阅读说明：本技术 一种纳米金胶束催化剂及其制备方法与应用 (Nano-gold micelle catalyst, and preparation method and application thereof ) 是由 冯德鑫 安东 梁凤兵 于 2019-11-27 设计创作，主要内容包括：一种纳米金胶束催化剂及其制备方法与应用,属于纳米金胶束催化剂技术领域。为了解决生物基脂肪醇水相转化制备脂肪酸酯缺乏高效催化剂的问题,本发明提供了一种纳米金胶束催化剂及其制备方法与应用。本发明所述的纳米金胶束催化剂的制备方法如下：将HAuCl<Sub>4</Sub>水溶液和mPEG-SH水溶液混合,20-30℃,500-1000rpm转速下搅拌30-50min,随后向其中逐滴滴加NaBH<Sub>4</Sub>水溶液,边滴加边搅拌,反应12-24h,得到mPEG化的Au-NPs溶液进行离心,所获上清液即纳米金胶束催化剂。本发明所述的纳米金胶束催化剂能够实现高效催化脂肪醇水相氧化制备脂肪酸酯。(A nano-gold micelle catalyst, a preparation method and application thereof, belonging to the technical field of nano-gold micelle catalysts. The invention provides a nanogold micelle catalyst, a preparation method and application thereof, and aims to solve the problem that a high-efficiency catalyst is lacked in fatty acid ester preparation through water phase conversion of bio-based fatty alcohol. The preparation method of the nano-gold micelle catalyst comprises the following steps: adding HAuCl 4 Mixing the aqueous solution and mPEG-SH aqueous solution, stirring at the rotation speed of 1000rpm at the temperature of 20-30 ℃ for 30-50min, and dropwise adding NaBH into the mixture 4 And (3) dropwise adding the aqueous solution while stirring, reacting for 12-24h to obtain an mPEG Au-NPs solution, and centrifuging to obtain a supernatant, namely the nano gold micelle catalyst. The inventionThe nano gold micelle catalyst can realize the efficient catalytic aqueous oxidation of fatty alcohol to prepare fatty acid ester.)

1. The nano gold micelle catalyst is characterized by comprising HAuCl₄，mPEG-SH，NaBH₄And water.

2. The preparation method of the nanogold micelle catalyst according to claim 1, which is characterized by comprising the following specific steps:

(1) adding HAuCl₄Mixing the aqueous solution with the mPEG-SH aqueous solution, and stirring for 30-50min at the rotating speed of 500-1000rpm under the condition of 20-30 ℃ to obtain a mixed solution;

(2) dropwise adding NaBH into the mixed solution obtained in the step (1)₄Reacting the aqueous solution for 12 to 24 hours to obtain mPEG Au-NPs solution;

(3) and (3) centrifuging the mPEG Au-NPs solution prepared in the step (2), and obtaining supernate, namely the nano gold micelle catalyst.

3. The method for preparing the nanogold micelle catalyst according to claim 2, wherein the HAuCl is prepared by reacting the nanogold micelle catalyst with the HAuCl₄Aqueous solution, HAuCl₄The concentration is 0.05-0.5 mol/L.

4. The method for preparing the nanogold micelle catalyst according to claim 3, wherein the concentration of the mPEG-SH in the mPEG-SH aqueous solution is 0.1 to 0.5 mol/L.

5. The method for preparing the nanogold micelle catalyst according to claim 4, wherein the HAuCl is added to the solution₄The volume ratio of the aqueous solution to the mPEG-SH aqueous solution is 1: 1.

6. The method for preparing the nanogold micelle catalyst according to claim 5, wherein the NaBH is₄Aqueous solution, NaBH₄The concentration is 0.1-0.3mol/L, and the total dropping amount is 0.4 mL.

7. The method for preparing the nanogold micelle catalyst according to claim 2, wherein the centrifugation conditions in the step (3) are 8000- "12000 r/min and 30-60 min.

8. Use of the nanogold micelle catalyst according to claim 1 in the preparation of fatty acid esters.

9. The use of claim 8, wherein the fatty alcohol, the nanogold catalyst, the alkali assistant and the water are mixed according to a ratio of 4 mmol: (0.5-3.0) mg: 0.5 mmol: mixing at a ratio of 15mL, introducing oxygen at a temperature of 50-100 ℃, stirring at 500-1000rpm, and reacting for 1-20h to obtain the fatty acid ester.

10. Use according to claim 9, wherein the base adjuvant is NaOAc, Et₃N,KH₂PO₄，K₂CO₃KOH, NaOH and [ Bmim ]]One of OH.

Technical Field

The invention relates to the technical field of nano-gold micelle catalysts, in particular to a nano-gold micelle catalyst and a preparation method and application thereof.

Background

The self-esterification of aliphatic alcohols, i.e.the oxidative esterification of alcohols, is a preferred means for producing fine chemicals and intermediates. To date, the development of economical and green oxidants for esterification of fatty alcohols into synthetic esters has been considered a subject of intense research. However, the self-esterification of aliphatic alcohols into esters in water remains a challenge due to the increasing demand for biological substrates and green chemical conversions. The research and development of the high-efficiency aqueous phase oxidation esterification catalyst for fatty alcohol is an important bottleneck problem for realizing the preparation of fatty acid ester by the aqueous phase conversion of bio-based fatty alcohol, and no method report for preparing fatty acid ester by using gold nano-micelle aqueous phase catalysis fatty alcohol exists at present.

Disclosure of Invention

The invention provides a nanogold micelle catalyst, a preparation method and application thereof, and aims to solve the problem that a high-efficiency catalyst is lacked in fatty acid ester preparation through water phase conversion of bio-based fatty alcohol. The nano gold micelle catalyst is prepared from HAuCl₄，mPEG-SH，NaBH₄And water.

The preparation method of the nanogold micelle catalyst comprises the following specific steps:

(1) adding HAuCl₄Mixing the aqueous solution with the mPEG-SH aqueous solution, and stirring for 30-50min at the rotating speed of 500-1000rpm under the condition of 20-30 ℃ to obtain a mixed solution;

(2) dropwise adding NaBH into the mixed solution obtained in the step (1)₄Reacting the aqueous solution for 12 to 24 hours to obtain mPEG Au-NPs solution;

(3) and (3) centrifuging the mPEG Au-NPs solution prepared in the step (2), and obtaining supernate, namely the nano gold micelle catalyst.

Preferably, the HAuCl is₄Aqueous solution, HAuCl₄The concentration is 0.05-0.5 mol/L.

Preferably, the concentration of the mPEG-SH in the mPEG-SH aqueous solution is 0.1-0.5 mol/L.

Preferably, the HAuCl is₄The volume ratio of the aqueous solution to the mPEG-SH aqueous solution is 1: 1.

Preferably, the NaBH is₄Aqueous solution, NaBH₄The concentration is 0.1-0.3mol/L, and the total dropping amount is 0.4 mL.

Preferably, the centrifugation conditions in step (3) are 8000-12000r/min and 30-60 min.

The application of the nanogold micelle catalyst in preparation of fatty acid ester is disclosed.

Preferably, the fatty alcohol, the nanogold catalyst, the alkali assistant and the water are mixed according to the ratio of 4 mmol: (0.5-3.0) mg: 0.5 mmol: mixing at a ratio of 15mL, introducing oxygen at a temperature of 50-100 ℃, stirring at 500-1000rpm, and reacting for 1-20h to obtain the fatty acid ester.

Preferably, the alkali assistant is NaOAc, Et₃N,KH₂PO₄，K₂CO₃KOH, NaOH and [ Bmim ]]One of OH.

Advantageous effects

The nano gold micelle catalyst, namely the monodisperse MPEG-modified AuNPS prepared by the invention can be in the O state₂Under flow (30mL/min), at 80 ℃ and basic ionic liquid [ BMIM]In the presence of OH, the catalyst effectively catalyzes the self-esterification reaction of inert fatty alcohol and is oxidized in water, the oxidation process is green, and the highest yield of the octyl caprylate substrate can reach 83.6 percent. By using MPEG stabilizers, the catalyst has good stability and does not show any aggregation of gold nanoparticles during the oxidation reaction. The water in the reaction is the only solvent, the catalyst is easy to enrich, separate and reuse, and the alkaline ionic liquid [ Bmim]OH has better auxiliary catalysis effect than reported inorganic base, and higher ester yield can be obtained.

The method can realize the preparation of fatty acid ester by the water-phase oxidation of fatty alcohol, mainly because the active center of the nano-gold particles contained in the catalyst has better catalytic oxidation performance and has good dispersibility in water under the modification of a sulfhydryl fatty chain, the substrate alcohol can be better contacted with the catalyst, better mass transfer is realized, the catalyst has good stability in water, and the catalyst still keeps good dispersion after reaction. In addition, the particle size of the catalyst is proper, the catalyst can be separated from the hydrosolvent under the centrifugal condition, the recovery is realized, the aqueous solution with good dispersibility is formed again after water is added again, the reutilization is realized, and the problems of poor mass transfer and low yield in the catalytic process are solved.

Drawings

FIG. 1 is an SEM photograph of mPEG-based Au-NPs catalyst prepared in specific example 1;

FIG. 2 is a graph of the particle size distribution of the mPEG-based Au-NPs catalyst prepared in example 1;

FIG. 3 is a schematic diagram of the synthesis of mPEG-based Au-NPs prepared in example 1.

Detailed Description

The experimental procedures used in the following examples are conventional unless otherwise specified.