Selective coupling of methyl radicals to produce C_(2) species(C2H4 and C2H6)is a key challenge for oxidative coupling of methane(OCM).In traditional OCM reaction systems,homogeneous transformation of methyl radicals ...Selective coupling of methyl radicals to produce C_(2) species(C2H4 and C2H6)is a key challenge for oxidative coupling of methane(OCM).In traditional OCM reaction systems,homogeneous transformation of methyl radicals in O_(2)‐containing gases are uncontrollable,resulting in limited C_(2) selectivity and yield.Herein,we demonstrate that methyl radicals generated by La_(2)O_(3)at low reaction temperature can selectively couple on the surface of 5 wt%Na2WO4/SiO_(2).The controllable surface coupling against overoxidation barely changes the activity of La_(2)O_(3)but boosts the C_(2)selectivity by three times and achieves a C_(2)yield as high as 10.9%at bed temperature of only 570℃.Structure‐property studies suggest that Na_(2)WO_(4) nanoclusters are the active sites for methyl radical coupling.The strong CH_(3)·affinity of these sites can even endow some methane combustion catalysts with OCM activity.The findings of the surface coupling of methyl radicals open a new direction to develop OCM catalyst.The bifunctional OCM catalyst system,which composes of a methane activation center and a CH_(3)·coupling center,may deliver promising OCM performance at reaction temperatures below the ignition temperature of C2H6 and C2H4(~600℃)and is therefore more controllable,safer,and certainly more attractive as an actual process.展开更多
There has been carried out the process of noncatalytic oxidation of natural methane in the presence of hydrogen peroxide at the temperatures 840-880 ℃ what permitted to obtain hydrogen with high yield of hydrogen （...There has been carried out the process of noncatalytic oxidation of natural methane in the presence of hydrogen peroxide at the temperatures 840-880 ℃ what permitted to obtain hydrogen with high yield of hydrogen （74%） with inconsiderable quantity of CO （0.4%） in converted gas. As observed in the experiment, a variation of H2O2 concentration in the aqueous solution and other basic parameters of the process may induce the synthesis of gas with given H2：CO ratio for its further application in methanol or ammonia synthesis. In the latter process low CO concentration is required. Compared with the common high-temperature conversion of natural gas and further carbon oxide conversion on a catalyst, the current process promotes process simplification： the reaction is implemented at relatively low temperature （860-900 ℃ instead of 1400-1600 ℃for existing non-catalytic processes of methane conversion） and an additional unit for catalytic conversion of carbon oxide is excluded （in NH3 production）. The mechanism of chemical conjugation in the CH4-H2O2-H2O system was elucidated and the inducing effect of H2O2 decomposition on the desired （secondary） reaction was quantitavely estimated. An adequate kinetic model was formulated on the basis of the proposed free-radical scheme.展开更多
A method for oxidative degradation of 1,4-dioxane （1,4-D） in waste water using a combination of ozone oxidation with UV irradiation （ozone/UV） treatment was investigated. The results showed that 1,4-D was degraded...A method for oxidative degradation of 1,4-dioxane （1,4-D） in waste water using a combination of ozone oxidation with UV irradiation （ozone/UV） treatment was investigated. The results showed that 1,4-D was degraded by ozone/UV treatment up to 90 min. The optimum concentration for the injected ozone gas was about 40 g·m^3 under a constant level of UV irradiation. Furthermore, solid phase extraction and GC-MS analysis showed no specific or reproducible peaks due to by-products of 1,4-D. It was therefore concluded that 1,4-D was completely degraded by ozone/UV treatment. In contrast, the amount of 1,4-D remaining decreased slowly in the presence of HCOf or CI. It was suggested that the degradation of 1,4-D, which results from .OH oxidation, was retarded by the presence of HCO3 or CI, which act as radical scavengers.展开更多
Ir-催化不对称全合成吲哚生物碱（-）-Communesin F J.Am.Chem.Soc.2017,139,3364-3367吲哚生物碱Communesin家族是八个具有复杂七环系的天然产物.因具有独特的化学结构（四个氮原子构成罕见的上下两个aminal基团,外加两个连续手性季碳...Ir-催化不对称全合成吲哚生物碱（-）-Communesin F J.Am.Chem.Soc.2017,139,3364-3367吲哚生物碱Communesin家族是八个具有复杂七环系的天然产物.因具有独特的化学结构（四个氮原子构成罕见的上下两个aminal基团,外加两个连续手性季碳）和有趣的生物活性而成为明星分子,尤其是Communesin F的全合成备受化学家青睐,包括我国秦勇、展开更多
文摘Selective coupling of methyl radicals to produce C_(2) species(C2H4 and C2H6)is a key challenge for oxidative coupling of methane(OCM).In traditional OCM reaction systems,homogeneous transformation of methyl radicals in O_(2)‐containing gases are uncontrollable,resulting in limited C_(2) selectivity and yield.Herein,we demonstrate that methyl radicals generated by La_(2)O_(3)at low reaction temperature can selectively couple on the surface of 5 wt%Na2WO4/SiO_(2).The controllable surface coupling against overoxidation barely changes the activity of La_(2)O_(3)but boosts the C_(2)selectivity by three times and achieves a C_(2)yield as high as 10.9%at bed temperature of only 570℃.Structure‐property studies suggest that Na_(2)WO_(4) nanoclusters are the active sites for methyl radical coupling.The strong CH_(3)·affinity of these sites can even endow some methane combustion catalysts with OCM activity.The findings of the surface coupling of methyl radicals open a new direction to develop OCM catalyst.The bifunctional OCM catalyst system,which composes of a methane activation center and a CH_(3)·coupling center,may deliver promising OCM performance at reaction temperatures below the ignition temperature of C2H6 and C2H4(~600℃)and is therefore more controllable,safer,and certainly more attractive as an actual process.
文摘There has been carried out the process of noncatalytic oxidation of natural methane in the presence of hydrogen peroxide at the temperatures 840-880 ℃ what permitted to obtain hydrogen with high yield of hydrogen （74%） with inconsiderable quantity of CO （0.4%） in converted gas. As observed in the experiment, a variation of H2O2 concentration in the aqueous solution and other basic parameters of the process may induce the synthesis of gas with given H2：CO ratio for its further application in methanol or ammonia synthesis. In the latter process low CO concentration is required. Compared with the common high-temperature conversion of natural gas and further carbon oxide conversion on a catalyst, the current process promotes process simplification： the reaction is implemented at relatively low temperature （860-900 ℃ instead of 1400-1600 ℃for existing non-catalytic processes of methane conversion） and an additional unit for catalytic conversion of carbon oxide is excluded （in NH3 production）. The mechanism of chemical conjugation in the CH4-H2O2-H2O system was elucidated and the inducing effect of H2O2 decomposition on the desired （secondary） reaction was quantitavely estimated. An adequate kinetic model was formulated on the basis of the proposed free-radical scheme.
文摘A method for oxidative degradation of 1,4-dioxane （1,4-D） in waste water using a combination of ozone oxidation with UV irradiation （ozone/UV） treatment was investigated. The results showed that 1,4-D was degraded by ozone/UV treatment up to 90 min. The optimum concentration for the injected ozone gas was about 40 g·m^3 under a constant level of UV irradiation. Furthermore, solid phase extraction and GC-MS analysis showed no specific or reproducible peaks due to by-products of 1,4-D. It was therefore concluded that 1,4-D was completely degraded by ozone/UV treatment. In contrast, the amount of 1,4-D remaining decreased slowly in the presence of HCOf or CI. It was suggested that the degradation of 1,4-D, which results from .OH oxidation, was retarded by the presence of HCO3 or CI, which act as radical scavengers.
文摘Ir-催化不对称全合成吲哚生物碱（-）-Communesin F J.Am.Chem.Soc.2017,139,3364-3367吲哚生物碱Communesin家族是八个具有复杂七环系的天然产物.因具有独特的化学结构（四个氮原子构成罕见的上下两个aminal基团,外加两个连续手性季碳）和有趣的生物活性而成为明星分子,尤其是Communesin F的全合成备受化学家青睐,包括我国秦勇、
