CN109772450B - Alkaline resin supported nano-gold catalyst and preparation and application thereof - Google Patents

Abstract

Translated fromChinese

本发明公开了一种碱性树脂负载纳米金催化剂，为以碱性树脂为载体，所述的金纳米粒子在催化剂中所占质量分数为0.2～18％；所述的碱性树脂为二乙烯基苯类单体与碱性乙烯基单体的交联共聚所得；所述的金纳米粒子尺寸范围为1～6nm。本发明催化剂催化效率高，在水介质中以氧气为唯一氧化剂催化不饱和脂肪醇的选择性氧化反应时对醛的选择性高、可以达到100％，反应结束后，催化剂可通过离心或过滤分离循环利用，绿色环保，更加符合可持续发展的要求。The invention discloses a basic resin-supported nano-gold catalyst. The basic resin is used as a carrier, and the mass fraction of the gold nanoparticles in the catalyst is 0.2-18%; the basic resin is diethylene It is obtained by cross-linking copolymerization of benzene-based monomers and basic vinyl monomers; the size of the gold nanoparticles ranges from 1 to 6 nm. The catalyst of the invention has high catalytic efficiency, and when oxygen is used as the only oxidant in an aqueous medium to catalyze the selective oxidation reaction of unsaturated aliphatic alcohol, the selectivity to aldehyde is high, which can reach 100%. After the reaction, the catalyst can be separated by centrifugation or filtration. Recycling, green and environmental protection, more in line with the requirements of sustainable development.

Description

Alkaline resin supported nano-gold catalyst and preparation and application thereof

Technical Field

The invention relates to the technical field of catalyst design, in particular to an alkaline resin-loaded nano-gold catalyst and a preparation method thereof, and application of the alkaline resin-loaded nano-gold catalyst in catalyzing selective oxidation of unsaturated fatty alcohol in an aqueous medium to prepare unsaturated fatty aldehyde.

Background

The catalytic oxidation of unsaturated fatty alcohols to aldehydes is an important functional group conversion reaction in organic chemistry, and generally, the oxidation of unsaturated fatty alcohols requires the use of stoichiometric amounts of inorganic oxidants such as permanganate and chromate. These reagents efficiently oxidize unsaturated fatty alcohols to desired products while also generating a large amount of harmful by-products, which are costly, difficult to separate, and environmentally unfriendly. Oxygen is taken as an oxidant, and the byproduct is only water. However, oxygen molecules are more difficult to activate than most other oxidizing agents, and once activated, the reaction is difficult to control over oxidation to inhibit the formation of acids and esters, and to avoid oxidation and isomerization of unsaturated double bonds. In addition, the use of a large amount of an organic solvent in an oxygen atmosphere is likely to cause danger.

At present, the catalyst for the oxidation of unsaturated fatty alcohol mainly comprises supported palladium, gold, platinum, ruthenium and the like, but the catalytic effect is not satisfactory, and further optimization and improvement are needed. Therefore, in the present day that green chemistry is increasingly regarded as important, from the viewpoint of environmental protection and sustainable development, and from the viewpoint of improvement of economic benefits, there is an urgent need to develop a green high-efficiency oxidation system using hydrogen peroxide or oxygen to replace the conventional oxidation system and using water as a solvent, and it is very important to develop a novel, high-efficiency, high-selectivity catalyst for aldehydes suitable for aqueous media.

The invention designs the nano gold catalyst loaded by the synthetic alkaline polyester aiming at the characteristic of selective oxidation reaction in the aqueous medium, is applied to the selective oxidation of unsaturated fatty alcohol into unsaturated fatty aldehyde, has the selectivity of the reaction on the aldehyde as high as 100 percent, avoids the oxidation and isomerization of unsaturated double bonds, inhibits excessive oxidation to a great extent, and saves a great deal of energy consumption for later separation.

Disclosure of Invention

The invention provides the basic resin supported nano-gold catalyst which is high in catalytic efficiency, good in selectivity and easy to recover.

The invention also provides a preparation method of the alkaline resin supported nano gold catalyst, which is simple to operate, easy to control and suitable for industrial production.

The invention also provides an application method of the alkaline resin supported nano gold catalyst in selective oxidation of unsaturated fatty alcohol in an aqueous medium, the selectivity of the catalyst on aldehyde is high, and the catalyst in the method can be recycled and reused.

A basic resin supported nano gold catalyst is characterized in that: taking alkaline resin as a carrier, wherein the mass fraction of the gold nanoparticles in the catalyst is 0.2-18%; the preferable range is 2-10%, the carrier waste can be caused when the loading amount is too small, and the gold particle size is easily larger when the loading amount is too high, so that the total specific surface area of gold is reduced, and the use efficiency is reduced

The basic resin supported nano gold catalyst is characterized in that the basic resin is obtained by cross-linking copolymerization of a divinylbenzene monomer and a basic vinyl monomer;

the mole ratio of the divinyl benzene monomer to the basic vinyl monomer in the copolymer is 0.5-20: 1, preferably 1-10: 1, the number of coordination sites in the carrier can be reduced due to the fact that the content of the divinyl benzene monomer is too high, so that loading of gold is not facilitated, and the generation of isomers due to the fact that the basicity of a catalytic system is stronger due to the fact that the content of the basic vinyl monomer is too high

Wherein the divinyl benzene monomer is a compound shown in a structural formula (I), the basic vinyl monomer is one or more than two compounds shown in a structural formula (II) or a structural formula (III):

formula (I);

in the formula (I), R₁、R₂、R₃、R₄And R₅Identical or different, R₁Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₂Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₃Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₄Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₅Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₁、R₂、R₃、R₄And R₅The same or different, and at least one is a vinyl group;

formula (II);

in the formula (II), R₆Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₇Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₈Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₉Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₆、R₇、R₈And R₉The same or different, and at least one is a vinyl group;

formula (III);

in the formula (III), R₁₀Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₁₁Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₁₂Is hydrogen,Alkyl or vinyl groups having 1 to 4 carbon atoms, R₁₃Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₁₀、R₁₁、R₁₂And R₁₃Identical or different and at least one is a vinyl group.

The size range of the gold nanoparticles is 1-6 nm, and preferably 2-5 nm.

According to the preparation method of the alkaline resin supported nano-gold catalyst, the alkaline resin supported nano-gold catalyst is a compound obtained by impregnating alkaline resin in an alcoholic solution of gold salt and then reducing the alkaline resin in sodium borohydride.

The gold salt is gold chloride or gold nitrate, the mass ratio of the gold salt to the alkaline resin is 5-40: 100, and the alcohol is C₁～C₄The molar ratio of the sodium borohydride to the gold salt is 5-20: 1.

The preparation method of the basic resin supported nano gold catalyst comprises the following steps: according to the mass ratio of the gold chloride to the alkaline resin, immersing the alkaline resin into a methanol solution containing the gold chloride and vigorously stirring for 8-24 hours, immersing a solid obtained by coordination of gold ions and nitrogen in the alkaline resin into the methanol solution prepared according to the molar ratio of the gold chloride to the sodium borohydride, and vigorously stirring for 8-18 hours to obtain the alkaline resin supported nano-gold catalyst.

A process for the selective oxidation of unsaturated fatty alcohols in an aqueous medium comprising adding to the aqueous medium a catalyst and an unsaturated fatty alcohol and carrying out the oxidation of the unsaturated fatty alcohol in the presence of a molecular oxygen-containing gas, characterized in that: the catalyst is the basic resin supported nano gold catalyst as set forth in any one of claims 1 to 4.

The temperature of the oxidation reaction is 50-100 ℃, the time of the oxidation reaction is 2-20 hours, preferably 6-16 hours, the too short reaction time is not beneficial to improving the conversion rate, and the too long reaction time is easy to cause excessive oxidation, so that the selectivity to aldehyde is reduced;

the oxidation reaction comprises the following raw materials in a molar ratio:

unsaturated fatty alcohol 1;

the gold in the catalyst is 0.002-0.1.

The oxygen-containing gas is oxygen, air or a gas formed by mixing oxygen and inert gas in various proportions (the volume proportion of the oxygen is more than 0), and the oxygen is used for oxidation in the mixed gas.

The unsaturated fatty alcohol is one of isopentenol, crotyl alcohol, geraniol, allyl alcohol, 2-methylallyl alcohol, 1, 4-butenediol, vaseline 2, 4-hexadiene-1-alcohol, 3-buten-2-alcohol, 2-methylene-1, 3-propanediol, cis-2-pentenol and cinnamyl alcohol.

The raw materials and reagents of the invention can adopt products sold in the market.

Compared with the prior art, the invention has the following remarkable progress:

the catalyst combines the characteristics of the nano gold particles and the basic polymer resin; the alkaline polymer resin has a spatial network structure, and trivalent gold ions are still fixed in the network after being subjected to coordination reduction with nitrogen in the trivalent gold ions; part of units in the carrier and the substrate have certain hydrophobicity, so that the concentration of the substrate can be locally increased, and meanwhile, the concentration of the catalyst is also locally increased by fixing the gold nanoparticles in the carrier, so that the oxidation reaction rate and the catalyst efficiency are effectively improved; after the gold nanoparticles are loaded on the basic resin, the basic resin can only swell but not dissolve, and can be recycled through simple filtration or centrifugation after the catalytic reaction is finished. The water solubility of unsaturated alcohol such as isopentenol is greatly improved after the unsaturated alcohol is oxidized into unsaturated aldehyde, so that the unsaturated alcohol can be quickly diffused into a water medium, the separation of a product and an active site is accelerated, and further, the further oxidation of the aldehyde is inhibited, and the enrichment of a substrate to the vicinity of an active center is promoted. When the catalyst is used for the selective oxidation of unsaturated fatty alcohol, the selectivity of the catalyst on unsaturated fatty aldehyde is 100%, the subsequent separation steps are reduced, and the utilization rate of raw materials is improved. Meanwhile, the synthetic method of the invention is simple and easy to implement, green and environment-friendly, safe and nontoxic, has wide development space and great market application value, and the unsaturated fatty alcohol oxidation reaction under the action of the catalyst takes water as a solvent and oxygen as an oxidant, does not need other additive auxiliaries, and meets the requirements of sustainable development.

Detailed Description

Example 1 preparation of basic resin-supported nanogold catalyst

In a three-necked flask, Divinylbenzene (DVB) (2.7g, 20mmol), Vinylimidazole (VI) (0.1932g, 2mmol), azobisisobutyronitrile (0.07g), and ethyl acetate (30ml) were added under nitrogen. After the reaction was completed at 100 ℃ for 24 hours, the solvent was dried to obtain 2.68g of a white powder which was a copolymer of divinylbenzene and vinylimidazole (PDVB-VI).

200mg of the white powder is immersed into a methanol solution (10mL) of gold chloride (10mg), stirred vigorously for 16h, centrifuged, washed with methanol, put into a methanol solution (10mL) of sodium borohydride (10mg), stirred vigorously for 16h, centrifuged, washed with methanol, and the basic resin supported nanogold catalyst with gold loading of 1.57% is obtained. The size of the gold nanoparticles is observed to be 1-4 nm through a transmission electron microscope

Examples 2 to 7

Basic resin supported nanogold catalyst was prepared by the method of example 1, except that the molar ratio of DVB to vinyl basic monomer was changed in the synthesis of PDVB-VI, as shown in table 1:

examples 8 to 11

Basic resin-supported nanogold catalyst was prepared by the method of example 1, except that the amount of gold chloride was changed, as shown in table 2:

EXAMPLE 12 Selective Oxidation of unsaturated fatty alcohols in aqueous media

In a jacketed reaction vessel equipped with a stirring paddle, a thermometer and a gas inlet and outlet, isopentenol (0.26mL, 2.5mmol) and 25mL of distilled water were added, and after stirring uniformly, the temperature of the reaction vessel was raised to 90 ℃, 54mg of the catalyst prepared in example 1 (Au/isopentenol-1/200) was added, oxygen was introduced, and the reaction was carried out for 6 hours at a stirring speed of 600 rotor/min. Extracting with ethyl acetate, centrifugally separating to recover catalyst, and recovering catalyst in 98.6% yield. The ethyl acetate solution was analyzed by gas chromatography to obtain isoamylene alcohol conversion 95.3%, product selectivity: 100% of iso-pentenal.

Examples 13 to 18

The method of example 12 was followed for the selective oxidation of unsaturated fatty alcohols in aqueous medium, except that the catalysts prepared in examples 2-7 were used, respectively, and the reaction results are shown in Table 3:

examples 19 to 22

The method of example 12 was followed for the selective oxidation of unsaturated fatty alcohols in aqueous medium, except that the catalysts prepared in examples 8-11 were used, respectively, and the reaction results are shown in Table 4:

examples 23 to 24

The selective oxidation of unsaturated aliphatic alcohols in an aqueous medium was carried out according to the procedure of example 12 except that the catalysts prepared in examples 2 and 3, respectively, were used in which the molar ratios of gold to monomer were 1/50, 1/100, respectively, and the results are shown in Table 5:

example 25

The selective oxidation of unsaturated fatty alcohols in aqueous medium was carried out as in example 12, except that isoamylol was replaced with allyl alcohol (0.39g, 2.5 mmol). The catalyst recovery rate is 97.8%, the allyl alcohol conversion rate is 90.3%, and the product selectivity is as follows: allyl aldehyde 100 percent.

Example 26

The selective oxidation of unsaturated fatty alcohols in aqueous medium was carried out according to the procedure of example 12, except that oxygen was replaced by air, the catalyst recovery was 96.7%, the isoamylene alcohol conversion was 92.1%, the product selectivity: 100% of iso-pentenal.

Example 27

The selective oxydehydrogenation of unsaturated fatty alcohols in aqueous medium was carried out as in example 12, except that the reaction temperature was 60 ℃ and the reaction time 12 hours. The catalyst recovery rate is 97.0%, the isoamylene alcohol conversion rate is 90.7%, and the product selectivity is as follows: 100% of iso-pentenal.

Example 28

Unsaturated fatty alcohol was selectively oxidized in aqueous medium according to the procedure of example 12 except that the catalyst obtained was recovered using example 23. The conversion rate of isoamylene alcohol is 87.8 percent, and the product selectivity is as follows: 100% of iso-pentenal.

TABLE 1

TABLE 2

Example number	Gold chloride dosage (mg)	Gold loading (%)
			8	5	0.61
9	20	2.80
			10	25	2.85
11	30	2.9

TABLE 3

TABLE 4

TABLE 5

Claims (8)

1. A process for the selective oxidation of an unsaturated fatty alcohol in an aqueous medium comprising adding to the aqueous medium a catalyst and the unsaturated fatty alcohol and carrying out the oxidation of the unsaturated fatty alcohol in the presence of a molecular oxygen-containing gas, characterized in that: the catalyst is an alkaline resin loaded nano-gold catalyst, the alkaline resin is used as a carrier, and the mass fraction of the gold nanoparticles in the catalyst is 0.2-18%;

the basic resin is obtained by cross-linking copolymerization of a divinylbenzene monomer and a basic vinyl monomer;

the molar ratio of the divinyl benzene monomer to the basic vinyl monomer in the copolymer is 0.5-20: 1;

wherein the divinyl benzene monomer is a compound shown in a structural formula (I), the basic vinyl monomer is one or more than two compounds shown in a structural formula (II) or a structural formula (III):

formula (I);

in the formula (I), R₁、R₂、R₃、R₄And R₅Identical or different, R₁Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₂Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₃Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₄Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₅Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₁、R₂、R₃、R₄And R₅The same or different, and at least one is a vinyl group;

formula (II);

in the formula (II), R₆Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₇Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₈Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₉Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₆、R₇、R₈And R₉The same or different, and at least one is a vinyl group;

formula (III);

in the formula (III), R₁₀Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₁₁Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₁₂Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₁₃Is hydrogen, alkyl or vinyl with 1 to 4 carbon atoms, R₁₀、R₁₁、R₁₂And R₁₃Identical or different and at least one is a vinyl group.

2. The method of claim 1, wherein the gold nanoparticles are in the size range of 1 to 6 nm.

3. The method of any of claims 1-2, wherein: the basic resin supported nano gold catalyst is a compound obtained by impregnating basic resin in an alcoholic solution of gold salt and then reducing the basic resin by sodium borohydride.

4. The method according to claim 3, wherein the gold salt is gold chloride or gold nitrate, the mass ratio of the gold salt to the alkaline resin is 5-40: 100, and the alcohol is C₁~C₄The molar ratio of the sodium borohydride to the gold salt is 5-20: 1.

5. A method as claimed in claim 3, comprising the steps of: according to the mass ratio of the gold chloride to the alkaline resin, immersing the alkaline resin into a methanol solution containing the gold chloride and vigorously stirring for 8-24 hours, immersing a solid obtained by coordination of gold ions and nitrogen in the alkaline resin into the methanol solution prepared according to the molar ratio of the gold chloride to the sodium borohydride, and vigorously stirring for 8-18 hours to obtain the alkaline resin supported nano-gold catalyst.

6. The process according to claim 1 for the selective oxidation of unsaturated fatty alcohols in an aqueous medium, characterized in that: the temperature of the oxidation reaction is 50-100 ℃, and the time of the oxidation reaction is 2-20 hours;

the oxidation reaction comprises the following raw materials in a molar ratio:

unsaturated fatty alcohol 1;

the gold in the catalyst is 0.002-0.1.

7. The method according to claim 1, wherein the oxygen-containing gas is oxygen, air, or a mixture of oxygen and an inert gas in various proportions, wherein the volume proportion of oxygen is greater than 0, and the oxygen is used for oxidation in the mixture.

8. The method of claim 1, wherein the unsaturated fatty alcohol is one or more of isopentenol, crotyl alcohol, geraniol, allyl alcohol, 2-methylallyl alcohol, 1, 4-butenediol, trans 2, 4-hexadiene-1-ol, 3-buten-2-ol, 2-methylene-1, 3-propanediol, cis-2-pentenol, and cinnamyl alcohol.