As a powerful and sensitive tool for the characterization of zeolite building units,UV Raman spectroscopy has been used to monitor interzeolite transformation from FAU to CHA and MFI zeolites.The results show that the...As a powerful and sensitive tool for the characterization of zeolite building units,UV Raman spectroscopy has been used to monitor interzeolite transformation from FAU to CHA and MFI zeolites.The results show that the behavior of double 6-membered rings(D6Rs)in the FAU zeolite framework plays an important role during the formation of the target product in the interzeolite transformation.For the transformation of FAU to CHA,because both zeolites contain the same D6R units,direct transformation occurs,in which the D6Rs were largely unchanged.In contrast,for the transformation of FAU to MFI,the D6Rs can be divided into two single 6-membered rings(S6Rs),which further assembled into the MFI structure.In this crystallization,5-membered rings(5Rs)are only observed in the MFI framework formation,suggesting that the basic building units in the transformation of FAU to MFI are S6Rs rather than 5Rs.These insights will be helpful for further understanding of the interzeolite transformation.展开更多
The formation and evolution of building units for zeolites play an important role during crystallization.Interzeolite transformation offers a better platform for investigating the conversion behaviors of such building...The formation and evolution of building units for zeolites play an important role during crystallization.Interzeolite transformation offers a better platform for investigating the conversion behaviors of such building units and the specific crystallization mechanism of zeolites.Herein,we show the different evolution of double six-membered rings(D6R)during the interzeolite transformation from FAU,MFI and ^(*)BEA into AEI zeolites based on UV Raman spectroscopy in combination with X-ray powder diffraction(XRD)and DFT calculations.It is found that a direct transfer of D6R occurs from the FAU into AEI zeolite since they share the same structural units(D6R),while towards the newly expanded synthetic strategy from pentasil-type zeolites MFI and ^(*)BEA into AEI zeolites,the formation of D6R units in the AEI framework results from the reassembly of single four-membered rings(S4R)and single six-membered rings(S6R)generated by breaking a large number of single five-membered rings(S5R)that are very fragile and easy to decompose under hydrothermal transformation conditions.Such results provide a clear and direct spectroscopic characterization at the molecular level,which will be of great significance in accomplishing a deep understanding of the interzeolite transformation mechanism.展开更多
Ge-containing Lewis acidic zeolites are typically synthesized using a conventional hydrothermal strategy from amorphous silica sources,through a long time-and energy-consuming approach limiting their wide applications...Ge-containing Lewis acidic zeolites are typically synthesized using a conventional hydrothermal strategy from amorphous silica sources,through a long time-and energy-consuming approach limiting their wide applications.This study reports a rapid synthesis strategy for a series of IWV aluminogermanosilicate zeolites(T-x-Al)with a wide range of Si/Ge molar ratios(5–15)by interzeolite transformation of dealuminated FAU(DA-FAU).Notably,Ge-rich IWV could be obtained with crystallization time as short as one day by the equimolecular Si/Ge ratio gel.The effect of synthetic parameters was investigated and the obtained T-x-Al samples were characterized by XRD,SEM,EDS,ICP,^(29)Si and^(27)Al MAS NMR,FTIR,and N_(2)physisorption analyses.Compared with a previously reported IWV germanosilicate(H-3),T-x-Al displayed a better catalytic activity in Baeyer-Villiger(BV)oxidation,attributed to the presence of the active framework Ge sites with the assistance of the extraframework Al species.The cyclic catalysis tests revealed that the presence of framework Al species contributed to the stability of the T-x-Al.Specifically,T-x-Al,with 14-membered ring(MR)supercages,outperformed the typical 12-MR Sn-beta catalyst in the BV oxidation of large ketone-like 2-admantanone,indicating a promising potential application in the macromolecular catalytic process.展开更多
The Baeyer-Villiger(BV)oxidation of cyclohexanone is explored using IWV-type aluminosilicates with different Al sites as heterogeneous catalysts.The IWV framework exhibits a two-dimensional 12-membered ring(MR)pore sy...The Baeyer-Villiger(BV)oxidation of cyclohexanone is explored using IWV-type aluminosilicates with different Al sites as heterogeneous catalysts.The IWV framework exhibits a two-dimensional 12-membered ring(MR)pore system intersected by 14-MR supercages,resembling typical beta zeolite.To address the constraints associated with hydrothermal synthesis,IWV aluminosilicates were synthesized via interzeolite transformation of various FAU-type zeolites.HF-assisted transformation of dealuminated FAU zeolite resulted in the formation of a high-silica IWV aluminosilicate(Si/Al=54.6),whereas the incorporation of aluminum isopropoxide enables the tuning of Si/Al ratio down to 18.7.The alkaline conversion of protonated FAU zeolites,utilizing Na^(+)ions as mineralizing agents,produces high-Al content IWV derivatives in just four days.Catalytic evaluation demonstrates that the high-silica IWV catalyst exhibits a higher turnover number than the other IWV catalysts,along with enhancedε-caprolactone(CL)selectivity relative to that of high-silica beta zeolite.Facile modifications are performed to adjust Al sites,as characterized by pyridine-adsorbed infrared spectroscopy.Experimental evidence confirms that Al Brønsted acid sites improves the selective oxidation of cyclohexanone,while concurrently enhancing CL hydrolysis.展开更多
Low-silica RHO zeolites have been recognized as efficient catalysts for synthesizing industrial intermediates monomethylamine(MMA)and dimethylamine(DMA)through the reaction of methanol(MeOH)with ammonia.However,they t...Low-silica RHO zeolites have been recognized as efficient catalysts for synthesizing industrial intermediates monomethylamine(MMA)and dimethylamine(DMA)through the reaction of methanol(MeOH)with ammonia.However,they typically suffer from rapid deactivation.Herein,we report the synthesis of highsilica RHO zeolite with small crystal sizes(1-2μm)via interzeolite conversion of SSZ-13,utilizing a reduced amount of organic structure-directing agent(OSDA)and without the use of fluoride.It was demonstrated that the double eight-membered rings of RHO zeolite can be formed using the single eight-membered ring of SSZ-13,resulting in a reduction of OSDA dosage by approximately 30%and Cs^(+)by about 38%.The resulting high-silica RHO zeolites exhibit an excellent methanol conversion of∼93%,a high MMA and DMA yield of∼90%,and good reaction durability under conditions more severe than those of industrial manufacture conditions,at 350℃with a liquid hourly space velocity at 11.7 h^(−1).Compared to directly synthesized high-silica RHO zeolites with larger crystal sizes(3-8μm),interzeolite-converted high-silica RHO zeolites with smaller crystal sizes show a 10-16%higher yield of MMA and DMA.These findings highlight the significant potential of high-silica RHO zeolites for the industrial manufacturing of MMA and DMA.展开更多
Zeolites,an important class of microporous crystals,have been widely utilized in the fields of catalysis,ion-exchange,separation,and sorption for a long time.In general,zeolites are synthesized in the presence of cost...Zeolites,an important class of microporous crystals,have been widely utilized in the fields of catalysis,ion-exchange,separation,and sorption for a long time.In general,zeolites are synthesized in the presence of costly organic templates under hydrothermal conditions by trial-and-error method,which is not only environmentally unfriendly but also labor-intensive.In recent years,novel concepts of design for zeolite synthesis,which are sustainable,cheap,simple,and efficient,have been developed.In this review,the recent advances in design for zeolite synthesis will be briefly summarized,mainly including the design of organic templates for directing the formation of zeolites,design of organotemplate-free route for zeolite synthesis,design of solvent-free strategy for zeolite synthesis,design for novel interzeolite transformation,and targeted control of zeolite morphologies.This review might be helpful for developing sustainable routes for targeted synthesis of zeolites in the future.展开更多
基金supported by the National Key R&D Program of China(2017YFB0702800)the National Natural Science Foundation of China(2152780065,91634201 and 21720102001)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB17000000)~~
文摘As a powerful and sensitive tool for the characterization of zeolite building units,UV Raman spectroscopy has been used to monitor interzeolite transformation from FAU to CHA and MFI zeolites.The results show that the behavior of double 6-membered rings(D6Rs)in the FAU zeolite framework plays an important role during the formation of the target product in the interzeolite transformation.For the transformation of FAU to CHA,because both zeolites contain the same D6R units,direct transformation occurs,in which the D6Rs were largely unchanged.In contrast,for the transformation of FAU to MFI,the D6Rs can be divided into two single 6-membered rings(S6Rs),which further assembled into the MFI structure.In this crystallization,5-membered rings(5Rs)are only observed in the MFI framework formation,suggesting that the basic building units in the transformation of FAU to MFI are S6Rs rather than 5Rs.These insights will be helpful for further understanding of the interzeolite transformation.
基金supported by the National Key Research and Development Program of China(2017YFB0702800)National Natural Science Foundation of China(91634201)Strategic Priority Research Program of Chinese Academy of Sciences(XBD17000000).
文摘The formation and evolution of building units for zeolites play an important role during crystallization.Interzeolite transformation offers a better platform for investigating the conversion behaviors of such building units and the specific crystallization mechanism of zeolites.Herein,we show the different evolution of double six-membered rings(D6R)during the interzeolite transformation from FAU,MFI and ^(*)BEA into AEI zeolites based on UV Raman spectroscopy in combination with X-ray powder diffraction(XRD)and DFT calculations.It is found that a direct transfer of D6R occurs from the FAU into AEI zeolite since they share the same structural units(D6R),while towards the newly expanded synthetic strategy from pentasil-type zeolites MFI and ^(*)BEA into AEI zeolites,the formation of D6R units in the AEI framework results from the reassembly of single four-membered rings(S4R)and single six-membered rings(S6R)generated by breaking a large number of single five-membered rings(S5R)that are very fragile and easy to decompose under hydrothermal transformation conditions.Such results provide a clear and direct spectroscopic characterization at the molecular level,which will be of great significance in accomplishing a deep understanding of the interzeolite transformation mechanism.
基金supported by the National Natural Science Foundation of China(22302116)the Natural Science Foundation of Shanxi Province(202203021212412)。
文摘Ge-containing Lewis acidic zeolites are typically synthesized using a conventional hydrothermal strategy from amorphous silica sources,through a long time-and energy-consuming approach limiting their wide applications.This study reports a rapid synthesis strategy for a series of IWV aluminogermanosilicate zeolites(T-x-Al)with a wide range of Si/Ge molar ratios(5–15)by interzeolite transformation of dealuminated FAU(DA-FAU).Notably,Ge-rich IWV could be obtained with crystallization time as short as one day by the equimolecular Si/Ge ratio gel.The effect of synthetic parameters was investigated and the obtained T-x-Al samples were characterized by XRD,SEM,EDS,ICP,^(29)Si and^(27)Al MAS NMR,FTIR,and N_(2)physisorption analyses.Compared with a previously reported IWV germanosilicate(H-3),T-x-Al displayed a better catalytic activity in Baeyer-Villiger(BV)oxidation,attributed to the presence of the active framework Ge sites with the assistance of the extraframework Al species.The cyclic catalysis tests revealed that the presence of framework Al species contributed to the stability of the T-x-Al.Specifically,T-x-Al,with 14-membered ring(MR)supercages,outperformed the typical 12-MR Sn-beta catalyst in the BV oxidation of large ketone-like 2-admantanone,indicating a promising potential application in the macromolecular catalytic process.
基金supported by the National Natural Science Foundation of China(No.22302116)the Fundamental Research Program of Shanxi Province(No.202203021212412)Qingchuang Technology Support Program of the University in Shandong Province(No.2023KJ246).
文摘The Baeyer-Villiger(BV)oxidation of cyclohexanone is explored using IWV-type aluminosilicates with different Al sites as heterogeneous catalysts.The IWV framework exhibits a two-dimensional 12-membered ring(MR)pore system intersected by 14-MR supercages,resembling typical beta zeolite.To address the constraints associated with hydrothermal synthesis,IWV aluminosilicates were synthesized via interzeolite transformation of various FAU-type zeolites.HF-assisted transformation of dealuminated FAU zeolite resulted in the formation of a high-silica IWV aluminosilicate(Si/Al=54.6),whereas the incorporation of aluminum isopropoxide enables the tuning of Si/Al ratio down to 18.7.The alkaline conversion of protonated FAU zeolites,utilizing Na^(+)ions as mineralizing agents,produces high-Al content IWV derivatives in just four days.Catalytic evaluation demonstrates that the high-silica IWV catalyst exhibits a higher turnover number than the other IWV catalysts,along with enhancedε-caprolactone(CL)selectivity relative to that of high-silica beta zeolite.Facile modifications are performed to adjust Al sites,as characterized by pyridine-adsorbed infrared spectroscopy.Experimental evidence confirms that Al Brønsted acid sites improves the selective oxidation of cyclohexanone,while concurrently enhancing CL hydrolysis.
基金the National Key Research and Development Program of China(2021YFA1500401,2021YFA1501202,2022YFB3504000)the National Natural Science Foundation of China(22288101,21991091)the‘111 Center’(B17020)for supporting this work.
文摘Low-silica RHO zeolites have been recognized as efficient catalysts for synthesizing industrial intermediates monomethylamine(MMA)and dimethylamine(DMA)through the reaction of methanol(MeOH)with ammonia.However,they typically suffer from rapid deactivation.Herein,we report the synthesis of highsilica RHO zeolite with small crystal sizes(1-2μm)via interzeolite conversion of SSZ-13,utilizing a reduced amount of organic structure-directing agent(OSDA)and without the use of fluoride.It was demonstrated that the double eight-membered rings of RHO zeolite can be formed using the single eight-membered ring of SSZ-13,resulting in a reduction of OSDA dosage by approximately 30%and Cs^(+)by about 38%.The resulting high-silica RHO zeolites exhibit an excellent methanol conversion of∼93%,a high MMA and DMA yield of∼90%,and good reaction durability under conditions more severe than those of industrial manufacture conditions,at 350℃with a liquid hourly space velocity at 11.7 h^(−1).Compared to directly synthesized high-silica RHO zeolites with larger crystal sizes(3-8μm),interzeolite-converted high-silica RHO zeolites with smaller crystal sizes show a 10-16%higher yield of MMA and DMA.These findings highlight the significant potential of high-silica RHO zeolites for the industrial manufacturing of MMA and DMA.
基金supported by the National Natural Science Foundation of China(22172141,21802121,21835002,and 92045303)the Fundamental Research Funds for the Central Universities(2021QNA4028)。
文摘Zeolites,an important class of microporous crystals,have been widely utilized in the fields of catalysis,ion-exchange,separation,and sorption for a long time.In general,zeolites are synthesized in the presence of costly organic templates under hydrothermal conditions by trial-and-error method,which is not only environmentally unfriendly but also labor-intensive.In recent years,novel concepts of design for zeolite synthesis,which are sustainable,cheap,simple,and efficient,have been developed.In this review,the recent advances in design for zeolite synthesis will be briefly summarized,mainly including the design of organic templates for directing the formation of zeolites,design of organotemplate-free route for zeolite synthesis,design of solvent-free strategy for zeolite synthesis,design for novel interzeolite transformation,and targeted control of zeolite morphologies.This review might be helpful for developing sustainable routes for targeted synthesis of zeolites in the future.
