以三甲基磷氧(TMPO)和三丁基磷氧(TBPO)为探针分子,用31P魔角旋转核磁共振(31P MAS NMR)法对稀土改性Y型分子筛的酸性进行了定性和定量分析.结果表明,以TMPO为探针分子的31P MAS NMR谱分别在δ=78,70,65,62,58,55和53处存在与酸中心相...以三甲基磷氧(TMPO)和三丁基磷氧(TBPO)为探针分子,用31P魔角旋转核磁共振(31P MAS NMR)法对稀土改性Y型分子筛的酸性进行了定性和定量分析.结果表明,以TMPO为探针分子的31P MAS NMR谱分别在δ=78,70,65,62,58,55和53处存在与酸中心相关的吸收峰,其中δ=78和70处吸收峰与分子筛内部和外部酸性有关,δ=65,62,58和53处吸收峰归属于TMPO在分子筛内部Brnsted酸中心上的贡献,δ=55处吸收峰归属于TMPO在分子筛内部Lewis酸中心上的贡献.随着稀土含量的增加,中等强度Brnsted酸中心(δ=62和58)数量显著增加,而强Brnsted酸中心(δ=65)和较弱Lewis酸中心(δ=55)数量显著降低.结合分子筛骨架铝和非骨架铝对分子筛酸性的影响进一步探讨了稀土改型Y分子筛的酸性.展开更多
In an effort to utilize NMR technique for the analysis of the structural components of wood and biomasses such as lignin, we made a comparative study of lignin contents of several types of lignocellulosie materials bo...In an effort to utilize NMR technique for the analysis of the structural components of wood and biomasses such as lignin, we made a comparative study of lignin contents of several types of lignocellulosie materials both before and after enzymatic hydrolyses. To this end, Eucalyptus Globulus, Norway spruce thermomeehanieal pulp（TMP） corn stover and Eucalyptus kraft pulp were ball-milled and treated with cellulase to prepare materials with high lignin contents. These materials were analyzed via ^31p NMR in ionic liquids. The results show that the contents of various functional groups for the lignocellulosic materials after enzymatic hydrolyses are generally in agreement with those from their corresponding enzymatic mild acidolysis liginins（EMALs）, indicating that ^31p NMR analysis of lignocellulosic materials in ionic liquids is a promising method for quantitative characterization of lignocellulosic materials.展开更多
基金supported by the National Basic Research Program of China (973 Program 2003CB615804)+1 种基金the National Natural Science Foundation of China (20673054)the National Key Technology R&D Program (2012BAE05B00)~~
文摘以三甲基磷氧(TMPO)和三丁基磷氧(TBPO)为探针分子,用31P魔角旋转核磁共振(31P MAS NMR)法对稀土改性Y型分子筛的酸性进行了定性和定量分析.结果表明,以TMPO为探针分子的31P MAS NMR谱分别在δ=78,70,65,62,58,55和53处存在与酸中心相关的吸收峰,其中δ=78和70处吸收峰与分子筛内部和外部酸性有关,δ=65,62,58和53处吸收峰归属于TMPO在分子筛内部Brnsted酸中心上的贡献,δ=55处吸收峰归属于TMPO在分子筛内部Lewis酸中心上的贡献.随着稀土含量的增加,中等强度Brnsted酸中心(δ=62和58)数量显著增加,而强Brnsted酸中心(δ=65)和较弱Lewis酸中心(δ=55)数量显著降低.结合分子筛骨架铝和非骨架铝对分子筛酸性的影响进一步探讨了稀土改型Y分子筛的酸性.
文摘农田生态系统中土壤磷形态转化,影响土壤磷对作物的有效供应。土壤磷分为无机磷和有机磷两大部分。化学连续提取法(chemical sequential fractionation,CSF)研究土壤磷形态分级,采用不同的化学提取剂,分级提取土壤中组成或分解能力接近的有机无机含磷化合物,是目前表征土壤磷素形态的重要方法。但该方法虽历经改进,仍难以确切反映土壤磷的实际组成,提取的不同磷形态间存在重叠,有机磷和无机磷组分分级存在一定的误差;不同分级磷组分对作物的有效性,需谨慎评估。核磁共振波谱技术(nuclear magnetic resonance,NMR)根据核磁共振波谱图上共振峰的位置、强度和精细结构来研究土壤中含磷化合物的分子结构。液相31PNMR可以同吋检测出土壤中多种磷组分,如正磷酸盐、磷酸单酯、磷酸二酯、膦酸脂、焦磷酸盐和多聚磷酸盐,识别土壤提取物磷形态,可将有机磷与无机磷分开。本文综述了应用31P-NMR技术研究土壤磷形态组分的一些进展,总结了样品制备过程、NMR测试参数及在土壤磷形态转化研究中的应用。二维31P-NMR技术发展为鉴定分析土壤中更多种类的含磷化合物提供了契机。
基金Supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education, China and the Scientific and Technological Development Programs of of Beijing Municipal Education Commission (No.KM201010011004)
文摘In an effort to utilize NMR technique for the analysis of the structural components of wood and biomasses such as lignin, we made a comparative study of lignin contents of several types of lignocellulosie materials both before and after enzymatic hydrolyses. To this end, Eucalyptus Globulus, Norway spruce thermomeehanieal pulp（TMP） corn stover and Eucalyptus kraft pulp were ball-milled and treated with cellulase to prepare materials with high lignin contents. These materials were analyzed via ^31p NMR in ionic liquids. The results show that the contents of various functional groups for the lignocellulosic materials after enzymatic hydrolyses are generally in agreement with those from their corresponding enzymatic mild acidolysis liginins（EMALs）, indicating that ^31p NMR analysis of lignocellulosic materials in ionic liquids is a promising method for quantitative characterization of lignocellulosic materials.
