Activated carbon supported metal catalyst based on ammonia-assisted microwave reaming as well as preparation method and application of activated carbon supported metal catalyst

Abstract

The invention belongs to the technical field of catalyst preparation, and discloses an activated carbon supported metal catalyst based on ammonia-assisted microwave reaming as well as a preparation method and application of the activated carbon supported metal catalyst. According to the activated carbon supported metal catalyst prepared through an ammonia water complexing route, metal ions can be more uniformly dispersed on an activated carbon carrier, the average size of particles is smaller, the dispersity of metal particles on the surface is high, and the catalyst has good catalytic activity. The metal precursor is dissolved in ammonia water, so that the defect of poor water solubility of partial metal is overcome, and the universality of catalyst preparation is expanded. Microwave heating is adopted for roasting and reduction, so that the catalyst preparation time is greatly shortened, and the energy consumption is reduced. In addition, the ammonia-assisted impregnation process is combined, the content of mesopores and macropores in the activated carbon metal catalyst is obviously increased, and a good pore expanding effect is achieved. The activated carbon supported metal catalyst shows better activity, selectivity and stability in high-carbon ketone synthesis reaction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst preparation, in particular to an activated carbon supported metal catalyst based on ammonia assisted microwave pore expansion and a preparation method and application thereof. BACKGROUND

[0002] High-carbon ketone compounds are key skeleton molecules in fine chemical industry, fragrances / flavors, medicines, pesticides and high-end solvents. The long chain or aryl structure on both sides of the carbonyl group of the product endows it with special volatility, liposolubility and reaction activity site. The current industrial route is still mainly based on alcohol oxidation, which has the disadvantages of many steps, high waste, unstable reaction selectivity, etc. Therefore, the development of one-step, high-atom economy catalyst system has become the key to the upgrading of high-carbon ketone technology.

[0003] Using carbon materials as carriers to load metal particles can not only improve the catalytic activity of carbon-based materials, but also prevent the dissolution of metal ions. Among them, activated carbon has a rich surface oxygen-containing functional group, a relatively high specific surface area and a low cost, and is a relatively ideal carbon carrier material for preparing activated carbon supported metal catalysts. However, in the preparation process of traditional activated carbon metal catalysts, water is usually used as the impregnation solvent, which will inevitably cause the prepared supported metal catalyst to have large particle size and low metal dispersion, resulting in poor catalytic performance of the catalyst. Therefore, it is of great significance to optimize the dispersion of metal particles on the surface of activated carbon metal catalysts through process improvement for catalytic reactions.

[0004] On the other hand, the traditional electric furnace calcination process is not very friendly to activated carbon supported metal catalysts, mainly because the electric furnace has a slow heating rate and a large temperature difference between the inner and outer walls of the activated carbon. Prolonged exposure to this environment can cause the collapse of the activated carbon pores, reduce the specific surface area of the catalyst, and cause the catalytic performance of the catalyst to decrease.

[0005] Therefore, there is an urgent need for a catalyst preparation method that can effectively dissolve metal precursor salt to improve the metal dispersion of the catalyst, effectively improve the activated carbon carrier pores, and not damage the carrier pores. SUMMARY

[0006] The present application relates to the technical field of catalyst preparation, in particular to an activated carbon supported metal catalyst based on ammonia assisted microwave pore expansion and a preparation method and application thereof.

[0007] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions: The application provides a preparation method of an activated carbon supported metal catalyst based on ammonia assisted microwave reaming, comprising the following steps: (1) mixing nickel salt and copper salt with ammonia water to obtain a complex solution; (2) adding an activated carbon carrier to the complex solution for mixing and standing to obtain a dispersion liquid of a catalyst precursor; (3) drying the dispersion liquid of the catalyst precursor to obtain a catalyst precursor; (4) roasting the catalyst precursor under microwave assistance to obtain a roasted catalyst precursor; (5) reducing the roasted catalyst precursor under microwave assistance to obtain an activated carbon supported metal catalyst.

[0008] Further, in the preparation method, the nickel salt in step (1) and the copper salt in step (1) are independently formate, acetate, nitrate, acetylacetone salt, sulfate, chloride, hydroxide or basic carbonate; The mass concentration of the ammonia water in step (1) is 5-20%.

[0009] Further, in the preparation method, the activated carbon carrier in step (2) is nutshell activated carbon, wood activated carbon, coal activated carbon or synthetic resin activated carbon, and the specific surface area of the activated carbon carrier in step (2) is 800-2000 m 2 / g.

[0010] Further, in the preparation method, the mass ratio of the activated carbon carrier in step (2), the nickel element in the nickel salt in step (1) and the copper element in the copper salt in step (1) is 100:1-10:1.

[0011] Further, in the preparation method, the mass ratio of the activated carbon carrier in step (2) to the volume of the ammonia water in step (1) is 50-200 g:200-400 mL.

[0012] Further, in the preparation method, the temperature of the mixing in step (2) is 15-25 DEG C, the time of the mixing in step (2) is 2-6 h, and the time of the standing in step (2) is 8-12 h.

[0013] Further, in the preparation method, the total microwave power of the microwave assistance in step (4) is ≤5 kW, and the microwave frequency of the microwave assistance in step (4) is 2450 MHz. The roasting temperature in step (4) is 200-400 DEG C, and the roasting time in step (4) is 1-6 h.

[0014] Further, in the preparation method, the total microwave power of the microwave-assisted condition in step (5) is less than or equal to 2 kW, and the microwave frequency of the microwave-assisted condition in step (5) is 2450 MHz. The reducing atmosphere in step (5) is H2 or a mixture of H2 and N2, the reducing temperature in step (5) is 300-600 DEG C, and the reducing time in step (5) is 1-6 hours.

[0015] The application further provides an activated carbon-supported metal catalyst.

[0016] The application further provides an application of the activated carbon-supported metal catalyst in catalyzing alcohol ketone condensation coupling to prepare high-carbon ketones.

[0017] According to the technical solution, compared with the prior art, the application has the following beneficial effects: (1) The preparation method of the application forms a metal precursor solution by pre-complexing a metal salt with ammonia water, and then impregnates the activated carbon, which is different from the traditional water solvent treatment method, to obtain an activated carbon-supported metal catalyst, which is used in alcohol ketone condensation coupling to prepare high-carbon ketone compounds. The metal ions of the activated carbon-supported metal catalyst prepared by the ammonia water complexing route can be more uniformly dispersed on the activated carbon carrier, the average size of the particles is smaller, the dispersion degree of the metal particles on the surface is high, the loading efficiency and the number of active sites of the catalyst are improved, and the catalyst has good catalytic activity. Dissolving the metal precursor in ammonia water effectively overcomes the poor water solubility of some metals and expands the universality of catalyst preparation.

[0018] (2) In the implementation process of the application, microwave heating is used in the calcination step and the reduction step, which greatly shortens the catalyst preparation time and reduces the energy consumption. Moreover, in combination with the ammonia water assisted impregnation process, the content of large pores in the prepared activated carbon metal catalyst is significantly improved, which plays a good hole expansion role.

[0019] (3) The activated carbon-supported metal catalyst prepared by the application has better activity, selectivity and stability in the synthesis of high-carbon ketones. DETAILED DESCRIPTION

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description.

[0021] Figure 1 The HRTEM images of sample A1 in Example 1 and sample B1 in Comparative Example 1. DETAILED DESCRIPTION

[0022] The application provides a preparation method of an activated carbon-supported metal catalyst based on ammonia water assisted microwave hole expansion, which comprises the following steps: (1) mixing a nickel salt, a copper salt and ammonia water to obtain a complex solution; (2) adding an activated carbon carrier to the complex solution and mixing, and standing to obtain a dispersion liquid of a catalyst precursor; (3) drying the dispersion liquid of the catalyst precursor to obtain a catalyst precursor; (4) under the condition of microwave assistance, calcining the catalyst precursor to obtain a calcined catalyst precursor; (5) under the condition of microwave assistance, reducing the calcined catalyst precursor to obtain an activated carbon supported metal catalyst.

[0023] In the present application, the nickel salt in step (1) and the copper salt in step (1) are independently preferably formate, acetate, nitrate, acetylacetone salt, sulfate, chloride, hydroxide or basic carbonate, further preferably acetylacetone salt, sulfate, chloride, hydroxide or basic carbonate, and more preferably acetylacetone salt. The anion of the nickel salt is preferably the same as the anion of the copper salt.

[0024] In the present application, the mass concentration of the ammonia water in step (1) is preferably 5-20%, further preferably 10-18%, and more preferably 15%.

[0025] In the present application, the activated carbon carrier in step (2) is preferably nutshell activated carbon, wood activated carbon, coal activated carbon or synthetic resin activated carbon, further preferably nutshell activated carbon or wood activated carbon, and more preferably wood activated carbon.

[0026] In the present application, the specific surface area of the activated carbon carrier in step (2) is preferably 800-2000 m 2 / g, further preferably 1000-1800 m 2 / g, and more preferably 1200-1500 m 2 / g.

[0027] In the present application, the mass ratio of the activated carbon carrier in step (2), the nickel element in the nickel salt in step (1) and the copper element in the copper salt in step (1) is preferably 100:1-10:1, further preferably 100:3-7:1, and more preferably 100:5:1.

[0028] In the present application, the ratio of the mass of the activated carbon carrier in step (2) to the volume of the ammonia water in step (1) is preferably 50-200 g:200-400 mL, further preferably 100-150 g:200-300 mL, and more preferably 100 g:200 mL.

[0029] In the present application, the temperature of the mixing in step (2) is preferably 15-25℃, further preferably 20-25℃, and more preferably 25℃; the time of the mixing in step (2) is preferably 2-6h, further preferably 4-6h, and more preferably 6h.

[0030] In the present application, the time of the standing in step (2) is preferably 8-12h, further preferably 9-11h, and more preferably 10h.

[0031] In the present application, the temperature of the drying in step (3) is preferably 80-120℃, further preferably 100-120℃, and more preferably 120℃. The time of the drying in step (3) is not limited, and the drying is performed until the catalyst precursor reaches a constant weight.

[0032] In the present application, the total microwave power of the microwave-assisted condition in step (4) is preferably ≤5kW, and the microwave frequency of the microwave-assisted condition in step (4) is preferably 2450MHz.

[0033] In the present application, the temperature of the calcination in step (4) is preferably 200-400℃, further preferably 300-400℃, and more preferably 400℃; the time of the calcination in step (4) is preferably 1-6h, further preferably 2-5h, and more preferably 3h.

[0034] In the present application, the microwave-assisted condition during the calcination in step (4) is specifically as follows: there are totally 5 microwave emission modules, and each microwave module has a maximum power of 1kW; taking the temperature of the calcination of 400℃ as an example, the program temperature rising condition includes: using 3 microwave emission modules, all 500W, rising the temperature to 60℃ in 0.5h; using 5 microwave emission modules, 3 of which are 500W and 2 of which are 500W, rising the temperature to 120℃ in 1h; using 5 microwave emission modules, 3 of which are 600W and 2 of which are 500W, rising the temperature to 200℃ in 0.5h; using 5 microwave emission modules, 3 of which are 800W and 2 of which are 500W, rising the temperature to 300℃ in 0.5h; using 5 microwave emission modules, 3 of which are 1000W and 2 of which are 500W, rising the temperature to 400℃ in 0.5h.

[0035] In the present application, the total microwave power of the microwave-assisted condition in step (5) is preferably ≤2kW; and the microwave frequency of the microwave-assisted condition in step (5) is preferably 2450MHz.

[0036] In the present application, the reducing atmosphere in step (5) is preferably H2 or H2+N2 mixed gas, further preferably H2+N2 mixed gas; in the H2+N2 mixed gas, the volume ratio of H2 to N2 is preferably 1:20-20:80, further preferably 1:10-20:80, more preferably 20:80; the temperature of the reduction in step (5) is preferably 300-600℃, further preferably 400-550℃, more preferably 500℃; the time of the reduction in step (5) is preferably 1-6h, further preferably 1-3h, more preferably 2h.

[0037] In the present application, the microwave-assisted conditions during the reduction in step (5) are specifically as follows: taking the temperature of the reduction as 500℃, the programmed temperature rising conditions include: 2000Wx80%, 1h to 300℃; 2000Wx90%, 1h to 500℃.

[0038] The present application further provides an activated carbon-supported metal catalyst.

[0039] The present application further provides an application of the activated carbon-supported metal catalyst in catalyzing alcohol ketone condensation coupling to prepare high-carbon ketones.

[0040] In the present application, the method for catalyzing alcohol ketone condensation coupling to prepare high-carbon ketones is not limited, and the method well known to those skilled in the art can be adopted.

[0041] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present application.

[0042] Embodiment 1

[0043] 23.04g of nickel acetylacetone (purity 95%, 5g of Ni) and 4.25g of copper acetylacetone (purity 97%, 1g of Cu) were weighed and dissolved in 200mL of 15% ammonia water solution to prepare a nickel-copper precursor solution; the precursor solution was impregnated into 100g of dry wooden activated carbon carrier (AC, specific surface area 1380m 2 / g (manufactured by Fujian Yuanli Activated Carbon Co., Ltd.), stirred at 25℃ for 6 hours, allowed to stand for 10 hours, dried in a 120℃ oven to constant weight, and then calcined in a microwave oven at 400℃ for 3 hours. The microwave temperature program was as follows: microwave frequency 2450MHz, 500W×3—60℃—0.5h, 500W×3+500W×2—120℃—1h, 600W×3+500W×2—200℃—0.5h, 800W×3+500W×2—300℃—0.5h, 1000W×3+500W×2—400℃—0.5h. The calcined loaded metal carrier was then hydrogenated and reduced in a microwave oven at 500℃ under a reducing atmosphere of 20% H2 / 80%. The N2 mixture was reduced for 2 hours, and the microwave temperature program was as follows: microwave frequency 2450MHz, 2000W×80%—300℃—1h, 2000W×90%—500℃—1h, to obtain an activated carbon-supported metal catalyst, denoted as A1.

[0044] Example 2

[0045] Weigh 8.20g of nickel hydroxide (61% Ni, 5g Ni) and 1.63g of copper hydroxide (94% purity, 1g Cu), and dissolve them in 200mL of 15% ammonia solution to prepare a nickel-copper precursor solution. Impregnate 100g of dry wood-based activated carbon carrier (specific surface area 1380m²) with the precursor solution. 2 / g, manufactured by Fujian Yuanli Activated Carbon Co., Ltd., was stirred at 25℃ for 6 hours, allowed to stand for 10 hours, and then dried in a 120℃ oven to constant weight. It was then calcined in a microwave device at 400℃ for 3 hours, with the microwave temperature program being the same as in Example 1. The calcined supported metal carrier was then hydrogenated and reduced in a microwave device at 500℃. The reduction atmosphere was a 20% H2 / 80% N2 mixture, and the reduction time was 2 hours. The microwave temperature program for reduction was the same as in Example 1, resulting in an activated carbon supported metal catalyst, denoted as A2.

[0046] Example 3

[0047] Weigh 22.91g of basic nickel carbonate (46.627% purity, 5g Ni) and 1.85g of basic copper carbonate (54.196% Cu, 1g Cu), and dissolve them in 200mL of 15% ammonia solution to prepare a nickel-copper precursor solution. Impregnate the precursor solution onto 100g of dry wood-based activated carbon carrier (specific surface area 1380m²). 2A3.

[0048] Comparative Example 1

[0049] 23.04 g of nickel acetylacetonate (purity 95%, 5 g of Ni) and 4.25 g of copper acetylacetonate (purity 97%, 1 g of Cu) were dissolved in 200 mL of deionized water to prepare a nickel-copper precursor solution; the precursor solution was impregnated onto 100 g of dried wooden activated carbon carriers (specific surface area 1380 m 2 / g, Fujian Yuanli Activated Carbon Co., Ltd.) at 25°C for 6 h, and then left to stand for 10 h; the impregnated carriers were placed in an oven at 120°C until constant weight, and then calcined in a microwave device at 400°C for 3 h; the calcined carriers were subjected to hydrogen reduction in a microwave device at a reduction temperature of 500°C, a reduction atmosphere of 20% H2 / 80% N2, and a reduction time of 2 h, and the reduction microwave program was the same as that of Example 1, to obtain an activated carbon-supported metal catalyst, which was recorded as B1.

[0050] Comparative Example 2

[0051] 23.04 g of nickel acetylacetonate (purity 95%, 5 g of Ni) and 4.25 g of copper acetylacetonate (purity 97%, 1 g of Cu) were dissolved in 200 mL of deionized water to prepare a nickel-copper precursor solution; the precursor solution was impregnated onto 100 g of dried wooden activated carbon carriers (specific surface area 1380 m 2 / g, Fujian Yuanli Activated Carbon Co., Ltd.) at 25°C for 6 h, and then left to stand for 10 h; the impregnated carriers were placed in an oven at 120°C until constant weight, and then calcined in a microwave device at 400°C for 3 h; the calcined carriers were subjected to hydrogen reduction in a microwave device at a reduction temperature of 500°C, a reduction atmosphere of 20% H2 / 80% N2, and a reduction time of 2 h, and the reduction microwave program was the same as that of Example 1, to obtain an activated carbon-supported metal catalyst, which was recorded as B1.

[0052] The wooden activated carbon carriers AC, the catalysts A1-A3 prepared in Examples 1-3, and the catalysts B1-B2 prepared in Comparative Examples 1-2 were subjected to the following physicochemical property tests, and the results are shown in Table 1.

[0053] Table 1. Physicochemical properties of each sample prepared

[0054] As can be seen from Table 1, the specific surface areas of the catalysts A1-A3 and B1-B2 after calcination and reduction are lower than that of the raw activated carbon. The mesopore and macropore contents of the catalysts A1-A3 prepared by the ammonia-assisted microwave calcination strategy are significantly higher than that of the raw activated carbon. The average diameter of the metal on the prepared catalysts is below 11 nm, and the dispersion is good. The specific surface area of the B2 catalyst prepared by using a muffle as a calcination device is the lowest, decreasing to 793 m 2 -1 g. By comparing the pore volumes of the A1 catalyst and the B1 catalyst, it is found that the mesopore and macropore contents are significantly improved by using ammonia-assisted impregnation, and the average diameter of the metal on the catalyst is only 11 nm, which is significantly better than that of the water impregnation solvent. By comparing the A1 catalyst and the B2 catalyst, it is found that the specific surface area of the catalyst is significantly reduced after long-time calcination using a muffle, and the pore expansion capability of the microwave calcination using a muffle device is not as good as that of the microwave heating device.

[0055] Figure 1 Figure 1 shows the HRTEM images of the sample A1 (left) in Example 1 and the sample B1 (right) in Comparative Example 1. As can be seen from the figure, Figure 1 the dispersion of the A1 catalyst on the left is good, the particles are clear, and the size of the metal particles is significantly smaller than that of the B1 catalyst on the right. The B1 catalyst on the right uses water as the impregnation solvent, and the poorly soluble precursor salt is mixed and stacked with the metal salt. The imaging area has a large and uneven metal loading.

[0056] Experimental Example 1

[0057] In a 100 mL high-pressure reaction kettle, 0.05 g of activated carbon-supported metal catalyst, 20 mL of ethanol and 20 mL of acetone were sequentially added, and the reaction conditions were a rotation speed of 500 r / min, a reaction temperature of 175°C and a reaction time of 2 h. The qualitative analysis of the product was performed by using a Shimadzu GC-MS instrument, and the quantitative analysis of the product was performed by using a gas chromatograph. The catalysts A1-A3 and B1-B2 were tested, and the results are shown in Table 2.

[0058] Table 2. Results of the analysis of the reaction product by gas chromatography

[0059] ​The reaction conversion rate of acetone and the selectivity of 2-pentanone are analyzed to compare the catalytic performance of the catalysts, and the details are shown in Table 2. By comparing the reaction results of A1 and B1 catalysts, it is found that the A1 catalyst is significantly better than the B1 catalyst in terms of both the reaction conversion rate of acetone and the selectivity of the product 2-pentanone. Compared with the catalyst A2 prepared by microwave calcination, the performance of the catalyst B2 prepared by muffle calcination is obviously reduced. The catalysts A1-A3 prepared by the ammonia-assisted microwave calcination strategy all have good catalytic performance. That is, the catalysts provided by the present application not only ensure a relatively high conversion rate of alcohol ketone condensation reaction, but also ensure excellent selectivity of the product 2-pentanone.

[0060] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method for preparing activated carbon supported metal catalyst based on ammonia water assisted microwave reaming, characterized in that, The preparation method comprises the following steps: (1) mixing a nickel salt, a copper salt and ammonia water to obtain a complex solution; (2) adding an activated carbon carrier to the complex solution and mixing to obtain a dispersion liquid of a catalyst precursor; (3) drying the dispersion liquid of the catalyst precursor to obtain the catalyst precursor; (4) roasting the catalyst precursor under microwave assistance to obtain a roasted catalyst precursor; (5) reducing the roasted catalyst precursor under microwave assistance to obtain an activated carbon-supported metal catalyst.

2. The production method according to claim 1, characterized by, The nickel salt in step (1) and the copper salt in step (1) are independently formate, acetate, nitrate, acetylacetone salt, sulfate, chloride, hydroxide or basic carbonate; The mass concentration of the ammonia water in step (1) is 5-20%.

3. The production method according to claim 1 or 2, characterized by, The activated carbon carrier in step (2) is nutshell activated carbon, wooden activated carbon, coal activated carbon or synthetic resin activated carbon, and the specific surface area of the activated carbon carrier in step (2) is 800-2000 m 2 / g.

4. The preparation method according to claim 3, characterized in that, The mass ratio of the activated carbon carrier in step (2), the nickel element in the nickel salt in step (1) and the copper element in the copper salt in step (1) is 100:1-10:

1.

5. The preparation method according to claim 4, characterized in that, The ratio of the mass of the activated carbon carrier in step (2) to the volume of the ammonia water in step (1) is 50-200g:200-400mL.

6. The method of claim 1, wherein, The temperature of the mixing in step (2) is 15-25℃, the time of the mixing in step (2) is 2-6h, and the time of the standing in step (2) is 8-12h.

7. The preparation method according to claim 1, characterized in that, The total microwave power of the microwave assistance in step (4) is ≤5kW, and the microwave frequency of the microwave assistance in step (4) is 2450MHz. The roasting temperature in step (4) is 200-400℃, and the roasting time in step (4) is 1-6h.

8. The preparation method according to claim 1, characterized in that, The total microwave power of the microwave assistance in step (5) is ≤2kW, and the microwave frequency of the microwave assistance in step (5) is 2450MHz. The reducing atmosphere in step (5) is H2 or H2+N2 mixed gas, the reducing temperature in step (5) is 300-600℃, and the reducing time in step (5) is 1-6h.

9. The activated carbon-supported metal catalyst prepared by the preparation method in any one of claims 1-8.

10. The use of the activated carbon-supported metal catalyst in claim 9 in the catalytic preparation of high-carbon ketones by alcohol-ketone condensation coupling.

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