Modified formic acid hydrogen production catalysts, their modification methods and applications

Abstract

This invention belongs to the field of formic acid hydrogen production, specifically relating to a method for modifying a formic acid hydrogen production catalyst. The method involves modifying the formic acid hydrogen production catalyst in a formate solution to obtain a highly efficient modified formic acid hydrogen production catalyst. This invention also includes the application of the modified catalyst in the catalytic hydrogen production of formic acid. The modification method described in this invention can significantly improve the activity and selectivity of formic acid hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of formic acid hydrogen production technology, specifically relating to formic acid hydrogen production catalysts. Background Technology

[0002] Currently, over 85% of energy consumption comes from finite and non-renewable fossil fuels, with only 10% from renewable resources. Heavy reliance on fossil fuels not only exacerbates the energy crisis but also leads to harmful environmental problems, making the development and utilization of green and environmentally friendly new energy sources an urgent task.

[0003] Hydrogen (H2) boasts advantages such as high energy density, wide availability, and environmental friendliness, making it considered one of the most ideal alternatives to fossil fuels. Benefiting from its high calorific value, sustainability, abundant reserves, and zero pollution, developing hydrogen energy can achieve truly green, clean, and sustainable development. Although hydrogen is the most abundant element on Earth, naturally occurring free hydrogen is relatively scarce. Therefore, specific hydrogen production technologies are needed to produce hydrogen on a large scale from hydrogen-containing feedstocks to meet the ever-increasing demand for hydrogen.

[0004] Currently, the main sources of hydrogen are still traditional industrial alkane reforming and industrial by-product hydrogen production. Although these methods are large-scale, technologically mature, and relatively inexpensive, the purity of H2 is low, purification costs are high, and the low volumetric energy density and high compression costs of H2 make its storage and transportation difficult. While water electrolysis can produce H2 with acceptable purity, its storage and transportation problems still limit its large-scale development. Therefore, chemical hydrogen storage materials with high hydrogen storage density, easy liquid filling, and convenient transportation have attracted widespread attention. Formic acid, as the only energetic molecule that can rapidly decompose at room temperature to provide hydrogen, stands out. Its mild reforming hydrogen production conditions allow the hydrogen production environment to be transferred from the plant to various hydrogen-using systems, enabling online, on-demand hydrogen production. This solves the difficulties associated with hydrogen storage and transportation. Furthermore, high-purity hydrogen can be obtained under the action of highly active and selective catalysts, which can be used to provide H2 as a feedstock for fuel cell anodes in situ.

[0005] Formic acid is the simplest carboxylic acid in nature and an important organic chemical raw material. It is a liquid at room temperature with a pungent odor and is corrosive. Its density at room temperature is 1.22 g·cm³. -3With a theoretical hydrogen storage capacity of approximately 4.4 wt%, it is easier to store and transport safely compared to most hydrogen storage materials, and is therefore considered a promising chemical hydrogen storage material. Formic acid decomposes via two pathways: dehydrogenation (HCOOH—H2+CO2) and dehydration (HCOOH—H2O+CO). The latter is undesirable, as the generated CO can poison the catalyst and should be avoided. The type of catalyst and reaction conditions significantly influence whether formic acid decomposes via dehydrogenation or dehydration. Current research on formic acid decomposition mainly focuses on the synthesis and preparation of high-performance, long-lifetime, and highly selective catalysts. Summary of the Invention

[0006] To address the problem of unsatisfactory hydrogen production efficiency of existing formic acid hydrogen production catalysts, the primary objective of this invention is to provide a modification method for formic acid hydrogen production catalysts, aiming to prepare modified formic acid hydrogen production catalysts with excellent catalytic activity for formic acid hydrogen production (this invention is also referred to as modified catalysts).

[0007] A second objective of this invention is to provide a modified formic acid hydrogen production catalyst prepared by the aforementioned modification method.

[0008] A third objective of this invention is to provide the application of the modified formic acid hydrogen production catalyst in the catalytic production of hydrogen from formic acid.

[0009] A method for modifying a formic acid hydrogen production catalyst involves modifying the formic acid hydrogen production catalyst in a formate solution to obtain a modified formic acid hydrogen production catalyst.

[0010] This invention demonstrates that innovative pretreatment of formic acid hydrogen production catalysts with formate can improve their microscopic physical and chemical properties, resulting in modified catalysts with specific sites. More importantly, the physicochemical properties imparted by this modification method can unexpectedly and significantly improve the catalytic activity of formic acid hydrogen production.

[0011] In this invention, the formic acid hydrogen production catalyst can be any catalyst known in the industry that can be used for the catalytic production of hydrogen from formic acid. For example, the formic acid hydrogen production catalyst is a supported catalyst containing Pd nanoparticles;

[0012] In this invention, the Pd-containing nano-active particles include at least one of Pd nanoparticles and Pd-M alloy nanoparticles. M can be, for example, at least one of Au, Ag, Pt, Ir, Ru, Rh, Cu, Bi, Ni, Fe, and Co.

[0013] In this invention, there are no special requirements for the type of support. For example, it can be at least one of TiO2, P25, carbon materials, graphene, SiO2, SBA-15, carbon nitrides, MOF, and molecular sieves.

[0014] In this invention, the content of Pd nanoparticles in the formic acid hydrogen production catalyst is not particularly required, as long as it meets the catalytic amount requirement. For example, it can be above 0.1 wt.%, and considering the processing cost, it can be further 0.2 to 1 wt.%.

[0015] In this invention, the formic acid hydrogen production catalyst can be prepared based on known processes such as photodeposition, NaBH4 reduction, and hydrogen reduction.

[0016] In this invention, the pre-modification of formate is key to constructing the microscopic physicochemical characteristics of formic acid catalytic adaptation. Based on this, further control of the treatment time can further construct the physicochemical structure of formic acid catalytic adaptation, which helps to further improve the catalytic activity of the modified catalyst.

[0017] Preferably, the formate in the formate solution is at least one of sodium formate, potassium formate, and ammonium formate.

[0018] In this invention, the concentration of the solute in the formate solution is 0.1–12 M, more preferably 2–8 M, and even more preferably 3–6 M;

[0019] Preferably, during the modification stage, the weight ratio of formate to formic acid hydrogen production catalyst in the formate solution is 16:1 or higher, more preferably 40–150:1, even more preferably 40–100:1, and even more preferably 45–55:1. Studies have shown that, at the preferred ratio, even better synergistic modification performance can be unexpectedly obtained.

[0020] Preferably, the modification treatment stage lasts for more than 5 minutes, more preferably more than 1 hour, and considering yield and efficiency, it can be further preferred to last for more than 2 hours, even more preferably 2 to 5 hours, and even more preferably 2.5 to 3.5 hours.

[0021] In this invention, there are no special requirements for the temperature of the modification process. For example, it can be above 10°C, preferably 20-60°C. Considering the simplicity of the process, it can be further set to room temperature (e.g., 20-45°C).

[0022] The present invention also provides a modified formic acid hydrogen production catalyst prepared by the aforementioned modification method.

[0023] The present invention has found that the modification method described above can endow the catalyst with special microscopic physicochemical characteristics, and the new modified catalyst with the microscopic physicochemical characteristics obtained by the modification method can unexpectedly exhibit excellent formic acid catalytic activity.

[0024] The present invention also provides a method for hydrogen production from formic acid, using a modified formic acid hydrogen production catalyst obtained by the modification method described in the present invention to catalyze the hydrogen production reaction of formic acid at room temperature.

[0025] In this invention, for the sake of process simplicity, formic acid can be directly added to the modified system containing the modified formic acid hydrogen production catalyst in the modification method to carry out formic acid hydrogen production.

[0026] In this invention, there are no particular requirements for the conditions of hydrogen production from formic acid. For example, the molar ratio of formic acid to formate used in the modification stage is less than or equal to 1, preferably 1:2 to 10, further preferably 1:2 to 6, and even more preferably 1:2.5 to 4. Studies have shown that, at the preferred ratio, superior synergistic modification performance can be unexpectedly obtained.

[0027] In this invention, the temperature of the hydrogen production reaction stage is 20–60°C;

[0028] In this invention, the hydrogen production reaction takes 1 to 15 minutes.

[0029] The beneficial effects of this invention are:

[0030] This invention innovatively uses formate to modify the formic acid hydrogen production catalyst, which improves its microscopic physical and chemical characteristics, resulting in a modified catalyst with special active sites. More importantly, the physicochemical properties imparted by this modification method can unexpectedly and significantly improve the catalytic activity of formic acid hydrogen production.

[0031] This invention employs a simple catalyst pretreatment modification method to significantly improve the room temperature decomposition hydrogen production rate of formic acid, which is beneficial to promoting the development and practical application of formic acid in the field of hydrogen production. Furthermore, this method has broad applicability to catalysts and has good development prospects and application space. Attached Figure Description

[0032] Figure 1 The images show the catalysts before modification in Example 1 and after modification in Example 1D, illustrating the changes in the macroscopic color of the catalysts.

[0033] Figure 2 XPS images of the catalyst before treatment in Example 1, the catalyst after pretreatment in Example 1D (labeled as SF pretreatment), and the catalyst after catalytic hydrogen production from formic acid in Example 1D via step 2 (labeled as FA reaction catalyst).

[0034] Figure 3 The image shows the gas chromatogram (GC) of hydrogen production from formic acid catalyzed by the modified catalyst of Example 1D in step 2.

[0035] Figure 4 The graph shows the gas production rate-time of hydrogen production from formic acid catalyzed by the modified catalyst in Example 1 after different modification times.

[0036] Figure 5The graph shows the hydrogen production performance of different experimental groups after modification treatment in Example 2.

[0037] Figure 6 The images show TEM images and metal particle size distribution diagrams of the catalyst modified for 1.5 hours in Example 3.

[0038] Figure 7 This is a time-varying graph showing the gas production of formic acid dehydrogenation catalyzed by catalysts modified for different times in Example 3.

[0039] Figure 8 This is a time-varying graph showing the gas production of formic acid dehydrogenation catalyzed by catalysts modified for different times in Example 4.

[0040] Figure 9 This is a gas production-time graph for the dehydrogenation of formic acid catalyzed by the modified catalyst in Example 5.

[0041] Figure 10 This is a gas production-time graph for the dehydrogenation of formic acid catalyzed by the modified catalyst in Example 6.

[0042] Figure 11 This is a gas production-time graph for the dehydrogenation of formic acid catalyzed by the catalyst in Comparative Example 1.

[0043] Figure 12 This is a gas production-time graph for the catalyst-catalyzed dehydrogenation of formic acid in Comparative Example 2.

[0044] Figure 13 The gas production-time graph is for the catalyst of Comparative Example 3 catalyzing the dehydrogenation of formic acid. Detailed Implementation

[0045] The following detailed description is provided in conjunction with the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the specific implementation.

[0046] In this invention, the pre-modified catalyst can be a conventional commercial product or prepared using known methods. For example, the 0.5 wt% Pd / TiO2 catalyst described in this invention is obtained as follows:

[0047] Photodeposition method: Methanol solution and deionized water are mixed evenly and loaded into a quartz reactor. TiO2 support is then fully dispersed in the above solution, and potassium hexachloropalladium solution is added. Ar gas is introduced under stirring, vacuum is applied, and Ar gas is introduced again three times. The mixed solution is irradiated with a high-pressure mercury lamp for 2-5 minutes to carry out the photodeposition reaction. The precipitate is collected, washed, and dried at 90°C for 4 hours to obtain 0.5wt% Pd / TiO2-photodeposition catalyst.

[0048] Chemical reduction method: TiO2 is fully dispersed in deionized water, potassium hexachloropalladate solution is added, and the mixture is stirred for 15 minutes. Then, NaBH4 (1.2 to 2 times the theoretical molar amount) is added under continuous stirring and the mixture is reacted for 1.5 hours to obtain a mixed suspension. The precipitate is collected, washed, and dried at 90°C for 4 hours to obtain 0.5 wt% Pd / TiO2-chemical reduction catalyst.

[0049] The 0.5wt% Pd / P25 catalyst is obtained in the same way as the 0.5wt% Pd / TiO2-photodeposition catalyst mentioned above, except that TiO2 is replaced with P25.

[0050] In this invention, there are no special requirements for the temperature of the modification process. Considering the simplicity of the process, it can be at room temperature (e.g., 20-40°C).

[0051] Example 1

[0052] Step 1:

[0053] 42.6 mg of 0.5 wt% Pd / TiO2-photodeposition catalyst prepared by photodeposition was weighed and placed in a double-necked flask, and dispersed in 10 ml of deionized water to obtain a homogeneous solution. 2.051 g of sodium formate (the concentration of sodium formate in the mixed solution was 3 M) was added, and the mixture was continuously stirred at 25 °C for modification treatment. The modification treatment times were as follows:

[0054] Group A: 5 min;

[0055] Group B: 1.5h;

[0056] Group C: 2 hours;

[0057] Group D: 2.5 hours;

[0058] Group E: 3 hours;

[0059] A comparison of optical photographs of catalyst samples before and after modification can be found in [link to image]. Figure 1 The catalyst's color changed from white to grayish-white, indicating a change on the surface of the catalyst sample.

[0060] Step 2:

[0061] Add 381 μl of formic acid (99%, with a molar ratio of 1:3 to sodium formate in step 1) to the modified system of step 1 and carry out the dehydrogenation reaction at 25 °C for 15 minutes.

[0062] XPS values ​​for the catalyst before modification, the catalyst after modification (group D) in step 1, and the catalyst after modification followed by formic acid catalytic dehydrogenation in step 2 are shown below. Figure 2 The modification treatment caused a shift in the peaks of the Pd phase.

[0063] The GC chromatogram of the gaseous products from the formic acid hydrogen production catalyzed by the modified catalyst of group D is shown below. Figure 3 The absence of CO indicates that the CO produced was below the GC detection limit of 100 ppm, meaning that the catalyst exhibits excellent selectivity in the reaction of formic acid to produce hydrogen at room temperature.

[0064] The activity graphs of the modified catalysts at different modification times for the formic acid dehydrogenation reaction are shown below. Figure 4 Therefore, by employing the aforementioned modification process and controlling the modification time, the catalytic activity can be further optimized.

[0065] Example 2

[0066] Compared with Example 1B, the only difference is that in step 1, the concentration of sodium formate in the initial stage of modification is controlled by changing the amount of sodium formate added. The experimental groups are: 0M, 1M (sodium formate amount is 0.68g, and its weight ratio with catalyst is 16:1), 3M (same as Example 1B), 6M (sodium formate 4.08g, its ratio with catalyst is 96:1), and 9M (sodium formate 6.12g, its ratio with catalyst is 144:1). The modification time is 1.5h for all groups, and the ratio of formic acid in step 2 to that in step 1 is the same as in Example 1. Other operations and parameters are the same as in Example 1.

[0067] The activity graphs of catalysts modified with sodium formate at different molar concentrations for the formic acid dehydrogenation reaction are shown below. Figure 5 (Among them, the experimental group with no SF and sodium formate addition of 0) shows that by adopting the above-described modification process and controlling the concentration of sodium formate, the catalytic activity can be further optimized.

[0068] Example 3

[0069] Step 1:

[0070] Weigh 42.6 mg of 0.5 wt% Pd / P25 catalyst prepared by photodeposition method and place it in a double-necked flask. Disperse it in 10 ml of deionized water to obtain a homogeneous solution. Add 2.051 g of sodium formate and stir continuously at 25 °C for 5 min or 1.5 h respectively to modify the catalyst.

[0071] The TEM image of the formic acid hydrogen production catalyst modified for 1.5 h is shown below. Figure 6 .

[0072] Step 2:

[0073] 381 μl of formic acid (99%) was added to the modified system in step 1 to carry out a dehydrogenation reaction (the dehydrogenation reaction was the same as in Example 1).

[0074] The activity graphs of the modified catalysts treated with different modification times for the formic acid dehydrogenation reaction are shown below. Figure 7Therefore, it is evident that by employing the aforementioned modification process and controlling the modification time, the catalytic activity can be further improved.

[0075] Example 4

[0076] Compared with Example 3, the only difference is that the catalyst before modification is a 0.5wt% Pd / TiO2-chemical reduction catalyst prepared by NaBH4 reduction method, and the other operations and parameters are the same as in Example 3.

[0077] The activity graphs of the modified catalysts treated with different modification times for the formic acid dehydrogenation reaction are shown below. Figure 8 Therefore, it is evident that by employing the aforementioned modification process and controlling the modification time, the catalytic activity can be further improved.

[0078] Example 5

[0079] Compared with Example 3, the only difference is that the catalyst before modification is 0.5wt% Pd3Au2 / TiO2 catalyst, and the other operations and parameters are the same as in Example 3.

[0080] The activity graphs of the modified catalysts at different modification times for the formic acid dehydrogenation reaction are shown below. Figure 9 Therefore, it is evident that by employing the aforementioned modification process and controlling the modification time, the catalytic activity can be further improved.

[0081] Example 6

[0082] Compared to Example 1D, the only difference is that the modification treatment temperature is 50°C; all other operations and parameters are the same as in Example 1. (The catalyst used here is the same as in Example 1.)

[0083] The activity graphs of the modified catalysts at different modification temperatures for the formic acid dehydrogenation reaction are shown below. Figure 10 It is evident that, using the aforementioned modification process, the control of the modification temperature has no significant impact on the catalytic activity.

[0084] Comparative Example 1:

[0085] Compared to Example 1D, the only difference is that the unmodified catalyst was directly placed in a solution containing the same proportions of sodium formate and formic acid for catalytic hydrogen production; all other operations and parameters were the same as in Example 1. Results are shown in [link to example]. Figure 11 .

[0086] Comparative Example 2:

[0087] Compared to Example 1D, the only difference is that sodium formate was replaced with sodium acetate for modification; all other operations and parameters are the same as in Example 1. Results are shown in […]. Figure 12 The results indicate that sodium acetate did not play a modifying role, and the catalyst activity was almost the same as that of the unmodified catalyst.

[0088] Comparative Example 3:

[0089] Compared to Example 1D, the only difference is that sodium formate was replaced with glucose for modification; all other operations and parameters are the same as in Example 1. Results are shown in […]. Figure 13 The results indicate that glucose did not have the same modifying effect on the catalyst as sodium formate.

Claims

1. A method for modifying a formic acid hydrogen production catalyst, characterized in that, A modified formic acid hydrogen production catalyst was prepared by modifying the formic acid hydrogen production catalyst in a formate solution. The formic acid hydrogen production catalyst is a supported catalyst with Pd nanoparticles. The Pd-containing nano-active particles include at least one of Pd nanoparticles and Pd-M alloy nanoparticles; wherein M is at least one of Au, Ag, Pt, Ir, Ru, Rh, Cu, Bi, Ni, Fe, and Co. The support in the supported catalyst is at least one of TiO2, carbon material, SiO2, MOF, and molecular sieve; The formic acid hydrogen production catalyst contains Pd nanoparticles at a content of 0.1 wt.% or more. The formate in the formate solution is at least one of sodium formate, potassium formate, and ammonium formate; During the modification treatment stage, the weight ratio of formate to formic acid hydrogen production catalyst in the formate solution is above 16:1; The modification treatment stage takes more than 2 hours.

2. The method for modifying the formic acid hydrogen production catalyst as described in claim 1, characterized in that, The formic acid hydrogen production catalyst described above was prepared using photodeposition, NaBH4 reduction, and hydrogen reduction methods. The formic acid hydrogen production catalyst contains 0.2~1 wt.% Pd nanoparticles.

3. The method for modifying the formic acid hydrogen production catalyst as described in claim 1, characterized in that, In formate solutions, the concentration of the solute is 0.1~12M.

4. The method for modifying the formic acid hydrogen production catalyst as described in claim 3, characterized in that, During the modification treatment stage, the weight ratio of formate to formic acid hydrogen production catalyst in the formate solution is 40~150:

1.

5. The method for modifying the formic acid hydrogen production catalyst according to any one of claims 1 to 4, characterized in that, The modification treatment stage takes 2-5 hours.

6. The method for modifying the formic acid hydrogen production catalyst as described in claim 1, characterized in that, The support in the supported catalyst is at least one of P25, graphene, and SBA-15.

7. A modified formic acid hydrogen production catalyst prepared by the modification method according to any one of claims 1 to 6.

8. A method for producing hydrogen from formic acid, characterized in that, The modified formic acid hydrogen production catalyst according to any one of claims 1 to 6 is used as a catalyst to catalyze the formic acid hydrogen production reaction.

9. The method for producing hydrogen from formic acid as described in claim 8, characterized in that, Formic acid is directly added to the modified system containing the modified formic acid hydrogen production catalyst in any one of the modification methods of claims 1 to 6 to carry out the formic acid hydrogen production reaction.

10. The method for producing hydrogen from formic acid as described in claim 8 or 9, characterized in that, The molar ratio of formic acid to formate used in the modification stage is less than or equal to 1.

11. The method for producing hydrogen from formic acid as described in claim 10, characterized in that, The molar ratio of formic acid to formate used in the modification stage is 1:2~10.

12. The method for producing hydrogen from formic acid as described in claim 11, characterized in that, The molar ratio of formic acid to formate used in the modification stage is 1:2~6.

13. The method for producing hydrogen from formic acid as described in claim 11, characterized in that, The molar ratio of formic acid to formate used in the modification stage is 1:2.5~4.

14. The method for producing hydrogen from formic acid as described in claim 8, characterized in that, The temperature during the hydrogen production reaction stage is 20~60℃.

15. The method for producing hydrogen from formic acid as described in claim 14, characterized in that, The hydrogen production reaction takes 1 to 15 minutes.

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