U.S. patent application number 15/987535 was filed with the patent office on 2018-09-20 for vanadium corrosion inhibitors in gas turbine applications.
This patent application is currently assigned to Saudi Arabian Oil Company. The applicant listed for this patent is Saudi Arabian Oil Company. Invention is credited to Ki-Hyouk Choi.
Application Number | 20180265798 15/987535 |
Document ID | / |
Family ID | 58641032 |
Filed Date | 2018-09-20 |
United States Patent
Application |
20180265798 |
Kind Code |
A1 |
Choi; Ki-Hyouk |
September 20, 2018 |
VANADIUM CORROSION INHIBITORS IN GAS TURBINE APPLICATIONS
Abstract
The present embodiments describe a method to reduce vanadium
corrosion in a gas turbine by adding an oleophilic corrosion
inhibitor into a combustion fuel, in which the oleophilic corrosion
inhibitor comprises carbon black support particles and magnesium
bonded to the carbon black support particles. The carbon black
support particles comprise a particle size less than 40 nanometer
(nm), and oxygen content less than 1 weight percent (wt %), and a
surface area of at least 50 square meters per gram
(m.sup.2/gram).
Inventors: |
Choi; Ki-Hyouk; (Dhahran,
SA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Saudi Arabian Oil Company |
Dhahran |
|
SA |
|
|
Assignee: |
Saudi Arabian Oil Company
Dhahran
SA
|
Family ID: |
58641032 |
Appl. No.: |
15/987535 |
Filed: |
May 23, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15482218 |
Apr 7, 2017 |
|
|
|
15987535 |
|
|
|
|
62324387 |
Apr 19, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10L 2230/08 20130101;
C08K 3/22 20130101; C10L 2200/0438 20130101; C01P 2002/72 20130101;
C10L 2200/0213 20130101; C08K 3/04 20130101; C08K 2003/222
20130101; C10L 10/04 20130101; C01P 2004/64 20130101; C10L 1/12
20130101; C10L 2270/04 20130101; F05D 2260/95 20130101; C09C 1/565
20130101; C10L 1/322 20130101; C01P 2006/12 20130101; C23F 11/187
20130101; C01P 2002/88 20130101; F02C 7/30 20130101; B82Y 30/00
20130101; C10L 2250/06 20130101; C10L 2290/24 20130101; F02C 3/30
20130101; C10L 1/1208 20130101; C10L 1/1233 20130101 |
International
Class: |
C10L 10/04 20060101
C10L010/04; C10L 1/32 20060101 C10L001/32; F02C 7/30 20060101
F02C007/30; C10L 1/12 20060101 C10L001/12; C08K 3/22 20060101
C08K003/22; C09C 1/56 20060101 C09C001/56; B82Y 30/00 20060101
B82Y030/00; C23F 11/18 20060101 C23F011/18 |
Claims
1. A method of making a vanadium corrosion inhibitor comprising:
oxidizing carbon black support particles to form oxidized carbon
black; mixing oxidized carbon black with a magnesium salt solution
to form a mixture; drying the mixture to yield a dried mixture of
oxidized carbon black and magnesium salt; and calcining the dried
mixture under flowing inert gas to produce the vanadium corrosion
inhibitor.
2. The method of claim 1, in which oxidizing carbon black support
particles comprises heating the carbon black support particles in
an oxidizing atmosphere.
3. The method of claim 1, in which oxidizing carbon black support
particles comprises immersing the carbon black support particles in
an oxidizing solution.
4. The method of making the vanadium corrosion inhibitor of claim
1, in which the magnesium salt solution comprises water and
magnesium salt.
5. The method of claim 4, in which the magnesium salt comprises at
least one of magnesium chloride, magnesium nitrate hexahydrate, and
magnesium sulfate.
6. The method of claim 1, in which the flowing inert gas comprises
at least one of nitrogen, helium, and argon.
7. The method of claim 1, in which the carbon black support
particles comprise: a particle size of less than 40 nm; an oxygen
content of less than 1 weight percent; and a surface area of at
least 50 m.sup.2/gram.
8. The method of claim 1, in which the carbon black support
particles comprise an ash content of less than 0.5 weight
percent.
9. The method of claim 1, in which the carbon black support
particles comprise a particle size of less than 20 nm.
10. The method of claim 1, in which the carbon black support
particles comprise a surface area of from 50 m.sup.2/gram to 100
m.sup.2/gram.
11. The method of claim 1, in which the vanadium corrosion
inhibitor comprises magnesium oxide and carbon black support
particles.
12. The method of claim 11, in which the magnesium oxide is
attached to the carbon black support particles.
13. The method of claim 1, in which the carbon black support
particles comprise acetylene black.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 15/482,218 filed Apr. 7, 2017, which claims
priority to U.S. Provisional Patent Application Ser. No. 62/324,387
filed Apr. 19, 2016, which is incorporated by reference herein in
its entirety.
TECHNICAL FIELD
[0002] Embodiments of the present disclosure generally relate to
combustion fuel additives, specifically vanadium corrosion
inhibitors in gas turbines.
BACKGROUND
[0003] One of the most popular methods to generate energy is
hydrocarbon combustion, which includes natural gas, petroleum gas,
coal and liquid hydrocarbons, such as petroleum crude oil.
Combustion generates heat, steam, electricity, and other types of
energy. Gas turbines, an internal combustion engine, have been a
representative machine to use hydrocarbons for generating energy. A
gas turbine has two main components, a combustion chamber and a
rotating turbine. Energy is generated from hydrocarbon combustion,
and the efficiency is strongly dependent on the firing
temperature--the greater the temperature the more efficient.
Current gas turbines can reach temperature of 1430.degree. C.
[0004] Liquid fuel is a common hydrocarbon used in various
machines, and diesel has been a common liquid fuel due to its low
viscosity and cleanness. Due to increasing demand, heavy oil is a
more acceptable alternative to diesel. In spite of its wide
availability and low economic value, heavy oil has many drawbacks.
Using heavy oil generates soot and other incomplete combustion
particles, air pollutants, and other pollutants, such as SO.sub.x
and NO.sub.x, during combustion and affects the air quality. Heavy
oil also contains metallic compounds. In most cases, those metals
are vanadium, nickel, iron, alkali, and alkaline earth
metal-containing compounds. The metal-containing compounds found in
the heavy oil can cause corrosion in the gas turbine during the
combustion process. Vanadium compounds can severely corrode the
metallic and protective layers when exposed to elevated
temperatures in the gas turbine. Vanadium compounds, which are
present as organometallic compounds in heavy oil, are converted to
vanadium oxide (V.sub.2O.sub.5) during combustion. Vanadium oxide
has a low melting point of 675.degree. C., which means vanadium
oxide melts at much lesser temperatures than the firing
temperatures of gas turbines. Melted vanadium oxide adheres to the
hot surface in gas turbine and reacts with metallic and protective
layers to cause corrosion.
SUMMARY
[0005] Adding additives to the heavy oil limits the corrosion
caused by vanadium oxide, and magnesium compounds are effective
additives. Magnesium oxide (MgO) reacts with vanadium oxide to form
magnesium-vanadium mixed oxide compound, which has a much greater
melting points than vanadium oxide (V.sub.2O.sub.5). The
magnesium-vanadium mixed oxides are present as ash and do not
adhere to the metallic and protective layer of the gas turbine,
thereby limiting the amount of corrosion caused by vanadium oxide.
A magnesium oxide slurry may be injected into gas turbines, but a
serious drawback is that solid state reactions, which lead to the
formation of refractory magnesium-vanadium mixed oxides, are
extremely slow even at elevated temperatures.
[0006] Embodiments of this disclosure describe methods to reduce
vanadium corrosion in a gas turbine by introducing an oleophilic
corrosion inhibitor into a combustion fuel, in which the oleophilic
corrosion inhibitor comprises carbon black support particles and
magnesium attached to the carbon black support particles. The
carbon black support particles comprise a particle size less than
40 nanometer (nm), and oxygen content less than 1 weight percent
(wt %), and a surface area of at least 50 square meters per gram
(m.sup.2/gram).
[0007] According to some embodiments, methods of making the
vanadium corrosion inhibitor comprises oxidizing carbon black
particles, mixing the oxidized carbon black with a magnesium salt
solution, drying the mixture to yield a dried mixture of oxidized
carbon black and magnesium salt, and then calcining the dried
mixture to produce the vanadium corrosion inhibitor. The vanadium
corrosion inhibitor comprises magnesium oxide bonded to the carbon
black support particles. The carbon black support particles
comprise a particles size less than 40 nm, an oxygen content less
than 1.0 weight percent, an ash content less than 0.5 weight
percent, and a surface area greater than 50 m.sup.2/gram.
[0008] The methods of making the vanadium corrosion inhibitor in
the preceding paragraph yield an oleophilic corrosion inhibitor.
The oleophilic corrosion inhibitor comprises oleophilic carbon
black support particles and magnesium attached to the carbon
support particles. The carbon black support particles comprise a
particle size less than 40 nm, an oxygen content less than 1.0
weight percent, an ash content less than 0.5 weight percent, and a
surface area of at least 50 m.sup.2/gram. The magnesium includes
magnesium oxide, elemental magnesium, or combinations thereof, in
which the magnesium content of the oleophilic corrosion inhibitor
includes at least 0.05 to 20 weight percent magnesium oxide.
[0009] Additional features and advantages of the described
embodiments will be set forth in the detailed description which
follows, and in part will be readily apparent to those skilled in
the art from that description or recognized by practicing the
described embodiments, including the detailed description which
follows, the claims, and the figures.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 includes stacked X-Ray Diffraction spectra of three
samples, in which sample 1 "(1)" and sample 2 "(2)" do not contain
magnesium loaded carbon black._Sample 3 "(3)" contains magnesium
oxide on a carbon black support. The dotted line is the x-ray
diffraction of vanadium oxide (V.sub.2O.sub.5).
[0011] FIG. 2 is a graph of a thermogravimetric analysis showing
the weight (normalized) of carbon black (dotted line) and magnesium
oxide on carbon black support (solid line) as a function of
temperature in degree Celsius.
DETAILED DESCRIPTION
[0012] Methods for reducing vanadium corrosion in a gas turbine
comprise adding an oleophilic corrosion inhibitor into a combustion
fuel, in which the oleophilic corrosion inhibitor includes carbon
black support particles and magnesium attached to the carbon black
support particles. The carbon black support particles include a
particles size less than 40 nm, oxygen content less than 1.0% by
weight, and a surface area of at least 50 m.sup.2/gram.
[0013] As used in this disclosure, the term "support" or
"supporting" in reference to "support particles" means weak
physical interactions or chemical binding between the support
particle (for example, carbon black) and the supported material
(such as magnesium). For example, when there are strong chemical
binding between the support particle and the supported material,
surface groups, such as silica hydroxide (Si--OH), react with metal
compounds to form strong chemical bonds such as Si--O--Mg. As for
carbon black, such strong chemical bindings are not expected.
[0014] The carbon black support particles may be oleophilic and
thus are able to disperse, dissolve, or otherwise become a solution
when mixed with liquid fuel. An oleophilic corrosion inhibitor
includes carbon black support and magnesium. The oleophilic
corrosion inhibitor may disperse in the oil, and more easily reacts
with the vanadium than the corrosion inhibitors based on oleophobic
magnesium compounds, which are generally dissolved in water before
injecting the aqueous solution into the combustion field.
[0015] Carbon black is a type of elemental carbon in the form of
colloidal particles that are produced by incomplete combustion or
thermal decomposition of gaseous or liquid hydrocarbons under
controlled conditions. The physical appearance of carbon black
appears black and is finely divided pellet or powder. In accordance
with one or more embodiments, the primary particle size, which may
be defined as "mean particle size" in accordance with ASTM D 3849,
should be less than 40 nm in diameter or less than 20 nm as
measured by electron microscope. The oxygen content of the carbon
black support particles may be less than 1.0 weight percent and in
some embodiments, less than 0.5 weight percent.
[0016] In one or more embodiments, carbon black includes acetylene
black, channel black, furnace black, lamp black, and thermal black.
In some embodiments, carbon black may be acetylene black. Acetylene
black may have a small ash content or a small amount of impurities.
The ash content of the carbon black support particles correlates to
the effectiveness of the carbon black, and may be less than 0.5
weight percent. In one or more embodiments, the ash content of the
carbon black support particles is less than 0.2 weight percent, and
in some embodiments the ash content is less than 0.1 weight
percent. "Ash content" in reference to carbon black means any
inorganic impurity, which is not combusted and remains after
burning at 750.degree. C. in air.
[0017] In one or more embodiments, magnesium is attached to the
carbon black support. The term "attached" may refer to a chemical
bond, a physical interaction, or otherwise connected to. The
greater the surface area of the carbon black support, the more
magnesium can attach to the support, and thereby reacting with more
of the corrosive material. One embodiment of the carbon black
support particles has a surface area from 50 m.sup.2/grams to 100
m.sup.2/grams. In another embodiment the surface area is from 75
m.sup.2/grams to 100 m.sup.2/grams.
[0018] The magnesium of the oleophilic corrosion inhibitor may be
elemental magnesium, magnesium oxide, or a combination of both
elemental magnesium and magnesium oxide. In some embodiments, the
magnesium of the oleophilic corrosion inhibitor includes at least
0.05 to 25.0 weight percent magnesium oxide based on the weight of
the oleophilic corrosion inhibitor. In other embodiments, the
amount of magnesium is from 0.05 and 20.0 weight percent or 0.1
weight percent to 10.0 weight percent magnesium oxide based on the
weight of the oleophilic corrosion inhibitor. In some embodiments,
the magnesium oxide is between 0.5 and 5.0 weight percent.
[0019] The oleophilic corrosion inhibitor is added into a
combustion fuel. The combustion fuel may include liquid oil. Liquid
oil is any hydrocarbon that can be combusted in gas turbines
without causing problems such as corrosion and plugging. Liquid oil
may include crude oil or diesel. The combustion fuel can be
selected from diesel, gasoline or any other hydrocarbon fuel having
a flash point greater than 35.degree. C. Unlike the magnesium oxide
used in prior art, this oleophilic corrosion inhibitor decreases
the formation of vanadium oxide during combustion, and thereby
decreases gas turbine corrosion.
[0020] The oleophilic vanadium corrosion inhibitor is synthesized
by oxidizing carbon black particles, then mixing the oxidized
carbon black with a magnesium salt containing solution or a
magnesium oxide aqueous solution. The carbon black and magnesium
solution is mixed vigorously by an agitator, an ultrasonic mixer,
or a homogenizer. After a certain time, the mixture is filtered.
The filtrate is dried. The dried mixture is then calcined by
heating under flowing inert gas to produce the oleophilic corrosion
inhibitor.
[0021] As stated in a preceding paragraph, carbon black is
oleophilic. Since acetylene black is oleophilic and not
hydrophilic, the reactivity between non-treated acetylene black and
an aqueous magnesium salt solution is limited. The carbon black
should be pretreated with an oxidizing agent before magnesium can
attach to the carbon support. An oxidizing agent increases the
amount of oxygen on the particles surface, which increases the
polarity and allows the carbon material to be more hydrophilic.
Non-limiting examples of oxidizing agents include nitric acid;
inorganic peroxides such as hydrogen peroxide; sulfuric acid,
peroxydisulfuric acid, peroxymonosulfuric acid; halogen compounds
such as chlorite, chlorate, perchlorate; hypochlorite; hexavalent
chromium compounds such as chromic and dichromic acids and chromium
trioxide; permanganate compounds; sodium perborate; and nitrous
oxide.
[0022] After the carbon support has been pretreated with an
oxidizing agent in solution, it is dried under the flow of inert
gas, such as argon, helium, or nitrogen, at temperature of from
200.degree. and 400.degree. C. or 250.degree. C. and 300.degree. C.
The term "solution" is non-limiting and can include polar, aqueous,
polar non-aqueous, and non-polar solvents. In one embodiment, an
aqueous solutions is utilized due to the ease of drying the
pretreated carbon.
[0023] Oxidizing the carbon support material creates a sufficient
affinity to a magnesium precursor. One method of oxidizing the
carbon black support is with an oxidizing agent or immersing the
particles in an oxidizing solution, as mentioned in a preceding
paragraph, but the carbon black particles can be oxidized by
heating the particles in an oxidizing atmosphere. The oxidizing
atmosphere can comprise oxygen and argon gas or oxygen and helium
gas, but is not limited to those two examples. Sufficient
temperatures, when heating the carbon in the oxidizing atmosphere,
would be of from 120.degree. C. to 800.degree. C. The temperature
is determined by measuring the weight loss under heating. The
selected temperature should give a 0.1 wt % to 10 wt % loss by
oxidation of the carbon black. The optimum temperature can be
selected by using Thermo Gravimetric Analysis (TGA). Though 0.1 wt
% loss is a relatively small decrease in weight percent, in FIG. 2,
the TGA graph shows that carbon black gains weight from chemical
adsorption of oxygen up to approximately 600.degree. C. Such weight
gain is from chemical, not physical, adsorption of oxygen, which
does not occur when carbon black is loaded with magnesium
oxide.
[0024] The corrosion inhibitor may be prepared or pretreated with
non-oxidizing chemicals, such as the anion of a magnesium salt
precursor, for example, nitrate ion (NO.sub.3.sup.-) of magnesium
nitrate. A nitrate ion may function as an oxidizing reagent. In
some embodiments, oxidation of the carbon black surface and the
subsequent attachment of magnesium compounds onto the oxidized
surface occur in the same solution.
[0025] The sequence or method of oxidation and addition of
magnesium may vary. One example, mentioned in the preceding
paragraph the oxidation of the carbon black and attachment of the
magnesium onto the carbon black occurs in one step. Another example
involves: first, pretreating the carbon black (meaning oxidizing
and drying), and then mixing the pretreated carbon black in a
magnesium salt solution or with a magnesium precursor. The
magnesium salt solution may be made by dissolving a magnesium salt
such as magnesium chloride, magnesium nitrate, magnesium sulfate,
or another magnesium salt in a suitable polar solvent, such as
water. The magnesium salt solution is mixed with the pretreated
carbon support. After a time, the solution is filtered and the
filtrate is dried by heating under flowing inert gas such as argon,
nitrogen or helium. The drying temperature is between 90.degree. C.
and 200.degree. C., more specifically between 110.degree. C. and
150.degree. C. After it is dried, the compound is calcined.
[0026] Calcination converts the magnesium precursor to magnesium
oxide and removes surface oxygen not consumed by bonding with
magnesium. However, some oxygen groups may remain, because
magnesium ions and magnesium can interact with the oxygen groups
due to the polarity of each group. To insure the oleophilic nature
of the carbon black/magnesium oxide complex, the carbon
black/magnesium oxide complex is heated under inert gas, which
removes the excess oxygen in the form of carbon dioxide (CO.sub.2)
or carbon monoxide (CO), and thus forming the oleophilic corrosion
inhibitor.
[0027] The oleophilic corrosion inhibitor is calcined by heating to
temperatures greater than the decomposition temperature,
approximately 350.degree. C. The calcination temperature is
selected to yield at least 20 weight percent of magnesium oxide
from loaded magnesium, and in some embodiments there is
approximately 100% by weight of magnesium oxide from the loaded
magnesium. A very high temperature is required to convert 100% of
the loaded magnesium to magnesium oxide, for example, temperatures
between 200.degree. C. and 900.degree. C., or even between
300.degree. C. and 500.degree. C., though in some embodiments the
temperature is between 500.degree. C. and 900.degree. C.
[0028] The process mentioned in the preceding paragraphs describes
a process to adhere magnesium oxide to a carbon support, which
creates an oleophilic corrosion inhibitor. Once the corrosion
inhibitor is synthesized, the oleophilic corrosion inhibitor is
added to the liquid fuel solvents or other combustible fuels. The
oleophilic magnesium additive can be mixed by agitator,
homogenizer, ultrasonic mixer, static mixer (such as mixing tee) or
anything known in the art. The amount of the oleophilic corrosion
inhibitor is added to the combustion fuel in excess of the
vanadium. The amount in excess can be from 2 to 1 by weight of MgO
to V.sub.2O.sub.5 or 3 to 1 by weight of MgO to V.sub.2O.sub.5, and
as much as 5 to 1 by weight of MgO to V.sub.2O.sub.5.
EXAMPLES
[0029] In order that the embodiments may be more easily understood,
reference is made to the following examples which are intended to
illustrate embodiments disclosed and described in the application.
The examples are in no ways limiting in scope.
[0030] The carbon black was pretreated with the following
procedure: Acetylene black, obtained from Denka and had a particle
size of 35 nm, a surface area of 68 m.sup.2/gram, and an ash
content of 0.01 weight percent, was soaked in nitric acid (2 normal
(N)) at room temperature for 24 hours. Then the carbon black was
filtered and dried at 250.degree. C. with flowing nitrogen gas
(N.sub.2). The dried carbon black was added to deionized water
(having a conductivity less than 0.056 microsiemens per centimeter
(.mu.S/cm); type I water by ASTM definition) and refluxed for at
least 6 hours before the magnesium compounds were added. The weight
ratio of dried carbon to water was 1 to 2. The carbon and water
mixture, called carbon black slurry (CBS), contained 98 grams of
dried carbon black and 196 grams of deionized water.
[0031] The magnesium precursor was prepared by dissolving magnesium
nitrate hexahydrate (Mg(NO.sub.3).sub.2.6H.sub.2O) in deionized
water to have a 0.1 molar magnesium concentration in aqueous
solution.
[0032] The magnesium precursor solution was added to the CBS. The
amount of magnesium nitrate solution was adjusted such that upon
oxidation the resultant solution would have 4 weight percent of
magnesium oxide. Specifically, 1,000 milliliters (mL) of magnesium
nitrate hexahydrate solution (0.1 mole of magnesium; 4.03 grams of
MgO) was added to 294 grams of CBS (MgO/(Carbon black+MgO) yields 4
weight %. The CBS and magnesium solution were vigorously mixed and
heated to 90.degree. C. for slow evaporation of about 50 weight %
of water. Then the mixture was cooled to room temperature. The
mixture was filtered, and the filtered mixture was dried at
150.degree. C. under flowing N.sub.2 for at least 6 hours. The
dried mixture was calcined at 450.degree. C. for at least 6 hours
under flowing N.sub.2.
[0033] The stock solution was prepared by adding the calcined
mixture to a ball mill with an alumina ball and pulverizing the
mixture. The pulverized mixture was mixed with diesel having
American Petroleum Institute (API) gravity of 40.degree. and flash
point of 55.degree. C., by using a blade type agitator for 24 hours
to form the stock solution. The ratio by weight of pulverized
mixture to diesel was 1:99.
[0034] Dispersion of the magnesium and carbon black support was
determined by taking several samples, for example 10 samples. As
much as 1 gram of the stock solution was dissolved in toluene.
After filtering the toluene solution, the filtrate was dried and
weighed to determine the amount of carbon black loaded with
magnesium in each sample. The difference of the weight of the
filtrate from each sample varied by plus or minus 10% in the stock
solution. Thus indicating oleophilic corrosion inhibitor was evenly
dispersed.
[0035] Once the oleophilic corrosion inhibitor was synthesized, it
was added to the combustion fuel. The stock solution was added to
the liquid fuel, specifically the fuel was Arab Medium crude oil,
which has an API Gravity of 31.degree., and a Vanadium content of
33 weight parts per million (ppm). The liquid fuel was prewashed
with water to remove alkali and alkaline earth metals. The amount
of stock solution to liquid fuel was prepared to give an excess of
3 to 1 by weight of MgO to V.sub.2O.sub.5.
[0036] The preparation addition of stock solution to the liquid
fuel as described above greatly reduced the corrosive effect of
vanadium.
[0037] FIG. 1 is an X-ray Diffraction spectrum showing the
presences of vanadium oxide in one of the three samples. Sample 1
and Sample 2 were prepared by combining vanadium oxide (0.3134
gram, powder, Sigma-Aldrich, <98%) and magnesium oxide (1.2114
gram, powder, Fisher-Scientific, A.C.S. Grade). The ratio of
MgO/V.sub.2O.sub.5 was 3.8 wt/wt. The powders were mixed by mortar
and pestle for 30 minutes, which produced a unified color. For
Sample 1, the mixed powder was calcined at 650.degree. C., and for
Sample 2, the mixed powder was calcined at 750.degree. C. Sample 3
was loaded carbon black, magnesium oxide on the carbon black
support, combined with vanadium oxide. The sample was prepared by
mixing 40 mL of purified water with carbon black (10.16 gram,
acetylene black, 99.9+%, Alfa Aesar) and Magnesium nitrate
hexahydrate (2.822 gram, [Mg(NO.sub.3).sub.2.6H.sub.2O],
Sigma-Aldrich, A.C.S. grade). In this example, the nitrate ion of
the magnesium nitrate functioned as the oxidizing reagent. This
combination created a paste, which was mixed for an hour. The paste
was dried under air at 90.degree. C. while mixing with a glass rod
until no water was found, which was approximately 4 hours. The
dried sample was placed in an oven at 105.degree. C. for 24 hours
in air to ensure dehydration of each sample. The dried sample was
calcined at 350.degree. C. for 6 hours under flowing N.sub.2. The
calcined sample (2.87 gram) was mixed with vanadium oxide (0.04
gram) by mortar and pestle for 30 minutes. The ratio of
MgO/V.sub.2O.sub.5 was 3.1 wt/wt. The mixed sample was calcined at
650.degree. C. for 2 hours in air. After the calcination process,
all three samples were ground by mortar and pestle for 30 minutes,
and then tested.
[0038] Referring to FIG. 1, this spectrum demonstrated that carbon
black supported magnesium oxide (Sample 3) had better solid state
reaction activity towards V.sub.2O.sub.5 than unsupported magnesium
oxide additives (MV-PM-2-650). Such enhanced solid state reaction
activity results from the excessive heat supply during local
burning of carbon black. Elevated calcination temperatures
increased the magnesium oxide and vanadium oxide solid state
reactivity, as evidenced by missing V.sub.2O.sub.5 signals as
indicated from the stars. This spectrum also demonstrated that
carbon black supported magnesium could remove V.sub.2O.sub.5
signals at 650.degree. C., while the V.sub.2O.sub.5 signal remained
when tested with unsupported magnesium at 650.degree. C.
[0039] The themogravimetric analysis (TGA), in FIG. 2, showed that
magnesium loaded carbon black (solid line) had weight loss at much
lesser temperature than carbon black. Without being bound by
theory, it is believed that the weight loss is most likely due to
the magnesium oxide on the carbon black reacting with the vanadium.
Without such metals, carbon black is more difficult to combust at
temperature lesser than 600 to 700.degree. C. Metals, such as
magnesium and vanadium, would increase the rate of carbon black
combustion. Carbon black combustion most likely produced the extra
heat at a localized area, which might help the formation of
magnesium-vanadium mixed oxide. As the magnesium and vanadium
formed a mixed metal oxide, the magnesium was no longer attached to
the carbon black, thereby causing the carbon black to decrease in
weight. In contrast, carbon black (represented by a dotted line),
which requires a greater incendiary temperature, retained a
constant weight at lesser temperatures. Additionally, the TGA data
shows that carbon black was not a barrier for magnesium to react
with vanadium at firing temperature (greater than 1000.degree. C.)
because it is combusted at lesser temperature.
[0040] Unless otherwise defined, all technical and scientific terms
used have the same meaning as commonly understood by one of
ordinary skill in the art to which the claimed subject matter
belongs. The terminology used in this description is for describing
particular embodiments only and is not intended to be limiting. As
used in the specification and appended claims, the singular forms
"a," "an," and "the" are intended to include the plural forms as
well, unless the context clearly indicates otherwise.
[0041] It is noted that terms like "preferably," generally," and
"typically" are not utilized to limit the scope of the appended
claims or to imply that certain features are critical, essential,
or even important to the function of the claimed subject matter.
Rather, these terms are merely intended to highlight alternative or
additional features that may or may not be utilized in a particular
embodiment.
[0042] It is noted that the terms "substantially" and "about" may
be utilized to represent the inherent degree of uncertainty that
may be attribute to any quantitative comparison, value,
measurement, or other representation. These terms are also utilized
to represent the degree by which a quantitative representation may
vary from a stated reference without resulting in a change in basic
function of the subject matter at issue.
[0043] It will be apparent to those skilled in the art that various
modifications and variations can be made to the embodiments
described without departing from the spirit and scope of the
claimed subject matter. Thus it is intended that the specification
cover the modifications and variations of the various described
embodiments provided such modification and variations come within
the scope of the appended claims and their equivalents.
* * * * *