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Role of methoxy and C_(α)-based substituents in electrochemical oxidation mechanisms and bond cleavage selectivity of β-O-4 lignin model compounds

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Green Energy & Environment 2024年第1期9卷 114-125页

作者： Yang Zhou Qiang Zeng Hongyan He Kejia Wu Fuqiao Liu Xuehui Li School of Chemistry and Chemical Engineering The Guangdong Provincial Key Laboratory of Green Chemical Product TechnologyState Key Laboratory of Pulp and Paper EngineeringSouth China University of TechnologyGuangzhouGuangdong510640China CAS Key Laboratory of Green Process and Engineering Institute of Process EngineeringChinese Academy of SciencesBeijing100190China

In order to better understand the specific substituent effects on the electrochemical oxidation process of β-O-4 bond, a series of methoxyphenyl type β-O-4 dimer model compounds with different localized methoxyl groups, including 2-(2-methoxyphenoxy)-1-phenylethanone, 2-(2-methoxyphenoxy)-1-phenylethanol, 2-(2-methoxyphenoxy)-1-(4-methoxyphenyl)ethanone, 2-(2-methoxyphenoxy)-1-(4-methoxyphenyl)ethanol, 2-(2,6-dimethoxyphenoxy)-1-(4-methoxyphenyl)ethanone, 2-(2,6-dimethoxyphenoxy)-1-(4-methoxyphenyl)ethanol have been selected and their electrochemical properties have been studied experimentally by cyclic voltammetry, and FT-IR spectroelectrochemistry. Combining with electrolysis products distribution analysis and density functional theory calculations, oxidation mechanisms of all six model dimers have been explored. In particular, a total effect from substituents of both para-methoxy(on the aryl ring closing to Cα) and Cα-OH on the oxidation mechanisms has been clearly observed, showing a significant selectivity on the Cα-Cβbond cleavage induced by electrochemical oxidations.

关键词： Lignin model compounds β-O-4 dimers Electrochemical oxidation oxidation mechanisms Substituent effect

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Fabrication of dense SiBCN monolith at a lower temperature and its high-temperature performance

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Journal of Advanced Ceramics 2024年第8期13卷 1198-1211页

作者： Zi-Bo Niu Daxin Li Dechang Jia Zhihua Yang Kunpeng Lin Yan Wang Paolo Colombo Ralf Riedel Yu Zhou Institute for Advanced Ceramics School of Materials Science and EngineeringHarbin Institute of TechnologyHarbin 150080China Key Laboratory of Advanced Structural-Function Integrated Materials and Green Manufacturing Technology Ministry of Industry and Information TechnologyHarbin 150080China State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150080China Department of Industrial Engineering University of PadovaPadova 3513iItaly Department of Materials Science and Engineering The Pennsylvania State UniversityUniversity Park 16802USA Institute of Materials Science Darmstadt University of TechnologyDarmstadt 64287Germany School of Materials Science and Engineering Harbin Institute of Technology(Shenzhen)Shenzhen 518055China

In this study,a crack-free pyrolysis process of partially cured precursor powder compacts was developed to prepare dense silicon boron carbonitride(SiBCN)monoliths at much lower temperatures(1300℃),thereby circumventing the challenges of sintering densification(>1800℃).Unlike the elastic fracture in over-cured precursors or the viscoelastic deformation in under-cured precursors,the partially cured precursor,exhibiting elastic-plastic deformation behavior,facilitates limited nanoscale pore formation in a dense structure,achieving a balance between crack-free pyrolysis and *** to SiBCN derived from the over-cured precursor(σ=~159 MPa,K_(IC)=1.9 MPa:m^(1/2),Vickers hardness(HV)=7.8 GPa,and E=122 GPa),the resulting SiBCN monolith exhibited significantly improved mechanical properties(σ=~304 MPa,K_(IC)=3.7 MPa-m12,HV=10.6 GPa,and E=161 GPa)and oxidation *** addition,this study investigated the high-temperature performance of SiBCN monoliths,including crystallization and oxidation,and determined the oxidation kinetics induced by pore structure healing and the different oxidation mechanisms of Si-C-N and B-C-N clusters in the amorphous *** to its unique composition and structure,the SiBCN ceramic oxide layer exhibits exceptional self-healing effects on repairing the nanoporous system in the initial stage and shows outstanding high-temperature stability during prolonged oxidation,mitigating adverse effects from bubble formation and *** to the nanoporous structure,the oxidation rate is initially controlled by gas diffusion following a linear law before transitioning to oxide layer diffusion characterized by a parabolic ***,due to different valence bond configurations,Si-C-N transforms into an amorphous SiCNO structure after phase separation,unlike the nucleation and growth of residual B-N-C.

关键词： silicon boron carbonitride(SiBCN)ceramics crack-free pyrolysis amorphous structure oxidation mechanisms kinetic law

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Numerical study of novel OME_(1-6) combustion mechanism and spray combustion at changed ambient environments

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Frontiers in Energy 2024年第4期18卷 483-505页

作者： Frederik WIESMANN Zeyan QIU Dong HAN Lukas STRAUβ Sebastian RIEβ Michael WENSING Thomas LAUER Institute of Powertrains and Automotive Technology TU Wien1060 ViennaAustria Key Laboratory for Power Machinery and Engineering of Ministry of Education Shanghai Jiao Tong UniversityShanghai 200240China Professorship for Fluid Systems Technology Friedrich-AlexanderUniversität Erlangen-Nürnberg91058 ErlangenGermany

For a climate-neutral future mobility,the socalled e-fuels can play an essential ***,oxygenated e-fuels containing oxygen in their chemical formula have the additional potential to burn with significantly lower soot *** particular,polyoxymethylene dimethyl ethers or oxymethylene ethers(PODEs or OMEs)do not contain carbon-carbon bonds,prohibiting the production of soot precursors like acetylene(C_(2)H_(2)).These properties make OMEs a highly interesting candidate for future climate-neutral compression-ignition ***,to fully leverage their potential,the auto-ignition process,flame propagation,and mixing regimes of the combustion need to be *** achieve this,efficient oxidation mechanisms suitable for computational fluid dynamics(CFD)calculations must be developed and *** present work aims to highlight the improvements made by developing an adapted oxidation mechanism for OME1-6 and introducing it into a validated spray combustion CFD model for *** simulations were conducted for single-and multi-injection patterns,changing ambient temperatures,and oxygen *** results were validated against high-pressure and high-temperature constantpressure chamber ****-chemiluminescence measurements accomplished the characterization of the auto-ignition *** experiments and simulations were conducted for two different *** improvements concerning the prediction of the ignition delay time were accomplished while also retaining an excellent agreement for the flame lift-off *** spatial zones of high-temperature reaction activity were also affected by the adaption of the reaction *** showed a greater tendency to form OH^(*) radicals within the center of the spray in accordance with the experiments.

关键词： oxygenated fuels reaction kinetics oxidation mechanisms computational fluid dynamics(CFD) oxymethylene ethers(OME) e-fuels multiinjection spray-combustion

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Interfacial reactions of chalcopyrite in ammonia–ammonium chloride solution

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Transactions of Nonferrous Metals Society of China 2018年第3期28卷 556-566页

作者： Xiao-ming HUA Yong-fei ZHENG Qian XU Xiong-gang LU Hong-wei CHENG Xing-li ZOU Qiu-shi SONG Zhi-qiang NING School of Metallurgy Northeastern UniversityShenyang 110004China State Key Laboratory of Advanced Special Steel Shanghai Key Laboratory of Advanced FerrometallurgySchool of Materials Science and EngineeringShanghai UniversityShanghai 200072China

The interfacial reactions of chalcopyrite in ammonia–ammonium chloride solution were *** chalcopyrite surface was examined by scanning electron microscopy and X-ray photoelectron spectroscopy(XPS)*** was found that interfacial passivation layers of chalcopyrite were formed from an iron oxide layer on top of a copper sulfide layer overlaying the bulk chalcopyrite,whereas CuFe1-xS2 or copper sulfides were formed via the preferential dissolution of *** copper sulfide layer formed a new passivation layer,whereas the iron oxide layer peeled off spontaneously and partially from the chalcopyrite *** state of the copper sulfide layer was discussed after being deduced from the appearance of S2-,S22-,Sn2-,S0 and SO42-.A mechanism for the oxidation and passivation of chalcopyrite under different pH values and redox potentials was ***,a model of the interfacial reaction on the chalcopyrite surface was constructed using a three-step reaction pathway,which demonstrated the formation and transformation of passivation layers under the present experimental conditions.

关键词： chalcopyrite interfacial reaction ammonia passivation layer oxidation mechanisms

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