KR19990023231A - Catalyst for dehydrogenating ethylbenzene to styrene - Google Patents

Abstract

A catalyst for dehydrogenating ethylbenzene to styrene, which is produced by a paste containing iron oxide, an oxide of an alkali and an alkaline earth metal, an oxide of a lanthanum element and an oxide of a group 6 metal, impregnated in an aqueous solution of a cerium salt, Treated, dried and then sintered to pre-form potassium ferric oxide, followed by the addition of other components or precursors of the catalyst.

Description

Catalyst for dehydrogenating ethylbenzene to styrene

The known catalysts for dehydrogenating ethylbenzene to styrene are based on iron oxide (Fe ₂ O ₃ ), and as accelerators and stabilizers, oxides of alkali and alkaline earth metals, oxides of lanthanide series elements and Group 6 metals of the periodic table Oxide. ≪ / RTI >

The composition of the catalyst is expressed in weight percent of the oxide and is comprised of 50 to 92 percent iron oxide, 5 to 20 percent alkali metal oxide, 0.5 to 14 percent alkaline earth metal oxide, 2 to 10 percent oxide of lanthanum element, And an oxide of a metal.

Preferred compositions are represented by oxides and include iron oxide, potassium oxide, calcium oxide and / or magnesium oxide, cerium oxide and molybdenum oxide and / or tungsten oxide.

Iron oxide is partially present in the form of potassium ferrate in the catalyst.

Potassium iron oxide is considered as the active catalyst component.

It has surprisingly been found that it is possible to obtain a catalyst having high activity and selectivity for the reaction even when working with a low weight ratio (S / O) between water and ethylbenzene used in the reaction of dehydrogenating ethylbenzene to styrene.

The catalysts of the present invention include iron oxide (Fe ₂ O ₃ ), alkali and alkaline earth metal oxides, lanthanum oxides, oxides of Group 6 metals of the periodic table, and crystalline potassium iron oxide having an average size of 2 microns or less. The crystalline potassium iron oxide is pre-formed by sintering the paste at a temperature of 600 to 900 DEG C after the action of aqueous KOH on the paste of iron oxide impregnated with an aqueous solution of cerium salt and drying.

Thereafter, the other components and precursors of the catalyst are added to the sintered product and mixed therewith and remixed.

The dried mixture is ground and extracted to obtain the granules of the catalyst in the intended form. The granules are then sintered for 1 to 6 hours at a temperature of 600 to 900 占 폚. It is surprising that the resulting catalyst exhibits high activity at a lower S / O ratio than the corresponding catalyst prepared by adding and mixing the components in a single step.

The ability to use a low S / O ratio has a significant energy saving effect because the amount of steam used is reduced. It is also surprising that the catalyst according to the invention has a high S / O ratio, that is, a high activity even under conditions where the dilution of ethylbenzene is higher and thus the partial pressure of this system is lowered.

The composition of the catalyst according to the present invention, expressed in weight percent of the oxide, comprises: 50 to 90% iron oxide (Fe ₂ O ₃ ), 5 to 15% potassium oxide, 2 to 15% calcium oxide and / magnesium, 2 to 10% cerium oxide (CeO _2), and 1 to 10% of molybdenum oxide and / or tungsten oxide.

Preferred compositions include:

a) 70~80% iron oxide, 8-10% potassium oxide, 8-10% cerium oxide, 2-5% calcium and magnesium oxide, 2-5% MoO _3, or

b) 70~80% iron oxide, 5-8% potassium oxide, 4-10% cerium oxide, 1-3% magnesium and / or calcium oxide, 4~7% WO _3.

Iron oxide (Fe ₂ O ₃ ) is a potassium iron oxide having an average crystal size within the range of 2 microns or less, more specifically 0.5 to 1.5 microns, that is, K ₂ O.nFe ₂ O ₃ (n is preferably 11) exist.

The size of the crystal is measured by a scanning electron microscope (SEM).

As mentioned above, the catalyst according to the present invention can be produced by, for example, extracting a paste of iron oxide (FeO (OH)) (yellow hydrated iron oxide) hydrated with an aqueous solution of a soluble cerium salt such as cerium nitrate and adding an aqueous potassium hydroxide solution . The paste is dried at 100 to 200 ° C and sintered at 600 to 900 ° C for 1 to 6 hours. The sintered product is ground and then mixed with molybdenum trioxide and / or WO ₃ , magnesium carbonate and / or calcium carbonate, and the paste is dried at 100 to 200 ° C and then extracted to obtain the intended geometric shape, Lt; 0 > C for 1 to 6 hours.

A variety of geometric shapes can be used, such as a simple cylindrical shape, a cylindrical shape with a cavity, and a cylindrical shape with a through hole and a lobe that are parallel and substantially equidistant to the holes of the cylindrical shape.

In the case of perforated granular catalysts with three lobes, the ratio between the surface and volume of the granules is at least 2.4 cm ^-1 .

In these granules, the ratio between the height of the housing of the holes and the distance is in the range of 1.5 to 2.5.

The diameter of the granules is generally 3 to 4 mm and the height is generally 3 to 5 mm.

Cylindrical granules of this type are disclosed in European Patent Publication No. 591792, the contents of which are incorporated herein by reference.

The lobate granules penetrated and lobed are extruded using an external lubrication technique: a male plug used to form the holes of the lubricant and a press mold that is disposed on the surface of the mold chamber It is prepared to be a tablet instead of being contained in a powder mass. .

Solid lubricants such as magnesium stearate and stearic acid are preferably used.

The use of granular catalysts pierced with lobes allows for a significant reduction in pressure drop in fixed bed reactors and improved catalyst activity and selectivity.

The reaction for dehydrogenating ethylbenzene to styrene is carried out under the conditions of a temperature of 540 to 650 占 폚 and a working condition of the same or a higher or lower pressure than the atmospheric pressure, the water / ethylbenzene weight ratio being 2.4 to 1.5, preferably 2 or less, And a stream of ethylbenzene is passed through a fixed catalyst bed. The space velocity of the ethylbenzene stream is 0.5 cm 3 / cm 3 / h of fixed bed.

Example 1

The paste was first prepared by mixing yellow hydrated iron oxide with an aqueous solution of cerium nitrate and then mixing with an aqueous solution of KOH. The paste was dried at 150 ° C for 2 hours and then sintered at 850 ° C for 2 hours.

The sintered product was ground, mixed with an aqueous suspension of molybdenum trioxide, magnesium carbonate and calcium carbonate, extracted and dried at 150 DEG C for 2 hours. The dried mixture was ground and refined to form cylindrical granules with three lobes with through-holes in the grooves. The holes are parallel to each other and parallel to the axis of the cylinder.

The inner diameter of the hole was 1.3 mm, the wall thickness was 0.8 mm, the outer diameter of the granule was 2.5 mm, and the height was 5 mm. This hole was located at the vertex of an equilateral triangle. Purification was carried out using stearic acid as an external lubricant and applied as a continuous stream of air to the male plugs for the walls and through-holes of the mold chamber.

The granules were sintered at 650 DEG C for 4 hours.

The components were used in this amount to give the following final composition expressed as weight percent of the oxide: Fe ₂ O ₃ = 77%, K ₂ O = 9.6%, CeO ₂ = 7%, MgO = 2%, CaO = 2%, MoO ₃ = 2.4%.

The axial tensile strength (with respect to the direction of the axis of the cylinder) was 25 N / particle.

The volume of the pore was 0.2 cm 3 / g, consisting of 25% pore with a diameter of 800-1000 Å, 50% pore with a diameter of 1000-2000 Å and 10% pore with a diameter of 2000-4000 Å.

No pores with a diameter of 50,000 A or more were present.

The surface area of the catalyst was 4 m < 2 > / g. The apparent density was 0.97 g / cm 3.

The average size of the crystals was 1 micron (measured by scanning electron microscope (SEM)).

Comparative Example 1

The paste was prepared by mixing hydrated yellow iron oxide with cerium nitrate, KOH, MoO ₃ , MgCO ₃ and CaCO ₃ and water.

The extracted mixture was dried at 150 ° C for 2 hours, ground, and purified as in Example 1 and sintered at 850 ° C for 2 hours.

The final composition was the same as in Example 1. The surface area was 5.3 m 2 / g, the pore volume was 0.28 cm 3 / g, and the apparent density was 0.87 g / cm 3.

Example 2

The catalyst of Example 1 and Comparative Example 1 was tested in a steel reactor with an internal diameter of 35 mm.

During each test, 200 cm 3 of catalyst was added to the reactor and supported by a steel lattice.

This test was performed at 590 캜 with varying weight ratios between water vapor and ethylbenzene (S / O), and the reagents were prepared to flow through the catalyst bed after being preheated to 590 캜.

The pressure at the outlet of the reactor was 1.05 atm and the space velocity per hour of ethylbenzene was 0.5 cm3 / cm3 / h of fixed bed. Samples of the reaction products were collected over 2 hours after the system was stabilized for at least 20 hours at each condition.

Selectivity of conversion and moles is listed in the following table.

[Table 1]

S / O Conversion% Selectivity%

Example 1 2.4 66.8 94.8

2 62.4 95.0

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Comparative Example 1 2.4 66.2 94.7

2 56.9 95.1

See above

Claims (10)

Dehydrating ethylene to styrene, comprising iron oxide (Fe ₂ O ₃ ), potassium oxide, magnesium oxide and / or calcium oxide, cerium oxide, tungsten oxide and / or molybdenum oxide and potassium ferric oxide having an average crystal size of at least 2 microns Wherein the catalyst is preformed by the action of aqueous KOH on a paste of hydrated iron oxide impregnated with an aqueous solution of a cerium salt and the resultant paste is dried and sintered prior to the addition of another component or precursor of the catalyst, The catalyst according to claim 1, wherein the sintering of the dried paste is performed at 600 to 900 占 폚. 3. The catalyst according to claim 1 or 2, wherein the potassium ferric oxide has an average crystal size of 0.5 to 1.5 microns. The catalyst according to any one of claims 1, 2 and 3, wherein the catalyst comprises 50 to 90% iron oxide, 5 to 15% potassium oxide, 2 to 15% calcium oxide and / Magnesium, 2 to 10% cerium oxide (CeO ₂ ), 1 to 10% molybdenum oxide (MoO ₃ ) and / or tungsten oxide (WO ₃ ). The catalyst composition of claim 4, wherein the catalyst composition comprises 70 to 80% iron oxide, 8-10% potassium oxide, 8-10% ceria, 2-5% calcium oxide and / or magnesium oxide, 2-5 % MoO ₃ . The method of claim 4, wherein the composition comprises 70-80% iron oxide, 5-8% potassium and 4-10% cerium oxide (CeO _2), 1~3% of calcium oxide, magnesium and / or oxide in weight percent of oxides, A catalyst comprising 4-7% tungsten oxide (WO ₃ ). 7. The catalyst according to any one of claims 1 to 6, wherein the catalyst is in the form of a cylindrical granule having a lobe and a through-hole in the lobe. 8. The catalyst of claim 7, wherein the granules have three lobes and through-holes in the lobes and have axes that are substantially parallel to and equidistant from the axis of the cylinder. A process for dehydrogenating ethylbenzene to styrene which is carried out by passing a stream of ethylbenzene and water vapor over the fixed catalyst bed according to claim 1 at a temperature of from 540 캜 to 650 캜. The method according to claim 9, wherein the weight ratio between steam and ethylbenzene is 2 or less.