A Comparison of Boat Introduction and Direct Injection using the Thermo Scientific ipro 5000 Series Combustion Analyzer

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1 Application Note: A Comparison of Boat Introduction and Direct Injection using the Thermo Scientific ipro 5000 Series Combustion Analyzer Kristian J. Hoffman, Angela Seipel, Application Specialists, Thermo Fisher Scientific, Cambridge, UK Key Words ipro 5000 Series ASTM D5762 ASTM D5453 Bunker C Oil Crude Oil jetpro direct spray injector Lubricating Oils Nitrogen Sulfur Introduction Low value products from crude refining are often converted to higher value blending stock using catalytic cracking processes. These low value products typically contain high concentrations of nitrogen and sulfur, both of which are detrimental to catalytic performance. Knowledge of the sulfur and nitrogen content of low value distillates is therefore required prior to processing into higher value products. Further uses of low value products (which typically have a high molecular weight) include domestic heating and maritime fuels. The sulfur and nitrogen content of these products is governed by ever more stringent legislation, necessitating the accurate determination of total sulfur and total nitrogen content. Traditionally, high molecular weight products with boiling points above 400 C have been analyzed for sulfur by X-ray fluorescence spectrometry (XRF) and for nitrogen using boat inlet oxidation. Boat inlet oxidation uses chemiluminescence-based nitrogen detection and is governed by ASTM D5762 [1] which is applicable to samples with nitrogen content in the range mg/kg. Analysis of sulfur by UV-fluorescence is governed by ASTM D5453 [2] and is applicable to samples containing 1.0 to 8000 mg/kg total sulfur, with boiling points less than 400 C and viscosities less than 20 cst at room temperature. Using direct spray injection allows the temperature range of ASTM D5453 to be extended above 400 C. This application note compares the technique of direct spray injection to that of boat inlet oxidation for the analysis of heavy hydrocarbons. Direct spray injection measurements were performed using the Thermo Scientific ipro 5000 Series Total Nitrogen and Total Sulfur (TN/TS) analyzer, fitted with a Thermo Scientific jetpro direct spray injector, whilst boat inlet oxidation was conducted using a Thermo Scientific TN/TS 3000 analyzer. Both instruments employ the same detection techniques: chemiluminescence based total nitrogen (TN) detection and UV-fluorescence based total sulfur (TS) detection. Experimental Calibration of the Thermo Scientific ipro 5000 NS analyzer, which is the Total Nitrogen and Total Sulfur configuration of the ipro 5000 Series TN/TS analyzers, and the Thermo Scientific TN/TS 3000 analyzer was achieved using standards containing equal molar quantities of sulfur and nitrogen derived from pyridine and thiophene dissolved in xylene. Several standards over the range 0 to 50 mg/kg were prepared by serial dilution of stock standards and provided calibration of the nitrogen and sulfur detectors. Six samples were selected for analysis from several ASTM Crosscheck Programs. The samples consisted of four lube oils, a crude oil and a Bunker C oil. Prior to introducing the samples into the furnace, they were firstly diluted by mass in xylene to yield the dilution factors presented in Table 1. Dilution was performed in order to reduce the viscosity of the samples, thereby allowing for the efficient injection of samples using a syringe. An additional benefit of dilution was that it allowed for a far wider range of total sulfur and total nitrogen concentrations to be determined using a given calibration range. Sample Sample Mass of Total mass of Dilution type Name sample sample and factor xylene g g Lubricating Oil ASTM LU Lubricating Oil ASTM LU Lubricating Oil ASTM LU Lubricating Oil ASTM LU Crude Oil ASTM CO Bunker Oil ASTM F Table 1: Dilution factors used during sample preparation.

2 TN/TS 3000 Procedure In the case of analysis using the Thermo Scientific TN/TS 3000 analyzer, samples were injected into a quartz boat contained within a solids module. A 100 µl Hamilton 700 Series MICROLITER Syringe was used to inject samples onto a small amount of quartz wool, which was packed into the quartz boat. The data acquisition and peak analysis was controlled by the Thermo Scientific ThEuS Software and the parameters used by the software for driving the boat into the furnace are presented in Table 2. System parameters employed on the TN/TS 3000 analyzer are presented in Table 3. Variable name Position Speed Wait time (mm) (mm/s) (s) Boat to position Boat to position Boat to position Boat to position Boat to position Boat to position Boat cooling time Parameter Argon carrier flow Oxygen primary flow Oxygen secondary flow Oxygen makeup flow Oxygen ozonator flow System value 320 ml/min 400 ml/min Temperature furnace I 1000 C Temperature furnace II 1100 C Injection speed 1.0 µl/s Sample volume 25 µl Table 4 System parameters for the ipro 5000 NS Analyzer. Results Presented in Figure 1 and Figure 2 are the nitrogen and sulfur calibration lines determined on the ipro 5000 NS analyzer. It is clear that both show excellent linearity, with R 2 = and R 2 = for the TN and TS channels, respectively. This linearity compared well with that of the Thermo Scientific TN/TS 3000 analyzer (not shown). Table 2 Parameters used to drive the boat into the furnace for analysis using the TN/TS 3000 analyzer. Parameter System value Argon flow 100 ml/min Oxygen primary flow 2 Oxygen turbo flow 100 ml/min Oxygen ozonator flow 100 mlmin Temperature furnace I 1100 C Temperature furnace II 1100 C Temperature outlet 300 C Injection speed 1 µl/s Sample volume 100 µl Table 3 System parameters for analysis using the TN/TS 3000 Analyzer. Figure 1: Linear calibration line fit for the ipro 5000 NS analyzer nitrogen detector. ipro 5000 NS Procedure A Thermo Scientific AS3000 Autosampler was used in conjunction with the ipro 5000 NS analyzer to directly inject samples into the furnace. Data acquisition and peak analysis was fully automated by the Thermo Scientific NSX Visual Software. System parameters were set by the NSX Visual Software according to the selected pre-loaded method and automatically resulted in the system parameters presented in Table 4. Figure 2: Linear calibration line fit for the ipro 5000 NS analyzer sulfur detector. Representative peak shapes for Total Nitrogen (TN) and Total Sulfur (TS) analysis using boat inlet oxidation are displayed in Figure 3 and Figure 4, respectively. The corresponding peaks for direct injection are shown in Figure 5 and Figure 6.

3 Figure 3: Representative peak shape for TN detection using a TN/TS 3000 analyzer. The figure pertains to the TN peak shape recorded for the sample Figure 5: Representative peak shape for TN detection using an ipro 5000 NS analyzer. The figure pertains to the TN peak shape recorded for the sample Figure 4: Representative peak shape for TS detection using a TN/TS 3000 analyzer. The figure pertains to the TS peak shape recorded for the sample Figure 6: Representative peak shape for TS detection using an ipro 5000 NS analyzer. The figure pertains to the TS peak shape recorded for sample Table 5 and Table 6 contain the results for TN and TS analysis on the TN/TS 3000 analyzer and Table 7 and Table 8 contain the corresponding data obtained using an ipro 5000 NS analyzer. A summary of the data obtained using the two different analyzers is presented in Table 9.

4 mg N/kg mg N/kg mg N/kg mg N/kg mg N/kg % ASTM LU ASTM LU ASTM LU ASTM LU ASTM CO ASTM F Table 5: TN concentration areas obtained using a TN/TS 3000 analyzer. Three replicates of 100 µl were performed for each of the diluted oils. mg S/kg mg S/kg mg S/kg mg S/kg mg N/kg % ASTM LU ASTM LU ASTM LU ASTM LU ASTM CO ASTM F Table 6: TS concentration areas obtained using a TN/TS 3000 analyzer. Three replicates of 100 µl were performed for each of the diluted oils. mg N/kg mg N/kg mg N/kg mg N/kg mg N/kg % ASTM LU ASTM LU ASTM LU ASTM LU ASTM CO ASTM F Table 7: TN concentration areas obtained using an ipro 5000 NS analyzer. Three replicates of 25 µl were performed for each of the diluted oils. mg S/kg mg S/kg mg S/kg mg S/kg mg N/kg % ASTM LU ASTM LU ASTM LU ASTM LU ASTM CO ASTM F Table 8: TS concentration areas obtained using an ipro 5000 NS analyzer. Three replicates of 25 µl were performed for each of the diluted oils. Sample name TN (ipro 5000) TN (3000 series) TN (ASTM result) TS (ipro 5000) TS (3000 series) TS (ASTM result) Total Analysis Total Analysis time time concentration concentration concentration concentration concentration concentration (ipro 5000) (3000 series) mg N/kg mg N/kg mg N/kg mg S/kg mg S/kg mg S/kg min min ASTM LU ± ± ± ± ± ± ASTM LU ± ± ± ± ± ± ASTM LU ± ± ± ± ± ± ASTM LU ± ± ± ± ± ± ASTM CO ± ± ± ASTM F ± ± ± ± ± ± Table 9: Summary of results comparing boat inlet oxidation with direct spray injection.

5 Conclusions The results presented in Table 9 demonstrate that direct spray injection and boat inlet oxidation give entirely equivalent results for total nitrogen and total sulfur content, whilst highlighting that direct spray injection results in a significantly shorter analysis time. These results show excellent agreement with the values reporting during the ASTM Crosscheck program studies for ASTM D5762 which are provided in Table 9. The Thermo Scientific ipro 5000 NS analyzer advances the success of the Thermo Scientific TN/TS 3000 analyzer by combining improved sample introduction and detection systems with the same rugged furnace design concept incorporated in the TN/TS 3000 instrument. The ipro 5000 Series TN/TS analyzer is less than half the size of its predecessor, the TN/TS 3000 instrument, however it provides significantly reduced analysis times for heavy refinery products. References [1] ASTM D Standard Test Method for Nitrogen in Petroleum and Petroleum Products by Boat-Inlet Chemiluminescence [2] ASTM D Standard Test Method for Determination of Total Sulfur in Light Hydrocarbons, Spark Ignition Engine Fuel, Diesel Engine Fuel, and Engine Oil by Ultraviolet Fluorescence In addition to these offices, Thermo Fisher Scientific maintains a network of represen - tative organizations throughout the world. Africa-Other Australia Austria Belgium Canada China Denmark Europe-Other Finland / Norway/ Sweden France Germany India Italy Japan Latin America Middle East Netherlands New Zealand Russia/CIS South Africa Spain Switzerland UK USA Thermo Fisher Scientific Inc. All rights reserved. ISO is the registered trademark of the International Standards Organisation. ASTM is a trademark of the American Society for Testing and Materials. MICROLITER is a trademark of Hamilton Corporation.. All other trademarks are the property of Thermo Fisher Scientific Inc. and its subsidiaries. Specifications, terms and pricing are subject to change. Not all products are available in all countries. Please consult your local sales representative for details. Thermo Electron Manufacturing Ltd (Cambridge) is ISO Certified. AN42165_E 07/11C Part of Thermo Fisher Scientific