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Sodium hydroxide-assisted desulphurization
of petroleum fluid coke
Zacheria M George and Linda G. Schneider
Albert a Research Coun cil , 17315-87 Avenu e, Edmon ton, Alberta, T6G 2C2, Canada
(Received 1 July 1982)
Desulphurization of a fluid coke produced commercially from a conventional petroleum crude oil was
attempted. Direct hydrodesulphurization of the coke at 700°C resulted in ~31 w% sulphur removal;
however, impregnation of the fluid coke with trace amounts of sodium hydroxide and subsequent
hydrodesulphurization resulted in > 80 wp/o sulphur removal primarily as Hz % A significant part of the
alkaline reagent could be recovered by hot water leaching of the desulphurized coke. The calorific value
of the desulphurized coke is slightly lower than that of the starting material. The mechanism appears to
be complex as the change in surface area was negligible upon impregnation and hydrodesulphurization.
Economic evaluation of the desulphurization process, carried out at the Alberta Research Council,
indicates that it has significant economic advantages over fluidized-bed combustion of the coke with
limestone or combustion of the coke with flue gas desulphurization.
(Keywords: desulphurization; fluid; coke; sodium hydroxide)
Although much work has been carried out on methods of
desulphurizing coal and coal chars, few studies are
reported in the literature on the desulphurization of
petroleum cokes. In coal, a significant portion of the
sulphur may be present as inorganic sulphides and
methods such as that of Meyer1 are very efficient for
removal of these sulphur compounds. In petroleum cokes
however, a considerable part of the sulphur may be
present as organic sulphur compounds and these
compounds are not easily desulphurized. Further,
petroleum cokes exhibit significant differences depending
upon the origin of the petroleum, coking process
employed and the amount and type of sulphur
compounds present in the petroleum.
El Kaddah and Ezz’ investigated thermal
desulphurization of petroleum coke containing 8.3 wt%
sulphur and observed 30 wt% sulphur removal in 30 min
at 1600°C. Sef3 studied hydrodesulphurization of
petroleum coke containing 2 wt% sulphur and reported
85 wt% sulphur removal using small particles of coke, a
pressure of 659 Pa, and high space velocities. Mahmoud et
al4
observed a maximum at 600°C for the
hydrodesulphurization of petroleum coke containing 3
wt% sulphur, this maximum being attributed to the onset
of sintering. George5 and Tollefson and Parmar have
studied the hydrodesulphurization of Athabasca oil sands
delayed coke and observed that the level of
desulphurization was not significant under the
experimental conditions and that the reaction was
controlled by pore diffusion. Mason7 has reported the
beneficial effects of preoxidation of coke on the
subsequent hydrodesulphurization;
however, the
optimum conditions of the preoxidation appear to vary
widely. Thakker* showed that impregnation of petroleum
coke with sodium carbonate enhances the level of sulphur
removal during hydrogenation. Ridley’ reported that
001~2361/82/12126%07%3.00
@ 1982 Butterworth & Co (Publishers) Ltd.
1260 FUEL, 1982, Vol 61, December
sodium hydroxide and sodium sulphide when
impregnated on coke particles aided desulphurization.
Lukasiewicz and Johnson” and Sabott” observed that
significant desulphurization of petroleum coke can be
achieved by impregnating the coke with an alkaline
reagent, calcination of the impregnated coke in an inert
atmosphere at elevated temperatures and subsequent hot
water leaching of the coke to remove the metal sulphides.
Parmar and Tollefson6 employed a fluidized-bed reactor
to evaluate several methods to desulphurize delayed coke
produced by Suncor Canada. George, Parmar and
Tollefson” investigated the desulphurization of oil sands
delayed coke involving impregnation with an alkaline
reagent,
and subsequent calcination, and George,
Schneider and
Tollefson’3 have reported the
desulphurization of a high sulphur fluid coke by this
method. These experiments showed that to achieve
significant desulphurization, large (twice stoichiometric
amount to form metal sulphides) quantities of the alkaline
reagents were necessary and posed serious corrosion and
environmental problems.
The objective of this investigation was to develop an
economically attractive process for the desulphurization
of petroleum coke prior to combustion. A sample of
petroleum fluid coke (sulphur content 7.3 f 0.3 wt%) was
obtained from Getty Oil Company, Delaware, USA, and
an attempt to desulphurize this coke was made so that the
sulphur dioxide level produced during combustion may
be tolerated with minimum environmental damage.
Whilst investigating methods of desulphurizing this
petroleum coke, it was observed that if the fluid coke were
impregnated with a small amount of base, such as sodium
hydroxide, and then hydrodesulphurized at M700°C
significant sulphur removal could be achieved. This Paper
summerizes results on this method of desulphurizing a
sample of Getty fluid coke.
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Desulphurizat ion of petroleum fluid coke: 2. M. George and 1. G. Schneider
Tab/e 1 Analysisof Gettyfluid coke (db)
Carbon
86.9 wt %
Hydrogen
1.8wt%
Sulphur
7.3 f 0.3 wl %
Nitrogen
1.3wt%
Ash
0.1 w-t%
Nickel
1 Ash
30 PPm
Vanadium 225 ppm
Tab/e 2 Sulphur content of fluid cokes examined
Source Sulphur mntent (wt %)
Getty Coke, Delaware, USA
7.3 ?: 0.3
Petrofina, Montreal 6.4 f 0.3
Imperial Oil, Sarnia 3.2 + 0.2
EXPERIMENTAL
Materials
Most of the experiments were carried out using fluid
coke obtained from Getty Oil Company, Delaware, USA.
Analysis of this coke is summarized in
Table 1.
Limited
experiments were performed on samples of fluid coke
obtained from Petrofina, Montreal, and Imperial Oil,
Sarnia, Canada. The sulphur contents of these cokes are
listed in Tabl e 2. The reagents used in this study were all
as-received grade. The surface area of the coke samples
was usually determined by the high speed surface area
analyser (Micromeritics Model 2200) and periodically by
the BET measurements.* The coke sample was activated
in dry helium for 4 h at 100°C before surface area
measurements.
For the sodium hydroxide-assisted desulphurization of
fluid coke the following steps are involved: (1)
impregnation of the coke particles with a suitable alkaline
reagent; (2) hydrodesulphurization; (3) leaching to remove
and
recover the alkaline reagent; (4) sulphur
determination in the coke.
1.
Impregnati on of he coke w it h alk ali ne reagents.
Coke
granules, 40/60 US mesh, were slurried with an aqueous
solution of the alkaline reagent and evaporated to dryness
at x 80°C with stirring. The ratio of the weight of alkaline
reagent to the weight of coke is defined as the weight ratio,
W/R.
Most of the experiments reported here involved
impregnation with 1M NaOH. Impregnation and drying
at higher temperatures or at room temperature resulted in
significantly lower desulphurizations during the
hydrogenation step. A few experiments were also carried
out using KOH and LiOH. Impregnation in an air or
inert atmosphere did not appear to influence the level of
sulphur removal in subsequent hydrogenation.
2. Hydrodesulphurization. A fixed-bed flow reactor
system
Figure I)
was constructed from 316 stainless steel
tubing except for the reactor which was made out of
quartz tubing.? The reactor consisted of a 3.2 cm i.d. x 61
cm long quartz tube and had a quartz fibre plug midway
to support the coke sample. The reagent-loaded coke (5.0
g) was charged into the reactor at room temperature, a
* BET surface
area measured by N, adsorption at 77K was only to
check the surface area measured by the one-point system
7 Initially, a stainless steel reactor was employed; but the reactor was
sulphided and interfered with gc. analysis.
hydrogen flow established, and the furnace switched on.
The reactor was heated by a Lindberg heavy duty furnace
(type 59344) equipped with a controller
_+
5’C). It took
= 30 min for the furnace to reach the desired temperature
Figure 2). The rate of hydrogen flow, 120 ml mine’,. was
measured at the reactor outlet under ambient condltlons.
The product stream was sampled and analysed every 5
min by gas chromatography and the reactor effluent was
scrubbed with NaOH prior to venting.
3.
Leaching.
After hyprodesulphurization the coke was
leached with tap water E 5 g coke/500 ml H,O) at 80°C
for 12 h. The water was then decanted and the sample
Hz He O2 HZS
H20
Flow
m t r
ie
Figure 1
Flow reactor for coke desulphurization. D, Sampling
10-0~; V, 7-port sampling valve; m, metering valve; T, thermomuple;
Tc, thermal mnductivity detector; CON, controller for the furnace;
El, electronic integrator; PS, Power supply for gas chromatograph
8o08533
Time (mln)
f&urel
Coke temperature (0) and H.# mncentration in the
reactor effluent gas; (A) as a function of time after reactor start-up.
5.0 g coke sample, 40160 US mesh, 2 h, 700°C, Hz flow = 120 ml
min-I,
W/t? =
0.04
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Desulphurizat ion of petroleum fluid co ke: Z. M. George and L . G. Schneider
Table3
Summary of preliminary experiments, Getty fluid coke, 7OO”C, 40160 US mesh, 2 h, 5.0 g sample. Gas flow: 120 ml min-’
Desulphurization
Desulphurization Surface area before
Surface area after
NaOH loading
medium
(96)
leaching (m2 g-l)
leaching (m2 9-l)
(Ml kg-‘)
None N2 2 11 11 30.24
W/R = 0.04 N2
29
<O.l
None “2 31 11
W/R = 0.04
‘42
90 <O.l 3 29.08a
W/R = 0.04 H, wet 85 10 3
W/R = 0.04 None None <O.l 5
W/R = Weight ratio,
Wt NaOH(g)
Wt coke(g)
a Leached sample
dried at 100°C in air. Leaching was practised as an
integral part of desulphurization as the NaOH used for
the impregnation of the coke is an expensive component
of desulphurization which could be recovered by leaching
and may be used for reagent make-up for further
impregnation.* Also, the presence of alkaline compounds
in the coke may lead to serious problems in the boiler
tubes during combustion. The rate of leaching was
significant initially but declined with time. Approxi-
mately 50% of the base could be extracted in E 1 h
and =7&75x in 12 h. Because of the small amount of
NaOH used in these experiments to achieve >80%
desulphurization and as a significant portion of the
alkaline reagent may be recovered by leaching and re-
used, the NaOH used appeared to act as a catalyst.
4.
Determinat ion of
sulphur
removal.
Gas
chromatographic
analysis and high temperature
combustion (ASTM D-3177-75) were employed
independently to determine desulphurization via H,S and
the total sulphur removal, respectively.
G.c. analysis
To quantitate sulphur removal from the coke as H,S or other
gaseous sulphur compounds during hydrodesulphurization,
the effluent of the reactor was analysed by g.c. every 5 min. By
switching a six-port sampling valve
Figure Z),
sample of the
effluent gas (2.0 ml) was swept into the analytical column, 8
feet of Poropak Q followed by 2 feet of Poropak T, maintained
at 15O”C,and analysed over a calibrated thermal conductivity
detector. During the initial stages of hydrodesulphurization,
CO, CH,, CO,, H,S and H,O were detected. Only H,S and
H,O remained during the later stages. COS, CS, and SO,
were not detected. Generally, the H,S concentration profile in
the product followed that of H,O. Integration of the H,S area
under the peak (i.e. graph of the partial pressure of H,S
uersus
time,
Figure
2) was used to determine the extent of
desulphurization by H,S.
Hi gh temperat ure sulphur determinat ion
This method is designed specifically for the rapid
determination of sulphur in coal and coke and consists of
burning a sample of coke within a tube furnace at * 1000°C
in a stream of oxygen. Sulphur oxides are absorbed in a
hydrogen peroxide solution, yielding sulphuric acid
(equation 1) which is titrated against standard NaOH to a pH
of 4.5.
SO, + H,O, -+H,SO,
(1)
* Although the composition of the leachate has not been determined, it
is probably a mixture of NaOH, Na,CO, with traces of Na,S.
The method was tested against the Standard Eschka
methodI
and agreement with 4% was obtained. Duplicate
analysis of the desulphurized and leached sample as well as a
single analysis of the starting material, were made for each
experiment.
The percentage desulphurization was
determined by comparing the percentage of sulphur in the
residue with that of the starting sample. Any residual basic
sodium compounds in the coke have been shown to form the
corresponding metal sulphates and these do not decompose
to form SO, during combustion. Unless specifically stated,
high temperature combustion was used for sulphur
determination.
RESULTS
Preliminary experiments
Before investigating the desulphurization of NaOH-
assisted fluid coke in detail, experiments were conducted
to investigate the sulphur removal by volatilization
(calcination to 700°C in flowing nitrogen) and by direct
hydrodesulphurization. Samples impregnated with
NaOH were investigated also under the same conditions
and the results are summarized in
Table 3.
The significant
effect of trace amounts of NaOH on the level of
desulphurization was evident; in particular the effect on
hydrodesulphurization was very pronounced in that,
whereas direct hydrodesulphurization resulted in 30 wt%
sulphur removal, incorporation of x 3 wt% NaOH in the
coke led to 90 wt% sulphur removal under the same
experimental conditions.
Reversibi l i ty of NaOH impregnati on
25 g
of the coke was impregnated with NaOH to a
weight ratio of 0.040 in a Teflon beaker. The reversibility
of the impregnation was examined by serial hot water
extraction of the base from a weighed sample of the
impregnated coke. Determination of the sodium in the
leachate by atomic absorption indicated that S&85% of
the base could be leached out. The remainder was
irreversibly adsorbed, probably within the coke matrix. A
similar experiment carried out on NaOH-impregnated
coke which had been hydrodesulphurized showed that
only x 70 wt% of the base could be recovered.
Loss
of base
could have resulted from chemical reaction with the coke
and with the quartz reactor, which was extensively
corroded.
Sodium balance
0.3 wt% sodium was determined in the desulphurized
and leached coke indicating that
x80
wt’? of the
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Desulphurization of petroleum fluid c oke: 2. M. George and L. G. Schneider
I
I
I
1
500 600 700 800 900
Coke tempemture (“C)
Figure3 Effect of coke temperature on desulphurization.
W/R = 0.040 NaOH. Conditions as in Figure 2
I
I I I I
1
I
004
I
I
008 0.12
(N&i-l/coke) mtlo
I
0.16 0.20
Figure 4
Effect of NaOH/coke ratio on desulphurization. Condi-
tions as in F&we 2
impregnated NaOH was removed during the process.
Whereas coke containing higher loadings of NaOH fused
during laboratory combustion, coke containing 0.3 wt%
sodium did not cause problems during laboratory
combustion at 1000°C.
Effect
of
process variables in the hydrodesulphuri zati on of
NaOH impregnated coke
Temperature. Results summarized in Figure 3 for a
weight ratio of 0.040 in the temperature range 55&85o”C
for 2 h show a maximum desulphurization at ~700°C.
The decrease in the extent of sulphur removal at > 700°C
may be associated with the collapse of the coke structure
or loss of NaOH by volatilization. To test this latter
possibility, the NaOH impregnated coke was heated to
and maintained at 700°C in a flow of helium (150 ml
min-‘) for 4 h. The effluent of the reactor, collected in
distilled water and analysed for sodium, indicated
negligible loss of sodium suggesting that the maximum
observed in the desulphurization may be due to factors
other
than
volatilization of NaOH. In these
desulphurization experiments, weight loss amounted to
z 15% of the initial charge of the coke. The sulphur
content of the coke was determined by the high
temperature combustion method.
Weight r ati o.
Coke samples with NaOH weight ratios
of 0.010, 0.020, 0.040, 0.100 and 0.200 were
hydrodesulphurized at 700°C and the results, summarized
in Figure 4, show that as the weight ratio (NaOH) is
increased, desulphurization increases quite rapidly and
reaches a constant level at E 85% at a weight ratio of 0.040.
32% desulphurization at 0 weight ratio refers to direct
hydrodesulphurization.
lime on stream. Data for these experiments presented in
Figure 5 demonstrate that sulphur removal increases with
time up to 2 h and reaches a constant level at ~85%
desulphurization. Consequently, desulphurization
experiments were set for 2 h.
Part i al pressure of hydrogen. Desulphurization was
investigated at different partial pressures of hydrogen at
700°C by keeping the total flow rate constant and diluting
helium with hydrogen. Results shown in Figure 6 indicate
a strong dependence on the partial pressure of hydrogen.
29% desulphurization at zero partial pressure of hydrogen
refers to desulphurization in helium under the same
experimental conditions.
Eflect of Na+, K+ and Li ’ on desulphurizat ion.
A few
experiments indicated that the effectiveness of the
I
I
I I
I
I
80-
1
I I I I
1
0 2 4 6 8
Time on streum (h)
F ure5
Effect of time on hydrodesulphurization
I-
O-
O
‘O-
O-
0
I I I
26.7 53.3 78.0
pH, (kPa)
Fgure 6 Effect of partial pressure of hydrogen
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Desulphurizat ion of petroleum fluid co ke: 2. M. George and L. G. Schneider
401
I I
I
I
0.04 006
0.08 0.10
Weight mtlo NaOH
Figure 7 Effect of NaOH/coke ratio on desulphurization via H2.S
(A) and total desulphurization (0). Conditionsas in Figure 2
reagents in hydrodesulphurization (700°C 4 h, a
hydrogen flow of 150 ml min- ‘) decreases in the order
NaOH > LiOH > KOH. With a metal/sulphur molar
ratio of 0.50, the respective desulphurizations were 88%
(MaOH), 61% (LiOH), and 53% (KOH).
Effect of NaOH loadi ng on desulphur izat ion vi a H,S.
Samples of coke were loaded with NaOH in the weight
ratio range 0.02-0.07. Aliquots of these samples were
hydrodesulphurized at 700°C for 2 hat 120 ml min-’ and
the extent of desulphurization via H,S (g.c.) and the
residual sulphur in the desulphurized coke were
determined by the high temperature combustion method.
Data summarized in Figure 7demonstrate that the level of
desulphurization increases up to a
W/R
of 0.04 after which
the total desulphurization as determined by the high
temperature combustion method remains constant, but
the level of desulphurization via H,S decreases. Up to a
weight ratio of 0.04, the extent of desulphurization was
primarily via H,S, as these desulphurized (not leached)
samples failed to show the presence of Na,S by X-ray
diffraction analysis or H,S production on heating the
samples with HCl. However, with samples containing
higher weight ratios of NaOH, significant quantities of
H,S could be detected during leaching of the
desulphurized sample which probably resulted from the
hydrolysis of Na,S:
Na,S + 2H,0+2NaOH + H,S
(2)
X-ray diffraction of this sample confirmed the presence of
Na,S, with d-spacings indicated at 0.380,0.232,0.198 and
0.164 nm.
Surface area
The starting material had a surface area of 11 O+ 2 m*
g
-l, which did not change during heating in nitrogen or
hydrogen.
Impregnation of the coke with NaOH resulted in
significant loss of surface area; this is not surprising as the
pores within the coke granules are probably filled with
adsorbed NaOH. Even after desulphurization at 700°C
where 90 wt% sulphur removal was achieved
Tabl e 3),
the
surface area was negligible. Hot water leaching of this
sample (x4.5 g sample, 500 ml tap water, 80°C overnight)
restored the surface area partially. Hydrodesul-
phurization
of the impregnated sample in wet
hydrogen resulted in 85 wt% sulphur removal, but the
original surface area was retained. These results,
summarized in
Tabl e 3,
suggest that there is no simple
relation between the surface area and the level of
desulphurization.
Diffusional l imi t at ions
Generally desulphurization of coke increases with the
rate of hydrogen flow and then reaches a constant level.
This has been attributed to the presence of a film of
products surrounding the coke granules, and the rate of
desulphurization depends upon the thickness or
concentration of this layer. As the hydrogen flow rate is
increased, the thickness of this layer is decreased, enabling
rapid diffusion of products (H,S) out of the coke granules
thereby increasing the extent of desulphurization.
Desulphurization experiments carried out at 550°C and
700°C at different rates of hydrogen flow, shown in Figure
8, show that, whereas little boundary layer diffusion
control exists at 55o”C, a diffusional barrier is apparent at
700°C where a high level of desulphurization was
attained. Experiments in which the coke particle size was
varied but the NaOH weight ratio maintained at 0.04
indicate that pore diffusion is not significant
Figure
9).
Although not shown in Figure 9, a similar trend
was observed at 700°C with a hydrogen flow rate of
120 ml min- ‘. This is one of the advantages of NaOH-
impregnation of
the
fluid
coke
prior to
hydrodesulphurization. In contrast, direct hydro-
desulphurization of a delayed coke produced by
I
I
I
I
I
I
,L *i
Fgure 8 Effect of hydrogen flow rate on hydrodesulphuristion
at 700°C (0) and 550°C (A)
I I I
1
0.10
030
050
070
0.9
Average coke partlcle diameter mm)
.
Figure9 Effect of coke particle size on hydrodesulphurization.
650°C. 2 h. H2 flow = 40 ml min-t
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Desulphurization of petroleum fluid co ke: Z. M. George and L . G. Schneider
Suncor appeared to be controlled by pore diffusion but level of sulphur removal achieved when the coke is
not film diffusion.5s6
impregnated with NaOH.
Scanning electron micrographs
No
significant difference could be detected between the
fluid coke sample as-received and after direct
hydrodesulphurization. However, hydrogenation of the
impregnated samples showed deep cracks and these
persisted during hot-water leaching. It is probably the
combination
of NaOH-impregnation
and high-
temperature hydrogenation that is responsible for these
cracks and these do not appear to have contributed to the
total surface area of the coke
Table 3).
Effect of wet hydrogen on desulphur izat ion
As the partial pressure of H,S closely followed that of
product water, and
wet hydrogen enhanced
desulphurization of oil sands fluid coke,15 the effect of wet
hydrogen on Getty Coke desulphurization was studied.
Constant partial pressure of water in hydrogen was
achieved by bubbling the hydrogen through a water
saturator maintained at constant temperature. Although
a systematic investigation was not undertaken, the
experiments indicated that for this fluid coke, the level of
desulphurization was not affected by water vapour in the
hydrogen.
It is likely that the organic sulphur compounds are
distributed uniformly within the coke granule. Hydrogen
can diffuse in and react with the sulphur compounds to
form H,S; however for H,S to diffuse out appears to be
difficult as the pores appear to be blocked. It is possible
that during impregnation and drying, which may be
considered as an activation process for this reaction, the
(C-S) bonds are weakened and these reactive sulphur
compounds may diffuse towards the surface of the
granules where they react readily with hydrogen to form
H,S. As H,S is now formed on the external surface of the
granules, the rate may be limited by film and not by pore
diffusion as observed,
Figures 8
and 9. The following
tentative mechanism may explain desulphurization of the
coke. It is probable that sulphur compounds in the coke
may be present as organic sulphides of the type
R-S-R,
where R could be an aromatic or aliphatic group:
R-S-R + HO-Na+ ZR-S-Na+ + ROH
(4)
R-S-Na+ + ROHgRONa+ + RSH
(5)
ROH+H RH+H,O
(6)
Effect of Na ,CO,
As Na,CO, can be mixed mechanically with coke,
thereby eliminating the impregnation step, and it is much
simpler to handle than NaOH, experiments were carried
out to determine the efficacy of Na,CO, compared to
NaOH. The results indicated that to achieve 80%
desulphurization, a weight ratio of 0.08 was required for
Na,CO, compared to 0.04 with NaOH.
To learn more about the mechanism of
desulphurization, particularly the role of sulphones, the
NaOH-impregnated coke was heated to 700° in a
stream of helium and the effluent of the reactor was
continuously monitored. SO, was not detected indicating
that for this coke desulphurization may not proceed
through a sulphone intermediate.
R-S-H + H, ZRH + H,S
(7)
R-0-Na+ + H,O ZROH + NaOH
(8)
Is possible that the NaOH generated
in-s i tu
(equation 8)
could aid in enhanced desulphurization.
Although the scanning electron micrograph indicates
cracks on the desulphurized coke granules, surface area
determinations do not support the hypothesis that during
hydrogenation of NaOH-impregnated coke, the pores
are opened up leading to enhanced desulphurization.
Further, as shown in Tabl e 3, no simple relation exists
between the desulphurization and surface area.
Possible explanations for the maximum observed at
x 7OO”C,
Figure 3,
are sintering, depletion of NaOH, and
the formation of stable (C-S) compounds by the reverse
reaction
Appli cati on of thi s method for desulphurizati on of other
fluid cokes
H,S+Cz(C-S)+H,
(9)
Detailed experimentation was not attempted; however,
at an NaOH weight ratio of 0.04 and
hydrodesulphurization at 700°C (5.0 g coke and a
hydrogen flow rate of 120 ml min-I), >80 wt% of the
sulphur was removed from the Imperial Oil and Petrolina
cokes.
The calorific value of the desulphurized Getty coke was
29.08 kJ kg- ‘, slightly lower than the starting sample and
the sulphur content of the product coke was 1.0 fO.l wt%
compared to 7.3 +0.3 wt% in the starting material. The
sulphur content of the product coke is within the limits
allowed by the Environmental Protection Agency of the
USA and would probably meet the specifications of the
Canadian and Alberta Governments.
As surface area does not appear to be related to the level of
desulphurization, and there is very little loss of the reagent
by volatilization, the decrease in desulphurization level at
temperatures > 700°C must be related to the formation of
new stable (C-S) sulphur compounds by the reverse
reaction.
The process described in this Paper is covered by
Canadian patent 1,090,464 granted to Z. M. George.
ACKNOWLEDGEMENTS
Valuable discussions with Prof E. Tollefson of the
University of Calgary are gratefully acknowledged. This
manuscript is ‘Alberta Research Council Contribution
No. 157’.
DISCUSSION
REFERENCES
The significant aspect of NaOH-assisted (catalysed)
hydrodesulphurization of this fluid coke is the very high
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Desulphurization of petroleum fluid co ke: Z. M. George and L. G. Schneider
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61,
December