Metal organic frameworks(MOFs)constructed from natural/biological units(amino acids)are prospective candidates as catalysts in CO2chemistry owing to their natural origin and high abundance of Lewis acid/base sites and...Metal organic frameworks(MOFs)constructed from natural/biological units(amino acids)are prospective candidates as catalysts in CO2chemistry owing to their natural origin and high abundance of Lewis acid/base sites and functional groups.Herein,we report the catalytic efficiency of an amino‐acid‐based Cu‐containing MOF,denoted as CuTrp(Trp=L‐tryptophan).The CuTrp catalyst was synthesized by direct mixing at room temperature using methanol as a solvent-a synthetic route with notable energy efficiency.The catalyst was characterized using various physicochemical techniques,including XRD,FT‐IR,TGA,XPS,ICP‐OES,FE‐SEM,and BET analysis.The catalytic activity of CuTrp was assessed in the synthesis of cyclic carbonates from epoxides and CO2.The CuTrp operated in synergy with the co‐catalyst tetrabutylammonium bromide under solvent‐free conditions.Several reaction parameters were studied to identify the optimal reaction conditions and a reaction mechanism was proposed based on experimental evidence and previous density functional theory studies.The CuTrp also exhibited satisfactory stability in water and could be reused more than three times without any significant loss of activity.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.展开更多
Although metal oxide-zeolite hybrid materials have long been known to achieve enhanced catalytic activity and selectivity in NO_(x)removal reactions through the inter-particle diffusion of intermediate species,their s...Although metal oxide-zeolite hybrid materials have long been known to achieve enhanced catalytic activity and selectivity in NO_(x)removal reactions through the inter-particle diffusion of intermediate species,their subsequent reaction mechanism on acid sites is still unclear and requires investigation.In this study,the distribution of Brønsted/Lewis acid sites in the hybrid materials was precisely adjusted by introducing potassium ions,which not only selectively bind to Brønsted acid sites but also potentially affect the formation and diffusion of activated NO species.Systematic in situ diffuse reflectance infrared Fourier transform spectroscopy analyses coupled with selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR)reaction demonstrate that the Lewis acid sites over MnO_(x)are more active for NO reduction but have lower selectivity to N_(2)than Brønsted acids sites.Brønsted acid sites primarily produce N_(2),whereas Lewis acid sites primarily produce N_(2)O,contributing to unfavorable N_(2)selectivity.The Brønsted acid sites present in Y zeolite,which are stronger than those on MnO_(x),accelerate the NH_(3)-SCR reaction in which the nitrite/nitrate species diffused from the MnO_(x)particles rapidly convert into the N_(2).Therefore,it is important to design the catalyst so that the activated NO species formed in MnO_(x)diffuse to and are selectively decomposed on the Brønsted acid sites of H-Y zeolite rather than that of MnO_(x)particle.For the physically mixed H-MnO_(x)+H-Y sample,the abundant Brønsted/Lewis acid sites in H-MnO_(x)give rise to significant consumption of activated NO species before their inter-particle diffusion,thereby hindering the enhancement of the synergistic effects.Furthermore,we found that the intercalated K+in K-MnO_(x)has an unexpected favorable role in the NO reduction rate,probably owing to faster diffusion of the activated NO species on K-MnO_(x)than H-MnO_(x).This study will help to design promising metal oxide-zeolite hybrid catalysts by identifying the role of the acid sites in two different constituents.展开更多
The experimental and numerical investigations of the flow with reaction of two gases: hydrogen chloride HC1 and ammonia NH3 were performed. The article contains description of the visualisation method of the formation...The experimental and numerical investigations of the flow with reaction of two gases: hydrogen chloride HC1 and ammonia NH3 were performed. The article contains description of the visualisation method of the formation and flow of particles of ammonia chloride NH4Cl. Analyses of mean concentration and variance of concentration fluctuations of dispersed phase were performed for different outputs of gases. Numerical calculations were performed for analysed phenomenon. Both numerical and visualisation results were matched and compared.展开更多
文摘Metal organic frameworks(MOFs)constructed from natural/biological units(amino acids)are prospective candidates as catalysts in CO2chemistry owing to their natural origin and high abundance of Lewis acid/base sites and functional groups.Herein,we report the catalytic efficiency of an amino‐acid‐based Cu‐containing MOF,denoted as CuTrp(Trp=L‐tryptophan).The CuTrp catalyst was synthesized by direct mixing at room temperature using methanol as a solvent-a synthetic route with notable energy efficiency.The catalyst was characterized using various physicochemical techniques,including XRD,FT‐IR,TGA,XPS,ICP‐OES,FE‐SEM,and BET analysis.The catalytic activity of CuTrp was assessed in the synthesis of cyclic carbonates from epoxides and CO2.The CuTrp operated in synergy with the co‐catalyst tetrabutylammonium bromide under solvent‐free conditions.Several reaction parameters were studied to identify the optimal reaction conditions and a reaction mechanism was proposed based on experimental evidence and previous density functional theory studies.The CuTrp also exhibited satisfactory stability in water and could be reused more than three times without any significant loss of activity.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.
文摘Although metal oxide-zeolite hybrid materials have long been known to achieve enhanced catalytic activity and selectivity in NO_(x)removal reactions through the inter-particle diffusion of intermediate species,their subsequent reaction mechanism on acid sites is still unclear and requires investigation.In this study,the distribution of Brønsted/Lewis acid sites in the hybrid materials was precisely adjusted by introducing potassium ions,which not only selectively bind to Brønsted acid sites but also potentially affect the formation and diffusion of activated NO species.Systematic in situ diffuse reflectance infrared Fourier transform spectroscopy analyses coupled with selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR)reaction demonstrate that the Lewis acid sites over MnO_(x)are more active for NO reduction but have lower selectivity to N_(2)than Brønsted acids sites.Brønsted acid sites primarily produce N_(2),whereas Lewis acid sites primarily produce N_(2)O,contributing to unfavorable N_(2)selectivity.The Brønsted acid sites present in Y zeolite,which are stronger than those on MnO_(x),accelerate the NH_(3)-SCR reaction in which the nitrite/nitrate species diffused from the MnO_(x)particles rapidly convert into the N_(2).Therefore,it is important to design the catalyst so that the activated NO species formed in MnO_(x)diffuse to and are selectively decomposed on the Brønsted acid sites of H-Y zeolite rather than that of MnO_(x)particle.For the physically mixed H-MnO_(x)+H-Y sample,the abundant Brønsted/Lewis acid sites in H-MnO_(x)give rise to significant consumption of activated NO species before their inter-particle diffusion,thereby hindering the enhancement of the synergistic effects.Furthermore,we found that the intercalated K+in K-MnO_(x)has an unexpected favorable role in the NO reduction rate,probably owing to faster diffusion of the activated NO species on K-MnO_(x)than H-MnO_(x).This study will help to design promising metal oxide-zeolite hybrid catalysts by identifying the role of the acid sites in two different constituents.
文摘The experimental and numerical investigations of the flow with reaction of two gases: hydrogen chloride HC1 and ammonia NH3 were performed. The article contains description of the visualisation method of the formation and flow of particles of ammonia chloride NH4Cl. Analyses of mean concentration and variance of concentration fluctuations of dispersed phase were performed for different outputs of gases. Numerical calculations were performed for analysed phenomenon. Both numerical and visualisation results were matched and compared.
