SUPPORTED CATALYST FOR BUTANE HYDROGENOLYIS, METHOD OF PRODUCING THE SUPPORTED CATALYST AND METHOD TO PRODUCE ETHANE

Abstract

Catalysts for the hydrogenolysis of butane are described. A supported catalyst for hydrogenolysis of butane to ethane can include a support and a catalytic crystalline bimetallic composition that can include a molybdenum-iridium (Mo—Ir) crystalline composition attached to the support. The supported catalyst has a BET specific surface area of at least 100 m.sup.2/g, preferably 100 m.sup.2/g to 500 m.sup.2/g. Method of use and methods of making the catalyst are also described.

Claims

1. A supported butane hydrogenolysis catalyst for hydrogenolysis of butane to ethane, the supported catalyst comprising: a support; and a crystalline catalytic bimetallic material comprising a crystalline catalytic molybdenum-iridium (Mo—Ir) composition attached to the support, wherein the supported catalyst has a Brunauer-Emmett-Teller (BET) surface area of 100 m.sup.2/g to 150 m.sup.2/g, wherein the supported catalyst has a butane conversion of at least 50%; and wherein the support comprises alumina, wherein the alumina is gamma-alumina.

2. The supported butane hydrogenolysis catalyst of claim 1, wherein the support comprises a member selected from the group consisting of zeolite, titania (TiO.sub.2) and silica (SiO.sub.2), or a combination thereof.

3. The supported butane hydrogenolysis catalyst of claim 1, wherein the support comprises a zeolite.

4. The supported butane hydrogenolysis catalyst of claim 1, wherein the BET surface area is 100 m.sup.2/g.

5. The supported butane hydrogenolysis catalyst of claim 1, wherein the Mo—Ir in the Mo—Ir composition has a molar ratio of 1:3 to 4:1, preferably 1:3.

6. The supported butane hydrogenolysis catalyst of claim 1, wherein the crystalline catalytic Mo—Ir composition comprises a MoIr.sub.3 crystalline structure, a Mo.sub.3Ir crystalline structure, or a MoIr.sub.4 crystalline structure, or a mixture thereof.

7. The supported butane hydrogenolysis catalyst of claim 6, comprising 0.1 wt. % to 5 wt. % of the Mo—Ir composition having the MoIr.sub.3 crystalline structure.

8. The supported butane hydrogenolysis catalyst of claim 7, comprising 0.4 wt. % to 0.8 wt. % of MoIr.sub.3 on a Al.sub.2O.sub.3 support.

9. The supported butane hydrogenolysis catalyst of claim 8, wherein the supported butane hydrogenolysis catalyst is a 0.6 wt. % MoIr.sub.3 on the Al.sub.2O.sub.3 support catalyst.

10. The supported butane hydrogenolysis catalyst of claim 1, wherein the supported butane hydrogenolysis catalyst has a BET surface area of 100 m.sup.2/g.

11. The supported butane hydrogenolysis catalyst of claim 3, wherein the supported butane hydrogenolysis catalyst has a BET surface area of 150 m.sup.2/g.

12. The supported butane hydrogenolysis catalyst of claim 3, wherein the supported butane hydrogenolysis catalyst has a BET surface area of 100 m.sup.2/g.

13. A method to produce ethane, the method comprising contacting the supported butane hydrogenolysis catalyst of claim 1, with butane under conditions sufficient for hydrogenolysis of butane and produce ethane wherein the contacting conditions comprise a temperature of 240° C. to 325° C., a pressure of 0.35 MPa to 1.4 MPa, a butane weighted hourly velocity of 1 to 10 hr.sup.−1, or any combination thereof.

14. The method of claim 13, wherein the conditions comprise a temperature of 260° C. to 300° C.

15. The method of claim 13, wherein the supported butane hydrogenolysis catalyst has a BET surface area of 100 m.sup.2/g.

16. The method of claim 13, wherein the supported butane hydrogenolysis catalyst has a BET surface area of 150 m.sup.2/g.

17. The method of claim 13, wherein the butane comprises n-butane, iso-butane, or a mixture thereof.

18. A method of producing the supported butane hydrogenolysis catalyst of claim 1, the method comprising: impregnating a support comprising gamma-alumina with a catalytic Mo/Ir precursor composition to form an impregnated support/Mo—Ir precursor composition material; drying the impregnated support/Mo—Ir precursor composition material to form a dried impregnated support/Mo—Ir precursor composition material; and calcining the dried impregnated support/Mo—Ir precursor composition material at a temperature of 85° C. to 100° C. for 2 to 24 hours to form the supported butane hydrogenolysis catalyst; wherein impregnating comprises adding the catalytic Mo/Ir precursor composition dropwise onto the support and agitating the impregnated support/catalytic Mo/Ir precursor composition for 2 to 24 hours; and heat-treating.

19. The method of any claim 18, wherein the support comprises a member selected from the group consisting of gamma-alumina extrudates, a zeolite, titania extrudates, silica extrudates, or a mixture thereof.

20. A supported butane hydrogenolysis catalyst produced by the method of claim 18.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings.

[0023] FIG. 1 is an illustration of a reactor system to produce ethane using the butane hydrogenolysis catalyst of the present invention.

[0024] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings. The drawings may not be to scale.

DETAILED DESCRIPTION OF THE INVENTION

[0025] At least one solution to the problems associated with converting butane to ethane has been discovered. The solution can include a cost-effective catalyst that has a carbon binding energy approximate to the carbon binding energy on Ir metal. The catalyst can include a crystalline Column 6 metal/Ir composition attached to a support. Preferably, the catalyst includes a catalytic bimetallic (e.g., Mo—Ir) composition attached to a support.

[0026] These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

A. Catalyst

[0027] The catalyst of the present invention can include a support and a catalytic bimetallic composition. The catalyst can have a specific surface area of at least 100 m.sup.2/g, or 100 m.sup.2/g to 500 m.sup.2/g, or 100 m.sup.2/g, 150 m.sup.2/g, 200 m.sup.2/g, 250 m.sup.2/g, 300 m.sup.2/g, 350 m.sup.2/g, 400 m.sup.2/g, 450 m.sup.2/g, or 500 m.sup.2/g, or any value or range there between. The support can be alumina (Al.sub.2O.sub.3), titania (TiO.sub.2), silica (SiO.sub.2), a zeolite, or mixtures, or combinations thereof. Non-limiting examples of zeolites include ZSM-5, ZSM-11, Y, high-silica Y, USY, EU-1, EU-2, beta, L, ferrierite, CHA, SSZ-16, Nu-3, sigma-1, silicalite-1, and combinations thereof. In some embodiments, the zeolite is ZSM-5. In a preferred embodiment, the support is gamma-Al.sub.2O.sub.3. The catalytic bimetallic composition can include crystalline catalytic Mo—Ir, Ir-platinum (Pt), and Ir/Ti compositions. In a preferred embodiment, crystalline catalytic Mo—Ir compositions can be used. The total molar ratio of Mo—Ir in the catalyst can range from 1:3 to 4:1, or 1:3, 2:3, 2:1, 3:1, or 4:1, or any range or value there between. In a preferred instance, the total molar ratio of Mo—Ir in the catalyst is 1:3. The total amount of crystalline catalytic bimetallic composition (e.g., crystalline Mo—Ir material) can range from 0.1 wt. % to 5 wt. %, or 0.2 to 1 wt. %, or 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5 wt. % or any range or value there between. In a preferred instance, the total amount of crystalline catalytic bimetallic composition can be about 0.55 to 0.65 or about 0.6 wt. %. The particle size of the crystalline catalytic bimetallic composition can range from 1 to 10 nm, or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 nm or any range or value there between. When the crystalline catalytic bimetallic composition includes Mo—Ir crystalline compositions, it can include a MoIr.sub.3 crystalline structure, a Mo.sub.3Ir crystalline structure, or a MoIr.sub.4 crystalline structure, or a mixture of MoIr.sub.3, Mo.sub.3Ir, and MoIr.sub.4 crystalline structures. These structures can each be attached to the support. The crystalline catalytic bimetallic composition (e.g., crystalline Mo—Ir compositions) can be attached to the surface of the metal oxide or zeolite surface or part of the crystal lattice of the catalyst. The attachment can be through chemical bonds. In particular instances, the bonds can be M—O bonds (where M is a metal from the catalyst and O is an oxygen from the support). The crystalline catalytic bimetallic composition is free of organic ligands (e.g., non-detectable or 0 to 0.001 wt %). In one embodiment, the crystalline Mo—Ir catalyst is free of cyclopentadiene ligands.

[0028] The catalyst can be made using impregnation methodology. In a preferred aspect, incipient wetness impregnation methodology can be used. Catalytic metal precursors can be dissolved in deionized water to form individual catalytic metal precursor solutions. Catalytic metal precursors can be obtained as a metal nitrate, a metal amine, a metal chloride, a metal coordination complex, a metal sulfate, a metal phosphate hydrate, metal complex, or any combination thereof. Examples of metal precursor compounds include hexachloroiridic acid and ammonium heptamolybdate. These metals or metal compounds can be purchased from any chemical supplier such as Sigma-Aldrich (St. Louis, Mo., USA), Alfa-Aeaser (Ward Hill, Mass., USA), and Strem Chemicals (Newburyport, Mass., USA). The two solutions can be mixed to form a combined catalytic metal precursor solution or used separately. The catalytic metal precursor solutions or combined catalytic metal precursor solution can be added to a known quantity of support (e.g., weighed alumina extrudates) and agitated for a period of time (e.g., 2 to 24 hours) at ambient temperature (e.g., 20° C. to 35° C.) to form a catalytic metal precursor/support composition. The water can be removed by drying the catalytic metal precursor/support composition at a temperature of 80° C. to 100° C., or about 90° C. Once dried, the catalytic metal precursor/support composition can be calcined in air at 275° C. to 350° C. or 275° C. to 285° C. or any range or value there between. Calcination of the catalytic metal precursor/support composition forms the catalytic crystalline bimetallic composition and attaches the composition to the support.

B. Methods of Producing Ethane from Butane

[0029] FIG. 1 depicts a schematic for a process for the hydrogenolysis of butane with one reactor using the catalyst of the present invention. Reactor 100 can include inlet 102 for a H.sub.2 reactant feed, inlet 104 for a butane reactant feed, reaction zone 106 (e.g., a fixed-bed reactor) that is configured to be in fluid communication with the inlets 102 and 104, and outlet 108 configured to be in fluid communication with the reaction zone 106 and configured to remove the hydrogenolysis product stream from the reaction zone. The reaction zone 106 can include the hydrogenolysis catalyst of the present invention. The H.sub.2 reactant feed can enter the reaction zone 106 via the inlet 102. The reactant feed can be a mixture of butanes (e.g., isobutane and n-butane). In some embodiments, the H.sub.2 reactant feed and/or the butane reactant feed can be used to maintain a pressure in the reaction zone 106. In some embodiments, the reactant feed streams include propane or trace C5s (e.g., hydrocarbons containing 5 carbon atoms). In some embodiments, the reactant feeds are premixed and provided at the same time. In some embodiments, the reactant feed can be provided in stages from H.sub.2 rich to the desired H.sub.2 to hydrocarbon ratio. The product stream can be removed from the reaction zone 106 via product outlet 108. The product stream can be sent to other processing units (e.g., separation units, isomerization units, and the like), stored, and/or transported.

[0030] Reactor 100 can include one or more heating and/or cooling devices (e.g., insulation, electrical heaters, jacketed heat exchangers in the wall) or controllers (e.g., computers, flow valves, automated values, etc.) that can be used to control the reaction temperature and pressure of the reaction mixture. While only one reactor is shown, it should be understood that multiple reactors can be housed in one unit or a plurality of reactors housed in one heat transfer unit. In some embodiments, a series of physically separated reactors with interstage cooling/heating devices, including heat exchangers, furnaces, fired heaters, and the like can be used.

[0031] The temperature, pressure, and WHSV can be varied depending on the reaction to be performed and is within the skill of a person performing the reaction (e.g., an engineer or chemist). Temperatures can range from 240° C. to about 325° C., 250° C. to 300° C., 270° C. to 290° C., or any value or range there between. Pressures can range from about 0.35 MPa to 1.4 MPa or 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3, 1.4 or any range or value there between. A butane WHSV can range from 1 to 10 hr.sup.−1, or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 hr.sup.−1 or any range or value there between.

[0032] The product stream can include methane, propane, ethane, and unreacted reactants. The products can be separated using known separation methodology. Produced methane can be used as a fuel for the system or can be reacted with steam to make hydrogen. Produced ethane can be sent to other processing units, for example sent to a steam cracker to produce ethylene. Produced propane can be sent to other processing units, for example, sent to a cracking unit together with ethane or used for on-purpose propylene production through propane dehydrogenation. Unreacted butane and/or hydrogen can be recycled to the reactor. In some embodiments, the unreacted butane that is includes isobutane can be sent to a reverse-isomerization unit to increase the amount of n-butane in the unreacted feed stream.

[0033] Using the catalyst of the present invention, the ethane selectivity can be at least 70%, 50 to 90%, 70% to 80%, or 70%, 75%, 80%, 85%, 90%, or any value or range there between. In a preferred embodiment, the ethane selectivity is at least about 75%. In some embodiments, butane conversion can at least 50%, 50 to 95%, 70 to 90%, or at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%, or any value or range there between at a reaction temperature of 240° C. to 290° C.

EXAMPLES

[0034] The present invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes only, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of noncritical parameters which can be changed or modified to yield essentially the same results.

Example 1

Synthesis of Mo—Ir/Alumina Catalysts

[0035] H.sub.2IrCl.sub.6.Math.(6H.sub.2O) (0.14 g, 0.51%, MilliporeSigma, USA) and (NH.sub.4).sub.6Mo.sub.7O.sub.24.Math.(4H.sub.2O) (0.02 g, 0.07%, MilliporeSigma) separately were dissolved in deionized water (5 mL) each. Each solution was thoroughly stirred and then mixed together. The mixture solution was added dropwise to weighted γ-alumina extrudates (10.0 g, Sasol, SG 6173, South Africa) and stirred for 3 hours at room temperature (25° C.). The extrudates then were dried in the oven at 90° C. for 3 hours, followed by calcination at 280° C. to produce a MoIr.sub.3 (0.6 wt %)/Al.sub.2O.sub.3catalyst.

Example 2

Synthesis of Ir/Alumina Comparative Catalyst

[0036] H.sub.2IrCl.sub.6.Math.(6H.sub.2O) (0.161 g, 0.80%) was dissolved in deionized water (5 mL). The solution was added dropwise to weighted γ-alumina extrudates (10 g) and stirred for 3 hours at room temperature (30° C.). The extrudates then were dried in the oven at 90° C. for 3 hours, followed by calcination at 280° C. to produce Ir (0.6 wt %)/Al.sub.2O.sub.3catalyst.

Example 3

Method to Produce Ethane Via Butane Hydrogenolysis

[0037] The inventive catalyst (Example 1, MoIr.sub.3 (0.6 wt %)/Al.sub.2O.sub.3) and the comparative catalyst (Example 2, Ir (0.6 wt %)/Al.sub.2O.sub.3) were tested under the same conditions. Testing was completed under isothermal conditions in a ½” O.D. (wall thickness 0.049”)×20” length seamless 316 stainless steel reactor tube heated by a 21”, three-zone Applied Test Systems (ATS) clamshell furnace. The reactor tube was fitted with an internal ⅛” seven-point thermocouple probe (Omega) to control furnace heating and monitor the temperature across the catalyst bed. The hydrocarbon feed (Airgas Research Grade) was introduced to the system as a liquid via a low-flow mini Coriolis mass flow meter (Bronkhorst model M12, 0-50 g hr-1), while the hydrogen (Praxair UHP) was introduced via a thermal mass flow controller (Brooks, model 5850E, 0-1000 sccm). The hydrocarbons were vaporized and the feeds were mixed upstream of the reactor at 140-150° C. A backpressure regulator (0-700 psig) located downstream of the reactor controlled the pressure of the system. The reactor bed was composed of three 4” layers: a central catalyst bed diluted with silicon carbide (Greystar, 30 grit) and silicon carbide layers on both sides. Approximately ⅛” of silanized glass wool (Supelco 20410) divided and supported each layer. The reactor bed was loaded such that the catalyst bed layer resided entirely within the central zone isothermal zone of the furnace. Three of the five internal thermocouple points were located at the top, middle, and bottom of the catalyst bed. In general, the ΔT across these three points was <1° C. Reaction conditions were WHSV=4 hr.sup.−1, H.sub.2/HC=2.5, the butane feed has an i-C.sub.4H.sub.10:n-C.sub.4H.sub.10 ratio of 3:7. Reaction temperatures ranged from 250° C. to 300° C.

[0038] Results of the runs are listed in Table 1 At the temperature of 250° C., the inventive catalyst (MoIr.sub.3/Al.sub.2O.sub.3) showed almost 10 times higher catalytic activity compared to the comparative catalyst (Ir/Al.sub.2O.sub.3), which showed only 1% n-butane conversion at that temperature. At temperature of 250° C., ethane selectivity on the inventive catalyst was higher by 7% as compared to the Ir/Al.sub.2O.sub.3catalyst.

TABLE-US-00001 TABLE 1 Ir/Al.sub.2O.sub.3 MoIr.sub.3/Al.sub.2O.sub.3 Temp Conversion C2 selectivity Conversion C2 selectivity [° C.] [%] [%] [%] [%] 250 10.2 62 95.7 69 275 61.3 60 100 60.4 300 100 60 100 34.3

Example 4

[0039] (Density Function Theory (DFT) Calculations)

[0040] Density function theory (DFT) calculations identified the rate-determining step (RDS) in butane hydrogenolysis as a C—C scission in the [CH.sub.3C—CCH.sub.3] intermediate, and the descriptor value as carbon binding energy. According to this correlation, the catalyst was predicted to have a carbon binding energy similar to carbon binding energy on Ir metal.

[0041] 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 can be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.