A series of Zn–Ca–Al oxides with different CaO and ZnO contents have been prepared and evaluated in the synthesis of propylene carbonate(PC) from 1,2-propylene glycol(PG) and urea in a batch reactor. The effect of c...A series of Zn–Ca–Al oxides with different CaO and ZnO contents have been prepared and evaluated in the synthesis of propylene carbonate(PC) from 1,2-propylene glycol(PG) and urea in a batch reactor. The effect of catalyst composition, basicity and reaction process parameters such as temperature, catalyst dose, molar ratio of PG to urea, purge gas flow and reaction time has been studied to find suitable reaction conditions for the PC synthesis. The PC selectivity and yield under the desired conditions could reach 98.4% and 90.8%, respectively. The best performing catalyst also exhibited a good reusability without appreciable loss in the PC selectivity and yield after five consecutive reaction runs. In addition, a stepwise reaction pathway involving a 2-hydroxypropyl carbamate intermediate was proposed for the urea alcoholysis to PC in the presence of Zn–Ca–Al catalysts, according to the time dependences of reaction intermediates and products.展开更多
The effect of stabilizing elements, such as Nb and Ti, on the microstructure and properties of low carbon ferritic stainless steel （FSS） has been investigated. The results of the Thermo-calc simulation have shown th...The effect of stabilizing elements, such as Nb and Ti, on the microstructure and properties of low carbon ferritic stainless steel （FSS） has been investigated. The results of the Thermo-calc simulation have shown that the interstitial elements, such as C and N, may be completely stabilized by the addition of Nb and Ti. With the increase of Nb and Ti contents ,the α ＋ γ two phases gradually transfer to a single α-phase under a high temperature condition ,and the content of the carbide M23 C6 gradually decreases. The microstructure has indicated that the combined addition of Nb and Ti can promote the recrystallization of the band structure and form more uniform equiaxed grains. Also, with the increase of Nb and Ti contents,the elongation, the r-value and the corrosion resistance of cold-rolled and annealed sheets are improved prominently. In comparison with the effect of Ti ,the addition of Nb is more beneficial to the increase of r-value and the corrosion resistance.展开更多
The objective of this study is to investigate the adsorption characteristics of granular activated carbon GAC/R-134a pair in the temperature range of 20℃?- 60℃?and pressure up to 10 bars. The Dubinin-Astakhov adsorp...The objective of this study is to investigate the adsorption characteristics of granular activated carbon GAC/R-134a pair in the temperature range of 20℃?- 60℃?and pressure up to 10 bars. The Dubinin-Astakhov adsorption equilibrium model is fit to experimental data with acceptable error limit. The pressure-temperature-concentration (P-T-X) diagram of the pair is also presented. The isosteric heat of adsorption of R-134a on activated carbon has been calculated using the Clausius-Clapeyron equation as a function of adsorption capacity. The maximum adsorption capacity was found to be 1.92 kgR134a/kg carbon at 20℃?after 1200 s. The experimental results also show that the increase of heat transfer area improves the adsorption capacity per kg of adsorber, which leads to the design of a finned tubes heat exchanger adsorption unit.展开更多
In order to improve the flexibility of poly（propylene carbonate） （PPC）, poly（1,2-propylene succinate） （PPSu） was used to plasticize PPC in a batch mixer. The effects of PPSu on the miscibility, thermal stabili...In order to improve the flexibility of poly（propylene carbonate） （PPC）, poly（1,2-propylene succinate） （PPSu） was used to plasticize PPC in a batch mixer. The effects of PPSu on the miscibility, thermal stability, mechanical and theological properties of the blends were investigated. PPC was partially miscible with PPSu. It was demonstrated that PPSu decreased the glass transition temperature and melt viscosity of PPC, as shown in the DSC and rheological curves. With the increase in PPSu content, the PPC/PPSu blends showed decreased tensile strength, however, the elongation at break was increased to 1100% for the 70/30 PPC/PPSu blend. The introduction of PPSu provided an efficient and novel plasticization method to extend the application area of PPC.展开更多
To facilitate the recovery of Pb/SiO_(2) catalyst,magnetic Pb/Fe_(3)O_(4)/SiO_(2) samples were prepared separately by emulsification,sol-gel and incipient impregnation methods.The catalyst samples were characterized b...To facilitate the recovery of Pb/SiO_(2) catalyst,magnetic Pb/Fe_(3)O_(4)/SiO_(2) samples were prepared separately by emulsification,sol-gel and incipient impregnation methods.The catalyst samples were characterized by means of X-ray diffraction and N_(2) adsorption-desorption,and their catalytic activity was investigated in the reaction for synthesizing propylene carbonate from urea and 1,2-propylene glycol.When the gelatin was applied in the preparation of Fe_(3)O_(4) at 60℃ and the pH value was controlled at 4 in the preparation of Fe_(3)O_(4)/SiO_(2),the Pb/Fe_(3)O_(4)/SiO_(2) sample shows good catalytic activity and magnetism.Under the reaction conditions of a reaction temperature of 180℃,reaction time of 2h,catalyst percentage of 1.7 wt-% and a molar ratio of urea to PG of 1∶4,the yield of propylene carbonate attained was 87.7%.展开更多
基金Supported by the Changcheng Scholars Program of Beijing(CIT&TCD 20150316)
文摘A series of Zn–Ca–Al oxides with different CaO and ZnO contents have been prepared and evaluated in the synthesis of propylene carbonate(PC) from 1,2-propylene glycol(PG) and urea in a batch reactor. The effect of catalyst composition, basicity and reaction process parameters such as temperature, catalyst dose, molar ratio of PG to urea, purge gas flow and reaction time has been studied to find suitable reaction conditions for the PC synthesis. The PC selectivity and yield under the desired conditions could reach 98.4% and 90.8%, respectively. The best performing catalyst also exhibited a good reusability without appreciable loss in the PC selectivity and yield after five consecutive reaction runs. In addition, a stepwise reaction pathway involving a 2-hydroxypropyl carbamate intermediate was proposed for the urea alcoholysis to PC in the presence of Zn–Ca–Al catalysts, according to the time dependences of reaction intermediates and products.
基金funded by the CITIC-CBMM R & D Subject Foundation(2010-D046).
文摘The effect of stabilizing elements, such as Nb and Ti, on the microstructure and properties of low carbon ferritic stainless steel （FSS） has been investigated. The results of the Thermo-calc simulation have shown that the interstitial elements, such as C and N, may be completely stabilized by the addition of Nb and Ti. With the increase of Nb and Ti contents ,the α ＋ γ two phases gradually transfer to a single α-phase under a high temperature condition ,and the content of the carbide M23 C6 gradually decreases. The microstructure has indicated that the combined addition of Nb and Ti can promote the recrystallization of the band structure and form more uniform equiaxed grains. Also, with the increase of Nb and Ti contents,the elongation, the r-value and the corrosion resistance of cold-rolled and annealed sheets are improved prominently. In comparison with the effect of Ti ,the addition of Nb is more beneficial to the increase of r-value and the corrosion resistance.
文摘The objective of this study is to investigate the adsorption characteristics of granular activated carbon GAC/R-134a pair in the temperature range of 20℃?- 60℃?and pressure up to 10 bars. The Dubinin-Astakhov adsorption equilibrium model is fit to experimental data with acceptable error limit. The pressure-temperature-concentration (P-T-X) diagram of the pair is also presented. The isosteric heat of adsorption of R-134a on activated carbon has been calculated using the Clausius-Clapeyron equation as a function of adsorption capacity. The maximum adsorption capacity was found to be 1.92 kgR134a/kg carbon at 20℃?after 1200 s. The experimental results also show that the increase of heat transfer area improves the adsorption capacity per kg of adsorber, which leads to the design of a finned tubes heat exchanger adsorption unit.
基金financially supported by the Science&Technology Bureau of Jilin Province of China(No.20126023)the National High Technology Research and Development Program of China(863 Program)(No.2012AA062904)the National Natural Science Foundation of China(No.51021003)
文摘In order to improve the flexibility of poly（propylene carbonate） （PPC）, poly（1,2-propylene succinate） （PPSu） was used to plasticize PPC in a batch mixer. The effects of PPSu on the miscibility, thermal stability, mechanical and theological properties of the blends were investigated. PPC was partially miscible with PPSu. It was demonstrated that PPSu decreased the glass transition temperature and melt viscosity of PPC, as shown in the DSC and rheological curves. With the increase in PPSu content, the PPC/PPSu blends showed decreased tensile strength, however, the elongation at break was increased to 1100% for the 70/30 PPC/PPSu blend. The introduction of PPSu provided an efficient and novel plasticization method to extend the application area of PPC.
基金This work has been supported by the National Natural Science Foundation of China(Grant No.20576025)the Hebei Provincial Fund for Natural Science(B2007000010).
文摘To facilitate the recovery of Pb/SiO_(2) catalyst,magnetic Pb/Fe_(3)O_(4)/SiO_(2) samples were prepared separately by emulsification,sol-gel and incipient impregnation methods.The catalyst samples were characterized by means of X-ray diffraction and N_(2) adsorption-desorption,and their catalytic activity was investigated in the reaction for synthesizing propylene carbonate from urea and 1,2-propylene glycol.When the gelatin was applied in the preparation of Fe_(3)O_(4) at 60℃ and the pH value was controlled at 4 in the preparation of Fe_(3)O_(4)/SiO_(2),the Pb/Fe_(3)O_(4)/SiO_(2) sample shows good catalytic activity and magnetism.Under the reaction conditions of a reaction temperature of 180℃,reaction time of 2h,catalyst percentage of 1.7 wt-% and a molar ratio of urea to PG of 1∶4,the yield of propylene carbonate attained was 87.7%.
