Preparation method and catalyst of heterogeneous formic acid dehydrogenation catalyst

Abstract

The present invention discloses a method for preparing a heterogeneous formic acid dehydrogenation catalyst. Using ZIF-67 as a precursor, it adsorbs furfuryl alcohol and polymerizes it into polyfurfuryl alcohol. The catalyst is then vacuum-calcined to synthesize a high-load single-atom catalyst. The catalyst prepared by this method has a high metal loading in single-atom form, exhibits high catalytic selectivity and hydrogen production rate in the formic acid dehydrogenation reaction, and exhibits good cyclic stability.

Description

Technical Field

[0001] The present invention relates to the field of formic acid dehydrogenation catalysis, and in particular to a preparation method and application of a heterogeneous formic acid dehydrogenation catalyst. Background Art

[0002] Formic acid (HCOOH) is a good hydrogen storage medium with high hydrogen storage capacity, non-toxicity, and a stable liquid compound at room temperature, making it easy to store and transport. Formic acid can be synthesized through sustainable pathways such as carbon dioxide hydrogenation or partial oxidation of biomass, and can produce hydrogen under catalysis.

[0003] Existing heterogeneous catalysts for formic acid dehydrogenation have the following shortcomings: they are mainly based on precious metals palladium and gold, which are expensive and limit the application of formic acid hydrogen storage methods; and non-precious metal heterogeneous single-atom catalysts require high-temperature calcination during preparation, the metals are prone to agglomeration, and it is difficult to achieve metal atomic-level dispersion. The Co-NC catalyst reported by Beller et al. in 2017 has high selectivity for formic acid dehydrogenation, but its hydrogen production rate is still far behind that of precious metals palladium and gold. Subsequently, in 2020, they reported the preparation of Co single-atom catalysts using ZIF-67 with a certain cobalt-zinc ratio as a precursor. The performance was significantly improved compared to Co-NC, but the loading of single-atom cobalt was still low, which limited the improvement in catalytic performance. Therefore, how to prepare formic acid dehydrogenation catalysts with higher single-atom metal loadings is a problem that needs to be further addressed. Summary of the Invention

[0004] The present invention aims to provide a method for preparing a heterogeneous formic acid dehydrogenation catalyst. The catalyst prepared by the method has a high metal loading, high catalytic selectivity and high hydrogen production rate in the formic acid dehydrogenation reaction, and good cycle stability.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a heterogeneous formic acid dehydrogenation catalyst comprises the following steps:

[0007] Step S1: preparing a ZIF-67 precursor having zinc and cobalt metal nodes, wherein the molar ratio of zinc to cobalt elements is 5 to 15:1;

[0008] Step S2: using a ZIF-67 precursor to adsorb furfuryl alcohol in a furfuryl alcohol solution to obtain a precursor adsorbing furfuryl alcohol, wherein the mass fraction of furfuryl alcohol in the furfuryl alcohol solution is 10 to 100%;

[0009] Step S3: heating the precursor adsorbing furfuryl alcohol under an inert atmosphere to polymerize the furfuryl alcohol, and then heating to 800° C. under vacuum conditions with a circulating water pump to carbonize and volatilize zinc, thereby obtaining a heterogeneous formic acid dehydrogenation catalyst.

[0010] Preferably, in the step S1, a mixture of zinc salt and cobalt salt is first prepared, and the molar ratio of zinc to cobalt is 5 to 15:1; then a 2-methylimidazole solution is added to the mixture of zinc salt and cobalt salt, and stirred to generate a precipitate to obtain a ZIF-67 precursor having zinc and cobalt metal nodes; in the step S2, the ZIF-67 precursor is first heated to 300°C under an inert atmosphere for activation, and then the activated ZIF-67 precursor is immersed in a furfuryl alcohol solution to adsorb furfuryl alcohol to obtain a precursor adsorbing furfuryl alcohol; in the step S3, the precursor adsorbing furfuryl alcohol is first heated to 80°C under an inert gas atmosphere and maintained for 2 to 14 hours, and then heated to 150°C and maintained for 1 to 8 hours to polymerize the furfuryl alcohol, and then heated to 800°C under vacuum conditions and maintained for 1 to 5 hours for carbonization.

[0011] Further preferably, in the step S1, the zinc salt and the cobalt salt are dissolved in methanol to prepare the mixed solution, the mass ratio of the zinc salt to the volume ratio of methanol is 1g:30-50mL; then, a methanol solution of 2-methylimidazole is added to the mixed solution of the zinc salt and the cobalt salt, the mass ratio of the 2-methylimidazole to the volume ratio of methanol is 1g:10-15mL, and the volume ratio of the mixed solution to the volume ratio of the 2-methylimidazole methanol solution is 2:1; in the step S2, the ZI The F-67 precursor is heated to 300° C. under an inert atmosphere and maintained for 1 to 3 hours for activation, and then the activated ZIF-67 precursor is immersed in a furfuryl alcohol solution to adsorb the furfuryl alcohol to obtain a furfuryl alcohol-adsorbed precursor; in step S3, the furfuryl alcohol-adsorbed precursor is first heated to 80° C. under an inert gas atmosphere and maintained for 2 to 14 hours, then heated to 150° C. and maintained for 1 to 8 hours to polymerize the furfuryl alcohol, and then heated to 800° C. under vacuum conditions and maintained for 1 to 5 hours for carbonization.

[0012] Preferably, the zinc salt is zinc nitrate, zinc carbonate or zinc acetate, and the cobalt salt is cobalt nitrate, cobalt carbonate or cobalt acetate.

[0013] Preferably, in step S2, the activated ZIF-67 precursor is immersed in a furfuryl alcohol solution and subjected to room temperature ultrasound to adsorb the furfuryl alcohol.

[0014] Preferably, in step S1, the molar ratio of zinc to cobalt is 10:1; and in step S2, the mass fraction of furfuryl alcohol in the furfuryl alcohol solution is 60%.

[0015] The present invention also provides a heterogeneous formic acid dehydrogenation catalyst, which is prepared by adopting the above preparation method.

[0016] The present invention has the following beneficial effects: (1) The present invention uses a ZIF-67 precursor with zinc-cobalt metal nodes to adsorb furfuryl alcohol, and then polymerizes the furfuryl alcohol in the framework material to form polyfurfuryl alcohol. The polyfurfuryl alcohol serves as a new supporting skeleton, which helps prevent structural collapse caused by carbonization and agglomeration of the catalytically active component cobalt, thereby increasing the loading amount of cobalt single atoms in the catalyst and further improving the catalytic performance of the catalyst per unit mass. (2) The catalyst prepared by the present invention can reach 778 mL / g when catalyzing formic acid dehydrogenation at a reaction temperature of 100°C using propylene carbonate (PC) as a solvent. cat The hydrogen production rate is 268 mL / g even under pure HCOOH conditions. cat h and exhibited good cycling stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Transmission electron microscope scanning images of the materials prepared in Examples 1-3 and Comparative Example 1;

[0018] Figure 2 XRD patterns of the materials prepared in Examples 1-3 and Comparative Example 1;

[0019] Figure 3 N2 adsorption-desorption isotherms of the materials prepared in Examples 1-3 and Comparative Example 1;

[0020] Figure 4 XPS images of the materials prepared in Example 1 and Comparative Example 1;

[0021] Figure 5 This is the X-ray absorption near-edge structure spectrum (XANES) of CoNC-300-60% PFA;

[0022] Figure 6 a) Thermogravimetric (TG) curves of 1:10ZIF-67, 1:10ZIF-67-300, 1:10ZIF-67-300-60% FA, and 1:10ZIF-67-300-60% PFA; b) differential thermogravimetric (DTG) curves; c) infrared spectra of 1:10ZIF-67, 1:10ZIF-67-300, 1:10ZIF-67-300-60% FA, 1:10ZIF-67-300-60% PFA, and 2-methylimidazole.

[0023] Figure 7 This is a catalytic stability analysis diagram of CoNC-300-60% PFA single atom catalyst. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the embodiments:

[0025] Example 1 Preparation of Heterogeneous Formic Acid Dehydrogenation Catalyst CoNC-300-60% PFA

[0026] Step S1: Weigh 2.02 g (6.8 mmol) of Zn(NO3)2·6H2O and 197 mg (0.68 mmol) of Co(NO3)2·6H2O (zinc-cobalt molar ratio of 10:1) respectively, add them to 80 ml of methanol solution, stir to completely dissolve them, and prepare a zinc-cobalt mixed solution; weigh 3.0 g (36.5 mmol) of 2-methylimidazole and dissolve it in 40 ml of methanol to prepare a solution, and then slowly pour the solution into the zinc-cobalt mixed solution. After stirring for 24 hours, centrifuge, wash with methanol, and vacuum dry to obtain a metal framework compound ZIF-67 precursor with zinc and cobalt as metal nodes;

[0027] Step S2: The ZIF-67 precursor was transferred to a ceramic boat and placed in a tube furnace. It was heated to 300°C at a heating rate of 2°C / min under a N2 atmosphere, maintained for 2 hours, and then naturally cooled to room temperature to obtain an activated precursor, recorded as ZIF-67-300; then 5.11 mL of furfuryl alcohol and 4.89 mL of methanol were mixed to obtain a methanol solution of furfuryl alcohol (the mass fraction of furfuryl alcohol was 60%), and ZIF-67-300 was immersed in the methanol solution of furfuryl alcohol to adsorb furfuryl alcohol, ultrasonicated for 40 minutes, and allowed to stand at room temperature overnight. Then, the methanol was removed by reduced pressure distillation to obtain the precursor ZIF-67-300-60% adsorbed with furfuryl alcohol.

[0028] Step S3: The precursor ZIF-67-300-60% that adsorbs furfuryl alcohol is heated to 80°C at a heating rate of 2°C / min under a N2 atmosphere and maintained for 14 hours, and then heated to 150°C and maintained for 6 hours to polymerize the furfuryl alcohol into polyfurfuryl alcohol. The obtained sample is recorded as ZIF-67-300-60% PFA; then, the ZIF-67-300-60% PFA is heated to 800°C under vacuum conditions of a circulating water vacuum pump for carbonization and volatilization of zinc. The heating rate is 5°C / min and maintained for 3 hours. The catalyst is then naturally cooled to room temperature to obtain a heterogeneous formic acid dehydrogenation catalyst, recorded as CoNC-300-60% PFA.

[0029] Example 2 Preparation of Heterogeneous Formic Acid Dehydrogenation Catalyst CoNC-300-10% PFA

[0030] Step S1: Weigh 2.02 g (6.8 mmol) of Zn(NO3)2·6H2O and 197 mg (0.68 mmol) of Co(NO3)2·6H2O (zinc-cobalt molar ratio of 10:1) respectively, add them to 80 ml of methanol solution, stir to completely dissolve them, and prepare a zinc-cobalt mixed solution; weigh 3.0 g (36.5 mmol) of 2-methylimidazole and dissolve it in 40 ml of methanol to prepare a solution, and then slowly pour the solution into the zinc-cobalt mixed solution. After stirring for 24 hours, centrifuge, wash with methanol, and vacuum dry to obtain a metal framework compound ZIF-67 precursor with zinc and cobalt as metal nodes;

[0031] Step S2: The ZIF-67 precursor was transferred to a ceramic boat and placed in a tube furnace. It was heated to 300°C at a heating rate of 2°C / min under a N2 atmosphere, maintained for 2 hours, and then naturally cooled to room temperature to obtain an activated precursor, recorded as ZIF-67-300; then 0.72 mL of furfuryl alcohol and 9.28 mL of methanol were mixed to obtain a methanol solution of furfuryl alcohol (the mass fraction of furfuryl alcohol was 10%), and ZIF-67-300 was immersed in the methanol solution of furfuryl alcohol to adsorb furfuryl alcohol, ultrasonicated for 40 minutes, and allowed to stand at room temperature overnight. Then, the methanol was removed by reduced pressure distillation to obtain the precursor ZIF-67-300-10% adsorbed with furfuryl alcohol.

[0032] Step S3: The precursor ZIF-67-300-10% that adsorbs furfuryl alcohol is heated to 80°C at a heating rate of 2°C / min under a N2 atmosphere and maintained for 14 hours, and then heated to 150°C and maintained for 6 hours to polymerize the furfuryl alcohol into polyfurfuryl alcohol. The obtained sample is recorded as ZIF-67-300-10% PFA; then, the ZIF-67-300-10% PFA is heated to 800°C under vacuum conditions of a circulating water vacuum pump for carbonization and volatilization of zinc. The heating rate is 5°C / min and maintained for 3 hours. The catalyst is then naturally cooled to room temperature to obtain a heterogeneous formic acid dehydrogenation catalyst, recorded as CoNC-300-10% PFA.

[0033] Example 3 Preparation of Heterogeneous Formic Acid Dehydrogenation Catalyst ZIF-67-300-100%

[0034] Step S1: Weigh 2.02 g (6.8 mmol) of Zn(NO3)2·6H2O and 197 mg (0.68 mmol) of Co(NO3)2·6H2O (zinc-cobalt molar ratio of 10:1) respectively, add them to 80 ml of methanol solution, stir to completely dissolve them, and prepare a zinc-cobalt mixed solution; weigh 3.0 g (36.5 mmol) of 2-methylimidazole and dissolve it in 40 ml of methanol to prepare a solution, and then slowly pour the solution into the zinc-cobalt mixed solution. After stirring for 24 hours, centrifuge, wash with methanol, and vacuum dry to obtain a metal framework compound ZIF-67 precursor with zinc and cobalt as metal nodes;

[0035] Step S2: The ZIF-67 precursor was transferred to a ceramic boat and placed in a tube furnace. It was heated to 300°C at a heating rate of 2°C / min under a N2 atmosphere, maintained for 2 hours, and then naturally cooled to room temperature to obtain an activated precursor, recorded as ZIF-67-300; then 10 mL of furfuryl alcohol (the mass fraction of furfuryl alcohol is 100%) was measured, and ZIF-67-300 was immersed in furfuryl alcohol to adsorb furfuryl alcohol, and ultrasonicated for 40 minutes to obtain the furfuryl alcohol-adsorbed precursor ZIF-67-300-100%.

[0036] Step S3: The furfuryl alcohol-adsorbed precursor ZIF-67-300-100% is heated to 80°C at a heating rate of 2°C / min under a N2 atmosphere and maintained for 14 hours, and then heated to 150°C and maintained for 6 hours to polymerize the furfuryl alcohol into polyfurfuryl alcohol. The obtained sample is recorded as ZIF-67-300-100% PFA; then, the ZIF-67-300-100% PFA is heated to 800°C under vacuum conditions of a circulating water vacuum pump for carbonization and volatilization of zinc. The heating rate is 5°C / min and maintained for 3 hours. The catalyst is then naturally cooled to room temperature to obtain a heterogeneous formic acid dehydrogenation catalyst, recorded as CoNC-300-100% PFA.

[0037] Example 4 Preparation of Heterogeneous Formic Acid Dehydrogenation Catalyst CoNC-300-60% FA Step S1: Weigh 2.02 g (6.8 mmol) of Zn(NO3)2·6H2O and 197 mg (0.68 mmol) of Co(NO3)2·6H2O (zinc-cobalt molar ratio of 10:1) respectively, add them to 80 ml of methanol solution, stir to completely dissolve them, and prepare a zinc-cobalt mixed solution; weigh 3.0 g (36.5 mmol) of 2-methylimidazole and dissolve it in 40 ml of methanol to prepare a solution, then slowly pour the solution into the zinc-cobalt mixed solution, stir for 24 hours, centrifuge, wash with methanol, and vacuum dry to obtain a metal framework compound ZIF-67 precursor with zinc and cobalt as metal nodes;

[0038] Step S2: The ZIF-67 precursor was transferred to a ceramic boat and placed in a tube furnace. It was heated to 300°C at a heating rate of 2°C / min under a N2 atmosphere, maintained for 2 hours, and then naturally cooled to room temperature to obtain an activated precursor, recorded as ZIF-67-300; then 5.11 mL of furfuryl alcohol and 4.89 mL of methanol were mixed to obtain a methanol solution of furfuryl alcohol (the mass fraction of furfuryl alcohol was 60%), and ZIF-67-300 was immersed in the methanol solution of furfuryl alcohol to adsorb furfuryl alcohol, ultrasonicated for 40 minutes, and allowed to stand at room temperature overnight. Then, the methanol was removed by reduced pressure distillation to obtain the precursor ZIF-67-300-60% adsorbed with furfuryl alcohol.

[0039] Step S3: The furfuryl alcohol-adsorbed precursor ZIF-67-300-60% was heated to 800°C under vacuum conditions using a circulating water vacuum pump for carbonization and volatilization of zinc. The heating rate was 5°C / min and maintained for 3 hours. The catalyst was then naturally cooled to room temperature to obtain a heterogeneous formic acid dehydrogenation catalyst, designated as CoNC-300-60% FA.

[0040] In this embodiment, no heating steps at 80° C. and 150° C. are provided in step S3 to polymerize furfuryl alcohol. However, furfuryl alcohol may still polymerize during the process of heating to 800° C.

[0041] Comparative Example 1 Preparation of Product CoNC-300 without Furfuryl Alcohol Impregnation

[0042] Step S1: Weigh 2.02 g (6.8 mmol) of Zn(NO3)2·6H2O and 197 mg (0.68 mmol) of Co(NO3)2·6H2O (zinc-cobalt molar ratio of 10:1) respectively, add them to 80 ml of methanol solution, stir to completely dissolve them, and prepare a zinc-cobalt mixed solution; weigh 3.0 g (36.5 mmol) of 2-methylimidazole and dissolve it in 40 ml of methanol to prepare a solution, and then slowly pour the solution into the zinc-cobalt mixed solution. After stirring for 24 hours, centrifuge, wash with methanol, and vacuum dry to obtain a metal framework compound ZIF-67 precursor with zinc and cobalt as metal nodes;

[0043] Step S2: The ZIF-67 precursor was transferred to a ceramic boat and placed in a tube furnace. It was heated to 300°C at a heating rate of 2°C / min under a N2 atmosphere, maintained for 2 h, and then naturally cooled to room temperature to obtain an activated precursor, which was recorded as ZIF-67-300.

[0044] Step S3: ZIF-67-300 was heated to 800°C under vacuum conditions using a circulating water vacuum pump for carbonization to volatilize zinc. The heating rate was 5°C / min and the temperature was maintained for 3 h. The ZIF-67-300 was naturally cooled to room temperature. The obtained material was recorded as CoNC-300.

[0045] Comparative Example 2 Preparation of CoNC without activation and furfuryl alcohol impregnation

[0046] Step S1: Weigh 2.02 g (6.8 mmol) of Zn(NO3)2·6H2O and 197 mg (0.68 mmol) of Co(NO3)2·6H2O (zinc-cobalt molar ratio of 10:1) respectively, add them to 80 ml of methanol solution, stir to completely dissolve them, and prepare a zinc-cobalt mixed solution; weigh 3.0 g (36.5 mmol) of 2-methylimidazole and dissolve it in 40 ml of methanol to prepare a solution, and then slowly pour the solution into the zinc-cobalt mixed solution. After stirring for 24 hours, centrifuge, wash with methanol, and vacuum dry to obtain a metal framework compound ZIF-67 precursor with zinc and cobalt as metal nodes;

[0047] Step S2: ZIF-67 was heated to 800°C under vacuum conditions using a circulating water vacuum pump for carbonization and volatilization of zinc. The heating rate was 5°C / min and the temperature was maintained for 3 h. The ZIF-67 was then naturally cooled to room temperature. The resulting material was recorded as CoNC.

[0048] Characterization analysis

[0049] The materials prepared in Examples 1-4 and Comparative Examples 1-2 were characterized and analyzed.

[0050] (1) Transmission electron microscopy (TEM)

[0051] like Figure 1 As shown in a, b, and c, CoNC-300-60% PFA, CoNC-300-10% PFA, and CoNC-300-100% PFA prepared from ZIF-67 impregnated with furfuryl alcohol maintain their structural stability. As the furfuryl alcohol content increases, the metal content decreases, and the material can be identified as metallic Co by its crystal lattice (0.206 nm). When the furfuryl alcohol content increases to 60% w / w, no crystalline Co metal nanoparticles are observed in the material ( Figure 1 a), indicating that Co is highly dispersed in the form of single atoms; when the furfuryl alcohol content is 10% or 100%, Co nanoparticles ( Figure 1 b. Figure 1 c), indicating that not all cobalt exists in the form of single atoms. Figure 1 As shown in (d), the Co / NC-300 prepared from ZIF-67 without furfuryl alcohol impregnation did not maintain the rhombic dodecahedral structure of ZIF-67.

[0052] (2) X-ray diffraction (XRD)

[0053] like Figure 2As shown in the XRD characterization of CoNC-300-60% PFA, CoNC-300-10% PFA, CoNC-300-100% PFA, and Co / NC-300, there is only the characteristic (002) plane of amorphous carbon at around 20°, so no diffraction peaks of Co-based compounds were found in the samples, indicating that the Co species are highly dispersed in the carbon matrix.

[0054] (3) N2 adsorption-desorption isotherm

[0055] CoNC-300-10% PFA, CoNC-300-60% PFA, CoNC-300-100% PFA, and Co / NC-300 all exhibit similar pore structures. Figure 3 It can be seen that the specific surface area of ​​Co / NC-300 prepared without furfuryl alcohol impregnation is 225m 2 ·g -1 The macropores are significantly reduced, which is because the sample does not maintain the morphology of ZIF-67. The specific surface areas of CoNC-300-10% PFA, CoNC-300-60% PFA, and CoNC-300-100% PFA are 378, 539, and 587 m 2 ·g -1 The nitrogen adsorption and desorption isotherms of CoNC-300-60% PFA have H4 type hysteresis loops and have a high specific surface area of ​​539m 2 ·g -1 , which helps to improve the catalytic performance of HCOOH dehydrogenation. (4) X-ray electron spectroscopy (XPS)

[0056] X-ray electron spectroscopy (XPS) was used to characterize the elemental composition and element valence of CoNC-300-60% PFA and Co / NC-300 materials. Figure 4 As shown in a, the material mainly includes five elements: Co, Zn, C, N, and O. The peaks of 1021eV, 781eV, 531eV, 398eV, and 284eV belong to Zn 2p, Co 2p, O 1s, N 1s, and C1s, respectively. Figure 4 As shown in b, the fitting peak at 779.6 eV in the high-resolution Co 2p spectrum belongs to Co 0 , the four fitting peaks at 780.8 / 796.5eV and 785.2 / 802.3eV belong to Co-N and the corresponding satellite signals, respectively. However, there is no Co in the XPS results of CoNC-300-60%PFA. 0 , this result was further confirmed by HRTEM images.

[0057] (5) X-ray absorption near-edge structure spectroscopy (XANES)

[0058] X-ray absorption near-edge structure (XANES) spectroscopy, such as Figure 5 As shown in Figure a, the absorption edge of CoNC-300-60% PFA is located between Co foil and Co3O4, indicating that the Co species in CoNC-300-60% PFA may be covalently bonded with N. Figure 5 b and 5c, the corresponding R space is obtained from the FEK3 weighted Fourier transform (FT), showing the bond length of the Co species. The curve of CoNC-300-60% PFA shows that There is a typical peak at , which may be attributed to the Co-N bond in the first shell. No Co-Co signal or Co-O signal was detected at the surface of the nanostructured carbon nanotubes. The results showed that the Co in CoNC-300-60% PFA was atomically dispersed and stable.

[0059] (6) Thermogravimetric analysis and infrared spectra

[0060] Figure 6 a, b are the thermogravimetric (TG) curves of 1:10ZIF-67, 1:10ZIF-67-300, 1:10ZIF-67-300-60%FA, and 1:10ZIF-67-300-60%PFA, respectively. Figure 6 a); b differential thermogravimetric (DTG) curve ( Figure 6 b) (1:10 is the molar ratio of cobalt to zinc).

[0061] Figure 6 Figures a and b show that at 200°C, 1:10 ZIF-67 exhibits a significant weight loss compared to the other materials due to the decomposition of dimethylimidazole and the generation of NH3. All materials experience significant weight loss at 650°C due to the carbonization and nitridation of ZIF-67. At 850°C, most materials lose weight as Zn evaporates primarily as Zn vapor. Comparison of the total thermal analysis results for 1:10 ZIF-67, 1:10 ZIF-67-300, 1:10 ZIF-67-300-60% FA, and 1:10 ZIF-67-300-60% PFA reveals that the introduction of polyfurfuryl alcohol significantly impacts the calcination of the ZIF-67 precursor. The formation of polyfurfuryl alcohol within the precursor effectively reduces the loss of carbon and nitrogen during calcination and promotes the formation of a high density of single-atom active sites.

[0062] Figure 6 c Infrared spectra of 1:10ZIF-67, 1:10ZIF-67-300, 1:10ZIF-67-300-60% FA, 1:10ZIF-67-300-60% PFA and 2-methylimidazole, respectively. Infrared image ( Figure 6c) shows that 1:10ZIF-67-300-60%FA and 1:10ZIF-67-300-60%PFA at 3500 cm -1 There is a peak at , which proves that furfuryl alcohol and polyfurfuryl alcohol are successfully incorporated into the internal pore structure of the precursor.

[0063] Catalytic performance analysis

[0064] (1) The catalytic performance of the materials prepared in Examples 1-4 and Comparative Examples 1-2 was analyzed respectively.

[0065] First, check the airtightness of the gas measuring tube connected to the reaction device. Then, add 10 mL of propylene carbonate to the reaction bottle, add 562 μL of formic acid, start stirring and heating, and wait until the temperature stabilizes at 100°C. After the device stabilizes, add 50 mg of catalyst and start reading. Read once every 10 minutes for a total of 2 hours. The results are shown in Table 1.

[0066] Table 1 Catalyst hydrogen production efficiency

[0067]

[0068] As can be seen from Table 1, the CoNC-300-60% PFA prepared by the present invention exhibits a 778 mL / g reaction temperature at 100°C using propylene carbonate (PC) as solvent. cat h; when the ratio of furfuryl alcohol to methanol was changed, the catalytic hydrogen production efficiency of CoNC-300-10% PFA and CoNC-100% PFA decreased; when furfuryl alcohol impregnation was not performed, the catalytic hydrogen production efficiency of CoNC-300 was only 451 mL / g cat ·h, the catalytic hydrogen production efficiency is significantly lower than that of CoNC-300-60% PFA. For CoNC-300-60% FA prepared in Example 4, its catalytic hydrogen production efficiency is 665mL / g cat h, slightly lower than 778 mL / g of CoNC-300-60% PFA cat ·h, which indicates that the polymerization of furfuryl alcohol by heating at 80℃ and 150℃ contributes to the improvement of catalytic performance. When activation and furfuryl alcohol impregnation are not performed, the catalytic hydrogen production efficiency of the prepared CoNC is only 226mL / g cat ·h, the catalytic hydrogen production efficiency is significantly lower than that of CoNC-300-60%PFA.

[0069] (2) CoNC-300-60% PFA catalyst stability test

[0070] like Figure 7As shown, the CoNC-300-60% PFA catalyst was reused in PC at 100°C for three times, and after being used, washed and dried, the catalyst still showed high activity and stability.

Claims

1. A method for preparing a heterogeneous formic acid dehydrogenation catalyst, characterized in that The steps include: Step S1: First, a mixture of zinc salt and cobalt salt is prepared, wherein the molar ratio of zinc to cobalt is 10:1; then, a 2-methylimidazole solution is added to the mixture of zinc salt and cobalt salt, and stirred to form a precipitate to obtain a ZIF-67 precursor having zinc and cobalt metal nodes; Step S2: first, heating the ZIF-67 precursor to 300° C. under an inert atmosphere for activation, and then immersing the activated ZIF-67 precursor in a furfuryl alcohol solution to adsorb furfuryl alcohol, thereby obtaining a furfuryl alcohol-adsorbed precursor, wherein the mass fraction of furfuryl alcohol in the furfuryl alcohol solution is 60%; Step S3: First, the precursor of the adsorbed furfuryl alcohol is heated to 80° C. in an inert gas atmosphere and maintained for 2 to 14 hours, then heated to 150° C. and maintained for 1 to 8 hours to polymerize the furfuryl alcohol, and then heated to 800° C. under vacuum conditions and maintained for 1 to 5 hours for carbonization.

2. The preparation method of the heterogeneous formic acid dehydrogenation catalyst according to claim 1, wherein: In step S1, a zinc salt and a cobalt salt are dissolved in methanol to prepare the mixed solution, wherein the mass ratio of the zinc salt to the volume ratio of methanol is 1 g:30-50 mL; then, a methanol solution of 2-methylimidazole is added to the mixed solution of the zinc salt and the cobalt salt, wherein the mass ratio of 2-methylimidazole to the volume ratio of methanol is 1 g:10-15 mL, and the volume ratio of the mixed solution to the volume of the 2-methylimidazole methanol solution is 2:1; In step S2, the ZIF-67 precursor is firstly heated to 300° C. under an inert atmosphere and maintained at 1 to 3 hours for activation, and then the activated ZIF-67 precursor is immersed in a furfuryl alcohol solution to adsorb furfuryl alcohol, thereby obtaining a precursor adsorbing furfuryl alcohol; In step S3, the precursor for adsorbing furfuryl alcohol is first heated to 80° C. under an inert gas atmosphere and maintained for 2 to 14 hours, then heated to 150° C. and maintained for 1 to 8 hours to polymerize the furfuryl alcohol, and then heated to 800° C. under vacuum conditions and maintained for 1 to 5 hours for carbonization.

3. The preparation method of the heterogeneous formic acid dehydrogenation catalyst according to claim 1 or 2, characterized in that: The zinc salt is zinc nitrate, zinc carbonate or zinc acetate, and the cobalt salt is cobalt nitrate, cobalt carbonate or cobalt acetate.

4. The preparation method of the heterogeneous formic acid dehydrogenation catalyst according to claim 2, wherein: In the step S2, the activated ZIF-67 precursor is immersed in a furfuryl alcohol solution and ultrasonicated at room temperature to adsorb the furfuryl alcohol.

5. A heterogeneous formic acid dehydrogenation catalyst, characterized in that The invention is prepared by the preparation method according to any one of claims 1 to 4.

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