DE1542457A1 - Oxidation catalyst - Google Patents

Description

DR.ING. F.WtTKSTHOFF 8MÜNCHBN9

DIPZKINe. G. VXTJjS 8CHWJCIQBRSTHASSKa

DR.K.T.PKOHMANN xaiBroir asoeoi PATENTAMWXLTE

1A-31 490 154245 '

Description of the patent application

SHEII INTERNATIONAL RESEARCH MAATSCHAPPIJ N.V. 30, Carel van Bylandtlaan, Hague, The Netherlands

concerning
Oxidation catalyst

This invention relates to an oxidation catalyst and its use for catalytic ^ Oxidation of olefinically unsaturated aliphatic compounds, especially the catalytic oxidative ones Conversion of propylene and isobutylene into acrolein or methacrolein.

The contraliated incomplete oxidative

of olefinically unsaturated aliphatic

carries two oheiaic products »which are of great importance for industry» ind. Untey you would have the {£ _t J $ "un $» 9 fed aliphatic

Acrolein and attains «Ie

mm the oxidation of olefins such as propylene isobutylene in $ tf anwart gavleaar Kmtalyeaiiora »ao

öotiti / 111

BAÖ ^ ORlÄAt.

can control that products are obtained which predominantly consist of the corresponding cc, β- unsaturated aldehydes. US Pat. No. 2,451,485 describes the use of catalysts which contain a copper oxide, while US Pat. No. 2,941,007 mentions bismuth molybdate catalysts; both catalysts effectively catalyze this reaction. These catalyst substances have been removed many times. converts to increase their effectiveness when used on an industrial scale.

Catalysts containing copper oxide have high activity at relatively low temperatures, but have certain limitations. The selectivity of these catalysts for acrolein and methacrolein is relatively sensitive to the oxygen concentration in the supplied Heaktionsgemisch and the maximum temperature achieved in the catalyst bed, the Proäuktionsgeachwindigkeit QTT is limited, since the copper Äeaktion. In general, at relatively low Sour taffkosjs ent rat ion is performed. Often 4 copper catalyst an oxygen conversion

i " sintm ^ estimate" range * "twa. at $ 90 »

woMrok Sobwierigfceitaa ^ ei ämit dtr 8a3iersta £ C) Be & ge im "ttgeftiterte" Sassge

mixed and caused by the selectivity for acrolein. Since the oxygen turnover is often incomplete, the gas mixture contains unreacted after leaving the heater Oxygen, causing a post reaction, which turns out to be a major cause of the clogging of the plant after the reactor proved.

The bismuth molybdate catalysts have the advantage that they are not highly sensitive to the oxygen concentration in the supplied gas mixture. As a result, the production of acrolein and methacrolein can often be increased by increasing the oxygen concentration in the gas mixture supplied; these catalysts can also be used with 100% oxygen consumption, the difficulties in controlling this oxygen supply and the secondary reaction being eliminated. In their presence, the selectivity for the desired product is not reduced with relatively high lerperetures in the catalyst bed,. äe :; sorer.anriten tv erhit-ur. ^ ste-.rerat; rer.,

this .vatal-eHtcre :; oft icilich, iie Sntsie.iur./ von uiier "Ä;::; = ■ c hta !:. ^ ace :: vroaukter. - .. eser-tlioh ~ u ν er

009816/1616

BATH

wrestle. However, these catalysts have the serious disadvantage that they require a higher carrier or oven temperature than can be obtained with the aid of conventional heat exchange liquids, such as conventional diphenyl / diphenyloxide mixtures. The effectiveness of Wismutmolybdatkatalysatoren gets critical worsened when they are heated to about 55O ⁰ C.

This invention provides an oxidation catalyst which is particularly effective in the catalytic oxidation of olefinically unsaturated, aliphatic compounds, especially in the 'Catalytic oxidative conversion of propylene and isobutylene into acrolein or methacrolein. He exhibits a high activity at a relatively low temperature and a high selectivity for the desired product, while it is relatively insensitive to the oxygen concentration of the iteaction mixture supplied.

The oxidation catalyst according to the invention contains 7 / ismut molybdate in an atomic ratio 7 / ismut: molybdenum from 1:24 to 3s 1 »preferably 1: 1, as well as copper in a length of 0.01 - 10 G-ew .- $, preferably 0.1-5% by weight, very particularly 0.1-1.0% by weight, calculated on the Y / ismut molybdate.

009816 / 16-18 BAD ORIGINAL

The activity of the catalysts according to the invention increases with increasing copper content. Compared with the "previously" known bismuth molybdate and copper catalysts, the catalysts according to the invention enable high conversions at low temperatures. The activity of the catalyst increases with higher temperatures. However, the selectivity for the desired products from the supplied gas mixture reaches a maximum at a certain temperature and a "certain copper concentration. The selectivity for the conversion of oxygen to acrolein reaches, for example, a maximum between 350-425 ⁰ O. Similarly, catalysts with a copper concentration of 0.1-1.0% by weight, calculated on the bismuth molybdate, have the highest Selectivity for the formation of acrolein by oxidation with oxygen. ■

The catalysts according to the invention can be prepared in various ways. They are not all of these methods are necessarily equivalent; certain methods are preferred. The copper is preferably made on the bismuth molybdate as a copper level by reducing a copper salt such as Copper (II) acetate, in the presence of an aqueous one

0 0 9816/1818

Ammonium hydroxide solution and hydrazine hydrate similar to that in US Pat. No. 2,847,475 described procedure, dejected. Another method is to bring the copper on. the bismuth molybdate by impregnating the latter with copper nitrate and then calcined. Another method is to mix metallic copper powder with 7 / ismutmolybdate. Finally, you can also use aqueous acidic solutions of copper and bismuth nitrates an aqueous molybdic acid-ammonium hydroxide solution mix and precipitate and calcine the resulting product.

Catalysts, which by depositing a copper mirror on a bismuth molybdate carrier, bismuth molybdate globules, for example, are most effective.

The catalysts according to the invention leave use themselves for the catalytic ^ oxidation of olefinically unsaturated aliphatic compounds, especially for the catalytic oxidative conversion of propylene and isobutylene to acrolein and Methacrolein.

009016/1616

One can oxidation by reacting the unsaturated aliphatic compounds, especially propylene, isobutylene and mixtures of propylene and isobutylene, with oxygen or an oxygen ■■-containing gas at 300 -. Conduct an oxidation catalyst 45O ⁰ C in the presence of bismuth molybdate with an atomic ratio of bismuth t molybdenum between 1:24 and 3 »1», preferably 1 t 1, and also copper in an amount of 0.01-10% by weight, preferably 0.1-5 »0 Gevr .- $, especially C, 1 - 1.0 wt .- # calculated on bismuth molybdate.

The size of the catalyst pellets can vary within a wide range. It depends on the diameter of the reactor. Pellets of bismuth moltate, which are or are impregnated with copper nitrate a copper mirror is deposited and which has a diameter of 3.1 - 4.7 mm and a length of 3.1 mm have been found to be satisfactory. It is preferable to have a diameter ratio of the Reactor: the diameter of the catalyst must not exceed 10i1. This relationship is important as there are undesirable effects caused by differences in the transfer of the reaction gases can be reduced significantly. Suitable catalysts were obtained by using the

009816/1616

Copper bismuth molybdate into a powder of grain size 840 - 59OyU ground.

You can use the catalyst as such, or, if necessary, the copper bismuth molybdate use on an inert carrier. Suitable solid support materials are, for example Silica in its various modifications, such as silica gel, silicates, fuller's earth, pumice stone, Kieseiguhr, clays, mica, zeolites and porcelain; Aluminum oxide, bauxite, thore earth, beryllium earth, Magnesia, magnesite, cerium oxide, titanium oxide, silicon carbide, zirconia, asbestos and graphite.

It is not necessary for the process according to the invention to supply the olefinically unsaturated aliphatic compounds, such as propylene and isobutylene, in the pure state. They can contain vaporous substances which do not undergo any significant reaction and which do not adversely affect the desired olefin oxidation under the reaction conditions of the process. A common SasbeSchickung can auizer propylene and / or isobutylene normalerv / else gaseous Praffinkchlenwasserstoffe how lie then! Than, propane, butanes ■ or other lower paraffins under

009816/1616

the claimed process conditions are gaseous. Contain suitable feed gases commercial fractions containing propylene and isobutylene. Sometimes the addition of diluents can be advantageous for the gas mixtures to be introduced be. Such diluents act as entraining agents for the Reaction mixture and have a beneficial effect on maintaining uniform reaction conditions. Other suitable olefinic feed gases are olefin-containing ones gaseous mixtures that occur in the pyrolytic or chemical conversion of hydrocarbons develop. These gaseous mixtures can all or part of the discharge from oxidation reactors in which olefins or other hydrocarbons thermal and / or catalytic oxidative reactions are subjected to contain.

The oxygen-containing gas used can

he

enriched oxygen, as K * is obtained in the fractionation of air, but this can also be less concentrated. A suitable oxygen-containing gas contains free oxygen mixed with an inert gas as a diluent, such as nitrogen, argon or carbon dioxide. You can also use air. All or part of the oxygen-containing gas can be added to the olefin prior to entry

009SU / $ 1ß1

Mix in the reaction zone or introduce this directly into the reaction zone. The oxygen-containing Gas and / or the olefinic gas can be fed into the reaction zone at several points will. 3-as out of circulation that does not contains converted olefins, oxygen and inert gases, can with further oxygen and / or Olefins are enriched before entering the reaction zone.

If necessary, the gas mixture supplied need not contain any diluents, but can simply consist of the olefinically unsaturated aliphatic compounds or a mixture thereof, such as propylene and isobutylene and oxygen. One of the advantages of the copper-modified bismitoolybdate catalyst is that it is not very sensitive to the oxygen concentration in the gas mixture fed in and that the production of olefinically unsaturated alpha aldehydes can be increased by increasing the oxygen concentration in the reaction mixture. A ^; Another advantage of using higher oxygen concentrations is that the formation of undesired by-products is rather reduced.

009816/1616

The amount of saturated when using the new oxidation catalyst aliphatic aldehyde and ketone increase with decreasing volume ratios of the olefinically unsaturated aliphatic compound to oxygen away. However, the activity of the catalyst also decreases. That is why it is in lower circumstances the olefinically unsaturated aliphatic compound to oxygen to achieve a 100% oxygen turnover necessary, higher Apply reaction temperatures than at higher ratios of olefinically unsaturated aliphatic connection to oxygen. In general, the molar ratios can be olefinically unsaturated aliphatic compound t oxygen vary between 4i1 to 25s1, with higher ratios result in better selectivities for the corresponding aldehydes and lower ratios less difficulty in separating By-products, such as saturated aliphatic aldehydes and ketones, are involved.

The Oxydationsreaktioii v.iri preferably between 550-425 ⁰ C executed kan MUI ensure da2 lieöctor temperatures over 450 ⁰ C are avoided because the catalyst is deactivated. However, the original activity can

009816/1616 BADORJGINAL

can be restored by treatment with aqueous ammonium hydroxide solution. One of the advantages of the copper-modified bismuth molybdate catalyst is that the reaction proceeds with significant product selectivities at temperatures above those required for 100% oxygen conversion, with difficulties in oxygen control, post-reactions and clogging of the previous copper catalysts occur, can be eliminated. Bismuth molybdate also works excellently at temperatures higher than those required for complete oxygen conversion. However, when using bismuth molybdate, the temperature ranges are considerably higher, around 1CO ⁰ C, than those required by the new copper-modified V / ismuth molybdate catalysts. The highest temperature in the catalyst bed, which is referred to here as "overheating attemper atur", is about 2C - 50 ⁰ C higher than the heakt local temperature. It is therefore a particular advantage of the invention that the oxidation of olefinically unsaturated aliphatic compounds, such as propylene and isobutylene to acrolein or methaceolein can be carried out with the help of the new catalysts at temperatures that can be achieved with conventional heat exchange

009816/1618

see liquids such as diphenyl / diphenyloxyd-G-enii can adhere to and causing problems when heating of the reactor to high temperatures, as occur with bismuth molybdate, eliminated will.

In the conversion of the olefinically unsaturated aliphatic gases to the corresponding aldehydes one can use atmospheric pressure or lower or higher pressures. However, it is preferable to work at about normal pressure.

The contact times used can depend on on the temperature and the specific catalyst concentrations used vary. In general, a contact time of 0.1-5 seconds, usually 0.3-2 seconds, is used. The contact time results from the throughput per reaction volume and is defined as that reduced volume of the total supplied gas

and amount, per volume of catalyst a · hour.

You can add steam to the system, however you have to make sure that no essential Amount of liquid water comes into contact with the catalyst during the course of the reaction. Other diluents, such as «« «· usually gaseous substances or substances which under the reactionary conditions in a gaseous state

009816/1616

BATH ORIGINAL

are present and are relatively inert and have no significant reaction during the process ^ - can be introduced into the system. Suitable diluents are e.g. paraffinic hydrocarbons, nitrogen, argon, helium and carbon dioxide. These gases are are best introduced into the system and help maintain the desired temperature and contact time. Gate introducing these diluents into the system can give you heat add or withdraw.

The invention is not limited to the separate supply of the olefinically unsaturated s aliphatic compounds in the reaction zone, but can also be applied to mixtures of these compounds. Exit the action zone Reaction products are suitable Liethoden for Subjected to separation of the process product, the resulting corresponding aldehydes be separated in the usual way in one or more stages, such as by condensation, distillation, Fractionation, extractive distillation, / = sprinkling, absorption, adsorption and liquid-liquid extraction.

009816/1616 ORIGINAL BATHROOM

The inventive method is preferably carried out semi-continuously or continuously. The catalyst is used in the form of a fixed catalyst bed or in flowable or suspended form. There can be several reaction zones running in parallel or arranged in rows. In the second or subsequent zone In a multi-stage process, arrangements can be made to prevent oxidation of unreacted 'olefinically unsaturated aliphatic compounds as well as further oxidation of unsaturated aldehydes to a higher oxidation level, for example to carry out the corresponding acid, such as acrylic and methacrylic acid. Therefore can be an already known oxidation catalyst for the oxidation of an aldehyde to a predominantly use unsaturated carboxylic acid. If necessary, one can in the system between the individual reactors of such a multi-stage Introduce oxygen into the system.

example 1

Copper (II) nitrate was dissolved in water and the solution mixed with bismuth molybdate particles. The lienge Eu ^ fer-II nitrate was reduced to the required

009816/1616 BAD OBIGfHAi.

Amount of copper matched and the volume of the solution was adjusted so that a thick Paste was obtained when mixed with the bismuth molybdate.

The paste was dried, calcined at 45O ⁰ C, to decompose the copper nitrate and milled with 2.5 $> stearic acid at 420 / U and pelletized. The pellets were calcined at 45O ⁰ C to the stearic acid to remove and to test for 840 - marry vu 590th

Catalysts were produced with 0.1 ^ 0.5, 1.0, 2.0, 5.0 and 10.0 wt. $ Copper based on bismuth molybdate.

Example 2

A copper mirror deposited on Vr'ismutmclybdat was made as follows:

Wismutmolytiat was pelletized with 2.5 i ° stearic acid and calcined at 45O ⁰ C prior to 34G - 590 / U was crushed. 1G, 6 g of copper (II) acetate monohydrate was dissolved in 200 ml of water.

009816/1616 BATH ORIGINAL

- 17 -: ■ - ■; ■; : ■: ■:

The solution was cooled to room temperature and 14 g of ammonium hydroxide were added. Was added to the solution, about 100 g of the comminuted Wismutmoljfcidats and heated to 70 ⁰ C. 20 g of hydrazine hydrate in 100 ml of water and the mixture was stirred for 30 min, filtered and washed with water and acetone "and in an oven at 5O ⁰ C. The analysis showed a copper content of 2.2% by weight. The catalysts prepared in this way proved to be the most active catalysts.

Example 3

Man "A catalyst was forth by intimately mixing copper powder (20 ^) with bismuth molybdate (80 fo). After addition of 2.5 fo stearic acid as a lubricant, the mixture stearic acid by calcination at 45O ⁰ G in an oven was pelleted, removed and grind the pellets to a powder with a grain size of 840-590 / U.

Example 4

A copper / bismuth molybdate catalyst was placed by common precipitation as follows}

008816/1618

-W-

200 g of bismuth nitrate, 152 g of copper (II) nitrate and 40 g of nitric acid were dissolved in 230 ml of water. This solution was mixed with a solution of 69.8 g of molybdic acid and 50 g of 28% ammonium hydroxide in 200 ml of water. The pE - '. Vert of the mixture was adjusted to 5 _f 5 by adding ammonium hydroxide and the precipitate was left to stand overnight. He? / Urde then filtered off, ^{dried at 125 0} G and calcined ^{at 450 0 O.} The catalyst was then crushed to 840-590 / rev for the investigation.

From the above examples it can be seen that some method of incorporating the desired Amount of copper in the catalyst can be used by just adding the ilenge of the Copper compound, which is used to make the catalysts, changed. As already mentioned is the percentage of copper in the catalyst for its activity and selectivity decisive with regard to the desired products. The catalyst activity is measured by the temperature at which the 100% conversion of the supplied oxygen takes place.

The following examples illustrate the advantages

of the copper-modified bismuth molybdate catalysts

molybdate compared to previous copper and bismuth catalysts,

009816/1616

Example 5

FIG. 1 explains the effect of the copper concentration in copper-modified Y / ismutmolybdate catalysts on the selectivity for acrolein, based on oxygen, "in the oxidation of propylene, and on the temperature necessary to achieve this selectivity. The reaction temperature in ⁰ C and the selectivity for acrolein in ^! 'i, based on oxygen, are plotted on the abscissa b :: w. of the Crdinate. The curves B, a, b, c, d and e show the effect of 0, 0.1, · C, 5, 1 , v, 2.0 and i?, 0. # Copper concentration in the catalyst on the mentioned selectivity and the heating temperature.

In the experiment, a 3 ml catalyst bed was placed in the center of a tubular reactor, the catalyst being produced by impregnation with copper nitrate according to Example T. 5 -Propylene existed. The contact time in the catalyst bed was 0.5 seconds and it was Ivormal ± uck ar.gevvar.at. At 50C ⁰ O, maximum selectivity was achieved with bismuth molybdate. ^{r it is a} xaxinun at 4OC 'C.

00 9816/1616 ORIGINAL BATHROOM

Increased copper content constantly lowers the temperature at which maximum selectivity is achieved. However, the highest selectivities were achieved with copper concentrations between 0.1 and 1.0 $. The temperatures with maximum selectivity for acrolein, based on the converted oxygen, for bismuth molybdate and copper bismuth molybdate are higher than those at 100% oxygen conversion. Figure 1 shows that for a given selectivity, the temperature required when using the copper-modified Wismutmolybdatkatalysators is lower by about 100 ⁰ C, than the temperature when using a usual Wismutmolybdatkatalysators.

The following four examples show the superiority of the new copper-modified bismuth molybdate catalysts over conventional catalysts. The catalyst A is a copper mirror Y / ismut molybdate catalyst with 2.2 % copper content, which was prepared according to Example 2j catalyst B bismuth molybdate with an atomic ratio of bismuth and molybdenum 1: 1. Catalyst C is a conventional copper mirror catalyst with 2.7 $> copper, deposited on silicon carbide. The greagemiseh fed to the reactor consisted of 4 - 5 $ oxygen,

009816/1616

:: _ 21 ■ - ■; ■■: ■■■ ..;: ■

93-94- ^ propylene and the remainder from others Hydrocarbons. Normal pressure was used and the contact time in the catalyst bed was 1.2 seconds.

Example 6

As mentioned, the catalyst activity measured by the minimum reactor temperature at which 100% oxygen conversion takes place.

Figure 2, in which the reaction ^{temperature in 0} G and the percentage oxygen conversion on the abscissa baw. plotted on the ordinate, shows the activities of a copper-modified bismuth molybdate catalyst with 2.2 $> copper content (A) and compares with a bismuth molybdate catalyst (B) and a catalyst with 2.7 # copper on silicon dioxide (C), as can be seen the catalyst A is significantly more active than the conventional catalysts B and Oe. By mixing copper with bismuth molybdate, a synergistic effect is surprisingly achieved in that the copper-modified bismuth molybdate catalyst exceeds the activity of both the copper level catalyst and the non-activated molybdate catalyst.

009816/1616

There is a particular advantage in using the highly active catalysts according to the invention in that there are essentially complete oxygen conversions with high selectivities for acrolein achieved at significantly lower temperatures than before, as shown in FIGS. 1 and Example 5 can be seen.

Example 7

Another advantage of this invention is that the rate of combustion of propylene and acrolein to carbon dioxide is much slower with copper on bismuth molybdate catalysts (A) than with copper on silicon carbide (C) or with bismuth molybdate catalyst (3). FIG. 3, in which the percentage oxygen conversion and the percentage content of acrolein in the outflowing xieaktorgas are plotted on the abscissa and the ordinate, shows the high conversion to acrolein when using the catalyst A on Sr and the high selectivity and low carbon dioxide formation, which results in a high propylene conversion and high ι acrolein formation results. As indicated in FIG. 3, for a given oxygen conversion, the amount of acrolein in the outflowing reactor gas is considerably greater in the case of catalyst (A) than

009816/1616

Catalysts B and C. The temperatures required, in which the various oxygen conversions with the catalysts A, B and C are obtained are varied, as can be seen from FIG. A comparison of Figures 2 and 3 shows the greater activity of Catalyst A and that it consequently produces a greater amount of process product than Catalysts B and C.

Example 8

In Example 7 it was found that the rate of carbon dioxide formation is slower when using catalyst A than when using catalysts B and G. In FIG for the catalysts A, B and C. Of the indicated ratios is seen that when using catalyst A is a much less carbon dioxide is formed. In addition, the slight decrease in the acrolein: carbon dioxide ratio when approaching 100% oxygen conversion shows that secondary reactions, such as the combustion of acrolein, are greatly inhibited when using catalyst A.

0 0981 6/1 616

Example 9

One of the advantages of the invention is that the reaction can be carried out at essentially 100% oxygen conversion. FIG. 5 compares the selectivity for acrolein, based on converted propylene, for catalysts A ₉ B and G, which is plotted on the ordinate as a puncture of the percentage oxygen conversion on the abscissa.

The high selectivity and the advantages of using catalyst A are evident. The selectivity does not decrease noticeably when approaching 100 $ oxygen conversion. Using however, of catalyst C in which copper is deposited on silicon carbide, the Selectivity decreases rapidly as the oxygen conversion increases. While the selectivity at Use of the catalyst B does not decrease as rapidly with increasing oxygen conversion as with the catalyst C, it does not have the activity or selectivity of catalyst A after all.

It can be seen from this that the copper-modified "iVismutinolybdate catalysts in the catalytic, Oxidation of propylene and isobutylene too

0 0 9 816/1616

Acrolein and methacrolein have several advantages over them have conventional catalysts and bismuth catalysts.

Claim

00 9816/1616

Claims (1)

DR. ING. F. WUKSTHOFF DIPI ₄ . ING. G. PULSE DR.K.Y.PECIIMANN PATENT LAWYERS 154245 ' EAT S TILIOIlHUAIIIIlltl PHOTBOTPATSNV MOVOHKM 1A-31 490 Claim Catalyst for the oxidation of olefins to the corresponding unsaturated aldehydes, characterized by a / combination of 7 / i smu tmolyb dat with an atomic ratio Bismuth: molybdenum from 1:24 to 3: 1, preferably 1: 1 with 0.01-10.0% by weight, preferably 0.1-5.0, in particular 0.1-1.0 Gi-ew.-p copper, calculated on bismuth molybdate. III61 009816/1616 - 17 - Blank page