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
·
催化化学
✓ 已验证
产品关联
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
ChemNanoMat
·
2018
·Vol. 4
·期 5
·487-495
·
IF 3.173
Zhinian Li,Shenliang Wang,Wei Hong,Shihui Zou,Liping Xiao,Jie Fan
Graphical Smart screens : An intelligent approach was developed to screen Na−Mn−W/SiO 2 catalysts for the oxidative coupling of methane (OCM). Effective composition regions other than the standard composition were successfully excavated. The wide range of the optimal composition allowed a fluctuation of composition during the reaction, which secured its excellent stability in the OCM reaction. Optimizing the performance and understanding the mechanism of metal oxide catalysts in the oxidative coupling of methane (OCM) is one of the most important projects in industrial catalysis. Here, we report an intelligent approach to screen Na−Mn−W/SiO 2 catalysts for the OCM reaction via ink-jet printing and multidimensional group testing. The ink-jet-printing-assisted (IJP-A) synthetic methodology ensured a fast synthesis of 1536 catalysts that were evaluated in 24 tests via a multidimensional group testing strategy (m-GT). After two-round synthesis-and-screening processes, several excellent groups with different composition space were screened out. Among the excellent catalysts, the OCM performance of Na−Mn−W/SiO 2 catalyst with higher Na, Mn and W content (G3 and G7) was less sensitive to its constituent than that of Na−Mn−W/SiO 2 catalyst with lower Na, Mn and W content (G1). These results indicated the sensitivity of performance to its Na, Mn and W content decreased in larger Na, Mn and W spaces, consistent with the complex homogeneous/heterogeneous reaction mechanism and multi-active sites. A series of Na−Mn−W/SiO 2 formulas with good performance also provide a reasonable explanation to its excellent stability for the OCM reaction. In addition, this intelligent optimization in total space offers a pathway to study the multicomponent metal oxide catalyst in the OCM reaction.
研究领域:
化学工程
·
催化
·
材料科学
✓ 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
·
催化科学
✓ 已验证
产品关联
DOI
高影响因子
Science Advances
·
2017
·Vol. 3
·期 6
·
IF 0
Pengwei Wang,Guofeng Zhao,Yu Wang,Yong Lu
Oxidative coupling of methane (OCM) is a promising method for the direct conversion of methane to ethene and ethane (C2 products). Among the catalysts reported previously, Mn2O3-Na2WO4/SiO2 showed the highest conversion and selectivity, but only at 800° to 900°C, which represents a substantial challenge for commercialization. We report a TiO2-doped Mn2O3-Na2WO4/SiO2 catalyst by using Ti-MWW zeolite as TiO2 dopant as well as SiO2 support, enabling OCM with 26% conversion and 76% C2-C3 selectivity at 720°C because of MnTiO3 formation. MnTiO3 triggers the low-temperature Mn2+↔Mn3+ cycle for O2 activation while working synergistically with Na2WO4 to selectively convert methane to C2-C3. We also prepared a practical Mn2O3-TiO2-Na2WO4/SiO2 catalyst in a ball mill. This catalyst can be transformed in situ into MnTiO3-Na2WO4/SiO2, yielding 22% conversion and 62% selectivity at 650°C. Our results will stimulate attempts to understand more fully the chemistry of MnTiO3-governed low-temperature activity, which might lead to commercial exploitation of a low-temperature OCM process.
研究领域:
化学工程
·
催化
·
能源化学
✓ 已验证
产品关联
DOI
PubMed
INORGANIC CHEMISTRY
·
2025
·
IF 4.7
Xiaomei Yu,Junwei Xu,Liang Guo,Jieqi Zhou,Rumeng Ouyang,Xiuzhong Fang,Jiating Shen,Xiang Wang
At present, there are still controversy viewpoints on the reactive oxygen sites in the OCM reaction on ABO3 perovskites. Some researchers believe that electron-deficient chemisorbed oxygen species (O2–, O22–, and O–) contribute to C2 product formation, and surface lattice oxygen (O2–) promotes the deep oxidation of methane, while others hold an opposite viewpoint. In addition, the influence of BOx polyhedra on the reactive sites and reaction performance has rarely been elucidated. Considering this, two types of LaAlO3 perovskites, comprising different contents of surface and bulk coordinatively unsaturated sites (AlO4 tetrahedra), were synthesized for the OCM reaction. Through a series of in situ and ex situ characterization techniques and combined with DFT calculations, a high oxygen vacancy concentration was revealed for the AlO4-rich LaAlO3 perovskite, leading to an abundance of reactive oxygen and promoting oxygen mobility. The study identified monatomic surface lattice oxygen O2– as the active sites for the deep oxidation of methane at low temperatures. The O22– species generated by oxygen vacancies promotes the formation of C2 products at high temperatures.
✓ 已验证
产品关联
DOI
PubMed
高影响因子
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