DE1518580C - Process for the catalytic isomerization of butenes - Google Patents

Description

The invention relates to a process for the catalytic isomerization of butenes at increased Temperature. The term isomerization is intended to mean both the conversion of n-butenes into isobutene as well as the conversion of isobutene to n-butenes.

Although it is well known that fluorinated alumina catalysts have various hydrocarbon conversions effect, it has now surprisingly been found that the fluorinated used Alumina catalysts must meet certain conditions in order to achieve a high degree of Obtain selectivity in the catalytic isomerization of butenes; it has turned out that not all aluminas make satisfactory catalysts.

The process of the invention for the catalytic isomerization of butenes is characterized in that that the isomerization is carried out at a temperature in the range from 250 to 550 ° C., if appropriate in the presence of a diluent gas, in the presence of 0.5 to 1.5 percent by weight, preferably 0.7 to 1.4 percent by weight, fluorine-containing aluminum oxide performs as a catalyst, the by fluorination of an aluminum oxide, which has a reversible benzene adsorption of at least 2 micromoles Has benzene per gram, measured at a benzene partial pressure of 0.11 mm Hg and a temperature of 190 ° C, with a fluorine compound of the general formula

Y-X-

in which X is carbon or sulfur and Y is fluorine or hydrogen, or with ammonium fluoride, hydrogen fluoride or ammonium hydrogen fluoride, preferably by slurrying an aqueous solution of an amount of ammonium fluoride, hydrogen fluoride or ammonium hydrogen fluoride calculated according to the required amount of fluorine in the finished catalyst, drying the sludge and subsequent calcining.

The use of reversible benzene adsorption to assess the suitability of various aluminum oxides for use in the low-temperature isomerization of C ₄ and higher paraffinic hydrocarbons is described in British Patent 1,042,885.

Reversible benzene adsorption is a measure of acidity; low values indicate low acidity . The measurement of the benzene adsorption of an aluminum oxide consists in bringing the aluminum oxide into contact with benzene vapors at a low partial pressure and a fixed temperature and measuring the amount of adsorbed and desorbed vapor. The amount of benzene adsorbed can change with the test conditions used and, in particular, with the partial pressure of the benzene vapor and the temperature. It is therefore necessary to standardize the conditions and for the purpose of the present invention the applied partial pressure is 0.11 mm Hg and the temperature 190 ⁰ C.

A description of a suitable method for measuring benzene adsorption and a device for this can be found in an article by R. C. P i tketh 1 y and A: G. G o b 1 e with the title: "The Adsorption of Benzene on Supported Platinum Catalysts, published in Actes du Deuxieme Congres International de Catalyse, Paris 1960, vol. 2, p. 1851. Adsorption at low partial pressures is usually attributable to chemosorption, with a relatively small contribution to physical adsorption, and the apparatus for measuring it has three Main parts, namely:

a) a device for introducing steam,

b) a holder for the solid to be examined,

c) a steam indicator.

The device for introducing steam has a

, ₅ source of carrier gas, e.g. B. for nitrogen or hydrogen, a container for the material to be adsorbed and a valve which allows either the gas alone or gas containing very small amounts of the substance to be adsorbed to be passed over the solid. The holder, which contains the catalyst or catalyst carrier, can be expanded in a wide range

'' Temperature range kept at constant temperature will. Gas that is passed over the catalyst then goes through the sampling valve to the Vapor indicator, which can be a hydrogen flame ionization detector. The display system can Gas chromatographic columns have when the relative rates of adsorption are different Substances are to be determined or if a reaction is likely under the test conditions and the composition of the reaction product is to be determined. It is not likely that this applies to the present invention.

By passing a gas stream containing the substance to be adsorbed over the catalyst or the catalyst base to be tested directs and the difference between that of the Catalyst or the catalyst base supplied amount of substance and the amount that is after the indicator goes, measures, the amount of substance adsorbed after a small correction for the dead space in the system to be determined. If the material flow is then interrupted and gas alone over the catalyst is passed, the amount of substance can also be determined which can be desorbed. The desor-

'■ Bierte amount is known as the reversible adsorption; the difference between the amounts adsorbed and desorbed is known as the irreversible adsorption.

The carrier gas for the benzene vapors should be inert to aluminum oxide and is preferably nitrogen.

The aluminum oxides to be tested are expediently given a standard pretreatment in order to bring them into a standardized chemical and physical state and in order to eliminate any effects which, for example, could be a result of different water contents. Prolonged heating in an inert atmosphere is preferred, for example heating between 100 and 800 ° C. in dry nitrogen for 1 to 75 hours. A particularly preferred pretreatment is heating for 16 hours at 47O ⁰ C in dry nitrogen.

Alumina suitable for use in the present invention have a reversible one Benzene adsorption of at least 2 μΜοΙ benzene per gram of aluminum oxide under the specified measuring conditions. The reversible is preferably

Benzene adsorption at least 3.5 μΜοΙ per gram. Fluorinated aluminum oxide catalysts based on aluminum oxides, which reversible benzene adsorption of less than 2 μΜοΙ per gram have proven to be relatively inactive catalysts proven for the mutual conversion of butenes.

The catalysts used in the process of the invention should have a fluorine content from 0.5 to 1.5 percent by weight. Although catalysts which are less than 0.5 percent by weight Contain fluorine, are active to a certain extent, they have a very short lifespan, while those containing more than 1.5 weight percent fluorine are in high proportions lead to cracked and polymeric products, to the disadvantage of the desired butene isomers. The amount of fluorine present in the catalyst is preferably 0.7 to 1.4 percent by weight.

Those used in the method of the invention Catalysts can be made in a number of ways. The aluminum oxide can be fluorinated by adding hydrogen fluoride, ammonium fluoride or ammonium hydrogen fluoride or an organic fluorine compound of the formula

Y-X-F

(where X is carbon or sulfur and each Y is fluorine or hydrogen) is used. the Compounds of the general formula are carbon tetrafluoride, fluoroform, methylene fluoride and the corresponding sulfur compounds. Carbon tetrafluoride is preferred. Carbon tetrafluoride is an extremely stable compound and is prima facie \ not an obvious choice for the production of fluorine-containing catalysts. Still it has Proven to be suitable and has certain advantages over some - other fluorination compounds. For example, compared to hydrogen fluoride, it is non-corrosive, easier to handle, convenient to use in the vapor phase and less prone to damage the alumina. Compared to alkyl fluorides, which contain a higher number of carbon atoms, for example tertiary butyl fluoride, it is less likely to be carbonaceous or hydrocarbonaceous Deposits can be generated on the catalysts during fluorination.

Preferably, non-reducing conditions are used when the alumina is present an organic fluorine compound is brought into contact. A common method of contacting consists in a stream of steam either alone or in admixture with a inert gas, for example nitrogen, or in a mixture with an oxygen-containing gas, for example Air through which aluminum oxide is passed.

When the above organic fluorine compounds are used to fluorinate the aluminum oxides are, in general, temperatures in the range from 200 to 500 ° C, in particular 300 to 350 ° C. In general, higher temperatures are used with shorter contact times and vice versa. However, it has been found to be used in the manufacture of the catalysts in the present invention using the above organic fluorine compounds often it is difficult to control the amount of fluorine absorbed by the oxide. So you can use catalysts obtained with fluctuating fluorine content, if the aluminum oxide to the organic Exposing fluorinating agents under identical fluorinating conditions. To get the catalysts in a reproducible manner, it is preferred that the method described in British patent specification 1,065,009 to use the method described, in which the aluminum oxide first steam at room temperature then partially dehydrated before exposure to the fluorinating agent will. Using this method, catalysts with essentially the same fluorine content can be used can be produced in a reproducible manner.

However, it has been found that the problem of reproducibility practically does not exist when the aluminum oxide is fluorinated with ammonium fluoride. Therefore, the catalysts come into use in the present invention, preferably by fluorinating the alumina with ammonium fluoride manufactured. ■

The alumina is slurried with an aqueous solution of ammonium fluoride, the amount of ammonium fluoride used being calculated to give the required amount of fluorine, ie, 0.5 to 1.5 percent by weight, in the finished catalyst. The slurry is then dried, calcined, for example at about 110 ⁰ C, and for example at 450 ° C in a nitrogen stream over a period of for example about 3 hours.

As mentioned above, the process according to the invention can be applied both to the conversion of n-butenes in isobutene as well as the conversion of isobutene to n-butenes can be applied. Hence the feed to the process may contain any butene isomer or a mixture of isomers, provided that the mixture does not correspond to the reaction conditions used Equilibrium mixture is.

The pressures of the process can be sub-atmospheric, atmospheric, or uber-atmospheric pressure and the hourly space velocity of the feed gases may vary depending on the Temperature range from 100 to 10,000. Preferably the starting olefin is the Reaction vessel mixed with a diluent gas, for example an inert gas such as nitrogen, fed.

The process according to the invention is explained in more detail by the following examples:

Examples 1 to 4

Four different aluminum oxides with different reversible benzene adsorption were found in in each case was greater than 2 μΜοΙ benzene per gram, measured at a benzene partial pressure of 0.11 mm Hg and 190 ° C, after a pretreatment in heating for 16 hours at 470 ° C. in dry nitrogen, each fluorinated by adding the aluminum oxide was slurried with an aqueous solution of ammonium fluoride which was used Amount of ammonium fluoride on the in that

finished catalyst required amount of fluorine was calculated.

The slurries were dried at 110 ° C and kept in a nitrogen stream for 3 hours Calcined 450 ° C. Table 1 shows the reversible benzene adsorption values for each alumina given together with the fluorine content of the catalysts. It became each of these catalysts contacted with one of two butene charges by the charge at a gas hourly space velocity (GHSV) of 1000 v / v with nitrogen at an hourly Gas hourly space velocity (GHSV) of 500 v / v was passed over the catalyst bed at 450 ° C. Liquid Products were caught in a trap at room temperature, and after flowing for 1 hour the gaseous product was based on (a) butenes, (b) cracked and saturated by-products with Carbon numbers less than or equal to 4 and (c) material with carbon numbers greater than 4 analyzed.

The results compiled in Table 1 show very clearly that the in Examples 1 to 4 used aluminum oxides, which reversible benzene adsorptions of at least 2 μΜοΙ per gram had provided satisfactory catalysts for the isomerization of butenes.

Comparative experiments a to d

There were four different aluminum oxides with ίο different reversible benzene adsorption under 2 μΜοΙ per gram, determined as in the previous one Examples treated in the manner described there and for the isomerization of butenes used. The isomerization was carried out in the manner described above. The results are also listed in Table 1.

These comparative experiments show that only a very slight hint of isomerization to isobutene takes place although there is an appreciable degree of isomerization of butene-2 in butene-1.

table

example
or.
Comparison
attempt Alu
minium
oxide Benzene,
adsorbed on
aluminum
oxide-
basis
μΜθΙ / g Weight percent
Fluorine on the
catalyst feed Cracked
and saturated
<C ₄ Gaseous form
Butene-2 ge product
Weight
Butene-1 e after a
percent
Isobutene r hour,
Products
> Q 1 A. 17.654 0.89 1 4.2 41.4 14.5 33.6 6.5 2 B. 9.09 0.94 2 8.0 38.4 12.8 32.2 8.6 3 C. 14,410 0.85 2 5.8 43.3 16.4 29.8 4.7 4th D. 3,549 1.00 2 4.5 45.4 15.4 29.6 5.0 a E. 0.231 0.92 1 0.7 67.9 21.6 9.4 0.4 b F. 1.074 0.92 1 1.0 65.1 23.0 9.9 14th C. G 1.649 0.93 1 0.9 70.7 24.8 3.2 0.4 d H 0.122 1.00 1 1.0 67.8, 25.1 . 4.8 1.2

Feed 1: butene-2, 98.4 weight percent; Butene-1, 0.6 percent by weight; n-butane, 0.8 weight percent; C ₅ , 0.2 weight percent Feed 2: butene-2, 93.2 weight percent; Butene-1, 3.5 percent by weight; n-butane, 2.5 percent by weight; Butadiene, 0.2 weight percent; C ₅ , 0.5%.
In each run, the liquor was less than 1 percent by weight of the charge over the course of an hour under the flow.

Comparative experiment e

45

A catalyst was used whose fluorine content was below 0.5 percent by weight, otherwise the procedure was as described in the previous examples.

The catalyst was fed with a butene charge containing 98.4% by weight butene-2, 0.6% butene-1, 0.8% n-butane and 0.2% C ₅ material under the same conditions as in the examples 1 to 4 are given, brought into contact and the product analyzed after the time given in Table 2 below.

The results and details are shown in Table 2. It can be seen that the percentage by weight Isobutene in the gaseous products has dropped considerably after only 98 minutes, a sign that the active life of the catalyst to achieve the desired isomerization is low.

Examples 5 to 10 ^{& 5}

The catalysts used are from the same alumina as that used in Comparative Example E, the fluorine content, however, lies in the claimed range of 0.5 to 1.5 weight percent distinguished clearly towards _r (s. Table 2). The isomerization was carried out in the manner described in Examples 1 to 4 with a charge of the composition given in Comparative Experiment e.

Comparative tests f, g, h, i

The procedure was the same as given in Examples 1 to 4 with the feed used in Comparative Experiment e, but had the catalyst has a higher fluorine content, as can be seen from Table 2. In the comparison tests For the preparation of the catalyst f and g became the same alumina as in the previous ones Examples used.

It can be seen from Table 2 that the selectivity increases as the percent by weight of fluorine in the catalyst increases for isobutene formation is maintained over longer times, but with fluorine contents above about 1.5 percent by weight increases the formation of cracked and polymeric products, so that such catalysts become undesirable.

table

example
or.
Comparison
attempt Aluminum oxide Weight
percent fluorine time
(Minutes) Cracked
and saturated Gas hairdryer
Butene-2 some product
Butene-1 e, weight p
Isobutene percent
Products
> Q 5 7.0 39.7 14.3 31.0 8.0 e A. 0.43 98 1.0 54.6 25.4 19.0 0 5 A. 0.50 5 2.4 43.6 15.2 30.8 7.9 60 2.1 54.7 19.1 21.1 3.0 150 2.8 54.1 20.2 19.6 3.3 6th A. 0.62 5 6.7 37.6 12.5 32.5 10.8 60 2.3 50.5 17.0 26.2 4.1 150 1.8 57.8 18.9 19.0 2.5 7th A. 0.77 5 10.9 36.4 12.0 31.8 9.0 60 3.3 44.6 14.8 31.2 6.2 120 2.9 47.2 15.6 29.4 5.0 8th A. 1.00 5 12.3 33.6 11.5 29.6 13.2 60 4.2 41.4 14.5 33.6 6.5 150 3.1 45.1 15.9 30.6 . 5.3 9 A. 1.33 5 17.1 30.1 .10.2 26.1 15.6 60 8.3 36.5 Ϊ2.0 - 31.5 11.6 120 7.2 38.0 12.1 32.1 ■ 10.6 10 A. 1.50 60 13.7 30.2 10.4 31.1 14.5 f A. 1.59 5 19.3 29.5 10.4 24.6 16.2 90 10.2 35.5 12.9 31.0 10.4 G A. 2.98 5 54.4 18.0 4.3 10.6 12.7 60 33.6 22.6 7.3 18.1 18.3 90 24.6 24.3 8.1 19.4 23.6 H E. 5.20 60 24.6 31.8 10.4 18.0 15.1 i F. 3.50 60 31.1 25.2 8.1 17.7 17.9

Example 11

In order to apply the process according to the invention to the conversion of isobutene into n-butenes To illustrate, a feed containing 0.6 percent by weight butene-2, 99.2 percent isobutene and 0.1% butadiene contained, on a fluorinated alumina catalyst similar to that in the example 8 used was identical, passed under the same reaction conditions. The products were analyzed after the set time and the results are listed in Table 3 below.

table example

Aluminum oxide

Weight percent
fluorine

Cracked and saturated

<C ₄ Gaseous products after one hour, percent by weight

Butene-2

Butene-1

Isobutene

Products
> Q

11th

1.00

7.2 35.0

13.2

36.0

8.6

Claims (1)

Claim: Process for the catalytic isomerization of butenes at elevated temperature, characterized in that the isomerization is carried out at a temperature in the range from 250 to 550 ⁰ C, optionally in the presence of a diluent gas, in the presence of 0.5 to 1.5 percent by weight, preferably 0, 7 to 1.4 per cent by weight, fluorine-containing aluminum oxide as a catalyst performs, by fluorination of an aluminum oxide having a reversible benzene adsorption of at least 2 μΜοΙ benzene per gram as measured at a benzene partial of 0.11 mm Hg and a temperature of 190 ⁰ C. , with a fluorine compound of the general formula Y
Y-X-F in which X is carbon or sulfur and Y is fluorine 009 587/390 9 10 or hydrogen, or the amount of ammonium fluoride calculated with ammonium, fluoride, hydrogen fluoride or ammonium hydrogen fluoride or ammonium hydrogen fluoride gene fluoride, preferably by means of slurry rid, drying the sludge and an aqueous solution corresponding to the subsequent calcining required amount of fluorine in the finished catalyst is 5.