Application of supported palladium catalyst in hydrogen production from formic acid

Abstract

The invention provides an application of a supported palladium catalyst in hydrogen production from formic acid, and belongs to the field of catalyst application. The preparation method of the supported palladium catalyst in the application comprises the following steps: mixing amino modified POSS, water and normal hexane, adding potassium chloropalladite for mixing, separating normal hexane, and adding sodium borohydride and sodium hydroxide to obtain the supported palladium catalyst. The preparation method of the amino modified POSS comprises the following steps: mixing gamma-aminopropyltriethoxysilane, tetrahydrofuran and water, refluxing, adding hydrochloric acid for reaction, adding tetrahydrofuran, separating, precipitating and washing. Compared with the prior art, the invention provides the application of the supported palladium catalyst in hydrogen production from formic acid, efficient hydrogen production from formic acid can be realized by using the catalyst with high-dispersion active components, and the adopted catalyst is short in preparation process and easy to separate.

Description

Technical Field

[0001] The present invention relates to the field of catalyst applications, and specifically relates to the application of a supported palladium catalyst in hydrogen production from formic acid. Background Art

[0002] Hydrogen has high electrochemical activity and is a fuel with no pollution in combustion products.

[0003] Formic acid is a liquid at room temperature and atmospheric pressure, with a hydrogen content of 4.34%. It can decompose to release a large amount of hydrogen. Compared with gaseous hydrogen, it is easier to store and transport. However, in the absence of a catalyst, formic acid is difficult to directly convert into hydrogen and carbon dioxide.

[0004] Based on the above characteristics, developing a catalyst for the formic acid decomposition reaction to produce hydrogen is one of the important means to achieve hydrogen production from formic acid.

[0005] In the prior art, adjusting the combination method and raw materials of the catalyst support and the noble metal catalyst is an effective way to construct a high-performance catalyst.

[0006] For example, patent application CN118179559A provides a palladium-based catalyst, its preparation method and application in hydrogen production from formic acid. The palladium-based catalyst provided is a molybdenum nitride-cobalt nitride supported palladium-based catalyst. The preparation process of the palladium-based catalyst includes: fully mixing water, molybdate, cobalt salt and nitrogen-containing compound, and performing a hydrothermal reaction to obtain a complex of cobalt molybdate and nitrogen-containing compound; pyrolyzing the complex of cobalt molybdate and nitrogen-containing compound to obtain a cobalt nitride-molybdenum nitride complex; loading a palladium precursor on the cobalt nitride-molybdenum nitride complex and reducing it to finally obtain the palladium-based catalyst provided in this application.

[0007] POSS is polyhedral oligomeric silsesquioxane, a class of compounds with nanomolecular size and organic-inorganic hybrid structure. It has a special structure with an inorganic Si-O-Si bond-based framework as the core and surrounded by organic substituents on the periphery, and has unique physical properties and chemical reactivity. It can be used as an additive, a polymer material and a ceramic precursor, and has the potential to be used as an efficient catalyst support.

[0008] For example, patent application CN117624616A provides a cage-type polyhedral oligomeric silsesquioxane (POSS) supported multinuclear boron catalyst, its preparation method and application. The POSS supported multinuclear boron catalyst provided has the advantages of high activity, simple preparation method, low cost, water and oxygen resistance, recyclability, etc. This type of catalyst can regulate the types of polymerization substrates and polymers by controlling reaction conditions, initiators, types of chain transfer agents, substrates, etc. Due to the synergistic effect and aggregation concentration amplification effect of multi-boron centers, polyethers, polyesters, polycarbonates and other polymers can be efficiently prepared, greatly expanding the types of macromolecular boron Lewis acid catalysts and polymers.

[0009] Therefore, how to provide an application of a catalyst prepared with a POSS structure as a catalyst support in hydrogen production from formic acid to achieve a higher hydrogen production efficiency from formic acid is one of the important issues studied by those skilled in the art. Summary of the Invention

[0010] To solve the problem that the hydrogen production performance of the catalyst in the prior art is difficult to meet the requirements, the present invention provides an application of a supported palladium catalyst in hydrogen production from formic acid, which can achieve a higher hydrogen production efficiency from formic acid.

[0011] To achieve the above technical effects, the technical solution of the present invention is as follows:

[0012] An application of a supported palladium catalyst in hydrogen production from formic acid, characterized in that:

[0013] The preparation method of the supported palladium catalyst includes the following steps:

[0014] (2) Mix amino-modified POSS, water and n-hexane to obtain a premixed solution;

[0015] (2) Add potassium chloropalladate to the premixed solution obtained in step (1) and mix, then separate n-hexane to obtain an intermediate solution;

[0016] (3) Add sodium borohydride and sodium hydroxide to the intermediate solution obtained in step (2) to obtain the supported palladium catalyst;

[0017] The preparation method of the amino-modified POSS in step (1) includes the following steps:

[0018] (a) Mix γ-aminopropyltriethoxysilane, tetrahydrofuran and water, and reflux to obtain an intermediate product;

[0019] (d) Add hydrochloric acid to the intermediate product obtained in step (a) for reaction to obtain a product to be treated;

[0020] (c) Add tetrahydrofuran to the product to be treated obtained in step (b), separate the precipitate, and wash to obtain amino-modified POSS.

[0021] Preferably, the dosage ratio of water, n-hexane and amino-modified POSS in step (1) is 0.8 - 1.2 mL: 5 - 15 mL: 50 mg.

[0022] Most preferably, the dosage ratio of water, n-hexane and amino-modified POSS in step (1) is 1 mL: 10 mL: 50 mg.

[0023] Preferably, the dosage ratio of potassium chloropalladate in step (2) to the amino-modified POSS in step (1) is 0.03 - 0.05 mmol:50 mg.

[0024] Most preferably, the dosage ratio of potassium chloropalladate in step (2) to the amino-modified POSS in step (1) is 0.03 mmol:50 mg.

[0025] Preferably, the mass dosage ratio of sodium borohydride to sodium hydroxide in step (3) is 7 - 8:40.

[0026] Most preferably, the mass dosage ratio of sodium borohydride to sodium hydroxide in step (3) is 37:200.

[0027] It should be noted that the functions of sodium borohydride and sodium hydroxide in the present invention are for alkaline reduction, so their total dosage is not specifically limited, aiming at the standard reduction of potassium chloropalladate by those skilled in the art.

[0028] Preferably, the molar ratio of γ-aminopropyltriethoxysilane, tetrahydrofuran and water in step (a) is 1:2.7 - 3.0:0.6 - 0.8.

[0029] Most preferably, the mass ratio of γ-aminopropyltriethoxysilane, tetrahydrofuran and water in step (a) is 1:2.9:0.7.

[0030] Preferably, the reflux temperature in step (a) is 57 - 62 °C.

[0031] Further preferably, the reflux temperature in step (a) is 60 °C.

[0032] Preferably, the mass ratio of hydrochloric acid in step (b) to γ-aminopropyltriethoxysilane in step (a) is 0.004 - 0.005:1.

[0033] Further preferably, the mass concentration of HCl in the hydrochloric acid is 32 - 38%.

[0034] Most preferably, the mass concentration of HCl in the hydrochloric acid is 36.5%.

[0035] Preferably, the reaction temperature in step (b) is 57 - 62 °C and the time is 60 - 80 h.

[0036] Preferably, the volume dosage of tetrahydrofuran in step (c) is the same as the volume of the product to be treated.

[0037] Preferably, the detergent used for washing in step (c) is tetrahydrofuran.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] (1) Adopting the technical solution of the present invention, based on the polarity of the amino group, the amino-modified POSS has strong hydrophilicity. The double-solvent method can transfer potassium tetrachloropalladate in the aqueous solution into the internal structure of POSS, restricting the growth sites of the catalyst.

[0040] (2) Adopting the technical solution of the present invention, based on the relatively small spatial size of the POSS structure, the growth of the catalyst inside the POSS will be restricted. Finally, the obtained catalyst has a large specific surface area and good catalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is the transmission electron micrograph of the supported palladium catalyst prepared in Example 1 of the present invention;

[0042] Figure 2 is the transmission electron micrograph of the supported palladium catalyst prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0043] To make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes the technical solutions of the present invention with reference to examples.

[0044] Except for the reagents and raw materials mentioned in the examples, others are all conventional commercially available products, which are not specifically defined herein.

[0045] Example 1 Preparation method of a supported palladium catalyst

[0046] The preparation method includes the following steps:

[0047] (1) 20.314 g of γ-aminopropyltriethoxysilane was added to a three-necked flask and stirred. After mixing 59.480 g of tetrahydrofuran and 14.207 g of distilled water, it was slowly added into the flask, and the temperature was raised to 60 °C for reflux to obtain an intermediate product;

[0048] (2) Then, 0.075 mL of hydrochloric acid with a mass fraction of 36.5% was added dropwise, and the reaction was carried out at a constant temperature for 72 h to obtain a product to be treated;

[0049] (3) The product to be treated was poured into an equal volume of tetrahydrofuran, the solution became turbid and a precipitate was formed. The precipitate was washed by vacuum filtration with tetrahydrofuran, and then vacuum dried at 60 °C to obtain amino-modified POSS;

[0050] (4) 50 mg of amino-modified POSS was dispersed in 10 mL of water, and stirred with 100 mL of n-hexane at room temperature for 30 min to obtain a premixed solution;

[0051] (5) During the process of stirring the premixed solution, slowly drop 10 mL of a solution containing 0.03 mmol of potassium tetrachloropalladate(II), and stir for 2 hours at room temperature. Let it stand for stratification, and draw the lower-layer solution to obtain an intermediate solution;

[0052] (6) Add 37 mg of sodium borohydride and 0.2 g of sodium hydroxide to the drawn solution, and stir for 10 min; centrifuge at a speed of 6000 r / min for 5 min to obtain a supported palladium catalyst with amino-caged silsesquioxane as the carrier.

[0053] Example 2 A preparation method of a supported palladium catalyst

[0054] The preparation method includes the following steps:

[0055] (1) Add 20.314 g of γ-aminopropyltriethoxysilane to a three-necked flask and stir. After mixing 59.940 g of tetrahydrofuran and 12.190 g of distilled water, slowly add them into the flask, and heat up to 62 °C for reflux to obtain an intermediate product;

[0056] (2) Then drop 0.067 mL of hydrochloric acid with a mass fraction of 36.5%, and carry out a constant-temperature reaction for 80 h to obtain a product to be treated;

[0057] (3) Pour the product to be treated into an equal volume of tetrahydrofuran, the solution becomes turbid and precipitates. Vacuum filter and wash the precipitate with tetrahydrofuran, and then vacuum dry at 60 °C to obtain amino-modified POSS;

[0058] (4) Take 50 mg of amino-modified POSS and disperse it in 8 mL of water, and stir with 150 mL of n-hexane at room temperature for 30 min to obtain a premixed solution;

[0059] (5) During the process of stirring the premixed solution, slowly drop 10 mL of a solution containing 0.05 mmol of potassium tetrachloropalladate(II), and stir for 2 hours at room temperature. Let it stand for stratification, and draw the lower-layer solution to obtain an intermediate solution;

[0060] (6) Add 37 mg of sodium borohydride and 0.2 g of sodium hydroxide to the drawn solution, and stir for 10 min; centrifuge at a speed of 6000 r / min for 5 min to obtain a supported palladium catalyst with amino-caged silsesquioxane as the carrier.

[0061] Example 3 A preparation method of a supported palladium catalyst

[0062] The preparation method includes the following steps:

[0063] (1) 20.314 g of γ-aminopropyltriethoxysilane was added to a three-necked flask and stirred. 54.852 g of tetrahydrofuran and 16.250 g of distilled water were mixed and slowly added to the flask. The temperature was raised to 57° C. and refluxed to obtain an intermediate product.

[0064] (2) adding 0.085 mL of 36.5% hydrochloric acid dropwise and reacting at a constant temperature for 60 h to obtain the product to be treated;

[0065] (3) The product to be treated is poured into an equal volume of tetrahydrofuran, the solution becomes turbid and a precipitate is precipitated, the precipitate is washed by vacuum filtration with tetrahydrofuran, and then vacuum dried at 60° C. to obtain amino-modified POSS;

[0066] (4) 50 mg of amino-modified POSS was dispersed in 12 mL of water and stirred with 50 mL of n-hexane at room temperature for 30 min to obtain a premixed solution;

[0067] (5) While stirring the premixed solution, slowly drop 10 mL of a solution containing 0.04 mmol of potassium chloropalladate and stir at room temperature for 2 hours. Allow to stand to separate the layers, and draw the lower layer to obtain an intermediate solution;

[0068] (6) Add 37 mg of sodium borohydride and 0.2 g of sodium hydroxide to the absorbed solution, stir for 10 min, and centrifuge at 6000 r / min for 5 min to obtain a supported palladium catalyst with amino cage silsesquioxane as a carrier.

[0069] Comparative Example 1 Preparation method of a supported palladium catalyst

[0070] The only difference between this comparative example and Example 1 is that γ-aminopropyltriethoxysilane is replaced by an amino cage-shaped silsesquioxane of equal mass.

[0071] The amino cage-shaped silsesquioxane was purchased from Xi'an Qiyue Biotechnology Co., Ltd.; the core is inorganic silsesquioxane, with organic isobutyl groups attached to seven corners of the cage and an aminopropyl group attached to the eighth corner; the molecular weight is 874.58.

[0072] Example 4 Application of a supported palladium catalyst in hydrogen production from formic acid

[0073] The supported palladium catalysts prepared in Examples 1-3 and Comparative Example 1 were dispersed in 3 mL of deionized water for 3 min by ultrasonic method, and the catalyst solution after ultrasonic dispersion was kept at a water temperature of 50° C. in a constant temperature water bath. The reaction started after adding 2 mL of an aqueous solution containing 6 mmol of formic acid. The performance of the catalyst was determined by the water displacement method and the experimental data was recorded.

[0074] Comparative Example 2 Application of a supported palladium catalyst in hydrogen production using ammonia borane

[0075] The difference between this comparative example and Example 4 is only that: the aqueous solution containing 6 mmol of formic acid is replaced by an aqueous solution containing 6 mmol of ammonia borane.

[0076] Catalyst performance characterization of Example 4 and Comparative Example 2 in the experimental examples

[0077] The performance of the catalyst was characterized by the turnover frequency (TOF) of the catalyst for dehydrogenation of the chemical hydrogen storage medium. According to the formula of turnover frequency TOF = P 0 V / (2RTnt), according to the atmospheric pressure P 0 (101325 Pa), the amount of hydrogen gas V (m 3 ) decomposed and generated during the catalytic process, the indoor temperature T (K), the total molar amount n (mol) of Pd in the catalyst, the ideal gas constant R (8.3145 m 3 ·Pa·mol -1 ·K -1 ), and the time interval t (h -1 ) from the addition of formic acid (or ammonia borane) to the catalyst to the cessation of gas generation, the turnover frequency of the catalyst at different temperatures can be calculated.

[0078] Each catalyst was experimented three times, and the average values of V and t were taken to calculate TOF.

[0079] It should be noted that since the ratio of the hydrogen gas volume generated by each unit of formic acid to ammonia borane is 1:3, for the convenience of comparison, the experimental results of Comparative Example 2 will be taken as 1 / 3 of the original results.

[0080] Table 1 TOF values of the catalysts of Examples 1 - 3 and Comparative Example 1 in Example 4

[0081] Example 1 Example 2 Example 3 Comparative Example 1 <![CDATA[TOF(h -1 )]]> 992 1048 1131 472

[0082] Table 2 TOF values of the catalysts of Examples 1 - 3 and Comparative Example 1 in Comparative Example 2

[0083] Example 1 Example 2 Example 3 Comparative Example 1 <![CDATA[TOF(h -1 )]]> 672 772 501 641

[0084] According to Table 1, for the supported palladium catalysts provided in Examples 1 - 3 of the present invention, by using a specific amino POSS as a raw material, the TOF value of the prepared catalyst for the hydrogen production reaction from formic acid can reach 1000 h -1 level, which can greatly increase the rate of hydrogen gas generation from the decomposition of formic acid; while in Comparative Example 1, a different amino-modified POSS was selected, resulting in a decrease in the reaction rate of the catalyst for hydrogen production from formic acid.

[0085] As can be seen from Table 2, the supported palladium catalysts provided in Examples 1-3 of the present invention were studied for the catalytic effect on another chemical hydrogen storage medium, ammonia borane. The results showed that the catalysts provided by the present invention were difficult to be applied to hydrogen production by ammonia borane decomposition, and the TOF value for the hydrogen production reaction from ammonia borane at 50 °C was less than 800 h -1 .

[0086] In summary, the supported palladium catalyst provided by the present invention can be well applied to hydrogen production from formic acid. At the same time, through Figure 1 and Figure 2 comparison, it can be seen that the particle size of the active component Pd particles (dark part) of the catalyst prepared in Example 1 is much smaller than that of the Pd particles of the catalyst prepared in Comparative Example 1, and at the same time, the distribution is more uniform, indicating that the present invention can achieve efficient hydrogen production from formic acid by using a catalyst with highly dispersed active components, and the catalyst preparation process adopted is short and easy to separate.

[0087] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Application of a supported palladium catalyst in hydrogen production from formic acid, characterized in that: The preparation method of the supported palladium catalyst comprises the following steps: (1) mixing amino-modified POSS, water and n-hexane to obtain a premixed solution; (2) adding potassium chloropalladate to the premixed solution obtained in step (1), mixing, and separating n-hexane to obtain an intermediate solution; (3) adding sodium borohydride and sodium hydroxide to the intermediate solution obtained in step (2) to obtain the supported palladium catalyst; the preparation method of the amino-modified POSS in step (1) comprises the following steps: (a) mixing γ-aminopropyltriethoxysilane, tetrahydrofuran and water, and refluxing to obtain an intermediate product; (b) adding hydrochloric acid to the intermediate product obtained in step (a) to react and obtain a product to be treated; (c) adding tetrahydrofuran to the product to be treated obtained in step (b), separating the precipitate, and washing to obtain amino-modified POSS.

2. The use according to claim 1, characterized in that: The usage ratio of water, n-hexane and amino-modified POSS in step (1) is 1 mL: 10 mL: 50 mg.

3. The use according to claim 1, characterized in that: The usage ratio of potassium chloropalladate described in step (2) to amino-modified POSS described in step (1) is 0.03-0.05mmol:50mg.

4. The use according to claim 1, characterized in that: The mass ratio of sodium borohydride to sodium hydroxide in step (3) is 7-8:

40.

5. The use according to claim 1, characterized in that: The molar ratio of γ-aminopropyltriethoxysilane, tetrahydrofuran and water in step (a) is 1:2.7-3.0:0.6-0.

8.

6. The use according to claim 5, characterized in that: The mass ratio of γ-aminopropyltriethoxysilane, tetrahydrofuran and water in step (a) is 1:2.9:0.

7.

7. The use according to claim 1, characterized in that: The reflux temperature in step (a) is 57-62°C.

8. The use according to claim 1, characterized in that: The mass ratio of the hydrochloric acid in step (b) to the γ-aminopropyltriethoxysilane in step (a) is 0.004-0.005:

1.

9. The use according to claim 8, characterized in that: The mass concentration of HCl in the hydrochloric acid is 32-38%.

10. The use according to claim 1, characterized in that: The reaction temperature in step (b) is 57-62° C. and the reaction time is 60-80 h.

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