but performing dehydration reactions in water remains one of the most challenging research topics. Alcohol condensations, including butanol and ethanol, are usually carried out in organic solvents, pure alcohols or dilute gas phases. Adding water to the reaction mixture is usually harmful to the catalyst. For example, Carlini and colleagues reported the application of [Pd(dppe)Cl2] or Pd / C in combination with BuONa to catalyze the self-condensation of butanol in a pure butanol phase at 180-280°C. The product 2-ethylhexanol has a yield of about 60% and good selectivity. However, the gradual hydrolysis of BuONa to inactive NaOH destroys the catalytic system. The reaction is usually carried out in a dry alcohol mixture. Summary of the invention
[0004] In order to overcome the problem of harsh reaction conditions in the preparation of high-carbon alcohols by low-temperature aqueous phase coupling of ethanol in the above-mentioned prior art, the present invention proposes a pure HCP phase dual-carbon source catalyst, which induces the HCP phase of metallic nickel through the amino group of polyethyleneimine, optimizes the electronic configuration and coordination environment of the metal surface, and realizes catalytic upgrading of biomass fermentation ethanol aqueous solution below 100°C.
[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is:
[0006] A method for preparing higher carbon alcohols by low-temperature aqueous phase coupling of ethanol, comprising the following steps in sequence: placing an ethanol solution, a Ni@PEI-PVP dual carbon source catalyst and an alkali solution in a mass ratio of 2-4:0.2-0.6:0.4-0.6 in a high-pressure reactor, reacting for 12-84 hours at 50-100° C. and an initial pressure of 0 MPa, cooling the reactor to room temperature after the reaction, centrifuging and filtering to obtain a liquid phase and a catalyst solid phase, and collecting gas phase and liquid phase products.
[0007] Furthermore, in the above-mentioned method for preparing high-carbon alcohols by low-temperature aqueous phase coupling of ethanol, the Ni@PEI-PVP dual carbon source catalyst uses layered nanocarbon as a carrier, and the active component embedded in the surface of the carbon layer is Ni in the HCP crystal phase; the active metal Ni loading amount is 10% to 50%, and the average particle size of the active component Ni is 10 to 50 nm.
[0008] Furthermore, in the above-mentioned method for preparing higher carbon alcohols by low temperature aqueous phase coupling of ethanol, the Ni@PEI-PVP dual carbon source catalyst is prepared by the following method:
[0009] S1: adding Ni metal salt, polyethyleneimine and polyvinyl pyrrolidone into an ethanol aqueous solution to completely dissolve them, and then drying the solution to obtain a Ni nanocatalyst precursor;
[0010] S2: The Ni nanocatalyst precursor obtained in S1 is calcined in an inert gas at 100-500°C for 15-120 min to obtain a HCP phase Ni@PEI-PVP dual carbon source catalyst;
[0011] The molar ratio of the Ni metal salt, polyethyleneimine and polyvinyl pyrrolidone is 1:(0.1-10);(0.1-10)
[0012] Furthermore, in the above-mentioned method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol, the Ni metal salt is one of nickel acetylacetonate, nickel chloride, nickel acetate, and nickel nitrate.
[0013] Furthermore, in the above-mentioned method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol, the weight average molecular weight of the polyethyleneimine is 300-10,000; and the weight average molecular weight of the polyvinyl pyrrolidone is 8,000-580,000.
[0014] Furthermore, in the above-mentioned method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol, the mass fraction of the ethanol aqueous solution is 10-99%.
[0015] Furthermore, in the above-mentioned method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol, the molar ratio of the Ni metal salt, polyethyleneimine and polyvinyl pyrrolidone is 1:2:2.
[0016] In the present invention, polyethyleneimine and polyvinyl pyrrolidone contain polar group amino groups, which induce the thermodynamically metastable HCP crystal phase of Ni. At the same time, polyvinyl pyrrolidone can be used as a metal carbon carrier after in-situ carbonization, so that the active HCP phase metal Ni is embedded in the carbon layer, which effectively protects the metal active center, so that the catalyst can reduce the reaction barrier and the generation of by-products under mild conditions, thereby realizing the catalytic upgrading of low-temperature biomass fermentation ethanol aqueous solution.
[0017] In the present invention, the average molecular weight of polyethyleneimine and polyvinylpyrrolidone, the ethanol concentration of the solvent, the molar ratio of Ni to C, the carbonization temperature, and the carbonization time have an impact on the metal particle size, metal content, and metal nickel crystal phase, and thus have an important impact on the catalytic performance of the catalyst. When the average molecular weight of polyethyleneimine is 300-10000, the average molecular weight of polyvinylpyrrolidone is 8000-580000, the ethanol concentration of the solvent is (10-99%), the molar ratio of Ni to the carbon source is 1: (1:10), and the carbonization temperature is 100-500°C, the prepared catalyst can reduce the generation of by-products at 100°C and improve the yield of C4+ alcohols.
[0018] During the preparation of the catalyst, when the molecular weight of PEI is less than 600, a large amount of metal nickel will aggregate, the metal particles will increase significantly, and the catalytic performance will be poor; when the molecular weight of PEI is greater than 1000, due to the flexibility of the polymer molecular chain, the precursor cannot form a solid during drying and preparation, and during subsequent calcination, the carbonization is not thorough enough, resulting in more active sites being covered, leading to a decrease in catalytic activity.
[0019] When the relative molecular weight of PVP is less than 10,000, the PVP molecular chain is too short, the carbon source nanolayer as a carrier has too many pores, the active metal Ni is prone to agglomeration, and the catalytic performance is reduced. However, when the molecular weight of PVP exceeds 130,000, a dense carbon carrier is formed after calcination, the nickel metal is wrapped inside the carbon carrier, the effective active sites become fewer, and ultimately the catalytic activity is reduced.
[0020] Furthermore, in the above-mentioned method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol, the drying temperature described in S1 is 50-150°C.
[0021] Furthermore, in the above-mentioned method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol, the carbonization described in S2 is carried out in an inert atmosphere at a temperature of 100-500°C.
[0022] When the calcination temperature is too low, the temperature at which nickel ions are reduced to nickel element cannot be met; when the calcination temperature is too high, the crystalline phase of metallic nickel will be completely transformed from the HCP phase to the FCC phase.
[0023] Furthermore, in the above-mentioned method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol, the inert atmosphere is one or more of nitrogen, helium and argon.
[0024] In the process of preparing the catalyst of the present invention, when the molar ratio of Ni metal salt, polyethyleneimine and polyvinyl pyrrolidone is greater than 1:10:10, the content of active nickel is low, and after calcination, the catalyst active sites are too few, and the catalytic activity is reduced; however, when the molar ratio of nickel salt to polyethyleneimine and polyvinyl pyrrolidone is less than 1:0.1:0.1, during the calcination process, the crystal phase of metal Ni is converted from an HCP phase to an FCC phase, and a large amount of metal nickel is aggregated, resulting in an increase in the particle size of the active metal, which is not conducive to the ethanol coupling reaction, the catalytic activity is reduced, and the yield of higher alcohols is low.
[0025] The temperature of the dual-carbon source HCP phase Ni-based nanocatalyst for preparing high-carbon alcohols by low-temperature coupling of biomass fermentation ethanol is 50-100°C.
[0026] The beneficial effects of the present invention are:
[0027] In the dual carbon source catalyst provided by the present invention, PEI can be used as an inducer to induce HCP phase, change the surface state of nickel metal, and reduce the reaction barrier under mild conditions. After high-temperature carbonization, PVP can form layered nanocarbon with a large specific surface area as a carrier of metal active sites. The particle size of the metal active component is 10-50nm. By changing the crystal phase of the active metal in the catalyst, the electronic configuration and coordination environment of the metal surface are optimized, and the catalytic upgrading of biomass fermentation ethanol aqueous solution is achieved below 100°C. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 The XRD diagrams of the nanocatalysts prepared in Examples 1 and 2 and Comparative Example 7 of the present invention are shown.
[0029] Figure 2 These are the XRD diagrams of the nanocatalysts prepared in Examples 1, 7, and 8 of the present invention.
[0030] Figure 3 XRD diagrams of nanocatalysts prepared in Example 1, Comparative Examples 1, 2, 8 and Example 9 of the present invention.
[0031] Figure 4 This is a transmission electron microscope image of the nanocatalyst prepared in Example 6 of the present invention.
[0032] Figure 5 This is a transmission electron microscope image of the nanocatalyst prepared in Example 1 of the present invention.
[0033] Figure 6 This is a transmission electron microscope image of the nanocatalyst prepared in Comparative Example 6 of the present invention. DETAILED DESCRIPTION
[0034] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0035] The raw materials used in the following examples are all commercially available or homemade.
[0036] Example 1
[0037] This embodiment provides a dual carbon source HCP phase Ni-based nanocatalyst, and its preparation method comprises the following steps:
[0038] S1: 2.5 g of nickel acetylacetonate, 0.83 g of polyethyleneimine (molecular weight: 600) and 2.16 g of polyvinyl pyrrolidone (molecular weight: 26000) were added to 200 ml of 50% by mass ethanol aqueous solution and completely dissolved. The solution obtained in S1 was dried at 80° C. for 24 hours to obtain a Ni nanocatalyst precursor;
[0039] S2: The Ni nanocatalyst precursor obtained in S1 was calcined at 400°C in an inert gas for 15 min to obtain a HCP phase Ni@PEI-PVP dual carbon source catalyst.
[0040] Example 2
[0041] This embodiment provides a dual-carbon source HCP phase Ni-based nanocatalyst, and its preparation method is different from that of Example 1 in that the nickel acetylacetonate in step S1 is replaced by nickel acetate.
[0042] Example 3
[0043] This embodiment provides a dual-carbon source HCP phase Ni-based nanocatalyst, and its preparation method is different from that of Example 1 in that the molecular weight of polyethyleneimine in step S1 is 300.
[0044] Example 4
[0045] This embodiment provides a dual-carbon source HCP phase Ni-based nanocatalyst, and its preparation method is different from that of Example 1 in that the molecular weight of polyvinyl pyrrolidone in step S1 is 140,000.
[0046] Example 5
[0047] The present embodiment provides a dual carbon source HCP phase Ni-based nanocatalyst, and the preparation method thereof is different from that of the embodiment 1 in that the molecular weight of the polyvinyl pyrrolidone in step S1 is 58000.
[0048] Example 6
[0049] The present embodiment provides a dual-carbon source HCP phase Ni-based nanocatalyst, and its preparation method is different from that of Example 1 in that the molar ratio of the nickel source, polyethyleneimine, and polyvinyl pyrrolidone in step S1 is replaced with 1:5:5.
[0050] Example 7
[0051] The present embodiment provides a dual-carbon source HCP phase Ni-based nanocatalyst, and its preparation method is different from that of Example 1 in that the molar ratio of the two carbon sources in step S1 is replaced with 3:7.
[0052] Example 8
[0053] This embodiment provides a dual-carbon source HCP phase Ni-based nanocatalyst, and its preparation method is different from that of Example 1 in that the molar ratio of the two carbon sources in step S1 is replaced with 7:3.
[0054] Example 9
[0055] This embodiment provides a dual-carbon source HCP phase Ni-based nanocatalyst, and its preparation method is different from that of Example 1 in that the calcination temperature in step S2 is replaced with 300°C.
[0056] Comparative Example 1
[0057] This embodiment provides a dual-carbon source HCP phase Ni-based nanocatalyst, and its preparation method is different from that of Example 1 in that the calcination temperature in step S2 is replaced with 100°C.
[0058] Comparative Example 2
[0059] This embodiment provides a dual-carbon source HCP phase Ni-based nanocatalyst, and its preparation method is different from that of Example 1 in that the calcination temperature in step S2 is replaced with 200°C.
[0060] Comparative Example 3
[0061] This embodiment provides a dual-carbon source HCP phase Ni-based nanocatalyst, and its preparation method is different from that of Example 1 in that the molecular weight of polyethyleneimine in step S1 is 10,000.
[0062] Comparative Example 4
[0063] The present embodiment provides a dual-carbon source HCP phase Ni-based nanocatalyst, and its preparation method is different from that of the embodiment 1 in that the molecular weight of the polyvinyl pyrrolidone in step S1 is 8000.
[0064] Comparative Example 5
[0065] The present embodiment provides a dual-carbon source HCP phase Ni-based nanocatalyst, and its preparation method is different from that of Example 1 in that the ethanol aqueous solution in step S1 is replaced by pure water.
[0066] Comparative Example 6
[0067] The present embodiment provides a dual-carbon source FCC phase Ni-based nanocatalyst, and the preparation method thereof is different from that of the embodiment 1 in that the molar ratio of the nickel source, polyethyleneimine, and polyvinyl pyrrolidone in step S1 is replaced with 1:1:1
[0068] Comparative Example 7
[0069] This embodiment provides a dual-carbon source FCC phase Ni-based nanocatalyst, and its preparation method is different from that of Example 1 in that the nickel acetylacetonate in step S1 is replaced by nickel chloride.
[0070] Comparative Example 8
[0071] This embodiment provides a dual-carbon source FCC phase Ni-based nanocatalyst, and its preparation method is different from that of Example 1 in that the calcination temperature in step S2 is replaced with 500°C.
[0072] The specific parameters for preparing dual carbon source HCP phase Ni-based nanocatalysts in Examples 1 to 9 and Comparative Examples 1 to 8 are shown in Table 1
[0073] metal crystal phase Loading amount (mol%) Ni particle size (nm) Example 1 HCP 22.14 15.13 Example 2 HCP 20.12 48.11 Example 3 HCP 24.81 36.48 Example 4 HCP 18.12 14.56 Example 5 HCP 23.67 16.12 Example 6 HCP 10.31 16.96 Example 7 HCP 20.14 18.23 Example 8 HCP 23.56 20.27 Example 9 HCP 21.29 18.23 Comparative Example 1 HCP 23.12 15.36 Comparative Example 2 HCP 25 16.22 Comparative Example 3 HCP 15.12 16.44 Comparative Example 4 HCP 20.37 40.29 Comparative Example 5 HCP 8.31 32.11 Comparative Example 6 FCC 20.12 25.33 Comparative Example 7 FCC 21.33 32.12 Comparative Example 8 FCC 23.17 13.42
[0074] Table 1 Specific parameters of dual carbon source HCP phase Ni-based nanocatalysts in Examples 1 to 9 and Comparative Examples 1 to 8
[0075] Performance Testing
[0076] (1) XRD detection
[0077] Figure 1 XRD patterns of nanocatalysts obtained for Examples 1 and 2 of the present invention and Comparative Example 7. Through the XRD patterns, we can see that the crystalline phase and grain size of the nickel element finally obtained are different for different Ni metal salts. HCP phase nickel is obtained using nickel acetate as the Ni metal salt, but the crystallinity is excellent, resulting in nickel aggregation, nickel particles of about 50nm, and poor catalytic performance. FCC phase nickel is obtained using nickel chloride as the Ni metal salt, and due to the presence of chlorine, some chloride salts that are not conducive to the catalytic reaction are eventually produced. Only the catalyst prepared using nickel acetylacetonate as the Ni metal salt has a complete HCP phase nickel, and the nickel particles are about 15nm, with good catalytic performance.
[0078] Figure 2The XRD patterns of the nanocatalysts prepared in Examples 1, 7, and 8 of the present invention are shown. Through the XRD patterns, we can see that as the ratios of the two carbon sources are different, the nickel metal is in the HCP phase, but the particle size of the nickel changes significantly. As the PVP content increases, the nickel metal particles show an increasing trend. Only when the ratios of the two carbon sources are coordinated, PEI regulates the nickel crystal phase, and PVP provides nickel metal attachment sites, can they play a key role in the catalytic reaction.
[0079] Figure 3 The XRD diagrams of the nanocatalysts prepared in Comparative Examples 1, 2, 8 and Example 9 of the present invention are shown. Through the XRD diagrams, we can see that as the carbonization temperature changes, the peak position gradually shifts to the right until the temperature rises to 500°C, and the crystalline phase of nickel is completely converted from the HCP phase to the FCC phase. When the carbonization temperature is too low, nickel cannot be reduced in situ, so that the ethanol conversion rate is too low in the subsequent catalytic reaction. At the same time, when it is completely converted into the FCC phase, the active sites that are conducive to low-temperature reaction are covered, and its ethanol conversion rate is also not good.
[0080] (2) Catalytic morphology
[0081] Transmission electron microscope images of Example 1, Comparative Example 6, and Example 6 of the present invention. Figure 5 We can see that the metal nanoparticles are very small, about 15nm, and the layered nanocarbon thickness of the catalysts prepared in the other embodiments is appropriate, which can well protect the nanometal and is not prone to metal loss and agglomeration. Figure 4 We can see that if the layered nanocarbon is too thick, it will easily wrap the metal, cover part of the active sites, and reduce the catalytic activity of the catalyst. Figure 6 We can see that if the carbon source content is too low, it may cause the nano-metal to agglomerate and the metal particles to be too large, resulting in reduced structural stability of the catalyst and easy metal loss.
[0082] Example 10
[0083] The present embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. 0.4 g of the dual-carbon source HCP phase Ni-based nanocatalyst prepared in Example 1, 3 g of water, 3 g of ethanol, and 0.52 g of sodium hydroxide are added into a 25 ml steel magnetic stirring reactor. The reaction temperature is 100° C., the initial pressure is 0 MPa, and the reaction time is 72 h. After the reaction, the reactor is cooled to room temperature, centrifuged and filtered to obtain a liquid phase and a catalyst solid phase. The gas phase and liquid phase products are collected and detected and analyzed by gas chromatography respectively. The main product of the organic phase is C4+ high carbon alcohol. The results are shown in Table 2 below.
[0084] Embodiment 11
[0085] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Example 2 is used. The experimental results are shown in Table 2 below.
[0086] Example 12
[0087] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Example 3 is used. The experimental results are shown in Table 2 below.
[0088] Example 13
[0089] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Example 4 is used. The experimental results are shown in Table 2 below.
[0090] Embodiment 14
[0091] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Example 5 is used. The experimental results are shown in Table 2 below.
[0092] Embodiment 15
[0093] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Example 6 is used. The experimental results are shown in Table 2 below.
[0094] Example 16
[0095] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Example 7 is used. The experimental results are shown in Table 2 below.
[0096] Embodiment 17
[0097] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Example 8 is used. The experimental results are shown in Table 2 below.
[0098] Embodiment 18
[0099] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Example 9 is used. The experimental results are shown in Table 2 below.
[0100] Embodiment 19
[0101] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those in Example 12, except that the reaction temperature is 50°C. The experimental results are shown in Table 2 below.
[0102] Embodiment 20
[0103] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those in Example 12. The reaction temperature is 80° C. The experimental results are shown in Table 2 below.
[0104] Embodiment 21
[0105] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those in Example 12, except that the reaction time is 24 hours. The experimental results are shown in Table 2 below.
[0106] Embodiment 22
[0107] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those in Example 12, except that the reaction time is 48 hours. The experimental results are shown in Table 2 below.
[0108] Embodiment 23
[0109] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those in Example 12, except that the amount of catalyst used is 0.3 g. The experimental results are shown in Table 2 below.
[0110] Embodiment 24
[0111] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those in Example 12, except that the amount of catalyst used is 0.5 g. The experimental results are shown in Table 2 below.
[0112] Comparative Example 9
[0113] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Comparative Example 1 is used. The experimental results are shown in Table 2 below.
[0114] Comparative Example 10
[0115] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Comparative Example 2 is used. The experimental results are shown in Table 2 below.
[0116] Comparative Example 11
[0117] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Comparative Example 3 is used. The experimental results are shown in Table 2 below.
[0118] Comparative Example 12
[0119] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Comparative Example 4 is used. The experimental results are shown in Table 2 below.
[0120] Comparative Example 13
[0121] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Comparative Example 5 is used. The experimental results are shown in Table 2 below.
[0122] Comparative Example 14
[0123] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Comparative Example 6 is used. The experimental results are shown in Table 2 below.
[0124] Comparative Example 15
[0125] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Comparative Example 7 is used. The experimental results are shown in Table 2 below.
[0126] Comparative Example 16
[0127] This embodiment provides a method for preparing higher carbon alcohols by low-temperature water phase coupling of ethanol. The preparation process and its parameters are the same as those of Example 12, except that the catalyst provided in Comparative Example 8 is used. The experimental results are shown in Table 2 below.
[0128] Table 2 Catalytic activity results of the products obtained from Examples 10 to 24 and Comparative Examples 9 to 16
[0129]
[0130] Comparing the data in Table 2, it can be seen that when Example 1 is compared with Comparative Examples 1 and 2, under the premise that other conditions remain unchanged, the calcination temperatures are 100°C and 200°C respectively, and the obtained catalyst is applied to the reaction of catalyzing biological fermentation ethanol to synthesize C4+ alcohols, and the ethanol conversion rates are 1.2% and 1.8% respectively, which is low. This is because when the calcination temperature is too low, the active metal nickel is not reduced enough, and there is not enough active metal to start the catalytic reaction.
[0131] Compared with Example 1 and Comparative Example 3, under the premise that other conditions remain unchanged, Comparative Example 3 changes the molecular weight of polyethyleneimine. When the molecular weight of polyethyleneimine is too high, due to the flexibility of the polymer chain, the catalyst precursor cannot be dried, and the subsequent carbonization at 400°C is not thorough enough, resulting in more active sites being covered and the catalyst surface groups being destroyed, resulting in poor catalytic effect.
[0132] Compared with Example 4, Example 1 changes the molecular weight of polyvinyl pyrrolidone in Example 4 under the premise that other conditions remain unchanged. When the molecular weight of polyvinyl pyrrolidone is too low, the carbon source nanolayer used as a carrier has too many pores and the metal particles are too large, which affects the stability of the catalyst structure, the active metal cannot be evenly dispersed, and the catalytic performance is reduced.
[0133] Compared with Comparative Examples 5 and 6, in Example 1, under the premise that other conditions remain unchanged, pure water is used as the solvent in Comparative Example 5. Since nickel acetylacetonate is slightly soluble in water, the nickel content in the catalyst is too low, and the catalytic performance is reduced; in Comparative Example 6, the ratio of the nickel source and the carbon source is changed. As the ratio of the carbon source decreases, the metal particles increase slightly, and the nickel crystal phase is completely transformed from the HCP phase to the FCC phase, and the catalytic performance is reduced.
[0134] Comparing the data in Table 2, it can be seen that the catalyst in Example 1 was used to discuss the catalyst dosage, reaction temperature, and reaction time in the low-temperature water phase coupling of ethanol to prepare higher carbon alcohols. The results show that too little catalyst leads to insufficient reaction active sites, the reaction temperature is too low, resulting in insufficient startup energy, and the reaction time is short, resulting in the reaction not being completely completed, and the catalytic performance is not ideal.
[0135] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.
Claims
1. A method for preparing higher alcohols by low-temperature aqueous phase coupling of ethanol, characterized in that: The method comprises the following steps in sequence: placing an ethanol solution, a Ni@PEI-PVP dual carbon source catalyst and an alkali solution in a mass ratio of 2-4:0.2-0.6:0.4-0.6 in a high-pressure reactor, reacting for 12-84 hours at 50-100° C. and an initial pressure of 0 MPa, cooling the reactor to room temperature after the reaction, centrifuging and filtering to obtain a liquid phase and a catalyst solid phase, and collecting gas phase and liquid phase products.
2. The method for preparing higher alcohols by low temperature aqueous phase coupling of ethanol according to claim 1, characterized in that: The ethanol solution consists of ethanol and water in a mass ratio.
3. The method for preparing higher alcohols by low temperature aqueous phase coupling of ethanol according to claim 1, characterized in that: The Ni@PEI-PVP dual carbon source catalyst is prepared by the following method: S1: adding Ni metal salt, polyethyleneimine and polyvinyl pyrrolidone into an ethanol aqueous solution to completely dissolve them, and then drying the solution to obtain a Ni nanocatalyst precursor; S2: The Ni nanocatalyst precursor obtained in S1 is calcined in an inert gas at 100-500°C for 15-120 min to obtain a HCP phase Ni@PEI-PVP dual carbon source catalyst; The molar ratio of the Ni metal salt, polyethyleneimine and polyvinyl pyrrolidone is 1:(0.1-10);(0.1-10).
4. The method for preparing higher alcohols by low temperature aqueous phase coupling of ethanol according to claim 3, characterized in that: The Ni metal salt is one of nickel acetylacetonate, nickel chloride, nickel acetate and nickel nitrate.
5. The method for preparing higher alcohols by low temperature water phase coupling of ethanol according to claim 3, characterized in that: The weight average molecular weight of the polyethyleneimine is 200-20000; the weight average molecular weight of the polyvinyl pyrrolidone is 6000-580000.
6. The method for preparing higher alcohols by low temperature aqueous phase coupling of ethanol according to claim 3, characterized in that: The mass fraction of the ethanol aqueous solution is 10-100%.
7. The method for preparing higher alcohols by low temperature aqueous phase coupling of ethanol according to claim 3, characterized in that: The molar ratio of the Ni metal salt, polyethyleneimine and polyvinyl pyrrolidone is 1:2:
2.
8. The method for preparing higher alcohols by low temperature aqueous phase coupling of ethanol according to claim 3, characterized in that: The drying temperature described in S1 is 50-150°C.
9. The method for preparing higher alcohols by low temperature aqueous phase coupling of ethanol according to claim 3, characterized in that: The carbonization in S2 is carried out in an inert atmosphere at a temperature of 50-600° C.; the inert atmosphere is one or more of nitrogen, helium and argon.
10. A Ni@PEI-PVP dual carbon source catalyst, characterized in that: The Ni@PEI-PVP dual carbon source catalyst uses layered nanocarbon as a carrier, and the active component embedded on the surface of the carbon layer is Ni in the HCP crystal phase; the active metal Ni loading amount is 10% to 50%, and the average particle size of the active component Ni is 10 to 50 nm.