HU204021B - Process for producing isomerization catalyst and process for producing butene-1 by isomerizing butene-2 or gas mixtures comprising butene-2 - Google Patents

Abstract

Prod. is obtd. from butene-2 or gas mixts. contg. butene-2-on an aluminum oxide catalyst impregnated with alkali-metal cpds. and heat-treated at 500-900 deg.C by passing the gas through the catalyst bed at a temp. below 500 deg.C.

Description

Λ description length: 8 pages (including figure 1)

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The present invention relates to a process for the preparation of an isomerization catalyst by impregnation and heat treatment of an alumina with an alkali metal, and to a process for the production of butene-1 by catalytic isomerization of a butene-2 or butene-2 gas mixture in the presence of an isomerization catalyst.

Butene-1 is one of the most valuable components of industrial Grg gas mixtures used primarily for the production of polymers or copolymers. In the case of apolymerization, the purity of the monomer is very stringent. It is well known that due to the thermodynamic stability conditions, industrial Gt mixtures generally contain higher amounts of butene-2 in addition to butene-1, which must be isolated from the desired final product.

Various solutions have been used for the separation of butenes, and there are known methods for the selective adsorption of zeolite adsorbents, such as the UOP Sorbutene process in which butene-1 is removed from the C ₄ mixture by selective adsorption, or Union Carbide Olefin Siv a process for the separation of n-butenes [Hydr. Proc. 9,217,220 (1980)]. The disadvantage of these processes is that the zeolite adsorbent used has a short lifetime and therefore requires continuous regeneration. For this reason, distillation-based separations are still used.

It is known that C ₄ hydrocarbon mixtures without butadiene can be fractionated into two fractions and the resulting head product contains butene-1, isobutene and isobutane, the bottom product contains n-butane and butene-2. However, these distillates cannot be further separated by distillation with sufficient efficiency. It follows from the above that butene-1 distillation with polymerization purity can be obtained only if the mixture does not contain isobutene and isobutane.

Polymerization grade - that i-butene and containing i-butane at most 500 ppm - in such a way can be obtained butene-l was' to C ₄ -szénhidrogénele- 4 marks butene-2 in the distillation bottoms of selectively butene-l isomerized so that no isobutene is produced during the reaction, so that the distillation product after isomerization contains only butene-1. The butene-2-containing bottom product can be recycled during the process. The preferred embodiment, if, before the first separation of the _C4 -mixture-2-butene content in a known manner, eg. hydro-isomerization of formed [Hydrocarbon Processing, 5 112 (1979)] l-butene is shed, so that the original C ₄ -eIegy n-butene content of 5 (more than 90% of m can be recovered polymerization grade butene-1ként.

The isomerization of butene-2 to butene-1 is a process leading to equilibrium, but increasing the temperature may increase the equilibrium ratio of butene-1, so it is advisable to run the reaction at a temperature as high as 5 pounds to achieve the highest conversion in one pass. However, care must be taken to avoid skeletal isomerization leading to the formation of isobutene as this would impair the purity of butene-1. The other possible side reaction leading to chain breakage should be suppressed as much as possible, as this also results in loss of butene. Experiments have shown that it is advisable to operate at a reaction temperature of 400-500 ° C, since the equilibrium butene-1 content reaches 25-30 m conversion. At this temperature, skeleton isomerization is carried out with catalysts promoting double bond isomerization.

D-distillation produces inseparable i-butene, and polymers and butene-decomposition products are formed which, although separable from butene-1, result in loss of material. By-products are more favorable at 200 ° C, but a 10-15% conversion is very disadvantageous in terms of productivity.

Several solutions have become known for the catalyst for the isomerization reaction.

For example, catalysing the butene-2 to-butene-1 reaction is described in U.S. Patent No. 4,229,610. U.S. Pat. No. 4,123,125 discloses that sodium oxide alumina is used in the preparation of sodium compound containing from 0.41 to 1.23% by weight of Na ₂ O to alumina. Thus, not only is the alkali compound deposited on the surface of Al2O3, it is unevenly distributed, depending on the degree of stirring, and, due to insufficient heat treatment, is only partially converted to sodium aluminate. As a result, an inhomogeneous catalyst is formed, the use of which does not permit the control of butene-2 isomerization. The result achieved does not meet the stated objective, since 1-2 m% isobutene is formed during the reaction. Based on our experimental experience, this deficiency is due to the fact that on the one hand, the sodium content and the small amount of sodium compound are not on the surface of the alumina, on the other hand, no aluminate is formed, thus not enough surface centers are formed. the desired isomerization of the double bonds of butenes.

Another solution can be found in U.S. Patent No. 3,642,933. U.S. Pat. Accordingly, 20% by weight of zirconia impregnated alumina is used for the isomerization. This solution does not lead to the production of a pure product either, as here again, 1-2 m% isobutene is produced, which is due to the relatively high acidity of the catalyst.

No. 4,289,919. U.S. Pat. No. 4,123,115 uses 0.76 wt% manganese oxide impregnated alumina in the absence of isobutene. To achieve this result, butene-2 is required to be diluted four times with nitrogen. Such a solution is so technologically disadvantageous that it can only be applied on a laboratory scale.

Chemical Abstracts 77, No. 128,658. According to his report, two types of catalysts are used in the Soviet Union:

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palladium on alumina;

- 4% alumina containing 4% K ₂ O.

They work with the former catalyst at 150 ° C and achieve only 8% conversion. The second catalyst gives a conversion of 26% at 400 ° C. However, it is not clear from the original Soviet literature what pre-treatment temperature was used; that is, there may be no possibility of the formation of potassium aluminate on the surface of the alumina. This could be inferred from the by-products, but no data are provided for them either.

The aim of our work was to develop a process for the preparation of butene-1 butene-2 or mixtures containing butene-1 with good conversion and high purity.

The results of our experiments have shown that butene2 can be converted to butene-1 with high selectivity at a temperature of up to 500 ° C when using a catalyst having a chemically modified surface, i.e., an alkali metal aluminate layer on the aluminum oxide surface.

It has been found in our work that the alkali metal compound is used in an amount of at least 2% and at most 20% by weight, preferably 10-15% by weight, depending on the specific surface area of the alumina. impregnation with an aqueous solution of the alkali metal compound followed by a heat treatment, whereby the surface reaction takes place within a few hours. The appropriate temperature of the heat treatment was investigated by physico-chemical methods, such as derivatographic or X-ray diffraction phase analysis, and the optimum temperature was found to be between 500 and 900 ° C.

Table I:

Effect of heat treatment conditions on the catalyst selectivity of 15% by weight in case of Na ₂ CO 3 tal-impregnated Al2O3 (Na content: 3.02 meq / g)

Heat treatment conditions Butene-2 -> Butene-1 By-products of isomerization at 450 'C Temperature Time, Clock 'C Cracked product,% m isobutene, m% 600 3 8.2 1.2 40 7.8 0.9 700 3 4.4 0.5 40 0.6 0.1 800 3 0.1 0 850 3 0.1 0 870 3 0.1 0

The catalyst thus prepared is used for the isomerization of butene-2 or butene-2 containing gas mixtures.

II. spreadsheet:

Activity of alumina catalyst with surface modified Na ₂ CO 3 at 450 ° C and by-products formed

Na ₂ CO3, Activity, Operational Side effects were recorded in Isobutene, m% cm ^ '-' h ⁴ time, hour i products, m% m% 1 0.18 1 1.8 22.0 10 0.4 2.3 2 0.20 1 0.7 7.2 10 0.3 0.6 4 0.30 1 0.5 4.3 10 0.2 0.2 8 0.40 1 0.5 2.2 10 0.2 0 15 1.6 1 0.3 0 20 1.7 10 0.2 0

It is most convenient to carry out the process on a fixed bed catalyst in a tubular reactor. After loading, the catalyst was heated at a temperature above the isomerization reaction temperature (preferably 500-600 ° C) in a neutral gas stream (preferably nitrogen) to remove carbon dioxide and water that had been trapped from the air.

The gas to be converted is then introduced into the reactor, where the temperature is conveniently maintained between 400 and 500 ° C. It has been found that at lower temperatures the conversion is small and thus too much gas must be recirculated, but at higher temperatures significant amounts of by-products are already produced. It has been found that the catalyst used in the process according to the invention remains very stable over a long period of time. The amount of butene-1 produced does not decrease over time and the product composition does not change over hundreds of hours. The process developed by us also has the advantage that regeneration of the catalyst used can be carried out simply by heating in an air stream and the catalyst is completely recovered after regeneration.

Figure 1 shows that the catalyst used in the present invention, for which the butene-1 content is indicated by full-circle and the isobutene content by blank, can produce gas mixtures of virtually unchanged, extremely favorable composition even after 80 hours of operation. By way of comparison, we present a series of data on the Italian catalyst which is currently considered the best, indicating that after 30 hours the activity of the catalyst is significantly reduced.

The process of the present invention is a step in the processing of catalytic cracking, pyrolysis of hydrocarbon distillates or other industrial C 1 mixtures to convert at least 90% of the original Crelegy n-butene-2 tartrate to polymerization grade butene-1.

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Our process allows the use of industrial mixtures, for example containing n-butane, for polymerization purposes without the need for separately preparing butene-2.

Without limiting the scope of the invention, the following Examples illustrate the process in more detail.

Example 2

Commercially formed molded alumina was impregnated with 15% w / w aqueous sodium carbonate solution and dried at 120 ° C and then air-cured at 870 ° C for 24 hours. The appropriate heat treatment temperature range was determined by derivatographic and X-ray diffraction. It was found that aluminate formation occurs between 620 and 850 ° C with strong evolution of carbon dioxide.

The catalyst prepared as described above was charged to a 300 cm ³ by 3 cm diameter tube, heated to 600 ° C under a stream of nitrogen and continued at this temperature for 2 hours. The reactor was then cooled to 450 ° C under a stream of nitrogen, then the nitrogen inlet was shut off and gas-atmospheric butene-2 was passed at 300 cm ³ / hr. The product mixture obtained contained 28% by weight of butene-1-25 and this butene-2-conveyance did not decrease in 500 hours.

Example 2 (comparative)

The catalyst was prepared according to Example 1, except that after impregnation and drying, the impregnated alumina was treated at a temperature not high enough to form a surface aluminate at 600 ° C. Further, as in Example 1, the product mixture contained 8% C2-C3 hydrocarbon and 5% isobutene with 25% butene-1 and 62% butene-2. In addition, strong coke formation has already been observed in a few operating hours, and traces of liquid products have been detected.

Example 3

The procedure described in Example 1 was followed except that 60% by weight of butene-2 and 40% by weight of n-butane was used as starting material. The n-butane content in the product mixture was unchanged, the conversion of butene-2 to butene-1 was 28%, and no by-product was formed.

Example 4

The procedure described in Example 1 was followed except that the alumina was impregnated with an aqueous solution containing 2% sodium carbonate.

The composition of the tea blend obtained with the catalyst thus prepared was as described in Example 1, but the content of butene-I after only 300 hours of operation was only 24%. Catalyst regenerated at 500 ° C in an air stream5 Recovered at original activity at 500 ° C Example 5 (comparative)

The procedure described in Example 1 was followed, except that only 1% sodium carbonate was impregnated with alumina. Using this catalyst, a mixture of teas containing 3% by weight of C2-C3 hydrocarbons and 1% by weight of isobutene was obtained.

She. example

Molded alumina was impregnated with 15% aqueous sodium nitrate solution, dried at 120 ° C and treated with hydrogen at 500 ° C for 4 hours (based on derivatographic studies, the formation of aluminate is between 400-480 ° C). then under a stream of nitrogen for 2 hours. In the following, the procedure of Example 1 was followed and the result was as described there.

Example 7

Example 6 was repeated, except that potassium nitrate was used for impregnation. The result was as described in Example 1.

Claims (5)

PATENT CLAIMS A process for the preparation of an isomerization catalyst comprising impregnating alumina with an aqueous solution of 5 to 20% by weight of an alkali metal compound, followed by heating the impregnated alumina at 500-900 ° C. Process according to claim 1, characterized in that the impregnation is carried out with 10-15% by weight of an alkali metal compound. 3. The process according to claim 1 or 2, wherein the alkali metal compound is sodium carbonate, sodium nitrate or potassium nitrate. 4. A process for the preparation of butene-1 by catalytic isomerization of a butene-2 or butene-2-containing gas mixture, characterized in that the isomerization is carried out according to claims 1-4. In the presence of a catalyst prepared according to any one of claims 1 to 4, it is carried out at a temperature not exceeding 500 ° C. 5. A process according to claim 4 wherein the gas mixture contains up to 50% n-butane.