CN117943073A - Mechanically stable VPO catalyst and method for preparing the same - Google Patents
Mechanically stable VPO catalyst and method for preparing the same Download PDFInfo
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- CN117943073A CN117943073A CN202211292982.7A CN202211292982A CN117943073A CN 117943073 A CN117943073 A CN 117943073A CN 202211292982 A CN202211292982 A CN 202211292982A CN 117943073 A CN117943073 A CN 117943073A
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- vpo catalyst
- vpo
- catalyst according
- catalyst
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- 230000001172 regenerating effect Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 229930195734 saturated hydrocarbon Natural products 0.000 description 1
- 150000003377 silicon compounds Chemical class 0.000 description 1
- 239000011684 sodium molybdate Substances 0.000 description 1
- TVXXNOYZHKPKGW-UHFFFAOYSA-N sodium molybdate (anhydrous) Chemical compound [Na+].[Na+].[O-][Mo]([O-])(=O)=O TVXXNOYZHKPKGW-UHFFFAOYSA-N 0.000 description 1
- 241000894007 species Species 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- VKFFEYLSKIYTSJ-UHFFFAOYSA-N tetraazanium;phosphonato phosphate Chemical compound [NH4+].[NH4+].[NH4+].[NH4+].[O-]P([O-])(=O)OP([O-])([O-])=O VKFFEYLSKIYTSJ-UHFFFAOYSA-N 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- VSAISIQCTGDGPU-UHFFFAOYSA-N tetraphosphorus hexaoxide Chemical compound O1P(O2)OP3OP1OP2O3 VSAISIQCTGDGPU-UHFFFAOYSA-N 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 description 1
- 229940078499 tricalcium phosphate Drugs 0.000 description 1
- 229910000391 tricalcium phosphate Inorganic materials 0.000 description 1
- 235000019731 tricalcium phosphate Nutrition 0.000 description 1
- DQWPFSLDHJDLRL-UHFFFAOYSA-N triethyl phosphate Chemical compound CCOP(=O)(OCC)OCC DQWPFSLDHJDLRL-UHFFFAOYSA-N 0.000 description 1
- WVLBCYQITXONBZ-UHFFFAOYSA-N trimethyl phosphate Chemical compound COP(=O)(OC)OC WVLBCYQITXONBZ-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 229930195735 unsaturated hydrocarbon Natural products 0.000 description 1
- 239000012002 vanadium phosphate Substances 0.000 description 1
- LRXTYHSAJDENHV-UHFFFAOYSA-H zinc phosphate Chemical compound [Zn+2].[Zn+2].[Zn+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LRXTYHSAJDENHV-UHFFFAOYSA-H 0.000 description 1
- 229910000165 zinc phosphate Inorganic materials 0.000 description 1
- 229910052984 zinc sulfide Inorganic materials 0.000 description 1
Landscapes
- Catalysts (AREA)
Abstract
The invention relates to a VPO catalyst in the form of a shaped body for oxidizing hydrocarbons with molecular oxygen, in particular for oxidizing butane to maleic anhydride with molecular oxygen, characterized in that the VPO catalyst comprises ZnO. The invention further relates to a process for preparing the inventive VPO catalyst in the form of a shaped body, comprising the following steps: a) providing a reaction mixture comprising a V (V) compound, a P (V) compound, optionally a Mo compound, a reducing agent and a solvent, b) at least partially reducing the V (V) compound with the reducing agent to vanadium hydrogen phosphate so as to obtain an intermediate product suspension, c) filtering the intermediate product suspension from step b) so as to obtain an intermediate product, d) drying and calcining the intermediate product at a temperature of up to 300 ℃ so as to obtain an intermediate product, d 1) optionally mixing the intermediate product with graphite and/or d 2) compacting the intermediate product, e) forming the intermediate product from step d) or d 1) and/or d 2) into particles, f) activating the particles in a gas mixture formed from nitrogen, oxygen and water vapour at a temperature above 200 ℃, characterized in that ZnO is added after step c) but before step f).
Description
Technical Field
The invention relates to a VPO catalyst in the form of a shaped body for oxidizing hydrocarbons with molecular oxygen, in particular for oxidizing butane to maleic anhydride with molecular oxygen, characterized in that the VPO catalyst comprises ZnO. Such VPO catalysts have improved mechanical stability.
The invention further relates to a process for preparing the inventive VPO catalyst, comprising the steps of:
a) Providing a reaction mixture comprising a V (V) compound, a P (V) compound, optionally a Mo compound, a reducing agent and a solvent,
B) At least partially reducing said V (V) compound to vanadium hydrogen phosphate with said reducing agent, so as to obtain an intermediate suspension,
C) Filtering the intermediate suspension from step b) in order to obtain an intermediate,
D) Drying and/or calcining the intermediate product at a temperature of up to 300 ℃ in order to obtain a dried intermediate product,
D 1) optionally mixing the dried intermediate product with graphite and/or d 2) compacting or granulating the dried intermediate product,
E) Forming the dried intermediate product from step d) or d 1) and/or d 2) into granules,
F) Activating the particles in a gas mixture formed from nitrogen, oxygen and water vapour at a temperature above 200 ℃,
Characterized in that ZnO is added after step c) but before step f).
The invention also relates to the use of ZnO for stabilizing VPO catalysts in shaped form or to the use of ZnO as binder for VPO catalysts in shaped form.
Background
Maleic anhydride is a chemical intermediate of great economic importance. For example, they are used alone or in combination with other acids in the preparation of alkyd resins and polyester resins. In addition, maleic anhydride is a flexibly usable intermediate for chemical synthesis, for example for the synthesis of gamma-butyrolactone, tetrahydrofuran and 1, 4-butanediol, which in turn can be used as solvents or can be further processed into polymers such as polytetrahydrofuran or polyvinylpyrrolidone.
The preparation of maleic anhydride is generally carried out by partial oxidation of n-butane with molecular oxygen or with a gas comprising molecular oxygen in the gas phase in the presence of a vanadium-phosphorus-oxygen catalyst (VPO catalyst) comprising vanadium pyrophosphate (VPP). Vanadium pyrophosphate has a valence of +4 in the pure state and is particularly suitable for the preparation of maleic anhydride from unbranched saturated or unsaturated hydrocarbons having at least four carbon atoms. Either a fixed bed reactor or a fluidized bed reactor may be used.
VPO catalysts have only low intrinsic reactivity in the reaction of n-butane to maleic anhydride. Therefore, a large amount of catalyst is required in order to obtain a sufficient conversion. In the case of VPO catalysts, it is also pointed out that they are entirely among the most expensive non-noble metal catalysts, in principle due to the high cost of their starting materials. It is therefore proposed to improve the catalyst properties (activity and selectivity) or also to improve the service life and mechanical stability of such catalysts. It is known from the prior art that the performance of a VPO catalyst can be improved by incorporating foreign elements into the vanadium-phosphorus-oxygen phase (VPO phase), for example by incorporating molybdenum (Mo promoter or Mo dopant).
US 5,929,256 discloses the synthesis of active vanadium-phosphorus catalysts modified with molybdenum for the preparation of maleic anhydride. Wherein a compound containing a majority of the vanadium of valence 5 is reacted with a compound containing phosphorus of valence 5 in an alcoholic medium suitable for reducing the vanadium to an oxidation valence less than 5. Molybdenum is inserted into the reaction product, wherein a solid precursor composition modified with molybdenum is formed. The alcohol is removed to obtain a dried, solid, molybdenum-modified precursor composition. A shaped body is formed comprising a dried, solid, precursor compound modified with molybdenum. The dried and shaped precursor composition modified with molybdenum is activated to convert it to an active catalyst.
US 5,070,060 discloses an improved way of oxidizing catalyst for partial oxidation of n-butane and comprising a mixed oxide of vanadium and phosphorus, a mixed oxide of zinc and lithium, which comprises adding a molybdenum compound modifier to the catalyst in an amount of about 0.005 to 0.025/1Mo/V during the reaction of reduced vanadium compound with concentrated phosphoric acid. The addition of Mo produced a catalyst that was very stable, formed a more active system and could be stored longer than the unmodified catalyst.
US 3,980,585 discloses a catalyst composite suitable for converting normal C 4 hydrocarbons to maleic anhydride in the gas phase, comprising the components vanadium, phosphorus and copper and one of the elements selected from the group consisting of: te, zr, ni, ce, W, pd, ag, mn, cr, zn, mo, re, sm, la, hf, ta, th, co, U and Sn, preferably having an alkali or alkaline earth metal.
US 4,056,487 discloses a catalyst suitable for the partial oxidation of alkanes to the corresponding anhydrides, for example the conversion of normal C 4 hydrocarbons to maleic anhydride in the gas phase, including the components vanadium, phosphorus and oxygen, nb, cu, mo, ni, co and Cr. Preferred are compositions additionally comprising one or more elements from Ce, nd, ba, hf, U, ru, re, li or Mg.
US 4,515,904 discloses a process for the preparation of a phosphorus-vanadium catalyst and a phosphorus-vanadium metal co-catalyst for use in the preparation of maleic anhydride from butane, wherein the process comprises: reacting a vanadium compound with a phosphorus halide in an organic ether solvent having from about 2 to 10 carbon atoms in the presence of water or a fatty alcohol having from about 1 to about 8 carbon atoms at a temperature of from about 0 ℃ to about 200 ℃; removing the solvent; and activating the catalyst by adding butane or another hydrocarbon starting product and a phosphorus compound at a temperature of about 300 ℃ to about 500 ℃.
US 5,158,923 discloses an improved way of oxidizing catalyst for partial oxidation of n-butane and comprising a mixed oxide of vanadium and phosphorus, a mixed oxide of zinc and lithium, which comprises adding a molybdenum compound modifier to the catalyst in an amount of about 0.005 to 0.025/1Mo/V during the decomposition of reduced vanadium compounds with concentrated phosphoric acid. The addition of Mo produced a catalyst that was very stable, formed a more active system and could be stored longer than the unmodified catalyst.
US 5,262,548 discloses an improved way of oxidizing catalyst for partial oxidation of n-butane and comprising a mixed oxide of vanadium and phosphorus, a mixed oxide of zinc and lithium, which comprises adding a molybdenum compound modifier to the catalyst in an amount of about 0.005 to 0.025/1Mo/V during the decomposition of reduced vanadium compounds with concentrated phosphoric acid. The addition of Mo results in a catalyst that forms a stable active system and has a longer service life than the unmodified catalyst.
WO 201306819 A1 discloses a method for preparing an enhanced VPO catalyst, wherein the catalyst comprises a mixed oxide of vanadium and phosphorus and wherein the catalyst is enhanced with at least one from the group of niobium, cobalt, iron, zinc, molybdenum or titanium, wherein the method comprises the steps of: (i) preparing a VPO catalyst comprising vanadium pyrophosphate as a major component and comprising less than 5wt% vanadium phosphate, (ii) contacting the VPO catalyst with a solution comprising as a metal source a compound having at least one metal selected from the group consisting of niobium, cobalt, iron, zinc, molybdenum or titanium so as to form a metal impregnated VPO catalyst, and (iii) drying the metal impregnated VPO catalyst so as to form the enhanced VPO catalyst. In one embodiment, a niobium activated VPO catalyst is prepared.
US 5,280,003 discloses an improved way of oxidizing catalysts for the partial oxidation of n-butane and comprising mixed oxides of vanadium and phosphorus, zinc, lithium and molybdenum, which consists in carrying out their preparation under static conditions which allow more uniform conditions of crystal growth. Static conditions are maintained by heating the solvent reflux during the crystallization period.
US 4,251,390 discloses an improved way of oxidizing catalysts for the partial oxidation of n-butane, comprising vanadium and phosphorus mixed oxides, characterized in that a zinc compound is added to the catalyst in an amount of 0.15 to 0.001Zn/V during the reaction of the reduced vanadium fraction with concentrated phosphoric acid. The addition of zinc produces a catalyst that is easily activated and very stable to the temperature increase of the reaction system. Small amounts of lithium compounds and silicon compounds also have the additional desired catalytic effect without reducing the advantages of zinc compounds.
DE 10 2014 004786 A1 relates to a catalyst comprising a vanadium-phosphorus oxide and an alkali metal, wherein the weight proportion of alkali metal in the vanadium-phosphorus oxide is in the range from 10 to 400ppm relative to the total weight of the vanadium-phosphorus oxide, to a process for its preparation and to the use of the catalyst for the gas phase oxidation of hydrocarbons, in particular for the preparation of maleic anhydride.
CN 101036891A discloses a process for regenerating a fluidized bed catalyst for oxidizing n-butane to maleic anhydride, comprising the steps of: preparing a precursor matrix powder and an auxiliary material; mixing catalyst ash captured with a fluidized bed apparatus with the prepared precursor matrix powder and an auxiliary material; adding a water-soluble resin binder and stirring under the condition of water-based temperature control; finally, shaping by spray drying to obtain a regenerated catalyst. The regenerated catalyst of the invention can supplement or replace the crude catalyst in the fluidized bed reactor and is equivalent thereto in terms of activity, particle size, use, and the like.
CN 1282631A discloses a vanadium-phosphorus oxide catalyst characterized by the addition of zirconium, molybdenum and zinc and having an atomic ratio between vanadium to phosphorus to zirconium to molybdenum to zinc of 1.0:1.0-1.5:0.02-0.06:0.02-0.06:0.02-0.06. In addition, a method for preparing the vanadium-phosphorus oxide catalyst is disclosed, which is characterized in that 6 parts by weight of vanadium pentoxide and 50-60 parts of concentrated hydrochloric acid are heated under reflux for 1-5 hours and phosphoric acid is then added. The amount added is designed such that the atomic ratio between vanadium and phosphorus is between 1.0:1.0-1.5 and the reflux step is continued for 1-5 hours. After cooling, a mixture of zirconium nitrate, ammonium dimolybdate and zinc acetate and 50-200 parts of water are added. The solution, zirconium nitrate, ammonium dimolybdate and zinc acetate were added to achieve an atomic ratio between vanadium to zirconium to molybdenum to zinc of 1.0:0.02-0.06:0.02-0.06:0.02-0.06, then the mixture was slowly and carefully evaporated in a water bath for 15-30 hours to obtain a viscous colloid, and the colloid was dried at 120 ℃ to obtain a dark green solid, which is the vanadium-phosphorus oxide catalyst of the invention.
CN 111701608A discloses a process for the preparation of a hydrotalcite modified vanadium-phosphorus-oxygen catalyst, comprising the steps of: preparing a vanadium-phosphorus-oxide precursor by mixing a vanadium source, benzyl alcohol and a C3 to C8 monohydric alcohol to obtain a mixture, then adding a phosphorus source, heating to 100 ℃ to 200 ℃, continuing the reaction, filtering the product and drying to obtain a vanadium-phosphorus-oxygen precursor; preparing a hydrotalcite additive by dissolving a water-soluble inorganic zinc source, an inorganic magnesium source and an inorganic aluminum source in water, adding an alkali metal source, heating to 65 ℃ to 200 ℃ to enable reaction, cooling and aging for 6 to 12 hours, filtering, washing, drying and calcining at a temperature between 350 ℃ to 550 ℃ to obtain the hydrotalcite additive, wherein the total amount of zinc and magnesium to the amount of aluminum in the inorganic zinc source, the inorganic magnesium source and the inorganic aluminum source is between 1 to 4:1, the molar ratio between magnesium and zinc is between 1 and 5:10; hydrotalcite additives are mixed with vanadium-phosphorus mixed oxide-oxygen precursors in a mass ratio of 1-10:100, heated to 300-500 ℃ and calcined to obtain hydrotalcite-modified vanadium-phosphorus-oxygen catalysts.
CN 106938197A discloses a process for the preparation of a vanadium-phosphorus-oxygen catalyst. The method comprises the following steps: preparing vanadium phosphate hydroxide hemihydrate catalyst precursor powder doped with a metal promoter, wherein the metal promoter is at least one from Fe, mo, co, ce, zr, nb and Ni, and the molar ratio of metal promoter to vanadium is between 0.06 and 0.15; and mixing the catalyst precursor powder with a binder and an auxiliary material and continuously extruding or tabletting to obtain the vanadium-phosphorus oxide catalyst, wherein the binder is at least one selected from phosphoric acid, pyrophosphoric acid, trimethyl phosphate, triethyl phosphate, aluminum dihydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, zinc phosphate, tricalcium phosphate, ammonium pyrophosphate and ammonium hexametaphosphate, the auxiliary material is at least one selected from graphite, carbon nanotubes, graphene and carbon powder, and the mass ratio among the catalyst precursor powder, the binder and the auxiliary material is 100 (0.1-15): (0.1-10). The preparation method of the vanadium-phosphorus oxide catalyst is simple and does not impose special requirements on production equipment, and the obtained catalyst has the advantages of high strength, good catalytic action and easy industrial production and application.
For the preparation of VPO catalysts comprising a VPP phase, the reduction of vanadium pentoxide (V 2O5) is generally carried out in the simultaneous presence of phosphoric acid in an organic alcoholic solvent and benzyl alcohol as reducing agent, wherein in addition to benzaldehyde Vanadium Hydrogen Phosphate (VHP) is also produced. The redox reaction ("reduction") carried out at this time is such that vanadium (V)) having the oxidation number V reacts to form a VHP phase, wherein the species of vanadium (VO 2+) is present as vanadium (V (IV)) having the oxidation number IV:
(1)V2O5+2H3PO4+Ph-CH2-OH→2VOHPO4*1/2H2O+Ph-CHO+2H2O
in the subsequent activation step, the VHP phase is converted into a vanadium pyrophosphate phase by the action of heat in the event of water splitting.
(2)2VOHPO4*1/2H2O→(VO)2P2O7+11/2H2O
A problem in the case of catalytic conversion of butane to maleic anhydride with VPO catalysts is that the process must be carried out under a mechanism limited by pore diffusion. The porosity then directly influences the catalytic yield here. Care must therefore be taken not to negatively affect the pore structure when shaping (e.g. by tabletting). However, as a result, the mechanical stability of the molded article is lost. However, the mechanical stability must be so great that the sheet withstands the filling process intact (falls into a reaction tube of about 6 meters in length). Otherwise, dynamic pressures in the process may be too high due to smaller fragments, which results in high compressor costs or reduced throughput. The technical aim is therefore to increase the mechanical strength of the shaped body without adversely affecting the pore structure.
Disclosure of Invention
It is therefore an object of the present invention to provide an improved VPO catalyst for the gas phase oxidation of hydrocarbons, in particular for the preparation of maleic anhydride, which has similar porosity and catalytic properties compared to the catalysts customary hitherto and at the same time has a significantly improved mechanical strength.
This object is achieved by a VPO catalyst in the form of a shaped body for oxidizing hydrocarbons with molecular oxygen, in particular for oxidizing butane to maleic anhydride with molecular oxygen, characterized in that the VPO catalyst comprises ZnO.
The VPO catalyst of the invention comprises, consists of or consists essentially of a VPO phase. For example, the VPO catalyst of the invention comprises a VPO phase in an amount of more than 70 wt%, preferably more than 80 wt%, more preferably more than 90 wt%, relative to the total weight of the VPO catalyst. In the remainder, the VPO catalyst may comprise VPP, dopants and unconverted oxides of the starting material, for example vanadium pentoxide or phosphorus oxide.
The VPO catalyst of the invention may optionally comprise Mo, for example, between 0.1 and 1 wt%, preferably between 0.4 and 0.7 wt%, relative to the total weight of the VPO catalyst.
The VPO catalyst of the invention may however also comprise alkali metals such as Na and/or K, preferably 80 to 300ppm alkali metals. Furthermore, the VPO catalyst of the invention may also comprise carbon, for example in the form of graphite, in an amount of for example 3 to 5 wt.%, relative to the total weight of the catalyst. The graphite present is used, for example, as a tableting aid.
The VPO catalyst of the invention has ZnO (zinc (II) oxide), but other zinc compounds may also be present. The Zn content in the VPO catalyst due to the presence of ZnO and possibly other Zn compounds must be between 0.2 and 10 wt%, preferably between 0.5 and 7 wt%, more preferably between 1 and 5 wt%, zn, respectively, relative to the total weight of the VPO catalyst.
The VPO catalyst preferably has the following elemental composition:
0.5 to 7 wt.% Zn,
0 To 0.7 wt.% Mo,
26 To 31% by weight of V,
17 To 21 wt.% of P,
3 To 5% by weight of C,
-The balance of oxygen, respectively with respect to the total weight of the VPO catalyst.
The VPO catalyst of the invention has Zn predominantly as ZnO and if the ZnO phase content is sufficiently high, the catalyst has a reflection typical for the ZnO phase in XRD powder diffraction patterns recorded using Cu-ka radiation. In particular, clear reflections at 31.7 ° to 31.9 °, 34.3 ° to 34.5 °, 36.2 ° to 36.4 ° are detected.
ZnO according to the invention promotes stabilization of the catalyst particles, giving them a higher mechanical strength than in the absence of such a compound. ZnO is preferably used to stabilize VPO catalysts in particulate form.
The VPO catalyst of the invention is present as a shaped body, the shape of which can be designed differently depending on the desired contact time, flow rate and dynamic pressure at the time of catalytic conversion. VPO catalyst in shaped form is understood to be shaped bodies prepared by shaping steps such as tabletting. In a tube bundle reactor, a plurality of shaped bodies according to the invention form a layer or catalyst bed through which the reactants butane, in particular n-butane and air, are led.
For example, the shaped bodies according to the invention can be present in the usual columnar shape. The cylinder then has a height (length along the cylinder axis) of 3mm to 8mm and a substantially circular bottom surface of 3mm to 8mm diameter. The cylinder preferably has a central axial opening, which may for example have a diameter of 1mm to 3 mm.
The shaped body according to the invention can, for example, have a height of 4.7mm, an outer diameter of 4.7mm and an intermediate axial opening of 1.3mm diameter. This shaped body then has a geometric surface area of 1.2cm 2, a volume of 0.075cm 3 and a mass of 0.12 g. A packing density of about 0.85g/cm 3 to 0.89g/cm 3 was obtained when a plurality of such shaped bodies were packed into a 21mm reactor.
The shaped body according to the invention can, for example, have a height of 5.6mm, an outer diameter of 5.5mm and an intermediate axial opening of 2.3mm diameter. These shaped bodies then have a geometric surface area of 1.77cm 2, a volume of 0.111cm 3 and a mass of 0.18 g. A packing density of about 0.72g/cm 3 to 0.76g/cm 3 was obtained when a plurality of such shaped bodies were packed into a 21mm reactor.
Preferred shaped bodies for the reactor concept according to the invention are those described in EP 2643086 A1. The preferred double alpha shape is characterized in particular in that each individual shaped body is formed in each case with an outer base [1], a cylindrical surface [2], a cylinder axis and at least one continuous opening [3] extending parallel to the cylinder axis, and the outer base [1] of the cylinder has at least four lobes [4a,4b,4c,4d ], wherein the geometric base surrounding the shaped body is a prism having a prism base with a length and a width, wherein the length is greater than the width and wherein the lobes [4a,4b,4c,4d ] are enclosed by the prism corners of the prism base (fig. 6).
Preference is given to shaped bodies in the form of double alpha, which have a height (length along the cylinder axis) of 3mm to 8mm, a length of 5mm to 9mm and a width of 4mm to 8mm and a hole inner diameter of 1mm to 4mm. For example, shaped bodies in the shape of double alpha are preferred, which have a height of 5.6mm, a length of 6.7mm, a width of 5.8mm and a hole inner diameter of 2.1 mm. These catalyst shaped bodies had a geometric surface area of 2.37cm 2, a volume of 0.154cm 3 and a mass of 0.24 g. A packing density of about 0.60g cm 3/to 0.62g/cm 3 was obtained when loading into a 21mm reactor.
The VPO catalyst or shaped body of the invention has a side pressure strength of more than 25N, preferably between 25N and 200N. Particularly preferred are side pressure strengths of the VPO catalyst or shaped body of greater than 30N to 150N, more preferably greater than 35N to 100N.
The VPO catalyst or shaped body of the invention in the form of a column has a side pressure strength of more than 25N, preferably between 25N and 50N. Particularly preferred are side pressure strengths of the VPO catalyst or shaped body of greater than 30N to 45N, more preferably greater than 35N to 40N.
The VPO catalyst or shaped body of the invention in the form of a double alpha has a side pressure strength of more than 50N, preferably between 50N and 200N. Particularly preferred are side pressure strengths of the VPO catalyst or shaped body of greater than 100N to 170N, more preferably greater than 120N to 150N.
The invention further relates to a process for preparing the inventive VPO catalyst in the form of a shaped body, comprising the following steps:
a) Providing a reaction mixture comprising a V (V) compound, a P (V) compound, optionally a Mo compound, a reducing agent and a solvent,
B) At least partially reducing said V (V) compound to vanadium hydrogen phosphate with said reducing agent, so as to obtain an intermediate suspension,
C) Filtering the intermediate suspension from step b) in order to obtain an intermediate,
D) Drying and/or calcining the intermediate product at a temperature of up to 300 ℃ in order to obtain a dried intermediate product,
D1 Optionally mixing the dried intermediate product with graphite and/or
D2 Compacting or granulating the dried intermediate product,
E) Forming the dried intermediate product from step d) or d 1) and/or d 2) into a shaped body,
F) Activating the shaped body in a gas mixture of nitrogen, oxygen and water vapour at a temperature above 200 ℃,
Characterized in that ZnO is added after step c) but before step f).
Providing the starting material for the reduction step b) in the reaction mixture in method step a) for the reduction. According to the invention, the reaction mixture comprises as starting materials V (V) compounds, P (V) compounds, optionally Mo compounds, reducing agents and solvents, preferably the reaction mixture consists of these starting materials. For example, the reaction mixture may consist of 45 to 90 wt.% of solvent, 5 to 15 wt.% of reducing agent, 5 to 15 wt.% of V (V) compound, up to 1 wt.% Mo compound and between 5 to 25 wt.% P (V) compound. Specifically, for example, 60 to 70% by weight of isobutanol, 5 to 15% by weight of benzyl alcohol, 5 to 15% by weight of vanadium pentoxide, 0.05 to 0.2% by weight (NH 4)2MoO4 and 10 to 20% by weight of phosphoric acid) may be previously placed as the reaction mixture, relative to the total weight of the reaction mixture.
The V (V) compound used as starting material in the reaction mixture according to step a) is a compound comprising vanadium of oxidation number V and is preferably V 2O5.
The P (V) compound used as starting material in the reaction mixture according to step a) is a compound containing phosphorus of the oxidation number V and is preferably phosphoric acid or a phosphate such as Na 3PO4. The phosphoric acid (H 3PO4) used is preferably anhydrous (100% phosphoric acid) or phosphoric acid containing only a small amount of water, that is to say having a concentration of 98% to 100%, preferably 99% to 100% (these values relate to the weight percentages by weight of pure phosphoric acid relative to the weight of the water-phosphoric acid mixture generally given). Alternatively, more than 100% phosphoric acid can be used in the preparation of the reaction mixture according to step a), which phosphoric acid immediately reacts with the water actually present at the beginning in the reaction mixture according to step a) to form phosphoric acid having a concentration of 98% to 100%, preferably 99% to 100%, preferably 100%, so that preferably no phosphoric acid of more than 100% is present in the reaction mixture according to step a) and at the same time no water of more than 0.2% by weight relative to the weight of the reaction mixture remains in the reaction mixture.
Mo compounds which can optionally be used as starting materials in the reaction mixture according to step a) are any molybdenum-containing compounds, for example molybdenum trioxide, ammonium heptamolybdate ((NH 4)6Mo7O24)*4H2 O), ammonium paramolybdate ((NH 4)6Mo7O2*4H2 O), meta-molybdates, molybdic acid (H 2MoO4) and salts thereof, such as (NH 4)2MoO4、Na2MoO4、K2MoO4 or (NH 4)2Mo2O7).
The reducing agent present in the reaction mixture according to step a) may be any reducing agent capable of reducing the V (V) compound to at least partially produce vanadium hydrogen phosphate. The reducing agent is preferably an organic reducing agent such as ethanol, isobutanol or aromatic alcohols, of which benzyl alcohol is especially preferred.
The solvent present in the reaction mixture according to step a) is preferably an alcohol, particularly preferably a high-boiling aliphatic alcohol, in particular isobutanol, alternatively ethanol or isopropanol.
The starting material is provided in a suitable reaction vessel which is capable of carrying out the subsequent reduction step b), that is to say the reaction mixture can be heated to a temperature above room temperature, for example up to 100 ℃. After the reduction, preferably with stirring in the reflux step, the reaction vessel is preferably provided with a reflux cooler and with means for stirring the reaction mixture. Optionally, the reaction vessel is equipped with means allowing the water produced during the reduction to be removed from the reaction mixture, that is to say a water separator, for example DEAN STARK water separator.
At least partial reduction of the V (V) compound to an intermediate product is carried out in process step b), which intermediate product comprises a vanadium hydrogen phosphate phase and optionally molybdenum and forms an intermediate product suspension together with the solvent and the remaining components from the partial conversion of step a). This reduction is preferably carried out under reflux at atmospheric pressure, where the temperature is increased depending on the boiling point of the solvent used, preferably in the process according to the invention only a single reflux step is carried out. The intermediate product preferably comprises vanadium hydrogen phosphate as the main phase or may even consist essentially of the vanadium hydrogen phosphate phase. Molybdenum, which may likewise be present in the intermediate product, may be present as a dopant for the vanadium hydrogen phosphate phase, wherein molybdenum dopant is understood to mean that molybdenum is either intercalated into the vanadium hydrogen phosphate phase or is present on its surface. However, in addition to the vanadium hydrogen phosphate phase, other vanadium-phosphorus mixed oxides can also be produced during the reduction, wherein the vanadium has an oxidation number of IV or even III. The reduction does not have to be carried out completely, so that a proportion of V (V) compounds and P (V) compounds remain in the intermediate product and thus in the intermediate product suspension. The reduced intermediate typically has an average vanadium oxidation number of 3.8 to 4.2.
The water produced during the reduction may be removed from the reaction mixture during the reduction. In the prior art, the removal of water during the reduction takes place either physically, for example by means of a water separator, or chemically by using water-binding compounds, that is to say for example desiccants or anhydrides, such as phosphoric acid having a concentration of more than 100%. The reaction mixture according to step a) may, for example, have an anhydride which reacts with and binds water, and the reaction mixture according to step a) may in particular have a concentration of phosphoric acid of more than 100%.
The filtration of the intermediate suspension in process step c), that is to say the intermediate suspension, can be carried out, for example, in an inert gas atmosphere, such as nitrogen or a noble gas. In this context, inert gas refers to any gas that does not react with the intermediate product when filtered under the given conditions but at the same time replaces oxygen from the air to minimize the explosion hazard. Filtration is carried out by means known to the person skilled in the art, typically by means of a filter press, a decanter or by Nutsche filters. By process step c) an uncalcined intermediate product is obtained which is still completely wetted with solvent.
In process step d), the intermediate product obtained by filtration (solid filtered residue) is dried at a temperature above room temperature, typically at a temperature of up to 150 ℃ under reduced pressure or under vacuum or inert gas, in order to obtain a dried intermediate product (dried intermediate product from step d)). In this context, inert gas refers to any gas that does not react with the intermediate product under dry conditions but at the same time replaces oxygen from the air to minimize the explosion hazard, such as nitrogen or noble gases. Drying is preferably carried out under reduced pressure or vacuum at between 50℃and 150℃and preferably between 90℃and 140 ℃.
Alternatively or optionally after drying, calcination may be carried out according to step d). Calcination is carried out under inert gas at elevated temperatures between 150 ℃ and 350 ℃, preferably between 230 ℃ and 290 ℃. In this context, inert gas refers to any gas that does not react with the intermediate product under calcination conditions but replaces oxygen from the air to minimize the explosion hazard, such as nitrogen or noble gases.
Optionally, one or more method steps d 1) and/or d 2) may follow method step d): according to optional method step d 1) 1 to 10 wt.% of graphite is mixed into the dried intermediate product in order to obtain the intermediate product mixture (dried intermediate product from step d 1). Compacting and/or granulating the dried intermediate product from step d) or d 1) according to optional process step d 2) in order to obtain a compacted or granulated dried intermediate product (dried intermediate product from step d 2). The dried intermediate product from step d) or d 1) is pressed into a plate with a pressing force of 190 bar, a gap width of 0.60mm and a roller speed of 7 revolutions per minute, for example, with a roller compactor and granulated through a screen of 1 mm.
In process step e), the dried intermediate product from step d), d 1) or d 2) is shaped into a shaped catalyst body, which can be carried out, for example, by tabletting. The pellets are pressed into the desired sheet form of the corresponding size, for example, using a circular track tablet press.
The activation of the catalyst shaped bodies obtained is carried out in a subsequent process step f) at a temperature of more than 200 ℃. The activation is typically carried out in a gas mixture consisting of air, inert gas and water vapor, wherein any other which does not react with the catalyst shaped body upon activation under the given conditions can be used as inert gas, in particular nitrogen or noble gas. Alternatively, the activation can be carried out in the process gas, that is to say in a gas mixture comprising air and butane. The activation is carried out at a temperature in the range 300 ℃ to 500 ℃, preferably in the range 350 ℃ to 450 ℃. The final VPO catalyst is obtained as a product of the process by means of activation. If the graphite-containing intermediate product mixture from step d 1) or d 2) which is shaped into a shaped body in process step e) is activated, a graphite-containing VPO catalyst is obtained as a product of the process. The tableted end product typically has a side pressure strength of greater than 25N, typically between 25N and 200N.
The preparation process according to the invention of the VPO catalyst in shaped form is characterized in that ZnO (zinc (II) oxide) is added after process step c) but before process step f), wherein ZnO is preferably added in the form of a powdery solid. ZnO may also be added as part of an adhesive having other constituents, which in a preferred embodiment includes one or more other metal compounds in addition to ZnO. Preferably, a solid Mg compound, such as MgO, is also included in the ZnO-containing binder.
The ZnO or ZnO-containing binder is preferably added in powder form, but the ZnO-containing binder may also be added in liquid form, for example as a suspension. In the simplest case, znO particles or ZnO crystallites are present in a form suspended in a liquid medium, such as water. It is also possible, however, that the adhesive comprising ZnO has an organic composition.
The addition of ZnO or of a ZnO-containing binder is carried out in a suitable manner, for example by mixing a powdered binder with the intermediate product or shaped body from the corresponding process step. This can also be done by means of feeding devices and mixers. In general, sufficient ZnO or a binder comprising ZnO is added to form the catalyst according to the present invention. For example, 0.5 to 7 wt.%, preferably 1 to 5 wt.%, more preferably 2 to 4 wt.% ZnO may be added relative to the weight of the dried intermediate product (ZnO-free) from step d), d 1) or d 2).
The invention also relates to the use of ZnO in solid form for stabilizing VPO catalysts in shaped form and to the use of ZnO as binder for VPO catalysts in shaped form.
As illustrated in the present invention, znO can be used as a binder for the VPO catalyst and thus improve the mechanical stability of the VPO catalyst in the form of a shaped body. Preferably, in use, znO is admixed in powder form between steps c) to f) in the preparation process described in the present invention, that is to say after step c) but before step f) is carried out, or preferably between steps c) to e) or during steps c), d) or e).
The invention further relates to a method for producing maleic anhydride by catalytic oxidation of n-butane, wherein reactant gases comprising oxygen and n-butane are led through a reactor tube in which the VPO catalyst according to the invention is in bulk form (schu ttung).
The bulk form of the VPO catalyst in the reactor tubes consists of the VPO catalyst or shaped bodies according to the invention which are fed into the reactor tubes and which, as a result of the tiling, produce the bulk form. The reactor tube is preferably part of a plurality of reactor tubes of a tube bundle reactor, as known to the person skilled in the art with respect to the industrial preparation of maleic anhydride. During the reaction, the bulk form of the VPO catalyst exists at a temperature between 300 ℃ and 420 ℃. The reactant gas may for example comprise between 0.2 and 10 volume% n-butane and between 5 and 50 volume% oxygen and be guided through the reactor tube at a space-time velocity of 1100h -1 to 2500h -1, preferably 1300h -1 to 2000h -1.
Drawings
Fig. 1: the effect of using ZnO or ZnO/MgO solids on VPO catalyst stability at the time of synthesis (examples 1 to 7).
Fig. 2: variation of side pressure strength and selectivity of VPO catalysts at different Zn additions.
Fig. 3: XRD diffractograms of VPO catalysts according to examples 1 to 5.
Fig. 4: XRD diffractograms of VPO catalysts with 2 wt.% ZnO added respectively a) at the beginning of the reflux step, b) after filtration and before vacuum drying, c) after vacuum drying and before calcination, d) after calcination and before tabletting (according to examples 8 to 10 and 5 respectively).
Fig. 5: a) according to example 11, b) according to example 12 and c) according to example 5.
Fig. 6: a view of the preferred catalyst particles, from four different angles, is "double alpha shape".
Detailed Description
Examples
Example 1 (comparative)
The instrument used
A mushroom heater (Heizpilz) was placed on the laboratory jacket, and there was a 2L four-necked flask. In the middle opening of the four-necked flask there is a half-moon shaped stirrer with a matching stirring plug connected to the stirrer by means of a stirring connection. There is a thermometer in the right hand opening and a riser tube to the reflux cooler in the left hand opening. The opening in front of the middle is used for filling with chemicals, where a nitrogen flushing device is then connected. The whole device can also be flushed with nitrogen. For this purpose, nitrogen is first led through the gas washing cylinder and then introduced into the device and led out again through the gas washing cylinder from above the cooler.
Preparation and reduction of the reaction mixture (method steps a) and b))
1069.5G of isobutanol and 156.0g of benzyl alcohol were initially introduced. 150g of V 2O5 are added with stirring. After the addition of V 2O5, 2.52g of ammonium dimolybdate were added. 232.50g of phosphoric acid (100% or anhydrous) were then added to the suspension and heated at reflux under N 2 for 10 hours.
Filtration (method step c)
After the intermediate suspension had cooled, it was transferred from the four-necked flask to a Nutsche filter and the liquid was pumped off. The moist press cake was dry pressed in a press overnight at 14 to 18 bar.
Drying/calcining (method step d)):
The pressed filter cake was charged to the evaporator flask of a rotary evaporator. The filter cake was dried overnight at 110 ℃ under water jet vacuum. The powder thus dried is placed in an oven in a suitable calciner and calcined at a temperature of 200 to 300 ℃ in an atmosphere of N 2 for 9 hours.
Compaction/tabletting (method steps d 1、d2 and e)):
5% by weight of graphite is added to the calcined powdered intermediate prior to compaction/tabletting and with the aid of a barrel hoop mixer Uniformly mixing. This powder was compacted into a plate with a roller compactor with a pressing force of 190 bar, a gap width of 0.60mm and a roller speed of 7 revolutions per minute and granulated through a 1mm sieve.
The pellets are compressed with a circular track tablet press into the desired sheet shape with corresponding dimensions, e.g. 5.6x5.6x2.3mm and side pressure strength.
Activation to pyrophosphate (method step f)):
the activation process to produce vanadium pyrophosphate is performed under controlled conditions in a flask mounted in a programmable oven. The calcined tablets were uniformly packed into a flask and sealed. The catalyst was then activated in a wet air-nitrogen mixture (50% absolute air humidity) first at above 300 ℃ for 5 hours, followed by activation at above 400 ℃ for 9 hours.
Examples 2 to 7 (according to the invention)
A VPO catalyst according to the invention was prepared analogously to example 1, except that 4.5g (example 2), 1.8g (example 3), 5.0g (example 4), 2.0g (example 5), 1.0g (example 6), 0.5g (example 7) of ZnO powder (commercially available ZnO with particle size <100 μm, impurities below 0.05% by weight) and 0.5g (example 2) and 0.2g (example 3) of MgO powder were admixed simultaneously with graphite per 100g of calcined powder from process step d). Thus obtained were calcined precursor powders having 5.0 wt% ZnO/MgO (example 2), 2.0 wt% ZnO/MgO (example 3), 5.0 wt% ZnO (example 4), 2.0 wt% ZnO (example 5), 1.0 wt% ZnO (example 6), 0.5 wt% ZnO (example 7).
The VPO catalysts according to examples 1 to 7 were tested for their breaking strength before and after activation (method step f)) respectively. In addition, the XRD diffractogram of the VPO catalyst was determined and its catalytic selectivity was tested.
The results shown in table 1 and fig. 1 show that by adding ZnO or ZnO/MgO after the calcination step, no systematic increase in side pressure Strength (SDF) could be observed when measured directly after the tablet fabrication. However, unexpectedly, an increase was observed after the subsequent step of activating the VPO catalyst plate. A systematic and very pronounced increase in the side pressure strength of the ZnO-or ZnO/MgO-added particles is shown here.
In addition to the increase in mechanical strength, the catalytic properties obtained are decisive even with such additions. The results of the catalytic test reactions in fig. 2 show that the stabilized catalyst shaped bodies of the invention have useful catalytic properties.
The XRD diffractogram in fig. 3 shows that the following features appear by the addition of ZnO:
31.7 to 31.9 ° (clear reflection, znO)
34.3 To 34.5 (clear reflection, znO)
36.2 To 36.4 (clear reflection, znO)
These characteristics become stronger with increasing ZnO content and are well consistent with ZnO (either in wurtzite structure or as zincite).
Comparative example 8, examples 9, 10
To examine the relationship between the presence of the ZnO phase acting as a stabilization and the addition time point of the binder, XRD diffractograms were recorded after different addition time points. In examples 2 to 7, znO was always added after calcination and before tabletting, whereas ZnO was added during process step a) at the point in time of the preparation of the reaction mixture, that is to say together with V 2O5 (comparative example 8), directly after filtration of process step c) (example 9), during process step d), that is to say after vacuum drying and before calcination (example 10). Here, 5.2g of ZnO were added, respectively, so that the finished catalyst nominally contained 2% by weight of ZnO, respectively.
Fig. 4 shows that when ZnO was added at the beginning of the reflow step, the XRD reflections observed when ZnO was added after calcination and before tabletting, especially at 31.7 to 31.9 °, 34.3 to 34.5 °, 36.2 to 36.4 °. (FIG. 4, corresponding to diffraction pattern a of comparative example 8).
Comparative examples 11 and 12
VPO catalysts according to comparative examples 11 and 12 were prepared similarly to the VPO catalyst according to example 1, wherein the activated tablets were impregnated with Zn (OAc) 2 solution. Two different concentrations were used here in order to obtain a Zn/V ratio of 0.008 (=0.29 wt% Zn with respect to the total weight of the catalyst) or 0.016 (corresponding to 0.58 wt% with respect to the total weight of the catalyst). After impregnation the catalyst was first dried at 100 ℃ for 18 hours and then dried in air at 350 ℃ for a further 20 minutes.
Fig. 5 shows XRD diffractograms of VPO catalysts according to comparative examples 11 and 12, compared to VPO catalysts prepared according to the invention according to example 5. It can be seen that by adding ZnO compounds to the activated sheet, no reflection was exhibited, especially at 31.7 to 31.9 °, 34.3 to 34.5 °, 36.2 to 36.4 °.
Comparative examples 13 and 13a
A VPO catalyst according to comparative example 13 was prepared similarly to the VPO catalyst according to example 2, wherein 10 wt% of type SECAR-71 binder and 4 wt% of graphite were added to the calcined powder.
The stability of VPO catalysts can be detected particularly well by measuring the stability with respect to by-product water, since during the reaction a large amount of water vapour is present due to the oxidation reaction, which may damage the catalyst. The inventive VPO catalyst according to example 4 was thus tested for stability with respect to by-product water compared to the VPO catalyst prepared with conventional binders according to comparative example 13. The selectivity of the untreated samples was additionally tested, followed by impregnating the two samples with water and repeating the selectivity test (comparative example 13 a). This shows that the catalyst of the invention does not suffer from a loss of selectivity within the measurement tolerances due to immersion in water.
Examples 14 and 15
VPO catalysts according to examples 14 and 15 were prepared similarly to the VPO catalyst according to example 1, but no ammonium dimolybdate was added so that the VPO catalyst obtained was Mo-free.
In addition, znO was added to the calcined powder after calcination and before tableting, either 1 wt% (example 14) or 2wt% (example 15) relative to the total weight of the calcined powder. As shown in table 1, the improvement of the side pressure strength was achieved even in the VPO catalyst containing no Mo.
Example 16 (comparative)
The instrument used
The same apparatus was used as in example 1.
Preparation and reduction of the reaction mixture (method steps a) and b))
150G of V 2O5 was first placed in a four-necked flask. To this was added 300mL of benzyl alcohol and 1200mL of isobutanol. The suspension was heated to reflux for 10 hours with stirring after inertization with N 2. After cooling to a maximum of 40℃with stirring, 7.51g of ammonium dimolybdate, 6.60g of iron (III) nitrate nonahydrate, 2.55g of cerium (III) nitrate hexahydrate and 4.5g of ammonium niobium oxalate were added. After adding 138mL of phosphoric acid (85%) with stirring within 15 minutes and inerting with N 2, the suspension was heated under reflux again with stirring for 24 hours.
Filtration (method step c)
After the intermediate suspension had cooled, it was transferred from the four-necked flask to a Nutsche filter and the liquid was pumped off. The wet cake was washed once with ethanol (100%) and the liquid was again aspirated off in the Nutsche filter. The same procedure was then carried out again with double distilled water.
Drying/calcining (method step d)):
The washed cake was charged to the evaporator flask of a rotary evaporator. The filter cake was dried overnight at 120 ℃ under water jet vacuum. The powder thus dried is placed in an oven in a suitable calciner and calcined at a temperature of 200 to 300 ℃ in an atmosphere of N 2 for 9 hours.
Compaction/tabletting (method steps d 1、d2 and e)):
2.1% by weight Zn 3(PO4)2 and then 4% by weight graphite are first added to the calcined powdered intermediate before compaction/tabletting and homogeneously mixed by means of a barrel hoop mixer. This powder was compacted into a plate with a roller compactor with a pressing force of 190 bar, a gap width of 0.60mm and a roller speed of 7 revolutions per minute and granulated through a 1mm sieve.
The pellets are compressed with a circular track tablet press into the desired sheet shape with corresponding dimensions, e.g. 5.6x5.6x2.3mm and side pressure strength.
And (3) temperature treatment:
The following temperature treatments were performed under controlled conditions in a flask mounted in a programmable oven. The calcined tablets were uniformly packed into a flask and sealed. The catalyst was then treated in an air stream at 120 ℃ for 18 hours.
Example 17 (comparative)
The VPO catalyst according to example 17 was formed similarly to the VPO catalyst according to example 1, wherein 2.1 wt% Zn 3(PO4)2 relative to the total weight of the calcined powder was added to the calcined powder after calcination and before tabletting.
Table 1: summary of results
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Method of
Breaking strength test
The breaking strength of the shaped bodies was measured using a Zwick Z0.5 apparatus in order to determine the force required for breaking. The measurements were made according to ASTM D4179 standard. In order to dry the shaped body before the measurement, it is stored in a drying oven at 100 ℃ for at least 3 hours and the subsequent breaking strength measurement is carried out within at most 1 hour after the end of the drying. The apparatus was operated at a constant force rate of 20.0N/s according to ASTM D4179 standard. For each example, 100 pieces were placed individually one after the other with the cylinder axis parallel to the measuring baking surface ("radial crush (RADIAL CRUSH)" standard ASTM D4179) and measured. Then, the average value corresponding to the average breaking force of the formed body was determined from 100 individual values of the force required for breaking the formed body, respectively. All values in the present application for the side pressure strength relate to the side pressure strength obtained by the method described herein.
Powder X-ray diffraction method (XRD)
The catalyst was characterized by means of X-ray powder diffraction (X-ray diffraction, XRD). In this case, the X-ray radiation is diffracted at different diffraction angles at crystalline regions of the sample. The diffraction angle is measured or recorded in 2 theta. Depending on the phase present, a characteristic reflection occurs here, depending on the angle of diffraction. By means of such a diffraction pattern, the database can be used to assign the diffraction pattern to the phases present.
Measurements were performed on a D4 Endeator from Bruce (Bruker) AXS with Cu-K alpha radiation and LYNXEYE detector. The diffraction pattern was recorded in 0.02 ° steps in an angular range 2 theta of 5 ° to 50 ° with a fixed diverging slit of 0.3 ° at a recording time of 1.5s per step. For the measurement, the sample was finely ground and pressed into a sample holder. Changing the diffraction angle can be achieved in the device by flipping the sample. All values in the present application for XRD reflections relate to XRD reflections obtained in this way.
For better comparability of the diffraction patterns, they were normalized separately. To this end, the data point with the smallest intensity value is first found for each diffraction pattern. This value is extracted from all intensity values of the corresponding diffraction pattern. The maximum intensity of the (024) reflection in the corresponding diffraction pattern (at 2 theta values of 28.4-28.5 deg.) is then obtained. All intensity values of the corresponding diffraction pattern are divided by this value.
Catalytic test reaction
To obtain catalyst performance, all catalysts after complete preparation (reflux, filtration, vacuum drying, calcination, compaction, tabletting, activation) were tested for their catalytic properties in a diluted catalyst bed (1:9 catalyst mixture: ceramic inert ring) in 1.5 mol% butane in air in a "Bench-Scale" reactor. Selectivity to Maleic Anhydride (MA) was obtained from experimental data at 5500l/kg/h GHSV with respect to mass.
Claims (25)
1. VPO catalyst in the form of a shaped body for the oxidation of hydrocarbons with molecular oxygen, in particular for the oxidation of butane to maleic anhydride with molecular oxygen, characterized in that the VPO catalyst comprises ZnO.
2. VPO catalyst according to claim 1, characterized in that the shaped body has a side pressure strength of more than 25N, preferably between 25N and 200N, wherein the side pressure strength is measured with a Zwick Z0.5 apparatus at a constant force rate of 20.0N/s using ASTM D4179 standard, wherein 100 pieces are each placed individually with the cylinder axis parallel to the measuring baking surface and measured in order to determine the average breaking force, which is the side pressure strength.
3. The VPO catalyst according to claim 1 or 2, characterized in that when the VPO catalyst is studied by powder X-ray diffraction, the VPO catalyst has a reflection at 31.7 ° to 31.9 °, 34.3 ° to 34.5 ° and 36.2 ° to 36.4 °, wherein the diffraction pattern is recorded in 0.02 ° steps in 2 θ in an angular range of 5 ° to 50 ° with a fixed divergent slit of 0.3 ° at a recording time of 1.5s per step, when measured with D4 Endeavor from Bruker (Bruker) AXS company with Cu-ka radiation and LYNXEYE detector.
4. VPO catalyst according to one of the preceding claims, characterized in that the VPO catalyst comprises Mo content between 0.1 and 1 wt. -%, preferably between 0.4 and 0.7 wt. -%, respectively, relative to the total weight of the VPO catalyst.
5. VPO catalyst according to one of the preceding claims, characterized in that the VPO catalyst comprises between 0.2 and 10 wt. -%, preferably between 0.5 and 7 wt. -%, more preferably between 1 and 5 wt. -% Zn, relative to the total weight of the VPO catalyst.
6. VPO catalyst according to one of the preceding claims, characterized in that the VPO catalyst has the following elemental composition:
0.5 to 7 wt.% Zn,
0 To 0.7 wt.% Mo,
26 To 31% by weight of V,
17 To 21 wt.% of P,
3 To 5% by weight of C,
-The balance of oxygen, respectively with respect to the total weight of the VPO catalyst.
7. VPO catalyst according to one of the preceding claims, characterized in that the shaped body has a double alpha shape with a height of 3mm to 8mm, a length of 5mm to 9mm, a width of 4mm to 8mm and a pore inner diameter of 1mm to 4 mm.
8. VPO catalyst according to one of claims 1 to 6, characterized in that the shaped body has a cylindrical shape with a height of 3mm to 8mm, a substantially circular bottom surface with a diameter of 3mm to 8mm and an intermediate axial opening with a diameter of 1mm to 3 mm.
9. A process for preparing a VPO catalyst according to one of claims 1 to 8, the process comprising the steps of:
a) Providing a reaction mixture comprising a V (V) compound, a P (V) compound, optionally a Mo compound, a reducing agent and a solvent,
B) At least partially reducing said V (V) compound to vanadium hydrogen phosphate with said reducing agent, so as to obtain an intermediate suspension,
C) Filtering the intermediate suspension from step b) in order to obtain an intermediate,
D) Drying and/or calcining the intermediate product at a temperature of up to 300 ℃ in order to obtain a dried intermediate product,
D 1) optionally mixing the dried intermediate product with graphite and/or d 2) compacting or granulating the dried intermediate product,
E) Forming the dried intermediate product from step d) or d 1) and/or d 2) into a shaped body,
F) Activating the particles in a gas mixture formed from an inert gas, oxygen and water vapour at a temperature above 200 ℃,
Characterized in that ZnO is added after step c) but before step f).
10. The process for preparing a VPO catalyst according to claim 9, characterized in that in step b) the solvent is an alcohol and the reducing agent is an organic reducing agent.
11. The process for preparing a VPO catalyst according to claim 9 or 10, characterized in that the reduction in step b) is carried out at a temperature above 40 ℃, preferably at atmospheric reflux.
12. Process for preparing a VPO catalyst according to one of claims 9 to 11, characterized in that the drying according to step d) is carried out under reduced pressure or under vacuum at between 90 ℃ and 140 ℃.
13. The process for preparing a VPO catalyst according to one of claims 9 to 12, characterized in that ZnO added is part of a binder with other constituents.
14. The method for preparing a VPO catalyst according to claim 13, characterized in that the binder comprises Mg compound, preferably MgO.
15. The process for preparing a VPO catalyst according to one of claims 9 to 14, characterized in that the activation step is carried out during a period of time from 1 to 24 hours at a temperature in the range of 300 to 500 ℃, preferably 350 to 450 ℃ in a gas mixture consisting of air, inert gas and water vapor.
16. The method for preparing a VPO catalyst according to claim 15, characterized in that the inert gas is nitrogen or a noble gas.
17. The process for preparing a VPO catalyst according to one of claims 9 to 16, characterized in that step c) is carried out as two steps c 1) and c 2), wherein during step c 1) drying is carried out in vacuo at between 90 ℃ and 140 ℃ and during step c 2) calcination is carried out in nitrogen at between 230 ℃ and 290 ℃.
18. The process for preparing a VPO catalyst according to one of claims 9 to 17, characterized in that step d 1) is carried out during a period of time between 5 and 48 hours and step d 2) is carried out during a period of time between 5 and 24 hours.
19. The method for preparing a VPO catalyst according to one of claims 9 to 18, characterized in that the activation of the VHP phase is performed in two successive steps e 1) and e 2), wherein the activation is performed during step e 1) at a temperature in the range of 250 ℃ to 350 ℃ during a period of between 1 hour and 8 hours and at a temperature in the range of 350 ℃ to 450 ℃ during a period of between 4 hours and 20 hours during step e 2).
Use of zno for stabilizing VPO catalysts in particulate form.
21. Use according to claim 20, wherein the VPO catalyst is prepared in the form of a shaped body according to the method of claims 9 to 19.
Use of zno as binder for VPO catalysts in shaped form.
23. A process for the preparation of maleic anhydride by catalytic oxidation of n-butane, wherein reactant gases comprising oxygen and n-butane are led through a reactor tube in which the VPO catalyst according to one of claims 1 to 8 is in bulk form.
24. The method of claim 23, wherein the bulk form of VPO catalyst in the reactor tube is present at a temperature between 300 ℃ and 420 ℃.
25. The method according to one of claims 23 or 24, characterized in that the reactant gas comprises between 0.2 and 10 volume% n-butane and between 5 and 50 volume% oxygen and is guided through the reactor tube at a space-time velocity of 1100h -1 to 1800h -1, preferably 1300h -1 to 2500h -1.
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| PCT/EP2023/079179 WO2024084002A1 (en) | 2022-10-21 | 2023-10-19 | Mechanically stable vpo catalyst and process for the production thereof |
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