Frontal polymerization (FP) is a mode of converting monomers into polymers via a localized reaction zone that propagates through the reaction system.The three reactants,polyether,toluene 2,4-diisocyanate and 1,4-butan...Frontal polymerization (FP) is a mode of converting monomers into polymers via a localized reaction zone that propagates through the reaction system.The three reactants,polyether,toluene 2,4-diisocyanate and 1,4-butanediol and the catalyst (stannous caprylate) were mixed together at room temperature along with nanosilica sol and dimethylbenzene (as the solvent).After the thermal ignition at one end of the tubular reactor and subsequent front formation,no further energy was required for polymerization to occur.The thermal front self-propagated throughout the vessel.The effect of different molecular weights of polyether and different concentration of catalyst on frontal polymerization were investigated,along with a comparison of frontal polymerization with batch polymerization.FT-IR,TEM and TGA were employed to characterize the polyurethane (PU) hybrids.The obtained polymer materials by FP displayed similar features compared with those obtained by batch polymerization (BP).The reaction time of FP is quite less than that of BP during preparing the PU hybrids.Nanosilica sol can be well dispersed in the polyurethane hybrid matrix even though no any stirring occurs during the FP process.展开更多
The paper chiefly compares the catalytic activity and stability of nano-sized nickel and Raney nickel in the catalytic hydrogenation of p-nitrophenol.The experimental results show that the catalytic activity and stabi...The paper chiefly compares the catalytic activity and stability of nano-sized nickel and Raney nickel in the catalytic hydrogenation of p-nitrophenol.The experimental results show that the catalytic activity and stability of nano-sized nickel are superior to those of Raney nickel under the same reaction conditions. The fresh and used nickel samples are characterized by nitrogen sorption and particle analyzer. The results suggest that particle size,surface structure,etc. may play a key role in determining the catalytic activity of nickel samples.The aggregation of nano-particles would lead to the deactivation of nano-sized nickel,while the jamming of pores would be one of the reasons for the deactivation of Raney nickel.展开更多
A new submerged membrane emulsification apparatus using ceramic external membrane was introduced, which is attractive due to its simplicity, lower energy consumption, easier to integrate with other processes and scale...A new submerged membrane emulsification apparatus using ceramic external membrane was introduced, which is attractive due to its simplicity, lower energy consumption, easier to integrate with other processes and scale-up. Using different pore size membranes, O/W emulsions with different particle sizes were prepared. The O/W emulsion with Sauter mean particle size of 1.98μm was obtained by using 0.69μm ceramic external membrane element, and the emulsion with Sauter mean particle size of 0.65μm was obtained by using 0.16μm external membrane element. The specific surface areas were respectively 3.78m 2·g -1and 10.8m 2·g -1, fit for extractive reaction and biphasic reaction.展开更多
文摘Frontal polymerization (FP) is a mode of converting monomers into polymers via a localized reaction zone that propagates through the reaction system.The three reactants,polyether,toluene 2,4-diisocyanate and 1,4-butanediol and the catalyst (stannous caprylate) were mixed together at room temperature along with nanosilica sol and dimethylbenzene (as the solvent).After the thermal ignition at one end of the tubular reactor and subsequent front formation,no further energy was required for polymerization to occur.The thermal front self-propagated throughout the vessel.The effect of different molecular weights of polyether and different concentration of catalyst on frontal polymerization were investigated,along with a comparison of frontal polymerization with batch polymerization.FT-IR,TEM and TGA were employed to characterize the polyurethane (PU) hybrids.The obtained polymer materials by FP displayed similar features compared with those obtained by batch polymerization (BP).The reaction time of FP is quite less than that of BP during preparing the PU hybrids.Nanosilica sol can be well dispersed in the polyurethane hybrid matrix even though no any stirring occurs during the FP process.
文摘The paper chiefly compares the catalytic activity and stability of nano-sized nickel and Raney nickel in the catalytic hydrogenation of p-nitrophenol.The experimental results show that the catalytic activity and stability of nano-sized nickel are superior to those of Raney nickel under the same reaction conditions. The fresh and used nickel samples are characterized by nitrogen sorption and particle analyzer. The results suggest that particle size,surface structure,etc. may play a key role in determining the catalytic activity of nickel samples.The aggregation of nano-particles would lead to the deactivation of nano-sized nickel,while the jamming of pores would be one of the reasons for the deactivation of Raney nickel.
文摘A new submerged membrane emulsification apparatus using ceramic external membrane was introduced, which is attractive due to its simplicity, lower energy consumption, easier to integrate with other processes and scale-up. Using different pore size membranes, O/W emulsions with different particle sizes were prepared. The O/W emulsion with Sauter mean particle size of 1.98μm was obtained by using 0.69μm ceramic external membrane element, and the emulsion with Sauter mean particle size of 0.65μm was obtained by using 0.16μm external membrane element. The specific surface areas were respectively 3.78m 2·g -1and 10.8m 2·g -1, fit for extractive reaction and biphasic reaction.
