Molybdenum based oxidation catalysts

FIELD OF TIHE INVENTION

[0001] This invention relates to compounds comprising molybdenum, oxygen and certain cations, and the use of these compounds as catalysts in C4 oxidation processes, especially butane oxidation processes.

TECHNICAL BACKGROUND

[0002] Oxidative organic processes are widely used in industrial operations. One commercially valuable process involves the oxidation of butane to maleic anhydride. Maleic anhydride is used as a raw material for products ranging from agricultural chemicals, paints, paper sizing and food additives to synthetic resins. To fill the high demand for this valuable chemical, a variety of commercial processes have been developed.

[0003] One important route to maleic anhydride involves the vapor phase oxidation of n-butane over a vanadium/phosphorus oxide (VPO) catalyst. The reaction step involves oxidation of n-butane with air (oxygen) to form maleic anhydride, carbon oxides, water and smaller amounts of partially oxidized by-products. Typically, the process is carried out in fixed-bed reactors, fluid-bed reactors, or more recently in recirculating solids reactors having two reaction zones in which two separate reactions take place with a catalyst (the solid) circulating between the two reaction zones and taking part in reactions in both zones.

[0004] A number of non-VPO catalysts have been reported in the literature. Zazhigalov, V. A. et al., in an article entitled “Oxidation of n-butane on Vanadium Molybdenum-Oxide Catalysts”, Inst. Fiz. Khim. im. Pisarzhevskogo, Kiev USSR Neftekhimiya (1977), 17 (2),268-73 describe the activity of V2O5—MoO3 catalysts in butane oxidation as passing through a maximum at 25% MoO3, and that a certain catalytic structure consisting of, V4+, V5+ and Mo6+ ions correspond to their preferred catalyst composition. These results obtained at 500-600° C. indicate low catalyst activity at normal operating temperatures.

[0005] Mazzochia, C. R. et al., in “Selective Oxidation of Butane in the Presence of NiO—MoO3 catalysts”; An. Quim. Ser. A 79, no. 1 108-113(1983) disclose nickel molybdate catalysts prepared by coprecipitation that exhibit low hydrocarbon conversions. At 475° C., 19% conversion of n-butane was noted with low selectivities to maleic anhydride.

[0006] Umit Ozkan and G. L. Schrader, in “Synthesis, Characterization and catalytic behaviour of cobalt molybdates for 1-butene oxidation to maleic anhydride”, Applied Catalysis, 23 (1986) 327-338 disclose the use of cobalt molybdate for the oxidation of 1-butene.

[0007] In spite of the progress in catalyst and process development over the years, a need still remains for improved non-VPO catalysts useful in the oxidation of C4 hydrocarbons, particularly n-butane, to maleic anhydride and especially catalysts which are active at lower temperatures and have shorter contact timnes; and it is to that end that the present invention is directed.

SUMMARY OF THE INVENTION

[0008] The present invention provides a catalyst, comprising a molybdenum compound of formula I, II, III, IV or V:

VqMoAyOz I

NiMoxByOz′ II

VNiwMoxCy′Oz″ III

CoNiwMoxDyOz′″ IV

VNiwCorMoxEyOz″″ V

[0009] wherein:

[0010] q is a number from 0.1 to 10;

[0011] r is a number from 0.1 to 10;

[0012] w is a number from 0.1 to 10;

[0013] x is a number from 0.1 to 10;

[0014] y is a number from 0.1 to 10;

[0015] y′ is a number from 0 to 10,

[0016] A is at least one cation selected from the group consisting of cations of: Cr, Sb, Co, Ce and Pb;

[0017] B is at least one cation selected from the group consisting of cations of: Sb, Al and W;

[0018] C is at least one cation selected from the group consisting of cations of: Fe, Zn, Al, Sb, Bi, W, Li, Ba, Nb and Sn;

[0019] D is at least one cation selected from the group consisting of cations of: Ba, Mn, Al, Sb, Sn, and W;

[0020] E is at least one cation selected from the group consisting of cations of: Fe, Ca, Mn, Sr, Eu, La, Zr, Ga, Sn and Pb; and

[0021] z, z′, z″, z′″, and z″″ are determined using the amounts and oxidation states of all cations present in each formula according to the following equations:

z
=((q times oxidation state of V)+(1 times oxidation state of Mo)+(y times oxidation state of A)) divided by 2 (oxidation state of oxygen);

z
=((1 times oxidation state of Ni)+(x times oxidation state of Mo)+(y times oxidation state of B)) divided by 2 (oxidation state of oxygen);

[0022]

z^{″} = ((1 times oxidation state of V) + (w times the oxidation state of Ni) + (x times oxidation state of Mo) + (y^{'} times oxidation state of C)) divided by 2 (oxidation state of oxygen);

z^{′′′} = ((1 times oxidation state of Co) + (w times the oxidation state of Ni) + (x times oxidation state of Mo) + (y^{'} times oxidation state of D)) divided by 2 (oxidation state of oxygen); and

z^{′′′′} = ((1 times oxidation state of V) + (w times the oxidation state of Ni) + (r times oxidation state of Co) + (x times oxidation state of Mo) + (y^{'} times oxidation state of E)) divided by 2 (oxidation state of oxygen) .

[0023] The present invention also provides a process for the oxidation of a C4 hydrocarbon to maleic anhydride, comprising: contacting the C4 hydrocarbon with a source of oxygen in the presence of a catalytic amount of a molybdenum catalyst comprising a compound of formula I, II, III or V, as defined above, to yield maleic anhydride.

[0024] The present invention further provides a process for the oxidation of n-butane to maleic anhydride, comprising: contacting n-butane with a source of oxygen in the presence of a catalytic amount of a molybdenum catalyst comprising a compound of formula IV, as defined above, wherein the molybdenum catalyst is in a bulk state, to yield maleic anhydride.

[0025] The present invention also provides a process for the oxidation of n-butane to maleic anhydride, comprising: contacting n-butane with a source of oxygen in the presence of a catalytic amount of a catalyst comprising a molybdenum compound of formula VI or VII in a crystalline, active phase

V9Mo6O40 VI

V2MoO8 VII

[0026] to yield maleic anhydride.

[0027] The present invention also provides a process for the preparation of a molybdenum compound comprising a crystalline oxide of formula I, II, III, IV or V, as described above, comprising the steps of: contacting at least one compound having a cation of the molybdenum compound with at least one cation containing compound for each of the other cations of the molybdenum compound in a solution comprising water to form a resultant solution or colloid; freezing the resultant solution or colloid to form a frozen material, freeze drying the frozen material; and heating the dried frozen material to yield the molybdenum compound of formula I, II, III, IV, V, VI or VII.

DETAILED DESCRIPTION OF TIHE INVENTION

[0028] Multicomponent catalyst systems have been identified herein wherein the presence of molybdenum in combination with other particular cations show a significant beneficial effect on catalyst performances compared with many non-VPO catalysts reported in the literature for n-butane oxidation. These new multicomponent catalysts of the present invention comprise a molybdenum compound of formula I, II, III, IV or V:

VqMoAyOz I

NiMoxByOz′ II

VNiwMoxCy′Oz″ III

CoNiwMoxDyOz′″ IV

VNiwCOrMoxEyOz″″ V

[0029] wherein: q is a number from 0.1 to 10; r is a number from 0.1 to 10; w is a number from 0.1 to 10; x is a number from 0.1 to 10; y is a number from 0.1 to 10; and y′ is a number from 0 to 10.

[0030] A is at least one cation selected from the group consisting of cations of: Cr, Sb, Co, Ce and Pb. A is preferably Sb, and a preferred compound of formula I is V1Mo1Sb1Oz. B is at least one cation selected from the group consisting of cations of: Sb, Al and W. B is preferably Sb, and a preferred compound of formula II is Ni1Mo2.3Sb1Oz′. C is at least one cation selected from the group consisting of cations of: Fe, Zn, Al, Sb, Bi, W, Li, Ba, Nb and Sn. C is preferably Bi, or Nb and Sn, and preferred compounds of formula III are V1Mo2.3Ni1Bi1Oz″ and V1Mo2.3Ni1Nb1Sn1Oz″. D is at least one cation selected from the group consisting of cations of: Ba, Mn, Mo, Al, Sb, Sn, and W. D is preferably Sn or W, and preferred compounds of formula IV are Co0.5Ni0.5Mo3Sn0.5Oz′″ and Mo3Co0.5Ni0.5W1Oz′″. E is at least one cation selected from the group consisting of cations of: Fe, Ca, Mn, Sr, Eu, La, Zr, Ga, Sn and Pb. E is preferably Fe, Sr, Zr, Ga or Pb, and preferred compounds of formula V are V1Mo2.3Ni0.5Co0.5Fe1Oz″″, V1Mo2.3Co0.5Ni0.5Sr1Oz″″, V1Mo2.3Co0.5Ni0.5Zr1Oz″″, V1Mo2.3Co0.5Ni0.5Ga1Oz″″ and V1Mo2.3Co0.5Ni0.5Pb1Oz″″.

[0031] The ranges for z, z′, z″, z′″, and z″″ defining the subscript for oxygen in the formulae I-V, varies widely. The value of z, z′, z″, z′″, and z″″ is defined using the range of possible oxidation states of all of the cations found in the molybdenum compound as shown below.

[0032] For the molybdenum compounds of formula I, the highest oxidation states of the A cations are: V5+, Mo6+, Cr6+, Sb5+, Co3+, Ce4+ and Pb4+; and the lowest oxidation states for the A cations are: V3+, Mo4+, Cr2+, Sb3+, Co2+, Ce3+and Pb2+. Therefore, for example, when the molybdenum compound of formula I is V10Mo1A10Oz, wherein A is Cr, the maximum value for z, zmax, is: zmax=((10×5)+(1×6)+(10×6))÷by 2=116/2=58. The minimum value for z, zmin, in formula I wherein A is Cr is: zmin=((10×3)+(1×4)+(10×2))÷by 2=54/2=27. When the molybdenum compound of formula I is V0.1Mo1A0.1Oz, wherein A is Pb, zmax=((0.1×5)+(1×6)+(0.1×4))÷by 2=6.9/2=3.45. The minimum value for z, zmin, in formula I wherein A is Pb is: zmin=((0.1×3)+(1×4)+(0.1×2))÷by 2=4.5/2=2.25. Thus, for molybdenum compounds of formula I, z ranges from 2.25 to 58.

[0033] For molybdenum compounds of formula II, the highest oxidation states are: Ni3+, Mo6+, Sb5+, Al3+, and W6+ and the lowest oxidation states are: Ni2+, Mo2+, Sb3+, Al3+, and W2+, z′max and z′min can be calculated as shown above for zmax and zmin of formula I.

[0034] For molybdenum compounds of formula III, the highest oxidation states are: V5+, Ni3+, Mo6+, Fe3+, Zn2+, Al3+, Sb5+, Bi5+, W6+, Li1+, Ba2+, Nb5+, and Sn4+, and the lowest oxidation states are: V2+, Ni2+, Mo2+, Fe2+, Zn2+, Al3+, Sb3+, Bi3+, W2+, Li1+, Ba2+, Nb3+, and Sn2+, z″max and z″min can be calculated as shown above for zmax and zmin of formula I. Since there can be mixtures of the C cations, these must be factored into the ranges for z.

[0035] For molybdenum compounds of formula IV, the highest oxidation states are: Co3+, Ni3+, Mo6+, Ba2+, Mn7+, Al3+, Sb5+, Sn4+, and W6+, and the lowest oxidation states are: Co2+, Ni2+, Mo2+, Ba2+, Mn2+, Al3+, Sb3+, Sn2+, and W2+, z′″max and z′″min can be calculated as shown above for zmax and zmin of formula I.

[0036] For molydbenum compounds of formula V, the highest oxidation states are: V5+, Ni3+, Co3+, Mo6+, Fe3+, Ca2+, Mn7+, Sr2+, Eu3+, La3+, Zr4+, Ga3+, Sn4+ and Pb4+, and the lowest oxidation states are: V2+, Ni2+, Co2+, Mo2+, Fe2+, Ca2+, Mn2+, Sr2+, Eu2+, La3+, Zr4+, Ga3+, Sn2+ and Pb2+, z″″max and z″″min can be calculated as shown above for zmax and zmin of formula I.

[0037] The catalysts of the present invention can be either a particular structure (containing a certain ratio of cations) or a combination of structures and thus comprise a mixture of the crystalline oxides of the molybdenum compound of formula I, II, III, IV or V and may further comprise the amorphous phase of the compound.

[0038] The molybdenum compounds of the present invention can be prepared by various methods, for example, by freeze drying, alcohol reflux and gel techniques. Spray roasting, spray drying and coprecipitation could also be employed. Ceramic methods, i.e., solid state techniques could be used but are, in general, less preferred. Certain compounds of formulas I-V are better prepared by one method over another as appreciated by one of ordinary skill in the art.

[0039] The catalyst preparative process is usually conducted at normal atmospheric pressure, but elevated or reduced pressures can be employed. Agitation is not required, but is usually provided to facilitate a homogeneous mix and to facilitate heat transfer.

[0040] One process for the preparation of a catalyst comprising a molybdenum compound of formulas I, II, III, IV, V, VI or VII, as described above, comprises contacting at least one cation containing compound with at least one cation containing compound for each of the other cations of the final molybdenum compound in a solution comprising water to form a resultant solution or colloid; freezing the resultant solution or colloid to form a frozen material, freeze drying the frozen material; and heating the dried frozen material to yield the molybdenum compound of formula I, II, III, IV, V, VI or VII.

[0041] The compound containing a cation of the final molybdenum compound of formula I, II, III, IV, V, VI or VII can be a salt, oxide or the like. The cation containing compounds are contacted with each other upon their addition to the solution comprising water. There is at least one cation containing compound for each of the cations in the molybdenum compound of formula I, II, III, IV, V, VI or VII. Each cation can be contained in a separate cation containing compound or more than one cation can be contained in the same cation containing compound. There can also be more than one cation containing compound for each cation in the final molybdenum compound of formulas I, II, III, IV. V, VI or VII. The cation containing compounds can be anumonium or sodium salts of molybdic acid, vanadic acid or tungstic acid, in addition to compounds containing the A, B, C, D, E cation of choice or other cations present in the final molybdenum compound of formulas I, II, III, IV, V, VI or VII. For example, the oxides or acetylacetonates, chlorides or acetates of Li, Cr, Mn, Mo, Fe, Co, Ni, Ce, W, Zn, Sr, Nb, Eu, Ba, Zr, Al, Ca, Sn, Pb, Sb, Bi, La and Ga can be cation containing compounds. Representative examples of such salts or oxides containing cations of the final molybdenum compound of formula I, II, III, IV, V, VI or VII can be found in Tables 1-6 of the present invention. Normal conmuercially available reagents can be used for the cation containing coinpounds used in the preparation of the molybdenum compound. The highest purity products attainable need not he emploved; however the putity of the reagents must be known in order to calculate the gross amount required. In addition the reagents should not be contaminated with any catalyst poison. The amount of reagent employed should be within plus or minus 5%, preferably within plus or minus 2% of the amount indicated by stoichiometry.

[0042] The cation containing compounds are dissolved in an appropriate solvent to form a solution or fine colloid. The formation of a solutions as opposed to a colloid, is generally preferred for most effective mixing.

[0043] In cases where NH4VO3 is the cation containing compound used, NH4VO3 salt can be dissolved in water prior to adding the other cation. containing compounds by heating water or other appropriate solvents. The additional cation containing compounds can then be added to form a resultant solution or a finely mixed colloid. The resultant solution or colloid is rapidly frozen at liquid nitrogen temperatures. Rapid freezing ensures the cation containing compounds will remain intimately mixed and will not segregate to any significant degree. The frozen material can then be transferred to a freeze drier, such as a Virtis Freeze Drier (Baltimore, Md.) equipped with a Unitop unit. The solution is kept frozen while water vapor is removed by evacuation. In order to prevent melting of the frozen material, the freeze drier can be maintained at a temperature ranging from about 0° C. to about −40° C., preferably between −40° C. to −20° C. with a vacuum of 2-10 millitorr. After at least 24 hours, preferably about 2-4 days, the dried sample can be calcined (heated) in air at a temperature ranging from about 250° C. to about 500° C., preferably about 400° C., for a time sufficient to decompose the cation containing compounds of formula I, II, III, IV, V, VI or VII to form metal oxide phases. This will require heating for a period of about 0.5 hours to about 24 hours.

[0044] Freeze drying methods can produce mixtures of solid cation containing compounds which are nearly as well mixed as their solution counterparts. The method is superior to slower solvent evaporation because homogeneity can be lost during the removal of solvent. In addition, in many cases because the cation containing compounds are well mixed, a lower calcination temperature can be used, and can allow for the synthesis of metal oxides with higher surface areas than typically observed by traditional high temperature ceramic syntheses. Choice of calcination temperature and protocols and atmosphere can also influence the types of phases synthesized.

[0045] Another process for the preparation of a catalyst comprising a molybdenum compound of formula I, II, III, IV, V, VI or VII, as described above, comprises the steps of: mixing a solution comprising at least one cation containing compound for each of the cations in the molybdenum compound of formula I, II, III, IV, V, VI, VI or VII and an alcohol to form a suspension; heating the suspension to reflux; and isolating the molybdenum compound of formula I, II, III, IV, V, VI or VII.

[0046] At least one cation containing compound for each of the cations in the molybdenum compound of formula I, II, III, IV, V, VI or VII are combined with an alcohol or combination of alcohols, such as ethyl alcohol, ethyl alcohol/benzyl alcohol mixtures, 1-propanol, 1-butanol, isobutyl alcohol, 2-methyl-2 propanol, 1-heptanol, neopentyl alcohol, phenol or the like, to form a suspension. The cation containing compounds can be those as described above for the freeze drying process. Mixing or agitation can be supplied via methods known in the art. The preparation can be carried out in a dry box to prevent any hydration. The resulting suspension is next heated to reflux under an inert atmosphere, such as nitrogen, for a time sufficient to ensure a proper solution. After the solution is formed, the solvent can be removed by freeze drying, rotary-evaporation, or a slow drying process after filtering, decanting or the like. The dried material can then be calcined at a temperature ranging from about 250° C. to about 500° C., preferably about 400° C., under air for a time sufficient to form the molybdenum compound of formula I, II, III, IV, V, VI or VII. This can take from about 0.5 hours to about 24 hours.

[0047] A further process for the preparation of a catalyst comprising a molybdenum compound of formula I, II, III, IV, V, VI or VII, as described above, comprises the steps of: contacting at least one cation containing compound for each cation of the molybdenum compound of formula I, II, III, IV, V, VI or VII with at least one cation containing compound for each of the other cations in the molybdenum compound of formula I, II, III, IV, V, VI or VII in a solution comprising water to form a resultant solution or colloid; stirring the resultant solution or colloid until gelation occurs; and drying the gel to yield the molybdenum compound of formula I, II, III, IV, V, VI or VII.

[0048] The cation containing compounds for this gel process can be those as described above for the freeze drying process. Following contact of the cation containing compounds with each other, the resultant solution or colloid is stirred until gelation occurs. In some cases an adjustment of pH is needed to induce gelation. Acid or base can be added depending on the nature of the other ingredients being used in the preparation of the molybdenum compound. Gelation can occur at room temperature at atmospheric pressure. The resulting gel can be dried and then calcined at a temperature ranging trom about 250° C. to about 450° C., preferably 400° C., under air for a time sufficient to thoroughly dry.

[0049] Compounds of formula I, II, III, and V of the present invention are useful as catalysts in the oxidation of C4 hydrocarbons. The present invention provides a process for the oxidation of C4 hydrocarbons to maleic anhydride, comprising: contacting the C4 hydrocarbon with a source of oxygen in the presence of a catalytic amount of a catalyst comprising a molybdenum compound of formula I, II, III or V as defined above. The C4 hydrocarbon is selected from the group consisting of: n-butane, 1-butene, 2-butene and butadiene, and isomers thereof.

[0050] In some instances the catalyst may be useful as a lattice oxygen catalyst in the oxidation of C4 hydrocarbons with the ability to selectively oxidize the C4 hydrocarbon in the absence of gas phase oxygen and thus can be the only source of oxygen.

[0051] The catalyst comprising the molybdenum compound of formula I, II, III or V can be used alone, supported on a catalyst support or impregnated in a carrier material. Typical support carrier materials are well known to those skilled in the art as are methods of preparing supported or impregnated catalysts. Typical materials comprise silica, titania, zirconia, alumina, thoria, silicon carbide and carbon. The catalyst comprising the molybdenum compound described herein can be used as isolated, or in cases where size and shape of the catalyst is dictated by the requirements of the equipment employed in the subsequent use of the catalyst, the catalyst can be processed or fabricated into various size and shape particles before use by grounding, pelletizing, briquetting, tabulating, or shaping in other ways as required.

[0052] A first group of compounds, listed in Table 1 as Examples 1-5, are of formula I: VqMoAyOz, where q varies from 0.1 to 10, y varies from 0.1 to 10, A is at least one cation selected from the group consisting of cations of Cr, Sb, Co, Ce and Pb, and z is calculated as above. The performance of these molybdenum compounds as catalysts in the oxidation of n-butane is shown in Table 1.

[0053] A second group of compounds, listed in Table 2 as Examples 6-9, are of formula II: NiMoxByOz′, where x varies from 0.1 to 10, y varies from 0.1 to 10, B is at least one cation selected from the group consisting of cations of Sb, Al and W and z′ is calculated as above. The performance of these molybdenum compounds as catalysts in the oxidation of n-butane is shown in Table 2.

[0054] A third group of compounds, listed in Table 3 as Examples 10-21, are of formula III: VNiwMoxCy′Oz″, where w varies from 0.1 to 10, x varies from 0.1 to 10, y′ varies from 0 to 10, C is at least one cation selected from the group consisting of cations of Fe, Zn, Al, Sb. Bi, W, Li, Ba, Nb and Sn and z″ is calculated as above. The performance of these molybdenum compounds as catalysts in the oxidation of n-butane is shown in Table 3.

[0055] Another group of compounds, listed in Table 5 as Examples 27-35, are of formula V: VNiwCorMoxEyOz″″, where w varies from 0.1 to 10, r varies from 0.1 to 10, x varies from 0.1 to 10, y varies from 0.1 to 10, E is at least one cation selected from the group consisting of cations of Fe, Ca, Mn, Sr, Eu, La, Zr, Ga, Sn and Pb and z″″ is calculated as above. The performance of these molybdenum compounds as catalysts in the oxidation of n-butane is shown in Table 5.

[0056] The present invention further provides a process for the oxidation of n-butane to maleic anhydride comprising contacting n-butane with a source of oxygen in the presence of a catalytic amount of a catalyst comprising a molybdenum compound of formula IV, as defined above, in a bulk state. In some instances the catalysts comprising a molybdenum compound of formula IV of the present invention are used as catalysts in the bulk state, i.e., not on a support, but as pure compounds. The catalyst comprising the molybdenum compound of formula IV may be the only source of oxygen. The catalytic oxidation can be carried out in a fixed or fluidized bed reactor.

[0057] A group of compounds, listed in Table 4 as Examples 22-26, are of formula IV: CoNiwMoxDyOz′″, where w varies from 0.1 to 10, x varies from 0.1 to 10, y varies from 0.1 to 10, D is at least one cation selected from the group consisting of cations of Ba, Mn, Al, Sb, Sn and W, and z′″ is calculated as above. The performance of these molybdenum compounds as catalysts in the oxidation of n-butane is shown in Table 4.

[0058] The present invention also provides a process for the oxidation of n-butane to maleic anhydride, comprising: contacting n-butane with a source of oxygen in the presence of a catalytic amount of a catalyst comprising a molybdenum compound of formula VI or VII in a crystalline, active phase

V9Mo6O40 VI

V2MoO8 VII

[0059] to yield maleic anhydride. Prepared as herein described, the molybdenum compound of formula VI or VII is formed with little MoO3 by-product. The performance of this molybdenum compound in a crystalline, active phase as a catalyst in oxidation of n-butane is shown in Example 36 of Table 6.

[0060] Comparative Examples 37-41, not of this invention, and the performance of these materials as catalysts in the oxidation of n-butane is listed in Table 7.

[0061] Prior to use in the microreactor, the catalysts described herein are typically formed into a convenient catalyst shape by pelletizing the catalyst at about 30,000 psi (2.07×106 kPa) or less, to form small disks and crushing the pellet through sieves. For fixed bed reactor evaluations, typically a −40, +60 mesh is used (U.S. Sieve Series). Optionally, one could blend the resultant powder with 1-3% of a die lubricant and pellet binder, such as graphite or Sterotex®, a hydrogenated cottonseed oil, commercially available from Capital City Products Company, Columbus. Ohio, before tabletting. For fluidized bed reactor use, the preferred size range is 20 to 150 micrometers.

[0062] Glass and stainless steel are usually employed as the material of construction for the microreactor. This is not critical as long as materials that contaminate the product with catalyst poisons are not employed.

[0063] Although processes of the invention are embodied in the following laboratory scale examples, Applicant notes that the invention can be practiced on an industrial scale by making the necessary engineering and design modifications which are customary in the art.

[0064] Catalytic oxidation using a catalyst comprising a molybdenum compound of formula I, II, III, IV, V, VI or VII can be carried out in a fixed or fluidized bed reactor or recirculating solids reactor. These catalysts can be utilized advantageously with regard to conversion and selectivity in the wide variety of conventional techniques and reactor configurations employed to conduct the vapor phase oxidation of C4 hydrocarbons to maleic anhydride. For example, the conversion can be conducted in a fixed-bed reactor, whereby the catalyst particles are maintained in a fixed position and are contacted with C4 hydrocarbon and a source of oxygen, typically molecular oxygen, both in appropriate amounts, optionally in the presence of one or more inert diluent gases, at a temperature varying between 200° C. and about 450° C., preferably between about 300° C. and about 350° C. The greatest advantages of using the catalyst of this invention are realized when the conversion of C4 hydrocarbon to maleic anhydride is carried out in a recirculating solids reactor, such as that described in U.S. Pat. No. 4,668,802. This patent discloses an improved process for the selective vapor phase oxidation of n-butane to maleic anhydride over a vanadium/phosphorus/oxygen (VPO) catalyst, whereby the amount of oxygen in the feed gas to the VPO catalyst is limited to less than the stoichiometric amount required for the total amount of n-butane converted in the process. The reduced catalyst resulting from the oxidation is separated from the gaseous product stream and is reoxidized, optionally in a separate reaction zone, before being contacted with n-butane.

[0065] The catalysts of the present invention demonstrate good results in activity, conversion and selectivity. Tables 1-6 below show conversion and selectivity after 1 sec and after 3 sec for various catalysts of the present invention and compare these results with those of other catalysts in the art (Table 7).

EXAMPLES

[0066] The reagents for the following examples are commercially available as follows: NH4VO3, Cr2O3, (CH3CO2)7Cr3(OH)2, Ce(SO4)2, Fe(NO3)3-9H2O, NbCl5, Co(NO3)2-6H2O, (CH3CO2)2Mn-4H2O, V2O5 and La(NO3)3-5H2O from Aldrich, Milwaukee, Wis.; NH4VO3, MoO3, Ni(OOCCH3)2-4H2O, NiCl2-6H2O, H2WO4, LiNO3 (anhydrous), SnCl2, (NH4)10W12O41-5H2O, Co(NO3)2-6H2O, and SnCl2 from Alfa, Ward Hill, Mass.; (NH4)6Mo7O24-4H2O), Ni(NO3)-6H2O, Al(NO3)3-9H2O, Bi(NO3)3-5H2O, Ni(NO3)2-6H2O, Co(NO3)2-6H2O, Al(NO3)3-9H2O, Ca(NO3)2-4H2O, and Ni(NO3)2, from Baker, Phillipsburg, N.J.; Pb(NO3)2, NiCl2-6H2O, Pb(NO3)2, and H3PO4 from EM Sciences, Gibbstown, N.J.; (NH4)6Mo7O24-4H2O) from Mallinchkrodt, Erie, Pa.; NH4VO3, Sb(OOCCH3)3, Co(OOCCH3)2, Zr(SO4)2-4H2O and Ga(NO3)3 from J&M, Ward Hill, Mass.; colloidal (Al2O3) from Nyacol, Ashland, Mass.; Zn(NO3)2-6H2O from Fisher, Fairlane, N.J.; and Ba(NO3)2 and EuCl2 from AESAR, Ward Hill, Mass.

[0067] General Procedure for Freeze Drying

[0068] The component salts (indicated in the tables) were added to the indicated amount of water. In cases where NH4VO3 was used, the salt was dissolved in water prior to adding the other components by bringing the solvent to a boil. The additional salts were then added to form the solution or finely mixed colloid/slurry. The resultant solutions/colloids were rapidly frozen in glass dishes (3″ diameter) using liquid nitrogen. The frozen material was then transferred to a Virtis Freeze Drier (Baltimore, Md.) equipped with a Unitop unit. In order to prevent melting of the frozen solid, the Unitop chamber shelves were maintained between −40 to −20° C. with a vacuum of 2-10 millitorr. After at least 24 hours (usually 24 days), the dried sample was calcined (heated) in air to 400° C. for 5 hours to produce the final catalyst product. Prior to microreactor evaluations, the material was pelletized at 20,000 psi and crumbled and screened on −40, +60 mesh screens.

[0069] General Procedure for Alcohol Reflux

[0070] Specific Preparation of V2MoO8

[0071] Vanadium pentoxide. V2O5, 90.94 g 0.500 mol, and molybdic oxide. MoO3, 71.97 g, 0.500 mol were combined in an round bottomed flask equipped with an agitator with 1034 ml of isobutyl alcohol and 95 ml of benzyl. The resulting suspension was heated to reflux under a nitrogen atmosphere for 16 hours. The resulting green suspension was filtered and the isolated product dried and then calcined at 400° C. under air for 5 hours.

[0072] General Procedure for Gel Method

[0073] Specific Preparation of NiMo2.3AlOz′

[0074] 35 ml of water was added to the colloidal alumina (20% by weight). The solid oxide and nickel acetate was added. The mixture was stirred until gelation occurred. The gel was dried then calcined at 400° C. under air for 5 hours.

[0075] Micro-Reactor Evaluation of Butane Oxidation Catalvsts

[0076] The catalysts were pelletized at 1.38×106 kPa into disks and subsequently crushed and sieved through (−40, +60) mesh screens. Approximately 0.9 cc of catalyst were used for each evaluation.

[0077] The catalyst testing facility consisted of six micro-reactors which were connected to a conunon feed source and a conmnon analytical gas chromatograph (GC). Each of the micro-reactors consisted of a 5.0 cm by 0.64 cm stainless steel tube which was immersed in an individual sandbath to maintain isothermal conditions. The feed composition and individual reactor flow rates were metered by commercially available mass flow controllers (Tylan Model FC-260, available from Tylan Corp., Torrance, Calif.). All exit gas lines were heated to 200° C. and connected to a multiport Valco valve for the on-line analysis of products using a commercially available GC (Hewlitt-Packard 5890 Series II, Hewlitt-Packard, Palo Alto, Calif.). A computer program controlled the Valco valve to select a reactor or feed stream to fill the 0.5 ml sample loop for injection in the GC. The GC was used to analyze for butane, maleic anhydride, acetic acid, acrylic acid, other C1 to C4 hydrocarbons, oxygen, carbon monoxide, carbon dioxide, nitrogen and water.

[0078] The standard testing protocol for butane oxidation catalysts was developed to measure maleic anhydride selectivities and yields under hydrocarbon-lean conditions (2% n-butane, 20% oxygen) over a range of butane conversions. Temperature was varied from 350° to 380° to 400° and back to 350° C., with three contact times (nominally 3, 1, and 0.5 s) evaluated at each temperature. The temperature was returned to 350° C. to provide information about the equilibration of the catalyst. The conversion and selectivity of two representative evaluations (at 380° C.) are reported in the tables below.

1TABLE 1380° C., 2.0% Butane/Air1 sec3 secCompositionGram MoleMethod ofConversionSelectivityConversionSelectivityVqMoAyOzExampleSalt UsedWeightSolventSynthesis%%%%V1Mo1Cr1Oz1NH4VO3, 50%116.98250 ml H2Ofreeze-dried416752V2O5 50%181.90Cr2O3151.99(CH3CO2)7Cr3(OH)2602.32(NH4)6Mo7O24-4H2O1235.90MoO3143.94V1Mo1Sb1Oz2NH4VO3116.98250 ml H2Ofreeze-dried757992(NH4)6Mo7O24-4H2O1235.90Sb(OOCCH3)3298.88V1Mo1Co1Oz3NH4VO3116.98250 ml H2Ofreeze-dried703990(NH4)6Mo7O24-4H2O1235.90Co(OOCCH3)2177.023V1Mo1Ce1Oz4NH4VO3116.965250 ml H2Ofreeze-dried189454(NH4)6Mo7O24-4H2O1235.9Ce(SO4)2332.24V1Mo1Pb1Oz5NH4VO3116.965250 ml H2Ofreeze-dried158334(NH4)6MO7O24-4H2O1235.9Pb(NO3)2331.2

[0079]

2

TABLE 2

380° C., 2.0% Butane/Air

1 sec
3 sec

Composition

Gram Mole

Method of
Conversion
Selectivity
Conversion
Selectivity

NiMoxByOz′
Example
Salt Used
Weight
Solvent
Synthesis
%
%
%
%

Ni1Mo2.3Sb1Oz′
6
Sb(OOCCH3)3
298.88
59 cc of
freeze-dried
10
21
26
12

(NH4)6Mo7O24-4H2O
1235.9
30% HCl

Ni(OOCCH3)2-4H2O
248.82

Ni1Mo2.3Al1Oz′
7
Ni(OOCCH3)2-4H2O
248.8212
35 ml H2O
gel
21
6
46
<1

(NH4)6Mo7O24-4H2O
1235.9

colloidal (Al2O3) 20%
101.9613

by wt.

Ni1Mo1.3W1Oz′
8
(NH4)6Mo7O24-4H2O
1235.86
50 ml H2O
freeze-dried
10
13
24
2

NiCl2-6H2O
237.71
70 ml NH4OH

H2WO4
249.86

Ni1Mo1W1.3Oz′
9
(NH4)6Mo7O24-4H2O
1235.86
40 ml H2O
freeze-dried
10
11
35
0

NiCl2-6H2O
237.71
90 ml NH4OH

H2WO4
249.86
25 ml H2O

[0080]

3

TABLE 3

380° C., 2.0% Butane/Air

Ex-

1 sec
3 sec

Composition
am-

Gram Mole

Method of
Conversion
Selectivity
Conversion
Selectivity

VNiwMoxCy′Oz″
ple
Salt Used
Weight
Solvent
Synthesis
%
%
%
%

V1Mo2.3Ni1Oz″
10
NH4VO3
116.98
100 cc H2O
freeze-dried
40
21
71
15

(NH4)6Mo7O24-4H2O
1235.86
100 cc H2O

NiCl2-6H2O
237.71
20 cc HCl

V1Mo2.3Ni1Fe1Oz″
11
NH4VO3
116.98
100 cc H2O
freeze-dried
28
7
60
<1

(NH4)6Mo7O24-4H2O
1235.86
100 cc H2O

Ni(NO3)-6H2O
290.81
20 cc HNO3

Fe(NO3)3-9H2O
404

V1Mo2.3Ni1Zn1Oz″
12
NH4VO3
116.98
100 cc H2O
freeze-dried
53
6
83
<1

(NH4)6Mo7O24-4H2O
1235.86
100 cc H2O

Ni(NO3)-6H2O
290.81
20 cc HNO3

Zn(NO3)2-6H2O
297.47

V1Mo2.3Ni1Al1Oz″
13
NH4VO3
116.98
100 cc H2O
freeze-dried
45
5
79
0

(NH4)6Mo7O24-4H2O
1235.86
100 cc H2O

Ni(NO3)-6H2O
290.81
20 cc HNO3

Al(NO3)3-9H2O
375.13

V1Mo2.3Ni1Sb1Oz″
14
NH4VO3
116.98
100 cc H2O
freeze-dried
39
10
69
5

(NH4)6Mo7O24-4H2O
1235.86
100 cc H2O

Ni(NO3)-6H2O
290.81
15 cc HNO3

Sb(OOCCH3)3
298.88
50 cc HCl

V1Mo2.3Ni1Bi1Oz″
15
NH4VO3
116.98
100 cc H2O
freeze-dried
20
15
50
7

(NH4)6Mo7O24-H2O
1235.86
100 cc H2O

Ni(NO3)-6H2O
290.81
20 cc HNO3

Bi(NO3)3-5H2O
485.07
30 cc HNO3

V1Mo2.3Ni1W1Oz″
16
NH4VO3
116.98
100 cc H2O
freeze-dried
30
10
71
2

(NH4)6Mo7O24-4H2O
1235.86
100 cc H2O

Ni(NO3)-6H2O
290.81
20 cc HNO3

H2WO4
249.86

V1Mo2.3Ni1Li1Oz″
17
NH4VO3
116.98
100 ml H2O
freeze-dried
11
17
20
11

(NH4)6Mo7O24-4H2O
1235.86

NiCl2-6H2O
237.71
15 ml HCl

LiNO3 (anhydrous)
68.9459

V1Mo2.3Ni1Ba1Oz″
18
NH4VO3
116.98
100 ml H2O
freeze-dried
35
10
66
2

(NH4)6Mo7O24-4H2O
1235.86
100 ml H2O

Ni(NO3)-6H2O
290.81
20 ml HNO3

Ba(NO3)2
261.3398

V1Mo2.3Ni1Nb1Fe1Oz″
19
NH4VO3
116.98
100 cc H2O
freeze-dried
30
3
60
<1

(NH4)6Mo7O24-4H2O
1235.86
50 cc H2O

NiCl2-6H2O
237.71
20 cc HCl

NbCl5
270.71
70 cc HCl

Fe(NO3)3-9H2O
404

V1Mo2.3Ni1Nb1Sn1Oz″
20
NH4VO3
116.98
100 ml H2O
freeze-dried
40
12
68
3

(NH4)6Mo7O24-4H2O
1235.86
70 ml H2O

NiCl2-6H2O
237.71
20 ml HCl

NbCl5
270.17
20 ml HCl

SnCl2
189.61
50 ml H2O

V1Mo2.3Ni1W1Sn1Oz″
21
(NH4)10W12O41-
3132.64
140 ml
freeze-dried
25
10
47
3

5H2O
1235.86
NH4OH

(NH4)5Mo7O24-4H2O
116.98

NH4VO3
290.81
50 ml H2O

Ni(NO3)2-5H2O
189.61

SnCl2

5 ml HCl

[0081]

4

TABLE 4

380° C., 2.0% Butane/Air

1 sec
3 sec

Composition

Gram Mole

Method of
Conversion
Selectivity
Conversion
Selectivity

CoNiwMoxDyOz″
Example
Salt Used
Weight
Solvent
Synthesis
%
%
%
%

Co0.5Ni0.5Mo3
22
Co(NO3)2-6H2O
291.03
20 ml H2O
freeze-dried
12.5
32
29
27

Sn0.5Oz′″

SnCl2
189.61

(NH4)6Mo7O24-4H2O
1235.86
50 ml H2O

NiCl2-6H2O
237.71
20 ml HNO3

Mo3Co0.5Ni0.5
23
Co(NO3)2-H2O
291.03
20 ml H2O
freeze-dried
1.3
4
2.3
11

Mn1Oz′″

(CH3CO2)2Mn-4H2O
245.09

(NH4)6Mo7O24-4H2O
1235.86
30 ml H2O

NiCl2-6H2O
237.71
20 ml H2O

Mo3Co0.5Ni0.5
24
Co(NO3)2-6H2O
291.03
20 ml H2O
freeze-dried
0.8
16
2.1
18

Ba1Oz′″

Ba(NO3)2
261.34

(NH4)6Mo7O24-4H2O
1235.86
80 ml H2O

NiCl2-6H2O
237.71
20 ml H2O

Mo3Co0.5Ni0.5
25
Co(NO3)2-6H2O
291.03
20 ml H2O
freeze-dried
3.9
15
10.5
8

Al1Oz′″

Al(NO3)3-9H2O
375.13

(NH4)6Mo7O24-4H2O
1235.86
150 ml H2O

NiCl2-6H2O
237.71
20 ml H2O

Mo3Co0.5Ni0.5
26
Co(NO3)2-6H2O
291.03
40 ml H2O
freeze-dried
4.2
27
14.2
15

W1Oz′″

(NH4)10W12O41-5H2O
3132.64

(NH4)6Mo7O24-4H2O
1235.86
50 ml H2O

NiCl2-6H2O
237.71
10 ml H2O

[0082]

5

TABLE 5

380° C., 2.0% Butane/Air

Ex-

1 sec
3 sec

Composition
am-

Gram Mole

Method of
Conversion
Selectivity
Conversion
Selectivity

VNiwCo1MoxEyO2′″
ple
Salt Used
Weight
Solvent
Synthesis
%
%
%
%

V1Mo2.3Ni0.5Co0.5
27
NH4VO3
116.98
50 ml H2O
freeze-dried
15
13
32
7

Fe1Oz″″

(NH4)6Mo7O24-4H2O
1235.86
20 ml H2O

Co(OOCCH3)2
177.02
20 ml HCl

Ni(NO3)2-6H2O
290.81

Fe(NO3)3-9H2O
404
20 ml H2O

V1Mo2.3Ni0.5Co0.5
28
NH4VO3
116.98
50 ml H2O
freeze-dried
14
10
34
4

Ca1Oz″″

(NH4)6Mo7O24-4H2O
1235.86

Co(OOCCH3)2
177.02
20 ml HCl

Ni(NO3)2-6H2O
290.81
5 ml HCl

Ca(NO3)2-4H2O
236.15

V1Mo2.3Co0.5Ni0.5
29
NH4VO3
116.98
50 ml H2O
freeze-dried
12.5
2.5
29.2
1

Mn1Oz″″

(NH4)6Mo7O24-4H2O
1235.86
20 ml H2O

Co(OOCCH3)2
177.02
20 ml HCl

Ni(NO3)2-6H2O
290.81

(CH3CO2)2Mn-4H2O
245.09
10 ml H2O

V1Mo2.3Co0.5Ni0.5
30
NH4VO3
116.98
50 ml H2O
freeze-dried
21
17
47
10

Sr1Oz″″

(NH4)6Mo7O24-4H2O
1235.86
20 ml HCl

Co(OOCCH3)2
177.02
10 ml H2O

Ni(NO3)2-6H2O
290.81

Sr(NO3)2
211.63

V1Mo2.3Co0.5Ni0.5
31
NH4VO3
116.98
50 ml H2O
freeze-dried
24
7.5
54
2

Eu1Oz″″

(NH4)6Mo7O24-4H2O
1235.86

Co(OOCCH3)2
177.02
20 ml HCl

Ni(NO3)2-6H2O
290.81

EuCl2
222.87
10 ml H2O

V1Mo2.3Co0.5Ni0.5
32
NH4VO3
116.98
50 ml H2O
freeze-dried
17
10
36
5

La1Oz″″

(NH4)6Mo7O24-4H2O
1235.86

Co(OOCCH3)2
177.02
20 ml HCl

Ni(NO3)2-6H2O
290.81

La(NO3)3-5H2O
415.01
10 ml H2O

V1Mo2.3Co0.5Ni0.5
33
NH4VO3
116.98
50 ml H2O
freeze-dried
20
17.5
46
12

Zr1Oz″″

(NH4)6Mo7O24-4H2O
1235.86

Co(OOCCH3)2
177.02
20 ml HCl

Ni(NO3)2-6H2O
290.81

Zr(SO4)2-4H2O
355.32
40 ml H2O

V1Mo2.3Co0.5Ni0.5
34
NH4VO3
116.98
50 ml H2O
freeze-dried
18
16.5
43
11

Ga1Oz″″

(NH4)6Mo7O24-4H2O
1235.86

Co(OOCCH3)2
177.02
20 ml HCl

Ni(NO3)2-6H2O
290.81

Ga(NO3)3
255.74

V1Mo2.3Co0.5Ni0.5
35
NH4VO3
116.98
50 ml H2O
freeze-dried
22
20
47
14

Pb1Oz″″

(NH4)6Mo7O24-4H2O
1235.86

(with dry ice

Co(OOCCH3)2
177.02
20 ml HCl
and acetone)

Ni(NO3)2-6H2O
290.81

Pb(NO3)2
331.2
100 ml HCl

86 ml NH4OH

[0083]

6

TABLE 6

380° C., 2.0% Butane/Air

1 sec
3 sec

Gram Mole

Method of
Conversion
Selectivity
Conversion
Selectivity

Composition
Example
Salt Used
Weight
Solvent
Synthesis
%
%
%
%

V2Mo1Ox
36
V2O5
90.94 g
181.88
1034 ml isobutyl alcohol
Alcohol
60
10
90
0

MoO3
71.97 g
143.94
95 ml benzyl alcohol
reflux

[0084]

7

TABLE 7

380° C., 2.0% Butane/Air

1 sec
3 sec

Comp.

Gram Mole

Method of
Conversion
Selectivity
Conversion
Selectivity

Composition
Example
Salt Used
Weight
Solvent
Synthesis
%
%
%
%

MoO3
37
(NH4)6Mo7O24-4H2O
1235.9

freeze-dried
11
<1

VPO
38
NH4VO3
116.965

freeze-dried
8
20

H3PO4
97.97

Ni1W2.3O1
39
H2WO4
249.86
50 ml H2O
freeze-dried
2.5
0
9
0

NiCl2-6H2O
237.71
180 ml NH4OH

Ni1Mo2.3P1O1
40
Ni(NO3)2
290.8
50 ml H2O
freeze-dried
6
12

(NH4)6Mo7O24-4H2O
1235.86
100 ml H2O

H3PO4
98

V2O5
41

freeze-dried
80
<1

	Number	Date	Country
Parent	09878645	Jun 2001	US
Child	10308900	Dec 2002	US
Parent	09269211	Mar 1999	US
Child	10308900	Dec 2002	US

Molybdenum based oxidation catalysts

Information

Publication Number

Date Filed

Date Published

Inventors

CPC

US Classifications

International Classifications

Abstract

Description

Claims

Provisional Applications (1)

Divisions (2)