DE1181194B - Process for the production of methacrolein by the catalytic oxidation of isobutylene - Google Patents

Description

Process for the production of methacrolein by catalytic oxidation of isobutylene Addition to registration: St 18918 IV v / 12 o -Auslegeschrift 1 177628 In the patent application St 18918 IV b / 120 (German Auslegeschrift 1 177 628) is a process for the production of acrolein or methacrolein by catalytic Oxidation of propylene or isobutylene with gases containing oxygen in the gas phase described at elevated temperature in the presence of antimony-containing catalysts, the reaction being carried out at 300 to 800 ° C. in the presence of a catalyst, that of mixtures and / or compounds of antimony and vanadium oxides or of Antimony, vanadium and phosphorus oxides, optionally in addition to small amounts of oxide of the elements titanium, manganese, iron, cobalt, nickel, zinc, cadrnium, lead, chromium and arsenic, optionally on a carrier and composed in such a way, that the atomic ratio between antimony and vanadium or between; antimony and the Sum of; vanadium. and P.hòsphor is a minimum of 0.5, - but a maximum of 1.5, at Throughput rates of at least about 14001 propylene or isobutylene each Liters of catalyst per hour in the presence of 0.1 to 1.0. Moles of oxygen each Moles of propylene or isobutylene; '. According to a preferred embodiment, contains the catalyst at the same time also contains bismuth oxide or one of bismuth oxide-derived substances Compound, where the atomic ratio of bismuth and antimony on the one hand and: vanadium or the sum of vanadium and fPhò-sphor, on the other hand, minimal in the catalyst 0.5, but not more than 1.5.

Experienced in this JV. it is assumed that pure olefins for example by fractionating a thermal and / or catalytic Cracking of petroleum fractions containing a mixture of lower hydrocarbons in action - Init essentially an equal number of hydrocarbons C 'atoms can be obtained. A »C4 faction« accruing in this way Apart from isobutylene, it mainly contains butylene (1), cis and trans butylene (2), Butadiene, n-butane and isobutane; for the production of pure isobutylene from such Fractional one more separation is required, but it is a rather costly one Matter is.

It has now been found that in the process according to the main patent application, if it is about the production of methacrolein, not necessarily must start from pure isobutylene, but also a starting product Hydrocarbon fraction, which is essentially predominantly unsaturated hydrocarbons with 4 carbon atoms, can use.

It has been found that the oxidation of Isobutylene to methacrolein under the conditions applicable to the process according to the main patent application is not affected by the presence of the remaining ~ C4 hydrocarbons and these other hydrocarbons only to a very small extent. Aldehydes or Acids are oxidized .--- Well will mostly be under the given circumstances some of the butylenes present with dehydrogenation to butadiene. converted.

From British patent specification 864 666 it is known that propylene or isobutylene is catalytically oxidized with oxygen-containing gases in the gas phase can be, even if the mixture is an inert diluent such as nitrogen, Contains propane, isobutane, CO2 or water vapor. . But this is what it is all about inert diluents, also in the case of propane and isobutane, since the saturated hydrocarbons can only be oxidized with great difficulty and are inert under these process conditions.

In contrast, a C4 fraction is used in the present process, the-predominantly unsaturated hydrocarbons, such as butylene- (l) and cis- and trans-butylene- (2), which one would expect to be oxidized.

The method of the invention has prior to the method according to the main patent application the advantage that now the preceding separation of isobutylene from the C4 fraction can be omitted in the production of methacrolein. It also falls on this Offer butadiene as a valuable by-product.

The procedure is also carried out entirely on the in the way mentioned in the main patent application. One derives from the above C4 fraction and an oxygen-containing gas mixture, if appropriate in the presence of inert gases or vapors - it is here the use of steam too prefer -, by a resting layer of the catalyst mass or by a catalyst fluidized bed. Carborundum offers particular advantages as a carrier for the catalysts.

The ratio between the C4 hydrocarbon fraction and oxygen can be used in the oxidation within the limits of 0.1 to 1.0 mol of oxygen per mole C4 hydrocarbon fluctuate. Addition of steam to the gas mixture can if used no catalysts on carborundum as a carrier material in most cases; in other cases, for example, good results are possible when steam is in abundance from 0.5 to 10 moles per mole of C4 hydrocarbon is carried along.

The rate at which the C4 hydrocarbon fraction passes through the catalyst bed is conducted is at least 1400 per liter of catalyst Hour; Throughputs up to 100001 gas mixture per liter of catalyst mass in of the hour can be achieved; however, there are also higher throughput rates possible.

Suitable oxidation temperatures are temperatures between 300 and 800 "C, preferably about 400 to 550" C. The reaction takes place in the preferred Embodiment under normal pressure, but higher or lower pressures can also be used can be applied.

Example For comparison purposes, hydrocarbon fractions, which essentially contain hydrocarbons with 4 carbon atoms in varying amounts, passed over a 50 ml catalyst resting layer, which mixtures and / or compounds of antimony, bismuth, vanadium and phosphorus oxides contains in an atomic ratio Antimony to bismuth = 1.0, sum of antimony and bismuth to sum of vanadium and Phosphorus = 1.0 and Vana- dium to phosphorus = 3.0, i.e. a composition Sb (VO3) 3 + SbPO4 + Bi2O3 accordingly. The catalyst contains carborundum as a carrier; the amount of said oxides in the catalyst is 24 percent by weight.

A hydrocarbon fraction with 35 volume percent isobutylene, 19.5 Volume percent butylene-1, 9.5 volume percent trans-butylene-2, 7.5 volume percent cis-butylene-2, 23.5 percent by volume butadiene and 5 percent by volume (butane + isobutane) is through this Catalyst mass performed, at such a rate that per liter of catalyst hourly 2800 l of this fraction and 3500 l of air pass through it. The reactor will kept at 475 "C. 6.0 mol percent of the C4 fraction now becomes methacrolein reacted with a yield of 72 mol percent, based on converted isobutylene. The daily yield of methacrolein is therefore 11.8 kg per liter of catalyst. the The amount of butadiene in the gas mixture emerging from the reactor corresponds approximately the amount present in the incoming gas mixture.

Claims (1)

Claim: Process for the production of methacrolein by Oxidation of isobutylene with oxygen-containing gases in the gas phase at 300 to 800 "C in the presence of a catalyst consisting of mixtures and / or compounds of Antimony and vanadium oxides or of antimony, vanadium and phosphorus oxides, if appropriate in addition to small amounts of oxide of the elements titanium, manganese, iron, cobalt, nickel, zinc, Cadmium, lead, chromium and arsenic, possibly on a carrier and such is composed that the atomic ratio between antimony and vanadium or between Antimony and the sum of vanadium and phosphorus is a minimum of 0.5, but a maximum of 1.5, at throughput rates of at least about 1400 liters of isobutylene per liter of catalyst per hour in the presence of 0.1 to 1.0 mole of oxygen per mole of isobutylene according to Patent application 3 .St 18918 IVb / 12o (German Auslegeschriftl 177628), marked thereby, that you can use the process in place of pure isobutylene with a hydrocarbon fraction performs, which essentially predominantly unsaturated hydrocarbons with Contains 4 carbon atoms. ~~~~~~~~ Publications considered: French patent specification No. 1,260,597; British Patent No. 864 666.