Zeolite supported catalyst and manufacturing method thereof

Abstract

A zeolite-supported catalyst and a method for manufacturing the same are provided. The zeolite-supported catalyst comprises a zeolite and a metal catalyst supported on the zeolite, wherein the zeolite is treated with a silicon-aluminum modifier and quaternary ammonium hydroxide before supporting the metal catalyst. The method for manufacturing the zeolite-supported catalyst comprises the steps of preparing a zeolite, post-treating the zeolite with a silicon-aluminum modifier and quaternary ammonium hydroxide, and supporting the metal catalyst on the post-treated zeolite.

Description

Technology Field

[0001] The present invention relates to a zeolite-supported catalyst and a method for manufacturing the same. Background Technology

[0002] By conducting the shale gas aromatization reaction under oxygen-free conditions, the high-value compound BTX can be produced without the naphtha process. However, in the aforementioned shale gas aromatization reaction, significant carbon deposition occurs on the outer surface of the catalyst, clogging the pores on the surface and ultimately causing the catalyst to become deactivated before all internal reaction active sites can be utilized. The problem to be solved

[0003] The present invention provides a zeolite-supported catalyst having excellent performance.

[0004] The present invention provides a method for manufacturing the above-mentioned zeolite-supported catalyst.

[0005] Other objects of the present invention will become clear from the following detailed description and the accompanying drawings. means of solving the problem

[0006] A zeolite-supported catalyst according to embodiments of the present invention comprises a zeolite and a metal catalyst supported on the zeolite, wherein the zeolite is treated with a silicon-aluminum modifier and quaternary ammonium hydroxide before supporting the metal catalyst.

[0007] A method for preparing a zeolite-supported catalyst according to embodiments of the present invention comprises the steps of preparing a zeolite, post-treating the zeolite with a silicon-aluminum modifier and quaternary ammonium hydroxide, and supporting a metal catalyst on the post-treated zeolite. Effects of the invention

[0008] The zeolite-supported catalyst according to the embodiments of the present invention has excellent performance. For example, the zeolite-supported catalyst has excellent structural stability and high regenerability, and can suppress coke formation. The zeolite-supported catalyst can increase catalyst stability by minimizing external acidity, and can increase the yield of BTX (benzene, toluene, xylene) by facilitating the diffusion of carbon intermediates during the reaction through increased micropore volume and control of the mesopore structure. It can maintain catalyst stability by suppressing dealumination of the catalyst and the formation of aluminum molybdate, and can prevent structural deterioration of the catalyst by preventing Mo migration and aggregation. Brief explanation of the drawing

[0009] Figure 1 shows the powder XRD pattern of a zeolite sample. Figure 2 shows the N2 adsorption-desorption isotherm of the zeolite sample. Figure 3 shows the BJH pore size distribution of the zeolite sample. Figure 4 shows the FT-IR spectrum of the zeolite sample in the OH stretching vibration range (after 4 hours of gas removal at 723K). Figure 5 shows the acidity based on the IR spectra of pyridine and 2,6-di-tert-butylpyridine of the zeolite sample. Figure 6 shows the TIPB(1,3,5-Triisopropylbenzene) conversion rate of the zeolite sample according to stream time. Figure 7 shows the Mo / (Si+Al) ratio based on XPS of a Mo-supported zeolite sample. Figure 8 shows the UV-VIS-DRS spectrum of a Mo-supported zeolite sample. Figure 9 shows the Mo K-edge XANES of a Mo-supported zeolite sample. Figure 10 shows the k of the Mo-supported zeolite sample. 2- Represents the magnitude of the weighted Fourier transform EXAFS spectrum. Figure 11 shows the total carbon conversion rate of the Mo-supported zeolite sample. Figure 12 shows the BTX yield of the Mo-supported zeolite sample. Figure 13 shows the naphthalene selectivity of the Mo-supported zeolite sample. Figure 14 shows the regenerability of a Mo-supported zeolite sample based on the cumulative BTX yield (completely deactivated) over 15 hours. Figure 15 shows the regenerability of a Mo-supported zeolite sample based on an initial activity of 4 hours. Figure 16 shows a raw Mo-supported zeolite sample. 27 Al MAS NMR spectrum is shown. Fig. 17 shows the Mo-supported zeolite sample regenerated five times. 27 Al MAS NMR spectrum is shown. Fig. 18 shows the raw sample and the reconstructed sample (EFAl P+O +Al-Mo B+D Represents the ) / FAl ratio (based on each peak area). Figure 19 shows the TGA profile of the Mo-supported zeolite sample after the fourth use. Figure 20 shows the hard / soft coke ratio of each sample after the 4th use of the Mo-supported zeolite sample (Spent-4th) and after the reaction of the raw Mo-supported zeolite sample (Spent-F). Specific details for implementing the invention

[0010] The present invention will be described in detail below through examples. The purpose, features, and advantages of the present invention will be easily understood through the following examples. The present invention is not limited to the examples described herein and may be embodied in other forms. The examples introduced herein are provided to ensure that the disclosed content is thorough and complete, and to ensure that the concept of the present invention is sufficiently conveyed to those skilled in the art to which the present invention pertains. Accordingly, the present invention should not be limited by the following examples.

[0012] A zeolite-supported catalyst according to embodiments of the present invention comprises a zeolite and a metal catalyst supported on the zeolite, wherein the zeolite is treated with a silicon-aluminum modifier and quaternary ammonium hydroxide before supporting the metal catalyst.

[0013] A method for preparing a zeolite-supported catalyst according to embodiments of the present invention comprises the steps of preparing a zeolite, post-treating the zeolite with a silicon-aluminum modifier and quaternary ammonium hydroxide, and supporting a metal catalyst on the post-treated zeolite.

[0014] The above zeolite can be treated with the above silicon-aluminum modifier and then treated with the above quaternary ammonium hydroxide.

[0015] The above zeolite may include ZSM-5, and the above metal catalyst may include molybdenum.

[0016] The above silicon-aluminum modifier may include ammonium hexafluorosilicate.

[0017] The above quaternary ammonium hydroxide may include at least one of tetrapropylammonium hydroxide, cetyltrimethylammonium hydroxide, and tetramethylammonium hydroxide.

[0018] The above silicon-aluminum modifier can perform dealumination, increase external silicon content, and form defect sites with respect to the zeolite.

[0019] The defect site formed by the above silicon-aluminum modifier can increase the mesopore volume of the zeolite.

[0020] The defect site formed by the above silicon-aluminum modifier can provide a treatment route for the quaternary ammonium hydroxide in the zeolite.

[0022] [Example of preparation of zeolite catalyst]

[0024] Catalyst materials

[0025] The materials used for catalyst synthesis are as follows: Commercial NH4 + ZSM-5 (Si / Al2 molar ratio 23:1), tetrapropylammonium hydroxide (TPAOH, 25% aqueous solution), and ammonium hexafluorosilicate (AHFS, 98.0%) were used for zeolite post-treatment. To use the zeolite without post-treatment, NH4 + -ZSM-5 was converted to the H-form by calcination at 580°C for 6 hours (indicated as “Z”).

[0027] Zeolite post-treatment

[0028] The TPAOH treatment procedure is as follows. NH4 +ZSM-5 was dissolved in a 0.2 M TPAOH solution (1 g / 15 mL) and stirred at room temperature for 2 hours to obtain a homogeneous synthetic gel. This synthetic gel was transferred to a Teflon-lined autoclave and subjected to hydrothermal treatment at 160 °C for 24 hours. After washing the resulting zeolite, it was calcined at 580 °C for 6 hours to remove OSDA (Organic Structure-Directing Agent) from the recrystallization region. After converting to the H-form through ion exchange with NH4NO3 (1 M), it was calcined again at 580 °C for 6 hours. The final sample obtained was designated as “ZT”.

[0029] The AHFS processing procedure is as follows. NH4 + ZSM-5 was dissolved in a 0.1 M AHFS solution (1 g / 15 mL) and stirred at 80°C for 1 hour. The resulting zeolite was calcined at 580°C for 6 hours to convert it to the H-form. The final sample obtained was designated as “ZA”.

[0030] The AHFS-TPAOH treatment procedure is as follows. After performing the AHFS treatment described above without calcination, 15 mL of 0.2 M TPAOH was immediately added. Hydrothermal treatment was performed at 160°C for 24 hours. After washing the resulting sample, it was calcined at 580°C for 6 hours to remove OSDA within the recrystallization region. After converting to the H-form through ion exchange with NH4NO3 (1 M), it was calcined again at 580°C for 6 hours. The final sample obtained was labeled “ZAT”.

[0032] Mo Damji

[0033] After the post-processing was completed, Mo was supported on the zeolite sample using the wetness impregnation method. A specific amount of ammonium molybdate tetrahydrate ((NH4)6Mo7O 24·4H2O) and zeolite (theoretically Mo content 5 wt.%) were dispersed in deionized water and stirred for 1 hour. Water was removed from the solution using a rotary evaporator, and the resulting solid sample was dried overnight under vacuum at 80°C. The dried sample was calcined at 500°C for 6 hours at a heating rate of 10°C / min. The final sample obtained was designated as Mo / (zeolite sample name) (e.g., “Mo / ZAT”).

[0035] [Catalytic Reaction and Regeneration]

[0037] Mo-loaded samples (particle size 425 ~ 850 μm) were mounted in a continuous flow fixed-bed reactor and precarburization treatment was performed in the following manner.

[0038] Simulated shale gas (mixture of 85% CH4, 10% C2H6, and 5% C3H8) was heated under a helium (He) stream after the reactor temperature reached 650°C at a flow rate ratio of 9:11 and a total gas volume space velocity (GHSV) of 6,000 mL / hg cat It was supplied as. The sample underwent a total carbonization process for 6 minutes and MoO x MoC, which is the active phase x It was converted to. After full carbonization, the reactor temperature was raised to 700°C and maintained under a He stream for 30 minutes. After reaching 700°C, shale gas and He were mixed at a flow rate of 1:1 and a GHSV of 3,000 mL / hg cat supplied under certain conditions.

[0039] Online gas chromatography was used for product analysis, which included a Carboxen-1000 packed column equipped with a thermal conductivity detector (TCD) and a GS-gaspro capillary column equipped with a flame ionization detector (FID). Helium (He) was used as an internal standard to calculate the yield based on reactant conversion, product selectivity, and carbon balance.

[0040] The regeneration process of the sample used was at 550°C with a 10% O2 / N2 stream (total GHSV 6,000 mL / hg cat It was performed for 1 hour under ) conditions. After the regeneration process was completed, the same reaction procedure described above was applied to evaluate the catalyst performance.

[0042] [Characterization of Post-Treated Zeolite]

[0044] Figure 1 shows the powder XRD pattern of the zeolite sample, Figure 2 shows the N2 adsorption-desorption isotherm of the zeolite sample, and Figure 3 shows the BJH pore size distribution of the zeolite sample.

[0045] Referring to Figures 1 through 3, the zeolite maintains a typical MFI structure without forming any other crystalline phases even after all post-treatments. In the N2 adsorption-desorption isotherms, ZT exhibits small hysteresis, indicating that additional mesopores were formed as a result of the dissolution-recrystallization process (DRP) via TPAOH treatment. ZAT exhibits greater hysteresis than ZT, implying the presence of more developed mesopority. This phenomenon is due to the addition of AHFS along with TPAOH. Defects formed by AHFS can promote mesopore formation because defects generated through AHFS treatment provide pathways for additional alkali treatment. The broader pore size distribution of ZAT supports results indicating more developed mesopority than that of ZT. ZA exhibits minimal changes in isotherms and pore size distribution compared to Z, which is because the treatment conditions used to prepare the ZA sample were insufficient to alter the pore structure.

[0046] Table 1 below shows the pore volume and structural characteristics of the zeolite samples.

[0047] [Table 1]

[0048]

[0049] Referring to Table 1, ZT exhibits an increase in mesopore volume and a decrease in micropore volume compared to Z. Mesopores generally tend to develop at the expense of micropores through alkali treatment (desiliconization and dealuminate). ZAT displays unique behavior regarding pore volume changes; compared to ZT, ZAT shows a decrease in mesopore volume and an increase in micropore volume, with both values ​​being greater than those of Z. This is attributed to the addition of AHFS along with TPAOH. AHFS (NH4SiF6) can act as a Si source that forms additional pore structures in conjunction with TPAOH (MFI frame-indicator) during the dissolution and recrystallization processes. Therefore, the increased micropore volume can be attributed to additionally developed micropores in the 2 nm region, as confirmed in Figure 3. The 2 nm pore density of ZAT is significantly higher than that of ZT. In addition, the pore density in the 5–20 nm range of ZAT decreases compared to ZT, which means that the mesopore region present in ZT has decreased. This change is due to the existing mesopore region being filled as additional pore structures are formed. This result can be explained by the increase in micropore volume, decrease in mesopore volume, decrease in total pore volume, decrease in external surface area, and decrease in mesopore surface area of ​​ZAT compared to ZT.

[0050] ZAT exhibits a higher pore density in a pore size range greater than 25 nm compared to ZT, which is associated with the mesopority more developed by AHFS. The defect sites generated by AHFS treatment are OH - It can play a role in increasing the mesopore volume by allowing ions to access the zeolite framework more easily.

[0052] Figure 4 shows the FT-IR spectrum of the zeolite sample in the OH stretching vibration range (after 4 hours of degassing at 723K), Figure 5 shows the acidity based on the pyridine and 2,6-di-tert-butylpyridine IR spectra of the zeolite sample, and Figure 6 shows the TIPB(1,3,5-Triisopropylbenzene) conversion rate of the zeolite sample as a function of stream time.

[0053] Referring to Fig. 4, the FT-IR spectrum is 3800–3200 cm⁻¹ -1 Represents the stretching vibration of the silanol group in the range. Each band is on the outer surface (3745 cm⁻¹). -1 ), inner surface (3725cm -1 ), aluminum excluding the frame (EFAl, 3650cm -1 ), aluminum within the frame (FAl, 3600cm -1 Corresponds to the OH group for ):

[0054] Compared to the initial state Z, ZT exhibits significantly increased band intensity across the entire range, indicating that ZT has the highest defect density. This phenomenon is a result of substantial desiliconization caused by alkali treatment, which can lead to the formation of silanol nests.

[0055] The fact that the external surface area of ​​ZT increased by more than double compared to Z (see Table 1) may be associated with an increase in defect density. This is because defect sites are formed as the Si-O-Si and Si-O-Al bonds constituting the zeolite framework are slightly decomposed during the post-processing stage. In the case of ZAT, the intensity of the IR spectrum decreases compared to ZT. This indicates that defect sites are annealed by the addition of AHFS. Defect annealing refers to the process in which zeolite crystal regions damaged during alkali treatment are recovered, which may result in a slight increase in micropore volume.

[0056] As desiliconization proceeds through TPAOH treatment, damaged or exposed crystal regions can be selectively recovered, and as a result, additional microporous structures can be formed. This phenomenon is also confirmed in actual experimental results. Furthermore, the defect annealing effect can be further enhanced through a dissolution-recrystallization process in which AHFS and TPAOH coexist. On the other hand, ZA exhibits a defect density similar to Z, which is related to their structural characteristics and is consistent with the fact that the difference in structural characteristics between Z and ZA is minimal, as confirmed in Table 1.

[0057] Referring to Fig. 5, for the spatial distribution and quantitative analysis of Brønsted acid sites (BAS) and Lewis acid sites (LAS), measurements were performed using FT-IR spectroscopy with pyridine (Py) and 2,6-detert-butylpyridine (2,6-DTBPy) as probe molecules. Pyridine (Py) represents Brønsted acid sites (BAS) and Lewis acid sites (LAS), and 2,6-DTBPy represents external Brønsted acid sites (BAS ext It represents ).

[0058] The amount of pyridine (Py) adsorbed to Brønsted acid sites (BAS) (nBAS) does not show significant differences among all samples, and this correlates with the bulk Si / Al ratio of the samples shown in Table 2. However, external Brønsted acid sites (BAS ext Amount of 2,6-DTBPy adsorbed on ) (nBAS ext ) indicates a meaningful difference for each sample.

[0059] [Table 2]

[0060]

[0061] In the case of ZT, external Brønsted acidity (nBAS ext ) decreases, which is believed to be due to the increase in the external Si / Al ratio as a result of the dissolution-recrystallization process, as shown in Table 2.

[0062] External Brønsted acidity of ZAT (nBAS ext ) decreases even more than ZT, which is consistent with a nearly threefold increase in the Si / Al ratio on the outer surface. The sharp decrease in the external acidity of ZAT can be interpreted as a result achieved by the combination of AHFS and TPAOH. AHFS (NH4SiF6) acts as a Si source to induce dealumination, which can ultimately lead to an increase in the Si / Al ratio on the outer surface during the dissolution-recrystallization process. Additionally, AHFS can form a fluorine medium, which can promote an increase in the external Si content. This is because when an AlFx complex is formed in a fluorine-containing medium, the insertion of Al into the zeolite framework is inhibited.

[0063] In the case of ZA, the Si / Al ratio and external Brønsted acidity (nBASext.) remain at levels nearly identical to those of ZT. However, the defect density and mesopority of ZA appear to be much lower than those of ZT. In other words, while the degree of demetallization of Si and Al is similar, the structural characteristics of the framework differ due to differences in the treatment method. These results indicate that AHFS and TPAOH play different roles in the post-treatment process.

[0064] To further investigate the external acidity of the post-treated zeolite samples, a 1,3,5-triisopropylbenzene (TIPB) decomposition reaction was performed. The TIPB decomposition reaction is used to evaluate external surface characteristics such as surface area and acidity, which can be analyzed by measuring the conversion rate of TIPB. Since TIPB molecules have a molecular diameter of approximately 0.74 nm, which is larger than the pore size of ZSM-5 (0.5 to 0.6 nm), they cannot penetrate into the internal pores. Therefore, TIPB molecules can selectively access the external surface, thereby directly reflecting the external acidity regarding catalytic reactivity.

[0065] Referring to Fig. 6, sample Z exhibits the highest TIPB conversion rate, ZAT shows the lowest value, and ZT is located in the middle. This trend is due to external acidity (surface Si / Al ratio and nBAS ext Shows results that match the order of ).

[0067] [Characterization of Mo-supported Zeolites]

[0069] Figure 7 shows the Mo / (Si+Al) ratio based on XPS of the Mo-supported zeolite sample, Figure 8 shows the UV-VIS-DRS spectrum of the Mo-supported zeolite sample, Figure 9 shows the Mo K-edge XANES of the Mo-supported zeolite sample, and Figure 10 shows the k of the Mo-supported zeolite sample 2 - Represents the magnitude of the weighted Fourier transform EXAFS spectrum. Table 3 shows the results of the elemental analysis of the Mo-supported zeolite sample.

[0070] Referring to Figure 7 and Table 3, the trend of Mo external distribution in the Mo-supported zeolite samples is consistent with the external Si / Al ratio, and no significant difference is observed in the overall Mo content (at the level of about 5 wt.%).

[0071] [Table 3]

[0072]

[0073] Mo / ZAT, which has the lowest external Al content, also has the lowest external Mo content, and the external Mo distribution appears in the order of Mo / Z > Mo / ZT > Mo / ZAT.

[0074] Referring to Fig. 8, compared to Mo / Z, the absorption bands of Mo / ZT and Mo / ZAT are better aligned with the Mo-O-Al species, indicating that the degree of Mo dispersion is slightly higher in these samples. This trend also correlates with the defect density identified in Fig. 4. This is because the defect sites act as anchors for the supported metal, contributing to the prevention of metal aggregation.

[0075] Referring to Fig. 9, the pre-edge peak appearing at 20,006 eV corresponds to the 1s-4d electronic transition, which is Mo within the sample 6+ It reflects the tetrahedral symmetry and is influenced by the structure and degree of aggregation of Mo. Additionally, edge peaks caused by 1s-5p transitions above 20,016 eV can provide information about domain size based on peak positions. In Mo-supported zeolite samples, all peaks appear at the same position, exhibiting a spectral pattern more similar to MoO3 than to Na2MoO4. Therefore, Mo-supported zeolite samples possess the same domain size and average local structure, indicating that Mo is in octahedral coordination.

[0076] Referring to Fig. 10, two major peaks appear in the Mo-supported zeolite samples, corresponding to Mo-O bonding (approx. 1.2 Å) and Mo-Mo scattering (approx. 3.1 Å), respectively. No distinct differences in the peaks are observed between the Mo-supported zeolite samples, and the Mo-Mo peak is related to the magnitude of the Mo dispersion, which remains nearly constant across all samples. In other words, there are no significant differences in the average local structure and geometry of the Mo species between the Mo-supported zeolite samples.

[0077] In the case of Mo / ZAT, even though external Al and Mo were significantly reduced and overall acidity was controlled, the average local Mo state was found to be no different from other samples. That is, differences in the distribution of Mo on the external surface do not affect the average local structure of Mo, and the average local structure of the Mo species is mainly determined by the Mo content.

[0079] [Catalytic Performance of Mo-Supported Zeolites in Shale Gas Dehydrogenation Aromatication]

[0081] Figures 11 to 13 show the shale gas aromaticization performance of Mo-supported zeolite samples. Figure 11 shows the total carbon conversion rate of the Mo-supported zeolite sample, Figure 12 shows the BTX yield of the Mo-supported zeolite sample, and Figure 13 shows the naphthalene selectivity of the Mo-supported zeolite sample.

[0082] Referring to Figure 11, the total carbon conversion rate of the simulated shale gas shows a similar trend in all samples during the first 4 hours of the reaction. The initial reactivity includes an induction period of about 2 hours. During this time, a hydrocarbon pool is formed, Mo undergoes a carburization process, and carbon-containing paper accumulates on the catalyst surface, processes that are essential for BTX production.

[0083] Referring to Fig. 12, the maximum BTX yield is reached within 4 hours of reaction, and thereafter, as the total carbon conversion rate decreases, the BTX yield also decreases. This means that each sample exhibits different deactivation behavior.

[0084] Compared to Mo / Z, Mo / ZT exhibits higher reaction stability, which is attributed to the reduction in external acidity (Al and Mo). Mo / ZAT demonstrates the best catalytic stability. This additional improvement in reaction stability can be attributed to factors such as further reduction in external acidity, increased micropore volume (providing shape selectivity), and increased mesopore surface area (enhancing the diffusion efficiency of carbon intermediates and coke precursors). As such, Mo / ZAT enhances the long-term stability of the catalyst by possessing more effective carbon intermediate diffusion and coke formation inhibition capabilities.

[0085] Referring to Figure 13, the naphthalene selectivity of Mo / ZAT is noticeably reduced. Since naphthalene acts as a precursor to coke and its formation can cause rapid deactivation of the catalyst, a reduction in selectivity is desirable. The reduced naphthalene selectivity in Mo / ZAT may be related to factors such as the deactivation of external Brønsted acid sites and a reduction in pore size due to coke accumulation. In other words, the low naphthalene selectivity in Mo / ZAT is associated with reduced external acidity and increased mesopore surface area. Furthermore, a higher ratio of acid sites to Mo species in the zeolite increases the likelihood of benzene being converted into heavy aromatic compounds through polycondensation reactions. Consequently, Mo / ZAT exhibits the least coke formation and accumulation, as well as the lowest coke combustion temperature, indicating that the overall coking process is minimized.

[0086] Mo / Z and Mo / ZA exhibit nearly identical deactivation trends. Analysis of coking behavior reveals that while there is no difference in total coke volume between Mo / Z and Mo / ZA, the coke combustion temperature of Mo / ZA is slightly higher than that of Mo / Z. This difference is likely due to the higher external Mo content in Mo / ZA. An increase in external Mo content may further promote the activation of carbon sources on the external surface, leading to the formation of more carbon deposits on the external surface of the MoCx species. These carbon deposits can interfere with the expression of shape selectivity of carbon intermediates within the ZSM-5 pores. This is confirmed by benzene selectivity. Benzene is a major product and exhibits a trend similar to that of BTX yield. Mo / ZA shows the lowest benzene selectivity during the first four hours of the reaction; since the total carbon conversion rate of all samples is nearly identical during this time, this can be interpreted as Mo / ZA exhibiting the lowest shape selectivity among the samples.

[0087] The olefin / aromatic ratio is closely related to the expression of morphoselectivity. Mo / Z and Mo / ZA have relatively high external Mo content, and their olefin / aromatic ratio increases sharply after 6 hours of reaction, which means that the formation of aromatic compounds is rapidly terminated. This phenomenon can be interpreted as a result of reduced morphoselectivity, leading to increased hard coke formation and a decrease in the amount of desirable products. On the other hand, Mo / ZAT, which has the lowest external Mo content, exhibits excellent resistance to the formation of undesirable olefins.

[0089] [Evaluation of Renewability of Mo-Supported Zeolite]

[0091] To expand the industrial applicability of shale gas aromatization and meet actual process requirements, it is crucial to enhance catalyst regenerability. To achieve this, the structural stability of the catalyst must be considered first, as structural degradation is inevitable during the regeneration cycle. While regenerability can be improved in short-term regeneration (two cycles) by controlling external acidity, this is due to increased reaction stability preventing rapid catalyst deactivation, rather than an improvement in structural stability or durability. Considering this, factors evaluating improved regenerability must include not only the recovery of initial activity but also structural stability related to dealumination and aluminum molybdate formation, which cause structural damage.

[0093] Figure 14 shows the regenerability of a Mo-supported zeolite sample based on the cumulative BTX yield (completely deactivated) over 15 hours, and Figure 15 shows the regenerability of a Mo-supported zeolite sample based on the initial activity of 4 hours. To evaluate regenerability, the regeneration temperature was set to 550°C based on TGA and DTG profiles.

[0094] Referring to Figure 14, Mo / ZAT shows the highest regenerative potential based on cumulative BTX yield over 15 hours of reaction, and the order is Mo / ZAT > Mo / ZT > Mo / Z.

[0095] Referring to Fig. 15, the recovery of activity of Mo / ZAT is more pronounced during the initial 4 hours, which means that Mo / ZAT maintains superior performance during the regeneration process compared to other samples. After 4 regenerations, Mo / ZAT exhibits an activity recovery rate of approximately 95% compared to the fresh sample. This can be a more practical characteristic for maximizing the utilization of the catalyst in actual industrial processes. Furthermore, the regeneration potential can be further enhanced by adjusting the reaction time before the catalyst becomes irreversibly deactivated.

[0097] Figure 16 shows a raw Mo-supported zeolite sample. 27 Figure 17 shows the Al MAS NMR spectrum of the Mo-supported zeolite sample regenerated five times. 27 Figure 18 shows the Al MAS NMR spectra of the raw sample and the reconstructed sample (EFAl P+O +Al-Mo B+D Represents the ) / FAl ratio (based on each peak area). After 5 regenerations to evaluate the structural stability of the Mo-supported zeolite sample 27The degree of dealumination and aluminum molybdate formation was analyzed using Al MAS NMR spectra. If dealumination and aluminum molybdate formation proceed due to the migration of Mo during the regeneration process, the framework may partially collapse.

[0098] Referring to Fig. 16, the Al phase that may exist in fresh Mo-supported ZSM-5 zeolite can be identified. The peaks at 55, 30, 0, 14, and -14 ppm represent aluminum within the tetrahedral framework (FAl, Framework Al) and extra-framework aluminum (EFAl), respectively. P , Penta-coordinated Al), octahedral (extra-framework) aluminum (EFAl) O , Octahedral Al), bulk aluminum molybdate (Al-Mo B , Bulk aluminum molybdate), dispersed aluminum molybdate (Al-Mo D , corresponds to Dispersed aluminum molybdate).

[0099] Referring to Fig. 17, Mo / ZAT is EFAl P (30ppm) and Al-Mo B It exhibits the lowest intensity in the (14 ppm) range, which means that dealumination and bulk aluminum molybdate formation occurred the least among the samples.

[0100] Referring to Fig. 18, the (EFAl of the raw sample and the reconstructed sample P+O +Al-Mo B+DThe overall resistance to dealuminization and aluminum molybdate formation was evaluated by comparing the ) / FAl ratio. Mo / ZAT exhibited the lowest variation and absolute value of this ratio, and dealuminization and Mo migration (including phase change and sintering) were most suppressed. This phenomenon is attributed to the reduced external Al and Mo content in Mo / ZAT. Additionally, defect sites appropriately introduced into ZAT can play a role in stabilizing the Mo species and suppressing Mo migration, thereby improving structural stability. Therefore, Mo / ZAT can be evaluated as the sample with the best structural stability.

[0101] Mo / ZT shows relatively improved regenerability, but (EFAl P+O +Al-Mo B+D The ratio of ) / FAl increases significantly, leading to extensive dealumination. This is attributed to excessive defect sites and intra-mesoporosity. These structural characteristics reduce thermal stability, which can weaken the durability of the catalyst and cause structural damage during repeated regeneration processes.

[0103] [Characterization of Regenerated Mo-Supported Zeolite]

[0105] TEM images were analyzed to investigate the morphology and distribution of Mo species in the spent and regenerated samples. In the Mo / Z-spent sample, large Mo particles were observed over a wide area, which contrasts with the other samples. The Mo / ZT-spent sample exhibited smaller Mo particles than the Mo / Z-spent sample, which may be due to a higher defect density. Since defect sites can act as anchors for the supported metal, metal aggregation is likely suppressed in the Mo / ZT-spent sample. In the Mo / ZAT-spent sample, no distinct Mo particles were observed on the outer surface, which may be related to the minimized external Al and Mo content in the original sample. Additionally, an appropriate defect density of ZAT may influence the inhibition of Mo's migration to the outer surface.

[0106] After five regeneration cycles, larger aggregated particles are observed on the outer surface of the Mo / Z-regenerated sample; these are likely Mo oligomers / clusters formed as Mo migrates to the outer surface under air calcination conditions. Mo cluster formation can be more pronounced in the absence of specific factors that inhibit Mo migration, such as controlling Al and Mo content or providing appropriate defect sites. Therefore, higher concentrations of Al and Mo in the outer surface region increase the likelihood of Mo aggregate formation on the exterior, which does not contribute to improved regeneration potential. Compared to the Mo / Z-regenerated sample, the Mo / ZT-regenerated sample exhibits smaller Mo particles on the outer surface and shows minimal changes in Mo shape and distribution, which is because Mo can be stabilized due to the influence of defect sites. In the Mo / ZAT-regenerated sample, compared to the Mo / ZAT-spent sample, no structural changes in the shape and distribution of Mo on the outer surface are observed. This is because the significantly reduced external Al and Mo content suppresses structural changes such as dealumination and the formation of aluminum molybdate. In addition, defect sites appropriately introduced into ZAT can enhance the interaction between Mo and the surface, thereby contributing to the stabilization of Mo in Mo / ZAT.

[0108] Figure 19 shows the TGA profile of the Mo-supported zeolite sample after the 4th use, and Figure 20 shows the hard / soft coke ratio of each sample after the 4th use of the Mo-supported zeolite sample (Spent-4th) and after the reaction of the raw Mo-supported zeolite sample (Spent-F).

[0109] Referring to Fig. 19, the combustion behavior of coke appears similar among the samples, but the sublimation behavior of Mo shows differences. In the inset image of Fig. 19, the relative weight of the Mo / Z-regenerated sample decreases sharply at 700–800°C, which corresponds to MoO3 sublimation, and the order of sublimation trends is Mo / Z-regenerated > Mo / ZT-regenerated > Mo / ZAT-regenerated. Since MoO3 clusters can be generated by Mo sintering under oxidizing conditions, Mo / ZAT has the highest interaction with the ZSM-5 surface, resulting in relatively the least formation of MoO3 clusters. This trend is correlated with the degree of dealumination and aluminum molybdate formation and may be associated with structural stability.

[0110] If the pore structure of the ZSM-5 framework is damaged due to dealumination and aluminum molybdate formation during the reaction-regeneration cycle, the expression of morph-selectivity for aromatic compounds may be inhibited, and as a result, hard coke formation is promoted; therefore, the hard / soft coke ratio is also related to the structural stability of the sample. In addition,

[0111] Referring to Figure 20, the hard / soft coke ratio of the Spent-F sample decreases as external acidity decreases, which can be interpreted as a result of reduced external coking (i.e., Mo / Z > Mo / ZT > Mo / ZAT). Also, the difference in ratio between Spent-F and Spent-4th becomes more pronounced as external acidity increases. Consequently, the hard / soft coke ratio is lowest in Mo / ZAT, and the difference between Spent-F and Spent-4th is also smallest in Mo / ZAT. This indicates that the shape selectivity is consistently maintained in Mo / ZAT with minimized external acidity during repeated reaction-regeneration cycles, implying that Mo / ZAT has superior structural stability compared to the other samples.

[0113] Specific embodiments of the present invention have been examined so far. Those skilled in the art will understand that the present invention may be embodied in modified forms without departing from the essential characteristics of the invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the claims, not by the foregoing description, and all variations within the scope of equivalents should be interpreted as being included in the present invention.

Claims

Claim 1 A zeolite-supported catalyst comprising: a zeolite; and a metal catalyst supported on the zeolite, wherein the zeolite is treated with a silicon-aluminum modifier and quaternary ammonium hydroxide before supporting the metal catalyst. Claim 2 A zeolite-supported catalyst according to claim 1, characterized in that the zeolite is treated with the silicon-aluminum modifier and then treated with the quaternary ammonium hydroxide. Claim 3 A zeolite-supported catalyst according to claim 1, characterized in that the zeolite comprises ZSM-5 and the metal catalyst comprises molybdenum. Claim 4 A zeolite-supported catalyst according to claim 1, characterized in that the silicon-aluminum modifier comprises ammonium hexafluorosilicate. Claim 5 A zeolite-supported catalyst according to claim 1, characterized in that the quaternary ammonium hydroxide comprises at least one of tetrapropylammonium hydroxide, cetyltrimethylammonium hydroxide, and tetramethylammonium hydroxide. Claim 6 A method for preparing a zeolite-supported catalyst comprising the steps of: preparing a zeolite; post-treating the zeolite with a silicon-aluminum modifier and quaternary ammonium hydroxide; and supporting a metal catalyst on the post-treated zeolite. Claim 7 A method for manufacturing a zeolite-supported catalyst according to claim 6, characterized in that the zeolite is treated with the silicon-aluminum modifier and then treated with the quaternary ammonium hydroxide. Claim 8 A method for manufacturing a zeolite-supported catalyst according to claim 6, characterized in that the zeolite comprises ZSM-5 and the metal catalyst comprises molybdenum. Claim 9 A method for manufacturing a zeolite-supported catalyst according to claim 6, characterized in that the silicon-aluminum modifier comprises ammonium hexafluorosilicate. Claim 10 A method for preparing a zeolite-supported catalyst according to claim 6, wherein the quaternary ammonium hydroxide comprises at least one of tetrapropylammonium hydroxide, cetyltrimethylammonium hydroxide, and tetramethylammonium hydroxide. Claim 11 A method for manufacturing a zeolite-supported catalyst according to claim 6, wherein the silicon-aluminum modifier performs dealumination, increase in external silicon content, and formation of defect sites with respect to the zeolite. Claim 12 A method for manufacturing a zeolite-supported catalyst according to claim 11, wherein the defect site formed by the silicon-aluminum modifier increases the mesopore volume of the zeolite. Claim 13 A method for manufacturing a zeolite-supported catalyst according to claim 11, characterized in that the defect site formed by the silicon-aluminum modifier provides a treatment route for the quaternary ammonium hydroxide in the zeolite.

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