Sulfur-containing organic ligand modified supported Pt nanoparticle catalyst, preparation method and application

Abstract

The invention discloses a sulfur-containing organic ligand modified loaded Pt nanoparticle catalyst, a preparation method and an application, wherein the carrier of the catalyst is porous silicon oxide, the catalyst contains Pt nanoparticles, the Pt content of the catalyst is 0.5-10 wt%, and the catalyst is modified by a sulfur-containing organic ligand, and the organic ligand content is 0.1-10 wt%. The preparation method is: the porous silicon oxide is impregnated into a Pt salt precursor solution by a solution impregnation method, and the loaded Pt nanoparticles are obtained by drying, roasting, and high-temperature hydrogen reduction; the organic ligand is dissolved in an organic solvent, and the prepared loaded Pt nanoparticles are added to the organic ligand solution, and the loaded Pt nanoparticles modified by the sulfur-containing organic ligand are obtained by centrifugation, washing, and vacuum drying. The catalyst prepared by the present invention has high catalytic activity, high selectivity of the target product and good stability.

Description

Technical Field

[0001] The present invention relates to a catalyst modified with a sulfur-containing organic ligand and loaded with Pt nanoparticles, a preparation method and an application thereof. Background Art

[0002] Biocatalytic reduction is an important approach for preparing high-value-added chemicals and pharmaceuticals. In enzymatic reactions, coenzymes, as hydrogen transfer reagents, bind to oxidoreductases, directly participate in the reactions and play important roles. Reduced coenzyme nicotinamide adenine dinucleotide (NADH) or its phosphorylated form (NADPH) is a coenzyme in enzymatic reduction. 90% of oxidoreductases require NAD(P)H (80% rely on NADH and 10% require NADPH). Since NAD(P)H is very expensive and unstable, using an equimolar amount of reduced coenzyme in the enzymatic reduction reaction is not feasible either economically or in actual operation. Therefore, the recycling of coenzymes is a prerequisite for the large-scale industrial application of enzymatic reduction processes.

[0003] Oxidized coenzyme NAD(P) + In addition to generating enzymatically active 1,4-NADH upon reduction, it is also possible to generate enzymatically inactive 1,6-NADH, dimers and other by-products. Once these by-products are generated, the recycling efficiency of the coenzyme will be greatly reduced. Therefore, in the chemical catalytic NAD(P) + regeneration reaction, selective control is very challenging. In the research on coenzyme-catalyzed regeneration, in the newly developed multi-phase coenzyme hydrogenation regeneration reaction in recent years, H + is the only by-product and the heterogeneous catalyst can be recycled, so it is a green route. However, supported metal catalysts have abundant surface active sites, such as edges, corners, platforms, metal-support interfaces, etc. These different sites will show different structural sensitivities to different reaction groups. Due to the non-uniform active sites of supported metal catalysts and the diverse adsorption modes of substrates, selective control is difficult. To improve the selectivity of multi-phase coenzyme hydrogenation regeneration, researchers have made a lot of efforts and attempts. For example, it has been reported that the selectivity of NADH can be increased to 63% by using the interaction between metal and support (ACS Sustainable Chemistry & Engineering, 2021, Vol. 9, pp. 6499–6506); the authors regulated the selectivity of NADH to 90% through a dual-metal Pt, Sn nanocatalytic strategy (Green Chemistry, 2022, Vol. 24, pp. 1451-1455).

[0004] Although the above strategies can improve the selectivity of coenzyme hydrogenation regeneration, developing highly efficient, highly selective and highly stable metal catalysts is still a technical problem in this field. Summary of the Invention

[0005] To solve the problems existing in the prior art, the present invention provides a sulfur-containing organic ligand-modified supported Pt nanoparticle catalyst, a preparation method thereof, and an application thereof. Similar to the ligand in homogeneous catalysis, the organic group modifies the nanoparticle, and the ligand modifies the metal active center, which can regulate the coordination environment of the active center and regulate the selectivity of the supported metal catalyst NAD + hydrogenation from both the electronic effect and the steric hindrance effect. This solution can be used to improve the selectivity of coenzyme hydrogenation regeneration.

[0006] To achieve the above object, the technical solution adopted by the present invention is a NAD(P) + selective hydrogenation catalyst. The carrier of the catalyst is porous silica, the catalyst contains Pt nanoparticles, the Pt content of the catalyst is 0.5-10 wt%, the catalyst is modified by a sulfur-containing organic ligand, and the content of the organic ligand is 0.1-10 wt%. The catalyst has the characteristics of high catalytic activity, high selectivity of the target product, and high stability.

[0007] In one embodiment of the present invention, the sulfur-containing organic ligand is an aliphatic thiol, an aliphatic thioether, an aromatic thiol, or an aromatic thioether.

[0008] In one embodiment of the present invention, the structural formula of the sulfur-containing organic ligand is:

[0009] ;

[0010] wherein, R 1 and R 2 are respectively selected from any one of F, Cl, Br, OCH 3 , CH 3 , OH, CN, NO 2 , C(CH 3 ) 3 , CH(CH 3 ) 2 , NH 2 , SH.

[0011] In one embodiment of the present invention, the sulfur-containing organic ligand is modified on the surface of the Pt nanoparticles.

[0012] A preparation method of a NAD(P) + selective hydrogenation catalyst. The porous silica is impregnated into the Pt salt precursor solution by the solution impregnation method, and the supported Pt nanoparticles are obtained by drying, calcining, and high-temperature hydrogen reduction;

[0013] Dissolve the organic ligand in an organic solvent, add the prepared Pt nanoparticles supported on a carrier to the organic ligand solution, and obtain the Pt nanoparticles supported on a carrier modified with a sulfur-containing organic ligand through centrifugation, washing, and vacuum drying.

[0014] In one embodiment of the present invention, the preparation steps are as follows:

[0015] 1) Dissolve soluble salts of Pt, such as chloroplatinic acid, sodium chloroplatinate, or potassium chloroplatinate, in water to form a solution, immerse the carrier in this solution, and then perform rotary evaporation for drying, calcination, and reduction. The drying temperature is 20 - 200 °C, the calcination temperature is 100 - 600 °C, and the reduction temperature is 100 - 300 °C.

[0016] 2) Dissolve the sulfur-containing organic ligand in an organic solvent, and perform ultrasonic treatment and stirring. The organic solvent is ethanol, methanol, tetrahydrofuran, ethyl acetate, chloroform, toluene, etc., and the sulfur-containing organic ligand is aliphatic thiol, aliphatic thioether, aromatic thiol, and aromatic thioether.

[0017] 3) Add the solid prepared in step 1 to the solution obtained in step 2 for impregnation adsorption, then centrifuge, wash the obtained solid thoroughly with an organic solvent, and finally perform vacuum drying at room temperature to obtain the Pt nanoparticles supported on a carrier modified with a sulfur-containing organic ligand.

[0018] In one embodiment of the present invention, the concentration of the Pt precursor solution is 1 mM - 5 mM, the amount of solvent is 0 - 50 ml of solvent added per 0.1 g of porous silica carrier, the impregnation time of silica in the Pt salt precursor solution is 1 - 48 h, and the impregnation temperature is from room temperature to 50 °C.

[0019] In one embodiment of the present invention, the Pt salt precursor is one or a mixture of two or more of chloroplatinic acid, sodium chloroplatinate, and potassium chloroplatinate.

[0020] In one embodiment of the present invention, the solvent used in the Pt salt precursor solution is one or a mixture of two or more of water, methanol, ethanol, n-hexane, dichloromethane, and tetrahydrofuran.

[0021] In one embodiment of the present invention, the organic ligand is dissolved in an organic solvent, and the organic solvent is one or a mixture of two or more of ethanol, methanol, tetrahydrofuran, ethyl acetate, chloroform, and toluene.

[0022] In one embodiment of the present invention, the calcination temperature is 100 - 600 °C, the calcination time is 1 - 5 h, the temperature of high-temperature hydrogen is 100 - 300 °C, and the reduction time is 1 - 5 h.

[0023] The NAD(P) mentioned above +Application of Selective Hydrogenation Catalyst in the Hydrogenation of Coenzyme NAD(P) + to NAD(P)H

[0024] In one embodiment of the present invention, the reaction conditions for the hydrogenation of coenzyme NAD(P) + are as follows: the reaction temperature is 0 - 45 °C, and the H 2 pressure is 0.1 - 3 MPa

[0025] The technical solution of the present invention has the following beneficial effects

[0026] 1) The sulfur-containing organic ligand modified Pt nanoparticle catalyst of the present invention modifies the surface of the supported metal catalyst with a sulfur-containing organic ligand to regulate the adsorption mode of NAD(P) + on the catalyst surface, and has the advantages of high catalytic activity, high selectivity for target products, and high stability

[0027] 2) The preparation method of the sulfur-containing organic ligand modified Pt nanoparticles of the present invention has a simple preparation process, low requirements for instrument equipment, mild reaction conditions. By a simple impregnation-H 2 reduction method, metal particles with uniform size and good dispersion are prepared. The average diameter of the metal particle particles reaches 1 - 3 nm. At room temperature, stirring can impregnate and adsorb the sulfur-containing organic ligand onto the surface of the supported metal catalyst. Through simple centrifugation, washing, and drying, the sulfur-containing organic ligand modified Pt nanoparticles can be obtained

[0028] 3) The application of the sulfur-containing organic ligand modified Pt nanoparticles of the present invention applies the catalyst to the reaction of hydrogenating coenzyme NAD(P) + to NAD(P)H. By modifying the surface of Pt nanoparticles with a sulfur-containing organic ligand, the microenvironment on the catalyst surface is changed. In addition to changing the electronic structure of Pt metal, a ligand modification layer is formed on the surface of the metal catalyst, forming a steric hindrance effect, allowing only NAD(P) + to adsorb and undergo hydrogenation reaction on the surface of Pt nanoparticles in a specific adsorption mode, effectively inhibiting the generation of by-products

[0029] 4) The application of the sulfur-containing organic ligand modified Pt nanoparticles of the present invention, due to the steric hindrance effect of the sulfur-containing organic ligand, inhibits the aggregation of Pt nanoparticles, thereby improving the stability of the catalyst. When using the catalyst of the present invention to catalyze the hydrogenation of coenzyme NAD(P) + to NAD(P)H, the selectivity of NAD(P)H reaches 95%, and the conversion rate of NAD(P) + is 100% Description of the Drawings

[0030] Figure 1Application schematic diagram of the sulfur-containing organic ligand modified Pt nanoparticle catalyst prepared by the present invention in the hydrogenation of coenzyme NAD(P) + to NAD(P)H;

[0031] Figure 2 TEM and EDX diagrams of the catalyst prepared in Example 1, where Figure 2 (a) in is the TEM diagram of Example 1; Figure 2 (b), (c) and (d) in are the EDX diagrams corresponding to Example 1;

[0032] Figure 3 NAD of the catalysts prepared in Examples 1-3 and Comparative Example 1 + Hydrogenation performance vs. time diagram;

[0033] Figure 4 Catalytic kinetic curves of the prepared catalysts, where Figure 4 (a) in is the catalytic kinetic curve of Example 1, Figure 4 (b) in is the catalytic kinetic curve of Comparative Example 1;

[0034] Figure 5 Cyclic stability test of the prepared catalysts, where Figure 5 (a) in is the cyclic stability test of Example 1, Figure 5 (b) in is the cyclic stability test of Comparative Example 1;

[0035] Figure 6 In-situ CO adsorption infrared spectra of the catalysts prepared in Examples 1-3 and Comparative Example 1;

[0036] Figure 7 XPS diagrams of the catalysts prepared in Examples 1-3. Detailed implementation mode

[0037] The application schematic diagram of the sulfur-containing organic ligand modified Pt nanoparticle catalyst prepared by the present invention in the reaction of hydrogenating coenzyme NAD(P)+ to NAD(P)H is as shown in Figure 1 shown. The present invention will be further described below in conjunction with examples and attached Figure 2 to attached Figure 7 drawings.

[0038] Example 1

[0039] Disperse 300 mg of porous silica in 4 mL of chloroplatinic acid aqueous solution (containing 3 mg of Pt), stir overnight and then rotary evaporate to remove water. Dry the sample in an oven at 100 °C for 12 h, then calcine it in a muffle furnace at 300 °C for 5 h, and finally use H at 200 °C 2After reduction for 5 h, a Pt / SiO catalyst with a Pt loading of 1% is obtained. 2 Dissolve 0.16 g of toluene-3,4-dithiol in 5.0 mL of ethanol, add 20 mg of the Pt / SiO 2 catalyst with a Pt loading of 1%, and then stir this mixture at room temperature for 20 h. Wash the mixture thoroughly with ethanol, centrifuge it, and finally vacuum out the solvent from the obtained solid at room temperature to obtain the toluene-3,4-dithiol modified Pt / SiO 2 catalyst. The TEM results show that the Pt nanoparticles are about 1.7 nm ( Figure 2 as shown in (a) of 2 ); the EDX results show that the Pt nanoparticles are evenly dispersed on the support SiO Figure 2 as shown in (b), (c), and (d) of

[0040] Example 2

[0041] Disperse 300 mg of porous silica in 4 mL of an aqueous solution of chloroplatinic acid (containing 30 mg of Pt), stir overnight and then remove the water by rotary evaporation. Dry the sample in an oven at 100 °C for 12 h, then calcine it in a muffle furnace at 400 °C for 4 h, and finally reduce it with H 2 at 200 °C for 4 h to obtain a Pt / SiO 2 catalyst with a Pt loading of 10%. Dissolve 1.7 g of adamantanethiol in 10.0 mL of ethanol, add 20 mg of the Pt / SiO 2 catalyst with a Pt loading of 10%, and then stir this mixture at room temperature for 20 h. Wash the mixture thoroughly with ethanol, centrifuge it, and finally vacuum out the solvent from the obtained solid at room temperature to obtain the adamantanethiol modified Pt / SiO 2 catalyst.

[0042] Example 3

[0043] Disperse 300 mg of porous silica in 4 mL of an aqueous solution of chloroplatinic acid (containing 15 mg of Pt), stir overnight and then remove the water by rotary evaporation. Dry the sample in an oven at 100 °C for 12 h, then calcine it in a muffle furnace at 500 °C for 3 h, and finally reduce it with H 2 at 300 °C for 3 h to obtain a Pt / SiO 2 catalyst with a Pt loading of 5%. Dissolve 0.41 g of naphthalenethiol in 10.0 mL of ethanol, add 20 mg of the Pt / SiO 2The catalyst, and then stir this mixture at room temperature for 20 h. Wash the mixture thoroughly with ethanol, centrifuge it, and finally vacuum-extract the solvent from the obtained solid at room temperature to obtain the naphthyl mercaptan-modified Pt / SiO 2 catalyst.

[0044] Example 4

[0045] Disperse 300 mg of porous silica in 4 mL of aqueous chloroplatinic acid solution (containing 1.5 mg of Pt), stir overnight and then remove the water by rotary evaporation. Dry the sample in an oven at 100 °C for 12 h, then calcine it in a muffle furnace at 600 °C for 2 h, and finally use H 2 to reduce it for 2 h to obtain the Pt / SiO with a Pt loading of 0.5% 2 catalyst. Dissolve 0.74 g of dibutyl sulfide in 10.0 mL of ethanol, add 20 mg of the Pt / SiO with a Pt loading of 0.5% 2 catalyst, and then stir this mixture at room temperature for 20 h. Wash the mixture thoroughly with ethanol, centrifuge it, and finally vacuum-extract the solvent from the obtained solid at room temperature to obtain the naphthyl mercaptan-modified Pt / SiO 2 catalyst.

[0046] Comparative Example 1

[0047] Disperse 300 mg of porous silica in 4 mL of aqueous chloroplatinic acid solution (containing 3 mg of Pt), stir overnight and then remove the water by rotary evaporation. Dry the sample in an oven at 100 °C for 12 h, then calcine it in a muffle furnace at 300 °C for 4 h, and finally use H 2 to reduce it for 2 h to obtain the Pt / SiO with a Pt loading of 1% 2 catalyst.

[0048] Example 5

[0049] For the application of the Pt nanoparticles described in Examples 1-4 and Comparative Example 1, place the catalyst (3 mg) and 2 mL of NAD + buffer solution (1.5 mM, pH = 8.7) in an ampoule, replace the air in the system with H 2 6 times and then start the reaction. The reaction is carried out at 37 °C and 2 MPa H 2 conditions. After stopping the reaction, separate the heterogeneous catalyst and the reaction solution by centrifugation, dilute the reaction solution to 0.075 mM with phosphate buffer solution, and quantitatively detect it by UV-vis spectroscopy. The detection and calculation result in NAD +Catalytic performance for the preparation of NADH by hydrogenation. The NADH yields of the catalysts obtained in Examples 1-3 and Comparative Example 1 as a function of reaction time are as Figure 3 shown; the NAD+ conversion rates and NADH product selectivities of the catalysts obtained in Example 1 and Comparative Example 1 as a function of time are as Figure 4 shown in (a) of Figure 4 and (b) of

[0050] Table 1

[0051]

[0052] a NAD + Product selectivity at 100% NAD conversion rate.

[0053] Example 6

[0054] The results of the stability investigation of the heterogeneous catalyst described in Example 1 are as Figure 5 shown in (a) of + . After 5 cycles of use, the NAD Figure 5 conversion rate remained around 45%, and the selectivity of NADH was always greater than 95%, indicating that the catalyst had good stability; the results of the stability investigation of the heterogeneous catalyst described in Comparative Example 1 are as + shown in (b) of

[0055] Example 7

[0056] In Comparative Example 1, since there was no organic ligand modification layer on the catalyst surface, the surface active sites of the Pt nanoparticles were not uniform, and there were many + adsorption modes of NAD on the catalyst surface, resulting in a decrease in the NADH product selectivity. At this time, in addition to the formation of enzymatically active 1,4-NADH, non-enzymatically active 1,6-NADH was also formed.

[0057] Example 8

[0058] The catalysts prepared in Examples 1-3 and Comparative Example 1 were subjected to in-situ infrared spectroscopy tests for CO adsorption ( Figure 6 ) and XPS characterization analysis ( Figure 7). It was found that after the modification with sulfur-containing organic ligands, the linear CO adsorption peak was greatly weakened, and the maximum absorption peak shifted to lower wavenumbers. The presence of S has a certain electron-donating effect on the active center Pt, resulting in an increase in the charge density of Pt. The XPS characterization results show that the proportion of Pt δ+ increases, and the metallic Pt 0 shifts to lower binding energy, indicating that the Pt surface is richer in electrons. The in-situ infrared spectroscopy of CO adsorption is consistent with the XPS characterization results.

[0059] The above specific embodiments are only used to explain the present invention, rather than limiting the present invention. Any changes and substitutions made to the present invention within the scope of the concept and claims of the present invention without creative labor shall fall within the protection scope of the present invention patent.

Claims

1. A NAD(P) + A selective hydrogenation catalyst, characterized in that The carrier of the catalyst is porous silicon oxide, the catalyst contains Pt nanoparticles, the Pt content of the catalyst is 0.5-10 wt%, the catalyst is modified by sulfur-containing organic ligands, the content of the organic ligands is 0.1-10 wt%; the sulfur-containing organic ligands are modified on the surface of the Pt nanoparticles; the sulfur-containing organic ligands are toluene-3,4-dithiol.

2. A NAD(P) + A method for preparing a selective hydrogenation catalyst, characterized in that: The porous silicon oxide is impregnated into a Pt salt precursor solution by a solution impregnation method, and the loaded Pt nanoparticles are obtained by drying, calcining, and high-temperature hydrogen reduction; the calcination temperature is 100-600°C, the calcination time is 1-5 h, the temperature of the high-temperature hydrogen is 100-300°C, and the reduction time is 1-5 h; The organic ligand is dissolved in an organic solvent, the prepared loaded Pt nanoparticles are added to the organic ligand solution, and the loaded Pt nanoparticles modified with the sulfur-containing organic ligand are obtained by centrifugation, washing, and vacuum drying; the sulfur-containing organic ligand is toluene-3,4-dithiol.

3. The preparation method according to claim 2, characterized in that: The concentration of the Pt salt precursor solution is 1 mM-5 mM, the amount of solvent is 0-50 ml per 0.1 g of porous silicon oxide carrier, the immersion time of silicon oxide in the Pt salt precursor solution is 1-48 h, and the immersion temperature is room temperature to 50°C.

4. The preparation method according to claim 2, characterized in that: The Pt salt precursor is one of chloroplatinic acid, sodium chloroplatinate, potassium chloroplatinate, or a mixture of two or more thereof.

5. The preparation method according to claim 2, characterized in that: The solvent used in the Pt salt precursor solution is one or a mixture of two or more of water, methanol, ethanol, n-hexane, dichloromethane, and tetrahydrofuran.

6. NAD(P) according to claim 1 + Selective hydrogenation catalysts in coenzyme NAD(P) + Application in hydrogenation to produce NAD(P)H.

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