WO2000072962A1

WO2000072962A1 - Process for improving activity and selectivity of ammoxidation catalyst

Info

Publication number: WO2000072962A1
Application number: PCT/US2000/014529
Authority: WO
Inventors: Mary Jennifer Young
Original assignee: Solutia Inc.
Priority date: 1999-05-27
Filing date: 2000-05-26
Publication date: 2000-12-07
Also published as: AU5165600A

Abstract

The present invention provides an improved process for producing a catalyst containing the elements iron, antimony, uranium, bismuth and molybdenum in a catalytically active oxidized state, which is useful in the preparation of unsaturated nitriles by ammoxidation of olefins and in the oxidation of olefins to the corresponding unsaturated aldehydes. One embodiment of the process comprises the steps of: (a) forming a mixed oxides component that comprises oxides of antimony, bismuth, iron, and uranium; (b) combining the mixed oxides component with a molybdate; (c) forming the mixed oxides component into particles; (d) heating the particles at a temperature between about 40 °C and about 120 °C for at least about 1 hour; (e) drying the particles; and (f) calcining the particles.

Description

PROCESS FOR IMPROVING ACTIVITY AND SELECTIVITY OF AMMOXIDATION CATALYST

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to a process for producing oxidation and/or ammoxidation catalysts containing the elements iron, antimony, uranium, bismuth, and molybdenum in a catalytically active oxidized state. Description of Related Art It is well known that olefins can be oxidized to oxygenated hydrocarbons such as unsaturated aldehydes and acids, for example, acrolein and methacrolein, and acrylic acid and methacrylic acid. Olefins can also be ammoxidized to unsaturated nitriles such as acrylonitrile and methacrylonitrile. Acrylonitrile is a valuable monomer used to produce a variety of polymeric products. Various catalytic processes are known for the oxidation and/or ammoxidation of olefins. Such processes commonly react an olefin or an olefin-ammonia mixture with oxygen in the vapor phase in the presence of a catalyst. For the production of acrolein and acrylonitrile, propylene is the generally used olefin reactant, and for the production of methacrolein and methacrylonitrile, isobutylene is the generally used olefin reactant. Catalysts for oxidation and ammoxidation have been previously described. For example U.S. Patent No. 4,487,850, the disclosure of which is incorporated herein by reference, discloses catalysts containing the elements iron, antimony, uranium, bismuth, and molybdenum in a catalytically active oxidized state. Although the yield and selectivity of the above catalyst and other catalysts are generally satisfactory, the commercial utility of a catalyst system is highly dependent upon the cost of the system, the conversion of the reactant(s), the yield of the desired product(s), and the stability of the catalyst during operation. In many cases, a reduction in the cost of a catalyst system on the order of a few cents per pound or a small percent increase in the yield of the desired product represents a tremendous commercial advantage. An increasingly higher yield and selectivity of the conversion of reactants is desired to minimize purification of the product and recycle streams, while an increase in activity of the catalyst would decrease the required amount of catalyst to generate a desired conversion. Therefore, a need exits for improved catalysts and improved processes for making those catalysts. Such catalysts and processes are disclosed and claimed herein.

SUMMARY OF THE INVENTION The present invention provides an improved process for producing a catalyst containing the elements iron, antimony, uranium, bismuth and molybdenum in a catalytically active oxidized state useful in the preparation of unsaturated nitriles by ammoxidation of olefins and in the oxidation of olefins to the corresponding unsaturated aldehydes. One embodiment of the present invention is a process for producing a catalyst, comprising the steps of:

(a) forming a mixed oxides component that comprises oxides of antimony, bismuth, iron, and uranium;

(b) combining the mixed oxides component with a molybdate; (c) forming the mixed oxides component into particles, which may be part of a slurry;

(d) heating the particles at a temperature between about 40°C and about 120°C for at least about 1 hour;

(e) drying the particles; and (f) calcining the particles.

The temperature used for heating in step (c) preferably is at least about 100°C, and the duration of the heating preferably is at least about 4 hours. In one especially preferred embodiment, the heating in step (c) is done at between about 100°C and about 105°C for about 4 hours. The mixed oxides component can suitably be formed into particles in step (b) by milling the mixed oxides component in the form of an aqueous slurry.

Another embodiment of the present invention is a process for producing a catalyst, which comprises the steps of:

(a) preparing a hydrated mixed oxides component containing antimony, uranium, iron, and bismuth by the steps of: (i) forming a mixed oxides mixture that comprises oxides or nitrates of bismuth and uranium and an oxide of antimony in nitric acid;

(ii) heating the mixture of step (i) at a temperature and for a time sufficient to induce formation of crystalline oxides of antimony; (iii) adding an aqueous solution of ferric nitrate to the mixed oxides mixture;

(iv) adjusting the pH of the mixed oxides mixture to a level between about 7 - 9, most preferably about 8, thereby forming a hydrated mixed oxides precipitate in an aqueous phase; (v) separating the hydrated mixed oxides precipitate from the aqueous phase, thereby forming a hydrated mixed oxides component;

(b) combining the hydrated mixed oxides component with a molybdate;

(c) forming the combination of step (b) into particles, which may be part of a slurry; (d) heating the particles at a temperature between about 40°C and about 120°C for at least about 1 hour;

(e) drying the particles; and

(f) calcining the particles.

This process can further comprise the step of adding a support material comprising from about 10% to about 90% by weight of the total weight of the catalyst prior to the heating of step (d). Preferably in this embodiment, the support material is added prior to step (c). The support material most preferably comprises from about 35% to about 65%> by weight of the total weight of the catalyst. A suitable support material is silica. Preferably the drying in step (e) of the embodiment of the invention is done by spray drying a slurry.

In a more specific embodiment of the invention, the process for producing the catalyst comprises:

(a) preparing a hydrated mixed oxides component containing antimony, uranium, iron, and bismuth by the steps of: (i) forming a mixture of oxides or nitrates of bismuth and uranium and an oxide of antimony in nitric acid; (ii) heating the mixed oxides mixture at a temperature and for a time sufficient to induce formation of crystalline oxides of antimony;

(iii) adding an aqueous solution of ferric nitrate to the mixed oxides mixture; (iv) adjusting the pH of the mixed oxides mixture to about 8, thereby forming a hydrated mixed oxide precipitate in an aqueous phase;

(v) separating the hydrated mixed oxide mixture from the aqueous phase;

(b) forming an aqueous slurry of the hydrated mixed oxides component;

(c) adjusting the pH of the hydrated mixed oxides component slurry to about 9; (d) adding a molybdate to the hydrated mixed oxides component slurry, thereby forming a combined oxides mixture slurry;

(e) adjusting the pH of the combined oxides mixture slurry to about 8-9;

(f) heating the combined oxides mixture at between 100 °C and 120 °C for at least about 4 hours; (g) forming the combined oxides mixture into dry particles; and

(h) calcining the dry particles to form the catalyst.

Other aspects of the present invention are (1) the catalysts prepared by any of the above-described processes, (2) processes for the oxidation of an olefin to a corresponding unsaturated aldehyde or acid, comprising contacting the olefin with oxygen in the presence of a catalyst prepared by any of the above-described processes, and (3) processes for the ammoxidation of an olefin to a corresponding unsaturated nitrile comprising contacting the olefin with oxygen and ammonia in the presence of a catalyst prepared by any of the above-described processes.

The catalysts produced by the present invention exhibit improved characteristics in oxidation and ammoxidation processes, including yield and selectivity, as compared to prior catalysts. Therefore, the present invention makes the production of the end products of the oxidation and ammoxidation processes more economical.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS The catalysts produced by the processes of the present invention contain antimony, uranium, iron, bismuth, and molybdenum in a catalytically active oxidized state useful for the oxidation and/or ammoxidation of olefins. These catalysts are represented by the empirical formula:

Sb_aU_bFe_cBi_dMo_eO_f where a is 1 to 10, b is 0.1 to 5, c is 0.1 to 5, d is 0.001 to 0.1, e is 0.001 to 0.2 and f is a number taken to satisfy the valence requirements of Sb, U, Fe, Bi and Mo in the oxidation states in which they exist in the catalyst. In more preferred embodiments, a is 1 to 5, b is 0.1 to 1, c is 0.1 to 1, d is 0.01 to 0.05 and e is 0.01 to 0.1.

The catalysts can be prepared in the following manner. A hydrated mixed oxides component containing antimony, uranium, iron, and bismuth is intimately mixed with a ferric molybdate or ammonium molybdate component (the preparation of each of these components is described below). The mixing of the components is accomplished in an aqueous slurry at a pH of about 9. Specifically, the hydrated mixed oxides component is first slurried in water at the prescribed pH. A catalyst support may be added, if desired, along with the hydrated mixed oxides component. In either case, whether a support is present or absent, a molybdate is then added to the slurry. The resultant slurry is ball milled for about 18 hours or until the solid particles are reduced to a size less than 10 microns in diameter. Thereafter, the pH of the slurry is adjusted, if necessary to about 8- 9.

The mixed slurry is then heat-treated at a temperature between about 40 °C and 120 °C, preferably at a temperature of about 100 °C. The slurry is suitably heat-treated for at least 1 hour, preferably between about 1 hour and about 6 hours, more preferably for about 4 hours. The slurry may be mixed during the heat-treating process to aid in heat transfer and assure a well-mixed slurry. Other combinations of heating times and temperatures can be used if they improve the activity and/or selectivity of the catalyst. The heat-treated slurry is then dried to remove the bulk (e.g., at least about 70-

75% by weight) of the aqueous phase. The concentrated slurry contains a certain amount of water and it is desirable to remove this water by some form of drying process to form a dry catalyst precursor. This can take the form of a simple oven drying process in which the water-containing solid phase is subjected to a temperature that is sufficiently high to vaporize the water and completely dry the solid phase. An alternate drying process which may be employed is the so-called spray-drying process. In this process, which is preferred for use in the present invention, water- containing solid phase particles are sprayed into contact with hot gas (usually air) so as to vaporize the water. The drying is controlled by the temperature of the gas and the distance the particles travel in contact with the gas. It is generally desirable to adjust these parameters to avoid too rapid drying as this results in a tendency to form dried skins on the partially dried particles of the solid phase which are subsequently ruptured as water occluded within the particles vaporizes and attempts to escape. At the same time, it is desirable to provide the catalyst in a form having as little occluded water as possible. Therefore, where a fluidized bed reactor is to be used and microspheroidal particles are desired, it is advisable to choose the conditions of spray-drying with a view to achieving substantially complete drying without particle rupture.

Following the drying operation, the catalyst precursor is calcined to form the active catalyst. The calcination is usually conducted in air at essentially atmospheric pressure and at a temperature of about 500 °C to about 1150 °C, preferably from about 750 °C to about 900 °C. The time to complete the calcination can vary and will depend upon the temperature employed. In general the time can be anything up to 24 hours, but for most purposes, a time period from about 1 hour to about 3 hours at the designated temperatures is sufficient. The catalyst can be employed without a support and will display excellent activity. However, in some applications, it may be advantageous to include in the catalyst a support material which functions by providing a large surface area for the catalyst and by creating a harder and more durable catalyst for use in the highly abrasive environment of a fluidized bed reactor. This support material can be any of those commonly proposed for such use, such as silica, zirconia, alumina, titania, antimony pentoxide sol, or other oxide substrates. From the point of view of availability, cost, and performance, silica is usually a satisfactory support material and is preferably in the form of silica sol for easy dispersion.

The proportions in which the components of the supported catalysts are present can vary widely, but it is usually preferred that the support provides from about 10%> to about 90% and more preferably about 35% to about 65% by weight of the total combined weight of the catalyst and the support. To incorporate a support into the catalyst, the support material is preferably slurried along with the hydrated mixed oxide component in water at a pH of 9 while maintaining slurry fluidity.

As previously noted, the hydrated mixed oxides component contains antimony, uranium, iron, and bismuth. It is prepared by mixing the oxides or nitrates of bismuth and uranium and an oxide of antimony (usually antimony trioxide) with nitric acid. The antimony trioxide is heated in the nitric acid. By so doing, the initially amorphous antimony trioxide is converted to crystalline oxides of antimony. In addition, at least a portion of the antimony trioxide is converted to higher oxidation states such as antimony tetroxide and antimony pentoxide.

The time required to induce the formation of the desired crystalline oxides of antimony can vary and will depend, at least in part, on the temperature employed. Generally, a time period of about 2 hours to about 6 hours at temperatures from about 90°C to about 110 °C, preferably at least 100 °C is sufficient. After the heating period is completed, an aqueous solution of ferric nitrate

[Fe(NO₃), ' 9H₂O] is added to the mixed oxides mixture, optionally having been cooled to ambient temperatures prior to the ferric nitrate addition. The pH of the resultant mixture is adjusted to between about 7-9, preferably to about 8, using aqueous ammonia. The resulting hydrated mixed oxides precipitate is then separated from the aqueous phase and thoroughly washed with slightly alkaline water (pH 8) to remove substantially all occluded impurities, most notably ammonium nitrate.

The molybdate may be introduced as any compound which does not interfere with catalysis or neutralize the catalyst. Ferric molybdate and ammonium molybdate have been successfully employed to introduce the molybdate. Ammonium molybdate is preferred, being the simplest to prepare (from molybdenum trioxide and aqueous ammonia). Ferric molybdate may be prepared by combining stoichiometric amounts of aqueous solutions of ammonium molybdate and ferric nitrate.

The catalyst preparation process of this invention yields an improved catalyst that exhibits exceptional utility in the production of nitriles from olefins. Olefins suitable for use in this invention include those characterized by having at least one methyl group attached to a trigonal carbon atom. Nonlimiting representatives of such olefins include propylene, isobutylene, 2-methyl-l-pentene, 1 ,4-hexadiene, and the like. Of particular importance is the production of acrylonitrile from propylene, although it should be understood that the described catalyst is also useful for ammoxidation of other suitable olefins and for oxidation of such olefins to aldehydes and acids. In the most frequently used ammoxidation processes, a mixture of olefin, ammonia, and oxygen (or air) is fed into a reactor and through a bed of catalyst particles at elevated temperatures. Such temperatures are usually in the range of about 400° C to about 550° C, and preferably about 425° C to about 500° C, and the pressure is from about 1 atmosphere to about 6 atmospheres (100 kPa to about 600 kPa). The ammonia and olefin are required stoichiometrically in equimolar amounts, but it is usually necessary to operate with a molar ratio of ammonia to olefin in excess of 1 to reduce the incidence of side reactions. Likewise, the stoichiometric oxygen requirement is 1.5 times the molar amount of olefin. The feed mixture is commonly introduced into the catalyst bed at a W/F (defined as the weight of the catalyst in grams divided by the flow of reactant stream in ml/sec at standard temperature and pressure) in the range of about 2 g- sec/ml to about 15 g-sec/ml, preferably from about 4 g-sec/ml to about 10 g-sec/ml.

The ammoxidation reaction is exothermic and for convenience in heat distribution and removal, the catalyst bed is desirably fluidized. However, fixed catalyst beds may also be employed with alternative heat removal means such as cooling coils within the bed.

The catalyst as prepared by the process of this invention is particularly well adapted for use in such a process in that improved yields of and selectivities to the desired product(s) are experienced due to the unique and novel preparation procedures employed herein. The following examples illustrating the best presently-known methods of practicing this invention are described in order to facilitate a clear understanding of the invention. It should be understood, however, that these examples, while indicating preferred embodiments, are given by way of illustration only and are not to be construed as limiting the invention since various changes and modifications within the spirit of the invention will become apparent to those skilled in the art from this description. As used herein, the following terms are defined in the following manner:

1. "WTF" is defined as the weight of the catalyst in grams divided by the flow rate of the reactant stream in ml/sec measured at STP, the units being g-sec/ml.

2. "Propylene (C₃H₆ ) conversion" is defined as: [(mols C₃H₆ in feed - mols C₃H₆ in effluent)/(mols C₃H₆ in feed)] x 100

3. "Acrylonitrile (AN) selectivity" is defined as: [(mols AN in effluent)/(mols C₃H₆ converted)] x 100

4. "Acrylonitrile (AN) yield" is defined as: [(mols AN formed)/(mols C₃H₆ feed)] x 100 In the following paragraphs, the catalysts of the examples were evaluated in a fluidized bed reaction vessel having an inside diameter of 41 mm to determine acrylonitrile selectivity and yield and propylene conversion. The amount of catalyst used in the evaluation ranged between 295 grams and 460 grams and was adjusted in order to get a propylene conversion between 98.5 - 99.2%>. A reactant mixture of 7.7 mole percent propylene (C₃H₆), 8.4 mole percent ammonia (NH₃), and the balance air, was passed upward through the catalyst bed at a rate of 0.35 ft/sec. The temperature was maintained at 460°C and the pressure at 207 kPa (30 psia).

Example 1

Two catalysts of the composition: Sb, _g6U₀₃₃Fe₀₆₉Bi₀₀₂Mo₀₀₄O_r45% SiO₂ were prepared in the following manner to illustrate the improved heat-treated catalysts.

A) Formation of hydrated mixed oxides (Sb, _g6U₀₃₃Fe₀₆₆Bi₀₀₂O_rxH₂0). Bismuth trioxide, Bi₂O₃ (10.6g, 0.023mol) was added with stirring to 975g of 70%> nitric acid in an 11 -liter stainless steel reactor. The solution was heated to about 60^°C before 210.3g (0.25mol) of uranium octoxide U₃O₈ was added within five to ten minutes. The generation of nitrogen oxides was contained to a minimum during the addition of U₃O_g. The mixture was then held at 90°C for 30 minutes. The solution was diluted with 300mL of water followed by the addition of 612.0g (2.1 mole) of antimony trioxide Sb₂O₃. The resulting mixture was heated to 100-105°C and maintained at this temperature for a period of time sufficient to convert the amorphous antimony trioxide to crystalline oxides of antimony, usually four hours. After the designated hold time a solution of 606g (1.5 mole) of ferric nitrate nonahydrate [Fe(NO₃)₃-9H₂O] in 5.6 liters of water was added to the mixture and the mixture was allowed to cool to room temperature. After mixing for one hour, the pH of the mixture was adjusted to 8.0 using about 1900ml of a 14%> by weight solution of aqueous ammonia (prepared by mixing equal volumes of concentrated aqueous ammonia and water) causing the precipitation of the hydrated mixed oxides. The precipitate was removed from the mother liquor using a filter press and the wet cake of the precipitate was reslurried in 20 liters of water and filtered again to remove the ammonium nitrate formed during precipitation as well as occluded impurities.

B) Preparation of ferric molybdate (Fe₂(MoO₄)₃). A solution of 12.9g (0.09 mole) MoO₃, 15mL of concentrated NH₄OH and 50mL water was prepared and then added drop wise to a flask containing 24.3g (0.06 mole) of Fe(NO₃)₃-9H₂O and 200mL of water. This mixture was heated for 1-2 hours at a temperature between 95-100°C. The precipitate formed changed from the initial light brown color to a bright yellow color. The aqueous phase was decanted from the precipitate, the precipitate was then reslurried in 500mL of water, filtered and washed again with another 500mL water.

C) Formation of Catalyst 1 A. The catalyst cake from step (A) and the ferric molybdate cake from step (B) were mixed in a ball mill jar. To this was added 2127g of SiO₂ suspension (40%> by weight), 40mL concentrated NH₄OH and 200mL water and the mixture was milled for 20 hours. The milled slurry was divided into two equal portions. One portion of the slurry, portion "1 A", was spray dried at a temperature of 83-85°C. The dried particles were then calcined at 850°C for one hour to give catalyst 1 A.

D) Formation of Catalyst IB. The other portion of the milled slurry from step (c), portion "IB", was transferred to a glass reactor, where it was stirred and heated to and kept at 102°C for 4 hours. The slurry was allowed to cool to room temperature before it was transferred to a ball mill jar and milled for 20 hours. The milled slurry was then spray dried and calcined as in step (C) to give Catalyst IB. E) Sample Performance

Table 1

Catalyst 1A Catalyst IB

Lab Reactor Performance

% Yield CO 5.02 5.13

% Yield CO₂ 7.22 7.37

% Yield HCN 7.40 7.02

% Yield AN 77.43 78.63

%> C₃H₆ Conversion 98.31 98.85

% Selectivity AN 79.07 79.55

Catalyst Reactor Charge, g 368 350

Physical Characterization

Surface Area, m²/g 55.476 57.216

Pore Volume, cm³/g 0.318 0.350

Average Pore Size, A 216.97 229.19

Example 2

Two catalysts of the composition Sb₂₂₅U₀₅₀Fe_{0 50}Bi₀₀₂ Mo₀₀₄O_r50%SiO₂ were prepared in the following manner to illustrate the improved heat-treated catalysts. A) Formation of hydrated mixed oxides (Sb₂₂₅U₀₅₀Fe₀₅₀Bi₀₀₂O_rxH₂0). Bismuth trioxide (10.08g, 0.022mol) was added to 1098g of 70% HNO₃ in a 11 -liter stainless steel reactor. The mixture was heated to 60°C before 302.4g (0.359mol) of U₃O₈ was added over a period of 5 to 10 minutes. The temperature of the mixture was raised to 90^°C and maintained between 90-95°C. for about 20 minutes to dissolve all of the U₃O₈. Nitrogen oxides were generated during this time period. Water (540mL) was then added to the reactor followed by 708g (2.429mol) of Sb₂O₃. The mixture was then heated to and kept between 102-104°C for 2 hours. The mixture was cooled to room temperature with the addition of a solution of 436.2g (1.08mol) of Fe(NO₃)₃»9H₂0 and 5.4 liters of water. After mixing for 1 hour the hydrated mixed oxides were precipitated from solution to a pH of 5 with a 14% by weight solution of NH₄OH (prepared by mixing equal volumes of concentrated NH₄OH and water). After a 15-minute hold at pH 5, additional NH₄OH was added until the slurry pH was brought to 8.0. The precipitate was filtered from the slurry using a filter press. The cake was reslurried with 20 liters of water and filtered again to remove the ammonium nitrate. B) Formation of Catalyst 2A. The filter cake obtained from step (A) was mixed with 3010g of SiO₂ sol (40% by weight) in a ball mill. After milling for 30 minutes, an ammonium heptamolybdate solution prepared by dissolving 12.5g (0.087mol) of MoO₃ in 200mL of water and 40mL concentrated NH₄OH was added to the slurry. The pH of the slurry was adjusted to approximately 9.0 with additional concentrated water before milling for 20 hours. The milled slurry was then divided into equal portions. One portion, portion "2A", was spray dried at a temperature of 83-85°C. The dried particles were then calcined in air at 400 C for 1 hour and then at 850°C. for 1 hour and 15 minutes to give catalyst 2A. C) Formation of Catalyst 2B. The other portion of the milled slurry from step

(B), portion "2B", was heated in a glass reactor with mixing for 4 hours at 102°C. After cooling the mixture to room temperature, it was then transferred to a ball mill and milled for 20 hours. The milled slurry was spray dried and calcined as in step (B) to give Catalyst 2B. D) Sample Performance

Table 2

Catalyst 2A Catalyst 2B

Lab Reactor Performance

% Yield CO 4.42 4.05

% Yield CO₂ 6.65 5.93

% Yield HCN 6.49 6.23

% Yield AN 78.93 80.48

%>C₃H₆ Conversion 98.84 98.97

% Selectivity AN 79.86 81.32

Catalyst Charge, g 350g 310g

Physical Characterization

Surface Area, m²/g 66.806 67.552

Pore Volume, cm³/g 0.348 0.395

Average Pore Size, A 203.89 228.86

Example 3 Two catalysts of the composition: Sb, ₈₆U₀₃₃ Fe₀₆₆Bi₀₀₂Mo₀₀₄O_r60%SiO₂ were prepared in the following manner to illustrate the improved heat-treated catalyst: A) Hydrated Mixed Oxides (Sb, ₈₆U₀₃₃ Fe₀₆₆Bi₀₀₂O_rxH₂O) - Bismuth oxide, Bi₂O₃ (10.6g, 0.023 mole) was added with stirring to 975g of 70% concentrated nitric acid in an 11 -liter stainless steel reactor. The solution was heated to about 60°C before 210.3g (0.25 mole) of uranium octoxide U₃O₈ was added within five to ten minutes. The mixture was then heated to and kept at 90°C for 30 minutes. The solution was diluted with 300 mL of water followed by the addition of 612. Og (2.1 mil) of antimony trioxide Sb₂O₃. The resulting mixture was heated to 100-105°C and maintained at this temperature for 4 hours. After the hold time, a solution of 606g (1.5 mole) of ferric nitrate nonahydrate [Fe(NO₃)₃*9H₂O] in 5.6 liters of water was added to the mixture and the mixture was allowed to cool to room temperature with mixing. The pH of the mixture was then adjusted to 8.0 with the addition of about 1900 mL of a 14% by weight solution of aqueous ammonia (prepared by mixing equal volumes of concentrated aqueous ammonia and water) causing the precipitation of the hydrated mixed oxides. The precipitate was removed from the mother liquor using the filter press and the wet cake of the precipitate was reslurried in 20 liters of water and filtered again to remove the ammonium nitrate formed during the precipitation as well as occluded impurities.

B) Catalyst 3 A - The wet cake from step (A) was mixed with 3840g of SiO₂ sol (40%) by weight) in a ball mill jar. After milling for 30 minutes, a solution of ammonium heptamolybdate, prepared by dissolving 12.9g (0.09 mole) of MoO₃ in 200 mL water and 40 mL of concentrated aqueous ammonia, was added to the slurry. The pH of the slurry was adjusted to pH 9.0 with additional concentrated aqueous ammonia before milling the slurry for 20 hours. The milled slurry was then divided into two equal portions. One portion was spray dried at a temperature of 83-85°C and the dried particles were then calcined in air at 400°C for 1 hour and then at 850°C for 1 hour and 15 minutes to give catalyst 3 A. C) Catalyst 3B - The other portion of the milled slurry, was heated in a glass reactor with mixing for 4 hours at 102 °C. After cooling the mixture to room temperature, the mixture was transferred to the ball mill jar and milled for 20 hours. The milled slurry was spray dried and calcined as in step (b) to give catalyst 3B. D) Sample Performance

Table 3

Catalyst 3A Catalyst 3B

Lab Reactor Performance

% Yield CO 4.92 4.68

% Yield CO₂ 6.64 6.30

% Yield HCN 7.45 7.35

% Yield AN 78.57 19.11

% C₃H₆ Conversion 98.82 99.08

% Selectivity AN 79.51 80.51

Catalyst Charge, g 445 365

Physical Characterization

Surface Area, m²/g 77.4 82.7

Pore Volume, cm³/g 0.365 0.392

Average Particle Size, A 183.4 188.3

The preceding description of specific embodiments of the present invention is not intended to be a complete list of every possible embodiment of the invention. Persons skilled in this field will recognize that modifications can be made to the specific embodiments described herein that would be within the scope of the present invention.

Claims

CLAIMS:

1. A process for producing a catalyst, comprising the steps of:

(a) forming a mixed oxides component that comprises antimony, bismuth, iron, and uranium;

(b) combining the mixed oxides component with a molybdate;

(c) forming the mixed oxides component into particles;

(d) heating the particles at a temperature between about 40°C and about 120°C for at least about 1 hour; (e) drying the particles; and

(f) calcining the particles.

2. The process of claim 1 , wherein the temperature in step (d) is at least about 100°C and the heating is performed for at least about 4 hours.

3. The process of claim 1, wherein the heating in step (d) is performed at between about 100°C and about 105°C for about 4 hours.

4. The process of claim 1, wherein the mixed oxides component is formed into particles in step (c) by milling the mixed oxides component in the form of an aqueous slurry.

5. The process of claim 1 further comprising milling the particles after the heating step.

6. A process for producing a catalyst, comprising the steps of:

(a) preparing a hydrated mixed oxides component containing antimony, uranium, iron, and bismuth by the steps of:

(i) forming a mixed oxides mixture that comprises oxides or nitrates of bismuth and uranium and an oxide of antimony in nitric acid;

(ii) heating the mixture of step (i) at a temperature and for a time sufficient to induce formation of crystalline oxides of antimony; (iii) adding an aqueous solution of ferric nitrate to the mixed oxides mixture; (iv) adjusting the pH of the mixed oxides mixture to about 8, thereby forming a hydrated mixed oxides precipitate in an aqueous phase; (v) separating the hydrated mixed oxides precipitate from the aqueous phase, thereby forming a hydrated mixed oxides component;

(b) combining the hydrated mixed oxides component with a molybdate;

(c) forming the combination of step (b) into particles; (d) heating the particles at a temperature between about 40°C and about 120°C for at least about 1 hour;

(e) drying the particles; and

(f) calcining the particles.

7. The process of claim 6, wherein the temperature in step (d) is at least about 100°C and the heating is performed for at least about 4 hours.

8. The process of claim 6, wherein the heating in step (d) is performed at between about 100°C and about 105°C for about 4 hours.

9. The process of claim 6, wherein the combination is formed into particles in step (c) by milling the combination in the form of an aqueous slurry.

10. The process of claim 6, further comprising the step of adding a support material comprising from about 10% to about 90% by weight of the total weight of the catalyst prior to the heating of step (d).

11. The process of claim 10, wherein the support material is added prior to step (c).

12. The process of claim 10, wherein the support material comprises from about 35% to about 65%o by weight of the total weight of the catalyst.

13. The process of claim 12, wherein the support material is silica.

14. The process of claim 6, wherein the drying of step (e) is done by spray drying a slurry.

15. The process of claim 6, wherein the molybdate is ferric molybdate.

16. The process of claim 6 wherein the molybdate is ammonium heptamolybdate.

17. A process for producing a catalyst comprising:

(i) forming a mixture of oxides or nitrates of bismuth and uranium and an oxide of antimony in nitric acid; (ii) heating the mixed oxides mixture at a temperature and for a time sufficient to induce formation of crystalline oxides of antimony;

(v) separating the hydrated mixed oxide mixture from the aqueous phase;

(b) forming an aqueous slurry of the hydrated mixed oxides component;

(e) adjusting the pH of the combined oxides mixture slurry to about 8-9;

(h) calcining the dry particles to form the catalyst.

18. The process of claim 17, wherein the heating of step (f) is performed under reflux.

19. The process of claim 17, wherein the heating of step (f) is performed while removing water and ammonium hydroxide.

20. A process for producing a catalyst, comprising the steps of:

(b) combining the mixed oxides component with a molybdate; (c) forming the mixed oxides component into particles;

(d) heating the particles at a temperature and for a time sufficient to improve the activity and/or selectivity of the resulting catalyst;

(e) drying the particles; and

(f) calcining the particles.

21. A catalyst prepared by the process of claim 1.

22. A catalyst prepared by the process of claim 6.

23. A catalyst prepared by the process of claim 17.

24. A process for the oxidation of an olefin to a corresponding unsaturated aldehyde or acid, comprising contacting the olefin with oxygen in the presence of a catalyst prepared by the process of claim 1.

25. A process for the ammoxidation of an olefin to a corresponding unsaturated nitrile comprising contacting the olefin with oxygen and ammonia in the presence of a catalyst prepared by the process of claim 1.