Note: Descriptions are shown in the official language in which they were submitted.
~1'~1894
1
Complete Catalytic Hydroconversion Process
for Heavy Petroleum Feedstocks
BACKGROUND OF INVENTION
This invention pertains to a catalytic two-stage hydroconversion process for
achieving
essentially complete hydroconversion of heavy petroleum-based feedstocks to
produce
lower-boiling hydrocarbon liquid products. It pertains particularly to such a
process
utilizing a high temperature first stage ebullated bed catalytic reactor and
lower
temperature second stage ebullated bed catalytic reactor, with extinction
recycle of all
distilled vacuum bottoms material back to the first stage reactor to provide
90-100 vol%
hydroconversio~ of the feedstocks.
For H-Oil~ catalytic hydroconversion processes for heavy petroleum feedstocks,
effective use of the catalyst, poor product quality and disposition of
unconverted residue
material have been concerns for potential users. The catalytic hydroconversion
of
petroleum residua in a single-stage ebullated bed catalytic reactor with
recycle of a
vacuum bottoms fraction to the reactor is well known, having been previously.
disclosed
't 5 in U.S. Patents No. 2,987,465 to Johanson and U.S. 3,412,010 to Alpert,
et al. Also, U.S.
Patent No. 3,322,665 to Chervenak et al discloses a process for catalytic
treatment of
heavy gas oil, in which a fractionator bottoms material is recycled to the
reactor for further
extinction reactions therein. U.S. No. 3,549,517 to Lehman discloses a single
stage
catalytic process in which a vacuum distillation side stream is recycled to
the reactor.
U.S. Patent No. 3,184,402 to Kozlowski, et al discloses a two-stage catalytic
hydrocracking process with intermediate fractionation and some recycle of a
distillation
bottoms fraction to either a first or second catalytic cracking zone. U.S.
Patent
No. 3,254,017 to Arey, Jr. et al discloses a two-stage process for
hydrocracking heavy
Oii~ ii iiiieiiy 6iiidii NviG ZCVIItC i:aialyji iii uC Sei:Gnu Stage
refii:ivr. U.J. Nti. J,i Ij,G~o
to Watkins, discloses a two-stage catalytic desulfurization process with
recycle of some
heavy oil fraction boiling above diesel fuel oil to a second stage fixed bed
type reactor.
U.S. No. 4,457,831 to Gendler discloses a two-stage catalytic hydroconversion
process
~1~18~4
in which vacuum bottoms residue material is recycled to the second stage
reactor for
further hydroconversion reactions. Also. U.S. No. 4,576,710 to Nongbri et al
discloses
a two-stage catalytic desulfurization process for petroleum residua feedstocks
utilizing
catalyst regeneration.
However, further process improvements are needed to achieve higher
hydroconversion
of heavy high boiling hydrocarbon liquid feedstocks, such as petroleum residua
normally
boiling above about 800'F, to produce desired low-boiling hydrocarbon liquid
products.
The present invention advantageously overcomes the concerns of potential users
and
provides a desirable improvement over the known prior art hydroconversion
processes
for heavy petroleum feedstocks.
SUMMARY OF INVENTION
This invention provides a catalytic two-stage ebullated bed hydroconversion
process
!1 ~ for heavy petroleum, residual oil and bitumen feedstocks, which process
effectively
hydroconverts essentially all of the high boiling residue material in the
feedstock to
desirable high quality lower boiling hydrocarbon liquid products. The process
is
particularly useful for those feedstocks containing 40-100 vol% 975'F'
petroleum resid
and 10-50 wt% Conradson carbon residue (CCR), and containing up to 1000 wppm
total
2o metals (V+Ni). Preferred feedstocks should contain 75-100 vol% 975'F+
residual material
with 15-40 wt% CCR, and 100-600 wppm total metals (V+Ni). Such feedstocks may
include but are not limited to heavy crudes, atmospheric bottoms and vacuum
resid
materials from Alaska, Athabasca, Bachaquero, Cold Lake, Lloydminster, Orinoco
and
Saudi Arabia.
In the process, the fresh feedstock is introduced together with hydrogen into
a first stage
catalytic ebullated bed type reactor, which is essentially a high temperature
hydroconversion reactor utilizing a particulate supported hydroconversion
catalyst. The
reactor is maintained at operating conditions of 820-875'F temperature, 1500-
3500 psig
hydrogen partial pressure, and space velocity of 0.30-1.0 volume feed per hour
per
j
volume of reactor (V,/hrN,). The catalyst replacement rate should be 0.15-0.90
pound
catalyst/barrel of fresh oil feed. The first stage reactor hydroconverts 70-95
vol.% of the
fresh feed material and recycled residue material to form lower boiling
hydrocarbon
materials.
The first stage reactor effluent material is phase separated, a gas fraction
is removed
and the resulting liquid fraction is passed together with additional hydrogen
on to a
second stage catalytic ebullated bed type reactor containing a particulate
high activity
catalyst and which is maintained at lower temperature conditions of 700-800'F
~~~ temperature and 0.10-0.80 V,/hrN, space velocity, so as to effectively
hydrogenate the
unconverted residue material therein. The second stage reactor catalyst
replacement rate
should be 0.15-0.90 pound catalyst/barrel feed to the second stage, which
hydroconverts
10-50 vol% of the second stage feed material to lower boiling hydrocarbon
materials.
The second stage reactor effluent material is passed to gas/liquid separation
and
distillation steps, from which hydrocarbon liquid product and distillation
vacuum bottoms
fraction materials are removed. The vacuum bottoms material boiling above at
least
850'F temperature and preferably above 900'F is recycled back to the first
stage catalytic
reactor inlet at a volume ratio to the fresh feedstock of 0.2-1.5/1, and
preferably at 0.5
~O 1.0/1 recycle ratio for further hydroconversion extinction reactions
therein.
Particulate catalyst materials which are useful in this petroleum
hydroconversion
process may contain 2-25 wt. percent total active metals selected from the
group
consisting of cadmium, chromium, cobalt, iron, molybdenum, nickel, tin,
tungsten, and
2 ~ mixtures thereof deposited on a support material selected from the group
of alumina,
silica and combinations thereof. Also, catalysts having the same
characteristics may be
used in both the first stage and second stage reactors.
The particulate catalyst will usually be in the form of extrudates or spheres
and have
3o the following useful and preferred characteristics:
.r.
Useful Preferred
Particle Diameter, in. 0.025-0.0830.030-0.065
Particle Diameter, mm 0.63-2.1 0.75-1.65
Bulk Density, Ib/ft' 25-45 30-40
S Particle Crush Strength, Ib/mm1.8 min 2.0 min.
Total Active Metals Content, 2-25 5-20
Wt%
Total Pore Volume, cmZgm* 0.30-1.50 0.50-1.20
Surface Area, m2/gm 100-400 150-350
Average Pore Diameter, Angstrom**50-350 100-250
~l o
* Determined by mercury penetration method at 60,000 psi.
Average pore diameter calculated by APD = 4 Poro Volume X 10°
* * Surface Area
Catalysts having unimodal, bimodal and trimodai pore size distribution are
useful in this
~ process. Preferred catalysts should contain 5-20 wt.% total active metals
consisting of
combinations of cobalt, molybdenum and nickel deposited on alumina support
material.
Thus for the present process, the heavy petroleum feedstock is first
catalytically
hydroconverted in the first stage catalytic higher temperature reactor, and
the remaining
2o resid fraction is catalytically hydrogenated in the second stage catalytic
lower temperature
reactor, after which a vacuum distilled 850'F' fraction is recycled back to
the first stage
reactor for further hydrocracking reactions at the higher temperature
maintained therein.
Passing the first stage reactor liquid phase effluent material to the second
stage reactor
operated at lower temperature and space velocity conditions concentrates
unconverted
2~ residue material, minimizes any gas velocity related problems in the second
stage reactor,
and reduces contaminant partial pressures (HZS, NH3, HZO). The second stage
catalytic
reactions increase the hydrogen/carbon ratio of the residue being processed
therein,
thereby decreasing aromaticity and increasing the hydrogen donor capability of
the
residue, so that by its recycle back to the first stage reactor the
hydrogenated residue can
30 donate hydrogen to the fresh feedstock and the hydrogenated residue can
also be more
readily hydroconverted to desirable lower boiling fractions. This approach is
more
~17189~
selective to producing high yields of desirable hydrocarbon liquid fuel
products, i.e.
reduced hydrocarbon gas contributes to high conversion operations. This
catalytic
hydroconversion process can also be further improved by selectively feeding
fresh
hydrogen to the second stage reactor and recycling hydrogen gas to the first
stage
reactor, so as to maximize hydrogen partial pressure in the more catalytic
second stage
hydrogenation reactor.
Also if desired, used catalyst in the second stage ebullated bed reactor can
be
withdrawn, treated to remove undesired fines, etc., and introduced into the
first stage
'10 ebullated bed reactor for further use therein, before the used catalyst is
withdrawn from
the first stage reactor and discarded. Because of the presence of metal
contaminants in
the fresh heavy feedstock and the more thermal nature of the first stage
reactions,
utilizing used second stage catalyst material in the first stage reactor is
appropriate and
beneficial, because use of fresh, high activity catalyst in the higher
temperature mainly
~ S thermal type reactor would not provide substantially improved catalytic
activity therein.
Also, by providing complete extinction of the feedstock resid fraction, any
disposition
problems usually related to an unconverted bottoms fraction material are
eliminated.
This process advantageously provides for improved matching of the reaction
conditions
and the catalytic activity needed in each stage reactor, by providing higher
reaction
temperature, and lower catalyst activity in the first stage reactor and lower
temperature
and higher catalyst activity in the second stage reactor, so as to achieve a
more complete
hydroconversion of the feedstock and effective use of the catalyst. This
combination of
the two staged reaction conditions is unexpectedly beneficial and results in
essentially
complete hydroconversion of heavy petroleum feedstocks to produce desirable
lower
boiling hydrocarbon liquid products, without substantially increasing reactor
volume over
the single stage approach to achieving high hydroconversion of the feedstock.
Other advantages of this catalytic two stage hydroconversion process for heavy
petroleum feedstocks include complete destruction of the feedstock heavy
residue fraction
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utilizing the selected catalytic reaction conditions, without producing
undesired cokes,
sediment or other such carbonaceous material in the reactors. The process also
provides
effective use of the catalyst by cascading used catalyst from the second stage
ebullated
bed reactor back to the first stage higher temperature ebullated bed reactor
for further
use therein. Optimal selection of reactor operating conditions and reactor
volumes
minimizes gas production and hydrogen consumption. After achieving effective
hydrogenation of the unconverted residue in the second stage reactor, recycle
of the
hydrogenated residue material back to the first stage reactor provides
effective
hydroconversion with minimal gas and light ends production and with minimal
additional
1J hydrogen consumption. Passing the first stage reactor effluent liquid
fraction to the
second stage reactor concentrates liquid residue in the second stage reactor,
and
minimizes any operating problems therein due to incompatibility (light end
fractions
already being removed) and due to excessive gas velocity. Distillate (700-
975'F) product
quality is superior relative to that obtained from typical high conversion
single stage H-Oil
process operations due to the selective hydrogenation of the feedstock resid
fractions in
the second stage reactor.
BRIEF DESCRIPTION OF DRAWING
Fig. i is a schematic flow diagram of a catalytic two-stage hydroconversion
process
2o for processing heavy petroleum feedstocks to produce lower-boiling liquid
and gas
products according to the invention.
DESCRIPTION OF INVENTION
This invention will now be described in greater detail for a catalytic two-
stage ebullated
ZS bed reaction process and system which is adapted for achieving
substantially complete
hydroconversion and destruction of residue material (975'F' fraction)
contained in heavy
petroleum oil, residual oil, or bitumen feedstocks, and for producing
desirable low-boiling
hydrocarbon liquid products. As shown by Fig. 1, a pressurized heavy petroleum
feedstock such as Cold Lake vacuum resid is provided at 10, combined with
hydrogen
30 at 12 and mixed with recycled hydrogenated heavy vacuum bottoms material at
13, and
CA 02171894 2005-02-23
7
the combined stream 14 is fed upwardly through flow distributor 15 in first
stage catalytic
ebullated bed upflow reactor 16 containing catalyst ebullated bed 18. The
total feedstock
consists of the fresh hydrocarbon feed material at 10 plus the recycled vacuum
bottoms
material at 13. The recycle rate for the vacuum bottoms material at 13 to the
first stage
reactor 16 is selected so as to completely destroy or extinct this residue
material in two
staged catalytic reactors, with the recycle volume ratio of the vacuum bottoms
material
to the fresh oil feedstock being in the range of 0.2-1.5/1, and preferably
0.50-1.0/1 recycle
ratio.
io
In the first stage reactor 16, the hydrocracking reactions are primarily
thermal type as
the reactor is maintained at a relatively high temperature of 820-875'F, at
1,500-3,500
psig hydrogen partial pressure, and liquid hourly space velocity of 0.30-1.0
volume
feed/hr/volume of reactor (V,/hrN~). The feedstock hydroconversion achieved
therein is
typically 70-95 vol %, with about 75-90 vol. % conversion usually being
preferred.
Preferred first stage reaction conditions are 825-850'F temperature, 2000-3000
psig,
hydrogen partial pressure, and 0.40-0.80 V,/hrN~ space velocity. The catalyst
bed 18 in
first stage reactor 16 is expanded by the upflowing gas and reactor liquid to
30-60%
above its settled height and is ebullated as described in more detail iri U.S.
Patent No.
20 3,322,665.
From first stage reactor 16, overhead effluent stream 19 is withdrawn and
passed to
phase separator 20. A liquid stream is withdrawn from the separator 20 through
downcomer conduit 22, and is recirculated through conduit 24 by ebullating or
recycle
pump 25 back to the reactor 16. For the first stage reactor 16, the
particulate catalyst
material added at 17 is preferably used extrudate catalyst withdrawn at 36
from second
30 stage reactor 30, and usually treated at zone 38 as desired to remove
particulate fines,
etc. at 37. Fresh make-up catalyst can be added as needed at 17a, and spent
catalyst
is withdrawn at connection 17b from catalyst bed 18.
CA 02171894 2005-02-23
8
From the phase separator 20, gaseous material at 21 is passed to a gas
purification
section 42, which is described further herein below. Also from the separator
20, a liquid
portion 26 from the liquid stream 22 provides the liquid feed (-700'F')
material upwardly
through flow distributor 27 into the second stage catalytic ebullated bed
reactor 30.
In the second stage catalytic reactor 30, which preferably has larger volume
and
provides lower space velocity than for the first-stage reactor 16, less
hydroconversion and
more catalytic hydrogenation type reactions occur. The second stage reactor 30
contains
ebullated catalyst bed 28 and is operated at conditions of 700-800'F
temperature, 1,500-
3,500 psig hydrogen partial pressure, and 0.10-0.80 V,/hrN, space velocity,
and thereby
maximizes resid hydrogenation reactions which occur therein. Preferred second
stage
reaction conditions are 730-780'F temperature, and 0.20-0.60 V,/hrN~ space
velocity.
Additional fresh hydrogen is provided at 32 to the second stage reactor 30, so
that a high
level of hydrogen partial pressure is maintained in the reactor.
The catalyst bed 28 is expanded by 30-60% above its settled height by the
upflowing
gas and liquid therein. Reactor liquid is withdrawn from an internal phase
separator 33
through downcomer conduit 34 to recycle pump 35, and is reintroduced upwardly
through
the flow distributor 27 into the ebullated bed 28. Used particulate catalyst
is withdrawn
at 36 from the second stage reactor bed 28 and fresh catalyst is added at .36a
as
needed to maintain the desired catalyst volume and catalytic activity therein.
This used
catalyst withdrawn, which is relatively low in metal contaminant
concentration, is passed
to a treatment unit 38 where it is washed, and screened to remove undesired
fines at 37,
and the recovered catalyst at 39 provides the used catalyst addition at 17 to
the first
stage reactor bed 18, together with any fresh make-up catalyst added at
connection 17a
as needed.
The catalyst particles in ebullated beds 18 and 28 usually have a relatively
narrow size
range for uniform bed expansion under controlled upward liquid and gas flow
conditions.
While the useful catalyst size range is between 6 and 60 mesh (U.S. Sieve
Series), the
21?'1894
9
catalyst size is preferably particles between 8 and 40 mesh size including
beads,
extrudates, or spheres of approximately 0.020-0.100 inch effective diameter.
In the
reactor, the density of the catalyst particles, the liquid upward flow rate,
and the lifting
effect of the upflowing hydrogen gas are important factors in the desired
expansion and
S~ operation of the catalyst bed.
From the second stage reactor 30, an effluent stream is withdrawn at 31 and
passed
to a phase separator 40. From this separator 40, a hydrogen-containing gas
stream 41
is passed to the purification section 42 for removal of contaminants such as
COZ, HxS,
~ 0 and NH3 at 43. Purified hydrogen at 44 is recycled back to each reactor 16
and 30 as
desired as the HZ streams 12 and 32, respectively, while fresh hydrogen is
added at 45
as needed.
Also from separator 40, a liquid fraction 46 is withdrawn, pressure-reduced at
47 to 0-
100 psig, and is introduced into fractionation unit 48. A gaseous product
stream is
withdrawn at 49 and a light hydrocarbon liquid product normally boiling
between
400-850'F are withdrawn at 50. A bottoms 850'F" fraction is withdrawn at 52,
reheated
at heater 53, and passed to vacuum distillation step at 54. A vacuum gas oil
liquid
product is withdrawn overhead at 55. Vacuum bottoms stream 56, which has been
20 hydrogenated in the second stage catalyst reactor 30, is completely
recycled back to the
first stage catalytic reactor 16 for predominantly thermal hydrocracking
reactions therein
using the low activity catalyst provided at 17. The recycle volume ratio for
vacuum
bottoms stream 56 to fresh feed 10 should be 0.2-1.5/1, and preferably should
be 0.50-
1.0/1. It is pointed out that by utilizing this two stage catalytic
hydroconversion process,
Z7 the thermal reactions and catalytic activity in each stage reactor are
effectively matched,
so that there is essentially no net 975'F' hydrocarbon material produced from
the
process.
-- 21'1894
The process of the present invention will be further described by use of the
following
examples, which are illustrative only and should not be construed as limiting
the scope
of the invention.
EXAMPLE 1
A typical heavy vacuum resid feedstock such as Cold Lake vacuum resid is
processed
by using the catalytic two-stage hydroconversion process with vacuum bottoms
recycle
arrangement of the present invention. This Cold Lake vacuum resid feedstock
contains
90 vol % 975'F' material, 5.1 wt.% sulfur, 19 wt.% CCR, and 350 wppm metals
(V+Ni),
~0 with the vacuum bottoms fraction normally boiling above 975'F being
recycled back to the
first stage catalytic reactor of the two-reactor system for further
hydroconversion reactions
and extinction recycle therein. The reaction conditions used and overall
conversion
results are summarized in Table 1 below.
Table 1
'I S Hydroconversion of Cold Lake Vacuum Resid Feedstock
Catalyst Used 16-20 wt.% Cobalt-moly on alumina
Hydroconversion, Vol% up to 100%
Reactor Reactor 2 Overall
1
Reaction Temperature, 'F 827 760 . --
HZ Partial Pressure, psig 2,000 2,000 --
2o Reactor Space velocity, V,/hr/V,0.40 0.20 --
HZ Consumption, SCF/Bbl Feed -- -- 2570
Recycle Ratio 0.75 -- --
Catalyst Repl. Rate, Lb/Bbl 0.435 0.40 0.40
Feed
(from 2nd (fresh catalyst)
reactor)
'
'
Residue (975 76 26 gg,6
F
) Conversion, V%
Hydrodesulfurization, W% 80 58 93.5
Hydrodemetallization, W% 84 57 gg
Hydrodenitrogenation, W% 35 20 67
Product Yields, % of Fresh Feed
C;-C~ Gas, UI% -- -- 3
9
C,-350'F, Naphtha, V% -- -- .
' 21.0
350-650 -- -- 52.2
F Mid Distillate, V%
'
650-975 -- -- 39.1
F Gas Oil, V%
'
975 -- -- 0
F' Residue, V% 4
C4-975'F Distillate, V% -- -- .
112.3
-~- ~1'~~894
'~1
As seen from the Table 1 results, by using the selected operating conditions
and
matching catalyst activity for the two staged reactors, the overall
hydroconversion of the
feedstock obtained by recycling the vacuum bottoms fraction back to the first
stage
reactor is 99.6 vol%, along with high percentage demetallization and
desulfurization of the
S feedstock. A comparable improvement is also shown for the distillate product
yields, with
the total yield of the 975'F' material being only 0.4% by volume.
Although this invention has been described broadly and in terms of preferred
embodiments, it will be understood that modifications and variations of the
process can
be made all within the spirit and scope of the invention, which is defined by
the following
claims.
