WO2017130081A1

WO2017130081A1 - Processes and systems for increasing selectivity for light olefins in co2 hydrogenation

Info

Publication number: WO2017130081A1
Application number: PCT/IB2017/050262
Authority: WO
Inventors: Venkatesan CHITHRAVEL; Rajitha VUPPULA; Bharmana MALVI
Original assignee: SABIC Global Technologies BV
Current assignee: SABIC Global Technologies BV
Priority date: 2016-01-27
Filing date: 2017-01-18
Publication date: 2017-08-03
Anticipated expiration: 2018-07-27

Abstract

Processes for conversion of CO₂ and H₂ into light olefins are provided. An exemplary process can include passing CO₂ and H₂ through a reactor that includes a temperature gradient, such that a reverse water gas shift reaction occurs at a relatively high temperature and a Fischer-Tropsch reaction subsequently occurs at a relatively low temperature. Systems for conversion of CO₂ and H₂ into light olefins are also provided.

Description

PROCESSES AND SYSTEMS FOR INCREASING SELECTIVITY FOR LIGHT

OLEFINS IN C02 HYDROGENATION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 62/287,765 filed January 27, 2016. The contents of the referenced application are incorporated into the present application by reference.

FIELD

[0002] The presently disclosed subject matter relates to processes and systems for increasing selectivity for light olefins in C0₂ hydrogenation.

BACKGROUND

[0003] Light olefins (e.g., C₂-C₄ olefins) are important industrial chemicals. Light olefins such as ethylene, propylene, and butene isomers (1-butene, czs-2-butene, trans-2-butene, and isobutylene) are widely used as feedstocks for polymerization, among many other uses.

[0004] There is interest in preparing light olefins and other chemical feedstocks from carbon dioxide (C0₂). C0₂ is an abundant and economical starting material. Use of C0₂ as a feedstock in chemical processes can reduce emissions of C0₂ and improve overall sustainability.

[0005] Light olefins can be prepared from C0₂ by reaction of C0₂ with hydrogen (H₂). This process can be described as a hydrogenation of C0₂. C0₂ and H₂ can be converted to light olefins through a two-step process. First, C0₂ and H₂ can be converted to carbon monoxide (CO) and water (H₂0) through a reverse water gas shift (RWGS) reaction. The RWGS reaction is endothermic and can be described by Equation 1 :

(1) C0₂ + H₂→ CO + H₂0 A_RH°3oo_°c = 38 kJ/mol CO formed in the RWGS reaction can be reacted with additional H₂ to provide a mixture of hydrocarbons that includes light olefins through a Fischer-Tropsch synthesis (FT) reaction. The FT reaction is exothermic and can be described by Equation 2:

(2) CO + 2H₂→ "CH₂" + H₂0 A_RH⁰ ₃₀o°c = -166 kJ/mol

In addition to the two-step process described in Equations 1 and 2, it may also be possible under certain conditions to convert C0₂ and H₂ directly to hydrocarbons through the exothermic reaction presented in Equation 3 :

(3) C0₂ + 3H₂ = "CH₂" +2H₂0 A_RH°₃OO°C = - 128 U/mol

In Equations 2 and 3, "CH₂" represents a generic hydrocarbon moiety that can be incorporated into a larger molecule, e.g., ethylene (C₂H₄).

[0006] Process conditions can alter the product distribution of the FT reaction. For example, increased space velocity can increase selectivity for light olefins, while increased temperature can reduce selectivity for light olefins. See, e.g., M. Hirsa, T. Galvis and K. P. de Jong, ACS Catal. 2013, 3, 2130-2149. However, selectivity for light olefins and the overall product distribution of a FT reaction can generally be governed by the Anderson- Schulz-Flory (ASF) model. Under the ASF model, C₂-C₄ content of the product mixture in an FT reaction can range up to about 56% maximum. See, e.g., M. Hirsa, T. Galvis and K. P. de Jong, ACS Catal. 2013, 3, 2130-2149.

[0007] Existing processes to convert C0₂ and H₂ to light olefins can involve conducting the RWGS reaction of Equation 1 and the FT reaction of Equation 2 in separate stages, which can increase cost and energy consumption. Some literature has described bifunctional catalysts capable of catalyzing both RWGS and FT reactions within a single reaction chamber. For example, U.S. Patent No. 5,140,049 to Fiato et al., European Patent Publication EP355229A1 to Fiato et al, International (PCT) Patent Publication No. WO 2014/111919 to Landau et al, Japanese Patent Publication No. JP01-190638A to Shikada et αί, and Chinese Patent No. 1,045,283 to Xu et al. describe direct conversion of C0₂ and H₂ to light olefins within a single reactor. However, with existing processes, it can be difficult to achieve high conversion, high yield, high selectivity for C₂-C₄ olefins, and energy efficiency. The RWGS reaction is endothermic and consequently can require a high reaction temperature, whereas the FT reaction is highly exothermic and consequently can require a lower reaction temperature. As noted above, conducting the FT reaction at high temperature can reduce selectivity for C₂-C₄ olefins and can induce undesirable olefin hydrogenation (to form alkane products).

[0008] Thus, there remains a need in the art for new processes and systems for conversion of C0₂ and H₂ into light olefins with improved conversion, yield, selectivity, and energy efficiency.

SUMMARY OF THE DISCLOSED SUBJECT MATTER

[0009] The presently disclosed subject matter provides processes and systems for conversion of C0₂ and H₂ into light olefins.

[0010] In one embodiment, an exemplary process for conversion of C0₂ and H₂ into light olefins can include providing a reactor that includes at least a first section and a second section. The temperature of the first section of the reactor can be higher than the temperature of the second section of the reactor. The reactor can include a catalyst. The process can further include passing a reaction mixture that includes C0₂ and H₂ through the first section of the reactor, to provide a mixture that includes CO, H₂0, and H₂. The process can additionally include passing the mixture that includes CO, H₂0, and H₂ through the second section of the reactor, to provide a product mixture that includes light olefins.

[0011] In certain embodiments, the reactor can be axially oriented.

[0012] In certain embodiments, the temperatures of the first and second sections of the reactor can be between about 250 °C and about 500 °C. The temperature of the first section of the reactor can be about 400 °C and the temperature of the second section of the reactor can be less than or equal to about 350 °C. The second section of the reactor can include a temperature gradient. The temperature gradient can span a temperature range of about 350 °C to about 325 °C. The temperature gradient can vary by about 4 °C per cm.

[0013] In certain embodiments, the reactor can include a catalyst bed. A first portion of the catalyst bed can be located in the first section of the reactor and a second portion of the catalyst bed can be located in the second section of the reactor. The catalyst bed can be axially oriented.

[0014] In certain embodiments, the catalyst can be solid-supported. The catalyst can be supported on alumina. The catalyst can include iron (Fe). The catalyst can include potassium (K). The catalyst can include both iron (Fe) and potassium (K).

[0015] The reaction mixture of C0₂ and H₂ can include C0₂ and H₂ in a molar ratio of about 1 :3. The product mixture can include one or more C₂-C₄ olefins selected from the group consisting of ethylene, propylene, 1-butene, czs-2-butene, trans-2-butene, and isobutylene. The product mixture can include at least 30 mol% C₂-C₄ olefins, on carbon basis.

[0016] In one embodiment, an exemplary system for conversion of C0₂ and H₂ into light olefins can include an axially oriented reactor that includes at least a first section and a second section. The temperature of the first section of the reactor can be higher than the temperature of the second section of the reactor. A catalyst bed can be positioned within the reactor. A first portion of the catalyst bed can be located in the first section of the reactor, and a second portion of the catalyst bed can be located in the second section of the reactor. The catalyst bed can include a catalyst capable of catalyzing both a reverse water gas shift reaction of C0₂ and H₂ to CO and H₂0 and a Fischer-Tropsch reaction of CO and H₂ to light olefins. The system can additionally include a reaction mixture feed line adapted to feed a reaction mixture that includes C0₂ and H₂ into the reactor. The system can further include a product mixture line adapted to remove a product mixture that includes light olefins from the reactor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a schematic diagram showing an exemplary system for conversion of C0₂ and H₂ into light olefins, in accordance with non-limiting embodiments of the disclosed subject matter.

[0018] FIG. 2 is a schematic diagram comparing an exemplary system for conversion of C0₂ and H₂ into light olefins, in accordance with non-limiting embodiments of the disclosed subject matter ("Non-isothermal conditions," FIG. 2B) with an exemplary isothermal system ("Isothermal conditions," FIG. 2A).

[0019] FIG. 3 includes a schematic diagram showing an exemplary system for conversion of C0₂ and H₂ into light olefins, in accordance with non-limiting embodiments of the disclosed subject matter (FIG. 3 A). FIG. 3 also includes a schematic diagram showing catalyst position within the exemplary system (FIG. 3B). FIG. 3 further includes a plot presenting temperature within the exemplary system, as compared to temperature within an isothermal system (FIG. 3C).

DETAILED DESCRIPTION

[0020] There remains a need in the art for new processes and systems for conversion of C0₂ and H₂ into light olefins. The presently disclosed subject matter provides processes and systems for preparation of light olefins from C0₂ and H₂ with improved conversion, yield, selectivity, and energy efficiency. The presently disclosed processes and systems can include use of a single reactor for direct conversion of C0₂ and H₂ and can take advantage of temperature gradient across the reactor, which can allow the reverse water gas shift (RWGS) and Fischer-Tropsch (FT) reactions to occur at different temperatures. [0021] 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.

[0022] Catalysts suitable for use in conjunction with the presently disclosed subject matter can be catalysts capable of catalyzing both RWGS and FT reactions. In other words, the catalyst can be a bifunctional or dual-function catalyst. The catalyst can be located in a packed bed, i.e., a catalyst bed.

[0023] In certain embodiments, the catalyst can include one or more transition metals. The transition metal can include iron (Fe), cobalt (Co), manganese (Mn), copper (Cu), zinc (Zn), or a mixture thereof. The catalyst can include an alkali metal, e.g., lithium (Li), sodium (Na), potassium (K), cesium (Cs), or a mixture thereof. The catalyst can include an alkaline earth metal, e.g., magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), or a mixture thereof.

[0024] 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 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 (A1₂0₃), silica (Si0₂), magnesia (MgO), titania (Ti0₂), zirconia (Zr0₂), cerium(IV) oxide (Ce0₂), or a combination thereof. The solid support can include a zeolite, e.g., silicalite-1, silicalite-2, mordenite, KL, ZSM-5, beta, HY, or a combination thereof.

[0025] The catalyst can be a catalyst that includes iron and potassium {i.e., a Fe-K catalyst) supported on alumina. When the catalyst includes one or more transition metals and one or more alkali metals on a solid support, the transition metal(s) and alkali metal(s) can be present in a combined amount of approximately 1% to about 50%, by weight, as compared to the total weight of the catalyst. By way of non-limiting example, the combined weight of metal can be about 25% of the total weight, e.g., 24%. When an Fe-K catalyst supported on alumina is used, Fe can constitute about 14% of the total weight of the catalyst and K can constitute about 10% of the total weight of the catalyst, with the remainder being alumina.

[0026] For the purpose of illustration and not limitation, FIGS. 1 and 2B present schematic representations of exemplary systems according to the disclosed subject matter. The exemplary system 100, 200 can be used to convert C0₂ and H₂ into light olefins. The system 100, 200 can include an axially oriented reactor 102, 202, i.e., a reactor laid out along a straight line. In certain embodiments, the reactor 102, 202 can be a fixed bed reactor or a moving bed reactor. As shown in FIG. 1, the axially oriented reactor 102, 202 can be vertically oriented such that reactants are added at the top and products are removed from the bottom, with a flow of material from top to bottom. The reactor 102, 202 can have a height greater than its width and can be mounted vertically. In certain embodiments, the height to width ratio of the reactor 102, 202, which can also be expressed as a length to diameter ratio, can be equal to or greater than about 10: 1, e.g., about 10: 1, about 12: 1, about 15: 1, about 18: 1, about 20: 1, about 22: 1, about 25: 1, about 30: 1, about 35: 1, about 40: 1, about 45: 1, about 50: 1, about 55: 1, about 60: 1, about 65: 1, about 70: 1, about 80: 1, about 90: 1, about 100 : 1 , or greater than about 100: 1. By way of non-limiting example, a laboratory scale reactor with a length of 40 cm can have an internal diameter (ID) of about 1 cm. The reactor 102, 202 can be tubular, cylindrical, or rectangular. In certain embodiments, the reactor 102, 202 can be tubular or cylindrical. The reactor 102, 202 can include a heating jacket and/or a heating mantle.

[0027] The reactor 102, 202 can include a first section 104, 204 and a second section 106, 206. As shown in FIG. 1, in certain embodiments, the first section 104, 204 can be positioned above the second section 106, 206. The temperature of the first section 104, 204 can be higher than the temperature of the second section 106, 206. A catalyst bed 107, 207 can be positioned within the reactor 102, 202 and can be axially oriented along the same axis as the reactor 102, 202. As shown in FIG. 1, a first portion 108 of the catalyst bed can be located in the first section of the reactor 104, and a second portion 109 of the catalyst bed can be located in the second section of the reactor 106. The catalyst bed 107, 207 can include a catalyst capable of catalyzing both a reverse water gas shift (RWGS) reaction of C0₂ and H₂ to CO and H₂0 and a Fischer-Tropsch (FT) reaction of CO and H₂ to light olefins. The system 100, 200 can additionally include a reaction mixture feed line 1 10, 210 adapted to feed a reaction mixture that includes C0₂ and H₂ into the reactor 102, 202. The system can further include a product mixture line 1 12, 212 adapted to remove a product mixture that includes light olefins from the reactor 102, 202.

[0028] The catalyst bed 107, 207 can occupy a portion of the reactor 102, 202 such that there are inert regions of the reactor 102, 202 above and below the catalyst bed 107, 207. The inert regions of the reactor can be packed with an inert material. The inert material can be an inert material known in the art and can include one or more ceramics, glasses (e.g., glass beads), metal oxides (e.g., aluminum oxide), carbides (e.g., silicon carbide), and metals. As shown in FIG. 3B, an exemplary laboratory scale reactor can be vertically oriented and can have a height of 40 cm. The catalyst bed can have a height of 18 cm and can occupy a central portion of the reactor. Inert regions of the reactor, each having a height of 1 1 cm, can be positioned above and below the catalyst bed.

[0029] As noted above, the temperature of the first section 104, 204 of the reactor 102, 202 can be higher than the temperature of the second section 106, 206 of the reactor. The temperatures of the first section 104, 204 and second section 106, 206 can be between about 250 °C and about 500 °C. By way of non-limiting example, the temperature in the first section 104, 204 can be between about 300 °C and about 500 °C, e.g., about 300 °C, about 310 °C, about 320 °C, about 330 °C, about 340 °C, about 350 °C, about 360 °C, about 370 °C, about 380 °C, about 390 °C, about 400 °C, about 410 °C, about 420 °C, about 430 °C, about 440 °C, about 450 °C, about 460 °C, about 470 °C, about 480 °C, about 490 °C, or about 500 °C. The temperature in the first section 104, 204 can be adjusted to improve the yield and selectivity of a RWGS reaction. By way of non-limiting example, the temperature in the second section 106, 206 can be between about 250 °C and about 400 °C, e.g., about 250 °C, about 260 °C, about 270 °C, about 280 °C, about 290 °C, about 300 °C, about 310 °C, about 320 °C, about 330 °C, about 340 °C, about 350 °C, about 360 °C, about 370 °C, about 380 °C, about 390 °C, or about 400 °C. The temperature in the second section 106, 206 can be adjusted to improve the yield and selectivity of a FT reaction.

[0030] FIG. 2 compares a system in accordance with the presently disclosed subject matter (FIG. 2B) with an isothermal system (FIG. 2A). In the isothermal system of FIG. 2, the temperature is constant throughout the reactor.

[0031] In certain embodiments, a temperature gradient can be established along a portion of the axis of the reactor 102, 202 such that the temperature gradually changes within one or both of the first section 104, 204 and the second section 106, 206. For example, a temperature gradient can be established within the second section of the reactor 106, 206. When a temperature gradient is established within the second section of the reactor 106, 206, the area of the second section nearest to the boundary between the second section of the reactor and the first section can be heated to a relatively high temperature, and the temperature can gradually be reduced at increasing distance from the boundary. The temperature gradient within the second section of the reactor 106, 206 can span a range of temperature from about 400 °C to about 250 °C, e.g., about 400 °C to about 350 °C, about 400 °C to about 375 °C, about 375 °C to about 350 °C, about 375 °C to about 325 °C, about 350 °C to about 325 °C, about 350 °C to about 300 °C, about 325 °C to about 300 °C, about 325 °C to about 275 °C, about 300 °C to about 275 °C, about 300 °C to about 250 °C, or about 275 °C to about 250 °C.

[0032] An exemplary temperature gradient is shown in FIG. 3. A vertically oriented reactor containing a catalyst bed is shown in FIG. 3A. As shown in FIGS. 3A and 3B, the catalyst bed has a length of 18 cm. FIG. 3C presents a plot of the temperature of catalyst bed at various points (e.g., at catalyst length = 0 cm (the top of the catalyst bed) and catalyst length = 18 cm (the bottom of the catalyst bed)). As shown in FIG. 3C, the temperature within the catalyst bed gradually decreases from Ti (400 °C) to T₃ (325 °C). Within the portion of the catalyst bed located in the second section of the reactor (i.e., the portion of the catalyst bed from approximately 9 cm to approximately 18 cm), the temperature gradient varies by 4.167 °C per cm, or about 4 °C per cm.

[0033] An exemplary process for conversion of C0₂ and H₂ into light olefins can include use of an exemplary system 100, 200 that includes a reactor 102, 202 divided into a first section 104, 204 and a second section 106, 206. The process can include feeding a reaction mixture that includes C0₂ and H₂ into the reactor 102, 202 through a reaction mixture feed line 110, 210. The ratio of C0₂ and H₂ in the reaction mixture can be varied as is known in the art. For example, the molar ratio of C0₂ and H₂ can be in a range from about 1 :2 to about 1 :5, e.g., about 1 :3. The reaction mixture can also include components other than C0₂ andH₂, e.g., CO. In certain embodiments, the reaction mixture can include CO and can include CO, C0₂, and H₂ in a ratio between about 0.05: 1 :2 and about 1 : 1 :5. The reaction mixture can be passed through the first section of the reactor 104, 204 and undergo a RWGS reaction, to provide a mixture that includes CO, H₂0, and unreacted H₂. The mixture that includes CO, H₂0, and H₂ can then be passed through the second section of the reactor 106, 206 to undergo a FT reaction and provide a product mixture that includes light olefins. As described above, the temperature of the first section 104, 204 can be higher than the temperature of the second section 106, 206. The temperature of the first section 104, 204 can be adjusted to a improve the conversion, yield, and selectivity of the RWGS reaction, while the temperature of the second section 106, 206 can be adjusted separately to improve the conversion, yield, and selectivity of the FT reaction.

[0034] The product mixture can be removed from the reactor 102, 202 through the product mixture line 112, 212. The product mixture can include one or more C2-C4 olefins. The one or more C2-C4 olefins can include ethylene, propylene, 1-butene, czs-2-butene, trans-2-butene, and/or isobutylene. The product mixture can include at least 20 mol% C2-C4 olefins, as measured on carbon basis (i.e., measured per mole of C0₂ consumed), e.g., about 20 mol%, about 22 mol%, about 25 mol%, about 30 mol%, about 35 mol%, about 40 mol%, about 45 mol%, about 50 mol%, or more than about 50 mol% C2-C4 olefins on carbon basis. The product mixture can also include CO2, CO, methane (CH₄) and other paraffins, and/or heavier olefins (e.g., C₅, C₆, C₇, C₈, and/or higher olefins). Components of the product mixture can be separated via techniques known in the art, e.g., cryogenic distillation.

[0035] The processes and systems of the presently disclosed subject matter can have advantages over other techniques for extraction and purification of butadiene. For example, operation of the second section of the reactor 106, 206 at a lower temperature than the first section of the reactor 104, 204 can reduce the required energy input, which can help to reduce overall energy consumption. As shown in the Examples, the presently disclosed subject matter also enables preparation of C2-C4 olefins with improved selectivity and yield and fewer side products (e.g., CO and methane) as compared to techniques that use an isothermal reactor. By way of non-limiting example, selectivity for C2-C4 olefins, on carbon basis, can be about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%), or about 50% higher in the processes and systems of the presently disclosed subject matter as compared to isothermal processes and systems.

EXAMPLES

EXAMPLE 1 - Comparison of Hydrogenation of CO? Under Isothermal and Non-Isothermal Conditions

[0036] An isothermal reactor in accordance with FIG. 2 A and a non-isothermal reactor in accordance with FIG. 2B were provided. The isothermal reactor had an internal temperature of 400 °C. The non-isothermal reactor included a temperature gradient, as shown in FIG. 2B, such that the temperature of the first section of the reactor was about 400 °C while the temperature of the second section of the reactor varied from about 350 °C to about 325 °C. Both reactors had a catalyst bed length of 18 cm, an internal diameter of 1 cm, and a catalyst bed volume of approximately 14 cc. Both reactors included an Fe-K catalyst supported on AI2O3, wherein 14% of the weight of the catalyst was Fe, 10% of the weight of the catalyst was K, and the remainder was alumina.

[0037] A reaction mixture that included C0₂ and H₂ in a molar ratio of 1 :3 was fed into the top of each reactor. The gas hourly space velocity (GHSV) of the reactors was 1500 h^"1. The pressure of the reactors was 2.1 MPa. A product mixture was removed from the bottom of each rector. The composition of the product mixture was then analyzed by GC.

[0038] The composition of the product mixture is presented in Table 1. Product selectivity is shown on carbon basis (i.e., measured per mole of C0₂ consumed), in mole percentages. In Table 1, "C₂-C4 products" include both alkanes and alkenes and include ethane, ethylene, propane, propylene, n-butane, 1-butene, czs-2-butene, tram--2-butene, and isobutylene. "Heavies" include C₅ and C₆ olefins, "o/p for C₂-C₄ products" is the olefin to paraffin ratio for the C₂-C4 products, i.e., the ratio of C₂-C₄ olefins to C₂-C₄ alkanes. Table 1.

[0039] Further details of the composition of the product mixture are presented in Table 2. As in Table 1, product selectivity is shown on carbon basis {i.e., measured per mole of carbon consumed), in mole percentages.

Table 2.

[0040] As shown in Table 1, the hydrogenation of C0₂ conducted in the non-isothermal reactor proceeded with higher selectivity for C₂-C₄ products as compared to hydrogenation of C0₂ conducted in the isothermal reactor: 45.4% selectivity as compared to 35.2%. Selectivity for C₂-C₄ products was accordingly approximately 30% higher in the non- isothermal reactor. Furthermore, as shown in Table 2, selectivity for C₂-C₄ olefins (light olefins) was higher in the non-isothermal reactor as compared to the isothermal reactor: 39.8%) selectivity as compared to 29.35%. Use of a non-isothermal reactor provided a process for conversion of C0₂ and H₂ into light olefins with greater than 30 mol%> selectivity for C2-C4 olefins, on carbon basis. Selectivity for C2-C4 olefins was approximately 36% higher in the non-isothermal reactor than in the isothermal reactor.

[0041] In addition, as shown in Table 1, reduced quantities of CH₄ and CO were formed in the non-isothermal reactor as compared to the isothermal reactor: 24.2% CH₄ and 14.8% CO in the non-isothermal reactor as compared to 30.0%> CH₄ and 27.8% CO in the isothermal reactor. Thus Example 1 shows that the non-isothermal reactors of the presently disclosed subject matter can provide C2-C4 olefins from C0₂ and H₂ with improved selectivity, improved yield, and reduced side product formation as compared to isothermal systems.

[0042] 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.

Claims

1. A process for conversion of C0₂ and H₂ into light olefins, the process comprising: a. providing a reactor comprising at least a first section and a second section, wherein:

i. the temperature of the first section of the reactor is higher than the temperature of the second section of the reactor; and ii. the reactor includes a catalyst;

b. passing a reaction mixture comprising C0₂ and H₂ through the first section of the reactor, to provide a mixture comprising CO, H₂0, and H₂; and c. passing the mixture comprising CO, H₂0, and H₂ through the second section of the reactor, to provide a product mixture comprising light olefins.

2. The process of claim 1, wherein the reactor is axially oriented.

3. The process of claim 1, wherein the temperatures of the first and second sections of the reactor are between about 250 °C and about 500 °C.

4. The process of claim 3, wherein the temperature of the first section of the reactor is about 400 °C and the temperature of the second section of the reactor is less than or equal to about 350 °C.

5. The process of any one of claims 1, 3, and 4, wherein the second section of the reactor comprises a temperature gradient.

6. The process of claim 5, wherein the temperature gradient spans a temperature range of about 350 °C and about 325 °C.

7. The process of claim 6, wherein the reactor is axially oriented and wherein the

temperature gradient varies by about 4 °C per cm.

8. The process of claim 1, wherein the reactor comprises a catalyst bed.

9. The process of claim 8, wherein a first portion of the catalyst bed is located in the first section of the reactor and a second portion of the catalyst bed is located in the second section of the reactor.

10. The process of claim 9, wherein the catalyst bed is axially oriented.

11. The process of claim 1, wherein the catalyst is solid-supported.

12. The process of claim 11, wherein the catalyst is supported on alumina (AI₂O₃).

13. The process of claim 1, wherein the catalyst comprises iron (Fe).

14. The process of claim 1, wherein the catalyst comprises potassium (K).

15. The process of claim 1, wherein the catalyst comprises iron (Fe) and potassium (K) supported on alumina (A1₂0₃).

16. The process of claim 1, wherein the reaction mixture comprising C0₂ and H₂

comprises C0₂ and H₂ in a molar ratio of about 1 :3.

17. The process of claim 1, wherein the product mixture comprises at least one C₂-C₄ olefin selected from the group consisting of ethylene, propylene, 1-butene, cis-2- butene, tra«s-2-butene, and isobutylene.

18. The process of claim 1, wherein the product mixture comprises at least 30 mol% C₂- C₄ olefins, on carbon basis.

19. A system for conversion of C0₂ and H₂ into light olefins, the system comprising: a. an axially oriented reactor comprising at least a first section and a second section, wherein the temperature of the first section of the reactor is higher than the temperature of the second section of the reactor;

b. a catalyst bed positioned within the reactor, wherein:

i. a first portion of the catalyst bed is located in the first section of the reactor and a second portion of the catalyst bed is located in the second section of the reactor; and ii. the catalyst bed comprises a catalyst capable of catalyzing both a reverse water gas shift reaction of C0₂ and H₂ to CO and H₂0 and a Fischer- Tropsch reaction of CO and H₂ to light olefins;

c. a reaction mixture feed line adapted to feed a reaction mixture comprising C0₂ and H₂ into the reactor; and

d. a product mixture line adapted to remove a product mixture comprising light olefins from the reactor.