A catalyst for dehydrogenation of ethanol to acetaldehyde and preparation and application thereof

Abstract

The application belongs to the technical field of catalytic dehydrogenation, and particularly relates to a catalyst for preparing acetaldehyde by dehydrogenating ethanol, and preparation and application of the catalyst. The catalyst uses silicon dioxide as a carrier, Cu as an active component, and a small amount of Ni and Zn as additives. The loading amount of the active component Cu in the catalyst is 2.0-25wt%, and the loading amounts of the additives Ni and Zn in the catalyst are 0.02wt%-2.0wt% and 0.01wt%-1.0wt% respectively. The catalyst has a simple preparation process, only a small amount of ammonia water is used as a precipitant, the catalyst avoids the need for excessive ammonia water and a complex ammonia evaporation process in the ammonia evaporation method, and the catalyst does not use organic silicon compared with the gel method, and the catalyst has low production cost. The catalyst has high catalytic activity, good acetaldehyde selectivity, and good long-period operation stability in the reaction of preparing acetaldehyde by dehydrogenating ethanol.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic dehydrogenation, and specifically relates to a catalyst for dehydrogenating ethanol to produce acetaldehyde, and its preparation and application. Background Art

[0002] Ethanol can be produced in large quantities through biomass fermentation and is the most promising biomass resource. Using it as a platform molecule to produce chemicals is expected to develop into a new alternative to petroleum resources, thereby enriching new chemical production processes and promoting the refinement and upgrading of industrial structure. This is in line with my country's energy resource development strategy of "energy conservation, emission reduction, and green and low-carbon development," and is of great significance to improving the ecological environment. Ethanol can be selectively dehydrogenated to acetaldehyde, which is then used as a raw material to synthesize high-value-added chemicals such as butanol, 1,3-butadiene, and 1,3-propylene glycol. This process is a key technology that connects ethanol to high-value-added chemicals, enriching and expanding the technology route for producing downstream chemicals from syngas.

[0003] Cu-based catalysts have been extensively studied in ethanol dehydrogenation and have been shown to hold the greatest commercial potential. Because Cu has a theoretical surface lattice migration temperature and sintering temperature of 134°C and 405°C, respectively, it is prone to migration, agglomeration, and even sintering during the reaction. Consequently, Cu-containing catalysts are susceptible to deactivation due to aggregation and sintering. To improve the stability of Cu-based catalysts, additives are often added. While the addition of nickel significantly enhances the activity and stability of Cu-based catalysts in ethanol dehydrogenation, nickel can easily cleave C—C bonds in ethanol, generating a large amount of CH byproduct and reducing acetaldehyde selectivity. Alternatively, the stability of ethanol dehydrogenation can be improved by modifying the preparation method of Cu-based catalysts. Patent CN114054079A discloses a Cu-based catalyst prepared by an ammonia evaporation process for ethanol dehydrogenation to acetaldehyde. This ammonia treatment strengthens the interaction between the copper particles and the silica support, resulting in excellent catalyst stability and stable operation for 500 hours. However, the ammonia evaporation process is cumbersome, and the recovery of ammonia raises environmental concerns, making the catalyst preparation process complex. Patent CN114054079A discloses a method for preparing a Cu-based catalyst using a gel method. Inorganic copper salts are dissolved in an organic silicate solution, and ammonia is added to adjust the solution to alkalinity to form a sol. The sol is then calcined to form a network structure in which copper oxide or cuprous oxide is dispersed in SiO2, thereby forming a highly stable Cu-based catalyst. Although the catalyst obtained by this preparation method has good performance, the use of organic silicon as a silicon source results in a high catalyst manufacturing cost. Summary of the Invention

[0004] The present invention aims to address the problems existing in the prior art and provide a catalyst for ethanol dehydrogenation to acetaldehyde, a preparation method thereof, and an application thereof. The present invention adopts Cu as an active component and Ni and Zn as auxiliary agents. The introduction of the Ni element can improve the dispersion of the Cu element on the carrier, thereby improving the activity and stability of the catalyst. The auxiliary agent Zn can affect the electronic structure of the Ni element through electron transfer between the Ni element and the Zn element. The change in the electronic structure of the elemental nickel affects the adsorption and activation of reactants on its surface, reduces the hydrogenolysis of the C—C bond in the ethanol molecule, reduces the generation of the byproduct CH4, and improves the selectivity of acetaldehyde. At the same time, in the catalyst preparation process of the present invention, only a small amount of ammonia water is used as a precipitant, thereby avoiding the need for excessive ammonia water and the complex ammonia distillation process in the ammonia distillation method. Compared with the gel method, no organic silicon is used, and the catalyst production cost is low.

[0005] In order to achieve the above object of the invention, the specific technical solution of the present invention is:

[0006] A Cu-Ni-Zn / SiO2 catalyst for ethanol dehydrogenation to acetaldehyde, comprising silicon dioxide as a carrier, Cu as an active component, and small amounts of Ni and Zn as additives. The active component, copper, is loaded in an amount of 2.0-25 wt% in the catalyst, while the additives, nickel and zinc, are loaded in amounts of 0.02 wt%-2.0 wt% and 0.02 wt%-2.0 wt% respectively. The remainder is the carrier, and the total mass percentages are 100%.

[0007] Another invention object of the present application is to provide the application of the above-mentioned Cu-Ni-Zn / SiO2 catalyst in the process of dehydrogenating ethanol to acetaldehyde.

[0008] The third invention object of this application is to protect a preparation method of the above catalyst, which comprises the following steps:

[0009] (1) Under stirring, add the soluble salt solution of Cu and Ni to a certain concentration of silica sol aqueous solution and stir evenly;

[0010] (2) adding a certain concentration of ammonia solution to the mixed solution obtained in step (1), adjusting the pH value of the solution, causing precipitation in the solution to obtain a slurry;

[0011] (3) heating and aging the slurry obtained in step (2), filtering, washing, drying, and calcining to obtain a Cu-Zn / SiO2 sample;

[0012] (4) A soluble salt solution of Zn is impregnated on a Cu-Ni / SiO2 sample, and then dried and calcined to obtain the catalyst Cu-Ni-Zn / SiO2.

[0013] As a better embodiment of the present application, in step (1), the soluble Cu salt and Ni salt are Cu(NO3)2 and Ni(NO3)2 and their hydrates respectively; in step (4), the soluble Zn salt is Zn(NO3)2 and its hydrate.

[0014] As a preferred embodiment of the present application, in the step (1), the silica sol aqueous solution is a silica sol solution to water mass ratio of 1:0-1:20 (specifically 1:0, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, etc.), more preferably 1:1-1:5; in the step (2), the mass concentration of ammonia water is 2wt%-25wt% (specifically 2wt%, 3wt%, 4wt%, 5wt%, 6wt%). %, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%), preferably 5wt%-10wt%, the pH of the solution is 6.5-8.0 (specifically 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, etc.), more preferably 7.0-7.5.

[0015] As a preferred embodiment in the present application, the temperature in step (3) is maintained at 50-90℃ (specifically, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, etc.), the aging time is 4-12h (specifically, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, etc.); the drying temperature is 50-200℃ (specifically, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, etc.), the drying time is 4-48h (specifically, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h, 29h, 30h, 31h, 32h, 33h, 34h, 35h, 36h, 37h, 38h, 39h, 40h, 41h, 42h, 43h, 44h, 45h, 46h, 47h, 48h, etc.), the calcination temperature is 300-500℃ (specifically, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, etc.), and the calcination time is 4-24h (specifically, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, etc.).

[0016] As a preferred embodiment of the present application, the drying temperature in step (4) is 50-200°C (specifically 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, etc.), and the drying time is 4-48h (specifically 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h , 22h, 23h, 24h, 25h, 26h, 27h, 28h, 29h, 30h, 31h, 32h, 33h, 34h, 35h, 36h, 37h, 3 8h, 39h, 40h, 41h, 42h, 43h, 44h, 45h, 46h, 47h, 48h, etc.), the roasting temperature is 300-500℃ (specifically 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃ , 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, etc.), and the calcination time is 4-24h (specifically 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, etc.).

[0017] As a preferred embodiment of the present application, the catalyst is used to catalyze the reaction of ethanol dehydrogenation to produce acetaldehyde, the reaction uses a fixed bed as a reactor, and the reaction steps are:

[0018] (1) The Cu-Ni-Zn / SiO2 catalyst is filled in a fixed bed and reduced with a hydrogen-nitrogen mixed gas with a volume content of 5%-20%, a reduction temperature of 250-500°C, and a reduction time of 4-24h.

[0019] (2) After reduction, the temperature is lowered to the reaction temperature, nitrogen is introduced, and an ethanol solution is pumped in to carry out the reaction; during the reaction, the reaction pressure is normal pressure-1.0 MPa, the reaction temperature is 200-300°C; the mass space velocity of ethanol is 0.1-4h-1; and the volume space velocity of the nitrogen is 2000-12000h-1.

[0020] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0021] (1) First, the Ni element is introduced to improve the dispersion of the Cu element on the support, thereby enhancing the activity and stability of the catalyst. Simultaneously, to reduce the hydrogenolysis of CC by the Ni element during the reaction, reduce the formation of the byproduct CH4, and improve the selectivity for acetaldehyde, a second additive, Zn, is introduced. Zn can transfer electrons between the Zn and Ni, affecting the electronic structure of Ni, thereby altering the Ni electronic structure and, in turn, affecting the adsorption and activation of reactants on its surface, thereby reducing the hydrogenolysis of the C—C bonds in the ethanol molecules during the reaction. The catalyst preparation method provided by the present invention maintains the advantages of the high activity and long life of the Ni element while reducing the disadvantage of the introduction of the Ni element, which can lead to excessive decomposition and reduced acetaldehyde selectivity.

[0022] (2) The catalyst preparation process of the present invention is simple and low-cost. Only a small amount of ammonia water is used as a precipitant, avoiding the need for excessive ammonia water and the complicated ammonia distillation process in the ammonia distillation method. Compared with the gel method, no organosilicon is used, and the catalyst production cost is low.

[0023] (3) The catalyst of the present invention is used in the ethanol dehydrogenation reaction to produce acetaldehyde, and has high catalyst activity, good acetaldehyde selectivity, and good long-term operation stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The catalyst activity data of the catalyst C in the long-term operation of Example

[0025] Figure 2 The catalyst activity data of the comparative catalyst E during long-term operation is shown in FIG. DETAILED DESCRIPTION

[0026] All features disclosed in this specification, or all steps in the disclosed methods or processes, except mutually exclusive features and / or steps, can be combined in any manner.

[0027] Any feature disclosed in this specification, unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0028] In this application, all unrecorded ratios are mass ratios; and all unspecified % are mass percentages.

[0029] Example 1

[0030] Take 3.80g Cu(NO3)2·3H2O and 0.50g Ni(NO3)2·6H2O and dissolve them in 200ml deionized water. Under stirring, add them dropwise to a certain amount of silica sol aqueous solution (silica sol: water = 1:1) and stir evenly. Then slowly add 5% ammonia water to the mixture until the solution precipitates until the pH value of the solution is maintained at around 7.0. Then heat it to 80℃ and continue stirring and aging for 4h. Finally, filter and wash it, dry it in an oven at 110℃ for 24h, and calcine it at 400℃ in a muffle furnace for 4h to obtain the Cu-Ni / SiO2 sample.

[0031] Take 0.45g Zn(NO3)2·6H2O and dissolve it in 50ml deionized water. Then add the Cu-Ni / SiO2 sample to the solution, stir evenly and soak for 4h, then dry it in an oven at 110℃ for 24h, and calcine it in a muffle furnace at 450℃ for 4h to obtain Cu-Ni-Zn / SiO2 catalyst A, in which the Cu content is 5.0wt%, the Ni content is 0.5wt%, and the Zn content is 0.5wt%.

[0032] Example 2

[0033] Take 7.61g Cu(NO3)2·3H2O and 0.99g Ni(NO3)2·6H2O and dissolve them in 300ml deionized water. Under stirring, add them dropwise to a certain amount of silica sol aqueous solution (silica sol: water = 1:2) and stir evenly. Then slowly add 10% ammonia water to the mixture until the solution precipitates until the pH value of the solution is maintained at around 7.0. Then heat it to 80℃ and continue stirring and aging for 4h. Finally, filter and wash it, dry it in an oven at 110℃ for 24h, and calcine it at 400℃ in a muffle furnace for 4h to obtain the Cu-Ni / SiO2 sample.

[0034] Take 0.45g Zn(NO3)2·6H2O and dissolve it in 50ml deionized water. Add the Cu-Ni / SiO2 sample to the solution, stir evenly and soak for 4h, then dry it in an oven at 110℃ for 24h, and calcine it in a muffle furnace at 450℃ for 4h to obtain Cu-Ni-Zn / SiO2 catalyst B, in which the Cu content is 10.0wt%, the Ni content is 1.0wt%, and the Zn content is 0.5wt%.

[0035] Example 3

[0036] Example 1

[0037] Example 2

[0038] Example 3

[0039] Example 4

[0040] Example 5

[0041] Comparative Example 1

[0042] Take 7.61g Cu(NO3)2·3H2O and dissolve it in 200ml deionized water. Under stirring, add it dropwise to a certain amount of silica sol aqueous solution (silica sol: water = 1:2) and stir evenly. Then, slowly add 10% ammonia water to the mixture until the solution precipitates until the pH value of the solution is maintained at around 7.0. Then, heat it to 80℃ and continue stirring and aging for 4h. Finally, filter and wash it, dry it in an oven at 110℃ for 24h, and calcine it at 400℃ in a muffle furnace for 4h to obtain Cu / SiO2 catalyst E, in which the Cu content is 10wt%.

[0043] Comparative Example 2

[0044] Take 7.61g Cu(NO3)2·3H2O and 0.99g Ni(NO3)2·6H2O and dissolve them in 200ml deionized water. Under stirring, add them dropwise to a certain amount of silica sol aqueous solution (silica sol: water = 1:2) and stir evenly. Then, slowly add 15% ammonia water to the mixture until the solution precipitates until the pH value of the solution is maintained at around 7.0. Then, heat it to 80℃ and continue stirring and aging for 4h. Finally, filter and wash it, dry it in an oven at 110℃ for 24h, and calcine it at 400℃ in a muffle furnace for 4h to obtain Cu-Ni / SiO2 catalyst F, in which the Cu content is 10.0wt% and the Ni content is 1.0wt%.

[0045] Comparative Example 3

[0046] Take 7.61g Cu(NO3)2·3H2O and dissolve it in 200ml deionized water. Under stirring, add it dropwise to a certain amount of silica sol aqueous solution (silica sol: water = 1:2) and stir evenly. Then slowly add 15% ammonia water into the mixture until the solution precipitates until the pH value of the solution is maintained at around 7.0. Then heat it to 80℃ and continue stirring and aging for 4h. Finally, filter and wash it, dry it in an oven at 110℃ for 24h, and calcine it at 400℃ in a muffle furnace for 4h to obtain the Cu / SiO2 sample.

[0047] Take 0.91g Zn(NO3)2·6H2O and dissolve it in 50ml deionized water. Add the Cu / SiO2 sample to the solution, stir it evenly and soak it for 4h. Then, dry it in an oven at 110℃ for 24h and calcine it in a muffle furnace at 450℃ for 4h to obtain Cu-Zn / SiO2 catalyst G, in which the Cu content is 10.0wt% and the Zn content is 1.0wt%.

[0048] The prepared catalyst AG was used in the experiment of ethanol dehydrogenation to acetaldehyde. The activity of the catalyst was evaluated using a fixed-bed continuous flow reactor. The inner diameter of the reaction tube was 1.2 cm, and 5 ml of catalyst was loaded. Quartz sand was loaded into the upper and lower ends of the catalyst for uniform distribution of the gas. Before the reaction, the catalyst was reduced by programmed temperature increase in a 5% H2-N2 atmosphere, and the temperature was increased to 300°C at a heating rate of 1°C / min for 4 hours. After the reduction, the reducing gas was switched to carrier N2, and 95% aqueous ethanol, a liquid raw material, was injected into the reactor at a certain flow rate. The reaction pressure was 1.0 MPa, the reaction temperature was 220°C, and the gas space velocity was 9500h -1 , liquid hourly space velocity is 2.4h -1 The dehydrogenation reaction was carried out under the conditions of , and after the system was stable, samples were taken for quantitative analysis by chromatography to calculate the dehydrogenation activity of the catalyst.

[0049] The performance test results of the embodiments are listed in Table 1. In addition, the stability test of the dehydrogenation of acetaldehyde of some catalysts is shown in the attached table. Figure 1 and 2 shown.

[0050] Table 1 Catalyst activity test results of the examples

[0051] catalyst Ethanol conversion rate% Acetaldehyde selectivity% <![CDATA[CH4选择性%]]> A 30.16％ 94.33％ 0.28％ B 35.44％ 93.03％ 0.76％ C 34.95％ 93.73％ 0.46％ D 37.25％ 92.76％ 0.54％ E 25.18％ 94.15％ 0.05％ F 35.83％ 86.73％ 8.63％ G 24.74％ 94.21％ 0.06％

[0052] As can be seen from the experimental results in Table 1, the catalysts AD prepared by the present invention have a high ethanol conversion rate (under these reaction conditions, the theoretical equilibrium conversion rate of the ethanol dehydrogenation reaction is 43%) and a high acetaldehyde selectivity at a reaction temperature of 220°C and 1 MPa. The selectivity of acetaldehyde is maintained at above 92%. In addition, with the increase of Cu content, the ethanol conversion rate gradually increases, while the acetaldehyde selectivity decreases slightly. Figure 1 The catalyst activity data of catalyst C during long-term operation are shown in Table 1. Compared with catalysts EG, catalyst E without Ni has higher acetaldehyde selectivity, but the stability of the catalyst is poor ( Figure 2 As shown in the figure), after adding Ni (catalyst F), the conversion rate of ethanol is significantly improved, but the selectivity of acetaldehyde is significantly reduced; the addition of the auxiliary agent Zn has little effect on the activity of the catalyst (catalyst G).

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A Cu-Ni-Zn / SiO2 catalyst for ethanol dehydrogenation to acetaldehyde in a catalytic reaction of ethanol dehydrogenation to produce acetaldehyde, characterized in that: The catalyst uses silicon dioxide as a carrier, Cu as an active component, and a small amount of Ni and Zn as additives; the loading amount of the active component copper element in the catalyst is 2.0-25wt%, the loading amounts of the additive nickel and zinc elements in the catalyst are 0.02wt%-2.0wt% and 0.01wt%-1.0wt%, respectively, and the balance is the carrier, and the total mass percentage is 100%; The preparation method of the catalyst comprises the following steps: (1) Under stirring, add the soluble salt solution of Cu and Ni to the silica sol aqueous solution of a certain concentration and stir evenly; (2) adding a certain concentration of ammonia solution to the mixed solution obtained in step (1), adjusting the pH value of the solution, causing precipitation in the solution to obtain a slurry; (3) heating and aging the slurry obtained in step (2), filtering, washing, drying, and calcining to obtain a Cu-Ni / SiO2 sample; (4) A soluble salt solution of Zn is impregnated on the Cu-Ni / SiO2 sample, and then dried and calcined to obtain the catalyst Cu-Ni-Zn / SiO2.

2. The use according to claim 1, characterized in that: In the step (1), the soluble Cu salt and Ni salt are respectively one of Cu(NO3)2 and Ni(NO3)2 and their hydrates; in the step (4), the soluble Zn salt is one of Zn(NO3)2 and its hydrates.

3. The use according to claim 1, characterized in that: In the step (1), the silica sol aqueous solution is a solution obtained by mixing silica sol solution and water in a mass ratio of 1:0-1:20; in the step (2), the mass concentration of ammonia water is 2wt%-25wt%, and the pH of the solution is 6.5-8.

0.

4. The use according to claim 1, characterized in that: In the step (3), the aging temperature is maintained at 50-90° C., and the aging time is 4-12 hours; the drying temperature is 50-200° C., and the drying time is 4-48 hours; the roasting temperature is 300-500° C., and the roasting time is 4-24 hours.

5. The use according to claim 1, characterized in that: In the step (4), the drying temperature is 50-200° C., the drying time is 4-48 hours, the roasting temperature is 300-500° C., and the roasting time is 4-24 hours.

6. The use according to claim 1, characterized in that The catalyst is used in a reactor for catalytic dehydrogenation of ethanol to produce acetaldehyde. The reaction uses a fixed bed as a reactor. The application method includes the following steps: (1) The Cu-Ni-Zn / SiO2 catalyst is filled in a fixed bed and reduced with a hydrogen-nitrogen mixed gas having a volume content of 5%-20% at a reduction temperature of 250-500°C for a reduction time of 4-24 hours; (2) After reduction, the temperature is lowered to the reaction temperature, nitrogen is introduced, and ethanol solution is pumped in to carry out the reaction.

7. The use according to claim 6, characterized in that: In step (2), the mass space velocity of ethanol is 0.1-4h-1; the volume space velocity of nitrogen is 2000-12000h-1.

8. The use according to claim 6, characterized in that: In step (2), the reaction pressure is normal pressure-1.0 MPa, and the reaction temperature is 200-300°C.

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