Direct synthesis of light olefins from carbon dioxide using yttria-stabilized zirconia support

Abstract

The present invention features a direct synthesis of light olefins through the hydrogenation of carbon dioxide. In.sub.2O.sub.3 supported on cubic phase yttria-stabilized zirconia is used as a catalyst and is mixed with a molecular sieve to perform the hydrogenation. The cubic crystal structure of the yttria-stabilized zirconium dioxide is an excellent support for indium oxide particles and prevents their deactivation during CO.sub.2 hydrogenation. This direct synthesis route promotes a stable and efficient method for producing light olefins.

Claims

1. A method of synthesizing a light olefin, the method comprising: a. precipitating an indium-based catalyst onto cubic phase yttria-stabilized zirconia (YSZ) to produce a supported indium-based catalyst; b. adding the supported indium-based catalyst into a reactor; c. mixing a molecular sieve with the supported indium-based catalyst in the reactor; d. introducing a stream of hydrogen gas and a stream of carbon dioxide gas into the reactor; and e. heating the reactor, wherein a hydrogenation reaction occurs between the hydrogen gas and carbon dioxide gas to synthesize the light olefin; wherein the cubic phase YSZ prevents deactivation of the indium-based catalyst during hydrogenation.

2. The method of claim 1, wherein the light olefin is ethylene, propylene, or butylene.

3. The method of claim 1, wherein the indium-based catalyst is indium oxide, metallic indium, an indium alloy, an indium single atom catalyst, or an indium single atom alloy.

4. The method of claim 1, wherein the molecular sieve is SAPO-34 zeolite, SAPO-5 zeolite, ZSM-5, zeolite beta, or zeolite Y.

5. The method of claim 1, wherein the reactor is heated at a temperature of about 250° C.-550° C.

6. The method of claim 1, wherein the reactor is maintained at a pressure of about 10 bar-100 bar.

7. The method of claim 1, wherein the ratio of hydrogen gas to carbon dioxide gas is at least 3.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

(1) The features and advantages of the present invention will become apparent from a consideration of the following detailed description presented in connection with the accompanying drawings in which:

(2) FIG. 1 shows X-ray diffraction (XRD) patterns of the synthesized In.sub.2O.sub.3/ZrO.sub.2 and In.sub.2O.sub.3/YSZ catalysts.

(3) FIGS. 2A-2B show the activity comparison between In.sub.2O.sub.3/ZrO.sub.2+SAPO-34 and In.sub.2O.sub.3/YSZ+SAPO-34.

(4) FIG. 3 shows the H.sub.2-temperature programmed reduction (H.sub.2-TPR) of the synthesized In.sub.2O.sub.3/ZrO.sub.2 and In.sub.2O.sub.3/YSZ catalysts.

(5) FIG. 4 shows the X-ray photoelectron spectroscopy (XPS) of the synthesized In.sub.2O.sub.3/ZrO.sub.2 and In.sub.2O.sub.3/YSZ catalysts.

(6) As used herein, the term “light olefin” refers to ethylene, propylene, and butylene (C.sub.2.sup.═-C.sub.4.sup.═).

(7) As known to one of ordinary skill in the art, the term “cubic phase” when referring to a crystal structure is a crystal phase where the unit cell is in the cubic shape.

(8) As used herein, the term “supported catalyst” refers to active catalysts distributed on a high surface area of a solid.

(9) As used herein, the term “molecular sieve” is a material with micro or meso pores of uniform size.

(10) In some embodiments, the present invention features a method of synthesizing a light olefin from carbon dioxide. The method comprises: 1) precipitating a catalyst onto zirconia to produce a supported catalyst; 2) adding the supported catalyst into a reactor; 3) mixing a molecular sieve with the supported catalyst in the reactor; 4) introducing hydrogen gas and carbon dioxide gas into the reactor; and 5) heating the reactor. A hydrogenation reaction occurs between the hydrogen gas and the carbon dioxide gas to synthesize the light olefin. Non-limiting embodiments of the synthesized light olefin produced by in the present invention include ethylene, propylene or butylene.

(11) In one embodiment, the catalyst is an indium-based catalyst. Non-limiting examples of indium-based catalysts include indium oxide (In.sub.2O.sub.3), metallic indium, indium alloys, indium single atom catalysts, or indium single atom alloys. In another embodiment, other metal-based catalysts can be used. Non-limiting examples of other metal-based catalysts include Cu-, Zn-, Cr-, or Fe-based catalysts.

(12) In preferred embodiments, the zirconia is cubic phase yttria-stabilized zirconia. In some embodiments, the supported catalyst may comprise about 1-20 wt % of the indium-based catalysts. For example, the supported catalyst may comprise at least 10 wt % of indium. In other embodiments, the supported catalyst may comprise about 1-10 wt % of indium. In some embodiments, the supported catalyst may comprise about 5-15 wt % of indium. In some other embodiments, the supported catalyst may comprise about 10-20 wt % of indium.

(13) In alternative embodiments, any reducible oxide can be used to support the catalyst. Non-limiting examples of other reducible oxides include CeO.sub.2, MnOx, TiO.sub.2, HfO.sub.2, Fe.sub.2O.sub.3, CoOx, VOx, PrOx, or SmOx. In other embodiments, non-limiting examples of the molecular sieves used in the reaction include SAPO-34 zeolite, SAPO-5 zeolite, ZSM-5, zeolite beta, zeolite Y, or a combination thereof.

(14) According to other embodiments, the present invention features a method of synthesizing a light olefin. The method may comprise 1) precipitating an indium-based catalyst onto cubic phase yttria-stabilized zirconia to produce an indium-based supported catalyst; 2) adding the indium-based supported catalyst into a reactor; 3) mixing a molecular sieve with the indium-based supported catalyst in the reactor; 4) introducing a stream of hydrogen gas and a stream of carbon dioxide gas into the reactor; and 5) heating the reactor. A hydrogenation reaction occurs between the hydrogen gas and the carbon dioxide gas to synthesize the light olefin.

(15) Non-limiting examples of indium-based catalysts include indium oxide (In.sub.2O.sub.3), metallic indium, indium alloys, indium single atom catalysts, or indium single atom alloys. In other embodiments, other metal-based catalysts can be used. Non-limiting examples of other metal-based catalysts include Cu-, Zn-, Cr-, or Fe-based catalysts. In other embodiments, the molecular sieve is SAPO-34 zeolite, SAPO-5 zeolite, ZSM-5, zeolite beta, or zeolite Y.

(16) In accordance with any of the methods described herein, the reactor can be heated to a temperature ranging from about 250° C. to about 550° C. In other embodiments, the reactor is heated to a temperature of about 250° C.-350° C. In some embodiments, the reactor is heated to a temperature of about 300° C.-400° C. In other embodiments, the reactor is heated to a temperature of about 350° C.-450° C. In some embodiments, the reactor is heated to a temperature of about 400° C.-500° C. In other embodiments, the reactor is heated to a temperature of about 450° C.-550° C.

(17) In accordance with any of the methods described herein, the reactor can be maintained at a pressure ranging from about 10 bar to about 100 bar. In some embodiments, the reactor is maintained at a pressure of about 10-30 bar during the hydrogenation reaction. In other embodiments, the reactor is maintained at a pressure of about 20-40 bar during the hydrogenation reaction. In some embodiments, the reactor is maintained at a pressure of about 30-50 bar during the hydrogenation reaction. In other embodiments, the reactor is maintained at a pressure of about 40-60 bar during the hydrogenation reaction. In some embodiments, the reactor is maintained at a pressure of about 50-70 bar during the hydrogenation reaction. In other embodiments, the reactor is maintained at a pressure of about 60-80 bar during the hydrogenation reaction. In some embodiments, the reactor is maintained at a pressure of about 70-90 bar during the hydrogenation reaction. In other embodiments, the reactor is maintained at a pressure of about 80-100 bar during the hydrogenation reaction.

(18) In accordance with any of the methods described herein, the mole ratio of hydrogen gas to carbon dioxide gas can range from about 2 to 5. In one embodiment, the mole ratio of hydrogen gas to carbon dioxide gas is at least 2. In another embodiment, the mole ratio of hydrogen gas to carbon dioxide gas is at least 3. In some embodiments, the mole ratio of hydrogen gas to carbon dioxide gas is at least 4. In other embodiments, the mole ratio of hydrogen gas to carbon dioxide gas is at least 5.

EXAMPLE

(19) The following is a non-limiting example of the present invention. It is to be understood that said example is not intended to limit the present invention in any way. Equivalents or substitutes are within the scope of the present invention.

(20) In.sub.2O.sub.3 supported on cubic phase YSZ and monoclinic ZrO.sub.2 are synthesized via an incipient wetness impregnation method. Indium nitrate hydrate is precipitated on the YSZ and ZrO.sub.2 supports, leading to 10 wt % of indium on each support. The precipitated In.sub.2O.sub.3/YSZ and In.sub.2O.sub.3/ZrO.sub.2 are then dried and calcined at 500° C. for 4 h.

(21) The synthesized supported In.sub.2O.sub.3 catalysts are physically mixed with SAPO-34 zeolite and evaluated for their CO.sub.2 hydrogenation activity. FIG. 1 shows XRD patterns of the synthesized In.sub.2O.sub.3/ZrO.sub.2 and In.sub.2O.sub.3/YSZ catalysts. XRD results confirm that In.sub.2O.sub.3/ZrO.sub.2 has a monoclinic phase of ZrO.sub.2 along with In.sub.2O.sub.3, whereas In.sub.2O.sub.3/YSZ has a cubic phase of ZrO.sub.2. The hydrogenation reaction is tested at 400° C. at 30 bar in a feed stream of H.sub.2 and CO.sub.2 with a H.sub.2:CO.sub.2 ratio of 3.

(22) FIGS. 2A-2B show the activity comparison between In.sub.2O.sub.3/ZrO.sub.2+SAPO-34 and In.sub.2O.sub.3/YSZ+SAPO-34. In FIG. 2A, for the conventional In.sub.2O.sub.3/ZrO.sub.2+SAPO-34, the light olefins selectivity decreases with increasing CO selectivity leading to a low light olefins yield after 45 h of reaction. In FIG. 2B, the In.sub.2O.sub.3/YSZ+SAPO-34 shows stable and high light olefins selectivity, leading to a higher light olefins yield during 45 h of reaction.

(23) FIGS. 3 and 4 show the H.sub.2-temperature programmed reduction (H.sub.2-TPR) and XPS of the synthesized In.sub.2O.sub.3/ZrO.sub.2 and In.sub.2O.sub.3/YSZ catalysts. In FIG. 3, the strong peak observed at 450° C. in the In.sub.2O.sub.3/ZrO.sub.2 represents the In.sub.2O.sub.3 reduction. In the case of In.sub.2O.sub.3/YSZ, the In.sub.2O.sub.3 reduction peak is not observed distinctly, indicating that In.sub.2O.sub.3/YSZ has a stronger metal-support interaction.

(24) Additionally, O 1 s core level XPS spectra in FIG. 4 shows that the In.sub.2O.sub.3/YSZ has a larger oxygen defect concentration (15.4%) than that of In.sub.2O.sub.3/ZrO.sub.2 (12.6%). The larger oxygen defect concentration on YSZ can increase lattice oxygen mobility which facilitates the movement of oxygen ions and improves the activity and selectivity for light olefins. CO.sub.2 hydrogenation is active at the oxygen vacancies of In.sub.2O.sub.3 whereas RWGS is active on metallic indium. It is also possible that the conventional In.sub.2O.sub.3/ZrO.sub.2 catalyst is getting reduced during the reaction leading to a high CO production. However, the In.sub.2O.sub.3/YSZ catalyst shows stable activity as it is not reduced due to the stronger interaction between In.sub.2O.sub.3 and YSZ.

(25) The conventional In.sub.2O.sub.3/ZrO.sub.2+SAPO-34 catalyst shows deactivation during CO.sub.2 hydrogenation. The initial undesired CO selectivity is 81.6% and increases up to 91.8% after 45 h of reaction. The light olefins selectivity is 9.7% in the beginning of the reaction, but decreases to 4.2% leading to a low light olefins yield of 0.336 mmol/h/g. However, the In.sub.2O.sub.3/YSZ+SAPO-34 catalyst does not deactivate during 45 h of reaction. The CO selectivity remains between 81.6-82.2%, and the light olefins selectivity improves and reaches up to 11.8% after 45 h of reaction. The light olefins yield is calculated to be 0.997 mmol/h/g, which is almost three times higher than the one observed in the conventional In.sub.2O.sub.3/ZrO.sub.2+SAPO-34 catalyst. The In.sub.2O.sub.3/YSZ+SAPO-34 catalyst would require less energy to operate while producing higher light olefins selectivity.

(26) Although there has been shown and described the preferred embodiment of the present invention, it will be readily apparent to those skilled in the art that modifications may be made thereto which do not exceed the scope of the appended claims. Therefore, the scope of the invention is only to be limited by the following claims. In some embodiments, the figures presented in this patent application are drawn to scale, including the angles, ratios of dimensions, etc. In some embodiments, the figures are representative only and the claims are not limited by the dimensions of the figures. In some embodiments, descriptions of the inventions described herein using the phrase “comprising” includes embodiments that could be described as “consisting essentially of” or “consisting of”, and as such the written description requirement for claiming one or more embodiments of the present invention using the phrase “consisting essentially of” or “consisting of” is met.

(27) As used herein, the term “about” refers to plus or minus 10% of the referenced number.