Method for producing hydrogen using biomass

Abstract

A method for producing hydrogen using biomass is introduced, comprising: a pretreatment step of weakening hydrogen bonds of biomass by pretreating biomass using an ionic liquid; and an extraction step of extracting hydrogen by reacting the pretreated biomass with an alkaline substance.

Description

Technology Field

[0001] The present invention relates to a method for producing hydrogen using biomass that increases the efficiency of hydrogen production using biomass through a pretreatment step of weakening the hydrogen bonds of the biomass by pretreating the biomass using an ionic liquid. Background Technology

[0003] Due to greenhouse gas emissions and global warming, the need to develop and expand new and renewable energy sources to replace fossil fuels is increasing, and hydrogen, regarded as a clean energy source, is garnering attention. Hydrogen is the most abundant element on Earth and exists in various forms, including fossil fuels, biomass, and water. To utilize hydrogen as fuel, it is crucial to produce it in a way that is economical while minimizing environmental impact.

[0004] To date, about 96% of hydrogen demand is met through reforming reactions using fossil fuels, while the amount of hydrogen produced using biomass remains very small. However, as biomass is considered a clean energy source because it allows for the circulation of carbon on Earth, there is a need to meet demand by producing hydrogen more efficiently and applying it to industry.

[0005] Hydrogen production methods include traditional methods using fossil fuel reforming reactions and renewable methods using biomass and water. Among these, traditional reforming methods such as steam reforming, partial oxidation, autothermal reforming, and gasification are not environmentally friendly because they emit greenhouse gases during hydrogen production.

[0006] Renewable methods are divided into thermochemical and biological methods using biomass, while water-based methods are divided into electrolysis, pyrolysis, and photolysis; among these, the thermochemical method using biomass holds the highest economic potential.

[0007] However, research on this topic has not been extensively conducted due to the problem of generating various by-product gases other than hydrogen depending on the type of biomass (wood, seaweed, green algae, food waste, etc.); however, a recent study has reported that hydrogen extraction can be increased by utilizing an alkaline heat treatment-based thermochemical reaction.

[0008] However, since side reactions still exist, it is necessary to develop methods to suppress side reactions (reactions in which by-product gases other than hydrogen are generated) and increase the selectivity of the hydrogen conversion reaction.

[0010] The matters described above as background technology are intended only to enhance understanding of the background of the present invention and should not be construed as an acknowledgment that they constitute prior art already known to those skilled in the art. Prior art literature

[0012] KR 10-2007-0073899 A The problem to be solved

[0013] The present invention is proposed to solve these problems and aims to provide a method for producing hydrogen using biomass that increases efficiency in hydrogen production using biomass by pretreating the biomass with an ionic liquid to weaken the hydrogen bonds of the biomass and extracting hydrogen from the pretreated biomass using an alkaline heat treatment-based thermochemical reaction. means of solving the problem

[0015] A method for producing hydrogen using biomass according to the present invention for achieving the above objective comprises: a pretreatment step of weakening hydrogen bonds of biomass by pretreating biomass using an ionic liquid; and an extraction step of extracting hydrogen by reacting the pretreated biomass with an alkaline substance.

[0016] The pretreatment step may include a reaction step for preparing a pretreatment solution by reacting biomass with an ionic liquid; and a separation step for separating the pretreated biomass from the pretreatment solution.

[0017] In the reaction step, the ionic liquid may be a liquid containing chloride ions (Cl-).

[0018] In the reaction step, an ionic liquid and biomass are mixed in a weight ratio within a predetermined range to prepare a mixed solution, and the mixed solution is heated at a temperature within a predetermined range for a predetermined time to prepare a pretreatment solution.

[0019] The mixed solution can be prepared by mixing an ionic liquid and biomass in a weight ratio of 90 to 99:1 to 10.

[0020] The pretreatment solution can be prepared by heating the mixed solution at a temperature of 75 to 100°C for 5 to 10 minutes.

[0021] In the pretreatment step, the ionic liquid may be [BMIM]Cl(1-butyl-3-methylimidazolium chloride).

[0022] In the separation step, distilled water is supplied to the pretreatment solution to mix the pretreatment solution and distilled water, and the pretreated biomass can be separated by removing the ionic liquid and distilled water from the pretreatment solution.

[0023] In the extraction step, hydrogen can be extracted by mixing an alkaline substance containing sodium hydroxide (NaOH) with pretreated biomass and heating it at a predetermined temperature for a predetermined time.

[0024] The alkaline substance and pretreated biomass are mixed in a molar ratio of 12:1 and heated at 500°C for 1 hour. Effects of the invention

[0026] According to the method for producing hydrogen using biomass of the present invention, the hydrogen bonds of the biomass are weakened by pre-treating the biomass using an ionic liquid, and the efficiency of hydrogen production using biomass can be increased by extracting hydrogen from the pre-treated biomass using an alkaline heat treatment-based thermochemical reaction. Brief explanation of the drawing

[0028] FIG. 1 is a flowchart of a method for producing hydrogen using biomass according to one embodiment of the present invention. Figure 2 is a diagram showing the structure of biomass with weakened hydrogen bonds through a pretreatment step and a TGA result graph in a method for producing hydrogen using biomass according to one embodiment of the present invention. Figure 3 is a graph showing a comparison of hydrogen production volume according to the presence or absence of a pretreatment step in a method for producing hydrogen using biomass according to one embodiment of the present invention. Figure 4 is a diagram showing the results of pre-treating biomass with each of three types of materials in a method for producing hydrogen using biomass according to one embodiment of the present invention. Specific details for implementing the invention

[0029] FIG. 1 is a flowchart of a method for producing hydrogen using biomass according to an embodiment of the present invention. FIG. 2 is a graph showing the structure of biomass with weakened hydrogen bonds through a pretreatment step and TGA results in a method for producing hydrogen using biomass according to an embodiment of the present invention. FIG. 3 is a graph showing a comparison of hydrogen production yields with and without a pretreatment step in a method for producing hydrogen using biomass according to an embodiment of the present invention. FIG. 4 is a graph showing the results of pretreating biomass with each of three types of materials in a method for producing hydrogen using biomass according to an embodiment of the present invention.

[0031] FIG. 1 is a flowchart of a method for producing hydrogen using biomass according to an embodiment of the present invention. FIG. 2 is a diagram showing the structure of biomass with weakened hydrogen bonds through a pretreatment step and a TGA result graph in a method for producing hydrogen using biomass according to an embodiment of the present invention. A method for producing hydrogen using biomass according to an embodiment of the present invention includes a pretreatment step (S100) of weakening hydrogen bonds of biomass by pretreating biomass using an ionic liquid; and an extraction step (S130) of extracting hydrogen by reacting the pretreated biomass with an alkaline substance.

[0032] The alkaline heat treatment-based thermochemical reaction used in the extraction step (S130) of the hydrogen production method using biomass according to one embodiment of the present invention extracts hydrogen from biomass composed of carbon, hydrogen, and oxygen, and the remaining carbon and oxygen react with alkali to be captured in the form of carbonates, thereby providing a new eco-friendly hydrogen production technology capable of producing high-purity hydrogen while suppressing greenhouse gas (carbon dioxide) emissions.

[0033] However, since the selectivity of alkali-based heat treatment reactions is not high, currently only about 50% of biomass is used for hydrogen production, and the rest is converted into hydrocarbons (such as methane), carbon dioxide, and carbon clusters. This is expected to be because alkali ions cannot come into contact with the biomass due to strong hydrogen bonding between biomass molecules.

[0034] Therefore, it is believed that if strong hydrogen bonds between biomass can be broken, the problem of reduced selectivity in the conventional alkaline heat treatment-based thermochemical reaction can be solved. A method for producing hydrogen using biomass according to one embodiment of the present invention can maximize the efficiency of the alkaline heat treatment-based thermochemical reaction of biomass by breaking strong hydrogen bonds between biomass. To this end, the biomass is pretreated with an ionic liquid to effectively break the hydrogen bonds of the biomass and weaken the hydrogen bonds between biomass, thereby improving the selectivity of the alkaline heat treatment reaction of the biomass.

[0035] Specifically, in the pretreatment step (S100) of the method for producing hydrogen using biomass according to one embodiment of the present invention, the ionic liquid may be [BMIM]Cl (1-butyl-3-methylimidazolium chloride). In addition, in the method for producing hydrogen using biomass according to one embodiment of the present invention, among various types of biomass, xylan, which is one of hemicellulose, may be used as the biomass. Referring to FIG. 2, the biomass before performing the pretreatment step (S100) has strong hydrogen bonds formed between the biomass particles, but after performing the pretreatment step (S100) using the ionic liquid, the hydrogen bonds in the biomass are partially broken by the ions in the ionic liquid, and it can be seen that the hydrogen bonds between the biomass particles are generally weakened. Referring to the TGA (thermogravimetric analysis) result graph on the right side of Fig. 2, it can be seen that when the pretreatment step (S100) is performed using an ionic liquid, a smaller amount remains after the extraction step (S130) compared to when the pretreatment step (S100) is not performed.

[0036] Meanwhile, in a method for producing hydrogen using biomass according to one embodiment of the present invention, the pretreatment step (S100) may include a reaction step (S110) for preparing a pretreatment solution by reacting biomass with an ionic liquid; and a separation step (S120) for separating the pretreated biomass from the pretreatment solution. Specifically, in the reaction step (S110), after mixing the ionic liquid and the biomass, 75 o Biomass is pretreated by heating at C for 5 minutes, and in the separation step (S120), the ionic liquid is recovered using distilled water to separate the remaining pretreated biomass, and then in the extraction step (S130), hydrogen is extracted by performing an alkaline heat treatment-based thermochemical reaction on the pretreated biomass.

[0038] FIG. 3 is a graph showing a comparison of hydrogen production volume according to the presence or absence of a pretreatment step in a method for producing hydrogen using biomass according to one embodiment of the present invention. FIG. 4 is a graph showing the results of pretreating biomass with each of three types of substances in a method for producing hydrogen using biomass according to one embodiment of the present invention. In the reaction step of the method for producing hydrogen using biomass according to one embodiment of the present invention, the ionic liquid may be a liquid containing chloride ions (Cl-).

[0039] First, referring to Figure 4, when biomass is pretreated with [BMIM][Cl], it can be seen that the bonds between biomass molecules are weakened and the distance between molecules widens. However, when pretreated with [BMIM][HCO2] and DES, the bonds between biomass molecules are not weakened, and the distance between molecules does not change significantly. Therefore, in the pretreatment step (S100), if an ionic liquid containing [BMIN][Cl] (1-Butyl-3-methylimidazolium chloride) or chloride ions (Cl-) is used, the hydrogen bonds between biomass molecules are weakened, and the hydrogen extraction efficiency may increase.

[0040] Meanwhile, in the reaction step (S110) of the method for producing hydrogen using biomass according to one embodiment of the present invention, a mixed solution may be prepared by mixing an ionic liquid and biomass in a weight ratio within a predetermined range, and a pretreatment solution may be prepared by heating the mixed solution at a temperature within a predetermined range for a predetermined time. Additionally, in the method for producing hydrogen using biomass according to one embodiment of the present invention, the mixed solution may be prepared by mixing an ionic liquid and biomass in a weight ratio of 90 to 99:1 to 10. Since the ionic liquid does not form a one-phase with the biomass if the ionic liquid falls below 90 in a weight ratio of 90:10, the biomass must be mixed in an amount of 90 or more, and it would be most preferable to mix the ionic liquid and biomass in a weight ratio of 95:5.

[0041] In addition, in a method for producing hydrogen using biomass according to one embodiment of the present invention, the pretreatment solution can be prepared by heating the mixed solution at a temperature of 75 to 100°C for 5 to 10 minutes. Considering the melting point of [BMIM][Cl], the mixed solution must be heated at a temperature of 75°C or higher, which is the minimum temperature at which [BMIM][Cl] becomes liquid. Since structural deformation of the mixed solution occurs in the XRD phase when heated for at least 5 minutes, the pretreatment solution will be prepared by heating the mixed solution at a temperature of 75°C or higher for 5 minutes.

[0042] Meanwhile, in the separation step (S120) of the method for producing hydrogen using biomass according to one embodiment of the present invention, distilled water is supplied to the pretreatment solution to mix the pretreatment solution with the distilled water, and the pretreated biomass can be separated by removing the ionic liquid and distilled water from the pretreatment solution. Since biomass is not soluble in water and ionic liquids mix well with water, only the pretreated biomass is separated by mixing distilled water with the pretreatment solution and removing the distilled water and ionic liquid together. In this case, acetonitrile or isopropanol may be used to ensure that no residue remains on the biomass.

[0043] In addition, in the extraction step (S130) of the method for producing hydrogen using biomass according to one embodiment of the present invention, hydrogen can be extracted by mixing an alkaline substance containing sodium hydroxide (NaOH) with pretreated biomass and heating at a predetermined temperature for a predetermined time. For example, the alkaline substance and the pretreated biomass can be mixed in a molar ratio of 12:1 and heated at 500°C for 1 hour. This is an alkaline heat treatment-based thermochemical reaction, and when the alkaline substance is sodium hydroxide, the alkaline substance and the pretreated biomass are mixed in a molar ratio of 12:1 according to the chemical formula below and heated at 500°C for 1 hour.

[0044] C6H 10O5+ 12NaOH + H2O -> Na2CO3+ 12H2

[0045] As a result of the extraction step (S130), referring to FIG. 3, when the pretreatment step (S100) was not performed, the hydrogen production was 0.826 (L / g-biomass) and the hydrogen purity was 73.96, and when the pretreatment step (S100) was performed, the hydrogen production was 0.939 (L / g-biomass) and the hydrogen purity was 75.01. It can be confirmed that when using the hydrogen production method according to one embodiment of the present invention, the hydrogen production increased by about 14% and the hydrogen purity also increased.

[0047] Although specific embodiments of the present invention have been illustrated and described, it will be obvious to those skilled in the art that the present invention can be modified and changed in various ways without departing from the technical spirit of the invention as provided by the following claims. Explanation of the symbols

[0049] S100: Pretreatment step S110: Reaction step S120: Separation step S130: Extraction step

Claims

Claim 1 A pretreatment step of weakening hydrogen bonds in biomass by pretreating biomass using an ionic liquid; A method for producing hydrogen using biomass, comprising: an extraction step for extracting hydrogen by reacting pretreated biomass with an alkaline substance; wherein the pretreatment step comprises a reaction step for preparing a pretreatment solution by reacting biomass with an ionic liquid; and a separation step for separating pretreated biomass from the pretreatment solution; wherein in the reaction step, a mixed solution is prepared by mixing the ionic liquid and biomass in a weight ratio of a predetermined range, and the mixed solution is prepared by heating the mixed solution at a temperature of a predetermined range for a predetermined time, wherein the mixed solution is prepared by mixing the ionic liquid and biomass in a weight ratio of 90~99:1~10; wherein in the extraction step, hydrogen is extracted by mixing the pretreated biomass with an alkaline substance containing sodium hydroxide (NaOH) and heating at a predetermined temperature for a predetermined time, wherein the alkaline substance and the pretreated biomass are mixed in a molar ratio of 12:1 and heated at 500℃ for 1 hour. Claim 2 delete Claim 3 A method for producing hydrogen using biomass according to claim 1, characterized in that the ionic liquid in the reaction step is a liquid containing chloride ions (Cl-). Claim 4 delete Claim 5 delete Claim 6 A method for producing hydrogen using biomass according to claim 1, characterized in that the pretreatment solution is prepared by heating a mixed solution at a temperature of 75 to 100°C for 5 to 10 minutes. Claim 7 A method for producing hydrogen using biomass according to claim 1, characterized in that the ionic liquid in the pretreatment step is [BMIM]Cl(1-butyl-3-methylimidazolium chloride). Claim 8 A method for producing hydrogen using biomass according to claim 1, characterized in that, in the separation step, distilled water is supplied to a pretreatment solution to mix the pretreatment solution and distilled water, and the pretreated biomass is separated by removing the ionic liquid and distilled water from the pretreatment solution. Claim 9 delete Claim 10 delete

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