Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
9~3~7~
BACK~OUN~ O~ Tll~, IN~ TIO~
Many metal oxide,s and other metal-based composi-
tions are kno~n as hetero~eneous catal~sts for gas and
liquid phase oxidation and reduction reactions ln the chemi-
cal process and petroleum refinlng lndustrles. However,
these catalyst composltlons often deterlorate in u~e, losing
their crystallo~raphic identity or active components through
volatilization, poisoning or crystallite growth.
For example, catalytic r~orming reau~res catalysts
that provide active acidic sites such as halogen. These ac-
id sites in conventional re~orming and hydrocracking cata-
lysts are continuously lost durin~ operation~ with concomi-
tant loss in catalyst utility.
Moreover, current envlronmental concerns require
catalysts capable o~ converting the ob~ectionable components
o~ industrial and automotive exhaust streams to innocuous sub-
stances. I~own catalysts have ~enerally been unable to ~rith-
stand the reducing atmospheres, hig~ temperatures, and anti~
knock additive residues cor~monly ~ound in such applications.
S~RY OF TII~ ~JVh~TION
The present invention provides catalysts which are
useful in catalytic oxidation-rcduction reactions, includlng
those found in chemical processes, petroleum refining applica-
tions, and exhaus-t stream conversions, and exhibit high the~nal
stability and enhanced resistance to reducin~ environments and
chemical poisoning,.
~pccifically, the prcscnt lnventlorl ~rovldes cataly-
tic compounds of the general forlllula A~O3 ~r and have a
perovsl;ite crystal structure ~hereln ~ and B are each cations
of at least one metal and at least, a~out 1~ o~ the Type B
74
catlons are derived rrOm at least one catalytic metal
selected ~rom those transltion metals }laving atomlc numbers
Or from 24 to 30 and the platinum metals; 0 is oxide; X ls
rluoride or chloride; and f is about from 0.01 to 1Ø
The invention further provides a process of
bringing lnto contact at least one oxidiæable reactant and
at least one reducible reactant in the presence o~ a catalyst
and under such conditions a~ to e~fect a change ln oxidation
state of at least one reactant, characterized in that the
reac~ants are brought lnto contact ln the presence Or at
least one catalytlc compound of the general ~ormula AB03 fX~
and having the perovskite crystal structure wherein A and
B are each cations Or at least one metal and at least
about 1% of the Type B catlons are dérived rrom at least
one catalyticaliy active metal selected from metals of
Groups VB, VIB, VIIB, VIII and IB of the Periodic Table;
0 is oxide, X is fluoride or chloride; and ~ is about from
0.01 to 2.5.
Preferably, the A and B cation sites are occupied
by ions which contribute to the catalytic activity or
- stability Or the compounds.
DETAILED DRSCRIPTION O~ THE INVENTI()N
The metal oxyhalides of this lnvention have a
perovskite crystalllne confie;uration.
Ideal perovskite structures contain cations of
appropriate relative sizes and coordination properties and
-~ have cubic crystalline forms in whlch the corners of the
unit cubes are occupied by the lar~,er l'ype A cations (each
coordlnated with twelve oxide ions), the centers of the cube~
3 are occupled b!y the smaller Type B cations (each coordinated
-3-
. . ~
~06~'7~
with six oxide lons), an~ the races Or the cubes are occu-
~ied by oxide ions. Variations and di~tortions of thls
fundamen~al cubic cr~stal structure are known among materi-
als commonly considered to he perovskltes or perovskite-like.
Distortions Or the cubic crystal structure o~ perovskite ànd
perovskite-like metal oxides include rhombohedral, orthorhom-
blc, pseudocubic, tetragonal, and pseudotetragonal modifica-
tions. In all tllese crystal structures, it is requlred that
the total number of A site cations should substantially equal
the total number of B si'~e cations, also that the combined
charge of the cations substantially equals the charge on the ~ -
oxy~en atoms~
The particular B site metals and A site metals '
present depend to some degree u~on the radii of the metal
cations. The lmportance of ionic radli in perovskite cry~
stal structures has been discussed by many authors, e.g., ~'
by Krebs in ~Fundamentals o~ Inorganic Crystal Chernistry,~
McGraw Hill, London (1968). ~he Type A catlons o~ the pres-
ent composlti.ons generally exhibit ionic radii o~ from about
o.8 to 1.65 Angstroms, while the Type B cations generall~
have lonic radii of from about 0.4 to 1.4 Angstroms. The
ionic radii referred to herein are those tabulated by
Shannon and Prewitt, Acta Cryst. B25 925 tl969) and B26
1046 (1970).
In the oxyhalides of thiæ invention, the same
compositional ion size, and steric relationships
pertain except that a ~ction of the divalent oxygen ions Or
the ~BO3 type perovskite crystal lattice haæ been repla¢ed
by monovalent halogen æelected from f'luoride and chlorlde ln
`' 3 amounts correspondln~ to an "f" value .in the ~ormula o~ about
--4--
374
~rom O.Ol to .~.O, ancl usllally O.O5 to O.5
T~le perovskite type metal oxyhalides o~ this in-
ventlon thus have the ~eneral emplrical formula AB03 rX~,
in which the total number o~ A cations substantially equals
the total number o~ B cations an~ the combined charge of the
A and B cations substantially eauals the combined charges o~
the oxide and halide lons.
In general, the stoichiometric requisites for the
metals, oxygen and halogen in the compounds of the pr~sent
invention are met. However, the pr~sent compounds can con-
tain de~ect structures with an excess or a deflciency of
metal ions of up to about 25 atomic percent o~ the re~uisite
for the ideal ABO3 fXf perovskite crystal structure without
seriously detractin~ from their desirable characteristics.
Since the halide valence Or one is less than the oxide
valence of two~ the electrical neutrality of the composi-
tion can be achieved~ if needed, by one or both of the ~ollowing
techniques. Two or more cations havin~ dlfferent valences can
be selected for incorporatlon into the A or B sites, or one
or more cations capable o~ assumlng di~ferent valence states
can be selected for use in the compounds.
The particular cations of Type A used in the
present compositions are not critical provided they exhibit
suitable ionic radii and are o~herwise capable of
entering into perovslcite formation alon~ wlth the other
components making up the cr~stal lattlce. Included are mono-,
di-, tri- and tetravalent cations. Thus, the metals of
Type A can be selected from metals of the Periodic Table
Groups IA, IB, IIA, II~,IIIB, A~ IVA, and ~A, rrom the
lanthanide rare ~arth metals (atomlc number.~ 58 through 71)
_5_
3874
and from the actinide rare e~,rth meta,l~, tatomic numbers 90
through 104).
Preferably they are cations Or metals whose ~irst
ionization potential is not ~,reater than about 6.9~, i.e.,
metals of Groups IA, IIA, IIIB, the rare earth series and
the actini~e series, in particular ~a, K, Ca, Sr, Ba, La or
a mixture of cations of lanthanide rare earth metals. One
~uch mixture of lanthanide rare earth metals con~alns about ,
one-half cerlum, one-third lanthanum one-slxth neodymlum, ;;~,
10 and smaller amounts of the remainin~ metals o~ atomlc numbers '`~
58 through 71. The~e metals provide stlll ~reater stabillty
to the present compoun~s.
The cat:ions of T~pe B also can be selected
~rom any cations havin~, suitable ionic radii and ~re
otherwise capable o~ enterin~ into the perovskite crystal-
line structure. At least about 1~ Or these cations should
be selected from catalytic metals having atomlc numbers 24
to 30, that is, Cr, rln, Fe, Co, N~, Zn and Cu, and the plati~
num metals Ru, Rh, Pd, Os, Pt and Ir. The polyvalent
metals of atomic num~ers 2ll to 29 and the ~latinum metals
platinum and ruthenium provide increased catalytic e~fect,
and are therefore preferred. When a platinum metal is
used, catalytic metals other than the platimum group metals
are pre~erably present in amounts corresponding to at
least about 10% Or the B sltes. When the catalytlc metal
ions lnclude one or more platlnum group metal ions, either
as the sole catalytic material or as a component of a mix-
'~ ture of catalytic material, the platinum ~,roup metal wlll
normally comprlse from ahout 1 to 20~ o~ the ~ t~pe metals.
.,
. - .
987~
Ruthenlum, osmium, rhodillrn anrl Ir:LdLum are capa-
ble of occu~,vin~ all of the rrype B catlon site5 in perov~kite
crystal structures, but little additional benefit is
achieved when more than about 20% of th~ sites are occupied
by these metals. Palladium an~1 platinum ions are lar~er
than ruthenium, osmium, rhodlum and irldium ions and general-
ly not more than about 10% of the Type B sites of cr,ystal-
line oxides of the ~B~3_fXf tvpe carl be occupled by the lons
o~ these metals wlth retention o~ a perovskite structure.
Palladium is ty~ically divalent; rhodium ls typically tri-
valent; ruthenium~ iridium and platinum are typlcally tetra-
valent; and osrnium can have a valence o~ four, ~ive, six or
seven in these compounds. Mixtures of the platinum métals
obtained by the partlal refinlng of their ores can also be
used in these com~ounds.
Many of these catal~tic metals can exhibit two or
more valences differing in lncrements of l or 2 valence
units. Com~ounds containin~ these metals are generally more
actlve catalysts, ~03slbly because these metals are capable
o~ existing in perovskite crystal structures in two or three
valences differing by one valence unit increments. Cata-
lysts of the present invention wherein a Type B metal is
present in two valences often exhibits increased catalytic
activity over similar compounds in which the metal ls pres-
ent in only a single valence, nossibly because of the en-
hanced electron mobility through their crystal structures
resulting from tl1e presence of a variable-valence metal.
For this reason too it may o~ten be advanta~eous ko employ
such variable-valent catalytic components alon~ with
nlatinum metal cata]~tlc components in the compositions Or
-7-
. :.. - - - ' '
'
~06987~
this invention. In such em~od~ments, at least about 5~ of
the B sites will be occupled by a variable-valent metal in a
first valence and at least about 5% b~ the same metal in a
second valence; the valences dlfferlnF, preferably by one -
unit.
An~ B tvpe sites not occuPied bv the catalytic
metals can be occupled bv other cat,ions of metals from
~7roups IA~ IIA, IIB, IIIA, III~, IVA, IVB, VA, VB, VIB~ and
VIIB o~ the Periodic Table havin~ the proper ion size and
valence for the particu]ar com~osition contem~latcd. For
maximum contribution to crystal lattice stability, it is
preferred to emplo~ filler catlons of metals whose first
ionization potential is not greater than 7.10 (i.e., metals
of Groups IA, IIA, IIIA, IIIB, the rare earth series, the
actinide series, IVB, VB AND VIB), preferably not greater
than 6.90. Aluminum imparts to perovskite crystal struc-
tures a high degree Or thermal stability, resistance to
lattice reduction in a reducing atmosphere and durability in ~ -
catalytic applications, and is accordingly particularly pre~
ferred as a dlluent material.
The Periodic T~ble to which reference is made
herein i~ that given at pages 448-449, "Handbook of
Chemistry and Physlcs," 40th Edition, Chemlcal Rubber
Publishing Company (1958-59).
It ls ~enerall,y prererred t;~at; the sever~] compon-
ents of thc present compositions be selected a~ to their
nature and proportions such that the l,attice Stabillty Index
(LSI) value of the composition 1.5 minimized and i8 not
greater than about ].3.2 electron volts, and preferably, not
greater than 12Ø In general, lower LSI values lndicate
.
. ,; .
-
~06"3~37~
more stable catalytic compositions~
The LSI value~ are the sum o~ the product~ o~ (a)
the atomic fraction of each A site cation and each B site
catlon times (b) t~e ~irst ionization potential of each such
metal. Accordingly, the I.5I value is calculated by the
following equation:
LSI = fl.Il + f2.I2 __ ~ fi Ii + ~l.Il ~ f2 I2
a a a a a a b b b b b b
where fa~ f2~ fa~ fbl~ fb2, ri are the atomic fractions o~
cations Al, A2, -- Al, Bl, B2, -- Bi~ respectively~ Ia~ 12
-- Ia are the first ionization potentials of the metals
corresponding to the A site cations and Ib, Ib ~~ Ib are the
~irst ioni.zation potentials Or the metals correspondlng to
the B site cations involved. When a variable-valence metal
is present in a composition, an atomic ~ractlon is assigned
to the amount of the metal in each valence consistent with
; the requirements Or electrical neutrality o~ the present
compositions.
By ionization potential is meant the gas phase
~irst ionizatlon potentlal of the element as given by
Vedeneyev et al, "~ond Energies, Ionization Potentials and
Electron Affinities," St. Martin's Press (1966).
The compositions of this invention can be pre-
pared by heatin~ mixtures of metal oxides and/or precursors
thereo~ with metal halides that are thermally stable below
9~0C. and relatively involatile under substantiall~ anhy-
drous conditions ror suf~icient times an(1 tem~eratures
which permit spontaneous formatlon of the compositions.
The metal compounds will provide the desired metal oxy~en
and halide moieties and ~referablv will be used in the
stoichiometric proportions correspondin~ to the composltion
_9_
~LO~'3137~
desired. The oxlde providin~ s~artln~ m~teri,als in¢lude
not only ~he oxi~le~ t~lemselves hut such precur~ors as the
carbonates, carboxylates (acetates, oxalates, tartrakes),
nitrites and nitrates which are converted to oxides by pro-
longed heating ln oxidizlng atmospheres at the temperatures
at which these com~ositlons are formed.
A metal chloride or fluoride Or one or more of
the metals involved, which may be of the A type and/or the
B type, in an amount providing the desired proportion o~
halogen in the flnal composi~ion, can be admixed wlth the
rest o~ the perovsklte-forming components, preferably in the
form of the metallic carbonates co~recipitated from aqueous
solution, the metal moieties of said material being Or the
A and~or B tynes as needed and in the desired proportions to
complete the perovskite formulation.
The present compounds are in many instances formed
by atomic diffusion, without melting o~ any of the starting
or potential intermediate materials, and are suhJect to
coating of unreacted particles by reaction products.
Accordingly, the mixture of materials which are heated should ~
generally be finely subdivided and intimately mixed before '
heating, and thoroughly ground and mixed by any conventlonal
technlques several tim~s durln~ the heating period. The
heating times and temperatures required for the formation o~
; significant amounts of these catalytic compounds depend upon
the particular compositions being formed, the times required
usually being shorter at higher temperatures. Temperatures
above about 900C. are usually sui,table for the formati,on of
these compounds, using flrin~. times of hours to days with
occasional intermediate grindin~, and mixln~ but tempera-
tures of from 500 to 1500C. can also he used.
-10~
r - ~
~;9~7~
The co~te-l ~erovsl~lte composLtlons Or the inven~
tion can be used as catalysts in the form o~ ~ree-flowing
po~rders, for example, in fluld-bed reactlon systems, or in
the form of shaped structures providing efficient contact
bet~een the catalyst and reactant ~.ases. The catal~st
composltions can contain minor or ma,~or amounts o~ catalyti-
cally inert materlals, with the catalytic compositions
primarlly on thc surfaces of the inert material or dispersed
throughout. For example, the powdered compounds can be
rormed into porous catalyst pellets in which they are dis-
persed throughout by conventional techniques employing pel-
let presses, rolling mixers or extruders. Dlspersants,
lubricants, and binders are often used in conJunction with
the preparation of such pellets.
Cataly`tic compositions of this invention are
preferably used in the form of coatings on suitable refractory
supports. The compositions of the present lnvention can be
applied to supports elther before or after the completion of
the catalytic compositions. For example, the perovskite -
substrates Or the present catal~tic com~ositions can be
formed on supports whlch are sufficiently high melting and
non-reactive to withstand the subsequent processing steps ln-
volved in the application of the catalytic metal oxide com-
positions to the perovskite substrate. Alternatively, the
cat~l~tic com~ositlon Or the lnvention can be preformed and
a~plied to the su~port structure in a slurr~
Thc metal oxyhalide~, of this invention can be used
in catalytic oxidation and reduction xeac~ions in which the
oxidation s-tate of at least one reactant is chan~ed. They
: ' .
~L069874
are especially use~ul as ca-t~lysts :~or the oxldatlon o~ o~i-
dizable carbon components to compoun~s oI hiFJher oxidation
states, tlle reductioll of car~on monoxide and of nltrogen oxides
to compounds of lo~er oxidation states and the reduction of
hydrocarbyl mercaptans and sul~ides to substantially sulfur-
~ree hydrocarbon composi-tions.
Incorporation of` the hali~e cornponent o~ the inven-
tion in~o the perovskite structure as de~ined pro~ides active
(~cidic) metal-halide ~roups in the crystal lattice, wllich
groups constitute the kind Or reac~ion sites considered import-
ant in re~o~ning and hydrocrackln~ petroleum chemical operations.
They can also be used as a valuable tneans of providin~ cataly-
tically active me~als in more than one valance state (di~ering
by a cllarge of one) in the sam~ crystal lattice, ~hich split-ting
of tlle valellce states can be beneficial in promot~.tg those re- .
actions which depend on t~e presence in the catalyst of a metal
in tlro or more valence states for higher catalytic activity.
Among the oxidation processes for which the present
catalysts can be used is the oxidation o.~ carbon monoxide to ~-
, .
carbon dloxide and o~ hydrocarbons to carbon dioxide.
Hydrocarbons which can he used include those having 1-20
carbon atoms, including those that are normally gaseous and
those that can be entrained in a gaseous stream such as the
liquefied petroleum gases and the volatile aromatic, ole~ln-
ic and parar~inic hydrocarbons which are commonly in
industrial solvents and i.n fuels ~or lnternal combustion en-
glne~. The oxidant for these processes can be oxy~en,nitrogen oxides, such as N0 and ~l02~ which components are
normally present ln the exhaust gase~ of internal combustion
; 30 engines.
~ -12-
.
~Lo~ 4
Thc compounds of this invention can also be used to
catal~ze the re~uctlon of such oxides of nitro~,en as nitric
oxide, nitrogen dioxide, dinitrogen trioxlde, dinitrogen
tetroxide and the hi~,her oxides of nitrogen such a~ may be
present in waste ~ases from the production and use of nitric
acid as well as in the exhaust gases o~ internal combustion
engines. The reductant ror these processes can be hydrogen,
carbon monoxide and suc~l hydrocarbons as descrlbed above and
as present in said exhaust gases.
10The metal oxyhalides of thls invention contalning
ruthenium are particularly useful as catalysts for the re-
duction of nitrogen oxides. They generally catalyze the
reduction of these oxides to innocuous compounds (e.g.,
nitrogen) instead of to ammonia. Metal oxyhalides contain--
ing platinum and palladium are particularly useful as
catalysts for the complete oxidation of carbon compounds to
carbon dioxide.
Thus the compositions Or this invention are useful
for the slmultaneous oxidation and reduction inrolved in -~
the cleanup Or the exhaust gases of automotive and other
internal combustion engines.
Still another hydrocarbon oxidation process that
can be catalyzed by metal oxyhalides of this invention is the
steam reforming of hydrocarbons. ~his process known also
as hydrocarbon rerorming involves reaction of methane or a
homolog thereor such as those ~ound in volatile naphthas wlth
steam in the presence of a catal~st o~ the invention. Those
containin~ Ni or Co or a platlnum metal selected rrom Pd, Pt,
Ir, Ru and Rh supported on alumina, magnesia, or a baslc
oxide composition are particularl,y well suited for th:lr,
-13-
,
~LO~i~8~7~
application. The resulting product stream contains CO and
H2~ normally accom~anied hy C~2 rormed by reaction of C0
with excess steam in the well-known water gas shift. Reac-
tion temperatures are normally in the range 450 to 1000C.,
usually not above 900C., at pressures up to about 700 psi
and usually at least about 100 to 200 psi for methane re-
forming at reactant ratios of from about 1.5 to 6 moles o~
steam per carbon in the hydrocarbon feed stock.
The metal oxyhalides Or this invention can also be
used in the water gas shift reactlon which involves reaction
o~ CO with H20 (steam) at moderatel~ elevated temperatures.
Particularly suitable are those catalysts containing catlon~
Or the first transition metal series, such as Fe, Co, Ni or
Cu, preferably Fe or Cu. The resulting product-stream is
depleted in C0 ànd contains C02 and H2. Tempera~ures in
general are in the 20~ to 500C. range, with hi~her conver-
sions favored at the lower temperatures, higher reaction
rates at the higher temperatures. The process appears to be
largely independent of pressure.
Still another hydrocarbon oxidation process that can
be catalyzed by metal oxyhalides as described herein is the
dehydrogenation o~ aliphatic, cycloaliphatic and alkylaro-
; matic hydrocarbons having 4 to 12 carbon atoms and at least
two saturated (i.e., nonolefinic and nonaromatic) -CH-
groups which are ad~acent or in 1,6-positions relative to one
another (corresponding to sald first oxidation state) to
hydrocarbons, usually Or the ~.ame carbon content, formed by
removal of the hydrogens ~ro~ one or more pairs Or sa~d -CH-
groups (correspondin~ to said seconcl oxidatlon state).
The presence Or halogen in the catalysts Or this inventlon
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'
~065'~374
in such reactions substantially reduce8 or eliminate~ the
need rOr the addition Or halogen-containing compounds to
the feed stream to be dehydrogenated.
In the catalytic reforming process Or the
petroleum refining industr~, a relativel,y low octane value
feed stream cont~ining dehydrocyclizable and aromatlzable
hydrocarbons is converted into a relatively high octane
value exit stream containing aromatic hydrocarbons of the
gasoline boilin~ ran~e as the essential components resulting
primarily from dehydroc~clization of open-chain compcnents
to cyclohexanes and aromatization o~ cyclohexanes. Accom-
panying reactions include hydrocrackin~ to lower carbon con-
tent components and isomerization of stralght-chain to high~
er octane value branched-chain components. The process i8
generally carried in the presence of hydrogen to suppress
side reactlons leading to carbonization and to produce a
composition which is largel~ satur~ted except for the aro-
matic hydrocarbon content.
Still further processes that can be catalyzed in
accordance with this invention are those ~ischer-Tropsch re-
actlons involving the reduction of carbon monoxide with
' hydrogen ln the presence of a metal oxyhalide catalyst as
defined, particularly those containing ~e, Co, Ni, or Ru at
elevated tem~eratures (usuall~ 150 to 600C.) and pressures
(up to 15000 psi) effective to Pro(luce one or more products
containing chemically bound C and ~I with or without chemi
cally bound O such as methane or one or more gaseous, liquid
or solid higher hydrocarbons~ with or wlthout alcohols~
aldehydes, ketones and ~atty acids.
-15-
' .. ' ' "'
~36~S7~
Another reduction ~,~roce~s catalv~ed b~ ox~halide~ de-
~ined herein ls the catalytlc desulfurization Or hydrogenaly-
sis of or~anic divalent sulfur compounds, such as those
naturally occurring in feed stocks used in the petroleum
chemical industry, ~or example~ those used for the productlon
of synthesis gas (C~ an~ ~12) bv steam reformln~. as described
earlier, which stocks include mercaptans, linear sulfides,
cycllc sulfides and the aromatic cycllc sulfide thiophene.
The invention is further illustrated by the following
speciric examples, in which parts and nercentages are by
weight unless otherwise indicated.
EXAMPLES 1-7
The catalytic compositlons of Examples 1-7 were pre-
pared by heating mixtures of ~recursor compounds containing
anpropriate stoichiometric amounts of the metals and halogens
involved. The mixed precursor compounds were obtained by one
of two procedures, as indicated in Table I:
Procedure A: An aaueous ~otassium carbonate solutlon
_
was added to ~n aqueous solution of metal nitrates
and the resulting insoluble materials were separated,
washed, dried, and ground and a powdered low-
volatility halogen compound (e.g., aluminum Pluoride,
lanthanum chloride, or thorium fluoride) was added.
Procedure B: ~n a~ueous ~.~otassium carbonate solutlon
was added to a slurry of a powdered water-insoluble
low-volatility compound (e.~., aluminum fluoride,
molybdenum oxide, or platinum oxide) in an aa~ueous
solutlon o~ metal nltrates and the resulting ln-
soluble rnaterials were separated, washed, dried,
30 and ground
-16-
:''' - . :
.
b~ ~
The mixed precur~or compound~ were heQted in cruci-
bles in air at 900 or 1000C. f`or ~everal da~s with occa-
~ional coolin~ rindln~s~ and mixing. The re~ultin~5 me~l
oxide compo~itlons were finely ground. ~he e~p~cted
pero~skite structure~ of the product~ w~r~ con~lrmed by
their æ-ray di~raction patterns .
TABLE I
etal O?~yhalide~
Preparation
10Example Metal Ox~halide Procedure
~] ~FeO 0 8A10 0 ~1 2 . 8FO . 2 A
2 [L~ CrO.8A1~ O2 9C10 1 B
3 [~;aO 2BaO ~ [CU0.5A10.1MO ~I2~7~Q.3 B
4 ~aO 9 rh0~ eO.5CrO~O2 6F~-4 A
CaO 5$rO ~1CA1O.9P~O.~IO2.6 0.4 B
[~ 0, 5sro. ~1 ~A~O . gP~ 0~;;l o2 6Clo 1.~. g
7 [~aO 75Sr~ ~ CAlo.~PtO.lC o.5~ 2.6 O~ ~ A
me catalyst~ were applled to ~u~p~rts ~or ca~al~-
tic per~ormance testing~ O~e part o~ '~lsp~ *M alumina
disper ant aIld binder ~obtained ~rom the Contine~al Oil
Compa~ urf'ace ~rea about 164 squ~re meter~ per gra~, de-
termiIled with ~itrogen by the Brunauer-~mmett-Teller methD~)
was mi;~ed wlth ~7 parts o~ water containing a ~ew drop8 0~
commerc~ oncentrated hydrochlorlc acid. To ~is mixture
was added 7.5 ;parts of the catalytic compo~iti~n to s~btain a ~:
~tabl~ thixotr~pic ~l~ry. A c~llnder o~ "T~rve;5s:"~' alumina
caramic honeycomb w~h ~traight-throu~h cell~ (obtai}~ed from
E.I. du Pont d~ Nemours & Company) wa~ ~oaked ln ~ater.
* denotes trade mark
-17-
,
.. . . .
~0~
This cylinder weig~red about 6 to 7 grams, was about 2.5
centimeters in diameter and thickness and nominally had a
cell size Or l/16 inch, wall thickness Or 0.018 inch, open
area of 50%, 253 hexagonal holes per square lnch, and a
nominal geometric surface area of 462 square feet per cubic
root. The water-soaked cylinder was dipped into the slurry
o~ the catalytic composition, the gross eY.CeSS Or slurry was
removed by blowing the cylinder with air, the cylinder was
dried, and the cyllnder coated with the catalytlc composltion
and binder was heated for about 30 minutes in air in a murfle
furnace at about 700C. The cyllnder was again soaked in
water, dlp~ed int~ the slurry, blown free of excess slurry,
and dried and then heated in air at about 700C. for two
hours. The percenta~e increase in weiF,ht o~ the cylinder due
to the adherent`catalytic composltion and binder was about
15-25~.
The catalytic activity of these compositions in the
reduction Or nitric oxide by carbon monoxide was determined.
The "Torvex" ceramic honeycomb c,ylinder coated with the
catalytic composition and blnder was installed in a stain-
less steel chamber with a nominal internal diameter of 2.5
centimeters, hei~ht of 2.5 centimeters, and volume o~ 12.3
cubic centimeters. Nitrogen containing about 2000 parts per
million of nitric oxide and about 10,000 parts per million
carbon monoxide was passed throu~,h the chamber at a
- nominal ~ourl,y sp<lce velocity Or abou~ 40,000 hr. l and
pressure of one pound per s~uare lnch gauge while the feed
gas and the catalyst charnber were heated so that the temper-
ature of the gas entering the catalyst chamber increased
from about 60C. to about 600C. over about 90 minutes.
w18-
Samples of the inlet and exit ga~e~ were obtained periodi-
cally. The nltric oxide in ~hese s~mple~ was oxldized to
nitrogen dioxide. r~he resulting gas mixture was anal~zed
and the percent reduction in ~he nitric oxide concentration
of the gas upon passine through the catalyst chamber was
calculated. A smooth plot was made o~ the degree o~ conver-
~ion of nitric oxide at di~erent catalyst chamber inlet
temperatures for each c~talytic compo~it~on. From a ~mooth
curve through ~ach plot, te~peratures were estim~ted ~or
"light-of~" (the lnt0rcept with the tempe~ature axis o~ ~n
extrapolation of the portion of the curve at which the de-
gree of conversion changed rapidly with temperature) and ~or
nitric ox~de con~ersiong of 25%~ 50%~ and 90~. me cataly~t
temperature was higher th~n the catalyst bed inlet tempera-
~ure with all the catalytic composition~ at nitric oxide
conversion3 greater than about 25~ Table II gives the e~-
timated temperatures ~or l'light-o~" and ~or 25~, 50~0~ and
90~ conversion o~ nitric oxide be~ore and a~ter heating the
catalyst-coated honeycomb cylinder~ ~or 100 hours at about
900C~
me catalytic act~vity o~ the "Tor~ex" cylinder
coated with the catalytic composition and blnder in the oxi-
dation o~ c~rbon monoxide wa~ determined in a similar
apparatus and by a similar procedure. Nltrogen containing
about 10 000 parts per million of carbon monoxide and 10 000
parts per mlllion o~ oxygen wa~ pas~ed through khe catalyst
chamber and the entering and exiting gas mixtures were
a~alyzed chromatoOE aphically using a column containing gran-
ules of "L~nde"* 13X molecular ~ieveO The estimated tempera-
tures ~or '71ight-o~t' and ~or 25~, 50%, and 90~ converg~ n
: * denote~ trade mark
-19 -
,c..~,~'
'~
..
o~ carbon mono~lde bef`ore a~d a~-ter heating the c~tal~t-
coated honeycomb cylind~r~ for 100 hour~ ~t about 900C. are
glven in Table II.
The catalyatic activlt~ of the ~Torve~ cylinder~
coated with the catalytic compoPition in ~he oxldation o~
propane Nere de~ermined in a simllar apparatu~ and by a
similar procedure. ~itrogen containing about 1300 part~
per million o~ propane was determine~ in a ~imilar appara~u3
and by a slmil~r procedure. Nl~rogen containi~ about 1300
part~ per million o~ propane and 8800 part~ per million o~
oxygen was passed through the cat~ly~t chamber and th~ en-
tering and exiting g~æes were ~nalyzad chromatographicall~
uslng a column containing 80-100 mesh "Poropak"* QO The
temperatures for ~ ht-of~ and ~or ~5~J ~0%, and 90% con-
v~r~ion o~ propane before a~d a~ter heating ~he ca~alyst-
coated honeycomb cylinder~ ~or 100 hour~ at about 900G are
~iven in T~ble II.
* denote~ trade mark
-20-
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--21--
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9~374
Small samplcs (about 60 to 80 milligram~) Or each
of the metal oxyha~ es of Examples l, 2, 5, 6 and 7 were
heated in a Du Pont ~odel 950 Thermogravimetric Analyæer in
an atmosphere contalning 1% hydrogen, 4% carbon monoxlde,
and g5% nitrogen (by volume, flowlng at a rate of 30 milli-
llters per minute), with the temperature lncreasing in a
programmed manner at a rate o~ 10C. per mlnute to a rinal
temperature of 1000C. The changes in weight given in
Table III indicate the stability of the crystal structures
of the Example metal oxyhalldes under the experimental con- -
ditions. Wlth the oxyrluorides:
(a) The metal oxyfluoride [La]~Feo.8Aloo2]o2.6Fo.4 (Example
l) d~d not change significantly in weight.
(b) The Example 5 and 7 metal oxyfluorides decreased in
weight by 5.9% and 2.6% and did not significantly in-
crease in weight in any temperature region up to 1000C.
The metal oxychlorides showed larger changes ln weight than
the metal oxyfluorides.
The x-ray diffraction patterns o~ all these metal
oxyhalides contained the same strong lines after heatlng in
the reducing atmosphere to 1000C. as before heating.
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-23-
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