Preparation of palladium nanowire catalyst by phosphine ligand palladium complex and application thereof

Abstract

The application discloses a phosphine ligand palladium complex catalyst for preparing palladium nanowire and application of the catalyst in selective hydrogenation of 2-methyl-3-butyn-2-ol, and the catalyst comprises a carrier, noble metal particles loaded on the carrier and phosphine ligands coordinated on the metal surface, the carrier of the catalyst is ZSM-5, the active component is noble metal Pd, and the noble metal Pd is loaded on the carrier in the structure of nanowire. In the in-situ reduction process of the phosphine ligand palladium complex, the common action of the structure regulating ligand and the carrier defects induces the palladium to form the nanowire structure, strengthens the activated hydrogen capacity and hydrogen migration, avoids the excessive retention and adsorption of hydrogen by large Pd particles, inhibits further hydrogenation, and realizes the unity of high activity and high selectivity. The catalyst has good conversion rate and selectivity when applied in the selective hydrogenation reaction of alkyne compounds.

Description

Technical Field

[0001] This invention relates to a phosphine ligand palladium complex for the preparation of palladium nanowire catalysts and its applications. Background Technology

[0002] The semi-hydrogenation of alkynes to alkenes is an important and versatile chemical reaction, essential for the synthesis of fine chemicals such as vitamins and fragrances. However, the high adsorption energy of alkenes on continuous palladium surfaces hinders rapid desorption, leading to hyperhydrogenation side reactions. Therefore, achieving high selectivity for the target product is crucial in industrial production.

[0003] For the semi-hydrogenation of alkynes, palladium-based catalysts are often considered ideal choices. Currently, Lindlar catalysts are commonly used in industry for alkyne semi-hydrogenation. Their activity and selectivity are improved through modification with poisons such as lead or quinoline. However, these poisons not only reduce Pd metal utilization but also have potential biotoxicity, limiting their sustainable development and application expansion. Therefore, developing an environmentally friendly catalyst that balances activity and selectivity for the semi-hydrogenation of alkynes is urgently needed.

[0004] To address the aforementioned trade-off between activity and selectivity, traditional strategies involve modifying the metal active sites or the support itself. Beller's team's nitrogen-doped graphite-modified silica-supported cobalt nanoparticle catalyst inherits the catalytic activity of cobalt nanoparticles and the stabilizing effect of the nitrogen-doped carbon layer. Utilizing the synergistic effect of cobalt and nitrogen species, they achieved highly selective semi-hydrogenation of various alkynes under mild conditions (ACS Catal. 2017, 17(3): 1526-1532). A Pd1 / WO3 single-atom catalyst prepared using a hydrophilic polar layer strategy exhibits polar repulsion of the single-atom Pd sites by the hydrogen overflow-induced hydrophilic polar layer on the WO3 support, achieving highly efficient semi-hydrogenation of 2-methyl-3-butyn-2-ol, with catalytic activity 26 times that of traditional Lindlar catalysts (Nature Communications, 2024, 15(1): 1128). In alkylamine-modified Pd catalysts (DETA / Pd), Pd nanoparticles and surface-anchored flexible alkylamines construct dynamic metal-support interaction (DMSI), promoting alkyne adsorption activation and olefin dynamic desorption. The rate-determining step changes from olefin hydrogenation to olefin desorption, thus significantly increasing the olefin selectivity in the alkyne semi-hydrogenation reaction from less than 60% to 94% (Acs Applied Materials & Interfaces, 2021, 13(27), 31775-31784). However, this strategy for catalyst preparation still has inherent drawbacks, such as cumbersome preparation process, high metal loading, and easy loss of active components, which limit the application of such catalysts.

[0005] Therefore, there is an urgent need to develop catalysts that are simple to prepare, environmentally friendly, have low metal loading, are stable, and highly efficient. Due to the unique ability of triphenylphosphine to coordinate and reduce metal ions, and to generate defects through interaction with the support, this invention directly uses a Pd(PPh3)2(O2CCH3)2 phosphine ligand palladium complex to prepare a highly efficient palladium nanowire catalyst through in-situ reduction. Summary of the Invention

[0006] To address the aforementioned technical problems in the existing technology, the present invention aims to provide a catalyst for preparing palladium nanowires using phosphine ligand palladium complexes and its application in the selective hydrogenation of 2-methyl-3-butyn-2-ol. The palladium nanowire catalyst is prepared by directly using the in-situ reduction method of phosphine ligand palladium complexes. When the catalyst of the present invention is applied to the selective hydrogenation reaction of alkyne compounds, it can react rapidly at ambient temperature and pressure and exhibits high selectivity and hydrogenation activity.

[0007] The technical solution adopted in this invention is as follows: A phosphine ligand palladium complex for preparing palladium nanowire catalysts includes a support, noble metal particles supported on the support, and phosphine ligands coordinated on the surface of the noble metal. The catalyst support is SiO2, S-1 molecular sieve, or ZSM-5 molecular sieve, and the active component is noble metal Pd, which is supported on the support in a nanowire structure.

[0008] The preparation method of the catalyst of the present invention includes the following steps: the support is added to glacial acetic acid and stirred thoroughly at room temperature, then a calculated amount of phosphine ligand palladium complex is added, and the catalyst is carried out by stirring in an oil bath at 50-110℃ for 2-11 hours for reduction reaction. Then the catalyst is obtained by filtration, washing, drying and grinding.

[0009] In the reduction reaction of the catalyst prepared in this invention, the ligand-induced reduction properties of the phosphine ligand palladium complex itself are utilized. Taking the Pd(PPh3)2(O2CCH3)2 phosphine ligand palladium complex as an example, under heating conditions, Pd(PPh3)2(OAc)2 first undergoes adsorption and anchoring at the defect sites on the outer surface of ZSM-5 via acetate, the Pd center, and the phosphine ligand. Subsequently, PPh3 is oxidized in the presence of acetate and trace amounts of water in glacial acetic acid to generate OPPh3, while Pd... 2+ Reduced to Pd 0 The generated Pd 0 The species does not completely lose its interaction with phosphine ligands; unreduced PPh3 can still interact with Pd via the lone pair electrons of the P atom. 0P-Pd coordination occurs at low-coordination Pd sites on the surface, stabilizing Pd particles and inhibiting their lateral aggregation. Under the combined influence of anchoring at relevant defect sites on the ZSM-5 surface and the steric hindrance of PPh3, Pd species tend to form one-dimensional connections along these defect sites, ultimately forming Pd nanowire structures. Glacial acetic acid mainly acts as a weakly acidic coordination modifier and proton transfer medium in this process. On the one hand, glacial acetic acid can maintain the AcOH / OAc ratio. - The equilibrium and stability of the Pd-OAc coordination structure promotes the adsorption and ligand exchange of Pd complexes on the ZSM-5 surface. On the other hand, glacial acetic acid can serve as a mild proton source to participate in the oxidation of PPh3 and the transformation of Pd intermediates, thus enabling Pd... 2 + To Pd 0 The reduction is slower and more controllable, preventing the rapid aggregation of Pd species into large particles. Therefore, glacial acetic acid helps to achieve controlled in-situ reduction and one-dimensional nanowire growth on the surface of the P complex ZSM-5.

[0010] Furthermore, the molar ratio of Pd to the mass of the support in the phosphine ligand palladium complex is 1 μmol: 10-100 mg, preferably 1 μmol: 40-60 mg.

[0011] Furthermore, the solid-liquid ratio of the carrier to glacial acetic acid is 1g:100-300mL.

[0012] Furthermore, the phosphine ligand palladium complex is Pd(PPh3)2Cl2, Pd(MePPh2)2Cl2, Pd(PPh3)4 or Pd(PPh3)2(O2CCH3)2, preferably Pd(PPh3)2(O2CCH3)2.

[0013] Furthermore, the silicon-to-aluminum ratio of the ZSM-5 molecular sieve is 25-70, preferably 25-30.

[0014] This invention also discloses the application of the aforementioned phosphine ligand palladium complex in the preparation of palladium nanowire catalysts in the selective hydrogenation reaction of alkynes.

[0015] Furthermore, the alkyne compound is mixed with a solvent, a catalyst is added, and the mixed reaction solution undergoes a hydrogenation reaction with hydrogen gas under the action of the catalyst to generate an olefin compound; wherein the reaction temperature is 0-100℃ and the reaction pressure is 0.1-4MPa; the solvent is water, ethanol, acetone or tetrahydrofuran.

[0016] Furthermore, the solvent is water or ethanol, preferably ethanol, and the dispersion concentration of the alkyne compound in the solvent is 0.01-0.1 g / mL.

[0017] Furthermore, the mass of the catalyst is 1 to 10% of the mass of the alkyne compound, preferably 4 to 6%.

[0018] Furthermore, the hydrogen pressure is from atmospheric pressure to gauge pressure of 1 MPa, preferably 0.1 MPa to 0.3 MPa, the reaction temperature is 15-80℃, preferably 30-50℃, and the reaction time is 5-30 min, preferably 10-20 min.

[0019] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: 1. This invention prepares a low-loaded palladium nanocatalyst via a one-step impregnation reduction method by directly adding the phosphine ligand palladium complex Pd(PPh3)2(O2CCH3)2, using ZSM-5 molecular sieve as a support. The catalyst preparation method is simple, time-saving, low-cost, and has a unique structure.

[0020] 2. During the in-situ reduction process, the complex, through the synergistic effect of the structure-regulating ligand and support defects, induces palladium to form a nanowire structure, resulting in smaller Pd nanoparticles supported on the support and significantly improving metal utilization. The catalyst preparation process in this invention is simple, time-consuming, and energy-efficient, with mild reaction conditions. Furthermore, the palladium nanowire catalyst exhibits good stability to air, water, and heat; after five cycles, its catalytic activity and selectivity for the hydrogenation of 2-methyl-3-butyn-2-ol remain unchanged, and the nanowire structure remains stable.

[0021] 3. This invention constructs a strongly coupled Pd nanowire-support interface by directly using a phosphine ligand palladium complex and simultaneously achieving in-situ reduction growth anchored to defects on the ZSM-5 surface. The continuous nanowire structure enhances the adsorption and enrichment of MBY, while simultaneously strengthening the ability to activate hydrogen and promote hydrogen migration. This avoids excessive retention of adsorbed hydrogen by large Pd particles, inhibiting further hydrogenation and achieving a balance between high activity and high selectivity. When using the catalyst of this invention to catalyze the hydrogenation reaction of 2-methyl-3-butyn-2-ol to prepare 2-methyl-3-buten-2-ol, the selectivity of the target product reaches as high as 94%, and the conversion rate is greater than 99%. Attached Figure Description

[0022] Figure 1a TEM image of the 0.2wt% Pd(PPh3)2(O2CCH3)2 / ZSM-5(25-30) catalyst of Example 1.

[0023] Figure 1b TEM image of the 0.2wt% Pd(PPh3)2(O2CCH3)2 / S-1 catalyst in Example 7.

[0024] Figure 1cTEM image of the 0.2wt% Pd(PPh3)2(O2CCH3)2 / ZSM-5(500) catalyst of Example 10.

[0025] Figure 2 The graph shows a comparison of the conversion rate and selectivity of 2-methyl-3-butyn-2-ol when the 0.2wt% Pd(PPh3)2(O2CCH3)2 / ZSM-5(25-30) catalyst prepared in Example 1 was applied to the catalytic hydrogenation reaction of 2-methyl-3-butyn-2-ol and the catalyst was reused. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0027] Example 1: Preparation of a catalyst supported on ZSM-5 (silicon-to-aluminum ratio 25-30) based on Pd(PPh3)2(O2CCH3)2 300 mg ZSM-5 (silicon-to-aluminum ratio 25-30) was placed in a 50 ml round-bottom flask, 30 ml glacial acetic acid was added, and the mixture was stirred thoroughly at room temperature for 0.5 h. Then, 5.6 μmol of Pd(PPh3)2(O2CCH3)2 was added and stirred in an oil bath at 80 °C for 3 h. After filtration, washing, drying, and grinding, the catalyst 0.2 wt% Pd(PPh3)2(O2CCH3)2 / ZSM-5(25-30) was obtained.

[0028] Example 1: Catalytic performance evaluation experiment of the catalyst: 194 μL of 2-methyl-3-butyn-2-ol (MBY), 10 mg of the catalyst prepared in Example 1, and 5 mL of ethanol were added to a 50 mL stainless steel autoclave. After tightening the autoclave, hydrogen gas was introduced. The air inside the autoclave was first purged five times with hydrogen gas, and then hydrogen gas was introduced until the gauge pressure reached 0.1 MPa and the autoclave was sealed. The reaction temperature was set at 30 °C, and the magnetic stirring speed was 800 r / min for selective hydrogenation reaction for 15 min. After the reaction was stopped, the residual hydrogen gas in the stainless steel autoclave was carefully discharged, and the reaction solution was taken out. The catalyst and reaction solution were separated by centrifugation. The reaction solution was detected by gas chromatography. The conversion rate of 2-methyl-3-butyn-2-ol (MBY) was calculated to be 99%, and the selectivity of 2-methyl-3-buten-2-ol (MBE) was 94%.

[0029] Example 2: Preparation of a catalyst supported on ZSM-5 (silicon-to-aluminum ratio 25-30) based on Pd(PPh3)2Cl2 Example 2 catalyst preparation steps are repeated in Example 1, except that "Pd(PPh3)2(O2CCH3)2 is replaced with an equal molar amount of Pd(PPh3)2Cl2", and the final catalyst is 0.2wt%Pd(PPh3)2Cl2 / ZSM-5(25-30).

[0030] Example 3: Preparation of catalysts supported on ZSM-5 (silicon-to-aluminum ratio 25-30) based on Pd(MePPh2)2Cl2 Example 3 The catalyst preparation steps were repeated in Example 1, except that "Pd(PPh3)2(O2CCH3)2 was replaced with an equal molar amount of Pd(MePPh2)2Cl2", and the final catalyst was 0.2wt%Pd(MePPh2)2Cl2 / ZSM-5(25-30).

[0031] Example 4: Preparation of catalysts supported on ZSM-5 (silicon-to-aluminum ratio 25-30) based on Pd(PPh3)4 Example 4: The catalyst preparation steps were repeated in Example 1, except that Pd(PPh3)2(O2CCH3)2 was replaced with an equal amount of Pd(PPh3)4. The final catalyst prepared was 0.2wt%Pd(PPh3)4 / ZSM-5(25-30).

[0032] Example 5: Catalyst based on Pd supported on Al2O3 Example 5: The catalyst preparation steps were repeated in Example 1, except that 300 mg ZSM-5 (silicon-to-aluminum ratio 25-30) was replaced with 300 mg Al2O3. The final catalyst was 0.2 wt% Pd(PPh3)2(O2CCH3)2 / Al2O3.

[0033] Example 6: Pd-supported catalyst based on SiO2 Example 6: The catalyst preparation steps were repeated in Example 1, except that 300 mg ZSM-5 (silicon-aluminum ratio 25-30) was replaced with 300 mg SiO2. The final catalyst was 0.2 wt% Pd(PPh3)2(O2CCH3)2 / SiO2.

[0034] Example 7: Catalyst based on S-1 supported Pd Example 7: The catalyst preparation steps were repeated in Example 1, except that 300 mg ZSM-5 (silicon-aluminum ratio 25-30) was replaced with 300 mg S-1 molecular sieve (purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.). The final catalyst prepared was 0.2 wt% Pd(PPh3)2(O2CCH3)2 / S-1.

[0035] Example 8: Pd-supported catalyst based on ZSM-5 (silicon-to-aluminum ratio 70) Example 6 The catalyst preparation steps were repeated in Example 1, except that "300 mg ZSM-5 (silicon-aluminum ratio 25-30) was replaced with 300 mg ZSM-5 (silicon-aluminum ratio 70)", and the final catalyst was 0.2 wt% Pd(PPh3)2(O2CCH3)2 / ZSM-5(70).

[0036] Example 9: Catalyst based on Pd supported on ZSM-5 (silicon-to-aluminum ratio 170) Example 9 The catalyst preparation steps were repeated in Example 1, except that "300 mg ZSM-5 (silicon-aluminum ratio 25-30) was replaced with 300 mg ZSM-5 (silicon-aluminum ratio 170)", and the final catalyst was 0.2 wt% Pd(PPh3)2(O2CCH3)2 / ZSM-5(170).

[0037] Example 10: Catalyst based on Pd supported on ZSM-5 (silicon-to-aluminum ratio 500) Example 10: The catalyst preparation steps were repeated in Example 1, except that "300 mg ZSM-5 (silicon-aluminum ratio 25-30) was replaced with 300 mg ZSM-5 (silicon-aluminum ratio 500)", and the final catalyst was 0.2 wt% Pd(PPh3)2(O2CCH3)2 / ZSM-5(500).

[0038] The catalysts prepared in Examples 1, 7, and 10 were characterized by high-resolution transmission electron microscopy (HRTEM). The silicon-to-aluminum ratios of Examples 1, 7, and 10 were 25-30, 0, and 500, respectively. The TEM characterization results of the three catalysts are shown in the figures below. Figure 1a , Figure 1b and Figure 1c .from Figure 1a It can be seen that when Pd is loaded onto the molecular sieve ZSM-5 with a suitable silicon-to-aluminum ratio (25-30), Pd exhibits a continuous nanowire structure. From... Figures 1b-1c It can be seen that when Pd is loaded onto molecular sieve S-1 (which has no Al content) or molecular sieve ZSM-5 (which has a low Al content, with a silicon-to-aluminum ratio of 500), Pd exists in a dispersed and disordered particle form. Therefore, palladium nanowire structures are only formed when loaded onto ZSM-5 with an appropriate silicon-to-aluminum ratio.

[0039] The catalysts in Examples 2-10 were subjected to performance evaluation experiments. The evaluation methods were the same as in Example 1. The results of the catalytic reaction for 15 min are summarized in Table 1.

[0040] Table 1 .

[0041] The conclusions can be drawn from Example 1 and Table 1: 1) By comparing the experimental results of the catalysts in Examples 1-4, it is shown that Pd(PPh3)2(O2CCH3)2 has stronger reducing properties, which is beneficial to the efficient hydrogenation of 2-methyl-3-butyn-2-ol.

[0042] 2) Comparing the experimental results of catalysts in Examples 1 and 5-10, it is shown that the ligand modification method provided by the present invention has good applicability to both metal oxide supports and molecular sieve supports, and exhibits excellent performance in the semi-hydrogenation reaction of alkynols. However, only when palladium nanowire structures exist on ZSM-5 supports with a suitable silicon-aluminum ratio do they exhibit even better performance.

[0043] In addition, a reuse experiment was conducted on the 0.2wt% Pd(PPh3)2(O2CCH3)2 / ZSM-5(25-30) catalyst from Example 1 for the selective hydrogenation of 2-methyl-3-butyn-2-ol. The experimental procedure for the catalytic reaction was repeated in Example 11. The reaction time for each batch of catalytic reaction was 15 min. After the reaction, the catalyst was separated from the reaction solution. The recovered catalyst was washed with ethanol, dried, and reused in the next batch of catalyst reuse reaction. Considering that a small amount of catalyst loss is inevitable during recovery, approximately 10%, about 3 mg of catalyst was added for each subsequent batch of catalyst reuse. The comparison of the conversion rate and selectivity of 2-methyl-3-butyn-2-ol when the catalyst was reused according to this experimental method is shown in the figure below. Figure 2 It can be seen that the palladium nanowire catalyst prepared by the phosphine ligand palladium complex has good stability, and the catalytic activity basically does not decrease after five consecutive uses.

[0044] Example 11: Semi-hydrogenation activity of catalysts prepared in Example 1 with different Pd loadings The catalyst was prepared according to the method of Example 1, except that the amount of "Pd(PPh3)2(O2CCH3)2" was changed to 2.8 μmol, 5.6 μmol, 11.2 μmol, 16.8 μmol, and 28 μmol Pd(PPh3)2(O2CCH3)2, so that the Pd content in the catalyst was 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%, respectively.

[0045] Example 11: Catalysts containing 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% Pd were subjected to performance evaluation experiments. The evaluation methods were the same as in Example 1. The experimental results under different catalytic reaction times were as follows: 1) When catalyzed by a catalyst with ZSM-5 (25-30) support and 0.1% Pd content: the conversion rate of 2-methyl-3-butyn-2-ol (MBY) was 17% within 5 min, the selectivity of 2-methyl-3-buten-2-ol (MBE) was 96%, and the conversion frequency was 43820 h. -1 ; 2) When the catalyst supported by ZSM-5 (25-30) and containing 0.2% Pd is used for catalysis: MBY conversion is 22% within 2 min, MBE selectivity is 95%, and conversion frequency is 70-556 h. -1 ; 3) When the catalyst supported by ZSM-5 (25-30) and containing 0.4% Pd is used for catalysis: MBY conversion is 28% within 3 min, MBE selectivity is 95%, and conversion frequency is 29904 h. -1 ; 4) When the catalyst with ZSM-5 (25-30) support and 0.6% Pd content is used for catalysis: MBY conversion is 19% within 1.5 min, MBE selectivity is 95%, and conversion frequency is 27385 h. -1 ; 5) When the catalyst with ZSM-5 (25-30) support and 0.8% Pd content is used for catalysis: MBY conversion is 25% within 2 min, MBE selectivity is 95%, and conversion frequency is 200-33 h. -1 ; 6) When the catalyst supported by ZSM-5 (25-30) and containing 1.0% Pd is used for catalysis: MBY conversion is 29% within 2 min, MBE selectivity is 95%, and conversion frequency is 18772 h. -1 ; The formula for calculating the Transition Frequency (TOF) is: .

[0046] In the formula, Conv. is the conversion rate; m is the catalyst mass; wt% is the Pd mass fraction in the catalyst as determined by ICP; n is the molar amount of MBY; M is the molecular weight of Pd; and T is the reaction time.

[0047] The comparison of the above experimental results shows that both insufficient and excessive palladium loading have an inhibitory effect. When the palladium content is 0.2%, its catalytic performance for the semi-hydrogenation of 2-methyl-3-butyn-2-ol is the best, and the palladium metal utilization rate is the highest.

[0048] Comparative Example 1: Preparation of 2-methyl-3-buten-2-ol using a Pd-supported catalyst based on ZSM-5 (25-30) The catalyst preparation includes the following steps: 300 mg of ZSM-5(25-30) was placed in a 50 mL beaker, 30 mL of glacial acetic acid was added, and the mixture was stirred thoroughly at room temperature for 0.5 h. Then, a calculated amount of 5.6 μmol Pd(O2CCH3)2 solution was added, and the mixture was stirred thoroughly for another 1 h. The suspension was then heated to 110 °C in an oil bath and stirred until dry. The powder adhering to the beaker was scraped off, placed in a porcelain boat, and then placed in a tube furnace. Reduction was carried out at 200 °C for 2 h under a hydrogen atmosphere to obtain the catalyst 0.2 wt% Pd / ZSM-5(25-30)-H2.

[0049] The catalyst of Comparative Example 1 was subjected to a performance evaluation experiment. The evaluation experiment method was the same as that in Example 1. The results of the catalytic reaction for 15 min were as follows: the conversion rate of 2-methyl-3-butyn-2-ol (MBY) was 18%, and the selectivity of 2-methyl-3-buten-2-ol (MBE) was 93%.

[0050] Comparative Example 2: Preparation of 2-methyl-3-buten-2-ol based on Pd-supported activated carbon catalyst The catalyst preparation includes the following steps: 300 mg of ZSM-5(25-30) was placed in a 50 ml round-bottom flask, 10 ml of deionized water was added, and the mixture was stirred thoroughly at room temperature for 0.5 h. Then, a calculated amount of 5.6 μmol Pd(O2CCH3)2 was added. After stirring thoroughly for another 1 h, an excess NaBH4 solution dissolved in deionized water was added, and the mixture was stirred for another 1 h. After filtration, washing, and drying, the catalyst 0.2 wt% Pd / ZSM-5(25-30)-NaBH4 was obtained.

[0051] The catalyst of Comparative Example 2 was subjected to a performance evaluation experiment. The evaluation experiment method was the same as that in Example 1. The results of the catalytic reaction for 15 min were as follows: the conversion rate of 2-methyl-3-butyn-2-ol (MBY) was 36%, and the selectivity of 2-methyl-3-buten-2-ol (MBE) was 96%.

[0052] Comparative Example 3: Preparation of 2-methyl-3-buten-2-ol based on Pd-supported activated carbon catalyst The catalyst preparation includes the following steps: 300 mg of activated carbon is placed in a 50 ml round-bottom flask, 10 ml of glacial acetic acid is added, and the mixture is stirred thoroughly at room temperature for 0.5 h. Then, a calculated amount of 5.6 μmol Pd(PPh3)2(O2CCH3)2 is added, and the mixture is stirred in an oil bath at 80 °C for 3 h. After filtration, washing, and drying, the catalyst 0.2 wt% Pd(PPh3)2(O2CCH3)2 / AC is obtained.

[0053] The catalyst of Comparative Example 2 was subjected to a performance evaluation experiment. The evaluation experiment method was the same as that in Example 1. The results of the catalytic reaction for 15 min were as follows: the conversion rate of 2-methyl-3-butyn-2-ol (MBY) was 13%, and the selectivity of 2-methyl-3-buten-2-ol (MBE) was 86%.

[0054] Comparative Example 4: Preparation of 2-methyl-3-buten-2-ol using a Pd-supported catalyst based on ZSM-5 (25-30) The catalyst preparation includes the following steps: 300 mg of ZSM-5(25-30) was placed in a 50 mL beaker, 30 mL of glacial acetic acid was added, and the mixture was stirred thoroughly at room temperature for 0.5 h. Then, a calculated amount of 5.6 μmol Pd(O2CCH3)2 solution was added, and the mixture was stirred thoroughly for another 1 h. Next, 5 mL of a PPh3 solution dissolved in glacial acetic acid (containing 11.2 μmol PPh3) was added, and the mixture was stirred in an oil bath at 80 °C for 3 h. After filtration, washing, and drying, the catalyst 0.2 wt% Pd / ZSM-5(25-30)-PPh3-2 was obtained.

[0055] The catalyst of Comparative Example 4 was subjected to a performance evaluation experiment. The evaluation experiment method was the same as that in Example 1. The results of the catalytic reaction for 15 min were as follows: the conversion rate of 2-methyl-3-butyn-2-ol (MBY) was 92.1%, and the selectivity of 2-methyl-3-buten-2-ol (MBE) was 94%.

[0056] The experimental results of Examples 1, 2, 3, and 4 show that the preparation method using phosphine ligand palladium complexes can significantly improve catalyst activity. Furthermore, the activity of metal oxides and molecular sieves as supports is superior to that of commercial activated carbon. The performance is not much different from that of the stepwise addition of palladium acetate and triphenylphosphine, and this preparation method is simpler.

[0057] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A method for preparing palladium nanowire catalysts using phosphine ligand palladium complexes, characterized in that, The catalyst includes a support, noble metal particles supported on the support, and phosphine ligands coordinated on the surface of the noble metal. The support for the catalyst is SiO2, S-1 molecular sieve, or ZSM-5 molecular sieve, and the active component is noble metal Pd, which is supported on the support in the form of nanowires. The catalyst preparation method includes the following steps: the support is added to glacial acetic acid and stirred thoroughly at room temperature, then a calculated amount of phosphine ligand palladium complex is added, and the reduction reaction is carried out by stirring in an oil bath at 50-110℃ for 2-11 hours. Then, the catalyst is obtained by filtration, washing, drying and grinding. In the phosphine ligand palladium complex, the molar ratio of Pd to the mass of the carrier is 1 μmol: 10-100 mg.

2. The preparation method according to claim 1, characterized in that, The solid-liquid ratio of the carrier to glacial acetic acid is 1g:100-300mL.

3. The preparation method according to claim 1, characterized in that, The molar ratio of Pd to the mass of the carrier in the phosphine ligand palladium complex is 1 μmol: 40-60 mg.

4. The preparation method according to claim 1, characterized in that, The phosphine ligand palladium complex is Pd(PPh3)2Cl2, Pd(MePPh2)2Cl2, Pd(PPh3)4 or Pd(PPh3)2(O2CCH3)2, preferably Pd(PPh3)2(O2CCH3)2.

5. The preparation method according to claim 2, characterized in that, The silicon-aluminum ratio of the ZSM-5 molecular sieve is 25-70, preferably 25-30.

6. The application of the palladium nanowire catalyst prepared by the phosphine ligand palladium complex as described in claim 1 in the selective hydrogenation reaction of alkyne compounds.

7. The application as described in claim 6, characterized in that... Alkynes are mixed with a solvent, and a catalyst is added. The resulting reaction solution undergoes a hydrogenation reaction with hydrogen gas under the action of the catalyst to produce olefins. The reaction temperature is 0–100°C, and the reaction pressure is 0.1–4 MPa. The solvent is water, ethanol, acetone, or tetrahydrofuran.

8. The application as described in claim 7, characterized in that... The solvent is water or ethanol, preferably ethanol, and the dispersion concentration of the alkyne compound in the solvent is 0.01-0.1 g / mL.

9. The application as described in claim 7, characterized in that... The mass of the catalyst is 1 to 10% of the mass of the alkyne compound, preferably 4 to 6%.

10. The application as described in claim 7, characterized in that... The hydrogen pressure is from atmospheric pressure to gauge pressure of 1 MPa, preferably 0.1 MPa to 0.3 MPa, the reaction temperature is 15-80℃, preferably 30-50℃, and the reaction time is 5-30 min, preferably 10-20 min.

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