针对新发展的管式连续结晶器和生产工艺,提出一种基于高斯过程回归(Gaussian Process Regression,GPR)的管式结晶器温度分布区间建模方法。通过测量DN15管式结晶器4个管段区间的温度,构建基于高斯过程回归的各区间温度分布模型。而且,...针对新发展的管式连续结晶器和生产工艺,提出一种基于高斯过程回归(Gaussian Process Regression,GPR)的管式结晶器温度分布区间建模方法。通过测量DN15管式结晶器4个管段区间的温度,构建基于高斯过程回归的各区间温度分布模型。而且,建立针对不同夹套流速操作条件的连续结晶管段温度分布预测模型,采用北方苍鹰优化算法确定模型中超参数,以提高模型预测准确性。通过L-谷氨酸连续结晶过程在不同夹套流速下的各管段温度分布测试实验,验证了本研究提出方法的有效性与优点。展开更多
In the cooling crystallization process of thiourea,a significant issue is the excessively wide crystal size distribution(CSD)and the abundance of fine crystals.This investigation delves into the growth kinetics and me...In the cooling crystallization process of thiourea,a significant issue is the excessively wide crystal size distribution(CSD)and the abundance of fine crystals.This investigation delves into the growth kinetics and mechanisms governing thiourea crystals during the cooling crystallization process.The fitting results indicate that the crystal growth rate coefficient,falls within the range of 10^(-7)to 10^(-8)m·s^(-1).Moreover,with decreasing crystallization temperature,the growth process undergoes a transition from diffusion-controlled to surface reaction-controlled,with temperature primarily influencing the surface reaction process and having a limited impact on the diffusion process.Comparing the crystal growth rate,and the diffusion-limited growth rate,at different temperatures,it is observed that the crystal growth process can be broadly divided into two stages.At temperatures above 25℃,1/qd(qd is diffusion control index)approaches 1,indicating the predominance of diffusion control.Conversely,at temperatures below 25℃,1/qd increases rapidly,signifying the dominance of surface reaction control.To address these findings,process optimization was conducted.During the high-temperature phase(35-25℃),agitation was increased to reduce the limitations posed by bulk-phase diffusion in the crystallization process.In the low-temperature phase(25-15℃),agitation was reduced to minimize crystal breakage.The optimized process resulted in a thiourea crystal product with a particle size distribution predominantly ranging from 0.7 to 0.9 mm,accounting for 84%of the total.This study provides valuable insights into resolving the issue of excessive fine crystals in the thiourea crystallization process.展开更多
Crystal habit and crystal form are critical elements in determining product properties and functions. In this work, we developed a microfluidic antisolvent crystallization technique to rapidly screen and accurately co...Crystal habit and crystal form are critical elements in determining product properties and functions. In this work, we developed a microfluidic antisolvent crystallization technique to rapidly screen and accurately control the solid form and crystal habit of triphenylmethanol(Ph_(3)COH). This advanced technique separates the primary mixing of solutions from crystal formation(nucleation and growth) by introducing the microfluidic device, avoiding clogging in microchannels to obtain high-quality crystals. The results show that we can achieve controllable preparation of pure 2Ph_(3)COH·DMSO(DMSO solvate), pure Ph_(3)COH(form β), and mixed crystals with different mass ratios. Moreover, the microscale can prompt the DMSO solvate to grow into hexagonal sheet-like and bulk crystals. We can regulate the aspect ratio of hexagonal sheet-like crystals in binary solvents and control the crystal habit of the form β to transition between long needle-like shapes and short hexagonal prisms in DMF-H_(2)O. Meanwhile, we revealed that the solvent ratio, the antisolvent flow rate, and the initial concentration of Ph_(3)COH are the main factors affecting the solid form selectivity and morphology transition. Such a novel method would be considered as a promising technique to be extended to screen and control key crystallization parameters of other substances.展开更多
In this work,we utilize a cocrystallization technique to solve the problem of high hygroscopicity of the high-energy oxidant ammonium dinitramide(ADN).For this purpose,a non-hygroscopic oxidant,triaminoguanidine nitra...In this work,we utilize a cocrystallization technique to solve the problem of high hygroscopicity of the high-energy oxidant ammonium dinitramide(ADN).For this purpose,a non-hygroscopic oxidant,triaminoguanidine nitrate(TAGN),is selected as the cocrystallization ligand.The ADN/TAGN system is simulated by using Material Studio 5.5 software,and the DFT of ADN and TAGN molecules are calculated by Gaussian09 software.The most stable molar ratio of the ADN/TAGN cocrystallization is determined to be 1:1,and the hydrogen bonding between the H atom of ADN and the O atom in the TAGN is the driving force for the formation of cocrystals in this system.Moreover,the electrostatic potential interaction pairing energy difference(ΔEpair)<0 kJ·mol^(-1)(-12.71 kJ·mol^(-1))for nADN:nTAGN=1:1 again indicates cocrystallization at this molar ratio.The crystal structure and crystal morphology is predicted.And the hygroscopicity of ADN/TAGN cocrystal at 20℃and 40%relative humidity is calculated to be only 0.45%.The mechanism of hygroscopicity is investigated by examining the roughness of each crystal surface.Overall,the more hygroscopic it is in terms of surface roughness,with the roughest crystal surface(012)having a hygroscopicity of 1.78,which corresponds to a saturated hygroscopicity of 0.61%.The results show that the(001)crystal surface has the smallest band gap(1.06 eV)and the largest sensitivity.Finally,the oxygen equilibrium value for the ADN/TAGN system is calculated to be-8.2%.展开更多
In this study,we prepared unentangled and slightly entangled poly(L-lactic acid)telechelic ionomer samples(Mn=5 and 16 kg/mol)based on sodium sulfonate groups.The telechelic samples exhibit extremely slow crystallizat...In this study,we prepared unentangled and slightly entangled poly(L-lactic acid)telechelic ionomer samples(Mn=5 and 16 kg/mol)based on sodium sulfonate groups.The telechelic samples exhibit extremely slow crystallization kinetics below the melting temperature T_(m) and above the glass transition temperature T_(g),which enables us to examine the linear viscoelasticity of the ionomer melt samples therein.The application of either the shear flow(at 85℃)or elongational flow(between 70 and 90℃)strongly accelerates the crystallization,leading to strong strain hardening and formation of highly orientedαcrystals.Depending on the relative average rates of the strain-induced dissociation and strain-induced crystallization,the stress evolution can be classified into two cases,and the critical work for strain-induced crystallization is higher in case where the strain-induced dissociation occurs earlier than the strain-induced crystallization.展开更多
文摘针对新发展的管式连续结晶器和生产工艺,提出一种基于高斯过程回归(Gaussian Process Regression,GPR)的管式结晶器温度分布区间建模方法。通过测量DN15管式结晶器4个管段区间的温度,构建基于高斯过程回归的各区间温度分布模型。而且,建立针对不同夹套流速操作条件的连续结晶管段温度分布预测模型,采用北方苍鹰优化算法确定模型中超参数,以提高模型预测准确性。通过L-谷氨酸连续结晶过程在不同夹套流速下的各管段温度分布测试实验,验证了本研究提出方法的有效性与优点。
基金supported by Priority Academic Program Development of Jiangsu Higher Educatior(PPZY2015A044).
文摘In the cooling crystallization process of thiourea,a significant issue is the excessively wide crystal size distribution(CSD)and the abundance of fine crystals.This investigation delves into the growth kinetics and mechanisms governing thiourea crystals during the cooling crystallization process.The fitting results indicate that the crystal growth rate coefficient,falls within the range of 10^(-7)to 10^(-8)m·s^(-1).Moreover,with decreasing crystallization temperature,the growth process undergoes a transition from diffusion-controlled to surface reaction-controlled,with temperature primarily influencing the surface reaction process and having a limited impact on the diffusion process.Comparing the crystal growth rate,and the diffusion-limited growth rate,at different temperatures,it is observed that the crystal growth process can be broadly divided into two stages.At temperatures above 25℃,1/qd(qd is diffusion control index)approaches 1,indicating the predominance of diffusion control.Conversely,at temperatures below 25℃,1/qd increases rapidly,signifying the dominance of surface reaction control.To address these findings,process optimization was conducted.During the high-temperature phase(35-25℃),agitation was increased to reduce the limitations posed by bulk-phase diffusion in the crystallization process.In the low-temperature phase(25-15℃),agitation was reduced to minimize crystal breakage.The optimized process resulted in a thiourea crystal product with a particle size distribution predominantly ranging from 0.7 to 0.9 mm,accounting for 84%of the total.This study provides valuable insights into resolving the issue of excessive fine crystals in the thiourea crystallization process.
基金supported by the National Natural Science Foundation of China (No.22278128)。
文摘Crystal habit and crystal form are critical elements in determining product properties and functions. In this work, we developed a microfluidic antisolvent crystallization technique to rapidly screen and accurately control the solid form and crystal habit of triphenylmethanol(Ph_(3)COH). This advanced technique separates the primary mixing of solutions from crystal formation(nucleation and growth) by introducing the microfluidic device, avoiding clogging in microchannels to obtain high-quality crystals. The results show that we can achieve controllable preparation of pure 2Ph_(3)COH·DMSO(DMSO solvate), pure Ph_(3)COH(form β), and mixed crystals with different mass ratios. Moreover, the microscale can prompt the DMSO solvate to grow into hexagonal sheet-like and bulk crystals. We can regulate the aspect ratio of hexagonal sheet-like crystals in binary solvents and control the crystal habit of the form β to transition between long needle-like shapes and short hexagonal prisms in DMF-H_(2)O. Meanwhile, we revealed that the solvent ratio, the antisolvent flow rate, and the initial concentration of Ph_(3)COH are the main factors affecting the solid form selectivity and morphology transition. Such a novel method would be considered as a promising technique to be extended to screen and control key crystallization parameters of other substances.
基金supported by the National Natural Science Foundation of China(22125802).
文摘In this work,we utilize a cocrystallization technique to solve the problem of high hygroscopicity of the high-energy oxidant ammonium dinitramide(ADN).For this purpose,a non-hygroscopic oxidant,triaminoguanidine nitrate(TAGN),is selected as the cocrystallization ligand.The ADN/TAGN system is simulated by using Material Studio 5.5 software,and the DFT of ADN and TAGN molecules are calculated by Gaussian09 software.The most stable molar ratio of the ADN/TAGN cocrystallization is determined to be 1:1,and the hydrogen bonding between the H atom of ADN and the O atom in the TAGN is the driving force for the formation of cocrystals in this system.Moreover,the electrostatic potential interaction pairing energy difference(ΔEpair)<0 kJ·mol^(-1)(-12.71 kJ·mol^(-1))for nADN:nTAGN=1:1 again indicates cocrystallization at this molar ratio.The crystal structure and crystal morphology is predicted.And the hygroscopicity of ADN/TAGN cocrystal at 20℃and 40%relative humidity is calculated to be only 0.45%.The mechanism of hygroscopicity is investigated by examining the roughness of each crystal surface.Overall,the more hygroscopic it is in terms of surface roughness,with the roughest crystal surface(012)having a hygroscopicity of 1.78,which corresponds to a saturated hygroscopicity of 0.61%.The results show that the(001)crystal surface has the smallest band gap(1.06 eV)and the largest sensitivity.Finally,the oxygen equilibrium value for the ADN/TAGN system is calculated to be-8.2%.
基金This work was financially supported by the National Natural Science Foundation of China(No.22173095).
文摘In this study,we prepared unentangled and slightly entangled poly(L-lactic acid)telechelic ionomer samples(Mn=5 and 16 kg/mol)based on sodium sulfonate groups.The telechelic samples exhibit extremely slow crystallization kinetics below the melting temperature T_(m) and above the glass transition temperature T_(g),which enables us to examine the linear viscoelasticity of the ionomer melt samples therein.The application of either the shear flow(at 85℃)or elongational flow(between 70 and 90℃)strongly accelerates the crystallization,leading to strong strain hardening and formation of highly orientedαcrystals.Depending on the relative average rates of the strain-induced dissociation and strain-induced crystallization,the stress evolution can be classified into two cases,and the critical work for strain-induced crystallization is higher in case where the strain-induced dissociation occurs earlier than the strain-induced crystallization.
