Silver nanoclusters and application thereof in photocatalytic decarboxylation reaction of lauric acid

Abstract

The application discloses silver nanoclusters and application of the silver nanoclusters in a photocatalytic decarboxylation reaction of lauric acid. 14 (SPh 3.5 (CF3)2) 12 (DPPF)3, wherein SPh 3.5 (CF3)2=3.5-bis(trifluoromethyl)benzenethiol, DPPF=1,1-bis(diphenylphosphino)ferrocene. The silver nanoclusters are compounded with TiO2 to be used as a catalyst, and the catalyst is used for catalyzing the decarboxylation reaction of lauric acid, and selectively generates undecane, and the yield reaches 85 %, thereby providing a reference for selection of a catalyst for a subsequent biomass decarboxylation reaction.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalytic decarboxylation of biomass fatty acids, and particularly relates to a silver nanocluster and application thereof in a lauric acid photocatalytic decarboxylation reaction. BACKGROUND

[0002] Long-chain alkanes are among the most important chemicals in modern society, as they are the main components of diesel and jet fuel and can be used as feedstocks for the production of olefins and aromatics. Producing such alkanes from renewable biomass instead of fossil resources is very attractive and of great importance for a sustainable supply of energy and chemicals. In this context, bio-derived fatty acids are promising candidates because of their inherent structural similarity to diesel-type hydrocarbons, inedibility, abundance, and low cost. Fatty acids can be converted to alkanes by hydrodeoxygenation. However, most established catalytic systems require harsh conditions (reaction temperature ≥ 250 °C, H2 pressure ≥ 2 MPa) leading to intensive energy input and excessive H2 consumption (≥ 3 molar ratio H2 per reactant) with unnecessary cracking and coke deposition. Such harsh reaction conditions greatly challenge the overall energy efficiency of the proposed alkane synthesis, and therefore it is highly desirable to find a way to effectively convert fatty acids to alkanes under mild conditions (ambient temperature, low reaction pressure).

[0003] In 2020, Wang's group used Pt-TiO2 to catalyze the decarboxylation reaction of lauric acid and obtained 93% of undecane. However, Pt as a noble metal cannot be ignored in terms of cost. SUMMARY

[0004] In order to overcome the deficiencies of the prior art, the application provides a silver nanocluster and application thereof in a lauric acid photocatalytic decarboxylation reaction. The synthesis method of the silver nanocluster of the application is simple, the conditions are mild, the operation steps are simple, the synthesized silver nanocluster has high stability and high yield, and at the same time has excellent catalytic performance.

[0005] The application replaces a noble metal catalyst with Ag. Silver nanoclusters are often used as catalysts for organic reactions due to their ultra-small size and atomically precise structure. Unlike traditional large-particle metal particles, metal nanoclusters are a kind of metal core with a size of about 1-2 nanometers, and the metal core (composed of several to several hundred metal atoms) is protected by an organic ligand shell (sulfate, phosphine, alkyne, etc.). Therefore, it is very meaningful and valuable to use Ag nanoclusters as catalysts for decarboxylation of biomass fatty acids.

[0006] The silver nanocluster of the application has a molecular formula of Ag 14 (SPh 3.5 (CF3)2) 12 (DPPF)3, wherein SPh3.5 (CF3)2=3.5-bis(trifluoromethyl)benzenethiol, DPPF=1,1-bis(diphenylphosphino)ferrocene.

[0007] The silver nanocluster of the present application is prepared by the following steps:

[0008] Silver nitrate is added to a 100 mL round bottom flask containing 10 mL of methanol, after stirring for five minutes, 3.5-bis(trifluoromethyl)benzenethiol is added, and stirring is carried out at room temperature to obtain a white turbid solution; after ten minutes, 1,1-bis(diphenylphosphino)ferrocene is added, and 15 mL of chloroform and 10 mL of ethanol are added at the same time, and after twenty-five minutes, a reducing agent is added to the system, and after 20 hours, the reaction solution becomes black purple; the obtained black purple reaction solution is centrifuged to remove insoluble substances, and the organic phase is treated by rotary evaporation, then dissolved in a small amount of dichloromethane and extracted with a large amount of n-hexane solvent to obtain purple Ag 14 (SPh 3.5 (CF3)2) 12 (DPPF)3nanocluster.

[0009] Application of the silver nanocluster of the present application in the photocatalytic decarboxylation reaction of lauric acid.

[0010] Specifically, the silver nanocluster is compounded with TiO2 to serve as a catalyst (Ag 14 @TiO2), which catalyzes the decarboxylation reaction of lauric acid.

[0011] The TiO2 is anatase TiO2.

[0012] The compounding process includes the following steps:

[0013] The silver nanocluster is dissolved in dichloromethane, and after uniform stirring and dispersion, TiO2 is added, and the mixture is fully stirred at room temperature for 5 hours, and the precipitate is obtained by centrifugation, and the precipitate is washed with ethanol for more than 3 times, and then dried in a vacuum drying oven at 50°C to obtain the Ag 14 @TiO2 catalyst.

[0014] The catalytic reaction includes the following steps:

[0015] Lauric acid (0.2 mmol, 40 mg) and 10 mg of Ag 14 @TiO2 catalyst are added in acetonitrile solvent. The reaction is carried out in an inert gas atmosphere. The reaction is stirred under LED light with a wavelength of 365 nm for 5 hours; at the end of the reaction, dodecane is added as an internal standard, and ethyl acetate is added to extract the organic matter, and the solution is diluted to a certain concentration to determine the yield of undecane by gas chromatography (CG).

[0016] The reaction route is shown as follows:

[0017] .

[0018] Compared with the prior art, the beneficial effects of the present application are embodied in:

[0019] 1、 The present application uses Ag nanoclusters as a metal source to catalyze the decarboxylation conversion reaction of biomass. Compared with the catalysts such as Pt and Ru used by the previous person, it is more cost-saving. The catalyst synthesis method is simple, the conditions are mild, the yield is high, and the synthesis of kilograms can be realized.

[0020] 2、 The Ag 14 @TiO2 can catalyze the decarboxylation reaction of lauric acid to selectively generate undecane, and the yield reaches 85%, which provides a reference for the selection of catalysts for subsequent biomass decarboxylation reactions.

[0021] 3、 The present application adopts photocatalysis, compared with high-temperature and high-pressure reaction, the conditions are mild, the operability is strong, and the idea of using clusters as catalysts for biomass reaction is novel and has strong innovation.

[0022] 4、 The reaction conditions used in the present application only require inert gas, and the previous research on the decarboxylation reaction needs to add hydrogen, which is not easy to operate and has safety hazards. DETAILED DESCRIPTION

[0023] Figure 1 The preparation flow chart of the catalyst of the present application.

[0024] Figure 2 The crystal structure diagram of the silver cluster of the present application.

[0025] Figure 3 The transmission electron microscope diagram of the catalyst of the present application.

[0026] Figure 4 The actual operation diagram of the decarboxylation of lauric acid to generate undecane of the present application.

[0027] Figure 5 The gas phase analysis diagram of the lauric acid reaction of the present application. DETAILED DESCRIPTION

[0028] The technical scheme of the present application will be further analyzed and described below through specific examples.

[0029] Example 1: Ag 14 (SPh 3.5 (CF3)2) 12 (DPPF)3 nanocluster synthesis

[0030] AgNO3(30 mg, 0.177 mmol) was added to 10 mL of methanol solvent, stirred for five minutes, then 3.5-bis(trifluoromethyl)benzenethiol was added, and after stirring for 5 min, 1,1-bis(diphenylphosphino)ferrocene (24.9 mg, 0.045 mmol) was added to the above solution, the color of the solution was yellow, 15 mL of chloroform and 10 ml of ethanol mixed solution was added, stirred for 15 min, then 2 mL of NaBH4 ethanol solution (0.474 mmol) was added dropwise to the reaction solution, the reaction solution changed from yellow to orange and finally to black, stirred for 20 h, centrifuged to remove the insoluble, dissolved in a small amount of dichloromethane and extracted with a large amount of n-hexane solvent, to obtain Ag 14 (SPh 3.5 (CF3)2) 12 (DPPF)3nanocluster.

[0031] Example 2: Ag 14 (SPh 3.5 (CF3)2) 12 (DPPF)3nanocluster supported

[0032] 1 mg of Ag 14 (SPh 3.5 (CF3)2) 12 (DPPF)3nanocluster was added to 50 mL of CH2Cl2, then 100 mg of TiO2 was added to the above solution and stirred at room temperature for 5 hours, centrifuged and dried at room temperature for 5 hours to obtain a supported silver catalyst with a loading of 1%, referred to as Ag 14 @TiO2.

[0033] Example 3: Lauric acid photocatalytic decarboxylation reaction

[0034] A 10 ml Schlenk tube was used, the upper end was connected to a tube connected to a balloon. 0.2 mmol (40 mg) of lauric acid was weighed into the tube, then 10 mg of Ag 14 @TiO2catalyst was weighed into the tube. The Schlenk tube was connected to a double-tube for vacuuming, the air in the tube was exhausted, at the same time, argon was introduced into the tube, the operation was repeated three times to ensure that no air entered, then 6 ml of anhydrous acetonitrile solution was injected into the tube as a reaction reagent. Close the valve, place the Schlenk tube under a 365 nm wavelength LED lamp and stir for 5 h. At the end of the reaction, the balloon was removed, 45 μL of dodecane liquid was added as an internal standard. Then organic solvents such as ethyl acetate and acetone were added to extract the products and raw materials, etc. The liquid was filtered through a filter membrane and placed in a gas phase bottle, and the product yield was analyzed by gas chromatography (85%).

[0035] Example 4: Lauric acid photocatalytic decarboxylation reaction (without Ag 14 Cluster)

[0036] A 10 ml Schlenk tube was used, and the upper end was connected to a tube connected to a balloon. 0.2 mmol (40 mg) of lauric acid was weighed into the tube, and 10 mg of TiO2 catalyst was weighed into the tube. The Schlenk tube was connected to a double-tube for vacuuming, and the air in the tube was exhausted, and at the same time, argon was introduced into the tube, and the operation was repeated three times to ensure that no air entered. 6 ml of anhydrous acetonitrile solution was injected into the tube as a reaction reagent. The valve was closed, and the Schlenk tube was placed under a 365 nm wavelength LED lamp for stirring reaction for 5 h. At the end of the reaction, the balloon was removed, and 45 μL of dodecane liquid was added as an internal standard. Ethyl acetate, acetone and other organic solvents were added to extract the product and raw materials, and the liquid was filtered through a filter membrane and placed in a gas phase bottle. The product yield was analyzed by gas chromatography (43%).

[0037] Example 4: Lauric acid photocatalytic decarboxylation reaction (without light, reaction at room temperature)

[0038] A 10 ml Schlenk tube was used, and the upper end was connected to a tube connected to a balloon. 0.2 mmol (40 mg) of lauric acid was weighed into the tube, and 10 mg of TiO2 catalyst was weighed into the tube. The Schlenk tube was connected to a double-tube for vacuuming, and the air in the tube was exhausted, and at the same time, argon was introduced into the tube, and the operation was repeated three times to ensure that no air entered. 6 ml of anhydrous acetonitrile solution was injected into the tube as a reaction reagent. The valve was closed, and the Schlenk tube was placed under a 365 nm wavelength LED lamp for stirring reaction for 5 h. At the end of the reaction, the balloon was removed, and 45 μL of dodecane liquid was added as an internal standard. Ethyl acetate, acetone and other organic solvents were added to extract the product and raw materials, and the liquid was filtered through a filter membrane and placed in a gas phase bottle. The product yield was analyzed by gas chromatography (43%).

[0039] Example 5: Lauric acid photocatalytic decarboxylation reaction (undecane yield under different reaction times)

[0040] Two 10 ml Schlenk tubes were used, the upper end of which was connected to a tube connected to a balloon. 0.2 mmol (40 mg) of lauric acid was weighed into the tube, and 10 mg of Ti02 catalyst was weighed into the tube. The Schlenk tube was connected to a double-tube for vacuuming, and the air in the tube was removed, while argon was introduced into the tube, and the operation was repeated three times to ensure that no air entered. 6 ml of anhydrous acetonitrile solution was injected into the tube as a reaction reagent. The valve was closed, and the Schlenk tube was stirred at room temperature in the dark for 2 h, 3 h, and 4 h, respectively. At the end of the reaction, the balloon was removed, and 45 μL of dodecane liquid was added as an internal standard. Ethyl acetate, acetone, and other organic solvents were added to extract the products and raw materials, and the liquid was filtered through a filter membrane and placed in a gas phase bottle. The product yield was analyzed by gas chromatography (32%, 54%, and 76%, respectively).

[0041] Example 6: Photocatalytic decarboxylation of lauric acid (changing the light source to a mercury lamp and a xenon lamp)

[0042] Two 10 ml Schlenk tubes were used, the upper end of which was connected to a tube connected to a balloon. 0.2 mmol (40 mg) of lauric acid was weighed into the tube, and 10 mg of Ti02 catalyst was weighed into the tube. The Schlenk tube was connected to a double-tube for vacuuming, and the air in the tube was removed, while argon was introduced into the tube, and the operation was repeated three times to ensure that no air entered. 6 ml of anhydrous acetonitrile solution was injected into the tube as a reaction reagent. The valve was closed, and the Schlenk tube was stirred at room temperature in the dark for 2 h, 3 h, and 4 h, respectively. At the end of the reaction, the balloon was removed, and 45 μL of dodecane liquid was added as an internal standard. Ethyl acetate, acetone, and other organic solvents were added to extract the products and raw materials, and the liquid was filtered through a filter membrane and placed in a gas phase bottle. The product yield was analyzed by gas chromatography (32%, 54%, and 76%, respectively).

Claims

1. The application of silver nanoclusters in the photocatalytic decarboxylation reaction of lauric acid, characterized in that: The molecular formula of the silver nanoclusters is Ag. 14 (SPh 3.5 (CF3)2) 12 (DPPF)3, where SPh 3.5 (CF3)2=3,5-bis(trifluoromethyl)benzylthiophenol, DPPF=1,1-bis(diphenylphosphine)ferrocene; Silver nanoclusters combined with TiO2 were used as a catalyst to catalyze the decarboxylation reaction of lauric acid. The compounding process includes the following steps: Silver nanoclusters were dissolved in dichloromethane and dispersed evenly. TiO2 was then added, and the mixture was stirred thoroughly at room temperature for 5 hours. The precipitate was collected by centrifugation, washed with ethanol, and dried under vacuum to obtain Ag. 14 @TiO2 catalyst; The catalytic reaction includes the following steps: Lauric acid and Ag were added to acetonitrile solvent respectively. 14 The reaction was carried out with a TiO2 catalyst in an inert gas atmosphere and stirred under LED light at a wavelength of 365 nm to produce undecane.

2. The application according to claim 1, characterized in that: The TiO2 is anatase TiO2.

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