U.S. patent application number 12/256561 was filed with the patent office on 2009-02-19 for multi-stage hydrocracker with kerosene recycle.
This patent application is currently assigned to Chevron U.S.A. Inc.. Invention is credited to Arthur J. Dahlberg, Jay B. Parekh, H. Alex Yoon.
Application Number | 20090045100 12/256561 |
Document ID | / |
Family ID | 40362121 |
Filed Date | 2009-02-19 |
United States Patent
Application |
20090045100 |
Kind Code |
A1 |
Yoon; H. Alex ; et
al. |
February 19, 2009 |
MULTI-STAGE HYDROCRACKER WITH KEROSENE RECYCLE
Abstract
This invention relates to a multi-stage process for
hydroprocessing gas oils. Preferably, each stage possesses at least
one hydrocracking zone. The second stage and any subsequent stages
possess an environment having a low heteroatom content. Light
products, such as naphtha, kerosene and diesel, may be recycled
from fractionation (along with light products from other sources)
to the second stage (or a subsequent stage) in order to produce a
larger yield of lighter products, such as gas and naphtha. Pressure
in the zone or zones subsequent to the initial zone is from 500 to
1000 psig lower than the pressure in the initial zone, in order to
provide cost savings and minimize overcracking.
Inventors: |
Yoon; H. Alex; (Richmond,
CA) ; Parekh; Jay B.; (Castro Valley, CA) ;
Dahlberg; Arthur J.; (Benicia, CA) |
Correspondence
Address: |
CHEVRON CORPORATION
P.O. BOX 6006
SAN RAMON
CA
94583-0806
US
|
Assignee: |
Chevron U.S.A. Inc.
San Ramon
CA
|
Family ID: |
40362121 |
Appl. No.: |
12/256561 |
Filed: |
October 23, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12138384 |
Jun 12, 2008 |
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12256561 |
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10922413 |
Aug 19, 2004 |
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12138384 |
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10162774 |
Jun 4, 2002 |
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10922413 |
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Current U.S.
Class: |
208/59 |
Current CPC
Class: |
C10G 65/10 20130101;
C10G 65/12 20130101 |
Class at
Publication: |
208/59 |
International
Class: |
C10G 65/12 20060101
C10G065/12 |
Claims
1. A method for hydroprocessing a hydrocarbon feedstock, wherein
the amount of naphtha product boiling in the range from
170.degree.-350.degree. F. is maximized, the method employing
multiple hydroprocessing zones within a single reaction loop
wherein at least one bed in each hydroprocessing zone contains
hydrocracking catalyst, wherein the pressure in the subsequent zone
or zones is from 500 to 1000 psig lower than the pressure in the
initial zone in order to provide cost savings and minimize
overcracking, said method comprising the following steps: (a)
passing a hydrocarbonaceous feedstock to a first hydroprocessing
zone having one or more beds containing hydroprocessing catalyst,
said catalyst comprising a cracking component and a hydrogenation
component, wherein the cracking component is selected from the
group consisting of Y, USY, REX and REY zeolites, the
hydroprocessing zone being maintained at hydroprocessing
conditions, wherein the feedstock is contacted with catalyst and
hydrogen to produce a vapor stream and a liquid stream as effluent;
(b) removing the vapor stream of step (a), which comprises
hydrogen, hydrogen sulfide and light hydrocarbonaceous gases
overhead; (c) combining the liquid stream of step (b) with the
liquid effluent from other hydroprocessing zones; (d) passing the
liquid stream of step (c), which comprises hydrocarbonaceous
compounds boiling in approximately the same range of the
hydrocarbonaceous feedstock, to fractionation; (e) separating the
liquid stream of step (d), in fractionation, into gas, naphtha,
kerosene and diesel fractions, in addition to the bottoms fraction;
(f) passing the bottoms fraction of step (e) to further processing
or recycling to one or more of the other hydroprocessing zones of
step (c); (g) passing one or more of the naphtha, kerosene and
diesel fractions to further processing as products or recycling one
or more of the fractions to one or more of the other
hydroprocessing zones of step (c), the kerosene, naphtha or diesel
fractions being in combination with kerosene, naphtha or diesel
fractions from other sources, said hydroprocessing zone or zones
being maintained at hydroprocessing conditions and at a pressure
that is 500 to 1000 psig lower than the initial hydroprocessing
zone, and possessing an environment substantially free of H.sub.2S,
NH.sub.3, or other heteroatom contaminants; (h) passing the
effluent of step (g) to fractionation; (i) recovering in
fractionation an increased amount of gas and naphtha, and a
decreased amount of kerosene, in the fractionation stage of step
(h) than in the fractionation step of step (e).
2. The process of claim 1, wherein at least one bed in each
hydroprocessing zone contains hydrocracking catalyst.
3. The process of claim 1, wherein the hydroprocessing conditions
of claim 1, step (a), and claim 1, step (g), comprise a reaction
temperature of from 400.degree. F.-950.degree. F. (204.degree.
C.-510.degree. C.), a reaction pressure in the range from 500 to
5000 psig (3.5-34.5 MPa), an LHSV in the range from 0.1 to 15
hr.sup.-1 (v/v), and hydrogen consumption in the range from 500 to
2500 scf per barrel of liquid hydrocarbon feed (89.1-445
m.sup.3H.sub.2/m.sup.3 feed).
4. The process of claim 3, wherein the hydroprocessing conditions
of claim 1, step (a), and claim 1, step (g), preferably comprise a
temperature in the range from 650.degree. F.-850.degree. F.
(343.degree. C.-454.degree. C.), reaction pressure in the range
from 1500-3500 psig (10.4-24.2 MPa), LHSV in the range from 0.25 to
2.5 hr.sup.-1, and hydrogen consumption in the range from 500 to
2500 scf per barrel of liquid hydrocarbon feed (89.1-445
m.sup.3H.sub.2/m.sup.3 feed).
5. The process of claim 1, wherein the feed to claim 1, step (a),
comprises hydrocarbons boiling above 392.degree. F.(200.degree.
C.).
6. The process of claim 5, wherein the feed is selected from the
group consisting of vacuum gas oil, heavy atmospheric gas oil,
delayed coker gas oil, visbreaker gas oil, demetallized oils, FCC
light cycle oil, vacuum residua deasphalted oil, Fischer-Tropsch
streams, and FCC streams.
7. The process of claim 1, wherein the hydrogenation component is
selected from Group VI, Group VII or Group VIII metals.
8. The process of claim 7, wherein the hydrogenation component is
selected from the group consisting of Ni, Mo, W, Pt and Pd or
combinations thereof.
9. The process of claim 7, wherein the Group VI, Group VII or Group
VIII metals may exist as either sulfides or oxides.
10. The process of claim 7, wherein the hydrogenation component
comprises 5 to 40 wt % of the catalyst.
11. The process of claim 8, wherein noble metals comprise from
about 0.1 wt % to about 2 wt % of the catalyst.
12. The process of claim 1, wherein the zeolitic component has a
SiO.sub.2/Al.sub.2O.sub.3 molecular ratio in the range from 3
through 60.
13. The process of claim 12, wherein the SiO.sub.2/Al.sub.2O.sub.3
molecular ratio is in the range from 5 through 20.
14. The process of claim 1, wherein the zeolitic component has a
unit cell size in the range from 24.25 through 24.60.
15. The process of claim 14, wherein the zeolitic component has a
unit cell size in the range from 24.30 through 24.55.
Description
[0001] This application is a continuation-in-part of the copending
application Ser. No. 12/138,384 filed Jun. 12, 2008. Ser. No.
10/922,413 now abandoned was filed Aug. 19, 2004, and is a
continuation-in-part of 10/162,774, filed Jun. 4, 2002.
FIELD OF THE INVENTION
[0002] This invention relates to a multi-stage hydrocracking
process in which light products from the first stage, such as
naphtha, kerosene and diesel, are joined with naphtha, kerosene and
diesel from other sources and recycled from fractionation to a
second stage (or subsequent stage) hydrocracker in order to produce
lighter products, such as gas and naphtha.
BACKGROUND OF THE INVENTION
[0003] Historically, there has been little interest in cracking
kerosene or other light products to even lighter products. In the
United States, there is little demand for gas or other very light
volatile products. Bottoms materials are usually the material
recycled in two-stage hydrocracking as practiced in the United
States. There is, however, a demand for products such as LPG and
LNG in Asia.
[0004] Although there has been demand for very light products in
some parts of the world, there was a belief by many experts that
light products would not crack in most reactors (using conventional
hydrocracking catalysts as opposed to FCC catalysts) because they
are in the vapor phase as opposed to the liquid phase. This belief
apparently originated due to the fact that the environment in a
single-stage hydrocracker, in the presence of H.sub.2S and
NH.sub.3, is not conducive to cracking of light products.
[0005] The concept of recycling bottoms material back to an initial
hydrocracking stage (rather than a second hydrocracking stage) is
well known. U.S. Pat. No. 6,261,441 (Gentry et al.) discloses
recycling of bottoms material which has been hydrocracked and
dewaxed back to a hydrocracker.
[0006] U.S. Pat. No. 5,447,621 (Hunter) discloses a middle
distillate upgrading process. A middle distillate side stream of a
conventional single-stage hydrocracking process is circulated to a
hydrotreating stage, such as an aromatics saturation reactor and/or
a catalytic dewaxing reactor in order to effect middle distillate
upgrade. The upgraded product is then finished in a fractionation
stage side-stripper column. This invention discloses passing middle
distillate to a hydrotreating stage. The middle distillates are
being upgraded, not cracked, as in the instant invention.
[0007] U.S. Pat. No. 4,789,457 (Fischer et al.) discloses a process
in which a highly aromatic substantially dealkylated feedstock is
processed directly to high octane gasoline by hydrocracking over a
catalyst preferably comprising a large pore zeolite such as zeolite
Y, in addition to a hydrogenation-dehydrogenation component. The
feedstock is preferably a light cycle oil. Light cycle oil is
heavier than the kerosene and naphtha cracked in the instant
invention, and only one hydrocracking stage is employed in Fischer
et al.
[0008] U.S. Pat. No. 3,037,930 (Mason) is directed to a two stage
conversion process for the production of aromatic product
fractions. High pressure separators are employed following both the
first and second conversion zones. There is no teaching or
suggestion of the maintenance of subsequent zones at lower
pressures, as seen in the instant invention. Mason teaches recycle
of bottoms from fractionation back to the first conversion zone and
recycle of lighter materials to other conversion zones. In the
instant invention bottoms are recycled to the second conversion
zone from fractionation, as are lighter fractions at times as well.
Mason does not contemplate the use of a zeolite hydrocracking
catalyst. Mason sends bottoms back to the first conversion zone in
order to maximize aromatics. Mason employs an amorphous
hydrocracking catalyst and does not contemplate the use of
zeolites.
[0009] The goal of Mason is to produce aromatic hydrocarbon
containing product fractions.
[0010] U.S. Pat. No. 4,921,595 (Gruia) teaches passing fractionator
bottoms back to the first zone or to hydrogenation or the second
zone. Although Gruia employs a hydrocracking catalyst which
comprises zeolite Y, the feed employed is composed of polynuclear
aromatics. The goal in Gruia is to prevent condensation reactions
resulting from heavy feed. The goal in the instant invention is to
maximize the amount of product in the naphtha range that is
produced.
SUMMARY OF THE INVENTION
[0011] The Applicants have found that in the environment of a clean
second-stage hydrocracker, with heteroatoms removed, light products
will crack. The examples demonstrate that the net yield of kerosene
decreased when recycled to the second stage on a raw feed blend
basis, while the qualities of the middle distillates remained the
same. Recycling the kerosene to the second stage increased the
yield of 170-350.degree. F. reformer naphtha, the product most
highly valued by the customer.
[0012] The invention disclosed herein is a process for the
production of light products, such as gas and naphtha, by
processing kerosene in a second stage (or a subsequent stage) of a
multi-stage hydrocracker. Kerosene, diesel and naphtha from other
sources are included in the recycle, and subsequent hydroprocessing
stages are maintained at lower pressures than the initial
hydroprocessing stage. This results in cost savings.
[0013] The instant invention is summarized as follows:
[0014] A method for hydroprocessing a hydrocarbon feedstock,
wherein the amount of naphtha product boiling in the range from
170.degree.-350.degree. F. is maximized, the method employing
multiple hydroprocessing zones within a single reaction loop
wherein at least one bed in each hydroprocessing zone contains
hydrocracking catalyst, and wherein the pressure in the subsequent
zone or zones is from 500 to 1000 psig lower than the pressure in
the initial zone in order to provide cost savings and minimize
overcracking, said method comprising the following steps: [0015]
(a) passing a hydrocarbonaceous feedstock to a first
hydroprocessing zone having one or more beds containing
hydroprocessing catalyst, said catalyst comprising a cracking
component and a hydrogenation component, wherein the cracking
component may be amorphous or zeolitic, the hydroprocessing zone
being maintained at hydroprocessing conditions, wherein the
feedstock is contacted with catalyst and hydrogen to produce a
vapor stream and a liquid stream as effluent; [0016] (b) removing
the vapor stream of step (a), which comprises hydrogen, hydrogen
sulfide and light hydrocarbonaceous gases overhead; [0017] (c)
combining the liquid stream of step (b) with the liquid effluent
from other hydroprocessing zones; [0018] (d) passing the liquid
stream of step (c), which comprises hydrocarbonaceous compounds
boiling in approximately the same range of the hydrocarbonaceous
feedstock, to fractionation; [0019] (e) separating the liquid
stream of step (d), in fractionation, into gas, naphtha, kerosene
and diesel fractions, in addition to the bottoms fraction; [0020]
(f) passing the bottoms fraction of step (e) to further processing
or recycling to one or more of the other hydroprocessing zones of
step (c); [0021] (g) passing one or more of the naphtha, kerosene
and diesel fractions to further processing as products or recycling
one or more of the fractions to one or more of the other
hydroprocessing zones of step (c), the kerosene, naphtha or diesel
fractions being in combination with kerosene, naphtha or diesel
fractions from other sources, said hydroprocessing zone or zones
being maintained at hydroprocessing conditions and at lower
pressure than the first hydroprocessing zone, and possessing an
environment substantially free of H.sub.2S, NH.sub.3, or other
heteroatom contaminants; [0022] (h) passing the effluent of step
(g) to fractionation; [0023] (i) recovering in fractionation an
increased amount of gas and naphtha, and a decreased amount of
kerosene, in the fractionation stage of step (h) than in the
fractionation step of step (e).
BRIEF DESCRIPTION OF THE DRAWING
[0024] The FIGURE illustrates a two-stage hydrocracking process
having the capability for recycle of bottoms fractions, diesel
fractions, kerosene fraction or naphtha fractions to the second
reactor stage.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Preheated oil feed in stream 1 is mixed with hydrogen in
stream 2 prior to its entrance into first stage or primary
hydroprocessing zone 10. This hydroprocessing zone is preferably a
downflow, fixed bed reactor. This reactor contains multiple beds of
hydroprocessing catalysts. At least one bed contains hydrocracking
catalyst.
[0026] The effluent 3 of the first stage reactor, which has been
hydrotreated and partially hydrocracked, comprises a liquid stream
and a vapor stream. The vapor stream 3(a) is removed overhead. It
comprises hydrogen, hydrogen sulfide and light hydrocarbonaceous
gases. The liquid stream 3(b) is combined with the liquid effluent
from other process zones, represented by stream 4. Stream 3(b) and
stream 4 are combined to create stream 5. Stream 5 is passed to the
fractionation unit 30, where it is separated into gas stream 6,
naphtha stream 7, kerosene stream 8, diesel stream 9, and bottoms
stream 14. The naphtha product may alternately be recycled, in
whole or in part, through stream 11 to stream 15, and ultimately to
second stage reactor 20. Kerosene product may alternately be
recycled, in whole or in part, through stream 12 to stream 15, and
ultimately to second stage reactor 20. Diesel product may be
alternately recycled, in whole or in part, through stream 13 to
stream 15, and ultimately to second stage reactor 20. Bottoms
material in stream 14 may be passed to further processing (in
stream 14a) or, alternately, may be recycled in stream 14(b) to
second reactor 20. Second reactor 20 represents hydroprocessing
zones subsequent to the first hydroprocessing zone. Each of these
zones possesses an environment substantially free of H.sub.2S,
NH.sub.3 or other heteroatom components.
Feeds
[0027] A wide variety of hydrocarbon feeds may be used in the
instant invention. Typical feedstocks include any heavy or
synthetic oil fraction or process stream having a boiling point
above 392.degree. F. (200.degree. C.). Such feedstocks include
vacuum gas oils, heavy atmospheric gas oil, delayed coker gas oil,
visbreaker gas oil demetallized oils, vacuum residua, atmospheric
residua, deasphalted oil, Fischer-Tropsch streams, and FCC
streams.
Products
[0028] Although emphasis is placed on the increased production of
gas and naphtha, the process of this invention is also useful in
the production of middle distillate fractions boiling in the range
of about 250-700.degree. F. (121-371.degree. C.). A middle
distillate fraction is defined as having an approximate boiling
range from about 250.degree. F. to 700.degree. F. At least 75 vol
%, preferably 85 vol %, of the components of the middle distillate
have a normal boiling point of greater than 250.degree. F. At least
about 75 vol %, preferably 85 vol %, of the components of the
middle distillate have a normal boiling point of less than
700.degree. F. The term "middle distillate" includes the diesel,
jet fuel and kerosene boiling range fractions. The kerosene or jet
fuel boiling point range refers to the range between 280.degree. F.
and 525.degree. F. (38-274.degree. C.). The term "diesel boiling
range" refers to hydrocarbons boiling in the range from 250.degree.
F. to 700.degree. F. (121-371.degree. C.).
[0029] Gasoline and naphtha production is emphasized in the process
of this invention. Gasoline or naphtha normally boils in the range
below 400.degree. F. (204.degree. C.), or C.sub.10--. Boiling
ranges of various product fractions recovered in any particular
refinery will vary with such factors as the characteristics of the
crude oil source, local refinery markets, and product prices.
[0030] Heavy hydrotreated gas oil, another product of this
invention, usually boils in the range from 550.degree. F. to
700.degree. F.
Conditions
[0031] Hydroprocessing conditions is a general term which refers
primarily in this application to hydrocracking or hydrotreating,
preferably hydrocracking. The first stage reactor, as depicted in
FIG. 1, is a partial conversion hydrocracker.
[0032] Typical hydrocracking conditions include a reaction
temperature of from 400.degree. F.-950.degree. F. (204.degree.
C.-510.degree. C.), preferably 650.degree. F.-850.degree. F.
(343.degree. C.-454.degree. C.). Reaction pressure ranges from 500
to 5000 psig (3.5-4.5 MPa), preferably 1500-3500 psig (10.4-24.2
MPa). LHSV ranges from 0.1 to 15 hr.sup.-1 (v/v), preferably
0.25-2.5 hr.sup.-1. Hydrogen consumption ranges from 500 to 2500
SCF per barrel of liquid hydrocarbon feed (89.1-445
m.sup.3H.sub.2/m.sup.3 feed). Reactors subsequent to the first
hydroprocessing reactor are operated at a pressure from 500 to 1000
psig lower than the first reactor.
Catalyst
[0033] Each hydroprocessing zone may contain only one catalyst, or
several catalysts in combination.
[0034] The hydrocracking catalyst generally comprises a cracking
component, a hydrogenation component, and a binder. Such catalysts
are well known in the art. The cracking component may include an
amorphous silica/alumina phase and/or a zeolite, such as a Y-type
or USY zeolite. Catalysts having high cracking activity often
employ REX, REY and USY zeolites. The most suitable zeolites of
this invention possess a SiO.sub.2/Al.sub.2O.sub.3 ratio of from 3
through 160, preferably of from 5 through 20. The unit cell size of
the zeolites of this invention is generally in the range from 24.25
through 24.60, and preferably in the range from 24.30 through
24.55. The binder is generally silica or alumina. The hydrogenation
component will be a Group VI, Group VII, or Group VIII metal or
oxides or sulfides thereof, preferably one or more of iron,
chromium, molybdenum, tungsten, cobalt, or nickel, or the sulfides
or oxides thereof. If present in the catalyst, these hydrogenation
components generally make up from about 5% to about 40% by weight
of the catalyst. Alternatively, noble metals, especially platinum
and/or palladium, may be present as the hydrogenation component,
either alone or in combination with the base metal hydrogenation
components iron, chromium molybdenum, tungsten, cobalt, or nickel.
If present, the platinum group metals will generally make up from
about 0.1% to about 2% by weight of the catalyst.
[0035] Hydrotreating catalyst usually is designed to remove sulfur
and nitrogen and provide a degree of aromatic saturation. It will
typically be a composite of a Group VI metal or compound thereof,
and a Group VIII metal or compound thereof supported on a porous
refractory base such as alumina. Examples of hydrotreating
catalysts are alumina supported cobalt-molybdenum, nickel sulfide,
nickel-tungsten, cobalt-tungsten and nickel-molybdenum. Typically,
such hydrotreating catalysts are presulfided.
[0036] Catalyst selection is dictated by process needs and product
specifications. In particular, a noble catalyst may be used in the
second stage when there is a low amount of H.sub.2S present.
[0037] The Examples below demonstrate the relative effectiveness of
recycling kerosene to produce lighter products of high quality, as
opposed to not recycling kerosene.
EXAMPLE
[0038] The "recycle" of kerosene was simulated by passing kerosene
from the first hydrocracking stage over the catalyst in the second
hydrocracking stage. The first stage kerosene possessed a smoke
point of 14 mm and 25 LV % aromatics. Net yields from the runs
where kerosene was "recycled" have been calculated by deducting the
supplemental kerosene feed from the gross, measured kerosene yield
(gross weight of kerosene product-weight of kerosene "recycled"=net
yield of kerosene product).
[0039] In kerosene recycle mode, a base metal zeolite hydrocracking
catalyst cracked a substantial fraction of the kerosene to naphtha
and gas (see Tables 1 and 2). The net yield of kerosene decreased
on a raw feed blend basis and the qualities of the middle
distillates remained the same. Recycling the kerosene to the second
stage did increase the yield of 170-350.degree. F. reformer
naphtha, a product in most demand by the customer.
TABLE-US-00001 TABLE 1 Two-Stage Hydrocracking of Vacuum Gas
Oil/Hydrocracking Gas Oil/ Light Cycle Oil Feed Blend Using
Hydrocracking Catalyst Run Hours 600-624 Reactor 1 Temp, .degree.
F. 725 Reactor 2 Temp, .degree. F. 669 Overall LHSV, hr.sup.-1 1.00
Per Pass Conversion 58 Total Pressure, PSIG 2297 No Loss Prod.
Yields Wt. % Vol. % C.sub.1 0.13 C.sub.2 0.18 C.sub.3 0.56 iC.sub.4
0.94 1.62 nC.sub.4 0.63 1.06 C.sub.5-170.degree. F. 3.43 5.04
170-350.degree. F. 13.04 16.48 350-550.degree. F. 29.99 33.44
550-RCP 15.57 16.92 Recycle Bleed 34.84 38.17 Recycle Cut Point,
.degree. F. 656 Total C.sub.4- 2.44 Total C.sub.5+ 96.87 110.04
Closure 99.6 // Fractionator Bottoms Nitrogen, ppm 24.5
TABLE-US-00002 TABLE 2 Two-Stage Hydrocracking of Vacuum Gas
Oil/Hydrocracked Gas Oil/ Light Cycle Oil Feed Blend Using
Hydrocracking Catalyst, with "Kerosene Recycle" Hours 816-840
Reactor 1 Temperature, .degree. F. 725 Reactor 2 Temperature,
.degree. F. 691 LHSV, 1/Hr 1.00 Per Pass Conversion, % 60 Total
Pressure, psig 2294 No Loss Product Yields Wt. % Vol % C.sub.1 0.13
C.sub.2 0.20 C.sub.3 0.80 iC.sub.4 1.80 nC.sub.4 0.99
C.sub.5-170.degree. F. 6.4 9.5 170-350.degree. F. 18.0 22.8
350-550.degree. F. 24.0 26.8 550-650.degree. F. 15.3 16.6
650.degree. F.+ 32.4 35.3 Recycle cut point 650.degree. F. Total
C.sub.5+ 96.1 111.0 Total C.sub.4- 3.72 Chemical H.sub.2
Consumption, SCF/B 2080 Closure, % 99.7 Fractionator Bottoms
Nitrogen, ppm 28
* * * * *