The location of aluminum within the framework or extra-framework of zeolites is a critical factor in determining its catalytic performance.Despite extensive research on the identification and formation mechanism of ex...The location of aluminum within the framework or extra-framework of zeolites is a critical factor in determining its catalytic performance.Despite extensive research on the identification and formation mechanism of extra-framework aluminum(EFAl),its impact on catalytic performance requires further investigation.Herein,mordenite(MOR)zeolites with comparable acid density within the 8MR and 12MR channels but different EFAl contents were prepared,and their catalytic roles were examined in syngas conversion.Intelligent gravimetric analysis,model experiment of ethylene conversion and thermogravimetric analysis demonstrate that the existence of EFAl species can inhibit the secondary conversion of ethylene to long chain hydrocarbons(i.e.,C_(5+))as well as the over-accumulation of carbonaceous species.However,excessive EFAl species lead to rapid deactivation due to restricted space and thus severe diffusion limitation.MOR zeolite with a moderate amount of EFAl species achieves a superior ethylene selectivity and exhibits an enhanced stability in syngas conversion when combined with ZnAlOx oxide.The insights gained in this work provide important guidance for the design of more efficient zeolite-based catalysts.展开更多
The development of green alkylation technology in the production of linear alkylbenzene based on zeolites is highly desired.Herein,a novel nanorod-like mordenite(MOR)zeolite is fabricated by employing a self-designed ...The development of green alkylation technology in the production of linear alkylbenzene based on zeolites is highly desired.Herein,a novel nanorod-like mordenite(MOR)zeolite is fabricated by employing a self-designed template,and the morphology of MOR zeolites can be tailored by tuning the alkalinity of the synthesis gel.It's pointed out that the specially designed template is composed of an ethylenediamine functional group and hydrophobic alkyl chains,and the aromatic-aromatic stacking interactions in hydrophobic alkyl chains may facilitate the self-assembly of micellar structures,while the ethylenediamine functional group is matched with building blocks of MOR zeolite,resulting in the formation of nanorod-like MOR zeolite.Moreover,it's demonstrated that the compact stacking nanorodlike particles can be transformed into loose nanorod-like morphology under high alkalinity conditions,in which the Si-O bands are depolymerized,leading to the exfoliation of the stacking nanorod-like particles.The resultant nanorod-like MOR zeolite(MOR-30)displays enhanced accessibility for BrФsted acid sites compared with conventional MOR,achieving over twice the catalytic activity of conventional MOR in the alkylation of benzene with 1-dodecene.展开更多
Seed‐assisted low alkalinity gel system was developed to explore the organic‐free synthesis of MORzeolite.MOR nanoassemblies with Si/Al ratio(SAR)up to 9.4 and high solid yield(84–94%)weresuccessfully obtained unde...Seed‐assisted low alkalinity gel system was developed to explore the organic‐free synthesis of MORzeolite.MOR nanoassemblies with Si/Al ratio(SAR)up to 9.4 and high solid yield(84–94%)weresuccessfully obtained under controlled low alkalinity conditions.Characterization results demonstratethat the acid strength increases in parallel with the SAR,while the total acid amount and theproton distribution in the main channels and the side pockets are similar for the samples.The protondistribution in the H‐MOR is not straightforwardly related to the Na+distribution in theas‐synthesized MOR,implying the transfer of the protons among the oxygen sites of framework Tatom.Relative to low‐silica samples I‐5.3 and I‐7.4,sample I‐9.4 displays the best mass transferperformance and accessibility of the acid sites by pyridine due to its relatively low Al density andmild dealumination degree.Correspondingly,sample I‐9.4(pyridine‐modified catalyst)shows thebest activity with ca.100%selectivity of methyl acetate(MAc)in the DME carbonylation reaction.The high steady MAc yield(6.8 mmol/g/h)over sample I‐9.4 suggests the promising application ofMOR nanoassemblies synthesized by this economical organic‐free strategy.展开更多
文摘The location of aluminum within the framework or extra-framework of zeolites is a critical factor in determining its catalytic performance.Despite extensive research on the identification and formation mechanism of extra-framework aluminum(EFAl),its impact on catalytic performance requires further investigation.Herein,mordenite(MOR)zeolites with comparable acid density within the 8MR and 12MR channels but different EFAl contents were prepared,and their catalytic roles were examined in syngas conversion.Intelligent gravimetric analysis,model experiment of ethylene conversion and thermogravimetric analysis demonstrate that the existence of EFAl species can inhibit the secondary conversion of ethylene to long chain hydrocarbons(i.e.,C_(5+))as well as the over-accumulation of carbonaceous species.However,excessive EFAl species lead to rapid deactivation due to restricted space and thus severe diffusion limitation.MOR zeolite with a moderate amount of EFAl species achieves a superior ethylene selectivity and exhibits an enhanced stability in syngas conversion when combined with ZnAlOx oxide.The insights gained in this work provide important guidance for the design of more efficient zeolite-based catalysts.
基金supported by National Natural Science Foundation of China(22278090 and 21978055).
文摘The development of green alkylation technology in the production of linear alkylbenzene based on zeolites is highly desired.Herein,a novel nanorod-like mordenite(MOR)zeolite is fabricated by employing a self-designed template,and the morphology of MOR zeolites can be tailored by tuning the alkalinity of the synthesis gel.It's pointed out that the specially designed template is composed of an ethylenediamine functional group and hydrophobic alkyl chains,and the aromatic-aromatic stacking interactions in hydrophobic alkyl chains may facilitate the self-assembly of micellar structures,while the ethylenediamine functional group is matched with building blocks of MOR zeolite,resulting in the formation of nanorod-like MOR zeolite.Moreover,it's demonstrated that the compact stacking nanorodlike particles can be transformed into loose nanorod-like morphology under high alkalinity conditions,in which the Si-O bands are depolymerized,leading to the exfoliation of the stacking nanorod-like particles.The resultant nanorod-like MOR zeolite(MOR-30)displays enhanced accessibility for BrФsted acid sites compared with conventional MOR,achieving over twice the catalytic activity of conventional MOR in the alkylation of benzene with 1-dodecene.
文摘Seed‐assisted low alkalinity gel system was developed to explore the organic‐free synthesis of MORzeolite.MOR nanoassemblies with Si/Al ratio(SAR)up to 9.4 and high solid yield(84–94%)weresuccessfully obtained under controlled low alkalinity conditions.Characterization results demonstratethat the acid strength increases in parallel with the SAR,while the total acid amount and theproton distribution in the main channels and the side pockets are similar for the samples.The protondistribution in the H‐MOR is not straightforwardly related to the Na+distribution in theas‐synthesized MOR,implying the transfer of the protons among the oxygen sites of framework Tatom.Relative to low‐silica samples I‐5.3 and I‐7.4,sample I‐9.4 displays the best mass transferperformance and accessibility of the acid sites by pyridine due to its relatively low Al density andmild dealumination degree.Correspondingly,sample I‐9.4(pyridine‐modified catalyst)shows thebest activity with ca.100%selectivity of methyl acetate(MAc)in the DME carbonylation reaction.The high steady MAc yield(6.8 mmol/g/h)over sample I‐9.4 suggests the promising application ofMOR nanoassemblies synthesized by this economical organic‐free strategy.
