查看更多>>摘要：Non-edible lipids are an alternative source of liquid hydrocarbon fuels,particularly aviation fuels.As a transformation pathway,the catalytic pyrolysis of lipids can remove oxygen atoms and modify molecular structures via carbon chain cracking and aromatisation.However,this pathway has not yet been certified for the production of alternative aviation fuels.Therefore,a detailed review of various heterogeneous catalysts for the conversion of lipids into hydrocarbon fuels with molecular weights and structures suitable for use in aviation is presented herein,with a focus on aspects such as their physical and chemical properties,pore distributions and structures,active sites,key functions,catalytic performance,and pyrolysis mechanisms.Metal oxides can effectively remove oxygen atoms,whereas zeolites can achieve long-carbon-chain cracking to yield desirable gasoline-,kerosene-,or diesel-range fuels.Moreover,zeolites typically permit aromatisation,which yields the aromatic hydrocarbons required for liquid fuels.Modification of the pore structures of zeolites to yield hierarchical pores can improve the production of C8-C_(16)-range liquid fuels to maximise the bio-kerosene yield.Therefore,composite catalysts(metal oxides supported on zeolites with hierarchical pores)can be effective for molecular-level structural modification in the pyrolytic production of alternative aviation fuels using lipids.However,rapid deactivation due to coking,poisoning,and sintering hinder the operation of these catalysts.Coking,which is predominantly responsible for pyrolysis catalyst deactivation,should be targeted in future research on novel catalysts.The synthetic strategy of catalysts and the mitigation of their issues are critical to the design of novel catalytic pyrolysis systems for the efficient cracking of triglyceride-rich feedstock to yield alternative aviation fuels.
查看更多>>摘要：The MnOx/TiO2-based NOx reduction catalyst showed moderate performance at low temperature and had the disadvantage of low N2 selectivity.Herein,the effect of Sm and Ce interactions on MnOx-based catalysts in selective catalytic reduction was investigated.Sm increased the redox properties of the MnOx catalyst and the ratio of Mn~(4+).Meanwhile,Ce enhanced the additional redox trait of the Sm-modified catalyst.When exposed to SO2/O2,Sm and Ce-modified MnOx not only suppressed performance degradation,but also increased N2 selectivity.Sm and Ce suppress the formation of N2O by inhibiting the formation of N2O4 intermediate species.Additionally,regardless of exposure to SO2/O2,Sm/Ce modified MnOx is an LH-ER mechanism(Langmuir-Hinshelwood and Eley-Rideal mechanism),but in the case of MnOx,it is suggested to be mainly an ER mechanism when exposed to SO2/O2.From these results,a strategy for improving the N2 selectivity/SCR performance of MnOx/TiO2-based catalysts with SO2 resistance was provided.
查看更多>>摘要：Efficient lean-burn gasoline engines cannot employ traditional three-way catalysts(TWCs)to control NOx emissions due to excess oxygen.Passive selective catalytic reduction(pSCR)is a process designed to control NOx by generating NH3 over the TWC during fuel-rich operation,storing it on a downstream SCR,and then converting NOx during fuel-lean operation.This work is focused on studying sulfur effects on this promising strategy.Two hydrothermally-aged commercial catalysts were studied for their effectiveness in the presence of SO2:a Pd-based TWC and a TWC with NOx storage.The sulfated samples were evaluated in a flow reactor under pSCR conditions and with targeted reactions.SO2 inhibited the water gas shift and steam reforming reactions,decreasing(but not eliminating)NH3 production; however,initial activity is recoverable after a simple thermal treatment at 650 ℃.This work will prove valuable in understanding,mitigating,and even reversing the effects of SO2 inhibition on real pSCR systems.
查看更多>>摘要：The heat effect on photocatalysis should be taken care because light absorption causes a temperature rise in semiconductor.In this research,bandgaps and action spectra of semiconductor photocatalysts were investigated at room and increased temperature.Throughout the photoelectrochemical,gas-phase,and liquid-phase photocatalysis experiments,we found that when the temperature is increased from room temperature to 75 or 90 ℃,not only the absorption originating from the bandgap excitation of titanium dioxide(TiO2)but also the action spectrum of the photocatalytic reaction shifted to lower energy.This phenomenon implies that the photocatalytic reaction can be driven by light with lower energy when the band structure is'modified'by heat energy.This result not only enables us to utilize more incident photons but also to control the reduction or oxidation ability.Thus,this'thermal modification'of metal oxide semiconductors provides a new strategy for engineering the bands of semiconductor photocatalysts.
查看更多>>摘要：The heterogeneous enantioselective hydrogenation of the C=C bond of aliphatic a,p-unsaturated carboxylic acids is a key asymmetric catalytic reaction because of its application in the production of pharmaceuticals.In this study,we investigated the enantioselective hydrogenation of(E)-2-methyl-2-butenoic acid over I cinchonidine-modified Pd catalysts.To improve the catalytic performance,a support material,mesocellular silica foam(MCF),was functionalized by grafting with primary amines.The use of the amine-functionalized MCF(NH2-MCF)support resulted in enhanced activity and enantioselectivity.The promoting effects originated from the increased electron density of the Pd nanoparticles and the selective blocking of low-coordinated Pd sites by the strong interaction of the amine groups with Pd nanoparticles.Promisingly,the Pd/NH2-MCF catalyst maintained its enantioselectivity over five successive cycles,thus demonstrating the reusability.Our results provide insights into the origin of the promoting effects of amine-functionalized supports and offer a strategy for improving supported catalysts for structure-sensitive reactions.
查看更多>>摘要：A dielectric barrier discharge(DBD)coupling MnCu/Ti oxidation and postpositioned wet electrostatic precipi-tator(WESP)system was built.The experimental results showed that WESP can significantly enhance the simultaneous conversion efficiency(ηC)of NO,SO2 and Hg° by the DBD coupling MnCu/Ti reactor.The best simultaneous removal efficiency(ηR)of NO,SO2 and Hg° reached 94.5%,100% and 100%,respectively.The ratio of catalyst active component(Mn/Cu)and catalyst filling amount were optimized.The effects of catalyst active component ratio,filling amount,flue gas component and energy density(SED)on the ηC of NO,SO2 and Hg° were determined.The effect of sodium humate(HA-Na)in the cleaning water on the ηR was also illustrated.Besides,we clarified the absorption mechanism and how WESP corona discharge oxidized NO,SO2 and Hg°,as well as the removal of NO2,SO2,and SO3 by HA-Na.Product analysis showed that NO2,SO2 and SO3 were converted into NO3 and SO_4~(2-),part of HgO was converted into Hg~(2+)in the cleaning water,and a small amount of Hg(NO3)2 and HgSO4 were converted into Hg~(2+),NO3 and SO_4~(2-).
查看更多>>摘要：The oxidation and catalytic oxidation products of pyrene was analyzed by electron paramagnetic resonance(EPR),matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF),Fourier-transform infrared spectroscopy(FT-IR),and gas chromatography-mass spectrometry(GC-MS).The in-situ transformation of Cu-based catalysts was analyzed.A qualitative model of pyrene oxidation with and without catalyst was built.CuO nanoparticles were in-situ formed as the active phases,and they decreased the polymerization and condensation of pyrene.The oxidation pathways of pyrene with and without CuO nanoparticles with the main product of 9-oxo-phenaleno-1-carbaldehyde were considered,which includes two elementary stages with the limiting Gibbs energy barrier of 227 kJ/mol.CuO increases the number of stages to diree and reduces the Gibbs activation energy by 20 % of the limiting stage of pyrene oxidation.These findings provide new insights into the initial oxidation of pyrene and its catalysis.The proposed model and methods using Density functional theory(DFT)calculation offer a new theoretical approach for investigating hydrocarbon oxidation as well as designing catalytic systems for accelerating their oxidation.
查看更多>>摘要：A novel BiOBr/BiFeO3 heterojunction sonocatalyst was prepared and characterized.The sonocatalytic activity of BiOBr/BiFeO3 composite was evaluated by the catalytic degradation of ciprofloxacin.BiOBr/BiFeO3 composite combined with persulfate had excellent sonocatalytic activity for ciprofloxacin degradation under ultrasonic irradiation,and the degradation rate was 73.64% ± 7.96%.The formation of Z-type heterojunction of BiOBr/BiFeO3 and the generation of hydroxyl radical,superoxide anion and hole were the key to the catalytic activity of BiOBr/BiFeO3.Free radicals will attack the positions of piperazine ring,cyclopropyl,C-F bond,carboxyl group and ethylenic linkage in ciprofloxacin structure,and gradually degrade ciprofloxacin through multiple paths.After the sonocatalytic degradation,the bacteriostatic effect of the solution decreased significantly and the environmental pollution decreased significantly.As a sonocatalyst,BiOBr/BiFeO3 composite has good degradation and removal effect on ciprofloxacin and has practical application potential.Meanwhile,it lays a foundation for the further practical application of sonocatalytic degradation technology.
查看更多>>摘要：Developing cost-effective bifunctional electrocatalysts is eagerly desirable for electrochemical energy applications.Herein,using the first-principles computations,the structural,electronic,magnetic,oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)catalytic properties of single platinum group metal(PGM)atom modified Janus WSSe monolayer systems are comprehensively investigated.The results reveal that the single PGM atom can be stably supported on me W top position of S side and effectively regulate the structural and electronic characteristics of Janus WSSe monolayer.Pd-and Pt-WSSe are effectively screened from the PGM-WSSe systems with the outstanding bifunctional catalytic activity elucidated,especially the Pd-WSSe exhibits even smaller overpotentials(η~(ORR)≈ 0.39 and η~(ORR)≈ 0.49 V).The mechanisms of prominent bifunctional catalytic activity of Pd-and Pt-WSSe are summarized including their moderate binding strength with O2 molecule,superior electrical conductivity,high intrinsic electric field and the d orbital occupancy of Pd and Pt atoms.Thus,the effective strategy to reduce the dosage of PGMs in PGM single atom catalysts(SACs)and to boost the bifunctional catalytic performance of Janus WSSe monolayer could be achieved,which would be useful to promote the exploration of novel bifunctional electrocatalysts.
查看更多>>摘要：In recent years,Ga-based catalysts attract much attention in propane dehydrogenation(PDH)reaction due to environmental friendliness and low cost.Nevertheless,it is still challenging to obtain high selectivity of propylene under harsh reaction conditions.In this work,the supported catalysts(Ga-xMg/ZSM-5)were prepared with the sequential impregnation method and applied in the PDH reaction.The results show that MgO as an additive reduces the acidity of the catalysts,promotes the dispersion of Ga2O3 and improves the selectivity of propylene.As a result,the average particle size of the Ga/ZSM-5 catalyst is larger(4.5 nm),and the initial propylene selectivity is only 71.0 %.In contrast,the optimal Ga-0.7Mg/ZSM-5 catalyst shows the smallest particle size(2.4 nm)and the highest propylene selectivity of 90.8 %.In comparison with the previous GaOx catalysts in literatures,the Ga-0.7Mg/ZSM-5 catalyst exhibits a superior production rate of propylene(r_(C3H6))based on either catalyst weight or Ga2O3 weight.
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