Method for obtaining homogeneous suspension using magnesium hydride

Abstract

FIELD: hydrogen energy.SUBSTANCE: invention is intended for use in energy sources based on hydrogen fuel cells. A method for obtaining a homogeneous suspension is proposed, characterized by the fact that magnesium hydride and an ester with a boiling point of more than 180 °C are used in a mass ratio of 1:1, chloride of metals of groups I and II A - in an amount of 5-15 wt.% of magnesium hydride and a thickener - inorganic salts or oxides of non-metals, or oxides of metals of groups I and II A in an amount of 0.1-0.2 wt.% of magnesium hydride. The suspension is obtained by adding chloride of metals of groups I and II A, an ester to magnesium hydride with stirring for at least 20 minutes and then adding a thickener to the resulting mixture, with stirring for at least 10 minutes.EFFECT: it is possible to obtain a safe, energy-intensive, homogeneous suspension based on magnesium hydride, providing a high yield of hydrogen.1 cl, 3 tbl, 8 ex

Description

[0001] The invention relates to the field of hydrogen energy and is intended for use in hydrogen fuel cell power sources. The method, which produces hydrogen through a chemical reaction, can be used as a safe source of hydrogen with a high energy storage density for hydrogen fuel cell power systems.

[0002] Amid the global environmental crisis, hydrogen technologies are becoming increasingly important as a solution to the issue of decarbonization. Hydrogen, as an energy carrier, has unique properties that make it an ideal candidate for the fuel of the future. It is the most energy-dense substance by mass, with a calorific value of approximately 140 MJ / kg, which is almost three times higher than traditional hydrocarbon fuels (gasoline – approximately 46 MJ / kg). Furthermore, the oxidation product in fuel cells is water, making this energy carrier completely environmentally friendly. The efficiency of converting hydrogen's chemical energy into electrical energy in modern fuel cells reaches approximately 70%, significantly exceeding the efficiency of internal combustion engines (25-30%).However, traditional hydrogen storage methods present significant technical challenges, as compressed gas storage requires high-pressure cylinders (350-700 bar), which creates safety, weight, and volume issues. Liquefaction of hydrogen, while increasing storage density, requires very low temperatures (-253°C) and complex insulation systems. These methods require expensive refueling station infrastructure, limiting their applicability. Therefore, the key requirements for a hydrogen storage and generation system are safety, ease of use, rapid refueling, and compactness.

[0003] A known method for producing hydrogen by hydrolysis of metal borohydride compounds using a catalytic method (US Patent No. 2005 / 0238573 A1). To increase hydrogen yield and reaction efficiency, an acid is added to the reaction mixture.

[0004] The disadvantage of this solution is the use of metal borohydride compounds in conjunction with a catalyst, which complicates the mixing of the reacting components, results in a low gravimetric hydrogen yield, and also leads to the dangerous formation of toxic products, particularly the violent release of diborane (B2H6 – hazard class 1, similar to phosgene). Furthermore, the use of acid in the reaction mixture can lead to its vapors from the reaction mixture entering other parts of the energy system, leading to its failure.

[0005] Methods for producing hydrogen by hydrolysis of lithium aluminum hydride (US 5702491 A) and lithium hydride (US 5514353), which release hydrogen when hydrolyzed with water, are also known.

[0006] The disadvantages of their use are: the high cost of these compounds, the difficulty of obtaining them and the danger of handling them, due to their reactivity when interacting with water, leading to an explosion, which complicates the control of the chemical reaction (analogues).

[0007] The closest to the claimed invention is a method for generating hydrogen using magnesium hydride used as a metal hydride fuel, which contains a hydride phase of at least 95%, for this purpose the metal hydride fuel is sieved and crushed, the filling is compacted in a chemical cartridge, heated and a reaction of the metal hydride fuel with water vapor is carried out (patent RU No. 2708001, published 03.12.2019).

[0008] Metal hydride fuel powder is mixed with additives of LiNO3, NaNO3, KNO3, RbNO3, LiOAc, NaOAc, KOAc, LiCl, and NaCl salts in amounts ranging from 0.5 to 15% by weight. The additives are added to the magnesium hydride powder in a ball mixer, with a mixing time of 15 to 45 minutes. Processing is carried out in an argon box or in a protective atmosphere. This known solution provides a high gravimetric hydrogen yield of 7 to 9% by weight.

[0009] The disadvantages of using magnesium hydride as a backfill are: the multi-stage nature of its preparation as a metal hydride fuel with an insufficiently high hydrogen yield, the use of MgH2 in the form of a finely dispersed powder with a large surface area, which is unsafe when interacting with water due to increased activity, which can lead to an uncontrolled hydrolysis reaction.

[0010] The technical challenge is to develop a method for producing a safe, energy-intensive, homogeneous suspension using magnesium hydride, providing a high yield of hydrogen.

[0011] The technical problem is solved by a method of obtaining a homogeneous suspension using magnesium hydride.

[0012] What is new is that for the preparation of a homogeneous suspension, additionally used are chloride of metals of groups I and II A, an ester with a boiling point of >180 °C and a thickener, magnesium hydride and ester in the composition of a homogeneous suspension are used in a weight ratio of 1:1, chloride of metals of groups I and II A - in an amount of 5-15% by weight of magnesium hydride, and inorganic salts or oxides of non-metals, or oxides of metals of groups I and II A in an amount of 0.1-0.2% by weight are used as a thickener. from magnesium hydride, whereby a homogeneous suspension is obtained by adding chloride of metals of groups I and II A, a complex ester to magnesium hydride and stirring for at least 20 minutes, then adding a thickener to the resulting mixture and stirring for at least 10 minutes, the resulting homogeneous suspension is used either in a fuel cell or as a safe storage of hydrogen.

[0013] Magnesium hydride was chosen to implement the method as a hydrogen-carrying compound. It was produced in Russia by Khimlab LLC in accordance with patent (RU No. 2686898C1) and meets the parameters listed in Table 1.

[0014] Table 1. Characteristics of magnesium hydride

[0015] Degree of hydrogenation 95-97 % Granulometry 0.1-0.5 µm Molecular weight 26.3209 g / mol Appearance Gray powder Density 1.45 g / cm3 Solubility in water It decomposes CAS 7693-27-8 Specific heat 35.4 J / mol⋅K Standard molar entropy 31.1 J / mol⋅K Standard enthalpy of formation -75.5 kJ / mol Gibbs free energy -35.9 kJ / mol

[0016] In experiments to obtain a homogeneous suspension (HS), magnesium hydride is used as part of a HS with the general formula MgH2⋅MCl m ⋅R⋅COOR1⋅ thickener, where MgH2 is magnesium hydride, MCl m – chloride of metals of groups I and II A in an amount of 5-15% by weight of magnesium hydride, R⋅COOR1- An ester with a boiling point of >180 ⁰C (R⋅COOR1 is the general formula for carboxylic acid esters in chemistry. These are compounds in which the hydrogen atom in the carboxyl group is replaced by a hydrocarbon radical. Butyl carbitol acetate (butyl diglycol acetate, butyl carbitol acetate) is a transparent, colorless, high-boiling organic liquid with low volatility and a faint ethereal odor. It is an ester of diethylene glycol and acetic acid). In this case, magnesium hydride and the ester are used in a homogeneous suspension in a weight ratio of 1:1. Inorganic salts or oxides of non-metals, or oxides of metals of groups I and IIA are used as a thickener in an amount of 0.1-0.2% by weight of magnesium hydride. After production, the HS is used either in a fuel cell or as a safe hydrogen storage facility.

[0017] The result is a safe, homogeneous suspension, whose safety is ensured by the presence of an ester with a boiling point of >180°C and the addition of Group I and IIA metals, which act as decomposition inhibitors and ensure homogeneity during mixing. Once obtained, the HS is used either in a fuel cell or as a safe hydrogen storage medium.

[0018] In a typical experiment, 50 g of magnesium hydride are loaded into a reactor equipped with an anchor stirrer, 5 g of a metal chloride of groups I or II A (e.g., 99% lithium chloride) and 50 ml of an ester (e.g., butyl carbitol acetate, t кип=241.5°C), the reaction is carried out at t=25°C with stirring with an anchor stirrer for at least 20 min, then a thickener is added (e.g., calcium oxide 0.1% of MgH2), and stirring is continued for at least another 10 min. A total stirring time of at least 30 min is required to obtain a uniform, homogeneous product. The boiling point of the ester is >180°C, which is necessary for low solvent volatility and also to address safety concerns.

[0019] As a result of the experiment, a homogeneous gray suspension was obtained in which the hydrogen content was from 8 to 10%. Table 2 shows the components of the homogeneous suspension and the hydrogen content in it.

[0020] The main criterion for selecting the composition is the hydrogen content in the resulting suspension. It was determined using a 5E-CHN 2200 elemental analyzer. The hydrogen determination method on the elemental analyzer is based on hydrogen extraction in an inert gas environment. This method allows for the determination of hydrogen content in a sample, including concentrations <2 ppm in sludge, refractory metals, aluminum alloys, and other inorganic materials.

[0021] Table 2. Components in the homogeneous suspension

[0022] No., p / p Taken to obtain GS Hydrogen content Hydrogen mass content, %, not less than 8.5 MgH2, g MClm, g Ester, ml Thickener, g Conditions for carrying out the synthesis t, °C τtotal, min., not less than Exit, % 1 5 0.5 LiCl Butyl carbitol acetate (BCA), 5 CaO, 0.05 25 30 98 9,03 2 5 0.5 CaCl2 BKA, 5 CaO, 0.1 25 30 99 8,8 3 5 0.5 CaCl2 BKA, 5 CaO, 0.1 25 30 97 8,38 Low hydrogen content 4 5 0.5 LiCl Dibutyl sebacate (DBS), 5 CaO, 0.05 25 30 97,8 9,57 5 5 0.5 MgCl2 DBS, 5 CaСO3, 0.05 25 30 99,5 8,94 6 5 0.5 CaCl2 Diethylene glycol diethyl ether (DEDH), 5 CaСO3, 0.1 25 40 97 8,32 Low hydrogen content 7 5 0.1 LiCl DEDG, 5 Na2SO4, 0.05 25 30 98 8,92 8 5 0.1 LiCl DEDG, 5 B2O3, 0.05 25 30 96,5 8,34 Low hydrogen content

[0023] As Table 2 shows, with the same component contents, the amount of hydrogen produced varies in each case when mixing in different solvents, depending on the thickener content and its nature. The highest hydrogen content is observed in a homogeneous suspension with a thickener content of no more than 0.1% of MgH2 (e.g., Example 1, Table 2; Example 4, Table 2).

[0024] Table 3 shows the technical characteristics of the obtained homogeneous suspension.

[0025] The advantage of this method for producing a homogeneous suspension is that it eliminates the need for special component preparation, as is required in its closest analog: crushing, sifting, compacting the fuel charge, and forming a bimodal charge consisting of crushed and sifted powder. The density of the resulting homogeneous suspension has been found to be between 1.15 and 1.20 g / cm3. 3This ensures the fluidity of the homogeneous suspension, which is important when refilling cartridges. The gradual interaction of the suspension with water results in the measured release of hydrogen.

[0026] Table 3. Characteristics of the resulting homogeneous suspension

[0027] Name of the indicator Norm 1. Appearance A homogeneous mass of creamy consistency from light gray to gray in color 2. Hydrogen content by mass, %, not less than 8,5 3. Dynamic viscosity 23 °C (speed 6 rpm), MPa⋅C, no more than 2000 4. Total mass loss in the range of 30-300 °C, % of mass, no more than in the range of 30-200 °C, % of mass, no more than 50 20 5. Chemical resistance at 110 °C, not less than an hour 6 6. Density at 20 °C, kg / m3, no more than 1200

[0028] The consistency of the resulting homogeneous suspension allows for easy pumping of the energy carrier into tanks. The homogeneous suspension is stable at temperatures up to 250°C, indicating its safety. It stores 10 times more energy than lithium-ion batteries of similar weight and significantly more than a hydrogen tank of the same size.

Claims

A method for producing a homogeneous suspension using magnesium hydride, characterized in that for the preparation of a homogeneous suspension, additionally used are chloride of metals of groups I and II A, an ester with a boiling point of more than 180 ° C and a thickener, magnesium hydride and an ester in the composition of a homogeneous suspension are used in a weight ratio of 1: 1, chloride of metals of groups I and II A - in an amount of 5-15 wt.% of magnesium hydride, and as a thickener, inorganic salts or oxides of non-metals, or oxides of metals of groups I and II A in an amount of 0.1-0.2 wt.% of magnesium hydride are used, wherein a homogeneous suspension is obtained by adding chloride of metals of groups I and II A, an ester to magnesium hydride and stirring for at least 20 minutes, then adding a thickener to the resulting mixture and stirring for at least 10 minutes, the resulting homogeneous suspension is used either in a fuel cell or as safe hydrogen storage.