CN102976268B - Method for generating hydrogen by hydrolyzing lithium borohydride and reacting device used for method - Google Patents

Abstract

The invention provides a method and a device for generating hydrogen by hydrolyzing lithium borohydride. The method comprises the following steps: dissolving lithium borohydride in an organic solvent that will not be adsorbed on a proton exchange membrane fuel cell membrane to form an organic saturated solution or an organic suspension The turbid liquid is then fed into liquid water, and the reaction hydrogen release rate is adjusted by adjusting the concentration of lithium borohydride, and finally the theoretical hydrogen content in lithium borohydride is completely released; the device includes a liquid water storage room (1), a The water capillary (2), the hydrolysis reaction chamber (3), the gas feedback pipeline (5) and the interface (4) connected to the fuel cell, one end of the water inlet capillary (2) communicates with the liquid water storage chamber (1), The other end is placed in the hydrolysis reaction chamber (3), one end of the gas feedback pipeline (5) is inserted into the liquid water in the liquid water storage chamber (1), and the other end communicates with the hydrolysis reaction chamber (3). The method has high dehydrogenation efficiency, and the dehydrogenation process is stable and controllable.

Description

A method for generating hydrogen by hydrolysis of lithium borohydride and its reaction device

technical field

The invention relates to the technical field of using hydrogen sources of micro-fuel cells, in particular to a method for generating hydrogen by hydrolysis of lithium borohydride, and a reaction device used in the method.

Background technique

In recent years, the state has put forward a strategic development plan for the active development and utilization of new energy, and increased financial and policy support for the new energy field, aiming to reduce greenhouse gas emissions, solve environmental problems, and at the same time deal with the energy crisis, realize economic and ecological development. Overall planning and coordinated development. One of the core technologies in the field of new energy: fuel cell technology has thus been developed rapidly. Fuel cells can be used not only as large-scale power sources, but also as small portable power sources, such as laptop computers and mobile communications. However, the storage and transportation of hydrogen, the biggest obstacle to the application of fuel cells, has not been effectively resolved. Especially for portable fuel cells, this contradiction becomes more prominent.

The hydrolysis of chemical hydrides (such as NaH, LiH, NaBH ₄ ) to generate hydrogen is a new type of hydrogen generation technology that is convenient, practical and can effectively produce high-purity hydrogen. The hydrogen produced by this technology is of high purity and can be directly used as a hydrogen source for fuel cells. However, LiH, NaH and water react too violently, so the surface of NaH should be coated with a layer of resin to reduce the contact area with water reaction. LiH should be mixed with light mineral oil to form a slurry, and it can only react smoothly with water under normal temperature and pressure. NaBH ₄ is relatively stable and easy to operate, so it is currently the hydrogen production technology route commonly used by researchers. However, the hydrogen in the hydride reaction between NaBH ₄ and water cannot be completely released, and NaBH ₄ will remain in the solid reaction product, and the reaction hydrogen release rate is low, requiring catalyst acceleration. The hydrolysis of NH ₃ BH ₃ system to generate hydrogen is also one of the most popular hydrolyzed materials in current research. Because the effective hydrogen capacity of NH ₃ BH ₃ is 5.8wt%, and NH ₃ BH ₃ can form a stable solution with water at room temperature, which is convenient for storage and transportation. However, the catalysts that catalyze the hydrolysis of NH ₃ BH ₃ to generate hydrogen are mostly noble metal materials, the preparation cost of which is high, and the number of cycles is not ideal. Kojima et al. studied the hydrolysis behavior of LiBH ₄ with a fixed ratio of H ₂ O/LiBH ₄ and found that the amount of hydrogen released was 1.3 mol/mol, but the rate of hydrogen generation was too fast to be controlled. Zhu et al. found that the hydrolysis of LiBH ₄ could not completely release the hydrogen in the compound. The commonly used chemical reagent for stabilizing borohydride is NaOH. However, LiBH ₄ is still unstable in NaOH solution. According to Kreevoy et al., borohydride has a half-life in a strong alkaline solution and will react slowly.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for generating hydrogen by hydrolyzing lithium borohydride. The method has high hydrogen desorption efficiency when producing hydrogen, and the dehydrogenation process is stable and controllable, and is suitable for use as a hydrogen source for micro-fuel cells.

The technical scheme adopted in the present invention is: a method for hydrolyzing lithium borohydride to generate hydrogen, the method comprising the following steps: dissolving lithium borohydride (LiBH ₄ ) in a proton exchange membrane fuel cell membrane that will not adsorb on the membrane of the proton exchange membrane fuel cell to cause the battery Organic solvents with reduced performance form organic saturated solutions or organic suspensions (or called slurry), and then pass into liquid water to make

Lithium borohydride and liquid water undergo a hydrolysis hydrogenation reaction, and the reaction hydrogen release rate is adjusted by adjusting the concentration of lithium borohydride dissolved in the organic solvent, and finally the theoretical hydrogen content in lithium borohydride is completely released.

Preferably, the organic solvent that will not be adsorbed on the proton exchange membrane fuel cell membrane is ether and nonane.

Preferably, the concentration range of the organic suspension is between the organic saturated solution and 10 molL ⁻¹ .

The theoretical hydrogen content of LiBH ₄ is 18.5wt%, and the hydrogen in the compound can be released in the form of hydrogen through pyrolysis and hydrolysis, so it can be used to realize the hydrogen production material as the hydrogen source of the fuel cell.

The inventors of the present invention have found through research that LiBH can form weak interactions with organic solvent molecules such as ether, and under this effect _, the hydrolysis process of _LiBH can be represented by the following equation:

LiBH ₄ + Organ → LiBH ₄ [Organ] (1)

LiBH ₄ ·[Organ] + 4H ₂ O → LiBO ₂ ·2H ₂ O + 4H ₂ + Organ (2)

The hydrolysis of LiBH ₄ decomposes hydrogen rapidly. After mixing with organic solvent, the reaction path is changed, thereby reducing the hydrogen release rate of the hydrolysis reaction product and the reaction temperature. The reaction rate can be reduced by 2 orders of magnitude from 6800 mLmin ^-1 g ^-1 . The reaction heat is greatly reduced, and the reaction temperature rise is reduced from 180°C to within 5°C, which improves the problem of LiBH ₄ hydrolysis and agglomeration, and the phenomenon of LiBH ₄ hydrolysis and agglomeration disappears, thereby increasing the hydrogen yield and completely releasing the hydrogen in LiBH ₄ . After the LiBH ₄ of the present invention is mixed with an organic solvent, by adjusting the concentration of LiBH ₄ dissolved in the organic solvent, the control and adjustment of the reaction hydrogen release rate is realized, and the released hydrogen is in a suitable temperature range for the fuel cell.

Another technical problem to be solved by the present invention is to provide a reaction device used in the above-mentioned method for hydrolyzing lithium borohydride to generate hydrogen.

The technical solution adopted in the present invention is: a reaction device used in the method for hydrolyzing lithium borohydride to generate hydrogen, the reaction device includes a liquid water storage room, a water inlet capillary, a hydrolysis reaction room, a gas feedback pipeline and a fuel cell One end of the water inlet capillary communicates with the liquid water storage chamber, the other end is placed in the hydrolysis reaction chamber, one end of the gas feedback pipeline is inserted into the liquid water in the liquid water storage chamber, and the other end is connected to the hydrolysis reaction chamber. The reaction chambers are connected. The hydrolysis reaction chamber is the place where lithium borohydride reacts with liquid water to release hydrogen gas. The liquid water is injected into the hydrolysis reaction chamber with a small amount of controllable liquid water through the water inlet capillary. The hydrogen generated by the hydrolysis reaction enters the fuel cell through the interface with the fuel cell. battery system. The setting of the gas feedback pipeline is to solve the volatilization problem of the organic solvent. When the organic solvent volatilization gas in the hydrolysis reaction chamber volatilizes, it can be returned to the hydrolysis reaction chamber through the gas feedback pipeline, thus ensuring the hydroboration The concentration of the lithium organic solution reduces the waste of organic solvents and a series of problems caused by volatilization.

The diameter of the water inlet capillary is 5-30 μm. Liquid water reacts with lithium borohydride through the water inlet capillary under natural pressure difference to produce hydrogen.

Compared with the prior art, the present invention has the following significant advantages and beneficial effects:

(1) The hydrogen desorption efficiency is high. LiBH ₄ is dissolved in an organic solvent, and the hydrogen capacity reduction defect caused by the aggregation and agglomeration of LiBH ₄ is effectively suppressed, and the hydrogen in LiBH ₄ can be completely released.

(2) The hydrolysis reaction rate of the present invention is 2 orders of magnitude lower than that of pure LiBH ₄ , the hydrogen generation rate is between 10 and 160 mLmin ^-1 g ^-1 , the hydrogen release reaction is stable and controllable, and the hydrogen released by the reaction can be safely stored and transported , in line with the hydrogen source supply requirements of micro fuel cells.

The invention controls the amount of the organic solvent to effectively control the heat/kinetics of hydrogen generation by mixing the lithium borohydride with organic solvents such as ether and nonane and then hydrolyzing them. This method of hydrolysis hydrogen production overcomes the defect that the production of pure LiBH ₄ is affected by agglomeration and agglomeration in hydrolysis; and without reducing the total hydrogen release rate, the hydrogen release rate is greatly reduced, which can fully meet the requirements of hydrogen fuel cells for low hydrogen sources. rate high-capacity output requirements. From a technical point of view, the method for generating hydrogen by hydrolyzing lithium borohydride in the present invention is an important breakthrough in the field of hydrogen storage and hydrogen production. The hydrogen production and storage technology of the fuel cell hydrogen source of the present invention is a low-cost and environment-friendly hydrogen generation technology. The application of the technology of the invention is of great and far-reaching significance to promote the practical progress of the high energy density fuel cell-hydrogen source system.

Description of drawings

What Fig. 1 shows is the structure diagram of the reaction device used in the method for generating hydrogen by hydrolyzing lithium borohydride of the present invention.

Among them: 1. Liquid water storage room; 2. Water inlet capillary; 3. Hydrolysis reaction room; 4. Interface with fuel cell; 5. Gas feedback pipeline.

Detailed ways

The present invention will be further described in detail below in conjunction with the examples, but not limited thereto.

Example 1:

The reaction device used in this embodiment is shown in Figure 1, including a liquid water storage chamber 1, a water inlet capillary 2, a hydrolysis reaction chamber 3, a gas feedback pipeline 5, and an interface 4 connected to a fuel cell. One end of the capillary 2 communicates with the liquid water storage chamber 1, the other end is placed in the hydrolysis reaction chamber 3, one end of the gas feedback pipeline 5 is inserted into the liquid water in the liquid water storage chamber 1, and the other end communicates with the hydrolysis reaction chamber 3 . The diameter of the water inlet capillary 2 is 5-30 μm.

Mix 1 gram of LiBH ₄ and 23 mL of diethyl ether solvent, place it in the hydrolysis reaction chamber 3 of the reaction device according to the ratio of the saturated solution, and mechanically stir at 100 rpm until a uniform solution is formed, then seal the reaction device and connect it with the fuel cell Connected, inject excess liquid water into the liquid water storage chamber 1 through the micro pump. The rate of hydrogen gas produced by the system was 31 mLmin ^-1 g ^-1 , and finally the hydrogen in LiBH ₄ was completely released.

Example 2:

The anyway device used in this embodiment is the same as in Embodiment 1.

Mix 1 gram of LiBH ₄ and 23 mL of diethyl ether solvent, that is, first place it in the hydrolysis reaction chamber 3 of the reaction device according to the ratio of the saturated solution, and mechanically stir at 100 rpm until a uniform solution is formed, then add 1 gram of LiBH ₄ solid powder, continue to stir for 2 hours, then seal the reaction device, communicate with the fuel cell, and inject excess liquid water into the liquid water storage chamber 1 through a micro pump. Liquid water drops into the hydrolysis reaction chamber 3 to react with the supernatant (saturated solution) of the supersaturated solution, and the generated reaction product is deposited at the bottom of the reactor, and the consumed LiBH ₄ will be continuously replenished by the dissolved LiBH ₄ solid at the bottom. The rate of hydrogen gas produced by the system was 72mLmin ^-1 g ^-1 , and finally the hydrogen in LiBH ₄ was completely released.

Example 3:

The anyway device used in this embodiment is the same as in Embodiment 1.

Mix 1 gram of LiBH ₄ and 23 mL of ether solvent, that is, first place it in the hydrolysis reaction chamber 3 of the reaction device according to the ratio of the saturated solution, and mechanically stir at 100 rpm until a uniform solution is formed, then add 3 grams of LiBH ₄ solid powder, continue to stir for 2 hours, then seal the reaction device, communicate with the fuel cell, and inject excess liquid water into the liquid water storage chamber 1 through a micro pump. Liquid water drops into the hydrolysis reaction chamber 3 to react with the supernatant (saturated solution) of the supersaturated solution, and the generated reaction product is deposited at the bottom of the reactor, and the consumed LiBH ₄ will be continuously replenished by the dissolved LiBH ₄ solid at the bottom. The rate of hydrogen gas produced by the system was 160mLmin ^-1 g ^-1 , and finally the hydrogen in LiBH ₄ was completely released.

Example 4:

The anyway device used in this embodiment is the same as in Embodiment 1.

Mix 1 gram of LiBH ₄ and 23 mL of diethyl ether solvent, that is, first place it in the hydrolysis reaction chamber 3 of the reaction device according to the ratio of the saturated solution, mechanically stir at 100 rpm until a uniform solution is formed, and then add 5 grams of LiBH ₄ solid powder, continue to stir for 2 hours, then seal the reaction device, communicate with the fuel cell, and inject excess liquid water into the liquid water storage chamber 1 through a micro pump. Liquid water drops into the hydrolysis reaction chamber 3 to react with the supernatant (saturated solution) of the supersaturated solution, and the generated reaction product is deposited at the bottom of the reactor, and the consumed LiBH ₄ will be continuously replenished by the dissolved LiBH ₄ solid at the bottom. The rate of hydrogen gas produced by the system was 1600mLmin ^-1 g ^-1 , and finally the hydrogen in LiBH ₄ was completely released.

The above-mentioned embodiments of the present invention are illustrations of the present invention and cannot be used to limit the present invention. Any changes within the meaning and scope equivalent to the claims of the present invention should be considered to be included in the scope of the claims.

Claims (1)

1. a lithium borohydride is hydrolyzed the method that hydrogen occurs, it is characterized in that comprising the following steps: lithium borohydride is dissolved in to the organic solvent that can not adsorb in proton exchange membrane fuel cell membrane and forms organic saturated solution or organic suspension liquid, then passing into liquid water makes lithium borohydride and liquid water that hydrolysis hydrogen discharge reaction occur, by regulating lithium borohydride to be dissolved in the adjusting of the concentration realization response hydrogen discharging rate of organic solvent, finally make the theoretical hydrogen in lithium borohydride discharge completely; The described organic solvent that can not adsorb in proton exchange membrane fuel cell membrane is ether or nonane; The concentration interval of described organic suspension liquid at organic saturated solution to 10molL ^-1between.