Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1~.8~677
PROCESS FOR CATALYTIC DEWAXING TO IMPROVE POUR POINT
USING ZSM-ll CATALYST CONTAINING
HYDROGENATION/DEHYDROGENATION COMPONENT
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is a process for catalytic dewaxing
of oil stocks using ZSM-ll, to improve pour point of the oil.
2. Prior Art
Modern petroleum refining is heavily dependent on
catalytic processes which chemically change the naturally
occurring constituents of petroleum. Such processes include
hydrocracking, catalytic cracking, reforming and
hydrotreating. Historically, the processes all depended on
the discovery that chemical change could be induced by
contacting a suitable petroleum fraction with a suitable
porous inorganic solid at elevated temperature. If hydrogen
under pressure is essential to the desired conversion, such
~ as in hydrocracking, a hydrogenation metal is included with
;~ 20 the porous catalyst to make the hydrogen effective.
The porous inorganic solids that were originally
found~useful for catalytic processes included certain clays,
aluminas, silica-aluminas and other silicas coprecipitated
:: :
~ 7 7
with magnesia, for example, and such solids are still
extensively used in the industry. In general, all of these
solids had pores that were not of uniform size, and most of
the pore volume was in pores having diameters larger than
about 30 Angstroms, with some of the pores as large or larger
that lO0 Angstroms. As will become evident from the
paragraphs which follow, a large fraction of the molecules
present in a hydrocarbon feed, such as a gas oil, is capable
of entering the pores of the typical porous solids described
above.
In recent years much attention has been given to the
synthesis and properties of a class of porous solids known as
~molecular sievesn. These are porous crystalline solids
usually composed of silica and alumina, and, because the pore
structure is defined by the crystal lattice, the pores of any
particular molecular sieve have a uniquely determined,
uniform pore diameter. The pores of these crystals are
further distinguished from those in the earlier used solids
by being smaller, i.e., by having effective pore diameters
not greater than about 13 Angstroms. These solids, when
dehydrated, act as sorbents that discriminate among molecules
of different shape, and for that reason were first called
"molecular sieves" by J. W. McBain. The term "effective pore
diameter~ as used herein means the diameter of the most
constricted part of the channels of the dehydrated crystal as
estimated from the diameter of the largest molecule that the
~; ~ crystal is capable of sorbing. Zeolite molecular sieves are
available that have effective pore diameters ranging from
about 3 Angstroms, which is too small to allow occlusion of
any hydrocarbon in the pores, to about 13
~ ~ .
~ -2-
X
~816~
Angstroms, which 3110ws occlusion of molecules as large as
1,3,5-triethylbenzene. The structures and uses of these solids
are dlescci~ed in "Zeolite Molecular Sieves," by Donald w.
8ceCK~ Jonn Wiley and Sons, New York (1974)-
As indicatea by Breck, the zeolite molecular sieves
ace use~ul as adsorbents (ibid, ~age 3), and in catalvsts
(ibia, page 2).
In s?ite of the small pores which are cnaracteristic
of zeolite molecular sieves, certain of these materi~ls have
been found to be highly effective as hydrocarbon conversion
catalysts. The conversion of gas oil to gasoline and
distillate by catalytic cracking, the alkylation of benzene to
ethylbenzene, the isomerization of xylenes and the
disproportionation of toluene all involve molecules which are
smaller in critical diameter than 1,3,5-triethylbenzene, and
such molecules are occluded and acted upon by zeolite molecular
sieves havinq an effective pore diameter of about 10
Angstroms. A particularly interesting catalytic transformation
whic'n requires a molecular sieve catalyst is the reduction o~
the pour point of waxy distillates and residual hydrocarbon
fractions. Effective pour point reduction depends on the
selective conversion of normal, high melting point paraffin
molecules that have an effective critical diameter of about 5
Angstroms to substances of lower molecular weight that are
easily separated fcom the low-pour product. ~ffective
; catalytic dewaxing depends at least in part on the regularity
of the pore size of the crystalllne zeolites, which allows
selective convecsion of unwanted constituents.
-3-
677
The developments briefly described above are only
indicative of the commercial importance of the molecular
sieve zeolites and of the academic interest in these
materials, which is more accurately reflected by the
thousands of patents and publications on the subject. By far
the major part of this importance stems from the catalytic
properties that may be found in appropriate circumstances
within the relatively small pores, together with the
regularity in the shape of the pores which permits the
molecular sieve catalyst to act selectively on molecules
having a particular shape. This latter phenomenon has come
to be known as ~shape-selective catalysis~. A review of the
state of the catalytic art is found in "Zeolite Chemistry and
Catalysis" by Jule A. Rabo, ACS Monograph 171, American
Chemical Society, Washington, D.C. (1976).
The dewaxing of oils by shape selective cracking and
hydrocracking over ZSM-5 zeolites is discussed and claimed in
Re 28,398 to Chen et al. U.S. Patent 3,956,102 discloses a
particular method for dewaxing a petroleum distillate with a
ZSM-5 catalyst. Typical aging curves as shown in sheet 2 of
the drawing of the 3,956,102 patent. U.S. 3,894,938 to
Gorring et al discloses that the cycle life of a ZSM-5
dewaxing catalyst is longer with a virgin feed strea~ than it
:
is with the same feedstream after it has been hydrotreated.
25~ Catalytic dewaxing of petroleum stocks in which a mordenite
type of molecular sieve catalyst is used is described in the
Oil and Gas Journal, January 6, 1975 issue at pages 69-73.
~See also U.S. Patent 3,668,113.
: :~
:
~ -4-
~ .
~ 7'7
Crystalline zeolite ZSM-ll is disclosed and claimed
in U.S. Patent 3,709,979.
In U.S Patent 3,709,979, the preparation of ZSM-ll
is disclosed. Example 9 of this patent taught fluid
S catalytic cracking at 8750F of a gas oil having a pour
point of 100F. High yields of olefins were obtained. The
pour point of the product was reduced.
Later patents relating to improvements in the
catalytic dewaxing process taught that the use of shape
selective zeolites for catalytic dewaxing was preferred.
These references taught that any shape selective zeolite with
a constraint index of l to 12, as hereafter defined, could be
used but that ZSM-5 and ZSM-ll were especially preferred.
The only work reported was done on ZSM-5 catalyst.
Typical of these patents is U.S. 4,181,598. This
patent taught making lube base stock oii of lower pour point
from a waxy crude oil fraction by solvent refining, catalytic
dewaxing over an intermediate pore size zeolite, e.g., ZSM-5,
followed by hydrotreating.
U.S. 4,332,670 taught catalytic dewaxing of middle
distillates to produce a low pour fuel oil by using an
intermediate pore size zeolite. There are no examples
showing use of ZSM-ll.
U.S. Patent 4,357,232, taught catalytic dewaxing of
~25 lubricating base stock oils using an intermediate pore size
zeolite, e.g., ZSM-5, along with other treatment steps. Use
of ZSM-5 and ZSM-ll as preferred is mentioned, although no
examples are reported showing use of ZSM-ll.
-5-
:~ '
.
8~.~7'7
U.S. Patent 4,348,363 taught a method of reducing
the pour point of a waxy hydrocarbon fuel oil by contact with
a zeolite sorbent, followed by catalytic dewaxing over an
intermediate pore size zeolite. Use of ZSM-5 and ZSM-ll as
preferred is mentioned, although no examples are reported
showing use of ZSM-ll.
U.S Patent 4,361,477 teaches catalytic dewaxing
using intermediate pore size zeolites having high silica to
alumina mole ratios, along with other treating steps. ZSM-5,
ZSM-ll and silicalite are taught, and claimed as being
suitable for use in this process. No examples using ZSM-ll
were presented.
Another method of producing low pour point
lubricating oil stock using catalytic dewaxing is disclosed
in U.S. 4,372,839. This patent taught use of intermediate
pore size zeolites such as ZSM-5 or ZSM-ll for catalytic
dewaxing, along with other processing steps. No examples of
use of ZSM-ll were given.
U.S. Patent 4,325,805 teaches lubricating oil
stabilization, involving catalytic dewaxing with an
intermediate pore size zeolite and other processing steps.
Taught as suitable intermediate pore size zeolites were
CZH-5, ZSM-5, ZSM-ll, ZSM-12, etc. The preferred zeolites
were ZSM-5 and CZH-5: No examples were provided of use of
ZSM-ll for catalytic dewaxing.
U.S. Patent 4,361,477 teaches stabilizing and
; ~ dewaxing lube oils using catalytic dewaxing with an
intermediate pore size zeolite and other processing steps.
-6-
.
~ 7 8
Taught as suitable intermediate pore size zeolites are ZSM-5,
ZSM-ll, ZSM-12, ZSM-21, etc. No examples are given using
ZSM-l].
In U.S. Patent 4,394,251, essentially aluminum-free
intermediate pore size zeolites analogous to ZSM-5 and ZSM-ll
are taught as suitable for cracking and hydrocracking. No
examples are given showing use of ZSM-ll for catalytic
dewaxing.
Although catalytic dewaxing is an important
commercial process, and although there has been extensive
work reported in the patent literature, apparently no one has
used ZSM-ll for catalytic dewaxing of fuel oil. Some
researchers imply an equivalence between the two, saying that
ZSM-5 and ZSM-ll are especially preferred, but invariably the
only zeolite actually tested for catalytic dewaxing are ZSM-5
zeolites.
Hydrocracking of n-decane with Pt-containing ZSM-11
has been reported in an article entitled ~Shape-Selectivity
Changes in High-Silica Zeolites", Jacobs et al, Faraday Disc.
Chem. Soc. (1982), 72,353.
We studied the work that others had done in this
:
area with a view to improving the process for catalytic
dewaxing of fuel to see if a way could be found to make this
good process even better by obtaining a catalyst of higher
~2~5 activity. We discovered that Pt-ZSM-ll, which has been
ignored experimentally by all prior workers in distillate
dewaxing, is better for catalytic dewaxing than Pt or
~ Ni-ZSM-5.
:~:
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~:
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~ ~8~677
BRIEF SUMMARY OF THE INVENTION
Accordingly~ the present invention provides a
process for reducing the pour point of a waxy hydrocarbon
fuel oil which comprises contacting said oil at catalytic
dewaxing conditions including a temperature about 450 to
850F in a reaction zone in the presence of hydrogen with a
catalyst comprising ZSM-ll and a
hydrogenation/dehydrogenation component to produce a dewaxed
fuel oil with reduced pour point.
In another embodiment, the present invention
provides a process for reducing the pour point of a waxy
hydrocarbon fuel oil which comprises contacting said oil at
catalytic hydrodewaxinq conditions including a temperature of
about 450 to 850F in a reaction zone containing a fixed
bed of catalyst comprising ZSM-ll and a platinum group
component and wherein catalytic hydrodewaxing conditions
include a hydrogen partial pressure of 25 to 1000 psia and a
ratio of hydrogen to hydrocarbon of 500 to 5000 SCFB and a
liquid hourly space velocity of 0.5 to 5 hours l to produce
a dewaxed fuel oil product with a reduced pour point.
DETAILED DESCRIPTION
2SM-ll
Details of preparation of ZSM-ll are given in U.S.
: ~ Patent 3,709,979.
~ :~ An important characteristic of the crystal structure
; ~;
of this novel class of zeolites is that it provides a
selective constrained access to and egress from the
~: :
~ : intracrystalline free space by virtue of having an effective
;
:~
~ 8-
::
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~ L~77
pore size intermediate between the small pore Linde A and the
large pore Linde X, i.e. the pore windows of the structure
are of about a size such as would be provided by 10-membered
rings of silicon atoms interconnected by oxygen atoms. It is
to be understood, of course, that these rings are those
formed by the regular disposition of the tetrahedra making up
the anionic framework of the crystalline zeolite, the oxygen
atoms themselves being bonded to the silicon (or aluminum,
etc.) atoms at the centers of the tetrahedra.
The silica to alumina mole ration referred to may be
determined by conventional analysis. This ratio is meant to
represent, as closely as possible, the ratio in the rigid
anionic framework of the zeolite crystal and to exclude
aluminum in the binder or in cationic or other form within
the channels. Although zeolites with silica to alumina mole
ratios of at least 12 are useful, it is preferred to use
zeolites having higher ratios than about 15, preferably about
15 to 200. In addition, zeolites as otherwise characterized
herein but which are substantially free of aluminum, that is
zeolites having silica to alumina mole ratios of up to
infinity, are found to be useful and even preferable in some
instances. Such "high silica~ or ~highly siliceous~ zeolites
are intended to be included within this description. Also
included within this definition are substantially pure silica
~25 analogues of the useful zeolites described herein, that is to
say those zeolites having no measurable amount of aluminum
(siliea to alumina mole ratio of infinity) but which
otherwise embody the characteristics disclosed.
In general, higher aluminum contents in the zeolite
~ '
_g_
lZ~ '7
framework give more acid activity to the catalyst. The acid
activity may be adjusted by crystallizing the ZSM-ll with
only a little, or a lot, of aluminum, steaming the ZSM-ll,
acid extracting, or any other means conventionally used to
adjust acid activity.
The novel class of zeolites, after activation,
acquire an intracrystalline sorption capacity for normal
hexane which is greater than that for water, i.e. they
exhibit "hydrophobic~ properties. This hydrophobic character
can be used to advantage in some applications.
The novel class of zeolites useful herein have an
effective pore size such as to freely sorb normal hexane. In
addition, the structure provides constrained access to larger
molecules.
The ~Con~traint Index~ as herein defined may be
detemined by passing continuously a mixture of an equal
weight of normal hexane and 3-methylpentane over a sample of
zeolite at atmospheric pressure according to the following
procedure. A sample of the zeolite, in the form of pellets
or extrudate, is crushed to a particle size about that of
coarse sand and mounted in a glass tube. Prior to testing,
the zeolite is treated with a stream of air at 1000F for
at least 15 minutes. The zeolite is then flushed with helium
and the temperature is adjusted between about 550F and
~25 ; 950F to give an overall conversion of between 10~ and
603. The mixture of hydrocarbons is passed at 1 liquid
hourly space velocity (i.e., 1 volume of liquid hydrocarbon
per volume of zeolite per hour) over the zeolite with a
helium dilution to give a helium to
- 1 0 -
: _ _
77
(total) hydrocarbon mole ratio of 4:1. After 20 minutes on
stream, ~ sample of the effluent is taken and analyzed, most
conveniently by gas chromatography, to determine the fraction
remaining ~nchanged for each of the two hydrocarbons.
While the above experimental procedure will enable one
to achieve the desired overall conversion of 10 to 60% for most
~eolite samples and represents preferred conditions, it may
occasionally be necessary to use somewhat more severe
con~itions tor samples of very low activity, such as those
having an exceptionally high silica to alumina mole ratio. In
those instances, a temperature of up to about 1000F and a
liquid hourly space velocity of less than one, such as 0.1 or
; less, can be employed in order to achieve a minimum total
l conversion of about 10~.
15 l The "Constraint Index" is calculated as follows:
Constraint Index =
(~-ct~n ~ ~e~ aining)
~lo (~rac ~
The Constraint Index approximates the ratio of the
cracking rate constants for the two hydrocarbons. Constraint
20 '1¦ Index (CI) values for some typical materials are: ¦
~ ! C.I.
ZSM-4 0.5
! ZSM-5 8.3
ZSM-ll 8.7
ZSM-12 2
2SM-23 9.1
2SM-3, 4.5
ZSM-38 2
ZSM-48 3-4
TMA Offretite 3.7
Clinoptilolite 3.4
H-Zeolon (mordenite) 0.4
REY
Amorphous Silica-Alumina 0.6
Erionite 38
:::
~8~77
CATALYTIC DEWAXING TO IMPROVE PO~R POINT
Catalytic dewaxing of high-pour gas oils to low-pour
fuel oils over a shape selective zeolite catalyst such as
ZSM-5 is described in U.S. Patent No. 3,700,585 and its
reissue, RE. 28,398.
A good general discussion of catalytic dewaxing to
improve pour point is shown in Chen, N. Y. et al "New Process
Cuts Pour Point of Distillatesn, Oil and Gas Journal, Vol.
75, No. 23, June 6, 1977, page 165 and Ireland et al
I0 ~Distallate Dewaxing in Operation~, Hydrocarbon Processing,
May, 1979.
In very general terms, catalytic hydrodewaxing
operates with a fixed or moving bed of catalyst, although
other types of catalyst beds such as ebulating bed, moving
bed, fluidized bed, may also be used.
Catalytic dewaxing for pour point improvement
usually requires somewhat higher temperatures than catalytic
dewaxing to prepare a lubricating oil base stock, i.e.,
temperatures of 450 to 850F, and preferably 500 to 800F
are commonly used for catalytic dewaxing to improve pour
point.
A certain amount of hydrogen partial pressure is
essential, both to minimize coke formation and laydown on the
catalyst, and also because hydrogen is consumed in cracking
~25~ ~ of normal paraffins to lighter molecules. Hydrogen is also
~ ~ helpful in promoting hydroisomerization of long chain
; ~ ~ paraffins or slightly branched paraffins to more highly
branched paraffins.
12-
~ 7 7
Hydrogen partial pressures of 15 to 2000 psia give
good results, while hydrogen partial pressures of 100 to 1000
psia give very qood results.
The ratio of catalyst to oil, expressed as liquid
hourly space velocity or volume per hour of normally liquid
feed measured at 0~ per volume of catalyst may range from
about 0.1 to 10 hours 1, preferably about 0.5 to 5 hours l
The alnount of hydrogen present may vary greatly,
ranging from 5dO to 5000 standard cubic feet per barrel of
oil. It is possible to operate with even less hydrogen,
although the catalyst will deactivate somewhat more ~uickly
than if the preferred minimum amount of hydrogen, 500 SCFB, is
added to the feed to the catalytic dewaxing zone. It is also !
I¦ possible to operate with even more hydrogen being pre-~ent,
however, it is expensive to circulate such large volumes of
hydrogen through the reactor, and the small increase in
catalyst life does not justify the expense of such high
hydrogen circulation rates.
20 I HYDROTREATING
, I . ~.. .
It ls frequently advantageous to conduct hydrotreating
either immediately before or after catalytic dewaxing.
~Hydrotreating will usually be practiced when necessary to
remove sulphur or nitrogen or to meet some other product
specification.
The advantage of hydrotreating the feed before
sub~ecting it to catalytic dewaxing, is that many catalyst
poisons will be either converted catalytically in the
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1'~8~77
hydrotreater, or deposited on the hydrotreating catalyst.
This may result in superior operation in the catalytic
dewaxing unit, and a longer operational life.
For some high sulfur oils it is better to conduct
dewaxing before the hydrotreating step. As discussed in U.S.
Patent 3,894,938, the advantages of dewaxing before
hydrotreating are disclosed.
Any conventional hydrotreating catalyst and
processing conditions may be used.
Preferably the hydrotreating process uses a catalyst
containing a hydrogenation component on a support, preferably
a non-acidic support, e.g., Co-Mo or Ni-Mo on alumina.
The hydrotreater usually operates at relatively low
temperatures, typically from 150 to 350C, and preferably
15 at temperatures of 200 to 300C.
The hydrotreating catalyst may be disposed as a
fixed, fluidized, or moving bed of catalyst, though down
flow, fixed bed operation is preferred because of its
simplicity. When the hydrotreating catalyst is disposed as a
fixed bed of catalyst, the liquid hourly space velocity, or
volume per hour of liquid feed measured at 0C per volume
of catalyst will usually be in the range of about 0.1 to 10,
and preferably about 1 to 5. In general higher space
velocities or throughputs require higher temperature
operation in the reactor to produce the same amount of
hydrotreating.
The hydrotreating operation is enhanced by the
presence of hydrogen, so typically hydrogen partial pressures
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1281~77
of l to 100 atmospheres, absolute are employed. Hydrogen can
be added to the feed on a once through basis, with the
hydrotreater effluent being passed directly to the wax
isomerization zone, or vice versa, as disclosed in U.S.
3,894,938.
If hydrotreating is done first, the hydrotreater
effluent is preferably cooled, and the hydrogen rich gas phase
recycled to the hydrotreater. Cooling of hydrotreater
effluent, and separation into vapor and liquid phases promotes
removal of some of the nitrogen and sulfur impurities which
would otherwise be passed into the catalytic dewaxing zone.
Other suitable hydrogenation components include one or
, more of the metals, or compounds thereof, selected from Groups
Il II, III, IV, V, VIB, VIIB, VIII and mixtures thereof of the
Periodic Table of the Elements. Preferred metals include
molybdenum, tungsten, vanadium, chromium, cobalt, titanium,
iron, nickel and mixtures thereof, e.g., Co-Mo or Ni-Mo.
Usually the hydrotreating metal component will be
present on a support in an amount equal to 0.1 to 20 weight
20 il percent of the support, with operation with 0.1 to 10 weight
percent hydrogenation metal, on an elemental basis, giving good
!
i results.
The hydrogenation components are ùsually disposed on a
support, preferably an amorphous support such as silica,
2~5 alumina, silica-alumina, etc. Any other conventional support
; , ~
material may also be used. It is also possible to include c~
the support an acid acting component, such as an acid exchan~
clay or a zeolite.
,~
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81677
It is also possible to cascade dewaxing and
desulfurization as described in U.S. Patent 4,394,249.
HYDROC;ENATION/DEHYDROGENATION COMPONENT OF DEWAXING CATALYST
An essential part of the process of the present
invent:ion is incorporation of a hydrogenation/dehydrogenation
component into the dewaxing catalyst.
The hydrogenation/dehydrogenation component is
believed to promote hydroisomerization activity in addition
to the shape selective cracking activities that occur with
ZSM-ll. This combination of activities gives higher
activity, better selectivity and lower pour point product
than can be achieved with ZSM-5 catalysts.
The hydrogenation/dehydrogenation component may be
added by ion exchange or impregnation, or any other method
known to the art of incorporating
hydrogenation/dehydrogenation components in a support, the
support in this instance being either ZSM-ll alone or in
admixture with a refractory inorganic oxide binder. Suitable
hydrogenation/dehydrogenation components may be selected from
one or more of the metals, or compounds thereof, selected
;~ ~ from Groups II, III, IV, V, VIB, VII~, VIII and mixtures
thereof of the Periodic Table of the Elements. Preferred
metals include molybdenum, tungsten, vanadium, chromium,
cobalt, titanium, iron, nickel and mixtures thereof, e.g.,
5~ `Co-Mo or Ni-Mo.
-16
77
The metal component may be incorporated into the
catalyst by impregnation, by ion exchange or by other means
by contacting either the catalyst or a component thereof with
a solution of a compound of the metal in an appropriate
amount necessary to provide the desired concentration within
the scope of the invention. The metal component may be
incorporated either in any step during preparation of the
catalyst`or after the finished catalyst has been prepared. A
preferred manner of incorporation is to ion-exchange a
crystalline aluminosilicate and then compositing the
ion-exchanged product with a porous matrix. Also useful is
the ion-exchanging or impregnation of siliceous solids or
clays. Suitable metal compounds include the metal halides,
preferably chlorides, nitrates, ammine halides, oxides,
sulfates, phosphates and other water-soluble inorganic salts;
and also the metal carboxylates of from 1 to 5 carbon atoms,
alcoholates. Specific examples include palladium chloride,
chloroplatinic acid, ruthenium penta-ammine chloride, osmium
chloride perrhenic acid, dioxobis (ethylenediamine) rhenium
(V) chloride, rhodium chloride and the like. Alternatively,
an oil-soluble or oil-dispersable compound of the metal may
be added in suitable amount of a hydrocarbon feedstock, such
as a gas oil charge stock, for incorporation in the catalyst
- as the charge is cracked. Such compounds include
: ~ :
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: ~ :
1~81~77
metal diketonates, carbonyls, metallocenes, olefin complexes of
2 to 20 carbons, acetylene complexes, alkyl or aryl phosphine
complexes and carboxylates of l to 20 carbons. Specific
examples of these are platinum acetylacetonate, tris
(acetylacetonato) rhodium (III), triiodoiridium (III)
tricarbonyl, -cyclopentadienylrhenium (I) tricarbonyl,
ruthenocene, -cyclopentadienylosmium (I) dicarbonyl dimer,
dichloro (ethylene) palladium (II) dimer ( -cyclopentadienyl)
(ethylene) rhodium (I), diphenylacetylenebis (triphenyl-
phosphino) platinum (O), bromomethylbis (triethylphosphino)palladium (II), tetrakis (triphenylphosphino)palladium (O),
chlorocarbonylbis(triphenylphosphino) iridium (I), palladium
;l acetate, and palladium naphthenate. i
~i
The hydrogenation/dehydrogenation component will also,
15 , to a certain extent, serve as a hydrogenation/dehydrogenation
promoter but that is not the primary purpose of adding this
component.
There will be a small amount of hydrotreating, i.e.,
removal of any sulfur and nitrogen compounds present, due to
20~l the presence of the e.g., platinum group component and this is
a beneficial, though unintended result. The hydrogenation/
dehydrogenation component is essential to promote
hydroisomerlzation of long chain normal or slightly branched
paraffins to more highly branched paraffins. This
25~ hydroisomerization converts the waxy long chain paraffins into
materials which are compatible with the fuel oil product,
; permitting increased yields of fuel oil when using the process
of the present invention. It is much more beneficial, from a
1281~77
liquid yield standpoint, to hyaroisomerize long chain paraffins
to other liquid products than it is to simply hydrocrack these
materials.
The amount of the hydrogenation/aehyarogenation
component a~ed to the catalytic dewaxing catalyst is not
narrowly critical an~ may range from about 0.01 to 3~ weight
percent, calculate~ as the elemental metal base~ upon the
weight of the entire catalyst.
Operation with O.û5 to 5 weight percent, calculated as
the elemental metal of a Pt group component gives good results,
with the preferred amount of Pt group metal component being
equal to 0.1 to 2.0 weight percent.
EXAMPLES
15 l
¦ Example 1 (Prlor Art)
This illustrates the dewaxing of distillate using a
conventional catalyst, a steamed O.9X Ni - 65% ZSM-5/35X
A1203 (Ni by exchange). The ZSM-5 had a SiO2:Al203
20 I ratio of about 70.
Commercially-prepared, extruded catalyst was
-laboratory steamed 6 hours at 900F. The steamed catalyst was
i used to hydrodewax feed having the properties shown in Table I.
:
1'~81~77
Table I
Gas Oil A Gas Oil ~ Gas Oil C
.
Gravity, API 35.9 24.8 28.0
Pour Point, F 75 65 85
Cloud Point, F 100 88
KV ~ 40C, cs 7.07 21.64 23.77
KV ~ lû0C, cs 2.186 4.169 4.4~3
Sulfur, wt ~ û.O9 2.25 0.84
~itrogen, ppm 18û 46û 560
Hydrogen, wt ~ 13.65 12.60 13.18
Bromine No. û.8 4.3 2.1
Carbon Residue
by MCRT, % 0.02 0.01 0.01
Vacuum Distillation - D1160
IBM 482 660 597
5 Vol X Distillated 531 703 693
551 714 726 `
585 724 755
615 736 771
i 40 641 749 782
15 ' 50 668 763 794
693 776 802
721 789 811
i 80 744 803 823
791 824 836
1 95 831 837 847
¦ End Point 875 837 870
!
The catalyst was disposed as a fixed bed of catalyst
in a reactor.
Reaction conditions and product properties are
: reported in the table, after Example 2.
I
Example 2 (Invention)
The catalyst used in thls study was prepare~
by flushing unsteamed HZSM-ll, 65 wt ~ ZS~-ll (with a
silica to alumina ratio, on a molar basis, of about 70)
and 35 wt % alumina in 14-25 mesh, with C02 for a few
-20-
i
' ~,
1-~81~77
minutes, followed by chloroplatinic acid-impregnation to 0.5%
platinum by weight. The platinum ZSM-ll catalyst was loaded
into the same fixed bed reactor used in Ex. I and reduced in
situ at 400 psig of hydrogen and 900F for one hour. Light
S neutral stock was then pumped into the reactor along with
hydrogen after the reactor temperature was lowered to the
deaired setting. After five days on stream with light neutral
stock, the feed was switched to bright stock. These runs were
~a~e at 540-585F, 400 psig of H2, 2500 SCF/bbl, and 0.75-1.0
LHSV. After five days, the feed was changed to Gas Oil A. The
runs were conducted at 700-750F, 400 psig of H2, 2000
SCF/bbl, and 1.0 LHSV. The dewaxed distillate products have a
pour point lower than -65F.
The properties of dewaxed distillate products
15 ~, processed with the Pt/ZSM-11 catalyst (invention) are compared
to Ni-ZSM-5 ~prior art), in the following Table II.
TABLE II
ProPertv comParison of Dewaxed Distillate
SteamedUnsteamed
~1 Ni-ZSM-5 Pt-ZSM-ll
; I ~eactor Temp., F 700 700 744
Pressure, psig 400 400 400
¦ LHSV
H2 Circ., SCF/bbl 2000 2000 2000
Days on Stream 15 13 14
1 25 Pour Point, F 20 LT -65 LT -65
Product Selectivity, wt %
l-C2 0.2 1.1 1.1
C3 5.3 12.7 11.6
C4 9.3 7.1 6.4
C5-330F 29.2 20.2 22.3
330F+ 56.0 58.9 58.6
. ~ ~
~ -21-
~8~
At 700F, the product from ZS~-ll has a pour point
lower than -65F while that from ~i-ZSM-5 has a 20F pour,
indicating that Pt-ZSM-ll is more active than ~i-ZS~-5 for
distillate aewaxing.
~oth catalysts gave the almost same distillate yields
at 700F, as shown in the table. For distillate dewaxing, the
lower the pour point, the lower the yield. Removal of waxy
components to reduce pour point usually results in removal of
product, and lower yields. Consequently, the distillate yiela
with Pt-ZSM-ll should be much higher than 60 wt ~ if the
reactor temperature was dropped to give a pour point of 20F.
Pt-ZS~-ll is far more selective than ZSM-5-
~ Lxample 3 (Invention)
15 I The catalyst of Example 2 was thereafter used for
dewaxing Gas Oil B with results reported in Table III.
Table III
PropertY Comparison of Dewaxed Distillate
20 l
SteamedUnsteamed
Ni-ZSM-5 Pt-ZSM-ll
Reactor Temp. F 700 625
Pressure, Psig H2 400
LHSV
~ H2 Circ., SCF/bbl 2000 2000
: 25 ! Pour Point, F
:
Product Selectivity, wt ~
C4 4.0 4.0
C5-330F 9.0 8.7
;1~ 330F+ 87.0 87.3
~ .
~ ~.
11
lX~ 77
For Gas Oil B, the Pt/ZS~-ll catalyst is 75F more
active than steamed ~i-ZSM-5 while the selectivities are
comparable.
Example 4 (Invention)
The catalyst of Example 3 was thereafter used for
dewaxing Gas Oil C. The results are shown in Table IV:
Ta~le IV
Property Comparison of Dewaxed Distillate
Steamed Unsteamed
Ni-ZS~-5 Pt-ZS1~1-ll
Reacto r Temp. F 710 655
Pressure~ Psig H2
LHSV 1 ` 1
H2 Circ., SCF/bbl 2000 2000
j Pour Point, F o o
¦ Prodùct Selectivity, wt X
i C~ 6.6 5.7
C5-330F 11.4 9.8
! 3300F+ 82.0 84.5
For Gas Oil C, the Pt/ZSM-ll catalyst offers a
catalyst activity advantage of 55F over steamed Ni-ZSM-5. In
addition, Pt/ZSM-ll improves the 330F+ selectivity by 2.5%.
Best Mode
If we were building a catalytic dewaxing unit to
reduce the pour point of distillate today, we would use a
~catalyst comprising 65 weight percent ZSI~1-11 and 35 weight
percent alumina and it would Contain about 0.5 weight percent
Pt added by impregnation. The ZSI~I-ll use~ would have a
SiO2:A1203 ratio of about 70 and would not be steamed.
The Pt would be calcined to fix it on the support, then reducea
~1 !
with hydrogen to the elemental state.
-23-
"
.
The catalyst would be disposed as a fixed bed in a
eeactor operated at the following conditions: 500-800F under
Ihydrogen pressure of 250-500 psig and with hydrogen circulation
of about 1500-2500 SCF/bbl. The preferred space velocity would
be about 0.5-2.0 LHSV.
.
- 2 4 -
~: :
.
" I
