CATALYST EFFECTIVE IN THE OXIDATIVE CONVERSION OF ETHYLENE TO ETHYLENE OXIDE

Abstract

The present invention provides a catalyst effective in the oxidative conversion of ethylene to ethylene oxide, comprising an alumina support and 20 to 45%by weight of the catalyst, of silver applied to the support, the catalyst meeting the following limitations (i) to (v): (i) an amount of cesium c(Cs) in mmol per Kg of catalyst of at least 2; (ii) an amount of rhenium c(Re) in mmol per Kg of catalyst of at least 3.0; (iii) an amount of tungsten c(W) in mmol per Kg of catalyst of at least 1.6; (iv) a silicon to alkaline earth metal molar ratio x of not higher than 1.80; (v) c(Cs)c(Re)c(W)4.Math.x0.5.

Claims

1. A catalyst effective in the oxidative conversion of ethylene to ethylene oxide, comprising an alumina support and 20 to 45% by weight of the catalyst, of silver applied to the support, the catalyst meeting the following limitations (i) to (v): (i) an amount of cesium c(Cs) in mmol per Kg of catalyst of at least 2; (ii) an amount of rhenium c(Re) in mmol per Kg of catalyst of at least 3.0; (iii) an amount of tungsten c(W) in mmol per Kg of catalyst of at least 1.6; (iv) a silicon to alkaline earth metal molar ratio x of not higher than 1.80; (v) c(Cs)c(Re)c(W)4.Math.x0.5.

2. The catalyst according to claim 1, wherein
c(Cs)c(Re)c(W)4.Math.x1.3.

3. The catalyst according to claim 2, wherein
c(Cs)c(Re)c(W)2.35.Math.x1.3.

4. The catalyst according to claim 1, wherein x is 0.1 to 1.46, preferably 0.1 to 1.10.

5. The catalyst according to claim 1, wherein c(Cs) is 4.5 to 11.3; and/or c(Re) is 3.0 to 9; and/or c(W) is 1.6 to 5.5.

6. The catalyst according to claim 1, comprising an amount of potassium c(K) in mmol per Kg of catalyst of 2.6 to 10.3.

7. The catalyst according to claim 1, comprising an amount of sodium c(Na) in mmol per Kg of catalyst of 0.2 to 10.8.

8. The catalyst according to claim 1, comprising an amount of lithium c(Li) in mmol per Kg of catalyst of 43 to 86.

9. The catalyst according to claim 1, comprising an amount of sulfur c(S) in mmol per Kg of catalyst of 0.3 to 3.

10. The catalyst according to claim 1, wherein the Cs:Re:W molar ratio is 12 to 19:9 to 12.5:4 to 6.

11. The catalyst according to claim 1, wherein the alumina support has a water absorption of 0.35 ml/g to 0.70 ml/g.

12. The catalyst according to claim 1, wherein the ratio of water absorption of the alumina support to BET surface area of the alumina support is in the range from 0.18 to 0.33 ml/m.sup.2.

13. A method for preparing the catalyst according to claim 1, comprising: (a) impregnating an alumina support having a silicon to alkaline earth metal molar ratio x of not higher than 1.80 with a silver impregnation solution, the silver impregnation solution containing sources of cesium, rhenium and tungsten; (b) calcining the impregnated alumina support.

14. The method according to claim 13, wherein the alumina support comprises 100 to 1000 ppm of calcium per total support weight, and/or 50 to 500 ppm of magnesium per total support weight.

15. The method according to claim 13, wherein the alumina support has a BET surface area from 1.5 to 2.5 m.sup.2/g.

16. A process for preparing ethylene oxide by gas-phase oxidation of ethylene by means of oxygen in the presence of the catalyst according to claim 1.

Description

EXAMPLES

[0073] Abbreviations [0074] AW.sub.Si atomic weight of Si in g/mol [0075] AW.sub.Ca atomic weight of Ca in g/mol [0076] AW.sub.Mg atomic weight of Mg in g/mol [0077] AW.sub.Cs atomic weight of Cs in g/mol [0078] AW.sub.Re atomic weight of Re in g/mol [0079] AW.sub.W atomic weight of W in g/mol [0080] Si.sub.Al2O3 weight of silicon per total support weight in ppm [0081] Ca.sub.Al2O3 weight of calcium per total support weight in ppm [0082] Mg.sub.Al2O3 weight of magnesium per total support weight in ppm [0083] Na.sub.Al2O3 weight of sodium per total support weight in ppm [0084] K.sub.Al2O3 weight of potassium per total support weight in ppm [0085] Fe.sub.Al2O3 weight of iron per total support weight in ppm [0086] Ag.sub.CAT weight of silver per total catalyst weight in wt-% [0087] K.sub.CAT weight of potassium per total catalyst weight in ppm [0088] Li.sub.CAT weight of lithium per total catalyst weight in ppm [0089] S.sub.CAT weight of sulfur per total catalyst weight in ppm [0090] W.sub.CAT weight of tungsten per total catalyst weight in ppm [0091] Cs.sub.CAT weight of cesium per total catalyst weight in ppm [0092] Re.sub.CAT weight of rhenium per total catalyst weight in ppm [0093] K.sub.ADD weight of potassium per total catalyst weight in ppm added to the catalyst from the applied impregnation solutions [0094] EC ethyl chloride [0095] EO ethylene oxide

[0096] 1. Characterization Methods

[0097] 1.1 Analysis of Total Amount of Ca-, Mg-, Si-, Fe-, K-, and Na-Contents in Alumina Carriers

[0098] 1.1.1 Sample Preparation for Measurement of Ca, Mg, Si and Fe

[0099] Approximately 100-200 mg (at an error margin of 0.1 mg) of the aluminum oxide carrier sample were weighted 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.

[0100] After cooling down, the melt was dissolved in deionized water by careful heating. Then, 10 ml of semi-concentrated hydrochloric acid (concentrated HCl diluted with deionized water, volume ratio 1:1 corresponds to about 6M) was added. Finally, the solution was filled up to a volume of 100 ml with deionized water.

[0101] 1.1.2 Measurement of Ca, Mg, Si and Fe

[0102] Ca, Mg, Si and Fe from the sample solution 1.1.1 were determined by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES).

[0103] Apparatus: ICP-OES Varian Vista Pro

[0104] Parameters: [0105] Wavelengths [nm]: Ca 317.933 [0106] Mg 285.213 [0107] Si 251.611 [0108] Fe 238.204 [0109] Integration time: 10 s [0110] Nebulizer: Conikal 3 ml [0111] Nebulizer pressure: 270 kPa [0112] Pump rate: 30 rpm [0113] Calibration: external (matrix-matched standards)

[0114] 1.1.3 Sample Preparation for Measurement of K and Na

[0115] Approximately 100-200 mg (at an error margin of 0.1 mg) of the aluminum oxide carrier sample were weighted into a platinum dish. 10 ml of a mixture of concentrated H.sub.2SO.sub.4 and deionized water (volume ratio 1:4), and 10 ml hydrofluoric acid (40%) was 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. Then 5 mL of semi-concentrated hydrochloric acid (concentrated HCl diluted with deionized water, volume ratio 1:1 corresponds to about 6M) were added. Finally, the solution was filled up to a volume of 50 ml with deionized water.

[0116] 1.1.4 Measurement of K and Na

[0117] Determination of K and Na in the sample solution 1.1.3 was carried out by Flame Atomic Absorption Spectroscopy (F-AAS).

[0118] Apparatus: F-AAS Shimadzu AA-7000

[0119] Parameters: [0120] Wavelengths [nm]: K 766.5 Na 589.0 [0121] Gas: Air/acetylene [0122] Slit width: 0.7 nm (K)/0.2 nm (Na) [0123] Nebulizer pressure: 270 kPa [0124] Calibration: external (matrix-matched standards)

[0125] 2. Alumina Supports

[0126] Si-, Ca- Mg-, Na-, K- and Fe-contents in the alumina support [ppm] per total weight of the support, support BET surface area and support water uptake are summarized in Table 1.

TABLE-US-00001 TABLE 1 Total Si-, Ca-, Mg-, Na-, K- and Fe- contents in the alumina support [ppm] per total weight of the support, support BET surface area [m.sup.2/g], and support water uptake [ml/g]. A B Si.sub.Al2O3 [ppm] 100 500 Ca.sub.Al2O3 [ppm] 300 400 Mg.sub.Al2O3 [ppm] 100 200 Na.sub.Al2O3 [ppm] 50 100 K.sub.Al2O3 [ppm] 85 185 Fe.sub.Al2O3 [ppm] <100 100 x [dimensionless].sup.1) 0.31 0.98 BET surface area [m.sup.2/g] 2.08 2.02 Water uptake [ml/g] 0.46 0.52 .sup.1)x = Si.sub.Al2O3/AW.sub.Si/(Ca.sub.Al2O3/AW.sub.Ca + Mg.sub.Al2O3/AW.sub.Mg)

[0127] A skilled person is well familiar with methods for preparing such alumina supports. He would rely on the general knowledge about the preparation of alumina supports in order to provide the desired BET surface area and water uptake. The preparation of alumina supports is, for example, described in EP 3 254 756 A1. BET surface area can be adjusted, for example, by combining two alpha alumina particles of different sizes, when the carrier is prepared (see, e.g. EP 0 902 726 B1 or WO 2011/153390 A2). As pointed out in WO 2012/143559 A1, an increase in the porosity can be achieved using organic additives having a placeholder function, thereby obtaining size distributions which are directly related to the grain sizes of the raw materials used. Additional methods for preparing support materials are described in WO 2012/143559 A1 and WO 2012/143557 A1. It is appreciated that the alumina support may have any of pore size distributions known in the prior art. Examples of suitable support pore size distributions are described in U.S. Pat. No. 7,714,152, U.S. Pat. No. 7,932,408, U.S. Pat. No. 7,977,274, EP 1 511 563 B1, WO 2006/133183, WO 2010/123729.

[0128] 3. Preparation of Catalysts

[0129] 3.1 Production of the Silver Complex Solution

[0130] Ag-Complex Solution CS-1:

[0131] 705.35 g DI H.sub.2O were mixed with 789.04 g of ethylene diamine (purity>99%, Merck) under stirring to form an aqueous ethylenediamine solution. The reaction temperature was maintained below 35 C. using cooling. To the resulting aqueous ethylenediamine solution, 43.13 g of 1 wt % aqueous KOH solution were added under stirring. The resulting mixture was cooled to a temperature of 22 C. to form an aqueous KOH ethylenediamine mixture. To the resulting mixture, 512.43 g of oxalic acid dihydrate were added under stirring. The reaction temperature was maintained at a temperature below 40 C. using cooling to produce an aqueous KOH/oxalic acid/ethylenediamine solution. The reaction temperature was cooled down to a temperature of 25 C. To the resulting aqueous KOH/oxalic acid/ethylenediamine solution, 905.75 g of high purity Ag.sub.2O (purity=99.9% by weight) were added under stirring. The reaction temperature was maintained at a temperature below 40 C. using cooling. After addition of the entire amount of Ag.sub.2O the reaction was stirred for further 3 hours while reaction temperature decreased to 32 C. Subsequently, the reaction mixture was centrifuged to remove a minor amount of not dissolved solid. The resulting Ag complex solution had a density of 1.531 g/ml and an Ag-content of 29.6% by weight.

[0132] Similarly, further silver complex solution batches CS-2-CS-4 were prepared with amounts of ingredients as listed in Table 2.

TABLE-US-00002 TABLE 2 Preparations and properties of Ag complex solutions CS-1 CS-2 CS-3 CS-4 Ethylene Diamine [g] 789.04 789.05 663.94 604.82 H.sub.2O [g] 705.35 688.14 586.29 540.65 1 wt % KOH [g] 43.13 60.33 43.50 33.04 Oxalic acid dihydrate [g] 512.43 512.44 431.19 392.78 Ag.sub.2O [g] 905.75 950.75 800.01 728.26 Ag-content [wt %] 29.6 29.6 29.6 29.5 Density [g/ml] 1.531 1.529 1.529 1.530 Target K in Ag complex 100 140 120 100 solution [ppm]

[0133] 3.2 Preparation of Ag-Containing Intermediate Products (1.sup.st Impregnation Step)

[0134] An amount of support A or B listed in Table 3 was placed into a 2 L glass flask. The flask was attached to a rotary evaporator which was set under vacuum pressure of 30 mbar. The rotary evaporator system was set in rotation of 30 rpm. An amount of silver complex solution CS1-CS4 listed in Table 3 prepared according to step 3.1 was added onto support A or B over 15 minutes under vacuum of 30 mbar. After addition of the silver complex solution, the rotary evaporator system was continued to rotate under vacuum for another 15 minutes. The impregnated support was then left in the apparatus at room temperature and atmospheric pressure for 1 hour and mixed gently every 15 minutes. The impregnated support was calcined for 12 minutes at 290 C. under 23 m.sup.3/h flowing nitrogen in a calcination oven to yield Ag-containing intermediate products.

TABLE-US-00003 TABLE 3 Support and amounts of ingredients used for the preparation of Ag-containing intermediate products 3.2.1-3.2.6. Intermediate Intermediate Intermediate Intermediate 3.2.1 3.2.2 3.2.3 3.2.4 Alumina support Support A Support A Support A Support B Amount of support [g] 261.2 262.0 261.1 350.2 Ag-complex solution CS-1 CS-2 CS-3 CS-4 Amount of Ag-complex 174.8219 174.7361 174.1359 264.6818 solution [g] Ag-content in Ag- 16.5 16.5 16.5 18.2 containing intermediate [wt %] K-content in Ag- 56 78 67 61 containing intermediate added from Ag complex solution [ppm] K-content in Ag- 71 71 71 151 containing intermediate from the used alumina support [ppm] Total K-content in Ag- 127 149 138 213 containing intermediate [ppm]

[0135] 3.3. Preparation of Final Catalysts (2.sup.nd Impregnation Step)

[0136] An amount of Ag-containing intermediate products 3.2.1-3.2.4 listed in Table 4 were placed into a 2 L glass flask. The flask was attached to a rotary evaporator which was set under vacuum pressure of 30 mbar. The rotary evaporator system was set in rotation of 80 rpm. An amount of the silver complex solution CS-1-CS-4 listed in Table 4 prepared according to step 3.1 was mixed with an amount of promoter solution I listed in Table 4, an amount of promoter solution II listed in Table 4, an amount of promoter solution III listed in Table 4. Promoter solution I was made from dissolving lithium nitrate (FMC, 99.3%) and ammonium sulfate (Merck, 99.4%) in DI water to achieve target Li and S contents listed in Table 4. Promoter solution II was made from dissolving tungstic acid (HC Starck, 99.99%) in DI water and cesium hydroxide in water (HC Starck, 50.42%) to achieve target Cs and W contents listed in Table 4. Promoter solution III was made from dissolving ammonium perrhenate (Engelhard, 99.4%) in DI water to achieve target Re content listed in Table 4. The combined impregnation solution containing silver complex solution, promoter solutions I, II, and III was stirred for 5 minutes. The combined impregnation solution was added onto the silver-containing intermediate products 3.2.1.-3.2.4 over 15 minutes under vacuum of 80 mbar. After addition of the combined impregnation solution, the rotary evaporator system was continued to rotate under vacuum for another 15 minutes. The impregnated support was then left in the apparatus at room temperature and atmospheric pressure for 1 hour and mixed gently every 15 minutes. The impregnated material was calcined for 10 minutes at 290 C. under 23 m.sup.3/h flowing nitrogen in a calcination oven to yield the final catalysts.

TABLE-US-00004 TABLE 4 Catalyst name and amounts of ingredients used for preparation of catalysts 3.3.1-3.3.3 and 3.3.15. Catalyst 3.3.1 3.3.2 3.3.3 3.3.15 Ag-containing Intermediate from Table 3 3.2.1 3.2.2 3.2.3 3.2.4 Amount of Ag-containing Intermediate [g] 105.7 105.5 105.6 200.8 Ag-complex solution CS-1 CS-2 CS-3 CS-4 Amount of Ag-complex solution [g] 41.3908 41.3282 41.3602 90.8649 Amount of promoter solution I [g] 1.9493 1.5425 1.9479 3.7653 Li-/S-content in promoter solution I [wt %] 2.85/0.21 2.85/0.21 2.85/0.21 2.85/0.21 Amount of promoter solution II [g] 1.5760 2.1243 1.8504 4.1106 Cs-/W-content in promoter solution II [wt %] 6.0/3.0 5.56/3.0 5.75/3.0 6.11/3.0 Amount of promoter solution III [g] 2.7155 2.7113 3.0327 6.1709 Re-content in promoter solution III [wt %] 3.7 3.7 3.7 3.7 Ag-content in the catalyst [wt %] 25.1 25.1 25.1 27.8 K.sub.ADD [ppm] 85 119 102 94 K-content in the catalyst added from Ag complex solution used in the 1.sup.st impregnation step and from the impregnation solution used in the 2.sup.nd impregnation step K-content in the catalyst from the used 63 63 63 133 alumina support [ppm] K.sub.CAT [ppm] 148 182 165 227 Total K-content in the catalyst

[0137] Further catalysts were prepared similarly to catalysts 3.3.1-3.3.3, 3.3.15 with catalyst compositions listed in Table 5. Promoter solutions I and III always used the same Li/S- and Re-contents as listed in Table 4. W-content in promoter solution II was fixed at 3 wt %. Cs-content in promoter solution II was varied to achieve a Cs/W ratio according to Table 5. Amounts of Ag complex solutions and promoter solutions I, II, and III were adjusted to achieve target Ag and promoter contents as listed in Table 5.

TABLE-US-00005 TABLE 5 Catalyst compositions (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-complex Ag- Ag.sub.CAT Li.sub.CAT S.sub.CAT W.sub.CAT Cs.sub.CAT Re.sub.CAT K.sub.ADD K.sub.CAT Example Support solution intermediate [wt-%] [ppm] [ppm] [ppm] [ppm] [ppm] [ppm] [ppm] 3.3.1 A CS-1 3.2.1 25.1 470 35 400 800 850 85 148 3.3.2 A CS-2 3.2.2 25.1 470 35 540 1000 850 119 182 3.3.3 A CS-3 3.3.3 25.1 470 35 470 900 950 102 165 3.3.4 A CS-1 3.2.1 25.1 470 35 540 1000 1050 85 148 3.3.5 A CS-2 3.2.2 25.1 470 35 540 800 1050 119 182 3.3.6 A CS-2 3.2.2 25.1 470 35 400 1000 1050 119 182 3.3.7 A CS-2 3.2.2 25.1 470 35 400 800 1050 119 182 3.3.8 A CS-2 3.2.2 25.1 470 35 400 1000 850 119 182 3.3.9 A CS-2 3.2.2 25.1 470 35 540 800 850 119 182 3.3.10 A CS-1 3.2.1 25.1 470 35 400 1000 1050 85 148 3.3.11 A CS-1 3.2.1 25.1 470 35 540 800 1050 85 148 3.3.12 A CS-1 3.2.1 25.1 470 35 540 1000 850 85 148 3.3.13 A CS-3 3.2.3 25.1 470 35 540 800 850 102 165 3.3.14 A CS-1 3.2.1 25.1 470 35 540 900 850 85 148 3.3.15 B CS-4 3.2.4 27.8 470 35 540 1100 1000 94 227 3.3.16 B CS-4 3.2.4 27.8 470 35 540 950 850 94 227 3.3.17 B CS-4 3.2.4 27.8 470 35 540 1250 850 94 227 3.3.18 B CS-4 3.2.4 27.8 470 35 540 950 1150 94 227 3.3.19 B CS-4 3.2.4 27.8 470 35 540 1250 1150 94 227 3.3.20 B CS-4 3.2.4 27.8 470 35 540 950 1000 94 227 3.3.21 B CS-4 3.2.4 27.8 470 35 540 1250 1000 94 227 3.3.22 B CS-4 3.2.4 27.8 470 35 540 1100 850 94 227 3.3.23 B CS-4 3.2.4 27.8 470 35 540 1100 1150 94 227

TABLE-US-00006 TABLE 6 Key catalyst properties with respect to claims Support BET surface area c(Cs) c(Re) c(W) c(Cs) c(Re) c(W) x .sup.1) Example [m.sup.2/g] [mmol/kg] [mmol/kg] [mmol/kg] [mmol/kg] [dimensionless] 3.3.1 2.08 6.02 4.56 2.18 0.72 0.31 3.3.2 2.08 7.52 4.56 2.94 0.02 0.31 3.3.3 2.08 6.77 5.10 2.56 0.89 0.31 3.3.4 2.08 7.52 5.64 2.94 1.05 0.31 3.3.5 2.08 6.02 5.64 2.94 2.56 0.31 3.3.6 2.08 7.52 5.64 2.18 0.29 0.31 3.3.7 2.08 6.02 5.64 2.18 1.80 0.31 3.3.8 2.08 7.52 4.56 2.18 0.78 0.31 3.3.9 2.08 6.02 4.56 2.94 1.48 0.31 3.3.10 2.08 7.52 5.64 2.18 0.29 0.31 3.3.11 2.08 6.02 5.64 2.94 2.56 0.31 3.3.12 2.08 7.52 4.56 2.94 0.02 0.31 3.3.13 2.08 6.02 4.56 2.94 1.48 0.31 3.3.14 2.08 6.77 4.56 2.94 0.73 0.31 3.3.15 2.02 8.28 5.37 2.94 0.03 0.98 3.3.16 2.02 7.15 4.56 2.94 0.35 0.98 3.3.17 2.02 9.40 4.56 2.94 1.90 0.98 3.3.18 2.02 7.15 6.18 2.94 1.97 0.98 3.3.19 2.02 9.40 6.18 2.94 0.29 0.98 3.3.20 2.02 7.15 5.37 2.94 1.16 0.98 3.3.21 2.02 9.40 5.37 2.94 1.10 0.98 3.3.22 2.02 8.28 4.56 2.94 0.77 0.98 3.3.23 2.02 8.28 6.18 2.94 0.84 0.98 .sup.1) x = Si.sub.Al2O3/AW.sub.Si/(Ca.sub.Al2O3/AW.sub.Ca + Mg.sub.Al2O3/AW.sub.Mg)

[0138] 4. Catalyst Testing

[0139] The catalyst screening was performed in a 16-fold parallel reactor system. Every reactor was simultaneously supplied with the same inlet gas, at same temperature and same pressure.

[0140] The reactor tubes were composed of stainless steel (1.4841) and had a length of 290 mm with an outer diameter of 10 mm and an inner diameter of 4.5 mm. The isothermal zone of the reactor has a length of 70 mm and this was heated using an indirect electrical heating. 1 mL catalyst with a particle size of 250 m to 315 m was placed in the isothermal zone of the reactor tube.

[0141] The filling scheme of the reactor tube is described in table 7. The filling scheme is a stacked bed with five individual zones. From reactor top to bottom the reactor filling consists of two inert stacks from steatite beads and quartz particles, followed by the catalyst located in the isothermal zone in the center of the reactor tube, followed by another two inert stacks, consisting of quartz particles and steatite beads. Zone 5 represents the top of the reactor tube, where the inlet gas was introduced into the reactor tube. The reactors are operated in once-through mode.

TABLE-US-00007 TABLE 7 Reactor tube filling Height Particle size Zone [mm] Material [m] 1 0-70 steatite beads 315-500 2 70-90 quartz particles 100-350 3 90-153 catalyst 250-315 4 153-173 quartz particles 100-350 5 173-290 steatite beads 315-500

[0142] The experiments were carried out at a reactor pressure of 15 bar g, at a gas hourly space velocity (GHSV) of about 4530 h.sup.1 and at reactor temperatures of 220 C. to 260 C. The inlet gas consisted of 35 vol. % ethylene, 7 vol. % oxygen, 5 vol. % argon and ethylene chloride (EC), which was dosed over a range of 1.3 ppmv to 3.3 ppmv. Nitrogen was used as carrier gas and argon as an internal standard.

[0143] The reactor outlet gas was quenched with nitrogen at a ratio of approximately 5:1 and was analyzed via online gas chromatography (GC).

[0144] Catalysts were tested at reactor temperatures of 230 C. or 235 C. and at EC concentrations ranging from 1.3 ppmv to 3.3 ppmv to optimize EO-selectivity. The results of the catalyst screening tests are shown in tables 8 and 9. EC concentrations in the tables 8 and 9 correspond to optimized EO-selectivity.

TABLE-US-00008 TABLE 8 Test reaction results reactor temperature: 230 C. reactor temperature: 235 C. time on stream: 879.4-950.4 hours time on stream: 950.4-1025.4 hours EC EC Ex. [ppm] S.sup.1) STY.sup.2) X.sup.3) Y.sup.4) [ppm] S.sup.1) STY.sup.2) X.sup.3) Y.sup.4) 3.3.1 1.9 87.6 189.6 6.9 6.0 2.3 87.2 249.8 9.1 7.9 3.3.2 1.3 88.2 123.6 4.4 3.9 1.3 86.9 146.0 5.3 4.6 3.3.3. 1.5 89.4 190.4 6.8 6.0 1.9 88.6 254.1 9.1 8.1 3.3.4 1.9 89.7 200.0 7.1 6.4 2.1 89.2 249.5 8.9 7.9 3.3.5 2.7 89.4 201.0 7.2 6.5 3.1 89.1 268.7 9.7 8.6 3.3.6 1.5 89.0 162.3 6.0 5.4 1.5 88.1 202.5 7.6 6.7 3.3.7 2.5 88.8 205.8 7.5 6.7 2.7 88.2 263.3 9.7 8.5 3.3.8 1.3 86.3 118.2 4.4 3.8 1.3 84.9 140.9 5.4 4.6 3.3.9 1.9 89.1 198.2 7.2 6.4 1.5 88.8 209.3 7.6 6.8 3.3.10 1.5 88.9 190.7 7.0 6.2 1.5 88.0 229.3 8.4 7.4 3.3.11 2.7 88.7 225.1 8.2 7.3 2.7 88.3 276.9 10.1 9.0 3.3.12 1.5 88.8 185.4 6.7 5.9 1.5 88.6 227.1 8.2 7.3 3.3.13 1.5 89.3 188.1 6.6 5.9 1.9 88.7 249.2 8.8 7.8 3.3.14 1.5 89.1 190.0 6.8 6.1 1.5 88.4 226.7 8.2 7.3 .sup.1)EO-selectivity [%] .sup.2)EO-space-time-yield [kg.sub.EO/(m.sup.3.sub.cath)] .sup.3)EO-conversion [%] .sup.4)EO-yield [%]

TABLE-US-00009 TABLE 9 Test reaction results reactor temperature: 230 C. reactor temperature: 235 C. time on stream: 311.3-379.5 hours time on stream: 379.5-448.6 hours EC EC Ex. [ppm] S.sup.1) STY.sup.2) X.sup.3) Y.sup.4) [ppm] S.sup.1) STY.sup.2) X.sup.3) Y.sup.4) 3.3.15 1.9 87.6 214.6 7.9 6.9 1.9 87.1 256.0 9.5 8.2 3.3.16 1.9 87.6 217.3 8.0 7.0 1.9 87.2 258.4 9.6 8.4 3.3.17 1.3 85.7 152.1 5.7 4.9 1.7 85.2 237.6 9.0 7.7 3.3.18 2.5 88.1 238.3 8.8 7.8 2.9 87.3 305.6 11.5 10.0 3.3.19 1.9 86.7 226.1 8.4 7.3 1.9 86.1 269.8 10.1 8.7 3.3.20 1.9 87.9 208.9 7.6 6.7 2.7 87.6 297.8 10.9 9.6 3.3.21 1.3 86.1 132.1 4.9 4.2 1.7 85.5 241.1 9.0 7.7 3.3.22 1.9 86.1 232.8 8.4 7.2 1.9 86.0 278.3 10.1 8.7 3.3.23 1.9 88.0 222.8 8.1 7.1 1.9 87.7 261.7 9.6 8.4 .sup.1)EO-selectivity [%] .sup.2)EO-space-time-yield [kg.sub.EO/(m.sup.3.sub.cath)] .sup.3)EO-conversion [%] .sup.4)EO-yield [%]