Oxidation of Benzyl Alcohol Compounds in the Presence of Carbon Hybrid Supported Platinum Nanoparticles (Pt@CHs)

The carbon hybrid supported platinum nanoparticles have been synthesized by our group for use in the synthesis of benzaldehyde derivatives from benzyl alcohol derivatives. As a result of experiments on different benzyl alcohol derivatives, the catalyst was found to be effective.

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Figure 1
Figure 1. Proposed mechanism for the oxidation reaction

The biggest difference in the products obtained is that the oxidation remains at the aldehyde step. When water was used as the solvent in the reaction, the formation of benzoic acid derivatives was observed. In addition, it was determined that the amount of benzoic acid obtained in the case of increasing temperature also increased. In the developed method, oxygen atmosphere and heat are important parameters. The uncontrolled increase in heat causes the formation of by-products. The oxygen atmosphere is an important parameter in the recovery of the catalyst. This situation is clearly seen in the reaction mechanism of the oxidation process (Figure 1) proposed in the article.

The proton separation processes are facilitated with the help of KOH used in the oxidation reaction. As a result, benzaldehyde derivatives were obtained from benzyl alcohol derivatives in quantitative yields by the selective oxidation reaction. Table 1 gives the results obtained from Pt@CHs catalyzed oxidation reactions. They were all oxidized to the respective benzaldehyde derivatives in the series of benzyl alcohol compounds being studied, with excellent yields in 3 hours at 80 oC.

Table 1. Pt@CHs catalyzed the oxidation of various benzyl alcohol compoundsa

Entry

Substrate

Product

Convb/Selc/Yieldd###/sup#<

Entry

Substrate

Product

Convb/Selc/Yieldd###/sup#<

1

(1)

(2)

>99/100/>99

8

(15)

(16)

>99/100/>99

2

(3)

(4)

>80/100/>80

9

 (17)

 

(18)

>99/100/>99

3

(5)

(6)

>99/100/>99

10

 (19)

 (20)

>99/100/>99

4

(7)

(8)

>99/100/>99

11

(21)

 

(22)

>82/100/>82

5

(9)

(10)

>99/100/>99

12

(23)

(24)

>99/100/>99

6

(11)

(12)

>99/100/>99

13

 (25)

(26)

>99/100/>99

7

(13)

(14)

>55/60/>55

14

(27)

(28)

>99/100/>99

a Reaction Conditions: 1 mmol substrate, 1.5 mmol KOH, 2 mg Pt@CHs catalyst (6.8 % wt metal content), 3 mL of toluene, 80 oC, 3 hours, the continuous stream of O2

b GC conversion based on aromatic substrates.

c Selectivity based on GC results.

d GC yield.

 

As a result of the characterization analysis (Figure 2), Pt@CHs catalyst, synthesized from Pt nanoparticles obtained at an average size of 2.83 nm, has been shown to be stable and reusable for the oxidation reaction that provides 95 % conversion after its 3rd consecutive use in the oxidation reaction of various compounds.

Figure 2
Figure 2. a) XRD pattern, b) Pt 4f electron spectra, c) High-resolution transition electron micrograph, and d) particle size histogram of Pt@CHs

In addition, the fact that the catalyst is easily isolated from the environment and used repeatedly without losing its effectiveness reveals that the developed method is economical and practical.

If you are interested in our study, you can find the full paper here: H. Göksu, H. Burhan, S. Demiroğlu Mustafov, F. Şen, Scientific Reports, 2020, 10, 5439.

 

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FATIH SEN

PROF. DR., DUMLUPINAR UNIVERSITY

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