A rutile phase titanium dioxide supported palladium monatomic catalyst and application thereof

Abstract

The application relates to a rutile phase titanium dioxide supported palladium monatomic catalyst and application thereof, wherein the rutile phase titanium dioxide supported palladium monatomic catalyst is composed of a carrier and an active component, palladium species is dispersed on the rutile phase titanium dioxide in a monatomic form, the rutile phase titanium dioxide supported palladium monatomic catalyst is synthesized by using a crystal phase engineering and thermal atomization method, and the particle size of the rutile phase titanium dioxide supported palladium monatomic catalyst is 30-40 nm. The rutile phase titanium dioxide supported palladium monatomic catalyst is synthesized by using a crystal phase transformation method, realizing the transformation of the carrier from a anatase phase to a rutile phase through high-temperature treatment, and realizing the atomic dispersion of palladium species by using a thermal atomization principle; the rutile phase catalyst is used for a Sonogashira reaction, and has the advantages of good selectivity, high conversion rate, strong stability and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of single-atom catalysis, in particular to a rutile phase titanium dioxide supported palladium single-atom catalyst and application thereof. BACKGROUND

[0002] Sonogashira reaction (Sonogashira Coupling) is an important cross-coupling reaction, which couples terminal alkyne with aryl or alkenyl halide (or halide derivative) through palladium catalyst (usually co-catalyzed with copper) to generate carbon-carbon triple bond (alkyne) structure. The reaction has wide application in the fields of organic synthesis, material science, medicinal chemistry, etc. Palladium-based homogeneous catalyst is often used in carbon-carbon coupling reaction. Although homogeneous catalyst has high selectivity and activity, the separation of product and recovery of catalyst are difficult to solve. In recent years, supported palladium-based nanocatalyst shows high catalytic activity and recycling performance in C-C coupling reaction. However, the high price of palladium metal makes it difficult to be applied on a large scale. Single-atom catalyst has unique physical and chemical properties, and its atomic structure is clear and adjustable, which has different electronic structure and properties from nanoscale catalyst. Single-atom catalyst can greatly reduce the amount of noble metal required and has the largest atomic utilization rate. Therefore, it is of great significance to design and prepare a palladium-based single-atom catalyst with strong stability, high conversion rate and good selectivity. SUMMARY

[0003] An object of the present application is to provide a rutile phase titanium dioxide supported palladium single-atom catalyst, which is used to solve the problems of palladium-based homogeneous catalyst or supported palladium-based nanocatalyst in the prior art, such as difficult separation of product and recovery of catalyst or high price; another object of the present application is to provide the application of the rutile phase titanium dioxide supported palladium single-atom catalyst.

[0004] The technical scheme adopted by the present application to solve its technical problems is that the rutile phase titanium dioxide supported palladium single-atom catalyst is composed of a carrier and an active component, and palladium species is dispersed on the rutile phase titanium dioxide in the form of single atom, and the rutile phase titanium dioxide supported palladium single-atom catalyst is synthesized by crystal phase engineering and thermal atomization method, specifically as follows:

[0005] Step 1, preparation of anatase phase titanium dioxide with oxygen defects: grind titanium dioxide and calcine under mixed gas, the mixed gas is H2 / Ar, the volume percentage of H2 in the H2 / Ar mixed gas is 5%, and the calcination time is 1-24 hours, and then the anatase phase titanium dioxide with oxygen defects is obtained after being cooled to room temperature;

[0006] Step 2, preparation of the anatase phase titanium dioxide loaded with palladium salt: the anatase phase titanium dioxide with oxygen defects obtained in step 1 is put into a ball mill, after being fully ball milled, a palladium salt is added, the molar ratio of the anatase phase titanium dioxide with oxygen defects and palladium metal in the palladium salt is 198:1~1391:1, the ball milling treatment is continued, and the anatase phase titanium dioxide loaded with palladium salt is obtained;

[0007] Step 3, preparation of the anatase phase titanium dioxide loaded with palladium particles: the anatase phase titanium dioxide loaded with palladium salt obtained in step 2 is calcined in air, the calcination temperature is 80-600 °C, the calcination time is 0.5-24 h, and after being reduced to room temperature, the anatase phase titanium dioxide loaded with palladium nanoclusters is obtained;

[0008] Step 4, preparation of the rutile phase titanium dioxide loaded with palladium single atom: the anatase phase titanium dioxide loaded with palladium nanoclusters obtained in step 3 is calcined under an argon atmosphere, the heating rate is 0.2-30 °C / min, the calcination time is 0.5-24 h, and after being reduced to room temperature, the rutile phase titanium dioxide loaded with palladium single atom, i.e., the rutile phase titanium dioxide loaded with palladium single atom catalyst, is obtained.

[0009] The particle size of the rutile phase titanium dioxide loaded with palladium single atom catalyst in the above scheme is 30-40 nm.

[0010] In the above scheme, when step 1 is calcined under a mixed gas, the heating rate is 0.2-30 °C / min, and the calcination temperature is 80-600 °C.

[0011] In the above scheme, the rotation speed of the ball mill in step 2 is 100-800 rpm, and the ball milling time is 0.5-6 h.

[0012] In the above scheme, the palladium salt in step 2 is any one of sodium chloropalladate, palladium acetate, palladium nitrate, palladium chloride, tetraammine palladium, palladium tetrachloride, palladium pivalate, palladium propionate, tetraammine palladium sulfate, and palladium acetylacetone.

[0013] In the above scheme, when step 3 is calcined in air, the heating rate is 0.2-30 °C / min.

[0014] In the above scheme, when step 4 is calcined under an argon atmosphere, the calcination temperature is 800-2000 °C.

[0015] The rutile phase titanium dioxide loaded with palladium single atom catalyst is used for the Sonogashira reaction, and catalyzes the iodobenzene and phenylacetylene to generate diphenylacetylene.

[0016] The method for generating diphenylacetylene from iodobenzene and phenylacetylene by using the rutile phase titanium dioxide supported palladium monatomic catalyst in the above scheme is as follows: 6 mg of rutile phase titanium dioxide supported palladium monatomic catalyst, 1 mmol of iodobenzene, 1.2 mmol of phenylacetylene, 2 mmol of potassium carbonate and 3 mL of ethanol are added into a reaction tube, and the reaction is carried out under an argon atmosphere at 80 °C for 5 h; after centrifugation, the supernatant is taken, rotary evaporation and crystallization are carried out, and diphenylacetylene solid is obtained. Advantages

[0017] (1) The rutile phase titanium dioxide supported palladium monatomic catalyst is prepared by using the phase transition method, the carrier is converted from anatase phase to rutile phase by high temperature treatment, and the atomic dispersion of palladium species is realized by using the thermal atomization principle; the rutile phase catalyst is successfully used in the Sonogashira reaction, and has the advantages of good selectivity, high conversion rate and strong stability.

[0018] (2) The rutile phase titanium dioxide supported palladium monatomic catalyst is prepared by using the phase engineering and high-temperature thermal atomization method; the anatase phase titanium dioxide is converted into more stable rutile phase titanium dioxide by high-temperature calcination, and the palladium nanoclusters are converted into palladium monatomic and anchored on the rutile phase titanium dioxide by using the high-temperature thermal atomization principle.

[0019] (3) The prepared supported monatomic catalyst has the advantages of low noble metal loading and high metal atom utilization rate, can be applied to the Sonogashira reaction, the product separation is easy, the catalyst recovery is easy, and the price is low.

[0020] (4) The preparation method of the monatomic catalyst provides a new idea for the synthesis of monatomic catalysts. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Fig. 1 is an XRD diagram of the rutile phase titanium dioxide carrier and the rutile phase titanium dioxide supported palladium monatomic catalyst of Example 1.

[0022] Figure 2 Fig. 2 is a TEM diagram of the rutile phase titanium dioxide supported palladium monatomic catalyst of Example 1.

[0023] Figure 3 Fig. 3 is an AC-STEM diagram of the rutile phase titanium dioxide supported palladium monatomic catalyst of Example 1.

[0024] Figure 4 Fig. 4 is a comparison of conversion rate and yield of the prepared rutile phase titanium dioxide supported palladium monatomic catalyst and other catalysts.

[0025] Figure 5 Fig. 5 is a comparison of turnover frequency of the prepared rutile phase titanium dioxide supported palladium monatomic catalyst and other catalysts. DETAILED DESCRIPTION

[0026] The application will be further described below with reference to the accompanying drawings: EMBODIMENT

[0027] The rutile phase titanium dioxide supported palladium monatomic catalyst is composed of a carrier and a metal active component, wherein the carrier is rutile phase titanium dioxide with oxygen vacancies, and the metal active component is a palladium monatomic atom, and the palladium species is dispersed on the rutile phase titanium dioxide in the form of a monatomic atom.

[0028] The rutile phase titanium dioxide supported palladium monatomic catalyst is prepared by the following steps:

[0029] Step 1, preparation of anatase phase titanium dioxide with oxygen defects: 2 g of titanium dioxide is ground and calcined under a hydrogen-argon mixed gas atmosphere, the heating rate is 5 ℃ / min, the calcination temperature is 500 ℃, and the calcination time is 2 h, to obtain anatase phase titanium dioxide containing oxygen defects;

[0030] Step 2, the anatase phase titanium dioxide with oxygen defects obtained in step 1 is placed into a ball mill, and after being fully ball milled, a palladium salt is added, wherein the molar ratio of the anatase phase titanium dioxide to the palladium metal in the palladium salt is 379:1, and the ball milling is continued, the ball milling speed is 400 rpm, and the ball milling time is 120 min, to obtain anatase phase titanium dioxide loaded with a palladium salt;

[0031] Step 3, the anatase phase titanium dioxide loaded with the palladium salt obtained in step 2 is calcined in air, the heating rate is 5 ℃ / min, the calcination temperature is 500 ℃, and the calcination time is 3 h, to obtain anatase phase titanium dioxide loaded with palladium nanoclusters;

[0032] Step 4, the anatase phase titanium dioxide loaded with palladium nanoclusters obtained in step 3 is calcined under an argon atmosphere, the heating rate is 5 ℃ / min, the calcination temperature is 950 ℃, and the calcination time is 2 h, to obtain a rutile phase titanium dioxide supported palladium monatomic catalyst, denoted as Pd1 / TiO 2-x .

[0033] The monatomic catalyst obtained in the above embodiment 1 is characterized.

[0034] As Figure 1 shown in FIG. 1 is the XRD spectrum of the rutile phase titanium dioxide supported palladium monatomic catalyst of embodiment 1, from which it can be seen that the rutile phase titanium dioxide supported palladium monatomic catalyst has a rutile phase structure, and the palladium monatomic atom is dispersed on the rutile phase titanium dioxide. Figure 1It can be seen that the titanium dioxide support of anatase phase after crystal phase engineering and hot atomization treatment, the catalyst support titanium dioxide has rutile phase, and after loading metal, there is no palladium metal peak, which proves that the palladium species in the rutile phase titanium dioxide supported palladium monatomic catalyst obtained in Example 1 is highly dispersed, and there is no aggregation of palladium metal atoms.

[0035] As shown in Figure 2 , it is the TEM spectrum of the rutile phase titanium dioxide supported palladium monatomic catalyst of Example 1, which illustrates that the particle size of the rutile phase titanium dioxide supported palladium monatomic catalyst obtained in Example 1 is 30-40 nm.

[0036] As shown in Figure 3 , it is the AC-STEM spectrum of the rutile phase titanium dioxide supported palladium monatomic catalyst of Example 1, in combination with Figure 1 , it is further proved that the palladium of the rutile phase titanium dioxide supported palladium monatomic catalyst obtained in Example 1 is dispersed in the form of isolated atoms on the rutile phase titanium dioxide.

[0037] The application of the above-mentioned rutile phase titanium dioxide supported palladium monatomic catalyst in catalyzing Sonogashira reaction is as follows:

[0038] 6 mg of Pd1 / TiO 2-x (the molar ratio of palladium metal to iodobenzene is 1:5000), 1 mmol of iodobenzene, 1.2 mmol of phenylacetylene, 2 mmol of potassium carbonate and 3 mL of ethanol were added into a reaction tube, and the reaction was carried out at 80 °C under argon atmosphere for 5 h. After centrifugation, the supernatant was taken, and the product was analyzed by gas chromatography, and the calculation result was obtained by area normalization method.

[0039] As shown in Figure 4 , it is the comparison chart of conversion frequency of the rutile phase titanium dioxide supported palladium monatomic catalyst prepared in Example 1 in catalyzing carbon-carbon coupling of iodobenzene and phenylacetylene to generate diphenylacetylene and other catalysts, as shown in Figure 4 , the conversion frequency of Pd1 / TiO 2-x in catalyzing carbon-carbon coupling of iodobenzene and phenylacetylene to generate diphenylacetylene is as high as 23809 h -1 , and the catalytic performance is far superior to that of commercial palladium on carbon catalyst and other palladium-based catalysts.

[0040] As shown in Figure 5 , it is the comparison chart of conversion frequency of the rutile phase titanium dioxide supported palladium monatomic catalyst prepared in Example 1 in catalyzing carbon-carbon coupling of iodobenzene and phenylacetylene to generate diphenylacetylene and other catalysts, as shown in Figure 5 , the conversion frequency of Pd1 / TiO 2-x in catalyzing carbon-carbon coupling of iodobenzene and phenylacetylene to generate diphenylacetylene is as high as 23809 h -1 , and the catalytic performance is far superior to that of commercial palladium on carbon catalyst and other palladium-based catalysts. Embodiment

[0041] The difference between this embodiment and embodiment 1 is that the molar ratio of anatase phase titanium dioxide and palladium metal in the palladium salt in this embodiment is 800:1.

[0042] The application of the above-mentioned rutile phase titanium dioxide supported low loading palladium monatomic catalyst in catalyzing carbon-carbon coupling of iodobenzene and phenylacetylene to generate diphenylacetylene is as described in embodiment 1, which will not be repeated here.

[0043] The palladium nanocluster catalyst is composed of a carrier and a metal active component, wherein the carrier is titanium dioxide with oxygen vacancies, and the metal active component is a palladium nanocluster.

[0044] The rutile phase titanium dioxide supported palladium nanocluster catalyst and its application are realized by the following steps:

[0045] Step 1, preparation of anatase phase titanium dioxide with oxygen defects: 2 g of titanium dioxide is ground and calcined under hydrogen-argon mixed gas, the heating rate is 5 ℃ / min, the calcination temperature is 500 ℃, and the calcination time is 2 h, to obtain anatase phase titanium dioxide containing oxygen defects;

[0046] Step 2, the anatase phase titanium dioxide with oxygen defects obtained in step 1 is put into a ball mill, and after being fully ball milled, a palladium salt is added (wherein the molar ratio of anatase phase titanium dioxide and palladium metal in the palladium salt is 144:1), and the ball milling treatment is continued, the ball milling speed is 400 rpm, and the ball milling time is 2 h, to obtain anatase phase titanium dioxide loaded with palladium salt;

[0047] Step 3, the anatase phase titanium dioxide loaded with palladium salt obtained in step 2 is calcined in air, the heating rate is 5 ℃ / min, the calcination temperature is 500 ℃, and the calcination time is 3 h, to obtain anatase phase titanium dioxide loaded with palladium nanoclusters;

[0048] Step 4, the anatase phase titanium dioxide loaded with palladium nanoclusters obtained in step 3 is calcined under argon atmosphere, the heating rate is 5 ℃ / min, the calcination temperature is 950 ℃, and the calcination time is 2 h, to obtain a rutile phase titanium dioxide supported palladium nanocluster catalyst through crystal phase transformation and high-temperature thermal atomization, which is denoted as Pd cluster / TiO 2-x .

[0049] 2 mg of Pd cluster / TiO 2-xThe catalyst prepared above (Example 1-2 and Comparative Example 1, where the molar ratio of palladium metal to iodobenzene is 1:5000), 1 mmol of iodobenzene, 1.2 mmol of phenylacetylene, 2 mmol of potassium carbonate and 3 mL of ethanol were added to a reaction tube and reacted under an argon atmosphere at 80 °C for 5 h. After centrifugation, the supernatant was taken and the product was analyzed using gas chromatography, and the results were calculated using the area normalization method. The results are shown in Table 1.

[0050] The catalyst prepared above (Example 1-2 and Comparative Example 1, where the molar ratio of palladium metal to iodobenzene is 1:5000), 1 mmol of iodobenzene, 1.2 mmol of phenylacetylene, 2 mmol of potassium carbonate and 3 mL of ethanol were added to a reaction tube and reacted under an argon atmosphere at 80 °C for 5 h. After centrifugation, the supernatant was taken and the product was analyzed using gas chromatography, and the results were calculated using the area normalization method. The results are shown in Table 1.

[0051] Table 1. Performance evaluation of catalysts for carbon-carbon coupling reactions

[0052] Rutile titanium dioxide has unique crystal structure and physical and chemical properties. First, it has high thermodynamic stability, and the tightly packed oxygen octahedral structure provides the possibility for the introduction of metal monatomic atoms and effectively prevents the aggregation of metal monatomic atoms, improving the durability of the catalyst. Second, it has abundant surface defect sites, such as oxygen vacancies and titanium defects, which can serve as anchoring sites for metal monatomic atoms, enhancing the electronic metal-support interaction and improving the catalytic activity. In addition, the energy band structure of rutile titanium dioxide is narrower than that of anatase, which helps to facilitate the charge transfer between metal monatomic atoms and the support, promoting the progress of the catalytic reaction. Finally, the coordination environment of rutile titanium dioxide supported monatomic atoms can be adjusted by doping or annealing treatment, providing the possibility for the development of high-efficiency catalytic systems.

Claims

1. A rutile phase titania supported palladium monatomic catalyst characterized by: This rutile titanium dioxide-supported palladium single-atom catalyst consists of a support and an active component. Palladium species are dispersed in single-atom form on the rutile titanium dioxide. The rutile titanium dioxide-supported palladium single-atom catalyst is synthesized using crystal phase engineering and thermal atomization, as detailed below: Step 1: Preparation of oxygen-deficient anatase phase titanium dioxide: After grinding the titanium dioxide, it is calcined under a mixed gas, which is H2 / Ar, with the volume percentage of H2 in the H2 / Ar mixed gas being 5%. The heating rate is 0.2-30 ºC / min, the calcination temperature is 500-600 ºC, and the calcination time is 1-24 hours. After cooling to room temperature, oxygen-deficient anatase phase titanium dioxide is obtained. Step 2: Preparation of palladium-loaded anatase phase titanium dioxide: The oxygen-deficient anatase phase titanium dioxide obtained in Step 1 is placed in a ball mill. After thorough ball milling, palladium salt is added. The molar ratio of the oxygen-deficient anatase phase titanium dioxide to the palladium metal in the palladium salt is 198:1~1391:

1. The ball milling process is continued to obtain palladium-loaded anatase phase titanium dioxide. Step 3: Preparation of palladium-loaded anatase phase titanium dioxide: The palladium-loaded anatase phase titanium dioxide obtained in step 2 is calcined in air at a temperature of 500-600 ºC for 0.5-24 h. After cooling to room temperature, palladium nanoclusters-loaded anatase phase titanium dioxide is obtained. Step 4: Preparation of palladium single-atom supported rutile phase titanium dioxide: The palladium nanoclusters supported anatase phase titanium dioxide obtained in step 3 are calcined under an argon atmosphere at a temperature of 800-950 ºC, a heating rate of 0.2-30 ºC / min, and a calcination time of 0.5-24 h. After cooling to room temperature, palladium single-atom supported rutile phase titanium dioxide is obtained, which is a palladium single-atom catalyst supported on rutile phase titanium dioxide.

2. The rutile phase titania-supported palladium monohydride catalyst of claim 1, wherein: The rutile phase titanium dioxide supported palladium single-atom catalyst has a particle size of 30-40 nm.

3. The rutile phase titania-supported palladium monohydride catalyst of claim 2, wherein: In step 2, the ball mill speed is 100-800 rpm and the ball milling time is 0.5-6 h.

4. The rutile phase titania-supported palladium monohydride catalyst of claim 3, wherein: In step 2, the palladium salt is any one of sodium chloropalladium, palladium acetate, palladium nitrate, palladium chloride, palladium tetrachloride tetraaminopalladium, palladium neopentanoate, palladium propionate, palladium tetraaminopalladium sulfate, and palladium acetylacetonate.

5. The rutile phase titania-supported palladium monatomic catalyst of claim 4, wherein: In step 3, when calcining in air, the heating rate is 0.2-30 ºC / min.

6. Use of the rutile phase titanium dioxide supported palladium monatomic catalyst of claim 5, characterized by: The rutile-phase titanium dioxide-supported palladium single-atom catalyst is used in the Sonogashira reaction to catalyze the reaction of iodobenzene and phenylacetylene to produce diphenylacetylene.

7. Use of a rutile phase titania supported palladium monatomic catalyst according to claim 6, characterized in that: The method for catalyzing the reaction of iodobenzene and phenylacetylene to produce diphenylacetylene using the rutile titanium dioxide-supported palladium single-atom catalyst is as follows: 6 mg of rutile titanium dioxide-supported palladium single-atom catalyst, 1 mmol of iodobenzene, 1.2 mmol of phenylacetylene, 2 mmol of potassium carbonate, and 3 mL of ethanol are added to a reaction tube and reacted at 80 ºC under an argon atmosphere for 5 h; after centrifugation, the supernatant is collected, rotary evaporated, and crystallized to obtain solid diphenylacetylene.

Images