KR920010008B1 - Dehydrogenation catalyst and process for preparing it - Google Patents

Abstract

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Description

Dehydrogenation catalyst and its manufacturing method

The present invention relates to a dehydrogenation catalyst and a preparation method thereof. The present invention also relates to the use of catalysts in the process for producing linear lepins by dehydrogenating linear paraffins.

The molecule contains a relatively large number of carbon atoms (more than 9) and linear olefins are widely used. In other words, linear olefins having, on average, about 12 carbon atoms per molecule are used for the production of alkylbenzenes with linear alkyl chains that constitute useful intermediates in the production of biodegradable detergents.

Conventionally, a method of producing linear olefins by dehydrogenating linear paraffins is known. Among these methods, a gaseous state composed of hydrogen and linear paraffins is contacted with a dehydrogenation catalyst and reacted at a high temperature under atmospheric or superatmospheric pressure. Suitable catalysts for this purpose generally include those in which a metal belonging to platinum or a platinum group is supported on silica, alumina, natural or synthetic silica aluminate, or the like.

Under the conditions in which these catalysts exhibit dehydrogenation, a number of secondary reactions occur such as pyrolysis, isomerization or cyclization of olefins and / or paraffins. Furthermore, the dehydrogenation reaction sometimes proceeds further, in which case a product having a higher unsaturated furnace than monoolefins, that is, diolefins is produced. Eventually, due to the usual phenomena occurring in dehydrogenation processes, catalyst deactivation occurs rapidly, usually carbon sand deposition, which shortens the life of the catalyst and places a serious burden on commercial scale manufacturing processes.

In order to improve the characteristics such as activity and selectivity of the catalyst appearing in the dehydrogenation process, a catalyst composition in which a metal belonging to platinum or a platinum metal and one or more other metals has been conventionally proposed.

For example, U.S. Patent No. 3,745,112 discloses a dehydrogenation catalyst in which platinum, tin or alkali metals are deposited on a support, and U.S. Patent No. 3,892,657 discloses a dehydrogenation catalyst in which platinum, indium, and alkali or alkaline earth metals are supported on a support. British Patent No. 1,499,297 describes at least one element selected from potassium, indium and thallium, a catalyst supporting platinum and an alkali metal on an alumina support. Finally, U.S. Patent No. 4,486,547 describes a white metal metal, Dehydrogen catalysts are shown in which tin, indium and alkali or alkaline earth metals are supported on a support.

However, these known catalysts are unsatisfactory in all respects, i.e. in the activity seen in the dehydrogenation process of linear paraffins, in the selectivity of useful reaction products and in the long term maintenance of such selectivity and activity.

Applicants have discovered that combining platinum, tin and thallium at mutually critical ratios yields catalyst compositions that exhibit good and long lasting activity in dehydrogenating linear paraffins to produce linear olefins.

Therefore, in relation to the first property of this catalyst, the present invention is a porous particulate support in solid phase and 0.05-1% by weight of platinum, 0.1-1% by weight of tin, 0.12-1% by weight of thallium, and 0-1% by weight of alkali metal, based on the total weight of the catalyst. And a dehydrogenation catalyst wherein the percentage of tin / thallium is equal to or less than 1/1 and the platinum / (tin + thallium) ratio is within the range of 0.15 / 1-0.5 / 1.

In a preferred embodiment, the catalyst of the present invention contains 1.0 to 2.5% by weight of the total amount of the catalyst metal compared to the same catalyst, and the weight ratio of tin to thallium in the catalyst metal is 0.4 / 1 to 0.8 / 1. It is.

In some cases, it has been confirmed that the catalyst of the present invention is maintained in various ways because of the presence of an alkali metal, and according to specific embodiments, an alkali metal is added to the catalyst of the present invention in addition to platinum, tin and thallium. In this case, it is advantageous to set the weight ratio of platinum to alkali metal in the range of 0.2 / 1-2.0 / 1, but the weight ratio is reduced for alkali metals having a small atomic weight.

Suitable supports for the catalysts of the invention are solid granular supports having a large surface area (usually at least 100 m 2 / g) and large porosity (usually at least 0.5 ml / g), usually selected from silica, alumina and natural or synthetic silica aluminates. do.

Preferred supports are alumina in the form of gamma crystals in the form of granules used in stationary bed reactors having a table area in the range of 100-400 m 2 / g and a total pore volume of 0.5-1.2 ml / g.

The process for preparing the catalyst is as follows: (a) impregnating the support with a water-soluble compound which decomposes at high temperatures, in particular salts of platinum, tin and thallium and acidic solutions of acids, in particular nitric acid; (b) drying the impregnated support; (c) if necessary, the dried support is impregnated with an alkali metal hydroxide; (d) dry the impregnated support twice; (e) calcining the dried support at high temperature; (f) reduce the calcined catalyst.

Examples of compounds that can be used in the impregnation process step (a) are platinum chloride, tin chloride and thallium nitrate.

In the impregnation process, the solution is supplied to the support, stirred, and impregnated at room temperature (20-25 ° C.) or close to room temperature. One impregnation or continuous impregnation is performed to impregnate an appropriate amount of catalyst metal.

The drying step (b) needs to be carried out when the volume of the impregnating solution is larger than the total pore volume of the support, which is essentially intended to remove excess (ie, unadsorbed) solvent.

This drying process is carried out at 100-130 ° C. in an air stream. A number of drying process steps are constructed to impregnate several times with a solution of platinum, tin and thallium compounds and then to dry.

An impregnation with an aqueous hydroxide solution of alkali metal is carried out according to the process described above in any process step (c), followed by the drying step (d).

In the calcination step (e), the catalyst is calcined by heating at 450-550 ° C. for 2-8 hours in an air stream.

In the reduction process step (f), the calcined catalyst is reduced by contact with hydrogen gas at a temperature of 350-500 ° C. under atmospheric pressure or a pressure greater than atmospheric pressure.

According to a practical embodiment, the calcination step (e) is carried out prior to the step (c) of impregnation with an alkali metal hydroxide, in which case also a useful catalyst suitable for the purpose of the present invention is obtained.

In another embodiment, the support is impregnated with an aqueous solution containing all the metal compounds for the catalyst, ie the alkali metal compound is impregnated with the compound added to the platinum, tin and thallium compounds. In this case, steps (c) and (d) may be omitted.

It is appropriate to treat the sulfiding agent, ie hydrogen sulfide, with the reduced catalyst in an amount such that the atomic ratio of sulfur to platinum is 2/1 for the same catalyst. This treatment may be accomplished by treating the hydrogen sulfide diluted in the nitrogen atmosphere supplied to the reduced catalyst with the reaction mixture under typical dehydrogenation conditions (temperature of 400-500 ° C.).

The catalyst prepared in this way has high activity and selectivity in the process of dehydrogenating linear paraffins to linear olefins, and these characteristics last for a long time.

Particularly dehydrogenated linear paraffins are those containing at least 9 carbon atoms, i.e. 9-20, in particular 10-14 carbon atoms in the molecule. These paraffins are supplied in a gaseous state with hydrogen (the number of moles of hydrogen and paraffin are 1 / 1-15 / 1) to a catalyst composed of a catalyst bed of a fixed bed reactor, and a pressure higher than atmospheric pressure in the temperature range of 400-550 ° C (0.5- Dehydrogenation with an hourly space velocity of 5-100 hours ⁻¹ for the liquid paraffin feed under 5 kg / cm).

Finally, the olefin is separated from the dehydrogenation product by known methods.

The present invention is explained according to the examples.

Example 1

As a catalyst support, a commercially available gamma alumina having the following characteristics is used:

Table Area: 196㎡ / g

Total volume: 0.75ml / g

Particle Size: 1.25-1.6mm

To 90 g of gamma alumina, 120 ml of a solution made of 0.83 g of thallium nitrate-(I) and 6 g of 65% nitric acid is slowly added with stirring.

The solution and gamma alumina are contacted with stirring at room temperature (20-25 ° C.) for 1 hour and then heated at 120 ° C. for 1 hour in an air stream to almost completely evaporate excess solvent.

120 ml of a solution containing 0.9 g of tin chloride, 2.2 g of platinum chloride (16% of platinum weight) and 6 g of 65% nitric acid was prepared and added slowly to the dried support while stirring at room temperature.

The solution and the support are contacted at room temperature for 1 hour with stirring, and then contacted at 120 ° C. for 1 hour in an air stream.

The dried solid obtained here is calcined at 500 ° C. for 4 hours in a muffle in air stream. Finally, the catalyst is cooled to obtain a catalyst. The composition of the catalyst is shown in Table 1.

Example 2

The dried support was impregnated with thallium, tin and platinum compounds, and then impregnated with 120 ml of a solution made of 1.35 g of lithium hydroxide, in the same manner as in Example 1.

After impregnating with a lithium hydroxide solution, the catalyst was dried under the conditions of Example 1 to be calcined to obtain a catalyst. The composition of the catalyst is shown in Table 1.

Example 3

To 90 g of the same commercially available gamma alumina in Example 1, 120 ml of a solution of 0.96 g of thallium nitrate (I) and 6 g (65 wt%) of nitric acid was slowly added at room temperature (20-25 ° C.) with stirring.

Contact was continued for 1 hour with constant stirring at room temperature (20-25 ° C.), followed by heating to 120 ° C. and holding at room temperature for 1 hour.

A solution of 1.2 g of tin chloride, 3.1 g of platinum chloride (16% by weight of platinum) and 6 g (65% by weight) of nitric acid was made up and slowly added to the dried solid with stirring at room temperature, followed by stirring of the solution and solid at room temperature. It is contacted for 1 hour and contacted again at 120 ° C in the atmosphere. The dried solid thus obtained is calcined at 500 ° C. in a muffle for 4 hours in air.

Finally, the catalyst is cooled to obtain a catalyst whose composition is shown in Table 1.

TABLE 1

Example 4

Using the catalysts prepared in Examples 1-3, dehydration of linear paraffins is carried out to prepare linear olefins.

For this purpose, 6 ml of each catalyst was charged into a fixed bed tubular micro-reactor, preliminarily reduced in hydrogen gas stream at 400 ° C. and 2 kg / cm 2 for 5 hours, and each catalyst was sulfided to yield an atomic ratio of S / Pt of about 2/1. To be. For this purpose, a normal mixture for the dehydrogenation reaction is supplied to the catalyst, wherein the hydrogen sulfide is 5% by volume in a nitrogen atmosphere at 460 ° C. and 2 kg / cm 2 pressure.

After these treatments, the linear (C ₁₀ -C ₁₃ ) paraffins, hydrogen and water were in a gaseous state with a molar ratio of H ₂ / linear patapins of 5/1 and 2,000 ppm by weight of water in the same mixture. The mixture was fed to the reactor and subjected to the dehydrogenation test rate.

The hourly space flow rate (liquid paraffin volume / catalyst volume / hour) is 25 hours ⁻¹ for the liquid paraffin mixture feed and dehydrogenated again at 488 ° C. and a pressure of 2 kg / cm 2.

Each test was carried out for 20 hours, and the average selectivity (%) of the linear paraffins in the following Table 2 was calculated for the converted linear paraffins in Example 1-3. Each reported catalyst is reported as follows.

TABLE 2

Claims (5)

Active in the dehydrogenation of linear paraffins to linear olefins, solid porous granular support, 0.05-1% by weight of platinum, 0.1-1% by weight of tin, 0.1-1% by weight of thallium, and 0-1% by weight of alkali metals based on the total weight of the catalyst And a tin / thallium ratio equal to or less than 1/1 and a platinum / (tin + thallium) ratio in the range of 0.15-0.5 / 1. A catalyst according to claim 1, which contains 1.0-2.5% by weight of platinum, tin, thallium or an alkali metal which may be added to the total weight of the catalyst, and the weight ratio of tin / thallium in the catalyst metal is 0.4 / 1-0.8 / 1. A catalyst, characterized in that. The catalyst of claim 1 wherein the weight ratio of platinum / alkali metal is 0.2 / 1-2.0 / 1. The catalyst of claim 3 wherein the alkali metal is lithium. The catalyst of claim 1 wherein the support is granular gamma alumina having a surface area of 100-400 m 2 / g and a total pore size of 0.5-1.2 ml / g.