US-12624461-B2 - Process and apparatus for synthesis of ammonia

US12624461B2US 12624461 B2US12624461 B2US 12624461B2US-12624461-B2

Abstract

A process and system for synthesis of ammonia includes an electrochemical main cell and an electrochemical preliminary cell upstream of the main cell. A voltage is applied between the anode and cathode of the preliminary cell and the main cell. The anodic half-cell of the preliminary cell is supplied with water, and the cathodic half-cell of the preliminary cell with nitrogen and oxygen. Oxygen is in the anodic half-cell of the preliminary cell, and nitrogen and water are in the cathodic half-cell of the preliminary cell. The anodic half-cell of the main cell is supplied with water, and the cathodic half-cell of the main cell with nitrogen that has been obtained in the cathodic half-cell of the preliminary cell. Oxygen is in the anodic half-cell of the main cell, and ammonia in the cathodic half-cell of the main cell.

Inventors

Martin Müller

Assignees

Forschungszentrum Jülich GmbH

Dates

Publication Date: 20260512
Application Date: 20210211
Priority Date: 20200401

Claims (20)

1 . A method for synthesis of ammonia, wherein an electrochemical main cell ( 2 ) comprising an anodic half-cell ( 4 ) with an anode ( 5 ) and a cathodic half-cell ( 6 ) with a cathode ( 7 ) is provided, wherein a membrane ( 8 ) is arranged between the anodic ( 4 ) and the cathodic half-cell ( 6 ), through which protons can pass from the anodic ( 4 ) into the cathodic half-cell ( 6 ), and wherein the anode ( 5 ) comprises at least one catalyst material, and the cathode ( 7 ) comprises at least one catalyst material, an electrochemical pre-cell ( 3 ), which is connected upstream of the main cell ( 2 ) and which comprises an anodic half-cell ( 4 ) with an anode ( 5 ) and a cathodic half-cell ( 6 ) with a cathode ( 7 ), is provided, wherein a membrane ( 8 ) is arranged between the anodic half-cell ( 4 ) and the cathodic half-cell ( 6 ), through which protons can pass from the anodic half-cell ( 4 ) into the cathodic half-cell ( 6 ), and wherein the anode ( 5 ) comprises at least one catalyst material, and the cathode ( 7 ) comprises at least one catalyst material, a voltage is applied between the anode ( 5 ) and cathode ( 7 ) of the pre-cell ( 3 ), a pre-cell voltage (UV), and a voltage is applied between the anode ( 5 ) and cathode ( 7 ) of the main cell ( 2 ), a main cell voltage (UH), water is supplied to the anodic half-cell ( 4 ) of the pre-cell ( 3 ) and nitrogen and oxygen are supplied to the cathodic half-cell ( 6 ) of the pre-cell ( 3 ), oxygen is obtained in the anodic half-cell ( 4 ) of the pre-cell ( 3 ) and nitrogen and water are obtained in the cathodic half-cell ( 6 ) of the pre-cell ( 3 ), water is supplied to the anodic half-cell ( 4 ) of the main cell ( 2 ), and nitrogen obtained in the cathodic half-cell ( 6 ) of the pre-cell ( 3 ) is supplied to the cathodic half-cell ( 6 ) of the main cell ( 2 ), oxygen is obtained in the anodic half-cell ( 4 ) of the main cell ( 2 ), and ammonia is obtained in the cathodic half-cell ( 6 ) of the main cell ( 2 ), an intermediate cell ( 18 ), which is connected downstream of the pre-cell ( 3 ) and upstream of the main cell ( 2 ) and which comprises an anodic half-cell ( 4 ) with an anode ( 5 ) and a cathodic half-cell ( 6 ) with a cathode ( 7 ), is provided, wherein a membrane ( 8 ) is arranged between the anodic half-cell ( 4 ) and the cathodic half-cell ( 6 ), through which protons can pass from the anodic ( 4 ) into the cathodic half-cell ( 6 ), and wherein the anode ( 5 ) comprises at least one catalyst material, and the cathode ( 7 ) comprises at least one catalyst material, a voltage is applied between the anode ( 5 ) and cathode ( 7 ) of the intermediate cell ( 18 ), an intermediate cell voltage (UZ), water is supplied to the anodic half-cell ( 4 ) of the intermediate cell ( 18 ), and oxygen is obtained in the anodic half-cell ( 4 ) of the intermediate cell ( 18 ), and hydrogen and permeating water are obtained in the cathodic half-cell ( 6 ) of the intermediate cell ( 18 ), and hydrogen and water obtained in the cathodic half-cell ( 6 ) of the intermediate cell ( 18 ) are supplied to the anodic half-cell ( 4 ) of the main cell ( 2 ).
2 . The method according to claim 1 , wherein water taken from the anodic half-cell ( 4 ) of the pre-cell ( 3 ) is supplied to the anodic half-cell ( 4 ) of the main cell ( 2 ).
3 . The method according to claim 1 , wherein the anode ( 5 ) of the main cell ( 2 ) comprises platinum as catalyst material.
4 . The method according to claim 1 , wherein the intermediate cell voltage (UZ) in the range of 1.2 to 2.5 volts is applied.
5 . The method according to claim 1 , wherein solar energy is used to provide the intermediate cell voltage (UZ), and wherein the intermediate cell voltage (UZ) is provided by at least one photovoltaic cell ( 9 ).
6 . The method according to one of the preceding claim 1 , wherein the pre-cell voltage (UV) of less than 1.7 volts is applied, and/or in that the main cell voltage (UH) in the range of 1 to 3 volts is applied.
7 . The method according to one of the preceding claim 1 , wherein solar energy is used for providing the pre-cell voltage (UV) and/or for providing the main cell voltage (UH), wherein the pre-cell voltage (UV) and/or the main cell voltage (UH) is provided by at least one photovoltaic cell ( 9 ), wherein the pre-cell voltage (UV) is provided by the at least one photovoltaic cell ( 9 ) associated with the pre-cell ( 3 ) and the main cell voltage (UH) is provided by a further photovoltaic cell ( 9 ) associated with the main cell ( 2 ).
8 . The method according to claim 1 , wherein the water is separated from the nitrogen and water obtained in the cathodic half-cell ( 4 ) of the pre-cell ( 3 ).
9 . The method according to claim 1 , wherein vaporous water is supplied to the anodic half-cell ( 4 ) of the main cell ( 2 ), wherein an evaporation device ( 13 ) connected upstream of the main cell ( 2 ) is used to obtain the vaporous water, and wherein the evaporation device ( 13 ) comprises at least one solar thermal collector ( 14 ) or is coupled to at least one solar thermal collector ( 14 ).
10 . The method according to claim 1 , wherein nitrogen exiting from the cathodic half-cell ( 6 ) of the main cell ( 2 ) is supplied again to the cathodic half-cell ( 6 ) of the main cell ( 2 ).
11 . An apparatus ( 1 ) for synthesis of ammonia, comprising: an electrochemical main cell ( 2 ) comprising an anodic half-cell ( 4 ) with an anode ( 5 ) and a cathodic half-cell ( 6 ) with a cathode ( 7 ), wherein a membrane ( 8 ) is arranged between the anodic half-cell ( 4 ) and the cathodic half-cell ( 6 ), through which protons can pass from the anodic ( 4 ) into the cathodic half-cell ( 6 ), and wherein the anode ( 5 ) comprises at least one catalyst material, and the cathode ( 7 ) comprises at least one catalyst material, a main cell voltage device ( 9 ) for providing a voltage (UH) between the anode ( 5 ) and the cathode ( 7 ), an electrochemical pre-cell ( 3 ) connected upstream of the electrochemical main cell ( 2 ), which comprises an anodic half-cell ( 4 ) with an anode ( 5 ) and a cathodic half-cell ( 6 ) with a cathode ( 7 ), wherein a membrane ( 8 ) is arranged between the anodic half-cell ( 4 ) and the cathodic half-cell ( 6 ), through which protons can pass from the anodic ( 4 ) into the cathodic half-cell ( 6 ), and wherein the anode ( 5 ) comprises at least one catalyst material, and the cathode ( 7 ) comprises at least one catalyst material, a pre-cell voltage device ( 9 ) for providing a voltage (UV) between the anode ( 5 ) and cathode ( 7 ) of the pre-cell ( 3 ), a fluid connection device ( 11 ) for fluidically connecting the cathodic half-cell ( 6 ) of the electrochemical pre-cell ( 3 ) to the cathodic half-cell ( 6 ) of the electrochemical main cell ( 2 ), an intermediate cell ( 18 ), which is connected downstream of the electrochemical pre-cell ( 3 ) and upstream of the electrochemical main cell ( 2 ), and which comprises an anodic half-cell ( 4 ) with an anode ( 5 ) and a cathodic half-cell ( 6 ) with a cathode ( 7 ), wherein a membrane ( 8 ) is arranged between the anodic halfcell ( 4 ) and the cathodic half-cell ( 6 ), through which protons can pass from the anodic ( 4 ) into the cathodic half-cell ( 6 ), and wherein the anode ( 5 ) comprises at least one catalyst material, and the cathode ( 7 ) comprises at least one catalyst material, intermediate cell voltage device ( 9 ) for providing a voltage (UZ) between the anode ( 5 ) and cathode ( 7 ) of the intermediate cell ( 18 ), fluid connection device ( 11 ) for fluidically connecting the anodic half-cell ( 4 ) of the electrochemical pre-cell ( 3 ) to the anodic half-cell ( 4 ) of the intermediate cell ( 18 ), and fluid connection device ( 11 ) for fluidically connecting the cathodic half-cell ( 6 ) of the intermediate cell ( 18 ) to the anodic half-cell ( 4 ) of the electrochemical main cell ( 2 ).
12 . The apparatus ( 1 ) according to claim 11 , wherein the fluid connection device ( 11 ) are provided for the fluidic connection of the anodic half-cell ( 4 ) of the pre-cell ( 3 ) to the anodic half-cell ( 4 ) of the main cell ( 2 ).
13 . The apparatus ( 1 ) according to claim 11 , wherein the anode ( 5 ) of the main cell ( 2 ) comprises platinum as catalyst material.
14 . The apparatus ( 1 ) according to claim 11 , wherein the intermediate cell voltage device ( 9 ) is configured to provide the voltage (UZ) in the range of 1.2 to 2.5 volts.
15 . The apparatus ( 1 ) according to claim 11 , wherein the intermediate cell voltage device ( 9 ) comprise at least one photovoltaic cell ( 9 ) or are provided by at least one photovoltaic cell ( 9 ).
16 . The apparatus according to claim 11 , wherein the pre-cell voltage device ( 9 ) is configured to provide the voltage (UV) of less than 1.7 volts, and/or that the main cell voltage device ( 9 ) is configured to provide the voltage (UH) in the range of 1 to 3 volts.
17 . Apparatus The apparatus according to claim 11 , wherein the pre-cell voltage device comprises at least one photovoltaic cell ( 9 ) or are given by at least one photovoltaic cell ( 9 ), and/or that the main cell voltage device comprises at least one photovoltaic cell ( 9 ) or are given by at least one photovoltaic cell ( 9 ).
18 . The apparatus according to claim 11 , wherein a separating device ( 17 ) connected upstream of the cathodic half-cell ( 6 ) of the main cell ( 2 ) is provided, so that water can be separated before it reaches the cathodic half-cell ( 6 ) of the main cell ( 2 ).
19 . The apparatus ( 1 ) according to claim 11 , wherein an evaporation device ( 13 ) connected upstream of the anodic half-cell ( 4 ) of the main cell ( 2 ) is provided, wherein the evaporation device ( 13 ) on the input side is fluidically connected to the anodic half-cell ( 4 ) of the pre-cell ( 3 ), and/or wherein the evaporation device ( 13 ) comprises at least one solar thermal collector ( 14 ).
20 . The apparatus ( 1 ) according to claim 11 , wherein at least one circulation pipe ( 12 ) is provided to feed nitrogen emerging from the cathodic half-cell ( 6 ) of the main cell ( 2 ) back to the input side of the cathodic half-cell ( 6 ).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM TO PRIORITY This application is a national stage application of International Application No. PCT/EP2021/053371 filed Feb. 11, 2021, which claims priority to German Patent Application No. 10 2020 109 016.1 filed Apr. 1, 2020, the disclosures of which are incorporated herein by reference and to which priority is claimed. FIELD OF THE INVENTION The invention relates to a method for synthesis of ammonia, wherein an electrochemical main cell comprising an anodic half-cell with an anode and a cathodic half-cell with a cathode is provided, wherein a membrane, in particular a cation exchange membrane, is arranged between the anodic and the cathodic half-cell, through which protons can pass from the anodic into the cathodic half-cell, and wherein the anode comprises at least one catalyst material, in particular iridium and/or ruthenium and/or platinum, and the cathode comprises at least one catalyst material, in particular ruthenium and/or titanium and/or iron, preferably ruthenium and titanium and iron. Furthermore, the invention relates to an apparatus for synthesis of ammonia, comprising an electrochemical main cell comprising an anodic half-cell with an anode and a cathodic half-cell with a cathode, wherein a membrane, in particular a cation exchange membrane, is arranged between the anodic half-cell and the cathodic half-cell, through which protons can pass from the anodic into the cathodic half-cell, and wherein the anode comprises at least one catalyst material, in particular iridium and/or ruthenium and/or platinum, and the cathode comprises at least one catalyst material, in particular ruthenium and/or titanium and/or iron, preferably ruthenium and titanium and iron, and means for providing a voltage between the anode and the cathode. BACKGROUND OF THE INVENTION Ammonia (NH3) represents a very important chemical which is used, among other things, as a fertilizer. For the production of ammonia, the Haber-Bosch method is known, which is a large-scale industrial chemical method. In this method, named after Fritz Haber and Carl Bosch, ammonia is synthesized from atmospheric nitrogen and hydrogen on a catalyst containing iron at high pressures and high temperatures. The pressure can be in the range of 150 to 350 bar in particular and the temperature in the range of 400 to 500° C. in particular. Almost all annual ammonia production is currently carried out using the Haber-Bosch method. It is sometimes considered a disadvantage that ammonia production via this method is only possible on an industrial scale and is characterized by comparatively high energy consumption and CO2 emissions. In the dissertation “Electrochemical Nitrogen Reduction for Ammonia Synthesis” by Kurt Kugler, Faculty of Mechanical Engineering at RWTH Aachen University, HBZ: HT018996649, published in 2016 on the publication server of RWTH Aachen University, it is proposed to perform an electrochemical ammonia synthesis in an electrochemical cell. The cell comprises two halves, namely an anodic and a cathodic half-cell, separated by a membrane, specifically a cation exchange membrane. In the dissertation, the electrochemical cell comprising a membrane is referred to as an electrochemical membrane reactor. The anodic half-cell comprises an anode and the cathodic half-cell comprises a cathode. Both the anode and the cathode are in the form of an electrode structure, each of which comprises at least one catalyst material. The anode and the cathode are in contact with opposite sides of the membrane. Specifically, they are pressed onto opposite sides of the membrane. The catalyst material proposed for the anode for water oxidation in the dissertation is iridium (Ir), specifically an iridium mixed metal oxide (IrMMO) catalyst. H+ required for ammonia synthesis can thus be produced in an environmentally friendly manner by water oxidation at the anode and pass through the membrane to the cathode. Titanium (Ti), iron (Fe) and ruthenium (Ru) were also selected as potential catalyst materials. For ammonia synthesis, a voltage is applied between the anode and the cathode and water vapor (H2O) is supplied to the anode and nitrogen (N2) is supplied to the cathode, which was obtained by cryogenic air separation. Oxygen (O2) is obtained at the anode and ammonia (NH3) at the cathode. It is proposed to use renewable energy, such as solar or wind energy, for the voltage supply of the electrochemical cell, so that the method can be particularly sustainable and environmentally friendly. The method for ammonia synthesis proposed in the dissertation “Electrochemical Nitrogen Reduction for Ammonia Synthesis” has great potential. However, there is still a need to improve the sustainability and environmental friendliness of ammonia production. SUMMARY OF THE INVENTION It is therefore an object of the present invention to further develop a method for ammonia synthesis of the type described above in such a way that it is ch