DE19932362A1 - Catalyst containing iron oxide, used in dehydrogenation of ethylbenzene to styrene, is produced from iron oxide obtained by spray roasting iron salt solution - Google Patents

Abstract

Catalyst containing iron oxide is produced from an iron oxide obtained by spray roasting an iron salt solution. An Independent claim is also included for the production of the catalyst by using an iron oxide obtained by spray roasting an aqueous iron solution.

Description

The invention relates to a catalyst containing iron oxide, a process for its manufacture and a process for Dehydrogenation of ethylbenzene to styrene in the presence of the Catalyst.

Natural and synthetic iron oxides, such as α-FeOOH, α-Fe ₂ O ₃ , γ-Fe ₂ O ₃ and Fe ₃ O _4, are generally used to produce styrene catalysts based on Fe ₂ O ₃ and K ₂ O. The synthetic iron oxides are usually produced by precipitation of iron salt solutions and thermal decomposition.

In addition to the usual iron oxides, there are also special iron oxides or modified iron oxides as iron components for the production described by dehydrogenation catalysts.

Those for the production of the dehydrogenation catalysts according to EP-A 0 532 078 ferrous compound used contains 10 to 100 Ge % by weight of a mica-like iron oxide with a preferred maximum platelet size of less than 100 µm.

US 5,023,225 describes the use of chromium-modified iron oxide for the production of dehydrogenation catalysts. The red iron oxide is made by mixing yellow iron hydrate with Chromium oxide or a chromium salt and heating the mixture poses.

WO 96/18 593 describes an iron-containing dehydrogenation catalyst gate, whose iron component in the catalyst has a bimodal pore has size distribution. Magnetic iron are preferred oxide compounds, such as magnetite, are used.

A pre-treated ("predoped") iron oxide is according to WO 96/18 458 used. The pretreatment is carried out with a pretreatment sub punch, which selected an element from the group Be, Mg, Ca, Sr, Ba, Sc, Ti, Zr, Hf, V, Ta, Mo, W, Mn, Tc, Re, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Hg, Al, Ga, In, Tl, Ge, Sn, Pb, Bi, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, contains and heating the iron oxide mixture to at least 600 ° C. The catalyst is then shaped.  

WO 96/18 594 describes an iron oxide catalyst with iron oxide particles which have an average longest dimension in the range from 2 to 10 μm. The average pore diameters are between 0.22 and 0.30 µm, the pore volumes between 0.16 and 0.22 cm ³ / g. An iron oxide α-FeOOH (Penniman iron oxide) produced from iron shavings by dehydration of a yellow α-Fe (OOH) intermediate was used for the production.

WO 96/18457 describes a process for the production of iron oxide catalysts in which the iron oxide, prior to mixing with one or more promoters, to give iron oxide particles with a BET surface area of less than 1.9 m ² / g and a particle length of 0.3 - 3 µm and a particle width of 0.2-2 µm is restructured. Compounds of the elements Mo, Cu, Ca, Zn, Mn, Sn, Ti, Bi, Co, Ce, W, Cr, Mg, and V are used as the restructuring agent.

The catalysts mentioned require iron oxides as raw materials, that require complex production or modification.

The object of the present invention was therefore to provide the aforementioned To remedy disadvantages and an inexpensive and easy to do catalyst for the dehydrogenation of ethylbenzene to styrene to find. In particular, the catalyst should have a high pore volume lumen with high activity, selectivity and high have mechanical stability.

Accordingly, a catalyst containing iron oxide was found wherein to produce the catalyst, an iron oxide, which by Spray roasting of an iron salt solution was used becomes.

The iron oxide used is preferably spray-roasted hydrochloric acid solution containing iron chloride according to the Ruthner method ren, as described for example in EP-A 0 850 881, ge won.

The solution containing iron chloride is placed in a spray roaster from above introduced and through spray nozzles into a reaction space, which is heated by a direct burner device. The temperature above the burner level arranged reaction area mes, in which fuel gases are sprayed cyclonically in counterflow th solution, the exhaust gas is around 400 ° C and in the Burner level at about 750 ° C, especially at about 650 ° C. In this Reaction zone is the thermal decomposition of iron chloride solution. The iron oxide falls out of the roaster's reaction zone  down and is around at a temperature lock system 450 ° C to 580 ° C carried out.

The iron is between the burner level and the granulate discharge oxide granulate in a cooling zone to a temperature below 450 ° C, preferably cooled between 300 ° C and 400 ° C. At the same time the volume fraction of hydrochloric acid gas in the spray roaster in this Be richly reduced below 10% by volume, in particular below 2% by volume.

After the iron oxide granulate has been discharged from the spray roaster it to a temperature that is maintained and heated with superheated steam preferably poured bed in a bed height below 10 mm applied between 2 mm and 5 mm. The bulk guidance of the egg Senoxide granules can be cocurrent or countercurrent to hot steam. The exposure time of the superheated steam can be below half of 5 min, preferably less than 2 min and in particular be less than 1 min. Iron oxide produced in this way usually has a residual chloride content below 500 ppm, esp especially below 100 ppm and 50 ppm.

An iron oxide produced by spray roasting with a density in the range from 0.6 to 1, preferably 0.7 to 0.8 g / cm ³ and a specific surface area in the range from 1 to 10, preferably 2, is suitable for the preparation of the catalysts according to the invention to 7, particularly preferably 3 to 4 m ² / g.

The pore volume of the catalysts according to the invention is at least 0.2 cm ³ / g and is preferably in the range from 0.25 to 0.5 cm ³ / g. The average pore diameter is at least 0.3 μm and is preferably in the range from 0.4 to 0.8 μm.

The catalysts of the invention generally contain at least one potassium compound in addition to iron oxide. Potassium carbonate, potassium hydroxide or potassium oxalate are preferably used as the potassium compound. The catalyst preferably contains 5 to 40% by weight of potassium, calculated as K ₂ O.

Furthermore, the catalyst can one or more of the usual Promoters to increase selectivity, activity or stability contained in usual concentrations. As a promoter connections of elements selected from the group Be, Mg, Ca, Sr, Ba, Sc, Ti, Zr, Hf, V, Ta, Mo, W, Mn, Tc, Re, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Hg, Al, Ga, In, Tl, Na, Cs, La, Li, Ge, Sn, Pb, Bi, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, which are used individually or in mixtures can be detected. Preferred promoters are compounds selects from the group Mg, Ca, Ce, V, Cr, Mo, W, Ti, Mn, Co and Al.  

Particularly preferred promoters are Mg, Ca, Ce, V, Cr, Mo and W. The catalysts can be one, preferably two, in particular three or more promoters from the group Mg, Ca, Ce, V, Cr, Mo, W ent hold. The promoters are preferred in amounts of 0 each to 15, in particular 1 to 10 wt .-%, calculated as the most stable Oxides added.

The iron oxides used according to the invention can also be whole or partly the potassium compound or the promoters mentioned hold. For this purpose, for example, part of the potassium compound and / or part of the promoters used for spray roasting Iron salt solution can be added.

The catalysts of the invention can be obtained by the known one- or multi-stage production processes, for example as described in EP-A 0 195 252 or EP-A 0 866 731. For this purpose, the iron oxide obtained by spray roasting an iron salt solution can be used alone or in addition to the usual natural or synthetic iron oxides such as α-FeOOH, γ-FeOOH, α-Fe ₂ O ₃ , γ-Fe ₂ O ₃ or Fe ₃ O ₄ become. The proportion of the iron oxide obtained by spray roasting an iron salt solution is 10 to 100 mol%, preferably 50 to 100 mol%, based on all the iron compounds used.

The finely powdered catalyst components can be mixed dry or suspended in water and spray dried. The dry powder is then tabletted into mechanically stable moldings or pasted into a pasty mass with the addition of water and extruded into strands and cut to length. Deformation aids such as stearates, walocel, graphite or starch can be used here. The catalyst mass is preferably solid or hollow strands with a diameter of 2.5-6 mm and a length of 5 to 50 mm. Strands with a star-shaped cross section, as shown in FIG. 1, are particularly preferred.

The extrudates are then continuous or discontinuous Usually at temperatures in the range of 80 to 140 ° C dried. The dried moldings can then be a staged or multi-staged at temperatures in the range of 200 to 1000 ° C annealed and / or calcined.

The catalysts of the invention are suitable for the non-oxide tive dehydrogenation of hydrocarbons, especially for de Hydrogenation of ethylbenzene to styrene. This is generally a mixture of water vapor and ethylbenzene in a molar ratio in the range from 2 to 20, preferably in the range from 5 to 15, and  at temperatures in the range of 500 to 700 ° C over the catalyst headed. In the adiabatic process, the temperature at the Re is actuator input usually 600 to 650 ° C and decreases due to the En dothermal of the reaction from 530 to 570 ° C. The is preferred Reaction carried out at atmospheric pressure or below.

The catalysts of the invention have a large pore volume men on. This will lower the liter weight of the catalyst 1.2 kg / l, measured on 3 mm full-strand catalysts, reduced without lowering the activity and selectivity. At the same time is the cutting hardness with over 20 N for technical use sufficient.

Examples example 1

900 g of iron oxide Hoogovens RIO-200 (from Hoogovens Staal BV) became a suspension of 168 g K ₂ CO ₃ , 200 g Ce ₂ (CO ₃ ) ₃ , 46 g CaCO ₃ , 29 g MoO ₃ and 61 g basic magnesium carbonate (4MgCO ₃ xMg (OH) 3.4H ₂ O) in 4.3 l of water with stirring. The spray mash was then spray dried at a solids content of 25% by weight. The spray powder obtained was processed with about 340 ml of water into a pasty mass within 30 minutes and shaped into cylindrical extrudates of 3 mm in diameter in an extrusion press and cut into pieces about 10 mm long. The catalyst strands were then dried in a forced-air oven at 120 ° C. for 1 hour and calcined in a calcining oven at 300 ° C. for 2 hours and then at 875 ° C. for 1 hour.

Comparative experiments V1 to V4

Example 1 was repeated with the difference that the following synthetic iron oxides were used in the same amounts as iron oxide.
V1: synthetic α-Fe ₂ O ₃ : Bayferrox 1360
V2: synthetic γ-Fe ₂ O ₃ : Bayferrox E AB 21 or
V3: synthetic α-Fe ₂ O ₃ : Bayferrox 720 N

The data measured on the catalyst strands are summarized in Table 1:
The ramming weight (liter weight) was measured using a ramming volumetric JEL from Engelsmann (Ludwigshafen). Before measuring the tamped density, the strands were tamped 750 times. The bulk weight is the weight before tamping the strands. The pore volumes were determined according to DIN standard 66133.

The contact angle of the mercury when determining the mean ren pore diameter was 140 ° (DIN 66133).

The cutting hardness was determined with a cutting edge of 0.3 mm exerted an increasing load on the extrudate until the It was cut (device from Zwick (Ulm). From 25 strands the mean was formed.

Table 1

Properties of the catalysts

Attempts at dehydration

The catalysts were get in an isothermal test facility continuous A reaction tube with an inner diameter of 30 mm was used 250 ml of the full-rod catalyst to be tested and filled with egg water vapor / ethylbenzene ratio (D / EB) of 1.25 kg / kg and operated at a liquid hourly space velocity (LHSV) of 0.45 / h. After 10 days, the catalyst had a stable turnover and Se Lectivity level reached and the composition of the liquid and gaseous reaction mixture was balanced.

Table 2 shows the catalysts from Example 1 and Comparative experiments at different temperatures Se selectivities and sales as well as the styrene calculated from them parts summarized.  

Table 2

Claims (10)

1. Catalyst containing iron oxide, characterized in that an iron oxide obtained by spray roasting an iron salt solution is used to produce the catalyst. 2. Catalyst according to claim 1, characterized in that the used iron oxide by spray roasting a hydrochloric acid egg solution containing senchlor obtained by the Ruthner method has been. 3. Catalyst according to claim 1 or 2, characterized in that the iron oxide used has a density in the range from 0.6 to 1 g / cm ³ and a specific surface area in the range from 1 to 10 m ² / g. 4. Catalyst according to one of claims 1 to 3, characterized in that the pore volume of the catalyst is at least 0.2 cm ³ / g. 5. Catalyst according to one of claims 1 to 4, characterized records that the average pore diameter of the catalyst is at least 0.3 µm. 6. Catalyst according to one of claims 1 to 5, containing additionally at least one potassium compound. 7. Catalyst according to one of claims 1 to 6, containing additionally at least one promoter selected from compounds group Mg, Ca, Ce, V, Cr, Mo, W. 8. A catalyst according to claim 6 or 7, characterized in that that at least part of the potassium compound or part the promoters of the iron salt solution for the spray roasting was set. 9. A method for producing a catalyst according to one of the Claims 1 to 8, characterized in that one through Spray roasting of an aqueous iron solution obtained iron oxide starts.   10. A process for the dehydrogenation of ethylbenzene to styrene, thereby characterized in that the dehydration in the presence of a Kata analyzer according to one of claims 1 to 8 is carried out.