High-grade alcohol synthesis catalyst capable of being mixed with ship fuel as well as preparation method and application of high-grade alcohol synthesis catalyst

Abstract

The invention provides a higher alcohol synthesis catalyst capable of being mixed with ship fuel as well as a preparation method and application of the higher alcohol synthesis catalyst, and belongs to the technical field of catalysts. The preparation method comprises the following steps: dissolving nickel salt and bismuth salt in deionized water, and stirring to form a homogeneous solution; adding CeO2 into the homogeneous solution, stirring, and drying to obtain a precursor; and roasting the precursor in an inert atmosphere to obtain the higher alcohol synthesis catalyst capable of being mixed with the ship fuel. According to the catalytic system, through well-designed metal-carrier interaction, reaction conditions are remarkably optimized, the selectivity of the catalyst to long-chain alcohol products is remarkably improved while high activity of the catalyst is kept, and adjustable oxygen vacancies on the surface of the CeO2 carrier in the catalyst can stabilize reaction intermediates and remove surface carbon deposition, so that the selectivity of the catalyst to the long-chain alcohol products is improved. A guarantee is provided for long-term recycling of the catalyst, and the catalyst is easy to separate, recycle and reuse in a higher alcohol preparation process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalysts, and particularly relates to a high-grade alcohol synthesis catalyst capable of being blended with ship fuel and a preparation method and application thereof. BACKGROUND

[0002] Methanol is one of the most critical organic raw materials in the modern coal chemical industry, and plays an important role in supporting basic materials. Water in nature produces hydrogen through photolysis of sunlight, and hydrogen generates methanol with carbon dioxide in the air. The carbon emission during the synthesis process is almost zero, which not only realizes energy saving and emission reduction, but also can be used as an internal combustion engine fuel like ethanol, thereby alleviating the current energy and chemical raw material gap in China. In the shipping industry, methanol can be used as a power fuel to reduce 80% of nitrogen oxide emissions and 99% of sulfur oxide emissions, and at most 25% of carbon dioxide emissions, and is regarded as an environmentally friendly ship fuel to replace LNG.

[0003] At present, the developed biomass fuel that can be replaced is mainly used in mixed use with traditional fuel. However, there is still a big gap in the physical and chemical properties of traditional fuel and small molecule methanol and ethanol, and there are still problems in the mixing ratio and storage and transportation. High-grade alcohols (such as n-butanol, isoamyl alcohol, n-hexanol, and iso-hexanol) have energy density closer to diesel, and have the advantages of small corrosion and convenient storage and transportation. In addition, the physical and chemical properties such as calorific value and cetane number of high-grade alcohols are close to those of diesel, and can be mixed with diesel at any ratio. Therefore, high-grade alcohol is a highly potential high-quality biomass-based fuel. The blending and application of high-grade alcohol and diesel as a power fuel for ships not only can solve the cost problem of methanol dual-fuel propulsion system, but also can greatly reduce the space of fuel storage tank, which will play a huge advantage in shipping transportation cost and fuel filling station scale.

[0004] Methanol-ethanol can be upgraded to high-grade alcohol through Guerbet coupling reaction. Cross-coupling mainly includes three steps: (1) methanol is dehydrogenated to formaldehyde, and ethanol is dehydrogenated to acetaldehyde; (2) aldehyde alcohol condensation and loss of one water molecule to obtain enal; (3) hydrogenation of enal to generate coupled alcohol.

[0005] In the field of catalytic coupling of alcohols, the existing catalytic system still faces several key challenges, which seriously restricts the economic and feasibility of the technology in industrial application. Traditional transition metal catalysts usually require high reaction temperature to achieve effective C-C coupling. Such harsh reaction conditions not only lead to high energy consumption, but also cause a series of side reactions, such as dehydration of alcohols to generate olefins, excessive dehydrogenation to generate aldehydes and ketones. More troublesome is that most catalytic systems have limited selectivity regulation ability for target products, making it difficult to realize the directional synthesis of specific carbon chain length products. SUMMARY

[0006] In order to overcome the problem that the existing catalysts have a high reaction temperature when used for synthesizing higher alcohols from small molecules in an aqueous phase, the application provides a higher alcohol synthesis catalyst that can be mixed with ship fuel, and a preparation method and application thereof.

[0007] In order to achieve the above object, the application provides the following technical solutions.

[0008] One of the technical solutions of the application is as follows:

[0009] A preparation method of a higher alcohol synthesis catalyst that can be mixed with ship fuel, comprising the following steps:

[0010] Dissolve a nickel salt and a bismuth salt in deionized water and stir to form a homogeneous solution;

[0011] Add CeO2 to the homogeneous solution and stir, and then dry to obtain a precursor;

[0012] Roast the precursor under an inert atmosphere to obtain the higher alcohol synthesis catalyst that can be mixed with ship fuel.

[0013] Further, the molar ratio of the nickel salt to the bismuth salt is (1-4):4; preferably, the molar ratio of the nickel salt to the bismuth salt is 1:2.

[0014] Further, the molar ratio of the nickel salt to CeO2 is (1-4):4; preferably, the molar ratio of the nickel salt to CeO2 is 1:2.

[0015] Further, the roasting temperature of the roasting is 300-600 DEG C, and the roasting time is 1-3 h; preferably, the roasting temperature of the roasting is 550 DEG C, and the roasting time is 2 h.

[0016] A nickel salt that is conventional in the art can be used in the application. Preferably, the nickel salt is selected from nickel nitrate.

[0017] A bismuth salt that is conventional in the art can be used in the application. Preferably, the nickel salt is selected from bismuth nitrate.

[0018] The second technical solution of the application is as follows:

[0019] The higher alcohol synthesis catalyst that can be mixed with ship fuel is prepared by the above preparation method.

[0020] The third technical solution of the application is as follows:

[0021] The application of the above higher alcohol synthesis catalyst that can be mixed with ship fuel in catalyzing the synthesis of higher alcohols from small molecule alcohols in an aqueous phase.

[0022] Further, the small molecule alcohols are methanol and ethanol, and the higher alcohols are alcohols with 5-16 carbon atoms.

[0023] More specifically, the method for synthesizing high-grade alcohol by using a high-grade alcohol synthesis catalyst for blending ship fuel to catalyze small-molecule alcohol in an aqueous phase comprises the following steps:

[0024] The prepared high-grade alcohol synthesis catalyst for blending ship fuel, sodium hydroxide, methanol, ethanol and water are mixed in a reactor in a mass ratio of 1:1:(10-40):(10-40):(10-40), and after leakage detection, high-purity hydrogen is used to replace the air in the reactor, and the reaction is carried out continuously at a reaction temperature of 180 DEG C, an initial pressure of 0.2 MPa and a stirring speed of 2000 rpm for 20 h. After the reaction, the substrate is spontaneously separated into oil and water phases, and after centrifugal separation, the oil phase and the water phase are detected and analyzed by gas chromatography.

[0025] The high-grade alcohol synthesis catalyst for blending ship fuel of the application significantly reduces the methanol-ethanol coupling reaction temperature through the synergistic effect of multiple components. The core mechanism lies in that the controllable oxygen vacancies on the surface of CeO2 can efficiently activate the O-H bond of alcohol molecules at low temperature to generate key alkoxy intermediates. Meanwhile, the Ni-Bi bimetallic component forms a unique electron transfer channel through the bridging of CeO2. The rich electron characteristics of the Ni site promote the polarization and breaking of the C-H bond, while the electron-deficient state of the Bi site effectively inhibits the beta-H elimination side reaction. The combination of the electron synergy between the metal and the carrier and the intrinsic activation ability of the oxygen vacancies not only reduces the activation energy barrier of C-C coupling, but also realizes high-selectivity conversion at low temperature by stabilizing the reaction intermediates, so that the reaction temperature window is reduced by 70-100 DEG C compared with traditional catalysts.

[0026] Compared with the prior art, the application has the following advantages and technical effects:

[0027] (1) The high-grade alcohol synthesis catalyst for blending ship fuel developed by the application exhibits unique advantages. Through the careful design of metal-carrier interaction, the catalyst system realizes significant optimization of the reaction conditions. The controllable oxygen vacancies on the surface of the CeO2 carrier not only greatly reduce the reaction activation energy and the required temperature, but also provide key intermediate stabilization. The Ni-Bi bimetallic component precisely controls the selectivity of C-H bond activation and C-C coupling through electron synergy effect. This multi-component synergistic mechanism enables the catalyst to maintain high activity while significantly improving the selectivity of long-chain alcohol products.

[0028] (2) The advanced alcohol synthesis catalyst for blending ship fuel developed by the present application exhibits excellent stability. The adjustable oxygen vacancies on the surface of the CeO2 carrier can not only stabilize the reaction intermediates, but also oxidize the accumulated carbon to volatile substances such as CO or CO2 by adsorbing and activating the oxygen-containing species in the reaction, thereby removing the accumulated carbon on the surface and providing a guarantee for the long-term cyclic use of the catalyst. These innovative designs provide new ideas for solving key scientific problems in alcohol coupling reactions and lay an important foundation for the development of related industrial processes

[0029] (3) The advanced alcohol synthesis catalyst for blending ship fuel of the present application is a heterogeneous catalyst, which is easy to separate, recover and reuse in the preparation of advanced alcohols. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and serve as an explanation of the illustrative embodiments of the present application and their description, and do not constitute improper limitations on the present application. In the drawings:

[0031] Figure 1 XRD pattern of the NiBi-CeO2 ternary catalyst prepared for Example 1. DETAILED DESCRIPTION

[0032] The various illustrative embodiments of the present application will now be described in detail below, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0033] It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or stated range and any other stated value or intermediate value within the stated range is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are concerned. In the event of any conflict between the content of this specification and any document incorporated by reference, the content of this specification will control.

[0035] Many modifications and variations to the illustrative embodiments described herein will be apparent to those of ordinary skill in the art from the foregoing description. Such modifications and variations are intended to fall within the scope of the present application. Other embodiments will be apparent to those of ordinary skill in the art from consideration of the description and practice of the present application. The description and examples are illustrative only.

[0036] As used herein, the terms "comprise", "comprising", "include", "including", "have" and "having" and the like are open-ended, i.e., are intended to mean comprising but not limited to.

[0037] The present application provides a preparation method of a high alcohol synthesis catalyst for blending marine fuel.

[0038] (1) dissolving a nickel salt and a bismuth salt in deionized water to form a homogeneous solution by stirring;

[0039] (2) adding CeO2 to the homogeneous solution by stirring, and drying to obtain a precursor;

[0040] (3) calcining the precursor under an inert atmosphere to obtain the high alcohol synthesis catalyst for blending marine fuel (denoted as NiBi-CeO2 ternary catalyst).

[0041] In the preferred embodiment of the present application, the molar ratio of the nickel salt to the bismuth salt is (1-4) : 4; more preferably, the molar ratio of the nickel salt to the bismuth salt is 1:2.

[0042] In the preferred embodiment of the present application, the molar ratio of the nickel salt to CeO2 is (1-4) : 4; more preferably, the molar ratio of the nickel salt to CeO2 is 1:2.

[0043] In the preferred embodiment of the present application, the calcination temperature of the calcination is 300-600°C, and the calcination time is 1-3h; more preferably, the calcination temperature of the calcination is 550°C, and the calcination time is 2h.

[0044] In the preferred embodiment of the present application, the stirring in step (2) is stirring at 40-100°C for 1-6h; more preferably, the stirring is stirring at 70°C for 2h.

[0045] The nickel salt used in the present application can be conventional in the art. Preferably, the nickel salt is selected from nickel nitrate.

[0046] The bismuth salt used in the present application can be conventional in the art. Preferably, the bismuth salt is selected from bismuth nitrate.

[0047] The present application also provides a high alcohol synthesis catalyst for blending marine fuel prepared by the above preparation method.

[0048] The prepared advanced alcohol synthesis catalyst for blending ship fuel in the embodiment of the present application can be used in the synthesis of advanced alcohol from small molecule alcohol in water phase, wherein the small molecule alcohol is methanol and ethanol, and the advanced alcohol is alcohol with 5-16 carbon atoms (i.e. C5+ advanced alcohol). More specifically, the method for synthesizing advanced alcohol from small molecule alcohol in water phase by using the advanced alcohol synthesis catalyst for blending ship fuel comprises the following steps:

[0049] The prepared advanced alcohol synthesis catalyst for blending ship fuel, sodium hydroxide, methanol, ethanol and water are mixed in a reactor in a mass ratio of 1:1:(10-40):(10-40):(10-40), and after leakage detection, high-purity hydrogen is used to replace the air in the reactor. The continuous reaction is carried out at a reaction temperature of 180℃, an initial pressure of 0.2 MPa and a stirring speed of 2000 rpm for 20 h. After the reaction, the substrate is spontaneously separated into oil and water phases, and the liquid phase and solid phase catalyst are separated by centrifugation and filtration. After standing, the liquid phase is naturally separated into oil and water phases, and the oil phase is the product of advanced alcohol.

[0050] The raw materials used in the embodiment of the present application are commercially available.

[0051] The technical solutions of the present application are further described by the following examples.

[0052] Example 1

[0053] A preparation method of an advanced alcohol synthesis catalyst for blending ship fuel comprises the following steps:

[0054] (1) Dissolve nickel nitrate and bismuth nitrate in deionized water to form a homogeneous solution, wherein the molar ratio of nickel nitrate to bismuth nitrate is 1:4, and the amount ratio of bismuth nitrate to deionized water is 0.01 mol:15 mL;

[0055] (2) Add CeO2 to the homogeneous solution obtained in step (1), stir at 70℃ for 2 h and dry to obtain a precursor, wherein the molar ratio of nickel nitrate to CeO2 is 1:4;

[0056] (3) Place the precursor obtained in step (2) in an inert atmosphere, and calcine at 550℃ for 2 h to obtain an advanced alcohol synthesis catalyst for blending ship fuel (NiBi-CeO2 ternary catalyst).

[0057] Example 2

[0058] The same as example 1, except that:

[0059] In step (1), the molar ratio of nickel nitrate to bismuth nitrate is 1:1 (i.e. 4:4);

[0060] In step (2), the molar ratio of nickel nitrate to CeO2 was 1 : 1 (i.e. 4:4);

[0061] The remaining steps were the same as in Example 1.

[0062] Example 3

[0063] The same as Example 1, except that:

[0064] In step (1), the molar ratio of nickel nitrate to bismuth nitrate was 1 : 2 (i.e. 2:4);

[0065] In step (2), the molar ratio of nickel nitrate to CeO2 was 1 : 2 (i.e. 2:4);

[0066] The remaining steps were the same as in Example 1.

[0067] Example 4

[0068] The same as Example 1, except that:

[0069] In step (1), the molar ratio of nickel nitrate to bismuth nitrate was 3:4;

[0070] In step (2), the molar ratio of nickel nitrate to CeO2 was 3:4;

[0071] The remaining steps were the same as in Example 1.

[0072] Example 5

[0073] The same as Example 1, except that:

[0074] In step (3), the precursor obtained in step (2) was calcined under an inert atmosphere at 400°C for 2h;

[0075] The remaining steps were the same as in Example 1.

[0076] Example 6

[0077] The same as Example 1, except that:

[0078] In step (3), the precursor obtained in step (2) was calcined under an inert atmosphere at 450°C for 2h;

[0079] The remaining steps were the same as in Example 1.

[0080] Example 7

[0081] The same as Example 1, except that:

[0082] In step (3), the precursor obtained in step (2) was calcined under an inert atmosphere at 500°C for 2h;

[0083] The remaining steps are consistent with Example 1.

[0084] Example 8

[0085] The same as Example 1, the only difference is that:

[0086] In step (3), the precursor obtained in step (2) is placed in an inert atmosphere and calcined at 600°C for 2h;

[0087] The remaining steps are consistent with Example 1.

[0088] Example 9

[0089] The same as Example 1, the only difference is that:

[0090] In step (3), the precursor obtained in step (2) is placed in an inert atmosphere and calcined at 300°C for 3h;

[0091] The remaining steps are consistent with Example 1.

[0092] Example 10

[0093] The same as Example 1, the only difference is that:

[0094] In step (3), the precursor obtained in step (2) is placed in an inert atmosphere and calcined at 500°C for 1h;

[0095] The remaining steps are consistent with Example 1.

[0096] Comparative Example 1

[0097] The same as Example 1, the only difference is that the addition of bismuth nitrate is omitted, a preparation method of a higher alcohol synthesis catalyst, comprising the following steps:

[0098] (1) Dissolve nickel nitrate and CeO2 in deionized water, stir to form a homogeneous solution, wherein the molar ratio of nickel nitrate and CeO2 is 1:4, and the ratio of the amount of bismuth nitrate to deionized water is 0.01 mol:15 mL;

[0099] (2) The homogeneous solution obtained in step (1) is stirred at 70°C for 2h and dried to obtain a precursor;

[0100] (3) The precursor obtained in step (2) is placed in an inert atmosphere and calcined at 550°C for 2h to obtain a higher alcohol synthesis catalyst.

[0101] Comparative Example 2

[0102] The same as Example 1, the only difference is that the addition of nickel nitrate is omitted, a preparation method of a higher alcohol synthesis catalyst, comprising the following steps:

[0103] (1) Bismuth nitrate, CeO2 were dissolved in deionized water to form a homogeneous solution, wherein the molar ratio of bismuth nitrate to CeO2 was 1:4, and the ratio of bismuth nitrate to deionized water was 0.01 mol: 15 mL;

[0104] (2) The homogeneous solution obtained in step (1) was stirred at 70°C for 2h and dried to obtain a precursor;

[0105] (3) The precursor obtained in step (2) was placed in an inert atmosphere and calcined at 550°C for 2h to obtain a higher alcohol synthesis catalyst.

[0106] Performance test

[0107] (1) XRD analysis

[0108] The XRD pattern of the NiBi-CeO2 ternary catalyst prepared in Example 1 is shown in Figure 1. Figure 1 As can be seen, the diffraction peak intensity of CeO2 as the carrier is higher, indicating that it has a higher content and better dispersion in the material, which may mean that CeO2 successfully forms a stable crystal structure in the material. The diffraction peak intensity of Ni is higher, indicating that it has a higher crystallinity and good dispersion on the CeO2 carrier, which may mean that Ni is successfully loaded on the CeO2 carrier and uniformly distributed. Although the diffraction peak of Bi is relatively low in intensity, it is still clear, which indicates that Bi is also successfully loaded on the CeO2 carrier and has a certain degree of dispersion. In general, in the NiBi-CeO2 ternary catalyst system, CeO2 as the carrier provides stable structural support for Ni and Bi, enabling Ni and Bi to be successfully dispersed and loaded on its surface or inside.

[0109] The XRD patterns of the higher alcohol synthesis catalysts for blending ship fuel obtained in Examples 2-8 all appeared Ni, Bi and CeO2 peaks.

[0110] (2) Catalytic experiment

[0111] The catalysts prepared in Examples 1-10 and Comparative Examples 1-2 were respectively put into a 70 ml autoclave, and used to catalyze the carbon-carbon cross-coupling reaction of methanol and ethanol to produce higher alcohols in the presence of a homogeneous base. Specifically, 0.5 g of the higher alcohol synthesis catalyst, 0.5 g of NaOH, 5 g of methanol, 5 g of ethanol and 10 g of water were added into the autoclave. After leak detection, the autoclave was replaced with high-purity hydrogen. The continuous reaction was carried out at a reaction temperature of 180°C, an initial pressure of 0.2 MPa and a stirring speed of 2000 rpm for 20 h. After the reaction, the reaction system was cooled to room temperature, and the gas phase was collected using a gas bag. The liquid phase and solid phase catalyst were separated by centrifugation and filtration, and the liquid phase was naturally separated into oil and water phases. The gas phase product, water phase and oil phase were analyzed by gas chromatography, and the results are shown in Table 1 below.

[0112] Table 1: Analysis results of qualitative and quantitative analysis of each example / comparative example

[0113]

[0114]

[0115] As can be seen from the results in Table 1, the higher alcohol synthesis catalysts for blending into marine fuel prepared by changing the ratio of soluble nickel salt to bismuth salt and CeO2 and the calcination temperature in Examples 1-10 can be used to prepare higher alcohols by cross-coupling methanol and ethanol, reduce the reaction temperature and improve the yield of C5+ higher alcohols. Among them, the catalyst prepared in Example 3 has the best performance, and the conversion rates of methanol and ethanol, the selectivity of C5+ higher alcohols in the liquid phase product and the yield of C5+ higher alcohols all reach a relatively high level. The experimental results of Comparative Examples 1 and 2 fully prove the necessity of the synergistic effect of bimetallic. In Comparative Example 1, although the introduction of Ni provides active centers for C-H bond dissociation, due to the lack of the electronic regulation effect of Bi, the Ni sites exhibit excessive dehydrogenation activity, resulting in the generation of a large amount of by-products and accelerating the carbon deposition and deactivation of the catalyst. In Comparative Example 2, although the Bi / CeO2 system can partially inhibit the side reaction through the electronic effect of Bi, the lack of the high-efficiency C-H bond activation ability of Ni significantly reduces the initial activation efficiency of alcohol molecules. The limitation of this single metal system is directly reflected in the key performance indicators: the conversion rates of methanol and ethanol decrease significantly, the selectivity of C5+ higher alcohols in the liquid phase product is insufficient, and ultimately the yield of C5+ higher alcohols is much lower than that of the NiBi-CeO2 ternary catalyst system formed in the examples.

[0116] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A process for the preparation of a catalyst for the synthesis of higher alcohols which can be blended with marine fuel, characterized in that, The method comprises the following steps: dissolving nickel salt and bismuth salt in deionized water and stirring to form a homogeneous solution; adding CeO2 into the homogeneous solution and stirring to dry to obtain a precursor; calcining the precursor in an inert atmosphere to obtain the high-grade alcohol synthesis catalyst for blending marine fuel.

2. The process for preparing a catalyst for the synthesis of higher alcohols for use in a blendable marine fuel according to claim 1, characterized in that, The molar ratio of the nickel salt to the bismuth salt is (1-4) :

4.

3. The process for preparing a catalyst for the synthesis of higher alcohols for use in a blendable marine fuel according to claim 2, characterized in that, The molar ratio of the nickel salt to the bismuth salt is 1:

2.

4. The method for preparing the advanced alcohol synthesis catalyst blendable with marine fuel according to claim 1, characterized in that, The molar ratio of the nickel salt to CeO2 is (1-4) :

4.

5. The method for preparing the advanced alcohol synthesis catalyst blendable with marine fuel according to claim 4, characterized in that, The molar ratio of the nickel salt to CeO2 is 1:

2.

6. The method of claim 1, wherein the advanced alcohol synthesis catalyst for a blendable marine fuel is prepared by the steps of: The calcination temperature is 300-600 ℃, and the calcination time is 1-3 h.

7. The process for preparing a catalyst for the synthesis of higher alcohols for use in a blendable marine fuel according to claim 6, characterized in that, The temperature is 550 ℃, and the calcination time is 2 h.

8. The high-grade alcohol synthesis catalyst for blending marine fuel prepared by the method of any one of claims 1-7.

9. The use of the high-grade alcohol synthesis catalyst for blending marine fuel of claim 8 in catalyzing the synthesis of high-grade alcohol from small-molecule alcohol in water phase.

10. Use of the catalyst for the synthesis of higher alcohols according to claim 9 for the catalytic synthesis of higher alcohols from small molecule alcohols in aqueous phase, characterized in that, The small-molecule alcohol is methanol and ethanol, the high-grade alcohol is alcohol with 5-16 carbon atoms, the temperature of the catalytic reaction is 180 ℃, and the time is 20 h.

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