Green catalysis method for improving hydrogenation selectivity of phenylacetylene and catalyst preparation method

Abstract

The invention relates to a green catalysis method for improving phenylacetylene hydrogenation selectivity and a catalyst preparation method. The method mainly solves the problems of high catalyst cost, difficult realization of large-scale commercialization and the like caused by large usage amount of noble metals in alkene preparation through alkyne selective hydrogenation at present. According to the green catalysis method for improving phenylacetylene hydrogenation selectivity and the catalyst preparation method, preparation is simple, the usage amount of precious metal is low, H2Ti3O7 intrinsic ion exchange performance is utilized, a Pd active phase is inserted into crystal lattices of the catalyst, continuous active sites are separated, styrene excessive hydrogenation reaction is inhibited, and the selectivity of the catalyst is improved.

Description

Technical Field

[0001] The invention relates to the field of preparing olefins by selective hydrogenation of alkynes, and in particular to a green catalytic method for improving the hydrogenation selectivity of phenylacetylene and a catalyst preparation method. Background Art

[0002] Selective hydrogenation of alkynes to produce olefins is widely used in many fields and is an important catalytic process in the modern chemical industry. Take styrene as an example. This important chemical monomer plays an important role in the preparation of styrene-butadiene rubber, polystyrene and expanded polystyrene materials. Styrene is mainly produced by dehydrogenation of ethylbenzene. However, there are often trace amounts of phenylacetylene impurities in ethylbenzene, which can seriously affect the production quality of polyolefins and poison the polymerization catalyst. This highlights the importance of selective hydrogenation of phenylacetylene to styrene in industrial applications.

[0003] Precious metals such as palladium (Pd) are widely used in hydrogenation reaction research due to their unique 4d electron configuration, which helps to activate hydrogen. Supported Pd-based nanocatalysts have been intensively developed and comprehensively studied in hydrogenation reactions, and significant progress has been made. However, the strong adsorption of olefins on the surface of Pd nanoparticles often leads to their further hydrogenation to alkanes, which seriously reduces the catalytic selectivity (Nat. Commun. 2021, 12, 5665). Studies have shown that the adsorption behavior of substrate molecules on catalysts is generally determined by the electronic structure and coordination environment of the active site (Chem. Soc. 2024, 146, 10798-10805). Therefore, designing palladium active sites with well-defined surface structures to promote the desorption of olefins from the catalyst surface is crucial to suppress thermodynamically favorable overhydrogenation.

[0004] Hu et al. (Adv. Mater. 2023, 35, 2304130) reported a Pd nanoparticle catalyst (Pd / DCN) loaded on nitrogen-deficient g-C3N4, where electrons were transferred from the carrier to the Pd nanoparticles to form a Schottky effect. Styrene is coordinated with Pd / DCN through weak bonds, and the adsorption energy barrier is increased, which makes styrene easy to dissociate and inhibits the occurrence of excessive hydrogenation reactions. After 1 hour of reaction, the selectivity of styrene can still be maintained above 90%. However, the selectivity of its hydrogenation reaction still needs to be improved. Tang et al. (ACS Catal. 2024, 14, 2463-2472) reduced the size of Pd nanoparticles to the nanocluster level and improved the selectivity of the catalyst for styrene by introducing ligands. However, the high coverage of the active sites by the ligands leads to reduced catalyst activity.

[0005] In summary, the existing catalytic systems are still challenging to improve the selectivity of phenylacetylene hydrogenation. The following problems still exist: (1) The large amount of precious metals used leads to high catalyst costs, making it difficult to achieve large-scale commercialization; (2) Improving the selectivity of phenylacetylene hydrogenation through various modification methods often comes at the expense of catalytic activity; (3) The preparation conditions of some catalysts are harsh. Summary of the invention

[0006] In order to overcome the shortcomings of the background technology, the present invention provides a green catalytic method for improving the selectivity of phenylacetylene hydrogenation and a catalyst preparation method, which mainly solves the problems of large amount of precious metals used in the current selective hydrogenation of alkynes to prepare olefins, resulting in excessively high catalyst costs and difficulty in large-scale commercialization.

[0007] The technical solution of the present invention is: A green catalytic method for improving the selectivity of phenylacetylene hydrogenation, using anhydrous methanol as solvent and hydrogen source, and using Pd-H 2 Ti 3 O 7 Catalyst for photocatalytic selective hydrogenation of phenylacetylene to styrene at room temperature.

[0008] The catalyst is Pd-H 2 Ti 3 O 7 , the mass content of Pd active phase is 0.2~1%.

[0009] The following steps are included: Step 1: The selective hydrogenation of phenylacetylene to prepare styrene, anhydrous methanol, catalyst Pd-H 2 Ti 3 O 7 , phenylacetylene is placed in the reactor; Step 2: Purge with high-purity argon gas at room temperature, then place the reactor under a xenon lamp light source, use a low-temperature thermostatic bath to control the reaction temperature, and turn on the light source to react.

[0010] In the step 1, the mass ratio of anhydrous methanol to phenylacetylene is 475:2, and the mass ratio of phenylacetylene to the catalyst is 475:1.

[0011] In the step 2, high-purity argon gas was purged at a flow rate of 50 mL / min for 20 min.

[0012] In the step 2, the xenon lamp light source power is 400W, the reaction temperature is controlled at 25°C in a low temperature thermostatic bath, and the mixture is stirred at a speed of 300 rpm for 20 min.

[0013] The preparation method of the catalyst used in the above-mentioned green catalytic method for improving the selectivity of phenylacetylene hydrogenation comprises the following steps: Step 1: Disperse nano-titanium dioxide in a NaOH solution and react for 24 to 72 hours to obtain Na 2 Ti 3 O 7 ; Step 2: The Na obtained in step 1 2 Ti 3 O 7 Disperse in hydrochloric acid solution and repeat the stirring operation several times to form H 2 Ti 3 O 7 ; Step 3: H obtained in step 2 2 Ti 3 O 7 Dispersed in PdCl 2 The mass content of Pd active phase in the solution is 0.2~1%, and stirring is performed to ensure that H + Ions and Pd 2+ The ion exchange reaction reaches equilibrium, centrifuges, washes and dries; the resulting solid is then heated in an Ar / H 2 Calcinate at 300℃~600℃ for 1~5h under atmosphere to obtain Pd-H 2 Ti 3 O 7 catalyst.

[0014] In step 1, the solid-to-liquid ratio of nano-titanium dioxide to NaOH solution is 25-75 g / L.

[0015] In step 2, Na 2 Ti 3 O 7 The solid-to-liquid ratio with hydrochloric acid solution is 1~10 g / L.

[0016] The beneficial effects of the present invention are as follows: the present invention provides a green catalytic method and a catalyst preparation method for improving the selectivity of phenylacetylene hydrogenation, which is simple to prepare, uses a low amount of precious metals, and utilizes H 2 Ti 3 O 7 The intrinsic ion exchange performance inserts the Pd active phase into its lattice, separates continuous active sites, inhibits the occurrence of excessive hydrogenation of styrene, and improves its selectivity. The catalyst preparation process is simple and has the potential for large-scale commercialization.

[0017] The present invention has the following advantages: 1) The amount of Pd precious metal used is small, which reduces the cost of catalytic reaction.

[0018] 2) The phenylacetylene hydrogenation reaction has high selectivity. All phenylacetylene is converted in 40 minutes. When the reaction time is extended to 90 minutes, the selectivity for styrene is always maintained above 97%, and no obvious over-hydrogenation reaction occurs.

[0019] In summary, the Pd-H prepared by ion exchange strategy 2 Ti 3 O 7 As a catalyst, anhydrous methanol as a solvent and hydrogen source can significantly improve the selectivity of the photocatalytic phenylacetylene hydrogenation reaction and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the H obtained in Example 1 and Example 2 2 Ti 3 O 7 、Pd-H 2 Ti 3 O 7 and Pd / H 2 Ti 3 O 7 X-ray diffraction (XRD) patterns of the samples.

[0021] Figure 2 The phenylacetylene in Pd-H 2 Ti 3 O 7 Time course of conversion and styrene selectivity.

[0022] Figure 3 The phenylacetylene in Pd-H 2 Ti 3 O 7 Time course of conversion and styrene selectivity.

[0023] Figure 4 In Example 4, Pd-H 2 Ti 3 O 7 Above is a time course of the distribution of phenylacetylene and styrene for the experiment with a mixed substrate (0.18 mmol styrene, 0.02 mmol phenylacetylene).

[0024] Figure 5 It is the conversion rate and corresponding olefin product selectivity spectrum of the hydrogenation reaction of different alkyne substrates in Example 5, Example 6, Example 7 and Example 8. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the accompanying drawings: A green catalytic method for improving the selectivity of phenylacetylene hydrogenation, using anhydrous methanol as a solvent and a hydrogen source, using Pd-H 2 Ti 3 O 7 Catalyst for photocatalytic selective hydrogenation of phenylacetylene to styrene at room temperature.

[0026] The catalyst is Pd-H 2 Ti 3 O 7 , the mass content of Pd active phase is 0.2~1%. The following steps are included: Step 1: The selective hydrogenation of phenylacetylene to prepare styrene, anhydrous methanol, catalyst Pd-H 2 Ti 3 O 7 , phenylacetylene is placed in a reactor (which may be a micro quartz reactor); Step 2: Purge with high-purity argon gas at room temperature, then place the reactor under a xenon lamp light source, use a low-temperature thermostatic bath to control the reaction temperature, and turn on the light source to react.

[0027] In the step 1, the mass ratio of anhydrous methanol to phenylacetylene is 475:2, and the mass ratio of phenylacetylene to the catalyst is 475:1.

[0028] In the step 2, high-purity argon gas was purged at a flow rate of 50 mL / min for 20 min.

[0029] In the step 2, the xenon lamp light source power is 400W, the reaction temperature is controlled at 25°C in a low temperature thermostatic bath, and the mixture is stirred at a speed of 300 rpm for 20 min.

[0030] The preparation method of the catalyst used in the above-mentioned green catalytic method for improving the selectivity of phenylacetylene hydrogenation comprises the following steps: Step 1: Disperse nano-titanium dioxide in a NaOH solution and react for 24 to 72 hours to obtain Na 2 Ti 3 O 7 ; Step 2: The Na obtained in step 1 2 Ti 3 O 7 Disperse in hydrochloric acid solution and repeat the stirring operation several times to form H 2 Ti 3 O 7 ; Step 3: H obtained in step 2 2 Ti 3 O 7 Dispersed in PdCl2 The mass content of Pd active phase in the solution is 0.2~1%, and stirring is performed to ensure that H + Ions and Pd 2+ The ion exchange reaction reaches equilibrium, centrifuges, washes and dries; the resulting solid is then heated in an Ar / H 2 Calcinate at 300℃~600℃ for 1~5h under atmosphere to obtain Pd-H 2 Ti 3 O 7 catalyst.

[0031] In step 1, the solid-to-liquid ratio of nano-titanium dioxide to NaOH solution is 25-75 g / L.

[0032] In step 2, Na 2 Ti 3 O 7 The solid-to-liquid ratio with hydrochloric acid solution is 1~10 g / L.

[0033] Example 1 The catalyst Pd—H 2 Ti 3 O 7 The preparation method is as follows: first, disperse nano-titanium dioxide in a 5-10 M NaOH solution (solid-to-liquid ratio of 25-75 g / L). Then transfer it to a stainless steel reactor and react at a certain temperature for 24-72 h to obtain Na 2 Ti 3 O 7 ; Then Na 2 Ti 3 O 7 Disperse in 0.5 M hydrochloric acid solution (solid-liquid ratio of 1-10 g / L), stir for 2 h, and repeat the stirring operation several times to form H 2 Ti 3 O 7 ; Then the obtained H 2 Ti 3 O 7 Dispersed in PdCl 2 The mass content of Pd active phase in the solution was 0.2~1%, and the solution was stirred for 24 h to ensure that H + Ions and Pd 2+ The ion exchange reaction reaches equilibrium, centrifuges, washes and dries. 2 Calcinate at 300℃~600℃ for 1~5h under atmosphere to obtain Pd-H 2 Ti 3 O 7 The optimal loading amount of Pd active phase is 0.5 wt%.

[0034] Example 2 In order to compare the catalyst Pd-H 2 Ti 3 O 7 The selectivity advantage in hydrogenation reaction was achieved by using the traditional impregnation method to prepare Pd / H 2 Ti 3 O 7 The catalyst Pd-H 2 Ti 3 O 7 The preparation method is as follows: first, disperse nano-titanium dioxide in a 5-10 M NaOH solution (solid-to-liquid ratio of 25-75 g / L). Then transfer it to a stainless steel reactor and react at a certain temperature for 24-72 h to obtain Na 2 Ti 3 O 7 ; Then Na 2 Ti 3 O 7 Disperse in 0.5 M hydrochloric acid solution (solid-liquid ratio of 1-10 g / L), stir for 2 h, and repeat the stirring operation several times to form H 2 Ti 3 O 7 ; The obtained H 2 Ti 3 O 7 Dispersed in 2 ml of PdCl 2 The precursor was stirred in anhydrous ethanol solution at 70 °C in a water bath until the solution evaporated to dryness. 2 Pd / H 2 T i3 O 7 Catalyst. The content of Pd active phase in the catalyst is 0.5 wt%.

[0035] Example 3 The catalyst was the same as in Example 1, the amount of catalyst was 10 mg, the amount of phenylacetylene was 0.2 mmol, the amount of methanol was 6 ml, a 400 W xenon lamp was used as the light source, and the reaction temperature was controlled at 25° C. by a low-temperature thermostatic bath. After turning on the light source, the catalytic hydrogenation reaction was carried out, and samples were collected every 10 minutes to test the corresponding phenylacetylene conversion rate and styrene selectivity. When phenylacetylene was completely converted, the reaction time was extended to 90 minutes to test the change in its selectivity to styrene.

[0036] Comparative Example 1 The catalyst was the same as in Example 2, with a catalyst dosage of 10 mg, a phenylacetylene dosage of 0.2 mmol, and a methanol dosage of 6 ml. A 400 W xenon lamp was used as a light source, and the reaction temperature was controlled at 25° C. by a low-temperature thermostatic bath. After turning on the light source, a catalytic hydrogenation reaction was carried out, and samples were collected every 10 minutes to test the corresponding phenylacetylene conversion rate and styrene selectivity. When phenylacetylene was completely converted, the reaction time was extended to 90 minutes to test the change in its selectivity to styrene.

[0037] Example 4 The catalyst was the same as in Example 1, with a catalyst dosage of 10 mg, a phenylacetylene dosage of 0.02 mmol, a styrene dosage of 0.18 mmol, and a methanol dosage of 6 ml. A 400 W xenon lamp was used as the light source, and the reaction temperature was controlled at 25° C. by a low-temperature thermostatic bath. After turning on the light source, a catalytic hydrogenation reaction was carried out, and samples were collected every 10 minutes. The phenylacetylene conversion rate and the selectivity to styrene were tested.

[0038] Example 5 The catalyst was the same as in Example 1, with a catalyst dosage of 10 mg, a 4-fluorophenylacetylene dosage of 0.2 mmol, and a methanol dosage of 6 ml. A 400 W xenon lamp was used as the light source, and the reaction temperature was controlled at 25° C. by a low-temperature thermostatic bath. After turning on the light source, a catalytic hydrogenation reaction was carried out, and samples were collected after 2 h to test the conversion rate of 4-fluorophenylacetylene and the selectivity to 4-fluorostyrene.

[0039] Example 6 The catalyst was the same as in Example 1, with a catalyst dosage of 10 mg, a 4-chlorophenylacetylene dosage of 0.2 mmol, and a methanol dosage of 6 ml. A 400 W xenon lamp was used as the light source, and the reaction temperature was controlled at 25° C. by a low-temperature thermostatic bath. After turning on the light source, a catalytic hydrogenation reaction was carried out, and samples were collected after 2 h to test the conversion rate of 4-chlorophenylacetylene and the selectivity to 4-chlorostyrene.

[0040] Example 7 The catalyst was the same as in Example 1, with a catalyst dosage of 10 mg, a 4-methylphenylacetylene dosage of 0.2 mmol, and a methanol dosage of 6 ml. A 400 W xenon lamp was used as the light source, and the reaction temperature was controlled at 25° C. by a low-temperature thermostatic bath. After turning on the light source, a catalytic hydrogenation reaction was carried out, and samples were collected after 2 h to test the conversion rate of 4-methylphenylacetylene and the selectivity to 4-methylstyrene.

[0041] Example 8 The catalyst was the same as in Example 1, with a catalyst dosage of 10 mg, a 4-methoxyphenylacetylene dosage of 0.2 mmol, and a methanol dosage of 6 ml. A 400 W xenon lamp was used as the light source, and the reaction temperature was controlled at 25° C. by a low-temperature thermostatic bath. After turning on the light source, a catalytic hydrogenation reaction was carried out, and samples were collected after 2 h to test the conversion rate of 4-methoxyphenylacetylene and the selectivity to 4-methoxystyrene.

[0042] Structural inspection The H obtained in Examples 1 and 2 2 T i3 O 7 、Pd-H 2 T i3 O 7 and Pd / H 2 T i3 O 7 The samples were subjected to X-ray diffraction test ( Figure 1 ), Pd-H 2 T i3 O 7 The XRD pattern shows that the characteristic peak at 2θ value of 9.68 disappears, which represents H 2 T i3 O 7 The (001) crystal plane is attributed to the 2+ Ions enter the interlayer through ion exchange reactions, destroying the H 2 T i3 O 7 The periodicity of atomic arrangement. 2 T i3 O 7 Characteristic peaks of XRD and support material H 2 T i3 O 7 The characteristic peaks are consistent and have not changed significantly, indicating that the Pd active phase prepared by the impregnation method is simply loaded onto H 2 T i3 O 7 surface without entering the crystal lattice.

[0043] Selective testing In order to evaluate the selectivity of the catalysts in Example 1 and Example 2 for the hydrogenation reaction of phenylacetylene, we evaluated their selectivity under the same conditions. Figure 2 The figure is a graph showing the conversion rate and selectivity of the phenylacetylene hydrogenation experiment performed in Example 3. Figure 3 The conversion rate and selectivity relationship diagram of the phenylacetylene hydrogenation experiment carried out in Comparative Example 1. It can be seen that when 0.2 mmol of phenylacetylene is completely converted, the reaction time is extended to 90 min, and Pd-H 2 Ti 3O 7 The selectivity of the catalyst for styrene remained basically unchanged, always above 97%. 2 Ti 3 O 7 The catalyst underwent an obvious over-hydrogenation reaction after 30 min, further hydrogenating styrene into ethylbenzene, and the selectivity for styrene dropped to 27% at 90 min. 2 Ti 3 O 7 The strategy of loading Pd active phase with intrinsic ion exchange properties can effectively inhibit the over-hydrogenation reaction of styrene and effectively improve the selectivity of phenylacetylene hydrogenation reaction.

[0044] To further explore the use of H 2 Ti 3 O 7 The strategy of supporting Pd active phase with intrinsic ion exchange properties has high selectivity for styrene. Figure 4 This is the test for the removal of trace phenylacetylene in a styrene-rich liquid in Example 4. It was found that after 0.02 mmol phenylacetylene was completely converted into styrene, Pd-H 2 Ti 3 O 7 The catalyst still showed a selectivity of more than 97%. 2 Ti 3 O 7 The strategy of loading the Pd active phase with intrinsic ion exchange properties has unique advantages in improving the selectivity of the hydrogenation reaction of phenylacetylene to produce styrene.

[0045] To explore the Pd-H 2 Ti 3 O 7 The universality of the catalyst for highly selective hydrogenation of alkynes, Figure 5 For Pd-H in Example 5, Example 6, Example 7 and Example 8 2 Ti 3 O 7 The selectivity profile of the catalyst for various alkynes. After 2 h of reaction, 0.2 mmol of the reaction substrate was completely converted, and the selectivity for the corresponding olefin product remained above 97%. This further confirms that the use of H 2 Ti 3 O 7 The strategy of loading Pd active phase with intrinsic ion exchange properties can indeed improve the selectivity of alkyne hydrogenation reaction and has great application prospects.

[0046] The embodiments described with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention. The embodiments should not be regarded as limiting the present invention, but any improvements made based on the spirit of the present invention should be within the scope of protection of the present invention.

Claims

1. A green catalytic method for improving the selectivity of phenylacetylene hydrogenation, characterized in that: Styrene was prepared by photocatalytic selective hydrogenation of phenylacetylene at room temperature using anhydrous methanol as solvent and hydrogen source over Pd-H2Ti3O7 catalyst.

2. A green catalytic method for improving the selectivity of phenylacetylene hydrogenation according to claim 1, characterized in that: The catalyst is Pd-H2Ti3O7, and the mass content of the Pd active phase is 0.2-1%.

3. A green catalytic method for improving the selectivity of phenylacetylene hydrogenation according to claim 1, characterized in that: The following steps are included: Step 1, the selective hydrogenation of phenylacetylene to prepare styrene, anhydrous methanol, catalyst Pd-H2Ti3O7, phenylacetylene is placed in a reactor; Step 2: Purge with high-purity argon gas at room temperature, then place the reactor under a xenon lamp light source, use a low-temperature thermostatic bath to control the reaction temperature, and turn on the light source to react.

4. A green catalytic method for improving the selectivity of phenylacetylene hydrogenation according to claim 3, characterized in that: In the step 1, the mass ratio of anhydrous methanol to phenylacetylene is 475:2, and the mass ratio of phenylacetylene to the catalyst is 475:

1.

5. A green catalytic method for improving the selectivity of phenylacetylene hydrogenation according to claim 3, characterized in that: In the step 2, high-purity argon gas was purged at a flow rate of 50 mL / min for 20 min.

6. A green catalytic method for improving the selectivity of phenylacetylene hydrogenation according to claim 3, characterized in that: In the step 2, the xenon lamp light source power is 400W, the reaction temperature is controlled at 25°C in a low temperature thermostatic bath, and the mixture is stirred at a speed of 300 rpm for 20 min.

7. A method for preparing a catalyst for a green catalytic method for improving the selectivity of phenylacetylene hydrogenation according to claims 1-6, characterized in that: The following steps are included: Step 1: Disperse nano-titanium dioxide in a NaOH solution and react for 24 to 72 hours to obtain Na2Ti3O7; Step 2: Disperse the Na2Ti3O7 obtained in step 1 in a hydrochloric acid solution, and repeat the stirring operation several times to form H2Ti3O7; Step 3: Disperse the H2Ti3O7 obtained in step 2 in a PdCl2 solution, wherein the mass content of the Pd active phase is 0.2-1%. Stir to ensure that H + Ions and Pd 2+ The ion exchange reaction reaches equilibrium, and the reaction is centrifuged, washed and dried. Finally, the obtained solid is calcined at 300°C to 600°C for 1 to 5 hours in an Ar / H2 atmosphere to obtain a Pd-H2Ti3O7 catalyst.

8. A method for preparing a catalyst for a green catalytic method for improving the selectivity of phenylacetylene hydrogenation as claimed in claim 7, characterized in that: In step 1, the solid-to-liquid ratio of nano-titanium dioxide to NaOH solution is 25-75 g / L.

9. A method for preparing a catalyst for a green catalytic method for improving the selectivity of phenylacetylene hydrogenation as claimed in claim 7, characterized in that: In step 2, the solid-liquid ratio of Na2Ti3O7 to hydrochloric acid solution is 1~10 g / L.

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