固体核磁碳结构参数的修正及其在煤结构分析中的应用

为消除~(13)C CP/M AS/TOSS NM R测试中碳核NOE效应,获得相对准确的碳结构参数,考察了不同模型化合物的碳核NOE效应强度。结果表明,不同模型化合物碳谱分峰拟合的测试值与样品碳结构参数的理论值之间存在明显误差,其中,脂肪碳在25%-125%、芳香碳为4%-50%,NOE效应在固体核磁碳谱测试中影响显著。为此,将模型化合物脂肪碳和芳香碳的实测值和理论值进行回归分析,得到非线性回归方程。用该方程对9,10-二甲基蒽进行碳结构修正,发现修正后脂肪碳实测值与理论值之间误差由不修正时的119.60%减小至7.84%,芳香碳误差为由不修正时的-17.10%到1.11%,修正后误差均在10%以内;同时用该回归方程修正了不同煤的碳结构参数,发现不同煤未修正的H/C原子比与其元素分析H/C原子比误差在45%-53%,修正后误差只有4%-13%,与元素分析结果具有一致性,表明非线性回归方程能够方便、准确地消除固体核磁NOE效应,为煤中碳结构分析提供新的技术支撑。

Calibration of solid state NMR carbon structural parameters and application in coal structure analysis

Carbon structure parameters were obtained accurately, if the NOE effect of carbon nucleus has been eliminated in ¹³C CP/MAS/TOSS NMR test. This study has investigated different model compounds NOE effect intensity. And the results show that there is an obvious carbon structure error between the fitting test value and theoretical value in the different model compounds. The aliphatic carbon error is 25%-125%, and the aromatic carbon is 4%-50%, the NOE effect has great influence in solid state NMR. Therefore, the nonlinear regression equation was obtained by regression analysis of the measured and theoretical values of the model compound aliphatic and aromatic carbon. And this equation was used to calibrate the carbon structure of 9,10-dimethylanthracene. It is found that after calibration the error between the measured value and the theoretical value of the modified aliphatic is reduced from 119.60% to 7.84%. The error of the aromatic carbon is reduced from -17.10% to 1.11%. And the error is within 10%. Then, the carbon structural parameters of different coal are calibrated by the regression equation. It is found that the H/C error of different coal is 45%-53% compared with elements analysis, and the calibration error is only 4%-13%, which is consistent with the results of elemental analysis. It indicated that the nonlinear regression equation could easily and precisely correct the solid state NMR carbon nuclear NOE effects and also provides new technical support for analysis of carbon structure in coal.