The dioxygen affinities and catalytic epoxidation performance of transition-metal hydroxamates were investigated for the first time. The effects of substituents on these properties were also discussed in the paper.
It has been well established that carbon dioxide(CO_(2))is one of the main greenhouse gasses and a leading driver of climate change.The chemical conversion of CO_(2) to substitute natural gas(SNG)in the presence of re...It has been well established that carbon dioxide(CO_(2))is one of the main greenhouse gasses and a leading driver of climate change.The chemical conversion of CO_(2) to substitute natural gas(SNG)in the presence of renewable hydrogen is one of the most promising solutions by a well-known process called CO_(2) methanation.There have been comprehensive efforts in developing effective and efficient CO_(2) methanation catalytic systems.However,the choice of competitive and stable catalysts is still a monumental obstruction and a great challenge towards the commercialization and industrialization of CO_(2) methanation.It is necessary to emphasize the critical understandings of intrinsic and extrinsic interactions of catalyst components(active metal,support,promoter,etc.)for enhanced catalytic performance and stability during CO_(2) methanation.This study reviews the up-to-date developments on CO_(2) methanation catalysts and the optimal synergistic relationship between active metals,support,and promoters during the catalytic activity.The existing catalysts and their novel properties for enhanced CO_(2) methanation were elucidated using the state-of-the-art experimental and theoretical techniques.The selection of an appropriate synthesis method,catalytic activity for CO_(2) methanation,deactivation of the catalysts,and reaction mechanisms studies,have been explicitly compared and explained.Therefore,future efforts should be directed towards the sustainable developments of catalytic configurations for successful industrial applications of CO_(2) utilization to SNG using CO_(2) methanation.展开更多
The oxygenation constants of transition-metal complexes with benzoin Schiff bases were measured and these complexes were first employed as models for mimicking monooxygenase in catalytic epoxidation of styrene. The hi...The oxygenation constants of transition-metal complexes with benzoin Schiff bases were measured and these complexes were first employed as models for mimicking monooxygenase in catalytic epoxidation of styrene. The highest conversion and selectivity were up to 39.6% and 100% respectively at ambient temperature and pressure. The effects of structures of the bridge group R in the ligands on the dioxygen affinities and catalytic activities to epoxidize styrene were also investigated.展开更多
The dioxygen affinities and biomimetic catalytic performance of transition-metal complexes with (15-crown-5) salophen and its substituted derivatives Mere examined. The oxygenation constants of Co(II) complexes with c...The dioxygen affinities and biomimetic catalytic performance of transition-metal complexes with (15-crown-5) salophen and its substituted derivatives Mere examined. The oxygenation constants of Co(II) complexes with crowned bis-Schiff bases were measured and their Mn(III) complexes were employed as models to mimic monooxygenase in catalytic epoxidation of styrene. The highest conversion and selectivity were up to 57.2% and 100% respectively at ambient temperature and pressure. The effects of crown ether ring and substituents R on the dioxygen affinities and catalytic activities were also investigated through comparing with the uncrowned analogues.展开更多
The oxygenation constants and thermodynamic parameter (ΔHo, ΔSo) of Co (II) complexes with unsymmetrical bis-Schiff baeses were measured and their Mn(III) complexes as models of mimicking monooxygenase were employed...The oxygenation constants and thermodynamic parameter (ΔHo, ΔSo) of Co (II) complexes with unsymmetrical bis-Schiff baeses were measured and their Mn(III) complexes as models of mimicking monooxygenase were employed to catalyze epoxidation of styrene. The effect of substituent R in a salicylidene of ML1~ML4 [ M = Co (II), Mn (III)Cl ] on the dioxygen affinities and biomimetic catalytic oxidation performance were also investigated. Among them, the MnL4Cl containing a pendant benzoaza crown ether ring showed highest conversion and selectiviy up to 54.9% and 96.9% respectively.展开更多
Carboxylation of aromatics by CO2 to generate corresponding carboxylic acids is recently providing a novel approach to utilize the green gas CO2, in which the activation of CO2 is the key procedure. Among the many cat...Carboxylation of aromatics by CO2 to generate corresponding carboxylic acids is recently providing a novel approach to utilize the green gas CO2, in which the activation of CO2 is the key procedure. Among the many catalytic systems employed in the carboxylation, the concept of “Frustrated Lewis Pairs” (FLPs) was scarcely mentioned, which perform excellently in activating small molecules like CO2. The FLPs are combinations of Lewis acids and Lewis bases which failed to form adducts due to their bulky steric congestion. In this paper, we first attempted various Si/Al Based FLPs to catalyze the carboxylation of aromatics through the activation of CO2, and a good yield of 62% - 97% was obtained. The reaction mechanism was proposed, involving the activation of CO2 mainly contributed by AlCl3 in cooperation with organosilane, forming an intermediate consisting of CO2, AlCl3, and R4Si, as well as the subsequent electrophilic attack to aromatics, thus to promote the carboxylation reaction.展开更多
文摘The dioxygen affinities and catalytic epoxidation performance of transition-metal hydroxamates were investigated for the first time. The effects of substituents on these properties were also discussed in the paper.
基金This research work was made possible by a Transdisciplinary Research Grant from Universiti Teknologi Malaysia(Grant No.06G52 and 06G53).
文摘It has been well established that carbon dioxide(CO_(2))is one of the main greenhouse gasses and a leading driver of climate change.The chemical conversion of CO_(2) to substitute natural gas(SNG)in the presence of renewable hydrogen is one of the most promising solutions by a well-known process called CO_(2) methanation.There have been comprehensive efforts in developing effective and efficient CO_(2) methanation catalytic systems.However,the choice of competitive and stable catalysts is still a monumental obstruction and a great challenge towards the commercialization and industrialization of CO_(2) methanation.It is necessary to emphasize the critical understandings of intrinsic and extrinsic interactions of catalyst components(active metal,support,promoter,etc.)for enhanced catalytic performance and stability during CO_(2) methanation.This study reviews the up-to-date developments on CO_(2) methanation catalysts and the optimal synergistic relationship between active metals,support,and promoters during the catalytic activity.The existing catalysts and their novel properties for enhanced CO_(2) methanation were elucidated using the state-of-the-art experimental and theoretical techniques.The selection of an appropriate synthesis method,catalytic activity for CO_(2) methanation,deactivation of the catalysts,and reaction mechanisms studies,have been explicitly compared and explained.Therefore,future efforts should be directed towards the sustainable developments of catalytic configurations for successful industrial applications of CO_(2) utilization to SNG using CO_(2) methanation.
文摘The oxygenation constants of transition-metal complexes with benzoin Schiff bases were measured and these complexes were first employed as models for mimicking monooxygenase in catalytic epoxidation of styrene. The highest conversion and selectivity were up to 39.6% and 100% respectively at ambient temperature and pressure. The effects of structures of the bridge group R in the ligands on the dioxygen affinities and catalytic activities to epoxidize styrene were also investigated.
基金the National Natural Science Foundation of China.
文摘The dioxygen affinities and biomimetic catalytic performance of transition-metal complexes with (15-crown-5) salophen and its substituted derivatives Mere examined. The oxygenation constants of Co(II) complexes with crowned bis-Schiff bases were measured and their Mn(III) complexes were employed as models to mimic monooxygenase in catalytic epoxidation of styrene. The highest conversion and selectivity were up to 57.2% and 100% respectively at ambient temperature and pressure. The effects of crown ether ring and substituents R on the dioxygen affinities and catalytic activities were also investigated through comparing with the uncrowned analogues.
文摘The oxygenation constants and thermodynamic parameter (ΔHo, ΔSo) of Co (II) complexes with unsymmetrical bis-Schiff baeses were measured and their Mn(III) complexes as models of mimicking monooxygenase were employed to catalyze epoxidation of styrene. The effect of substituent R in a salicylidene of ML1~ML4 [ M = Co (II), Mn (III)Cl ] on the dioxygen affinities and biomimetic catalytic oxidation performance were also investigated. Among them, the MnL4Cl containing a pendant benzoaza crown ether ring showed highest conversion and selectiviy up to 54.9% and 96.9% respectively.
文摘Carboxylation of aromatics by CO2 to generate corresponding carboxylic acids is recently providing a novel approach to utilize the green gas CO2, in which the activation of CO2 is the key procedure. Among the many catalytic systems employed in the carboxylation, the concept of “Frustrated Lewis Pairs” (FLPs) was scarcely mentioned, which perform excellently in activating small molecules like CO2. The FLPs are combinations of Lewis acids and Lewis bases which failed to form adducts due to their bulky steric congestion. In this paper, we first attempted various Si/Al Based FLPs to catalyze the carboxylation of aromatics through the activation of CO2, and a good yield of 62% - 97% was obtained. The reaction mechanism was proposed, involving the activation of CO2 mainly contributed by AlCl3 in cooperation with organosilane, forming an intermediate consisting of CO2, AlCl3, and R4Si, as well as the subsequent electrophilic attack to aromatics, thus to promote the carboxylation reaction.
