SHAPED CATALYST BODY FOR THE PRODUCTION OF ETHYLENE OXIDE

Abstract

A shaped catalyst body for producing ethylene oxide by gas-phase oxidation of ethylene, having a BET surface area in the range of 2 to 20 m2/g and comprising silver and a rhenium promotor deposited on a porous alpha-alumina catalyst support, characterized in that the support has a calcination history of at least 1460° C. The catalyst support has a high surface area and little ethylene oxide isomerization and/or decomposition activity. The invention further relates to a porous alpha-alumina catalyst support having a BET surface area of 1.7 to 10 m2/g, the porous alpha-alumina catalyst support being obtainable by a) preparing a precursor material comprising a transition alumina and/or an alumina hydrate; b) forming the precursor material into shaped bodies; and c) calcining the shaped bodies at a temperature of 1460° C. to 1700° C. to obtain the porous alpha-alumina support. The invention also 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.-15. (canceled)

16. A shaped catalyst body for producing ethylene oxide by gas-phase oxidation of ethylene, having a BET surface area in the range of 2 to 20 m.sup.2/g and comprising silver and a rhenium promotor deposited on a porous alpha-alumina catalyst support, characterized in that the support has a calcination history of at least 1460° C.

17. The shaped catalyst body according to claim 16, wherein the support has a calcination history of being exposed to a temperature of 1460 to 1700° C.

18. The shaped catalyst body according to any claim 16, wherein the shaped catalyst body comprises silver in an amount of 8 to 40 wt.-%, relative to the total weight of the shaped catalyst body.

19. The shaped catalyst body according to claim 16, wherein the shaped catalyst body comprises rhenium in an amount of 200 to 2000 ppm, relative to the total weight of the shaped catalyst body.

20. The shaped catalyst body according to claim 16, wherein the shaped catalyst body comprises a further promoter selected from the group consisting of cesium, potassium, lithium, tungsten, sulfur, and combinations thereof.

21. The shaped catalyst body according to claim 16, obtained by depositing silver and rhenium on a porous alpha-alumina support having a BET surface area of 1.7 to 10 m.sup.2/g and a calcination history of at least 1460° C.

22. The shaped catalyst body according to claim 16, the porous alpha-alumina support being obtained by i) preparing a precursor material comprising a transition alumina and/or an alumina hydrate; ii) forming the precursor material into shaped bodies; and iii) calcining the shaped bodies at a temperature of at least 1460° C. to obtain the porous alpha-alumina support.

23. The shaped catalyst body according to claim 22, wherein the precursor material comprises at least 50 wt.-% of transition alumina.

24. The shaped catalyst body according to claim 22, wherein the precursor material comprises at most 30 wt.-% of alumina hydrate.

25. The shaped catalyst body according to claim 22, wherein the transition alumina has a loose bulk density of at most 600 g/L, a pore volume of at least 0.7 mL/g, as determined by nitrogen sorption, and a median pore diameter of at least 15 nm, as determined by nitrogen sorption.

26. The shaped catalyst body according to claim 22, wherein the transition alumina comprises a phase selected from gamma-alumina, delta-alumina and theta-alumina.

27. The shaped catalyst body according to claim 22, 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.

28. The shaped catalyst body according to claim 22, wherein the alumina hydrate comprises boehmite and/or pseudoboehmite.

29. A porous alpha-alumina catalyst support having a BET surface area of 1.7 to 10 m.sup.2/g, the porous alpha-alumina catalyst support being obtained by a) preparing a precursor material comprising a transition alumina and/or an alumina hydrate; b) forming the precursor material into shaped bodies; and c) calcining the shaped bodies at a temperature of 1460° C. to 1700° C. to obtain the porous alpha-alumina support.

30. 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 16.

Description

EXAMPLE 1

Preparation of Porous Alpha-Alumina Catalyst Supports

[0217] The properties of the transition aluminas and alumina hydrates used to obtain porous alpha-alumina catalyst supports are shown in Table 1. The transition aluminas and alumina hydrates were obtained from Sasol.

TABLE-US-00001 TABLE 1 Transition Aluminas Bulk Pore Volume Median Pore Density [g/L] [mL/g] * Diameter [nm] * Puralox TH 200/70 300 1.23 37.4 Puralox SCFa 140 650 0.57 10.0 Puralox TM 100/150 UF 150 0.88 18.4 Alumina Hydrates Bulk Pore Volume Median Pore Density [g/L] [mL/g] Diameter [nm] Pural SB1 680 0.55 8.4 Pural TH 200 340 1.20 37.6 * determined by nitrogen sorption

[0218] Transition aluminas and alumina hydrates, 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.

TABLE-US-00002 TABLE 2 Transition Alumina Processing Support Alumina Hydrate Binder Aid Liquid A Puralox TH 200/70 Pural TH Silica Petroleum Water 320 g 200 17 g Sol Jelly 439 g Puralox TM 100/150 UF 1.5 g 23.8 g 138 g B * Puralox SCFa 140 Pural SB1 Silica Petroleum Water 320 g 17 g Sol Jelly 364 g Puralox TM 100/150 UF 1.5 g 23.9 g 138 g * comparative example

[0219] 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. Subsequently, the extrudates were heat treated at 1,500° C. for 4 h (to obtain support A), and at 1425° C. for 4 h, respectively (to obtain support B). Heat treatment was performed in an atmosphere of air

[0220] Table 3 shows the Si—, Ca—Mg—, Na—, K— and Fe-contents in alumina supports A and B, relative to the total weight of the support.

TABLE-US-00003 TABLE 3 Si.sub.Al2O3 Na.sub.Al2O3 K.sub.Al2O3 Fe.sub.Al2O3 Ca.sub.Al2O3 Mg.sub.Al2O3 Support [ppmw] [ppmw] [ppmw] [ppmw] [ppmw] [ppmw] A 700 40 <30 300 <100 <100 B * 800 50 <30 100 100 <100 * comparative example

[0221] Support A had a BET surface area of 4.8 m.sup.2/g. Support B had a BET surface area of 4.4 m.sup.2/g.

EXAMPLE 2

Preparation of Catalysts

[0222] Shaped catalyst bodies were prepared by impregnating supports A and B with a silver impregnation solution. The catalyst compositions and BET surface areas are shown in Table 4 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-00004 TABLE 4 BET Surface Ag.sub.CAT ** Li.sub.CAT S.sub.CAT W.sub.CAT Cs.sub.CAT Re.sub.CAT K.sub.ADD *** Area Catalyst Support [wt-%] [ppm] [ppm] [ppm] [ppm] [ppm] [ppm] [m.sup.2/g] 1 A 10.0 282 21 342 570 720 31 4.9 2 * B 10.0 282 21 342 570 720 31 5.1 * 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

2.1 Production of a Silver Complex Solution

[0223] 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.

2.2 Production of Catalyst 1

[0224] 94.9 g of support A as described in Example 1 were placed into a 1 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.

[0225] 36.03 g of the silver complex solution prepared according to production example 2.1 was mixed with 1.045 g of promoter solution I, 1.203 g of promoter solution II, and 2.054 g of promoter solution III. Promoter solution I was made from dissolving lithium nitrate (FMC, 99.3%) and ammonium sulfate (Merck, 99.4%) in deionized water to achieve a Li content of 2.85 wt.-% and S content of 0.21 wt.-%. Promoter solution II was made from dissolving tungstic acid (HC Starck, 99.99%) in deionized water and cesium hydroxide in water (HC Starck, 50.42%) to achieve a Cs content of 5.0 wt.-% and W content of 3.0 wt.-%. Promoter solution III was made from dissolving ammonium perrhenate (Engelhard, 99.4%) in deionized water to achieve a Re content of 3.7 wt.-%.

[0226] The combined impregnation solution containing the silver complex solution and promoter solutions I, II, and III was stirred for 5 min. The combined impregnation solution was added onto the support A over 15 min under a vacuum 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 and atmospheric pressure for 1 h and mixed gently every 15 min. The impregnated material was placed on a net forming 1 to 2 layers (about 100 too 200 g per calcination run). The net was subjected to 23 m.sup.3/h nitrogen flow (oxygen content: <20 ppm). The impregnated material was heated up to a temperature of 290° C. at a heating rate of about 30 K/min and then held at 290° C. for 8 min.

2.3 Production of Comparative Catalyst 2

[0227] Catalyst 2 was prepared in the same manner as Catalyst 1, except that support B was used instead of support A.

2.4 Catalyst Testing

[0228] 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 reactor temperatures below refer to the temperature of the hot oil. The reactor was filled to a height of 212 mm with inert steatite balls (1.0-1.6 mm), packed with 26.4 g of catalyst, and then again packed with an additional 707 mm inert steatite balls (1.0 to 1.6 mm). Prior to filling the catalyst into the reactor, the catalyst shaped bodies were gently broken into pieces of 0.3 to 0.7 mm. The inlet gas was introduced to the top of the reactor in a “once-through” operation mode.

[0229] The catalyst was conditioned in the inlet gas 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 152.7 NL/h, at a pressure of about 15 bar. During the conditioning phase, the catalyst was heated up from 210° C. to 250° C. at a heating ramp of 4° C./h. Then the catalyst was held at 250° C. for 8 hours. Then, within an hour, the temperature was reduced to 240° C. and held for 4 hours. Then, within an hour, the temperature was reduced to 230° C. and held for 2 hours. Then, within two hours, the temperature was reduced to 220° C. and held for 17 hours.

[0230] After the conditioning phase, 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 1.95 vol-%. The EC concentration was varied in the range of 2.2 to 3.5 ppmv to optimize the catalyst selectivity. Results of the catalyst tests at an optimal EC concentration are summarized in Table 5.

TABLE-US-00005 TABLE 5 Test Reaction Results Support Reactor Calcination Catalyst EO- Temper- Temperature Amount Selectivity ature Catalyst Support [° C.] [g] [%] [° C.] 1 A 1,500 26.4 78.5 210.5 2 * B 1,425 26.4 71.6 ** 220.5-217.0 * comparative example ** catalyst 2 exhibited an initial selectivity of 71.6%, which quickly fell to 51.8%

[0231] It is evident that catalyst 1, based on support A, shows a much higher selectivity than catalyst 2, based on support B. Catalyst 1 also shows a higher activity than catalyst 2, as is evident from the lower reactor temperature. Moreover, catalyst 2 did not allow for a stable operation at the final inlet gas composition.