Ammonia decomposition catalyst systems
Disclosed are ruthenium-based catalyst systems, hafnium-based catalyst systems, and yttrium-based catalyst systems for use in ammonia decomposition. Catalyst systems include ruthenium, hafnium, and/or yttrium optionally in combination with one or more additional metals that can be catalytic or catalyst promoters. Hafnium-based and yttrium-based catalyst systems can be free of ruthenium. The catalyst systems also include a support material. Disclosed catalyst systems can decompose ammonia at relatively low temperatures and can provide an efficient and cost-effective route to utilization of ammonia as a carbon-free hydrogen storage and generation material.
1. A hydrogen formation system comprising:
an ammonia source;
a reactor fluidly connected to the ammonia source such that ammonia flows from the ammonia source to the reactor;
an ammonia decomposition catalyst system comprising a support material and a trimetallic catalyst component carried on the support material and within the reactor, wherein the trimetallic catalyst component includes no more than three metals comprising a first metal being ruthenium, a second metal selected from the group consisting of magnesium, calcium, hafnium, scandium, rhenium, strontium, and yttrium, and a promoter comprising an alkali metal, wherein the ruthenium and the second metal are present in a weight ratio to one another of from about 8:1 to about 1:8, wherein the ruthenium is present in an amount of less than 4 wt. % of the catalyst system and the promoter is present in an amount of from about 5 wt. % to about 20 wt. % of the catalyst system;
a first heat exchanger located between the ammonia source and the reactor and configured to heat the ammonia; and
a hydrogen selective membrane fluidly connected to the catalyst system such that reaction product from the catalyst system contacts the hydrogen selective membrane.
2. The hydrogen formation system of claim 1 , wherein the promoter is a single metal selected from the group consisting of sodium, potassium, rubidium, and cesium.
3. The hydrogen formation system of claim 1 , wherein the support material comprises an inorganic oxide.
4. The hydrogen formation system of claim 1 , wherein the second metal is hafnium.
5. The hydrogen formation system of claim 1 , wherein the second metal is yttrium.
6. The hydrogen formation system of claim 1 , wherein the catalyst system comprises the promoter in an amount of from about 8 wt. % to about 15 wt. % of the catalyst system.
7. The hydrogen formation system of claim 1 , wherein the catalyst system comprises the ruthenium in an amount of 3 wt. % or less.
8. The hydrogen formation system of claim 1 , wherein the catalyst system comprises the ruthenium in an amount of 2 wt. % or less.
9. The hydrogen formation system of claim 1 , wherein the catalyst system comprises the ruthenium in an amount of 1 wt. % or less.
10. The hydrogen formation system of claim 1 , wherein the promoter is potassium.
11. The hydrogen formation system of claim 1 , further comprising a hydrogen collection tank fluidly connected to a first side of the hydrogen selective membrane.
12. The hydrogen formation system of claim 1 , further comprising a fuel cell fluidly connected to a first side of the hydrogen selective membrane.
13. The hydrogen formation system of claim 1 , further comprising a second heat exchanger between the ammonia source and the reactor and configured to heat the ammonia.
14. The hydrogen formation system of claim 13 , wherein the second heat exchanger is fluidly connected to a second side of the hydrogen selective membrane.
15. The hydrogen formation system of claim 1 , wherein the hydrogen selective membrane is selected from the group consisting of a polymer membrane, a ceramic membrane, and a metal membrane.
16. The hydrogen formation system of claim 1 , wherein the hydrogen selective membrane comprises palladium.