DE1196631B - Process for the production of unsaturated aldehydes - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Erroneous, α .:

Number:
File number:
Registration date:
Display day:

C07c

German KI .: 12 ο -7/03

Stl9123IVb / 12o
April 19, 1962
July 15, 1965

The present invention relates to a process for the production of unsaturated, preferably aliphatic Aldehydes by catalytic conversion of olefins and oxygen, the conversion of the Olefins to corresponding unsaturated aldehydes on an industrial scale in consistently high yields can be carried out.

There are processes for making unsaturated aldehydes, such as acrolein, by reacting olefins and oxygen in the presence of various catalysts known (see German Auslegeschriften 1079 615, 1092473, 1103911, 1125 901, the British Patent 839 808, French Patent 1208 444 and 1247786 and Chemical Abstracts, 55 [1961], column 6377h). Particularly favorable results are obtained with those in the German Auslegeschrift 1129 150 described catalysts bismuth molybdate and bismuth phosphorus molybdate achieved. It is proposed in this patent, the molar ratio between oxygen and Olefin in the reaction mixture fed to the reaction vessel from 0.5: 1 to 5: 1, preferably of about 1: 1. If appropriate, the product mixture used can also use steam contain. However, when this procedure was carried out extensively, the observation was made that that the degree of conversion of the olefin to the unsaturated aldehyde gradually increases in the course of the process declines, an observation that is also made when using catalysts other than bismuth molybdate or bismuth phosphorus molybdate can be made. This gradual drop in the degree of implementation appears to be caused by a decrease in the activity of the catalyst. Of the The catalyst can usually be restored to its original state by treatment with air at elevated temperatures Activity state can be brought when there is a decrease in activity during its use made noticeable. However, this regeneration of the catalyst is unproductive because of the time loss, and for economic reasons it is therefore desirable to have these regeneration periods avoid or at least keep it to a minimum.

A process has now been found which converts the reaction to the unsaturated aldehydes longer periods of time without a significant decrease in the degree of conversion of olefin to unsaturated Aldehyde enables.

The invention relates to a process for the preparation of unsaturated aldehydes by reaction a gaseous mixture of an olefin and process for the preparation of unsaturated aldehydes

Applicant:

The Standard Oil Company,

Cleveland, Ohio (V. St. A.)

Representative:

Dr.-Ing. Dr. jur. F. Redies,
Dipl.-Chem. Dr. rer. nat. B. Redies
and Dr. D. Türk, patent attorneys,
Opladen, Rennbaumstr. 27

Named as inventor:

Ernest C. Milberger,

Maple Heights, Ohio (V. St. A.)

Claimed priority:

V. St. v. America April 20, 1961 (104 254)

Oxygen in the presence of bismuth molybdate or bismuth phosphorus molybdate, optionally on one Carrier as an oxidation catalyst. The method is characterized in that the reaction vessel leaving gaseous reaction product continuously or at suitable time intervals for its oxygen content is analyzed and oxygen to the gas mixture fed to the reaction vessel in a such an amount is added that the oxygen content in the gaseous leaving the reaction vessel Reaction product is always greater than 0.1 mol percent. Higher concentrations of oxygen can be accepted. In general, however, there is no advantage when using higher concentrations of oxygen are contained in the reaction mixture leaving the reaction vessel. In the practical When performing the process, the upper limit is generally about 7 mole percent.

The determination of the oxygen content of the reaction mixture leaving the reaction vessel can according to the various methods known per se for determining the oxygen content of a gas. If these measurements show that the oxygen content in the Reaction mixture leaving the reaction vessel below the predetermined required minimum content falls, it is only necessary to adjust the amount of oxygen in the reaction mixture fed to the reaction vessel

509 600 / 414-

to increase the mixture in order to achieve the desired effect on the reaction mixture leaving the reaction vessel

reach. the amount of oxygen contained automatically and

In terms of the technical implementation of the process, it is independent of the operating personnel on the

the oxygen content in which the reaction vessel can be kept at the desired level,

leaving the reaction mixture through several fac- 5 The process is preferably carried out at increased

gates affected. Apart from the amount of air temperature carried out.

or oxygen fed to the reaction vessel. The method of the invention is preferred

the amount of oxygen consumed to produce acrolein can be done. In this

Depending on the temperature and the contact time, propylene is used as an olefin and a catalyst as the case

be. If a mixture of io preferably bismuth phosphorus molybdate is used as the starting product,

Propylene and propane is used, the amount of which is obtained as unsaturated aldehyde acrolein varies

Amount of oxygen consumed in the reaction is.

when a change in the ratio of these two ders obtained by the method of the invention

Components occurs. Some of these factors are technological advances will be seen in the following

not completely detectable. It is therefore necessary to explain 15 examples
borrowed the oxygen content in which the reaction vessel

leaving the reaction mixture continuously to Example 1
monitor. This gives you quick knowledge

of a possible reduction in oxygen. This example was carried out in a laboratory content in the reactor exiting the reaction vessel. The catalyst used was a reaction mixture, independently of the fluidized bed of bismuth phosphorus molybdate, which caused the change in the oxygen content. The catalyst was according to example 2 of the basis. When the technical system far- German Auslegeschrift 1129 150 produced. If it is to be automated, a continuous reaction temperature of 427 ° C. and an oxygen determination apparatus operating at a constant pressure of 0.21 kg / cm ² can be used. The bogus are used. There will then be a continuous face contact time of 10 seconds. This is achieved during measurement of the oxygen content in the reaction mixture leaving the reaction vessel for the reaction to carry out the reaction. The reaction mixture supplied had the following consistently different types of continuously operating:
Oxygen determination devices are commercially available. 30 mole percent component
sustainable. _{Air 52 2}

Such continuously working oxygen water 391

Mood apparatus can have automatic control proüvleri 87

control valves that regulate the amount of oxygen, '

which is fed to the reaction vessel. On this 35 the results obtained in the implementation are

Thus, the following table shows how to pull the reaction vessel. In this

led amount of oxygen and thus also the one in the table means:

", _TT weight of the propylene converted to acrolein

% Conversion = ^, - r-rr-j— _s * ^ - - · 100.

Weight of the propylene in the feed

Samples were taken after the periods of time indicated in the table.

Table I.

\ Ta pe ι % / *! ■ * e— implementation Amount of oxygen in which the V Cl 0 UL-IIa "
H PIIPl * Leaving the reaction vessel UCtUCl ° / o Reaction mixture hours 23.6 Mole percent 1.0 21.6 1.2 4.5 26.2 1.6 8.5 24.8 1.1 12.5 23.7 0.8 16.5 29.2 1.0 20.0 26.3 1.3 24.0 1.1

the modification that the composition of the reaction mixture fed to the reaction vessel 45 had the following composition by reducing the proportion of air:

Ingredient mole percent

Air 48.6

Water 41.5

⁵⁰ propylene 9.8

The result of the experiment is given in the following table:

From this table it can be seen that if there is an excess of oxygen in the The reaction mixture leaving the reaction vessel shows the degree of conversion of propylene to acrolein on a was kept high.

Comparative experiment ⁵

It was worked in the same apparatus under the same conditions as in Example 1, but with

Table II

implementation Amount of oxygen in which the Y CIa UL-IIa-
ΗίΠΙίΜ * Leaving the reaction vessel UdUCX Vo Reaction mixture hours 24.0 Mole percent 1.1 27.9 0.03 4.5 22.7 0.01 8.5 16.9 0.01 12.5 12.7 0.02 16.5 9.7 0.06 18.5 8.4 0.04 23.3 0.00

From this example it can be seen that the degree of conversion of propylene to acrolein is gradual drops to very low values if the reaction mixture leaving the reaction vessel only contains a very small amount of oxygen. s

When comparing the results shown in Tables I and II it can be seen that after the process of the invention can be carried out over long periods of time with a high degree of conversion can, with little or no decrease in the activity of the catalyst occurs.

Example 2

An apparatus with a fixed bed catalyst was used which contained 37.65 kg of a bismuth phosphorus molybdate catalyst which was prepared according to Example 2 of German Auslegeschrift 1129 150. The catalyst was in the form of tablets, each tablet being about 4.75 mm in diameter and about 6.35 mm long. A reaction temperature of 427 ° C. and an overpressure of 0.21 kg / cm ^{2 were} used. Propylene was used in the amount given in Table III. Oxygen was added to the starting gas mixture in such amounts that the gases emerging from the reaction vessel always contained about 4 mol percent oxygen, these gases being continuously analyzed for their oxygen content. The data in Table III show how the air / propylene ratio had to be varied as a function of the amount of propylene fed per unit of time. Table III lists the results of three runs. As a result of the changes in the propylene feed, the apparent contact time also changed. With a feed of only 1.8 kg of propylene per hour, the contact time is relatively long. This gives a very high overall conversion, but a high air-to-propylene ratio of 14: 1 is necessary to maintain the desired oxygen content in the final gaseous product. At the other extreme of the experiment, in which the propylene supply was very high and the contact time was correspondingly shorter, the reaction was more selective, the total conversion of propylene was lower, the water conversion (CO ₂ , CO, etc.) was lower and, as a result, the air-propylene ratio to the Maintaining the 4% oxygen content in the gases leaving the reaction vessel is only 6.9: 1. This shows how a single variable, namely the propylene flow rate, can influence the amount of oxygen required. It can be seen from this that it is not sufficient merely to maintain a fixed oxygen-propylene ratio in the gases fed to the reaction vessel, because the reaction conditions can influence the necessary amount of oxygen and consequently the air-propylene ratio continuously by increasing or decreasing the proportion of air or must be changed by changing the propylene content in order to maintain a constant oxygen content in the end gases.

Table ΙΠ

Kilograms of propylene
fed per hour Molar ratio
Air to propylene
in the source gas Conversion to acrolein
per pass in ° / o Total conversion
per pass in ° / o 1.8
5.6
9.2 14: 1
10: 1
6.9: 1 31.9
45.4
38.0 94.8
87.2
70.4

Example 3

The procedure was as in Example 2 using the same apparatus, the temperature varied and three bismuth phosphomolybdate catalysts with different activities were used. Such catalysts were prepared according to Example II of U.S. Patent 2,941,007, wherein The activity of the catalysts is determined by the duration of the heat treatment to which the catalysts were subjected in the last manufacturing stage. Table IV shows the effect of the three catalysts which are chemically the same, but in their activity due to the different heating times and the different specific surfaces caused thereby were different. With every approach the oxygen content of the gases leaving the reaction vessel was controlled and in the amount of Maintained 2 to 4 mole percent. The ones necessary to maintain this oxygen content Air to propylene molar ratios are given in Table IV for each catalyst. With the least active catalyst had a relatively low overall conversion of the Propylene and a low conversion of propylene to acrolein and a very modest air to propylene ratio of 4.9: 1 achieved. At the other extreme of the experiment, namely when using the highly active catalyst, it was necessary to lower the temperature in order to take control of the Preserve Response; the total conversion was still relatively high and the air-propylene ratio had to be increased to 11.0: 1 in order to maintain the correct oxygen content in the end gases.

Table IV

Catalyst activity Reaction temperature
⁰ C Molar ratio
Air to propylene conversion
in acrolein
per pass in ° / o Total conversion
per pass in% Low
middle
High 465
454
427 4.9: 1
9.2: 1
11.0: 1 21.8
38.5
38.8 44.5
75.0
83.2

Example 4

The procedure of Examples 2 and 3 was carried out on a large scale with a fixed bed catalyst repeated. The conditions in the reaction vessel and the results are given in Table V. the The starting gas composition was essentially as follows:

Air 77.0%

Steam 15.4%

Propylene 7.6%

However, the air and / or propylene content in the source gas was adjusted to maintain an oxygen content of 2 to 4 mole percent in the effluent gases as recorded by a continuous oxygen meter. The reaction temperature was kept between 454 and 482 ° C., and it was maintained with a contact time of 2 to 2.2 seconds and an excess pressure of 0.35 to 0.56 kg / cm ² . A bismuth phosphorus molybdate catalyst of medium activity in tablet form was used as the catalyst. The total run time was 942 hours with no significant variation in the amount of propylene to acrolein conversion. The fluctuations in the air-propylene ratio were the result of both the temperatures of 454 and 482 ° C. and, secondarily, of other variables which were not controlled or which could not be controlled. So caused z. B. an occasional acceleration of the reaction pressure changes in the reaction vessel. It was necessary to continuously analyze the effluent gases and to adjust the air-propylene ratio in the supplied gases in order to maintain the desired oxygen content in the end gases. In this procedure, as shown in Table III, a satisfactory rate of conversion of propylene to acrolein was maintained over the entire long reaction time without the need to periodically regenerate the catalyst.

Table V

Reak
tion time Tempe
rature conversion
of propylene
in acrolein Air propylene
Molar ratio hours ⁰ C »/ Ο 24 454 37.6 8.1 120 454 37.1 7.7 168 454 36.6 7.6 288 482 35.3 8.8 456 482 40.3 8.0 572 482 38.7 8.4 686 482 41.5 7.0 814 482 41.8 7.5 982 482 39.7 7.1

Claims (1)

Claim: Process for the production of unsaturated aldehydes by converting a gaseous one Mixture of an olefin and oxygen in the presence of bismuth molybdate and / or bismuth phosphorus molybdate, optionally on a support as oxidation catalyst, characterized in that the gaseous reaction product leaving the reaction vessel is analyzed continuously or at suitable time intervals for its oxygen content and oxygen is added to the gas mixture fed to the reaction vessel in such an amount, that the oxygen content in the gaseous reaction product leaving the reaction vessel is always greater than 0.1 mole percent. Considered publications:
German Auslegeschrift No. 1079 615,
1092473; British Patent No. 839,808;
Italian patent specification No. 580 541.