Characteristics of the Fe/Cr/Cu catalyst pellet in the high-temperature water-gas shift reaction

Characteristics of the Fe/Cr/Cu catalyst pellet in the high-temperature water-gas shift reaction | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Characteristics of the Fe/Cr/Cu catalyst pellet in the high-temperature water-gas shift reaction Sang-Hyeok Jeong, Chang-Jun Lee, Cheol-Hwi Ryu, Gab-Jin Hwang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6203088/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The Fe/Cr/Cu catalyst pellet was prepared for application in the high-temperature water-gas shift reaction (HTWGSR) to produce hydrogen from the gasified gases of waste plastics. The Fe/Cr/Cu catalyst pellet was synthesized using a compression molding method with the prepared catalyst powder. The HTWGSR was conducted using the prepared catalyst pellet with CO: H 2 O ratios of 1: 2 and 1: 3 at a temperature range of 300 ℃ to 400 ℃. The maximum average CO conversion of the Fe/Cr/Cu catalyst pellet was observed at a CO: H 2 O ratio of 1: 2, with a value of 87%. These results suggest that the prepared Fe/Cr/Cu catalyst pellet is suitable for high-temperature water-gas shift reactions in terms of CO conversion. Hydrogen Production Water gas shift reaction High temperature shift reaction Catalyst Catalyst pellet Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Plastics are widely used due to their versatility, but many problems arise from the disposal of waste plastics after use. Waste plastics are either buried in landfills, incinerated or recycled, but these methods contribute to water and air pollution or incur high cost. In particular, incineration waste plastics has the disadvantage of emitting carbon dioxide, a major environmental pollutant [ 1 ], and the low degradability of plastic is causing serious marine environmental problems [ 2 , 3 ]. Therefore, the management of waste plastics is emerging as an urgent issue that must be addressed. Recently, pyrolysis and gasification technologies for converting waste plastics into valuable products have been receiving significant attention [ 1 , 4 – 6 ]. Thermal decomposition of waste plastics is an efficient method for producing chemicals by heating plastic waste to a temperature range of 400 ℃~1,000 ℃, selectively yielding wax, light olefins, and monomers [ 7 – 12 ]. However, the commercialization of the thermal decomposition process of waste plastics is not yet fully underway [ 13 ]. Gasification of waste plastics produces gases such as H 2 , CO, CO 2 , CH 4 , etc., by reacting waste plastics with oxygen or air at a high-temperature range of approximately 700 ℃~1,500 ℃. This process primarily focuses on producing fuels such as synthetic petroleum, dimethyl ether (DME), methanol, and energy carriers like hydrogen, from the generated syngas (CO + H 2 ) [ 7 ]. In order to produce high-purity hydrogen from syngas, a water-gas shift reaction (WGSR) is essential, converting CO into CO 2 while also producing additional hydrogen. The WGSR is a moderately exothermic reaction, and its equilibrium constant decreases as the temperature increases. WGSR proceeds as follows: $$\:\text{C}\text{O}+{H}_{2}\text{O}\:\to\:{H}_{2}+\text{C}{O}_{2}\:\:\:\:\:\varDelta\:{H}_{298}^{0}=-41.09\:\text{k}\text{J}/\text{m}\text{o}\text{l}\:\:$$ 1 Generally, the WGSR favors the forward conversion of CO and the production of H 2 due to its two main characteristics: its exothermic reaction and its reversibility. However, the reaction rate is significantly reduced at lower temperatures due to kinetic limitations. Therefore, a two-step catalytic process is employed in commercial applications to achieve both a high reaction rate and a high conversion rate simultaneously. This process consists of a high-temperature water-gas shift reaction (HTWGSR) conducted at 300 ℃~500 ℃, followed by a low-temperature water-gas shift reaction (LTWGSR) at 150 ℃~250 ℃ [ 14 ]. This two-step process aims to maximize hydrogen production by achieving a high reaction rate at high temperatures while further increasing CO conversion and hydrogen yield at lower temperatures. In previous research, a continuous two-step catalytic process was conducted at 350 ℃~400 ℃ for HTWGSR using a commercial Fe/Cr catalyst pellet, and at 200 ℃~220 ℃ for LTWGSR using a commercial Cu/Zn/Al catalyst pellet. It was confirmed that a CO conversion rate of 95% was achieved as a result [ 15 ]. Many investigates are being conducted to develop catalysts that improve stability against deactivation and enhance the CO conversion rate since the development of the Fe/Cr oxide catalyst for high-temperature water-gas shift reactions [ 14 , 16 – 24 ]. The steam-to-CO ratio (CO: H 2 O) is a critical variable in the WGSR. A low CO: H 2 O ratio negatively impacts the process, leading to side reactions such as carbon deposition and methanation instead of the WGSR. At low CO: H 2 O ratio, the Fe/Cr catalyst used in the HTWGSR promotes the formation of iron carbide, which acts as an active catalyst of methanation during the HTWGSR. Therefore, the CO: H 2 O ratio in HTWGSR is typically maintained above 1: 1, and with a recommended range of 1: 2 to 1: 4 for optimal performance [ 14 ]. Furthermore, it is known that adding promoters such as metals or metal oxides (Zn, Mn, etc.) to Fe/Cr catalysts enhances their activity by increasing the reaction rate and shifting maximum conversion to lower temperatures [ 14 , 16 , 23 – 25 ]. In this paper, to enhance catalytic activity in the high-temperature water-gas shift reaction (HTWGSR), the catalyst powder was prepared via the co-precipitation method by adding a promoter, such as Cu, to Fe/Cr. The Fe/Cr/Cu catalyst pellet was then synthesized through a compression molding method for application in HTWGSR, utilizing the prepared catalyst powder. In the HTWGSR, only CO and steam were used as reaction gases to evaluate the properties of the prepared catalyst pellet, rather than using real gas mixtures (containing H 2 , CO, CO 2 , CH 4 ). The HTWGSR was conducted using the prepared catalyst pellets under CO: H 2 O ratios of 1: 2 and 1: 3, a gas hourly space velocity (GHSV) of 10,000 h − 1 , and temperatures ranging of 300 ℃~400 ℃. And then the CO conversion of the prepared catalyst pellet was evaluated. 2. Experimental 2.1. Preparation of the catalyst powder The Fe/Cr/Cu catalyst powder was prepared using the co-precipitation method. The Fe/Cr/Cu catalyst powder was synthesized as follows: 1M (mol∙L -1 ) Fe(NO 3 ) 3 ∙9H 2 O (Samchun Co., 98.5%), 1M Cr(NO 3 ) 3 ∙9H 2 O (Samchun Co., 98%), 1M Cu(NO 3 ) 3 ∙3H 2 O (Samchun Co., 80%) were mixed under continuous stirring. The mixing ratio of Fe: Cr: Cu was 70: 25: 5 (wt.%). The 2 M NaOH solution was then added under continuous stirring at 70 ℃ for 4 hrs, maintaining the pH of the reaction mixture at 7.0 ± 0.5. The resulting co-precipitate was aged for 1 hr at room temperature. The obtained precipitate was filtered via vacuum filtration, washed with deionized water, and dried at 100 ℃ for 24 hrs to remove the byproducts and unreacted agent. The dried product was then crushed into powder, sieved through a 212-mesh sieve for uniform particle size, and sintered at 350 ℃ for 4 hrs in the muffle furnace under an air atmosphere. 2.2. Preparation of the catalyst pellet The prepared Fe/Cr/Cu catalyst powder was dissolved in α-terpineol. Polyethylene glycol (PEG, Junsei Co.) was added as a binder, and the mixture was ball-milled at 300 rpm and room temperature for 1 hr. The weight ratio of catalyst powder to solvent to binder was 30: 1: 2. A cylindrical pellet was then formed by applying 40 MPa of pressure to the prepared catalyst slurry using a molding machine for 15 mins. The prepared cylindrical pellet was sintered at 600 ℃ for 4 hrs in the muffle furnace under an air atmosphere to obtain the final cylindrical catalyst pellet (outer diameter: about 6 mm, length: about 5.5 mm). 2.3. Characterizations of the catalyst powder and catalyst pellet The crystalline structure of the prepared catalyst powder was analyzed using X-ray diffraction (XRD). The XRD pattern was obtained using an Empyrean (Panalytical B.V Co.) with Cu-Ka radiation and a nickel filter, operating in goniometer mode. Diffraction angles were measured between 10° [2θ] and 90° [2θ]. The morphology and elemental composition of the prepared catalyst powder were analyzed using scanning electron microscopy (SEM, FEI Co.) and energy dispersive X-ray spectroscopy (EDXS, Oxford Co.), respectively. The surface area and pore diameter of the prepared catalyst powder and catalyst pellet were measured using the Brunauer-Emmett-Teller (BET) method (Quantachrome Co.). Additionally, the compressive strength of the prepared catalyst pellet was evaluated using a compressive strength meter (DBBP-500, Test One Co.). 2.4. High temperature water gas shift reaction Figure 1 shows the experimental apparatus for the high-temperature water-gas shift reaction using the prepared catalyst pellet. A cylindrical SUS reactor (inner diameter: 34 mm, length: 300 mm) was placed inside an electric furnace, as shown in Fig. 1 . The prepared catalyst pellets were placed on the SUS support inside the cylindrical reactor, occupying a volume of approximately 3.16 mL. The flow rate of the mixed gas (CO, H 2 O, and N 2 ) was about 528 mL∙min − 1 . The feed flow rate of steam (H 2 O) was fixed at approximately 310 mL∙min − 1 , supplied by a steam generator at 120 ℃. The CO gas flow rate was adjusted to maintain a CO: H 2 O ratio of either 1: 2 or 1: 3, with the remaining flow rate supplemented by N 2 gas to achieve the total mixed gas flow rate. For a CO: H 2 O ratio of 1: 2, the flow rates of CO, H 2 O, and N 2 were 155 mL∙min − 1 , 310 mL∙min − 1 , and 63 mL∙min − 1 , respectively. For a CO: H 2 O ratio of 1: 3, the flow rates of CO, H 2 O, and N 2 were 103 mL∙min − 1 , 310 mL∙min − 1 , and 115 mL∙min − 1 , respectively. The gas hourly space velocity (GHSV), calculated by dividing the mixed gas flow rate by the catalyst pellet volume, was approximately 10,000 h − 1 . The high-temperature water-gas shift reaction was conducted at 300 ℃, 350 ℃, and 400 ℃ for 70 mins. The gases produced from the HTWGSR, including CO, CO 2 , H 2 and N 2 , were analyzed using gas chromatography (GC) (Chrozen, Youngin Co.). A 0.25 mL sample was taken for GC analysis. Gas analyses of CO, CO 2 , H 2 , and N 2 were performed after establishing a calibration curve for each gas. The CO conversion rate was then calculated using Eq. ( 2 ) based on the obtained GC data. $$\:\text{C}\text{O}\:\text{c}\text{o}\text{n}\text{v}\text{e}\text{r}\text{s}\text{i}\text{o}\text{n}\:\:\left(\text{\%}\right)=$$ $$\:[1-\raisebox{1ex}{$CO\:quantity\:after\:reaction$}\!\left/\:\!\raisebox{-1ex}{$CO\:quantity\:before\:reaction$}\right.]\times\:100$$ 2 3. Results and discussion 3.1. Characterizations of the catalyst powder and catalyst pellet Figure 2 shows the XRD pattern of the prepared Fe/Cr/Cu catalyst powder. The peaks obtained from the XRD analysis were identified and analyzed using the Joint Committee on Powder Diffraction Standards (JCPDS) database. As shown in Fig. 2 , the XRD pattern of the prepared Fe/Cr/Cu catalyst powder revealed two peaks corresponding to hematite (Fe 2 O 3 ) and copper iron chromate (CuCrFeO 4 ) phases. The XRD pattern provides evidence of the formation of a copper-containing spinel structure (CuCrFeO 4 ). The XRD analysis confirmed that the Fe/Cr/Cu catalyst powder possesses a crystalline spinel-phase structure. Generally, it is known that the spinel structure (AB 2 O 4 ) in catalysts enhances catalytic activity, leading to increased CO conversion and improved thermal stability [ 14 , 16 , 20 , 22 – 25 ]. From these findings, it is estimated that the spinel structure formed in the prepared catalyst powder would be contribute to the increase CO conversion by enhancing the catalyst’s activity. As shown in Fig. 4 , the pore diameter, pore volume, and the surface area of the prepared Fe/Cr/Cu catalyst powder were 1.91 nm, 0.176 cc∙g -1 , and 152.81 m 2 ∙g -1 , respectively. In contrast, the pore diameter, pore volume, and the surface area of the prepared Fe/Cr/Cu catalyst pellet were 0.98 nm, 0.012 cc∙g -1 , and 3.91 m 2 ∙g -1 , respectively. BET analysis indicated that the pore diameter, pore volume, and surface area decreased when the powder was formed into the pellet. Table 1 presents the compressive strengths of the prepared catalyst pellet and the commercial catalyst pellet. The compressive strength of the prepared Fe/Cr/Cu pellet was 20.01 MPa, while that of the commercial Fe/Cr catalyst pellet (A company) for HTWGSR was 6.50 MPa. The prepared catalyst pellet exhibited a higher compressive strength compared to the commercial Fe/Cr catalyst pellet. From this result, it is estimated that the prepared catalyst pellet possesses good mechanical durability due to its high compressive strength. Table 1 Compressive strengths of the prepared catalyst pellet and the commercial catalyst pellet Name Cross-section area (mm 2 ) Maximum load (kg f ) Compressive strength (MPa) Prepared Fe/Cr/Cu catalyst pellet 29.40 60 20.01 Commercial Fe/Cr catalyst pellet (A company) 27.14 18 6.50 3.2. High-temperature water-gas shift reaction At 350 ℃ in the HTWGSR, for a CO: H 2 O ratio of 1: 2, the CO gas ratio as a reactant gas rapidly decreased from 29.3–2.5% during the first 10 mins of reaction time, then slightly increased to 4.2% after 70 mins. The H 2 gas ratio as a product gas increased from 0–19.5% during the first 10 mins, then decreased to 6.9% after 25 mins, and slightly increased to 7.3% after 70 mins. The CO 2 gas ratio as a product gas increased from 0–1.2% during the first 10 mins and then slightly increased to 2.0% after 70 mins. For a CO: H 2 O ratio of 1:3, the CO gas ratio rapidly decreased from 19.5–3.3% during the first 10 mins, then increased over next 40 mins, and finally decreased to 3.4% after 70 mins. The H 2 gas ratio rapidly increased from 0–20.4% during the first 10 mins, then fluctuated (increasing and decreasing) over the next 55 mins, and finally slightly decreased to 17.9% after 70 mins. The CO 2 gas ratio increased from 0–1.2% during the first 10 mins, remained nearly constant, and then slightly decreased to 0.8% after 70 mins. At 400 ℃ in the HTWGSR, for a CO: H 2 O ratio of 1: 2, the CO gas ratio as a reactant gas rapidly decreased from 29.3–6.9% during the first 25 mins of reaction time and then slightly decreased to 5.2% after 70 mins. The H 2 gas ratio as a product gas increased from 0–6.2% during the first 25 mins, remained nearly constant, and then slightly increased to 6.4% after 70 mins. Similarly, the CO 2 gas ratio as a product gas increased from 0–2.5% during the first 25 mins, remained nearly constant, and then slightly increased to 2.8% after 70 mins. For a CO: H 2 O ratio of 1: 3, the CO gas ratio rapidly decreased from 19.5–3.4% during the first 10 mins, remained nearly constant, and then slightly increased to 3.6% after 70 mins. The H 2 gas ratio rapidly increased from 0–16.3% during the first 10 mins, fluctuated over the next 55 mins, and then decreased to 9.8% after 70 mins. The CO 2 gas ratio increased from 0–2.1% during the first 10 mins, remained nearly constant, and then slightly increased to 2.2% after 70 mins. As shown in Fig. 5 , the H 2 and CO 2 gas ratios as product gases increased from an initial value of 0% in the HTWGSR, while the CO gas ratio as a reactant gas decreased from its initial value. This trend reflects the typical water-gas shift reaction, where the reactant gas decreases and the product gases increase. At all reaction temperatures of 300 ℃, 350 ℃, and 400 ℃, the rate of increase in H 2 gas ratio over time for a CO: H 2 O ratio of 1: 3 was higher than that for a CO: H 2 O ratio of 1: 2. Conversely, the rate of decrease in the CO gas ratio over time for a CO: H 2 O ratio of 1: 2 was higher than that for a CO: H 2 O ratio of 1: 3. Additionally, the CO 2 gas ratios for both CO: H 2 O ratios of 1: 2 and 1: 3 remined nearly identical over the reaction time. It is generally known that the higher H 2 production in the water-gas shift reaction (WGSR), compared to the stoichiometric quantity, is due to the water decomposition reaction occurring on the catalyst [ 27 ]. Although the CO 2 gas ratio remained unchanged, the rate of increase in H 2 gas ratio for a CO: H 2 O ratio of 1: 3 was higher than that for a CO: H 2 O ratio of 1: 2. This is likely due to the more active occurrence of the water decomposition reaction in the catalyst pellet, along with the WGSR, in the CO: H 2 O ratio of 1: 3 compared to that of 1: 2. Figure 6 shows the relationship between reaction time and CO conversion for each CO: H 2 O ratio and temperature during the high-temperature water-gas shift reaction using Fe/Cr/Cu catalyst pellets. At 300 ℃ in the HTWGSR, for a CO: H 2 O ratio of 1: 2, CO conversion at 25 mins of reaction time was 47.3%, increasing to 76% at 70 mins. For a CO: H 2 O ratio of 1: 3, CO conversion at 10 mins was 70.1%, reaching to 77% at 70 mins. At a reaction temperature of 300 ℃, CO conversion over reaction time for a CO: H 2 O ratio of 1: 2 exhibited a significant increasing trend, whereas for a CO: H 2 O ratio of 1: 3, the increase was less substantial. At 350 ℃ in the HTWGSR, for a CO: H 2 O ratio of 1: 2, CO conversion at 10 mins of reaction time was 91.3%, decreasing to 85.7% at 70 mins. For a CO: H 2 O ratio of 1: 3, CO conversion at 10 mins was 83.1%, remaining nearly unchanged at 82.8% at 70 mins. At a reaction temperature of 350 ℃, CO conversion over reaction time for a CO: H 2 O ratio of 1: 2 exhibited a slight decreasing trend, while for a CO: H 2 O ratio of 1: 3, the value remained almost constant. At 400 ℃ in the HTWGSR, for a CO: H 2 O ratio of 1: 2, CO conversion at 25 mins of reaction time was 76.5%, increasing to 82.4% at 70 mins. For a CO: H 2 O ratio of 1: 3, CO conversion at 10 mins was 82.7%, slightly decreasing to 81.5% at 70 mins. At a reaction temperature of 400 ℃, CO conversion over reaction time for a CO: H 2 O ratio of 1: 2 exhibited a slight increasing trend, while for a CO: H 2 O ratio of 1: 3, the value remained nearly constant. Figure 7 shows the relationship between reaction temperature and average CO conversion for each CO: H 2 O ratio in the high-temperature water-gas shift reaction using Fe/Cr/Cu catalyst pellets, as calculated from the data in Fig. 6 . At 300 ℃ in the HTWGSR, the average CO conversions for CO: H 2 O ratios of 1: 2 and 1: 3 were 67.5% and 73.8%, respectively. At 350 ℃, the average CO conversions for CO: H 2 O ratios of 1: 2 and 1: 3 were 87.0% and 81.2%, respectively. At 400 ℃, the average CO conversions for CO: H 2 O ratios of 1: 2 and 1: 3 were 80.0% and 78.8%, respectively. The average CO conversion for both CO: H 2 O ratios of 1: 2 and 1: 3 at a reaction temperature of 350 ℃ was higher than at 300 ℃ and 400 ℃. Additionally, the average CO conversion for a CO: H 2 O ratio of 1: 2 at 350 ℃ was higher than that for 1: 3. The maximum average CO conversion was 87% for a CO: H 2 O ratio of 1: 2 at 350 ℃. From those results, it appears that the high-temperature water-gas shift reaction using Fe/Cr/Cu catalyst pellets is suitable carried out at a reaction temperature of 350 ℃ and a CO: H 2 O ratio of 1: 2 to achieve high CO conversion. It has been reported that CO conversion of an Fe/Cr catalyst was 68% at 400 ℃ and 75% at 450 ℃ with the CO: H 2 O ratio of 1: 3.5 and a GHSV of 60,000 h -1 [ 28 ]. Although a direct comparison is challenging, the CO conversion of the prepared Fe/Cr/Cu catalyst pellet, measured at 300 ℃~400 ℃ in the HTWGSR, exhibited higher values compared to the Fe/Cr catalyst. This result suggests that the addition of promoter, such as Cu, to Fe/Cr enhanced catalyst activity and shifted the maximum conversion to a low temperature, even at a lower CO: H 2 O ratio. From the above results, a CO: H 2 O ratio of 1: 3 in the HTWGSR using the prepared catalyst pellet at each reaction temperature is estimated to be more effective than a ratio of 1: 2 in terms of H 2 gas production. Conversely, a CO: H 2 O ratio of 1: 2 is estimated to be more effective than a ratio of 1: 3 in terms of CO conversion. Additionally, the maximum average CO conversion in the prepared catalyst pellets exceeded 80%. This indicates that the prepared Fe/Cr/Cu catalyst pellet is suitable for use in high-temperature water-gas shift reactions in terms of CO conversion. As shown in Fig. 4 , the pore diameter and surface area of the prepared catalyst pellet were smaller than that those of the prepared catalyst powder. Generally, the pore structure of the catalyst powder affects the HTWGSR, as larger particle sizes and smaller surface areas lead to reduced catalytic activity and lower CO conversion [ 26 ]. However, the effect of pore structure in catalyst pellets on the HTWGSR has not yet been fully clarified. Therefore, it seems that further studies are necessary to investigate how changes in the pore structure of catalyst pellets, caused by the pressure applied during compressing molding, affect the HTWGSR. Additionally, the stability of the prepared catalyst pellet is one of the key metrics for evaluating catalyst performance. Thus, it appears that further studies are required to asses the long-term stability of the catalyst pellet, particularly regarding changes in CO conversion over extended reaction times under the real mixted gases (containing H 2 , CO, CO 2 , CH 4 ) in the HTWGSR. 4. Conclusions In this study, the Fe/Cr/Cu catalyst pellet was prepared for application in the high-temperature water-gas shift reaction (HTWGSR). The Fe/Cr/Cu catalyst pellet was synthesized using the prepared catalyst powder, which was prepared via the co-precipitation method by adding a promoter, such as Cu, to Fe/Cr to enhance catalytic activity. In the HTWGSR, CO gas and steam were used as reaction gases to evaluate the properties of the prepared catalyst pellet. The HTWGSR was conducted using the prepared catalyst pellet under CO: H 2 O ratios of 1: 2 and 1: 3, a gas hourly space velocity (GHSV) of 10,000 h − 1 , and at temperatures ranging of 300 ℃~400 ℃. The CO conversion of the prepared catalyst pellet was then evaluated. Based on the results, this study concluded as follows: (1) The H 2 gas production rates of the prepared catalyst pellet at a CO: H 2 O ratio of 1: 3 was higher than those at a CO: H 2 O ratio of 1: 2 across the temperature range of 300 ℃~400 ℃. (2) In the Fe/Cr/Cu catalyst pellet, for a CO: H 2 O ratio of 1: 2, the average CO conversion at 350 ℃ was higher than at 300 ℃ and 400 ℃, while for a CO: H 2 O ratio of 1: 3, the average CO conversion at 400 ℃ was higher than at 300 ℃ and 350 ℃. (3) The maximum average CO conversion was 87% at 350 ℃ with a CO: H 2 O ratio of 1: 2. (4) The prepared Fe/Cr/Cu catalyst pellet is considered suitable for use in high-temperature water-gas shift reactions in terms of CO conversion. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6203088","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":431160474,"identity":"de688022-7ac9-46f5-af30-b771c2d2ab3b","order_by":0,"name":"Sang-Hyeok Jeong","email":"","orcid":"","institution":"Hoseo University - Asan Campus: Hoseo University","correspondingAuthor":false,"prefix":"","firstName":"Sang-Hyeok","middleName":"","lastName":"Jeong","suffix":""},{"id":431160475,"identity":"6e4dbfc1-8ff2-47aa-a9fb-7139eb2c591c","order_by":1,"name":"Chang-Jun Lee","email":"","orcid":"","institution":"Hoseo University - Asan Campus: Hoseo University","correspondingAuthor":false,"prefix":"","firstName":"Chang-Jun","middleName":"","lastName":"Lee","suffix":""},{"id":431160476,"identity":"2e002940-115b-48e3-bd87-054066ee1690","order_by":2,"name":"Cheol-Hwi Ryu","email":"","orcid":"","institution":"Hoseo University - Asan Campus: Hoseo University","correspondingAuthor":false,"prefix":"","firstName":"Cheol-Hwi","middleName":"","lastName":"Ryu","suffix":""},{"id":431160477,"identity":"be740773-7316-4800-b697-27f496e8714c","order_by":3,"name":"Gab-Jin Hwang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzUlEQVRIiWNgGAWjYFCCM2BSzgDKZWwgVosxKVp4wGTiBqK1yDuePSbxc0dt+nb29ocPPjDYyG44QECL4YFzaZK9Z47n7uw5Y2w4gyHNmLCWhjNmN3jbjuVuuJHDJs3DcDiRKC03/7YdSze4kf78Nw/Df8Ja5BnOmN3mbatJMLiRYMbMw3CAsBYDhjPmv2XbDhhuOHPGWHKGQbLxTIK2zAD6+m1bnbzB8faHHz5U2Mn2EbTlBljFYbilhIF8fwOIqiNC6SgYBaNgFIxYAAA7AU0NiTQjgwAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0002-8350-8154","institution":"Hoseo University - Asan Campus: Hoseo University","correspondingAuthor":true,"prefix":"","firstName":"Gab-Jin","middleName":"","lastName":"Hwang","suffix":""}],"badges":[],"createdAt":"2025-03-11 12:40:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6203088/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6203088/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":79443351,"identity":"ce4d4547-ed1e-461b-83fa-651f492813fd","added_by":"auto","created_at":"2025-03-28 13:24:35","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":35359,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental apparatus for the high-temperature water-gas shift reaction using the prepared catalyst pellet.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6203088/v1/a622419d19029c12230ab9e5.png"},{"id":79443362,"identity":"0f9ec371-3f1e-4de6-90da-6e4947fdb2b7","added_by":"auto","created_at":"2025-03-28 13:24:35","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":44624,"visible":true,"origin":"","legend":"\u003cp\u003eXRD pattern of the prepared Fe/Cr/Cu powder.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6203088/v1/402cded868c12c838e494e45.png"},{"id":79443352,"identity":"5afcb029-fc39-4cce-b20f-90b40378075b","added_by":"auto","created_at":"2025-03-28 13:24:35","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":149148,"visible":true,"origin":"","legend":"\u003cp\u003eSEM image and EDXS analysis results of the prepared Fe/Cr/Cu catalyst powder.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6203088/v1/8a49aa6210380e9040368111.png"},{"id":79443364,"identity":"07a1a5c1-ec8a-4eae-a5c5-9afec00fa4e9","added_by":"auto","created_at":"2025-03-28 13:24:35","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":99962,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between cumulative pore volume and pore radius (width) of the prepared catalyst powder and catalyst pellet, as determined by BET analysis.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6203088/v1/cff13969bdc12242c4f570ca.png"},{"id":79443365,"identity":"36a49075-de45-48a1-b32e-eee0ca667d46","added_by":"auto","created_at":"2025-03-28 13:24:35","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":89512,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between reaction time and the production gas ratios of CO, H\u003csub\u003e2\u003c/sub\u003e and CO\u003csub\u003e2\u003c/sub\u003e for each CO: H\u003csub\u003e2\u003c/sub\u003eO ratio and temperature during the high-temperature water-gas shift reaction using Fe/Cr/Cu catalyst pellets (close symbol: CO: H\u003csub\u003e2\u003c/sub\u003eO=1: 2, open symbol: CO: H\u003csub\u003e2\u003c/sub\u003eO=1: 3).\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6203088/v1/9e1928205353302318ca757e.png"},{"id":79443358,"identity":"02ab8581-35c2-41d9-8c53-00c7f922f439","added_by":"auto","created_at":"2025-03-28 13:24:35","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":45902,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between reaction time and CO conversion for each CO: H\u003csub\u003e2\u003c/sub\u003eO ratio and temperature during the high-temperature water-gas shift reaction using Fe/Cr/Cu catalyst pellets (circle symbol: 300 ℃, square symbol: 350 ℃, triangle symbol: 400 ℃).\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6203088/v1/0e8f1065b884fff65d51b6a3.png"},{"id":79443360,"identity":"e87d92f5-1f97-4fb2-b286-bccc860b01d5","added_by":"auto","created_at":"2025-03-28 13:24:35","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":31063,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between reaction temperature and average CO conversion for each CO: H\u003csub\u003e2\u003c/sub\u003eO ratio in the high-temperature water-gas shift reaction using Fe/Cr/Cu catalyst pellets (close symbol: CO: H\u003csub\u003e2\u003c/sub\u003eO=1: 2, open symbol: CO: H\u003csub\u003e2\u003c/sub\u003eO=1: 3), as calculated from the data in Fig. 6.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6203088/v1/216ec39b0b90fd67c13265ca.png"},{"id":83957719,"identity":"074ab2de-c975-4f75-8316-44c79523c14f","added_by":"auto","created_at":"2025-06-05 03:48:49","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1052853,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6203088/v1/f8b3e079-7fe5-4d39-864a-cf2f73ddf2c1.pdf"}],"financialInterests":"","formattedTitle":"Characteristics of the Fe/Cr/Cu catalyst pellet in the high-temperature water-gas shift reaction","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003ePlastics are widely used due to their versatility, but many problems arise from the disposal of waste plastics after use. Waste plastics are either buried in landfills, incinerated or recycled, but these methods contribute to water and air pollution or incur high cost. In particular, incineration waste plastics has the disadvantage of emitting carbon dioxide, a major environmental pollutant [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], and the low degradability of plastic is causing serious marine environmental problems [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Therefore, the management of waste plastics is emerging as an urgent issue that must be addressed.\u003c/p\u003e \u003cp\u003eRecently, pyrolysis and gasification technologies for converting waste plastics into valuable products have been receiving significant attention [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Thermal decomposition of waste plastics is an efficient method for producing chemicals by heating plastic waste to a temperature range of 400 ℃~1,000 ℃, selectively yielding wax, light olefins, and monomers [\u003cspan additionalcitationids=\"CR8 CR9 CR10 CR11\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. However, the commercialization of the thermal decomposition process of waste plastics is not yet fully underway [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Gasification of waste plastics produces gases such as H\u003csub\u003e2\u003c/sub\u003e, CO, CO\u003csub\u003e2\u003c/sub\u003e, CH\u003csub\u003e4\u003c/sub\u003e, etc., by reacting waste plastics with oxygen or air at a high-temperature range of approximately 700 ℃~1,500 ℃. This process primarily focuses on producing fuels such as synthetic petroleum, dimethyl ether (DME), methanol, and energy carriers like hydrogen, from the generated syngas (CO\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003e) [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn order to produce high-purity hydrogen from syngas, a water-gas shift reaction (WGSR) is essential, converting CO into CO\u003csub\u003e2\u003c/sub\u003e while also producing additional hydrogen. The WGSR is a moderately exothermic reaction, and its equilibrium constant decreases as the temperature increases. WGSR proceeds as follows:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:\\text{C}\\text{O}+{H}_{2}\\text{O}\\:\\to\\:{H}_{2}+\\text{C}{O}_{2}\\:\\:\\:\\:\\:\\varDelta\\:{H}_{298}^{0}=-41.09\\:\\text{k}\\text{J}/\\text{m}\\text{o}\\text{l}\\:\\:$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eGenerally, the WGSR favors the forward conversion of CO and the production of H\u003csub\u003e2\u003c/sub\u003e due to its two main characteristics: its exothermic reaction and its reversibility. However, the reaction rate is significantly reduced at lower temperatures due to kinetic limitations. Therefore, a two-step catalytic process is employed in commercial applications to achieve both a high reaction rate and a high conversion rate simultaneously. This process consists of a high-temperature water-gas shift reaction (HTWGSR) conducted at 300 ℃~500 ℃, followed by a low-temperature water-gas shift reaction (LTWGSR) at 150 ℃~250 ℃ [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. This two-step process aims to maximize hydrogen production by achieving a high reaction rate at high temperatures while further increasing CO conversion and hydrogen yield at lower temperatures.\u003c/p\u003e \u003cp\u003eIn previous research, a continuous two-step catalytic process was conducted at 350 ℃~400 ℃ for HTWGSR using a commercial Fe/Cr catalyst pellet, and at 200 ℃~220 ℃ for LTWGSR using a commercial Cu/Zn/Al catalyst pellet. It was confirmed that a CO conversion rate of 95% was achieved as a result [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMany investigates are being conducted to develop catalysts that improve stability against deactivation and enhance the CO conversion rate since the development of the Fe/Cr oxide catalyst for high-temperature water-gas shift reactions [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan additionalcitationids=\"CR17 CR18 CR19 CR20 CR21 CR22 CR23\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe steam-to-CO ratio (CO: H\u003csub\u003e2\u003c/sub\u003eO) is a critical variable in the WGSR. A low CO: H\u003csub\u003e2\u003c/sub\u003eO ratio negatively impacts the process, leading to side reactions such as carbon deposition and methanation instead of the WGSR. At low CO: H\u003csub\u003e2\u003c/sub\u003eO ratio, the Fe/Cr catalyst used in the HTWGSR promotes the formation of iron carbide, which acts as an active catalyst of methanation during the HTWGSR. Therefore, the CO: H\u003csub\u003e2\u003c/sub\u003eO ratio in HTWGSR is typically maintained above 1: 1, and with a recommended range of 1: 2 to 1: 4 for optimal performance [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Furthermore, it is known that adding promoters such as metals or metal oxides (Zn, Mn, etc.) to Fe/Cr catalysts enhances their activity by increasing the reaction rate and shifting maximum conversion to lower temperatures [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn this paper, to enhance catalytic activity in the high-temperature water-gas shift reaction (HTWGSR), the catalyst powder was prepared via the co-precipitation method by adding a promoter, such as Cu, to Fe/Cr. The Fe/Cr/Cu catalyst pellet was then synthesized through a compression molding method for application in HTWGSR, utilizing the prepared catalyst powder. In the HTWGSR, only CO and steam were used as reaction gases to evaluate the properties of the prepared catalyst pellet, rather than using real gas mixtures (containing H\u003csub\u003e2\u003c/sub\u003e, CO, CO\u003csub\u003e2\u003c/sub\u003e, CH\u003csub\u003e4\u003c/sub\u003e). The HTWGSR was conducted using the prepared catalyst pellets under CO: H\u003csub\u003e2\u003c/sub\u003eO ratios of 1: 2 and 1: 3, a gas hourly space velocity (GHSV) of 10,000 h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and temperatures ranging of 300 ℃~400 ℃. And then the CO conversion of the prepared catalyst pellet was evaluated.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Preparation of the catalyst powder\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe Fe/Cr/Cu catalyst powder was prepared using the co-precipitation method.\u003c/p\u003e \u003cp\u003eThe Fe/Cr/Cu catalyst powder was synthesized as follows: 1M (mol∙L\u003csup\u003e-1\u003c/sup\u003e) Fe(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e∙9H\u003csub\u003e2\u003c/sub\u003eO (Samchun Co., 98.5%), 1M Cr(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e∙9H\u003csub\u003e2\u003c/sub\u003eO (Samchun Co., 98%), 1M Cu(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e∙3H\u003csub\u003e2\u003c/sub\u003eO (Samchun Co., 80%) were mixed under continuous stirring. The mixing ratio of Fe: Cr: Cu was 70: 25: 5 (wt.%). The 2 M NaOH solution was then added under continuous stirring at 70 ℃ for 4 hrs, maintaining the pH of the reaction mixture at 7.0\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5. The resulting co-precipitate was aged for 1 hr at room temperature. The obtained precipitate was filtered via vacuum filtration, washed with deionized water, and dried at 100 ℃ for 24 hrs to remove the byproducts and unreacted agent. The dried product was then crushed into powder, sieved through a 212-mesh sieve for uniform particle size, and sintered at 350 ℃ for 4 hrs in the muffle furnace under an air atmosphere.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Preparation of the catalyst pellet\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe prepared Fe/Cr/Cu catalyst powder was dissolved in α-terpineol. Polyethylene glycol (PEG, Junsei Co.) was added as a binder, and the mixture was ball-milled at 300 rpm and room temperature for 1 hr. The weight ratio of catalyst powder to solvent to binder was 30: 1: 2. A cylindrical pellet was then formed by applying 40 MPa of pressure to the prepared catalyst slurry using a molding machine for 15 mins. The prepared cylindrical pellet was sintered at 600 ℃ for 4 hrs in the muffle furnace under an air atmosphere to obtain the final cylindrical catalyst pellet (outer diameter: about 6 mm, length: about 5.5 mm).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Characterizations of the catalyst powder and catalyst pellet\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe crystalline structure of the prepared catalyst powder was analyzed using X-ray diffraction (XRD). The XRD pattern was obtained using an Empyrean (Panalytical B.V Co.) with Cu-Ka radiation and a nickel filter, operating in goniometer mode. Diffraction angles were measured between 10\u0026deg; [2θ] and 90\u0026deg; [2θ]. The morphology and elemental composition of the prepared catalyst powder were analyzed using scanning electron microscopy (SEM, FEI Co.) and energy dispersive X-ray spectroscopy (EDXS, Oxford Co.), respectively. The surface area and pore diameter of the prepared catalyst powder and catalyst pellet were measured using the Brunauer-Emmett-Teller (BET) method (Quantachrome Co.). Additionally, the compressive strength of the prepared catalyst pellet was evaluated using a compressive strength meter (DBBP-500, Test One Co.).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. High temperature water gas shift reaction\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the experimental apparatus for the high-temperature water-gas shift reaction using the prepared catalyst pellet.\u003c/p\u003e \u003cp\u003eA cylindrical SUS reactor (inner diameter: 34 mm, length: 300 mm) was placed inside an electric furnace, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The prepared catalyst pellets were placed on the SUS support inside the cylindrical reactor, occupying a volume of approximately 3.16 mL. The flow rate of the mixed gas (CO, H\u003csub\u003e2\u003c/sub\u003eO, and N\u003csub\u003e2\u003c/sub\u003e) was about 528 mL∙min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The feed flow rate of steam (H\u003csub\u003e2\u003c/sub\u003eO) was fixed at approximately 310 mL∙min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, supplied by a steam generator at 120 ℃. The CO gas flow rate was adjusted to maintain a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of either 1: 2 or 1: 3, with the remaining flow rate supplemented by N\u003csub\u003e2\u003c/sub\u003e gas to achieve the total mixed gas flow rate. For a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2, the flow rates of CO, H\u003csub\u003e2\u003c/sub\u003eO, and N\u003csub\u003e2\u003c/sub\u003e were 155 mL∙min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 310 mL∙min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 63 mL∙min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. For a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3, the flow rates of CO, H\u003csub\u003e2\u003c/sub\u003eO, and N\u003csub\u003e2\u003c/sub\u003e were 103 mL∙min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 310 mL∙min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 115 mL∙min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. The gas hourly space velocity (GHSV), calculated by dividing the mixed gas flow rate by the catalyst pellet volume, was approximately 10,000 h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The high-temperature water-gas shift reaction was conducted at 300 ℃, 350 ℃, and 400 ℃ for 70 mins.\u003c/p\u003e \u003cp\u003eThe gases produced from the HTWGSR, including CO, CO\u003csub\u003e2\u003c/sub\u003e, H\u003csub\u003e2\u003c/sub\u003e and N\u003csub\u003e2\u003c/sub\u003e, were analyzed using gas chromatography (GC) (Chrozen, Youngin Co.). A 0.25 mL sample was taken for GC analysis. Gas analyses of CO, CO\u003csub\u003e2\u003c/sub\u003e, H\u003csub\u003e2\u003c/sub\u003e, and N\u003csub\u003e2\u003c/sub\u003e were performed after establishing a calibration curve for each gas. The CO conversion rate was then calculated using Eq.\u0026nbsp;(\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) based on the obtained GC data.\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:\\text{C}\\text{O}\\:\\text{c}\\text{o}\\text{n}\\text{v}\\text{e}\\text{r}\\text{s}\\text{i}\\text{o}\\text{n}\\:\\:\\left(\\text{\\%}\\right)=$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:[1-\\raisebox{1ex}{$CO\\:quantity\\:after\\:reaction$}\\!\\left/\\:\\!\\raisebox{-1ex}{$CO\\:quantity\\:before\\:reaction$}\\right.]\\times\\:100$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Characterizations of the catalyst powder and catalyst pellet\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the XRD pattern of the prepared Fe/Cr/Cu catalyst powder.\u003c/p\u003e \u003cp\u003eThe peaks obtained from the XRD analysis were identified and analyzed using the Joint Committee on Powder Diffraction Standards (JCPDS) database.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the XRD pattern of the prepared Fe/Cr/Cu catalyst powder revealed two peaks corresponding to hematite (Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) and copper iron chromate (CuCrFeO\u003csub\u003e4\u003c/sub\u003e) phases. The XRD pattern provides evidence of the formation of a copper-containing spinel structure (CuCrFeO\u003csub\u003e4\u003c/sub\u003e).\u003c/p\u003e \u003cp\u003eThe XRD analysis confirmed that the Fe/Cr/Cu catalyst powder possesses a crystalline spinel-phase structure. Generally, it is known that the spinel structure (AB\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e) in catalysts enhances catalytic activity, leading to increased CO conversion and improved thermal stability [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan additionalcitationids=\"CR23 CR24\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. From these findings, it is estimated that the spinel structure formed in the prepared catalyst powder would be contribute to the increase CO conversion by enhancing the catalyst\u0026rsquo;s activity.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the pore diameter, pore volume, and the surface area of the prepared Fe/Cr/Cu catalyst powder were 1.91 nm, 0.176 cc∙g\u003csup\u003e-1\u003c/sup\u003e, and 152.81 m\u003csup\u003e2\u003c/sup\u003e∙g\u003csup\u003e-1\u003c/sup\u003e, respectively. In contrast, the pore diameter, pore volume, and the surface area of the prepared Fe/Cr/Cu catalyst pellet were 0.98 nm, 0.012 cc∙g\u003csup\u003e-1\u003c/sup\u003e, and 3.91 m\u003csup\u003e2\u003c/sup\u003e∙g\u003csup\u003e-1\u003c/sup\u003e, respectively. BET analysis indicated that the pore diameter, pore volume, and surface area decreased when the powder was formed into the pellet.\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents the compressive strengths of the prepared catalyst pellet and the commercial catalyst pellet.\u003c/p\u003e \u003cp\u003eThe compressive strength of the prepared Fe/Cr/Cu pellet was 20.01 MPa, while that of the commercial Fe/Cr catalyst pellet (A company) for HTWGSR was 6.50 MPa. The prepared catalyst pellet exhibited a higher compressive strength compared to the commercial Fe/Cr catalyst pellet. From this result, it is estimated that the prepared catalyst pellet possesses good mechanical durability due to its high compressive strength.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCompressive strengths of the prepared catalyst pellet and the commercial catalyst pellet\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eName\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCross-section area\u003c/p\u003e \u003cp\u003e(mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMaximum load\u003c/p\u003e \u003cp\u003e(kg\u003csub\u003ef\u003c/sub\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCompressive strength\u003c/p\u003e \u003cp\u003e(MPa)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePrepared Fe/Cr/Cu catalyst pellet\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e29.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e20.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCommercial Fe/Cr catalyst pellet\u003c/p\u003e \u003cp\u003e(A company)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e27.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6.50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.2. High-temperature water-gas shift reaction\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAt 350 ℃ in the HTWGSR, for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2, the CO gas ratio as a reactant gas rapidly decreased from 29.3\u0026ndash;2.5% during the first 10 mins of reaction time, then slightly increased to 4.2% after 70 mins. The H\u003csub\u003e2\u003c/sub\u003e gas ratio as a product gas increased from 0\u0026ndash;19.5% during the first 10 mins, then decreased to 6.9% after 25 mins, and slightly increased to 7.3% after 70 mins. The CO\u003csub\u003e2\u003c/sub\u003e gas ratio as a product gas increased from 0\u0026ndash;1.2% during the first 10 mins and then slightly increased to 2.0% after 70 mins. For a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1:3, the CO gas ratio rapidly decreased from 19.5\u0026ndash;3.3% during the first 10 mins, then increased over next 40 mins, and finally decreased to 3.4% after 70 mins. The H\u003csub\u003e2\u003c/sub\u003e gas ratio rapidly increased from 0\u0026ndash;20.4% during the first 10 mins, then fluctuated (increasing and decreasing) over the next 55 mins, and finally slightly decreased to 17.9% after 70 mins. The CO\u003csub\u003e2\u003c/sub\u003e gas ratio increased from 0\u0026ndash;1.2% during the first 10 mins, remained nearly constant, and then slightly decreased to 0.8% after 70 mins.\u003c/p\u003e \u003cp\u003eAt 400 ℃ in the HTWGSR, for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2, the CO gas ratio as a reactant gas rapidly decreased from 29.3\u0026ndash;6.9% during the first 25 mins of reaction time and then slightly decreased to 5.2% after 70 mins. The H\u003csub\u003e2\u003c/sub\u003e gas ratio as a product gas increased from 0\u0026ndash;6.2% during the first 25 mins, remained nearly constant, and then slightly increased to 6.4% after 70 mins. Similarly, the CO\u003csub\u003e2\u003c/sub\u003e gas ratio as a product gas increased from 0\u0026ndash;2.5% during the first 25 mins, remained nearly constant, and then slightly increased to 2.8% after 70 mins. For a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3, the CO gas ratio rapidly decreased from 19.5\u0026ndash;3.4% during the first 10 mins, remained nearly constant, and then slightly increased to 3.6% after 70 mins. The H\u003csub\u003e2\u003c/sub\u003e gas ratio rapidly increased from 0\u0026ndash;16.3% during the first 10 mins, fluctuated over the next 55 mins, and then decreased to 9.8% after 70 mins. The CO\u003csub\u003e2\u003c/sub\u003e gas ratio increased from 0\u0026ndash;2.1% during the first 10 mins, remained nearly constant, and then slightly increased to 2.2% after 70 mins.\u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e5\u003c/span\u003e, the H\u003csub\u003e2\u003c/sub\u003e and CO\u003csub\u003e2\u003c/sub\u003e gas ratios as product gases increased from an initial value of 0% in the HTWGSR, while the CO gas ratio as a reactant gas decreased from its initial value. This trend reflects the typical water-gas shift reaction, where the reactant gas decreases and the product gases increase.\u003c/p\u003e \u003cp\u003eAt all reaction temperatures of 300 ℃, 350 ℃, and 400 ℃, the rate of increase in H\u003csub\u003e2\u003c/sub\u003e gas ratio over time for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3 was higher than that for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2. Conversely, the rate of decrease in the CO gas ratio over time for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2 was higher than that for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3. Additionally, the CO\u003csub\u003e2\u003c/sub\u003e gas ratios for both CO: H\u003csub\u003e2\u003c/sub\u003eO ratios of 1: 2 and 1: 3 remined nearly identical over the reaction time. It is generally known that the higher H\u003csub\u003e2\u003c/sub\u003e production in the water-gas shift reaction (WGSR), compared to the stoichiometric quantity, is due to the water decomposition reaction occurring on the catalyst [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Although the CO\u003csub\u003e2\u003c/sub\u003e gas ratio remained unchanged, the rate of increase in H\u003csub\u003e2\u003c/sub\u003e gas ratio for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3 was higher than that for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2. This is likely due to the more active occurrence of the water decomposition reaction in the catalyst pellet, along with the WGSR, in the CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3 compared to that of 1: 2.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows the relationship between reaction time and CO conversion for each CO: H\u003csub\u003e2\u003c/sub\u003eO ratio and temperature during the high-temperature water-gas shift reaction using Fe/Cr/Cu catalyst pellets.\u003c/p\u003e \u003cp\u003eAt 300 ℃ in the HTWGSR, for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2, CO conversion at 25 mins of reaction time was 47.3%, increasing to 76% at 70 mins. For a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3, CO conversion at 10 mins was 70.1%, reaching to 77% at 70 mins. At a reaction temperature of 300 ℃, CO conversion over reaction time for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2 exhibited a significant increasing trend, whereas for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3, the increase was less substantial.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAt 350 ℃ in the HTWGSR, for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2, CO conversion at 10 mins of reaction time was 91.3%, decreasing to 85.7% at 70 mins. For a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3, CO conversion at 10 mins was 83.1%, remaining nearly unchanged at 82.8% at 70 mins. At a reaction temperature of 350 ℃, CO conversion over reaction time for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2 exhibited a slight decreasing trend, while for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3, the value remained almost constant.\u003c/p\u003e \u003cp\u003eAt 400 ℃ in the HTWGSR, for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2, CO conversion at 25 mins of reaction time was 76.5%, increasing to 82.4% at 70 mins. For a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3, CO conversion at 10 mins was 82.7%, slightly decreasing to 81.5% at 70 mins. At a reaction temperature of 400 ℃, CO conversion over reaction time for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2 exhibited a slight increasing trend, while for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3, the value remained nearly constant.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e shows the relationship between reaction temperature and average CO conversion for each CO: H\u003csub\u003e2\u003c/sub\u003eO ratio in the high-temperature water-gas shift reaction using Fe/Cr/Cu catalyst pellets, as calculated from the data in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eAt 300 ℃ in the HTWGSR, the average CO conversions for CO: H\u003csub\u003e2\u003c/sub\u003eO ratios of 1: 2 and 1: 3 were 67.5% and 73.8%, respectively. At 350 ℃, the average CO conversions for CO: H\u003csub\u003e2\u003c/sub\u003eO ratios of 1: 2 and 1: 3 were 87.0% and 81.2%, respectively. At 400 ℃, the average CO conversions for CO: H\u003csub\u003e2\u003c/sub\u003eO ratios of 1: 2 and 1: 3 were 80.0% and 78.8%, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe average CO conversion for both CO: H\u003csub\u003e2\u003c/sub\u003eO ratios of 1: 2 and 1: 3 at a reaction temperature of 350 ℃ was higher than at 300 ℃ and 400 ℃. Additionally, the average CO conversion for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2 at 350 ℃ was higher than that for 1: 3. The maximum average CO conversion was 87% for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2 at 350 ℃. From those results, it appears that the high-temperature water-gas shift reaction using Fe/Cr/Cu catalyst pellets is suitable carried out at a reaction temperature of 350 ℃ and a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2 to achieve high CO conversion.\u003c/p\u003e \u003cp\u003eIt has been reported that CO conversion of an Fe/Cr catalyst was 68% at 400 ℃ and 75% at 450 ℃ with the CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3.5 and a GHSV of 60,000 h\u003csup\u003e-1\u003c/sup\u003e [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Although a direct comparison is challenging, the CO conversion of the prepared Fe/Cr/Cu catalyst pellet, measured at 300 ℃~400 ℃ in the HTWGSR, exhibited higher values compared to the Fe/Cr catalyst. This result suggests that the addition of promoter, such as Cu, to Fe/Cr enhanced catalyst activity and shifted the maximum conversion to a low temperature, even at a lower CO: H\u003csub\u003e2\u003c/sub\u003eO ratio.\u003c/p\u003e \u003cp\u003eFrom the above results, a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3 in the HTWGSR using the prepared catalyst pellet at each reaction temperature is estimated to be more effective than a ratio of 1: 2 in terms of H\u003csub\u003e2\u003c/sub\u003e gas production. Conversely, a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2 is estimated to be more effective than a ratio of 1: 3 in terms of CO conversion. Additionally, the maximum average CO conversion in the prepared catalyst pellets exceeded 80%. This indicates that the prepared Fe/Cr/Cu catalyst pellet is suitable for use in high-temperature water-gas shift reactions in terms of CO conversion.\u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the pore diameter and surface area of the prepared catalyst pellet were smaller than that those of the prepared catalyst powder. Generally, the pore structure of the catalyst powder affects the HTWGSR, as larger particle sizes and smaller surface areas lead to reduced catalytic activity and lower CO conversion [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. However, the effect of pore structure in catalyst pellets on the HTWGSR has not yet been fully clarified. Therefore, it seems that further studies are necessary to investigate how changes in the pore structure of catalyst pellets, caused by the pressure applied during compressing molding, affect the HTWGSR. Additionally, the stability of the prepared catalyst pellet is one of the key metrics for evaluating catalyst performance. Thus, it appears that further studies are required to asses the long-term stability of the catalyst pellet, particularly regarding changes in CO conversion over extended reaction times under the real mixted gases (containing H\u003csub\u003e2\u003c/sub\u003e, CO, CO\u003csub\u003e2\u003c/sub\u003e, CH\u003csub\u003e4\u003c/sub\u003e) in the HTWGSR.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn this study, the Fe/Cr/Cu catalyst pellet was prepared for application in the high-temperature water-gas shift reaction (HTWGSR). The Fe/Cr/Cu catalyst pellet was synthesized using the prepared catalyst powder, which was prepared via the co-precipitation method by adding a promoter, such as Cu, to Fe/Cr to enhance catalytic activity. In the HTWGSR, CO gas and steam were used as reaction gases to evaluate the properties of the prepared catalyst pellet. The HTWGSR was conducted using the prepared catalyst pellet under CO: H\u003csub\u003e2\u003c/sub\u003eO ratios of 1: 2 and 1: 3, a gas hourly space velocity (GHSV) of 10,000 h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and at temperatures ranging of 300 ℃~400 ℃. The CO conversion of the prepared catalyst pellet was then evaluated.\u003c/p\u003e \u003cp\u003eBased on the results, this study concluded as follows:\u003c/p\u003e \u003cp\u003e(1) The H\u003csub\u003e2\u003c/sub\u003e gas production rates of the prepared catalyst pellet at a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3 was higher than those at a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2 across the temperature range of 300 ℃~400 ℃.\u003c/p\u003e \u003cp\u003e(2) In the Fe/Cr/Cu catalyst pellet, for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2, the average CO conversion at 350 ℃ was higher than at 300 ℃ and 400 ℃, while for a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 3, the average CO conversion at 400 ℃ was higher than at 300 ℃ and 350 ℃.\u003c/p\u003e \u003cp\u003e(3) The maximum average CO conversion was 87% at 350 ℃ with a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2.\u003c/p\u003e \u003cp\u003e(4) The prepared Fe/Cr/Cu catalyst pellet is considered suitable for use in high-temperature water-gas shift reactions in terms of CO conversion.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAcknowledgement\u003c/h2\u003e \u003cp\u003eThis research was financially supported by the Ministry of Environment (ME) of Korea and Korea Environmental Industry and Technology Institute (KEITI) for the project of waste plastic utilization raw material and fuel technology development (No. 2022003490001).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eD. 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Catal., 253, 91 (2008).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Hydrogen Production, Water gas shift reaction, High temperature shift reaction, Catalyst, Catalyst pellet","lastPublishedDoi":"10.21203/rs.3.rs-6203088/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6203088/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Fe/Cr/Cu catalyst pellet was prepared for application in the high-temperature water-gas shift reaction (HTWGSR) to produce hydrogen from the gasified gases of waste plastics. The Fe/Cr/Cu catalyst pellet was synthesized using a compression molding method with the prepared catalyst powder. The HTWGSR was conducted using the prepared catalyst pellet with CO: H\u003csub\u003e2\u003c/sub\u003eO ratios of 1: 2 and 1: 3 at a temperature range of 300 ℃ to 400 ℃. The maximum average CO conversion of the Fe/Cr/Cu catalyst pellet was observed at a CO: H\u003csub\u003e2\u003c/sub\u003eO ratio of 1: 2, with a value of 87%. These results suggest that the prepared Fe/Cr/Cu catalyst pellet is suitable for high-temperature water-gas shift reactions in terms of CO conversion.\u003c/p\u003e","manuscriptTitle":"Characteristics of the Fe/Cr/Cu catalyst pellet in the high-temperature water-gas shift reaction","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-28 13:24:30","doi":"10.21203/rs.3.rs-6203088/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"629d0bb4-0993-4162-aef9-d33d7bafe767","owner":[],"postedDate":"March 28th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-06-05T03:40:42+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-28 13:24:30","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6203088","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6203088","identity":"rs-6203088","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}