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Hybrid catalysts in a double-layered bed reactor for the production of C2–C4 paraffin hydrocarbons
Catalysis Communications 127 (2019) 29–33
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Catalysis Communications journal homepage: www.elsevier.com/locate/catcom
Short communication
Hybrid catalysts in a double-layered bed reactor for the production of C2–C4 paraffin hydrocarbons
T
Seong Bin Joa, Tae Young Kimb, Chul Ho Leea, Suk-Hwan Kangc, Joon Woo Kimd, Moon Jeonge, ⁎ ⁎ Soo Chool Leea, , Jae Chang Kimb, a
Research Institute of Advanced Energy Technology, Kyungpook National University, Daegu 41566, Republic of Korea Department of Chemical Engineering, Kyungpook National University, Daegu 41566, Republic of Korea c Institute for Advanced Engineering, Yongin 41718, Republic of Korea d Research Institute of Industrial Science and Technology, Pohang 37673, Republic of Korea e Construction Engineering Service Co., LTD., Gunpo 15850, Republic of Korea b
A R T I C LE I N FO
A B S T R A C T
Keywords: Fischer–Tropsch (FT) Cracking Hybrid catalyst Double-layered bed reactor
Hybrid catalysts in a double-layered bed reactor were used to produce light C2–C4 paraffin hydrocarbons. Combinations of Fischer–Tropsch (FT) and cracking catalysts in a double-layered bed reactor configuration were studied. SAPO-34 and Ni-based cracking catalysts (hybrid catalyst) were used to convert C5+ into CH4 and C2–C4 paraffin hydrocarbons. Activity tests in the double-layered bed reactor at 10 bar and 300 °C and using a H2/CO feed gas ratio of 3.0 revealed that the hybrid catalyst showed lower C5+ and higher CH4 and C2–C4 selectivities than the FT catalyst alone. The Ni-based catalyst enabled additional CO conversion and CO2 methanation.
1. Introduction Synthetic natural gas (SNG) appears as potential substitute for fossil fuels because the production of SNG via syngas reaction (CO + 3H2 → CH4 + H2O) from coal and biomass is an effective and environmentally friendly method [1–5]. However, the heating value of CH4 (the main component of SNG) is typically lower than the standard heating value for power generation (especially in South Korea and Japan) [6–11]. For power generation, liquefied petroleum gas (LPG, C3–C4 hydrocarbons) must be added to low-calorie SNG to improve its heating value. The addition of LPG can be replaced by the addition of a mixture of synthetic light hydrocarbons in the C2–C4 range produced in the Fischer–Tropsch (FT) synthesis reaction. Moreover, the product gas must have a high paraffin ratio because olefins not only exhibit a low heating value but also are more susceptible than paraffins to liquefaction of the same carbon chain length hydrocarbons under high-pressure pipeline conditions. To date, several researchers have made efforts to enhance the heating value of SNG for power generation. Inui et al. [6] reported a catalyst for the preparation of high-calorie gas that is comparable to natural gas with added C2–C4 hydrocarbons via a “high-calorific methanation” process. The Co-Mn-Ru/Al2O3catalyst exhibited high CO conversion (98.8%) and C2–C4 selectivity (19.1%). Lee et al. [7] examined the role of each component in the Co-Mn-Ru/Al2O3catalyst, and proposed an optimal composition for Co-Mn-Ru/Al2O3. They also ⁎
developed FeeZn and FeeCu catalysts which were tested under varying gas pretreatment conditions (carburization and reduction) [8–10]. In an earlier report, bimetallic CoeFe catalysts supported on γ-alumina were developed and the effects of the H2/CO gas ratio and reaction temperature on the catalytic behavior were investigated. Among the bimetallic CoeFe catalysts, it was found that 5Co-15Fe/γ-Al2O3 catalysts showed high C2–C4 selectivity (28.2%) at high CO conversion (91.5%) and after using a H2/CO ratio of 3.0 at 300 °C, because the reducibility of the iron phase was enhanced in the presence of cobalt [11]. Recently, several studies have employed hybrid catalysts in a double-layered bed reactor system because of the high selectivity achieved for products such as dimethyl ether (DME), light hydrocarbons and liquid hydrocarbons via intermediates [12–14]. In the hybrid catalyst process, the SAPO-34 zeolite is the main catalyst used to convert methanol to light hydrocarbons following syngas-to-methanol catalysis within the hybrid catalytic system [15–20]. In a previous report [11], the FT catalyst (5Co-15Fe/γ-Al2O3) has shown to have high C2–C4 selectivity at high CO conversions, but this led to substantial byproduct formation, such as C5+ hydrocarbons and CO2·In this study, a double-layered bed reactor system is introduced to convert liquid and waxy hydrocarbons (C5+) into light hydrocarbons (CH4 and C2–C4) by adding a layer of cracking catalyst below the FT catalyst layer. The current work is focused on the combination of an FT catalyst (5Co-15Fe/γ-Al2O3) and cracking catalyst (SAPO-34 or Ni
Corresponding author at: Research Institute of Advanced Energy Technology, Kyungpook National University, Daegu 41566, Republic of Korea. E-mail addresses: [email protected] (S.C. Lee), [email protected] (J.C. Kim).
https://doi.org/10.1016/j.catcom.2019.05.002 Received 21 January 2019; Received in revised form 26 April 2019; Accepted 2 May 2019 Available online 06 May 2019 1566-7367/ © 2019 Published by Elsevier B.V.
Catalysis Communications 127 (2019) 29–33
S.B. Jo, et al.
chromatography (GC) column. The outlet gas mixture was analyzed using an Agilent 6890 gas chromatograph equipped with both a thermal conductivity detector (TCD) and a flame ionization detector (FID). A packed column (Carboxen 1000) was connected to the TCD to analyze the CO, H2, N2 and CO2 gases, while a capillary column (GS Gas Pro) was connected to the FID to analyze the hydrocarbon gas products. The CO conversion and selectivity for each product were calculated using the following Eqs. (1)–(4): CO conversion (carbon mole %)
catalyst) in this double-layered bed reactor system. Moreover, Ni-based catalysts are well-known as CO and CO2 methanation catalysts [21–24]. Thus, the catalytic behavior of the solids in single- and double-layered bed reactors was analyzed at 10 bar and 300 °C and using an H2/CO ratio of 3.0. In addition, catalysts characterization for crystal phases and metal particle size was performed using the X-ray diffraction (XRD) technique. 2. Experimental
CO in the product gas (mol/min) ⎞ = ⎜⎛1 − ⎟ × 100 CO in the feed gas (mol/min) ⎠ ⎝
2.1. Fischer–Tropsch catalyst The FT catalyst was synthesized by the wet impregnation of γ-alumina with Co(NO3)2·6H2O and Fe(NO3)3·9H2O (Sigma–Aldrich). The impregnation procedure (5Co-15Fe/γ-Al2O3) to deposit cobalt and iron metal phases on γ-alumina was as follows: alumina was added to a solution containing cobalt and iron nitrates with anhydrous ethanol. This mixture was stirred with a magnetic stirrer for 24 h. The weight percentage (wt%) of cobalt and iron metal in the catalyst were 5 and 10%, respectively. After stirring, the solvent was removed in a rotary evaporator at 40–60 °C. The samples were then dried at 120 °C for 12 h and subsequently calcined at 400 °C for 8 h at a temperature ramping rate of 10 °C/min.
(1)
Selectivity for hydrocarbons with carbon number n (carbon mole %)
=
n × Cn hydrocarbon in the product gas (mol/min) × 100 (total carbon −unreacted CO) in the product gas (mol/min) (2) Selectivity for carbon dioxide (carbon mole %)
=
CO2 in the product gas (mol/min) × 100 (total carbon −unreacted CO) in the product gas (mol/min) (3) Yield for hydrocarbons and carbon dioxide
2.2. Cracking catalysts
= SAPO-34 and Ni-based catalysts were used as cracking catalysts. A commercially available SAPO-34 zeolite was used (Tianjin Hutong Global Co., Ltd.). The Ni-based catalyst (10Ni/γ-Al2O3) was synthesized following the same wet impregnation procedure as that of the FT catalyst but using Ni(NO3)2·6H2O and γ-alumina (Sigma–Aldrich). The nickel metal loading of the catalyst was 10 wt%.
CO conversion×Selectivity 100
(4)
3. Results and discussion The powder XRD patterns of the FT and cracking catalysts in fresh and reduced states are shown in Fig. 1, and metal content (wt%) and crystallite size of FT and Ni-based catalysts are listed in Table 1. The catalysts were reduced at 500 °C for 1 h in a 10% H2/N2 gas mixture. As listed in Table 1, metal content in FT and Ni catalysts is almost consistent with the intended metal loading. In addition to reflections
2.3. Catalysts characterization The crystal structures of the FT (5Co-15Fe/γ-Al2O3) and cracking (SAPO-34 and 10Ni/γ-Al2O3) catalysts were analyzed using Cu-KαX-ray radiation produced by a Phillips XPERT powder XRD unit at the Korea Basic Science Institute in Daegu. In addition, the crystallite size of the metal particles and of the support (primary crystals) were obtained using the Scherrer equation. The metal content in the catalysts was measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES; Thermo Jarrell Ash IRISAP).
(a) 5Co-15Fe/ -Al2O3 Fresh
Intensity (a.u.)
Reduced
2.4. Catalytic activity testing A fixed-bed stainless-steel reactor with a diameter of 1/2 in. was used to carry out the activity tests. Each catalyst was sieved in the 150–250 μm range. For the single-layered bed reactor, the catalyst (0.5 g) was placed in a fixed-bed reactor. For the double-layered bed reactor, a layer of cracking catalyst (0.3 g) was added below that of the FT catalyst (0.5 g) in the fixed-bed reactor. These layers were separated from each other by a thin layer of inert quartz wool. Then, the singleand double-layered bed reactors were placed in an electric furnace and reduced with a 10 vol% H2/N2 gas mixture at ~1 bar and 500 °C for 1 h. Subsequently, the feed gas stream was fed to the reactor at the H2/CO/ N2 molar ratio of 72/24/4 and total gas flow rate of 50 mL/min. N2 gas was used as an internal standard in the feed gas. The reactor was pressurized to 10 bar with the feed gas using a back-pressure regulator and heated to 200 °C. Then, the temperature of the reactor was increased to 300 °C, which was maintained during the reaction. All volumetric gas flows were measured at standard temperature and pressure. To prevent the condensation of water vapor and hydrocarbons, the inlet and outlet gas lines of the reactor were maintained above 250 °C, and the liquid and waxy products were collected in a cold trap (0 °C) before the injection of the gas to the reactor and gas
(b) SAPO-34
Fresh
Reduced
(c) 10Ni/ -Al2O3
Fresh Reduced
20
30
40
50
60
70
80
2 Fig. 1. Powder XRD patterns of the (a) FT catalyst (5Co-15Fe/γ-Al2O3), (b) SAPO-34 zeolite and (c) Ni catalyst (10Ni/γ-Al2O3) in fresh and reduced states. (●) Co3O4, (▲) CoO, (△) Cometal, (♦) Fe2O3, (■) Fe3O4, (□) Fe metal, (▼) NiO, and (▽) Ni metal. 30
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CO2. The FT catalyst obviously has high C2–C4 yield at high CO conversion but this leads to substantial byproduct formation, such as C5+hydrocarbons and CO2. This high CO2 production of the FT catalyst is attributed to the water–gas shift reaction (WGS: CO + H2O ↔ CO2 + H2) [26]. Fig. 3 shows a schematic of the experiments using each component of the hybrid catalysts, such as the FT catalyst (5Co-15Fe/γ-Al2O3) and cracking catalysts (SAPO-34 and 10Ni/γ-Al2O3) in a single-layered bed reactor, and the hybrid catalyst (FT + cracking catalyst) in the doublelayered bed reactor. Catalytic activity tests were conducted using each component of the hybrid catalysts in a single-layered bed reactor to investigate the function of each component. The layer of cracking catalyst (SAPO-34 or Ni catalyst) was loaded below that of the FT catalyst in the double-layered bed reactor, and these two layers were separated from each other using quartz wool, for the conversion of liquid and waxy hydrocarbons (C5+) into light hydrocarbons (CH4 and C2–C4) in the cracking catalyst after the FT synthesis reaction. The activity tests were conducted with a H2/CO ratio of 3.0, pressure of 10 bar and temperature of 300 °C. The catalytic performance of the FT catalyst, SAPO-34, and Ni-based catalyst in the single-layered bed reactor and the hybrid catalyst (FT + cracking catalyst) in the double-layered bed reactor is shown in Fig. 4 and summarized in Table 2. The CO conversion in all catalysts did not change during 10 h on reaction stream, as shown in Fig. S2 (ESI). For single-layered bed reactor, the FT catalyst (5Co-15Fe/γ-Al2O3) afforded a CO conversion of 91.5% and selectivity values of 23.5% CH4, 28.2% C2–C4, 26.0% C5+ and 22.3% CO2. The 10Ni/γ-Al2O3 catalyst exhibits a CO conversion of 98.8% and selectivity values of 90.2% and 9.8% for CH4 and CO2, respectively, whereas syngas did not react on the SAPO-34 catalyst. For the double-layered bed reactor, adding a layer of SAPO-34 below that of the FT catalyst did not change the CO conversion, as expected. The selectivity values of the hybrid catalyst using SAPO-34 after the FT catalyst were found to be 27.5% CH4, 31.2% C2–C4, 22.7% C5+ and 19.3% CO2. Compared to the FT catalyst in the single-layered bed reactor, the selectivity for liquid and waxy hydrocarbons (C5+) decreased, whereas that for light hydrocarbons (CH4 and C2–C4) increased over the hybrid catalyst (FT + SAPO-34) in the double-layered bed reactor; in contrast, that of CO2 did not change. On the other hand, adding a layer of Ni-based catalyst below that of the FT catalyst in the double-layered bed reactor resulted in 100% CO conversion and selectivity values of 59.1% CH4, 25.6% C2–C4, 8.4% C5+ and 7.0% CO2. This improvement in CO conversion over the hybrid catalyst (FT + Ni catalyst) in the double-layered bed reactor is due to the additional conversion of unreacted CO with H2 over the Ni-based catalyst. Compared to the FT catalyst in the single-layered bed reactor, the CH4 selectivity increased dramatically, but those of the C5+ and C2–C4 hydrocarbons decreased because the Ni catalyst positioned after the FT catalyst cracked the C5+ and C2–C4 hydrocarbons. In terms of hydrocarbon yield, however, Ni catalyst in the double-layered bed reactor did not affect the cracking of the C2–C4 hydrocarbons as shown in Table 3. In addition, the CO2 produced by the FT catalyst also reacted with H2 and produced CH4. Based on the present experimental results, the SAPO-34 zeolite and Ni/γ-Al2O3 catalysts are effective cracking catalysts in the doublelayered bed reactor. When compared to the single-layered FT catalyst, hybrid catalysts using SAPO-34 or the Ni/γ-Al2O3 catalyst produced less liquid and waxy hydrocarbon content (C5+) and more light hydrocarbons (CH4 and C2–C4) by converting C5+ hydrocarbons into CH4 and C2–C4 light hydrocarbons. Furthermore, the Ni/γ-Al2O3 catalyst enabled additional CO conversion as well as CO2 methanation. Therefore, the use of hybrid catalyst (FT + cracking) in a double-layered bed reactor system allows notable improvement in C2–C4 hydrocarbon production, although much optimization work is required. The effects of the process conditions and the FT-to-cracking-catalyst ratio on the catalytic performance in the double-layered bed reactor system will be explored in future studies.
Table 1 Characterization of FT (5Co-15Fe/γ-Al2O3) and Ni (10Ni/γ-Al2O3) catalysts in fresh and reduced states. Catalyst
Metal contenta (wt%)
Crystallite sizeb (nm) Fresh
FT (5Co-15Fe/ γ-Al2O3) 10Ni/γ-Al2O3
Reduced
Co
Fe
Ni
CoO
Fe2O3
NiO
Co0
Fe0
Ni0
5.2
14.1
–
4.7
–
–
–
20
–
–
–
10.4
–
–
9.0
–
–
5.9
a
Metal contents were determined by ICP-AES. Crystallite size of the metal phase was calculated using the Scherer equation. b
corresponding to γ-Al2O3, the powder XRD patterns of the FT catalyst (5Co-15Fe/γ-Al2O3) show CoO and Fe2O3 phases, and the Fe2O3 was reduced into Fe metal, although it was difficult to assign the exact crystal phase because of the high dispersion of iron in the γ-alumina [25]. As summarized in Table 1, the calculated crystallite size of the CoO on the fresh FT catalyst (5Co-15Fe/γ-Al2O3) is 4.7 nm, while those of Fe2O3 could not be calculated because of the too broad peaks of Fe2O3 as mentioned above. As reported previously, the reducibility of the iron phase was enhanced in the presence of cobalt [11,25]. The XRD patterns of the fresh and reduced monometallic and bimetallic CoeFe catalysts are shown in Fig. S1 (ESI) [11]. In the case of reduced FT catalyst, crystallite sizes of the Fe metal are ~20 nm. For the SAPO-34 zeolite, the XRD patterns are consistent with previous reports and did not change after reduction [16–18]. From the XRD patterns of the Ni catalyst (10Ni/γ-Al2O3), it was found that NiO was reduced to Ni metal. As listed in Table 1, the crystallite size of NiO is 9.0 nm for the fresh Ni catalyst, while that of Ni metal is 5.9 nm in the reduced state of Ni catalyst. In previous reports [11], catalytic activity tests were conducted over FT catalyst (5Co-15Fe/γ-Al2O3) using a H2/CO ratio of 3.0, P = 10 bar and different reaction temperatures (250–400 °C) to investigate the effect of reaction temperature on catalyst's performance, and results are shown in Fig. 2. With increasing reaction temperature, CO conversion initially increases remarkably up to 300 °C, and then increases slightly. CH4-yield increases with increasing reaction temperature, while C2+hydrocarbons (C2-C4 and C5+) yield initially increases and achieved values up to 25.8% at 300 °C, and decreases at higher temperatures. At 300 °C, the FT catalyst (5Co-15Fe/γ-Al2O3) provided a CO conversion of 91.5% and yields of 21.5% CH4, 25.8% C2–C4, 23.8% C5+ and 20.4%
80
50 CO conversion CH4
40
C2-C4 C5+ CO2
30
60
40
20
20
10
0
Yield (%)
CO conversion (%)
100
0 250
300
350
400
Temperature (oC) Fig. 2. CO conversion and hydrocarbon yield of FT catalyst (5Co-15Fe/γ-Al2O3) in the single-layered bed reactor at 10 bar and a H2/CO ratio of 3.0 at different reaction temperatures [25]. 31
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Fig. 3. Schematic of the reaction process for each component in the hybrid catalyst, such as FT catalyst (5Co-15Fe/γ-Al2O3), SAPO-34 and Ni catalyst in the singlelayered bed system, and hybrid catalyst using SAPO-34 zeolite and Ni catalysts in the double-layered bed reactor system.
Table 3 Hydrocarbon yield of each component in the hybrid catalyst, such as FT catalyst (5Co-15Fe/γ-Al2O3), SAPO-34 and Ni catalyst (10Ni/γ-Al2O3) in the singlelayered bed reactor and those of the hybrid catalyst in the double-layered bed reactor at 10 bar and a H2/CO ratio of 3.0 at 300 °C.
S(CH4) S(C2-C4) S(C5+) S(CO2) CO conversion Single-layered bed
Catalyst Double-layered bed
CH4
C2–C4
C5+
CO2
21.5 – 89.0 23.9 59.1
25.8 – 0 28.8 25.6
23.8 – 0 18.6 8.4
20.4 – 9.7 18.0 7.0
100
80
80
60
60
40
40
20
20
0
FT (5Co-15Fe/γ-Al2O3) SAPO-34 10Ni/γ-Al2O3 FT + SAPO-34 FT + 10Ni/γ-Al2O3
CO conversion (%)
100
Selectivity (%)
Yield (%)
Compared to the FT catalyst (5Co-15Fe/γ-Al2O3) in a single-layered bed reactor, the SAPO-34 and Ni catalysts affect the cracking of C5+ hydrocarbons into light hydrocarbons (CH4 and C2–C4) in the doublelayered bed reactor. Moreover, the Ni catalyst improves the CO conversion and reduces the CO2 selectivity via methanation. The hybrid catalyst (FT + cracking) in the double-layered bed reactor shows good catalytic performance for CO hydrogenation, producing C2–C4 light paraffin hydrocarbons, compared to the single-layered FT catalyst.
0 FT SAPO-34 Ni
FT + SAPO-34
FT + Ni
Fig. 4. Selectivity of each component and CO conversion in the hybrid catalyst such as FT catalyst (5Co-15Fe/γ-Al2O3), SAPO-34 and Ni catalyst (10Ni/γAl2O3) in the single-layered bed reactor, and the hybrid catalyst using SAPO-34 zeolite and Ni catalysts in the double-layered bed reactor at 10 bar and an H2/ CO ratio of 3.0 at 300 °C.
Acknowledgments This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20182010600530). This research was also supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (No. 2017R1A2B4008275).
4. Conclusions The FT catalyst (5Co-15Fe/γ-Al2O3) obviously has high C2–C4 selectivity (28.2%) at high CO conversion (91.5%) but suffers from substantial byproduct formation, including C5+ hydrocarbons (26.0%) and CO2 (22.3%). In this study, hybrid catalysts (FT + cracking) in a double-layered bed reactor were introduced to convert the liquid and waxy hydrocarbons (C5+) into light hydrocarbons (CH4 and C2–C4). SAPO-34 zeolite and Ni catalysts were used as cracking catalysts.
Appendix A. Supplementary data Supplementary data to this article can be found online at https://
Table 2 Catalytic performance of each component in the hybrid catalyst, such as FT catalyst (5Co-15Fe/γ-Al2O3), SAPO-34 and Ni catalyst (10Ni/γ-Al2O3) in the singlelayered bed reactor and those of the hybrid catalyst in the double-layered bed reactor at 10 bar and a H2/CO ratio of 3.0 at 300 °C. Catalyst
CO conv. (%)
Selectivity (%) CH4
FT (5Co-15Fe/γ-Al2O3) SAPO-34 10Ni/γ-Al2O3 FT+ SAPO-34 FT + 10Ni/γ-Al2O3
91.5 ± 1.0 – 99.1 ± 1.2 89.9 ± 0.2 100 ± 0.0
23.5 – 89.3 27.1 64.2
± 0.8 ± 0.3 ± 0.4 ± 4.2
32
C2–C4
C5+
CO2
28.2 ± 0.7 – 0 31.4 ± 0.4 25.6 ± 2.6
26.0 ± 1.8 – 0 21.8 ± 0.5 5.8 ± 1.4
22.3 ± 0.4 – 10.7 ± 0.3 19.7 ± 0.3 6.7 ± 0.3
Catalysis Communications 127 (2019) 29–33
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doi.org/10.1016/j.catcom.2019.05.002.
carbon, J. Environ. Eng. Manage. 18 (2008) 371–376. [13] T. Horie, Y. Sato, T. Aida, S. Nishiyama, N. Ohmura, Oxidative coupling of propane with a two-layered catalyst bed reactor, Chem. Prod. Process. Model. 4 (2009). [14] M. Lu, I. Maddox, J. Brooks, Application of a multi-layer packed-bed reactor to citric acid production in solid-state fermentation using Aspergillus niger, Process Biochem. 33 (1998) 117–123. [15] Y. Chen, Y. Xu, D.g. Cheng, Y. Chen, F. Chen, X. Lu, Y. Huang, S. Ni, C2–C4 hydrocarbons synthesis from syngas over CuO–ZnO–Al2O3/SAPO-34 bifunctional catalyst, J.Chem. Technol.Biotechnol. 90 (2015) 415–422. [16] Y. Chen, Y. Xu, D.-g. Cheng, Y. Chen, F. Chen, X. Lu, Y. Huang, S. Ni, Synthesis of CuO–ZnO–Al2O3@ SAPO-34 core@ shell structured catalyst by intermediate layer method, Pure Appl. Chem. 86 (2014) 775–783. [17] J. Li, X. Pan, X. Bao, Direct conversion of syngas into hydrocarbons over a core–shell Cr-Zn@ SiO2@ SAPO-34 catalyst, Chin. J. Catal. 36 (2015) 1131–1135. [18] D.L. Nieskens, A. Ciftci, P.E. Groenendijk, M.F. Wielemaker, A. Malek, Production of light hydrocarbons from syngas using a hybrid catalyst, Ind.Eng. Chem. Res. 56 (2017) 2722–2732. [19] R. Thomson, C. Montes, M. Davis, E. Wolf, Hydrocarbon synthesis from CO hydrogenation over Pd supported on SAPO molecular sieves, J.Catal. 124 (1990) 401–415. [20] Y. Yu, Y. Xu, D.-g. Cheng, Y. Chen, F. Chen, X. Lu, Y. Huang, S. Ni, Transformation of syngas to light hydrocarbons over bifunctional CuO–ZnO/SAPO-34 catalysts: The effect of preparation methods, React. Kinet. Mech. Catal. 112 (2014) 489–497. [21] W. Ahmad, M.N. Younis, R. Shawabkeh, S. Ahmed, Synthesis of lanthanide series (La, Ce, Pr, Eu, & Gd) promoted Ni/γ-Al2O3 catalysts for methanation of CO2 at low temperature under atmospheric pressure, Catal. Commun. 100 (2017) 121–126. [22] H. Arandiyan, G. Kasaeian, B. Nematollahi, Y. Wang, H. Sun, S. Bartlett, H. Dai, M. Rezaei, Self-assembly of flower-like LaNiAlO3-supported nickel catalysts for CO methanation, Catal.Commun. 115 (2018) 40–44. [23] J. Gao, Q. Liu, F. Gu, B. Liu, Z. Zhong, F. Su, Recent advances in methanation catalysts for the production of synthetic natural gas, RSC Adv. 5 (2015) 22759–22776. [24] T.A. Le, M.S. Kim, S.H. Lee, T.W. Kim, E.D. Park, CO and CO2 methanation over supported Ni catalysts, Catal. Today 293 (2017) 89–96. [25] A. Griboval-Constant, A. Butel, V.V. Ordomsky, P.A. Chernavskii, A. Khodakov, Cobalt and iron species in alumina supported bimetallic catalysts for Fischer–Tropsch reaction, Appl. Catal.,A: Gen. 481 (2014) 116–126. [26] H.M. Torres Galvis, K.P. de Jong, Catalysts for production of lower olefins from synthesis gas: A review, ACS Catal. 3 (2013) 2130–2149.
References [1] Z. Binran, Z. Chen, Y. Chen, X. Ma, Syngas methanation over Ni/SiO2 catalyst prepared by ammonia-assisted impregnation, J.Hydrogen Energy 42 (2017) 27073–27083. [2] S.H. Hwang, J. Lee, U.G. Hong, J.G. Seo, J.C. Jung, D.J. Koh, H. Lim, C. Byun, I.K. Song, Methane production from carbon monoxide and hydrogen over nickelalumina-xerogel catalyst: Effect of nickel content, J. Ind. Eng. Chem. 17 (2011) 154–157. [3] J. Kopyscinski, T.J. Schildhauer, S. Biollaz, Production of synthetic natural gas (SNG) from coal and dry biomass – A technology review from 1950 to 2009, Fuel 89 (2010) 1763–1783. [4] Z.-Z. Wang, W.-F. Han, H.-Z. Liu, Hydrothermal synthesis of sulfur-resistant MoS2 catalyst for methanation reaction, Catal. Commun. 84 (2016) 120–123. [5] B. Nematollahi, M. Rezaei, E. Amini, E.N. Lay, Preparation of high surface area Ni/ MgAl2O4nanocatalysts for CO selective methanation, Int. J. Hydrog. Energy 43 (2018) 772–780. [6] T. Inui, A. Sakamoto, T. Takeguchi, Y. Ishigaki, Synthesis of highly calorific gaseous fuel from syngas on cobalt-manganese-ruthenium composite catalysts, Ind. Eng.Chem. Res. 28 (1989) 427–431. [7] Y.H. Lee, H. Kim, H.S. Choi, D.-W. Lee, K.-Y. Lee, Co-Mn-Ru/Al2O3 catalyst for the production of high-calorific synthetic natural gas, Korean J. Chem. Eng. 32 (2015) 2220–2226. [8] Y.H. Lee, K.-Y. Lee, Effect of surface composition of Fe catalyst on the activity for the production of high-calorie synthetic natural gas (SNG), Korean J. Chem. Eng. 34 (2017) 320–327. [9] Y.H. Lee, D.-W. Lee, H. Kim, H.S. Choi, K.-Y. Lee, Fe–Zn catalysts for the production of high-calorie synthetic natural gas, Fuel 159 (2015) 259–268. [10] Y.H. Lee, D.-W. Lee, K.-Y. Lee, Production of high-calorie synthetic natural gas using copper-impregnated iron catalysts, J.Mol. Catal. A 425 (2016) 190–198. [11] S.B. Jo, H.J. Chae, T.Y. Kim, C.H. Lee, J.U. Oh, S.-H. Kang, J.W. Kim, M. Jeong, S.C. Lee, J.C. Kim, Selective CO hydrogenation over bimetallic Co-Fe catalysts for the production of light paraffin hydrocarbons (C2–C4): Effect of H2/CO ratio and reaction temperature, Catal. Commun. 117 (2018) 74–78. [12] M.-B. Chang, S.-S. Hsiau, S.-H. Chang, K.-H. Chi, W.-C. Lo, J. Smid, Reduction of dioxin emission by multi-layer moving bed reactor with bead-shaped activated
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Catalysis Communications journal homepage: www.elsevier.com/locate/catcom
Short communication
Hybrid catalysts in a double-layered bed reactor for the production of C2–C4 paraffin hydrocarbons
T
Seong Bin Joa, Tae Young Kimb, Chul Ho Leea, Suk-Hwan Kangc, Joon Woo Kimd, Moon Jeonge, ⁎ ⁎ Soo Chool Leea, , Jae Chang Kimb, a
Research Institute of Advanced Energy Technology, Kyungpook National University, Daegu 41566, Republic of Korea Department of Chemical Engineering, Kyungpook National University, Daegu 41566, Republic of Korea c Institute for Advanced Engineering, Yongin 41718, Republic of Korea d Research Institute of Industrial Science and Technology, Pohang 37673, Republic of Korea e Construction Engineering Service Co., LTD., Gunpo 15850, Republic of Korea b
A R T I C LE I N FO
A B S T R A C T
Keywords: Fischer–Tropsch (FT) Cracking Hybrid catalyst Double-layered bed reactor
Hybrid catalysts in a double-layered bed reactor were used to produce light C2–C4 paraffin hydrocarbons. Combinations of Fischer–Tropsch (FT) and cracking catalysts in a double-layered bed reactor configuration were studied. SAPO-34 and Ni-based cracking catalysts (hybrid catalyst) were used to convert C5+ into CH4 and C2–C4 paraffin hydrocarbons. Activity tests in the double-layered bed reactor at 10 bar and 300 °C and using a H2/CO feed gas ratio of 3.0 revealed that the hybrid catalyst showed lower C5+ and higher CH4 and C2–C4 selectivities than the FT catalyst alone. The Ni-based catalyst enabled additional CO conversion and CO2 methanation.
1. Introduction Synthetic natural gas (SNG) appears as potential substitute for fossil fuels because the production of SNG via syngas reaction (CO + 3H2 → CH4 + H2O) from coal and biomass is an effective and environmentally friendly method [1–5]. However, the heating value of CH4 (the main component of SNG) is typically lower than the standard heating value for power generation (especially in South Korea and Japan) [6–11]. For power generation, liquefied petroleum gas (LPG, C3–C4 hydrocarbons) must be added to low-calorie SNG to improve its heating value. The addition of LPG can be replaced by the addition of a mixture of synthetic light hydrocarbons in the C2–C4 range produced in the Fischer–Tropsch (FT) synthesis reaction. Moreover, the product gas must have a high paraffin ratio because olefins not only exhibit a low heating value but also are more susceptible than paraffins to liquefaction of the same carbon chain length hydrocarbons under high-pressure pipeline conditions. To date, several researchers have made efforts to enhance the heating value of SNG for power generation. Inui et al. [6] reported a catalyst for the preparation of high-calorie gas that is comparable to natural gas with added C2–C4 hydrocarbons via a “high-calorific methanation” process. The Co-Mn-Ru/Al2O3catalyst exhibited high CO conversion (98.8%) and C2–C4 selectivity (19.1%). Lee et al. [7] examined the role of each component in the Co-Mn-Ru/Al2O3catalyst, and proposed an optimal composition for Co-Mn-Ru/Al2O3. They also ⁎
developed FeeZn and FeeCu catalysts which were tested under varying gas pretreatment conditions (carburization and reduction) [8–10]. In an earlier report, bimetallic CoeFe catalysts supported on γ-alumina were developed and the effects of the H2/CO gas ratio and reaction temperature on the catalytic behavior were investigated. Among the bimetallic CoeFe catalysts, it was found that 5Co-15Fe/γ-Al2O3 catalysts showed high C2–C4 selectivity (28.2%) at high CO conversion (91.5%) and after using a H2/CO ratio of 3.0 at 300 °C, because the reducibility of the iron phase was enhanced in the presence of cobalt [11]. Recently, several studies have employed hybrid catalysts in a double-layered bed reactor system because of the high selectivity achieved for products such as dimethyl ether (DME), light hydrocarbons and liquid hydrocarbons via intermediates [12–14]. In the hybrid catalyst process, the SAPO-34 zeolite is the main catalyst used to convert methanol to light hydrocarbons following syngas-to-methanol catalysis within the hybrid catalytic system [15–20]. In a previous report [11], the FT catalyst (5Co-15Fe/γ-Al2O3) has shown to have high C2–C4 selectivity at high CO conversions, but this led to substantial byproduct formation, such as C5+ hydrocarbons and CO2·In this study, a double-layered bed reactor system is introduced to convert liquid and waxy hydrocarbons (C5+) into light hydrocarbons (CH4 and C2–C4) by adding a layer of cracking catalyst below the FT catalyst layer. The current work is focused on the combination of an FT catalyst (5Co-15Fe/γ-Al2O3) and cracking catalyst (SAPO-34 or Ni
Corresponding author at: Research Institute of Advanced Energy Technology, Kyungpook National University, Daegu 41566, Republic of Korea. E-mail addresses: [email protected] (S.C. Lee), [email protected] (J.C. Kim).
https://doi.org/10.1016/j.catcom.2019.05.002 Received 21 January 2019; Received in revised form 26 April 2019; Accepted 2 May 2019 Available online 06 May 2019 1566-7367/ © 2019 Published by Elsevier B.V.
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chromatography (GC) column. The outlet gas mixture was analyzed using an Agilent 6890 gas chromatograph equipped with both a thermal conductivity detector (TCD) and a flame ionization detector (FID). A packed column (Carboxen 1000) was connected to the TCD to analyze the CO, H2, N2 and CO2 gases, while a capillary column (GS Gas Pro) was connected to the FID to analyze the hydrocarbon gas products. The CO conversion and selectivity for each product were calculated using the following Eqs. (1)–(4): CO conversion (carbon mole %)
catalyst) in this double-layered bed reactor system. Moreover, Ni-based catalysts are well-known as CO and CO2 methanation catalysts [21–24]. Thus, the catalytic behavior of the solids in single- and double-layered bed reactors was analyzed at 10 bar and 300 °C and using an H2/CO ratio of 3.0. In addition, catalysts characterization for crystal phases and metal particle size was performed using the X-ray diffraction (XRD) technique. 2. Experimental
CO in the product gas (mol/min) ⎞ = ⎜⎛1 − ⎟ × 100 CO in the feed gas (mol/min) ⎠ ⎝
2.1. Fischer–Tropsch catalyst The FT catalyst was synthesized by the wet impregnation of γ-alumina with Co(NO3)2·6H2O and Fe(NO3)3·9H2O (Sigma–Aldrich). The impregnation procedure (5Co-15Fe/γ-Al2O3) to deposit cobalt and iron metal phases on γ-alumina was as follows: alumina was added to a solution containing cobalt and iron nitrates with anhydrous ethanol. This mixture was stirred with a magnetic stirrer for 24 h. The weight percentage (wt%) of cobalt and iron metal in the catalyst were 5 and 10%, respectively. After stirring, the solvent was removed in a rotary evaporator at 40–60 °C. The samples were then dried at 120 °C for 12 h and subsequently calcined at 400 °C for 8 h at a temperature ramping rate of 10 °C/min.
(1)
Selectivity for hydrocarbons with carbon number n (carbon mole %)
=
n × Cn hydrocarbon in the product gas (mol/min) × 100 (total carbon −unreacted CO) in the product gas (mol/min) (2) Selectivity for carbon dioxide (carbon mole %)
=
CO2 in the product gas (mol/min) × 100 (total carbon −unreacted CO) in the product gas (mol/min) (3) Yield for hydrocarbons and carbon dioxide
2.2. Cracking catalysts
= SAPO-34 and Ni-based catalysts were used as cracking catalysts. A commercially available SAPO-34 zeolite was used (Tianjin Hutong Global Co., Ltd.). The Ni-based catalyst (10Ni/γ-Al2O3) was synthesized following the same wet impregnation procedure as that of the FT catalyst but using Ni(NO3)2·6H2O and γ-alumina (Sigma–Aldrich). The nickel metal loading of the catalyst was 10 wt%.
CO conversion×Selectivity 100
(4)
3. Results and discussion The powder XRD patterns of the FT and cracking catalysts in fresh and reduced states are shown in Fig. 1, and metal content (wt%) and crystallite size of FT and Ni-based catalysts are listed in Table 1. The catalysts were reduced at 500 °C for 1 h in a 10% H2/N2 gas mixture. As listed in Table 1, metal content in FT and Ni catalysts is almost consistent with the intended metal loading. In addition to reflections
2.3. Catalysts characterization The crystal structures of the FT (5Co-15Fe/γ-Al2O3) and cracking (SAPO-34 and 10Ni/γ-Al2O3) catalysts were analyzed using Cu-KαX-ray radiation produced by a Phillips XPERT powder XRD unit at the Korea Basic Science Institute in Daegu. In addition, the crystallite size of the metal particles and of the support (primary crystals) were obtained using the Scherrer equation. The metal content in the catalysts was measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES; Thermo Jarrell Ash IRISAP).
(a) 5Co-15Fe/ -Al2O3 Fresh
Intensity (a.u.)
Reduced
2.4. Catalytic activity testing A fixed-bed stainless-steel reactor with a diameter of 1/2 in. was used to carry out the activity tests. Each catalyst was sieved in the 150–250 μm range. For the single-layered bed reactor, the catalyst (0.5 g) was placed in a fixed-bed reactor. For the double-layered bed reactor, a layer of cracking catalyst (0.3 g) was added below that of the FT catalyst (0.5 g) in the fixed-bed reactor. These layers were separated from each other by a thin layer of inert quartz wool. Then, the singleand double-layered bed reactors were placed in an electric furnace and reduced with a 10 vol% H2/N2 gas mixture at ~1 bar and 500 °C for 1 h. Subsequently, the feed gas stream was fed to the reactor at the H2/CO/ N2 molar ratio of 72/24/4 and total gas flow rate of 50 mL/min. N2 gas was used as an internal standard in the feed gas. The reactor was pressurized to 10 bar with the feed gas using a back-pressure regulator and heated to 200 °C. Then, the temperature of the reactor was increased to 300 °C, which was maintained during the reaction. All volumetric gas flows were measured at standard temperature and pressure. To prevent the condensation of water vapor and hydrocarbons, the inlet and outlet gas lines of the reactor were maintained above 250 °C, and the liquid and waxy products were collected in a cold trap (0 °C) before the injection of the gas to the reactor and gas
(b) SAPO-34
Fresh
Reduced
(c) 10Ni/ -Al2O3
Fresh Reduced
20
30
40
50
60
70
80
2 Fig. 1. Powder XRD patterns of the (a) FT catalyst (5Co-15Fe/γ-Al2O3), (b) SAPO-34 zeolite and (c) Ni catalyst (10Ni/γ-Al2O3) in fresh and reduced states. (●) Co3O4, (▲) CoO, (△) Cometal, (♦) Fe2O3, (■) Fe3O4, (□) Fe metal, (▼) NiO, and (▽) Ni metal. 30
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CO2. The FT catalyst obviously has high C2–C4 yield at high CO conversion but this leads to substantial byproduct formation, such as C5+hydrocarbons and CO2. This high CO2 production of the FT catalyst is attributed to the water–gas shift reaction (WGS: CO + H2O ↔ CO2 + H2) [26]. Fig. 3 shows a schematic of the experiments using each component of the hybrid catalysts, such as the FT catalyst (5Co-15Fe/γ-Al2O3) and cracking catalysts (SAPO-34 and 10Ni/γ-Al2O3) in a single-layered bed reactor, and the hybrid catalyst (FT + cracking catalyst) in the doublelayered bed reactor. Catalytic activity tests were conducted using each component of the hybrid catalysts in a single-layered bed reactor to investigate the function of each component. The layer of cracking catalyst (SAPO-34 or Ni catalyst) was loaded below that of the FT catalyst in the double-layered bed reactor, and these two layers were separated from each other using quartz wool, for the conversion of liquid and waxy hydrocarbons (C5+) into light hydrocarbons (CH4 and C2–C4) in the cracking catalyst after the FT synthesis reaction. The activity tests were conducted with a H2/CO ratio of 3.0, pressure of 10 bar and temperature of 300 °C. The catalytic performance of the FT catalyst, SAPO-34, and Ni-based catalyst in the single-layered bed reactor and the hybrid catalyst (FT + cracking catalyst) in the double-layered bed reactor is shown in Fig. 4 and summarized in Table 2. The CO conversion in all catalysts did not change during 10 h on reaction stream, as shown in Fig. S2 (ESI). For single-layered bed reactor, the FT catalyst (5Co-15Fe/γ-Al2O3) afforded a CO conversion of 91.5% and selectivity values of 23.5% CH4, 28.2% C2–C4, 26.0% C5+ and 22.3% CO2. The 10Ni/γ-Al2O3 catalyst exhibits a CO conversion of 98.8% and selectivity values of 90.2% and 9.8% for CH4 and CO2, respectively, whereas syngas did not react on the SAPO-34 catalyst. For the double-layered bed reactor, adding a layer of SAPO-34 below that of the FT catalyst did not change the CO conversion, as expected. The selectivity values of the hybrid catalyst using SAPO-34 after the FT catalyst were found to be 27.5% CH4, 31.2% C2–C4, 22.7% C5+ and 19.3% CO2. Compared to the FT catalyst in the single-layered bed reactor, the selectivity for liquid and waxy hydrocarbons (C5+) decreased, whereas that for light hydrocarbons (CH4 and C2–C4) increased over the hybrid catalyst (FT + SAPO-34) in the double-layered bed reactor; in contrast, that of CO2 did not change. On the other hand, adding a layer of Ni-based catalyst below that of the FT catalyst in the double-layered bed reactor resulted in 100% CO conversion and selectivity values of 59.1% CH4, 25.6% C2–C4, 8.4% C5+ and 7.0% CO2. This improvement in CO conversion over the hybrid catalyst (FT + Ni catalyst) in the double-layered bed reactor is due to the additional conversion of unreacted CO with H2 over the Ni-based catalyst. Compared to the FT catalyst in the single-layered bed reactor, the CH4 selectivity increased dramatically, but those of the C5+ and C2–C4 hydrocarbons decreased because the Ni catalyst positioned after the FT catalyst cracked the C5+ and C2–C4 hydrocarbons. In terms of hydrocarbon yield, however, Ni catalyst in the double-layered bed reactor did not affect the cracking of the C2–C4 hydrocarbons as shown in Table 3. In addition, the CO2 produced by the FT catalyst also reacted with H2 and produced CH4. Based on the present experimental results, the SAPO-34 zeolite and Ni/γ-Al2O3 catalysts are effective cracking catalysts in the doublelayered bed reactor. When compared to the single-layered FT catalyst, hybrid catalysts using SAPO-34 or the Ni/γ-Al2O3 catalyst produced less liquid and waxy hydrocarbon content (C5+) and more light hydrocarbons (CH4 and C2–C4) by converting C5+ hydrocarbons into CH4 and C2–C4 light hydrocarbons. Furthermore, the Ni/γ-Al2O3 catalyst enabled additional CO conversion as well as CO2 methanation. Therefore, the use of hybrid catalyst (FT + cracking) in a double-layered bed reactor system allows notable improvement in C2–C4 hydrocarbon production, although much optimization work is required. The effects of the process conditions and the FT-to-cracking-catalyst ratio on the catalytic performance in the double-layered bed reactor system will be explored in future studies.
Table 1 Characterization of FT (5Co-15Fe/γ-Al2O3) and Ni (10Ni/γ-Al2O3) catalysts in fresh and reduced states. Catalyst
Metal contenta (wt%)
Crystallite sizeb (nm) Fresh
FT (5Co-15Fe/ γ-Al2O3) 10Ni/γ-Al2O3
Reduced
Co
Fe
Ni
CoO
Fe2O3
NiO
Co0
Fe0
Ni0
5.2
14.1
–
4.7
–
–
–
20
–
–
–
10.4
–
–
9.0
–
–
5.9
a
Metal contents were determined by ICP-AES. Crystallite size of the metal phase was calculated using the Scherer equation. b
corresponding to γ-Al2O3, the powder XRD patterns of the FT catalyst (5Co-15Fe/γ-Al2O3) show CoO and Fe2O3 phases, and the Fe2O3 was reduced into Fe metal, although it was difficult to assign the exact crystal phase because of the high dispersion of iron in the γ-alumina [25]. As summarized in Table 1, the calculated crystallite size of the CoO on the fresh FT catalyst (5Co-15Fe/γ-Al2O3) is 4.7 nm, while those of Fe2O3 could not be calculated because of the too broad peaks of Fe2O3 as mentioned above. As reported previously, the reducibility of the iron phase was enhanced in the presence of cobalt [11,25]. The XRD patterns of the fresh and reduced monometallic and bimetallic CoeFe catalysts are shown in Fig. S1 (ESI) [11]. In the case of reduced FT catalyst, crystallite sizes of the Fe metal are ~20 nm. For the SAPO-34 zeolite, the XRD patterns are consistent with previous reports and did not change after reduction [16–18]. From the XRD patterns of the Ni catalyst (10Ni/γ-Al2O3), it was found that NiO was reduced to Ni metal. As listed in Table 1, the crystallite size of NiO is 9.0 nm for the fresh Ni catalyst, while that of Ni metal is 5.9 nm in the reduced state of Ni catalyst. In previous reports [11], catalytic activity tests were conducted over FT catalyst (5Co-15Fe/γ-Al2O3) using a H2/CO ratio of 3.0, P = 10 bar and different reaction temperatures (250–400 °C) to investigate the effect of reaction temperature on catalyst's performance, and results are shown in Fig. 2. With increasing reaction temperature, CO conversion initially increases remarkably up to 300 °C, and then increases slightly. CH4-yield increases with increasing reaction temperature, while C2+hydrocarbons (C2-C4 and C5+) yield initially increases and achieved values up to 25.8% at 300 °C, and decreases at higher temperatures. At 300 °C, the FT catalyst (5Co-15Fe/γ-Al2O3) provided a CO conversion of 91.5% and yields of 21.5% CH4, 25.8% C2–C4, 23.8% C5+ and 20.4%
80
50 CO conversion CH4
40
C2-C4 C5+ CO2
30
60
40
20
20
10
0
Yield (%)
CO conversion (%)
100
0 250
300
350
400
Temperature (oC) Fig. 2. CO conversion and hydrocarbon yield of FT catalyst (5Co-15Fe/γ-Al2O3) in the single-layered bed reactor at 10 bar and a H2/CO ratio of 3.0 at different reaction temperatures [25]. 31
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Fig. 3. Schematic of the reaction process for each component in the hybrid catalyst, such as FT catalyst (5Co-15Fe/γ-Al2O3), SAPO-34 and Ni catalyst in the singlelayered bed system, and hybrid catalyst using SAPO-34 zeolite and Ni catalysts in the double-layered bed reactor system.
Table 3 Hydrocarbon yield of each component in the hybrid catalyst, such as FT catalyst (5Co-15Fe/γ-Al2O3), SAPO-34 and Ni catalyst (10Ni/γ-Al2O3) in the singlelayered bed reactor and those of the hybrid catalyst in the double-layered bed reactor at 10 bar and a H2/CO ratio of 3.0 at 300 °C.
S(CH4) S(C2-C4) S(C5+) S(CO2) CO conversion Single-layered bed
Catalyst Double-layered bed
CH4
C2–C4
C5+
CO2
21.5 – 89.0 23.9 59.1
25.8 – 0 28.8 25.6
23.8 – 0 18.6 8.4
20.4 – 9.7 18.0 7.0
100
80
80
60
60
40
40
20
20
0
FT (5Co-15Fe/γ-Al2O3) SAPO-34 10Ni/γ-Al2O3 FT + SAPO-34 FT + 10Ni/γ-Al2O3
CO conversion (%)
100
Selectivity (%)
Yield (%)
Compared to the FT catalyst (5Co-15Fe/γ-Al2O3) in a single-layered bed reactor, the SAPO-34 and Ni catalysts affect the cracking of C5+ hydrocarbons into light hydrocarbons (CH4 and C2–C4) in the doublelayered bed reactor. Moreover, the Ni catalyst improves the CO conversion and reduces the CO2 selectivity via methanation. The hybrid catalyst (FT + cracking) in the double-layered bed reactor shows good catalytic performance for CO hydrogenation, producing C2–C4 light paraffin hydrocarbons, compared to the single-layered FT catalyst.
0 FT SAPO-34 Ni
FT + SAPO-34
FT + Ni
Fig. 4. Selectivity of each component and CO conversion in the hybrid catalyst such as FT catalyst (5Co-15Fe/γ-Al2O3), SAPO-34 and Ni catalyst (10Ni/γAl2O3) in the single-layered bed reactor, and the hybrid catalyst using SAPO-34 zeolite and Ni catalysts in the double-layered bed reactor at 10 bar and an H2/ CO ratio of 3.0 at 300 °C.
Acknowledgments This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20182010600530). This research was also supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (No. 2017R1A2B4008275).
4. Conclusions The FT catalyst (5Co-15Fe/γ-Al2O3) obviously has high C2–C4 selectivity (28.2%) at high CO conversion (91.5%) but suffers from substantial byproduct formation, including C5+ hydrocarbons (26.0%) and CO2 (22.3%). In this study, hybrid catalysts (FT + cracking) in a double-layered bed reactor were introduced to convert the liquid and waxy hydrocarbons (C5+) into light hydrocarbons (CH4 and C2–C4). SAPO-34 zeolite and Ni catalysts were used as cracking catalysts.
Appendix A. Supplementary data Supplementary data to this article can be found online at https://
Table 2 Catalytic performance of each component in the hybrid catalyst, such as FT catalyst (5Co-15Fe/γ-Al2O3), SAPO-34 and Ni catalyst (10Ni/γ-Al2O3) in the singlelayered bed reactor and those of the hybrid catalyst in the double-layered bed reactor at 10 bar and a H2/CO ratio of 3.0 at 300 °C. Catalyst
CO conv. (%)
Selectivity (%) CH4
FT (5Co-15Fe/γ-Al2O3) SAPO-34 10Ni/γ-Al2O3 FT+ SAPO-34 FT + 10Ni/γ-Al2O3
91.5 ± 1.0 – 99.1 ± 1.2 89.9 ± 0.2 100 ± 0.0
23.5 – 89.3 27.1 64.2
± 0.8 ± 0.3 ± 0.4 ± 4.2
32
C2–C4
C5+
CO2
28.2 ± 0.7 – 0 31.4 ± 0.4 25.6 ± 2.6
26.0 ± 1.8 – 0 21.8 ± 0.5 5.8 ± 1.4
22.3 ± 0.4 – 10.7 ± 0.3 19.7 ± 0.3 6.7 ± 0.3
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doi.org/10.1016/j.catcom.2019.05.002.
carbon, J. Environ. Eng. Manage. 18 (2008) 371–376. [13] T. Horie, Y. Sato, T. Aida, S. Nishiyama, N. Ohmura, Oxidative coupling of propane with a two-layered catalyst bed reactor, Chem. Prod. Process. Model. 4 (2009). [14] M. Lu, I. Maddox, J. Brooks, Application of a multi-layer packed-bed reactor to citric acid production in solid-state fermentation using Aspergillus niger, Process Biochem. 33 (1998) 117–123. [15] Y. Chen, Y. Xu, D.g. Cheng, Y. Chen, F. Chen, X. Lu, Y. Huang, S. Ni, C2–C4 hydrocarbons synthesis from syngas over CuO–ZnO–Al2O3/SAPO-34 bifunctional catalyst, J.Chem. Technol.Biotechnol. 90 (2015) 415–422. [16] Y. Chen, Y. Xu, D.-g. Cheng, Y. Chen, F. Chen, X. Lu, Y. Huang, S. Ni, Synthesis of CuO–ZnO–Al2O3@ SAPO-34 core@ shell structured catalyst by intermediate layer method, Pure Appl. Chem. 86 (2014) 775–783. [17] J. Li, X. Pan, X. Bao, Direct conversion of syngas into hydrocarbons over a core–shell Cr-Zn@ SiO2@ SAPO-34 catalyst, Chin. J. Catal. 36 (2015) 1131–1135. [18] D.L. Nieskens, A. Ciftci, P.E. Groenendijk, M.F. Wielemaker, A. Malek, Production of light hydrocarbons from syngas using a hybrid catalyst, Ind.Eng. Chem. Res. 56 (2017) 2722–2732. [19] R. Thomson, C. Montes, M. Davis, E. Wolf, Hydrocarbon synthesis from CO hydrogenation over Pd supported on SAPO molecular sieves, J.Catal. 124 (1990) 401–415. [20] Y. Yu, Y. Xu, D.-g. Cheng, Y. Chen, F. Chen, X. Lu, Y. Huang, S. Ni, Transformation of syngas to light hydrocarbons over bifunctional CuO–ZnO/SAPO-34 catalysts: The effect of preparation methods, React. Kinet. Mech. Catal. 112 (2014) 489–497. [21] W. Ahmad, M.N. Younis, R. Shawabkeh, S. Ahmed, Synthesis of lanthanide series (La, Ce, Pr, Eu, & Gd) promoted Ni/γ-Al2O3 catalysts for methanation of CO2 at low temperature under atmospheric pressure, Catal. Commun. 100 (2017) 121–126. [22] H. Arandiyan, G. Kasaeian, B. Nematollahi, Y. Wang, H. Sun, S. Bartlett, H. Dai, M. Rezaei, Self-assembly of flower-like LaNiAlO3-supported nickel catalysts for CO methanation, Catal.Commun. 115 (2018) 40–44. [23] J. Gao, Q. Liu, F. Gu, B. Liu, Z. Zhong, F. Su, Recent advances in methanation catalysts for the production of synthetic natural gas, RSC Adv. 5 (2015) 22759–22776. [24] T.A. Le, M.S. Kim, S.H. Lee, T.W. Kim, E.D. Park, CO and CO2 methanation over supported Ni catalysts, Catal. Today 293 (2017) 89–96. [25] A. Griboval-Constant, A. Butel, V.V. Ordomsky, P.A. Chernavskii, A. Khodakov, Cobalt and iron species in alumina supported bimetallic catalysts for Fischer–Tropsch reaction, Appl. Catal.,A: Gen. 481 (2014) 116–126. [26] H.M. Torres Galvis, K.P. de Jong, Catalysts for production of lower olefins from synthesis gas: A review, ACS Catal. 3 (2013) 2130–2149.
References [1] Z. Binran, Z. Chen, Y. Chen, X. Ma, Syngas methanation over Ni/SiO2 catalyst prepared by ammonia-assisted impregnation, J.Hydrogen Energy 42 (2017) 27073–27083. [2] S.H. Hwang, J. Lee, U.G. Hong, J.G. Seo, J.C. Jung, D.J. Koh, H. Lim, C. Byun, I.K. Song, Methane production from carbon monoxide and hydrogen over nickelalumina-xerogel catalyst: Effect of nickel content, J. Ind. Eng. Chem. 17 (2011) 154–157. [3] J. Kopyscinski, T.J. Schildhauer, S. Biollaz, Production of synthetic natural gas (SNG) from coal and dry biomass – A technology review from 1950 to 2009, Fuel 89 (2010) 1763–1783. [4] Z.-Z. Wang, W.-F. Han, H.-Z. Liu, Hydrothermal synthesis of sulfur-resistant MoS2 catalyst for methanation reaction, Catal. Commun. 84 (2016) 120–123. [5] B. Nematollahi, M. Rezaei, E. Amini, E.N. Lay, Preparation of high surface area Ni/ MgAl2O4nanocatalysts for CO selective methanation, Int. J. Hydrog. Energy 43 (2018) 772–780. [6] T. Inui, A. Sakamoto, T. Takeguchi, Y. Ishigaki, Synthesis of highly calorific gaseous fuel from syngas on cobalt-manganese-ruthenium composite catalysts, Ind. Eng.Chem. Res. 28 (1989) 427–431. [7] Y.H. Lee, H. Kim, H.S. Choi, D.-W. Lee, K.-Y. Lee, Co-Mn-Ru/Al2O3 catalyst for the production of high-calorific synthetic natural gas, Korean J. Chem. Eng. 32 (2015) 2220–2226. [8] Y.H. Lee, K.-Y. Lee, Effect of surface composition of Fe catalyst on the activity for the production of high-calorie synthetic natural gas (SNG), Korean J. Chem. Eng. 34 (2017) 320–327. [9] Y.H. Lee, D.-W. Lee, H. Kim, H.S. Choi, K.-Y. Lee, Fe–Zn catalysts for the production of high-calorie synthetic natural gas, Fuel 159 (2015) 259–268. [10] Y.H. Lee, D.-W. Lee, K.-Y. Lee, Production of high-calorie synthetic natural gas using copper-impregnated iron catalysts, J.Mol. Catal. A 425 (2016) 190–198. [11] S.B. Jo, H.J. Chae, T.Y. Kim, C.H. Lee, J.U. Oh, S.-H. Kang, J.W. Kim, M. Jeong, S.C. Lee, J.C. Kim, Selective CO hydrogenation over bimetallic Co-Fe catalysts for the production of light paraffin hydrocarbons (C2–C4): Effect of H2/CO ratio and reaction temperature, Catal. Commun. 117 (2018) 74–78. [12] M.-B. Chang, S.-S. Hsiau, S.-H. Chang, K.-H. Chi, W.-C. Lo, J. Smid, Reduction of dioxin emission by multi-layer moving bed reactor with bead-shaped activated
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