Method for preparing higher alcohol through continuous catalytic conversion of ethanol

Abstract

The invention discloses a method for preparing higher alcohols through continuous catalytic conversion of ethanol, the method is carried out in a fixed bed reaction device, the fixed bed reaction device comprises a feeding system, a reactor and a product collecting system, the top of the reactor is provided with a feeding port, the bottom of the reactor is provided with a discharging port, and the product collecting system is connected with the feeding system. Putting the supported copper oxide-rare earth metal oxide catalyst into the reactor, and carrying out in-situ reduction treatment on the catalyst by taking nitrogen as carrier gas and carrying ethanol; after the reduction is finished, pressurizing the whole reaction system to 0.5-1.5 MPa by using nitrogen, then cutting off the nitrogen, and continuously injecting the material ethanol into the reactor from a top feed port, so that the ethanol flows through a catalyst bed layer from top to bottom and is subjected to catalytic conversion to generate higher alcohol. By reducing the reaction pressure and omitting the inert carrier gas, the process flow is simplified while high ethanol conversion rate and high selectivity are obtained, and the equipment manufacturing cost and the operation energy consumption are remarkably reduced.

Description

(I) Technical Field

[0002] This invention relates to a method for the continuous catalytic conversion of ethanol to higher alcohols under mild conditions. (II) Background Technology

[0004] In recent years, the greenhouse effect caused by carbon emissions has become increasingly severe, and developing a low-carbon economy and seeking effective alternatives to fossil fuels has become a global consensus. Against this backdrop, the efficient utilization of biomass, as a renewable carbon resource, is crucial. Bioethanol, as the most successful and highest-volume biomass-based platform chemical, is considered an ideal green chemical feedstock and energy carrier due to its outstanding advantages such as renewable source, green production process, low toxicity, and biodegradability. However, the current fuel ethanol market is becoming saturated, and its inherent defects, such as low energy density, easy miscibility with water, and high vapor pressure, limit its wider application. Therefore, upgrading ethanol to higher value-added alcohols (such as n-butanol, n-hexanol, and n-octanol) through catalytic condensation technology has become a key route in the field of biomass refining. Higher alcohols, while retaining the green characteristics of biomass feedstocks, exhibit superior comprehensive performance and broader application prospects: First, as a new generation of biofuels or fuel additives, their energy density, hydrophobic properties, and compatibility with traditional fuels are all superior to ethanol, and they can effectively promote clean combustion and reduce particulate matter and nitrogen oxide emissions; second, as an important bulk chemical raw material, they can be used to synthesize plasticizers, high-grade solvents, surfactants, and fragrances; in addition, as high-value-added fine chemicals, they also have important applications in pharmaceuticals, pesticides, cosmetics, and specialty materials. Therefore, developing ethanol-to-higher alcohol catalysts with high activity, high stability, and excellent selectivity, along with matching reaction processes, is of great strategic significance for alleviating ethanol overcapacity, extending the biomass industrial chain, improving economic efficiency, and ultimately achieving high-value utilization of all components of biomass resources.

[0005] The dehydrogenation coupling of ethanol to higher alcohols follows the Guerbet reaction mechanism, which includes the dehydrogenation of ethanol to acetaldehyde, the aldol condensation of acetaldehyde to 3-hydroxybutyraldehyde, the dehydration of 3-hydroxybutyraldehyde to crotonaldehyde, and finally the hydrogenation of crotonaldehyde at the hydrogenation active site to give n-butanol. n-Butanol can also react with ethanol or itself via the Guerbet reaction to produce primary alcohols with higher carbon numbers, such as n-hexanol and n-octanol.

[0006] In published literature, ruthenium pincer complexes have been used to catalyze Guerbet-type reactions. In an alkaline reaction environment provided by sodium ethoxide (EtONa), the system achieved an ethanol conversion of 73.4% and produced butanol in a yield of 35.8%. When a pre-catalyst is used, only a catalytic amount of base is required to generate the catalytically active species. Another possible outcome when a large amount of base is used is the deprotonation of the intermediate aldehyde, followed by aldehyde-alcohol condensation to generate an α,β-unsaturated aldehyde, which then reacts with in-situ generated H2 to form a longer-chain alcohol. Based on its catalytic mechanism, the deactivation of the catalyst was also determined to be caused by the reaction of the water, ethanol and EtONa generated in the reaction to form non-catalytically active NaOAc [Journal of the American Chemical Society, 2016, 138(29): 9077-9080]. Ir-based complex catalysts, in combination with nickel or copper hydroxides, have also been applied to the tandem catalytic reaction of ethanol to butanol. In this reaction, the Ir-intermediate species is responsible for the dehydrogenation of ethanol to acetaldehyde, while the basic copper and nickel hydroxides catalyze the aldol condensation of acetaldehyde to produce the key intermediate crotonaldehyde. This results in a 37% ethanol conversion and an ultra-high butanol selectivity of >99% at 423 K for 24 h. The high butanol selectivity is attributed to the sterically hindered Cu and Ni ligands, which only allow small molecules to undergo condensation reactions, inhibiting the formation of long-chain Guerbet products [Journal of the American Chemical Society, 2015, 137(45): 14264-14267]. Although these catalysts exhibit good catalytic activity in the ethanol dehydrogenation condensation reaction, their synthesis methods are relatively cumbersome. Especially in the aldol condensation stage of acetaldehyde, soluble strong base catalysts such as sodium ethoxide, basic copper, and sodium nickel hydroxide are often required. Such catalysts are not only difficult to recover, but also generate a large amount of wastewater and have a long reaction time, making them difficult to adapt to continuous production processes, thus restricting their large-scale industrial application. In recent years, supported metal catalysts have received increasing attention in the reaction of ethanol to higher alcohols due to their excellent performance and have shown good application prospects. For example, a series of alumina-supported transition metal catalysts (M / Al2O3) have been applied to the reaction of ethanol to butanol in the liquid phase. Among them, Ni / Al2O3 catalyst showed a conversion rate of 25% and a yield of 20% of n-butanol. Kinetic experiments showed that the formation of butanol from ethanol on M / Al2O3 catalyst follows the Guertbet reaction mechanism [Catalysts, 2012, 2(1): 68-84].Magnesium-aluminum layered bimetallic composite oxides loaded with Ag exhibited a 44% ethanol conversion rate and a 32.8% butanol yield (butanol being the main product) at a fixed-bed reaction temperature of 350°C. However, the use of the precious metal Ag significantly increases catalyst costs, and the excessively high reaction temperature leads to high energy consumption, which to some extent restricts its industrial application [ChemistryOpen, 2021, 10, 1095-1103]. Patent CN117645528B also discloses a two-stage fixed-bed process, in which the reactant ethanol enters from the bottom of the reactor, flows upward through the catalyst bed, and the reacted material overflows from the top of the reactor. However, this process relies on high reaction pressure to maintain the reaction rate and suppress side reactions, which not only places higher demands on the materials of the reaction equipment but also increases the system complexity and safety risks. Patent CN113332989B discloses a reaction method in which a carrier gas carries the ethanol feedstock from the top of the reactor, flows downward through the catalyst bed for catalytic conversion, and flows out from the bottom of the reactor. During this process, a large amount of inert gas is mixed into the reaction products, which not only increases the energy consumption brought about by gas separation and circulation, but may also introduce certain impurities, thereby affecting the long-term stability of the catalyst and the quality of the products.

[0007] This invention provides a method for the continuous catalytic conversion of ethanol to higher alcohols. The method involves catalytically converting ethanol to higher alcohols under mild conditions with low pressure and no carrier gas. This method offers significant advantages in terms of mild reaction conditions and a simple process, greatly reducing equipment manufacturing costs. Simultaneously, after the nitrogen gas is cut off, the original nitrogen in the system is gradually diluted and replaced by the continuously introduced ethanol and reaction products, increasing the concentration of raw materials and intermediate species. The higher partial pressure of ethanol directly leads to a higher reaction rate, particularly accelerating the rate-determining step—the dehydrogenation of ethanol to acetaldehyde—thus providing sufficient power for the entire chain reaction, macroscopically manifested as an increase in conversion rate. This invention uses a low-pressure, carrier gas-free fixed-bed continuous reaction method, and the reactor outlet material does not contain inert dilution gases, thereby reducing the equipment and operating costs of the separation and circulation system, saving investment and reducing energy consumption. (III) Summary of the Invention

[0009] The purpose of this invention is to improve upon existing technologies and provide a method for the continuous and efficient catalytic conversion of ethanol into higher alcohols under mild conditions.

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

[0011] This invention provides a method for the continuous catalytic conversion of ethanol to higher alcohols. The method is carried out in a fixed-bed reactor, which includes a feed system, a reactor, and a product collection system. The reactor has a feed inlet at the top and a discharge outlet at the bottom. A supported copper oxide-rare earth metal oxide catalyst for the catalytic conversion of ethanol to higher alcohols is placed in the reactor. Nitrogen gas is used as a carrier gas to carry ethanol for in-situ reduction of the catalyst. After reduction, the entire reaction system is pressurized with nitrogen to between 0.5 and 1.5 MPa. Then, the nitrogen gas is cut off, and ethanol is continuously injected into the reactor through the top feed inlet, allowing the ethanol to flow from top to bottom through the catalyst bed and undergo catalytic conversion to higher alcohols.

[0012] As a preferred option, the reaction conditions for the catalytic conversion of ethanol to higher alcohols are: ethanol at a flow rate of 0.5~5 mL / (g) cat •h) (more preferably 0.5~2 mL / (g) cat A liquid hourly space velocity (LHSV) of 1 h is introduced into the reactor inlet. The reactor temperature is set to 240–280 °C (more preferably 255–265 °C) and the reaction pressure to 0.5–1.5 MPa for the continuous catalytic conversion of ethanol to higher alcohols. Under these reaction conditions, the method described in this invention is applied to the continuous catalytic synthesis of higher alcohols from ethanol, exhibiting high selectivity and yield of higher alcohols.

[0013] The low-pressure, carrier gas-free reaction method described in this invention has a simple process flow and eliminates the problems of separating and recycling carrier gas nitrogen, thereby greatly reducing equipment investment.

[0014] The higher alcohols mentioned in this invention refer to C4~C10 alcohols, including aliphatic primary alcohols such as n-butanol, 2-ethylbutanol, n-hexanol, 2-ethylhexanol, n-octanol, 2-ethyloctanol, and n-decanol.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) The method for catalytic conversion of ethanol to higher alcohols under low pressure and without carrier gas described in this invention has significant advantages such as mild reaction conditions and convenient operation. Without nitrogen dilution, the reactants and intermediates have high partial pressures on the catalyst surface, resulting in a fast reaction rate and high space-time yield of the higher alcohol products. Simultaneously, the system itself generates hydrogen with a low partial pressure, effectively suppressing side reactions such as excessive hydrogenation, thereby significantly improving the selectivity of the target higher alcohols.

[0017] (2) Pressurize the entire reaction system with nitrogen to the required pressure, and then cut off the nitrogen. The original nitrogen in the system will be gradually diluted and replaced by the continuously introduced ethanol and the products generated in the reaction. The concentration of raw materials and intermediate species will continue to increase, and the higher partial pressure of ethanol will directly lead to a higher reaction rate, especially accelerating the rate-determining step - the reaction rate of ethanol dehydrogenation to acetaldehyde, thus providing sufficient power for the entire chain reaction, which is macroscopically manifested as an increase in conversion rate.

[0018] (3) The present invention performs the catalytic conversion of ethanol to higher alcohols under low-pressure reaction conditions, which significantly reduces the equipment manufacturing cost. At the same time, the low-pressure and carrier gas-free fixed-bed reaction method also reduces the burden on downstream separation. Because the reactor outlet stream does not contain inert dilution gas, the equipment and operating costs of the separation circulation system are reduced, thereby significantly saving investment and reducing energy consumption. (iv) Description of the attached drawings

[0020] Figure 1 and Figure 2 These are schematic diagrams of two different reaction apparatuses for the continuous catalytic conversion of ethanol to higher alcohols. The difference between the two is: the first reaction apparatus (such as...) Figure 1 In the first type of reactor, ethanol, the reactant, enters from the top and flows downward through the catalyst bed; the reacted material exits from the bottom. In the second type of reactor (such as...), the reactant ethanol enters from the top and flows downward through the catalyst bed; the reacted material exits from the bottom. Figure 2 In this reactor, the raw materials are fed from the bottom and flow from bottom to top through the catalyst bed. After the reaction, the material flows out from the top of the reactor.

[0021] Figure 1 In the diagram, 1-ethanol raw material bottle, 2-high pressure constant flow pump, 3-three-way valve, 4-first check valve, 5-nitrogen cylinder, 6-pressure reducing valve, 7-first shut-off valve, 8-mass flow meter, 9-second check valve, 10-reactor, 11-reaction furnace, 12-catalyst bed, 13-condenser, 14-condensate outlet, 15-condensate inlet, 16-filter, 17-back pressure valve, 18-product collection tank, 19-second shut-off valve.

[0022] Figure 2 In the middle, 20-ethanol raw material bottle, 21-high pressure constant flow pump, 22-first three-way valve, 23-first check valve, 24-nitrogen cylinder, 25-pressure reducing valve, 26-first shut-off valve, 27-mass flow meter, 28-second three-way valve, 29-second check valve, 30-reactor, 31-catalyst bed, 32-reactor, 33-third check valve, 34-fourth check valve, 35-third three-way valve, 36-condenser, 37-condensate outlet, 38-condensate inlet, 39-filter, 40-back pressure valve, 41-product collection tank, 42-second shut-off valve. (V) Detailed Implementation Methods

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below, but the scope of protection of this invention is not limited thereto. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0025] Fixed-bed reactor

[0026] This invention provides a method for the continuous catalytic conversion of ethanol to higher alcohols, wherein the reaction is carried out in a fixed-bed reactor, which includes a feed system, a reactor, and a product collection system.

[0027] This invention provides two fixed-bed reactors for the continuous catalytic conversion of ethanol into higher alcohols, as described below. Figure 1 and Figure 2 As shown.

[0028] In some embodiments, a schematic diagram of the fixed-bed reactor is shown below. Figure 1 As shown, the fixed-bed reactor adopts top feeding, specifically as follows: the ethanol raw material bottle 1 is connected to the top inlet of the reactor 10 via a high-pressure constant flow pump 2, a three-way valve 3, and a first one-way valve 4; the nitrogen cylinder 5 is connected to the top inlet of the reactor 10 via a pressure reducing valve 6, a first shut-off valve 7, a mass flow meter 8, and a second one-way valve 9; the bottom outlet of the reactor 10 is connected to the top inlet of the condenser 13; the bottom outlet of the condenser 13 is connected to the product collection tank 18; the product collection tank 18 is also connected to the back pressure valve 17 via a filter 16; in addition, the bottom of the product collection tank 18 is provided with a discharge port, controlled by a second shut-off valve 19; the reactor 10 is equipped with a catalyst bed 12, which is heated by a reactor 11.

[0029] In some embodiments, a schematic diagram of the fixed-bed reactor is shown below. Figure 2As shown, the fixed-bed reactor uses bottom feeding, specifically as follows: the ethanol raw material bottle 20 is connected to the feed inlet at the bottom of the reactor 32 via a high-pressure constant flow pump 21, a first three-way valve 22, and a first one-way valve 23; the nitrogen cylinder 24 is connected to the product collection tank 41 via a pressure reducing valve 25, a first shut-off valve 26, a mass flow meter 27, a second three-way valve 28, a fourth one-way valve 34, a third three-way valve 35, and a condenser 36; in addition, the nitrogen cylinder 24 can also be connected to the product collection tank 41 via a pressure reducing valve 25, a first shut-off valve 26, a mass flow meter 27, a second three-way valve 28, a fourth one-way valve 34, a third three-way valve 35, and a condenser 36; The three-way valve 28 and the second one-way valve 29 are connected to the feed inlet at the bottom of the reactor 32; the discharge outlet at the top of the reactor 32 is connected to the feed inlet at the top of the condenser 36 via the third one-way valve 33 and the third three-way valve 35; the discharge outlet at the bottom of the condenser 36 is connected to the product collection tank 41; the product collection tank 41 is also connected to the back pressure valve 40 via the filter 39; in addition, the product collection tank 41 has a product outlet, which is controlled by the second shut-off valve 42; the reactor 32 is equipped with a catalyst bed 31, which is heated by the reactor 30.

[0030] Catalyst

[0031] The supported copper oxide-rare earth metal oxide catalyst of this invention is a type of catalyst used for the catalytic conversion of ethanol to higher alcohols. The support for the supported copper oxide-rare earth metal oxide catalyst can be one of activated carbon, alumina, silicon oxide, etc. The rare earth metal oxide can be at least one of lanthanum oxide, cerium oxide, samarium oxide, etc. In some embodiments, the mass percentage content of copper oxide in the catalyst is 0.25%~10% (more preferably 2%~8%, even more preferably 5%~8%), and the molar ratio of copper to rare earth metal is 3:1~3 (more preferably 3:1~2).

[0032] The supported copper oxide-rare earth metal oxide catalyst can be prepared according to methods reported in existing literature, such as those described in Chinese patent CN113976184.

[0033] In some embodiments, the supported copper oxide-rare earth metal oxide catalyst is prepared by the following method: copper salt and rare earth metal salt are dissolved in a solvent, a support is added, the mixture is mixed and impregnated for 1-48 h, the resulting mixture is dried by rotary evaporation and then calcined in a muffle furnace at 400-800°C for 0.5-48 h (preferably 1-20 h, more preferably 3 h) to obtain the supported copper oxide-rare earth metal oxide catalyst. The copper salt, rare earth metal salt, and support are added according to the required loading of active components.

[0034] In some preferred embodiments, the copper salt is a soluble copper salt, and is one or a mixture of several selected from copper nitrate, copper chloride, copper acetate, and copper acetylacetonate; the rare earth metal salt is a soluble salt of a rare earth metal, and is one or a mixture of several selected from rare earth metal nitrates and acetylacetonate salts; the solvent is deionized water, methanol, ethanol, isopropanol, acetylacetonate, chloroform, tetrahydrofuran, or N,N A mixture of one or more of dimethylformamide and the like. More preferably, the amount of the copper salt is 0.05~1.0 mol / L based on the volume of the solvent, and the amount of the rare earth metal salt is 0.05~1.0 mol / L based on the volume of the solvent.

[0035] In some preferred embodiments, the rotary drying conditions are as follows: first, rotary drying at 10~60℃ and 0.005~0.1 MPa for 0.5~24 h; then, rotary drying at 65~95℃ and 0.005~0.1 MPa for 0.5~10 h.

[0036] Before being applied to the reaction of ethanol to higher alcohols, the supported copper oxide-rare earth metal oxide catalyst requires a reduction pretreatment. In this invention, the supported copper oxide-rare earth metal oxide catalyst is placed in the reactor, and nitrogen is used as the carrier gas to carry ethanol for in-situ reduction treatment of the catalyst.

[0037] In some embodiments, the conditions for the in-situ reduction of ethanol are: temperature 150~300℃, reaction pressure atmospheric pressure to 4.0 MPa, and liquid hourly space velocity of ethanol 0.5~5.0 mL / (g). cat The volume ratio of carrier gas to ethanol is 100~600:1. Preferably, the conditions for the in-situ ethanol reduction treatment are: temperature 240~280℃ (preferably 255~265℃), reaction pressure 0.5~1.5 MPa, and liquid hourly space velocity (LHSV) of the ethanol 0.5~2 mL / (g·h). cat In the above in-situ reduction process, nitrogen is used as the carrier gas for ethanol, and the volume ratio of nitrogen to ethanol is 100~400:1.

[0038] Example 1

[0039] Weigh 0.4562 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) and 0.4088 g of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and add them to 10 ml of ethanol. After they are fully dissolved, add 2 g of alumina support (granular, with a particle diameter of 0.2~5 mm and a specific surface area of ​​291 μm). 2 / g, average pore size 10.1 nm, pore volume 0.74 mL / g (all examples and comparative examples used this support) and shaken and impregnated for 4 h. The mixture was then dried on a rotary evaporator at 50 °C and 0.01 MPa for 3 h, followed by rotary drying at 80 °C and 0.01 MPa for 2 h. The remaining solid was then calcined in a muffle furnace at 450 °C in air for 3 h to obtain the catalyst. The catalyst contained 6.52 wt% copper oxide, 6.67 wt% lanthanum oxide, and the remainder was alumina support.

[0040] Fixed-bed reactor for continuous catalytic conversion of ethanol to higher alcohols, such as Figure 1 As shown.

[0041] Weigh 2 g of catalyst and load it into the isothermal zone of the reactor. The specific method for in-situ ethanol reduction is as follows: Open the cylinder valve at the top of nitrogen cylinder 5, allowing nitrogen gas to enter reactor 10 via pressure reducing valve 6, first shut-off valve 7, mass flow meter 8, and second one-way valve 9, and pressurize the entire reaction system to the required pressure; turn on high-pressure constant flow pump 2, allowing ethanol to enter reactor 10 from raw material bottle 1 via three-way valve 3 and first one-way valve 4; heat the reactor to the required temperature at a rate of 10℃ / min, while simultaneously using nitrogen gas to carry the preheated ethanol raw material from top to bottom into the reactor for in-situ ethanol reduction of the catalyst. The reduced material flows out from the bottom of reactor 10, is condensed by condenser 13, enters product collection tank 18, and is finally discharged for analysis through second shut-off valve 19. The conditions for in-situ ethanol reduction are: reaction pressure of 1 MPa, and ethanol liquid hourly space velocity of 1 mL / (g). cat The catalyst bed temperature was 260℃, and the volume ratio of nitrogen to ethanol was 250:1.

[0042] The specific reaction method for producing higher alcohols from ethanol is as follows: Open the cylinder valve at the top of nitrogen cylinder 5, allowing nitrogen gas to enter reactor 10 via pressure reducing valve 6, first shut-off valve 7, mass flow meter 8, and second one-way valve 9. Pressurize the entire reaction system to the required pressure, then cut off the nitrogen supply. Turn on high-pressure constant flow pump 2, allowing ethanol feedstock to enter from the top of reactor 10 sequentially through three-way valve 3 and first one-way valve 4. Flowing downwards through the catalyst bed, it is catalytically converted into higher alcohols. After the reaction, the material flows out from the bottom of reactor 10, is condensed by condenser 13, and enters product collection tank 18. Finally, it is discharged for analysis through second shut-off valve 19. Reaction conditions: Reaction pressure is 1 MPa, ethanol liquid hourly space velocity is 1 mL / (g). cat ·h), reaction temperature 260℃.

[0043] Example 2

[0044] The catalyst preparation, reduction, and reaction methods are the same as in Example 1, except that the reaction conditions are: reaction pressure of 1.5 MPa and ethanol liquid hourly space velocity of 1 mL / (g). cat ·h), reaction temperature 260℃.

[0045] Example 3

[0046] The catalyst preparation, reduction, and reaction methods are the same as in Example 1, except that the reaction conditions are: reaction pressure of 0.5 MPa and ethanol liquid hourly space velocity of 1 mL / (g). cat ·h), reaction temperature 260℃.

[0047] Example 4

[0048] The catalyst preparation, reduction, and reaction methods are the same as in Example 1, except that the reaction conditions are: reaction pressure of 1 MPa and ethanol liquid hourly space velocity of 1 mL / (g). cat ·h), reaction temperature 255℃.

[0049] Example 5

[0050] The catalyst preparation, reduction, and reaction methods are the same as in Example 1, except that the reaction conditions are: reaction pressure of 1 MPa and ethanol liquid hourly space velocity of 1 mL / (g). cat ·h), reaction temperature 265℃.

[0051] Example 6

[0052] The catalyst preparation, reduction, and reaction methods are the same as in Example 1, except that the reaction conditions are: reaction pressure of 1 MPa and ethanol liquid hourly space velocity of 0.5 mL / (g). cat ·h), reaction temperature 260℃.

[0053] Example 7

[0054] The catalyst preparation, reduction, and reaction methods are the same as in Example 1, except that the reaction conditions are: reaction pressure of 1 MPa and ethanol liquid hourly space velocity of 1.5 mL / (g). cat ·h), reaction temperature 260℃.

[0055] Example 8

[0056] The catalyst preparation, reduction, and reaction methods are the same as in Example 1, except that the reaction conditions are: reaction pressure of 1 MPa and ethanol liquid hourly space velocity of 2 mL / (g). cat ·h), reaction temperature 260℃.

[0057] Comparative Example 1

[0058] The catalyst preparation, reduction, and reaction methods are the same as in Example 1, except that the reaction conditions are: atmospheric pressure and ethanol liquid hourly space velocity (LHSV) of 1 mL / (g). cat ·h), reaction temperature 260℃.

[0059] Comparative Example 2

[0060] The catalyst preparation, reduction, and reaction methods are the same as in Example 1, except that the reaction conditions are: reaction pressure of 2 MPa and ethanol liquid hourly space velocity of 1 mL / (g). cat ·h), reaction temperature 260℃.

[0061] Comparative Example 3

[0062] The catalyst preparation and reduction methods are the same as in Example 1, but a fixed-bed reactor for the continuous catalytic conversion of ethanol to higher alcohols is adopted by top feeding and simultaneous carrier gas flow. Figure 1 shows the reactor.

[0063] Weigh 2 g of catalyst and load it into the isothermal zone of the reactor. The specific reaction method is as follows: Open the cylinder valve at the top of nitrogen cylinder 5, allowing nitrogen gas to enter reactor 10 via pressure reducing valve 6, first shut-off valve 7, mass flow meter 8, and second one-way valve 9, pressurizing the entire reaction system to the required pressure; turn on high-pressure constant flow pump 2, allowing ethanol feedstock, carried by nitrogen gas, to enter from the top of reactor 10 via three-way valve 3 and first one-way valve 4, flowing downwards through the catalyst bed and undergoing catalytic conversion to produce higher alcohols. After the reaction, the material flows out from the bottom of reactor 10, is condensed by condenser 13, and enters product collection tank 18, finally being discharged for analysis through second shut-off valve 19. The reaction conditions are: reaction pressure 1 MPa, ethanol liquid hourly space velocity 1 mL / (g) cat The reaction temperature was 260℃, and the volume ratio of nitrogen to ethanol was 250:1.

[0064] Comparative Example 4

[0065] The catalyst preparation and reduction methods are the same as in Example 1, but a bottom-feed reaction method without carrier gas is used. The fixed-bed reactor for the continuous catalytic conversion of ethanol to higher alcohols is as follows: Figure 2 As shown.

[0066] Weigh 2 g of catalyst and load it into the isothermal zone of the reactor. The specific method for in-situ ethanol reduction is as follows: Open the cylinder valve at the top of nitrogen cylinder 24, allowing nitrogen gas to enter reactor 32 via pressure reducing valve 25, first shut-off valve 26, mass flow meter 27, second three-way valve 28, and second one-way valve 29, and pressurize the entire reaction system to the required pressure; turn on high-pressure constant flow pump 21, allowing ethanol to enter from the bottom of reactor 32 from raw material bottle 20 via first three-way valve 22 and first one-way valve 23; heat the reactor to the required temperature at a rate of 10℃ / min, while simultaneously using nitrogen gas to carry the preheated ethanol raw material from bottom to top into the reactor for in-situ ethanol reduction of the catalyst. After reduction, the material overflows from the top of reactor 32, is condensed by condenser 36, and enters product collection tank 41, finally being discharged for analysis through second shut-off valve 42. The conditions for in-situ ethanol reduction are: reaction pressure of 1 MPa, and ethanol liquid hourly space velocity of 1 mL / (g). cat The catalyst bed temperature was 260℃, and the volume ratio of nitrogen to ethanol was 250:1.

[0067] The specific reaction method for producing higher alcohols from ethanol is as follows: Open the cylinder valve at the top of nitrogen cylinder 24, allowing nitrogen gas to pass through pressure reducing valve 25, first shut-off valve 26, mass flow meter 27, second three-way valve 28, fourth one-way valve 34, third three-way valve 35, and condenser 36, entering the product collection tank 41. Pressurize the entire reaction system to the required pressure, then cut off the nitrogen supply. Turn on the high-pressure constant flow pump 21, allowing the ethanol feedstock to enter from the bottom of reactor 32 sequentially through the first three-way valve 22 and first one-way valve 23. After flowing upwards through the catalyst bed and undergoing catalytic conversion into higher alcohols, the material overflows from the top of reactor 32, is condensed by condenser 36, and enters the product collection tank 41. Finally, it is discharged for analysis through the second shut-off valve 42. The reaction conditions are: reaction pressure 1 MPa, ethanol liquid hourly space velocity 1 mL / (g) cat ·h), reaction temperature 260℃.

[0068] Comparative Example 5

[0069] The catalyst preparation method is the same as in Example 1, but a bottom-feed reaction method with simultaneous carrier gas flow is used. The fixed-bed reactor for the continuous catalytic conversion of ethanol to higher alcohols is as follows: Figure 2 As shown.

[0070] Weigh 2 g of catalyst and load it into the isothermal zone of the reactor. The specific method for in-situ ethanol reduction is as follows: Open the cylinder valve at the top of nitrogen cylinder 24, allowing nitrogen to enter reactor 32 via pressure reducing valve 25, first shut-off valve 26, mass flow meter 27, second three-way valve 28, and second one-way valve 29, and pressurize the entire reaction system to the required pressure; turn on high-pressure constant flow pump 21, allowing ethanol to enter from the bottom of reactor 32 from raw material bottle 20 via first three-way valve 22 and first one-way valve 23; heat the reactor to the required temperature at a rate of 10℃ / min, while simultaneously using nitrogen to carry the preheated ethanol raw material from bottom to top into the reactor for in-situ ethanol reduction of the catalyst. After reduction, the material overflows from the top of reactor 32, is condensed by condenser 36, and enters product collection tank 41, finally being discharged for analysis through second shut-off valve 42. The conditions for in-situ ethanol reduction are: reaction pressure of 1 MPa, and ethanol liquid hourly space velocity of 1 mL / (g). cat The catalyst bed temperature was 260℃, and the volume ratio of nitrogen to ethanol was 250:1.

[0071] The specific reaction method for producing higher alcohols from ethanol is as follows: Open the cylinder valve at the top of nitrogen cylinder 24, allowing nitrogen gas to enter reactor 32 via pressure reducing valve 25, first shut-off valve 26, mass flow meter 27, second three-way valve 28, and second one-way valve 29, pressurizing the entire reaction system to the required pressure. Turn on high-pressure constant flow pump 21, allowing ethanol feedstock, carried by nitrogen gas, to enter reactor 32 from the bottom through first three-way valve 22 and first one-way valve 23, flowing upwards through the catalyst bed and undergoing catalytic conversion to produce higher alcohols. After the reaction, the material overflows from the top of reactor 32, is condensed by condenser 36, and enters product collection tank 41, finally being discharged for analysis through second shut-off valve 42. The reaction conditions are: reaction pressure 1 MPa, ethanol liquid hourly space velocity 1 mL / (g). cat The reaction temperature was 260℃, and the volume ratio of nitrogen to ethanol was 250:1.

[0072] The reaction conditions and results of the continuous fixed-bed catalytic conversion of ethanol to higher alcohols are shown in Tables 1 and 2.

[0073] Table 1 Summary of reaction conditions for the continuous catalytic conversion of ethanol to higher alcohols in a fixed bed

[0074]

[0075] Table 2. Results of the continuous catalytic conversion of ethanol to higher alcohols in a fixed-bed catalytic bed.

[0076]

[0077] As shown in Table 2, compared to reaction methods such as top-feed with carrier gas, bottom-feed without carrier gas, and bottom-feed with carrier gas, the low-pressure top-feed without carrier gas reaction method not only significantly improves ethanol conversion but also significantly enhances the selectivity and yield of higher alcohols. Under the low-pressure, carrier gas-free feed mode, the concentration of raw materials and intermediate species is higher, thus achieving a dual breakthrough in ethanol conversion and higher alcohol selectivity. The low-pressure top-feed without carrier gas reaction method also effectively reduces the complexity of the process and equipment manufacturing costs, thereby saving investment and reducing energy consumption.

Claims

1. A method for the continuous catalytic conversion of ethanol to higher alcohols, characterized in that: The method is carried out in a fixed-bed reactor, which includes a feeding system, a reactor and a product collection system. The reactor has a feed inlet at the top and a discharge outlet at the bottom. A supported copper oxide-rare earth metal oxide catalyst for the catalytic conversion of ethanol to higher alcohols is placed in the reactor, and nitrogen is used as a carrier gas to carry ethanol to perform in-situ reduction treatment on the catalyst. After the reduction is complete, the entire reaction system is pressurized with nitrogen to between 0.5 and 1.5 MPa. Then the nitrogen gas is cut off, and ethanol is continuously injected into the reactor through the top feed inlet. The ethanol flows from top to bottom through the catalyst bed and undergoes catalytic conversion to produce higher alcohols.

2. The method as described in claim 1, characterized in that: The reaction conditions for the catalytic conversion of ethanol to higher alcohols are: ethanol at a flow rate of 0.5~5 mL / (g) cat The reactor is fed with a liquid hourly space velocity (LHSV) of h, and the reactor is set with a reaction temperature of 240-280°C and a reaction pressure of 0.5-1.5 MPa to carry out the continuous catalytic conversion of ethanol to higher alcohols.

3. The method as described in claim 2, characterized in that: The reaction temperature is 255~265℃.

4. The method as described in claim 2, characterized in that: The liquid hourly space velocity (LHSV) of ethanol is 0.5–2 mL / (g). cat ·h).

5. The method according to any one of claims 1-4, characterized in that: The support for the supported copper oxide-rare earth metal oxide catalyst is one of activated carbon, alumina, and silicon oxide; the rare earth metal oxide in the supported copper oxide-rare earth metal oxide catalyst is at least one of lanthanum oxide, cerium oxide, and samarium oxide.

6. The method as described in claim 5, characterized in that: In the supported copper oxide-rare earth metal oxide catalyst, the mass percentage content of copper oxide is 0.25%~10%, preferably 2%~8%, more preferably 5%~8%, and the molar ratio of copper to rare earth metal is 3:1~3.

7. The method according to any one of claims 1-4, characterized in that: The supported copper oxide-rare earth metal oxide catalyst is prepared according to the following method: copper salt and rare earth metal salt are dissolved in a solvent, a support is added, the mixture is mixed and impregnated for 1-48 h, the resulting mixture is dried by rotary evaporation and then calcined in a muffle furnace at 400-800℃ for 0.5-48 h to obtain the supported copper oxide-rare earth metal oxide catalyst.

8. The method according to any one of claims 1-4 and 6, characterized in that: The conditions for in-situ reduction of the catalyst using nitrogen as a carrier gas to carry ethanol are as follows: treatment temperature 150~300℃, pressure atmospheric pressure to 4.0 MPa, and liquid hourly space velocity of the ethanol 0.5~5.0 mL / (g). cat The volume ratio of carrier gas to ethanol is 100~600:

1.

9. The method as described in claim 8, characterized in that: The conditions for in-situ reduction of the catalyst using nitrogen as a carrier gas to carry ethanol are as follows: treatment temperature 240~280℃, pressure 0.5~1.5 MPa, and liquid hourly space velocity of the ethanol 0.5~2 mL / (g). cat ·h), wherein the volume ratio of nitrogen to ethanol is 100~400:

1.

10. The method as described in claim 9, characterized in that: The temperature for in-situ reduction of the catalyst using nitrogen as a carrier gas to carry ethanol is 255~265℃.

Images