Note: Descriptions are shown in the official language in which they were submitted.
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PRETREATIJENT OF A CATALYST SUPPORT TO ENHANCE
CATALYTIC DEHYDROGENATION OF A HYDROQUINONE
This is a continuation-in-part application of application Serial No.
08/315,174 filed on September 29, 1994, which is a continuation-in-part
application of application Serial No. 08/172,007 filed on December 22, 1993.
R~r~Kt~Rt~l lNn ~F THF INVFNTI-~N
Technical Field:
The present invention relates to a p.ocass for pr~pa,ing a catalyst
system used to dehy h~efiale a hydroquinone, and more partlcularly, to such
a ~rucess v.:,er~in the support of the catalyst system is pr~trdated to enhance
the conversion of the hydroquinone to its cl;-lds4orldi.~ quinone and hydrogen.
Background Infol",dtion:
Catalytic del-yJ~ogd.,alion of a hydroquinone to its cGI~esponding
quinone and hydrogen is generally known. For exampls, the following
puh' c~tions inco"~,dted herein by reference; Plummer, ~Sulfur and I Iyd~en
from H2S~, H~J~ocaiL,on r~ocessin~, April 1987; U.S. Patent 4,592,905 to
Plummer ~t a~ and U.S. Patent 5,334,363 to Plummer, all teach pn~cesses for
recovering solid sulhr and hyd~en gas frDm a gas stream co,lta;ning
hydrogen sulfide, wherein the step of catalytically del-JJ~ugu~ndling an
anthrahydroquinone to its corresponding anthraquinone and hydrogen is
integral to each process.
In ac~r~nce with the abovo ~efe~nc~J prior art processes hydrogen
sulfide contained in a gas strearn, such as a l"~d,~rbon refinery off-gas, is
dissolved in a solvent also having an a,ltl.r~uinone d;ssolvod therein. The
hydrogen sulfide and a,ltl-raquinone are ,e~,leJ in sDlution to obtain solid
sulfur and the cG..~sponding al~thrdhydroquinone of the a.nl,.~uinone. The
30 solid sulfur product is recovered from the rea,tiol- so~ution and the
a, Itl ,ra~uinone is .~enerdte.l for recycle to the hydrogen sulfide reaction step
by catalytically dehydrogenating the al ~tl,rdl)~droquinone. Hydrogen gas also
results as a product of the anthraquinone regefi~r~tion step.
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W O96/33015 PCT~US96/02532
The p.ucess taught by Plummer in ~h~L~I) r~ss,i-g invesli~es
a number of ~Jiffer6nl suppGIl~ metal catalyst systems for use in the
regeneration step to de~r",ine the effect of the different systems on the
conversion of anthrahydroquinone to its corresponding anthraquinone. It is
5 believed that the selectivity of the conversion step is allùl)~ly dependent on the
catalyst system parameters, which, if in"~rop~tly ~~l~cted. can undesirably
result in re~uced yields of the co"espol,ding a.)~l..~uinone and concurrently
increased yields of less desirable con"~ounds, such as the c~"dsponding
anthrone and anthranol.
The Plummer process found that the s~ecific type of metal catalyst
selected is an i""~Gilant parameter for the catalvtic conversion of the
ar,ll,rdl"~droquinone to anthraquinone. The Plummer prucess also found that
the catalytic dehyd~uyenation step is strongiy dependent on the characte,islics
of the matefial selected as a support for the metal catalyst. In particular, the15 Plummer p,ucess found that selective dehydrogenation of the
ar,ll ,rdhydroquinone back to a, ~l "~uinone is favored by the use of only slightly
acidic catalyst supports such as silica or alumina, or by the use of basic
supports such as ",synesium oxide. More addic catalyst supports such as
silica-alumina ur,desi,dbly yield relatively low conversions of
20 a,ltl,rdhydroquinone to anthraquinone and yield relatively high conversions of
anthrahydroquinone to anll,ru,)e.
The present invention re~yni es a need for an improved catalytic
dehydrogenation ~.lucess that converts a hydroquinone to hydrogen gas and
its co"e,spording quinone. Aocordingly, it is an object of the pnasenl invention25 to provide a catalytic dehyJ~uger,ation pr~cess havin~ enl~anced selectivityfor
the conversion of a hydroquinone to its co.,~spo.,ding quinone. More
particularly, it is an obiect of the p.es6nt invention to provide a catalyst system
including a catalyst support, having onl)anc6J selectivity for the catalytic
conversion of a hydroquinone to its cGIlespGncling quinone. It is further an
30 object of the present invention to provide a p,ucess for pl~,e~ting a catalyst
support that enl~ances the selectivity thereof when employed in a process for
catalytically convértin~ a hydroquinone to its cG"~spo.,ding quinone. It is yet
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another object of the prese"l invention to provide a pru~ess for recovering
sulfur and g~seolJs hydro~en from a hydro~en sulfide containing gas stream
employing a quinone, wherein a dehyd~nalio,) catalyst effectively
regene.~les the quinone from its correspor,din~ hydroquinone. These objects
5 and others are achieved in ac~rdance with the invention .Jeselibed her~ner.
~1 IMMARY nF THF INVF~TlnN
In accG,~a,)ce with one e"t,GJ;",ent, the pr~e.ll invention is a plucess
for preparing a catalyst system containing a c~aly~t support and an ~coc: ~ed
10 catalyst used to catalytically deh~dl ~ ~ndt~a a hydroquinone, selectively
converting the hydroquinone to its cGr,espond;n~ quinone and hydr~en gas.
In accordance with anotl,er ei,d~i"~nl, the prdsent invention is a pf~cess for
pr~l,eatinç~ the ~talyst support used in conjunction with the ~ te-l catalyst
to dehy Jt~endte the hydr~quinone. In ac~,Jano~ with a further elllL~i,llel)l,
1~ the present invention is the catalyst system prepared in accG'dance with the
process d;sclQsed herein. In ac~,~nce with a more particular e"~b~i."enl,
the present invention is a prucess employing a quinone to f~vGr sulfur and
g~ceo~s h~J~ugen from a h~d~ugen sulfide con~niny gas stream, wl,erein the
catalyst system of the p,~ser~ invention is used to regenerate the quinone from
20 its corresponding hydroquinone.
The pr~senl prucess of pr~l,e~ting a ~t~ l support cG~".Iises
selecting a porous catalyst support from among sized alumina or silica and
calcining the selected support. The calcined support is cont~t~J with an
~queous solution conlaining a salt selQcte~ from the group consisli,)~ of alkali25 metal salts, alkaline earth metal salts, rare earth metal salts, and mixturesthereof, thereby l,eating the surface of the support with the ~ 1~J salt. The
salt-treated support is then dried and cal~n2~1 converting the salt to a
corresponding metal oxide. The desired pretn~ateJ catalyst support is
produced ll,ereby, having a sufficient quantity of metal oxide placed on the
30 catalyst support to reduce the acidity of the support.
The pr~s6,~ prucess of pr~ a catalyst system co""~,is~s s~le 1ing
a metal catalyst from the group consisting of nickel, cobalt. the platinum group
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W O96/33015 4 PCTrUS96/02532
metals and mixtures thereof. A pretreated catalyst support prepared in the
above-descliL~ ,l~nerisconla,1ecl with an ~qlJec~s so!ution conl~ning the
selected metal catalyst preferably in a metal salt form. The metal catalyst
solution augments the metal oxide on the pret,dal~l catalyst support with the
5 selected metal catalyst. The metal catalyst-l.aal~ caldly~l support is then
dried and calcined producing the d6Sil'13CI eatulyal system thereby, comprising
the catalyst placed on the pr~t,e~ted catalyst support. The catalyst system of
the present invention has enhnnced utility in the selective conversion of a
hydroquinone to its corrssponding quinone and hydro~en gas. The invention
10 will be further understood both as to its use and cG~ Gs;tion, from the
accompanying descriplion.
RRIFF nF~r~RlpTlt~N ~~F THF nRAwlN~
The figure is a plot of te."~,er~lJre pr~._.,.."~ c~dsG-~tion (TPD)
15 profiles for a catalyst support treat6d in acc~nJance with the process of the present invention and for a co",~rable urlt,dal~ cat~ly;,l support.
nF.~:CRlPTI~ N t-)F l'lt~ HI~ ) FME~ODIMENTS
The present invention relates to the catalytic dehydrogGndtion of a
20 hydroquinone to its cGIld~rK~in~ quinone and h1J~u~en (H2). Hydroquinones
having utility herein include anll,rah~droquinones, Len ohydroquinones
naphthahydroquinones, and mixtures tl,er~r. CGIl~spGndin~ quinones having
utility herein include a,ltl,raq.linones, ben~uinones, naphll,~.Jinones, and
mixtures thereof, respecti./ely. The dehydrogGndtio~ z_tion is typically one
25 stage of a multi-stage industrial pn~cess, wherein the quinone is ,~enerdled
from the hydroquinone for use in another stage of the pr~cess and hydrogen
is recovered as a product gas.
For example, the dehydrogenation ,~tiGn is employed to regenerata
a quinone from a hydroquinone as a stage of an industrial pr~ss to recover
30 sulfur from hydrogen sulfide ~H2S). In the sulfur recove.lr prucess, a selected
quinone is Jissolved in a s9'~ted polar oryan c sotvent. Suitable polar organic
solvents include N-methyl-2-pyrrolidinone, N,N~L"atl-~rlaceta"lide, N,N-
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dimethylfomlamaide, sulfolane (tetrahyJ~-~tll:sphene~ 3ioxi-J~), aeetonitrile,
2-nitropropane, propylene Ch bonale and mixtures ll ,er~of. The most pr~fe, .
solvent is N-methyl-2-pyrrolidinone (NMP). Suitable quir,ones are those having
relatively high solubilities in the above li~led polar or~anic solvents, and
5 include sueh antl"~uinones as ethyl a,ltl.r~uinone, t-butyl anthr~inone, t-
amyl anthraquinone, s-amyl anthraquinone or mixtures ll,er~of.
The quinone-conlaining solvent is fed to an H2S conversion reactor
along with a feed gas stream wnta nir~ a h~ aon sulfide gas. If the feed gas
stream a~ilionally col-t;ans large quanLL ~s of other ~ases that are inert to the
10 process, such as nitrogen, carbon dioxide, ,etl.ana or other low molQ~Ji~r
weight hydrocarbon gases, the feed gas stream is initially conla~,1ecJ with the
quinone-containing solvent in an a~sG,L,er ahead of the H2S conversion reactor.
In any case, the solvent preferentialiy solubili~es the h~d~u~en sulfide in the
feed gas stream upon conlact fomming a re~,tiGn sDlu~ion that is ",ainlained in
the reactor at a te---pe-~ure from about 0~C to about 70~C, an H2S partial
pressure from about 0.05 to about 4.0 dt---ospheres, and for a time sufficient to
convert the hydrogen sulfide and quinone in the r~.;tion solution to insoluble
sulfur and the co-,esponJing hydroquinone.
Upon conversion of the .~ t~, the re~1ion solution is removed from
the H2S conversion reactor and the insoluble sulfur product, in the form of S
or other sulfur polymers, is separated from the r~a~tion so'~ion by filtration,
centrifugation or any other means known in the art. The l~--,aincJer of the
,ea~tion solution, which contains the polar organic solvGnt, hydroquinone, any
ur,rt:~tecl quinone, and any L"~reacteJ constituents of the feed gas stream, is
heated to a temperature from about 100~C to about 150~C at al.-,Gsphe,ic
pressure and fed to a flash tank. Any unre~l~ teed gas constituents, such as
hy.J~ugen sulfide and car~on dioxide, are r~e.r~ from the rba~,1iGn sol~nion
in the flash tank and recycled to the H2S conversion rb~.,tor. The remaining
solution is v:;lh.l~ .l from the flash tank and pr~fer~ly heated further to a
te" ,~r~lure from about 1 50~C to about 350~C at a pressure at least sufficient
to prevent solvent boiling. The heated s~!l tion is then fed to a
dehydrogenation reactor where the hydroquinone is catalytically converted to
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W O96/33015 6 PCTnUS96/02532
quinone and hydrogen gas under the above-stated temperature and pressure
conditions.
In ac~iJance with the present invention, it has been discovered that a
catalyst system including a metal catalyst and a catalyst support, wherein the
5 catalyst system is prepared in a speoific ..,anner, une~tpecte~ly results in
improved h~nltu~en and quinone selectivity when a hydroquinone is catalytically
dehyd~enal~. In particular, it has been discovered that pr~t.eal."ent of the
catalyst support in a sp~ific "~nn~rto reduce the acidity ~I,or~of unexpectedly
results in improved l"~J~en and quinone selecffvity. Co,lt,s~ncJi, !aly, the
10 present invention results in .lecreasecl produ~tion of undesirable by-prod~cts,
such as anthrones and/or ar,ll,rdnols, during the dehyJ~enalion rea~.tiGn.
Pretleatl~lent of the catalyst support cG"".,ises ssl~ting a porous
catalyst support from among either alumina (Al2O,) or silica (SiQ ). The
catalyst support has a surface area of at least about 100 m2/~ and pr~fer~ly
15 at least about 200 m2/g. The catalyst support can be cn~shed and sieved to a
desil~ average particle size gid~terthan about 0.3 mm, and pr~,fe.~ greater
than about 0.5 mm. The sized catalyst support is calci.-eJ for several hours or
more at a temperature of at least about 1 20~C, and ~,r~fer~ly at least about
500~C. The calcined support is then contactecl with an ~lneous solution of a
20 salt s~ te~ from the group con~sli,~ of alkali metal salts, alkaline earth metal
salts, rare earth metal salts, and mixtures thereof. A pl~.fe..~J salt is a rareearth metal salt, such as a salt of lanlhanum, and in particular lantl.anum
nitrate.
Contacting ot the catalyst support with the salt solution can be
ac~-"plished by ~,~te,ir~ a solution of the s219cte~ salt onto the support whilemixing and shaking the support to obtain good contacting bet~raon the support
surface and the selected salt. Conla,tin~ of the cataiyst support with the salt
solution can altematively be accGi"plished by other means ~pardnl to the r
skilled artisan. In any case, conla,ting between the catalyst support and the
selected salt places the selected salt on the surface of the catalyst support.
Treal."ent of the catalyst support is completed by ~~."o~ing the salt-
treated support from the ~ueovs salt solution and drying the support with an
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air flow heated to a te"~per~ re of at least about 120~C. The dried catalyst
support is then caicined, pr~6,al~!y under s~bP~ntialiy the same cor,.JiliGns asdescribed above, thereby converting the 5elected sait on the surface of the
catalyst support to a cGr,~sponding basic alicali metal oxide, alicaline earth
5 metal oxide, rare earth metal oxide, or mixture tl,oreof, ~specti./eiy. A
prefellt~d basic metal oxide is a rare earth metal oxide, such as an oxide of
lanthanum.
A suffident quantity of the basic metal oxide is placed on the support to
reduce the acidity ll ,e~of. The amount of metal oxide placed on the cataiyst
support is generally within a range between about 1.0 weight % and aioout 10.0
weight %, and p,~felabiy within a rar~e between about 2.0 wei~ht % and about
5.0 weight %.
i~reparation of the cataiyst system is imple.,.anle~l with s~l3~tion of a
metal catalyst from the group consislin~ of nickel, cobalt, the platinum ~roup
15 metals, and mixtures tl,ereof. The platinum group metals as cJefine~ herein
consist of platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), osmium
(Os) and iridiurr (Ir). Of the metal caWysts ~ os~J herein the platinum ~roup
metals are piefe,-ed, and platinum is most pr~f~..~. The 5~ led metal
catalyst is placed on the prel~eale.l catalyst support by contacting the
20 pretreated catatyst support with a solution of the sGlected metal catalyst,
pr~fe(al~ly in the form ot one of its salts, such as a solution of platinum chloride.
Contacting of the catalyst support with the seleute~ metal catalyst
sol ~tion can be acoon,,l shed in su~ tially the same ,..anner as desc,;~ed
above or, alternatively, by other means appar~nt to the skilled artisan. In any
25 case, conla~ting between the catalyst support and the sele.AeJ metal catalyst solution places the metal catalyst on the surface of the ç~ l support
augmenting the metal oxide treatment. A sufficient quantity of the metal
catalyst is placed on the support to enable orr~ti~o pe,h,r--.e..)ce of the
resulting catalyst system in the conversion of hydroquinone to its co. .~ponding30 quinone. The amount of metal catalyst placed on the ~r~lr~ated catalyst
support is generally within a range bet-.3E., about 0.01 weight % and about 3.0
weight %, and pr~ferdbly within a range between about 0.1 wei~ht % and about
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W O96/33015 PCTrUS96/02532
2.0 weight %. The resulting catalyst system is then dried and calcined in
s~ st~ntially the same manner as desciibe J above.
The catalyst system preF~.~ in the "~nner of the pr~senl invention has
specific utility in the above~lescrlbecl dehy~ Gnalion r~a~tion of the sulfur
recovery process, wherein the catalyst converts a hydroquinone dissolved in
the polar solvent to hydlogan gas that is recovered as a co,n",er~al product
and to the corr6s~0n.iing quinone that is recycled to the H2S conversion
reactor.
The following examples delllonalldle the p~ arK~ utility of the
present invention, but are not to be constnued as limitin~ the scope tl,erdof.
FXAMPI F 1
A series of test runs are pelh,r",ed in a dehydro~enation reactor to
c~ele""ine the selechvity that ditf~,e,lt c~atyst systerns exhibit in the conversion
of an anthrahydroquinone to its cor,aspoi-~in~ arni-,~ inone and hy.J~u~on.
The reactor feed co--~osiliGn for all runs is pr~areJ co,..~,n~inç~ a mixture oft-butyl anthrahydroquinone (H2T8AQ) and t-butyl a,nilra~ inone (TBAQ) in a
N-rnethyl-2-pyrrolidinone (NMP) solvent. The relative quantity of total quinone
species (H2TBAQ and TBAQ) in the feed is 25 % by weight. The mole ratio of
H2TBAQ to T8AQ in the feed is 76.0:24Ø
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In each test run, the catalytic dehyd~enalion r~t~r is charged with
a different catalyst system comprising a catalyst and a catalyst support. The
reactor is a packed stainlsss steel tube having a diameter of 1.27 cm. The
different catalyst systems are characterized below:
Catalyst Catalyst Wt % on Support Oxide Wt%C~
.System Typa .~, ~rt Ty~a ~ nn ,
A Pt 2.75 SjO2 La2O3 2.50
B Pt 2.75 SiO2
C Cr2O3 12 Al2O3
The silica (SiO2) type catalyst support is D~vidson ~7 having a pore
volume of 1.0 cm3 and contains 99.5 % SiO2 by weiç~ht. The alumina (A~O3)
type catalyst support is Norton having a pore volume of 0.57 to 0.67 cm3 and
contains 99.85 % Al2O3 by weight. Each of the catalyst supports has a surface
area of 260 m2/g.
Catalyst system A is a catalyst system of the pr~sent invenlion having
a prel. ealed catalyst support p~pareJ in ac~ance with the manner
described herein. The support is initially crushed and sieved to an av~r~e
particle size of 0.56 mm. The sized support is calcinecl ovemight at a
tamperature of 500~C. Lantl,an.lm oxide (La2O3) is placed on the calcined
support by d~.~pN;5~ adding an ~ eous solutien of la.lt~ m nitrate
(La2(NO3)3) to the support while continuously mixin~ and shaking the support,
thereby producing a la"ll-~)~Jm nitrate on the support surface. The tlt~al6d
support is then dried with air flow for 2 hours at 120~C and calcined ovemight
at 500~C to obtain the desired lanthanum oxide~ te~ support. A platinum
(Pt) catalyst is then placed on the pr~t,edled support by ~l~o,~/;3a adding an
~clueous solution of platinum chlGiilJe (PtCI~) to the pret,~dted support while
continuously mixing and shaking the support. The catalyst system is dried with
air flow for 2 hours at 120~C, calcined ovemi~ht at 500~C, cooled to room
temperature, and stored in a ~lesi~tsr for use.
Catalyst systems B and C are prior art oalaly--l systems prepared in
sub~lPnlially the same manner as cJes~-ib6~1 above, but without pret.eat",ent
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W O9613301S PCTrUS96/02532
of the catalyst support. The alumina eatalyst support is crushed and sieved to
a particle size from 14 to 20 mesh.
The amount of catalyst system ~ ,ary~ to the packed bed of the reactor
in each nun is 7.8 em~. The reaetor is ",aintained at a te""~cr~.lre betwGGn
265~C and 275~C and at a hyJ~en pressure bet-v600 430 kPa and 500 kPa.
In eaeh run the feed is retained in the dehyd~u~enatiGn reaetor for a residence
time of 1 minute. The product is then removed from the reactor and analyzed
to .Jet6""i,-e the degree of total H2TBAQ conversion and conversion of H2TBAQ
to TBAQ and hydro~en. The results are set forth in the table below.
TABLE OF RESULTS
Run Catalyst H2TBAQ Conv~,sion (mole%)
ystem IQ~al To TR~
A 100 53
2 B 95 32
3 C 21 o
Run 1 ~e"lûr,~ dles the enhanced pe,h,r-"ance of a cata~l system of
the present invention for selectively con~e. ting H2TBAQ to TBAQ and
hydrogen. The catalyst system of nun 1 has a pr~lddt~J catalyst support as
compared to the prior art catalyst systems ot nuns 2 and 3 having u-lt-eate-l
catalyst supports.
FXAMpl F ~
An analytical prucedure is performed on a pair of catalyst support
samples to dele"-ine the relative acidities of the two sarnples. Sample 1 is an
alurnina r~talyst support treated in acoor~lance with the pr.cess of the presentinvention placing lanthanum oxide on the cata~-l support. Sample 2 is an
alumina catalyst support subst~ntially identieal to the ~taly~l support of
Sample 1, but lac~ing a lanlhdnum oxide l,~at,-.ont.
Eaeh sample is initially conla~ 1~1 with a""-,on;a to saturate the surface
thereof. The a"""onia saturated samples are then heated to drive off the
adsorLeJ a"""onia, while measuring the amount of ~,....on;a d~sG,LeJ as a
function of temperature by a teehnique tellll~ t~."pcrdture pru~r~,,,med
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W O96/33015 11 PCT~US96/02532
desorption (TPD). The desGiL.ecl ammonia from each sample is coilected in
sulfuric add solutions and the solutions are titrated upon cGi"pletion of the TPD
runs to determine the total amount of deso,~ a"""~nia from each sample.
The resuits of the TPD runs are shown in the Fiç~ure, wherein a TPD
profile for each sample is ~oneral~J by plottin~ the intensty of the a"""onia
signal on the y-axis (which is p,opo,tiol-al to the rate of a"""onia deso,~,lion)
against te",~er~re on the x-axis. The amount of a"""onia d~50l~1 from the
sample is a function of the amount of ~"I"Gn;a ~GIbed onto the sa"lpla,
which in turn is a function of the acidity of the sample. Ac~,~lin~ly a sample
having more ammonia .lesGibeJ tl.~re~,u.,, is relative~y more acidic than a
sample having less ammonia desorbed II,er~f~ul,-.
The TPD profile of Sarnple 2 in the Figure shows that untledl~ alumina
contains both weak and strong acid sites. The weak acid sites are evidenced
on the TPD profile of Sample 2 by a tel",~r~ture peak around 290~C,
cGr,espûnding to a ",axi-"um dasû~Jtiûn rate at this te-"pe.dture. The strong
acid sites are evi~6nc6c~ on the T~D profile of Sample 2 by a pronounced
shoulder center~cl around 400~C. The area under the TPD profile of Sample
2 is greater than that of Sample 1 indicating that the lladt~ alumina deso,Ls
less a-",nol,ia than the u-lt~a~ecl alumina and is, ll.erefere, less acidic than the
untreated alumina. Although the TPD profile of Sample 1 exhibits a
temperature peak around 290~C cGr,espondi"g to the temperature peak of
Sample 2 indicatin~ the pr~sence of weak acid sites on Sample 1, there are
fewer such sites on Sample 1 as e~,ic;E.-c~ by a lower pea~ The TPD profile
of Sample 1 also does not exhibit the shoulder centereJ around 400~C
2~ exhibited by the TPD profile of Sample 2, sug~estin~ that l.a~",enl of the
alumina catalyst support in the ",anner of the pr~s~.,l inve.~tion su~sl~nliall~ reduces the number ot strong acid sites lhereon.
The rne~ ~red value of total a"",~nia deSG ~ from Sample 2 is 3.6 std
cm3/g and the measured value of.total ~"., ~nia desci.l~l from Sample 1 is 2.9
std cm3/g, col-firl"ing the fi~nJings of the TPD prohles that the present treatment
process favorably reduces the acidity of the alumina ~lalysl support.
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W O96/33015 12 PCTrUS96/02532
FXAMPI F ~
An analytical procedure is performed on a pair of catalyst system
samples to dete",i,le the relative ~d~ities of the two sarnples. The first sample
is a palladium catalyst on a y-alumina support that has been prepared in
accGi~ance with the p.ucess of the pl~enl invention, pr~ dlin~ the catalyst
support by placinçl lanthanum oxide II,ereon. The second sample is a
p~ urn catalyst on a y-alumina support subsl~- Itially ide. ,lical to the lreale~l
catalyst support of the first sample, but lackin~ la.ltl.an.lm oxide. The catalyst
concentration of both samples is 0.5 % by weight. The la-ltl~,um oxide
concentration of the first sample is 7.0 % by weis~ht.
A ,.~tl,anol dehydl~ion le~tion is carried out in the presence of each
catalyst system sarnple at 300~C and the relative rates of Ji...etll~l ether (DME)
production for each sample are measured. A higher rate of DME pro~ tion
indicates the prt,sence of more acid sites on the catalyst system be~Jse such
sites are required for the dehyd.atiGo feaction. DME production in the
presence of the first sal-lple is 1.5 mole %, while DME pro~-~ction in the
presence of the second sample is 10.9 mole %. The results show that the
catalyst system prepared by the p,weas of the pr6s~nl invention has
subsl~nlially fewer acid sites than a c~",pa.~ble cataly~l system lacWng
lanthanum oxide on the catalyst support.
While the for~oing plefe"~ e.,l~iments of the inventiol, have been
desc~ e.l and shown it is u~elat~ that altematives and Ill~lific~tiGnâ such
as those su~e~t~ I and others, may be made tl ,er~to and fall within the scope
~ of the present inve.ltiGn.
