Ammoxidation catalyst having selective byproduct HCN production

Abstract

To provide an improved process and catalyst for the ammoxidation of propylene to acrylonitrile, hydrogen cyanide and acetonitrile.SOLUTION: The invention provides a catalytic composition and process useful for the conversion of an olefin selected from the group consisting of propylene, isobutylene and a mixture thereof into acrylonitrile, methacrylonitrile, hydrogen cyanide, acetonitrile and a mixture thereof, where the catalyst exhibits increased selectivity for hydrogen cyanide compared to prior art catalysts.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an improved catalyst for use in the ammoxidation of unsaturated hydrocarbons to the corresponding unsaturated nitriles, which unexpectedly provides an increased yield of hydrogen cyanide (HCN) co-product without a significant decrease in the yield of unsaturated nitrile. In particular, the present invention is directed to an improved catalyst composition for the ammoxidation of propylene and / or isobutylene to acrylonitrile and / or methacrylonitrile, and to hydrogen cyanide (HCN) and acetonitrile by-products, wherein the catalyst exhibits increased selectivity for hydrogen cyanide compared to prior art catalysts, the catalyst comprises a composite of metal oxides containing bismuth, molybdenum, iron, cerium and other promoter elements, and the catalyst is characterized by the ratio of iron to bismuth and cerium contained in the catalyst.

Background Art

[0002] Catalysts containing oxides of iron, bismuth and molybdenum promoted with suitable elements have been used for many years for the conversion of propylene and / or isobutylene at high temperatures in the presence of ammonia and oxygen (usually in the form of air) to produce acrylonitrile and / or methacrylonitrile. In particular, British Patent No. 1,436,475; U.S. Patent Nos. 4,766,232; 4,377,534; 4,040,978; 4,168,246; 5,223,469 and 4,863,891 are each directed to bismuth-molybdenum-iron catalysts that can be promoted with Group II elements to produce acrylonitrile. Further, U.S. Patent Nos. 5,093,299; 5,212,137; 5,658,842; 5,834,394 and Chinese Patent CN103418400 are directed to catalysts promoted with bismuth-molybdenum that exhibit high yields for acrylonitrile. In part, the present invention relates to a bismuth-molybdenum-iron catalyst promoted with cerium containing a cerium-bismuth-molybdenum phase having a greater amount of scheelite crystal structure than the early occurrence of a compositionally similar catalyst. Such catalysts are taught in U.S. Patent Nos. 8,153,546; 8,258,073; 8,350,075; 8,420,566; 8,455,388; 9,211,572; 9,358,528 and U.S. Patent Publication No. 2016 / 0175817. In part, the present invention relates to a promoted bismuth-molybdenum-iron ammoxidation catalyst that provides enhanced hydrogen cyanide production. U.S. Patent No. 5,840,648 teaches a promoted bismuth-molybdenum-iron ammoxidation catalyst incorporating calcium that provides increased hydrogen cyanide production without a significant decrease in acrylonitrile production. U.S. Patent No. 7,576232 teaches the addition of various molybdate compounds to an ammoxidation catalyst to increase the yield of hydrogen cyanide and modify the catalyst performance to inhibit molybdenum loss from such ammoxidation catalysts. SUMMARY OF THE INVENTION

[0003] The present invention is directed to improved methods and catalysts for the ammoxidation of propylene to acrylonitrile, hydrogen cyanide and acetonitrile. The methods and catalysts are characterized by a greater overall conversion of propylene to hydrogen cyanide and a greater overall conversion of propylene to acrylonitrile, hydrogen cyanide and acetonitrile than achieved previously with other methods and catalysts. Historically, catalysts that provided an increase in hydrogen cyanide yield provided an increase in hydrogen cyanide yield with a corresponding decrease in the yield of acrylonitrile. The catalysts of the present invention do not conform to this historical trend. The methods and catalysts of the present invention provide an increase in hydrogen cyanide production without a significant decrease in acrylonitrile production and provide an overall increase in the production of acrylonitrile, hydrogen cyanide and acetonitrile.

[0004] In one embodiment, the present invention is a catalyst composition comprising a metal oxide composite, The relative ratios of the elements listed in the catalyst are represented by the following formula: Mo m Bi a Fe b A c D d E e F f G g Ce h Cr n Q q O x (where A is at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium; D is at least one element selected from the group consisting of nickel, cobalt, manganese, zinc, magnesium, calcium, strontium, cadmium, and barium; E is at least one element selected from the group consisting of tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium, and tellurium; F is at least one element selected from the group consisting of lanthanum, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, aluminum, gallium, indium, thallium, silicon, lead, and germanium; G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum, and mercury; Q is at least one of samarium, praseodymium, and neodymium, and a, b, c, d, e, f, g, h, n, m, and x are the atomic ratios of bismuth (Bi), iron (Fe), A, D, E, F, G, cerium (Ce), chromium (Cr), molybdenum (Mo), and oxygen (O) to "m" atoms of molybdenum (Mo), respectively, where a is from 0.05 to 7, b is from 0.1 to 7, c is from 0 to 5, d is between 0.1 and 12. e is between 0 and 5. f is between 0 and 5. g is between 0 and 0.2. h is between 0.01 and 5. m is between 10 and 15. n is between 0 and 5. q is 0 to 2.476, and x is the number of oxygen atoms required to satisfy the valence requirements of the other constituent elements present; 0.4

[0005] In other embodiments of the above composition, independently, 0.3 ≤ (a + h) / d ≤ 1, 0.8 ≤ h / b ≤ 5, 0.5 ≤ a / h < 1.5, 0.45 ≤ (a + h) / d ≤ 1, 0 ≤ q / (a+h+q) < 0.16, and / or 0≦m-(3a+2b+c+2d+3h+3n) / 2≦1.0 That is the case.

[0006] The present invention also relates to a propylene ammoxidation catalyst formulation capable of providing yields of useful nitrile products, including acrylonitrile and HCN, within a variable and invertible range. This variation in yield can be achieved during catalyst operation by the appropriate addition of specific catalyst additives. In particular, the yield of hydrogen cyanide is given by formula: A2Mo z O 4+3(z-1) (In the formula, A is Rb, Li, Na, K, Cs or a mixture thereof) z is increased compared to the amounts of acrylonitrile and methacrylonitrile produced in the process by adding at least one molybdate compound (represented by 1 to approximately 8) to the catalyst. The alkali molybdate may be used with or without a support. ​

[0007] Furthermore, if molybdates are added to the catalyst for the purpose of increasing hydrogen cyanide production, this tendency can be reversed by adding to the catalyst a molybdenum oxide compound selected from the group consisting of MoO3, ammonium molybdate, ammonium heptamolybdate, ammonium dimolybdate and mixtures thereof, and an alkali molybdate mixture that catalyzes the ammoxidation process. Thus, the addition of molybdenum oxide to the catalyst and alkali molybdate mixture increases the yields of acrylonitrile and methacrylonitrile relative to the amount of hydrogen cyanide produced in the process (i.e., the amounts of acrylonitrile and methacrylonitrile and hydrogen cyanide produced will reach or be restored to their pre-molybdate addition levels). [Modes for carrying out the invention]

[0008] The present invention relates to improved mixed metal oxide catalysts and methods for the ammoxidation of propylene and / or isobutylene. In particular, the present invention relates to improved catalyst compositions for the ammoxidation of propylene and / or isobutylene to acrylonitrile and / or methacrylonitrile, and to hydrogen cyanide (HCN) and acetonitrile byproducts, wherein the catalyst exhibits increased selectivity for hydrogen cyanide compared to prior art catalysts, and the catalyst comprises a metal oxide complex containing bismuth, molybdenum, iron, cerium, and other promoter elements, and the catalyst is characterized by the iron-to-bismuth-to-cerium ratio contained in the catalyst. As used herein, “catalyst composition” and “catalyst” are synonymous and interchangeable.

[0009] catalyst: In part, the present invention relates to a multi-component mixed metal oxide ammoxidation catalyst composition comprising a catalyst oxide complex, The elements and their relative ratios in the catalyst composition are given by the following formula: Mo m Bi aFe b A c D d E e F f G g Ce h Cr n Q q O x (wherein A is at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium; D is at least one element selected from the group consisting of nickel, cobalt, manganese, zinc, magnesium, calcium, strontium, cadmium, and barium; E is at least one element selected from the group consisting of tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium, and tellurium; F is at least one element selected from the group consisting of lanthanum, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, aluminum, gallium, indium, thallium, silicon, lead, and germanium; G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum, and mercury; Q is at least one element of samarium, praseodymium, and neodymium, and a, b, c, d, e, f, g, h, n, m, and x are the atomic ratios of bismuth (Bi), iron (Fe), A, D, E, F, G, cerium (Ce), chromium (Cr), molybdenum (Mo), and oxygen (O) relative to m molybdenum (Mo) atoms, respectively. Here, a is between 0.05 and 7. b is between 0.1 and 7. c is between 0 and 5. d is between 0.1 and 12. e is between 0 and 5. f is between 0 and 5. g is between 0 and 0.2. h is between 0.01 and 5. m is between 10 and 15. n is between 0 and 5. q is between 0 and 2.476. x is the number of oxygen atoms required to satisfy the valence requirements of the other constituent elements present; 0.4

[0010] In one embodiment, A is at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium. In one embodiment, the catalyst composition does not contain potassium. In one embodiment, D is at least one element selected from the group consisting of nickel, cobalt, and magnesium. In one embodiment, D is nickel.

[0011] In one embodiment, the catalyst does not contain tellurium, antimony, or selenium. In another embodiment, the component or element designated by "E" in the above formula may include tellurium and / or antimony. In another embodiment, the component or element designated by "E" in the above formula is at least one element selected from the group consisting of chromium, aluminum, gallium, indium, arsenic, antimony, and tellurium. In another embodiment, "e" is zero (i.e., the composition described above does not contain the component or element designated by "E" in the above formula). In one embodiment, h is 0.01 to 5. In one embodiment, "F" may further contain lead (Pb). In another embodiment, "F" does not contain lead (Pb). In one embodiment, "m" is 12.

[0012] ​Partially, the catalyst composition can be characterized by the relationship b / (a+h) (where "b" is the relative amount of iron in the catalyst, "a" is the relative amount of bismuth in the catalyst, and "h" is the relative amount of cerium). In one embodiment, 0.4 Partially, catalyst compositions can be characterized by the relationship (a+h) / d, where "a" is the relative amount of bismuth in the catalyst, "h" is the relative amount of cerium in the catalyst, and "d" is the relative amount of nickel, cobalt, manganese, zinc, magnesium, calcium, strontium, cadmium, and barium in the catalyst. These relative amounts are subscripts of the elements in the catalyst formula, or, in the case of "d", the sum of the subscripts obtained from the catalyst formula for any nickel, cobalt, manganese, zinc, magnesium, calcium, strontium, cadmium, and barium present in the catalyst. In one embodiment, 0.3 ≤ (a+h) / d. In another independent embodiment, 0.15 ≤ (a+h) / d. Other independent embodiments are (each column below is an embodiment): 0.15 ≤ (a + h) / d ≤ 1, 0.3 ≤ (a + h) / d ≤ 1, 0.3 ≤ (a + h) / d ≤ 0.8, 0.3 ≤ (a + h) / d ≤ 0.6, 0.3 ≤ (a + h) / d ≤ 0.4, (a+h) / d≦1, (a+h) / d≦0.8, (a+h) / d≦0.6, (a+h) / d≦0.5, and (a+h) / d ≤ 0.4.

[0013] ​The catalyst composition may also be characterized by the relationship "m-[(3a+2b+c+2d+3h+3n) / 2]" (where "m" is the relative amount of molybdenum in the catalyst, "a" is the relative amount of bismuth in the catalyst, "b" is the relative amount of iron in the catalyst, "c" is the relative amount of element "A" (i.e., lithium, sodium, potassium, rubidium, and cesium) in the catalyst, "d" is the relative amount of element "D" (i.e., nickel, cobalt, manganese, zinc, magnesium, calcium, strontium, calcium, and barium) in the catalyst, "h" is the relative amount of cerium in the catalyst, and "n" is the relative amount of chromium in the catalyst). These relative quantities are either subscripts of elements in the catalytic formula, or, in the case of "a", the sum of subscripts obtained from the catalytic formula for any lithium, sodium, potassium, rubidium, and cesium present in the catalyst, or in the case of "d", the sum of subscripts obtained from the catalytic formula for any nickel, cobalt, manganese, zinc, magnesium, calcium, strontium, cadmium, and barium present in the catalyst. In one embodiment, 0 ≤ [m - [(3a + 2b + c + 2d + 3h + 3n) / 2]] ≤ 1.0.

[0014] In one embodiment, "Q" is samarium. In other embodiments, the catalyst does not contain the element "Q" (i.e., "q" is zero). In other embodiments, "q" is greater than zero. In other embodiments, "q" is between 0 and 2.476.

[0015] The catalyst composition may be characterized by the relationship q / (a+h+q) (where "q" is the relative amount of samarium, praseodymium, and neodymium in the catalyst, "a" is the relative amount of bismuth in the catalyst, and "h" is the relative amount of cerium in the catalyst). These relative amounts are subscripts of the elements in the catalyst formula, or, in the case of "q", the sum of the subscripts obtained from the catalyst formula for any samarium, praseodymium, and neodymium present in the catalyst. In one embodiment, 0 ≤ q / (a+h+q) and q / (a+h+q) < 0.16. In another embodiment, 0 ≤ q / (a+h+q) and q / (a+h+q) < 0.05. In yet another embodiment, 0.01 0 ≤ q / (a+h+q), 0.01 0.02 0.03 0.04 q / (a+h+q)<0.16, q / (a+h+q)<0.14, q / (a+h+q)<0.12, q / (a+h+q)<0.10, q / (a+h+q)<0.08, q / (a+h+q)<0.06, and q / (a+h+q)<0.05.

[0016] The catalyst composition may be characterized by the relationship h / b (where "h" is the relative amount of cerium in the catalyst and "b" is the relative amount of iron in the catalyst). These relative amounts are subscripts of the elements in the catalyst formula. In one embodiment, 0.8 ≤ h / b ≤ 5. Other independent embodiments are (each column below is an embodiment): 1.2 ≤ h / b ≤ 5, 1.5 ≤ h / b ≤ 5, 1.2 ≤ h / b, 1.5 ≤ h / b, 0.8 ≤ h / b, and ​​​​​h / b ≤ 5. It was found that catalysts described within the range of 0.8 ≤ h / b ≤ 5 tend to be more powerful in that they exhibit lower friction losses than measured by immersion jet friction tests.

[0017] The catalyst composition may be characterized by the relationship (a / h) (where "a" is the relative amount of bismuth in the catalyst and "h" is the relative amount of cerium in the catalyst). These relative amounts are subscripts of the elements in the catalyst formula. In one embodiment, 0 0.2 ≤ a / h ≤ 1.5, 0.3 ≤ a / h ≤ 1.5, 0.4 ≤ a / h ≤ 1.5, 0.45 ≤ a / h ≤ 1.5, 0.5 ≤ a / h ≤ 1.5, 0.2 ≤ a / h, 0.3 ≤ a / h, 0.4 ≤ a / h, 0.45 ≤ a / h, 0.65 ≤ a / h, 0.5 ≤ a / h, 0.7 ≤ a / h, 0.8 ≤ a / h, 0.90 ≤ a / h, a / h ≤ 1.2, and a / h ≤ 1.5.

[0018] In an alternative embodiment of the catalyst of the present invention, the present invention provides a catalyst composition comprising a metal oxide complex, wherein the relative ratio of the enumerated elements in the catalyst is given by the following formula: Mo m Bi a Fe b A c D d E e F f G g Ce h Ni i Co j Mn k Mg l Q q O x ​ (wherein A is at least one element selected from the group consisting of sodium, potassium, rubidium, and cesium; and D is at least one element selected from the group consisting of zinc, calcium, strontium, cadmium, and barium; E is at least one element selected from the group consisting of chromium, tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium, and tellurium; F is at least one element selected from the group consisting of lanthanum, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, aluminum, gallium, indium, thallium, silicon, germanium, and lead in amounts less than approximately 10 ppm; G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum, and mercury; Q is at least one of samarium, praseodymium, and neodymium. Here, a is between 0.05 and 7. b is between 0.1 and 7. c is between 0.01 and 5. d is between 0 and 12. e is between 0 and 5. f is between 0 and 5. g is between 0 and 0.2. h is between 0.01 and 5. i is between 0.1 and 12. j is between 0 and 12. k is between 0 and 12. l is between 0 and 12. m is between 10 and 15. q is between 0 and 2.476. x is the number of oxygen atoms required to satisfy the valence requirements of the other constituent elements present; 0.4 <b / (a+h)、 0.2 This is a catalyst composition represented by z = d + i + j + k + l and 0.3 ≤ (a + h) / z.

[0019] The catalyst of the present invention may be used either supported or unsupported (i.e., the catalyst may include a support). Suitable supports are silica, alumina, zirconium, titania, or mixtures thereof. Typically, the support acts as a binder for the catalyst, resulting in a stronger (i.e., greater friction resistance) catalyst. However, for commercial applications, a suitable blend of both the active phase (i.e., the composite of the catalyst oxides described above) and the support is essential to obtain acceptable activity and hardness (friction resistance) as a catalyst. Typically, the support contains between 40 and 60 mass percent of the supported catalyst. In one embodiment of the present invention, the support may contain less supported catalyst, about 30 mass percent. In another embodiment of the present invention, the support may contain more supported catalyst, about 70 mass percent.

[0020] In one embodiment, the catalyst is supported using a silica sol. Typically, the silica sol contains some amount of sodium. In one embodiment, the silica sol contains less than 600 ppm of sodium. In another embodiment, the silica sol contains less than 200 ppm of sodium. Typically, the average colloidal particle diameter of the silica sol is between about 15 nm and about 50 nm. In one embodiment of the present invention, the average colloidal particle diameter of the silica sol is about 10 nm and may be as low as about 4 nm. In another embodiment of the present invention, the average colloidal particle diameter of the silica sol is about 100 nm. In another embodiment of the present invention, the average colloidal particle diameter of the silica sol is about 20 nm. In another embodiment of the present invention, the average colloidal particle diameter of the silica sol is about 40 nm.

[0021] Nitrogen utilization ​The present invention relates to the relative yields of acrylonitrile, acetonitrile, and hydrogen cyanide produced in the process, and / or the following: α=[(%AN+(3×%HCN)+(1.5×%ACN))÷%PC]×100 (wherein %AN is the acrylonitrile yield and %AN ≥ 82, %HCN is the hydrogen cyanide yield and %HCN ≥ 5. %ACN is the acetonitrile yield. %PC is the propylene conversion rate. The invention also relates to methods and novel catalysts for the production of acrylonitrile, acetonitrile, and hydrogen cyanide, characterized by catalysts defined by α (where α is greater than 102.5).

[0022] In other embodiments, independently, %AN is 82.5 or greater; %PC is greater than 90; %PC is greater than 95; %PC is greater than 98; and α is greater than 103. As used herein, “acrylonitrile yield” means the molar percentage yield of acrylonitrile, calculated as follows (expressed as a number without any percent signs): The "hydrogen cyanide yield" is calculated as follows (moles of acrylonitrile produced ÷ moles of propylene supplied to the reactor) × 100. The "hydrogen cyanide yield" is the mole percentage yield of hydrogen cyanide calculated as follows (expressed as a number without any percentage signs): [(moles of hydrogen cyanide produced ÷ 3) ÷ moles of propylene supplied to the reactor] × 100. The "acetonitrile yield" is calculated as follows (expressed as a number without any percentage signs): [(moles of acetonitrile produced ÷ 1.5) ÷ moles of propylene supplied to the reactor] × 100. The propylene conversion rate is the mole percentage conversion rate of propylene to products and by-products calculated as follows (expressed as a number without any percentage signs): [(moles of propylene supplied to the reactor minus moles of propylene leaving the reactor) ÷ moles of propylene supplied to the reactor] × 100. "α" is a criterion for "nitrogen insertion" or "nitrogen utilization" (i.e., combining the nitrogen obtained from ammonia during the ammoxidation reaction with propylene to form a compound having the functional group "-CN"; as such, the larger "α", the greater the overall conversion of propylene to acrylonitrile, hydrogen cyanide, and acetonitrile). The catalysts of the present invention are characterized by a high "α" (i.e., greater than 10².5), which is a criterion for how efficient the catalyst is in utilizing ammonia for the ammoxidation of propylene to acrylonitrile.

[0023] Catalyst preparation: The catalyst may be prepared by any of the many methods of catalyst preparation known to those skilled in the art. A typical preparation method begins with the formation of a mixture of water, a molybdenum source compound, and a support material (e.g., silica sol). The source compounds for the remaining elements in the catalyst, alone, are combined with water to form a second mixture. These two mixtures are then combined with stirring at a slightly elevated temperature (approximately 65°C) to form a catalyst precursor slurry. The catalyst precursor slurry is then dried, denitrified, and subsequently calcined as described below. In one embodiment, the elements in the catalyst composition identified above are combined with an aqueous catalyst precursor slurry, the resulting aqueous precursor slurry is dried to form a catalyst precursor, and the catalyst precursor is calcined to form a catalyst. However, the method of the present invention is unique in the following: (i) In an aqueous solution, combine source compounds of Bi and Ce, and optionally combine one or more of Li, Na, K, Rb, Cs, Ca, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium, Pb, and W to form a mixture (i.e., the first mixture), (ii) Adding a molybdenum source compound to the mixture (i.e., the first mixture) and reacting it with the mixture to form a precipitate slurry, (iii) Combining the precipitate slurry with the source compounds for the remaining elements in the catalyst and the remaining molybdenum to form an aqueous catalyst precursor slurry. That is the case.

[0024] As used herein, “source compound” is a compound containing and / or providing one or more metals for a mixed metal oxide catalyst composition. As used herein, “remaining elements” or “remaining elements in the catalyst” refers to the elements represented by “A”, “D”, “E”, “F”, and “G” in the above formula that were not present in the first mixture, and the amounts of those elements. In one embodiment, some elements may be part of both the first and second mixtures. Furthermore, as used herein, “remaining molybdenum” or “remaining molybdenum in the catalyst” refers to the amount of molybdenum required in the finished catalyst that was not present in the precipitate slurry (i.e., not included in the preparation of ~). Finally, the sum of the amounts of molybdenum provided by the source compounds for the molybdenum added to (ii) and (iii) is equal to the total amount of molybdenum present in the catalyst.

[0025] In the catalyst preparation described above, the source compounds for the remaining elements and remaining molybdenum combined with the precipitate slurry may be a combination of such remaining elements and remaining molybdenum in any order or in any combination thereof. In one embodiment, a mixture of source compounds for the remaining elements and remaining molybdenum is combined with the precipitate slurry to form an aqueous catalyst precursor slurry. In another embodiment, (i) a mixture of source compounds for the remaining elements is combined with the precipitate slurry, and (ii) the source compounds for the remaining molybdenum are added separately to the precipitate slurry to form an aqueous catalyst precursor slurry. In yet another embodiment, the source compounds for the remaining elements and remaining molybdenum are added individually (i.e., one at a time) to the precipitate slurry. In yet another embodiment, a mixture of multiple (i.e., more than one) mixtures of source compounds for the remaining elements and remaining molybdenum, each mixture containing one or more source compounds for the remaining elements or remaining molybdenum, is added separately to the precipitate slurry (i.e., one mixture at a time, or multiple mixtures added simultaneously) to form an aqueous catalyst precursor slurry. In yet another embodiment, a mixture of source compounds for the remaining elements is combined with a source compound for molybdenum, and the resulting mixture is then added to a precipitate slurry to form a catalyst precursor slurry. In yet another embodiment, the support is silica (SiO2), and the silica is combined with a source compound for the remaining molybdenum before the remaining molybdenum is combined with the precipitate slurry (i.e., the silica and the source compounds for the remaining molybdenum are combined to form a mixture, and this mixture is then added individually to the precipitate slurry, or added in combination with one or more source compounds for the remaining elements).

[0026] In the catalyst preparation described above, molybdenum is added both in the preparation of the precipitate slurry and in the preparation of the aqueous catalyst precursor slurry. At the atomic level, the minimum amount of molybdenum added to form the precipitate slurry is determined by the following relationship: Mo = 1.5(Bi + Ce) + 0.5(Rb + Li + Na + K + Cs) + (Ca) + 1.5(total number of atoms of lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium) + (Pb) - (W) Here, in the above relationship, "Mo" is the number of molybdenum atoms added to the first mixture, and "Bi", "Ce", "Rb", "Li", "Na", "K", "Cs", "Ca", "Pb", and "W" are the number of bismuth, cerium, rubidium, lithium, sodium, potassium, cesium, calcium, lead, and tungsten atoms present in the first mixture, respectively.

[0027] In the catalyst preparation described above, typically, the amount of molybdenum added to the first mixture to form a precipitate slurry is about 20-35% of the total molybdenum in the final catalyst. In one embodiment, the source compound for the remaining molybdenum present in the catalyst is added to the mixture of the remaining elemental source compounds (i.e., the second mixture) before combining the mixture of the remaining elemental source compounds with the precipitate slurry to form a catalyst precursor slurry. In other embodiments, the molybdenum source compound containing the remaining molybdenum present in the catalyst is added to the precipitate slurry either before, after, or simultaneously with the mixture of the remaining elemental source compounds (i.e., the second mixture) to form a catalyst precursor slurry. In the above preparation, Bi and Ce source compounds, along with one or more Li, Na, K, Rb, Cs, Ca, rare earth elements, Pb, and W (optionally) are combined in aqueous solution to form a mixture. In one embodiment, bismuth nitride and optionally other metal nitrides (i.e., nitrides of Li, Na, K, Rb, Cs, Ca, rare earth elements, and / or Pb) are dissolved in aqueous solution of ammonium cerium nitrate. If tungsten is added, the source compound is typically ammonium paratungstate, (NH4) 10It is H2(W2O7)6. As used herein, “rare earth elements” means at least one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, scandium, and yttrium.

[0028] A molybdenum source compound is added to a mixture containing bismuth and cerium (and optionally one or more of Li, Na, K, Rb, Cs, Ca, rare earth elements, Pb, and / or W). In one embodiment, this molybdenum source compound is ammonium heptamolybdate dissolved in water. Upon addition of the molybdenum source compound to the mixture containing bismuth and cerium, a reaction occurs, producing a precipitate, and the resulting mixture is a precipitate slurry. Subsequently, the precipitate slurry is combined with a mixture of the source compounds for the remaining elements of the catalyst and the source compound for molybdenum to form an aqueous catalyst precursor slurry. The mixture of the source compounds for the remaining elements and the source compound for molybdenum may be prepared by combining the source compounds for the remaining elements in aqueous solution (e.g., combining the source compounds in water) and then adding the source compound for molybdenum. In one embodiment, this source compound for molybdenum is ammonium heptamolybdate, which is dissolved in water. When combining the precipitate slurry with the remaining elements / molybdenum mixture, the order of addition is not important; that is, the precipitate slurry may be added to the remaining elements / molybdenum mixture, or the remaining elements / molybdenum mixture may be added to the precipitate slurry. The aqueous catalyst precursor slurry is maintained at a high temperature.

[0029] The amount of aqueous solvent in each of the aqueous mixtures and slurries described above may vary due to the solubility of the source compounds to be combined to form a particular mixed metal oxide. The amount of aqueous solvent should be at least sufficient to obtain a slurry or mixture of solids and liquids that can be stirred. In any case, the source compounds are preferably combined and / or reacted by a protocol that includes mixing the source compounds during the combination and / or reaction steps. The specific mixing mechanism is not critical and may include, for example, mixing the components during the reaction by any effective method (e.g., stirring or agitating). Such methods include, for example, shaking, rotating or vibrating the container containing the components to agitate the contents of the container. Such methods also include, for example, agitation by using a driving force that is at least partially positioned in the reaction vessel or connected to the reaction vessel to supply relative motion between the stirring member and the reaction vessel. The stirring member may be a shaft-driven and / or shaft-supported stirring member. The driving force may be connected directly to the stirring member or indirectly to the stirring member (e.g., via electromagnetic coupling). Mixing is sufficient to allow for effective reaction between the components of the reaction medium, and is generally preferable to form a more homogeneous reaction medium compared to an unmixed reaction (e.g., producing a more homogeneous mixed metal oxide precursor). This results in more efficient consumption of the starting materials and a more homogeneous mixed metal oxide product. Mixing the precipitate slurry during the reaction steps also causes the precipitate to form in solution rather than on the sides of the reaction vessel. Even more advantageously, allowing the precipitate to form in solution allows for particle growth across the entire surface of the particles rather than a limited exposed surface, if growth occurs outside the reaction vessel walls.

[0030] Possible molybdenum source compounds include molybdenum(VI)(MoO3), ammonium heptamolybdate, or molybdate salts. The molybdenum source compound can be introduced from any molybdenum oxide, such as dioxide, trioxide, pentoxide, or heptaoxide. However, hydrolyzable or decomposable molybdenum salts are preferred as the molybdenum source compound. Typical source compounds for the catalysts bismuth, cerium, and the remaining elements are metallic nitrides. Such nitride salts are readily available and easily soluble. Source compounds for bismuth may include oxides or salts that will yield oxides by calcination. Water-soluble salts that disperse easily by heat treatment but form stable oxides are preferred. In one embodiment, the source compound for bismuth is bismuth nitride, Bi(NO3)3·5H2O.

[0031] The cerium source compound may be an oxide or salt that will yield an oxide by calcination. Water-soluble salts that disperse easily by heat treatment but form stable oxides are preferred. In one embodiment, the cerium source compound is cerium ammonium nitrate, (NH4)2Ce(NO3)6. In another embodiment, the cerium source compound is cerium nitride, Ce(NO3)3·6H2O. The iron source compound may be obtained from any iron compound that will produce an oxide upon calcination. If other elements are used, water-soluble salts are preferred because they can be easily dispersed uniformly within the catalyst. The most preferred is ferric nitride.

[0032] Source compounds for the remaining elements can be derived from any suitable source. For example, cobalt, nickel, and magnesium can be introduced into the catalyst using nitride salts. Furthermore, magnesium can be introduced into the catalyst as an insoluble carbonate or hydroxide, which yields an oxide through heat treatment. Phosphorus can be introduced into the catalyst as an alkali metal salt, alkali rare earth metal salt, or ammonium salt, but it is preferably introduced as phosphoric acid. The source compound for the alkaline component of the catalyst may be introduced into the catalyst as an oxide or as a salt, which will be obtained by calcination. In addition to water, solvents may, but are not limited to, be used to prepare the mixed metal oxides according to the present invention, including methanol, ethanol, propanol, alcohols such as diols (e.g., ethylene glycol, propylene glycol, etc.), organic acids such as acetic acid, and other polar solvents known in the art. The metal source compound is at least partially soluble in the solvent. As noted previously, the catalyst of the present invention may be used either supported or unsupported (i.e., the catalyst may include a support). Suitable supports are silica, alumina, zirconia, titania, or mixtures thereof. The support may be added at any time before the catalyst precursor slurry is dried. The support may be added at any time during or after the preparation of any mixture of elements, precipitate slurry, or catalyst precursor slurry. Furthermore, the support does not need to be added at a single point or step (i.e., the support may be added at multiple points in the preparation). In one embodiment, the support is combined with the other components during the preparation of the aqueous catalyst precursor slurry. In one embodiment, the support is added to the precipitate slurry (i.e., after the precipitate slurry has been prepared). In one embodiment, the support is combined with the molybdenum source compound to form the “second mixture” shown above, before combining the molybdenum source compound with the source compounds of the remaining elements in the catalyst.

[0033] The catalyst precursor slurry is dried and denitrified (i.e., nitrides are removed) to obtain the catalyst precursor. In one embodiment, the catalyst precursor slurry is dried to form catalyst particles. In one embodiment, the catalyst precursor slurry is spray-dried into fine spherical catalyst particles. In one embodiment, the spray dryer outlet temperature is between 110°C and 350°C, preferably between 110°C and 250°C, and most preferably between 110°C and 180°C. In one embodiment, the spray dryer is a co-flow spray dryer (i.e., particles are sprayed in a co-flow with the gas flow). In another embodiment, the spray dryer is counterflow (i.e., particles are sprayed counterflow with respect to the gas flow). In yet another embodiment, the spray dryer is a pressure nozzle type spray dryer. In such a spray drying process, water-containing solid phase particles are sprayed in contact with a hot gas (usually air) to vaporize the water. Drying is controlled by the gas temperature and the distance the particles travel in contact with the gas. This is because if water trapped within the particles vaporizes and attempts to leak, it tends to form a dry surface on the partially dried particles of the solid phase, which then bursts. Therefore, adjusting these parameters to achieve excessively fast drying is generally undesirable. Similarly, it is desirable to provide the catalyst in a form with as little trapped water as possible. Thus, when a fluid bed reactor is used and fine spherical particles are desired, it is desirable to select spray drying conditions to achieve complete drying without particle bursting. The dried catalyst material is then heated to remove any remaining nitrides. The denitrification temperature may be in the range of 100°C to 500°C, preferably 250°C to 450°C.

[0034] Finally, the dried and denitrified catalyst precursor is calcined to form a finished catalyst. In one embodiment, calcination is achieved in air. In another embodiment, calcination is achieved in an inert atmosphere. In one embodiment, the catalyst precursor is calcined in nitrogen. Calcination conditions include a temperature range of about 300°C to about 700°C, more preferably about 350°C to about 650°C, and in some embodiments, calcination may be about 600°C. In one embodiment, calcination may be completed in multiple stages at increasing temperatures. In one embodiment, a first calcination stage is carried out at a temperature in the range of about 300°C to about 450°C, followed by a second calcination stage at a temperature in the range of about 500°C to about 650°C.

[0035] Ammonoxidation Process The catalyst of the present invention is useful in ammoxidation processes for converting olefins selected from the group consisting of propylene, isobutylene, or mixtures thereof into acrylonitrile, methacrylonitrile, and mixtures thereof, respectively, by reacting the olefins in the gas phase, at high temperature and pressure, in the presence of the catalyst, with a gas containing molecular oxygen and ammonia. The catalyst of the present invention is also useful for the ammoxidation of methanol to hydrogen cyanide and the ammoxidation of ethanol to acetonitrile. In one embodiment using the catalyst described herein, methanol and / or ethanol may be supplied concurrently to a process for the ammoxidation of propylene, isobutylene, or mixtures thereof to acrylonitrile, methacrylonitrile, or mixtures thereof in order to increase the production of hydrogen cyanide and / or acetonitrile byproducts obtained from such a process.

[0036] Preferably, the ammoxidation reaction is carried out in a fluidized bed reactor, but other types of reactors, such as transport line reactors, are also conceivable. Fluidized bed reactors for the production of acrylonitrile are well known in the prior art. For example, the reactor design described in U.S. Patent No. 3,230,246, incorporated herein by reference, is suitable. The conditions for the ammoxidation reaction to occur are well known in the prior art, as demonstrated by U.S. Patents No. 5,093,299; No. 4,863,891; No. 4,767,878 and No. 4,503,001, and are incorporated herein by reference. Typically, the ammoxidation process is carried out by contacting propylene or isobutylene with a fluidized bed catalyst at high temperature in the presence of ammonium and oxygen to produce acrylonitrile or methacrylonitrile. Any source of oxygen can be used; however, for economic reasons, air is preferred. The typical molar ratio of oxygen to olefin in the supply should be in the range of 0.5:1 to 4:1, preferably 1:1 to 3:1.

[0037] The molar ratio of ammonia to olefin in the feed during the reaction may vary between 0.5:1 and 2:1. While there is no practical upper limit on the ammonia-olefin ratio, generally, there is no reason to exceed a ratio of 2:1 for economic reasons. Suitable feed ratios for use with the catalyst of the present invention for the production of acrylonitrile from propylene are an ammonia-to-propylene ratio in the range of 0.9:1 to 1.3:1 and an air-to-propylene ratio of 8.0:1 to 12.0:1. The catalyst of the present invention can provide high yields of acrylonitrile at relatively low ammonia-to-propylene feed ratios of about 1:1 to about 1.05:1. These “low ammonia conditions” help reduce unreacted ammonia in the reactor wastewater, a condition known as “ammonia breakthrough,” which subsequently helps reduce process waste. In particular, unreacted ammonia must be removed from the reactor wastewater before the recovery of acrylonitrile. Unreacted ammonia is typically removed by contacting the reactor waste with sulfuric acid to obtain ammonium sulfide, or by contacting the reactor waste with acrylic acid to obtain ammonium acrylate, which in both cases results in a stream of process waste that is treated and / or discarded.

[0038] The reaction takes place at a temperature between approximately 260°C and 600°C, with a preferred range of 310°C to 500°C, and a particularly preferred range of 350°C to 480°C. The contact time is not critical, but is generally in the range of 0.1 to 50 seconds, with a preferred contact time of 1 to 15 seconds. The reaction products may be recovered or purified by any method known to those skilled in the art. One such method involves purifying the exhaust gas from the reactor with cold water or a suitable solvent to remove the reaction products, and then purifying the reaction products by distillation. The first utility of the catalyst prepared by the method of the present invention is for the ammoxidation of propylene to acrylonitrile. Other utility includes the ammoxidation of propane to acrylonitrile, the ammoxidation of an alcohol selected from the group consisting of methanol, ethanol, or mixtures thereof to hydrogen cyanide (HCN), acetonitrile, and mixtures thereof, and the ammoxidation of glycerol to acrylonitrile. The catalyst prepared by the method of the present invention may also be used for the oxidation of propylene to acrolein and / or acrylic acid. Such a method is typically a two-step process in which propylene is first converted to acrolein in a first step in the presence of the catalyst, and acrolein is first converted to acrylic acid in a second step in the presence of the catalyst. The catalyst described herein is suitable for use in the first step for the oxidation of propylene to acrolein.

[0039] Modification of HCN production during ammoxidation In one embodiment of the present invention, the yield of hydrogen cyanide is given by the formula: A2Mo z O 4+3(z-1) (In the formula, A is Rb, Li, Na, K, Cs or a mixture thereof) The addition of at least one alkali molybdate compound (where z is 1 to about 8) to the catalyst increases the amount of acrylonitrile and methacrylonitrile produced in the process. The alkali molybdate compound may be unsupported or supported on a suitable support such as silica, alumina, zirconia, titania, or a mixture thereof. If supported, the support or carrier contains a combination of alkali molybdate compound and support between 1% by mass and 99% by mass. The amount of alkali molybdate compound added to the catalyst is in the range of 0.01% by mass to about 10% by mass relative to the mass of the catalyst composition. For catalyst systems described earlier in this specification (i.e., 0.4

[0040] ​Furthermore, if an alkali molybdate compound is added to the catalyst for the purpose of increasing hydrogen cyanide production, this tendency can be reversed by adding a molybdenum oxide compound selected from the group consisting of MoO3, ammonium molybdate, ammonium heptamolybdate, ammonium dimolybdate, and mixtures thereof to the catalyst and the alkali molybdate mixture catalyzing the ammoxidation process. Thus, the addition of a molybdenum oxide compound to the catalyst and the alkali molybdate mixture increases the yields of acrylonitrile and methacrylonitrile relative to the amount of hydrogen cyanide produced in the process (i.e., the amount of acrylonitrile and / or methacrylonitrile produced will increase until it approaches or returns to the level present before the addition of the alkali molybdate, and the amount of hydrogen cyanide will decrease until it approaches or returns to the level present before the addition of the alkali molybdate). The molybdenum oxide compound may or may not be supported on a suitable support such as silica, alumina, zirconia, titania, or mixtures thereof. When supported, the support or carrier contains a combination of the molybdenum oxide compound and the support in an amount between 1% by mass and 99% by mass. The amount of the molybdenum oxide compound added to the catalyst is in the range of 0.01% by mass to about 10% by mass, relative to the mass of the catalyst composition.

[0041] Alkali molybdate compounds and / or molybdenum oxide compounds may be added in situ, i.e., to the catalyst so that it operates in the reactor, or added to the catalyst outside the reactor. In one embodiment, an alkali molybdate compound or molybdenum oxide compound is added to a new fluidized bed ammoxidation catalyst (i.e., mixed with ), and then added to the reactor as a "make-up" catalyst to maintain the catalyst bed height in the reactor, or to replace the catalyst due to loss from the reactor in wastewater or friction. Specific Embodiments To illustrate the present invention, catalysts prepared according to the present invention were evaluated and compared under similar conditions with similar catalysts prepared by prior art methods outside the scope of the present invention. These examples are provided for illustrative purposes only. For each example, the catalyst composition is as shown after the example number. Examples designated with "C" are comparative examples.

[0042] (Comparative Example C1) Ni4Mg3Fe 0.9 Rb 0.2 Cr 0.05 Bi 1.25 Ce 1.25 Mo 12.85 Ox+50 mass% 38.2nm SiO2 Reaction mixture A was prepared by heating 1370.303 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (1245.730 g) while stirring for 30 minutes to form a colorless, transparent solution. Reaction mixture B was prepared by heating 257.123 ml of deionized water to 55°C, and then adding Fe(NO3)3·9H2O (285.052 g), Ni(NO3)2·6H2O (911.870 g), Mg(NO3)2·6H2O (603.024 g), and Cr(NO3)3·9H2O (15.685 g) while stirring. Reaction mixture C was prepared by heating 586.185 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (532.896 g) while stirring for 30 minutes to form a colorless, transparent solution.

[0043] (i) Heating 1074.497 g of a 50% by mass aqueous solution of (NH4)2Ce(NO3)6 to 55°C, and (ii) while the solution was being stirred and heated, reaction mixture D was prepared by successively adding Bi(NO3)3·5H2O (475.357 g) and RbNO3 (23.121 g). Reaction mixture E was prepared by adding silica sol (5487.8 g, 41% by mass silica) to reaction mixture A while stirring, followed by the addition of reaction mixture B. Reaction mixture C was added to reaction mixture D to prepare reaction mixture F, which resulted in the formation of an orange solid precipitate (the resulting mixture was a precipitate slurry). The precipitate slurry was stirred for 15 minutes while the temperature was maintained in the range of 50-55°C. Subsequently, reaction mixture F was added to reaction mixture E to form the final catalyst precursor slurry. The catalyst precursor slurry was stirred for 1 hour while being cooled to approximately 40°C. It was then homogenized in a blender at 5000 rpm for 3 minutes. The slurry was then spray-dried in a spray dryer at an inlet / outlet temperature of 325 / 140°C. The resulting powder was denitrified by heating in air at 290°C for 3 hours, followed by a further 3 hours at 425°C. The powder was then calcined in air at 560°C for 3 hours.

[0044] (Comparative Example C2) Ni6Mg1Fe 0.7 Rb 0.1 Cr 0.05 Bi 0.83 Ce 1.67 Mo 12.85 O x +50% by mass 38.2nm SiO2 Reaction mixture A was prepared by heating 304.303 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (276.639 g) while stirring for 30 minutes to form a colorless, transparent solution. Reaction mixture B was prepared by heating 38.310 ml of deionized water to 55°C, and then adding Fe(NO3)3·9H2O (48.962 g), Ni(NO3)2·6H2O (302.070 g), Mg(NO3)2·6H2O (44.391 g), and Cr(NO3)3.9H2O (11.547 g) while stirring. Reaction mixture C was prepared by heating 127.774 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (116.158 g) while stirring for 30 minutes to form a colorless, transparent solution.

[0045] (i) Heating 317.026 g of a 50% by mass aqueous solution of (NH4)2Ce(NO3)6 to 55°C, and (ii) while stirring and heating the solution, continuously adding Bi(NO3)3·5H2O (69.706 g) and RbNO3 (8.510 g) prepared reaction mixture D. Reaction mixture E was prepared by adding silica sol (1219.5 g, 41% by mass silica) to reaction mixture A while stirring, followed by the addition of reaction mixture B. Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which yielded an orange solid precipitate (this resulting mixture was a precipitate slurry). The precipitate slurry was stirred for 15 minutes while the temperature was maintained in the range of 50–55°C. Subsequently, reaction mixture F was added to reaction mixture E to form the final catalyst precursor slurry. The catalyst precursor slurry was stirred for 1 hour while being cooled to approximately 40°C. It was then homogenized in a blender at 5000 rpm for 3 minutes. The slurry was then spray-dried in a spray dryer at an inlet / outlet temperature of 325 / 140°C. The resulting powder was denitrified by heating in air at 290°C for 3 hours, followed by a further 3 hours at 425°C. The powder was then calcined in air at 560°C for 3 hours.

[0046] (Examples 1 and 2) Ni4Mg3Fe 1.2 Rb 0.2 Cr 0.05 Bi 1.25 Ce 1.25 Mo 12.85 O x +50 mass% 38.2nm SiO2 Reaction mixture A was prepared by heating 1358.961 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (1235.419 g) while stirring for 30 minutes to form a colorless, transparent solution. Reaction mixture B was prepared by heating 265.465 ml of deionized water to 55°C, and then adding Fe(NO3)3·9H2O (376.923 g), Ni(NO3)2·6H2O (904.322 g), Mg(NO3)2·6H2O (598.033 g), and Cr(NO3)3·9H2O (15.555 g) while stirring. Reaction mixture C was prepared by heating 581.333 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (528.485 g) while stirring for 30 minutes to form a colorless, transparent solution.

[0047] (i) Heating 1065.603 g of a 50% by mass aqueous solution of (NH4)2Ce(NO3)6 to 55°C, and (ii) Adding Bi(NO3)3·5H2O (471.422 g) and RbNO3 (22.930 g) in succession while stirring and heating the solution, reaction mixture D was prepared. Reaction mixture E was prepared by adding silica sol (5487.8 g, 41% by mass silica) to reaction mixture A while stirring, followed by the addition of reaction mixture B. Reaction mixture C was added to reaction mixture D, and reaction mixture F was prepared by producing an orange solid precipitate (the resulting mixture was a precipitate slurry). The precipitate slurry was stirred for 15 minutes while maintaining the temperature in the range of 50-55°C. Subsequently, reaction mixture F was added to reaction mixture E to form the final catalyst precursor slurry. The catalyst precursor slurry was stirred for 1 hour while being cooled to approximately 40°C. It was then homogenized in a blender at 5000 rpm for 3 minutes. The slurry was then spray-dried in a spray dryer at an inlet / outlet temperature of 325 / 140°C. The resulting powder was heat-treated in air at 290°C for 3 hours, followed by denitrification by heating at 425°C for a further 3 hours. The powder was then calcined in air at 560°C for 3 hours.

[0048] (Examples 3 and 4) Ni6Mg1Fe1Rb0.2 Cr 0.05 Bi1Ce 1.22 Mo 12.505 O x +50 mass% 38.2nm SiO2 Reaction mixture A was prepared by heating 1399.413 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (1272.194 g) while stirring for 30 minutes to form a colorless, transparent solution. Reaction mixture B was prepared by heating 259.349 ml of deionized water to 55°C, and then adding Fe(NO3)3·9H2O (320.780 g), Ni(NO3)2·6H2O (1385.318 g), Mg(NO3)2·6H2O (203.582 g), and Cr(NO3)3·9H2O (15.886 g) while stirring. Reaction mixture C was prepared by heating 528.924 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (480.840 g) while stirring for 30 minutes to form a colorless, transparent solution. (i) Heating 1062.136 g of a 50% by mass aqueous solution of (NH4)2Ce(NO3)6 to 55°C, and (ii) Adding Bi(NO3)3·5H2O (385.155 g) and RbNO3 (23.417 g) in succession while stirring and heating the solution, reaction mixture D was prepared.

[0049] Reaction mixture E was prepared by adding silica sol (5263.2 g, 41% by mass silica) to reaction mixture A while stirring, followed by the addition of reaction mixture B. Reaction mixture C was added to reaction mixture D, and reaction mixture F was prepared by producing an orange solid precipitate (the resulting mixture was a precipitate slurry). The precipitate slurry was stirred for 15 minutes while maintaining the temperature in the range of 50-55°C. Subsequently, reaction mixture F was added to reaction mixture E to form the final catalyst precursor slurry. The catalyst precursor slurry was stirred for 1 hour while cooling to approximately 40°C. It was then homogenized in a blender at 5000 rpm for 3 minutes. The slurry was then spray-dried in a spray dryer at an inlet / outlet temperature of 325 / 140°C. The resulting powder was denitrified by heating in air at 290°C for 3 hours, followed by a further 3 hours at 425°C. Finally, the powder was calcined in air at 560°C for 3 hours.

[0050] (Example 5) Ni4Mg3Fe 1.2 Rb 0.2 Cr 0.05 Bi 1.25 Ce 1.25 Mo 12.730 O x +50wt 38.2nm SiO2 Reaction mixture A was prepared by heating 150.66 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (136.60 g) while stirring for 30 minutes to form a colorless, transparent solution. Reaction mixture B was prepared by heating 29.93 ml of deionized water to 55°C, and then adding Fe(NO3)3·9H2O (42.2625 g), Ni(NO3)2·6H2O (101.42 g), Mg(NO3)2·6H2O (67.0604 g), and Cr(NO3)3·9H2O (1.7441 g) while stirring. Reaction mixture C was prepared by heating 71.75 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (59.3332 g) while stirring for 30 minutes to form a colorless, transparent solution. (i) Heating 119.53 g of a 50% by mass aqueous solution of (NH4)2Ce(NO3)6 to 55°C, and (ii) Adding Bi(NO3)3·5H2O (52.8606 g) and RbNO3 (2.7027 g) in succession while stirring and heating the solution, reaction mixture D was prepared. While stirring, silica sol (609.76 g, 41% by mass silica) was added to reaction mixture A, and then reaction mixture B was added to prepare reaction mixture E. Reaction mixture C was added to reaction mixture D, and reaction mixture F was prepared by producing a precipitate of orange solid matter (the resulting mixture was a precipitate slurry). The precipitate slurry was stirred for 15 minutes while maintaining the temperature in the range of 50-55°C. Subsequently, reaction mixture F was added to reaction mixture E to form the final catalyst precursor slurry. The catalyst precursor slurry was stirred for 1 hour while being cooled to approximately 40°C. It was then homogenized in a blender at 5000 rpm for 3 minutes. The slurry was then spray-dried in a spray dryer at an inlet / outlet temperature of 325 / 140°C. The resulting powder was denitrified by heating in air at 290°C for 3 hours, followed by a further 3 hours at 425°C. The powder was then calcined in air at 560°C for 3 hours.

[0051] (Example 6) Ni4Mg3Fe 1.2 Rb 0.2 Cr 0.05 Bi 1.25 Ce 1.25 Mo 12.130 O x +50 mass% 38.2nm SiO2 Reaction mixture A was prepared by heating 144.67 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (131.32 g) while stirring for 30 minutes to form a colorless, transparent solution. Reaction mixture B was prepared by heating 30.87 ml of deionized water to 55°C, and then adding Fe(NO3)3·9H2O (43.5883 g), Ni(NO3)2·6H2O (104.57 g), Mg(NO3)2·6H2O (69.1397 g), and Cr(NO3)3.9H2O (1.7983 g) while stirring. Reaction mixture C was prepared by heating 74.12 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (61.1793 g) while stirring for 30 minutes to form a colorless, transparent solution.

[0052] (i) Heating 123.30 g of a 50% by mass aqueous solution of (NH4)2Ce(NO3)6 to 55°C, and (ii) Adding Bi(NO3)3·5H2O (54.5021 g) and RbNO3 (2.7847 g) in succession to the solution while stirring and heating, was used to prepare reaction mixture D. Reaction mixture E was prepared by adding silica sol (609.80 g, 41% by mass silica) to reaction mixture A while stirring, followed by the addition of reaction mixture B. Reaction mixture C was added to reaction mixture D, and reaction mixture F was prepared by producing an orange solid precipitate (the resulting mixture was a precipitate slurry). The precipitate slurry was stirred for 15 minutes while maintaining the temperature in the range of 50-55°C. Subsequently, reaction mixture F was added to reaction mixture E to form the final catalyst precursor slurry. The catalyst precursor slurry was stirred for 1 hour while being cooled to approximately 40°C. It was then homogenized in a blender at 5000 rpm for 3 minutes. The slurry was then spray-dried in a spray dryer at an inlet / outlet temperature of 325 / 140°C. The resulting powder was denitrified by heating in air at 290°C for 3 hours, followed by a further 3 hours at 425°C. The powder was then calcined in air at 560°C for 3 hours.

[0053] (Example 7) Ni4Mg3Fe1.2Rb0.192Cr0.05Bi1.0Sm0.1Ce1.5Mo12.996Ox+50% by mass 38.2nm SiO2 Reaction mixture A was prepared by heating 152.49 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (139.06 g) while stirring for 30 minutes to form a colorless, transparent solution. Reaction mixture B was prepared by heating 28.35 ml of deionized water to 55°C, and then adding Fe(NO3)3·9H2O (41.73229 g), Ni(NO3)2·6H2O (100.16 g), Mg(NO3)2·6H2O (66.2090 g), and Cr(NO3)3.9H2O (1.7272 g) while stirring. Reaction mixture C was prepared by heating 70.69 ml of deionized water to 65°C, and then adding ammonium heptamolybdate (58.4395 g) while stirring for 30 minutes to form a colorless, transparent solution.

[0054] (i) Heating 141.57 g of a 50% by mass aqueous solution of (NH4)2Ce(NO3)6 to 55°C, and (ii) Adding Bi(NO3)3·5H2O (41.7512 g), RbNO3 (2.4389 g), and Sm(NO3)3·6H2O (3.8270 g) in succession to the solution while stirring and heating, thereby preparing reaction mixture D. Reaction mixture E was prepared by adding silica sol (609.76 g, 41% by mass silica) to reaction mixture A while stirring, followed by the addition of reaction mixture B. Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in the formation of an orange solid precipitate (the resulting mixture was a precipitate slurry). The precipitate slurry was stirred for 15 minutes while maintaining the temperature in the range of 50-55°C. Subsequently, reaction mixture F was added to reaction mixture E to form the final catalyst precursor slurry. The catalyst precursor slurry was stirred for 1 hour while being cooled to approximately 40°C. It was then homogenized in a blender at 5000 rpm for 3 minutes. The slurry was then spray-dried in a spray dryer at an inlet / outlet temperature of 325 / 140°C. The resulting powder was denitrified by heating in air at 290°C for 3 hours, followed by a further 3 hours at 425°C. Finally, the powder was calcined in air at 560°C for 3 hours.

[0055] (Example 8) The catalyst in the example was prepared using the same preparation as in Example 7, except that 0.094 grams of K2MoO4 solid crystals were added to the finishing catalyst. (Example 9) This example was a continuation of the catalyst test in Example 8. After 382 hours in the stream, 0.144 grams of MoO3 were added to the catalyst in Example 8, and the test for ammoxidation of propylene to acrylonitrile was continued.

[0056] Catalyst testing All catalysts were tested in a bench-scale reactor for the ammoxidation of propylene to acrylonitrile using 30 g of catalyst. All tests were performed in a 40 cc fluidized bed reactor. Propylene was supplied into the reactor at rates shown in Tables 1 and 3, between 0.080 and 0.100 WWH (i.e., mass of propylene / mass of catalyst / hour). The pressure inside the reactor was maintained at 10 psig. The reaction temperature was 430°C. Samples of the reaction product were collected several days after the test (between approximately 140 and 190 hours in the stream). Reactor wastewater was collected using a bubble scrubber containing a cold HCl solution. The off-gas rate was measured with a soap film meter, and the off-gas composition was determined at the end of the operation with the assistance of gas column chromatography equipped with a split column gas analyzer. At the end of the recovery process, the total scrubber solution was diluted with diluent water to approximately 200 grams. The weighed amount of 2-butanone was used as an internal standard in an aliquot of approximately 50 grams. A 2 μl sample was analyzed by GC equipped with a flame ionization detector and a Carbowax® column. The amount of NH3 was determined by titrating for excess free HCl with NaOH solution. The propylene conversion rate and acrylonitrile yield for the tested catalysts are shown in Tables 1 and 3. HCN was analyzed by titration with AgNO3 solution after the addition of caustic iodide.

[0057] [Table 1]

[0058] [Table 2]

[0059] [Table 3]

[0060] Notes on Tables 1, 2, and 3 (where applicable): 1. "WWH" is the mass of propylene per unit time per unit mass of catalyst being supplied. 2. "T℃" is the reactor temperature in Celsius. 3. "HOS" is time in a stream. 4. "%C3", "Conv", or "%PC" is the propylene conversion rate (i.e., the mole percent per pass of propylene conversion to all products). 5. "%AN yield" is the acrylonitrile yield percentage. 6. "%AN yield" is the acrylonitrile yield percentage. 7. "% Aceto yield" refers to the acetonitrile yield. 8. "α" is calculated as follows: α = [(%AN + (3 × %HCN) + (1.5 × %ACN)) ÷ %PC] × 100 9. b / (a+h) is the ratio of iron atoms to cerium atoms in the bismuth atom composition. 10. "(a+h) / d" is the ratio of atoms in bismuth plus cerium atoms to atoms in the composition of elements D (i.e., nickel, cobalt, manganese, zinc, magnesium, calcium, strontium, cadmium, and barium). 11. For catalysts suitable for the formula description described herein, "m-[(3a+2b+c+2d+3h+3n) / 2]" is a value obtained by subtracting the sum of [(3×number of bismuth atoms 0 + (2×number of iron atoms) + (number of lithium, sodium, potassium, rubidium and cesium atoms) + (2×number of nickel, cobalt, manganese, zinc, magnesium, calcium, strontium, cadmium and barium atoms) + (3×number of cerium atoms) + (3×number of chromium atoms)] divided by 2 from the number of molybdenum atoms (subscript "m" from the formula).

[0061] The present invention relates to an improved and novel mixed metal oxide catalyst for the ammoxidation of propylene and / or isobutylene. This improved catalyst provides a large overall conversion of propylene and / or isobutylene to hydrogen cyanide while maintaining acrylonitrile and / or methacrylonitrile production levels at substantially the same level as prior art catalysts. The data in Tables 1 and 2 clearly demonstrate the benefits of the present invention. Examples 1 to 6 have “b / (a+h)” and “(a+h) / d” values ​​within the scope of the claimed invention (i.e., 0.4

[0062] ​The data in Table 3 clearly demonstrate one embodiment of the present invention. In particular, when the catalyst of the present invention (i.e., the composition of Example 7) is combined with an alkali molybdate, the ammoxidation of propylene to acrylonitrile using hydrogen cyanide produced as a byproduct (i.e., the mixture of Example 8) will result in a further increase in HCN yield and nitrogen efficiency, as indicated by the increase in the α factor. As shown in Example 9, this effect can be reversed. Example 9 demonstrates that the catalyst mixture of Example 8 can be returned to a state that provides a high yield of acrylonitrile by adding molybdenum oxide (i.e., in Example 9, the catalyst returns to the performance of the base composition exemplified as Example 7).

[0063] While the foregoing description and the embodiments described above are typical for the implementation of the present invention, it is obvious that many substitutes, modifications, and variations will be apparent to those skilled in the art in this regard. Accordingly, all such substitutes, modifications, and variations are, and are intended to be, included within the concept and broad scope of the accompanying claims.

Claims

1. A catalyst composition for ammoxidation of unsaturated hydrocarbons, comprising a metal oxide complex, The relative ratio of the listed elements in the catalyst composition is given by the following formula: Mo m Bi a Fe b A c D d E e F f G g Ce h Cr n Q q O x (wherein A is at least one element selected from the group consisting of lithium, sodium, rubidium, and cesium; D is at least one element selected from the group consisting of nickel, cobalt, manganese, zinc, magnesium, calcium, strontium, cadmium, and barium; E is at least one element selected from the group consisting of tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium, and tellurium; F is at least one element selected from the group consisting of lanthanum, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, thallium, silicon, lead, and germanium; G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum, and mercury; Q is at least one of samarium, praseodymium, and neodymium; a, b, c, d, e, f, g, h, n, m, and x are the atomic ratios of bismuth (Bi), iron (Fe), A, D, E, F, G, cerium (Ce), chromium (Cr), molybdenum (Mo), and oxygen (O) relative to m molybdenum (Mo) atoms, respectively. Here, a is between 0.05 and 7. b is between 0.1 and 7. c is between 0 and 5. d is between 0.1 and 12. e is between 0 and 5. f is between 0 and 5. g is between 0 and 0.

2. h is between 0.01 and 5. m is between 10 and 15. n is between 0 and 5. q is between 0 and 2.

476. x is the number of oxygen atoms required to satisfy the valence requirements of the other constituent elements present; 0.4 < b / (a+h) and 0.3 ≤ (a+h) / d, 0 ≤ m - (3a + 2b + c + 2d + 3h + 3n) / 2 ≤ 1.0, A catalyst composition represented by (0.8 ≤ h / b ≤ 5).

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