Note: Descriptions are shown in the official language in which they were submitted.
75i
6117A ~prll 6, '~91
IMMOBILIZATION OF VANADIA DEPOSITED
ON SORBENT MATFRIALS DURING
T~EATMENT OF CARBO-~ETALLIC OILS
DescriPtion
Technical Field
. This invention relates to processes for producing a
; high grade of oil feed having lowered metals and Conradson
carbon values for use a3 feedstocks for reduced crude con-
version processes and/or for typical FCC processes from a
poor grade of carbo-metallic oil having extremely high
metals and Conradson carbon values. More particularly,
this invention is related to a method of immobilizing vana-
dium compounds deposited on the sorbent during pretreatment
of the oil feed.
Background Art
The introduction of catalytic cracking to the petro-
leum industry in the 1930's constitu~ed a major advance
over previous techniques with the object of increasing the
yield of gasoline and its quality. Early fixed bed, moving
bed, and fluid bed catalytic cracking FCC processes em-
ployed vacuum gas oils (VGO) from crude sources that were
considered sweet and light. The terminology of sweet re-
fers to low sulfur content and light refers to the amount of
material boiling below appro~imately 1000-1025F.
The catalysts employed in early homogenous fluid dense
beds were of an amorphous siliceous material, prepared syn
thetically or from naturally occurring materials activated
by acid leaching. Tremendous strides were made in the
1950's in FCC technology in the areas of metallurgy, pro-
; cessing equipment, regeneration and new more-active and more
stable amorphous catalysts. However, increasing demand with
respect to quantity of gasoline and increased octane number
; requirements to satisfy the new high horsepower-high com-
pression engines being promoted by the auto industry, put
axtreme pressure on the petroleum industry to increase FCC
"; ~
~L7~37S
capacity and severity of operation.
A major breakthrough in FCC catalysts came in the early
1960's with the introduction of molecular sieves or zeo-
lites. These materials were incorporated into the matrix of
amorphous and/or amorphous/kaolin materials constituting the
FCC catalysts of that time. These new zeolitic catalysts,
containing a crystalline aluminosilicate zeolite in an amor-
phous or amorphous/kaolin matrix of silica, alumina, silica-
alumina, kaolin, clay or the like, were at least 1000-10,000
times more active for cracking hydrocarbons than the earlier
amorphous or amorphous/kaolin containing silica-alumina
catalysts. This introduction of zeolitic cracking catalysts
revolutionized the fluid catalytic cracking process. Inova-
tions were developed to handle these high activities, such
as riser cracking, shortened contact times, new regeneration
processes, new improved zeolitic catalyst developments, and
the like.
The new catalyst developments revolved around the de-
velopment of various zeolites such as synthetic types X and
Y and naturally occurring faujasites; increased thermal-
steam (hydrothermal) stability of zeolites through the in-
clusion of rare earth ions or ammonium ions via ion-exchange
techniques; and the development of more attrition resistant
matrices for supporting the zeolites.
These zeolitic catalyst developments gave the petroleum
industry the capability of greatly increasing through put of
feedstock with increased conversion and selectivity while
employing the same units witbout expansion and without re-
quiring new unit construction.
After the introduction of zeolite containing catalysts,
the petroleum industry began to suffer from a lack of crude
availability as to quantity and quality accompanied by in-
creasing demand for gasoline with increasing octane values.
The world crude supply picture changed dramatically in the
late 1960's and early 1970's. ~rom a surplus of light,
sweet crudes the supply situation changed to a tighter sup-
ply with an ever increasing amount of heavier crudes with
,,
3L~L7~3~S
higher sulfur contents. These heavier and higher sulfur
crudes presented processing problems to the petroleum re-
finer in that these heavier crudes invariably also contained
much higher metals and Conradson carbon values, with accom-
panying significantly increased asphaltic content.
Fractionation of the total crude to yield cat crackercharge stocks also required much better control to ensure
that metals and Conradson carbon values were not carried
overhead to contaminate the FCC charge stock. The effects
of heavy ~etal and Conradson carbon on a zeolite-containing
FCC catalyst have been described in the literature as to
their unfavorable effect in lowering catalyst activity and
selectivity for gasoline production and their equally harm-
ful effect on catalyst life.
As mentioned previously, these heavier crude oils also
contained more of the heavier fractions and yielded less or
lower volume of the high quality FCC charge stocks which
normally boil below about 1025F and are usually processed
so as to contain total metal levels below 1 ppm, preferably
below 0.1 ppm, and Conradson carbon values substantially
below 1Ø
With the increasing supply of heavier crudes, which
meant lowered yields of gasoline, and the increasing demand
for liquid transportation fuels, the petroleum industry be-
gan a search for processing schemes to utilize these heaviercrudes in producing glsoline. Many of these processing
schemes have been described in the literature. These in-
clude Gulf's Gulfining and Union Oil's Unifining processes
~or treating residuum, UOP's Aurabon process, Hydrocarbon
Research's H-Oil process, Exxon's Flsxicoking process to
produce thermal gasoline and coke, H-Oil's Dynacracking and
PhiIlip's ~eavy Oil Cracking (HOC) processes. These pro-
cesses utili2e thermal cracking or hydro-treating followed
by FCC or hydrocracking operations to handle the higher con-
tent of metal contaminants (Ni-V-Fe-Cu-Na) and high Conrad-
son carbon values of 5-15. Some of the drawbacks of these
types of processing are as follovs: Coking yields thermally
1~7~375
cracked gasoline which has a much lower octane value than
cat cracked gasoline and is uns~able due to the production
of gum from diolefins and recuires further hydrotreating
and reforming to produce a high octane product; gas oil
quality is degraded due to thermal reactions which produce
a product containing refractory polynuclear aromatics and
high Conradson carbon levels which are highly unsuitable for
catalytic cracking; and hydrotreating requires expensive
; high pressure hydrogen, multi-reactor systems make of spe-
cial alloys, costly operations, and a separate costly fa-
cility for the production of hydrogen.
To better understand the reasons why the industry has
progressed along the processing schemes described, one must
understand the known and established effects of contaminant
metals (Ni-V-~e-Cu-Na) and Conradson carbon on the zeolite
containing cracking catalysts and the operating parameters
of an FCC unit. Metal content and Conradson carbon are two
very effective restraints on the operation of an FCC unit
and may even impose undesirable restraints on a Reduced
Crude Conversion (RCC) unit from the standpoint of obtaining
maximum conversion, selectivity and life. Relatively low
levels of these contaminants are highly detrimental to an
FCC unit. As metals and Conradson carbon levels are in-
creased still further, the operating capacity and efficiency
of an RCC unit may be adversely affected or made uneconomi-
cal. These adverse effects occur even though there is
enough hydrogen in the feed to produce an ideal gasoline
consisting of only toluene and isomeric pentenes ~assuming a
catalyst with such ideal selectivity could be devised).
The effect of increased Conradson carbon is to increase
that portion of the feedstock converted to coke deposited
on the catalyst. In typical VGO operations employing a zeo-
lite containing catalyst in an FCC unit, the amount of coke
deposited on the catalyst averages about 4-5 wt~ of the
feed. This coke production has been attributed to four dif-
ferent coking mechanisms, namely, contaminant coke from ad-
; verse reactions caused by metal deposits, catalytic coke
117~37~
eaused by acid site cracking, entrained hydrocarbons resul-
ting from pore structure adsorption and/or poor stripping,
and Conradson carbon resulting from pyrolytic distillation
of hydrocarbons in the conversion zone. There has been pos-
tulated two other sourees of eoke present in reduced erudesin addition to the four present in VGO. They are: ~l) ad-
sorbed and absorbed high boiling hydrocarbons which do not
vaporize and eannot be removed by normally efficient strip-
ping, and (2) high moleeular weight nitrogen eontaining hy-
droearbon eompounds adsorbed on the eatalyst's acid sites.Both of these two new types of eoke producing phenomena add
greatly to the complexity of residue processing. Therefore,
in the proeessing of higher boiling fraetions, e.g., reduced
crudes, residual fractions, topped erude, and the like, the
eoke produetion based on feed is the su~mation of the four
types present in VGO proeessing (the Conradson earbon value
generally being mueh higher than for ~GO), plus coke from
the higher boiling unstrippable hydroearbons and eoke asso-
eiated with the high boiling nitrogen eontaining molecules
whieh are adsorbed on the catalyst. Coke production on
clean eatalyst, when processing reduced erudes, may be esti-
mated as approximately 4 wt% of the feed plus the Conradson
carbon value of the heavy feedstock.
The eoked catalyst is brought back to equilibrium ae-
tivity by burning off the deaetivating coke in the regenera-
tion zone in the presenee of air, and the regenerated cata-
lyst is reeyeled baek to the reaetion zone. The heat genera-
ted during regeneration is removed by the eatalyst and ear-
ried to the reaetion zone for vaporization of the feed and
to provide heat for the endothermic eracXing reaction. The
temperature in the regenerator is normally limited because
of metallurgieal limitations and the hydrothermal sta~ility
of the eatalyst.
The hydrothermal stability of the zeolite-containing
catalyst is determined by the temperature and steam partial
pressure at whieh the zeolite begins to rapidly lose its
crystalline strueture to yield a low activity amorphous ma-
1~L'75375
- 6 -
terial. The presence of steam ls highly critical and is
generated by the burning of adsorbed and absorbed (sorbed)
carbonaceous material which has a slgnificant hydrogen
content (hydrogen to carbon atomic ratios generally greater
than about 0.5). This carbonaceous material is principally
the high boiling sorbed hydrocarbons with boiling points as
high as 1500-1700F or above that have a modest hydrogen
content and the high boiling nitrogen containing hydrocarbons,
as well as related porphyrins and asphaltenes. The high
molecular weight nitrogen compounds usually boil above
1025F and may be either basic or acidic in nature. The
basic nitrogen compounds may neutralize acid sites whiles
those that are more acidic may be attracted to metal sites
on the catalyst. The prophyrins and asphaltenes also generally
boil above 1025F and may contain eIements other than carbon
and hydrogen. As used in this specification, the term
"heavy hydrocarbons" includes all carbon and hydrogen
containing compounds that do not boil below about 1025 F,
; regardless of whether other elements are also prèsent in the
compound.
The heavy metals in the feed are generally present
as porphyrins and/or asphaltenes. However, certain of these
metals, particularly iron and copper, may be present as the
free metal or as inorganic compoundc resulting from either
corrosion of process equipment or contaminants from other
refining processes.
As the Conradson carbon value of the feedstock
increases, coke produc-tion increases and this increased load
; will raise the regeneration temperature; thus the unit may
3p be limited as to the amount of feed that can be processed
. . /
~1~537S
- 6a -
because of its Conradson carbon content. Earlier VGO units
operated with the regenerator at 1050-1250 F. A new
development in reduced cxude processing, namely, Ashland Oil's
"Reduced Crude Conversion Process", as described in the
pending Canadian applications Serial Nos. 364,647, 364,655
364,665 and 364,666 all filed on November 14, 1980, can
operate at regenerator temperatures in the range of 1350-1400 F.
But
~ .~
1~7~i3~7S
--7--
even these higher regenerator temperatures place a limit on
the Conradson carbon value of the feed at approximately 8,
which represents about 12-13 wt% coke on the catalyst based
on the weight of feed. This level is controlling unless
considerable water is introduced to further control tempera-
ture, which addition is also practiced in Ashland's RCC pro-
cesses.
The metal containing fractions of reduced crudes
contain Ni-V-Fe-Cu in the form of porphyrins and asphaltenes.
These metal containing hydrocarbons are deposited on the
catalyst during processing and are cracked in the riser to
deposit the metal or are carried over by the coked catalyst
as the metallo-porphyrin or asphaltene and converted to
cause non-selective or degradative cracking and dehydrogena-
tion to produce increased amounts of coke and light gasessuch as hydrogen, methane and ethane. These mechanisms ad-
versely affect selectivity, resulting in poor yields and
quality of gasoline and light cycle oil. The increased pro-
duction of light gases, while impairing the yield and selec-
tivity of the processes, also puts an increased demand onthe gas compressor capacity. The increase in coke produc-
tion, in addition to its negative impact on yield, also ad-
versely affects catalyst activity-selectivity, greatly in-
creases regenerator air demand and compressor capacity, and
may result in uncontrollable and/or dangerous regenerator
temperatures.
These problems of the prior art have been greatly
minimized by the development at Ashland Oil, Inc. of its
Reduced Crude Conversion (RCC) Processes described in co-
pending applications referenced above. The new process can
handle reduced crudes or crude oils containing high metals and
Conradson carbon values previously not susceptible to direct pro-
cessing. Normally, these crudes require expensive vacuum distilla-
tion to isolate suitable feedstocks and produce as a by-product
high sulfur containing vacuum still bottoms. Ashland's RCC
process avoids these'prior art disadvantages. Ho~ever, cer-
~L17537~ji
tain crudes such as Mexican Mayan or Venezuelan contain ab-
normally high metal and Conradson carbon values. If these
poor grades of crude are processed in a reduced crude pro-
cess, they may lead to an uneconomical operation because of
the high load on the regenerator and the high catalyst ad-
dition rate required to maintain catalyst activity and se-
lectivity. The addition rate can be as high as 4-8 lbs/bbl
which, at today's catalyst prices, can add as much as $2-8/
bbl of additional catalyst cost to the processing economics.
On the other hand, it is desirable to develop an economical
means of processing poor grade crude oils, such as the Mexi-
can Mayan, because of their availability and cheapness as
compared to Middle East crudes.
The literature suggests many processes for the reduc-
tion of metals content and Conradson carbon values of re-
duced crudes and other contaminated oil fractions. One such
process is that described in U.S. Patent 4,243,514 and Ger-
man Patent No. 29 04 230 assigned to Engelhard Minerals and
Chemicals, Inc.
Basically, these prior art processes involve
contacting a reduced crude fraction or other contaminated
oil with sorbent at elevated temperature in a sorbing zone,
such as a fluid bed, to produce a product of reduced metal
and Conradson carbon value. One of the sorbents described
in Patent No. 4,243,514 is an inert solid initially composed
of kaolin, which has been spray dried to yield microspheri-
; cal particles having a surface area below 100 m2/g and a
catalytic cracking micro-activity (MAT) value of less ~han 20
and subsequently calcined at high temperature so as to
achieve better attrition resistance.
As the vanadia content on such sorbents increases, into
the range of 10,000-30,000 ppm, the elevated temperatures
encountered in regeneration zones cause the vanadia to flow
and form a liquid coating on the sorbent particles. Any in-
terruption or decrease in particle flow may result in co-
alescence between the liquid-coated particles, which inter-
rupts fluidization, and may cause unit shutdown.
., ,
~7~375
For example, at lO00 ppm vanadium, this phenomena be-
gins to be observed and by lO,000 ppm vanadium particle co-
alescence becomes a major factor in unit operation. ~y ap-
plying the methods of this invention, one can now operate in
the upper ranges of vanadium levels (30,000 to 50,000 ppm)
without vanadium deposition causing particle coalescence or
excessive sintering of the sorbent structure.
In the treatment of feeds of varying vanadium content.
the rate of vanadium buildup on the sorbent and the equili-
brium or steady state of vanadium on the sorbent is a func-
tion of vanadium content of the feed and especially the sor-
bent addition and withdrawal rates which are equal at equi-
librium conditions. The following table presents a typical
case for a 40,000 bbl/day unit in which the vanadium content
of the feed is varied from l ppm (treatment of an FCC feed
comprised of VGO and 5 to 20 percent of a heavy hydrocarbon
fraction) up ~o 25 to 400 ppm (treatment of a reduced crude
for RCC operations). In order to maintain various levels of
vanadium on the sorbent at the equilibriu~ state after long
term opera~ion (50 to 150 days), the sorbent addition rate
can be varied to yield equilibrated vanadium values of from
5000 to 30,000 ppm.
TABLE I
2~ Sorbent Addition Rates Required to ~old Vanadium
At a Given ~evel on Sorbent for Feeds
With Varying Levels of Vanadium Content
40,000 BBL./DAY UNIT
~otal
Vanadium # Metal Level on Equilibrium Material
PPM _ DaY 5000 lO,000 Z0,000 30,000
~: -
0.5~ l.0~ 2.0% 3.0
Daily Tonna~e Replacement _
400 5~00 500 250 l~5 8~
~7~375
10-
TABLE (Cont'd.)
Total
Vanadium # Metal
PPM Da~_ _ Daily Tonnage Replacement
5 200 2600250 125 65 42
100 1300125 63 32 21
. 50 65063 32 16 10
32532 16 8 5
Summary of the Inv0ntion
In accordance with this invention a process has been
provided ~or treating a hydrocarbon oil feed having a sig-
nificant content of vanadium and Conradson carbon to pro-
vide a product substantially lower in vanadium and Conrad-
son carbon. In carrying out this process the hydrocarbonoil feed is contacted with a sorbent und'er conditions where-
by coke and vanadium in an oxidation state lower than ~5 are
deposited on said sorbent, the sorbent is separated from the
remaining feed, and is regenerated in the presence of an
oxygen-containing gas under conditions whereby the vanadium
is retained in an oxidation state lower than +5. The re-
::
generated sorbent is recycled to contact fresh feed.
Vanadium in an oxidation state of +5 melts at a tem-
perature within the range at which the regeneration is car-
ried out; however, vanadium in the +3 or +4 oxidation stata
melts at temperatures significantly greater than those en-
countered in the regenerator, and therefore does not pre-
sent the problems resulting from coalescence of particles
as does vanadium in the~+5 oxidation state.
The invention provides a method of producing a high
grade of reduced crude conversion (RCC) feedstocks having
lowered metals and Conradson carbon values relative to a
poor grade of reduced crude or othcr carbo-metallic oil
having extremely high metals and Conradson carbon values.
The invention may further be used for processing crude
oils or crude oil fractions with significant levels of
metals and/or Conradson carbon to provide an improved feed-
.
':,
:, r '`
.
3~5
stock for typical fluid catalytic (FCC) cracking processes.
The invention thus provides an improved method fortreating petroleum oil feeds containing significant levels
of vanadium tat leas~ about 1.0 ppm). More particularly,
this invention reduces particle coalescence and loss of
fluidization caused by the vanadium contaminants in oil
fe~ds of all types utilized in FCC and/or RCC operations.
The invention is particularly useful in the pretreatment of
carbo-metallic oil feeds to be utilized in RCC units.
Brief Description of the Drawings
Figs. l and 2 are schematic designs of sorbent regen-
eration and associated cracking apparatus which may be used
in carrying out this invention.
~est and Various Other Modes
For Carrying Out the Invention
The invention may be carried out by controlling the re-
generation of the spent, vanadium-containing sorbent using
several methods, alone or in combination. The objective of
these methods is to retain vanadium in a low oxidation
state, either by not exposing the vanadium to oxidizing con-
ditions, or by exposing vanadium to oxidizing conditions for
too short a time to oxidize a significant amount of vanadium
to the +5 state.
The concentration of vanadium on the sorbent partlcles
increases as the catalyst is recycled, and the vanadium on
the sorbent introduced into the reactor becomes coated with
coke formed in the reactor. In one method of carrying out
the invention, the regenerator conditions are selected to
ensure that at least enough coke is retained on the sorbent
to keep vanadia in a reduced state. This coke may serve
either to ensure a reducing environment for the vanadium,
or to provide a barrier to the movement of oxidizing gas to
underlying vanadium. ~he concentration of coke on ~he sor-
bent particles is preferably at least about 0.05 percent
and a more preferred coke concentration is at least about
~175375
-12-
0.15 percent.
In one method of carrying out this invention, which may
be combined with the foregoing method of retaining at least
about 0.05 percent coke on the sorbent or may be used to
achieve lower concentrations of coke, the regeneration is
carried out in an environment which is non-oxidizing for
the vanadium in an oxidation state less than +5. This may
be accomplished by adding reducing gases such as, for exam-
ple, CO or ammonia to the regenerator, or by regenerating
under oxygen-deficient conditions. Oxygen-deficient re-
generation increases the ratio of CO to CO2 and in this
method of providing a non-oxidizing atmosphere the CO/CO2
ratio is at least about 0.25, preferably is at least about
0.3, and most preferably is at least about 0.4. The CO/CO2
ratio may be controlled by controlling the extent of oxygen
deficiency within the regenerator.~ The CO/CO2 ratio may
also be increased by providing chlorine to the regenerator
oxidizing atmosphere, preferably in concentrations of about
100 to about 400 ppm. ~hese methods of increasing the CO/
CO2 ratio are disclosed in copending application 398,960
: ~iled ~arch 22, 1982, "Addition of MgC12 Cata- O
lyst"
~5 Regeneration in a reducing atmosphere is especially
useful in combusting coke in zones where the coke level ap-
~proaches or is reduced below about 0.05 percent, and it is
preferred to have a CO/C~2 ratio of at least about 0.25 in
zones where the coke loading is less than about 0.05 percent
by weight.
It~is especia}ly contemplated in carrying out this
method that a reducing atmosphere will be employed in zones
within the regenerator wherein the sorbent particles are in
a relatively dense bed, such as in a dense fluidized or set-
tled bed. It is especially useful to keep the vanadium in
a reduced state under such conditions wherein the particles
are in contact or in relatively frequent contact with each
: .
,.~';~,
~7~37~ii
.
-13-
other, and are thus more likely to coalesce. In carrying
out this method a reducing gas, such as for example C0,
methane, or ammonia may be added to a zone having a dense
catalyst phase, such as for example a bed having a density
S of about 25 to about 50 pounds per cubic foot.
In another method of carrying out this invention, which
is particularly useful in regenerating sorbent to a coke
level below about 0.15 percent, and is especially useful to
attain a coke level below about 0.05 percent, the sorbent
is regenerated in one or more stages, in one stage of which,
preferably the final regeneration state, the sorbent parti-
cles are in contact with an oxidizing atmosphere for a short
period of time, such as for example, less than 2 seconds,
and more preferably less than one second. In the preferred
method of contacting the sorbent in a~n ~oxidizing atmosphere
the sorbent particles are in a dispersed rather than a dense
phase.
In ~he preferred method of carrying out this aspect of
the invention, a riser regenerator is used as the sta~e in
a multi-state regenerator to contact the catalyst with an
oxidizing atmosphere for a short period of time, such as
for example less than about two seconds and preferably less
~ than about one second. The riser stage of the regenerator
I has the advantage in reducing the carbon concentration to a
level less than about 0.15 percent or less than about 0.05
percent, that vanadium, which is no longer protected by a
coating of carbon, may not be in an oxidizing atmosphere for
a long enough time to form molten +5 vanadium. Further, the
low density of the particles in the riser-regenerator, mini-
mizes coalescence of those particles which may have liquid
pentavalent vanadia on their surfaces.
~n the preferred method of using a riser regenerator,
the parti~les are contacted with a reducing atmosphere, such
as one containing C~ or other reducing gas, after lea~ing
the riser and before accumulating in a dense bed of regen-
erated particles.
~h~ preferred rlser regenerator i5 similar to the ven-
~L~7~37S
ted riser reactor as is disclosed in U.S. Patents ~,066,533
and 4,070,159 to Myers et al which achieves ballistic separa-
tion of gaseous products from catalyst. This apparatus has
the advantages of achieving virtually instantaneous separa-
tion of the regenerated catalyst, now containins some vana-
dia to which any oxygen present would have access, from the
oxidizing atmosphere.
In the preferred method of reducing the coke concentra-
tion to a level less than about 0.15 and especially to less
than 0.05~ the catalyst is contacted with a reducing atmos-
phere, preferably immediately after its separation fro~ the
oxidizing atmosphere and most preferably also in collection
zones for the regenerated catalyst.
This invention may be used in processing any hydrocar-
bon feed containing a significant concentration of vanadium.
It i5, however, especially useful in processing reduced
crudes having high metal and high Conradson carbon values,
and the invention will be described in detail with respect
to its use in processing an RCC feed.
; 20 RCC feed having a high metal and Conradson carbon
values is preferably contacted in a riser with an inert
solid sorbent of low surface area at temperatures above
about 900F. Residence time of the oil in the riser is be-
low 5 seconds, preferably 0.5-2 seconds. The preferred sor-
bent is a spray-dried composition in the form of micro-
spherical particles generally in the size range of 10 to 200
microns, preferably 20 to 150 microns, and more preferably
between 40 and 80 microns, to ensure adequate fluidization
properties.
The sorbents useful in this invention include solids of
low catalytic activity, such as spent catalyst, clays, ben-
tonite, kaolin, n~ntmorillonite, smectites, and other 2-
layered lamellar silicates, mullite, pumice, silica, later-
ite, and combinations of one or more of these or like ma-
terials. The surface area of these sorbents are preferably
below 25 m2/g, have a pore volume of approximately 0.2 cc~g
or greater and a micro-activity value as measured by the
~;
I~
.
~L7S375
-15-
A5TM Test Method No. D3907-80 of below 20.
The RCC feed is introduced at the bottom of the riser
and contacts the sorbent at a temperature of 1150-1400F to
yield a temperature at the exit of the riser in the sorbent
disengagement vessel of approximately 900-1100F. Along
with the RCC feed, water, steam, naphtha, flue gas, or other
vapors or gases may be introduced to aid in vaporization and
act as a lift gas to control residence time.
Coked sorbent is rapidly separated from the hydrocarbon
vapors at the exit of the riser by employing the vented ri-
ser concept developed by Ashland Oil, Inc., and described in
U.S. Patent Nos. 4,066,533 and 4,070,159 to Myers, et al.
During
the course of the treatment in the riser, the metal and Con-
radson carbon compounds are deposited on the sorbent. After
separation in the vented riser, the coked sorbent is deposi-
ted as a dense but fluffed bed at the bottom of the disen-
gagement vessel, transferred to a stripper and then to the
regeneration zone. The coked sorbent is then contacted with
an oxygen-containing gas to remove the carbonaceous material
through combustion to carbon oxides to yield a regenerated
sorbent in accordance with this invention. The regenerated
sorbent is then recycled to the bottom of the riser where it
again joins high metal and Conradson carbon containing feed
to repeat the cycle.
This vanadia immobilization method is preferably em-
; ployed to provide an RCC feedstock for the processes for
carbo-metallic oil conversion described in copending
applications Ser. Nos. 364,64i, 364,655/ 364,665 and 364.666
referred to z~ove.
The preferred feeds capable of being cracked by these
RCC methods and apparatuses are comprised of 100~ of less of
650F+ material of which at least 5 wt~, preferably at least
10 wt~, does not boi} below about 1025F. ~he terms "high
molecular weight" and/or "heavy" hydrocarbons refer to those
hydrocarbon fractions having a normal boiling point of at
least 1025P and include non-boiling hydrocarbons, i.e.,
~r .
~`.,`,\
37~i
-16-
those materials which may not boil under any conditions.
A carbo-metallic feed for purposes of this invention is
one having a heavy metal content of at least about 4 ppm
nickel equivalents, (ppm total metals being converted to
nickel equivalents by the formula: Ni Eq. = Ni + V/4.8 +
Fe/7.1 I Cu/1.23) a Conradson carbon residue value greater
than about l.0, and a vanadium content of at least l.0 ppm.
The feedstocks or which the invention is particuiarly use-
ful will have a heavy metal content of at least about 5 ppm
of nickel equivalents, a vanadium content of at least 2.0
ppm, and a Conradson residue of at least about 2Ø The
greater the heavy metal content and the greater the propor-
tion of vanadium in that heavy metal content, the more ad-
vantageous the processes of this invention become.
A particularly preferred feedstock for treatment by the
process of the invention includes a reduced crude comprising
70~ or more of a 650F+ material having a fraction greater
than 20~ boiling about 1025F at atmospheric pressure, a
metals content of greater than 5.5 ppm nickel equivalents
~ 20 of which at least 5 ppm is vanadium, a vanadium to nickel
; atomic radio of at least 1.0, and a Conradson carbon residue
greater than 4Ø This feed may also have a hydrogen to
carbon ratio of less than about 1.8 and coke precursors in an
amount sufficient to yield about 4 to 14~ coke by weisht
based on fresh feed.
Sodium vanadates have low melting points and may also
flow and cause particle coalescence in the same manner as
vanadium pentoxide. Thus, it is desirable to maintain low
sodium levels in the feed in order to minimize coalescence
as well as to avoid sodium vanadates on the sorbent.
With respect to the tolerance levels of heavy metals on
the sorbent itself, such metals may accumulate on the sor-
bent to levels in the range of from about 3000 to 70,000 ppm
of total metals, preferably lO,000 to 30,000 ppm, of which
5 to 100%, preferably 20 to 80% is vanadium.
The treating process according to the methods of the
invention will produce coke in amounts of l to 14 percent by
.. .
~)
1~L7S37S
-17-
weight based on weight of fresh feed. This coke is laid
down on the sorbent in amounts in the range of about 0.3 to
3 percent by weight of sorbent, depending upon the sorbent
to oil ratio (weight of sorbent to weight of feedstock) in
the riser. The severity of the process should be sufficient-
ly low so that conversion of the feed to gasoline and light-
er products is below 20 volume percent, preferably below 1
volume percent. Even at these low levels of severity, the
treatment process is effective to reduce Conradson carbon
values by at least 20 percent, preferably in the range of 40
to 70 percent, and heavy metals content by at least 50 per-
cent, preferably in the ranqe of 75 to 90 percent.
The feed, with or without pretreatment, is introduced
as shown in Fig. 1 into the bottom of the riser along with
a suspension of hot sorbent. Steam, naphtha, water, flue
gas and~or some other diluent is pr,eferably introduced into
the riser along with feed. These diluents may be from a
; fresh source or may be recycled from a process stream in the
refinery. Where recycle diluent streams are used, they may
contain hydrogen sulfide and other sulfur compounds which
may help passivate adverse catalytic activity by heavy
metals accumulating on the catalyst. It is to be understood
that water diluents may be introduced either as a liquid or
! as steam. Water is added primarily as a source of vapor for
dispersing the feed and accelerating the feed and sorbent to
achieve the vapor velocity and residence time desired.
Other diluents as such need not be added but where used, the
total amount of diluent specified includes the amount of
water used. Extra diluent would further increase the vapor
velocity and further lower the feed partial pressure in the
riser.
As the feed travels up the riser, it forms basically
four products known in the industry as dry gas, wet gas,
naphtha, and RCC or FCC feedstock. At the upper end of the
riser, the sorbent particles are ballistically separated
from product vapors as previously described. The sorbent
which then contains the coke formed in the riser is sent to
~L~7~37S
-18-
the regenerator to burn off the eoke and the separated pro-
duct vapors are sent to a fractionator for further separa-
tion and treatment to provide the four basic products indi-
cated. The preferred conditions for contacting feed and
sorbent in the riser are summarized in Table C, in which the
abbreviations used have the following meanings: "Temp." for
temperature, "Dil. n for diluent,.~pp" for partial pressure,
"wgt" for weight, ~V~ for vapor, "Res." for residence, "S/O"
for sorbent to oil ratios, "sorb.~ for sorbentn, "bbl" for
barrel, ~MAT~ for microactivity by the MAT test using a
standard Davison feedstock, ~Vel." for velocity, "cge" for
charge, "d" for density and "Reg." for regenerated.
TABLF II -Sorbent Riser Conditions
Operating Preferred
Paramet_r Range _ Range
Feed Temp. 400-800F 400-650F
Steam Temp. 20-500F 300-400F
Reg. Sorbent Temp. 900-1500F 1150-1400F
Riser Exit Temp. 800-1400F 900-1100~F
Pressure 0-100 psia 10-50 psia
Water/Feed 0.01-0130 0.04-0.15
Dil. pp/Fzed pp 0.25-3.0 1.0-2.5
Dil. wgt/Feed wgt ~0.4 0.1-0.3
V. Res. Time 0.1-5 0.5-3 sec.
S/O, wtg. 3-18 5-12
Lbs. Sorb./bbl Feed 0.1-4.0 0.2-2.0
Inlet Sorb. MAT <25 vol.~ 20
Outlet Sorb. MAT <20 vol.% 10
V. Vel. 25-90 ft./sec. 30-60
V. Vel./Sorb. Vel. ~1.0 1.2-2.0
Dil. Cgs. Vel 5-90 ft./sec. 10-50
. Oil Cgs. Vel. 1-50 ft./sec. 5-50
~` 35 Inlet Sorb. d 1-9 lbs./ft.3 2-6
Outlet Sorb. d 1-6 lbs.ift.3 1-3
.
~.~`J
.
1~'7~i3~
--19-- .
In treating carbo-metallic feedstocks in accordance
with the present invention, the regenerating gas may be any
gas which can provide oxygen to convert car~on to carbon
oxides. Air is highly suitable for this purpose in view of
its ready availability The amount of air required per
pound of coke for combustion depends upon the desired carbon
dioxide to carbon monoxide ratio in the effluent gases and
upon the amount of other combustible materials present in
the coke, such as hydrogen, sulfur, nitrogen and other ele-
ments capable of forming gaseous oxides at regenerator con-
ditions.
The regenerator is operated at temperatures in the
range of about 900 to 1500~F, preferably 1150 to 1400F,
most preferably 1200 to 1300F, to achieve adequate combus-
tion while keeping sorbent temperatures below those at which
~ significant sorbent degradation ~an occur. In order to
; control these temperatures, it is necessary to control the
rate of burning which, in turn, can be controlled at least
i in part by the relative amounts of oxidizing gas and carbon
introduced into the regeneration zone per unit time.
Referring in detail to the drawings, in Fig. 1, petro-
}eum feedstock is introduced into the lower end of riser re-
actor 2 through inlet line 1 at which point it is mixed with
hot regenerated sorbent coming from regenerator 9 through
line 3.
The feedstock is partially catalytically cracked in
passing up riser 2 and the product vapors are separated from
;~ coke-coated sorbent in vessel 8. The sorbent par~icles move
upwardly from riser 2 into the space within vessel 8 and
fall downwardly into dense bed 16. The cracking products
together with some ~orbent fines pass through horizontal
line 4 into cyclone 5. The gases are separated from the
sorbent and pass out through line 6. The sorbent fines drop
into bed 16 through dipleg 19.
The spent sorbent, coated with coke and vanadium in a
reduced state, passes through line 7 into upper dense flu-
idized bed 18 within regenerator 9. The spent sorbent is
.,'
7~i375
-20~
fluidized with a mixture of air, CO and CO2 passing through
porous plate 21 from lower zone 20, is partially regenerated
in bed 18 and is pass~d into the lower portion of vented ri-
ser 13 through line 11. Air is introduced into riser 13
through line 12 where it is mixed with the partially regen-
erated sorbent which is forced rapidly upwards through the
riser and falls into dense settled bed 17. Line 14 pro-
vides a source of reducing gas such as CO for bed 17 to keep
the regenerated sorbent in a reducing atmosphere ~nd thus
keep vanadium present in a reduced oxidation state.
Regenerated sorbent i5 returned to the riser reactor
2 through line 3, which is provided with a source of a re-
ducing gas such as CO through line 22.
In Fig. 2 spent sorbent coated with coke and vanadium
in a reduced state flow into dense fluidized bed 3Z of re-
generator 31 through inlet line 33. Air to combust the coke
and fluidize the sorbent is introduced through line 34 and
porous plate 35 which distributes the air. Coke is burned
and the partially regenerated sorbent passes upwardly into
riser regenerator 36. The partially regenerated sorbent
which reaches the riser 36 is con~acted with air from line
37 which completes the regeneration and helps move the sor-
bent rapidly up the riser. The regenerated sorbent passes
,~ ~ upwardly from the top of the riser 36 and falls down into
dense settled bed 37; Dense bed 37 and the zone above 37
through which the regenerated sorbent fails are supplied
with a reducing gas such as CO through lines 40 and 41. The
regenerated sorbent is returned to the reactor through line
; 38, and the CO-rich flue gases leave the regenerator through
line 39.
Having thus described this invention the following Ex-
ample is offered to illustrate it in more detail.
: : :
Example
A carbo-metallic feed at a temperature of about 400F
is fed at a rate of about 2000 pounds per hour into the bot-
~J
3L~L7~37S
tom of a vented riser reactor where it is mixed with sor-
bent at a temperature of about 1275F and a sorbent to oil
ratio by weight of about 11.
The carbo-metallic feed has a heavy metal content of
about 200 ppm Nickel Equivalents of heavy metals including
100 ppm vanadium, and has a Conradson carbon content of
about 12 percent. About 83 percent of the feed boils above
650F and about 20 percent of the feed boils above 1025F.
The temperature within the reactor is about 1000F and
the pressure is about 27 psia. About 20 percent of the feed
is converted to fractions boiling at a temperature less than
430F and about 10 percent of the feed is converted to gaso-
line. During the reaction, about 11 percent of the feed is
converted to coke.
The sorbent containing about one percent by weight of
coke contains about 20,000 ppm Nickel ~quivalents including
about 12,000 ppm vanadium. The sorbent is stripped with
steam at a temperature of about 1000F to remove volatiles
and the stripped sorbent is introduced into the upper zone
; 20 of the regenerator as shown in Fig. 1 at a rate of about
23,000 pounds per hour, and is partially regenerated to a
coke concentration of about 0.2 percent by a mixture of air,
CO and CO2. The CO/CO2 ratio in the fluidized bed in the
upper zone is about 0.3.
The partially regene-ated sorbent is passed to the bot-
tom of a riser reactor where it is contacted with air in an
amount sufficient to force the sorbent up the riser with a
residence time of about 1 second. The regenerated catalyst,
having a coke loading of about 0.05 percent exits from the
top of the riser and falls into a dense bed having a redu-
cing atmosphere comprising CO. The regenerated catalyst is
recycled to the riser reactor for contact with additional
feed.
IndustriaI Applicability
The invention is useful in the treatment of both FCC
and RCC feeds as described above. The present invention is
'
.. ~
~.................................................................. .
1~i7S3~
particularly useful in the treatment of high boiling carbo-
metallic feedstock of extremely high metals-Conradson carbon
values to provide products of lowered metals-Conradson
carbon values suitable for use as feedstocks for FCC and/or
RCC units. Examples of these oils are reduced crudes and
other crude oils or crude oil fractions containing metals
and/or residua as above defined.
This invention is particularly useful in processing
feedstocks containing vanadium in a concentration of over
about lO0 ppm or over about 200 ppm and having Conradson
carbon values greater than about 8~. Feedstocks for which
the invention is particularly useful are those in whic~ the
vanadium content is at least about 50 percent of the heavy
metal content. However, this invention has applicability in
; 15 treating other feedstocks containing significant levels of
vanadium and is applicable, for example, for treating a gas
oil having a vanadium concentration greater than about 0.1
ppm and having a Conradson carbon value of less than about
1.
I 20 Although the treating process is preferably conducted ~ j
in a riser reactor of the vented type, other types of risers ''
and other types of reactors with either upward or downward
fIow may be employed. Thus, the treating operation may be
conducted with a moving bed of sorbent which moves in coun-
ter-current relation to liquid (unvaporized~ feedstock under
suitable contact conditions of pressure; temperature and
weight hourly space velocity. The process conditions, sor-
bent and~feed flows and schematic flow of a moving bed
operation are described in the literature, such as those
disclosed, for example, in articles entitled "T.C. Refor-
ming", Pet. Engr., April (1954); and "Hyperforming", Pet.
Engr., Aprll (1954)~
... .
