A SELECTIVE OXIDATION CATALYST AND A METHOD FOR OXIDIZING C2 HYDROCARBONS IN THE PRESENCE OF THE SELECTIVE OXIDATION CATALYST

Abstract

Methods of producing a catalyst for oxidation of C.sub.2 hydrocarbons and methods of using the catalyst are disclosed. Molybdenum, vanadium, and niobium metal or metal containing compounds are used to form a slurry in water. After agitating the slurry for at least 15 minutes, palladium or a palladium containing compound is added to the slurry. After further agitation, a precipitate is collected, dried and calcined to obtain an active catalyst, with palladium primarily distributed on a surface of the catalyst. The active catalyst is capable of catalyzing the conversion of C.sub.2 hydrocarbons into acetic acid.

Claims

1. A catalyst produced by a process, the process comprising: (a) combining each of a molybdenum, vanadium, and niobium metal or metal-containing compound in water to form a slurry; (b) agitating the slurry for a period of time of at least 15 minutes; (c) after at least 15 minutes of agitating the slurry comprising molybdenum, vanadium, and niobium, adding palladium or a palladium-containing compound to the slurry; and (d) collecting, drying, and calcining the slurry to obtain an active catalyst.

2. The catalyst of claim 1, wherein the active catalyst has a formula of Mo.sub.xV.sub.yNb.sub.zPd.sub.nO.sub.m, where x is in a range of 1 to 5, y is in a range of greater than 0 to 0.5, z is in a range of 0.01 to 0.5, n is in a range of greater than 0 to 0.2 and m is a number determined by the valence requirements of the other elements in the composition.

3. The catalyst of claim 1, wherein the molybdenum metal-containing compound is ammonium heptamolybdate, sodium molybdate, ammonium orthomolybdate, ammonium paramolybdate, or an acetate, oxalate, mandelate, or glycolate salt, or a combination thereof.

4. The catalyst of claim 1, wherein the vanadium metal-containing compound is ammonium metavanadate, sodium metavanadate, sodium decavanadate, or sodium orthovanadate, or an acetate, oxalate, or tartrate salt, or a combination thereof.

5. The catalyst of claim 1, wherein the niobium metal containing compound is lithium niobate, potassium niobate, strontium barium niobate, niobium oxalate, niobium oxide, niobium hydrate oxide, or a combination thereof.

6. The catalyst of claim 1, wherein the palladium containing compound includes a palladium salt, a palladium complex, palladium on a support, or a combination thereof.

7. The catalyst of claim 1, wherein 10 to 500 ppm of palladium is distributed on a surface of the active catalyst.

8. The catalyst of claim 1, wherein the agitating is performed at a temperature in a range of 70 to 100° C.

9. The catalyst of claim 1, wherein the active catalyst is not supported on a support material.

10. The catalyst of claim 1, wherein the drying is performed at a drying temperature of 80 to 300° C.

11. The catalyst of claim 1, wherein the calcining is performed by heating to a temperature from 250 to 400° C.

12. The catalyst of claim 9, wherein the calcining has a calcination duration of from one to sixteen hours.

13. A method for oxidizing a C.sub.2 hydrocarbon, the method comprising: reacting the C.sub.2 hydrocarbon with an oxidant in the presence of the active catalyst of claim 1 to produce an oxidized hydrocarbon.

14. The method of claim 13, wherein the C.sub.2 hydrocarbon comprises ethane and the oxidized hydrocarbon comprises acetic acid.

15. The method of claim 13, wherein the reacting is performed at a reaction temperature of 200 to 320° C.

16. The method of claim 13, wherein the reacting is performed at a reaction pressure of 10 to 35 bar.

17. The method of claim 13, wherein the catalyst is disposed in a fixed bed reactor and/or a fluidized bed reactor.

18. The method of claim 13, wherein the reacting is performed at a Weight Hourly Space Velocity of 1,000 to 10,000 hr.sup.−1.

19. The method of claim 13, wherein the C.sub.2 hydrocarbon in the reacting step has a delta ethane ranging from 0.1 to 10 mol. %.

20. The method of claim 14, wherein the C.sub.2 hydrocarbon in the reacting step has a delta ethane ranging from 0.1 to 10 mol. %.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0023] FIG. 1 shows a schematic flowchart of a process of producing a catalyst, according to embodiments of the invention.

[0024] FIG. 2 shows a schematic flowchart of a method for oxidizing a C.sub.2 hydrocarbon, according to embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0025] Currently, C.sub.2 hydrocarbon oxidation can be performed in a single reactor using mixed metal oxides as a catalyst. However, the conventional mixed metal oxides have limited efficiency for converting C.sub.2 hydrocarbon oxidation into acetic acid. The present invention provides a solution, at least in part, to the problem. The solution is premised on a method that produces a catalyst that comprises molybdenum, vanadium, niobium and palladium metals or metal-containing compounds. In this method, palladium and/or palladium containing compounds are added into a slurry of molybdenum, vanadium, and niobium metals or metal-containing compounds after agitating the slurry for at least 15 minutes such that palladium is primarily distributed on the surface of the catalyst. Therefore, the palladium in the catalyst of the present invention has sufficient contact with the reactant to convert ethylene to acetic acid, resulting in an increased efficiency of producing acetic acid. These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

A. Methods of Producing a Catalyst for Oxidation of C.SUB.2 .Hydrocarbon

[0026] As shown in FIG. 1, embodiments of the invention include method 100 of producing a catalyst for oxidation of C.sub.2 hydrocarbon. According to embodiments of the invention, method 100 may include combining each of a molybdenum, vanadium, and niobium metal or metal containing compound in water to form a slurry (step (a)), as shown in block 101. In embodiments of the invention, the molybdenum metal containing compound comprises an ammonium salt, such as ammonium heptamolybdate, sodium molybdate, ammonium orthomolybdate, or ammonium paramolybdate, or an organic acid salt of molybdenum such as an acetate, oxalate, mandelate, glycolate, or a combination thereof. In embodiments of the invention, vanadium metal-containing compound is ammonium metavanadate, sodium metavanadate, sodium decavanadate, or sodium orthovanadate, or an organic salt of vanadium such as an acetate, oxalate, tartrate, or a combination thereof. In embodiments of the invention, the niobium metal containing compound comprises lithium niobate, potassium niobate, strontium barium niobate, niobium oxalate, niobium oxide, niobium hydrate oxide or a combination thereof. In embodiments of the invention, the slurry is formed via precipitation of molybdenum, vanadium, and niobium metal or metal containing compounds.

[0027] According to embodiments of the invention, method 100 may further include agitating the slurry for a period of time of at least 15 minutes, as shown in block 102 (step (b)). In embodiments of the invention, agitating at block 102 may be performed at a temperature of 70 to 100° C. and all ranges and values there between.

[0028] According to embodiments of the invention, as shown in block 103, method 100 may further include adding palladium or a palladium-containing compound to the slurry after at least 15 minutes of agitating the slurry comprising molybdenum, vanadium, and niobium (step (c)). In embodiments of the invention, substantially all molybdenum, vanadium, and niobium from step (a) may be precipitated before adding palladium or a palladium-containing compound at block 103.

[0029] In embodiments of the invention, the palladium-containing compound may include a palladium salt, a palladium complex, or palladium on a support, such as Pd/SiO.sub.2, Pd/Al.sub.2O.sub.3, Pd/TiO.sub.2, or a combination thereof. In embodiments of the invention, the slurry may be agitated after adding palladium or the palladium-containing compound therein. In embodiments of the invention, the slurry may be agitated for 5 to 200 minutes after adding the palladium or the palladium containing compound therein.

[0030] In embodiments of the invention, method 100 may further include collecting, drying, and calcining the slurry to obtain an active catalyst (step (d)), as shown in block 104. In embodiments of the invention, drying at block 104 may include spray drying, air drying, drum drying, vacuum drying, combinations thereof, or other drying methods known to those of skill in the art. The drying at block 104 may be performed at a drying temperature of 80 to 300° C. and all ranges and values there between. In embodiments of the invention, calcining at block 104 may have a calcination temperature of 100 to 400° C. and all ranges and values there between. A temperature ramp may be in a range of 0.1 to 5° C./min and all ranges and values there between. The temperature ramp may include multiple temperature-ramping and temperature-holding steps. A calcination duration at block 104 may be in a range of 1 to 24 hrs and all ranges and values there between. In embodiments of the invention, the calcining at block 104 may be conducted within ambient environment comprising air, nitrogen, or combinations thereof.

[0031] In embodiments of the invention, 10 to 500 ppm, preferably 50 to 300 ppm of palladium from the palladium metal or metal containing compound is distributed on a surface of the active catalyst. According to embodiments of the invention, the active catalyst may have a formula of Mo.sub.xN.sub.yNb.sub.zPd.sub.nO.sub.m, where x is in a range of 1 to 5, y is in a range of greater than 0 to 0.5, z is in a range of 0.01 to 0.5, n is in a range of greater than 0 to 0.2 and m is a number determined by the valence requirements of the other elements in the composition.

[0032] In embodiments of the invention, the active catalyst may have a surface area in a range of 15 to 40 m.sup.2/g and all ranges and values there between. According to embodiments of the invention, the active catalyst may have an absolute porosity of 0.1 to 0.5 ml/g and all ranges and values there between. In embodiments of the invention, the active catalyst may not include a support material.

B. Methods for Oxidizing a C.SUB.2 .Hydrocarbon

[0033] As shown in FIG. 2, embodiments of the invention include method 200 for oxidizing a C.sub.2 hydrocarbon. Method 200 may be implemented by the active catalyst produced via method 100, as shown in FIG. 1. According to embodiments of the invention, method 200 may include placing the active catalyst produced via method 100 in a reactor, as shown in block 201. In embodiments of the invention, the reactor may include a fixed bed reactor, for example, a multi-tubular reactor having catalyst positioned within the tubes, or a fluidized bed reactor.

[0034] According to embodiments of the invention, method 200 may further include reacting the C.sub.2 hydrocarbon with an oxidant in the presence of the active catalyst to produce an oxidized hydrocarbon, as shown in block 202. In embodiments of the invention, the C.sub.2 hydrocarbon may include ethane, ethylene, or combinations thereof. The oxidized hydrocarbon may be acetic acid, in embodiments. In embodiments of the invention, the oxidant at block 202 may include oxygen gas or steam.

[0035] In embodiments of the invention, the reacting at block 202 may have a reaction temperature in a range of 200 to 320° C. and all ranges and values there between. The reacting at block 202 may further include a reaction pressure of 5 to 40 bar and all ranges and values there between. A weight hourly space velocity at block 202 may be in a range of 1,000 to 10,000 hr.sup.−1 and all ranges and values there between. In embodiments of the invention, the reacting at block 202 may include an oxygen concentration in the range of 1 to 10 mol. %, and all ranges and values there between.

[0036] A selectivity for acetic acid for the reacting step at block 202 may be in a range of 10 to 100 and all ranges and values there between. In embodiments of the invention, an effluent from the reactor may include 0.01 to 5 mol. % acetic acid and all ranges and values there between. In some aspects, delta ethane may range from 0.1 to 10 mol. %, preferably from 0.1 to 6 mol. %. In embodiments of the invention, method 200 may further include separating the effluent from the reactor to produce purified acetic acid.

[0037] Although embodiments of the present invention have been described with reference to blocks of FIGS. 1 and 2, it should be appreciated that operation of the present invention is not limited to the particular blocks and/or the particular order of the blocks illustrated in FIGS. 1 and 2. Accordingly, embodiments of the invention may provide functionality as described herein using various blocks in a sequence different than that of FIGS. 1 and 2.

[0038] In the context of the present invention, at least the following 19 embodiments are described. Embodiment 1 is a catalyst produced by a process. The process includes: (a) combining each of a molybdenum, vanadium, and niobium metal or metal-containing compound in water to form a slurry, (b) agitating the slurry for a period of time of at least 15 minutes, (c) after at least 15 minutes of agitating the slurry containing molybdenum, vanadium, and niobium, adding palladium or a palladium-containing compound to the slurry, and (d) collecting, drying, and calcining the slurry to obtain an active catalyst. Embodiment 2 is the catalyst of embodiment 1, wherein the active catalyst has a formula of Mo.sub.xV.sub.yNb.sub.zPd.sub.nO.sub.m, where x is in a range of 1 to 5, y is in a range of greater than 0 to 0.5, z is in a range of 0.01 to 0.5, n is in a range of greater than 0 to 0.2 and m is a number determined by the valence requirements of the other elements in the composition. Embodiment 3 is the catalyst of either embodiment 1 or 2, wherein the molybdenum metal-containing compound is ammonium heptamolybdate, sodium molybdate, ammonium orthomolybdate, ammonium paramolybdate, or an acetate, oxalate, mandelate, or glycolate salt, or a combination thereof. Embodiment 4 is the catalyst of any of embodiments 1 to 3, wherein the vanadium metal-containing compound is ammonium metavanadate, sodium metavanadate, sodium decavanadate, or sodium orthovanadate, or an acetate, oxalate, or tartrate salt, or a combination thereof. Embodiment 5 is the catalyst of any of embodiments 1 to 4, wherein the niobium metal containing compound is lithium niobate, potassium niobate, strontium barium niobate, niobium oxalate, niobium oxide, niobium hydrate oxide, or a combination thereof. Embodiment 6 is the catalyst of any of embodiments 1 to 5, wherein the palladium containing compound includes a palladium salt, a palladium complex, palladium on a support, or a combination thereof. Embodiment 7 is the catalyst of any of embodiments 1 to 6, wherein 10 to 500 ppm of palladium is distributed on a surface of the active catalyst. Embodiment 8 is the catalyst of any of embodiments 1 to 7, wherein the agitating is performed at a temperature in a range of 70 to 100° C. Embodiment 9 is the catalyst of any of embodiments 1 to 8, wherein the active catalyst is not supported on a support material. Embodiment 10 is the catalyst of any of embodiments 1 to 9, wherein the drying is performed at a drying temperature of 80 to 300° C. Embodiment 11 is the catalyst of any of embodiments 1 to 8, wherein the calcining is performed by heating to a temperature from 250 to 400° C. Embodiment 12 is the catalyst of embodiment 9, wherein the calcining has a calcination duration of from one to sixteen hours.

[0039] Embodiment 13 is a method for oxidizing a C.sub.2 hydrocarbon. The method includes reacting the C.sub.2 hydrocarbon with an oxidant in the presence of the active catalyst of any of embodiments 1 to 12 to produce an oxidized hydrocarbon. Embodiment 14 is the method of embodiment 13, wherein the C.sub.2 hydrocarbon contains ethane and the oxidized hydrocarbon contains acetic acid. Embodiment 15 is the method of either of embodiments 13 or 14, wherein the reacting is performed at a reaction temperature of 200 to 320° C. Embodiment 16 is the method of any of embodiments 13 to 15, wherein the reacting is performed at a reaction pressure of 10 to 35 bar. Embodiment 17 is the method of any of embodiments 13 to 16, wherein the catalyst is disposed in a fixed bed reactor and/or a fluidized bed reactor. Embodiment 18 is the method of any of embodiments 13 to 17, wherein the reacting is performed at a Weight Hourly Space Velocity of 1,000 to 10,000 hr.sup.−1. Embodiment 19 is the method of any of embodiments 13 to 18, wherein the C.sub.2 hydrocarbon in the reacting step has a delta ethane ranging from 0.1 to 10 mol. %.

[0040] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.