U.S. patent number 3,894,933 [Application Number 05/457,311] was granted by the patent office on 1975-07-15 for method for producing light fuel oil.
This patent grant is currently assigned to Mobil Oil Corporation. Invention is credited to Hartley Owen, Paul B. Venuto.
United States Patent |
3,894,933 |
Owen , et al. |
July 15, 1975 |
Method for producing light fuel oil
Abstract
A dual riser cracking operation of restricted hydrocarbon
conversion is described wherein an intermediate fuel oil product of
cracking higher boiling than the desired light fuel oil product is
recovered and recracked in a first riser cracking zone in the
presence of freshly regenerated catalyst and catalyst separated
from the gasiform product of the first riser cracking zone is used
in admixture with freshly regenerated catalyst in a second riser to
crack higher boiling hydrocarbon charge in the presence of heavy
recycle oil product under restricted conversion conditions to
desired light fuel oil product. The riser may discharge into the
lower portion of a dense fluid bed of catalyst.
Inventors: |
Owen; Hartley (Belle Mead,
NJ), Venuto; Paul B. (Cherry Hill, NJ) |
Assignee: |
Mobil Oil Corporation (New
York, NY)
|
Family
ID: |
23816232 |
Appl.
No.: |
05/457,311 |
Filed: |
April 2, 1974 |
Current U.S.
Class: |
208/77; 208/68;
208/70; 208/74; 208/76; 208/95 |
Current CPC
Class: |
C10G
51/026 (20130101); C10G 11/18 (20130101) |
Current International
Class: |
C10G
11/18 (20060101); C10G 11/00 (20060101); C10G
51/00 (20060101); C10G 51/02 (20060101); C10g
037/06 (); C01b 033/28 () |
Field of
Search: |
;208/77,95 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gantz; Delbert E.
Assistant Examiner: Schmitkons; G. E.
Attorney, Agent or Firm: Huggett; Charles A. Farnsworth;
Carl D.
Claims
We claim:
1. A method for producing light cycle oil from higher boiling
hydrocarbon feed materials which comprises,
passing a relatively high boiling hydrocarbon feed material with a
cracking catalyst of limited activity through a first conversion
zone maintained under conditions to limit conversion of the
hydrocarbon feed to gasoline and lower boiling products,
recovering a hydrocarbon phase from said first conversion zone and
separating in a fractionation zone said hydrocarbon phase into a
desired light fuel oil product, an intermediate cycle oil product
and a higher boiling cycle oil product,
passing said higher boiling cycle oil product to said first
conversion zone,
passing said intermediate cycle oil product to a second conversion
zone for contact with a cracking catalyst of limited activity under
limited conversion conditions particularly selected to produce
light fuel oil product, and recovering said light fuel oil product
in said fractionation zone,
passing catalyst separated from said second conversion zone to said
first conversion zone, and
reducing the pour point of said light fuel oil product recovered
from said conversion operations by contact with a ZSM-5 type of
crystalline zeolite.
2. The method of claim 1 wherein the hydrocarbon conversion steps
are restricted not to exceed about 30 volume percent in each
zone.
3. The method of claim 1 wherein the activity of the catalyst
employed in the conversion steps is restricted to within the range
of 15 to 50 FAI.
4. The method of claim 1 wherein hot regenerated catalyst is passed
to each of said conversion zones.
5. The method of claim 1 wherein each of said conversion zones
comprises at least a riser conversion zone and the hydrocarbon
residence time within the first conversion zone is restricted to
within the range of 2 to 60 seconds.
6. The method of claim 1 wherein the catalyst of selected and
limited activity is made from catalyst components selected from the
group comprising amorphous silica alumina, crystalline zeolites of
the faujasite type and mixtures thereof in combination with one or
more of a ZSM-5 type of crystalline aluminosilicate and a mordenite
type of crystalline zeolite.
7. The method of claim 1 wherein the intermediate cycle oil product
of cracking used as feed in the second conversion zone boils in the
range of about 550.degree.F. up to about 800.degree.F.
8. The method of claim 1 wherein the light fuel oil product of the
hydrocarbon conversion zones boils in the range of 320.degree.F. to
about 700.degree.F. and contact thereof with the ZSM-5 type
catalyst reduces its pour point to within the range of -30.degree.
to about 15.degree.F.
9. The method of claim 1 wherein each of said conversion zones
comprises a riser conversion zone discharging into a fluid bed of
catalyst before separation of a hydrocarbon phase from a catalyst
phase is effected.
10. A method for producing light fuel oil product of desired pour
point which comprises,
separating an intermediate cycle oil product of cracking higher
boiling than desired fuel oil product obtained as hereinafter
defined,
recracking said separated intermediate cycle oil product in a first
riser cracking operation in the presence of freshly regenerated
catalyst of restricted activity under conditions selected to
restrict conversion thereof to less than 30 vol. percent,
separating the product of said recracking operation to recover a
hydrocarbon phase from a first catalyst phase and passing said
hydrocarbon phase to a product fractionation zone,
passing catalyst from said first catalyst phase to a second riser
conversion zone, passing freshly regenerated catalyst along with
fresh gas oil feed and heavy cycle oil product of cracking to said
second riser cracking zone,
effecting cracking of the hydrocarbon feed passed to said second
riser cracking operation under conversion condition restricted to
less than about 40 vol. percent,
separating the product of said second riser cracking operation into
a hydrocarbon phase and a second catalyst phase, passing the
hydrocarbon phase to said product fractionation zone, and
reducing the pour point of a light cycle oil separated from the
product of cracking operation by contacting a ZSM-5 type of
crystalline zeolite under selected conversion conditions.
Description
BACKGROUND OF THE INVENTION
The cracking of hydrocarbon charge stocks comprising gas oils and
higher boiling residual material in the presence of finely divided
catalyst particles has been a part of the petroleum refining
procedure since the early forties. The cracking operations were for
the purpose of producing gasoline along with lower and higher
boiling products. It was also contemplated effecting the cracking
operation in stages so that in one stage a more suitable feed could
be produced for use in a latter hydrocarbon conversion stage. Such
an operation including a restricted conversion operation is
disclosed in the prior art of Jewell U.S. Pat. No. 2,882,218. In
recent years crystalline aluminosilicate containing cracking
catalysts have been developed and used for effecting cracking
operations particularly for the production of gasoline as well as
higher boiling products of the cracking operation. The present
invention is concerned with the processing of crude oil
distillation products in a novel combination of operating steps
under conditions designed to particularly improve the recovery of
desired light fuel oil product.
SUMMARY OF THE INVENTION
The present invention is concerned with an arrangement and
combination of processing steps for producing a light fuel oil
product. More particularly, the present invention is concerned with
a limited hydrocarbon conversion operation and combination of
processing steps particularly arranged to substantially maximize
the production of light fuel oils boiling in the range of
320.degree.F. up to about 700.degree.F. from higher boiling gas oil
type feed material separated from crude oil. In yet another aspect,
the present invention is concerned with a dual riser hydrocarbon
conversion operation maintained under particularly restricted
hydrocarbon conversion conditions in the presence of cracking
catalysts of selected activity. In the combination operation of
this invention, a relatively light cycle oil product of the
cracking operation generally higher boiling than the desired light
fuel oil product and hereinafter referred to as a light
intermediate cycle oil boiling from about 550.degree.F. up to about
800.degree.F. is selectively recracked in the presence of a freshly
regenerated cracking catalyst under severely restricted or limited
hydrocarbon conversion conditions not exceeding and preferably less
than about 30 volume percent conversion. The freshly regenerated
catalyst so used is thereafter stripped to remove entrained
hydrocarbons and then cascaded to a second riser conversion zone
along with added freshly regenerated cracking catalyst for
conversion of fresh high boiling feed material such as a gas oil
and higher boiling range materials under cracking conditions
selected to restrict conversion thereof not to exceed about 40
percent and preferably the conversion is restricted to less than
about 30 percent. Residual oils, atmospheric and vacuum reduced
crude may be used with or in place of the gas oil feed.
In the combination operation comprising this invention, a light
intermediate cycle oil (ICO) product of a restricted or limited
hydrocarbon conversion or cracking operation and boiling in the
range of about 550.degree.F. up to about 800.degree.F. is subjected
to a restricted catalytic recracking operation in a first riser
reactor wherein the conversion is restricted to less than about 30
volume percent and preferably less than 20 volume percent. In this
operation, the light intermediate cycle oil feed is admixed with
hot freshly regenerated cracking catalyst of selected activity to
form a suspension providing a catalyst/oil ratio in the range of
about 2 to 10 and more usually less than about 8. The suspension is
formed to provide a temperature less than about 950.degree.F. and
preferably the suspension temperature is within the range of
850.degree.F. to about 900.degree.F. The thus formed suspension is
provided a hydrocarbon residence time in a riser conversion zone
within a range of 2 seconds up to about 2 minutes before
encountering cyclonic separation. Thus, the riser reactor may
discharge into the lower portion of a dense fluid bed of catalyst
to provide increased residence time if desired. The longer
residence time is particularly desired when the cracking catalyst
includes ZSM-5 type of crystalline zeolite as an active
component.
The catalyst is separated preferably by cyclonic means from the
product of the intermediate cycle oil conversion operation and
after stripping of the catalyst with gasiform material to remove
entrained hydrocarbons, the stripped catalyst is cascaded to the
inlet of a second riser conversion zone more fully discussed
below.
In the second riser conversion zone, the high boiling fresh feed
plus any cycle oil boiling heavier than the intermediate cycle oil
is combined with the previously used and cascaded catalyst combined
with freshly regenerated catalyst to form a second suspension
thereof at an elevated temperature providing a catalyst/oil ratio
within the range of 4 to about 15. The oil-feed-catalyst mixture
thus formed in the second riser is maintained at a temperature
within the range of 850.degree.F. to about 950.degree.F. during
passage upwardly through the second riser conversion zone. A
hydrocarbon residence time within the range of 2 to about 60
seconds in conjunction with the other operating parameters herein
referred to restricts conversion of the heavy hydrocarbon feed to
gasoline and lower boiling products not to exceed about 30 volume
percent conversion and more usually not to exceed about 20 volume
percent conversion. In the event, however, a more prolonged
residence time for the gas oil conversion step is desired beyond
that provided in the riser reactor, the second riser reactor may
also discharge into a dense fluid bed of catalyst.
The catalyst compositions of desired and selected activity
characteristics which may be employed in the combination operation
of this invention may be formed from a number of different catalyst
materials known in the art. That is, the catalyst may be an
amorphous silica-alumina catalyst, a crystalline silica-alumina
catalyst or preferably a crystalline zeolite catalyst of the "X" or
"Y" type of faujasite. The faujasite and amorphous cracking
components may be admixed with one another or either one or both of
the larger pore materials may be mixed with a zeolite of a smaller
pore size than the faujasite crystalline zeolite. In particular
they may be mixed with either a ZSM-5 type of crystalline zeolite
or a mordenite type of crystalline zeolite or a combination of each
may be employed in relatively small amounts not exceeding and
usually less than about 10 wt. percent.
Thus, it is contemplated employing catalyst compositions of
restricted activity as measured by the fluid activity index (FAI)
test within the range of from about 15 up to about 50 FAI. The FAI
test is defined as the conversion obtained to a 356.degree.F. at 90
percent ASTM gasoline product processing a light cost Texas gas oil
at a temperature of 850.degree.F., 2 c/o, 6 WHSV for 5 minutes on
stream time.
In the table below various catalyst compositions are shown which
were tested and found to be suitable for use in the combination
operation of the present invention.
______________________________________ Catalyst FAI Wt.% C Vol.%
Conv. on Cat ______________________________________ Silica + 10%
Al.sub.2 O.sub.3 Steamed at 1450.degree. F. 22.7 0.16 Silica + 25%
Al.sub.2 O.sub.3 Steamed at 1400.degree. F. 31.5 0.35 2% REY on
Silica-clay- zirconia matrix 40.0 0.104 2% REY + 2% ZSM-5 on
silica-clay-zirconia matrix 40.9 0.10 2% REY + 10% ZSM-5 on
silica-clay-zirconia matrix 48.5 0.17 2% HZSM-5 17.7 0.06 2% REY +
2% H mordenite 41.4 0.094 2% REY + 10% H mordenite 38.6 0.095
______________________________________
BRIEF DESCRIPTION OF THE DRAWING
The drawing is a diagrammatic sketch in elevation of a dual riser
conversion system with product fractionator and interconnecting
conduit means for practicing the concepts of the invention.
DISCUSSION OF SPECIFIC EMBODIMENTS
Referring now to the drawing by way of example, there is shown a
dual riser conversion system and related downstream steps for
producing light cycle oil of desired pour point. In the arrangement
of the drawing, an intermediate cycle oil product of the restricted
conversion operation and boiling the the range of from about
550.degree.F. up to about 800.degree.F. is recovered from the
product fractionation tower and passed by conduit 2 to riser
conversion zone 4 of the dual riser conversion operation. Hot
freshly regenerated catalyst is introduced to the lower portion of
riser 4 by conduit 6 containing flow control valve 8. The freshly
regenerated catalyst thus introduced is admixed with the recycled
intermediate cyclo-oil product of cracking to form a relatively
dilute suspension therewith at a temperature restricted to within
the range of about 850.degree.F. to about 900.degree.F. The
suspension at a catalyst to oil ratio within the range of 2 to 10
is caused to pass through the riser conversion zone to separation
means provided adjacent, if not on, the discharge end thereof. In
riser conversion zone 4, the hydrocarbon residence time is
restricted to within the range of 2 to about 10 seconds but may be
extended by discharging the riser into the lower portion of a dense
fluid bed of catalyst. Conversion of the intermediate cycle oil to
gasoline and lower boiling hydrocarbons is limited to less than 30
percent and preferably less than 20 percent.
The suspension passed through riser 4 discharges, when not passed
into a dense fluid bed of catalyst, into cyclonic separation zone
10 wherein gasiform hydrocarbon material is separated from
entrained catalyst particles. Separated hydrocarbons are passed
overhead by conduit 12 to plenum chamber 14. Separated catalyst
particles are passed from separator 10 by dipleg 16 to a bed of
catalyst 18. Catalyst bed 18 is separated from an adjacent bed of
catalyst discussed below by a vertical baffle member 20. The
catalyst comprising bed 18 is stripped with stripping gas
introduced by conduit 22 as the catalyst moves generally downward
through a stripping zone 24 provided in the lower portion of vessel
26. Stripped catalyst is withdrawn from a lower portion of
stripping zone 24 by conduit 28 provided with a flow control valve
30. The catalyst in conduit 28 is combined with freshly regenerated
catalyst in conduit 32 provided with flow control valve 34. The
catalyst stream thus formed is passed to the lower portion of a
second riser conversion zone 36 to which fresh feed is introduced
by conduit 38.
In the combination operation of this invention a heavy cycle oil
product of the restricted conversion operation is recycled to the
lower portion of riser 36 by conduit 40 for admixture with fresh
gas oil feed.
In the lower portion of riser conversion zone 36, a suspension of
catalyst particles in relatively heavy hydrocarbon feed material,
such as gas oils and heavy cycle oil, is formed having a
temperature within the range of 850.degree.F. to about
1100.degree.F. and a catalyst to oil ratio within the range of 5 to
about 20. A relatively inert gasiform material such as steam or
light gaseous products of cracking may be combined with the heavy
feeds passed to riser 36 to assist with vaporizing and mixing the
oil charge with catalyst particles. In conversion zone 36,
conversion of the high boiling feed materials is restricted to
below an upper limit of about 30 percent, it being preferred to
restrict the level of conversion to be less than about 20 percent.
A space velocity within the range of 50 to about 200 v/v/hr. may be
employed in cooperation with a selected temperature and catalyst to
oil ratio so as to limit conversion of the oil charge as herein
provided. The suspension is passed upwardly through riser 36 and
into cyclonic separating means 42 when a dense fluid bed of
catalyst is not employed, provided on the discharge end of riser
36. Gasiform hydrocarbon material separated from the catalyst is
passed from separator 42 by conduit 44 to plenum 14. Separated
catalyst particles are passed by dipleg 46 to a bed of catalyst 48
confined within a separate stripping section 50 in the lower
portion of vessel 26. Catalyst bed 48 is separated from catalyst
bed 18 by vertical baffle 20. Stripping gas is introduced to a
lower portion of bed 48 by conduit 52 for flow upwardly through the
descending bed of catalyst.
Stripped products of hydrocarbon conversion and stripping gas
removed from the upper surfaces of catalyst beds 18 and 48 pass
upwardly through the vessel 26 to cyclone separation means 54
wherein stripped hydrocarbons and stripping gases are separated
from any entrained catalyst particles. Separated catalyst is
returned by dipleg 56 to a bed of catalyst shown to be bed 18 and
vaporous material is passed by conduit 58 to plenum 14.
The hydrocarbons separated from catalyst and passed to plenum
chamber 14 are removed therefrom by conduit 60 communicating with a
fractionation tower 62. In fractionation zone 62 a separation is
made to recover materials lower boiling than desired light fuel oil
product from an upper portion thereof by conduit 64. The material
withdrawn by conduit 64 and comprising gasoline and lower boiling
hydrocarbons may be separated in equipment not shown into desired
components for further treatment as desired.
A light fuel oil product boiling in the range of 320.degree.F. to
about 750.degree.F. and preferably in the range of 400.degree.F. to
about 675.degree.F. is withdrawn by conduit 64 communicating with
zone 68 wherein the light fuel oil pour point is improved by
contact with a ZSM-5 type of crystalline zeolite conversion
catalyst. In zone 68, the ZSM-5 catalyst retained as a fluid bed of
catalyst at a temperature in the range of 500.degree. to
850.degree.F. and a pressure in the range of 50 to 100 psig reduces
the pour point of the light fuel oil charge depending upon the
severity of the operation employed to within a range of -30.degree.
to about +15.degree.F. Light fuel oil of desired reduced pour point
is withdrawn by conduit 70. Recently issued U.S. Pat. No. 3,702,886
describing and claiming ZSM-5 type crystalline aluminosilicate is
incorporated herein by reference.
A relatively sloppy intermediate cycle oil fraction boiling in the
range of from about 550.degree.F. to about 800.degree.F. is
withdrawn from the fractionator 62 by conduit 72 communicating with
conduit 2 and is recycled as the feed to the first riser conversion
zone as discussed above.
A heavy cycle oil product fraction boiling in the range of
600.degree.F. to about 950.degree.F. is withdrawn from fractionator
62 by conduit 74. All or a portion of this heavy cycle oil may be
recycled by conduit 40 for admixture with the fresh feed as herein
provided.
A clarified slurry oil fraction is withdrawn from a bottom portion
of lower 62 by conduit 76.
In the arrangement of the drawing, the lower portion of vessel 26
is shown separated by baffle 20 into two separate stripping zones
24 and 50. Stripped catalyst is withdrawn from the lower portion of
zone 50 containing catalyst bed 48 by conduit 78 provided with flow
control valve 80 for passage to a catalyst regeneration zone not
shown wherein deposited carbonaceous material more often referred
to as coke is removed from the catalyst by burning thereby heating
the catalyst to a desired elevated temperature within the range of
1,200.degree. to 1400.degree.F. The catalyst thus heated is then
available for use and return to the riser conversion zones by
conduits 6 and 32 as shown. In the catalyst system of this
invention it is contemplated discharging each riser or either one
into the lower portion of a catalyst bed for flow upwardly
therethrough as herein before provided, or employing a single bed
of catalyst collected from each riser conversion zone in a
stripping zone from which catalyst is cascaded to both the
regeneration zone as well as the second riser conversion zone. In
this latter arrangement, a desired relatively high catalyst to oil
ratio may be provided for promoting a restricted conversion of the
oil charged to the riser.
It is also contemplated using the dual riser conversion operation
herein defined so that the fresh gas oil feed rather than the
intermediate light fuel oil is passed to riser 1 for contact with
freshly regenerated catalyst, the intermediate cycle oil product
rather than fresh feed is passed to riser 2 for contact with a
catalyst mixture which is primarily freshly regenerated catalyst.
It is contemplated employing a single bed catalyst stripping zone
with provisions for recycling catalyst to either riser for
adjustment of catalyst to oil ratio and temperature best suited for
performing the restricted conversion operation of this invention.
In any of the arragements employed, it is important to recrack the
intermediate cycle oil separately under conversion conditions
preferably limited to less than 20 percent conversion. On the other
hand, the heavy cycle oil may be processed with the fresh feed
passed to the combination operation whether it be a gas oil or
higher boiling residual material as herein contemplated.
In addition, feed preheat may be practiced on feed passed to either
riser up to the maximum allowable before substantial thermal
cracking of the feed occurs.
Having thus generally described the method and concepts of the
present invention and discussed specific embodiments going to the
very essence thereof, it is to be understood that no undue
restrictions are to be imposed by reason thereof except as defined
by the following claims.
* * * * *