ACS Catalysis
·
2022
·
IF 13.7
Jiaqi Si,Guofeng Zhao,Tian Lan,Jiayong Ni,Weidong Sun,Ye Liu,Yong Lu
The MnOx-Na2WO4-based catalysts show the most promise for practical application in the oxidative coupling of methane (OCM), but its working mechanism is still open for debate. Herein, we attempt to reveal the role of Na2WO4 in a low-temperature light-off Mn7SiO12–Na2WO4/Cristobalite catalyst system. Three catalysts with Mn7SiO12–Na2WO4, Mn7SiO12, and Na2WO4 supported on cristobalite were rationally tailored, tested in the OCM reaction, and deeply characterized by 17O-labeling solid state nuclear magnetic resonance and Raman combined with temperature-programmed reaction/desorption methods. The OCM reaction proceeds via the Na2WO4-modulating Mn7SiO12 ↔ MnSiO3 redox with CH4/O2. The Na2WO4 substantially reduces the trigger temperature of such a redox cycle and gets it running selectively instead of combustion. Neither direct redox of Na2WO4 nor oxygen spillover between Na2WO4 and Mn7SiO12 was observed. Nevertheless, oxygen exchange between O2 and Na2WO4 will still occur via the Td-WO4 ↔ Oh-WO6 tautomerization only in case of re-oxidizing MnWO4 (Oh-WO6) formed during reaction at >750 °C back to Mn7SiO12 and Na2WO4 (Td-WO4).
研究领域:
催化化学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
Catalysis Science & Technology
·
2025
·
IF 4.2
Yilin Zhao,Fangwei Liu,Jingbo Hu,Yang Yang,Jianzhou Wu,Shihui Zou,Jie Fan
The Mn–Na2WO4/SiO2 catalyst for oxidative coupling of methane (OCM) is highly appealing and promising but its high light-off temperature (>800 °C) hinders its industrial application. Engineering catalysts for efficient catalytic performance is attractive yet challenging. In this study, we demonstrate that the incorporation of small amounts of silver into the Mn–Na2WO4/SiO2 catalyst significantly improves its performance, achieving a C2 yield of up to 20% at 750 °C. Characterization results indicate that silver facilitates O2 activation and promotes C–H bond activation, thereby further enhancing CH4 conversion. The findings offer valuable insights into advancing the design concept of high-performance OCM catalysts.
研究领域:
化学工程
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催化材料科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2020
·Vol. 104
·期 5
·2125-2133
·
IF 3.502
Naichao Chen,Bin Xiao,Xinwei Xu,Tao Sun,Fei Jin,Meiyu Chen,Xianqiang Chen,Hong Wang
(1- x )Na 2 WO 4 – x Ni 0.2 Cu 0.2 Zn 0.6 Fe 2 O 4 (NWO-NCZO) ceramic composites ( x = 0–0.6) were successfully prepared by the cold sintering method under a uniaxial pressure of 200 MPa at 150°C for 30 min. The microstructures and electromagnetic properties of (1- x )NWO- x NCZO ceramic composites with different NCZO contents have been systematically investigated. The obtained biphasic NWO-NCZO ceramic composites possess dense microstructures. The 0.4NWO–0.6NCZO ceramic composite exhibits a matched relative permittivity and relative permeability of around 8 in the frequency range from 10 to 200 MHz, which is beneficial for impedance matching between antenna and free space. A prototype of microstrip antenna based on the developed NWO-NCZO ceramic composite is designed and to demonstrate its application in miniaturized antennas. The simulation results revealed that the size of the radiation patch of the antenna can be reduced by 60% yet with bandwidth being enhanced 26.5 times when the 0.4NWO–0.6NCZO ceramic composite is selected as the substrate instead of pure NWO ceramic.
研究领域:
材料科学
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电磁工程
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陶瓷工程
✓ 已验证
DOI
高影响因子
Catalysis Science & Technology
·
2023
·Vol. 13
·期 8
·2493-2499
·
IF 5
Junxing Wang,Fangwei Liu,Jianzhou Wu,Shihui Zou,Jie Fan
Engineering Mn–Na2WO4 catalysts for efficient oxidative coupling of methane (OCM) at low temperatures (T ≤ 700 °C) is appealing yet challenging. Herein, we report a LaCeZr ternary oxide supported Mn–Na2WO4 catalyst, which achieves 20.9% C2 yield at 700 °C with at least 50 hour stability. Characterizations suggest that LaCeZr ternary oxides can promote the redox properties of Mn–Na2WO4 catalysts, which facilitate O2 activation at low reaction temperatures and generate more active oxygen species to activate CH4 into C2 products.
研究领域:
化学工程
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催化科学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Jiayong Ni,Tian Lan,Pu Liu,Yong Lu
The fluidized-bed reactor with excellent heat and mass transfer features has great appeal for application in the oxidative coupling of methane (FB-OCM), whereas qualified fluid catalysts represent a grand challenge. Herein, we report a high-performance Mn 2 O 3 -Na 2 WO 4 /TiO 2 fluid catalyst (5.4 wt% Mn 2 O 3 and 2 wt% Na 2 WO 4 ), which was obtained by the incipient-wetness impregnation method and examined in the OCM reaction in an electric-heating quartz fluidized-bed reactor (i.d., 2 cm). The standard normalization method on the basis of carbon atom was used for calculating the CH 4 conversion and C 2- C 3 selectivity. This catalyst achieves 35.5 % CH 4 conversion, 66 % C 2 -C 3 selectivity and particularly 15.1 % single-pass yield of C 2 H 4 for a feed of CH 4 /O 2 /H 2 O=3/1/1 with a catalyst dosage of 20 mL at 700 °C and a total GHSV of 7200 h −1 . Such catalyst is stable for at least 50 h without signs of deactivation and agglomeration/defluidization. The catalyst particle size is crucial for the FB-OCM reaction with respect to the reaction light-off and catalyst fluidization. The catalyst with preferable particle size of 450–600 μm can not only trigger the OCM reaction at a relatively low temperature of 630 °C but also warrant active bubbling fluidization. Furthermore, thanks to the low amount of Na 2 WO 4 and interpenetrating structure of TiO 2 -nanorod, such catalyst achieves good anti-aggregation and robust mechanical strength (with a low attrition index of 1.9 %). The effects of water-adding amount in feedstock and catalyst particle size distribution on the hydrodynamics behaviour were investigated in a laboratory-scale fluidized-bed OCM reactor by using numerical simulation method.
研究领域:
化学工程
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催化化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY
·
2017
·Vol. 17
·期 12
·8818-8826
·
IF 1.483
Liu Jingwei,Huo Minfeng,Zhu Yan
Mn–Na2WO4/SiO2 synthesized by Urea-assisted hydrothermal-Impregnation route has more and stronger surface basic sites, and more surface lattice oxygen, leading to higher methane conversion with higher selectivity toward ethane and ethylene in oxidative
coupling of methane reaction, compared to Mn–Na2WO4/SiO2 produced by Co-precipitation-Impregnation (CPI) and Sequential Impregnation (SI) methods.
研究领域:
催化化学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF CATALYSIS
·
2021
·
IF 7.92
Weidong Sun,Ya Gao,Guofeng Zhao,Jiaqi Si,Ye Liu,Yong Lu
Ethylene in principle can be obtained via oxidative coupling of methane (OCM), but it is urgently calling for a low-temperature active and selective catalyst. To accomplish this goal, the Ce x Zr 1-x O 2 solid solutions with varied Ce/Zr molar ratio were modified with Mn 2 O 3 -Na 2 WO 4 to fabricate OCM catalysts. The effects of Ce/Zr ratio and Mn 2 O 3 -Na 2 WO 4 doping were investigated on the catalyst reactivity for the OCM, showing that the reaction light-off temperature, activity and selectivity are subject to the Ce/Zr molar ratio and Mn 2 O 3 -Na 2 WO 4 doping. The promising catalyst with Ce/Zr molar ratio of 0.15/0.85 achieves 25% CH 4 conversion with 67% selectivity to C 2 -C 3 at 660 °C and is stable for at least 100 h. The catalysts were systematically studied by CH 4 -TPSR, O 2 -TPO/-TPD, CH 4 -pulse, in-situ FT-IR, EPR and XPS, showing that the Mn 2 O 3 -Na 2 WO 4 doped Ce 0.15 Zr 0.85 O 2 can generate more O 2 – species thereby leading to a markedly improved activity and selectivity at much lowered reaction temperature.
研究领域:
催化化学
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材料科学
✓ 已验证
DOI
高影响因子
CHINESE JOURNAL OF CATALYSIS
·
2018
·
IF 3.525
Pengwei Wang,Xin Zhang,Guofeng Zhao,Ye Liu,Yong Lu
Mn 2 O 3 -Na 2 WO 4 /SiO 2 is considered as the most promising catalyst for the oxidative coupling of methane (OCM) process; however, it only has a better catalytic performance over 800 °C. To improve its low-temperature performance, an attempt has been made to modify the Mn 2 O 3 -Na 2 WO 4 /SiO 2 catalyst using TiO 2 , MgO, Ga 2 O 3 , and ZrO 2 . Among the synthesized catalysts, the TiO 2 -modified Mn 2 O 3 -Na 2 WO 4 /SiO 2 catalyst shows markedly improved low-temperature OCM performance, achieving a high CH 4 conversion of ~23% and a good C 2 -C 3 selectivity of ~73% at 700 °C (the catalyst bed temperature), along with promising stability for at least 300 h without signs of deactivation. In comparison with the unmodified Mn 2 O 3 -Na 2 WO 4 /SiO 2 catalyst, the TiO 2 modification results in significant improvement in the low-temperature activity/selectivity, whereas the MgO modification has almost no impact and the Ga 2 O 3 and ZrO 2 modifications have a negative effect. The X-ray diffraction (XRD) and Raman results reveal that the formation of a MnTiO 3 phase and a MnTiO 3 -dominated catalyst surface is crucial for the improvement of the low-temperature activity/selectivity in the OCM process.
研究领域:
化学工程
·
催化科学
✓ 已验证
DOI
高影响因子
FUEL
·
2021
·
IF 6.609
Jiaqi Si,Weidong Sun,Guofeng Zhao,Yong Lu
The MnO x -Na 2 WO 4 catalyst for oxidative coupling of methane (OCM) is highly attractive but its high light-off temperature (>800 °C) is a major obstacle for commercialization. In-depth understanding of reaction light-off relevant chemistry is particularly desirable. We explored the OCM light-off over several metal-oxide-supported MnO x -Na 2 WO 4 catalysts. As CH 4 conversion above 15% with acceptable C 2-3 selectivity is considered as the sign of OCM light-off, support-dependent OCM light-off is clearly observed over MnO x -Na 2 WO 4 supported on SnO 2 (660 °C), TiO 2 (670 °C), MgO (690 °C), and ZnO (720 °C), being tightly linked with the redox rate of Mn 3+ (or Mn 4+ ) ↔ Mn 2+ cycle governed by support oxides.
研究领域:
化学工程
·
催化科学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Tian Lan,Weidong Sun,Xuerong Shi,Yong Lu
Intrinsic safety chemical looping-oxidative coupling of methane (CL-OCM) is an attractive method for direct conversion of methane to ethylene, but well-qualified oxygen carrier catalyst still remains challenging. Herein, we report a promising Na 2 WO 4 -doped Mn 2 O 3 -TiO 2 catalyst toward high-efficiency CL-OCM process. The standout Na 2 WO 4 /2Mn1Ti (Mn 2 O 3 /TiO 2 weight ratio of 2/1) catalyst, with good cycling performance, achieves a high space time yield of 27.8 (or 22.9) g C2-C3 kg cat −1 h −1 with 19.5 % (or 15.7 %) CH 4 conversion and 80 % (or 82.7 %) C 2 -C 3 selectivity at 740 (or 720) o C and a low catalyst/CH 4 weight ratio of 13.5. The TiO 2 substantially lowers the CL-OCM reaction temperature, due to the establishment of a low-temperature light-off “Mn 2 O 3 + TiO 2 ↔ MnTiO 3 ” redox cycle with CH 4 /O 2 . The enabling role of Na 2 WO 4 in modulating the reaction of Mn 2 O 3 with CH 4 into OCM instead of combustion is theoretically unveiled, which in nature benefits the *CH 3 transfer and spontaneous desorption to form ∙CH 3 radicals.
研究领域:
化学工程
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催化科学
✓ 已验证
产品关联
DOI
高影响因子
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
·
2022
·Vol. 61
·期 18
·e202117201
·
IF 16.823
Jiaqi Si,Guofeng Zhao,Weidong Sun,Jincun Liu,Cairu Guan,Yong Yang,Xue-Rong Shi,Yong Lu
Graphical For the oxidative coupling of methane (OCM) reaction, the MnO x -Na 2 WO 4 /SiO 2 catalyst enriched with Q 2 units in the SiO 2 carrier achieves 23 % CH 4 conversion and 72 % C 2–3 selectivity at 660 °C. A large number of Q 2 units in MnO x -Na 2 WO 4 /SiO 2 is a trigger for markedly lowering the light-off temperature of the Mn 3+ ↔Mn 2+ redox cycle because of the easy formation of MnSiO 3 . Oxidative coupling of methane (OCM) catalyzed by MnO x -Na 2 WO 4 /SiO 2 has great industrial promise to convert methane directly to C 2–3 products, but its high light-off temperature is the most challenging obstacle to commercialization and its working mechanism is still a mystery. We report the discovery of a low-temperature active and selective MnO x -Na 2 WO 4 /SiO 2 catalyst enriched with Q 2 units in the SiO 2 carrier, being capable of converting 23 % CH 4 with 72 % C 2–3 selectivity at 660 °C. From experiments and theoretical calculations, a large number of Q 2 units in the MnO x -Na 2 WO 4 /SiO 2 catalyst is a trigger for markedly lowering the light-off temperature of the Mn 3+ ↔Mn 2+ redox cycle involved in the OCM reaction because of the easy formation of MnSiO 3 . Notably, the MnSiO 3 formation proceeds merely through the SiO 2 -involved reaction in the presence of Na 2 WO 4 : Mn 7 SiO 12 +6 SiO 2 ↔7 MnSiO 3 +1.5 O 2 . The Na 2 WO 4 not only drives the light-off of this cycle but also gets it working with substantial selectivity toward C 2–3 products. Our findings shine a light on the rational design of more advanced MnO x -Na 2 WO 4 based OCM catalysts through establishing new Mn 3+ ↔Mn 2+ redox cycles with lowered light-off temperature.
研究领域:
催化化学
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材料科学
·
能源化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
FUEL
·
2021
·
IF 6.609
Tao Wang,Yunfei Gao,Yongzhuo Liu,Minghang Song,Jingjing Liu,Qingjie Guo
Chemical looping oxidative dehydrogenation (CL-ODH) of ethane utilizes lattice oxygen of oxygen carrier, to substitute molecular oxygen, which makes high oxygen capacity as significant as ethane conversion and ethylene selectivity. Promoter were usually used to increased ethylene selectivity of bare oxygen carriers, but the overall oxygen capacity is limited to 3 wt%. In the current work, a core-shell oxygen carrier with Na 2 WO 4 as the shell material and spinel-type CuMn 2 O 4 as oxygen source was prepared. The core-shell structure were characterized by SEM, HTEM and XPS. Deep reduction with thirty consecutive ethane pulses was exhibited in a fixed bed. At 720 °C, up to 58.8% ethane conversion, 86.4% ethylene selectivity, and effective oxygen capacity up to 4.8 wt% were achieved with H 2 conversion > 90%. Furthermore, in the light of effective oxygen capacity, the phase transformation from CuMn 2 O 4 to Cu, MnO, Mn 3 O 4 and CuMnO 2 is determined as the desired phase change for this CL-ODH process. The connection between the dynamic phase change and the enlarged oxygen capacity will also shed light in future oxygen carrier design for chemical looping processes for chemical productions.
研究领域:
化学工程
·
材料科学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）