Binary cocrystalline sugar alcohol sodium borohydride blended hydrogen-generating material and its preparation method

Abstract

This invention discloses a binary cocrystalline sugar alcohol sodium borohydride blend hydrogen-producing material. The ratio of sodium borohydride to the binary cocrystalline sugar alcohol sodium borohydride blend hydrogen-producing material is 1:0.3-2 (molar ratio). The binary cocrystalline sugar alcohol is a blend of two selected from xylitol, erythritol, sorbitol, or arabinol, and the melting range of the binary cocrystalline sugar alcohol is 80-94℃. In this solution, the binary cocrystalline sugar alcohol has a lower melting point than the single sugar alcohol, reducing the initial hydrogen release temperature and increasing the hydrogen release yield. The resulting hydrogen-producing material has an initial hydrogen release temperature below 70℃ and a hydrogen release yield above 2.1 wt.%, with a maximum of 4.5 wt.%.

Description

Technical Field

[0001] This invention relates to a binary cocrystalline sugar alcohol sodium borohydride blend hydrogen-producing material, and also to a method for preparing the hydrogen-producing material, belonging to the technical field of hydrogen separation from hydrogen-containing mixtures. Background Technology

[0002] Sodium borohydride (NaBH4) is considered one of the more ideal hydrogen carriers among traditional hydrogen storage materials, possessing a high hydrogen storage capacity of 10.8 wt.%, low cost, and non-toxic byproducts. However, its strong thermodynamic stability severely hinders its application in hydrogen production and storage. NaBH4 is a hydride anion carrier; to obtain hydrogen from NaBH4, suitable hydrogen protons are required. In current technologies, the main sources of protons are liquid alcohols or water. However, NaBH4 hydrolysis for hydrogen production requires excessive water and expensive catalysts to achieve complete and rapid hydrogen release. Furthermore, the addition of liquid water also causes some problems, such as a decrease in the volumetric hydrogen storage density of the composite material and difficulty in controlling the reaction rate between NaBH4 and water.

[0003] Studies have shown that polyhydroxyl xylitols can serve as a proton source for hydrogen release from sodium borohydride (Enabling easy and efficient hydrogen release below 80 °C from NaBH4 with multi-hydroxyl xylitol[J]. International Journal of Hydrogen Energy, 2021.DOI:10.1016 / j.ijhydene.2021.06.052.). At room temperature, polyhydroxyl xylitols are solid, and this hydrogen-releasing material is solid during preparation and remains solid during hydrogen release, which helps reduce the material's volume and makes it easier to carry. However, the initial hydrogen release temperature of this material is 70–80 °C, which is still relatively high, and it is difficult to increase the hydrogen release rate when the initial temperature is lowered. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a binary cocrystalline sugar alcohol sodium borohydride blended hydrogen-producing material with a lower initial hydrogen release temperature. Another purpose of this invention is to provide a method for preparing hydrogen-producing materials that helps to reduce the initial hydrogen release temperature of hydrogen storage materials.

[0005] Technical solution: The present invention discloses a binary cocrystalline sugar alcohol and sodium borohydride blended hydrogen-producing material, characterized in that, based on the molar ratio, the ratio of sodium borohydride to the binary cocrystalline sugar alcohol is 1:0.3~2, the binary cocrystalline sugar alcohol is a blend of two of xylitol, erythritol, sorbitol, or arabitol (CAS:2152-56-9), and the melting range of the binary cocrystalline sugar alcohol is 80~94 °C. Research has shown that the hydrogen release temperature of the binary cocrystalline sugar alcohol-NaBH4 blend hydrogen-releasing material is related to the melting point of the sugar alcohol. The binary cocrystalline sugar alcohol has a lower melting point than the single sugar alcohol. Therefore, the positively charged hydrogen in the binary sugar alcohol can couple with the negatively charged hydrogen in NaBH4 to release hydrogen at a lower temperature. In this scheme, the binary cocrystalline sugar alcohol obtained by mixing two different sugar alcohols has a lower melting point than the single sugar alcohol, which reduces the initial hydrogen release temperature and increases the hydrogen release amount. The resulting hydrogen-releasing material has an initial hydrogen release temperature below 70 °C and a hydrogen release amount above 2.1 wt.%, with a maximum of 4.45 wt.%. Further experiments revealed that the melting range of the binary cocrystalline sugar alcohol should not be too low. If the theoretical hydrogen release temperature is too low, the heat generated during the mixing process will cause partial hydrogen release, reducing the hydrogen storage effect.

[0006] Preferably, in order to ensure that the hydrogen production of the hydrogen-producing material is within a better ratio range, the molar ratio of sodium borohydride to sugar alcohol is 1:0.4~1.7.

[0007] Preferably, to balance the initial hydrogen production temperature and the safety of the preparation process, the binary cocrystalline sugar alcohol is a blend of xylitol and erythritol or sorbitol, and the binary cocrystalline sugar alcohol mixture is coated on NaBH4. More preferably, the xylitol content is not higher than 40 mol%. When the binary cocrystalline sugar alcohol is prepared by mixing 52 mol% xylitol and 48 mol% sorbitol, the heat generated during the mixing process will cause partial hydrogen release.

[0008] Preferably, the binary cocrystalline sugar alcohol is a two-component mixture of xylitol and erythritol in a 3:1 ratio. This binary cocrystalline sugar alcohol mixture destabilizes NaBH4 and reacts with NaBH4, allowing hydrogen to be released rapidly at low temperatures.

[0009] The method for preparing hydrogen-producing materials according to the present invention includes the aforementioned sugar alcohol sodium borohydride blended hydrogen-producing material, characterized by comprising the following steps:

[0010] (1) Weigh out the two sugar alcohols according to the proportion, grind and mix them to obtain a binary cocrystalline sugar alcohol mixture A;

[0011] (2) Weigh out the binary eutectic sugar alcohol mixture A and sodium borohydride in proportion, and ball mill them in an inert atmosphere to obtain the hydrogen-producing material.

[0012] Preferably, in step (2), the ball milling conditions are: the ball milling speed is 100~200 rpm and the ball milling time is 5~25 min.

[0013] Preferably, in step (2), the inert atmosphere is a water atmosphere with a pressure of less than 0.1 MPa and an argon atmosphere with an oxygen content of less than 0.1 ppm.

[0014] Preferably, in step (2), the ball milling time is 10-20 min. This ball milling condition enables the initial hydrogen release temperature of the binary cocrystalline sugar alcohol sodium borohydride blend to be below 70 °C, and more than 80% of the hydrogen in the material can be effectively released.

[0015] When the ball milling time is 10-20 min, a binary cocrystalline sugar alcohol is used. The binary sugar alcohol has a lower eutectic point. The initial hydrogen release temperature of the binary cocrystalline sugar alcohol sodium borohydride blend is lower than that of the single sugar alcohol sodium borohydride blend.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. The initial hydrogen release temperature of the hydrogen storage material is reduced and the hydrogen release capacity is increased; 2. The preparation process is simple; 3. The price is low and the hydrogen release rate is controllable; 4. The entire reaction process is a solid-state reaction with no liquid phase generated. Attached Figure Description

[0017] Figure 1 These are the heating and hydrogen release curves of the hydrogen-producing materials obtained in Examples 1 to 5 of this invention;

[0018] Figure 2 These are the heating and hydrogen release curves of the hydrogen-producing materials obtained in Embodiments 6 and 7 of this invention;

[0019] Figure 3 These are hydrogen release curves of different types of hydrogen-producing materials after being heated and kept at a constant temperature, obtained from embodiments of the present invention.

[0020] Figure 4 This is the X-ray diffraction (XRD) spectrum of the hydrogen-evolving material obtained in an embodiment of the present invention;

[0021] Figure 5 These are differential scanning calorimetry (DSC) spectra of different types of hydrogen-producing materials obtained in embodiments of the present invention. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings. In the following embodiments, the inert atmosphere is water with a pressure of less than 0.1 MPa and argon atmosphere with an oxygen content of less than 0.1 ppm. NaBH4 (Aladdin, 98%), xylitol (Aladdin, 98%), and erythritol (Aladdin, 98%) are used directly without further purification.

[0023] Example 1: Preparation of a binary cocrystalline sugar alcohol sodium borohydride blend for hydrogen generation

[0024] (1) Xylitol and erythritol were mixed by grinding and mixing in a molar ratio of 3:1 to obtain a binary cocrystalline sugar alcohol mixture A.

[0025] (2) Mix NaBH4 and mixture A uniformly according to a molar ratio of 19:8, and ball mill at a revolution speed of 100 rpm for 10 min in an inert atmosphere to obtain 19NaBH4-8 mixture A low-temperature hydrogen production material.

[0026] Example 2: The steps are the same as in Example 1, except that the molar ratio of NaBH4 and mixture A is 19:32, and the resulting material is denoted as 19NaBH4-32 mixture A.

[0027] Example 3: The steps are the same as in Example 1, except that the molar ratio of NaBH4 and mixture A is 19:16, and the resulting material is denoted as 19NaBH4-16 mixture A.

[0028] Example 4: The steps are the same as in Example 1, except that the molar ratio of NaBH4 and mixture A is 57:64, and the resulting material is denoted as 57NaBH4-64 mixture A.

[0029] Example 5: The steps are the same as in Example 1, except that the molar ratio of NaBH4 and mixture A is 57:32, and the resulting material is denoted as 57NaBH4-32 mixture A.

[0030] Example 6: The steps are the same as in Example 1, except that the sugar alcohol used is a single xylitol B, and the molar ratio of NaBH4 to xylitol B is 5:4. The resulting material is denoted as 5NaBH4-4xylitol.

[0031] Example 7: The steps are the same as in Example 1, except that the sugar alcohol used is a single erythritol C, and the molar ratio of NaBH4 to erythritol C is 1:1. The resulting material is denoted as NaBH4-erythritol.

[0032] Example 8: Performance Testing of Hydrogen Production Materials

[0033] 8.1 Effect of Heating Method on Hydrogen Production Performance

[0034] Gradient heating: 100-120 mg of the samples obtained in Examples 1-5 were weighed into the apparatus, evacuated, and leak-checked before starting the test. The temperature was increased to 300 °C at a rate of 2 °C / min using a programmed method to investigate the effect of the mixing molar ratio on the hydrogen release performance of the low-temperature hydrogen production material NaBH4-mixture A. The test results are shown in […]. Figure 1 .

[0035] like Figure 1 By comparing the hydrogen release curves of low-temperature hydrogen production materials with different molar ratios, it was found that different mixing molar ratios caused different hydrogen release performances in the composite hydrogen production materials. The sample obtained in Example 3, with a NaBH4 and mixture A molar ratio of 19:16, exhibited the highest hydrogen release capacity, a significantly reduced initial hydrogen release temperature of 57.5℃, and an increased hydrogen release rate, thus improving kinetic performance. The hydrogen release capacity continuously increased, reaching a hydrogen release amount of 4.45 wt.%. The initial hydrogen release temperature of 19NaBH4-8 mixture A was 67℃, with a hydrogen release amount of 2.93 wt.%. The initial hydrogen release temperature of 57NaBH4-32 mixture A was 64℃, with a hydrogen release amount of 3.43 wt.%. The initial hydrogen release temperatures of 57NaBH4-64 mixture A and 19NaBH4-32 mixture A were 58℃ and 62℃, respectively, corresponding to hydrogen release amounts of 3.1 wt.% and 2.4 wt.%.

[0036] The materials obtained in Examples 6 and 7 were tested under the same testing conditions, and the test results are shown below. Figure 2 Testing revealed that the initial hydrogen release temperature of the hydrogen-evolving material obtained in Example 6 was 61.4 °C, with a hydrogen release amount of 3.02 wt.%, while the initial hydrogen release temperature of the hydrogen-evolving material obtained in Example 7 was 67.2 °C, with a hydrogen release amount of 2.98 wt.%. The data indicate that changing the ball milling time also reduces the initial hydrogen release temperature of the single-component sugar alcohol and sodium borohydride mixture, but the decrease is not as significant as that of the binary cocrystalline sugar alcohol.

[0037] Gradient heating followed by holding: 150-250 mg of the sample obtained in Example 3 was placed in the device from a glove box, evacuated, leak-proof, and the test was started and data recorded. The temperature was increased to the predetermined temperature (80 °C, 100 °C, 120 °C, and 140 °C) at a rate of 5 °C / min using a program, and held for 85 min. The effect of temperature on the heating and hydrogen desorption performance of the 19NaBH4-16 mixture A low-temperature hydrogen production material was investigated. The test results are shown in […]. Figure 3 .

[0038] like Figure 3At temperatures of 80 °C, 100 °C, 120 °C, and 140 °C, the hydrogen release amounts were 1.53 wt.%, 1.68 wt.%, 2.6 wt.%, and 3.5 wt.%, respectively. The increase in temperature significantly improved the hydrogen release performance of the 19NaBH4-16 mixture A low-temperature hydrogen production material, forming a hydrogen release system with controllable hydrogen release.

[0039] 8.2 Reaction Mechanism Test

[0040] XRD testing: The low-temperature hydrogen production material of 19NaBH4-16 mixture A was characterized by XRD using an X-ray diffractometer, such as... Figure 4 The results showed that the phases in the low-temperature hydrogen production material were NaBH4, xylitol, and erythritol, with no other phases produced. This indicates that the formed diol eutectic and sodium borohydride low-temperature hydrogen production material did not produce any new substances; they were merely physically mixed without any chemical changes.

[0041] Differential scanning calorimetry (DSC) test: Samples obtained in Examples 2-5 were weighed in a test chamber, with each sample weighing less than 5 mg. The temperature was increased from room temperature to 300 °C at a rate of 2 °C / min for DSC testing to investigate the effect of temperature-induced hydrogen release performance of the low-temperature hydrogen production material of air-NaBH4- mixture A. The test results are shown in […]. Figure 4 .

[0042] like Figure 5 The DSC results show that the dehydrogenation reaction of the NaBH4-mixture A low-temperature hydrogen production material is an exothermic one-step reaction, with only one obvious exothermic DSC peak below 100℃, proving that the reaction between protons and negatively charged hydrogen in the NaBH4-mixture A low-temperature hydrogen production material is exothermic. The dehydrogenation peak temperature of the 19NaBH4-8 mixture A low-temperature hydrogen production material was measured to be 87.2℃, and that of NaBH4-8 mixture A was 86.2℃. For the 19NaBH4-16 mixture A low-temperature hydrogen production material, the peak temperature further decreased to 86.1℃. The dehydrogenation peak temperatures of the 57NaBH4-64 mixture A and the 19NaBH4-32 mixture A low-temperature hydrogen production materials were lower, at 82.2℃ and 78.6℃, respectively. DSC results showed that as the amount of mixture A increased, the dehydrogenation peak temperature of the NaBH4-mixture A low-temperature hydrogen production material decreased, further indicating that the binary co-crystal sugar alcohol composed of xylitol and erythritol has a strong destabilizing effect on the dehydrogenation of NaBH4.

Claims

1. A binary eutectic sugar alcohol sodium borohydride blended hydrogen generating material, characterized in that, The ratio of the sodium borohydride and the binary eutectic sugar alcohol is 1:32 / 57~16 / 19 in terms of molar ratio, the binary eutectic sugar alcohol is a blend of xylitol and erythritol at a ratio of 3:1, and the binary eutectic sugar alcohol has a melting range of 80~94 ℃.

2. A method of producing the hydrogen-producing material according to claim 1, characterized by, The method comprises the following steps: (1) two kinds of sugar alcohols are weighed in proportion respectively, ground and mixed to obtain a binary eutectic sugar alcohol mixture A; (2) the mixture A and sodium borohydride are weighed in proportion and ball milled in an inert atmosphere to obtain the hydrogen production material.

3. The method of claim 2, wherein the hydrogen production material is prepared by a method comprising: In the step (2), the ball milling condition is that the revolution speed of ball milling is 100~200 rpm, and the ball milling time is 5~25 minutes.

4. The method of claim 2, wherein the hydrogen production material is prepared by a method comprising: In the step (2), the inert atmosphere is an argon atmosphere with a water pressure of less than 0.1 Mpa and an oxygen content of less than 0.1 ppm.

5. The method of claim 3, wherein the hydrogen production material is prepared by a method comprising: In the step (2), the ball milling time is 10~20 minutes.

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