NANOSTRUCTURED HYBRID IRON-ZEOLITE CATALYSTS

Abstract

The present invention relates to a hybrid iron nanoparticle catalyst comprising: i) 1 to 50 wt. % nanoparticles comprising iron and at least one of a metal M selected from the group consisting of alkali metals, alkaline earth metals, transition metals of groups 3 to 7 and 9 to 11 of the Periodic Table of Elements, lanthanides and combinations of M thereof; and ii) 50 to 99 wt. % of an aluminosilicate or silicoaluminophosphate zeolite, based on the total weight of the catalyst, wherein said nanoparticle has a diameter of about 2 to 50 nm. The present invention also relates to a method of preparing the hybrid iron nanoparticle catalyst and a process for the production of light olefins using the hybrid iron nanoparticle catalyst.

Claims

1. A hybrid iron nanoparticle catalyst comprising: i) 30 wt. % to 70 wt. % of nanoparticles comprising iron and at least one of a metal M selected from the group consisting of alkali metals, alkaline earth metals, transition metals of groups 3 to 7 or 9 to 11 of the Periodic Table of Elements lanthanides, and combinations of M thereof; and ii) 70 wt. % to 30 wt. % of an aluminosilicate or silicoaluminophosphate zeolite, based on a total weight of the catalyst, wherein said nanoparticle has a diameter of 2 nm to 50 nm, and a total wt. % of the nanoparticles and zeolite is 100 wt. %.

2. The catalyst of claim 1, wherein said metal M comprises 10 wt. % to 50 wt. % based on a weight of the iron nanoparticle.

3. The catalyst of claim 1, wherein the nanoparticles adopt a spinel crystalline phase, or a spinel crystalline phase having the formula FeM.sub.2O.sub.4, or wherein the aluminosilicate zeolite is selected from pentasil zeolite or faujasite zeolite, or wherein the silicoaluminophosphate zeolite is selected from the group consisting of SAPO 11 or SAPO 34.

4. The catalyst of claim 3, wherein the pentasil zeolite or faujasite zeolite is selected from the group consisting of zeolite X, ZSM-5, zeolite Y, ZSM-12, ZSM-22, and HY zeolite.

5. The catalyst of claim 1, wherein a mole ratio of alumina to silica in the zeolite is about 1:2 to 1:90, or wherein a weight ratio of the zeolite to the iron nanoparticle is about 1:0.5 to 1:10, or wherein the iron nanoparticles further comprise an oxide of a halogen.

6.-8. (canceled)

9. The catalyst of claim 5, wherein the oxide of the halogen is present in an amount of about 0.1 wt. % to 50 wt. %, based on a weight of the nanoparticles.

10. The catalyst of claim 1, wherein the iron nanoparticles further comprise a transition metal of groups 3 to 7 and 9 to 11 of the Periodic Table of Elements, or wherein the iron nanoparticles further comprise a SiO.sub.2 matrix.

11. The catalyst of claim 10, wherein a molar ratio of iron to the transition metal is 1:1 to 50:1.

12. (canceled)

13. A method of preparing a hybrid nanoparticle iron catalyst, the method comprising i) mixing an iron salt with an aqueous surfactant to form a mixture; ii) adding a basic salt solution comprising a salt of an element selected from the group consisting of alkali metals, alkaline earth metals, transition metals of groups 3 to 7 or 9 to 11 of the Periodic Table of Elements, lanthanides, and combinations of elements thereof, to the mixture of step (i) to form a precipitate; iii) heating the precipitate of step (ii) in the presence of air and oxygen; and iv) mixing the precipitate of step (iii) with an aluminosilicate or a silicoaluminophosphate zeolite to yield a hybrid iron catalyst.

14. The method of claim 13, wherein said salt of the element comprises hydroxide, carbonate, or bicarbonate anions, or wherein the surfactant is an ionic surfactant, said surfactant comprises an anion selected from the group consisting of halides, sulfonates, sulfates, phosphates, and carboxylates.

15. The method of claim 13, wherein a molar ratio of the iron to the element of the basic salt is 1:2 to 1:25, or wherein the molar ratio of iron to the surfactant is 1:0.5 to 1:15, or wherein the heating step is carried out at a temperature of 300° C. to 600° C. or for 1 hour to 10 hours.

16. (canceled)

17. The method of any claim 13, wherein the iron salt is an iron (II) or iron (III) salt or the iron salt comprises an anion selected from the group consisting of nitrate, chloride, fluoride, bromide, iodide, phosphate, pyrophosphate, and perchlorate.

18.-19. (canceled)

20. The method of claim 13, further comprising, prior to step (iii), the steps of: collecting the precipitated nanoparticle catalyst; and drying said precipitated nanoparticle catalyst in air.

21. The method of claim 20, wherein the collection of the precipitated nanoparticle catalyst is by centrifugation or filtration.

22. The method of claim 13, further comprising, prior to step (ii), adding a solution of a salt of a transition metal to the mixture of step (i), or prior to step (ii), introducing a solution of a silicate to the mixture of step (i).

23. (canceled)

24. The method of claim 22, wherein the silicate comprises alkoxy groups of 2 to 15 carbon atoms, or wherein the molar ratio of iron to said silicate is 1:1 to 1:50.

25. (canceled)

26. A catalyst of prepared according to the method of claim 13, wherein the catalyst comprises: i) 30 wt. % to 70 wt. % of nanoparticles comprising iron and at least one of a metal M selected from the group consisting of alkali metals, alkaline earth metals, transition metals of groups 3 to 7 or 9 to 11 of the Periodic Table of Elements lanthanides, and combinations of M thereof; and ii) 70 wt. % to 30 wt. % of an aluminosilicate or silicoaluminophosphate zeolite, based on a total weight of the catalyst, wherein said nanoparticle has a diameter of 2 nm to 50 nm, and a total wt. % of the nanoparticles and zeolite is 100 wt. %.

27. A process for the production of light olefins, the process comprising a step of: i) heating the catalyst of claim 1 in the presence of a gas comprising one or more oxides of carbon and hydrogen to activate said catalyst; and ii) contacting said activated catalyst of step (i) with a gas stream comprising one or more oxides of carbon and hydrogen to partially or fully convert said one or more oxides of carbon to said light olefins, said light olefins comprising between 2 to 4 carbon atoms, wherein methane is substantially absent from said light olefins, or constitutes less than 20% of said light olefins.

28. The process of claim 27, wherein step (i) is carried out at a temperature of 200° C.-350° C., or wherein step (ii) is carried out at a temperature of 200° C.-450° C., or wherein step (i) is carried out at a pressure of 5-30 bar, or wherein step (ii) is carried out at a pressure of 5 to 50 bar, or wherein the space velocity of the gas stream in step (ii) is 1500 ml/g.Math.h to 5000 ml/g.Math.h, or wherein the molar ratio of hydrogen to the one or more oxides of carbon in the gas is 4:1 to 1:3.

29.-30. (canceled)

31. The process of claim 27, further comprising, prior to step (i), reducing the catalyst by contacting said catalyst with a stream of hydrogen gas.

32. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0117] The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

[0118] FIG. 1

[0119] FIG. 1 shows the transmission electron microscope (TEM) images of A) FeNa sample prepared by precipitation of Fe(NO.sub.3).sub.3 with NaOH, scale bar 20 nm, and B) magnification to show the Fe-based particulates, scale bar 10 nm. The microstructure is composed of smaller Fe nano-particles of 4-5 nm in size.

[0120] FIG. 2

[0121] FIG. 2A shows the X-ray diffraction (XRD) diffraction patterns of FeNa prepared through two methods. The first was prepared at room temperature with no aging (202) while the second was prepared at 70° C. and left to age for 16 hours (204).

[0122] FIG. 2B shows the X-ray diffraction (XRD) diffraction patterns of FeNa (208) in comparison to the simulated pattern of FeNa.sub.2O.sub.4 (206).

[0123] FIG. 3

[0124] FIG. 3 shows the extended X-ray absorption fine structure (EXAFS) of the FeNa catalyst (Fe.sub.2O.sub.3—Na) (302) showing the Fe—O coordination peak (308) and Fe—Fe coordination peak (310) that the Fe—Fe coordination peak is lacking a shoulder (312) typically seen in Fe.sub.2O.sub.3 (306) and Fe.sub.3O.sub.4 (304).

[0125] FIG. 4

[0126] FIG. 4 shows the electron dispersive x-ray spectrum (EDS) of FeNa showing a uniform dispersion of A) Fe, B) Br, C) Na and D) O. O acts as a reference for the distribution of minority elements such as Na and Br. Scale bar is 2.5 μm.

[0127] FIG. 5

[0128] FIG. 5 shows the electron dispersive x-ray spectrum (EDS) of FeNa—Mn, showing a uniform distribution of A) Fe, B) Br, C) Na, D) Mn and E) O. O acts as a reference for the distribution of minority elements such as Na and Br. Scale bar is 2.5 μm.

[0129] FIG. 6

[0130] FIG. 6 shows the X-ray photoelectron spectroscopy (XPS) spectrum of FeNa showing the contribution from Br in the catalyst.

[0131] FIG. 7

[0132] FIG. 7 shows the transmission electron microscope (TEM) images of s-FeNa where the Fe-based nanoparticles are well dispersed throughout a 90 wt. % silica matrix. Scale bar is 10 nm.

[0133] FIG. 8

[0134] FIG. 8 shows the light olefin ratio (O/(O+P)) versus CO conversion for the FeNa catalyst (Fe.sub.2O.sub.3—Na) activated at different conditions. The performance of the catalyst may be improved through parametric optimization.

[0135] FIG. 9

[0136] FIG. 9 shows the comparison of long term stability between FeNa (Fe.sub.2O.sub.3—Na) catalyst with Fe/CNF (carbon nanofibers) from the prior art. The inventive catalyst continues to improve in performance after 170 hours, while the performance of the benchmark (prior art) catalyst dropped to less than half its initial performance after 100 hours.

EXAMPLES

[0137] Non-limiting examples of the invention will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.

Example 1: General Synthesis

[0138] Three general classes of catalysts are disclosed:

[0139] 1) Hybrid Nanostructured Fe-Zeolite Catalysts

[0140] In one example, the present disclosure provides a method of producing hybrid nanostructured Fe-zeolite catalysts. The method begins by mixing a salt of Fe, such as Fe(NO.sub.3).sub.3, with a surfactant, such as cetyl trimethylammonium bromide (CTAB), in deionized H.sub.2O to form a well-mixed solution. An alkali base, such as NaOH, is subsequently used to precipitate the iron in the solution. The precipitate is collected without washing via centrifugation and dried in air before calcination at 550° C. for 2 hours to obtain Fe-based spinel nanoparticles. This method produces Na-promoted nano-particles of about 4-5 nm in size in a single precipitation and calcination step without the need for any washing protocol to remove the Na cation and offers good performance in light olefin (C2-C4) selectivity and yield. These nanoparticles are then physically mixed with a zeolite, such as ZSM-5, to form the hybrid catalyst. The hybrid catalyst Fe oxide catalyst is then activated in syngas at 10 bar and 290° C. for 24 hours, followed by tracking the performance of the catalyst at 370° C. and 20 bar in flowing syngas with H.sub.2/CO=1. Upon reaching a high activity (>90 C mol. % CO conversion), the temperature and/or H.sub.2/CO ratio is tuned to maximize light olefin yield.

[0141] 2) Hybrid Nanostructured Fe-Zeolite Catalysts Promoted with X

[0142] In another example, the present disclosure provides a method of producing hybrid nanostructured Fe-zeolite catalysts promoted with X, where X=Ni, Mn, Mg, Ca, La, Co, Li, K, Ce, or any of the combination thereof. The method of producing nano-sized Fe-based catalysts is carried out by mixing a salt of Fe, such as Fe(NO.sub.3).sub.3, and a promoter salt, such as Mn(NO.sub.3).sub.2, with a surfactant, such as CTAB, in deionized H.sub.2O to form a well-mixed solution. An alkali base, such as NaOH, is subsequently used to precipitate the iron in the solution. The precipitate is collected via centrifugation without washing and dried in air before calcination in air at 500° C. for at least 2 hours or 5 hours to obtain Fe-based spinel nanoparticles. This method produces X-promoted nano-particles of about 4-5 nm in size in a single precipitation and calcination step without the need for any washing protocol to remove the X cation and offers good performance in light olefin (C2-C4) selectivity and yield. These nanoparticles are then physically mixed with a zeolite, such as ZSM-5, to form the hybrid catalyst. The hybrid catalyst is then activated in syngas at 10 bar and 290° C. for 24 hours, followed by tracking the performance of the catalyst at 370° C. and 20 bar in flowing syngas with H.sub.2/CO=1. Upon reaching a high activity (>90 C mol. % CO conversion), the temperature and/or H.sub.2/CO ratio ca be tuned to maximize light olefin yield.

[0143] 3) Hybrid nanostructured supported-Fe-zeolite catalysts, optionally promoted with X In another example, the present disclosure provides a method of producing hybrid nanostructured supported-Fe-zeolite catalysts, which may or may not be promoted with X, where X=Ni, Mn, Mg, Ca, La, Co, Li, K, Ce or any of the combination thereof. The method begins by mixing a salt of Fe, such as Fe(NO.sub.3).sub.3, a salt of X if promotion with X is desired, and cetyl trimethyl ammonium bromide (CTAB) in deionized water. NaOH solution is used to precipitate the iron and X from the solution. Tetraethyl orthosilicate (TEOS) and hydrolyzed to form a structural promoter in the form of SiO.sub.2, to form a silica matrix. The precipitate is then collected via centrifugation without washing and dried in air before being calcined in air at 500° C. or higher for at least 2 hours. This method produces X-promoted nano-particles of about 4-5 nm in size in a single precipitation and calcination step without the need for any washing protocol to remove the Na cation and offers good performance in light olefin (C2-C4) selectivity, yield and enhanced stability. The supported Fe-based particles are then physically mixed with a zeolite, such as ZSM-5, to form the hybrid catalyst. The hybrid catalyst is then activated in syngas at 10 bar and 290° C. for 24 hours, followed by tracking the performance of the catalyst at 370° C. and 20 bar in flowing syngas with H.sub.2/CO=1. Upon reaching a high activity (>90 C mol. % CO conversion), the temperature and/or H.sub.2/CO ratio can be tuned to maximize light olefin yield.

Example 2: Fe-Zeolite Hybrid Catalyst (FeNa)

[0144] Fe-zeolite hybrid catalyst (FeNa+H—Y) was prepared by first mixing 10.81 g of Fe(NO.sub.3).sub.3.9H.sub.2O with 10 g CTAB in 400 ml deionized H.sub.2O to form a well-mixed solution. 4 g of NaOH in 80 ml deionized H.sub.2O was subsequently used to precipitate the iron in the solution. The suspension was allowed to age at room temperature for 5 minutes before collection of the precipitate via centrifugation. No washing of the precipitate was performed in order to allow the Na to remain as a promoter. The precipitate was then dried in air before calcination at 550° C. for 2 hours. This resulted in a FeNa catalyst with a Na promotion of about 10 wt. %. Subsequently, H—Y zeolites were physically mixed with FeNa in a 1:1 weight ratio to yield the hybrid catalyst.

[0145] The hybrid catalyst was transferred to a fixed bed reactor and reduced in flowing H.sub.2. It was then activated in syngas at 10 bar and 290° C. for 24 hours, followed by tracking the performance of the catalyst at 370° C. and 20 bar in flowing syngas with H.sub.2/CO=1 at a space velocity of 2,000 ml/g.Math.h. Upon reaching a high activity (>90 C mol. % CO conversion), the temperature and/or H.sub.2/CO ratio could be tuned to maximize light olefin yield.

[0146] High resolution transmission electron micrographs were acquired using a field emission transmission electron microscope (TEM) (Tecnai G2 TF20 S-twin, FEI Company) operated at 200 kV. FIG. 1A shows the transmission electron microscopy (TEM) images of the FeNa catalysts, where the nanoparticles are clustered together and can be made out clearly in magnified FIG. 1B.

[0147] X-ray diffraction (XRD) spectra were collected at room temperature using a Bruker D8 Advance diffractometer (Bruker AXS GmbH, Germany) equipped with Cu-Kα radiation source (λ=1.54056 Å) operated at 40 kV and 30 mA. The samples were scanned using Bragg-Brentano geometry within the range of 20=10°-90°. The crystal phase of the Fe-based particles is shown in FIG. 2 where the X-ray diffraction (XRD) patterns indicate an as-yet unidentified spinel structure. FIG. 2A shows the X-ray diffraction (XRD) diffraction patterns of FeNa with precipitation occurring at room temperature and without aging showing mixed phases of spinel and haematite (202), and at 70° C. with 16 hours aging (204), where the spinel phase becomes dominant. It can be seen that aging promotes the formation of the spinel phase (FeNa.sub.2O.sub.4), which can be seen from the lack of peaks around 33°, 35.8°, and 54°.

[0148] FIG. 2B shows the X-ray diffraction (XRD) diffraction patterns of FeNa (208) in comparison to the simulated pattern of FeNa.sub.2O.sub.4 (206). FIG. 2B shows the good correspondence between measured and simulated patterns with an error range for peak position of about ±1%. The measured spectrum was smoothed to improve the signal-to-noise ratio and then LiMn.sub.2O.sub.4 was used as a starting structure, where Li was replaced with Na and Mn was replaced with Fe. A periodic unit cell was constructed and discrete Fourier transform (DFT) performed to obtain its ground state using Quantum Espresso. The XRD pattern for FeNa.sub.2O.sub.4 was subsequently simulated using Visualizaton for Electronic and Structural Analysis (VESTA).

[0149] X-ray absorption spectra (XAS) of Fe K edge was recorded at the X-ray Absorption Fine Structure For Catalysis (XAFCA) beamline at the Singapore Synchrotron Light Source. The samples were first mixed and ground thoroughly with boron nitride, followed by pressing into a small circular disc with a diameter of 1 cm. XAS spectra of the catalysts were then collected in He at room temperature.

[0150] Extended X-ray absorption fine structure analysis (EXAFS) analysis was done by Athena software. EXAFS of FeNa (302) in FIG. 3 showed that the Fe—O coordination peak (308) may be found at a radial distance of 1.4 Å, while the first Fe—Fe coordination peak (310) may be found at 2.6 Å. The second Fe—Fe coordination peak (312) may be found at around 3.1 Å, which is typical for Fe.sub.3O.sub.4 (304) and existed as shoulder for Fe.sub.2O.sub.3 (306) due to less Fe in the chemical composition. FIG. 3 revealed a missing Fe—Fe coordination peak (312) for FeNa (Fe.sub.2O.sub.3—Na)(302) typically seen in Fe.sub.2O.sub.3 (306) and Fe.sub.3O.sub.4 (304) phases, which may suggest a substitution of the Fe atom with that of another element, hypothetically Na.

[0151] Elemental composition analysis of the FeNa catalyst was performed using electron dispersive x-ray spectrum (EDS), shown in FIG. 4. The EDS shows uniform dispersion of positively identified Fe (FIG. 4A), Br (FIG. 4B), Na (FIG. 4C) and O (FIG. 4D) contributions. EDS was carried out using field emission scanning electron microscopy (FE-SEM, JEOL JSM 6700) at a beam energy of 5 keV with Oxford instrument EDS system.

[0152] Table 1 shows the performance of FeNa and FeNa combined with various zeolites, at 370° C., 20 bar, H.sub.2/CO=1 and gas hourly space velocity (GHSV) of 2,000 ml/g.Math.h.

[0153] Specifically, FeNa catalyst were pelletized at 40 kN and sieved to 250-500 μm particles. Then 0.5 g of the FeNa catalyst was loaded to a fixed bed reactor for testing after mixing with SiC at a volume ratio=1:1. Reduction was carried out at 600° C. for 6 hours in H.sub.2 and ambient pressure at a space velocity of 2000 ml/(g.Math.h). Activation was carried out at 290° C. for 24 hours in CO and H.sub.2 with H.sub.2/CO ratio=2 at 10 barg and a space velocity of 2000 ml/(g.Math.h). The CO reaction was carried out at 370° C. in CO and H.sub.2 with H.sub.2/CO ratio=2 at 20 barg and a space velocity of 2000 ml/(g.Math.h).

[0154] The reaction data in Table 1 shows an improvement in activation time (from 40 hours to between 10-16 hours), as well as a general increase in C2-C4 hydrocarbon selectivity. It would appear that H—Y zeolites can change the hydrocarbon distribution by cracking C5+ to shorter chain hydrocarbons. Further, olefinicity was also improved when FeNa was combined with zeolites such as H—Y (80) and ZSM-5 (80). Higher SiO.sub.2-to-A12O.sub.3 ratio results in higher olefinicity from both H—Y and ZSM-5 zeolites Yields for light olefins over FeNa+H—Y (80) increased over that for FeNa alone, shown also in Table 1. This shows that the activity, selectivity and olefinicity can be tuned by mixing the catalyst with various zeolites.

TABLE-US-00001 TABLE 1 Performance of hybrid FeNa + zeolite combination for FTO at 370° C., 20 bar, 2000 ml/g.h and H.sub.2/CO = 1. Hydrocarbon LO Conv. CH.sub.4 CO.sub.2 distribution (mol LO/(O + P) (mol Yield TOS (mol (mol (mol C %) C %) (mol Catalyst (hr) C %) C %) C %) CH.sub.4 C2-C4 C5+ C2 C3 C4 C %) FeNa 40 92 8 43 20 49 31 59 89 83 20 FeNa + 16 94 12 43 28 54 18 30 77 43 15 H-Y (5) FeNa + 16 95 8 42 21 51 28 62 89 80 22 H-Y (80) FeNa + 16 94 8 43 21 55 24 51 87 53 19 ZSM-5 (30) FeNa + 10 92 7 43 17 49 34 67 90 80 20 ZSM-5 (80) FeNa + 12 93 10 39 24 53 23 42 85 62 20 SAPO11 FeNa + 16 95 10 41 24 51 25 33 78 53 16 SAPO34 TOS: Time on Stream O: Olefin P: Paraffin LO: light olefin The numbers in the brackets in the name of catalyst indicate the SiO.sub.2/Al.sub.2O.sub.3 mole ratio for the zeolites.

[0155] Similar hybrid systems reported in the art typically exploits ZSM-5 for its shape and size selectivity and targets the production of paraffinic hydrocarbons in the gasoline range. In contrast, the present system aims to maximize light olefin selectivity and yield. A comparison with similar hybrid systems is shown in Table 2. Olefinicity is dramatically enhanced with the hybrid FeNa-ZSM-5 system.

TABLE-US-00002 TABLE 2 Performance of FeNa + ZSM-5 combination compared with similar systems in the art Reaction of FeNa + ZSM-5 was carried out at 370° C., 20 bar, 2000 ml/g.h and H/CO = 1. Hydrocarbon LO Conv. CH.sub.4 CO.sub.2 distribution (mol LO/(O + P) (mol Yield (mol (mol (mol C %) C %) (mol Catalyst C %) C %) C %) ch.sub.4 C2-C4 C5+ C2 C3 C4 C %) FeNa + ZSM-5 94 8 43 21 55 24 51 87 53 19 (30) Fe-Cu- 81 38 18 25 57 ← 40 .fwdarw. 5 K/ZSM-5 (25)* FeNa + ZSM-5 92 7 43 17 49 34 67 90 80 20 (80) Fe + ZSM-5 96 43 17 35 48 ← 0 .fwdarw. 0 (80)** *Reaction carried out at 300° C., 10 bar, 2000 ml/g.h and H.sub.2/CO = 2 (comparative example) **Reaction carried out at 300° C., 10 bar, 2240 ml/g.h and H.sub.2/CO = 1 (comparative example)

[0156] The examples in Table 2 were precipitated with NaOH (with the exception of Fe—Cu—K/ZSM-5 (25), which was precipitated with KOH, and Fe+ZSM-5 (80), which was precipitated with NH.sub.4OH) using nitrate salts of Fe and Cu. The examples were then mixed with ZSM-5 for testing. FeNa (inventive catalyst) is Fe.sub.2O.sub.3—Na, while Fe (comparative example) is purely Fe.sub.2O.sub.3 and Fe—Cu (comparative example) is mixture of iron oxide and copper oxide.

Example 3: Mn Promoted Fe-Zeolite Hybrid Catalyst

[0157] Mn promoted Fe-zeolite hybrid catalyst (FeNa+H—Y) was prepared by first synthesizing a Mn promoted FeNa (FeNa—Mn) catalyst by mixing 9.73 g of Fe(NO.sub.3).sub.3.9H.sub.2O and 0.67 g of Mn(NO.sub.3).sub.2.4H.sub.2O with 10 g CTAB in 400 ml deionized H.sub.2O to form a well-mixed solution. 4 g of NaOH in 80 ml deionized H.sub.2O was subsequently used to precipitate the metals in the solution. The suspension was allowed to age at room temperature for 5 minutes, before collection of the precipitate via centrifugation. No washing of the precipitate was performed in order to allow the Na to remain as a promoter. The precipitate was then dried in air before calcination at 550° C. for 2 hours. This resulted in a FeNa—Mn catalyst with a Na promotion of about 10 wt. % and an Fe to Mn ratio of about 9. Subsequently, H—Y zeolites were physically mixed with FeNa—Mn in a 1:1 weight ratio to yield the hybrid catalyst.

[0158] The hybrid catalyst was then transferred to a fixed bed reactor and reduced in flowing H.sub.2. An activation protocol flowing syngas in the ratio H.sub.2/CO=1, 10 bar and 290° C. for 24 hours was used to activate the catalyst. Finally, an induction period was observed by tracking the performance of the catalyst at 370° C. and 20 bar in flowing syngas with H.sub.2/CO=1 at a space velocity of 2,000 ml/g.Math.h. Upon reaching a high activity (>90 C mol. % CO conversion), the temperature and/or H.sub.2/CO ratio may be tuned to maximize light olefin yield.

[0159] FIG. 5 shows the electron dispersive x-ray spectrum (EDS) mapping of the constituent atoms in the FeNa—Mn catalyst. The images show a well dispersed and uniform distribution of Fe (FIG. 5A), Br (FIG. 5B), Na (FIG. 5C) and Mn (FIG. 5D), as well as the oxygen content present in oxide form (FIG. 5E). X-ray photoelectron spectroscopy (XPS) was performed on a VG ESCALAB 250 spectrometer equipped with a monochromatic Mg Kα radiation source. All binding energies were adjusted to the line position of C1s at 284.6 eV as a reference.

[0160] FIG. 6 shows the XPS spectrum of FeNa for Br, where the binding energy suggests that Br is present in the form of bromate and can be reduced to bromide during the reduction process in H.sub.2. The reduced bromide may then play a role in Fe.sub.5C.sub.2 formation.

TABLE-US-00003 TABLE 3 Performance of FeNa-Mn at 370° C., 20 bar, H/CO = 1 and GHSV of 12,000 ml/g.h with and without the mixing with H-Y zeolite. Hydrocarbon LO Conv. CH.sub.4 CO.sub.2 distribution (mol LO/(O + P) (mol Yield TOS (mol (mol (mol C %) C %) (mol Catalyst (hr) C %) C %) C %) CH.sub.4 C2-C4 C5+ C2 C3 C4 C %) FeNa-Mn 24 95 8 42 21 49 30 54 88 79 20 FeNa-Mn +  4 95 8 41 22 52 26 49 86 68 20 H-Y (80)

[0161] Table 3 shows that the hybridization with H—Y zeolite improved the FTO reaction by shortening the activation time by 6 fold, while increasing the light hydrocarbon fraction.

Example 4: FeNa Catalyst in Silica Matrix

[0162] FIG. 7 shows a transmittance electron microscopy (TEM) micrograph of s-FeNa where the Fe-based nanoparticles are well dispersed throughout a 90 wt. % silica matrix.

[0163] Typically, 10.81 g of the iron precursor Fe(NO.sub.3).sub.3.9H.sub.2O were dissolved in 400 ml of deionized (DI) H.sub.2O and mixed with 10 g of cetyl trimethylammonium bromide (CTAB). The precipitating reagent was prepared by dissolving 4 g of NaOH in 80 ml of DI H.sub.2O, of which 60 ml was subsequently added instead of the usual 80 ml in order to obtain spherical Fe nanoparticles through pH control. It should be noted that precipitating with 80 ml of NaOH solution would have yielded rod-like Fe structures. The encapsulation of the iron catalyst was done by first preparing the unsupported catalyst up till the precipitation step (i.e. before the step of drying in air and calcination) according to Example 2, followed by the addition of SiC.sub.8H.sub.20O.sub.4 (TEOS) according to the weight percent required. For example, 10Fe.sub.2O.sub.3@SiO.sub.2 which comprises 10 wt % Fe.sub.2O.sub.3 required 143 ml of TEOS dissolved in 200 ml of ethanol. The TEOS was allowed to undergo hydrolysis for at least 8 hours before the mixture was centrifuged and dried at 80° C. for 48 hours before use.

Example 5: Performance Comparison

[0164] The performance of the inventive catalyst was compared to a benchmark comparative example.

TABLE-US-00004 TABLE 4 Performance of FeNa, FeNa + H-Y, 10FeNa@SiO.sub.2 in comparison to a comparative example, Fe(Na + S)/CNF C2-C4 CO CO.sub.2 C2-C4 Paraff LO O/(O + Conv. Sel. CH.sub.4 Olefin ins C5+ Yield P) (mol (mol (mol (mol (mol (mol (mol (mol Catalyst C %) C %) C %) C %) C %) C %) C %) C %) FeNa 92 43 20 38 11 31 20 77.6% FeNa + 95 42 21 39 12 28 22 76.5% H-Y (80) 10FeNa@ 61 44 32 30 25 13 11 54.5% SiO2 Fe(Na + 87 42 10 37 23 30 19 61.7% S)/CNF* Conv. stands for conversion Sel. stands for selectivity *Comparative example from: Torres Galvis, Hirsa M., et al. “Iron particle size effects for direct production of lower olefins from synthesis gas.” Journal of the American Chemical Society 134.39 (2012): 16207-16215.

[0165] The comparative example was made by an impregnation method and supported on carbon nanofibers (CNF), whereas the inventive catalyst was formed by precipitation.

[0166] The inventive catalysts in Table 4 (first and second rows) were observed to have better olefin percentage (O/(O+P)) than the comparative example (fourth row), with the inventive catalyst having significantly higher olefin percentage.

[0167] The above was further supported by FIG. 8 which shows the light olefin ratio (O/(O+P)) versus CO conversion for the inventive catalyst FeNa (Fe.sub.2O.sub.3—Na) activated at different conditions. The performance of the catalyst was shown to be improved through parametric optimization. FIG. 9 further shows the comparison of long term stability between Fe.sub.2O.sub.3—Na with Fe/CNF from the prior art. The inventive catalyst continues to improve in performance after 170 hours, while the performance of the benchmark (prior art) catalyst dropped to less than half its initial performance after 100 hours.

[0168] Table 4, FIG. 8 and FIG. 9 show that the inventive catalysts were able to achieve similar if not higher olefin selectivity compared to the comparative example, similar if not higher activity compared to the comparative example, and a milestone light olefin (LO) yield of 20%.

Example 6: CO.SUB.2 .to Olefins

[0169] The use of the catalyst for the conversion of CO.sub.2 to olefins was also investigated. FeNa catalyst washed with deionized water were pelletized at 40 kN and sieved to 250-500 μm particles. Then 0.5 g of the FeNa catalyst was loaded to a fixed bed reactor for testing after mixing with SiC at a volume ratio=1:1. Reduction was carried out at 580° C. for 6 hours in H.sub.2 and ambient pressure at a space velocity of 2000 ml/(g.Math.h). Activation was carried out at 300 HC for 4 hours in CO and H.sub.2 with H.sub.2/CO ratio=2 at 10 barg and a space velocity of 2000 ml/(g.Math.h). The CO.sub.2 reaction was carried out at 350° C. in CO.sub.2 and H.sub.2 with H.sub.2/CO.sub.2 ratio=3 at 15 barg and a space velocity of 5500 ml/(g.Math.h).

[0170] The catalytic performance of the FeNa catalyst for CO.sub.2 to olefins reaction is presented in Table 5.

TABLE-US-00005 TABLE 5 Performance of the FeNa catalyst for CO2 to olefins reaction, with X(CO.sub.2) being the conversion of CO.sub.2, and S(CH.sub.4) and S(CO) being the selectivity towards CH.sub.4 and CO respectively. Light X(CO.sub.2) (LO) TOS mol S(CH.sub.4) S(CO) Yield % of Olefins Hydrocarbon distribution (hrs) C % mol C % mol C % Olefin C2 C3 C4 C2-C4 CH.sub.4 C2-C4 C5+ 2 42 11 14  9.1 79 89 84 84.5 13 30 57 4 44 12 13 10.0 79 90 83 84.6 14 30 56 6 44 13 12 10.2 80 90 84 85.0 14 31 55 8 44 13 12  9.9 80 90 85 85.5 13.8 29.7 56.5 10 45 13 12 10.2 80 91 85 85.8 14.1 30.0 55.9 18 45 13 11 10.2 81 91 86 86.6 13.8 29.3 56.8 20.0 46 13 11 10.4 81 91 88 87.4 14.0 29.4 56.6 22.0 46 13 11 10.6 82 91 85 86.5 14.2 30.2 55.6 26.0 46 13 11 10.8 82 91 85 86.5 14.1 30.6 55.3

[0171] The above shows that the FeNa catalyst can achieve a light olefin yield of 10.8% at a CO.sub.2 conversion of 46% with very high percentage of olefin in C2-C4 and relatively low CH.sub.4 and CO selectivity. Further optimization to improve the olefin yield may be possible.

INDUSTRIAL APPLICABILITY

[0172] The hybrid nanoparticle iron catalyst as disclosed herein may be used in Fischer Tropsch synthesis to convert CO, CO.sub.2 or a mixture of CO and CO.sub.2 and H.sub.2 as feedstock to produce light olefins. The catalyst may be useful in the process of synthesizing light olefins, whereby the process may have high selectivity for light olefins over methane, longer chain olefins or paraffins, and the catalyst may have a significantly shorter activation time. The method of preparing the catalyst as disclosed herein may allow for the catalyst to be prepared by co-precipitation of an iron nanoparticle catalyst with a basic salt solution, making the preparation of the catalyst facile. Further, the process as disclosed herein may be used in the preparation of light olefins, whereby the process may be highly selective for light olefins. The catalyst may also be useful in converting CO and/or CO.sub.2 feedstocks to other hydrocarbons such as alcohols and C5+ hydrocarbons.

[0173] It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.