IL31274A - Uranium,arsenic,antimony and molybdenum oxidation catalysts and promoters therefor - Google Patents

Description

Uranium, arsenio, antimony and molybdenum oxidation catalysts and promoters therefor THE STANDARD Oil, COMPANY C: 29531 hle invention relates to the catalytic oxidation of .

Olefins in the vapor phasef and to catalysts therefor.

According to the invention there is rovided a process for the oxidation of olefins, which is characterized by contacting in the vapor phase a mixture of a molecular oxygen-containing gas and an olefin, and optionally ammonia, with a catalyst composition which consists essentially of activated catalytic oxide complexes A, B and/or C, optionall promoted -by at least one .of the elements cerium, antimony, tungsten, zinc, manganese, iron, chromium, bismuth, nickel, tin, vanadium, boron, molybdenum and arsenic, wherein A Is defined by the empirical formula ϋχ Moy 0z wherein 'x» ranges from 1 to 25, *y* ranges from 1 to 25 and 'zf is a number taken to satisfy the average valences of uranium and molybdenum in the oxidation states in which they exist in said catalyst; wherein B Is defined by the empirical formula θχ Uy wherein 'χ· ranges from 1 to 10, ry' ranges from 1 to 25 and 'a' is a numbeijtaken to satisfy the average valences of arsenic and uranium i the oxidation states in which they exist in said catalyst] wherein G is defined by the empirical formula S a ΐί¾ oQ wherein ' 1 ranges from 3 to 15, 'b' ranges from 1 to 3, 'c' ranges from 0.001 to 0.5 and ' d' is a number taken to satisfy the average valences of antimony, uranium and molybdenum in the oxidation states in which they exist in said catalyst; each of said catalysts being formed by heating the mixed oxides of the elements of the base catalyst In the presence of oxygen at an elevated temperature above 500°F. but below their melting elfept for a time sufficient to form said active catalytic oxide.*; By the process according to the invention it is possible to perforin, for example, the catalytic oxidation of olefins to unsaturated aldehydes and acids, conjugated dienes, and the catalytic ammoxidation of olefins to unsaturated nltriles.,' The catal tic acrolein and acrylic acid, the oxidation of isobutylene to methacrolein, the oxydehydrogenation of an olefin having four to eight carbons, such as the oxydehydrogenation of butene-1 or . , bw¾ne-2 to butad ene-1,3 » the ammoxidation of propylene to acrylonltrile and the ammoxidation of isobutylene to methacrylo-nitrile.. - , The ammoxidation aforesaid can he effected, for example, by contacting in the vapor phase at a temperature within the range from about 65Q°F. to about 1100°.F. and in the presence of the catalyst a mixture of ammonia, a molecular oxygen-containing gas and either propylene or ieobutylene, or mixtures thereof in a molar ratio of olefin to ammonia of from It 0.05 to 1:5, and a molar ratio of oxygen to olefin within the range from 0.5 tl to si.

The oxydehydrogena on may be carried out, for example, by contacting a mixture o oxygen and an olefin having at least four and up to about eight non-quaternary carbon atoms of which at least four are arranged in a straight chain in the vapor phase at temperature at which the oxidative dehydrogenation proceeds in the presence of the catalyst.

The inventio also consists in catalysts of t e kind defined above.

Though the unsupported catalyst of the invention gives good results a preferred Gatalyst contains from 5 to 95 pe cen by weight of any imown catalyst support, silica being preferred.

In the preparation of the base catalyst the oxides of the elements can be blended together or can be formed separately and then blended, o formed separately or together in situ.

The preferred manner of arriving at the oxides of the to.ofcc.nt base catalyst is by the use of water-soluble salts of the W ortho-arsenic acid, for antimony is a slurry of hydrous antimony oxide formed n situ by the addition of the metal in nitric acid.

Of course, various other salts, soluble at least to some extent in water, may be used to form the solutions which when subjected to the steps to be outlined hereinafter will yield the desired' oxides of the base catalyst. Similarly, the catalyst may also be prepared by co-preoipitation of the oxides, or of ;salt's' which result In the oxides upon heat-treating and impregnation of one or more of the metals which upon heat-treating result in the oxides.

Irrespective of the method of incorporating the catalyst components into a base catalyst, it is" found that the components present in the ranges disclosed exhibit unexpected and highly desirable characteristics for the carrying out of the process set out hereinbefore.

The catalytic activity of the base catalyst is enhanced by heating the catalyst at an elevated temperature. Preferabl the catalyst mixture is. dried and heated at a temperature of from 500 to 1100°F., more preferably at about 600 to 800°F, for from 2 to 24 hours. If the activity is still insufficient, the catalys can be further heat-treated at a temperature above about 8Q0°F bu below a temperature deleterious to the catalyst, especially below the melting point of the oxides, preferably in the range from about 800°P to about 14C0°F for from 1 to 48 hours, In the presence of oxygen or an oxygen-containing gas such as air.

It has also been found that some of the instant catalysts can be further activated by subjecting heat-treated catalyst to a reducing atmosphere for a period of from about k hours to about 8 hours at a temperature in the range from about 00°F to about 1000°F. This reducing treatment is conveniently accomplished by flowing a reducing gas such as ammonia , hydrogen or the like over the catalyst. It was found that catalysts treated with a reducing gas gave higher conversions after a short period of time during which the conversions were actually lower than those given by the same catalysts without the reducing treatment.

Where the base catalyst is the oxides of antimony, uranium and molybdenum the base catalyst may be promoted by the oxide or oxides of iron present in the range from 0 .001 to less than 0 . 75 atom of iron per atom of uranium.

Where the base catalyst has the elements uranium and molybdenum, various metal oxides selected from Groups I-A, I-B, II-A, II-B, III-B, IV-A, IV-B, V-B, VI-B VII-B and VIII of the Periodic Table (See Handbook, of Chemistry, 38th Edition, Chemical Rubber Publishing Co., Periodic Chart of the Elements, pg. 39^ and 395 ) are useful promoters. Particularly effective are the oxides of arsenic, bismuth, tin, vanadium, iron, nickel and cobalt in an amount in the range from 0 . 001 to 1 per atomic equivalent of either uranium or molybdenum.

Where the base catalyst has the elements uranium and arsenic, various metal oxides selected from Groups I-A, I-B, II-A, II-B, III-B, IV-A, IV-B, V-B, VI-B, VII-B and VIII of the Periodic Table (refer to above) are useful promoters. Particularly effective are the oxides of molybdenum, boron, vanadium, tin, nickel, bismuth, chromium, iron, manganese, zinc and tungsten in an amount corresponding to less than 1 atomic equivalent of either uranium or arsenic.

Promoter oxides may be incorporated into the base catalyst by blending into the gel before calcining, or by blending into the oven-dried base catalyst before calcining. A preferred manner of incorporating a promoter element is by forming an aqueous solution of its salt, mixing this solution with the solutions of salts of the elements of the base catalyst, and stirring while continuously heatin until the solution gels. The gel is spooned into trays and oven-dried at 120°C overnight. The dried catalyst is then calcined at 800°F. A further calcination at a higher temperature may also be given to increase the activity of the catalyst complex .

Oxidation of olefins having three carbon atoms in a straight chain is accomplished at a reactor pressure in the range from -10 to 100 psig, a reactor temperature in the range from 500 to 1100°F and apparent contact times which may vary from 0.1 to 50 seconds. A molar ratio of oxygen to olefin between about 0.5".1 to 5:1 gives satisfactory results.

Olefins with three carbon atoms in a straight chain may be converted to the nitriles under similar conditions as described hereinabove, except that ammonia is introduced into the reactor along with the oxygen.

A desirable ammonia to olefin ratio is about 1:1, as it has been found that generally undesirable, olefinically unsaturated oxygenated products are formed when this ratio is in the range over 0.15:1 to 0.75:1. Water is formed as a product of reaction, and additional water may be added both to improve conversions as well as to control the thermal condition of t.ie reactor.

Olefins having at least four and up to about eight non-quaternary carbon atoms, of which at least four are arranged in series in a straight chain or ring may be oxidatively dehydrogenated to diolefins and aro-matics. Preferred olefins are either normal straight chain or tertiary olefins, and both cis- and trans-isomers are useful. From about 0.3 to 3 moles of oxygen per mole of olefin may be used for oxydehydrogenation of the olefins, a slight molar excess of oxygen being preferred. Reaction temperatures may range from about 325 to 1000°C, provisions being made for removal of the exothermic heat of reaction particularly when reactor temperatures exceed 550°C. Pressures, temperatures and contact times are in the same range as those for the reactions described hereinabove.

The apparent contact time is defined as the length of time in seconds which the unit volume of gas measured under conditions of reaction is in contact with the apparent unit volume of the catalyst. It is calculated from the apparent volume of the catalyst bed, the average pressure and temperature of the reactor and the flow rates of the several components of the reaction mixture.

The percent per pass conversion is defined as the moles of the unsaturated product recovered divided "by the moles of the monoolefin introduced in the feed, multiplied by 100.

Any type of reaction apparatus suitable for carrying out vapor phase oxidation reactions may be employed, preferred reactors being of the fixed bed and fluid bed types. Examples, in which all 'parts' are parts by weight unless otherwise specified, of a base catalyst are set forth as follows: Example 1 Unpromoted catalyst is made by dissolving 53-2 parts of ammonium molybdate in 100 parts water: and 50.2 parts of uranyl nitrate (U< ) (Ν03)2·6Η20 were dissolved in 100 parts water.

The two solutions were added* to 49 parts Ludox® AS, a 30 by weight dispersion of silica in water. The resulting mixture was heated until it gelled and dried first at 120°C for 24 hours and then at 800°F for 21 1/2 hours.

Example 2 In a typical preparation of the unpromoted catalyst, 87.8 g of uranyl nitrate (U02) .6H20 were dissolved in about 100 cc of hot water; 154.3 g of ortho-arsenic acid were dissolved in about 400 cc of hot water. The uranyl nitrate solution was added to the dilute ortho-arsenic acid and the mixture stirred. To this mixture was added II6.8 g of Ludox® AS. The mixture was continuously heated with constant stirring until it gelled. The gel was spooned into trays, placed in an atmospheric convection oven at 120°C and dried overnight. The oven-dried catalyst was then heat-treated in a furnace open to the atmosphere, starting at 800°F and being raised to 900°F over a period of about 2 hours. The catalyst was calcined overnight at 900°F. The catalyst obtained had a composition which may be written as 82.5$ UAs^ 8°17 5 ~ ^ Si02- Example 3 An unpromoted antimony-uranium-molybdenum catalyst is prepared by impregnating the molybdenum on to the antimony and uranium components, as follows: Part A: 3.9 Parts of antimony oxide (SbgO^) and I.65 parts uranium oxide (υ^Οβ) were dissolved in 15 parts of nitric acid; the mixture is heated for about 2.5 hours in a vessel equipped with a reflux condenser and an agitator. Add 6.1 parts of water and cool to about 50°C. Add 5 parts Ludox® AS and mix vigorously to keep the solids in suspension. Adjust the pH of the mixture to about 8.5 with 30$ NH^OH solution. Filter the catalyst and dry the filter cake overnight in an oven at 120°F.

Remove the oven-dried catalyst and calcine it in a furnace open to the atmosphere for about 2 hours at 800°F. A further calcination is obtained by increasing the temperature to about 1700°F and heat-treating for a period of about 2.5 hours. 2.5 Parts of the solids thus obtained are blended with 8.3 parts of Ludox®. If the mixture does not gel, add a few drops of 20$ NH^HO^. The gelled mixture is spooned into trays and dried overnight at low temperatures . The dried mixture is again calcined for about 2 hours at about 172 °F, cooled, ground and Part B: 0.375 Parts of ammonium molybdate is dissolved in 400 parts water and the solution is poured over 636 parts of catalyst prepared as in Part A above. The mixture is stirred thoroughly and dried overnight at 120°C in a conventional oven and then heat-treated at 1000°F for 2 hours. The result is a catalyst which has been impregnated with the molybdenum component and which has a surface area of about 20 sq. meters/gram.

Results obtained from runs utilizing some of the above-described catalysts in the ammoxidation of an olefin to the unsaturated nit rile are tabulated in Table I. In this, as in other tables, only the metallic elements of the catalyst are listed, it being presumed that sufficient oxygen is present to satisfy the oxidation state in which the catalyst exists after calcination followed by a final heat-treatment where necessary .

Table II sets forth the results obtained in the oxidation of olefins to unsaturated aldehydes.

Minor quantities of unsaturated acids which are also formed are not quantified.

Table III sets forth the results obtained in the oxydehydrogenation of butenes, 1-butene being a preferred feed, to butadiene. In each case the approxi -mate molar ratio of butenes to air was 1:12. As in the other tables, minor quantities of oxidation byproducts that are formed are not quantified.

Heat-treatments., of 1000°F and over, indicated in the tables are generally to enhance activation after calcination at 800°P for from l6 to 24 hours.

Example 4 Iron and bismuth promoters were incorporated within the catalyst of Example I as follows: 48.2 g of Fe( 02)3.9H20 were dissolved in 100 ml water and 9-7 g of acid solution. 60.3 g U02( 03)2.6H20 and 42.4 g were dissolved in about 500 ml water and the ferric nitrate and bismuth nitrate solutions added. 59.0 g of Ludox® AS were added to the total and the mixture stirred and heated, until it thickened. It was then dried at about 130°C overnight, then heat-treated in a furnace open to the atmosphere at 800°F for l6 hours and further heat-treated at 1050°F - 1100°F for 3 hours . The composition of the promoted catalyst formed may be written 82.5$ FegUgBi^Mb-^O - 17. $ Si0x and 'X1 is thought to be about 65.5.

Arsenic and iron promoters were similarly incorporated within the unpromoted catalyst by the addition of the soluble salt solutions, the nitrates of the promoter elements being preferred. The amount of Ludox® AS solution used is determined by the proportion of 'active' material to catalyst support desired.

Example 5 An ammonium molybdate solution was mixed with a solution of uranyl nitrate and ortho-arsenic acid and the mixture stirred. To the mixture was added a sufficient quantity of Ludox® AS solution so that upon continuous heating at about 100°C, and upon stirring the mixture gelled. The gel was then treated in the same manner as the gel formed with the elements of the base Example 6 An iron promoted antimony-uranium-molybdenum catalyst is prepared by impregnating the molybdenum and iron on to antimony and uranium components., as follows: 0.45 Parts of ferric nitrate, and O.O6 parts of ammonium molybdate ( H^)gMo^02^.4H20 were dissolved in about 20 parts distilled water added thereto. The aqueous solution was poured over 50 parts of the composition obtained in Part A of Example 3 hereinabove with constant stirring to obtain uniform wetting of the solids. The wet solids were then dried at 120°C overnight and subsequently heat-treated for 2 hours at 1000°F.

The following Table II sets forth results obtained using various promoters with the base catalyst wherein the olefin to air molar ratios in the feed are approximately 1:12 for the conversion of the olefin to the unsaturated aldehyde. Minor quantities of acrylic acid which are formed are not specifically quantified.

Example 7 An unpromoted antimony-uranium-molybdenum catalyst is prepared by impregnating the molybdenum on to the antimony and uranium components as follows: Step A: 3.9 Parts SbgO^ and I.65 parts U^Og are dissolved in 15 parts HNO3 acid; the mixture is heated for 2 1/2 hours under reflux. 6.1 Parts water are added and the mixture cooled to 50°C Add 5 parts Ludox® AS mixed vigorously, adjust the pH of the mixture to about 8.5 with 30$ NH OH solution, filter and dry the cake overnight at 120°C, then calcine in a furnace open to the atmosphere for 2 hours at 800°F and then at a temperature of 1700°F for 2 1/2 hours. 2 1/2 Parts of solids thus obtained are blended with 8 .3 parts Ludox® and gelled and dried. The dried mixture is calcined for 2 hours at 1725°F.

Step B; . 375 Parts is dissolved in 400 parts water and the solution poured over 636 parts of catalyst prepared as in Step A above. The mixture is stirred and dried overnight, then heat-treated at 1000°F for 2 hours.

TABLE I Feed Catalyst Elements Atomic Heat Treat Composition Ratio Temp. F & Ti (molar ratios) C3=/NH3/Air= Mo, U Mo:U=3:l 800 1/1.1/12 C3=/H3/Air As, U As:U=5.8:l 1200 1/1.1/12 iC^/Air/NH Sb:U:Mo= Sb3 U, Mo 1000 1/14/1.2 4.56: 1 : .01 C3=/NH3/Air Mo j U promoted Mo:U:As= 1075 1/1.1/12 with As 3: 3: 0.25 C3=/NH3/Air U, As promoted U:As:Mo= 1800 1/1.1/12 with Mo 1: 3 : 0.1 i¾=/NH3/Ai Sb, U„ Mo Sb:U:Mo:Fe= promoted 1000 1/1.2/14 with Fe 4.56: 1: .01 : .033 TABLE II Catalyst Elements Atomic Ratio Heat Treatment Temp.°F & Time,hrs.

Mo, U Mo:U=12:l 1075 3 U, As U:As=l:5 1200 3 Sb:U:Mo= Sb, U, Mo 1000 2 4.56:1: .025 Mo:U:Bi= Mo, U, Bi 1075 3 3:3:0.25 U:As:Mo= U, As, Mo 1100 3 1:1: .25 Sb:U:Mo:Fe= Sb, U, Mo, Fe 1000 2 4.56:1: .025: .1 TABLE III Catalyst Element Atomic Ratio Heat Treatment Temp.°F & Time,hrs.

Mo, U Mo:U=2:l 1050 3 U:As:Fe- U, As, Fe looo 3 1:3:0.1 Sb:U:Mo= Sb, U, Mo 1000 2 4.56:1: .01 Mo:U:Bi= Mo, U, Bi 1075 3 3:3:0.25 Mo:U:Bi:Ni Mo, U, Bi, Ni, 1075 3 12:6:1:3:3 Sb:U:Mo:Fe Sb, U, Mo, Fe 1000 2 4.56:1: .01

Claims (13)

1. 31274/2 CLAIMS. 1 '. A process for , the oxidation, of olefins characterized by contacting in the vapor phase a mixture of a molecular oxygen-containing gas and an olefin;, and optionally- ammonia, with a catalyst composition which consists essentially of . activated catalytic oxide complexes A,. B' and/or C, optionally', promoted by at least one of the elements- cerium, antimony, tungsten/ zinc, . manganese, iron, chromium, bismuth, nickel, tin, vanadium, . boron, molybdenum and arsenic, wherein A. is . defined by the empirical. formula Ux- Moy 0Z wherein 'χ' ranges from 1 to 25, 'y' ranges from 1 to 25 and 'ζ' is a number taken to satisfy the average valences of uranium and molybdenum in the oxidation states in which they exist in said catalyst; wherein B is defined by the empirical formula Asx Uy 02 wherein 'χ' ranges from 1 to 10, ,'y' ranges from 1 to 25 and 'ζ' is a number taken to satisfy the average valences of arsenic and uranium in the oxidation states in which they exist in said catalyst; wherein C is defined, by the empirical formula Sba Moc wherein 'a' ranges from 3 to 15, 'b' ranges from I to 3, 'c* · ranges from 0 .001 to 0.5 and 'd' is a number taken to satisfy the average valences of antimony, uranium and molybdenum in the oxidation states in which they exist in said catalyst; each .of said .catalysts being formed by heating the mixed oxides of the element's of the base catalyst in the presence of oxygen at an elevated temperature above 500°F. but below their melting point for a time sufficient to form said active catalytic oxide.. -17 31274/3

2. A process according to Claim 1 for the ammoxidatio of propylene and isobutylene tc form aerylonltrile and methacrylo- . nitrile, respectively, characterized by contacting in. the vapor phase at a temperature within the range from about 650°P to about 1100°F and in the presence of the catalyst a mixture of anuaonia, ^molecula oxygen-containing gas and either propylene or isobutyiene, or mixtures thereof in a mflLar ratio of olefin to ammonia of from It0.05 to 1«5, and a molar ratio of oxygen to olefin within the range from 0.!?tl to 4«1.

3. A process according to Claim 1 for the oxidative dehydro-genation of olef ns characterized by c ontacting a mixture of oxygen and an olefin having at leas four and up to about eight non- uaternary carbon atoms of which at least four are arranged in a straight chain in the vapor phase at a temperature at which the oxidative dehydrogenation proceeds in the presence of the catalyst,

4. A process according to Claim 1, characterized by passing a feed mixture of a monoolefin and a member selected from the grou consisting of (a) a molecular oxygen-containing gas and (b) a molecular oxygen-containing gas and ammonia over the catalyst at a temperature within the range from about 650°F to about lloo°P.

5. Processes according to Claim 1 for the ammoxidation of olefins, substantially as described herein with reference to Table I.

6. Processes according to Claim 1 for the oxidation of olefins to unsaturated aldehydes, substantially as described herein with reference to Table II.

7. Processes according to Claim 1 for the oxydehydrogenation of butenes, substantially as described herein with reference to

8. Catalysts for carrying out the processes according to any one of Claims 1 to 7, consisting essentially of activated catalytic oxide complexes A, B and/or C, optionally promoted by at least one of the elements cerium, sjitimony, tungsten, zinc, manganese, iron, chromium, bismuth, nickel, tin, vanadium, boron, molybdenum and arsenic, wherein A is defined by the empirical formula u"xMoy 0 wherein ·χ· ranges from 1 to 29, ?y' ranges from 1 to 29 and •a1 is a number taken to satisfy the average valences of uranium and molybdenum in the oxidation states in which they exist in said catalyst} wherein B is defined by the empirical formula Αβχ Uy 02 wherein 'x' ranges from 1 to 10, •y* ranges from 1 to 29 and ' ζ· is a number taken to satisfy the average valences of arsenic and uranium in the oxidatio states in which they exist in said catalyst; wherein C is defined b the empirical formula Sb& Moc Gd wherein ' ' ranges from 3 to 15, · b* ranges from 1 to 3, ♦ C ranges from 0;.Q01 to 0.5 and •d' , is a number taken to satisfy the average valences of antimony, ¾.ranium and molybdenum in the oxidation states in which they exist in said catalyst } each of said catalysts being formed by heating the mixed oxides of the elements of the base catalyst in the presence of oxygen at an elevated temperature above 500°F but below their melting point for a time sufficient to orm said active catalytic oxide.

9. Ca a¾^¾.ts according to Claim 8, containing from 5 to 95 per cent by weight of a conventional catalyst support, e«g. silica.

10. A method of preparing a catalyst according to Claim 8, wherein the oxides of the elements are formed separately and blended together. 0

11. A method of preparing a catalyst according to Claim 8* wherein the oxides of the elements are formed in situ, separately or together.

12. A method according* to Claims 10 or 11, wherein the oxides are formed from water-soluble salts of the catalyst elements.

13. Methods of preparing catalysts according to Claim 8, substantially as described herein with reference to any one of Examples 1 to 7· RC.ed