RUTHENIUM-DOPED ALUMINA-SUPPORTED COBALT/NICKEL CATALYST FOR AMMONIA DECOMPOSITION TO HYDROGEN AND NITROGEN

Abstract

A method for ammonia (NH.sub.3) decomposition to hydrogen (H.sub.2) and nitrogen (N.sub.2) using a ruthenium-doped alumina-supported cobalt/nickel (RuCoNi/Al.sub.2O.sub.3) catalyst. The method includes introducing and passing an NH.sub.3-containing feed gas stream into a reactor to contact the NH.sub.3-containing feed gas stream with a reduced RuCoNi/Al.sub.2O.sub.3 catalyst at a temperature of 100 to 1000 C. thereby converting at least a portion of the NH.sub.3 to H.sub.2 and regenerating the RuCoNi/Al.sub.2O.sub.3 catalyst particles to form a regenerated RuCoNi/Al.sub.2O.sub.3 catalyst, and producing a residue gas stream leaving the reactor.

Claims

1: A method for ammonia (NH.sub.3) decomposition to hydrogen (H.sub.2) and nitrogen (N.sub.2), including: introducing a H.sub.2-containing feed gas stream into a reactor containing a ruthenium-doped alumina-supported cobalt/nickel (RuCoNi/Al.sub.2O.sub.3) catalyst including RuCoNi/Al.sub.2O.sub.3 catalyst particles; wherein Ru is present in the RuCoNi/Al.sub.2O.sub.3 catalyst at a concentration of 0.01 to 5 wt. % based on a total weight of the RuCoNi/Al.sub.2O.sub.3 catalyst; passing the H.sub.2-containing feed gas stream through the reactor to contact the H.sub.2-containing feed gas stream with the RuCoNi/Al.sub.2O.sub.3 catalyst particles at a temperature of 500 to 900 C. to form a reduced RuCoNi/Al.sub.2O.sub.3 catalyst; terminating the introducing the H.sub.2-containing feed gas stream; introducing and passing an NH.sub.3-containing feed gas stream through the reactor to contact the NH.sub.3-containing feed gas stream with the reduced RuCoNi/Al.sub.2O.sub.3 catalyst at a temperature of 100 to 1000 C. thereby converting at least a portion of the NH.sub.3 to H.sub.2 and regenerating the RuCoNi/Al.sub.2O.sub.3 catalyst particles to form a regenerated RuCoNi/Al.sub.2O.sub.3 catalyst, and producing a residue gas stream leaving the reactor; and separating the H.sub.2 from the residue gas stream to generate a H.sub.2-containing product gas stream.

2: The method of claim 1, wherein the RuCoNi/Al.sub.2O.sub.3 catalyst includes irregular shaped particles and spherical shaped particles.

3: The method of claim 2, wherein the spherical shaped particles have an average particle size in a range of 100 to 200 nanometers (nm).

4: The method of claim 1, wherein Al.sub.2O.sub.3 is present in the RuCoNi/Al.sub.2O.sub.3 catalyst at a concentration of 30 to 70 wt. % based on the total weight of the RuCoNi/Al.sub.2O.sub.3 catalyst.

5: The method of claim 1, wherein a molar ratio of Co to Ni present in the RuCoNi/Al.sub.2O.sub.3 catalyst is in a range of 20:1 to 1:20.

6: The method of claim 1, wherein the H.sub.2 is present in the H.sub.2-containing feed gas stream at a concentration of 90 to 99.99 vol. % based on a total volume of the H.sub.2-containing feed gas stream.

7: The method of claim 1, wherein the NH.sub.3 is present in the NH.sub.3-containing feed gas stream at a concentration of 5 to 20 vol. % based on a total volume of the NH.sub.3-containing feed gas stream.

8: The method of claim 1, wherein the NH.sub.3-containing feed gas stream further includes an inert gas selected from the group consisting of nitrogen, argon, and helium, wherein the residue gas stream leaving the reactor includes ammonia, nitrogen, helium, and hydrogen, and wherein a volume ratio of the NH.sub.3 to the inert gas present in the NH.sub.3-containing feed gas stream is in a range of 1:4 to 1:20.

9: The method of claim 1, wherein the reactor is at least one selected from the group consisting of a fixed-bed reactor, a trickle-bed reactor, a moving bed reactor, a rotating bed reactor, a fluidized bed reactor, and a slurry reactor.

10: The method of claim 1, wherein the reactor is a fixed-bed reactor in the form of a cylindrical reactor including: a top portion; a cylindrical body portion; a bottom portion; a housing having an open top and open bottom supportably maintained with the cylindrical body portion; wherein the RuCoNi/Al.sub.2O.sub.3 catalyst is supportably retained within the housing permitting fluid flow therethrough; at least one propeller agitator disposed in the bottom portion of the reactor; wherein the bottom portion is cone shaped or pyramidal; and wherein a plurality of recirculation tubes fluidly connects the bottom portion of the cylindrical reactor with the cylindrical body portion of the cylindrical reactor.

11: The method of claim 10, wherein the reactor has an aspect ratio of length (L) to inner diameter (ID) of 10:1 to 50:1.

12: The method of claim 1, wherein the passing the H.sub.2-containing feed gas stream through the reactor at a weight hourly space velocity of about 18,000 L/Kg.sub.cat/hr at a temperature of about 700 C.

13: The method of claim 1, wherein the passing the NH.sub.3-containing feed gas stream through the reactor at a weight hourly space velocity of about 20,400 L/Kg.sub.cat/hr at a temperature of from 400 to 700 C.

14: The method of claim 13, wherein the method has an ammonia conversion of 60 to 99% based on an initial concentration of the NH.sub.3 in the feed gas stream.

15: The method of claim 1, further including: preparing the RuCoNi/Al.sub.2O.sub.3 catalyst by: grinding and mixing a cobalt salt, a nickel salt, and an alumina support to form a first mixture; and calcining the first mixture at a temperature of about 500 C. to form a CoNi/Al.sub.2O.sub.3 composite; grinding and mixing a ruthenium salt and the CoNi/Al.sub.2O.sub.3 composite to form a second mixture; and calcining the second mixture at a temperature of about 500 C.

16: The method of claim 15, wherein a weight ratio of the cobalt salt to the nickel salt present in the first mixture is in a range of 20:1 to 1:20.

17: The method of claim 15, wherein the alumina support is at least one selected from the group consisting of a gamma-alumina support (-Al.sub.2O.sub.3), an alpha-alumina support (-Al.sub.2O.sub.3), and a delta-alumina support (-Al.sub.2O.sub.3).

18: The method of claim 15, wherein the cobalt salt includes cobalt sulfate, cobalt acetate, cobalt citrate, cobalt iodide, cobalt chloride, cobalt perchlorate, cobalt nitrate, cobalt phosphate, cobalt triflate, cobalt bis(trifluoromethanesulfonyl)imide, cobalt tetrafluoroborate, cobalt bromide, and/or its hydrate.

19: The method of claim 15, wherein the nickel salt includes nickel sulfate, nickel acetate, nickel citrate, nickel iodide, nickel chloride, nickel perchlorate, nickel nitrate, nickel phosphate, nickel triflate, nickel bis(trifluoromethanesulfonyl)imide, nickel tetrafluoroborate, nickel bromide, and/or its hydrate.

20: The method of claim 15, wherein the ruthenium salt includes ruthenium sulfate, ruthenium acetate, ruthenium citrate, ruthenium iodide, ruthenium chloride, ruthenium perchlorate, ruthenium nitrate, ruthenium phosphate, ruthenium triflate, ruthenium bis(trifluoromethanesulfonyl)imide, ruthenium tetrafluoroborate, ruthenium bromide, and/or its hydrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] A more complete appreciation of this disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

[0033] FIG. 1A is a method flowchart for ammonia (NH.sub.3) decomposition to hydrogen (H.sub.2) and nitrogen (N.sub.2), according to certain embodiments;

[0034] FIG. 1B is a method flowchart for preparing ruthenium-doped alumina-supported cobalt/nickel (RuCoNi/Al.sub.2O.sub.3) catalyst, according to certain embodiments;

[0035] FIG. 1C is a pictorial representation of ammonia cracking, according to certain embodiments;

[0036] FIG. 2A shows X-ray diffraction (XRD) patterns of Ni/Al.sub.2O.sub.3, Co/Al.sub.2O.sub.3, CoNi/Al.sub.2O.sub.3 catalysts, according to certain embodiments;

[0037] FIG. 2B shows XRD patterns of 0.5% ruthenium (Ru) doped catalysts, namely RuNi/Al.sub.2O.sub.3, RuCo/Al.sub.2O.sub.3, RuCoNi/Al.sub.2O.sub.3 catalysts, according to certain embodiments;

[0038] FIG. 3A is a scanning electron microscopic (SEM) image of the Ni/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0039] FIG. 3B is a SEM image of the Co/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0040] FIG. 3C is a SEM image of the CoNi/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0041] FIG. 3D is a SEM image of the 0.5% Ru-doped Ni/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0042] FIG. 3E is a SEM image of the 0.5% Ru-doped Co/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0043] FIG. 3F is a SEM image of the 0.5% Ru-doped CoNi/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0044] FIG. 4A is an energy dispersive X-ray spectroscopic (EDS)-elemental mapping image of the Ni/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0045] FIG. 4B is an EDS-elemental mapping image of the Co/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0046] FIG. 4C is an EDS-elemental mapping image of the CoNi/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0047] FIG. 4D is an EDS-elemental mapping image of the 0.5% Ru-doped Ni/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0048] FIG. 4E is an EDS-elemental mapping image of the 0.5% Ru-doped Co/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0049] FIG. 4F is an EDS-elemental mapping image of the 0.5% Ru-doped CoNi/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0050] FIG. 5A is an EDS spectrum of the 0.5% Ru-doped Ni/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0051] FIG. 5B is an EDS spectrum of the 0.5% Ru-doped Co/Al.sub.2O.sub.3 catalyst, according to certain embodiments;

[0052] FIG. 5C is an EDS spectrum of the 0.5% Ru-doped CoNi/Al.sub.2O.sub.3 catalyst, according to certain embodiments; and

[0053] FIG. 6 is a graph depicting NH.sub.3 decomposition with 10% NH.sub.3 flow balanced with 90% helium (He) gas using 100 milligrams (mg) of catalyst under 24000 gas hourly speed velocity (GHSV), according to certain embodiments.

DETAILED DESCRIPTION

[0054] When describing the present disclosure, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

[0055] Embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings wherever applicable, in that some, but not all embodiments of the disclosure are shown.

[0056] In the drawings, like reference numerals designate identical or corresponding parts throughout the several views. Further, as used herein, the words a, an and the like generally carry a meaning of one or more, unless stated otherwise.

[0057] As used herein, the words about, approximately, or substantially similar may be used when describing magnitude and/or position to indicate that the value and/or position described is within a reasonable expected range of values and/or positions. For example, a numeric value may have a value that is +/0.1% of the stated value (or range of values), +/1% of the stated value (or range of values), +/2% of the stated value (or range of values), +/5% of the stated value (or range of values), +/10% of the stated value (or range of values), +/15% of the stated value (or range of values), or +/20% of the stated value (or range of values). Within the description of this disclosure, where a numerical limit or range is stated, the endpoints are included unless stated otherwise. Also, all values and subranges within a numerical limit or range are specifically included as if explicitly written out.

[0058] As used herein, the term porosity refers to a measure of the void or vacant spaces within a material.

[0059] As used herein, the terms particle size and pore size may be thought of as the lengths or longest dimensions of a particle and of a pore opening, respectively.

[0060] As used herein, the term sonication refers to the process in which sound waves are used to agitate particles in a solution.

[0061] As used herein the term deionized water refers to the water that has (most of) the ions removed.

[0062] As used herein, the term calcination refers to heating a compound to a high temperature, under a restricted supply of ambient oxygen. This is performed to remove impurities or volatile substances and to incur thermal decomposition.

[0063] As used herein, the term thermal decomposition (or thermolysis) refers to a chemical decomposition initiated by heat. The decomposition temperature is the temperature at which a substance undergoes chemical decomposition.

[0064] As used herein, the term aspect ratio refers to the ratio of length to width of cylinder.

[0065] As used herein, the term weight hourly space velocity (WHSV) refers to the weight of feed flowing per unit weight of the catalyst per hour.

[0066] A weight percent of a component, unless specifically stated to the contrary, is based on the total weight of the formulation or composition in which the component is included. For example, if a particular element or component in a composition or article is said to have 5 wt. %, it is understood that this percentage is in relation to a total compositional percentage of 100%.

[0067] The present disclosure is intended to include all hydration states of a given compound or formula, unless otherwise noted or when heating a material.

[0068] The present disclosure is intended to include all isotopes of a given compound or formula, unless otherwise noted.

[0069] Aspects of the present disclosure are directed toward use of a ruthenium-doped alumina-supported cobalt/nickel (RuCoNi/Al.sub.2O.sub.3) catalyst for low-temperature ammonia decomposition to produce high-purity hydrogen.

[0070] FIG. 1A illustrates a flow chart of a method 50 for ammonia (NH.sub.3) decomposition to hydrogen (H.sub.2) and nitrogen (N.sub.2) using RuCoNi/Al.sub.2O.sub.3 catalyst. The order in which the method 50 is described is not intended to be construed as a limitation, and any number of the described method steps can be combined in any order to implement the method 50. Additionally, individual steps may be removed or skipped from the method 50 without departing from the spirit and scope of the present disclosure.

[0071] At step 52, the method 50 includes introducing a H.sub.2-containing feed gas stream into a reactor containing ruthenium-doped alumina-supported cobalt/nickel (RuCoNi/Al.sub.2O.sub.3) catalyst including RuCoNi/Al.sub.2O.sub.3 catalyst particles. In some embodiments, the H.sub.2 is present in the H.sub.2-containing feed gas stream at a concentration of 90-99.99 vol. %, preferably 90.5-99.5 vol. %, preferably 91-99 vol. %, preferably 91.5-98.5 vol. %, preferably 92-98 vol. %, preferably 92.5-97.5 vol. %, preferably 93-97 vol. %, preferably 93.5-96.5 vol. %, preferably 94-96 vol. %, preferably 94.5-95.5 vol. %, based on the total volume of the H.sub.2-containing feed gas stream. Other ranges are also possible.

[0072] In some embodiments, Ru is present in the RuCoNi/Al.sub.2O.sub.3 catalyst at a concentration of 0.01 to 5 wt. %, preferably 0.05-4.5 wt. %, preferably 0.1-4 wt. %, preferably 0.5-3.5 wt. %, preferably 1-3 wt. %, and preferably 1.5-2.5 wt. %, based on the total weight of the RuCoNi/Al.sub.2O.sub.3 catalyst. Other ranges are also possible. In a preferred embodiment, Ru is present in the RuCoNi/Al.sub.2O.sub.3 catalyst at a concentration of 0.5 wt. %. Other ranges are also possible.

[0073] In some embodiments, Al.sub.2O.sub.3 is present in the RuCoNi/Al.sub.2O.sub.3 catalyst at a concentration of 30-70 wt. %, preferably 31-69 wt. %, preferably 32-68 wt. %, preferably 33-67 wt. %, preferably 34-66 wt. %, preferably 35-65 wt. %, preferably 36-64 wt. %, preferably 37-63 wt. %, preferably 38-62 wt. %, preferably 39-61 wt. %, preferably 40-60 wt. %, preferably 41-59 wt. %, preferably 42-58 wt. %, preferably 43-57 wt. %, preferably 44-56 wt. %, preferably 45-55 wt. %, preferably 46-54 wt. %, preferably 47-53 wt. %, preferably 48-52 wt. %, and preferably 49-51 wt. %, based on the total weight of the RuCoNi/Al.sub.2O.sub.3 catalyst. Other ranges are also possible.

[0074] In some embodiments, a molar ratio of Co to Ni present in the RuCoNi/Al.sub.2O.sub.3 catalyst is in a range of 20:1-1:20, preferably 19:2-2:19, preferably 18:3-3:18, preferably 17:4-4:17, preferably 16:5-5:16, preferably 15:6-6:15, preferably 14:7-7:14, preferably 13:8-8:13, preferably 12:9-9:12, preferably 11:8-8:11, and preferably 10:9-9:10. Other ranges are also possible.

[0075] In some embodiments, the particles of the RuCoNi/Al.sub.2O.sub.3 catalyst may exist in various morphological shapes, such as rods, spheres, wires, crystals, rectangles, triangles, pentagons, hexagons, prisms, disks, cubes, ribbons, blocks, beads, toroids, discs, barrels, granules, whiskers, flakes, foils, powders, boxes, stars, tetrapods, belts, flowers, etc. and mixtures thereof. In a preferred embodiment, the RuCoNi/Al.sub.2O.sub.3 catalyst includes irregular-shaped particles and spherical-shaped particles. In some embodiments, the spherical-shaped particles have an average particle size in a range of 100-200 nanometers (nm), preferably 110-190 nm, preferably 120-180 nm, preferably 130-170 nm, and preferably 140-160 nm. Other ranges are also possible.

[0076] At step 54, the method 50 includes passing the H.sub.2-containing feed gas stream through the reactor in contact with the RuCoNi/Al.sub.2O.sub.3 catalyst particles at a temperature of 500-900 degrees Celsius ( C.), preferably 510-890 C., preferably 520-880 C., preferably 530-870 C., preferably 540-860 C., preferably 550-850 C., preferably 560-840 C., preferably 570-830 C., preferably 580-820 C., preferably 590-810 C., preferably 600-800 C., preferably 610-790 C., preferably 620-780 C., preferably 630-770 C., preferably 640-760 C., preferably 650-750 C., preferably 660-740 C., preferably 670-730 C., preferably 680-720 C., preferably 690-710 C., to form a reduced RuCoNi/Al.sub.2O.sub.3 catalyst. Other ranges are also possible. In a preferred embodiment, the H.sub.2-containing feed gas stream is passed through the reactor in contact with the RuCoNi/Al.sub.2O.sub.3 catalyst particles at a temperature of 700 C. Other ranges are also possible.

[0077] In some embodiments, the passing of the H.sub.2-containing feed gas stream through the reactor is carried out at a weight hourly space velocity (WHSV) of about 14000-20000 L/Kg.sub.cat/h, preferably 14500-19500, preferably 15000-19000, preferably 15500-18500, preferably 16000-18000, and preferably 16500-17500 L/Kg.sub.cat/h at a temperature of about 500-900 C., preferably 510-890 C., preferably 520-880 C., preferably 530-870 C., preferably 540-860 C., preferably 550-850 C., preferably 560-840 C., preferably 570-830 C., preferably 580-820 C., preferably 590-810 C., preferably 600-800 C., preferably 610-790 C., preferably 620-780 C., preferably 630-770 C., preferably 640-760 C., preferably 650-750 C., preferably 660-740 C., preferably 670-730 C., preferably 680-720 C., and preferably 690-710 C. Other ranges are also possible. In a preferred embodiment, the passing of the H.sub.2-containing feed gas stream through the reactor is carried out at a WHSV of about 18,000 L/Kg.sub.cat/h at a temperature of about 700 C. Other ranges are also possible. The process described thus far results in catalyst activation by reduction.

[0078] At step 56, the method 50 includes terminating the introducing the H.sub.2-containing feed gas stream. Once the catalyst is activated, the supply of H.sub.2 to the reactor is stopped. The reactor temperature is subsequently set to the targeted study condition under a continuous flow of an inert gas, preferably nitrogen, preferably argon, and more preferably helium. In a preferred embodiment, the reactor temperature is subsequently set to the targeted study condition under a continuous flow of helium.

[0079] At step 58, the method 50 includes introducing and passing an NH.sub.3-containing feed gas stream through the reactor in contact with the reduced RuCoNi/Al.sub.2O.sub.3 catalyst at a temperature of 100-1000 C., preferably 125-975 C., preferably 150-950 C., preferably 175-925 C., preferably 200-900 C., preferably 225-875 C., preferably 250-850 C., preferably 275-825 C., preferably 300-800 C., preferably 325-775 C., preferably 350-750 C., preferably 375-725 C., preferably 400-700 C., preferably 425-675 C., preferably 450-650 C., preferably 475-625 C., preferably 500-600 C., and preferably 525-575 C., thereby converting at least a portion of the NH.sub.3 to H.sub.2. Other ranges are also possible. In a preferred embodiment, the NH.sub.3-containing feed gas stream is introduced and passed through the reactor in contact with the reduced RuCoNi/Al.sub.2O.sub.3 catalyst at a temperature of 900 C.

[0080] In some embodiments, the NH.sub.3-containing feed gas stream further includes an inert gas selected from the group consisting of nitrogen, argon, and helium. In a preferred embodiment, the inert gas is helium. In some embodiments, the volume ratio of the NH.sub.3 to the inert gas present in the NH.sub.3-containing feed gas stream is in the range of 1:4-1:20, preferably 1:5-1:19, preferably 1:6-1:18, preferably 1:7-1:17, preferably 1:8-1:16, preferably 1:9-1:15, preferably 1:10-1:14, and preferably 1:11-1:13.

[0081] In some embodiments, the passing the NH.sub.3-containing feed gas stream through the reactor is carried out at a WHSV of 13000-21000 L/Kg.sub.cat/h, preferably 13500-20500, preferably 14000-20000, preferably 14500-19500, preferably 15000-19000, preferably 15500-18500, preferably 16000-18000, and preferably 16500-17500 L/Kg.sub.cat/h at a temperature of about 400-700 C., preferably 410-690 C., preferably 420-680 C., preferably 430-670 C., preferably 440-660 C., preferably 450-650 C., preferably 460-640 C., preferably 470-630 C., preferably 480-620 C., preferably 490-610 C., preferably 500-600 C., preferably 510-590 C., preferably 520-580 C., preferably 530-570 C., and preferably 540-560 C. Other ranges are also possible. In a preferred embodiment, the passing the NH.sub.3-containing feed gas stream through the reactor is carried out at a WHSV of 20,400 L/Kg.sub.cat/h at a temperature of about 430 C. Other ranges are also possible.

[0082] In some embodiments, the reactor is at least one selected from the group consisting of a fixed-bed reactor, a trickle-bed reactor, a moving bed reactor, a rotating bed reactor, a fluidized bed reactor, and a slurry reactor. In a preferred embodiment, the reactor is a stainless-steel fixed bed tubular reactor. In an embodiment, the reactor is the fixed-bed reactor in the form of a cylindrical reactor including a top portion, a cylindrical body portion, a bottom portion, and a housing having an open top and open bottom supportably maintained with the cylindrical body portion. In some embodiments, the RuCoNi/Al.sub.2O.sub.3 catalyst is supportably retained within the housing permitting fluid flow therethrough. In some embodiments, the bottom portion is cone-shaped or pyramidal. In some embodiments, at least one propeller agitator is disposed of in the bottom portion of the reactor. In some embodiments, a plurality of recirculation tubes fluidly connects the bottom portion of the cylindrical reactor with the cylindrical body portion of the cylindrical reactor. In some embodiments, the reactor has an aspect ratio of length (L) to the inner diameter (ID) of 10:1-50:1, preferably 15:1-45:1, preferably 20:1-40:1, and preferably 25:1-35:1. In a preferred embodiment, the reactor has an aspect ratio of 22:1.

[0083] In some embodiments, the NH.sub.3 is present in the NH.sub.3-containing feed gas stream at a concentration of 5-20 vol. %, preferably 6-19 vol. %, preferably 7-18 vol. %, preferably 8-17 vol. %, preferably 9-16 vol. %, preferably 10-15 vol. %, preferably 11-14 vol. %, and preferably 12-13 vol. %, based on a total volume of the NH.sub.3-containing feed gas stream. Other ranges are also possible. In a preferred embodiment, the NH.sub.3 is present in the NH.sub.3-containing feed gas stream at a concentration of about 10 vol. %.

[0084] At step 60, the method 50 includes regenerating the RuCoNi/Al.sub.2O.sub.3 catalyst particles to form a regenerated RuCoNi/Al.sub.2O.sub.3 catalyst and producing a residue gas stream leaving the reactor. In some embodiments, the catalytic particles may be regenerated by any method known to a person skilled in the artfor example, thermal treatment. The residue gas stream leaving the reactor includes ammonia, nitrogen, helium, and hydrogen. In some embodiments, hydrogen is released as a result of the reduction of ammonia to hydrogen by RuCoNi/Al.sub.2O.sub.3 catalyst. In some embodiments, NH.sub.3 conversion of 60-99%, preferably 61-98%, preferably 62-97%, preferably 63-96%, preferably 64-95%, preferably 65-94%, preferably 66-93%, preferably 67-92%, preferably 68-91%, preferably 69-90%, preferably 70-89%, preferably 71-88%, preferably 72-87%, preferably 73-86%, preferably 74-85%, preferably 75-84%, and preferably 76-83% occurs based on an initial concentration of the NH.sub.3 in the feed gas stream. Other ranges are also possible.

[0085] At step 62, the method 50 includes separating the H.sub.2 from the residue gas stream to generate a H.sub.2-containing product gas stream. In some embodiments, the separating the H.sub.2 is performed by techniques such as pressure swing adsorption (PSA), membrane separation, cryogenic distillation, chemical reactions, water-gas shift reaction, and/or other techniques that are known to those skilled in the art.

[0086] In some embodiments, the separating is performed by introducing the residue gas stream into a hydrogen purification device including one or more hydrogen-selective membranes. Hydrogen purification device is configured to separate hydrogen from the residue gas stream and purifying the same. In an example, the hydrogen purification device may be a palladium membrane hydrogen purifier. The palladium membrane may include metallic tubes of palladium and silver alloy for allowing only monatomic hydrogen to pass through its crystal lattice when it is heated above 300 C. The hydrogen-selective membranes are permeable to hydrogen gas but are at least substantially impermeable to other components in the residue gas stream. In some embodiments, the plurality of hydrogen-selective membranes in the hydrogen purification device is arranged in parallel, and each membrane of the plurality of hydrogen-selective membranes is placed in a plane perpendicular to a direction of the gas mixture flow in the hydrogen purification device. The method 50 may further include passing the residue gas stream through the plurality of hydrogen-selective membranes in the hydrogen purification device thereby allowing hydrogen gas to pass through the hydrogen-selective membrane and rejecting other components in the residue gas stream to form a residue composition. The method 50 may further include collecting the hydrogen gas after passing and recycling the residue composition.

[0087] FIG. 1B illustrates a flow chart of a method 80 for preparing the RuCoNi/Al.sub.2O.sub.3 catalyst. The order in which the method 80 is described is not intended to be construed as a limitation, and any number of the described method steps can be combined in any order to implement the method 80. Additionally, individual steps may be removed or skipped from the method 80 without departing from the spirit and scope of the present disclosure.

[0088] At step 82, the method 80 includes grinding and mixing a cobalt salt, a nickel salt, and an alumina support to form a first mixture. In some embodiments, the grinding may be carried out using any suitable means, for example, ball milling, blending, etc., using manual method 100s (e.g, mortar) or machine-assisted methods such as using a mechanical blender, or any other apparatus known to those of ordinary skill in the art. In some embodiments, the mixing may be carried out manually. In some embodiments, a weight ratio of the cobalt salt to the nickel salt present in the first mixture is in a range of 20:1-1:20, preferably 19:2-2:19, preferably 18:3-3:18, preferably 17:4-4:17, preferably 16:5-5:16, preferably 15:6-6:15, preferably 14:7-7:14, preferably 13:8-8:13, preferably 12:9-9:12, preferably 11:8-8:11, and preferably 10:9-9:10. Other ranges are also possible.

[0089] The cobalt salt includes cobalt sulfate, cobalt acetate, cobalt citrate, cobalt iodide, cobalt chloride, cobalt perchlorate, cobalt nitrate, cobalt phosphate, cobalt triflate, cobalt bis(trifluoromethanesulfonyl)imide, cobalt tetrafluoroborate, cobalt bromide, and/or its hydrate. In a preferred embodiment, the cobalt salt is cobalt nitrate [Co(NO.sub.3).sub.2.Math.6H.sub.2O].

[0090] In some embodiments, the nickel salt includes nickel sulfate, nickel acetate, nickel citrate, nickel iodide, nickel chloride, nickel perchlorate, nickel nitrate, nickel phosphate, nickel triflate, nickel bis(trifluoromethanesulfonyl)imide, nickel tetrafluoroborate, nickel bromide, and/or its hydrate.

[0091] In some embodiments, the alumina support is at least one selected from the group consisting of a gamma-alumina support (-Al.sub.2O.sub.3), an alpha-alumina support (-Al.sub.2O.sub.3), and a delta-alumina support (-Al.sub.2O.sub.3). In a preferred embodiment, the alumina support is -Al.sub.2O.sub.3.

[0092] At step 84, the method 80 includes calcining the first mixture at a temperature of about 400-600 C., preferably 410-590 C., preferably 420-580 C., preferably 430-570 C., preferably 440-560 C., preferably 450-550 C., preferably 460-540 C., preferably 470-530 C., preferably 480-520 C., and preferably 490-510 C., to form a CoNi/Al.sub.2O.sub.3 composite. Other ranges are also possible. In some embodiments, the calcination is carried out by heating it to a high temperature, under a restricted supply of ambient oxygen. This is performed to remove impurities or volatile substances and to incur thermal decomposition. In a preferred embodiment, the calcining of the second mixture is done at a temperature of 500 C. Typically, the calcination is carried out in a furnace preferably equipped with a temperature control system, which may provide a heating rate of up to 50 C./min, preferably up to 40 C./min, preferably up to 30 C./min, preferably up to 20 C./min, preferably up to 10 C./min, preferably up to 5 C./min, and more preferably up to 1 C./min. Other ranges are also possible. In a preferred embodiment, the calcination is carried out in a furnace at a heating rate of 4 C./min.

[0093] At step 86, the method 80 includes grinding and mixing a ruthenium salt and the CoNi/Al.sub.2O.sub.3 composite to form a second mixture. In some embodiments, the ruthenium salt includes ruthenium sulfate, ruthenium acetate, ruthenium citrate, ruthenium iodide, ruthenium chloride, ruthenium perchlorate, ruthenium nitrate, ruthenium phosphate, ruthenium triflate, ruthenium bis(trifluoromethanesulfonyl)imide, ruthenium tetrafluoroborate, ruthenium bromide, and/or its hydrate. In some embodiments, the grinding may be carried out using any suitable means, for example, ball milling, blending, etc., using manual method 100s (e.g., mortar) or machine-assisted method 100s such as using a mechanical blender, or any other apparatus known to those of ordinary skill in the art. The mixing may be carried out manually.

[0094] At step 88, the method 80 includes calcining the second mixture at a temperature of about 400-600 C., preferably 410-590 C., preferably 420-580 C., preferably 430-570 C., preferably 440-560 C., preferably 450-550 C., preferably 460-540 C., preferably 470-530 C., preferably 480-520 C., and preferably 490-510 C. Other ranges are also possible. In a preferred embodiment, the calcining of the second mixture is done at a temperature of 500 C. Other ranges are also possible. In some embodiments, the calcination is carried out in a furnace preferably equipped with a temperature control system, which may provide a heating rate of up to 50 C. per minute ( C./min), preferably up to 40 C./min, preferably up to 30 C./min, preferably up to 20 C./min, preferably up to 10 C./min, preferably up to 5 C./min, and more preferably up to 1 C./min. Other ranges are also possible. In a preferred embodiment, the calcination is carried out in a furnace at a heating rate of 3 C./min. Other ranges are also possible.

[0095] The crystalline structures of various Ni/Al.sub.2O.sub.3, Co/Al.sub.2O.sub.3, CoNi/Al.sub.2O.sub.3 catalysts, and the Ru-impregnated Co/Al.sub.2O.sub.3, Ni/Al.sub.2O.sub.3 and CoNi/Al.sub.2O.sub.3 catalysts, may be characterized by X-ray diffraction (XRD). The XRD patterns are collected in a Rigaku diffractometer equipped with a Cu-K radiation source (=0.15406 nm) for a 20 range extending between 5 and 100, preferably 15 and 80, further preferably 30 and 60 at an angular rate of 0.005 to 0.04 s.sup.1, preferably 0.01 to 0.03 s.sup.1, or even preferably 0.02 s.sup.1.

[0096] Referring to FIG. 2A, XRD profiles for Ni/Al.sub.2O.sub.3, Co/Al.sub.2O.sub.3, CoNi/Al.sub.2O.sub.3 catalysts. In some embodiments, the Ni/Al.sub.2O.sub.3 catalyst has peaks with a 2 theta () value in a range of 10 to 20, preferably 16 to 19; 32 to 39, preferably 35 to 37; 40 to 50, preferably 45 to 47; and 60 to 70, preferably 65 to 68. Other ranges are also possible. In some embodiments, the Co/Al.sub.2O.sub.3 catalyst has peaks with a 2 value in a range of 10 to 20, preferably 17 to 19.5; 30 to 40, preferably 36 to 39; 40 to 50, preferably 45 to 48; and 60 to 70, preferably 64 to 69. Other ranges are also possible. In some embodiments, the CONi/Al.sub.2O.sub.3 catalyst has peaks with a 2 value in a range of 30 to 40, preferably 35.5 to 39.5; 40 to 50, preferably 45.5 to 48.5; and 62 to 70, preferably 65 to 69. Other ranges are also possible.

[0097] Referring to FIG. 2B, XRD profiles for RuNi/Al.sub.2O.sub.3, RuCo/Al.sub.2O.sub.3, RuCoNi/Al.sub.2O.sub.3 catalysts. In some embodiments, the RuNi/Al.sub.2O.sub.3 catalyst has peaks with a 2 theta () value in a range of 10 to 15, preferably 13 to 15; 15 to 20, preferably 15.5 to 17.5; 35 to 40, preferably 36 to 39; 45 to 50, preferably 46 to 48; and 62 to 70, preferably 65 to 68. Other ranges are also possible. In some embodiments, the RuCo/Al.sub.2O.sub.3 catalyst has peaks with a 2 value in a range of 13 to 20, preferably 15 to 17.5; 30 to 40, preferably 36 to 39; 40 to 50, preferably 45 to 48; and 60 to 70, preferably 64 to 69. Other ranges are also possible. In some embodiments, the RuCONi/Al.sub.2O.sub.3 catalyst has peaks with a 2 value in a range of 15 to 20, preferably 16 to 17.5; 30 to 40, preferably 36 to 38.5; 40 to 50, preferably 45 to 48; and 60 to 70, preferably 64 to 69. Other ranges are also possible.

EXAMPLES

[0098] The following examples demonstrate the method for the ammonia (NH.sub.3) decomposition to hydrogen (H.sub.2) and nitrogen (N.sub.2) using ruthenium-doped alumina-supported cobalt/nickel (RuCoNi/Al.sub.2O.sub.3) catalyst. The examples are provided solely for illustration and are not to be construed as limitations of the present disclosure, as many variations thereof are possible without departing from the spirit and scope of the present disclosure.

Example 1: Materials

[0099] All chemicals were purchased from Sigma-Aldrich and used as received. Dry and deoxygenated solvents were produced using standard procedures wherever needed. De-ionized water (DI) water (specific conductivity: 18.2 M) was used in all experiments.

Example 2: Synthesis of Co/Al.SUB.2.O.SUB.3 .Composite

[0100] The catalysts were prepared using the dry mix method without using any solvent. Firstly, an appropriate/equimolar amount of the Co(NO.sub.3).sub.2.Math.6H.sub.2O was added to Al.sub.2O.sub.3 and ground with a mortar pestle for, e.g., preferably about 30 min to obtain the Co/Al.sub.2O.sub.3 composite. The resultant mixture was calcined at 500 degrees Celsius ( C.) in air with a temperature ramp of, e.g., preferably about 4 C./min with a temperature holding time of 5 h. A similar method was adopted to prepare the Ni/Al.sub.2O.sub.3 and the CoNi/Al.sub.2O.sub.3 composites.

Example 3: Synthesis of Ni/Al.SUB.2.O.SUB.3 .Composite

[0101] The catalysts were prepared using the dry mix method without using any solvent. Firstly, an appropriate/equimolar amount of the Ni(NO.sub.3).sub.2.Math.6H.sub.2O was added to Al.sub.2O.sub.3 and ground with a mortar pestle for, e.g., preferably about 30 min to obtain the Ni/Al.sub.2O.sub.3 composite. The resultant mixture was calcined at 500 degrees Celsius ( C.) in air with a temperature ramp of, e.g., preferably about 4 C./min with a temperature holding time of, e.g., preferably about 5 h.

Example 4: Synthesis of CoNi/Al.SUB.2.O.SUB.3 .Composite

[0102] The catalysts were prepared using the dry mix method without using any solvent. Firstly, an appropriate/equimolar amount of the Ni(NO.sub.3).sub.2.Math.6H.sub.2O, Co(NO.sub.3).sub.2.Math.6H.sub.2O was added to Al.sub.2O.sub.3 and ground with a mortar pestle for, e.g., preferably about 30 min to obtain the CoNi/Al.sub.2O.sub.3 composite. The resultant mixture was calcined at 500 degrees Celsius ( C.) in air with a temperature ramp of, e.g., preferably about 4 C./min with a temperature holding time of, e.g., preferably about 5 h.

Example 5: Synthesis of Ru-Impregnated Co/Al.SUB.2.O.SUB.3., Ni/Al.SUB.2.O.SUB.3 .and CoNi/Al.SUB.2.O.SUB.3 .Composites

[0103] The same procedure was followed except for adding Ru precursors to the above-calcined samples. About 0.5% (wt. %) of Ru was added in the form of Ru(NO.sub.3) to each calcined sample of Co/Al.sub.2O.sub.3, Ni/Al.sub.2O.sub.3, and CoNi/Al.sub.2O.sub.3 composite and ground again. Subsequently, the obtained mixture was treated with heat at, e.g., preferably about 500 C. for another 5 h with a temperature gradient of, e.g., preferably about 3 C./min.

Example 6: Catalyst Characterization

[0104] X-ray diffraction (XRD) patterns were recorded on a Rigaku model Ultima-IV diffractometer employing Cu-K radiation (=1.5406 angstrom ()) at 40 kilovolts (kV) and 25 milliamperes (mA) over a 2 range between 2 and 130. All XRD patterns were recorded in an air atmosphere. Samples for scanning electron microscope (SEM) were prepared by applying ethanolic suspensions on single-sided alumina tape on alumina stubs. For the elemental analysis and mapping, energy-dispersive X-ray spectra (EDS) were collected on a Lyra 3 (Tescan from the Czech Republic) attachment in the SEM.

Example 7: Methods

[0105] A stainless-steel fixed bed tubular reactor (12.7 millimeters (mm) diameter, 280 mm length) was utilized for the decomposition of ammonia (NH.sub.3). The reactor contained, e.g., preferably about 0.1 grams (g) of catalyst and operated under atmospheric pressure, with a quartz wool plug positioned below the catalyst. A K-type thermocouple was placed at the catalyst bed center to monitor the reactor temperature. Before the reaction initiation, the catalyst underwent a reduction process by exposing it to a hydrogen gas (H.sub.2) stream at, e.g., preferably about 700 C. and a flow rate of, e.g., preferably about 30 milliliters per minute (mL/min) for, e.g., preferably about 20 min, with a ramp rate of, e.g., preferably about 1 C. per minute ( C./min). Following the reduction step, any residual hydrogen gas was effectively purged using helium gas (He). The reactor temperature was then adjusted to the desired experimental conditions while maintaining a constant helium flow rate. FIG. 1C shows a pictorial representation of ammonia cracking.

[0106] For the reaction, a diluted mixture of ammonia (NH.sub.3) with a 10% vol concentration, balanced with helium gas (He), was introduced into the catalyst bed. The flow rate of the mixture through the catalyst bed was set at, e.g., preferably about 34 mL/min, corresponding to an equivalent space velocity of, e.g., preferably about 20,400 L/kgcat/hr. The conversion of NH.sub.3 was estimated once conditions attained a stable state. To quantify the NH.sub.3 concentration, an Agilent 7890B gas chromatograph (GC) equipped with a thermal conductivity detector (TCD) was employed. The GC analysis was performed isothermally at 50 C. using an HP-PLOT U column (30 meters in length, 0.32 mm internal diameter). Helium gas served as the carrier gas for the gas composition analysis. NH.sub.3 conversion was calculated according to the appropriate formula-

[00001]$\begin{array}{cc}N{H}_3\mathrm{conversion}=\frac{{\mathrm{NH}}_{3,in}-{\mathrm{NH}}_{3,\mathrm{out}}}{{\mathrm{NH}}_{3,in}}100& \left(2\right)\end{array}$

Example 8: Catalyst Characterization

[0107] The appropriate amount of nitrate salt of Co precursors was added to the -Al.sub.2O.sub.3 (e.g., preferably about 1 g) in a mortar-pestle and grinded for 30 min, and the resultant mixture was calcined at, e.g., preferably about 500 C. The ultrasmall metal oxides (Ni or Co) nanoparticles tend to block the pores of Al.sub.2O.sub.3, resulting in a lower surface area for the catalyst developed by the wet impregnation technique. Additionally, the homogeneous distribution of constituent elements, ease of preparation, control over the catalytic composition, and the higher prospect of scalability of this dry mixing technique make them a viable method for industrial application.

Example 9: XRD Characterization

[0108] The XRD characterization was performed to attain the catalysts' structural information. FIG. 2A shows the XRD patterns of Ni/Al.sub.2O.sub.3, Co/Al.sub.2O.sub.3, CoNi/Al.sub.2O.sub.3 while FIG. 2B shows corresponding Ru-impregnated Ni/Al.sub.2O.sub.3, Co/Al.sub.2O.sub.3, CoNi/Al.sub.2O.sub.3 samples. The results are compared with the Al.sub.2O.sub.3. The diffraction patterns demonstrated a poor crystallinity of the material (See: J. Zhang, H. Xu, X. Jin, Q. Ge, W. Li, Appl. Catal. A Gen. 2005, 290, 87-96, which is incorporated herein by reference in its entirety). The intense reflections for CoO and NiO peaks are visible in the spectrum as the dopant amount was about 50 wt. % to the Al.sub.2O.sub.3. The broad peaks at reflection 2=37.5, 45.5, and 67 are attributed to the bare amorphous alumina. Meanwhile, when two metals (CoNi) were added to alumina, their individual characteristics and diffraction patterns in the XRD were observed, suggesting the incorporation into the surface of alumina separately instead of in the bimetallic form. With regards to the Ru-impregnated samples, no significant changes in diffraction patterns were observed. This may be due to the Ru was well-dispersed all over the samples, as evidenced by the elemental mapping.

Example 10: FE-SEM Characterization

[0109] Field emission scanning electron microscopy (FE-SEM) imaging studies were performed to examine the prepared materials' surface, shape, and size. FIG. 3A-3C show SEM images of Ni/Al.sub.2O.sub.3, Co/Al.sub.2O.sub.3, and CoNi/Al.sub.2O.sub.3 while FIG. 3D-3F shows SEM images of Ru-impregnated Ni/Al.sub.2O.sub.3, Co/Al.sub.2O.sub.3, and CoNi/Al.sub.2O.sub.3 samples, showing highly agglomerated spherical particles distributed as a chunk all over the frame, and this trend continues from Ni/Al.sub.2O.sub.3 to CoNi/Al.sub.2O.sub.3. However, after the impregnation of the Ru into the system, the morphology of the catalysts improved drastically towards more dispersion of the constituents. The spherically shaped particles with sizes range from 100-200 nm.

Example 11: EDS Characterization

[0110] The Energy dispersive X-ray spectroscopic (EDS) studies were performed to examine the dispersion of the constituent elements in the composition. FIG. 4A-4C show EDS-elemental mapping images of Ni/Al.sub.2O.sub.3, Co/Al.sub.2O.sub.3, and CoNi/Al.sub.2O.sub.3. The uniform and homogeneous distribution of the Ni on the alumina was observed, and this trend was observed in all the samples. FIG. 4D-4F show EDS-elemental mapping images of Ru-impregnated Ni/Al.sub.2O.sub.3, Co/Al.sub.2O.sub.3, CoNi/Al.sub.2O.sub.3 samples. The Ru distribution all over the surface of the Al.sub.2O.sub.3 was also supported by XRD diffraction patterns. The constituent elements, such as Ni, Co, Al, and Ru, were identified by their electron emission energies. FIG. 5A-5C show EDS spectra of Ru-impregnated Ni/Al.sub.2O.sub.3, Co/Al.sub.2O.sub.3, and CoNi/Al.sub.2O.sub.3 samples, respectively.

Example 12: Catalyst Test

[0111] The catalytic performances of Ni/Al.sub.2O.sub.3, Co/Al.sub.2O.sub.3, CoNi/Al.sub.2O.sub.3, and its corresponding 0.5 wt. % Ru-impregnated catalysts in NH.sub.3 decomposition reactions are presented in FIG. 6. The pre-treated catalysts (e.g., preferably about 100 mg) with H.sub.2 at, e.g., preferably about 700 C. and 10% NH.sub.3 were used with the gas hourly space velocity (GHSV) of, e.g., preferably about 24000 mLg.sub.cat.sup.1 h.sup.1. FIG. 6 shows that as the temperature increased, the NH.sub.3 conversion was also increased even without the catalyst (dotted line, blank), which agrees with the nature of the endothermic reaction. However, when the Co/Al.sub.2O.sub.3 sample is placed, the activity toward ammonia cracking becomes evident in lower temperatures. For instance, 50% of the introduced ammonia is cracked at, e.g., preferably about 550 C., and about 96% of the ammonia is converted to H.sub.2 at, e.g., preferably about 708 C. An improvement is observed with the replacement of the same amount of Co with Ni, and the 98% conversion of ammonia to H.sub.2 is achieved at, e.g., preferably about 654 C.

[0112] Furthermore, combining both active metals and keeping the metal-to-alumina ratio (Co+Ni=50 wt. % to Al.sub.2O.sub.3) unchanged, the catalyst started to crack the ammonia at, e.g., preferably about 380 C. and reached up to >99% at, e.g., preferably about 625 C. Notably, further enhancement is recorded with the addition of a trace amount of Ru into the Ni/Al.sub.2O.sub.3, Co/Al.sub.2O.sub.3, and CoNi/Al.sub.2O.sub.3. Here, RuNi/Al.sub.2O.sub.3 catalyst demonstrated much better activity than its monometallic counterpart RuCo/Al.sub.2O.sub.3. At the lower temperature, both catalysts follow the same trend up to 400 C., and then a reasonably faster rate of decomposition of ammonia is noted with the Ni/Al.sub.2O.sub.3 catalyst. Additionally, it follows a similar path as that of the bimetallic system with Ru (RuCoNi/Al.sub.2O.sub.3).

[0113] The use of cobalt (Co) and nickel (Ni) is done as earth-abundant and economically viable elements for the synthesis of catalyst. The cost-effective Co and Ni metal on alumina-supported catalysts were prepared through a dry mixing method. The RuCoNi/Al.sub.2O.sub.3 catalyst demonstrates enhanced ammonia decomposition activity. The results show that Ni cracks ammonia at a relatively lower temperature than Co, and the combination of both metals surpassed the ammonia decomposition reaction even lower temperature than each Co and Ni. The reactivity trend in 0.5% Ru-dopped catalysts from cracking 50% ammonia can be established as 0.5% RuCoNi/Al.sub.2O.sub.3 (430 C.)>0.5% RuNi/Al.sub.2O.sub.3 (450 C.)>0.5% RuCo/Al.sub.2O.sub.3 (465 C.). On the other hand, metal on alumina decomposes 50% ammonia at 550 C. for Co/Al.sub.2O.sub.3, 530 C. for Ni/Al.sub.2O.sub.3, and 485 C. for CoNi/Al.sub.2O.sub.3.

[0114] Numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.