A Cu / ZrO2@NC catalyst for catalyzing synthesis of high carbon alcohol from ethanol and a preparation method and application thereof

Abstract

The application discloses a Cu / ZrO2@NC catalyst for catalyzing synthesis of high-carbon alcohol, a preparation method and application thereof, and relates to the technical field of high-carbon alcohol compound synthesis. The catalyst is prepared by adding copper salt and zirconium salt and polyacrylamide into water to dissolve and mix, heating and stirring to form a complex homogeneous solution, and drying to obtain a copper-zirconium catalyst precursor. The copper-zirconium catalyst precursor is calcined under an inert gas atmosphere to obtain the Cu / ZrO2@NC catalyst. The Cu / ZrO2@NC catalyst prepared by the application has the characteristics of high loading, low particle size and high directional reaction activity for high-carbon alcohol. The catalyst can effectively realize the effective coupling of aldehyde-ketone condensation and hydroxy-aldehyde condensation for synthesis of high-carbon alcohol from ethanol, and can obtain an oil phase product mainly composed of C6+ high-carbon alcohol with high selectivity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a Cu / ZrO2@NC catalyst for synthesizing high-carbon alcohols from ethanol, and the application also relates to a preparation method and application of the catalyst. BACKGROUND

[0002] With the increasing emphasis on energy independence and sustainability, there is widespread interest in developing renewable fuels and fine chemicals. C6+ high-carbon alcohols have high energy density, low corrosion, and are not easy to absorb water, and are one of the ideal substitutes for diesel fuel. However, the synthesis of high-carbon alcohols from ethanol is mainly through Guerbet coupling in a batch reactor to synthesize high-carbon alcohols from ethanol in an aqueous phase, which has problems such as difficulty in continuous synthesis, low carbon number range of synthesized high-carbon alcohols, and many by-product gases. Therefore, it is urgent to study a method for preparing high-carbon alcohols from ethanol, to improve the conversion rate of ethanol and promote the growth of the carbon chain of high-carbon alcohols. SUMMARY

[0003] In view of the above technical problems, the application provides a Cu / ZrO2@NC catalyst for synthesizing high-carbon alcohols from ethanol; the catalyst effectively solves the problems of many by-product gases, low selectivity of C6+ products, and low conversion efficiency of ethanol in the process of synthesizing high-carbon alcohols from ethanol.

[0004] Another object of the application is to provide a preparation method of the Cu / ZrO2@NC composite catalyst.

[0005] The last object of the application is to provide a method for synthesizing high-carbon alcohols from ethanol using the above Cu / ZrO2@NC composite catalyst, and the method provided by the application can obtain an oil phase product mainly composed of C6+ high-carbon alcohols with high selectivity

[0006] To this end, the first technical solution provided by the application is as follows:

[0007] A preparation method of a Cu / ZrO2@NC catalyst for synthesizing high-carbon alcohols from ethanol, which comprises the following steps in sequence:

[0008] 1) Dissolve and mix copper salt and zirconium salt with polyacrylamide in water, form a complex homogeneous solution by heating and stirring, and dry to obtain a copper-zirconium catalyst precursor;

[0009] 2) Calcine the copper-zirconium catalyst precursor prepared in step 1) in an inert gas atmosphere to obtain a Cu / ZrO2@NC catalyst;

[0010] The molar ratio of copper ions in the copper salt, copper ions in the zirconium salt, and polyacrylamide is (0.1-0.5) : 1 : (0.5-2).

[0011] Furthermore, in the preparation method of the above-mentioned Cu / ZrO2@NC catalyst for catalyzing the synthesis of higher alcohols from ethanol, the copper salt is one or more of copper nitrate, copper chloride and copper acetate.

[0012] Furthermore, in the preparation method of the above-mentioned Cu / ZrO2@NC catalyst for catalyzing the synthesis of higher alcohols from ethanol, the zirconium salt is one or more of zirconium nitrate, zirconium citrate and zirconium hydroxide.

[0013] Furthermore, in the preparation method of the above-mentioned Cu / ZrO2@NC catalyst for catalyzing the synthesis of higher alcohols from ethanol, the calcination parameters are: heating rate 5°C / min, temperature 500-600°C, and time 3h.

[0014] The present invention provides a Cu / ZrO2@NC catalyst for catalyzing the synthesis of higher alcohols from ethanol, which is prepared by the preparation method described in the first technical solution.

[0015] The present invention also has a technical solution to provide the above-mentioned Cu / ZrO2@NC catalyst for catalyzing the synthesis of higher alcohols from ethanol for use in catalyzing the synthesis of higher alcohols from ethanol.

[0016] Another technical solution of the present invention provides a method for synthesizing higher alcohols from ethanol, which comprises the following steps in sequence:

[0017] 1) 1 ml Cu / ZrO2@NC catalyst and 2 ml quartz sand were loaded into a fixed bed reactor and mixed evenly; the temperature was raised from room temperature to 400 °C at a rate of 5 °C / min under a hydrogen atmosphere and kept at this temperature for 2400 h. -1 Hydrogen gas space velocity 0.1MPa reduction for 2h;

[0018] 2) Keep the H2 gas atmosphere unchanged, increase the pressure to 2.5Mpa, the reaction temperature to 310℃, and -1 Anhydrous ethanol was added to the reactor at a liquid rate of 3600 h. -1 , reaction 12h;

[0019] 3) Collect the generated gas and perform detection and analysis by FID-TCD gas analysis spectrum. At the same time, centrifuge the liquid product to separate the layers, let it stand, take the upper organic phase and the lower aqueous phase, and perform detection and analysis by gas chromatography.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] This invention synthesizes higher alcohols by comprehensively considering elementary reaction steps such as aldehyde-ketone coupling and Guerbet coupling. A Cu / ZrO2@NC catalyst is constructed via a sol-gel method, uniformly dispersing Cu on a ZrO2 oxide support. Carbon and nitrogen are simultaneously doped to introduce alkaline centers, promoting the continuous catalytic conversion of ethanol to C6+ higher alcohols via aldol and aldehyde-ketone condensations. The appropriate ratio of copper and zirconium metals effectively promotes carbon chain growth and breaks the traditional carbon chain distribution. The synthetic method provided by this invention offers advantages such as simple preparation, low cost, high loading, low particle size, excellent catalytic efficiency, and high reactivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the XRD pattern of the Cu / ZrO2@NC catalyst used in the synthesis method of the present invention.

[0023] Figure 2 TEM image of the Cu / ZrO2@NC catalyst used in the synthesis method of the present invention. DETAILED DESCRIPTION

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] The C6+ higher alcohols described in the present invention refer to the total amount of higher alcohols having a carbon number of 6 or more (including 6).

[0026] The raw materials used in the present invention are all purchased from the market.

[0027] Example 1

[0028] (1) Preparation of Cu / ZrO2@NC catalyst:

[0029] 10.02g zirconium nitrate and 1.689g copper nitrate were dissolved in distilled water to prepare a 0.1M copper-zirconium metal salt solution. 1.66g polyacrylamide was added to the copper-zirconium metal salt solution. The copper-zirconium metal salt solution with polyacrylamide was stirred at 80°C for 2 hours to uniformly mix and form a homogeneous complex solution. The solution was then dried at 105°C for 12 hours to fully dry the sample. The sample was then placed in a tube furnace in an inert gas atmosphere and heated to 550°C at 5°C / min and calcined for 3 hours to obtain a Cu / ZrO2@NC catalyst.

[0030] Figure 1 This is the XRD pattern of the Cu / ZrO2@NC catalyst prepared in Example 1 of the present invention. Figure 2 TEM schematic diagram of the Cu / ZrO2@NC catalyst used in the synthesis method of the present invention. Figure 1 、Figure 2 It can be seen that Cu is evenly dispersed on the ZrO2 support.

[0031] Examples 2-8

[0032] Example 2-8 A method for preparing a Cu / ZrO2@NC catalyst for catalyzing the synthesis of higher alcohols from ethanol, the steps are the same as those in Example 1, and the differences are shown in Table 1. The parameter variables in Table 1 refer to the parameter changes in step (1).

[0033] Table 1. Reaction parameters of the synthesis method of Examples 1-8

[0034] Calcination temperature (°C) Zirconium: Carbon (molar ratio) Copper: Zirconium (molar ratio) Example 1 550 1:1 0.3:1 Example 2 500 1:1 0.3:1 Example 3 600 1:1 0.3:1 Example 4 550 0.5:1 0.3:1 Example 5 550 0.8:1 0.3:1 Example 6 550 2:1 0.3:1 Example 7 550 1:1 0.1:1 Example 8 550 1:1 0.5:1

[0035] Note: The carbon in the above table refers to the carbon in polyacrylamide.

[0036] Comparative Example 1

[0037] The steps are the same as those in Example 1, except that the molar ratio of carbon to zirconium in step (1) is set to 0:1.

[0038] Comparative Example 2

[0039] The steps are the same as those in Example 1, except that the molar ratio of copper to zirconium in step (1) is 0:1.

[0040] Application Example 1

[0041] 1 ml of Cu / ZrO2@NC catalyst was loaded into a fixed bed reactor and 2 ml of quartz sand was mixed in to maintain a certain catalyst bed layer. The temperature was raised from room temperature to 400 °C at a rate of 5 °C / min under a hydrogen atmosphere and kept warm for 2400 h. -1 Hydrogen gas space velocity 0.1MPa reduction for 2h;

[0042] (2) Keeping the H2 gas atmosphere unchanged, the pressure was increased to 2.5 MPa, the reaction temperature was 310 °C, and the reaction temperature was 0.6 h. -1 Anhydrous ethanol was added to the reactor at a liquid rate of 3600 h. -1 , react for 12h.

[0043] (3) The generated gas was collected and analyzed by FID-TCD gas analysis spectrum. At the same time, the liquid product was centrifuged and separated into layers. After standing, the upper organic phase and the lower aqueous phase were taken and analyzed by gas chromatography. The results are shown in Table 2.

[0044] Application Example 2

[0045] The parameters and steps involved in this application example are the same as those in application example 1. The difference is that the catalyst used is the catalyst provided in example 2. The results are shown in Table 2.

[0046] Application Example 3

[0047] The parameters and steps involved in this application example are the same as those in application example 1. The difference is that the catalyst used is the catalyst provided in Example 3. The results are shown in Table 2.

[0048] Application Example 4

[0049] The parameters and steps involved in this application example are the same as those in application example 1. The difference is that the catalyst used is the catalyst provided in Example 4. The results are shown in Table 2.

[0050] Application Example 5

[0051] The parameters and steps involved in this application example are the same as those in application example 1. The difference is that the catalyst used is the catalyst provided in Example 5. The results are shown in Table 2.

[0052] Application Example 6

[0053] The parameters and steps involved in this application example are the same as those in application example 1. The difference is that the catalyst used is the catalyst provided in Example 6. The results are shown in Table 2.

[0054] Application Example 7

[0055] The parameters and steps involved in this application example are the same as those in application example 1. The difference is that the catalyst used is the catalyst provided in Example 7. The results are shown in Table 2.

[0056] Application Example 8

[0057] The parameters and steps involved in this application example are the same as those in application example 1. The difference is that the catalyst used is the catalyst provided in Example 8. The results are shown in Table 2.

[0058] Comparative Application Example 1

[0059] The parameters and steps involved in this comparative application example are the same as those in application example 8. The difference is that the catalyst used is the catalyst provided in comparative example 1. The results are shown in Table 2.

[0060] Comparative Application Example 2

[0061] The parameters and steps involved in this comparative application example are the same as those in Application Example 1. The difference is that the catalyst used is the catalyst provided in Comparative Example 2. The results are shown in Table 2.

[0062] Table 2 Analysis of reaction results of various embodiments and comparative examples

[0063]

[0064] As shown in Table 2, the production of higher alcohols in Comparative Example 1 is significantly reduced, indicating that appropriate carbon and nitrogen doping can introduce base centers to promote the coupling of higher aldehydes and ketones to form long-chain alcohols. In Comparative Example 2, no C6+ higher alcohols could be synthesized, indicating that the long-chain alcohol production requires a Cu metal active center for ethanol dehydrogenation followed by C-C coupling condensation to extend the carbon chain.

[0065] The present invention uses Cu / ZrO2@NC catalyst to achieve one-step catalytic conversion of ethanol to C6+ higher carbon alcohols. The ethanol conversion rate can reach as high as 92.4%, and the C6+ higher carbon alcohol selectivity can reach as high as 44.68%. The selectivity of C6 alcohol is greater than that of C4 alcohol, breaking the traditional carbon number distribution and taking into account the balance of high ethanol conversion rate, long carbon chain of higher carbon alcohol and high selectivity.

[0066] The above are only preferred specific implementation methods of the present application, but the scope of protection of the present application is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in this application should be included in the scope of protection of the present application; therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for synthesizing higher alcohols from ethanol, characterized in that: The method includes the following steps in sequence: S1: 1 mL of Cu / ZrO2@NC catalyst and 2 mL of quartz sand were loaded into a fixed bed reactor and mixed evenly. The temperature was raised from room temperature to 400 °C at a rate of 5 °C / min under a hydrogen atmosphere and kept at this temperature for 2400 h. -1 Hydrogen gas space velocity 0.1MPa reduction for 2h; S2: Keep the H2 gas atmosphere unchanged, increase the pressure to 2.5Mpa, the reaction temperature to 310℃, and heat for 0.6h. -1 Anhydrous ethanol was added to the reactor at a liquid rate of 3600 h. -1 , reaction 12h; S3: Collect the generated gas and perform detection and analysis by FID-TCD gas chromatography. Meanwhile, the liquid product is centrifuged and separated into layers. After standing, the upper organic phase and the lower aqueous phase are taken and detected and analyzed by gas chromatography. The Cu / ZrO2@NC catalyst for catalyzing the synthesis of higher alcohols from ethanol is prepared by the following steps: Copper salt, zirconium salt and polyacrylamide are added into water, dissolved and mixed, heated and stirred to form a homogeneous complex solution, and dried to obtain a copper-zirconium catalyst precursor; The copper-zirconium catalyst precursor prepared in step 1) is calcined under an inert gas atmosphere to obtain a Cu / ZrO2@NC catalyst; The molar ratio of the copper ions in the copper salt, the zirconium ions in the zirconium salt, and the carbon of the polyacrylamide is (0.1-0.5):1:(0.5-2).

2. The method for synthesizing higher alcohols from ethanol according to claim 1, wherein The copper salt is one or more of copper nitrate, copper chloride and copper acetate.

3. A method for synthesizing higher alcohols from ethanol according to claim 1, characterized in that: The zirconium salt is one or more of zirconium nitrate, zirconium citrate and zirconium hydroxide.

4. A method for synthesizing higher alcohols from ethanol according to claim 1, characterized in that: The calcination parameters are: heating rate 5°C / min, temperature 500-600°C, and time 3h.

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