U.S. patent application number 12/890904 was filed with the patent office on 2012-03-29 for liquid phase hydroprocessing with low pressure drop.
This patent application is currently assigned to UOP LLC. Invention is credited to Peter Kokayeff, John A. Petri, Paul A. Sechrist.
Application Number | 20120074038 12/890904 |
Document ID | / |
Family ID | 45869560 |
Filed Date | 2012-03-29 |
United States Patent
Application |
20120074038 |
Kind Code |
A1 |
Petri; John A. ; et
al. |
March 29, 2012 |
LIQUID PHASE HYDROPROCESSING WITH LOW PRESSURE DROP
Abstract
A process for hydroprocessing a hydrocarbonaceous feedstock in a
continuous liquid phase utilizes a hydroprocessing catalyst
comprising pills that have a largest dimension that averages no
more than 1.27 mm ( 1/20 inch) and more than 100 nm to produce a
hydrocarbonaceous product stream.
Inventors: |
Petri; John A.; (Wauconda,
IL) ; Kokayeff; Peter; (Naperville, IL) ;
Sechrist; Paul A.; (South Barrington, IL) |
Assignee: |
UOP LLC
Des Plaines
IL
|
Family ID: |
45869560 |
Appl. No.: |
12/890904 |
Filed: |
September 27, 2010 |
Current U.S.
Class: |
208/59 ;
208/108 |
Current CPC
Class: |
C10G 65/12 20130101;
C10G 65/10 20130101; C10G 65/04 20130101 |
Class at
Publication: |
208/59 ;
208/108 |
International
Class: |
C10G 65/10 20060101
C10G065/10; C10G 47/02 20060101 C10G047/02 |
Claims
1. A process for hydroprocessing a hydrocarbonaceous feedstock
which comprises: introducing a liquid phase stream comprising a
hydrocarbonaceous feedstock and a sufficiently low hydrogen
concentration to maintain a continuous liquid phase into a
hydroprocessing reactor containing hydroprocessing catalyst
comprising pills that have a largest dimension that averages no
more than 1.27 mm ( 1/20 inch) and more than 100 nm to produce a
first hydrocarbonaceous product stream.
2. The process of claim 1 wherein the pills have a largest
dimension that averages no more than 0.85 mm ( 1/30 inch) and no
less than 0.51 mm ( 1/50 inch).
3. The process of claim 1 wherein the pills have a largest
dimension that averages no more than 0.51 mm ( 1/50 inch).
4. The process of claim 1 further comprising: introducing at least
a portion of the first hydrocarbonaceous product stream into a
subsequent hydroprocessing reactor containing hydroprocessing
catalyst with a sufficiently low hydrogen concentration to maintain
a continuous liquid phase to produce a subsequent hydrocarbonaceous
product stream.
5. The process of claim 4 wherein said hydroprocessing catalyst in
said subsequent hydroprocessing reactor comprises pills that have a
largest dimension that averages no more than 1.27 mm ( 1/20 inch)
and more than 100 nm.
6. The process of claim 5 further comprising mixing said first
hydrocarbonaceous product stream with additional hydrocarbonaceous
feedstock before entering into said subsequent hydroprocessing
reactor.
7. The process of claim 1 wherein the hydroprocessing reactor is
operated at a mass flux of more than 29,300 kg/h-m.sup.2 (6,000
lb/h-ft.sup.2).
8. The process of claim 1 wherein the hydroprocessing catalyst
comprises a fixed bed.
9. A process for hydroprocessing a hydrocarbonaceous feedstock
which comprises: introducing a liquid phase stream comprising a
hydrocarbonaceous feedstock and a sufficiently low hydrogen
concentration to maintain a continuous liquid phase into a
hydroprocessing reactor containing hydroprocessing catalyst
comprising pills that have a largest dimension that averages no
more than 0.85 mm ( 1/30 inch) and no less than 0.51 mm ( 1/50
inch).
10. The process of claim 9 further comprising: introducing at least
a portion of the first hydrocarbonaceous product stream into a
subsequent hydroprocessing reactor containing hydroprocessing
catalyst with a sufficiently low hydrogen concentration to maintain
a continuous liquid phase to produce a subsequent hydrocarbonaceous
product stream.
11. The process of claim 10 wherein said hydroprocessing catalyst
in said subsequent hydroprocessing reactor comprises pills that
have a largest dimension that averages no more than 0.85 mm ( 1/30
inch) and no less than 0.51 mm ( 1/50 inch).
12. The process of claim 10 further comprising mixing said first
hydrocarbonaceous product stream with additional hydrocarbonaceous
feedstock before entering into said subsequent hydroprocessing
reactor.
13. The process of claim 9 wherein the hydroprocessing reactor is
operated at a mass flux of more than 29,300 kg/h-m.sup.2 (6,000
lb/h-ft.sup.2).
14. The process of claim 9 wherein the hydroprocessing catalyst
comprises a fixed bed.
15. A process for hydroprocessing a hydrocarbonaceous feedstock
which comprises: introducing a stream comprising a
hydrocarbonaceous feedstock and hydrogen into a hydroprocessing
reactor containing a fixed bed of hydroprocessing catalyst
comprising pills having a largest dimension that averages no more
than 0.51 mm ( 1/50 inch).
16. The process of claim 15 further comprising: introducing at
least a portion of the first hydrocarbonaceous product stream into
a subsequent hydroprocessing reactor containing hydroprocessing
catalyst with a sufficiently low hydrogen concentration to maintain
a continuous liquid phase to produce a subsequent hydrocarbonaceous
product stream.
17. The process of claim 16 wherein said hydroprocessing catalyst
in said subsequent hydroprocessing reactor comprises pills that
have a largest dimension that averages more than 100 nm.
18. The process of claim 16 further comprising mixing said first
hydrocarbonaceous product stream with additional hydrocarbonaceous
feedstock before entering into said subsequent hydroprocessing
reactor.
19. The process of claim 15 wherein the hydroprocessing reactor is
operated at a mass flux of more than 29,300 kg/h-m.sup.2 (6,000
lb/h-ft.sup.2).
Description
FIELD OF THE INVENTION
[0001] The field of art to which this invention pertains is the
catalytic hydroprocessing of hydrocarbons to useful hydrocarbon
products. More particularly, the invention relates to catalytic
hydroprocessing in continuous liquid phase.
BACKGROUND OF THE INVENTION
[0002] Petroleum refiners often produce desirable products such as
turbine fuel, diesel fuel, middle distillates, and gasoline boiling
hydrocarbons among others by hydroprocessing a hydrocarbon
feedstock derived from crude oil or heavy fractions thereof.
Hydroprocessing can include, for example, hydrocracking,
hydrotreating, hydroisomerization, hydrodesulfurization and the
like. Feedstocks subjected to hydroprocessing can be vacuum gas
oils, heavy gas oils, and other hydrocarbon streams recovered from
crude oil by distillation. For example, a typical heavy gas oil
comprises a substantial portion of hydrocarbon components boiling
above about 371.degree. C. (700.degree. F.) and usually at least
about 50 percent by weight boiling above 371.degree. C.
(700.degree. F.), and a typical vacuum gas oil normally has a
boiling point range between about 315.degree. C. (600.degree. F.)
and about 565.degree. C. (1050.degree. F.).
[0003] Hydroprocessing is a process that uses a hydrogen-containing
gas with suitable catalyst(s) for a particular application. In many
instances, hydroprocessing is generally accomplished by contacting
the selected feedstock in a reaction vessel or zone with the
suitable catalyst under conditions of elevated temperature and
pressure in the presence of hydrogen as a separate phase in a
three-phase system (gas/liquid/solid catalyst). Such
hydroprocessing is commonly undertaken in a trickle-bed reactor
where the continuous phase is gaseous and not liquid.
[0004] In the trickle bed reactor, an excess of the hydrogen gas is
present in the continuous gaseous phase. In many instances, a
typical trickle-bed hydroprocessing reactor requires up to about
1,685 Nm.sup.3 of hydrogen per m.sup.3 of oil (10,000 SCF/bbl) at
pressures up to 17.3 MPa gauge (2500 psig) to effect the desired
reactions. However, even though the trickle bed reactor has a
continuous gaseous phase due to the excess hydrogen gas, it is
believed that the primary reactions are taking place in the
liquid-phase in contact with the catalyst, such as in the liquid
filled catalyst pores. As a result, for the hydrogen gas to get to
the active sites on the catalyst, the hydrogen must first diffuse
from the gas phase into the liquid-phase and then through the
liquid to the reaction site adjacent the catalyst.
[0005] Under some hydroprocessing conditions the hydrogen supply
available at the catalytic reaction site may be a rate limiting
factor in the hydroprocessing conversions. For example, hydrocarbon
feedstocks can include mixtures of components having greatly
differing reactivities. While it may be desired, for example, to
reduced the nitrogen content of a vacuum gas oil to very low levels
prior to introducing it as a feed to a hydrocracking reactor, the
sulfur containing compounds of the vacuum gas oil will also undergo
conversion to hydrogen sulfide. Many of the sulfur containing
compounds tend to react very rapidly at the operating conditions
required to reduce the nitrogen content to the desired levels for
hydrocracking. The rapid reaction rate of the sulfur compounds to
hydrogen sulfide will tend to consume hydrogen that is available
within the catalyst pore structure thus limiting the amount of
hydrogen available for other desired reactions, such as
denitrogenation. In these circumstances, if the diffusion of
hydrogen through the liquid to the catalyst surface is slower than
the kinetic rates of reaction, the overall reaction rate of the
desired reactions (i.e., denitrogenation, for example) may be
limited by the hydrogen supply and diffusion. Ideas to overcome the
limitations posed by this phenomenon of hydrogen depletion, by
manufacturing hydroprocessing catalysts in small sizes and more
conventional shapes such as spheres or cylinders are dismissed in
conventional continuous gas phase hydroprocessing due to the
concern that such small catalysts can create large pressure drops
in the reactor.
[0006] The catalyst pill size in hydroprocessing is limited to
larger sizes and special shapes such as pills with largest
dimensions larger than 1.27 mm ( 1/20 inch) and trilobes or
quadralobes with lengths as large as 3.2 mm (1/8 inch) to reduce
pressure drop. The pressure drop under typical trickle-bed
hydroprocessing reaction conditions is exacerbated by recycle rates
of hydrogen-rich gas that are five to ten times the chemical
hydrogen consumption. Even with the larger catalyst dimensions,
mass flux rates have been kept below 29,300 kg/h-m.sup.2 (6,000
lb/h-ft.sup.2) to avoid excessive pressure drop in
hydroprocessing.
[0007] Continuous liquid phase hydroprocessing with a liquid
hydrocarbon stream and solid catalyst has been proposed to convert
certain hydrocarbon streams into more valuable hydrocarbon streams
in some cases with less hydrogen requirements.
[0008] Although a wide variety of process flow schemes, operating
conditions and catalysts have been used in commercial activities,
there is always a demand for new hydroprocessing methods which
provide lower costs, ease of construction, higher liquid product
yields and higher quality products.
BRIEF SUMMARY OF THE INVENTION
[0009] In continuous liquid phase hydroprocessing the recycle gas
stream is eliminated. Therefore, the pressure drop under these
conditions becomes very low even at higher than typical
conventional technology trickle-bed mass fluxes. We have found that
flow distribution can be problematic with very low pressure drop
per length of reactant flow path.
[0010] The present invention is a process for hydroprocessing a
hydrocarbonaceous feedstock which comprises introducing a liquid
phase stream comprising a hydrocarbonaceous feedstock and a
sufficiently low hydrogen concentration to maintain a continuous
liquid phase into a hydroprocessing reactor. The hydroprocessing
reactor contains hydroprocessing catalyst comprising pills that
have a largest dimension that averages no more than 1.27 mm ( 1/20
inch) and more than 100 nm to produce a first hydrocarbonaceous
product stream. In an aspect the pills have a largest dimension
that averages no more than 0.85 mm ( 1/30 inch) and no less than
0.51 mm ( 1/50 inch). In an additional aspect, the pills have a
largest dimension that averages no more than 0.51 mm ( 1/50
inch).
[0011] Other embodiments of the present invention encompass further
details such as types and descriptions of feedstocks, hydrocracking
catalysts, hydrotreating catalysts, and preferred operating
conditions including temperatures and pressures, all of which are
hereinafter disclosed in the following discussion of each of these
facets of the invention.
BRIEF DESCRIPTION OF THE DRAWING
[0012] The FIGURE is a simplified process flow diagram of preferred
embodiments of the present invention. The FIGURE is intended to be
schematically illustrative of the present invention and not be a
limitation thereof. While the FIGURE depicts a reactor as operating
in a downflow mode it is presented for illustrative purposes and is
not intended to exclude an upflow mode of operation.
DETAILED DESCRIPTION OF THE INVENTION
[0013] This invention uses catalyst pills with smaller effective
diameter than is commercially practiced in a hydroprocessing flow
scheme. The minimum particle size commercially practiced is
typically at least 1.27 mm ( 1/20 inch). This invention uses a pill
smaller than 1.27 mm. Under continuous liquid phase hydroprocessing
conditions, a pressure drop per length of catalyst path equivalent
to a conventional continuous gas phase hydroprocessing unit can be
achieved with much smaller pill sizes. This smaller pill size has
two significant effects. The small pill size in continuous liquid
phase reaction conditions creates equivalent pressure drop, which
will facilitate flow distribution, as is typical for
hydroprocessing in a conventional continuous gas phase. The small
pill size also reduces diffusional resistance and potentially can
enhance hydroprocessing reaction rates. The small pill size can be
used under continuous liquid phase hydroprocessing conditions with
or without hydrogen recycle.
[0014] The methods described herein are particularly useful for
hydroprocessing a hydrocarbonaceous feedstock containing
hydrocarbons, and typically other organic materials, to produce a
product containing hydrocarbons or other organic materials of lower
average boiling point, lower average molecular weight, as well as
reduced concentrations of contaminants, such as sulfur and nitrogen
and the like. In an aspect, the process utilizes an initial
hydrogen addition that provides all the hydrogen requirements for
the reactor without the use of hydrogen sourced from a hydrogen
recycle gas compressor. In other words, the hydrogen is not
recycled within the hydroprocessing unit, but is supplied from
outside the hydroprocessing unit.
[0015] As used herein, the term "communication" means that material
flow is operatively permitted between enumerated components. The
term "downstream communication" means that at least a portion of
material flowing to the subject in downstream communication may
operatively flow from the object with which it communicates. The
term "upstream communication" means that at least a portion of the
material flowing from the subject in upstream communication may
operatively flow to the object with which it communicates.
[0016] The hydrocarbonaceous feedstocks that may be processed using
the methods and apparatuses comprise mineral oils and synthetic
oils (e.g., shale oil, tar sand products, etc.) and fractions
thereof that may be subjected to hydroprocessing and hydrocracking.
Illustrative hydrocarbon feedstocks include those containing
components boiling above about 150.degree. C. (300.degree. F.),
such as atmospheric gas oils, vacuum gas oils, vacuum and
atmospheric residua, hydrotreated or mildly hydrocracked residual
oils, coker distillates, straight run distillates,
solvent-deasphalted oils, pyrolysis-derived oils, high boiling
synthetic oils, cycle oils, catalytic cracker distillates, and
Fischer-Tropsch derived liquids. One preferred feedstock is a gas
oil or other hydrocarbon fraction having at least about 50 wt-%,
and preferably at least about 75 wt-%, of its components boiling at
a temperature above about 371.degree. C. (700.degree. F.). For
example, another preferred feedstock contains hydrocarbon
components which boil above about 288.degree. C. (550.degree. F.)
with at least about 25 percent by volume of the components boiling
between about 315.degree. C. (600.degree. F.) and about 565.degree.
C. (1050.degree. F.). Other suitable feedstocks may have a greater
or lesser proportion of components boiling in this range.
[0017] With reference to the FIGURE, an integrated hydroprocessing
unit 10 is illustrated where a hydrocarbonaceous feedstock is
introduced perhaps by pump into the process via a fresh
hydrocarbonaceous feed lines 12 and 14. The hydrocarbonaceous
feedstock is provided at a first temperature which may be a
temperature well below reactor temperature such as between about
200.degree. and about 300.degree. F. (90.degree. and 150.degree.
C.) because the feedstock has yet been subjected to heating.
[0018] A hydrogen-rich gaseous stream is provided via a hydrogen
lines 20 and 22 via a make-up gas compressor 24. In an aspect,
hydrogen in line 22 is only provided via a make-up gas compressor
24. The hydrogen supply line 20 which may perhaps be a line from a
general refinery hydrogen supply provides hydrogen to hydrogen line
22. The hydrogen-rich gaseous stream from line 22 is admixed with
the fresh feed in the hydrocarbonaceous feed line 14 to provide an
admixture of the hydrocarbonaceous feedstock and hydrogen in line
16. The feed is heated to the appropriate reaction temperature with
a heater either upstream of the joinder with the hydrogen line 22
in line 14 (not shown) or downstream thereof in line 16. The heater
18 may be one or more fired heaters and/or heat exchangers
represented by fired heater 18. Alternatively or additionally, the
hydrogen in line 22 may be heated by a heat exchanger 26 or other
means and mixed with the fresh feed to thereby heat the
hydrocarbonaceous feedstock from line 14 to the appropriate
reaction temperature.
[0019] The heated, mixed stream in line 28 is introduced into a
hydroprocessing reactor 40 via an inlet 42. The hydroprocessing
reactor contains at least one bed 44 of hydroprocessing catalyst
which in an aspect may be a fixed bed of catalyst. The
hydroprocessing reactor 40 may have at least a single catalyst bed
44 and may have a plurality of catalyst beds. As mentioned above,
the hydroprocessing reactor 40 is designed to be operated in a
continuous liquid phase with the hydrogen requirement supplied from
the combined stream of hydrogen from line 22.
[0020] The hydrocarbonaceous feedstock is subjected to
hydroprocessing in a continuous liquid phase in the hydroprocessing
reactor 40. Hydroprocessing can include, without limit,
hydrotreating such as hydrodesulfurization, hydrocracking and
hydroisomerization. Continuous liquid phase hydroprocessing
involves introducing a liquid phase hydrocarbonaceous feedstock and
hydrogen into a hydroprocessing reactor. The hydrogen should be
present in a sufficiently low concentration to maintain a
continuous liquid phase in the hydroprocessing reactor but high
enough to provide sufficient hydrogen for hydroconversion of the
hydrocarbon feed. In other words, a continuous plenum of
hydrocarbon liquid should extend from the feed inlet 42 for the
reactor 40 to the product outlet 46 for the reactor to establish a
continuous liquid phase. Hydrogen gas may be present outside of the
liquid plenum or inside of the liquid plenum in the forms of slugs
or bubbles. At the very least, the volume of the liquid in the
reactor will be greater than the volume of the gas in the
reactor.
[0021] During the hydroconversion reactions occurring in the
hydroprocessing reactor, hydrogen is necessarily consumed. Hydrogen
may be provided to the reactor in excess or replaced by one or more
hydrogen inlet points located in the reactor. The flow rate of
hydrogen added at these locations is controlled to ensure that the
reactor operates in a continuous liquid phase. The maximum flow
rate of hydrogen that may be added to the reactor is less than the
flow rate which would cause a transition from a continuous liquid
phase to a continuous vapor phase.
[0022] In some aspects, the hydrocarbonaceous feedstock does not
contain recycled product from a hydroprocessing reactor or other
hydrocarbon diluent. In other aspects, a recycle stream 64 or
diluent may be incorporated into the fresh hydrocarbonaceous
feedstock prior to hydroprocessing the feedstock to provide
additional volume to the process zone to provide added
hydrogen-carrying capacity to the product stream or to provide
additional mass to reduce the temperature rise in catalyst bed 44.
In such aspects, any recycled product 64 or diluent typically is
introduced into the feedstock in line 14 before a hydrogen stream
in line 22 is mixed with the feedstock, and no further recycled
product is incorporated into the process flow. Typically, such
recycled product may be previously stripped of a vaporous hydrogen
sulfide, nitrogen or nitrogen containing compositions, and any
other vapor phase materials. In an aspect, recycled product in line
64 is optionally recycled to help carry hydrogen into the
hydroprocessing reactor 40 via lines 16 and 28 or reduce the
temperature rise in catalyst bed 44.
[0023] In one aspect, the fresh hydrocarbonaceous feed in line 14
is provided and mixed with a hydrogen flow in line 22 from a
make-up gas compressor or other similar hydrogen sources. The
hydrogen flow is mixed into the fresh hydrocarbonaceous feed for
the hydroprocessing reactor 40 and is provided at a rate at least
sufficient to satisfy the hydrogen requirement of the first reactor
and subsequent reactors if any. If multiple catalyst beds are
provided in a reactor, the hydrogen rate may be at least sufficient
to satisfy the hydrogen requirement of the first catalyst bed and
subsequent catalyst beds in the same or subsequent reactors if any.
In some instances, the rate of added hydrogen will include an
amount in excess of the predicted hydrogen requirements of the
particular catalyst bed(s) as reserve in event the hydrogen
consumption exceeds the expected rate at a particular bed or in the
reactor(s) as a whole.
[0024] In other aspects, hydrogen is added to the fresh feed stream
to provide sufficient hydrogen to exceed the saturation point of
the hydrocarbonaceous liquid so that a small vapor phase is present
throughout the substantially liquid phase. Thus, there is, in some
aspects, sufficient additional hydrogen in the small vapor phase to
provide additional dissolved hydrogen to the continuous liquid
hydrocarbon phase as the reaction consumes hydrogen. For example,
the amount of added hydrogen to each catalyst bed may be about 10
to 20 wt-% greater than the expected collective hydrogen
requirements of each bed of hydroprocessing catalyst. In yet other
aspects, it is expected that the amount of hydrogen may be up to
about 100 percent of saturation to about 1000 percent of the
saturated liquid phase hydrocarbon. Excess hydrogen is carried in
the effluent from the catalyst bed and/or reactor in solution, in
gaseous phase, or both in gaseous phase and in solution in the
liquid effluent streams. In this aspect, no other hydrogen is added
to the catalyst bed or reactor. In other aspects, hydrogen may be
added to a downstream catalyst bed or a downstream reactor that
supplements hydrogen exiting the upstream catalyst bed or upstream
reactor, respectively. It will be appreciated, however, that the
rate of hydrogen added to a reactor or a catalyst bed can vary
depending on the feed composition, operating conditions, desired
output, and other factors. In an aspect, the liquid
hydrocarbonaceous feed may include about 67 to about 135 Nm.sup.3
hydrogen per m.sup.3 oil (400 to 800 scf/bbl). In this aspect, a
continuous gas phase may exist along with the continuous liquid
phase extending from hydrogen inlet to product outlet. As such,
about 4 to about 25 Nm.sup.3 hydrogen per m.sup.3 oil (25 to 150
scf/bbl) may exit a respective catalyst bed or reactor at its
outlet.
[0025] The "hydroprocessing" that may be performed in the
hydroprocessing reactor may be "hydrotreating". Hydrotreating is a
process wherein hydrogen gas is contacted with hydrocarbon in the
presence of suitable catalysts which are primarily active for the
removal of heteroatoms, such as sulfur and nitrogen from the
hydrocarbon feedstock. In hydrotreating, hydrocarbons with double
and triple bonds may be saturated. Suitable hydrotreating catalysts
for use in the present invention are any known conventional
hydrotreating catalysts and include those which are comprised of at
least one Group VIII metal, preferably iron, cobalt and nickel,
more preferably cobalt and/or nickel and at least one Group VI
metal, preferably molybdenum and tungsten, on a high surface area
support material, preferably alumina. Other suitable hydrotreating
catalysts include zeolitic catalysts, as well as noble metal
catalysts where the noble metal is selected from palladium and
platinum. It is within the scope of the present invention that more
than one type of hydrotreating catalyst be used in the same
reaction vessel. The Group VIII metal is typically present in an
amount ranging from about 2 to about 20 wt-%, preferably from about
4 to about 12 wt-%. The Group VI metal will typically be present in
an amount ranging from about 1 to about 25 wt-%, preferably from
about 2 to about 25 wt-%.
[0026] Preferred hydrotreating reaction conditions include a
temperature from about 204.degree. C. (400.degree. F.) to about
482.degree. C. (900.degree. F.), a pressure from about 3.5 MPa (500
psig) to about 17.3 MPa (2500 psig), a liquid hourly space velocity
of the fresh hydrocarbonaceous feedstock from about 0.1 hr.sup.-1
to about 10 hr.sup.-1 with a hydrotreating catalyst or a
combination of hydrotreating catalysts.
[0027] The "hydroprocessing" that may be performed in the
hydroprocessing reactor may be "hydrocracking". Hydrocracking
refers to a process in which hydrocarbons crack in the presence of
hydrogen to lower molecular weight hydrocarbons. Depending on the
desired output, the hydrocracking zone may contain one or more beds
of the same or different catalyst. In one aspect, for example, when
the preferred products are middle distillates, the preferred
hydrocracking catalysts utilize amorphous bases or low-level
zeolite bases combined with one or more Group VIII or Group VIB
metal hydrogenating components. In another aspect, when the
preferred products are in the gasoline boiling range, the
hydrocracking zone contains a catalyst which comprises, in general,
any crystalline zeolite cracking base upon which is deposited a
minor proportion of a Group VIII metal hydrogenating component.
Additional hydrogenating components may be selected from Group VIB
for incorporation with the zeolite base.
[0028] The zeolite cracking bases are sometimes referred to in the
art as molecular sieves and are usually composed of silica, alumina
and one or more exchangeable cations such as sodium, magnesium,
calcium, rare earth metals, etc. They are further characterized by
crystal pores of relatively uniform diameter between about 4 and
about 14 Angstroms (10.sup.-10 meters). It is preferred to employ
zeolites having a relatively high silica/alumina mole ratio between
about 3 and about 12. Suitable zeolites found in nature include,
for example, mordenite, stilbite, heulandite, ferrierite,
dachiardite, chabazite, erionite and faujasite. Suitable synthetic
zeolites include, for example, the B, X, Y and L crystal types,
e.g., synthetic faujasite and mordenite. The preferred zeolites are
those having crystal pore diameters between about 8-12 Angstroms
(10.sup.-10 meters), wherein the silica/alumina mole ratio is about
4 to 6. One example of a zeolite falling in the preferred group is
synthetic Y molecular sieve.
[0029] The natural occurring zeolites are normally found in a
sodium form, an alkaline earth metal form, or mixed forms. The
synthetic zeolites are nearly always prepared first in the sodium
form. In any case, for use as a cracking base it is preferred that
most or all of the original zeolitic monovalent metals be
ion-exchanged with a polyvalent metal and/or with an ammonium salt
followed by heating to decompose the ammonium ions associated with
the zeolite, leaving in their place hydrogen ions and/or exchange
sites which have actually been decationized by further removal of
water. Hydrogen or "decationized" Y zeolites of this nature are
more particularly described in U.S. Pat. No. 3,130,006.
[0030] Mixed polyvalent metal-hydrogen zeolites may be prepared by
ion-exchanging first with an ammonium salt, then partially back
exchanging with a polyvalent metal salt and then calcining. In some
cases, as in the case of synthetic mordenite, the hydrogen forms
can be prepared by direct acid treatment of the alkali metal
zeolites. In one aspect, the preferred cracking bases are those
which are at least about 10 percent, and preferably at least about
20 percent, metal-cation-deficient, based on the initial
ion-exchange capacity. In another aspect, a desirable and stable
class of zeolites is one wherein at least about 20 percent of the
ion exchange capacity is satisfied by hydrogen ions.
[0031] The active metals employed in the preferred hydrocracking
catalysts of the present invention as hydrogenation components are
those of Group VIII, i.e., iron, cobalt, nickel, ruthenium,
rhodium, palladium, osmium, iridium and platinum. In addition to
these metals, other promoters may also be employed in conjunction
therewith, including the metals of Group VIB, e.g., molybdenum and
tungsten. The amount of hydrogenating metal in the catalyst can
vary within wide ranges. Broadly speaking, any amount between about
0.05 percent and about 30 percent by weight may be used. In the
case of the noble metals, it is normally preferred to use about
0.05 to about 2 wt-%.
[0032] The method for incorporating the hydrogenating metal is to
contact the zeolite base material with an aqueous solution of a
suitable compound of the desired metal wherein the metal is present
in a cationic form. Following addition of the selected
hydrogenating metal or metals, the resulting catalyst powder is
then filtered, dried, pelleted with added lubricants, binders or
the like if desired, and calcined in air at temperatures of, e.g.,
about 371.degree. to about 648.degree. C. (about 700.degree.to
about 1200.degree. F.) in order to activate the catalyst and
decompose ammonium ions. Alternatively, the zeolite component may
first be pelleted, followed by the addition of the hydrogenating
component and activation by calcining.
[0033] The foregoing catalysts may be employed in undiluted form,
or the powdered zeolite catalyst may be mixed and copelleted with
other relatively less active catalysts, diluents or binders such as
alumina, silica gel, silica-alumina cogels, activated clays and the
like in proportions ranging between about 5 and about 90 wt-%.
These diluents may be employed as such or they may contain a minor
proportion of an added hydrogenating metal such as a Group VIB
and/or Group VIII metal. Additional metal promoted hydrocracking
catalysts may also be utilized in the process of the present
invention which comprises, for example, aluminophosphate molecular
sieves, crystalline chromosilicates and other crystalline
silicates. Crystalline chromosilicates are more fully described in
U.S. Pat. No. 4,363,718.
[0034] By one approach, the hydrocracking conditions may include a
temperature from about 232.degree. C. (450.degree. F.) to about
468.degree. C. (875.degree. F.), a pressure from about 3.5 MPa (500
psig) to about 16.5 MPa (2400 psig) and a liquid hourly space
velocity (LHSV) from about 0.1 to about 30 hr.sup.-1. In some
aspects, the hydrocracking reaction provides conversion of the
hydrocarbons in the process stream to lower boiling products, which
may be the conversion of at least about 5 vol-% of the process
flow. In other aspects, the per pass conversion in the
hydrocracking zone may be in the range from about 15 percent to
about 70 percent and, preferably, the per-pass conversion is in the
range from about 20 percent to about 60 percent. In such aspects,
the processes herein are suitable for the production of naphtha,
diesel or any other desired lower boiling hydrocarbons.
[0035] The "hydroprocessing" that may be performed in the
hydroprocessing reactor may be "hydroisomerization".
Hydroisomerization may also include catalytic dewaxing.
Hydroisomerization is a process in which in one aspect at least
about 10 percent, in another aspect, at least about 50 percent and,
in yet another aspect, about 10 to about 90 percent of the
n-paraffins of the hydrocarbon feedstock are converted into
iso-paraffins effective to provide an effluent with at least one of
a cloud point value of about 0.degree. C. (32.degree. F.) or less,
a pour point value of about 0.degree. C. (32.degree. F.) or less,
and/or a cold filter plugging point (CFPP) value of about 0.degree.
C. (32.degree. F.) or less. In general, such hydroisomerization
conditions include a temperature from about 260.degree. C.
(500.degree. F.) to about 371.degree. C. (700.degree. F.), a
pressure from about 1.38 MPa (200 psig) to about 8.27 MPa (1200
psig), a liquid hourly space velocity of the fresh hydrocarbon
feedstock from about 0.1 hr.sup.-1 to about 10 hr.sup.-1. However,
other hydroisomerization conditions are also possible depending on
the particular feedstocks being treated, the compositions of the
feedstocks, desired effluent compositions, and other factors.
[0036] Suitable hydroisomerization catalysts are any known
conventional hydroisomerization catalysts. For example, suitable
catalysts can include zeolite components,
hydrogenation/dehydrogenation components, and/or acidic components.
In some forms, the catalysts can include at least one Group VIII
metal such as a noble metal (i.e., platinum or palladium). In other
forms, the catalyst may also include silico alumino phosphate
and/or zeolite alumino silicate. Examples of suitable catalysts are
disclosed in U.S. Pat. No. 5,976,351; U.S. Pat. No. 4,960,504; U.S.
Pat. No. 4,788,378; U.S. Pat. No. 4,683,214; U.S. Pat. No.
4,501,926 and U.S. Pat. No. 4,419,220; however, other isomerization
catalysts may also be used depending on the feedstock composition,
operating conditions, desired output, and other factors.
[0037] In an aspect of the invention, the hydroprocessing reactor
40 houses a hydroprocessing catalyst bed 44 containing
hydroprocessing catalyst. In an aspect, the catalyst bed is fixed,
such that the catalyst particles do not leave the bed with the
exiting hydrocarbon. The hydroprocessing catalyst comprises pills
that have a largest dimension that averages no more than 1.27 mm (
1/20 inch) and more than 100 nm to produce a first
hydrocarbonaceous product stream. In a further aspect, the
hydroprocessing catalyst pills have a largest dimension that
averages no more than 0.85 mm ( 1/30 inch) and no less than 0.51 mm
( 1/50 inch). In an even further aspect, the hydroprocessing
catalyst pills have a largest dimension that averages no more than
0.51 mm ( 1/50 inch) and more than 100 nm. The small catalyst pills
are useable in continuous liquid phase hydroprocessing because the
overall mass flux may be lower when the gas-to-liquid ratio is such
that a liquid continuous phase is formed as described above and
because the substantially lower gas rates have a lower gas velocity
over the small catalyst pills, thus generating a smaller pressure
drop through the bed than a continuous gas phase operation would.
However, pressure drop also serves a distributional purpose, so
some pressure drop is desired. The smaller catalyst pills also
serve to distribute the feed across the catalyst bed by virtue of
axial dispersion over that which would be provided by
conventionally large catalyst particles used for continuous gas
phase hydroprocessing. Lastly, the small catalyst pills provide
more surface area and a shorter diffusion path into the pores of
the smaller catalyst pills, thereby enhancing hydroconversion to
products.
[0038] The catalysts of the present invention may take any shape
such as extruded trilobes or quadralobes, pellets, oil dropped
spheres, layered spheres, spray dried particles, etc. without
limitation.
[0039] We have found that with smaller catalyst particles, the
hydroprocessing reactor can be operated with a higher mass flux.
Conventional hydroprocessing reactors are rarely operated to
approach a mass flux of 29,300 kg/h-m.sup.2 (6,000 lb/h-ft.sup.2).
We have found that the hydroprocessing reactor can be operated with
a mass flux of more than 29,300 kg/h-m.sup.2 with the catalyst pill
sizes of the present invention. We have found that the
hydroprocessing reactor can be operated at a mass flux that can
reach 50,000 kg/h-m.sup.2 (10,000 lb/h-ft.sup.2).
[0040] A hydrocarbonaceous product stream exits from the
hydroprocessing reactor 40 via an outlet 46 in a hydroprocessed
effluent line 48. The hydrocarbonaceous product may be recovered as
product or further processed.
[0041] In an aspect, at least a portion of the hydrocarbonaceous
product may be fed to a subsequent hydroprocessing reactor 50 via
inlet 52. In this aspect, hydroprocessing reactor 40 is a first
hydroprocessing reactor. The subsequent hydroprocessing reactor 50
contains at least one bed 54 of hydroprocessing catalyst which in
an aspect is a fixed bed of catalyst. The hydroprocessing reactor
50 may have at least a single catalyst bed 54 and may have a
plurality of catalyst beds. The hydroprocessing reactor 50 may be
operated in a continuous liquid phase with the hydrogen requirement
supplied from unreacted hydrogen exiting from the first
hydroprocessing reactor 40 in line 48. In such a case, a large
excess of hydrogen will be added to the first hydroprocessing
reactor via lines 22, 16 and 28. In another aspect, hydrogen may be
added to the subsequent hydroprocessing reactor 50 by bypassing the
first hydroprocessing reactor via lines 30, 68 and 32.
[0042] The hydroprocessing that occurs in the subsequent
hydroprocessing reactor 50 may be different from the
hydroprocessing that occurs in the first hydroprocessing reactor
40. For example, hydrotreating may be conducted in the first
hydroprocessing reactor 40 and either hydrocracking or
hydroisomerization may be conducted in the subsequent
hydroprocessing reactor 50. In another example, hydrocracking may
be conducted in the first hydroprocessing reactor 40 and either
hydrotreating or hydroisomerization may be conducted in the
subsequent hydroprocessing reactor 50. In a further example,
hydroisomerization may be conducted in the first hydroprocessing
reactor 40 and either hydrotreating or hydrocracking may be
conducted in the subsequent hydroprocessing reactor 50. Moreover,
the same type of hydroprocessing may be conducted in both the first
hydroprocessing reactor 40 and the subsequent hydroprocessing
reactor 50. Lastly, more than one subsequent reactor 50 may be used
in an aspect using the same or different type of hydroprocessing
than the other hydroprocessing reactors.
[0043] In an aspect, the hydrocarbonaceous feedstock in line 12 may
be separated into a first portion of fresh feed in a first
hydrocarbonaceous portion line 14 and at least one additional
portion of fresh feed in a second hydrocarbonaceous portion line
60. The first portion of fresh feed is fed in lines 16 and 28 into
the first hydroprocessing reactor 40 and at least one portion of
the resulting first hydrocarbonaceous product stream in line 48 is
mixed with the additional portion of hydrocarbonaceous feed in the
second hydrocarbonaceous portion line 60 via lines 62 and 68 and
the mixture is fed via line 32 into the subsequent hydroprocessing
reactor 50 through inlet 52. The additional portion of fresh feed
in second hydrocarbonaceous portion line 60 serves to quench the
first hydrocarbonaceous product stream in line 48 and regulate
temperature before entering the subsequent hydroprocessing reactor
50.
[0044] The subsequent hydroprocessing reactor 50 may have a single
catalyst bed 54 or may have a plurality of catalyst beds. The
subsequent hydroprocessing reactor 50 may be operated in a
continuous liquid phase or a continuous gas phase. The continuous
liquid phase is preferred with the hydrogen requirement supplied
from the mixed stream of unreacted hydrogen from the first
hydroprocessing reactor 40 in line 48 and in an aspect hydrogen
also optionally provided from lines 30, 68 and 32. The hydrogen
concentration should be kept sufficiently low to maintain a
continuous liquid phase if desired but high enough to provide
sufficient hydrogen for hydroconversion of the hydrocarbon feed. A
subsequent hydrocarbonaceous product stream exits the subsequent
hydroprocessing reactor 50 through outlet 56 into line 34.
[0045] In an aspect of the invention, the subsequent
hydroprocessing reactor may house a fixed catalyst bed and contain
hydroprocessing catalyst comprising pills that have a largest
dimension that averages no more than 1.27 mm ( 1/20 inch) and more
than 100 nm to produce the subsequent hydrocarbonaceous product
stream. In a further aspect, the hydroprocessing catalyst pills in
the subsequent hydroprocessing reactor 50 have a largest dimension
that averages no more than 0.85 mm ( 1/30 inch) and no less than
0.51 mm ( 1/50 inch). In an even further aspect, the
hydroprocessing catalyst pills in the subsequent hydroprocessing
reactor 50 have a largest dimension that averages no more than 0.51
mm ( 1/50 inch) and more than 100 nm. The hydroprocessing catalyst
pills in the subsequent hydroprocessing reactor 50 need not have
the same general size as in the first hydroprocessing reactor 40.
The subsequent hydroprocessing reactor may also be operated with a
higher mass flux of more than 29,300 kg/h-m.sup.2 (6,000
lb/h-ft.sup.2) when loaded with catalyst having sizes according to
the present invention. We have also found the mass flux can reach
50,000 kg/h-m.sup.2 (10,000 lb/h-ft.sup.2) if operated with the
catalyst having sizes of the present invention.
[0046] The first hydrocarbonaceous product stream in line 48 or the
subsequent hydrocarbonaceous product stream in line 34 may be
transported into a separation zone 70. A vaporous stream is removed
from the separation zone 70 via line 72 and may be further
separated into a hydrogen rich stream, contaminants, such as
hydrogen sulfide and ammonia, and low boiling point hydrocarbons.
In this case, stream 72 may be cooled, low boiling point
hydrocarbons separated in a flash drum with the ensuing gas being
scrubbed with an aqueous solution of absorbent such as an amine.
The resulting hydrogen-rich stream may be sent to a general
refinery hydrogen supply, but is not directly recycled back to the
hydroprocessing reactor 40 or 50 unless optionally recycled through
the make-up gas compressor 24 after mingling with the general
refinery hydrogen supply. Consequently, the hydrogen line 22 is out
of downstream communication with the hydroprocessing reactors 40 or
50 but optionally through a make-up gas compressor 24. The
remaining liquid product is removed from the separation zone via
line 74 and is directed in line 78 to further processing or to a
fractionation zone for further separation into its
constituents.
[0047] An alternative embodiment is shown in phantom in the FIGURE.
The remaining liquid phase is removed from the separation zone via
line 74 and, optionally, a portion of the liquid phase is
externally recycled in line 76, such that the external recycle is
added as a diluent as desired to one or all of the streams of fresh
hydrocarbonaceous feed 14 or 60 through lines 64 or 66,
respectively. In another aspect, the external recycle is added as a
diluent entirely to the first portion of fresh feed 14 in line 64.
The remaining liquid phase from the separation zone 70 is directed
by line 78 to further processing treatments and/or to a
fractionation zone for further separation into its
constituents.
[0048] Product recycle in line 64 may be mixed with the first
portion of hydrocarbonaceous feed in line 14 and hydrogen from line
22 and is carried in lines 16 and 28 into the first hydroprocessing
reactor 40. Product recycle in line 66 may be mixed with the second
portion of hydrocarbonaceous feed in line 60 and transported in
line 62. Optional hydrogen from line 30 may be mixed into line 62
and the mixture may be carried in line 68 to be mixed with first
hydrocarbonaceous effluent from line 48 and the mixture fed to the
subsequent hydroprocessing reactor 50 in line 32. In an aspect, the
hydrogen in line 30 is not preheated before mixing with the first
hydrocarbonaceous effluent in line 48.
[0049] In an aspect in which no subsequent hydroprocessing reactor
50 is present, the hydroprocessed product in line 48 may be
delivered to the separator 70. Product recycle may be fed in lines
76 and 64 just to the hydroprocessing reactor 40 via lines 16 and
28.
[0050] Without further elaboration, it is believed that one skilled
in the art can, using the preceding description, utilize the
present invention to its fullest extent. The preceding preferred
specific embodiments are, therefore, to be construed as merely
illustrative, and not limitative of the remainder of the disclosure
in any way whatsoever.
[0051] In the foregoing, all temperatures are set forth in degrees
Celsius and, all parts and percentages are by weight, unless
otherwise indicated.
[0052] From the foregoing description, one skilled in the art can
easily ascertain the essential characteristics of this invention
and, without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
* * * * *