Method of making highly porous, stable aluminum oxides doped with silicon

Patent metadata

Field	Value
Publication number	US-9289750-B2
Application number	US-201414201538-A
Country	US
Kind code	B2
Filing date	Mar 7, 2014
Priority date	Mar 9, 2013
Publication date	Mar 22, 2016
Grant date	Mar 22, 2016

Abstract

The present invention relates to a method for making high surface area and large pore volume thermally stable silica-doped alumina (aluminum oxide) catalyst support and ceramic materials. The ability of the silica-alumina to withstand high temperatures in presence or absence of water and prevent sintering allows it to maintain good activity over a long period of time in catalytic reactions. The method of preparing such materials includes adding organic silicon reagents to an organic aluminum salt such as an alkoxide in a controlled quantity as a doping agent in a solid state, solvent deficient reaction followed by calcination. Alternatively, the organic silicon compound may be added after calcination of the alumina, followed by another calcination step. This method is inexpensive and simple. The alumina catalyst support material prepared by the subject method maintains high pore volumes, pore diameters and surface areas at very high temperatures and in the presence of steam.

First claim

What is claimed is:

1. A method for preparing a silicon-doped alumina consisting essentially of:
a) bringing together as reactants at least one aluminum salt from the group consisting of an aluminum alkoxide, aluminum phenoxide and combinations thereof and at least one of polydimethylsiloxane or an organic silicon compound of the structure

 wherein R is selected from the group consisting of C 1 -C 12 alkyl, C 5 -C 12 cycloalkyl, aryl, a polyalkyl siloxane radical and combinations thereof, and water, in an amount sufficient to hydrolyze without dissolving the reactants, to produce an alumina nanoparticle precursor; and
b) calcining the product of step (a) at a temperature of 300-1200° C.;
wherein said silicon-doped alumina is substantially in the gamma phase when heated to at least 1200° C. for 2 hours.

2. The method of claim 1 wherein the aluminum salt is represented by the formula Al(O—R) 3 where R is selected from the group consisting of C 1 -C 12 alkyl, C 5 -C 12 cycloalkyl, aryl and combinations thereof.

3. The method of claim 1 wherein the organic aluminum salt is selected from the group consisting of aluminum isopropoxide, aluminum sec-butoxide, aluminum phenoxide, aluminum ethoxide, aluminum tert-butoxide, and aluminum hexoxide.

4. The method of claim 1 wherein the aluminum salt is aluminum isopropoxide.

5. The process of claim 1 wherein the organic silicon compound is at least one compound having the following structure:

6. The method of claim 5 wherein R is selected from the group consisting of C 1 -C 12 alkyl, C 5 -C 12 cycloalkyl, aryl, a polyalkyl siloxane radical and combinations thereof.

7. The method of claim 6 wherein R is C 1 -C 12 alkyl.

8. The method of claim 7 wherein the organic silicon compound is selected from the group consisting of tetraethyl ortho silicate, tetra-n-butyloxysilane, tetra n-propoxy silane, polydimethyl siloxane and triethoxy methyl silane.

9. The method of claim 1 wherein the organic silicon compound is employed in a proportion to provide about 1%-30% silica by weight of the final product.

10. The method of claim 1 wherein the organic silicon compound is employed in a proportion to provide about 1%-30% silica by weight of the final product.

11. The method of claim 1 wherein the reaction of step a) is carried out in the presence of a diluent selected from the group consisting of an alcohol, a ketone, an ether or a combination thereof to adjust the pore characteristics of the final product.

12. The method of claim 8 wherein the organic silicon compound is tetraethyl ortho silicate.

13. The method of claim 12 wherein the aluminum salt is aluminum isopropoxide.

Assignees

• Univ Brigham Young

Inventors

• Khosravi-Mardkhe Maryam
• Woodfield Brian F
• Bartholomew Calvin H
• Huang Baiyu

Classifications

• C01P2004/04

  obtained by TEM, STEM, STM or AFM · CPC title

• B01J35/109

  Operations & Transport · mapped topic

• B01J35/1061

  Operations & Transport · mapped topic

• C01P2004/53

  bimodal size distribution · CPC title

• C01P2002/72

  by d-values or two theta-values, e.g. as X-ray diagram · CPC title