DE2358254A1 - Aldehyde or ketone prodn. by alcohol dehydrogenation - with a doped zinc chromite catalyst contg. extra chromium oxide - Google Patents

Abstract

In a process for the prodn. of aldehydes or ketones by dehydrogenation of prim. or sec. 5-15C alcohols in the presence of a Zn chromite catalyst (ZnO:Cr2O3 molar ratio=0.8-1.2:0.5-0.8) doped with 2-10 wt.% CuO and 0.5-5 wt.% CdO, an additional 5-15 (pref. 8-10) wt.% Cr2O3 is incorporated in the catalyst by adding NH4 dichromate and heating at 300-450 degrees C. Addn. of Cr2O3 increases the activity selectivity and life of the catalyst; dehydration side reactions are totally eliminated and by-product formation (aldehydes or ketones with fewer C atoms) is limited to 1.5 wt.%; conversions of 85-90% can be achieved.

Description

WACKER-CKFHIE Munich., On November 9, 1973

GMBH

Wa 7311

Process for the production of aldehydes or ketones by the catalytic dehydrogenation of alcohols

The catalytic ^ dehydrogenation of primary alcohols to the corresponding Aldehydes are known to be difficult because the catalysts required for the dehydrogenation in addition to their dehydrogenating Effect in the cone exert a not insignificant denydrating effect on the alcohols, creating olefins arise as by-products and the aldehyde yield is reduced. In addition, acids, Esters and acetals and in some cases even by decomposition of the resulting carbonyl compounds hydrocarbons and Carbon monoxide and polymers occur *

A variety of metals and their oxides have been proposed as dehydrogenation catalysts. Copper and nickel, as well as their oxides, have been used successfully in some cases, but numerous disadvantages had to be accepted with the use of such metals; because reducible oxides or their metals are mostly susceptible to poisoning. Heavy reducible oxides such as zinc oxide _e, despite resistance to poisoning usually less active and require relatively high temperatures to activate them, thereby reducing the effect dehydx-atisieren.de usually increased.

From US Pat. No. 2,178,761, the use of a zinc chromite contact, doped with copper and eadmium oxide, known, but with low conversions with a high amount of by-products .be achieved.

This invention relates to a process for the preparation of Aldehydes or ketones by catalytic dehydrogenation of primary or secondary alcohols and alkenols with 5-15 carbon atoms in the presence of a zinc chromite catalyst in which the molar ratio

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of zinc oxide to chromium-III-oxide 0.8 to 1.2: 0,5 - 0.8 and with 2-10% by weight of copper, preferably 3-5% by weight cupric oxide and from 0.. ,% _T cadmium oxide is preferably 1-1.5 wt.% Ka & miumoxyd is 5-5 wt. doped, at elevated temperature. The method is characterized in that the zinc chromite catalyst * 5-15 wt.% Chromium-III-oxide, are added, based on the catalyst, wherein the Chroin-III-oxide 3? Oria of Ammondichronvat added and the catalyst then through Tempering at 300-4-50 ⁰ C in a «
Catalyst is transferred *

Annealing at. 300-4-50 C in a highly active distributed zinc chx'onite

According to an advantageous embodiment of the present method are 8-10 wt.% Chromium-III-oxide, based on the catalyst, eye sets. *. ■

The highly active, finely divided catalyst is obtained by the contact composition obtained in a known manner by precipitation, which is a metal Aiamonchromat, thermally decomposed, then with the appropriate amount of ammond dichromate mixed and tempered at the specified temperatures «

The specified percentages of cupric oxide and cadmium oxide relate to the finished raw contact, which is caused by thermal decomposition of the Ketall-Aramonchroiaat-Pällung; obtain will.

The tempering process consists in heating the contact matrix obtained to 300-400 ° C. for several hours. Suitable times for tempering are 3-5 hours. Cheap Temperresultate be achieved with a 4-hour heat treatment at 400 ⁰ C.

i) the catalyst can be molded or by any of the usual methods applied to an inert carrier such as pumice, burned to death Alxiiainiumoxide, silicon carbide or kieselguhr are used come..

Furthermore, the contact in fluidized bed, but preferably as Fixed bed, geüäß the known methods can be used.

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Cheap VerfahrenEer ^ ebnisse be eezielt when the dehydrogenation at temperatures of 270-4-50 ⁰ C, preferably at 350-400 ⁰ C and a pressure of 0.01-2 ata, preferably 0.5-1 ata, is performed .

The contact time depends on the working temperature and the desired Degree of implementation. At the temperatures mentioned, high conversions and few by-products are obtained if the residence time of alcohol vapors, based on the empty reactor volume ΊΟ-βΟ sec., Preferably 25-35 sec. ,lies"

Particularly favorable conversion values are achieved if, in addition, the water content of the alcohols used is low. For the The present process has proven to be advantageous if the water content of the alcohols used is 0.2 wt. %, based on the alcohol used.

Starting compounds suitable for the production of aldehydes or ketones are primary or secondary saturated alcohols having 5-15 carbon atoms, but also the corresponding unsaturated representatives of this class _v such as alkenols. All of the compounds mentioned are alcohols with both straight and branched carbon chains.

It is surprising that the catalyst has an increased activity due to the addition of trivalent chromium oxide, which is also retained over a longer period of time. Symptoms of poisoning or deactivation cannot be determined even with continuous exposure over a long period of time. So is z «. B _c in the dehydrogenation of 2-EthyTbutanol after 12 months of uninterrupted operation using the catalyst described in Example 1, no decrease in conversion and selectivity can be found.

The selectivity is very good. There are almost no by-products. No dehydrating effect was observed. The by-products are less than 1.5 wt.,% And consist almost entirely of aldehydes bsw »ketones with low C-Atoiaaahl together,

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which almost exclusively boil before the desired aldehyde or ketone. Conversions of 85-90% by weight are easily achieved.

Due to the high Uraformungswcrt, the extremely high selectivity, low percentage of by-products and the remarkably long life of the catalyst, there is the possibility of the aldehyde-alcohol mixture or ketone-alcohol mixture emerging from the contact furnace in a downstream activating column to separate »The bubble outlet, the higher boiling one, not converted alcohol part is held in Uralauf and continuously added to the starting product «.

If the cleavage product is condensed after the catalytic dehydrogenation, an aseotropic distillation takes place almost throughout to separate the aldehyde or ketone from the alcohol with water as a tug. The one obtained in this procedure saturated with water Eetour alcohol is used because of its sensitivity to water the catalyst expediently by passing through a Molecular sieve bed dehydrated.

The prosent numbers for catalyst activity, conversion and selectivity given in the examples below are to be understood as% by weight .

si game 1

The catalyst according to the invention is made by dissolving the salts zinc nitrate; 0.825 mol, copper nitrate 0.1 KoI and Ivsdr <iium ~ nitr & jt 0.0188 Hol in Was & er until a saturated solution and subsequent precipitation with 0.5 mol Arümondiehromat, evenly dissolved in V / water (400 ml), by dropwise Addition of 25 Seiger ammonia! ösi.mg (60 ml) prepared "Tn IABT the like egg nrsame solution of Hitratsalze one vox under Hühren Temperivbui at a ^1: 50 ⁰ C, the Anmiondichromatlösung slowly added dropwise. The precipitate that separates out contains the zinc chloride adduct. Through the further neutralization of the "mother liquor with ammonia" bi.B W [Jm. pH = 7, the promoters are quantitatively found as adducts. The precipitated precripity is scented in portions ^r rb little ^: ν ·· ^ ιν: -. Ri: distance öer ITitiv-ite, uuei Lei 60 ° G ge-t ^ oel-uct.

The ketall-Arauonchromat obtained is ar.sci) Lassenerj.d in Ginci .: Rotary kiln thermally decomposed. This is done by careful Heating the raw adduct to κυ Oi «ntor; pe:.? R.tUi?cn

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between 150-200 ⁰ C ₀ The rolling contact is obtained black -and- shows Röntgendiagreami no interference. -This multicomponent mixture of oxides of zinc, copper, cadmium and chromium has a dehydrating effect in its amorphous nature. The activity is still low, as is the selectivity. To achieve high activities, conversions and high selectivity of the catalytic matrix, 24.57 g of ammonium dichromate is added to the rolling contact, which is present in an amount of 150 g, and this contact matrix is then heated at 400 ° C. for 4 hours. The catalyst produced in this way is very specific for dehydrogenation reactions of alcohols in the vapor phase and has a high activity and selectivity _o Its spec. Surface is 48 m / g (BET method, measurement Ip). ". .Ü

23 g of the catalyst powder obtained are applied to 75 g of Bimsteiri. To do this, the contact is suspended in water, then pumice stones are added and the surface of the pumice stones with contact is sucked over by slowly evaporating the water while rotating. These are filled into a glass tube with a clear width of 16 mm and a length of 1,200 mm.In the axis of the tube there is a thermocouple which is slidably arranged in a thin glass tube connected «The hot reaction gases emerging from the reaction tube are condensed in a water cooler and the hydrogen formed is discharged separately« With an hourly load of 80 ecm of anhydrous 2-Atb.ylbubai.iol and oiiioj? Reaktionstenperatur of 375 ⁰ C box Atmonphäronäruck betrögt dor Uiasa-fcz 85% _t the selectivity is 99.8%.

With dev: <the same catalyst _s but under different conditions, werder. obtained the following results when using the rhymed alcohol above:

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2-ethylbutanol reaction activity d. Conversion selectivity metering temperature catalyst io v. 2-eth.ylbutau.al ccin / h

⁰ O ok 73 68 93 350 77 75 98.4 Il 84 85 99.4 Il 84.5 84 99.8 Il 84 ' 80 98.5 Il 80 75 97.7 Il 40.5 38 94.0 250 - 73.0 73 90 300 86.7 85 99.8 350 _s

375 * '92.7 86 99.8

This experiment is carried out with a zinc chromite catalyst which has been tempered according to US Pat. No. 2,178,761, Example II, but without Ammond dichromate additives. 23 g of the catalyst v / earth in the example 1 listed. Test arrangement checked. With an hourly exposure of 80 ecm of anhydrous 2 -1 thy 1 "but a no!, A reaction temperature of 375 ⁰ G and atmospheric pressure, the following result is obtained:

Activity of the catalyst Conversion Selectivity of 2-ethyl s butanal

78 £ 67 Io 87

Example 2

Kit, the catalyst prepared according to Example 1 and the described device and under the conditions specified there, 70 ccn / h of anhydrous n-hexariol at a temperature of 375 ⁰ O are passed over the contact. The following result is obtained:

Activity o.ev ITatoiysa fcors sales; Bel c> tImitate of Crn ^v '. * On ~

aldcljyci

$ 85 87 fo £ 98.3

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Example 3

80 g / h of anhydrous pentanol (3) are passed over the catalyst used in Example 1 at a temperature of 375 ^° C. in the dehydrogenation apparatus described there under the same conditions. The following result is obtained;

Activity of the catalyst Conversion Selectivity v.

Pentanone (3)

95 Io. 91 % .99, -9 fo

Example 4 ■

The procedure of Example 1 was repeated. The water content of 2-ethylbutanol was 0.20% by weight based on 2-ethylbutanol. Under these conditions:

Activity of the catalyst Conversion Selectivity of _2 ~ 'Athyi. Io 84 '60 Io. ■ 95 % . '"butanal

Example5

Using the catalyst described in Example 1 and under the conditions specified there, 80 ml / h of penten (4) ol (1) are fed into the dehydration furnace. get the following result:

Activity of the catalyst Uiasata selectivity -v. Pentene

(4) al

81 io 78 $> . $ 93

The catalyst prepared according to Example i is also used in the Yersucheappcratur described there used. Hourly 80 ecm Deeanol (1) are passed over the catalyst. at a dehydration temperature of 400 C and atmospheric pressure the following result is obtained:

Activity of the catalyst Conversion Selectivity of decanal (84 5S. 77 % 85? B

-8th-

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Claims (2)

Claims Process for the preparation of aldehydes or ketones by catalytic dehydrogenation of primary or secondary alcohols with 5-15 carbon atoms in the presence of a zinc chromite catalyst "in which the molar ratio of zinc oxide to chromium (III) oxide is 0.8-1.2 .:. Deträgt 0.5-0.8 and 2-10 wt # cupric oxide, and 0.5-5 wt% cadmium oxide is doped, characterized in at an elevated temperature such that the catalyst Zinkcliromit 5-15 wt ·% chromium-III-oxide, bE i on the catalyst, can be added, the chromium-III-oxide blended in the form of Ainmondichromat vmd d \ irch Q'iempern "at 5OO -. 450 ⁰ C distributed in a highly active Zinc chromite catalyst is transferred, 2. The method according to claim 1, characterized in that 8-10 wt "? £ Chrom-J.II ~ o> r.yd, bez. on the catalyst , can be added. BAD QR * G5f4AL S 0 9 8 2 3/1 0 0 8