CuM / Cu-foam heterogeneous catalyst as well as preparation and application thereof

Abstract

The invention discloses a CuM / Cu-foam heterogeneous catalyst as well as preparation and application thereof. The catalyst is prepared by an in-situ deposition precipitation reduction method. The catalyst comprises a main active element, an auxiliary active element and a carrier, the main active element and the auxiliary active element are loaded on the carrier; the main active element is Cu, and the auxiliary active element is a metal element M; the carrier is foamy copper; the metal M is any one of Ce, Zn, Cs, Co, Fe and La. The problems that an existing Cu-based catalyst is low in Tman temperature and prone to agglomeration under the reaction condition, so that the catalytic performance is reduced, and the reaction is unstable are solved, the prepared catalyst has high catalytic activity at the reaction temperature of 180-240 DEG C, and the acetaldehyde selectivity reaches up to 98.3%; and the catalyst can continuously and stably run for more than 400 hours at the reaction temperature of 220 DEG C and the ethanol mass space velocity of 2.0 h <-1 >.

Description

TECHNICAL FIELD

[0001] The application relates to an ethanol aerobic catalyst, in particular to a CuM / Cu-foam heterogeneous catalyst and preparation and application thereof. BACKGROUND

[0002] The ethanol aerobic catalytic dehydrogenation process for preparing acetaldehyde is safe, simple in equipment, low in waste and high in atom utilization rate, and is an ideal process. The process can be realized through a fixed bed reactor, and has obvious advantages of small equipment investment and simple operation process.

[0003] However, the Cu-based catalysts commonly used in the prior art have low Tamman temperature, and are prone to agglomeration under reaction conditions, resulting in problems such as decline in catalytic performance and unstable reaction, which greatly limits the industrial application of the ethanol catalytic dehydrogenation process for preparing acetaldehyde. The existing document 1 (Tailoring the Surface Structure of Silicon Carbide Support for Copper Catalyzed Ethanol Dehydrogenation. ChemCatChem 2019, 11, 481) shows that the Cu / SiO2 / SiC catalyst has a high conversion rate (81.4%) at 280 DEG C, but the catalyst is deactivated after 8 hours of operation, and there is a problem that activity and long life cannot be simultaneously considered.

[0004] Therefore, developing a catalyst with high catalytic activity and long life at a lower temperature is an effective measure to solve the stability, and has a positive effect on promoting the development of the ethanol dehydrogenation process for preparing acetaldehyde. SUMMARY

[0005] The application aims to provide a CuM / Cu-foam heterogeneous catalyst and preparation and application thereof, and solves the problems of low Tamman temperature, easy agglomeration under reaction conditions, decline in catalytic performance and unstable reaction of the existing Cu-based catalyst. The prepared catalyst has the characteristics of high catalytic activity and good selectivity under relatively mild reaction temperature conditions, is beneficial to long-period operation of the catalyst, and has good industrial application potential.

[0006] In order to achieve the above-mentioned purpose, the application provides a CuM / Cu-foam heterogeneous catalyst, which is prepared by an in-situ deposition precipitation reduction method; the catalyst comprises a main active element, an auxiliary active element and a carrier; the main active element and the auxiliary active element are both loaded on the carrier; the main active element is Cu, and the auxiliary active element is a metal element M; the carrier is a foam copper; and the metal M is any one of Ce, Zn, Cs, Co, Fe and La.

[0007] The main influencing factors of the catalyst are the foam copper carrier and the addition of the metal element M of the auxiliary active element. By using the foam copper carrier, the loaded Cu nanoparticles are more stable, the catalyst has a more abundant pore structure, and has good mass and heat transfer effects. The addition of the metal element M of the auxiliary active element makes the loaded Cu better dispersed and not easy to agglomerate, further improving the stability of the catalyst.

[0008] Preferably, the mass ratio of the main active element, the auxiliary active element and the carrier is (2-10):(0.1-1):100.

[0009] Preferably, the length and width of the foam copper are both 0.3cm-0.7cm, and the thickness is 0.1cm-0.5cm.

[0010] The application provides a preparation method of the CuM / Cu-foam heterogeneous catalyst as described. (1) mixing a soluble copper salt solution and a soluble salt solution containing metal M to obtain a mixed solution, adding foam copper at 0°C and stirring; (2) dropping hydrazine hydrate solution or NaBH4 solution, continuously stirring, filtering, and drying at 80-120°C to obtain the CuM / Cu-foam heterogeneous catalyst.

[0011] Preferably, the soluble copper salt is copper nitrate, copper acetate, copper sulfate or copper chloride.

[0012] Preferably, the total concentration of Cu 2+ and metal M ions in the mixed solution is 0.1M-0.3M, and the mass ratio of Cu 2+ and metal M ions is (2-10):(0.1-1); and the concentration of the hydrazine hydrate solution or the NaBH4 solution is 2M-4M.

[0013] Preferably, the concentration of the hydrazine hydrate solution or the NaBH4 solution is 4-10 times the total concentration of Cu 2+ and metal M ions in the mixed solution.

[0014] The application provides application of the CuM / Cu-foam heterogeneous catalyst as described in the reaction of preparing acetaldehyde from ethanol dehydrogenation.

[0015] Preferably, the temperature of the reaction is 180°C-240°C.

[0016] Preferably, in the reaction, the mass space velocity of ethanol is 1h -1 -10 h -1 .

[0017] The application discloses a CuM / Cu-foam heterogeneous catalyst and a preparation method and application thereof, and solves the problems of low Tamman temperature, easy agglomeration under reaction conditions, and unstable reaction of the existing Cu-based catalyst, and has the following advantages. 1、 the application uses the foamed copper carrier to make the loaded Cu nanoparticles more stable, the catalyst has more abundant pore structure, and good mass and heat transfer effects are achieved; the addition of the auxiliary active element metal element M enables the loaded Cu to be better dispersed and not prone to agglomeration, and the catalyst stability is further improved.

[0018] 2、 the catalyst has high catalytic activity under a reaction temperature of 180 DEG C to 240 DEG C; has high acetaldehyde selectivity, up to 98.3%; under a reaction temperature of 220 DEG C, an ethanol mass space velocity of 2.0 h -1 , and a hydrogen pressure of 4.0 MPa, the catalyst can be continuously and stably operated for more than 400 hours. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the application will be clearly and completely described below; obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0020] The manufacturers, models and specifications of the fixed-bed reactors involved in the following embodiments are as follows: The manufacturer is Quzhou Wade Instrument Co., Ltd., and the model is high-temperature fixed-bed catalyst evaluation device VDRT-200SMT.

[0021] Embodiment 1 A preparation method of a CuM / Cu-foam heterogeneous catalyst, and the method comprises the following steps: (1) 10 mmol of copper nitrate and 0.5 mmol of cerium nitrate are weighed and dissolved in 100 mL of water, and then the mixture is placed in an ice bath, 10 grams of foamed copper with a size of 0.5 cm*0.5 cm and a thickness of 0.1 cm is added, and stirring is performed for 3 hours; (2) then, 20 mL of an aqueous solution containing 50 mmol of NaBH4 is added dropwise, and stirring is continuously performed for 5 hours; then, the foamed copper loaded with active metals is filtered and dried at 100 DEG C for 4 hours to obtain a catalyst, which is denoted as CAT-1.

[0022] Embodiment 2 A preparation method of a CuM / Cu-foam heterogeneous catalyst, and the method is different from that in Embodiment 1. In step (1), 10 mmol of copper nitrate, 0.5 mmol of cerium nitrate was adjusted to 10 mmol of copper acetate, 0.5 mmol of iron nitrate, and the stirring for 3 hours was adjusted to stirring for 5 hours; In step (2), 20 mL of an aqueous solution containing 50 mmol of NaBH4was adjusted to 20 mL of an aqueous solution containing 50 mmol of hydrazine hydrate, stirring for 5 hours was adjusted to stirring for 10 hours, and drying at 100°C for 4 hours was adjusted to drying at 120°C for 3 hours to obtain a catalyst, denoted as CAT-2.

[0023] Example 3 A method for preparing a CuM / Cu-foam heterogeneous catalyst was the same as that of Example 2, except that: In step (1), 10 mmol of copper acetate, 0.5 mmol of iron nitrate was adjusted to 10 mmol of copper chloride, 1.0 mmol of zinc nitrate, the thickness of the copper foam was adjusted from 0.1 cm to 0.5 cm, and stirring for 5 hours was adjusted to stirring for 3 hours. In step (2), 20 mL of an aqueous solution containing 50 mmol of hydrazine hydrate was adjusted to 30 mL of an aqueous solution containing 100 mmol of hydrazine hydrate, and stirring for 10 hours was adjusted to stirring for 5 hours to obtain a catalyst, denoted as CAT-3.

[0024] Example 4 A method for preparing a CuM / Cu-foam heterogeneous catalyst was the same as that of Example 1, except that: In step (1), 10 mmol of copper nitrate, 0.5 mmol of cerium nitrate was adjusted to 10 mmol of copper sulfate, 0.5 mmol of cesium nitrate, and the size of the copper foam was adjusted from 0.5 cm x 0.5 cm to 0.3 cm x 0.3 cm. In step (2), 20 mL of an aqueous solution containing 50 mmol of NaBH4was adjusted to 30 mL of an aqueous solution containing 105 mmol of hydrazine hydrate, and drying at 100°C for 4 hours was adjusted to drying at 80°C for 5 hours to obtain a catalyst, denoted as CAT-4.

[0025] Example 5 A method for preparing a CuM / Cu-foam heterogeneous catalyst was the same as that of Example 4, except that: In step (1), 10 mmol of copper sulfate, 0.5 mmol of cesium nitrate was adjusted to 10 mmol of copper acetate, 0.17 mmol of cobalt nitrate, and 10 grams of copper foam with a size of 0.3 cm x 0.3 cm and a thickness of 0.1 cm was adjusted to 10 grams of copper foam with a size of 0.7 cm x 0.7 cm and a thickness of 0.3 cm. In step (2), the 30 mL aqueous solution containing 105 mmol of hydrazine hydrate was adjusted to a 20 mL aqueous solution containing 45 mmol of hydrazine hydrate to obtain the catalyst, denoted as CAT-5.

[0026] Example 6 The preparation method of the CuM / Cu-foam heterogeneous catalyst is the same as that of Example 1, except that: In step (1), the 10 mmol of copper nitrate and 0.5 mmol of cerium nitrate were adjusted to 10 mmol of copper acetate and 0.5 mmol of lanthanum nitrate, the thickness of the copper foam was adjusted from 0.1 cm to 0.2 cm, and the stirring time was adjusted from 3 hours to 4 hours; In step (2), the amount of NaBH4 was adjusted from 50 mmol to 70 mmol, the stirring time was adjusted from 5 hours to 8 hours, and the drying time was adjusted from 4 hours to 5 hours to obtain the catalyst, denoted as CAT-6.

[0027] Example 7 The preparation method of the CuM / Cu-foam heterogeneous catalyst is the same as that of Example 6, except that: In step (1), the 0.5 mmol of lanthanum nitrate was adjusted to 0.15 mmol of zinc nitrate; In step (2), the amount of NaBH4 was adjusted from 70 mmol to 60 mmol; The catalyst was obtained by the same operation as Example 6, denoted as CAT-7.

[0028] Example 8 The preparation method of the CuM / Cu-foam heterogeneous catalyst is the same as that of Example 7, except that: In step (1), the 0.15 mmol of zinc nitrate was adjusted to 0.5 mmol of zinc nitrate; The catalyst was obtained by the same operation as Example 7, denoted as CAT-8.

[0029] Example 9 The preparation method of the CuM / Cu-foam heterogeneous catalyst is the same as that of Example 7, except that: In step (1), the 0.15 mmol of zinc nitrate was adjusted to 1.0 mmol of zinc nitrate; The catalyst was obtained by the same operation as Example 7, denoted as CAT-9.

[0030] Example 10 The preparation method of the CuM / Cu-foam heterogeneous catalyst is the same as that of Example 7, except that: In step (1), 0.15 mmol of zinc nitrate was adjusted to 1.5 mmol of zinc nitrate; The catalyst was obtained by the same operation as in Example 7, and was recorded as CAT-10.

[0031] Example 11 A method for preparing a CuM / Cu-foam heterogeneous catalyst was the same as in Example 7, except that: In step (1), 10 mmol of copper acetate and 0.15 mmol of zinc nitrate dissolved in 100 mL of water were adjusted to 3.1 mmol of copper acetate and 0.5 mmol of zinc nitrate dissolved in 30 mL of water; In step (2), the amount of NaBH4 was adjusted from 60 mmol to 64 mmol; The catalyst was obtained by the same operation as in Example 7, and was recorded as CAT-12.

[0032] Example 12 A method for preparing a CuM / Cu-foam heterogeneous catalyst was the same as in Example 7, except that: In step (1), 10 mmol of copper acetate and 0.15 mmol of zinc nitrate dissolved in 100 mL of water were adjusted to 3.1 mmol of copper acetate and 0.5 mmol of zinc nitrate dissolved in 30 mL of water; In step (2), the amount of NaBH4 was adjusted from 60 mmol to 64 mmol; The catalyst was obtained by the same operation as in Example 7, and was recorded as CAT-12.

[0033] Conversion rate and selectivity test The catalysts of Examples 1-12 (2 g) were loaded into a fixed bed reactor, and the catalytic dehydrogenation of ethanol was carried out on the fixed bed at a reaction temperature of 240℃ and an ethanol mass space velocity of 10.0 h-1. -1 The conversion rate of ethanol and the selectivity of acetaldehyde were measured respectively after 24 h of reaction, and the results are shown in Table 1.

[0034] Table 1 Test results of catalytic performance of Examples 1-12 From Table 1, the catalysts of Examples 1-6 all have good reaction effects (240°C); Examples 7-12 are single-factor comparative examples, mainly changing the amount of added co-catalyst Zn, while Examples 8, 11 and 12 change the amount of added copper acetate, but the amount of water in the first step and the reducing agent sodium borohydride in the second step also change (relatively speaking, this is not the main factor). Comprehensive analysis, under the conditions of a reaction temperature of 240°C and a relatively high ethanol mass space velocity, the catalysts prepared in Examples 1-12 all have good reaction activity. For the CuZn / Cu-foam catalyst, with the increase of Cu loading (Examples 8, 11 and 12), the ethanol conversion rate increases from 17.6% to 28.5%, taking into account the cost comprehensive factors, the 10.0 mmol of copper acetate added in Example 8 is the best. From Examples 7-10, it can be seen that when the amount of Zn increases from 0.5 mmol to 1.0 mmol while the Cu content remains unchanged, the ethanol conversion rate also increases, but when the amount of zinc nitrate further increases, the ethanol conversion rate decreases, so Example 9 is determined to be the best catalyst in terms of economic efficiency and implementation effect.

[0035] 240°C mainly shows the reaction at a high ethanol space velocity, and the catalyst activity is better at a higher temperature (including Examples 7-10). Further performance testing of different Cu loadings of Examples 7-10 at a low temperature (180°C) also shows good reaction activity. The catalysts of Examples 7-10 are loaded in a fixed bed reactor, and the catalytic dehydrogenation of ethanol is carried out on the fixed bed, the reaction temperature is 180°C, the ethanol mass space velocity is 1.0 h -1 , and the ethanol conversion rate and the selectivity of acetaldehyde are measured respectively after 24 hours of reaction, and the results are shown in Table 2.

[0036] Table 2 Test results of the catalytic performance of Examples 7-10 From Table 2, it can be seen that the CuZn / Cu-foam catalysts of Examples 7-10 also have good ethanol dehydrogenation activity under low-temperature reaction conditions (180°C).

[0037] From Tables 1 and 2, it can be seen that the CAT-9 catalyst of Example 9 exhibits the best test results, followed by the CAT-12 catalyst of Example 12.

[0038] Example 2 Life test of the catalyst The catalyst CAT-9 prepared in Example 9 is tested for stability on a fixed bed, the reaction temperature of the catalytic dehydrogenation of ethanol is 220°C, the ethanol mass space velocity is 2.0 h -1 , and it is found that the catalyst can be continuously and stably operated for more than 400 hours, and the ethanol conversion rate and the selectivity of acetaldehyde at different reaction times are shown in Table 3.

[0039] Table 3 Results of life test of catalyst of Example 9 From Table 3, it can be seen that the catalyst CAT-9 prepared in Example 9 has good stability at a reaction temperature of 220℃ and a mass space velocity of 2.0 h -1 ethanol, and has good industrial application prospect.

[0040] Although the present application has been described in detail by the above preferred embodiments, it should be appreciated that the above description should not be considered as limiting the present application. Various modifications and substitutions to the present application will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present application should be defined by the appended claims.

Claims

1. A CuM / Cu-foam hetero-phase catalyst, characterized in that, The catalyst is prepared by in-situ deposition-precipitation reduction method; the catalyst comprises a main active element, an auxiliary active element and a carrier; the main active element and the auxiliary active element are both loaded on the carrier; The main active element is Cu, and the auxiliary active element is a metal element M; The carrier is foamed copper; The metal M is any one of Ce, Zn, Cs, Co, Fe and La.

2. The CuM / Cu-foam heterogeneous catalyst according to claim 1, characterized in that, The mass ratio of the main active element, the auxiliary active element and the carrier is (2-10):(0.1-1):

100.

3. The CuM / Cu-foam heterogeneous catalyst according to claim 1, characterized in that, The length and width of the foamed copper are both 0.3-0.7 cm, and the thickness is 0.1-0.5 cm.

4. A process for the preparation of a CuM / Cu-foam heterogeneous catalyst according to any one of claims 1 to 3, characterized in that, The method comprises: (1) mixing a soluble copper salt solution and a soluble salt solution containing the metal M to obtain a mixed solution, adding foamed copper at 0 ℃ and stirring; (2) dropping hydrazine hydrate solution or NaBH4 solution, continuously stirring, filtering, drying at 80-120 ℃ to obtain the CuM / Cu-foam heterogeneous catalyst.

5. The preparation method according to claim 4, characterized in that, The soluble copper salt is copper nitrate, copper acetate, copper sulfate or copper chloride.

6. The preparation method according to claim 4, characterized in that, The total concentration of Cu 2+ and metal M ions is 0.1 M to 0.3 M, and the mass ratio of Cu 2+ and metal M ions is (2 to 10) : (0.1 to 1); the concentration of the hydrazine hydrate solution or the NaBH4 solution is 2 M to 4 M.

7. The preparation method according to claim 6, characterized in that, The concentration of the hydrazine hydrate solution or NaBH4 solution is 4 to 10 times the total concentration of Cu 2+ and metal M ions in the mixed solution.

8. Application of the CuM / Cu-foam heterogeneous catalyst according to any one of claims 1-3 in a reaction of dehydrogenation of ethanol to acetaldehyde.

9. Use according to claim 8, characterized in that, The temperature of the reaction is 180-240 ℃.

10. Use according to claim 9, characterized in that, The mass space velocity of ethanol in the reaction is 1 h -1 -10 h -1 .

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