SYNGAS FOR PRODUCTION OF OLEFINS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 62/255,937, filed November 16, 2015. The contents of the referenced application are incorporated into the present application by reference.

FIELD

[0002] The presently disclosed subject matter relates to methods for high temperature conversion of carbon dioxide (C0 ₂ ) into synthesis gas (syngas) via hydrogenation of C0 ₂ .

BACKGROUND

[0003] Synthesis gas (also known as syngas) is a mixture of carbon monoxide (CO) and hydrogen (H ₂ ). Syngas can be prepared by reacting C0 ₂ with H ₂ . This process can be described as a hydrogenation of C0 ₂ . C0 ₂ and H ₂ can react to form carbon monoxide (CO) and water (H ₂ 0) through a reverse water gas shift (RWGS) reaction. The RWGS reaction is endothermic and can be described by the following equation:

(1) C0 ₂ + H ₂ → CO + H ₂ 0 A _R H°3oo _° c = 38 kJ/mol

The RWGS reaction is reversible; the reverse reaction (from CO and H ₂ 0 to C0 ₂ and H ₂ ) is known as the water gas shift reaction. The RWGS reaction can be conducted under conditions that provide partial conversion of C0 ₂ and H ₂ , thereby creating an overall product mixture that includes C0 ₂ , H ₂ , CO, and H ₂ 0. C0 ₂ and H ₂ 0 can optionally be removed from such a product mixture, thereby providing a purified syngas mixture containing primarily CO and H ₂ .

[0004] Syngas is a versatile mixture that can be used to prepare light olefins, methanol, acetic acid, aldehydes, and many other important industrial chemicals. However, the efficiency of the preparation of different chemicals, for example, methanol versus light olefins, from syngas can depend on the composition of the syngas. Syngas containing H ₂ and CO in a molar ratio (H ₂ :CO) of about 2: 1 can be useful for olefin synthesis.

[0005] A disadvantage of many existing methods of preparing syngas is that they tend to produce syngas having a high H ₂ :CO molar ratio which is not suitable for olefin synthesis. Additionally, reactions at high temperatures can lead to fusing of the active sites of mixed oxide catalysts to non-oxide catalysts, limiting the reaction.

[0006] Thus, there remains a need in the art for new methods for conversion of C0 ₂ into syngas with H ₂ :CO ratios compatible with olefin synthesis, improved catalyst stability, improved yield, and improved overall economy. SUMMARY OF THE DISCLOSED SUBJECT MATTER

[0007] The presently disclosed subject matter provides a method of preparing syngas, which can include providing a reaction chamber that comprises a catalyst comprising Cu and Mn. The method can further include feeding a reaction mixture comprising H ₂ and C0 ₂ to the reaction chamber and contacting H ₂ and C0 ₂ with the catalyst at a reaction temperature greater than 800 °C to provide a product mixture that comprises H ₂ and CO.

[0008] In certain embodiments, the catalyst can include Cu and Mn in a molar ratio of about 4: 1 to about 1 :4, or a molar ratio of about 1 : 1.

[0009] In certain embodiments, the catalyst can further include one or more solid supports selected from the group consisting of A1 ₂ 0 ₃ , MgO, Si0 ₂ , Ti0 ₂ , and Zr0 ₂ .

[0010] In certain embodiments, the catalyst can include one or more additional metals selected from the group consisting of La, Ca, K, W, and Al. In certain embodiments, the catalyst includes Al.

[0011] In certain embodiments, the catalyst can include about 10% Cu and about 10% Mn, by weight.

[0012] In certain embodiments, the reaction mixture can include H ₂ and C0 ₂ in a molar ratio (H ₂ : C0 ₂ ) of about 1.5 : 1.

[0013] In certain embodiments, the reaction temperature is greater than about 800 °C, greater than about 825 °C, or is about 850 °C.

[0014] In certain embodiments, the product mixture can include H ₂ and CO in a molar ratio (H ₂ :CO) of about 1 : 1 to about 3 : 1, about 1.5: 1 to about 3 : 1, about 2: 1 to about 3 : 1, about 2.36: 1 or about 2.26: 1.

[0015] In certain embodiments, the product mixture further includes C0 ₂ and H ₂ 0. In certain embodiments, the product mixture can include less than about 25% C0 ₂ , by mole or less than about 15% C0 ₂ , by mole.

[0016] In certain embodiments, the method can include separating at least a portion of C0 ₂ and H ₂ 0 from the product mixture to provide purified syngas.

[0017] The presently disclosed subject matter provides a method of preparing light olefins, which can include providing a reaction chamber that can include a catalyst comprising Cu and Mn. In certain embodiments, the method further includes feeding a reaction mixture comprising H ₂ and C0 ₂ to the reaction chamber and contacting H ₂ and C0 ₂ with the catalyst at a reaction temperature greater than or equal to about 800 °C to provide a product mixture that comprises H ₂ , CO, C0 ₂ , and H ₂ 0. In certain embodiments, the method further includes separating at least a portion H ₂ 0 from the product mixture. In certain embodiments, the method also includes subjecting the product mixture to a Fischer-Tropsch synthesis (FT) reaction to provide light olefins.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is a schematic diagram presenting an exemplary process for integration of C0 ₂ to the syngas process for producing olefins. [0019] FIG. 2 is a schematic diagram presenting an exemplary process for integration of C0 ₂ to the syngas process for producing olefins.

[0020] FIG. 3 is a schematic diagram presenting an exemplary process for integration of CO ₂ to the syngas process for producing olefins.

DETAILED DESCRIPTION

[0021] There remains a need in the art for new methods of preparing syngas from CO ₂ . The presently disclosed subject matter provides novel methods of converting CO ₂ and H ₂ into syngas at high temperatures with H ₂ :CO ratios compatible with olefin synthesis and improved catalyst stability. The presently disclosed subject matter also provides improved methods of preparing light olefins. The presently disclosed subject matter includes the surprising discovery that Copper-Manganese-Aluminum (Cu-Mn-Al) catalysts can be used to promote hydrogenation of CO ₂ at temperatures including and above about 800 °C. Such catalysts can be stable at these high temperatures and the use of reaction temperatures including and greater than 800 °C can provide improved conversion of C0 ₂ , improved ratios of H ₂ :CO, and improved yield.

[0022] As used herein, the term "about" or "approximately" means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, i.e., the limitations of the measurement system. For example, "about" can mean a range of up to 20%, up to 10%, up to 5%), and or up to 1% of a given value.

Reactors and Reaction Chambers

[0023] The methods of the present disclosure can involve fixed bed isothermal or adiabatic reactors suitable for reactions of gaseous reactants and reagents catalyzed by solid catalysts. The reactor can be constructed of any suitable materials capable of holding high temperatures, for example from about 800°C to about 850°C. Non-limiting examples of such materials can include metals, alloys (including steel), glasses, ceramics or glass lined metals, and coated metals. The reactor can also include a reaction vessel enclosing a reaction chamber.

[0024] The dimensions of the reaction vessel and reaction chamber are variable and can depend on the production capacity, feed volume, and catalyst. The geometries of the reactor can be adjustable in various ways known to one of ordinary skill in the art.

[0025] In certain embodiments, reaction conditions within the reaction chamber can be isothermal. That is, hydrogenation of C0 ₂ can be conducted under isothermal conditions. In certain alternative embodiments, a temperature gradient can be established within the reaction chamber. For example, hydrogenation of C0 ₂ can be conducted across a temperature gradient using an adiabatic reactor.

[0026] The pressure within the reaction chamber can be varied, as is known in the art. In certain embodiments, the pressure within the reaction chamber can be atmospheric pressure, i.e., about 1 bar.

Catalysts

[0027] Catalysts suitable for use in conjunction with the presently disclosed matter can be catalysts capable of catalyzing RWGS reactions, i.e., hydrogenation of C0 ₂ . In certain embodiments, the catalyst can be a solid catalyst, e.g., a solid-supported catalyst. The catalyst can be a metal oxide or mixed metal oxide. In certain embodiments, the catalyst can be located in a fixed packed bed, i.e., a catalyst fixed bed. In certain embodiments, the catalyst can include solid pellets, granules, plates, tablets, or rings.

[0028] In certain embodiments, the catalyst can include one or more transition metals. The catalyst can include copper (Cu) or manganese (Mn). In certain embodiments, the catalyst can include both Cu and Mn. In certain embodiments, the catalyst can include Cu and Mn in a molar ratio of about 10: 1 to about 1 : 10, about 4: 1 to about 1 :4, or about 1 : 1 (Cu:Mn). By way of non-limiting example, the molar ratio of Cu:Mn in the catalyst can be about 10: 1, 9: 1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2.5:1, 2:1, 1.8:1, 1.6:1, 1.5:1, 1.4:1, 1.3:1, 1.2:1, 1.1:1, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.8, 1:2, 1:2.5, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.

[0029] In certain embodiments, the catalyst can include a solid support. That is, the catalyst can be solid-supported. In certain embodiments, the solid support can include various metal salts, metalloid oxides, and/or metal oxides, e.g., titania (titanium oxide), zirconia (zirconium oxide), silica (silicon oxide), alumina (aluminum oxide), magnesia (magnesium oxide), and magnesium chloride. In certain embodiments, the solid support can include alumina (A1 ₂ 0 ₃ ), silica (Si0 ₂ ), magnesia (MgO), titania (Ti0 ₂ ), zirconia (Zr0 ₂ ), cerium(IV) oxide (Ce0 ₂ ), or a combination thereof. The amount of the solid support present in the catalyst can be between about 40% and about 95%, by weight, relative to the total weight of the catalyst. By way of non-limiting example, the solid support can constitute about 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95% of the total weight of the catalyst.

[0030] In certain embodiments, the catalyst can include one or more additional metals in addition to Cu and Mn. The additional metal(s) can include lanthanum (La), calcium (Ca), potassium (K), tungsten (W), and/or aluminum (Al). In certain embodiments, the additional metal(s) can be present in an amount between about 1% and 25%, relative to the total weight of the catalyst. For example, the catalyst can include about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 18%, 20%, 22%, or 25% of the additional metal(s), by weight.

[0031] In certain embodiments, the catalyst can include about 1% to about 25% Cu, by weight. For example, the catalyst can include about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 18%, 20%, 22%, or 25% Cu, by weight. In certain embodiments, the catalyst can include about 1% to about 25% Mn, by weight. For example, the catalyst can include about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 18%, 20%, 22%, or 25% Mn, by weight. In certain embodiments, the catalyst can include about 10% Cu and about 10% Mn, by weight. The remainder of the catalyst can be oxygen (i.e., the oxygen present in a metal oxide) and solid support (e.g., A1 ₂ 0 ₃ ).

[0032] Catalysts that include Cu and Mn can include Cu and Mn in various oxidation states. For example, Cu can be present in the catalyst as Cu(I) oxide (Cu ₂ 0) and/or Cu(II) oxide (CuO). For example, Mn can be present in the catalyst as oxide (MnO). In certain embodiments, higher oxides of Mn initially present in the catalyst can be reduced in situ in the presence of H ₂ .

[0033] The catalysts of the presently disclosed subject matter can be prepared according to various techniques known in the art. For example, metal oxide catalysts suitable for use in RWGS reactions can be prepared from various metal nitrates, metal halides, metal salts of organic acids, metal hydroxides, metal carbonates, metal oxyhalides, metal sulfates, and the like. In certain embodiments, a transition metal oxide (e.g., a Cu or Mn oxide, or a mixed Cu/Mn oxide) can be precipitated along with a solid support (e.g., A1 ₂ 0 ₃ ). In certain embodiments, and as exemplified in the Examples below, catalysts can be prepared by precipitation of metal nitrates.

Reaction Mixtures

[0034] The presently disclosed subject matter provides methods of converting mixtures of H ₂ and C0 ₂ into syngas via the reverse water gas shift (RWGS) reaction. A mixture of H ₂ and C0 ₂ can be termed a "reaction mixture." The mixture of H ₂ and C0 ₂ can alternatively be termed a "feed mixture" or "feed gas."

[0035] The C0 ₂ in the reaction mixture can be derived from various sources. In certain embodiments, the C0 ₂ can be a waste product from an industrial process. In certain embodiments, C0 ₂ that remains unreacted in the RWGS reaction can be recovered and recycled back into the RWGS reaction.

[0036] Reaction mixtures suitable for use with the presently disclosed methods can include various proportions of H ₂ and C0 ₂ . In certain embodiments, the reaction mixture can include H ₂ and C0 ₂ in a molar ratio (H ₂ :C0 ₂ ) between about 5:1 and about 1:2, e.g., about 5:1, 4:1, 3:1, 2.8:1, 2.6:1, 2.5:1, 2.4:1, 2.3:1, 2.2:1, 2.1:1, 2:1, 1.9:1, 1.8:1, 1.7:1, 1.6:1, 1.5:1, 1.4:1, 1.3:1, 1.2:1, 1.1:1, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1:2. The reaction mixture can include H ₂ and C0 ₂ in a molar ratio (H ₂ :C0 ₂ ) of about 2:1 to about 1:1. In certain embodiments, the reaction mixture can include H ₂ and C0 ₂ in a molar ratio (H ₂ :C0 ₂ )of about 1.5:1.

Methods of Preparing Syngas and Light Olefins

[0037] The methods of the presently disclosed subject matter include methods of preparing syngas. In one embodiment, an exemplary method can include providing a reaction chamber, as described above. The reaction chamber can include a solid-supported catalyst, as described above. The method can further include feeding a reaction mixture, as described above, to the reaction chamber. The method can additionally include contacting H ₂ and C0 ₂ (present in the reaction mixture) with the catalyst at a reaction temperature greater than or equal to about 800 °C, thereby inducing a RWGS reaction to provide a product mixture that includes H ₂ and CO. The product mixture can further include H ₂ 0 (a product of the RWGS reaction, as shown in Equation 1) and unreacted C0 ₂ .

[0038] The reaction mixture can be fed into the reaction chamber at various flow rates. The flow rate and gas hourly space velocity (GHSV) can be varied, as is known in the art. In certain embodiments, the flow rate can be about 5 to about 50 cc/min. In certain embodiments, the flow rate can be about 10 to about 25 cc/min. In certain embodiments, the flow rate can be about 15 cc/min. In certain embodiments, the flow rate can be about 22.5 cc/min.

[0039] The reaction temperature can be understood to be the temperature within the reaction chamber. The reaction temperature can influence the RWGS reaction, including conversion of C0 ₂ and H ₂ , the ratio of H ₂ :CO in the product mixture, and the overall yield. In certain embodiments, the reaction temperature can be greater than or equal to about 750 °C, e.g., greater than or equal to about 760 °C, 770 °C, 780 °C, 790 °C, 800 °C, 810 °C, 820 °C, 830 °C, 840 °C, or 850 °C. In certain embodiments, the reaction temperature can be greater than or equal to about 800 °C, e.g., greater than or equal to about 810 °C, 820 °C, 830 °C, 840 °C, or 850 °C. In certain embodiments, the reaction temperature can be between about 900 °C and about 700 °C. In certain embodiments, the reaction temperature can be about 800 °C. In certain embodiments, the reaction temperature can be about 850 °C.

[0040] The RWGS can proceed with partial conversion of C0 ₂ and H ₂ , thus providing a product mixture that includes CO, H ₂ 0, C0 ₂ , and H ₂ . In certain embodiments, the RWGS reaction can be performed from about 50% to about 70% conversion of C0 ₂ . In certain embodiments, the RWGS reaction can be performed to about 70% conversion of C0 ₂ . In certain embodiments, the RWGS reaction can be performed to about 65.3% conversion of C0 ₂ . In certain embodiments, the RWGS reaction can be performed to about 68% conversion of C0 ₂ . Adjustment of the degree of conversion of C0 ₂ and H ₂ as well as adjustment of the ratio of C0 ₂ and H ₂ in the reaction mixture can therefore influence the ratio of H ₂ and CO in the syngas product formed. For example, use of a higher molar ratio of H ₂ :C0 ₂ in the reaction mixture can increase the molar ratio of H ₂ :CO in the product mixture.

[0041] In certain embodiments, the product mixture can include H ₂ and CO in a molar ratio (H ₂ :CO) of about 0.5: 1 to about 5: 1. In certain embodiments, the product mixture can include H ₂ and CO in a molar ratio (H ₂ :CO) of about 1 : 1 to about 3 : 1, e.g., about 1 : 1, 1.1 : 1, 1.2: 1, 1.3 : 1, 1.4: 1, 1.5 : 1, 1.6: 1, 1.7: 1, 1.8: 1, 1.9: 1, 2: 1, 2.1 : 1, 2.2: 1, 2.3 : 1, 2.4: 1, 2.5 : 1, 2.6: 1, 2.7: 1, 2.8: 1, 2.9: 1, or 3 : 1. In certain embodiments, the product mixture can include H ₂ and CO in a molar ratio (H ₂ :CO) of about 1.5 : 1 to about 3 : 1, about 2: 1 to about 3 : 1, about 2.36: 1 or about 2.26: 1. As noted above, the molar ratio (H ₂ :CO) of the product mixture can be influenced by the molar ratio (H ₂ :C0 ₂ ) of the reaction mixture.

[0042] In certain embodiments, the RWGS can be performed to relatively high conversion. That is, the amount of C0 ₂ present in the product mixture can be relatively low. In certain embodiments, the product mixture can include less than about 25% C0 ₂ , by mole or less than about 20%) C0 ₂ , by mole. For example, the product mixture can include about 24%>, 23%>, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 1 1%, 10%, 9%, 8% by mole. In certain embodiments, the product mixture can include about 13.6% C0 ₂ by mole. In certain embodiments, the product mixture can include about 12.5% C0 ₂ by mole.

[0043] In certain embodiments, the methods of the presently disclosed subject matter can include separating at least a portion of C0 ₂ and/or H ₂ 0 from the product mixture, to provide purified syngas. C0 ₂ and/or H ₂ 0 can be separated by various techniques known in the art. By way of non-limiting example, H ₂ 0 can be separated by condensation, e.g. , by cooling the product mixture. In certain embodiments, C0 ₂ can be removed from the product mixture and contributed to the reaction mixture, thereby recycling C0 ₂ through the RWGS reaction and improving overall economy of the process.

[0044] The presently disclosed subject matter also provides methods of preparing light olefins. In one embodiment, an exemplary method of preparing light olefins can include conducting a RWGS reaction to convert C0 ₂ and H ₂ into a product mixture that includes H ₂ , CO, C0 ₂ , and H ₂ 0, as described above. The method can additionally include separating at least a portion of C0 ₂ and H ₂ 0 from the product mixture, to provide purified syngas. The method can further include subjecting purified syngas to a Fischer-Tropsch synthesis (FT) reaction to provide light olefins.

[0045] For the purpose of illustration and not limitation, FIG. 1 is a schematic representation of an exemplary process 100 according to the disclosed subject matter. In certain embodiments, a RWGS reaction 102 can be integrated with a FT reaction 105. As shown in FIG. 1, C0 ₂ 107 can be removed from the product mixture 103 obtained from a RWGS mixture to provide syngas, and the syngas can be fed into a FT reaction 105. C0 ₂ and products can optionally be separated from the product mixture 106 from the FT reaction in the same separation unit 103.

[0046] In certain embodiments, the process 200 can include separating water and C0 ₂ 203 from the product mixture from the RWGS reaction 202. As shown in FIG. 2, C0 ₂ 208 can optionally be separated from and recycled back into the RWGS reaction 201. Products 205 from the FT reaction 204 can also be separated 207 into hydrocarbons 206 and C0 ₂ 209. The C0 ₂ 209 from this reaction can also be recycled back into the RWGS reaction 201.

[0047] In certain alternative embodiments, as shown in FIG. 3, the product mixture from the RWGS reaction 302 can be fed directly into the FT reaction 304 without removal of C0 ₂ . In certain embodiments, FT catalysts can tolerate the presence of C0 ₂ , and C0 ₂ itself can participate in FT-type reactions. As shown in FIG. 3, products from the FT reaction can also be separated 305 into hydrocarbons 306 and C0 ₂ . The C0 ₂ 307 from this reaction can then be recycled back into the RWGS reaction 301.

[0048] The methods of the presently disclosed subject matter can have advantages over other techniques for preparation of syngas and preparation of light olefins. The presently disclosed subject matter includes the surprising discovery that catalysts containing Cu and/or Mn can be used to promote RWGS reactions at temperatures greater than or equal to about 800 °C without sacrificing product purity or catalyst stability. [0049] Additional advantages of the presently disclosed subject matter can include preparation of syngas with improved H ₂ :CO ratios. As demonstrated in the Examples, the methods of the presently disclosed subject matter can provide syngas containing H ₂ and CO in a molar ratio of about 2: 1 (e.g., 2.26: 1), suitable for use in FT reactions. Moreover, the methods of the presently disclosed subject matter can prepare syngas via hydrogenation of C0 ₂ with minimal side reactions, good catalyst stability, good conversion of C0 ₂ (e.g., greater than 50%), and good yields of syngas. Additional advantages of the presently disclosed subject matter can include improved energy efficiency and overall economy.

EXAMPLES

[0001] The following examples are merely illustrative of the presently disclosed subject matter and should not be considered as limiting in any way.

EXAMPLE 1 - Preparation of Catalyst

[0050] This Example describes the preparation of a Cu-Mn-Al catalyst.

[0051] The nitrate salts of Cu(N0 ₃ ) ₂ , Mn(N0 ₃ ) ₂ and A1(N0 ₃ ) ₃ were dissolved in 200 ml of water. H ₄ OH was added drop wise until the pH of the mixture was about 8. The precipitate was washed and filtrated. The mass after filtration was dried for 12 hours at 120°C and then calcined for 8 hours at 650°C. The catalyst composition after calcination contained 10%Cu and 10%Mn (both weight % ) on A1 ₂ 0 ₃ .

EXAMPLE 2 - Hydrogenation at 800°C

[0052] This Example describes C0 ₂ hydrogenation with a Cu-Mn-Al catalyst.

[0053] C0 ₂ was hydrogenated by H ₂ at 800°C in the presence of pellets of 10%Cu- 10%Mn/Al ₂ O ₃ catalyst. The pellets were prepared by pelletizing precipitated, dried gel of Cu-Mn-Al metals. The catalyst loading was 8.4g. The flow rates of hydrogen and C0 ₂ were H ₂ at 22.5 cc/min and C0 ₂ at 15 cc/min. The outlet gas composition after the reaction and after the separation of water is summarized in Table 1. Table 1. Outlet gas composition (% mol)

EXAMPLE 3 - Hydrogenation at 850°C

[0054] This Example describes C0 ₂ hydrogenation with a Cu-Mn-Al catalyst at a reaction temperature of 850°C.

[0055] C0 ₂ was hydrogenated by H ₂ at 850°C in the presence of 10%Cu-10%Mn/Al ₂ O ₃ catalyst pellets impregnated on A1 ₂ 0 ₃ . The catalyst loading was 8.4g. The flow rates of hydrogen and C0 ₂ were H ₂ at 22.5cc/min and C0 ₂ at 15 cc/min. The outlet gas composition, after, separation of water is summarized in Table 2.

Table 2. Outlet gas composition (% mol)

EXAMPLE 4 - Olefin synthesis

[0056] The hydrogenation products of Examples 2 or 3 are mixed with the FT reaction products and separated. EXAMPLE 5 - Separation of products

[0057] The hydrogenation products of Examples 2 or 3 are separated from C0 ₂ , separate of FT reaction products. In this case, separation cost is decreased due to the low concentration of C0 ₂ (not more than 13%).

EXAMPLE 6 - Separation of products

[0058] Unconverted C0 ₂ in the hydrogenation products of Examples 2 or 3 is not separated from hydrogenation products. The unconverted C0 ₂ is used as a feed for FT reactions.

EXAMPLE 7 - Evidence of Catalyst Stability

[0059] The catalysts used in Examples 2-3 were tested for 60 days. During this time, there was no observable change in catalyst activity, evidencing the stability of the catalysts under the reaction conditions.

* * *

[0060] Although the presently disclosed subject matter and its 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 disclosed subject matter as defined by the appended claims. Moreover, the scope of the disclosed subject matter is not intended to be limited to the particular embodiments described in the specification. Accordingly, the appended claims are intended to include within their scope such alternatives.