Method for producing hydrogen through steam reforming of light oil

Abstract

The present invention relates to a method for producing hydrogen through steam reforming of light oil. More specifically, disclosed is a method for producing hydrogen through steam reforming of light oil, the method being characterized by comprising: a catalyst activation step for reducing and activating a catalyst in which a metal is supported on a carrier; and a steam reforming step for supplying light oil and steam to the activated catalyst to steam reform the light oil, wherein, in the steam reforming step, the light oil and the steam are reacted at a temperature of 600-850 °C and a steam / carbon ratio of 1.5-3.5 to suppress carbon deposition by using the activated noble metal, and carbon-hydrogen bonds of the light oil are broken to promote hydrogen production. According to the present invention, it is possible to achieve technology for producing hydrogen using light oil that cannot be utilized due to a low flash point. In addition, reaction condition factors for preventing decreases in energy efficiency and equipment durability in process operation can be derived.

Description

Method for producing hydrogen through the steam reforming reaction of light oil

[0001] The present invention relates to a method for producing hydrogen through a steam reforming reaction of light oil, and more specifically, to a method for producing hydrogen through a steam reforming reaction of light oil that controls the reaction conditions of the steam reforming reaction to break down carbon-hydrogen bonds of light oil and promote hydrogen production.

[0002] Although the global production of waste plastic is continuously increasing, the recycling rate remains at a mere 9%, emerging as a global issue. Most plastic waste is disposed of through landfilling or incineration, while some leaks into the environment, becoming a source of pollution for oceans and rivers. In particular, marine plastic waste, which accounts for more than 80% of marine debris, amounted to 14 million tons in 2016 and is projected to increase to 37 million tons by 2040. This is predicted to cause serious marine environmental pollution, making it urgent to devise countermeasures.

[0003] Waste plastic treatment technologies include recycling, incineration, landfilling, and thermochemical treatment. Waste plastic recycling involves reprocessing waste plastic to utilize it as plastic with its original structure and quality, or converting it into other forms of plastic through decontamination processes, remelting, remolding, and re-extrusion. While this is the most environmentally friendly treatment method, it has the disadvantage that plastic waste consists of a mixture of various plastics and is often combined with other materials, making recycling impossible. Incineration and landfilling are traditional waste disposal methods that should be avoided due to the environmental pollution they cause. Thermochemical treatment of waste plastic is broadly classified into gasification and pyrolysis; gasification is a technology that generates synthesis gas in a high-temperature environment, while pyrolysis is a technology that produces pyrolysis oil under conditions where oxygen is absent or nearly non-existent. Thermochemical treatment has the advantage of being able to produce high-value materials while simultaneously processing waste plastic.

[0004] In particular, pyrolysis is a technology that has recently garnered significant attention due to its advantages, such as the production of diverse end products, relatively simple operation, and lower reaction temperatures compared to gasification. The pyrolysis process of waste plastics primarily generates gas, oil, and tea; the generated gaseous components are used as an internal energy source for the process, while the oil is mainly utilized as an alternative fuel. 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 serves 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. Notably, 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, thus restricting its sale or use. Therefore, a process to convert light oil into other substances is required.

[0005] As a solution to these problems, utilizing a steam reforming reaction 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 necessary to determine the optimal steam input amount that is suitable for the steam reforming reaction of waste plastic-derived light oils while maintaining high activity. Furthermore, the steam reforming reaction of hydrocarbons (C n +H m Since the reaction +nH2O → nCO+(n+0.5m)H2) is endothermic, it is dominant at high temperatures; however, high-temperature conditions can lead to reduced energy efficiency and equipment durability in process operations, so it is necessary to determine the optimal reaction temperature.

[0006] In addition, it has been reported that the amount of steam input in conventional reforming reactions has a significant impact on the conversion rate of hydrocarbons and the formation of carbon deposits on the catalyst, and the results of the present invention also showed results consistent with experiments of the prior art. However, since the injection of excessive steam lowers energy efficiency and leads to increased treatment costs for unreacted water, it is important to determine the optimal ratio for the steam / carbon molar ratio.

[0007] Accordingly, the inventors investigated the effects of the reaction temperature and steam input amount of the light oil reforming reaction on the hydrogen production yield using a commercial catalyst for reforming light oil derived from waste plastics and natural gas, evaluated the stability of the commercial catalyst to identify the optimal reaction conditions for the steam reforming reaction to produce hydrogen from light oil derived from waste plastics, and completed the present invention.

[0008] Accordingly, the present invention provides a method for producing hydrogen through a steam reforming reaction of light oil as a technical problem.

[0009] In order to solve the above technical problem, the present invention,

[0010] A catalyst activation step of activating a catalyst in which a metal supported on a support is reduced; and

[0011] A steam reforming step comprising supplying light oil and steam to the activated catalyst to perform a steam reforming reaction on the light oil;

[0012] The above steam reforming step is,

[0013] The above light oil and steam are reacted under conditions of a temperature of 600 to 850 ℃ and a steam / carbon ratio of 1.5 to 3.5,

[0014] The present invention provides a method for producing hydrogen through a steam reforming reaction of light oil, characterized by inhibiting carbon deposition by the activated catalyst and promoting hydrogen production by breaking down the carbon-hydrogen bonds of the light oil.

[0015] In the present invention, the metal is characterized by comprising at least one of rhodium (Rh), platinum (Pt), ruthenium (Ru), palladium (Pd), osmium (Os), iridium (Ir), silver (Ag), and gold (Au).

[0016] In the present invention, the light oil is characterized as being a hydrocarbon having 7 to 12 carbon atoms derived from waste plastic.

[0017] In the present invention, the steam reforming step comprises 0.1 to 5 cm of the light oil 3 / min and the above water vapor 0.1 ~ 1.0 cm 3 It is characterized by supplying at a flow rate of / min.

[0018] In the present invention, the steam reforming step comprises 10,000 to 150,000 mL·g of the light oil and steam. cat -1 ·h -1 It is characterized by further including reacting under space velocity (GHSV) conditions.

[0019] According to the present invention based on the solution means of the present invention, efficient and stable hydrogen production reaction conditions can be derived to effectively produce hydrogen through the steam reforming reaction of light oil components.

[0020] Furthermore, according to the method for producing hydrogen through the steam reforming reaction of light oil of the present invention, it is possible to secure a technology for producing hydrogen using light oil that cannot be utilized due to its low flash point. In addition, reaction condition factors can be derived to prevent a decrease in energy efficiency and equipment durability during process operation.

[0021] FIG. 1 is a conceptual diagram of a method for producing hydrogen by steam reforming reaction of light oil derived from waste plastic according to an embodiment of the present invention.

[0022] Figure 2 is GC-MS data for light oil and pyrolysis oil extracted from plastic waste according to an embodiment of the present invention.

[0023] Figure 3 is a graph showing the XRD analysis results of an Rh / Al2O3 catalyst according to an embodiment of the present invention.

[0024] Figure 4 is a graph showing the TPR analysis results of the Rh / Al2O3 catalyst according to an embodiment of the present invention.

[0025] Figure 5 shows the composition of the reaction gas generated according to the water vapor / carbon ratio according to an embodiment of the present invention.

[0026] Figure 6 is a graph showing the hydrogen yield and light oil conversion rate according to the water vapor / carbon molar ratio according to an embodiment of the present invention.

[0027] Figure 7 is a graph showing the gas composition according to the reaction temperature of the present invention.

[0028] Figure 8 is a graph showing the hydrogen yield and dodecane conversion rate according to the reaction temperature in accordance with an embodiment of the present invention.

[0029] FIG. 9 is a graph showing hydrogen yield and light oil conversion rate according to space velocity in an embodiment of the present invention.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] The present invention relates to a method for producing hydrogen through a steam reforming reaction of light oil. In this regard, FIG. 1 is a conceptual diagram schematically illustrating a method for producing hydrogen through a steam reforming reaction of light oil. Referring to FIG. 1, the method for producing hydrogen according to the present invention comprises: a catalyst activation step in which a catalyst having a metal supported on a carrier is reduced and activated; and a steam reforming step in which light oil and steam are supplied to the activated catalyst to perform a steam reforming reaction of the light oil. The steam reforming step is characterized by reacting the light oil and steam under conditions of a temperature of 600 to 850 ℃ and a steam-to-carbon ratio of 1.5 to 3.5, thereby suppressing carbon deposition by the activated precious metal and decomposing the carbon-hydrogen bonds of the light oil to promote hydrogen production.

[0034] In this invention, a commercial catalyst is used in light oil, and reaction conditions such as the reaction temperature, steam / carbon ratio, and space velocity of the steam reforming step are set to play an important role in promoting an efficient and stable hydrogen production reaction.

[0035] 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.

[0036] Steam reforming refers to a process that produces hydrogen (H2) by reacting light oil with steam (H2O) at high temperatures (e.g., 600–850°C), and this process relies heavily 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. For the application of catalysts in commercial processes, catalyst stability is a crucial factor, just as important as excellent activity. Specifically, catalyst stability significantly affects the catalyst replacement cycle; ensuring a catalyst lifespan exceeding a certain level is essential for commercial process operation, considering not only the cost of replacement but also the energy required for process shutdown and startup. In other words, commercial catalysts exhibiting high resistance to carbon deposition and sintering are required for the ethanol steam reforming reaction.

[0037] First, a catalyst activation step is described, in which a catalyst having a metal supported on a carrier is activated by reduction. The catalyst of the present invention may be a commercially available catalyst and may consist of an active material and a carrier. Preferably, the active material of the catalyst may include at least one of rhodium (Rh), platinum (Pt), ruthenium (Ru), palladium (Pd), osmium (Os), iridium (Ir), silver (Ag), and gold (Au). The carrier may include at least one of alumina, silica, zeolite, molecular sieve, metal monolith, and metal oxide ceramic. It is preferable that the weight ratio of the active material and the carrier is 0.01 to 5 : 95 to 99.99, respectively.

[0038] The above catalyst is a reduced form of a substrate in which a precious metal, which is an active material, and a support are chemically bonded. Due to the support having many hydroxyl groups, the precious metal, which is an active material, interacts strongly with the support. As a result, the sintering phenomenon, which is a cause of catalyst deactivation, can be suppressed and the lifespan of the catalyst can be extended, so it can be used in the commercial process of the present invention.

[0039] Next, a steam reforming step is described, in which light oil and steam are supplied to the activated catalyst to perform a steam reforming reaction on the light oil. It is preferable to produce hydrogen by reacting in the steam reforming step at a reaction temperature of 600 to 850 °C and a steam-to-carbon ratio of 1.5 to 3.5. In addition to the reaction temperature and steam-to-carbon ratio, 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).

[0040] Since the hydrocarbon reforming reaction is an endothermic reaction, high-temperature reaction conditions may be advantageous. While increasing the reaction temperature is beneficial for increasing hydrogen production, raising the reaction temperature increases the energy input to the process, which can lower operational efficiency; therefore, it is desirable to perform the reaction at a temperature of 600 to 850°C. If the reaction temperature is below 600°C, the reforming reaction of light oil may not proceed sufficiently, leading to a decrease in the hydrogen production rate. If the temperature exceeds 850°C, the thermal stability of the catalyst is compromised, and operational efficiency of the process decreases, which may result in reduced catalyst activity and lower hydrogen production efficiency. Preferably, the reaction can be performed at a temperature of 650 to 800°C.

[0041] In addition, 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 result in blockage of catalyst active sites, leading to conversion into a liquid substance rather than into hydrogen gas. If the steam / carbon ratio exceeds 3.5, problems may arise such as reduced reaction efficiency and increased energy consumption of the process due to excessive steam usage. More preferably, the steam / carbon ratio may be 2.0 to 3.0.

[0042] In addition, while a high space velocity can increase the total amount of product, it is necessary to derive an appropriate space velocity by reducing the contact time with the catalyst. A gas space velocity of 10,000 mL·g per hour 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 -1If it exceeds this value, the amount of gas injected per unit time increases, reducing the contact time between the catalyst and the reactants, which may decrease hydrogen yield and light oil conversion rate. Furthermore, high space velocities should be avoided to maintain catalyst stability, as they can increase carbon deposition and accelerate sintering. More preferably, the space velocity is 50,000 to 100,000 mL·g cat -1 ·h -1 It could be.

[0043] In addition, in the steam reforming step described above, the amount of steam injected can have a significant effect on the hydrocarbon conversion rate and the formation of carbon deposits on the catalyst. In the present invention, the steam and light oil derived from waste plastic are each 0.1 to 5 cm 3 / min and 0.1–1.0 cm 3 It is desirable to inject at a flow rate of / min. Therefore, water vapor 0.1 cm 3 If injected at a rate of / min or less, the amount of injected steam is insufficient to fully realize the effects of steam reforming, and some light oil may react with the steam to form liquid products, and the injection volume is 5 cm 3 If it exceeds / min, it may not be economical as it lowers energy efficiency and leads to increased treatment costs for unreacted water. In addition, light oil 0.1 cm 3 If injected at a rate of less than / min, the relative increase in the water vapor / carbon ratio may lead to higher treatment costs for unreacted water, making it uneconomical, and the injection volume is 1 cm 3 If it exceeds / min, the relative water vapor / carbon ratio decreases, so conversion to gaseous substances such as hydrogen does not occur and conversion to liquid substances may occur.

[0044] In the present invention, between the catalyst activation step and the steam reforming step, a raw material gasification step may be further included, wherein the steam is heated to 100 to 300 ℃ and the light oil is heated to 300 to 500 ℃ to gasify it; and it is preferable that each temperature be performed differently from each other.

[0045] 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 3.5, 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.

[0046]

[0047] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

[0048]

[0049] <Example 1> Selection of Standard Samples

[0050] The sample used was light oil derived from waste plastic generated at a waste plastic processing company located in Okcheon. In this regard, FIG. 2 is GC-MS data for light oil and pyrolysis oil extracted from plastic waste according to an embodiment of the present invention, and Table 1 below summarizes the data of FIG. 2.

[0051] RT(min)FormulaNameArea(%)3.02C7H 14 1-Heptene8.33.16C7H 16 Heptane6.03.21C7H 12 3-Hexyne, 2-methyl-1.93.67C7H 14 Cyclohexane, methyl-1.54.75C7H8Toluene11.54.84C7H 12Cyclohexane, methylene-1.35.54C8H 16 1-Octene5.95.81C8H 18 Octane5.26.45C9H 20 Heptane, 2,4-dimethyl-1.56.77C9H 18 2,3,3-Trimethyl-1-hexene4.77.02C9H 18 2,4-Dimethyl-1-heptene10.57.58C8H 10 Ethylbenzene5.68.39C 10 H 20 4-Nonene, 2-methyl-6.18.60C9H 20 Nonane2.610.63C 10 H 20 1-Decene1.410.88C 10 H 22 Octane, 3,5-dimethyl-1.012.16C 12 H 24 4-Octene, 2,3,6,7-tetramethyl-0.714.19C 12 H 26 Dodecane0.5

[0052] Referring to Table 1 and Figure 2 above, it was confirmed through GC-MS analysis that the carbon number of the included hydrocarbons in the waste plastic pyrolysis oil ranged from 7 to 25, and the carbon number of the waste plastic-derived light oil ranged from 7 to 12. Since the characteristics of the waste plastic pyrolysis oil vary depending on the input sample, it was necessary to select a standard sample to evaluate the performance of the catalyst. Although the amount of carbon number in the analyzed light oil was highest at around 7 to 10, carbon deposition on the catalyst, which causes catalyst deactivation, can easily occur as the carbon number increases; therefore, in this invention, dodecane was selected as the standard sample among the hydrocarbons with the highest carbon number of 12 in the waste plastic-derived light oil components under harsh conditions where carbon deposition can easily occur. For the catalyst used in the reaction experiments, the Rh / Al2O3 catalyst, a precious metal catalyst commercially utilized in natural gas reforming reactions, was employed. Since precious metal catalysts are reported to possess high activity and high resistance to carbon deposition and sintering—causes of deactivation—it was expected that they would exhibit catalytic activity for the conversion of dodecane and hydrogen production, even without being a catalyst specifically tailored for waste plastic-derived light oil. In particular, Rh exhibits high activity due to its excellent ability to break CH bonds in hydrocarbon reforming reactions, while Al2O3 demonstrates excellent thermal stability and can enhance sintering resistance through interaction with the active material, Rh.

[0053]

[0054] <Example 2> Catalyst Characterization

[0055] Characterization was performed to analyze the correlation between the performance and properties of the catalyst. Since the reforming reaction of light oil derived from waste plastics is an oxidation-reduction reaction, Temperature Programmed Reduction (TPR) was conducted using an AutoChem II 2920 to verify the reduction characteristics of the catalyst. The catalyst was heated from 50°C to 1,000°C at a rate of 10°C / min under 10% H2 / Ar gas conditions. After reduction, the catalyst was cooled to 50°C, and H2 gas was injected in pulses to chemisorb onto the catalyst. X-ray diffraction (XRD) analysis was performed to confirm the crystallographic characteristics of the catalyst. XRD analysis was conducted using an X′ Pert PRO MPD diffractometer (PANalytical, Netherlands), with 2θ ranging from 20° to 80°. Thermogravimetric analysis (TGA) was performed to confirm carbon deposition on the catalyst after the reaction. After the reaction of 8.5 mg, the catalyst was heated from 25 ℃ to 800 ℃ at a rate of 10 ℃ / min under oxygen conditions to oxidize the carbon deposited on the catalyst.

[0056]

[0057] <Example 3> Catalytic Reaction

[0058] The reaction experiment for the reforming of light oil derived from waste plastics was conducted by fixing a catalyst in a quartz reactor. The quartz reactor was cylindrical in shape with a diameter of 4–6 mm and structured to accommodate quartz wool in the middle. 20 mg of Rh / Al2O3 catalyst (SIGMA-ALDRICH) was injected onto the quartz wool, and a thermocouple was installed in the center of the catalyst layer to measure the reaction temperature. The quartz reactor was installed inside a heating jacket composed of insulation. The catalyst layer was heated at a rate of 6.5 ℃ / min to reach 800 ℃ and maintained for 3 hours. During this process, 5% H2 / N2 gas was supplied at a rate of 20 cm using a mass flow controller. 3The catalyst was reduced by injecting at a flow rate of / min. After the reduction was complete, the reactants, water vapor and dodecane, were supplied using a syringe and syringe pump with controlled flow rates. The water vapor was 0.5–2.0 cm 3 It was injected at a flow rate of / min, and dodecane was 0.15–0.6 cm 3 Water vapor and dodecane were gasified using a preheater before being injected into the catalyst bed. Considering the boiling points of each raw material, the temperature of the preheater was set to 200°C to generate water vapor and 350°C to convert dodecane into vapor. After the reaction, the gas was passed through a test tube in a constant temperature water bath maintained at -2°C and a glass tube filled with a hygroscopic agent (Drierite) to completely remove moisture and liquid products, and then analyzed using gas chromatography (Agilent Micro GC-490).

[0059] To investigate optimal reaction conditions, reaction experiments were conducted by controlling the reaction temperature between 650 and 800 °C and the water vapor to carbon ratio between 1.5 and 3.0. Additionally, to investigate the effect of changes in space velocity on the reaction, space velocities were varied from 44,770 to 128,770 mL·g cat -1 ·h -1 The experiment was performed by setting it to .

[0060]

[0061] <Results and Evaluation>

[0062] (1) Results of catalyst characteristic analysis

[0063] Figure 3 is a graph showing the XRD analysis results of a Rh / Al2O3 catalyst according to an embodiment of the present invention. Referring to Figure 3, since the loading amount of Rh is low at 0.5 wt%, no XRD diffraction peaks were observed, and diffraction peaks of η-Al2O3 were observed. Conventionally, η-Al2O3 has been reported to be manufactured by extrusion of bayerite Al(OH)3, which is an aluminum hydroxide. η-Al2O3 manufactured from a hydroxide has a large number of hydroxyl groups on the catalyst surface, which can promote strong interactions with the active material during the catalyst manufacturing process. The strong interaction between the active material and the support can suppress the sintering phenomenon, which is one of the causes of catalyst deactivation, thereby extending the lifespan of the catalyst.

[0064] Figure 4 is a graph showing the TPR analysis results of the Rh / Al2O3 catalyst according to an embodiment of the present invention. Referring to Figure 4, a single reduction peak was observed at temperatures above 500°C, which is attributed to the reduction of the Rh(AlO2)y species formed by the chemical bonding of the active material Rh and the support Al2O3. It is believed that the numerous hydroxyl groups generated during the manufacturing process, as shown in the XRD graph above, by using bayerite Al(OH)3 as a precursor to prepare the Al2O3 support, strengthened the interaction between Rh and Al2O3. In particular, although it has been reported that a peak due to Rh2O3 reduction with weak interaction with the support Al2O3 appears at low temperatures below 300°C, the fact that this peak was not observed in the Rh / Al2O3 catalyst used in the present invention also indicates a strong interaction. Strong interaction between the active material and the support has the effect of extending the lifespan of the catalyst by suppressing the sintering phenomenon, which is a cause of catalyst deactivation.

[0065]

[0066] (2) Results of light oil reforming reaction derived from waste plastic according to water vapor / carbon ratio

[0067] Figure 5 shows the composition of the reaction gas generated according to the water vapor / carbon ratio in accordance with an embodiment of the present invention. The water vapor / carbon ratio, along with the reaction temperature, significantly affects the hydrocarbon conversion rate and hydrogen production yield, and is a key factor capable of suppressing carbon deposition, which is a cause of catalyst deactivation; it was determined that the influence of the water vapor / carbon ratio is greater than that of the reaction temperature. Referring to Figure 5, almost no gases other than nitrogen were detected up to a water vapor / carbon ratio of 2.0. This suggests that when the ratio of water vapor is low, liquid products are formed by the reaction of some dodecane with water vapor rather than the dodecane being reformed into gas. Gaseous products such as hydrogen, methane, carbon monoxide, and carbon dioxide were observed from a water vapor / carbon ratio of 2.5 or higher. As the water vapor / carbon ratio increased, the hydrogen production increased. This is attributed to the fact that the supply of an excess amount of water vapor is advantageous for the hydrocarbon reforming reaction and simultaneously promotes the water-gas shift reaction. In the case of methane, it decreased as the water vapor supply increased, which is because the excess water vapor supplied reacted with methane. It was observed that as the water vapor supply increased, the amount of carbon monoxide produced decreased and the amount of carbon dioxide produced increased; this is believed to be due to the water-gas shift reaction occurring in which the excess water vapor reacts with carbon monoxide, resulting in the generation of carbon dioxide. Consequently, it was confirmed that the ratio of water vapor significantly affects the conversion of dodecane and the hydrogen production yield, and that dodecane is converted into a gaseous substance only when a certain level of water vapor is supplied.

[0068] FIG. 6 is a graph showing the hydrogen yield and light oil conversion rate according to the water vapor / carbon molar ratio according to an embodiment of the present invention. Referring to FIG. 6, by controlling the water vapor / carbon molar ratio to 1.5 to 3.5, a reaction temperature of 800°C and a space velocity of 72,540 mL·g cat -1 ·h -1The hydrogen yield and light oil conversion rate were confirmed under the reaction conditions. When the steam injection amount was 2.0 or less, the light oil was converted into a liquid substance; however, the light oil conversion rate shown here was 0% because the conversion to a gaseous substance was calculated. When the steam injection amount was 2.5 or more, the light oil was converted into a gaseous substance, and it was confirmed that the dodecane conversion rate and hydrogen yield increased with increasing steam injection amount. It has been reported that in conventional reforming reactions, the steam injection amount has a significant impact on the hydrocarbon conversion rate and the formation of carbon deposits on the catalyst, and the results of the present invention were consistent with those of experiments in the prior art. However, since excessive steam injection lowers energy efficiency and leads to increased treatment costs for unreacted water, determining the optimal ratio for the steam / carbon molar ratio is important. Therefore, in the present invention, high energy efficiency was confirmed by setting the optimal ratio to a steam / carbon ratio of 2.5, which is the point at which the light oil is converted into a gas.

[0069]

[0070] (3) Results of the reaction to modify light oil derived from waste plastic according to reaction temperature

[0071] Figure 7 is a graph showing the gas composition according to the reaction temperature of the present invention. Referring to Figure 7, under the condition of 25°C, dodecane and water vapor do not react, so only nitrogen was analyzed by GC. Since nitrogen does not participate in the reforming reaction, no change was observed with respect to changes in reaction temperature. Hydrogen is generated through the reforming reaction, and since the reforming reaction is an endothermic reaction that is advantageous at high reaction temperatures, it was confirmed that the production of hydrogen increased as the reaction temperature increased. In the case of methane, it was confirmed that the amount generated decreased as the reaction temperature increased, as it is a hydrocarbon separated during the reforming reaction of dodecane. This is because the methane steam reforming reaction (CH4+H2O → CO+3H2, ΔH = 206 kJ / mol), in which water vapor reacts with methane, is advantageous at high temperatures as the reaction temperature increases. Since the product of the steam reforming reaction of methane is hydrogen, the production of hydrogen increases as this reaction is promoted. Carbon monoxide is produced through the steam reforming reaction, and like hydrogen, its production increases as the reaction temperature increases. Carbon dioxide is produced through the water-gas shift reaction (CO + H2O → H2 + CO2, ΔH = -41 kJ / mol), in which carbon monoxide reacts with water vapor. Although the amount of the reactant, carbon monoxide, increased with increasing temperature, carbon dioxide showed similar production amounts except at a reaction temperature of 650 ℃. This is because the water-gas shift reaction is an exothermic reaction preferred at low temperatures, so it is suppressed at high temperatures; consequently, the production amount did not increase despite the large amount of reactants.

[0072] Figure 8 is a graph showing the hydrogen yield and dodecane conversion rate according to the reaction temperature in an embodiment of the present invention. Referring to Figure 8, it was confirmed that the hydrogen yield and dodecane conversion rate increased as the reaction temperature increased. This result was due to the fact that high-temperature reaction conditions are advantageous because the hydrocarbon reforming reaction is an endothermic reaction. In conclusion, while increasing the reaction temperature is a method to increase hydrogen production, it was confirmed that appropriate control of the reaction temperature is necessary because increasing the reaction temperature increases the energy input to the process, thereby lowering the operational efficiency of the process and affecting the durability of the equipment.

[0073] Therefore, in the present invention, the hydrogen yield and dodecane conversion rate increased twofold at a reaction temperature of at least 700 ℃ compared to 650 ℃, and increased by 1.3 times at 750 ℃ ​​and 1.1 times at 800 ℃. It was determined that a lower increase effect would be observed with subsequent temperature increases, so it was confirmed that the optimal reaction temperature range is 750~800 ℃.

[0074]

[0075] (4) Results of the reaction to modifying light oil derived from waste plastics and the results of the stability evaluation according to space velocity

[0076] Figure 9 is a graph showing the hydrogen yield and light oil conversion rate according to the space velocity in an embodiment of the present invention. Referring to Figure 9, the effect of space velocity on catalyst performance at the optimal water vapor / carbon molar ratio and reaction temperature can be confirmed. While a high space velocity can increase the total amount of product, it reduces the contact time with the catalyst, so it is necessary to determine an appropriate space velocity. In the present invention, it was confirmed that the hydrogen yield and light oil conversion rate decreased as the space velocity increased. This was attributed to the fact that as the space velocity increased, the amount of gas injected per unit time increased, thereby reducing the contact time between the catalyst and the reactants. Furthermore, since an increase in space velocity can increase carbon deposition and accelerate sintering, high space velocities should be avoided in terms of maintaining catalyst stability. However, if the space velocity is too low, process productivity decreases; therefore, it is determined that the space velocity should be designed by considering the conversion rate, yield, and absolute production volume. Accordingly, to this end, the present invention uses a space velocity of 72,540 mL·g cat -1 ·h -1 The reaction conditions of were derived.

[0077]

[0078] In summary, the present invention optimized the reforming reaction conditions for converting light oil, a byproduct generated during the plastic pyrolysis process, into hydrogen. The steam-to-carbon ratio was a critical variable that needed to be controlled to produce synthesis gas from light oil, and it was confirmed that gas generation began at a ratio of 2.5 or higher. Although it was confirmed that hydrogen production and the conversion rate of light oil increased when the steam-to-carbon ratio increased to 3.0, the optimal ratio was determined to be 2.5 because an increase in steam input can lead to reduced energy efficiency and increased water treatment costs. Since hydrocarbon reforming is advantageous at high temperatures, it was confirmed that the hydrogen yield and the conversion rate of light oil increased as the reaction temperature increased. However, as the reaction temperature increased, the rate of increase in hydrogen yield and light oil conversion rate with increasing temperature showed a decrease; furthermore, high reaction temperatures can cause problems such as reduced process energy efficiency, accelerated catalyst deactivation, and reduced thermal durability of equipment, so it was confirmed that the optimal temperature for the above reaction is 750 ℃. Additionally, reaction experiments were conducted by controlling the space velocity, and it was confirmed that the hydrogen yield and dodecane conversion rate decreased with increasing space velocity. It was confirmed that this was because the contact time between the reactants and the catalyst decreased as the space velocity increased.

[0079]

Claims

1. A catalyst activation step of activating a catalyst in which a metal is supported on a support by reducing it; and A steam reforming step comprising supplying light oil and steam to the activated catalyst to perform a steam reforming reaction on the light oil; The above steam reforming step is, The above light oil and steam are reacted under conditions of a temperature of 600 to 850 ℃ and a steam / carbon ratio of 1.5 to 3.5, A method for producing hydrogen through a steam reforming reaction of light oil, characterized by suppressing carbon deposition by the activated catalyst and breaking down the carbon-hydrogen bonds of the light oil to promote hydrogen production.

2. In Paragraph 1, The above metal is, A method for producing hydrogen through a steam reforming reaction of light oil, characterized by including at least one of rhodium (Rh), platinum (Pt), ruthenium (Ru), palladium (Pd), osmium (Os), iridium (Ir), silver (Ag), and gold (Au).

3. In Paragraph 1, The above light oil is, A method for producing hydrogen through a steam reforming reaction of light oil, characterized by being a hydrocarbon having 7 to 12 carbon atoms derived from waste plastic.

4. In Paragraph 1, The above steam reforming step is, The above light oil is 0.1 to 5 cm 3 / min and the above water vapor 0.1 ~ 1.0 cm 3 A method for producing hydrogen through a steam reforming reaction of light oil, characterized by supplying at a flow rate of / min.

5. In Paragraph 1, The above steam reforming step is, The above light oil and steam at 10,000 to 150,000 mL·g cat -1 ·h -1 A method for producing hydrogen through a steam reforming reaction of light oil, characterized by further including reacting under a space velocity (GHSV) condition.

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