查看更多>>摘要：Light olefins'(C2-C4)production from syngas(H2 +CO)through Fischer-Tropsch synthesis(FTS)benefits from Fe-based catalysts supported on carbon nanotubes(CNTs).Two-level full factorial design was applied for K and/or Mo-promoted Fe/CNTs catalyst to investigate the effects of synthesis conditions including Mo/K mass ratio,ultrasonic time,and iron loading on light olefins'yield.These catalysts were characterized to perform an in-depth study of Mo/K binary promoter effects on Fe/CNTs catalyst in Fischer-Tropsch to light olefins.CO chemisorption and TEM revealed that molybdenum plays a significant role in metal dispersion,leaving structural defects on CNTs support.Additionally,H2-TPR confirmed that K as promoter facilitates reducibility of Fe/CNTs catalysts,which promoted CO conversion in FTS.Compared with the un-promoted Fe/CNTs catalysts,addition of molybdenum as a promoter increased light olefins'selectivity by 33.4%,while potassium led to an increase in CO conversion by 96.3%.The optimum formulation(0.5K5Mo10Fe/CNTs)obtained olefins'yield of 35.5%.
查看更多>>摘要：The Binder Jetting 3D printing technique was used to fabricate spherical Ni-Al CO2 methanation catalysts from co-precipitated catalyst precursor powder.Catalysts with different nickel loadings were prepared by varying the molar Ni/Al ratio(1/1,2/1,3/1,5/1)during precipitation or the amount of admixed precursor powder(10,20,30 wt.%)for printing.XRD and TG analysis revealed phase composition and reducibiliry characteristics analogous to conventionally prepared Ni-Al catalysts.TEM displayed nickel particle sizes as small as 3.9 run with a Ni dispersion of up to 13.4 % determined by H2 chemisorption.Moreover,meso-and macroporous catalyst pellets were generated with a specific surface area of up to 192 m~2/gcat-The catalysts NiAl11-20,NiA121-20 and NiA151-20 were exemplarily tested in a single pellet string reactor where CO2 conversions of up to 99 % and a high selectivity towards CH4 was observed at p_(tot)= 9 bar upon reaching thermodynamic equilibrium.
查看更多>>摘要：A series of novel nanosized x-ZF/ZM-y zeolites for glycerol to aromatics(GTA)were synthesized by using ZIF-8 as a template.The crystallization time and ZIF-8 dosage were systematically studied to clarify the crystallization process,structural characteristics and physicochemical properties of the prepared x-ZF/ZM-y.The results indi-cated that the growth of x-ZF/ZM-y zeolites involved two stages:attachment-impregnation and crystallization,The addition of ZIF-8 could introduce the active Zn species(ZnOH~+)and induce the formation of smaller HZSM-5 nanocrystals in x-ZF/ZM-y,which could effectively facilitate the dehydrogenation-aromatization and aldol condensation steps in GTA and enhance the coke resistance.Furthermore,me ZIF-8 dosage had important in-fluences on the catalytic performances of x-ZF/ZM-y.In particular,the 0.45-ZF/ZM-48 with 0.45 g ZIF-8 dosage and 48 h crystallization time all existed as nanocrystals of 20-40 nm,and possessed a proper redistribution of acid sites,resulting in 59.5% total aromatics yield and 11 h catalyst lifetime over 0.45-ZF/ZM-48 owing to the synergistic effect among the ZnOH~+,inter-crystalline mesopores and HZSM-5 nanocrystals.
查看更多>>摘要：Catalytic hydrogenation of 5-hydroxymethylfurfural(HMF)to 2,5-bis(hydroxymethyl)furan(BHMF)is an important reaction for biomass valorization.We report that metal oxides(including MgO,ZnO,SiO2 and TiO2)supported Pt catalysts show vastly different BHMF selectivity towards the hydrogenation of HMF.The basic metal oxide MgO supported Pt catalyst affords 99 % selectivity of BHMF,while the typical acidic metal oxide TiO2 supported Pt catalyst displays only 28 % selectivity of BHMF.HMF chemisorption on these catalysts show that the basic sites of metal oxide bonding to the C=0 group of HMF promote the BHMF selectivity,while the acidic sites of metal oxide favor the adsorption of C=C group of HMF,which decreases the BHMF selectivity.It is proposed that the cooperation between basic sites and Pt atoms(activating H2)boosted the BHMF selectivity.Comprehensive studies including reactivity,recyclability,stability,solvent effect on the Pt/MgO catalyst were also carried out.
查看更多>>摘要：Oxidative dehydrogenation(ODH)of n-hexane to olefins provides an alternative strategy for efficient utilization of n-hexane.Here,we report that hexagonal boron nitride(h-BN)is selective in ODH of n-hexane,achieving 89.611 % selectivity to olefins at n-hexane conversion of 16.3 % and 550 ℃.We found that low temperatures and oxygen rich conditions favor the selective hydrogen abstraction from C-H bond over the cleavage of C-C bond,and the presence of gas phase free radical greatly improves the reaction rate of ODH of n-hexane over h-BN.In addition,an anomalous seagull type of relationship exists between the conversion of n-hexane and reaction temperature,which may be related to the re-distribution of the active sites.
查看更多>>摘要：Niobium and nitrogen co-doped titanium dioxide(Nb-N-TiO2)semiconductor nanostructures were synthesized through a facile sol-gel protocol using titanium tetra iso-propoxide(TTIP),urea and niobium pentoxide as precursors followed by calcination at 450 ℃ for 4 h.The synthesized nanomaterial(Nb-N-TiO2)was characterized via Fourier Transform Infrared(FTIR)and Raman spectroscopy,UV-Visible(UV-Vis)Spectroscopy,Atomic Force Microscopy(AFM),Scanning Electron Microscopy(SEM),X-Ray Diffraction(XRD),Brunauer-Emmett-Teller(BET)technique,Dynamic Light Scattering(DLS)technique and ZETA Potential analysis.The band gap of Nb-N-TiO2 was reduced as compared to TiO2 due to reduced space between valance and conduction band which also reduced the electron-hole(e-,h+)recombination and led to better photocatalytic activity of the Nb-N-TiO2 as confirmed by TAUC plot.Photocatalytic activity of Nb-N-TiO2 was investigated for degradation of methylene blue(MB)dye under sunlight as cheaper light source.Factors like dye concentration,dosage of catalyst,volume of solution time and pH were studied and optimized for MB degradation.Under finally opti-mized conditions,97% of 25 ppm MB was degraded just in one minute using 45 mg of photocatalyst.The co-doped nanocatalyst,was re-used for MB degradation upto 4th cycle with its efficiency reduced to 75% which shows a better catalytic role by the catalyst.Degradation products of MB were recognized through electrospray ionization coupled mass spectroscopy(ESI-MS)and liquid chromatography coupled mass spectroscopy(LC-MS)techniques.The catalyst was also applied for MB degradation in tap water sample.
查看更多>>摘要：Zirconia-supported sodium-salt-modified Au(0)nanoparticles(NPs)(Na-Au/ZrO2)catalyst was prepared,and it was stable and recyclable in the intramolecular cyclization of alkynoic acids.In particular,the effect of sodi species in Na-Au/ZrC>2,which has been overlooked in previous studies,was studied,and they were found to play an essential role in the reaction.In addition,the relationship between the kinetics and size of Au NPs revealed that the active sites of the catalyst are located on the surface of the supported Au NPs.Moreover,detailed kinetic studies revealed that the cyclization was a zero-order reaction with respect to substrate concentration,and the rate-determining step of the reaction is presumed to be protodeauration.The maximum turnover number(TON)of the reaction of 5-hexynoic acid in a continuous flow reactor exceeded 9000,which is the highest TON obtained in the presence of a heterogeneous Au catalyst.
查看更多>>摘要：Selective hydrogenation of carbonyl groups in biobased chemicals to alcohols is crucial to the economics of broadly sustainable product portfolios.Furfuryl alcohol(FOL),the most prominent chemical of hemicellulose,has been produced by furfural(FAL)hydrogenation over heterogeneous catalysts.In this work,we show the outstanding activity,selectivity,and stability of supported bimetallic PtCo nanoparticle(np)synthesized from a pre-made stock solution of zero valent atomic Pt precursor and Co2(CO)8.With only 0.5 wt% Pt on TiO2,the np-PtCo/TiO2 catalyst exhibits TOF of 14,023 h~(-1)at 30 ℃ with>99.9% FOL selectivity.The stability of the np-PtCo/TiO2 catalyst is verified by the steady performance in reuses at both moderate and full conversions.The oxyphilic Co~(δ+)in the PtCo nanoparticles induces nucleophilic chemisorption of-C=O,resulting in deeply polarized-C=O bond.DFT calculated FAL adsorption energies on np-Pt and np-PtCo are-0.22 eV and-0.74 eV,respectively.
查看更多>>摘要：We report the immobilization of Cu(0)nanoparticles(NPs)with an average size of 7-8 nm on a template-free carbon-nitride oxide surface(g-C3N4O)in water medium.The heterogeneous surface containing Cu(0)NPs offers Lewis basic sites,which facilitate Chan-Lam N-arylation of anilines,azoles and indoles with phenylboronic acids.Good to moderate yields(55-93 %)of synthetically important JV-arylanilines,W-aryl-1H-imidazoles,N-aryl-1H-benzimidazoles and JV-aryl-1H-indoles are obtained,all of which have wide pharmaceutical applications.The reaction takes place under heterogeneous catalysis and the catalyst can be reused up to five catalytic cycles of the reaction.The stability of Cu(O)on the g-C3N4O surface,utilization of greener solvents for syntheses and extension of scope of Chan-Lam cross-coupling reaction through the introduction of Cu(0)catalysis are some of the significant achievements of this work.
查看更多>>摘要：We report the detailed surface chemistry of platinum,palladium,rhodium,and ruthenium substituted into lanthanum strontium cobaltate perovskite catalysts toward CO oxidation.The catalysts were synthesized by the solution combustion method and characterized in detailed using a series of techniques.To explore the effect of noble metal ion substitution on CO oxidation,surface intermediates were probed by operando diffuse reflectance infrared Fourier transform spectroscopy.It was recognized that La_(1-x)SrxCo_(1-y)MyO3 and La_(1-x)SrxCo_(1-y)MyO3 show the best activities for the reaction.DFT calculations were set up to unravel the details of the surface phenomena responsible for altering the CO oxidation activity upon noble metal ion substitution.The computational analysis conclusively demonstrated the experimentally hypothesized role of surface carbonate formation and revealed the altered mechanism for CO oxidation over the synthesized perovskites upon noble metal ion substitution.
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