Process for the preparation of ethylenically unsaturated aldehydes and / or ethylenically unsaturated carboxylic acids at the catalyst fixed bed of a tube bundle reactor

Abstract

This invention relates to a method for preparing vinyl unsaturated aldehydes and / or vinyl unsaturated carboxylic acids, wherein the corresponding vinyl unsaturated aldehydes and / or vinyl unsaturated carboxylic acids are obtained by multiphase catalytic gas-phase partial oxidation of at least one olefin using molecular oxygen at elevated temperatures in a catalyst fixed bed of a tube bundle reactor. At least two catalyst layers are arranged in the axial direction of the tubes of the tube bundle reactor, each comprising a catalytically active multi-element oxide, such that multi-layer packing is achieved and the composition of the multi-element oxide in one catalyst layer differs from the composition of the multi-element oxide in at least one of the other catalyst layers. Specifically, the stoichiometric ratio L1 of Fe to Mo in the catalyst layer with the highest temperature inside the catalyst fixed bed is greater than the stoichiometric ratio L2 of Fe to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side, and the stoichiometric ratio M1 of Bi to Mo in the catalyst layer with the highest temperature inside the catalyst fixed bed is less than or equal to the stoichiometric ratio M2 of Bi to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side.

Description

describe

[0001] The present invention relates to a method for preparing vinyl unsaturated aldehydes and / or vinyl unsaturated carboxylic acids in a catalyst fixed bed of a tube bundle reactor having at least two catalyst layers.

[0002] Furthermore, the present invention relates to a tubular reactor and a catalyst bed of a tubular reactor used according to the present invention.

[0003] Catalyst beds comprising at least two catalyst layers composed of different catalysts are generally referred to as structured catalyst beds. Such structured catalyst beds or their use in the preparation of unsaturated aldehydes and / or unsaturated carboxylic acids are known in EP 3 023406 A1, EP 3 321 247 A1 and EP 1 074 538 A1.

[0004] The catalyst layer contains multi-element oxides with different compositions and catalytic activities. For example, multi-element oxides containing Mo, Bi, Fe and Co are known from EP 3 740 310 A1 and EP 2 731 715 A1.

[0005] A drawback of using known structured catalyst beds in tubular reactors to prepare vinyl unsaturated aldehydes and / or vinyl unsaturated carboxylic acids is the low yield of valuable products.

[0006] Therefore, the object of the present invention is to provide an improved method for preparing vinyl unsaturated aldehydes and / or vinyl unsaturated carboxylic acids. The improved method should, in particular, achieve higher yields of valuable products with less catalyst.

[0007] Therefore, a method for preparing vinyl unsaturated aldehydes and / or vinyl unsaturated carboxylic acids is provided, wherein at least one olefin is partially oxidized in the gas phase by molecular oxygen at an elevated temperature using a catalyst fixed bed in a tube bundle reactor to obtain the corresponding vinyl unsaturated aldehyde and / or vinyl unsaturated carboxylic acid, wherein at least two catalyst layers are arranged in the axial direction of the tubes of the tube bundle reactor, each of these catalyst layers comprising a catalytically active multi-element oxide, such that multi-layer packing is achieved and the composition of the multi-element oxide in one catalyst layer differs from the composition of the multi-element oxide in at least one of the other catalyst layers, characterized in that the stoichiometric ratio L1 of elemental Fe to Mo in the catalyst layer with the highest temperature inside the catalyst fixed bed is greater than the stoichiometric ratio L2 of elemental Fe to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side, and the stoichiometric ratio M1 of elemental Bi to Mo in the catalyst layer with the highest temperature inside the catalyst fixed bed is less than or equal to the stoichiometric ratio M2 of elemental Bi to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side.

[0008] Preferably, the composition of the catalytically active multi-element oxide conforms to general formula (I).

[0009] Mo 12 Bi a Fe b Co c Ni d X e Y f Z g O n (I)

[0010] in,

[0011] X = K, Cs, and / or Rb,

[0012] Y=Ca, Sr, Ba, Li, Na, Cr, W, Mn, Cu, Zn, Ga, P, B, As, Sn, Sb, Te, Nb, Ta, Pb, Ce and / or La,

[0013] Z = Si, Al, Ti, Zr and / or Mg,

[0014] in

[0015] a = 0.2 to 2,

[0016] b = 1 to 4,

[0017] c = 3 to 9,

[0018] d = 0 to 4,

[0019] c+d=4 to 9.5

[0020] e = 0.01 to 0.5

[0021] f = 0 to 10,

[0022] g = 0 to 10, and

[0023] n = a number determined by the valence and abundance of elements other than oxygen in general formula I.

[0024] Preferably, in general formula (I), X=K, Z=Si, a=0.4 to 1.5, preferably 0.5 to 1.0, more preferably 0.6 to 0.8, b=1.3 to 3.7, preferably 1.5 to 3.4, more preferably 1.7 to 3.1, c=3.8 to 8.5, preferably 4.3 to 8.0, more preferably 4.8 to 7.8, d=0 to 3.5, preferably 0 to 3.0, more preferably 0 to 2.7, c+d=5 to 9.0, preferably 6.0 to 8.7, more preferably 6.9 to 8.5, e=0.02 to 0.3, preferably 0.025 to 0.2, more preferably 0.03 to 0.15, f=0, g=0 to 7, preferably 0 to 4, more preferably 0 to 1.8.

[0025] Preferably, the stoichiometric ratio N1 of element K to Mo in the catalyst layer with the highest temperature inside the catalyst fixed bed is greater than the stoichiometric ratio N2 of element K to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side.

[0026] According to the present invention, each tube of the tube bundle reactor has: a gas inlet side, wherein a reaction gas mixture comprising olefins and molecular oxygen is introduced into the reaction tube; and a gas outlet side, wherein at least partially reacted reaction gas mixture is discharged from the reaction tube.

[0027] Preferably, the stoichiometric ratio of Fe to Mo in the catalyst layer with the highest temperature inside the catalyst fixed bed is 0.15 to 0.35, more preferably 0.18 to 0.32, and even more preferably 0.22 to 0.28.

[0028] Preferably, the composition of the multi-element oxides with the highest catalytic activity in the catalyst layer inside the catalyst fixed bed conforms to general formula (II).

[0029] Mo 12 Bi a Fe b Co c Ni d X e Y f Z g O n (II).

[0030] Preferably, in general formula (II), X=K, Z=Si, a=0.3 to 1.5, preferably 0.4 to 1.0, more preferably 0.5 to 0.7, b=1.8 to 3.7, preferably 2.5 to 3.4, more preferably 2.9 to 3.1, c=3.7 to 8.5, preferably 4.2 to 8.0, more preferably 4.8 to 7.6, d=0 to 3.5, preferably 0 to 3.0, more preferably 0 to 2.7, c+d=5 to 8.8, preferably 6.0 to 8.2, more preferably 6.9 to 7.6, e=0.03 to 0.4, preferably 0.05 to 0.25, more preferably 0.07 to 0.15, f=0, g=0 to 7, preferably 0 to 4, more preferably 0 to 1.6.

[0031] Preferably, the catalyst layer arranged along the pipeline axis on the farthest gas outlet side has a catalytically active multi-element oxide composition that conforms to general formula (III).

[0032] Mo 12 Bi a Fe b Co c Ni d X e Yf Z g O n (III).

[0033] Preferably, in general formula (III), X=K, Z=Si, a=0.3 to 1.8, preferably 0.4 to 1.6, more preferably 0.5 to 1.5, b=1.3 to 3.7, preferably 1.5 to 3.4, more preferably 1.7 to 3.1, c=4 to 8.5, preferably 5 to 8.2, more preferably 6.0 to 7.8, d=0 to 3.5, preferably 0 to 3.0, more preferably 0 to 2.7, c+d=5.0 to 9.0, preferably 6.0 to 8.7, more preferably 6.9 to 8.5, e=0.02 to 0.33, preferably 0.025 to 0.2, more preferably 0.03 to 0.09, f=0, g=0 to 7, preferably 0 to 4, more preferably 0 to 1.7.

[0034] Preferably, the vinyl unsaturated aldehyde is acrolein, and the vinyl unsaturated carboxylic acid is acrylic acid. Preferably, the olefin is propylene.

[0035] Preferably, each catalyst layer is composed of a solid catalyst mold and / or a shell catalyst.

[0036] Preferably, the ratio of L1 to L2 is 1.1 to 1.6, more preferably 1.15 to 1.5, and even more preferably 1.2 to 1.4.

[0037] Preferably, the ratio of M1 to M2 is 0.5 to 1, more preferably 0.6 to 1, and even more preferably 0.7 to 1.

[0038] Preferably, the ratio of N1 to N2 is 1.5 to 3.3, more preferably 1.6 to 3.2, and even more preferably 1.7 to 3.1.

[0039] Surprisingly, it has been found that, according to the present invention, by constructing the catalyst bed structure using the claimed element ratios, it is possible to obtain particularly high yields of valuable products with less catalyst.

[0040] Another subject of the invention is a tube bundle reactor for preparing vinyl unsaturated aldehydes and / or vinyl unsaturated carboxylic acids by multiphase catalytic gas-phase partial oxidation of at least one olefin using molecular oxygen at elevated temperatures in a catalyst fixed bed of a tube bundle reactor, wherein at least two catalyst layers are arranged in the axial direction of the tubes of the tube bundle reactor, each of these catalyst layers comprising catalytically active multi-element oxides such that there is multilayer packing and the composition of the multi-element oxides in one catalyst layer differs from the composition of the multi-element oxides in at least one of the other catalyst layers, characterized in that the stoichiometric ratio L1 of elemental Fe to Mo in the catalyst layer with the highest temperature inside the catalyst fixed bed is greater than the stoichiometric ratio L2 of elemental Fe to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side, and the stoichiometric ratio M1 of elemental Bi to Mo in the catalyst layer with the highest temperature inside the catalyst fixed bed is less than or equal to the stoichiometric ratio M2 of elemental Bi to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side.

[0041] Furthermore, one aspect of the present invention is a catalyst fixed bed arranged within at least one tube of a tube bundle reactor for preparing vinyl unsaturated aldehydes and / or vinyl unsaturated carboxylic acids by multiphase catalytic gas-phase partial oxidation of at least one olefin using molecular oxygen at elevated temperatures. At least two catalyst layers are arranged in the axial direction of the tube bundle reactor, each comprising a catalytically active multi-element oxide, such that multi-layer packing exists and the composition of the multi-element oxide in one catalyst layer differs from the composition of the multi-element oxide in at least one of the other catalyst layers. The catalyst fixed bed is characterized in that the stoichiometric ratio L1 of Fe to Mo in the catalyst layer with the highest internal temperature is greater than the stoichiometric ratio L2 of Fe to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side, and the stoichiometric ratio M1 of Bi to Mo in the catalyst layer with the highest internal temperature is less than or equal to the stoichiometric ratio M2 of Bi to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side.

[0042] The preparation of solid catalyst molds is described below:

[0043] The solid catalyst molded bodies obtainable according to the present invention are generally molded essentially into geometrically molded bodies, calcined, and used for catalytic partial oxidation of corresponding heterogeneous gases (particularly partial oxidation of propylene to acrolein). Essentially, the desired geometry of the solid catalyst is not limited.

[0044] In principle, solid catalyst molds can be prepared in a simple manner by preparing a tightly packed, preferably finely separated dry mixture from a suitable source of its elemental composition (particularly a source other than oxygen), the composition of which corresponds to the stoichiometry of the solid catalyst mold to be prepared, and calcining the dry mixture at a temperature of 350°C to 650°C after prior molding to form a precursor mold, optionally using molding aids. Calcination can be carried out under an inert gas and oxidizing atmosphere, such as air (or another mixture of an inert gas and molecular oxygen, which may also contain a relatively low proportion of reducing active components), or under a reducing atmosphere (e.g., a mixture of inert gases, NH3, CO and / or H2, which may also contain a relatively low proportion of oxidizing active components) or under vacuum. Calcination time can range from a few minutes to several days, generally decreasing with increasing calcination temperature.

[0045] As a source of elemental components for a solid catalyst mold (i.e., a starting compound containing at least one chemically bonded elemental component (at least one element contained in the solid catalyst mold), consider compounds that are already oxides (typically existing in a solid aggregate state under normal conditions (1 atm-abs, 0 °C)) (e.g., metal oxides) and / or compounds that are converted to oxides (typically existing in a solid aggregate state under normal conditions) by heating (heat treatment at high temperatures), at least in the presence of gaseous oxygen and / or in the presence of components that release gaseous (e.g., molecular) oxygen. In principle, the oxygen source can be a component of the mixture to be calcined, for example, in the form of peroxides. Typically, the starting compound can be a source of several elemental components for the solid catalyst mold.

[0046] In addition to oxides, suitable starting compounds (sources) are particularly halides, nitrates, formates, acetates, oxalates, citrates, carbonates, amine complexes, ammonium salts and / or hydroxides, as well as hydrates of the above salts.

[0047] Compounds such as NH4OH, (NH4)2CO3, NH4NO3, NH4CHO2, CH3COOH, NH4CH3CO2, and / or ammonium oxalate, which decompose substantially completely and / or decompose into gaseous compounds (e.g., ammonia, CO2, CO, H2O, nitrogen oxides) during subsequent calcination, can be additionally incorporated into a tightly packed dry mixture. Such substances decomposed during calcination are also organic materials, such as stearic acid, malonic acid, ammonium salts of the above acids, starches (e.g., potato starch, corn starch), ground nut shells, and finely separated plastic powders (e.g., polyethylene, polypropylene, etc.).

[0048] When the elemental source portion used to produce a dry mixture that is as close as possible and preferably finely separated is organic (e.g., in the case of acetate, formate, oxalate and / or citrate) or contains hydroxide ions, carbonate ions, bicarbonate ions, ammonium ions, halide ions, hydrogen phosphate ions and / or nitrate ions that typically decompose during calcination, gaseous compounds are usually formed (released) within the scope of the heat treatment.

[0049] The close mixing of the starting compound (source) used to prepare the solid catalyst mold can be carried out in either dry or wet form. If carried out in dry form, the starting compound (source) is advantageously used as a finely separated powder and calcined after mixing and compaction to form the geometric precursor mold.

[0050] However, according to the present invention, the close mixing of the (elemental) sources is preferably carried out in a wet form.

[0051] In this case, the starting compounds are mixed together in the form of solutions and / or suspensions, and the resulting wet (preferably aqueous) mixture M is then dried to form a compact dry mixture. The solvent and / or suspending agent preferably used is water or an aqueous solution, and the resulting wet mixture M is an aqueous mixture M.

[0052] In the above mixing process, if the mixture is started only from a source existing in dissolved form and / or from a colloidal dissolved source of the elemental component, a very particularly dense dry mixture is obtained. As previously mentioned, the starting compound can be a source of only one or more elemental components. Correspondingly, the above solution or colloidal solution can contain only one or more elemental components of the relevant solid catalyst mold to be prepared. As previously mentioned, the preferred solvent is water. The drying of the resulting aqueous mixture is preferably carried out by spray drying.

[0053] When referring to a solution of a source (starting compound, starting substance) in a solvent (particularly water) in this literature, the term "dissolution" here refers to a molecular or ionic solution. That is, the largest geometric unit of the starting substance (source) dissolved in the solution must have a "molecular" size, and the solution appears "optically empty".

[0054] In contrast, colloidal solutions represent a link between real (molecular and / or ionic) solutions and suspensions. In these colloidal dispersions, there exists a small accumulation of molecules or atoms, invisible to the naked eye or microscope. Colloidal solutions appear optically completely transparent (although often colored) because the particles they contain have diameters ranging from 1 nm to 250 nm (preferably up to 150 nm, particularly preferably up to 100 nm).

[0055] Due to their small size, colloidally dissolved particles cannot be separated by conventional filtration. However, they can be separated from their "solvent" by ultrafiltration using membranes of plant, animal, or artificial origin, such as parchment, pig bladder, or cellophane. Unlike optically empty real (molecular and / or ionic) solutions, a beam of light cannot pass through a colloidal solution without deflection. The beam is scattered and deflected by the colloidally dissolved particles. To maintain the stability of colloidal solutions and prevent further particle aggregation, they typically contain wetting agents and dispersants, as well as other added additives.

[0056] To prepare a wet (preferably aqueous) mixture M, elements other than silicon (elemental composition) of the solid catalyst molded body are preferably introduced from a source in the form of a solution (particularly preferably in an aqueous solution), and silicon is preferably introduced in the form of a silica sol to prepare the wet (preferably aqueous) mixture M.

[0057] Silica sol is a colloidal solution of nearly spherical polysilicic acid particles. The particle diameter is within the colloidal range, between 5 nm and 75 nm depending on the type. The particles are non-porous. They have a surface-hydroxylated SiO2 core. Individual spherical particles are not cross-linked to each other. For stability reasons, some hydroxyl groups are usually present in silica sol in the form of neutralization with alkali metal hydroxides and / or ammonium hydroxide. This means that the counterion is not a proton in some cases, but an alkali metal ion (e.g., Na+). + ) and / or NH4 + Cationic. The SiO2 content of silica sol suitable for preparing wet (preferably aqueous) mixtures M can be, for example, 30% to 60% by weight of the silica sol. Silica sol is typically aqueous and does not contain precipitable components. It can usually be stored for many years without precipitation.

[0058] A particularly suitable silicon source is LUDOX silica sol from Grace GmbH & KG. ® Address: Hollerecke 1, D-67545 Worms. Its particles are discrete, homogeneous silica spheres with no internal surface or detectable crystallinity. The majority of its composition is dispersed in an alkaline medium, which reacts with the hydroxylated surfaces and generates a repulsive negative charge.

[0059] Suitable silica sols can have very narrow (basically monodisperse) or very wide (polydisperse) particle sizes.

[0060] The silica sol particularly suitable for the purposes of this invention (for the preparation of wet (preferably aqueous) mixtures M) is silica sol LUDOX TM50 from Grace Company. Silica sol LUDOX TM50 has a substantially monodisperse (d=22nm) particle size distribution. Its pH value (1 atm-abs, 25°C) is 9.0. The alkali metal ion that substituted part of the hydroxyl protons is Na.+ The SiO2 content of LUDOX™ 50 is 50% of the weight of the hydrogel. The specific surface area of ​​the SiO2 particles contained in the LUDOX™ 50 colloidal solution is 140 m². 2 / g. The mass density (1 atm-abs, 25℃) of LUDOX TM50 is 1.40 g / cm³. 3 .

[0061] The titratable alkali content (calculated as Na2O) of LUDOX TM50 is 0.21% by weight (based on the weight of silica sol).

[0062] The dynamic viscosity of LUDOX TM50 is 40 mPas (1 atm-abs, 25°C). The Cl of LUDOX TM50... - The content (calculated as NaCl) of SO4 in LUDOX TM50 is 0.03% by weight. 2- The content (calculated as Na2SO4) is 0.08% by weight (based on the weight of LUDOX TM50 in each case).

[0063] Of course, in the solution used to prepare a wet (especially aqueous) mixture M, at least one elemental source of molecular and / or ionic dissolution and one or more other elemental sources of colloidal dissolution may also be present side by side.

[0064] A favorable source of molybdenum is ammonium heptamolybdate tetrahydrate. This is primarily due to its excellent solubility in water. According to Ullmann's Encyclopedia of Industrial Chemistry, Vol. 22, 2003, WILEY-VCH, pp. 320 / 321, ammonium molybdate tetrahydrate has a saturated solubility of 30% by weight (calculated as anhydrous salt) in an aqueous solution at 25°C and 1 atm-abs.

[0065] During preparation, ammonium molybdate tetrahydrate may be contaminated by small amounts (typically ppm) of isopolymolybdates insoluble in water (due to non-strict adherence to process parameters during preparation). If ammonium heptamolybdate tetrahydrate contaminated in this manner dissolves in water, an aqueous solution is formed, which exhibits turbidity due to small amounts of undissolved, finely separated isopolymolybdates. The applicant's own research indicates that even ammonium molybdate tetrahydrate contaminated with isopolymolybdates, its aqueous solution (as measured as described in WO 2016 / 147324) exhibiting turbidity of 20 NTU, or 50 NTU, or 70 NTU, or 100 NTU, or 150 NTU, or 200 NTU, or 250 NTU, or 300 NTU, is suitable for preparing solid catalyst molds according to the invention, and its performance is not significantly impaired when used as a catalyst for the heterogeneous partial gas-phase oxidation of propylene as the main product and acrolein as a byproduct.

[0066] Other suitable molybdenum sources include, for example, ammonium orthomolybdate ((NH4)2MoO4), ammonium dimolybdate ((NH4)2Mo2O7), and ammonium tetramolybdate dihydrate ((NH4)2Mo4O7). 13 x 2 H2O) and ammonium decamolybdate dihydrate ((NH4)4Mo 10 O 32 (x 2 H2O). However, molybdenum trioxide can also be used in principle.

[0067] In the context of preparing solid catalyst molds, the preferred source of alkali metals is their hydroxides. However, in principle, nitrates of these elements and hydrates of these nitrates can also be used as such sources. That is, the preferred K source is KOH, but in principle, KNO3 or its hydrate can also be used as a K source.

[0068] The preferred Bi source is a bismuth salt, where Bi is Bi2. 3+ Suitable salts are, for example, bismuth(III) oxide, bismuth(III) nitrate oxide (bismuth subnitrate), and bismuth(III) halides (e.g., fluorides, chlorides, bromides, iodides), especially bismuth(III) nitrate pentahydrate. Of course, solutions of elemental Bi in aqueous nitric acid can also be used as Bi sources, where Bi is in the form of Bi... 3+ It exists in the form of Bi. 3+ When an aqueous solution of nitrate or its hydrate is used as the source (preferred according to the invention) (such a solution can also be produced by dissolving elemental Bi in an aqueous nitric acid solution), according to the invention, a high pH value (1 atm-abs, 25°C) is advantageous because it counteracts the undesirable Bi content in the aqueous solution. 3+ Precipitation formation. The pH value is preferably ≤1, more preferably ≤0.5. However, typically the pH value is ≥-2, and usually ≥0. This aqueous solution is advantageously nitric acid. That is, its low pH value is caused by excess nitric acid (in this case, the aqueous solution contains NO3). - molar quantity (n) N o 3- ) and B contained in aqueous solutions i3 + molar quantity (n) Bi3+ molar ratio (n) N o 3- ) / (n Bi3+ )>3).

[0069] The preferred Fe source is Fe 3+Salts, particularly preferred being various ferric(III) nitrate hydrates (see, for example, DE 102007 003076 A1). According to the invention, ferric(III) nitrate nonahydrate is particularly preferred as the Fe source for the aforementioned purpose. Of course, Fe... 2+ Salts can also be used as a source of Fe.

[0070] To prepare a solid catalyst mold, based on the total molar amount of Fe contained therein, at least 50 molar percentage, more preferably at least 75 molar percentage, and most preferably at least 95 molar percentage or 100 molar percentage of Fe is advantageously introduced in the form of an Fe source. 3+ Simultaneously possesses Fe 3+ and Fe 3+ The Fe source can also be used for this purpose.

[0071] Particularly suitable sources of Co are its salts, which possess Co properties. 2+ and / or Co 3+ Co in the form of nitrate. Examples that can be mentioned are cobalt(II) nitrate hexahydrate, Co3O4, CoO, cobalt(II) formate, and cobalt(III) nitrate. For the purposes described above, the former of these sources is particularly preferred. Of course, a solution of elemental Co in an aqueous nitric acid solution can also be used as a Co source, wherein Co is in the form of nitrate. 2+ It exists in the form of.

[0072] Given the elemental composition Ni, Ni is preferred. 2+ Salts. These are particularly nickel(II) carbonate, nickel(II) sulfate, nickel(II) oxide, nickel(II) acetate, nickel(II) formate, nickel(II) hydroxide, nickel(II) oxalate, and nickel(II) nitrate, and their corresponding hydrates. Hydrates of nickel(II) nitrate (e.g., its hexahydrate) are particularly preferred as Ni sources. Of course, solutions of elemental Ni in aqueous nitric acid can also be used as Ni sources, wherein Ni is in Ni... 2+ It exists in the form of ammonium nitrate. Such solutions usually also contain a certain proportion of ammonium nitrate.

[0073] To improve the solubility of salts such as Fe, Co and / or Ni in aqueous media, ammonia (also as their aqueous solution) and / or nitric acid (especially as their aqueous solution) may be added to the corresponding solution as needed.

[0074] Basically, the preparation of a wet (e.g., aqueous) mixture M can be carried out in various gaseous atmospheres (e.g., air, argon, nitrogen, water vapor, and / or carbon dioxide). According to the invention, the preparation of the wet (e.g., aqueous) mixture M is preferably carried out in air (the aqueous mixture M is advantageously saturated in air). When Co 2+ Salt and Fe 3+This is especially true when salts are used as sources of cobalt and iron, particularly when these salts are nitrates and / or their hydrates.

[0075] As previously stated, according to the present invention, the wet mixture M is preferably an aqueous mixture M, which is particularly advantageously prepared in the following manner.

[0076] An aqueous solution A with a pH value ≤3, preferably ≤2, particularly preferably ≤1, and very particularly preferably ≤0 is prepared from at least one element Fe source, at least one element Bi source, at least one element Co source, and optionally at least one element Ni source. (In this specification, the pH value of the aqueous solution generally (unless otherwise explicitly stated) refers to a measurement performed at 1 atm-abs and at the temperature at which the corresponding aqueous solution was prepared using a glass electrode designed as a single-bar measuring chain; the calibration of the single-bar measuring chain required in this regard is performed under the same conditions using an aqueous buffer solution whose pH value is known under these conditions and close to the desired measurement value; the Mettler Toledo pH electrode Inpro 4260 / 425 / Pt 100 is particularly suitable for determining such pH values, as it is a single-bar measuring chain with an integrated temperature sensor Pt 100 for automatic temperature compensation.) Typically, the pH value of aqueous solution A is not less than -2, and particularly advantageously in the range of -1 to 0. Aqueous solution A is preferably an aqueous solution of the nitrate or nitrate hydrate of the above-mentioned elements. Aqueous solution A is particularly preferred to be an aqueous solution of these nitrates or nitrate hydrates in an aqueous nitric acid solution. Solutions of related elements in an aqueous nitric acid solution are also particularly suitable as element sources for preparing this solution.

[0077] Aqueous solution B is prepared from at least one elemental Mo source and optionally at least one alkali metal source. The pH of aqueous solution B is advantageously (at 1 atm-abs and at the temperature at which solution B is prepared) <7. The pH of aqueous solution B is particularly preferably ≤6.5, and very particularly advantageously ≤6. Typically, the pH of aqueous solution B is ≥3. The advantageous pH of solution B used according to the invention is 4 to 6. According to the invention, an elemental hydroxide of an alkali metal (e.g., KOH) is preferably used as the alkali metal source for preparing aqueous solution B. The preferred Mo source for preparing aqueous solution B is ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O). 24 x 4 H2O), which is completely soluble in water at 25°C (1 atm-abs) to saturation solubility (30% by weight, anhydrous).

[0078] According to the present invention, based on the total amount of aqueous solution A, the total content of metal components such as Bi, Fe, Co, Ni, etc. in aqueous solution A is advantageously from 5% to 20% by weight, and advantageously from 10% to 15% by weight.

[0079] According to the invention, based on the total amount of aqueous solution B, the total Mo content of aqueous solution B is advantageously from 2% to 25% by weight, advantageously from 3% to 20% by weight, and particularly advantageously from 5% to 15% by weight.

[0080] Then, aqueous solution A and aqueous solution B are advantageously mixed together. Advantageously, aqueous solution A is continuously stirred into aqueous solution B. Advantageously, the initially introduced aqueous solution B is vigorously stirred.

[0081] According to the present invention, based on the total amount of the aqueous mixture, the total content of metal components such as Bi, Fe, Co, Ni, Mo, etc. in the resulting aqueous mixture of aqueous solution A and aqueous solution B is advantageously from 3% to 20% by weight, and advantageously from 5% to 15% by weight.

[0082] The temperature of the initially introduced aqueous solution B, the temperature during stirring of the aqueous solution A, and the temperature of the aqueous solution A itself are advantageously (preferably throughout the mixing process) ≤80°C and ≥0°C. These temperatures are preferably ≤75°C and ≥30°C, particularly preferably ≤70°C and ≥50°C or ≤65°C and ≥55°C.

[0083] Advantageously, aqueous solutions A and B, as well as the aqueous mixture produced when aqueous solution A is stirred into aqueous solution B, have the same temperature. Preferably, this is 60 °C. More preferably, the temperatures of aqueous solutions A, B, and the resulting aqueous mixture are kept constant during the stirring process. This can be achieved, for example, by means of a water bath. When aqueous solution A is stirred into aqueous solution B, the working pressure is suitably 1 atm-abs (1.01 bar-abs).

[0084] The aqueous solution A is preferably stirred into the initially introduced aqueous solution B within a time range of 5 to 60 minutes, particularly preferably within 10 to 30 minutes, and very particularly preferably within 15 to 25 minutes. The resulting aqueous mixture is then conveniently stirred for 5 to 60 minutes, preferably 10 to 30 minutes, particularly advantageously 15 to 25 minutes, while preferably maintaining the stirring temperature.

[0085] The pH of the aqueous mixture of aqueous solution A and aqueous solution B is preferably ≤3, more preferably ≤2. Typically, its value is ≥0.

[0086] If the solid catalyst molding contains the elemental component Si, according to the invention, it is preferable to use an aqueous silica sol as its source and stir it into an aqueous mixture of aqueous solution A and aqueous solution B. Water can be advantageously added to this aqueous mixture before stirring. The aqueous silica sol and water can be conveniently added at once. In this case, the temperature of both the water and the aqueous silica sol advantageously corresponds to the temperature of the aqueous mixture of aqueous solution A and aqueous solution B. Finally, it is conveniently stirred for up to 30 minutes. During subsequent stirring, the aforementioned temperature is advantageously maintained. The SiO2 content of the added aqueous silica sol can be 15% to 60% by weight, or 20% to 60% by weight, or 30% to 60% by weight, preferably 40% to 60% by weight, and particularly preferably 45% to 55% by weight (in each case based on its total weight).

[0087] Instead of initially introducing aqueous solution B into the thermostatically stirred vessel, and then introducing aqueous solution A while stirring, aqueous solutions B and A can also be continuously supplied to the stirred vessel (e.g., via a "3-way T-type mixer"). In principle, aqueous solution B can also be continuously stirred into the initially introduced aqueous solution A. However, this method is less preferred.

[0088] Typically, the available aqueous mixture M is an aqueous suspension (preferably, the aqueous mixture M also has the aforementioned advantageous ratio V (containing NH3 + NH4)). + The total molar amount of the aqueous mixture M and the molar amount of Mo contained therein; furthermore, the pH of the available aqueous mixture M is advantageously ≤3, typically 0 to 2. The available aqueous mixture M advantageously contains no more than or less than 60 molar percentages of the total molar amount of Co and / or Ni dissolved therein in the aqueous medium (at the temperature and operating pressure at which the aqueous mixture M is produced). Preferably, the above-mentioned content AT dissolved in the aqueous medium of the aqueous mixture M is ≤90 molar percentages relative to the total molar amount of Co and / or Ni contained in the aqueous mixture M, particularly preferably ≤80 molar percentages, or ≤70 molar percentages or ≤60 molar percentages. According to the invention, based on the amount of the aqueous mixture M, the total content of Bi, Fe, Mo, etc. in the aqueous mixture M to be dried (preferably spray dried) is conveniently from 3 wt% to 20 wt%, advantageously from 5 wt% to 15 wt%. Typically, AT ≥ 3 wt% or ≤ 50 wt%.

[0089] According to the invention, the aqueous mixture M is preferably converted into a finely separated, tightly packed dry mixture by spray drying (the drying of the aqueous mixture M is preferably carried out as quickly as possible before its preparation). That is, the aqueous mixture M is first separated (sprayed) into finely separated droplets in a spray dryer, and then dried in the spray dryer. Spray drying is preferably carried out in a hot gas stream. However, in principle, other hot gases (e.g., nitrogen or air diluted with nitrogen and other inert gases) can also be used for the above-described spray drying.

[0090] Spray drying can be carried out in a co-current or counter-current flow of droplets relative to hot gas. Typically, the gas inlet temperature is in the range of 250°C to 450°C, preferably 270°C to 370°C. Typically, the gas outlet temperature is in the range of 90°C to 160°C. Preferably, spray drying is carried out in a co-current flow of droplets and hot gas.

[0091] The resulting sprayed powder typically has an average particle size of 10µm to 100µm, preferably 15µm to 60µm, and particularly preferably 25µm to 50µm (diameter determined by light scattering of the sprayed powder dispersed in air (dispersion pressure 2.0 bar) according to ISO 13320-1). Generally, references to standards in this document refer to the standard version that was valid as of the priority date of this patent application, and whose publication date has the smallest time difference from the priority date of this patent application.

[0092] The tap density (25°C, 1 atm-abs) of the sprayed powder is typically 500 g / l to 1300 g / l, preferably 700 g / l to 1100 g / l.

[0093] The annealing loss of sprayed powder (after static annealing in excess air at 600°C (powder temperature) for 3 hours) is typically 20% to 40% of its starting weight, preferably 25% to 35% of its starting weight.

[0094] Prior to further processing, the sprayed powder can preferably be stored in an airtight container (e.g., a plastic drum). The storage temperature should not exceed 70°C, and preferably ≤50°C. Storage temperatures are generally not lower than -10°C. Since sprayed powder is typically hygroscopic, prolonged contact with humid air should be avoided. Contact with humid air will impair the processability of the sprayed powder (e.g., its flowability) and ultimately reduce the catalytic activity of the solid catalyst molded body prepared from it.

[0095] Of course, the aqueous mixture M can also be dried by other methods, such as conventional evaporation (preferably under reduced pressure; the drying temperature typically does not exceed 150 °C). In principle, the aqueous mixture M can also be dried by freeze-drying or Spin-Flash drying.® It is done by drying.

[0096] The sprayed powder can be coarsened first, for example, by subsequent pre-compaction. "Pre-compaction" refers to the initial compaction of the powder before subsequent compaction to obtain a precursor molded body. If the pre-compaction is dry, fine-particle graphite, dry inorganic fibers, and / or other molding aids (e.g., lubricants, reinforcing agents, and / or pore-forming agents) can be mixed into the sprayed powder prior to pre-compaction. Mixing is carried out using a mixer, such as a rotary mixer, oscillating mixer, belt mixer, airfoil mixer, or high-intensity mixer, preferably a mixer with shearing action, such as a mixer equipped with a shredder.

[0097] Preferably, the inorganic fiber is glass fiber, alumina fiber, silica fiber, carbon fiber, asbestos, silicon carbide, potassium titanate, or a mixture of the above fibers. Particularly preferably, the inorganic fiber is glass fiber. Preferably, the inorganic fiber has an average fiber length of 25µm to 750µm, more preferably 50µm to 500µm, more preferably 75µm to 400µm, and particularly preferably 100µm to 300µm. Preferably, the inorganic fiber has an average fiber diameter of 3µm to 18µm, more preferably 5µm to 15µm, and more preferably 8µm to 12µm. Preferably, the solid catalyst molding body comprises 0.1% to 15% by weight, preferably 0.5% to 13% by weight, more preferably 1.0% to 11% by weight, particularly preferably 2% to 10% by weight, especially preferably 2.5% to 9% by weight, and even more preferably 3% to 8% by weight of inorganic fiber, based on the weight of the solid catalyst molding body.

[0098] For example, precompaction can be performed using a calender with two steel rollers in opposite directions. The precompacted material can then be directionally crushed into a particle size suitable for further use. This can be achieved in the simplest way possible, for example, by pressing the precompacted material through a sieve with a defined mesh size.

[0099] However, precompaction can also be carried out under moist conditions. For example, spray powder can be kneaded by adding water. After kneading, the kneaded composition can be further pulverized to the desired fineness for subsequent use (see, for example, DE 100 49 873 A1) and dried.

[0100] Solid catalyst molds are prepared by pressing (compressing or compacting) precursor molds with regular or irregular geometries and then heat-treating them. These molds are formed from finely separated precursor compositions (fine, compact, dry mixtures of elemental composition sources).

[0101] As molding aids for further fine separation, such as lubricants like graphite, carbon black, polyethylene glycol, polyacrylic acid, stearic acid, starch, mineral oil, vegetable oil, water, boron trifluoride, and / or boron nitride, can be added again to the precursor composition for fine separation. Furthermore, suitable molding aids are reinforcing agents, such as microfibers of glass, asbestos, silicon carbide, or potassium titanate, which have a beneficial effect on the cohesiveness of the resulting compact (the molded body) after molding is completed by compression. Pore-forming agents such as ammonium nitrate, ammonium carbonate, water, and / or malonic acid are also suitable as molding aids. During heat treatment, the pore-forming agent decomposes or evaporates, forming pores. For example, the common use of lubricants in the respective molding processes is described in documents DE 10 2007 004961 A1, WO 2008 / 087116, WO 2005 / 030393, US2005 / 0131253, WO 2007 / 017431, DE 10 2007 005606 A1 and DE 10 2008 040093 A1.

[0102] Preferably, only fine-grained graphite is used as a lubricant. In this case, the fine-grained graphite that can be used is particularly those recommended in WO 2005 / 030393, US 2005 / 0131253, WO 2008 / 087116, and DE 10 2007 005606 A1. This is especially true for the graphite used in the examples and comparative examples in these documents. Very particularly preferred graphite is from Asbury Graphite Mills, Inc., New Jersey 08802, USA (Asbury 3160 and Asbury 4012), and Timcal Ltd., 6743 Bodio, Switzerland (Timrex). ® T44.

[0103] Based on the weight of the fine-particle precursor composition to be molded, and based on its total weight, the fine-particle precursor composition may contain, for example, up to 15% by weight of a fine-particle lubricant (e.g., graphite). However, in most cases, the lubricant content in the finely separated precursor composition to be molded (in a finely separated, tightly dry mixture) is ≤9% by weight, in many cases ≤5% by weight, and in many cases ≤4% by weight; this is especially true when the finely separated lubricant is graphite. Typically, the above-mentioned addition amount is ≥0.5% by weight, and usually ≥2.5% by weight.

[0104] Typically, by applying external force (pressure) to the precursor composition, a finely separated precursor composition (a finely separated, tightly packed dry mixture) optionally containing molding aids is compressed into the desired geometry of the precursor molded body. There are no limitations on the molding equipment or molding method used in this case.

[0105] For example, compression molding can be achieved by tableting. In this case, contact drying is preferably performed using a finely separated precursor composition (a finely separated, tightly packed dry mixture). However, it may contain, for example, up to 10% by weight of additives that are liquid under normal conditions (25°C, 1 atm-abs (1.01 bar-abs)). The finely separated precursor composition (a finely separated, tightly packed dry mixture) may also contain solid solvates (e.g., hydrates) that comprise such liquid substances in chemically and / or physically bound forms. Of course, the finely separated precursor composition may also be completely free of these substances.

[0106] The preferred molding method for the finely separated precursor composition (a finely separated, tightly packed dry mixture) by compression is tableting. The basic principles of tableting are described, for example, in Die Tablette, a manual for development, preparation and quality assurance, Waritschel and A. Bauer-Brandl, 2nd edition, Edition Verlag Aulendorf, 2002, and can be transferred in a completely corresponding manner to the tableting method according to the invention.

[0107] Tableting is a process of suppressing agglomerates. A free-flowing feed mixture is introduced into a pressing tool with a die between two punches, and compressed by uniaxial compression to form a solid tablet. Tableting can be divided into four parts: metering inlet, compression (elastic deformation), plastic deformation, and discharge. Tableting is performed, for example, on a rotary press or an eccentric press.

[0108] The outer surface of the tableting catalyst carrier consists of a circumferential surface corresponding to the inner wall of the mold cavity and a first end face and a second side face corresponding to the operating head of the punch. The tableting catalyst carrier can be flat or have curved ends, i.e., at least one of the first and second side faces is curved. For example, curved sides can be obtained by using a concave lower punch and / or an upper punch. If desired, the upper punch and / or lower punch may include protruding pins to form internal channels. Multiple pins can also be provided for the pressing punch, such that, for example, a punch with four pins can be prepared to prepare a molded body with four holes (channels). Typical design features of such pressing tools can be found, for example, in US 8,865,614.

[0109] Pressing tools typically consist of a die, an upper punch, a lower punch, and a pin (if the die body has a channel). Suitable materials for pressing tools are tool steel, tungsten carbide (WC)-based cemented carbide, and ceramic materials. Preferred tool materials have a Rockwell C hardness greater than 55. Examples of tool steel materials are DIN tool steels 1.2210, 1.2343, 1.2436, 1.2379, 1.2601, 1.2080, 1.25550 and high-speed steels, Vanadis 4 Extra from Uddeholm D-40549 Düsseldorf, and Vanadis 8 from Uddeholm D-40549 Düsseldorf. Suitable WC-based materials are described in US 8,865,614. An example of such WC-based materials is Hartmetall, located at D70497 Stuttgart. ® G10-Ni and Hightech-Ceram ® HTC-KR17 ® An example of a ceramic material is yttrium-stabilized zirconia (YSZ).

[0110] WC-based cemented carbide and ceramic materials are particularly suitable for tool inserts in which lined molds made of WC-based cemented carbide or ceramic are inserted into steel housings made of tool steel (e.g., 1.2379).

[0111] Pressing tools typically have surface coatings to improve surface hardness, corrosion resistance, wear resistance, abrasion resistance, and non-adhesion. Examples of surface coating types are diamond, such as carbon (DLC), boron nitride, titanium nitride, chromium nitride, plasma-plated chromium, and hard chromium. The layer thickness ranges from 1 μm to 10 μm, preferably from 1 μm to 5 μm.

[0112] The surface of the compression tool that comes into contact with the feed mixture and the resulting tablets preferably has a low surface roughness. According to DIN 4768, the arithmetic mean roughness value Ra of the compression tool surface is preferably 0.01 μm to 0.5 μm, particularly preferably 0.02 μm to 0.3 μm, even more preferably 0.02 μm to 0.2 μm, and very particularly preferably 0.02 μm to 0.1 μm.

[0113] The length of the straight tip of the lower punch is preferably 2 mm to 7 mm, particularly preferably 2 mm to 6 mm, and very particularly preferably 2.5 mm to 5 mm. Excessive tip straightness can lead to high friction, especially when adhesion of the precursor molded body occurs. Preferably, the upper and lower edges of the lower punch tip are not rounded, but sharp. Sharp edges reduce powder clogging at the punch-mold interface and the pinhole interface (for tablet molds with channels). Powder clogging can lead to powder adhesion and leakage.

[0114] The tip length of the upper punch is preferably greater than 2 mm, and is typically in the range of 2 mm to 10 mm. Unlike the lower punch, the high tip length does not cause friction problems because the upper punch only inserts a few millimeters into the die during the tableting cycle.

[0115] If the tablet mold has a channel, the lower punch and upper punch have holes for receiving pins. The upper punch should have at least one vent hole to allow air to escape from the mold cavity through the upper punch hole to the outside of the upper punch hole during the pressing process. Such an upper punch with a vent hole is disclosed in US2010 / 0010238 (see [link]). Figure 4 (a, 4b, 4c, and 4d).

[0116] The distance between the die hole and the outer surface of the lower punch is preferably 3 μm to 50 μm, particularly preferably 5 μm to 35 μm, and very particularly preferably 6 μm to 26 μm. Similarly, the distance between the die hole and the outer surface of the upper punch is preferably 3 μm to 50 μm, particularly preferably 5 μm to 35 μm, and very particularly preferably 6 μm to 26 μm. The distance is ensured by selecting an appropriate combination of dimensional tolerances for the die and the lower punch. Dimensional tolerances are typically expressed according to ISO shaft tolerances as defined in ISO 286-2. Examples of dimensional tolerance combinations for the die hole and the outer surface of the punch shown in ISO tolerance codes are H6 / f7, H6 / g6, H6 / g7, H7 / g6, H7 / f7, F8 / h6, G7 / h6, and F7 / h6 (die hole / lower punch outer surface).

[0117] When the tablet mold has a channel, the pressing tool includes a pin. The distance between the pin hole of the lower punch and the pin is preferably 3 μm to 50 μm, particularly preferably 5 μm to 35 μm, and very particularly preferably 6 μm to 26 μm. Similar to the distance between the mold hole and the outside of the punch, this distance is ensured by selecting an appropriate combination of dimensional tolerances for the mold and the lower punch.

[0118] The die orifice preferably has a slight taper starting from a defined depth in the direction of the die top. The tapered portion of the die orifice has a gradually increasing orifice size in the direction of the die top, thus creating an additional distance between the die orifice wall and the straight outer surface of the tip of the lower punch. This extra space helps to expel air contained in the mixed feed during compression in the die, thereby reducing powder blow-off and unstable tableting due to poor air expulsion. Another advantage of the tapered die is easier ejection after compression. Due to the embossing through the tapered die orifice, compression into tablets at the tapered location of the die orifice produces tablets with slightly tapered outer surfaces. During the ejection phase, where the lower punch pushes the tablet upwards in the die, the tablet is easily ejected from the die wall because the slight lifting of the tablet due to the tapered structure forces the tablet to separate from the die wall. When the die orifice is not tapered, the tablet does not separate from the die wall, and therefore the entire ejection process (i.e., the tablet is pushed upwards from the depth where compression occurs to the top of the die) is subject to friction between the outer surface of the tablet and the die wall, and between the straight outer surface of the tip and the die wall. This friction results in an unfavorable ejection force.

[0119] The depth of the die taper (i.e., the depth from the top of the die) should be selected so that the formed tablet is primarily located in the tapered region before ejection. To achieve this, the depth of the die taper can be oriented by adding the height of the tablet within the die before elastic recovery (i.e., the minimum distance between the upper and lower punches) and the insertion depth of the upper punch. For example, a taper depth of 12mm to 15mm can be used for a 12mm tablet height within the die and an insertion depth of 2mm for the upper punch.

[0120] The taper angle of the mold is typically 0.1° to 0.6°, and the size increase of the upper mold hole is preferably 0.03 mm to 0.2 mm, particularly preferably 0.05 mm to 0.14 mm. The increase in size can be mathematically derived from the taper angle and the taper depth.

[0121] In tablet molds with channels, the compression tool includes a pin. The pin is fixed to a turntable such that it is positioned within the mold cavity where the tablet is formed, allowing it to exit the tablet channel. Similar to the mold, the pin does not move vertically during the compression cycle, unlike the upper and lower punches. The vertical plane of the upper end of the pin is equal to or slightly lower than the height of the upper surface of the mold. Especially when the tablet has curved sides and the lower punch surface is concave, the vertical plane of the upper end of the pin should be slightly lower than the level of the upper front side of the mold so that the pin does not protrude from the lower punch surface.

[0122] In tablet dies with channels, adhesion typically occurs on the pin surface, leading to disadvantages such as high ejection forces due to high friction at the pin-tablet interface. This problem is particularly pronounced in multi-channel dies with multiple pins. Typically, pins exhibit a higher tendency to adhere than the die walls and the tips of the downstroke line.

[0123] When a tablet mold has channels, the pin preferably has a slight taper of a defined length in the upper region. The tapered portion of the pin shows that the pin diameter gradually decreases towards the upper end of the pin. The main advantage of a tapered pin is that it is easier to eject after compression. Due to the embossing of the tapered pin, compression into a tablet at the tapered position of the pin results in a tablet channel with a slightly tapered inner surface. The diameter of the tablet channel decreases slightly from bottom to top along the axial direction. During the ejection phase, where the lower punch pushes the tablet upward in the mold while the pin and mold remain perpendicular, the tablet is easily ejected from the pin because the slight lifting of the tablet due to the tapered structure forces the tablet to separate from the pin. When the pin has no taper, the tablet will not separate from the pin, so the entire ejection process (i.e., pushing the tablet upward from the depth of compression to the upper end face of the mold) is subject to friction at the tablet-pin interface, resulting in high ejection force. Tapered pins are particularly advantageous when the tablet has multiple channels.

[0124] The length of the pin's taper should be chosen so that the formed tablet is primarily located in the tapered zone before ejection. To achieve this, the length of the pin's taper can be oriented by adding the height of the tablet within the die before elastic recovery (i.e., the minimum distance between the upper and lower punches) and the insertion depth of the upper punch. For example, a taper length of 12mm to 15mm can be used for a 12mm tablet height within the die and an insertion depth of 2mm for the upper punch.

[0125] The angle of the mold taper is typically 0.1° to 0.6°, and the reduction in the diameter of the top pin is preferably 0.05 mm to 0.3 mm, particularly preferably 0.1 mm to 0.2 mm. This reduction can be mathematically derived from the angle and length of the taper.

[0126] The industrial-scale production of tablets is preferably carried out on a rotary tableting machine. Commercially available rotary tableting machines can be used in this invention. Examples of rotary tableting machines are the Korsch XT-600 HD, Korsch XT-600, Korsch TPR 700, Korsch TRP 1200, Korsch XL 400 MFP, Kilian RX, and Kilian Synthesis.

[0127] Rotary tablet presses typically have two clamping rollers for performing two-stage clamping, including pre-clamping and main clamping. The main clamping pressure ranges from 5 MPa to 500 MPa, preferably from 8 MPa to 400 MPa, and particularly preferably from 10 MPa to 300 MPa. The pre-clamping pressure is typically from 5% to 50% of the applied main clamping pressure, preferably from 7% to 40%, and particularly preferably from 10% to 35%.

[0128] The pressing tool is selected based on the desired geometry of the pressing body. The size and shape of the pressing body and the catalyst are selected such that the catalyst body obtained from the pressing body can be suitably filled into the reactor tube. The catalyst obtained from the pressing body suitable for the catalyst according to the invention is preferably used in reactor tubes with a length of 2 m to 5 m, preferably 2.5 m to 4 m, more preferably 3.4 m, and an inner diameter of 15 mm to 50 mm, preferably 18 mm to 40 mm, more preferably 20 mm to 30 mm, particularly preferably 23 mm to 29 mm, and even more particularly preferably 25 mm to 27 mm.

[0129] The shape of the compressive element is not particularly limited and can be any technically feasible shape, depending on the molding process. For example, the support can be a solid tablet or a hollow tablet, such as a hollow cylinder. According to another embodiment, the support can be characterized by a multi-lobed structure. A multi-lobed structure refers to a cylindrical structure with multiple cavities, such as grooves or channels extending along the circumference of the cylinder along its height. Typically, the cavities are arranged substantially equidistantly around the circumference of the cylinder.

[0130] The pressure during tableting affects the compaction of the free-flowing feed mixture, thereby influencing, for example, the density and / or mechanical stability of the compressed body. In practice, it has proven useful to selectively adjust the lateral compressive strength of the tableted catalyst support by choosing an appropriate pressure and testing it with random samples. For the purposes of this invention, lateral compressive strength is the force required to break the tableted catalyst support located between two parallel flat plates, wherein the two parallel flat end faces of the catalyst support are perpendicular to the parallel flat plates.

[0131] To improve tableting performance, the free-flowing feed mixture can be further processed, for example by sieving, preheating, and / or pre-granulation, i.e., pre-compression. For pre-granulation, roller compactors, such as the Chilsonator from Fitzpatrick, can be used. ® .

[0132] Further information on tableting, particularly regarding pregranulation, sieving, lubricants, and tools, can be found in WO2010 / 000720. For more information on tableting, see Powder Technology Handbook, Chapter 16: Tableting, K. Pitt and C. Sinka, Vol. 11, 2007, pp. 735–778.

[0133] Advantageously, tableting is performed as described in documents WO 2005 / 030393, DE 10 2008040093 A1, DE 10 2008 040094 A1 and WO 2007 / 017431. Here, the temperature around the tableting machine is typically 25°C. Selectively, as a result of preliminary coarsening by compaction, the particle size of the precursor composition to be compacted (a dense dry mixture of fine particles) is suitably in the range of 100 μm to 2000 μm, preferably 150 μm to 1500 μm, particularly preferably 200 μm to 1250 μm, or 300 μm to 1000 μm, or 400 μm to 800 μm (molding aids mixed before compaction are not considered here).

[0134] Similar to molding equipment or molding methods used for pressing, the desired geometry of the resulting molded body is not limited in the method according to the invention.

[0135] A preferred ring geometry (the geometry of the uncalcined green body and the solid catalyst molded body grown therefrom by calcination is generally substantially the same) is a geometry of 5 mm × 5 mm × 2 mm (outer diameter × height (length) × inner diameter). This is because a fixed bed of catalyst composed of rings of this geometry produces particularly low pressure loss when flowing through the reactant gas mixture of the fixed bed of catalyst (especially in reaction tubes with an inner diameter of 22 mm to 30 mm). Low pressure loss is particularly advantageous when operating under high loads (high gas flow rates) of the reactant gas mixture catalyzed by the fixed bed of catalyst. Another preferred ring geometry (especially in reaction tubes with a smaller inner diameter (e.g., 21 mm), which has advantageous filling behavior) is a geometry of 5 mm × 3 mm × 2 mm (outer diameter × height (length) × inner diameter). However, of course, all geometries disclosed and recommended in WO 02 / 062737 and WO 2015 / 067656 are also suitable.

[0136] Especially in the case of annular precursor moldings (precursor moldings are also referred to as green bodies in the literature, regardless of their shape), molding compaction should advantageously be carried out in such a manner that the lateral compressive strength SDF of the resulting molding body is [missing information]. V (Compare DE10 2008 040093 A1, DE 10 2008 040094 A1, and WO 2005 / 030393) The relation 5N≤SDF is satisfied. V ≤100N, preferably 8N≤SDF V ≤80N, and particularly preferred 12N≤SDF V ≤50N.

[0137] The experimental determination of lateral compressive strength is performed as described in documents WO 2005 / 030393 and WO 2007 / 017431. Of course, according to the invention, the annular green body recommended as in DE 10 2008 040093 A1 is particularly preferred. In the described method for preparing the green body according to the invention, the end faces of the annular or annular molded body can be planar (two or only one of the two end faces) and outwardly (convex) arched (bent) (particularly compared to DE 10 2007 004961 A1, EP 0184 790 A2, DE 10 2008 040093 A1 (e.g., paragraph

[0032] ) and DE 10 200804009 A1 (e.g., paragraph

[0074] ) and the embodiments described individually in these documents). This convex curvature is generally not considered in determining / indicating the height of such a geometric molded body in this document. Rings or annular molded bodies with convex curved (bent) end faces (preferably with both end faces having the same curvature) are advantageous because a catalyst bed with a ring or annular molded body having convex curved (bent) end faces (otherwise having the same geometry) results in less pressure loss of the reactant gas mixture flowing through the catalyst bed than a catalyst bed with a ring or annular molded body having flat end faces (especially in catalyst beds in reaction tubes). This is particularly suitable for ring geometries of 5 mm × 5 mm × 2 mm (outer diameter × height (length) × inner diameter). The radius of this convex curvature is typically 0.4 to 5 times (e.g., 0.8 to 4 times, or 1.2 to 3 times, or 1.6 to 2.6 times) the cylindrical outer diameter of the catalyst ring. As previously mentioned, catalyst beds resulting in lower pressure losses are particularly advantageous when partial oxidation catalyzed by a catalyst bed operates under high loads on the reactant gas mixture (at high flow rates of the reactant gas mixture flowing through the catalyst bed).

[0138] A particularly advantageous ring geometry of molded bodies obtained by compressing a precursor composition of fine particles (a dense dry mixture of fine particles) satisfies the condition that height (length) / outer diameter = H / A = 0.3 to 1.5 or to 1.2. H / a = 0.5 to 1.1 or to 1.0 is particularly preferred. Furthermore, a ratio I / A (where I is the inner diameter of the ring geometry) of 0.3 to 1.5, preferably 0.6 to 1.1, is advantageous for annular or ring-shaped green bodies according to the invention.

[0139] The aforementioned ring geometry is particularly advantageous if it simultaneously possesses one of the favorable H / A ratios and one of the favorable I / A ratios. Such possible combinations are, for example, H / A = 0.3 to 1.5 or 1.2, and I / A = 0.3 to 1.5 or 0.6 to 1.1. Alternatively, H / A can be 0.5 to 1.1 or 1.0, and I / A can simultaneously be 0.3 to 1.5 or 0.6 to 1.1. Furthermore, a ring geometry is advantageous when H is 2 mm to 7 mm, preferably 2 mm to 6 mm or 3 mm to 6 mm. Additionally, a ring geometry is advantageous if A is 4 mm to 8 mm, preferably 4 mm to 6 mm. The preferred ring geometry has a wall thickness of 1 mm to 2 mm or up to 1.5 mm.

[0140] Therefore, the possible ring geometry according to the present invention is (A × H × I) 5mm × 5mm × 2mm, or 5mm × 2mm × 2mm, or 5mm × 3mm × 2mm, 5mm × 5mm × 2.5mm, or 5mm × 3mm × 2.5mm, or 5.5mm × 5.5mm × 2.5mm, or 5.5mm × 5.5mm × 3mm, or 5mm × 3mm × 3mm, or 5.5mm × 3mm × 3.5mm, or 6mm × 3mm × 4mm, or 6mm × 6mm × 3mm, or 6mm × 6mm × 3.5mm, or 6.5mm × 3mm × 4.5mm, or 7mm × 3mm × 5mm, or 7mm × 7mm × 3mm, or 7mm × 3mm × 4mm, or 7mm × 7mm × 4mm.

[0141] Unless otherwise expressly stated, all information regarding the specific surface area of ​​solids in this literature is based on measurements according to DIN 66131 (specific surface area of ​​solids by gas adsorption (N2) according to Brunauer-Emmert-Teller (BET)).

[0142] All information regarding total pore volume and its pore size distribution in this literature is based on measurements using a mercury porosity determination method at 23°C using an Auto Pore V 9600 (MicroActiveInteractive Dara analysis software) apparatus (range: 0.5 to 60000) from Micromeritics GmbH, D-52072 Aachen (evaluated using the Washburn equation, with a mercury contact angle of 140° and a mercury surface tension of 480 mN / m = 480 dyn / cm). The total pore volume here refers to the total pore volume of pores with diameters greater than 0.03 µm to less than 300 µm.

[0143] According to the invention, the precursor molded body advantageously has the lowest possible residual moisture content. This is especially true when the close mixing of various sources of elemental components other than oxygen is wet (particularly when it occurs by forming an aqueous mixture M).

[0144] Preferably, the residual moisture content of the green body is ≤10% by weight, more preferably ≤8% by weight, even more preferably ≤6% by weight, and most preferably ≤4% by weight or ≤2% by weight (the determination of residual moisture can be carried out as described here in Die Bibliothek der Technik, Vol. 229, Thermogravimetric Determination of Moisture in Materials, Fundamentals and Practical Applications, Horst Nagel, Verlag moderne industrie (e.g., by means of Computrac MAX 5000 XL from Arizona Instruments).

[0145] If the green body comes from an aqueous mixture M (so that its residual moisture content consists of water), the determination of residual moisture is suitably performed from an application technology point of view using halogen heating (e.g., using a Mettler Toledo HC103 halogen moisture analyzer).

[0146] In this context, the spray drying of a wet (e.g., aqueous) mixture M should be carried out in such a way that the resulting spray powder has the lowest possible residual moisture content.

[0147] Considering the aspects mentioned above, if possible, the green blanks should be stored in ambient air free of atmospheric humidity (preferably in anhydrous inert gas or pre-dried air or in a sealed container until calcination).

[0148] Advantageously, the molding / forming and storage of finely separated, tightly dry mixtures have been carried out in the absence of ambient air (including atmospheric humidity) (e.g., under an N2 atmosphere).

[0149] Calcination of the green body is typically carried out at a temperature of at least 350°C or usually exceeding 350°C (calcination temperature). However, during calcination, the temperature generally does not exceed 650°C (in this document, the term calcination temperature refers to the temperature present in the calcined material (advantageously, the calcined material has the most uniform calcination temperature possible; this also applies to other calcination conditions)). During calcination, the temperature advantageously does not exceed 600°C, preferably does not exceed 570°C, and usually does not exceed 550°C. Furthermore, during the above-mentioned calcination process, it is preferable to...

[0150] Temperatures exceeding 380°C, advantageously exceeding 400°C, particularly advantageously exceeding 420°C, and very especially preferably exceeding 440°C. Calcination can also be divided into several parts according to time sequence.

[0151] Prior to calcination, it is advantageous to perform a heat pretreatment at temperatures ≥120°C and <350°C, preferably ≥150°C and ≤320°C, and particularly preferably ≥170°C and ≤290°C. From an application perspective, it is advantageous to perform this heat pretreatment until the components contained in the composition to be heat-treated and decomposed into gaseous compounds under the heat treatment conditions have substantially (preferably completely) decomposed into gaseous compounds (this time can be, for example, 3 to 15 hours, typically 4 to 10 hours or 5 to 8 hours). Generally, on the one hand, the molar amount of cations other than metal ions contained in the subsequently calcined composition is ≤20 molar percentages (preferably ≤10 molar percentages) relative to the total molar amount of contained cations; on the other hand, the molar amount of cations contained in the same composition other than O... 2- The molar amount of other anions relative to the total molar amount of included anions is also ≤20 molar percentage (preferably ≤10 molar percentage).

[0152] Therefore, the favorable temperature window for the final calcination temperature is in the temperature range of 400°C to 600°C, or preferably in the temperature range of 420°C to 570°C, or particularly preferably in the temperature range of 450°C to 550°C.

[0153] The total duration of calcination typically exceeds 0.5 hours and often exceeds 2 hours. The processing time during calcination generally does not exceed 45 hours or 30 hours. Typically, the total calcination time is less than 25 hours. In principle, at higher calcination temperatures, a shorter calcination time is usually sufficient than at lower calcination temperatures. According to an advantageous embodiment of the invention, the calcination temperature does not exceed 550°C, and the calcination duration extends from >4 hours to ≤25 hours within the temperature window of ≥430°C and ≤550°C.

[0154] The entire heat treatment (including the decomposition stage) of the precursor composition (e.g., green body) can be carried out in an inert gas and oxidizing atmosphere, such as air (or other mixtures of inert gases and molecular oxygen), and in a reducing atmosphere (e.g., a mixture of inert gases, NH3, CO and / or H2, or methane). Of course, heat treatment can also be carried out under a vacuum. The atmosphere can also be variable during heat treatment.

[0155] Heat treatment (especially the calcination stage) is preferably carried out in an oxidizing atmosphere. From an application perspective, it mainly consists of stagnant or (preferably) moving air (particularly preferably an airflow passing through the composition to be heat-treated (calcined material)). However, the oxidizing atmosphere can also consist of, for example, a mixture of 25 volume percent N2 and 75 volume percent air, or 50 volume percent N2 and 50 volume percent air, or 75 volume percent N2 and 25 volume percent air (a treatment atmosphere of 100 volume percent N2 is also possible).

[0156] In principle, heat treatment (e.g., calcination) of the precursor composition (e.g., green material) can be carried out in various types of furnaces, such as heatable circulating air chambers (circulating air furnaces, e.g., circulating air shaft furnaces), tray furnaces, rotary kilns, belt calcining furnaces, or shaft furnaces. According to the invention, heat treatment (e.g., calcination) is advantageously carried out in a belt calcining apparatus, as recommended by DE 100 46957 A1 and WO 02 / 24620. In this case, the formation of hot spots within the material to be treated (within the calcining material) is largely avoided because, with the aid of a fan, the increased volumetric flow rate of the calcining atmosphere through the permeable conveyor belt carrying the calcining material ensures the most uniform calcination temperature possible within the calcining material.

[0157] In the context of heat treatment of the precursor composition (e.g., green body) as described above, the commonly used molding aids can either remain in the resulting catalyst mold or undergo thermal and / or chemical decomposition to form gaseous compounds (e.g., CO, CO2), escaping at least partially in gaseous form from the latter. The molding aids remaining in the catalyst mold essentially serve only as diluents for the active material in its catalytic application. Essentially, the heat treatment can be carried out as described in US 2005 / 0131253.

[0158] Typically, the lateral compressive strength of the annular solid catalyst molded body obtainable according to the present invention is 4N to 30N, preferably 6N to 25N, more preferably 8N to 20N, and particularly preferably 9N to 17N.

[0159] The specific (BET) surface area of ​​the solid catalyst molded body is advantageously 2 m². 2 / g to 20m 2 / g or up to 15m 2 / g, preferably 3m 2 / g to 10m 2 / g, with 4m being the preferred choice 2 / g to 8m 2 / g.

[0160] Here, according to the invention, the associated total pore volume (mercury porosity determination method) is advantageously within 0.30 cm³. 3 / g to 0.70cm 3 Within the range of / g, preferably within 0.3cm 3 / g to 0.6cm 3 Within the range of / g, 0.39cm is preferred. 3 / g to 0.60cm 3 / g, more preferably 0.40cm 3 / g to 0.55cm 3 / g, with a particularly preferred value of 0.41cm 3 / g to 0.50cm 3 Within the range of / g.

[0161] If the aperture is plotted in µm on the horizontal axis, and in cm... 3 Aperture in g versus cm 3 Plotting the logarithm of the differential contribution of the total pore volume in units of g on the ordinate, the solid catalyst molded according to the invention, which is particularly advantageous, typically exhibits a substantially unimodal distribution (with only a distinct maximum value). Here, if the contribution of pores with a pore radius ≤0.1µm to the total pore volume is ≤0.05cm², then... 3 / g, resulting in exceptionally good overall target product selectivity (e.g., in the case of heterogeneous catalytic partial oxidation of propylene to acrolein and / or acrylic acid). In such cases, the contribution of the relatively narrow pores to the total pore volume is >0.05 cm⁻¹. 3 In the case of / g, according to the present invention, this contribution can be advantageously reduced by increasing the calcination time and / or calcination temperature.

[0162] Furthermore, if the contribution of pores with pore radii in the range of 0.1µm to 1µm to the total pore volume is 85% to 99% of the total pore volume, advantageously 87% to 97% of the total pore volume, and particularly preferably 89% to 95% of the total pore volume, it is proven to be beneficial to increase the overall selectivity of the target product.

[0163] Of course, solid catalyst molded bodies can also be used together with diluted inert materials for the partial gas-phase oxidation of heterogeneous catalysis. Suitable inert diluent materials are especially elemental oxides calcined at high temperatures and therefore having relatively few pores, such as alumina, silica, thorium dioxide, and zirconium dioxide. However, finely separated silicon carbide or finely separated silicates such as magnesium silicate and aluminum silicate or talc can also be used for the above purposes. For example, it is advantageous to grind the calcined active composition into a finely separated powder. This powder is then mixed with a finely separated diluent material, and the resulting mixed powder is shaped into a geometric molded body using the molding method proposed in this document (preferably by tableting). The latter is then converted into the associated solid catalyst molded body through subsequent further calcination. Of course, the finely separated inert diluent material can also be incorporated into a wet (e.g., aqueous) mixture M, for example, before drying. Furthermore, the finely separated inert diluent material can be incorporated into a finely separated dry mixture. However, this method is less preferred according to the invention.

[0164] In particular, the solid catalyst molded body prepared according to the advantageous preparation method is distinguished by the fact that it is essentially free of local centers of elemental oxides. Instead, these elements are largely composed of complex mixed oxymolybdates containing Bi, Fe, and Mo. This has proven advantageous because, in the context of relevant heterogeneous catalytic partial oxidation, undesirable complete combustion of the organic reactive gas mixture components is minimized according to the invention.

[0165] Furthermore, from the perspective of making the most efficient use of materials, the method described in WO 2010 / 066645 is advantageous for the preparation of solid catalysts.

[0166] The solid catalyst molded body according to the invention is applicable not only to the heterogeneous catalytic partial oxidation of propylene to acrolein, but also generally applicable to the heterogeneous catalytic partial gas-phase oxidation of alkanes, alkanols, alkenes and / or alkenes having 3 to 6 carbon atoms (in this document, partial oxidation should be specifically understood as those reactions of organic compounds in the presence of molecular oxygen, wherein the organic compound to be partially oxidized contains at least one more chemically bonded oxygen atom after the reaction is completed than before partial oxidation). However, in this document, the term partial oxidation should also include oxidative dehydrogenation and partial ammonia oxidation, i.e., partial oxidation in the presence of ammonia.

[0167] The solid catalyst molded body according to the present invention is particularly suitable for catalyzing the partial gas-phase oxidation of propylene to acrolein, the partial gas-phase oxidation of isobutylene to methacrolein, and the partial gas-phase ammoxidation of propylene to acrylonitrile and the partial gas-phase ammoxidation of isobutylene to methacrolein.

[0168] As previously described, the first stage of the two-stage heterogeneous catalytic partial gas-phase oxidation of propylene (isobutylene and / or tert-butanol) to acrolein (methacrylaldehyde) forms the first stage of the heterogeneous partial gas-phase oxidation of propylene (isobutylene and / or tert-butanol) to acrylic acid (methacrylic acid), as illustrated in WO 2006 / 42459.

[0169] Therefore, the formation of acrylic acid (methacrylic acid) byproducts associated with the heterogeneous catalytic partial gas-phase oxidation of propylene (isobutylene) to acrolein (methacrylaldehyde) is generally undesirable and is often included in the formation of the desired valuable product.

[0170] The above conditions are particularly applicable to the annular solid catalyst molded body according to the present invention.

[0171] Heterogeneous catalytic partial oxidation (especially the partial oxidation of propylene to acrolein) can be exemplified by, for example, references DE 102007 004961 A1, WO 02 / 49757, WO 02 / 24620, DE 10 2008 040093 A1, WO 2005 / 030393, EP0 575 897 A1, WO 2007 / 082827, WO 2005 / 113127, WO 2005 / 047224, WO 2005 / 042459, WO2007 / 017431, DE 10 2008 042060 A1, WO 2008 / 087116, DE 10 2010 048405 A1, DE 102009 047291 A1, DE 10 2008 042064 A1, DE 10 2008 042061 A1, WO 2015 / 067656 and DE10 2008 040094 A1 are performed as described for similar catalysts (in particular, the process can be performed here in a manner corresponding to the exemplary embodiments in these documents).

[0172] However, the advantages of the available solid catalyst moldings (especially annular ones) also exist when the catalyst fixed bed in the reactor is subjected to a load of propylene, isobutylene, and / or tert-butanol (or its methyl ether) contained in the reactant gas inlet mixture of ≥90 Nl / l catalyst charge·h, or ≥110 Nl / l·h, or ≥120 Nl / l·h, or ≥130 Nl / l·h (in this literature, when considering the load, the pre-filling and / or post-filling of purely inert material is not considered part of the catalyst fixed bed; furthermore, the volume of the catalyst fixed bed is its filling volume in the reactor). Under normal circumstances, the above-mentioned loads on the catalyst fixed bed will be ≤400 Nl / l·h, typically ≤300 Nl / l·h, more typically ≤250 Nl / l·h or ≤230 Nl / l·h. Loads in the range of ≥90 Nl / l·h or ≥100 Nl / l·h to ≤220 Nl / l·h or ≤200 Nl / l·h or ≤190 Nl / l·h are particularly suitable.

[0173] In this literature, the load on the catalyst fixed bed borne by the reactant gas inlet mixture is understood as the amount of reactant gas inlet mixture in standard liters (= Nl; the volume in liters that the corresponding amount of reactant gas inlet mixture would occupy under standard conditions of 0 °C and 1 atm-abs (1.01 bar-abs), based on the volume of its bed (excluding the bed portion of purely inert material), i.e., based on its bed volume per hour (-> unit = Nl / l·h). In this literature, standard volume units, such as Nl or Nm, are used. 3 "" always refers to the standard conditions of 0°C and 1 atm-abs (1.01 bar-abs) (unless otherwise explicitly stated).

[0174] The load can also be based on only one component of the reactant gas inlet mixture (e.g., only on the organic starting compound to be partially oxidized). In this case, the load is the volume of that component (e.g., the partially oxidized organic starting compound) supplied to the catalyst stationary bed per hour, based on the volume of its packing material.

[0175] Of course, the (e.g., cyclic) solid catalyst molded bodies available according to the invention, as catalysts for the partial oxidation of propylene to acrolein or isobutylene and / or tert-butanol (or its methyl ether) to methacrolein, can still operate advantageously in the manner of the invention even when the catalyst fixed bed is subjected to a loading of the starting compound to be partially oxidized ≤130 Nl / l·h, or ≤120 Nl / l·h, or ≤110 Nl / l·h, or ≤100 Nl / l·h, or ≤90 Nl / l·h. Typically, however, this loading value will be ≥20 Nl / l·h, or ≥30 Nl / l·h, or ≥40 Nl / l·h, or ≥50 Nl / l·h, or ≥60 Nl / l·h, or ≥70 Nl / l·h, or ≥80 Nl / l·h.

[0176] In principle, the load on the catalyst fixed bed of the reactor to be partially oxidized (propylene, isobutylene, and / or tert-butanol (or its methyl ether)) can be set via two adjusting screws:

[0177] a) The catalyst fixed bed bears the load of the reactant gas inlet mixture (the reactant gas mixture fed into the catalyst fixed bed), and / or

[0178] b) The content of the reactant gas inlet mixture and the starting compound to be partially oxidized.

[0179] The (e.g., annular) solid catalyst molds available according to the present invention are also particularly suitable for situations where the load of the organic compound to be partially oxidized on the catalyst fixed bed is higher than 120 Nl / l·h, and the load adjustment is mainly carried out via the aforementioned adjusting screw a).

[0180] Typically, for example, the percentage of propylene (isobutylene or tert-butanol (or dimethyl ether)) in the reactant gas inlet mixture is substantially independent of the catalyst fixed bed load and ranges from 4 to 10 volume percent, typically from 5 to 9 volume percent, or from 5.5 to 8.0 volume percent, or from 6.0 to 7.5 volume percent (in each case based on the total volume (flow) of the reactant gas inlet mixture flowing into the catalyst fixed bed).

[0181] Typically, a gas-phase partial oxidation method (substantially independent of load) catalyzed by a solid catalyst molded body (e.g., cyclic) according to the invention, as described above, is carried out in a volume ratio of the (organic) compound to be partially oxidized (e.g., propylene): oxygen: inert gas (including water vapor) at the reaction gas inlet mixture of 1:(1.0 to 3.0):(5 to 25), preferably 1:(1.5 to 2.3):(10 to 20).

[0182] In this context, an inert gas (or inert gas) is understood to be a gas that remains chemically unchanged for at least 95 molar percentage, preferably at least 98 molar percentage, during the partial oxidation of the reactant gas mixture in a single pass through the catalyst bed.

[0183] In the above-mentioned reactant gas inlet mixture, the inert gas may consist of molecular nitrogen of ≥20, ≥30, ≥40, ≥50, ≥60, ≥70, ≥80, ≥90, or ≥95 volume percentages.

[0184] However, when the catalyst fixed bed in the reactor is subjected to a high load of organic compounds to be partially oxidized (e.g., ≥150 Nl / L·h), it is recommended (but not mandatory) to use a dilution gas with a higher molar heat capacity and / or thermal conductivity, such as propane, ethane, methane, pentane, butane, CO2, CO, water vapor, and / or inert gases, for the reaction gas inlet mixture. However, these inert gases and mixtures thereof can generally also be used when the catalyst fixed bed is subjected to a lower load of organic compounds to be partially oxidized. Recycled gases can also be used as dilution gases. Recycled gases refer to the residual gases remaining after the target compounds have been substantially selectively separated from the partially oxidized product gas mixture. It should be taken into consideration that the partial oxidation to acrolein or methacrolein using a toroidal solid catalyst molded according to the invention can only be the first stage of a two-stage partial oxidation of acrylic acid or methacrylic acid, which are the actual target compounds, such that the formation of the circulating gas typically occurs only after the second stage (typical circulating gas compositions for the heterogeneous catalytic partial oxidation of propylene to acrolein and / or acrylic acid are shown in DE 102 32 482 A1, paragraphs

[0063] and

[0075] ). In the case of such two-stage partial oxidation, the product gas mixture of the first stage is typically supplied to the second partial oxidation stage after cooling and / or a secondary addition of oxygen (typically as air).

[0185] In the case of partial oxidation of propylene to acrolein, using a (e.g., cyclic) solid catalyst molded according to the invention, which is available as described above, the typical composition of the reaction gas inlet mixture measured at the reactor inlet (regardless of the selected load) may include, for example, the following components.

[0186] Propylene content ranging from 5% to 8.0% by volume.

[0187] 1% to 15% by volume of H2O

[0188] CO2 from 0% to 3% by volume x ,

[0189] Acrolein, ranging from 0.01% to 0.1% by volume.

[0190] Oxygen content ranging from 8% to 15.5% by volume

[0191] Make up to 100% by volume of molecular nitrogen as the balance;

[0192] or

[0193] Propylene content ranging from 6% to 7.5% by volume.

[0194] 1% to 5% by volume of H2O

[0195] 0.2% to 2% CO x ,

[0196] Acrolein at concentrations ranging from 0.015 to 0.06% by volume.

[0197] Oxygen content ranging from 9.4% to 14.5% by volume

[0198] Make up to 100% by volume of molecular nitrogen as the balance.

[0199] Alternatively, the reaction gas inlet mixture of the composition according to Example 1 of EP 0 990 636 A1, or Example 2 of EP 0 990 636 A1, or Example 3 of EP 1 106 598 A2, or Example 26 of EP 1 106 598 A2, or Example 53 of EP 1 106 598 A2, or the embodiment of WO 2021 / 013640 can also be used for the partial oxidation of propylene to acrolein according to the present invention.

[0200] Solid catalyst molded bodies according to the invention, such as ring-shaped ones, as described above, are also applicable to the methods of DE 102 46119 A1 and DE 102 45 585 A1.

[0201] When using a solid catalyst molded according to the invention (e.g., a ring-shaped one) as described, the reaction temperature for the heterogeneous catalytic partial oxidation of propylene to acrolein according to the invention is typically 300°C to 450°C or up to 400°C or up to 380°C. A particularly preferred reaction temperature window is 305°C to 365°C. This also applies to the case of methacrolein as the target compound.

[0202] For the above partial oxidation, the reaction pressure is typically 0.5 bar-abs to 5 bar-abs or up to 4 bar-abs, or preferably 1.1 bar-abs or 1.5 bar-abs to 3.5 bar-abs or up to 3.3 bar-abs (unless otherwise explicitly stated, absolute pressure (-abs) is always referred to in this literature).

[0203] In the partial oxidation described above according to the invention, the catalyst fixed bed typically bears a total load of 1000 Nl / l·h to 10000 Nl / l·h, mostly 1500 Nl / l·h to 5000 Nl / l·h, and usually 2000 Nl / l·h to 4000 Nl / l·h.

[0204] Suitable propylene for use in the reactant gas inlet mixture, particularly polymer-grade and chemical-grade propylene, as described, for example, in WO 2004 / 007405.

[0205] Air (optionally along with circulating gas) is typically used as the oxygen source.

[0206] In the simplest case, as described in DE 4431 957 A1, EP 0 700 714 A1 and EP 0 700 893 A1, partial oxidation using a solid catalyst molded body (e.g., annular) according to the invention, which is available as described, can be carried out, for example, in a single-zone tubular fixed-bed reactor.

[0207] In the aforementioned tube bundle reactors, the contact tubes are typically made of ferritic steel and generally have a wall thickness of 1 mm to 3 mm. Their inner diameter is typically 20 mm to 30 mm, and usually 21 mm to 26 mm. Typical contact tube lengths are, for example, 3.50 m, 4.00 m, or 4.50 m. The number of contact tubes housed in the tube bundle container conveniently reaches at least 1000, preferably at least 5000. The number of contact tubes housed in the reaction vessel is typically 15000 to 40000. Tube bundle reactors with more than 45000 contact tubes are exceptions. Under normal circumstances, the contact tubes are arranged in a uniform distribution within the vessel, wherein this distribution is conveniently chosen such that the distance between the central inner axes of the nearest contact tubes (the so-called contact tube spacing) is 35 mm to 45 mm (see EP 0 468 290 B1).

[0208] However, partial oxidation can also be carried out in multi-zone (e.g., “dual-zone”) tube bundle fixed-bed reactors, as recommended by DE 19910 506 A1, DE 103 13213 A1, DE 103 13208 A1, and EP 1 106 598 A2, particularly when the catalyst fixed bed in the tube bundle reactor is subjected to an increased load of the organic compound to be partially oxidized. In the case of a dual-zone tube bundle fixed-bed reactor, the typical contact tube length is 3.50 m, 4.00 m, or 4.50 m. Everything else is essentially as described for a single-zone tube bundle fixed-bed reactor. In each tempering zone of a single-zone or multi-zone tube bundle fixed-bed reactor (a single-zone tube bundle fixed-bed reactor has only one tempering zone), the heat exchange medium is directed around the contact tube where the catalyst fixed bed is located. Suitable melts are, for example, melts of salts such as potassium nitrate, potassium nitrite, sodium nitrite, and / or sodium nitrate, or melts of low-melting-point metals such as sodium, mercury, and alloys of various metals. The flow rate of the heat exchange medium in the corresponding tempering zone is usually selected so that the temperature of the heat exchange medium rises from 0°C to 15°C from the position entering the tempering zone to the position leaving the tempering zone, usually 1°C to 10°C, or 2°C to 8°C, or 3°C to 6°C.

[0209] Considering the corresponding tempering zone, the inlet temperature of the heat exchange medium, which can be transported co-currently or counter-currently with the reactant gas mixture, is preferably selected as recommended in documents EP 1 106 598 A2, DE 19948523 A1, DE 199 48248 A1, DE 103 13209 A1, EP 0 700 714 A1, DE 103 13208 A1, DE 103 13 213 A1, WO 00 / 53557, WO 00 / 53558, WO 01 / 36364, WO 00 / 53557, and other documents cited as prior art in these documents. Within the tempering zone, the heat exchange medium is preferably guided in a zigzag manner. When considering the longitudinal portion of the catalytically active (not purely inert) part of the fixed-bed catalyst, located within the tempering zone, the difference between the highest and lowest temperatures of the heat exchange medium within the tempering zone should advantageously be ≥0°C and ≤5°C (preferably very small). Typically, the tube-bundle fixed-bed reactor additionally includes heat pipes (heat pipes and reaction tubes housed in the same fixed bed) for measuring the temperature of the reactant gases in the catalyst bed. Advantageously, the inner diameter of the heat pipes and the diameter of the receiving sleeve (heat sheath) for thermocouples, located inside the heat pipes and extending parallel to their longitudinal axis, are selected such that, in the case of the heat pipes and the working tubes, the ratio of the volume generating the heat of reaction to the heat dissipation surface is the same or only slightly different.

[0210] Based on the same GHSV (the intensity of the volumetric flow rate of the reactant gas mixture entering the pipe divided by the volume of the catalyst fixed bed located in the pipe), the pressure losses in the working pipe and the heat pipe should be identical. The pressure loss in the heat pipe can be compensated, for example, by adding split catalyst to the solid catalyst mold. This compensation advantageously occurs uniformly along the entire length of the heat pipe. Furthermore, the filling of the heat pipe can be configured as described in EP 0 873783 A1.

[0211] The method according to the invention for preparing vinyl unsaturated aldehydes and / or vinyl unsaturated carboxylic acids by heterogeneous catalytic gas-phase partial oxidation of at least one olefin using molecular oxygen in a tube-buffered reactor uses at least two catalyst layers, each comprising a catalytically active multi-element oxide. The catalyst layer according to the invention comprises at least one catalytically active multi-element oxide. The catalyst fixed bed comprises all catalyst layers.

[0212] According to the present invention, the catalyst fixed bed contains at least two catalyst layers, wherein the number of catalyst layers is preferably 2 to 6, more preferably 2 to 5, particularly preferably 2 to 4, and especially preferably 2 to 3. The number of catalyst layers is preferably determined along the direction of the reactant gas flow from the gas inlet side to the gas outlet side.

[0213] In principle, the local temperature of the catalyst bed at a specific axial position along the reactor tube length / axis is the result of the simultaneous generation and dissipation of heat at that given axial position. Heat generation is due to the exothermic catalytic oxidation reaction occurring at the location in question. Heat dissipation (provided the local temperature of the catalyst bed is higher than the local temperature of the heat exchange medium) is due to heat exchange driven by the temperature difference between the catalyst bed and the heat exchange medium surrounding the reactor tube. The heat generation density, primarily influenced by the concentration of reactants (such as propylene and oxygen) and catalytic activity, varies along the axial position. Therefore, the temperature of the catalyst bed (essentially the same as the temperature of the reactant gases) exhibits a non-constant distribution characteristic depending on its position along the reactor tube length / axis; this distribution characteristic is called the temperature distribution characteristic. The local temperature of the catalyst bed at a specific axial position can be determined by measuring the temperature within the heat jacket located at the center of the reactor tube cross-section. The temperature distribution characteristic is created by measuring the local catalyst bed temperature at different axial positions. The intervals for local bed temperature measurements are preferably <20 cm, more preferably <15 cm, particularly preferably <10 cm, and even more particularly preferably <6 cm.

[0214] A temperature distribution characteristic has at least one local maximum, called a "local hotspot". Among all local hotspots, the one with the highest temperature is called a "hotspot". A "hotspot" is also called a hotspot.

[0215] According to the method of the present invention, the hot spot should not occur in the last catalyst layer (i.e., the catalyst layer closest to the reactor gas outlet). If there are two catalyst layers, the hot spot should occur in the first catalyst layer (the farthest gas inlet side). If there are three catalyst layers, the hot spot should occur in either the first or second catalyst layer with respect to the reactor gas inlet. If there are more than three catalyst layers, the hot spot should occur in either the first or second catalyst layer with respect to the reactor gas inlet.

[0216] According to a preferred embodiment, the hot spot temperature is 360°C to 450°C, preferably 370°C to 440°C, more preferably 380°C to 430°C, particularly preferably 390°C to 425°C, and even more preferably 400°C to 420°C. According to a preferred embodiment, the difference between the hot spot temperature and the heat exchange medium temperature (at the axial position of the hot spot along the pipe axis) is 40°C to 120°C, preferably 50°C to 100°C, more preferably 60°C to 95°C, and particularly preferably 70°C to 90°C. Furthermore, the design is preferably such that when the heat exchange medium temperature at each location in the catalyst fixed bed increases by 1°C, the temperature difference increases by >0°C and ≤+9°C, preferably ≤+7°C, more preferably ≤+5°C, and particularly preferably ≤+3°C (see also EP 1 106 598 A1).

[0217] In order for hot spots to appear in the catalyst layers required above, it is necessary to configure (1) the ratio of volume ratio of catalytic activity of each catalyst layer and (2) the ratio of (axial) length of the catalyst layer (along the tube axis).

[0218] Volumetric catalytic activity is the catalytic activity per unit reactor tube volume, including the catalyst mold and the cavity between the mold.

[0219] Volumetric activity can be adjusted by changing the volumetric activity of the catalyst mold itself. Specifically, this is achieved by altering the catalyst composition and processing conditions (e.g., composition, calcination temperature, bulk density) to change the inherent activity of the catalyst mold. Alternatively, a reduction in volumetric activity can be achieved in a simpler way, such as by uniformly diluting a uniformly prepared amount of solid catalyst mold (e.g., a toroidal mold) with an inert diluent. A higher proportion of the chosen diluent mold results in lower active material content or catalyst activity per unit volume of catalyst layer. However, a reduction can also be achieved by altering the geometry of the solid catalyst mold, thereby reducing the amount of active material contained within a unit volume of the reaction tube.

[0220] As previously mentioned, to prepare a catalyst layer with reduced volumetric activity, only readily available (e.g., cyclic) solid catalyst molds can be used, or a substantially homogeneous mixture of readily available (e.g., cyclic) solid catalyst molds and a mold that is essentially inert relative to the partially gas-phase oxidation of heterogeneous catalysis can be used. Suitable materials for such inert molds are, for example, porous or non-porous alumina, silica, zirconium dioxide, silicon carbide, silicates such as magnesium silicate or aluminum silicate, and / or talc (e.g., C220 from CeramTec, DE). Preferably, the BET surface area of ​​the inert mold is <0.5 m². 2 / g, preferably <0.3m 2 / g, more preferably <0.1m 2 / g. The lower limit of the BET surface area of ​​the inert molded body is preferably 0.001m². 2 / g, more preferably 0.01m 2 / g. The geometry of this inert dilution molded body is whatever is desired. That is, it can be, for example, a sphere, a polygon, a solid cylinder, or it can be a ring, as in the case of a ring-shaped catalyst molded body. Typically, inert dilution molded bodies are those whose geometry corresponds to the geometry of the catalyst molded body to which it is to be diluted. However, the geometry of the catalyst molded body can be changed, or catalyst molded bodies with different geometries can be mixed substantially uniformly for use.

[0221] According to a preferred embodiment, when the number of catalyst layers is two, the volume ratio of the catalytic activity of the first catalyst layer (located on the gas inlet side) to the second catalyst layer (located on the gas outlet side) is 50% to 95%, preferably 55% to 90%, more preferably 60% to 85%, and particularly preferably 65% ​​to 80%. Preferably, regarding the gas inlet side, the length of the first catalyst layer is 15% to 50% of the total length of the catalyst fixed bed (i.e., the sum of the lengths of the first and second catalyst layers), preferably 20% to 45%, more preferably 22% to 43%, and particularly preferably 24% to 40%.

[0222] According to a preferred embodiment, if the number of catalyst layers is three or more, the catalyst fixed bed is typically advantageously designed such that the volumetric activity remains constant or increases in the direction of flow of the reactant gas mixture.

[0223] If the number of catalyst layers is 3, the preferred ratio of the volumetric catalytic activity of the second catalyst layer (located between the first and third catalyst layers) to the third catalyst layer (located on the gas outlet side) is 50% to 95%, preferably 55% to 90%, more preferably 60% to 85%, and particularly preferably 65% ​​to 80%. In these cases, the preferred ratio of the volumetric catalytic activity of the first catalyst layer (on the gas inlet side) to the second catalyst layer (between the first and third catalyst layers) is 70% to 95%, preferably 75% to 90%, and more preferably 78% to 88%. Preferably, the same multi-element oxide with the same catalytic activity is used for the first and second catalyst layers. If the number of catalyst layers is 3, the total length of the first and second catalyst layers is 20% to 60% of the total length of the catalyst bed (i.e., the sum of the lengths of the first, second, and third catalyst layers), preferably 25% to 55%, more preferably 30% to 50%, and particularly preferably 35% to 45%.

[0224] In the flow direction of the reactant gas mixture, the bed of inert molded body can be positioned upstream of the actual catalyst fixed bed, with the aim of, for example, raising the inlet temperature of the reactant gas mixture to the temperature of the heat exchange medium.

[0225] Furthermore, the heterogeneous catalytic partial oxidation for the preparation of acrolein (from propylene) or methacrolein (from the C4 precursor compounds mentioned in this document) can advantageously be carried out using a ring-shaped solid catalyst mold prepared according to the invention, which corresponds exactly to the statement in WO 2015 / 067656.

[0226] In general, when using a readily available (e.g., cyclic) solid catalyst mold as a catalyst for partial oxidation to prepare acrolein or methacrolein, the catalyst fixed bed, reactant gas inlet mixture, load, and reaction temperature are typically selected such that the conversion of the partially oxidized organic compound (propylene, isobutylene, tert-butanol, or its methyl ether) is at least 90 mol% or at least 92 mol%, preferably at least 93 mol%, at least 94 mol%, at least 95 mol%, or at least 97 mol%, but typically ≤99 mol%, when the reactant gas mixture passes through the catalyst fixed bed once. In this case, the selectivity for the valuable product (the sum of acrolein and acrylic acid or the sum of methacrolein and methacrylic acid) is typically ≥80 mol%, or ≥85 mol%, or ≥90 mol%.

[0227] Finally, it can be noted that the solid catalyst molded body according to the invention, which is available as described above, also exhibits favorable fracture behavior during reactor filling.

[0228] A fixed bed of catalysts of the present invention comprising fresh (e.g., toroidal) solid catalyst molds can be started, for example, as described in DE 103 37 788 A1 or DE 10 2009 047291 A1.

[0229] The formation of the solid catalyst molded body obtainable according to the present invention can be accelerated by increasing the load on the catalyst fixed bed of the reactant gas inlet mixture at a substantially constant conversion rate.

[0230] Furthermore, the solid catalysts available according to the present invention are generally suitable for catalytically oxidizing the gas-phase fraction (ammonia) of alkanols, alkanal aldehydes, alkenes, alkanes and alkenal aldehydes containing 3 to 6 (i.e. 3, 4, 5 or 6) carbon atoms to, for example, unsaturated aldehydes and / or carboxylic acids and corresponding nitriles, as well as the gas-phase catalytic oxidative dehydrogenation of the aforementioned organic compounds containing 3, 4, 5 or 6 carbon atoms.

[0231] The industrial-scale preparation of the solid catalyst molded body according to the invention is conveniently carried out in a manner similar to that described in DE 10 2008 040093A1 and DE 10 2008 040094 A1 (particularly advantageously as described in the exemplary embodiments of these documents).

[0232] A shell catalyst preferably comprises a geometric support molded body, a catalytically active multi-element oxide applied to the outer surface of the geometric support molded body, and optionally a binder. The shell catalyst is prepared by applying the catalytically active multi-element oxide and optionally the binder to the outer surface of the geometric support molded body.

[0233] Example Preparation of solid catalyst molds K1 to K10:

[0234] Preparation of solid catalyst precursor molding body K1, wherein the active multimetal oxide has a stoichiometric ratio of Mo 12 Bi 0.6 Fe3Co7Si 1.6 K 0.08 O x .

[0235] In each case, the mixing vessel used is filled in the presence of ambient air. During stirring / mixing, it is hermetically sealed with a lid that has an overpressure valve open to the atmosphere (1.01 bar-abs).

[0236] a) Preparation of aqueous solution B

[0237] 430 kg of fully softened water is introduced into a 1.75 m stainless steel (EN 1.4541) temperature-controlled cylindrical mixing vessel equipped with a stirrer. 3The contents were placed in a container with an internal volume of 1.3 m in diameter and heated to 60 °C with stirring (70 rpm).

[0238] Subsequently, while continuously stirring and maintaining a temperature of 60°C, 0.61 kg of an aqueous solution of potassium hydroxide (47.5% by weight KOH) at 20°C was added over one minute. While maintaining 60°C, 136.2 kg of finely granulated ammonium heptamolybdate tetrahydrate (54.3% by weight Mo, supplier: NIPPON INORGANIC COLOUR & CHEMICAL CO., LTD., 3-14-1 Funado Itabashi-ku Tokyo 174-0041 Japan) was added in batches with constant stirring at 25°C, and then stirred again at 60°C (70 rpm). The resulting aqueous solution (which exhibited slight turbidity due to the slightest insoluble polymolybdate impurities) was then stirred for 60 minutes.

[0239] b) Preparation of aqueous solution A

[0240] 212 kg of cobalt(II) nitrate aqueous solution (12.5 wt% Co, 27 wt% nitrate, prepared by dissolving cobalt metal from MFT Metals % Ferro-Alloys Trading GmbH, D-41474 Viersen, with a purity >99.6 wt% Co, <0.3 wt% Ni, <100 mg / kg Fe, <50 mg / kg Cu) in an aqueous nitric acid solution was introduced into a 1.75 m stainless steel (EN 1.4541) temperature-controlled cylindrical stirred vessel equipped with a stirrer. 3 The contents were placed in a container with an internal volume of 1.3 m in diameter and heated to 60 °C with stirring (70 rpm).

[0241] While continuing stirring (70 rpm) and tempering to 60°C, metered 78 kg of ferric(III) nonhydrate melt (13.8 wt% Fe, <0.4 wt% alkali metal, <0.01 wt% chloride, <0.02 wt% sulfate, from Dr. Paul Lohmann GmbH, D-81857Emmerthal) was added at 60°C, and stirred again at 70 rpm for 30 minutes.

[0242] Add 72.6 kg of an aqueous bismuth nitrate solution (11.1 wt% Bi, 13 wt% nitrate, prepared by dissolving bismuth metal from Sidech SA, BE-1495 Tilly, with a purity >99.997 wt% Bi, <7 mg / kg Pb, <5 mg / kg each of Ni, Ag, and Fe, <3 mg / kg each of Cu and Sb, and <1 mg / kg each of Cd and Zn) at 60 °C to the aqueous solution obtained therein, while maintaining the temperature at 60 °C and continuing to stir (70 rpm), and then stirring again at 60 °C (70 rpm) for 30 minutes.

[0243] c) Mix aqueous solution A with aqueous solution B

[0244] Aqueous solution A, heated to 60°C, was continuously metered into aqueous solution B, which was stirred vigorously (70 rpm) at 60°C, over 15 minutes. The resulting aqueous suspension was then stirred at 60°C for another 15 minutes.

[0245] d) Adding silica sol yields an aqueous mixture M

[0246] After re-stirring, immediately add 12.6 kg of LU-DOX TM50 silica gel (47.5% by weight SiO2) from Grace GmbH & KG, In der Hollerecke 1, D-67545 Worms at 60°C to the aqueous mixture obtained in c).

[0247] e) Spray drying of aqueous mixture M

[0248] The aqueous mixture M was spray-dried immediately after preparation. In each case, the aqueous mixture (suspension) M, further stirred at 60°C with the aid of a stirrer (40 rpm) (also during spray drying), was spray-dried in a spray tower made of stainless steel 1.4541 with a centrifugal atomizer and atomizing wheel under hot air in a co-current flow (gas inlet temperature: 350 ± 10°C, gas outlet temperature: 140 ± 5°C, airflow intensity: 2200 ± 100 Nm). 3 / h, atomizer wheel speed: 20000rpm).

[0249] The obtained spray powder was temporarily stored in an airtight container (200 L or 1000 L internal volume, 25 °C, atmospheric pressure) until further processing (10 calendar days; shorter or longer temporary storage, up to 30 calendar days, had no effect on the results). The loss on ignition of the obtained spray powder (annealed at 600 °C (powder temperature) in excess still air for 3 h) was 31 ± 2% of its initial weight. At an absolute dispersion pressure of 2.0 bar, the D50 of the spray powder was 35 ± 10 µm (D50 represents 50% of the particles being smaller than the specified value).

[0250] f) Preparation of the annular precursor mold

[0251] 100 kg of spray powder and 1 kg of graphite (from Asbury Graphite Mills Inc., New Jersey 08802, Class 3160) were introduced into an inclined layer mixer (VIL type, fill volume: 200 l, Aachener Misch- und Knetmaschinenfabrik), which has mixing and cutting blades (mixing blade speed: 39 rpm, cutting blade speed: 3000 rpm) and premixed for 5 minutes.

[0252] The resulting mixture was then compacted in a K300 / 200 compactor from Hosokawa Bepex GmbH, which has grooved smooth rollers (roller diameter 300 mm, roller length 200 mm, gap width: 2.8 mm, roller speed: 3.6 rpm, pressure setting: 180 kN, length-to-pressure setting 9 kN / cm).

[0253] The compressed strips are crushed in a pulverizer (Alexanderwerk VZ 200, 138 rpm) and then granulated in a granulator (Alexanderwerk RFG 250 DL, equipped with an 800µm mesh sieve). The compacted material, with particle sizes primarily between 100µm and 1000µm, is separated by a vibrating screen (oversize: 1000µm, undersize: 100µm) using 22mm diameter sieve balls. The oversize and undersize materials are continuously recycled back into the compactor.

[0254] For tableting, an additional 2.5% by weight of graphite (Grade 3160, from Asbury Graphite Mills Inc., New Jersey 08802) is mixed into the compact within 2 minutes in a turbulent mixer from Drais.

[0255] Subsequently, the generated granules are compacted (tabletted) in a dry air atmosphere using a Korsch XT-600 rotator (with a 65 EURO B matrix) to form an annular precursor molded body with a geometry of A×H×I=5mm×5mm×2mm, having non-curved (i.e., flat) end faces, and a mass (M v The concentration was 185 mg. The applied pre-compression force (compression force) was 0.7 kN, and the applied main compression force (compression force) was 2.7 kN. The rotor speed was 40 rpm. The lateral compressive strength (SDFv) of the resulting annular precursor molded body was 22 N.

[0256] Heat pretreatment and calcination of the cyclic precursor molded body prepared in g)f)

[0257] The molded ring is placed on the belt of a belt calcining apparatus (as described in WO 2002 / 024620) having eight chambers (chamber width 100cm, chamber length 150cm).

[0258] Chambers 1 to 8 each have a fan for generating air circulation, and the temperatures are controlled at 150°C, 190°C, 225°C, 380°C, 430°C, 520°C, and 520°C, respectively. Heated air is metered into each chamber. The air supply to chambers 1 to 8 is 130 Nm³. 3 / h, 190Nm 3 / h, 254Nm 3 / h、90Nm 3 / h, 150Nm 3 / h、90Nm 3 / h、90Nm 3 / h and 140Nm 3 / h. Exhaust gas is discharged from each chamber via a fan. The air volume discharged from chambers 1 to 8 is 136 Nm³ each. 3 / h, 300Nm 3 / h, 315Nm 3 / h, 154Nm 3 / h, 145Nm 3 / h、90Nm 3 / h、90Nm 3 / h and 137Nm 3 / h.

[0259] The filling height of chambers 1 to 4 is 40 mm. The filling height of chambers 5 to 8 is 75 mm. Within the chambers, the temporal and spatial deviations of the temperature from the target value are consistently ≤10 ℃.

[0260] The conveyor belt speed results in a dwell time of 105 minutes in the first four chambers and 270 minutes in the fifth through eighth chambers.

[0261] In this manner, 2.6 t of solid catalyst molded body K1 was prepared.

[0262] Preparation of solid catalyst precursor molding body K2, wherein the active polymetallic oxide has a stoichiometric ratio of Mo 12 Bi 0.6 Fe3Co 7.5 K 0.14 O x .

[0263] In each case, the mixing vessel used is filled in the presence of ambient air. During stirring / mixing, it is hermetically sealed with a lid that has an overpressure valve open to the atmosphere (1 atm-abs, 1.01 bar-abs).

[0264] a) Preparation of aqueous solution B

[0265] 3.9 kg of fully softened water is introduced into a stainless steel (EN 1.4541) temperature-controlled cylindrical mixing vessel (10 L internal volume) equipped with an anchor stirrer and heated to 60 °C while stirring (150 rpm).

[0266] Subsequently, while continuously stirring and maintaining a temperature of 60°C, 27.5 g of a 47 wt% aqueous solution of potassium hydroxide (47 wt% KOH) at a temperature of 20°C was added. While maintaining 60°C, 1161 g of finely granulated ammonium heptamolybdate tetrahydrate (54.3 wt% Mo, supplier: NIPPON INORGANIC COLOUR & CHEMICAL CO., LTD., 3-14-1 Funado ltabashi-ku Tokyo 174-0041 (JP); with a turbidity of 219 NTU as determined according to WO 2016 / 147324) was added in batches with constant stirring at 25°C. The resulting aqueous solution (which exhibited slight turbidity due to the slightest insoluble polymolybdate impurities) was stirred at 60°C (150 rpm) for 20 minutes.

[0267] b) Preparation of aqueous solution A

[0268] 5763g of an aqueous solution of cobalt(II) nitrate (12.6% by weight Co, 27% by weight nitrate (NO3)) was added. -The cobalt metal was prepared by dissolving it in an aqueous nitric acid solution from MFT Metals % Ferro-Alloys Trading GmbH, D-41474 Viersen, with a purity of >99.6% by weight Co, <0.3% by weight Ni, <100 mg / kg Fe, and <50 mg / kg Cu. The solution was introduced into a stainless steel (EN 1.4541) temperature-controlled cylindrical stirring vessel (5 L internal volume) equipped with an anchor stirrer and heated to 60 °C with stirring (150 rpm). While continuing stirring (150 rpm) and tempering to 60°C, 1994 g of ferric(III) nonahydrate melt (13.8 wt% Fe, <0.4 wt% alkali metal, <0.01 wt% chloride, <0.02 wt% sulfate, from Dr. Paul Lohmann GmbH, D-81857 Emmerthal) at 60°C was metered in, and the mixture was stirred again at 150 rpm for 10 min at 60°C. To the resulting aqueous solution, 618.6 g of bismuth nitrate aqueous solution (11.1 wt% Bi, 13 wt% nitrate) at 60°C was added. 3- Bismuth metal from Sidech SA, BE-1495 Tilly, with a purity >99.997% by weight (Bi, <7 mg / kg Pb, <5 mg / kg each of Ni, Ag, and Fe, <3 mg / kg each of Cu and Sb, and <1 mg / kg each of Cd and Zn), was prepared by dissolving it in an aqueous nitric acid solution, followed by stirring at 60°C (150 rpm) for 10 min.

[0269] c) Mix aqueous solution A and aqueous solution B to obtain aqueous mixture M.

[0270] Aqueous solution A at 60°C was continuously metered over 15 minutes using a peristaltic pump (model: BVP, company: Ismatec SA, Labortechnik-Analytik, Feldeggstraße 6, CH-8152 Glattbrugg, setting: 320 units) into aqueous solution B, which was being vigorously stirred and maintained at 60°C using an Ultra-Turax agitator (from Janke & Kunkel GmbH & Co. KG -IKA-Labortechnik, Janke & Kunkel-Str. 10, DE-79219 Staufen, shaft type: 550KR-G45fein, shaft tube diameter: 25mm, stator diameter: 45mm, rotor diameter: 40mm, setting: 5 levels). Here, aqueous solution A was injected to the height of the Ultra-Turax agitator rotor, approximately 0.5cm to 1cm from the outer edge of the rotor. The resulting aqueous suspension was stirred at 60°C for another 15 minutes.

[0271] d) Spray drying of aqueous mixture M

[0272] The aqueous mixture M was spray-dried immediately after preparation. In each case (also during spray drying), the aqueous mixture (suspension) M was further stirred at 60°C using an anchor agitator (150 rpm) in a spray tower (from Niro A / S, Gladsaxevej 305, 2860 Soborg, Denmark). ™ The 2000 (MM-I) model, equipped with an F01A centrifugal atomizer and an SL24-50 atomizer wheel, is used for spray drying in a co-current flow of hot air (gas inlet temperature: 350±10℃, gas outlet temperature: 140±5℃, throughput: 4.7 kg water mixture M / h, and flow rate: 8.5 Nm). 3 / h hot air flow). The portion of the aqueous mixture M that has not yet been spray-dried is continuously stirred at 60°C. The atomizer wheel speed is set to 25,000 rpm. The resulting spray powder is temporarily stored in an airtight container (200 L internal volume, 25°C, atmospheric pressure) until further processing (10 calendar days; shorter or longer temporary storage (maximum 30 calendar days) has no effect on the results). The loss on ignition of the resulting spray powder (after static annealing in (excessive) air at 600°C (powder temperature) for 3 h) is 31% by weight of its initial weight.

[0273] e) Preparation of cyclic solid catalyst precursor molding

[0274] 3 kg of spray powder, 3.5 wt% graphite (grade 3160 from Asbury Graphite Mills Inc., New Jersey 08802), based on the mass of the spray powder, and 3 wt% glass fiber (type F2F 160 E glass fiber from Profill GmbH Heidelberg, Kirchheimerstr. 1 D-69214 Eppelheim, nominal fiber size: 10 µm diameter, 200 µm length, BET specific surface area 0.4 m²) were used. 2 Mix (g) in a mixer equipped with a shredder (from Gebrüder Lödige Maschinenbau GmbH, Elsener Straße 7-9 33102Paderborn, Germany, model L5 / 10) for 10 minutes, with the shredder blades used intermittently for a total of 1 minute.

[0275] Subsequently, the powder mixture produced as described above was compacted (tableted) in a dry air atmosphere using a Kilian E150+ rotator (with a 21 EURO D mold) to form an annular precursor molded body with a geometry of A×H×I=5mm×5mm×2mm, having non-curved (i.e., flat) end faces, and a mass (Mv) of 160mg (bulk density 1.94g / ml). The applied pressure (P) v The compressive strength (SDF) of the resulting annular polymetallic oxide precursor molded body is 1.6 kN. The rotor speed is 15 rpm-20 rpm. V No measurements were taken.

[0276] The thermal pretreatment and calcination of the cyclic solid catalyst precursor mold prepared in f)e)

[0277] 1000g of the prepared solid catalyst precursor mold was uniformly distributed on four side-by-side grids, each with a base surface of 150mm × 150mm (fill height: 15mm), and placed in a circulating air shaft furnace (from Nabertherm GmbH, D-28865 Lilienthal; furnace model S60 / 65A). Pre-dried air (inlet temperature 140°C) at a rate of 4500 Nl / h flowed through the furnace (the circulating air furnace was located in an environment of 25°C). Subsequently, while maintaining the airflow (including its inlet temperature), the temperature changes within the circulating air shaft furnace were as follows (temperature data represent the temperature of the corresponding applied bulk material; this was determined by four thermocouples, each located at the geometric center of the four grids, with one thermocouple providing the actual value for temperature control of the circulating air shaft furnace; the other thermocouples confirmed that the temperature was the same within ±0.1°C). The temperature increase was substantially linear over time. The mixture was heated from 25°C to 130°C over 72 min. This temperature was held for 72 min, then increased to 190°C over 36 min. 190°C was held for 144 min, then increased to 220°C over 36 min. 220°C was held for 72 min, then increased to 380°C over 93 min. 380°C was held for 187 min, then increased to 430°C over 93 min. 430°C was held for 187 min, then increased to the final calcination temperature of 480°C over 93 min. This was held for 467 min. It was then cooled to 25°C over 12 h. For this purpose, the heating of the circulating air shaft furnace and the gas flow preheating were turned off (however, the gas flow itself of 4500 Nl / h remained constant; the gas flow inlet temperature was 25°C). The resulting cyclic solid catalyst molding body K2 was stored in an airtight container at 25°C and atmospheric pressure until it was used to catalyze heterogeneous catalytic partial oxidation reactions (e.g., propylene to acrolein).

[0278] Preparation of solid catalyst precursor molding body K3, wherein the active polymetallic oxide has a stoichiometric ratio of Mo 12 Bi 0.6 Fe 2.4 Co 7.7 K 0.08 O x .

[0279] The preparation of solid catalyst molded body K3 is the same as that of solid catalyst molded body K2. However, the amount of source of elemental components other than Mo added is determined according to the stoichiometric ratio of Mo present in the aqueous mixture M. 12 Bi06Fe 24 Co 7.7 K 0.08 O xAdjustments will be made.

[0280] Based on the amount of sprayed powder, the amount of glass fiber in step e) is adjusted to 4.0% by weight.

[0281] The conditions for tablet compression in step e) are as follows:

[0282] M V =150mg (body density 1.83g / ml)

[0283] P V =0.8kN

[0284] SDF V =14N

[0285] The final calcination temperature in step f) is adjusted to 470℃.

[0286] Preparation of solid catalyst precursor molding body K4, wherein the active polymetallic oxide has a stoichiometric ratio of Mo 12 Bi 0.6 Fe3Co 4.9 Ni 2.6 K 0.12 O x .

[0287] The preparation of solid catalyst molded body K4 is similar to that of solid catalyst molded body K2. However, the amount of source of elemental components other than Mo added is determined according to the stoichiometric ratio of Mo present in the aqueous mixture M. 12 Bi 0.6 Fe3Co 4.9 Ni 2.6 K 0.12 O x Adjustments will be made.

[0288] In production step b), the nickel component is introduced into solution A. A nickel (II) nitrate solution (13.8 wt% Ni, 0.6 wt% free nitric acid, prepared by dissolving nickel metal in an aqueous nitric acid solution) is used as the nickel source. Ten minutes after the addition of the bismuth nitrate solution, the nickel (II) nitrate solution is added. After the addition of the nickel (II) nitrate solution, solution A is stirred at 60°C for 10 minutes.

[0289] The production step e) for forming the complete catalyst precursor mold is modified as follows: 3 kg of the obtained spray powder is mixed with 2% by weight of graphite (grade 3160 from Asbury Graphite Mills Inc., New Jersey 08802) at 30 rpm for 30 minutes, based on the weight of the spray powder.

[0290] Subsequently, the powder mixture produced as described above was compacted (tableted) in a dry air atmosphere using a Kilian E150+ rotator (with a 21 EURO D mold) to form an annular precursor molded body with a geometry of A×H×I=5mm×3mm×2mm, having non-curved (i.e., flat) end faces, and a mass of 102mg. The applied pressure was 2.0kN.

[0291] The resulting tablets were crushed on a vibrating screen crusher using a sieve (800µm mesh size) and iron balls. The crushed particles were mixed with 1.5% by weight of the same 3160 grade graphite in a rotary drum mixer (30 rpm, 15 min) to obtain granules. Subsequently, the granules thus produced were compressed (pressed into flakes) in a dry air atmosphere using a Kilian E150+ rotator (with 21 EURO D matrix) to form an annular precursor molded body with a geometry of A×H×I=5mm×5mm×2mm, having non-curved (i.e., flat) end faces, and a mass (M V The concentration was 185 mg (volume density 2.24 g / ml). The applied pressure was 3.4 kN. The lateral compressive strength (SDF) of the resulting cyclic polymetallic oxide precursor molded body was... V The value is 25N.

[0292] The precursor molded body is calcined according to production step f) to obtain K2, wherein the final calcination temperature is set to 500°C.

[0293] Preparation of solid catalyst precursor molding body K5, wherein the active polymetallic oxide has a stoichiometric ratio of Mo 12 Bi 0.6 Fe 2.4 Co 6.1 Ni 1.6 K 0.04 O x .

[0294] The preparation of solid catalyst molded body K5 is similar to that of solid catalyst molded body K4. However, the amount of source of elemental components other than Mo added is determined according to the stoichiometric ratio of Mo present in the aqueous mixture M. 12 Bi 0.6 Fe 2.4 Co 6.1 Ni 1.6 K 0.04 O x Adjustments will be made.

[0295] The conditions for tablet compression in step e) are as follows:

[0296] M V =190mg (body density 2.30g / ml)

[0297] P V =3.2kN

[0298] SDF V =25N

[0299] The precursor molded body is calcined according to production step f) to obtain K4, wherein the final calcination temperature is set to 500°C.

[0300] Preparation of solid catalyst precursor molding body K6, wherein the active polymetallic oxide has a stoichiometric ratio of Mo 12 Bi 1.4 Fe 1.8 Co 6.1 Ni 2.5 K 0.08 O x .

[0301] The preparation of solid catalyst molded body K6 is similar to that of solid catalyst molded body K4. However, the amount of source of elemental components other than Mo added is determined according to the stoichiometric ratio of Mo present in the aqueous mixture M. 12 Bi 1.4 Fe 1.8 Co 6.1 Ni 2.5 K 0.08 O x Adjustments will be made.

[0302] The conditions for tablet compression in step e) are as follows:

[0303] M V =196mg (body density 2.38g / ml)

[0304] P V =2.9kN

[0305] SDF V =25N

[0306] The precursor molded body is calcined according to production step f) to obtain K4, wherein the final calcination temperature is set to 500°C.

[0307] Preparation of solid catalyst precursor molding body K7, wherein the active multimetal oxide has a stoichiometric ratio of Mo 12 Bi 0.6 Fe3Co 4.9 Ni 2.6 K 0.12 O x .

[0308] The preparation of solid catalyst molded body K7 is similar to that of solid catalyst molded body K2. However, the amount of source of elemental components other than Mo added is determined according to the stoichiometric ratio of Mo present in the aqueous mixture M. 12 Bi 0.6 Fe3Co 4.9 Ni 2.6 K 0.12 O x Adjustments will be made.

[0309] In production step b), the nickel component is introduced into solution A. A nickel (II) nitrate solution (13.8 wt% Ni, 0.6 wt% free nitric acid, prepared by dissolving nickel metal in an aqueous nitric acid solution) is used as the nickel source. Ten minutes after the addition of the bismuth nitrate solution, the nickel (II) nitrate solution is added. After the addition of the nickel (II) nitrate solution, solution A is stirred at 60°C for 10 minutes.

[0310] Adjust the amount of glass fiber in step e) to 0% by weight, i.e., do not add glass fiber.

[0311] The conditions for tablet compression in step e) are as follows:

[0312] M V =150mg (body density 1.82g / ml)

[0313] P V =1.2kN

[0314] The precursor molded body is calcined according to production step f) to obtain K2, wherein the final calcination temperature is set to 540°C.

[0315] Preparation of solid catalyst precursor molding body K8, wherein the active multimetal oxide has a stoichiometric ratio of Mo 12 Bi 0.6 Fe 2.4 Co 6.1 Ni 1.6 K 0.04 O x .

[0316] The preparation of solid catalyst molded body K8 is similar to that of solid catalyst molded body K7. However, the amount of source of elemental components other than Mo added is determined according to the stoichiometric ratio of Mo present in the aqueous mixture M. 12 Bi 0.6 Fe 2.4 Co 6.1 Ni 1.6 K 0.04 O x Adjustments will be made.

[0317] The conditions for tablet compression in step e) are as follows:

[0318] M V =150mg (body density 1.82g / ml)

[0319] P V =1.1kN

[0320] The precursor molded body is calcined according to production step f) to obtain K2, wherein the final calcination temperature is set to 510℃.

[0321] Preparation of solid catalyst precursor molding body K9, wherein the active multimetal oxide has a stoichiometric ratio of Mo 12 Bi 0.6 Fe3Co 4.9 Ni 2.6 K 0.12 O x .

[0322] The preparation of solid catalyst molded body K9 is similar to that of solid catalyst molded body K7. However, the amount of source of elemental components other than Mo added is determined according to the stoichiometric ratio of Mo present in the aqueous mixture M. 12 Bi 0.6 Fe3Co 4.9 Ni 2.6 K 0.12 O x Adjustments will be made.

[0323] Based on the amount of sprayed powder, adjust the amount of glass fiber in step e) to 3% by weight.

[0324] The conditions for tablet compression in step e) are as follows:

[0325] M V =160mg (body density 1.94g / ml)

[0326] P V =1.6kN

[0327] The precursor molded body is calcined according to production step f) to obtain K2, wherein the final calcination temperature is set to 500°C.

[0328] Preparation of solid catalyst precursor molding body K10, wherein the active polymetallic oxide has a stoichiometric ratio of Mo 12 Bi 0.6 Fe 2.4 Co 6.1 Ni 1.6 K 0.04 O x .

[0329] The preparation of solid catalyst molded body K10 is similar to that of solid catalyst molded body K9. However, the amount of source of elemental components other than Mo added is determined according to the stoichiometric ratio of Mo present in the aqueous mixture M. 12 Bi 0.6 Fe 2.4 Co 6.1 Ni 1.6 K 0.04 O x Adjustments will be made.

[0330] The conditions for tablet compression in step e) are as follows:

[0331] M V =160mg (body density 1.94g / ml)

[0332] P V =1.6kN

[0333] The precursor molded body is calcined according to production step f) to obtain K2, wherein the final calcination temperature is set to 500°C.

[0334] All calcined catalysts K1-K10 have a ring geometry of A×H×I=4.9mm×4.9mm×1.9mm.

[0335] The specific surface area (BET) of the calcined catalyst was determined by nitrogen adsorption at 77 K on a Micromeritics ASAP 2420. Before measurement, the sample was degassed under vacuum at 200 °C for 15 hours. The specific surface area A was calculated using the multi-point Brunauer-Emmett-Teller (BET) method within a pressure range of P / P0 = 0.05–0.20. s Assuming the cross-sectional area of ​​N2 is 16.2 Å 2 .

[0336] The pore volume (PV) of calcined catalysts was determined at room temperature using the mercury porosimetry method under a pressure range of 0.0034 MPa–420 MPa on MicromeriticsAutoPore V9600 (software: MicroActive 1.03.01). Assuming a contact angle of 140° and a surface tension of 485 mN / m, the pore size distribution was calculated based on the intrusion volume (as a function of intrusion pressure).

[0337] Table 1 shows the physical properties and stoichiometry of the obtained solid catalyst molds.

[0338]

[0339] Catalytic experiments on the selective oxidation of propylene to acrolein and acrylic acid

[0340] During testing, a reaction tube (type 1.4541 stainless steel (EU standard number EN 10088-3); outer diameter 33.7 mm; wall thickness 2 mm; inner diameter 29.7 mm; length 400 cm; 4 mm heat sleeve) was used.

[0341] The reaction tube was flushed along its length with two stirred and externally electrically heated salt baths (a mixture of 53 wt% potassium nitrate, 40 wt% sodium nitrite, and 7 wt% sodium nitrate; 50 kg molten salt) at a flow rate of 3 m / s. 3 / h (in a plane perpendicular to the longitudinal axis of the tube). The first salt bath covers a length of 0cm-191cm from the bottom of the reaction tube. Conversely, the second salt bath covers a length of 191cm-400cm from the bottom of the reaction tube. The temperatures of the salt baths are independently controlled, thus forming two temperature zones (Zone 1: lower part; Zone 2: upper part).

[0342] The reaction tube is loaded with materials from top to bottom as follows:

[0343] Part 1: 50cm length

[0344] Prefilled with talc rings (outer diameter × length × inner diameter; C220 talc from CeramTec) with a geometry of 7mm × 3mm × 4mm;

[0345] Part 2: 300cm in length;

[0346] The catalyst bed consists of two layers (see Table 2; here, layer 1 is closest to the reactor inlet).

[0347] Part 3: 20cm length

[0348] Refilling consisting of talc rings identical to those in part 1;

[0349] Part 4: 30cm length

[0350] Empty pipe.

[0351] The structure of the reaction zone is shown in Table 2. To set the relative volumetric catalyst activity, a solid catalyst mold was diluted with an inert talc ring with a geometry of 5 mm × 5 mm × 2 mm (outer diameter × length × inner diameter, C220 talc from CeramTec).

[0352] Table 2 shows the composition of the corresponding catalyst layers and the corresponding Fe / Mo, Bi / Mo and K / Mo ratios.

[0353] The reactor's supply gas consists of a mixture of propylene (industrial or polymer grade), air, nitrogen, and water. The gas mixture is preheated to 200°C. Table 4 shows the concentrations of propylene and oxygen. The water vapor to propylene ratio is 0.3. The reactor's supply gas is pumped upwards from the bottom to the top of the reactor tubes (upward flow).

[0354] Temperature in the catalyst bed is continuously measured using thermocouples placed in heated sleeves within the reactor tubes and propelled upwards from the bottom using a traction device. The highest temperature measured corresponds to the hot spot temperature T. H .

[0355] In this literature, propylene conversion (X (molar percentage)) is understood as:

[0356]

[0357] In this literature, the yield (Y (molar percentage)) of value product formation is understood as:

[0358]

[0359] (In each case, the conversion rate is based on the reaction gas mixture passing through the catalyst fixed bed in a single pass).

[0360] Table 3 shows the catalytic performance data.

[0361] Figures 1 to 5 This displays the temperature distribution characteristics of the selected example. A graph is plotted here showing the relationship between the temperature T of the catalyst stationary bed measured in the hot mantle and the axial position P of the catalyst stationary bed along the gas inlet side to the gas outlet side.

[0362] Figure 1 This shows the temperature distribution characteristics of example E1. Figure 2 This shows the temperature distribution characteristics of example E4. Figure 3 This shows the temperature distribution characteristics of example E5. Figure 4 This shows the temperature distribution characteristics of example E6. Figure 5 This shows the temperature distribution characteristics of example E7.

[0363] Comparing these examples, it can be seen that, with the same propylene loading (130 Nl / lh or 180 Nl / lh), the method according to the present invention has a higher yield of valuable products (with lower catalyst quality).

[0364]

[0365]

Claims

1. A method for preparing vinyl unsaturated aldehydes and / or vinyl unsaturated carboxylic acids, wherein, By using molecular oxygen at elevated temperatures to perform heterogeneous catalytic gas-phase partial oxidation of at least one olefin in a fixed catalyst bed of a tube bundle reactor, the corresponding vinyl unsaturated aldehydes and / or vinyl unsaturated carboxylic acids are obtained. At least two catalyst layers are arranged in the axial direction of the tubes of the tube bundle reactor, each catalyst layer comprising a catalytically active multi-element oxide, such that multi-layer packing is achieved and the composition of the multi-element oxide in one catalyst layer differs from the composition of the multi-element oxide in at least one of the other catalyst layers. Its features are, The stoichiometric ratio L1 of Fe to Mo in the catalyst layer with the highest temperature inside the catalyst fixed bed is greater than the stoichiometric ratio L2 of Fe to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side. The stoichiometric ratio M1 of Bi to Mo in the catalyst layer with the highest internal temperature in the catalyst fixed bed is less than or equal to the stoichiometric ratio M2 of Bi to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side.

2. The method according to claim 1, characterized in that, The composition of the catalytically active multi-element oxide conforms to general formula (I). Mo 12 Bi a Feb b Co c Ni d X e Y f Z g O n (I) in, X = K, Cs, and / or Rb, Y=Ca, Sr, Ba, Li, Na, Cr, W, Mn, Cu, Zn, Ga, P, B, As, Sn, Sb, Te, Nb, Ta, Pb, Ce and / or La, Z = Si, Al, Ti, Zr and / or Mg, in a = 0.2 to 2, b = 1 to 4, c = 3 to 9, d = 0 to 4, c+d=4 to 9.5 e = 0.01 to 0.5 f = 0 to 10, g = 0 to 10, and n = a number determined by the valence and abundance of elements other than oxygen in general formula I.

3. The method according to claim 1 or 2, characterized in that, The stoichiometric ratio N1 of element K to Mo in the catalyst layer with the highest internal temperature in the catalyst bed is greater than the stoichiometric ratio N2 of element K to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side.

4. The method according to any one of claims 1 to 3, characterized in that, The stoichiometric ratio of Fe to Mo in the catalyst layer, which has the highest temperature inside the catalyst fixed bed, is between 0.15 and 0.

35.

5. The method according to any one of claims 1 to 4, characterized in that, The composition of the catalytically active multi-element oxides in the catalyst layer with the highest internal temperature in the catalyst fixed bed conforms to general formula (II). Mo 12 Bi a Feb b Co c Ni d X e Y f Z g O n (II).

6. The method according to any one of claims 1 to 4, characterized in that, The composition of the catalytically active multi-element oxides in the catalyst layer arranged along the pipeline axis on the farthest gas outlet side conforms to general formula (III). Mo 12 Bi a Feb b Co c Ni d X e Y f Z g O n (III).

7. The method according to any one of claims 1 to 6, characterized in that, The vinyl unsaturated aldehyde is acrolein, and the vinyl unsaturated carboxylic acid is acrylic acid.

8. The method according to any one of claims 1 to 7, characterized in that, The olefin is propylene.

9. The method according to any one of claims 1 to 8, characterized in that, Each catalyst layer is composed of a solid catalyst and / or a shell catalyst.

10. The method according to any one of claims 1 to 9, characterized in that, The ratio of L1 to L2 is 1.1 to 1.

6.

11. The method according to any one of claims 1 to 10, characterized in that, The ratio of M1 to M2 is 0.5 to 1.

12. The method according to any one of claims 3 to 11, characterized in that, The ratio of N1 to N2 is 1.5 to 3.

3.

13. The method according to any one of claims 2 to 12, characterized in that, In general formula (I), X=K, Z=Si, a=0.4 to 1.5, b=1.7 to 3.1, c=4.8 to 7.8, d=0 to 2.7, c+d=6.9 to 8.5, e=0.03 to 0.15, f=0, g=0 to 1.

8.

14. The method according to any one of claims 5 to 13, characterized in that, In general formula (II), X=K, Z=Si, a=0.5 to 0.7, b=2.9 to 3.1, c=4.8 to 7.6, d=0 to 2.7, c+d=6.9 to 7.6, e=0.07 to 0.15, f=0, g=0 to 1.

6.

15. The method according to any one of claims 6 to 14, characterized in that, In general formula (III), X=K, Z=Si, a=0.5 to 1.5, b=1.7 to 3.1, c=4.8 to 7.8, d=0 to 2.7, c+d=6.9 to 8.5, e=0.03 to 0.09, f=0, g=0 to 1.

8.

16. A tube bundle reactor for preparing vinyl unsaturated aldehydes and / or vinyl unsaturated carboxylic acids by multiphase catalytic gas-phase partial oxidation of at least one olefin using molecular oxygen at elevated temperatures in a catalyst fixed bed of a tube bundle reactor, wherein at least two catalyst layers are arranged in the axial direction of the tubes of the tube bundle reactor, each catalyst layer comprising a catalytically active multi-element oxide, such that multi-layer packing exists and the composition of the multi-element oxide in one catalyst layer differs from the composition of the multi-element oxide in at least one of the other catalyst layers, characterized in that, The stoichiometric ratio L1 of Fe to Mo in the catalyst layer with the highest temperature inside the catalyst fixed bed is greater than the stoichiometric ratio L2 of Fe to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side. The stoichiometric ratio M1 of Bi to Mo in the catalyst layer with the highest internal temperature in the catalyst fixed bed is less than or equal to the stoichiometric ratio M2 of Bi to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side.

17. A catalyst fixed bed arranged within at least one tube of a tube bundle reactor for preparing vinyl unsaturated aldehydes and / or vinyl unsaturated carboxylic acids by heterogeneous catalytic gas-phase partial oxidation of at least one olefin using molecular oxygen at elevated temperatures, wherein at least two catalyst layers are arranged in the axial direction of the tube of the tube bundle reactor, each catalyst layer comprising a catalytically active multi-element oxide, such that there is multi-layer packing and the composition of the multi-element oxide in one catalyst layer differs from the composition of the multi-element oxide in at least one of the other catalyst layers. Its features are, The stoichiometric ratio L1 of Fe to Mo in the catalyst layer with the highest temperature inside the catalyst fixed bed is greater than the stoichiometric ratio L2 of Fe to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side. The stoichiometric ratio M1 of Bi to Mo in the catalyst layer with the highest internal temperature in the catalyst fixed bed is less than or equal to the stoichiometric ratio M2 of Bi to Mo in the catalyst layer arranged along the tube axis on the farthest gas outlet side.

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