CN111420656A

CN111420656A - Catalyst for preparing isooctanoic acid by selective oxidation of isooctanol and preparation method thereof

Info

Publication number: CN111420656A
Application number: CN202010371568.XA
Authority: CN
Inventors: 冯俊婷; 贾雪飞; 刘雅楠; 李殿卿
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2020-05-06
Filing date: 2020-05-06
Publication date: 2020-07-17

Abstract

The invention discloses a catalyst for preparing isooctanoic acid by selective oxidation of isooctanol and a preparation method thereof, wherein the preparation method comprises the steps of taking an oxide SO with a B basic site and an L basic site as a carrier, loading a double-noble metal active component, and forming discontinuous active sites on the surface of the oxide carrier by two noble metal particles to obtain a catalyst with high selectivity, wherein the catalyst is expressed as M₁‑M₂In which M is₁Represents a noble metalPt；M₂Represents one of noble metals Pd, Au and Ag; the loading capacity of the double noble metals is 0.1-1.5%; m₁、M₂The particles are uniformly dispersed on the surface of the SO carrier and are separated from each other to form discontinuous active sites, M₁、M₂The particle size range is 1.5-4.0 nm. The catalyst is applied to the reaction of preparing the isooctanoic acid by selectively oxidizing isooctanol, has high activity and high selectivity of the isooctanoic acid, and has outstanding catalytic performance.

Description

Catalyst for preparing isooctanoic acid by selective oxidation of isooctanol and preparation method thereof

Technical Field

The invention relates to the field of catalyst preparation, in particular to a catalyst for preparing acid by selective oxidation of alcohol and a preparation method thereof.

Background

Isooctanoic Acid (2-ethylhexanoic Acid, 2-Thylhexanoic Acid) is an important branched chain saturated fatty Acid, can be combined with various metallizations to form isooctane metal salt, is a practical chemical raw material with excellent performance and wide application, and is mainly used as an unsaturated polyester resin accelerator, a catalyst, a drier in the paint and ink industries, a polyvinyl chloride processing aid, a metal processing and lubricating aid and the like. At present, isooctyl acid is synthesized industrially by an isooctaldehyde oxidation method, isooctaldehyde is prepared by synthesizing isooctenal through propylene carbonyl and then selectively hydrogenating, the process route is long, the process is complex, and isooctaldehyde oxidation steps generally adopt manganese, cobalt and alkali metal or alkaline earth metal carboxylate as catalysts, so that the selectivity of isooctyl acid is low, the energy consumption is high, and the cost is high. The isooctanol is prepared by using propylene and synthesis gas in petroleum as raw materials to generate n-butyl aldehyde and then performing condensation hydrogenation, so that the initial raw materials of the process route are easy to obtain, the process is relatively simple, and the route for preparing the isooctanol by using isooctanol as the raw material through selective oxidation is concerned. For example, overseas japan chemical and eastern ocean synthesis companies, domestic shenyang application technology laboratory plants, Jingzhou city group forestry plants, Henan Kaifeng suburban chemical plants, and Jiangxi Tianhe fine plants, but the production route of the process mostly adopts strong acid, strong base, high-valence metal salt or metal oxide as an oxidation catalyst, so that the selectivity of isooctanoic acid is low, the production cost is high, especially the environmental pollution is serious, a plurality of companies are in the production stop stage, and finally domestic isooctanoic acid products are difficult to compete with foreign products, and the import is mainly used. In order to solve the situation, domestic green catalytic technology is increasingly paid attention, namely, isooctanol is selectively oxidized to prepare isooctanoic acid by taking air, oxygen or hydrogen peroxide as an oxidant in one step.

Patent US20180127347a1 discloses a process for the oxidation of alcohols with oxygen containing gases to produce the corresponding carboxylic acids. The alcohol disclosed in this patent includes saturated alcohols, branched aliphatic alcohols, etc., and the catalyst contains a gold compoundAnd a copper compound, wherein the carrier is zinc oxide, and the size of the catalyst is 2-10 nm. However, the method needs to react in an alkaline solvent, the product needs to be acidified after the reaction is finished, the product is difficult to separate after the reaction, and the environmental pollution is serious. Das et al used 5 mol% CuBr in Cu (II) bromide catalysis of Aldehydes and Alcohols Applied Organometallic Chemistry,25(6), 437-442 (2011)₂The/70% t-BuOOH/DMSO catalytic system can convert aliphatic containing branches into corresponding carboxylic acids. Such as Me (CH)₂)₂CH₂Product Me (CH) of OH reaction at room temperature₂)₂The yield of COOH reaches 88 percent, but the reaction conditions are more severe along with the increase of the steric hindrance of the fatty alcohol, and a certain amount of halogen needs to be added into a reaction system, so that the environment is polluted to a certain extent. Akada et al in A Practical O₂-Oxidation of FunctionalizedAlcohols Producing Carboxylic Acids Catalyzed by the Pd-C/Pb(OAc)₂System, Bulletin of the Chemical Society of Japan,66(5), 1511-1515 (1993), preparation of Pd-C/Pb (OAc)₂The catalyst shows good catalytic activity in the process of preparing corresponding carboxylic acid by reacting various long-chain primary alcohols. For example, the yield of the product of the reaction with n-octanol reaches 76%. However, when the catalyst is reacted with branched alcohol with larger steric hindrance, the C-C bond is easy to break, and the selectivity of the target product is reduced. In A nanoplattum catalyst for aerobic oxidation of alcohols in water, Angelidange Chemie 119(5), 718-720 (2007), Yamada et al obtained stable and recyclable ARP-Pt catalyst by loading Pt nanoparticles on amphoteric resin ARP. The catalyst has high activity on fatty alcohol with double bond, benzene ring and other unsaturated bond, but has low activity on saturated branched fatty alcohol.

As described above, the technique for producing carboxylic acid by selective oxidation using alcohol as a raw material has the following problems: the alkaline reaction solvent plays a decisive role in the selectivity of carboxylic acid, so that the product needs to be acidified, and the environmental pollution is serious; the activity to isooctyl alcohol with high steric hindrance is low; the addition of solvent in the catalytic reaction leads to a complex subsequent separation process; when the reaction substrate is high steric hindrance saturated aliphatic alcohol with long chain and branched chain, the catalytic performance of the single noble metal catalyst is extremely limited, and the like. Therefore, in order to overcome the above disadvantages, it is necessary to develop a catalyst for the reaction of producing isooctanoic acid by catalytic oxidation of isooctanol, which has high selectivity of target products, simplifies the product separation steps, and reduces environmental pollution.

Supported bimetallic catalytic systems are an important area of selective oxidation systems for alcohols. This is because the interaction between different metals in the supported bimetallic catalyst can not only change the electronic and geometric properties of the two metals to generate a new synergistic effect, but also change the coordination effect and the overall effect of the catalyst; the carrier not only plays a role in stabilizing and modifying the active nano particles, but also can interact with the active components of the catalyst, namely, a synergistic effect is generated, so that the catalytic performance, such as activity and selectivity, can be enhanced to a certain extent. Therefore, the reasonable design and preparation of the high-performance supported high-dispersion bimetallic nano-catalyst have important application prospects for the development of catalytic oxidation of isooctyl alcohol.

Disclosure of Invention

The invention aims to provide a catalyst for the reaction of preparing isooctanoic acid by selective oxidation of isooctanol and a preparation method thereof.

The catalyst provided by the invention is represented as M₁-M₂In which M is₁Represents a noble metal Pt; m₂Represents one of noble metals Pd, Au and Ag; the loading amount of the noble metal is 0.1-1.5%; m₁And M₂The molar ratio of S0 is 0.5-2.0, S0 represents non-noble metal oxide carrier, which is one or two of oxides of Mg, Al, Cu, Cr and Co, SO has B basic site and L basic site, M₁And M₂The nano particles are uniformly dispersed on the surface of the SO carrier and are mutually spaced to form discontinuous active sites, M₁、 M₂The particle size range is 1.5-4.0 nm.

The loading amount of the noble metal is noble metal M₁And M₂Accounts for the percentage content of the total mass of the catalyst.

The preparation method of the catalyst comprises the steps of taking an oxide S0 with B basic sites and L basic sites as a carrier, and loading a double-precious metal active component to enable active precious metal particles to form discontinuous active sites on the surface of the oxide carrier, so that the catalyst with high selectivity is obtained.

The invention provides a catalyst for preparing isooctanoic acid by selective oxidation of isooctanol, which comprises the following steps:

A. preparing a metal salt solution by using deionized water, wherein the total molar concentration of metal is 0.1-0.8 mol/L, and the metal ion in the metal salt solution is Mg²⁺、Al³⁺、Cu²⁺、Cr³⁺、Co³⁺One or two of them, preferably Al³⁺(ii) a The anion of the metal salt is CO₃ ^2-、NO₃ ^-、Cl^-Or SO₄ ^2-Is one of (1), preferably NO₃ ^-。

B. And C, simultaneously adding the metal salt solution and the alkali solution in the step A into the reactor, uniformly stirring to obtain a mixed solution, and controlling the pH value to be 9-11, wherein the alkali solution is a sodium hydroxide solution with the concentration of 2.0-3.0 mol/L, and the adding amount is such that the pH value of the mixed solution is 9-11.

C. Crystallizing the mixed solution at 80-120 ℃ for 0.5-24 h, naturally cooling to room temperature, separating, washing a filter cake with deionized water until the pH value of supernatant liquid is approximately equal to 7, transferring to a tubular furnace, roasting at 450-900 ℃ for 4-7 h in a nitrogen atmosphere, and naturally cooling to room temperature to obtain the metal oxide carrier SO.

D. Determination of the solubility M according to the Components of the target catalyst₁、M₂The amount of the noble metal salt is calculated by₁、M₂The noble metal salt is dissolved in deionized water to prepare a noble metal double-mixed solution with the metal concentration of 0.002-0.010 mol/L, the noble metal double-mixed solution is dropwise added into a dispersing agent solution at the dropping speed of 1-10 ml/min, wherein the mass of the dispersing agent is 1-2 times of that of the noble metal double-salt, a reducing agent sodium borohydride is added, and the molar ratio of the reducing agent to noble metal double-cations in the solution is 2-10, so that the noble metal double-colloid solution is obtained.

The M is₁The noble metal salt is H₂PtCl₆[Pt(NH₃)₄]Cl₂、H₂PtCl₆·6H₂One of O; the M is₂The noble metal salt is Pd (NO)₃)₂、Na₂PdCl₄、HAuCl₄、NaAuCl₄、AgNO₃、AgC₂H₃O₂One of (1); the dispersant solution is one of aqueous solutions of polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP) and diethylene glycol (DEG), and the concentration of the dispersant solution is 0.05-0.15%.

E. D, soaking the carrier SO into the noble metal nano-M solution in the step D according to the loading capacity of the target catalyst, stirring for 0.5-2 h, filtering, washing a filter cake with deionized water, and drying to obtain the supported noble metal nano-M₁-M₂In the presence of an/SO catalyst, wherein M₁And M₂Nanoparticles are uniformly dispersed on the surface of the SO carrier, M₁、M₂The particle size range is 1.5-4.0 nm.

The method is characterized in that the coordination number of non-noble metal components and oxygen on the surface of an oxide carrier treated at high temperature in inert gas is lower than that of a main body, so that the oxide carrier has a B basic site and an L basic site, which is beneficial to the removal of α -H and the insertion reaction of-OH, double noble metal active components are dispersed on the surface of the carrier by a sol fixation method, the basic sites of the carrier have the function of anchoring the active components, the dispersion degree of the active components is greatly enhanced, the active components have smaller particle size, the atom utilization rate of a catalyst can be improved, and the active component M has the advantages of high activity, high stability, high catalytic activity₁Is active component M₂Diluting, reducing the number of adjacent atoms of the active component M1, facilitating the approach of a large steric hindrance reactant to the active adsorption site of the catalyst, changing the adsorption mode of the reactant on the surface of the catalyst, and further improving the catalytic performance.

FIG. 1(a) shows Pt prepared in example 1₃Pd₂/Al₂O₃High Resolution Transmission Electron Microscopy (HRTEM) pictures of the catalyst. As can be seen from the figure, in the supported catalyst, the active metal component was uniformly dispersed on the surface of the carrier, and FIG. 1(b) shows Pt in example 1₃Pd₂/Al₂O₃The particle size distribution diagram of the catalyst shows that the active metal particles in the supported catalystThe size range is 1.5-4.0 nm, and the average grain diameter is 2.49 nm.

FIG. 2 shows Pt prepared in example 1₃Pd₂/Al₂O₃X-ray photoelectron spectroscopy (XPS) photographs of the catalyst. It can be seen from the figure that in the supported catalyst, active metal components have stronger interaction.

FIG. 3 shows Pt in example 1₃Pd₂/Al₂O₃CO of catalyst₂The adsorption in-situ infrared spectrogram shows that obvious interaction exists between Pt-Pd bimetal and between the Pt-Pd bimetal and a carrier, so that the surface of the catalyst simultaneously has a strong L basic site, a medium-strong basic site and a weak B basic site.

FIG. 4 shows Pt prepared in example 1₃Pd₂/Al₂O₃The CO adsorption in-situ infrared spectrogram of the catalyst shows that only a triple adsorption peak and a linear adsorption peak are arranged on the catalyst, and the active component Pt atom is isolated and diluted by a Pd atom.

FIG. 5 shows Pt prepared in example 1₃Pd₂/Al₂O₃The curve of isooctanol conversion rate versus isooctanoic acid selectivity of the catalyst in isooctanol selective oxidation reaction. When the reaction temperature is 100 ℃, the conversion rate of isooctanol is 15%, and the selectivity of corresponding isooctanoic acid is 89%.

FIG. 6(a) shows Pt prepared in example 2₁Pd₁/Al₂O₃High Resolution Transmission Electron Microscopy (HRTEM) pictures of the catalyst. It can be seen from the figure that the active metal component in the supported catalyst is uniformly dispersed on the surface of the carrier, and FIG. 6(b) is Pt in example 2₁Pd₁/Al₂O₃The particle size distribution diagram of the catalyst shows that the size range of active metal particles in the supported catalyst is 1.5-4.0 nm, and the average particle size is 2.27 nm.

The invention has the beneficial effects that:

the preparation method provided by the invention is characterized in that an oxide with B basic sites and L basic sites is prepared as a carrier, a bi-component noble metal is loaded, and nano-particles of the active noble metal are mutually isolated and diluted on the surface of the oxide carrier to form discontinuous active sites, so that the catalyst with high selectivity is obtained.

Drawings

FIG. 1(a) shows Pt in example 1₃Pd₂/Al₂O₃High Resolution Transmission Electron Microscope (HRTEM) photograph of the catalyst, and FIG. 1(b) shows Pt in example 1₃Pd₂/Al₂O₃Particle size distribution diagram of catalyst

FIG. 2 shows Pt in example 1₃Pd₂/Al₂O₃X-ray photoelectron spectroscopy (XPS) spectrum of catalyst

FIG. 3 shows Pt in example 1₃Pd₂/Al₂O₃CO of catalyst₂Adsorption in-situ infrared spectrogram

FIG. 4 shows Pt in example 1₃Pd₂/Al₂O₃CO adsorption in-situ infrared spectrogram of catalyst

FIG. 5 shows Pt in example 1₃Pd₂/Al₂O₃Selectivity of isooctanoic acid of catalyst in selective oxidation reaction of isooctanol at different conversion rates of isooctanol

FIG. 6(a) shows Pt in example 2₁Pd₁/Al₂O₃High Resolution Transmission Electron Microscope (HRTEM) photograph of the catalyst, and FIG. 6(b) is Pt in example 2₁Pd₁/Al₂O₃Particle size distribution diagram of catalyst

Detailed Description

Example 1

Preparation of Pt₃Pd₂/Al₂O₃The catalyst, wherein the Pt + Pd loading is 0.1%, and the molar ratio of Pt to Pd is 3: 2.

A. 37.6g of Al (NO) are weighed out₃)₃·9H₂O is dissolved in 200ml of ionized water to prepare a salt solution of metal salt, and the molar concentration is 0.5 mol/L.

B. The salt solution in step a was added dropwise to a three-necked flask together with a 3.0 mol/L NaOH solution and stirred well, controlling the pH at 10.

C. And crystallizing the mixed solution at 95 ℃ for 1h, and washing the separated solid with deionized water until the pH value of the supernatant is approximately equal to 7. Transferring the separated solid to a tubular furnace, roasting for 5 hours at 800 ℃ in nitrogen atmosphere, and naturally cooling to room temperature to obtain a metal oxide carrier Al₂O₃。

D. 0.004g of PdCl₂And 0.016g H₂PtCl₆·6H₂Dissolving O in 20ml of deionized water to prepare a solution with the concentration of 0.010 mol/L, wherein the molar ratio of Pt to Pd is 3:2, dropwise adding soluble Pt and Pd noble metal salt into 36.0ml of 0.1% dispersing agent PVA aqueous solution at the speed of 3ml/min, and reducing by using sodium borohydride to obtain the Pt-Pd bimetallic colloid solution.

E. According to the Pt + Pd loading of the catalyst of 0.1%, 7.91g of carrier Al₂O₃Adding into Pt-Pd bimetallic colloidal solution, stirring for 1h, separating, washing the separated solid with deionized water for 3 times, and drying to obtain supported highly-dispersed bimetallic nano Pt₃Pd₂/Al₂O₃A catalyst.

The catalyst prepared above was used in selective oxidation reaction experiments of isooctyl alcohol:

weighing 200mg of catalyst, placing the catalyst into a glass reaction vessel with magnetic stirring, adding 20ml of isooctanol into the reaction solution, and performing O reaction at the temperature of 100 ℃ and the pressure of 0.1MPa₂Testing for 2h under the condition, sampling and filtering every 5min after reaching the temperature, taking 1,3, 5-trimethylbenzene as an internal standard substance, and analyzing the components of reactants and products by using a gas chromatography by using an internal standard method, wherein the result is shown in figure 5. As can be seen, when the reaction temperature is 100 ℃, the isooctanol conversion rate is 15%, and the corresponding selectivity of isooctanoic acid is 89%.

Example 2

Preparation of Pt₁Pd₁/Al₂O₃The catalyst, wherein the Pt + Pd loading is 1.0%, and the molar ratio of Pt to Pd is 1: 1.

A. 37.6g of Al (NO) are weighed out₃)₃·9H₂Dissolving O in 200ml of ionized water, preparing salt solution of metal salt, and obtaining the productThe molar concentration was 0.5 mol/L.

D. 0.004g of PdCl₂And 0.013g H₂PtCl₆·6H₂Dissolving O in 10ml of deionized water to prepare a solution with the concentration of 0.010 mol/L, wherein the molar ratio of Pt to Pd is 1:1, dripping soluble Pt and Pd noble metal salt into 34.7ml of 0.1 percent dispersant PVA aqueous solution at the speed of 3ml/min, and reducing by using sodium borohydride to obtain the Pt-Pd bimetallic colloid solution.

E. According to the Pt + Pd loading of the catalyst of 1.0 percent, 0.75g of carrier Al₂O₃Adding into Pt-Pd bimetallic colloidal solution, stirring for 1h, separating, washing the separated solid with deionized water for 3 times, and drying to obtain supported highly-dispersed bimetallic nano Pt₁Pd₁/Al₂O₃A catalyst.

Example 3

Preparation of Pt₁Pd₂/Al₂O₃The catalyst, wherein the Pt + Pd loading is 0.1%, and the molar ratio of Pt to Pd is 1: 2.

D. 0.005g of PdCl₂And 0.021g H₂PtCl₆·6H₂Dissolving O in 10ml of deionized water to prepare a solution with the concentration of 0.016 mol/L, wherein the molar ratio of Pt to Pd is 1:2, dripping soluble Pt and Pd noble metal salt into 43.3ml of 0.1 percent dispersant PVA aqueous solution at the speed of 3ml/min, and reducing by using sodium borohydride to obtain the Pt-Pd bimetallic colloid solution.

E. 6.02g of carrier Al according to the Pt + Pd loading of the catalyst being 0.1%₂O₃Adding into Pt-Pd bimetallic colloidal solution, stirring for 1h, separating, washing the separated solid with deionized water for 3 times, and drying to obtain supported highly-dispersed bimetallic nano Pt₁Pd₂/Al₂O₃A catalyst.

Example 4

Preparation of Pt₃Pd₂/CoAlO₃The catalyst, wherein the Pt + Pd loading is 0.1%, and the molar ratio of Pt to Pd is 3: 2.

A. 18.8g Al (NO) are weighed out₃)₃·9H₂O，14.4g Co(NO₃)₃·9H₂Dissolving O in 200ml of ionized water to prepare a salt solution of metal salt, wherein the molar concentration is 0.5 mol/L, and the molar ratio of Al to Co is 1: 1.

C. Crystallizing the mixed solution at 95 ℃ for 1h, naturally cooling to room temperature, and washing the separated solid with deionized water until the pH value of supernatant is approximately equal to 7. Transferring the separated solid to a tubular furnace, roasting for 5h at 800 ℃ in a nitrogen atmosphere, naturally cooling to room temperature to obtain a metal oxide carrier CoAlO₃。

D. 0.004g of PdCl₂And 0.016g H₂PtCl₆·6H₂Dissolving O in 10ml of deionized water to prepare a solution with the concentration of 0.010 mol/L, wherein the molar ratio of Pt to Pd is 3:2, dropwise adding soluble Pt and Pd noble metal salt into 36.0ml of 0.1% dispersing agent PVA aqueous solution at the speed of 3ml/min, and reducing by using sodium borohydride to obtain the Pt-Pd bimetallic colloid solution.

E. According to the Pt + Pd loading of the catalyst of 0.1%, 7.91g of carrier CoAlO₃Adding into Pt-Pd bimetallic colloidal solution, stirring for 1h, separating, washing the separated solid with deionized water for 3 times, and drying to obtain supported highly-dispersed bimetallic nano Pt₃Pd₂/CoAlO₃A catalyst.

Example 5

D. 0.004g of PdCl₂And 0.013g H₂PtCl₆·6H₂Dissolving O in 10ml of deionized water to prepare a solution with the concentration of 0.010 mol/L, wherein the molar ratio of Pt to Pd is 1:1, dripping soluble Pt and Pd noble metal salt into 69.4ml of 0.05 percent dispersant PVP aqueous solution at the speed of 3ml/min, and reducing by using sodium borohydride to obtain the Pt-Pd bimetallic colloid solution.

Example 6

Preparation of Pt₁Pd₁/Al₂O₃Catalyst and process for preparing sameWherein the Pt + Pd loading amount is 1.3%, and the molar ratio of Pt to Pd is 1: 1.

D. 0.004g of PdCl₂And 0.013g H₂PtCl₆·6H₂Dissolving O in 10ml of deionized water to prepare a solution with the concentration of 0.010 mol/L, wherein the molar ratio of Pt to Pd is 1:1, dropwise adding soluble Pt and Pd noble metal salt into 23.1ml of 0.15% aqueous solution of a dispersant DEG at a rate of 3ml/min, and reducing by using sodium borohydride to obtain a Pt-Pd bimetallic colloid solution.

E. According to the Pt + Pd loading of the catalyst of 1.3%, 0.58g of carrier Al₂O₃Adding into Pt-Pd bimetallic colloidal solution, stirring for 1h, separating, washing the separated solid with deionized water for 3 times, and drying to obtain supported highly-dispersed bimetallic nano Pt₁Pd₁/Al₂O₃A catalyst.

Example 7

Preparation of Pt₁Ag₁/Al₂O₃The catalyst has Pt + Ag loading of 1.0% and Pt/Ag molar ratio of 1: 1.

B. The salt solution in step a was added dropwise to a three-necked flask simultaneously with a 2.0 mol/L NaOH solution and stirred well, controlling the pH at 10.

C. Crystallizing the mixed solution at 95 ℃ for 1h,the separated solid is washed by deionized water until the pH value of the supernatant is approximately equal to 7. Transferring the separated solid to a tubular furnace, roasting for 5 hours at 800 ℃ in nitrogen atmosphere, and naturally cooling to room temperature to obtain a metal oxide carrier Al₂O₃。

D. 0.004g of AgNO₃And 0.013g H₂PtCl₆·6H₂Dissolving O in 10ml of deionized water to prepare a solution with the concentration of 0.010 mol/L, wherein the molar ratio of Pt to Ag is 1:1, dripping soluble Pt and Ag noble metal salt into 34.7ml of 0.1% dispersing agent PVA aqueous solution at a rate of 3ml/min, and reducing by using sodium borohydride to obtain the Pt-Ag double metal colloid solution.

E. According to the Pt + Ag loading of 1.0% in the catalyst, 0.75g of carrier Al₂O₃Adding into Pt-Ag bimetallic colloidal solution, stirring for 1h, separating, washing the separated solid with deionized water for 3 times, and drying to obtain supported highly-dispersed bimetallic nano Pt₁Ag₁/Al₂O₃A catalyst.

Example 8

Preparation of Pt₁Au₁/Al₂O₃The catalyst has Pt + Au loading of 1.0% and Pt/Au molar ratio of 1: 1.

D. 0.010g of HAuCl₄And 0.013g H₂PtCl₆·6H₂Dissolving O in 10ml deionized water to prepare a solution with the concentration of 0.010 mol/L and the molar ratio of Pt to Au of 1:1, dissolving soluble Pt and Au noble metalThe salt was added dropwise to 34.7ml of 0.1% aqueous PVA dispersant solution at 3ml/min, and reduced with sodium borohydride to obtain a Pt-Au bimetallic colloidal solution.

E. According to the Pt + Au loading of 1.0% in the catalyst, 0.75g of carrier Al₂O₃Adding into Pt-Au bimetallic colloidal solution, stirring for 1h, separating, washing the separated solid with deionized water for 3 times, and drying to obtain supported highly-dispersed bimetallic nano Pt₁Au₁/Al₂O₃A catalyst.

Example 9

Preparation of Pt₃Pd₂/CrAlO₃The catalyst, wherein the Pt + Pd loading is 0.1%, and the molar ratio of Pt to Pd is 3: 2.

A. 18.8g Al (NO) are weighed out₃)₃·9H₂O，11.9g Cr(NO₃)₃Dissolving the mixture in 200ml of ionized water to prepare a salt solution of metal salt, wherein the molar concentration is 0.5 mol/L, and the molar ratio of Al to Cr is 1: 1.

B. The salt solution in step a was added dropwise to a three-necked flask simultaneously with a 2.5 mol/L NaOH solution and stirred well, controlling the pH at 10.

E. According to the Pt + Pd loading of 0.1% in the catalyst, 7.91g of the carrier CrAlO₃Adding into Pt-Pd bimetallic colloidal solution, stirring for 1h, separating, washing the separated solid with deionized water for 3 times, and drying to obtain supported highly-dispersed bimetallic nano Pt₃Pd₂/CrAlO₃A catalyst.

Claims

1. A preparation method of a catalyst for preparing isooctanoic acid by selective oxidation of isooctanol comprises the following steps:

A. preparing a metal salt solution by using deionized water, wherein the total molar concentration of metal is 0.1-0.8 mol/L, and the metal ion in the metal salt solution is Mg²⁺、Al³⁺、Cu²⁺、Cr³⁺、Co³⁺One or two of them; the anion of the metal salt is CO₃ ^2-、NO₃ ^-、Cl^-Or SO₄ ^2-One of (1);

B. adding the metal salt solution and the alkali solution in the step A into a reactor at the same time, uniformly stirring to obtain a mixed solution, and controlling the pH value to be 9-11, wherein the alkali solution is a sodium hydroxide solution with the concentration of 2.0-3.0 mol/L, and the adding amount is such that the pH value of the mixed solution is 9-11;

C. crystallizing the mixed solution at 80-120 ℃ for 0.5-24 h, naturally cooling to room temperature, separating, washing a filter cake with deionized water until the pH value of supernatant liquid is approximately equal to 7, transferring to a tubular furnace, roasting at 450-900 ℃ for 4-7 h in a nitrogen atmosphere, and naturally cooling to room temperature to obtain a metal oxide carrier SO;

D. determination of the solubility M according to the Components of the target catalyst₁、M₂The amount of the noble metal salt is calculated by₁、M₂Dissolving noble metal salt in deionized water to prepare a noble metal double-solution with metal concentration of 0.002-0.010 mol/L, and dropwise adding the noble metal double-solution into a dispersant solution at a dropping speed of 1-10 ml/min, wherein the mass of the dispersant is 1-2 times of that of the noble metal double-salt, and then adding a reducing agent sodium borohydride, wherein the molar ratio of the reducing agent to noble metal double-ions in the solution is 2-10, so as to obtain a noble metal double-colloid solution;

the M is₁The noble metal salt is H₂PtCl₆[Pt(NH₃)₄]Cl₂、H₂PtCl₆·6H₂One of O; the M is₂The noble metal salt is Pd (NO)₃)₂、Na₂PdCl₄、HAuCl₄、NaAuCl₄、AgNO₃、AgC₂H₃O₂One of (1); the dispersing agent solution is one of aqueous solutions of polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP) and diethylene glycol (DEG), and the concentration of the dispersing agent solution is 0.05-0.15%;

E. soaking the carrier SO in the noble metal colloidal solution obtained in the step D according to the loading capacity of the target catalyst, stirring for 0.5-2 h, filtering, washing a filter cake with deionized water, and drying to obtain the supported noble metal nano M₁-M₂In the presence of an/SO catalyst, wherein M₁And M₂Nanoparticles are uniformly dispersed on the surface of the SO carrier, M₁、M₂The particle size range is 1.5-4.0 nm.

2. The process for preparing a catalyst for selective oxidation of isooctanol to isooctanoic acid as claimed in claim 1, wherein the metal ion in said metal salt solution is Al³⁺(ii) a The anion of the metal salt being NO₃ ^-。

3. A catalyst for the selective oxidation of isooctanol to isooctanoic acid prepared by the process of claim 1, represented by M₁-M₂In which M is₁Represents a noble metal Pt; m₂Represents one of noble metals Pd, Au and Ag; the loading amount of the noble metal is 0.1-1.5%; m₁And M₂The molar ratio of S0 is 0.5-2.0, S0 represents non-noble metal oxide carrier, which is one or two of oxides of Mg, Al, Cu, Cr and Co, SO has B basic site and L basic site, M₁And M₂The particles are uniformly dispersed on the surface of the SO carrier and are separated from each other to form discontinuous active sites, M₁、M₂The particle size range is 1.5-4.0 nm.