Application Note · multi EA® 5000

Heavy Fuel Oil, Feed Materials and Residues– Trustable Determination of High Nitrogen
Contents in Viscous, Complex Matrices
Introduction
The worldwide growing demand for energy and the fact that the easy-to-find andcheap crude oil reserves are basically gone, force oil companies to process heavy
crude oil and heavy fractions of the refining process (e.g. distillation residues,
heavy fuel oil etc.) in an increasing extent.

Challenge
Analysis of TN in difficult todigest, highly viscous samplematrices

SolutionHigh temperature combustion
within O2+ parameter mode for
optimal digestion of the sample
followed by chemoluminescence
detection (CLD)

Heavy fractions, as thick as molasses, are not only difficult to transport andhandle, but also require advanced strategies for the compulsory quality control.
For such matrices especially the nitrogen content is of interest due to its negative
effects on the refining process (e.g. by poisoning of catalysts, unwanted sideproducts etc.).
The TN determination by means of high temperature combustion followed bychemoluminescence detection (CLD) is approved for analysis of light fractions
like naphtha, gasoline, heating oil. The nitrogen compounds present are easydigestable pyridine and quinoline derivatives. The heavier the fraction, the higher
is the content of more complex, poly-condensed nitrogen compounds (e.g.
porphyrin). When being analyzed with the same method, these matrices deliver
up to 25 % too low results for TN.

2

Heavy Fuel Oil, Feed Materials and Residues – Trustable Determination of High Nitrogen Contents in Viscose, Complex Matrices

The typical boiling points of above 400 °C and relatively high nitrogen content exceeding 0.5 wt-% make the investigation ofthese materials non-trivial. A dilution step before analysis to decrease the extremely high nitrogen content is often applied
for small improvement, but it cannot eliminate this effect. An additional optimization of the digestion process is required tomaximize the recovery up to ratios between 95 – 100 %. For this purpose we have developed the O2+ parameter mode.
Instrumentation
The multi EA® 5000 N equipped with chemoluminescence detector covers a unique wide measurement range from ultratrace contents (30 ppb) up to the weight percent range (1 wt-%). The flexible adaptation of the sample volume(1 – 100 µl), based on the expected nitrogen content, allows the operator to benefit from high precision combined with shortanalysis times.
The analyses have been run with the multi EA® 5000 N with automatic boat drive ABD in the horizontal operation mode. The
multi matrix sampler MMS 5000 in liquids configuration was used for the fully automatic injection of 10 µl of the dilutions.
The samples were decomposed at 1050 °C catalyst-free in a two-phase combustion process. To ensure an optimal digestioneven of complex compounds such as porphyrin, the O2+ parameter mode was applied (see table 1). In this mode, additional
oxygen is already present during the evaporation of the sample matrix at lower temperatures. The ABD parameter program
used, consists of three waiting positions and is presented below in table 1. Due to the waiting and the slow rate of sample
boat introduction into the combustion tube, the evaporation is slowed down remarkably. This ensures optimal conditions
for the conversion of even challenging nitrogen compounds, thus improves the yield of the NOx compared to unwanted sideproducts such as N2O and N2, which cannot be detected by the chemoluminescence.
The generated reaction gas was dried and purified, before the included NOx was quantified by means of achemoluminescence detector (CLD).
Thanks to the excellent reproducibility, a triplicate analysis was sufficient to achieve reliable results.
Table 1: O2+ parameter mode – ABD parameter set
Waiting Positions

Speed

Stop Position

Waiting Period

1600 mm/min

100 mm0s

260 mm/min

180 mm0s

330 mm/min

307 mm0s

Samples and Reagents
Sample Preparation
The provided samples were dark-colored and high-viscous oil samples (VGO, HCR feed etc.). All were diluted to enable acomfortable sample introduction by means of the autosampler as well as to allow optimal conversion of the included complex
nitrogen compounds. To get homogeneous aliquots, the samples were heated up in a water bath (80 °C, 10 - 15 min) andafterwards they were shaken thoroughly. Then dilution of the samples was done to the level of 50 mg/kg by using o-xylene
as solvent.

Heavy Fuel Oil, Feed Materials and Residues – Trustable Determination of High Nitrogen Contents in Viscose, Complex Matrices

Calibration
The calibration of the multi EA® 5000 N was carried out by different concentrated liquid standards (0 - 75 ppm N), based on
acridine in o-xylene.

Figure 1: Calibration curve of acridine in o-xylene, calibration range 10 – 75 ppm N

Results and Discussion
In table 2 the results gained by using a common procedure resp. the O2+ parameter mode are compared. The corresponding
TN analysis curves are shown in Fig. 2 – 4.
Table 2: Results of TN determination by means of different strategies
SampleTN nominal

RecoveryCommon procedure

O2+ parameter mode

Residual fuel 1

0.64 wt-%

73 %

95 %

Residual fuel 20.70 wt-%

71 %

97 %

Heavy fuel oil

0.50 wt-%

75 %

100 %

When using the O2+ parameter mode acceptable high recovery rates can be gained with a good reproducibility, even fordifficult to digest matrices.

Figure 2: TN determination “residual fuel 1”

Figure 3: TN determination “residual fuel 2”3

4

Heavy Fuel Oil, Feed Materials and Residues – Trustable Determination of High Nitrogen Contents in Viscose, Complex Matrices

Figure 4: TN determination “heavy fuel oil”

Conclusion
The multi EA® 5000 N in combination with the O2+ parameter mode guarantees best results for the TN measurement ofdifficult to digest, highly viscous sample matrices such as VGO, heavy fuel oil, residues etc..
The multi EA® 5000 N can be upgraded with suitable accessory modules for automatic determination of Sulfur (TS), Chlorine(TX) and Carbon (TC) in solid, liquid, gaseous and LPG sample matrices.

Headquarters

Analytik Jena AG
Konrad-Zuse-Strasse 107745 Jena · Germany

Phone
Fax+49 36 41 77 70+49 36 41 77 9279

info@analytik-jena.com
www.analytik-jena.com

en · 05/2016© Analytik Jena AG | Pictures ©: Istock/graffizone