Density functional theory was employed to study the dehydration mechanism of MgCI_2·4H_2O. Analysis of potential energy surface(PES) of possible pathways indicated that the most possible way was one of the water ...Density functional theory was employed to study the dehydration mechanism of MgCI_2·4H_2O. Analysis of potential energy surface(PES) of possible pathways indicated that the most possible way was one of the water molecules halfly dissociated with an elongated bond distance with Mg^(2+),where electrostatic interaction played a leading role; another water molecule dissociated sequentially. It was in agreement with the result from differencial thermal analysis. The dehydration process of MgCI_2·4H_2O was clarified theoretically,promoting the theoretical study of dehydration of MgCI_2·2H_2O.展开更多
The present study investigated the vaporization kinetics of MgCl_2,CaCl_2 and their binary melts in a fluidized bed at1073-1273 K,and developed a vaporization model for the binary melts to explore the possibility of a...The present study investigated the vaporization kinetics of MgCl_2,CaCl_2 and their binary melts in a fluidized bed at1073-1273 K,and developed a vaporization model for the binary melts to explore the possibility of achieving enhanced vaporization rate for the feedstock containing CaO greater than 0.2 wt%.The vaporization rate constant of MgCl_2 is more than seven times than that of CaCl_2 at 1273 K.The vaporization rate of the binary melt was significantly affected by the composition,a small quantity of CaCl_2 can remarkably deteriorate the overall vaporization rate.Experimental results coincide well with the numerical simulation by the vaporization model which regards the evolution of vaporization rate with melts composition.A correlation between the necessary operation temperature and the CaO/(CaO + MgO) of the feedstock was proposed.Predictions reveal that a similar vaporization rate for 0.2 wt%-0.4 wt%CaO content feedstock with 0.2 wt%could be achieved at lower than 1365 K.展开更多
A novel MgCl2-supported Ziegler-Natta catalyst containing diethyl diisopropylsuccinate donor was prepared and propylene polymerizations with the combination of such catalyst and four external donors were investigated ...A novel MgCl2-supported Ziegler-Natta catalyst containing diethyl diisopropylsuccinate donor was prepared and propylene polymerizations with the combination of such catalyst and four external donors were investigated in detail. The catalyst was compared with a commercial one with phthalate as internal donor in terms of catalytic activity, hydrogen sensitivity and stereospecificity in propylene polymerization. The molecular weight,molecular weight distribution and microstructure of the produced polypropylenes were compared also. It was found that the novel catalyst containing succinate internal donor showed higher activity and higher stereospecificity than those with phthalate as internal donor. Consequently, polypropylenes obtained by the succinate-based catalyst showed high molecular weight, high melting temperature, high isotactic index and broad molecular weight distribution than those obtained with the commercial catalyst.展开更多
The hydrolysis of MgH_(2) delivers high hydrogen capacity(15.2 wt%),which is very attractive for real-time hydrogen supply.However,the formation of a surface passivation Mg(OH)_(2) layer and the large excess of H_(2)O...The hydrolysis of MgH_(2) delivers high hydrogen capacity(15.2 wt%),which is very attractive for real-time hydrogen supply.However,the formation of a surface passivation Mg(OH)_(2) layer and the large excess of H_(2)O required to ensure complete hydrolysis are two key challenges for the MgH_(2) hydrolysis systems.Now,a low-cost method is reported to synthesize MgH_(2)@Mg(BH_(4))_(2) composite via ball-milling MgH_(2) with cheap and widely available B2O_(3)(or B(OH)3).By adding small amounts of B2O_(3),the in-situ formed Mg(BH_(4))_(2) could significantly promote the hydrolysis of MgH_(2).In particular,the MgH_(2)–10 wt%B2O_(3) composite releases 1330.7 mL·g^(−1) H_(2)(close to 80%theoretical hydrogen generation H_(2))in H_(2)O and 1520.4 mL·g^(−1) H_(2)(about 95%)in 0.5 M MgCl2 in 60 min at 26℃ with hydrolysis rate of 736.9 mL·g^(−1)·min^(−1) and 960.9 mL·g^(−1)·min^(−1) H_(2) during the first minute of the hydrolysis,respectively.In addition,the MgCl2 solution allows repeated use by filtering and exhibits high cycle stability(20 cycles),therefore leading to much reduced capacity loss caused by the excess H_(2)O.We show that by introducing B2O_(3) and recycling the 0.5 M MgCl2 solution,the system hydrogen capacity can approach 5.9 wt%,providing a promising hydrogen generation scheme to supply hydrogen to the fuel cells.展开更多
基金supported by the National Natural Science Foundation of China(No.21361021)
文摘Density functional theory was employed to study the dehydration mechanism of MgCI_2·4H_2O. Analysis of potential energy surface(PES) of possible pathways indicated that the most possible way was one of the water molecules halfly dissociated with an elongated bond distance with Mg^(2+),where electrostatic interaction played a leading role; another water molecule dissociated sequentially. It was in agreement with the result from differencial thermal analysis. The dehydration process of MgCI_2·4H_2O was clarified theoretically,promoting the theoretical study of dehydration of MgCI_2·2H_2O.
基金Supported by the National Natural Science Foundation of China(NSFC)Distinguished Young Scholar project(No.21325628)
文摘The present study investigated the vaporization kinetics of MgCl_2,CaCl_2 and their binary melts in a fluidized bed at1073-1273 K,and developed a vaporization model for the binary melts to explore the possibility of achieving enhanced vaporization rate for the feedstock containing CaO greater than 0.2 wt%.The vaporization rate constant of MgCl_2 is more than seven times than that of CaCl_2 at 1273 K.The vaporization rate of the binary melt was significantly affected by the composition,a small quantity of CaCl_2 can remarkably deteriorate the overall vaporization rate.Experimental results coincide well with the numerical simulation by the vaporization model which regards the evolution of vaporization rate with melts composition.A correlation between the necessary operation temperature and the CaO/(CaO + MgO) of the feedstock was proposed.Predictions reveal that a similar vaporization rate for 0.2 wt%-0.4 wt%CaO content feedstock with 0.2 wt%could be achieved at lower than 1365 K.
文摘A novel MgCl2-supported Ziegler-Natta catalyst containing diethyl diisopropylsuccinate donor was prepared and propylene polymerizations with the combination of such catalyst and four external donors were investigated in detail. The catalyst was compared with a commercial one with phthalate as internal donor in terms of catalytic activity, hydrogen sensitivity and stereospecificity in propylene polymerization. The molecular weight,molecular weight distribution and microstructure of the produced polypropylenes were compared also. It was found that the novel catalyst containing succinate internal donor showed higher activity and higher stereospecificity than those with phthalate as internal donor. Consequently, polypropylenes obtained by the succinate-based catalyst showed high molecular weight, high melting temperature, high isotactic index and broad molecular weight distribution than those obtained with the commercial catalyst.
基金supported by the Basic and Applied Basic Research Foundation of Guangdong Province(No.2022A1515011832 and 2021A1515110676)supported by GDAS’Project of Science and Technology Development(2022GDASZH-2022010104,2022GDASZH-2022030604-04).
文摘The hydrolysis of MgH_(2) delivers high hydrogen capacity(15.2 wt%),which is very attractive for real-time hydrogen supply.However,the formation of a surface passivation Mg(OH)_(2) layer and the large excess of H_(2)O required to ensure complete hydrolysis are two key challenges for the MgH_(2) hydrolysis systems.Now,a low-cost method is reported to synthesize MgH_(2)@Mg(BH_(4))_(2) composite via ball-milling MgH_(2) with cheap and widely available B2O_(3)(or B(OH)3).By adding small amounts of B2O_(3),the in-situ formed Mg(BH_(4))_(2) could significantly promote the hydrolysis of MgH_(2).In particular,the MgH_(2)–10 wt%B2O_(3) composite releases 1330.7 mL·g^(−1) H_(2)(close to 80%theoretical hydrogen generation H_(2))in H_(2)O and 1520.4 mL·g^(−1) H_(2)(about 95%)in 0.5 M MgCl2 in 60 min at 26℃ with hydrolysis rate of 736.9 mL·g^(−1)·min^(−1) and 960.9 mL·g^(−1)·min^(−1) H_(2) during the first minute of the hydrolysis,respectively.In addition,the MgCl2 solution allows repeated use by filtering and exhibits high cycle stability(20 cycles),therefore leading to much reduced capacity loss caused by the excess H_(2)O.We show that by introducing B2O_(3) and recycling the 0.5 M MgCl2 solution,the system hydrogen capacity can approach 5.9 wt%,providing a promising hydrogen generation scheme to supply hydrogen to the fuel cells.
基金This study was supported by the National Natural Science Foundation of China （Nos. 51374138, 51174125, 51234003）, National Science and Technology Support Plan of China （No. 2013BAC14B02）, and Key Scientific and Technical Project con- cerned with coal-bearing resources in Shanxi province （No. MC2014-06）.
