Cu-SSZ-13(CHA topology)zeolites are commonly used in diesel engines for the selective catalytic reduction(NH3-SCR)of nitrogen oxides(NO_(x)).However,their synthesis typically requires long crystallization times and th...Cu-SSZ-13(CHA topology)zeolites are commonly used in diesel engines for the selective catalytic reduction(NH3-SCR)of nitrogen oxides(NO_(x)).However,their synthesis typically requires long crystallization times and their durability in NH3-SCR is limited.Herein,we achieved a significant reduction in crystallization time,synthesizing SSZ-13 zeolites in just 6 h by using SAPO-18 seeds and a minimal amount of an organic structure-directing agent(OSDA).The OSDA/Si ratio was reduced by a factor of 16 compared to conventional methods.Crystallization studies revealed that SAPO-18 seeds promoted the formation of four-membered rings(4MRs),which quickly combined into double 6-membered rings(D6Rs)with the assistance of the OSDA,enabling rapid crystallization of SSZ-13.The resulting Cu-SSZ-13 demonstrated comparable NH3-SCR performance to conventionally synthesized Cu-SSZ-13(Cuconv-SSZ-13).Moreover,we introduced Ce ions into Cu-SSZ-13 to enhance its hydrothermal stability and explored the effects of different metal precursors on the catalytic performance.The optimized CuCe(Ⅲ)0.5-SSZ-13 exhibited superior hydrothermal stability compared to Cu-SSZ-13.Conversely,CuCe(Ⅳ)1.0-SSZ-13 and CuCe(Ⅲ)0.5Ce(Ⅳ)1.0-SSZ-13 displayed reduced hydrothermal stability.Characterization revealed that using the Ce(Ⅲ)precursor inhibited CuO_(x) formation during hydrothermal ageing,while the Ce(Ⅳ)precursor favored the formation of CeO2,decreasing the zeolite stability and promoting CuO_(x) formation.This work presents a novel approach for rapid SSZ-13 synthesis and highlights the critical role of metal precursors in the performance of bimetallic SSZ-13 zeolites.展开更多
Marine natural products represent an important class of biologically active compounds critical for drug discovery.To date,17 marine-derived drugs,including trabectedin and eribulin,have been approved by the US FDA for...Marine natural products represent an important class of biologically active compounds critical for drug discovery.To date,17 marine-derived drugs,including trabectedin and eribulin,have been approved by the US FDA for clinical use and 33 others are in clinical trials[1].However,their medicinal investigation and clinical trials are often hampered by the scarcity of natural sources and by the difficulties of their harvesting in the delicate marine environment.Therefore,efficient and scalable approaches for the synthesis of promising marine natural products are essential to overcome supply issues for drug development.展开更多
High-spectral resolution infrared sounders on board satellites can measure atmospheric trace gases confined to the planetary boundary layer(PBL).However,their sensitivity to the PBL depends on the temperature differen...High-spectral resolution infrared sounders on board satellites can measure atmospheric trace gases confined to the planetary boundary layer(PBL).However,their sensitivity to the PBL depends on the temperature difference between the surface and the atmosphere,the so-called thermal contrast(TC).After reviewing the physical aspects of TC and how it drives measurement sensitivity,we characterize the global and temporal behavior of TC in clear-sky conditions.Combining land surface temperatures from the Copernicus Global Land Services dataset with air temperatures from the European Centre for Medium-Range Weather Forecasts reanalysis v5,we obtain global monthly averages of TC at high spatial(31 km)and temporal(1 h)resolution.TCs are analyzed as a function of time of the day,time of the year,location and land cover.Daytime maxima are observed from 1130 to 1330 local time,from 5-10 K in winter to 10-30 K in summer.A large dependency on land cover type is observed,both in the magnitude of the daily variations,and in the seasonality.For bare soils,shrublands,sparse and herbaceous vegetation,a maximum is seen in summer with daily TC amplitudes over 30 K.In contrast,for forests,wetlands,and croplands,the seasonal maximum occurs in spring,with daily variations below 15 K.Nighttime TCs typically range between−5 and−10 K.Occasionally,very favorable nighttime measurement conditions occur during winter and autumn due to large temperature inversions.Throughout the paper,we illustrate important concepts by means of satellite observations of NH3 over the Po Valley(Italy).展开更多
基金the National Natural Science Foundation of China(22301209,22476147,22288101,22405293)the Zhejiang Province Science Technology Planning Project(no.2021C03023)+1 种基金the Zhejiang Provincial Natural Science Foundation of China(no.ZCLQ24B0101)the‘111 Center’(B17020)for supporting this work.
文摘Cu-SSZ-13(CHA topology)zeolites are commonly used in diesel engines for the selective catalytic reduction(NH3-SCR)of nitrogen oxides(NO_(x)).However,their synthesis typically requires long crystallization times and their durability in NH3-SCR is limited.Herein,we achieved a significant reduction in crystallization time,synthesizing SSZ-13 zeolites in just 6 h by using SAPO-18 seeds and a minimal amount of an organic structure-directing agent(OSDA).The OSDA/Si ratio was reduced by a factor of 16 compared to conventional methods.Crystallization studies revealed that SAPO-18 seeds promoted the formation of four-membered rings(4MRs),which quickly combined into double 6-membered rings(D6Rs)with the assistance of the OSDA,enabling rapid crystallization of SSZ-13.The resulting Cu-SSZ-13 demonstrated comparable NH3-SCR performance to conventionally synthesized Cu-SSZ-13(Cuconv-SSZ-13).Moreover,we introduced Ce ions into Cu-SSZ-13 to enhance its hydrothermal stability and explored the effects of different metal precursors on the catalytic performance.The optimized CuCe(Ⅲ)0.5-SSZ-13 exhibited superior hydrothermal stability compared to Cu-SSZ-13.Conversely,CuCe(Ⅳ)1.0-SSZ-13 and CuCe(Ⅲ)0.5Ce(Ⅳ)1.0-SSZ-13 displayed reduced hydrothermal stability.Characterization revealed that using the Ce(Ⅲ)precursor inhibited CuO_(x) formation during hydrothermal ageing,while the Ce(Ⅳ)precursor favored the formation of CeO2,decreasing the zeolite stability and promoting CuO_(x) formation.This work presents a novel approach for rapid SSZ-13 synthesis and highlights the critical role of metal precursors in the performance of bimetallic SSZ-13 zeolites.
文摘Marine natural products represent an important class of biologically active compounds critical for drug discovery.To date,17 marine-derived drugs,including trabectedin and eribulin,have been approved by the US FDA for clinical use and 33 others are in clinical trials[1].However,their medicinal investigation and clinical trials are often hampered by the scarcity of natural sources and by the difficulties of their harvesting in the delicate marine environment.Therefore,efficient and scalable approaches for the synthesis of promising marine natural products are essential to overcome supply issues for drug development.
基金funding from the Belgian State Federal Office for Scientific,Technical and Cultural Affairs(Prodex HIRS)the Air Liquide Foundation(TAPIR project)+3 种基金supported by the FED-tWIN project ARENBERG(“Assessing the Reactive Nitrogen Budget and Emissions at Regional and Global Scales”)funded through the Belgian Science Policy Office(BELSPO)supported by the Belgian F.R.S.-FNRSsupport from a FRIA(Fund for scientific Research in Industry and Agriculture)grant from the Belgian F.R.S-FNRS.
文摘High-spectral resolution infrared sounders on board satellites can measure atmospheric trace gases confined to the planetary boundary layer(PBL).However,their sensitivity to the PBL depends on the temperature difference between the surface and the atmosphere,the so-called thermal contrast(TC).After reviewing the physical aspects of TC and how it drives measurement sensitivity,we characterize the global and temporal behavior of TC in clear-sky conditions.Combining land surface temperatures from the Copernicus Global Land Services dataset with air temperatures from the European Centre for Medium-Range Weather Forecasts reanalysis v5,we obtain global monthly averages of TC at high spatial(31 km)and temporal(1 h)resolution.TCs are analyzed as a function of time of the day,time of the year,location and land cover.Daytime maxima are observed from 1130 to 1330 local time,from 5-10 K in winter to 10-30 K in summer.A large dependency on land cover type is observed,both in the magnitude of the daily variations,and in the seasonality.For bare soils,shrublands,sparse and herbaceous vegetation,a maximum is seen in summer with daily TC amplitudes over 30 K.In contrast,for forests,wetlands,and croplands,the seasonal maximum occurs in spring,with daily variations below 15 K.Nighttime TCs typically range between−5 and−10 K.Occasionally,very favorable nighttime measurement conditions occur during winter and autumn due to large temperature inversions.Throughout the paper,we illustrate important concepts by means of satellite observations of NH3 over the Po Valley(Italy).
