PLATINUM-SULFUR-BASED SHELL CATALYST, PRODUCTION AND USE THEREOF IN THE DEHYDROGENATION OF HYDROCARBONS

Abstract

The invention relates to the use of a supported, platinum-containing and sulfur-containing shell catalyst for the partial or complete dehydrogenation of perhydrogenated or partially hydrogenated cyclic hydrocarbons. The present invention also relates to a method for producing a platinum-containing and sulfur-containing shell catalyst and to a platinum-containing and sulfur-containing shell catalyst. The present invention further relates to a method for the partial or complete dehydrogenation of perhydrogenated or partially hydrogenated cyclic hydrocarbons.

Claims

1. The use of a shell catalyst for partial or complete dehydrogenation of perhydrogenated or partly hydrogenated cyclic hydrocarbons, wherein the shell catalyst comprises: (a) a shaped support body, (b) platinum in an amount in the range of 0.01-1% by weight, preferably in the range of 0.1-1.0% by weight, more preferably in the range of 0.2-0.5% by weight, especially in the range of 0.2-0.4% by weight, based on the total weight of the shell catalyst, and (c) sulfur, wherein the atomic ratio of platinum to sulfur is 1:1-1:10, preferably 1:1.5-1:5, more preferably 1:1.5-1:2.5, especially 1:2.

2. The use as claimed in claim 1, wherein the perhydrogenated or partly hydrogenated cyclic hydrocarbon is selected from the group consisting of cyclohexane, methylcyclohexane, decalin, perhydrogenated or partly hydrogenated benzyltoluene, perhydrogenated or partly hydrogenated N-alkylated carbazole, especially perhydrogenated or partly hydrogenated N-ethylcarbazole, and perhydrogenated or partly hydrogenated dibenzyltoluene and isomers thereof.

3. The use as claimed in claim 1 or 2, wherein the dehydrogenation is performed continuously in a reactor selected from a fixed bed reactor, a flow bed reactor or a fluidized bed reactor, and preferably in a fixed bed reactor.

4. The use as claimed in claim 1, 2 or 3, wherein the dehydrogenation is effected at a temperature in the range from 200 C. to 400 C., more preferably at a temperature in the range from 230 C. to 330 C., especially at a temperature in the range from 260 C. to 310 C., and preferably at a pressure in the range of 1-5 bar, more preferably in the range of 2-4 bar, especially at a pressure of about 3 bar.

5. The use as claimed in any of claims 1 to 4, wherein the shell catalyst has an outer shell including 85% by weight or more, preferably 90% by weight or more, especially 95% by weight or more, of the platinum present and sulfur present in the shell catalyst, wherein the thickness of the outer shell, determined by EDX linescan, is in the range from 20 m to 500 m, preferably in the range from 40 m to 250 m, especially in the range from 60 m to 120 m.

6. The use as claimed in any of claims 1 to 5, wherein the shaped support body comprises alumina (Al.sub.2O.sub.3), silicon dioxide (SiO.sub.2), titanium dioxide (TiO.sub.2), zirconium dioxide (ZrO.sub.2), silicon carbide (SiC) or mixtures thereof, more preferably alumina, preferably selected from gamma-alumina, theta-alumina, delta-alumina, alpha-alumina or mixtures thereof, and especially gamma-alumina.

7. The use as claimed in any of claims 1 to 6, wherein the shell catalyst has a BET surface area in the range from 1 m.sup.2/g to 300 m.sup.2/g, more preferably 1 m.sup.2/g to 250 m.sup.2/g, preferably in the range from 2 m.sup.2/g to 150 m.sup.2/g, especially in the range from 3 m.sup.2/g to 100 m.sup.2/g.

8. The use as claimed in any of claims 1 to 7, wherein the pore volume of the shell catalyst, determined by Hg intrusion methods to DIN 66133, is 0.1 to 1.0 cm.sup.3/g, especially 0.3 to 0.6 cm.sup.3/g.

9. The use as claimed in any of claims 1 to 8, wherein the shaped support body is in the form of extrudates, such as strands or ribbed strands, tablets, rings, ring tablets, spheres, pellets, honeycombs, or granules.

10. A process for producing a platinum-containing and sulfur-containing shell catalyst, comprising the following steps: (a) applying a solution, preferably an aqueous solution, of platinum sulfite acid (H.sub.3Pt(SO.sub.3).sub.2OH) to a shaped support body to obtain a laden shaped support body, (b) optionally washing and/or drying the laden shaped support body, wherein the drying is effected at a temperature in the range from 70 C. to 150 C., especially at about 120 C., over a period of 1 h to 15 h, preferably over a period of 5 h to 10 h, especially over a period of about 8 h, (c) calcining the optionally washed and/or dried, laden shaped support body at a temperature in the range from 200 C. to 390 C., preferably in the range from 250 C. to 370 C., especially at about 350 C., over a period of 0.25 h to 5 h, preferably over a period of 0.5 h to 4 h, especially over a period of about 2 h, to obtain a calcined platinum-containing and sulfur-containing shaped shell catalyst body, and (d) reducing the calcined platinum-containing and sulfur-containing shaped shell catalyst body in the presence of hydrogen at a temperature in the range from 200 C. to 500 C., preferably in the range from 300 C. to 450 C., especially at about 400 C., over a period of 0.25 h to 5 h, preferably over a period of 0.5 h to 4 h, especially over a period of about 2 h.

11. A shell catalyst comprising (a) a shaped support body, (b) platinum in an amount in the range of 0.01-1% by weight, preferably in the range of 0.1-1.0% by weight, more preferably in the range of 0.2-0.5% by weight, especially in the range of 0.2-0.4% by weight, based on the total weight of the shell catalyst, and (c) sulfur, wherein the atomic ratio of platinum to sulfur is 1:1-1:10, preferably 1:1.5-1:5, more preferably 1:1.5-1:2.5, especially 1:2.

12. The shell catalyst as claimed in claim 11, comprising an outer shell including 85% by weight or more, preferably 90% by weight or more, especially 95% by weight or more, of the platinum and sulfur present in the shell catalyst, wherein the thickness of the outer shell, determined by EDX linescan, is in the range from 20 m to 500 m, preferably in the range from 40 m to 250 m, especially in the range from 60 m to 120 m.

13. The shell catalyst as claimed in either of claims 11 and 12, wherein the shaped support body comprises alumina (Al.sub.2O.sub.3), silicon dioxide (SiO.sub.2), titanium dioxide (TiO.sub.2), zirconium dioxide (ZrO.sub.2), silicon carbide (SiC) or mixtures thereof, more preferably alumina, preferably selected from gamma-alumina, theta-alumina, delta-alumina, alpha-alumina or mixtures thereof, and especially gamma-alumina.

14. The shell catalyst as claimed in any of claims 11 to 13, wherein the shell catalyst has a BET surface area in the range from 1 m.sup.2/g to 300 m.sup.2/g, more preferably 1 m.sup.2/g to 250 m.sup.2/g, preferably in the range from 2 m.sup.2/g to 150 m.sup.2/g, especially in the range from 3 m.sup.2/g to 100 m.sup.2/g.

15. The shell catalyst as claimed in any of claims 11 to 14, wherein the pore volume of the shell catalyst, determined by Hg intrusion methods to DIN 66133, is 0.1 to 1.0 cm.sup.3/g, especially 0.3 to 0.6 cm.sup.3/g.

Description

DESCRIPTION OF THE FIGURES

[0103] FIG. 1 shows the catalytic activity of various catalysts. What is shown is the degree of dehydrogenation of perhydrogenated dibenzyltoluene over a period of 2 hours under the following conditions: temperature 310 C., pressure: ambient pressure, ratio of platinum content to perhydrogenated dibenzyltoluene: 0.1 mol %.

[0104] FIG. 2 shows a scanning electron micrograph of a section through the catalyst of the invention from example 1 (FIG. 2a) and the intensity curve for the elements platinum and sulfur, determined by EDX linescan for this catalyst (FIG. 2b).

DETERMINATION OF PHYSICAL PARAMETERS

[0105] The physical parameters cited in the present invention, unless stated otherwise, are determined as described below:

[0106] Determination of BET surface area: BET surface area is determined by the single-point nitrogen method in accordance with DIN 66132.

[0107] Pore volume: Pore volume is determined by mercury intrusion to DIN 66133.

[0108] Shell thickness: Shell thickness is determined by EDX linescan.

[0109] For this purpose, the sample is cut down the middle into two halves with a sharp knife and then ground flat with a rotating abrasive paper. The adhering dust is removed with oil-free compressed air. After this sample preparation, the sample is fixed on the sample holder with the ground surface upward. Subsequently, the sample is transferred into a scanning electron microscope. The following parameters are used for the EDX linescan:

[0110] Scanning electron microscope: LEO 1530 from LEO Zeiss

[0111] Detector: Quantax with XFlash 4010 from Bruker

[0112] Voltage:

[0113] Aperture:

[0114] Working distance: about 16 mm

[0115] Magnification: about 55-fold

[0116] Measurement duration: about 10-30 min

[0117] Distance from measurement point to measurement point: 2-5 m

[0118] Ignition loss: The determinations of ignition loss are effected by determining the weight of about 1-2 g of a sample of the material to be analyzed and then heating it to 900 C. under ambient atmosphere and storing it at this temperature for 3 h. Subsequently, the sample is cooled down under protective atmosphere and the remaining weight is measured. The difference in weight before and after thermal treatment corresponds to the ignition loss.

Platinum Content/Sulfur Content:

[0119] Determination of platinum: A suitable starting weight of the sample is digested in concentrated hydrochloric acid and concentrated nitric acid in a ratio of 3:1 in a microwave oven at 180 C. for 15 minutes and then cooled back down to about 20 C. A suitable amount of water is added to prepare a standard solution and centrifuged to obtain clear solutions that are analyzed using the ICP instrument (SPECTRO ARCOS type from Spectro Analytical Instruments GmbH). In the context of the present invention, platinum contents are based on the catalysts after ignition loss.

Determination of Sulfur:

[0120] A homogenized pulverulent sample (weight: 100 to 200 mg) is analyzed in the CS-200 instrument from Leco. The determination is effected via combustion of the bound sulfur in an oxygen stream and quantitative analysis of the product gases by means of an infrared measurement cell. In the context of the present invention, sulfur contents are based on the catalysts after ignition loss.

Platinum Dispersion:

[0121] Platinum dispersion is determined by carbon monoxide (CO) chemisorption and subsequent methanation of the metal-bound CO. For this purpose, the platinum catalyst is first oxidized with synthetic air, reduced with an excess of hydrogen and saturated with carbon monoxide at room temperature. Excess carbon monoxide is removed in a hydrogen stream. The carbon monoxide chemisorbed on the precious metal is quantitatively methanated in the hydrogen atmosphere. The methane is determined quantitatively in a flame ionization detector (Trace 1300 GC, Thermo Scientific).

EXAMPLES

[0122] The invention is elucidated in detail by the nonlimiting examples that follow. Even though these examples describe specific embodiments of the invention, they serve merely to illustrate the invention and should not be regarded as limiting the invention in any way. As the person skilled in the art is aware, numerous changes can be made thereto without departing from the scope of protection of the invention as defined by the appended patent claims.

Comparative Example 1 (Pt Eggshell Catalyst Prepared Via Spray Application)

[0123] By the method described in DE 102007025356 A1, an aqueous solution of K.sub.2[Pt(OH).sub.6] is applied to an alumina support (delta/theta-Al.sub.2O.sub.3; spheres with a diameter of 2 to 4 mm, BET 115 m.sup.2/g; pore volume 0.8 ml/g; bulk density 560 g/l). For this purpose, 0.62 gram of K.sub.2[Pt(OH).sub.6] is dissolved in 150 ml of water, and the solution obtained is then applied to 100 g of the support by spray application. The support is continually agitated in the fluidized bed during the application. Subsequently, the solids obtained are calcined at 400 C. The Pt content of the catalyst is 0.3% by weight. The Pt dispersion is 32%, the BET surface area 115 m.sup.2/g.

Comparative Example 2 (Pt Eggshell Catalyst Prepared Via Spray Application) in Reduced Form

[0124] The catalyst from comparative example 1 is reduced in a hydrogen stream at about 450 C. for a period of 15 hours. The platinum content is 0.3% by weight. The Pt dispersion is 30%, the BET surface area 115 m.sup.2/g.

Comparative Example 3 (Pt Eggshell Catalyst Prepared Via Spray Application)

[0125] By the method described in DE102007025356 A1, an aqueous solution of K.sub.2[Pt(OH).sub.6] is applied to an alumina support (gamma-Al.sub.2O.sub.3; spheres with a diameter of 1 to 2 mm; BET 290 m.sup.2/g; pore volume 0.45 ml/g; bulk density 800 g/l). For this purpose, 0.62 gram of K.sub.2[Pt(OH).sub.6] is dissolved in 150 ml of water, and the solution obtained is then applied to 100 g of the support by spray application. The support is continually agitated in the fluidized bed during the application. Subsequently, the solids obtained are calcined at 400 C. The Pt content of the catalyst is 0.3% by weight. The Pt dispersion is 29%, the BET surface area 290 m.sup.2/g.

Comparative Example 4 (Pt Eggshell Catalyst Prepared Via Impregnation)

[0126] 120 ml of an aqueous solution of H.sub.2PtCl.sub.6 (0.0025 g/ml, based on Pt) is contacted at room temperature under continual agitation with 100 g of an alumina support (delta/theta-Al.sub.2O.sub.3; spheres with a diameter of 2 to 4 mm, BET 115 m.sup.2/g; pore volume 0.8 ml/g; bulk density 560 g/l). The volume of the aqueous solution corresponds at least to the water absorption capacity of the support. After 15 min, the supernatant solution is removed and the support is washed with water to remove the chloride released. This is followed by drying at 150 C. to a relative drying loss of 8% by weight, followed by calcining at 500 C. The Pt content of the catalyst is 0.3%. The Pt dispersion is 52%, the BET surface area 115 m.sup.2/g.

Comparative Example 5 (Through-Impregnated Catalyst Produced Via Incipient Wetness Method)

Step 1: Application of Sulfur to the Support

[0127] 100 g of an alumina support (delta/theta-Al.sub.2O.sub.3; spheres with a diameter of 2 to 4 mm, BET 115 m.sup.2/g; pore volume 0.8 ml/g; bulk density 560 g/l) are impregnated at room temperature with an aqueous ammonium sulfate solution (concentration 0.38 mol/l). The volume of the aqueous solution corresponds at least to the water absorption capacity of the support. The impregnated supports are then dried at 120 C. over a period of 3 hours and then calcined at 350 C. over a period of 3 hours. The sulfur content is 0.5% by weight.

Step 2: Application of Platinum to the Support

[0128] The sulfur-containing supports are then contacted at room temperature under continual agitation with 70 ml of an aqueous solution of H.sub.2PtCl.sub.6, pH 2.0 (0.0085 g/ml, based on Pt). The impregnated supports are then dried at 120 C. over a period of 3 hours and then calcined at 400 C. over a period of 3 hours. Then the calcined supports were reduced in a hydrogen stream in a flow apparatus at about 450 C. for a period of 15 hours. The platinum content is 0.6% by weight. The Pt dispersion is 49%, the BET surface area 115 m.sup.2/g.

Comparative Example 6 (Through-Impregnated Catalyst Produced Via Incipient Wetness Method)

Step 1: Application of Sulfur to the Support

[0129] 100 g of an alumina support (gamma-Al.sub.2O.sub.3; spheres with a diameter of 1 to 2 mm; BET 290 m.sup.2/g; pore volume 0.45 ml/g; bulk density 800 g/l) are impregnated at room temperature with an aqueous ammonium sulfate solution (concentration 0.38 mol/l). The volume of the aqueous solution corresponds at least to the water absorption capacity of the support. The impregnated supports are then dried at 120 C. over a period of 3 hours and then calcined at 350 C. over a period of 3 hours. The sulfur content is 0.5% by weight.

Step 2: Application of Platinum to the Support

[0130] The sulfur-containing supports are then contacted at room temperature under continual agitation with 50 ml of an aqueous solution of H.sub.2PtCl.sub.6, pH 2.0 (0.012 g/ml, based on Pt). Subsequently, excess liquid is removed with the aid of an evaporator. The impregnated supports are then dried at 120 C. over a period of 3 hours and then calcined at 400 C. over a period of 3 hours. Then the calcined supports were reduced in a hydrogen stream in a flow apparatus at about 450 C. for a period of 15 hours. The platinum content is 0.6% by weight. The Pt dispersion is 47%, the BET surface area 290 m.sup.2/g.

Comparative Example 7 (Through-Impregnated Catalyst)

Step 1: Application of Sulfur to the Support

[0131] 100 g of an alumina support (delta/theta-Al.sub.2O.sub.3; spheres with a diameter of 2 to 4 mm, BET 115 m.sup.2/g; pore volume 0.8 ml/g; bulk density 560 g/l) are impregnated at room temperature with an aqueous ammonium sulfate solution (concentration 0.38 mol/l). The volume of the aqueous solution corresponds at least to the water absorption capacity of the support. Subsequently, excess liquid is removed with the aid of an evaporator. The impregnated supports are then dried at 120 C. over a period of 3 hours and then calcined at 350 C. over a period of 3 hours. The sulfur content is 0.25% by weight.

Step 2: Application of Platinum to the Support

[0132] The sulfur-containing supports are then contacted at room temperature under continual agitation with 70 ml of an aqueous solution of H.sub.2PtCl.sub.6, pH 2.0 (0.043 g/ml, based on Pt). Subsequently, excess liquid is removed with the aid of an evaporator. The impregnated supports are then dried at 120 C. over a period of 3 hours and then calcined at 400 C. over a period of 3 hours. Then the calcined supports were reduced in a hydrogen stream in a flow apparatus at about 450 C. for a period of 15 hours. The platinum content is 0.3% by weight. The Pt dispersion is 54%, the BET surface area 115 m.sup.2/g.

Example 1 (Pt Eggshell Catalyst of the Invention, Prepared Via Incipient Wetness Method)

[0133] An aqueous solution of platinum-sulfurous acid (15.1% by weight, based on Pt; from Heraeus) is diluted with water to a concentration of about 0.43% by weight, based on Pt. Subsequently, 70 ml of the diluted solution is contacted at room temperature under continual agitation with 100 g of an alumina support (delta/theta-Al.sub.2O.sub.3; spheres with a diameter of 2 to 4 mm, BET 115 m.sup.2/g; pore volume 0.8 ml/g; bulk density 560 g/l). The volume of the aqueous solution corresponds at least to the water absorption capacity of the support. After 15 min, the supernatant solution is removed with the aid of an evaporator and the support is dried at 120 C. over a period of eight hours. Then the dried support is calcined at 350 C. over a period of two hours and then reduced in a hydrogen stream at 400 C. for a period of 15 hours. The platinum content is 0.3% by weight; the sulfur content is 0.19% by weight. The Pt dispersion is 29%, the BET surface area 115 m.sup.2/g.

Example 2 (Pt Eggshell Catalyst of the Invention, Prepared Via Spray Application)

[0134] An aqueous solution of platinum-sulfurous acid (15.1% by weight, based on Pt; from Heraeus) is diluted with water to a concentration of about 0.20% by weight, based on Pt. Subsequently, by the method described in DE102007025356 A1, the diluted solution is applied to an alumina support at 70 C. (gamma-Al.sub.2O.sub.3; spheres with a diameter of 1 to 2 mm, BET 290 m.sup.2/g; pore volume 0.45 ml/g; bulk density 800 g/l). For this purpose, 150 ml of the 2% platinum-sulfuric acid solution are applied by spraying to 100 g of the support. The support is continually agitated in the fluidized bed during the application. In addition, the support is dried at 120 C. over a period of eight hours. Then the dried support is calcined at 350 C. over a period of two hours and then reduced in a hydrogen stream at 400 C. for a period of 15 hours. The platinum content is 0.3% by weight; the sulfur content is 0.18%. The Pt dispersion is 41%, the BET surface area 290 m.sup.2/g.

Example 3

[0135] An aqueous solution of platinum-sulfurous acid (15.1% by weight, based on Pt; from Heraeus) is diluted with water to a concentration of about 0.67% by weight, based on Pt. Subsequently, 45 ml of the diluted solution is contacted at room temperature under continual agitation with 100 g of an alumina support (delta/theta-Al.sub.2O.sub.3; spheres with a diameter of 2 to 4 mm, BET 35 m.sup.2/g; pore volume 0.5 ml/g; bulk density 780 g/l). The volume of the aqueous solution corresponds at least to the water absorption capacity of the support. After 15 min, the supernatant solution is removed with the aid of an evaporator and the support is dried at 120 C. over a period of eight hours. Then the dried support is calcined at 350 C. over a period of two hours and then reduced in a hydrogen stream at 400 C. for a period of 15 hours. The platinum content is 0.3% by weight; the sulfur content is 0.18% by weight. The Pt dispersion is 21%, the BET surface area 35 m.sup.2/g.

Example 4

[0136] An aqueous solution of platinum-sulfurous acid (15.1% by weight, based on Pt; from Heraeus) is diluted with water to a concentration of about 0.86% by weight, based on Pt. Subsequently, 35 ml of the diluted solution is contacted at room temperature under continual agitation with 100 g of an alumina support (delta/theta-Al.sub.2O.sub.3; spheres with a diameter of 2 to 4 mm, BET 5 m.sup.2/g; pore volume 0.4 ml/g; bulk density 910 g/l). The volume of the aqueous solution corresponds at least to the water absorption capacity of the support. After 15 min, the supernatant solution is removed with the aid of an evaporator and the support is dried at 120 C. over a period of eight hours. Then the dried support is calcined at 350 C. over a period of two hours and then reduced in a hydrogen stream at 400 C. for a period of 15 hours. The platinum content is 0.3% by weight; the sulfur content is 0.19% by weight. The Pt dispersion is 24%, the BET surface area 5 m.sup.2/g.

Example 5 (Measurements of Activity)

[0137] The activity of the catalysts is examined as follows. The substrate used is perhydrogenated dibenzyltoluene (H18-DBT). The atmospheric oxygen in a 250 ml three-neck flask with reflux condenser is completely removed by purging with nitrogen. Thereafter, the substrate is brought to a reaction temperature of 310 C. at ambient pressure, and the catalyst is added (ratio of platinum to perhydrogenated dibenzyltoluene of 0.1 mol %). The progress of the reaction is monitored over a period of 2 hours via the amount of hydrogen that forms and the conversion of the liquid starting material (NMR).

[0138] NMR instrument: AVANCE III HD NMR 400 MHz from Bruker;

[0139] Solvent:

[0140] FIG. 1 shows the degree of dehydrogenation using the catalysts described as a function of time. The improved activity of the catalysts of the invention is clearly apparent by comparison with the comparative catalysts.