Hydrogen transport method using dehydrogenation catalyst and liquid organic hydrogen carrier produced by waste polystyrene pyrolysis, dehydrogenation catalyst therefor, and method for producing same

Abstract

The present invention relates to a hydrogen transport method using a dehydrogenation catalyst and a liquid organic hydrogen carrier, a dehydrogenation catalyst therefor, and a method for producing same. More specifically, the present invention relates to a technology capable of effectively recycling waste polystyrene, wherein the waste polystyrene is converted into a liquid organic hydrogen carrier through pyrolysis, hydrogen is transported through hydrogenation and dehydrogenation, and a dehydrogenation catalyst having a high conversion rate and excellent coke resistance is used during dehydrogenation. A hydrogen transport method according to an embodiment of the present invention comprises: an aromatic compound production step of pyrolyzing waste polystyrene to produce an aromatic compound; a hydrogenation reaction step of combining hydrogen with the aromatic compound to produce a cyclic compound; and a dehydrogenation reaction step of releasing hydrogen from the cyclic compound having completely undergone the hydrogenation reaction, by using a dehydrogenation catalyst.

Description

Hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, the dehydrogenation catalyst, and the method for manufacturing the same

[0001] The present invention relates to a method for transporting hydrogen using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, the dehydrogenation catalyst, and a method for manufacturing the same. More specifically, the invention relates to a method for transporting hydrogen using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, the dehydrogenation catalyst, and a method for manufacturing the same, wherein waste polystyrene is pyrolyzed to convert it into a liquid organic hydrogen carrier (LOHC), hydrogen is transported through hydrogenation and dehydrogenation, and waste polystyrene can be effectively and practically recycled by using a dehydrogenation catalyst having a high conversion rate and excellent coke resistance during the dehydrogenation process.

[0002] Plastic pollution is an urgent global environmental issue. While plastic is lightweight, durable, and high-value due to its low cost, its surging use is placing a significant burden on the environment. Since its mass production began in the 1950s, usage has increased exponentially, leading to a sharp rise in the volume of plastic waste. Most of this waste is disposed of in landfills or incinerated, potentially polluting the environment through various pathways, including soil, groundwater, and the atmosphere. Consequently, the importance of developing efficient methods to recycle plastic waste is becoming increasingly apparent.

[0003] Currently, the utilization of plastic waste is evolving into mechanical and chemical methods. While mechanical recycling is simple and cost-effective, its applications are limited, whereas chemical recycling can chemically decompose plastic polymers to generate raw materials usable in various chemical industries. Among these, aromatic compounds hold significant value as they serve as important raw materials in diverse industries, including plastics, synthetic fibers, paints, pharmaceuticals, and pesticides. Currently, many companies and researchers are exploring methods to produce aromatic compounds from plastic waste, and these technologies can provide sustainable solutions to meet the demand for these compounds. For example, Nuwayo has demonstrated a method to convert polystyrene (PS) into aryl ketones and organosulfur compounds, and Zhiwen has elucidated the process of converting polyethylene terephthalate (PET) into p-xylene and ethylene glycol.

[0004] Polystyrene is produced at a rate of over 25 million tons annually and is widely used in food packaging, insulation, and synthetic rubber. However, polystyrene is a low-quality recycled plastic characterized by low density and susceptibility to contamination, with a recycling rate of only 0.9% even after mechanical recycling. Since polystyrene consists of 74% aromatic rings by weight and has a lower decomposition temperature of 310°C compared to other polymers, aromatic compounds can be obtained in high yields through thermal decomposition. Thanks to these characteristics, if a method to efficiently upcycle polystyrene is developed, the problem of its low recycling rate could be resolved.

[0005] Furthermore, Liquid Organic Hydrogen Carrier (LOHC) systems are a promising technology for storing and transporting hydrogen (H2) using aromatic compounds. In these systems, hydrogen can be transported by being stored and released through the repetitive hydrogenation and dehydrogenation processes of aromatic compounds. Although H2 has a low volumetric energy density, LOHCs allow for long-term storage at ambient temperatures and pressures, and efficient hydrogen storage and transport are possible due to compatibility with existing petroleum infrastructure. LOHC technology is attracting attention as an important method to solve the problems of hydrogen storage and transport. However, among existing LOHC materials, homocyclic LOHCs are fossil fuel-based and have environmental issues, while heterocyclic LOHCs have problems with complex synthesis processes and low yields.

[0006] Therefore, given the current need for the development of eco-friendly and high-yield LOHC technologies, if a method is proposed to utilize waste polystyrene as LOHC through thermal decomposition, it would not only significantly expand the related technology sector but also enable the practical and efficient recycling of polystyrene, thereby drastically reducing the amount of plastic waste.

[0007] The present invention was created to solve the aforementioned problems, and more specifically, aims to provide a method for transporting hydrogen using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene, which can significantly reduce the amount of plastic waste by practically and efficiently recycling polystyrene, by presenting a method of producing LOHC by pyrolyzing waste polystyrene and transporting hydrogen using the produced LOHC.

[0008] In addition, since hydrogen release is an endothermic process, a high-temperature environment is required during the hydrogen release step of the hydrogen transport process; therefore, the present invention aims to provide a hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene using an effective catalyst for this process.

[0009] In addition, the present invention aims to provide a method for manufacturing a dehydrogenation catalyst that is well activated and inhibits coke formation by supporting Pt on an excellent support.

[0010] In addition, the present invention aims to provide a dehydrogenation catalyst that is well activated and inhibits coke formation by supporting Pt on an excellent support.

[0011] A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene according to one embodiment of the present invention is characterized by comprising: an aromatic compound production step of producing an aromatic compound by pyrolyzing waste polystyrene; a hydrogenation reaction step of producing a cyclic compound by combining hydrogen with the aromatic compound; and a dehydrogenation reaction step of releasing hydrogen using a dehydrogenation catalyst on the cyclic compound after the hydrogenation reaction is completed.

[0012] More specifically, the above-mentioned aromatic compound production step is characterized by using waste polystyrene, such as polystyrene beads, styrofoam, big red cups, tableware, and scale plates.

[0013] More specifically, the aromatic compound production step is characterized by being performed in a semi-batch reactor comprising: a reaction vessel in which the thermal decomposition of waste polystyrene takes place; and a collection vessel for collecting the liquid product by cooling the thermal decomposition product of waste polystyrene.

[0014] More specifically, the reaction vessel is characterized by comprising: an N2 supply pipe that receives N2 from an N2 supply unit; a heater that surrounds the reaction vessel or is provided on the outer wall of the reaction vessel; and a connecting pipe that sends the thermal decomposition product of waste polystyrene produced in the reaction vessel to a collection tank.

[0015] More specifically, the aromatic compound production step is characterized by being performed in an N2 environment at a temperature in the range of 200 ℃ to 500 ℃ for 0.2 to 10 hours.

[0016] More specifically, the aromatic compound production step is characterized by being performed at a temperature range of 325°C to 375°C for 0.25 to 5 hours.

[0017] More specifically, the collection tank is characterized by further including a vent that releases the remaining gaseous product after cooling the pyrolysis product collected from the reaction tank.

[0018] More specifically, the hydrogenation reaction step is characterized by being performed in an autoclave reactor.

[0019] More specifically, the autoclave reactor is characterized by having an H2 supply pipe that receives H2 from an H2 supply unit; and a heater that surrounds the autoclave reactor or is provided on the outer wall of the autoclave reactor.

[0020] More specifically, the hydrogenation reaction step is characterized by mixing and stirring the aromatic compound produced in the aromatic compound production step with a Ru / C catalyst, and supplying H2 to produce a cyclic compound.

[0021] More specifically, the hydrogenation reaction step is characterized by being carried out for 0.5 hours to 2 hours at a temperature of 30°C to 90°C in an autoclave reactor filled with H2 gas at a pressure of 40 bar to 60 bar.

[0022] More specifically, the hydrogen transport method is characterized by further including a distillation step for distilling the reactant after the hydrogenation reaction is completed, following the hydrogenation reaction step.

[0023] More specifically, the dehydrogenation reaction step is characterized by using a dehydrogenation catalyst in which Pt is supported in the pores of a mesoporous Al2O3 support.

[0024] More specifically, the above dehydrogenation catalyst is characterized by containing 1 wt% of Pt.

[0025] More specifically, the dehydrogenation catalyst is characterized by being produced by: a mesoporous NA-Al2O3 support synthesis step in which a mesoporous nanosheet-assembled Al2O3 (NA-Al2O3) support is synthesized by a hydrothermal synthesis method; and a step of supporting Pt particles in the pores of the mesoporous NA-Al2O3 support using an impregnation method.

[0026] More specifically, the dehydrogenation catalyst is characterized by being produced by: a mesoporous SDP-Al2O3 support synthesis step of synthesizing a mesoporous SDP-Al2O3 support using a solvent-deficient precipitation method; and a step of supporting Pt particles in the pores of the mesoporous SDP-Al2O3 support using an impregnation method.

[0027] A method for preparing a dehydrogenation catalyst according to one embodiment of the present invention comprises: a mesoporous NA-Al2O3 support synthesis step of synthesizing a mesoporous nanosheet-assembled Al2O3 (NA-Al2O3) support by a hydrothermal synthesis method; a mesoporous SDP-Al2O3 support synthesis step of synthesizing a mesoporous SDP-Al2O3 support by a solvent-deficient precipitation method; and a Pt particle loading step of loading Pt particles into the pores of the mesoporous NA-Al2O3 support and the mesoporous SDP-Al2O3 support by an impregnation method.

[0028] A dehydrogenation catalyst according to one embodiment of the present invention is characterized by being produced by the dehydrogenation catalyst manufacturing method.

[0029] A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene according to one embodiment of the present invention has the effect of enabling sustainable and eco-friendly recycling of waste polystyrene by producing a liquid organic hydrogen carrier, which is an aromatic compound utilized for hydrogen storage and transport, from discarded plastic waste, and transporting hydrogen through the repeated hydrogenation and dehydrogenation of this compound.

[0030] In addition, a hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene according to one embodiment of the present invention has the effect of extending the lifespan of the catalyst and enabling the catalyst to operate more efficiently by further including a distillation step to remove polycyclic compounds.

[0031] In addition, the hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene according to one embodiment of the present invention has the effect of increasing the hydrogen transport efficiency using the liquid organic hydrogen carrier by enabling dehydrogenation while consuming less energy by supporting platinum on a mesoporous Al2O3 support having superior dehydrogenation performance compared to commercial platinum catalysts.

[0032] In addition, the method for manufacturing a dehydrogenation catalyst according to one embodiment of the present invention has the effect of being able to manufacture a catalyst that has high Pt dispersion and high activity and can reduce the formation of coke.

[0033] In addition, the dehydrogenation catalyst according to one embodiment of the present invention has the effect of having high Pt dispersion and high activity, and being able to reduce the formation of coke.

[0034] Therefore, the hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene according to one embodiment of the present invention has the effect of simultaneously pursuing carbon neutrality and a leap toward a hydrogen economy.

[0035] FIG. 1 is a flowchart illustrating the sequence of a hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene according to one embodiment of the present invention.

[0036] FIG. 2 is a diagram illustrating the structure of a semi-batch reactor in which an aromatic compound production step takes place in a hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene according to one embodiment of the present invention.

[0037] FIG. 3 is a schematic diagram illustrating the structure of an autoclave reactor in which a hydrogenation reaction step takes place in a hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene according to one embodiment of the present invention.

[0038] FIG. 4 is a flowchart illustrating the sequence of a method for manufacturing a dehydrogenation catalyst according to one embodiment of the present invention.

[0039] Figure 5 is a graph showing XRD results according to the catalyst support.

[0040] Figure 6 shows TEM images according to the support of the catalyst.

[0041] Figure 7 is a graph showing the results of ECH dehydrogenation according to the catalyst support.

[0042] Figure 8 is a graph showing XRD results according to the manufacturing method of the alumina support.

[0043] Figure 9 is a figure showing TEM images according to the manufacturing method of an alumina support.

[0044] Figure 10 is a graph showing the results of ECH dehydrogenation according to the manufacturing method of the alumina support.

[0045] Figure 11 is a table showing compounds identified in the GC-MS spectrum of the residue collected after distilling hydrogenated pyrolysis oil.

[0046] Figure 12 is a diagram illustrating the coke formation process that can be derived from hydrocarbon 12 shown in Figure 11.

[0047] Figure 13 is a graph showing the GC-MS spectrum of the residue shown in Figure 11.

[0048] Figure 14 is a graph comparing the dehydrogenation performance of hydrogenated LOHC depending on whether it is distilled.

[0049] The following detailed description of the invention refers to the accompanying drawings, which illustrate specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that various embodiments of the invention are different but need not be mutually exclusive. For example, specific shapes, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in relation to one embodiment.

[0050] Furthermore, it should be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the invention. Accordingly, the following detailed description is not intended to be taken in a limiting sense, and the scope of the invention is limited only by the appended claims, including all equivalents thereof, provided appropriately described. Similar reference numerals in the drawings refer to the same or similar functions across various aspects.

[0051] Hereinafter, in order to enable a person skilled in the art to easily practice the present invention, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

[0052]

[0053] First, with reference to FIGS. 1 to 3, a method for transporting hydrogen using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene according to one embodiment of the present invention will be described.

[0054]

[0055] FIG. 1 is a flowchart illustrating the sequence of a hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene according to one embodiment of the present invention, FIG. 2 is a diagram illustrating the structure of a semi-batch reactor in which an aromatic compound production step occurs in a hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene according to one embodiment of the present invention, and FIG. 3 is a diagram illustrating the structure of an autoclave reactor in which a hydrogenation reaction step occurs in a hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene according to one embodiment of the present invention.

[0056] As illustrated in FIG. 1, the hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene according to the present invention comprises an aromatic compound production step (S100) of producing an aromatic compound by pyrolyzing waste polystyrene, a hydrogenation reaction step (S200) of producing a cyclic compound by combining hydrogen (H2) with the aromatic compound, and a dehydrogenation reaction step (S300) of releasing hydrogen using a dehydrogenation catalyst on the cyclic compound after the hydrogenation reaction is completed.

[0057]

[0058] First, the above-mentioned aromatic compound production step is a step of producing aromatic compounds by thermally decomposing waste polystyrene.

[0059] More specifically, the waste polystyrene mentioned above may include polystyrene beads, styrofoam, large red cups, tableware, and scale plates.

[0060] More specifically, the aromatic compound production step is carried out in a semi-batch reactor consisting of a reaction vessel in which the thermal decomposition of waste polystyrene takes place and a collection vessel in which the thermal decomposition product of waste polystyrene is cooled to collect the liquid product, as shown in FIG. 2.

[0061] The above reaction vessel is characterized by having an N2 supply pipe that receives N2 from an N2 supply unit, a heater that surrounds the reaction vessel or is installed on the outer wall of the reaction vessel, and a connecting pipe that sends the thermal decomposition product of waste polystyrene produced in the reaction vessel to a collection tank, wherein waste polystyrene and a magnetic stirrer are introduced into the reaction vessel, and the waste polystyrene in the reaction vessel is evenly thermally decomposed as the reaction vessel is heated by the heater and the magnetic stirrer performs stirring simultaneously.

[0062] The pyrolysis occurring in the above-mentioned reaction vessel is carried out in an N2 environment at a temperature range of 200 ℃ to 500 ℃ for 0.2 to 10 hours. More specifically, the pyrolysis is characterized by being carried out at a temperature range of 325 ℃ to 375 ℃ for 0.25 to 5 hours. This is because the decomposition temperature of polystyrene is approximately 310 ℃, and it was confirmed that the conversion rate of polystyrene continuously increased as the temperature increased and the heating time increased, as shown in [Table 1]. In addition, the conversion rate when polystyrene beads, Styrofoam, Big Red cups, tableware, and scale plates were pyrolyzed at 375 ℃ for 2 hours was as shown in [Table 2], from which it was confirmed that waste polystyrene is also sufficiently converted under the above-mentioned pyrolysis conditions. The conversion rate can be calculated as in [Equation 1], and the weight of the reaction vessel includes the weight of the stirrer, reactants, and / or products.

[0063]

[0064] Temperature (℃)Time (h)Conversion (%)250203002032528.0350240.9375277.23750.2525.03750.552.8375171.2375483.9

[0065] CommodityConversion (%)Beads77.2Foam81.5BRC73.3CT64.0SP43.1

[0066]

[0067] An experiment to pyrolyze waste polystyrene was conducted according to one embodiment of the present invention. After performing pyrolysis at 375 °C for 2 hours, gas chromatography (GC) and Fourier transform nuclear magnetic resonance (FT-NMR) analysis of the collected products revealed that most of the products were monoaromatic compounds. Monoaromatic compounds are chemically stable, have high hydrogen storage efficiency, and are easy to reuse, making them suitable for use as LOHCs.

[0068]

[0069] Next, the collection tank cools the pyrolysis product collected from the reaction tank. The collection tank may be equipped with an internal or external cooler to cool the incoming material, and any gaseous products remaining from the cooled material that are not liquefied may be discharged to the outside through a vent provided in the collection tank. This is to remove light gaseous byproducts while leaving only the target material, the aromatic compound.

[0070]

[0071] Next, the hydrogenation reaction step is a step of forming a cyclic compound by bonding hydrogen to the aromatic compound produced in the aromatic compound production step.

[0072] The above hydrogenation reaction step is performed in a batch reactor, so that the temperature, pressure, etc. inside the reactor can be easily controlled and maintained while hydrogenation is in progress.

[0073] In particular, according to one embodiment of the present invention, an autoclave may be used as the batch reactor, because the autoclave has the advantage of being able to create a high temperature and high pressure environment while simultaneously enabling continuous monitoring and control.

[0074] In addition, as illustrated in FIG. 3, the batch reactor is characterized by having an H2 supply pipe that receives H2 from an H2 supply unit and a heater that surrounds the batch reactor or is installed on the outer wall of the batch reactor. The H2 supply pipe is a device for introducing hydrogen for hydrogenation and is a device for increasing the hydrogen pressure inside the reactor. More specifically, since hydrogenation occurs more effectively when the hydrogen partial pressure inside the reactor is higher, the gas inside the batch reactor can be flushed with H2 to remove remaining air and filled with H2 before the hydrogenation reaction begins, thereby preparing for the hydrogenation reaction. In particular, the H2 gas can be filled into the batch reactor at a pressure in the range of 40 bar to 60 bar.

[0075] Afterwards, the aromatic compound contained in the batch reactor is stirred and heated simultaneously to create an optimal environment for the hydrogenation reaction, thereby allowing the hydrogenation reaction to occur. At this time, a Ru / C catalyst can be added as a hydrogenation catalyst to promote the hydrogenation reaction.

[0076] At this time, the hydrogenation reaction step is characterized by being performed for 0.5 hours to 2 hours in the range of 30 ℃ to 90 ℃. This condition was determined considering reaction efficiency and energy efficiency, as the Ru / C catalyst showed excellent efficiency in the range of 30 ℃ to 90 ℃ as shown in [Table 3] and showed a conversion rate of over 90% within 2 hours in the same temperature range. In addition, the conversion rate when pyrolysis oil obtained from the pyrolysis of polystyrene beads, styrofoam, big red cups, tableware, and scale plates was hydrogenated at 30 ℃ to 90 ℃ for 2 hours was as shown in [Table 4], and from this, it was confirmed that pyrolysis oil obtained by pyrolyzing waste polystyrene was also sufficiently converted under the above hydrogenation conditions.

[0077] Temperature (℃)Time (h)Conversion (%)Yield (%)EBiPBMCHECHiPCH30294.972.67.73.06.20.450297.646.26.45.734.92.07 00.596.654.16.94.926.21.470110033.26.08.349.92.6702100008.383.08.6

[0078] PolystyreneTemperature (℃)Time (h)Conversion (%)Yield (%)MCHECHiPCHBeads7021008.383.08.6Foam90210010.477.711.9BRC90210012.269.917.9CT90210013.071.016.0SP90210011.969.019.1

[0079]

[0080] In addition, a hydrogen transport method according to one embodiment of the present invention may further include a distillation step in which the reactant from which the hydrogenation reaction is completed is distilled after the hydrogenation reaction step. This is a step for removing polycyclic compounds by distilling the product of the hydrogenation reaction, and since polycyclic compounds have complex molecular structures and large sizes, they can be removed by distillation. Polycyclic compounds may be present in the product of the thermal decomposition of polystyrene, and there is a problem that the dehydrogenation catalyst may be rapidly deactivated if polycyclic compounds are present. This is because polycyclic compounds play a significant role in coke formation, thereby forming coke and interfering with the activity of the catalyst.

[0081] As shown in FIGS. 11 and 13, among the compounds identified by GC-MS spectrum of the residue remaining after distilling the reaction product after hydrogenation in a hydrogen transport method according to one embodiment of the present invention, polycyclic compounds accounted for a large amount, and polycyclic compound No. 12 of FIG. 11, which accounts for the largest proportion of residual hydrocarbons as shown in FIG. 12, can easily become a coke precursor and form coke through various routes.

[0082] Therefore, removing large molecular weight polycyclic compounds through distillation can suppress the formation of coke, which hinders the activity of the dehydrogenation catalyst and shortens its lifespan, thereby improving the efficiency of the catalyst.

[0083]

[0084] Next, the dehydrogenation reaction step is a step of placing the cyclic compound, upon completion of the hydrogenation reaction, at a location to transport hydrogen and releasing hydrogen using a dehydrogenation catalyst.

[0085] The dehydrogenation catalyst used in the above dehydrogenation reaction step is characterized by being a dehydrogenation catalyst in which Pt is supported in the pores of a mesoporous Al2O3 support. More specifically, the Pt is characterized by being 1 wt% of the total weight of the catalyst.

[0086] More specifically, the dehydrogenation catalyst is characterized by being prepared by a mesoporous NA-Al2O3 support synthesis step in which a mesoporous nanosheet-assembled Al2O3 (NA-Al2O3) support is synthesized by a hydrothermal synthesis method, and a Pt loading step in which Pt particles are loaded into the pores of the mesoporous NA-Al2O3 support using an impregnation method.

[0087] The above step of synthesizing a mesoporous NA-Al2O3 support involves dissolving aluminum nitrate 9-hydrate, urea, and potassium sulfate in deionized water, hydrothermally treating the solution at 100°C to 250°C, filtering and drying the precipitate obtained as a result of the hydrothermal treatment, and then calcining it in a muffler furnace at 600°C for 2 hours to obtain a mesoporous NA-Al2O3 support. At this time, the temperature rise rate of the muffler furnace is maintained at 5°C per minute. Hydrothermal synthesis is a method of synthesizing compounds using water or aqueous solutions in a high-temperature and high-pressure environment, and is a method capable of producing high-purity nanoparticles. By creating an alumina support through hydrothermal synthesis, a precise pore structure can be formed, allowing for efficient platinum support and efficient catalyst activation.

[0088] Next, the Pt loading step utilizes an impregnation method in which potassium(II) tetrachloroplatinate (K2PtCl4) is dissolved in deionized water, and the mesoporous NA-Al2O3 support produced in the mesoporous NA-Al2O3 support synthesis step is loaded into the solution. Afterward, the wet powder is dried in an electric oven at 80°C, and then the dried powder is calcined in a muffler furnace at 300°C for 2 hours. At this time, the temperature rise rate of the muffler furnace is maintained at 5°C per minute. The impregnation method is a technique used to evenly load active materials, such as metals, into the pores of a solid support, and is a method that can increase the activity and efficiency of the catalyst by evenly loading the active material.

[0089] Or, more specifically, the dehydrogenation catalyst is characterized by being prepared by a mesoporous SDP-Al2O3 support synthesis step in which a mesoporous SDP-Al2O3 support is synthesized using a solvent-deficient precipitation method, and a Pt support step in which Pt particles are supported in the pores of the mesoporous SDP-Al2O3 support using an impregnation method.

[0090] The above step of synthesizing the mesoporous SDP-Al2O3 support involves mixing aluminum nitrate 9-hydrate and ammonium bicarbonate in a mortar for 20 minutes, and then calcining the mixed paste-form precipitate in a muffler furnace at 600°C for 2 hours to obtain a mesoporous SDP-Al2O3 support. At this time, the temperature rise rate of the muffler furnace is maintained at 5°C per minute. Solvent-deficient precipitation is a method of precipitating a substance in a solution by limiting the amount of solvent, and has the advantages of enabling precise control of particle size at a relatively low cost, forming a uniform pore structure, and obtaining a high-purity material.

[0091] Next, the Pt loading step utilizes an impregnation method in which potassium(II) tetrachloroplatinate (K2PtCl4) is dissolved in deionized water, and the mesoporous SDP-Al2O3 support produced in the mesoporous SDP-Al2O3 support synthesis step is loaded into the solution. Afterward, the wet powder is dried in an electric oven at 80°C, and then the dried powder is calcined in a muffler furnace at 300°C for 2 hours. At this time, the temperature rise rate of the muffler furnace is maintained at 5°C per minute.

[0092]

[0093] Next, with reference to FIG. 4, a method for manufacturing a dehydrogenation catalyst according to one embodiment of the present invention will be described.

[0094]

[0095] FIG. 4 is a flowchart illustrating the sequence of a method for manufacturing a dehydrogenation catalyst according to one embodiment of the present invention.

[0096] As illustrated in FIG. 4, a method for manufacturing a dehydrogenation catalyst according to one embodiment of the present invention is characterized by comprising: a mesoporous NA-Al2O3 support synthesis step in which a mesoporous nanosheet-assembled Al2O3 (NA-Al2O3) support is synthesized by a hydrothermal synthesis method; a mesoporous SDP-Al2O3 support synthesis step in which a mesoporous SDP-Al2O3 support is synthesized by a solvent-deficient precipitation method; and a Pt particle loading step in which Pt particles are loaded into the pores of the mesoporous NA-Al2O3 support and the mesoporous SDP-Al2O3 support by an impregnation method.

[0097] First, the mesoporous NA-Al2O3 support synthesis step is the step of synthesizing a mesoporous nanosheet-assembled Al2O3 (NA-Al2O3) support using a hydrothermal synthesis method.

[0098] More specifically, the step of synthesizing the mesoporous NA-Al2O3 support is a step of dissolving aluminum nitrate 9-hydrate, urea, and potassium sulfate in deionized water, then hydrothermally treating the solution at 100°C to 250°C, filtering and drying the precipitate obtained as a result of the hydrothermal treatment, and then calcining it in a muffler furnace at 600°C for 2 hours to obtain a mesoporous NA-Al2O3 support. At this time, the temperature rise rate of the muffler furnace is maintained at 5°C per minute.

[0099] Next, the step of synthesizing the mesoporous SDP-Al2O3 support is to synthesize the mesoporous SDP-Al2O3 support using the solvent-deficient precipitation method.

[0100] More specifically, the step of synthesizing the mesoporous SDP-Al2O3 support is a step of mixing aluminum nitrate 9-hydrate and ammonium bicarbonate in a mortar (mortar and pestle) for 20 minutes, and calcining the mixed paste-form precipitate in a muffler furnace at 600°C for 2 hours to obtain a mesoporous SDP-Al2O3 support. At this time, the temperature rise rate of the muffler furnace is maintained at 5°C per minute.

[0101] Finally, the Pt particle loading step is a step of loading Pt particles into the pores of the mesoporous NA-Al2O3 support and the mesoporous SDP-Al2O3 support using an impregnation method.

[0102] More specifically, potassium(II) tetrachloroplatinate (K2PtCl4) is dissolved in deionized water, and an impregnation method is used in which the mesoporous SDP-Al2O3 support produced in the synthesis step of the mesoporous SDP-Al2O3 support is supported in the solution. After that, the wet powder is dried in an electric oven at 80°C, and then the dried powder is calcined in a muffler furnace at 300°C for 2 hours. At this time, the temperature rise rate of the muffler furnace is maintained at 5°C per minute.

[0103] In this way, by preparing a catalyst by supporting Pt in the pores of a mesoporous NA-Al2O3 support produced by hydrothermal synthesis and a mesoporous SDP-Al2O3 support produced by solvent-deficient precipitation, the structure of the pores of the support can be diversified to increase catalytic efficiency, and there is an effect of being able to produce a catalyst that exhibits optimized performance under various reaction conditions.

[0104]

[0105] Next, a dehydrogenation catalyst according to one embodiment of the present invention will be described.

[0106] A dehydrogenation catalyst according to one embodiment of the present invention is manufactured by the above-described manufacturing method and includes both alumina supports produced by hydrothermal synthesis and solvent-deficient precipitation, thereby providing a precise pore structure and a uniform pore distribution, respectively, enhancing catalyst loading and activation efficiency, and having the effect of enabling performance optimized for mass production and various reaction conditions.

[0107] Furthermore, if an incomplete reaction occurs or hydrocarbons decompose at high temperatures during the dehydrogenation reaction, coke—a solid material with a high concentration of accumulated carbon—may form. This can block or coat the surface of the catalyst, thereby reducing its activity. Since this leads to a decrease in catalyst efficiency, the formation of coke in the dehydrogenation reaction must be suppressed. The dehydrogenation catalyst according to one embodiment of the present invention has the effect of promoting a complete dehydrogenation reaction with high crystallinity, which not only reduces the amount of coke generated but also allows the catalyst to remain active even if a small amount of coke is produced due to the high dispersion of Pt.

[0108]

[0109] [Experimental Example]

[0110] The present invention will be explained in more detail through the following experimental examples. The embodiments described in the following experimental examples are intended to provide examples of the present invention, and the scope of the present invention is not limited to the following embodiments.

[0111]

[0112] Example 1. Pt / NA-Al2O3 prepared by a mesoporous NA-Al2O3 support synthesis step in which a mesoporous nanosheet-assembled Al2O3 (NA-Al2O3) support is synthesized by a hydrothermal synthesis method, and a Pt loading step in which Pt particles are loaded into the pores of the mesoporous NA-Al2O3 support using an impregnation method.

[0113]

[0114] Example 2. Pt / SDP-Al2O3 prepared by a mesoporous SDP-Al2O3 support synthesis step in which a mesoporous SDP-Al2O3 support is synthesized using a solvent-deficient precipitation method, and a Pt loading step in which Pt particles are loaded into the pores of the mesoporous SDP-Al2O3 support using an impregnation method.

[0115]

[0116] Comparative Example 1. Pt / Com-Al2O3 prepared by supporting Pt particles in the pores of a commercial Al2O3 support using an impregnation method.

[0117]

[0118] Comparative Example 2. Pt / CeO2 prepared by supporting Pt particles in the pores of a commercial CeO2 support using an impregnation method.

[0119]

[0120] Comparative Example 3. Pt / SiO2 prepared by supporting Pt particles in the pores of a commercial SiO2 support using an impregnation method.

[0121]

[0122] Comparative Example 4. Pt / TiO2 prepared by supporting Pt particles in the pores of a commercial TiO2 support using an impregnation method.

[0123]

[0124] Experimental Example 1. Evaluation of catalyst performance according to catalyst support

[0125] We intended to select the best support by evaluating the performance of the catalysts of Comparative Examples 1 to 4 using different supports.

[0126] 1-1. X-ray Diffraction (XRD) Results

[0127] As shown in Fig. 5, X-ray diffraction (XRD) tests were performed on the catalysts of Comparative Examples 1 to 4, and for Comparative Examples 1, 2, and 4, no distinct peaks for the metal or oxidized Pt phases were present. However, for Comparative Example 3, a peak appeared at 39.8°, confirming that the Pt was not evenly loaded and had aggregated.

[0128] 1-2. Transmission Electron Microscopy (TEM) Results

[0129] As shown in Fig. 6, when the catalysts of Comparative Examples 1 to 4 were observed by TEM, it was confirmed that the Pt particles were well dispersed in Comparative Examples 1, 2, and 4, but the Pt particles were aggregated in Comparative Example 3.

[0130] 1-3. Pt Dispersion Calculated via CO Pulse Chemiadsorption

[0131] The results of calculating the Pt dispersion of the catalysts of Comparative Examples 1 to 4 through CO pulse chemical adsorption are as shown in [Table 5]. Consequently, it was confirmed that the Pt particles were not properly dispersed in the catalyst of Comparative Example 3.

[0132] SamplePt dispersion (%)Pt / Com-Al2O335.0Pt / CeO230.6Pt / SiO27.6Pt / TiO238.5

[0133] 1-4. N2 adsorption isotherm and surface area

[0134] For the catalysts of Comparative Examples 1 to 4, information regarding the pores was obtained by measuring the amount of nitrogen gas adsorbed when the pressure changed at a constant temperature, and the surface area was calculated using BET theory based on this data. The results are as shown in [Table 6]. Consequently, it was confirmed that Comparative Example 1 had the largest surface area.

[0135] SampleSurface area (m 2 g -1 )Pore volume (cm 3 g -1 )Pore size (nm)Pt / Com-Al2O3164.20.4210.3Pt / CeO238.90.1515.7Pt / SiO25.60.0532.2Pt / TiO242.50.4672.3

[0136] 1-5. Dehydrogenation of Ethylcyclohexane (ECH)

[0137] The thermal decomposition products of polystyrene are mainly styrene monomers, which produce ethylcyclohexane (ECH) when completely hydrogenated. Therefore, the catalysts of four comparative examples were reduced, and the dehydrogenation reaction of ECH was carried out in a temperature range of 250 °C to 350 °C under an N2 stream. As shown in Fig. 7, the conversion rate of Comparative Examples 1, 2, and 4 increased with increasing temperature, whereas almost no conversion occurred in Comparative Example 3; in particular, in the case of Comparative Example 1, it was confirmed that almost all of the ECH was dehydrogenated at a temperature of 300 °C. In particular, the liquid products collected during the reaction were analyzed by GC-MS, and in the case of the dehydrogenation of Comparative Example 1, it was confirmed that most of the dehydrogenation products were ethylbenzene rather than styrene. Through this, it was confirmed that the catalyst of Comparative Example 1 is efficiently activated even at high temperatures.

[0138] 1-6. Sintering

[0139] Based on the experimental results above, Pt / Com-Al2O3 exhibited the best catalytic performance due to high Pt dispersion, complete ECH conversion, and a high surface area, while Pt / SiO2 showed very low efficiency in the reaction due to low Pt dispersion and Pt aggregation.

[0140]

[0141] Experimental Example 2. Evaluation of Pt / Al2O3 catalyst according to support manufacturing method

[0142] Since the dehydrogenation catalyst made of an Al2O3 support in Experimental Example 1 above showed the best dehydrogenation performance, the dehydrogenation catalysts of Example 1, Example 2, and Comparative Example 1 made of various Al2O3 supports were compared.

[0143] 2-1. X-ray Diffraction (XRD) Results

[0144] As shown in FIG. 8, X-ray diffraction (XRD) tests were performed on the catalysts of Examples 1 and 2 and Comparative Example 1, and all three catalysts showed a γ-phase, and no Pt peak (111) appeared. In addition, in the case of Example 1, an Al2O3 peak (222) appeared at 39.5°, which is a result indicating the high crystallinity of NA-Al2O3 and that Pt is well dispersed on the support.

[0145] 2-2. Transmission Electron Microscopy (TEM) Results

[0146] As shown in Fig. 9, TEM observation of the catalysts of Examples 1 and 2 and Comparative Example 1 revealed that Example 1 was in the form of a nanosheet assembly, Example 2 was in the form of small particles, and Comparative Example 1 was in the form of large particles. This result was consistent with the XRD analysis results.

[0147] 2-3. Pt Dispersion Calculated via CO Pulse Chemiadsorption

[0148] The results of calculating the Pt dispersion of the catalysts of Examples 1 and 2 and Comparative Example 1 through CO pulse chemical adsorption are as shown in [Table 7]. Consequently, it was confirmed that the Pt particles were better dispersed in the catalysts of Examples 1 and 2 than in the catalyst of Comparative Example 1.

[0149] SamplePt dispersion (%)Pt / NA-Al2O369.7Pt / SDP-Al2O370.8Pt / Com-Al2O335.0

[0150] 2-4. N2 Adsorption Isotherm and Surface Area

[0151] For the catalysts of Examples 1 and 2 and Comparative Example 1, information about the pores was obtained by measuring the amount of nitrogen gas adsorbed when the pressure changed at a constant temperature, and the surface area was calculated using BET theory based on this data. The results are as shown in [Table 8]. Consequently, it was confirmed that Example 2 had the largest surface area.

[0152] SampleSurface area (m 2 g -1 ) a Pore ​​volume (cm 3 g -1 ) b Pore ​​size (nm) b Pt / NA-Al2O3143.61.249.3Pt / SDP-Al2O3255.90.745.2Pt / Com-Al2O3164.20.4210.3

[0153] 2-5. Dehydrogenation of Ethylcyclohexane (ECH)

[0154] The pyrolysis products of polystyrene are mainly styrene monomers, which produce ethylcyclohexane (ECH) when fully hydrogenated. Therefore, the catalysts of Examples 1 and 2 and Comparative Example 1 were reduced, and the dehydrogenation reaction of ECH was carried out in a temperature range of 250 °C to 350 °C under an N2 stream. As shown in Fig. 10, the catalyst of Example 1 exhibited the highest ECH conversion rate across all temperature ranges, which is attributed to its nanosheet form and larger pores. In particular, the liquid products collected during the reaction were analyzed by GC-MS, confirming that for all three catalysts, the majority of the dehydrogenation products were ethylbenzene rather than styrene. This confirmed that catalysts supported by alumina are efficiently activated even at high temperatures.

[0155] 2-6. Sintering

[0156] Based on the experimental results above, Pt / NA-Al2O3 exhibits excellent dehydrogenation efficiency because the use of a support with high crystallinity not only provides a more uniform and precise pore structure but also facilitates the influx and dispersion of Pt particles due to the presence of large pores. Additionally, Pt / SDP-Al2O3 has the effect of enabling the loading of a larger number of Pt particles due to the use of a support with a high surface area.

[0157]

[0158] Experimental Example 3. Evaluation of the activity of Pt / Al2O3 catalyst by distillation

[0159] To determine the utility of the distillation step for distilling aromatic compounds after the hydrogenation reaction is complete, the dehydrogenation performance of the Pt / Com-Al2O3 catalyst was evaluated depending on whether distillation was performed. To evaluate this, the conversion rate according to temperature and time was compared for cases where distillation was performed at 140 °C for 5 minutes and cases where distillation was not performed.

[0160] As shown in Fig. 14, in the case of distillation, dehydrogenation occurred very stably depending on temperature and time, and it was confirmed that complete dehydrogenation occurred, especially at 300°C. However, in the case of non-distillation, almost no dehydrogenation occurred.

[0161]

[0162] Although the present invention has been described above with specific details such as specific components, limited embodiments, and drawings, this is provided only to aid in a more comprehensive understanding of the invention, and the invention is not limited to the above embodiments, and a person skilled in the art to which the invention belongs can make various modifications and variations from this description.

[0163] Accordingly, the scope of the present invention should not be limited to the embodiments described above, and all modifications equivalent to or equivalent to the claims set forth below, as well as the claims described below, shall be considered to fall within the scope of the concept of the present invention.

Claims

1. Aromatic compound production step of producing aromatic compounds by thermally decomposing waste polystyrene; A hydrogenation reaction step of forming a cyclic compound by bonding hydrogen (H2) to the above aromatic compound; and A method for transporting hydrogen using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, comprising: a dehydrogenation reaction step in which hydrogen is released using a dehydrogenation catalyst on a cyclic compound after the hydrogenation reaction is completed.

2. In Paragraph 1, The above aromatic compound production step is, A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by using waste polystyrene such as polystyrene beads, styrofoam, big red cups, tableware, and scale plates.

3. In Paragraph 1, The above aromatic compound production step is, A reaction vessel in which the thermal decomposition of waste polystyrene takes place; and A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by being performed in a semi-batch reactor comprising a collection tank for cooling the pyrolysis product of waste polystyrene to collect the liquid product.

4. In Paragraph 3, The above reaction vessel is, N2 supply pipe receiving N2 from the N2 supply section; A heater that surrounds the reaction vessel or is provided on the outer wall of the reaction vessel; and A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by having a connecting pipe that sends the pyrolysis product of waste polystyrene produced in a reaction tank to a collection tank.

5. In Paragraph 1, The above aromatic compound production step is, A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by being performed in an N2 environment at a range of 200 ℃ to 500 ℃ for 0.2 to 10 hours.

6. In Paragraph 5, The above aromatic compound production step is, A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by being performed for 0.25 to 5 hours in the range of 325 ℃ to 375 ℃.

7. In Paragraph 3, The above collection group is, A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by further including a vent for releasing remaining gaseous products after cooling the pyrolysis product collected from the reaction vessel.

8. In Paragraph 1, The above hydrogenation reaction step is, Hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by being performed in a batch reactor 9. In Paragraph 1, The above batch reactor is, H2 supply pipe receiving H2 from the H2 supply unit; and A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by having a heater that surrounds the batch reactor or is provided on the outer wall of the batch reactor.

10. In Paragraph 1, The above hydrogenation reaction step is, A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by mixing and stirring the aromatic compound produced in the above-mentioned aromatic compound production step with a Ru / C catalyst, and supplying H2 to produce a cyclic compound.

11. In Paragraph 1, The above hydrogenation reaction step is, In a batch reactor filled with H2 gas at a pressure ranging from 40 bar to 60 bar, A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by being performed for 0.5 to 2 hours in the range of 30 ℃ to 90 ℃.

12. In Paragraph 1, The above hydrogen transport method is, After the hydrogenation reaction step, A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by further including a distillation step for distilling the reactant after the hydrogenation reaction is completed.

13. In Paragraph 1, The above dehydrogenation reaction step is, A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by using a dehydrogenation catalyst in which Pt is supported in the pores of a mesoporous Al2O3 support.

14. In Paragraph 13, The above dehydrogenation catalyst is, A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene, characterized by containing 1 wt% Pt, and a dehydrogenation catalyst.

15. In Paragraph 13, The above dehydrogenation catalyst is, A mesoporous NA-Al2O3 support synthesis step for synthesizing a mesoporous nanosheet-assembled Al2O3 (NA-Al2O3) support by a hydrothermal synthesis method; and A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by being manufactured by a Pt loading step in which Pt particles are loaded into the pores of the mesoporous NA-Al2O3 support using an impregnation method.

16. In Paragraph 13, The above dehydrogenation catalyst is, A mesoporous SDP-Al2O3 support synthesis step for synthesizing a mesoporous SDP-Al2O3 support using a solvent-deficient precipitation method; and A hydrogen transport method using a liquid organic hydrogen carrier produced by the pyrolysis of waste polystyrene and a dehydrogenation catalyst, characterized by being manufactured by a Pt loading step in which Pt particles are loaded into the pores of the mesoporous SDP-Al2O3 support using an impregnation method.

17. A mesoporous NA-Al2O3 support synthesis step for synthesizing a mesoporous nanosheet-assembled Al2O3 (NA-Al2O3) support by a hydrothermal synthesis method; A mesoporous SDP-Al2O3 support synthesis step for synthesizing a mesoporous SDP-Al2O3 support using a solvent-deficient precipitation method; and A method for preparing a dehydrogenation catalyst comprising: a Pt particle loading step of loading Pt particles into the pores of the mesoporous NA-Al2O3 support and the mesoporous SDP-Al2O3 support using an impregnation method.

18. Dehydrogenation catalyst prepared by the manufacturing method of Claim 17 above

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