# US 9,433,926 B2 · Platinum/carbon nanotube catalyst, the preparation process and use thereof

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- Number: US 9,433,926 B2
- Document ID: US9433926B2
- Status: Granted
- Kind: B2
- Application number: 14/673,427
- Filed: 2015-03-30
- Published: 2015-08-06
- Granted: 2016-09-06
- Earliest claimed: 2009-10-21
- Assignees: Dalian Institute of Chemical Physics, Chinese Academy of Sciences
- Applicants: Dalian Institute of Chemical Physics, Chinese Academy of Sciences
- Inventors: Can Li; Zhijian Chen
- Web page: https://patentgrep.com/patent/US9433926B2

## CPC

- B01J 23/42: Platinum
- B01J 21/185: {Carbon nanotubes (carbon nanotubes per se C01B32/15)}
- B01J 35/45: Nanoparticles
- B01J 37/009: {Preparation by separation, e.g. by filtration, decantation, screening}
- B01J 37/0201: {Impregnation}
- B01J 37/16: Reducing
- B01J 37/343: {of ultrasonic wave energy}
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- C07B 35/02: Reduction
- C07C 67/30: by modifying the acid moiety of the ester, such modification not being an introduction of an ester group
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- C07B: GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR (preparation of carboxylic acid esters by telomerisation C07C67/47; telomerisation C08F)
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS

## Abstract

A platinum/carbon nanotube catalyst applicable to heterogeneous asymmetric hydrogenation, which is fabricated by supporting platinum on carbon nanotube carriers, and prepared by the steps of: heating purified carbon nanotubes in nitric acid, filtering and washing the same with water until pH value of the filtrate becomes neutral, drying the carbon nanotubes; immersing the carbon nanotube carriers obtained in an aqueous chloroplatinic acid solution and carrying out ultrasonic treatment at room temperature; immersing the mixture of the carbon nanotubes and the aqueous chloroplatinic acid solution under stirring; drying the material by heating to 110° C. from room temperature and maintaining this temperature; grinding the product to fine powders, reducing the fine powders with an aqueous sodium formate solution under a heating condition, filtering and washing the product with deionized water, and drying the product.

## Claims

### Claim 1

A platinum/carbon nanotube catalyst for heterogeneous asymmetric hydrogenation wherein platinum nanoparticles are loaded on the outer surfaces of the tube cavities of carbon nanotubes, said platinum/carbon nanotube catalyst takes carbon nanotubes as carriers, and said platinum nanoparticles are 2-10 wt % based on the weight of the carbon nanotubes loaded with the platinum nanoparticles, wherein the platinum/carbon nanotube catalyst is prepared by the steps of:
1) preparing carbon nanotube carriers by treating purified carbon nanotubes in nitric acid at 110-160° C. for 4-16 hours, filtering and washing the carbon nanotubes with water until pH value of the filtrate becomes neutral, drying the carbon nanotubes at 50-120° C. so as to obtain functionalized carbon nanotube carriers;
2) adding xylene to the carbon nanotube carriers under stirring and carrying out ultrasonic treatment for 1-4 hours;
3) adding an aqueous chloroplatinic acid solution to the product obtained in step 2) under stirring, and then adding deionized water, and stirring the product continuously for 15-30 minutes;
4) adding sodium formate with a purity ≧99.5 wt % to the product obtained in step 3) to perform reduction at 70-120° C. under stirring for 0.5-3 hours, and cooling the product;
5) after cooling and layer separation, decanting a supernatant, adding absolute ethanol and stirring for dispersion, and carrying out separation; and
6) dispersing the product obtained in step 5) into deionized water, filtering, and washing with water until pH value of the filtrate becomes neutral, drying at 50-120° C. so as to obtain a platinum/carbon nanotube catalyst wherein platinum nanoparticles are loaded on the outer surfaces of the tube cavities of carbon nanotubes.

### Claim 2 (depends on 1)

A process for preparing the platinum/carbon nanotube catalyst wherein platinum nanoparticles are loaded on the outer surfaces of the tube cavities of carbon nanotubes as claimed in claim 1, comprising the steps of:
1) preparing carbon nanotube carriers by treating purified carbon nanotubes in nitric acid with a concentration of 65-68 wt % at 110-160° C. for 4-16 hours, filtering and washing the carbon nanotubes with water until pH value of the filtrate becomes neutral, drying the carbon nanotubes at 50-120° C. so as to obtain functionalized carbon nanotube carriers;
2) adding xylene to the carbon nanotube carriers under stirring and carrying out ultrasonic treatment for 1-4 hours;
3) adding an aqueous chloroplatinic acid solution to the product obtained in step 2) under stirring, and then adding deionized water, and stirring the product continuously for 15-30 minutes;
4) adding sodium formate with a purity ≧99.5 wt % to the product obtained in step 3) to perform reduction at 70-120° C. under stirring for 0.5-3 hours, and cooling the product;
5) after cooling and layer separation, decanting a supernatant, adding absolute ethanol and stirring for dispersion, and carrying out separation; and
6) dispersing the product obtained in step 5) into deionized water, filtering, and washing with deionized water until pH value of the filtrate becomes neutral, drying at 50-120° C. so as to obtain a platinum/carbon nanotube catalyst wherein platinum nanoparticles are loaded on the outer surfaces of the tube cavities of carbon nanotubes.

### Claim 3 (depends on 2)

The process as claimed in claim 2, wherein the carbon nanotubes are single-wall carbon nanotubes or multi-wall carbon nanotubes.

### Claim 4 (depends on 2)

The process as claimed in claim 2, wherein the concentration of the aqueous chloroplatinic acid solution is 0.8-10 mg Pt/ml, and the amount of the aqueous chloroplatinic acid solution as compared with the carbon nanotubes is 5-60 ml/g.

### Claim 5 (depends on 2)

The process as claimed in claim 2, wherein an ultrasonic oscillator is used for the ultrasonic treatment, wherein the output power of the ultrasonic oscillator is 120-1000 W, the working frequency thereof is 40-60 KHz.

### Claim 6 (depends on 2)

The process as claimed in claim 2, wherein the concentration of the aqueous sodium formate solution is 24-42 mg/ml, and the mole ratio of sodium formate to the reduced platinum is 10-20:1.

### Claim 7 (depends on 1)

A process for asymmetric hydrogenation of α-ketoester substrates comprising conducting the asymmetric hydrogenation of α-ketoester substrates in the presence of the platinum/carbon nanotube catalyst of claim 1 and under the modification of a chiral modifier, wherein:
the substrates are α-ketoesters, and the formula of α-ketoesters is R1C(O)C(O)OR2, in which R1 is CH3—, C6H5— or C6H5(CH2)3—; R2 is CH3— or C2H5—;
the chiral modifier is one or more selected form cinchona alkaloids;
the solvent is one or two selected from the group consisting of methanol, ethanol, acetic acid, toluene, dichloromethane and tetrahydrofuran; and
the hydrogenation is carried out at a temperature of 0-35° C., a stirring speed of 400-1800 rpm and a hydrogen pressure of 1.0-10 MPa.

### Claim 8 (depends on 7)

The process of claim 7, wherein the platinum/carbon nanotube catalyst is pretreated in a hydrogen gas stream at 200-400° C. for 1.5-2 hours before use.

### Claim 9 (depends on 7)

The process of claim 7, wherein the cinchona alkaloid is cinchonidine or dihydrocinchonidine.