A copper-based catalyst, its preparation method and use

Abstract

The application discloses a copper-based catalyst and a preparation method and application thereof, and belongs to the technical field of catalysts. The copper-based catalyst provided by the application comprises a coating layer and a metal substrate, the coating layer is coated outside the metal substrate, the metal substrate contains CeO2 and Cu, and the coating layer contains nitrogen-doped carbon material. The nitrogen-doped carbon material NC is used as the coating layer to coat the metal substrate containing CeO2 and Cu, and the obtained copper-based catalyst Cu-CeO2@NC has excellent stability and excellent catalytic performance, and has good catalytic effect in alcohol catalytic dehydrogenation, especially in the reaction of glycerol catalytic dehydrogenation for preparing lactic acid, the glycerol conversion rate and lactic acid selectivity are high, in addition, the copper-based catalyst can be regenerated without high-temperature calcination, which is beneficial to realize the recycling of the catalyst, and the catalyst provided by the application has wide application in alcohol catalytic dehydrogenation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalysts, and particularly relates to a copper-based catalyst and a preparation method and application thereof. BACKGROUND

[0002] Lactic acid is an organic acid with high added value, and is widely used in the fields of cosmetics, medicine, food and agriculture. Lactic acid can also be used to synthesize polylactic acid, which is a biodegradable plastic and has a wide range of applications and broad market prospects. At present, lactic acid is mainly prepared by sugar fermentation method. It is still necessary to develop efficient and green chemical methods to produce lactic acid.

[0003] Biodiesel is a green energy, and in recent years the biodiesel industry has developed rapidly. In the process of preparing biodiesel, glycerol byproduct is produced, and glycerol is oversupplied in the market. Glycerol can be converted into lactic acid through catalytic dehydrogenation process, which is one of the potential routes for industrial production of lactic acid.

[0004] Supported Cu-based heterogeneous catalysts are widely used in the catalytic dehydrogenation of glycerol to prepare lactic acid under nitrogen atmosphere. Common supports include CNF, ZrO2, MgO, HAP, CeO2, ZIF-8 and rGO, among which the hydrothermal stability of the CeO2 support is better. There are documents that have reported CeO2-supported Cu, Co3O4 and AuCu nanoparticles catalyzing the dehydrogenation of glycerol to prepare lactic acid. However, the above catalysts need high-temperature calcination to realize the regeneration of the catalysts in the recycling experiment. Therefore, it is still necessary to develop efficient CeO2-modified Cu-based catalysts to catalyze the dehydrogenation of glycerol to prepare lactic acid. SUMMARY

[0005] In order to overcome the problems existing in the prior art, one of the purposes of the present application is to provide a copper-based catalyst which can realize regeneration without high-temperature calcination, and has excellent catalytic performance, good stability, high glycerol conversion rate and lactic acid selectivity in the reaction of catalytic dehydrogenation of glycerol to prepare lactic acid.

[0006] The second purpose of the present application is to provide a preparation method of the above-mentioned copper-based catalyst.

[0007] The third purpose of the present application is to provide an application of the above-mentioned copper-based catalyst in the catalytic dehydrogenation of alcohols.

[0008] In order to achieve the above-mentioned purposes, the technical solution adopted by the present application is as follows:

[0009] The first aspect of the present application provides a copper-based catalyst, which comprises a coating layer and a metal substrate, the coating layer is coated outside the metal substrate, the metal substrate contains CeO2 and Cu, and the coating layer contains nitrogen-doped carbon material.

[0010] Preferably, in the copper-based catalyst, the particle size of the metal matrix is 80-160 nm; more preferably, in the copper-based catalyst, the particle size of the metal matrix is 90-150 nm; and more preferably, in the copper-based catalyst, the particle size of the metal matrix is 100-120 nm.

[0011] Preferably, in the copper-based catalyst, Cu in the metal layer is loaded on CeO2.

[0012] The second aspect of the present application provides a preparation method of the copper-based catalyst of the first aspect of the present application, comprising the following steps: performing a solvothermal reaction on a surfactant, a carbon source, a nitrogen source, a copper salt and a cerium salt to obtain a CuCe-MOF precursor; and performing calcination on the CuCe-MOF precursor to obtain the copper-based catalyst.

[0013] Preferably, in the preparation method of the copper-based catalyst, the surfactant comprises polyvinylpyrrolidone, cetyltrimethylammonium bromide or a combination thereof; more preferably, in the preparation method of the copper-based catalyst, the surfactant is selected from polyvinylpyrrolidone.

[0014] Preferably, in the preparation method of the copper-based catalyst, the carbon source is selected from trimesic acid.

[0015] Preferably, in the preparation method of the copper-based catalyst, the nitrogen source is selected from an amine solvent; more preferably, in the preparation method of the copper-based catalyst, the amine solvent comprises N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC) or a combination thereof; and more preferably, in the preparation method of the copper-based catalyst, the amine solvent is selected from N,N-dimethylformamide.

[0016] Preferably, in the preparation method of the copper-based catalyst, the copper salt comprises at least one of copper nitrate, copper chloride or copper sulfate; more preferably, in the preparation method of the copper-based catalyst, the copper salt comprises copper nitrate, copper chloride or a combination thereof; and more preferably, in the preparation method of the copper-based catalyst, the copper salt is selected from copper nitrate.

[0017] Preferably, in the preparation method of the copper-based catalyst, the cerium salt comprises at least one of cerium nitrate, cerium chloride or cerium sulfate; more preferably, in the preparation method of the copper-based catalyst, the cerium salt comprises cerium nitrate, cerium chloride or a combination thereof; and more preferably, in the preparation method of the copper-based catalyst, the cerium salt is selected from cerium nitrate.

[0018] Preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant and the carbon source is 1:(0.8-2.2); more preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant and the carbon source is 1:(1-1.9); even more preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant and the carbon source is 1:(1.2-1.7).

[0019] Preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant and the nitrogen source is 1:(25-90); more preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant and the nitrogen source is 1:(30-80); even more preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant and the nitrogen source is 1:(40-70).

[0020] Preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant and the copper salt is 1:(1-2.5); more preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant and the copper salt is 1:(1.3-2.3); even more preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant and the copper salt is 1:(1.5-2).

[0021] Preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant and the cerium salt is 1:(0.8-1.7); more preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant and the cerium salt is 1:(0.95-1.5); even more preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant and the cerium salt is 1:(1-1.2).

[0022] Preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant, the carbon source, the nitrogen source, the copper salt and the cerium salt is 1:(0.8-2.2):(25-90):(1-2.5):(0.8-1.7); more preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant, the carbon source, the nitrogen source, the copper salt and the cerium salt is 1:(1-1.9):(30-80):(1.3-2.3):(0.95-1.5); even more preferably, in the preparation method of the copper-based catalyst, the mass ratio of the surfactant, the carbon source, the nitrogen source, the copper salt and the cerium salt is 1:(1.2-1.7):(40-70):(1.5-2):(1-1.2).

[0023] Preferably, the temperature of the solvothermal reaction in the preparation method of the copper-based catalyst is 70-150°C; more preferably, the temperature of the solvothermal reaction in the preparation method of the copper-based catalyst is 80-130°C; and even more preferably, the temperature of the solvothermal reaction in the preparation method of the copper-based catalyst is 90-120°C.

[0024] Preferably, the time of the solvothermal reaction in the preparation method of the copper-based catalyst is 10-60h; more preferably, the time of the solvothermal reaction in the preparation method of the copper-based catalyst is 12-50h; and even more preferably, the time of the solvothermal reaction in the preparation method of the copper-based catalyst is 18-30h.

[0025] Preferably, the atmosphere for calcination in the preparation method of the copper-based catalyst is an inert gas atmosphere; more preferably, the inert gas comprises at least one of nitrogen, argon or helium; and even more preferably, the inert gas is selected from nitrogen.

[0026] Preferably, the calcination temperature in the preparation method of the copper-based catalyst is 500-900°C; more preferably, the calcination temperature in the preparation method of the copper-based catalyst is 550-800°C; and even more preferably, the calcination temperature in the preparation method of the copper-based catalyst is 600-750°C.

[0027] Preferably, the calcination time in the preparation method of the copper-based catalyst is 0.5-5h; more preferably, the calcination time in the preparation method of the copper-based catalyst is 0.8-4h; and even more preferably, the calcination time in the preparation method of the copper-based catalyst is 1-3h.

[0028] Preferably, the polyvinylpyrrolidone, the trimesic acid, the copper salt, the cerium salt and the amine solvent are mixed before the solvothermal reaction in the preparation method of the copper-based catalyst.

[0029] Preferably, the mixing temperature for mixing the polyvinylpyrrolidone, the trimesic acid, the copper salt, the cerium salt and the amine solvent is 20-30°C; more preferably, the mixing temperature is 22-28°C; and even more preferably, the mixing temperature is 24-26°C.

[0030] Preferably, the mixing time for mixing the polyvinylpyrrolidone, the trimesic acid, the copper salt, the cerium salt and the amine solvent is 0.5-4h; more preferably, the mixing time is 0.8-3h; and even more preferably, the mixing time is 1-2h.

[0031] The third aspect of the present application provides a use of the copper-based catalyst of the first aspect of the present application in catalytic dehydrogenation of an alcohol.

[0032] Preferably, the use is catalytic dehydrogenation of an alcohol to produce lactic acid; more preferably, the use is catalytic dehydrogenation of glycerol to produce lactic acid.

[0033] Preferably, the use comprises the step of mixing an aqueous glycerol solution, the copper-based catalyst and a base in an inert gas atmosphere to produce the lactic acid.

[0034] Preferably, in the use, the inert gas comprises at least one of nitrogen, argon or helium; more preferably, in the method of producing the lactic acid, the inert gas is selected from nitrogen.

[0035] Preferably, in the use, the base is selected from alkali hydroxides.

[0036] Preferably, in the use, the base comprises at least one of sodium hydroxide, potassium hydroxide or calcium hydroxide; more preferably, in the use, the base comprises sodium hydroxide, potassium hydroxide or a combination thereof; more preferably, in the use, the base is selected from sodium hydroxide.

[0037] Preferably, in the use, the concentration of the aqueous glycerol solution is 1-35 wt%; more preferably, in the use, the concentration of the aqueous glycerol solution is 2-30 wt%; more preferably, in the use, the concentration of the aqueous glycerol solution is 5-20 wt%.

[0038] Preferably, in the use, the mass ratio of the aqueous glycerol solution to the copper-based catalyst is 1:(0.001-0.04); more preferably, in the use, the mass ratio of the aqueous glycerol solution to the copper-based catalyst is 1:(0.003-0.035); more preferably, in the use, the mass ratio of the aqueous glycerol solution to the copper-based catalyst is 1:(0.005-0.02).

[0039] Preferably, in the use, the molar ratio of glycerol to base is 1:(1-1.6); more preferably, in the use, the molar ratio of glycerol to base is 1:(1.01-1.5); more preferably, in the use, the molar ratio of glycerol to base is 1:(1.05-1.25).

[0040] Preferably, in the use, the catalytic reaction temperature is 150-250°C; more preferably, in the use, the catalytic reaction temperature is 170-230°C; more preferably, in the use, the catalytic reaction temperature is 180-220°C.

[0041] Preferably, in the application, the catalytic reaction time is 10-100 min; more preferably, in the application, the catalytic reaction time is 20-90 min; and more preferably, in the application, the catalytic reaction time is 30-60 min.

[0042] Preferably, in the application, the catalytic reaction pressure is 0.05-3 MPa; more preferably, in the application, the catalytic reaction pressure is 0.1-2 MPa; and more preferably, in the application, the catalytic reaction pressure is 0.5-1.5 MPa.

[0043] Preferably, in the application, the glycerol conversion rate is 90-100%; more preferably, in the application, the glycerol conversion rate is 92-100%; and more preferably, in the application, the glycerol conversion rate is 95-100%.

[0044] Preferably, in the application, the lactic acid selectivity is 72-87%; more preferably, in the application, the lactic acid selectivity is 75-85%; and more preferably, in the application, the lactic acid selectivity is 78-83%.

[0045] The present application has the following advantages:

[0046] The present application coats a metal substrate containing CeO2 and Cu with a nitrogen-doped carbon material NC to obtain a copper-based catalyst Cu-CeO2@NC, which has excellent stability and excellent catalytic performance, and is good in catalytic effect in alcohol catalytic dehydrogenation, especially in glycerol conversion rate and lactic acid selectivity in glycerol catalytic dehydrogenation to lactic acid. In addition, the copper-based catalyst can be regenerated without high-temperature calcination, which is conducive to the recycling of the catalyst. The catalyst provided by the present application has wide application in alcohol catalytic dehydrogenation.

[0047] Specifically, compared with the prior art, the present application has the following advantages:

[0048] 1. The present application stabilizes Cu-CeO2 nanoparticles by coating the Cu-CeO2 nanoparticles with NC, so that the copper-based catalyst Cu-CeO2@NC has excellent stability and can be recycled multiple times. The preparation method of the catalyst is simple, the raw material cost is low, and batch preparation is easy.

[0049] 2. The present application can regenerate the catalyst without high-temperature calcination, which can realize the recycling of the catalyst and effectively reduce the energy consumption in the production process.

[0050] 3、The application applies the copper-based catalyst Cu-CeO2@NC to the reaction of preparing lactic acid by catalytic dehydrogenation of glycerol, and the preparation method of lactic acid has the advantages of high glycerol conversion rate, high lactic acid selectivity, excellent catalyst stability and short reaction time, and has a good industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 It is a TEM characterization graph of the copper-based catalyst Cu-CeO2@NC.

[0052] Figure 2 It is an XRD characterization graph of the copper-based catalyst Cu-CeO2@NC.

[0053] Figure 3 It is an XRD characterization graph of the copper-based catalyst Cu-CeO2@NC after being used for 6 times. DETAILED DESCRIPTION

[0054] The content of the application is further illustrated in detail through specific examples. It should also be understood that the following examples are only used to further illustrate the application, and cannot be understood as limiting the protection scope of the application. Some non-essential improvements and adjustments made by those skilled in the art according to the principles set forth in the application all belong to the protection scope of the application. The following example specific process parameters are only one example in the appropriate range, that is, those skilled in the art can make appropriate choices within the scope through the description herein, and are not limited to the specific data of the following examples. The raw materials, reagents or devices used in the following examples and comparative examples are commercially available or can be obtained by known methods unless otherwise specified.

[0055] Catalyst preparation example

[0056] The preparation steps of the copper-based catalyst Cu-CeO2@NC are as follows:

[0057] 1) Synthesis of CuCe-MOF: 1.4 g of trimesic acid, 1.0 g of polyvinylpyrrolidone, 1.81 g of copper nitrate, 1.09 g of cerium nitrate and 60 mL of DMF were sequentially added into a 200 mL beaker, and then stirred at room temperature for 1.5 h to obtain a mixed solution. The mixed solution was transferred to a hydrothermal reaction kettle, and reacted at 100 DEG C for 24 h. Finally, CuCe-MOF precursor was obtained by centrifugal filtration, washing and vacuum drying.

[0058] 2) Preparation of Cu-CeO2@NC catalyst: the CuCe-MOF precursor of step 1) was calcined at 700 DEG C for 2 h under N2 atmosphere to obtain the copper-based catalyst Cu-CeO2@NC.

[0059] Figure 1TEM characterization graph of copper-based catalyst Cu-CeO2@NC, Figure 1 In the TEM characterization graph of copper-based catalyst Cu-CeO2@NC, the spherical particles are Cu nanoparticles, and the Cu nanoparticles are coated with a coating layer NC, and the CeO2 nanoparticles are uniformly dispersed on the NC. Figure 2 XRD characterization graph of copper-based catalyst Cu-CeO2@NC, Figure 2 In the XRD characterization graph of copper-based catalyst Cu-CeO2@NC, the diffraction peaks at 43.3°, 50.5° and 74.1° are attributed to Cu. The above results show that the active component on the prepared catalyst is Cu nanoparticles.

[0060] The following examples and comparative examples further illustrate the Cu-CeO2@NC catalyzing glycerol dehydrogenation to prepare lactic acid. The conversion rate of glycerol is calculated from the quantitative results of the gas chromatography of glycerol. The quantitative results of lactic acid are calculated according to the test results of the high performance liquid chromatography of the product.

[0061] The conversion rate of glycerol is calculated according to the following formula:

[0062] The conversion rate of glycerol = (mass of glycerol before reaction - mass of glycerol after reaction) / (mass of glycerol before reaction) x 100%.

[0063] The selectivity of lactic acid is calculated based on C atom conservation, and the calculation formula is as follows:

[0064] The selectivity of lactic acid = (molar mass of lactic acid) x (number of carbon atoms in the molecular formula of lactic acid) / [(molar mass of glycerol reacted) x (number of carbon atoms in the molecular formula of glycerol)] x 100%.

[0065] Example 1

[0066] The method of this example for Cu-CeO2@NC catalyzing glycerol dehydrogenation to prepare lactic acid includes the following steps:

[0067] 5wt% glycerol aqueous solution, NaOH (the molar ratio of glycerol to NaOH is 1:1.2) and Cu-CeO2@NC catalyst (the addition amount is 2% of the mass of the glycerol aqueous solution) were sequentially added into a 100mL reaction kettle, and the reaction kettle was sealed. The air in the reaction kettle was replaced with N2 for 6 times, and then N2 was filled into the reaction kettle to a pressure of 1MPa, and reacted at 180℃ for 60min. After the reaction was completed, the sample was taken for gas and liquid analysis to determine the conversion rate of glycerol and the selectivity of lactic acid. The test results show that the conversion rate of glycerol is 96%, and the selectivity of lactic acid is 80%.

[0068] Example 2

[0069] The method of this example for Cu-CeO2@NC catalyzing glycerol dehydrogenation to prepare lactic acid includes the following steps:

[0070] Into a 100 mL autoclave, 10 wt% glycerol aqueous solution, NaOH (molar ratio of glycerol to NaOH is 1:1.15) and Cu-CeO2@NC catalyst (added amount is 1% of the mass of the glycerol aqueous solution) were sequentially added, and the autoclave was sealed. The air in the autoclave was replaced with N2for 6 times, and then N2was filled into the autoclave to a pressure of 1 MPa, and reacted at 200℃ for 60 min. After the reaction was completed, sampling was performed for gas phase and liquid phase analysis to determine the conversion rate of glycerol and the selectivity of lactic acid. It was tested that the conversion rate of glycerol was 100%, and the selectivity of lactic acid was 79%.

[0071] Example 3

[0072] The method of this example for preparing lactic acid by dehydrogenation of glycerol catalyzed by Cu-CeO2@NC includes the following steps:

[0073] Into a 100 mL autoclave, 8 wt% glycerol aqueous solution, NaOH (molar ratio of glycerol to NaOH is 1:1.05) and Cu-CeO2@NC catalyst (added amount is 1.2% of the mass of the glycerol aqueous solution) were sequentially added, and the autoclave was sealed. The air in the autoclave was replaced with N2for 6 times, and then N2was filled into the autoclave to a pressure of 1 MPa, and reacted at 220℃ for 30 min. After the reaction was completed, sampling was performed for gas phase and liquid phase analysis to determine the conversion rate of glycerol and the selectivity of lactic acid. It was tested that the conversion rate of glycerol was 98%, and the selectivity of lactic acid was 80%.

[0074] Example 4

[0075] The method of this example for preparing lactic acid by dehydrogenation of glycerol catalyzed by Cu-CeO2@NC includes the following steps:

[0076] Into a 100 mL autoclave, 20 wt% glycerol aqueous solution, NaOH (molar ratio of glycerol to NaOH is 1:1.2) and Cu-CeO2@NC catalyst (added amount is 2% of the mass of the glycerol aqueous solution) were sequentially added, and the autoclave was sealed. The air in the autoclave was replaced with N2for 6 times, and then N2was filled into the autoclave to a pressure of 1 MPa, and reacted at 220℃ for 60 min. After the reaction was completed, sampling was performed for gas phase and liquid phase analysis to determine the conversion rate of glycerol and the selectivity of lactic acid. It was tested that the conversion rate of glycerol was 95%, and the selectivity of lactic acid was 78%.

[0077] Example 5

[0078] The method of this example for preparing lactic acid by dehydrogenation of glycerol catalyzed by Cu-CeO2@NC includes the following steps:

[0079] Into a 100 mL autoclave, 5 wt% glycerol aqueous solution, NaOH (molar ratio of glycerol to NaOH was 1:1.25) and Cu-CeO2@NC catalyst (added amount was 0.5% of the mass of the glycerol aqueous solution) were sequentially added, and the autoclave was sealed. The air in the autoclave was replaced with N2for 6 times, and then N2was filled into the autoclave to a pressure of 1 MPa, and reacted at 220°C for 60 min. After the reaction was completed, sampling was performed for gas phase and liquid phase analysis to determine the conversion rate of glycerol and the selectivity of lactic acid. The conversion rate of glycerol was 100%, and the selectivity of lactic acid was 81%.

[0080] Example 6

[0081] The method of the present example for preparing lactic acid by catalyzing glycerol dehydrogenation with Cu-CeO2@NC includes the following steps:

[0082] Into a 100 mL autoclave, 10 wt% glycerol aqueous solution, NaOH (molar ratio of glycerol to NaOH was 1:1.1) and Cu-CeO2@NC catalyst (added amount was 2% of the mass of the glycerol aqueous solution) were sequentially added, and the autoclave was sealed. The air in the autoclave was replaced with N2for 6 times, and then N2was filled into the autoclave to a pressure of 1 MPa, and reacted at 220°C for 60 min. After the reaction was completed, sampling was performed for gas phase and liquid phase analysis to determine the conversion rate of glycerol and the selectivity of lactic acid. The conversion rate of glycerol was 100%, and the selectivity of lactic acid was 83%.

[0083] The recycling steps of the catalyst Cu-CeO2@NC of the present example are as follows:

[0084] After the reaction was completed, the Cu-CeO2@NC catalyst was separated by centrifugation, washed with water for 4 times, and directly used for the next reaction, and the reaction conditions were the same as the above reaction method. The catalyst was recycled for 6 times, and Table 1 shows the performance test results of the recycling of the catalyst Cu-CeO2@NC.

[0085] Table 1 Performance test results of the recycling of the catalyst Cu-CeO2@NC

[0086] Number of recycling times Glycerol conversion rate (%) Lactic acid selectivity (%) 1 100 83 2 100 82 3 100 81 4 100 80 5 100 79 6 100 78

[0087] Comparative Example 1

[0088] The published literature (Ruben Palacio, Sebastian Torres, Sebastien Royer, et al. CuO / CeO2 catalysts for glycerol selective conversion to lactic acid [J]. Dalton Transactions, 2018, 47(13): 4572-4582.) reports the experimental results of the cyclic use of CuO / CeO2 catalyst in the reaction of glycerol dehydrogenation to prepare lactic acid. From the above published literature, it is known that CuO / CeO2 catalyst needs to use high-temperature calcination to realize the regeneration of the catalyst during the cyclic use, and the CuO / CeO2 catalyst can only be cyclically used for 5 times.

[0089] Comparative Example 2

[0090] The published literature (Zhang Junjie, Zheng Jiabao, Hong Peiping, Mai Yuliang, Hu Wei, CeO2 modified Cu / AC catalyst for glycerol conversion to lactic acid, Modern Chemical Industry, 2020, 40(9): 126-130) reports the experimental results of the cyclic use of Cu-CeO2 / AC catalyst in the reaction of glycerol dehydrogenation to prepare lactic acid. The Cu-CeO2 / AC catalyst can only be cyclically used for three times, and the glycerol conversion rate significantly decreases in the third cyclic experiment.

[0091] Examples 1-5 show that the copper-based catalyst Cu-CeO2@NC of the present application exhibits high catalytic performance and stability in the reaction of catalyzing glycerol dehydrogenation to prepare lactic acid, and the glycerol conversion rate in the catalytic reaction is 95-100%, and the lactic acid selectivity is 78-83%. The copper-based catalyst Cu-CeO2@NC prepared by the present application still has high catalytic performance after being cyclically used for 6 times. Figure 3 is the XRD characterization graph of the copper-based catalyst Cu-CeO2@NC after being cyclically used for 6 times. From the XRD characterization graph, it can be seen that the diffraction peak of the Cu nanoparticles in the Cu-CeO2@NC is almost the same before and after the reaction, which further indicates that the catalyst has good stability. Figure 2 and Figure 3 It can be seen from the comparison of and that the diffraction peak of the Cu nanoparticles in the Cu-CeO2@NC is almost the same before and after the reaction, which further indicates that the catalyst has good stability.

[0092] Compared with Comparative Example 1 which needs high-temperature calcination to realize the regeneration of the catalyst, the present application uses nitrogen-doped carbon to coat Cu-CeO2 nanoparticles, thereby improving the stability of the catalyst, and the catalyst does not need to be regenerated by high-temperature calcination, and the cyclic use of the catalyst can be realized.

[0093] Compared with the Cu-CeO2 / AC catalyst of Comparative Example 2, the Cu-CeO2 nanoparticles are coated with nitrogen-doped carbon in the application, thereby improving the stability of the catalyst, and the catalyst Cu-CeO2@NC can be recycled for 6 times without obvious reduction in glycerol conversion rate.

[0094] The copper-based catalyst Cu-CeO2@NC is applied to the reaction of preparing lactic acid by catalytic dehydrogenation of glycerol in the application, and the obtained preparation method of lactic acid has the advantages of high glycerol conversion rate, high lactic acid selectivity, excellent catalyst stability and short reaction time, and the catalyst provided in the application has wide application in the preparation of lactic acid.

Claims

1. Use of a copper-based catalyst in the catalytic dehydrogenation of alcohols, characterized in that, The application is catalytic dehydrogenation of alcohol to prepare lactic acid; the application comprises the following steps: mixing glycerol aqueous solution, copper-based catalyst and alkali in inert gas atmosphere to carry out catalytic reaction, so as to obtain the lactic acid; the temperature of the catalytic reaction is 150-250℃; the time of the catalytic reaction is 30-60 min; the pressure of the catalytic reaction is 0.05-3 MPa; the concentration of the glycerol aqueous solution is 1-35 wt%; the mass ratio of the glycerol aqueous solution and copper-based catalyst is 1:(0.001-0.04); the molar ratio of the glycerol and alkali is 1:(1-1.6); The copper-based catalyst comprises a cladding layer and a metal substrate, the cladding layer is coated outside the metal substrate, the metal substrate contains CeO2 and Cu, and the cladding layer contains nitrogen-doped carbon material; the particle size of the metal substrate is 80-160 nm; The copper-based catalyst is prepared by a preparation method comprising the following steps: carrying out solvothermal reaction of surfactant, carbon source, nitrogen source, copper salt and cerium salt to obtain CuCe-MOF precursor; and carrying out calcination of the CuCe-MOF precursor to obtain the copper-based catalyst; the surfactant comprises polyvinylpyrrolidone, cetyltrimethylammonium bromide or a combination thereof; the carbon source is selected from trimesic acid; the nitrogen source is selected from amine solvents; the amine solvents comprise N,N-dimethylformamide, N,N-dimethylacetamide or a combination thereof; the mass ratio of surfactant and carbon source is 1:(0.8-2.2); the mass ratio of surfactant and nitrogen source is 1:(25-90); the mass ratio of surfactant and copper salt is 1:(1-2.5); the mass ratio of surfactant and cerium salt is 1:(0.8-1.7); the temperature of the calcination is 600-750℃; the temperature of the solvothermal reaction is 70-150℃; the time of the solvothermal reaction is 10-60 h; the atmosphere of the calcination is inert gas atmosphere; and the time of the calcination is 0.5-5 h.

2. Use according to claim 1, characterized in that, The copper salt comprises at least one of copper nitrate, copper chloride or copper sulfate; And / or, the cerium salt comprises at least one of cerium nitrate, cerium chloride or cerium sulfate.

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