Process for the preparation of isooctyl aldehyde by selective hydrogenation of isooctene aldehyde

Abstract

The present application belongs to the technical field of catalytic hydrogenation, and relates to a method for preparing iso-octyl aldehyde by selectively hydrogenating iso-octyl aldehyde. The iso-octyl aldehyde, hydrogen and a nickel catalyst are subjected to a contact reaction. The nickel catalyst comprises an alumina carrier and an active component nickel dispersed on the alumina carrier. The alumina carrier is prepared by using a rotary strengthening device, and the preparation comprises the following steps: an aluminum sulfate solution and an aluminum hydroxide-sodium hydroxide mixed solution are jointly pumped into a rotary strengthening reactor by using a liquid pump to form a slurry; the slurry is sprayed into the inside of a wire mesh packing through a solution mixing distributor, and the rotary wire mesh packing shears the slurry into small units; the small units are introduced into a crystallization kettle through the outlet of the rotary strengthening reactor to perform crystallization to obtain crystallized materials, and after filtration, washing and drying, the materials are calcined to obtain the alumina carrier. The present application uses commonly used industrial nickel components and alumina carriers, the reaction condition is mild, the selectivity of iso-octyl aldehyde is high, and the present application has certain industrial application prospects.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalytic hydrogenation, and particularly relates to a method for preparing iso-octyl aldehyde by selectively hydrogenating iso-octyl aldehyde. BACKGROUND

[0002] 2-ethylhexanal (industrial iso-octyl aldehyde) is an important chemical intermediate, which can be oxidized to iso-octanoic acid to be used as a coating and resin modifier, and can be reduced to octanol to be used for producing plasticizer dioctyl phthalate (DOP). Meanwhile, iso-octyl aldehyde is also a flavor additive used for toilet soap and synthetic detergent.

[0003] At present, the preparation of iso-octyl aldehyde in industry mainly has propylene carbonyl synthesis method and acetaldehyde aldol condensation method. The propylene carbonyl synthesis method is to obtain butyl aldehyde from propylene and synthesis gas under the action of a cobalt or ruthenium catalyst, and then to obtain 2-ethyl-2-hexenal (industrial iso-octyl aldehyde) by condensation and dehydration, and finally to obtain iso-octyl aldehyde by selective hydrogenation. The acetaldehyde aldol condensation method is to obtain butyl aldehyde from acetaldehyde by condensation, dehydration and hydrogenation, and the subsequent process is consistent with the propylene carbonyl synthesis method. In the preparation process of iso-octyl aldehyde, the selective hydrogenation of iso-octyl aldehyde is a key process. However, it is still difficult and challenging to selectively hydrogenate iso-octyl aldehyde to obtain saturated octyl aldehyde, because the iso-octyl aldehyde molecule contains C=O bond and C=C bond at the same time, from the thermodynamic point of view, the bond energy of C=O bond is 715 KJ / mol, the bond energy of C=C bond is 615 KJ / mol, and they have conjugation effect; and from the kinetic point of view, it is difficult to hydrogenate only the C=C bond without hydrogenating the C=O bond.

[0004] The noble metal palladium is a commonly used noble metal hydrogenation active component in industry, and due to its special valence electron structure, it has excellent catalytic hydrogenation activity.

[0005] However, the carriers of the palladium catalyst in the prior art are mostly inorganic carriers, mainly alumina. In US4018831A, a Pd-Ni / Al2O3 catalyst is used, and iso-octyl aldehyde is prepared by catalytic hydrogenation at 90-180 ℃ and 0.7-3.5 MPa pressure, with a space velocity of 0.5-3 and a hydrogen / oil ratio of 2:1-3:1 (mol / mol). By controlling the hydrogen flow and reaction conditions, the liquid phase flows through the catalyst bed, which improves the selectivity of the target product and reduces the generation of by-product iso-octanol. However, the iso-octyl aldehyde conversion rate is 74%, the iso-octyl aldehyde selectivity is 97.5%, and the overall yield of the target product is low.

[0006] CN107930647B discloses a catalyst using Al2O3 as a carrier and loaded with Pd, Ag, and one or two of Co and Rh, wherein the Pd content is 0.01-1.0 wt%, and the total content of Ag, Co, and Rh is 0.01-0.5 wt‰. Under conditions of a temperature of 180-220°C, a pressure of 0.5-2 MPa, a space velocity of 30 g / (g·h), and a molar ratio of hydrogen to aldehyde groups of 2-15:1 based on the total mass of the vaporized portion of isooctylaldehyde, the conversion rate of isooctylaldehyde can reach 99%, and the selectivity for isooctylaldehyde can also reach 99%. However, the catalyst is used in a gas-phase reaction, and the reaction temperature is too high.

[0007] CN201811205777.6 discloses a Pd-polymer composite catalyst that exhibits high conversion and selectivity for the selective hydrogenation of isooctylaldehyde to isooctylaldehyde. However, the polymer carrier has limited application, and the use of palladium, a precious metal, is expensive, and therefore has no industrial application prospects.

[0008] Metal Ni catalyst is a widely used hydrogenation catalyst in the oil refining and chemical industries. However, the high activity of Ni catalyst can easily lead to the complete hydrogenation of unsaturated aldehydes to form saturated alcohols, resulting in a low yield of saturated aldehydes.

[0009] GB 1102796A discloses a Ni / diatomaceous earth catalyst that uses sulfide to partially poison the Ni catalyst to improve selectivity for saturated aldehydes. When used in the hydrogenation of isooctenal, this catalyst achieves a conversion of 98% and a selectivity of 97%. However, this reaction is a vapor-phase hydrogenation reaction, requiring a relatively high temperature of 225°C and resulting in the side reaction of raw material cracking.

[0010] CN202011152640.6 discloses a sulfur-doped carbon-supported nickel-based catalyst. The carrier carbon is obtained by polymer carbonization, and the doped sulfur element is obtained by decomposing the crosslinking agent sulfuric acid. The sulfur poisons the nickel in the catalyst, improving the selectivity of isooctylaldehyde to as high as approximately 90%. However, the carbonization of the polymer generates large amounts of alkanes and tar, which consumes a lot of energy and is highly polluting, making it unsuitable for industrial application.

[0011] CN114082421A discloses an alumina-supported nickel catalyst having high activity in the octenal hydrogenation reaction, with the octenal conversion rate reaching 100% and the octanal yield reaching 98%, but the reaction temperature needs to be 100°C.

[0012] In summary, the catalysts in the prior art need to be subjected to high temperature conditions to achieve the purpose of high isooctyl aldehyde selectivity. There is an urgent need to provide a catalyst with high isooctyl aldehyde selectivity and mild reaction conditions. Summary of the Invention

[0013] To solve the problems encountered in the prior art, the present invention provides a method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde. The method has mild reaction conditions, high isooctyl aldehyde selectivity, and uses commonly used nickel components and alumina carriers in industry, thus having certain industrial application prospects.

[0014] In order to achieve the above object, the present invention provides a method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde, wherein isooctyl aldehyde, hydrogen and a nickel catalyst are contacted and reacted, wherein the nickel catalyst comprises a carrier alumina and an active component nickel dispersed thereon;

[0015] The preparation method of the carrier alumina is carried out using a rotary strengthening device, which includes: a rotary strengthening reactor, at least two liquid pumps, a crystallization kettle and a motor;

[0016] The rotary intensified reactor comprises a rotary intensified reaction device shell, a wire mesh filler, and a solution mixing and distributing device. The wire mesh filler is located inside the rotary intensified reaction device shell, and a certain space is formed inside the wire mesh filler. The solution mixing and distributing device is placed in the space. The motor is connected to the wire mesh filler.

[0017] The liquid pump is provided with a liquid pump discharge pipeline, the rotary enhanced reaction device housing is provided with a rotary enhanced reactor inlet and a rotary enhanced reactor outlet, the liquid pump discharge pipeline is connected to the solution mixing distributor through the rotary enhanced reactor inlet, and the rotary enhanced reactor outlet is connected to the crystallization kettle;

[0018] The steps include:

[0019] (1) using a liquid pump to pump the aluminum sulfate solution and the aluminum hydroxide-sodium hydroxide mixed solution into the rotary enhanced reactor from the inlet of the rotary enhanced reactor to form a suspension;

[0020] (2) spraying the suspension into the inner side of the wire mesh filler through a solution mixing distributor, and rotating the wire mesh filler driven by a motor to shear the suspension into small units;

[0021] (3) The micro-units obtained in step (2) are passed through the outlet of the rotary intensified reactor into a crystallization kettle for crystallization to obtain a crystallized material. The crystallized material is filtered, washed, dried, and then calcined to obtain the alumina carrier.

[0022] In the present invention, the preparation method of the carrier alumina is as follows Figure 1The shown rotating intensified impregnation equipment diagram is carried out, in the intensified hydrolysis process, the reaction liquid is dispersed into fine droplets and liquid membranes on the high-speed rotating wire mesh, the microenvironment of the precipitation reaction is more uniform, and thus the crystal seed with uniform size is obtained. After crystallization and calcination, the carrier alumina with stable structure and performance is obtained.

[0023] According to the present application, preferably, the concentration of the aluminum sulfate solution is 0.5-2 mol / L.

[0024] According to the present application, preferably, the concentration of the aluminum hydroxide in the aluminum hydroxide-sodium hydroxide mixed solution is 0.5-1 mol / L, and the concentration of the sodium hydroxide is 1-1.5 mol / L.

[0025] According to the present application, preferably, the flow ratio of the aluminum sulfate solution to the aluminum hydroxide-sodium hydroxide mixed solution is 1:(0.5-2).

[0026] According to the present application, preferably, in step (2), the rotating speed of the wire mesh packing is 2800-3200 rpm.

[0027] According to the present application, preferably, in step (3), the crystallization conditions include: temperature 60-100℃, time 2-24h.

[0028] According to the present application, preferably, the drying conditions include: temperature 60-120℃, time 4-12h.

[0029] According to the present application, preferably, the calcination conditions include: temperature 400-800℃, time 4-8h.

[0030] According to the present application, preferably, the alumina carrier has the following characteristics: specific surface area 300-800m 2 / g, preferably 400-700m 2 / g, average pore size 10-40nm, preferably 20-35nm.

[0031] According to the present application, preferably, the preparation method of the nickel catalyst comprises the following steps:

[0032] a) using the excess impregnation method to immerse the carrier alumina into the nickel salt solution, to obtain the carrier alumina impregnated with the nickel salt solution;

[0033] b) directly drying and calcining the carrier alumina impregnated with the nickel salt solution obtained in step a), to obtain the nickel catalyst.

[0034] In the present application, step a) is only carried out once, and the carrier alumina impregnated with the nickel salt solution is directly dried and calcined to obtain the nickel catalyst.

[0035] According to the present invention, preferably, in step (a), the nickel salt solution is a water-soluble nickel salt solution, preferably at least one of a nickel nitrate solution, a nickel carbonate solution and a nickel sulfate solution.

[0036] According to the present invention, preferably, the concentration of the nickel salt solution is 3-5 mol / L, and the immersion time is 30-120 min.

[0037] According to the present invention, preferably, in step (b), the drying conditions include: a temperature of 110-130° C. and a drying time of 4-12 h.

[0038] According to the present invention, preferably, the calcination conditions include: a temperature of 600-800° C. and a time of 4-8 hours.

[0039] According to the present invention, preferably, based on the total weight of the nickel catalyst, the content of the active component nickel is 30-70 wt%, preferably 40-60 wt%, and the content of the carrier alumina is 30-70 wt%, preferably 40-60 wt%.

[0040] According to the present invention, preferably, the contact reaction conditions include: hydrogen pressure 1-10 MPa, reaction temperature 40-60°C.

[0041] The invention uses nickel components and alumina carrier commonly used in industry, has mild reaction conditions, high selectivity of isooctyl aldehyde, and has certain industrial application prospects.

[0042] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0044] Figure 1 Schematic diagram of the rotary strengthening equipment.

[0045] Description of Reference Numerals

[0046] 1-1. Aluminum sulfate solution; 1-2. Aluminum hydroxide-sodium hydroxide mixture; 1-3, 1-4. Liquid pumps; 1-5. Solution mixing distributor; 1-6. Wire mesh filler; 1-7. Rotary intensified reaction device housing; 1-8. Reactant outlet; 1-9. Crystallization kettle; 1-10. Motor. DETAILED DESCRIPTION

[0047] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0048] The present invention will be further described below with reference to the examples, but the scope of the present invention is not limited to these examples.

[0049] The test instruments and test conditions used in the examples are as follows:

[0050] The BET surface area and average pore size of the nickel catalyst were measured by N2 adsorption-desorption method.

[0051] The sources of raw materials used in the examples are as follows:

[0052] All other reagents used were commercially available and of analytical grade.

[0053] Example 1

[0054] Carrier alumina: Prepare a 0.5 mol / L aqueous solution of aluminum sulfate, a mixture of aluminum hydroxide and sodium hydroxide at 1 mol / and 1 mol / respectively, and the flow ratio of aluminum sulfate solution to aluminum hydroxide-sodium hydroxide mixed solution is 1:0.7. Turn on the motor to drive the rotating filler at a speed of 3000 rpm. The two liquids are pumped into the liquid distributor through a horizontal flow pump to mix and spray into the enhanced reactor. Under the shearing action of the rotating filler, the mixed reaction liquid is sheared into tiny suspension droplets and finally enters the crystallization kettle from the bottom of the enhanced reactor and crystallizes at 80°C for 20 hours. After crystallization, it is filtered and washed with deionized water, and then dried at 80°C for 20 hours. Finally, the dried powder is calcined in an air atmosphere at 400°C to obtain an alumina carrier. The specific surface area of ​​the alumina carrier obtained by the enhanced hydrolysis method is 698m 2 / g, and the average pore diameter is 21nm.

[0055] Nickel catalyst: The above-mentioned carrier alumina was immersed in a 4 mol / L nickel nitrate aqueous solution, filtered after 30 min, dried at 120°C, and calcined at 400°C to obtain a nickel catalyst with a NiO loading of 55%, which was designated as A-1.

[0056] Example 2

[0057] Carrier alumina: Prepare a 2 mol / L aqueous solution of aluminum sulfate, a mixture of aluminum hydroxide and sodium hydroxide at 0.5 mol / and 1.5 mol / respectively, and the flow ratio of aluminum sulfate solution to aluminum hydroxide-sodium hydroxide mixed solution is 1:2. Turn on the motor to drive the rotating filler at a speed of 3000 rpm. The two liquids are pumped into the liquid distributor through a horizontal flow pump and mixed and sprayed into the enhanced reactor. Under the shearing action of the rotating filler, the mixed reaction liquid is sheared into tiny suspension droplets, and finally enters the crystallization kettle from the bottom of the enhanced reactor and crystallizes at 80°C for 20 hours. After crystallization, it is filtered and washed with deionized water, and then dried at 80°C for 20 hours. Finally, the dried powder is calcined in an air atmosphere at 500°C to obtain an alumina carrier. The specific surface area of ​​the alumina carrier obtained by the enhanced hydrolysis method is 412m 2 / g, and the average pore diameter is 32nm.

[0058] Nickel catalyst: The above-mentioned carrier alumina was immersed in a 4 mol / L nickel nitrate aqueous solution, filtered after 30 min, dried at 120°C, and calcined at 400°C to obtain a nickel catalyst with a NiO loading of 48%, which was designated as A-2.

[0059] Example 3

[0060] Carrier alumina: Prepare a 1 mol / L aqueous solution of aluminum sulfate, a mixture of 0.5 mol / and 1.5 mol / of aluminum hydroxide and sodium hydroxide respectively, and the flow ratio of the aluminum sulfate solution to the aluminum hydroxide-sodium hydroxide mixed solution is 1:1.2. Turn on the motor to drive the rotating filler at a speed of 3000 rpm. The two liquids are pumped into the liquid distributor through a horizontal flow pump to mix and spray into the enhanced reactor. Under the shearing action of the rotating filler, the mixed reaction liquid is sheared into tiny suspension droplets and finally enters the crystallization kettle from the bottom of the enhanced reactor and crystallizes at 80°C for 20 hours. After crystallization, it is filtered and washed with deionized water, and then dried at 80°C for 20 hours. Finally, the dried powder is calcined in an air atmosphere at 800°C to obtain an alumina carrier. The specific surface area of ​​the alumina carrier obtained by the enhanced hydrolysis method is 581m 2 / g, and the average pore diameter is 23nm.

[0061] Nickel catalyst: The above-mentioned carrier alumina was immersed in a 4 mol / L nickel nitrate aqueous solution, filtered after 30 min, dried at 120°C, and calcined at 450°C to obtain a nickel catalyst with a NiO loading of 51%, which was designated as A-3.

[0062] Comparative Example 1

[0063] The alumina support was prepared using a conventional co-precipitation method: a 1 mol / L aqueous solution of aluminum sulfate, a mixture of 0.5 mol / L aluminum hydroxide and 1.5 mol / L sodium hydroxide, respectively, was added dropwise to a stirred kettle at a flow rate ratio of 1:1.2. The reaction precipitate was transferred to a crystallization vessel and crystallized at 80°C for 20 hours. After crystallization, it was filtered, washed with deionized water, and dried at 80°C for 20 hours. The dried powder was finally calcined at 500°C in air to obtain the alumina support. The alumina support obtained by the enhanced hydrolysis method had a specific surface area of ​​406 m2 / g and an average pore size of 13 nm, as determined by N2 adsorption-desorption.

[0064] Nickel catalyst: The above-mentioned carrier alumina was immersed in a 4 mol / L nickel nitrate aqueous solution, filtered after 30 min, dried at 120°C, and calcined at 450°C. A nickel catalyst with a NiO loading of 21% was obtained through one impregnation, which was recorded as D-1.

[0065] In the comparative example, the alumina carrier prepared by ordinary stirring was used, the average pore diameter was reduced, and the loading amount in one impregnation was reduced.

[0066] Experimental Example 1

[0067] Comparison of isooctene aldehyde hydrogenation performance:

[0068] The catalyst's catalytic performance for the hydrogenation of isooctenal was evaluated in an autoclave. Prior to use, the catalyst was reduced in pure hydrogen at 450°C for 4 hours. 2g of the catalyst, 5g of isooctenal, and 45g of dioxane were placed in a completely sealed stainless steel autoclave. The air in the autoclave was then replaced three times with high-purity hydrogen. The reaction temperature was set at 50°C, the pressure at 3 MPa, and the stirring rate at 200 rpm. The reaction was continued for 5 hours, and the product was analyzed by gas chromatography.

[0069] The catalysts A1-3 and D1 were evaluated according to the above evaluation method. Table 1 shows the reaction results.

[0070] Table 1

[0071]

[0072] As shown in Table 1, the structure of the support determines the performance of the catalyst. The alumina support prepared using the enhanced hydrolysis method has a more uniform structure, increasing the specific surface area and average pore size. Therefore, when impregnating the active component, the primary loading of the active component can be significantly increased, and the active component is more evenly dispersed, significantly improving the selectivity of isooctylaldehyde. This also reduces the reaction temperature, meeting the goals of energy conservation and carbon reduction.

[0073] Embodiments of the application have been described above, as well as examples. None of the above description is exhaustive or complete with respect to the practice of the disclosed embodiments. Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the before disclosure.

[0074] The endpoints of the ranges and any values described herein are not limited to the precise values recited as exactly that endpoint point, but rather are intended to cover values approximating that range or that point. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within

Claims

1. A method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde, characterized in that: isooctene aldehyde, hydrogen and a nickel catalyst are contacted and reacted, wherein the nickel catalyst comprises a carrier alumina and an active component nickel dispersed thereon; The carrier alumina is prepared by using a rotary strengthening device, which includes: a rotary strengthening reactor, at least two liquid pumps, a crystallization kettle and a motor; The rotary intensified reactor comprises a rotary intensified reaction device shell, a wire mesh filler, and a solution mixing and distributing device. The wire mesh filler is located inside the rotary intensified reaction device shell, and a certain space is formed inside the wire mesh filler. The solution mixing and distributing device is placed in the space. The motor is connected to the wire mesh filler. The liquid pump is provided with a liquid pump discharge pipeline, the rotary enhanced reaction device housing is provided with a rotary enhanced reactor inlet and a rotary enhanced reactor outlet, the liquid pump discharge pipeline is connected to the solution mixing distributor through the rotary enhanced reactor inlet, and the rotary enhanced reactor outlet is connected to the crystallization kettle; The steps include: (1) A liquid pump is used to pump the aluminum sulfate solution and the aluminum hydroxide-sodium hydroxide mixed solution into the rotary intensified reactor from the inlet of the rotary intensified reactor to form a suspension; (2) The suspension is sprayed into the inner side of the wire mesh filler through a solution mixing distributor, and the wire mesh filler is rotated under the drive of a motor to shear the suspension into small units; (3) The micro-units obtained in step (2) are passed through the outlet of the rotary intensified reactor into a crystallization kettle for crystallization to obtain a crystallized material. The crystallized material is filtered, washed, dried, and then calcined to obtain the alumina carrier.

2. the method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde according to claim 1, wherein, The concentration of the aluminum sulfate solution is 0.5-2 mol / L; The aluminum hydroxide-sodium hydroxide mixed solution has an aluminum hydroxide concentration of 0.5-1 mol / L and a sodium hydroxide concentration of 1-1.5 mol / L; The flow ratio of the aluminum sulfate solution to the aluminum hydroxide-sodium hydroxide mixed solution is 1: (0.5~2).

3. the method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde according to claim 1, wherein, In step (2), the mesh filler rotates at a speed of 2800-3200 rpm.

4. the method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde according to claim 1, wherein, In step (3), the crystallization conditions include: temperature of 60-100°C and time of 2-24h; The drying conditions include: temperature of 60-120°C and time of 4-12 hours; The calcination conditions include: a temperature of 400-800° C. and a calcination time of 4-8 hours.

5. the method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde according to claim 1, wherein, The alumina carrier has the following characteristics: a specific surface area of ​​300-800 m 2 / g, and the average pore size is 10~40nm.

6. the method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde according to claim 5, wherein, The alumina carrier has the following characteristics: a specific surface area of ​​400-700 m 2 / g, and the average pore size is 20~35nm.

7. according to the method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde described in any one of claims 1-6, wherein, The preparation method of the nickel catalyst comprises the following steps: a) impregnating the carrier alumina into a nickel salt solution by an over-impregnation method to obtain a carrier alumina impregnated with the nickel salt solution; b) directly drying and calcining the carrier alumina impregnated with the nickel salt solution obtained in step a) to obtain the nickel catalyst.

8. the method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde according to claim 7, wherein, In step (a), the nickel salt solution is a water-soluble nickel salt solution; The concentration of the nickel salt solution is 3-5 mol / L, and the immersion time is 30-120 min.

9. the method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde according to claim 8, wherein, The nickel salt solution is at least one of a nickel nitrate solution, a nickel carbonate solution and a nickel sulfate solution.

10. The method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde according to claim 7, wherein In step (b), the drying conditions include: a temperature of 110-130°C and a drying time of 4-12 hours; The calcination conditions include: temperature of 600-800°C and time of 4-8 hours.

11. The method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde according to claim 7, wherein Based on the total weight of the nickel catalyst, the content of the active component nickel is 30-70 wt%, and the content of the carrier alumina is 30-70 wt%.

12. The method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde according to claim 11, wherein Based on the total weight of the nickel catalyst, the content of the active component nickel is 40-60 wt%, and the content of the carrier alumina is 40-60 wt%.

13. The method for preparing isooctyl aldehyde by selective hydrogenation of isooctyl aldehyde according to claim 1, wherein The conditions for the contact reaction include: hydrogen pressure of 1-10 MPa and reaction temperature of 40-60°C.

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