WO1994007601A1 - Aerosol et catalyseur a l'oxyde phosphorique de vanadium et procede de preparation - Google Patents

Aerosol et catalyseur a l'oxyde phosphorique de vanadium et procede de preparation Download PDF

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Publication number
WO1994007601A1
WO1994007601A1 PCT/US1993/009234 US9309234W WO9407601A1 WO 1994007601 A1 WO1994007601 A1 WO 1994007601A1 US 9309234 W US9309234 W US 9309234W WO 9407601 A1 WO9407601 A1 WO 9407601A1
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Prior art keywords
vanadium
phosphorus oxide
catalyst
precursor
vpo
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PCT/US1993/009234
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English (en)
Inventor
Phyllis L. Brusky
Harold H. Kung
Peter Michalakos
William R. Moser
Larry C. Satek
Walter Partenheimer
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Battelle Memorial Institute
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Priority to AU52935/93A priority Critical patent/AU5293593A/en
Publication of WO1994007601A1 publication Critical patent/WO1994007601A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
    • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
    • C07C51/215—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of saturated hydrocarbyl groups
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/14—Phosphorus; Compounds thereof
    • B01J27/186—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J27/195—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium with vanadium, niobium or tantalum
    • B01J27/198—Vanadium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
    • B01J37/0027—Powdering
    • B01J37/0054—Drying of aerosols
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts

Definitions

  • This invention relates to catalysts used for the selective oxidation of hydrocarbons to oxygen-containing derivatives. More specifically, this invention relates to a new vanadium phosphorus oxide (VPO) catalyst that is active and selective for hydrocarbon oxidative reactions and especially for the oxidation of butane to maleic anhydride.
  • VPO vanadium phosphorus oxide
  • VPO vanadium phosphorus oxide
  • U.S. patent 4,209,423 and British Patent 330,354 describe liquid phase syntheses using an aqueous medium which gives rise to the term "aqueous catalysts.”
  • aqueous catalysts typically a vanadium-containing compound such as V 2 0 5 is reduced and dissolved in aqueous HC1.
  • other starting materials used such as NH 4 V0 3 and oxalic acid can also be used.
  • a phosphorus-containing compound such as H 3 P0 is then added.
  • the strength and amount of reducing agent determines the average oxidation state of vanadium in solution.
  • various precursors are obtained. The more common ones are V0HP0 4 .0.5H 2 0 and (VO) 2 F 2 ° 1 • 2H 2 ° with VO(NH 4 )P0 4 .4H 2 0 being obtained from ammoniated media.
  • the surface area of the activated catalysts are in the range of 1 to 15 m 2 /g.
  • Industrial catalysts are preferentially prepared with an organic solvent using methods such as those described in U.S. Patents 4,569,925, 4,562,268, and 4,132,670. Such catalysts are termed "organic catalysts.”
  • the starting material is typically a V(V) containing material dissolved in an organic solvent, usually an alcohol, which also serves as the reducing agent.
  • the vanadium is reduced to V(IV) with the formation of H 2 0.
  • Sufficient phosphorus-containing material such as H 3 P0 4 is aded to obtain a mixture with a phosphorus to vanadium atomic ratio of about one.
  • a precipitate is produced on addition of the phosphorus-containing material.
  • the precipitate is strongly agitated to suspend it in the reaction medium.
  • the precursor typically a V-P-O containing hydrate such as vanadium phosphate hemihydrate (VOHP0 4 .5H 2 0) is obtained by filtration of the suspended precipitate and drying of the solid.
  • Vanadyl pyrophosphate, (VO) 2 P 2 ⁇ 7/ is prepared by the solid state reaction of NH 4 H 2 P0 4 and V 2 0 5 .
  • the mixture is mixed and heated at 200°C for 4 hrs in oxygen, then at 400°C for 4 hrs in oxygen, for 2 hrs at 400°C in nitrogen, then 760°C for 36 hrs and finally cooled to 300°C at 50°C/hr.
  • V0P0 4 A similar procedure (minus the nitrogen treatment) is used to prepare V0P0 4 .
  • the surface area of the (VO) 2 P 2 ⁇ 7 is about 1.90 m 2 /g, and the surface area of the VOP0 4 is about 1.0 m 2 /g.
  • the final VPO synthesis method is vapor-phase reaction.
  • vapors of P0C1 3 and V0C1 3 at 500°C are reacted with each other using N 2 as a carrier gas in the presence of an air/water flow to produce a powder of ( -VOP0 4 .2H 2 0) .
  • the precursors prepared by the above methods are commonly activated to transform them into working catalysts.
  • the properties of the working catalyst are influenced by the nature of the precursor and the activation procedure.
  • the crystalline phase of the working catalyst derived from these precursors is vanadyl pyrophosphate (VO) 2 2 ° 7 -
  • VO vanadyl pyrophosphate
  • Studies of the effect of pretreatment conditions on maleic anhydride yield have shown that for catalysts used for butane oxidation, the best activation procedure is to convert VOHPO * 0.5H 2 O to (VO) 2 P 2 ⁇ 7 with an in situ pretreatment using a mixture of 0.5-4% butane in air at 375-500°C. This pretreatment reduces most of the V(V) that may be present. In some cases the average vanadium valence (AW) drops from +5 to almost +4.
  • U.S. Patent 4,569,925 teaches that the use of air alone for catalyst pretreatment has detrimental effects on catalyst yield.
  • the majority of phases formed by calcination in air at 500°C are the various oxidized forms of V0P0 4 and amorphous V(V) compounds. At very slow or very rapid heating rates, V(IV) compounds are sometimes formed.
  • ammoniated precursors a study of air calcination has shown that water is lost at 200°C and ammonia above 300°C. Phases obtained by air activation show inferior yields to those obtained from activation in hydrocarbon-air mixtures.
  • the AW of air activated catalysts in usually 4.5 and above. This is higher than the AW of high-yield catalysts obtained by hydrocarbon- air activation which is 4.0-4.2.
  • Pretreatment could also be carried out in nitrogen.
  • the sample weight loss is from ammonia release.
  • dehydration occurs.
  • Reduction of low P/V ratio catalysts with hydrogen gives rise to increased conversion and selectivity.
  • the preferred catalyst contains an excess of phosphorus (P/V atomic ratio > 1) with the optimum bulk P/V being 1.1.
  • Samples of lower P/V are more susceptible to oxidation and are less selective for maleic anhydride.
  • Catalysts of P/V ratios of 1.2 and greater are more selective but less active, such that the highest yields (conversion multiplied by selectivity) are reported for a P/V of 1.1.
  • X-ray photoelectron spectroscopy suggests the surface P/V ratios for high yield catalysts to be 1.6- 3, while a secondary ion mass spectroscopy (SIMS) study suggests that the surface layer P/V might be as high as 6.
  • SIMS secondary ion mass spectroscopy
  • the object of this invention is to improve the activity and selectivity of vanadium phosphorous oxide (VPO) catalysts.
  • VPO vanadium phosphorous oxide
  • One of the features of this invention is the use of an aerosol technique to produce VPO precursors.
  • the aerosol technique has the advantage of producing a high-purity product from multicomponent materials with a controlled morphology and high reaction rates.
  • a feature of the use of the aerosol technique for the formation of VPO catalysts is the unexpected formation of a new VPO composition using a water solvent.
  • This new composition has the unexpected advantage of having a high phosphorus to vanadium (P/V) atomic ratio with good activity and selectivity for the conversion of butane to maleic anhydride.
  • This new VPO composition has the characteristic powder x-ray data given in Table 1 and Figure 1. Preliminary results indicate that the new VPO composition has a bulk phosphorus:vanadium atomic ratio in the range of 1:1 to 1.8:1 and an average vanadium valence ranging
  • the vanadium phosphorus oxide catalysts of this invention are prepared by dissolving a vanadium composition and a phosphorus composition in a solvent to form a solution. An aerosol is then formed from the vanadium and phosphorus-containing solution. The aerosol is heated to react the vanadium and phosphorus to form a vanadium phosphorus oxide precursor. The vanadium phosphorus oxide precursor is activated to afford an activated vanadium phosphorus oxide composition with catalytic activity.
  • the activated vanadium phosphorus oxide composition with the powder x-ray diffraction data given in Table 1 and Figure 1 is useful in a process for the oxidation of hydrocarbons.
  • the process involves contacting a hydrocarbon and oxygen mixture with the activated catalyst to form an oxygen-containing derivative of the hydrocarbon.
  • hydrocarbon includes both saturated and unsaturated hydrocarbons having six or fewer carbon atoms.
  • Such hydrocarbons include saturated hydrocarbons such as ethane, propane, butane, isobutane and their mixtures and unsaturated hydrocarbons such as propene, butene, and isobutene and their mixtures and even mixtures of saturated and unsaturated hydrocarbons.
  • oxygen containing derivatives formed from these hydrocarbons include carbon monoxide, carbon dioxide, acetic acid, acrylic acid, methacrolein, acrolein, and phthalic anhydride.
  • carbon monoxide carbon dioxide
  • acetic acid acrylic acid
  • methacrolein acrolein
  • phthalic anhydride a hydrocarbon that is a mixture of organic acids
  • large amounts of product ethene have been observed.
  • both the formation of oxygen derivatives and unsaturated hydrocarbons are considered as equivalent products from this new catalyst.
  • a vanadium compound and a phosphorus compound are dissolved in a suitable solvent to form a solution.
  • the vanadium compound may be any vanadium compound such as NH V0 3 that is readily soluble in a suitable solvent and capable of forming a vanadium oxide.
  • the phosphorus compound may be any phosphorus compound such as H 3 P0 4 that is readily soluble in a suitable solvent and capable of forming a phosphorus oxide.
  • a suitable solvent is any solvent that is capable of dissolving both the vanadium and phosphorus compounds and includes both water and organic solvents such as isobutanol, tetrahydrofuran, methanol, acetic acid, allyl alcohol, crotyl alcohol, t-butyl alcohol, and mixtures thereof.
  • a mineral acid such as hydrochloric acid, HC1, or a carbon-containing acid such as oxalic or tartaric acid may be used to enhance the solubility of the vanadium and phosphorus compounds.
  • vanadium and phosphorous compounds, solvents, and solubility enhancers that produce unwanted solid or liquid by-products that contaminate the VPO precursor are to be avoided.
  • An aerosol is formed from the vanadium and phosphorus composition containing solution such as by mixing the solution with air or nitrogen and passing the resulting air and solution mixture through a nozzle. It is to be understood that there are a wide variety of ways of forming aerosols all of which are considered equivalent for this invention. In addition it is to be understood that aerosols of the individual components such as a vanadium salt could be formed individually and then contacted with a separate phosphorus salt containing aerosol or even with the phosphorus salt in non-aerosol form to afford the VPO catalyst. Such aerosol formation and reaction arrangements and modifications are considered equivalent for the purposes of this invention.
  • the aerosol of vanadium and phosphorus is injected into a furnace at a suitable temperature with temperatures of from 200 to 1000°C being preferred, a temperature of between about 500 and 800°C more preferred and a temperature of about 550 to about 700°C being most preferred. While at this temperature, the solvent evaporates from the aerosol and the vanadium and phosphorus compounds react to form the vanadium phosphorus oxide precursor. Typical residence times in the furnace are about
  • the vanadium exists as a mixture of +5, +4, and +3 oxidation states. As such it is convenient to describe the overall oxidation state of the catalyst as an average vanadium valence (AW) .
  • AW average vanadium valence
  • a suitable reducing agent that lowers the vanadium to the appropriate average valence state can be used, typically by incorporating the reducing agent into the initial phosphorous and vanadium containing solution.
  • the appropriate valence state will depend on the ultimate use of the vanadium-containing catalyst.
  • Mild reducing agents include hydrochloric acid, oxalic acid, NH 2 OH, N 2 H 4 .2HC1, ethylene glycol, glycerol, metallic tungsten, mixtures of HC1 and oxalic acid.
  • Oxalic acid can be used as a vanadium reducing agent, typically by using the oxalic acid and vanadium in a mole ratio ranging from 0 to 1.0.
  • the phosphorous:vanadium atomic ratio in the initial solution is adjusted to about 1.0 to 1.8 (1:1 to 1.8:1) with a ratio of 1.1 to 1.7 (1.1:1 to 1.7:1) being preferred, and a ratio of 1.2 (1.2:1) being most preferred.
  • a suitable technique is then used to collect the VPO precursor and remove any remaining solvent. Such techniques include collection on a heated metal rod, a mesh steel grating or a paper filter.
  • the VPO precursor is activated by heating.
  • One of the purposes of such heating is to drive off gases such as water and ammonia from the precursor.
  • the heating is typically carried out in a nonreactive gas such as nitrogen or helium. Air may be used. However the use of a nitrogen environment has been found to reduce the crystallinity of the resulting activated catalyst.
  • the precursor VPO composition for butane conversion to maleic anhydride, it is preferred to heat the precursor VPO composition in 0.5-4 volume % butane and a mixture of 18-22% oxygen and the remainder being a nonreactive gas such as nitrogen.
  • the butane component is about 1.0 to 2.0% and the oxygen and nonreactive gas mixture may be satisfied by using air.
  • the temperature of activation is about 375- 500°C with a temperature of about 425-475°C being preferred.
  • a vanadium salt such as NH 4 V0 3 that reacts to release a volatile ammonia gas and vanadium oxide.
  • a reducing agent has also been provided in the initial solution when it is desired to reduce the vanadium valence. It is to be understood however that other salts such as VC1 3 could be used with the oxygen necessary to oxidize and form the vanadium oxide being provided by sufficient oxygen in the gas used to form the aerosol or otherwise provided in the environment of the reaction furnace.
  • a reducing agent could be supplied as a separate aerosol or otherwise provided in the furnace environment.
  • the following aerosol method was used to prepared the VPO catalyst having the characteristic powder x-ray diffraction data given in Table 1 and Figure 1.
  • the range of parameters are not limiting but serves only to illustrate the range of values that have produced the new VPO composition.
  • the method consists of dissolving NH V0 3 and H 3 P0 4 in water to give a phosphorus:vanadium atomic ratio in the solution in the range of 1:1 to 1.8:1 with the concentration of vanadium being 0.12M.
  • the aerosol is formed by passing a mixture of the solution and air through a nozzle.
  • the aerosol is injected into a furnace where it is heated to a temperature in the range of 350 to 700°C to react the vanadium and phosphorus compounds to give a vanadium phosphorus oxide precursor with an average vanadium valence in the range of 3.9 to 5.0.
  • the vanadium phosphorus oxide precursor is activated by heating the precursor in a medium of nitrogen or 0.5 to 4.0 volume % butane, 18 to 22 volume % oxygen with the balance helium.
  • Figure 1 is a graph of the powder x-ray diffraction pattern (XRD) of the activated catalyst of this invention as prepared in Example 2.
  • the intensity of the diffraction peaks is presented in counts per second (cps) on the left vertical axis (Y) .
  • Degrees 2 ⁇ are given on the lower horizontal axis (X) .
  • Figure 2 is a graph of the powder x-ray diffraction pattern (XRD) of a catalyst prepared from an organic solvent as described in Example 3.
  • the intensity of the diffraction peaks is presented in counts per second (cps) on the left vertical axis (Y) .
  • Degrees 2 ⁇ are given on the lower horizontal axis (X) .
  • Figure 3 is a graph showing the activity of the catalyst of this invention with a precursor P/V ratio of 1.2 as prepared in Example 2 (o) as compared to two aqueous catalysts with P/V ratios of 1.1 and 1.2 from Examples 4 ( ⁇ ) and 5 (x) , respectively.
  • the left vertical axis (Y) shows the activity of the catalyst in micromoles of C 4 (butane) converted per gram of catalyst per minute ( ⁇ mol C 4 /g min) .
  • the lower horizontal (X) axis shows the reaction temperature in degree centigrade (°C) at which the butane is passed over the catalyst.
  • Figure 4 is a graph showing the yield of maleic anhydride (MA) from the catalyst of this invention with a precursor V/P ratio 1.2 as prepared in Example 2 (o) as compared to two aqueous catalysts with P/V ratios of 1.1 and 1.2 from Examples 4 ( ⁇ ) and 5 (x) , respectively.
  • the left vertical axis (Y) shows the maleic anhydride yield from the catalyst in micromoles of maleic anhydride produced per gram of catalyst per minute ( mol/g min) .
  • the lower horizontal axis (X) shows the reaction temperature in degrees centigrade (°C) at which the maleic anhydride is produced.
  • Figure 5 is a schematic diagram illustrating the aerosol process of this invention.
  • the invention disclosed here is a new aerosol vanadium phosphorus oxide catalyst for the oxidative reactions of hydrocarbons, and especially for the production of maleic anhydride by the selective oxidation of butane.
  • This catalyst consists of a vanadium phosphorus oxide (VPO) composition that is quite different from those found in known catalysts.
  • the activated catalyst has the characteristic powder x-ray diffraction pattern (XRD) given in Table 1 and shown graphically in Figure 1.
  • d spacings are ⁇ 0.025 at low 2 ⁇ , ⁇ 0.007 at a medium 2 ⁇ , and ⁇ 0.001 A at high 2 ⁇ .
  • This catalyst is prepared by an aerosol technique in which a feed solution containing at least one vanadium- containing composition and one phosphorus-containing composition dissolved in water is formed into an aerosol that is sprayed into a heated chamber to produce a VPO catalyst precursor.
  • the phosphorus to vanadium atomic ratio of the feed is between 1.0 and 1.8.
  • Other processes that result in a precursor of well mixed components by rapid drying of the precursor can also be used.
  • the precursor is converted into a working catalyst by heating. As shown in Figure 5, a carrier gas 12 and solution feed 14 are mixed and passed through a nozzle 16 to form aerosol 18.
  • the aerosol 18 passes through furnace 20 in cocurrent upward (or downward) flow with secondary gas 30.
  • Recycle line 32 is used to remove excess solution from the furnace and can be recycled with solution 14 through nozzle 16.
  • the furnace is held at a temperature in the range between 200°C and 1000°C. Furnace temperatures outside of this range may be used but with considerably less effective results.
  • the solvent evaporates and the salts react and decompose in the furnace 20.
  • the feed solution mixture 14 is typically an aqueous solution composed of at least one vanadium- containing composition and at least one phosphorus- containing composition.
  • the vanadium composition is preferably a salt containing oxygen with vanadium in a +5 oxidation state and having components that yield volatile products such as ammonia on heating, e.g., NH 4 V0 3 .
  • the phosphorus- containing composition should meet similar criteria, i.e., contain oxygen with phosphorous in the appropriate oxidation state and react to give volatile components, e.g. H 3 P0 4 .
  • compositions that contain components that decompose to yield solid contaminants of the VPO catalyst are to be avoided.
  • Organic solvents include alcohols such as isobutanol, methanol, ethanol, allyl alcohol, crotyl alcohol, acids such as acetic acid, oxygen-containing polar solvents such as tetrahydrofuran, mixtures such as allyl alcohol and t-butyl alcohol and mixtures of organic solvents and water.
  • the composition of feed solution 14 is determined by the solubility of the vanadium compounds and the desired valence state of vanadium.
  • a mineral acid such as HC1, or a carbon-containing acid such as oxalic or tartaric acid may be added to the feed solution 14 to enhance vanadium and phosphorus composition solubility or reduce the vanadium ion valence or both.
  • materials that produce undesirable residues are to be avoided.
  • Reducing agents include oxalic acid (H 2 C 4 0 2 ) , glycerol, isobutanol, allyl alcohol, crotyl alcohol, 1-hydroxyethylidene-l,1-diphosphinic acid and mixtures of N 2 H 4 and 2HC1, allyl alcohol and t-butyl alcohol, and H 2 C 4 0 2 and propan-2-ol.
  • the mole ratio of a reducing agent such as oxalic acid to vanadium can range from 0:1 to 1:1.
  • the concentrations of the various components in the feed solution 14 are adjusted to obtain: (1) the desired average vanadium valence state, (2) the desired particle size of the catalyst, (3) thorough drying of the aerosol in the spray pyrolysis furnace, (4) formation of the desired precursor composition, and (5) easy operation of the aerosol equipment.
  • Excessively concentrated component feed solutions 14 are undesirable because of clogging of the aerosol nozzle 16 while excessively dilute feed solutions 14 require undesirably long residence times in furnace 20.
  • the preferable range of vanadium concentration is 0.05 to 0.2 M, the more preferable range is 0.8 to 0.15 M, and the most preferable range is 0.10 to about 0.12 M.
  • P/V ratio phosphorus/vanadium ratio in the feed solution.
  • the more preferred range of P/V ratios are those that give catalysts with the highest maleic anhydride yields, that is, a ratio of 1.0 to 1.8.
  • the more preferred ratio is about 1.1 to 1.7 with the most preferred ratio being 1.2.
  • the average vanadium valence (AW) of a working catalyst ranges from 3.9 to 5.0.
  • the more preferred range is 4.5 to 4.9, and the most preferred range being from 4.6 to 4.8.
  • Furnace synthesis temperatures below 200 °C afford samples of low stability while syntheses temperatures above 1000°C provide highly sintered materials. Thus, synthesis at the optimum temperature is critical in forming the VPO catalyst precursor.
  • the preferred range of furnace temperatures is between 200 and 1000°C, the more preferred range is between about 500 and 800°C. and the most preferred range is between about 550 and about 700°C with a residence time of 1 to 12 seconds in furnace 20.
  • a carrier gas 12 is used to form aerosol 18 from the feed solution 14.
  • a secondary gas 30 is used to transport the drying and reacting aerosol droplets and precursor particles through the synthesis furnace 20 and connector 22 to collection device 24.
  • Any suitable carrier gas 12 and secondary gas 30, such as air, nitrogen, helium, argon, carbon dioxide or their mixtures may be used.
  • previous oxidizing and reducing gases may be provided mixed with carrier gas 12 or secondary gas 30 to achieved the desired oxidation states of vanadium, phosphorus or both.
  • a vacuum can be applied to exit line 36 to assist in the flow of aerosol, solvent, gaseous byproducts, and precursor through apparatus 10.
  • the typical residence time in the furnace is about 1 to 12 seconds.
  • the preferred residence time depends on the furnace temperature, the concentrations of the feed solution, nozzle size, and other operating variables.
  • residence times were measured in a plexiglas flow reactor at ambient conditions using pulsed injection and a visual measurement of the velocity of the aerosol passing up through the tube. These settings for the air velocities were used in the synthesis runs corresponding to the desired residence times.
  • the normal residence time was 8 seconds. It was not possible to specify a precise residence time under actual synthesis conditions due to the change in particle drag with temperature and the changing density and size of the particle and degree of particle back-mixing. As such, the observed residence times tend to be maximum residence times. Calculations of the residence time for normal reactor synthesis conditions at 700 °C give an idealized residence time of about 3.0 seconds. Actual residence times appear to be between the 8 and 3 second value.
  • collectors 24 can be used for the precursor. The preferred ones are those that collect the particles exiting the furnace without loss and in a dry form without agglomeration.
  • a heated metal rod or mesh steel grating can be used.
  • a paper filter on a water- cooled housing can also be used.
  • the connection 22 leading to the collector and collector 24 are heated to prevent unwanted condensation of the solvent on the apparatus walls.
  • a vacuum applied to exit line 36 promotes precursor drying in collector 24.
  • the precursor is activated by heating.
  • One activation technique involves heating the precursor in a flow of unreactive gas such as nitrogen. After a short heating period in nitrogen, the materials are partially activated as determined by the x-ray diffraction (XRD) pattern, which shows the characteristic peaks of both precursor and active catalyst.
  • XRD x-ray diffraction
  • Precursors show a weight loss of 12 to 20% during thermogravimetric analysis (TGA) while a nitrogen-activated catalyst shows less than a 5% loss.
  • TGA thermogravimetric analysis
  • a typical TGA of a nitrogen-activated catalyst shows that most of the weight loss occurs at lower temperatures.
  • Nitrogen-activated catalysts also tend to have a lower average vanadium valence (AW) . This resembles the phenomena observed for ammoniated precursors reduced by the release of NH 3 during heating in nitrogen.
  • AW average vanadium valence
  • the most preferred method of precursor activation to form an active working catalyst with the highest maleic anhydride yields is to heat the precursor in a reaction mixture of 0.5-4% volume % butane, or more preferably 1.0- 2.0% butane, and 18-22% oxygen, the balance being an unreactive gas such as nitrogen or helium, at or slightly above the desired reaction temperature at which the catalyst is to be used.
  • Percent Conversion is defined as the number of moles of reacted reactant/total moles of reactant x 100.
  • Percent Selectivity is defined as the number of moles of a particular product/number of moles of all products x 100.
  • Molar Yield is defined as the number of moles of a particular product formed/(grams of catalyst x unit of time) OR number of moles of a particular product formed/ (square meters of catalyst x unit of time) . Percent Yield is defined as the number of moles of a particular product/number of moles of reactant x 100.
  • Activity is defined as the moles of reacted reactant/(grams of catalyst x unit of time) OR the moles of reacted reactant/(square meters of catalyst x unit of time) .
  • Example 1 details the preparation of the new VPO composition catalyst and illustrates its utility as an active catalyst for the selective oxidation of butane to maleic anhydride.
  • Examples 2-5 were carried out to show the differences between the new VPO composition catalyst and conventional aqueous and organic catalysts. Data from Examples 2-5 is presented in Figures 1-4 and Tables 1-4 and 7. As seen in Figure 3, the activity of the aerosol VPO composition catalyst for butane conversion is comparable to aqueous catalysts at 425 °C and is better at temperatures above 425 °C.
  • the aerosol catalyst is intermediate between the aqueous catalysts from Examples 4 ( ⁇ ) and 5 (x) .
  • the aerosol VPO composition catalyst and the aqueous catalyst from Example 5 have identical solution P/V ratios of 1.2 while Example 4 has a solution P/V ratio of 1.1.
  • a comparison of the results in Examples 2 (o) and 4 reveals that although the aqueous catalyst in Example 4 has higher maleic anhydride yield due to higher selectivity to maleic anhydride ( Figure 4) , the relative activity per gram is lower than that of Example 2 ( Figure
  • Example 22 illustrates the effect of residence time on catalyst yield as a function of grams of catalyst and specific surface area of the catalyst.
  • Example 22 is a repeat of Examples 2 and 8 but with different residence time. Results are presented in Table 12.
  • Example 23 is an example of the use of the aerosol VPO catalyst for the selective oxidation of selected hydrocarbons. Results are presented in Table 13.
  • Table 14 summarizes the catalytic properties of the catalysts with the highest yields. The Example numbers refer to the description found in the specific Examples.
  • VPO VANADIUM PHOSPHORUS OXIDE
  • aqueous fed solution with a 1:1 molar ratio of NH 4 V0 3 :H 3 P0 4 was processed by the spray pyrolysis method.
  • the aerosol was formed by injecting the solution through a nozzle cocurrently upward with air into a furnace.
  • the furnace housing was a Mullite cylinder 4" inch (10.2 cm) diameter and 8 feet (2.4 m) high that rested on the spray nozzle apparatus.
  • the furnace volume was 9.9 1 and the pressure was 0.1" H 2 0 (24.9 Pa) .
  • Typical production parameters were: carrier gas 12 ( Figure 5) feed rate of 2.4 1/min, secondary gas 30 feed rate of 52 1/min and solution 14 feed rate of 7.5 ml/min.
  • the furnace temperature was 650°C, and the P/V atomic ratio of the aqueous feed solution 14 was 1.0.
  • the residence time was 8 seconds, the recycle ratio was 3:1 injected solution:recycled solution and the vanadium concentration in the feed solution was 0.12M.
  • the precursor product was dry as collected.
  • the bulk P/V of the precursor was higher than that of the solution, 1.23, possibly because of precipitation of vanadium salt.
  • the precursor exhibited the powder x-ray diffraction (XRD) data given in Table 2.
  • the activity for butane oxidation and selectivity to maleic anhydride were measured by flow reaction studies.
  • the reactor consisted of a quartz tube of 14 mm OD (outside diameter) .
  • a 3 mm quartz thermowell running coaxially through the center of the tube was used to encase a thermocouple to monitor the temperature of the catalyst bed.
  • the bed itself consisted of 2 g of catalyst and was 13 cm in length.
  • the feed to the reactor was 2.5% butane, 22% oxygen, and the balance helium, with a total flow rate of 70 ml/min.
  • the testing procedure involved initially heating the precursor slowly to 400°C in the reaction mixture, measuring the catalytic properties after 2 hours, then measuring the properties after two hours each at 425, 450, 475°C.
  • reaction data for subsequent examples are quoted for the third cycle at 475°C.
  • the butane conversion was 26% and the selectivity to maleic anhydride (MA) was 40%.
  • the surface area of the catalyst after use was 0.31 m 2 /g.
  • Example 1 The precursor collected in Example 1 consisted of highly dispersed, smooth, hollow spheres of diameters between 1 and 10 ⁇ m. After 24 hours of reaction, the particles had agglomerated and the surfaces had become rougher. After an additional 100 hours of reaction, most spheres had broken into pieces, and the morphology began to resemble the disordered platelet structure of conventional VPO catalysts. Accompanying these changes, the P/V ratio in the near-surface region as determined by energy dispersion x-ray analysis (EDAX) were 1.02, 1.63, and 0.91 at these three stages.
  • EDAX energy dispersion x-ray analysis
  • the TGA of the fresh catalyst showed a 23% weight loss.
  • the TGA data for all catalysts were collected in argon from 25 to 900°C, at 5°C/min. About 15% of this weight loss occurred below 200°C, and 3% occurred above 700°C.
  • the weight loss at low temperature was probably due to desorption of water, which suggests that these materials are hygroscopic.
  • the weight loss at intermediate temperatures was probably due to ammonia and water trapped from synthesis. After reaction, the TGA shows only a 8.8% loss, of which 3% occurs at high temperatures, and the rest at low temperatures.
  • the above results indicate that the aerosol catalysts have a different activation mechanism and that their interaction with moisture/absorbed water is greater.
  • a VPO catalyst was prepared by an organic synthesis technique with a P/V 1.1.
  • a mixture of 15g V 2 0 5 , 60 ml of benzyl alcohol and 90 ml of isobutyl alcohol was stirred under reflux for 3 hours, and then stirred overnight at room temperature.
  • Orthophosphoric acid crystals (99%; 16.7 g) were added and stirred under reflux for 2 hours.
  • the solid was obtained by suction filtration, dried, and activated in a flow of 2% butane, 22% oxygen, the balance helium, at 400°C for 24 hours.
  • the catalyst displayed the XRD data given in Table 4.
  • the XRD data differs from that of Examples 1 and 2.
  • a visual comparison of the XRD patterns from Examples 2 and 3 is given in Figures 1 and 2, respectively.
  • a VPO catalyst was prepared using a conventional aqueous solution technique with a P/V of 1.1 by dissolving 20g V 2 0 5 in 250 ml of 37% HC1 and refluxing for 90 min., after which 27.9g of 85% H 3 P0 4 was added.
  • the solid precursor was obtained by evaporation, dried and activated in a flow of 2% butane, 22% oxygen, and the balance helium, for 8 h at 475°C.
  • the catalytic data were collected using reaction cycles in the same manner as in Example 1.
  • the working catalyst had an x-ray pattern similar to Example 3 with respect to the location of the peaks, but the width and height of the peaks differed.
  • a catalyst was prepared as in Example 4, except that additional phosphorus (H 3 P0 4 ) was added to give a P/V atomic ratio of 1.2.
  • the x-ray pattern was similar to Example 4.
  • a comparison of the catalytic activities is shown in Figure 3.
  • the catalyst of Example 2 (o) is more active than those of Examples 4 ( ⁇ ) and 5 (x) .
  • Figure 4 shows the comparison of yields of maleic anhydride in Examples 2, 4, and 5.
  • the catalyst was prepared as in Example 1 except that the feed P/V was 1.2, resulting in a fresh product with a bulk P/V of 1.43. At a butane conversion of 17%, the selectivity to maleic anhydride (MA) was 39%. After an additional 100 hours at 475°C, the selectivity to maleic anhydride was 46% at a butane conversion of 30%, for a yield of 2.00 ⁇ (MA) /g minute (see Table 14).
  • the powder XRD of the catalyst was similar to that of Example 1.
  • This catalyst was prepared as in Example 1 except that the P/V of the starting solution was 1.4 resulting in a fresh bulk of P/V of 1.61. After three cycles of reaction, at a butane conversion of 8%, the selectivity to maleic anhydride was 37% and the XRD was similar to that in Example 1.
  • EXAMPLE 8 AEROSOL VPO CATALYST FROM FEED P/V RATIO OF 1.2 AT 700°C
  • a catalyst was prepared as in Example 1 except that the furnace temperature was 700°C, and the feed P/V was 1.2 but with no recycle. Consequently, the bulk P/V ratio was also 1.2.
  • the XRD pattern featured a small set of peaks at 29°and the most intense peak at 12.5° 29. In between these two peaks was a broad and weak peak around 24°. After three cycles of reaction, the catalyst exhibited a pattern which showed a decrease in the intensity of the 12.5° peak with a new peak at 21°.
  • the XRD data are given in Table 5.
  • AEROSOL VPO CATALYST FROM FEED P/V RATIO OF 1.2 AT 650°C The catalyst was prepared as in Example 8 except that the furnace temperature was at 650°C.
  • the selectivity to maleic anhydride was 37% at a butane conversion of 26%.
  • the XRD after reaction was similar to that presented in Table 1.
  • AEROSOL VPO CATALYST FROM P/V RATIO OF 1.2 AT 550°C The catalyst was prepared as in Example 8 except that the furnace temperature was at 550°C.
  • the selectivity to maleic anhydride was 48% at a butane conversion of 8%.
  • the XRD after reaction was similar to that presented in Table 1.
  • AEROSOL VPO CATALYST FROM FEED P/V RATIO OF 1.2 AT 500°C The catalyst was prepared as in Example 8 except that the furnace temperature was at 500°C.
  • the selectivity to maleic anhydride was 40% at a butane conversion of 56%.
  • the XRD after reaction was similar to that presented in Table 1.
  • EXAMPLE 12 AEROSOL VPO CATALYST FROM FEED P/V RATIO OF 1.2 AT 450°C
  • the catalyst was prepared as in Example 8 except that the furnace temperature was at 450°C.
  • the selectivity to maleic anhydride was 40% at a butane conversion of 24%.
  • the XRD resembled that presented in Table 1, but the 21° peak was broadened and extended to about 30° 2 ⁇ .
  • This catalyst was prepared as in Example 8 except that the furnace temperature was 350°C.
  • the selectivity to maleic anhydride was 33% at a butane conversion of 58%.
  • the XRD resembled that of the catalyst in Example 12.
  • the catalyst was prepared as in Example 8 but then heated at 450°C in N 2 for 3 hours.
  • the XRD pattern of the catalyst after this treatment is given in Table 6.
  • the average vanadium valence (AW) was 4.44%.
  • the selectivity to maleic anhydride was 34% at a butane conversion of 66%.
  • the catalyst was prepared as in Example 9 but then was treated in a flow of N 2 for 3 hours at 450°C before use in a butane oxidation reaction. After reaction, the XRD resembled that of the catalyst in
  • Example 9 The selectivity to maleic anhydride was 27% at a butane conversion of 36%.
  • the catalyst was prepared as in Example 10 except that the catalyst was treated in a flow of N for 3 hours at 450°C before reaction.
  • the AW was 4.26.
  • the selectivity to maleic anhydride was 35% at a butane conversion of 48%.
  • the XRD after reaction was similar to Example 10 but the peaks were of weaker intensity.
  • the catalyst was prepared as in Example 11 except that after preparation it was heated in a flow of N 2 for 3 hours at 450°C.
  • the AW was 4.00 after the treatment.
  • the selectivity to maleic anhydride was 34% at a butane conversion of 54%.
  • the XRD after reaction was similar to that obtained in Example 11.
  • This catalyst was prepared as in Example 12 except that the catalyst was heated in a flow of N 2 for 3 hours at 450°C after preparation before use in a reaction.
  • the AW was 4.46 after this treatment.
  • the XRD after reaction was similar to that found for the sample in Example 12.
  • This catalyst was prepared as in Example 1, but the furnace temperature was 1000°C.
  • the resulting product had an average vanadium valence (AW) of 4.53.
  • This catalyst was prepared as in Example 19 except the starting solution contained oxalic acid as a reducing agent in the molar ratio 1:1:0.05
  • This catalyst was prepared as in Example 19 except the starting solution was of a molar ratio of 1:1:1 NH V0 3 :H 3 P0 4 :C 2 H 0 2 .
  • the product had an average vanadium valence (AW) of 4.00.
  • Example 2 was repeated with a residence time of 2.67 sec and Example 8 was repeated using a residence time of 8 sec, all other parameters being similar.
  • the data are given in Table 12.
  • This example shows the usefulness of the new VPO catalyst to be used for the selective oxidation of selected hydrocarbons including ethane, propane and isobutane.
  • the catalyst (2.75g) for this reaction was used as in Example 1.
  • the complete set of data is given in Table 13.
  • the catalyst was active and selective for the oxidative dehydrogenation of ethane to ethene in the range 425 to 500°C, at ethane conversions of 7 to 34%, with selectivities to ethene from 70 to 27%, respectively.
  • iso-butane oxidation major products were carbon oxides, even at low conversion.
  • Acetic acid is selectively formed on conventional VPO, but here only small amounts of maleic anhydride, methacrolein, and acetic and acrylic acids are formed.
  • conventional VPO the oxidation of propane is not selective.
  • 10% of the product selectivity is divided between C 2 and C 3 products and acrylic and acetic acids. Here no acids are formed but acrolein is detected. Activities and selectivities are reported in Table 13.

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Abstract

Nouveau catalyseur à l'oxyde phosphorique de vanadium (OPV) produit à l'aide d'une nouvelle technique de préparation d'oxyde phosphorique de vanadium. La composition d'OPV se caractérise par son schéma de diffraction aux rayons X de la poudre illustré dans le graphique 1. La nouvelle technique de préparation d'OPV comprend les étapes suivantes: 1) on dissout des compositions de vanadium et de phosphore dans un solvant tel que de l'eau pour former une solution, 2) on forme un aérosol avec la solution résultante, 3) on chauffe l'aérosol pour obtenir un précurseur d'OPV , et 4) on active le précurseur d'OPV pour produire le catalyseur à l'OPV. Le catalyseur à l'OPV activé présente une activité d'oxydation sélective des hydrocarbures et une bonne conversion et sélectivité pour l'oxydation du butane en anhydre maléique.
PCT/US1993/009234 1992-09-30 1993-09-29 Aerosol et catalyseur a l'oxyde phosphorique de vanadium et procede de preparation WO1994007601A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113457700A (zh) * 2021-06-24 2021-10-01 浙江大学 一种用于羟醛缩合的钒磷氧催化剂及其制备方法和应用

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US4374043A (en) * 1980-12-29 1983-02-15 The Standard Oil Company Preparation of fluidizable vanadium phosphorus oxide catalysts using a mixed phosphorus source
US4418003A (en) * 1982-05-26 1983-11-29 Standard Oil Company (Indiana) Catalysts for the production of maleic anhydride
EP0225062A2 (fr) * 1985-11-27 1987-06-10 E.I. Du Pont De Nemours And Company Catalyseurs résistants à l'attrition, précurseurs de catalyseurs et supports de catalyseurs
JPH01201016A (ja) * 1987-10-12 1989-08-14 Mitsubishi Kasei Corp バナジウム−リン系結晶性酸化物又はそれを含有する触媒の製造法
EP0362817A1 (fr) * 1988-10-05 1990-04-11 Mitsubishi Kasei Corporation Procédé de préparation d'un oxyde cristallin du système vanadium-phosphore et catalyseur contenant cet oxyde cristallin
EP0397644A1 (fr) * 1989-05-09 1990-11-14 Maschinenfabrik Andritz Actiengesellschaft Procédé de préparation de catalyseurs

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US4374043A (en) * 1980-12-29 1983-02-15 The Standard Oil Company Preparation of fluidizable vanadium phosphorus oxide catalysts using a mixed phosphorus source
US4418003A (en) * 1982-05-26 1983-11-29 Standard Oil Company (Indiana) Catalysts for the production of maleic anhydride
EP0225062A2 (fr) * 1985-11-27 1987-06-10 E.I. Du Pont De Nemours And Company Catalyseurs résistants à l'attrition, précurseurs de catalyseurs et supports de catalyseurs
JPH01201016A (ja) * 1987-10-12 1989-08-14 Mitsubishi Kasei Corp バナジウム−リン系結晶性酸化物又はそれを含有する触媒の製造法
EP0362817A1 (fr) * 1988-10-05 1990-04-11 Mitsubishi Kasei Corporation Procédé de préparation d'un oxyde cristallin du système vanadium-phosphore et catalyseur contenant cet oxyde cristallin
EP0397644A1 (fr) * 1989-05-09 1990-11-14 Maschinenfabrik Andritz Actiengesellschaft Procédé de préparation de catalyseurs

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DATABASE WPI Week 8938, Derwent World Patents Index; AN 89-275006 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113457700A (zh) * 2021-06-24 2021-10-01 浙江大学 一种用于羟醛缩合的钒磷氧催化剂及其制备方法和应用

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