NEX QC—Analysis of S, Ni, V, Fe in Residual Oil
Scope
The analysis of sulfur (S), nickel (Ni), vanadium (V), and iron (Fe) in residual oil is demonstrated.
Background
Residual oil is the low-grade oil that remains after the distillation and refining of crude oil. Residual oil, also called resid, has many uses, including in the blending of bunker fuel, and the production of adhesives and asphalt. In some regions resid can be burned as a secondary fuel and may be further refined as a heating fuel. Characterization of the nickel and vanadium content is important for many reasons. Chief among these is that nickel and vanadium are considered catalyst poisons and need to be removed prior to the cracking of petroleum crude or residual oils. Applied Rigaku Technologies meets the industry analytical need with the NEX QC series of EDXRF analyzers. Fast and simple, the NEX QC provides an ideal tool for monitoring the concentrations of nickel, vanadium, and iron in resid as well as the sulfur content.
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Model: NEX QC
Calibration
Empirical calibrations were built using a suite of 12 commercially available residual oil calibration standards. Alpha corrections are then employed to automatically compensate for variations in X-ray absorption and enhancement effects within the sample due to the independent variations in element concentration. A summary of the empirical calibrations is shown here.
| Element | Concentration range |
| S | 0.24 – 5.50 % |
| Ni | 3 – 100 ppm |
| V | 25 – 500 ppm |
| Fe | 15 – 500 ppm |
Repeatability
To demonstrate repeatability (precision), two typical calibration standards were
selected. Each was measured in 10 repeat analyses without moving the sample
between measurements.
| Sample: Std 2 | ||||
| Element | Standard value | Average value | Std. dev | % Relative dev |
| S | 0.50 % | 0.503 | 0.007 | 1.4 |
| Ni | 10 ppm | 11 | 0.6 | 6.0 |
| V | 500 ppm | 501 | 5 | 1.0 |
| Fe | 300 ppm | 300 | 3 | 1.0 |
| Sample: Std 12 | ||||
| Element | Standard value | Average value | Std. dev | % Relative dev |
| S | 5.50 % | 5.52 | 0.012 | 0.2 |
| Ni | 100 ppm | 98 | 1.7 | 1.7 |
| V | 51 ppm | 53 | 1.4 | 2.7 |
| Fe | 50 ppm | 48 | 2.1 | 4.2 |
| Sample: Std 5 | ||||
| Element | Standard value | Average value | Std. dev | % Relative dev |
| S | 2.00 % | 2.03 | 0.008 | 0.4 |
| Ni | 40 ppm | 42 | 1.3 | 3.3 |
| V | 100 ppm | 102 | 1.1 | 1.1 |
| Fe | 201 ppm | 198 | 4.6 | 2.3 |
Conclusion
The NEX QC offers analysts a simple yet powerful and versatile system for quantifying elemental composition using the empirical approach. The results of this study indicate that given stable samples, proper sample handling, and proper calibration technique, the Rigaku NEX QC EDXRF can achieve excellent results in monitoring the concentration of sulfur, nickel, vanadium, and iron in residual oil.
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