Boron modified catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of catalysts and relates to a boron modified catalyst as well as a preparation method and application thereof. The invention provides a preparation method of a boron-modified catalyst, which comprises the following steps: carrying out hydrothermal reaction on a CuZnAl catalyst and a glucose solution to obtain a C-CuZnAl catalyst, dipping the C-CuZnAl catalyst in a solution containing a boron source, drying, and finally calcining to obtain the boron-modified catalyst. When the catalyst provided by the invention is used for hydrogen production by methanol reforming, compared with a CuZnAl catalyst, the catalyst has better stability, lower hydrogen production temperature, higher hydrogen production rate, lower CO selectivity and higher methanol conversion rate.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts and relates to a boron-modified catalyst and a preparation method and application thereof. Background Art

[0002] Through methanol reforming, hydrogen can be efficiently produced, providing more ways for energy utilization. Methanol reforming hydrogen production technology mainly includes methanol steam reforming, methanol decomposition, methanol partial oxidation reforming and oxidative methanol steam reforming. Among them, methanol steam reforming hydrogen production is the most widely studied and most in-depth hydrogen production method. The advantages of this method are mild reaction conditions, high hydrogen purity and low CO content. Through methanol steam reforming, the amount of hydrogen that can be produced per mole of methanol is also the highest.

[0003] In the process of methanol steam reforming to produce hydrogen, the selection and performance optimization of catalysts are key. Among many catalysts, copper-based catalysts are favored because of their low price, high activity and low CO selectivity. Copper-based catalysts can not only realize the reforming reaction of methanol under mild conditions, but also have a high purity of the target product hydrogen, which avoids the problem of CO poisoning at the anode in hydrogen-oxygen fuel cells to the greatest extent. In order to improve the catalytic performance of copper-based catalysts, researchers have conducted a lot of research and optimization work. They improve the activity and stability of the catalyst by regulating the active valence state and active crystal plane of copper, and introducing different composite oxides to produce synergistic effects with copper. Boron-modified copper-based catalysts refer to the introduction of boron elements into copper-based catalysts to improve their catalytic performance. Through boron modification, the structure and active sites of the catalyst can be adjusted, thereby improving its catalytic activity and stability. Excessive boron elements may cause the destruction of the catalyst structure and the reduction of active sites, thereby affecting its catalytic effect. Summary of the invention

[0004] The object of the present invention is to provide a boron-modified catalyst and a preparation method and application thereof. When the catalyst is used for hydrogen production by methanol reforming, the catalyst has better stability, lower hydrogen production temperature, faster hydrogen production rate, lower CO selectivity and higher methanol conversion rate than CuZnAl catalyst.

[0005] On the one hand, the present invention relates to a method for preparing a boron-modified catalyst, which comprises: hydrothermally reacting a CuZnAl catalyst and a glucose solution to obtain a C-CuZnAl catalyst, impregnating the C-CuZnAl catalyst with a solution containing a boron source, drying the solution, and finally calcining the solution to obtain a boron-modified catalyst.

[0006] The CuZnAl catalyst of the present invention is also called CuO / ZnO / Al 2 O 3 Catalyst or Cu / ZnO / Al2 O 3 The catalyst is a copper-based catalyst widely used in methanol reforming to produce hydrogen.

[0007] Furthermore, in the method for preparing a boron-modified catalyst provided by the present invention, the hydrothermal reaction time is 1 to 4 hours and the temperature is 150 to 300°C.

[0008] Furthermore, in the preparation method of the boron-modified catalyst provided by the present invention, the impregnation conditions include: immersing the C-CuZnAl catalyst in the solution containing the boron source for 1 to 4 hours, and continuously stirring.

[0009] Furthermore, in the method for preparing a boron-modified catalyst provided by the present invention, the solution containing a boron source is an aqueous solution of boric acid.

[0010] Furthermore, in the preparation method of the boron-modified catalyst provided by the present invention, the mass ratio of the boric acid in the boric acid aqueous solution to the C-CuZnAl catalyst is 1-8:10.

[0011] Furthermore, in the method for preparing a boron-modified catalyst provided by the present invention, the glucose solution is an aqueous glucose solution.

[0012] Furthermore, in the method for preparing the boron-modified catalyst provided by the present invention, the mass ratio of glucose monohydrate in the glucose aqueous solution to the CuZnAl catalyst is 1-5:10.

[0013] Furthermore, in the preparation method of the boron-modified catalyst provided by the present invention, the CuZnAl catalyst is prepared by a co-precipitation method from a precursor solution containing a copper source, a zinc source and an aluminum source.

[0014] Specifically, the copper source is a soluble salt of copper, the zinc source is a soluble salt of zinc, and the aluminum source is a soluble salt of aluminum.

[0015] Generally, the zinc source is at least one of nitrate, chloride and sulfate of Zn; The aluminum source is at least one of Al nitrate, Al chloride and Al sulfate; The copper source is at least one of nitrate, chloride and sulfate of Cu.

[0016] On the other hand, the present invention relates to a boron-modified catalyst, which is prepared by the preparation method of the boron-modified catalyst.

[0017] On the other hand, the present invention relates to the use of the boron-modified catalyst in hydrogen production by methanol reforming.

[0018] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages: The boron-modified catalyst provided by the present invention shows better stability than the traditional CuZnAl catalyst in the process of hydrogen production from methanol reforming, can reduce the hydrogen production temperature, save energy and improve production efficiency; at the same time, the catalyst has a faster hydrogen production rate, which can meet the application scenario of high hydrogen demand. In addition, when hydrogen is produced from methanol reforming, the catalyst can significantly reduce the selectivity of CO, improve the purity and quality of hydrogen, and the conversion rate of methanol is also significantly improved, reducing the waste of raw materials. More importantly, by combining glucose modification and boron modification, the various properties of the CuZnAl catalyst are synergistically improved, making the performance of the catalyst more superior. In addition, the present invention further improves the dosage range of boron modification through a specific preparation method, which is conducive to large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A flow chart for preparation.

[0021] Figure 2 The results of the test of the catalyst prepared in Example 5 for hydrogen production by methanol reforming are shown in Figure A, and Figure B is the results of the cycle test, and Figure B is the results of the hydrogen production rate. DETAILED DESCRIPTION

[0022] The technical scheme of the present invention is described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0023] Example 1: This example provides the preparation of CuZnAl catalyst, referring to Figure 1 The preparation process of copper-aluminum-zinc catalyst.

[0024] Copper nitrate, zinc nitrate and aluminum nitrate were dissolved in 150 mL of distilled water at a molar ratio of 4:4:2.5. Subsequently, the mixture was stirred at room temperature and the pH was adjusted to 10.0 by adding 0.3 mol / L NaOH solution to obtain a precipitate. The mixture was aged at 60 °C for 8 h, then filtered and the precipitate was washed with deionized water to remove excess ions. The precursor was dried in an oven at 80 °C overnight to obtain the precursor. The dried precursor was calcined at 450 °C for 5 h to obtain the CuZnAl catalyst (i.e. Figure 1 copper-aluminum-zinc catalyst in the

[0025] Example 2: This example provides the preparation of a general boron-modified CuZnAl catalyst.

[0026] The required amount of boric acid was dissolved in 150 mL of deionized water to prepare a boric acid aqueous solution. The CuZnAl catalyst prepared in Example 1 was then placed in the boric acid aqueous solution and stirred for 3 hours using a mechanical stirrer. The mass ratio of boric acid to CuZnAl catalyst in the boric acid aqueous solution was 4:10. The water was then removed under continuous stirring and heating to 60°C, and finally dried in an oven at 80°C overnight to obtain a precursor.

[0027] The dried precursor was calcined at 450°C for 5 h to obtain a general boron-modified CuZnAl catalyst.

[0028] Example 3: This example provides the preparation of excess boron-modified CuZnAl catalyst.

[0029] This embodiment is the same as Embodiment 2, except that the mass ratio of boric acid to CuZnAl catalyst in the boric acid aqueous solution is 8:10.

[0030] Example 4: This example provides the preparation of glucose-modified CuZnAl catalyst.

[0031] The required amount of glucose monohydrate was dissolved in 150 mL of deionized water to prepare a glucose aqueous solution. The CuZnAl catalyst prepared in Example 1 was then placed in the glucose aqueous solution, and the mass ratio of glucose monohydrate to the CuZnAl catalyst in the glucose aqueous solution was 3:10. A hydrothermal reaction was then carried out at 200°C for 2 hours, and after filtration, it was dried in an oven at 80°C overnight to obtain a precursor (i.e., C-CuZnAl catalyst).

[0032] The dried precursor was calcined at 450°C for 5 h to obtain the glucose-modified CuZnAl catalyst.

[0033] Example 5: This example provides the preparation of a boron-modified catalyst.

[0034] Reference Figure 1According to the preparation process in, the required amount of boric acid is dissolved in 150 mL of deionized water to prepare a boric acid aqueous solution. Then the C-CuZnAl catalyst prepared in Example 4 is placed in the boric acid aqueous solution and stirred for 3 hours with a mechanical stirrer. The mass ratio of boric acid to CuZnAl catalyst in the boric acid aqueous solution is 4:10. Then, the water is removed under continuous stirring and heating to 60°C, and finally dried in an oven at 80°C overnight to obtain a precursor.

[0035] The dried precursor was calcined at 450 °C for 5 h to obtain a boron-modified catalyst (i.e. Figure 1 B-modified C-CuZnAl catalyst in ).

[0036] Example 6: This example is the same as Example 5, except that the mass ratio of boric acid in the boric acid aqueous solution to the CuZnAl catalyst is 1:10, and the mass ratio of glucose monohydrate in the glucose aqueous solution to the CuZnAl catalyst is 5:10; the hydrothermal reaction time is 1 hour, the temperature is 150°C; and the immersion time is 4 hours.

[0037] Example 7: This example is the same as Example 5, except that the mass ratio of boric acid in the boric acid aqueous solution to the CuZnAl catalyst is 8:10, and the mass ratio of glucose monohydrate in the glucose aqueous solution to the CuZnAl catalyst is 1:10; the hydrothermal reaction time is 4 hours, the temperature is 300°C; and the immersion time is 1 hour.

[0038] Test Example: This test example tests the effect of the catalysts prepared in Examples 1 to 7 on methanol reforming to produce hydrogen.

[0039] The catalytic performance of methanol steam reforming was determined in a fixed-bed flow quartz reactor with an inner diameter of 6 mm and a length of 300 mm at atmospheric pressure. In the test, 0.4 g of catalyst (40-60 mesh) and 0.4 g of quartz sand (40-60 mesh) were thoroughly mixed and placed in the reactor between two quartz wool plugs. The gas hourly space velocity (GHSV) was 9000 mL / (g·h), and nitrogen was used as the balance gas and internal standard gas. Before the measurement, the catalyst was reduced in the reactor at 300 °C for 2 h with a flow rate of 60 mL / min and a flow rate of 5% H 2 / Ar (volume ratio). Then, a mixture of water and methanol in a molar ratio of 1:3 was preheated to 150°C and injected into the reactor through an HPLC pump at a flow rate of 0.03 mL / min. The pipeline between the reactor and the gasifier was insulated at different temperatures by a heating belt. The minimum hydrogen production temperature (the temperature when the hydrogen production rate is higher than 60 μmol / (g·s)), the hydrogen production rate at 250°C, CO selectivity, methanol conversion rate and the number of cycles (the number of times the hydrogen production rate decays by more than 10% relative to the first reaction) were measured. The catalyst prepared in Example 5 was subjected to a cycle test at 250°C. The relationship between temperature and hydrogen production rate is as follows: Figure 2 As shown, the commercial catalyst is the CuZnAl catalyst prepared in Example 1. The test results are shown in Table 1.

[0040] Table 1: Catalyst performance test results

[0041] Comparing Example 1 and Example 2, it can be seen that boron doping is beneficial to reducing the hydrogen production temperature of the CuZnAl catalyst, improving the hydrogen production rate, CO selectivity, methanol conversion rate and the number of cycles. Comparing Example 2 and Example 3, it can be seen that excessive boron doping will cause the performance of the catalyst to be impaired. Comparing Example 1 and Example 4, it can be seen that the modification of glucose is beneficial to improving the hydrogen production rate, CO selectivity and methanol conversion rate of the CuZnAl catalyst, but there is a greater adverse effect on the number of cycles, which may be because the catalyst modified by glucose is more likely to form carbonaceous deposition on the surface, resulting in the catalyst being more easily deactivated. It can be seen from Examples 5 to 7 that the present invention, by combining glucose modification and boron modification, synergistically reduces the hydrogen production temperature and CO selectivity of the CuZnAl catalyst, improves the hydrogen production rate, methanol conversion rate and the number of cycles, especially in CO selectivity, reaching less than 10ppm. On the other hand, the present invention, by combining glucose modification and boron modification, the dosage range of boron modification is further improved, which is conducive to large-scale industrial production.

[0042] The embodiments described above are part of the embodiments of the present invention, but not all of them. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but only represents selected embodiments of the present invention. All other embodiments obtained without creative work and related deductions and substitutions made by ordinary technicians in the field under the conditions of the concept of the present invention belong to the scope of protection of the present invention.

Claims

1. A method for preparing a boron-modified catalyst, characterized in that: include: The CuZnAl catalyst and glucose solution are hydrothermally reacted to obtain a C-CuZnAl catalyst, the C-CuZnAl catalyst is impregnated with a solution containing a boron source, then dried, and finally calcined to obtain a boron-modified catalyst.

2. The method for preparing a boron-modified catalyst according to claim 1, characterized in that: The hydrothermal reaction time is 1-4 hours, and the temperature is 150-300°C.

3. The method for preparing a boron-modified catalyst according to claim 1, characterized in that: The impregnation conditions include: immersing the C-CuZnAl catalyst in the solution containing the boron source for 1 to 4 hours, and continuously stirring.

4. The method for preparing a boron-modified catalyst according to claim 1, characterized in that: The solution containing a boron source is an aqueous solution of boric acid.

5. The method for preparing a boron-modified catalyst according to claim 4, characterized in that: The mass ratio of the boric acid in the boric acid aqueous solution to the C-CuZnAl catalyst is 1-8:

10.

6. The method for preparing a boron-modified catalyst according to claim 1, characterized in that: The glucose solution is a glucose aqueous solution.

7. The method for preparing a boron-modified catalyst according to claim 6, characterized in that: The mass ratio of glucose monohydrate in the glucose aqueous solution to the CuZnAl catalyst is 1-5:

10.

8. The method for preparing a boron-modified catalyst according to claim 1, characterized in that: The CuZnAl catalyst is prepared by a co-precipitation method using a precursor solution containing a copper source, a zinc source and an aluminum source.

9. A boron-modified catalyst, characterized in that: The catalyst is prepared by the method for preparing a boron-modified catalyst according to any one of claims 1 to 8.

10. Use of the boron-modified catalyst according to claim 9 in hydrogen production by methanol reforming.

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