catalyst

摘要： Electrochemical reduction of carbon dioxide(CO_(2)ER)into formate plays a crucial role in CO_(2)conversion and utilization.However,it still faces the problems of high overpotential and poor catalytic stability.Herein,we report a hybrid CO_(2)ER electrocatalyst composed of layered bismuth sulfide(Bi_(2)S_(3))and bismuth oxide(Bi_(2)O_(3))supported on carrageenan derived carbon(Bi-CDC)prepared by a combined pyrolysis with hydrothermal treatment.In such 3 D hybrid,layered Bi_(2)O_(3)and Bi_(2)S_(3)are uniformly grown on nanocarbon supports.Benefiting from strong synergistic effect between Bi_(2)O_(3)/Bi_(2)S_(3)and nanocarbon,Bi-CDC-1:2 displays a high Faradic efficiency(FE)of>80%for formate production in the range of-0.9 V to-1.1 V with the maximum formate FE of 85.6%and current density of 14.1 mA·cm^(-2) at-1.0 V.Further,a positive onset potential of-0.5 V,a low Tafel slope of 112.38 mV·dec^(-1),and a slight performance loss during long-term CO_(2)ER tests are observed on Bi-CDC-1:2.Experimental results shows that the better CO_(2)ER performance of Bi-CDC-1:2 than that of Bi_(2)O_(3)can be attributed to the strong interfacial interactions between nanocarbons and Bi_(2)O_(3)/Bi_(2)S_(3).In situ ATR-FTIR measurements reveal that the rate-determining step in the CO_(2)ER is the formation of HCOO^(*) intermediated.Compared with carbon support,Bi-CDC-1:2 can promote the production of HCOO^(*) intermediate and thus promoting CO_(2)ER kinetic.

摘要： Rational design of Zn-containing HZSM-5 zeolite(Zn/HZSM-5)with high reactivity and excellent aromatization performance for olefin aromatization is crucially desired.We develop a new and uncomplicated method to synthesize Zn/HZSM-5(IMX/Z5)with superior aromatization performance in the paper.Compared to incipient wetness impregnation(IMP/Z5)and mechanical mixing(MIX/Z5),the asprepared IMX/Z5 presents a higher amount of surface ZnOH^(+)species(2.87%)while keeping identical bulk zinc content.As a result,more surface ZnOH^(+)favor both the aromatization of 1-hexene and cyclohexane dehydrogenation.For the two olefin aromatization pathways(hydrogen transfer and dehydrogenation),it is the first time found both the hydrogen transfer ability and the dehydrogenation ability increase linearly with the amount of surface ZnOH^(+)species while keeping identical bulk zinc content.We believe that the linear relationships are essential to design next generation olefin aromatization catalysts.

摘要： More stringent environmental legislation imposes severe requirements to reduce the sulfur content in diesel to ultra-low levels with high efficient catalysts.In this paper,a series of CoMo/NDC@alumina catalysts were synthesized by combination of the chemical vapor deposition of nitrogen-doped carbon(NDC)using 1,10-phenanthroline and co-impregnation of Mo and Co active components.The optimal catalyst with additive of 25%1,10-phenanthroline was screened by a series of property characterization and the hydrodesulfrization(HDS)active test.The amount of“CoMoS”active phase of the optimal CoMo/C3 catalyst increased 5.3%as compared with the CoMo/c-Al_(2)O_(3).The introduction of NDC improved the sulfidation degree of Mo by 21.8%as compared to the CoMo/c-Al_(2)O_(3) catalyst,which was beneficial to form more active sites.The HDS conversion of the NDC supported catalysts are higher than CoMo/c-Al_(2)O_(3) whether for the dibenzothiophene(DBT)or 4,6-dimethyl dibenzothiophene(4,6-DMDBT).Further hydroprocessing evaluation with Dagang diesel revealed that the CoMo/C3 catalyst possessed higher HDS property and the removal rate of DBTs in the diesel increased by 4%–11%as compared to the CoMo/c-Al_(2)O_(3) catalyst.

摘要： Al-S batteries are promising next generation energy storage devices due to their high theoretical energy density(1340 Wh kg^(-1)),low cost,and safe operation.However,the electrochemical performance of Al-S batteries suffers poor reversibility owing to slow kinetic processes determined by the difficulty of reversible conversion between Al and S.Here,we proposed a single-atom catalysts comprising Co atoms embedded in a nitrogen-doped graphene(Co NG)as an electrochemical catalyst in the sulfur cathode that renders a reduced discharge-charge voltage hysteresis and improved sulfur utilization in the cathode.The structural and electrochemical analyses suggest that the Co NG facilitated both the formation and oxidation of Al S;during the electrochemical reactions of the sulfur species.Consequently,the Co NG-S composite can deliver a considerably reduced voltage hysteresis of 0.76 V and a reversible specific capacity of 1631 m Ah g^(-1) at 0.2 A g^(-1) with a sulfur utilization of more than 97%.

摘要： The nature and distribution of Cu species in Cu-SSZ-13 play a vital role in selective catalytic reduction of NO by NH3(NH3-SCR),but existing methods for adjusting the Cu distribution are complex and difficult to control.Herein,we report a simple and effective ion-exchange approach to regulate the Cu distribution in the one-pot synthesized Cu-SSZ-13 that possesses sufficient initial Cu species and thus provides a“natural environment”for adjusting Cu distribution precisely.By using this proposed strategy,a series of Cu-SSZ-13x zeolites with different Cu contents and distributions were obtained.It is shown that the dealumination of the as-synthesized Cu-SSZ-13 during the ion-exchange generates abundant vacant sites in the double six-membered-rings of the SSZ-13 zeolite for relocating Cu2+species and thus allows the redistribution of the Cu species.The catalytic results showed that the ion-exchanged Cu-SSZ-13 zeolites exhibit quite different catalytic performance in NH3-SCR reaction but superior to the parent counterpart.The structure–activity relationship analysis indicates that the redistribution of Cu species rather than other factors(e.g.,crystallinity,chemical composition,and porous structure)is responsible for the improved NH3-SCR performance and SO_(2) and H_(2)O resistance.Our work offers an effective method to precisely adjust the Cu distribution in preparing the industrial SCR catalysts.

摘要： Rich burn industrial natural gas engines offer best in class post catalyst emissions by using a non-selective catalyst reduction aftertreatment technology. However, they operate with reduced power density when compared to lean burn engines. Dedicated exhaust gas recirculation (EGR) offers a possible pathway for rich burn engines to use non-selective catalyst reduction aftertreatment technology without sacrificing power density. In order to achieve best in class post catalyst emissions, the precious metals and washcoat of a non-selective catalyst must be designed according to the expected exhaust composition of an engine. In this work, a rich burn industrial natural gas engine operating with dedicated EGR was paired with a commercially available non-selective catalyst. At rated brake mean effective pressure (BMEP) the air-fuel ratio was swept between rich and lean conditions to compare the catalyst reduction efficiency and post catalyst emissions of rich burn and dedicated EGR combustion. It was found that due to low oxides of nitrogen (NOx) emissions across the entire air-fuel ratio range, dedicated EGR offers a much larger range of air-fuel ratios where low regulated emissions can be met. Low engine out NOx also points towards a possibility of using an oxidation catalyst rather than a non-selective catalyst for dedicated EGR applications. The location of the NOx-CO tradeoff was shifted to more rich conditions using dedicated EGR.

摘要： A series of bifunctional Zn Ce@SBA-15 catalysts with different Zn/Ce ratios were prepared by a solid-state grinding strategy and used in the conversion of ethanol to 1,3-butadiene(ETB).For the supported metal oxides,Zn O serves as the active sites for the dehydrogenation of ethanol,and CeO_(2) promotes the aldolcondensation reaction.Based on the results of Py-FTIR and NH_(3)-TPD,it suggests that the yield of 1,3-butadiene is positively correlated with the number of weak Lewis acid sites on the catalyst surface,given their benefit for aldol-condensation reactions.The catalyst with an optimal Zn/Ce ratio of about 1:5 has the highest concentration of weak Lewis acid.Coupling with the Zn O sites,it contributes to a 98.4%conversion of ethanol and a 45.2%selective of 1,3-butadiene under relatively mild reaction conditions(375°C,101.325 k Pa,and 0.54 h^(-1)).

摘要： A series of B-doped V_(2)O_(5)/TiO_(2) catalysts has been prepared the by sol-gel and impregnation methods to investigate the influence of B-doping on the selective catalytic reduction(SCR)of NOxwith NH_(3).X-ray diffraction,Brunauer-Emmett-Teller specific surface area,scanning electron microscope,X-ray photoelectron spectroscopy,temperature-programmed reduction of H_(2) and temperature-programmed desorption of NH_(3)technology were used to study the effect of the B-doping on the structure and NH_(3)-SCR activity of V_(2)O_(5)/TiO_(2) catalysts.The experimental results demonstrated that the introduction of B not only improved the low-temperature SCR activity of the catalysts,but also broadened the activity temperature window.The best SCR activity in the entire test temperature range is obtained for VTiB_(2.0) with 2.0%doping amount of B and the NO_(x) conversion rate is up to 94.3%at 210°C.The crystal phase,specific surface area,valence state reducibility and surface acidity of the active components for the as-prepared catalysts are significantly affected by the B-doping,resulting in an improved NH_(3)-SCR performance.These results suggest that the V_(2)O_(5)/TiO_(2) catalysts with an appropriate B content afford good candidates for SCR in the low temperature window.

摘要： 5-Hydroxymethylfurfural(5-HMF),as a key platform compound for the conversion of biomass to various biomass-derived chemicals and biofuels,has been attracted extensive attention.In this research,using Pickering high internal phase emulsions(Pickering HIPEs)as template and functional metal-organic frameworks(MOFs,UiO-66-SO;H and UiO-66-NH;)/Tween 85 as co-stabilizers to synthesis the dual acid-base bifunctional macroporous polymer catalyst by one-pot process,which has excellent catalytic activity in the cascade reaction of converting cellulose to 5-HMF.The effects of the emulsion parameters including the amount of surfactant(ranging from 0.5%to 2.0%(mass)),the internal phase volume fraction(ranging from 75%to 90%)and the acid/base Pickering particles mass ratio(ranging from 0:6 to 6:0)on the morphology and catalytic performance of solid catalyst were systematically researched.The results of catalytic experiments suggested that the connected large pore size of catalyst can effectively improve the cellulose conversion,and the synergistic effect of acid and base active sites can effectively improve the 5-HMF yield.The highest 5-HMF yield,about 40.5%,can be obtained by using polymer/MOFs composite as catalyst(Poly-P12,the pore size of(53.3±11.3)μm,the acid density of 1.99 mmol·g^(-1)and the base density of 1.13 mol·g^(-1))under the optimal reaction conditions(130°C,3 h).Herein,the polymer/MOFs composite with open-cell structure was prepared by the Pickering HIPEs templating method,which provided a favorable experimental basis and theoretical reference for achieving efficient production of high addedvalue product from abundant biomass.

摘要： Reducing the loading of noble Pt-based catalyst is vital for the commercialization of proton exchange membrane fuel cell(PEMFC),However,severe mass transfer polarization loss resulting in fuel cell performance decline will be encountered in ultra-low Pt PEMFC.In this work,mild oxidized multiwalled carbon nanotubes(mMWCNT)were adopted to construct the catalyst layer,and by varying the loading of carbon nanotubes,the catalyst layer structure was optimized.A high peak power density of 1.23 W·cm^(-2) for the MEA with mMWCNT was obtained at an ultra-low loading of 120μg·cm^(-2) Pt/PtRu(both cathode and anode),which was 44.7%higher than that of MEA without mMWCNT.Better catalyst dispersion,low charge transfer resistance,more porous structure and high hydrophobicity of catalyst layer were ascribed for the reasons of the performance improvement.

摘要： A new route of methane utilization，in which methane is simultaneously converted to H2，CO and C2H4 with equal mole ratio，and so that this producing mixture could be used as feed for the synthesis of propanal，is raised.Gas phase partial oxidation Was combined with the catalytic oxidative coupling of methane over Mn/Na2WO4/SiO2 to concomitantly acquire ethylene and syngas with close concentration. A ratio of CO：H2：C2H4=1.0：1：0.9 was obtained with a yield of 7.3％and a selectivity of 43％to ethylene.and a total selectivity of C to the target products of 68％and a CO2 selectivity of 18.1％under the optimal reaction conditions.

摘要： A new route of methane utilization，in which methane is simultaneously converted to H2，CO and C2H4 with equal mole ratio，and so that this producing mixture could be used as feed for the synthesis of propanal，is raised.Gas phase partial oxidation Was combined with the catalytic oxidative coupling of methane over Mn/Na2WO4/SiO2 to concomitantly acquire ethylene and syngas with close concentration. A ratio of CO：H2：C2H4=1.0：1：0.9 was obtained with a yield of 7.3％and a selectivity of 43％to ethylene.and a total selectivity of C to the target products of 68％and a CO2 selectivity of 18.1％under the optimal reaction conditions.

摘要： A new route of methane utilization，in which methane is simultaneously converted to H2，CO and C2H4 with equal mole ratio，and so that this producing mixture could be used as feed for the synthesis of propanal，is raised.Gas phase partial oxidation Was combined with the catalytic oxidative coupling of methane over Mn/Na2WO4/SiO2 to concomitantly acquire ethylene and syngas with close concentration. A ratio of CO：H2：C2H4=1.0：1：0.9 was obtained with a yield of 7.3％and a selectivity of 43％to ethylene.and a total selectivity of C to the target products of 68％and a CO2 selectivity of 18.1％under the optimal reaction conditions.

摘要： A new route of methane utilization，in which methane is simultaneously converted to H2，CO and C2H4 with equal mole ratio，and so that this producing mixture could be used as feed for the synthesis of propanal，is raised.Gas phase partial oxidation Was combined with the catalytic oxidative coupling of methane over Mn/Na2WO4/SiO2 to concomitantly acquire ethylene and syngas with close concentration. A ratio of CO：H2：C2H4=1.0：1：0.9 was obtained with a yield of 7.3％and a selectivity of 43％to ethylene.and a total selectivity of C to the target products of 68％and a CO2 selectivity of 18.1％under the optimal reaction conditions.

摘要： A new route of methane utilization，in which methane is simultaneously converted to H2，CO and C2H4 with equal mole ratio，and so that this producing mixture could be used as feed for the synthesis of propanal，is raised.Gas phase partial oxidation Was combined with the catalytic oxidative coupling of methane over Mn/Na2WO4/SiO2 to concomitantly acquire ethylene and syngas with close concentration. A ratio of CO：H2：C2H4=1.0：1：0.9 was obtained with a yield of 7.3％and a selectivity of 43％to ethylene.and a total selectivity of C to the target products of 68％and a CO2 selectivity of 18.1％under the optimal reaction conditions.

摘要： A new route of methane utilization，in which methane is simultaneously converted to H2，CO and C2H4 with equal mole ratio，and so that this producing mixture could be used as feed for the synthesis of propanal，is raised.Gas phase partial oxidation Was combined with the catalytic oxidative coupling of methane over Mn/Na2WO4/SiO2 to concomitantly acquire ethylene and syngas with close concentration. A ratio of CO：H2：C2H4=1.0：1：0.9 was obtained with a yield of 7.3％and a selectivity of 43％to ethylene.and a total selectivity of C to the target products of 68％and a CO2 selectivity of 18.1％under the optimal reaction conditions.