Nanostructured mixed metal oxides as catalysts and method of making thereof

Patent metadata

Field	Value
Publication number	US-2019169043-A1
Application number	US-201816208785-A
Country	US
Kind code	A1
Filing date	Dec 4, 2018
Priority date	Dec 4, 2017
Publication date	Jun 6, 2019
Grant date	—

Abstract

A method of forming a metal oxide material having a rod shape or polyhedral nanostructure includes preparing a first reverse micro-emulsion system comprising an aqueous precipitating agent dispersion and a second reverse micro-emulsion system containing an aqueous metal salt dispersion; combining the micro-emulsions together to initiate a reaction; allowing the reaction to continue to form a product mixture comprising a metal oxide gel and aqueous media; separating the metal oxide gel from the aqueous media; collecting the metal oxide gel; and calcining the metal oxide gel to form the metal oxide material. The metal oxide material corresponds to the chemical formula of La2MxNi1-xO4, Pr2-yAyNiO4, or La2-zDzNiO4, wherein M is copper, cobalt, iron, manganese, chromium, aluminum, or platinum; A is lanthanum or neodymium; D is calcium, barium or strontium; x ranges from 0 to 1; y ranges from 0 to 2; and z ranges from 0 to 0.25.

First claim

What is claimed is:

1 . A method of forming a metal oxide material having a rod shape or a polyhedral nanostructure; the method comprising:
preparing a first reverse micro-emulsion system comprising a precipitating agent dispersed in a first aqueous medium; preparing a second reverse micro-emulsion system containing a metal salt dispersed in a second aqueous medium; combining the first and second reverse micro-emulsions together to initiate a reaction; allowing the reaction to continue for a predetermined amount of time to form a product mixture comprising a metal oxide gel and the first and second aqueous media; separating the metal oxide gel from the first and second aqueous media; collecting the metal oxide gel; and calcining the metal oxide gel to form the metal oxide material; wherein the metal oxide material corresponds to the chemical formula of La 2 M x Ni 1-x O 4 , Pr 2-y A y NiO 4 , or La 2-z D z NiO 4 , wherein M is copper (Cu), cobalt (Co), iron (Fe), manganese (Mn), chromium (Cr), aluminum (Al), or platinum (Pt); A is lanthanum (La) or neodymium (Nd); D is calcium (Ca), barium (Ba) or strontium (Sr); x ranges from 0 to 1; y ranges from 0 to 2; and z ranges from 0 to 0.25.

2 . The method according to claim 1 , wherein the first and second aqueous media further comprises one or more of a surfactant, a co-surfactant, and a co-solvent, such that the surfactant is cetyl tetrammoniabromide (CTAB), the co-surfactant is an aliphatic hydrocarbon that has at least six carbon atoms, and the co-solvent is an aliphatic alcohol.

3 . The method according to claim 2 , wherein the co-surfactant is hexane and the co-solvent is n-butanol.

4 . The method according to claim 1 , wherein the first and second aqueous media comprises a molar ratio (Wo) of water to surfactant that is controlled at a value of about 1.6.

5 . The method according to claim 1 , wherein the metal salt comprises a combination of metal cations that are independently selected from the elements of La, Pr, Mn, Cr, Ni, Fe, Co, Cu, Pt, Nd, Ca, Ba, or Sr, and an anion that is independently selected from a nitrate, an acetate, a chloride, or a combination thereof.

6 . The method according to claim 1 , wherein the precipitating agent is an alkali metal hydroxide, an alkali metal carbonate, or a combination thereof.

7 . The method according to claim 1 , wherein the predetermined amount of time is at least 4 hours.

8 . The method according to claim 1 , wherein separating the metal oxide gel from the first and second aqueous media comprises filtering or centrifuging the product mixture.

9 . The method according to claim 1 , wherein the method further comprises washing the metal oxide gel with water/ethanol and drying the metal oxide gel in an oven at 80° C. prior to calcination.

10 . The method according to claim 1 , wherein the calcination is performed at a temperature that is in the range of about 700° C. to about 1,000° C.

11 . The method according to claim 1 , wherein at least one of the metal salt and the precipitating agent are present in a stoichiometric amount.

12 . The method according to claim 1 , wherein the metal oxide material is a Ruddlesden-Popper (R-P) oxide material.

13 . A metal oxide material having a rod shape or a polyhedral nanostructure prepared according to the method of claim 1 ;
wherein the metal oxide material corresponds to the chemical formula of La 2 M x Ni 1-x O 4 , Pr 2-y A y NiO 4 , or La 2-z D z NiO 4 , wherein M is copper (Cu), cobalt (Co), iron (Fe), manganese (Mn), chromium (Cr), aluminum (Al), or platinum (Pt); A is lanthanum (La) or neodymium (Nd); D is calcium (Ca), barium (Ba) or strontium (Sr); x ranges from 0 to 1; y ranges from 0 to 2; and z ranges from 0 to 0.25.

14 . The metal oxide material according to claim 13 , wherein the metal oxide material is a Ruddlesden-Popper (R-P) oxide material.

15 . The metal oxide material according to claim 13 , wherein the metal oxide material comprises alternating rock-salt (LaO or PrO) layers and perovskite (LaM x Ni 1-x O 3 , Pr 2-y A y NiO 3 , or La 2-z D z NiO 3 ) layers.

16 . Use of a catalyst comprising the metal oxide material of claim 13 in an electrochemical reaction, a methane reforming reaction, or an oxygen transport or surface oxygen exchange reaction.

17 . A metal oxide material having a rod shape or a polyhedral nanostructure that corresponds to the chemical formula of La 2 M x Ni 1-x O 4 , such that M is manganese (Mn), chromium (Cr), or platinum (Pt), and x ranges from 0 to 0.25.

18 . The metal oxide material according to claim 17 , wherein the metal oxide material is a Ruddlesden-Popper (R-P) oxide material

19 . The metal oxide material according to claim 17 , wherein M is platinum (Pt) and x is less than or equal to 0.05.

20 . Use of a catalyst comprising the metal oxide material of claim 17 in an electrochemical reaction, a methane reforming reaction, or an oxygen transport or surface oxygen exchange reaction.

Assignees

• Univ Wayne State

Inventors

• Nikolla Eranda
• Wang Bingwen
• Nacy Ayad

Classifications

• B82Y30/00

  Nanotechnology for materials or surface science, e.g. nanocomposites · CPC title

• C01G53/006 Primary

  Chemistry & Metallurgy · mapped topic

• B01J23/894

  with rare earths or actinides · CPC title

• C01P2002/34

  perovskite-type (ABO3) · CPC title

• B01J37/08

  Heat treatment {(B01J37/0009, B01J37/0018 take precedence)} · CPC title