EFFECTS OF K_2O AND MnO PROMOTERS ON THE PRODUCTION OF LIGHT ALKENES VIA SYNGAS OVER Fe/SILICALITE-2 CATALYST IL REDUCIBILITY OF K-Fe-MnO/SILICALITE-2 CATALYST

K_2O and MnO are two kinds of necessary promoters to theselective production of light alkenes from CO hydrogenation over silicalite-2(Si-2) zeolite supported Fe catalyst. The addition of both K_2O and MnOpromoters into Fe/Si-2 catalyst leads to a remarkable increase in the COconversion and the selectivity to light oletins. Silicalite-2 zeolite as Fe-MnOcatalyst support can suppress the formation of α-Fe_2MnO_3 or/andα-Fe_(2-y)Mn_yO_3 as Well as α-Fe_2O_3 and/or α-Mn_2O_3, being favorable for(?)ncreasing the dispersion of active metal component. So MnO can promotethe reduction of Fe~(3-) and enhance the capacity of CO adsorption, which canimprove the activity of the activity of the catalyst for CO hydrogenation. While K_2Opromoter is unfavorable for reduction of Fe~(3-) to some degree with formation of Fe~(2-) as a new species after reduction. However, K_2O promoter can enhance the capacity and strength of CO adsorption greatly.So K_2O can alsoimprove the activity of catalyst for CO hydrogenation.     

Surface Oxidation of Single-walled-carbon-nanotubes with Enhanced Oxygen Electroreduction Activity and Selectivity

Electrochemical oxygen reduction reaction(ORR) with 2-electron process is an alternative for decentralized H_2O_2 production, but it remains high challenging to develop highly active and selective catalysts for this process. In this work, we present a selective and efficient nonprecious electrocatalyst, prepared through an easily scalable mild oxidation of single-walled carbon nanotubes(SWNTs) with different oxidative acids including sulfur acid, nitride acid and mixed sulfuric/nitric acids, respectively. The high-degree oxidized SWNTs treated by mixed acids exhibit the highest activity and selectivity of electroreduction of oxygen to synthesize H_2O_2 at low overpotential in alkaline and neutral media. Spectroscopic characterizations suggested that the C–O is vital for catalyzing 2-electron ORR, providing an insightful understanding of defected carbon surface as the active catalytic sites for 2-electron ORR.     

Dioxygen oxidation of hydrocarbons by a methane monooxygenase-like system: diiron complex-O_2-Zn/HOAc-MV~(2 )

The activation of dioxygen and incorporation into hydrocarbons have been achieved under mild conditions by a methane monooxygenase (MMO)-like system using a dinuclear iron complex [Fe_2Dhist(OAc)_2]BPh_4·3H_2O as the model complex, zinc powder as the electron donor, HOAc as the proton source and methylviologen as the electron transfer agent. The results show that styrene is oxygenated predominantly to styrene oxide (1 396 mol/100 mol of the Fe_2 complex), benzaldehyde (16160) and acetophenone (986), and cyclohexane to cyclohexanol (9370) and cyclohexanone (2670). EPR studies indicate that the hypervalent ironoxo spiecs Fe~ⅣFe~Ⅳ(?)O, derived from Fe~ⅢFe~Ⅲ core via reduction, O_2-binding and protonation, is the active intermediate which inserts the activated oxygen atom into C(?)C or C—H bond giving each product. The system closely resembles MMO and its close relative hemerythrin in the aspects of reaction phenomena, EPR characteristics and product distributions. The Mn_2 analog cmplex、Fe-Zn hetero     

Solvothermal Synthesis of α-Fe_2O_3 Porous Nanobelts and Their Enhanced Acetone-sensing Properties

Porous α-Fe_2O_3 nanobelts have been prepared via a solvothermal route and subsequent calcination. The as-prepared nanostructure was characterized by XRD, FESEM, TEM, N_2 adsorption-desorption isotherms, etc. The α-Fe_2O_3 nanobelts presented obvious porous structures with the length of ca. 1～2μm, width of ca. 200～350 nm and thickness of ca. 30～60 nm. It was found that the assistance of inorganic additives played an important role in the shape control of α-Fe_2O_3 nanostructure. The gas-sensing performance of the fabricated sensor based on α-Fe_2O_3 nanobelts sample was also investigated, and the response towards 1000 ppm acetone can reach 24.4. In addition, the gas-sensing conductive mechanism of the sensor was also proposed.     

α-Fe_2O_3 immobilized benzimidazolium tribromide as novel magnetically retrievable catalyst for one-pot synthesis of highly functionalized piperidines

Nanostructured α-Fe_2O_3 were prepared by precipitation followed by calcination method.Cetyltrimethylammonium bromide(CTAB) was used as surfactant.The nano α-Fe_2O_3 was then silanized with(3-chloropropyl)-triethoxysilane(CPTES) by room temperature mixing of α-Fe_2O_3 and CPTES to produce silane coated α-Fe_2O_3(ClPr-Si@Fe_2O_3).As-synthesized ClPr-Si@Fe_2O_3 was functionalized via covalent grafting of benzimidazole to produce 3-(l-benzimidazole)Pr-Si@Fe_2O_3.This was further reacted with bromine to afford α-Fe_2O_3 immobilized benzimidazolium tribromide(α-Fe_2O_3-BIM tribromide).This ionic liquid(IL)α-Fe_2O_3 BIM tribromide was characterized by FT-IR,XRD,TEM,SEM,TGA,VSM,EDX and BET analysis.The as-synthesized IL tribromide was used as catalyst for one-pot synthesis of highly substituted piperidines.The method is greener in terms of solvent selection,recovery of the catalyst and efficiency.     

Study of Manganese Promoter on a Precipitated Iron-Based Catalyst for Fischer-Tropsch Synthesis

The effects of Manganese(Mn)incorporation on a precipitated iron-based Fischer-Tropsch synthesis(FTS)catalyst were investigated using N_2 physical adsorption,air differential thermal analysis (DTA),H_2 temperature-programmed reduction(TPR),and M(?)ssbauer spectroscopy.The FTS perfor- mances of the catalysts were tested in a slurry phase reactor.The characterization results indicated that Mn increased the surface area of the catalyst,and improved the dispersion ofα-Fe_2O_3 and reduced its crystallite size as a result of the high dispersion effect of Mn and the Fe-Mn interaction.The Fe-Mn inter- action also suppressed the reduction ofα-Fe_2O_3 to Fe_3O_4,stabilized the FeO phase,and(or)decreased the carburization degree of the catalysts in the H_2 and syngas reduction processes.In addition,incorporated Mn decreased the initial catalyst activity,but improved the catalyst stability because Mn restrained the reoxidation of iron carbides to Fe_3O_4,and improved further carburization of the catalysts.Manganese suppressed the formation of CH_4 and increased the selectivity to light olefins(C_(2-4)~=),but it had little effect on the selectivities to heavy(C_(5 )) hydrocarbons.All these results indicated that the strong Fe-Mn interaction suppressed the chemisorptive effect of the Mn as an electronic promoter,to some extent,in the precipitated iron-manganese catalyst system.     

Distinctive electrochemical performance of novel Fe-based Li-rich cathode material prepared by molten salt method for lithium-ion batteries

For constructing next-generation lithium-ion batteries with advanced performances,pursuit of highcapacity Li-rich cathodes has caused considerable attention.So far,the low discharge specific capacity and serious capacity fading are strangling the development of Fe-based Li-rich materials.To activate the extra-capacity of Fe-based Li-rich cathode materials,a facile molten salt method is exploited using an alkaline mixture of LiOH–LiNO_3–Li_2O_2 in this work.The prepared Li_(1.09)(Fe_(0.2)Ni_(0.3)Mn_(0.5))_(0.91)O_2 material yields high discharge specific capacity and good cycling stability.The discharge specific capacity shows an upward tendency at 0.1 C.After 60 cycles,a high reversible specific capacity of ～250 m Ah g~(-1)is delivered.The redox of Fe~(3+)/Fe~(4+)and Mn~(3+)/Mn~(4+)are gradually activated during cycling.Notably,the redox reaction of Fe~(2+)/Fe~(3+)can be observed reversibly below 2 V,which is quite different from the material prepared by a traditional co-precipitation method.The stable morphology of fine nanoparticles(100–300 nm)is considered benefiting for the distinctive electrochemical performances of Li_(1.09)(Fe_(0.2)Ni_(0.3)Mn_(0.5))_(0.91)O_2.This study demonstrates that molten salt method is an inexpensive and effective approach to activate the extra capacity of Fe-based Li-rich cathode material for high-performance lithium-ion batteries.     

ROLE OF POTASSIUM MODIFIER IN COPPER-BASED CATALYSTS FOR MIXED ALCOHOL SYNTHESIS STUDIED BY XPS

The surface states of CuO-ZnO-Al_2O_3-K_2CO_3 catalysts for mixed al-cohol synthesis and the role of potassium as modifier were studied by XPS mea-surements under simulated real reaction conditions.After reduction and reac-tion,no stable Cu~+ and Cu~(2+)ions were found.Only Cu~0 was detected.Cu~0 isbelieved to be dispersed on oxygen-deficient species ZnO_x(x<1)and Al_2O_3 inthe form of microcrystallites.It is proposed that Cu~0 is one of the active compo-nents on the surface for the reaction.The active units exist as(is oxygen vacancy)for mixed alcohol as well as for CH_3OH synthesis.The potassium modifier was bondedto Al_2O_3.In the absence of Al_2O_3,surface enrichment of K was observed.There is strong electronic interaction between K and reduced CuO,with K actingas a donor and transferring electrons to CuO.But no obvious electronic interac-tion between K and Cu~0 was detected during the reaction.it is suggested thatbesides the possible action of neutralizing the acidity of Al_2O_3,K can act on Cuthrough ZuO to stabilize oxygen-containing intermediates,promoting C-C chaingrowth and improving higher alcohol selectivity.     

MECHANISM OF SULFUR POISONING AND REGENERATION METHODS FOR SUPPORTED METAL CATALYSTS Ⅰ. MECHANISM OF SULFUR POISONING OF Pd(Pt)/Al_2O_3 CATALYSTS IN H_2-O_2 REACTION

Sulfur poisoning mechanism of Pd(Pt)/Al_2O_3 catalysts for H_2—O_2 reaction was studied by means of micro-catalytic reaction chromatograph, TPR, XPS, AES, XRD and IR. The results show that the tolerance of Pd/Al_2O_3 catalysts to surfur poisoning is significantly affected by the O_2/H_2 ratio and enhanced with the increase of the ratio. In″weak″oxidizing atmosphere, the deactivation is swift and irreversible because of the active components, particularly at the surface, being seriously sulfided by S~(-2). In ″strong″ oxidizing atmosphere, the poisoning caused by S~(-2) is reversible to great extent owing to the reaction M_s—S/Al_2O_3(O_2,H_2O)/catalyst(M_s(M_sO)/Al_2O_3-SO_3-H_2O)where M_s signifies Pd or Pt on the surface. But, when the sulfate in catalyst is accumulated in large amount, it could cover or block the active sites, which may be an important cause of the catalyst deactivation in addition to the sulfidization of metal components.     

Theory assisted design of N-doped tin oxides for enhanced electrochemical CO2 activation and reduction

Clearly understanding the structure-function relationship and rational design of efficient CO_2 electrocatalysts are still the challenges.This article describes the molecular origin of high selectivity of formic acid on N-doped SnO_2 nanoparticles,which obtained via thermal treatment of g-C_3N_4 and SnCl_2·2H_2O precursor.Combined with density functional theory(DFT)calculations,we discover that N-doping effectively introduces oxygen vacancies and increases the charge density of Sn sites,which plays a positive role in CO_2 activation.In addition,N-doping further regulates the adsorption energy of*OCHO,*COOH,*H and promotes HCOOH generation.Benefited from above modulation,the obtained N-doped SnO_2 catalysts with oxygen vacancies(Ov-N-SnO_2)exhibit faradaic efficiency of 93% for C_1 formation,88% for HCOOH production and well-suppression of H_2 evolution over a wide range of potentials.     

Composite Electrodeposited PbO_2/Co_3O_4 on a Ti Substrate as Positive Electrode Materials for a Hybrid Supercapacitor

PbO_2/Co_3O_4 composites were prepared on a Ti substrate by means of a composite electrodeposition method in Pb~(2+) plating solution containing dissolved nano-Co_3O_4 particles. X-ray diffraction(XRD), scanning electron microscopy(SEM), energy dispersive spectrometry(EDS) and transmission electron microscopy(TEM) were used to characterize the chemical composition and morphology of the PbO_2/Co_3O_4 composites. The electrochemical and capacitance performance of the composites were investigated by cyclic voltammetry(CV), charge-discharge tests and electrochemical impedance(EIS). The results indicate that the composites comprise rutile phase Co_3O_4 and β-PbO_2. In addition, the surface of the composite electrode is rough and porous. The PbO_2/Co_3O_4 composites exhibit a high specific capacitance up to 215 F/g, which is ten times higher than that of the pure-PbO_2 and two times higher than that of the pure-Co_3O_4 in 1 mol/L NaOH electrolytes.     

Preparation of porous α-Fe2O3-supported Pt and its sensing performance to volatile organic compounds

Porous α-Fe2O3 was synthesized by a simple hydrothermal treatment of FeCl3 aqueous solution followed by a calcination process. In the synthesis of porous α-Fe2O3, no templates or pore-directing agents were used. The as-prepared porous α-Fe2O3 was further employed as a support for loading Pt nanoparticles. The gas sensing performance of the obtained porous α-Fe2O3-supported Pt to VOCs was investigated. The sensor presented a high response and fast response-recovery characteristic to several VOCs including acetone, ether, methanol, ethanol, butanol and hexanol. Meanwhile, it exhibited a much higher response than the pure α-Fe2O3 at the operating temperature of 260°C. The enhanced sensing properties may be related to the unique porous structure of the α-Fe2O3 support and the promoting effect of active Pt nanoparticles for the sensing reactions.     

STUDIES OF MULTICOMPONENT COMPLEX OXIDE CATALYSTS FOR OXIDATIVE COUPLING OF METHANE VI.SURFACE BASICITY AND SURFACE ACTIVE OXYGEN SPECIES OF LiTi_xLa_(1-x)O_2 λ MULTICOMPONENT OXIDE CATALYSTS

The surface basicity of Ti-La-Li multicoinponent oxides has been investigated by means of CO2-TPD. The experiment results show that C2 (C2H6 C2H4) selectivity is related to surface basic strength. The surface active oxygen species have also been characterized by means of XPS, O2-TPD and so on. It has been indicated that C2 selectivity and CH4 conversion are correlated with lattice oxygen and the adsorbed oxygen on the surface of the catalyst respectively In the O2-TPD experiments, it has also been found that there are three kinds of oxygen species on the surface of the series catalvsts, which are a (100℃ 750℃) Among them α-oxvgen causes deep oxidation whileβand γ oxygen species are related to oxidalive coupling of methane (OCM).     

STUDY OF CARBON MONOXIDE HYDROGENATION OVER SUPPORTED IRON CLUSTER CATALYSTS

Fe_3(CO)_(12)-derived Fe/r-AL_2O_3 and Fe/zeolite catalysts have higher catalytic activity than those derived from Fe(NO_3)_3. The existence of metal-metal bond in cluster species and the congruity of the adsorption of CO and H_2 are important for increasing the catalytic activity. Carbon deposition for Fe_5C(CO)_(15)-derived Fe/r-AL_2O_3 catalyst is discussed.     

OXIDATIVE COUPLING OF METHANE OVER Na_2O-La_2O_3/BaCO_3 CATALYSTS

The oxidative coupling of methane over various alkali metal oxidespromoted LaO_2O_3/BaCO_3 catalysts and the effects of Na_2O content on the performance of Na_2O-La_2O_3/Ba_2CO_3 catalyst have been studied.It was found thatNa_2O promoted La_2CO_3/BaCO_3 catalyst showed advantages of high CH_4 conver-sion,C_2 selectivity and C_2H_4/C_2H_6 ratio,Na_2O might affect the properties ofcatalyst through elctronic and geometric effuts.The highest C_2yield(19.0一20.6%)over Na_2-9wt%La_2O_3/BaCO_3 catalysts was obtained in the Na_2Ocontent range of 1.0—3.0%.Effects of reaction conditions on OCM over3wt% Na_2O-9wt%La_2CO_3/BaCO_3 catalyst were also investigated.The catalystswere characterized by BET,TPD,and XRD.TPD studies on 3wt% Na_2O-9wt%La_2O_3/BaCO_3 catalyst demonstrated that CO_2,CH_4.O_2could bestrongly on the catalyst.This might be related to the activation of CH_4 and theformation and reseneration of active oxygen soecies.     

A highly selective magnetic sensor with functionalized Fe/Fe3O4 nanoparticles for detection of Pb2+

A magnetic sensor for detection of Pb~(2+) has been developed based on Fe/Fe_3O_4 nanoparticles modified by3-(3,4-dihydroxyphenyl)propionic acid(DHCA). The carboxyl groups of DHCA have a strong affinity to coordination behavior of Pb~(2+) thus inducing the transformation of Fe/Fe_3O_4 nanoparticles from a dispersed to an aggregated state with a corresponding decrease, then increase in transverse relaxation time(T_2) of the surrounding water protons. Upon addition of the different concentrations of Pb~(2+) to an aq. solution of DHCA functionalized Fe/Fe_3O_4 nanoparticles(DHCA-Fe/Fe_3O_4 NPs)([Fe] = 90 mmol/L), the change of T_2 values display a good linear relationship with the concentration of Pb~(2+) from 40 μmol/L to 100 μmol/L and from 130 μmol/L to 200 μmol/L, respectively. Owing to the especially strong interaction between DHCA and Pb~(2+), DHCA-Fe/Fe_3O_4 NPs exhibited a high selectivity over other metal ions.     

STUDY ON OXYGEN ADSORPTION AND CATALYTIC PROPERTIES OF TiO_2-BASED CATALYSTS

The active oxygen species and active sites for MOC(methane ox-idative coupling)over TiO_2-based catalysts are studied by ESR method.Oxy-gen chemisorption on TiO_2,La/TiO_2 and Li/TiO_2 was measured by dynamicESR technique from 295 K to 105 K.The process of oxygen adsorption onTiO_2 is discussed.The spectra show that O_2~- ions exist largely on TiO_2 but lit-tle on Li/TiO_2 due to the decrease of surface density of electrons caused bythe substitution of Li~+ for lattice Ti~(4+) in Li/TiO_2.O~- was not detected on allsamples.Both O_2~- and O~- are not likely to be the active species in MOC reac-tion.Two triplet peaks in ESR spectra of Li/TiO_2 are attributed to Ti~(3+)(Ⅱ)and Ti~(3+)(Ⅲ)of low coordination numbers,which are active in the presenceof oxygen.Sites of low coordinated Ti~(3+) or Ti~(4+) are suggested to be responsi-ble for the formation of active oxygen species.     

Porous Iron-and Cobalt-based Single Crystals with Enhanced Electrocatalysis Performance

Porous single crystals have the characteristics of long-range ordering structure and large specific surface area,which will significantly enhance their electrochemical performance.Here,we report a method different from the conventional porous single crystal growth method.This method is to directly convert single crystal precursors Co₃O₄ and Fe₃O₄ into Co₂N and Fe₂N,and then further reduces them to porous single crystals Co and Fe particles under H2/Ar atmosphere.The removal of O^2–in the lattice channel at the pressure of 25~300 torr and the temperature of 300~600℃ will promote nitridation of the single-crystalline Co–O and Fe–O frames,and further remove N^3–in H2/Ar atmosphere and recrystallize as Co and Fe.These porous single crystals exhibit enhanced electrochemical properties due to their structural coherence and highly active surface.We demonstrated that the aminobenzene yield was up to 91%and the selectivity reached 92%in the electrochemical reduction of nitrobenzene.     

A ternary phased SnO_2-Fe_2O_3/SWCNTs nanocomposite as a high performance anode material for lithium ion batteries

A new SnO_2-Fe_2O_3/SWCNTs(single-walled carbon nanotubes) ternary nanocomposite was first synthesized by a facile hydrothermal approach.SnO_2 and Fe_2O_3 nanoparticles(NPs) were homogeneously located on the surface of SWCNTs,as confirmed by X-ray diffraction(XRD),transmission electron microscope(TEM) and energy dispersive X-ray spectroscopy(EDX).Due to the synergistic effect of different components,the as synthesized SnO_2-Fe_2O_3/SWCNTs composite as an anode material for lithium-ion batteries exhibited excellent electrochemical performance with a high capacity of 692 mAh·g~(-1) which could be maintained after 50 cycles at 200 mA·g~(-1).Even at a high rate of2000 mA·g~(-1),the capacity was still remained at 656 mAh·g~(-1).     

XPS STUDY ON THE ROLE OF CO_2 IN LOW-PRESSURE METHANOL SYNTHESIS

Surface characterization of CuO-ZnO-Al_2O_3 catalysts for low pres-sure methanol synthesis was carried out by using X-ray photoelectron spec-troscopy(XPS)combined with reaction chamber under simulated industrialoperating condition.Under the reduction and reaction conditions,no stableCu~(2+) or Cu~+ ions were found,only Cu~0 species was detected.ZuO could be re-duced with result of forming oxygen-deficient structure ZnO_x(X<1)andoxygen vacancy on the surface.The presence of enough amount of CO_2 infeed gas enhanced copper dispersion.It is believed that highly dispersed Cu~0 in intimate contact with ZnO is one of the active components for methanol syn-thesis and the optimal structure of the active unit is Cu——Zn—O(“□”is oxygen vacancy).It is proposed that the main role of CO_2 is to establish anoxidation potential of syngas so as to accelerate the oxidation-reduction cyclebetween Cu~0 and Cu~(δ+)/or Cu~+ during methanol synthesis as well as to preventCu~0 crystallites from aggregating and thus to maintain the catalyst in high ac-tivity and have long life.