Mechanically stable hollow cylindrical shaped catalyst bodies for gas phase oxidation of an alkene to an unsaturated aldehyde and/or an unsaturated carboxylic acid

Abstract

A hollow cylindrical shaped catalyst body for gas phase oxidation of an alkene to an ,-unsaturated aldehyde and/or an ,-unsaturated carboxylic acid comprises a compacted multimetal oxide having an external diameter ED, an internal diameter ID and a height H, wherein ED is in the range from 3.5 to 4.5 mm; the ratio q=ID/ED is in the range from 0.4 to 0.55; and the ratio p=H/ED is in the range from 0.5 to 1. The shaped catalyst body is mechanically stable and catalyzes the partial oxidation of an alkene to the products of value with high selectivity. It provides a sufficiently high catalyst mass density of the catalyst bed and good long-term stability with acceptable pressure drop.

Claims

1. A hollow cylindrical shaped catalyst body, comprising a compacted multimetal oxide comprising the elements molybdenum, iron and bismuth having an external diameter ED, an internal diameter ID and a height H, wherein (i) ED is from 3.5 to 4.5 mm; (ii) a ratio q according to the following equation $q=\frac{\mathrm{ID}}{\mathrm{ED}}$ is from 0.45 to 0.55; and (iii) a ratio p according to the following equation $p=\frac{H}{\mathrm{ED}}$ is from 0.5 to 0.95 wherein a ratio of the geometric surface area of the shaped catalyst body to a geometric volume of the shaped catalyst body is from 26 to 30.01 cm.sup.1.

2. The catalyst body according to claim 1, wherein ED from 3.7 to 4.3 mm.

3. The catalyst body according to claim 1, wherein p is from 0.65 to 0.9.

4. The catalyst body according to claim 1, wherein a geometric volume of the shaped catalyst body is from 22 to 34 mm.sup.3.

5. The catalyst body according to claim 1, wherein a density of the shaped catalyst body is from 1.2 to 2.0 g/cm.sup.3.

6. The catalyst body according to claim 1, wherein a value WT according to the following equation $\mathrm{WT}=\frac{\mathrm{ED}-\mathrm{ID}}{2}$ is from 0.8 to 1.2 mm.

7. The catalyst body according to claim 1, wherein ED is from 3.7 to 4.3 mm, H is from 2.8 to 3.2 mm and ID is from 1.8 to 2.2 mm.

8. The catalyst body according to claim 1, obtained by a process comprising: (i) producing an intimate dry mixture of sources of the elemental constituents of the multimetal oxide, (ii) compacting the intimate dry mixture to obtain a hollow cylindrical shaped precursor body, (iii) and calcining at a temperature of from 350 to 650 C.

9. The catalyst body according to claim 8, wherein the intimate dry mixture is compacted to the hollow cylindrical shaped precursor body by tableting.

10. The catalyst body according to claim 8, obtained by thermally pretreating the hollow cylindrical shaped precursor body prior to the calcination under conditions under which a maximum relative decrease in mass of the shaped catalyst precursor body does not exceed a value of 1% per minute.

11. A process for preparing an ,-unsaturated aldehyde an ,-unsaturated carboxylic acid, or both, comprising contacting an alkene with molecular oxygen over a fixed catalyst bed comprising a bed of hollow cylindrical shaped catalyst bodies according to claim 1.

12. The process according to claim 11, wherein the process obtains acrolein by gas phase oxidation of propene.

13. The process according to claim 11, wherein the fixed catalyst bed comprises a bed having a plurality of reaction zones, the bed comprises inert shaped diluent bodies in a reaction zone, and a proportion of inert shaped diluent bodies in at least two reaction zones is different.

14. The process according to claim 13, wherein a bed in the reaction zone which comprises the lowest proportion of inert shaped diluent bodies, if any inert shaped diluent bodies, comprises the hollow cylindrical shaped catalyst bodies.

15. The process according to claim 13, wherein a bed in the reaction zone in which the highest local temperature in the fixed catalyst bed occurs, comprises the hollow cylindrical shaped catalyst bodies.

16. The process according to claim 11, wherein the bed further comprises other shaped catalyst bodies which are not in accordance with the hollow cylindrical shaped catalyst bodies.

Description

Examples

Mechanically Stable Hollow Cylindrical Shaped Catalyst Bodies for Gas Phase Oxidation of an Alkene to an Unsaturated Aldehyde and/or an Unsaturated Carboxylic Acid

(1) I) Preparation of hollow cylindrical shaped catalyst bodies having the following stoichiometry of the active composition: [Bi.sub.2W.sub.2O.sub.92 WO.sub.3].sub.0.50[Mo.sub.12Co.sub.5.4Fe.sub.3.1Si.sub.1.5K.sub.0.08O.sub.x].sub.1.

(2) a) Preparation of starting material 1 (Bi.sub.1W.sub.2O.sub.7.5=Bi.sub.2W.sub.2O.sub.91 WO.sub.3)

(3) In a 1.75 m.sup.3 stainless steel jacketed vessel (temperature control water flowed through the interspace) with a crossbeam stirrer, 214.7 kg of tungstic acid at 25 C. (74.1% by weight of W, mean particle size (according to manufacturer determined to ASTM B 330) from 0.4 to 0.8 m, ignition loss (2 h at 750 C. under air) 6-8% by weight, H. C. Starck, D-38615 Goslar) were stirred (70 rpm) in portions into 780 kg of an aqueous bismuth nitrate solution in nitric acid at 25 C. (11.2% by weight of Bi; free nitric acid: 3 to 5% by weight; prepared with nitric acid from bismuth metal from Sidech S.A., 1495 Tilly, Belgium, purity: >99.997% by weight of Bi, <7 mg/kg of Pb, <5 mg/kg each of Ni, Ag, Fe, <3 mg/kg each of Cu, Sb, and <1 mg/kg each of Cd, Zn) at 25 C. within 20 min. The resulting aqueous mixture was then stirred at 25 C. for another 3 h and then spray-dried. The spray-drying was effected in a Niro FS 15 rotary-disk spray tower in hot air cocurrent at a gas inlet temperature of 30010 C., a gas outlet temperature of 10010 C., a disk speed of 18 000 rpm, a throughput of 200 l/h and an air rate of 1800 m.sup.3 (STP)/h. The resulting spray powder had an ignition loss of 12.8% by weight (calcine under air at 600 C. for 3 h in a porcelain crucible (which had been calcined to constant weight at 900 C.)) and had (at a dispersion pressure of 1.1 bar absolute) a d.sub.50 of 28.0 m (d.sub.10=9.1 m, d.sub.90=55.2 m).

(4) The resulting spray powder was subsequently converted to a paste with 16.7% by weight (based on the powder) of water at 25 C. in a discharging kneader for 30 min, and kneaded at a speed of 20 rpm and extruded by means of an extruder to extrudates of diameter 6 mm. These were cut into 6 cm sections, dried under air on a 3-zone belt dryer with a residence time of 40 min per zone at temperatures of 90-95 C. (zone 1), 115 C. (zone 2) and 125 C. (zone 3), and then calcined at a temperature in the region of 830 C. (in a rotary tube oven with air flow (reduced pressure 0.3 mbar, 200 m.sup.3 (STP)/h of air, 50 kg/h of extrudate, speed: 1 rpm)). The preformed calcined mixed oxide thus obtained was ground with a 500 BQ biplex crossflow classifying mill from Hosokawa Alpine AG, Augsburg, at 2500 rpm, such that the d.sub.50.sup.A1 value of the finely divided starting material 1 was 2.8 m (measured at a dispersion pressure of 2.0 bar absolute), the BET surface area was 0.6 m.sup.2/g (measured by nitrogen adsorption after activation under reduced pressure at 200 C. for 4 h) and the -Bi.sub.2WO.sub.6 content was 2 intensity %, calculated as the ratio of the intensity of the reflection of -Bi.sub.2WO.sub.6 in the x-ray powder diffractogram at 2=28.4 (CuK radiation) to the intensity of the reflection of Bi.sub.2W.sub.2O.sub.9 at 2=30.0. Before the further processing described under c), the finely divided starting material 1 was mixed in portions of 20 kg each in a tilted mixer with mixing and cutting blades (mixing blade speed: 60 rpm, cutting blade speed: 3000 rpm) homogeneously with 0.5% by weight (based on the particular finely divided starting material 1) of Sipernat D17 finely divided hydrophobized S102 from Degussa (tapped density: 150 g/l; d.sub.50 of the SiO.sub.2 particles (laser diffraction to ISO 13320-1)=10 m, the specific surface area (nitrogen adsorption to ISO 5794-1, Annex D)=100 m.sup.2/g) within 5 min.

(5) b) Preparation of the Starting Material 2 (Mo.sub.12Co.sub.5.4Fe.sub.3.1Si.sub.1.5K.sub.0.08O.sub.x)

(6) A solution A was prepared by metering 1.075 kg of an aqueous potassium hydroxide solution (47.5% by weight KOH) at a temperature of 60 C. and subsequently, via a differential metering balance at a metering rate of 600 kg/h, 237.1 kg of ammonium heptamolybdate tetrahydrate at a temperature of 25 C. (white crystals with a particle size d of <1 mm, 81.5% by weight of MoO.sub.3, 7.0-8.5% by weight of NH.sub.3, max. 150 mg/kg of alkali metals, H.C. Starck, D-38642 Goslar) into 660 l of water at a temperature of 60 C. in a water-heated 1.75 m.sup.3 stainless steel jacketed vessel with a crossbeam stirrer at 60 C. with stirring (70 rpm) within one minute, and the resulting solution was stirred at 60 C. for 60 min (70 rpm).

(7) A solution B was prepared by initially charging a water-heated 1.75 m.sup.3 stainless steel jacketed vessel with a crossbeam stirrer at 60 C. with 282.0 kg of an aqueous cobalt(II) nitrate solution at a temperature of 60 C. (12.5% by weight of Co, prepared with nitric acid from cobalt metal from MFT Metals & Ferro-Alloys Trading GmbH, D-41747 Viersen, purity >99.6% by weight, <0.3% by weight of Ni, <100 mg/kg of Fe, <50 mg/kg of Cu), and 142.0 kg of an iron(III) nitrate nonahydrate melt at 60 C. (13.8% by weight of Fe, <0.4% by weight of alkali metals, <0.01% by weight of chloride, <0.02% by weight of sulfate, Dr. Paul Lohmann GmbH, D-81857 Emmerthal) were metered into it with stirring (70 rpm). Subsequently, the mixture was stirred for a further 30 minutes while maintaining the 60 C.

(8) While maintaining the 60 C., solution B was discharged into the initially charged solution A and stirred at 70 rpm at 60 C. for a further 15 minutes. Subsequently, 19.9 kg of a Ludox TM 50 silica sol from Grace at 25 C. (50.1% by weight of SiO.sub.2, density: 1.29 g/ml, pH 8.5 to 9.5, alkali metal content max. 0.5% by weight) were added to the resulting aqueous mixture which was then stirred at 70 rpm at 60 C. for a further 15 minutes.

(9) This was followed by spray-drying in a Niro FS-15 rotary disk spray tower in hot air countercurrent at a disk speed of 18 000 rpm (gas inlet temperature: 35010 C., gas outlet temperature: 1405 C., throughput: 270 kg/h). The resulting spray powder had an ignition loss of 31% by weight (calcine under air at 600 C. for 3 h in a porcelain crucible (which had been calcined to constant weight at 900 C.)) and had (at a dispersion pressure of 1.1 bar absolute) a d.sub.50 of 33.0 m.

(10) c) Production of the Hollow Cylindrical Shaped Catalyst Bodies from the Starting Materials 1 and 2

(11) 134 kg of starting material 2 were then initially charged in a tilted mixer (VIL type, fill volume: 200 l, Aachener Misch- and Knetmaschinenfabrik) with mixing and cutting blades (mixing blade speed: 39 rpm, cutting blade speed: 3000 rpm) and premixed for 1 min. Within 10 min, with continued mixing, via a star feeder, starting material 1 was metered thereto in the amount required for a multimetal oxide active material of stoichiometry:
[Bi.sub.2W.sub.2O.sub.92WO.sub.3].sub.0.50[Mo.sub.12Co.sub.5.4Fe.sub.3.1Si.sub.1.5K.sub.0.08O.sub.x].sub.1
within 10 min. The mixing operation was then continued for a further 15 min in order to achieve an intensive and complete homogenization (including the breaking apart of any agglomerates present) of the two starting materials. Based on the aforementioned overall composition, 1% by weight of TIMREX T44 graphite from Timcal AG was mixed in within a further 2 min.

(12) The resulting mixture was then compacted in a K200/100 compactor from Hosokawa Bepex GmbH with concave, fluted smooth rollers (gap width: 2.8 mm, roller speed: 9 rpm, target pressing force: approx. 75 kN). Integrated vibrating screens from Allgaier (oversize screen size: 1.5 mm, undersize screen size: 400 m) with ball-type screening aids (diameter 22 mm) were used to isolate a compactate having a particle size for the most part between 400 m and 1.5 mm.

(13) For the tableting, a further 2.5% by weight of the TIMREX T44 graphite from Timcal AG were added to the compactate in a turbulent mixer from Drais over the course of 2 min.

(14) Subsequently, the pulverulent aggregate obtained as described was compacted (tableted) under an air atmosphere with the aid of a Korsch PH 865 rotary press (Korsch AG, D-13509 Berlin). Hollow cylindrical shaped bodies having the following dimensions (external diameterheightinternal diameter; in mm) were produced:

(15) 432

(16) 422

(17) 532

(18) The rotation rate of the rotary press was 35 to 45 rpm.

(19) In all cases, the tableting was conducted such that the density of the hollow cylindrical shaped bodies (ratio of tablet mass and tablet volume) was identical and was 2.5 g per milliliter.

(20) For the final thermal treatment, 250 g in each case of each of the hollow cylindrical shaped bodies produced with the different dimensions were installed together on 4 mesh grids arranged alongside one another, each having a square surface area of 150 mm150 mm (bed height: about 15 mm), in an air circulation shaft furnace (from Nabertherm; furnace model S60/65A) through which air heated to a temperature of 140 C. flowed at 4500 l (STP)/h. Subsequently, the furnace was first heated from room temperature (25 C.) to 130 C. within 72 min. The temperature was measured here by 4 measuring elements, each of which is in the middle of each of the 4 mesh grids, directly within the catalyst bed, and one of these measuring elements provides the actual value for temperature regulation of the furnace. This temperature was maintained for 72 min and then increased to 190 C. within 36 min. The 190 C. was maintained for 72 min, before the temperature was increased further to 220 C. within 36 min. The 220 C. was maintained for 72 min, before the temperature was increased further to 265 C. within 36 min. The 265 C. was maintained for 72 min, before the temperature was increased further to 380 C. within 93 min. The 380 C. was maintained for 187 min, before the temperature was increased further to 430 C. within 93 min. The 430 C. was maintained for 187 min, before the temperature was increased further to the final calcination temperature of 464 C. within 93 min. The final calcination temperature was maintained for 467 min. Thereafter, the furnace was cooled to room temperature within 12 h. For this purpose, the furnace heating and the additional air stream preheating described above were switched off, while maintaining the air flow rate of 4500 l (STP)/h.

(21) II) Gas Phase Oxidation

(22) A reaction tube (V2A steel; external diameter 21 mm, wall thickness 3 mm, internal diameter 15 mm, length 120 cm) was charged from the top downward in flow direction as follows: Section 1: length about 30 cm 40 g of steatite spheres with a diameter of 1.5 to 2.0 mm as a preliminary bed. Section 2: length about 70 cm catalyst charge of a homogeneous mixture of 40 g of the hollow cylindrical calcined shaped bodies produced in l) and 60 g of hollow steatite cylinders (dimensions: 532; external diameterheightinternal diameter, in mm).

(23) The temperature of the reaction tube was in each case controlled by means of a molecular nitrogen-sparged salt bath having the salt bath temperature T.sup.SB of 380 C. (53% by weight of potassium nitrate, 40% by weight of sodium nitrite and 7% by weight of sodium nitrate). The salt bath was within a cylindrical shell. The cylindrical shell had the same length as the reaction tube. The latter was conducted from the top downward within the cylindrical shell such that the two axes of symmetry coincided. The nitrogen stream sparged into the salt bath from the bottom was 40 l (STP)/h. The heat losses of the salt bath to the environment were greater than the heat of reaction produced by the reactor during the partial oxidation. The salt bath was therefore held at its temperature T.sup.SB ( C.) by means of electrical heating. In this way, it was ensured that the outer wall of the reaction tube always had the appropriate temperature T.sup.SB ( C.).

(24) The reactor was charged continuously with a charge gas mixture (mixture of air, polymer grade propylene and nitrogen) of the composition: 5% by vol. of propene, 9.5% by vol. of oxygen and, as the remainder to 100% by vol., N.sub.2.

(25) The mixed gas flow rate was regulated such that the propene conversion C (based on a single pass of the reaction gas mixture through the reaction tube, in mol %), defined as

(26) $\frac{\mathrm{total}\mathrm{number}\mathrm{of}\mathrm{moles}\mathrm{of}\mathrm{propene}\mathrm{converted}}{\mathrm{total}\mathrm{number}\mathrm{of}\mathrm{moles}\mathrm{of}\mathrm{propane}\mathrm{supplied}}100.$
was 95.4 mol % at a salt bath temperature of 380 C. The inlet pressure in the reaction tube was 1.2 bar absolute.
Drop Test

(27) 50 g of catalyst were allowed to fall through a vertical tube of length 3 m having an internal diameter of 23 mm. The catalyst fell into a porcelain dish directly underneath the tube and was separated from the dust and fractured material which arise on impact. The shaped catalyst bodies separated intact from the dust were weighed. The proportion of intact shaped catalyst bodies was determined by comparison of the mass determined here with the mass of the shaped catalyst bodies used for the drop test (see Drop test column in table 1). The proportion of intact shaped catalyst bodies is a measure of mechanical stability of the shaped catalyst bodies. The results are listed in table 1 below.

(28) The load, as a measure of activity, corresponds to the volume flow rate of propene supplied to the reactor (in l (STP)/h) based on the mass of catalyst (in grams) present in the reactor. A higher load corresponds to a higher activity.

(29) The product of value selectivity (mol %) corresponds to the following formula:

(30) $\frac{\begin{array}{c}\mathrm{number}\mathrm{of}\mathrm{moles}\mathrm{of}\mathrm{propene}\\ \mathrm{converted}\mathrm{to}\mathrm{acrolein}\mathrm{and}\mathrm{acrylic}\mathrm{acid}\end{array}}{\mathrm{number}\mathrm{of}\mathrm{moles}\mathrm{of}\mathrm{propene}\mathrm{converted}}100.$

(31) The determination of load and product of value selectivity followed an initial period of more than 7 days, after which activity and product of value selectivity are essentially unchanged over the course of time.

(32) TABLE-US-00001 TABLE 1 Shaped Load Drop test catalyst body (=activity) Product [% intact dimensions [I (STP) of value shaped (AD.sup.1) H.sup.2) ID.sup.3)) of propene/(g selectivity catalyst Ex. [mm] of catalyst h)] [mol %] bodies] 1 4 3 2 0.09 95.6 88 2 4 2 2 0.08 95.4 91 3*.sup.) 5 3 2 0.06 94.9 88 *.sup.)comparative example .sup.1)external diameter .sup.2)height .sup.3)internal diameter

(33) The inventive shaped catalyst bodies are stable (more than 85% intact shaped catalyst bodies in the drop test) and assure a high product of value selectivity of more than 95.3 mol %. In comparative example 3, the product of value selectivity is distinctly inferior to that in inventive examples 1 and 2 (94.9 mol %). The activity of the inventive catalysts is higher (greater than or equal to 0.08 l (STP) of propene/(g of catalyst and hour)) than that of the noninventive catalyst of example 3 (0.06 l (STP) of propene/(g of catalyst and hour)).