A nickel-magnesium-boron catalyst for synthesizing higher alcohols and a preparation method thereof

Abstract

The present invention provides a preparation method of a nickel-magnesium-boron catalyst for synthesizing higher alcohols, which comprises mixing a nickel salt solution with a magnesium salt solution and a boric acid solution, adding a precipitant under stirring, carrying out a stirring reaction at 0-100 °C for 0.5-50 h, filtering to remove the solvent to obtain a precipitate cake, washing with water and then drying at 50-220 °C; then carrying out a calcination treatment at 400-700 °C for 0.5-48 h, cooling, and carrying out a reduction reaction at 450-700 °C for 0.5-24 h in a reducing atmosphere to obtain the nickel-magnesium-boron catalyst. Experiments show that the catalyst prepared by the present invention has the advantages of high activity, high selectivity, high stability, etc. in the reaction of ethanol conversion to higher alcohols, and its reaction raw materials are cheap, the cost of the catalyst is low, and it can be recycled, which is of great significance for industrial production.

Description

Technical Field

[0001] The present invention relates to a preparation method of a nickel-magnesium-boron composite catalyst, which is mainly used in the synthesis of directly obtaining higher alcohols from ethanol, and belongs to the fields of chemical engineering technology and composite materials. Background Art

[0002] Higher alcohols have a very wide range of applications, such as in detergents, high-grade cosmetics and fragrances, high-grade emulsifiers and dispersants, plasticizers, alcohol fuel additives, etc. The production methods of higher alcohols include the hydroformylation of olefins, the hydrogenation of natural oils, the selective oxidation of alkanes, the Fischer-Tropsch synthesis method, etc. The hydroformylation method is a production process widely used in industry. It uses rhodium and cobalt metals as catalysts to carry out hydroformylation of olefins in the presence of ligands such as phosphines and nitrogens, and converts olefins, carbon monoxide and hydrogen into alcohols with one more carbon atom than the olefin. For example, to prepare hexanol, pentene is used as the raw material, and one carbon atom is added to the end group of the olefin to form an alcohol. The alkane oxidation method uses alkanes as raw materials, generates borate esters under the action of boric acid, and then obtains secondary alcohols with the same number of carbon atoms as the alkanes in the raw material through multiple steps such as esterification, flash evaporation, hydrolysis, saponification, and separation. This method has a relatively long process flow and a low yield. The natural oil hydrogenation method uses vegetable oils such as coconut oil and palm oil or animal oils such as beef tallow as raw materials and excessive methanol, and generates fatty acid methyl esters through transesterification under the action of acid-base catalysts. Then, a hydrogenation reaction is carried out under a high pressure of 10-30 MPa to obtain straight-chain higher alcohols.

[0003] Compared with the above processes, directly obtaining higher alcohols from ethanol is a convenient, green and clean route. The raw material source is sustainable and can be obtained from biomass raw materials. The key to this ethanol-to-higher-alcohol technology is still a catalyst with high activity, high selectivity and stability. For example, in 2017, the research group of Professor Liu Qiang at Tsinghua University developed a new type of inexpensive metal manganese-based catalyst, which realized the efficient catalysis of the ethanol condensation reaction by combining manganese with a pincer ligand. After reacting at 180 °C for 48 h, the ethanol conversion rate was 14.7%, and the main product was butanol. At the same time, a certain amount of higher alcohols with more than C6 could also be obtained (Fu, S.; Shao, Z.; Wang, Y.; Liu, Q., Manganese-Catalyzed Upgrading of Ethanol into 1-Butanol. J Am Chem Soc 2017, 139(34), 11941 - 11948.). CN202110309324.3 discloses a cheap nickel - magnesium - boron catalyst for synthesizing higher alcohols and its preparation method, which is to obtain bone powder by subjecting animal bones to a series of heat treatments; then reacting the bone powder with nickel salts and then performing calcination and reduction treatments. This catalyst does not use homogeneous bases such as sodium methoxide and sodium hydroxide in the reaction for producing higher alcohols and does not require additional hydrogen, resulting in very low equipment requirements and high safety. However, more stable and efficient catalysts still need to be developed to meet the process production requirements. Summary of the Invention

[0004] The main object of the present invention is to provide a preparation method for a nickel - magnesium - boron catalyst with high activity, high selectivity, and high stability for the production of higher alcohols from ethanol.

[0005] The preparation method of the nickel - magnesium - boron catalyst of the present invention is to mix a nickel salt solution with a magnesium salt solution and a boric acid solution, and add a precipitant under stirring, stir and react at 0 - 100 °C for 0.5 - 50 h, filter to remove the solvent to obtain a precipitate cake, wash with water and then dry at 50 - 220 °C; then perform calcination treatment at 400 - 700 °C for 0.5 - 48 h, and after cooling, perform a reduction reaction at 450 - 700 °C in a reducing atmosphere for 0.5 - 24 h to obtain the nickel - magnesium - boron catalyst Ni - Mg - B - X, denoted as NMP - X.

[0006] The nickel salt is any one or a combination of two or more of nickel nitrate, nickel chloride, nickel sulfate, nickel acetate, and nickel acetylacetonate; the concentration of the nickel salt in the mixed system is 0.01 - 1.1 mol / L.

[0007] The magnesium salt is any one or a combination of two or more of magnesium nitrate, magnesium chloride, magnesium acetate, magnesium sulfate, magnesium chlorate, and magnesium perchlorate, and the concentration of the magnesium salt in the mixed system is 0.01 - 2.5 mol / L.

[0008] The concentration of boric acid in the mixed system is 0.01 - 0.8 mol / L.

[0009] The precipitant is sodium hydroxide, sodium carbonate, or ammonia water, and the concentration of the precipitant in the mixed system is 0.01 - 4.0 mol / L.

[0010] The temperature of the drying treatment is 60 - 150 °C, and the time is 2 - 200 h.

[0011] The atmosphere for the calcination treatment is air, nitrogen, or argon atmosphere; the temperature of the calcination treatment is 400 - 700 °C, and the treatment time is 0.5 - 48 h.

[0012] In the reduction reaction, the reducing atmosphere is hydrogen, hydrogen-nitrogen mixture, or hydrogen-argon mixture; the temperature of the reduction reaction is 500 - 600 °C, and the reaction time is 1 - 12 h.

[0013] The composition of the nickel-magnesium-boron catalyst prepared by the above method is as follows: nickel 3 - 30 wt%, magnesium 15 - 30 wt%, and boron 9 - 30 wt%, with the balance being oxygen element.

[0014] Figure 1 This is the XRD pattern of the nickel-magnesium-boron catalyst prepared in Example 3 of the present invention. From Figure 1 it can be seen that there are magnesium oxide phase, boric acid compound phase, and nickel metal phase in the catalyst. From the broadened peaks, it can be seen that the particle size of the catalyst is relatively small.

[0015] Figure 2 This is the infrared spectrum of the nickel-magnesium-boron catalyst prepared in Example 3 of the present invention. From Figure 2 it can be seen that there are vibration peaks of magnesium oxide and boron-oxygen structure on the infrared spectrum of the catalyst.

[0016] Figure 3 This is the 3D-X-ray micrograph of the nickel-magnesium-boron catalyst prepared in Example 3 of the present invention. From Figure 3 it can be seen the internal 3D structure of the well-shaped catalyst.

[0017] Figure 4 This is the Ni-XPS spectrum of the nickel-magnesium-boron catalyst prepared in Example 3 of the present invention. From Figure 4 it can be seen that there are nickel in different valence states in the catalyst, among which the content of zero-valent nickel is 33% and the content of divalent nickel is 67%. Therefore, the nickel element in the nickel-magnesium-boron catalyst is semi-reduced nickel, and the reduction degree of nickel in the nickel-magnesium-boron catalyst is 20 - 90%.

[0018] In summary, the nickel-magnesium-boron catalyst provided by the present invention has the advantages of high activity, high selectivity, and high stability in the reaction of ethanol conversion to higher alcohols. Moreover, its reaction raw materials are cheap, the cost of the catalyst is low, and it can be recycled, which is of great significance for industrial production. Description of the Drawings

[0019] Figure 1 This is the XRD pattern of the nickel-magnesium-boron catalyst prepared in Example 3 of the present invention.

[0020] Figure 2 This is the infrared spectrum of the nickel-magnesium-boron catalyst prepared in Example 3 of the present invention.

[0021] Figure 3 This is the 3D-X-ray micrograph of the nickel-magnesium-boron catalyst prepared in Example 3 of the present invention.

[0022] Figure 4Ni-XPS diagram of the nickel-magnesium-boron catalyst prepared in Example 3 of the present invention. Detailed implementation mode

[0023] The preparation of the nickel-magnesium-boron catalyst of the present invention and its catalytic activity in the production of higher alcohols from ethanol are evaluated through specific examples below.

[0024] The preparation method of the nickel-magnesium-boron catalyst for the production of higher alcohols from ethanol in Example 1 includes:

[0025] Prepare a solution of a magnesium salt, where the magnesium salt is magnesium nitrate, or magnesium chloride, or magnesium acetate, or magnesium sulfate, or magnesium chlorate, or magnesium perchlorate, and the concentration of the magnesium salt is preferably 0.01 mol / L, or 0.1 mol / L, or 0.5 mol / L, or 1 mol / L, or 1.5 mol / L, or 2.5 mol / L, or a concentration within the range formed by these values.

[0026] Prepare a nickel salt solution, where the nickel salt is nickel acetate, nickel sulfate, nickel chloride, nickel nitrate, or nickel acetylacetonate. The concentration of the nickel salt is preferably 0.01 mol / L, 0.1 mol / L, 0.25 mol / L, 0.5 mol / L, 1.1 mol / L, or a concentration within the range formed by these values. Take a magnesium salt solution and add it to the nickel salt solution, and mix them evenly. Prepare a boric acid solution, with a concentration preferably of 0.01 mol / L, 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.8 mol / L, or a concentration within the range formed by these values. Take the boric acid solution and add it to the mixed solution of the magnesium salt and the nickel salt under stirring conditions. Prepare a precipitant solution, where the precipitant is sodium hydroxide, sodium carbonate, or ammonia water. The concentration of the precipitant is preferably 0.01 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 4 mol / L, or a concentration within the range formed by these values. At a temperature of 0 °C, 25 °C, 50 °C, 70 °C, 100 °C, or a temperature within the range formed by these values, under stirring conditions, add the precipitant dropwise to the mixed solution containing boric acid, magnesium salt, and nickel salt. The stirring duration is 0.5 h, 5 h, 10 h, 25 h, 50 h, or a duration within the range formed by these values. Then, filter to remove the solution to obtain a solid filter cake, and wash the filter cake with water 1 time, 5 times, 10 times, or a number of times within the range formed by these values. Dry at a temperature of 50 °C, 80 °C, 120 °C, 180 °C, 220 °C, or a temperature within the range formed by these values for 2 h, 12 h, 24 h, 50 h, 100 h, or a duration within the range formed by these values. Then, calcine at a temperature of 400 °C, 500 °C, 600 °C, 700 °C, or a temperature within the range formed by these values for 0.5 h, 2 h, 12 h, 24 h, 48 h, or a duration within the range formed by these values. Then, transfer it to a hydrogen atmosphere and reduce it at a temperature of 450 °C, 500 °C, 600 °C, 700 °C, or a temperature within the range formed by these values for 0.5 h, 3 h, 6 h, 12 h, 24 h, or a duration within the range formed by these values to obtain the required nickel-magnesium-boron catalyst NMP-1.

[0027] Example 2 Preparation of Nickel-Magnesium-Boron Catalyst

[0028] Mix 50 mL of a Mg(NO3)2 solution with a concentration of 0.68 mol / L, 50 mL of a boric acid solution with a concentration of 0.51 mol / L, and 50 mL of a Ni(NO3)2 solution with a concentration of 0.085 mol / L. After stirring well for 3 h, slowly add dropwise 160 mL of 1 M NaOH solution while observing the precipitation situation of the solution. Raise the temperature of the solution to 75 °C and stir for 12 h. After cooling, filter to remove the solution to obtain the precipitate. Wash the precipitate 3 times with deionized water. And place it in an oven and dry at 80 °C for 12 h. Place the dried solid in a crucible and put it into a muffle furnace for calcination, and calcine in an air atmosphere at 400 °C for 4 hours. After cooling to room temperature, grind the calcined catalyst into powder; then place the powder in a quartz boat and put it into the constant temperature section of a tubular furnace, and reduce it at 500 °C in a hydrogen atmosphere for 4 hours. After cooling, take it out and carry out catalyst forming to obtain the required catalyst NMP-2.

[0029] Preparation of nickel-magnesium-boron catalyst in Example 3

[0030] Mix 50 mL of a Mg(NO3)2 solution with a concentration of 0.68 mol / L, 50 mL of a boric acid solution with a concentration of 0.68 mol / L, and 50 mL of a Ni(NO3)2 solution with a concentration of 0.085 mol / L. After stirring well for 3 h, slowly add dropwise 180 mL of 1 M NaOH solution. Then raise the temperature of the solution to 75 °C and stir for 12 h. After cooling, filter to remove the solution to obtain the precipitate and wash it 3 times with deionized water. Place it in an oven and dry at 90 °C for 12 h. Place the dried solid in a muffle furnace and calcine at 400 °C for 4 h. After cooling, grind the calcined catalyst into powder and put it into the constant temperature section of a tubular furnace, and reduce it at 600 °C in a hydrogen atmosphere for 4 h. After cooling, take it out and carry out catalyst forming to obtain the required catalyst NMP-3.

[0031] Preparation of nickel-magnesium-boron catalyst in Example 4

[0032] Mix 100 mL of a magnesium acetate solution with a concentration of 0.011 mol / L, 50 mL of a boric acid solution with a concentration of 0.01 mol / L, and 100 mL of a nickel acetate solution with a concentration of 0.014 mol / L. After stirring well for 50 h, slowly add dropwise 390 mL of 0.01 mol / L ammonia water. Then keep the solution at 0 °C and stir for 50 h. After cooling, obtain the solid by high-speed centrifugation and wash it 1 time with deionized water. Place it in an oven and dry at 50 °C for 100 h. Place the dried solid in a muffle furnace and calcine at 700 °C for 0.5 h. After cooling, grind the calcined catalyst into powder and put it into the constant temperature section of a tubular furnace, and reduce it at 700 °C in a 5% hydrogen-nitrogen mixed atmosphere for 0.5 h. After cooling, take it out and carry out catalyst forming to obtain the required catalyst NMP-4.

[0033] Example 5 Preparation of Nickel-Magnesium-Boron Catalyst

[0034] Mix 50 mL of magnesium chloride solution with a concentration of 2.52 mol / L, 50 mL of boric acid solution with a concentration of 0.049 mol / L, and 6 mL of nickel sulfate solution with a concentration of 1.07 mol / L. After stirring thoroughly at 100 °C for 10 h, slowly drip 69 mL of 4 mol / L sodium hydroxide solution. Then, stir the solution at 100 °C for 0.5 h. After cooling, obtain the solid by filtration and wash it 10 times with deionized water. Place it in an oven and dry it at 220 °C for 10 h. Put the dried solid into a muffle furnace and calcine it at 400 °C for 48 h. After cooling, grind the calcined catalyst into powder and place it in the isothermal section of a tubular furnace. Reduce it at 450 °C in a 10% hydrogen-argon mixed atmosphere for 24 h. After cooling, take it out and perform catalyst shaping to obtain the required catalyst NMP-5.

[0035] Example 6 Preparation of Nickel-Magnesium-Boron Catalyst

[0036] Mix 100 mL of magnesium perchlorate solution with a concentration of 0.0045 mol / L, 100 mL of boric acid solution with a concentration of 0.016 mol / L, and 6 mL of nickel acetylacetonate solution with a concentration of 0.102 mol / L. After stirring thoroughly at 20 °C for 1 h, slowly drip 35 mL of 0.1 mol / L sodium carbonate solution. Then, stir the solution at 20 °C for 20 h. After cooling, obtain the solid by filtration and wash it 3 times with deionized water. Place it in an oven and dry it at 100 °C for 20 h. Put the dried solid into a muffle furnace and calcine it at 500 °C for 10 h. After cooling, grind the calcined catalyst into powder and place it in the isothermal section of a tubular furnace. Reduce it at 550 °C in a hydrogen atmosphere for 10 h. After cooling, take it out and perform catalyst shaping to obtain the required catalyst NMP-6.

[0037] Example 7 Reaction Activity Test

[0038] Use the nickel-magnesium-boron catalyst NMP-2 prepared in the example for the reaction of ethanol conversion to higher alcohols. Put anhydrous ethanol into a reaction kettle and add 10 wt.% of the catalyst NMP-2. After sealing the reaction kettle, displace the atmosphere with nitrogen, heat the temperature to 200 °C, maintain the reaction for 24 h, then cool down and take samples. After gas chromatography analysis, it is found that the single-pass conversion rate of ethanol reaches 34.8%, the selectivity for higher alcohols with C4 or more reaches 97%, and the selectivity for higher alcohols with C6 or more reaches 46%.

[0039] Example 8 Reaction Activity Test

[0040] The nickel-magnesium-boron catalyst NMP-3 prepared in the examples was used in the reaction for the conversion of ethanol to higher alcohols. Anhydrous ethanol was placed in a reaction kettle, and the catalyst NMP-3 with a mass fraction of 10% was added. After the reaction kettle was sealed, the atmosphere was replaced with nitrogen at atmospheric pressure, the temperature was heated to 200 °C, and the reaction was maintained for 24 h. After cooling and temperature reduction, a sample was taken. Through gas chromatography analysis, it was found that the single-pass conversion rate of ethanol reached 33.4%, the selectivity for higher alcohols with four or more carbon atoms reached 98%, and the selectivity for higher alcohols with six or more carbon atoms reached 48%.

[0041] Example 9: Reaction activity test for stability

[0042] The nickel-magnesium-boron catalyst NMP-3 prepared in the examples was used in the reaction for the conversion of ethanol to higher alcohols. The stability of the catalyst was tested by recycling in the same manner as in Example 9. Anhydrous ethanol was placed in a reaction kettle, and the catalyst NMP-3 with a mass fraction of 10% was added. After the reaction kettle was sealed, the atmosphere was replaced with nitrogen, the temperature was heated to 200 °C, and the reaction was maintained for 24 h. After cooling and temperature reduction, a sample was taken. Through gas chromatography analysis, it was found that the catalyst had good stability and could be recycled (see Table 1).

[0043]

[0044] Comparative Example 1: Change in preparation conditions

[0045] In the catalyst preparation process in Example 2, the reduction temperature was changed to 400 °C, and other conditions remained unchanged. It was used in the reaction for the conversion of ethanol to higher alcohols, and the reaction conditions were the same as in Example 8. It was found that the single-pass conversion rate of ethanol reached 8%, the selectivity for higher alcohols with four or more carbon atoms reached 30%, and the selectivity for C6 alcohols reached 3.5%. By comparing with Example 8, it was found that the preparation method had a very great influence on the activity of the catalyst. Changing a certain factor could lead to a significant decrease in the activity of the catalyst. A highly efficient catalyst could not be obtained directly through speculation without creative labor.

[0046] Comparative Example 2: Change in preparation method - impregnation method

[0047] Change the catalyst preparation conditions in Example 2. Mix 50 mL of a Mg(NO3)2 solution with a concentration of 0.68 mol / L and 50 mL of a boric acid solution with a concentration of 0.68 mol / L. After stirring well for 3 h, slowly drip into a 1 M NaOH solution to produce a precipitate. Then raise the solution temperature to 75 °C and stir for 12 h. After cooling, filter to remove the solution to obtain the precipitate and wash it 3 times with deionized water. Place it in an oven and dry it at 90 °C for 12 h. Put the dried solid into a muffle furnace and calcine it at 400 °C for 4 h. Mix the calcined solid powder with 50 mL of a Ni(NO3)2 solution with a concentration of 0.085 mol / L for impregnation. Then dry it at 90 °C for 12 h, calcine it at 400 °C for 4 h, and after cooling, grind the calcined catalyst into powder and place it in the isothermal section of a tubular furnace. Reduce it at 500 °C in a hydrogen atmosphere for 4 h. After cooling, take it out, shape the catalyst to obtain the required catalyst NMP-3-imp. Use the catalyst NMP-3-imp for the reaction of ethanol conversion to higher alcohols, and the reaction conditions are the same as those in Example 8. It is found that the single-pass conversion rate of ethanol reaches 0.6%, the selectivity of higher alcohols with C4 and above reaches 80.3%, and the selectivity of alcohols with C6 and above reaches 18.1%. By comparing with Example 2 and 8, it is found that the preparation method has a very large impact on the activity of the catalyst. Changing a certain factor can lead to a significant decrease in the activity of the catalyst. An efficient catalyst cannot be obtained directly through speculation without creative labor.

[0048] Comparative Example 3 Magnesium Oxide Impregnation Method

[0049] For the directly purchased magnesium oxide powder particles, according to the ratio in Example 2, refer to the process in Comparative Example 2 for catalyst impregnation. That is, mix 3 g of magnesium oxide powder with 50 mL of a Ni(NO3)2 solution with a concentration of 0.085 mol / L for impregnation. Then dry it at 90 °C for 12 h, calcine it at 400 °C for 4 h, and after cooling, grind the calcined catalyst into powder and place it in the isothermal section of a tubular furnace. Reduce it at 500 °C in a hydrogen atmosphere for 4 h. After cooling, take it out, shape the catalyst to obtain the required catalyst NM-imp. Use the catalyst NM-imp for the reaction of ethanol conversion to higher alcohols, and the reaction conditions are the same as those in Example 8. It is found that the single-pass conversion rate of ethanol reaches 0.7%, the selectivity of higher alcohols with C4 and above reaches 81%, and the selectivity of C6 alcohols reaches 18%.

[0050] Comparative Example 4

[0051] Use commercial Raney nickel as the catalyst, and under the same reaction conditions as in Example 8, after obtaining the liquid-phase product and analyzing it by gas chromatography, higher alcohols with C6 and above cannot be obtained.

[0052] In the above examples and comparative examples, the conversion rate of the reactant ethanol is defined as:

[0053]

[0054] The selectivity of the product higher carbon alcohol is defined as:

[0055] 。

Claims

1. Application of a nickel-magnesium-boron catalyst in the synthesis of higher alcohols from ethanol, characterized in that: The preparation method of the nickel-magnesium-boron catalyst is to mix a nickel salt solution with a magnesium salt solution and a boric acid solution, add a precipitant under stirring, stir and react at 0-100 °C for 0.5-50 h, filter to remove the solvent to obtain a precipitate cake, wash with water, dry and then calcine at 400-700 °C for 0.5-48 h, and after cooling, carry out a reduction reaction at 450-700 °C for 0.5-24 h in a reducing atmosphere to obtain the nickel-magnesium-boron catalyst; the composition of the nickel-magnesium-boron catalyst is as follows: nickel 3-30 wt%, magnesium 15-30 wt% and boron 9-30 wt%, and the balance is oxygen element.

2. The application of a nickel-magnesium-boron catalyst in the synthesis of higher alcohols from ethanol according to claim 1, characterized in that: The nickel salt is any one or a combination of two or more of nickel nitrate, nickel chloride, nickel sulfate, nickel acetate and nickel acetylacetonate; the concentration of the nickel salt in the mixed system is 0.01-1.1 mol / L.

3. The application of a nickel-magnesium-boron catalyst in the synthesis of higher alcohols from ethanol according to claim 1, wherein: The magnesium salt is any one or a combination of two or more of magnesium nitrate, magnesium chloride, magnesium acetate, magnesium sulfate, magnesium chlorate and magnesium perchlorate, and the concentration of the magnesium salt in the mixed system is 0.01-2.5 mol / L.

4. The application of a nickel-magnesium-boron catalyst in the synthesis of higher alcohols from ethanol according to claim 1, characterized in that: The concentration of the boric acid in the mixed system is 0.01-0.8 mol / L.

5. The application of a nickel-magnesium-boron catalyst in the synthesis of higher alcohols from ethanol according to claim 1, characterized in that: The precipitant is sodium hydroxide, sodium carbonate or ammonia water, and the concentration of the precipitant in the mixed system is 0.01-4.0 mol / L.

6. The application of a nickel-magnesium-boron catalyst in the synthesis of higher alcohols from ethanol according to claim 1, characterized in that: The temperature of the drying treatment is 60-150 °C and the time is 2-200 h.

7. The application of a nickel-magnesium-boron catalyst in the synthesis of higher alcohols from ethanol according to claim 1, characterized in that: The atmosphere for the calcination treatment is air, nitrogen or argon atmosphere.

8. The application of a nickel-magnesium-boron catalyst in the synthesis of higher alcohols from ethanol according to claim 1, wherein: In the reduction reaction, the reducing atmosphere is hydrogen, hydrogen-nitrogen mixture or hydrogen-argon mixture.

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