Method for synthesizing isooctanol by one-pot method in reducing atmosphere and catalyst used in method

Abstract

The invention belongs to the field of organic synthesis, and particularly relates to a preparation method for synthesizing isooctanol from n-butyraldehyde through a one-pot method. Firstly, the invention provides a preparation method of a supported noble metal (palladium and platinum) catalyst for synthesizing isooctanol, and secondly, the invention also provides a method for synthesizing isooctanol by a one-pot method in a reducing atmosphere, which comprises the following steps: adding the supported noble metal catalyst and a sodium hydroxide solution into a high-pressure kettle, pumping n-butyraldehyde into the high-pressure kettle, and reacting for 2-4 hours; a reaction is carried out under specific reaction conditions, and then corresponding post-treatment is carried out to obtain the isooctanol. The synthetic route provided by the invention has the characteristics of simple process, higher yield and high product quality, thereby having better application prospect and being suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the field of organic synthesis, and particularly relates to a method for preparing isooctyl alcohol by synthesizing n-butyraldehyde in one pot. Background Art

[0002] Isooctanol (CAS registration number 26952-21-6) is a colorless to light yellow oily liquid with a sweet and light floral aroma. It can be mainly used to produce: dioctyl phthalate (DOP), dioctyl oxalate (DOA), trioctyl trimellitate (TOTM), other plasticizers, octyl acrylate, surfactants, lubricant additives, mining, diesel fuel additives, solvents and preparations, rust inhibitor esters, and other chemicals.

[0003] The structural formula of isooctyl alcohol is:

[0004]

[0005] At present, the mainstream preparation method is that n-butyraldehyde is first condensed into isooctylaldehyde, and then the isooctylaldehyde is hydrogenated into isooctyl alcohol.

[0006] CN 113480417B proposes a method for synthesizing isooctylaldehyde from n-butyraldehyde in one step by a solid catalyst. The prepared Pd / solid acid-base@C solid catalyst is used for synthesizing isooctylaldehyde from n-butyraldehyde in one step. The reaction is carried out in an autoclave at 170°C and a hydrogen pressure of 2.0 MPa for 8 hours to prepare isooctylaldehyde. The conversion rate of n-butyraldehyde is 97%, and the selectivity of isooctylaldehyde is 99.5%. Although the method provides a one-step method for preparing isooctylaldehyde, it has the defect of incomplete conversion of n-butyraldehyde.

[0007] The invention of CN 202210679242.2, "A method for preparing isooctylaldehyde from crotonaldehyde in one step", informs that: the raw materials crotonaldehyde and hydrogen are continuously subjected to hydrogenation I, condensation dehydration, and hydrogenation II reactions under the action of a catalyst to obtain isooctylaldehyde in one step; the catalyst is a nickel-zirconium catalyst based on biomass carbon. The nickel-zirconium-based active component in the catalyst mainly catalyzes the selective hydrogenation of crotonaldehyde to generate n-butyraldehyde (hydrogenation I) and the selective hydrogenation of isooctylaldehyde to generate isooctylaldehyde (hydrogenation II), and the alkalinity of the biomass carbon carrier can catalyze the condensation dehydration of n-butyraldehyde to generate isooctylaldehyde.

[0008] The above two methods only react to isooctyl aldehyde in one step, but cannot be further hydrogenated to isooctyl alcohol. The reason is that the catalysts are only selective for hydrogenating carbon-carbon double bonds.

[0009] CN 114933514 B proposes a method of preparing isooctyl alcohol by hydrogenation-condensation-hydrogenation reaction in a fixed bed with biomass crotonaldehyde and hydrogen as raw materials under the joint action of catalyst A and catalyst B. Catalyst A is a solid superacid supported palladium catalyst, and catalyst B is a copper-based catalyst or a nickel-based catalyst. Although this method completes the preparation of isooctyl alcohol from n-butyraldehyde in the same reactor, it is divided into two stages of reaction and is not a one-step method for preparing isooctyl alcohol. Summary of the invention

[0010] The technical problem to be solved by the present invention is to provide a method for synthesizing isooctyl alcohol in one pot under a reducing atmosphere and a catalyst used therefor. The present invention is a method for synthesizing isooctyl alcohol in one pot under a reducing atmosphere and an alkaline environment by setting a gradient temperature and pressure so as to control the condensation of n-butyraldehyde and the hydrogenation of isooctyl aldehyde.

[0011] In order to solve the above technical problems, the present invention provides a method for preparing a supported noble metal (palladium, platinum) catalyst for synthesizing isooctyl alcohol, comprising the following steps:

[0012] S1, adding palladium chloride and platinum chloride to water, and adding hydrochloric acid and an organic solvent, stirring and reacting at 50° C. to 80° C. for 2 h to 4 h (preferably stirring and reacting at 60° C. for 2 h), to obtain a reaction solution 1;

[0013] The mass ratio of palladium chloride to platinum chloride is 1:0.1-0.3 (preferably 1:0.2-0.3), and the mass ratio of palladium chloride to hydrochloric acid is 1:2-10;

[0014] S2, adding activated carbon to water, and then adding reaction solution 1 under stirring conditions, stirring at 50°C to 80°C for 2h to 4h (stirring at 60°C for 2h), to obtain reaction solution 2;

[0015] The mass ratio of the activated carbon to the palladium chloride in step S1 = 10-14:1 (preferably 12:1);

[0016] S3, adding sodium borohydride aqueous solution (for reducing precious metals) to the reaction solution 2, adjusting the pH to 8-13 (preferably pH 9-10), stirring the reaction at 70°C-90°C for 2h-4h (stirring the reaction at 80°C for 2h), and then aging at room temperature for 5h-10h;

[0017] Sodium borohydride: palladium chloride in step S1 = mass ratio of 0.7-1.5:1 (preferably 1.2-1.3:1); mass concentration of sodium borohydride solution is 20%-50% (preferably 30%-40%);

[0018] S4, filtering the aged material obtained in S3, and then washing the filter cake with a washing solvent (until the eluent is neutral), and drying to a moisture content of 30% to 70% (preferably 30 to 50%, more preferably 40 to 50%) to obtain a supported precious metal catalyst.

[0019] Note: The supported noble metal catalyst of the present invention needs to retain moisture, otherwise it is easy to deactivate.

[0020] As an improvement of the preparation method of the supported noble metal catalyst for synthesizing isooctyl alcohol of the present invention, in the step S1:

[0021] Palladium chloride: water = mass ratio of 1:30 to 50 (preferably 1:40);

[0022] The organic solvent is at least one (ie, one or more) of methanol, ethanol, and ethylene glycol, and the mass ratio of palladium chloride to organic solvent is 1:0.5-2.

[0023] As a further improvement of the preparation method of the supported noble metal catalyst for synthesizing isooctyl alcohol of the present invention, in step S2:

[0024] The reaction solution 1 is added dropwise for 30 to 45 minutes;

[0025] Activated carbon: water = mass ratio of 1:1.5~2.

[0026] As a further improvement of the preparation method of the supported noble metal catalyst for synthesizing isooctyl alcohol of the present invention, in the step S3: the pH is adjusted using a sodium hydroxide solution with a mass concentration of 5 to 10%.

[0027] As a further improvement of the method for preparing the supported noble metal catalyst for synthesizing isooctyl alcohol of the present invention, in step S4: the cleaning solvent is distilled water.

[0028] The cleaning frequency is generally 5 to 15 times.

[0029] The present invention also provides a method for synthesizing isooctyl alcohol in one pot under a reducing atmosphere, using a supported noble metal catalyst prepared by any of the above methods, and sequentially performing the following steps:

[0030] 1) One-pot condensation-hydrogenation:

[0031] Add a supported noble metal catalyst and a sodium hydroxide solution with a mass concentration of 1% to 3% into an autoclave, heat it to 50°C to 70°C, replace it with hydrogen, pressurize it to 0.5MPa to 1.5MPa (preferably 1 to 1.5MPa), pump n-butyraldehyde into the autoclave (a metering pump can be used to pump n-butyraldehyde into the autoclave), react at 50°C to 70°C for 2h to 4h, and maintain the pressure at 0.5MPa to 1.5MPa (preferably 1 to 1.5MPa) by introducing hydrogen during the reaction; then heat it to 100°C to 150°C, pressurize the hydrogen to 2.0MPa to 3.0MPa, and react for 5h to 11h;

[0032] The supported noble metal catalyst: n-butyraldehyde = 0.1wt% to 10wt% (preferably 3 to 7wt%), sodium hydroxide solution: n-butyraldehyde = 20wt% to 40wt%;

[0033] Description: Sodium hydroxide solution is used as a catalyst for the condensation reaction of n-butyraldehyde, and a supported noble metal catalyst is used as an isooctylaldehyde hydrogenation catalyst. Under the system set by the present invention, the n-butyraldehyde condensation reaction and the isooctylaldehyde hydrogenation reaction are carried out simultaneously; after reacting at 50°C to 70°C for 2h to 4h, the n-butyraldehyde is basically converted completely as detected by GC;

[0034] In the present invention, "reacting at 50℃~70℃ for 2h~4h" is to realize the condensation of n-butyraldehyde into isooctylaldehyde, and isooctylaldehyde has been hydrogenated to isooctylaldehyde in this process; the present invention sets the reaction at low temperature and low pressure mainly to reduce the generation of n-butanol. Since the hydrogenation of carbon-carbon double bonds is easy, the conditions are mild; while the activation energy of hydrogenation of carbon-oxygen double bonds is high and higher conditions are required; subsequently, "reacting at 100℃~150℃ and pressurizing hydrogen to 2.0MPa~3.0MPa for 5h~11h" is to realize the hydrogenation of isooctylaldehyde to isooctylaldehyde, and further hydrogenation to isooctyl alcohol.

[0035] 2) After the reaction time of step 1) is reached, the temperature is lowered and the pressure is released, the mixture is filtered, and the liquid phase is separated. The upper organic phase obtained by separation is the crude isooctyl alcohol (colorless and transparent).

[0036] Note: The lower aqueous phase (colorless and transparent aqueous phase) obtained by separation is recovered.

[0037] As an improvement of the method for synthesizing isooctyl alcohol in one pot in a reducing atmosphere of the present invention:

[0038] The pumping time of n-butyraldehyde is 40 to 60 minutes.

[0039] In the present invention, the volume of the autoclave is 500 ml, and the pumping rate of n-butyraldehyde can be about 6 ml / min to 7 ml / min.

[0040] As a further improvement of the method for synthesizing isooctyl alcohol in one pot in a reducing atmosphere of the present invention:

[0041] Step 2) The lower aqueous phase obtained by separation can be used as the sodium hydroxide solution required for the next batch of reactions after post-treatment, thereby achieving application.

[0042] The post-treatment method of the lower aqueous phase is:

[0043] The lower aqueous phase is subjected to reduced pressure (vacuum degree is -0.2MPa to -0.1MPa) at 40°C to 60°C to evaporate excess water generated by the reaction (i.e., the weight of the aqueous phase after dehydration is approximately equal to the weight of the sodium hydroxide solution used in step 1), and its alkalinity is detected, and then corresponding sodium hydroxide is added according to the alkalinity until the sodium hydroxide concentration is 1% to 3% (mass %).

[0044] Reaction formula of the present invention is:

[0045]

[0046] In the present invention, palladium in the supported noble metal (palladium, platinum) catalyst mainly provides the selectivity of carbon-carbon double bond hydrogenation, while platinum provides the selectivity of carbon-oxygen double bond hydrogenation so that aldehyde can be converted into alcohol. In addition, the present invention reduces the occurrence of side reactions by controlling the reaction conditions; in the present invention, although condensation and hydrogenation are carried out simultaneously, the selectivity of hydrogenation of carbon-oxygen double bonds is reduced by lower reaction temperature and reaction pressure at the beginning; at the same time, due to the presence of hydrogen, the carbon-carbon double bond can be hydrogenated, and the isooctylaldehyde generated by condensation is hydrogenated to isooctylaldehyde, thereby promoting the condensation reaction of n-butyraldehyde. Then the reaction temperature and reaction pressure are increased, so that the isooctylaldehyde and isooctylaldehyde obtained by condensation are hydrogenated to generate isooctyl alcohol.

[0047] That is, the palladium metal in the catalyst of the present invention has a strong selectivity for hydrogenation of carbon-carbon double bonds, while platinum has a selectivity for hydrogenation of carbon-oxygen double bonds. Therefore, the catalyst of the present invention can hydrogenate carbon-oxygen double bonds, and since the hydrogenation of carbon-carbon double bonds is easy to occur, it can be carried out under mild conditions, while the hydrogenation of carbon-oxygen double bonds needs to be carried out at a higher temperature.

[0048] The method of the present invention is used to prepare isooctyl alcohol, which has the following technical advantages:

[0049] 1. The present invention conducts the condensation-hydrogenation reaction in a one-pot process, thereby reducing the material loss in the intermediate steps (i.e., reducing the material loss in the two-step reaction process of condensation and hydrogenation), and improving the reaction yield and product content, as well as the raw material conversion rate.

[0050] 2. The present invention provides a preparation method of a supported noble metal catalyst for the hydrogenation reaction of isooctene aldehyde; at the same time, the reaction environment provided by the present invention can effectively reduce the generation of n-butanol as a byproduct during the condensation process of n-butyraldehyde.

[0051] 3. The sodium hydroxide solution catalyst of the present invention is recycled and reused, which greatly reduces the discharge of waste water.

[0052] In summary, the synthetic route of the present invention has the characteristics of simple process, high yield and high product quality, and therefore has good application prospects and is suitable for industrial production. DETAILED DESCRIPTION

[0053] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0054] In the present invention:

[0055] The concentration of hydrochloric acid is 36%;

[0056] The stirring in the preparation method of the supported noble metal catalyst is stirring at a conventional speed, which is about 400 rpm to 1000 rpm;

[0057] The synthesis of isooctyl alcohol is carried out in an autoclave under stirring conditions, with a stirring speed of about 600 rpm to 1000 rpm. The volume of the autoclave is 500 ml.

[0058] The contents of n-butyraldehyde, isooctene aldehyde, isooctyl aldehyde, isooctyl alcohol, etc. can be detected by gas phase detection method, and % represents mass %.

[0059] The product obtained by the present invention can be confirmed to be isooctyl alcohol through conventional nuclear magnetic resonance verification and the like.

[0060] Catalyst Example 1: A method for preparing a supported noble metal catalyst for synthesizing isooctyl alcohol, comprising the following steps:

[0061] S1. Add 5 g of palladium chloride and 1 g of platinum chloride to 200 g of water, and add 10 g of hydrochloric acid and 10 g of ethanol, and stir at 60° C. for 2 h to obtain reaction solution 1.

[0062] S2. Add 60 g of activated carbon to 100 g of water, and then add all the reaction solution 1 obtained in step S1 dropwise under stirring (the dropping time is 30 to 45 minutes), stir at 60° C. for 2 hours to obtain reaction solution 2.

[0063] S3. Add 20 g of 30% (mass %) sodium borohydride aqueous solution to the entire reaction solution 2 obtained in step S2 to reduce the precious metal, adjust the pH to 9 with sodium hydroxide solution (concentration of 5%), stir the reaction at 80°C for 2 hours, and then age at room temperature for 10 hours.

[0064] S4. Filter the material obtained by aging S3, and wash the filter cake with distilled water (generally at least 5 times) until the eluent is neutral, and then dry it to a moisture content of 50% to obtain about 123.31 g of supported precious metal catalyst.

[0065] Catalyst Example 2, relative to Catalyst Example 1, made the following changes:

[0066] The amount of platinum chloride used was changed from 1 g to 0.5 g, and the rest was the same as in Catalyst Example 1.

[0067] Catalyst Example 3, relative to Catalyst Example 1, made the following changes:

[0068] The amount of platinum chloride used was changed from 1 g to 1.5 g, and the rest was the same as in Catalyst Example 1.

[0069] Catalyst Example 4, relative to Catalyst Example 1, made the following changes:

[0070] Change “dried to a moisture content of 50%” to “dried to a moisture content of 30%”, and the rest is the same as Catalyst Example 1.

[0071] Catalyst Example 5, relative to Catalyst Example 1, made the following changes:

[0072] Change “dried to a moisture content of 50%” to “dried to a moisture content of 70%”, and the rest is the same as Catalyst Example 1.

[0073] Catalyst Comparative Example 1, relative to Catalyst Example 1, the following changes were made:

[0074] The use of platinum chloride is eliminated, that is, the amount of platinum chloride used is 0, and the rest is the same as Catalyst Example 1.

[0075] Catalyst Comparative Example 2, relative to Catalyst Example 1, was modified as follows:

[0076] The “dried to a moisture content of 50%” was changed to “dried to a constant weight (ie, a moisture content close to 0)”, and the rest was the same as Catalyst Example 1.

[0077] Example 1: A method for preparing isooctyl alcohol in one pot under a reducing atmosphere, comprising the following steps:

[0078] 1) One-pot condensation-hydrogenation:

[0079] 10g of the supported noble metal catalyst prepared in Catalyst Example 1 and 60g of 2% (mass %) sodium hydroxide solution were added to the autoclave, and the temperature was raised to 60°C. After the gas in the autoclave was replaced 3 times with hydrogen, the pressure was increased to 1.0MPa, and 200g of n-butyraldehyde was slowly introduced into the autoclave at a flow rate of about 6ml / min using a metering pump (i.e., the n-butyraldehyde introduction time was about 40 minutes). When the n-butyraldehyde was completely introduced, hydrogen was continuously introduced to maintain the pressure at 1.0MPa, and the reaction was carried out at 60°C for 3h; at this time, the n-butyraldehyde was completely converted by sampling GC detection; then the temperature was raised to 120°C, pressurized and maintained at a hydrogen pressure of 3.0MPa, and the reaction was continued for 6h.

[0080] 2) After the reaction time of step 1) is reached, the temperature is lowered and the pressure is released (to room temperature, normal pressure) to terminate the reaction, and the liquid phase obtained by filtration is separated. The upper organic phase obtained by separation is 173.66g of colorless and transparent crude isooctyl alcohol, wherein the isooctyl alcohol content is 95.26%, the n-butyraldehyde content is 0% (i.e., below the detection limit and cannot be detected), the n-butanol content is 2.12%, and the isooctylaldehyde content is 0.07%; 83.22g of the lower aqueous phase (colorless and transparent aqueous phase) obtained by separation can be recycled.

[0081] Examples 2-3: Compared with Example 1, the amount of supported noble metal catalyst and the reaction time were changed (as shown in Table 1 below), and the rest were the same as Example 1; the results are shown in Table 1.

[0082] Table 1. Experimental conditions and results of Examples 1-3

[0083]

[0084] Note:

[0085] Embodiments 4 to 7: Compared with Embodiment 1, the dosage, concentration and reaction time of the sodium hydroxide solution were changed (as shown in Table 2 below), and the rest were the same as Embodiment 1. The results are shown in Table 2.

[0086] Table 2. Experimental conditions and results of Examples 1, 4 to 7

[0087]

[0088]

[0089] Example 8: Recycling Case

[0090] The 83.22 g of aqueous phase recovered in Example 1 was distilled out at 40° C. under a reduced pressure of -0.1 MPa to remove 23.22 g of water generated by a one-pot condensation-hydrogenation reaction. The base value was titrated to obtain a sodium hydroxide concentration of 1.65%. Sodium hydroxide (about 0.21 g) was added to restore the concentration of the sodium hydroxide solution to 2%. The solution was named as the applicable sodium hydroxide solution.

[0091] The above-mentioned applicable sodium hydroxide solution was used to replace 60 g of 2% sodium hydroxide solution in Example 1, and the rest was the same as Example 1. The results were as follows: the crude isooctyl alcohol was 174.22 g, the isooctyl alcohol content was 94.97%, the n-butyraldehyde content was 0%, the n-butanol content was 2.24%, the isooctylaldehyde content was 0.12%, and the product yield was 91.61%.

[0092] Note: The above is the first reuse. The results of the seventh reuse in the same manner as above were not significantly different from those of the first reuse.

[0093] Example 9: The supported noble metal catalyst in Example 1 is changed from that prepared by Catalyst Example 1 to that prepared by Catalyst Examples 2 to 5, and that prepared by Catalyst Comparative Examples 1 to 3, and the rest is the same as Example 1.

[0094] The results are shown in Table 3.

[0095] Table 3, Experimental conditions and results of Example 1 and Example 9

[0096]

[0097]

[0098] Comparative Example 1: Using the supported noble metal catalyst prepared in Catalyst Example 1, isooctyl alcohol was prepared by a two-step process:

[0099] Condensation reaction: add 60g of 2% sodium hydroxide solution into an autoclave, heat it to 60°C, replace it with nitrogen three times, and then slowly introduce 200g of n-butyraldehyde into the autoclave with a metering pump at a flow rate of 1ml / min. After reacting for 3h at normal pressure, cool it to room temperature and pour out the separated liquid to recover 171.22g of crude isooctenal in the upper organic phase, with an isooctenal content of 97.67% and n-butyraldehyde content of 1.19%, and the lower layer is the aqueous phase.

[0100] Hydrogenation reaction: Add the organic phase obtained above to an autoclave and add 10g of a supported noble metal catalyst, heat to 120°C, replace the gas in the autoclave with hydrogen three times, pressurize to 3.0MPa with hydrogen, and react for 8h. Cool down, release the pressure, and filter to obtain 167.23g of crude isooctyl alcohol, with an isooctyl alcohol content of 94.48%, a n-butyraldehyde content of 0.23%, a n-butanol content of 0.96%, and an isooctylaldehyde content of 1.17%. The corresponding results are shown in Table 3.

[0101] The comparison between Comparative Example 1 and Example 1 is shown in Table 4 below.

[0102] Table 4, Example 1, Comparative Example 1 Results

[0103] Example 1 Comparative Example 1 Reaction method One Pot Method Step-by-step approach Reaction time / h 9 11 Product weight / g 173.66 167.23 Raw material conversion rate / % 100 98.8 Product content / % 95.26 94.48 Product yield / % 91.60 87.49 n-Butanol content / % 2.12 0.96 Isooctylaldehyde content / % 0.07 1.17

[0104] Description: The one-pot method can effectively shorten the reaction time and improve the product yield and raw material conversion rate.

[0105] Comparative Example 2: With respect to Example 1, the following changes were made:

[0106] The method of “using a metering pump to slowly introduce 200 g of n-butyraldehyde into the autoclave at a flow rate of about 6 ml / min (i.e., the introduction time of n-butyraldehyde is about 40 minutes)” is changed to “adding 200 g of n-butyraldehyde directly into the reactor at one time”; the rest is the same as Example 1.

[0107] The results obtained are as follows: 171.88 g of crude isooctyl alcohol, the isooctyl alcohol content is 91.12%, the n-butyraldehyde content is 0.42%, the n-butanol content is 4.22%, the isooctylaldehyde content is 0.58%, and the product yield is 86.72%.

[0108] Comparative Example 3: Change the following in Example 1: “After the introduction of n-butyraldehyde is complete, hydrogen is continuously introduced to maintain the pressure at 1.0 MPa, and the reaction is carried out at 60° C. for 3 h; at this time, the conversion of n-butyraldehyde is complete as determined by GC sampling; and then the temperature is raised to 120° C., pressurized and the hydrogen pressure is maintained at 3.0 MPa, and the reaction is continued for 6 h” to “After the introduction of n-butyraldehyde is complete, the temperature is raised to 120° C., hydrogen is continuously introduced to maintain the pressure at 3.0 MPa, and the reaction is continued for 9 h”; the rest is the same as in Example 1.

[0109] The results obtained are: 172.24g of crude isooctyl alcohol, with an isooctyl alcohol content of 67.22%, a n-butyraldehyde content of 0%, a n-butanol content of 26.14%, an isooctylaldehyde content of 0.04%, and a product yield of 64.11%. This case shows that the selectivity of carbon-oxygen double bond hydrogenation is improved at high temperature, and n-butanol is easily generated as a by-product.

[0110] Comparative Example 4: Change the following steps in Example 1: “After the n-butyraldehyde is completely introduced, hydrogen is continuously introduced to maintain the pressure at 1.0 MPa, and the reaction is carried out at 60° C. for 3 h; at this time, the conversion of n-butyraldehyde is completely confirmed by sampling GC detection; then the temperature is raised to 120° C., pressurized and the hydrogen pressure is maintained at 3.0 MPa, and the reaction is continued for 6 h” to “After the n-butyraldehyde is completely introduced, hydrogen is continuously introduced to maintain the pressure at 1.0 MPa, and the reaction is continued at 60° C. for 12 h”; the rest is the same as in Example 1.

[0111] The results obtained are: 170.06 g of crude product, 13.24% isooctyl alcohol content, 0% n-butyraldehyde content, 1.97% n-butanol content, 83.25% isooctyl aldehyde content, and the product yield is 12.47%. Therefore, it is shown that the selectivity of carbon-oxygen double bond hydrogenation is low under low temperature conditions, and the conversion rate of isooctyl aldehyde to isooctyl alcohol is low.

[0112] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A method for preparing a supported noble metal catalyst for synthesizing isooctyl alcohol, characterized in that The following steps are involved: S1, adding palladium chloride and platinum chloride into water, and adding hydrochloric acid and an organic solvent, stirring and reacting at 50° C. to 80° C. for 2 h to 4 h to obtain a reaction solution 1; The mass ratio of palladium chloride to platinum chloride is 1:0.1-0.3, and the mass ratio of palladium chloride to hydrochloric acid is 1:2-10; S2, adding activated carbon to water, and then adding reaction solution 1 under stirring conditions, stirring at 50° C. to 80° C. for 2 h to 4 h to obtain reaction solution 2; The activated carbon: palladium chloride in step S1 = 10-14:1 in mass ratio; S3, adding sodium borohydride aqueous solution to the reaction solution 2, adjusting the pH to 8-13, stirring the reaction at 70°C-90°C for 2h-4h, and then aging at room temperature for 5h-10h; Sodium borohydride: palladium chloride in step S1 = 0.7-1.5:1 mass ratio; the mass concentration of the sodium borohydride solution is 20%-50%; S4, filtering the aged material obtained in S3, then washing the filter cake with a washing solvent, and drying it to a moisture content of 30% to 70% to obtain a supported noble metal catalyst.

2. The method for preparing a supported noble metal catalyst for synthesizing isooctyl alcohol according to claim 1, characterized in that In step S1: Palladium chloride: water = mass ratio of 1:30 to 50; The organic solvent is at least one of methanol, ethanol and ethylene glycol, and the mass ratio of palladium chloride to organic solvent is 1:0.5-2.

3. The method for preparing a supported noble metal catalyst for synthesizing isooctyl alcohol according to claim 2, characterized in that In step S2: The reaction solution 1 is added dropwise for 30 to 45 minutes; Activated carbon: water = mass ratio of 1:1.5~2.

4. The method for preparing a supported noble metal catalyst for synthesizing isooctyl alcohol according to claim 3, characterized in that In step S3: The pH is adjusted using a sodium hydroxide solution with a mass concentration of 5 to 10%.

5. The method for preparing a supported noble metal catalyst for synthesizing isooctyl alcohol according to claim 4, characterized in that In step S4: the cleaning solvent is distilled water.

6. A method for synthesizing isooctyl alcohol in one pot under reducing atmosphere, characterized in that: Using the supported noble metal catalyst prepared by any one of the methods of claims 1 to 5, the following steps are performed in sequence: 1) One-pot condensation-hydrogenation: A loaded noble metal catalyst and a sodium hydroxide solution with a mass concentration of 1% to 3% are added to an autoclave, the temperature is raised to 50°C to 70°C, the pressure is increased to 0.5MPa to 1.5MPa after replacement with hydrogen, n-butyraldehyde is pumped into the autoclave, the reaction is first carried out at 50°C to 70°C for 2h to 4h, and the pressure is maintained at 0.5MPa to 1.5MPa by introducing hydrogen during the reaction; the temperature is then raised to 100°C to 150°C, and the hydrogen is pressurized to 2.0MPa to 3.0MPa for reaction for 5h to 11h; The supported noble metal catalyst: n-butyraldehyde = 0.1wt% to 10wt%, sodium hydroxide solution: n-butyraldehyde = 20wt% to 40wt%; 2) After the reaction time of step 1) is reached, the temperature is lowered and the pressure is released, the liquid phase is filtered, and the liquid phase is separated. The upper organic phase obtained by separation is the crude isooctyl alcohol.

7. The method for synthesizing isooctyl alcohol in one pot under reducing atmosphere according to claim 6, characterized in that: The pumping time of n-butyraldehyde is 40 to 60 minutes.

8. The method for synthesizing isooctyl alcohol in one pot under reducing atmosphere according to claim 7, characterized in that: Step 2) The lower aqueous phase obtained by separation can be used as the sodium hydroxide solution required for the next batch of reactions after post-treatment, thereby achieving application.

9. The method for synthesizing isooctyl alcohol in one pot under reducing atmosphere according to claim 8, characterized in that: The post-treatment method of the lower aqueous phase is: The excess water generated by the reaction is evaporated from the lower aqueous phase under reduced pressure at 40°C to 60°C, and then its alkalinity is detected. Then, corresponding sodium hydroxide is added according to the alkalinity until the concentration of sodium hydroxide is 1% to 3%.

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