JP2007535511A - Process for producing acrylic acid by gas phase partial oxidation of at least one C3-hydrocarbon precursor compound with a heterogeneous catalyst - Google Patents

Abstract

The present invention relates to a method for producing acrylic acid by partially oxidizing at least one C ₃ -hydrocarbon precursor compound with a heterogeneous catalyst, wherein the amount of subcomponents formed in the method is ≦ 1.5 mol% Is related to the method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for producing acrylic acid by gas phase partial oxidation of at least one C ₃ -hydrocarbon precursor compound with a heterogeneous catalyst.

  Acrylic acid is an important monomer used by itself or in the form of its alkyl ester, for example in the production of polymers suitable as adhesives.

The acrylic acid is a hydrocarbon precursor compound each having 3 C atoms (referred to herein as a “C ₃ -hydrocarbon precursor compound”) at least one of propene and propane with a heterogeneous catalyst. It is known to produce by gas phase partial oxidation.

  The process of partial gas phase oxidation of propane with a heterogeneous catalyst to obtain acrylic acid is carried out in principle in two successive stages, in this first stage obtaining acrolein from propene and then in the second stage So this acrolein brings acrylic acid. Gas phase partial oxidation of propene to acrylic acid by heterogeneous catalysis, in principle, is possible because in both stages, there is a catalyst that can be adapted to catalyze only one of the stages. Can be carried out independently or in two or more spatially continuous reaction stages, each of which is characterized by its catalyst charge and other accessories, generally by the specific reaction conditions. ing.

  A two-stage process for obtaining acrylic acid by partial vapor phase oxidation of propene with a heterogeneous catalyst is known, for example, from DE-A 19927624, DE-A 1948523, WO 00/53557, DE-A 1948248 and WO 00/53558. It is.

  Starting from propane, partial gas phase oxidation with a heterogeneous catalyst to obtain acrylic acid can be carried out as well, alone or in two or more spatially continuous reaction stages. In particular, according to the teachings of DE-A 10245585 and DE-A 10246119, the formation of acrylic acid starting from propane is generally carried out in three distinct stages, where usually the first stage Is the formation of propene. The description of the one-step partial oxidation of propane to acrylic acid is given, for example, in documents EP-A 608838, WO0029106, JP-A 1036311, DE-A 10316465, EP-A 1129987, EP-A 1193240 and DE-A 10338529. included. The three-stage partial oxidation of propane to acrylic acid is described, for example, in WO 01/96270. Catalysts for the respective stages of partial oxidation of propene and partial oxidation of propane generally include multi-element oxides, some of which are described in the cited state of the art.

A common feature of all known methods for producing acrylic acid by gas-phase partial oxidation of at least one C ₃ -hydrocarbon precursor compound with a heterogeneous catalyst is the process performed in the course of gas-phase oxidation using the catalyst. Rather than pure acrylic acid, preferably on the basis of numerous parallel reactions and subsequent reactions, and generally based on inert diluent gases, which are generally to be used especially for avoiding explosive gas mixtures In addition to acrylic acid, a reaction mixture is obtained, which is an intermediate product acrolein that can be returned to partial oxidation, optionally unreacted propene and / or propane, inert diluent gas (in partial oxidation). Does not react primarily, i.e., this gas is usually greater than 95 mol%, preferably greater than 97 mol% or 99 mol during partial oxidation. Remains unchanged to greater than), carbon oxides CO and / or CO _2, acetate relatively easily separated may reaction products of acrylic acid (e.g., the product gas mixture by stripping - is removed from the adsorbent material And water and optionally molecular oxygen as residual oxidant, at least one oxygen atom, at least one carbon atom, and many other compounds having at least one hydrogen atom. . Other compounds are integrated as accessory components in this document.

In obtaining acrylic acid from the product gas mixture of the partial oxidation of at least one C ₃ -hydrocarbon precursor compound by heterogeneous catalyst, acrylic acid must be separated from this product gas mixture, which is generally A combination of absorption, extraction and / or distillation or rectification separation techniques (e.g. EP-A 854129, US-A 4317926, DE-A 19375520, DE-A 19606877, DE-A 19501325, DE-A). A10247240, DE-A19924532, EP-A982289, DE-A1740253, DE-A1740252, EP-A695736, EP-A982287 and EP-A1041062).

  The disadvantages of this separation method are that they are very expensive (energy and investment concentration), and that the optimization can be achieved by skillfully combining a single separation means known and considered per se for this. It is indispensable. However, the results of these tests cannot be generally satisfied.

  The object of the present invention is therefore to achieve avoidance of the above-mentioned problem range.

Surprisingly, detailed examination has led to the result that one possible avoidance route has not been substantially adopted or considered. This route produces a process in which at least one C ₃ -hydrocarbon precursor compound is partially oxidized with a heterogeneous catalyst, producing a total amount of components that make it difficult to separate acrylic acid from the product gas mixture in a specific manner. The modification is to reduce the amount of acrylic acid contained in the gas mixture as much as possible.

  As such components, subcomponents already defined by the applicant have been identified. These include, in particular, lower aldehydes different from acrolein, such as formaldehyde, acetaldehyde, methacrolein, propionaldehyde, n-butyraldehyde, benzaldehyde, furfural and crotonaldehyde, which are especially acrylic acids in the case of thermal separation methods. It is known to promote the inclination to undesired radical polymerization in a specific manner (see, for example, EP-A 854129). However, this subcomponent also includes lower alkene / alkanecarboxylic acids or their anhydrides different from acetic acid, such as formic acid, propionic acid, methacrylic acid, crotonic acid, butyric acid and maleic anhydride. Also included are compounds such as anemonin, acetone, and benzaldehyde.

Therefore, a solution to the problem described in the present application is to select all of the subcomponents in a method for producing acrylic acid by partially oxidizing at least one C ₃ -hydrocarbon precursor compound with a heterogeneous catalyst. It is to provide a method characterized in that the rate _Sges is ≦ 1.5 mol%.

In this case, the selectivity S _i (mol%) for the formation of the individual subcomponents i is that the molar formation amount of the subcomponents i is at least one C ₃ -hydrocarbon precursor reacted in the partial oxidation with the heterogeneous catalyst. This is 100 times the quotient divided by the molar amount of the compound. The total selectivity S _{gees for the} formation of subcomponents is _understood here as the sum of the various individual selectivities S _i for all types of subcomponents i.

According to the invention, S _ges 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%, particularly preferably ≦ 0.80 mol% or ≦ 0.70 mol% or ≦ 0.60 mol% or ≦ 0.50 mol%, especially preferably ≦ 0. .40 mol% or ≦ 0.30 mol% or ≦ 0.20 mol% or ≦ 0.10 mol% or 0 mol%.

In the process according to the invention, in particular S _ge 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 ≦ 0.80 mol% or ≦ 0.70 mol%.

If the starting material for the partial gas phase oxidation with a heterogeneous catalyst according to the invention is propene, the above-mentioned S _ges value usually has a propene molar conversion (reaction gas mixture throughout all reaction stages). single pass for) U ^Pen is accompanied in this conversion ≧ 95 mol%, or ≧ 96 mol%, or ≧ 97 mol%, preferably ≧ 98 mol% (for each propene starting amount). In particular, the conversion of propene with the aforementioned S _ges value is ≦ 99.5 mol%, or ≦ 99 mol% or ≦ 98.5 mol%.

Further, the value of the above-described S _ges, (consisting of the molar amount of converted propene) generally entails selectivity S ^AS _Pen acrylic acid formation, the selectivity of ≧ 80 mol%, or ≧ 85 mol %, Or ≧ 90 mol% or ≧ 92 mol%, in particular ≧ 93 mol% or ≧ 94 mol%, preferably ≧ 95 mol% or ≧ 96 mol%. In particular, the value of S ^AS _Pen described above is a value of ≦ 99 mol%, or ≦ 98 mol%, or ≦ 97 mol%. In this case, the value of the above-mentioned S ^AS _Pen may be accompanied by the value of each of the above-mentioned U ^Pens .

If the starting material for the partial gas phase oxidation with the heterogeneous catalyst according to the invention is propane, the above-mentioned S _ges value usually has a molar conversion of propane (reaction gas mixture throughout all reaction stages). single pass for) U ^Pan is accompanied of this conversion, ≧ 20 mol%, or ≧ 25 mol%, or ≧ 30 mol%, preferably ≧ 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% It is. In particular, the value of U ^Pan mentioned above is ≦ 95 mol%, often ≦ 90 mol%.

Furthermore, the value of the above-described S _ges, (consisting of the molar amount of converted propane) generally entails selectivity S ^AS _Pan acrylic acid formation, the selectivity of ≧ 50 mol%, or ≧ 55 mol %, Or ≧ 60 mol%, preferably ≧ 65 mol%, particularly preferably ≧ 70 mol% or ≧ 75 mol%. In particular, the value of S ^AS _Pan described above is a value of ≦ 95 mol%, or ≦ 90 mol%, or ≦ 85 mol%.

Appropriately applied technically, the process according to the invention is in particular the first customary, eg described in the state of the art, of at least one C ₃ -hydrocarbon precursor compound (mixture from propane and propene). It can be easily carried out so that a method of performing partial oxidation from (may be) to acrylic acid with a heterogeneous catalyst is carried out (main reaction). For example, the implementation of these conventional methods (of the main reaction) is described in documents WO 01/96270, DE-A 10344264, DE-A 10353594, DE-A 10313213, DE-A 19927624, DE-A 10254279, DE-A 10344265. DE-A 10246119, DE-A 10245585, DE-A 10313208, DE-A 10303526, DE-A 10302715, DE-A 10261186, DE-A 10254279, DE-A-10254278, DE-A 10316465 and quotation As described in the state of the art.

The resulting product gas mixture with a relatively high content of subcomponents (for example, subcomponent formation ≧ 1.7 mol%) is then optionally mixed with an inert gas (for example N ₂ , CO ₂ , water vapor or These mixtures), or a mixture of molecular oxygen or a mixture of molecular oxygen and an inert gas, is then passed through the catalyst charge at an elevated temperature in the post-reaction stage, at which time the reaction gas mixture While the acrylic acid contained therein is obtained mainly remaining unchanged, the secondary component is at least partially burned into carbon oxide and water, which means that the overall selectivity of secondary component formation throughout the process ( (According to the present invention, preferably S _ges (mol%) reduces the S _ges) is by at least 0.3% fraction, preferably by at least 0.5% min, only particularly preferably at least 0.8% min , Particularly preferably, it is reduced by at least 1% or more), however, the selectivity of acrylic acid formation is not significantly inhibited (according to the invention, preferably the selectivity of acrylic acid formation (S ^AS _Pen or S ^AS _Pan , respectively) Mol%) is at least less than 2%, preferably less than 1.5%, particularly preferably less than 1%, particularly preferably less than 0.8%, particularly preferably 0.6%. Less than, in particular, preferably less than 0.4%, more preferably less than 0.2 or less than 0.1% (or less). Advantageously, the selectivity for acrylic acid formation is increased by 1% or less, or by 0.5 or 0.3% or less. According to the present invention, the above-described changes in _Sges and% of S ^AS _Pen or S ^AS _Pan can be realized in any combination.

The total selectivity S _{gees for the} formation of subcomponents is usually a value of ≧ 1.7 mol%, or ≧ 1.8 mol% or ≧ 1.9 mol% during the main reaction.

If the starting material for partial gas phase oxidation with a heterogeneous catalyst according to the present invention is propene, the above-mentioned main reaction value of S _ges usually _accompanies the main reaction molar conversion U ^Pen of propene, The conversion is ≧ 95 mol%, or ≧ 96 mol%, preferably ≧ 98 mol% (in each case relative to the propene starting amount). In particular, the propene conversion with the _Sges value of the main reaction described above is ≦ 99.5 mol%, or ≦ 99 mol% or ≦ 98.5 mol%. Furthermore, in the main reaction, the above S _ge values are generally _accompanied by the selectivity S ^AS _Pen for acrylic acid formation (consisting of the molar amount of propene converted in the main reaction), this selectivity being ≧ 80 Mol%, or ≧ 85 mol%, or ≧ 90 mol% or ≧ 92 mol%, in particular ≧ 93 mol% or ≧ 94 mol%, preferably ≧ 95 mol% or ≧ 96 mol%. In particular, the value of S ^AS _Pen described above is a value of ≦ 99 mol%, or ≦ 98 mol%, or ≦ 97 mol%. In this case, the value of S ^AS _Pen for the main reaction described above may be accompanied by the value of U ^Pen for each of the main reactions described above.

If the starting material for partial gas phase oxidation with a heterogeneous catalyst according to the present invention is propane, the main reaction value of the above S _{ges in} the main reaction is usually accompanied by the molar conversion of propane U ^Pan , The conversion is ≧ 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%. In particular, the value of U ^Pan for the main reaction described above is ≦ 95 mol%, often ≦ 90 mol%. Furthermore, the S _ge value of the main reaction described above is generally _accompanied by a selectivity S ^AS _Pan for acrylic acid formation (consisting of the molar amount of propane converted in the main reaction), this selectivity being ≧ 50 mol% Or ≧ 55 mol%, or ≧ 60 mol%, preferably ≧ 65 mol%, particularly preferably ≧ 70 mol% or ≧ 75 mol%. In particular, the value of S ^AS _{Pan in} the above main reaction is a value of ≦ 95 mol%, or ≦ 90 mol%, or ≦ 85 mol%.

Examples of the active material of the catalyst in the post-reaction stage (post-catalyst) are, for example, the general formula I
^{_{Mo 12 V a X 1 b X}} 2 c X 3 d X 4 e X 5 f X 6 g X 7 h O n (I)
[Wherein the variables have the following meanings:
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 ³ = Sb and / or Bi, preferably Sb,
X ⁴ = one or more kinds of alkali metals,
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,
a = 1 to 6,
b = 0.2-4,
c = 0.5-18, preferably 0.5-5, particularly preferably 2-5,
d = 0 to 40, preferably> 0 to 40, particularly preferably 0.5 to 10,
e = 0-2,
f = 0-4,
g = 0 to 40,
h = 0 to 1, preferably> 0 to 1, particularly preferably 0.01 to 0.05, and n = a number determined by the valence and frequency of an element different from oxygen of formula I] An oxide material is mentioned.

According to the invention, preferred embodiments within the scope of the active multimetal oxide I are those in which the variables of the general formula I have the following meanings:
X ¹ = W, Nb and / or Cr, preferably W
X ² = Cu, Ni, Co and / or Fe, preferably Cu and / or Fe,
X ³ = Sb and / or Bi,
X ⁴ = Na and / or K,
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 = 1.5-5,
b = 0.5-2,
c = 0.5-5, preferably 2-5,
d = 0-2, preferably 0.5-2,
e = 0-2,
f = 0-4,
g = 0 to 40,
h = 0 to 1, preferably> 0 to 1, particularly preferably 0.01 to 0.05, and n = a number determined by the valence and frequency of an element different from the oxygen of formula I.

However, according to the invention, particularly preferred multimetal oxides I are of the general formula II
MO ₁₂ V _{a '} Y ¹ _b' Y ² _{c '} Y ³ _d' Y ⁴ _{e '} Y ⁵ _f' Y ⁶ _{g 'On '} (II)
[Wherein Y ¹ = W and / or Nb, preferably W,
Y ² = Cu and / or Fe,
Y ³ = Sb and / or Bi,
Y ⁴ = Ca and / or Sr,
Y ⁵ = Si and / or Al,
Y ⁶ = Pd, Pt, Ag, Rh and / or Ir, preferably Pd,
a ′ = 2 to 4,
b ′ = 1 to 1.5,
c ′ = 2 to 5,
d ′ = 0 to 2, preferably 0.5 to 2,
e ′ = 0 to 0.5,
f ′ = 0 to 8,
g ′ = 0 to 1, preferably> 0 to 1, particularly preferably 0.01 to 0.05, and n ′ = a number determined by the valence and frequency of an element different from oxygen in formula II. ] Is a multi-metal oxide.

In principle, the multimetal oxide material I is obtained from a suitable source of its elemental components to obtain as complete a dry mixture as possible, preferably in the form of fine particles, corresponding to its stoichiometric ratio, And it can manufacture easily by calcination at the temperature of 350-600 degreeC. This calcination can be carried out even under an inert gas, in an oxidizing atmosphere such as air (mixture of inert gas and oxygen) and in a reducing atmosphere (eg inert gas and reducing gas such as H ₂ , NH ₃ , CO 2). , Methane and / or acrolein or a gas exhibiting the above-mentioned reducing action itself). The calcination time can be from a few minutes to a few hours and usually decreases with temperature. According to the present invention, this calcination (as well as catalyst production) is preferably carried out as described in DE-A 10360057 or DE-A 10360058. Sources of elemental constituents of the multi-metal oxide material I include compounds that are already oxides and / or compounds that can be converted to oxides in the presence of at least oxygen by heating.

  The complete mixing of the starting compounds for the production of the multimetal oxide material I can be carried out dry or wet. If this is carried out dry, the starting compound is suitably used as a finely divided powder, which is subjected to calcination after mixing and optionally compacting. However, according to the present invention, it is preferred that the complete mixing is carried out wet.

  In this case, the starting compounds are usually mixed with one another in the form of an aqueous solution and / or suspension. In this case, in particular, a complete dry mixture is obtained in the above-described mixing method, starting from a source of elemental constituents that are present exclusively in dissolved form. It is preferable to use water as the solvent. The resulting aqueous material is then dried, wherein the drying step is preferably carried out by spray drying the aqueous mixture at an outlet temperature of 100-150 ° C.

  The obtained multi-metal oxide material I can be used in powder form or formed into a predetermined catalyst shape for the method according to the present invention. It can be carried out before or after calcination. For example, from the powder form of this active material or its uncalcined precursor material, a full catalyst is produced by compression (for example by tableting, extrusion or extrusion) into the desired catalyst shape, In some cases, auxiliary agents such as graphite or stearic acid as lubricants and / or microfibers from molding aids and reinforcing agents such as glass, asbestos, silicon carbide or potassium titanate may be mixed. Suitable perfect catalyst shapes are for example solid cylinders or hollow cylinders with an outer diameter and length of 2 to 10 mm. In the case of a hollow cylinder, the wall thickness is suitably 1 to 3 mm. Of course, this complete catalyst may have a spherical shape with a spherical diameter of 2 to 10 mm.

  Of course, the shaping of the powder form active substance or its powder form precursor which has not yet been calcined may be carried out by application onto a preformed inert catalyst support. The coating of the support for the production of the shell catalyst is generally carried out in a suitable rotating vessel, for example as known from DE-A 29 09671, EP-A 293859 or EP-A 714700. .

  For the coating of the carrier, it is appropriate to wet the powder material to be applied and to dry it again after application, for example with hot air. The layer thickness of the powder material applied on this carrier is suitably selected in the range from 10 to 1000 μm, preferably in the range from 50 to 500 μm, particularly preferably in the range from 150 to 250 μm.

  In this case, conventional porous or non-porous aluminum oxide, silicon dioxide, thorium dioxide, zircon dioxide, silicon carbide or silicates such as magnesium silicate or aluminum silicate are used as the carrier material. The support may be regularly or irregularly shaped, and is preferably a regularly shaped support with a clearly defined surface roughness, for example a sphere with a coating of strips or a hollow cylinder. Mainly non-porous, rough surface (see DE-A2135620), steatite (especially the Steatite C220 from Fa. CeramTec) with a diameter of 1-8 mm, preferably 4-5 mm. It is preferable to use a spherical carrier. However, it is also suitable to use a corresponding cylinder having a length of 2 to 10 mm and an outer diameter of 4 to 10 mm as the carrier. In the case of an annular body as a carrier, the wall thickness is more commonly 1 to 4 mm. The annular carrier to be preferably used has a length of 2 to 6 mm, an outer diameter of 4 to 8 mm, and a wall thickness of 1 to 2 mm.

  In particular, a ring having a shape of 7 mm × 3 mm × 4 mm (outer diameter × length × inner diameter) is also suitable as the carrier. Of course, the fineness of the catalytically active oxide material to be applied on the support surface is adapted to the desired shell thickness (see EP-A 714700, DE-A 10360057, DE-A 10360058). )

Sources for the production of the multimetal oxide I include, in addition to the oxidizing elements, in particular halides of the desired elemental constituents, nitrates, formates, oxalates, citrates, acetates, carbonates, amine complexes include ammonium salts and / or hydroxides (e.g., at the latest collapse gaseous compounds desorbed during the subsequent calcination, and / or degradation which may be compounds, for example NH ₄ OH, (NH _{4 2} CO ₃ , NH ₄ NO ₃ , NH ₄ CHO ₂ , CH ₃ COOH, NH ₄ CH ₃ CO ₂ and / or ammonium oxalate may additionally be introduced into the complete dry mixture).

However, it goes without saying that the multi-metal oxide material used in this case as an element source for the production of the multi-metal oxide I may be preformed from the elemental part quantity. Corresponding production methods are described, for example, in EP-A 668104, DE-A 197 36 105, DE-A 10046928, DE-A-19040493 and DE-A 19528646. For example, such a partial amount of multi-metal oxide material includes FeSb ₂ O ₆ .

However, the active material of the catalyst in the post-reaction stage according to the present invention has the general formula (III)
^{_{Mo 1 V a M 1 b M}} 2 c M 3 d O n (III)
[Wherein the variables have the following meanings:
At least one element from the group having M ¹ = Tb and Sb;
At least one element from the group having M ² = Nb, Ti, W, Ta and Ce;
M ³ = Pb, Ni, Co, Bi, Pd, Ag, Pt, Cu, Au, Ga, Zn, Sn, In, Re, Ir, Sm, Sc, Y, Pr, Nd and at least from the group having Tb One element;
a = 0.01-1
b => 0-1
c => 0-1
d = 0-0.5, preferably> 0-0.5, and n = a number determined by the valence and frequency of an element different from the oxygen of formula III]
The X-ray diffraction pattern shows diffraction reflections h, i and k, and the peak positions are diffraction angles (2θ) 22.2 ± 0.5 ° (h), 27.3 ± 0.5 ° (i), And 28.2 ± 0.5 ° (k),
This diffractive reflection h is the maximum intensity in this X-ray diffractogram, and exhibits a half-width of 0.5 ° at the highest,
The intensity P _i of the diffraction reflection _i and the intensity P _k of the diffraction reflection k satisfy the relationship of 0.20 ≦ R ≦ 0.85, where R is the expression R = P _i / (P _i + P _k )
In addition, a multi-metal oxide material having an intensity ratio defined by the above and having a half-value width of diffractive reflection i and diffractive reflection k of ≦ 1 ° is also included.

  According to the invention, preferably 0.3 ≦ R ≦ 0.85, more preferably 0.4 ≦ R ≦ 0.85, particularly preferably 0.65 ≦ R ≦ 0.85, still more preferably 0.67. ≦ R ≦ 0.75, particularly preferably R = 0.69 to 0.75 or R = 0.71 to 0.74 or R = 0.72.

  Furthermore, if the X-ray diffraction diagram of the multi-metal oxide material III is a material that does not exhibit diffraction reflection having a peak position at 2θ = 50.0 ± 0.3 ° (i-phase), the method according to the present invention. Is advantageous.

  The description relating to the X-ray diffractogram in this specification relates to an X-ray diffractogram obtained under the application of Cu-Kα-radiation as X-ray radiation (Siemens diffractometer Theta-Theta D-5000, tube voltage: 40 kV. , Tube current: 40 mA, aperture stop V20 (variable), collimator stop V20 (variable), secondary monochromator stop (0.1 mm), detector stop (0.6 mm), measurement interval (2θ): 0.02 ° Measurement time per step: 2.4 seconds, detector: scintillation counter; the definition of the intensity of diffraction reflections in the X-ray diffractogram is defined in this document as DE-A 19835247, DE-A 10122027, and DE- A10051419 and DE-A10046672 are related to the definition; Also true).

The X-ray diffraction pattern of the multimetal oxide material (III) to be used according to the present invention generally has a peak position at the following diffraction angle (2θ) in addition to the diffraction reflections h, i and k. Including additional diffractive reflections:
9.0 ± 0.4 ° (l)
6.7 ± 0.4 ° (o) and 7.9 ± 0.4 ° (p).

  Furthermore, it is advantageous if the X-ray diffractogram additionally comprises a diffractive reflection with a diffraction angle (2θ) = 45.2 ± 0.4 ° (q) and a peak position.

  In particular, the X-ray diffraction pattern of this multi-metal oxide material (III) further includes reflections 29.2 ± 0.4 ° (m) and 35.4 ± 0.4 ° (n) (peak position).

According to the present invention, when the diffraction reflection h is an intensity of 100, it is advantageous if the diffraction reflections i, l, m, n, o, p, and q have the following intensity on the same intensity scale. :
i: 5-95, especially 5-80, partly 10-60;
l: 1-30;
m: 1-40;
o: 1-30;
p: 1-30; and q: 5-60.

  If the X-ray diffractogram of the multimetal oxide material (III) advantageous according to the invention contains the additional diffraction reflections mentioned above, its half-value width is generally ≦ 1 °.

The specific surface area of the multi-metal oxide material (III) to be used according to the invention is often 1 to 40 m ² / g, usually 11 or 12 to 40 m ² / g, in particular 15 or 20 to 40 or 30 m ² / g (BET method, measured by nitrogen).

  According to the invention, the stoichiometric coefficient a of the multimetal oxide material (III) suitable according to the invention is independent of the advantageous range of other stoichiometric coefficients of the multimetal oxide material (III). , Preferably 0.05 to 0.6, particularly preferably 0.1 to 0.6 or 0.5.

  The stoichiometric coefficient b is preferably 0.01 to 1, particularly preferably 0.01 or 0.00, irrespective of the advantageous range of other stoichiometric coefficients of the multimetal oxide material (III). 1 to 0.5 or 0.4.

  The stoichiometric coefficient c of the multimetal oxide material (III) to be used according to the invention is advantageously independent of the advantageous range of other stoichiometric coefficients of the multimetal oxide material (III). 0.01 to 1, particularly preferably 0.01 or 0.1 to 0.5 or 0.4. A particularly preferred range of stoichiometric coefficient c can be combined here with all other advantageous ranges, and other stoichiometry of the multimetal oxide material (III) to be used according to the invention. Regardless of the advantageous range of coefficients, it is in the range of 0.05 to 0.2.

  According to the invention, the stoichiometric coefficient d of the multimetal oxide material (III) suitable according to the invention is independent of the advantageous range of other stoichiometric coefficients of the multimetal oxide material (III). , Preferably 0.00005 or 0.0005 to 0.5, particularly preferably 0.001 to 0.5, especially 0.002 to 0.3, most often 0.005 or 0.01. ~ 0.1.

The multimetal oxide material (III) is particularly advantageous for the process according to the invention if its stoichiometric coefficients a, b, c and d are simultaneously in the following ranges:
a = 0.05-0.6;
b = 0.01-1 (or 0.01-0.5);
c = 0.01-1 (or 0.01-0.5); and d = 0.005-0.5 (or 0.001-0.3).

The multimetal oxide material (III) according to the invention is particularly preferred if its stoichiometric coefficients a, b, c and d are simultaneously in the following ranges:
a = 0.1-0.6;
b = 0.1-0.5;
c = 0.1-0.5; and d = 0.001-0.5, or 0.002-0.3, or 0.005-0.1.

M ¹ is preferably Te.

All of the above descriptions are, in particular, when at least 50 mol% of the total amount of M ² is Nb, particularly preferably when at least 75 mol% of the total amount of M ² or up to 100 mol% is Nb. Is true.

However, this is especially true regardless of the meaning of M ² , where M ³ is at least one element from the group comprising Ni, Co, Bi, Pd, Ag, Au, Pb and Ga, or Ni, Co This is also the case for at least one element from the group having Pd and Bi.

However, all of the above descriptions indicate that at least 50 mol% or at least 75 mol% or up to 100 mol% of the total amount of M ² is Nb, and M ³ is Ni, Co, Bi, Pd, Ag. This is also the case for at least one element from the group comprising, Au, Pd and Ga.

However, all the above descriptions are up to at least 50 mol% or at least up to 75 mol% or up to 100 mol% of the total amount of M ² and M ³ has Ni, Co, Pd and Bi. This is also the case for at least one element from the group.

All statements regarding the stoichiometric coefficient apply particularly preferably when M ¹ = Te, M ² = Nb and M ³ = at least one element from the group having Ni, Co and Pd.

  The process for producing the multimetal oxide material III can be found in the state of the art. This includes in particular DE-A 10122027, DE-A10119933, DE-A10033121, EP-A1192987, DE-A10029338, JP-A2000-143244, EP-A962253, EP-A895809, DE-A19835247. , WO 00/29105, WO 00/26106, EP-A 529853 and EP-A 608838 (in all examples of both EP-A 529853 and EP-A 608838, spray drying is applied as the drying method) For example, the inlet temperature is 300-350 ° C. and the outlet temperature is 100-150 ° C .; countercurrent or cocurrent).

  The principle of the target method for producing a multimetal oxide material III having an i-phase structure (in the X-ray diffractogram no diffractive reflection with a peak position of 2θ = 50.0 ± 0.3 ° is shown) is, for example It is disclosed in WO02 / 06199 and the cited references described in this document. According to this, as is known per se, a polymetal having a stoichiometric ratio III at first but generally a mixed crystal system completely mixed from an i phase and another phase (for example, k phase) An oxide material (precursor multimetal oxide) is produced. From this mixture, only the i-phase part can be isolated by washing the other phases, for example the k-phase, with a suitable liquid. Examples of the liquid include an aqueous solution of an organic acid (for example, oxalic acid, formic acid, acetic acid, citric acid, and tartaric acid), an aqueous solution of an inorganic acid (for example, nitric acid), alcohol, and hydrogen peroxide. Further, JP-A 7232071 discloses a method for producing an i-phase multi-metal oxide material.

  The multimetallic oxide material III which is a mixed crystal system from the i phase and another phase, for example, the k phase, is generally obtained by a production method described in the following technical level (for example, DE-A 198335247). EP-A 529853, EP-A 603836, EP-A 608838, EP-A 895809, DE-A 19835247, EP-A 962253, EP-A 1080784, EP-A 1090684, EP-A 1123738, EP-A 1129987 EP-A 1 192986, EP-A 1 192 882, EP-A 1 199283 and EP-A 1 129 888). According to this method, as complete as possible, preferably a finely divided dry mixture is produced from a suitable source of elemental constituents of the multi-metal oxide material and is produced at 350-700 ° C. or 400-650. Heat treatment is performed at a temperature of 400C or 400-600C. In principle, this heat treatment can be carried out in an oxidizing atmosphere, a reducing atmosphere, or an inert atmosphere. Examples of the oxidizing atmosphere include air, air enriched with molecular oxygen, or air with reduced oxygen. However, this heat treatment is preferably carried out under an inert atmosphere, i.e. under molecular nitrogen and / or noble gases, for example. This heat treatment is conventionally carried out at normal pressure (1 atm). Of course, this heat treatment may be performed under vacuum or overpressure.

  If this heat treatment is performed in a gaseous atmosphere, the atmosphere may be stationary or distributed. This atmosphere is preferably distributed. This heat treatment may require up to a total of 24 hours or longer.

  This heat treatment is preferably carried out first in an oxidizing (containing oxygen) atmosphere (for example in air) at a temperature of 150-400 ° C. or 250-350 ° C. (= pre-decomposition stage). Following this, it is appropriate to continue this heat treatment at 350-700 ° C or 400-650 ° C or 450-600 ° C under an inert gas. This heat treatment involves tableting the catalyst precursor material first (optionally after powdering) prior to its heat treatment (optionally adding 0.5-4 or 2% by weight of finely divided graphite), then heat treating, Of course, it may be carried out by grinding again.

  Thorough mixing of the starting compounds can be carried out dry or wet.

  If this is carried out dry, it is appropriate to use the starting compound as a finely divided powder which is subjected to calcination (heat treatment) after mixing and optionally compacting.

  However, according to the present invention, this complete mixing is preferably carried out wet. In this case, it is customary to mix the starting compounds with one another in the form of an aqueous solution (optionally combined with a complexing agent; see, for example, DE-A 10145958) and / or in the form of a suspension. The aqueous material is then dried and calcined after the drying. Suitably the aqueous material is an aqueous solution or an aqueous dispersion. This drying step is carried out directly after the preparation of this aqueous mixture (especially in the case of aqueous solutions; see, for example, JP-A 7315842) and spray drying (exit temperature is generally 100-150 ° C .; Spray drying can be carried out in co-current or counter-current), so that a complete dry mixture is obtained, in particular when the aqueous material to be spray-dried is an aqueous solution or suspension. Is brought about. However, it can also be dried by evaporation in a vacuum, by freeze-drying or by conventional evaporation.

  Sources of elemental constituents include, for example, oxides and / or during heating (possibly in air) within the scope of carrying out the above-described process for producing i-phase / k-phase-mixed crystal-multimetallic oxide materials. All types of sources capable of forming hydroxide are mentioned. As a starting compound, it goes without saying that the oxides and / or hydroxides of elemental constituents may already be used together or used alone. That is, all the starting compounds mentioned in the recognized state of the art are mentioned, DE-A 10254279 being part of it.

  For example, i-phase / k-phase-mixed crystal-multimetallic oxide materials obtained as described above (pure i-phase multimetallic oxides are optionally obtained randomly by the above-described method mode). Thus, suitable washing (for example according to DE-A 10254279) can be converted into the preferred i-phase multimetallic oxide (III) according to the invention.

  The increase of the i-phase part (and preferably the substantially pure i-phase) is achieved during the production of the multimetal oxide which can be converted into the multimetal oxide (III) suitable according to the invention by the washing described above. This occurs when the production is carried out by the hydrothermal method described, for example, in DE-A 1029338 and JP-A 2000-143244.

  However, the production of the multi-metal oxide material (III) to be used according to the invention first produces a multi-metal oxide material III ′ which differs from the multi-metal oxide material III only in that d = 0. Can also be implemented.

Such a multi-metal oxide material III ′, preferably finely granulated, is then impregnated (eg by spraying) with a solution of element M ³ (eg an aqueous solution) and then dried (preferably at a temperature of ≦ 100 ° C.), then Calcination (preferably in an inert gas stream) as already described for the precursor multimetal oxide (preferably omitting pre-decomposition in air). Nitrate and / or use and / or elemental M ³ is an organic compound of an aqueous halide solution element M ³ (e.g., acetates or acetylacetonates) use of an aqueous solution in the form of complexes with the variant of the production Is particularly advantageous.

  The metal oxide (III) obtained as described above is itself [for example as a powder or tableted powder (especially 0.5-2% by weight of finely divided graphite) in the post-reaction stage according to the invention. After addition), and then pulverized after crushing into strips] or formed into a shaped body and used.

  Molding into a shaped body can be carried out by application onto a carrier as described, for example, in DE-A 10118814, PCT / EP / 02/04073 or DE-A 10051419.

  As carrier materials, according to the invention, in particular aluminum oxide, silicon dioxide, silicates such as clay, kaolin, steatite (steatite with a slight alkali content soluble in water is advantageous). , Pumice, aluminum silicate and magnesium silicate, silicon carbide, zircon dioxide and thorium dioxide. Steatite C220 manufactured by Firma CeramTec is preferred, and a support having a substantially nonporous core and simply a porous shell is particularly preferred.

  The carrier surface may be a smooth surface or a rough surface. The carrier surface is advantageously rough. This is because high surface roughness generally increases the adhesion strength of the applied active material shell (see, for example, DE-A 2135620).

In particular, the surface roughness R _z of the support is in the range of 5 to 200 μm, usually in the range of 20 to 100 μm (according to DIN 4768 page 1, “DIN-ISO for surface measurement values” by Fa. Hommelwerke, Germany). "Hommel type tester" (measured using a Hommel Tester fuel DIN-ISO Overflame messgrossen).

  Furthermore, the support material may be porous or nonporous. Suitably the support material is nonporous (the total volume of the pores of the support volume is ≦ 1% by volume). A carrier material having a nonporous core and a porous shell is preferred (see DE-A 2135620).

  The shell thickness of the active oxide material III present on the shell catalyst to be used according to the invention is customarily between 10 and 1000 μm. However, this thickness may be 50-700 μm, 100-600 μm or 150-400 μm. Possible shell thicknesses are 10-500 μm, 100-500 μm or 150-300 μm.

  In principle, any carrier shape can be mentioned for the method according to the invention. The maximum dimension is generally 1-10 mm. However, it is preferred to apply a sphere or cylinder, in particular a hollow cylinder, as the carrier. The spherical carrier is advantageously 1.5 to 4 mm in diameter. If a cylindrical body is used as a carrier, its length is preferably 2 to 10 mm, and its outer diameter is preferably 4 to 10 mm. If the carrier is annular, its wall thickness is more commonly 1 to 4 mm. An annular carrier suitable according to the invention may have a length of 3-6 mm, an outer diameter of 4-8 mm and a wall thickness of 1-2 mm. However, carrier shapes of 7 mm × 3 mm × 4 mm or 5 mm × 3 mm × 2 mm (outer diameter × length × inner diameter) are also possible.

  The production of such a shell catalyst to be used according to the present invention involves pre-forming the oxide material of the general formula (III) to be used according to the present invention, which is converted to a particulate form, and then with a liquid binder on the support surface. Can be easily implemented. For this purpose, the surface of the support is very easily wetted with a liquid binder and a layer of active material is deposited on this wetted surface by contact with a finely divided active oxide material of general formula (III). Let Finally, the coated carrier is dried. Of course, this process may be repeated periodically to achieve an increase in layer thickness. In this case, the coated support becomes a new “carrier” or the like.

ここで：
Ｄ=粒子の直径
ｘ＝直径が≧Ｄである粒子の％の割合；、かつ
ｙ＝直径が＜Ｄである粒子の％の割合。 Of course, the fineness of the catalytically active oxide material of the general formula (III) to be applied on the support surface is adapted to the desired shell thickness. Shell thickness ranges of 100-500 μm include, for example, at least 50% of the total number of powder particles passing through a sieve having a mesh width of 1-20 μm and a proportion by the number of particles having a maximum dimension greater than 50 μm is less than 10% An active material powder is preferred. Generally, the maximum size distribution of the powder particles corresponds to a Gaussian distribution as a manufacturing condition. In particular, the particle size distribution is as follows:

here:
D = particle diameter x = percentage of particles whose diameter is ≧ D; and y = percentage of particles whose diameter is <D.

  In order to carry out the above-mentioned coating process on an industrial scale, it is recommended to apply the method principle disclosed, for example, in DE-A 290971 and DE-A 10051419. The carrier to be coated is preferably inclined (the inclination angle is generally ≧ 0 ° and ≦ 90 °, preferably ≧ 30 ° and ≦ 90 °; this inclination) The angle is an angle relative to the horizontal of the rotating container central axis) and is loaded into a rotating rotating container (eg, a rotating table or a coating drum). This rotating rotating container guides, for example, a spherical or cylindrical carrier through two metering devices arranged continuously at a predetermined interval. The first device of both metering devices suitably sprays a liquid binder onto a carrier that rolls in a rotating turntable and a controlled moistening nozzle (e.g. a spray that operates with compressed air). Nozzle). A second metering device is present outside the conical spray of the sprayed liquid binder and is utilized to supply the particulate oxide active material (eg, by a vibrating channel or powder screw). A controlled and wet spherical carrier contains the supplied active material powder, which is compressed by rolling on the outer surface of, for example, a cylindrical or spherical carrier, resulting in an intimate shell.

  If necessary, the support thus coated with the base is again connected to the spray nozzle in the course of the subsequent rotation, in which case it is moistened in a controlled manner and in the course of further movements a finely divided oxide active material. Can be accommodated (intermediate drying is generally not necessary). In this case, the finely divided oxide active material and the liquid binder are generally fed continuously and simultaneously.

This liquid binder can be removed after the coating is complete, for example by the action of a hot gas, such as N ₂ or air. It is noteworthy that the above-described coating method satisfactorily satisfies the adhesion of successive layers as well as the adhesion of the base layer on the carrier surface.

  With respect to the above-mentioned coating mode, it is important to control the wetting of the surface of the carrier to be coated. Briefly, the support surface is wetted so that it has adequately adsorbed liquid binder, but the liquid phase itself is not visually recognized on the support surface. If the support surface is too wet, the finely divided catalytically active oxide material will condense without reaching the surface and become separate aggregates. Detailed descriptions in this regard are found in DE-A 2909671 and DE-A 10051419.

  The final removal of the used liquid binder can be controlled and carried out, for example, by evaporation and / or sublimation. Very simply, this can be carried out by the action of a hot gas at a corresponding temperature (in particular 50 to 500 ° C., in particular 150 ° C.). However, only the preliminary drying can be performed by the action of the high-temperature gas. Final drying can then be performed, for example, in any type of drying oven (eg, a band dryer) or reactor. In this case, it is desirable that the working temperature does not exceed the calcination temperature applied in the production of the oxide active material. Of course, this drying may be carried out exclusively in a drying furnace.

  As binders for the coating process, the following binders can be used irrespective of the type and shape of the support: water, monohydric alcohols such as ethanol, methanol, propanol and butanol, polyhydric alcohols such as ethylene. Glycol, 1,4-butanediol, 1,6-hexanediol or glycerin, monovalent or polyvalent organic carboxylic acids such as propionic acid, oxalic acid, malonic acid, glutaric acid or maleic acid, amino alcohols such as ethanolamine Or diethanolamine and mono- or polyvalent organic amides such as formamide. Mixtures consisting of 20-90% by weight of water and 10-80% by weight of organic compounds dissolved in water are also advantageous binders, the boiling point or sublimation temperature of this organic compound being> 100 ° C. at atmospheric pressure (1 atm), Preferably> 150 ° C. This organic compound is advantageously selected from the possible organic binders listed above. The ratio of the organic matter in the binder aqueous solution is preferably 10 to 50% by mass, particularly preferably 20 to 30% by mass. In this case, the organic components include monosaccharides and oligosaccharides such as glucose, fructose, saccharose or lactose and polyethylene oxide and polyacrylate.

  It is important that the production of a shell catalyst suitable according to the invention can be carried out not only by application of a ready-to-use micronized active oxide material of general formula (III) onto the wet support surface.

  Rather, instead of the active oxide material, the finely divided precursor material is applied on a wet carrier surface (under the same coating method and binder application) and after the coated carrier is dried. Calcination may be carried out (the support may be impregnated with the precursor solution, then dried and then calcined). Finally, if necessary, a phase different from the i phase may be washed.

  Such finely divided precursor materials are, for example, first prepared as completely as possible from the source of the elemental constituents of the desired active oxide material of the general formula (III), preferably in a finely divided dry mixture (for example , By spray drying of an aqueous suspension or solution of the source) and the finely divided dry mixture (optionally after tableting with addition of 0.5-2% by weight of finely divided graphite), 150- Material obtained by heat treatment (several hours) in an oxidizing (oxygen-containing) atmosphere (for example in air) at a temperature of 350 ° C., preferably 250-350 ° C., and finally grinding if necessary Is mentioned.

  After the support is coated with the precursor material, it can then be calcined at a temperature of 360-700 ° C or 400-650 ° C or 400-600 ° C under an inert gas atmosphere (including all other types of atmospheres). preferable.

  The molding of the multimetal oxide material (III) that can be used according to the present invention can also be achieved by extrusion and / or tableting of the particulate multimetal oxide material (III). Of course, it can also be carried out by extrusion and / or tableting of the finely divided precursor material (if necessary, a phase different from the i phase may be finally washed).

  In this case, examples of the shape include a sphere, a solid cylinder, and a hollow cylinder (ring). In this case, the maximum dimension of the above-mentioned shape is generally 1 to 10 mm. In the case of a cylindrical body, the length is preferably 2 to 10 mm, and the outer diameter is preferably 4 to 10 mm. In the case of an annular body, the wall thickness is more commonly 1 to 4 mm. An annular complete catalyst suitable according to the invention may have a length of 3-6 mm, an outer diameter of 4-8 mm, and a wall thickness of 1-2 mm. However, a complete catalyst ring shape of 7 mm × 3 mm × 4 mm or 5 mm × 3 mm × 2 mm (outer diameter × length × inner diameter) is also possible.

  Of course, the shape of the multimetal oxide active material (III) to be used for the process according to the invention includes all shapes of DE-A 10101695 (thus, the multimetal oxide The reference made for the formation of the product III catalyst is also applicable to the formation of the multimetal oxide I catalyst).

  The definition of the intensity of diffraction reflection in the X-ray diffractogram is referred to in this specification by referring to the definitions described in DE-A 19835247 and DE-A 10051419 and DE-A 10046672 as already described. Yes.

That is, when viewed along the intensity axis perpendicular to the 2θ axis in the straight line of the X-ray diffraction diagram, A ¹ represents the peak position of reflection 1 and B ¹ is the left side of the peak position A ¹ . Is the obvious minimum located in the nearest neighbor (ignoring the smallest value with a reflective shoulder), and B ² is the obvious minimum located right next to the peak position A ¹ and C 2 ^{When 1} is a point where a straight line drawn perpendicularly to the 2θ axis from the peak position A ¹ intersects with a line connecting points B ¹ and B ² , the intensity of reflection 1 is from the peak position A ¹ to the point. the straight section a ¹ C ¹ which extends in C ¹ is the length. In this case, the expression minimum means the point at which the gradient slope of the tangent to the curve in the base region of reflection 1 shifts from a negative value to a positive value, or the point at which the slope gradient goes to zero. To determine the slope, consider the coordinates of the 2θ axis and the intensity axis.

Correspondingly, in this specification, the half width is the length of the straight section obtained between the intersections H ¹ and H ² when a line parallel to the 2θ axis is drawn at the center of the straight section A ¹ C ^1. Where H ¹ and H ² mean the first intersection of this parallel line with the X-ray diffractogram lines defined above, on the left and right sides of A ¹ , respectively.

  An example of the determination of the half width and the intensity is also described in FIG. 6 of DE-A 10046672.

  The multi-metal oxide material (III) to be used according to the invention is a catalyst in the form of a particulate, for example colloidal material, such as diluted with silicon dioxide, titanium dioxide, aluminum oxide, zircon oxide, niobium oxide. Of course, it can be used as an active material in the post-reaction step according to the invention.

  In this case, the ratio of diluent materials may be up to 9 (diluent): 1 (active material). Thus, possible dilution material ratios are, for example, 6 (diluent): 1 (active material) and 3 (diluent): 1 (active material). This introduction of diluent may be carried out before and / or after calcination, generally further before drying.

  If this introduction is carried out prior to drying or calcination, the diluent must be selected so that it is substantially retained in the fluid medium or upon calcination. This is the case, for example, for oxides that are generally suitable to be fired at high temperatures.

At least one C ₃ -hydrocarbon precursor compound is partially oxidized with a heterogeneous catalyst to obtain acrylic acid (main reaction), the conventional methods described in the state of the art are catalyst fixed bed, catalyst moving bed or catalyst flow Just as can be carried out in the bed, the post-reaction stage according to the invention can also be carried out in a catalyst fixed bed, a catalyst moving bed or a catalyst fluidized bed.

  In the case of partial oxidation of propene to acrylic acid, the conventional partial oxidation (main reaction) using a heterogeneous catalyst is preferably carried out in either one-stage embodiment or two-stage embodiment, for example in the document DE It is carried out in the tube bundle reactor described in A10246119 and DE-A10245585.

  The catalyst charge is present in a contact tube leading to the reaction mixture, while a heat exchange medium is guided around the contact tube (typically a salt bath). It goes without saying that a plurality of heat exchange media that are spatially continuous and independent from each other may be guided around the associated contact tube section along the contact tube of the tube bundle reactor. In this case, a reactor having a plurality of temperature zones is quoted.

  The post-reaction stage according to the invention may be carried out in a separate post-reactor which is spatially post-connected in conventional partial oxidation, or may be carried out in an integrated manner in the main reaction reactor. In this case, as for the post-reactor type, in principle, all types of post-reactor types suitable for the main reaction can be mentioned.

  For example, conventional partial oxidation (main reaction) using a heterogeneous catalyst from propene to acrylic acid in two tube bundle reactors connected in series (each may have one or more temperature zones) In the first tube bundle reactor, acrolein is mainly obtained from propene in the first tube bundle reactor, and in the second tube bundle reactor, the acrolein formed in the first tube bundle reactor is oxidized to acryl. If an acid is to be obtained, it is suitable from an application standpoint that a post-catalyst bed may be added in this contact tube upstream of the outlet of the reaction mixture from the second tube bundle reactor (alternatively this The inside of the contact tube end may be coated with a post-catalyst; this coating may be carried out, for example, as described in DE-A 19839782.) If the main reaction product gas mixture is passed through the post-catalyst bed, the secondary component content of the main reaction product gas mixture is reduced according to the invention. In this case, the post-catalyst bed preferably covers the section of the tube having its own independent temperature zone in the contact tube. The length of the subsequent reaction bed is preferably 10 to 30% with respect to the total length of the catalyst bed of the main reaction and the side reaction.

  If it is desired to carry out the post-reaction of the main reaction product gas mixture in advance with molecular oxygen or with a mixture of molecular oxygen and inert gas, the post-catalyst is spatially post-connected. Alternative variants which are present in a separate reactor are advantageous.

  This reactor is likewise a tube bundle reactor, but may be a fluidized bed reactor or a moving bed reactor.

  In particular for the realization of the post-reaction stage in an adiabatic operation, a single-shaft blast furnace in which the hot product gas mixture of the main reaction is flowed axially and / or radially after optionally pre-intermediate cooling. It is worth noting that the reactor is sufficient as a fixed bed reactor.

  In this case, the reactor has a very simple internal diameter of 0.1 to 10 m, if necessary 0.5 to 5 m, and a fixed catalyst bed is applied on a support device (for example a grid). Given a single reaction tube. The catalyst-clad reaction tube, which is insulated in the adiabatic operation, in this case causes the hot reaction gas mixture containing secondary components and excess molecular oxygen to flow axially. In this case, the catalyst shape may be spherical, cylindrical or annular as described above. However, according to the invention, this catalyst can also be applied in the form of strips in the above case. In order to achieve a radial flow of the reaction gas mixture containing the auxiliary components, the post-reactor is composed of, for example, two cylindrical lattice networks which are present in a jacket cover and are provided concentrically, And the post catalyst bed is placed in the annular gap. In the case of insulation, it is desirable to insulate the jacket cover again.

  The recommended post-catalysts are generally suitable for partial oxidation of acrolein to acrylic acid (in this regard, this catalyst also has an increased activity, especially in a given range) and is used as described above. Within the range of post-reaction steps to be performed, the acrolein content in the main reaction product gas mixture is simultaneously reduced. Usually the acetic acid content is also reduced.

The reaction temperature in this post-reaction stage is preferably selected in terms of applied technology from 200 to 300 ° C., in particular from 220 to 290 ° C., particularly preferably from 230 to 250 ° C. The reaction pressure in the post reaction stage is preferably from 0.5 to 5 atm, usually from 1 to 3 atm. The load on the reaction gas mixture of the post-reaction catalyst charge is in particular 1500 to 2500 h ⁻¹ or 1500 to 4000 h ⁻¹ . Normally, substantially no hydrocarbon oxidation is performed in the post-reaction stage. Therefore, the oxygen content of the reaction gas mixture conveyed in the post-reaction stage is included in the product gas mixture, in order to completely combust the additional components acrolein, CO and acetic acid containing subcomponents. It is desirable to supply up to 5 times the oxygen content required for the process. If molecular oxygen is added to the product gas mixture of the main reaction before the post reaction, this is preferably carried out in the form of air.

  What has been described for the partial oxidation of propene to acrylic acid using a heterogeneous catalyst can be applied correspondingly to the partial oxidation of propane to acrylic acid.

According to the present invention, in the case of the multistage implementation of partial oxidation by heterogeneous catalyst from at least one C ₃ -hydrocarbon precursor compound to acrylic acid, the subcomponent oxidation (subcomponent reduction) as described above. In principle can be carried out downstream of each reaction stage, and it is important that the total selectivity for the formation of subcomponents falls to a value of ≦ 1.5 mol% over all reaction stages (total reactions). is there.

  Thus, in the case of a two-stage propene partial oxidation, the majority of the side-component formation identified over both reaction stages already occurs in the first “propene to acrolein oxidation stage”. That is, the secondary component oxidation connected upstream of the post-connected “acrolein to acrylic acid” oxidation stage acts according to the present invention to achieve its purpose. This may be achieved, for example, by charging it with the required post-catalyst, usually in an intercooler connected between both oxidation stages. Alternatively, the post-catalyst may be coated on the inner surface of the intercooler leading to the reaction gas mixture to be cooled. For example, such an inner surface may be the surface of a cooling tube in the case of a tube bundle heat exchanger. In particular, a metal helix, for example, is inserted at the inlet of such a cooling tube to improve heat conversion. Of course, according to the present invention, the surface of such a spiral may be coated with a post-catalyst as well. Such a coating makes it possible at the same time to show the anti-carbonization action of the intercooler. The finish of such a coating is described, for example, in DE-A 19839782.

In other respects, during the process of producing acrylic acid by partial oxidation using a heterogeneous catalyst of at least one C ₃ -hydrocarbon precursor compound, the total selectivity for secondary component formation is reduced, and this It was confirmed that the C ₃ -hydrocarbon precursor compound was pure. That is, it is preferable to use high-purity propene and high-purity propane in the method according to the present invention. Examples of such propane are propane recommended in DE-A 10246119 and DE-A 10245585. As propene to be used, in this connection it is recommended, inter alia, to use polymer grade propene of the following composition:
Propene ≧ 99.6% by mass,
Propane ≦ 0.4% by mass,
Ethane and / or methane ≦ 300 ppm by mass,
C ₄ -hydrocarbon ≦ 5 mass ppm,
Acetylene ≦ 1 mass ppm,
Ethylene ≦ 7 ppm by mass,
Water ≦ 5 mass ppm,
O ₂ ≦ 2 mass ppm,
Sulfur-containing compound ≦ 2 mass ppm (calculated as sulfur),
Chlorine-containing compound ≦ 1 mass ppm (calculated as chlorine),
CO ≦ 5 mass ppm,
CO ₂ ≦ 5 mass ppm,
Cyclopropane ≦ 10 mass ppm,
Propadiene and / or propyne ≦ 5 mass ppm,
C _{≧ 5} -hydrocarbon ≦ 10 mass ppm, and carbonyl group-containing compound ≦ 10 mass ppm (calculated as Ni (CO ₄ )).

However, the concept of the post-reaction stage described above is that propene and / or propane containing impurities within a particular range are used for partial oxidation using a heterogeneous catalyst of at least one C ₃ -hydrocarbon precursor compound. When used, it is even more important. According to the invention, suitably the post-reaction stage according to the invention is connected immediately downstream of the stage of converting propane to propene (eg downstream of the dehydrogenation stage using a catalyst according to WO 01/96270). Also good. For such post-oxidation stages, multimetal oxides, for example based on VPO oxides, have also proved to be advantageous post-reaction stage catalysts.

  An alternative possibility to achieve the object according to the invention is that the process is carried out in at least two steps and after the reaction step of forming propene from propane and / or after the reaction step of forming acrolein from propene. The secondary components formed from the intermediate product formed are each separated and thus used in the subsequent reaction step in purified form. This separation may be carried out as described, for example, in documents WO 01/96270 and DE-A 102 13998. Furthermore, it is advantageous for the process according to the invention to use a catalyst in which the desired target compound is particularly selectively formed in the individual reaction steps. Such catalysts are disclosed for example in WO 01/96270.

  In order to achieve the object according to the present invention, it is needless to say that all the means cited as useful in this specification may be applied in combination or in part.

  An advantage of the process mode according to the invention is that the separation of acrylic acid from the product gas mixture can be significantly facilitated. In this case, for example, document DE-A10235847, EP-A792867, WO98 / 01415, EP-A1015411, EP-A1015410, WO99 / 50219, WO00 / 53560, DE-A19924532, WO02 / 09839, DE-A10235847, WO03 / 041833, DE-A10223058, DE-A102443625, DE-A10336386, EP-A854129, US-A4317926, DE-A19837520, DE-A-19606877, DE-A19501325 No., DE-A10247240, DE-A19924532, EP-A982289, DE-A19740253, DE-A1740252, EP-A The separation methods known per se described in U.S. Pat. No. 95736, EP-A 982287 and EP-A 1041062 can be applied in principle (in this case, the remaining gas remaining in the main reaction as a circulating gas is known per se). May be returned). However, these methods are remarkably small in terms of equipment (especially separation towers) and / or simple and can therefore be constructed advantageously in terms of cost. For example, following the performance of the method according to the invention, the separation of acrylic acid by adsorption (the adsorbent may be, for example, water, a high-boiling organic solvent or acrylic acid itself or other liquid), Rather, for example, in a packed tower that may be packed with Raschig rings, it may be carried out in a simplistic and cocurrent or countercurrent manner because the polymerization tendency is reduced due to a decrease in the content of secondary components. is there. Alternatively, the same configuration may be operated at a higher flow rate (eg, a slight reflux in the rectification column). If advantageous according to the invention, the acrylic acid that can be used to produce the superadsorbent is condensed from the product gas mixture of the gas phase oxidation by freezing on cooling fingers or optionally by fractional condensation. May be obtained directly. In particular, the method according to the present invention is characterized in that the main partial oxidation using a heterogeneous catalyst is carried out in two stages (for example in two reactors connected in series, for example in a bundle reactor, for example on a fixed catalyst bed (first Stage is mainly the partial oxidation of propene to acrylic acid (providing acrolein from propene and the second stage mainly resulting from acrolein to acrylic acid), with the catalyst (fixed) bed of the first reaction stage Both the loading with propene and the loading with catalyst (fixed) bed acrolein in the second reaction stage are ≧ 120 Nl / l / h, or ≧ 130 Nl / l / h, or ≧ 140 Nl / l / h, or ≧ 150 Nl / l / h and within the range of ≦ 300 Nl / l / h, that is, when applied as a so-called high load method (Hochlastverhahren) It is possible. Of course, the method according to the present invention can be applied in the above-described arrangement even when both loads are ≦ 100 Nl / l / h.

  Each of these (high load) reaction stages is preferably carried out in a reactor having one or more (preferably two) temperature zones (see, for example, DE-A 10313213 and DE-A 10313212). )

In this case, a chemical grade propene with the following specifications may be used as the propene:
Propene ≧ 94 mass%,
Propane ≦ 6% by mass
Methane and / or ethane ≦ 0.2% by mass,
Ethylene ≦ 5 ppm by mass,
Acetylene ≦ 1 mass ppm,
Propadiene and / or propyne ≦ 20 mass ppm,
Cyclopropane ≦ 100 mass ppm,
Butene ≦ 50 mass ppm,
Butadiene ≦ 50 mass ppm,
C ₄ -hydrocarbon ≦ 200 mass ppm,
C _{≧ 5} −hydrocarbon ≦ 10 mass ppm,
Sulfur-containing compound ≦ 2 mass ppm (calculated as sulfur),
Sulfide ≦ 0.1 mass ppm (calculated as H ₂ S),
Chlorine-containing compound ≦ 1 mass ppm (calculated as chlorine),
Chloride ≦ 1 mass ppm (calculated as Cl ⁻ ) and water ≦ 30 mass ppm.

  Otherwise, this high load-main partial oxidation may be carried out as described, for example, in documents DE-A 10313213 and DE-A 10313208.

The process according to the invention is correspondingly also a process for producing methacrylic acid by partial oxidation of at least one C ₄ -hydrocarbon precursor compound (eg isobutene or isobutane) using a heterogeneous catalyst. Applicable.

Examples and Comparative Examples A) Stoichiometric ratio [Bi ₂ W ₂ O ₉ · 2WO ₃ ] _0.5 [Mo ₁₂ Co _5.5 Fe _2.94 Si _1.59 K _0.06 O _x ] ₁
Preparation of a cyclic fully-catalyzed VKH for the first reaction stage (propene → acrolein) of the main reaction with Preparation of starting material 1 Tungstic acid in 775 kg in small portions at 25 ° C. in nitric acid aqueous solution of bismuth nitrate (Bi 11.2% by mass; free nitric acid 3 to 5% by mass; material density 1.22 to 1.27 g / ml) (W 72.94% by mass) 209.3 kg was introduced with stirring. The resulting aqueous mixture was then further stirred at 25 ° C. for 2 hours and then spray dried.

This spray drying was carried out countercurrently in a rotating disk spray tower with a gas inlet temperature of 300 ± 10 ° C. and a gas outlet temperature of 100 ± 10 ° C. The resulting spray powder (particle size is substantially uniform and 30 μm) has a loss on ignition (ignitioned in air at 600 ° C. for 3 hours) of 12% by mass, and then 16.8% by mass of water (this And kneading in a kneader and extrusion molding using an extruder (torque: ≦ 50 Nm) to obtain an extrudate having a diameter of 6 mm. This extrudate is cut into 6 cm pieces and air dried at a temperature of 90-95 ° C. (zone 1), 125 ° C. (zone 2) and 125 ° C. (zone 3) with a residence time of 120 minutes in a 3-zone belt dryer. And then heat-treated at a temperature in the range of 780 to 810 ° C. (calcination; in a rotary kiln with an air flow through (internal capacity 1.54 m ³ , 200 Nm ³ air / h)). In accurately adjusting the calcination temperature, it is important to make this adjustment based on the composition of the target phase of the calcination product. The phases WO ₃ (monoclinic) and Bi ₂ W ₂ O ₉ are desirable, and the presence of γ-Bi ₂ WO ₆ (russelite) is not desirable. Thus, if the compound γ-Bi ₂ WO ₆ is still detectable after calcination using reflection in powder X-ray diffraction with a reflection angle 2θ = 28.4 ° (CuKα-radiation), this adjustment It should be repeated and the calcination temperature should be increased within the above temperature range or the residence time should be extended at the same calcination temperature until the disappearance of this reflection is achieved. The preformed calcined mixed oxide obtained in this way is the X ₅₀ value of the resulting particles (Woolman Industrial Chemistry Encyclopedia 6th edition (1998) electronic version, Chapter 3.1.4 (Ullmann's Encyclopedia of Industrial Chemistry, 6th). edition (1998) Electronic Release, Kapitel 3.1.4) or DIN 66141)). Then, the pulverized product, Degussa Corp. of Sipernat ^(R) type finely divided SiO ₂ in (bulk density 150g / l; X ₅₀ value of the SiO ₂ particles are 10 [mu] m, BET surface area was 100 m ² / g) 1% by weight (based on this ground product) was mixed.

2. Preparation of starting material 2 Ammonium heptamolybdate tetrahydrate (213 kg, 81.5% by weight MoO ₃ ) was dissolved in 600 l of water with stirring at 60 ° C., and the resulting solution was maintained at 60 ° C. with stirring. Solution A was prepared by adding 0.97 kg (KOH 46.8% by mass) of an aqueous potassium hydroxide solution at 20 ° C.

Solution B was prepared by placing 116.25 kg (Fe 14.2% by mass) of iron (III) nitrate aqueous solution at 60 ° C. in 262.9 kg (Co 12.4% by mass) Co (II) nitrate aqueous solution. This solution B was then continuously pumped into solution A charged over 30 minutes while maintaining 60 ° C. It was then stirred at 60 ° C. for 15 minutes. Next, 19.16 kg of Ludox type silica gel manufactured by Dupont (46.80% by mass of SiO ₂ , density: 1.36 to 1.42 g / ml, pH 8.5 to 9.5, alkali metal) was added to the obtained aqueous mixture. The maximum content was 0.5% by weight) and was then stirred at 60 ° C. for a further 15 minutes.

  Subsequently, it was spray-dried countercurrently in a rotating disk type spray tower (gas inlet temperature: 400 ± 10 ° C., gas outlet temperature: 140 ± 5 ° C.). The obtained spray powder had a loss on ignition (heated in air at 600 ° C. for 3 hours) of about 30% by mass, and had substantially uniform particles of 30 μm.

Production of multi-metal oxide active material Starting material 1 and starting material 2 are mixed in a stoichiometric ratio [Bi ₂ W ₂ O ₉ .2WO ₃ ] _0.5 [MO ₁₂ Co ₅ . ₅ Fe _2.94 Si _1.59 K _0.08 O _x ] ₁
Homogeneously mixed in a mixer equipped with a cutter head in the amount required for the multi-metal oxide active material. 1% by weight of Fa. Timcal AG (San Antonio, USA) TIMREXP44 type granular graphite (sieving analysis: minimum 50% by weight <24 μm, maximum 10% by weight ≧ 24 μm and ≦ 48 μm, maximum 5% by weight was> 48 μm and BET surface area: 6-13 m ³ / g) was additionally added uniformly. The resulting mixture was then led into a Kompaktor K200 / 100 type compressor (Fa. Hosokawa Bepex GmbH D-74211 Rheingarten) equipped with a concave grooved finishing roll (gap width: 2.8 mm, sieve) (Width: 1.0 mm, Sift width: 400 μm, Set compression force: 60 kN, Screw rotation speed: 65 to 70 rotations / minute). The resulting compact has a hardness of 10 N and has substantially uniform particles of 400 μm to 1 mm.

  The compact is then further mixed with 2% by weight of the same graphite, based on its weight, and then Fa. 5 mm x 3 mm x 2 mm (outside diameter) having a side compression strength of 19 N ± 3 N, compressed in a nitrogen atmosphere in an R x 73 type Kilian Rundlaufer (tablet molding machine) from Kilian (D-50735 Cologne) An annular complete catalyst precursor molded product having a shape of (length × inner diameter) was obtained.

  In this case, in this specification, the lateral compressive strength is the compressive strength when the annular complete catalyst precursor compact is compressed perpendicularly to the cylindrical surface (that is, parallel to the surface of the ring opening). It is understood that there is.

  In this case, all lateral compression strengths in this specification are Firm. Zwick GmbH & Co. (D-89079 Ulm) It is based on the measurement using the Z2.5 / TS1S type material testing machine of the company. This material testing machine is designed for quasi-static stress with constant, stationary, increasing or changing course. This material testing machine is suitable for tensile test, compression test and bending test. Farma. A. S. Attach a load cell of serial number 03-2038 of KAF-TC type of company T (D-01307 Dresden), in this case, calibrated according to DIN EN ISO 7500-1 and usable for measuring range 1-500N (Relative measurement uncertainty: ± 0.2%).

This measurement was performed with the following parameters:
Initial force: 0.5N
Initial force-speed: 10 mm / min Test speed: 1.6 mm / min.

  In this case, first, the upper plunger was slowly lowered to just before the cylindrical surface of the annular complete catalyst precursor. The upper plunger was then stopped, and then the plunger was lowered at an apparently slow test speed with the minimum initial force required for further lowering.

  The initial force for forming cracks in the completely catalyst precursor is the side compression strength (SDF).

  For the final heat treatment, first, 1000 g of the complete catalyst precursor compacts were respectively heated at 180 ° C./h in a muffle furnace (internal capacity 60 l, 1 l / h air per 1 g of the complete catalyst precursor compacts) through which air was passed. It heated from room temperature (25 degreeC) to 190 degreeC with the heating rate. This temperature was maintained for 1 hour and then heated to 210 ° C. at a heating rate of 60 ° C./h. The 210 ° C. was again maintained for 1 hour, after which the temperature was heated to 230 ° C. at a heating rate of 60 ° C./h. This temperature was likewise maintained for 1 hour, after which it was again increased to 265 ° C. at a heating rate of 60 ° C./h. This 265 ° C. was then maintained for 1 hour as well. It was then first cooled to room temperature, thereby substantially terminating the decomposition stage. It was then heated to 465 ° C. at a heating rate of 180 ° C./h and this calcination temperature was maintained for 4 hours.

  In this case, a cyclic complete catalyst VKH was obtained from the cyclic complete catalyst precursor.

For the resulting cyclic complete catalyst VKH, the specific surface area O, the total pore volume V, the pore diameter d ^max showing the largest contribution to this total pore volume, and the diameter> 0.1, and The percentage of the pore diameter relative to the total pore volume where ≦ 1 μm was as follows:
O = 7.6 cm ² / g
V = 0.27 cm ³ / g
d ^max [μm] = 0.6
V ^0.1 ₁ -% = 79.

  Furthermore, the ratio R (as defined in EP-A 1340538) of the apparent mass density to the true mass density ρ was 0.66.

In large industrial quantities, it was carried out using a belt calciner as described in Example 1 of DE-A 1 0046 957 (however, in this case, the filling height is preferably reduced (chamber 1). In 4) at a residence time of 1.46 hours per chamber and 44 mm, and in calcination (chambers 5 to 8) preferably at a residence time of 4.67 hours it reaches 130 mm); With a uniform chamber length of 1.40 m (with a bottom area of 1.29 m ² (decomposition) and 1.40 m ² (calcination)), 75 Nm ³ / h of air flows from below through a coarse belt. This air was sucked by a rotary aerator. In these rooms, the temporal and positional temperature difference from the set value was always ≦ 2 ° C. Otherwise, it was carried out as described in Example 1 of DE-A 10046957.

Alternatively, for the first reaction step, the same shape and mode of manufacture, except that the stoichiometric ratio [Bi ₂ W _1.91 O ₉ · _1.91 WO ₃ ] _0.5 [Mo _12.7 Co _5.79 Fe _3.22 Si _1.66 A cyclic complete catalyst with K _0.08 O _x ] ₁ may be used.

B) Preparation of a cyclic shell catalyst SKH1 for the second reaction stage (acrolein → acrylic acid) of the main reaction of the active material with a stoichiometric ratio of Mo ₁₂ V ₃ W _1.2 Cu _2.4 O _x General Description of Rotary Kiln Used for Calcination A constitutive description of a rotary kiln is shown in FIG. 1 attached to this specification. The following quotes indicate the symbols in FIG.

  The central element of the rotary kiln is the rotating tube (1). This rotating tube has a length of 4000 mm and an inner diameter of 700 mm. This rotary tube is made of stainless steel 1.4893 and has a wall thickness of 10 mm.

  On the inner wall of the rotary kiln, a lifting lance (Hublanzen) having a height of 5 cm and a length of 23.5 cm is provided. This lifting lance is used for the purpose of first lifting the material to be heat-treated in the rotary kiln and thereby thoroughly mixing it.

  One rotary kiln has the same height and is equidistant around it (each 90 ° apart), each with four lifting lances (quadruple). Along this rotary kiln there are eight such four-part structures (23.5 cm spacing each). The two adjacent four-part lifting lances are staggered around their periphery. The lifting lance is not present at the tip and end (first and last 23.5 cm) of the rotary kiln.

  This rotating tube freely rotates in a parallelepiped (2) having four heating zones of the same length (resistance heating) of the same length continuous in the length of the rotating tube surrounding the rotary kiln. . Each heating zone can heat the corresponding section of the rotating tube to a temperature between room temperature and 850 ° C. The maximum heating efficiency of each heating zone is 30 kW. The distance between the electric heating zone and the outer surface of the rotary tube is about 10 cm. The distal end and the distal end of the rotating tube protrude about 30 cm from the parallelepiped.

  The rotation speed can be variably adjusted at 0 to 3 rotations per minute. This rotary tube can rotate left or right. In the case of right rotation, the material remains in the rotary tube, and in the case of left rotation, the material is sent from the inlet (3) to the outlet (4). The angle of inclination of the rotary tube with respect to the horizontal can be variably adjusted from 0 ° to 2 °. This tilt angle is virtually 0 ° in the case of discontinuous operation. In the case of continuous operation, the lowest position of the rotary tube is when the material is discharged. This rapid cooling of the rotary tube can be carried out by switching off the electric heating zone and switching on the aerator (5). This ventilator draws in ambient air through a hole (6) present in the lower floor of the parallelepiped and sends it out through three valves (7) with variable adjustable openings present in the cover.

  Material loading is controlled via a rotary star feeder (mass control). The discharge of the material is controlled over the direction of rotation of the rotating tube as described above.

  In the case of discontinuous operation of the rotating tube, a material amount of 250 to 500 kg can be heat-treated. In this case, this material is usually present exclusively in the heating section of the rotary tube.

  From the lance (8) present on the central axis of the rotating tube, a total of three thermocouples (9) are vertically communicated with the material at an interval of 800 mm. This thermocouple makes it possible to measure the material temperature. In the present specification, the material temperature is understood as an average value of the three thermocouple temperatures. In the material present in this rotating tube, the maximum difference between the two measured temperatures is preferably less than 30 ° C., preferably less than 20 ° C., particularly preferably less than 10 ° C., in particular according to the invention. Preferably it is 5 degreeC or less than 3 degreeC.

  This rotating tube can guide the gas flow, thereby adjusting the calcination atmosphere of the material or generally the heat treatment atmosphere.

  The heater (10) provides an opportunity to heat the gas stream directed into the rotating tube to a desired temperature (eg, to a desired temperature for the material in the rotating tube) prior to entering the rotating tube. . The maximum output of this heater is 1 × 50 kW + 1 × 30 kW. Here, in principle, the heater (10) is, for example, an indirect heat exchanger. Such a heater can in principle also be used as a cooler. In general, however, this heater is an electric heater that conducts the gas stream on a metal wire heated by an electric current (CSN flow heater, Fa. C. Schniewindt KG (58805 Neuerlde Germany) 97D / 80 type is suitable).

  In principle, this rotating tube arrangement provides the opportunity to circulate partially or completely the gas stream conducted to the rotating tube. The circulation path necessary for this is movably connected to the rotary tube via a ball bearing or a graphite compression body at the rotary tube inlet and the rotary tube outlet. This connection part is cleaned with an inert gas (for example, nitrogen) (barrier gas). Both wash streams (11) replenish the gas stream conducted to the rotating tube at the inlet to the rotating tube and at the outlet from the rotating tube. In this case, it is appropriate that the rotary pipe is narrow at the tip and the end thereof and enters the supply pipe or the discharge pipe of the circulation path.

  A cyclone (12) is present downstream of the outlet of the gas stream guided by this rotating tube for the separation of solid particles that flow with the gas stream (this centrifuge is a solid suspended in the gas phase). Particles are separated by the interaction of centrifugal force and gravity: the centrifugal force of the gas stream rotating as a spiral vortex promotes the settling of suspended particles).

  The transport (gas circulation) of this circulating gas stream (24) is carried out by a circulating gas compressor (13) (ventilator), which sucks in the direction of the cyclone and applies pressure in the other direction. Immediately downstream of the circulating gas compressor, the gas pressure is generally above 1 atmosphere. A circulation gas discharge port exists downstream of the circulation gas compressor (the circulation gas can pass through the control valve (14)). Ejection is facilitated by a diaphragm (a cross section shrinkage factor of about a factor of 3, a decompressor) (15) existing downstream of the outlet.

  The pressure can be controlled downstream of the rotary tube outlet via a control valve. This control consists of a pressure sensor (16) provided downstream of the rotary tube outlet, an exhaust gas compressor (17) (ventilator) that sucks in the direction of the control valve, a circulating gas compressor (13), and a supply of fresh gas. It is performed by interaction. The pressure (immediately) downstream of the rotary tube outlet can be adjusted to be, for example, up to +1.0 mbar and up to -1.2 mbar, for example, compared to the external pressure.

  That is, the pressure of the gas stream flowing through the rotating tube may be less than the ambient pressure of the rotating tube upon exiting the rotating tube.

  If it is intended that the gas flow guided by the rotating tube is not at least partially circulated, the connection between the cyclone (12) and the circulating gas compressor (13) is closed by a three-way cock (26), and The gas stream is led directly to the exhaust gas purification device (23). In this case, the connection to the exhaust gas purification device present downstream of the circulating gas compressor is likewise closed by a three-way cock. In this case, if the gas flow consists essentially of air, this gas flow is sucked (27) via the circulating gas compressor (13). The connection to the cyclone is closed by a three-way cock. In this case, the gas flow is preferably sucked by the rotating tube, so that the internal pressure of the rotating tube is small compared to the ambient pressure.

  When continuously operating the rotary kiln device, it is advantageous to adjust the pressure downstream of the rotary tube outlet to be -0.2 mbar below the external pressure. When operating the rotary kiln device discontinuously, it is advantageous to adjust the pressure downstream of the outlet of the rotary tube to be -0.8 mbar below the external pressure. This slight vacuum is used to avoid contaminating the circulating air with the gas mixture from the rotary kiln.

  Between the circulating gas compressor and the cyclone, for example, there is a sensor (18) that measures the ammonia content and oxygen content in the circulating gas. The ammonia sensor advantageously operates on the optical measurement principle (absorption of light of a given wavelength is proportionally related to the ammonia content of the gas), which is a Fa. A Perkin & Elmer device MCS100 is suitable. The oxygen sensor is based on the paramagnetism of oxygen. Oxymat SF 7MB1010-2CA01-1AA1-Z type Oximat from Siemens is suitable.

  Between the diaphragm (15) and the heater (10), a gas, for example air, nitrogen, ammonia or other gas, can be metered into the actually recirculated circulating gas fraction (19). . In particular, base load nitrogen is metered in (20). A separate nitrogen / air splitter (21) can be used to react to the oxygen sensor readings.

The discharged circulating gas component (22) (exhaust gas) contains a gas that is not particularly completely concerned, for example, NO _x , acetic acid, NH _{3 and the} like. (23).

  For this purpose, it is usually the case that the exhaust gas is first led to the washing tower (mainly a column containing a packing with a separating action upstream of the outlet, without internal structures; the exhaust gas and the water spray are cocurrent And guided in countercurrent (two spray nozzles with opposite spray directions).

  This exhaust gas is guided from the cleaning tower into an apparatus containing a fine dust filter (usually a bundle pipe including a tubular filter), and the exhaust gas that has entered is excluded from the inside. Then, it is finally burned in the muffle.

  Fa. KURZ Instruments, Inc. Using a Model 455 Jr type sensor (28) from Monterey, USA (USA), the amount of gas flow supplied to a rotating tube different from the barrier gas is measured and adjusted (measuring principle: isothermal-anemometer Mass flow measurement by thermal convection under application).

  In the case of continuous operation, the material and the gas phase are passed through the rotary kiln in countercurrent.

  Nitrogen always means nitrogen of purity> 99% by volume in connection with this example.

2. Production of precursor material for the purpose of producing a multi-metal oxide material of stoichiometric ratio Mo ₁₂ V ₃ W _1.2 Cu _2.4 O _x 16.3 kg of copper (II) acetate hydrate (content: CuO 40.0 % By weight) was dissolved in 274 l of water at a temperature of 25 ° C. with stirring. A clear solution 1 was obtained.

Separately, 614 l of water was heated to 40 ° C., and 73 kg of ammonium heptamolybdate tetrahydrate (MoO ₃ 81.5% by weight) was introduced with stirring while maintaining 40 ° C. It was then heated to 90 ° C. within 30 minutes with stirring, and 12.1 kg of ammonium metavanadate and 10.7 kg of ammonium paratungstate heptahydrate in the order described above while maintaining this temperature continuously. (88.9% by weight WO ₃ ) (instead of this 12.1 kg of ammonium metavanadate, alternatively used at 11.3 kg, otherwise operated as described above; In this case, a substitute for the stoichiometric ratio Mo ₁₂ V _2.8 W _1.2 Cu _2.4 O _x is obtained as an active material substitute). A clear solution 2 was obtained.

This solution 2 was cooled to 80 ° C., and then solution 1 was stirred into solution 2. The resulting mixture was mixed with 130 l NH ₃ 25 wt% aqueous solution at a temperature of 25 ° C. This was stirred to produce a clear solution with a temperature of 65 ° C. and a pH value of 8.5 in a short time. This solution was again added to 20 l of water at a temperature of 25 ° C. The temperature of the resulting solution is then raised again to 80 ° C. and then it is Spray drying was performed using an S-50-N / R type spray dryer manufactured by Niro-Atomizer (Copenhagen) (gas inlet temperature: 350 ° C., gas outlet temperature: 110 ° C.). The particle size of the spray powder was 2 to 50 μm. 60 kg of the spray powder thus obtained was added to Fa. Weigh into a kneader of model AM160 (Sigma blade) from AMK (Achener Misch-und Knetmaschinen Fabrik) and add 5.5 l of acetic acid (≈100% by weight glacial acetic acid) and 5.2 l. Water was kneaded (screw rotation speed: 20 rpm). After a kneading time of 4-5 minutes, an additional 6.5 l of water was added and the kneading process was continued until 30 minutes had passed (kneading temperature about 40-50 ° C.). The kneaded product is then discharged into an extruder and molded using this extruder (Fa. Bonnet Company, Ohio, mold: G103-10 / D7A-572K (6 ″ Extruder W Packer)). An extrudate (length: 1-10 cm; diameter: 6 mm) was obtained and dried on a belt dryer for 1 hour at a temperature of 120 ° C. (material temperature). A precursor material to be heat treated was formed.

3. Production of catalytically active material by heat treatment of the precursor material in the rotary kiln apparatus (calcination of the precursor material) This heat treatment was carried out in the rotary kiln according to FIG. 1 described in “B) 1” and under the following conditions:
The heat treatment was carried out discontinuously on a quantity of 300 kg of material produced as described in “B) 2”;
The angle of inclination of the rotating tube relative to the horizontal ≈ 0 °;
-The rotating tube was rotated right at 1.5 rev / min;
-During this entire heat treatment, the rotary tube is energized (after evacuating the initially contained air) with a 205 Nm ³ / h gas flow configured as follows and its outlet from the rotary tube Supplemented with an additional 25 Nm ³ / h of nitrogen in the barrier gas;
Base load nitrogen (20) and gas released in the rotary tube 80 Nm ³ / h,
Barrier gas nitrogen (11) 25 Nm ³ / h,
Air (splitter (21)) 30 Nm ³ / h; and recirculated circulating gas 70 Nm ³ / h.

  The barrier gas nitrogen was supplied at a temperature of 25 ° C. Each of the other gas stream mixtures came from a heater and led into the rotating tube at the temperature indicated by the material in the rotating tube.

Heating the material temperature 25 ° C. substantially linearly to 300 ° C. within 10 hours;
The material temperature is then heated to 360 ° C. substantially linearly within 2 hours;
The material temperature is then reduced to 350 ° C. substantially linearly within 7 hours;
The material temperature is then increased substantially linearly to 420 ° C. within 2 hours and the material temperature is maintained for 30 minutes;
-Then, 30 Nm ³ / h of air in the gas flow through the rotating tube is replaced with a corresponding increase in temperature with nitrogen at the base load (thus completing the original heat treatment process), heating the rotating tube And the material was cooled to a temperature below 100 ° C. by switching on quenching of the rotating tube by inhalation of ambient aspiration within 2 hours and finally cooled to ambient temperature; In this case, this gas stream was fed to the rotary tube at a temperature of 25 ° C .;
-During the entire heat treatment, the (immediately) downstream pressure at the outlet of the rotating tube of the gas stream was 0.2 mbar below the external pressure.

  The oxygen content of the gas atmosphere in the rotating tube was 2.99% by volume in all phases of the heat treatment. The ammonia concentration in the gas atmosphere in the rotating tube averaged 4% by volume over the entire reduction heat treatment time.

  FIG. 2 shows the amount of ammonia released from the precursor material as a percentage of the total amount of ammonia released from the precursor material during the entire heat treatment as a function of material temperature (° C.).

  FIG. 3 shows the ammonia concentration (volume%) of the atmosphere in which the heat treatment is performed, depending on the material temperature (° C.) during the heat treatment.

  FIG. 4 shows the kg precursor material and the molar amounts of molecular oxygen and ammonia per hour introduced into the rotating tube along with the gas flow over the heat treatment, depending on the material temperature.

4). Molding of multi-metal oxide material The catalytically active material obtained in "B) 3" Using a Hosokawa-Alpin (Augsburg) biplex crossflow classifier (BQ500), grind into fine powder, pass 50% of the powder particles through a sieve with a mesh width of 1-10 μm, and The proportion of particles whose maximum dimension was greater than 50 μm was less than 1%.

Here, this molding was carried out as follows:
70 kg annular carrier (outer diameter 7.1 mm, length 3.2 mm, inner diameter 4.0 mm; Fa. CeramTec C220 type steatite, which has a surface roughness R _z of 45 μm and has a total capacity with respect to the carrier volume The pore volume was ≦ 1% by volume; see DE-A 2135620) in a 200 l internal volume Dragierksel (tilt angle 90 °; Hicoater, Fa. Loedige, Germany) Filled. The coating pan was then rotated at 16 revolutions / minute. An aqueous solution of 3.8 to 4.2 liters from 75% by weight of water and 25% by weight of glycerin was sprayed on the support within 25 minutes via a nozzle. At the same time, within the same time, 18.1 kg of crushed multi-metal oxide material (its specific surface area was 13.8 m ² / g) was passed through the floor groove and outside the conical spray of the spray nozzle. Were continuously metered. During this coating, the supplied powder was completely contained on the support surface and no aggregation of fine oxide active material was observed. After completion of the addition of the active material powder and water, hot air (about 400 m ³ // 100 ° C.) (alternatively 80-120 ° C.) over 40 minutes (alternatively 15-60 minutes) at a rotational speed of 2 revolutions / minute. h) was sprayed into the coating pan. An annular shell catalyst SKH1 was obtained, and the proportion of the oxide active material was 20% by mass relative to the whole material. The shell thickness was 170 ± 50 μm on the surface of one carrier and on the surfaces of various carriers.

  FIG. 5 shows the pore distribution before molding of this crushed active material powder. On the abscissa, the pore diameter is plotted in μm (logarithmic scale).

On the right ordinate, the logarithm of the differentiated contribution of each pore diameter to the total pore volume is plotted in ml / g (curve ◯). This maximum value represents the pore diameter showing the largest contribution to the total pore volume. On the left ordinate, the integral for each contribution of each pore diameter to the total pore volume is plotted in ml / g (curve □). This endpoint is the total pore volume (in this specification, all statements regarding the measurement of total pore volume and the diameter distribution for this total pore volume are made by Fa. Micromeritics GmbH, unless otherwise stated. (4040 Neuss Germany) by means of mercury porosimetry applying the device AutoPore 9220 (belt width 30 mm to 0.3 mm); in this specification all descriptions for the measurement of specific surface area or micropore volume are described in DIN 66131 (Measurement of the specific surface area of the solid by gas adsorption (N ₂ ) with Brunauer-Emmet-Teller (BET)).

  FIG. 6 shows each of the individual pore diameters (abscissa, angstrom, logarithmic scale) in the micropore range for the total pore volume for this pre-molded active material powder (ml / g) (ordinate). Indicates the contribution.

FIG. 7 is similar to FIG. 5 except that the multi-metal oxide active material is additionally separated from the annular shell catalyst by mechanical scraping (its specific surface area is 12.9 m ² / g. )

  FIG. 8 is similar to FIG. 6 but relates to a multi-metal oxide active material that is additionally separated from the annular shell catalyst by mechanical scraping.

C) Preparation of a cyclic shell catalyst SKN1 for the post-reaction stage with an active material of stoichiometric ratio Mo ₁₂ V ₃ W _1.2 Cu _2.4 Pd _0.03 O _x This preparation was carried out in the same way as the preparation of SKH1 However, 225 g of solid Pd (NO ₃ ) ₂ hydrate (manufacturer: Sigma-Aldrich) is added to the mixture obtained in this case after the solution 1 is stirred and introduced into the solution 2 and before the aqueous NH ₃ solution is added. Was introduced with stirring.

D) Preparation of a cyclic shell catalyst SKN2 for the post-reaction stage with an active material of stoichiometric ratio Mo ₁₂ V ₃ W _1.2 Cu _2.4 Fe _1.2 O _x This preparation was carried out in the same way as the preparation of SKH 1 However, after the solution 1 was stirred and introduced into the solution 2, before the NH ₃ aqueous solution was added to the mixture obtained in this case, 16.7 kg of solid Fe (NO ₃ ) ₂ × 9H ₂ O (manufacturer: Riedel- de Haen, 97%) was introduced with stirring.

E) Preparation of a cyclic shell catalyst SKN3 for the post-reaction stage with an active material of stoichiometric ratio Mo ₁₂ V ₃ W _1.2 Cu _4.8 O _x This preparation was carried out in the same way as the preparation of SKH 1 except that the solution 1 contained 32.6 kg of the same copper (II) acetate hydrate instead of 16.3 kg of copper (II) acetate hydrate.

F) Preparation of a cyclic shell catalyst SKN4 for the post-reaction stage with the stoichiometric ratio (Mo ₁₂ V ₃ W _1.2 Cu _1.9 O _x ) (Fe ₁ Sb ₂ O ₅ ) _0.5 as the active material. The production was carried out in the same way as with the following differences:
-Solution 1 contained only 12.9 kg of the same copper (II) acetate hydrate instead of 16.3 kg of copper (II) acetate hydrate;
- However, the spray powder obtained with a stoichiometric ratio _{Mo 12 V 3 W 1.2 Cu 1.9} , rather than further processed in a kneader, the mass ratio of the finely divided FeSb ₂ O ₆ 15: homogeneously with 1 mixed did;
This fine FeSb ₂ O ₆ was produced as follows:
838.36 g of antimony trioxide (Sb ₂ O ₃ , flamingite) was added in fine form to 3545 g of water, then 728.47 g of H ₂ O ₂ 30 wt% aqueous solution was added for 5 hours at atmospheric pressure The solution 1 was obtained by heating at reflux.

  500 g of iron acetate II (31.5% by mass, Lieferfarma: ABCR) was dissolved in 3545 g of water to obtain a solution 2. Then, the solution 2 showing room temperature was added to the solution 1 which reached the boiling point within 30 minutes. The temperature of the resulting mixture was 70 ° C. This yellowish suspension is stirred for a further 3 hours at 80 ° C. and finally the Fa. Spray drying was performed using a Niro-Atomizer (Copenhagen) spray dryer (gas inlet temperature: 350 ° C., gas outlet temperature: 110 ° C.). The particle size of the obtained spray powder was 2 to 50 μm.

G) Preparation of a cyclic shell catalyst SKN5 for the post-reaction step with an active material of stoichiometric ratio Mo ₁ V _0.29 Te _0.14 Nb _0.13 O _{x In} 3040 ml water, 87.61 g ammonium metavanadate (80 ° C.) V ₂ O ₅ 78.55 mass%, Fa.GfE., Germany-Nuremberg) was dissolved in a three-necked glass flask equipped with a stirrer, thermometer, reflux condenser and radiator. A clear yellow solution resulted. The solution was cooled to 60 ° C., and then, in the above-described continuous order, while maintaining 60 ° C., 117.03 g of telluric acid (H ₆ TeO ₆ 99% by mass, Fa. Aldrich) was first introduced with stirring, and then 400 g of ammonium heptamolybdate tetrahydrate (82.52% by mass of MoO _3, Fa. Starck (Goslar, Germany)) was introduced with stirring. The resulting deep red solution was cooled to 30 ° C., thus obtaining solution A.

  Separately, 112.67 g of ammonium niobium oxalate (Nb 20.8 mass%, Fa. Starck (Germany-Goslar)) was dissolved in 500 ml of water at 60 ° C. to obtain a solution B. Solution B was similarly cooled to 30 ° C. and combined with solution A at this temperature, with solution B being stirred into solution A. This stirring was continuously introduced within a period of 5 minutes. An aqueous dispersion having an orange color was obtained.

Next, this dispersion was spray-dried (T _{charging vessel} = 30 ° C., T ^inlet = 320 ° C., T ^outlet = 110 ° C., drying time: about 1.5 hours, Fa. Niro (Germany) Atomizer type Spray tower). This spray was similarly orange.

This spray is composed of 1% by weight of fine graphite (sieving analysis: at least 50% by weight <24 μm, at most 10% by weight ≧ 24 μm and ≦ 48 μm, at most 5% by weight > 48 μm, and BET surface area: 6 to 13 m ³ / g) was mixed and introduced.

  The resulting mixture was compressed into a hollow cylinder (ring) shape of 16 mm × 2.5 mm × 8 mm (outer diameter × height × inner diameter). As a result, the lateral compression strength of the obtained ring was about 10 N. It was.

200 g of this ring were calcined in a rotating sphere furnace (Drehkugelofen) according to FIG. For this purpose, the rotary sphere furnace contents are heated from 25 ° C. to 275 ° C. within 27.5 minutes with a linear heating ramp under an air flow of 50 Nl / h and at this temperature the air flow is 1 Maintained over time. Then, within 32.5 minutes, this linear heating ramp was used to heat from 275 ° C. to 600 ° C., with a nitrogen flow of 50 Nl / h. The 600 ° C. and nitrogen flow was maintained for 2 hours, then the entire furnace was left to cool to 25 ° C. while maintaining the nitrogen flow. A black ring with the composition Mo _1.0 V _0.33 Te _0.19 Nb _0.11 O _x (weighed: Mo _1.0 V _0.33 Te _0.22 Nb _0.11 O _x ) was obtained.

This ring was pulverized in a Retsch pulverizer until the particle size was ≦ 100 μm. 100 g of this ground material is stirred in 1000 ml of a 10% strength by weight aqueous solution of HNO ₃ for 7 hours at reflux at 70 ° C., the solid is separated from the resulting slurry, filtered and made nitrate free with water Until washed. The filter cake was dried at 110 ° C. under air overnight in a muffle furnace. The composition of the active material obtained was Mo _1.0 V _0.29 Te _0.14 Nb _0.13 O _x . This X-ray diffraction pattern (see FIG. 9) showed a pure i phase with R = 0.74. This figure did not show the peak position of diffraction reflection at 2θ = 50.0 ± 0.3 °.

  FIG. 10 shows the results of the accompanying mercury pore measurement test. The abscissa indicates the pore diameter (μm) (logarithmic plot). This right ordinate (curve ◯) shows the integral in ml / g for the contribution of individual pore diameters to total pore volume. The left ordinate (curve +) indicates the logarithm of the contribution of individual pore diameters to total pore volume in ml / g. FIG. 11 shows the corresponding test results of this crushed ring before washing with nitric acid.

  This active material was shaped into a circular shell catalyst SKN5 after pulverization, similar to the active material of SKH1.

H) Stoichiometric ratio (Mo ₁₂ V ₃ W _1.2 Cu _4.8 O _x ) _{9 parts by weight} (Mo ₁ V _0.29 Te _0.14 Nb _0.13 O _x ) with _{1 part} by _weight of active material, cyclic for the post-reaction stage Production of shell catalyst SKN6 This production was carried out in the same way as production of SKH1, except that this molding consists of the active material powder used for the production of SKH1 up to 90% by mass and up to 10% by mass for the production of SKN5. This was carried out with a homogeneous mixture of active material powder used (mixed uniformly on a turntable for 2 hours).

I) For the second reaction stage (acrolein → acrylic acid), a stoichiometric ratio (Mo ₁₂ V _3.46 W _1.39 ) _0.87 (CuMo _0.5 O ₄ ) _0.4 (CuSb ₂ O ₆ ) _0.4 as active material Production of Shell Catalyst SKH2 Preparation of starting material 1 (phase 1) with stoichiometric ratio Cu ₁ Mo _0.5 W _0.5 O ₄ To 603 l of water was added 98 l of a 25% by weight aqueous solution of NH ₃ . Then 100 kg of copper (II) acetate hydrate (content: 40.0% by weight of CuO) was dissolved in this aqueous mixture, resulting in a clear, deep blue solution 1 which was 3. It contained 9% by mass of Cu and showed room temperature.

Regardless of Solution 1, 620 l of water was heated to 40 ° C. In this, 27.4 kg of ammonium heptamolybdate tetrahydrate (MoO ₃ 81.5% by mass) was dissolved with stirring within 20 minutes while maintaining 40 ° C. Then 40.4 kg of ammonium paratungstate heptahydrate (WO ₃ 88.9% by weight) was fed and heated to 90 ° C. within 45 minutes before being dissolved at this temperature with stirring. A clear aqueous solution 2 having a yellow-orange color was obtained.

  Subsequently, this aqueous solution 1 was stirred and introduced into the solution 2 showing 90 ° C., at which time the temperature of the whole mixture did not drop below 80 ° C. The resulting aqueous suspension was further stirred at 80 ° C. for 30 minutes. This suspension is then referred to as Fa. Spray drying was performed using a S-50-N / R type spray dryer manufactured by Niro-Atomizer (Copenhagen) (gas inlet temperature: 315 ° C., gas outlet temperature: 110 ° C., parallel flow). The particle size of the spray powder was 2 to 50 μm.

100 kg of the light green spray powder obtained in this way was subjected to Fa. It was metered in a kneader of type VIU160 (Sigma blade) manufactured by AMK (Achener Misch-und Knetmaskinen Fabrik) and kneaded while adding 8 l of water (retention time: 30 minutes, temperature: 40-50 ° C.) . The kneaded product is then discharged into an extruder and molded using this extruder (Fa. Bonnet Company, Ohio, mold: G103-10 / D7A-572K (6 ″ Extruder W Packer)). An extrudate (length: 1-10 cm; diameter 6 mm) was obtained, which was dried on a belt dryer for 1 hour at a temperature of 120 ° C. (material temperature). The product was heat treated (calcined) in the rotary kiln described in “1.” as follows:
The heat treatment was carried out continuously with the material carried in at 50 kg / h of extrudate;
The tilt angle of the rotating tube with respect to the horizontal was 2 ° C;
A 75 Nm ³ / h air flow countercurrent to the material, the rotating tube is conducted and replenished with a total (2 × 25) 50 Nm ³ / h of 25 ° C. barrier gas;
The pressure downstream of the rotary tube outlet was 0.8 mbar lower than the external pressure;
The rotating tube was rotated left at 1.5 revolutions / minute;
-Circulating gas operation formula was not applied;
During the first pass of the extrudate through the rotating tube, the temperature of the outer wall of the rotating tube was adjusted to 340 ° C. and an air flow was introduced into the rotating tube at a temperature of 20-30 ° C .;
-The extrudate is then passed through the rotating tube at the same flow rate and under the same conditions, except that the following conditions are different:
The temperature of the rotating tube wall was adjusted to 790 ° C;
The air stream was heated to a temperature of 400 ° C. and led into the rotating tube.

Then, this reddish brown extrudate is referred to as Fa. It grind | pulverized until it became an average particle diameter of 3-5 micrometers on the biplex type | mold crossflow classification grinder (BQ500) of Hosokawa-Alpin (Augsburg). The BET surface area of the starting material 1 thus obtained was <1 m ² / g. The following phases were confirmed by X-ray diffraction:
1. CuMoO ₄ -III having an iron manganese barite structure;
2. HT-copper molybdate.

2. Production of starting material 2 with a stoichiometric ratio CuSb ₂ O ₆ (phase 2) 52 kg of antimony trioxide (99.9% by weight of Sb ₂ O ₃ , Ananite) into 216 l of water (25 ° C.) Suspended with stirring. The resulting aqueous suspension was heated to 80 ° C. Next, the mixture was further stirred for 20 minutes while maintaining 80 ° C. Next, 40 kg of a 30% by mass aqueous hydrogen peroxide solution was added within 1 hour, maintaining a temperature of 80 ° C. during that time. The mixture was further stirred for 1.5 hours while maintaining this temperature. 20 l of 60 ° C. hot water were then added, thus obtaining an aqueous suspension 1. To this suspension, at a temperature of 70 ° C., 618.3 kg of ammoniacal copper (II) acetate aqueous solution (in 618.3 kg of solution, 60.8 g of copper acetate and 75 l of 25% by mass of ammonia per kg of solution) Aqueous solution) was introduced with stirring. It was then heated to 95 ° C. and further stirred at this temperature for 30 minutes. It was then replenished with 50 liters of 70 ° C. hot water and heated to 80 ° C.

  Finally, this aqueous suspension was spray dried (F. Niro-Atomizer (Copenhagen) S-50-N / R type spray dryer, gas inlet temperature 360 ° C., gas outlet temperature 110 ° C. Flow). The particle size of the spray powder was 2 to 50 μm.

  75 kg of the spray powder thus obtained was added to Fa. It was metered into a kneader of type VIU160 (Sigma blade) from AMK (Achener Misch-und Knetmaschinen Fabrik) and kneaded while adding 12 l of water (residence time: 30 minutes, temperature: 40-50 ° C.) . The kneaded product is then discharged into an extruder (the same extruder as in the manufacture of Phase 1) and molded using this extruder to obtain an extrudate (length 1-10 cm; diameter 6 mm). It was. The extrudate was dried on a belt dryer at a temperature of 120 ° C. (material temperature) for 1 hour.

250 kg of the extrudate thus obtained was heat-treated (calcined) in the rotary kiln according to FIG. 1 (details are described in “B) 1.” as follows:
The heat treatment was carried out discontinuously with a material mass of 250 kg;
The angle of inclination of the rotating tube relative to the horizontal ≈ 0 °;
-The rotating tube was rotated right at 1.5 rev / min;
A gas flow of 205 Nm ³ / h was passed through the rotating tube; at the start of the heat treatment it consisted of 180 Nm ³ / h air as barrier gas and 1 × 25 Nm ³ / h N ₂ ; The incoming gas stream was further supplemented with 1 × 25 Nm ³ / h of N ₂ ; 22-25% by volume of this total stream was returned to the rotary tube and the remainder was discharged; this discharge was a barrier gas, And the remaining amount was replaced with fresh air;
-The gas stream was led into a rotating tube at 25 ° C;
The pressure downstream of the rotary tube outlet was 0.5 mbar lower than the external pressure (normal pressure);
The temperature in the material is first increased linearly from 25 ° C. to 250 ° C. within 1.5 hours; then the temperature of the material is increased linearly from 250 ° C. to 300 ° C. within 2 hours and this temperature is increased to 2 Then the temperature of the material was increased linearly from 300 ° C. to 405 ° C. within 3 hours and then maintained for 2 hours; the heating zone was switched off and the rapid cooling of the rotating tube was activated by air suction By doing so, the temperature in the material was lowered to a temperature of less than 100 ° C. within 1 hour, and finally cooled to ambient temperature.

The powdery starting material 2 thus obtained had a BET specific surface area of 0.6 m ₂ / g and a composition of CuSb ₂ O ₆ . This powder X-ray diffractogram of the obtained powder substantially showed diffraction reflection of CuSb ₂ O ₆ (comparison spectrum 17-0284 of JCPDS-ICDD index).

3. Preparation of starting material 3 with stoichiometric ratio Mo ₁₂ V _3.35 W _1.38 900 l of water was charged into a stirring vessel with stirring at 25 ° C. Then 122.4 kg of ammonium heptamolybdate tetrahydrate (MoO ₃ 81.5% by weight) was added and heated to 90 ° C. with stirring. Next, while maintaining 90 ° C., 22.7 kg of ammonium metavanadate is first stirred and introduced, and finally 20.0 kg of ammonium paratungstate heptahydrate (WO ₃ 88.9% by mass) is stirred and introduced. did. By stirring at 90 ° C. for a total of 80 minutes, a clear orange solution was obtained. The solution was cooled to 80 ° C. Next, while maintaining 80 ° C., 18.8 kg of acetic acid (≈100% by mass of glacial acetic acid) was first introduced with stirring, and then 24 l of a 25% by mass aqueous solution of ammonia was introduced with stirring.

  This solution remained clear and orange, and it was replaced with Fa. Spray drying was performed using a S-50-N / R type spray dryer manufactured by Niro-Atomizer (Copenhagen) (gas inlet temperature: 260 ° C., gas outlet temperature: 110 ° C., cocurrent flow). The resulting spray powder formed starting material 3 and the particle size was 2-50 μm.

4). Production of a dry material to be heat-treated having a stoichiometric ratio (Mo ₁₂ V _3.46 W _1.39 ) _0.87 (CuMo _0.5 W _0.5 O ₄ ) _0.4 (CuSb ₂ O ₆ ) _0.4 75 kg of starting material 3, 5.2 l of water and 6.9 kg of acetic acid (100% by mass of glacial acetic acid) are placed in a VIU160 type kneader equipped with two sigma blades from AMK (Achener Mischund Knetmaskinen Fabric) Charged and kneaded for 22 minutes. Then 3.1 kg of starting material 1 and 4.7 kg of starting material 2 were added and kneaded for a further 8 minutes (T≈40-50 ° C.).

  The kneaded product is then discharged into an extruder (the same extruder as in the manufacture of Phase 1) and molded using this extruder to obtain an extrudate (length 1-10 cm; diameter 6 mm). It was. The extrudate was dried on a belt dryer at a temperature of 120 ° C. (material temperature) for 1 hour.

The 306 kg of dried extrudate was then heat treated as follows in a rotary kiln according to FIG. 1 (details are described in “B) 1”:
The heat treatment was carried out discontinuously with a material mass of 306 kg;
The tilt angle of the rotating tube relative to the horizontal ≈ 0 °;
-The rotating tube was rotated right at 1.5 rev / min;
-Initially the material temperature was heated from 25 ° C to 100 ° C substantially linearly within 2 hours;
Within this time, a (substantially) nitrogen gas flow of 205 Nm ³ / h was fed through the rotating tube. In steady state (after evacuating the originally contained air) it had the following composition:
Base load nitrogen (20) 110 Nm ³ / h,
Barrier gas nitrogen (11) 25 Nm ³ / h and recirculated gas (19) 70 Nm ³ / h.

  The barrier gas nitrogen was supplied at a temperature of 25 ° C. Each of the other nitrogen stream mixtures were each introduced into the rotating tube at the temperature indicated by the material in the rotating tube.

-The material temperature was then heated from 100 ° C to 320 ° C at a heating rate of 0.7 ° C / min;
A gas stream with the following composition of 205 Nm ³ / h was introduced into the rotating tube until the material temperature reached 300 ° C .:
Base load nitrogen (20) and gas released in rotating tube 110 Nm ³ / h,
Barrier gas nitrogen (11) 25 Nm ³ / h and recirculated circulating gas (19) 70 Nm ³ / h.

  The barrier gas nitrogen was supplied at a temperature of 25 ° C. Each mixture of both other gas streams was led into the rotating tube at the temperature indicated by the material in the rotating tube.

From exceeding the material temperature of 160 ° C. until the material temperature of 300 ° C. is reached, 40 mol% of the total ammonia M ^A released in the course of the total heat treatment of this material is released from this material. It was done.

  When the material temperature of 320 ° C. was reached, the oxygen content of the gas stream fed to the rotary tube was increased from 0% to 1.5% by volume and subsequently maintained for 4 hours.

  At the same time, the temperature occupying the four heating zones heating the rotating tube was reduced by 5 ° C. (to 325 ° C.) and then maintained for 4 hours.

  In this case, the material temperature passed the maximum temperature above 325 ° C., which did not exceed 340 ° C. before the material temperature dropped again to 325 ° C.

Over the course of 4 hours, the composition of the 205 Nm ³ / h gas stream conducted to the rotating tube changed as follows:
Base-load nitrogen (20) and gas released in the rotating tube 95 Nm ³ / h;
Barrier gas nitrogen (11) 25 Nm ³ / h;
Recirculated circulating gas 70 Nm ³ / h; and air through the splitter (21) 15 Nm ³ / h.

  The barrier gas nitrogen was supplied at a temperature of 25 ° C.

  Each of the other gas stream mixtures was led into the rotating tube at the temperature indicated by the material in the rotating tube.

By the time 4 hours have passed since the material temperature exceeded 300 ° C., 55 mol% of the total amount M ^A of ammonia released in the course of the total heat treatment of the material was released from the material (this caused , until the lapse of 4 hours, a total of 40 mole% + 55 mol% = 95 mole% of the amount of ammonia M ^a was released).

  -After 4 hours, the material temperature was increased to 400 ° C within about 1.5 hours at a heating rate of 0.85 ° C / min.

  This temperature was then maintained for 30 minutes.

Over this time, the composition of the 205 Nm ³ / h gas stream conducted to the rotating tube was as follows:
Base-load nitrogen (20) and gas released in the rotating tube 95 Nm ³ / h;
Air (splitter (21)) 15 Nm ³ / h;
Barrier nitrogen (11) 25 Nm ³ / h and recirculated gas 70 Nm ³ / h.

  The barrier gas nitrogen was supplied at a temperature of 25 ° C. Each of the other gas stream mixtures was led into the rotating tube at the temperature indicated by the material in the rotating tube.

-The calcination was completed by lowering the material temperature; for this, the heating zone was switched off, the rotary tube was quenched by air suction and the material temperature was reduced to 100 within 2 hours. Cooled to a temperature below 0 ° C. and finally cooled to ambient temperature;
When the heating zone was switched off, the composition of the 205 Nm ³ / h gas stream conducted to the rotating tube was changed to the following mixture:
Base-load nitrogen (20) and gas released in the rotating tube 110 Nm ³ / h;
Air (splitter (21)) 0 Nm ³ / h;
Barrier gas nitrogen (11) 25 Nm ³ / h; and recycled circulating gas 70 Nm ³ / h.

  This gas stream was supplied to the rotary tube at a temperature of 25 ° C.

  -Over the entire heat treatment, the pressure (immediately) downstream of the rotary tube outlet was lower by 0.2 mbar compared to the external pressure.

Figure 12 shows the percentage of% of M ^A as a function of the material was temperature (° C.). FIG. 13 shows the ammonia concentration (volume%) of the atmosphere A through the heat treatment according to the material temperature (° C.).

6). Molding of multi-metal oxide material The catalytically active material obtained in “5.” is pulverized into a fine powder using a biplex type cross-flow classifier (BQ500) (Fa. Hosokawa-Alpin, Augsburg). 50% of the powder particles were passed through a sieve having a mesh width of 1-10 μm, and the proportion of particles whose maximum dimension was greater than 50 μm was less than 1%.

70 kg annular carrier (outer diameter 7.1 mm, length 3.2 mm, inner diameter 4.0 mm; Fa. CeramTec C220 type steatite, which has a surface roughness R _z of 45 μm and has a total capacity with respect to the carrier volume The pore volume is ≦ 1% by volume; see DE-A 2135620) in an internal volume of 200 l coating pan (tilt angle 90 °; Hicoater from Fa. Loedige, Germany). The coating pan was then rotated at 16 revolutions / minute. A 3.8-4.2 liter aqueous solution of 75% by weight water and 25% by weight glycerin was sprayed onto the carrier through a nozzle within 25 minutes. At the same time, within the same time, 18.1 kg of crushed multi-metal oxide material was continuously metered out of the spray nozzle conical spray via a vibrating channel. During this coating, the supplied powder was completely contained on the support surface and no aggregation of fine oxide active material was observed. After completion of the addition of the active material powder and water, hot air (approximately 400 m ³ // 100 ° C.) (over 80-120 ° C.) over 40 minutes (alternatively 15-60 minutes) at a rotational speed of 2 revolutions / minute h) was sprayed into the coating pan. An annular shell catalyst SKH2 was obtained, and its oxide active material component was 20% by mass relative to the total material. The shell thickness was 170 ± 50 μm on the surface of one carrier and on the surfaces of various carriers.

FIG. 14 further shows the pore distribution before molding of this pulverized active material powder (its BET specific surface area was 21 m ² / g). On the abscissa, the pore diameter is plotted in μm (logarithmic scale).

On the right ordinate, the logarithm of the differentiated contribution of each pore diameter to the total pore volume is plotted in ml / g (curve O). This maximum represents the pore diameter with the largest contribution to the total pore volume. On the left ordinate, the integral for each contribution of each pore diameter to the total pore volume is plotted in ml / g (curve □). This endpoint is the total pore volume (in this specification, all statements regarding the measurement of total pore volume and diameter distribution for this total pore volume are made by Fa. Micromeritics GmbH, unless otherwise stated) (4040 Neuss Germany) by means of mercury porosimetry applying the apparatus AutoPore 9220 (belt width 30 mm to 0.3 mm); in this specification all descriptions for the measurement of specific surface area or micropore volume are described in DIN 66131 (Measurement of the specific surface area of the solid by gas adsorption (N ₂ ) by Brunauer-Emmet-Teller (BET)) Figure 15 shows the active material powder (ml / ml) before molding g) for each (in the ordinate) in the micropore range for the total pore volume Pore diameter (abscissa Å, logarithmic scale) shows the individual contributions of.

FIG. 16 is similar to FIG. 14 except for the multi-metal oxide active material that was additionally separated from the annular shell catalyst by mechanical scraping (its specific surface area was 24.8 m ² / g). ).

  FIG. 17 is similar to FIG. 15 but relates to a multi-metal oxide active material that is additionally separated from the annular shell catalyst by mechanical scraping.

  By virtue of the doping described in the case of the shell catalysts SKN1 to SKN6 (for example increasing the Pd or Fe or Cu content) and / or mixing, the shell catalyst for the post-reaction stage according to the invention is replaced by SKH2. Can be manufactured.

K) Description of test sequence and reaction description for both reaction stages and post-reaction stages of the main reaction First reaction stage of the main reaction Reaction tube (V2A steel; outer diameter 30 mm, wall thickness 2.5 mm, inner diameter 25 mm, Length: 320 cm) was charged from top to bottom as follows:
Section 1: Length 50cm
7mm x 7mm x 4mm (outer diameter x length x inner diameter) steatite ring as a spare floor.

Section 2: Length 100cm
A catalyst charge having a uniform mixture of a steatite ring having a shape of 5 mm × 3 mm × 2 mm (outer diameter × length × inner diameter) and 70% by mass of a cyclic complete catalyst VKH.

Section 3: Length 170cm
Catalyst charge with exclusively cyclic complete catalyst VKH.

  This reaction tube was thermostatically controlled using a salt bath (53% by mass of potassium nitrate, 40% by mass of sodium nitrite and 7% by mass of sodium nitrate) in which nitrogen was passed in countercurrent.

Second reaction stage of the main reaction A reaction tube (V2A steel; outer diameter 30 mm, wall thickness 2.5 mm, inner diameter 25 mm, length 320 cm) was charged with the following from top to bottom:
Section 1: 20cm in length
A preliminary floor from a steatite ring having a shape of 7 mm × 7 mm × 4 mm (outer diameter × length × inner diameter).

Section 2: Length 100cm
7 mass × 3 mm × 4 mm (outer diameter × length × inner diameter) shape steatite ring 25% by mass and cyclic shell catalyst SKH1 (here, SKH2 may be used alternatively) 75% by mass Catalyst charge having a homogeneous mixture.

Section 3: Length 200cm
Catalyst charge with exclusively annular shell catalyst SKH1 (here alternatively SKH2 may be used).

  The reaction tube was thermostatically controlled using a salt bath (53% by mass of potassium nitrate, 40% by mass of sodium nitrite and 7% by mass of sodium nitrate) in which nitrogen was passed in countercurrent.

  Between both reaction stages, there is an intercooler filled with inert material, which leads to the product gas mixture of the first reaction stage, which is heated to a temperature of 250 ° C. by indirect cooling. It was what cooled.

This first reaction stage is continuously charged with a reaction gas starting mixture of the following composition:
Propene (polymer grade) 6-6.2% by volume,
H ₂ O 3 to 3.2% by volume,
CO 0.3-0.5% by volume,
CO ₂ 0.9~1.1% by volume,
Acrolein 0.01-0.02% by volume,
10.2 to 10.6% by volume of O ₂ and about 100% by volume of molecular nitrogen as the remaining amount.

  The loading of this catalyst charge with propene is selected up to 100 Nl / h. The salt bath temperature in the first reaction stage was 338 ° C. The salt bath temperature in the second reaction stage was 264 ° C. The product gas mixture leaving the intercooler having a temperature of 250 ° C. is metered with a large amount of compressed air at a temperature of 140 ° C., so that a reaction gas starting mixture is supplied to the second reaction stage, in which the molecules The ratio of oxygen to acrolein (volume% ratio) was 1.3.

According to gas chromatographic analysis, the following results were shown at the outlet of the second reaction stage (the condensate of the gas mixture leaving the second reaction stage was analyzed; boiling point (1 atm) ≧ −50 Condensed all components at ℃):
Propen conversion: 97.5 mol%;
Selectivity of acrylic acid formation (S ^AS _Pen ): 91.7 mol%;
Total selectivity for subcomponent formation ( _Sges ): 1.7 mol%.

In addition, the following contents were present at the outlet of the second reaction stage:
Acrolein: 500 vol ppm;
Acetaldehyde: 0.03% by volume;
Acetic acid: 0.14% by volume.

Post-reaction stage A reaction tube (V2A steel; outer diameter 30 mm, wall thickness 2.5 mm, inner diameter 25 mm, length 320 cm) was charged with an annular shell catalyst SKH1 to SKH6 over its entire length. The reaction tube was thermostatically controlled using a salt bath (53% by mass of potassium nitrate, 40% by mass of sodium nitrite and 7% by mass of sodium nitrate) in which nitrogen was passed in countercurrent.

The reaction gas mixture leaving the second reaction stage was led directly to the post-reaction stage without intermediate air supply and without intermediate cooling. The reaction gas mixture exiting the post reaction tube was analyzed by gas chromatography (appropriately, for example as already described for the reaction gas mixture exhausted from the second reaction stage of the main reaction). In this case, depending on the selected post-reaction charge and salt bath temperature, the following results were obtained:
SKN1, salt bath temperature = 270 ° C .:
Propen conversion: 97.5 mol%;
S ^AS _Pen : 90.8 mol%;
S _ges : 0.85 mol%;
Acrolein: 90 vol ppm;
Acetaldehyde: 0.02% by volume;
Acetic acid: 0.07% by volume.

SKN2, salt bath temperature = 250 ° C .:
Propen conversion: 97.5 mol%;
S ^AS _Pen : 90.7 mol%;
S _ges : 0.83 mol%;
Acrolein: 41 vol ppm;
Acetaldehyde: 0.01% by volume;
Acetic acid: 0.15% by volume. 0,15 Vol .-%.
SKN3, salt bath temperature = 250 ° C .:
Propen conversion: 97.5 mol%;
S ^AS _Pen : 91.7 mol%;
S _ges : 0.74 mol%;
Acrolein: 20 vol ppm;
Acetaldehyde: 0.01% by volume;
Acetic acid: 0.17% by volume.

SKN4, salt bath temperature = 250 ° C .:
Propen conversion: 97.5 mol%;
S ^AS _Pen : 91.7 mol%;
S _ges : 0.69 mol%;
Acrolein: 30 ppm by volume;
Acetaldehyde: <0.01% by volume;
Acetic acid: 0.15% by volume.

SKN5, salt bath temperature = 270 ° C .:
Propen conversion: 98.5 mol%;
S ^AS _Pen : 92.2 mol%;
S _ges : 0.78 mol%;
Acrolein: 80 vol ppm;
Acetaldehyde: <0.01% by volume;
Acetic acid: 0.19% by volume.

SKN6, salt bath temperature = 230 ° C .:
Propen conversion: 97.7 mol%;
S ^AS _Pen : 91.7 mol%;
S _ges : 0.83 mol%;
Acrolein: 30 ppm by volume;
Acetaldehyde: <0.01% by volume;
Acetic acid: 0.16% by volume.

Instead of one of the cyclic shell catalysts SKN1 to SKN6, this post-reaction stage was charged with the following shell catalyst in further tests and in this case the following results were obtained:
SKN7:
Stoichiometric ratio of active material: Mo ₁₂ V ₃ W _1.2 Cu _2.4 Bi _1.0 O _x
This production was carried out in the same way as the production of SKH1, except that after introducing solution 1 into solution 2 with stirring, 17.0 kg solids were added to the resulting mixture before adding aqueous NH ₃ solution. Bi (NO ₃ ) ₃ .5H ₂ O (manufacturer: ABCR, 98%) was introduced with stirring.

result:
Salt bath temperature = 250 ° C
Propen conversion: 97.5 mol%;
S _Pen ^AS : 91.8 mol%
S _ges : 0.69 mol%
Acrolein: 20 vol ppm;
Acetaldehyde: <0.01% by volume;
Acetic acid: 0.16% by volume.

SKN8:
Stoichiometric ratio of active material: Mo ₁₂ V ₃ W _1.2 Cu _2.4 Co _1.0 O _x
This production was carried out in the same way as the production of SKH1, except that after introducing solution 1 into solution 2 with stirring, 10.5 kg solids before adding aqueous NH ₃ solution to the mixture obtained in this case Co (NO ₃ ) ₂ · 6H ₂ O (manufacturer: ABCR, 98%) was introduced with stirring.

result:
Salt bath temperature = 250 ° C .:
Propen conversion: 97.5 mol%;
S _Pen ^AS : 91.7 mol%;
S _ges : 0.70 mol%;
Acrolein: 24 vol ppm;
Acetaldehyde: 0.01% by volume;
Acetic acid: 0.16% by volume.

  US Provisional Patent Application No. 60/567398, filing date Apr. 30, 2004, is hereby incorporated by reference. Various modifications and variations of the present invention are possible in light of the above teachings. Accordingly, the present invention may be modified within the scope of the appended claims, differing from the specific description herein.

It is a figure which shows the structure of a rotary kiln. FIG. 5 is a diagram showing the amount of ammonia released from a precursor material as a percentage of the total amount of ammonia released from the precursor material during the entire heat treatment as a function of material temperature (° C.). It is a figure which shows the ammonia concentration (volume%) of the atmosphere where heat processing is implemented according to the material temperature (degreeC) during heat processing. FIG. 4 is a diagram showing 1 kg of precursor material introduced into a rotating tube together with a gas flow over a heat treatment, and molar amounts of molecular oxygen and ammonia per hour, depending on the material temperature. It is a figure which shows the pore distribution before shaping | molding of the pulverized active material powder The figure which shows each contribution part of each pore diameter (abscissa, angstrom, logarithmic scale) in the fine pore range with respect to the total pore volume about the active material powder (ml / g) (ordinate) before molding Is FIG. 4 is a diagram showing the pore distribution of a multi-metal oxide active material additionally separated from an annular shell catalyst by mechanical scraping. Individual pore diameters (abscissa, angstroms, logarithmic scale) in the micropore range for the total pore volume for multimetal oxide active materials additionally separated from the annular shell catalyst by mechanical scraping It is a figure which shows each contribution of It is an X-ray diffraction pattern of an active material Shows the result of mercury pore measurement test of active material It is a figure which shows the result of the mercury pore measurement test before nitric acid washing | cleaning of the grind | pulverized ring. Is a diagram showing the percentage of M ^A as a function of the material was temperature (℃) It is a figure which shows the ammonia concentration (volume%) of the atmosphere A through heat processing according to material temperature (degreeC). It is a figure which shows the pore distribution before shaping | molding of the pulverized active material powder The figure which shows the individual contribution of each pore diameter (abscissa, angstrom, logarithmic scale) in the micropore range with respect to the total pore volume about the active material powder (ml / g) (ordinate) before molding Is FIG. 4 is a diagram showing the pore distribution of a multi-metal oxide active material that is additionally separated from the annular shell catalyst by mechanical scraping. For multimetal oxide active materials additionally separated from the cyclic shell catalyst by mechanical scraping, for each pore diameter (abscissa, angstrom, logarithmic scale) in the micropore range for the total pore volume It is a figure which shows each contribution

Explanation of symbols

  1 rotary tube, 2 parallelepiped, 3 inlet, 4 outlet, 5 ventilator, 6 holes, 7 valves, 8 lance, 9 thermocouple, 10 heater, 11 cleaning flow, 12 cyclone, 13 circulating gas compressor, 14 control Valve, 15 Diaphragm, 16 Pressure sensor, 17 Exhaust gas compressor, 18 Sensor, 19 Circulating gas component, 20 Nitrogen, 21 Splitter, 22 Circulating gas component, 23 Exhaust gas purification device, 24 Circulating gas flow, 26 Three-way cock, 27 Gas flow , 28 sensors

Claims (23)

In the method for producing acrylic acid by partially oxidizing at least one C ₃ -hydrocarbon precursor compound with a heterogeneous catalyst, the total selectivity S _{ges for the} formation of subcomponents is ≦ 1.5 mol% Feature method. 2. A process according to claim 1, characterized in that _Sges is ≦ 1.3 mol%. 2. A process according to claim 1, characterized in that _Sges is ≦ 1.0 mol%. The process according to claim 1, characterized in that _Sges is _≤0.8 mol%. The process according to claim 1, wherein the C ₃ -hydrocarbon precursor compound is propene and the conversion U ^{Pen of the} propene is ≧ 95 mol%. 5. The process according to claim 1, wherein the C ₃ -hydrocarbon precursor compound is propene and the conversion U ^{Pen of the} propene is ≧ 96 mol%. The process according to claim 1, wherein the C ₃ -hydrocarbon precursor compound is propene and the conversion U ^{Pen of the} propene is ≧ 97 mol%. The process according to claim 1, wherein the C ₃ -hydrocarbon precursor compound is propene and the conversion U ^{Pen of the} propene is ≧ 98 mol%. C ₃ - hydrocarbon precursor compound is propene, and wherein the selectivity ratio S ^AS _Pen acrylic acid formation is ≧ 90 mol% A method according to any one of claims 1 to 8 . C ₃ - hydrocarbon precursor compound is propene, and wherein the selectivity ratio S ^AS _Pen acrylic acid formation is ≧ 92 mol% A method according to any one of claims 1 to 8 . C ₃ - hydrocarbon precursor compound is propene, and wherein the selectivity ratio S ^AS _Pen acrylic acid formation is 94 mol% ≧, method according to any one of claims 1 to 8 . First, by partially oxidizing at least one C ₃ -hydrocarbon precursor compound with a heterogeneous catalyst in the main reaction, the total selectivity S _{ges for} forming the secondary component of acrylic acid is ≧ 1.7 mol%. The product gas mixture obtained in this way is then increased in the post-reaction stage, optionally after addition of inert gas, or molecular oxygen, or a mixture of molecular oxygen and inert gas. By passing the catalyst charge, the acrylic acid contained in the product gas mixture is obtained in a substantially unconverted state, while at least a secondary component contained in the product gas mixture is present. 12. A method according to any one of the preceding claims, characterized in that it is partially burned into carbon oxide and water. C ₃ - hydrocarbon precursor compound, characterized in that propane, The method of claim 12. C ₃ - hydrocarbon precursor compound, characterized in that a propene The method of claim 12. The process according to claim 14, characterized in that the propene conversion U ^Pen in the main reaction is ≧ 95 mol%. The process according to claim 14, characterized in that the propene conversion U ^Pen in the main reaction is ≧ 96 mol%. The selectivity S ^AS _Pen acrylic acid formation in the main reaction, characterized in that it is a ≧ 90 mol% A method according to any one of claims 14 to 16. The selectivity S ^AS _Pen acrylic acid formation in the main reaction, characterized in that it is a ≧ 95 mol% A method according to any one of claims 14 to 16.   In the main reaction, acrylic acid is produced by partial oxidation of propene with a two-stage heterogeneous catalyst, in which the loading of the catalyst bed of the first reaction stage with the propene is also the same as that of the catalyst bed of the second reaction stage. The method according to any one of claims 14 to 18, characterized in that the load on the acrolein is also in the range ≧ 120 Nl / l / h and ≦ 300 Nl / l / h.   Both the loading of the catalyst bed of the first reaction stage with propene and the loading of the catalyst bed of the second reaction stage with acrolein are ≧ 130 Nl / l / h and ≦ 300 Nl / l / h. The method according to claim 19, wherein: The active material of the post-reaction stage catalyst charge is represented by the general formula I
^{_{Mo 12 V a X 1 b X}} 2 c X 3 d X 4 e X 5 f X 6 g X 7 h O n (I)
[Wherein X ¹ = W, Nb, Ta, Cr and / or Ce,
X ² = Cu, Ni, Co, Fe, Mn and / or Zn,
X ³ = Sb and / or Bi,
X ⁴ = one or more kinds of alkali metals,
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,
a = 1 to 6,
b = 0.2-4,
c = 0.5-18,
d = 0 to 40,
e = 0-2,
f = 0-4,
g = 0 to 40,
from h = 0 to 1, and n = a number determined by the valence and frequency of an element different from the oxygen of formula I]. 21. The method according to any one of up to 20. The active material of the post-reaction stage catalyst charge has the general formula III
^{_{Mo 1 V a M 1 b M}} 2 c M 3 d O n (III)
Wherein at least one element from the group having M ¹ = Tb and Sb;
At least one element from the group having M ² = Nb, Ti, W, Ta and Ce;
M ³ = Pb, Ni, Co, Bi, Pd, Ag, Pt, Cu, Au, Ga, Zn, Sn, In, Re, Ir, Sm, Sc, Y, Pr, Nd and at least from the group having Tb One element;
a = 0.01-1
b => 0 to 1,
c => 0 to 1,
d = 0-0.5, preferably> 0-0.5, and n = a number determined by the valence and frequency of an element different from the oxygen of formula III]
The X-ray diffraction pattern shows diffraction reflections h, i and k, and the peak positions are diffraction angles (2θ) 22.2 ± 0.5 ° (h), 27.3 ± 0.5 ° (i), And 28.2 ± 0.5 ° (k),
This diffractive reflection h is the maximum intensity in this X-ray diffraction pattern, and shows a half-width of 0.5 ° at the highest.
The intensity P _i of the diffraction reflection _i and the intensity P _k of the diffraction reflection k satisfy the relationship of 0.20 ≦ R ≦ 0.85, where R is the expression R = P _i / (P _i + P _k )
21. The at least one multi-metal oxide, wherein the diffraction reflection i and the diffraction reflection k have a half-value width of ≦ 1 °, respectively. The method according to any one of the above. The process according to claim 1, wherein the C ₃ -hydrocarbon precursor compound is propane.

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