Note: Descriptions are shown in the official language in which they were submitted.
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HYDROPROCESS1NG FCC NAPHTHAS
This invention relates generally to the upgrading of hydrocarbon
materials. More particularly the present invention concerns lowering the
amount
of sulfur contaminants in hydrocarbon materials that contain olefins without
materially hydrogenating the olefins.
Back~-ound of the Invenrion
Naphtha streams, especially those that are products of a cracking process
such as fluidized catalytic cracking, contain sulfur contaminants which are
undesirable. For example, gasolines which are blended naphtha streams are
restricted in the permissible level of sulfur contaminants because of the
effect
such contaminants have on the functioning of catalytic converters. While
sulfur
contaminated naphthas can be desulfurized by a great many hydrodesulfurization
(HDS) catalysts and processes, often hydrotreating also results in severe
octane
loss due to extensive reduction of the olefins in the naphtha stream. Numerous
attempts, of course, have been made to devise catalysts and processes which
will
favor hydrodesulfurization (HDS) over olefin hydrogenation; and although some
success has been achieved in obtaining greater selectivity often the
selectivity
gain is obtained at the expense of activity loss.
Thus, there remains a need for improved catalysts and processes for
hydrodesulfurization of cracked naphtha with minimum hydrogenation of
olefins.
Summary of the Invention
Briefly stated, a process is provided for reducing the sulfur content of a
hydrocarbon feedstock containing an olefinic component which comprises
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contacting the feedstock with a sulfided catalyst and hydrogen under hydro-
desulfiuization conditions, the catalyst comprising (i) at least one non-noble
metal of Group VIII; (ii) at least one metal of Group VIB; and (iii) at least
one
metal of Group IB, IIB and IVA, on an inorganic oxide support thereby
effecting
the hydrodesulfurization of the feedstock without substantially hydrogenating
the olefmic component.
Detailed Description of the Invention
The feedstock treated according to the invention typically is one
commonly designated as a cracked naphtha or gasoline blend stock. A fluid
catalytic cracked (FCC) naphtha is a specific example of a suitable feedstock
capable of being processed in accord with the invention.
The self ded catalyst suitable for the practice of the invention comprises
(i) at least one non-noble metal of Group VIII; (ii) at least one metal of
Group
VIB; and (iii) at least one metal of Group IB, IIB and IVA, on an inorganic
oxide support. Typically the Group VIII metal is present in an amount ranging
from about 0.1 to about 15 wt%; the Group VIB metal from about 0.1 to about
40 wt% and the Group IB, IIB and IVA metals from about 0.01 to about
wt% based on the total weight of the catalyst. Representative examples of
suitable catalysts include Co-Mo-Cu, Co-Mo-Zn, Co-Mo-Sn, Co-Mo-Cu-Zn,
Co-Mo-Sn-Zn and the like.
The support of the catalyst includes inorganic oxides such as alumina,
silica, titania, magnesia, silica-alumina and mixtures of these. Alumina is a
preferred support, and aluminas characterized as large pore aluminas are more
preferred providing superior activity and activity maintenance. Typically
large
pore aluminas have a surface area greater than about 100 mZ/g, a pore volume
greater than about 0.60 ml/g and an average pore diameter greater than about
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IOS Angstroms. Preferred aluminas have a surface area greater than I70 m2/g
and an average pore diameter greater than 115 Angstroms.
The catalyst metals are deposited on the support by techniques well
known in the art. The order in which the metals are deposited on the support
can
vary widely. For example, the metals may be deposited simultaneously,
sequentially, or two metals may be deposited simultaneously and the third
metal
separately either prior to or after the deposition of the other two metals.
Prefer-
ably the metals are introduced to the support by the incipient wetness method.
After depositing the metal well known techniques for drying and calcining may
be employed. Thus drying and calcining may be conducted after each metal
addition or after complete metal addition. Drying and calcining may be
conducted, for example, in air at 100°C to about 600°C.
Similarly, known
techniques for activation of the catalyst are employed. Thus the sulfiding
treatment of the catalyst may be achieved with blends of hydrogen sulfide and
hydrogen or hydrogen sulfide precursors in the presence of hydrogen.
In the practice of the invention the feedstock is contacted with the
sulfided catalyst under hydrodesulfurization conditions. These conditions will
vary depending upon the feed and the catalyst; however, suitable conditions
are
set forth in Table 1.
TABLE 1
Condition Broad Ran Preferred Ran More Preferred
a a
Tem erature, C 200-400 250-375 275-300
Pressure, si 10-1000 50-800 100-600
H dro en, SCFB 100-6000 500-4000 1000-3000
LHSV 0.1-20 1-15 2-10
H dro en Puri 60-100 80-99 85-95
, v%
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The following Examples will serve to further illustrate the present
invention.
Example I. (Comparative) A commercial HDS catalyst containing
4.0 wt% Co0 and 15.0 wt% Mo03 was activated by treating with 10% hydrogen
sulfide in hydrogen. The catalyst was evaluated on a feed comprising about
33 wt% each of n-heptane, octene-1, m-xylene, 2000 wppm sulfur as
2-methylthiophene, and 20 wppm nitrogen as aniline. The results of this
evaluation are presented in Table 2.
Example 2. The commercial HDS catalyst of Example 1 was
impregnated with copper nitrate to incorporate about 2 wt% Cu. After
pretreatment and activation the Co-Mo-Cu catalyst was tested on the feed of
Example 1. The results are summarized in Table 2.
Example 3. The commercial HDS catalyst of Example 1 was
impregnated with tin chloride to incorporate about 3 wt% Sn. After
pretreatment
and activation the Co-Mo-Zn catalyst was tested on the feed of Example 1. The
results are summarized in Table 2.
TABLE
2
Selective
HDS With
Co-Mo,
Co-Mo-Cu,
and Co-Mo-Sn
Catalysts
275-300C,
200 psig,
2000
SCF/B,
7-10
LHSV
Exam 1e Catal st HDS, wt% OS, wt% Selectivi Factor
1 Co-Mo 98 90 0.8
2 Co-Mo-Cu 97 83 2.0
3 Co-Mo-Sn 98 80 2.5
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Reaction conditions for the catalysts of Table 2 were selected to permit
comparison of relative selectivity at equivalently high levels of HDS. OS is a
measure of the degree of olefin saturation, and the selectivity factor is
calculated
from the rates of HDS and OS. Table 1 illustrates that the catalysts of this
invention modified by the addition of Cu and Sn are substantially more
selective
than the base case catalyst.
Examples 4 (Comparative) and 5-8. A Co-Mo HDS catalyst was
synthesized by impregnating alumina with cobalt carbonate and ammonium
heptamolybdate. After being dried and calcined at 400°C for 3 hrs, the
Co-Mo
catalyst was impregnated with copper nitrate to prepare a series of Co-Mo-Cu
catalysts containing about 3 wt% CoO, 11 wt% Mo03 and 1-6 wt% Cu. The
catalysts were tested as described in Example 1, and the results are
summarized
in Table 3.
TABLE
3
Selective
HDS With
Co-Mo,
and Co-Mo-Cu
Catalysts
275C,
200 psig,
2000
SCFB,
LHSV
Exam 1e Cu, wt% HDS, wt% OS, wt% Selectivi Factor
4 0.0 94 85 1.5
5 0.9 96 80 ~ 2.1
6 1.6 96 82 2.0
7 3.6 96 80 2.0
8 5.3 96 83 1.9
The data of Table 3 illustrate that the catalysts of this invention are more
selective than their Cu-free analog.
Example 9 (Comparative). The catalyst of Example 4 and the catalyst of
Example 7 were tested as in Example 1 at process conditions providing a
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common level of HDS at a common temperature. The data shown in Table 4
confirm that the Co-Mo-Cu catalyst of this invention is intrinsically more
selective and that the selectivity credit is not an artifact of the reaction
conditions.
TABLE 4
285C, 200 psig,
2000 SCFB
Catal st Co-Mo Co-Mo-Cu
LHSV 10 4
Selectivi Factor1.2 1.7
OS, Wt% 90 84
HDS, Wt% 94 96
Example 10 (Comparative). A vendor HDS catalyst containing about
2 wt% CoO, 7 wt% Mo03, and 0.6 wt% K was pretreated and tested as in
Example 1. The results of the test are presented in Table 5.
Example 11. The catalyst of Example 10 was modified by the addition of
about 0.9 wt% Cu. The catalyst was activated and tested as described in
Example 1. The data from the test are included in Table 5.
TAB LE 5
Selective HDS With
Co-Mo and Co-Mo-Cu
Catalysts
275C, 200 psig,
2000 SCFB, 10
LSHV
Exam 1e 10 11
Catal st Co-Mo Co-Mo-Cu
HDS,Wt% 98 96
OS, Wt% 94 86
Selecfiivi Factor ' I.5 1.7
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The data of Tables 2, 3 and 5 show that the Co-Mo-Cu catalysts of this
invention
are more selective than the reference catalysts independent of metals
loadings.
Example 12. The catalyst of Example 7 was activated and tested as
described in Example 1. The catalyst was subjected to high severity process
conditions favoring selectivity by operating at high temperatures and low
pressures. Representative data at selected periods of this test are presented
in
Table 6.
TABLE 6
Effect of Reaction
Conditions
on Selectivity
and Stability
2000 SCFB, 4
LHSV
Balance Period 1 2 3 4 5 6
Hr. on Oil 38 43 52 133 232 235
Tem erature, 285 300 325 310 300 300
C
Pressure, si 200 50 50 25 15 50
HDS, Wt% 96 96 99 89 69 90
OS, Wt% 84 81 89 57 32 58
Selectivi Factor1.7 2.0 2.2 2.6 3.0 2.7
Table 6 illustrates that as reaction temperature increases and pressure
decreases,
olefin saturation is less favorable, and the selectivity of the reaction
increases.
Comparison of balances 2 and 6 at common conditions shows that after extended
operations at high severity conditions the catalyst of this invention retains
high
HDS activity, decreased olefin saturation activity, and a substantially higher
selectivity factor. The data indicate that the catalyst of this invention
resists
deactivation at high severity conditions that favor HDS over OS.
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Example 13 (Comparative). A vendor catalyst containing about 1 wt%
Co0 and 4 wt% Mo03 was used to process a 200-450°F cat naphtha at
500°F,
235 psig H2, 2600 SCFB, 6.5 LHSV. The results are summarized in Table 7.
Example 14. The catalyst of Example 2 was used to process a 200-450
°F
cat naphtha at 500°F, 235 psig H2, 2600 SCFB, 6.5 LHSV. The results are
summarized in Table 7.
TABLE 7
Selective HDS of
200-450F Cat Naphtha
With Co-Mo and
Co-Mo-Cu Catalysts
500F, 235 psig H2
2600 SCFB, 6.5
LSHV
Exam 1e 13 14
Catal st Co-Mo Co-Mo-Cu
HDS, Wt% 68 ' 80
OS, Wt% 16 17
Selectivi Factox 0.7 0.9
Activi 150 hr 250 250
Activi 300 hr 180 250
The catalyst of this invention is more selective than the reference catalyst
for the
processing of this feedstock. Table 7 confirms the superior stability of the
catalyst of this invention which experienced no deactivation over a 150 hr
period
while the reference catalyst activity decreased by about 30%.
Example 15. (Comparative) The catalyst of Example 4 was used to
process a 200-450°F cat naphtha. The results are summarized in Table 8.
Example 16. The catalyst of Example 6 was used to process a 200-
450°F
cat naphtha. The results are summarized in Table 8.
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TABLE 8
HDS of 200-450F
Cat Naphtha
With Co-Mo
and Co-Mo-Cu
Catalysts
Exam 1e 15 16 15 16
Catal st Co-Mo Co-Mo-Cu Co-Mo Co-Mo-Cu
Conditions 273C, 293C, 125
300 si si
Activi 200 hr 80 39 -- --
Activi 800 hr 80 39 -- --
Activi 900 hr -- -- 480 170
Activi 1100 -- -- 380 160
hr
The data show that at the initial process conditions neither catalyst
experienced
deactivation through 800 hr on oil. When high temperature, low pressure
conditions favoring selectivity were imposed the catalyst of this invention
resisted deactivation while the reference catalyst experienced 20%
deactivation
within 200 hours.
Example 17. (Comparative) A Co-Mo HDS catalyst was synthesized by
impregnating a large pore alumina with cobalt carbonate and ammonium
heptamolybdate. After being dried and calcined at 400°C for 3 hr, the
catalyst
was tested as in Example 1. The results are summarized in Table 9.
Example 18. A Co-Mo HDS catalyst was synthesized by impregnating a
large pore alumina with cobalt carbonate and ammonium heptamolybdate. After
being dried and calcined at 400°C for 3 hr, the catalyst was
impregnated with
copper nitrate to prepare a Co-Mo-Cu catalyst containing about 3 wt% CoO,
11 wt% Mo03 and 4 wt% Cu. The catalyst was tested as in Example 1. The
results are summarized in Table 9.
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TAELE 9
Selective
HDS With
Co-Mo,
and Co-Mo-Cu
Catalysts
275C, 200
psig,
2000 SCFB,
10 LHSV
Exam 1e Cu, Wt% HDS, Wt/a OS, Wt% Selectivi
Factor
4 0.0 94 85 1.5
17 0.0 99 97 1.3
7 3.6 96 80 2.0
18 3.8 94 70 2.3
The results illustrate that the Co-Mo catalyst prepared on the large pore
alumina
is more active than its conventional alumina analog. The Co-Mo-Cu catalyst on
the large pore alumina is more selective at comparable activity than its
conven-
tional alumina analog.
