Method for making highly porous, stable metal oxides with a controlled pore structure
Methods for making high-surface area, high-porosity, stable metal oxides, such as, but not limited to materials used as adsorbents and catalyst supports include (i) forming a solvent deficient precursor mixture from a metal salt and a base and reacting the metal ions and base ions in the solvent deficient precursor mixture to form an intermediate hydroxide product (e.g., metal hydroxide or metal oxide hydroxide), (ii) causing the intermediate hydroxide to form nanoparticles (e.g., by heating), and (iii) calcining the intermediate nanoparticles to sinter the nanoparticles together and yield a highly porous, stable metal oxide aggregate having a pore structure.
1. A method for manufacturing a highly porous, stable metal oxide alumina catalyst support consisting essentially of:
mixing aluminum phenoxide or at least one metal salt of an aluminum alkoxide with water as the only base reactant;
to form a solvent deficient precursor mixture
allowing the aluminum phenoxide or at least one metal salt of an of aluminum alkoxide and the water to react in the solvent deficient precursor-to form intermediate nanoparticles; and
calcining the intermediate nanoparticles to yield a stable metal oxide having a pore structure;
wherein the anion of the metal salt is chosen to control the pore structure of the stable metal oxide and the pore diameter of the porous metal oxide is controlled to a range of from about 2-50 nm.
2. A method according to claim 1 wherein the alkoxide is from the group consisting of ethoxide, isopropoxide, pentoxide, sec-butoxide, tert-butoxide, tributoxide, tri-sec-butoxide, an hexoxide, and combinations thereof.
3. A method according to claim 2 wherein the alkoxide is isopropoxide.
4. The method of claim 1 wherein the molar ratio of water to Al is from about 2-10.
5. A method according to claim 1 wherein the intermediate nanoparticles are rinsed with water or an organic solvent prior to calcining.
6. A method according to claim 5 wherein the intermediate nanoparticles are rinsed with an alcohol prior to calcining.
7. A method according to claim 1 wherein a different metal salt is included in the reaction mixture as a dopant to increase the thermal stability of the resulting metal oxide.
8. A method according to claim 7 wherein the different metal salt is a titanium salt present in an amount to provide 1-30% by weight of titania in the final metal oxide product.