Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
  • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
  • C07C51/25—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of unsaturated compounds containing no six-membered aromatic ring
  • C07C51/252—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of unsaturated compounds containing no six-membered aromatic ring of propene, butenes, acrolein or methacrolein
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
  • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
  • C07C51/25—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of unsaturated compounds containing no six-membered aromatic ring
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation

Definitions

• the present invention relates to a process for the preparation of acrylic acid by heterogeneously catalyzed gas phase partial oxidation of at least one C 3 hydrocarbon precursor compound.
• Acrylic acid is an important monomer which, as such or in the form of its alkyl esters, is used to produce polymers suitable, for example, as adhesives.
• the process of heterogeneously catalyzed gas phase partial oxidation of propene to acrylic acid basically takes place in two successive steps, the first step leading from propene to acrolein and the second step from acrolein to acrylic acid. Since there are catalysts that can catalyze both, as well as tailor-made, only one of the two steps, the heterogeneously catalyzed gas phase partial oxidation of propene to acrylic acid can in principle be carried out in a single as well as in two or more spatially successive reaction stages, the each reaction stage is characterized by its catalyst feed and the associated other, usually specific, reaction conditions.
• a method of two-stage heterogeneously catalyzed partial gas phase oxidation of propene to acrylic acid is e.g. known from DE-A 19927624, from DE-A 19948523, from WO 00/53557, from DE-A 19948248 and from WO 00/53558.
• the heterogeneously catalyzed partial gas phase oxidation to acrylic acid can also be carried out in a single or in two or more spatially successive reaction stages.
• the formation of acrylic acid starting from propane usually takes place in three successive steps, of which the first step is normally the formation of propene.
• a description of a partial one-stage propane oxidation to acrylic acid is contained, for example, in the documents EP-A 608838, WO 0029106, JP-A 10-36311, DE-A 10316465, EP-A 1192987, EP-A 1193240 and DE-A 10338529.
• a three-stage partial Propane oxidation to acrylic acid is described, for example, in WO 01/96270.
• catalysts for both the respective steps of partial propene and partial propane oxidation are generally multi-element oxides, some of which are described in the cited prior art.
• a common feature of all known processes for the production of acrylic acid by heterogeneously catalyzed gas phase partial oxidation of at least one C 3 hydrocarbon precursor compound is that due to numerous parallel and subsequent reactions taking place in the course of the catalytic gas phase oxidation, and also because, as a rule, among other things to avoid explosive gas mixtures Dilution gases to be used, preferably essentially inert, are not pure acrylic acid but a reaction gas mixture which, in addition to acrylic acid and the intermediate product acrolein which can be recycled into the partial oxidation, optionally unreacted propene and / or propane, inert dilution gases (are essentially not converted in the partial oxidation , ie they normally remain unchanged at more than 95 mol%, preferably more than 97 or more than 99 mol% during the partial oxidation), the carbon oxides CO and / or CO 2 , that of acrylic acid re comparatively easily separable reaction products acetic acid (can be removed, for example, by stripping from a product gas
• acrylic acid When acrylic acid is obtained from the product gas mixture of a heterogeneously catalyzed partial oxidation of at least one C 3 hydrocarbon precursor compound, the acrylic acid must be separated from the product gas mixture, which is usually carried out by means of combinations of absorptive, extractive and / or distillative or rectificative separation processes (cf. e.g. EP-A 854129, US-A 4317926, DE-A 19837520, DE-A 19606877, DE-A 19501325, DE-A 10247240, DE-A 19924532, EP-A 982289, DE-A 19740253, DE-A 19740252, EP-A 695736, EP-A 982287 and EP-A 1041062).
• absorptive, extractive and / or distillative or rectificative separation processes cf.g. EP-A 854129, US-A 4317926, DE-A 19837520, DE-A 19606877, DE-A 19501325, DE-A 10247
• the object of the present invention was therefore to remedy the problem described above. In-depth considerations have surprisingly led to the result that a possible remedy has so far essentially neither been taken nor considered.
• This consists in modifying the process of heterogeneously catalyzed partial oxidation of at least one C 3 hydrocarbon precursor compound such that the total amount of those constituents which make the removal of acrylic acid from the product gas mixture particularly difficult, in the product gas mixture, based on the amount contained therein Acrylic acid is as low as possible.
• the applicant has identified the secondary components already defined as such components.
• lower aldehydes other than acrolein such as formaldehyde, acetaldehyde, methacrolein, propionaldehyde, n-butyraldehyde, benzaldehyde, furfural and crotonaldehyde, which are known for their presence, especially in thermal separation processes, to increase the tendency of acrylic promotes acid to undesired radical polymerization in a special way (see, for example, EP-A 854129).
• the secondary components also include lower alkene VA alkanecarboxylic acids or their anhydrides such as formic acid, propionic acid, methacrylic acid, crotonic acid, butyric acid and maleic anhydride, but also compounds such as protoanemonine, acetone and benzaldehyde.
• lower alkene VA alkanecarboxylic acids or their anhydrides such as formic acid, propionic acid, methacrylic acid, crotonic acid, butyric acid and maleic anhydride, but also compounds such as protoanemonine, acetone and benzaldehyde.
• C hydrocarbon precursor compound is provided, which is characterized in that the overall selectivity S tot of the secondary component formation is ⁇ 1.5 mol%.
• the formation of an individual secondary component i in mol% is understood to be a hundred times the quotient from the molar formation amount of the secondary component i divided by the molar amount of the at least one C 3 -hydrocarbon precursor compound converted in the heterogeneously catalyzed partial oxidation.
• the overall selectivity S tot of the secondary component formation is understood in this document as the sum of the various individual selectivities Sj over all secondary components i.
• S tot is preferably ⁇ 1.4 mol% or ⁇ 1.3 mol%, particularly preferably ⁇ 1.2 mol% or ⁇ 1.1 mol% or ⁇ 1.0 mol% or ⁇ 0.9 mol%, very particularly preferably ⁇ 0.80 mol% or ⁇ 0.70 mol% or ⁇ 0.60 mol% or ⁇ 0.50 mol%, and most preferably S tot according to the invention is ⁇ 0.40 mol% or ⁇ 0.30 mol% or ⁇ 0.20 mol% or ⁇ 0.10 mol% or 0 mol%.
• S tot is > 0.1 mol% and ⁇ 1.5 mol% or> 0.20 mol% and ⁇ 1.0 mol%, or> 0.30 mol% or > 0.40 mol% and
• the aforementioned values for Sg ⁇ S are usually accompanied by molar propene conversions (based on a single pass of the reaction gas mixture through all reaction stages) U Pen which is> 95 mol% or> 96 mol% %, or> 97 mol%, preferably> 98 mol% (in each case based on the starting propene amount).
• U Pen which is> 95 mol% or> 96 mol% %, or> 97 mol%, preferably> 98 mol% (in each case based on the starting propene amount).
• the S tot values accompanying, propene, or ⁇ 99 mol% and ⁇ 98.5 mol% will amount.
• the aforementioned values for S tot are usually accompanied by (based on the molar amount of propene converted) selectivities of the acrylic acid formation S AS P ⁇ ⁇ , which are> 80 mol%, or> 85 mol%, or> 90 mol -% or> 92 mol%, - often 93 mol% or> 94 mol%, preferably> 95 mol% or> 96 mol%.
• the above-mentioned values for S AS Pen are frequently at values ⁇ 99 mol%, or
• Each of the aforementioned values for U Pen can be associated with the aforementioned values for S AS P ⁇ n .
• the aforementioned values for S tot are normal. accompanied by molar propane conversions (based on a single pass of the reaction gas mixture through all reaction stages) U Pan which are> 20 mol%, or> 25 mol%, or> 30 mol%, or> 35 mol%, or> 40 mol -%, or> 45 mol%, or> 50 mol%, or> 55 mol%, or> 60 mol%, or> 65 mol%, or> 70 mol%, or> 75 mol% %, or> 80 mol%, or> 85 mol%.
• the above-mentioned values for U Pan will often be ⁇ 95 mol%, in many cases ⁇ 90 mol%.
• the above-mentioned values for S tot are usually accompanied by (based on the molar amount of propane converted) selectivities of acrylic acid formation S AS p on , which are> 50 mol%, or> 55 mol%, or> 60 mol -%, preferably> 65 mol% and particularly preferably> 70 mol% or> 75 mol%.
• the aforementioned values for S AS Pan will often be values ⁇ 95 mol%, or ⁇ 90 mol% or ⁇ 85 mol%.
• the process according to the invention can be carried out in a particularly simple manner in such a way that first a conventional process, as described in the prior art, of a heterogeneously catalyzed partial oxidation of at least one C 3 hydrocarbon precursor compound (can also be a mixture of propane and propene) Acrylic acid is carried out (main reaction).
• a conventional process as described in the prior art, of a heterogeneously catalyzed partial oxidation of at least one C 3 hydrocarbon precursor compound (can also be a mixture of propane and propene) Acrylic acid is carried out (main reaction).
• the product gas mixture which is obtainable and has a comparatively increased secondary component content (for example a secondary component formation> 1.7 mol%) is then, optionally after addition of inert gas (for example N 2 , CO 2 , water vapor or any of their mixtures) or of molecular oxygen or of a mixture of molecular oxygen and inert gas, in a post-reaction stage at an elevated temperature through a catalyst feed in such a way that the acrylic acid contained in the product gas mixture remains essentially unchanged, while the secondary components are at least partially burned to carbon oxides and water, which increases the overall selectivity of the secondary component formation (S tot ) over the entire process (preferably according to the invention, S tot (in mol%) increases by at least 0.3, preferably by at least 0.5, particularly preferably by at least 0.8 and very particularly preferably by at least 1 percentage point or more ab) without the selectives to significantly impair the quality of acrylic acid formation (according to the invention, the selectivity of acrylic acid formation (S AS Pen or S AS Pan , in each
• the selectivity of the acrylic acid formation even increases by up to 1, or by up to 0.5 or 0.3 percentage points.
• the aforementioned percentage point changes of Sg ⁇ s and S AS Pen or S AS Pan can be implemented according to the invention in any combination.
• the overall selectivity of the formation of secondary components S ges Hegt in the main reaction usually at values> 1, 7 mol% or> 1, 8 mol% or 1, 9 mol%.
• the aforementioned main reaction values for S ges are usually accompanied-propene main reaction U Pe ⁇ of molar that> 95 mol%, or> 96 mol%, preferably> 98 mol % (in each case based on the initial propene quantity).
• the propene conversion accompanying the S tot values of the main reaction as described above will be ⁇ 99.5 mol%, or ⁇ 99 mol% or ⁇ 98.5 mol%.
• the aforementioned values for S tot are usually accompanied by (based on the molar amount of propene converted in the main reaction) selectivities of acrylic acid formation S AS Pen which are> 80 mol% or> 85 mol%, or> 90 mol%, or> 92 mol%, often> 93 mol%, or> 94 mol%, preferably> 95 mol% or> 96 mol%.
• the aforementioned are common Values for S AS Pen of the main reaction are values ⁇ 99 mol%, or ⁇ 98 mol%, or ⁇ 97 mol%.
• the above-mentioned values for S AS Pen of the main reaction can be accompanied by any of the above-mentioned values for U Pen .
• the aforementioned main reaction values for S tot in the main reaction are normally accompanied by molar propane conversions U Pan which are> 20 mol%, or> 25 mol%, or> 30 mol -%, or ⁇ 35 mol%, or> 40 mol%, or> 45 mol%, or> 50 mol%, or> 55 mol%, or> 60 mol%, or> 65 mol% %, or> 70 mol%, or> 75 mol%, or> 80 mol%, or> 85 mol%.
• the above-mentioned values for U Pan of the main reaction are frequently ⁇ 95 mol%, many times
• the above-mentioned values for S tot of the main reaction are generally accompanied by (based on the molar amount of propane reacted in the main reaction) selectivities of acrylic acid formation S AS Pa ⁇ which are> 50 mol%, or> 55 mol%, or> 60 mol%, preferably> 65 mol% and particularly preferably> 70 mol% or> 75 mol%.
• selectivities of acrylic acid formation S AS Pa ⁇ which are> 50 mol%, or> 55 mol%, or> 60 mol%, preferably> 65 mol% and particularly preferably> 70 mol% or> 75 mol%.
• the aforementioned values for S AS Pan of the main reaction will be values ⁇ 95 mol%, or ⁇ 90 mol% or ⁇ 85 mol%.
• the active composition of catalysts of such a post-reaction stage are, for example, multimetal oxide compositions of the general formula I
• X 1 W, Nb, Ta, Cr and / or Ce, preferably W,
• X 2 Cu, Ni, Co, Fe, Mn and / or Zn, preferably Cu and / or Fe,
• X 5 one or more alkaline earth metals
• X 6 Si, Al, Ti and / or Zr
• X 7 Pd, Pt, Ag, Rh and / or Ir, preferably Pd
• X 1 W, Nb and / or Cr, preferably W,
• X 5 Ca, Sr, and / or Ba
• X 6 Si, Al and / or Ti
• X 7 Pd, Pt, Ag, Rh and / or Ir, preferably Pd.
• a 1.5 to 5
• b 0.5 to 2
• c 0.5 to 5, preferably 2 to 5
• d 0 to 2, preferably 0.5 to 2
• e 0 to 2
• f 0 to 4
• g 0 to 40
• h 0 to 1, preferably> 0 to 1 and particularly preferably 0.01 to 0.05
• n a number which is different from the value and frequency of those other than oxygen Elements in I is determined.
• particularly preferred multimetal oxides I are those of the general formula II, Mo 12 V a .Y 1 b Y 2 c ⁇ 3 d ⁇ 4 e .Y 5 f Y 6 g .O n , (II),
• Y 3 Sb and / or Bi
• Y 4 Ca and / or Sr
• Y 6 Pd, Pt, Ag, Rh and / or Ir, preferably Pd,
• n ' a number which is determined by the valency and frequency of the elements other than oxygen in II.
• multimetal oxide active materials I can be prepared in a simple manner by generating an intimate, preferably finely divided, dry mixture of suitable stoichiometry from suitable sources of their elemental constituents and calcining them at temperatures of 350 to 600 ° C.
• the calcination can take place both under inert gas and under an oxidative atmosphere such as air (mixture of inert gas and oxygen) and also under a reducing atmosphere (eg mixtures of inert gas and reducing gases such as H 2 , NH 3 , CO, methane and / or Acrolein or the reducing gases mentioned.
• the calcination time can range from a few minutes to a few hours and usually decreases with temperature.
• the calcination (and the overall catalyst preparation) is preferably carried out as described in DE-A 10360057 or DE-A 10360058.
• Suitable sources for the elementary constituents of the multimetal oxide active materials I are those compounds which are already oxides and / or those compounds which can be converted into oxides by heating, at least in the presence of oxygen.
• the intimate mixing of the starting compounds for the production of multimetal oxide compositions I can be carried out in dry or in wet form. If it is carried out in dry form, the starting compounds are expediently used as finely divided powders and, after mixing and optionally compacting, are subjected to the calcination. However, the intimate mixing is preferably carried out in wet form.
• the starting compounds are mixed together in the form of an aqueous solution and / or suspension.
• Particularly intimate dry mixtures are obtained in the mixing process described if only sources of the elementary constituents present in dissolved form are used. Water is preferably used as the solvent.
• the aqueous composition obtained is then dried, the drying process preferably being carried out by spray drying the aqueous mixture at exit temperatures of 100 to 150 ° C.
• the resulting multimetal oxide materials I can be used for the process according to the invention both in powder form and in the form of certain catalyst geometries, the shaping being carried out before or after the final calcination can be done.
• solid catalysts can be produced from the powder form of the active composition or its uncalcined precursor composition by compression to the desired catalyst geometry (for example by tableting, extrusion or extrusion), where appropriate auxiliaries such as graphite or stearic acid as lubricants and / or shaping auxiliaries and reinforcing agents such as glass microfibers, Asbestos, silicon carbide or potassium titanate can be added.
• Suitable full catalyst geometries are, for example, full cylinders or hollow cylinders with an outer diameter and a length of 2 to 10 mm.
• a wall thickness of 1 to 3 mm is appropriate.
• the full catalytic converter can also have a spherical geometry, the spherical diameter being 2 to 10 mm.
• the powdery active composition or its powdery, not yet calcined, precursor composition can also be shaped by application to preformed inert catalyst supports.
• the coating of the support bodies for the production of the coated catalysts is usually carried out in a suitable rotatable container, as is e.g. is known from DE-A..2909671, EP-A 293859 or from EP-A 714700.
• the powder mass to be applied is expediently moistened and, after application, e.g. using hot air, dried again.
• the layer thickness of the powder composition applied to the carrier body is expediently selected in the range from 10 to 1000 ⁇ m *, preferably in the range from 50 to 500 ⁇ m and particularly preferably in the range from 150 to 250 ⁇ m.
• carrier materials Conventional porous or non-porous aluminum oxides, silicon dioxide, thorium dioxide, zirconium dioxide, silicon carbide or silicates such as magnesium or aluminum silicate can be used as carrier materials.
• the carrier bodies can have a regular or irregular shape, with regularly shaped carrier bodies with a clearly formed surface roughness, e.g. Balls or hollow cylinders with a split layer are preferred. It is suitable to use essentially non-porous, surface-roughened (cf. DE-A 2135620) spherical supports made of steatite (in particular of steatite C220 from CeramTec), the diameter of which is 1 to 8 mm, preferably 4 to 5 mm.
• corresponding cylinders as carrier bodies, the length of which is 2 to 10 mm and the outside diameter is 4 to 10 mm.
• the wall thickness is also usually 1 to 4 mm.
• Annular support bodies to be used preferably have a length of 2 to 6 mm, an outer diameter of 4 to 8 mm and a wall thickness of 1 to 2 mm.
• Rings of geometry 7 mm x 3 mm x 4 mm are particularly suitable as carrier bodies.
• the fineness of the catalytically active oxide materials to be applied to the surface of the carrier body becomes naturally adapted to the desired shell thickness (cf. EP-A 714700, DE-A 10360057, DE-A 10360058).
• sources for the production of multimetal oxides I in addition to the element oxides, halides, nitrates, formates, oxalates, citrates, acetates, carbonates, amine complexes, ammonium salts and / or hydroxides of the desired elemental constituents (compounds such as NH 4 OH , (NH 4 ) 2 CO 3 , NH NO 3 , NH 4 CHO 2 , CH 3 COOH, NH CH 3 CO 2 and / or ammonium oxalate, which can decompose and / or be decomposed into gaseous compounds at the latest during later calcination can also be incorporated into the intimate dry mix).
• compounds such as NH 4 OH , (NH 4 ) 2 CO 3 , NH NO 3 , NH 4 CHO 2 , CH 3 COOH, NH CH 3 CO 2 and / or ammonium oxalate which can decompose and / or be decomposed into gaseous compounds at
• multimetal oxide materials can also be pre-formed from elemental parts, which are then used as element sources for the production of multimetal oxides I.
• Corresponding manufacturing processes are described, for example, in EP-A 668104, DE-A 19736105, DE-A 10046928, DE-A 19740493 and DE-A 19528646.
• FeSb O 6 can be considered as such a partial multimetal oxide mass.
• multimetal oxide compositions of the general formula III also come as active compositions of catalysts of an after-reaction stage according to the invention.
• M 1 at least one of the elements from the group comprising Te and Sb;
• M 2 at least one of the elements from the group comprising Nb, Ti, W, Ta and Ce
• M 3 at least one of the elements from the group comprising Pb, Ni, Co, Bi, Pd, Ag, Pt, Cu, Au, Ga, Zn, Sn, In, Re, Ir, Sm, Sc, Y, Pr, Nd and Tb;
• n a number determined by the valency and frequency which is determined from elements other than oxygen in III
• the diffraction reflex h is the most intense within the X-ray diffractogram and has a half-value width of at most 0.5 °
• the intensity Pj of the diffraction reflex i and the intensity P k of the diffraction reflex k satisfy the relationship 0.20 ⁇ R ⁇ 0.85, in the R by the formula is defined intensity ratio
• the half-width of the diffraction reflex i and the diffraction reflex k is each ⁇ 1 °.
• R ⁇ 0.85 particularly preferably 0.65 ⁇ R ⁇ 0.85, even more preferably 0.67 ⁇ .
• the X-ray diffractogram of multimetal oxide materials (III) to be used according to the invention generally also contains further diffraction reflections, the apex of which lies at the following diffraction angles (2 ⁇ ):
• the X-ray diffractogram of multimetal oxide masses (III) also contains the reflections 29.2 ⁇ 0.4 ° (m) and 35.4 ⁇ 0.4 ° (n) (peak positions).
• the intensity 100 is assigned to the diffraction reflex h, it is advantageous according to the invention if the diffraction reflexes i, I, m, n, o, p, q have the following intensities in the same intensity scale:
• Multimetal oxide compositions (III) to be used according to the invention is in many cases. up to 40 m 2 / g, often 11 or 12 to 40 m 2 / g and often 15 or 20 to 40 or 30 m 2 / g. (determined according to the BET method, nitrogen).
• the stoichiometric coefficient a of multimetal oxide compositions (III) suitable according to the invention is independent of the preferred ranges for the other stoichiometric coefficients of the multimetal oxide compositions (III), 0.05 to 0.6, particularly preferably 0.1 to 0.6 or 0, 5th
• the stoichiometric coefficient b is preferably 0.01 to 1, and particularly preferably 0.01 or 0.1 to 0.5 or 0.4.
• the stoichiometric coefficient c of the multimetal oxide compositions (IM) to be used according to the invention is advantageously 0.01 to 1 and particularly preferably 0.01 or 0.1 to 0.5 or 0.4.
• a very particularly preferred range for the stoichiometric coefficient c which, regardless of the preferred ranges for the other stoichiometric coefficients of the multimetal oxide materials (III) to be used according to the invention, can be combined with all other preferred ranges in this document, is the range 0.05 to 0.
• the stoichiometric coefficient d of multimetal oxide compositions (III) suitable according to the invention is 0.00005 or 0.0005 to 0.5, particularly preferably 0.001 to 0.5 , often 0.002 to 0.3 and often 0.005 or 0.01 to 0.1.
• Multimetal oxide materials (III) whose stoichiometric coefficients a, b, c and d are simultaneously in the following grid are particularly favorable for the process according to the invention:
• Multimetal oxide compositions (III) according to the invention are particularly favorable, their stoichiometric coefficients a, b, c and d simultaneously lying in the following grid:
• M 1 is preferably Te ;
• M 2 is at least 50 mol% of its total amount of Nb and very particularly preferably when M 2 is at least 75 mol% of its total amount or 100 mol% of its total amount of Nb.
• M 3 comprises at least one element from the group comprising Ni, Co, Bi, Pd, Ag, Au, Pb and Ga or at least one element from the group Ni, Co, Pd and Bi is.
• M 2 contains at least 50 mol% of its total amount, or at least 75 mol%, or 100 mol% Nb and M 3 contains at least one element from the group comprising Ni, Co, Bi, Pd, Ag, Au, Pb and Ga.
• M 2 contains at least 50 mol%, or at least 75 mol%, or 100 mol% of its total amount of Nb and M 3 at least one element from the group comprising Ni, Co, Pd and Bi is.
• M 1 Te
• M 2 Nb
• M 3 at least one element from the group comprising Ni, Co and Pd.
• Manufacturing processes for multimetal oxide active materials III can be found in the prior art. These include in particular DE-A 10122027, DE-A 10119933, DE-A 10033121, EP-A 1192987, DE-A 10029338, JP-A 2000-143244, EP-A 962253, EP- A 895809, DE-A 19835247, WO 00/29105, WO 00/29106, EP-A 529853 and EP-A 608838 (in all exemplary embodiments of the latter two documents, spray drying is to be used as the drying method; for example with a Inlet temperature of 300 to 350 ° C and an outlet temperature of 100 to 150 ° C; countercurrent or cocurrent).
• JP-A 7- 232071 also discloses a process for producing i-phase multimetal oxide materials.
• an intimate, preferably finely divided, dry mixture is generated from suitable sources of the elementary constituents of the multimetal oxide composition and this is thermally treated at temperatures of 350 to 700 ° C. or 400 to 650 ° C. or 400 to 600 ° C.
• the thermal treatment can take place both under oxidizing, reducing and also under an inert atmosphere.
• the oxidizing atmosphere is, for example, air with molecular air enriched with oxygen or air de-oxygenated.
• the thermal treatment is preferably carried out under an inert atmosphere, ie, for example under molecular nitrogen and / or noble gas.
• the thermal treatment is usually carried out at normal pressure (1 atm).
• the thermal treatment can of course also be carried out under vacuum or under positive pressure.
• the thermal treatment takes place in a gaseous atmosphere, it can both stand and flow. It preferably flows. In total, the thermal treatment can take up to 24 hours or more.
• the thermal treatment can also be carried out in such a way that the catalyst precursor tablets first (if necessary after pulverization) tablets before their thermal treatment (optionally with the addition of 0.5 to 4 or 2% by weight of finely divided graphite), then thermally treated and subsequently again is split.
• the intimate mixing of the starting compounds can take place in dry or in wet form.
• the starting compounds are expediently used as finely divided powders and, after mixing and optionally compacting, are subjected to the calcination (thermal treatment).
• the intimate mixing is preferably carried out in wet form.
• the starting compounds are usually mixed with one another in the form of an aqueous solution (if appropriate with the use of complexing agents; see, for example, DE-A 10145958) and / or suspension.
• the aqueous mass is then dried and, after drying, calcined.
• the aqueous mass is expediently an aqueous solution or an aqueous suspension.
• the drying process is preferably carried out immediately after the preparation of the aqueous mixture (in particular in the case of an aqueous solution; see, for example, JP-A 7-315842) and by spray drying (the outlet temperatures are generally 100 to 150 ° C .; spray drying can be carried out in cocurrent or in countercurrent), which requires a particularly intimate dry mixture, especially when the aqueous composition to be spray-dried is an aqueous solution or suspension. However, it can also be dried by evaporation in a vacuum, by freeze-drying or by conventional evaporation.
• Suitable sources for the elementary constituents in carrying out the above-described preparation of, for example, i- / k-phase crystal multi-metal oxide materials are all those which are capable of forming oxides and / or hydroxides when heated (if appropriate in air). It goes without saying that oxides and / or hydroxides of the elemental constituents can also be used as the starting compounds or used exclusively. That is to say, in particular, all of the starting compounds mentioned in the documents of the acknowledged prior art, to which DE-A 10254279 belongs, can be considered.
• the e.g. i- / k-phase mixed crystal multimetal oxide masses (pure i-phase multimetal oxides are obtained randomly according to the procedure described) can then, as described, be washed (e.g. according to DE-A 10254279) in suitable i-phase multimetal oxides (III) according to the invention. be transferred. • -
• solutions for example aqueous
• elements M 3 for example by spraying
• caicinized preferably in an inert gas stream
• pre-decomposition in air is preferably avoided here.
• organic compounds for example acetates or acetylacetonates
• the multimetal oxides (III) obtainable as described can be shaped as such [for example as a powder or after tabletting the powder (often with addition of 0.5 to 2% by weight of finely divided graphite) and subsequent splitting to form chippings) or else into shaped bodies can be used for the after-reaction stage according to the invention.
• the shaping into shaped bodies can be carried out, for example, by application to a carrier body, as described in DE-A 10118814 or PCT / EP / 02/04073 or DE-A 10051419.
• aluminum oxide, silicon dioxide, silicates such as clay, kaolin, steatite (preferably with a low water-soluble alkali content), pumice, aluminum silicate and magnesium silicate, silicon carbide, zirconium dioxide and thorium dioxide are particularly suitable as material for the carrier bodies.
• Steatite C220 from CeramTec is preferred, with support bodies with a core that is essentially free of pores and only a porous shell being particularly advantageous.
• the surface of the carrier body can be both smooth and rough.
• the surface of the carrier body is advantageously rough, since an increased surface roughness generally results in an increased adhesive strength of the applied active material shell (see e.g. DE-A 2135620).
• the surface roughness R z of the support body is often in the range from 5 to 200 ⁇ m, often in the range from 20 to 100 ⁇ m (determined in accordance with DIN 4768 Sheet 1 using a "Hommel Tester for DIN-ISO surface measurement parameters" from Hommelwerke, DE).
• the carrier material can be porous or non-porous.
• the carrier material is expedient! non-porous (total volume of the pores related to the volume of the carrier body,. pers ⁇ 1% by volume).
• Support material with a non-porous core and a porous shell (cf. DE-A 2135620) is preferred.
• the thickness of active oxide mass III shells located on coated catalysts to be used according to the invention is usually from 10 to 1000 ⁇ m. However, it can also be 50 to 700 ⁇ m, 100 to 600 ⁇ m or 150 to 400 ⁇ m. Possible shell thicknesses are also 10 to 500 ⁇ m, 100 to 500 ⁇ m or 150 to 300 ⁇ m.
• any geometries of the carrier bodies can be considered for the method according to the invention.
• Their longest dimension is usually 1 to 10 mm.
• balls or cylinders, in particular hollow cylinders are preferably used as carrier bodies.
• Favorable diameters for carrier balls are 1.5 to 4 mm.
• cylinders are used as carrier bodies, their length is preferably 2 to 10 mm and their outside diameter is preferably 4 to 10 mm.
• the wall thickness is also usually 1 to 4 mm.
• Annular carrier bodies suitable according to the invention can also have a length of 3 to 6 mm, an outer diameter of 4 to 8 mm and a wall thickness of 1 to 2 mm.
• a carrier ring geometry of 7 mm x 3 mm x 4 mm or 5 mm x 3 mm x 2 mm (outer diameter x length x inner diameter) is also possible.
• the preparation of such coated catalysts to be used according to the invention can be carried out in a very simple manner by forming oxide compositions of the general formula (III) to be used according to the invention, converting them into a finely divided form and finally applying them to the surface of the support body with the aid of a liquid binder.
• the surface of the carrier body is moistened in the simplest manner with the liquid binder, and a layer of the active composition is attached to the moistened surface by contacting it with finely divided active oxide composition of the general formula (III).
• the coated carrier body is dried.
• the process can be repeated periodically to achieve an increased layer thickness. In this case the coated base body becomes the new "support body” etc.
• the fineness of the catalytically active oxide composition of the general formula (III) to be applied to the surface of the support body is of course adapted to the desired shell thickness.
• the shell thickness range from 100 to 500 ⁇ m, z. B. those active mass powders, of which at least 50% of the total number of powder particles pass a sieve with a mesh size of 1 to 20 ⁇ m and whose numerical proportion of particles with a longest dimension above 50 ⁇ m is less than 10%.
• the distribution of the longest dimensions of the powder particles corresponds to a Gaussian distribution due to the manufacturing process.
• the grain size distribution is often as follows:
• D diameter of the grain
• x the percentage of the grains whose diameter is> D
• y the percentage of grains whose diameter is ⁇ D.
• the substrates to be coated bodies are rotated in a preferably inclined (the angle of inclination is usually> 0 ° and ⁇ 90 °, usually> 30 ° and ⁇ 90 °; the angle of inclination is the angle of the central axis of the rotating container against the horizontal) (e.g. rotating plate or Coating drum) submitted.
• the rotating rotary container leads the z.
• spherical or cylindrical carrier body under two consecutively arranged metering devices.
• the first of the two metering devices suitably corresponds to a nozzle (for example an atomizing nozzle operated with compressed air) through which the carrier bodies rolling in the rotating turntable are sprayed with the liquid binder and moistened in a controlled manner.
• the second metering device is located outside the atomizing cone of the sprayed-in liquid binder and serves to supply the finely divided oxidic active material (for example via a shaking channel or a powder screw).
• the controlled moistened carrier balls take up the supplied active mass powder, which is caused by the rolling movement on the outer surface of the z.
• the base coating coated in this way again passes through the spray nozzles in the course of the subsequent rotation, is moistened in a controlled manner in order to be able to take up a further layer of finely divided oxidic active composition, etc. (intermediate drying is generally not necessary). Fine-particle oxidic active material and liquid binder are usually fed in continuously and simultaneously.
• the removal of the liquid binder can be done after the coating z. B. by the action of hot gases such as N 2 or air.
• hot gases such as N 2 or air.
• the coating method described brings about both a fully satisfactory adhesion of the successive layers to one another and also the base layer on the surface of the carrier body.
• the moistening of the surface of the carrier body to be coated is carried out in a controlled manner.
• the carrier surface is expediently moistened in such a way that, although it has adsorbed liquid binder, no liquid phase as such appears visually on the carrier surface. If the surface of the carrier body is too moist, the finely divided catalytically active oxide mass agglomerates into separate agglomerates instead of being drawn onto the surface. Detailed information on this can be found in DE-A 2909671 and in DE-A 10051419.
• the aforementioned final removal of the liquid binder used can be carried out in a controlled manner, for. B. by evaporation and / or sublimation. In the simplest case, this can be done by exposure to hot gases of the appropriate temperature (often 50 to 300, often 150 ° C). By exposure to However, only pre-drying can be effected with gases. The final drying can then take place, for example, in a drying oven of any type (for example a belt dryer) or in the reactor. The acting temperature should not be above the calcination temperature used to produce the oxidic active material. Of course, drying can also be carried out exclusively in a drying oven.
• binders for the coating process water, monohydric alcohols such as ethanol, methanol, propanol and butanol, polyhydric alcohols such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol or glycerol, mono- or polyvalent organic carboxylic acids such as propionic acid, oxalic acid, malonic acid, glutaric acid or maleic acid, amino alcohols such as ethanolamine or diethanoiamine and mono- or polyvalent organic amides such as formamide.
• monohydric alcohols such as ethanol, methanol, propanol and butanol
• polyhydric alcohols such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol or glycerol
• mono- or polyvalent organic carboxylic acids such as propionic acid, oxalic acid, malonic acid, glutaric acid or maleic acid
• amino alcohols such as ethanol
• binders are also solutions consisting of 20 to 90% by weight of water and 10 to 80% by weight of an organic compound dissolved in water, whose boiling point or sublimation temperature at normal pressure (1 atm)> 100 ° C., preferably> 150 ° C, is.
• the organic compound is advantageously selected from the above list of possible organic binders.
• the organic proportion of the aforementioned aqueous binder solutions is preferably 10 to 50 and particularly preferably 20 to 30% by weight.
• Monosaccharides and oligosaccharides such as glucose, fructose, sucrose or lactose as well as polyethylene oxides and polyacrylates are also suitable as organic components.
• the shell catalysts suitable according to the invention can be produced not only by applying the finished, finely ground active oxide compositions of the general formula (III) to the moistened surface of the carrier body.
• the active oxide mass it is also possible to apply a finely divided precursor mass to the moistened carrier surface (using the same coating methods and binders) and to carry out the calcination after drying the coated carrier body (carrier bodies can also be impregnated with a precursor solution, subsequently dried and then caicinized). Finally, if necessary, the phases different from the i phase can be washed out.
• a finely divided precursor mass z. B the mass which can be obtained by first generating an intimate, preferably finely divided, dry mixture from the sources of the elemental constituents of the desired active oxide mass of the general formula (III) (for example by spray drying an aqueous suspension or solution of the sources) and this finely divided corner mixture (optionally after tableting with addition of 0.5 to 2% by weight of finely divided graphite) at a temperature of 150 to 350 ° C., preferably 250 to 350 ° C. under an oxidizing (oxygen-containing) atmosphere (e.g. under Air) thermally treated (a few hours) and then subjected to grinding if necessary.
• an oxidizing (oxygen-containing) atmosphere e.g. under Air
• caicination is then carried out, preferably under an inert gas atmosphere (all other atmospheres are also possible) at temperatures of 360 to 700 ° C. or 400 to 650 ° C. or 400 to 600 ° C.
• the shaping of multimetal oxide compositions (III) which can be used according to the invention can also be carried out by extrusion and / or tableting both of finely divided multimetal oxide composition (III) and of finely divided precursor mass of a multimetal oxide composition (III) (if necessary, washing out of the i-phase in different phases).
• Balls, solid cylinders and hollow cylinders can be considered as geometries.
• the longest dimension of the aforementioned geometries is usually 1 to 10 mm.
• their length is preferably 2 to 10 mm and their outside diameter is preferably 4 to 10 mm.
• the wall thickness is usually 1 to 4 mm.
• Annular unsupported catalysts suitable according to the invention can also have a length of 3 to 6 mm, an outer diameter of 4 to 8 mm and a wall thickness of 1 to 2 mm.
• a full catalyst ring geometry of 7 mm x 3 mm x 4 mm or 5 mm x 3 mm x 2 mm (outer diameter x length x inner diameter) is also possible.
• the definition of the intensity of a diffraction reflex in the X-ray diffractogram relates to the definition set out in DE-A 19835247 and in DE-A 10051419 and DE-A 10046672.
• A denotes the vertex of a reflex 1 and denotes B 1 in the line of the X-ray diffractogram when viewed along the intensity axis perpendicular to the 2 Achse axis the closest pronounced minimum (minima showing reflex shoulders are not taken into account) to the left of the vertex A 1 and B 2 in a corresponding manner
• the expression minimum means a point at which the gradient gradient of a tangent applied to the curve in a base region of the reflex 1 changes from a negative value to a positive value, or a point at which the gradient gradient goes towards zero, whereby for the definition of the gradient gradient, the coordinates of the 2 ⁇ axis and the intensity axis are used.
• the full width at half maximum is correspondingly the length of the straight section which results between the two intersection points H 1 and H 2 when a line parallel to the 2 ⁇ axis is drawn in the middle of the straight section A 1 C 1 , where H 1 , H 2 mean the first intersection of these parallels with the line of the X-ray diffractogram as defined above on the left and right of A 1 .
• FIG. 6 in DE-A 10046672 also shows an example of how the half-width and intensity are determined.
• multimetal oxide compositions (III) to be used according to the invention can also be used with finely divided, e.g. colloidal, materials such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, niobium oxide, dilute form as catalytic active materials for the post-reaction stage according to the invention.
• finely divided, e.g. colloidal, materials such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, niobium oxide, dilute form as catalytic active materials for the post-reaction stage according to the invention.
• the dilution mass ratio can be up to 9 (thinner): 1 (active mass). That is, possible dilution mass ratios are e.g. 6 (thinner): 1 (active composition) and 3 (thinner): 1 (active composition).
• the thinners can be incorporated before and / or after the calcination, usually even before drying.
• the thinner must be selected so that it is essentially retained in the fluid medium or during calcination. This is e.g. in the case of oxides fired at correspondingly high temperatures, as a rule.
• the postreaction step according to the invention can also be carried out in the catalyst Fixed bed, moving bed or fluidized bed.
• the conventional heterogeneously catalyzed partial oxidation (the main reaction) is carried out both in the one-stage as well as in the two-stage embodiment are preferred in tube bundle reactors, as are described, for example, in the documents DE-A 10246119 and DE-A 10245585.
• a heat exchange medium (usually a salt bath) is passed around the catalyst tubes.
• a plurality of mutually independent heat exchange means can also be guided around the associated contact tube sections along the contact tubes of a tube bundle reactor in a spatially successive manner. In this case we speak of a multi-temperature zone reactor.
• the post-reaction stage according to the invention can now take place both in a separate post-reactor which is spatially downstream of the conventional partial oxidation and in an integrated reactor in the main reaction.
• all are suitable for the post-reactor type which are also suitable for the main reaction.
• the post-catalyst bed preferably occupies a tube section in the contact tubes which has its own independent temperature zone. Based on the total length of the catalyst bed for the main and post-reaction, the post-reaction bed length should be 10 to 30%.
• the product gas mixture of the main reaction is to be supplemented with molecular oxygen or a mixture of molecular oxygen and inert gas beforehand, the alternative variant in which the post-catalysts are located in a spatially separate downstream reactor is advantageous.
• This can also be a tube bundle reactor, but also a fluidized bed or moving bed reactor.
• a simple shaft furnace reactor as a fixed bed reactor is sufficient, through which the hot product gas mixture of the main reaction, if necessary after intermediate cooling, has flowed axially and / or radially.
• this is a single reaction tube, the inside diameter of which is 0.1 to 10 m, possibly also 0.5 to 5 m, and in which the fixed catalyst bed is applied to a carrier device (e.g. a grating).
• the reaction tube charged with catalyst which is thermally insulated in adiabatic operation, is flowed through axially with the hot reaction gas mixture containing the secondary components and excess molecular oxygen.
• the catalyst geometry can be both spherical or cylindrical or annular. In a suitable manner according to the invention, however, the catalyst can also be used in split form in the above case.
• the post-reactor can e.g. consist of two cylindrical grids located in a casing, placed one inside the other, and the post-catalyst bed arranged in its annular gap. In the adiabatic case, the jacket would again be thermally insulated.
• the recommended Mach catalysts are generally also suitable for a partial oxidation of acrolein to acrylic acid (in this regard, they often even have a particularly high activity)
• the acrolein content in the product gas mixture of the main reaction is also reduced in the course of the post-reaction stage to be used as described.
• the content of acetic acid is usually also reduced.
• the reaction temperature in the post-reaction stage is advantageously chosen from 200 to 300 ° C., frequently from 220 to 290 ° C. and particularly advantageously from 230 to 250 ° C.
• the reaction pressure in the post-reaction stage is advantageously 0.5 to 5, usually 1 to 3 atm.
• the loading of the after-reaction catalyst feed with reaction gas mixture is frequently 1500 to 2500 h "1 or up to 4000 h " 1 .
• the oxygen content of the reaction gas mixture fed into the post-reaction stage should therefore be such that it is up to 5 times what is required to completely burn the secondary components contained in the product gas mixture, including the additional components acrolein, CO and acetic acid.
• molecular oxygen is added to the product gas mixture of the main reaction beforehand, this is preferably done in the form of air.
• What has been carried out for the heterogeneously catalyzed partial oxidation of propene to acrylic acid can also be applied in a corresponding manner to the partial oxidation of propane to acrylic acid.
• a secondary component oxidation (secondary component reduction) as described above can in principle be carried out behind each of the reaction stages in order to reduce the overall selectivity of the secondary component education over all reaction stages (total reaction) to press ⁇ 1.5 mol%.
• a level component oxidation connected before the downstream “acrolein to acrylic acid” oxidation stage has a purposeful effect according to the invention. It could also be implemented, for example, in the intermediate cooler that is normally connected between the two oxidation stages by charging it with the required post-catalyst. Alternatively, one can also coat inner surfaces of the intercooler, along which the reaction gas mixture to be cooled is guided, with a post-catalyst.
• such inner surfaces can be the surfaces of the cooling tubes in the case of a shell-and-tube heat exchanger. Frequently. are in the entrance of such cooling pipes e.g. Metal spirals introduced, etc. improve arms transfer.
• the surface of such spirals can expediently also be coated with a post-catalyst. Such coatings are able to counteract coking of the intercooler at the same time. The production of such coatings is e.g. described in DE-A 19839782.
• an after-reaction stage according to the invention can also be connected directly after the stage (for example behind the catalytic dehydrogenation stage according to WO 01/96270) in which propane is converted to propene.
• the stage for example behind the catalytic dehydrogenation stage according to WO 01/96270
• propane is converted to propene.
• multi-element oxides based on VPO oxides for example, have also proven to be inexpensive post-reaction stage catalysts.
• An alternative way of achieving the aim according to the invention is to carry out the process at least in two stages and, after the reaction stage in which propane is formed from propane and / or after the reaction stage in which acrolein is formed from propane, the intermediate formed by separate the secondary components formed and use them in such purified form in the subsequent reaction stage.
• the separation can e.g. as described in the documents WO 01/96270 and DE-A 10213998.
• the advantage of the procedure according to the invention is based on the fact that the separation of the acrylic acid from the product gas mixture can be considerably simplified.
• an absorptive separation of acrylic acid (absorbent can be, for example, water, a high-boiling organic solvent or acrylic acid itself or another liquid) as a result of the reduced tendency to polymerize owing to the reduced content of secondary components instead of in a bottom column are carried out in a simplified manner in cocurrent or countercurrent design in a packed column, for example using Raschig rings. can be filled. Alternatively, the same design can be used with a higher throughput (eg less return in the rectification columns).
• acrylic acid can be used to produce superabsorbers.
• the product gas mixture of the gas phase oxidation can be obtained directly by freezing out on a cold finger or by condensing out, optionally by means of fractional condensation v .
• the process according to the invention can also be used in particular when the heterogeneously catalyzed main partial oxidation involves a two-stage (the first stage essentially leads from propene to acrolein and the second stage essentially leads from acrolein to acrylic acid)
• a fixed catalyst bed in, for example, two reactors connected in series, such as, for example, tube bundle reactors, both the loading of the catalyst (fixed) bed in the first reaction stage with propene and the loading of the catalyst (fixed) bed in the second reaction stage with acrolein in the range> 120 Nl / l / h, or> 130 Nl / l / h, or> 140 Nl / l / h, or> 150 Nl / l / h and ⁇ 300 Nl / l / h, ie it is carried out as a so-called high-load process.
• the method according to the invention can also be used in the aforementioned constellation if the two loads are ⁇
• propene Chemical grade propene of the following specification can also be used as propene:
• propene > 94% by weight propene, ⁇ 6% by weight of propane, ⁇ 0.2% by weight of methane and / or ethane ⁇ 5% by weight of ethylene, ⁇ 1% by weight of acetylene, ⁇ 20% by weight of propadiene and / or propyne, ⁇ 100% by weight ppm cyclopropane, ⁇ 50 ppm ppm butene, ⁇ 50 ppm ppm butadiene, ⁇ 200 ppm ppm C 4 hydrocarbons, ⁇ 10 ppm ppm C> 5 hydrocarbons, ⁇ 2 ppm ppm sulfur-containing compounds (calculated as sulfur) , ⁇ 0.1 ppm by weight of sulfides (calculated as H 2 S), ⁇ 1 ppm by weight of chlorine-containing compounds (calculated as chlorine), ⁇ 1 ppm by weight of chloride (calculated as CI ⁇ ) and ⁇ 3Q. Ppm water.
• the high-load main partial oxidation can be carried out as described in DE-A 10313213 and DE-A 10313208.
• the present method according to the invention is in a corresponding manner also at least a method for producing methacrylic acid by heterogeneously catalyzed partial oxidation.
• a C 4 hydrocarbon precursor compound for example isobutene or isobutane
• isobutene or isobutane can be used.
• the spray drying was carried out in a rotary disc spray tower in countercurrent at a gas inlet temperature of 300 ⁇ 10 ° C and a gas outlet temperature of 100 ⁇ 10 ° C.
• the spray powder obtained (particle size essentially uniform 30 ⁇ m), which had a loss on ignition of 12% by weight (glow in air at 600 ° C. for 3 h), was then pasted with 16.8% by weight (based on the powder) of water in a kneader and by means of an extruder ( Torque: ⁇ 50 Nm) extruded into strands with a diameter of 6 mm. These were cut into 6 cm sections on a 3-zone belt dryer with a residence time of 120 min at temperatures of 90-95 ° C.
• zone 1 and 125 ° C. (zone 2) and 125 ° C. (zone 3) Air dried and then thermally treated at a temperature in the range from 780 to 810 ° C (caicinated; in a rotary kiln with air flow (1.54 m 3 internal volume, 200 Nm 3 air / h)). It is essential for the exact setting of the calcination temperature that it has to be based on the desired phase composition of the caicination product.
• the phases WO 3 (monoclinic) and Bi 2 W 2 O 9 are desired, and the presence of ⁇ -Bi 2 WO 6 (russellite) is undesirable.
• the preparation must be repeated and the cafination temperature within the specified temperature range or increase the residence time at a constant calcination temperature until the reflex disappears.
• the resulting preformed calcium-defined oxide was milled so that the X 50 value (cf..
• a solution A was prepared by dissolving 213 kg of ammonium heptamolybdate tetrahydrate (81.5% by weight of MoO 3 ) at 60 ° C. with stirring in 600 l of water and the resulting solution while maintaining the 60 ° C. and stirring at 0.97 kg a 20 ° C aqueous potassium hydroxide solution (46.8 wt .-% KOH).
• a solution B was prepared by at 116 ° C. in 262.9 kg of an aqueous Co (II) balt nitrate solution (12.4% by weight Co) 116.25 kg of an aqueous iron (III) nitrate solution (14 , 2% by weight of Fe).
• Solution B was then pumped continuously into solution A over a period of 30 minutes while maintaining the 60 ° C. The mixture was then stirred at 60 ° C for 15 minutes. Then 19.16 kg of a silica gel from Dupont of the Ludox type (46.80% by weight SiO 2 , density: 1.36 to 1.42 g / ml, pH 8.5 to 9) were added to the resulting aqueous mixture. 5, alkali content max. 0.5% by weight) and then stirred for a further 15 minutes at 60 ° C.
• Spray drying was carried out in counter-current in a turntable spray tower (gas inlet temperature: 400 ⁇ 10 ° C, gas outlet temperature: 140 ⁇ 5 ° C).
• the result Spray powder had a loss on ignition of approx. 30% by weight (3 hours at 600 ° C. in air) and an essentially uniform grain size of 30 ⁇ m.
• the starting mass 1 was compared with the starting mass 2 in the stoichiometry for a multimetal oxide active mass
• the resulting mixture was then run in a compactor (Hosokawa Bepex GmbH, D-74211 Leingart) from the Jyp compactor K200 / 100 with concave, corrugated smooth rollers (gap width: 2.8 mm, screen width: 1.0 mm, screen size undersize: 400 ⁇ m, nominal press force: 60 kN, screw speed: 65 to 70 revolutions per minute).
• the resulting compact had a hardness of 10 N and an essentially uniform grain size of 400 ⁇ m to 1 mm.
• the compact was then mixed with, based on its weight, a further 2% by weight of the same graphite and then in a Kilian rotary machine (tablet machine) of the R x 73 type, from Kilian, D-50735 Cologne, under a nitrogen atmosphere annular solid catalyst precursor bodies of geometry (outer diameter x length x inner diameter) 5 mm x 3 mm x 2 mm with a lateral compressive strength of 19 N ⁇ 3 N compressed.
• side compressive strength is understood to mean the compressive strength when the annular fully shaped catalyst precursor body is compressed perpendicular to the cylinder surface (i.e., parallel to the surface of the ring opening).
• All side compressive strengths of this document relate to a determination by means of a material testing machine from Zwick GmbH & Co. (D-89079 Ulm) of the type Z 2.5 / TS1S.
• This material testing machine is designed for quasi-static loads with rapid, stationary, swelling or changing course. It is suitable for tensile, compression and bending tests.
• the installed KAF-TC force transducer from AST (D-01307 Dresden) with the production number 03-2038 was calibrated in accordance with DIN EN ISO 7500-1 and could be used for the measuring range 1-500N (relative measurement uncertainty: + 0, 2%). The measurements were carried out with the following parameters:
• Preload 0.5 N.
• Preload speed 10 mm / min.
• Test speed 1.6 mm / min.
• the upper punch was first lowered slowly until just before the cylindrical surface of the annular shaped full catalyst precursor body. Then the upper punch was stopped in order to then be lowered at the significantly slower test speed with minimal pre-force required for further lowering.
• the preload at which the shaped catalyst precursor body shows cracking is the lateral compressive strength (SDF).
• SDF lateral compressive strength
• 1000 g of the shaped catalyst precursor body would first be heated in a muffle furnace through which air flows (60 I internal volume, • 1 l / h air per gram shaped catalyst precursor body) at a heating rate of 180 ° C / h from room temperature (25 ° C) Heated to 190 ° C. This temperature was maintained for 1 h and then increased to 210 ° C at a heating rate of 60 ° C / h. The 210 ° C was again maintained for 1 h before being increased to 230 ° C at a heating rate of 60 ° C / h.
• This temperature was maintained h also 1 "before, was again raised at a heating rate of 60 ° C / h to 265? C.
• the 265 ° C was then also maintained for 1 h.
• the mixture was first cooled to room temperature, essentially completing the decomposition phase.
• the mixture was then heated to 465 ° C. at a heating rate of 180 ° C./h and this calcination temperature was maintained for 4 hours.
• annular unsupported catalysts VKH were obtained from the annular unsupported shaped catalyst precursors.
• the ratio R of apparent mass density to true mass density p (as defined in EP-A 1340538) was 0.66.
• the same annular catalyst was advantageously treated by thermal treatment as in Example 1 of DE-A 10046957 (the bed height in the decomposition (chambers 1 to 4) was 44 mm with a residence time per chamber of 1.46 h and in the calcination (chambers 5 to 8) it advantageously amounted to 130 mm with a residence time of 4.67 h) produced using a belt calciner; the chambers had a base area (with a uniform chamber length of 1.40 m) of 1.29 m 2 (decomposition) and 1.40 m 2 (calcination) and were flowed through from below through the coarse-mesh belt of 75 Nm 3 / h of supply air which were sucked in by means of rotating fans. Within the chambers, the time and place deviation of the temperature from the setpoint was always ⁇ 2 ° C. Otherwise, the procedure was as described in Example 1 of DE-A 10046957.
• FIG. 1 A schematic representation of the rotary kiln is shown in FIG. 1 attached to this document. The following reference numbers refer to this FIG. 1.
• the central element of the rotary kiln is the rotary tube (1). It is 4000 mm long and has an inside diameter of 700 mm. It is made of stainless steel 1.4893 and has a wall thickness of 10 mm.
• lances On the inner wall of the rotary kiln, lances are attached, which have a height of 5 cm and a length of 23.5 cm. They primarily serve the purpose of lifting the material to be treated thermally in the rotary kiln and thereby mixing it.
• the rotary tube rotates freely in a cuboid (2) which has four electrically heated (resistance heating) heating zones, which each follow the same length in the length of the rotary tube, each of which encloses the circumference of the rotary tube furnace.
• Each of the heating zones can heat the corresponding rotary tube section to temperatures between room temperature and 850 ° C.
• the maximum heating output of each heating zone is 30 kW.
• the distance between the electrical heating zone and the outer surface of the rotary tube is approximately 10 cm. At the beginning and at the end, the rotary tube protrudes approx. 30 cm from the cuboid.
• the speed of rotation can be variably set between 0 and 3 revolutions per minute.
• the rotary tube can be turned left as well as right. When turning to the right, the material remains in the rotary tube, when turning to the left, the material is conveyed from the entry (3) to the discharge (4).
• the angle of inclination of the rotary tube to the horizontal can be variably set between 0 ° and 2 °. In discontinuous operation, it is actually 0 °. In continuous operation, the lowest point of the rotary tube is at the material discharge.
• the rotary tube can be rapidly cooled by switching off the electrical heating zones and switching on a fan (5). This sucks in ambient air through holes (6) in the bottom of the cuboid, and conveys it through flaps (7) with a variably adjustable opening.
• the material input is checked via a rotary valve (mass control).
• the material discharge is controlled via the direction of rotation of the rotary tube.
• a material quantity of 250 to 500 kg can be thermally treated. It is usually only in the heated part of the rotary tube.
• thermocouples From a lance (8) lying on the central axis of the rotary tube, a total of three thermocouples (9) lead vertically into the material at intervals of 800 mm. They enable the temperature of the material to be determined.
• the temperature of the material is understood to mean the arithmetic mean of the three thermocouple temperatures.
• the maximum deviation of two measured temperatures is expediently less than 30 ° C., preferably less than 20 ° C., particularly preferably less than 10 ° C. and very particularly preferably less than 5 or 3 ° C.
• Gas streams can be passed through the rotary tube, by means of which the calcining atmosphere or generally the atmosphere of the thermal treatment of the material can be adjusted.
• the heater (10) offers the possibility of heating the gas flow into the rotary tube to the desired temperature in advance of its entry into the rotary tube (for example to the temperature desired for the material in the rotary tube).
• the maximum output of the heater is 1 x 50 kW + 1 x 30 kW.
• the heater (10) can be an indirect heat exchanger, for example.
• such a heater can also be used as a cooler.
• it is an electric heater in which the gas flow is conducted over metal wires heated by current (expediently a CSN instantaneous heater, type 97D / 80 from C. Schniewindt KG, 58805 Neuerade - DE).
• the rotary tube device provides the possibility of partially or completely circulating the gas flow guided through the rotary tube.
• the circular line required for this is movably connected to the rotary tube at the rotary tube inlet and at the rotary tube outlet via ball bearings or via graphite press seals. These compounds are flushed with inert gas (e.g. nitrogen) (sealing gas).
• inert gas e.g. nitrogen
• the rotary tube expediently tapers at its beginning and at its end and protrudes into the tube of the circular line that leads in and out.
• the centrifugal separator separates solid particles suspended in the gas phase by the interaction of centrifugal and gravitational forces; the centrifugal force of the as a spiral vortex rotating gas flow accelerates the sedimentation of the suspended particles).
• the circulating gas flow (24) (the gas circulation) is conveyed by means of a circulating gas compressor (13) (fan) which draws in in the direction of the cyclone and presses in the other direction.
• a circulating gas compressor (13) fan
• the gas pressure is usually above one atmosphere.
• a cover located behind the outlet (cross-sectional tapering by a factor 3, pressure reducer) (15) facilitates the outlet.
• the pressure behind the rotary tube outlet can be regulated via the control valve. This is done in conjunction with a pressure sensor (16) attached behind the rotary tube outlet, the exhaust gas compressor (17) (fan), which draws in towards the control valve, the circulating gas compressor (13) and the fresh gas supply. Relative to the external pressure, the pressure (directly) behind the rotary tube outlet can be set, for example, up to +1.0 mbar above and, for example, down to -1.2 mbar below. That is, the pressure of the gas stream flowing through the rotary tube can be below the ambient pressure of the rotary tube when it leaves the rotary tube.
• connection between the cyclone (12) and the cycle gas compressor (13) is closed according to the three-way valve principle (26) and the gas flow is passed directly into the exhaust gas purification device (23) guided.
• the connection to the exhaust gas cleaning device located behind the cycle gas compressor is also closed in this case according to the three-way valve principle. If the gas flow consists essentially of air, in this case it is sucked in (27) via the cycle gas compressor (13).
• the connection to the cyclone is closed according to the three-way valve principle.
• the gas stream is preferably drawn through the rotary tube, so that the internal pressure of the rotary tube is less than the ambient pressure.
• the pressure behind the rotary tube outlet is advantageously set to -0.2 mbar below the external pressure.
• the pressure behind the rotary tube outlet is advantageously set to -0.8 mbar below the external pressure.
• the slight negative pressure serves the purpose of avoiding contamination of the ambient air with gas mixture from the rotary kiln.
• the ammonia sensor preferably works according to an optical measuring principle (the absorption of light of a certain wavelength correlates proportionally to the ammonia content of the gas) and is expediently a device from Perkin & Eimer of type MCS 100.
• the oxygen sensor is based on the paramagnetic properties of oxygen and is expediently an oximat from Siemens of the type Oxymat MAT SF 7MB1010-2CA01-1AA1-Z.
• Gases such as air, nitrogen, ammonia or other gases can be metered in between the orifice (15) and the heater (10) to the actually recirculated gas fraction (19).
• a base load of nitrogen is often added (20).
• nitrogen / air splitter (21) you can react to the measured value of the oxygen sensor.
• the discharged cycle gas portion (22) (exhaust gas) often contains not completely harmless gases such as NO x , acetic acid, NH 3 , etc.), which is why these are normally separated off in an exhaust gas cleaning device (23).
• the exhaust gas is generally first passed through a scrubbing column (is essentially a column free of internals, which has a separating action before its exit. contains same package; the exhaust gas and aqueous spray mist are conducted in cocurrent and in countercurrent (2 spray nozzles with opposite spray direction).
• a scrubbing column is essentially a column free of internals, which has a separating action before its exit. contains same package; the exhaust gas and aqueous spray mist are conducted in cocurrent and in countercurrent (2 spray nozzles with opposite spray direction).
• the exhaust gas is led into a device which contains a fine dust filter (usually a bundle of bag filters), from the inside of which the penetrated exhaust gas is led away. Then it is finally burned in a muffle.
• a fine dust filter usually a bundle of bag filters
• nitrogen always means nitrogen with a purity> 99% by volume.
• Solution 2 was cooled to 80 ° C. and then solution 1 was stirred into solution 2.
• the resulting mixture was mixed with 130 l of a 25% by weight aqueous NH 3 solution which had a temperature of 25 ° C. With stirring, a clear solution was formed which briefly had a temperature of 65 ° C. and a pH of 8.5. A further 20 l of water at a temperature of 25 ° C. were added to this. The temperature of the resulting solution then rose again to 80 ° C. and this was then sprayed with a spray dryer from Niro-Atomizer (Copenhagen) of type S- 50-N / R spray dried (gas inlet temperature: 350 ° C, gas outlet temperature: 110 ° C).
• Niro-Atomizer Copenhagen
• the spray powder had a particle diameter of 2 to 50 ⁇ m.
• the kneaded material was then emptied into an extruder and, using the extruder (Bonnot Company (Ohio), type: G 103-10 / D7A-572K (6 "extruder W packer), into strands (length: 1-10 cm; diameter 6
• the strands were dried on the belt dryer for 1 hour at a temperature of 120 ° C. (material temperature).
• the thermal treatment was carried out in the rotary kiln according to FIG. 1 described under "B) 1.” and under the following conditions: the thermal treatment was carried out discontinuously with a material quantity of 300 kg, which, as in "B) 2.” had been produced; the angle of inclination of the rotary tube to the horizontal was ⁇ 0 °; the rotary tube rotated clockwise at 1.5 revolutions / min; During the entire thermal treatment, a gas flow of 205 Nm 3 / h was passed through the rotary tube, which (after displacement of the air originally contained) was composed as follows and supplemented by a further 25 Nm 3 / h barrier gas nitrogen at its outlet from the rotary tube has been:
• Nm 3 / h composed of base load nitrogen (20) and gases released in the rotary tube, 25 Nm 3 / h barrier gas nitrogen (11), 30 Nm 3 / h air (splitter (21)); and 70 Nm 3 / h recirculated cycle gas (19).
• the sealing gas nitrogen was supplied at a temperature of 25 ° C.
• the mixture of the other gas streams coming from the heater was fed into the rotary tube at the temperature that the material had in the rotary tube.
• the material temperature was heated from 25 ° C to 300 ° C essentially linearly within 10 h; the material temperature was then heated essentially linearly to 360 ° C within 2 h; subsequently the material temperature was reduced substantially linearly to 350 ° C within 7 h; the material temperature was then increased substantially linearly to 420 ° C.
• the oxygen content of the gas atmosphere in the rotary kiln was 2.99 vol.% In all phases of the thermal treatment. Arithmetically averaged over the total duration of the reductive thermal treatment, the ammonia concentration in the gas atmosphere in the rotary kiln was 4% by volume.
• Fig. 4 shows, depending on the material temperature, the molar amounts of molecular oxygen and ammonia, which were fed into the rotary tube per kg of precursor mass and hour via the thermal treatment with the gas stream. 4. Shape of the multimetal oxide active material
• the catalytically active material obtained under "B) 3.” was ground using a Biplex cross-flow classifying mill (BQ 500) (from Hosokawa-Alpine Augsburg) to a finely divided powder, of which 50% of the powder particles were a sieve with a mesh size of 1 to 10 ⁇ m passed and its proportion of particles with a longest expansion above 50 ⁇ m was less than 1%.
• BQ 500 Biplex cross-flow classifying mill
• 70 kg ring-shaped carrier body (7.1 mm outer diameter, 3.2 mm length, 4.0 mm inner diameter; steatite of the type C220 from CeramTec with a surface roughness R z of 45 ⁇ m and a total pore volume based on the volume of the carrier body ⁇ 1 Vol .-%; see DE-A 2135620) were filled into a coating pan (inclination angle 90 °; Hicoater from Lödige, DE) with an internal volume of 200 l. The coating pan was then set in rotation at 16 rpm. 3.8 to 4.2 liters of an aqueous solution of 75% by weight of water and 25% by weight of glycerol were sprayed onto the support bodies in the course of 25 minutes via a nozzle.
• Ring-shaped coated catalysts SKH1 were obtained, the proportion of active oxide mass, based on the total mass, of 20% by weight.
• the shell thickness viewed both over the surface of a carrier body and over the surface of various carrier bodies, was 170 ⁇ 50 ⁇ m.
• FIG. 5 also shows the pore distribution of the ground active mass powder before it is shaped.
• the pore diameter is plotted in ⁇ m on the abscissa (logarithmic scale).
• the logarithm of the differential contribution in ml / g of the respective pore diameter to the total pore volume is plotted on the right ordinate (curve O).
• the maximum shows the pore diameter with the largest contribution to the total pore volume.
• the integral over the individual contributions of the individual pore diameters to the total pore volume is plotted on the left ordinate in ml / g (curve ⁇ ).
• total pore volume all information in this document on determinations of total pore volumes and of diameter distributions to them Unless otherwise stated, total pore volumes relate to determinations using the mercury porosimetry method using the Auto Pore 9220 device from Micromeritics GmbH, 4040 Neuss, DE (bandwidth 30 A to 0.3 mm); All information in this document on determinations of specific surfaces or micropore volumes refer to determinations according to DIN 66131 (determination of the specific surface of solids by gas adsorption (N 2 ) according to Brunauer-Emmet-Teller (BET))).
• FIG. 6 shows the individual contributions of the individual pore diameters (abscissa, in angstroms, logarithmic scale) in the micropore range to the total pore volume for the active mass powder in ml / g (ordinate) before it is shaped.
• FIG. 7 shows the same as FIG. 5, but for the multimetal oxide active composition subsequently detached from the annular coated catalyst by mechanical scraping (its specific surface area was 12.9 m 2 / g). ; ->
• FIG. 8 shows the same as FIG. 6, but for the multimetal oxide active composition subsequently detached from the annular coated catalyst by mechanical scraping.
• the preparation was carried out as in the preparation of -SKH1, but with the difference that after stirring solution 1 into solution 2 to the resulting mixture before adding the aqueous NH 3 solution, 225 g of solid Pd (NO 3 ) 2 hydrate (manufacturer: Sigma-Aldrich) were stirred in.
• the preparation was carried out as in the production of SKH1, but with the difference that after stirring solution 1 into solution 2 to the resulting mixture before adding the aqueous NH 3 solution, 16.7 kg of solid Fe (NO 3 ) 2 x 9 H 2 O (manufacturer: Riedel-de Haen, 97%) were stirred in.
• solution 1 contained only 12.9 kg of the same copper (II) acetate hydrate; however, the resulting spray powder of the stoichiometry Mo 12 V 3 W 1
• the resulting mixture was compacted (pressed) into hollow cylinders (rings) with a geometry of 16 mm x 2.5 mm x 8 mm (outer diameter x height x inner diameter) such that the resulting lateral compressive strength of the rings was approximately 10 N.
• the rings were dry ground to a grain size ⁇ 100 ⁇ m. 100 g of the ground material were in 1000 ml
• FIG. 10 shows the result of the associated mercury porosimetric examination.
• the abscissa shows the pore diameter in ⁇ m (logarithmic plot).
• the right ordinate shows the integral of the contributions of the individual pore diameters to the total pore volume in ml / g.
• the left ordinate shows the logarithm of the contribution of the individual pore diameter to the total pore volume in ml / g.
• Figure 11 shows the corresponding test result for the ground rings before washing them with nitric acid.
• this active composition was shaped like the active composition of the SKH1 into an annular shell catalyst SKN5.
• the resulting aqueous suspension was 30 min. stirred at 80 ° C. Then it was spray-dried with a spray dryer from Niro-Atomizer (Copenhagen), type S-50-N / R (gas inlet temperature: 315 ° C, gas outlet temperature: 110 ° C, direct current).
• the spray powder had a particle diameter of 2 to 50 ⁇ m.
• 100 kg of the light green spray powder obtained in this way were metered into a kneader from AMK (Aachen mixing and kneading machine factory) of the type VI U 160 (Sigma blades) and kneaded with the addition of 8 l of water (residence time: 30 min, temperature: 40 up to 50 ° C).
• the kneaded material was then emptied into an extruder and, using the extruder (Bonnot Company (Ohio), type: G 103-10 / D7A-572K (6 "extruder W / packer)), into strands (length: 1-10 cm; Diameter: 6 mm).
• the strands were dried for 1 h at a temperature of 120 ° C. (material temperature).
• the dried strands were then dried in under “1.” described rotary kiln thermally treated (caicinated) as follows: the thermal treatment was carried out continuously with a material input of 50 kg / h of stranded material; the angle of inclination of the rotary tube to the horizontal was 2 °; in counterflow to the material, an air flow of 75 Nm 3 / h was passed through the rotary tube, which was supplemented by a total of (2 x 25) 50 Nm 3 / h sealing gas at a temperature of 25 ° C; - The pressure behind the rotary tube outlet was 0.8 mbar below the external pressure; the rotary tube rotated counterclockwise at 1.5 revolutions / min; no cycle gas procedure was used; the first time the extrudates passed through the rotary tube, the temperature of the outer tube of the rotary tube was set to 340 ° C., the air flow was conducted into the rotary tube at a temperature of 20 to 30 ° C.
• the extrudates were then passed through the rotary tube with the same throughput and apart from the following differences under the same conditions: the temperature of the rotary tube wall was set to 790 ° C .; the air flow was heated to a temperature of 400 ° C and led into the rotary tube.
• the strands which had a red-brown color, were then ground on a biplex cross-flow classifier mill (BQ 500) from Hosokawa-Alpine (Augsburg) to an average particle diameter of 3 to 5 ⁇ m.
• the initial mass 1 had a BET surface area ⁇ 1 m 2 / g.
• the following phases were determined by means of X-ray diffraction:
• the aqueous suspension was spray-dried (spray dryer from Niro-Atomizer (Copenhagen), type S-50-N / R, gas inlet temperature 360 ° C., gas outlet temperature 110 ° C., direct current).
• the spray powder had a particle diameter of 2 to 50 ⁇ m.
• 75 kg of the spray powder obtained in this way were metered into a kneader from AMK (Aachen mixing and kneading machine factory of type VI U 160 (Sigma blades)) and kneaded with the addition of 12 l of water (residence time: 30 min, temperature 40 to 50 ° C).
• the kneaded material was then emptied into an extruder (same extruder as in phase 1 production) and shaped into strands (length 1-10 cm; diameter 6 mm) by means of the extruder.
• the strands were dried on a belt dryer for 1 hour at a temperature of 120 ° C. (material temperature).
• 250 kg of strands thus obtained were thermally treated (caicinated) in the rotary kiln according to FIG. 1 (described in more detail in "B) 1.") as follows: the thermal treatment was carried out discontinuously with a material quantity of 250 kg; - the angle of inclination of the rotary tube to The horizontal was 0 °, the rotary tube rotated clockwise at 1.5 revolutions / min; a gas flow of 205 Nm 3 / h was passed through the rotary tube; at the beginning of the thermal treatment, this consisted of 180 Nm 3 / h air and 1 x 25 Nm 3 / h N 2 as sealing gas; the gas stream leaving the rotary tube was supplemented by a further 1 x 25 Nm 3 / h N 2 ; 22 - 25 vol .-% of this total flow were returned to the rotary tube and the rest were left out; the outlet volume was supplemented by the sealing gas and the remaining volume by fresh air; the gas stream was fed into the rotary tube at 25 ° C
• the resulting powdery starting mass 2 had a specific BET surface area of 0.6 m 2 / g and the composition CuSb 2 O 6 .
• the powder- . X-ray diagram of the powder obtained essentially showed the diffraction reflections of CuSb) (comparison spectrum 17-0284 of the JCPDS-ICDD file).
• the kneaded material was then emptied into an extruder (same extruder as in phase 1 production) and shaped into strands (1 to 10 cm in length, 6 mm in diameter) by means of the extruder. These were dried on a belt dryer for 1 h at a temperature (material temperature) of 120 ° C.
• the material temperature was heated linearly from 25 ° C to 100 ° C within 2 h; during this time, a (substantially) nitrogen flow of 205 Nm 3 / h is fed through the rotary tube.
• a (substantially) nitrogen flow of 205 Nm 3 / h is fed through the rotary tube.
• the stationary state after displacement of the air originally contained, it is composed as follows:
• the sealing gas nitrogen was supplied at a temperature of 25 ° C.
• the mixture of the other two gas streams was fed into the rotary tube at the temperature that the material had in the rotary tube.
• the material temperature passed through a temperature maximum above 325 ° C, which did not exceed 340 ° C before the material temperature dropped again to 325 ° C.
• the composition of the gas flow of 205 Nm 3 / h passed through the rotary tube was changed as follows during this period of 4 h:
• the sealing gas nitrogen was supplied at a temperature of 25 ° C.
• the composition of the gas flow of 205 Nm 3 / h fed to the rotary tube was as follows: .... ⁇ .. 95 Nm 3 / h composed of base load - nitrogen (20) and gases released in the rotary tube; - 15 Nm 3 / h air (splitter (21)); 25 Nm 3 / h sealing gas nitrogen (11); and 70 Nm 3 / h recirculated cycle gas.
• the sealing gas nitrogen was supplied at a temperature of 25 ° C.
• the mixture of the other gas streams was fed into the rotary tube at the temperature that the material had in the rotary tube.
• the calcination was terminated by reducing the temperature of the material; For this purpose, the heating zones were switched off and the rapid cooling of the rotary tube was switched on by sucking in air, and the temperature of the material goods was reduced to a temperature below 100 ° C.
• the composition of the gas flow supplied to the rotary tube was changed from 205 Nm 3 / h to the following mixture: 1.10 Nm 3 / h composed of base load - nitrogen (20) and gases released in the rotary tube; 0 Nm 3 / h air (splitter (21)); 25 Nm 3 / h sealing gas nitrogen (11); and 70 Nm 3 / h recirculated cycle gas.
• the gas stream was fed to the rotary tube at a temperature of 25 ° C. During the entire thermal treatment, the pressure (immediately) behind the rotary tube outlet was 0.2 mbar below the external pressure.
• Figure 12 shows the percentage of M A as a function of the material temperature in ° C.
• FIG. 13 shows the ammonia concentration of the atmosphere A in% by volume via the thermal treatment as a function of the material temperature in ° C.
• the catalytically active material obtained in "5.” was ground using a biplex cross-flow classifier (BQ 500) (from Hosokawa-Alpine Augsburg) into a finely divided powder, of which 50% of the powder particles had a sieve with a mesh size of 1 up to 10 ⁇ m and the proportion of particles with a longest expansion above 50 ⁇ m was less than 1%.
• BQ 500 biplex cross-flow classifier
• 70 kg ring-shaped carrier body (7.1 mm outer diameter, 3.2 mm length, 4.0 mm inner diameter; steatite of the type C220 from CeramTec with a surface roughness R z of 45 ⁇ m and a total pore volume based on the volume of the carrier body ⁇ 1 Vol .-%; see DE-A 2135620) were filled into a coating pan (inclination angle 90 °; Hicoater from Lödige, DE) with an internal volume of 200 l. The coating pan was then run at 16 rpm ; n Rotation offset.
• Ring-shaped coated catalysts SKH2 were obtained, the proportion of active oxide mass, based on the total mass, of 20% by weight.
• the shell thickness viewed both over the surface of a carrier body and over the surface of various carrier bodies, was 170 ⁇ 50 ⁇ m.
• FIG. 14 also shows the pore distribution of the ground active mass powder before it was shaped (its specific BET surface area was 21 m 2 / g).
• the pore diameter is plotted in ⁇ m on the abscissa (logarithmic scale).
• the logarithm of the differential contribution in ml / g of the respective pore diameter to the total pore volume is plotted on the right ordinate (curve O).
• the maximum shows the pore diameter with the largest contribution to the total pore volume.
• the integral over the individual contributions of the individual pore diameters to the total pore volume is plotted on the left ordinate in ml / g (curve D).
• the end point is the total pore volume (all information in this document on determinations of total pore volumes and of diameter distributions on these total pore volumes refer to determinations with the method of mercury porosimetry using the Auto Pore 9220 device from Fa., Unless stated otherwise.
• FIG. 15 shows the individual contributions of the individual pore diameters (abscissa, in angstroms, logarithmic scale) in the micropore range to the total pore volume for the active mass powder before it is shaped in ml / g (ordinate).
• FIG. 16 shows the same as FIG. 14, but for the multimetal oxide active composition subsequently detached from the ring-shaped shell catalyst by mechanical scraping (its specific surface area was 24.8 m 2 / g).
• FIG. 17 shows the same as FIG. 15, but for the multimetal oxide active composition subsequently detached from the annular coated catalyst by mechanical scraping.
• shell catalysts SKN1 to SKN6 e.g. with Pd or Fe, or increasing the Cu content
• shell catalysts can be produced for an after-reaction stage according to the invention instead of the SKH2.
• reaction tube V2A steel; 30 mm outer diameter, 2.5 mm wall thickness
• Section 2 100 cm length of catalyst feed with a homogeneous mixture of steat rings with a geometry of 5 mm x 3 mm x 2 mm. (Outer diameter x length x inner diameter) and 70 wt .-% of the ring-shaped full catalyst VKH.
• Section 3 170 cm length of catalyst feed with exclusively circular full catalyst VKH.
• the reaction tube was thermostatted in countercurrent by means of a nitrogen-bubbled salt bath (53% by weight potassium nitrate, 40% by weight sodium nitrite and 7% by weight sodium nitrate)
• reaction tube V2A steel; 30 mm outside diameter, 2 S 5 mm wall thickness, 25 mm inside diameter, length: 320 cm
• Section 1 20 cm long pre-fill from steatite rings of geometry 7 mm x 7 mm x 4 mm (outer diameter x length x inner diameter).
• Section 2 100 cm length of catalyst feed with a homogeneous mixture of 25% by weight of steatite rings of geometry 7 mm x 3 mm x 4 mm (outer diameter x length x inner diameter) and 75% by weight of the ring-shaped coated catalyst SKH1 (alternative the SKH2 can also be used here).
• Section 3 200 cm length of catalyst feed with only a ring-shaped cup catalyst SKH1 (alternatively, the SKH2 can also be used here).
• the reaction tube was thermostatted in countercurrent by means of a nitrogen-bubbled salt bath (53% by weight of potassium nitrate, 40% by weight of sodium nitrite and 7% by weight of sodium nitrate).
• the first reaction stage was continuously charged with a reaction gas starting mixture of the following composition:
• the loading of the catalyst feed with propene was chosen to be 100 Nl / ⁇ -h.
• the salt bath temperature of the first reaction stage was 338 ° C.
• the salt bath temperature of the second reaction stage was 264 ° C. So much compressed air, which had a temperature of 140 ° C., was added to the product gas mixture leaving the intermediate cooler at a temperature of 250 ° C. that a reaction gas starting mixture was added to the second reaction stage was supplied in which the ratio of molecular oxygen to acrolein (ratio of vol .-% proportions) was 1.3.
• Acrolein 500 vol.ppm; Acetaldehyde: 0.03% by volume; Acetic acid: 0.14% by volume.
• reaction tube V2A steel; 30 mm outer diameter, 2.5 mm wall thickness
• reaction gas mixture leaving the second reaction stage was fed directly into the post-reaction stage without intermediate air feed and without intermediate cooling.
• the reaction gas mixture leaving the after-reaction tube was analyzed by gas chromatography (in a corresponding manner as already described for the reaction gas mixture emerging from the second reaction stage of the main reaction). The following results were obtained depending on the chosen post-reactor feed and salt bath temperature:
• Acetaldehyde 0.02% by volume; Acetic acid: 0.07% by volume.
• Acetaldehyde 0.01% by volume
• Acetic acid 0.15% by volume.
• Acetaldehyde 0.01% by volume
• Acetic acid 0.17 vol.%.
• Acetaldehyde . ⁇ 0.01 vol%
• Acetic acid 0.15 vol%.
• Acetaldehyde ⁇ 0.01% by volume
• Acetic acid 0.19% by volume.
• Acrolein 30 vol.ppm; Acetaldehyde:. ⁇ 0.01 vol%;
• Acetic acid 0.16% by volume.
• Salt bath temperature 250 ° C propene conversion: 97.5 mol%; Sp en AS : 91.8 mol% S tot : 0.69 mol% acrolein: 20 vol.ppm; Acetaldehyde: ⁇ 0.01% by volume; Acetic acid: 0.16% by volume.
• salt bath temperature 250 ° C propene conversion: 97.5 mol%; S Pe ⁇ AS : 91.7 mol% S tot : 0.70 mol% acrolein: 24 vol.ppm; Acetaldehyde: 0.01% by volume; Acetic acid: 0.16% by volume.

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