Catalyst for steam reforming of light oil, preparation method thereof, and hydrogen production method using same

Abstract

The present invention relates to a catalyst for steam reforming of waste plastic-derived light oil, a preparation method thereof, and a hydrogen production method using same. The present invention comprises: a mesoporous cerium-zirconium composite oxide carrier formed by combining cerium oxide and zirconium oxide in the form of a lattice-structured solid solution; and a non-noble metal-based active metal supported on the cerium-zirconium composite oxide carrier, wherein oxygen vacancies are generated as cerium ions in the lattice of the cerium-zirconium composite oxide carrier are replaced by zirconium ions, and thus carbon deposition is suppressed by the oxygen vacancies and hydrogen production is promoted during steam reforming of light oil.

Description

Catalyst for steam reforming of light oil, method for manufacturing the same, and method for producing hydrogen using the same

[0001] The present invention relates to a catalyst for steam reforming light oil derived from waste plastics, a method for manufacturing the same, and a method for producing hydrogen using the same.

[0002] In modern society, plastic has established itself as an essential material in various industries and daily life; however, the issue of plastic waste disposal is emerging as a serious environmental challenge worldwide. To address this, the 5th United Nations Environment Assembly (UNEA-5.2), held in Nairobi in March 2022, agreed to establish a legally binding international plastics convention aimed at ending plastic pollution by 2024. Approximately 170 UN member states unanimously adopted regulations to prevent pollution throughout the entire lifecycle of plastics, and consequently, efforts to reduce the amount of plastic waste generated and to process it effectively are now in full swing.

[0003] To solve the plastic waste problem, simply reducing production volume is insufficient; technological alternatives capable of effectively recycling and processing existing waste plastics are essential. Recently, chemical recycling technology, which chemically decomposes waste plastics to convert them into high-value-added products, has been gaining attention. Chemical recycling methods include depolymerization, gasification, and pyrolysis; among these, pyrolysis is considered a promising technology due to its ability to process various types of waste plastic raw materials and its relatively low initial investment costs.

[0004] Pyrolysis is a technology that produces gas and pyrolysis oil by reacting waste plastics at high temperatures of 300 to 800°C under oxygen-free conditions. The generated gas is utilized as a heat source for the pyrolysis process, and the pyrolysis oil is classified into light oil, heavy oil, and high-boiling point wax based on its boiling point range and physical properties. In particular, light oil poses a high risk of explosion due to its low flash point, typically below 20°C; furthermore, under the Waste Management Act, it cannot be used directly as fuel, so its sale or use is restricted. Therefore, a process to convert light oil into other substances is required.

[0005] To address these issues, utilizing steam reforming reactions enables the production of hydrogen, a clean energy source, from light oils derived from waste plastics. This not only allows for the useful utilization of light oils that would otherwise be unsellable but also provides the additional value of hydrogen production. However, to stably produce high-quality and high-purity hydrogen, it is essential to develop customized catalysts that are suitable for the steam reforming of waste plastic-derived light oils while maintaining high activity.

[0006] In hydrocarbon reforming reactions, catalytic performance is directly linked to process operating costs and hydrogen productivity, and catalysts play a key role in accelerating the reaction by lowering the activation energy. In general hydrocarbon reforming reactions, catalysts composed of metals and metal oxides are primarily utilized, consisting of an active material, a support, and a co-catalyst. The active material plays a crucial role in facilitating reactant conversion; however, in the steam reforming of light oils, carbon deposition on the catalyst surface can degrade performance by blocking active sites. Therefore, the development of catalysts that exhibit high activity while possessing resistance to carbon deposition is critical.

[0007] In general, precious metal catalysts such as platinum (Pt), palladium (Pd), and rhodium (Rh) are most widely used in hydrocarbon reforming reactions and are characterized by high activity and stability even with low loading amounts. However, precious metal catalysts are susceptible to sintering at high temperatures and have the disadvantage of being economical and practical for large-scale processes due to high manufacturing costs. To address these issues, the development of catalysts utilizing non-precious metal active materials has recently attracted attention. However, research on the suitability of non-precious metal active materials for the steam reforming reaction of light oil derived from waste plastics has not yet been sufficiently conducted.

[0008] Accordingly, the inventors developed a catalyst using nickel (Ni), cobalt (Co), copper (Cu), or iron (Fe) as the active material, and utilizing a support composite of cerium oxide, which has excellent oxygen storage capacity, and zirconium oxide, which has excellent thermal stability, to solve the problem of carbon deposition. Through this, they succeeded in developing a new catalyst suitable for the steam reforming reaction of light oil derived from waste plastics that satisfies both economic efficiency and stability, and based on this, completed the present invention.

[0009] The present invention was developed to resolve the above problems, and its technical objective is to provide a catalyst for steam reforming of light oil derived from waste plastics that has excellent oxygen storage capacity to effectively suppress carbon deposition and promote hydrogen production, a method for manufacturing the same, and a method for producing hydrogen using the same.

[0010] To solve the above technical problem, the present invention provides a catalyst for steam reforming light oil, comprising: a cerium-zirconium composite oxide carrier having a mesoporous structure formed by bonding cerium oxide and zirconium oxide in the form of a solid solution having a lattice structure; and a non-precious metal active metal supported on the cerium-zirconium composite oxide carrier, wherein the cerium-zirconium composite oxide carrier is characterized by generating oxygen vacancies as cerium ions within the lattice are substituted with zirconium ions, thereby suppressing carbon deposition and promoting hydrogen production through the oxygen vacancies during steam reforming of light oil.

[0011] In the present invention, the non-precious metal active metal is characterized by being supported in an amount of more than 3 wt% and less than 10 wt% with respect to the total weight of the catalyst.

[0012] In the present invention, the non-precious metal active metal is characterized by being composed of at least one of nickel (Ni), cobalt (Co), copper (Cu), and iron (Fe).

[0013] In the present invention, the cerium oxide and the zirconium oxide are characterized by being composed in a molar ratio of 7 to 9:1 to 3.

[0014] In the present invention, the light oil is characterized as being a hydrocarbon having 7 to 12 carbon atoms derived from waste plastic.

[0015] Meanwhile, to solve the above technical problem, the present invention provides a method for manufacturing a catalyst for steam reforming of light oil, characterized by comprising the steps of: reacting a cerium precursor, a zirconium precursor, and a non-precious metal active metal precursor by a co-precipitation method to form a cerium-zirconium composite oxide carrier having a mesoporous structure and supporting a non-precious metal active metal on the cerium-zirconium composite oxide carrier; and washing and calcining the cerium-zirconium composite oxide carrier supported with the non-precious metal active metal to produce a catalyst in powder form.

[0016] On the other hand, in order to solve the above technical problem, the present invention uses the catalyst to react light oil and water vapor at a reaction temperature of 650 to 800 °C, a water vapor / carbon ratio of 1.5 to 3.0, and 10,000 to 150,000 mL·g cat -1 ·h -1 A method for producing hydrogen using a catalyst for steam reforming light oil is provided, characterized by producing hydrogen by reacting at a gas hourly space velocity (GHSV).

[0017] According to the present invention, which is a means for solving the above problem, a Ni-CeZrO2 catalyst capable of effectively producing hydrogen through a steam reforming reaction of light oil components derived from waste plastics and a method for manufacturing the same can be provided. The catalyst of the present invention is based on a cerium-zirconium composite oxide support having excellent oxygen storage capacity, and by providing a high specific surface area through a mesoporous structure, it enables efficient contact between the reactant and the catalyst, thereby having the effect of improving reaction efficiency.

[0018] In particular, the co-precipitation method used in this invention utilizes cerium and zirconium precursors to uniformly form a mesoporous structure and evenly distribute non-precious metal active metals within the catalyst. As a result, the manufacturing process offers high reproducibility and is suitable for mass production, enabling the stable production of high-quality catalysts. The formation of oxygen vacancies effectively suppresses carbon deposition on the catalyst surface, thereby extending the catalyst's lifespan and maintaining stable reaction efficiency.

[0019] Furthermore, the catalyst of the present invention promotes reduction-oxidation reactions through its high oxygen storage capacity and enables the complete conversion of light oil components such as dodecane. This significantly improves the efficiency of hydrogen production and strengthens the catalyst's resistance to carbon deposition, thereby maintaining a stable reaction for a long period of time.

[0020] By supporting non-precious metal active metals on a cerium-zirconium composite oxide carrier, economic efficiency is improved compared to existing precious metal-based catalysts. Strong metal-support interaction (SMSI) between the carrier and the active metal enhances the catalyst's sintering resistance and offers the advantage of maintaining structural stability even during long-term use.

[0021] Therefore, the Ni-CeZrO2 catalyst synthesized through the present invention enables the resource recovery and high-value utilization of waste plastics and can be used as a core technology in sustainable hydrogen production processes; thus, significant effects can be expected, such as contributing to the solution of environmental problems and establishing itself as a foundational technology for the hydrogen economy.

[0022] FIG. 1 is a conceptual diagram schematically showing the mesopore structure and the supported state of the active metal of a catalyst for the steam reforming reaction of light oil derived from waste plastic according to the present invention.

[0023] FIG. 2 is a conceptual diagram schematically illustrating a co-precipitation method according to the present invention.

[0024] Figure 3 is a TEM-EDS image of the catalyst synthesized in Example 1 and Comparative Examples 1, 2, and 3.

[0025] Figure 4 is a graph showing the N2 adsorption-desorption isotherms of the catalysts synthesized in Example 1 and Comparative Examples 1, 2, and 3.

[0026] Figure 5 is a graph showing the pore size distribution and pore volume of the catalysts synthesized in Example 1 and Comparative Examples 1, 2, and 3.

[0027] Figure 6 is a graph showing the XRD patterns of the catalysts synthesized in Example 1 and Comparative Examples 1, 2, and 3.

[0028] Figure 7 is a graph showing the H2-TPR patterns of the catalysts synthesized in Example 1 and Comparative Examples 1, 2, and 3.

[0029] Figure 8 is a graph showing the XPS spectra of the catalysts synthesized in Example 1 and Comparative Examples 1, 2, and 3.

[0030] Figure 9 is a graph showing the hydrogen yield and dodecane conversion rate using the catalysts synthesized in Example 1 and Comparative Examples 1, 2, and 3.

[0031] Figure 10 is a graph showing the Raman analysis results of the catalysts synthesized in Example 1 and Comparative Examples 1, 2, and 3.

[0032] The present invention is susceptible to various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the invention to specific embodiments, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention. Similar reference numerals have been used for similar components in the description of each drawing.

[0033] The terms used in this invention are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this invention, terms such as "comprising" or "having" are intended to specify the presence of the features, numbers, steps, reactions, components, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, reactions, components, or combinations thereof.

[0034] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0035] The present invention relates to a catalyst for steam reforming light oil derived from waste plastics. In this regard, FIG. 1 is a conceptual diagram schematically showing the structure of a catalyst according to the present invention. Referring to FIG. 1, the catalyst of the present invention consists of a cerium-zirconium composite oxide carrier having a mesoporous structure formed by bonding cerium oxide and zirconium oxide in the form of a solid solution with a lattice structure, and a non-precious metal active metal supported on the carrier.

[0036] In particular, the cerium-zirconium composite oxide carrier in the present invention is a cerium ion (Ce) within the lattice. 4+ ) zirconium ions (Zr 4+It is characterized by the formation of oxygen vacancies as it is substituted with ). The oxygen vacancies inhibit carbon deposition on the catalyst surface during the steam reforming reaction of light oil and play an important role in promoting the hydrogen production reaction.

[0037] Light oils primarily contain low molecular weight hydrocarbons (C7 to C12) and are characterized by low specific gravity and a relatively low boiling point. This applies not only to low molecular weight hydrocarbons separated from crude oil but also to light oils obtained from the pyrolysis of waste plastics.

[0038] Steam reforming refers to a process of producing hydrogen (H2) by reacting light oil with steam (H2O) at a high temperature (e.g., 650 to 800 °C), and this process depends significantly on the activity and stability of the catalyst. In particular, in steam reforming, the structural stability and carbon deposition resistance of the catalyst have a significant impact on the efficiency and sustainability of hydrogen production. In such a reaction, a support that supports the uniform dispersion and stability of non-precious metal active metals plays a key role in the catalyst, and in the present invention, a cerium-zirconium composite oxide support is used as the catalyst support.

[0039] In other words, the cerium-zirconium composite oxide carrier, which serves as a support for the catalyst in this invention, is a solid solution formed by the combination of cerium oxide (CeO2) and zirconium oxide (ZrO2). A solid solution refers to a state in which two or more components are substituted for each other and uniformly distributed within a single crystal lattice. Cerium oxide and zirconium oxide are formed through reactions such as co-precipitation, during which zirconium ions substitute for cerium ion sites. At this time, since the radius of the zirconium ion is smaller than that of the cerium ion, the lattice structure is partially deformed, and oxygen is released to create oxygen vacancies. The greater the number of oxygen vacancies, the improved mobility of oxygen ions enhances the redox reactivity of the catalyst. Furthermore, oxygen vacancies provide essential active sites for oxidizing and removing carbon deposited on the catalyst surface; thus, by suppressing carbon deposition, they enable the maintenance of the catalyst's long-term stability and performance.

[0040] Cerium oxide can be, for example, ceria (CeO2), which is an oxide with a fluorite crystal structure, and cerium ions (Ce 4+ ) and oxygen ions (O 2- It forms a body-centered cubic lattice structure arranged in a 1:2 ratio. This structure plays an important role in catalytic reactions by providing high oxygen ion mobility and the ability to generate oxygen vacancies.

[0041] Zirconium oxide, namely zirconia (ZrO2), is added to ceria (CeO2) to form Ce 4+ Zr in place 4+ A solid solution is formed through substitution. Oxygen vacancies are naturally generated during the solid solution formation process, which contributes to increasing the catalyst's oxygen storage capacity and improving redox performance. This solid solution structure exhibits superior thermal stability and durability against repeated reduction-oxidation cycles compared to the use of ceria alone.

[0042] Furthermore, the catalyst of the present invention achieves both practicality and economic efficiency by supporting a non-precious metal active metal, such as nickel (Ni), cobalt (Co), copper (Cu), or iron (Fe), on a cerium-zirconium composite oxide carrier, thereby providing high activity while being more economical compared to precious metal catalysts. The non-precious metal active metal provides excellent active sites in the steam reforming reaction of light oil, and interacts with oxygen vacancies to suppress carbon deposition and enable continuous hydrogen production.

[0043] To explain specifically using nickel as an example among non-precious metal active metals, nickel is an active metal that promotes the steam reforming reaction. It activates the hydrocarbons (CH₃ and CC₆ bonds) of light oils to facilitate decomposition and rearrangement reactions, thereby accelerating the reaction to rapidly generate carbon monoxide and hydrogen.

[0044] Meanwhile, a catalyst having the above characteristics is manufactured through the following steps: reacting a cerium precursor, a zirconium precursor, and a non-precious metal active metal precursor by a coprecipitation method to form a cerium-zirconium composite oxide carrier with a mesoporous structure, and supporting a non-precious metal active metal on the cerium-zirconium composite oxide carrier (S10); and washing and calcining the cerium-zirconium composite oxide carrier supported with the non-precious metal active metal to produce a catalyst in powder form (S20).

[0045] According to the above-described manufacturing method, a cerium precursor, a zirconium precursor, and a non-precious metal active metal precursor are reacted by a co-precipitation method to form a cerium-zirconium composite oxide carrier with a mesoporous structure, and after a non-precious metal active metal is supported on the cerium-zirconium composite oxide carrier (S10), the cerium-zirconium composite oxide carrier supported with the non-precious metal active metal is washed and calcined to produce a catalyst in powder form (S20).

[0046] Before providing a detailed explanation, the coprecipitation method is a process of simultaneously precipitating multiple metal ions from a solution to form a homogeneous solid solution. This step consists of forming a mesoporous cerium-zirconium composite oxide carrier using the coprecipitation method and supporting a non-precious metal active metal on the carrier. To achieve this, a precursor solution is first prepared.

[0047] Cerium nitrate (Ce(NO3)3·6H2O) is used as the cerium precursor, and zirconium nitrate (Zr(NO3)4 or zirconyl nitrate (ZrO(NO3)2)) is used as the zirconium precursor. Nickel nitrate (Ni(NO3)2·6H2O), cobalt nitrate (Co(NO3)2·6H2O), or iron nitrate (Fe(NO3)3·9H2O) is selected as the non-precious metal active metal precursor.

[0048] The above precursors are dissolved in distilled water in appropriate proportions to prepare a homogeneous solution, wherein the molar ratio of cerium oxide to zirconium oxide is set in the range of 7 to 9:1 to 3 to form a solid solution.

[0049] FIG. 2 is a conceptual diagram schematically illustrating a coprecipitation method according to the present invention, showing a process of generating a precipitate by adding a precipitating agent, such as a 15 wt% potassium hydroxide (KOH) solution, dropwise to a reaction solution containing a cerium precursor, a zirconium precursor, and a non-precious metal active metal precursor. In the coprecipitation process of FIG. 2, the temperature of the solution is maintained at 80 ℃, and the solution is continuously stirred to ensure a uniform reaction and precipitation.

[0050] In the precipitation reaction, a precipitate in the form of a hydroxide is formed during the process of adjusting the pH of the solution to approximately 10.5 by adding a 15 wt% KOH solution dropwise. That is, cerium ions and zirconium ions simultaneously precipitate in the form of a hydroxide to form a cerium-zirconium complex oxide. Non-precious metal active metal ions (Ni 2+ , Co 2+ , Fe 3+(etc.) is evenly supported on the surface of the cerium-zirconium composite oxide support and within the mesopores, which enhances the activity and stability of the catalyst through strong metal-support interaction (MSMI) with the support.

[0051] The precipitates combine with each other to be converted into complex oxides in the form of a solid solution of ceria and zirconia, and in this process, cerium (Ce) 4+ ) and zirconium (Zr 4+ A cerium-zirconium composite oxide support is formed by exchanging or substituting sites within the lattice structure. In particular, the mesoporous structure is naturally formed during the bonding process between particles during the precipitation reaction, and subsequently develops as moisture and impurities are removed during the washing and calcination processes. The mesoporous structure significantly increases the surface area of ​​the support and promotes the loading of non-precious metal active metals, allowing light oil and water vapor to easily access the catalyst surface. Non-precious metal active metal ions contained in the reaction solution are evenly distributed on the surface of the support and within the mesopores during the precipitation process. As the active metal ions bind to the surface of the support and within the mesopores, they exhibit high dispersion, thereby acting as active sites for the catalyst in the steam reforming reaction to maximize hydrogen yield and hydrocarbon conversion efficiency.

[0052] On the other hand, in a method for producing hydrogen using a catalyst having the above characteristics, light oil separated and obtained by pyrolyzing waste plastics and steam are reacted at a reaction temperature of 650 to 800 °C, a steam / carbon ratio of 1.5 to 3.0, and 10,000 to 150,000 mL·g cat -1 ·h -1 High-efficiency hydrogen production can be achieved by reacting at the gas hourly space velocity (GHSV).

[0053] If the reaction temperature is below 650 ℃, the reforming reaction of light oil may not proceed sufficiently, which may result in a decrease in hydrogen production rate, and if it exceeds 800 ℃, the thermal stability of the catalyst may be compromised and the sintering of non-precious metal active metals may be promoted, which may lead to a decrease in catalyst activity and a decrease in hydrogen production efficiency.

[0054] If the steam / carbon ratio is less than 1.5, the reforming reaction proceeds incompletely due to a lack of steam, which promotes carbon deposition and may lead to the blocking of catalyst active sites. If the steam / carbon ratio exceeds 3.0, problems may arise such as reduced reaction efficiency and increased energy consumption of the process due to excessive steam usage.

[0055] The gas space velocity per hour is 10,000 mL·g cat -1 ·h -1 If it is less than, the reactant processing capacity per catalyst unit is low, which may lead to reduced productivity, and 150,000 mL·g cat -1 ·h -1 If it exceeds, heat transfer within the reactor proceeds inefficiently, which may degrade reaction performance.

[0056] Accordingly, the hydrogen production method using the catalyst of the present invention utilizes light oil derived from waste plastics and water vapor under optimal conditions (reaction temperature of 650 to 800 ℃, water vapor / carbon ratio of 1.5 to 3.0, and 10,000 to 150,000 mL·g cat -1 ·h -1 By reacting waste plastics in the GHSV, it can be utilized as a sustainable technology that converts waste plastics into high-value resources and enables clean energy production.

[0057] The embodiments of the present invention will be described in more detail below. However, the following embodiments are provided merely to aid in understanding the present invention and do not limit the scope of the present invention.

[0058] <Example 1> Preparation of 5 wt% Ni-CeZrO2 catalyst

[0059] First, the CeZrO2 of the carrier was configured to consist of 80 mol% CeO2 and 20 mol% ZrO2, and Ce(NO3) 3· 6H2O (99.9%, Aldrich) and zirconium nitrate solution (20 wt% based on ZrO2, MEL Chemicals) were used as precursors.

[0060] Ni(NO3) to prepare a catalyst by the coprecipitation method 2· 6H2O (97%, Junsei Chemicals) 0.7662 g, Ce(NO3) 3· 6.1602 g of 6H2O (99.9%, Aldrich) and 1.5056 mL of zirconium nitrate solution (20 wt% based on ZrO2, MEL Chemicals) were dissolved in 500 ml of distilled water.

[0061] After dissolution, the solution was stirred in a round-bottom flask while slowly adding 15% KOH (w / w) aqueous solution dropwise at 80 °C to adjust the pH to 10.5. During the co-precipitation reaction, the mixture was aged for 72 hours at 80 °C to produce a precipitate. The product was filtered, and K was washed 5 times with distilled water until the pH reached 7.0. + , OH - and NO3 - Impurities such as ions were removed.

[0062] The product obtained after washing was dried in an oven at 100°C for 12 hours, and the dried product was calcined in a kiln at 800°C for 6 hours, and then ground into a fine powder with a particle size of 150 to 300 μm to prepare a catalyst in powder form.

[0063] <Comparative Example 1> Preparation of 1 wt% Ni-CeZrO2 catalyst

[0064] In Comparative Example 1, Ni(NO3) is used under the same conditions as Example 1 so that the nickel loading is 1 wt%. 2·6H2O (97%, Junsei Chemicals) 0.1532 g, Ce(NO3) 3· A catalyst was prepared using 6.4196 g of 6H2O (99.9%, Aldrich) and 1.5690 mL of zirconium nitrate solution (20 wt% based on ZrO2, MEL Chemicals).

[0065] <Comparative Example 2> Preparation of 3 wt% Ni-CeZrO2 catalyst

[0066] In Comparative Example 2, Ni(NO3) is used under the same conditions as Example 1 so that the nickel loading is 3 wt%. 2· 6H2O (97%, Junsei Chemicals) 0.4597 g, Ce(NO3) 3· A catalyst was prepared using 6.2599 g of 6H2O (99.9%, Aldrich) and 1.5373 mL of zirconium nitrate solution (20 wt% based on ZrO2, MEL Chemicals).

[0067] <Comparative Example 3> Preparation of 10 wt% Ni-CeZrO2 catalyst

[0068] In Comparative Example 3, Ni(NO3) is used under the same conditions as Example 1 so that the nickel loading is 10 wt%. 2· 6H2O (97%, Junsei Chemicals) 1.5323 g, Ce(NO3) 3· A catalyst was prepared using 5.8360 g of 6H2O (99.9%, Aldrich) and 1.4264 mL of zirconium nitrate solution (20 wt% based on ZrO2, MEL Chemicals).

[0069] <Test Example 1> Analysis of Microstructure and Elemental Distribution of Catalyst

[0070] In this test example, TEM-EDS elemental mapping results were observed to analyze the morphology and composition of the catalysts synthesized in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0071] In this regard, FIG. 3(a) shows the TEM-EDS images of the catalysts synthesized in Comparative Example 1, FIG. 3(b) shows Comparative Example 2, FIG. 3(c) shows Example 1, and FIG. 3(d) shows Comparative Example 3. According to FIG. 3, the microstructure and elemental distribution of each catalyst can be confirmed, and through elemental mapping of nickel (Ni), cerium (Ce), zirconium (Zr), and oxygen (O), it was observed that the active metal and support components within the catalyst are uniformly distributed.

[0072] In particular, it was confirmed that nickel particles were uniformly distributed on the carrier in all samples of Comparative Example 1, Comparative Example 2, and Comparative Example 3, including Example 1, and it was also confirmed in the EDS image that each element (Ni, Ce, Zr, O) was evenly distributed.

[0073] In addition, EDS analysis results confirmed that each sample was uniformly doped with nickel at 1 wt%, 3 wt%, 5 wt%, and 10 wt%.

[0074] Through this test example, it was confirmed that nickel, a non-precious metal active metal, is uniformly distributed on a cerium-zirconium composite oxide support in the catalyst according to the present invention. This demonstrates that even loading of the active metal is possible due to the catalyst's excellent manufacturing process reproducibility and mesoporous structure. It was determined that this uniform distribution of the active metal can contribute to maximizing the utilization of the catalyst's active sites and maintaining stable performance during the steam reforming reaction.

[0075] <Test Example 2> Analysis of Catalyst Properties According to Nickel Content

[0076] In this test example, the physicochemical properties (specific surface area, nickel dispersion, nickel active sites, nickel grain size) of Ni-CeZrO2 catalysts synthesized by the co-precipitation method with different nickel contents in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were analyzed.

[0077] In this regard, first, the characteristics of Ni-CeZrO2 catalysts prepared with different nickel loading amounts are shown in Table 1 below.

[0078] Specific surface area (m²) 2 / g) Nickel dispersion (%) Nickel active sites (10 -7 gmol / g cat Nickel grain size (nm) Comparative Example 1 (Ni 1 wt%) 56 1.1 1.9 - Comparative Example 2 (Ni 3 wt%) 53 1.2 5.9 - Example 1 (Ni 5 wt%) 60 0.7 6.1 19.17 Comparative Example 3 (Ni 10 wt%) 77 0.7 12.7 18.56

[0079] Referring to Table 1, the BET specific surface areas measured by the N2 adsorption / desorption method using the Micromeritics ASAP 2020 instrument were 56, 53, 60, and 77 m², respectively. 2 It was measured as / g and showed an increasing trend as the nickel loading increased from 1 wt% to 10 wt%.

[0080] In this regard, Fig. 4 is an N2 adsorption-desorption isotherm graph of the catalysts synthesized in Example 1 and Comparative Examples 1, 2, and 3. Fig. 4(a) is Comparative Example 1, Fig. 4(b) is Comparative Example 2, Fig. 4(c) is Example 1, and Fig. 4(d) is Comparative Example 3. All samples exhibit a Type IV hysteresis loop, confirming that they exhibit a mesoporous structure regardless of the nickel loading amount.

[0081] Among them, the 1 wt% Ni-CeZrO2 catalyst of Comparative Example 1 in Fig. 4(a) and the 3 wt% Ni-CeZrO2 catalyst of Comparative Example 2 in Fig. 4(b) exhibit an H1-type hysteresis loop with a narrow and uniform pore size distribution, while the 5 wt% Ni-CeZrO2 catalyst of Example 1 in Fig. 4(c) and the 10 wt% Ni-CeZrO2 catalyst of Comparative Example 3 in Fig. 4(d) exhibit an H2-type hysteresis loop with a complex pore network and a wide pore size distribution.

[0082] In addition, FIG. 5(a) is a graph showing the pore size distribution and pore volume of the catalyst synthesized in Comparative Example 1, FIG. 5(b) is a graph showing Comparative Example 2, FIG. 5(c) is a graph showing Example 1, and FIG. 5(d) is a graph showing Comparative Example 3. The pore size distribution and volume were analyzed using the Barrett-Joyner-Halenda (BJH) method, and a well-developed pore structure can provide many reaction sites and promote the good dispersion of nickel.

[0083] Nickel dispersion and nickel active sites shown in Table 1 were measured via CO-chemisorption using a Micromeritics AutoChem II 2920. It was confirmed that higher nickel dispersion was observed as the nickel loading decreased, which is a general phenomenon. The number of nickel active sites on the catalyst surface was calculated by considering both nickel dispersion and nickel loading; while nickel dispersion was high in catalysts with low nickel loading, the number of nickel active sites showed an opposite trend.

[0084] Regarding the nickel grain size in Table 1, this can be confirmed through the XRD patterns of the Ni-CeZrO2 catalyst according to the nickel loading amount. Figure 6 is a graph showing the XRD patterns of the catalysts synthesized in Example 1 and Comparative Examples 1, 2, and 3. The nickel (Ni of Comparative Examples 1 and 2 0 Although the intensity of the peak corresponding to ) was too broad to calculate the grain size, the nickel grain size of Example 1 was calculated to be 19.17 nm, and the nickel grain size of Comparative Example 3 was calculated to be 18.56 nm. Through these results, it was found that nickel is well dispersed and the grain size decreases at low nickel loading amounts, and that the number of active sites on the catalyst surface tends to decrease.

[0085] Looking closely at the XRD pattern in Fig. 6, peaks corresponding to ceria (CeO2) with a cubic fluorite structure at 28.5°, 33.1°, 47.5°, 56.3°, 59.1°, 69.4°, 76.7°, and 79.1° were observed in all catalysts of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0086] A notable point here is that the zirconia (ZrO2) peak was not detected. This was determined to be because the zirconia ionic radius (0.084 nm) is smaller than the ceria ionic radius (0.097 nm), so zirconia was substituted into ceria through the insertion process, forming a uniform Ce-ZrO2 solid solution.

[0087] Therefore, by analyzing the physicochemical properties of the catalyst according to changes in nickel content in the present test example, it was confirmed that the cerium-zirconium composite oxide support forms a uniform solid solution structure, and that the interaction between the support and nickel, a non-precious metal active metal, influences catalytic properties such as the specific surface area, nickel dispersion, active sites, and grain size of the catalyst. The above results indicate that the catalyst of the present invention plays an important role in exhibiting high activity and stability in the steam reforming reaction.

[0088] <Test Example 3> Oxidation-Reduction Analysis of Catalyst

[0089] In this test example, H2-TPR (hydrogen temperature programmed reduction) analysis was performed to investigate the reducing properties of the catalyst.

[0090] In this regard, FIG. 7 is a graph showing the H2-TPR patterns of the catalysts synthesized in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, and four reduction peaks were observed in all catalysts.

[0091] The first reduction peak is observed around 395°, which is attributed to the reduction of free NiO particles with weak interaction with the support. This peak occurs in the free state of nickel particles, and the hydrogen consumption showed a similar trend.

[0092] The second reduction peak corresponds to the reduction of the composite NiO, which exhibits a relatively strong interaction with the support. While the catalysts of Comparative Examples 1 and 2 showed similar trends, the reduction peak was observed at a higher temperature for the catalyst of Example 1. This indicates strong metal-support interaction (SMSI), and the stronger the interaction between the metal and the support, the more effective it is in preventing coking by promoting the generation of mobile oxygen during the dodecane reforming reaction. Furthermore, it was expected that the sintering resistance of the catalyst would also be improved due to the SMSI. On the other hand, in the case of Comparative Example 3, more hydrogen was consumed at the second peak due to the high nickel content.

[0093] The third reduction peak is Ce on the CeO2 surface 4+ Ga Ce 3+ This is attributed to reduction. This peak may be closely related to oxygen storage capacity, and it was determined that when the nickel loading is 10 wt%, the reducing power of ceria is improved by overlapping with nickel species, and accordingly, the peak shifted to a lower temperature.

[0094] The final reduction peak corresponds to the reduction of bulk CeO2, indicating the process of internal oxygen reduction in the support.

[0095] As a result of H2-TPR analysis, it was confirmed that the 5 wt% Ni-CeZrO2 catalyst of Example 1 exhibited strong metal-support interactions and demonstrated excellent oxygen mobility and reducing properties, making it effective in preventing coking and maintaining continuous activity. This supports the conclusion that the catalyst of Example 1 is the optimal choice for high-efficiency hydrogen production in the steam reforming reaction of light oil.

[0096] <Test Example 4> Analysis of Oxygen Vacancies and Oxygen Storage Capacity (OSC) of the Catalyst

[0097] In this test example, XPS and H2-O2 pulse reaction analysis were performed to investigate the oxygen vacancies and oxygen storage capacity of the catalysts synthesized in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0098] Figure 8 is a graph showing the XPS spectra of the catalysts synthesized in Example 1 and Comparative Examples 1, 2, and 3. Figure 8(a) shows the XPS spectra of the Ce 3d spectrum of the catalysts synthesized in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3. The Ce 3d spectrum is decomposed into 10 peaks, of which five peaks v0, v, v', v", v'" correspond to Ce 3d5 / 2, and the remaining five peaks u0, u, u', u", u'" correspond to Ce 3d3 / 2. Six peaks v, v", v'", u, u", u'" correspond to CeO2, and four peaks v0, v', u0, u' are attributed to Ce2O3. The presence of both Ce species implies that the catalyst was partially reduced and oxygen vacancies were generated, and also Ce 3+ The presence of implies that oxygen vacancies have formed in the CeO2 lattice. From this, Ce 3+ It was confirmed that the concentration is directly related to the amount of oxygen vacancies generated in the Ni-CeZrO2 catalyst. Among the total Ce, Ce 3+ Concentration of (Ce 3+ / (Ce 3+ +Ce 4+ )) was calculated by summing the peak areas of CeO2 and Ce2O3, and the results are summarized in Table 2 below.

[0099] Classification Ce 3+ Concentration = (Ce 3+ / (Ce 3+ +Ce 4+ )) (%)O D Ratio = O D / (O L +OD +O H ) (%) OSC (μmol / g) Comparative Example 1 32.2 32.1 0.82 Comparative Example 2 44.4 54.8 0.99 Example 1 48.8 58.01 12 Comparative Example 3 38.2 36.8 0.85

[0100]

[0101] Referring to Table 2, the catalyst of Example 1 has the highest Ce 3+ The concentrations were shown in the order of Example 1 > Comparative Example 2 > Comparative Example 3 > Comparative Example 1.

[0102] Figure 8(b) shows the XPS spectra of the O 1s spectra of the catalysts synthesized in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3. As a result of the O 1s spectrum analysis, three peaks were observed. The first peak (O L , 529.25–529.45 eV) corresponds to lattice oxygen, and the second peak (O D , 531 eV) is attributed to defective oxygen (oxygen vacancies), and the third peak (O H , 533 eV) corresponds to a surface hydroxyl group.

[0103] Using the peak area of ​​each oxygen species O D The results of calculating the ratios are summarized in Table 2. The 5 wt% Ni-CeZrO2 catalyst of Example 1 had the highest O D It represented the ratio, and O D The order of the ratios was confirmed to be Example 1 (58.0%) > Comparative Example 2 (54.8%) > Comparative Example 3 (36.8%) > Comparative Example 1 (32.1%).

[0104] In particular, Table 2 shows the oxygen vacancies of the catalysts synthesized in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively. Oxygen storage capacity is the ability to exchange lattice oxygen under oxidation and reduction conditions, and a higher oxygen storage capacity of the catalyst indicates the presence of more oxygen vacancies. Oxygen storage capacity was quantitatively calculated through an H2-O2 pulse reaction, and the catalyst of Example 1 showed the highest oxygen storage capacity value. The order of oxygen storage capacity was confirmed to be Example 1 (1.12 μmol / g) > Comparative Example 2 (0.99 μmol / g) > Comparative Example 3 (0.85 μmol / g) > Comparative Example 1 (0.82 μmol / g). The results of the H2-O2 pulse reaction are consistent with the results obtained from the XPS in Figure 8. As for the oxygen storage capacity, since it is a value resulting from complex interactions, as shown in Table 2, the oxygen storage capacity of the catalyst in Example 1 was measured to be 1.12 μmol / g, which is higher than that of Comparative Examples 1, 2, and 3, proving that the catalyst performance is the highest.

[0105] For reference, oxygen vacancies play a crucial role in enhancing catalytic performance, particularly by acting as active sites for H2O dissociation to promote reduction-oxidation reactions. Additionally, high oxygen storage capacity inhibits carbon deposition, thereby maintaining catalyst stability and providing a sustainable reaction environment for a long period.

[0106] Therefore, Ce confirmed by XPS analysis in this test example 3+ Wow O D It can be seen that concentration and oxygen storage capacity values ​​measured through the H2-O2 pulse reaction both serve as important performance indicators of the catalyst in the dodecane steam reforming reaction. Among them, the 5 wt% Ni-CeZrO2 catalyst of Example 1 exhibited the highest oxygen vacancies and oxygen storage capacity values, and was determined to provide excellent catalytic performance and reaction stability.

[0107] <Test Example 5> Catalytic Reaction Analysis

[0108] In this test example, catalytic reaction analysis was performed to evaluate the performance of the catalysts synthesized in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 in the dodecane steam reforming reaction.

[0109] In this regard, FIG. 9(a) is a graph showing the hydrogen yield using the catalyst synthesized in Example 1 and Comparative Examples 1, 2, and 3, and FIG. 9(b) is a graph showing the dodecane conversion rate.

[0110] The dodecane steam reforming reaction was carried out in a fixed-bed tubular reactor at 750 °C. The catalyst was reduced at 750 °C in a 5% H2 / N2 atmosphere, and under reaction conditions, the GHSV was 133,950 mL·g cat -1 ·h -1 The reaction was initiated. Under reaction conditions, the steam / carbon ratio was maintained at 2.5, and dodecane and steam were introduced into the reactor in a preheated state. After the reaction, the exhaust gas was analyzed using GC after moisture removal, and the hydrogen yield and dodecane conversion rate were calculated using standard formulas.

[0111] The catalyst of Comparative Example 1 had the lowest number of Ni active sites, and as a result, the hydrogen yield and dodecane conversion rate were the lowest. The initial hydrogen yield was about 30%, and the dodecane conversion rate was about 55%.

[0112] The catalyst of Example 1 showed the best catalytic performance. The initial hydrogen yield was approximately 54% and the dodecane conversion rate was approximately 90%, and stable performance was maintained for 50 hours. This was analyzed to be because the catalyst of Example 1 provided resistance to carbon deposition and sintering through high oxygen storage capacity and strong metal-support interaction (SMSI).

[0113] The catalyst of Comparative Example 2 showed similar initial performance to the catalyst of Example 1, but the catalyst performance decreased relatively rapidly as the reaction time increased. This is believed to be because the oxygen storage capacity of the catalyst in Comparative Example 2 was relatively low, which showed limitations in catalyst stability.

[0114] The catalyst of Comparative Example 3 was measured to have an initial hydrogen yield of approximately 48.5% and a dodecane conversion rate of approximately 82.5%, but showed the greatest performance degradation after 50 hours. This was found to be due to increased carbon formation caused by an excessive distribution of nickel active sites and low oxygen storage capacity, which led to catalyst deactivation.

[0115] Through these results, Ce 0.8 Zr 0.2 The optimal nickel loading on the O2 support was identified as 5 wt%. The 5 wt% Ni-CeZrO2 catalyst exhibited the most stable and efficient performance in the dodecane steam reforming reaction due to its high oxygen storage capacity, appropriate nickel active sites, and strong metal-support interaction (SMSI).

[0116] After a 50-hour stability test, Raman analysis was performed on all samples, and the spectra are shown in Fig. 10. Fig. 10 is a graph showing the results of Raman analysis of the catalysts synthesized in Example 1 and Comparative Examples 1, 2, and 3. Raman spectroscopy is an important tool for confirming the presence of oxygen vacancies and structural characteristics within the catalyst, and it provides additional information regarding redox properties and catalyst stability. Through this, it was possible to evaluate the structural changes and the degree of carbon deposition after the reaction of each catalyst.

[0117] Referring to Fig. 10, the D-band (approx. 1,330 cm) -1 ) is the characteristic peak of amorphous carbon, sp 2 Corresponds to the vibration of the coupling. G-band (approx. 1,580 cm⁻¹) -1 ) is a characteristic peak of graphite or fibrous carbon, representing the sp of aromatic clusters. 2It corresponds to the stretching vibration of the coupling. In Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, two peaks corresponding to the D-band and G-band were observed.

[0118] I shown in Fig. 10 D / I G is an indicator used in Raman spectroscopy to evaluate the structural characteristics of carbon materials, and can confirm the degree of defective carbon structures. D / I G The smaller the value, the fewer defects and higher crystallinity sp 2 Indicates that it has a carbon structure, and I D / I G A higher value indicates more defects. I D / I G I in the order of Comparative Example 3 (1.91) > Comparative Example 1 (1.43) = Comparative Example 2 (1.43) > Example 1 (1.20). D / I G A value appeared. However, I D / I G 1,330 ± 50 cm in the wavenumber region of the Raman spectrum -1 Maximum peak intensity (I) measured at D ) and, 1,580 ± 50 cm -1 Maximum peak intensity (I) measured at G It is a value calculated as the ratio of ).

[0119] I of the 10 wt% Ni-CeZrO2 catalyst synthesized in Comparative Example 3 D / I G It was found that the highest value indicated that more amorphous carbon had accumulated on the catalyst surface. According to Table 2, it was confirmed that because the oxygen storage capacity of the catalyst in Comparative Example 3 was low, it was relatively difficult to oxidize the deposited carbon, leading to the accumulation of amorphous carbon and accelerated deactivation of the catalyst.

[0120] Unlike Comparative Example 3, the I of the catalyst synthesized in Example 1 D / I GThe value was the lowest. This implies that the proportion of graphitized carbon over amorphous carbon on the catalyst surface is higher compared to other catalysts. These results demonstrate the catalyst's high oxygen storage capacity and its effective inhibition of amorphous carbon deposition.

[0121] From the results of the above test examples, it was confirmed that the nickel loading significantly influences the catalytic performance of Ni-CeZrO2 catalysts synthesized by the co-precipitation method. It was confirmed that the nickel loading affects the catalyst's active sites, oxygen storage capacity, and strong metal-support interaction (SMSI), acting as a key factor in determining the hydrogen production efficiency and catalyst stability during the dodecane steam reforming reaction.

[0122] In particular, the 5 wt% Ni-CeZrO2 catalyst synthesized in Example 1 exhibited excellent reaction performance and long-term stability through a high oxygen storage capacity, strong metal-support interaction (SMSI), and an appropriate balance of nickel active sites. These characteristics contributed to preventing catalyst performance degradation by suppressing the formation of amorphous carbon and increasing the proportion of graphitized carbon. In contrast, the 1 wt% Ni-CeZrO2 catalyst synthesized in Comparative Example 1 showed low reforming reaction efficiency due to a lack of active sites, while the 10 wt% Ni-CeZrO2 catalyst synthesized in Comparative Example 3 actually promoted catalyst deactivation due to excessive carbon deposition. From this, it can be seen that the 5 wt% Ni-CeZrO2 catalyst possesses an optimal nickel loading for hydrogen production via the dodecane steam reforming reaction and provides an ideal balance between the availability of active sites and oxygen storage capacity. These results indicate that it can be smoothly used as a catalyst for high-efficiency hydrogen production.

[0123] In summary, the present invention relates to a catalyst comprising a cerium-zirconium composite oxide carrier having a mesoporous structure formed by bonding cerium oxide and zirconium oxide in the form of a lattice-structured solid solution, and a non-precious metal active metal supported on the cerium-zirconium composite oxide carrier. The cerium-zirconium composite oxide carrier is characterized by the generation of oxygen vacancies as cerium ions within the lattice are substituted with zirconium ions, thereby inhibiting carbon deposition and promoting hydrogen production through the oxygen vacancies during the steam reforming of light oil.

[0124] According to these characteristics, the catalyst of the present invention can provide a high hydrogen production rate and catalytic stability in the steam reforming reaction of light oil separated by the pyrolysis of waste plastics, which is significant in that it has the potential for industrial application in the clean energy field as an economical and practical catalyst.

[0125] In particular, the present invention is expected to secure core technology for high-efficiency hydrogen production processes by achieving efficient catalytic performance without using precious metals, thereby significantly reducing catalyst manufacturing costs, and maintaining stable catalytic performance for a long time through high oxygen storage capacity and the mesoporous structure of the support.

[0126] The foregoing description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications and variations within the scope of the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are intended to explain, not to limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by such embodiments. The scope of protection of the present invention shall be interpreted by the claims, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention.

Claims

1. A mesoporous cerium-zirconium composite oxide carrier formed by bonding cerium oxide and zirconium oxide in the form of a solid solution with a lattice structure; and A non-precious metal active metal supported on the above-mentioned cerium-zirconium composite oxide carrier; comprising In the above cerium-zirconium composite oxide carrier, oxygen vacancies are generated as cerium ions within the lattice are substituted with zirconium ions, A catalyst for steam reforming light oil, characterized by inhibiting carbon deposition by the oxygen vacancies and promoting hydrogen production during steam reforming of light oil.

2. In Paragraph 1, A catalyst for steam reforming light oil, characterized in that the above-mentioned non-precious metal active metal is supported in an amount of more than 3 wt% and less than 10 wt% with respect to the total weight of the catalyst.

3. In Paragraph 1, A catalyst for steam reforming light oil, characterized in that the above-mentioned non-precious metal active metal is composed of at least one of nickel (Ni), cobalt (Co), copper (Cu), and iron (Fe).

4. In Paragraph 1, A catalyst for steam reforming light oil, characterized in that the cerium oxide and the zirconium oxide are composed in a molar ratio of 7 to 9:1 to 3.

5. In Paragraph 1, A catalyst for steam reforming light oil, characterized in that the light oil is a hydrocarbon having 7 to 12 carbon atoms derived from waste plastic.

6. A step of reacting a cerium precursor, a zirconium precursor, and a non-precious metal active metal precursor by a co-precipitation method to form a cerium-zirconium composite oxide carrier having a mesoporous structure, and supporting a non-precious metal active metal on the cerium-zirconium composite oxide carrier; and The method includes the step of preparing a catalyst in powder form by washing and calcining the cerium-zirconium composite oxide carrier supported with the above-mentioned non-precious metal active metal; A method for manufacturing a catalyst for steam reforming light oil, characterized by manufacturing a catalyst for steam reforming according to any one of claims 1 to 5.

7. Using the catalyst of any one of claims 1 to 5, Light oil and steam at a reaction temperature of 650 to 800 °C, a steam / carbon ratio of 1.5 to 3.0, and 10,000 to 150,000 mL·g cat -1 ·h -1 A method for producing hydrogen using a catalyst for steam reforming light oil, characterized by producing hydrogen by reacting at a gas hourly space velocity (GHSV).

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