Analysis of Methanol Content in Methanol Gasoline Based on Calibration of Portable Raman Spectrometer
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摘要: 甲醇汽油作为汽油的替代燃料,具有经济环保的特点,其甲醇浓度对热值、抗爆性、燃烧效率等都有显著影响。作为一种无损、快速、便携、易操作、成本低的分析方法,便携式拉曼光谱已经被应用于甲醇汽油甲醇含量分析,然而便携式拉曼光谱仪的非线性拉曼频移示值误差影响分析建模的准确性。提出一种用于便携式拉曼光谱仪校正的甲醇汽油甲醇含量分析方法,使用拉曼频移标准物质聚苯乙烯进行多点校正,对校正拉曼光谱使用寻峰算法,基于两个甲醇特征峰,提出二元线性回归方法建立定量分析模型。模型的预测结果和评价指标均表明本方法可以对甲醇含量进行比较准确的预测。Abstract: As an alternative fuel to gasoline, methanol gasoline is economical and environmentally friendly, and its methanol concentration has a significant effect on calorific value, explosion resistance, and combustion efficiency. As a nondestructive, rapid, portable, easy-to-operate, and low-cost analytical method, portable Raman spectroscopy has been applied to the analysis of the methanol content of methanol gasoline. However, the nonlinear Raman frequency-shift demonstration error of portable Raman spectrometers affects the accuracy of analytical modeling. A method for methanol content analysis of methanol gasoline with portable Raman spectrometer calibration is proposed. The polystyrene Raman frequency-shifted reference material is used for multi-point calibration, and a peak detection algorithm is used for the calibration of Raman spectra. Based on two characteristic peaks of methanol, a binary linear regression method is proposed to establish a quantitative analysis model. The prediction results and evaluation indexes of the model show that this method can predict the methanol content more accurately.
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表 1 聚苯乙烯特征峰拉曼频移修正值
Table 1. Raman frequency shift correction of polystyrene characteristic peaks
拉曼频移
(cm−1)修正值
(cm−1)拉曼频移
(cm−1)修正值
(cm−1)621.2 +5.2 1449.0 +4.9 795.5 +4.8 1583.2 +5.8 1001.0 +4.4 1602.4 +4.1 1031.2 +4.0 2851.3 +1.6 1154.6 +3.7 2907.5 +7.5 表 2 38组甲醇汽油样品的配制方法
Table 2. Preparation method of 38 groups of methanol gasoline samples
甲醇浓度(%) 甲醇体积(mL) 汽油体积(mL) 1 0.1 9.9 2 0.2 9.8 3 0.3 9.7 … … … 37 3.7 6.3 38 3.8 6.2 表 3 模型评价指标比较
Table 3. Comparison of model evaluation indicators
建模
方法校正集 预测集 RMSECV $R_{ {{\rm{CV}}} }^2$ RMSEP $R_{{\rm{P}}}^2$ PLS 1.637 0.9787 1.276 0.9848 二元线性回归 1.672 0.9796 1.717 0.9771 -
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