Examine the Aromatic Content of Gasoline with Spectroscopy

Most of the combustion properties of gasoline are determined by its aromatic content. It is desired to have accurate measurements of this parameter as it also impacts the fuel’s environmental characteristics. The conventional analytical method used for measuring aromatics is either an older method called fluorescent indicator adsorption (FIA) or gas chromatography (GC), both of which are time and labor intensive. This article explains the application of Guided Wave hardware and software tools for measuring % aromatics in fuel products using fiber optic-based, Near-Infrared (NIR) spectroscopy. NIR can either be applied in real time directly in process monitoring or as a laboratory procedure. In both cases, NIR is a money- and time-saving alternative to conventional methods.

Figure 1.NIR Spectra of Gasoline Samples

测量背景

电磁光谱的NIR区域可实现O-H，N-H和C-H基本面的叠声和组合带的使用。可以通过测量已知芳香族浓度的一系列燃料样品的NIR光谱来开发定量模型。该模型将仅取决于其NIR光谱，在将来的样品中对％芳香剂进行测量。指导波分析仪系统使用光纤，使样品探针可以放置在远离分光光度计本身的偏远位置。

图2。实验室与NIR％芳香学（散点图）

Experiment

用一个引导波NIR-O™工艺分析仪分光光度计，一组已知芳香族浓度范围为2.0至62.0％芳香族的大量不同工艺汽油样品的NIR光谱在1000至1600 nm之间测量。图1中所示的是一些使用具有1 cm路径长度的在线工艺探针获得的一些代表性汽油样品的吸光度光谱。对于此应用程序，数据预处理包括一个简单的2分基线校正，以消除任何偏移。浓度数据和光谱已提交给Unscrambler^TMsoftware, and using PLS regression methodology, a calibration model was developed. For a discussion of PLS and other multivariate calibration techniques, refer Martens & Naes¹和ASTM E1655²。

图3。Laboratory vs NIR % Aromatics (trend plot)

Results

The model was used for predicting aromatic concentrations over a time period of three months. This was done by using an in-situ probe inserted in a gasoline process stream measuring in real time. In Figures 2 and 3, the results for this are shown as a scatter plot and a trend plot, respectively. The model yielded a prediction RMSEP (root mean square error of prediction) of 2.5% aromatics. This corresponds with the accuracy of the standard laboratory method.

Conclusion

通过利用本文中描述的引导波软件和硬件工具，使用NIR光谱法测量汽油中的芳香剂既快速又可靠。该技术减少了对实验室样本收集的需求。在其他复杂的碳氢化合物流中，有实时（秒）的实时（秒）可用结果。

References

1. H. Martens，T。Naes，多元校准，John Wiley＆Sons，1989年。
2. ASTM E1655 Standard Practices for Infrared, Multivariate, Quantitative Analysis.

This information has been sourced, reviewed and adapted from materials provided by Guided Wave.

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