Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2~ 6
RACKGROUND OF THE INVENTION
. ~
I. Field of the Invention
This lnventlon relates to lmprovementa in a pro-
cess for the converslon o~ methanol to hydrocarbons, to
improvements ln a Flacher-Tropsc~l process for the production
of hydrocarbon~, and to improvements made ln catalysts
employed to conduct such processe~s. In partLcular, it
relates to improved cobalt catalysts, and proCess for uslng
such catalyats in the converslon of methanol, and Fiacher-
Tropsch synthesis to produce hydrocarbons, eapsclally C
diatillate ruela, and other valuable produots.
II. Back~round
A need exlsts for the creation, development, and
improvement of catalysts and processes, uqe~ul ror the con-
version of methanol and synthesis gaaes to hydrocarbona,
eapeclally high quality tranqportatlon fuels. Methane is
avallable in large quantlties, either as an undesirable by-
product or off-gas from process units, or from oll and gas
field~. The exi tence of large methane, natural gas
reserves coupled with the need to produce premiu~ grade
transportation Yuela, particularly middle distillate fuels,
thus poses a ~ajor incentive for the eevelopment of new gas-
to-liquids procesae3. However, whereas technology i9 avail-
able for the conversion of nat~ral gaa to methanol, in order
to utlllze this technology there is a need for new or
improvcd catalysts, and processes suitable for the conver-
sion of methanol to high quality transportation fuel~,
particularly middle distillate fuela.
The technology needed to convert natural g~s, or
methane, to synthesis 8as is also well e~tat~li3hed. It ls
also known that synthesis gas can be converted to hydro-
carbona via Fischer-Tropsch synthesi~, though new or
improved catalysta, and processes for carrylng out Fischer-
Tropsch reactions are much needed. Fischer-Tropsch
". ,
synthesls ~or the production Or hydrocarbon~ rrom carbon
monoxlde and hydrogen l~ weil known in the technical and
patent llterature. Commercial units have also bee~
operated, or are belng operated in ~ome parts Or the
world. The rirst commercial Fi3cher-Tropsch operation
utlllzed a cobalt catalyst, thou~h later more actlve iron
catalysts were also commercialized. An l~portant advance ln
Flscher-Tropsch catalysta occurred with the use of nic~el-
thoria on Kieselguhr in the early thirties. Thl9 catalyst
was followed within a year by the! correspondin6 cobalt
catalyst, 100 Co:18 ThO2:lO0 Kle~elguhr, parts by weight,
and over the next few year~ by catalysts constltuted to lO0
cO la ThO2:200 ~leselguhr and 100 Co:5 ~hO2:8 M80:200
Kie~elguhr, respectively. The ~roup VIII non-noble metals,
i.e., lron, cobalt, and nlckel, have been-wldely used ln
Fischer-Tropsch reactions, and these metalR have been pro-
moted with various other metals, and supported in various
ways on various substrate~. Most commercial experLence has
been based on cobalt and lron cataly3ts. The cobalt cata-
ly9t9, howe~er, are Or generally low activlty necessitating
a muItiple 3taged proces3, as well as low ynthesls gas
throughput. The lron catalysts, on the other hand, are not
really suitable for natural gas conversion due to the high
degree o~ water gas shift activity possessed by iron cata-
lyst3. Thus, more of the synthesis sas is converted to
carbon dioxide in accordance with the equation: H2 + 2C0
(CH2)X + C02; with too iittle Or the synthesis ~as being
converted to hydrocarbons and water a~ in the more desiraole
reaction, represented by the equation: 2H2 ~ C0 ~ (CH2)x
~2
The need for a catalyst compositlon, and process
useful ~or the converslon Or methanol or synthesi~ 3as at
high conversion levels, and at high yields to premium grade
transportation fuels, particularly without the production of
excessive amounts of ca-bon dioxide, were met in large part
by the novel cataly3t composltion~, and proce~se3 described
in U.S. Patent Nos. 4,542,122; 4,595,703; and 4,556,752. The
-- 2
1;~ 1 39~26
-
prererred catalysts therein descrlbed are characterized as
particulate catalyst composltions con3tituted Or a titania
or titania-conealning support, preferably a tltania support
having a rutlle:anata3e content of at least about 2:3, upon
which there 19 dispersed a catalytically active amount of
cobalt, or cobalt and thoria. These cataly3t compo~itions
po~se~s good activity and stabilLty and can be employed over
long periods to produce hydrocarbons from methanol, or to
syntheslze hydrocarbon~ from carbon monoxide and hydrogen.
These cobalt-titanla catalysts lt was found, like
most hydrocarbon synthesLq catalysts, became coated during
an "on-oil" run with a carbonaceous residue, l.e., coke,
formed either during extended periods Or operation or durlng
feed or temperature up~ets. The initially high activity of
che cataly3ts declines during the operatLon due to the coke
deposits thereon, and the operating temperature must be
increased to maintain an acceptable level Or conversion.
Eventually the catalysts become deactivated to a point where
the temperature required to maintain an acceptable conver-
lon level causes excessive formation of methane and other
light hydrocarbon ga3es at the e~pense Or the desired C10
hydrocarbons, at which point it ~ecomes neces~ary to
regenerate, and reactivate the catalyst. Unli~e many other
catalysts commonly used by the re~ining industry however,
when the coke deposits were t~urned from tne cobalt-titania
catalysts at oxidizing conditions by contact with air (or
oxygen) at elevated tempe aturet, and tne catalysts there-
a~ter trea~ed with hydrogen to reduce the cobalt metal
component, the initially high activity of the cobalt-t.tania
cataly~ts did not return to that of a rresh catalyst.
Rather, thelr activity wa3 considerably les~ than that of
fresh cobalt-titania catalysts. Moreover, after the
regeneration, and reactivation of the catalyst~, there was
no improvement in the rate Or deactivation and the deactiva-
tlon proceeded rrom a lower initial activity. This loss in
~2~39126
the overall activity brought about by burnlng the coke from
these catalysts at elevated temperatures in the presence of
air (oxygen) is not only detrimental per se, but severely
restricts the overall life of the catalyst, and threatens
their full utilization in commercial operations.
III. Objects
It is, accordingly, a primary objective of the
present invention to obviate this problem.
In particular, it is an object to provide novel
and improved cobalt-titania catalysts, and processes
utilizing such catalysts, for the conversion of methanol or
synthesis gas to high quality transportation fuels,
especially distillate fuels characterized generally as
admixtures of C10+ linear paraffins and olefins.
A more specific object is ~o provide new and im-
proved supported cobalt-titania catalysts, which in methanol
conversion and Fischer-Tropsch synthesis reactions are not
only highly active and stable prior to regeneration, and
reactivation, but capable after regeneration, and reactiva-
tion, of recovering their initial high activity, while main-
taining their stability.
A further object is to provide a process which
utilizes such catalysts for the preparation of hydrocarbons,
notably high quality middle distillate fuels characterized
generally as admixtures of linear paraffi.ns and olefins,
from methanol, or from a feed mixture of carbon monoxide and
hydrogen via the use of which catalysts.
IV. The Invention
These objects and others are achieved in accor-
dance with the present invention which, in general,
embodies:
(A) A particulate catalyst composition consti-
tuted of titania, or a titania-containing support, on which
there is dispersed a catalytically active amount of cobalt
sufficient to provide good activity and stability in the
production of hydrocarbons from methanol, or in the produc-
tion of hydrocarbons via carbon monoxide-hydrogen synthesis
-- 4
L2~i
reactlons, and sufficient of a metal promoter selected from
the group consisting of zirconium, hafnium Li.e., Group VIs
metals of the Periodic Table of the Elements (E. H. Sargent
& Co., Copyright 1962, Dyna-Slide Co.) having an atomic
weight greater -than 90] cerium (a lanthanium series metal),
and uranium (an actinium series metal), or admixture of
these metals with each other or with other metals, such that
after oxidizing the cobalt at elevated temperature, as
occurs after the deposition of coke thereon during an
operating run, the catalyst can be regenerated by burning
the coke therefrom by contact at elevated temperature with
oxygen or an oxygen-containing gas (e.g., air), and then
reactivated by contact of the catalyst with a reducing gas,
particularly hydrogen, to reduce the cobalt metal component
such that the activity and stability of the catalyst is
thereby restored. Suitably, in terms of absolute concentra-
tions the cobalt is present in amounts ranging from about 2
percent to about 25 percent, preferably from about 5 percent
to about 15 percent, calculated as metallic metal based on
the total weight of the catalyst composition (dry basis).
The zirconium, hafnium, cerium, or uranium in the form of a
salt or compound of said promoter metal, is added to the
cobalt-titania ca-talyst, in amount sufficient to form a
catalyst composite the activity and stabllity of which after
regeneration, and reactivation, approximates that of a fresh
cobalt-titania catalyst, i.e., a catalyst, cobalt-titania
catalyst which has never been regenerated. The promoter
metal is quite effective in low concentrations, concentra-
tions greater than that required to provide the desired
regenerability generally offering little, or no further
benefit. The efficiency of the promoter metals is believed
generally related to their highly dispersed physical state
over the surface of the titania support. Suitably, a
cobalt-titania catalyst can be made regenerable by composit-
ing therewith a zirconium, hafnium, cerium, or uranium metal
in weight ratio of metal:cobalt greater than about 0.010:1,
preferably from about 0.025:1 to about 0.10:1. One of more
-- 5 --
~g~6
Or aald promoter metala--vlz.. zirconium, hafnium, cerium,
or uranium--ls dlspersed with the catalytlcally actlve
amount Or cob~lt upon a titania support, partlcularly a
titania support wherein the rutile:anataqe wel~ht ratio is
at least about 2:3. The rutile:anataae ratlo is determined
in accordance with ASTM D 3720-78: Standard Teat Method for
Ratio Or Anataae to Rutile in Titanlum Dioxide Pi~menta 3y
Use Or X-Ray Dirrraction. The absolute concentratlon of the
cobalt and promoter metal is preaelected to provide the
desired ratio of the zirconium, hafnium, cerium, or uranium
metal:cobalt. Zirconium i~ a prererred Group IVB metal in
term~ of ita cost-efrectivene~s, and a cobalt-titania
catalyst to which zirconium i9 added in wei~ht ratio of
zirconla:cobalt greater than 0.010:1, prererably ~rom about
0.04:1 to about 0.25:1 has been found to form a catalyst
which is highly regeneration atable. This catalyst haa been
found capable of continued sequences of regeneratlon with
esaentially complete recovery Or its lnitial activity when
the catalyst is returned to an on-oil operation, and there
ia no loas in ~tability in elther methanol conversion or
hydrocarbon syntheais reactions. ~he cobalt-titanla cata-
lyst compositions when stabilized with any one, or admixture
of zirconlum, hafnium, cerium, or uranium, it has been
found, prcduce a product which is predorninately C10~ linea-
paraffins and olerins, with very l~ttle oxygenates. These
promoted catalyst species provide essentially the same hign
selectivity, high activlty, ar.d high activity maintenance
arter regeneration in methano1 conversion, or in the conver-
aion o~ the carbon monoxide and hydrogen to distillate
fuels, as ~reshly prepared unpromoted cobalt-titania cata-
lyata (i.e., catalysta otherw.~e similar except that no
zirconium, hafnium, cerium or uranium have been compoaited
therewith) which have never ~een regenerated, or subjected
to regeneration conditions. The promoted cobalt-titania
catalysta are thus highly regeneration ~table, the activity
and stability of the promoted catalyst being reatored a~ter
regeneration to t~at of an unpromoted cobalt-titania
-- 6
~2~ 6
catalyst which has never been regenerated by burning off the
coke at hi8h temperature in air under oxidizing condLt1Ons.
(B) A process wherein the partlculate zirconium,
harnium, cerium, or uranium promoted cobalt-tltanla catalyst
compo~ition of (A), supra, ls formed lnto a bed, and the bed
Or catalyst contacted at reaction condltionq wlth a methanol
feed, or feed comprlsed of an ad~ixture Or carbon monoxide
and hydrogen, or compound decompo~able ln situ within the
bed to generate carbon monoxide and hydrogen, to produce a
middle distillate fuel product constituted predominately of
linear pararfins and olefins, particul~rly Cl0+ linear
parafrins and olefins.
(i) In conducting the methanol reactlon the
partial pre~sure Or methanol within the reaction
mixture i~ generally malntained above about 100
pounds per square lnch at~olute (psia), and pref-
erably above about 200 psia. It is often prefer-
able to add hydrogen with the methanol. Suitably,
methanol and hydrogen are employed in molar ratio
Or CH3OH:H2 a~ove about 4:1, and preferably a~ove
8:1, to increase the concentration of Cl01 hydro-
carbons in the product. Suitably, the CH30~:H2
molar ratio, where hydrogen is employed, ranges
from at~out 4:1 to a~out 60:1, and prefera~l~ t~e
methanol and hydrogen are employed in molar ratLo
ranging from about 9:1 to a~out 30:l. Inlet
h~drogen partial pressures prefera~ly range oelow
about 80 p31a, and more preferably below about 40
ps a; inlet hydrogen partial pressures preferabiy
ranging from about 5 psia to about 80 psia, and
more prererably from about l0 psia to about 40
psla. In general, the reaction Ls carrled out at
llquid hourly ~pace velocities ranging from about
0.l hr l to about l0 hr 1, preferat~ly from about
0.2 hr l to about 2 hr l, and a~ temperatures
ranging from about 150C to about 350C, prefera-
bly from about 180C to about 250C. Methanol
~2~126
..
partial pressures preferably ran~e from about 100
psla to about 1000 psia, more preferably from
about 200 psia to about`700 pRia.
(li) The synthe~i~ reaction Ls generally carried
out at an H2:C0 mole ratio of greater than about
0.5, and preferably the H2:C0 mole ratlo ranses
~rom about 0.1 to about 10, more preferably from
about 0.5 to about 4, at gas hourly ~pace veloci-
ties rangin8 from about 100 ~/Hr/V to about 5000
V/Hr/V, preferat~ly from about 300 V/Hr/~ to about
1500 V/Hr/V, at temperatureg ranging from about
160C to about 290C, preferably from about 190C
to about 260C, and pressures above about 80 p9ig,
prefera~ly ranging from about 80 pslg to about 600
psLg, more preferably from about 140 p~ig to about
400 p9ig.
~he product of either the methanol conversion reactlon, or
synthesis reaction generally and preferably contaln3 45 per-
cent or greater, more preferably 60 percent or greater, C10+
llquld hydrocarbons which boll above 160C (320F).
In forming the catalyst, titania is used as a
support, or in combinatlon with other materlals for form~n~
a support. The titania used for the support in eitner
meehanol or syn~as conversions, however, is prefera~ly one
where the rutile:anatase ratio is at laast abGut 2:3 as
determined by x-ray diffraction ~AaT.~ D 3720-7~). ?refer-
ably, the tltania used for the catalyst support of catalysts
usad ln ~yngas conversion is one wherein the rutile:anata~e
ratio i9 at least about 3:2. Sui~ably the titania used for
~yngas conversions is one containin~ a rutile:anatase ratio
of form about 3:2 to about 100:1, or higher, preferably from
about 4:1 to about 100:1, or higher. A preferred, and more
selectlve catalyst for use in methanol conversion reactions
is one containing titania wherein the rutile:anatase ranges
from about 2:3 to about 3:2. The surface area of such forms
of titanla are less than about 50 m2/g. This weight of
rutile provldes generally optimum act.vity, and C10 hydro-
carbon selectivity without signlrlcant gas and C02 make.
31%6
The zirconium, hafnium, cerium, or uranium
promoted cobalt-titania catalyst prior to regeneration, it
was found, will have essentially the same high activity as
the corresponding unpromoted cobalt-titania catalyst. Thus,
during an initial, on-oil operating run, or run wherein
hydrocarbons are being produced over the fresh catalyst by
methanol conversion or hydrocarbon synthesis from carbon
monoxide and hydrogen the activity of the two different
catalysts is not essentially different. Unlike an unpro-
moted cobalt-titania catalyst, or catalyst otherwise similar
except that it does not contain zirconium, hafnium, cerium,
or uranium, however, the initial high activity of the pro-
moted cobalt-titania catalyst will be maintained even after
regeneration of the coked catalyst which is accomplished by
burning off the coke deposits at elevated temperature in an
oxygen-containing gas (e.g., air), and the catalyst then
reduced, as by contact of the catalyst with hydrogen, or a
hydrogen-containing gas. Moreover, the stability of the
promoted cobalt-catalyst will be maintained, this catalyst
deactivating in an on-oil run at corresponding conditions at
no greater rate than that of any unpromoted cobalt-titania
catalyst, or catalyst otherwise similar except that it does
not contain zirconium, hafnium, cerium, or uranium, which
has never been regenerated. Whereas the unpromoted, fresh
cobalt-titania catalyst was thus found to possess an initial
high activity in an on-oil operation, it was subsequently
found that the activity of this catalyst was not completely
restored after regeneration, the catalyst recovering only
about 50 percent of the activity formerly possessed by the
fresh catalyst. Moreover, after initiation of an on-oil
operation, the activity of the regenerated zirconium,
hafnium, cerium, or uranium promoted cobalt-titania will
decline at about the same rate as that of the fresh unpro-
moted cobalt-titania catalyst. Retention of this activity
and stability by the promoted cobalt-titania catalysts thus
effectively ellminates the disadvantages formerly associated
with unpromoted cobalt-titania catalysts, and makes possible
. ~ .
121~91~6
full utilization of cobalt~titania catalysts in commercial
operations.
Cobalt-titania catalysts, like most hydrocarbon
synthesis catalysts are primarily deactivated during on-oil
operation by the deposition thereon of a carbonaceous
residue, i.e., coke, formed either during extended periods
of operation or during feed or temperature upsets. It was
thought that the coked catalyst could be regenerated and its
initial activity restored by burning the coke from the cata-
lyst. Air burns at, e.g., 400-500C, are thus normally
effec-tive in removing essentially all of the carbon from a
catalyst, this offering a relatively simple, commercially
feasible technique for regenera-ting deactivated cobalt-
titania catalysts. However, in order for air regeneration
to restore activity, the catalytic cobalt metal must be
maintained in dispersed state at both on-oil and regenera-
tion conditions. Albeit the unpromoted cobalt catalyst upon
which the cobalt was well dispersed was found to be stable
during an on-oil operation, the cobalt agglomerated during
high temperature air treatment. It is found however, that
even in low concentration, zirconium, hafnium, cerium, or
uranium, or admixture thereof, could be used as an additive
to stabilize the cobalt-titania catalyst not only by main-
taining the cobalt in a dispersed state upon the titania
during on-oil operations, but also during air burns, thus
providing a readily regenerable catalyst.
Whereas Applicants do not wish to be bound by any
specific mechanistic theory, it is believed that the action
of the zirconium, hafnium, cerium, or uranium metals in
promoting the regenerability of a cobalt-titania catalyst
during an air burn can be explained, at least in part.
Thus, during an air burn the crystallites of metallic cobalt
of a cobalt-titania catalyst are oxidized to form Co3O4
which agglomerates at temperatures above about 350C. After
reactivation of the catalyst by contact with hydrogen cobalt
metal agglomerates are formed which are of larger crystal-
lite size than the original metallic crystallites of cobalt
-- 10 --
,
.
.
~.2~
metal. Large a$glomerates of cobalt form cataly3ts which
are la~s actlve than catalyst3 formed with more flnely di3-
persed cobalt. The zlrconium, hafnium, cerlum, or uranium
promoter metals of the promoted cobalt-titanla catalyst are
present a3 highly di3per~ed oxides over the TiO2 support
surface, and all are Or a cublc crystal 3tructure (except
for Ce which can exist either a3 cut~ic CeO2, or hexagonal
Ce203). These oxldes ars believed to form a 3trong 3urface
interaction wlth Co304 which i9 also of cubic crystal
structure. The cubic oxide promoters are thus belleved to
form a matrix, or act as a "glue" between the Co304 and
TiO2, and maintain the cobalt in finely dlaper3ed form upon
the support ~urface.
The cataly3ts Or thl3 invention may be prepared t~y
techniques known in the art for the preparation of other
catalysts. The catalyst can, e.g., be prepared by ~ella-
tion, or co3ellation techniques. Sultably, however, the
cobalt, zirconium, hafnium, cerium, or uranium metal3, or
admlxtures of the3e metals with each other, or with other
metals, can be deposited on a previously pilled, pelleted,
beaded, extruded, or sieved ~upport materlal by the impreg-
nation method. In preparing cataly~t~, the metal3 are
deposited from solution on the support in preselected
amount3 ~o provide the desired absolute amounts, and wei~ht
ratio of the respective metal3, e.g., cobalt and zirconium
or hafnium, or cobalt and an admi~ture of zirconiu~ and
hafnlum. Suitably, the cobalt ana zirconium, hafnium,
cerium, or uranium metals are composited with the support ~y
contacting the 3upport with a solutlon Or a cobalt-contain-
ing compcund, or salt, e.g., cobalt nitrate, acetate,
acetylacetonate, napthenate, carbonyl, or the li~e, and a
promoter metal-containing compound, or salt. One metal can
be compoaited with the support, and then the other. For
example, the promoter matal can first be impregnated upon
the support, foliowed by impre nacion of the cobalt, or vice
versa. Optionally, the promoter metal and cobalt can be
colmpregnated upon the 3upport. The cobalt and promoter
9~26
metal compounds used in the impregnatlon can be any organo-
metalllc or inorganic compounds which wlLl decompose to give
cobalt, and zLrconlum, ha~nlum, cerium, or uranium oxides
upon calcination, e.g., a cobalt, zirconium, or hafnium
nitrate, acetate, acetylacetonate, naphthenate. carbonyl, or
the like. The amount of lmpregnation solution used should
be su~iclent to completely immerae the carri~r, usually
within the range rrom about 1 to 20 times Or the carrier ~y
volume, depending on the metal, or metals, concentration in
the impregnation solution. The impregnation treatment can
be carried out under a wide range o~ conditlons including
ambient or ele~ated temperatures. Metal components other
than cobalt and a promoter metal, or metal~" can al~o be
added. The introduction Or an additional metal, or metal~,
into the catalyst can ~e carried out by any method and at
any time of the catalyst preparation, for example, prior to,
rollowing, or simultaneously with the impregnation of the
support with the cobalt and zirconium, haflium, cerium, or
uranium metal components. In the usual operation, the
addltional component is introduced simu1taneously with the
incorporation o~ the cobalt and the zirconlum, and hafnium,
cerium, or uranium components.
It is preferred to first impregnate the zirconium,
hafnium, cerium, or uranium metal, or metals onto the
support, or ~o coimpregnate the zirconium, hafnium, cerium,
or uranium metal, or metal with the cobalt into the titania
support, and then to dry and c~lcine the catalyst. Thus, in
one technique for preparing a catalyst a titania, or
tltania-containing support, is first impregnated with the
zirconium, hafnium, cerium, or uranium metal salt, or com-
pound, and then dried~or calcined at conYentional condi-
tion~. Cobalt is then dispersed on the precalcined support
on which the zirconium~ hafnium, cerium, or uranium metal,
or meta10" has been di~per~,ed and the catalyo,t asain dried,
and calcined. Or, the zirconium, hafnium, cerium, or
uranium metal, or metals, may be coLmpregnated onto the
~upport, and the catalyst then dried, and calcined. The
l26
zlrconium, harnium, cerlum and uranlum metals are believed
to exlqt ln the rlnished freshly calclned catalyst as an
oxlde, ~he metal oxLde~ being more closely assoclated with
the tltania ~upport than wlth the cobalt.
The promoted cobalt-tltanla cataly~t, after
lmpregnation of the support, i9 drLed by heatlng at a
temperature above about 30C, prererably between 30C and
125C, in the presence of n1trogen or oxygen, or both, or
alr, in a ga3 stream or under vacuum. It i9 neceasary to
activate the finished catalyst prlor to uqe. Preferably,
ths catalyst ls contacted in a firat step wlth oxygen, air,
or other oxygen-containing 8as a~; temperature surricient to
oxldlze the cobalt, and convert the cobalt to Co304.
Temperatures ranging above about l50C, and preferably above
about 200C, are satisfactory to convert the cobalt to the
oxide, but temperatures up to about 500C, such a~ might be
used in the regeneratlon Or a severely deactivated catalyst,
can be tolerated. Suitably, the oxidatlon Or the cobalt is
achleved at temperatures ranging from about 150C to about
300C. The cobalt oxLde contained on the catalyst i~ then
reduced to cobalt metal to actiYate the catalyst. Reductlon
iq performed by contact Or the catalyst, whether or not
prevlou ly oxldized, with a reducing gas, suitably with
hydrogen or a hydrogen-containing ga~ strsam at temperatur=3
above about 250C; preferably above about 30GC. Suitably,
the catalyst i3 reduced at temperatures ranging from about
250C to a~out 500C, and preferably from about 300C to
about 450C, ~or periods rangin; from about 0.5 to about 24
hours at pressures ranging from ambient to about 40 atmo-
~phere~. Hydrogen, or a gas containing hydrogen and inert
components in admixture i~ sa~isfactory for use in carryin~
out the reduction.
In tre regeneration ~tep, the coke is burned from
the cataly~t. The catalyst can be contacted w1th a dilute
oxygen-containing gas and the coke burned from the catalyst
at controlled temperature below the sintering temperature of
the catalyst. The temperature of the burn i~ maintained at
- 13 -
~2~ 6
the de.~lred level by controlllng the oxy~en concentratlon
and Inlet Bas temperature, thl~ ta~lng lnto conslderation
the amount of eoke to be removed and the time de3ired to
complete the burn. Generally, the eataly~t is treated with
a ga~ havlng an oxygen partlal pressure above about O.l
pound~ per ~quare ineh (psl), and preferably ln the range of
from about 0.3 p91 to about 2.0 psl, to prov$de a tempera-
ture ranglng from about 300C to about 550C, at statle or
dynamle eondltion~, preferably the latter, for a time
su~rleient to remove the coke deposits. Coke burn-ofr can
be aeeomplished by rir~t lntrodueing only enough oxygen to
Inltlate the burn whlle malntalnlng a temperature on the low
slde Or thls range, and gradually lnereaslng the temperature
as the flame front i9 advanced by addltlonal oxygen inJee-
tlon untll the temperature has reaehed optimum. Most Or the
eo~e ean generally be removed in this ~ay. The eatalyst is
then reaetivated by treatment wlth hydrogen or hydrogen-con-
tainlng gas as with a rresh catalyst.
The invention will be more fully understood by reference to
the accompanying drawings and to the following demonstratio~s and
examples which present comparative data illustrating its more
salient features. AlI parts are given in te~ms of weight except as
otherwise specified. Feed compositions are expressed as molar
ratios of the compoments.
In the accompanying drawings, Figures 1 and 2 are graphical
depictions of test results upon various catalysts according to the
invention.
The addition of a small amount of hafnium,
zireonium, eerium, or uranium, respec~.veIy, to a Co-TiO2
eataly~t maintains the eobalt in a high state of dispersien
and stabillzes the catalyst during nigh temperature air
treatments. The added zireonium, hafnium, eerium, or
uranlum metal thus maintains during and after regeneratior.
the ~ery high intrinsle activitY of the eataly t which .s
eharaeterlstie of a fresh eatalyst having well-dispersed
eobalt on the TiO~. The high intrinsic activity of c..e
promoted Co-riO2 permits, after regener~tlon, the same ~ h
converslon cperations at iow tem?er~ture, where exeellent
seleetivity ls obtained in the conversion of methanol o^
syngas to ClO~ hydrocarbons as with a fresh catalyst.
- l4 -
~2~
In the rollowlng example, the result~ Or a series
or runs are gl~en whereln various metals, lncluslve or
zlrconlum, hafnium, cerlum, and uranlum, re3pectlvely, were
added to portlons Or a rreshly prepared Co-T102 catalyst,
these speclmens of catalyst being compared with a portion Or
the Co-T102 catalyst to whlch no promoter metal was added.
These catalysts ~ere calclned by contact wlth alr at
elevated temperature in a slmulated coke burn, actlYated by
contact wlth hydrogen, and then employed ln a Fl~cher-
Tropsch reaction. The metal lmpregnated catalyst~ are
compared wlth the control, or portion Or the Co-TiO2
catalyat slmllarly treated except that no promoter metal was
added thereto. The ef~ectiYeness of the metal added to the
Co-T102 catalyst, or metal promoter, i9 demonstrated by the
amount Or C0 conversion obtalned wlth each of the catalyst~
arter the simulated regeneratlon.
EXAMPLE 1
Tltania (Degussa P-25 TiO2) was used as the sup-
port ror preparatlon of several catalysts. The Degus~a P-25
T102 was admlxed wlth Sterotex~(a vegetable 3tearlne used as
a lubrlcant; a product of Capital Clty Products Co.) and,
arter pllllng, grindin6, screenlng to 80-150 me~h (Tyler),
was calcined in aLr at 6500C for 16 hours to glve rlo2
supports w1th the following properties:
Rutlle:Anata,se Surrace Area Pore Volume
Welght Ratio`1) m2/g _ ml/~
97:3 14 0.16
(1) ASTM D 3720-78.
A ~eries Or promoted 11S Co-TiO2 catalyst3 was
prepared by impreznation of the TiO2 support using a rotary
e~aporator as described below, and the~e compared wlth an
unpromoted 11 S Co-TiO2 catalyst in conducting a hydrocarbo~.
synthesis operation.
* Trade Mark
.
3L,'~9~.26
-
The promoter metal9 were applled to the rio2 9Up-
port simultaneously wlth the cobalt, the lmpregnatlng
~olvent u~ed being acetone, ace~one/15-20~ H20, or water
(Preparatlon A, ~, or C), or by sequentlal impregnatlon rrom
solutlon Or a promoter metal, with lntermedlate aLr treat-
ment at temperatures ranging rrom 140C to 500C, wlth a
rinal lmpregnatlon of the drled promoter-containing TiO2
composlte wlth a solution o~ cobaltous nltrate (Preparatlons
D, E, F, G, and H). These catalyst preparatlon procedures
are described below in Table I.
Table I
Catalyst Preparat~on Procedures
.
Slmultaneous Impregnatlons _Solvent_ _ _
A Acetone
a Acetone/15-20% H20
C H20
Solvent
Intermedlate ror 2nd
Solvent for l~t Air Treat Impregnation
Sequentlal Impregnatlon Temperature (Cobalt
(-Promoter) C Nitrate)
D Isopropanol140 Acstone
E Acetone/15S H20 140 Acetone
Acetone/15~ H20 500 Acetone
G H20 140 Acetone
H H 0 500 H20
Cataly~ts lmpregnated in thls manner were dried in
a vacuum oven at 140C ror about 20 hours. Air treatments
were made in rorced-air ovens at varlous temperatures for 3
hours. The catalysts were d-luted 1:1 by volume with 80-150
me h T102 (to minimize temperature gradient~), charged to a
1/4 inch ID reactor tube, reduced in H2 at 450C, 5000
V/Hr/V catalyst for one hour, and then reac~ed with syn~as
3t 200C, 280 psig, CHSV~1500 (on cataly~t), and H2/C0~2 f~r
at least 16 hour~. The performance Or each catalyst was
- 16 -
.,
'~'.
~2~ 26
monltored by conventional GC analysls uslng neon as an
lnternal standard (4~ in the ~eed). Activity results are
tabulated ln Table II and shown in graphical form in Figures
1 and 2. Hlgh sslectlvity to heavy parafrlnlc hydrocarbons
was ob~alned over all Or these Co-TlO2 catalysts independent
Or the promoters present. Thus, methane selectlvlty was
about 3-5 ~ol. % and C02 selectlrity waa le~s than about 0.2
mol. % ln all runs. The balance Or ehe product was C
hydrocarbona.
- 17 -
~8~6
,...
Table II
Results of Catalyst Tests
Air Treat
_ Prep. Temp. % C0
Element ~ e~ Wt.S Procedure C-3 Hr. Conversion
None - - A -- 78
n 250 73
n 400 63
500 48
" 550 32
~ 600 28
Hf HfO(N03)2 0.06 A 500 48
0 . 31 n 400 78
" 0.31 " 500 73
" 0.50 " 500 70
n 0.50 1~ 600 58
" 0.63 " 500 71
1.89 1~ 500 78
" 3.0 . " 500 81
Ce (NH4)2Ce(NO3)6 o 55 B 500 79
n 0. 5 E 500 78
" 0.5 F 500 76
' 0.5 B 600 63
2. 0 E~ 500 64
~ 2.0 H 500 i~1
7r Zr~0C3H7)4 0.5 D __ 85
" 0.5 D 500 31
zro(02CCH3)2 0.3 C -- 75
n 0. 3 C -- 75
0 . 3 C 500 03
" ~. 6 C 500 68
0. 9 C ~~ 80
0.9 C 500 70
" 1.1 C 500 74
U U02(N03)2 1.0 A 500 79
. .
It i9 clear from these re3ults, a3 deplcte~ by
reference to Figure 1, that the zirconium, hafnium, cerium,
or uranlum promote, and maintaln the actlvlty of the lls Co-
TlO2 catalyst after calcinatlon. The actlvity of promoted
11S Co-TiO2 thus remalns high and virtually constant after
- 18 -
...
~2~9~21~
calcinatlon as high aa 500C whereas, in contra~t, the
actlYlty o~ the unpromoted 11% Co-TiO2 catalyAt declines
rapldly, and sharply; the rate of actlvlty decreacing
dependent upon the temperature o~ calalnatlon.
The data depicted in Figure 2 clearly show the
efrectlYeness Or small amounts Or ~irconium, ha~nium,
cerium, and uranlum to enhance the re~enerabllity of a 11
Co-TlO2 cataly~t, promotera in concentratlon of about 0.5
wt. percent being adequate for n~ear-maxlmum stabillzation.
Promoters ln greater concentration do not appear to produce
any signlflcant additlonal benefit, lf an~.
The hydrocarbon product dlstributlon was further
defined ln a run of an 11.2S Co-0.5S Hf-TlO2 catalyat. The
catalyst (150 cc) was dlluted with 110 cc TlO2, char~ed to a
1/2 lnch ID reactor, reduced with H2 at 450C ~or 4 hours,
and then used for the converslon of syn~as to hydro-
carbona. Operating condltlons and product distrlbution data
are shown ln Table III. The results conrirm the formatlon
o~ very heavy hydrocarbons over Co-Hf-TiO2 catalyst.
Table III
Hydrocarbon Product Dlstrlbution From Co-Hr-TiO2
Temperature, C
Sandbath 20~
Reactor Average 206
Cas Houriy Space Velocity on c~taiyst 10CO
Pre~3ure, p~lg 280
H2/CO Inlet Ratio 2.09
S CO Con~er~ion g9
Hydrocarbon Product Distribution, '~t. S
C1 5.6
C2-C4 3,4
C~-550F 15.1
5~0-700F 10.0
700-1050F 29.2
,050~ 36.7
.. . . .
9~2~
The followlng example lllustrate~ tha catalysts of
thia lnventlon used for the conversion of methanol to hydro-
carbon3.
EXAMPLE 2
Sitanla ln the form of spherlcal beadq was
elupplied by a catalyst manu~acturer and employed to make
ca~alysts. The titanLa was of 14-20 me~h e~lze (Tyler), and
characterlzed as havln~ a rutile:anatase ratlo of 86:14, a
e~urface area of 17 m2/g, and pora volume of 0.11 ml/~m.
Cataly~ts were prepared from por~;ions of the tltania by
aimultaneoua lmpregnation with aqueous solution~ containing
cobalt nltrate and a salt of ZrO(02CCH3)2, HfO(N03)2,
~NH4)2Ce(N03)6 and U02(N03)2, ree~pectively. Each catalyst,
after impregnation, was dried and alr treated at 500C for
three hours. The composltion of each of these catalysts in
terms of wel3ht percent cobalt and weight percent concentra-
tion Or the promoter (1 wt. S) is given in Table IV.
In separa~e runs, each of the promoted Co-TiO2
cataly~lt~ were charKed to a 3/8 inch ID reactor tube,
reduced ln hydrogen at 450C, 1000 GHSV, and 0 psig for one
hour. A feed admixture of hydrogen, argon, and methanol in
molar ratio of 20 CH30H:1H2:4Ar at CH30H LHSV - 0.67, 230C
and 400 psi~ was then passed over each of the catalysts.
The performance of each c~talyst was monitored by
conventional CC analy~i~ of the product with the resul~s
given in Sable IV.
- 20 -
8~
Table IV
CONVERSION OF METHANOL TO HYOROCAR~ONS
(230~C~ 400 PSIG, LHSV ~ 0.67, 20 CH30H:lH2:4 Ar)
Catalyst Compos1tion on TlO2
~t. ~ Co 5~0 4~344~654~55 4~73
Promoter (1 Wt. %) None Zr Hr Ce U
S CH30H Converglon 31 37 34 49 46
Rate, g CH30H Converted/1.6 2. 3 1 ~ 92.8 2.6
hr./g Co
Carbon Product
Dlstributlon, Wt. %
C0 16 13 16 10 9
C2 8 9 7 9 13
CH4 8 8 8 7 9
c2~ 68 70 69 74 69
~ .
The results show that the promoted catalysts are
more active than unpromoted Co-TiO2 catalyst~, calclned at
500C; whlch 19 best shown by the methanol converslon
rate. Cerlum, as wlll be observed, i9 an eapecially good
promoter rOr methanol conversion, the cerlum promoted Co-
T102 catalyst giving the highest activity and best selec- -
tlvity to C2~ hydrocarbons. The ~electivity of the Co-Ti~2
catalyst generally by ad~ition thereto of the respective
promoter remains high, and to some extent improved by the
pre~ence Or the promoter.
It is apparent that various modificatLons and
change~ can be made without departing the spirit and scope
of the present invention.
What is claimed i3:
