EP4642571A1

EP4642571A1 - A plasma-catalytic gliding discharge system for the decomposition of ammonia and use thereof

Info

Publication number: EP4642571A1
Application number: EP24727851.8A
Authority: EP
Inventors: Michal MLOTEK; Michalina PERRON; Krzysztof Krawczyk; Bogdan Ulejczyk
Original assignee: Politechnika Warszawska
Current assignee: Politechnika Warszawska
Priority date: 2023-03-31
Filing date: 2024-03-29
Publication date: 2025-11-05
Also published as: PL444277A1; WO2024205436A1; PL247910B1

Abstract

The object of the invention is a plasma-catalytic system for the decomposition of ammonia in gliding discharge plasma characterized in that it contains a gliding discharge reactor containing at least one catalytic bed (5) containing a metallic catalyst selected from a group including Ni and Co in an amount in a range of 2-20% by weight deposited on the Al2O3 substrate. Another object of the invention is the plasma-catalytic system of the invention for use in the decomposition of ammonia, characterized in that the mixture to be decomposed contains at least 60% ammonia and at least 40% another component selected from nitrogen and hydrogen with a flow rate in a range of 160-200 Ndm3/h.

Description

A PLASMA-CATALYTIC GLIDING DISCHARGE SYSTEM FOR THE DECOMPOSITION OF AMMONIA AND USE THEREOF

The invention discloses a plasma-catalytic system for the decomposition of ammonia in gliding discharge plasma with a production of hydrogen and use of this system for the decomposition of ammonia, wherein the plasma-catalytic system is equipped with a gliding discharge reactor which contains a catalytic bed.

Non-equilibrium plasma is currently used in lighting technology, in dust removal processes of gases, for the generation of ozone in water treatment processes, in the packaging industry, in electronics, in chemical analysis, and in surface processing of organic materials. Nonequilibrium plasma may be generated through discharge of various types, such as corona, glow, gliding and barrier discharge. The presence in the non-equilibrium plasma of the high- energy electrons cause the occurrence of the favorable conditions in which reactants are activated, and reactions may proceed at a higher speed, and the physicochemical properties of materials being processed may change.

For studying processes that occur in non-equilibrium gliding discharge plasma, reactors are currently mainly used whose designs are known from US5711859, US5993761 and US6007742 as well as from FR2773500. A different method for generating discharge is known from patent specification Pat. 196319, Pat. 209109. Gliding discharge may also be generated in a reactor disclosed in Ru. 070846, wherein the reactor consists of a conical vertical chamber with a conduit in which at least two electrodes powered by an electric system and an inlet opening which feeds a stream of gas are fitted. Below the gas inlet, a preliminary cyclone chamber is located with a gas inlet fitted inside, wherein the gas inlet is placed tangentially with regard to the inner wall of the preliminary cyclone chamber. In addition, a process for the production of gliding discharge plasma is known, according to Pat. 207074 in a reactor with at least 2 spiral electrodes with changing diameters that increase along the reactor wall in a way that their coils in a section along the vertical reactor axis define a funnel shape, and according to patents Pat. 238468 or Pat. 240976 with a central electrode.

Industrial growth since the Industrial Revolution has been closely related to the production, storage, and conversion of energy. Development of low-emission and renewable energy sources has been particularly emphasized during recent years, for example to reduce the mean temperature increase by less than 2°C. Hydrogen may be one of such sources; when used as fuel, it may play an important role in the process of achieving climate neutrality, the principal objective of the European and global energy policy. It is expected according to the EU Strategy published in 2018, that the share of hydrogen in Europe’s energy basket in 2050 will increase from the current level of less than 2% to 13-14%.

Hydrogen may be used as fuel in fuel cells, boilers, burners, and internal combustion engines. Its widespread use would significantly reduce the emission of gases with an adverse environmental impact. The use of hydrogen as an energy carrier is difficult due to its volatility and the size of molecules, and this translates into problems with its transport and storage. Binding hydrogen chemically in a compound with a high hydrogen content could solve this problem. This condition is met by ammonia, which contains 17.8 wt.% of hydrogen. Ammonia is a compound that may be easily liquefied at a pressure of about 1 MPa at room temperature, and it is produced on a large scale, so storage and transport technologies are well known. To use ammonia as hydrogen storage, it is necessary to develop an inexpensive, quick, and effective method for its decomposition, which would be no more expensive than the production of H₂ itself. Examples of such a process are plasma and plasma-catalytic processes with gliding discharge.

Plasma reactors with arc, gliding or barrier discharge have been used to decompose ammonia. The global research into the decomposition of ammonia in non-equilibrium plasma focuses on barrier and arc discharge. The Akiyama [1] group from the Tuo University in Tokyo studied barrier discharge using a gas flow rate in a range of 6-12 L/h. The effect of the material on the high-voltage electrode, residence time, and discharge power on the yield of hydrogen production was investigated. It was found that the electrode material had a minor effect on the course of the process. A high rate of ammonia conversion was achieved. The Zhao [2] group performed an ammonia decomposition reaction in arc discharge. The energy yield of the process at a flow of 2.4 L/h and discharge power of 48 W was approx. 7.8 kWh/m³ H₂.

The inventors of the solution, being the object of this application, developed a plasma process for the decomposition of ammonia in gliding discharge [3], in which a plasma system with gliding discharge was used for the first time. A high ammonia conversion in gas containing high concentration of NH₃ was achieved.

A process for the decomposition of ammonia in a catalytic process conducted at temperatures above 400°C is known. Carrier systems are most commonly used as catalysts in which the active substance is metallic nickel, cobalt, iron or ruthenium. The processes reported in the literature are based only on the activity of the catalyst, which requires the catalytic bed to be heated to a temperature at which the catalyst is active. To conclude, no use of a plasma-catalytic system for the decomposition of ammonia as hydrogen storage has been published in the art.

The object of the invention was to develop a plasma-catalytic system useful for the rapid and effective decomposition of ammonia as hydrogen storage or transport medium, as well as to develop its use for the decomposition of ammonia.

The invention discloses a plasma-catalytic system for the decomposition of ammonia in gliding discharge plasma, characterized in that it contains a gliding discharge reactor containing at least one catalytic bed 5 (Fig. 1) containing a metallic catalyst selected from a group including Ni and Co in an amount in a range of 2-20% by weight deposited on AI₂O₃ carrier.

The amount of the metallic catalyst is preferably in a range of 8-12 wt.%.

The gliding discharge reactor preferably contains a reactor base 1 in which is fitted a reactor body 6 and a nozzle 2 feeding a mixture of ammonia with nitrogen, wherein ceramic isolation 3 surrounding the nozzle 2 is located on the reactor base so that the upper end of the nozzle extends above the surface of the ceramic isolation 3; in addition, the reactor contains at least two electrodes 4 located inside the reactor body 6 so that their lower ends pass through the ceramic isolation 3 and the reactor base 1 and connect to a power source, while the catalytic bed 5 having a flattened shape is contained inside the reactor body 6, wherein its cross section matches the cross-section of the reactor body 6 and walls contact the inner surface of the walls of the reactor body 6, wherein a thermocouple 7 is inserted into the inside of the catalytic bed 5 through an inlet found in the upper part of the reactor body 6.

More preferably, the reactor body 6 has a shape selected from cylindrical, conical and cuboid and it is made of a ceramic material, preferably from AI₂O₃.

Even more preferably, the reactor body 6 has a cylindrical shape with an inner diameter in a range of 30-70 mm.

Preferably, the catalytic bed 5 is placed above a discharge zone 8 without catalytic bed 5a.

Preferably, the catalytic bed 5a is placed in the discharge zone 8 without catalytic bed 5.

Preferably, the system of the invention contains two catalytic beds 5 and 5a, the catalytic bed 5a is placed in the discharge zone 8 and the catalytic bed 5 is placed above the discharge zone 8. Preferably the catalytic bed 5a placed in the discharged zone 8 can be a moving bed and/or the catalytic bed 5 placed above the discharge zone 8 can be a solid bed. Preferably, the length of the electrodes 4 is in a range of 5-18 cm, more preferably in a range of 7-12 cm, wherein the electrodes 4 have a cross-section selected from rectangular, circular and combinations thereof.

More preferably, the cross section of the electrodes 4 is rectangular, wherein the system contains two electrodes 4.

Even more preferably, the distance between the electrodes 4 varies throughout their length and is in a range of between 2 mm and 25 mm.

More preferably, the cross section of the electrodes 4 is circular, wherein the system contains one electrode 4 with a circular cross section and one electrode 4 with a rectangular cross section.

Preferably, electrodes 4 are made of a material selected from a group including metals and their alloys resistant to the action of ammonia.

More preferably, the material is selected from a group including nickel, iron and their alloys.

Even more preferably, the material is heat-resistant stainless steel.

Preferably, the power source is an electrical system producing current with a voltage of up to 6 kV and power in a range of 80-500 W.

Another object of the invention is a plasma-catalytic system of the invention for use in the decomposition of ammonia, characterized in that the mixture to be decomposed contains at least 60% ammonia and at least 40% another component selected from nitrogen and hydrogen with a flow rate in a range of 160-200 Ndm³/h.

Preferably, the mixture contains 70% ammonia and 30% nitrogen, more preferably 80% ammonia and 20% nitrogen, even more preferably 90% ammonia and 10% nitrogen.

Preferably, the mixture contains 90% ammonia and 10% hydrogen.

Preferably, the mixture contains 100% ammonia.

An advantage of the solution of the invention is that in the plasma-catalytic system containing the gliding discharge reactor, the chemical process is rapidly initiated and completed. The use of the plasma-catalytic system with gliding discharge enables the bed to be heated more rapidly with preliminary activation of reactants in plasma, which can achieve a synergy effect of the two methods. In addition, additional heating or cooling of the catalyst bed is not needed. Temperature is set by itself proportionately to discharge power. Various types of active particles, radicals or even ions are generated in ammonia through gliding discharge, which react further on the catalyst surface. In a classic catalytic process, the catalyst must first be heated to an adequate temperature so that a reaction can proceed on the catalyst. In addition, gases reach the catalyst surface, which is only heated but not activated, unlike in the plasma process.

The invention has been illustrated by the drawings, in which:

Fig. 1 shows the plasma-catalytic system containing the gliding discharge reactor and the catalytic bed 5.

Fig. 2 shows the plasma-catalytic system containing the gliding discharge reactor and the catalytic beds 5 and 5a.

Fig.3 shows the plasma-catalytic system containing the gliding discharge reactor and the catalytic bed 5a

A plasma-catalytic system is used for the process, which essential part is the gliding discharge reactor fitted with the catalytic bed 5.

It was found based on research that the catalytic bed 5 may be located above or inside the discharge zone 8 or simultaneously in both locations, that is, two catalytic beds 5 and 5a may be found in the reactor. The catalytic bed 5 contains a metallic catalyst selected from Co and Ni in an amount of 2-20 wt.%, preferably in an amount 5-17 wt.%, more preferably in an amount of 8-12 weight % and an AI₂O₃ carrier.

The reactor body may have a cylindrical, conical or cuboid shape.

The invention has been illustrated by the following embodiments.

The processes illustrated in the embodiments were conducted using the plasma-catalytic system containing the gliding discharge reactor (a process conducted in gliding discharge plasma) which example design is shown in Fig. 1.

The reactor contains the reactor base 1, and the reactor body 6 has a cylindrical shape in the form of a ceramic pipe tapering toward the top and thus forming an outlet, wherein the reactor body 6 is made of a ceramic material in the form of aluminum oxide (AI₂O₃) and it is mounted in the reactor base 1. In addition, the reactor contains the nozzle 2 feeding a mixture of ammonia with nitrogen or hydrogen, wherein the nozzle 2 is mounted in the reactor base 1 and ceramic isolation 3 mounted in the reactor base 1 surrounding the nozzle 2 so that the upper end of the nozzle 2 extends above the surface of the ceramic isolation 3. In addition, the reactor contains electrodes 4 located inside the reactor body 6 so that their lower ends pass through the ceramic isolation 3 and the reactor base 1. In addition, the catalytic bed 5 is found inside the reactor, preferably in a solid bed form, for example in a form of a disk or bed of granular material with a grain size 0.5-12 mm, preferably 4 mm, which contacts the walls of the reactor body 6, while the thermocouple 7 is inserted into the inside of the catalytic bed 5 through an outlet of the reactor. In this case, the catalytic bed 5 is placed above the discharge zone 8. The discharge zone 8 is a reactor space between the electrodes 4 in which gliding discharge is generated.

It is also emphasized that the shape of the catalytic bed 5 matches the cross section of the reactor body 6, and it is flattened.

The length of the electrodes 4 is in a range of 5-18 cm, and the distance between the electrodes in the point in which it is the shortest is 2 mm and increases to 25 mm. The electrodes 4 are powered by an electrical system with a voltage of up to 6 kV and power in a range of 80-500 W. The material from which the electrodes 4 are made is selected from a group including metals and their alloys resistant to the action of ammonia, including nickel and its alloys and iron and its alloys, such as for example heat-resistant stainless steel, wherein the materials are copper-free because ammonia reacts with copper. In addition, the electrodes have a rectangular cross section, and they are flattened. Their cross-section may also be circular. The catalytic bed may be placed also in the discharge zone. Preferably, catalytic bed 5a is placed in the discharged zone 8 without catalytic bed 5 placed above the discharged zone 8, as shown on Fig. 3. Preferably, the system of the invention contains two catalytic beds 5 and 5a, the catalytic bed 5a is placed in the discharge zone 8 and the catalytic bed 5 is placed above the discharge zone 8 as presented on Fig.2. Preferably, catalytic bed 5 maybe in a form of a solid bed, and the catalytic bed 5a maybe in a form of a moving bed, preferably a fountain bed.

The invention has been presented in the following embodiments, which, however, are not limiting in nature, and their purpose is merely to illustrate the invention.

Example 1.

A plasma-catalytic system containing the reactor discussed above - Fig.1 - was used in the example, in which electrodes 4 had a length of 9 cm, and they were made of heat-resistant stainless steel, and had a rectangular cross section, while the reactor body 6 had a shape of a tube with an inner diameter of 50 mm.

Above the discharge zone, the catalytic bed 5 containing 10 wt.% Co on the AI₂O₃ carrier was placed in the reactor.

A mixture of ammonia with nitrogen with an ammonia concentration of 70% and a flow rate of 180 Ndm³/h was fed into the reactor. The main products of the process were hydrogen and nitrogen, and the ammonia conversion rate was 46%.

Example 2.

The reactor was as in Example 1, but gas containing a mixture of ammonia and nitrogen with an ammonia concentration of 90% and a flow rate of 180 Ndm³/h was passed through the reactor. The catalytic bed 5 containing 10 wt.% Ni on the AI₂O₃ carrier was placed in the reactor. An ammonia conversion rate of 40% was achieved in the reaction.

Example 3.

The reactor was as in Example 1, but gas containing a mixture of ammonia and hydrogen with an ammonia concentration of 90% and a flow rate of 180 Ndm³/h was passed through the reactor. The catalytic bed 5 containing 10 wt.% Ni on the AI₂O₃ carrier was placed in the reactor. An ammonia conversion rate of 35% was achieved in the reaction.

Example 4.

The reactor was as in Example 1, but gas containing pure ammonia at a flow rate of 180 Ndm³/h was passed through the reactor. The catalytic bed 5 containing 10 wt.% Ni on the AI₂O₃ carrier was placed in the reactor. An ammonia conversion rate of 40% was achieved in the reaction.

Example 5.

The reactor contained two vertical electrodes 4 made of heat-resistant stainless steel, placed in a ceramic tube with an inner diameter of 50 mm. The electrodes were powered by the electrical system. A catalyst containing 10 wt.% Co on the AI₂O₃ carrier was placed in the reactor in the discharge zone in the spouted catalytic bed 5a. A mixture of ammonia with nitrogen with an ammonia concentration of 70% and a flow rate of 180 Ndm³/h was fed into the reactor. The main products of the process were hydrogen and nitrogen, and the ammonia conversion rate was 49%.

Example 6

The reactor was designed according to patent Pat. 238468 with a central electrode with a circular cross section and six vertical electrodes with a rectangular cross section, made of heat-resistant stainless steel, placed in a ceramic tube with an inner diameter of 50 mm. The electrodes were powered by the electrical system. The catalytic bed 5 containing 10 wt.% Co on the AI₂O₃ carrier was placed in the reactor above the electrodes. A mixture of ammonia and nitrogen with an ammonia concentration of 70% and a flow rate of 180 Ndm³/h was fed into the reactor. The main products of the process were hydrogen and nitrogen, and the ammonia conversion rate was 47%.

Example 7 The reactor was designed according to patent Pat. 238468 with a central electrode with a circular cross section and six vertical electrodes with a rectangular cross section, placed in a ceramic tube with an inner diameter of 50 mm. The electrodes were powered by the electrical system. The catalytic bed 5 containing 10 wt.% Ni on the AI₂O₃ carrier was placed in the reactor above the electrodes. A mixture of ammonia and nitrogen with an ammonia concentration of 70% and a flow rate of 180 Ndm³/h was fed into the reactor. The main products of the process were hydrogen and nitrogen, and the ammonia conversion rate was 43%.

List of reference symbols Fig.1

1 - reactor base;

2 - nozzle;

3 - ceramic isolation;

4 - electrodes;

5 - catalytic bed;

6 - reactor body;

7 - thermocouple;

8 - discharge zone.

List of reference symbols Fig.2

1 - reactor base;

2 - nozzle;

3 - ceramic isolation;

4 - electrodes;

5 - catalytic bed, in a form of a solid bed

5a - moving catalytic bed, in a form of a spouted bed

6 - reactor body;

7 - thermocouple;

8 - discharge zone.

List of reference symbols Fig.3

1 - reactor base;

2 - nozzle;

3 - ceramic isolation;

4 - electrodes;

5a - moving catalytic bed, in a form of a spouted bed

6 - reactor body;

7 - thermocouple; 8 - discharge zone.

References

[1] M. Akiyama, K. Aihara, T. Sawaguchi, M. Matsukata, M. Iwamoto, Ammonia decomposition to clean hydrogen using non-thermal atmospheric-pressure plasma. Int. J. Hydrogen Energy. 43, 2018, 14493. [2] Y. Zao, L. Wang, J. Zhang, H, Guo, Enhancing the ammonia to hydrogen (ATH) energy efficiency of alternating current arc discharge, Int. J. Hydrogen Energy. 39(15), 2014, 7655.

[3] M. Mlotek, M. Perron, K. Krawczyk, Ammonia Decomposition in a Gliding Discharge Plasma, Energy Technol. 2021, 9, 2100677.

Claims

1. A plasma-catalytic system for the decomposition of ammonia in gliding discharge plasma, characterized in that it contains a gliding discharge reactor containing at least one catalytic bed (5) containing a metallic catalyst selected from a group including Ni and Co in an amount in a range of 2-20% by weight deposited on an AI₂O₃ substrate.

2. The plasma-catalytic system of claim 1, characterized in that the amount of the metallic catalyst is in a range of 8-12 wt.%.

3. The plasma-catalytic system of claim 1 or 2, characterized in that the gliding discharge reactor contains a reactor base (1) in which is fitted a reactor body (6) and a nozzle (2) feeding a mixture of ammonia with nitrogen, wherein ceramic isolation (3) is mounted in the reactor base surrounding the nozzle (2) so that the upper end of the nozzle extends above the surface of the ceramic isolation (3); in addition, the reactor contains at least two electrodes (4) located inside the reactor body (6) so that their lower ends pass through the ceramic isolation (3) and the reactor base (1) and connect to a power source, while the catalytic bed (5) having a flattened shape is contained inside the reactor body (6), wherein its cross section matches the cross section of the reactor body (6) and walls contact the inner surface of the walls of the reactor body (6), wherein a thermocouple (7) is inserted into the inside of the catalytic bed (5) through an inlet found in the upper part of the reactor body (6).

4. The plasma-catalytic system of claim 3, characterized in that the reactor body (6) has a shape selected from cylindrical, conical and cuboid and it is made of a ceramic material, preferably of AI₂O₃.

5. The plasma-catalytic system of claim 4, characterized in that the reactor body (6) has a cylindrical shape with an inner diameter in a range of 30-70 mm.

6. The plasma-catalytic system of any of claims 3 to 5, characterized in that the catalytic bed (5) is placed above the discharge zone (8).

7. The plasma-catalytic system of any of claims 3 to 5, characterized in that the catalytic bed (5a) is placed in the discharge zone (8).

8. The plasma-catalytic system of any of claims 3 to 5, characterized in that it contains two catalytic beds (5) and (5a), the catalytic bed (5a) placed in the discharge zone (8) and the catalytic bed (5) placed above the discharge zone (8), preferably the catalytic bed (5a) placed in the discharged zone (8) is a moving bed and/or the catalytic bed (5) placed obove the discharge zone (8) is a solid bed.

9. The plasma-catalytic system of any of claims 3 to 8, characterized in that the length of the electrodes (4) is in a range of 5-18 cm, preferably in a range of 7-12 cm, wherein the electrodes (4) have a cross section selected from rectangular, circular and combinations thereof.

10. The plasma-catalytic system of claim 9, characterized in that the cross section of the electrodes (4) is rectangular, wherein the system contains two electrodes (4).

11. The plasma-catalytic system of claim 10, characterized in that the distance between the electrodes (4) varies throughout their length and is in a range of between 2 mm and 25 mm.

12. The plasma-catalytic system of claim 9, characterized in that the cross section of the electrodes (4) is circular and rectangular, wherein the system contains one electrode (4) with a circular cross section and six electrodes (4) with a rectangular cross section.

13. The plasma-catalytic system of any of claims 3 to 12, characterized in that the electrodes (4) are made of a material selected from a group including metals and their alloys resistant to the action of ammonia.

14. The plasma-catalytic system of claim 13, characterized in that the material is selected from a group including nickel, iron and their alloys.

15. The plasma-catalytic system of claim 14, characterized in that the material is heat- resistant stainless steel.

16. The plasma-catalytic system of any of claims 3 to 15, characterized in that the power source is an electrical system producing current with a voltage of up to 6 kV and power in a range of 80-500 W.

17. The plasma-catalytic system as defined in any of claims 1 to 16 for use for the decomposition of ammonia, characterized in that the mixture to be decomposed contains at least 60% ammonia and at least 40% of another component selected from nitrogen and hydrogen with a flow rate in a range of 160-200 Ndm³/h.

18. The plasma-catalytic system for use of claim 17, characterized in that the mixture contains 70% ammonia and 30% nitrogen, preferably 80% ammonia and 20% nitrogen, more preferably 90% ammonia and 10% nitrogen.

19. The plasma-catalytic system for use of claim 17, characterized in that the mixture contains 90% ammonia and 10% hydrogen.

20. The plasma-catalytic system for use of claim 17, characterized in that the mixture contains 100% ammonia.