A facile and efficient procedure has been developed systematically for the oxidative cleavage of cinna-maldehyde to benzaldehyde by sodium hypochlorite with water as the only solvent in the presence of β-cyclodextrin...A facile and efficient procedure has been developed systematically for the oxidative cleavage of cinna-maldehyde to benzaldehyde by sodium hypochlorite with water as the only solvent in the presence of β-cyclodextrin （abbreviated as β-CD）. Different factors influencing cinnamaldehyde oxidation e.g. reaction temperature, the amount of catalyst and oxidant, have been investigated. The yield of benzaldehyde reaches 76% under the optimum conditions （333 K, 4 h, molar ratio of cinnamaldehyde to β-CD is 1：1）. Furthermore, a feasible reaction mecha-nism including the formation of benzaldehyde and the two main byproducts （phenylacetaldehyde and epoxide of cinnamaldehyde） has been proposed.展开更多
A water leakage on the surface of heat transfer tube in a steam generator of sodium-cooled fast reactor causes SWR （sodium-water reaction）. The SWR damages the leak surface and gives rise to the leak enlargement. Mo...A water leakage on the surface of heat transfer tube in a steam generator of sodium-cooled fast reactor causes SWR （sodium-water reaction）. The SWR damages the leak surface and gives rise to the leak enlargement. Most of initial leakage starts from micro leak （less than 0.5 g/s）. However, the leak rate increases more than two orders of magnitude and the resultant leak damages surrounding heat transfer tubes and it brings secondary failure of the heat transfer tube. Evaluation of the leak enlargement is necessary to assess the leak rate increase, so that evaluate the possibility of secondary failure. In this study, a simulant experiment, which uses neutralization reaction, is proposed to reproduce the leak enlargement. To examine the feasibility of the experiment, numerical simulations are carried out. From the result, a funnel-shaped nozzle enlargement is observed and the shape similar to the shape of the enlarged nozzle from the SWAT （sodium-water reaction test loop） experiment.展开更多
Birnessite occurs in a wide variety of natural environments, and plays animportant role in soil chemistry. A modified Staehli procedure was used to synthesize sodiumbirnessite in an alkali medium by O_2 oxidation. The...Birnessite occurs in a wide variety of natural environments, and plays animportant role in soil chemistry. A modified Staehli procedure was used to synthesize sodiumbirnessite in an alkali medium by O_2 oxidation. The effects of preparative parameters on thesynthesis of birnessite, such as pretreatment on solutions with N2, reaction temperature, O_2 flowrate, fluxion velocity of the reaction suspension, and dehydration conditions were investigated. Thefluxion velocity of the reactive suspension and O_2 flow rate significantly influenced thesynthesis of birnessite. Vigorous stirring raised the fluxion velocity of the reaction suspensionand easily allowed synthesis of pure crystalline birnessite. However pretreatment of the reactingsolutions with N_2 and the reaction temperature had little effect on the synthesis. Diffusion of O_2was the controlling step during the course of oxidation. The optimum synthetic conditions for purebirnessite were: a NaOH to Mn molar ratio of 13.7, an O_2 flow rate of 2 L min^(-1), and oxidationfor 5 hours with vigorous stirring at normal temperatures. The chemical composition of thesynthesized pure birnessite was Na_(0.25)MnO_(2.07)·0.66H_2O.展开更多
基金Supported by the National＇Natural Science Foundation of China （21036009, 21176268）, the Higher-level Talent Project tor Guangdong Provincial Universities and the Fundamental.Research Funds for the Central Universities.
文摘A facile and efficient procedure has been developed systematically for the oxidative cleavage of cinna-maldehyde to benzaldehyde by sodium hypochlorite with water as the only solvent in the presence of β-cyclodextrin （abbreviated as β-CD）. Different factors influencing cinnamaldehyde oxidation e.g. reaction temperature, the amount of catalyst and oxidant, have been investigated. The yield of benzaldehyde reaches 76% under the optimum conditions （333 K, 4 h, molar ratio of cinnamaldehyde to β-CD is 1：1）. Furthermore, a feasible reaction mecha-nism including the formation of benzaldehyde and the two main byproducts （phenylacetaldehyde and epoxide of cinnamaldehyde） has been proposed.
文摘A water leakage on the surface of heat transfer tube in a steam generator of sodium-cooled fast reactor causes SWR （sodium-water reaction）. The SWR damages the leak surface and gives rise to the leak enlargement. Most of initial leakage starts from micro leak （less than 0.5 g/s）. However, the leak rate increases more than two orders of magnitude and the resultant leak damages surrounding heat transfer tubes and it brings secondary failure of the heat transfer tube. Evaluation of the leak enlargement is necessary to assess the leak rate increase, so that evaluate the possibility of secondary failure. In this study, a simulant experiment, which uses neutralization reaction, is proposed to reproduce the leak enlargement. To examine the feasibility of the experiment, numerical simulations are carried out. From the result, a funnel-shaped nozzle enlargement is observed and the shape similar to the shape of the enlarged nozzle from the SWAT （sodium-water reaction test loop） experiment.
基金Project supported by the National Natural Science Foundation of China (Nos. 40101017 and 40071048) the Senior Visitor Foundation of Chinese Educational Ministry.
文摘Birnessite occurs in a wide variety of natural environments, and plays animportant role in soil chemistry. A modified Staehli procedure was used to synthesize sodiumbirnessite in an alkali medium by O_2 oxidation. The effects of preparative parameters on thesynthesis of birnessite, such as pretreatment on solutions with N2, reaction temperature, O_2 flowrate, fluxion velocity of the reaction suspension, and dehydration conditions were investigated. Thefluxion velocity of the reactive suspension and O_2 flow rate significantly influenced thesynthesis of birnessite. Vigorous stirring raised the fluxion velocity of the reaction suspensionand easily allowed synthesis of pure crystalline birnessite. However pretreatment of the reactingsolutions with N_2 and the reaction temperature had little effect on the synthesis. Diffusion of O_2was the controlling step during the course of oxidation. The optimum synthetic conditions for purebirnessite were: a NaOH to Mn molar ratio of 13.7, an O_2 flow rate of 2 L min^(-1), and oxidationfor 5 hours with vigorous stirring at normal temperatures. The chemical composition of thesynthesized pure birnessite was Na_(0.25)MnO_(2.07)·0.66H_2O.
