Hydrothermal treatment method of MWW type zeolite supports and Manufacturing method of Mo-based methane dehydroaromatization catalysts using MWW type zeolite supports dealuminated by hydrothermal treatment

Abstract

The present invention relates to a hydrothermal treatment method for a MWW-type zeolite support and a method for manufacturing a Mo-based methane dehydrogenation aromaticization catalyst using a MWW-type zeolite support that has been dealuminated by hydrothermal treatment, wherein the method comprises the steps of: synthesizing a proton-type zeolite support; and hydrothermally treating the synthesized proton-type zeolite support at 300°C to 450°C under an air flow containing a certain amount of water vapor to obtain a dealuminated zeolite support, thereby providing a hydrothermally treated MWW-type zeolite support and a Mo-based methane dehydrogenation aromaticization catalyst manufactured using the same. According to the present invention, Brønsted acid sites can be controlled and hard coke formation reduced through dealumination treatment of zeolite, thereby increasing the selectivity of BTX (benzene, toluene, xylene) in the MDA (methane dehydroaromatication) reaction. The performance of the manufactured Mo-based methane dehydroaromatication catalyst can be improved.

Description

Technology Field

[0001] The present invention relates to a hydrothermal treatment method for a MWW type zeolite support for dealuminization and a method for producing a Mo-based methane dehydrogenation aromaticization catalyst using a MWW type zeolite support that has been dealuminized by hydrothermal treatment. Background Technology

[0002] The high-value conversion of methane, widely known as the main component of natural gas, is considered one of the most important strategies for securing sustainable energy and chemical sources in the future. Against this backdrop, active research is currently being conducted on high-value conversions, such as the conversion of methane into hydrogen, olefins, oxygenated compounds, and aromatic compounds. Currently, indirect conversion methods that utilize methane as a feedstock have the disadvantage of consuming a large amount of energy due to their highly endothermic nature and inevitably producing CO2. Therefore, research is being conducted on direct methane conversion methods that are environmentally friendly and practically applicable even on a small scale.

[0003] The methane dehydroaromatization reaction is a process for converting methane due to the demand for aromatic compounds such as benzene, toluene, and xylene (hereinafter referred to as 'BTX'). Zeolite supports capable of providing Brønsted acid sites are widely used for the methane dehydroaromatization reaction, and catalytic performance can be enhanced by supporting Mo (molybdenum) metal on the zeolite. Among zeolites, MCM-22, a MWW type with 10-MR and 12-MR pores, is widely used. In MCM-22 zeolites supported with Mo, the Mo species act as dehydrogenation sites for methane to produce C2 intermediates, while simultaneously, the Brønsted acid sites of MCM-22 form aromatics within the zeolite pores.

[0004] However, Brønsted acid sites also play a role in lowering the selectivity of BTX (benzene, toluene, xylene) by simultaneously forming coke. Therefore, catalysts with appropriate acid sites must be developed to improve the performance of the methane dehydroaromatication reaction.

[0005] Dealumination of zeolites is a method that can effectively control acid sites by selectively removing aluminum (Al) atoms within the zeolite structure. Zeolites can be dealuminated through hydrothermal or acid treatment, and this process is widely used industrially for catalytic processing. Prior art literature

[0006] (Patent Document 0001) KR 10-2295224 B1 (2021.08.24) The problem to be solved

[0007] According to one aspect of the present invention, a hydrothermal treatment method for a MWW type zeolite support for dealuminization and a method for producing a Mo-based methane dehydroaromatication catalyst using a MWW type zeolite support that has been dealuminized by hydrothermal treatment are provided.

[0008] According to one aspect of the present invention, there is to provide a hydrothermal treatment method for a MWW type zeolite support that can control Brønsted acid sites and reduce hard coke formation through dealumination treatment of the zeolite, thereby increasing the selectivity of BTX (benzene, toluene, xylene) in the MDA (methane dehydroaromatication) reaction, and a method for manufacturing a Mo-based methane dehydroaromatication catalyst using a dealumination-treated MWW type zeolite support.

[0009] According to one aspect of the present invention, a hydrothermal treatment method for a MWW type zeolite support that can improve the performance of a methane dehydroaromatication (MDA) catalyst and increase the production yield of aromatic compounds, and a method for manufacturing a Mo-based methane dehydroaromatication catalyst using a dealuminated MWW type zeolite support are provided.

[0011] The problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0012] A hydrothermal treatment method for an MWW type zeolite support according to one aspect of the present invention may include: a step of synthesizing a proton-type zeolite support; and a step of hydrothermally treating the synthesized proton-type zeolite support at 300°C to 450°C under an air flow containing a certain amount of water vapor to obtain a dealuminated zeolite support.

[0013] According to one embodiment, the step of synthesizing the proton-type zeolite support can be performed by synthesizing a zeolite support having a Si / Al ratio of 5 to 60.

[0014] According to one embodiment, the step of obtaining the dealuled zeolite support comprises 1 to 80 mol% of water vapor and 50 to 5000 mL·min -1 It can be processed under the airflow.

[0015] According to one embodiment, the step of obtaining the dealuminated zeolite support comprises using 1 to 100 mL·h of deionized water. -1 It is possible to process the sequence while injecting at a fixed rate.

[0016] According to one embodiment, the step of synthesizing the proton-type zeolite support comprises: a step of preparing an MCM-22 zeolite precursor; a step of synthesizing the prepared MCM-22 zeolite precursor by stirring it under conditions of 100 to 500 rpm; a step of obtaining a solid product by heat-treating the synthesized MCM-22 zeolite precursor for 6 to 12 days at a temperature of 120 to 150 ℃ and a rotation condition of 10 to 100 rpm; a step of obtaining a calcined MCM-22 zeolite by heat-treating the solid product for 3 to 48 hours under conditions of a constant air flow rate and 400 to 650 ℃; and a step of ion-exchange treating the calcined MCM-22 zeolite. and the step of heat-treating the ion-exchanged MCM-22 zeolite for 3 to 48 hours under conditions of a constant air flow and 400 to 650 ℃ to obtain a protonated MCM-22 zeolite support; may be included.

[0017] According to one embodiment, the step of preparing the MCM-22 zeolite precursor comprises: a step of preparing a precursor solution by dissolving hexamethyleneimine (HMI), sodium aluminate, and sodium hydroxide in deionized water; and a step of adding fuming silica to the precursor solution to obtain an MCM-22 zeolite precursor having a Si / Al ratio of 5 to 60; wherein the sodium aluminate may have a composition of 355 wt% Al2O and 45 wt% Na2O.

[0018] According to one embodiment, the step of obtaining the calcined MCM-22 zeolite is 50 to 5000 mL·min -1 1~5 ℃·min under airflow -1 Heat treatment can be performed at a heating rate of 400 to 650 ℃ for 3 to 48 hours.

[0019] According to one embodiment, the step of ion exchange treatment of the calcined MCM-22 zeolite involves adding the calcined MCM-22 zeolite to an aqueous NH4NO3 solution and stirring at room temperature for 12 to 24 hours, wherein Na among the components of the calcined MCM-22 zeolite + Ion exchange treatment is possible.

[0020] According to one embodiment, the step of obtaining the protonated MCM-22 zeolite support is 50 to 5000 mL·min -1 1~5 ℃·min under airflow -1 A proton-type MCM-22 zeolite support can be obtained by calcining at a heating rate of 400–650 ℃ for 12–24 hours.

[0021] A method for preparing a Mo-based methane dehydrogenation aromaticization catalyst using a MWW type zeolite support that has been dealuminated by hydrothermal treatment according to one aspect of the present invention may comprise: a step of supporting Mo (molybdenum) on a proton-type MCM-22 zeolite support that has been hydrothermally treated through an impregnation method; a step of drying the proton-type MCM-22 zeolite support supported with Mo at 60 to 80 ℃ for 12 to 24 hours; and a step of synthesizing a Mo-based methane dehydrogenation aromaticization catalyst by calcining the proton-type MCM-22 zeolite support supported with Mo that has undergone the drying process at a temperature of 500 to 600 ℃ and under a constant air flow rate for 3 to 48 hours.

[0022] According to one embodiment, the step of supporting Mo (molybdenum) on a hydrothermally treated proton-type MCM-22 zeolite support through the impregnation method comprises

[0023] Ammonium heptamolybdate tetrahydrate[(NH4)6Mo7O 24 Mo (molybdenum) can be supported by impregnating a hydrothermally treated protonated MCM-22 zeolite support with an aqueous solution of [·4H2O].

[0024] According to one embodiment, the step of supporting Mo (molybdenum) on a hydrothermally treated protonate MCM-22 zeolite support through the impregnation method may support Mo (molybdenum) on the hydrothermally treated protonate MCM-22 zeolite support with a supporting amount of 1 to 10 weight percent.

[0025] According to one embodiment, the step of synthesizing a Mo-based methane dehydrogenation aromaticization catalyst by heat treatment is 250 to 350 mL·min -1 1~5 ℃·min under airflow -1 It can be fired at 500~600 ℃ at a heating rate.

[0026] According to one embodiment, the hydrothermally treated protonated MCM-22 zeolite support may be a protonated MCM-22 zeolite support hydrothermally treated by the hydrothermally treated method of the MWW type zeolite support described above. Effects of the invention

[0027] According to the present invention, a zeolite support of the MWW type (proton type MCM-22) can be modified and dealuminization can be performed through hydrothermal treatment.

[0028] According to the present invention, Brønsted acid sites can be controlled and hard coke formation reduced through dealumination treatment of zeolite, thereby increasing the selectivity of BTX (benzene, toluene, xylene) in the MDA (methane dehydroaromatication) reaction.

[0029] According to the present invention, the performance of a methane dehydrogenation aromaticization (MDA) catalyst can be improved, and the production yield of aromatic compounds can be increased. Brief explanation of the drawing

[0030] FIG. 1 is a diagram showing a hydrothermal treatment method of an MWW type zeolite support according to one embodiment of the present invention. FIG. 2 is a diagram showing the step of synthesizing a proton-type zeolite support in a hydrothermal treatment method of an MWW-type zeolite support according to one embodiment of the present invention. FIG. 3 is a diagram showing the zeolite precursor manufacturing step in a hydrothermal treatment method of an MWW type zeolite support according to one embodiment of the present invention. FIG. 4 is a diagram showing a method for manufacturing a Mo-based methane dehydrogenation aromaticization catalyst using a MWW type zeolite support that has been dealuminated by hydrothermal treatment according to one embodiment of the present invention. Figure 5 is a figure showing data obtained by measuring Py adsorption FT-IR and NH3-TPD to confirm the change in acid sites of a Mo-based methane dehydrogenation aromaticization catalyst according to one embodiment of the present invention. Figure 6 is a diagram showing data measuring the MDA reaction of a Mo-based methane dehydrogenation aromaticization catalyst according to one embodiment of the present invention. FIG. 7 is a diagram showing measurement data including the MDA reaction of a catalyst hydrothermally treated at 200 to 600 °C in a Mo-based methane dehydrogenation aromaticization catalyst according to one embodiment of the present invention. FIG. 8 is a diagram showing data obtained by performing coke analysis of a Mo-based methane dehydrogenation aromaticization catalyst according to one embodiment of the present invention. Specific details for implementing the invention

[0031] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The advantages and features of the present invention, and the methods for achieving them, will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in different forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and to ensure that the spirit of the present invention is sufficiently conveyed to those skilled in the art, and the present invention is defined only by the scope of the claims. Throughout the entire specification, the same reference numerals refer to the same components.

[0032] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, 'comprises' and / or 'comprising' do not exclude the presence or addition of one or more other components, steps, actions, and / or elements to the mentioned components, steps, actions, and / or elements. Furthermore, as they are based on preferred embodiments, the reference numerals presented in the order of description are not necessarily limited to that order.

[0034] The present invention will be described below with reference to the attached drawings.

[0035] FIG. 1 is a diagram showing a hydrothermal treatment method for an MWW type zeolite support according to one embodiment of the present invention, FIG. 2 is a diagram showing a step of synthesizing a proton type zeolite support in a hydrothermal treatment method for an MWW type zeolite support according to one embodiment of the present invention, and FIG. 3 is a diagram showing a step of manufacturing a zeolite precursor in a hydrothermal treatment method for an MWW type zeolite support according to one embodiment of the present invention.

[0036] Referring to FIG. 1, a hydrothermal treatment method for an MWW type zeolite support according to one embodiment of the present invention may include a step of synthesizing a proton type zeolite support (S100) and a hydrothermal treatment step (S200).

[0037] The step (S100) of synthesizing the above proton-type zeolite support can be performed by synthesizing a zeolite support with a Si / Al ratio of 5 to 60. For example, it can be performed by synthesizing a zeolite support with a Si / Al ratio of 15, 30, or 50.

[0038] Referring to FIG. 2, the step of synthesizing the proton-type zeolite support (S100) comprises: a step of preparing an MCM-22 zeolite precursor (S110); a step of synthesizing the prepared MCM-22 zeolite precursor by stirring under conditions of 100 to 500 rpm (S120); a step of obtaining a solid product by heat-treating the synthesized MCM-22 zeolite precursor for 6 to 12 days at a temperature of 120 to 150 ℃ and a rotation condition of 10 to 100 rpm (S130); a step of obtaining a calcined MCM-22 zeolite by heat-treating the solid product for 3 to 48 hours under conditions of a constant air flow and 400 to 650 ℃ (S140); a step of ion-exchange treating the calcined MCM-22 zeolite (S150); and a step of heat-treating the ion-exchanged MCM-22 zeolite under a constant air flow and It may include a step (S160) of obtaining a proton-type MCM-22 zeolite support by heat treatment for 3 to 48 hours under conditions of 400 to 650 ℃.

[0039] At this time, the step of manufacturing the MCM-22 zeolite precursor (S110) may include, with reference to FIG. 3, a step of manufacturing a precursor solution (S112) and a step of obtaining the MCM-22 zeolite precursor (S114).

[0040] The above precursor solution preparation step (S112) can be performed by dissolving hexamethyleneimine (HMI), sodium aluminate, and sodium hydroxide in deionized water to produce the precursor solution.

[0041] The above sodium aluminate may be composed of a mixture of 355% by weight of Al2O and 45% by weight of Na2O.

[0042] The above MCM-22 zeolite precursor obtaining step (S114) can obtain an MCM-22 zeolite precursor having a Si / Al ratio of 5 to 60 by adding fuming silica to the precursor solution prepared through the above precursor solution preparation step (S112).

[0043] In the step (S140) of obtaining the above-mentioned calcined MCM-22 zeolite, 50 to 5000 mL·min -1 1~5 ℃·min under airflow -1 Heat treatment can be performed at a heating rate of 400 to 650 ℃ for 3 to 48 hours.

[0044] In the step (S150) of ion exchange treatment of the calcined MCM-22 zeolite, the calcined MCM-22 zeolite is added to an aqueous NH4NO3 solution and stirred at room temperature for 12 to 24 hours, so that among the components of the calcined MCM-22 zeolite, Na + Ion exchange treatment is possible. Among the components of the above-mentioned calcined MCM-22 zeolite, Na + The ion exchange treatment can be repeated one or more times.

[0045] The step (S160) of obtaining the above protonated MCM-22 zeolite support is 50 to 5000 mL·min -1 1~5 ℃·min under airflow -1 A proton-type MCM-22 zeolite support can be obtained by calcining at a heating rate of 400–650 ℃ for 12–24 hours.

[0046] The above hydrothermal treatment step (S200) can obtain a dealuminated zeolite support by hydrothermally treating the synthesized proton-type zeolite support at 300°C to 450°C under an air flow containing a certain amount of water vapor.

[0047] In the hydrothermal treatment step (S200) for obtaining the dealuminated zeolite support, 1 to 80 mol% of water vapor is contained and 50 to 5000 mL·min -1 It can be processed under the airflow.

[0048] And, at this time, 1~5 mL·h of deionized water -1 It is possible to process the sequence while injecting at a fixed rate.

[0050] FIG. 4 is a diagram showing a method for manufacturing a Mo-based methane dehydrogenation aromaticization catalyst using a MWW type zeolite support that has been dealuminated by hydrothermal treatment according to one embodiment of the present invention.

[0051] Referring to FIG. 4, a method for manufacturing a Mo-based methane dehydrogenation aromaticization catalyst using a MWW type zeolite support that has been dealuminated by hydrothermal treatment according to one embodiment of the present invention may include a Mo (molybdenum) supporting step (310), a drying step (S320), and a catalyst synthesis step (S330) by calcination treatment.

[0052] The above Mo (molybdenum) loading step (310) can load Mo (molybdenum) onto a hydrothermally treated proton-type MCM-22 zeolite support through an impregnation method.

[0053] Here, the hydrothermally treated protonated MCM-22 zeolite support may be a protonated MCM-22 zeolite support hydrothermally treated by the hydrothermally treated method of the MWW type zeolite support described above.

[0054] In the above Mo (molybdenum) loading step (310), ammonium heptamolybdate tetrahydrate [(NH4)6Mo7O containing a Mo (molybdenum) component is used. 24 Mo (molybdenum) can be supported by impregnating a hydrothermally treated protonated MCM-22 zeolite support with an aqueous solution of [·4H2O].

[0055] In the above Mo (molybdenum) loading step (310), Mo (molybdenum) can be loaded onto a hydrothermally treated protonated MCM-22 zeolite support with a loading amount of 1 to 10 weight percent. For example, Mo (molybdenum) can be loaded onto a hydrothermally treated protonated MCM-22 zeolite support with a loading amount of 6 weight percent.

[0056] The above drying step (S320) can dry the proton-type MCM-22 zeolite support loaded with Mo at 60 to 80 ℃ for 12 to 24 hours.

[0057] The catalyst synthesis step (S330) by the above calcination treatment can synthesize a Mo-based methane dehydrogenation aromaticization catalyst by heat-treating the Mo-supported proton-type MCM-22 zeolite support, which has undergone the above drying process, at a temperature of 500 to 600 ℃ and under a constant air flow rate for 3 to 48 hours.

[0058] In the catalyst synthesis step (S330) by the above calcination treatment, 50 to 5000 mL·min -1 1~5 ℃·min under airflow -1 It can be fired at 500~600 ℃ at a heating rate.

[0060] Below, more specific examples will be provided regarding the hydrothermal treatment method of a MWW type zeolite support according to the present invention and the method for manufacturing a Mo-based methane dehydrogenation aromaticization catalyst using a MWW type zeolite support treated with dealumination by hydrothermal treatment.

[0062] 1. Synthesis of Zeolite Support

[0063] MCM-22 (MWW type zeolite) was obtained from the MCM-22 precursor.

[0064] Hexamethyleneimine (HMI, 99%, Sigma-Aldrich), sodium aluminate (about 55% Al2O3 and 45% Na2O, Sigma-Aldrich), and sodium hydroxide (98%, anhydrous pellet, Sigma-Aldrich) were dissolved in 50 mL of deionized water (DI water) in a polypropylene bottle. Then, fuming silica (Cab-O-Sil M-5, Cabot Corporation) was added to the solution.

[0065] The final molar composition of the mixture is 100 SiO2: x Al 3+ : y Na + : 49.3 HMI: 4400 H2O, with a Si / Al ratio of approximately 15( x : y It was made so that it became = 6.4:23.9).

[0066] The mixture prepared for the synthesis of MCM-22 was stirred at room temperature in a stirrer (200 rpm) until the mixture became a homogenized gel.

[0067] Subsequently, the gel was transferred to a Teflon liner, placed in a stainless steel autoclave, and sealed. Hydrothermal synthesis was carried out in an oven at 135 °C for 11 days while rotating the autoclave at 60 rpm. After the reaction was complete, the autoclave was quenched and cooled with tap water. After sufficient washing and centrifugation, the solid product was dried at 70 °C prior to calcination.

[0068] The dried product that became MCM-22 is 500 mL·min -1 1 ℃·min under airflow -1 Calcined MCM-22 zeolite was obtained by calcining at 550 ℃ for 12 hours at a heating rate.

[0069] To obtain a protonated zeolite support (H-MCM-22), MCM-22 underwent an ion exchange process. For this purpose, 1 g of MCM-22(C) was added to 100 g of a 1 M aqueous NH4NO3 solution (98%, Sigma-Aldrich) and stirred using a mixer at room temperature for at least 12 hours. Na + The ion exchange process was repeated three times to ensure sufficient ion exchange. After ion exchange, the product was dried overnight at 70 °C, and finally 300 mL·min -1 1 ℃·min under airflow -1 H-MCM-22 zeolite support (proton type zeolite support) was obtained by calcining at 550 ℃ for 12 hours at a heating rate.

[0071] 2. Hydrothermal treatment of zeolite support

[0072] Hydrothermal treatment of an H-MCM-22 zeolite support with a Si / Al ratio of approximately 15 was performed using an air flow containing 10 mol% water vapor (approx. 400 mL·min -1 It was performed under ). This treatment was carried out in a kiln at specific temperatures (400, 500, 600 ℃). H-MCM-22 (approx. 1.0 g) was dispersed and placed in a quartz glass container. When the target temperature was reached, 2 mL·h of deionized water was added. -1 It was injected at a fixed rate, and the line connected to the quartz tube of the kiln was covered with heating tape to provide 10 mol% of steam.

[0073] That is, a dealuminated H-MCM-22 zeolite support was obtained by hydrothermal treatment.

[0075] 3. Preparation of Mo-based Methane Dehydrogenation Aromatication Catalyst

[0076] Ammonium heptamolybdate tetrahydrate[(NH4)6Mo7O 24An aqueous solution of [·4H2O, 99% purity, Sigma-Aldrich] was impregnated onto a hydrothermally treated H-MCM-22 zeolite support. The amount of Mo (molybdenum) impregnated was fixed at 6 wt%.

[0077] After impregnation, dry at 70 ℃ overnight, then 1 ℃·min -1 300 mL·min at 550 ℃ for 12 hours at a heating rate -1 It was fired under an airflow.

[0079] 4. Characteristic Analysis

[0080] For the samples for characterization analysis, the H-MCM-22 zeolite support was named 'M', and the dealuminated H-MCM-22 zeolite support was named 'M_x(x = 400, 500, 600)'.

[0081] For the samples for characterization, the Mo-supported H-MCM-22 zeolite support was named 'Mo / M', and the Mo-supported dealuminized H-MCM-22 zeolite support was named 'Mo / M_x(x = 400, 500, 600)'.

[0083] (1) Characteristics of scatter point change according to hydrothermal treatment temperature (400, 500, 600 ℃)

[0084] Py adsorption FT-IR and NH3-TPD were measured to confirm the scatter point changes of Mo / M and Mo / M_x (x = 400, 500, 600), and additionally, to confirm the state of Al in the zeolite after dealulumization treatment, M and M_x (x = 400, 500, 600) 27 Al MAS NMR was measured, and the analysis results are shown in Figure 5.

[0085] Figure 5 shows the characteristics of Mo / M and Mo / M_x (x = 400, 500, 600) according to hydrothermal treatment temperature, where (a) is Py adsorption FT-IR analysis data, (b) is NH3-TPD analysis data, and (c) is of M and M_x (x = 400, 500, 600).27 This is Al MAS NMR analysis data. In Figure 5(a), BAS and LAS represent Brønsted scatter sites and Lewis scatter sites, respectively.

[0086] In addition, the scatter points based on the results of Py adsorption FT-IR analysis and NH3-TPD analysis were quantitatively summarized and shown in Table 1.

[0087] In Figures 5(a) and 5(b), Py adsorption FT-IR analysis results confirmed that Brønsted acid sites and Lewis acid sites decreased as the hydrothermal treatment temperature increased. NH3-TPD analysis results also confirmed that Brønsted acid sites decreased as the hydrothermal treatment temperature increased. For example, Mo / M_400 (501.3 μmol·g -1 ) is Mo / M(530.2 μmol·g -1 Compared to ), it shows a slight decreasing trend in Brønsted acid points but maintains a relatively large number of acid points. It demonstrates that the hydrothermal treatment temperature of 400 ℃ exhibits superior acid point change characteristics compared to hydrothermal treatment temperatures of 500 ℃ or 600 ℃. In the case of Py-IR, the Mo / M_400 sample shows a slight increasing trend in Brønsted acid points compared to the Mo / M_500 and Mo / M_600 samples. This suggests that the reduction in BAS caused by dealumination due to hydrothermal treatment of Mo / M_400 generates additional BAS as Mo is supported.

[0088] In Fig. 5(c), to check the state of Al in the zeolite after dealulumization, M and M_x (x = 400, 500, 600) 27Based on the Al MAS NMR data, it was confirmed that Al was dealuminated within the zeolite framework by observing that the peak corresponding to 56 ppm tetrahedral Al decreased with increasing hydrothermal treatment temperature. It was confirmed that the decreasing trend of tetrahedral Al in the zeolite framework as the hydrothermal treatment temperature increases is identical to the decreasing trend of Brønsted acid sites in the Py adsorption FT-IR and NH3-TPD results. In other words, the hydrothermal treatment temperature of 400 ℃ demonstrates superior dealumination change characteristics compared to hydrothermal treatment temperatures of 500 ℃ or 600 ℃.

[0089]

[0091] (2) MDA reaction characteristics according to hydrothermal treatment temperature

[0092] The MDA (methane dehydroaromatization) reaction was carried out by pretreating 0.2 g of the Mo-based methane dehydroaromatization catalyst prepared through the specific example above at a temperature of 550 °C and under a He (helium) flow for 1 hour, and then 2 °C·min -1 The temperature was raised to 700 ℃ at a rate and switched to a reaction gas flow. To confirm catalytic activity after the methane completely covered the catalyst layer, initial catalyst measurements were started 10 minutes after the reactants were supplied.

[0093] The MDA reaction of Mo / M and Mo / M_x (x = 400, 500, 600) was analyzed, and the results are shown in Figure 6.

[0094] Figure 6(a) shows the MDA reaction result data for Mo / M and Mo / M_x (x = (b) 400, (c) 500, (d) 600), (e) shows the BT yield of all samples, and (f) shows the methane conversion rate. Here, all MDA reactions were carried out for 32 hours at 700 °C and atmospheric pressure. Reactant CH4 / Ar ( v / v =9 / 1) is approximately 1500 mL·g based on CH4. -1 ·h -1 supplied at the spatial velocity of.

[0095] Figures 6(a) to (d) show the MDA catalytic performance of four samples, namely Mo-based methane dehydroaromatication catalysts (Mo / M and Mo / M_x; x = 400, 500, 600), over a reaction time (TOS) of 32 hours. For clarity, Figures 6(e) and (f) show individual graphs of the benzene + toluene (BT) production rate and CH4 conversion rate as a function of TOS, respectively. All four catalysts exhibited similar time-dependent BT production trends, consisting of three main stages (activation, induction, and deactivation). The activation stage refers to a period during which little to no BT product is initially detected, as Mo oxide must be carbonized into active Mo carbide by the CH4 source (TOS approx. 0.2 hours). After proper activation, the BT product was first identified at TOS approx. 0.9 hours, which may represent the induction period. Subsequently, all four catalysts reached maximum BT generation rates, but at different TOS. Specifically, for Mo / M, Mo / M_400, Mo / M_500, and Mo / M_600, the rates were confirmed to be approximately 2.3, 3.8, 2.2, and 1.6 hours, respectively. Finally, the BT generation rates decreased due to inevitable deactivation.

[0096] The Mo / M_400 catalyst exhibited the best MDA performance, and referring to Figure 6(e), it shows that a higher BT generation rate than Mo / M was achieved throughout the entire TOS until complete catalyst deactivation. Regarding hydrothermal treatment (HT) time, 24 hours of treatment showed the best catalytic performance for Mo / M_400 compared to other reaction times of 12, 36, and 48 hours. In contrast, at higher hydrothermal treatment (HT) temperatures of 500 and 600 °C, the BT generation rate was not further improved but rather accelerated deactivation. Furthermore, the order of increase in BT generation rate was Mo / M_400 > Mo / M > Mo / M_500 > Mo / M_600. It was confirmed that this order of increase in BT generation rate closely corresponds to the order of increase in naphthalene generation rate throughout the entire TOS, as well as the order of increase in CH4 conversion rate between approximately 4 and 20 TOS hours, as shown in Figure 6(f). With respect to CH4 conversion rates, these results indicate that the spatial interaction between Mo and Brønsted acid sites (BAS) within the zeolite support differs for each catalyst.

[0097] In addition, it was confirmed that the BT yield after a 32-hour MDA reaction was in the order of Mo / M_400 > Mo / M > Mo / M_500 > Mo / M_600. Mo / M_400 exhibited the highest catalytic activity with a BT yield of 8.5%, and it was confirmed that it showed higher activity than Mo / M, which had a BT yield of approximately 7.7%. It was confirmed that appropriate dealumination and consequently reduced Brønsted acid sites through hydrothermal treatment at 400°C resulted in higher activity than Mo / M, and that catalytic activity actually decreased when the hydrothermal treatment temperature for dealumination was increased above 400°C. In particular, Mo / M_600 showed low performance with a maximum BT yield of 6.9% due to hydrothermal treatment under too harsh conditions.

[0098] FIG. 7 is a diagram showing measurement data including the MDA reaction of a catalyst hydrothermally treated at 200 to 600 °C in a Mo-based methane dehydrogenation aromaticization catalyst according to one embodiment of the present invention.

[0099] Figure 7 shows the results of screening performed for each of (Mo / M_x; x = 200, 250, 300, 350, 400, 450, 500, 600).

[0100] It is shown that the Mo / M_400 catalyst exhibits the highest performance. At hydrothermal treatment temperatures below 400°C, the catalyst performance tends to improve compared to the control catalyst, Mo / M. It is shown that at hydrothermal treatment temperatures above 400°C within a given reaction time, the performance of the catalysts is no longer improved. When comparing the characteristics of the catalysts based on the control catalyst, Mo / M, Mo / M_400 shows maximum performance, Mo / M_500 shows nearly similar performance, and Mo / M_600 shows inferior performance.

[0101] In other words, the catalyst sample prepared by hydrothermal treatment at 400 ℃ showed the best MDA reaction data.

[0103] (3) Analysis of the coke of the catalyst after MDA reaction at different hydrothermal treatment temperatures

[0104] FIG. 8 is a diagram showing data obtained by performing coke analysis of a Mo-based methane dehydrogenation aromaticization catalyst according to one embodiment of the present invention.

[0105] Figure 8 (a) is TGA measurement data showing the amount of coke accumulated in 10-MR or 12-MR pores according to reaction time of Mo / M and Mo / M_x (x = 400, 500, 600), and (b) is a graph showing the ratio of the amount of coke accumulated in 12-MR pores and the amount of coke accumulated in 10-MR pores according to reaction time of Mo / M and Mo / M_x (x = 400, 500, 600).

[0106] Coke analysis of Mo / M and Mo / M_x (x = 400, 500, 600) catalysts after the MDA reaction was performed through TGA and Ar adsorption / desorption analysis.

[0107] In the case of the Mo / M_400 catalyst dealularized by hydrothermal treatment, it can be confirmed that the amount of coke formed in the 10-MR pores is relatively smaller compared to the Mo / M catalyst due to the appropriately controlled BAS (which can promote the production of BT). This suggests that the stability of Mo / M_400 is enhanced due to the reduction in the amount of coke within the aromatic-selective 10-MR pores, as well as the 12-MR pores' capacity to accommodate improved coke deposits during long-term reactions.

[0109] Accordingly, through the present invention, a MWW type (proton type MCM-22) zeolite support can first be modified and dealuminated through hydrothermal treatment. Furthermore, through such dealuminated treatment of the zeolite, Brønsted acid sites can be controlled and hard coke formation can be reduced, thereby increasing the selectivity of BTX (benzene, toluene, xylene) in the MDA (methane dehydroaromatization) reaction. Ultimately, the performance of the methane dehydroaromatization (MDA) catalyst can be improved and the production yield of aromatic compounds can be increased.

[0110] The present invention can provide a modified MWW type (proton type MCM-22) zeolite support that has been dealuminated through hydrothermal treatment, and thereby a catalyst can be manufactured using the modified MWW type (proton type MCM-22) zeolite support. The catalyst manufactured using such a modified MWW type (proton type MCM-22) zeolite support can be effectively utilized in a wider variety of catalytic reaction fields requiring zeolite catalysts, in addition to the methane dehydroaromatication (MDA) reaction described above.

[0112] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

Claim 1 A hydrothermal treatment method for an MWW type zeolite support, comprising: a step of synthesizing a proton-type zeolite support; and a step of hydrothermally treating the synthesized proton-type zeolite support at 300°C to 450°C under an air flow containing a certain amount of water vapor to obtain a dealuminated zeolite support. Claim 2 The hydrothermal treatment method of a MWW type zeolite support according to claim 1, wherein the step of synthesizing the proton-type zeolite support is to synthesize a zeolite support having a Si / Al ratio of 5 to 60. Claim 3 In claim 1, the step of obtaining the dealuminated zeolite support comprises 1 to 80 mol% of water vapor and 50 to 5000 mL·min -1 Hydrothermal treatment method of an MWW type zeolite support under an airflow. Claim 4 In claim 1, the step of obtaining the dealuminated zeolite support comprises deionizing water at a rate of 1 to 100 mL·h -1 Hydrothermal treatment method of an MWW type zeolite support, which is hydrothermally treated while injecting at a fixed rate. Claim 5 In claim 1, the step of synthesizing the proton-type zeolite support comprises: a step of preparing an MCM-22 zeolite precursor; a step of synthesizing the prepared MCM-22 zeolite precursor by stirring under conditions of 100 to 500 rpm; a step of obtaining a solid product by heat-treating the synthesized MCM-22 zeolite precursor for 6 to 12 days at a temperature of 120 to 150 ℃ and a rotation condition of 10 to 100 rpm; a step of obtaining a calcined MCM-22 zeolite by heat-treating the solid product for 3 to 48 hours under conditions of a constant air flow rate and 400 to 650 ℃; and a step of ion-exchange treating the calcined MCM-22 zeolite. A hydrothermal treatment method for an MWW type zeolite support comprising: a step of heat-treating the ion-exchanged MCM-22 zeolite for 3 to 48 hours under conditions of a constant air flow rate and 400 to 650 ℃ to obtain a proton-type MCM-22 zeolite support. Claim 6 A hydrothermal treatment method for an MWW type zeolite support according to claim 5, wherein the step of preparing the MCM-22 zeolite precursor comprises: a step of preparing a precursor solution by dissolving hexamethyleneimine (HMI), sodium aluminate, and sodium hydroxide in deionized water; and a step of adding fuming silica to the precursor solution to obtain an MCM-22 zeolite precursor having a Si / Al ratio of 5 to 60, wherein the sodium aluminate has a composition of 355 wt% Al2O and 45 wt% Na2O. Claim 7 In claim 5, the step of obtaining the calcined MCM-22 zeolite is 50 to 5000 mL·min -1 1~5 ℃·min under airflow -1 Hydrothermal treatment method of an MWW type zeolite support, heat-treating at a heating rate of 400 to 650 ℃ for 3 to 48 hours. Claim 8 In claim 5, the step of ion exchange treatment of the calcined MCM-22 zeolite comprises adding the calcined MCM-22 zeolite to an aqueous NH4NO3 solution and stirring at room temperature for 12 to 24 hours, wherein Na among the components of the calcined MCM-22 zeolite + Hydrothermal treatment method of an MWW type zeolite support for ion exchange treatment. Claim 9 In claim 5, the step of obtaining the protonated MCM-22 zeolite support is 50 to 5000 mL·min -1 1~5 ℃·min under airflow -1 A hydrothermal treatment method for an MWW type zeolite support, wherein a proton-type MCM-22 zeolite support is obtained by calcining at a heating rate of 400 to 650 ℃ for 12 to 24 hours. Claim 10 A method for preparing a Mo-based methane dehydrogenation aromaticization catalyst using a MWW type zeolite support that has been dealuminated by hydrothermal treatment, comprising: a step of supporting Mo (molybdenum) on a proton-type MCM-22 zeolite support that has been hydrothermally treated through an impregnation method; a step of drying the proton-type MCM-22 zeolite support supported with Mo at 60 to 80 ℃ for 12 to 24 hours; and a step of synthesizing a Mo-based methane dehydrogenation aromaticization catalyst by calcining the Mo-supported proton-type MCM-22 zeolite support that has undergone the drying process at a temperature of 500 to 600 ℃ and under a constant air flow rate for 3 to 48 hours. Claim 11 In claim 10, the step of supporting Mo (molybdenum) on a hydrothermally treated protonate MCM-22 zeolite support through the impregnation method comprises ammonium heptamolybdate tetrahydrate [(NH4)6Mo7O 24 A method for preparing a Mo-based methane dehydrogenation aromaticization catalyst using a hydrothermally treated MWW type zeolite support that supports Mo (molybdenum) by impregnating a hydrothermally treated proton type MCM-22 zeolite support with an aqueous solution of ·4H2O. Claim 12 A method for manufacturing a Mo-based methane dehydrogenation aromaticization catalyst using a MWW type zeolite support that has been dealuled by hydrothermal treatment, wherein the step of supporting Mo (molybdenum) on a hydrothermally treated proton-type MCM-22 zeolite support through the impregnation method is to support Mo (molybdenum) on the hydrothermally treated proton-type MCM-22 zeolite support with a supporting amount of 1 to 10 weight%. Claim 13 In claim 10, the step of synthesizing a Mo-based methane dehydrogenation aromaticization catalyst by calcination treatment is 50 to 5000 mL·min -1 1~5 ℃·min under airflow -1 A method for preparing a Mo-based methane dehydrogenation aromaticization catalyst using a MWW type zeolite support that has been dealuminated by hydrothermal treatment, calcined at a heating rate of 500 to 600 ℃. Claim 14 A method for producing a Mo-based methane dehydrogenation aromaticization catalyst using a MWW-type zeolite support that has been dealuminated by hydrothermal treatment, wherein the hydrothermally treated protonated MCM-22 zeolite support is a protonated MCM-22 zeolite support that has been hydrothermally treated by the hydrothermal treatment method of any one of claims 1 to 9.

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