Thermochemical gas reduction process using poly-cation oxide

Patent metadata

Field	Value
Publication number	US-2018118576-A1
Application number	US-201715796766-A
Country	US
Kind code	A1
Filing date	Oct 28, 2017
Priority date	Oct 28, 2016
Publication date	May 3, 2018
Grant date	—

Abstract

A two-step thermochemical gas reduction process based on poly-cation oxides includes repeatedly cycling a thermal reduction step and a gas reduction step. In the thermal reduction the poly-cation oxide is heated to produce a reduced poly-cation oxide and oxygen. In the gas reduction step, the reduced poly-cation oxide is reacted with a gas to reduce the gas, while reoxidizing the poly-cation oxide. The poly-cation oxide has at least two distinct crystal structures at two distinct temperatures and is capable of undergoing a reversible phase transformation between the two distinct crystal structures. For example, the poly-cation oxide may be an entropy tuned mixed metal oxide, such as an entropy stabilized mixed metal oxide, where the entropy-tuning is achieved via change in crystal structure of one of more of the compounds involved. The gas reduction process may be used for water splitting, CO 2 splitting, NO x reduction, and other gas reduction processes.

First claim

1 . A two-step thermochemical gas reduction process comprising repeatedly cycling a thermal reduction step and a gas reduction step;
wherein the thermal reduction step comprises heating a poly-cation oxide (MeO x ) under a reduced partial oxygen pressure, producing a reduced poly-cation oxide (MeO x-1 ) and oxygen gas (O 2 ); wherein the gas reduction step comprises reacting the reduced poly-cation oxide (MeO x-1 ) with a first gas to produce a second gas and reoxidized poly-cation oxide (MeO x ), wherein the first gas is reduced into the second gas; wherein the poly-cation oxide has at least two distinct crystal structures at two distinct temperatures corresponding to two distinct average oxidation states of at least one transition metal in a transformation between MeO x and MeO x-1 and is capable of undergoing a reversible phase transformation between the two distinct crystal structures.

2 . The two-step thermochemical gas reduction process of claim 1 wherein the poly-cation oxide is an entropy tuned mixed metal oxide;

3 . The two-step thermochemical gas reduction process of claim 2 wherein the entropy tuned mixed metal oxide (MeO x ) is an entropy stabilized mixed metal oxide, where the entropy-tuning is achieved via change in crystal structure of one of more of the compounds involved.

4 . The two-step thermochemical gas reduction process of claim 1 wherein the mixed metal oxide (MeO x ) is a mixture of multiple metal oxides Me 1 O, . . . , Me n O.

5 . The two-step thermochemical gas reduction process of claim 4 wherein the mixed metal oxide is (Mg,Ni,Co,Zn,Fe)O x , i.e., an equimolar mixture of MgO, CoO, NiO, FeO and ZnO.

6 . The two-step thermochemical gas reduction process of claim 1 wherein the gas reduction process is a water splitting process for hydrogen gas production; wherein the gas reduction step is a water splitting step; wherein the first gas is water vapor and the second gas is hydrogen gas.

7 . The two-step thermochemical gas reduction process of claim 1 wherein the gas reduction process is a CO 2 splitting process for CO gas production; wherein the gas reduction step is a CO 2 splitting step; wherein the first gas is CO 2 and the second gas is CO.

8 . The two-step thermochemical gas reduction process of claim 1 wherein the gas reduction process is a NO x reduction process for N 2 gas production; wherein the gas reduction step is a NO x reduction step; wherein the first gas is NO x and the second gas is N 2 .

Assignees

• Univ Leland Stanford Junior

Inventors

• Ahlborg Nadia L
• Chueh William C
• Jin Hyungyu
• Majumdar Arunava
• Zhai Shang
• Rojas Herrera Jimmy A

Classifications

• C01B21/02

  Preparation of nitrogen (by decomposition of ammonia C01B3/047) · CPC title

• C01G53/66

  containing alkaline earth metals, e.g. SrNiO3 or SrNiO2 · CPC title

• C01B3/063

  Cyclic methods · CPC title

• C01B32/40 Primary

  Carbon monoxide · CPC title

• C01G53/68

  containing rare earths, e.g. (La1.62 Sr0.38)NiO4 · CPC title