Method for preparing isopentaldehyde by oxygen-free dehydrogenation of isopentyl alcohol catalyzed by zinc oxide-based catalyst

Abstract

This invention discloses a method for the oxygen-free dehydrogenation of isopentyl alcohol to isopentylaldehyde catalyzed by a zinc oxide-based catalyst, comprising: catalyzing the oxygen-free dehydrogenation of isopentyl alcohol in an inert atmosphere using a zinc oxide-based catalyst to generate isopentylaldehyde; the zinc oxide-based catalyst includes a support and zinc oxide supported on the support; the support is hydroxyapatite. This invention uses a zinc oxide-based catalyst, ensuring the stability of the active components of the catalyst during the oxygen-free dehydrogenation of isopentyl alcohol to isopentylaldehyde, preventing sintering, reduction, and loss. The method of this invention is simple to operate and economically efficient. The catalyst is green and efficient, suitable for the oxygen-free dehydrogenation of isopentyl alcohol, and conducive to large-scale production, showing good industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of heterogeneous catalysis technology, specifically to a method for preparing isopentaldehyde by catalyzing the oxygen-free dehydrogenation of isopentyl alcohol using a zinc oxide-based catalyst. Background Technology

[0002] Isovaleraldehyde is a multifunctional chemical product. It is itself an edible flavoring agent used in the formulation of various fruit-based flavorings. Furthermore, it is an important raw material for many pharmaceutical intermediates. With the development of processes for using isovaleraldehyde in the preparation of isophytol, an important intermediate for vitamin E, the demand for isovaleraldehyde continues to increase.

[0003] Traditional processes for preparing isopentaldehyde include: ① Liquid-phase oxidation of isopentyl alcohol, using catalysts such as sulfuric acid and dichromate, which suffers from significant environmental pollution and numerous side reactions. ② Hydroformylation of olefins, using isobutylene and syngas to produce isopentaldehyde. The catalyst used is a rhodium complex formed by the combination of a bisphosphite ligand and metallic rhodium. This catalyst is costly and difficult to recycle. Furthermore, the high temperature and pressure conditions place high demands on equipment, and auxiliary safety measures are complex. ③ Gas-phase dehydrogenation of isopentyl alcohol, using a dehydrogenation catalyst to catalyze the one-step dehydrogenation of gas-phase isopentyl alcohol to produce isopentaldehyde. This method offers high atom economy, meets the requirements of green chemistry, and has promising application prospects.

[0004] Currently, most reported gas-phase dehydrogenation catalysts for isoamyl alcohol are copper-based. While copper-based catalysts exhibit good dehydrogenation performance, the active component copper has a low Taman temperature (405℃), making it prone to sintering at high temperatures. This results in poor catalyst stability and easy deactivation. Chinese patent CN1261399C mentions a method for catalyzing the oxidation of isoamyl alcohol to isopentaldehyde using brass-based catalysts. This method uses copper-zinc, copper-nickel, or copper-tin alloys as catalysts. These catalysts have a very small active surface area per unit mass, resulting in very low activity and a reaction space velocity of only 0.3-0.5 h⁻¹. -1 Furthermore, the conversion rate is low at low temperatures, requiring reaction temperatures above 400℃, and the catalyst is prone to sintering and carbon deposition at high temperatures. Chinese patent application CN111718247A uses porous organometallic copper as a catalyst to catalyze the gas-phase oxidative dehydrogenation of isopentyl alcohol to prepare isopentyl aldehyde. This catalyst preparation process uses organic ligands, is complex, and costly. In addition, the active metal of the catalyst forms chelates with organic matter in ionic form, resulting in low tolerance to reaction temperatures. At lower reaction temperatures, the volume hourly space velocity (VHSV) of isopentyl alcohol is low (1.0 h⁻¹). -1 The low efficiency is not conducive to large-scale industrial production.

[0005] Furthermore, Chinese patent applications CN106117024A and CN106008180A mention the use of mixed metal oxides as catalysts. The catalytic dehydrogenation reaction temperature is 800℃ or 500℃. At high reaction temperatures, the acid-base sites on the mixed metal oxides catalyze various side reactions, resulting in low selectivity for isovaleraldehyde and requiring complex post-treatment.

[0006] In view of the shortcomings of the above-mentioned process and catalyst preparation, there is an urgent need to develop a new method for the gas-phase dehydrogenation of isopentyl alcohol to prepare isopentyl aldehyde, so as to overcome the problems of high catalyst production cost, easy deactivation, low yield, low product selectivity and serious environmental pollution in the current production. Summary of the Invention

[0007] To address the aforementioned technical problems and shortcomings in the field, this invention provides a method for the preparation of isopentaldehyde by the oxygen-free dehydrogenation of isopentol using a zinc oxide-based catalyst. The zinc oxide-based catalyst, which has only zinc oxide as an active component, can catalyze the oxygen-free dehydrogenation of isopentol to produce isopentaldehyde with high selectivity and high stability.

[0008] A method for preparing isopentaldehyde by catalytic dehydrogenation of isopentyl alcohol using a zinc oxide-based catalyst includes: catalyzing the dehydrogenation of isopentyl alcohol in an inert atmosphere using a zinc oxide-based catalyst to generate isopentaldehyde;

[0009] The zinc oxide-based catalyst comprises a support and zinc oxide supported on the support;

[0010] The carrier is hydroxyapatite.

[0011] The zinc oxide-based catalyst can be loaded onto a hydroxyapatite support by means of ammonia distillation or precipitation.

[0012] The zinc oxide-based catalyst may contain zinc oxide nanoparticles. Furthermore, the average particle size of the zinc oxide nanoparticles may be 1–5 nm. Zinc oxide-based catalysts within this particle size range exhibit superior catalytic activity and isovaleraldehyde selectivity when used for the anaerobic dehydrogenation of isopentyl alcohol to isovaleraldehyde.

[0013] In a preferred embodiment, the preparation method of the zinc oxide-based catalyst includes: using ammonia water as a precipitant, adding excess ammonia water and hydroxyapatite to an aqueous solution containing soluble zinc salt, stirring the reaction at 75-85°C, preferably 80°C, separating the solid and liquid after the reaction, washing and drying the solid, and calcining it at 390-410°C, preferably 400°C, to obtain the zinc oxide-based catalyst. The zinc oxide-based catalyst prepared using ammonia water as a precipitant exhibits superior catalytic activity and isopentaldehyde selectivity when used to catalyze the oxygen-free dehydrogenation of isopentyl alcohol to isopentaldehyde.

[0014] In the preparation method of the zinc oxide-based catalyst, excess ammonia water can be added to an aqueous solution containing soluble zinc salt and stirred for 5 to 15 minutes before adding hydroxyapatite.

[0015] In the preparation method of the zinc oxide-based catalyst, the concentration of NH3 in the ammonia water can be 25wt% to 28wt%.

[0016] In the preparation method of the zinc oxide-based catalyst, the soluble zinc salt may be at least one of zinc nitrate, zinc sulfate, zinc chloride, and zinc acetate.

[0017] In the preparation method of the zinc oxide-based catalyst, the stirring reaction time can be 5 to 7 hours, and more specifically 6 hours.

[0018] In the preparation method of the zinc oxide-based catalyst, the calcination time can be 2 to 4 hours, and more specifically 3 hours.

[0019] The zinc oxide-based catalyst may contain only zinc oxide as an active component. Further, the zinc oxide-based catalyst may be composed of hydroxyapatite and zinc oxide.

[0020] The zinc content in the zinc oxide-based catalyst can be 1wt% to 30wt%, further 3wt% to 15wt%, and even further 7wt% to 15wt%. At this content, the catalyst can simultaneously exhibit excellent catalytic activity and isovaleraldehyde selectivity.

[0021] The method for preparing isopentaldehyde by catalytic dehydrogenation of isopentyl alcohol using zinc oxide-based catalyst can employ one or more combinations of fixed-bed reactors and trickle-bed reactors.

[0022] The method for preparing isovaleraldehyde by catalytic dehydrogenation of isopentyl alcohol using the zinc oxide-based catalyst described above, wherein the temperature of the anaerobic dehydrogenation reaction can be 240–360°C, and more specifically 330–360°C. At this temperature, the catalyst can simultaneously exhibit excellent catalytic activity and isovaleraldehyde selectivity.

[0023] The method for preparing isopentaldehyde by catalytic dehydrogenation of isopentyl alcohol using a zinc oxide-based catalyst can be carried out at atmospheric pressure.

[0024] The method for preparing isopentaldehyde by catalytic anaerobic dehydrogenation of isopentyl alcohol using a zinc oxide-based catalyst, wherein the weight hourly space velocity of the anaerobic dehydrogenation reaction can be 2–35 h⁻¹. -1 Further, it can be 5-15 hours. -1 Furthermore, it can be 9.6–15 hours. -1 The catalyst exhibits both excellent catalytic activity and isovaleraldehyde selectivity at this gravity hourly space velocity.

[0025] The inert atmosphere described in this invention refers to an atmosphere that does not participate in or affect the oxygen-free dehydrogenation reaction, specifically a nitrogen atmosphere and / or a rare gas atmosphere (such as argon, helium, etc.).

[0026] As a general inventive concept, the present invention also provides the application of the zinc oxide-based catalyst in the catalytic oxygen-free dehydrogenation of isopentyl alcohol to isopentylaldehyde.

[0027] The zinc oxide-based catalyst of the present invention has the following characteristics:

[0028] 1) The catalyst support hydroxyapatite itself has good stability and can maintain the stability of the catalyst structure at the reaction temperature. Calcium ions on hydroxyapatite can undergo ion exchange reactions with zinc ions, and the hydroxyl groups on hydroxyapatite are conducive to the adsorption of zinc ions. This promotes the uniform distribution of zinc ions on the catalyst support, which is beneficial for the formation of uniformly distributed zinc oxide nanoparticles (1-5 nm) after calcination.

[0029] 2) The active component of the catalyst, zinc oxide, exhibits good stability. At the reaction temperature, zinc oxide is not easily sintered at high temperatures to form large-sized zinc oxide particles, nor is it easily reduced to elemental zinc at high temperatures, thus maintaining the stability of the active centers.

[0030] 3) Hydroxyapatite alone has very low activity; the main reactions that occur are side reactions catalyzed by its acid-base sites, leading to isopentaldehyde with very low selectivity. In the preparation of zinc oxide-based catalysts, by loading zinc ions onto hydroxyapatite, the acidity and basicity of the catalyst are effectively adjusted, side reactions are suppressed, the selectivity of isopentaldehyde is effectively improved, and carbon deposition is reduced.

[0031] Compared with the prior art, the beneficial effects of this invention are as follows:

[0032] This invention employs a zinc oxide-based catalyst, ensuring the stability of the active components in the oxygen-free dehydrogenation of isopentyl alcohol to isopentaldehyde, preventing sintering, reduction, and loss. The method is simple to operate and economically efficient. The catalyst is green and highly efficient, making it suitable for large-scale production and demonstrating promising industrial application prospects.

[0033] The catalyst support hydroxyapatite itself possesses excellent stability, maintaining its structural stability at high temperatures without the need for additional molecular sieves, alumina, or other forming agents. During catalyst preparation, calcium ions on the hydroxyapatite support can undergo ion exchange reactions with zinc ions, and the hydroxyl groups on the hydroxyapatite facilitate the adsorption of zinc ions, promoting a uniform distribution of zinc ions on the catalyst support. This is beneficial for the formation of uniformly distributed zinc oxide nanoparticles (1–5 nm) after calcination. The catalyst preparation process is simple and requires no complex operations.

[0034] The zinc oxide-based catalyst used in this invention has zinc oxide as its active component, exhibiting excellent stability. Compared to the copper-based catalysts used previously, it allows for higher reaction temperatures, promoting the oxygen-free dehydrogenation reaction and increasing the conversion rate of isopentyl alcohol. Furthermore, at the reaction temperature, zinc oxide is less prone to sintering or reduction at high temperatures, maintaining the stability of the active sites and preserving the high selectivity of isopentyl alcohol. The catalyst's active component is stable, has a long service life, and is beneficial for industrial production.

[0035] According to the zinc oxide-based catalyst used in this invention, during the catalyst preparation process, zinc ions are precipitated and loaded onto hydroxyapatite, effectively adjusting the catalyst's acidity and alkalinity, suppressing side reactions, effectively improving reaction selectivity, and reducing carbon deposition. In one embodiment, the catalytic dehydrogenation of isopentyl alcohol to isopentyl aldehyde exhibits high isopentyl alcohol conversion and isopentyl aldehyde selectivity.

[0036] The zinc oxide-based catalyst used in this invention maintains good activity and selectivity at higher temperatures and higher space velocities, and has a long catalyst life. The reaction, conducted in a fixed-bed or trickle-bed reactor, allows for continuous production. Compared to previous batch operations and low-temperature, low-space-velocity reaction conditions, this method is more suitable for the large-scale industrial production of isopentyl alcohol to isopentyl aldehyde. Attached Figure Description

[0037] Figure 1 The image shows the UV-Vis spectrum of the catalyst in Example 5.

[0038] Figure 2 The particle size distribution of catalyst A is shown in the high-angle annular dark-field scanning transmission (HADDF-STEM) plot.

[0039] Figure 3 The X-ray diffraction (XRD) patterns of the catalysts in Examples 6-8 are shown below.

[0040] Figure 4 This is a graph showing the yield of the catalyst at different weight space velocities in Example 10;

[0041] Figure 5 This is a graph showing the catalytic effect of the catalyst in Example 11 after 50 hours of reaction. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise specified, the ammonia water used in the following embodiments and comparative examples is commercially available concentrated ammonia water with an NH3 concentration of 25wt% to 28wt%, and the pressure of the anaerobic dehydrogenation reaction is atmospheric pressure.

[0043] Example 1

[0044] 0.6498 g of zinc nitrate hexahydrate was weighed and added to a beaker, where water was added and stirred to dissolve. 10 mL of ammonia was added and stirred for 10 min. Then, 1.6 g of hydroxyapatite was added, and the mixture was stirred at 80 °C for 6 h. After filtration and washing, the mixture was dried in an oven at 80 °C and then calcined in a muffle furnace at 400 °C for 3 h to obtain zinc oxide-based catalyst A. ICP-MS analysis showed that the zinc content was approximately 7.4%.

[0045] Example 2

[0046] 0.6498 g of zinc nitrate hexahydrate was weighed and added to a beaker, where water was added and stirred to dissolve it. Then, it was added together with a 0.5 wt% excess sodium carbonate solution to a 1.6 g hydroxyapatite dispersion. The mixture was stirred at 70 °C for 1 h, then filtered, washed, dried in an oven at 80 °C, and finally calcined in a muffle furnace at 400 °C for 3 h to obtain zinc oxide-based catalyst B. ICP-MS analysis showed that the zinc content was approximately 7.2%.

[0047] Example 3

[0048] 0.6498 g of zinc nitrate hexahydrate was weighed and added to a beaker, where water was added and stirred to dissolve. 1.6 g of hydroxyapatite was then added, and the mixture was stirred at 80 °C for 6 h. After filtration and washing, the solution was dried in an oven at 80 °C and then calcined in a muffle furnace at 400 °C for 3 h to obtain zinc oxide-based catalyst C. ICP-MS analysis showed that the zinc content was approximately 6.9%.

[0049] Example 4

[0050] 0.6498 g of zinc nitrate hexahydrate was weighed and added to a beaker, where water was added and stirred to dissolve. 1.6 g of hydroxyapatite was then added, and the mixture was stirred at 90 °C for 12 h until evaporated to dryness. The resulting product was then dried in an oven at 80 °C and calcined in a muffle furnace at 400 °C for 3 h to obtain zinc oxide-based catalyst D. ICP-MS analysis showed that the zinc content was approximately 6.5%.

[0051] Example 5

[0052] The preparation of isopentaldehyde from isopentyl alcohol using catalyst AD: The catalyst was compressed into tablets, then pulverized into 40-60 mesh particles, loaded into a fixed bed, and heated to 330℃ under nitrogen purging, with a weight hourly space velocity of 9.6 h⁻¹. -1 The reaction was initiated by pumping in isoamyl alcohol. The results are shown in Table 1.

[0053] Table 1

[0054] catalyst A B C D Isoamyl alcohol conversion rate 30％ 27％ 20％ 6％ Isovaleraldehyde selectivity 99％ 98％ 98％ 99.9％

[0055] Table 1 compares four catalysts, A, D, and E. Catalyst A uses ammonia water as a precipitant and is prepared via ammonia distillation. Catalyst B uses sodium carbonate as a precipitant and is prepared via precipitation. Catalyst C does not use a precipitant; it is prepared by the ion exchange reaction between Zn ions and Ca ions on the hydroxyapatite support, or by the adsorption of Zn ions by hydroxyl groups on the hydroxyapatite surface. Catalyst D does not use a precipitant and is prepared via impregnation. The experimental results show that the catalysts exhibit varying effects on the oxygen-free dehydrogenation of isopentyl alcohol to isopentyl aldehyde using different preparation methods. Among them, zinc oxide-based catalyst A, prepared via ammonia distillation, shows the best catalytic effect. The particle size of zinc oxide in the catalysts is analyzed using UV-Vis. Figure 1 As shown, the zinc oxide particles at 246 nm are small-diameter, those at 294 nm are larger clusters, and those at 370 nm are large-diameter zinc oxide particles. The small-diameter zinc oxide peak is more pronounced in catalyst A compared to other catalysts. Figure 2 As shown, HADDF-STEM analysis revealed that the average particle size of zinc oxide in catalyst A was approximately 1.6 nm. This indicates that small-particle-size zinc oxide has a better reaction effect on the dehydrogenation of isopentyl alcohol to prepare isopentyl aldehyde.

[0056] Examples 6-8

[0057] The effect of different metal loading on the oxygen-free dehydrogenation of isopentyl alcohol to prepare isopentyl aldehyde.

[0058] The catalyst preparation in Examples 6-8 differed from that in Example 1 only in the amount of zinc nitrate hexahydrate added, which was changed to 0.0591 g (Example 6), 0.3078 g (Example 7), and 1.462 g (Example 8), respectively. All other parameters remained the same, yielding catalysts E, F, and G, respectively. Catalyst performance was evaluated according to Example 5. The experimental results are shown in Table 2.

[0059] Table 2

[0060] catalyst A E F G Isoamyl alcohol conversion rate 30％ 15％ 29％ 32％ Isovaleraldehyde selectivity 99％ 99％ 99％ 99％

[0061] Table 2 shows the effects of different zinc oxide loadings achieved using the ammonia distillation method. The results indicate that initially, the conversion rate of isoamyl alcohol increased with increasing zinc content; however, further increases in zinc loading resulted in minimal changes in catalytic effect. XRD analysis was used to determine the crystal phase of ZnO in the catalyst. Figure 3 As shown, with the continuous increase of zinc content, obvious zinc oxide peaks appeared in the crystal phase structure of the catalyst. This indicates that with the increase of zinc content, zinc oxide nanoparticles with better crystallinity and larger particle size appeared.

[0062] Example 9

[0063] The effect of different reaction temperatures on the oxygen-free dehydrogenation of isopentyl alcohol to prepare isopentyl aldehyde.

[0064] Using the catalyst from Example 1, the catalyst performance was evaluated according to Example 5. The temperature of the oxygen-free dehydrogenation reaction was changed and raised to 240℃, 270℃, 300℃, and 360℃ under nitrogen purging, while the other temperatures remained the same. The experimental results are shown in Table 3.

[0065] Table 3

[0066] reaction temperature 240℃ 270℃ 300℃ 330℃ 360℃ Isoamyl alcohol conversion rate 3％ 5％ 12％ 30％ 50％ Isovaleraldehyde selectivity 99.9％ 99％ 99％ 99％ 98％

[0067] Table 3 shows the effect of different reaction temperatures on the preparation of isopentaldehyde from isopentyl alcohol via oxygen-free dehydrogenation. The results indicate that the conversion rate of isopentyl alcohol increases with increasing reaction temperature, while isopentyl alcohol maintains high selectivity.

[0068] Example 10

[0069] Effect of different weight hourly space velocities on the oxygen-free dehydrogenation of isopentyl alcohol to prepare isopentyl aldehyde.

[0070] The catalyst from Example 1 was used, and its performance was evaluated according to Example 5, by varying the heavy hourly space velocity (WHV) to 2.2 h⁻¹. -1 5.4h -1 15h -1 19.4h -1 24.6h -1 30.2h -1 The rest are the same. The results are shown in Table 4.

[0071] Table 4

[0072] Heavy space speed <![CDATA[2.2h -1 ]]> <![CDATA[5.4h -1 ]]> <![CDATA[9.6h -1 ]]> <![CDATA[15h -1 ]]> <![CDATA[19.4h -1 ]]> <![CDATA[25.4h -1 ]]> <![CDATA[30.2h -1 ]]> Isoamyl alcohol conversion rate 59％ 39％ 30％ 27％ 22％ 19％ 16％ Isovaleraldehyde selectivity 96％ 98％ 99％ 99％ 99％ 99％ 99％

[0073] Table 4 shows the effect of different weight hourly space velocities on the oxygen-free dehydrogenation of isopentyl alcohol to isopentylaldehyde. The results show that although the conversion rate of isopentyl alcohol decreases continuously with increasing weight hourly space velocity, the yield of isopentylaldehyde increases. Figure 4As shown in the figure, this result indicates that with increasing gravity hourly space velocity, the catalyst of this invention can process more isopentyl alcohol and generate more isopentyl aldehyde, and the amount of isopentyl aldehyde generated per unit time is increasing, indicating that the catalyst of this invention has great catalytic activity potential.

[0074] Example 11

[0075] Catalyst A was subjected to a long-term experiment under the test conditions of Example 5, at a temperature of 330°C and a liquid weight hourly space velocity of 9.6 h⁻¹. -1 It runs continuously for 50 hours.

[0076] The results are as follows Figure 5 As shown, catalyst A can maintain an isopentyl alcohol conversion rate of about 30% and an isopentyl aldehyde selectivity of 99% within 50 hours, indicating that zinc oxide-based catalyst A can still maintain high selectivity and high stability at high space velocities.

[0077] Comparative Example 1

[0078] The catalyst was evaluated using hydroxyapatite as a support, according to Example 5.

[0079] According to the test results, the conversion rate of isoamyl alcohol in this comparative example was about 6%, and the selectivity of isoamyl aldehyde was 13%.

[0080] Hydroxyapatite as a standalone carrier has certain acidity and alkalinity, which can catalyze the side reaction of isopentyl alcohol at high temperatures, resulting in very low selectivity for isopentyl aldehyde.

[0081] Comparative Example 2

[0082] According to Example 2, zinc oxide was prepared using sodium carbonate as a precipitant without bulk hydroxyapatite, and its catalyst performance was evaluated according to Example 5.

[0083] According to the test results, the conversion rate of isoamyl alcohol in this comparative example was approximately 10%, and the selectivity of isoamyl aldehyde was 91%.

[0084] Zinc oxide prepared by precipitation is in the form of large-sized zinc oxide particles, which have low activity for the oxygen-free dehydrogenation of isopentyl alcohol to isopentyl aldehyde. In addition, the large-sized zinc oxide also has certain acidity and alkalinity, which may lead to certain side reactions.

[0085] Comparative Example 3

[0086] Different catalyst supports were selected: SiO2, MgO, Al2O3 and ZrO2, which replaced hydroxyapatite by equal mass. Catalyst HK was prepared using the catalyst preparation conditions of Example 1. It was applied to the oxygen-free dehydrogenation of isopentyl alcohol to prepare isopentyl aldehyde. The reaction conditions were the same as in Example 5. The results are shown in Table 5.

[0087] Table 5

[0088] catalyst H I J K carrier <![CDATA[SiO2]]> MgO <![CDATA[Al2O3]]> <![CDATA[ZrO2]]> Isoamyl alcohol conversion rate 14％ 2％ 14％ 4％ Isovaleraldehyde selectivity 28％ 99％ 35％ 96％

[0089] Table 5 shows that different catalyst supports exhibit significant differences in the oxygen-free dehydrogenation of isopentyl alcohol to isopentylaldehyde catalyzed by zinc oxide-based catalysts. Specifically, the acidic supports SiO2 and Al2O3 can catalyze other side reactions of isopentyl alcohol at the reaction temperature, resulting in very low selectivity for isopentylaldehyde. While the weakly basic supports MgO and ZrO2, although exhibiting fewer side reactions compared to acidic supports, still result in very low catalyst activity at the reaction temperature.

[0090] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing isopentaldehyde by oxygen-free dehydrogenation of isopentyl alcohol catalyzed by a zinc oxide-based catalyst, characterized in that, include: An oxygen-free dehydrogenation reaction of isoamyl alcohol to isovaleraldehyde was catalyzed by a zinc oxide-based catalyst in an inert atmosphere; the temperature of the oxygen-free dehydrogenation reaction was 330–360 °C; the pressure of the oxygen-free dehydrogenation reaction was atmospheric pressure; and the weight hourly space velocity of the oxygen-free dehydrogenation reaction was 5–15 h⁻¹. -1 ; The zinc oxide-based catalyst comprises a support and zinc oxide supported on the support; the zinc oxide-based catalyst has only zinc oxide as an active component. The zinc oxide is zinc oxide nanoparticles with an average particle size of 1-5 nm. The carrier is hydroxyapatite; The preparation method of the zinc oxide-based catalyst includes: using ammonia water as a precipitant, adding excess ammonia water to an aqueous solution containing soluble zinc salt and stirring for 5-15 minutes, then adding hydroxyapatite, stirring and reacting at 75-85°C, separating the solid and liquid after the reaction, taking the solid, washing and drying it, and calcining it at 390-410°C to obtain the zinc oxide-based catalyst; the soluble zinc salt is at least one of zinc nitrate, zinc sulfate, zinc chloride, and zinc acetate; the calcination time is 2-4 hours.

2. The method for preparing isopentaldehyde by oxygen-free dehydrogenation of isopentyl alcohol catalyzed by the zinc oxide-based catalyst according to claim 1, characterized in that, In the preparation method of the zinc oxide-based catalyst: The concentration of NH3 in the ammonia water is 25wt% to 28wt%. Stirred reaction at 80℃; The stirring reaction time is 5 to 7 hours; Calcination at 400℃.

3. The method for preparing isopentaldehyde by catalytic oxygen-free dehydrogenation of isopentyl alcohol using a zinc oxide-based catalyst according to claim 2, characterized in that, In the preparation method of the zinc oxide-based catalyst: The stirring reaction time is 6 hours; The roasting time is 3 hours.

4. The method for preparing isopentaldehyde by oxygen-free dehydrogenation of isopentyl alcohol catalyzed by the zinc oxide-based catalyst according to claim 1, characterized in that, The zinc oxide-based catalyst is composed of hydroxyapatite and zinc oxide; The zinc content in the zinc oxide-based catalyst is 1 wt% to 30 wt%.

5. The method for preparing isopentaldehyde by oxygen-free dehydrogenation of isopentyl alcohol catalyzed by the zinc oxide-based catalyst according to claim 1, characterized in that, The zinc content in the zinc oxide-based catalyst is 3 wt% to 15 wt%.

6. The method for preparing isopentaldehyde by catalytic oxygen-free dehydrogenation of isopentyl alcohol using a zinc oxide-based catalyst according to claim 5, characterized in that, The zinc content in the zinc oxide-based catalyst is 7wt% to 15wt%.

7. The method for preparing isopentaldehyde by oxygen-free dehydrogenation of isopentyl alcohol catalyzed by the zinc oxide-based catalyst according to claim 1, characterized in that, The weight hourly space velocity (WHSV) of the oxygen-free dehydrogenation reaction is 9.6–15 h⁻¹. -1 .

8. The method for preparing isopentaldehyde by oxygen-free dehydrogenation of isopentyl alcohol catalyzed by the zinc oxide-based catalyst according to claim 1, characterized in that, The inert atmosphere is a nitrogen atmosphere and / or a rare gas atmosphere.

9. The method for preparing isopentaldehyde by oxygen-free dehydrogenation of isopentyl alcohol catalyzed by the zinc oxide-based catalyst according to claim 1, characterized in that, The method for preparing isopentaldehyde by catalytic dehydrogenation of isopentyl alcohol using zinc oxide-based catalyst employs one or more combinations of fixed-bed reactors and trickle-bed reactors.

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