A large pore alumina supported copper-based catalyst, its preparation and use

Abstract

This invention discloses a copper-based catalyst supported on macroporous alumina, its preparation, and its application. The macroporous alumina-supported copper-based catalyst comprises a macroporous alumina support and copper oxide and lanthanum oxide supported on its surface. The macroporous alumina-supported copper-based catalyst is particulate with a specific surface area of ​​250-500 μm. 2 / g, pore volume 1.0~2.0 cm³ 3 The copper-based catalyst supported on macroporous alumina has an average pore size of 16-30 nm. The content of each component in the catalyst, expressed as a mass percentage, is as follows: macroporous alumina support 79%-98.9%, copper oxide 0.1%-6%, and lanthanum oxide 1%-15%. The macroporous alumina-supported copper-based catalyst of this invention exhibits high catalytic activity and selectivity for higher alcohols in the ethanol-to-higher alcohol reaction, particularly showing higher selectivity for C6-C10 fatty alcohols.

Description

Technical Field

[0001] This invention relates to a copper-based catalyst supported on macroporous alumina, its preparation method, and its application in the reaction of ethanol to higher alcohols. Background Technology

[0002] Biomass is the only renewable organic carbon resource in nature. Through catalytic conversion, it can produce high-value-added fuels and chemicals, playing a vital role in addressing global climate change, implementing resource substitution strategies, ensuring national energy security, and promoting the sustainable development of the chemical industry. Bioethanol, as a renewable and clean fuel, is widely used as a gasoline additive in Europe, the United States, Brazil, and China. However, as a fuel, ethanol has problems such as low energy density, high hygroscopicity, and the potential to cause cylinder corrosion in automobile engines, making it an undesirable gasoline blending component. Compared to ethanol, n-butanol has a higher calorific value, lower water solubility, and a lower heat of vaporization. It can be mixed with gasoline in a higher proportion and can be used directly without structural modifications to existing engines, thus showing potential to become a new generation of biofuel for widespread use. Similar to butanol, higher alcohols such as hexanol and octanol can also serve as excellent fuel blending components. In particular, they have high cetane numbers, making them suitable as diesel additives to increase the oxygen content of diesel fuel, thereby significantly reducing particulate matter and nitrogen oxides produced during diesel combustion. Besides being used as fuel, these higher alcohols are also important industrial solvents and raw materials for organic synthesis, and can be used in industries such as coatings, rubber, plastics, cosmetics, and fragrances.

[0003] Under relatively mild reaction conditions, the dehydrogenation coupling of ethanol follows the Guerbet reaction mechanism, with the formation of the target product n-butanol involving four cascaded reaction steps: first, ethanol molecules dehydrogenate to acetaldehyde; then, acetaldehyde undergoes aldol condensation to form 3-hydroxybutanal; subsequently, 3-hydroxybutanal dehydrates to form crotonaldehyde; and finally, crotonaldehyde is hydrogenated to form n-butanol. The product n-butanol and ethanol can further undergo the Guerbet reaction to generate alcohols with higher carbon numbers (such as n-hexanol, 2-ethylbutanol, n-octanol, 2-ethylhexanol, etc.). Besides the main reaction, there are also a series of side reactions, such as ethanol dehydrating to form diethyl ether and ethylene, and ethanol reacting with acetaldehyde to form ethyl acetate and 1,1-diethoxyethane, which are detrimental to improving the selectivity of higher alcohols such as n-butanol and n-hexanol.

[0004] The Guerbet mechanism involves four tandem basic reactions, encompassing multiple catalytically active sites such as metal centers and acid-base centers. Metal catalysts supported on porous solid acid-base materials are widely used in the dehydrogenation coupling of ethanol to higher alcohols. For example, Benito et al. prepared Cu-Mg-Al composite oxide catalysts with 1.0–7.6% Cu loading for the ethanol Guerbet reaction. After 6 h of reaction at 488 K and 4 MPa (N2), the Cu1.0 catalyst exhibited a 24% ethanol conversion, a 13% butanol yield, and a 21.6% selectivity for higher alcohols [Journal of Cleaner Production, 2019, 209: 1614–1623]. He et al. reported a single-atom Ru catalyst supported on a layered Mg-Al composite oxide and applied it to the ethanol condensation reaction to higher alcohols, achieving good results at 623 K, 0.1 MPa N2, and WHSV = 3.2 h. -1 Under the given reaction conditions, the Ru / Mg3Al1-LDO catalyst with a Ru loading of 1.04 wt% exhibited an ethanol conversion of 29.6% and a higher alcohol selectivity of 82.6% [Applied Catalysis B: Environmental, 2022, 309: 121271-121280]. While the above catalyst exhibits high selectivity for higher alcohols, its low ethanol conversion increases the cost of separating and recovering ethanol feedstock. Furthermore, the use of the precious metal Ru, with its high price, makes it difficult to apply in practice. Jiang et al. reported a 3Cu1CeO2 / AC catalyst in a reactor (reaction conditions: 523 K, 0.1 MPa N2, reaction time 48 h) and a fixed-bed reactor (reaction conditions: 523 K, 2 MPa N2, LHSV = 4 mL / (h·g)). catThe catalysts exhibited n-butanol yields of 21.6% and 19.1% respectively [Chemical Communications, 2016, 52(95): 13749-13752]; subsequently, a series of M-CeO2 / AC catalysts loaded with different metals (M=Cu, Fe, Co, Ni and Pd) were prepared, among which Pd-CeO2 / AC catalyst showed the highest n-butanol selectivity (67.6%), while Cu-CeO2 / AC showed the highest ethanol conversion (46.2%) [Catalysis Communications, 2017, 100: 15-18]. Although Cu-CeO2 / AC catalyst showed high butanol selectivity, its reaction activity and selectivity for higher alcohols were still not ideal, and the high copper loading resulted in high catalyst cost; while Pd-CeO2 / AC catalyst had high butanol selectivity, its low catalytic activity and the use of expensive precious metals were also its drawbacks. Patent CN113443964A also reports a Cu-MO x / Al2O3 catalyst (MO x It is a rare earth metal oxide, which exhibits an ethanol conversion rate of 45.6% and a higher alcohol yield of 26.9% in the continuous catalytic conversion of ethanol to higher alcohols in a fixed bed. Comparative Examples 1-3 of patent CN115814805A used particles with a diameter of 0.2–5 mm and a specific surface area of ​​229.2 μm. 2 Alumina-supported CuO-La2O3 catalysts were prepared using a particulate alumina support with an average pore size of 10.0 nm and a pore volume of 0.77 mL / g. These catalysts exhibited ethanol conversion rates of 41.8-43.4% and higher alcohol yields of 21.6-27.3% in the continuous catalytic conversion of ethanol to higher alcohols in a fixed bed.

[0005] In summary, to date, existing catalysts for the production of higher alcohols from ethanol have struggled to achieve both high ethanol conversion and high selectivity for higher alcohols, particularly for those with higher carbon numbers than butanol, where the selectivity is relatively low.

[0006] This invention prepares a macroporous alumina support and uses it as a support to prepare a macroporous copper-based catalyst. Its large pore size and specific surface area facilitate the diffusion of reactants and reaction intermediates and the conversion of the reaction to higher alcohols with higher carbon numbers. This allows the catalyst to maintain high activity even with a low Cu loading, while also promoting the formation of higher alcohols with larger molecular weights, thus giving it higher selectivity for higher alcohols (especially C6-C10 aliphatic alcohols). Summary of the Invention

[0007] The first technical problem to be solved by the present invention is to provide a copper-based catalyst supported on macroporous alumina for the reaction of ethanol to higher alcohols, so as to improve the ethanol conversion and the selectivity of higher alcohols, thereby improving the yield of higher alcohols.

[0008] The second technical problem to be solved by the present invention is to provide a method for preparing a copper-based catalyst supported on macroporous alumina for the reaction of ethanol to higher alcohols.

[0009] The third technical problem of the present invention is to provide the application of the copper-based catalyst supported on the macroporous alumina in the reaction of ethanol to higher alcohols.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a copper-based catalyst supported on macroporous alumina for the reaction of ethanol to higher alcohols. The macroporous alumina-supported copper-based catalyst comprises a macroporous alumina support and copper oxide and lanthanum oxide supported on its surface. The content of each component in the macroporous alumina-supported copper-based catalyst is expressed as a mass percentage as follows:

[0012] Large-pore alumina carrier: 79%~98.9%

[0013] Copper oxide 0.1%~6%

[0014] Lanthanum oxide 1%~15%

[0015] The large-pore alumina-supported copper-based catalyst is granular with a specific surface area of ​​250-500 μm. 2 / g, pore volume 1.0~2.0 cm³ 3 / g, with an average pore size of 16~30 nm.

[0016] Preferably, the content of each component in the copper-based catalyst supported on macroporous alumina is expressed as a mass percentage as follows:

[0017] Large-pore alumina carriers: 83%~97.9%

[0018] Copper oxide 0.1%~5%

[0019] Lanthanum oxide 2%~12%.

[0020] As a further preferred embodiment, the content of each component in the copper-based catalyst supported on macroporous alumina is expressed as a mass percentage as follows:

[0021] Large-pore alumina carrier: 89%~92%

[0022] Copper oxide 0.5%~3%

[0023] Lanthanum oxide 7%~10%.

[0024] Preferably, the large-pore alumina-supported copper-based catalyst is particulate with a specific surface area of ​​250~450 μm. 2 / g, pore volume 1.0~2.0 cm³ 3 / g, with an average pore size of 17~30 nm.

[0025] The copper-based catalyst supported on alumina with large pore size described in this invention may contain other components that do not substantially affect its catalytic performance, such as small amounts of impurities introduced due to the use of alumina support, copper precursor, and lanthanum precursor.

[0026] Secondly, the present invention provides a method for preparing a copper-based catalyst supported on macroporous alumina for the reaction of ethanol to higher alcohols, comprising the following steps:

[0027] (1) Immerse the prepared large-pore alumina support in a mixed solution of copper and lanthanum precursors, shake to mix, and let stand for 1 to 48 h.

[0028] (2) The mixture obtained in step (1) is dried so that the copper and lanthanum precursors are uniformly loaded onto the inner and outer surfaces of the macroporous alumina carrier.

[0029] (3) The large-pore alumina support loaded with copper and lanthanum precursors obtained in step (2) is placed in a muffle furnace and calcined at 300~800℃ in air or inert gas atmosphere for 0.5~24 h to obtain the copper-based catalyst supported on large-pore alumina.

[0030] In the above preparation method, the large-pore alumina support can be obtained in the following way:

[0031] A pre-prepared aluminum precursor salt solution and alkaline precipitant solution were mixed and stirred at 40-95℃ for 20-120 min to obtain a milky white suspension. The suspension was then filtered to obtain a filter cake, which was thoroughly washed with deionized water. The wet filter cake was mixed with a nonionic surfactant and deionized water to form a slurry, which was then added to a reaction vessel and reacted at 20-120℃ for 1-12 h. After the reaction was complete, the mixture was centrifuged to obtain a solid deposit. The solid deposit was placed in an oven and dried at 40-120℃ for 2-8 h, and then calcined in a muffle furnace at 400-800℃ for 2-8 h to obtain the macroporous alumina support.

[0032] In the above-mentioned method for preparing large-pore alumina, the aluminum precursor salt is at least one of soluble aluminum salts such as aluminum nitrate, aluminum sulfate, and aluminum chloride, and the mass percentage concentration of the aluminum precursor salt in the aluminum precursor salt solution is 5% to 60%; the alkaline precipitant is at least one of alkaline substances such as sodium hydroxide, sodium carbonate, sodium bicarbonate, and ammonia, and the mass percentage concentration of the alkaline precipitant in the alkaline precipitant solution is 5% to 75%; the molar ratio of the aluminum precursor to the alkaline precipitant is 1:0.5 to 1:5; the nonionic surfactant is at least one of fatty alcohol polyoxyethylene ether and fatty alcohol amide, and the mass percentage concentration of the nonionic surfactant in the slurry prepared by mixing wet filter cake, nonionic surfactant, and deionized water is 5% to 50%.

[0033] In the above-mentioned method for preparing copper-based catalysts supported on large-pore alumina, the copper precursor can be at least one of soluble copper salts such as copper nitrate, copper chloride, copper acetate, and copper acetylacetonate. The lanthanum precursor can be at least one of lanthanum nitrate and lanthanum acetylacetonate. The solvent for preparing the mixed solution of copper and lanthanum precursors can be at least one of deionized water, methanol, ethanol, isopropanol, acetylacetonate, chloroform, tetrahydrofuran, and N,N-dimethylformamide. The drying process in step (2) is carried out in a rotary evaporator and an oven. First, the evaporator is dried at 10~60℃ and 0.005~0.1MPa for 1~24 h, and then dried in an oven at 50~150℃ for 1~48 h.

[0034] Thirdly, the present invention provides the application of the copper-based catalyst supported on macroporous alumina according to the first aspect in the reaction of ethanol to higher alcohols.

[0035] The reaction of ethanol to higher alcohols catalyzed by the large-pore alumina-supported copper-based catalyst is carried out continuously in a fixed-bed reactor.

[0036] The application of the copper-based catalyst supported on macroporous alumina in the reaction of ethanol to higher alcohols includes the following steps:

[0037] (1) Before the copper-based catalyst supported on the large-pore alumina is applied to the reaction of ethanol to higher alcohols, it is first reduced in situ with ethanol. The in-situ reduction conditions of ethanol are: temperature of 100~325℃ (preferably 150~300℃), nitrogen gas is introduced to control the pressure in the reactor, the pressure is atmospheric pressure~6.0 MPa (preferably atmospheric pressure~5.0 MPa), and the liquid hourly space velocity of ethanol is 0.2~6.0 mL / (g) cat •h ) (preferably 0.5~5.0 mL / (g) catThe volume ratio of carrier gas nitrogen to ethanol is 10~1000:1 (preferably 100~800:1), and the reduction time is 0.5~12 h;

[0038] (2) Ethanol and carrier gas nitrogen are continuously introduced into a fixed-bed reactor to carry out a reaction to produce higher alcohols. The reaction conditions for the ethanol-to-higher-alcohol reaction are: temperature of 150~325℃ (preferably 200~300℃), pressure of atmospheric pressure to 6.0 MPa (preferably atmospheric pressure to 5.0 MPa), and liquid hourly space velocity of ethanol of 0.2~6.0 mL / (g) cat (·h) (preferably 0.5~5.0 mL / (g)) cat The volume ratio of carrier gas nitrogen to ethanol is 10~1000:1 (preferably 100~800:1).

[0039] The higher alcohols described in this invention include C4-C10 alcohols, namely, aliphatic primary carbon alcohols such as n-butanol, 2-ethylbutanol, n-hexanol, 2-ethylhexanol, n-octanol, 2-ethyloctanol, and n-decanol.

[0040] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0041] (1) When the copper-based catalyst supported on alumina with large pore size provided by the present invention is applied to the reaction of ethanol to higher alcohols, its large pore size is conducive to the diffusion of raw materials, reaction intermediates and the like in the pores, especially to the generation of higher alcohols with relatively large molecular weight. Therefore, the catalyst has high reactivity and high selectivity for higher alcohols, especially higher selectivity for C6-C10 fatty alcohols.

[0042] (2) The large-pore alumina support provided by the present invention has both large pore size and high specific surface area. The large pore size significantly improves the diffusion rate of raw materials and reaction intermediates in the catalyst channels. The high surface area makes copper highly dispersed on the catalyst surface, so even with a low Cu loading, it still maintains high catalytic activity, which reduces the production cost of the catalyst. At the same time, the catalyst preparation method is simple and reliable and the reaction conditions are relatively mild, which brings great advantages to the industrial application of the catalyst. Attached Figure Description

[0043] Figure 1 Schematic diagram of a fixed-bed reactor for the dehydrogenation condensation of ethanol to higher alcohols using catalysts: 1-Hydrogen cylinder, 2-Nitrogen cylinder, 3-Raw material cylinder, 4-High-pressure constant flow pump, 5-Three-way valve, 6-Pressure reducing valve, 7-Stop valve, 8-Mass flow meter, 9-Check valve, 10-Reaction tube, 11-Reaction furnace, 12-Condenser, 13 and 14-Condensate inlet and outlet, 15-Filter, 16-Back pressure valve, 17-Product collection tank, 18-Catalyst bed. Detailed Implementation

[0044] The present invention will be further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0045] Unless otherwise specified in the embodiments of this invention, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained through conventional technical means or commercially available.

[0046] like Figure 1 As shown, the reaction apparatus used in this invention includes a nitrogen cylinder 2, a raw material cylinder 3, a fixed-bed reactor, a condenser 12, and a product collection tank 17;

[0047] The fixed-bed reactor includes a reaction tube 10 and a reactor 11. The reaction tube 10 is provided with a catalyst bed 18, a feed inlet is provided at the top, and a discharge outlet is provided at the bottom. The reactor 11 is used to control the temperature of the reaction tube 10.

[0048] The nitrogen cylinder 2 and the raw material cylinder 3 are respectively connected to the inlet of the reaction tube 10. A pressure reducing valve 6, a shut-off valve 7, a mass flow meter 8, and a one-way valve 9 are sequentially installed between the nitrogen cylinder 2 and the reaction tube 10. A high-pressure constant flow pump 4 and a three-way valve 5 are sequentially installed between the raw material cylinder 3 and the reaction tube 10.

[0049] The discharge port of the reaction tube 10 is connected in sequence to the condenser 12 and the product collection tank 17. The condenser 12 is provided with a condensate outlet 13 and an inlet 14. The product collection tank 17 is provided with an air outlet at the top and a discharge port at the bottom. The air outlet is connected in sequence to a filter 15 and a back pressure valve 16 for exhaust gas discharge.

[0050] Example 1

[0051] 56.2775 g of Al(NO3)3·9H2O was dissolved in 100 mL of deionized water, and 37.2685 g of NaHCO3 was dissolved in 250 mL of deionized water. The two solutions were then mixed at 80 °C and stirred for 60 min to form a white suspension, which was then filtered to obtain a white filter cake. The filter cake was slurried and washed in 600 mL of deionized water for 60 min and then filtered again, repeating this process three times. The obtained filter cake, 11.3110 g of fatty alcohol polyoxyethylene ether (AEO-9), and 100 mL of deionized water were then added to a polytetrafluoroethylene-lined reactor and reacted at 100 °C for 6 h. The resulting suspension was centrifuged to obtain a solid deposit. The obtained solid deposit was dried in an oven at 80 °C for 6 h, and then calcined in a muffle furnace at 600 °C for 2 h to obtain the macroporous alumina support.

[0052] Weigh 0.0380 g Cu(NO3)2·3H2O and 0.2385 g La(NO3)3·6H2O and add them to 12 mL of deionized water. After they are completely dissolved and mixed evenly, add 1 g of macroporous alumina support and shake to impregnate for 4 h. The mixture is then rotary evaporated at 60 °C and 0.01 MPa for 1 h. The solid material after rotary evaporation is dried in an oven at 110 °C for 4 h. Finally, it is calcined in a muffle furnace at 600 °C in air atmosphere for 3 h to obtain catalyst A. The specific surface area, pore volume, and average pore size of catalyst A were determined by N2 physical adsorption. The specific test method is as follows: First, the sample was degassed under vacuum at 200℃ for 4 h to remove adsorbed moisture and impurity gases. Then, N2 physical adsorption was performed at liquid nitrogen temperature (-196℃). Finally, the adsorption-desorption isotherms of the sample were obtained using the static method. The specific surface area of ​​the sample was calculated from the adsorption isotherms according to the Brunauer-Emmett-Teller (BET) equation. Then, the pore volume and average pore size were calculated from the desorption isotherms using the single-point method (P / P0=0.99) and the BJH equation. The specific surface area of ​​catalyst A was measured to be 298 m². 2 / g, pore volume 1.41 cm 3 / g, with an average pore size of 18.2 nm. The mass percentages of CuO, La2O3, and Al2O3 in catalyst A are 1.14%, 8.14%, and 90.73%, respectively.

[0053] Example 2

[0054] The preparation method of catalyst B is the same as in Example 1, but the amount of Cu(NO3)2·3H2O weighed is 0.0761 g. The specific surface area, pore volume, and average pore size of catalyst B are determined using the same method as in Example 1, and the specific surface area of ​​catalyst B is measured to be 282 m². 2 / g, pore volume 1.37 cm³ 3 / g, with an average pore size of 18.6 nm. The mass percentages of CuO, La2O3, and Al2O3 in catalyst B are 2.25%, 8.05%, and 89.71%, respectively.

[0055] Example 3

[0056] The preparation method of catalyst C is the same as in Example 1, but the amount of Cu(NO3)2·3H2O weighed is 0.0190 g. The specific surface area, pore volume, and average pore size of catalyst C are determined using the same method as in Example 1, and the specific surface area of ​​catalyst C is measured to be 295 m². 2 / g, pore volume 1.40 cm³ 3 / g, with an average pore size of 18.1 nm. The mass percentages of CuO, La2O3, and Al2O3 in catalyst C are 0.57%, 8.19%, and 91.24%, respectively.

[0057] Example 4

[0058] The preparation method of catalyst D is the same as in Example 1, but the calcination temperature of the catalyst in the muffle furnace is 500°C. The specific surface area, pore volume, and average pore size of catalyst D are determined using the same methods as in Example 1, and the specific surface area of ​​catalyst D is measured to be 301 m². 2 / g, pore volume 1.39 cm³ 3 / g, with an average pore size of 17.9 nm. The mass percentages of CuO, La2O3, and Al2O3 in catalyst D are 1.13%, 8.15%, and 90.72%, respectively.

[0059] Example 5

[0060] The preparation method of catalyst E is the same as in Example 1, but the calcination temperature of the catalyst in the muffle furnace is 700°C. The specific surface area, pore volume, and average pore size of catalyst E are determined using the same methods as in Example 1, and the specific surface area of ​​catalyst E is measured to be 275 m². 2 / g, pore volume 1.34 cm 3 / g, with an average pore size of 19.9 nm. The mass percentages of CuO, La2O3, and Al2O3 in catalyst E are 1.11%, 8.16%, and 90.73%, respectively.

[0061] Comparative Example 1

[0062] The catalyst F was prepared using the same method as in Example 1, but the support used was commercially available alumina (surface area 250.5 m²). 2 / g, pore volume 0.77 cm³ 3 / g, average pore size 7.6 nm). The specific surface area of ​​catalyst F was measured to be 235.2 m². 2 / g, pore volume 0.74cm 3 / g, with an average pore size of 7.7 nm. The mass percentages of CuO, La2O3, and Al2O3 in catalyst F were 1.14%, 8.13%, and 90.73%, respectively. In this comparative example, the specific surface area, pore volume, and average pore size of the support and catalyst F were determined using the same methods as in Example 1.

[0063] Comparative Example 2

[0064] The catalyst G was prepared using the same method as in Example 1, but the support used was commercially available alumina (surface area 250.5 m²). 2 / g, pore volume 0.77 cm³ 3The catalyst G has an average pore size of 7.6 nm (g), and the amount of Cu(NO3)2·3H2O weighed is 0.2281 g. The specific surface area of ​​catalyst G is measured to be 222.5 m². 2 / g, pore volume 0.69 cm³ 3 / g, with an average pore size of 7.5 nm. The mass percentages of CuO, La2O3, and Al2O3 in catalyst G are 6.45%, 7.70%, and 85.85%, respectively. In this comparative example, the specific surface area, pore volume, and average pore size of the support and catalyst G were determined using the same methods as in Example 1.

[0065] Comparative Example 3

[0066] The preparation method of catalyst H is the same as that of comparative example 2, but the support used is a commercially available alumina support (specific surface area of ​​291 m²). 2 / g, pore volume 0.74 mL / g, average pore size 10.1 nm). The specific surface area of ​​catalyst H was measured to be 266.8 m². 2 / g, pore volume 0.68 cm³ 3 / g, with an average pore size of 9.9 nm. The mass percentages of CuO, La2O3, and Al2O3 in catalyst G are 6.50%, 7.72%, and 85.78%, respectively. In this comparative example, the specific surface area, pore volume, and average pore size of the support and catalyst H were determined using the same methods as in Example 1.

[0067] Example 6

[0068] Reaction apparatus such as Figure 1 As shown, catalysts A, B, C, D, E, F, G, and H prepared in the above examples and comparative examples were respectively loaded into the reaction tubes of a fixed-bed reactor for continuous fixed-bed catalytic synthesis of higher alcohols. The specific steps are as follows: ethanol and carrier gas nitrogen were continuously introduced into the fixed-bed reactor. The reaction conditions were: temperature 260℃, pressure 3 MPa, and ethanol liquid hourly space velocity 2 mL / (g). cat The carrier gas nitrogen and ethanol were mixed at a volume ratio of 250:1. After the reaction reached stability, the liquid product was analyzed using a gas chromatograph equipped with a flame ionization detector (FID) and an HP-5 column (30 m, 0.25 mm). 2-Ethylhexanol was used as an internal standard for quantification of the liquid product.

[0069] The methods for calculating ethanol conversion rate, higher alcohol selectivity, and yield are as follows:

[0070]

[0071]

[0072]

[0073] The carbon molar number refers to the total number of carbon atoms contained in the product or raw material ethanol.

[0074] The reaction results are shown in Table 1.

[0075] Table 1. Reaction performance of different catalysts in the continuous catalytic synthesis of higher alcohols from ethanol in a fixed-bed reactor.

[0076]

[0077] As shown in Table 1, compared with Cu-based catalysts prepared on commercial alumina supports with smaller pore sizes, Cu-based catalysts supported on macroporous alumina exhibit significantly improved ethanol conversion and selectivity for higher alcohols, particularly a marked increase in the selectivity for higher-value C6-C10 fatty alcohols. The larger pore size and specific surface area not only increase the diffusion rate of raw material ethanol and reaction intermediates within the pores but also facilitate the formation of higher molecular weight alcohols, thus significantly improving catalyst activity (maintaining a high ethanol conversion even at lower Cu loadings) and significantly enhancing the selectivity for higher alcohols, especially the higher-value C6-C10 higher alcohols.

Claims

1. A copper-based catalyst supported on macroporous alumina for the reaction of ethanol to higher alcohols, characterized in that: The macroporous alumina-supported copper-based catalyst comprises a macroporous alumina support and copper oxide and lanthanum oxide supported on its surface. The content of each component in the macroporous alumina-supported copper-based catalyst is expressed as a mass percentage as follows: Large-pore alumina carrier: 89%~92% Copper oxide 0.5%~3% Lanthanum oxide 7%~10% The macroporous alumina-supported copper-based catalyst is granular with a specific surface area of ​​250-500 m². 2 / g, pore volume 1.0~2.0 cm³ 3 / g, with an average pore size of 16~30 nm; the macroporous alumina support is obtained by the following method: The pre-prepared aluminum precursor salt solution and alkaline precipitant solution were mixed and stirred at 40-95℃ for 20-120 min to obtain a milky white suspension. The suspension was then filtered to obtain a filter cake, which was thoroughly washed with deionized water. The wet filter cake was mixed with a nonionic surfactant and deionized water to form a slurry, which was then added to a reaction vessel and reacted at 20-120℃ for 1-12 h. After the reaction was complete, the mixture was centrifuged to obtain a solid deposit. The solid deposit was placed in an oven and dried at 40-120℃ for 2-8 h, and then calcined in a muffle furnace at 400-800℃ for 2-8 h to obtain the macroporous alumina carrier.

2. The copper-based catalyst supported on macroporous alumina for the reaction of ethanol to higher alcohols as described in claim 1, characterized in that: The macroporous alumina-supported copper-based catalyst is granular with a specific surface area of ​​250-450 m². 2 / g, pore volume 1.0~2.0 cm³ 3 / g, with an average pore size of 17~30 nm.

3. A method for preparing a copper-based catalyst supported on macroporous alumina for the reaction of ethanol to higher alcohols as described in claim 1 or 2, characterized in that: The preparation method includes the following steps: (1) Immerse the large-pore alumina support in a mixed solution of copper and lanthanum precursors, shake to mix, and let stand for 1 to 48 h. (2) The mixture obtained in step (1) is dried so that the copper and lanthanum precursors are uniformly loaded onto the inner and outer surfaces of the macroporous alumina carrier. (3) The large-pore alumina support loaded with copper and lanthanum precursors obtained in step (2) is placed in a muffle furnace and calcined at 300~800℃ in air or inert gas atmosphere for 0.5~24 h to obtain the copper-based catalyst supported on large-pore alumina.

4. The application of the copper-based catalyst supported on macroporous alumina as described in claim 1 or 2 in the reaction of ethanol to higher alcohols.

5. The application as described in claim 4, characterized in that: The reaction for producing higher alcohols from ethanol is carried out continuously in a fixed-bed reactor.

6. The application as described in claim 5, characterized in that: The application includes the following steps: (1) Before the copper-based catalyst supported on the large-pore alumina is applied to the reaction of ethanol to higher alcohols, it is first reduced in situ with ethanol. The in-situ reduction conditions of ethanol are: temperature of 100~325℃, nitrogen gas is introduced to control the pressure in the reactor, the pressure is atmospheric pressure~6.0 MPa, and the liquid hourly space velocity of ethanol is 0.2~6.0 mL / (g) cat The volume ratio of carrier gas nitrogen to ethanol is 10~1000:1, and the reduction time is 0.5~12 h. (2) Ethanol and carrier nitrogen are continuously introduced into a fixed-bed reactor to carry out a reaction to produce higher alcohols. The reaction conditions for the ethanol-to-higher-alcohol reaction are: temperature of 150~325℃, pressure of atmospheric pressure to 6.0 MPa, and liquid hourly space velocity of ethanol of 0.2~6.0 mL / (g) cat The volume ratio of carrier gas nitrogen to ethanol is 10~1000:

1.

7. The application as described in claim 6, characterized in that: The application includes the following steps: (1) Before the copper-based catalyst supported on macroporous alumina is applied to the reaction of ethanol to higher alcohols, it is first reduced in situ with ethanol. The in-situ reduction conditions for ethanol are: temperature of 150~300℃, nitrogen gas is introduced to control the pressure in the reactor, the pressure is atmospheric pressure to 5.0 MPa, and the liquid hourly space velocity of ethanol is 0.5~5.0 mL / (g) cat The volume ratio of carrier gas nitrogen to ethanol is 100~800:1, and the reduction time is 0.5~12 h. (2) Ethanol and carrier nitrogen are continuously introduced into a fixed-bed reactor to carry out a reaction to produce higher alcohols. The reaction conditions for the ethanol-to-higher-alcohol reaction are: temperature of 200~300℃, pressure of atmospheric pressure to 5.0 MPa, and liquid hourly space velocity of ethanol of 0.5~5.0 mL / (g) cat The volume ratio of carrier gas nitrogen to ethanol is 100~800:1.

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