Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity a...Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity and selectivity of rare-earth compounds along with no residual impact on polymer product's performance,highly efficient catalytic reduction systems containing sodium borohydride(NaBH_(4))and rare-earth chloride(RECl_(3))were specifically designed for a telechelic carboxyl-terminated liquid fluoroeslastomer,aiming to facilitate the conversion of chainend carboxyl groups into hydroxyl groups and improvement in end-group reactivity.To achieve this,lanthanum chloride(LaCl_(3)),cerium chloride(CeCl_(3)),and neodymium chloride(NdCl_(3))were used separately to form catalytic reduction systems with NaBH_(4).The effects of solvent dosage,reaction temperature,reaction time length,and reductant dosage on carboxylic conversion were investigated,and the molecular chain structure,molecular weight,and functional group content of the raw materials and the products were analyzed and characterized by means of infrared spectroscopy(FTIR),proton nuclear magnetic resonance(^(1)H-NMR),fluorine-19 nuclear magnetic resonance(^(19)F-NMR),gel permeation chromatography(GPC),and chemical titration.Moreover,the catalytic activity and selectivity of the rare-earth chlorides,as well as the corresponding underlying interactions were discussed.Results indicated that the rare-earth-containing catalytic reduction systems studied in this work could efficiently convert the chain-end carboxyl groups into highly active hydroxyl groups,with a highest conversion up to 87.0%and differing catalytic reduction activities ranked as NaBH_(4)/CeCl_(3)>NaBH_(4)/LaCl_(3)>NaBH_(4)/NdCl_(3).Compared with the conventional lithium aluminum hydride(LiAIH_(4))reduction system,the NaBH_(4)/RECl_(3)systems provide multiple advantages such as mild reaction conditions,high conversion ratio with good selectivity,and environmental innocuity,and are potentially applicable as new reduction-catalysis combinations for the synthesis and functionalization of polymer materials.展开更多
With the aim of achieving a high 5-hydroxymethylfurfural(HMF)yield from glucose with H-ZSM-5 catalyst at low cost,three inexpensive biphasic reaction systems,H2O?tetrahydrofuran(THF),H2O?2-methyltetrahydrofuran(MeTHF)...With the aim of achieving a high 5-hydroxymethylfurfural(HMF)yield from glucose with H-ZSM-5 catalyst at low cost,three inexpensive biphasic reaction systems,H2O?tetrahydrofuran(THF),H2O?2-methyltetrahydrofuran(MeTHF)and H2O?2-butanol,were discovered and proved to be particularly effective in promoting the formation of HMF from glucose over H-ZSM-5 zeolite.In order to determine the optimal process conditions,the effects of various experimental variables,such as reaction temperature,reaction time,catalyst dosage,volume of organic solvent,as well as inorganic salt type on glucose conversion to HMF in three systems were investigated in detail.It was found that under optimal reaction conditions,H2O?THF,H2O?2-butanol and H2O?MeTHF allowed the glucose dehydration process to achieve HMF yields of up to 61%,59%,and 50%,respectively.Moreover,in the three biphasic systems,the H-ZSM-5 catalyst was also demonstrated to maintain excellent stability.Thus,the catalytic approach proposed in this paper can be believed to have potential prospects for industrially efficient and low-cost production of HMF.展开更多
文摘Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity and selectivity of rare-earth compounds along with no residual impact on polymer product's performance,highly efficient catalytic reduction systems containing sodium borohydride(NaBH_(4))and rare-earth chloride(RECl_(3))were specifically designed for a telechelic carboxyl-terminated liquid fluoroeslastomer,aiming to facilitate the conversion of chainend carboxyl groups into hydroxyl groups and improvement in end-group reactivity.To achieve this,lanthanum chloride(LaCl_(3)),cerium chloride(CeCl_(3)),and neodymium chloride(NdCl_(3))were used separately to form catalytic reduction systems with NaBH_(4).The effects of solvent dosage,reaction temperature,reaction time length,and reductant dosage on carboxylic conversion were investigated,and the molecular chain structure,molecular weight,and functional group content of the raw materials and the products were analyzed and characterized by means of infrared spectroscopy(FTIR),proton nuclear magnetic resonance(^(1)H-NMR),fluorine-19 nuclear magnetic resonance(^(19)F-NMR),gel permeation chromatography(GPC),and chemical titration.Moreover,the catalytic activity and selectivity of the rare-earth chlorides,as well as the corresponding underlying interactions were discussed.Results indicated that the rare-earth-containing catalytic reduction systems studied in this work could efficiently convert the chain-end carboxyl groups into highly active hydroxyl groups,with a highest conversion up to 87.0%and differing catalytic reduction activities ranked as NaBH_(4)/CeCl_(3)>NaBH_(4)/LaCl_(3)>NaBH_(4)/NdCl_(3).Compared with the conventional lithium aluminum hydride(LiAIH_(4))reduction system,the NaBH_(4)/RECl_(3)systems provide multiple advantages such as mild reaction conditions,high conversion ratio with good selectivity,and environmental innocuity,and are potentially applicable as new reduction-catalysis combinations for the synthesis and functionalization of polymer materials.
基金Project(3207049713)supported by the Scientific Research Foundation of Graduate School of Southeast University,China
文摘With the aim of achieving a high 5-hydroxymethylfurfural(HMF)yield from glucose with H-ZSM-5 catalyst at low cost,three inexpensive biphasic reaction systems,H2O?tetrahydrofuran(THF),H2O?2-methyltetrahydrofuran(MeTHF)and H2O?2-butanol,were discovered and proved to be particularly effective in promoting the formation of HMF from glucose over H-ZSM-5 zeolite.In order to determine the optimal process conditions,the effects of various experimental variables,such as reaction temperature,reaction time,catalyst dosage,volume of organic solvent,as well as inorganic salt type on glucose conversion to HMF in three systems were investigated in detail.It was found that under optimal reaction conditions,H2O?THF,H2O?2-butanol and H2O?MeTHF allowed the glucose dehydration process to achieve HMF yields of up to 61%,59%,and 50%,respectively.Moreover,in the three biphasic systems,the H-ZSM-5 catalyst was also demonstrated to maintain excellent stability.Thus,the catalytic approach proposed in this paper can be believed to have potential prospects for industrially efficient and low-cost production of HMF.
