查看更多>>摘要：The influence of temperature,H2 pressure and erythritol concentration on the hydrogenolysis of erythritol was studied using Ir/ReOx/TiO2.Under the conditions used here,four reaction routes coexist:isomerization,dehydration,C-0 and C-C hydrogenolysis.The initial rates as well as reaction orders and activation energy were estimated for each pathway.The variation of the hydrogen pressure produced slight changes in the isomerization,dehydration,and C-C hydrogenolysis routes,whereas C-0 hydrogenolysis showed order 1 with respect to this reagent.The change in erythritol concentration affected more the dehydration,resulting in a reaction order for this reactant close to 1,while for the other routes the order was close to 0.5.Regarding the influence of the temperature,dehydration of erythritol showed the highest activation energy(212.1 kJ mol~(-1))and the isomerization the lowest(20.0 kJ mol~(-1)).Furthermore,it was found that the ruptures of C-C bonds require higher energy than C-0 bonds break.
查看更多>>摘要：A serial of WaCo_(0.4)TiOx catalysts(a = 0.04,0.06,0.08,0.10)was synthesized by sol-gel method,which exhibited high NH3-SCR denitrification performance in a wide activity temperature window.W_(0.08)Co_(0.4)TiOx achieve best SCR activity(over 90% NO conversion)at 190-430 ℃ and good resistance to H2O/SO2.Various characterizations were used to investigate the influence of W doping on physicochemical property of these catalysts.Especially,in-situ DRIFTS were used to evaluate the type of acid sites,NOx adsorption,the reactivity of surface adsorption species,and the influences of H2O/SO2 on adsorption of NOx and NH3.The doping of W enhanced the acidity and weakened the oxidation capacity of WaCo_(0.4)TiOx,but higher surface acidity,especial more Br0nsted acid sites,can compensate for the effect of the decrease in the oxidation capacity on low-temperature activity.The optimal activity over W_(0.08)Co_(0.4)TiOx can be derived from the synergistic effect of surface acidity and oxidation performance.
查看更多>>摘要：The magnetically separable Ni/NiO nanocatalyst was synthesized for hydrogenation of substituted aromatics in renewable biokerosene fuel.The catalyst showed acidity of 0.21 mmol/g and ferromagnetic character.The catalytic activity was compared with the traditional noble metal-based catalysts(Pd/NiO,Ni/Al2O3,Pd/Al2O3,and Pt/Al2O3).Among all the catalysts,the non-noble metal catalysts(Ni/NiO,N1/AI2O3)showed complete conversion(100%)of aromatics to cycloalkanes at the optimal reaction conditions of temperature = 150 °G,Pressure = 100 bar,catalyst mass = 0.6 g,and reaction time = 14 hr.The activation energy for the Ni/NiO catalyst was 51 kjmol~(-1),similar to Ni/Al2O3(53 kjmol~(-1)).The coke deposition was much lower for Ni/NiO(<1 wt%)which was lower than Ni/Al2O3 catalyst.Furthermore,FTIR analysis also confirmed the absence of any observable carbon deposition in the used Ni/NiO catalyst while spent M/Al2O3 showed prominent peaks due to deposited carbonaceous compounds.
查看更多>>摘要：A series of organic-inorganic hybrid bifunctional organosiliceous catalysts with accessible pendant amine groups as single basic sites(such as propylamine,diethylamine,pyrrolidine)and Pd nanoparticles was prepared from suitable synthesis processes.Pd/MCM-41 silica decorated with propylamine groups was highly active and selective for the single-reactor tandem aldol condensation/crotonization reaction between furfural with methyl isobutyl ketone,followed by hydrogenation,to access renewable biosolvent and biofuel precursors in the branched alkane range at mild temperature(80-100 ℃).The catalyst was characterized in detail using XRD,C and N elemental analysis,ICP-OES,TGA/DTA,HR-TEM,N2 adsorption/desorption at 77 K,solid-state ~(13)C and ~(29)Si MAS NMR and FT-IR spectroscopy CO2 as acid probe.The catalyst was robust when operated in a dual fixed-bed reactor achieving steady 20 % furfural conversion for 12 h on stream with preferential formation of l-(furan-2-yl)-5-methylhexan-3-one.
查看更多>>摘要：In this study,we used cotton as the source of the carbon layer and prepared Cu°-carbon@Y-Al2O3 composites by spray drying and calcination method.Cu~0-carbon@Y-Al2O3 composites were prepared to degrade polyvinyl alcohol(PVA),Reactive Red X-3B,and rhodamine B.The SEM and TEM analysis reveal the Cu° particles loaded on the carbon layers and y-Al2O3 were the active sites for the catalytic reaction.The electron paramagnetic resonance(EPR)analysis and quenching experiments indicated the generation of·OH,~1O_2,and HO2·during the catalytic reaction.The catalytic reactions maintained a high catalytic efficiency of more than 82% when the Cu°-carbon@γ-Al2O3 composites were reused 10 times.This study will promote wide applications of Cu° as a functional material and provide new ideas for broadening the application field of cotton.Meanwhile,this study also demonstrated that Cu°-carbon@γ-Al2O3 is a promising composite material for advanced oxidation technology.
查看更多>>摘要：A series of NbCoOx catalysts with different Nb/Co molar ratios were synthesized via a slurry method to investigate the catalytic activity of oxidizing toluene.Among them,Nb_(0.67)Co_(0.33)Ox exhibited the highest toluene combustion efficiency.It was found that the incorporation of amorphous niobium provided the surface acid sites and abundant oxygen vacancies for the adsorption and activation of the reactants which was demonstrated by NH3-TPD,XRD,UV-vis DRS,XPS and Toluene-TPD.Furthermore,the strong interaction between niobium and cobalt can also affect its physical and chemical properties related to SEM,H2-TPR and XPS.Multiply TP-experiments were conducted to investigate the migration and transformation of oxygen species and find out that the reaction followed the MVK mechanism.
查看更多>>摘要：Reversible ionic liquids(RevILs)are ionic liquids that can be switched between molecular and ionic forms via two stimuli,and they can assist in the synthesis of colloidal gold nanoparticles.The RevIL-stabilized gold nanoparticles are deposited in the pores of SBA-15 mesoporous silica via incipient wetness without the func-tionalization of the SBA-15 surface.The location of nanoparticles inside the pores was confirmed by transmission electron microscopy technique and by a measured increase in the thermal stability of the nanoparticles in SBA-15 compared to non-porous silica.The porous gold catalysts are active in the selective oxidation of benzyl alcohol without calcination due to the absence of the ligands on the gold surface after deposition.Additionally,they are more active than the non-porous gold catalysts,indicating that the pore geometry enhances catalytic performance.Ultimately,the catalysts prepared by RevIL technique are thermally stable and active and show fine control over particle size.
查看更多>>摘要：With the quickly development of industry and energy requirement,huge amounts of various pollutants are inevitably released into rivers,lakes and underground water.The efficient elimination or in-situ solidification of pollutants in the environment is crucial to human health as the pollutants could be transferred to human body through food chain.The applications of covalent organic frameworks(COFs)and COF-based nanomaterials for sorption-photocatalytic reduction for heavy metal ions or radionuclides from high valence to low valence,and sorption-photodegradation for organic contaminants were summarized.The interaction mechanism was evaluated and discussed from the results of batch results,advanced spectroscopic analysis and theoretical calculation at molecular level.The COFs and COF-based nanomaterials are promising materials for the effective elimination of pollutants with high sorption capacity and selectivity if COFs are constructed with required channels,defects and special functional groups/sites.In the end,the challenge for possible real application of COFs is described.
查看更多>>摘要：Excessive price and scarcity of Pt species make it very necessary to enhance the atom utilization and catalytic efficiency of Pt catalysts for implementing their industrial practicality.Here,natural cotton is adopted as the precursor to in-situ support well-dispersed and uniform-sized Ni nanoparticles,which then work as nanoislands to effectively deposit single-atom Pt via the galvanic replacement reaction.On the resulting fibrous carbon matrix,the monocrystalline Ni particles are verified to tightly anchor isolated Pt atoms to form the alloyed PtNi nanoparticles.In the 4-nitrophenol(4-NP)reduction to 4-aminophenol(4-AP),the catalytic activity of the bimetallic PtNi/C catalyst with the low Pt loading(0.81%)maximally reaches 25 times as high as the primary Ni/C product.Simulated calculations demonstrate that the single-atom Pt centers on PtNi nanoparticles rapidly capture and split H2 molecules,while Ni atoms strongly adsorb 4-NP molecule to activate the-NO2 group.Therefore,the trapped H atom could easily attack the-NO2 and reduce 4-NP.
Essossimna DjatoubaiMuhammad Shuaib KhanSajjad ul Haq
10页
查看更多>>摘要：Tuning the electronic structure of a semiconductor via defects engineering is an effective strategy to modulate its I band structure and charge carrier transport for superior photocatalytic properties.Herein,we report visible-light driven photocatalytic water oxidation on BiFeO3 nanoplates with Ti-dopants and oxygen vacancies,synthesized via facile hydrothermal method followed by thermal treatment in H2 atmosphere.The gradual increase of Ti-1 dopants progressively changes BiFeO3 morphology from rectangular cuboids to nanoplates.The introduction of Ti-dopants and oxygen vacancies tuned the band-gap of BiFeO3,enhanced visible light absorption,improved photogenerated charge-carrier dynamics,and higher driving force for O2 evolution to demonstrate excellent O2 evolution at a rate of 274 pmol h~(-1)g~(-1)which is 2.6 times higher compared to pristine BiFeO3.Furthermore,threefold higher photocurrent density and superior surface photovoltage(SPV)results confirm improved charge carrier dynamics in BiFeO3 with Ti-dopants and oxygen vacancies,which make BiFeO3-based nanoplates promising material for photocatalytic applications.
NSTL