An organic phosphonic acid modified noble metal catalyst, a preparation method and application thereof

Abstract

The application provides an organic phosphonic acid modified noble metal catalyst and a preparation method and application thereof, and the method comprises the following steps: (1) preparing an organic phosphonic acid solution, adding a noble metal catalyst or a catalyst carrier under stirring, and stirring at room temperature; (2) centrifuging the obtained mixed solution, and drying the solid after centrifugation in air; (3) washing the dried solid with a solvent for multiple times, centrifuging, drying, and obtaining an organic phosphonic acid modified noble metal catalyst or catalyst carrier; when the organic phosphonic acid modified catalyst carrier is obtained, a noble metal is loaded to obtain an organic phosphonic acid modified noble metal catalyst. The organic phosphonic acid modification forms an organic phosphonic acid monolayer on the surface of the noble metal catalyst carrier, has the characteristics of high CO poisoning resistance, no change of the original catalyst structure, no influence on the original catalyst activity, high thermal stability and wide application range.

Description

Technical Field

[0001] This invention belongs to the technical field of catalyst preparation, specifically, it relates to an organophosphonic acid modified noble metal catalyst, its preparation method and application. Background Technology

[0002] Noble metal catalysts are widely used in hydrogenation reactions due to their highly efficient catalytic hydrogenation capabilities and superior heat resistance, oxidation resistance, and corrosion resistance compared to non-noble metal catalysts. However, typical noble metals such as Pt and Pd are susceptible to CO poisoning due to the preferential and strong adsorption of trace amounts of CO from crude hydrogen on their surfaces, leading to blockage of the catalyst's active hydrogenation sites. Therefore, developing a highly active hydrogenation catalyst compatible with crude hydrogen and resistant to CO poisoning is of significant scientific and economic importance. In recent years, researchers have made great efforts to improve the CO poisoning resistance of noble metal catalysts, mainly through the following approaches, according to current reports:

[0003] (1) Adjusting the electronic properties of noble metals to weaken the binding energy between the metal and CO. For example, the journal article Journal of the American Chemical Society, 2016, 138(20):6396-6399 reported that single-atom Pt-Cu alloy catalysts have a weaker binding energy with CO than single-metal Pt catalysts, with a higher proportion of CO-free Pt sites. The rate retention rate of the selective hydrogenation of acetylene to ethylene under CO crude hydrogen conditions is over 50%, which is about 15 times that of Pt nanoparticle catalysts; (2) Introducing oxyphilic neighboring sites to adsorb hydroxyl groups to eliminate adsorbed CO, for example, the journal Nature Materials 2008, 7: 333-338 reported that Ru@Pt core-shell nanoparticle catalysts can preferentially oxidize CO in H2 streams containing 1000ppm and complete hydrogen ignition at 30℃, which is significantly better than traditional PtRu nanoalloy catalysts (85℃). The enhanced catalytic activity of core-shell nanoparticles is due to the increased availability of CO-free Pt surface sites on Ru@Pt nanoparticles and the combination of hydrogen-mediated low-temperature CO oxidation process; (3) Selectively exposing specific surfaces with optimal adsorption energy of key surface materials, for example, the journal Nature Catalysis. 2020, 3: 454-462 reports a Ru catalyst (Ru@TiO2) partially confined in a sea urchin-like TiO2 lattice that can efficiently catalyze the HOR (Hot Oxygen Orbit) to a potential of 0.9 VRHE under both acidic and basic conditions, exhibiting higher mass activity than PtRu catalysts. Furthermore, the HOR activity of this Ru@TiO2 catalyst is unaffected by 1000 ppm CO. Even at a high CO content of 10 vol%, Ru@TiO2 still selectively catalyzes the HOR. The confined Ru clusters grow along the TiO2 lattice, forming abundant Ru-Ti bonds. This atomic connection provides efficient electron permeation from electron-rich TiO2 to Ru metal, resulting in slow CO adsorption kinetics during the HOR.

[0004] The aforementioned strategies can be achieved using atomically dispersed noble metals, single-atom alloy catalysts, metal-support interactions enhanced by core-shell structures, or noble metal nanoparticles with controllable morphologies. These catalysts exhibit excellent resistance to CO poisoning in many important reactions, such as the hydrogenation of acetylene, toluene, and nitrobenzene, the electro-oxidation of methanol, the electro-oxidation of formic acid, and the hydrogenation reaction. However, in many cases, these methods require complex catalyst synthesis steps and are not suitable for noble metal catalysts traditionally prepared via initial wet impregnation. Catalyst versatility is also a crucial issue that urgently needs to be addressed.

[0005] Therefore, we need to develop and construct a novel noble metal catalyst resistant to CO poisoning to overcome the existing technical deficiencies. Summary of the Invention

[0006] The first objective of this invention is to provide a method for preparing an organophosphonic acid-modified noble metal catalyst for CO poisoning resistance. The prepared organophosphonic acid-modified noble metal catalyst has the characteristics of strong CO poisoning resistance, no change to the original catalyst structure, no impact on the original catalyst activity, high thermal stability, and wide applicability.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0008] A method for preparing an organophosphonic acid-modified noble metal catalyst includes the following steps:

[0009] (1) Prepare an organophosphonic acid solution by adding an appropriate amount of noble metal catalyst M / S or catalyst support S under stirring conditions and stirring at room temperature.

[0010] (2) Centrifuge the mixture obtained in step (1) and dry the solid after centrifugation in air;

[0011] (3) The solid dried in step (2) is washed with solvent multiple times and centrifuged and dried to obtain organophosphonic acid modified noble metal catalyst PA-M / S or organophosphonic acid modified catalyst support PA-S.

[0012] When the catalyst support S is added in step (1), so that the catalyst support PA-S modified with organophosphonic acid is obtained in step (3), the preparation method further includes step (4):

[0013] (4) The noble metal M is supported on the organic phosphonic acid modified catalyst support PA-S obtained in step (3), and the noble metal catalyst M / PA-S is obtained by modifying the organic phosphonic acid.

[0014] The present invention is further configured such that the noble metal M is one or both of Pt and Pd. The support S of the noble metal catalyst or the catalyst support S is one or more of Al2O3, CNTs, SiO2 and TiO2.

[0015] The present invention is further configured such that, when the noble metal M is Pt, the above preparation method is based on modifying the organophosphonic acid with a noble metal catalyst or on modifying the organophosphonic acid with a catalyst support and then loading the noble metal, that is, the noble metal catalyst M / S or the catalyst support S is added in step (1), and a noble metal catalyst modified with organophosphonic acid with excellent performance can be obtained in the end; when the noble metal M includes Pd, the above preparation method is preferably based on modifying the organophosphonic acid with a catalyst support and then loading the noble metal, that is, the catalyst support S is preferably added under stirring conditions in step (1).

[0016] The present invention is further configured such that, in step (1), the organophosphonic acid PA is one or more of methylphosphonic acid (MPA), octadecylphosphonic acid (ODPA), chloromethylphosphonic acid (CLMPA), and chlorodrophosphonic acid (CDNA); the solvent for preparing the organophosphonic acid solution is selected from one or more of methanol, ethanol, isopropanol, and tetrahydrofuran, preferably tetrahydrofuran. Those skilled in the art can select the type of organophosphonic acid, the type of solvent, the type of noble metal, and the type of carrier as needed.

[0017] The present invention is further configured such that, in step (1), the concentration of the organophosphonic acid solution is maintained at about 4 to 12 mM, and the mass ratio of the added noble metal catalyst M / S or catalyst support S to the mass of organophosphonic acid is (1 to 3): 1, so that the amount of acid in the solution is about 8 to 12 times the amount of acid required to form an organophosphonic acid monolayer on the surface of the noble metal catalyst support or catalyst support.

[0018] It should be noted that the purpose of preparing the organophosphonic acid solution is to dissolve the organophosphonic acid. The applicant found that if too much organophosphonic acid is added, its dissolution effect is poor. Good dissolution of organophosphonic acid is one of the prerequisites for ensuring uniform and effective modification of the noble metal catalyst support surface with an organophosphonic acid monolayer. Optimally, a mass-to-volume ratio of organophosphonic acid to solvent of 1 mg:1 mL can achieve good dissolution of the organophosphonic acid. Generally, a range of 1 mg:(0.5–1) mL is feasible.

[0019] The present invention is further configured such that, in step (1), the stirring speed is 600-800 r / min, and the stirring time after adding the noble metal catalyst M / S or the catalyst support S is 16-24 h.

[0020] The present invention is further configured such that, in step (2), the centrifugation speed is controlled at 8000–10000 r / min, and the centrifugation time is 8–10 min. The drying step is controlled at 110–130 °C, and the time is 14–18 h.

[0021] It should be noted that, under the conditions of controlling the centrifugation speed at 8000–10000 r / min and the centrifugation time at 8–10 min, the effective separation of the organophosphonic acid-modified noble metal catalyst or catalyst support from the organophosphonic acid solution can be ensured. In this invention, the solid obtained after centrifugation is dried in air to evaporate the solvent contained in the solid while ensuring that the organophosphonic acid forms bonds with the surface of the catalyst support, thus forming an organophosphonic acid-modified noble metal catalyst or catalyst support. Optimally, the drying temperature is 120℃ and the drying time is 16 h.

[0022] It should be further noted that the control of the drying step in the above technical solution of the present invention is crucial. It must be controlled at 110-130°C for 14-18 hours to ensure that the organophosphonic acid is effectively modified on the surface of the catalyst support. This ensures that the organophosphonic acid-modified noble metal catalyst or catalyst support does not dissolve and fall off the support during subsequent centrifugation, and ensures that the surface of the final organophosphonic acid-modified noble metal catalyst support has abundant and uniform organophosphonic acid deposition, providing a good foundation for the strong CO poisoning resistance of the noble metal catalyst.

[0023] The present invention is further configured such that, in step (3), the solvent used for washing is selected from one or more of methanol, ethanol, isopropanol, and tetrahydrofuran, preferably consistent with the solvent selection in step (1); the number of washing cycles is 3 to 8, preferably 5, which can wash away some unmodified organophosphonic acid on the surface of the catalyst support; the volume of solvent used for each washing and centrifugation is 40 to 50 mL; the centrifugation speed is controlled at 8000 to 10000 r / min, and the centrifugation time is 8 to 10 min; after multiple washing and separation, the solid is dried at room temperature for 10 to 12 h, which can completely evaporate and remove the remaining solvent in the solid.

[0024] The present invention is further configured such that, in step (4), the organophosphonic acid modified catalyst support PA-S is loaded with noble metal M by impregnation, including the following steps:

[0025] (a) Take a certain amount of organophosphonic acid modified catalyst support PA-S and slowly add a certain amount of water; after each addition of water, use a vortex mixer to mix; repeat the above steps until a state between solid and liquid is reached, record the volume of water added, and obtain the pore volume in mL / mg.

[0026] (b) Based on the measured pore volume, a certain amount of the noble metal precursor solution was transferred and mixed with the organophosphonic acid-modified catalyst support. After the material was vortexed and mixed, it formed a flowing slurry between liquid and solid. After being placed at room temperature and dried, it was then reduced in an H2 / Ar atmosphere to obtain the organophosphonic acid-modified noble metal catalyst M / PA-S.

[0027] The present invention is further configured such that, among the organophosphonic acids, the noble metal catalyst modified by the chloromethylphosphonic acid or chlorodrophosphonic acid has better resistance to CO poisoning.

[0028] Preferably, the chlorodrophosphonic acid-modified noble metal catalyst has excellent resistance to CO poisoning and can also improve the hydrogenation activity of the noble metal catalyst.

[0029] More preferably, in step (1), the solvent is selected from tetrahydrofuran, and the concentration of the organophosphonic acid solution is controlled to be 10 mM; the stirring speed is 800 r / min, and the stirring time after adding the noble metal catalyst or catalyst support is 16 h.

[0030] In step (2), the centrifugation speed is 10000 r / min, the centrifugation time is 10 min, the drying temperature is 120℃, and the drying time is 16 h. Under the above conditions, the obtained organophosphonic acid modified noble metal catalyst support has abundant and uniform organophosphonic acid deposits on its surface, exhibiting the best resistance to CO poisoning.

[0031] In step (3), the solvent is selected from tetrahydrofuran, which includes 5 washings. The volume of tetrahydrofuran solvent used for each centrifugation is 50 mL, the centrifugation speed is 10000 r / min, the centrifugation time is 10 min, and the drying time is 12 h.

[0032] The second objective of this invention is to provide an organophosphonic acid-modified noble metal catalyst, prepared by the above-described method for preparing organophosphonic acid-modified noble metal catalysts, wherein an organophosphonic acid monolayer is formed on the surface of the support of the noble metal catalyst.

[0033] The third objective of this invention is to provide the application of the above-mentioned organophosphonic acid modified noble metal catalyst for resisting CO poisoning in hydrogenation reactions, including benzyl alcohol hydrogenation deoxygenation reaction, acetylene selective hydrogenation to ethylene reaction, nitrobenzene hydrogenation to aniline reaction, methanol electro-oxidation reaction, formic acid electro-oxidation reaction, and hydroxide reaction, etc.

[0034] Preferably, the reaction conditions for the benzyl alcohol hydrogenation deoxygenation reaction are: reaction temperature 160-200℃, more preferably 180℃, atmospheric pressure, total gas flow rate 50-90mL / min, more preferably 70mL / min, and CO concentration 1500-5000ppm.

[0035] Preferably, the reaction conditions for the selective hydrogenation of acetylene to ethylene are: reaction temperature 90-110℃, more preferably 100℃, atmospheric pressure, total gas flow rate 60-80 mL / min, and CO concentration 1500-5000 ppm.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) The method for preparing the organophosphonic acid modified noble metal catalyst of the present invention is applicable to traditional supported noble metal catalysts and can be used with a variety of different noble metals and supports, such as Pt and Pd, Al2O3, CNTs, TiO2 and SiO2, etc. This method is achieved by the self-assembly of an organophosphonic acid ligand monolayer deposited on the catalyst support.

[0038] (2) Furthermore, the alkyl tail of organophosphonic acids modulates the near-surface environment of noble metals by repelling the adsorption of noble metals and CO molecules through steric non-covalent interactions. Considering the flexible structure of the modified ligands, for example, organophosphonic acid ligands with different electron-withdrawing groups and alkyl tail lengths, the electronic effects on the catalyst surface can be precisely tuned through steric non-covalent interactions.

[0039] (3) Simultaneously, the organophosphonic acid-modified noble metal catalyst of the present invention is applicable to hydrogenation reactions such as the hydrodeoxygenation of benzyl alcohol and the selective hydrogenation of acetylene. After modification with organophosphonic acid, the resulting organophosphonic acid-modified noble metal catalyst exhibits strong resistance to CO poisoning under crude hydrogen conditions containing different CO concentrations (1500–5000 ppm CO), while the unmodified noble metal catalyst rapidly deactivates under the same reaction conditions. Moreover, the degree of CO resistance can be adjusted by controlling the molecular structure of the organophosphonic acid ligand, and a CO-resistant organophosphonic acid-modified noble metal catalyst can be constructed without affecting or even enhancing the inherent hydrogenation activity of the original noble metal catalyst.

[0040] Diffuse reflectance in situ infrared spectroscopy using CO as a probe molecule revealed that after modification with organophosphonic acid, the catalyst exhibited a significant decrease in the bonding strength with various types of CO.

[0041] X-ray absorption spectroscopy and molecular dynamics simulations revealed that the alkyl tail of organophosphonic acids modulates their near-surface environment through spatial non-covalent interactions, thereby resisting the adsorption of noble metals and CO molecules.

[0042] DFT calculations revealed that the deposition of various organophosphonic acids on the support weakened the adsorption energy of noble metals and CO, indicating that the modification of organophosphonic acids weakened the binding strength between CO and noble metals.

[0043] In summary, this technique utilizes the deposition of organophosphonic acid ligands on a noble metal catalyst support to form a monolayer on the catalyst support surface, thereby achieving single-assembly modification of the catalyst surface with organophosphonic acids. The organophosphonic acid head groups influence the electronic properties of the metal through surface electron-withdrawing effects. This technology is highly versatile, applicable not only to various noble metals and supports but also to a variety of traditional catalytic hydrogenation reactions. Furthermore, it has the potential to transform traditional supported noble metal catalysts into CO-poison-resistant catalysts suitable for even more types of important hydrogenation reactions. Attached Figure Description

[0044] Figure 1 The X-ray diffraction patterns of 5% Pt / Al2O3 modified with organophosphonic acid prepared in Examples 1-4 are shown.

[0045] Wherein: curve a represents the X-ray diffraction pattern of unmodified 5% Pt / Al2O3 in Comparative Example 1; curve b represents the X-ray diffraction pattern of methylphosphonic acid modified 5% Pt / Al2O3 in Example 1; curve c represents the X-ray diffraction pattern of octadecylphosphonic acid modified 5% Pt / Al2O3 in Example 2; curve d represents the X-ray diffraction pattern of chloromethylphosphonic acid modified 5% Pt / Al2O3 in Example 3; curve e represents the X-ray diffraction pattern of chlorodrophosphonic acid modified 5% Pt / Al2O3 in Example 4; Al2O3: JCPDS#46-1131 is the Al2O3 standard card corresponding to this set of patterns; Pt: JCPDS#04-0802 is the Pt standard card corresponding to this set of patterns.

[0046] Figure 2 The X-ray diffraction patterns of the organophosphonic acid-modified 5% Pd / Al2O3 prepared in Examples 5-8 are shown.

[0047] Wherein: curve a represents the X-ray diffraction pattern of unmodified 5% Pd / Al2O3 in Comparative Example 2; curve b represents the X-ray diffraction pattern of methylphosphonic acid modified 5% Pd / Al2O3 in Example 5; curve c represents the X-ray diffraction pattern of octadecylphosphonic acid modified 5% Pd / Al2O3 in Example 6; curve d represents the X-ray diffraction pattern of chloromethylphosphonic acid modified 5% Pd / Al2O3 in Example 7; curve e represents the X-ray diffraction pattern of chlorophosphonic acid modified 5% Pd / Al2O3 in Example 8; Al2O3: JCPDS#46-1131 is the Al2O3 standard card corresponding to this set of patterns; Pd: JCPDS#46-1043 is the Pd standard card corresponding to this set of patterns.

[0048] Figure 3 Transmission electron microscopy (TEM) images and particle size distributions of the organophosphonic acid-modified 5% Pt / Al2O3 prepared in Examples 1-4 are shown.

[0049] Wherein: a represents the transmission electron microscopy (TEM) image and particle size distribution of unmodified 5% Pt / Al2O3 in Comparative Example 1; b represents the TEM image and particle size distribution of methylphosphonic acid modified 5% Pt / Al2O3 in Example 1; c represents the TEM image and particle size distribution of octadecylphosphonic acid modified 5% Pt / Al2O3 in Example 2; d represents the TEM image and particle size distribution of chloromethylphosphonic acid modified 5% Pt / Al2O3 in Example 3; and e represents the TEM image and particle size distribution of chlorodrophosphonic acid modified 5% Pt / Al2O3 in Example 4.

[0050] Figure 4 Transmission electron microscopy images and particle size distributions of the organophosphonic acid-modified 5% Pt / CNTs prepared in Examples 9-11 are shown.

[0051] Wherein: a represents the transmission electron microscopy (TEM) image and particle size distribution of the unmodified 5% Pt / CNTs in Comparative Example 3; b represents the TEM image and particle size distribution of the octadecylphosphonic acid-modified 5% Pt / CNTs in Example 9; c represents the TEM image and particle size distribution of the chloromethylphosphonic acid-modified 5% Pt / CNTs in Example 10; and d represents the TEM image and particle size distribution of the chlorodrophosphonic acid-modified 5% Pt / CNTs in Example 11.

[0052] Figure 5 The thermogravimetric curves of 5% Pt / Al2O3 modified with organophosphonic acid prepared in Examples 2-4 are shown.

[0053] Wherein: curve a represents the thermogravimetric curve of unmodified 5% Pt / Al2O3 in Comparative Example 1; curve b represents the thermogravimetric curve of 5% Pt / Al2O3 modified with octadecylphosphonic acid in Example 2; curve c represents the thermogravimetric curve of 5% Pt / Al2O3 modified with chloromethylphosphonic acid in Example 3; and curve d represents the thermogravimetric curve of 5% Pt / Al2O3 modified with chlorodrophosphonic acid in Example 4.

[0054] Figure 6 The infrared spectra of 5% Pt / Al2O3 modified with organophosphonic acid prepared in Examples 1-4 are shown.

[0055] Wherein: curve a represents the infrared spectrum of unmodified 5% Pt / Al2O3 in Comparative Example 1; curve b represents the infrared spectrum of methylphosphonic acid modified 5% Pt / Al2O3 in Example 1; curve c represents the infrared spectrum of octadecylphosphonic acid modified 5% Pt / Al2O3 in Example 2; curve d represents the infrared spectrum of chloromethylphosphonic acid modified 5% Pt / Al2O3 in Example 3; and curve e represents the infrared spectrum of chlorodrophosphonic acid modified 5% Pt / Al2O3 in Example 4.

[0056] Figure 7 The infrared spectra of 5% Pd / Al2O3 modified with organophosphonic acid prepared in Examples 5-8 are shown.

[0057] Wherein: curve a represents the infrared spectrum of unmodified 5% Pd / Al2O3 in Comparative Example 2; curve b represents the infrared spectrum of methylphosphonic acid modified 5% Pd / Al2O3 in Example 5; curve c represents the infrared spectrum of octadecylphosphonic acid modified 5% Pd / Al2O3 in Example 6; curve d represents the infrared spectrum of chloromethylphosphonic acid modified 5% Pd / Al2O3 in Example 7; and curve e represents the infrared spectrum of chlorodrophosphonic acid modified 5% Pd / Al2O3 in Example 8.

[0058] Figure 8 The in-situ diffuse reflectance infrared spectra (CO-DRIFTs) of the CO probe molecules of 5% Pt / Al2O3 modified with organophosphonic acid prepared in Examples 1-4 are shown.

[0059] Wherein: curve a represents the in-situ infrared spectrum of unmodified 5% Pt / Al2O3 in Comparative Example 1; curve b represents the in-situ infrared spectrum of methylphosphonic acid modified 5% Pt / Al2O3 in Example 1; curve c represents the in-situ infrared spectrum of octadecylphosphonic acid modified 5% Pt / Al2O3 in Example 2; curve d represents the in-situ infrared spectrum of chloromethylphosphonic acid modified 5% Pt / Al2O3 in Example 3; and curve e represents the in-situ infrared spectrum of chlorodrophosphonic acid modified 5% Pt / Al2O3 in Example 4. Detailed Implementation

[0060] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. It should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar with the art. As used herein, "room temperature" means 10-30°C, preferably 20-25°C.

[0061] Example 1: Preparation of catalyst MPA / 5% Pt / Al2O3

[0062] The preparation of the catalyst MPA / 5% Pt / Al2O3 in this embodiment includes the following steps:

[0063] (a) Dissolve 125 mg MPA (methylphosphonic acid, purity 99.99%) in a beaker containing 125 mL tetrahydrofuran (purity 99.9%) and stir with a magnetic stirrer for 30 min until completely dissolved to obtain a tetrahydrofuran solution of methylphosphonic acid; pour 250 mg 5% Pt / Al2O3 catalyst into the solution; seal the mouth of the beaker with plastic wrap to prevent tetrahydrofuran from evaporating, and continue stirring at room temperature for 16 h with the magnetic stirrer speed at 800 r / min.

[0064] (b) Dispense the mixture from step (a) into centrifuge tubes and centrifuge at 10,000 rpm for 10 minutes. After centrifugation, discard the supernatant and collect the solid in the centrifuge tubes. Place the solid in an oven to dry at 120°C for 16 hours.

[0065] (c) Take out the dried solid and cool it to room temperature. Disperse the solid in a centrifuge tube with 50 mL of tetrahydrofuran and centrifuge. Repeat this operation to wash 5 times. Each time, the centrifuge speed is set to 10000 r / min and the centrifugation time is 10 min. Dry the solid obtained from the fifth centrifugation at room temperature for 12 h to obtain the methylphosphonic acid modified 5% Pt / Al2O3 catalyst, which is calculated as MPA / 5%Pt / Al2O3.

[0066] Examples 2-4: Preparation of catalysts ODPA / 5% Pt / Al2O3, CLMPA / 5% Pt / Al2O3, and cDNA / 5% Pt / Al2O3

[0067] The preparation steps of the catalysts in Examples 2-4 are basically the same as those in Example 1, except that:

[0068] In Example 2, in step (a), 125 mg MPA was replaced with 250 mg ODPA (octadecylphosphonic acid, purity 99.99%), and in step (b), the drying temperature was 110 °C and the drying time was 14 h. The resulting catalyst was calculated as ODPA / 5% Pt / Al2O3.

[0069] In Example 3, in step (a), 125 mg MPA was replaced with 125 mg CLMPA (chloromethylphosphonic acid, purity 99.9%), and in step (b), the drying temperature was 130 °C and the drying time was 16 h. The resulting catalyst was calculated as CLMPA / 5% Pt / Al2O3.

[0070] In step (a) of Example 4, 125 mg MPA was replaced with 125 mg CDNA (chlorodrodinic acid, purity 99.97%), and in step (b), the drying temperature was 120 °C and the drying time was 18 h. The resulting catalyst was calculated as CDNA / 5% Pt / Al2O3.

[0071] The X-ray diffraction patterns of the catalysts prepared in Examples 1-4 are as follows: Figure 1 As shown in b, c, d, and e, the structures of MPA / 5% Pt / Al2O3, ODPA / 5% Pt / Al2O3, CLMPA / 5% Pt / Al2O3, and CDNA / 5% Pt / Al2O3 are compared with those of the unmodified 5% Pt / Al2O3 catalyst. Figure 1 a) The structures are basically the same.

[0072] Transmission electron microscopy images and particle size distributions of the catalysts prepared in Examples 1-4 are shown below. Figure 3 As shown in b, c, d, and e, the Pt particles are uniformly dispersed, with average particle sizes of 2.7 nm, 2.8 nm, 2.6 nm, and 2.6 nm, respectively. This is different from the unmodified 5% Pt / Al₂O₃ catalyst (…). Figure 3a) The morphology and average particle size are basically the same.

[0073] The thermogravimetric curves of the catalysts prepared in Examples 2-4 are as follows: Figure 5 As shown in b, c, and d, compared to the unmodified 5% Pt / Al2O3 catalyst ( Figure 5 a) Weight loss occurs at around 350℃, which is caused by the decomposition of organophosphonic acids.

[0074] The infrared spectra of the catalysts prepared in Examples 1-4 are as follows: Figure 6 As shown in b, c, d, and e, compared to the unmodified 5% Pt / Al2O3 catalyst ( Figure 6 a) MPA / 5% Pt / Al2O3 and ODPA / 5% Pt / Al2O3 at 2920 cm⁻¹ -1 Characteristic peaks of CH stretching vibrations appear on both sides, with CLMPA / 5% Pt / Al2O3 and CDNA / 5% Pt / Al2O3 showing peaks at 2870-2920 cm⁻¹. -1 The presence of CH stretching vibration peaks on both sides proves the effective modification by organophosphonic acid.

[0075] CO-DRIFTs plots of the catalysts prepared in Examples 1-4 are shown below. Figure 8 As shown in b, c, d, and e, compared to the unmodified 5% Pt / Al2O3 catalyst ( Figure 8 a) The adsorption characteristic peak intensities of Pt and CO in various bonding modes were all weakened, proving that the modification of the catalyst support surface by organophosphonic acid effectively inhibited the adsorption of CO and the catalyst.

[0076] The amount of phosphonic acid modification in the modified catalysts prepared in Examples 1-4 was determined by inductively coupled plasma mass spectrometry, and the specific surface area of ​​the catalysts was determined by nitrogen physical adsorption-desorption. The phosphonic acid modification in the catalysts prepared in Examples 1-4 was calculated to be a monolayer.

[0077] Example 5: Preparation of 5% Pd / MPA-Al2O3 catalyst

[0078] The preparation of the 5% Pd / MPA-Al2O3 catalyst in this embodiment includes the following steps:

[0079] (a) Replace the 5% Pt / Al2O3 catalyst in step (a) of Example 1 with the same mass of Al2O3 support, and perform the remaining steps exactly the same to obtain methylphosphonic acid modified MPA-Al2O3 support.

[0080] (b) Pore volume measurement: Take 250 mg MPA-Al2O3 and slowly add a certain amount of water; after each addition of water, use a vortex mixer to mix; repeat the above steps until a state between solid and liquid is reached, and record the volume of water added as approximately A mL, and obtain the pore volume unit as mL / mg.

[0081] (c) Preparation of 5% Pd / MPA-Al2O3 by reverse impregnation method: A mL of PdCl2 solution (Pd: 11.4 mg / mL) was transferred to a 10 mL beaker, and then 250 mg of MPA-Al2O3 support was added. After vortex mixing, the material was in a flowing slurry state between liquid and solid. After mixing, it was left at room temperature for 1.5 h, and then dried in an oven at 120 °C for 12 h. The dried catalyst was ground into an extremely fine powder, and then the powder was reduced at 250 °C in a 50% H2 / Ar atmosphere for 2 h to obtain a 5% Pd / MPA-Al2O3 catalyst.

[0082] Examples 6-8: Preparation of 5% Pd / ODPA-Al2O3, 5% Pd / CLMPA-Al2O3, and 5% Pd / cDNA-Al2O3 catalysts

[0083] The preparation steps of Examples 6-8 are basically the same as those of Example 5, except that:

[0084] In step (a) of Example 6, the 125 mg MPA is replaced with 250 mg ODPA;

[0085] In step (a) of Example 7, the 125 mg MPA is replaced with 125 mg CLMPA;

[0086] In Example 8, the 125 mg MPA in step (a) was replaced with 125 mg cDNA.

[0087] The X-ray diffraction patterns of the catalysts prepared in Examples 5-8 are as follows: Figure 2 As shown in b, c, d, and e, the structures of 5% Pd / MPA-Al2O3, 5% Pd / ODPA-Al2O3, 5% Pd / CLMPA-Al2O3, and 5% Pd / cDNA-Al2O3 are compared with those of the unmodified 5% Pd / Al2O3 catalyst. Figure 2 The structures of a) are basically the same.

[0088] The infrared spectra of the catalysts prepared in Examples 5-8 are as follows: Figure 7 As shown in b, c, d, and e, compared to the unmodified 5% Pd / Al2O3 catalyst ( Figure 7 a) 5% Pd / MPA-Al2O3 at 3000 cm⁻¹ -1Characteristic peaks of CH stretching vibrations appear on both sides; for 5% Pd / ODPA-Al2O3, 5% Pd / CLMPA-Al2O3, and 5% Pd / cDNA-Al2O3, the peaks are at 2870 and 2920 cm⁻¹. -1 The presence of characteristic peaks for CH stretching vibrations on both sides confirms the effective modification by organophosphonic acid.

[0089] Examples 9-11: Preparation of organophosphonic acid modified 5% Pt / CNT catalysts

[0090] The preparation steps of Examples 9-11 are basically the same as those of Examples 2-4, except that:

[0091] In step (a) of Examples 9-11, the 5% Pt / Al2O3 catalyst was replaced with the 5% Pt / CNTs catalyst to prepare ODPA / 5% Pt / CNTs, CLMPA / 5% Pt / CNTs, and CDNA / 5% Pt / CNTs catalysts, respectively.

[0092] Transmission electron microscopy and particle size distribution diagrams of the catalysts prepared in Examples 9-11 are shown below. Figure 4 As shown in b, c, and d, the average particle sizes are 1.39 nm, 1.35 nm, and 1.42 nm, respectively, compared to the unmodified 5% Pt / CNT catalyst. Figure 4 a) The morphology and average particle size of the catalysts are basically the same.

[0093] Examples 12-15: Preparation of organophosphonic acid modified 5% Pt / SiO2 catalysts

[0094] The preparation steps of Examples 12-15 are basically the same as those of Example 1, except that:

[0095] In step (a) of Examples 12-15, the 5% Pt / Al2O3 catalyst of Example 1 was replaced with a 5% Pt / SiO2 catalyst; and

[0096] In step (a) of Example 13, 125 mg MPA is replaced with 250 mg ODPA;

[0097] In step (a) of Example 14, 125 mg MPA is replaced with 125 mg CLMPA;

[0098] In step (a) of Example 15, 125 mg MPA was replaced with 125 mg cDNA.

[0099] Examples 16-19: Preparation of organophosphonic acid modified 5% Pt / TiO2 catalysts

[0100] The preparation steps of Examples 16-19 are basically the same as those of Example 1, except that:

[0101] In step (a) of Examples 16-19, the 5% Pt / Al2O3 catalyst of Example 1 was replaced with a 5% Pt / TiO2 catalyst; and

[0102] In step (a) of Example 17, 125 mg MPA is replaced with 250 mg ODPA;

[0103] In step (a) of Example 18, 125 mg MPA is replaced with 125 mg CLMPA;

[0104] In step (a) of Example 19, 125 mg MPA was replaced with 125 mg cDNA.

[0105] Comparative Example 1: Preparation of Pt / Al2O3 catalyst

[0106] (a) Take 250 mg of Al2O3 and slowly add a certain amount of water; after each addition of water, use a vortex mixer to mix; repeat the above steps until a state between solid and liquid is reached, and record the volume of water added as approximately A mL, and obtain the pore volume unit as mL / mg.

[0107] (b) Transfer A mL of H₂PtCl₆ solution (prepared from 99.99% pure chloroplatinic acid hexahydrate) into a 10 mL beaker, then add 250 mg of Al₂O₃ support. After vortex mixing, the material becomes a flowing slurry between liquid and solid states. After mixing, let it stand at room temperature for 1.5 h, then dry it in an oven at 120 °C for 12 h. Grind the dried catalyst into an extremely fine powder, then reduce the powder at 250 °C in a 50% H₂ / Ar atmosphere for 2 h to obtain a 5% Pt / Al₂O₃ catalyst.

[0108] Comparative Example 2: Preparation of Pd / Al2O3 catalyst

[0109] The preparation steps of this comparative example are basically the same as those of comparative example 1, except that palladium chloride (purity 99.99%) is used instead of chloroplatinic acid to obtain a 5% Pd / Al2O3 catalyst.

[0110] Comparative Example 3: Preparation of Pt / CNTs Catalyst

[0111] The preparation steps of this comparative example are basically the same as those of comparative example 1, except that: ultra-high purity hydroxylated single-walled carbon nanotubes (short, diameter 1-2 nm, length 1-3 μm, purity 95%) are used instead of Al2O3 to obtain a 5% Pt / CNTs catalyst.

[0112] Comparative Example 4: Preparation of Pt / SiO2 catalyst

[0113] The preparation steps of this comparative example are basically the same as those of comparative example 1, except that SiO2 (purity 99.9%) is used instead of Al2O3 to obtain a 5% Pt / SiO2 catalyst.

[0114] Comparative Example 5: Preparation of Pt / TiO2 catalyst

[0115] The preparation steps of this comparative example are basically the same as those of comparative example 1, except that TiO2 (purity 99.5%) is used instead of Al2O3 to obtain a 5% Pt / TiO2 catalyst.

[0116] Example 20: Evaluation of resistance to CO poisoning during the hydrodeoxygenation reaction of benzyl alcohol

[0117] The organophosphonic acid-modified noble metal catalysts prepared in Examples 1-8 and 12-19 were evaluated for the hydrodeoxygenation reaction of benzyl alcohol under crude hydrogen containing different concentrations of CO. The performance evaluation of the hydrodeoxygenation reaction of benzyl alcohol was carried out on the rapid screening and analysis system for atmospheric / high-pressure fixed-bed catalysts at East China University of Science and Technology.

[0118] The hydrodeoxygenation reaction of benzyl alcohol was analyzed online using an Agilent 8860 gas chromatograph equipped with an HP-5 capillary column (30m long, 0.32mm inner diameter, 0.5μm film thickness).

[0119] Evaluation conditions: The total inlet flow rate was 70 mL / min; the feedstock was a bubbler containing benzyl alcohol, bubbled in a water bath at 53.1℃; the gas molar fraction was: 0.03% benzyl alcohol, 20% ultra-high purity hydrogen or 20% crude hydrogen (1500–5000 ppm CO), and the remainder was helium; the reaction temperature was 180℃; the reaction pressure was atmospheric pressure; the catalyst loading was 0.5 mg; and the conversion rate was controlled at approximately 20%.

[0120] Weigh 0.5 mg of catalyst sample, mix it thoroughly with 100 mg of quartz sand, and then fill the constant temperature zone of the quartz reaction tube. After the catalyst is filled, first check the reaction system for leaks by introducing helium gas (10 bar) at a certain pressure into the reaction system. If the pressure remains unchanged, it indicates that the reaction system has good sealing performance and can be used for evaluation experiments.

[0121] The helium flow rate through the bubbler was set to 16 sccm (standard cubic centimeter per minute), and the flow rate of ultra-high purity hydrogen or crude hydrogen was set to 14 sccm. Helium was bubbled through benzyl alcohol in the bubbler and then mixed with hydrogen before reaching the catalyst bed. Each reaction ran for approximately 240 minutes, with the first stage (120 minutes) running under ultra-high purity hydrogen and the second stage (120 minutes) switching to simulated crude hydrogen (1500–5000 ppm CO).

[0122] First, set the flow rates of each reaction component. After the gas ratio and reaction temperature stabilize under bypass conditions, switch the valve to the reaction tube, allowing the mixed gas to enter the mixing tank and then pass into the quartz reaction tube to start the reaction. The gas exiting the reaction tube is then detected by online chromatography.

[0123] The resistance of the catalysts of the present invention to CO poisoning in the hydrogenation deoxygenation reaction of benzyl alcohol was evaluated by testing the benzyl alcohol conversion C and toluene selectivity S of the organophosphonic acid modified noble metal catalysts prepared in Examples 1-8 and 12-19, wherein:

[0124]

[0125]

[0126] Table 1. Evaluation results of organophosphonic acid-modified noble metal catalysts in the hydrodeoxygenation reaction of benzyl alcohol.

[0127]

[0128] As can be seen from the data in Table 1, this example selected the hydrodeoxygenation reaction of benzyl alcohol to investigate the CO resistance of four groups of catalysts: unmodified and organophosphonic acid modified 5% Pt / Al2O3 (Comparative Example 1, Examples 1-4), 5% Pd / Al2O3 (Comparative Example 2, Examples 5-8), 5% Pt / SiO2 (Comparative Example 4, Examples 12-15), and 5% Pt / TiO2 (Comparative Example 5, Examples 16-19).

[0129] The selectivity for toluene in the hydrodeoxygenation of 5% Pt / Al2O3 modified with organophosphonic acid was significantly improved compared with that of unmodified 5% Pt / Al2O3. Furthermore, the conversion rate of cDNA-modified 5% Pt / Al2O3 in the hydrodeoxygenation of benzyl alcohol was also significantly improved compared with the unmodified catalyst. The slightly lower conversion rate of ODPA-modified 5% Pt / Al2O3 may be due to the interaction between reactant molecules and near-surface C... 18 This is due to the interaction between the tails of long-chain alkyl groups.

[0130] The 5% Pt / Al2O3 in Comparative Example 1 was almost completely deactivated under simulated conditions containing 1500 ppm CO and crude hydrogen. In contrast, the MPA / 5% Pt / Al2O3 catalyst in Example 1 still retained nearly one-third of its activity under the same conditions, with the 5% Pt / Al2O3 modified with strong electron-withdrawing groups CLMPA (Example 3), CDNA (Example 4), and ODPA (Example 2) with long-chain alkyl tails retaining a higher conversion rate, still exceeding 50%.

[0131] The selectivity for toluene also decreased significantly after switching from ultrapure hydrogen to crude hydrogen. This is because, for the hydrodeoxygenation of aromatic alcohols / aldehydes on noble metals, the bridging and multiple bonding modes of Pt with CO sites lead to more CC cleavage than CO cleavage. Organophosphonic acid modification weakens the CO binding strength of bridging and multiple bonding modes more than the linear bonding strength, making the 5% Pt / Al₂O₃ in Comparative Example 1 less accessible to reactant molecules in the presence of CO, thus leading to catalyst poisoning.

[0132] The data in the table show that the CO poisoning resistance of the 5% Pt / Al2O3 catalyst modified with organophosphonic acid was significantly improved under crude hydrogen containing a high concentration of CO (e.g., 5000 ppm).

[0133] Furthermore, we expanded the types of organophosphonic acid-modified catalysts to 5% Pd / Al2O3 and other supports, such as 5% Pt / SiO2, 5% Pt / TiO2, etc., and also obtained a similar trend of resistance to CO poisoning as in Examples 1-4.

[0134] Example 21: Evaluation of CO poisoning resistance in the selective hydrogenation of acetylene to ethylene

[0135] The organophosphonic acid-modified noble metal catalysts prepared in Examples 1-4 and 9-11 were evaluated for selective hydrogenation of acetylene to ethylene under crude hydrogen containing different concentrations of CO. The performance evaluation of the selective hydrogenation of acetylene to ethylene was conducted on the atmospheric / high-pressure fixed-bed catalyst rapid screening and analysis system at East China University of Science and Technology.

[0136] Online analysis of the products of the selective hydrogenation of acetylene to ethylene was performed using an Agilent 8860 gas chromatograph equipped with a GS-alumina packed column (30m long, 0.32mm inner diameter, 0.5μm film thickness).

[0137] Evaluation conditions: Total inlet flow rate was 80 mL / min; gas molar fraction was 1.5–2% acetylene, 20% ultra-high purity hydrogen or 20% crude hydrogen (1500–5000 ppm CO), and the remainder was helium; reaction temperature was 100℃; reaction pressure was atmospheric pressure; catalyst loading was 0.5 mg; conversion rate was controlled at approximately 20%.

[0138] Weigh 0.5 mg of catalyst sample, mix it thoroughly with 100 mg of quartz sand, and then fill the constant temperature zone of the quartz reaction tube. After the catalyst is filled, first check the reaction system for leaks by introducing helium gas (10 bar) at a certain pressure into the reaction system. If the pressure remains unchanged, it indicates that the reaction system has good sealing performance and can be used for evaluation experiments.

[0139] First, the flow rates of each reaction component were set. After the gas ratio and reaction temperature stabilized under bypass conditions, the valve was switched to the reaction tube, allowing the mixed gas to enter the mixing tank and then the quartz reaction tube to begin the reaction. The gas exiting the reaction tube was then detected by online chromatography. Each reaction was first run under ultra-high purity hydrogen until stable, and the activity data were recorded. Then, it was switched to simulated crude hydrogen (1500–5000 ppm CO) until stable, and the activity data were recorded.

[0140] The resistance of the catalysts of the present invention to CO poisoning in the selective hydrogenation of acetylene to ethylene was evaluated by testing the acetylene conversion C and ethylene selectivity S of the organophosphonic acid-modified noble metal catalysts prepared in Examples 1-4 and 9-11, wherein:

[0141]

[0142]

[0143] Table 2. Evaluation results of the selective hydrogenation reaction of acetylene using organophosphonic acid-modified noble metal catalysts.

[0144]

[0145]

[0146] As can be seen from the data in Table 2, under ultra-high purity hydrogen conditions, the conversion rates of 5% Pt / Al2O3 prepared in Comparative Example 1 and the organophosphonic acid-modified 5% Pt / Al2O3 prepared in Examples 1-4 are similar. The conversion rate of ODPA / 5% Pt / Al2O3 prepared in Example 2 is slightly lower, which is similar to the results in Example 20. This may be due to the interaction between the reactant molecules and the near-surface C 18 This is due to the interaction between the tails of long-chain alkyl groups.

[0147] When using simulated crude hydrogen, the conversion rate of the 5% Pt / Al2O3 prepared in Comparative Example 1 rapidly decreased to 0 with increasing CO concentration (from 1500 ppm to 5000 ppm), while the activity retention rate of the organophosphonic acid-modified 5% Pt / Al2O3 catalysts prepared in Examples 1-4 was all above 1 / 3. This demonstrates that the organophosphonic acid-modified 5% Pt / Al2O3 catalyst has better resistance to CO poisoning.

[0148] Meanwhile, under crude hydrogen, the ethylene selectivity of the acetylene hydrogenation reaction is enhanced. This is because the blocking of the CO-reacting sites on Pt by organophosphonic acids interferes with the adsorption of metals by H2 / C2H4.

[0149] Furthermore, we expanded the types of organophosphonic acid-modified catalysts to other supports, such as 5% Pt / CNTs, and also obtained a similar trend of resistance to CO poisoning as in Examples 1-4.

[0150] This application provides a detailed description, the purpose of which is to enable those skilled in the art to understand and implement the content of this application, but it should not be used to limit the scope of protection of this application. All equivalent changes or modifications made in accordance with the spirit and essence of this application should be included within the scope of protection of this application.

Claims

1. The application of an organophosphonic acid-modified noble metal catalyst, characterized in that, The catalyst is used to combat CO poisoning in hydrogenation reactions, including the hydrogenation deoxygenation of benzyl alcohol and the selective hydrogenation of acetylene to ethylene. The preparation method of the organophosphonic acid-modified noble metal catalyst includes the following steps: (1) Prepare an organophosphonic acid solution by adding a noble metal catalyst or catalyst support under stirring conditions and stirring at room temperature; (2) Centrifuge the mixture obtained in step (1) and dry the solid after centrifugation in air; (3) The solid dried in step (2) is washed multiple times with solvent and centrifuged, then dried to obtain an organophosphonic acid-modified noble metal catalyst or an organophosphonic acid-modified catalyst support; when the organophosphonic acid-modified catalyst support is obtained in step (3), the preparation method further includes step (4): (4) The noble metal is loaded onto the catalyst support modified with organophosphonic acid obtained in step (3) to obtain the noble metal catalyst modified with organophosphonic acid. In step (1), the organophosphonic acid is chlorophosphonic acid, and the mass ratio of the added noble metal catalyst or catalyst support to the mass of the organophosphonic acid is (1-3):1; the noble metal is one or both of Pt and Pd; the support of the noble metal catalyst or the catalyst support is one or more of Al2O3 or CNTs. The reaction conditions for the hydrogenation and deoxygenation of benzyl alcohol are: reaction temperature 160-200℃, atmospheric pressure, total gas flow rate 50-90 mL / min, and CO concentration 1500-5000 ppm. The reaction conditions for the selective hydrogenation of acetylene to ethylene are: reaction temperature 90-110℃, atmospheric pressure, total gas flow rate 60-80 mL / min, and CO concentration 1500-5000 ppm.

2. The application of the organophosphonic acid-modified noble metal catalyst according to claim 1, characterized in that, When the noble metal includes Pd, the above preparation method adopts a scheme based on first modifying the organic phosphonic acid on the catalyst support and then loading the noble metal, that is, the catalyst support is added in step (1).

3. The application of the organophosphonic acid-modified noble metal catalyst according to claim 1, characterized in that, In step (1), the solvent for preparing the organophosphonic acid solution is selected from one or more of methanol, ethanol, isopropanol, and tetrahydrofuran; the concentration of the organophosphonic acid solution is 4-12 mM.

4. The application according to claim 1, characterized in that, In step (2), the centrifugation speed is 8000-10000 r / min and the centrifugation time is 8-10 min; the drying temperature is 110-130℃ and the time is 14-18 h.

5. The application according to claim 1, characterized in that, In step (3), the solvent used for washing is selected from one or more of methanol, ethanol, isopropanol, and tetrahydrofuran; the number of washings is 3 to 8; the volume of solvent used for each washing is 40 to 50 mL; the centrifugation speed is 8000 to 10000 r / min and the centrifugation time is 8 to 10 min; after multiple washings and separations, the product is dried at room temperature for 10 to 12 h.

6. The application according to claim 1, characterized in that, In step (1), the solvent for the organophosphonic acid solution is selected from tetrahydrofuran, and the concentration of the organophosphonic acid solution is controlled at 10 mM; in step (2), the centrifugation speed is 10000 r / min, the centrifugation time is 10 min, the drying temperature is 120℃, and the drying time is 16 h; in step (3), the solvent is selected from tetrahydrofuran, including 5 washes, each centrifugation uses 50 mL of tetrahydrofuran solvent, the centrifugation speed is 10000 r / min, the centrifugation time is 10 min, and the drying time is 12 h.

7. An organophosphonic acid-modified noble metal catalyst, characterized in that, The catalyst prepared using any of the applications described in claims 1-6 has an organophosphonic acid monolayer formed on the support surface of the noble metal catalyst.

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