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Rh/Al_(2)O_(3)催化剂在丙烷脱氢反应中的表面变化
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作者 李书毅 穆长乐 +3 位作者 何念秋 徐杰 郑燕萍 陈明树 《Chinese Journal of Catalysis》 SCIE CAS CSCD 2024年第7期145-155,共11页
丙烯是一种重要的化工原料,需求量较大且逐年增加.丙烷脱氢(PDH)是一种高效的生产丙烯过程,正逐步取代石脑油裂解成为重要的丙烯生产工艺.开发高效且稳定的PDH催化剂将对PDH工业发展起到积极的推动作用.Rh因其较好的C-H键活化能力,展现... 丙烯是一种重要的化工原料,需求量较大且逐年增加.丙烷脱氢(PDH)是一种高效的生产丙烯过程,正逐步取代石脑油裂解成为重要的丙烯生产工艺.开发高效且稳定的PDH催化剂将对PDH工业发展起到积极的推动作用.Rh因其较好的C-H键活化能力,展现出作为PDH催化剂的巨大潜力,但关于Rh应用于PDH的报道较少.明确Rh物种尺寸对PDH产物选择性的影响,对后续设计高效且稳定的Rh基PDH催化剂至关重要.多相催化反应主要发生在催化剂的表面,因此,催化剂的表面状态对其催化性能具有重要的影响.在催化反应过程中,一些催化剂的表面状态会发生显著变化,这些变化会导致活性、产物选择性明显变化.通过采用(准)原位表面研究手段,能够清晰地了解催化剂在反应过程中的表面变化,这对于建立催化剂结构与反应性能之间的构效关系具有非常重要的意义.本文通过沉积-沉淀法制备了不同负载量的Rh/Al_(2)O_(3)催化剂,旨在探究Rh物种尺寸对PDH产物选择性的影响.球差电镜(AC-HAADF-STEM)观察显示,Rh物种以团簇和单原子的形式共存于Al_(2)O_(3)载体上.进一步通过准原位X射线光电子能谱(XPS)证实了不同化学态的Rh物种.通过固定床反应器对Rh/Al_(2)O_(3)催化剂的PDH性能进行测试,结果表明,催化剂在反应初始阶段需要经历诱导期.在此期间,甲烷的选择性显著降低,而丙烯的选择性显著升高,同时,丙烷的转化率显著降低.碳平衡计算表明,诱导期内产生了大量积碳.采用准原位XPS、低能离子散射谱(LEIS)和CO吸附红外光谱(CO-FTIR)研究了Rh/Al_(2)O_(3)催化剂在诱导期的表面变化.结果表明,在反应初始阶段,催化剂表面有大量积碳产生,这些积碳主要聚集在Rh物种表面,覆盖了Rh团簇,而Rh单原子则保持暴露状态,并作为PDH反应的活性中心.AC-HAADF-STEM结果表明,PDH反应4 h后,仍有Rh单原子存在于催化剂表面.结合Rh/Al_(2)O_(3)催化剂的PDH性能和准原位表征结果认为,丙烷在Rh团簇表面发生C-C键断裂反应,生成甲烷和积碳.积碳对Rh团簇的覆盖抑制了丙烷裂解反应,导致甲烷的选择性在诱导期显著降低;而Rh单原子则仍然暴露,具有催化PDH反应活性,并且是高选择性地生成丙烯的位点.该选择性的差异由丙烯在不同尺寸Rh物种上的吸附方式不同引起的,在Rh团簇表面以di-σ键吸附方式为主,吸附强度较强,丙烯不易脱附,并进一步发生裂解产生甲烷和积碳;而在Rh单原子上,丙烯以π键吸附方式存在,吸附强度较弱,不易发生副反应.对反应后的Rh/Al_(2)O_(3)催化剂进行分析,发现积碳主要为碳氢化合物和石墨碳,且随着反应进行,积碳从Rh团簇表面向Al_(2)O_(3)载体上转移.综上所述,本文通过使用准原位XPS,LEIS和CO-FTIR等技术探究了Rh/Al_(2)O_(3)催化剂在PDH反应中的表面变化,揭示了Rh物种尺寸对PDH产物选择性的影响.结果表明,Rh单原子对丙烯选择性有利,而在Rh团簇表面PDH产物主要为甲烷并产生积碳,同时积碳导致了催化剂在反应初始阶段的快速失活.本工作为后续高效Rh基PDH催化剂的设计提供参考. 展开更多
关键词 丙烷脱氢 积碳 单原子 准原位谱学 表面变化
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Differences in Precipitation and Related Wind Dynamics and Moisture and Heat Features in Separate Areas of the South China Sea before and after Summer Monsoon Onset
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作者 Chunyan ZHANG Donghai WANG +3 位作者 Kaifeng ZHANG Wanwen HE yanping zheng Yan XU 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2024年第8期1643-1660,共18页
Using surface and balloon-sounding measurements, satellite retrievals, and ERA5 reanalysis during 2011–20, this study compares the precipitation and related wind dynamics, moisture and heat features in different area... Using surface and balloon-sounding measurements, satellite retrievals, and ERA5 reanalysis during 2011–20, this study compares the precipitation and related wind dynamics, moisture and heat features in different areas of the South China Sea(SCS) before and after SCS summer monsoon onset(SCSSMO). The rainy sea around Dongsha(hereafter simply referred to as Dongsha) near the north coast, and the rainless sea around Xisha(hereafter simply referred to as Xisha) in the western SCS, are selected as two typical research subregions. It is found that Dongsha, rather than Xisha, has an earlier and greater increase in precipitation after SCSSMO under the combined effect of strong low-level southwesterly winds, coastal terrain blocking and lifting, and northern cold air. When the 950-h Pa southwesterly winds enhance and advance northward, accompanied by strengthened moisture flux, there is a strong convergence of wind and moisture in Dongsha due to a sudden deceleration and rear-end collision of wind by coastal terrain blocking. Moist and warm advection over Dongsha enhances early and deepens up to 200 h Pa in association with the strengthened upward motion after SCSSMO, thereby providing ample moisture and heat to form strong precipitation. However, when the 950-h Pa southwesterly winds weaken and retreat southward, Xisha is located in a wind-break area where strong convergence and upward motion centers move in. The vertical moistening and heating by advection in Xisha enhance later and appear far weaker compared to that in Dongsha, consistent with later and weaker precipitation. 展开更多
关键词 Dongsha Xisha South China Sea summer monsoon onset PRECIPITATION wind dynamics MOISTURE HEAT
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Field-assisted conductive substrate sparks the redox kinetics of Co_(9)S_(8) in Li-and Na-ion batteries
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作者 Huanhuan Li Yuxin Chen +4 位作者 Huiqin Chen Yantao Wang Jinlong Li yanping zheng Linlin Zhang 《Journal of Energy Chemistry》 SCIE EI CSCD 2023年第12期114-122,I0005,共10页
As a promising candidate electrode material in both Li-and Na-ion batteries(L/SIBs),the application of Co_(9)S_(8) is being hindered by its unsatisfactory electrochemical performance caused by the sluggish ion diffusi... As a promising candidate electrode material in both Li-and Na-ion batteries(L/SIBs),the application of Co_(9)S_(8) is being hindered by its unsatisfactory electrochemical performance caused by the sluggish ion diffusion kinetics and drastic volume expansion.Herein,a hybrid material composed of Co_(9)S_(8-x),N-doped carbon foam that seeded with Co nanoparticles(Co_(9)S_(8-x)@Co-NC) is constructed.Particularly,theoretical and experimental results imply that a built-in electric field at the interface of Co and NC is observed due to the variation of Fermi levels,forming rich Mott-Schottky-like heterointerfaces,which can significantly enhance the charge transfer capability between the active materials of Co_(9)S_(8) and conductive NC skeleton.Moreover,the sulfur defects in Co_(9)S_(8-x)can not only effectively lower the energy barrier of the ion diffusion and charge transfer processes,but also endow the target sample with more storage/adsorption/active sites for Li^(+)/Na^(+) ions,thus improving the rate performance of the Co_(9)S_(8-x)@Co-NC composite.As a result,the Co_(9)S_(8-x)@Co-NC exhibits fast surface-controlled redox kinetics and robust cycling stability.For instance,the Co_(9)S_(8-x)@Co-NC displays impressive Li-storage properties in both half and full cells with a high reversible capacity of 1007.4 mA h g^(-1)at 0.1 A g^(-1)after 100 cycles and superior rate capability up to 5 A g^(-1).Moreover,based on these comprehensive merits,the Co_(9)S_(8-x)@Co-NC composite shows decent electrochemical performance(472.2 and 311.1 mA h g^(-1)at 0.1 and 10 A g^(-1),respectively) as an anode for SIBs.This work presents an effective strategy for the construction of Mott-Schottky-like heterointerfaces in Co_(9)S_(8) based materials and provides specific inspiration for future works designing high-performance electrodes via interfacial engineering. 展开更多
关键词 Sulfur defects Mott-Schottky-like heterointerfaces Sodium lon Battery ANODE Full cell
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液滴微流控中空气/CF_(4)等离子体表面改性环烯烃共聚物 被引量:1
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作者 李洋 郑艳萍 +4 位作者 梁帅 张慧儒 林计良 王帅超 万卓 《高分子材料科学与工程》 EI CAS CSCD 北大核心 2021年第7期162-169,共8页
环烯烃共聚物(COC)是一种新型的微流控材料,其疏水性虽然可以保证油包水微滴生成,却极大降低了芯片的键合强度。采用空气/CF_(4)射频放电低温等离子体对COC进行表面改性,成功制备了高亲水性到高疏水性的COC表面,并利用接触角测量、X射... 环烯烃共聚物(COC)是一种新型的微流控材料,其疏水性虽然可以保证油包水微滴生成,却极大降低了芯片的键合强度。采用空气/CF_(4)射频放电低温等离子体对COC进行表面改性,成功制备了高亲水性到高疏水性的COC表面,并利用接触角测量、X射线光电子能谱、扫描电子显微镜和傅里叶变换红外光谱对处理后的表面进行了分析和表征。通过微滴生成实验与剥离实验研究了等离子体表面改性对COC芯片微滴生成、流动行为和键合强度的影响,并监测了改性表面的时效性。结果表明,空气等离子体处理后芯片黏接性能与润湿性能显著提高,但此时生成水包油微滴。经过空气等离子体活化后再经过CF_(4)等离子体处理的芯片疏水性恢复并超越本征,油包水微滴再度生成。因此,低温等离子体改性可以成为在不影响芯片功能的前提下实现芯片结构强化的有效方法,另外改性后芯片的生物应用值得进一步探索。 展开更多
关键词 环烯烃共聚物 表面改性 等离子体 液滴微流控 X射线光电子能谱
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Applications,of fluorescence lifetime imaging in clinical medicine 被引量:2
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作者 Zhanwen Wang yanping zheng +7 位作者 Deqiang Zhao Ziwei Zhao Lixin Liu Artem Pliss Feiqi Zhu Jun Liu Junle Qu Ping Luan 《Journal of Innovative Optical Health Sciences》 SCIE EI CAS 2018年第1期106-122,共17页
Fluorescence lifetime is not only associated with the molecular structure f fuorophores,but alsostrongly depends on the environment around them,which llows fuorescence lifetime imagingmicroscopy(FLIM)to be used as a t... Fluorescence lifetime is not only associated with the molecular structure f fuorophores,but alsostrongly depends on the environment around them,which llows fuorescence lifetime imagingmicroscopy(FLIM)to be used as a tool for precise measurement of the cell or tisue microenvironment,This review introduces the basic principle of fuorescence lifetime imagingtechnology and its application in clinical medicine,including research and diagnosis of diseases inskin,brain,eyes,mouth,bone,blood vessels and cavity organs,and drug evaluation.As anoninvasive,nontoxic and nonionizing radiation technique,FLIM demonstrates excellent per-formance with high sensitivity and specificity,which allows to determine precise position of thelesion and,thus,has good potential for application in biomedical research and clinical diagnosis. 展开更多
关键词 Fluorescence lifetime fluorescence lifetime imaging microscopy clinical medicine
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Study for System of Nonlinear Differential Equations with Riemann-Liouville Fractional Derivative 被引量:1
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作者 yanping zheng Wenxia Wang 《Applied Mathematics》 2013年第7期5-8,共4页
In this work, we study existence theorem of the initial value problem for the system of fractional differential equations where Dα denotes standard Riemann-Liouville fractional derivative, 0 and A ?is a square matrix... In this work, we study existence theorem of the initial value problem for the system of fractional differential equations where Dα denotes standard Riemann-Liouville fractional derivative, 0 and A ?is a square matrix. At the same time, power-type estimate for them has been given. 展开更多
关键词 Riemann-Liouville FRACTIONAL DERIVATIVE WEIGHTED Cauchy-Type Problem FRACTIONAL Differential EQUATIONS
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A Preliminary Analysis on the Applicability of ERA5 Reanalysis Data in Guangdong Province 被引量:2
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作者 yanping zheng 《Meteorological and Environmental Research》 CAS 2020年第2期37-42,48,共7页
In order to effectively use the ERA5 reanalysis data,observation data in and around Guangdong Province was used to evaluate the reanalysis data by analyzing the correlation coefficient and deviation. The results showe... In order to effectively use the ERA5 reanalysis data,observation data in and around Guangdong Province was used to evaluate the reanalysis data by analyzing the correlation coefficient and deviation. The results showed that among the surface elements,the sea level pressure and air temperature performed the best reproducibility,second the relative humidity and wind speed,and they had better performance in the Pearl River Delta and its surrounding areas,while the worst was wind direction. Except the relative humidity,elements had better performance at higher levels than lower levels among the ERA5 reanalysis upper-air data. 展开更多
关键词 REANALYSIS ERA5 APPLICABILITY
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Dynamic tracking of exsolved PdPt alloy/perovskite catalyst for efficient lean methane oxidation
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作者 Yanling Yang Zhenfa Ding +8 位作者 Huimin Wang Jianhui Li yanping zheng Hongquan Guo Li Zhang Bing Yang Qingqing Gu Haifeng Xiong Yifei Sun 《Chinese Chemical Letters》 SCIE CAS CSCD 2024年第4期170-175,共6页
Supported Pd based catalysts are considered as the efficient candidates for low-carbon alkane oxidation for their outstanding capability to break C-H bond. Whereas, the irreversible deactivation of Pd based catalysts ... Supported Pd based catalysts are considered as the efficient candidates for low-carbon alkane oxidation for their outstanding capability to break C-H bond. Whereas, the irreversible deactivation of Pd based catalysts was still frequently observed. Herein, we reinforced the extruded Pd nanoparticles with quantitive Pt to assemble the evenly distributed Pd Pt nanoalloy onto ferrite perovskite(Pd Pt-LCF) matrix with strengthened robustness of metal/oxide support interface. We further co-achieved the enhanced performance, anti-overoxidation as well as resistance of vapor-poisoning in durability measurement. The operando X-ray photoelectron spectroscopy(O-XPS) combined with various morphology characterizations confirms that the accumulation of surface deep-oxidation species of Pd^(4+) is the culprit for fast activity loss in exsolved Pd system, especially at high temperature of 400 ℃. Conversely, it could be completely suppressed by in-situ alloying Pd with equal amount of Pt, which helps maintain the metastable Pd^(2+)/Pd shell and metallic solid-solution core structure. The density function theory(DFT) calculations further buttress that the dissociation of C–H was facilitated on alloy/perovskite interface which is, on the contrary, resistant toward O–H bond cleavage, as compared to Pd/perovskite. Our work suggests that the modification of exsolved metal/oxide catalytic interface could further enrich the toolkit of heterogeneous catalyst design. 展开更多
关键词 EXSOLUTION PdPt alloy Operando characterization Methane conversion Deep-oxidation
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Catalysis under shell: Improved CO oxidation reaction confined in Pt@h-BN core-shell nanoreactors 被引量:6
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作者 Mengmeng Sun Qiang Fu +4 位作者 Lijun Gao yanping zheng Yangyang Li Mingshu Chen Xinhe Bao 《Nano Research》 SCIE EI CAS CSCD 2017年第4期1403-1412,共10页
Core-shell nanostructures consisting of active metal cores and protective shells often exhibit enhanced catalytic performance, in which reactants can access a small part of the core surfaces through the pores in the s... Core-shell nanostructures consisting of active metal cores and protective shells often exhibit enhanced catalytic performance, in which reactants can access a small part of the core surfaces through the pores in the shells. In this study, we show that Pt nanoparticles (NPs) can be embedded into few-layer hexagonal boron nitride (h-BN) overlayers, forming Pt@h-BN core-shell nanocatalysts. The h-BN shells not only protect the Pt NPs under harsh conditions but also allow gaseous molecules such as CO and 02 to access a large part of the Pt surfaces through a facile intercalation process. As a result, the Pt@h-BN nanostructures act as nanoreactors, and CO oxidation reactions with improved activity, selectivity, and stability occur at the core-shell interfaces. The confinement effect exerted by the h-BN shells promotes the Pt-catalyzed reactions. Our work suggests that two-dimensional shells can function as robust but flexible covers on nanocatalyst surfaces and tune the surface reactivity. 展开更多
关键词 CORE-SHELL CO oxidation PT hexagonal boron nitride NANOREACTOR
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Effect of a comprehensive therapy plus Gushenyutai plaster administered at Guanyuan(CV 4) on male infertility associated with semen non-liquefaction 被引量:6
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作者 Shaofang Peng yanping zheng +6 位作者 Kangzhuang zheng Ke Lin Juhong Wu Wenqin zheng Yongzhong Li Yang Li Chuangjian Lin 《Journal of Traditional Chinese Medicine》 SCIE CAS CSCD 2014年第6期666-672,共7页
OBJECTIVE: To observe the clinical effect of Gushenyutai plaster administered at the Guanyuan(CV4) acupoint on male infertility associated with semen non-liquefaction.METHODS: Sixty-two male patients with infertility ... OBJECTIVE: To observe the clinical effect of Gushenyutai plaster administered at the Guanyuan(CV4) acupoint on male infertility associated with semen non-liquefaction.METHODS: Sixty-two male patients with infertility caused by semen non-liquefaction were random-ized into a treatment and control group. The control group received comprehensive therapy, which included oral administration of clarithromycin sustained release tablets, hip bath with Zhongyaoxiaoyan granules, prostate massage, and transurethral microwave treatment. The treatment group was administered Gushenyutai plaster in addition to the comprehensive therapy. Both groups were treated for 8 weeks. After treatment, the clinical effect and pregnancy rate were assessed and compared between the two groups.RESULTS: The effective rate of the treatment group was significantly higher than that of the control group(96.77% vs 70.97%, P<0.05) and the pregnancy rates of the treatment group and control groups were 38.71% and 16.13%, respectively(P<0.05).CONCLUSION: The effect of Gushenyutai plaster plus comprehensive therapy was better than that of the comprehensive therapy alone on male infertility induced by semen non-liquefaction. 展开更多
关键词 Infertility male Treatment outcome Point CV 4 (Guanyuan) Semen non-liquefaction Gushenyutai plaster
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Tensile properties analysis of CFRP-titanium plate multi-bolt hybrid joints 被引量:2
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作者 yanping zheng Chaoyu ZHANG +2 位作者 Ying TIE Xu WANG Mingkun LI 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2022年第3期464-474,共11页
Hybrid joints have better tensile properties than pure bonded and bolted bolts,and are increasingly used in the aerospace field.Tensile tests are carried out for the Hybrid Bonded/Bolted(HBB)joints of Carbon Fiber Rei... Hybrid joints have better tensile properties than pure bonded and bolted bolts,and are increasingly used in the aerospace field.Tensile tests are carried out for the Hybrid Bonded/Bolted(HBB)joints of Carbon Fiber Reinforced Polymer(CFRP)laminate and titanium alloy plate under different bolt numbers,and the corresponding load–displacement curves are obtained.At the same time,based on Continuum Damage Mechanics(CDM)theory,which is derived from 3D Hashin failure criteria,and a Cohesive Zone Model(CZM),the tensile strength prediction model of the composite laminate-titanium alloy plate multi-bolted HBB joint was established,and the numerical simulation results were in good agreement with the experimental height,which validate the feasibility of the model.The difference in the bearing capacity of HBB joints under different numbers of bolts is compared and analyzed.On this basis,the influence of inter-bolt distance on the tensile properties of the HBB joints is explored.The results show that the double-nail HBB joints can effectively improve the end warpage and low bearing capacity of the single-nail HBB joints.The tensile failure load of the double-nail HBB joints under the standard lap width(30 mm)is 82.6%higher than that of the single nail,the tensile failure load of the three-bolt HBB joints is 34.1%higher than that of the double nail.For the three-bolt HBB joint,the joint strength is controlled by the adhesive and the external bolt,while the internal bolt is redundant,the hybrid joint can be simplified by reducing the middle bolt.The inter-bolt distance has a great influence on the failure load of the hybrid joint.Increasing the inter-bolt distance can effectively improve the bearing capacity of the structure. 展开更多
关键词 CFRP laminate Finite element model Hybrid(bonded/bolted)joint Multi-bolt Tensile properties
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