Note: Descriptions are shown in the official language in which they were submitted.
~737~
Aromatic pi'cches such as coal ~ar pitch or petrol-
2 eum pitch are made of a comlplex mixture of al3cvl-substituted
3 polycondensed axomatics having a high desree of aromatic
4 ring condensation (as e~tidenced by the carbon/hydrogen
5 atomic ratio). C~ne simple method to charac~erize these
6 pitches is by the use of solvent analysis, for example,
7 the degree o~ insolubility in benzene, toluene, pvridine,
~ ~uinoline, or anthracene. For the pur~oses of the present
9 in~ention, aromatic pitches are characterized by t.'leir
1~ insolubilities in toluene and c~uinoline.
11 The solubility analysis for determining quinoline
12 insolubles is conducted according to ASTM D 2318-66; the
13 solubility analysis for determining toluene insolubilities
1~ is conducted by mixing 40 grams of a sample in 320 ml of
15 toluene over an 18-hour time period, filtering, washing
16 the insolubles in additional toluene, drying, and calculat-
17 ing the yield of insolubles as a percentage of initial
1~ sample.
lS The production of a highly aromatic pitch which
~0 will yield a non-ordered, isotroPic carbon has previously
21 been described in my United States Patent No. 3,721,658.
22 ~ore particularly, this patent describes a process for
23 prepari~g an aromatic pitch by the catalytic air oxidation
24 of an aromatic feedstock such as st~ cracked tar, at a
25 temperatura of 240-260C. This pitch has low toluene in-
26 solubles (about 15%) and ~ery low quinoline insolubles.
27 ~3ecause of the chemical structure o~ the pitch, and not
28 because of the toluene or quinoline insolubles content,
29 ~his pitch on melting or carbonizing will yield a highly
30 isotro~ic carbon.
31 A~other exam~le of aromatic pitch l~roduction may
32 be found in United States Patent No. 4,086,156. This pat-
33 ent describes a method for preparing an a-omatic ~itch by
34 the ~hermal treat.nent o~ steam crac~ser tar in the absence
35 of oxvgen a~d at a t~nperature of 380-390C. The pitch
36 obtained by this method contains a low concentration of
~73~Z
1 toluene and quinoline insolubles and will produce an iso-
2 tropic carbon on melting or carbonizing.
3 In addition, my U.S. patent 4,271,006 discloses
4 the production of an aromatic, low Ti pitch. However, this
5 pitch requires a two-stage extraction process in order to
6 prepare carbon precursor.
7 Accordingly, the process of the present invention
8 describes a method of preparing a highly polycondensed aro-
9 matic hydrocar~on pitch.w~t~ a defined composition ~y ~h~
0 catalytic or ~on-catalyt;c thermal trea~ment of a low
molecular weight feed comprised of alkyl-substîtuted poly-
condensed hydrocar~on aroma~ic fraction obtained from cata-
3 lytic cracking resid~e (cat crac~er bottoms or CC~l having
4 a spec~ic c~emical and molecuIar structure~
The important feature of t~e pitc~ produced ~y
the method according to the present invention is t~at it
proauces carbon on melting or car~onization with anisotrop-
ic structure, that is,an ordered or crystalline structure,
as determined ~y meas~ ing t~e optical activity~ of the car-
21 ~on via polarized light micros~opy. T~is type of pitch is
22 use~ul ~or the production of car~on products wi ~ aniso-
23 tropic structure such as pitcE~ carE~on fiBer or needle co~se.
24 ~ore particularly, the process of ~e present
25 in~ention specifically descri~es a me ~od to prepare a low
26 softening point C200-300CL aromatic pitc~i wit~i a de'inite
27 composition. T~e p~tc~ maae in accordance with the pres-
28 ent invention contains a ~i:g~ toluene insolu~Sle content
29 C5Q-~Q weight ~ercent~ and a high quinoline insolu~}e con-
30 ~ent ua-6Q weight pe~cent~ The high content s:f toluene
31 and quinoline insoluEles is desired in this pitcEi (~IQ
32 pitch~ as thi~ fraction is essential for development o~ an-
33 isotropic st~ucture wnen melting or car~onizing ~e pitch
~377~.
-- 3 --
1 in an inert atmosphere.
2 Not all aromatic compounds containing polycon-
3 densed aromatic rings are suitable for the production of
4 ~T~Q pitch with the desired composition and characteris-
S tics. For example, coal tars from the high temperature
6 car~onization o~ coal, steam cracker ~ar from the steam
7 cracking of ~as oil or naphtha, or coal tar from coal gas-
8 ification or liquefaction are highly aromatic and composed
9 of polyconde~sed aromatics but are not suitable for the
production of ~T~Q pitch because they do not have the de~
11 sired chemical and moleculzr structure needed. According-
12 ly, the prodllction of an aromatic pitch which will yield a
13 highly ordered anisotropic structured carbon requires a
14 specific polycondensed aromatic feed with a definite chem-
ical and molecular structure.
16 U.S. Patent No. 4,005,183, for example, describes
17 the produc~ion of pitch with hi~h guinoline insolubles by
18 the atmospheric heat soaking of a high softening point
19 (110-115C) petrole~m pitch. The procPss described in U.S.
Patent No. 4,005,183 requires a feed which is physically,
21 chemically, and thermally diffexent from CCB or fractions
22 which are mainly low molecular weight polycondensed aro-
23 matics. The present invention's three-stage process is
24 also di~feren~ from the process desc_ibed in U.5. Patent
No. 4,005,183, which is done by heating a petroleum pitch
26 at 400C for 32 hours at atmospheric pressure until the
2~ high quinoline insolubles content is formed in the pitch.
28 Table I illustrates the chemical and physical differences
29 between petroleum pitch and cat cracker bottom feedstock.
~ 7 ~72
-- 4 --
1 ~BLE I
2 PetroleumCCB Vacuum
3 PitchDistillate Strip~ed CCB
4 Toluene Insolu~les (%) 10 0 0
5 Softening Point, C 122 Liquid 20-4a
6 Arom2tic Car~on
7 (atom %) 84 55-65 55-65
8 Coking Value at
9 5;0C (wt.%) 56 0 14
10 Asphaltene Content,
11 wt.% ~n-heptane
12 insolubles) 70 0 4
13 Car~on/~ydrogen
14 Atomlc Ratio 1.5 0.g5 1.0
A suita~le aromat~c feea for ~e production of
16 RT~Q pitc~, as noted a~ove, ~s t~e aromatic residu~ o~tained
17 from the cracking of refinery distillates. This residual
18 feedstcck, called cat cracker ~ottoms CCCBI, reers to
19 that fraction of the product of t~e cat cracking proce~s
which boils in t~e range o~ fro~ a~out 20a to a~out SQQC,
21 and i5 presently a by-~roduct residue. Its chemical struc-
22 ture can be defined ~y quantitatively measuring its car~on
23 and proton nuclear magnetic resonance spectroscopy (CMR and
24 NMR); a typical distribution is given in Ta~le II.
.
Ta~L~ II
26 Ca~o~ and P~oton Distri~t~on of 3
27 Aromatic car~on (atom %1 55-65
28 Aromatic protons (~1 24-35
29 Ben~ylic protons ~%j 27-31
Para~f~ic protons ~ 47~33
31 ~ore particularly, t~e specifications ~or a ty~i~
32 cal cat crac~er ~ottomsthat is 2 suita~le eedstoc~ ror the
33 present in~ention are given in Table III.
~ 3 f ~
- s -
TABLE III
2 ~tlarac~eristics of Cat Crac~ce~ 3Ot~oms
.__
3 ~hysical C~a~ ac,eris~ics
4 Viscosity cst at 210C 1. 0-10 0
As'n Con'cent, ~t % O . 010-2 . O
6 Coking Value (wt ~ at 550C) 6.U-18.0
7 Asphaltene l(n-heptane i~solubles), % 0.1-12.0
8 Toluene In~ les (0 - 35~ Q . 010-1. 0
9 Num~er ~verage Mol. wt:. 220-2~0
Ele:mental ~nalysis
11 Carbon, ~ 88 . 0-90 . 32
12 ~ydrogen, ~6 7. 74-7. 4C
13 Oxygen, % 0.10-0.30
14 Sulfur, ~ - 1.0-~.5
15 Car~on/Hydrogen Atomic Rat~o ~90-l.Q
16 Chemic21 Analysis by Proton NM~
17 ~romatic Carbcn ~atom %) 5;-65
18 Aro~2tic R~n~ Distribution (by Mass Spectroscopy)
19 ~ g (96) 102
20 2 Rin~s ~96) 23. 6
21 3 ~i~ss ( % ) 3 7 . 5
22 4 Rinss (~) 31. 8
23 5 ~ings (%) 3. 8
24 6 ~ings ~)
25 Molecular ~ight Dis'~ri~ution (bv Mass S~ectrosco~y)
26 175 200 ~%) 2 D 9
27 200-225 (~) 13.4
28 225-2~0 (%) 29.
29 ~50-275 (~) 23.
30 27~-300 ~) 15.5
31 300-325 (%) ~-
32 32~-350 (%)
33 Composition by Clay-Silica G21 Chromatography
34 Aromatic, ~ 62 . 2
35 Saturat~, % 17. O
36 Polar, % 18. 3
~73~
- 6 -
~lthough the total cat cracker bottoms fraction can be used
as feedstock Eor the manufacture of the aromatic pitch according
to my invention, this would require the thermal treatment of the
feedstock -to be carried out under pressure; this requires the
cost of equipment capable of operating under pressure.
One method of performing the required thermal treatment under
atmospheric pressure is by first removing the low boiling point
fraction, that is, the fraction which boils below the desired
thermal treatment temperature. This can be carried out using
various methods, such as
(1~ by the vacuum stripping of cat cracker bottoms at
- elevated temperatures and reduced (1~100 mm Hg) pressures or
(2~ by the fractional distillation of cat cracker bottoms
at elevated temperatures, for example, between 200 and 300C,
and reduced pressures, for example, between 200-500 microns of
mercury. Fractional distillation results in either a single or
several distillate fractions and a residue referred to as CCB
residue which is that fraction not distillable at temperatures
of up to 530C and at a pressure of about 350 to 450 microns of
mercury. The distillate fraction has a boiling point in the
range of from about 500F to about 1000 F.
The CCB distillate and CCB residue obtained by fractionation
are highly aromatic, being composed of poly-condensed aromatics,
but vary in their molecular weight, aromatic ring distribution~
and coking characteristics. The following Table 4 graphically
summarizes some of these differences.
~l7~77~2
-- 7 --
1 T~B~ rv
2 Charac~eris-ics of CCB Distiliate and ~esidue
3 CCB CCB
4 Distillate Residue
Aromatic Car~ons (a~om~
6 ~y NMR) 62 68
7 ~olecular Weight 270 329
8 Aromatic Ring Distribution
9 2 rings ~%) 12 0
3 rings (~) 29 0
11 4 ring~ 46 0
12 5 rings (%) 8 0
13 6 rings+(~) 1 10
14 The CCB distillate is composed o aromaticshaving
3, 4, and 5 aromatic rings polycondensed with hydrogen and
16 carbon as the main component, and also containing (but to
17 a lesser extent) polycondensed aromatics with polar atoms
18 such as sulfur or oxygen. Typical of thë polycondensed
19 aromatic compounds found în CCB feed or distillate are
napthenonaphthalene,acenap~h nes, phenanthrene, naphtheno~
21 phenanthrene, pyrenes, chrysenes, cholanthrenes, benzopyr-
22 enes, indothiophenes, naphthothiophenes, naphthano-naphthothio-
23 phenes, acenaphthylene-thiophenes, and anthracenothiophenes
24 I have discovered tnat there are several process
variations which can ~e used to transform CCB or its frac-
26 tions into a ~T~Q pitch with tie desired composition. For
27 example, ~THQ pitch may ~a made by a thermal treatment at
28 high temperatures o~ CCB feedstoc~ under atmospheric,
2~ or Eigh pressure, and ~urthermore such treabment m~
30 be in the presence or absence of a catalyst (sucn as a
31 Priedel-Crafts catalyst), and in the presence of an inert
32 or hyd~ogen atmosphere. Because of the economic savings
33 invol~ed, my preferred process is to carry out the process
34 o~ this invention at atmospheric pressure in an inert at-
mosphere such as ~itrocen.
36 . In general, my~invention can be considered to be
37 composed of a three-stage process for the production of a
-- 8 --
3~7Z
HTHQ pitch. This process requires high temperatures in the range
of about 380 to about 450C. The required temperature is, of
course, dependent upon the CCB fraction used as a feedstock, and
whether or not a catalyst is presenk. When CCB distillate is
used as the feedstock, for example, temperature in the range of
about 420 to about 450C is required; when CCB residue is used as
a feedstock, temperature in the range of about 380 to about
440C is required. The treatment of the CCB distillate fraction
can be carried out in a temperature range of from about 400C to
about 450C and for a period of time ranging from 30 minutes to
1200 minutes.
The first stage of my process comprises the vacuum stripping
or fractional distillation of CCB at elevated temperatures. The
second stage comprises the thermal treatment of the vacuum
stripped CCB or CCB distillate at a high temperature of about 380
to about 450C. This treatment may be carried out under atmos-
pheric pressure, high pressure, or low pressure. In addition, the
treatment may be carried out in the absence or presence of a
suitable aromatic condensation catalyst. Such catalysts are well
known in the art as being Friedel-Crafts catalysts such as
anhydrous aluminum chloride or anhydrous ferric chloride. The
treating can be conducted in the presence of a catalyst and in a
temperature range of about 370C to 400C. The third and last
stage of my inVention comprises the vacuum stripping of the
thermally treated mixture from stage two at a low temperature of
about 300 to about 360C, and at a pressure of about l to about 5
mm of mercury. The objective of this stage is to remove all un-
desirable oils thus concentrating and increasing the liquid
crystal fraction, that is,Ti and Qi in the pitch. To accomplish
this, the u~e of the low temperature is critical at this stage.
To be more specific, in the laboratory experimental pro-
cedure to prepare HTHQ pitch, the total CCB is vacuum stripped
- 9 -
~L~73~
or fractionally distilled at elevated temperatures to prepare the
desired fraction of CCB. The desired frackion is then thermally
treated under atmospheric pressure conditions, and in the presence
or absence of a catalyst (continuous agitation of the fraction at
this time will avoid coke formation). After treatment, the
temperature of the mixture is rapidly lowered to around 300C and
the pressure is reduced to about 1 to about 10 mm Hg, after which
the temperature is increased slowly, with agitation, to about 360
to about 370C to remove at least 1% of the distillable oil from
the mixture, preferably more than 10~. The mixture is then cooled
to room temperature under reduced pressure or under nitrogen
atmosphere.
Alternatively, the thermal treatment stage can also be
carried out under reduced (10-200 mm Hg) pressure. The treating
can be carried out in a temperature range of about 400C to about
450C, and 10-200 mm Hg for a period of time ranging from about
30 minutes to about 600 minutes. In this instance, when the
thermal treatment is completed, the mixture is cooled to room
temperature under reduced pressure or a nitrogen atmosphere.
The time required to produce HTHQ pitch is dependent on the
temperature used during the thermal treatment of the CCB fraction.
Generally, the higher the temperature of the thermal treatment,
the shorter is the time required to produce a HTHQ pitch. The
desired time and temperature required to produce a HTHQ pitch
depends on the CCB fraction. When using a CCB residue which has
a higher molecular weight and aromatic ring distribution than the
CCB distillate, less time and lower temperature will be required
to produce a HTHQ pitch.
It is believed that one of ordinary skill in the art can,
using the preceding description, utilize the present invention to
its fullest extent. The following specific embodiments are,
therefore, to be construed as merely illustrative of this
invention, and are not meant to limit the remainder of the speci-
fication and claims in any way whatsoever.
~73~2
- 9a -
Examples 1-4 illustrate the production of HTHQ pitch,
according to the present invention by the atmospheric thermal
treatment of vacuum stripped CCB;
Examples 5-8 illustrate the production of HTHQ pitch,
according to the present invention, by the atmospheric heat
soaking of a CCB distillate fraction;
Example 9 illustrates the production of HTHQ pitch, according
to the present invention, by the vacuum heat soaking of vacuum
stripped CCB; and
Example 10 illustrates the production of ~THQ pitch, accord-
ing to the present invention, by the catalytic heat soaking of a
vacuum stripped CCB fraction.
'~ . . ..
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: ~7377~
- 10
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- 13 -
1 From the foregoing descri~tion one s~illed in
2 the art can easily ascertain the essential characteristics
3 of this invention and wi~hout departinq from the spirit and
4 scope ~heraof can make various changes and/or modifications
to the invention for adaDting it to various usages and con-
6 ditions. Accordingly, such changes and modifications are
7 properly intended to be within the full range of equiva-
8 lents of the following claims.
9 ~aving thus described my invention and .he manner
and process of making and using it in such full, clear,
11 concise and exact terms as to enable any ~erson skilled in
12 the art to which it pertains, or with which it is most near-
13 ly connected, to make and use the same, and having setforth
14 the best modes for carrying out my invention:
.
~'
i .
