以醋酸甲酯合成为模型反应,研究浆料催化精馏过程。对浆料催化精馏过程建立拟均相稳态平衡级模型,用A spen P lus软件进行模拟。考察精馏塔内温度分布、汽液相组成及流率情况,得到醋酸中水含量、反应段塔板数和液相持液量对合成醋酸甲...以醋酸甲酯合成为模型反应,研究浆料催化精馏过程。对浆料催化精馏过程建立拟均相稳态平衡级模型,用A spen P lus软件进行模拟。考察精馏塔内温度分布、汽液相组成及流率情况,得到醋酸中水含量、反应段塔板数和液相持液量对合成醋酸甲酯收率和塔顶醋酸甲酯纯度的影响。计算得出在模拟实验塔内优化操作条件为:23块理论板数,醋酸进料口和甲醇进料口分别位于第7和第17块理论板;酸与醇的摩尔比为1.2∶1.0;催化剂与醋酸的质量比为0.03;回流比1.3;塔板总持液量2 560mL;塔釜持液量1 200mL;控制塔顶采出流率0.485。在此条件下,醋酸甲酸收率大于95%,塔顶产品中酯的质量分数大于96%。展开更多
Two major challenges,high cost and short lifespan,have been hindering the commercialization process of lowtemperature fuel cells.Professor Wei's group has been focusing on decreasing cathode Pt loadings without lo...Two major challenges,high cost and short lifespan,have been hindering the commercialization process of lowtemperature fuel cells.Professor Wei's group has been focusing on decreasing cathode Pt loadings without losses of activity and durability,and their research advances in this area over the past three decades are briefly reviewed herein.Regarding the Pt-based catalysts and the low Pt usage,they have firstly tried to clarify the degradation mechanism of Pt/C catalysts,and then demonstrated that the activity and stability could be improved by three strategies:regulating the nanostructures of the active sites,enhancing the effects of support materials,and optimizing structures of the three-phase boundary.For Pt-free catalysts,especialiy carbon-based ones,several strategies that they proposed to enhance the activity of nitrogen-/heteroatom-doped carbon catalysts are firstly presented.Then,an indepth understanding of the degradation mechanism for carbon-based catalysts is discussed,and followed by the corresponding stability enhancement strategies.Also,the carbon-based electrode at the micrometer-scale,faces the challenges such as low active-site density,thick catalytic layer,and the effect of hydrogen peroxide,which require rational structure design for the integral cathodic electrode.This review finally gives a brief conclusion and outlook about the low cost and long lifespan of cathodic oxygen reduction catalysts.展开更多
Carbonate electrolytes are one of the most desirable electrolytes for high-energy lithium-sulfur batteries(LSBs)because of their successful implementation in commercial Li-ion batteries.The low-polysulfide-solubility ...Carbonate electrolytes are one of the most desirable electrolytes for high-energy lithium-sulfur batteries(LSBs)because of their successful implementation in commercial Li-ion batteries.The low-polysulfide-solubility feature of some carbonate solvents also makes them very promising for overcoming the shuttle effects of LSBs.However,regular sulfur electrodes experience undesired electrochemical mechanisms in carbonate electrolytes due to side reactions.In this study,we report a catalytic redox mechanism of sulfur in propylene carbonate(PC)electrolyte based on a compari-son study.The catalytic mechanism is characterized by the interactions between polysulfides and dual N/O functional groups on the host carbon,which largely prevents side reactions between polysulfides and the carbonate electrolyte.Such a mechanism coupled with the low-polysulfide-solubility feature leads to stable cycling of LSBs in PC electrolyte.Favorable dual N/O functional groups are identified via a density functional theory study.This work provides an alternative route for enabling LSBs in carbonate electrolytes.展开更多
基金supported by the National Key Research and Development Program of China(No.2020YFB1506002,2019YFB1504503,2016YFB0101202)National 973 Program of China(No.2012CB215501)National Natural Science Foundation of China(No.52021004,22022502(2021),21822803(2019),21576031(2016),51272297(2013),20936008(2010),20676156(2007),20376088(2004),20176066(2002),29976047(2000)).
文摘Two major challenges,high cost and short lifespan,have been hindering the commercialization process of lowtemperature fuel cells.Professor Wei's group has been focusing on decreasing cathode Pt loadings without losses of activity and durability,and their research advances in this area over the past three decades are briefly reviewed herein.Regarding the Pt-based catalysts and the low Pt usage,they have firstly tried to clarify the degradation mechanism of Pt/C catalysts,and then demonstrated that the activity and stability could be improved by three strategies:regulating the nanostructures of the active sites,enhancing the effects of support materials,and optimizing structures of the three-phase boundary.For Pt-free catalysts,especialiy carbon-based ones,several strategies that they proposed to enhance the activity of nitrogen-/heteroatom-doped carbon catalysts are firstly presented.Then,an indepth understanding of the degradation mechanism for carbon-based catalysts is discussed,and followed by the corresponding stability enhancement strategies.Also,the carbon-based electrode at the micrometer-scale,faces the challenges such as low active-site density,thick catalytic layer,and the effect of hydrogen peroxide,which require rational structure design for the integral cathodic electrode.This review finally gives a brief conclusion and outlook about the low cost and long lifespan of cathodic oxygen reduction catalysts.
文摘Carbonate electrolytes are one of the most desirable electrolytes for high-energy lithium-sulfur batteries(LSBs)because of their successful implementation in commercial Li-ion batteries.The low-polysulfide-solubility feature of some carbonate solvents also makes them very promising for overcoming the shuttle effects of LSBs.However,regular sulfur electrodes experience undesired electrochemical mechanisms in carbonate electrolytes due to side reactions.In this study,we report a catalytic redox mechanism of sulfur in propylene carbonate(PC)electrolyte based on a compari-son study.The catalytic mechanism is characterized by the interactions between polysulfides and dual N/O functional groups on the host carbon,which largely prevents side reactions between polysulfides and the carbonate electrolyte.Such a mechanism coupled with the low-polysulfide-solubility feature leads to stable cycling of LSBs in PC electrolyte.Favorable dual N/O functional groups are identified via a density functional theory study.This work provides an alternative route for enabling LSBs in carbonate electrolytes.
