CA1191828A - Method for the preparation of high activity phosphomolybdic acid based catalysts - Google Patents

Abstract

Abstract of the Disclosure The present invention relates to a method for the preparation of phosphomolybdic acid based catalysts by forming a solution of hydrated phosphomolybdic acid in a substantially anhydrous alkyl alcohol, optionally adding a base to the solution, evaporating the solution to yield a catalyst powder and thereafter drying and calcining the powder to form the active catalyst. A second method for preparation is also provided and includes the steps of forming a solution of hydrated phosphomolybdic acid in a substantially anhydrous alkyl alcohol evaporating the solution to form a concentrate, impregnating a catalyst support material with the concentrate, contacting the impregnated support with ammonia gas in an amount sufficient to form an insoluble precipitate of ammonium alkyl phosphomolybdic acid within the pore structure of said support material and thereafter drying and calcining said impregnated support material so as to form a coated catalyst.

Description

(5493/94) METHOD FOR THE PREPARATION OF HIGH ACTIVITY
~LY~DIC ACID BASE~ CATALYSTS

l'echnical Field =~
Cataly~ts comprising pho~phomolybdic acid and various ~altR thereof have reeognized utility in ~everal ~reas of petrochemical proces~in~8. An area of particular importance which relPtes to the present invention i~ tbe u~e of pho~phomolybdic acid bssed compound~ 98 cataly~ts for the ~elective direct oxidation of aldehyde. 8uch a~
isobutyraldehyde and methacrolein eo their corresponding carboxylic acid, methacrylic acid. Ca~aly8i8 with supported or unsupported dehydra~ed phosphomolybdic acid in combination with lo ~mall amounts of promoters BUCh a8 antimony, 3rsenic, bismuth~
copper, tellurium an~ hydroxide~ or decomposable ~alts of alkali and alkaline earth metals iB a process of specific economic inte~est, The ~ubject invention 8et8 forth a method for the prepara~ion of pbosphomolybdic acid ba~ed cataly~ts having a high activity for the more efficient con~erRion of aldehydes to un~aturated carboxylic ~cId~.

Cataly~ts for the oxidation of uns~tura~ed aldehydes to un~atur~ted acid6 are generally well known in the literature and in various paten~. UOS. Pat~. No. 2,865,873 and 3,8B2,047 and Japanese Pat. No. 47-33082 disclose ~uch catalysts wberein ammonia or an smmonium~containirag compound i8 iincorporated in the preparation of the catalyst~O

~ (5493/94) U.S. Pat. No. 2,865,B73 in Column 13, Example~ 101 to 104 di~closes 9 proces~ for the prep~r~tion of methacrylic ~cid using catalysts consi~ting of molybdenum, pho~p~orus, titanium and oxygen, wherein ammonium para-molybdate i~ employsd in the prep~ration of the catalyises. The highest yleld of methacrylic ~cid produced i5 about 39.56%.
U.S. Pat. No. 3,882,047 discloses the prepar~tion of meth~crylic ~rid using c~l:aly3t8 cont~ining molybdenum~
pbo~phorus, ~t least one e~lement ~uch a~ thallium, rubidium, cesium and potassium, and at lea~t one element ~uch a~
chromium, silicon, aluminum, iron ~nt titanium. ThiR referenGe teache~ the incorporation of ~mmonl~ or ammonium~eontaining compound~ in the prepara~ion of cataly8t8 ~xemplified in the oxid~tion of methacrolein or acrolein; pho~phomolybdic acid i~
~mployed in ~he preparatlon of vir~ually ~11 catalyst~
exemplified; and in a few examples, ~mmonium molybdate is employed. This pat~nt di~closes in Column 3, lines 30-40 a~
~ol low8:
"It is pr~ferred that the c~talyse be prepared 80 that the con~ti~uent elements will form complex COmpOUnd8 ~UCtl a8 heteropoly~cid~, then acid salts or ammoni um sa lt B - l~
Japanese P~lto No. 47-33û82 dlsclo~es ~9 proce~s for recl~ iming an ammonia -modi f ied phosphorous-molybdenum-X-oxyger ~5 cataly8t, wherein X is at le~st one element sele~ted from the - group con~ ing of flntimony~ arsenic, bismu~h, cadmium, germ~nium, indium, iron, lefld, ~ilicont thallium, ~in and tungsten. Prepar~tion of the catalyst involves tr~stin8 the catalys~ with the aD~monia and wa~er by oxidizing the cat~ly~t (5~93/94)

2~
~n edv~nce or by ox~dizIng ie ~lmult~o~JI31y ~lth ~he ~re~t~n@nt of ~mmonia ~nd wster. This p~tene di~clo6e~ thae ehe ~mmoni~
forms a complex eompound with the oth~r elements present.
Preparation of pho~phomolybdic ~cid b~sed catalyse in 5 the absenc~ of Ammonia or ammonia-containing co~3pound i8 de~cribed in U.S. Pat. No. 4,136,110, commonly o~ned by et-e Assign~e of record herein. How~ver~ ehe procc~s ~et forth therein i8 slso dlrected toward cat~ly~t preparaeion from molybdenum trioxide. Thus, the prior ~rt of whicb we ~re ~ware 10 has not 8et forth a method by which ~ pho phomolybic ~cid ba~ed.
cataly~t can be prepared in aqueous media rola pho~phomolybic acid in the ~b~ence o.E ammonia or oeher b3sic compound.
United states Patent 4,424,141 by Gras~elli ee ~1., a~igned by our common A~3~gnee herein, is dlreceed ~o 15 the preparaeion of fir~t 6tage oxide cataly~ts coneaining molybdenu~ ~nd one of bi~muth or tellurium in ~n org2nic liguid preferably ~dmixed wittl 5 to 35X water.
U.S. Paeene Nos. 3,959,182 ~nd 4,035,417 disclo~e the preparation of molybdenum van~date catfllyst~ h~ving a 20 molybdenum ostide to v~nadium oxide w~ighe ratio of 2:1 to 8:1 in an agueous ~olu~ion eo which i~ ~dded v~riou~ org~nic reducing agent3. ~he liquid media exempllfied cont~ln between 4 to 8Z organics by w~ight.
U.S. PaE~ne No. 4,ooo9ns8 di~clo~e~ the ~queou~
25 preparation of pho~phomolybdic acid b~ed c~t~lys~ utilizing a solution of cata1y~t components, th~t upon mixing with aqueous 28a ~mmonia water, re~ult~ in ~ 3uapen~10n.
Thus it csn be l~een that the prior srt i~
chs r~ cte ri zed by t he u t i ;l i za t i on of ~mmoni~ or a n 30 ~mmonia-containing compound for the preparation o ~9~ (54~3/94) pho~phomolybdic acid ba~ed cataly~tR. It i~ b~lieved ~hat treatment with ~mmonia has been employed to react with group~
in ~he cataly~t which would otherwise undergo cro~31inking during drying and early calcination, a process which 5 significantly deactivates the cataly~t beEore it i8 even used.
Preparation of pho~phomolybdic acid based cAtalysts in alcohol i6 believed to provide protection for more of ~he~e group than when an aqueous ammoniatior! proce3R i8 employed thereby providing a bigher activity of the pbosphomolybdic acid ba~ed ~ catalyst.
DIS URE_OF THE INVENTION
It i~ therefore an object of the pre~ent inv~ntion to provid~ methods for ehe preparation of phosphomolybic acid based catalyst~ utilized in the oxidation of aldehyde~ to unsaturated carboxylic acids.
It i8 another object of the present invention to provide methods for the preparation of pho~phomolybdic acid baAed catalyst~ utilizing phosphomolybdic acid in the presence of alcohol follow~d by the ~ddition of ammonia or an amine ba~e to provide a resulting catalyst o~ high activity.
It i8 yet ~nother object of the pre~ent lnven~ion to provide method~ for the preparation of pho~phomolybdic acid based c~talyst~ in an alcoholic cataly~t solueion tbereby avoiding gros~ precipitation of ~olids.
It is ~till another-object of the pr@sent inveneion to provide methods for the preparation of phosphomolybdic flcid bas~d cataly~ts ln an alcoholic catalyst solutiDn which permits tt~e imprcgnaeion of porous preform~d ~upport~O

These and other objects, together with the advantages thereof over known methods, which shall become apparen-t from the specification which follows, are accomplished by the invention as hereinafter described and claimed.
In yeneral, the method of the present invention involves the steps of forming a solution of hydrated phosphomolybdic acid in a substantially anhydrous alcohol, heating the solution to form a dried catalys-t precursor, and calcining the catalyst precursor. In one embodiment, a base is also added to the solution of phosphomolybdic acid in alcohol.
In the alternative, the solution can be heated to form a concentrate or a dried precursor powder, and a catalyst support is coated with the concentrate or with the precursor powder (e.g., by method set forth in U.S. Patent No. 4,077,912).
Thereafter, the coated catalyst is formed by calcining. Suitable promoter-containing eompounds may optionally be added during the step of forming a solution. ~lternatively, the alcoholie phosphomolybdie aeid solution, wi-th or without the additional eomponents described hereinabove, may be emp]oyed to impregnate a porous preformed support material. Drying the impregnated support to remove the alcoholic solvent, followed by calcining, completes this alternate catalyst preparation procedureu In yet another method, catalyst component solution is obtained and used to impregnate a catalyst support material.
Treatment with a volatile base follows which includes the step of contacting the impregnated catalyst support material with ammonia gas, and thereafter drying and calcining -the impregnated support.

~ (5~93/94) The inventive catalyst preparation techoigue i~
~pplicable to phosphomolybic acid ba~ed c~t~lysts which ~re ~nown in the art ~9 ~econd ~t~ge ca~&ly~t~. Tbls 18 in contra~t to th~ method disclQ~ed in U.S. Patent 4,424,141 to Gr~sselli et ul., a3æigned to our common A6signee ~nd directed to the prepar~t50n of bismuth molybdste fir~t ~t~Be c~e~lyst~
in a precat~lys~ Rlurry in an organic liquid or 3 mix ure of an orgsnic liquid and water. By "fir~t ~tage" cat21y~t~ i~ me~nt that the catalys~s ~how good aceivity in the conver~ion of olefins to aldehyde~ such ~8 propyleno to ~eroloin but poor ~ctiviey in the conv~rsion of ~ldebyd~8 to acids ~uch ~8 acrolein to ~crylic ucid. First ~tag~ ~at~ly~e~ ere distlnguished from "second s~ge" caealy~t~, which are catalysts showing poor activity in ~he conver~ion of propylene to ~crolein but good aceivity in the conver~ion of ~crolein to acrylic ecid, and still other oxidation catalysts which are neither first stage cataly6ts nor ~econd 6tage c~t~ly~t~, ~.,g.
maleic anhydride catalyst6.
BecsuQe of the complexity of oxide complex oxidation 0 eacalysts, there i~ no clear under~tanding in the ~rt of ex3ctly what fe~tures of a catalyst (e.g. composition, cryst~l seruc~ure~ c~lcinatioD hi~tory, etc.~ ~ke it function ~ a first atage, ~econd ~t~ge or differen~ type of c~lyst.
Certain ob~ervaeions, however, ean be m~d~. For example, second ~t~ge catalyl3t~ cannot normally be cale~n~d for any length of time at temperatur@~ above ~bout l,000F (537C), aince they lo~e mosl: i not ~11 o their ~ctivity if treated in this w~y. On the ot:her hand, f~r~t ~tage eat~ly0ts work be~t ~ (5493/94) if calcined (final calcinati4nj ~bove 1,000F, such ~ for example a~ 610C. In addition, it appear~ that fir~t stage catalysts are "neutr~ll' in character while second stage catalysts are "acidic" in character.
Emplrically i~ i8 pos~ible to make a rougb approximation of the acidic or bssic character of an oxide complex by comparing the total po~itive valences of the cationic element~ with the total negatlve valence~ of tbe metalate moi~tie~ derived from the ~nionic ~cting element~
Because ~ome cationic elements sucb ~ iron may exist in more than one valence state and because of ~he ~mpho~eric ~lement~, this approxima~ion cannot be too exact. In flny ~vent, ~ing this type ~naly~il3 it appears th~t mo~t second tage caealysts have a significan~: exce~s of anionic ~pecies, i.e. are highly acidic, while most first stage catalyst have a reasonable balance of cationic and anionic ingredients and hence are relatively neutral. Analytically~ however, it i~ exeremely difficult or impo~sible to determine if ~uch oxide complexe~, which are oxide~ amd not acids or bases, exhibit sn acidic or basic characterO ]For thi~ rea~on, the "neutral"/'~acid"
designations for first and ~econd Btage caealyst~ are still regarded a~ unconfirmed ~peculation. However, it i3 known that firat and Recond ge~ge catalyst~ are materially different from one another ~nd from c2talysts exbibitin8 neither firs~ ~tage activity or second stflge activity ~nd th~t these di~ference~
can e~sily be deter:mined by teRting tbe catalyst in the first and second ~ta8e raactions a~ descrlbed above.
The catalyst commonly employed in the preparation of methacrylic acid from m~thacroleio or isobutyr~ldehyde and acrylic acid from acrolein ia a,phosphomolybdic ~cid b~sed catalyst which can be provid~d with one or more met~llic promoter~ and whicb h~s ebe general fo~mula Mo~PyAaBbCcDdEeOz. Suitable pramoters includ~

8~1~ (5493/94 eh~ following: wherein A. i~ am~onlu~a, C~8iUllD, pot98~ium9 rubidium ~nd/or thallium; B i~ copper and/or van~dium; C i8 an~imony, arsenic, bismuth aFId/or tellur~um; D i~ p~lladium; E
i8 aluminum, b~rium, calcium, cerium, chromium, cobalt, iron, magne~ium, manganese~ nickel, tantalum, titanium, tungsten, zinc, zirconium, chlorinc ~nd/or bromine; and, wherein x can be 6 to lb~ and iR preferably 9 to 12~ y can b~ 0.1 to 15 and i8 preferably 1 to 1. 5~ a can be 0.1 to 3 and i~ preferably 1 to 2, b can be 0.1 to 3 ~nd i~ prefer~bly û.l eO 1, c can be 0 to 2 and is preferably 0 to 007, d can be 0 to 2 and i~ preferably 0 ~o 1, e can be 0 to 4 and i~ pr~fera~ly 0 to 1, ~nd z iB a number nece~,ary to catisfy the otber elemene3. Suitable catalysts and the preparation thereof h~ve been de~crib@d in ~everal U.S. patents commonly owned by the Assignee of record herein and include, for instance, U.S. Pats. No. 4,083,805 snd 4,138,366. 0~ the~e many cataly~t~, ehose having a ratio of molybdenum to pho~phorus or from about 3:1 to a~ high a~ 15:1 can be employed with 9 o 12:1 being preferred. Addition of these promoters can be made by employing the aclds or decompo~able salts of the promoter~.
Ina~much a8 these catalysts are. ~nown, the specific compo~ition i8 not critical to the practice of the method set forth herein. Thu~, while a partiLcular formulation i~ employed 15 in this disclosure by way of exemplification, it ls to be understood that phosphomolybdic acid based compoRitions having other promoters could also be prepar0d according to the pre ent i nve nt i on .

(543/94) Actual preparation of the c~t~lyst ~Dvolve~ ~æ fl firet 20 step the dissolving of hydrated phospbomolybdic acid isl a sub~tantially anhydrous alkyl alcohol. The preferred alcohol employed i~ ethanol ~lthough other lower fllkyl alcohols having one to about five carbon atoms can be 3ubstituted therefor.
Representative a;lcohols înclude bue ~re not limited to 25 methanol, ethano]., isoprop~nol, isobut~nol and tbe like. The c atalyst ptomoters can be added in some instance~ as ~cid8 or 1~9 salts~ The one or more that i8 selected iB ~l~o preferably di~solved ln the substaneially anbydrous ~lcohol ~o tbat the cllcohol solution compri8e9 a mixture of hydraeed phosphomolybdic ~cld ~nd the promotercont~ining compounds.
It is nece~sary th~t t~e al ohol i~ sub~tantially snhydrou~. The pre~ence of signific~nt amoun~s of water in the solution diminishes the enhancement of catalyst processing and aetivity achieved by utilization of tbe alcohol solution.
The next step of the proces~ involves he~ting the solution to form a concentrate. This i~ conducted at about the boiling polnt of t~e alcohol wi~h stirring until either the volume has been reduced sufflciently for ~be cstalyat mixture to fill the pore volume and wet-out the ~urface of ~ preformed fluid cat~lyst ~upport or until tbe point of sol1difica~i3n i~

3~ reached. In ehe lat~er ~n8t3nce, tbe ~olidified re~idue o~
c~talyst precursor may be t~bletted, pellet~d, or may be moistened with alcohol and used to impregnate or coat a cataly6~ support. Suitable support materials include silica, alumina, alumina-sllica, silicon carbide, niobium oxide, boron-phosphate, titania, zirconia aDd the like and preXerably Alundum as well a~ mixtures thereof. Irre~pec~ive of the point at whicb th~ support is impregneeed or coated with the ~9~8 (5~93/94) concentrate, original solu~ion or ~ th~ redi~olved or powdered residue, the amount of 2ctive ingredient in ~he 1~ finished supported catalyst i8 ~enerally from about 10 to 100 percent by weight and preferably up to abou~ 70 percent.
Additionally, inert diluents known in ~he art may be incorporated lnto the pelleted, tabletted or supported catalyst.
The formed catalyst i8 finally giYen a ~tep of heating 1'~ fir~t ~o evaporate any remnsnt alcohol then sub~equently to dry and c~lcine the catalyst. Evapor~tion iB conducted at ~pproximately the boiling point of the al~ohol, drying at about 150C and calcining above 300G. A~ will be recognized by those skilled in the ~rt, temperatures high enougb to degrade the c~talyst ~hould be avoided.
In cxamP1e 1 which follows, a phospbomolybdic acid based cataly~t having the composition MolOPAsO 2CuO ~0z was prepared ~nd coated on Alundum having a p~rti~l~ size between 10 and 20 mesh. Weight percent of ~o~ive c8t~1y8t was 2~ 28.6. The catalyst thus prepared was thereafter te~t~d for methacrolein oxidation at 375C. In order eo ev~lu~ee tbe effectivene s of the method set forth herein, a m~s~urement of percen~ per single pass yield or perc~n~ yield W3~ m~de, whlch i~ defined as follows:
P~rcent Single Pa~ Yield ~ Moles of product recovered 1-2510 gm of 20 MoO3-2H3P04-48H2o was ~J dissolved in 15 cc of substantially anhydrous eth~nol with hea~ing and stirring. Two ~ddi~ion21 ~olution~ were m~de by '10 .

2~
(5493/94) dissolving 0.0202 gm of H3AsO4qO,5H2O ~nd 0.0254 gm oE
Cu(C2H3O2)2 H20 in 5 cc of substantially anhydrou~ .
ethanol each. Both oE these 801ution8 were then added to the 1~ phosphomolybdic acid solution and the resulting mixture was heated with stirring at moderate heat until it ju~t solidified. The residue that formed W88 redi~olved in several drops of substantially anhydrous alcohol and impregnated on 2.5 gm 10-20 mesh Alundum particles in a jar followed by alternate heating and rotstion of the jar to evapor~te the alcohol. The i~lpregnated catalyst was thereafter dried or 30 minute~ at 150C and then calcined for 2 hours a~ 320C. The calcined particles were again screened to inaure a 10-20 mesh siz~
fraction.
The resulting second stage cataly~t was thereafter utilized with a conventional first stage catalyst to oxidize isobutylene to methacrolein and then methacrylic acid as follows: 2 cc of the second st~ge phosphomolybdic acid ba&ed catalyst wa~ plaoed over 4 cc of the first ~tsge oxidation ~'~ catalyst. Te~ting wa~ conducted in a flow microreactor consisting of a 0O79 cm I~Do x 16~51 om long gtainless steel tube immersed ln a molten salt bath at 375C and ~tmospheric pre~sure. Reac~an~ feed comprising air, water and i~obutylene, molar ratio of 12:3:1, wa introduced into the bottom of the 3 reactor through a 0.48 om O.D. stainle~s ~teel preheat leg; the re~ctor and prehea~ leg formirlg 8 U-eube configur~tion. Within ehe reactor wa~ a sui~able first stage cae~ly~t foF the conversion of i~obutylene to methacrolein on ~op of which was stacked the candidate second 6tage catalyst for the conversion of methacrolein to methacryllc acid~ Process water wa~ fed through a ~ilicone rubber sepeum ~t eh~ top of the prehest leg 5493/94) with ~ model 355 Sag~ ~yring~ pump being u~ed to regulate th~
process water flow rat~. Firse st~ge conYer~lon, i.e., isobutylene to me~h~crolein, W~8 conducted by feeding isobutylene, air and water through the microreac~or fo~ an app~rent contact time with 4 cc of the firat stage c~ealyst of two seconds. The particular first st~ge c~ta1yst employed was 20~ silica and 80% active ingredientR,the latter comprising a nickel-cobalt promoted bismuth molybdate cataly~t a~ disclosed in U.S. Patent No. 3,642,930. Result~ of the first stage oxidation were 98% total conversion with 76V~ yield of methacrolein, 11~ methacrylic acid and the remainder being oxides of carbo:n. For the second stage COnverBiOn, methacrolein to meehacrylic acid, ~n ~pparene contact time of one second was provided. The aecond ~tage caealyst wa~ at the 28.6 weight percent level, supporeed on 10-20 mesh Alundum ~n par~icles. Percent yields after the second 8t9ge oxidation were as follows: 1 Meehacrolein 21.9 Meth~cry1ic Acid 56.0 ~' From an analysi~ of the products it W&8 determined ehat i~obutylene conver~ion w~ 100 percent. The formu1a for iBObUtylene COnVerSiOD i8 a~ follow~: ;

Mole~ of isobuey1ene reaceed Mo1e ~ 100 In another embo~lm~t o~ the invention, hydrated phosphomolybdic acid is dissolved in a substantially anhydrous alkyl alcohol. Next, the solution can be heated after which a base is added such as ammonium hydroxide to orm insoluble salts having the formula (NH4)XRvPMA, where R is the residue from the alcohol and x and y are believed to be the integers 1 or 2 with the proviso that they not be the same. Suitable 12.

(5493/94) bases also inclu~ ~e~raalkyl ammoniu~ hydroxldes, wherein ~he alkyl group contains four to about 16 carbon atoms, and various amines such as trimethylamine.
The fir~t he~ting i~ conducted at ~ ~emp~rature ~bout 78C, the boiling point of he 31cohol, i.e., for ethanol, for approximately 15 minute~. Addition of the base ~hould bring the pH eO about 2 to 6. The ~olution i8 thereafter evaporated ~nd heated at ~bo~t 150C, le~ving a powder or residue which is, in turn, calcined ~bove 300C ~or about 2 hours tb yield the sctive cataly~t. The c~t21yst m~y be eabletted or pelleeed. If desired, the solid~fied residue c~n be disper~ed in ~lcohol and u~ed eo eo~t ~ c~talyst support.
Altern~tlvely, the cat~ly~ suppo~t cen be wetted with the alcohol flnd coseed with the catalyst powder. (~.g. by the meehod set forth io U,S. Patent No. 4,077,912.) Sultable 25 ~upport mater~als include ~ilica ~ ~lumina, silica-~lumin~
boron-phosphaee, silicon-carbide, nioblum oxide, tit~nia, zirconia 3nd th~ e and preferably Alundum ~ well ~8 mlxtures thercof; ~be amount of ~ctive lngredient in the finish~d catalyst being from sbout 10 to 100 percen~ by weight and preferably up to abou~ 70 per entD The coated catalyst i~
then given the ~tep of calcining.
In examDle 2 which follows, ~ pho~phomolybdic ~cid based cat~lyst having the composition MolOPA~O 2CuO 2z was prepared ~nd coated on Alundum h~ving ~ particle Rize between lO and 20 me~h. Weight perc~nt of active catalys~ wa~
28.6, The cat~ly~t thus prep~red was thereafter teseed for methacrol~in oxidation ~t 375C as i.n examnle 1.

~ (5493/~4) , ~
1-2510 gm of 20 MoO3 2H3P04~48H2o w~s dissolved in 10 cc of sub~tantially anhydrou~ ethanol with heating and stirring. Two additional solution~ were m~de by dissolving 000202 gm of H3AsO4~0.5H20 ~nd 0.0254 gm of Cu(C2H3O2)2~H2O in 3 cc of substantially anbydrous ethanol each. Both of these golutions Wers then added tO the phosphomolybdic ~cid ~olution and ~he re~ulting mixture wa~
heated with stirring at moderate heat for 15 minute~. Then he pH was ~djusted to 5 by adding 29.8% ammonium hydroxide drop-wise. The re8ulting mixture ~8 evapor~ted and dried for 30 minutes at 150~C to yield a powder. The powder wa~ u~ed to coat 10 to 20 mesh Alundum p~reicles at tbe ~8.5 weigbt percen~ level which particlea were thereafter dried for two hours at 150C and c~lcined or two hour~ at 320C
The resulting second stage catalyst was thereafter tested under the same conditions as in example 1. The second stage ca~aly~t was ~t th~ 28.6 weigbt percent level; aupported on 10-20 me~h Alundum particles. Percent yield~ after the second stage oxidation were a8 follo~s:
Methacrolein 24.4 Methacrylic Acid 54.0 From an analysis of ehe products ie wa~ deeermined th~t isobutylene conver~ion WaB 100 percent.
According to another ~mbod~ent Drovided herein, th~
aolution of phosphomolybdic acid and oeber catAlyst component~
is prepared as disclosed in the foregoing exampleO Without the addition of ~mmonium hydroxide, the alcoholic solution is bolled down to ~ volume sufficient to fill ehe pores and wet-out t~e ~urf~ce of preformed fluid Alundum particles auch 14.

~ (S493/9~) that the finlshed catalys~ ~ill h~v~ ~ concentr~tion of about 25 percent by weigh~ aC~iYe ingredien~O At thi~ point, the catalyst is contac~ed wieh ammonifl gas in an amount sufflcient to cause the insoluble pr~cipitate NH4(C~H5)~PMA to be formed with the pore structure of the support material.
Such contacting with ~mmonia gas m~y be ~ccomplished by diluting the ammonia with ~ir or nitrogen and conducting the gas~solid expo~ure in a fluidized-bed, if desired. After the 25 in-particle precipitation i8 accomplished, the tempera~ure of the cataly~t bed i8 rai~ed from an initial temperatur~ of ~out 80C to about 320C over th~ course of 2 hours. The catalyst is maintained at th~ 320C calclna~ion temper~turc for an ~dditional ~ hour~ and after thi~ treatment i~ ready for process ~ervice. It will be under~ood thAt other caleining tempera~ures, i.e~, 300C to about 450C, could be u~ed for aleernate catalyst compo~ition~.
Thu~, it can be seen that the methods set foreh herein are effective in th~ preparation of phosphomolybdic acid based catalyst~. Unlike conventional activaeion method~, which employ aqueous solutions of phosphomolybdic acid with or without promoters, the use of an 31coholic solution does not depend solely upon treatment with ammoni~ or similar ba~ic compound~ to provide the catalyst material. The utility of the lower alcohols in this regard depends on their solvency for phosphomolybdic acid ~nd other cat~lyst conseituents and on their ~bility to undergo chemical reaceion witb and solubilize th~ phosphomolybdic ~cid.

(5493/94) Ans~ther ~mportant ~spec~ of ~ s metbod of cæt~lyst 15 prep~ration is in the fact ~h~ by uti,izing an alcoholic catalyst solution, ~he proper~ie~ of a erue solution are maintained, t:hat i8~ there iS no ~gros~ precipitation of solids~
e-Jen ill ni,~ly cs:~aceotrated fiolLIt.to~,, ho~ever, t~e ptecipitale can ~ventually be formed ~y the u~e of ammonia. By contrast, in the conventional prepflrations from aqueous solueion, ~mmonium lon mu t be introduced leading to gros8 precipit~tion of in~oluble an~onium phosphomolybdate.
Another important conseguence of the ~alution properey of the phosphomolybdic ~cid ~lcohol 8y8tem i~ that it permi~s 25 the impregnation o porous preformed ~upports. This opportunity i~ not present where a lflrge amount of the catalyst componen~ exist a8 su~pended solids w~tbin the impregnating fluid. The ability to impr~gnate ~ p~eformed porous support to produce an active and attrition resistant catalyst particle i8 ~0 particularly import~nt in fluid-bed catalytic proc~s~ing applicationc .
A further advantage o~ the phosphomolybdic acid-alcohol system resides in the protection of particular chemical groupings in the final drying and early calcination stages of catalyst preparation. This superiority of the alcohol is reflected in the high level of ac~ivi~y of the finished phosphomolybdic acid b sed catalyst.

16.

~ 2~ (5~93/94) A further ~dv~neage of the phospha~olybd~c ~cid-alcohol-ammonia ~y~tem resides ln the be~er protection of particular chemical grouping3 in the final drying flnd early calcination stages of catalyst prepar~tion, afforded first by use of ~lcohol rather than ammonium ion, subseguently followed by treatment ~o incorporate the ammonlum ion. This superiority of the alcohol in combination with ammonla i~ reflec~e~ in the high level of ~ctivity of the finished phosphomolybdic acid ba sed ca ta lyst 0 The present invention provides a process for the production of un~aturated carboxylic acids from their corresponding ~31dehydes, saturated or un~aturated, in the presence of ~ pbosphomolybdic acid ba~ed catalys~ prep~red a8 deRcribed above. The aldehyde iB contac~ed with molecular oxygen in the ~por phase ~t a reaction temperatur~ of about 200C to about 50UC in the presence of ~he catalyse.
Reaction pres~llre may be subatmospheric, atmospheric, or superatmo~pheric. The reaction may be conducted in fixed or fluid bed reactor~.
B~s~d upon the sa~ififactory yield~ of methacrylic acid that have be~n ob~ained when pho~phomolybdic acid b~sed catalyst are E~repared according to the methods sgt fortb herein, it should be apparent that th~ obj~ct of the invention have been met. I~ i8 to be under~tood that the preparaeion 25 disclosed herein i8 applicable in general to pho~pbomolybdic acid based catalys ~ which, as stat0d b~reinabove, c~n include one or more promoters or promoter-containirlg compounds.
Presence or 3bsence of thefie additional elements or compounds slill not ~ffect the method of prepar~tion ~et forth herein.

17 .

(5493/~4~
It ~hould alL~o be apparent to tbo~@ ~killed in the ~rt that the subject inven~ion i~ oper~ble on pho~phomolybdic acid based catalys~ having certain ratios o molybdenum to phosphorous and it ;i8 operable when cert~.in alcohols, base~, temperatures and cat:alyst support~ are employed. I~ l~ to be under~tood that the~e variables fall wlthln the ~cope of the claimed invention ~nd th~t ~he ~ubjec~ invention i8 not to be limited by the example se~ forth herein. It h~s been provided merely to provide ~ demonstra~ion ~f operability ~nd it is believed ehat the selection of specific ~lcohols &nd reaction conditions c~n be de~ermined wi~hout depar~ g from ehe ~pirit of the invention h~rein disclosed ~nd described, and th~t the scope of the invention shall include all mod~fic~tions and variations thst fall wi~hin the ~cop~ of the ~et~ched claims~

18.

Claims (47)

WE CLAIM:

1. A method for the preparation of second stage phosphomolybdic acid based catalysts comprising the steps of:
forming a solution of hydrated phosphomolybdic acid in a substantially anhydrous alkyl alcohol;
heating said solution to form a concentrate; and drying and calcining said concentrate so as to form the catalyst.

2. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 1, including the additional step of treating a catalyst support material with said concentrate, and thereafter drying and calcining said concentrate and said support material treated herewith.

3. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 1, including the additional step of adding at least one promoter-containing compound selected from the group consisting of acids and decomposable salts of promoters selected from the group consisting of, cesium, potassium, rubidium, thallium, copper, vanadium, antimony, arsenic, bismuth, tellurium, palladium, aluminum, barium, calcium, cerium, chromium, cobalt, iron, magnesium, manganese, nickel, tantalum, titanium, tungsten, zinc, zirconium, chlorine and bromine.

4. A method for the preparation of phosphomolybdic acid based catalysts,as set forth in claim 1, wherein the step of heating is conducted until a solidified residue is formed.

19.

5. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 4, including the further steps of moistening said residue with a substantially .
anhydrous alcohol and thereafter treating a catalyst support material therewith.

6. A method for the preparation Of phosphomolybdic acid based catalysts, as set forth in claim 1, wherein the step of heating is conducted until the volume has been reduced sufficiently for the catalyst mixture to fill the pore volume and wet-out the surface of a catalyst support material.

7. A method for the preparation of phosphomolybdic acid based catalysts,as set forth in claim 2, wherein said catalyst support material is selected from the group consisting of alumina, Alundum, boron-phosphate, silica, alumina-silica, silicon carbide, niobium oxide, titania, and zirconia and mixtures thereof.

8. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 1, wherein said anhydrous alkyl alcohol has from one to about five carbon atoms.

9. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 8, wherein said anhydrous alkyl alcohol is ethanol.

10. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 1, wherein the step of drying is conducted at a temperature of at least 150°C and the step of calcining is conducted at a temperature of at least 300°C

20.

11. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 3, wherein said phosphomolybdic acid based catalyst has the formula MoxPyAaBbCcDdEeOz, wherein A is selected from the group consisting of, cesium, potassium rubidium and thallium; B is selected from the group consisting of copper and vanadium; C is selected from the group consisting of antimony, arsenic, bismuth and tellurium; D is palladium; E is aluminum, barium calcium, cerium, chromium, cobalt, iron, magnesium, manganese, nickel, tantalum, titanium, tungsten, zinc, zirconium, chlorine and bromine; x is 6 to 14; y is 0.1 to 15;
a is 0.1 to 3; b is 0.1 to 3; c is 0 to 2; d is 0 to 2; e is 0 to 4 and z is a number necessary to satisfy the other elements.

12. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 11, wherein x is 9 to 12; y is 1 to 1.5; a is 1 to 2; b is 0.1 to 1; c is 0 to 0.7; d is 0 to 1 and e is 0 to 1.

13. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 12, wherein the composition of said phosphomolybdic acid based catalyst is Mo10PAs0.2Cu0.Z0z,

14. A process for the production of an unsaturated carboxylic acid by the oxidation of its corresponding aldehyde, with molecular oxygen in the vapor phase at a reaction temperature of about 200°C to about 500°C the presence of a phosphomolybdic acid based catalyst prepared by:
forming a solution of hydrated phosphomolybdic acid in a substantially anhydrous alkyl alcohol;
heating said solution to form a concentrate; and drying and calcining said concentrate so as to form the catalyst.

21.

15. A process as in claim 14, wherein the catalyst is prepared including the additional step of adding at least one promoter-containing compound selected from the.group consisting of acids and decomposable salts of promoters selected from the group consisting of, cesium, potassium, rubidium, thallium, copper, vanadium, antimony, arsenic, bismuth, tellurium, palladium, aluminum, barium, calcium, cerium, chromium, cobalt, iron, magnesium, manganese, nickel, tantalum, titanium, tungsten, zinc, zirconium, chlorine and bromine.

16. A process as in claim 15, wherein said phosphomolybdic acid based catalyst has he formula MoxPyAaBbCcDdEeOz, wherein A is selected from the group consisting of cesium, potassium, rubidium and thallium; B is selected from the group consisting of copper and vanadium; C is selected from the group consisting of antimony, arsenic, bismuth and tellurium; D is palladium; E is aluminum, barium, calcium, cerium, chromium, cobalt, iron, magnesium, manganese, nickel, tantalum, titanium, tungsten, zinc, zirconium, chlorine and/or bromine; x is 6 to 14; y is 0.1 to 15; a is 0.1 to 3; b is 0.1 to 3; c is 0 to 2; d is 0 to 2; e is 0 to 4 and z is a number necessary to.satisfy the other elements.

17. A process as in claim 14, wherein said anhydrous alkyl alcohol has from one to about 5 carbon atoms.

18. A process as in claim 14, wherein methacrylic acid is produced from isobutyraldehyde.

19. A process as in claim 14, wherein methacrylic acid is produced from methacrolein.

20. A process as in claim 14, wherein acrylic acid is produced from acrolein.

22.

21. A method for the preparation of second stage phosphomolybdic acid based catalysts comprising the steps of:
forming a solution of hydrated phosphomolybdic acid in a substantially anhydrous alkyl alcohol;

adding a base to said solution;
evaporating said solution to yield a catalyst powder;
and drying and calcining said powder to form the active catalyst.

22. A method for the preparation of second stage phosphomolybdic acid based catalysts comprising the steps of:
forming a solution of hydrated phosphomolybdic acid in a substantially anhydrous alkyl alcohol;
evaporating said solution to form a concentrate;
treating a catalyst support material with said concentrate;
contacting said treated support with ammonia gas in an amount sufficient to form an insoluble precipitate of ammonium alkyl phosphomolybdic acid within the pore structure of said support material; and drying and calcining said treated support material so as to form the final catalyst.

23. A method for the preparation of phosphomolybdic acid based catalyst, as set forth in claim 21, including the additional step of adding at least one promoter-containing compound selected from the group consisting of acids and decomposable salts of promoters selected from the group consisting of ammonium, cesium, potassium, rubidium, thallium, 23.

copper, vanadium antimony, arsenic, bismuth, tellurium, palladium, aluminum, barium, calcium, cerium, chromium, cobalt, iron, magnesium, manganese, nickel, tantalum, titanium, tungsten, zinc, zirconium, chlorine and bromine.

24. a method for the preparation of phosphomolybdic acid based catalysts as set forth in claim 21, wherein said base is selected from the group consisting of ammonium hydroxide, amines and tetraalkl ammonium hydroxides having from four to about 16 carbon atoms.

25. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 24, wherein said base is ammonium hydroxide.

26. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 21, including the additional steps of dispersing said catalyst powder in a substantially anhydrous alkyl alcohol; and impregnating a catalyst support material therewith prior to said steps of drying and calcining.

27. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 21, including the additional steps of wetting a catalyst support material with a substantially anhydrous alkyl alcohol; and mixing said catalyst powder with said wetted support prior to said steps of drying and calcining.

24 .

28. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 22, wherein the step of evaporating is conducted until the volume has been reduced sufficiently for the catalyst mixture to fill the pore volume and wet-out the surface of said catalyst support material.

29. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 22, wherein the step of evaporating is conducted until said concentrate is a powder, and the step of treating a catalyst support includes the steps of wetting said catalyst support with a substantially anhydrous alkyl alcohol; and mixing said powder with said wetted support.

30. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 22, wherein the step of treating said catalyst support material including the steps of dispersing said concentrate in 3 substantially anhydrous alkyl alcohol;
impregnating said support material therewith; and evaporating said alcohol.

31. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 21 or wherein said substantially anhydrous alkyl alcohol has from one to about five carbon atoms .

32. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 31, wherein said substantially anhydrous alkyl alcohol is ethanol.

25.

33. A method for the preparation of phosphomolybdic acid based catalysts as set forth in claim 22, wherein said catalyst support material is selected from the group;
consisting of alumina, Alundum, boron-phosphate, silica, a1umina-si1ica,si1icon carbide, niobium oxide,titania, zirconia and mixtures thereof.

34. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 21 or 22, wherein the step of drying is conducted at a temperature of at least 150°C and the step of calcining is conducted at a temperature of at least 300°C.

35. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 23, wherein said phosphomolybdic acid based catalyst has the formula MoxPyAaBbCcDdEeOz wherein A is selected from the group consisting of ammonium, cesium, potassium, rubidium and thallium; B is selected from the group consisting of copper and vanadium; C is selected from the group consisting of antimony, arsenic, bismuth and tellurium; D is palladium; E is aluminum, barium, calcium, cerium, chromium, cobalt, iron, magnesium, manganese, nickel, tantalum, titanium, tungsten, zinc, zirconium, chlorine and bromine; x is 6 to 14; y is 0.1 to 15, a is 0.1 to 3; b is 0.1 to 3; c is 0 to 2; d is 0 to 2;
e is 0 to 4 and z is a number necessary to satisfy the other elements.

36. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 35, wherein x is 9 to 12; y is 1 to 1.5; a is 1 to 2; b is 0.1 to 1; c is 0 to 0.7; d is 0 to 1 and e is 0 to 1.

26.

37. A method for the preparation of phosphomolybdic acid based catalysts, as set forth in claim 36, wherein the composition of said phosphomolybdic acid based catalyst is Mo10PAs0.2Cu0.20z.

38. A process for the production of an unsaturated carboxylic acid by the oxidation of its corresponding aldehyde with molecular oxygen in the vapor phase at a reaction temperature of about 200°C to about 500°C in the presence of a phosphomolybdic acid based catalyst prepared by:
forming a solution of hydrated phosphomolybdic acid in a substantially anhydrous alkyl alcohol;
adding a base to said solution;
evaporating said solution to yield a catalyst powder;
and drying and calcining said powder to form the active catalyst.

39. A process for the preparation of an unsaturated carboxylic acid by the oxidation of its corresponding aldehyde with molecular oxygen in the vapor phase at a reaction temperature of about 200°C to about 500°C in the presence of a phosphomolybdic acid based catalyst prepared by:
forming a solution of hydrated phosphomolybdic acid in a substantially anhydrous alkyl alcohol;
evaporating said solution to form a concentrate;
treating a catalyst support material with said concentrate;

27 .

contacting said impregnated support with ammonia gas in an amount sufficient to form an insoluble precipitate of ammonium alkyl phosphomolybdic acid within the pore structure of said support material; and drying and calcining said impregnated support material so as to form the final catalyst.

40. A process as in claim 38, wherein said catalyst is prepared by including the additional step of adding at least one promoter-containing compound selected from the group con-sisting of acids and decomposable salts of promoters selected from the group consisting of ammonium, cesium, potassium, rubidium, thallium, copper, vanadium, antimony, arsenic, bismuth, tellurium, palladium, aluminum, barium, calcium, cerium, chromium, cobalt, iron, magnesium, manganese, nickel, tantalum, titanium, tungsten, zinc, zirconium, chlorine, and bromine.

41. A process as in claim 39, wherein said catalyst is prepared by including the additional step of adding at least one promoter-containing compound selected from the group con-sisting of acids and decomposable salts of promoters selected from the group consisting of ammonium, cesium, potassium, rubidium, thallium, copper, vanadium, antimony, arsenic, bismuth, tellurium, palladium, aluminum, barium, calcium, cerium, chromium, cobalt, iron, magnesium, manganese, nickel, tantalum, titanium, tungsten, zinc, zicronium, chlorine and bromine.

` 42. A process as in claim 40 or 41 wherein said catalyst has the formula MoxPyAaBbCcDdEeOz wherein A is selected from the group consisting of ammonium, cesium, potassium, rubidium and thallium; B is selected from the group consisting of copper and vanadium; C is selected from the group consisting of antimony, arsenic, bismuth and tellurium; D is palladium; E is aluminum, barium, calcium, cerium, chromium, cobalt, iron, magnesium, manganese, nickel, tantalum, titanium, tungsten, zinc, zirconium, chlorine and bromine; x can be 6 to 14; y can be 0.1 to 15;
a can be 0.1 to 3; b can be 0.1 to 3; c can be O to 2; d can be 0 to 2; e can be 0 to 4 and z is a number necessary to satisfy the other elements.

43. A process as in claim 33, wherein said base 19 selected from the group consisting of ammonium hydroxide, amines and tetraalkyl ammonium hydroxides having from four to about 16 carbon atoms.

44. A process as in claim 38 or 39 wherein said catalyst substantially anhydrous alkyl alcohol has from one to about five carbon atoms.

45. A process as in claim 38 or 39 wherein methacrylic acid is produced from isobutyraldehyde.

46. A process as in claim 38 or 39 wherein methacrylic acid is produced from methacrolein.

47. A process as in claim 38 or 39 wherein acrylic acid is produced from acrolein.