PROCESS FOR PRODUCING A POROUS ALPHA-ALUMINA CATALYST SUPPORT

Abstract

A process for producing a porous alpha-alumina catalyst support, comprising i) preparing a precursor material comprising, based on inorganic solids content, at least 50 wt.-% of a transition alumina having a loose bulk density of at most 600 g/L, a pore volume of at least 0.6 mL/g and a median pore diameter of at least 15 nm; and at most 30 wt.-% of an alumina hydrate; ii) forming the precursor material into shaped bodies; and iii) calcining the shaped bodies to obtain the porous alpha-alumina catalyst support. The catalyst support has a high overall pore volume, thus allowing for impregnation with a high amount of silver, while keeping its surface area sufficiently large so as to provide optimal dispersion of catalytically active species, in particular metal species. The invention further relates to a shaped catalyst body for producing ethylene oxide by gas-phase oxidation of ethylene, comprising at least 15 wt.-% of silver, relative to the total weight of the catalyst, deposited on a porous alpha-alumina catalyst support obtained in the process described above. The invention also relates to a process for preparing a shaped catalyst body as described above comprising impregnating a porous alpha-alumina catalyst support obtained in the process described above with a silver impregnation solution, preferably under reduced pressure; and optionally subjecting the impregnated porous alumina support to drying; and b) subjecting the impregnated porous alpha-alumina support to a heat treatment; wherein steps a) and b) are optionally repeated. The invention further relates to a process for producing ethylene oxide by gas-phase oxidation of ethylene, comprising reacting ethylene and oxygen in the presence of a shaped catalyst body as described above.

Claims

1.-14. (canceled)

15. A process for producing a porous alpha-alumina catalyst support, comprising i) preparing a precursor material comprising, based on inorganic solids content, at least 50 wt.-% of a transition alumina having a loose bulk density of at most 600 g/L, a pore volume of at least 0.6 mL/g and a median pore diameter of at least 15 nm; and at most 30 wt.-% of an alumina hydrate; ii) forming the precursor material into shaped bodies; and iii) calcining the shaped bodies to obtain the porous alpha-alumina catalyst support.

16. The process according to claim 15, wherein the transition alumina has a loose bulk density in the range of 50 to 600 g/L and a pore volume of 0.6 to 2.0 mL/g.

17. The process according to claim 15, wherein the precursor material comprises 1 to 30 wt.-% of the alumina hydrate.

18. The process according to claim 15, wherein the transition alumina comprises a phase selected from gamma-alumina, delta-alumina and theta-alumina.

19. The process according to claim 15, wherein the transition alumina comprises at least 50 wt.-% of a transition alumina having an average particle size of 10 to 100 μm based on the total weight of transition alumina.

20. The process according to claim 15, wherein the alumina hydrate comprises boehmite and/or pseudoboehmite.

21. The process according to claim 15, wherein the precursor material further comprises a liquid.

22. The process according to claim 15, wherein the precursor material further comprises pore-forming materials, lubricants, organic binders, and/or inorganic binders.

23. The process according to claim 15, wherein the precursor material is formed into shaped bodies via extrusion, tableting, granulation casting, molding, or micro-extrusion.

24. The process according to claim 15, wherein calcining is performed at a temperature of at least 1300° C.

25. A shaped catalyst body for producing ethylene oxide by gas-phase oxidation of ethylene, comprising at least 15 wt.-% of silver, relative to the total weight of the catalyst, deposited on a porous alpha-alumina catalyst support obtained in the process according to claim 15.

26. The shaped catalyst body according to claim 25, comprising 15 to 70 wt.-% of silver relative to the total weight of the shaped catalyst body.

27. A process for preparing a shaped catalyst body as defined in claim 25 comprising a) impregnating the porous alpha-alumina catalyst support with a silver impregnation solution, preferably under reduced pressure; and optionally subjecting the impregnated porous alumina support to drying; and b) subjecting the impregnated porous alpha-alumina support to a heat treatment; wherein steps a) and b) are optionally repeated.

28. A process for producing ethylene oxide by gas-phase oxidation of ethylene, comprising reacting ethylene and oxygen in the presence of a shaped catalyst body according to claim 25.

Description

[0191] FIG. 1 shows the log differential intrusion [mL/g] and cumulative intrusion [mL/g] relative to the pore size diameter [mL/g] of inventive porous alpha-alumina catalyst support A, obtained by a process according to the invention.

[0192] FIG. 2 shows the log differential intrusion [mL/g] and cumulative intrusion [mL/g] relative to the pore size diameter [mL/g] of inventive porous alpha-alumina catalyst support B, obtained by a process according to the invention.

[0193] FIG. 3 shows the log differential intrusion [mL/g] and cumulative intrusion [mL/g] relative to the pore size diameter [mL/g] of comparative porous alpha-alumina catalyst support C.

[0194] FIG. 4 shows the log differential intrusion [mL/g] and cumulative intrusion [mL/g] relative to the pore size diameter [mL/g] of inventive porous alpha-alumina catalyst support D, obtained by a process according to the invention.

[0195] FIG. 5 shows the log differential intrusion [mL/g] and cumulative intrusion [mL/g] relative to the pore size diameter [mL/g] of inventive porous alpha-alumina catalyst support E, obtained by a process according to the invention.

[0196] FIG. 6 shows the log differential intrusion [mL/g] and cumulative intrusion [mL/g] relative to the pore size diameter [mL/g] of comparative porous alpha-alumina catalyst support F.

[0197] FIG. 7 shows an image of inventive porous alpha-alumina catalyst support D, as obtained by scanning electron microscopy.

[0198] FIG. 8 shows an image of comparative porous alpha-alumina catalyst support F, as obtained by scanning electron microscopy.

[0199] FIG. 9 shows the shape of the porous alpha-alumina catalyst supports S and T.

METHOD 1: NITROGEN SORPTION

[0200] Nitrogen sorption measurements were performed using a Micrometrics ASAP 2420. Nitrogen porosity was determined in accordance with DIN 66134. The sample was degassed at 200° C. for 16 h under vacuum prior to the measurement.

METHOD 2: MERCURY POROSIMETRY

[0201] Mercury porosimetry was performed using a Micrometrics AutoPore V 9600 mercury porosimeter (140 degrees contact angle, 485 dynes/cm Hg surface tension, 61,000 psia max head pressure). Mercury porosity was determined in accordance with DIN 66133.

[0202] Samples were dried at 110° C. for 2 h and degassed under vacuum prior to analysis to remove any physically adsorbed species, such as moisture, from the sample surface.

METHOD 3: LOOSE BULK DENSITY

[0203] The loose bulk density was determined by pouring the transition alumina or alumina hydrate into a graduated cylinder via a funnel, taking care not to move or vibrate the graduated cylinder. The volume and weight of the transition alumina or alumina hydrate were determined. The loose bulk density was determined by dividing the volume in milliliters by the weight in grams.

METHOD 4: BET SURFACE AREA

[0204] The BET surface area was determined in accordance with DIN ISO 9277 using nitrogen physisorption conducted at 77 K. The surface area was obtained from a 5-point-BET plot. The sample was degassed at 200° C. for 16 h under vacuum prior to the measurement.

[0205] In the case of shaped alpha-alumina supports, more than 4 g of the sample were applied due to its relatively low BET surface area.

METHOD 5: SCANNING ELECTRON MICROSCOPY

[0206] Scanning electron microscopy was performed using a Hitachi SU3500 VP SEM (12 nm Pt coating).

METHOD 6: ANALYSIS OF THE TOTAL AMOUNT OF CA-, MG-, SI-, FE-, K-, AND NA-CONTENTS IN ALPHA-ALUMINA SUPPORTS

[0207] 6A. Sample Preparation for Measurement of Ca, Mg, Si and Fe

[0208] About 100 to 200 mg (at an error margin of ±0.1 mg) of a carrier sample were weighed into a platinum crucible. 1.0 g of lithium metaborate (LiBO.sub.2) was added. The mixture was melted in an automated fusion apparatus with a temperature ramp up to max. 1150° C.

[0209] After cooling down, the melt was dissolved in deionized water by careful heating. Subsequently, 10 mL of semi-concentrated hydrochloric acid (concentrated HCl diluted with deionized water, volume ratio 1:1, corresponds to about 6 M) was added. Finally, the solution was filled up to a volume of 100 mL with deionized water.

[0210] 6B. Measurement of Ca, Mg, Si and Fe

[0211] The amounts of Ca, Mg, Si and Fe were determined from the solution described under item 5A by Inductively Coupled Plasma—Optical Emission Spectroscopy (ICP-OES) using an ICP-OES Varian Vista Pro.

[0212] Parameters:

[0213] Wavelengths [nm]: Ca 317.933 [0214] Mg 285.213 [0215] Si 251.611 [0216] Fe 238.204

[0217] Integration time: 10 s

[0218] Nebulizer: Conikal 3 ml

[0219] Nebulizer pressure: 270 kPa

[0220] Pump rate: 30 rpm

[0221] Calibration: external (matrix-matched standards)

[0222] 6C. Sample Preparation for Measurement of K and Na

[0223] About 100 to 200 mg (at an error margin of ±0.1 mg) of a carrier sample were weighed into a platinum dish. 10 mL of a mixture of aqueous concentrated H.sub.2SO.sub.4 (95 to 98%) and deionized water (volume ratio 1:4), and 10 mL of aqueous hydrofluoric acid (40%) were added. The platinum dish was placed on a sand bath and boiled down to dryness. After cooling down the platinum dish, the residue was dissolved in deionized water by careful heating. Subsequently, 5 mL of semi-concentrated hydrochloric acid (concentrated HCl diluted with deionized water, volume ratio 1:1, corresponds to about 6 M) were added. Finally, the solution was filled up to a volume of 50 mL with deionized water.

[0224] 6D. Measurement of K and Na

[0225] The amounts of K and Na were determined from the solution described under item 5C by Flame Atomic Absorption Spectroscopy (F-AAS) using an F-AAS Shimadzu AA-7000.

[0226] Parameters:

[0227] Wavelengths [nm]: K 766.5 Na 589.0

[0228] Gas: Air/acetylene

[0229] Slit width: 0.7 nm (K)/0.2 nm (Na)

[0230] Nebulizer pressure: 270 kPa

[0231] Calibration: external (matrix-matched standards)

[0232] Preparation of Porous alpha-Alumina Catalyst Supports

[0233] The properties of the alumina raw materials used to obtain porous alpha-alumina catalyst supports are shown in Table 1. The transition aluminas and alumina hydrates were obtained from Sasol (Puralox®, and Pural®) and UOP (Versal®). alpha-Alumina was prepared by heating Puralox TH 200/70 at 1200° C. for 4 h.

TABLE-US-00001 TABLE 1 Median Pore Bulk Density Pore Volume Diameter [g/L] [mL/g] [nm] alpha-Alumina Puralox TH 200/70, 556  0.60 ** 58.8 ** heated at 1200° C. Transition Aluminas *** Puralox SCFa 140 650 0.57 * 10.0 *  Puralox 200/90 460 0.68 * 37.4 *  Puralox 400/50 390  0.90 ** 112.4 **  Puralox TM 100/150 420 0.87 * 21.0 *  Puralox TM 100/150UF 150 0.88 * 18.4 *  Puralox TH 200/70 300 1.23 * 37.4 *  Puralox TH 300/100 250  1.36 ** 57.0 ** Puralox TH 500/80 240  1.27 ** 80.6 ** Versal VGL-15 310 0.86 * 21.7 *  Alumina Hydrates *** Pural SB1 680 0.55 * 8.4 * Pural 200 560 0.66 * 35.6 *  Pural 400 450  0.93 ** 107.4 **  Pural TH 200 340 1.20 * 37.6 *  Pural TH 300 260  1.30 ** 57.0 ** Pural TH 500 300  1.19 ** 84.6 ** Versal V-250 360 0.79 * 9.9 * * determined by nitrogen sorption ** determined by mercury porosimetry *** Puralox products are transition aluminas derived from Pural products, i.e. boehmite; Versal VGL-15 is a gamma-alumina derived from Versal V-250, i.e. pseudoboehmite

EXAMPLE 1—PREPARATION OF SUPPORTS A, B, C AND G

[0234] Alumina raw materials, as specified in Table 1, were mixed to obtain a powder mixture. Kollidon® VA64 (a vinylpyrrolidone-vinyl acetate copolymer from BASF) was added to the powder mixture. Water was then added to obtain a malleable precursor material. The amounts of all components are shown in Table 2.

[0235] The malleable precursor material was mixed to homogeneity via a mix-muller and subsequently extruded using a ram extruder to form shaped bodies. The shaped bodies were in the form of hollow cylinders having an outer diameter of about 10 mm and an inner diameter of about 5 mm. The extrudates were dried at 110° C. for approximately 16 h, followed by heat treatment in a muffle furnace at 600° C. for 2 h with 5° C./min of ramping speed and subsequently at 1,500° C. for 2 h with 2° C./min of ramping speed. Heat treatment was performed in an atmosphere of air.

EXAMPLE 2—PREPARATION OF SUPPORTS D, E, F, H, I, J AND K

[0236] Alumina raw materials, as specified in Table 1, were mixed to obtain a powder mixture. Colloidal silica (Ludox® AS 40, Grace & Co.) and petroleum jelly (Vaseline®, Unilever) were added to the powder mixture. Water was then added to obtain a malleable precursor material. The amounts of all components are shown in Table 2.

[0237] The malleable precursor material was mixed to homogeneity via a mix-muller and subsequently extruded using a ram extruder to form shaped bodies. The shaped bodies were in the form of hollow cylinders having an outer diameter of about 10 mm and an inner diameter of about 5 mm. The extrudates were dried at 110° C. for approximately 16 h, followed by heat treatment in a muffle furnace at 600° C. for 2 h with 5° C./min of ramping speed and subsequently at 1,425° C. for 4 h with 2° C./min of ramping speed. Heat treatment was performed in an atmosphere of air.

EXAMPLE 3—PREPARATION OF SUPPORTS L, M, N, O, P, Q AND R

[0238] Alumina raw materials, as specified in Table 1, were mixed to obtain a powder mixture. Dispersible boehmite (Disperal® HP 14/7, Sasol) pre-dispersed in water and petroleum jelly (Vaseline®, Unilever) were added to the powder mixture. Water was then added to obtain a malleable precursor material. The amounts of all components are shown in Table 2.

[0239] The malleable precursor material was mixed to homogeneity via a mix-muller and subsequently extruded using a ram extruder to form shaped bodies. The shaped bodies were in the form of hollow cylinders having an outer diameter of about 10 mm and an inner diameter of about 5 mm. The extrudates were dried at 110° C. for approximately 16 h, followed by heat treatment in a muffle furnace at 600° C. for 2 h with 5° C./min of ramping speed and subsequently at 1,425° C. for 4 h with 2° C./min of ramping speed. Heat treatment was performed in an atmosphere of air.

TABLE-US-00002 TABLE 2 Support Transition Alumina Alumina Hydrate Binder Processing Aid Liquid A Puralox TH 200/70 340 g Pural SB1 146 g Kollidon VA64 15 g — Water 454 g B Puralox TM 100/150 340 g Pural SB1 146 g Kollidon VA64 15 g — Water 439 g C * Puralox SCFa 140 340 g Pural SB1 146 g Kollidon VA64 15 g — Water 379 g G * Puralox TH 200/70 Pural SB1 117 g Kollidon VA64 12 g — Water 233 g Calcined at 1200° C. 271 g D Puralox TH 200/70 320 g Pural TH 200 17 g Silica Sol 1.5 g Petroleum Jelly 23.6 g Water 411 g Puralox TM 100/150 UF 138 g E Puralox 200/90 256 g Pural 200 13 g Silica Sol 1.2 g Petroleum Jelly 19.0 g Water 253 g Puralox TM 100/150 UF 110 g H Puralox 400/50 256 g Pural 400 14 g Silica Sol 1.2 g Petroleum Jelly 19.1 g Water 234 g Puralox TM 100/150 UF 110 g I Puralox TH 300/100 256 g Pural TH 300 13 g Silica Sol 1.2 g Petroleum Jelly 19.1 g Water 333 g Puralox TM 100/150 UF 110 g J Puralox TH 500/80 256 g Pural TH 500 13 g Silica Sol 1.2 g Petroleum Jelly 19.0 g Water 300 g Puralox TM 100/150 UF 110 g K Versal VGL-15 256 g Versal V-250 13 g Silica Sol 1.2 g Petroleum Jelly 19.0 g Water 335 g Puralox TM 100/150 UF 110 g F * Puralox SCFa 140 320 g Pural SB1 17 g Silica Sol 1.5 g Petroleum Jelly 23.3 g Water 347 g Puralox TM 100/150 UF 138 g L Puralox TH 200/70 198 g Pural TH 200 74 g Dispersible Petroleum Jelly 18.6 g Water 310 g Puralox TM 100/150 UF 108 g Boehmite 1.8 g M Puralox TH 200/70 198 g Pural TM 100 74 g Dispersible Petroleum Jelly 18.6 g Water 315 g Puralox TM 100/150 UF 108 g Boehmite 1.8 g N Puralox TH 300/100 198 g Pural TH 300 74 g Dispersible Petroleum Jelly 19.1 g Water 272 g Puralox TM 100/150 UF 107 g Boehmite 1.9 g O Puralox 200/90 198 g Pural 200 74 g Dispersible Petroleum Jelly 19.0 g Water 233 g Puralox TM 100/150 UF 107 g Boehmite 1.9 g P Versal VGL-15 198 g Versal V-250 74 g Dispersible Petroleum Jelly 19.0 g Water 335 g Puralox TM 100/150 UF 107 g Boehmite 1.9 g Q * Puralox SCFa 140 198 g Pural SB1 74 g Dispersible Petroleum Jelly 18.5 g Water 291 g Puralox TM 100/150 UF 107 g Boehmite 1.8 g R * Puralox TH 200/70 Pural TH 200 74 g Dispersible Petroleum Jelly 19.0 g Water 219 g Calcined at 1200° C 198 g Boehmite 1.9 g Puralox TM 100/150 UF 107 g * comparative example

[0240] Table 3 shows the physical properties of all the supports prepared as shown in table 2. FIGS. 1 to 16 show the log differential intrusion and cumulative intrusion relative to the pore size diameter of all the supports prepared as shown in table 2.

TABLE-US-00003 TABLE 3 BET Pore Pore Volume Contained in Pores [mL/g] ** Surface Area Volume (Proportion of the Total Pore Volume) Support [m.sup.2/g] [mL/g] ** <0.1 μm 0.1-1 μm 1-10 μm 10-100 μm >100 μm r.sub.pv *** A 1.57 0.27 0 (0%) 0.21 (77.9%) 0.05 (16.9%) 0.01 (5.2%) 0 (0%) 0.23 B 1.65 0.26 0 (0%) 0.18 (71.0%) 0.07 (25.9%) 0.01% (3.1%) 0 (0%) 0.39 C * 1.30 0.29 0 (0%) 0.12 (42.9%) 0.16 (53.6%) 0.01 (3.5%) 0 (0%) 1.33 G * 0.37 0.06 0 (0%) 0.05 (83.3%) 0.01 (17.7%) 0 (0%) 0 (0%) 0.2 D 4.76 0.38 0 (0%) 0.37 (97.4%) 0.00 (0.0%) 0.01 (2.6%) 0 (0%) 0.00 E 5.69 0.32 0 (0%) 0.31 (96.9%) 0.00 (0.0%) 0.01 (3.1%) 0 (0%) 0.00 H 5.15 0.33 0 (0%) 0.33 (100%) 0 (0%) 0 (0%) 0 (0%) 0.00 I 5.79 0.40 0 (0%) 0.40 (100%) 0 (0%) 0 (0%) 0 (0%) 0.00 J 5.61 0.40 0 (0%) 0.39 (97.5%) 0.01 (2.5%) 0 (0%) 0 (0%) 0.03 K 5.79 0.38 0 (0%) 0.38 (100%) 0 (0%) 0 (0%) 0 (0%) 0.00 F * 3.20 0.32 0 (0%) 0.20 (62.5%) 0.12 (37.5%) 0.00 (0.0%) 0 (0%) 0.60 L 2.77 0.32 0 (0%) 0.32 (100%) 0 (0%) 0 (0%) 0 (0%) 0.00 M 2.64 0.34 0 (0%) 0.32 (94.1%) 0.01 (2.9%) 0.01 (2.9%) 0 (0%) 0.03 N 2.60 0.29 0 (0%) 0.29 (100%) 0 (0%) 0 (0%) 0 (0%) 0.00 O 2.50 0.27 0 (0%) 0.26 (96.3%) 0.01 (3.7%) 0 (0%) 0 (0%) 0.04 P 2.97 0.33 0 (0%) 0.33 (100%) 0 (0%) 0 (0%) 0 (0%) 0.00 Q * 2.16 0.28 0 (0%) 0.17 (60.7%) 0.10 (35.7%) 0.01 (3.6%) 0 (0%) 0.59 R * 0.79 0.12 0 (0%) 0.10 (83.3%) 0.02 (17.7%) 0 (0%) 0 (0%) 0.2 * comparative example ** determined by mercury porosimetry *** r.sub.pv = ratio of the pore volume contained in pores with a diameter in the range of more than 1 to 10 μm to the pore volume contained in pores with a diameter in the range of 0.1 to 1 μm

[0241] It is evident that the inventive supports exhibit advantageously high proportions of pores with a diameter in the range of 0.1 to 1 μm in comparison to the comparative supports C, F and Q. The inventive supports also exhibit lower r.sub.pv values than the comparative supports C, F and Q. The surface areas of the inventive supports are significantly larger than that of the comparative supports C, F and Q.

[0242] Compared to the comparative supports G and R, which are derived from alpha-alumina, the inventive supports exhibit significantly larger total pore volume and BET surface area.

[0243] Concurrently, the inventive supports exhibit a more open pore structure in comparison to the comparative supports, as is evident from the comparison of FIG. 7 (inventive support D) and FIG. 8 (comparative support F).

EXAMPLE 4—PREPARATION OF SUPPORTS S AND T FOR CATALYST PERFORMANCE TEST

[0244] Transition aluminas and alumina hydrates, as specified in Table 1, were mixed to obtain a powder mixture. Processing aids (Vaseline®, Unilever and Glycerin, Sigma-Aldrich) and water were added to the powder mixture. Vivapur® MCC Spheres 200 (Microcrystalline Cellulose, JRS Pharma) was added to the mixture. Additional water was then added to obtain a malleable precursor material. The total amounts of all components are shown in Table 4.

TABLE-US-00004 TABLE 4 Support Transition Alumina Alumina Hydrate Pore Former Processing Aid Liquid S Puralox TH 200/70 173 g Pural TH 200 67 g Vivapur MCC Vaseline 8.5 g Water 454 g Puralox TM 100/150 UF 93 g Spheres 200 250 g Glycerin 8.4 g T * Puralox SCFa 140 173 g Pural SB1 67 g Vivapur MCC Vaseline 8.3 g Water 479 g Puralox TM 100/150 UF 93 g Spheres 200 250 g Glycerin 8.3 g * comparative example

[0245] The malleable precursor material was mixed to homogeneity via a mix-muller and subsequently extruded using a ram extruder to form shaped bodies. The shaped bodies were in the form of a trilobe with 4 passageways, as depicted in FIG. 9. The extrudates were dried at 110° C. overnight (for approximately 16 h), followed by heat treatment in a muffle furnace at 600° C. for 2 h with 5° C./min of ramping speed and subsequently at high temperature (1475° C. for support S, 1430° C. for support T) for 4 h with 2° C./min of ramping speed. Heat treatment was performed in an atmosphere of air.

[0246] The dimensions of the dried supports were determined using a caliper. The diameter of the circumscribed circle of the cross-section perpendicular to the support height was 11.6 cm. The term “circumscribed circle” refers to the smallest circle that completely contains the trilobed cross-section within it. The diameter of the inscribed circle of the cross-section perpendicular to the support height was 5.3 cm. The term “inscribed circle” refers to the largest possible circle that can be drawn inside the trilobed cross-section. The central passageway had a diameter of 1.92 cm. The three outer passageways had a diameter of 1.46 cm.

[0247] The resulting supports S and T had an alpha-alumina content of more than 98 wt.-% and Na-, K-, Mg-, Ca-contents below 100 ppm. The Fe-content in both supports was 200 ppm. The Si-content in support S was 100 ppm. The Si-content in support T was 200 ppm.

[0248] Table 5 shows the physical properties of inventive support S and comparative support T.

TABLE-US-00005 TABLE 5 BET Pore Pore Volume Contained in Pores [mL/g] ** Surface Area Volume (Proportion of the Total Pore Volume) Support [m.sup.2/g] [mL/g] ** <0.1 μm 0.1-1 μm 1-10 μm 10-100 μm >100 μm r.sub.pv *** S 2.00 0.57 0 (0%) 0.40 (70.2%) 0.12 (21.1%)  0.04 (7.0%) 0.01 (1.8%) 0.30 T * 1.95 0.53 0 (0%) 0.22 (41.5%) 0.21 (39.6%) 0.09% (17.0%) 0.01 (1.9%) 0.95 * comparative example ** determined by mercury porosimetry *** r.sub.pv = ratio of the pore volume contained in pores with a diameter in the range of more than 1 to 10 μm to the pore volume contained in pores with a diameter in the range of 0.1 to 1 μm

EXAMPLE 5—PREPARATION OF CATALYSTS

[0249] Shaped catalyst bodies were prepared by impregnating supports S and T with a silver impregnation solution. The catalyst compositions are shown in Table 6 below. Silver contents are provided in percent, relative to the total weight of the catalyst. Dopant values are provided in parts per million, relative to the total weight of the catalyst.

TABLE-US-00006 TABLE 6 Catalyst composition (Ag-contents are reported in percent by weight of total catalyst, dopant values are reported in parts per million by weight of total catalyst) Ag.sub.CAT ** Li.sub.CAT S.sub.CAT W.sub.CAT Cs.sub.CAT Re.sub.CAT K.sub.ADD *** Catalyst Support [wt-%] [ppm] [ppm] [ppm] [ppm] [ppm] [ppm] 1 S 27.7 450 35 615 1025 1270 85 2 * T * 27.7 450 35 615 1025 1270 85 * comparative example ** Ag and all promoter values are calculated values; *** K.sub.ADD is understood to mean the amount of potassium added during impregnation and does not include the amount of potassium comprised in the alumina support prior to impregnation.

[0250] 5.1 Production of a Silver Complex Solution

[0251] A silver complex solution was prepared according to Production Example 1 of WO 2019/154863 A1. The silver complex solution had a density of 1.529 g/mL, a silver content of 29.3 wt.-% and a potassium content of 90 ppm.

[0252] 5.2. Preparation of Intermediate Catalysts

[0253] 100.0 g of support S (intermediate 1.1) or 100.4 g of support T (intermediate 1.2) were each placed into a 2 L glass flask. The flask was attached to a rotary evaporator, which was set under a vacuum pressure of 80 mbar. The rotary evaporator system was set in rotation of 30 rpm. 76.55 g (intermediate 1.1) or 76.86 g (intermediate 1.2) of silver complex solution prepared according to step 2.1 were added onto support S (intermediate 1.1) or support T (intermediate 1.2) over 15 min under a vacuum pressure of 80 mbar. After addition of the silver complex solution, the rotary evaporator system was continued to rotate under vacuum for a further 15 min. The impregnated support was then left in the apparatus at room temperature (approximately 25° C.) and atmospheric pressure for 1 h and mixed gently every 15 min.

[0254] The impregnated material was placed on a net forming 1 to 2 layers. The net was subjected to 23 Nm.sup.3/h of air flow, wherein the gas flow was pre-heated to a temperature of 305° C. The impregnated material was heated up to a temperature of 290° C. at a heating rate of about 30 K/min and then maintained at 290° C. for 8 min to yield Ag-containing intermediate products according to Table 7. The temperatures were measured by placing three thermocouples at 1 mm below the net. Subsequently, the catalysts were cooled to ambient temperature by removing the intermediate catalyst bodies from the net using an industrial vacuum cleaner.

TABLE-US-00007 TABLE 7 Ag containing intermediate catalysts (Ag-contents are reported in percent by weight of total catalyst, dopant values are reported in parts per million by weight of total intermediate catalyst) Intermediate Support Ag.sub.CAT ** [wt.-%] K.sub.ADD *** [ppm] 1.1 S 18.3 56 1.2 T * 18.3 56 * comparative example ** Ag and all promoter values are calculated values; *** K.sub.ADD is understood to mean the amount of potassium added during impregnation and does not include the amount of potassium comprised in the alumina support prior to impregnation;

[0255] 5.3. Preparation of Catalysts

[0256] 120.5 g of Ag-containing intermediate product 1.1 or 122.2 g of Ag-containing intermediate product 1.2 as prepared according to step 2.2 were each placed into a 2 L glass flask. The flask was attached to a rotary evaporator which was set under vacuum pressure of 80 mbar. The rotary evaporator system was set in rotation of 30 rpm. For the catalyst 1, 53.80 g of the silver complex solution prepared according to step 2.1 was mixed with 2.16 g of promoter solution I, 2.80 g of promoter solution II, and 4.69 g of promoter solution III. For the catalyst 2, 54.56 g of the silver complex solution prepared according to step 2.1 was mixed with 2.19 g of promoter solution I, 2.84 g of promoter solution II, and 4.76 g of promoter solution III.

[0257] Promoter solution I was obtained by dissolving lithium nitrate (Merck, 99.995%) and ammonium sulfate (Merck, 99.4%) in DI water to achieve a Li content of 2.85 wt.-% and a S content of 0.22 wt.-%. Promoter solution II was obtained by dissolving tungstic acid (HC Starck, 99.99%) in DI water and cesium hydroxide in water (HC Starck, 50.42%) to achieve a target Cs content of 5.0 wt.-% and a W content of 3.0 wt.-%. Promoter solution III was obtained by dissolving ammonium perrhenate (Buss & Buss Spezialmetalle GmbH, 99.9%) in DI water to achieve a Re content of 3.7 wt.-%.

[0258] The combined impregnation solution containing silver complex solution and promoter solutions I, II, and III was stirred for 5 minutes. The combined impregnation solution was added onto each of the silver-containing intermediate products 1.1 or 1.2 over 15 min under a vacuum pressure of 80 mbar. After addition of the combined impregnation solution, the rotary evaporator system was continued to rotate under vacuum for another 15 min. The impregnated support was then left in the apparatus at room temperature (about 25° C.) and atmospheric pressure for 1 h and mixed gently every 15 min.

[0259] The impregnated material was placed on a net forming 1 to 2 layers. The net was subjected either to 23 Nm.sup.3/h nitrogen flow (oxygen content: <20 ppm), wherein the gas flow was pre-heated to a temperature of 305° C. The impregnated materials were heated up to a temperature of 290° C. at a heating rate of about 30 K/min and then maintained at 290° C. for 7 min to yield catalysts according to Table 4. The temperatures were measured by placing three thermocouples at 1 mm below the net. Subsequently, the catalysts were cooled to ambient temperature by removing the catalyst bodies from the net using an industrial vacuum cleaner.

EXAMPLE 6—CATALYST TESTING

[0260] An epoxidation reaction was conducted in a vertically-placed test reactor constructed from stainless steel with an inner diameter of 6 mm and a length of 2.2 m. The reactor was heated using hot oil contained in a heating mantel at a specified temperature. All temperatures below refer to the temperature of the hot oil. The reactor was filled with 9 g of inert steatite balls (0.8 to 1.1 mm), onto which 26.4 g of crushed catalyst screened to a desired particle size of 1.0 to 1.6 mm were packed, and thereon an additional 29 g of inert steatite balls (0.8-1.1 mm) were packed. The inlet gas was introduced to the top of the reactor in a “once-through” operation mode.

[0261] The catalysts were charged into the reactor at a reactor temperature of 90° C. under nitrogen flow of 130 N L/h at a pressure of 1.5 bar absolute. Then, the reactor temperature was ramped up to 210° C. at a heating rate of 50 K/h and the catalysts were maintained at this condition for 15 h. Then, the nitrogen flow was substituted by a flow of 114 N L/h methane and 1.5 NL/h CO.sub.2. The reactor was pressurized to 16 bar absolute. Then 30.4 NL/h ethylene and 0.8 NL/h of a mixture of 500 ppm ethylene chloride in methane were added. Then, oxygen was introduced stepwise to reach a final flow of 6.1 NL/h. At this point the inlet composition consisted of 20 vol.-% ethylene, 4 vol.-% oxygen, 1 vol.-% carbon dioxide, and ethylene chloride (EC) moderation of 2.5 parts per million by volume (ppmv), with methane used as a balance at the total gas flow rate of 152.8 NL/h. The reactor temperature was ramped up to 225° C. at a heating rate of 5 K/h and afterwards to 240° C. at a heating rate of 2.5 K/h. The catalysts were maintained at this condition for 135 hours. Afterwards, EC concentration was decreased to 2.2 ppmv, and the temperature was decreased to 225° C. Then, the inlet gas composition was gradually changed to 35 vol.-% ethylene, 7 vol.-% oxygen, 1 vol.-% carbon dioxide with methane used as a balance and a total gas flow rate of 147.9 NL/h. The temperature was adjusted to achieve an ethylene oxide (EO) concentration in the outlet gas of 3.05%. The EC concentration was adjusted to optimize the selectivity. Results of the catalyst tests are summarized in Table 8.

TABLE-US-00008 TABLE 8 Summary of Catalyst Tests Time on Reactor stream** EO-Selectivity Temperature Catalyst Support [h] [%] [° C.] 1 S 600 89.0 235 2 * T * 600 87.9 234 * comparative example **Time on stream begins from the point of introduction of oxygen to the ethylene containing feed

[0262] It is evident that catalyst 1 obtained from inventive support S shows much higher selectivity than catalyst 2 obtained from comparative support T.