Note: Descriptions are shown in the official language in which they were submitted.
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Case No. ICR 8152
DIRECT PROCESS ROUTE TO ORGANOMETALLIC CONTAINING TT('HRR
FOR SPINNING INTO PITCH CARAC1N FIBERS
1. Field of the Invention
The present invention resides in an improved process for
producing a soluble, aromatic organometallic compound containing
mesophase pitch which is suitable for carbon fiber manufacture, more
particularly, the invention relates to a process for making high
strength carbon fibers which exhibit superior tensile strength, and
modulus properties. The process comprises adding a soluble,
aromatic-organometallic compound to a carbonaceous feedstock and heat
treating said carbonaceous feedstock with gas sparge to produce a
metals containing mesophase pitch. The resulting metals containing
mesophase pitch is suitable for melt spinning into a fiber artifact.
2. The Prior Art
Processes for producing mesophase pitch and/or carbon fibers
are known and are currently practiced commercially.
U.S. Patent 3,385,915, issued May 28, 1968, discloses a
process for producing metal oxide fibers which consists of
impregnating a preformed organic polymeric material with a metal.
Cellulose and rayon are described as suitable organic polymeric
materials.
U.S. Patent 4,042,486, issued August 16, 1977 relates to a
process for converting pitch to a crystalloid which consists of
coating solid amorphous pitch particles with a metal or metal salt
prior to gas sparging and heat soaking to produce a mesophase pitch.
U.5. Patents 4,460,454 and 4,460,455, both issued July 17,
1989 disclose a process for producing a pitch which is suitable for
use in preparing carbon fibers. A hydrogenation step in the process
either reduces or removes sulfur, nitrogen, oxygen, metals and
asphaltenes from petroleum heavy residual oil.
U.5. Patent 4,554,148, issued November 19, 1985 relates to a
process for the preparation of carbon fibers which consists of
subjecting a raw material oil to thermal cracking conditions to obtain
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a pitch product containing at least 5 weight percent mesophase. A
substantially mesophase free pitch is obtained by removing mesophase
of a particular particle size from the pitch product. The raw
material oil is derived from a napthene base or intermediate base
petroleum crude and contains metals.
U.S. Patent 4,600,496, issued July 15, 1986, discloses a
process for converting pitch into mesophase in the presence of
catalytically effective amounts of oxides, diketones, carboxylates and
carbonyls of certain metals. The mesophase pitch obtained is
described as suitable for use in the production of carbon fibers.
U.S. Patent 4,704,333 relates to a process for the formation
of carbon fibers produced from the pitch described in U.S. Patent
4,600,496 above. The process consists of extruding said mesophase to
form fibers, cooling the extruded fibers and subjecting the fibers to
elevated temperature to carbonize said fibers.
As can readily be determined from the above references,
there is an ongoing research effort to determine new and more advanced
processes and methods of producing mesophase pitch and carbon fibers.
Summary of the Invention
The present invention resides in a process for producing a
metals containing mesophase pitch which is readily spinnable into
carbon fibers. The process for producing the metals containing
mesophase pitch herein comprises adding a soluble aromatic,
organometallic compound to a graphitizable carbonaceous feedstock.
Next, the metals containing feedstock is heat soaked preferably with
gas sparge to produce a pitch product containing mesophase pitch. The
resulting mesophase pitch contains from about 50 PPM to about 20,000
PPM of the metals from the soluble organometallic compound.
Thereafter, the mesophase pitch is isolated from the pitch product.
The metals containing mesophase pitch herein provides fibers having
enhanced oxidative reactivity and enhanced tensile strength and
modulus properties. Thus, the present invention provides for a metals
containing, mesophase pitch which is readily spinnable into a carbon
fiber.
Detailed Description of the Invention
In accordance with the present invention a soluble aromatic,
organometallic compound is added to a carbonaceous feedstock. The
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metals containing carbonaceous feedstock is heat soaked, preferably
with gas sparge to produce a pitch product containing anisotropic
pitch (mesophase pitch). The resulting mesophase pitch contains a
substantial amount of the soluble aromatic, organometallic compound
added to the carbonaceous feedstock.
It should be noted that some carbonaceous feedstocks nay
contain minor or trace amounts of metal compounds therein. Whenever
this occurs, it is desirable to adjust the metal content of the
carbonaceous feedstock to the desired concentration. This is
l0 accomplished by adding the soluble aromatic organometallic compounds
herein to the carbonaceous feedstock thereby adjusting said metals
content of the carbonaceous feedstock to the desired concentration.
The carbonaceous feedstocks used in the process of the
invention are heavy aromatic petroleum fractions and coal-derived
heavy hydrocarbon fractions, including preferably materials designated
as pitches. All of the feedstocks employed are substantially free of
mesophase pitch.
The term "pitch" as used herein means petroleum pitches,
natural asphalt and heavy oil obtained as a by-product in the naphtha
cracking industry, pitches of high carbon content obtained from
petroleum asphalt and other substances having properties of pitches
produced as by-products in various industrial production processes.
The term "petroleum pitch" refers to the residuum
carbonaceous material obtained from the thermal and catalytic cracking
of petroleum distillates or residues.
The term "anisotropic pitch or mesophase pitch" means pitch
comprising molecules having an aromatic structure which through
interaction have associated together to form optically ordered liquid
crystals.
The term "isotropic pitch" means pitch comprising molecules
which are not aligned in optically ordered liquid crystals. Fibers
produced from such pitches are inferior in quality to fibers made from
mesophase pitches.
Generally, feedstocks having a high degree of aromaticity
are suitable for carrying out the present invention. Carbonaceous
pitches having an aromatic carbon content of from abut 40 percent to
about 90 percent as determined by nuclear magnetic resonance
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spectroscopy are particularly useful in the process. So, too are high
boiling, highly aromatic streams containing such pitches or that are
capable of being converted into such pitches.
On a weight basis, useful feedstocks will contain from about
88 percent to about 93 percent carbon and from about 9 percent to
about 4 percent hydrogen. While elements other than carbon and
hydrogen, such as sulfur and nitrogen, to mention a few, are normally
present in such pitches, it is important that these other elements do
not exceed about 5 percent by weight of the feedstock. Also, these
useful feedstocks typically will have an average molecular weight of
the order of about 200 to about 1,000.
In general, any petroleum or coal-derived heavy hydrocarbon
fraction may be used as the carbonaceous feedstock in the process of
this imrention. Suitable feedstocks in addition to petroleum pitch
include heavy aromatic petroleum streams, ethylene cracker tars, coal
derivatives, petroleum thermal tars, fluid catalytic cracker residues,
and aromatic distillates having a boiling range of from 650° -
950°F.
The use of petroleum pitch-type feed is preferred.
The soluble organometallic compounds of this invention may
be either naturally occurring or synthetic organometallic compounds.
It should be noted that the naturally occurring soluble organometallic
compounds are preferred herein. The naturally occurring, soluble
organometallic compounds of this invention are at least partially
aromatic and exhibit good thermal stability when dissolved in aromatic
hydrocarbons. Generally, they come from the family of organometallic
complexes found in the asphaltic fraction of crude petroleum. The
aromatic-organo constituent of the organometallic compounds herein
include porphyrins and related macrocyclic compounds with altered
porphin ring structures. They also include porphins with added
aromatic rings and/or with sulfur and oxygen as well as nitrogen
ligands. Preferred organometallic compounds are relatively thermally
stable porphin type structures which are readily dissolved in the
carbonaceous feedstocks herein. These compounds often have fused aryl
substituents.
The metal constituent of the organometallic compounds herein
is a metal or mixture of metals selected from the Groups IIA, IB, IIB,
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IVB, VB, VIB and VIII metals of the Periodic Table, with the Group VB
and Group VIII metals being preferred.
Especially preferred metals from the above-described groups
include vanadium, nickel, magnesium, zinc, iron, copper, irridium,
manganese and titanium and mixtures thereof. It should be noted that
while all of the metals herein are suitable for use in the invention,
vanadium and nickel are highly preferred with vanadium being
,. especially preferred.
Applicants do not wish to be bound by theory, however, it is
believed that the metals described above complex with the
aromatic-organo constituents of the organometallic compounds and form
chelates which are substantially soluble in the carbonaceous
feedstocks herein.
One source for naturally occurring soluble aromatic,
organometallic compounds suitable for use in this invention is Mayan
crude. The Mayan crude is concentrated into a concentrate which
contains a substantial amount of soluble aromatic, organometallic
compounds.
Representative examples of soluble synthetic, organometallic
compounds suitable for use include 5, 10, 15, 20 - tetraphenyl - 21H,
23H - porphine vanadium (IV) oxide; 5, 10, 15, 20 - tetraphenyl - 21H,
23H - porphine nickel (11); 5, 10, 15, 20 - tetraphenyl - 21H, 23H -
porphine zinc; 5, 10, 15, 20 - tetraphenyl - 21H, 23H - porphine
cobalt (11) and 5, 10, 15, 20 - tetraphenyl - 21H, 23H - porphine
copper and mixtures thereof. The synthetic vanadium organometallic
compound is especially preferred. These synthetic organometallic
compounds are manufactured and sold commercially by the Aldrich
Chemical Company, located in Milwaukee, Wisconsin.
The herein described organometallic compounds, including
both naturally occurring and synthetic organometallic compounds can be
incorporated in the carbonaceous feedstock in any convenient manner.
Thus, the organometallic compounds can be added directly to the
carbonaceous feedstock by dissolving the desired organometallic
compound in the carbonaceous feedstock at the desired level of
concentration. Normally, the organometallic compound is added to the
carbonaceous feedstock in a sufficient amount to impart a metals
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concentration in mesophase pitch produced from the carbonaceous
feedstock of from about 50 PPM to about 20,000 PPM.
Alternatively, the organometallic compounds herein may be
blended with suitable solvents to form an organometallic
compound-solvent mixture that can be readily dissolved in the
appropriate carbonaceous feedstock at the desired concentration. If
an organometallic compound-solvent mixture is employed, it normally
will contain a ratio of organometallic compound to solvent of from
about 0.05:20, to about 0.15:10 respectively.
Solvents suitable for use in forming the concentrates herein
include, petroleum based compounds, for example, gas oils, benzene,
xylene and toluene and mixtures thereof. The particular solvent
selected should, of course, be selected so as not to adversely affect
the other desired properties of the ultimate carbonaceous feedstock
composition.
The soluble aromatic, organometallic compounds are added to
a carbonaceous feedstock and the metals containing feedstock is
subjected to a heat soak process, preferably with gas sparge to
produce a pitch product containing mesophase pitch. The
organometallic compound is added to the carbonaceous feedstock at a
concentration sufficient to impart from about 50 PPM to about 20,000
PPM, especially from about 80 PPM to about 1,000 PPM, preferably from
about 100 PPM to about 500 PPM of the metals from the organometallic
compound in the mesophase pitch after the heat soak process.
Conversion of the metals containing feedstock to mesophase
pitch is effected by subjecting the feedstock in a molten state to
elevated temperatures, usually at atmospheric pressure with agitation
and with gas sparging. The gas continuously passes through the metals
containing feedstock during the sparge for maximum contact and
conversion of the feedstock to a metals containing mesophase pitch.
The heat soak process conditions employed are well known in
the art and include temperatures in the range of from about 350°C to
about 500°C, preferably from about 370°C to abut 425°C;
at a pressure
of from about 0.1 atmospheres to about 1 or 3 atmospheres. However,
higher pressures may be used if desired. The gas sparging time period
may vary widely depending upon the carbonaceous feedstock, gas feed
rate, temperature, etc.
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Normally, the heating and/or gas sparging steps are
conducted over a time period of from about 2 to about 100 hours,
especially from about 2 to about 60 hours, preferably from about 2 to
about 30 hours. The sparging gas is usually contacted with the
carbonaceous feedstock at a rate of from about 1 to about 20 SCF of
gas per pound of feedstock per hour.
The sparging gas employed may be an inert gas, an oxidative
reactive gas, or an inert gas-oxidative reactive gas mixture.
Suitable inert gases include nitrogen, argon, xenon, helium, methane,
hydrocarbon based flue gas and steam and mixtures thereof, with
nitrogen being the preferred inert gas. Oxidative reactive gases
which can be used herein are air, oxygen, ozone, hydrogen peroxide,
nitrogen dioxide, formic acid vapor and hydrogen chloride vapor and
mixtures thereof. Oxygen is the preferred oxidative reactive gas.
When a nitrogen gas-oxygen gas mixture is used in the process, oxygen
preferably comprises from about 0.05 to about 5 percent of the gas
mixture.
Generally the pitch production is greater than 70% mesophase
and suitable for spinning into carbon fibers. If, however, the
produced pitch has a lower mesophase content than desired, the pitch
can be separated by means such as gravity separation, as taught in the
art, to produce a mesophase pitch containing up to 100% mesophase and
suitable for spinning.
The mesophase pitch of this invention contains from about 50
PPM to about 20,000 PPM metals from the soluble aromatic,
organometallic compound which was added to the carbonaceous feedstock
and may be spun into anisotropic carbon fibers by conventional
procedures such as melt spinning, centrifugal spinning, blow spinning
and the like.
The following examples serve to demonstrate the best mode of
how to practice the invention herein and should not be construed as a
limitation thereof.
Ex~ple I
A vanadium containing mesophase pitch was prepared by sparge
heat soaking an aromatic residue containing added vanadium porphyrin
in accordance with the following procedure:
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Mid-Continent refinery decant oil was topped to produce an
850°F + residue. This residue was mixed with 0.05 percent 5, 10, 15,
20 - tetraphenyl - 21H, 23H - porphine vanadium (IV) oxide and 10
percent toluene cosolvent. The toluene was distilled from the mixture
and the residue was heat soaked 32 hours at 385°C. Nitrogen was
bubbled through the heat soak unit at a rate of 4 SCF nitrogen gas per
hour per pound of feedstock during the heat soak. Residue product
yield was 19.6 percent. It should be noted that some of the feed was
lost during start up of the gas sparge which resulted in a lower yield
of residue product as compared to Examples I and II. The product
tested 100 percent mesophase pitch, melting at 300°C as determined by
hot stage microscopy. When ached, this pitch product yielded 190 PPM
residue which tested greater than 90 percent vanadium oxides as
analyzed by emission spectroscopy.
The vanadium containing mesophase pitch was melt spun into
carbon fibers with very good spinnability at 335°C. The stabilized,
carbonized fibers tested 425 Mpsi tensile strength and 38 MMpsi
tensile modulus.
Ex~ple II
A vanadium containing mesophase pitch was prepared by sparge
heat soaking an aromatic residue containing added vanadium porphyrin
in accordance with the following procedure:
Mid-Continent refinery decant oil was topped to produce an
850°F + residue. This residue was mixed with 0.15 percent 5, 10, 15,
20 - tetrophenyl - 21H, 23H - porphine vanadium (IV) oxide and 10
percent toluene cosolvent, The toluene was distilled from the mixture
and the residue was heat soaked 32 hours at 385°C. Nitrogen was
bubbled through the heat soak unit at a rate of 4 SCF nitrogen gas per
hour per pound of feedstock during the heat soak. Residue product
yield was 23.9 percent. The product tested 100 percent mesophase
pitch melting at 320°C. When ached, this pitch product yielded 644
PPM residue which tested greater than 90 percent vanadium oxides as
analyzed by emission spectroscopy.
The vanadium containing mesophase pitch was melt spun into
carbon fibers with fair spinnability at 320°C. The stabilized,
carbonized fibers tested 380 Mpsi tensile strength and 45 MMpsi
tensile modulus. Oxidative DSC was run on the as-spin fiber. A level
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of oxidation corresponding to stabiliation was reached 13% sooner with
this fiber compared to the control fiber of Example 111.
E~le III
A metals free aesophase pitch was prepared in accordance
with the procedure set forth in Example I with the following
exception:
The vanadium porphyrin compound, 5, 10, 15 20 - tetraphenyl
- 21H, 23H - porphine, was not added to the 850°F + decant oil.
A 23.0 percent yield of residual product resulted. This
product tested 100 percent mesophase which melted at 300°C as
determined by hot stage microscopy. The ash content of the pitch
tested less than 5 PPM. The pitch showed good spinnability when spun
into carbon fibers at 320°C. The stabilized, carbonized fibers tested
390 Mpsi tensile strength and 36 MMpsi tensile modulus.
Table I below sets forth the process conditions and results
of the tests conducted in Examples I to III.
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Ex. I Ex. II Ex. III
Decant Oil Decant Oil Decant
Oil
850F+ 850F+ 850F+
and and and
Feed 0.05%TPVP(1) 0.15%TPVP(1)Control,
Sparge Preparation
Tine, Hr. 32 32 32
Temp., C 385 385 385
N2 Rate, SCF/Hr.-lb. Feed 4 4 4
Mesophase Yield, Wt.% 19.6 (2) 23.9 23.0
Mesophase Properties
Hot Stage, % Mesophase 100 100 100
Hot Stage Melt temp., C 300 320 300
Ash, PPM 190 644 < 5
Spinning Results
Spin Temp., C 335 360 320
Attenuation very good fair good
Tensile Strength, Mpsi 425 380 390
Elongation, % .91 .70 .93
Tensile Modulus, MMpsi 38 45 36
(1)TPVP - 5, 10, 15, 20 - tetraphenyl - 21H, 23H - porphine
vanadium oxide
(2)Some feed was lost during start-up of sparge which resulted in a
lower yield of mesophase
As can readily be determined from the above test results,
the metals containing mesophase pitches produced according to the
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procedure set forth herein resulted in a carbon fiber with superior or
comparable properties when compared to the control mesophase pitch.
Obviously, many modifications and variations of the
im~ention, as herein above set forth, can be made without departing
from the spirit and scope thereof, and therefore only such limitations
should be imposed as are indicated in the appended claims.
