以MOF-5为改性剂对纤维素水凝胶进行掺杂改性,通过FT-IR、XRD和SEM对其结构进行了表征,并研究了掺杂量、pH、盐溶液浓度、温度对复合纤维素水凝胶保水性能的影响及其可循环利用特性。结果表明,纤维素水凝胶表面的活性基团,有利于MOF-5...以MOF-5为改性剂对纤维素水凝胶进行掺杂改性,通过FT-IR、XRD和SEM对其结构进行了表征,并研究了掺杂量、pH、盐溶液浓度、温度对复合纤维素水凝胶保水性能的影响及其可循环利用特性。结果表明,纤维素水凝胶表面的活性基团,有利于MOF-5与其结合,与纯纤维素水凝胶相比,吸水率最高达4294.94%,提高了1725.63%。保水性实验发现,复合水凝胶在NaCl、AlCl3盐溶液中的保水效果随着浓度增大而减小;当MOF-5掺杂量为20%、pH=12、盐溶液浓度为4 m mol/L时具有最佳的保水效果,且在40℃,放置175 min,最佳掺杂量的复合纤维素水凝胶保水率仍在50%以上。可循环利用性实验证实,复合纤维素水凝胶循环使用3次时,其保有率仍高于50%。实验结果表明该复合水凝胶在高温农业生产领域有潜在应用价值。展开更多
Polyhydroxyalkanoate(PHA),a well-known biodegradable polymer,featuresβ-lactones as its monomers,which can be selectively synthesized through ring-expansion carbonylation of epoxides using well-defined[Lewis acid]^(+)...Polyhydroxyalkanoate(PHA),a well-known biodegradable polymer,featuresβ-lactones as its monomers,which can be selectively synthesized through ring-expansion carbonylation of epoxides using well-defined[Lewis acid]^(+)[Co(CO)_(4)]^(-)catalysts.However,the decomposition of[Co(CO)_(4)]^(-)species at temperatures exceeding 80℃presents a hurdle for the development of commercially viable processes under high-temperature reaction conditions to reduce reaction time.Drawing insights from stable{(acyl)Co(CO)n}intermediates involved in historical HCo(CO)_(4)-catalyzed hydroformylation processes,we sought to the high-temperature catalytic activity of epoxide ring-expansion carbonylation.The developed catalyst system,[(acetyl)Co(CO)_(2)dppp]and[(TPP)CrCl],exhibited exceptional catalytic performance with an unprecedented initial turnover frequency of 4700 h^(-1)at 100℃and a turnover numbers of 93000.Notably,the catalyst displayed outstanding stability,operating at 80℃for 168 h while selectively generatingβ-lactones.展开更多
The conversion of levulinic acid to γ-valerolactone is one of the most important reactions from biomass platform molecule to value-added chemicals.Rubased catalysts have shown high activity and selectivity in previou...The conversion of levulinic acid to γ-valerolactone is one of the most important reactions from biomass platform molecule to value-added chemicals.Rubased catalysts have shown high activity and selectivity in previous studies but always required complex synthetic method or harsh reaction conditions.In this work,biomass-derived chitosan was used to prepare nitrogen doped carbon.After the loading of Ru,the Ru/NC(NC:nitrogen-doped carbon)catalyst was employed in the solvent-free hydrogenation of levulinic acid under ambient hydrogen pressure at 50−80℃ to reach full conversion.The calcination temperature was optimized to get Ru/NC-800 catalyst with high intrinsic turnover frequency of 358 h^(−1).The apparent activation energy was studied by kinetic experiments.More significantly,the catalyst was small-scaled tested for 36 h in a fix-bed reactor with 620 g/day productivity of γ-valerolactone.The catalyst can be easily synthesized and have high activity and stability,underscoring the potential of future commercial production of γ-valerolactone from levulinic acid.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
文摘以MOF-5为改性剂对纤维素水凝胶进行掺杂改性,通过FT-IR、XRD和SEM对其结构进行了表征,并研究了掺杂量、pH、盐溶液浓度、温度对复合纤维素水凝胶保水性能的影响及其可循环利用特性。结果表明,纤维素水凝胶表面的活性基团,有利于MOF-5与其结合,与纯纤维素水凝胶相比,吸水率最高达4294.94%,提高了1725.63%。保水性实验发现,复合水凝胶在NaCl、AlCl3盐溶液中的保水效果随着浓度增大而减小;当MOF-5掺杂量为20%、pH=12、盐溶液浓度为4 m mol/L时具有最佳的保水效果,且在40℃,放置175 min,最佳掺杂量的复合纤维素水凝胶保水率仍在50%以上。可循环利用性实验证实,复合纤维素水凝胶循环使用3次时,其保有率仍高于50%。实验结果表明该复合水凝胶在高温农业生产领域有潜在应用价值。
文摘Polyhydroxyalkanoate(PHA),a well-known biodegradable polymer,featuresβ-lactones as its monomers,which can be selectively synthesized through ring-expansion carbonylation of epoxides using well-defined[Lewis acid]^(+)[Co(CO)_(4)]^(-)catalysts.However,the decomposition of[Co(CO)_(4)]^(-)species at temperatures exceeding 80℃presents a hurdle for the development of commercially viable processes under high-temperature reaction conditions to reduce reaction time.Drawing insights from stable{(acyl)Co(CO)n}intermediates involved in historical HCo(CO)_(4)-catalyzed hydroformylation processes,we sought to the high-temperature catalytic activity of epoxide ring-expansion carbonylation.The developed catalyst system,[(acetyl)Co(CO)_(2)dppp]and[(TPP)CrCl],exhibited exceptional catalytic performance with an unprecedented initial turnover frequency of 4700 h^(-1)at 100℃and a turnover numbers of 93000.Notably,the catalyst displayed outstanding stability,operating at 80℃for 168 h while selectively generatingβ-lactones.
基金financially supported by the National Natural Science Foundation of China (No.21905266)the Fundamental Research Funds for the Central Universities (WK3530000013)。
文摘The conversion of levulinic acid to γ-valerolactone is one of the most important reactions from biomass platform molecule to value-added chemicals.Rubased catalysts have shown high activity and selectivity in previous studies but always required complex synthetic method or harsh reaction conditions.In this work,biomass-derived chitosan was used to prepare nitrogen doped carbon.After the loading of Ru,the Ru/NC(NC:nitrogen-doped carbon)catalyst was employed in the solvent-free hydrogenation of levulinic acid under ambient hydrogen pressure at 50−80℃ to reach full conversion.The calcination temperature was optimized to get Ru/NC-800 catalyst with high intrinsic turnover frequency of 358 h^(−1).The apparent activation energy was studied by kinetic experiments.More significantly,the catalyst was small-scaled tested for 36 h in a fix-bed reactor with 620 g/day productivity of γ-valerolactone.The catalyst can be easily synthesized and have high activity and stability,underscoring the potential of future commercial production of γ-valerolactone from levulinic acid.
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.
