Preparation and application of supported bimetallic catalyst for palmitic acid hydrodeoxygenation-aromatization
By preparing bimetallic catalysts supported by ZSM-5 molecular sieve with Ni, Zn, Cu and Ga, the problems of low palmitic acid conversion and limited precious metal resources are solved, efficient hydrodeoxygenation and aromatization are achieved, and high-value chemicals are produced.
Patent Information
- Application Number
- CN202510406997.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-02
- Publication Date
- 2025-07-01
AI Technical Summary
In the process of hydrodeoxygenation and aromatization of palmitic acid, existing catalysts have problems such as low conversion, large catalyst usage, high oxygen content and low calorific value, and precious metal catalysts have high prices and few resources, which limit their industrial applications.
A supported bimetallic catalyst with ZSM-5 molecular sieve as the support, Ni as the main metal, and Zn, Cu and Ga as the secondary metals was prepared by equal volume impregnation method to realize the integrated reaction of hydrodeoxygenation and aromatization of palmitic acid. The catalyst was reduced to zero valence under the atmosphere of H2, and combined with the Lewis acid and Browns acid of the molecular sieve to undergo cracking and cyclization reactions.
Complete hydrodeoxygenation and high selectivity conversion of palmitic acid into benzene compounds are achieved. The catalyst has high catalytic activity and economic value, and is suitable for the conversion of palmitic acid into high-value chemicals in one step.
Smart Images
Figure FT_1 
Figure SMS_1 
Figure SMS_2
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of energy chemistry, and particularly relates to a supported bimetallic catalyst for integrated hydrogenation deoxygenation - aromatization of palmitic acid, its preparation, and its application in the one-step conversion of palmitic acid into benzene compounds. Background Art
[0002] Compared with non-renewable energy sources such as coal, petroleum, and natural gas, biomass energy is a renewable energy source with good development prospects. Different from energy sources such as solar energy, wind energy, and nuclear energy, biomass energy can be stored as liquid fuel. Among them, palmitic acid is a saturated higher fatty acid, which generally exists in animal and vegetable oils in the form of glycerides, is widely distributed in nature, and has been used as a potential raw material for deoxygenation of biomass materials and production of biodiesel and jet fuel. However, due to problems such as low conversion rate, large catalyst dosage, high oxygen content, and low calorific value of the produced bio-oil, it is difficult to be directly used. Aromatic compounds are important chemical products and important raw materials for preparing resins, etc. There are mainly three technologies for preparing aromatics from biomass: one is that biomass is first gasified into syngas (a mixture of carbon monoxide and hydrogen), and then converted through methanol-to-aromatics or Fischer-Tropsch synthesis technology; the second is direct conversion into aromatic products through catalytic pyrolysis; the third is to comprehensively use methods such as hydrolysis, fermentation, and catalysis to make biomass gradually generate aromatics through a series of intermediate reactions. Among them, the one-step conversion of biomass into benzene compounds through catalytic pyrolysis is one of the most promising thermochemical technologies for energy enrichment and solving the energy crisis, and an effective catalyst is the core of its catalytic conversion. Therefore, the development of a composite catalyst capable of simultaneously having hydrogenation deoxygenation and aromatization is crucial for the catalytic pyrolysis of biomass.
[0003] Common noble metal catalysts such as Pd, Pt, Ru, etc. have been widely studied in the catalytic conversion of palmitic acid hydrogenation deoxygenation. Their d electron orbitals are in an unfilled state, which is easy to adsorb H and O atoms and has good hydrogenation deoxygenation activity. However, due to high price and scarce resources, their large-scale application in industrial production is limited. Relatively speaking, Ni-based materials have basically the same catalytic activity as noble metal catalysts during the catalytic conversion process and are inexpensive. At the same time, in addition to the selection of metal active components, different supports may also form different products. Jae et al. synthesized a series of different types of molecular sieve catalysts to study the influence of different pore structures on the yield of aromatics. The results showed that catalysts with small pore structures could not produce any aromatics; the yield of aromatics from macroporous molecular sieves was also low, and the carbon deposition content on the catalysts was high; only catalysts with an average pore diameter in the range of 5.2 - 5.9 Å produced higher yields of aromatic compounds. Summary of the Invention
[0004] The present invention aims to construct a supported bimetallic catalyst for the integrated reaction of palmitic acid hydrodeoxygenation - aromatization, which is economical and effective, has stable performance, and high catalytic activity, and has great application value in the production of high - value chemicals by palmitic acid hydrodeoxygenation.
[0005] To achieve the above object, the present invention adopts the following technical solutions: A supported bimetallic catalyst for palmitic acid hydrodeoxygenation - aromatization, and its preparation method comprises the following steps: 1) Add aluminum isopropoxide to a mixed solution containing sodium hydroxide and tetrapropylammonium hydroxide, stir evenly, then add tetraethyl orthosilicate and stir well. After reaction, a solid - liquid mixture is obtained. Then, the solid - liquid mixture is centrifuged, dried, and calcined to obtain sodium - type ZSM - 5 molecular sieve. Then, the sodium - type ZSM - 5 molecular sieve is subjected to ion exchange and secondary calcination to finally obtain ZSM - 5 molecular sieve; 2) Stir and mix nickel salt and the second metal salt in deionized water, then add this mixed solution to the ZSM - 5 molecular sieve obtained in step (1). After standing, drying, and grinding, a catalyst precursor is obtained; 3) Pyrolyze the catalyst precursor obtained in step (2) in an air atmosphere to obtain the supported bimetallic catalyst.
[0006] Further, the molar ratio of sodium hydroxide to tetrapropylammonium hydroxide in the mixed solution in step (1) is 1:(2 - 4).
[0007] Further, the molar ratio of aluminum isopropoxide, tetraethyl orthosilicate to sodium hydroxide in the mixed solution used in step (1) is 0.167:10:1, and the mass ratio of the addition amount of tetraethyl orthosilicate to deionized water in the mixed solution is 1:(15 - 40).
[0008] Further, the temperature when adding aluminum isopropoxide in step (1) is 25 - 50 °C, and tetraethyl orthosilicate is added while maintaining this temperature; the stirring time after adding tetraethyl orthosilicate is 2 - 8 h.
[0009] Further, the temperature of the reaction in step (1) is 160 - 200 °C, and the time is 16 - 36 h.
[0010] Further, the calcination in step (1) is carried out by heating to 400 - 600 °C at a rate of 2 - 5 °C / min and roasting for 1 - 6 h.
[0011] Further, the ion exchange in step (1) is carried out by stirring in a 1.0 mol / L ammonium chloride solution at 80 °C for 4 h and repeating the operation three times.
[0012] Further, the secondary calcination in step (1) is carried out by heating to 400 - 600 °C at a rate of 2 - 5 °C / min and roasting for 1 - 6 h.
[0013] Further, the nickel salt in step (2) is one of nickel nitrate, nickel acetate, nickel sulfate, and nickel chloride.
[0014] Further, the second metal salt in step (2) is a gallium salt, a copper salt, or a zinc salt.
[0015] Specifically, the gallium salt is one of gallium nitrate, gallium sulfate, and gallium chloride. The copper salt is one of copper nitrate and copper acetate. The zinc salt is one of zinc nitrate and zinc chloride.
[0016] Further, the molar ratio of the ZSM-5 zeolite to the nickel salt used in step (2) is 1:0.1 - 1:0.2, and the molar ratio of the ZSM-5 zeolite to the second metal salt used is 1:0 - 1:0.04.
[0017] Further, the pyrolysis in step (3) is carried out by heating to 400 - 600 °C at a rate of 2 - 5 °C / min and roasting for 1 - 6 h.
[0018] The obtained supported bimetallic catalyst can be used for catalyzing the hydrodeoxygenation-aromatization integrated reaction of palmitic acid to prepare benzene-based compounds. In the hydrodeoxygenation-aromatization reaction of palmitic acid, NiO and GaO, ZnO, CuO on the surface of the catalyst zeolite can be reduced to zero valence, realizing the hydrodeoxygenation of palmitic acid to long-chain alkanes, and cracking into short-chain alkanes and olefinic compounds and undergoing cyclization dehydrogenation under the action of Lewis acid and Brønsted acid of the zeolite to form benzene-based compounds.
[0019] Further, specifically, palmitic acid and the supported bimetallic catalyst are put into a batch reactor, and the air in the reactor is purged with N2, and then high-purity hydrogen is charged for reaction; after the reaction is completed, the reaction product is filtered, methyl esterified, and extracted to obtain a liquid product.
[0020] Furthermore, the dosage of the supported bimetallic catalyst is 5% of the mass of palmitic acid.
[0021] Furthermore, the temperature of the reaction is 200 - 400 °C, the pressure is 1.5 - 4 MPa, and the time is 1 - 4 h.
[0022] Furthermore, the methyl esterification is carried out by mixing the reaction product with methanol at a volume ratio of 1:(0.5 - 1) under acidic conditions and reacting at a constant temperature of 65 °C for 30 min.
[0023] Furthermore, the obtained liquid product mainly contains aromatics, alkanes, cycloalkanes, and alkenes, and also contains a small amount of esters and ketones.
[0024] The present invention has the following advantages and beneficial effects: (1) In the present invention, ZSM-5 is used as the carrier, nickel is used as the main metal active component, and gallium is used as the secondary metal active component to prepare a supported catalyst capable of realizing the integrated reaction of palmitic acid hydrodeoxygenation and aromatization. NiO, GaO, ZnO, and CuO supported on the catalyst can be reduced to zero valence in an H2 atmosphere, realizing the hydrodeoxygenation of palmitic acid to form long-chain alkane compounds. At the same time, under the action of the Lewis acid and Bronsted acid of the molecular sieve, it is cracked into short-chain alkanes and alkene compounds and undergoes cyclization dehydrogenation to form benzene compounds.
[0025] (2) The supported bimetallic catalyst prepared in the present invention overcomes the limitations of single-functional catalysts and has properties such as high catalytic activity and high economic value. Moreover, it is first applied in the reaction of directly converting palmitic acid into benzene compounds, and has the characteristics of high palmitic acid hydrodeoxygenation degree, high aromatic selectivity and yield. Therefore, it has great application value in the production of high-value chemicals by palmitic acid hydrodeoxygenation. Description of the Drawings
[0026] Figure 1 XRD pattern of the catalyst prepared for the examples. Detailed Embodiments
[0027] A supported bimetallic catalyst for palmitic acid hydrodeoxygenation and aromatization, the preparation of which includes the following steps: 1) At 25-50 °C, aluminum isopropoxide is added to a mixed solution containing sodium hydroxide and tetrapropylammonium hydroxide with a molar ratio of 1:(2-4), and after stirring evenly, tetraethyl orthosilicate is added, and stirring is continued for 2-8 h. Then it is transferred into a polytetrafluoroethylene inner liner and reacted in an oven at 160-200 °C for 16-36 h to obtain a solid-liquid mixture. Then the solid-liquid mixture is centrifuged and dried, and heated to 400-600 °C at a rate of 2-5 °C / min and calcined for 1-6 h to obtain sodium-type ZSM-5 molecular sieve. Then the sodium-type ZSM-5 molecular sieve is stirred in a 1.0 mol / L ammonium chloride solution at 80 °C for 4 h and the operation is repeated three times to complete ion exchange, and then heated to 400-600 °C at a rate of 2-5 °C / min and calcined for 1-6 h to finally obtain ZSM-5 molecular sieve; 2) Nickel salt and the second metal salt are stirred and mixed in deionized water, and then this mixed solution is added to the ZSM-5 molecular sieve obtained in step (1), and after standing, drying, and grinding, a catalyst precursor is obtained; 3) The catalyst precursor obtained in step (2) is heated in an air atmosphere at a rate of 2 - 5 °C / min to 400 - 600 °C and calcined for 1 - 6 h to obtain the supported bimetallic catalyst.
[0028] Among them, the molar ratio of aluminum isopropoxide, tetraethyl orthosilicate to sodium hydroxide in the mixed solution used in step (1) is 0.167:10:1, and the mass ratio of the added amount of tetraethyl orthosilicate to deionized water in the mixed solution is 1:(15 - 40).
[0029] The nickel salt in step (2) is one of nickel nitrate, nickel acetate, nickel sulfate, and nickel chloride. The second metal salt in step (2) is a gallium salt, a copper salt, or a zinc salt. Specifically, the gallium salt is one of gallium nitrate, gallium sulfate, and gallium chloride. The copper salt is one of copper nitrate and copper acetate. The zinc salt is one of zinc nitrate and zinc chloride. The molar ratio of the used ZSM-5 molecular sieve to the nickel salt is 1:0.1 - 1:0.2, and the molar ratio of the used ZSM-5 molecular sieve to the second metal salt is 1:0 - 1:0.04.
[0030] To make the content of the present invention more understandable, the technical solutions of the present invention are further described below in conjunction with specific embodiments, but the present invention is not limited thereto.
[0031] The nickel salt, gallium salt, copper salt, and zinc salt used in the examples were all purchased from Shanghai Titan Technology Co., Ltd. The USY molecular sieve and Hβ molecular sieve were all purchased from Tianjin Nanhua Catalyst Co., Ltd. Other reagents can be conventionally purchased from the market without special instructions.
[0032] Example 1 0.015 mol of sodium hydroxide and 0.0375 mol of tetrapropylammonium hydroxide were added to 67.5 g of deionized water, stirred to form a mixed solution, then 0.0025 mol of aluminum isopropoxide was added, and after stirring and mixing evenly, 31.25 g (0.15 mol) of tetraethyl orthosilicate was gradually added at 35 °C. After continuing to stir for 4 h, it was transferred to a polytetrafluoroethylene inner liner and reacted in an oven at 170 °C for 24 h. The obtained solid-liquid mixture was centrifuged, dried, and calcined at 550 °C for 6 h to obtain sodium-type ZSM-5 molecular sieve. Then, it was stirred in a 1.0 mol / L ammonium chloride solution at 80 °C for 4 h and the operation was repeated three times, and then calcined at 550 °C for 6 h to obtain ZSM-5-120 molecular sieve.
[0033] Weigh 2.2322 g (7.7 mmol) of nickel nitrate hexahydrate, dissolve it in 0.9 ml of deionized water. After complete dissolution, add it dropwise to 3 g of the prepared ZSM-5-120 molecular sieve. After stirring evenly, let it stand overnight at room temperature, then dry it in an oven at 100 °C for 6 h. After grinding, transfer it to a muffle furnace and heat it up to 550 °C at a rate of 2 °C / min in an air atmosphere, and calcine it at a constant temperature for 4 h to obtain a gray solid, which is the 15Ni / ZSM-5-120 catalyst. Among them, the mass percentage of Ni relative to the carrier ZSM-5-120 is 15%.
[0034] Example 2 Add 0.015 mol of sodium hydroxide and 0.0375 mol of tetrapropylammonium hydroxide to 67.5 g of deionized water, stir to form a mixed solution, then add 0.025 mol of aluminum isopropoxide, stir and mix evenly, and gradually add 31.25 g (0.15 mol) of tetraethyl orthosilicate at 35 °C. After continuing to stir for 4 h, transfer it to a polytetrafluoroethylene inner liner and react in an oven at 170 °C for 24 h. After the obtained solid-liquid mixture is centrifuged and dried, calcine it at 550 °C for 6 h to obtain a sodium-type ZSM-5 molecular sieve. Then, stir it in a 1.0 mol / L ammonium chloride solution at 80 °C for 4 h and repeat the operation three times, and then calcine it at 550 °C for 6 h to obtain the ZSM-5-120 molecular sieve.
[0035] Weigh 2.2322 g (7.7 mmol) of nickel nitrate hexahydrate and 0.11 g (0.43 mmol) of gallium nitrate hydrate, dissolve them in 0.9 ml of deionized water. After complete dissolution, add it dropwise to 3 g of the prepared ZSM-5-120 molecular sieve. After stirring evenly, let it stand overnight at room temperature, then dry it in an oven at 100 °C for 6 h. After grinding, transfer it to a muffle furnace and heat it up to 550 °C at a rate of 2 °C / min in an air atmosphere, and calcine it at a constant temperature for 4 h to obtain a gray solid, which is the 15Ni1Ga / ZSM-5-120 catalyst. Among them, the mass percentage of Ni relative to the carrier ZSM-5-120 is 15%, and the mass percentage of Ga relative to the carrier ZSM-5-120 is 1%.
[0036] Example 3 0.015 mol of sodium hydroxide and 0.0375 mol of tetrapropylammonium hydroxide were added to 67.5 g of deionized water, and stirred to form a mixed solution. Then, 0.025 mol of aluminum isopropoxide was added. After stirring and mixing evenly, 31.25 g (0.15 mol) of tetraethyl orthosilicate was gradually added at 35 °C. After continuing to stir for 4 h, it was transferred into a polytetrafluoroethylene inner liner and reacted in an oven at 170 °C for 24 h. After that, the obtained solid-liquid mixture was centrifuged, dried, and calcined at 550 °C for 6 h to obtain sodium-type ZSM-5 zeolite. Then, it was stirred in 1.0 mol / L ammonium chloride solution at 80 °C for 4 h and the operation was repeated three times, and then calcined at 550 °C for 6 h to obtain ZSM-5-120 zeolite.
[0037] 2.2322 g (7.7 mmol) of nickel nitrate hexahydrate and 0.22 g (0.86 mmol) of gallium nitrate hydrate were weighed and dissolved in 0.9 ml of deionized water. After complete dissolution, it was dropped into 3 g of the prepared ZSM-5-120 zeolite, stirred evenly, and left overnight at room temperature. Then it was dried in an oven at 100 °C for 6 h, ground and transferred to a muffle furnace, and heated to 550 °C at a rate of 2 °C / min in an air atmosphere and calcined at a constant temperature for 4 h to obtain a gray solid, which is the 15Ni2Ga / ZSM-5-120 catalyst. Among them, the mass percentage of Ni relative to the carrier ZSM-5-120 is 15%, and the mass percentage of Ga relative to the carrier ZSM-5 is 2%.
[0038] Example 4 0.015 mol of sodium hydroxide and 0.0375 mol of tetrapropylammonium hydroxide were added to 67.5 g of deionized water, and stirred to form a mixed solution. Then, 0.025 mol of aluminum isopropoxide was added. After stirring and mixing evenly, 31.25 g (0.15 mol) of tetraethyl orthosilicate was gradually added at 35 °C. After continuing to stir for 4 h, it was transferred into a polytetrafluoroethylene inner liner and reacted in an oven at 170 °C for 24 h. After that, the obtained solid-liquid mixture was centrifuged, dried, and calcined at 550 °C for 6 h to obtain sodium-type ZSM-5 zeolite. Then, it was stirred in 1.0 mol / L ammonium chloride solution at 80 °C for 4 h and the operation was repeated three times, and then calcined at 550 °C for 6 h to obtain ZSM-5-120 zeolite.
[0039] Weigh 2.2322 g (7.7 mmol) of nickel nitrate hexahydrate and 0.33 g (1.3 mmol) of gallium nitrate hydrate, dissolve them in 0.9 ml of deionized water. After complete dissolution, drop the solution into 3 g of the prepared ZSM-5-120 molecular sieve. Stir evenly and let it stand overnight at room temperature, then dry it in an oven at 100 °C for 6 h. After grinding, transfer it to a muffle furnace and heat it up to 550 °C at a rate of 2 °C / min in an air atmosphere, and calcine it at a constant temperature for 4 h to obtain a gray solid, which is the 15Ni3Ga / ZSM-5-120 catalyst. Among them, the mass percentage of Ni relative to the carrier ZSM-5-120 is 15%, and the mass percentage of Ga relative to the carrier ZSM-5 is 3%.
[0040] Example 5 Add 0.015 mol of sodium hydroxide and 0.0375 mol of tetrapropylammonium hydroxide to 67.5 g of deionized water, stir to form a mixed solution, then add 0.025 mol of aluminum isopropoxide, stir and mix evenly, and gradually add 31.25 g (0.15 mol) of tetraethyl orthosilicate at 35 °C. Continue to stir for 4 h and then transfer it to a polytetrafluoroethylene inner liner, react in an oven at 170 °C for 24 h. After the obtained solid-liquid mixture is centrifuged, dried, and calcined at 550 °C for 6 h to obtain the sodium form ZSM-5 molecular sieve, stir it in a 1.0 mol / L ammonium chloride solution at 80 °C for 4 h and repeat the operation three times, and then calcine it at 550 °C for 6 h to obtain the ZSM-5-120 molecular sieve.
[0041] Weigh 2.2322 g (7.7 mmol) of nickel nitrate hexahydrate and 0.23 g (0.92 mmol) of copper nitrate trihydrate, dissolve them in 0.9 ml of deionized water. After complete dissolution, drop the solution into 3 g of the prepared ZSM-5-120 molecular sieve. Stir evenly and let it stand overnight at room temperature, then dry it in an oven at 100 °C for 6 h. After grinding, transfer it to a muffle furnace and heat it up to 550 °C at a rate of 2 °C / min in an air atmosphere, and calcine it at a constant temperature for 4 h to obtain a gray solid, which is the 15Ni2Cu / ZSM-5-120 catalyst. Among them, the mass percentage of Ni relative to the carrier ZSM-5-120 is 15%, and the mass percentage of Cu relative to the carrier ZSM-5 is 2%.
[0042] Example 6 0.015 mol of sodium hydroxide and 0.0375 mol of tetrapropylammonium hydroxide were added to 67.5 g of deionized water, and stirred to form a mixed solution. Then, 0.025 mol of aluminum isopropoxide was added, and after stirring and mixing evenly, 31.25 g (0.15 mol) of tetraethyl orthosilicate was gradually added at 35 °C. After continuing to stir for 4 h, it was transferred into a polytetrafluoroethylene inner liner and reacted in an oven at 170 °C for 24 h. The obtained solid-liquid mixture was centrifuged, dried, and calcined at 550 °C for 6 h to obtain sodium-type ZSM-5 zeolite. Then, it was stirred in a 1.0 mol / L ammonium chloride solution at 80 °C for 4 h and the operation was repeated three times, and then calcined at 550 °C for 6 h to obtain ZSM-5-120 zeolite.
[0043] 2.2322 g (7.7 mmol) of nickel nitrate hexahydrate and 0.29 g (1.4 mmol) of zinc nitrate hydrate were weighed and dissolved in 0.9 ml of deionized water. After complete dissolution, it was added dropwise to 3 g of the prepared ZSM-5-120 zeolite, stirred evenly, placed overnight at room temperature, and then dried in an oven at 100 °C for 6 h. After grinding, it was transferred to a muffle furnace and heated to 550 °C at a rate of 2 °C / min in an air atmosphere and calcined at a constant temperature for 4 h to obtain a gray solid, which was the 15Ni2Zn / ZSM-5-120 catalyst. Among them, the mass percentage of Ni relative to the carrier ZSM-5-120 was 15%, and the mass percentage of Zn relative to the carrier ZSM-5 was 2%.
[0044] Figure 1 XRD patterns of the catalysts prepared in the examples. As can be seen from the figure, a series of synthesized catalysts all have characteristic diffraction peaks of the MFI topological structure at 2θ = 7.9°, 8.8°, 23.0°, 23.9°, and 24.3°. Characteristic diffraction peaks of typical NiO appear at 2θ = 37.3°, 43.3°, and 62.8°, which are consistent with the NiO standard card (PDF#47-1049), corresponding to the (111), (200), and (220) crystal planes of NiO respectively, indicating that the introduction of metals does not change the crystal form structure of the carrier, and the crystallinity after loading metals decreases, which indicates that alloy structures may be formed between metals. At the same time, characteristic diffraction peaks of the second metal do not appear because the relative content of the second metal is small and its distribution on the zeolite is relatively uniform.
[0045] Comparative Example 1 Weigh 2.2322 g (7.7 mmol) of nickel nitrate hexahydrate, dissolve it in 0.9 ml of deionized water. After complete dissolution, add it dropwise to 3 g of USY zeolite. Stir evenly and let it stand overnight at room temperature, then dry it in an oven at 100 °C for 6 h. After grinding, transfer it to a muffle furnace and heat it to 550 °C at a rate of 2 °C / min in an air atmosphere, and calcine it at a constant temperature for 4 h to obtain a gray solid, which is the 15Ni / USY catalyst. Among them, the mass percentage of Ni relative to the carrier USY is 15%.
[0046] Comparative Example 2 Weigh 2.2322 g (7.7 mmol) of nickel nitrate hexahydrate, dissolve it in 0.9 ml of deionized water. After complete dissolution, add it dropwise to 3 g of Hβ zeolite. Stir evenly and let it stand overnight at room temperature, then dry it in an oven at 100 °C for 6 h. After grinding, transfer it to a muffle furnace and heat it to 550 °C at a rate of 2 °C / min in an air atmosphere, and calcine it at a constant temperature for 4 h to obtain a gray solid, which is the 15Ni / Hβ catalyst. Among them, the mass percentage of Ni relative to the carrier Hβ is 15%. Performance test Add 2.5 g of 15Ni / ZSM-5-120 catalyst and 50 g of palmitic acid into a high-pressure reactor, stir to mix them evenly, seal and connect a hydrogen cylinder, and purge the air in the reaction device with H2. Then introduce 3.0 MPa, heat the reaction device to 370 °C in a programmed temperature rise mode, set the stirring rate to 500 r / min, and the reaction time to 4 h. After the reaction is completed, wait for it to cool naturally to room temperature, then take out the reaction product. After filtration, take 10 ml of the filtrate, add 5 - 10 ml of methanol and 3 - 5 drops of concentrated sulfuric acid, mix them and react in a constant temperature water bath at 65 °C for 30 min. After the reaction is completed, extract the product with dichloromethane. After stratification, collect the lower liquid product, and use a GC-MS device to qualitatively and quantitatively analyze the liquid product.
[0047] The calculation formulas for the liquid product yield, palmitic acid conversion rate, and monomer selectivity are as follows:
[0048] Among them, Y is the liquid product yield, C is the palmitic acid conversion rate, S is the monomer selectivity, m tg 、m p are the initial mass of palmitic acid and the mass of the liquid product, y tg 、y p are the initial mass fraction of palmitic acid and the mass fraction in the liquid product, y i is the mass fraction of the product.
[0049] Table 1 Evaluation results of the hydrodeoxygenation reaction of palmitic acid
[0050] Table 2 Composition and Selectivity of Products from Hydrodeoxygenation of Palmitic Acid
[0051] Combining Tables 1 and 2, it can be seen that the conversion rate of palmitic acid for each catalyst prepared in the examples is 100%. Moreover, with the introduction of the second metal, the liquid yield decreases. This is because as the metal ratio increases, the acidic sites formed by the metal and the molecular sieve increase, resulting in an increase in the cracking ability of the catalyst. At the same time, compared with the catalyst prepared without adding the second metal (Example 1), the aromatic selectivity of the catalyst prepared using Ga as the second metal (Examples 2-4) shows a trend of first increasing and then decreasing, while the selectivity of other hydrocarbons shows the opposite trend, and the selectivity of ketone compounds also shows an increasing trend. This is because the metal nickel and gallium can form L-acid acidic sites with the molecular sieve, enabling other hydrocarbon compounds to cyclize to form benzene-based compounds. Among them, when the dosage of gallium is 3%, the aromatic yield is the largest, reaching 79.2%.
[0052] At the same time, under the condition of the same dosage, the selectivity of the catalysts loaded with different second metals for aromatics varies significantly. When the second metal loaded is gallium, a greater improvement in the selectivity for aromatics can be achieved. This is because the interaction between the metal nickel and the ZSM-5 molecular sieve generates a certain amount of L-acid, which is beneficial for cyclizing and dehydrogenating alkane compounds to form aromatic compounds.
[0053] In addition, compared with Comparative Examples 1 and 2, it can be seen that the catalyst prepared using the ZSM-5 molecular sieve as the carrier has the highest conversion rate of palmitic acid and selectivity for aromatics. This is because the appropriate L / B acid of the ZSM-5 molecular sieve enables palmitic acid to have sufficient active sites for hydrodeoxygenation, and its mutually intersecting pore structure has good shape selectivity for aromatics.
[0054] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.
Claims
1. A method for preparing a supported bimetallic catalyst for palmitic acid hydrodeoxygenation-aromatization, characterized in that: The following steps are involved: 1) Aluminum isopropoxide is added to a mixed solution containing sodium hydroxide and tetrapropylammonium hydroxide and stirred evenly, then tetraethyl orthosilicate is added and stirred evenly, and then a solid-liquid mixture is obtained by reaction, and then the solid-liquid mixture is centrifuged, dried, and calcined to finally obtain a ZSM-5 molecular sieve; 2) mixing the nickel salt and the second metal salt in deionized water and stirring to mix, then adding the mixture to the ZSM-5 molecular sieve obtained in step 1), standing, drying and grinding to obtain a catalyst precursor; 3) The catalyst precursor obtained in step 2) is pyrolyzed in an air atmosphere to obtain the supported bimetallic catalyst.
2. The method for preparing a supported bimetallic catalyst according to claim 1, characterized in that: Step 1) The molar ratio of sodium hydroxide to tetrapropylammonium hydroxide in the mixed solution is 1:(2-4); the molar ratio of aluminum isopropoxide, tetraethyl orthosilicate to sodium hydroxide in the mixed solution is 0.167:10:
1.
3. The method for preparing a supported bimetallic catalyst according to claim 1, characterized in that: Step 1) The reaction temperature is 160-200°C and the reaction time is 16-36 h; the calcination is carried out by heating the mixture to 400-600°C at a rate of 2-5°C / min and calcining the mixture for 1-6 h.
4. The method for preparing a supported bimetallic catalyst according to claim 1, characterized in that: Step 2) the nickel salt is one of nickel nitrate, nickel acetate, nickel sulfate and nickel chloride; the second metal salt is a gallium salt, a copper salt or a zinc salt, wherein the gallium salt is one of gallium nitrate, gallium sulfate and gallium chloride, the copper salt is one of copper nitrate and copper acetate, and the zinc salt is one of zinc nitrate and zinc chloride.
5. The method for preparing a supported bimetallic catalyst according to claim 1, characterized in that: The molar ratio of the ZSM-5 molecular sieve to the nickel salt used in step 2) is 1:0.1-1:0.2, and the molar ratio of the ZSM-5 molecular sieve to the second metal salt used is 1:0-1:0.
04.
6. The method for preparing a supported bimetallic catalyst according to claim 1, characterized in that: Step 3) The pyrolysis is carried out by heating the mixture to 400-600°C at a rate of 2-5°C / min and calcining the mixture for 1-6 hours.
7. A supported bimetallic catalyst prepared by the method according to any one of claims 1 to 6.
8. Use of the supported bimetallic catalyst as claimed in claim 7 in preparing benzene compounds by hydrodeoxygenation of palmitic acid, characterized in that: Palmitic acid and the supported bimetallic catalyst are placed in a batch reactor, and the air in the reactor is purged with N2, and then high-purity hydrogen is filled in for reaction; after the reaction is completed, the reaction product is filtered, methylated, and extracted to obtain a liquid product containing benzene compounds.
9. The use according to claim 8, characterized in that The amount of the supported bimetallic catalyst is 5% of the mass of palmitic acid; the reaction temperature is 200-400°C, the pressure is 1.5-4 MPa, and the reaction time is 1-4 h.
10. The use according to claim 8, characterized in that The methyl esterification is carried out under acidic conditions by mixing the reaction product with methanol in a volume ratio of 1:(0.5-1) and then reacting at a constant temperature of 65°C for 30 minutes.