Preparation method and application of catalyst Co-Nd / ATP for hydrogen production through ammonia decomposition

Abstract

The invention relates to the technical field of hydrogen production through ammonia decomposition, in particular to preparation and application of a catalyst Co-Nd / ATP for hydrogen production through ammonia decomposition. The conventional transition metal-based catalyst is very difficult to realize the ammonia decomposition conversion rate of about 90% at the temperature of lower than 700 DEG C. In order to solve the problems, the invention provides the catalyst Co-Nd / ATP for hydrogen production through ammonia decomposition, two catalytic active elements Co and Nd are introduced on the surface of an attapulgite material, the catalyst has good catalytic activity on the reaction of hydrogen production through ammonia decomposition, the catalyst is used for catalyzing the reaction at the temperature of about 600 DEG C, and the catalytic activity of the catalyst is greatly improved. The ammonia decomposition conversion rate can reach 90% or above, and the transition metal-based catalyst has a better catalytic effect compared with a conventional transition metal-based catalyst for hydrogen production through ammonia decomposition.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen production by decomposing ammonia, and in particular to a preparation method and application of a catalyst Co-Nd / ATP for hydrogen production by decomposing ammonia. Background Art

[0002] The world is facing the problem of energy depletion and environmental pollution caused by the use of fossil fuels, and there is an urgent need to develop efficient green clean energy. Hydrogen energy has become the focus of research due to its clean and efficient characteristics. The demand for hydrogen energy is growing rapidly worldwide. However, there are still major difficulties in the storage and utilization of hydrogen. Ammonia, as a hydrogen carrier, has the advantages of high yield, high hydrogen content (17.8wt%), low storage pressure, and long-term storage stability.

[0003] Ammonia decomposition reaction is one of the important ways to produce hydrogen. A large amount of hydrogen can be obtained by catalytically decomposing ammonia, which is crucial for the development of hydrogen economy. The catalysts used in the ammonia decomposition reaction to produce hydrogen are usually ruthenium-based catalysts or transition metal-based catalysts. Ruthenium-based catalysts are expensive and costly. Conventional transition metal-based catalysts are difficult to achieve a 90% ammonia decomposition conversion rate in the ammonia decomposition reaction to produce hydrogen at a temperature below 700°C. Summary of the invention

[0004] The problem in the prior art is that it is difficult for conventional transition metal-based catalysts to achieve an ammonia decomposition conversion rate of more than 88% at a temperature below 700°C. In view of the above problem, the present invention provides an ammonia decomposition hydrogen production catalyst Co-Nd / ATP, which comprises the following preparation steps:

[0005] (1) impregnating attapulgite powder (ATP carrier powder) in an aqueous solution of a soluble neodymium salt, and after the impregnation is completed, drying to obtain a Nd / ATP precursor;

[0006] (2) calcining the Nd / ATP precursor in an air atmosphere to obtain Nd / ATP;

[0007] (3) uniformly dispersing Nd / ATP in an aqueous solution formed by mixing a soluble cobalt salt and citric acid, heating and stirring the solution for reaction, and after the reaction is completed, drying is performed to obtain a Co-Nd / ATP precursor;

[0008] (4) The Co-Nd / ATP precursor is calcined in an air atmosphere to obtain Co-Nd / ATP.

[0009] Preferably, in step (1), the mass ratio of the ATP carrier powder to the neodymium element in the aqueous solution is 1:0.025-0.07.

[0010] Preferably, the soluble neodymium salt is neodymium nitrate hexahydrate, and the mass ratio of the ATP carrier powder to the neodymium nitrate hexahydrate is 0.5:0.076.

[0011] Preferably, the immersion time in step (1) is not less than 24 hours.

[0012] Preferably, the drying temperature in step (1) is not greater than 100°C.

[0013] Preferably, the calcination temperature in step (2) is not higher than 500° C., and the calcination time is not more than 3 hours.

[0014] Preferably, in step (3), the soluble cobalt salt is cobalt nitrate, and the mass ratio of the Co-Nd / ATP precursor to the cobalt element and citric acid is 0.3:0.59:0.38-0.40.

[0015] Preferably, the calcination temperature in step (4) is not higher than 700° C., and the calcination time is not more than 4 hours.

[0016] The present invention has the following beneficial effects:

[0017] (1) The Co-Nd / ATP obtained in the present invention has good catalytic activity for the ammonia decomposition hydrogen production reaction. When the catalyst is used to catalyze the reaction at a temperature of about 600°C, the ammonia decomposition conversion rate can reach more than 90%, which has a better catalytic effect than conventional transition metal-based catalysts for ammonia decomposition hydrogen production;

[0018] (2) The present invention has found through research that during the preparation of Co-Nd / ATP, the amount of Nd element added during the reaction has a significant effect on the catalytic activity of the obtained catalyst. When the mass ratio of ATP carrier powder to neodymium nitrate hexahydrate during the reaction is 0.5:0.076, the catalyst obtained has better catalytic activity than those at other mass ratios of the two. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 : Comparison chart of the test results of ammonia decomposition conversion rate in the process of catalytic ammonia decomposition to produce hydrogen by the catalysts obtained in Examples 1-3 and Comparative Example 1 respectively.

[0020] Figure 2 : Comparison chart of the test results of hydrogen generation rate in the process of catalytic ammonia decomposition and hydrogen production by the catalysts obtained in Examples 1-3 and Comparative Example 1 respectively.

[0021] Figure 3 : Comparison of the reaction activation energy test results of the catalysts obtained in Examples 1-3 and Comparative Example 1 in the process of catalytic ammonia decomposition to produce hydrogen.

[0022] Figure 4: XRD comparison diagram of ATP carrier powder, 40Co5Nd / ATP and 40Co / ATP.

[0023] Figure 5 : TEM image of 40Co / ATP.

[0024] Figure 6 : TEM image of 40Co5Nd / ATP. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the examples. However, it should be understood that the following examples are only illustrative of the embodiments of the present invention, and are not intended to limit the scope of the present invention.

[0026] The catalytic activity of the catalysts obtained in the following examples and comparative examples of the present invention for hydrogen production by decomposition of ammonia was tested according to the following steps:

[0027] A quartz tube was used as a reactor. The inner diameter of the quartz tube was 4 mm and the length was 0.5 m. 0.1 g of catalyst was placed in the quartz tube. The temperature of the reactor was then raised to different specified temperatures and kept constant for 30 min. NH3 was then continuously and evenly introduced from one end of the quartz tube and discharged from the other end at a flow rate of 50 mL / min. The gases discharged at different temperatures were collected within the same sampling time and the volume content of NH3 in the product was analyzed using a thermal conductivity detector of a Beifen gas chromatograph. The detector temperature was set to 150 °C. H2 was used as the chromatograph carrier gas with a carrier gas flow rate of 40 mL / min. The chromatographic column used was a special column for amine analysis produced by Shanghai Ouni, and the column temperature was set to 110 °C.

[0028] The ammonia decomposition conversion rate is calculated according to the following formula:

[0029]

[0030] in,

[0031] in, is the NH3 conversion rate, is the total amount of ammonia in the feed gas, is the volume content of unreacted NH3.

[0032] The ATP carrier powder in the following examples and comparative examples of the present invention was purchased from Yuanye Biotechnology Co., Ltd., and the product number is S28335

[0033] Example 1

[0034] The preparation method of the ammonia decomposition hydrogen production catalyst Co-Nd / ATP is as follows:

[0035] (1) Weigh 0.5 g of ATP carrier powder and 0.045 g of Nd(NO3)3·6H2O into 20 mL of deionized water, stir and disperse them evenly, let them stand for 24 h, and then dry the mixture at 100°C for 8 h to obtain a Nd / ATP precursor;

[0036] (2) placing the Nd / ATP precursor in a muffle furnace, calcining at 500°C for 3 h, and naturally cooling to room temperature to obtain Nd / ATP. The heating rate during the calcination process is 5°C / min;

[0037] (3) Weigh 0.3 g Nd / ATP and 0.59 g Co(NO3)2·6H2O and add them to 50 mL deionized water, stir and disperse them evenly, add 0.427 g citric acid monohydrate during stirring, heat and stir at 85°C for 8 h, and after the reaction is completed, dry the reaction solution at 100°C for 12 h to obtain Co-Nd / ATP precursor;

[0038] (4) The Co-Nd / ATP precursor was then placed in a muffle furnace and calcined at 700 °C for 4 h. After naturally cooling to room temperature, the target catalyst was obtained, which was recorded as 40Co3Nd / ATP. The heating rate during the calcination process was 5 °C / min.

[0039] Example 2 is the same as Example 1, except that the amount of Nd(NO3)3·6H2O added in step (1) of Example 2 is 0.076 g. The catalyst obtained in Example 2 is denoted as 40Co5Nd / ATP.

[0040] Example 3 is the same as Example 1, except that the amount of Nd(NO3)3·6H2O added in step (1) of Example 3 is 0.076 g. The catalyst obtained in Example 3 is denoted as 40Co7Nd / ATP.

[0041] Comparative Example 1

[0042] (1) Weigh 0.3 g ATP and 0.59 g Co(NO3)2·6H2O and add them to 50 mL deionized water and stir them evenly. During the stirring process, add 0.427 g citric acid monohydrate and heat and stir at 85°C for 8 h. After the reaction is completed, place the reaction solution at 100°C and dry it for 12 h to obtain a Co / ATP precursor.

[0043] (2) Finally, the Co / ATP precursor was placed in a muffle furnace and calcined at 700°C for 4 h. After naturally cooling to room temperature, the target catalyst was obtained, which was recorded as 40Co / ATP. The heating rate during the calcination process was 5°C / min.

[0044] The ammonia decomposition conversion rate, hydrogen generation rate and reaction activation energy of the catalysts obtained in Examples 1-3 and Comparative Example 1 in the process of catalyzing ammonia decomposition and hydrogen production are as shown in the attached specification. Figure 1-3 As shown in the test results, 40Co5Nd / ATP has the best performance. When 40Co5Nd / ATP catalyzes the decomposition of ammonia, the NH3 conversion rate reaches 94.6% at 600℃, and the hydrogen generation rate is 31.66mmol gcat -1 min -1 The activation energy of the reaction is 67.97 kJ mol -1 .

[0045] When 40Co3Nd / ATP catalyzes the decomposition of ammonia, the NH3 conversion rate reaches 88.7% at 600℃, and the hydrogen generation rate is 29.7mmol gcat -1 min -1 The activation energy of the reaction is 52.5 kJ mol -1 .

[0046] When 40Co7Nd / ATP catalyzes the decomposition of ammonia, the NH3 conversion rate reaches 91.7% at 600℃, and the hydrogen generation rate is 30.71mmol gcat -1 min -1 The activation energy of the reaction is 75.71 kJ mol -1 .

[0047] When 40Co / ATP catalyzes the decomposition of ammonia, the NH3 conversion rate reaches 85.4% at 600℃, and the hydrogen generation rate is 28.61mmol gcat -1 min -1 The activation energy of the reaction is 83.63 kJ mol -1 .

[0048] The XRD diffraction patterns of ATP carrier powder, 40Co5Nd / ATP and 40Co / ATP are shown in the attached manual. Figure 4 As shown in the image, the ATP carrier has obvious diffraction peaks at 2θ=22.3° and 28.6°, and the 40Co5Nd / ATP and 40Co / ATP catalysts have characteristic diffraction peaks of Co3O4 at 2θ=31.2°, 36.8° and 65.2°, corresponding to their (220), (311) and (440) crystal planes, respectively (PDF#09-0418). The characteristic diffraction peaks of Nd2O3 of the 40Co5Nd / ATP catalyst were not clearly observed in the XRD spectrum, which may be due to the low loading content and small particle size of Nd2O3.

[0049] The TEM image of 40Co / ATP is attached to the instruction manual. Figure 5As shown in the image, the catalyst Co3O4 particles are evenly distributed on the support. The corresponding HRTEM image clearly shows that the Co3O4 lattice fringe spacing is 0.244nm, belonging to the (311) crystal plane of the Co3O4 crystal, which is consistent with the XRD results.

[0050] TEM image of 40Co5Nd / ATP is attached to the instruction manual. Figure 6 As shown in the image, the catalyst Co3O4 and Nd2O3 particles are evenly distributed on the carrier, and the corresponding HRTEM image clearly shows that the lattice fringe spacing of Co3O4 is 0.244nm, belonging to the (311) crystal plane of Co3O4 crystal. The lattice fringe spacing of Nd2O3 is 0.335nm, belonging to the (100) crystal plane of Co3O4 crystal, which is consistent with the XRD results.

[0051] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A catalyst Co-Nd / ATP for hydrogen production by decomposition of ammonia, characterized in that: The preparation method comprises the following steps: (1) impregnating ATP carrier powder in an aqueous solution of a soluble neodymium salt, and after the impregnation is completed, drying to obtain a Nd / ATP precursor; (2) calcining the Nd / ATP precursor in an air atmosphere to obtain Nd / ATP; (3) uniformly dispersing Nd / ATP in an aqueous solution formed by mixing a soluble cobalt salt and citric acid, heating and stirring the solution for reaction, and after the reaction is completed, drying is performed to obtain a Co-Nd / ATP precursor; (4) The Co-Nd / ATP precursor is calcined in an air atmosphere to obtain Co-Nd / ATP.

2. The ammonia decomposition hydrogen production catalyst Co-Nd / ATP according to claim 1, characterized in that: In step (1), the mass ratio of the ATP carrier powder to the neodymium element in the aqueous solution is 1:0.025-0.

07.

3. The catalyst Co-Nd / ATP for hydrogen production by decomposition of ammonia according to claim 2, characterized in that: The soluble neodymium salt is neodymium nitrate hexahydrate, and the mass ratio of the ATP carrier powder to the neodymium nitrate hexahydrate is 0.5:0.

076.

4. The ammonia decomposition hydrogen production catalyst Co-Nd / ATP according to claim 1, characterized in that: The immersion time in step (1) is not less than 24 hours.

5. The ammonia decomposition hydrogen production catalyst Co-Nd / ATP according to claim 1, characterized in that: The drying temperature in step (1) is not greater than 100°C.

6. The ammonia decomposition hydrogen production catalyst Co-Nd / ATP according to claim 1, characterized in that: The calcination temperature in step (2) is not higher than 500° C. and the calcination time is not more than 3 hours.

7. The ammonia decomposition hydrogen production catalyst Co-Nd / ATP according to claim 1, characterized in that: In step (3), the soluble cobalt salt is cobalt nitrate, and the mass ratio of the Co-Nd / ATP precursor to the cobalt element and citric acid is 0.3:0.59:0.38-0.

40.

8. The ammonia decomposition hydrogen production catalyst Co-Nd / ATP according to claim 1, characterized in that: The calcination temperature in step (4) is not higher than 700° C. and the calcination time is not more than 4 hours.

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