Developing effective iron-incorporated zeolites and determining their active centers for the direct oxidation of CH_4 to oxygenates have remained challenging topics so far.In this paper,we successfully prepare the hig...Developing effective iron-incorporated zeolites and determining their active centers for the direct oxidation of CH_4 to oxygenates have remained challenging topics so far.In this paper,we successfully prepare the highly-dispersed iron supported Y zeolites by a facile solid-state ion-exchange method with ferrocene,which was conducted under water-free conditions followed by a series of calcination.Moreover,extra-framework dinuclear Fe^(2+)complexes are identified as so-called activeα-iron sites on zeolites.ICP-OES,N_2 adsorption–desorption test,X-ray diffraction,solid-state^(27)Al NMR,N_2O titration,TEM,EPR and^(57)Fe M?ssbauer spectra were carried out to characterize properties of sample structure,acid sites,as well as the supported iron species.Characterization results indicate that high-temperature treatments have no effect on the typical structure feature of zeolites.Compared with catalysts synthesized by conventional impregnation,the samples prepared by the facile approach possess abundant dinuclear Fe^(2+)complexes but no Fe_2O_3 bulks and show weak acidity.These lead to a higher oxygenate selectivity in CH_4 oxidation to oxygenates.Remarkably,the oxygenate(HCHO and CH_3OH)selectivity of 6.5% at 375°C can be eventually obtained.展开更多
The rapid diversification of early animals during the Ediacaran(635–541 Ma) and early Cambrian(ca.541–509 Ma) has frequently been attributed to increasing oceanic oxygenation. However, the pattern of oceanic oxygena...The rapid diversification of early animals during the Ediacaran(635–541 Ma) and early Cambrian(ca.541–509 Ma) has frequently been attributed to increasing oceanic oxygenation. However, the pattern of oceanic oxygenation and its relationship to early animal evolution remain in debate. In this review,we examine the redox structure of Ediacaran and early Cambrian oceans and its controls, offering new insights into contemporaneous oceanic oxygenation patterns and their role in the coevolution of environments and early animals. We review the development of marine redox models which, in combination with independent distal deep-ocean redox proxies, supports a highly redox-stratified shelf and an anoxia-dominated deep ocean during the Ediacaran and early Cambrian. Geochemical and modeling evidence indicates that the marine redox structure was likely controlled by low atmospheric O2 levels and low seawater vertical mixing rates on shelves at that time. Furthermore, theoretical analysis and increasing geochemical evidence, particularly from South China, show that limited sulfate availability was a primary control on the attenuation of mid-depth euxinia offshore, in contrast to the existing paradigm invoking decreased organic carbon fluxes distally. In light of our review, we infer that if oceanic oxygenation indeed triggered the rise of early animals, it must have done so through a shelf oxygenation which was probably driven by elevated oxidant availability. Our review calls for further studies on EdiacaranCambrian marine redox structure and its controls, particularly from regions outside of South China, in order to better understand the coevolutionary relationship between oceanic redox and early animals.展开更多
Archaeological and ancient DNA studies revealed that Shandong,a multi-culture center in northern coastal China,was home to ancient populations having ancestry related to both northern and southern East Asian populatio...Archaeological and ancient DNA studies revealed that Shandong,a multi-culture center in northern coastal China,was home to ancient populations having ancestry related to both northern and southern East Asian populations.However,the limited temporal and geographical range of previous studies have been insufficient to describe the population history of this region in greater detail.Here,we report the analysis of 86 complete mitochondrial genomes from the remains of 9500 to 1800-year-old humans from12 archaeological sites across Shandong.For samples older than 4600 years before present(BP),we found haplogroups D4,D5,B4 c1,and B5 b2,which are observed in present-day northern and southern East Asians.For samples younger than 4600 BP,haplogroups C(C7 a1 and C7 b),M9(M9 a1),and F(F1 a1,F2 a,and F4 a1)begin to appear,indicating changes in the Shandong maternal genetic structure starting from the beginning of the Longshan cultural period.Within Shandong,the genetic exchange is possible between the coastal and inland regions after 3100 BP.We also discovered the B5 b2 lineage in Shandong populations,with the oldest Bianbian individual likely related to the ancestors of some East Asians and North Asians.By reconstructing a maternal genetic structure of Shandong populations,we provide greater resolution of the population dynamics of the northern coastal East Asia over the past nine thousand years.展开更多
基金Support by the National Key R&D Program of China(2016YFA0202900)the National Natural Science Foundation of China(21622606)+2 种基金the Natural Science Foundation of Zhejiang Province(LR18B060001)Basic Research Project of Sinopec Group(415025)the Fundamental Research Funds for the Central Universities
文摘Developing effective iron-incorporated zeolites and determining their active centers for the direct oxidation of CH_4 to oxygenates have remained challenging topics so far.In this paper,we successfully prepare the highly-dispersed iron supported Y zeolites by a facile solid-state ion-exchange method with ferrocene,which was conducted under water-free conditions followed by a series of calcination.Moreover,extra-framework dinuclear Fe^(2+)complexes are identified as so-called activeα-iron sites on zeolites.ICP-OES,N_2 adsorption–desorption test,X-ray diffraction,solid-state^(27)Al NMR,N_2O titration,TEM,EPR and^(57)Fe M?ssbauer spectra were carried out to characterize properties of sample structure,acid sites,as well as the supported iron species.Characterization results indicate that high-temperature treatments have no effect on the typical structure feature of zeolites.Compared with catalysts synthesized by conventional impregnation,the samples prepared by the facile approach possess abundant dinuclear Fe^(2+)complexes but no Fe_2O_3 bulks and show weak acidity.These lead to a higher oxygenate selectivity in CH_4 oxidation to oxygenates.Remarkably,the oxygenate(HCHO and CH_3OH)selectivity of 6.5% at 375°C can be eventually obtained.
基金supported by the National Natural Science Foundation of China-Research Councils United Kingdom_Natural Environment Research Council Program (41661134048)the National Natural Science Foundation of China (41825019, 41821001), the National Key Research & Development Program of China (2016YFA0601100)+1 种基金111 Project of China (BP0820004) to Chao Li. Meng Chengsupport from the National Natural Science Foundation of China (41703008, 41902027)。
文摘The rapid diversification of early animals during the Ediacaran(635–541 Ma) and early Cambrian(ca.541–509 Ma) has frequently been attributed to increasing oceanic oxygenation. However, the pattern of oceanic oxygenation and its relationship to early animal evolution remain in debate. In this review,we examine the redox structure of Ediacaran and early Cambrian oceans and its controls, offering new insights into contemporaneous oceanic oxygenation patterns and their role in the coevolution of environments and early animals. We review the development of marine redox models which, in combination with independent distal deep-ocean redox proxies, supports a highly redox-stratified shelf and an anoxia-dominated deep ocean during the Ediacaran and early Cambrian. Geochemical and modeling evidence indicates that the marine redox structure was likely controlled by low atmospheric O2 levels and low seawater vertical mixing rates on shelves at that time. Furthermore, theoretical analysis and increasing geochemical evidence, particularly from South China, show that limited sulfate availability was a primary control on the attenuation of mid-depth euxinia offshore, in contrast to the existing paradigm invoking decreased organic carbon fluxes distally. In light of our review, we infer that if oceanic oxygenation indeed triggered the rise of early animals, it must have done so through a shelf oxygenation which was probably driven by elevated oxidant availability. Our review calls for further studies on EdiacaranCambrian marine redox structure and its controls, particularly from regions outside of South China, in order to better understand the coevolutionary relationship between oceanic redox and early animals.
基金supported by the National Natural Science Foundation of China(41672021,41925009,91731303,and 41630102)“Research on the Roots of Chinese Civilization”of Zhengzhou University(XKZDJC202006)+4 种基金the Chinese Academy of Sciences(XDB26000000,XDA1905010,and QYZDB-SSW-DQC003)the Tencent Foundation through the XPLORER PRIZEthe Howard Hughes Medical Institute(55008731)the National Social Science Foundation of China(15CKG013)the Shandong University Multidisciplinary Research and Innovation Team of Young Scholars(2020QNQT018)。
文摘Archaeological and ancient DNA studies revealed that Shandong,a multi-culture center in northern coastal China,was home to ancient populations having ancestry related to both northern and southern East Asian populations.However,the limited temporal and geographical range of previous studies have been insufficient to describe the population history of this region in greater detail.Here,we report the analysis of 86 complete mitochondrial genomes from the remains of 9500 to 1800-year-old humans from12 archaeological sites across Shandong.For samples older than 4600 years before present(BP),we found haplogroups D4,D5,B4 c1,and B5 b2,which are observed in present-day northern and southern East Asians.For samples younger than 4600 BP,haplogroups C(C7 a1 and C7 b),M9(M9 a1),and F(F1 a1,F2 a,and F4 a1)begin to appear,indicating changes in the Shandong maternal genetic structure starting from the beginning of the Longshan cultural period.Within Shandong,the genetic exchange is possible between the coastal and inland regions after 3100 BP.We also discovered the B5 b2 lineage in Shandong populations,with the oldest Bianbian individual likely related to the ancestors of some East Asians and North Asians.By reconstructing a maternal genetic structure of Shandong populations,we provide greater resolution of the population dynamics of the northern coastal East Asia over the past nine thousand years.
