Note: Descriptions are shown in the official language in which they were submitted.
10~4491
This invention relates to the treatment of hydrocarbon
oils and, more particularly, to the hydrogenation and hydro-
cracking of relatively heavy hydrocarbon oils to produce
improved products of lower boiling range.
Hydrocracking processes for the conversion of heavy
hydrocarbon oils to light and intermediate naphthas of good
quality for reforming feedstocksJ fuel oil and gas-oil are well
known. In such processes, it is normally desirable to be able
to control at least to some extent the relative amounts of
various products produced. For instance, it may some times be
desirable to produce relatively large quantities of gasoline
boiling range products, while at other times relatively greater
quantities of slightly higher boiling products such as those
suitable for fuel oils may be desired.
The heavy hydrocarbon oils to which this invention is
directed can be such materials as petroleum crude oil, atmospheric
tar bottoms products, vacuum tar bottoms products, heavy cycle
oils, crude oil residuum, top crude oils and the heavy hydro-
carbonaceous oils extracted from tar sands. Of particular
interest are the oils extracted from tar sands and which contain
wide boiling range materials from naphthas through kerosene, gas
oil, tar, etc. and which contain a large portion of material
boilin~ above 975F.
The heavy hydrocarbon oils of the above type tend to
contain nitrogenous and sulfurous compounds in exceedingly large
quantities. In addition, such heavy hydrocarbon fractions
frequently contain excessive quantities of organo-metallic
contaminants which tend to be extremely detrimental to various
catalytic processes that may subsequently be carried out, such
as hydroforming. Of the metallic contaminants, those containing
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` 10~4491
nickel and vanadium are most common, although other metals
are often present. These metallic contaminants, as well as
others, are usually present within the hydrocarbonaceous
material as organo-metallic compounds of relatively high
molecular weight. A considerable quantity of the organo-
metallic complexes are linked with asphaltenic material and
contain sulfur. Of course, in catalytic hydrocracking
procedures, the presence of large quantitites of asphaltenic
material and organo-metallic compounds interfers considerably
with the activity of the catalyst with respect to the
destructive removal of nitrogenous, sulfurous and oxygenated
compounds.
Of the non-metallic impurities, nitrogen is probably
most undesirable because it effectively poisons most catalysts
which may be employed in the conversion of petroleum franctions.
They are particularly damaging to reforming and catalytic cracking
catalysts. It is , therefore, particularly necessary that
nitrogenous compounds be removed substantially completely
from the lighter hydrocarbon oils being obtained from the
heavy oils. The nitrogenous and su]furous compounds are further
objectionable because combustion of fuels containing these
impurities results in release of nitrogen and sulfur oxides
which are noxious, corrosive and present a serious problem with
respect to pollution of the atmosphere. Furthermore, with
respect to motor fuels, sulfur is particularly objectionable
because of odour, gum and varnish formation, and significantly
decreased lead susceptibility.
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The necessity for the removal of the above contam-
inants is well known in petroleum processing. One of the
techniques used in this impurity removal has been catalytic
hydrocracking. In this process, the oil is passed with
hydrogen, into a fixed bed or an ebullated bed of catalysts.
However, the fixed bed catalytic process has been extremely
difficult to operate. This is mainly due to bed plugging
and catalyst deactivation by metals, coke and carbonaceous
materials deposited on the catalysts and interstitial spaces.
In the ebullated bed process some of the problems are overcome
as the catalyst can be added and removed continuously.
However, catalyst cost is high due to rapid deactivation of
the catalysts. The catalyst can be reused if it is possible
to regenerate the catalyst. This requires high capacity
catalyst regeneration equlpment in order to implement the
process on a continuous basis.
Following the hydrocracking step, the product is
distilled to produce naphtha (IBP-204C), light gas-oil
~; (204-343C) and heavy gas-oil (343-524C) and these are further
treated individually to remove sulphur and nitrogen compounds.
Industry has always treated the product in individual fractions
through tradition and because of fears that nitrogen compounds
would migrate to the naphtha fraction, producing off-
specification material. Once-through treatment of the distillates
together has advantages in the reduction of capital and operating
costs for distillation facilities and hydrotreaters. Further
reduction in costs can be obtained if the hot hydrocracked
product from the first stage is treated directly without
pressure let-down or condensation.
There are various specific examples in the literature
of attempts to overcome some of the above problems and one
such attempt is described in Ga~sis U.S. Patent 3,453,206, issued
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July 1, 1969. That patent describes a multi-stage hydrocracking
process for heavy oils in the first stage of which the heavy
oil (containing fractions boiling above the gasoline range) is
treated with a mixture of hydrogen and water (from about 2 to
30% by weight of water) and in the second stage is treated in
the presence of a catalyst at hydrofining conditions. In the
first stage, the reactor is packed with stainless steel turnings
and the liquid is passed downwardly while the hydrogen-water
mixture is passed upwardly countercurrently.
It is the object of the present invention to provide
a hydrocracking process which is effective in removing various
, contaminating influences from heavy hydrocarbon oils and
, particularly those extracted from tar sands.
SUMMARY OF THE INVENTION
~, Thus, in accordance with the present invention there
is described a process for hydrocracking a heavy hydrocarbon
oil, at least about 50% by volume of which boils above 975F
^i which comprises:
, a) passing the heavy hydrocarbon oil in the presence
20 of 500 to 50,000 Scf of hydrogen per barrel of oil
upwardly through a first vertical hydrocracking zone in the
absence of a catalyst, the hydrocracking zone being maintained
at a temperature between about 400 and 470C, a pressure between
about 500 and 2500 psig. and a space velocity of between about
0.5 and 1.5 volume of hydrocarbon oil per hour per volume of
hydrocracking zone capacity,
b) removing from the top of the hydrocracking zone a
mixed effluent containing a gaseous phase comprising hydrogen
~ and vapourous hydrocarbons and a liquid phase comprising un-
;~ 30 vapourized hydrocarbons,
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~0~449~.
c) separating the effluent into a gaseous stream
containing wide boiling range material from naphtha to heavy
gas oil and a liquid stream containing heavy oils,
d) recycling at least a portion of the above
liquid stream as part of the heavy hydroca~bon oil feed to
; the first hydrcracking zone,
e) passing the above gaseous stream together with
added hydrogen upwardly through a second vertical hydrocracking
zone containing a hydrogenating catalyst, this second hydrocracking
; 10 zone being maintained at a temperature between about 400 and 470C,
a pressure the same as the first hydrocracking zone and a space
velocity between about 0.5 and 1.5 volume of hydrocarbon oil
; per hour per volume of hydrocracking zone capacity,
f) removing from the top of this second hydrocracking
zone a second mixed effluent containing a gaseous phase comprising
hydrogen and vapourous hydrocarbons and a liquid phase, and
g) separating this second effluent in a low tempera-
ture - high pressure separator into a liquid product stream and
a gaseous stream comprising hydrogen with minor amounts of gaseous
hydrocarbons and impurities.
The process of this invention is particularly well
suited for the treatment of heavy oils having a large portion,
preferably at least 50% by volume, which boils above about 975F
and which contains a wide boiling range of materials from ~aphtha
through kerosene, gas oil and tar.
-` By mixing the charge stock and hydrogen together and
passing these upwardly through a vertical empty column in the
absence of catalyst under the conditions as set out above, it
has been found that the high molecular weight compounds hydro-
genate and/or hydrocrack into lower boiling ranges. For example,
in the case of Athabaska bitumen, about 80% of the material
boiling above 975F is converted to lower boiling materials.
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109~491
About 50~ of the sulfur and 15~ of the nitrogen are also
removed in this first stage.
The mixture of gas and liquid removed from the top
of the first stage is preferably separated in a hot separator
which is kept at the same temperature as the reactor. A
portion of heavy oil stream separated from the hot separator
is recycled into the first stage as part of the charge stock
with a portion of this recycled stream being drawn off to prevent
the build-up of metals and mineral matter within the first
10 stage reactor. The pitch (material boiling above 975F)
can be separated from the heavy oil purge. The pitch can either
be gasified or sold as a by-product.
The gaseous s~ream from the hot separator, contain-
ing wide boiling range materials, is sent directly to a
catalytic hydrocracking zone which again is a vertical zone,
! preferably in the form of a fixed bed catalytic reactor.
The pressure in the catalytic reactor is the same as the
first stage and this pressure is maintained through the separator
between the reactors. The gaseous stream from the hot separator
is preferably passed through the catalytic zone in an upward
flow with the size of the catalyst bed being adjusted to give
the space velocity between 0.5 and 1.5 hr 1 The temperature
within this zone is selected so as to meet desired product
specifications with fresh make up hydrogen being added to
maintain hydrogen purity.
Suitable hydrogenation catalysts include the oxides
and/or sulfides of cobalt, nickel, and molybdenum. These metals
may be supported on a base such as silica, alumina, magnesia or
mixtures of these.
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1094491
The upward flow through the catalytic hydrocracker is
particularly preferred because in this manner the naphtha leaves
the reactor fastest, followed by kerosene-range material and
; finally the gas-oil range material. This provides longer contact
time for heavier boiling materials.
The gases from the catalytic hydrocracker are separated
in a low temperature - high pressure separator and by using this
type of separator the gaseous stream obtained contains mostly
hydrogen with some impurities such as hydrogen sulfide and
10 light hydrocarbon gases. This gaseous stream is passed through .
a scrubber and recycled as part of the hydrogen feed to the
first hydrocracking stage. The recycled hydrogen gas purity
is maintained by adding make up hydrogen.
The liquid stream from the low temperature -;high
pressure separator represents the product of the present
process and it can be sent to a fractionator. There it can be
conveniently broken down into different fractions including a
naphtha fraction, a light gas oil fraction and a heavy gas oil
fraction. As has been pointed above, nitrogen is highly
2d poisonous to reforming catalysts and is also a pollutant. This
has made it necessary for naphtha feeds to be pretreated to
reduce nitrogen content below about 1 ppm before sending it to
` a catalytic reformer. With the procedure of the present inven-
tion, the naphtha fraction from the fractionator already has a
nitrogen level below 1 ppm and can be used without further
treatment as reformed feedstock. The light gas-oil and heavy
gas-oil fractions meet the fuel oils and catalytic cracking gas-
oil specifications respectively. Thus, the present inventions
~; eliminates the need for secondary refining of distillates in
separate stages.
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- 1094~91
According to an alternative feature of the present
invention, the above process sequence can be modified whereby
the gas - liquid mixture effluent from the first stage hydro-
craclcigg zone is fed directly to a catalytic hydrocracking unit
without separating the heavy bottoms. Although the high boiling
materials such as asphaltenes and metal complexes are well known
to poison the hydrocracking catalyst, the first stage hydrocracking
of the present invention has been found to be capable of converting
sufficient of the pitch into lower boiling fractions, that the life
10 of the catalyst is considerable extended. Again with this
procedure~ the gases from the catalytic hydrocracking unit are
separated in a low-temperature, high-pressure separator and the
liquid component is sent to a fractionator.
For a better understanding of the invention, reference
is made to the accompanying drawing which illustrates diagra-
1 matically a preferred embodiment of the present invention.
Hydrocarbon oil feed 10 together with recycled hydrogen
, and make up hydrogen from line 11 is introduced through oil-heater
12 into the bottom of an empty tower 13. A gas-liquid mixture is
withdrawn from the top of the tower through line 14 and introduced
into a hot separator 15 in which the temperature is maintained at
that of the outlet of tower 13. In the hot separator 15 the
effluent from tower 13 is separated into a gaseous stream lô and
a liquid stream 16. The liquid stream 16 is in the form of heavy
pitch bottoms and this is recycled into the oil in feed line 10
with a portion of the recycle being drawn off through line 17.
The gaseous stream from hot separator 15 is carried by
; way of line 18 into the bottom of a catalyst tower 19 which
contains a hydrogenation catalyst. This gaseous stream travels
upwardly through tower 19 together with hydrogen being added
through line 20.
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1094491
The effluent from the catalyst tower 19 is drawn off at
the top through line 21 and is fed into a high pressure - low
temperature separator 22. Within this separator the product is
separated into a gaseous stream rich in hydrogen which is drawn
off through line 24. This hydrogen rich stream is passed through
scrubber 25 and is combined with fresh make up hydrogen added
through line 28 and recycled through gas compressor 27 and
line 11 back to tower 13.
The liquid stream from separator 22 represents the
final product of the invention and is drawn off through line
23 aad can be fed to a fractionator, etc.
EXAMPLE
The charge stock employed was an Athabaska bitumen
having the following characteristics:
I. Specific gravity, 60/60F 1.009
2. Sulphur, % by wt 4.48
3. Ash, % by wt 0.59
4. Conradson Carbon Residue,
% by wt 13.3
5. Pentane Insolubles, % by wt 15.5
: 20
6. Benzene Insolubles, % by wt 0.72
7. Vanadium content, PPM by wt 213
~ 8. Nickel content, PPM by wt 67
: 9. Total Acid number 2.77
10. Total Base number 1.89
11. Carbon, %-by wt 83.36
12. Hydrogen, % by wt10.52
`~ 13. Nitrogen, % (Dohrmann micro-
coulometer) 0.43
~ 14. Oxygen, % - ----
:` 30 15. Chlorine, % 0.00
16. Viscosity at 210F
kinematic centispokes 133.3
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10!~491
The above feed stock was passed through a reaction
sequence as shown in the attached drawing, with the operating
conditions in the first hydrocracking tower being as follows:
Pressure = 2000 psig
Temperature = 450C
Space velocity = 1.0 hr (4500 gms/hr)
Hot separator
temperature = 450C
Hydrogen = 5000 c.ft/bbl
Recycle oil = 9060 gms/hr
The second stage catalytic hydrocracking was
; simulated using a bench scale reactor unit. The reactor contained
as catalyst a product available from Harshaw Chemical Co. under
- the designation Ho. HT 400 E. It contains 3 wt. % CoO and
15 wt % MoO3 supported on an alumina base. The operating
conditions in the reactor were as follows:
~- Pressure = 2000 psig
Temperature = 400 to 450C
Space velocity = 1 hr
20,
Hydrogen = 5000 c.ft/bbl
The gas stream collected from separator 15 and fed
to the catalytic hydrocracking reactor had the following
properties:
Boiling range = IBP to 950F
Specific gravi-ty
60/60F = 0.872
Sulphur, wt % = 1.97
Nitrogen, ppm = lg50
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1094~1
\
Distilled Fractions:
Naphtha (IBP to 400F)
Content, vol % = 32.7
Specific gravity,
60/60F = 0.768
Sulphur, wt % = 0.88
Nitrogen, ppm = 575
Light Gas Oil (400 to 650F)
Content, vol % = 46.0
Specific gravity,
60!60F = 0.897
Sulphur, wt ~ = 2.18
Nitrogen, ppm = 1404
Heavy Gas Oil (650 to 950F)
Content, vol % = 21.3
; Specific gravity,
60/60F = 0-991
Sulphur, wt % = 2.82
Nitrogen, ppm = 4542
The liquid product from the bench scale reactor
(from separator 22 and collected by line 23 in the actual
process) had the following properties:
Specific gravity,
60/60F = 0-825
Sulphur, wt % = 0-15
Nitrogen, ppm = 15
Distilled Fractions: -
Naphtha (IBP - 400F)
Content, vol % = 40-6
Specific gravity,
60/60F = 0-764
Sulphur, wt % = 0.04
; Nitrogen, ppm = 0-5
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Light Gas Oil (400 - 650F)
Content, vol % = 52.8
Specific gravity,
; 60/60F = 0.867
Sulphur, wt % = 0.06
Nitrogen, ppm = 10
Heavy Gas Oil (650 - 950F)
Content, vol % = 6.6
Specific gravity,
60160F = O. 901
Sulphur, wt % = --~~~
rogen, pp~ = 99
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