Method for preparing high-purity hydrogen from ethanol

Abstract

The invention discloses a method for preparing high-purity hydrogen from ethanol, and belongs to the technical field of hydrogen production. Comprising the following steps: conveying liquid ethanol to a vaporizer, and vaporizing the liquid ethanol into gaseous ethanol under certain temperature and pressure conditions; the vaporized gaseous ethanol is introduced into a reforming reactor filled with a catalyst for a reforming reaction, and through the reforming reaction, the ethanol is subjected to decomposition and dehydrogenation reactions to generate a mixed gas of hydrogen, carbon monoxide and carbon dioxide; introducing the mixed gas after the reforming reaction into a water-gas shift reactor for water-gas shift reaction, and in the reactor, further reacting carbon monoxide in the mixed gas with water vapor under the action of a catalyst to generate carbon dioxide, hydrogen and mixed gas mixed with water vapor; and conveying the mixed gas after the water vapor shift reaction to a heat exchanger, condensing and separating water vapor in the mixed gas, and then separating and purifying the mixed gas of carbon dioxide and hydrogen by adopting a pressure swing adsorption technology to obtain hydrogen.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen production, and in particular to a method for preparing high-purity hydrogen from ethanol. Background Art

[0002] As a clean energy carrier, hydrogen has broad application prospects in many fields such as fuel cells and chemical synthesis. Traditional hydrogen production methods such as water electrolysis and fossil fuel reforming have problems such as high cost, high energy consumption or large greenhouse gas emissions. Ethanol, as a renewable biomass energy, has a wide range of sources and can be mass-produced through biological methods such as fermentation. The preparation of hydrogen using ethanol as a raw material has the advantages of renewable raw materials and low carbon emissions. Therefore, it is of great significance to develop efficient ethanol hydrogen production methods. Summary of the invention

[0003] The object of the present invention is to provide a method for preparing high-purity hydrogen from ethanol to solve the problems raised in the above background technology.

[0004] In view of the above problems, the technical solution proposed by the present invention is: A method for preparing high-purity hydrogen from ethanol comprises the following steps: Step 1: transporting liquid ethanol to a vaporizer and vaporizing it into gaseous ethanol under certain temperature and pressure conditions; Compared with solid or liquid ethanol, the catalyst can better contact with gaseous ethanol. In the gaseous state, ethanol molecules have higher kinetic energy and fluidity, and can be more evenly dispersed on the catalyst surface. Compared with the liquid state, gaseous ethanol can more fully contact the active sites of the catalyst. The reforming reaction generally needs to be carried out at a higher temperature (400℃-600℃) and a specific pressure (0.1MPa-0.5MPa). Under such conditions, the existence of ethanol in gaseous form is more conducive to the stability and control of the reaction system. If liquid ethanol directly enters the reforming reactor, it may cause volume expansion and other problems due to rapid vaporization in a high temperature environment, causing impact and damage to the equipment.

[0005] Step 2: The vaporized gaseous ethanol is passed into a reforming reactor equipped with a catalyst to carry out a reforming reaction, through which the ethanol undergoes decomposition and dehydrogenation reactions to generate a mixed gas of hydrogen, carbon monoxide and carbon dioxide; In the ethanol reforming reaction, the following reactions are mainly included: Ethanol decomposition reaction: ; Methane reforming reaction: ; Finally, ethanol is decomposed into a mixture of hydrogen and carbon monoxide. At the same time, there will be a trace amount of oxygen remaining in the reaction system, so the following reactions will also occur: Oxidation reaction of carbon monoxide: ; Oxidation reaction of ethanol: ; Finally, a mixed gas of hydrogen, carbon monoxide and carbon dioxide is obtained.

[0006] Step 3: passing the mixed gas after the reforming reaction into a water gas shift reactor for a water gas shift reaction, in which the carbon monoxide and water vapor in the mixed gas further react under the action of a catalyst to generate a mixed gas of carbon dioxide and hydrogen mixed with water vapor; The water vapor shift reaction of the mixed gas includes the following reactions: ; The carbon monoxide in the mixed gas of hydrogen, carbon monoxide and carbon dioxide is converted into carbon dioxide, and finally a mixed gas of carbon dioxide and hydrogen is obtained. This reaction is a reversible reaction. In the actual water gas shift reaction process, the temperature is controlled at 200℃-350℃ and the pressure is controlled at 0.1MPa-0.3MPa to promote the reaction to the right, thereby increasing the production of hydrogen and reducing the content of carbon monoxide.

[0007] Step 4: The mixed gas after the water vapor shift reaction is transported to a heat exchanger to condense and separate the water vapor therein, and then the mixed gas of carbon dioxide and hydrogen is separated and purified by pressure swing adsorption technology to obtain hydrogen.

[0008] Pressure swing adsorption (PSA) separation of carbon dioxide and purification of hydrogen is mainly based on the adsorption selectivity of the adsorbent for different gases. The adsorbent is a material with a porous structure and adsorption sites on its surface. The interaction forces between different gas molecules and the adsorption sites are different, resulting in differences in adsorption capacity. For carbon dioxide and hydrogen, commonly used adsorbents (such as activated carbon, molecular sieves, etc.) have a much greater adsorption affinity for carbon dioxide than for hydrogen.

[0009] The specific method is: the mixed gas (including hydrogen and carbon dioxide) enters the adsorption tower equipped with adsorbent under a certain pressure (such as 0.5-3.0MPa). When the mixed gas passes through the adsorbent bed, the carbon dioxide molecules will be adsorbed by the adsorption sites on the adsorbent surface due to their strong adsorption affinity, while the hydrogen molecules are more difficult to be adsorbed, so they can pass through the adsorbent bed smoothly. The preferential adsorption of carbon dioxide by the adsorbent is used to preliminarily separate the hydrogen from the mixed gas, and obtain higher purity hydrogen from the outlet of the adsorption tower.

[0010] Specifically, for the separation of hydrogen and carbon dioxide, commonly used adsorbents include activated carbon and molecular sieves.

[0011] As a preferred technical solution of the present invention, the vaporization temperature is controlled at 150°C-250°C, and the pressure is controlled at 0.5MPa-1.5MPa.

[0012] Specifically, the boiling point of ethanol is 78.4°C. Properly increasing the temperature to 150°C-250°C can ensure that ethanol is quickly and completely vaporized. Maintaining a certain pressure helps ethanol remain in a gaseous state and allows it to enter the subsequent reforming reactor at a stable flow rate. Appropriate pressure can work synergistically with temperature to promote the vaporization process of ethanol.

[0013] As a preferred technical solution of the present invention, the catalyst is a supported catalyst, the active components include one or more of nickel, cobalt, and copper, and the carrier is one or more of alumina, silicon dioxide, and zirconium oxide.

[0014] As a preferred technical solution of the present invention, the reforming reaction temperature is controlled at 400°C-600°C, the pressure is controlled at 0.1MPa-0.5MPa, and the contact time between gaseous ethanol and the catalyst is 0.5s-2s.

[0015] As a preferred technical solution of the present invention, the temperature of the water vapor shift reaction is controlled at 200°C-350°C, the pressure is 0.1MPa-0.3MPa, and the catalyst is a copper-zinc-aluminum catalyst or an iron-chromium catalyst.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The method for preparing high-purity hydrogen from ethanol uses ethanol as a raw material. Ethanol can be obtained in large quantities through renewable means such as biomass fermentation. Compared with the traditional method of hydrogen production relying on fossil fuels, it reduces the dependence on non-renewable resources, reduces the environmental damage and greenhouse gas emissions caused by the exploitation and use of fossil fuels, and meets the requirements of the energy strategy for sustainable development; 2. The method for preparing high-purity hydrogen from ethanol. The ethanol gasification step can ensure the stable supply of raw materials in gaseous form, so that the catalyst and reactants are fully in contact in the subsequent reforming reaction, thereby increasing the reaction rate. The reforming reaction can promote the efficient decomposition and dehydrogenation of ethanol under a specific temperature and pressure and the action of a high-efficiency supported catalyst, thereby generating a large amount of hydrogen and intermediate products such as carbon monoxide. The water gas shift reaction further converts carbon monoxide into hydrogen and reduces its content, thereby optimizing the yield and quality of hydrogen. The synergistic effect of each step makes the entire hydrogen production process highly efficient. 3. The method for preparing high-purity hydrogen from ethanol has a relatively clear process flow, and the reaction conditions and equipment in each step have a certain adjustment range, which is convenient for process optimization and adjustment according to actual production needs and raw material supply conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a schematic flow chart of a method for preparing high-purity hydrogen from ethanol disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] See also Figure 1 The present invention provides a technical solution: a method for preparing high-purity hydrogen from ethanol, comprising the following steps: Step 1: transporting liquid ethanol to a vaporizer and vaporizing it into gaseous ethanol under certain temperature and pressure conditions; Step 2: The vaporized gaseous ethanol is passed into a reforming reactor equipped with a catalyst to carry out a reforming reaction, through which the ethanol undergoes decomposition and dehydrogenation reactions to generate a mixed gas of hydrogen, carbon monoxide and carbon dioxide; Step 3: passing the mixed gas after the reforming reaction into a water gas shift reactor for a water gas shift reaction, in which the carbon monoxide and water vapor in the mixed gas further react under the action of a catalyst to generate a mixed gas of carbon dioxide and hydrogen mixed with water vapor; Step 4: The mixed gas after the water vapor shift reaction is transported to a heat exchanger to condense and separate the water vapor therein, and then the mixed gas of carbon dioxide and hydrogen is separated and purified by pressure swing adsorption technology to obtain hydrogen.

[0020] According to an embodiment of the present invention, further, the vaporization temperature is controlled at 150° C.-250° C., and the pressure is controlled at 0.5 MPa-1.5 MPa.

[0021] In one embodiment of the present invention, further, the catalyst is a supported catalyst, the active components include one or more of nickel, cobalt, and copper, and the carrier is one or more of alumina, silica, and zirconia.

[0022] According to an embodiment of the present invention, further, the reforming reaction temperature is controlled at 400°C-600°C, the pressure is controlled at 0.1MPa-0.5MPa, and the contact time between the gaseous ethanol and the catalyst is 0.5s-2s.

[0023] According to an embodiment of the present invention, further, the temperature of the water vapor shift reaction is controlled at 200°C-350°C, the pressure is 0.1MPa-0.3MPa, and the catalyst is a copper-zinc-aluminum catalyst or an iron-chromium catalyst.

[0024] See also Figure 1 The present invention provides a technical solution: a method for preparing high-purity hydrogen from ethanol, first, liquid ethanol with a purity of 95% is transported to a vaporizer at a flow rate of 100 mL / min, and vaporized at 200° C. and 1.0 MPa, then, the gaseous ethanol is introduced into a reforming reactor equipped with a nickel-alumina catalyst (nickel loading is 10%), the reaction temperature is set to 500° C., the pressure is 0.3 MPa, and the contact time is 1 s, and the mixed gas after the reforming reaction then enters a water gas shift reactor, which is filled with a copper-zinc-aluminum catalyst, the reaction temperature is 300° C., and the pressure is 0.2 MPa, the mixed gas after the reaction is cooled to 40° C., the water vapor is condensed and separated, and finally separated and purified by a pressure swing adsorption device to obtain hydrogen with a purity of 99.95%, and the hydrogen yield is 5.5 mol / mol ethanol.

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] See also Figure 1 The present invention provides a technical solution: a method for preparing high-purity hydrogen from ethanol, wherein 98% liquid ethanol is taken and enters a vaporizer at a speed of 80 mL / min, the vaporization temperature is 180°C and the pressure is 0.8 MPa, the gaseous ethanol reacts in a reforming reactor equipped with a cobalt-silicon dioxide catalyst (cobalt loading is 8%), the reaction temperature is 450°C, the pressure is 0.2 MPa, and the contact time is 1.5 s, and a subsequent water vapor shift reaction is carried out under the action of an iron-chromium catalyst at a temperature of 250°C and a pressure of 0.15 MPa. After cooling, it is treated by pressure swing adsorption to obtain hydrogen with a purity of 99.92%, and the hydrogen yield is 5.2 mol / mol ethanol.

[0027] It can be seen from the above examples that the method for preparing high-purity hydrogen from ethanol of the present invention can effectively convert ethanol into high-purity hydrogen, has good application prospects and economic benefits, and can provide a feasible technical solution for the industrial production of hydrogen.

Claims

1. A method for preparing high-purity hydrogen from ethanol, characterized in that: The following steps are involved: Step 1: transporting liquid ethanol to a vaporizer and vaporizing it into gaseous ethanol under certain temperature and pressure conditions; Step 2: The vaporized gaseous ethanol is passed into a reforming reactor equipped with a catalyst to carry out a reforming reaction, through which the ethanol undergoes decomposition and dehydrogenation reactions to generate a mixed gas of hydrogen, carbon monoxide and carbon dioxide; Step 3: passing the mixed gas after the reforming reaction into a water gas shift reactor for a water gas shift reaction, in which the carbon monoxide and water vapor in the mixed gas further react under the action of a catalyst to generate a mixed gas of carbon dioxide and hydrogen mixed with water vapor; Step 4: The mixed gas after the water vapor shift reaction is transported to a heat exchanger to condense and separate the water vapor therein, and then the mixed gas of carbon dioxide and hydrogen is separated and purified by pressure swing adsorption technology to obtain hydrogen.

2. The method for preparing high-purity hydrogen from ethanol according to claim 1, characterized in that: The vaporization temperature is controlled at 150° C.-250° C., and the pressure is controlled at 0.5 MPa-1.5 MPa.

3. The method for preparing high-purity hydrogen from ethanol according to claim 1, characterized in that: The catalyst is a supported catalyst, the active components of which include one or more of nickel, cobalt and copper, and the carrier is one or more of alumina, silicon dioxide and zirconium oxide.

4. The method for preparing high-purity hydrogen from ethanol according to claim 1, characterized in that: The reforming reaction temperature is controlled at 400° C.-600° C., the pressure is controlled at 0.1 MPa-0.5 MPa, and the contact time between gaseous ethanol and the catalyst is 0.5 s-2 s.

5. The method for preparing high-purity hydrogen from ethanol according to claim 1, characterized in that: The temperature of the water gas shift reaction is controlled at 200° C.-350° C., the pressure is 0.1 MPa-0.3 MPa, and the catalyst is a copper-zinc-aluminum catalyst or an iron-chromium catalyst.

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