U.S. patent application number 14/827406 was filed with the patent office on 2015-12-10 for rutile titanium dioxide microspheres and ordered botryoidal shapes of same.
This patent application is currently assigned to Cristal Inorganic Chemicals Switzerland Ltd. The applicant listed for this patent is Cristal Inorganic Chemicals Switzerland Ltd. Invention is credited to Guoyi Fu, Mark B. Watson.
Application Number | 20150353374 14/827406 |
Document ID | / |
Family ID | 51229944 |
Filed Date | 2015-12-10 |
United States Patent
Application |
20150353374 |
Kind Code |
A1 |
Fu; Guoyi ; et al. |
December 10, 2015 |
RUTILE TITANIUM DIOXIDE MICROSPHERES AND ORDERED BOTRYOIDAL SHAPES
OF SAME
Abstract
Rutile TiO.sub.2 microspheres and microparticles in a botryoidal
morphology which form from ordered acicular aggregates of elongated
TiO.sub.2 crystallites that resemble nano-sized flower bouquets
and/or triangular funnels, and process for their preparation by
thermally hydrolyzing a soluble TiO.sub.2 precursor compound in
aqueous solution in the presence of a morphology controlling agent
selected from carboxylic acids and amino acids.
Inventors: |
Fu; Guoyi; (Glenwood,
MD) ; Watson; Mark B.; (Kensington, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cristal Inorganic Chemicals Switzerland Ltd |
Baar |
|
CH |
|
|
Assignee: |
Cristal Inorganic Chemicals
Switzerland Ltd
Baar
CH
|
Family ID: |
51229944 |
Appl. No.: |
14/827406 |
Filed: |
August 17, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13842608 |
Mar 15, 2013 |
9108862 |
|
|
14827406 |
|
|
|
|
Current U.S.
Class: |
428/402 ;
423/610 |
Current CPC
Class: |
B82Y 30/00 20130101;
C01P 2004/90 20130101; C01P 2004/03 20130101; C01P 2004/32
20130101; C01P 2004/61 20130101; C01P 2004/45 20130101; C01P
2002/72 20130101; C01P 2006/12 20130101; C01P 2004/04 20130101;
C01G 23/0538 20130101; C01P 2006/14 20130101; Y10T 428/2982
20150115; C01G 23/053 20130101; C01P 2004/62 20130101; C01G 23/0536
20130101; C01P 2004/64 20130101; C01G 23/047 20130101; C01G 23/026
20130101 |
International
Class: |
C01G 23/053 20060101
C01G023/053; C01G 23/047 20060101 C01G023/047 |
Claims
1-7. (canceled)
8. Rutile TiO.sub.2 microparticles which comprise generally
spherical structures in the range of from 1 to 2 microns in
diameter, said spherical structures comprising ordered acicular
aggregates of elongated TiO.sub.2 crystallites having a thickness
in the range of from 3 nm to 5 nm in which one end of each of said
elongated TiO.sub.2 crystallites are joined into a cluster such
that the opposite ends of each of said elongated TiO.sub.2
crystallites extend outwardly and terminate at an angle normal to
the outer surface forming said spherical structure.
9. Rutile TiO.sub.2 microparticles which comprise generally
spherical structures in the range of from 1 to 2 microns in
diameter, said spherical structures comprising ordered acicular
aggregates of elongated TiO.sub.2 crystallites, produced by the
process comprising: (a) forming an aqueous solution of a soluble
titanium compound at a titanium concentration of from 0.5 to 1.0
moles per liter; (b) introducing a morphology controlling agent
selected from the group consisting of an .alpha.-hydroxy carboxylic
acid of the formula R--CH(OH)COOH, an .alpha.-hydroxy carboxamide
of the formula R--CH(OH)CONH.sub.2 or an .alpha.-amino acid of the
formula R--CH(NH.sub.2)COOH, wherein R is an alkane, alkene,
alkyne, arene, or cycloalkane group having 4 or fewer carbon atoms,
into the solution at an acid- or carboxamide-to-titanium molar
ratio of from 0.02 to 0.2 while simultaneously heating the solution
to a temperature in the range of from 75.degree. C. to 80.degree.
C. with constant stirring; (c) maintaining the stirred solution at
a temperature in the range of from 75.degree. C. to 80.degree. C.
for a period of from one to 3 hours; (d) elevating the temperature
of the stirred solution to a value of from 100.degree. C. to the
refluxing temperature and maintaining said temperature for a period
of from 2 hours to 4 hours to form a reaction product; (e)
optionally neutralizing the reaction mixture which results from
step (e); (f) cooling the reaction mixture to room or ambient
temperature; and (h) separating and drying the reaction
product.
10. The rutile TiO.sub.2 microparticles of claim 9 wherein said
elongated TiO.sub.2 crystallites have a length of from 20 nm to 50
nm and a thickness of from 3 nm to 5 nm.
11. The rutile TiO.sub.2 microparticles of claim 10 wherein one of
the ends from each of said elongated TiO.sub.2 crystallites
assemble into a cluster whereby the opposite ends of each of said
crystallites extend outwardly and terminate at an angle normal to
the outer surface forming said spherical structure.
12. The rutile TiO.sub.2 microparticles of claim 9 wherein said
morphology controlling agent is selected from lactic acid
(CH.sub.3CH(OH)COOH); 2-hydroxybutyric acid
(C.sub.2H.sub.5CH(OH)COOH); 2-hydroxypentanoic acid
(C.sub.3H.sub.7CH(OH)COOH); 2-Hydroxyhexanoic acid
(C.sub.4H.sub.9CH(OH)COOH); 2-Hydroxyisocaproic acid
(CH.sub.3CH(CH.sub.3)CH.sub.2CH(OH)COOH); alanine
(CH.sub.3CH(NH.sub.2)COOH); valine
(CH.sub.3CH(CH.sub.3)CH(NH.sub.2)COOH); norvaline
(C.sub.3H.sub.7CH(NH.sub.2)COOH); isoleucine
(C.sub.2H.sub.5CH(CH.sub.3)CH(NH.sub.2)COOH); leucine
(CH.sub.3CH(CH.sub.3)CH.sub.2CH(NH.sub.2)COOH); and norleucine
(C.sub.4H.sub.9CH(NH.sub.2)COOH) and mixtures thereof.
13. The rutile TiO.sub.2 microparticles of claim 9 wherein said
soluble titanium compound is selected from titanium oxychloride
(TiOCl.sub.2), titanium oxybromide (TiOBr.sub.2), titanium
oxyiodide (TiOI.sub.2), titanium oxynitrate (TiO(NO.sub.3).sub.2),
titanium trichloride (TiCl.sub.3), titanium tribromide(TiBr.sub.3),
titanium oxalate (Ti.sub.2(C.sub.2O.sub.4).sub.3), potassium
hexafluorotitanate(K.sub.2TiF.sub.6), ammonium hexafluorotitanate
((NH.sub.4).sub.2TiF.sub.6), potassium titanyloxolate
(K.sub.2TiO(C.sub.2O.sub.4).sub.2), ammonium titanyloxolate
((NH.sub.4).sub.2TiO(C.sub.2O.sub.4).sub.2), titanium bis(ammonium
lactate) dihydroxide ([CH.sub.3CH(O)COONH.sub.4].sub.2Ti(OH).sub.2)
and mixtures thereof.
14. The rutile TiO.sub.2 microparticles of claim 12 wherein said
soluble titanium compound is selected from titanium oxychloride
(TiOCl.sub.2), titanium oxybromide (TiOBr.sub.2), titanium
oxyiodide (TiOI.sub.2), titanium oxynitrate (TiO(NO.sub.3).sub.2),
titanium trichloride (TiCl.sub.3), titanium tribromide(TiBr.sub.3),
titanium oxalate (Ti.sub.2(C.sub.2O.sub.4).sub.3), potassium
hexafluorotitanate(K.sub.2TiF.sub.6), ammonium hexafluorotitanate
((NH.sub.4).sub.2TIF.sub.6), potassium titanyloxolate
(K.sub.2TiO(C.sub.2O.sub.4).sub.2), ammonium titanyloxolate
((NH.sub.4).sub.2TiO(C.sub.2O.sub.4).sub.2), titanium bis(ammonium
lactate) dihydroxide ([CH.sub.3CH(O)COONH.sub.4].sub.2Ti(OH).sub.2)
and mixtures thereof.
15. The rutile TiO.sub.2 microparticles of claim 14 wherein said
morphology controlling agent is lactic acid (CH.sub.3CH(OH)COOH),
and said soluble titanium compound is titanium oxychloride
(TiOCl.sub.2).
16. A method for preparing rutile TiO.sub.2 particles which
comprise structures in a botryoidal morphology having a size in the
range of from 10 to 20 microns, said structures being aggregates of
elongated TiO.sub.2 crystallites having a thickness of from 3 nm to
5 nm, said method comprising: (a) forming an aqueous solution of a
soluble titanium compound at a titanium concentration of from 0.5
to 1.0 moles per liter; (b) introducing a morphology controlling
agent selected from an .alpha.-hydroxy carboxylic acid of the
formula R--CH(OH)COOH, an a-hydroxy carboxamide of the formula
R--CH(OH)CONH.sub.2 or an a-amino acid of the formula
R--CH(NH.sub.2)COOH, wherein R is an alkane, alkene, alkyne, arene,
or cycloalkane group having 4 or fewer carbon atoms, into the
solution at an acid- or carboxamide-to-titanium molar ratio of from
0.02 to 0.2 while simultaneously heating the solution to a
temperature in the range of from 75.degree. C. to 80.degree. C.
with constant stirring; (c) introducing TiO.sub.2 seeds into the
stirred solution at a seed-to-TiO.sub.2 molar ratio of from 0.0005
to 0.0015 and maintaining the stirred solution at a temperature in
the range of from 75.degree. C. to 80.degree. C. for a period of
from one to 3 hours; (d) elevating the temperature of the stirred
solution to a value of from 100.degree. C. to the refluxing
temperature and maintaining said temperature for a period of from 2
hours to 4 hours to form a reaction product; (e) optionally
neutralizing the reaction mixture resulting from step (d); (f)
cooling the reaction mixture to room or ambient temperature; and
(g) separating and drying the reaction product.
17. The method of claim 16 wherein said morphology controlling
agent is selected from lactic acid (CH.sub.3CH(OH)COOH);
2-hydroxybutyric acid (C.sub.2H.sub.5CH(OH)COOH);
2-hydroxypentanoic acid (C.sub.3H.sub.7CH(OH)COOH);
2-Hydroxyhexanoic acid (C.sub.4H.sub.9CH(OH)COOH);
2-Hydroxyisocaproic acid (CH.sub.3CH(CH.sub.3)CH.sub.2CH(OH)COOH);
alanine (CH.sub.3CH(NH.sub.2)COOH); valine
(CH.sub.3CH(CH.sub.3)CH(NH.sub.2)COOH); norvaline
(C.sub.3H.sub.7CH(NH.sub.2)COOH); isoleucine
(C.sub.2H.sub.5CH(CH.sub.3)CH(NH.sub.2)COOH); leucine
(CH.sub.3CH(CH.sub.3)CH.sub.2CH(NH.sub.2)COOH); and norleucine
(C.sub.4H.sub.9CH(NH.sub.2)COOH) and mixtures thereof.
18. The method of claim 16 wherein said soluble titanium compound
is selected from titanium oxychloride (TiOCl.sub.2), titanium
oxybromide (TiOBr.sub.2), titanium oxyiodide (TiOI.sub.2), titanium
oxynitrate (TiO(NO.sub.3).sub.2), titanium trichloride
(TiCl.sub.3), titanium tribromide(TiBr.sub.3), titanium oxalate
(Ti.sub.2(C.sub.2O.sub.4).sub.3), potassium
hexafluorotitanate(K.sub.2TiF.sub.6), ammonium hexafluorotitanate
((NH.sub.4).sub.2TiF.sub.6), potassium titanyloxolate
(K.sub.2TiO(C.sub.2O.sub.4).sub.2), ammonium titanyloxolate
((NH.sub.4).sub.2TiO(C.sub.2O.sub.4).sub.2), titanium bis(ammonium
lactate) dihydroxide ([CH.sub.3CH(O)COONH.sub.4].sub.2Ti(OH).sub.2)
and mixtures thereof.
19. The method of claim 17 wherein said soluble titanium compound
is selected from titanium oxychloride (TiOCl.sub.2), titanium
oxybromide (TiOBr.sub.2), titanium oxyiodide (TiOI.sub.2), titanium
oxynitrate (TiO(NO.sub.3).sub.2), titanium trichloride
(TiCl.sub.3), titanium tribromide(TiBr.sub.3), titanium oxalate
(Ti.sub.2(C.sub.2O.sub.4).sub.3), potassium
hexafluorotitanate(K.sub.2TiF.sub.6), ammonium hexafluorotitanate
((NH.sub.4).sub.2TiF.sub.6), potassium titanyloxolate
(K.sub.2TiO(C.sub.2O.sub.4).sub.2), ammonium titanyloxolate
((NH.sub.4).sub.2TiO(C.sub.2O.sub.4).sub.2), titanium bis(ammonium
lactate) dihydroxide ([CH.sub.3CH(O)COONH.sub.4].sub.2Ti(OH).sub.2)
and mixtures thereof.
20. The method of claim 19 wherein said morphology controlling
agent is lactic acid (CH.sub.3CH(OH)COOH), and said soluble
titanium compound is titanium oxychloride (TiOCl.sub.2).
21. Rutile TiO.sub.2 microparticles comprising structures in a
botryoidal morphology having a size in the range of from 10 to 20
microns and formed by the process of: (a) forming an aqueous
solution of a soluble titanium compound at a titanium concentration
of from 0.5 to 1.0 moles per liter; (b) introducing a morphology
controlling agent selected from an .alpha.-hydroxy carboxylic acid
of the formula R--CH(OH)COOH, an .alpha.-hydroxy carboxamide of the
formula R--CH(OH)CONH.sub.2 or an .alpha.-amino acid of the formula
R--CH(NH.sub.2)COOH, wherein R is an alkane, alkene, alkyne, arene,
or cycloalkane group having 4 or fewer carbon atoms, into the
solution at an acid- or carboxamide-to-titanium molar ratio of from
0.02 to 0.2 while simultaneously heating the solution to a
temperature in the range of from 70.degree. C. to 80.degree. C.
with constant stirring; (c) introducing TiO.sub.2 seeds into the
stirred solution at a seed-to-TiO.sub.2 molar ratio of from 0.0005
to 0.0015 and maintaining the stirred solution at a temperature in
the range of from 70.degree. C. to 80.degree. C. for a period of
from one to 3 hours; (d) maintaining the stirred solution at a
temperature in the range of from 70.degree. C. to 80.degree. C. for
a period of from one to 3 hours; (e) elevating the temperature of
the stirred solution to a value of from 100.degree. C. to the
refluxing temperature and maintaining said temperature for a period
of from 2 hours to 4 hours to form a reaction product; (f)
optionally neutralizing the reaction mixture resulting from step
(e); (g) cooling the reaction mixture to room or ambient
temperature and separating and drying the reaction product.
22. The rutile TiO.sub.2 microparticles of claim 21 wherein: (a)
said morphology controlling agent is selected from lactic acid
(CH.sub.3CH(OH)COOH); 2-hydroxybutyric acid
(C.sub.2H.sub.5CH(OH)COOH); 2-hydroxypentanoic acid
(C.sub.3H.sub.7CH(OH)COOH); 2-Hydroxyhexanoic acid
(C.sub.4H.sub.9CH(OH)COOH); 2-Hydroxyisocaproic acid
(CH.sub.3CH(CH.sub.3)CH.sub.2CH(OH)COOH); alanine
(CH.sub.3CH(NH.sub.2)COOH); valine
(CH.sub.3CH(CH.sub.3)CH(NH.sub.2)COOH); norvaline
(C.sub.3H.sub.7CH(NH.sub.2)COOH); isoleucine
(C.sub.2H.sub.5CH(CH.sub.3)CH(NH.sub.2)COOH); leucine
(CH.sub.3CH(CH.sub.3)CH.sub.2CH(NH.sub.2)COOH); and norleucine
(C.sub.4H.sub.9CH(NH.sub.2)COOH) and mixtures thereof, and (b) said
soluble titanium compound is selected from titanium oxychloride
(TiOCl.sub.2), titanium oxybromide (TiOBr.sub.2), titanium
oxyiodide (TiOI.sub.2), titanium oxynitrate (TiO(NO.sub.3).sub.2),
titanium trichloride (TiCl.sub.3), titanium tribromide(TiBr.sub.3),
titanium oxalate (Ti.sub.2(C.sub.2O.sub.4).sub.3), potassium
hexafluorotitanate(K.sub.2TiF.sub.6), ammonium hexafluorotitanate
((NH.sub.4).sub.2TiF.sub.6), potassium titanyloxolate
(K.sub.2TiO(C.sub.2O.sub.4).sub.2), ammonium titanyloxolate
((NH.sub.4).sub.2TiO(C.sub.2O.sub.4).sub.2), titanium bis(ammonium
lactate) dihydroxide ([CH.sub.3CH(O)COONH.sub.4].sub.2Ti(OH).sub.2)
and mixtures thereof.
23. Rutile TiO.sub.2 microparticles in a botryoidal morphology
having a size in the range of from 10 to 20 microns which comprise
an assembly of generally spherical structures in the range of from
1 to 2 microns in diameter, said spherical structures comprising
ordered acicular aggregates of elongated TiO.sub.2 crystallites
having a thickness in the range of from 3 nm to 5 nm in which one
end of each of said elongated TiO.sub.2 crystallites are joined
into a cluster such that the opposite ends of each of said
elongated TiO.sub.2 crystallites extend outwardly and terminate at
an angle normal to the outer surface forming said spherical
structure.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE
STATEMENT
[0001] The present application is a Divisional of U.S. application
Ser. No. 13/842,608, filed Mar. 15, 2013. The entirety of which is
hereby expressly incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The presently described and claimed inventive concept(s)
relates to a novel chemical structure comprising rutile titanium
dioxide (TiO.sub.2) microspheres which are formed by aggregation of
funnel-shaped rutile nanoparticles in which the broader dimension
of the funnels assemble during hydrolysis to become the outer
surface of the microspheres. More particularly, ordered aggregates
of such microspheres further aggregate to resemble a larger
botryoidal morphology.
[0003] Titanium dioxide (TiO.sub.2) is known as a typical solid
compound having photocatalytic activity and having utility in
electronic, photovoltaic and photonic applications. Rutile and
anatase crystal forms are known as major crystal forms of TiO.sub.2
which display higher chemical stability and larger refractive
indices than those of amorphous TiO.sub.2. It has also been
recognized that TiO.sub.2 particles having a high degree of
crystallinity can exhibit a desirable level of photocatalytic
activity.
[0004] U.S. Patent Publication No. 2012/0132515, for example,
describes rutile TiO.sub.2 nanoparticles wherein each has an
exposed crystal face, making the nanoparticles useful as a
photocatalyst and oxidation catalyst. The TiO.sub.2 nanoparticles
are produced by subjecting a titanium compound to a hydrothermal
treatment in an aqueous medium in the presence of a hydrophilic
polymer, which is polyvinylpyrrolidone. The titanium compound, when
hydrothermally treated in an aqueous medium, generally gives a
rod-like crystal of rutile titanium dioxide having (110) and (111)
faces. However, when hydrothermally treated in an aqueous medium in
the presence of polyvinylpyrrolidone, the rod-like crystal which
results exhibits a novel exposed crystal face (001). It is noted
that the hydrophilic polymer acts as a steric stabilizer or capping
agent to thereby prevent aggregation of the rod-like crystals of
rutile titanium dioxide.
[0005] The need exists for improved methods for producing novel
types of rutile titanium dioxide (TiO.sub.2) nano- and
microparticles which have high surface areas, e.g., in the range of
from 120 m.sup.2/g to 160 m.sup.2/g, and high refractive indices
for improved UV blocking capability and which demonstrate high
performance levels in catalysis, e.g., biomass conversion, and in
electronic applications, such as lithium ion batteries and fuel
cells.
SUMMARY OF THE INVENTION
[0006] The described and claimed inventive concepts(s) comprise, in
one embodiment, a method for preparing a novel form of rutile
TiO.sub.2 nanoparticles which are ordered acicular aggregates of
elongated TiO.sub.2 crystallites. The elongated TiO.sub.2
crystallites are rod-like, e.g., slender and/or needle-like, having
a thickness of from 3 nm to 5 nm and a length which can vary from
20 nm up to 50 nm, although longer and shorter lengths may also be
present. However, the elongated TiO.sub.2 crystallites assemble
together during the process in a manner which results in ordered
acicular aggregates that resemble nano-sized flower bouquets or
triangular funnels. By controlling the hydrolysis conditions
according to the inventive concept(s) described herein, the
nano-sized flower bouquets or triangular funnel-shaped
nanoparticles further aggregate into somewhat larger spherical
structures, i.e., microspheres, having a diameter of from 1 to 2
microns. The particles aggregate in such a manner that the broader
ends of the funnel-shaped particles become the outer surfaces of
the microspheres where the tips of the funnels join, i.e., become
assembled together, at the center of the microspheres.
[0007] The method for preparing the microspheres comprises:
[0008] (a) forming an aqueous solution of a soluble titanium
compound at a titanium concentration of from 0.5 to 1.0 moles per
liter;
[0009] (b) introducing a morphology controlling agent selected from
an .alpha.-hydroxy carboxylic acid of the formula R--CH(OH)COOH, an
.alpha.-hydroxy carboxamide of the formula R--CH(OH)CONH.sub.2 or
an .alpha.-amino acid of the formula R--CH(NH.sub.2)COOH, wherein R
is an alkane, alkene, alkyne, arene, or cycloalkane group having 4
or fewer carbon atoms, into the solution at an acid- or
carboxamide-to-titanium molar ratio of from 0.02 to 0.2 while
simultaneously heating the solution to a temperature in the range
of from 75.degree. C. to 80.degree. C. with constant stirring;
[0010] (c) maintaining the stirred solution at a temperature in the
range of from 75.degree. C. to 80.degree. C. for a period of from
one to 3 hours;
[0011] (d) elevating the temperature of the stirred solution to a
value of from 100.degree. C. to the refluxing temperature and
maintaining said temperature for a period of from 2 hours to 4
hours to form a reaction product;
[0012] (e) optionally neutralizing the reaction mixture which
results from step (e);
[0013] (f) cooling the reaction mixture to room or ambient
temperature; and
[0014] (h) separating and drying the reaction product.
[0015] The reaction product can then be calcined. Calcining, which
can be adjusted over a wide range for time and temperature,
operates to enhance the properties of the resulting nanoparticles
by expanding or opening the pore structure and/or increasing the
refractive index.
[0016] The morphology controlling agent is selected from lactic
acid (CH.sub.3CH(OH)COOH); 2-hydroxybutyric acid
(C.sub.2H.sub.5CH(OH)COOH); 2-hydroxypentanoic acid
(C.sub.3H.sub.7CH(OH)COOH); 2-Hydroxyhexanoic acid
(C.sub.4H.sub.9CH(OH)COOH); 2-Hydroxyisocaproic acid
(CH.sub.3CH(CH.sub.3)CH.sub.2CH(OH)COOH); alanine
(CH.sub.3CH(NH.sub.2)COOH); valine
(CH.sub.3CH(CH.sub.3)CH(NH.sub.2)COOH); norvaline
(C.sub.3H.sub.7CH(NH.sub.2)COOH); isoleucine
(C.sub.2H.sub.5CH(CH.sub.3)CH(NH.sub.2)COOH); leucine
(CH.sub.3CH(CH.sub.3)CH.sub.2CH(NH.sub.2)COOH); and norleucine
(C.sub.4H.sub.9CH(NH.sub.2)COOH) and mixtures thereof.
[0017] The soluble titanium compound is selected from titanium
oxychloride (TiOCl.sub.2), titanium oxybromide (TiOBr.sub.2),
titanium oxyiodide (TiOI.sub.2), titanium oxynitrate
(TiO(NO.sub.3).sub.2), titanium trichloride (TiCl.sub.3), titanium
tribromide(TiBr.sub.3), titanium oxalate
(Ti.sub.2(C.sub.2O.sub.4).sub.3), potassium
hexafluorotitanate(K.sub.2TiF.sub.6), ammonium hexafluorotitanate
((NH.sub.4).sub.2TiF.sub.6), potassium titanyloxolate
(K.sub.2TiO(C.sub.2O.sub.4).sub.2), ammonium titanyloxolate
((NH.sub.4).sub.2TiO(C.sub.2O.sub.4).sub.2), titanium bis(ammonium
lactate) dihydroxide ([CH.sub.3CH(O)COONH.sub.4].sub.2Ti(OH).sub.2)
and mixtures thereof.
[0018] According to another embodiment, the described and claimed
inventive concept(s) relates to a method for preparing rutile
TiO.sub.2 particles which comprise structures in a botryoidal
morphology having a size in the range of from 10 to 20 microns. The
botryoidal structures, also being aggregates of elongated TiO.sub.2
crystallites having a thickness of from 3 nm to 5 nm, are formed by
introducing TiO.sub.2 seeds into the stirred solution at a
seed-to-TiO.sub.2 molar ratio of from 0.0005 to 0.0015 following
introduction of the morphology controlling agent. The stirred
solution is then maintained at a temperature in the range of from
75.degree. C. to 80.degree. C. for a period of from one to 3 hours,
and the process is further carried out as described above.
[0019] The described and claimed inventive concept(s) include, in
other embodiments, the microspheres and the botryoidal particles
produced by the described processes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is an SEM (Scanning Electron Microscopy) image (9500
magnification) of spherical-shaped rutile TiO.sub.2 microparticles
according to the invention.
[0021] FIG. 2 is an enlarged SEM image (50,000 magnification) which
illustrates in more detail the spherical-shaped rutile TiO.sub.2
microparticles according to the invention.
[0022] FIG. 3 is an SEM image (10,000 magnification) which
illustrates spherical- shaped rutile TiO.sub.2 microparticles
arranged in structures which resemble a botryoidal morphology
according to the invention.
[0023] FIG. 4 is an enlarged SEM image (50,000 magnification) which
illustrates the botryoidal morphology according to the invention in
more detail.
[0024] FIGS. 5 and 6 are SEM images of rutile TiO.sub.2
microparticles prepared by thermal hydrolydsis according to Example
3, but without benefit of a morphology controlling agent.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The described and claimed inventive concepts(s) comprise, in
one embodiment, a method for preparing a novel form of rutile
TiO.sub.2 nanoparticles which are ordered acicular aggregates of
elongated TiO.sub.2 crystallites. The elongated TiO.sub.2
crystallites are rod-like and have a thickness of from 3 nm to 5 nm
and a length which can vary generally from 20 nm up to 50 nm.
However, the elongated TiO.sub.2 crystallites assemble together
during the process in a manner which results in ordered acicular
aggregates that resemble nano-sized flower bouquets or triangular
funnels. By controlling the hydrolysis conditions according to the
inventive concept(s) described and claimed herein, the nano-sized
flower bouquets or triangular funnel-shaped nanoparticles further
aggregate into somewhat larger spherical structures, i.e.,
microspheres, having a diameter of from 1 to 2 microns. Detailed
examination under an electron microscope confirms that the
microspheres are indeed formed by aggregation of the funnel-shaped
nanoparticles. The microspheres can be seen in FIGS. 1 and 2. The
hydrolysis conditions are controlled in such a manner that the
nanoparticles aggregate so that the broader ends of the
funnel-shaped particles become the outer surfaces of the
microspheres, and the tips of the funnels join, i.e., assemble
together, at the center of the microspheres. The structure observed
for the microspheres indicates a large number of rutile nano-rods
with various lengths radiating outwardly from the center of the
spherical structures with each of the rods aligning at an angle
normal to the surface of the spheres.
[0026] The novel rutile TiO.sub.2 microspheres are prepared by
thermally hydrolyzing a soluble TiO.sub.2 precursor compound, or a
mixture of such compounds, in aqueous solution in the presence of a
morphology controlling agent, or a mixture of morphology
controlling agents, under specific conditions. The process is a wet
chemical hydrolysis method in which the structure of the
microspheres is controlled by controlling the structure of the
nano-sized flower bouquets or triangular funnel-shaped
nanoparticles. A morphology controlling agent, or a mixture of
morphology controlling agents, is used that is selected from (i) an
.alpha.-hydroxy carboxylic acid of the formula R--CH(OH)COOH, (ii)
an .alpha.-hydroxy carboxamide of the formula R--CH(OH)CONH.sub.2,
or (iii) an .alpha.-amino acid of the formula R--CH(NH.sub.2)COOH,
wherein R is an alkane, alkene, alkyne, arene, or cycloalkane group
having 4 or fewer carbon atoms.
[0027] The process begins by forming an aqueous solution of a
soluble titanium compound at a titanium concentration of from 0.1
to 1.5 moles per liter, but preferably 0.5 to 1.0 moles per liter,
optionally in the presence of a mineral acid. Distilled or
deionized water can be used to form the aqueous solution, and a
mineral acid, e.g., hydrochloric acid (HCl), can be introduced as
needed for controlling the rate of hydrolysis.
[0028] The morphology controlling agent, or a mixture thereof, is
introduced into the solution at an acid- or carboxamide-to-titanium
molar ratio of from 0.02 to 0.4, although best results have been
observed when the ratio is from 0.02 to 0.2. The solution is
simultaneously heated to a temperature in the range of from
75.degree. C. to 80.degree. C. with constant stirring.
[0029] The temperature of the stirred solution is next elevated to
a value of from 100.degree. C. to the refluxing temperature and
maintained at that level for a period of from 2 hours to 4 hours
during which time a reaction product is formed. The solution, i.e.,
reaction mixture, is then cooled to room or ambient temperature,
and, optionally, it can be neutralized, e.g., pH of 5 to 8, with
introduction of a base, such as an ammonia solution or a sodium
hydroxide solution. The reaction product is then separated by
filtration and washed with dionized water to remove salts generated
during hydrolysis. The resulting filter cake can then be dried in
an oven or re-slurried with water and spray dried.
[0030] As noted above, the reaction product can then be calcined as
desired over a wide range of time and temperature to enhance the
properties of the resulting nanoparticles, such as by expanding or
opening the pore structure and/or increasing the refractive
index.
[0031] For best results the soluble titanium precursor compound is
selected from titanium oxychloride (TiOCl.sub.2), titanium
oxybromide (TiOBr.sub.2), titanium oxyiodide (TiOI.sub.2), titanium
oxynitrate (TiO(NO.sub.3).sub.2), titanium trichloride
(TiCl.sub.3), titanium tribromide(TiBr.sub.3), titanium oxalate
(Ti.sub.2(C.sub.2O.sub.4).sub.3), potassium
hexafluorotitanate(K.sub.2TiF.sub.6), ammonium hexafluorotitanate
((NH.sub.4).sub.2TiF.sub.6), potassium titanyloxolate
(K.sub.2TiO(C.sub.2O.sub.4).sub.2), ammonium titanyloxolate
((NH.sub.4).sub.2TiO(C.sub.2O.sub.4).sub.2), and titanium
bis(ammonium lactate) dihydroxide
([CH.sub.3CH(O)COONH.sub.4].sub.2Ti(OH).sub.2). Other commercially
available soluble titanium precursor compounds can be deployed in
the process and produce satisfactory results and, although not
specifically named herein, they are embraced within the described
and claimed inventive concept(s).
[0032] As noted above, morphology controlling agents, or mixtures
thereof, for carrying out the inventive concept(s) include (i)
.alpha.-hydroxy carboxylic acids of the formula R--CH(OH)COOH, (ii)
.alpha.-hydroxy carboxamides of the formula R---CH(OH)CONH.sub.2,
and (iii) .alpha.-amino acids of the formula R--CH(NH.sub.2)COOH,
wherein R is an alkane, alkene, alkyne, arene, or cycloalkane group
having 4 or fewer carbon atoms. Examples of such morphology
controlling agents include, but are not limited to, lactic acid
(CH.sub.3CH(OH)COOH); 2-hydroxybutyric acid
(C.sub.2H.sub.5CH(OH)COOH); 2-hydroxypentanoic acid
(C.sub.3H.sub.7CH(OH)COOH); 2-Hydroxyhexanoic acid
(C.sub.4H.sub.9CH(OH)COOH); 2-Hydroxyisocaproic acid
(CH.sub.3CH(CH.sub.3)CH.sub.2CH(OH)COOH); alanine
(CH.sub.3CH(NH.sub.2)COOH); valine
(CH.sub.3CH(CH.sub.3)CH(NH.sub.2)COOH); norvaline
(C.sub.3H.sub.7CH(NH.sub.2)COOH); isoleucine
(C.sub.2H.sub.5CH(CH.sub.3)CH(NH.sub.2)COOH); leucine
(CH.sub.3CH(CH.sub.3)CH.sub.2CH(NH.sub.2)COOH); and norleucine
(C.sub.4H.sub.9CH(NH.sub.2)COOH) and mixtures thereof.
[0033] It has also been discovered according to the inventive
concept(s) described herein that the hydrolysis conditions can be
further adjusted to produce even larger aggregates of about 10 to
20 microns in size which exhibit a botryoidal morphology or
texture. A botryoidal texture is one in which the particle has a
globular external form resembling, for example, a bunch of grapes.
The botryoidal structures, also being aggregates of the elongated
TiO.sub.2 crystallites, form when TiO.sub.2 seeds are introduced
into the stirred solution at a seed-to-TiO.sub.2 molar ratio of
from 0.0005 to 0.0015 following introduction of the morphology
controlling agent. The stirred solution is then maintained at a
temperature in the range of from 75.degree. C. to 80.degree. C. for
a period of from one to 3 hours, and the process is further carried
out as described above. The rutile TiO.sub.2 microspheres and the
botryoidal particles become denser and their pore volumes become
lower in comparison with the funnel-shaped triangular
nanoparticles, although the powder specific surface areas for the
particle varieties are similar to one another, i.e., in the range
from 120 m.sup.2/g to 160 m.sup.2/g. Typical pore volumes for the
microspheres and botryoidal particles are in the range of from 0.1
cm.sup.3/g-0.3 cm.sup.3/g.
EXAMPLES
[0034] The present invention will be illustrated in further detail
with reference to the working examples which follow and FIGS. 1-8.
It should be noted, however, that these examples should not be
construed to limit the scope of the described and claimed inventive
concept(s).
Example 1
Preparation of TiO.sub.2 Microspheres Using Carboxylic Acids
[0035] 1,255 g of deionized water, 6.6 g lactic acid (85% solution
from Alfa Aesar), 97 g HCl solution (37% from Fisher Scientific),
and 397 g of titanium oxychloride solution (25.2% in TiO.sub.2,
from Millennium Inorganic Chemicals) were mixed together in a
heated reactor equipped with a glass condenser and an overhead
stirrer. While being constantly stirred, the mixture was heated to
75.degree. C., and the hydrolysis reaction was maintained at
75.degree. C. for 2 hours. The reaction temperature was then
increased to 103.degree. C., and that temperature was maintained
for 4 hours. The hydrolysis was essentially complete at this
stage.
[0036] The resulting reaction mixture was then cooled to room
temperature and transferred to a different container where the
particles formed were allowed to settle for a few hours. After
essentially all of the particles were observed to have settled to
the bottom of the container, the mother liquor, i.e., liquid
reaction medium, was removed and about the same volume of fresh
deionized water was added to the container. The reaction mixture
was then stirred to re-slurry the particles, and then the pH of the
slurry was increased to a value of about 7 by slow addition of an
ammonia solution (.about.29%, Fisher Scientific). The particles
comprising the reaction product were then separated from the liquid
reaction mixture using a Buchner filter and washed with deionized
water until the conductivity of the filtrate was lowered to about
500 .mu.S/cm. The wet filter cake sample was then stored as a
slurry by re-slurring the filter cake with a small amount of
deionized water. The powder form of the sample was obtained by
drying the slurry sample in an oven overnight at 90.degree. C.
X-ray Diffraction (XRD) measurement on the powder sample indicates
that the sample contained 100% rutile with crystallite size about
7.6 nm. BET measurement on the powder sample showed that the powder
had a specific surface area of 122 m.sup.2/g and a pore volume of
0.1 cm.sup.3/g.
[0037] SEM images of the slurry sample are shown in FIG. 1 at a
magnification of 9,500 where the spherical microspheres can be
observed. Enlarged microspheres can be seen more clearly in FIG. 2
at a magnification of 50,000.
[0038] The TiO.sub.2 microspheres shown in FIGS. 1 and 2 can be
calcined, which can be adjusted for time and temperature, to
enhance the properties of the resulting microparticles by expanding
or opening the pore structure and/or increasing the refractive
index.
Example 2
Preparation of Botryoidal Micro-Particles Using Carboxylic
[0039] The same procedure was followed as was followed in Example
1, except that 13.2 g of lactic acid (85% solution from Alfa Aesar)
was added. In addition, the final hydrolysis temperature was
maintained at 95.degree. C. for 4 hours instead of 103.degree. C.
SEM images of the sample are shown in FIG. 3 at a magnification of
10,000. A botryoidal texture can be observed in which the particle
has a globular external form resembling, for example, a bunch of
grapes. FIG. 4 shows an enlarged SEM image (b 50,000 magnification)
which illustrates the botryoidal morphology in more detail.
[0040] XRD measurement of the sample confirmed that the sample
contained 100% rutile TiO.sub.2 with a crystallite size of 7.8 nm.
BET measurement showed a specific area of 161 m.sup.2/g and a pore
volume of 0.12 cm.sup.3/g.
Comparative Example 3
Hydrolysis without a Morphology Controlling Agent(s)
[0041] The same procedure was followed as was followed for Example
1, except that no organic acids (morphology controlling agent) were
added during the procedure. SEM images of the sample can be seen in
FIGS. 5 and 6. XRD measurement showed that the sample contained
100% rutile TiO.sub.2, however, the SEM images show clearly that
the sample prepared by thermal hydrolysis without a morphology
controlling agent has a different morphology than the microsphere
and botryoidal particle samples shown in FIGS. 1-4 in which a
morphology controlling agent was used.
* * * * *