After the Big Bang,chemical reactions of hydrogen with LiH and its isotopic variants played an important role in the late stage of recombination.Moreover,these reactions have attracted the attention of experts in the ...After the Big Bang,chemical reactions of hydrogen with LiH and its isotopic variants played an important role in the late stage of recombination.Moreover,these reactions have attracted the attention of experts in the field of molecular dynamics because of its simple structure.Electronically non-adiabatic effects play a key role in many chemical reactions,while the related studies in LiH2 reactive system and its isotopic variants are not enough,so the microscopic mechanism of this system has not been fully explored.In this work,the microscopic mechanism of H+LiD reaction are performed by comparing both the adiabatic and non-adiabatic results to study the non-adiabatic effects.The reactivity of R1(H+LiD→Li+HD)channel is inhibited,while that of R2(H+LiD→D+LiH)channel is enhanced when the non-adiabatic couplings are considered.For R1 channel,a direct stripping process dominates this channel and the main reaction mechanism is not influenced by the non-adiabatic effects.For R2 channel,at relatively low collision energy,the dominance changes from a rebound process to the complex-forming mechanism when the non-adiabatic effects are considered,whereas the rebound collision approach still dominates the reaction at relatively high collision energy in both calculations.The presented results provide a basis for further detailed study on this importantly astrophysical reaction system.展开更多
A new material with heat-resistant and adiabatic characteristics and high strength was prepared using the combustion synthesis method by mixed powders of CrO3, Al, Al2O3, and NaF in atmospheric gas. The reaction dynam...A new material with heat-resistant and adiabatic characteristics and high strength was prepared using the combustion synthesis method by mixed powders of CrO3, Al, Al2O3, and NaF in atmospheric gas. The reaction dynamic process of the Al-CrO3-NaF-Al2O3-N2-O2 new material system by the combustion synthesis method was discussed based on the observation results by SEM, EDS, and XRD in combination with the combustion front quenching method （CFQM） and the relation curves between reaction free enthalpies and the corresponding temperatures. The combustion synthesis mechanism and the formation reasons of the phase in the combustion product were analyzed.展开更多
The kinetics of dibutyltin dilaurate(DBTDL) catalyzed fast urethane polymerization of polyoxypropylenepolyoxyethlene triol with uretonimine modified 4, 4’-diphenylmethane diisocyanate (l-MDI) in RIM was studied by in...The kinetics of dibutyltin dilaurate(DBTDL) catalyzed fast urethane polymerization of polyoxypropylenepolyoxyethlene triol with uretonimine modified 4, 4’-diphenylmethane diisocyanate (l-MDI) in RIM was studied by infrared spectroscopy and adiabatic temperature rise. For isothermal reaction, the overall reaction order was found to change from 3/2 to 2 with increasing reaction temperature. For adiabatic reaction, the overall reaction order was found to change from 3/2 to 2 with increasing catalyst concentration and hard segment content. The phase separation occured during the RIM urethane polymerization leads to a deviation of the kinetics relationships for higher conversion from those for lower.展开更多
In the field of adiabatic correction for complex reactions,a simple one-stage kinetic model was used to estimate the real reaction kinetics.However,this assumption simplified the real process,inevitably generated inac...In the field of adiabatic correction for complex reactions,a simple one-stage kinetic model was used to estimate the real reaction kinetics.However,this assumption simplified the real process,inevitably generated inaccurate or even unsafe results.Therefore,it was necessary to find a new correction method for complex reactions.In this work,esterification of acetic anhydride by methanol was chosen as an object reaction of study.The reaction was studied under different conditions by Reaction Calorimeter(RC1).Then,Thermal Safety Software(TSS)was used to establish the kinetic model and estimate the parameters,where,activation energies for three stages were67.09,81.02,73.77 kJ?mol^(-1)respectively,and corresponding frequency factors in logarithmic form were 16.05,19.59,15.72 s^(-1).In addition,two adiabatic tests were performed by Vent Sizing Package2(VSP2).For accurate correction of VSP2 tests,a new correction method based on Enhanced Fisher method was proposed.Combined with kinetics,adiabatic correction of esterification reaction was achieved.Through this research,accurate kinetic parameters for a three-step kinetic model of the esterification reaction were acquired.Furthermore,the correlation coefficients between simulated curves and corrected curves were 0.976 and 0.968,which proved the accuracy of proposed new adiabatic correction method.Based on this new method,conservative corrected results were able to be acquired and be applied in safety assessment.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11774043).
文摘After the Big Bang,chemical reactions of hydrogen with LiH and its isotopic variants played an important role in the late stage of recombination.Moreover,these reactions have attracted the attention of experts in the field of molecular dynamics because of its simple structure.Electronically non-adiabatic effects play a key role in many chemical reactions,while the related studies in LiH2 reactive system and its isotopic variants are not enough,so the microscopic mechanism of this system has not been fully explored.In this work,the microscopic mechanism of H+LiD reaction are performed by comparing both the adiabatic and non-adiabatic results to study the non-adiabatic effects.The reactivity of R1(H+LiD→Li+HD)channel is inhibited,while that of R2(H+LiD→D+LiH)channel is enhanced when the non-adiabatic couplings are considered.For R1 channel,a direct stripping process dominates this channel and the main reaction mechanism is not influenced by the non-adiabatic effects.For R2 channel,at relatively low collision energy,the dominance changes from a rebound process to the complex-forming mechanism when the non-adiabatic effects are considered,whereas the rebound collision approach still dominates the reaction at relatively high collision energy in both calculations.The presented results provide a basis for further detailed study on this importantly astrophysical reaction system.
基金the National High-Tech Research and Development Program of China (863 Program) (No. 2006AA03Z351).
文摘A new material with heat-resistant and adiabatic characteristics and high strength was prepared using the combustion synthesis method by mixed powders of CrO3, Al, Al2O3, and NaF in atmospheric gas. The reaction dynamic process of the Al-CrO3-NaF-Al2O3-N2-O2 new material system by the combustion synthesis method was discussed based on the observation results by SEM, EDS, and XRD in combination with the combustion front quenching method （CFQM） and the relation curves between reaction free enthalpies and the corresponding temperatures. The combustion synthesis mechanism and the formation reasons of the phase in the combustion product were analyzed.
文摘The kinetics of dibutyltin dilaurate(DBTDL) catalyzed fast urethane polymerization of polyoxypropylenepolyoxyethlene triol with uretonimine modified 4, 4’-diphenylmethane diisocyanate (l-MDI) in RIM was studied by infrared spectroscopy and adiabatic temperature rise. For isothermal reaction, the overall reaction order was found to change from 3/2 to 2 with increasing reaction temperature. For adiabatic reaction, the overall reaction order was found to change from 3/2 to 2 with increasing catalyst concentration and hard segment content. The phase separation occured during the RIM urethane polymerization leads to a deviation of the kinetics relationships for higher conversion from those for lower.
文摘In the field of adiabatic correction for complex reactions,a simple one-stage kinetic model was used to estimate the real reaction kinetics.However,this assumption simplified the real process,inevitably generated inaccurate or even unsafe results.Therefore,it was necessary to find a new correction method for complex reactions.In this work,esterification of acetic anhydride by methanol was chosen as an object reaction of study.The reaction was studied under different conditions by Reaction Calorimeter(RC1).Then,Thermal Safety Software(TSS)was used to establish the kinetic model and estimate the parameters,where,activation energies for three stages were67.09,81.02,73.77 kJ?mol^(-1)respectively,and corresponding frequency factors in logarithmic form were 16.05,19.59,15.72 s^(-1).In addition,two adiabatic tests were performed by Vent Sizing Package2(VSP2).For accurate correction of VSP2 tests,a new correction method based on Enhanced Fisher method was proposed.Combined with kinetics,adiabatic correction of esterification reaction was achieved.Through this research,accurate kinetic parameters for a three-step kinetic model of the esterification reaction were acquired.Furthermore,the correlation coefficients between simulated curves and corrected curves were 0.976 and 0.968,which proved the accuracy of proposed new adiabatic correction method.Based on this new method,conservative corrected results were able to be acquired and be applied in safety assessment.
