Hydrogen production via chemical looping reforming of coke oven gas

Coke oven gas(COG)is one of the most important by-products in steel industry,and the conversion of COG to value-added products has attracted much attention from both economic and environmental views.In this work,we use the chemical looping reforming technology to produce pure H_(2) from COG.A series of La1-xSrxFeO_(3)(x?0,0.2,0.3,0.4,0.5,0.6)perovskite oxides were prepared as oxygen carriers for this purpose.The reduction behaviors of La1-xSrxFeO_(3) perovskite by different reducing gases(H_(2),CO,CH4 and the mixed gases)are investigated to discuss the competition effect of different components in COG for reacting with the oxygen carriers.The results show that reduction temperatures of H_(2) and CO are much lower than that of CH4,and high temperatures(>800℃)are requested for selective oxidation of methane to syngas.The co-existence of CO and H_(2) shows weak effect on the equilibrium of methane conversion at high temperatures,but the oxidation of methane to syngas can inhibit the consumption of CO and H_(2).The doping of suitable amounts of Sr in LaFeO_(3) perovskite(e.g.,La0.5Sr0.5FeO_(3))significantly promotes the activity for selective oxidation of methane to syngas and inhibits the formation of carbon deposition,obtaining both high methane conversion in the COG oxidation step and high hydrogen yield in the water splitting step.The La0.5Sr0.5FeO_(3) shows the highest methane conversion(67.82%),hydrogen yield(3.34 mmol g^(-1))and hydrogen purity(99.85%).The hydrogen yield in water splitting step is treble as high as the hydrogen consumption in reduction step.These results reveal that chemical looping reforming of COG to produce pure H_(2) is feasible,and an O_(2)-assistant chemical looping reforming process can further improves the redox stability of oxygen carrier.

Interfacial charge effects of supported-metal-cluster heterostructures on azo hydrogenation catalyzation

The impact of interfacial charge on catalytic performance of supported-metal-cluster(SMC)heterostructures remains unclear,hindering efforts to develop high-performance SMC catalysts.Herein we systematically investigated interfacial charge effects of SMCs using a model system of graphene-supported gold-nanoclusters(AuNCs/rGO)for azo hydrogenation.Three types of SMCs with different interfacial charges were synthesized by anchoring electropositive 2-aminoethanethiol(CSH),amphoteric cysteine(Cys),and electronegative 3-mercaptopropionic-acid(MPA)onto AuNCs/rGO,respectively.All three SMCs exhibited high and selective catalytic activity to azo-hydrogenation in four representative azo dyes.The catalytic activity of Cys@AuNCs/rGO was lower than that of CSH@AuNCs/rGO but higher than that of MPA@AuNCs/rGO.However,the cyclic stability of Cys@AuNCs/rGO was inferior to that of both CSH@AuNCs/rGO and MPA@AuNCs/rGO.Further mechanistic studies revealed that amino ligands modified CSH@AuNCs and Cys@AuNCs agglomerated into large-size gold nanoparticles on rGO surface during catalytic reaction under NaBH_(4) action,leading to reduced efficiency and cyclic stability.Conversely,non-amino ligand modified MPA@AuNCs only partially detached from rGO surface without agglomeration,resulting in better cyclic stability.Protection of amino groups in ligands such as modifying-NH_(3)^(+)group in Cys into imine to form N-isobutyryl-L-cysteine(NIBC)substantially improved the cyclic stability while maintaining the high activity in the NIBC@AuNCs/rGO catalyst system.Our work provides an approach for developing a highly-active and stable SMC heterostructure catalyst via manipulating interfacial charges in SMC.

Preparation of Optically Active 2,2'-Dibromo-6,6'-diiodo-1,1'-biphenyl:A Powerful Precursor for Modular Synthesis of Functionalized Atropisomers

The widespread applications of atropisomeric compounds have led to an increasing demand for their synthesis.Rather than synthesizing different functionalized atropisomers individually,an attractive alternative is to identify a key intermediate or precursor that can be readily elaborated and functionalized to realize divergent synthesis of this class of compounds.Building on our previous research on asymmetric ring-opening of cyclic diaryliodoniums,in this work we developed a copper-catalyzed enantioselective ring-opening reaction of ortho,ortho’-dibromo substituted cyclic diaryliodonium with lithium iodide.The resulting optically active product 2,2'-dibromo-6,6'-diiodo-1,1'-biphenyl,possessing two C—Br bonds and two C—I bonds,can be selectively advanced to form different functionalities.Remarkably,the utilities of the product were highlighted by successively demonstrating C—I and C—Br metalation,followed by carboxylation,boroylation,oxygenation,allylation,phosphinylation,etc.,all of which provide a new and convenient approach to synthesizing a range of functionalized axially chiral biphenyls.

Transition-Metal-Catalyzed Carbon-Carbon Bond Activation in Asymmetric Synthesis

Catalytic asymmetric transformations involving carbon-carbon bond cleavages open intriguing strategies for the synthesis of chiral complex molecules.The transient organometallic species mainly generate from the oxidative addition of cyclic compounds with low valence metals or from β-carbon elimination of tert-alkoxyl metals.This overview covers the recent advances in transition-metal-catalyzed carbon-carbon bond activation in asymmet-ric synthesis.

Ag_(2)S基近红外Ⅱ区荧光量子点的水相合成优化探究

具有近红外Ⅱ区荧光的Ag_(2)S量子点(QDs)因具有带隙窄、Stokes位移大及光稳定性好等优点而在生物成像领域具有广阔应用前景.然而,传统有机相合成的Ag_(2)S量子点水溶性与生物相容性较差,而水相合成Ag_(2)S量子点的荧光又很难到近红外Ⅱ区,这严重制约了Ag_(2)S量子点的生物医学应用推广.因此,优化探究具有近红外Ⅱ区荧光发射的Ag_(2)S基量子点的水相合成方法具有重要意义.采用核掺杂ZnS、表面阳离子(Zn_(2)+)改性以及调控表面配体制备出一系列Ag_(2)S基量子点,发现核掺杂和表面阳离子改性均使Ag_(2)S基量子点的荧光呈现剂量依赖性蓝移;而将表面配体由树枝状短链(Captopril)更换为长直链(11-巯基十一烷酸,MUA)时,Ag_(2)S基量子点的发射峰红移至1105 nm(近红外Ⅱ区)且半峰宽更窄.本研究发现,相比核掺杂和表面阳离子改性,优化表面配体更容易在水相中制备出具有近红外Ⅱ区荧光的Ag_(2)S基量子点.本工作为近红外荧光量子点的水相合成及优化提供了基础研究数据.

Visible Light Accelerated Vinyl C-H Arylation in Pd-Catalysis：＂ Application in the Synthesis of ortho Tetra-substituted Vinylarene Atropisomers

A visible light accelerated C-H functionalization reaction in palladium-catalyzed arylation of vinyl arenes with diaryliodonium salts is reported in the absence of additional photosensitizer. The kinetic isotope effect （kH/kD） was changed from 3.6 （under darkness） to 1.1 when irradiated by visible light, which indicated that the C-H functionalization step was the rate determining step under darkness and significantly accelerated by the irradia- tion of visible light. Finally the synthesis of ortho tetra-substituted vinylarene atropisomers with high enantiospecificity was realized via this protocol.

1,4-Migration of Transition Metals in Organic Synthesis

Generation of carbon-metal species is extremely important in transition metal-catalyzed organic synthesis.Among the various methods,1,4-metal migration is a very useful way to create new carbon-metal species,which are not readily accessible via classic methods.This review summarized recent advances in transition metal-catalyzed reactions,which involved one or more steps of 1,4-metal migration.It focused mostly on the achievements in Pd and Rh-catalyzed reactions,along with some of the remarkable results in Pt,Ir,Co,Fe-involved transformations.

Mailuoning prevents high-glucose-mediated human umbilical vein endothelial cells apoptosis

OBJECTIVE： To investigated the role of Mailuoning in the prevention of highglucosemediated cell apoptosis in human umbilical vein endothelial cells （HUVEC） and the mechanisms involved. METHODS： MTT assay was used to investigate cell viability, western blot was used to investigate pro tein expression, and flow cytometric detection technology was used to detect cell apoptosis. RESULTS： Exposure of HUVEC to high glucose （50 mM） significantly suppressed cell viability and increased cell apoptosis compared with normal glu cose （11 mM） （all P〈0.05）. However, Mailuoning pre vented highglucoseinduced HUVEC apoptosis in dosedependent manner. Further studies indicated that Mailuoning suppressed highglucoseinduced p38 mitogenactivated protein kinase phosphoryla tion, but had no effect on extracellular signalregu lated kinase 1/2 and Akt phosphorylation. CONCLUSION： Mailuoning can prevent highglu coseinduced HUVEC apoptosis by suppressing p38 activation.

Two at the price of one: kinetic resolution of multi-substituted metallocenes

Molecules containing the key planar chiral scaffold are commonly used as ligands in asymmetric catalysis [1]. As such, developing efficient methods to rapidly functionalize planar chiral scaffolds has received substantial attention, and several elegant synthetic strategies have been developed to this end. Over the past decade, transition-metal-catalyzed enantioselective C–H functionalization has become one of the most powerful strategies in the field [2].

Palladium-Catalzyed Atroposelective 16-Membered Macrocyclization: Total Synthesis of lsoplagiochin D

Summary of main observation and conclusion Isoplagiochin D is a ring-strained macrocyclic bisbibenzylis,which showed stable axial chirality in one biaryl structure,and semistable axial chirality in the other biaryl moiety.We reported here an unprecedented example for the catalytically asymmetric synthesis of ring-strained atropisomers via Pd-catalyzed macrocyclization between benzyl halides and carbenes.This newly developed Pd-catalyzed asym-metric macrocyclization protocol enabled us a quick synthesis of isoplagiochin D in a highly enantioselective manner.

Paddlewheel dirhodium(II)complexes with N-heterocyclic carbene or phosphine ligand:New reactivity and selectivity

The dirhodium(II)-catalyzed organic reactions,including asymmetric transformation,are significantly benefitted from the discovery of simple and efficient protocols to introduce various bridging ligands,e.g.carboxylic acids,amide and phosphoric acids.Ligands lying at axial position of dirhodium(II)complexes could strongly affect the activity and selectivity of these metal complexes involved reactions.This review summarizes the newly explored reactivity of dirhodium(II)complexes with N-heterocyclic carbenes or phosphines as the axial ligands.The asymmetric tries are also highlighted,where their stereo-induction were solely from the axial ligand of dirhodium(II)complexes.In the last part,the reactions catalyzed by inherent chiral ortho-metalated dirhodium(II)/phosphine complexes are also discussed.