AN-NIR-024
2020-03
Quality control of pyrolysis gasoline
Determination of diene value within one minute using NIRS
Summary
Pyrolysis gasoline (Pygas) is a byproduct of ethylene production, which contains unwanted conjugated diolefins making it unsuitable as a motor fuel. To overcome this limitation, the olefin content needs to be reduced below 2 mg/g pygas in a selective hydrogenation unit (SHU). The diene value, or maleic anhydride value (MAV), is usually determined by the Diels-Alder wet chemical method (UOP326-17).
This wet chemical method requires several hours to perform by highly trained analysts. In contrast to the primary method, near-infrared spectroscopy (NIRS) is a cost-efficient and fast analytic solution for the determination of diene value in pyrolysis gasoline.
Result
The obtained Vis-NIR spectra (Figure 2) were used to create a prediction model for the diene value determination. To verify the quality of the prediction model, correlation diagrams were created which display the correlation between Vis-NIR prediction and primary method values (Figure 3). The respective figures of merit (FOM) display the expected precision of a prediction during routine analysis.
Figures of merit | Value |
---|---|
R2 | 0.9253 |
Standard error of calibration | 0.42 mg/g |
Standard error of cross-validation | 0.46 mg/g |
Conclusion
This application note shows the feasibility of NIR spectroscopy for the analysis of diene value in pyrolysis gasoline. In comparison to the wet chemical method UOP326-17 (Table 3), the time to result is a major advantage of NIR spectroscopy, since a single measurement is performed within one minute.
Parameter | Method | Time to result and workflow |
---|---|---|
Diene value | Diels Alder (UOP326-17) | ∼6 hr; reflux, hydrolysis, titration |