TABLETED ALPHA-ALUMINA CATALYST SUPPORT

Abstract

A tableted catalyst support, characterized by an alpha-alumina content of at least 85 wt.-%, a pore volume of at least 0.40 mL/g, as determined by mercury porosimetry, and a BET surface area of 0.5 to 5.0 m.sup.2/g. The tableted catalyst support is an alpha-alumina catalyst support obtained with high geometrical precision and displaying a high overall pore volume, thus allowing for impregnation with a high amount of silver, while exhibiting a surface area sufficiently large so as to provide optimal dispersion of catalytically active species, in particular metal species. The invention further provides a process for producing a tableted alpha-alumina catalyst support, which comprises i) forming a free-flowing feed mixture comprising, based on inorganic solids content, at least 50 wt.-% of a transition alumina; ii) tableting the free-flowing feed mixture to obtain a compacted body; and iii) heat treating the compacted body at a temperature of at least 1100° C., preferably at least 1300° C., more preferably at least 1400° C., in particular at least 1450° C., to obtain the tableted alpha-alumina catalyst support. The invention moreover relates to a compacted body obtained by tableting a free-flowing feed mixture which comprises, 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, as determined, and a median pore diameter of at least 15 nm. The invention moreover 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 the tableted alpha-alumina catalyst support. The invention moreover relates to a process for producing ethylene oxide by gas-phase oxidation of ethylene, comprising reacting ethylene and oxygen in the presence of the shaped catalyst body.

Claims

1.-19. (canceled)

20. A tableted catalyst support, characterized by an alpha-alumina content of at least 85 wt.-%, a pore volume of at least 0.40 mL/g, as determined by mercury porosimetry, and a BET surface area of 0.5 to 5.0 m.sup.2/g.

21. The catalyst support according to claim 20, wherein the pore volume contained in pores with a diameter of less than 0.1 μm constitutes less than 5% of the total pore volume, as determined by mercury porosimetry.

22. The catalyst support according to any claim 20, wherein at least one passageway extends from the first face side surface to the second face side surface.

23. The catalyst support according to claim 20, wherein at least one of the first face side surface and the second face side surface is curved.

24. A plurality of catalyst supports according to claim 20, wherein the supports have a height with no more than a 5% sample standard deviation s from the mean height.

25. A plurality of catalyst supports according to claim 20, wherein the supports have an outer diameter with no more than a 1% sample standard deviation s from the mean outer diameter.

26. A process for producing a tableted alpha-alumina catalyst support, which comprises i) forming a free-flowing feed mixture comprising, based on inorganic solids content, at least 50 wt.-% of a transition alumina, wherein the free-flowing feed mixture further comprises a pore-forming material; ii) tableting the free-flowing feed mixture to obtain a compacted body; and iii) heat treating the compacted body at a temperature of at least 1100° C. to obtain the tableted alpha-alumina catalyst support.

27. The process according to claim 26, wherein the transition alumina has 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.

28. The process according to claim 26, wherein the compacted body is dried prior to heat treating.

29. The process according to claim 26, wherein the transition alumina comprises a phase selected from gamma-alumina, delta-alumina and theta-alumina.

30. The process according to claim 26, wherein the free-flowing feed mixture comprises, based on inorganic solids content, an alumina hydrate in an amount of at most 40 wt.-%.

31. The process according to claim 30, wherein the alumina hydrate comprises gibbsite, bayerite, boehmite and/or pseudoboehmite.

32. The process according to claim 26, wherein the pore-forming material is selected from the group consisting of thermally decomposable materials, burnout materials and organic polymers.

33. The process according to claim 32, wherein the pore-forming material is selected from water-soluble pore formers.

34. The process according to claim 26, wherein the free-flowing feed mixture further comprises a lubricant.

35. A compacted body obtained by tableting a free-flowing feed mixture which comprises, 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, as determined, and a median pore diameter of at least 15 nm.

36. 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 tableted alpha-alumina catalyst support according to claim 20.

37. The shaped catalyst body of claim 36, wherein the shaped catalyst body comprises 400 to 2000 ppm of rhenium relative to the total weight of the shaped catalyst body.

38. 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 36.

Description

[0207] The invention is described in more detail by the accompanying drawings and the subsequent examples.

[0208] FIG. 1 shows the cumulative intrusion [mL/g] relative to the pore size diameter [mL/g] of an inventive tableted catalyst support A.

[0209] FIG. 2 shows the cumulative intrusion [mL/g] relative to the pore size diameter [mL/g] of an inventive tableted catalyst support B.

[0210] FIG. 3 shows the cumulative intrusion [mL/g] relative to the pore size diameter [mL/g] of an inventive tableted catalyst support C.

[0211] FIG. 4 shows the cumulative intrusion [mL/g] relative to the pore size diameter [mL/g] of an inventive tableted catalyst support D.

[0212] FIG. 5 shows the cumulative intrusion [mL/g] relative to the pore size diameter [mL/g] of an inventive tableted catalyst support E.

[0213] FIG. 6 shows the cumulative intrusion [mL/g] relative to the pore size diameter [mL/g] of an inventive extruded catalyst support F.

METHOD 1: NITROGEN SORPTION

[0214] 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

[0215] 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.

[0216] 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

[0217] 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

[0218] 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.

[0219] 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: DIMENSION OF SHAPED BODIES AND SAMPLE STANDARD DEVIATION S

[0220] The dimensions of the shaped bodies were measured using a digital caliper (Holex 412811). The “length” was the height of the shaped body, i.e., the along the longitudinal axis. The “outer diameter” was the diameter of the circumscribed circle of the cross-section perpendicular to the support height. Geometric precision is described as the sample standard deviation s of length and outer diameter of a plurality of 100 catalyst supports which were calculated as follows. First, the mean (average) length and outer diameter of 100 catalyst supports were determined. The deviations of each length and outer diameter value from the mean were calculated, and the result of each deviations were squared. The sum of the squared deviations is divided by the value of 99 and the square root of the resulting value constitutes the sample standard deviation s of length and outer diameter. The obtained result is reported relative to the sample mean, i.e., the obtained value is divided by the sample mean value and is expressed as a percentage of the sample mean.

[0221] Preparation of Tableted Catalyst Supports A, B, C, D and E

[0222] 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 (Versan.

TABLE-US-00001 TABLE 1 Loose Median Bulk Pore Pore Density Volume Diameter [g/L] [mL/g] ** [nm] ** Transition Aluminas * Puralox TM 100/150 UF 150 0.88 18.4 Puralox TH 200/70 300 1.23 37.4 Versal VGL-15 310 0.86 21.7 Alumina Hydrates * Pural TH 200 340 1.20 37.6 Versal V-250 360 0.79 9.9 * 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 ** determined by nitrogen sorption

[0223] Alumina raw materials, as specified in Table 1, and pore former were mixed with Cutina® HR (hydrogenated castor oil waxy mass from BASF) and Timrex® T44 (graphite from TimCal Graphite & Carbon) as processing aids to obtain a powder mixture. The amounts of all components are shown in Table 2.

[0224] The pore formers used are listed in Table 2. Olive stone granule (olive stone granules, BioPowder), pulp granule (Technocel® 200G, CFF) and microcrystalline cellulose bead (MCC 200, Zhongbao Chemicals) were used as received without any pretreatment. The particle size of the pore formers was in the range between 100 μm and 300 μm. Malonic acid (M1296, purity 99.0%, Sigma-Aldrich) was gently ground in a mortar and sieved prior to use. The particles of malonic acid used for the sample preparation were collected in between 60 mesh and 200 mesh.

[0225] The powder mixture was subjected to a tableting machine equipped with a hollow cylinder punch having an outer diameter of 6.6 mm and an inner diameter of 3.7 mm. The obtained tablets were thermally treated in a muffle furnace. The furnace temperature was ramped up to 600° C. at a heating rate of 5° C./min, held at 600° C. for 2 h, then ramped up to 1,464° C. at a heating rate of 2° C./min and held at 1,464° C. for 4 h. Subsequently, the active heating was switched off and the furnace cooled down to room temperature (about 23° C.) overnight. Heat treatment was performed under lean air with 5 vol.-% of oxygen.

TABLE-US-00002 TABLE 2 Transition Alumina Processing Support Alumina Hydrate Pore Former Aid A Puralox TH Pural TH Olive Stone Cutina HR 5 g 200/70 52 g 200 20 g Granule 75 g Timrex T44 3 g Puralox TM 100/150 UF 28 g B Puralox TH Pural TH Pulp Granule Cutina HR 5 g 200/70 80 g 200 20 g 75 g Timrex T44 3 g C Puralox TH Pural TH Microcrystalline Cutina HR 5 g 200/70 80 g 200 20 g Cellulose Beads Timrex T44 3 g 75 g D Versal Versal Olive Stone Cutina HR 5 g VGL-15 80 g V-250 20 Granule 50 g TimrexT44 3 g E Puralox TH Pural TH Malonic Acid Cutina HR 5 g 200/70 80 g 200 20 g 50 g TimrexT44 3 g

[0226] Preparation of Comparative Extrudate F

[0227] A commercial alpha-alumina support for ethylene oxide catalyst was obtained from EXACER s.r.l. (Via Puglia 2/4, 41049 Sassuolo (MO), Italy), under the lot number COM 46/20. The support was produced by extrusion.

[0228] FIGS. 1 to 6 show the log differential intrusion and cumulative intrusion relative to the pore size diameter of the supports A to F.

[0229] Table 3 shows the physical properties of the supports A to F.

TABLE-US-00003 TABLE 3 Sample Standard BET Total Deviation s *** Surface Pore Pore Volume Contained in Pores [mL/g] ** Outer Area Volume (Proportion of the Total Pore Volume) Length Diameter Support [m.sup.2/g] [mL/g] <0.1 μm 0.1-1 μm 1-10 μm >10 μm [%] [%] A 2.01 0.70 0 0.18 0.11 0.41 1.9 0.2 (0%) (25.7%) (15.7%) (58.6%) B 2.05 0.65 0 0.21 0.11 0.33 1.8 0.2 (0%) (32.3%) (16.9%) (50.8%) C 2.40 0.59 0 0.20 0.11 0.28 1.5 0.3 (0%) (33.9%) (18.6%) (47.5%) D 2.55 0.70 0 0.33 0.11 0.26 3.2 0.2 (0%) (47.2%) (15.7%) (37.1%) E 1.95 0.43 0 0.22 0.14 0.07 1.0 0.2 (0%) (51.2%) (32.5%) (16.3%) F * 2.01 0.53 0 0.29 0.07 0.17 5.5 2.4 (0%) (54.7%) (13.2%) (32.1%) * comparative example ** determined by mercury porosimetry *** obtained from 100 samples of each support

[0230] It is evident that the inventive supports A to E prepared by tableting exhibit a similar BET surface area and total pore volume as comparative support F. Moreover, supports A to E were obtained with significantly higher geometrical precision than comparative support F.