Porous SnO2 nanocrystalline thin films were successfully electrodeposited from an oxygen-saturated acid aqueous solution of SnCl2 containing different concentrations of butyl-rhodamine B（BRhB） at 70℃.BRhB with subs...Porous SnO2 nanocrystalline thin films were successfully electrodeposited from an oxygen-saturated acid aqueous solution of SnCl2 containing different concentrations of butyl-rhodamine B（BRhB） at 70℃.BRhB with substitute of amidocyanogen can be dissolved in the acid deposition solution,where HCl was added to suppress hydrolysis of SnCl2.So it was used as a structure-directing agent to promote the crystal growth of SnO_2.The formed porous morphology and tetragonal rutile crystalline structure of the electrodeposited thin films were controlled by the addition of BRhB with different amounts.展开更多
Zeolites have been widely applied in many chemical processes owing to their featured microporous framework structures.Organic structure-directing agents(OSDAs) play an important role during of the formation of zeolite...Zeolites have been widely applied in many chemical processes owing to their featured microporous framework structures.Organic structure-directing agents(OSDAs) play an important role during of the formation of zeolite frameworks via non-bonding host-vip interactions.Understanding these interactions is crucial to the design of OSDAs and the synthesis of target zeolites.Here,we report a molecular simulation study in the host-vip interactions between zeolite framework STW and 21 alkylated imidazolium and pyrazolium cations that have been used as the OSDAs for the synthesis of STW-type zeolites.We find that OSDAs that have successfully directed the formation of STW exhibit stronger host-vip interactions than unsuccessful ones.Furthermore,we find all successful OSDAs possess relatively more negative atomic charges on nitrogen atoms and smaller dipole moments.According to this finding,we have designed seven new alkylated imidazolium and pyrazolium cations that may be suitable for zeolite STW,and verified their structure-directing capability by molecular simulation calculations.展开更多
Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure‐directing agents(OSDAs),which are chronically hazardous to humans and the environment.It is a growing trend to ...Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure‐directing agents(OSDAs),which are chronically hazardous to humans and the environment.It is a growing trend to develop an eco‐friendly and nuisanceless OSDA for zeolite synthesis.Herein,choline is employed as a non‐toxic and green OSDA to synthesize high silica Y zeolite with SiO2/Al2O3 ratios of 6.5–6.8.The prepared Y zeolite samples exhibited outstanding(hydro)thermal stability at ultrahigh temperature owing to the higher SiO2/Al2O3 ratio.The XRF,SEM,29Si‐NMR and 13Na+results suggested that choline plays a structure‐directing role in the synthesis of Y zeolite,while the feed molar fraction of Na+is a crucial determinant for the framework SiO2/Al2O3 ratio and the crystal morphology.展开更多
We report a computational study of the distribution of germanium ions among the double four-membered rings(D4Rs)in SCM-14 germanosilicate and the influence of a structure-directing agent(SDA)on the stability of the as...We report a computational study of the distribution of germanium ions among the double four-membered rings(D4Rs)in SCM-14 germanosilicate and the influence of a structure-directing agent(SDA)on the stability of the as-synthesized material.For the pure zeolite structure,the calculations suggested clustering of Ge ions and the formation of D4Rs populated entirely by Ge heteroatoms,while part of the D4Rs contain only Si as T-atoms.As a general trend,structures with more Ge–O–Ge bridges are more stable.展开更多
Non-surfactant diquaternary ammonium compounds have already been used for obtaining various zeolites in nanocrystalline form. However, facile synthesis of nanocrystals of mordenite (MOR) and beta (BEA) in this way rem...Non-surfactant diquaternary ammonium compounds have already been used for obtaining various zeolites in nanocrystalline form. However, facile synthesis of nanocrystals of mordenite (MOR) and beta (BEA) in this way remains challenging. Here, we present the direct synthesis of nanosized mordernite (MOR) and beta (BEA) zeolites with hexane- and p-xylene-bridged bis-methylpyrrolidinium, -methylpiperidinium and -DABCO diquats, which can be synthesized in a single step from common chemicals. Optimized recipes are presented for nanosized MOR (20–50 nm) and BEA (15–30 nm) zeolites. By investigating the solid products obtained during hydrothermal synthesis, the formation of nanocrystals can be linked to the strong interaction between diquat templates and aluminosilicate species during the induction stage, which limits the amorphous precursor particles to a size below 50 nm. Based on the textural and acidic properties, catalytic performance data are discussed evidencing the clear benefits of these nanosized zeolites over bulk reference samples in Friedel–Crafts reactions and n-alkane hydroconversion.展开更多
We report results from computational modeling of the relative stability of germanosilicate SCM-15 structure due to different distribution of germanium heteroatoms in the double four-member rings(D4Rs)of the framework ...We report results from computational modeling of the relative stability of germanosilicate SCM-15 structure due to different distribution of germanium heteroatoms in the double four-member rings(D4Rs)of the framework and the orientation of the structure directing agent(SDA)molecules in the as-synthesized zeolite.The calculated relative energies of the bare zeolite framework suggest that structures with germanium ions clustered in the same D4Rs,e.g.,with large number of Ge–O-Ge contacts,are the most stable.The simulations of various orientations of the SDA in the pores of the germanosilicate zeolite show different stability order-the most stable models are the structures with germanium spread among all D4Rs.Thus,for SCM-15 the stabilization due to the presence of the SDA and their orientation,is thermodynamic factor directing both the formation of specific framework type and Ge distribution in the framework during the synthesis.The relative stability of bare structures with different germanium distribution is of minor importance.This differs from SCM-14 germanosilicate,reported earlier,for which the stability order is preserved in presence of SDA.Thus,even for zeolites with the same chemical composition and SDA,the characteristics of their framework lead to different energetic preference for germanium distribution.展开更多
基金supported by the National Natural Science Foundation of China(Nos.20873162,50872007)the State Key Laboratory of Pollution Control and Resource Reuse Foundation(No.PCRRF09006)Beijing Natural Science Foundation(No.8092022).
文摘Porous SnO2 nanocrystalline thin films were successfully electrodeposited from an oxygen-saturated acid aqueous solution of SnCl2 containing different concentrations of butyl-rhodamine B（BRhB） at 70℃.BRhB with substitute of amidocyanogen can be dissolved in the acid deposition solution,where HCl was added to suppress hydrolysis of SnCl2.So it was used as a structure-directing agent to promote the crystal growth of SnO_2.The formed porous morphology and tetragonal rutile crystalline structure of the electrodeposited thin films were controlled by the addition of BRhB with different amounts.
基金the National Natural Science Foundation of China(Nos.21622102,21621001 and 21920102005)the National Key Research and Development Program of China(No.2016YFB0701100)+1 种基金the National 111 Project(No.B17020)Program for JLUSTIRT and High Performance Computing Center of Jilin University。
文摘Zeolites have been widely applied in many chemical processes owing to their featured microporous framework structures.Organic structure-directing agents(OSDAs) play an important role during of the formation of zeolite frameworks via non-bonding host-vip interactions.Understanding these interactions is crucial to the design of OSDAs and the synthesis of target zeolites.Here,we report a molecular simulation study in the host-vip interactions between zeolite framework STW and 21 alkylated imidazolium and pyrazolium cations that have been used as the OSDAs for the synthesis of STW-type zeolites.We find that OSDAs that have successfully directed the formation of STW exhibit stronger host-vip interactions than unsuccessful ones.Furthermore,we find all successful OSDAs possess relatively more negative atomic charges on nitrogen atoms and smaller dipole moments.According to this finding,we have designed seven new alkylated imidazolium and pyrazolium cations that may be suitable for zeolite STW,and verified their structure-directing capability by molecular simulation calculations.
基金supported by the National Natural Science Foundation of China(Grant No.21802136)~~
文摘Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure‐directing agents(OSDAs),which are chronically hazardous to humans and the environment.It is a growing trend to develop an eco‐friendly and nuisanceless OSDA for zeolite synthesis.Herein,choline is employed as a non‐toxic and green OSDA to synthesize high silica Y zeolite with SiO2/Al2O3 ratios of 6.5–6.8.The prepared Y zeolite samples exhibited outstanding(hydro)thermal stability at ultrahigh temperature owing to the higher SiO2/Al2O3 ratio.The XRF,SEM,29Si‐NMR and 13Na+results suggested that choline plays a structure‐directing role in the synthesis of Y zeolite,while the feed molar fraction of Na+is a crucial determinant for the framework SiO2/Al2O3 ratio and the crystal morphology.
文摘We report a computational study of the distribution of germanium ions among the double four-membered rings(D4Rs)in SCM-14 germanosilicate and the influence of a structure-directing agent(SDA)on the stability of the as-synthesized material.For the pure zeolite structure,the calculations suggested clustering of Ge ions and the formation of D4Rs populated entirely by Ge heteroatoms,while part of the D4Rs contain only Si as T-atoms.As a general trend,structures with more Ge–O–Ge bridges are more stable.
文摘Non-surfactant diquaternary ammonium compounds have already been used for obtaining various zeolites in nanocrystalline form. However, facile synthesis of nanocrystals of mordenite (MOR) and beta (BEA) in this way remains challenging. Here, we present the direct synthesis of nanosized mordernite (MOR) and beta (BEA) zeolites with hexane- and p-xylene-bridged bis-methylpyrrolidinium, -methylpiperidinium and -DABCO diquats, which can be synthesized in a single step from common chemicals. Optimized recipes are presented for nanosized MOR (20–50 nm) and BEA (15–30 nm) zeolites. By investigating the solid products obtained during hydrothermal synthesis, the formation of nanocrystals can be linked to the strong interaction between diquat templates and aluminosilicate species during the induction stage, which limits the amorphous precursor particles to a size below 50 nm. Based on the textural and acidic properties, catalytic performance data are discussed evidencing the clear benefits of these nanosized zeolites over bulk reference samples in Friedel–Crafts reactions and n-alkane hydroconversion.
文摘We report results from computational modeling of the relative stability of germanosilicate SCM-15 structure due to different distribution of germanium heteroatoms in the double four-member rings(D4Rs)of the framework and the orientation of the structure directing agent(SDA)molecules in the as-synthesized zeolite.The calculated relative energies of the bare zeolite framework suggest that structures with germanium ions clustered in the same D4Rs,e.g.,with large number of Ge–O-Ge contacts,are the most stable.The simulations of various orientations of the SDA in the pores of the germanosilicate zeolite show different stability order-the most stable models are the structures with germanium spread among all D4Rs.Thus,for SCM-15 the stabilization due to the presence of the SDA and their orientation,is thermodynamic factor directing both the formation of specific framework type and Ge distribution in the framework during the synthesis.The relative stability of bare structures with different germanium distribution is of minor importance.This differs from SCM-14 germanosilicate,reported earlier,for which the stability order is preserved in presence of SDA.Thus,even for zeolites with the same chemical composition and SDA,the characteristics of their framework lead to different energetic preference for germanium distribution.
