Gd-containing, anti-coking solid acid catalysts and preparation method and use thereof

Abstract

The present invention relates to an anti-coking catalyst having a physical property of reducing coke formation, which comprises a solid acid catalyst containing gadolinium (Gd) on the surface, a preparation method thereof, and a use thereof. The preparation method includes a first step of determining the amount of gadolinium (Gd) or a Gd-providing precursor to be used relative to the total weight of the solid acid catalyst, which reducing the coking of a specific solid acid catalyst below a specific level under a specific reaction condition; and a second step of preparing a Gd-containing solid acid catalyst using the amount determined in the first step. The catalyst according to the present invention is a catalyst in which an appropriate weight ratio of gadolinium is supported on the surface of a pure solid acid substance or solid acid substance on which a specific metal is supported. Therefore, the production of coke on the catalyst surface is inhibited while maintaining the activity of the solid acid catalyst in a hydrocarbon conversion reaction, and as a result, the catalyst of the present invention exhibits an effect of improving its lifespan.

Claims

1. A method of preparing a gadolinium (Gd)-containing anti-coking solid acid catalyst having a physical property of reducing coke formation, the method comprising: a first step of determining an amount of Gd or Gd-providing precursor to be used relative to the total weight of the solid acid catalyst that does not include Gd, wherein the determined amount of Gd reduces the coking of the solid acid catalyst below a specific level under a specific reaction condition in which the solid acid catalyst is intended to be used; and a second step of preparing the Gd-containing anti-coking solid acid catalyst using the amount determined in the first step, the second step comprising: obtaining an aqueous solution containing the Gd or the Gd-providing precursor; mixing the aqueous solution with a solid acid; drying the mixture to obtain a catalyst precursor material; and calcining the catalyst precursor material to obtain the Gd-containing anti-coking solid acid catalyst having the physical property of reducing coke formation.

2. The method according to claim 1, wherein the Gd-containing anti-coking solid acid catalyst prepared in the second step has an increased number of a base site by the presence of gadolinium when compared to the solid acid catalyst that does not include Gd.

3. The method according to claim 1, wherein the Gd-containing anti-coking solid acid catalyst prepared in the second step has a film containing Gd metal or gadolinium oxide formed on the surface of the solid acid catalyst with a nano-size thickness.

4. The method according to claim 1, wherein the amount of gadolinium to be used relative to the total weight of the solid acid catalyst is determined from the temperature-programmed desorption curve of carbon dioxide, base strength, or base site density per gadolinium content.

5. The method according to claim 1, further comprising a third step of determining the supported state of gadolinium in the solid acid catalyst prepared in the second step.

6. The method according to claim 1, wherein the specific reaction condition is a condition in which a reaction of forming coke intermediates exhibiting a basic property during the reaction occurs.

7. The method according to claim 6, wherein the reaction of forming coke intermediates having a basic property during the reaction is a hydrocarbon conversion reaction.

8. The method according to claim 1, wherein the specific reaction condition is a condition in which a reaction, selected from the group consisting of ethylene oligomerization reaction, methanol-to-gasoline reaction, hexane cracking reaction, and dehydrogenation reaction of a hydrocarbon formed by Fischer-Tropsch synthesis from syngas, in which the solid acid catalyst is intended to be used, occurs.

9. The method according to claim 1, wherein the Gd-containing anti-coking solid acid catalyst is a zeolite-based catalyst.

10. The method according to claim 1, wherein the Gd-providing precursor is at least one selected from the group consisting of gadolinium chloride (GdCl.sub.3), gadolinium bromide (GdBr.sub.3), gadolinium fluoride (GdF.sub.3), gadolinium iodide (GdI.sub.3), gadolinium chloride hexahydrate (GdCl.sub.3.6H.sub.2O), gadolinium nitrate hexahydrate ((GdNO.sub.3).sub.3.6H.sub.2O), gadolinium chloride hydrate (GdCl.sub.3.xH.sub.2O), gadolinium acetate hydrate (Gd(CH.sub.3CO.sub.2).sub.3.xH.sub.2O), gadolinium sulfate octahydrate (Gd.sub.2(SO.sub.4).sub.3.8H.sub.2O), gadolinium oxalate hydrate (Gd.sub.2(C.sub.2O.sub.4).sub.3.xH.sub.2O), gadolinium sulfate (Gd.sub.2(SO.sub.4).sub.3), gadolinium tris(isopropoxide) (C.sub.5H.sub.21GdO.sub.3), gadolinium carbonate hydrate (Gd.sub.2(CO.sub.3).sub.3.xH.sub.2O), gadolinium hydroxide hydrate (Gd(OH).sub.3.xH.sub.2O), gadolinium boride (GdB.sub.6), and a mixture thereof.

11. A method of preparing a hydrocarbon by performing ethylene oligomerization reaction, methanol-to-gasoline reaction, hexane cracking reaction, or dehydrogenation reaction of a hydrocarbon formed by Fischer-Tropsch synthesis from syngas, using the solid acid catalyst prepared by the method of claim 1, which comprises gadolinium on the surface, the method comprising: contacting an ethylene containing feed stream with the solid acid catalyst under conditions sufficient to perform the ethylene oligomerization reaction, contacting a methanol containing feed stream with the solid acid catalyst under conditions sufficient to perform the methanol-to-gasoline reaction, contacting a hexane containing feed stream with the solid acid catalyst under conditions sufficient to perform the hexane cracking reaction, or contacting a hydrocarbon formed by Fischer-Tropsch synthesis from syngase with the solid acid catalyst under conditions sufficient to perform the dehydrogenation reaction.

12. The method according to claim 11, wherein the solid acid catalyst has an increased number of a base site by the presence of gadolinium.

13. The method according to claim 11, wherein, for preventing the absorption of a coke intermediate physically, chemically by the acid-base characteristic of the catalyst surface, or both physically and chemically, a nano-sized gadolinium or gadolinium oxide-containing film is formed on the surface of the solid acid catalyst, or Gd.sup.3+ is ion-exchanged to an acid site of the solid acid catalyst, or supported by an electrostatic adsorption method.

14. The method according to claim 11, wherein the Gd-containing solid acid catalyst further comprises a transition metal, a post-transition metal, and a rare-earth metal.

15. The method according to claim 11, wherein the Gd-containing solid acid catalyst is prepared by an impregnation method, an ion-exchange method, or an electrostatic adsorption method.

16. The method according to claim 11, wherein a film containing Gd metal or gadolinium oxide is formed on the surface of the solid acid catalyst with a nano-size thickness.

17. An anti-coking catalyst having a physical property of reducing coke formation, which is a Gd-containing solid acid catalyst wherein a film comprising Gd metal or gadolinium oxide is present on the surface of the solid acid catalyst with a nano-size thickness.

18. The anti-coking catalyst of claim 17, which is prepared by a method comprising: a first step of determining an amount of gadolinium (Gd) or Gd-providing precursor to be used relative to the total weight of the solid acid catalyst that does not include Gd, wherein the determined amount of Gd reduces the coking of the solid acid catalyst below a specific level under a specific reaction condition in which the solid acid catalyst is intended to be used; and a second step of preparing a Gd-containing solid acid catalyst using the amount determined in the first step, the second step comprising: obtaining an aqueous solution containing the Gd or the Gd-providing precursor; mixing the aqueous solution with a solid acid; drying the mixture to obtain a catalyst precursor material; and calcining the catalyst precursor material to obtain the Gd-containing solid acid catalyst having the physical property of reducing coke formation.

19. A method of preparing a hydrocarbon by performing ethylene oligomerization reaction, methanol-to-gasoline reaction, hexane cracking reaction, or dehydrogenation reaction of a hydrocarbon formed by Fischer-Tropsch synthesis from syngas, using the anti-coking catalyst of claim 17, the method comprising: contacting an ethylene containing feed stream with the anti-coking catalyst of claim 17 under conditions sufficient to perform the ethylene oligomerization reaction, contacting a methanol containing feed stream with the anti-coking catalyst of claim 17 under conditions sufficient to perform the methanol-to-gasoline reaction, contacting a hexane containing feed stream with the anti-coking catalyst of claim 17 under conditions sufficient to perform the hexane cracking reaction, or contacting a hydrocarbon formed by Fischer-Tropsch synthesis from syngas with the anti-coking catalyst of claim 17 under conditions sufficient to perform the dehydrogenation reaction.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

(1) FIG. 1 is scanning transmission electron microscope (STEM) images showing the distribution of gadolinium in the catalyst prepared in Example 1.

(2) FIG. 2 is a graph showing the oxidation state of gadolinium in the catalyst prepared in Example 1 using the analysis of X-ray adsorption spectroscopy.

(3) FIG. 3 is a graph showing the temperature-programmed desorption curve of ammonia per gadolinium content in the catalyst, in which coke formation is inhibited, prepared in Examples 7 to 9.

(4) FIG. 4 is a graph showing the temperature-programmed desorption curve of carbon dioxide per gadolinium content in the catalyst, in which coke formation is inhibited, prepared in Examples 7 to 9.

(5) FIG. 5 is a graph showing the temperature-programmed desorption curve of ammonia in the catalyst, in which coke formation is inhibited, prepared according to the ion-exchange and impregnation methods

(6) FIG. 6 is a graph showing the temperature-programmed desorption curve of carbon dioxide in the catalyst, in which coke formation is inhibited, prepared according to the ion-exchange and impregnation methods.

(7) FIG. 7 is high angle annular dark-field (HAADF) STEM images showing the catalyst, in which coke formation is inhibited, prepared according to the electrostatic adsorption method.

DETAILED DESCRIPTION OF THE EMBODIMENT

(8) Hereinbelow, the present invention will be described in detail with accompanying exemplary embodiments. However, the exemplary embodiments disclosed herein are only for illustrative purposes and should not be construed as limiting the scope of the present invention.

Comparative Example 1

Catalyst (HZSM-5, Si/Al=25)

(9) In order to covert ammonium (NH.sub.4)-type ZSM-5 zeolite (Zeolyst; CBV5524, Si/Al=25) into hydrogen (H)-type ZSM-5, the zeolite was calcined in an air atmosphere at 600? C. for 6 hours. The pore volume of the HZSM-5 zeolite support according to Comparative Example 1 was 0.35 cm.sup.3/g.

Comparative Example 2

Catalyst (HZSM-5, Si/Al=15)

(10) In order to convert ammonium (NH.sub.4)-type zeolite (Zeolyst; CBV3024E, Si/Al=15) into hydrogen (H)-type ZSM-5, the zeolite was calcined in an air atmosphere at 600? C. for 6 hours.

Example 1

Impregnation MethodCatalyst (GdWI/HZSM-5, Si/Al=25)

(11) An appropriate amount of gadolinium nitrate hexahydrate (GdNO.sub.3).sub.3.6H.sub.2O), which satisfies the mass of gadolinium (0.05 g) per 1 g of the HZSM-5 zeolite support of Comparative Example 1, was dissolved in 0.4 mL of deionized water per 1 g of HZSM-5. The support was mixed with the aqueous solution of the precursor, and then the mixture was evenly stirred so that the prepared gadolinium precursor can be supported on the HZSM-5 zeolite support by the incipient wetness impregnation method. The obtained gadolinium-HZSM-5 (Gd.sub.WI/HZSM-5) catalyst was dried in an air atmosphere at 110? C. for 12 hours, and then calcined in an air atmosphere at 550? C. for 5 hours.

(12) FIG. 1 shows STEM images of the catalyst (Gd.sub.WI/HZSM-5, Si/Al=25) of Example 1. As a result of the STEM analysis, it was observed that the HZSM-5 crystals were covered by a thin film having a thickness of 1 nm to 3 nm. It was confirmed that this thin film showed a clear lattice exhibited only in metals or metal oxides, and as a result of EDS mapping, the gadolinium ingredients were evenly distributed on the entire surface of HZSM-5.

(13) The oxidation state of gadolinium was analyzed in the catalyst synthesized by the method of Example 1 using an analysis of X-ray adsorption spectroscopy (FIG. 2). FIG. 2 is a graph showing the oxidation state of gadolinium in the catalyst synthesized by the method of Example 1 using an analysis of X-ray adsorption spectroscopy. The X-ray absorption near edge spectra (XANES) of gadolinium oxide (Gd.sub.2O.sub.3) as reference sample and 5Gd/HZSM-5 (Example 1) were exactly expressed at 7.25 keV, and the two spectra showed shapes that are almost identical to each other. As a result, it can be seen that the gadolinium supported on HZSM-5 exists in the oxidation state which is identical to that of Gd.sub.2O.sub.3, the reference sample. Therefore, a nano-sized film of gadolinium oxide is formed on the HZSM-5 support during synthesis of the catalyst, and this film physically hinders the adsorption of the coke precursors formed during the conversion reaction of hydrocarbons, resulting in the reduction of coke formation.

Example 2

Ion-Exchange MethodCatalyst (GdIE/HZSM-5, Si/Al=15)

(14) 50 mL of a 0.5 M aqueous solution of the gadolinium precursor per 1 g of the HZSM-5 support of Comparative Example 2 was prepared, and gadolinium nitrate hexahydrate ((GdNO.sub.3).sub.3.6H.sub.2O) was used as the gadolinium precursor. The HZSM-5 zeolite support was mixed in the aqueous solution of the gadolinium precursor, and the solid acid slurry was stirred at 60? C. for 3 hours for ion exchange. The solid acid slurry obtained by repeating the above procedure three times was centrifuged to separate only a solid acid catalyst, and the obtained solid acid catalyst was washed using deionized water and then again separated by centrifugation. The solid acid catalyst (Gd.sub.IE/HZSM-5, Si/Al=15) obtained by repeating the above washing procedure three times was dried and calcined by the method described in Example 1.

Example 3

Impregnation MethodCatalyst (GdWI/HZSM-5, Si/Al=15)

(15) A catalyst was prepared in the same manner as in Example 1, except that the HZSM-5 (Si/Al=15) zeolite of Comparative Example 2 was used as a support.

Example 4

Impregnation MethodCatalyst (GaGdWI/HZSM-5, Si/Al=15)

(16) Gallium (Ga) metal was further supported on the Gd.sub.WI/HZSM-5 catalyst of Example 3.

(17) An appropriate amount of gallium nitrate hexahydrate ((GaNO.sub.3).sub.3.xH.sub.2O), which satisfies the mass of gallium (0.03 g) per the Gd.sub.WI/HZSM-5 support (1 g) of Example 3, was dissolved in 0.4 mL of deionized water per 1 g of Gd.sub.WI/HZSM-5. The support, Gd.sub.WI/HZSM-5, was mixed with the aqueous solution of the gallium precursor, and then the mixture was evenly stirred so that the prepared gallium precursor can be supported on Gd.sub.WI/HZSM-5 by the incipient wetness impregnation method. The obtained gallium-gadolinium-HZSM-5 (GaGd.sub.WI/HZSM-5) catalyst was dried in an air atmosphere at 110? C. for 12 hours, and then calcined in an air atmosphere at 550? C. for 5 hours.

Comparative Example 3

Catalyst (GaWI/HZSM-5, Si/Al=15)

(18) Gallium was supported on the HZSM-5 support of Comparative Example 2 according to the impregnation method according to Example 4.

Example 5

Impregnation MethodCatalyst (GdWI/zeolite Y, Si/Al=40)

(19) A catalyst was prepared in the same manner as in Example 1, except that hydrogen (H)-type zeolite Y (Zeolyst; CBV720, Si/Al=40) was used as a solid acid support.

Comparative Example 4

Catalyst (GdWI/zeolite Y, Si/Al=40)

(20) The hydrogen (H)-type zeolite Y (Zeolyst; CBV720, Si/Al=40) used in Example 5 was prepared as a solid acid catalyst.

(21) Table 1 shows conditions of the catalyst synthesis of each Example and Comparative Example.

(22) TABLE-US-00001 TABLE 1 Supporting Example Name Support Gd Precursor Metal Method Example 1 Gd.sub.WI/HZSM-5, HZSM-5, Si/Al = 25 the gadolinium nitrate Impregnation Si/Al = 25 (Comparative hexahydrate method Example 1) (GdNO.sub.3).sub.36H.sub.2O, in an appropriate amount, which satisfies the mass of gadolinium (0.05 g) per support (1 g) Example 2 Gd.sub.IE/HZSM-5, HZSM-5, Si/Al = 15 (GdNO.sub.3).sub.36H.sub.2O, Ion-exchange Si/Al = 15 (Comparative 50 mL of a 0.5M method Example 2) aqueous solution of the gadolinium precursor per 1 g of HZSM-5 Example 3 Gd.sub.WI/HZSM-5, HZSM-5, Si/Al = 15 (GdNO.sub.3).sub.36H.sub.2O, Impregnation Si/Al = 15 (Comparative in an appropriate method Example 2) amount, which satisfies the mass of gadolinium (0.05 g) per the support (1 g) Example 4 Gd.sub.WI/HZSM-5, HZSM-5, Si/Al = 15 (GdNO.sub.3).sub.36H.sub.2O, Gallium Impregnation Si/Al = 15 (Comparative in an appropriate (Ga) metal method Example 2) amount, which (0.03 g per satisfies the mass of 1 g of the gadolinium (0.05 g) support) per the support (1 g) Example 5 Gd.sub.WI/zeolite Y, zeolite Y, Si/Al = 40 (GdNO.sub.3).sub.36H.sub.2O, Impregnation Si/Al = 40 in an appropriate method amount, which satisfies the mass of gadolinium (0.05 g) per the support (1 g) Comparative HZSM-5, HZSM-5, Si/Al = 25 Example 1 Si/Al = 25 Comparative HZSM-5, HZSM-5, Si/Al = 15 Example 2 Si/Al = 15 Comparative Gd.sub.WI/HZSM-5, HZSM-5, Si/Al = 15 Gallium Impregnation Example 3 Si/Al = 15 (Ga) metal method (0.03 g per 1 g of the support) Comparative Gd.sub.WI/zeolite Y, zeolite Y, Si/Al = 40 Example 4 Si/Al = 40

Example 6

Electrostatic Adsorption MethodCatalyst (GdEA-HZSM-5)

(23) Gadolinium was supported by an electrostatic adsorption method using HZSM-5 (CBV3024E) as a solid acid support. The pH of an aqueous solution of the gadolinium precursor was adjusted according to the point of zero charge of a solid acid material and the charge of the gadolinium precursor. Gadolinium(III) nitrate hexahydrate (Gd(NO.sub.3).sub.36H.sub.2O; MW: 451.36) was used as the gadolinium precursor. A 0.05 M aqueous solution of the precursor was prepared, and then the aqueous solution of the precursor, the pH of which was 1, 3, 5, 6, 7, 8, 9, and 10, was prepared using hydrochloric acid (HCl) and an ammonia solution (NH.sub.4OH; 35%). The HZSM-5 catalyst was mixed with the aqueous solution of the precursor at room temperature for 1 hour, and then the aqueous solution and catalyst were separated by a centrifuge. The catalyst was washed with deionized water, and then once more centrifuged for separation. The solid acid catalyst (Gd.sub.EA/HZSM-5, Si/Al=15) obtained by repeating the above washing procedure three times was dried and calcined by the method described in Example 1.

Examples 7 to 9

Catalysts According to Gadolinium Content

(24) Catalysts were prepared in the same manner as in Example 1, except that a weight ratio of the gadolinium content in the catalyst relative to the catalyst was 1, 5, and 10, respectively.

(25) The synthesis conditions of Examples 7 to 9 are shown in Table 2 below.

(26) TABLE-US-00002 TABLE 2 Supporting Example Name Support Gd Precursor Metal Method Example 1 Gd.sub.WI/HZSM-5, HZSM-5, gadolinium nitrate Impregnation Si/Al = 25 Si/Al = 25 hexahydrate method (Comparative ((GdNO.sub.3).sub.36H.sub.2O), Example 1) in an appropriate amount, which satisfies the mass of gadolinium (0.05 g) per the support (1 g) Example 7 Gd.sub.WI/HZSM-5, HZSM-5, Gadolinium nitrate Impregnation Si/Al = 25 Si/Al = 25 hexahydrate method (Comparative ((GdNO.sub.3).sub.36H.sub.2O) Example 1) the weight ratio 1 relative to catalyst Example 8 Gd.sub.WI/HZSM-5, HZSM-5, Gadolinium nitrate Impregnation Si/Al = 25 Si/Al = 25 hexahydrate method (Comparative ((GdNO.sub.3).sub.36H.sub.2O) Example 1) the weight ratio 5 relative to catalyst Example 9 Gd.sub.WI/HZSM-5, HZSM-5, Gadolinium nitrate Impregnation Si/Al = 25 Si/Al = 25 hexahydrate method (Comparative ((GdNO.sub.3).sub.36H.sub.2O) Example 1) the weight ratio 10 relative to catalyst

Experimental Example 1

Reactivity and Coke formation Rate of Catalyst of Example 1 comparative Example 1 in Ethylene Oligomerization

(27) The reactivity and coke formation rate of the solid acid catalysts of Example 1 (Gd.sub.WI/HZSM-5) and Comparative Example 1 (HZSM-5) in the oligomerization of ethylene were compared. In the center of a ?-inch stainless steel fixed bed reactor, the catalyst (2 g) and silicon carbide (SiC) as a diluent were charged, and then catalyst activation was carried out at 300? C. for 1 hour while supplying helium (He) at 100 mL/min. For the oligomerization of ethylene, a feed gas (C.sub.2H.sub.4 74%+Ar 26%) satisfying a weight hourly space velocity of 419.6 h.sup.?1 was supplied at a reaction pressure of 20 bar and reaction temperature of 350? C. The composition of each product was analyzed using on-line gas chromatography (GC-TCD&FID) and GC-FID.

(28) The amount of coke deposited on the surface of the catalyst was analyzed by thermogravimetric analysis to compare the rate of coke formation against reaction time. During the oligomerization of ethylene for 15 hours, the conversion rate of ethylene for both catalysts was 97% or more, and the selectivity of the light hydrocarbons (C.sub.1 to C.sub.5) and the heavy hydrocarbons (C.sub.6 or more) was 47% and 53% in Example 1, and 44% and 56% in Comparative Example 1, respectively. The coke formation rate in each catalyst was 0.157 mg/h in Example 1 and 0.178 mg/h in Comparative Example 1; that is, the coke formation rate in Example 1 was decreased by 11.8% compared to that of Comparative Example 1. Table 3 shows the reactivity and coke formation rate of the catalysts in Example 1 and Comparative Example 1.

(29) TABLE-US-00003 TABLE 3 Light Heavy Ethylene Hydrocarbon Hydrocarbon Coke Conversion (C.sub.1 to C.sub.5) (C.sub.6 or more) Formation Example Name Rate Selectivity Selectivity Rate Note Example 1 Gd.sub.WI/HZSM-5, 97% or 47% 53% 0.157 Coke formation Si/Al = 25 higher mg/h rate decreased by 11.8% compared to Comparative Example 1 Comparative HZSM-5, 97% or 44% 56% 0.178 Example 1 Si/Al = 25 higher mg/h

Experimental Example 2

Analysis of Catalyst According to Gadolinium Content

(30) The acidity and basicity of the catalysts, adjusted to have weight ratio of the gadolinium content in the catalysts relative to the catalysts as 1, 5, and 10 according to Examples 7 to 9, were analyzed using the temperature-programmed desorption of ammonia (NH.sub.3-TPD) and the temperature-programmed desorption of carbon dioxide (CO.sub.2-TPD).

(31) FIG. 3 and Table 4 show the temperature-programmed desorption curve of ammonia and the amount of acid sites quantified per gadolinium content; and FIG. 4 and Table 5 show the temperature-programmed desorption curve of carbon dioxide and the amount of base sites quantified per gadolinium content.

(32) It was observed that the change in the acid strength was insignificant because although weak acid sites were increased and strong acid sites were decreased as the gadolinium content increased, there was no positional shift of the curve. On the contrary, the base strength became stronger (the temperature at which desorption of carbon dioxide is maximum is increased) and the amount of the base sites were increased as the gadolinium content of the catalyst increased.

(33) Since the coke intermediates, such as olefins or aromatic carbons which have a potential to grow as coke by adsorbing to the catalyst surface and which are formed during the reaction, have a basicity that shares electron pairs, the adsorption of the coke intermediates tends to be inhibited on the surface of the HZSM-5 catalyst in which the basicity is increased due to the presence of gadolinium. Therefore, the adsorption of the coke intermediates, which were formed during the conversion reaction of hydrocarbons, to the surface of the zeolite catalyst is not only physically hindered by the film of gadolinium oxide with a nano-size thickness, but also chemically reduced by the acid-base properties of the zeolite surface modified by gadolinium, and as a result, the zeolite catalyst on which gadolinium is supported reduces the inactivation caused by coking.

(34) Tables 4 and 5 show the acid sites and base sites according to the gadolinium content, respectively.

(35) TABLE-US-00004 TABLE 4 Acid sites quantified by the NH.sub.3-temperature-programmed desorption (NH.sub.3-TPD) per gadolinium content Weak acid site Strong acid site Total Example Catalyst (?mol/g) (?mol/g) (?mol/g) Comparative HZ 702 606 1308 Example 1 Example 7 1 GdZ 692 569 1261 Example 8 5 GdZ 754 345 1099 Example 9 10 GdZ 871 267 1138

(36) TABLE-US-00005 TABLE 5 Base sites quantified by the CO.sub.2-temperature-programmed desorption (CO.sub.2-TPD) per gadolinium content Temperature Total base site Example Catalyst (? C.) (?mol/g) Comparative Example 1 HZ 187 146.5 Example 7 1 GdZ 191 197.6 Example 8 5 GdZ 259 257.2 Example 9 10 GdZ 287 281.3

(37) The result of the CO.sub.2-temperature programmed desorption (CO.sub.2-TPD) shows that the CO.sub.2 desorption in Comparative Example 1 (Base ZSM-5) started at 150? C. and became maximum at 187? C. (FIG. 4 and Table 5). Meanwhile, as the content of gadolinium increased, the temperature at which the CO.sub.2 desorption began and the temperature at which the desorption became maximum were gradually increased, and thus the CO.sub.2 desorption of the catalyst (10GdZ; Example 9), in which 10 wt % gadolinium was impregnated, became maximum at 287? C. Additionally, as the content of gadolinium increased, the number of base sites also increased. Accordingly, it can be seen that the base strength and the density of the base sites on the surface of the zeolite catalyst became stronger and increased as the content of gadolinium increased.

(38) Olefins or aromatic carbons formed during the conversion of hydrocarbons inherently have weak Lewis bases. These products are strongly adsorbed to the acid sites of zeolite, which is a solid acid catalyst, cyclized, and then dehydrogenated, thereby growing into coke comprising of a complex aromatic structure. In the case of the zeolite catalyst on which gadolinium is supported, the chemical adsorption of olefins or aromatic carbons must be hindered due to the increased basicity, and as a result, the coke formation is also reduced.

Experimental Example 3

Conversion of Methanol to Aromatic Compound Using GdWI-HZSM-5 Catalyst

(39) In the process of converting methanol to a monocyclic aromatic compound (MTA), the reactivity and the amount coke formed on the surface of the HZSM-5 zeolite catalysts on which gadolinium was supported by the impregnation method according to Example 1 were compared. The reaction was carried out in a 0.5-inch fixed bed reactor. The powder catalysts (1 g) were placed in the center of the reactor tube, and the other parts were filled with quartz wool and SiC. The catalysts before the reaction were pretreated in a helium atmosphere at 400? C. for 1 hour. Thereafter, pure methanol (0.2 mL/min) was flowed together with 50 sccm helium at 400? C. in the MTA reaction. The reaction was carried out for 24 hours, and then the conversion rate of methanol and the selectivity of the monocyclic aromatic compound when using Comparative Example 1 (HZSM-5) and Example 1 (5Gd.sub.WI-HZSM-5) were analyzed over time, and the results therefrom are summarized in Table 6.

(40) Both catalysts showed a 99% conversion rate of methanol until 14 hours of the reaction, but the catalysts showed a tendency that such conversion rate was gradually decreased after 12 hours. In the case of Comparative Example 1, the rapid decrease in the conversion rate occurred, and thus the conversion rate decreased to 30% or below after 24 hours of the reaction; whereas in the case of Example 1, although the decrease in the conversion rate of methanol occurred, 78% of the conversion rate of methanol was maintained even after 24 hours of the reaction. In the case of Comparative Example 1, the selectivity of the C.sub.6 to C.sub.9 aromatics also showed a value close to 0% after 24 hours of the reaction. However, in the case of Example 1, 57.5% of the selectivity was maintained. As a result of analyzing the amount of carbon deposition of the catalysts after the reaction by using an elemental analyzer, it was shown that 23 wt % of carbon was deposited in the catalyst of the Comparative Example 1, and that 17 wt % of carbon was deposited in the catalyst of Example 1. Therefore, the catalyst on which gadolinium is supported showed an improved lifespan in the conversion of methanol to an aromatic compound, and also showed that the coke deposition was reduced by 26%.

(41) TABLE-US-00006 TABLE 6 Comparative Example 1 Example 1 (HZSM-5) (Gd.sub.WI-HZSM-5) Selectivity Selectivity Reaction Conversion (C.sub.6 to C.sub.9 Conversion (C.sub.6 to C.sub.9 time rate (%) Aromatics; %) rate (%) Aromatics; %) 2 100.0 82.5 100.0 82.1 4 100.0 76.0 100.0 72.2 6 100.0 73.5 100.0 64.2 8 100.0 76.3 100.0 68.2 10 100.0 69.9 100.0 67.3 12 99.1 71.8 98.2 55.1 14 92.5 66.5 96.1 61.2 16 83.7 65.8 94.1 62.7 18 62.5 58.7 90.5 60.5 20 55.1 22.9 84.6 58.8 22 22.9 11.8 90.4 58.7 24 28.3 4.5 78.1 57.5

Experimental Example 4

Reactivity and Coke Formation Rate of Catalyst in Process of Synthesizing Monocyclic Aromatic Compound and Long-Chain Olefin Compound from Syngas

(42) In the process of synthesizing a monocyclic aromatic compound and a long-chain olefin compound from syngas, the reactivity and the amount of coke formed on the surface of the HZSM-5 zeolite catalysts on which gadolinium was supported were compared.

(43) First, an iron-based catalyst (1 g) having a composition ratio of 100Fe-6Cu-16Al-4K was charged into a ?-inch stainless steel fixed bed reactor. The syngas, the composition ratio of which is CO.sub.2/(CO+CO.sub.2)=0.5 and H.sub.2/(2CO+3CO.sub.2)=1, was supplied at a flow rate of 1,800 mL/g-cat.Math.h, and the Fischer-Tropsch synthesis was carried out at a reaction temperature of 320? C. and a reaction pressure of 20 bar. Meanwhile, a dehydrogenation process was carried out using the hydrocarbons prepared by the Fischer-Tropsch synthesis. Before performing the dehydrogenation of the prepared hydrocarbons, the C.sub.1 to C.sub.15 short-chain hydrocarbons were separated through a distillation process and used. In particular, the distillation apparatus maintained an internal temperature of 136? C. and an internal pressure of 20 bar. In order to carry out the dehydrogenation process, the solid acid catalysts (0.6 g) of each of Examples and Comparative Examples were charged into a ?-inch stainless steel fixed bed reactor, and the reaction was carried out at a reaction temperature of 300? C. and a reaction pressure of 10 bar, and thus a monocyclic aromatic compound and a long-chain olefin compound were prepared. The composition of each product was analyzed using on-line gas chromatography (GC-TCD&FID) and GC/MS.

(44) The structure of the reaction apparatus above is further described in detail in Korean Patent Application No. 10-2015-0002900.

(45) Table 7 shows the results of analyzing the composition difference in the products and the production amount of the coke deposited on the catalyst surface by using a thermogravimetric analysis method when the catalysts of Examples 2 to 4 and Comparative Examples 2 and 3 were used in the process of synthesizing the monocyclic aromatic compound and long-chain olefin compound from the syngas.

(46) TABLE-US-00007 TABLE 7 Product distribution Amount of Coke (mol %) Produced Example BETX Paraffin Olefin (wt %) Note Example 2 34 39 12 4.2 The amount of coke produced was reduced by 18% compared to Comparative Example 2 Example 3 37 41 7 3.1 The amount of coke produced was reduced by 39% compared to Comparative Example 2 Example 4 50 31 9 3.3 The amount of coke produced was reduced by 40% compared to Comparative Example 2 Comparative 41 37 6 5.1 Example 2 Comparative 53 28 6 5.5 Example 3

(47) According to Table 7, in the case of the HZSM-5 catalysts (Examples 2 and 3) on which gadolinium is supported, there was no significant change in the product distribution, but the amount of the coke formed on the catalyst surface after the reaction at the equivalent reaction time was each reduced by 18% and 39% compared to that of the pure HZSM-5 catalyst (Comparative Example 2) on which gadolinium is not supported. Additionally, in the case of the HZSM-5 catalyst (Example 4) on which gadolinium and gallium are supported, it was observed that there was also no significant change in the product distribution, but the amount of the coke formed on the catalyst surface after the reaction at the equivalent reaction time was reduced by 40% compared to that of the HZSM-5 catalyst (Comparative Example 3) on which gallium is solely supported.

Experimental Example 5

Property Analysis of ZSM-5 Catalyst on which Gadolinium is Supported Using Ion-exchange Method

(48) The HZSM-5 catalyst on which gadolinium is supported using the ion-exchange method according to Example 2 was only ion-exchanged to the acid sites of Gd.sup.3+, and thus the film of gadolinium oxide with a nano-size thickness could not be observed.

(49) FIG. 5 is a graph showing the temperature-programmed desorption curve of ammonia of the anti-coking catalyst prepared by the ion-exchange and impregnation methods.

(50) FIG. 6 is a graph showing the temperature-programmed desorption curve of carbon dioxide of the anti-coking catalyst prepared by the ion-exchange and impregnation methods.

(51) Tables 8 and 9 each show the acid sites quantified by the temperature-programmed desorption of ammonia and the base sites quantified by the temperature-programmed desorption of carbon dioxide according to ion-exchange and impregnation methods.

(52) As shown in FIGS. 5 and 6 and Tables 8 and 9, the catalysts synthesized by the ion-exchange method also showed a decrease in the acid sites and an increase in the base sites. It was found that range of the decrease in the acid sites was large while that of the increase in the base sites was small compared to those of the catalysts synthesized so that the equivalent amount of gadolinium was supported using the impregnation method (Example 1). Therefore, since a physical adsorption-hindering factor is not developed in the catalysts synthesized by the ion-exchange method, it can be considered that reduction of the inactivation of the catalysts is less than that of the catalysts synthesized by the impregnation method.

(53) TABLE-US-00008 TABLE 8 Acid Sites Quantified by Temperature-programmed Desorption of Ammonia (Comparison between Ion-exchange Method and Impregnation Method) Weak acid Strong acid Total acid Example Samples (?mol/g) (?mol/g) (?mol/g) Comparative HZSM-5 702 606 1308 Example 1 Example 1 Impregnation 692 569 1261 method Example 2 Ion-exchange 497 472 969 method

(54) TABLE-US-00009 TABLE 9 Base Sites Quantified by Temperature-programmed Desorption of Carbon Dioxide (Comparison between Ion-exchange Method and Impregnation Method) Temperature Total base Example Samples (? C.) (?mol/g) Comparative HZSM-5 187 146.5 Example 1 Example 1 Impregnation method 191 197.6 Example 2 Ion-exchange method 177 170.2

Experimental Example 6

Analysis of Catalyst Prepared Using HZSM-5(CBV3024E) and Electrostatic Adsorption Method

(55) FIG. 7 is high angle annular dark-field (HAADF) STEM images of the anti-coking catalys prepared by adsorbing gadolinium using electrostatic adsorption and HZSM-5 (CBV3024E) as a support according to Example 6. In the HAADF mode, a substance or atom with a high atomic number exhibits a bright color. It was confirmed in the images of FIG. 7 that thin films having a thickness of 1 nm to 3 nm covered the crystals. As a result of the energy dispersed X-ray analysis, high-density gadolinium atoms were detected in thin nano-size films having a bright color. High-density gadolinium atoms were detected in brightly colored areas inside the crystals, and further, the gadolinium atoms were also evenly detected in the other areas.

(56) Accordingly, gadolinium not only always forms a film covering carriers at a certain amount or more regardless of synthesis methods, but also a considerable amount of gadolinium exists in the ion-exchanged state or in the monoatomic film in the zeolite pores or on the surface.