CA1049553A - Preparation of acrylic acid and methacrylic acid from propylene or isobutylene in a one-reactor, fluid-bed system - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Acrylic acid and methacrylic acid are prepared by reacting propylene or isobutylene with molecular oxygen at a temperature of about 200° to about 600°C. in a fluid-bed reactor using a catalyst charge containing two different catalysts--the first catalyst being one that is especially effective for pre-paring the acrolein or methacrolein from the propylene or isobutylene; and the second catalyst being one that is especially effective for preparing acrylic acid or methacrylic acid from acrolein or methacrolein. Unexpectedly high yields of acrylic acid and methacrylic acid are obtained.

Description

BACKGROIJND OF THE INVENTI(~N
The oxidation of propylene or isobutylene to acrylic acid or meth-. . .
acrylic acid has been conducted in two fixed-bed reactors containing two different catalysts for the best yields. Combining the two catalysts into one reactor has not been considered to be advisable because the second catalyst attacks the olefin in such a manner that by-products are formedO Thus, before the desired r eaction could occur, undesirable by-products, rather than the desired unsaturated acids, are formed.
Various catalysts that are effective for the conversion of propylene or is obutylene ar e well known . Repr e s entative patents that exemplify s uch20 catalysts include- U.S. 2,941,007; 3,248,340; 3,639,269; 3,362,998;
3,629,148; 3,576,764; 3,171,859; Netherlands 769,689; Belgium 767,659;
774,905; and 777,476; which show bismuth molybdate and other molybdate catalysts; U.S. 3,428,674; 3,431,292; 3,542,842; 3,544,616; and 3,551,470 which show v,arious uranium catalysts that are effective for preparing the unsaturated aldehydes from propylene and isobutylene; and other catalysts ', that are effective in this olefin oxidation are represented by U.S, 3,264,225;
3,197,419; 3,200,081; 3,282,982; 3,468,958; 3,408,400; Netherlands 7018091;
' British 1,091,961.
The second catalysts that are used in the invention are also known.
30 Catalysts that are representative of the second catalyst of the invention arerepresentedby U,S, 3,567,773 ~,567,772 Belgium773,851; Nstherlands ~, . - , . . ~, - . . :

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, ~9D4~55;3 72055~)5; Catlacla t~93 :1~5; I~ L~iun~ 77~,3Z9; Gorman 2 217,77a~; andGorman

2,~ () whic:h ~.lhow oxidal~iotl oE un~aluratod al.d~hyck: oxiclati.on eataJ.ysts hy U~IO ol' e.l~alytJI:0 eor~ ainin~ al; l~a~t; rnol.y'btlonum. Otho* eataly~t~ for pl~r)arink~ aei.dH ar~ ~hown'by U.S. 2,~1,2:1~; 2,881,213; 2,881,212;

3,3~)5 :17~ ';orrrl.arl 2 046 ~1.1; Japan~o 7Z/11969; ancl Bo1~ium 784 Z63.
Ttl~ eorrlb:inatic~rl o~ two eal;aly~t~ inl:o ono reaetor in a fluid-bed o~klal:ic n olt ~ho o:Lo~in ~o l:he aeid, howevor i~ not known ~19O, th~ very (lo~lir blo yiolcl.t3 o.f aerylic: a~i:id and m~l:haerylie aeicl o'btained 'by tho pre~ont .irlVOntiOll GOUI.d nol: I;)o oxp~ t~cl ;lirorrl th~ art ~U:MM~E~Y C)'F rrI-[.13 INV.E~.NI'ION
Xl: tla~l now boon clitJeov~r(3d aeeording to the presenl: invention that 1:he '.
proparal:ie~n oL aerylie aeitl and mel:ha.ery1ie aeid'by the reaetion of propylene ' '' Or iHo'hul;yl.erl~ wil:h moloeu:lar oxy~on in the presenee of an o~siclation eatalyst lrJ lmprovecl'by a.) eoncluetin~ l:he roaetiol~ in a Eluid-bed reaetor wherein ' ' Illo oxiclal:iorl C I:a'ly~ 3 maintairlocl in one, ~ubstantially undivided reaetion ~lono irl ~ueh a mannor l:hal: th~ o.xid. l:ion eatalyflt ean move to any point in th~ .r~aetion ~on~, an~:l 'b) ~lsinK as t:he o~ida1:ion eatalyst a eatalyst eontaining ':' l:wo liîfo:ronl: eal:aly~ts--the first eatalyst being one l:hat i9 espeeial1y offe~ctivcl .l't.~r l:ho o~cLdaLion o.f propylene or i~obutyleno to acroloin or rn~th-;~0 acloloin; ~ncl lho ~-~concl catalsrst b~ g ona that is ~specially effectivo for t:ht~ oxi~lation o.f acrolQxirl o~r tn~ hacroloin t:o acrylic acicl or m~3thacrylic acid.
Sulprlsi~ 1y, u~o of the proc~ss of l:he ir~ventioll re~;ull:s in higtl per pass convol ~ions to us~3f~1 acicl procl-lct~ whilc th~ capital c:o~t of two separatc . ..
r~lactor syHI:~m~ olllployocl in the art is avoiclecl.
~ s notocl i'bovo, I:hc present invcnl:ioll is a procc9s for proparin~
acryl.ic a clcl or m~thacrrlic acicl from propylcno or isobutylcne u~ing process . .
`~ e.c)n~litiQn~ ~ r~actallt f~3~d~ a n(l :raaction paramotcrs within the ranges describcd ;`
1~ tht-~ a rl~ 'ho t:rux of tl~o pr~i~s~nt invt~ntit)n is thc usc of a 1uicl-bed reacto n~ atl t~x}cl~tiotl catalyHt: cOtlta}nin~ two diert~nt catalysts .3() .

1al 9~553 Fluid-bed reactors suitable for use in the present invention are well ~ -known. Broadly, these reactors contain a fine particle bed of the oxidation catalyst which is expanded by the flow of reactants through the catalyst. In the preferred practice of the invention, the oxidation catalyst in the fluid-bed reactor has a particle size of less than about 300 microns; and during operation of the reactor, the volume of the bed of oxidation catalyst is about 5 to about 50% greater than the volume of the unexpanded bedO -~
The fluid-bed reactor may have essentially any design that is com-patible with the process of the invention. One basic criterion is that there 10 is one, substantially undivided reaction zone formed by the fluid-bed reactorO
In the reaction zone, the reactants form the desired products in the presence of the oxidation catalyst. One important aspect~of this reaction zone is that the oxidation catalyst of the invention can move throughout the reaction zone. Of course, in the actual design of a fluid-bed reactor there are areas where movement of the oxidation catalyst is substantially greater than the movement in other areas; therefore, the limitation of the invention should not be read to demand equal movement of all catalyst particles throughout the bed. Instead, this limitation implies that the particles of the oxidation catalyst in the normal operation of the fluid-bed reactor are capable of 20 moving to any point in the reaction zone.
The 1uid-bed reactor of the invention may be an open-bed reactor where there is little or no restriction to the flow of the oxidation catalyst, or the fluid-bed reactor could be constructed having sieve trays, such as those described in U.SO 3,Z30,246 for improving the contact of the reactants with the catalyst while at the same time allowing relatively free movement `
of the oxidation catalyst throughout the reaction zoneO In addition to the possible use of sieve trays, most reactors would use cooling coils in the ;
reactor where a heat transfer fluid is indirectly contacted with the hot gases generated in the exothermic reaction. ~11 of these reactor modifications provide a substantially undivided reaction zone as is required by the present inventionO

; _ 3 _ , ~13495'93 The second major aspect of the present invention is the particular oxidation catalyst employed. As noted, there are not one but two different catalysts. The first catalyst is selected from the group of those catalysts that are known to be especially effective for the conversion of propylene or isobutylene to acrolein or methacrolein. The second catalyst is selected from those catalysts that are especially effective for the oxidation of acrolein or methacrolein to acrylic acid or methacrylic acid.
The first catalyst, as noted, is effective for the production of acrolein ;, ` or methacrolein from the corresponding olefin. Broadly, these catalysts are capable of selectively attacking propylene or isobutylene on the d carbon atom that does not have a double bond. In either olefin, the catalyst abstracts 2 hydrogens from an alpha carbon atom and substitutes oxygen in its place to form the carbonyl compound. Catalysts capable of accomplishing this ~-function are widely known, see for example the patents cited in the Back-ground of the Invention. Any such catalyst may be used as the first catalyst in the oxidation catalyst of the present invention. These catalysts are oxides in the oxidation state designated by the surroundingsO By the term "oxides" is meant oxides, mixed oxides, oxide complexes, solid-state `
solutions and other such structures.
Preferred catalysts which are used for the first catalyst are those that contain at least an oxide of molybdenum.. Of these catalysts, those containing at least the oxides of bismuth and molybdenum are preferred, with those of the following formula being especially preferred.
. Aa Bb Fec Dd Bie M12 x :' wherein A is an alkali metal, alkaline earth metal, Zn, Cd, Tl, In, ;
Nb, Ta, a rare earth metal or mixture thereof;
B is a nickel, cobalt, manganese or mixture thereof;

D is phosphorus, arsenic, antimony, boron, tungsten, chromium, vanadium or mixture thereof; and wherein a and c are numbers from 0 to about 10:
b is a number from 0 to about 20;
e is a number greater than zero but less than 10;

- 4 - ;

1~9~53 d is a number from zero to about 5; and x is the number o oxygens required to satisfy the valence requirements of the other elements present.
Of these catalysts described by the formula, the catalysts wherein b is a positive number are preferred because of the especially desirable results obtained with their use. Also, desirable catalysts are prepared by substi-tuting at least some tellurium for bismuth in the formula above.
The second catalyst contained in the oxidation catalyst is the catalyst that forms the acid from the aldehydeO This catalyst may be selected from any catalyst that is capable of incorporating oxygen into the carbonyl moiety of the aldehyrde to form the corresponding acidO Representative examples of these catalysts that are known are shown in the Background of the Invention.
These catalysts are also oxides that contain a number of oxygens dictated by their surroundings.
Preferred are those catalysts that contain at least an oxide of molybdenum, with those catalysts that contain at least vanadium and molybdenum being of special interest, and those catalysts described by the following formula being especially preferred.
zO Eg Gh Ji M12 ~

wherein E is Sn, Cu, Ge, Sb, Bi, Te, Mn, Fe, Mg, Zn, Ni or mixture thereof;
G is W, Cr or mixture thereof; and J is V, P, Sb, Co or mixture thereof.
wherein g and h are from zero to about 20;
i is from greater than zero to about 20; and x is the number of oxygens required to satisfy the valence requirements of the other elements present.
In the formula, those catalysts where G is tungsten and J is vanadium are 30 preferred; with those catalysts containing tungsten, vanadium and tin, i. e.
G is tungsten, J is vanadium and E in tin, being especially preferred; and those catalysts containing tungsten, vanadium, tin and at least one of copper, nickel, iron, cobalt or manganese, i.e. G is tungsten, J is vanadi~nt E is a mixture of tin and at least one of copper, nickel, iron, cobalt or manganese, being of special interest because of the very desirable catalytic effect on the reaction of the invention.

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10495iS3 Also of great interest with respect to the second catalyst of the formula are those catalysts that contain copper as one of the ingredientsO
This is accomplished in the formula when E is at least copperO
The two catalysts which comprise the oxidation catalyst employed in the present invention are those that are shown in the art. Although the particular method of preparation is important to catalytic activity, this is not the point of the invention, and methods of preparing certain catalysts are shown in the examples.
As discussed above, the oxidation catalyst of the invention contains 10 two different catalysts. In a preferred practice of the present invention, the oxidation catalyst comprises a physical mixture of separate particles of the first catal~st and separate particles of the second catalyst. Other techniques for bringing the different catalysts into a single fluid-bed reactor are easily conceived. For example, the catalyst charge of the invention could comprise particles containing a mixture of the two catalysts.
Another irnportant aspect of the oxidation catalyst is the relative pro~
portion of the two different catalysts. In the preferred practice of the ;
invention, it has been found that essentially complete conversion of the ; reactants to the acids with low yields of aldehydes can be formed by starting 20 with an oxidation catalyst that contains more than about 95% by weight of the first catalyst which is used to oxidize the olefin to the aldehydeO This catalyst mixture is run under a given set of conditions and portions of the second catalyst (the catalyst that converts aldehydes to acids) are added until a desirably low (less than 5%) concentration of aldehydes is obtained.
Alternatively, a relatively high concentration of aldehydes can be recovered in the reactor effluent for use as the aldehyde or for use as recycle feed to the fluid-bed reactorO
In the preferred practice of the invention, about 5 to about 40% by , .
,1 weight of the active ingredients of the oxidation catalyst is the second catalyst, 30 with about 10 to about 30% by weight being more preferred. These concentra-tions give small yields of undesirable by-products, such as acetic acid, and high yields of acrylic acid and methacrylic acid.

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. : ", ~0149,SS3 Although the oxidation catalyst of the invention usually contains only two catalysts, it is also contemplated by the invention that more than two catalysts could be used by selecting more than one catalyst from either or both of the groups of catalysts or by employing another catalyst that does not deleteriously affect the reaction of the present inventionO Also, in addition to the active catalysts J it is technically feasible to add to the oxida-tion catalyst a solid particulate diluent to improve fluidization, to act as a force to moderate the heat of the reaction or for some other purpose.
As noted above, the process conditions, reactant ratios and reaction 10 parameters employed in the present invention are substantially the same as the art. The temperature of the reaction generally ranges between about 200 and about 600Co J with temperatures of about 300 to about 500C.
being preferred. Atmospheric, subatmospheric or superatmospheric pr es sure s may b e conveniently employed.
- While the ratio of molecular oxygen may vary within broad limits, the molar ratio of molecular oxygen to olefin is normally about 1 to about 4.
In terms of air, this would mean that about 5 to about 20 volumes of air are employed per volume of olefin. In addition to the reactants, inert diluent ~;
gases such as steam, nitrogen and carbon dioxide could be conveniently 20 included in the feed to improve the temperature control and increase the selectivity to the acid.
The other aspects of the process of the invention are not criticalO
Specific procedures for conducti~g the reaction are shown in the Specific ` Embodiments. The important factor of the invention is the discovery that use of two different catalysts mixed in a fluid-bed reactor give surprisingly high yields of acrylic acid and methacrylic acid.
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SPECIFIC EMBODIMENT
., .
Example - Preparation of acrylic acid.

A first catalyst which is useful for the preparation of acrolein from propylene andhaving a formula of 9o-4%Ko.lNi2osco4.sFe3Bilpo.sMol2ox and 9. 6% SiOz was prepared as follows:
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1645 gO of Fe(NO3)3 9H2O, 986 g, Ni(N3)2 6H2~ 1777 g.
Co(NO3)2- 6H2O and 658 g. of Bi(NO3)3.5H2O were melted and 13.7 gO
KNO3 dissolved in an equal,weight of water were added. Separately, 6325 gO
(NH4)6M7~2.g- 4H20 was di~solved in water, and 7802 g. of 85% H3PO4 ~-and 397 g. silica were added. The metal nitrates and molybdenum slurry were combined, and the mixture was placed in a blender at high speed for a few seconds~ The resulting material was spray dried and calcined for 4 hours at 540C. The catalyst was screened to give a particle distribution as follows: 25% under 44 microns, 70% between 44 and 88 microns, and 10 5%between 88-106 micronsO
A second catalyst especially useful for the production of acrylic acid from acrolein and having the formula 62% Wl 2V3Mol2ox and 38% SiO2 was prepared as follows: water was heated in a stainless steel container to a ;-~
temperature of 75C. To the water was added 3923 g. of (NH4)6Mo7O24O `~
4H20, 606 g- of (NH4)6W7O24o6H2o and 650 g. of NH4VO3 and 7604 g. of - -silica. The mixture was spray dried and heated to 400C. for four hours, and screened to give the same particle sizes as the first catalyst.
A fluid-bed reactor was constructed of a 3.8 cmO inside diameter stainless steel tube having an inlet for reactants at the bottom and an exit 20 for products at the top. Cn the inside of the reactor and spaced along the length of the reactor were 12 sieve traysO The sieve trays were constructed and installed in such a manner that the catalyst particles are able to move throughout the reaction zoneO
A physical mixture of 500 g. of the first catalyst and 55.5 g. of the second catalyst was charged to the reactor to give a total catalyst charge approximately 0.5 meter higho Under a flow of air, the catalytic bed was brought to a temperature of 340C~
A flow of reactants in the molar proportion of propylene:air:steam of 1: 10.1 5 was fed over the catalyst at linear velocity of 4~ 2 cm/secO, and 30 the weight of propylene per weight of catalyst per hour (WWH) was 0.031 The reaction was run at a temperature of 340C., and the effluent gases .~ ' ~' .

- 8 - ~
'`' ' .
:, , were scrubbed with waterO The reactor was prerun for 30 minutes, and the product was collected for 15 minutes. The product was analyzed by gas-liquid chromatography. The percent per pass conversion defined as the moles of a certain product obtained x 100 divided by the moles of propylene fed wer e calculated . The per pas s conver s ion to acrylic acid was 75 . 6 %
and the per pass conversion to acrolein was 9. 8%. Thus, the per pass conversion to acrylic acid and acrolein was 85. 4%0 Less than 00 05% acetic acid was found in the product. The acrolein formed could be recycled or more of the second catalyst could be added to eliminate the production of 10 acrolein.
In the same manner as shown for the reaction of propylene above, isobutylene can be reacted in the presence of a mixture of two catalysts to obtain good yields of methacrylic acid.
Also in the same manner as shown above, other catalyst compositions are used to prepare unsaturated acids. Representative examples of the first catalysts include: BigMol20x; Fe40 sBi4. 5~0. 5M12x; Usb50X; Fesb9x;

W(:~.uo sTe2FeSb30x; Bio~2cuoo8oxBpo4; Sb2Bi6M12x; Sn2sb4x; ':
TezCeMolzOx; and U3MolzOx. Representative examples of the second catalyst include: V6Mol20x; Cr3V8M12X; P3M12X; W6VlM12x;
20 CuzSno~2w2v4Mol2ox; Cu2w3vloMoox; Fe0.2~0. 1sb2M3x;

Po. 5sb2Mo3ox; Mn2WV3Mo120X; Fe3NiCr2VgMol20x; and Co3SnzWzV6MolzOx. In a preferred preparation for some oE the catalysts, the molybdenum oxide is reduced with a finely divided metal, such as tungsten.
Also, in the same manner as shown above where the catalysts were combined with a silica support, the catalysts may be supported by other materials such as alumina, titania, zirconia, Alundum, calcium phosphate or any other support that is suitable for use with the present catalysts.

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Claims (16)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows

1. In the process for the preparation of acrylic acid and methacrylic acid by the reaction of propylene or isobutylene with molecular oxygen at an elevated temperature in the presence of an oxidation catalyst, the improvement comprising:
a) conducting the reaction in a fluid-bed reactor wherein the oxidation catalyst is maintained in one, substantially undivided reaction zone in such a manner that the oxidation catalyst can move to any point in the reaction zone; and b) using as the oxidation catalyst a catalyst containing two different catalysts--the first catalyst being one that is especially effective for the oxidation of propylene or isobutylene to acrolein or methacrolein and the second catalyst being one that is especially effective for the oxidation of acrolein or methacrolein to acrylic acid or methacrylic acid.

2. The process of Claim l wherein the oxidation catalyst has a particle size of less than about 300 microns and the volume of the bed during operation of the reactor is about 5 to about 50% greater than the volume of the unexpanded bed.

3. The process of Claim 1 wherein said first catalyst contains at least an oxide of molybdenum.

4. The process of Claim 1 wherein said first catalyst contains at least the oxides of bismuth and molybdenum.

5. The process of Claim 1 wherein said first catalyst has the formula Aa Bb Fec Dd Bie Mo12Ox wherein A is an alkali metal, alkaline earth metal, Zn, Cd, Tl, ln, Nb, Ta, a rare earth metal or mixture thereof;
B is nickel, cobalt, manganese or mixture thereof;
D is phosphorus, arsenic, antimony, boron, tungsten, chromium, vanadium or mixture thereof; and wherein a and c are numbers from 0 to about 10;
b is a number from 0 to about 20;
e is a number greater than zero but less than 10;
d is a number from zero to about 5; and x is the number of oxygens required to satisfy the valence requirements of the other elements present.

6. The process of Claim 5 wherein b of the formula is a positive number.

7. The process of Claim 1 wherein said second catalyst contains at least an oxide of molybdenum.

8. The process of Claim 1 wherein said second catalyst is described by the formula:
Eg Gh Ji Mo12Ox wherein E is Sn, Cu, Ge, Sb, Bi, Te, Mn, Fe, Mg, Zn, Ni or or mixture thereof;
G is W, Cr or mixture thereof; and J is V, P, Sb, Co or mixture thereof.
wherein g and h are from zero to about 20;
i is from greater than zero to about 20; and x is the number of oxygens required to satisfy the valence requirements of the other elements present.

9. The process of Claim 8 wherein G is tungsten and J is vanadium.

10. The process of Claim 8 wherein G is tungsten, J is vanadium and E is tin.

11. The process of Claim 8 wherein G is tungsten, J is vanadium and E is a mixture of tin and at least one of copper, nickel, iron, cobalt or manganese.

12. The process of Claim 8 wherein E is at least copper.

13. The process of Claim 1 wherein the oxidation catalyst comprises a physical mixture of separate particles of the first catalyst and separate particles of the second catalyst.

14. The process of claim 1 wherein the first catalyst and the second catalyst are contained in the same particle.

15. The process of Claim 1 wherein enough of the second catalyst is present in the oxidation catalyst to maintain the concentration of acrolein in the product at less than about 5%.

16. The process for the preparation of acrylic acid from propylene comprising contacting a mixture of propylene, air and steam in the ratio of 1/10.1/5 with a fluid-bed catalyst in a fluid-bed reactor at a temperature of 340°C. and a linear velocity of 4.2 cm/sec. wherein the fluid-bed catalyst is a physical mixture of 90% by weight of a fluid-bed catalyst consisting essentially of 90.4% K0.1Ni2.5Co4.5Fe3Bi,P0.5Mo12Ox and 9.6% SiO2 and 10% by weight of a second fluid-bed catalyst consisting essentially of 60% of W1.2V3Mo12Ox and 38% SiO2.