Ammoxidation catalyst with selective co-product 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 the 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, respectively, and hydrogen cyanide (HCN) and acetonitrile co-products, which catalyst exhibits increased selectivity for hydrogen cyanide compared to prior art catalysts, which catalyst comprises a complex of metal oxides containing bismuth, molybdenum, iron, cerium and other promoter elements, and which is characterized by the ratio of iron to bismuth and cerium contained in the catalyst. [Background technology]

[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 in the presence of ammonia and oxygen (usually in the form of air) at high temperatures to produce acrylonitrile and / or methacrylonitrile.In particular, British Patent No. 1436475; 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. Additionally, U.S. Patent Nos. 5,093,299, 5,212,137, 5,658,842, 5,834,394 and Chinese Patent CN103418400 are directed to bismuth-molybdenum promoted catalysts that exhibit high yields for acrylonitrile. In part, the present invention relates to a cerium promoted bismuth-molybdenum-iron catalyst that contains a greater amount of a cerium-bismuth-molybdenum phase having a scheelite crystal structure than earlier occurrences of compositionally similar catalysts. 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 promoted bismuth-molybdenum-iron ammoxidation catalysts that provide enhanced hydrogen cyanide production. U.S. Patent No. 5,840,648 teaches promoted bismuth-molybdenum-iron ammoxidation catalysts incorporating calcium that provide increased hydrogen cyanide production without a significant decrease in acrylonitrile production. U.S. Patent No. 7,576,232 teaches the addition of various molybdate compounds to ammoxidation catalysts to modify catalytic performance to increase hydrogen cyanide yields and inhibit molybdenum loss from such ammoxidation catalysts. Summary of the Invention

[0003] The present invention is directed to an improved process and catalyst for the ammoxidation of propylene to acrylonitrile, hydrogen cyanide and acetonitrile. The process and catalyst 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 previously achieved with other processes and catalysts. Historically, catalysts that provided increased hydrogen cyanide yields provided increased hydrogen cyanide yields with a corresponding decrease in the yield of acrylonitrile. The catalysts of the present invention do not conform to this historical trend. The process and catalysts of the present invention provide increased 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 provides a catalyst composition comprising a metal oxide composite, comprising: The relative proportions of the recited elements in the catalyst are determined according to 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, 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; Here, a is 0.05 to 7. b is 0.1 to 7; c is 0 to 5; d is 0.1 to 12; e is 0 to 5; f is 0 to 5; g is 0 to 0.2; h is 0.01 to 5; m is 10 to 15; n is 0 to 5; q is between 0 and 2.476; and x is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present; 0.4

[0005] In another embodiment 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 It is.

[0006] The present invention also relates to a propylene ammoxidation catalyst formulation capable of providing a variable and reversible range of yields of useful nitrile products including acrylonitrile and HCN. This variation in yield can be effected during operation of the catalyst by appropriate addition of certain catalyst additives. In particular, the yield of hydrogen cyanide can be calculated according to the formula: A2Mo z O 4+3(z-1) (wherein A is Rb, Li, Na, K, Cs or a mixture thereof; where z is from 1 to about 8), the amount of acrylonitrile and methacrylonitrile produced in the process is increased relative to the amount of molybdate produced by the process. The alkali molybdate may be used with or without a support. ​

[0007] Furthermore, when molybdate is added to the catalyst for the purpose of increasing hydrogen cyanide production, this trend can be reversed by the addition to the catalyst of 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 to catalyze the ammoxidation process. Thus, the addition of molybdenum oxide to the catalyst and alkali molybdate mixture increases the yield of acrylonitrile and methacrylonitrile relative to the amount of hydrogen cyanide produced in the process (i.e., the amount of acrylonitrile and methacrylonitrile and hydrogen cyanide produced will reach or be restored to their pre-molybdate addition levels). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present invention is directed to an improved mixed metal oxide catalyst and method for the ammoxidation of propylene and / or isobutylene. 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 hydrogen cyanide (HCN) and acetonitrile by-products, respectively, which exhibits increased selectivity for hydrogen cyanide compared to prior art catalysts, the catalyst comprising a complex 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. As used herein, "catalyst composition" and "catalyst" are synonymous and are used interchangeably.

[0009] catalyst: In part, the invention provides a multi-component mixed metal oxide ammoxidation catalyst composition comprising a composite catalyst oxide, the composition comprising: The elements and relative ratios of the elements in the catalyst composition are determined according to 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 selected from the group consisting 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; Here, a is 0.05 to 7. b is 0.1 to 7; c is 0 to 5; d is 0.1 to 12; e is 0 to 5; f is 0 to 5; g is 0 to 0.2; h is 0.01 to 5; m is 10 to 15; n is 0 to 5; q is 0 to 2.476; x is the number of oxygen atoms required to satisfy the valence requirements of the other component 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 is free of 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 include lead (Pb). In another embodiment, "F" does not include lead (Pb). In one embodiment, "m" is 12.

[0012] ​In part, the catalyst composition may 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, the catalyst composition may be characterized by a 0.4 In part, the catalyst composition may 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 taken 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. Another independent embodiment is (each row 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 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 "A" elements (i.e., lithium, sodium, potassium, rubidium, and cesium) in the catalyst, "d" is the relative amount of "D" elements (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 amounts are subscripts of the elements in the catalyst formula or, in the case of "a", the sum of the subscripts taken from the catalyst formula for any lithium, sodium, potassium, rubidium and cesium present in the catalyst, and in the case of "d", the sum of the subscripts taken from the catalyst 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 another embodiment, the catalyst does not contain a "Q" element (i.e., "q" is zero). In another embodiment, "q" is greater than zero. In another embodiment, "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 taken 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 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 row 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 has been found that catalysts falling within the range described by 0.8≦h / b≦5 tend to be more powerful in that they exhibit lower friction losses as measured by a submerged jet attrition test.

[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 composite, the relative proportions of the recited elements in said catalyst being in accordance with 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 less than about 10 ppm lead; 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 0.05 to 7. b is 0.1 to 7; c is 0.01 to 5; d is 0 to 12; e is 0 to 5; f is 0 to 5; g is 0 to 0.2; h is 0.01 to 5; i is 0.1 to 12; j is 0 to 12, k is 0 to 12; l is 0 to 12; m is 10 to 15; q is 0 to 2.476; x is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present; 0.4 <b / (a+h)、 0.2 z=d+i+j+k+l and 0.3≦(a+h) / z.

[0019] The catalysts 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 serves as a binder for the catalyst, resulting in a stronger (i.e., greater attrition resistance) catalyst. However, for commercial applications, a proper blend of both the active phase (i.e., the composite of catalytic oxides described above) and the support is essential to obtain acceptable activity and hardness (attrition resistance) of the catalyst. Typically, the support comprises between 40 and 60 weight percent of the supported catalyst. In one embodiment of the present invention, the support may comprise as little as about 30 weight percent of the supported catalyst. In another embodiment of the present invention, the support may comprise as much as about 70 weight percent of the supported catalyst.

[0020] In one embodiment, the catalyst is supported using a silica sol. Typically, the silica sol contains some sodium. In one embodiment, the silica sol contains less than 600 ppm sodium. In another embodiment, the silica sol contains less than 200 ppm 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 can 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 is characterized by the relative yields of acrylonitrile, acetonitrile and hydrogen cyanide produced in the process and / or by 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; The present invention also relates to a process and a novel catalyst for the production of acrylonitrile, acetonitrile and hydrogen cyanide, characterized by a catalyst defined by (α is greater than 102.5).

[0022] In other embodiments, independently, %AN is greater than or equal to 82.5; %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 mole percent yield of acrylonitrile calculated as follows (expressed as a number without any percent sign): (moles of acrylonitrile produced ÷ moles of propylene fed to reactor) × 100. "Hydrogen cyanide yield" means the mole percent yield of hydrogen cyanide calculated as follows (expressed as a number without any percent sign): [(moles of hydrogen cyanide produced ÷ 3) ÷ moles of propylene fed to reactor] × 100. "Acetonitrile yield" means the mole percent yield of acetonitrile calculated as follows (expressed as a number without any percent sign): [(moles of acetonitrile produced ÷ 1.5) ÷ moles of propylene fed to reactor] × 100. Propylene conversion means the mole percent conversion of propylene to products and by-products calculated as follows (expressed as a number without any percent sign): [(moles of propylene fed to reactor minus moles of propylene leaving reactor) ÷ moles of propylene fed to reactor] × 100. "α" is a measure of "nitrogen insertion" or "nitrogen utilization" (i.e., the nitrogen obtained from ammonia during the ammoxidation reaction combines with propylene to form a compound having the functional group "-CN"; as such, the higher the "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 measure of 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 numerous 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). Separately, the source compounds of the remaining elements in the catalyst 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 then calcined as described below. In one embodiment, the elements in the catalyst composition identified above are combined with an aqueous catalyst precursor slurry, the aqueous precursor slurry so obtained is dried to form a catalyst precursor, and the catalyst precursor is calcined to form a catalyst. However, unique to the method of the present invention is the following: (i) combining, in an aqueous solution, source compounds of Bi and Ce, and optionally 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., a first mixture); (ii) adding a source compound of molybdenum to the mixture (i.e., the first mixture) to react with the mixture to form a precipitate slurry; and (iii) combining the precipitate slurry with source compounds of the remaining elements in the catalyst and of the remaining molybdenum to form an aqueous catalyst precursor slurry. It is.

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

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

[0026] In the above catalyst preparation, 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) where in the above relationships, "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 numbers of bismuth, cerium, rubidium, lithium, sodium, potassium, cesium, calcium, lead and tungsten atoms present in the first mixture, respectively.

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

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

[0029] The amount of aqueous solvent in each of the aqueous mixtures and slurries described above can vary due to the solubility of the source compounds that are 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 either case, the source compounds are preferably combined and / or reacted by a protocol that includes mixing the source compounds during the combining and / or reacting steps. The particular mixing mechanism is not critical and can include, for example, mixing the components during the reaction (e.g., stirring or agitating) by any effective method. Such methods include, for example, stirring the contents of the vessel, for example, by shaking, rotating or vibrating the vessel containing the components. Such methods also include stirring, for example, by using a driving force coupled to a stirring member disposed at least partially within the reaction vessel or to the reaction vessel to provide relative motion between the stirring member and the reaction vessel. The stirring member can be a shaft-driven and / or shaft-carried stirring member. The driving force can be directly coupled to the stirring member or can be indirectly coupled to the stirring member (e.g., via electromagnetic coupling). Mixing is generally preferred to be sufficient to mix the components of the reaction medium to allow for efficient reaction between the components, forming a more homogeneous reaction medium (e.g., resulting in a more homogeneous mixed metal oxide precursor) as compared to an unmixed reaction. This results in more efficient consumption of the starting materials and results in a more homogeneous mixed metal oxide product. Mixing the precipitate slurry during the reaction step also causes the precipitate to form in solution rather than on the sides of the reaction vessel. Even more advantageously, having the precipitate form in solution allows particle growth on all surfaces of the particle rather than on limited exposed surfaces where growth occurs out from the reaction vessel walls.

[0030] The source compound of molybdenum may include molybdenum (VI) oxide (MoO3), ammonium heptamolybdate or molybdate salts. The source compound of molybdenum may be derived from any molybdenum oxide, such as the dioxide, trioxide, pentoxide or heptaoxide. However, it is preferred that a hydrolyzable or decomposable molybdenum salt is utilized as the source compound of molybdenum. Typical source compounds for the bismuth, cerium and remaining elements of the catalyst are nitride salts of the metals. Such nitride salts are readily available and easily soluble. The source compound for bismuth may include oxides or salts that will yield oxides upon calcination. Water-soluble salts that are easily dispersed 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 source compound for cerium may include an oxide or a salt that will yield an oxide upon calcination. Water-soluble salts that are easily dispersed by heat treatment but form stable oxides are preferred. In one embodiment, the source compound for cerium is ammonium cerium nitrate, (NH4)2Ce(NO3)6. In another embodiment, the source compound for cerium is cerium nitride, Ce(NO3)3·6H2O. The source compound of iron may be derived from any compound of iron that will yield an oxide upon calcination. When other elements are used, water-soluble salts are preferred due to the ease with which they can be uniformly dispersed within the catalyst. Most preferred is ferric nitride.

[0032] The source compounds for the remaining elements may be derived from any suitable source. For example, cobalt, nickel and magnesium may be introduced into the catalyst using nitride salts. Additionally, magnesium may be introduced into the catalyst as an insoluble carbonate or hydroxide which upon heat treatment will yield the oxide. Phosphorus may be introduced into the catalyst as an alkali metal or alkaline rare earth metal salt or ammonium salt, but is preferably introduced as phosphate. The source compounds for the alkaline component of the catalyst may be introduced into the catalyst as oxides, which will give the oxides upon calcination, or as salts. In addition to water, solvents may be used to prepare mixed metal oxides according to the present invention, including, but not limited to, alcohols such as methanol, ethanol, propanol, diols (e.g., ethylene glycol, propylene glycol, etc.), organic acids such as acetic acid, as well as other polar solvents known in the art. The metal source compound is at least partially soluble in the solvent. As noted above, 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 need not be added at a single point or stage (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 is prepared). In one embodiment, the support is combined with the source compound of molybdenum to form the "second mixture" shown above, before the source compound of molybdenum is combined 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 a 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 to form 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-current spray dryer (i.e., the particles are sprayed co-current to the gas flow). In another embodiment, the spray dryer is counter-current (i.e., the particles are sprayed counter-current to the gas flow). In 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 temperature of the gas and the distance the particles travel in contact with the gas. It is generally undesirable to adjust these parameters to achieve too rapid drying, as this will result in the tendency of the water trapped within the particle to vaporize and form a dry skin on the partially dried particles of the solid phase, which will then tend to burst if they attempt to escape. Similarly, it is desirable to provide the catalyst in a form having as little trapped water as possible. Thus, where a fluid bed reactor is used and fine spherical particles are desired, it is desirable to select spray drying conditions with the objective of achieving complete drying without particle bursting. The dried catalyst material is then heated to remove any remaining nitrides. Denitrification temperatures may range from 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 accomplished in air. In another embodiment, calcination is accomplished 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, the calcination may be at about 600° C. In one embodiment, the calcination may be completed in multiple stages at increasing temperatures. In one embodiment, a first calcination stage is performed 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] Ammoxidation Process The catalyst of the present invention is useful in an ammoxidation process for converting an olefin selected from the group consisting of propylene, isobutylene or mixtures thereof to acrylonitrile, methacrylonitrile or mixtures thereof, respectively, by reacting said olefin with a gas containing molecular oxygen and ammonia in the presence of the catalyst at high temperature and pressure in the gas phase. The catalyst of the present invention is also useful in 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 can be co-fed to a process for the ammoxidation of propylene, isobutylene or mixtures thereof to acrylonitrile, methacrylonitrile or mixtures thereof to increase the production of hydrogen cyanide and / or acetonitrile by-products obtained from such process.

[0036] Preferably, the ammoxidation reaction is carried out in a fluidized bed reactor, although other types of reactors, such as transport line reactors, are envisioned. Fluidized bed reactors for the production of acrylonitrile are well known in the prior art. For example, the reactor design described in U.S. Pat. No. 3,230,246, incorporated herein by reference, is suitable. The conditions for the ammoxidation reaction to occur are also well known in the prior art as evidenced by U.S. Patents 5,093,299; 4,863,891; 4,767,878 and 4,503,001, which are incorporated herein by reference. Typically, the ammoxidation process is carried out by contacting propylene or isobutylene with a fluidized bed catalyst in the presence of ammonium and oxygen at high temperature to produce acrylonitrile or methacrylonitrile. Any source of oxygen can be used. However, for economic reasons, it is preferred to use air. The typical molar ratio of oxygen to olefin in the feed 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. There is no practical upper limit for the ammonia-olefin ratio, but 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 ammonia to propylene ratios ranging from 0.9:1 to 1.3:1, and air to propylene ratios 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 effluent, conditions known as "ammonia breakthrough," which in turn helps reduce process waste. In particular, unreacted ammonia must be removed from the reactor effluent prior to recovery of acrylonitrile. Unreacted ammonia is typically removed by contacting the reactor effluent with sulfuric acid to obtain ammonium sulfide, or by contacting the reactor effluent with acrylic acid to obtain ammonium acrylate, which in both cases produces a process waste stream that is treated and / or disposed of.

[0038] The reaction is carried out at a temperature between the range of about 260° C. and 600° C., with the preferred range being 310° C. to 500° C., and particularly preferred being 350° C. to 480° C. The contact time is not critical but is generally in the range of 0.1 to 50 seconds, with contact times of 1 to 15 seconds being preferred. The products of the reaction may be recovered or purified by any of the methods known to those skilled in the art. One such method involves scrubbing the exhaust gases from the reactor with cold water or a suitable solvent to remove the products of the reaction, followed by purification of the reaction products by distillation. The primary utility of the catalyst prepared by the process of the present invention is for the ammoxidation of propylene to acrylonitrile. Other utilities include the ammoxidation of propane to acrylonitrile, the ammoxidation of alcohols 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-stage process in which propylene is first converted to acrolein in the first stage in the presence of a catalyst, and acrolein is first converted to acrylic acid in the second stage in the presence of a catalyst. The catalyst described herein is suitable for use in the first stage 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 determined according to the formula: A2Mo z O 4+3(z-1) (wherein A is Rb, Li, Na, K, Cs or a mixture thereof; The addition of at least one alkali molybdate compound represented by the formula (I) (z is 1 to about 8) to the catalyst increases the amount of acrylonitrile and methacrylonitrile produced in the process compared to that of the catalyst. The alkali molybdate compound may be unsupported or supported on a suitable support such as silica, alumina, zirconia, titania or mixtures thereof. If supported, the support or carrier contains between 1% and 99% by weight of the combination of the alkali molybdate compound and the support. The amount of the alkali molybdate compound added to the catalyst is in the range of 0.01% to about 10% by weight based on the weight of the catalyst composition. For the catalyst systems previously described herein (i.e., 0.4

[0040] ​Furthermore, when an alkali molybdate compound is added to the catalyst for the purpose of increasing hydrogen cyanide production, this trend can be reversed by the addition of a molybdenum oxide compound selected from the group consisting of MoO3, ammonium molybdate, ammonium heptamolybdate, ammonium dimolybdate, and mixtures thereof, to the catalyst and alkali molybdate mixture catalyzing the ammoxidation process. Thus, the addition of a molybdenum oxide compound to the catalyst and alkali molybdate mixture increases the yield 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 is returned to the level present before the addition of the alkali molybdate, and the amount of hydrogen cyanide will decrease until it approaches or is returned to the level present before the addition of the alkali molybdate). The molybdenum oxide compound may be unsupported or supported on a suitable support such as silica, alumina, zirconia, titania, or mixtures thereof. When supported, the support or carrier comprises between 1% and 99% by weight of the combination of the molybdenum oxide compound and the support. The amount of the molybdenum oxide compound added to the catalyst ranges from 0.01% to about 10% by weight compared to the weight of the catalyst composition.

[0041] The alkali molybdate compound and / or molybdenum oxide compound may be added to the catalyst in situ, i.e., as the catalyst operates in the reactor, or may be added to the catalyst outside the reactor. In one embodiment, the alkali molybdate compound or molybdenum oxide compound is added to (i.e., mixed with) fresh fluidized bed ammoxidation catalyst, which is then added to the reactor as "make-up" catalyst to maintain the catalyst bed height in the reactor, be lost from the reactor in effluent, or replace the catalyst due to attrition. Specific Embodiments To illustrate the invention, catalysts prepared according to the invention were evaluated and compared under similar conditions to similar catalysts prepared by prior art methods outside the scope of the invention. These examples are provided for illustrative purposes only. The catalyst composition for each example is as indicated 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., then adding ammonium heptamolybdate (1245.730 g) with stirring for 30 minutes to form a clear, colorless solution. Reaction mixture B was prepared by heating 257.123 ml of deionized water to 55 °C, followed by the addition of 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 a relative amount of 586.185 ml of deionized water to 65° C., followed by addition of ammonium heptamolybdate (532.896 g) with stirring over a period of 30 minutes to form a clear, colorless solution.

[0043] Reaction mixture D was prepared by (i) heating 1074.497 g of a 50 wt% aqueous (NH4)2Ce(NO3)6 solution to 55 °C, and (ii) sequentially adding Bi(NO3)3·5H2O (475.357 g) and RbNO3 (23.121 g) while the solution was stirred and heated. Reaction mixture E was prepared by adding silica sol (5487.8 g, 41 wt % silica) to reaction mixture A followed by reaction mixture B with stirring. Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D to cause precipitation of an orange solid (the resulting mixture was a precipitate slurry). Stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. Reaction Mixture F was then added to Reaction Mixture E to form the final catalyst precursor slurry. The catalyst precursor slurry was allowed to stir for 1 hour while it was cooled to approximately 40°C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at inlet / outlet temperatures of 325 / 140°C. The resulting powder was denitrified by heat treatment at 290°C in air for 3 hours, followed by 425°C for an additional 3 hours. The powder was then calcined at 560°C in air 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., then adding ammonium heptamolybdate (276.639 g) with stirring for 30 minutes to form a clear, colorless 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) with 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) with stirring over 30 minutes to form a clear, colorless solution.

[0045] Reaction mixture D was prepared by (i) heating 317.026 g of a 50 wt% aqueous (NH4)2Ce(NO3)6 solution to 55 °C, and (ii) sequentially adding Bi(NO3)3·5H2O (69.706 g) and RbNO3 (8.510 g) while stirring and heating the solution. Reaction mixture E was prepared by adding silica sol (1219.5 g, 41 wt % silica) to reaction mixture A followed by addition of reaction mixture B with stirring. Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in the precipitation of an orange solid (the resulting mixture was a precipitate slurry). Stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the range of 50-55°C. Reaction Mixture F was then added to Reaction Mixture E to form the final catalyst precursor slurry. The catalyst precursor slurry was allowed to stir for 1 hour while it was cooled to approximately 40°C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at inlet / outlet temperatures of 325 / 140°C. The resulting powder was denitrified by heat treatment at 290°C in air for 3 hours, followed by 425°C for an additional 3 hours. The powder was then calcined at 560°C in air 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% by mass 38.2nm SiO2 Reaction mixture A was prepared by heating 1358.961 ml of deionized water to 65° C., followed by the addition of ammonium heptamolybdate (1235.419 g) with stirring for 30 minutes to form a clear, colorless solution. Reaction mixture B was prepared by heating 265.465 ml of deionized water to 55 °C, followed by the addition of 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) with stirring. Reaction mixture C was prepared by heating 581.333 ml of deionized water to 65° C., then adding ammonium heptamolybdate (528.485 g) with stirring for 30 minutes to form a clear, colorless solution.

[0047] Reaction mixture D was prepared by (i) heating 1065.603 g of a 50 wt% (NH4)2Ce(NO3)6 aqueous solution to 55 °C, and (ii) successively adding Bi(NO3)3·5H2O (471.422 g) and RbNO3 (22.930 g) while stirring and heating the solution. Reaction mixture E was prepared by adding silica sol (5487.8 g, 41 wt % silica) to reaction mixture A followed by addition of reaction mixture B with stirring. Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, resulting in the precipitation of an orange solid (the resulting mixture was a precipitate slurry). Stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. Reaction Mixture F was then added to Reaction Mixture E to form the final catalyst precursor slurry. The catalyst precursor slurry was allowed to stir for 1 hour while it was cooled to approximately 40°C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer with inlet / outlet temperatures 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 an additional 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% by mass 38.2nm SiO2 Reaction mixture A was prepared by heating 1399.413 ml of deionized water to 65° C., then adding ammonium heptamolybdate (1272.194 g) with stirring for 30 minutes to form a clear, colorless solution. Reaction mixture B was prepared by heating 259.349 ml of deionized water to 55 °C, followed by the addition of 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., followed by the addition of ammonium heptamolybdate (480.840 g) with stirring for 30 minutes to form a clear, colorless solution. Reaction mixture D was prepared by (i) heating 1062.136 g of a 50 wt% aqueous (NH4)2Ce(NO3)6 solution to 55 °C, and (ii) sequentially adding Bi(NO3)3·5H2O (385.155 g) and RbNO3 (23.417 g) while stirring and heating the solution.

[0049] Reaction mixture E was prepared by adding silica sol (5263.2 g, 41 wt % silica) to reaction mixture A followed by reaction mixture B with stirring. Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, resulting in the precipitation of an orange solid (the resulting mixture was a precipitate slurry). Stirring of the precipitate slurry was continued for 15 minutes while maintaining the temperature in the range of 50-55°C. Reaction Mixture F was then added to Reaction Mixture E to form the final catalyst precursor slurry. The catalyst precursor slurry was allowed to stir for 1 hour while cooling to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at inlet / outlet temperatures of 325 / 140° C. The resulting powder was denitrified by heat treatment at 290° C. in air for 3 hours, followed by another 3 hours at 425° C. The powder was then calcined at 560° C. in air 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., then adding ammonium heptamolybdate (136.60 g) with stirring for 30 minutes to form a clear, colorless 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) with stirring. Reaction mixture C was prepared by heating 71.75 ml of deionized water to 65° C., followed by addition of ammonium heptamolybdate (59.3332 g) with stirring for 30 minutes to form a clear, colorless solution. Reaction mixture D was prepared by (i) heating 119.53 g of a 50 wt% aqueous (NH4)2Ce(NO3)6 solution to 55 °C, and (ii) successively adding Bi(NO3)3·5H2O (52.8606 g) and RbNO3 (2.7027 g) while stirring and heating the solution. Reaction mixture E was prepared by adding silica sol (609.76 g, 41 wt % silica) to reaction mixture A followed by reaction mixture B with stirring. Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, resulting in precipitation of an orange solid (the resulting mixture was a precipitate slurry). Stirring of the precipitate slurry was continued for 15 minutes while maintaining the temperature in the range of 50-55°C. Reaction Mixture F was then added to Reaction Mixture E to form the final catalyst precursor slurry. The catalyst precursor slurry was stirred for 1 hour while it was allowed to cool to approximately 40°C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at inlet / outlet temperatures of 325 / 140°C. The resulting powder was denitrified by heat treatment in air at 290°C for 3 hours, followed by 425°C for an additional 3 hours. 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% by mass 38.2nm SiO2 Reaction mixture A was prepared by heating 144.67 ml of deionized water to 65° C., then adding ammonium heptamolybdate (131.32 g) with stirring for 30 minutes to form a clear, colorless 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) with stirring. Reaction mixture C was prepared by heating 74.12 ml of deionized water to 65° C., then adding ammonium heptamolybdate (61.1793 g) with stirring for 30 minutes to form a clear, colorless solution.

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

[0053] Example 7 Ni4Mg3Fe1.2Rb0.192Cr0.05Bi1.0Sm0.1Ce1.5Mo12.996Ox+50 mass% 38.2nm SiO2 Reaction mixture A was prepared by heating 152.49 ml of deionized water to 65° C., then adding ammonium heptamolybdate (139.06 g) with stirring for 30 minutes to form a clear, colorless 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) with stirring. Reaction mixture C was prepared by heating 70.69 ml of deionized water to 65° C., followed by addition of ammonium heptamolybdate (58.4395 g) with stirring for 30 minutes to form a clear, colorless solution.

[0054] Reaction mixture D was prepared by (i) heating 141.57 g of a 50 wt % aqueous (NH4)2Ce(NO3)6 solution to 55 °C and (ii) successively adding Bi(NO3)3·5H2O (41.7512 g), RbNO3 (2.4389 g), and Sm(NO3)3·6H2O (3.8270 g) to the solution while stirring and heating. Reaction mixture E was prepared by adding silica sol (609.76 g, 41 wt % silica) to reaction mixture A followed by addition of reaction mixture B with stirring. Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in the precipitation of an orange solid (the resulting mixture was a precipitate slurry). Stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. Reaction Mixture F was then added to Reaction Mixture E to form the final catalyst precursor slurry. The catalyst precursor slurry was allowed to stir for 1 hour while it was cooled to approximately 40°C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at inlet / outlet temperatures of 325 / 140°C. The resulting powder was denitrified by heat treatment at 290°C in air for 3 hours, followed by 425°C for an additional 3 hours. The powder was then calcined at 560°C in air for 3 hours.

[0055] Example 8 The example catalyst was prepared using the same formulation as in Example 7, except that 0.094 grams of K2MoO4 solid crystals were added to the finished catalyst. Example 9 This example was a continuation of the catalyst testing of Example 8. After 382 hours on stream, 0.144 grams of MoO3 was added to the Example 8 catalyst and the test for the 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 carried out in a 40 cc fluidized bed reactor. Propylene was fed into the reactor at rates between 0.080 and 0.100 WWH (i.e., mass of propylene / mass of catalyst / hour) as shown in Tables 1 and 3. The pressure inside the reactor was maintained at 10 psig. The reaction temperature was 430°C. Reaction product samples were collected after several days of testing (between about 140 and about 190 hours on stream). The reactor effluent was collected in a bubble-type scrubber containing 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 run with the aid of a gas column chromatograph equipped with a split column gas analyzer. At the end of the recovery run, the total scrubber liquor was diluted to approximately 200 grams with dilution water. A weighed amount of 2-butanone was used as an internal standard in approximately 50 gram aliquots of the diluted solution. A 2 μl sample was analyzed on a GC equipped with a flame ionization detector and a Carbowax™ column. The amount of NH3 was determined by titrating the free HCl excess with NaOH solution. The propylene conversion and acrylonitrile yield for the tested catalysts are shown in Tables 1 and 3. HCN was analyzed by titrating with AgNO3 solution after adding caustic iodide.

[0057] [Table 1]

[0058] [Table 2]

[0059] [Table 3]

[0060] Notes for Tables 1, 2 and 3 (where available): 1. "WWH" is the mass of propylene per mass of catalyst per hour in the feed 2. "T°C" is the reactor temperature in degrees Celsius 3. "HOS" is time on stream. 4. "%C3", "Conv" or "%PC" is the propylene conversion (i.e., the mole percent per pass conversion of propylene to all products). 5. "% AN Yield" is the percent acrylonitrile yield. 6. "% AN Yield" is the percent acrylonitrile yield. 7. "% Acetonitrile Yield" is the acetonitrile yield 8. "α" is calculated as follows: α = [(%AN + (3 x %HCN) + (1.5 x %ACN)) ÷ %PC] x 100. 9. "b / (a+h) is the ratio of atoms of iron to atoms of cerium plus atoms of bismuth in a composition. 10. "(a+h) / d" is the ratio in a composition of atoms of bismuth plus atoms of cerium to atoms of the D elements (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 the number obtained by subtracting from the number of molybdenum atoms (the subscript "m" from the formula) the sum of [(3×number of bismuth atoms0+(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.

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

[0062] ​The data in Table 3 clearly demonstrates 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 salt, there will be a further increase in HCN yield and a further increase in nitrogen efficiency for the ammoxidation of propylene to acrylonitrile with hydrogen cyanide produced as a by-product (i.e., the mixture of Example 8), as shown by the increase in alpha 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 with the addition of molybdenum oxide (i.e., in Example 9, the catalyst reverts to the performance of the base composition exemplified as Example 7).

[0063] While the foregoing description and embodiments are exemplary of the practice of the invention, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in view of this description, and all such alternatives, modifications and variations are intended to be embraced and fall within the concept and broad scope of the appended claims.

Claims

1. A catalyst composition comprising a metal oxide composite, The relative proportions of the recited elements in said catalyst composition are determined according to 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, 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; 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; Here, a is 0.05 to 7; b is 0.1 to 7; c is 0 to 5; d is 0.1 to 12; e is 0 to 5; f is 0 to 5; g is 0 to 0.2; h is 0.01 to 5; m is 10 to 15; n is 0 to 5; q is 0 to 2.476; x is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present; 0.4<b / (a+h) and 0.3≦(a+h) / d.

2. 2. The catalyst composition of claim 1, wherein 0≦m−(3a+2b+c+2d+3h+3n) / 2≦1.

0.

3. 2. The catalyst composition of claim 1, wherein 0.3≦(a+h) / d≦1.

4. 2. The catalyst composition of claim 1, wherein 0.45≦(a+h) / d≦1.

5. 2. The catalyst composition of claim 1, wherein 0.8≦h / b≦5.

6. 2. The catalyst composition of claim 1, wherein 0.5≦a / h<1.

5.

7. 2. The catalyst composition of claim 1, wherein 0≦q / (a+h+q) and q / (a+h+q)<0.

16.

8. 10. The catalyst composition of claim 1, wherein D is nickel.

9. formula: A 2 Mo z O 4+3(z-1) wherein A is Rb, Li, Na, K, Cs or a mixture thereof; z is 1 to about 8.

10. The catalyst composition of claim 1 further comprising at least one alkali molybdate compound represented by:

10. 10. The alkali molybdate compound of claim 9, comprising a support selected from the group consisting of silica, alumina, zirconia, titania or mixtures thereof, the support comprising between 1% and 99% by weight of the combination of the molybdate and the support.

11. 10. The catalyst composition of claim 9, comprising between 0.01 wt.% and about 10 wt.% of an alkali molybdate compound, based on the total weight of the catalyst composition.

12. Advantageous Effects of Invention When the catalyst composition is used as a catalyst for the production of acrylonitrile, acetonitrile and hydrogen cyanide in a process comprising contacting propylene, ammonia and oxygen in the vapor phase in the presence of a catalyst at an elevated temperature, the relative yields of acrylonitrile, acetonitrile and hydrogen cyanide from said process are as follows: α=[(%AN+(3×%HCN)+(1.5×%ACN))÷%PC]×100 (wherein %AN is the acrylonitrile yield and %AN≧82; %HCN is hydrogen cyanide yield and %HCN≧5 %ACN is the acetonitrile yield; %PC is the propylene conversion; α is greater than 102.5) 2. The catalyst composition of claim 1, wherein the catalyst composition is defined by:

13. 1. A process for converting an olefin selected from the group consisting of propylene, isobutylene and mixtures thereof, together with hydrogen cyanide produced as a by-product, to acrylonitrile, methacrylonitrile and mixtures thereof, by reacting in the vapor phase, at high temperature and pressure, with a gas containing molecular oxygen and ammonia in the presence of a catalyst, wherein the relative ratios of the recited elements in said catalyst satisfy 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, 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; 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; Here, a is 0.05 to 7; b is 0.1 to 7; c is 0 to 5; d is 0.1 to 12; e is 0 to 5; f is 0 to 5; g is 0 to 0.2; h is 0.01 to 5; m is 10 to 15; n is 0 to 5; q is 0 to 2.476; x is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present; 0.4<b / (a+h) and 0.3≦(a+h) / d) The method is represented by

14. The yield of hydrogen cyanide is calculated according to the formula: A 2 Mo z O 4+3(z-1) wherein A is Rb, Li, Na, K, Cs or a mixture thereof; z is 1 to about 8.

14. The process according to claim 13, wherein the amount of acrylonitrile and methacrylonitrile produced in the process is increased by the addition of at least one alkali molybdate compound represented by:

15. 14. The method of claim 13, wherein the catalyst composition comprises between 0.01 wt.% and about 10 wt.% of the alkali molybdate compound, based on the total weight of the catalyst composition.

16. The yield of acrylonitrile and methacrylonitrile is MoO 3 14. The method of claim 13, wherein the amount of hydrogen cyanide produced in the process is increased compared to the amount of hydrogen cyanide produced by the addition to the catalyst of a molybdenum oxide compound selected from the group consisting of ammonium molybdate, ammonium heptamolybdate, ammonium dimolybdate and mixtures thereof.

17. 17. The method of claim 16, wherein the amount of the molybdenum oxide compound added to the catalyst ranges from 0.01% to about 10% by weight based on the weight of the catalyst.

18. 14. The method of claim 13, wherein 0≦m−(3a+2b+c+2d+3h+3n) / 2≦1.0 in the catalyst.

19. 14. The process of claim 13, wherein 0.3≦(a+h) / d≦1 in the catalyst.

20. 14. The process of claim 13, wherein 0.45≦(a+h) / d≦1 in the catalyst.

21. 14. The process of claim 13, wherein 0.8≦h / b≦5 in the catalyst.

22. 14. The process according to claim 13, wherein 0.5≦a / h<1.5 in the catalyst.

23. 14. The method of claim 13, wherein 0≦q / (a+h+q) and q / (a+h+q)<0.16 in the catalyst.

24. 14. The method of claim 13, wherein D is nickel in the catalyst.

25. below: 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; α is greater than 102.5) The method of claim 13 , wherein the compound is defined by:

26. A catalyst composition comprising a metal oxide composite, the relative proportions of the recited elements in said catalyst being in accordance with 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 MM l Q q O x wherein A is at least one element selected from the group consisting of sodium, potassium, rubidium, and cesium; 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 less than about 10 ppm lead; 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 0.05 to 7; b is 0.1 to 7; c is 0.01 to 5; d is 0 to 12; e is 0 to 5; f is 0 to 5; g is 0 to 0.2; h is 0.01 to 5; i is 0.1 to 12; j is 0 to 12; k is 0 to 12; l is 0 to 12; m is 10 to 15; q is 0 to 2.476; x is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present; 0.4<b / (a+h), 0.2<i / (i+j+k+l), and z=d+i+j+k+l and 0.3≦(a+h) / z.

27. 27. The catalyst composition of claim 26, wherein 0≦m−(3a+2b+c+2d+3h+3n) / 2≦1.

0.

28. 27. The catalyst composition of claim 26, wherein 0.3≦(a+h) / d≦1.

29. 27. The catalyst composition of claim 26, wherein 0.45≦(a+h) / d≦1.

30. 27. The catalyst composition of claim 26, wherein 0.8≦h / b≦5.

31. 27. The catalyst composition of claim 26, wherein 0.5≦a / h<1.

5.

32. 27. The catalyst composition of claim 26, wherein 0≦q / (a+h+q) and q / (a+h+q)<0.

16.

33. formula: A 2 Mo z O 4+3(z-1) wherein A is Rb, Li, Na, K, Cs or a mixture thereof; wherein z is from 1 to about 8.

34. 34. The catalyst composition of claim 33, wherein the alkali molybdate compound comprises a support selected from the group consisting of silica, alumina, zirconia, titania or mixtures thereof, and the support comprises between 1% and 99% by weight of the combination of the alkali molybdate and the support.

35. 34. The catalyst composition of claim 33, comprising between 0.01 wt.% and about 10 wt.% of an alkali molybdate compound, based on the total weight of the catalyst composition.

36. Advantageous Effects of Invention When the catalyst composition is used as a catalyst for the production of acrylonitrile, acetonitrile and hydrogen cyanide in a process comprising contacting propylene, ammonia and oxygen in the vapor phase in the presence of a catalyst at an elevated temperature, the relative yields of acrylonitrile, acetonitrile and hydrogen cyanide from said process are as follows: 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; α is greater than 102.5) 27. The catalyst composition of claim 26, wherein the catalyst composition is defined by:

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