Extension of analytical methods for detailed characterization of advanced combustion engine emissions.
Advanced combustion strategies used to improve efficiency, emissions, and performance in internal combustion engines (IC) alter the chemical composition of engine-out emissions. The characterization of exhaust chemistry from advanced IC engines requires an analytical system capable of measuring a wide range of compounds. For many years, the widely accepted Coordinating Research Council (CRC) Auto/Oil procedure[1,2] has been used to quantify hydrocarbon compounds between [C.sub.1] and [C.sub.12] from dilute engine exhaust in Tedlar polyvinyl fluoride (PVF) bags. Hydrocarbons greater than [C.sub.12+] present the greatest challenge for identification in diesel exhaust. Above [C.sub.12], PVF bags risk losing the higher molecular weight compounds due to adsorption to the walls of the bag or by condensation of the heavier compounds. This paper describes two specialized exhaust gas sampling and analytical systems capable of analyzing the mid-range ([C.sub.10] - [C.sub.24]) and the high range ([C.sub.24+]) hydrocarbon in exhaust. An automated gas chromatograph equipped with a mass spectrometer (GC-MS) sampling system was used to sample middle range hydrocarbons from raw exhaust. A separate sampling system consisting of a filter and XAD traps was used for the collection of particulate-phase and semi-volatile-phase hydrocarbons up to [C.sub.24+] in dilute exhaust. After extraction, hydrocarbons trapped by the particulate filter and the XAD traps were speciated by a two dimensional gas chromatography mass spectroscopy (GCxGC-MS) technique. These two novel systems allowed more than 2000 compounds to be detected in the exhaust thus extended the analytical capacity in emission characterization.
CITATION: Kroll, S., Fanick, E., and Favela, K., "Extension of Analytical Methods for Detailed Characterization of Advanced Combustion Engine Emissions," SAE Int. J. Engines 9(4):2016.
Boosting the efficiency of IC engines through advanced combustion strategies has demonstrated that these strategies will alter the chemical composition of engine-out emissions. Changes in exhaust chemistry affect the performance of typical exhaust aftertreatment devices used to meet tailpipe emissions standards. As advanced combustion strategies are developed, new technologies for exhaust aftertreatment will need to be developed. Detailed chemical characterization of the exhaust is an essential for future exhaust aftertreatment design. Although the characterization for short chain volatile hydrocarbons between [C.sub.1] and [C.sub.12] has been used widely for more than 25 years, the longer chain hydrocarbons (semi-volatile-and particulate-phase) present special analytical challenges. The CRC Auto/Oil method designed for hydrocarbons up to [C.sub.12] does not allow for the identification and quantification of potential exhaust greater than [C.sub.12].
Longer chain hydrocarbons in the exhaust are typically lost on the particulate filters or condense before the gas phase analyzers. The objective of the work described in this paper was to develop supplementary sampling and analytical systems to cover a larger range of hydrocarbons in the exhaust. Two specialized exhaust sampling and analytical systems were developed and validated. The first specialized automated exhaust gas sampling and analytical system was designed for characterization of middle range hydrocarbons (from [C.sub.10] through [C.sub.24]). A GC-MS was used to identify these compounds. The system was also able to measure hydrogen ([H.sub.2]), which is not one of the components typically identified on a regular basis. The quantification of [H.sub.2] was another important improvement necessary for the characterization of new technologies of advanced aftertreatment. Another important objective was to evaluate the effect of sample line temperatures on the quantification of hydrocarbons with high boiling points. Currently, 191[degrees]C is the required temperature for sample lines used to deliver exhaust from the engine to the gas analyzers. However, some of the hydrocarbons in diesel exhaust have a significantly higher boiling point than 191[degrees]C. The new chromatographic system was able to handle gases delivered by sample lines at 300[degrees]C. Therefore, it provided an opportunity to compare the efficiency of the currently accepted temperature for collection of hydrocarbons.
The second sampling system, consisting of a particulate filter and several XAD traps, was used for the collection of particulate and semi-volatile compounds. This system was capable of analyzing engine exhaust for heavier hydrocarbon compounds to about [C.sub.40+]. After extraction, hydrocarbons trapped by the particulate filter and the XAD traps were speciated by GCxGC-MS. More than 2000 individual compounds were identified and separated by hydrocarbon class and carbon number. This paper describes these two novel sampling and analytical systems.
PART 1 - IN-SITU AUTOMATIC GC-MS GAS SAMPLING SYSTEM FOR DETAILED CHARACTERIZATION OF HYDROCARBON UP TO [C.sub.24]
To evaluate this analytical technique, a heavy-duty diesel engine (Engine 1) was installed in a state-of-the-art test cell compliant with the U.S. Code of Federal Regulations, Title 40, Part 1065. Exhaust emissions were generated and collected using one of the test conditions taken from the ramped modal cycle (RMC) as specified in Title 40 Code of Federal Regulations (CFR) Part 86.1362(a). The test condition was 1450 rpm at 195 Nm. Emission measurements included:
* Regulated emissions including total hydrocarbons (THC), carbon monoxide (CO), carbon dioxide (C[O.sub.2]), and the oxides of nitrogen (N[O.sub.x])
* Speciation of hydrocarbon compounds above [C.sub.10]
Raw exhaust sampling included a modified automated valve system and the sample distribution system that delivered two separate sample portions concurrently to two separate gas chromatography (GC) columns through a proprietary distribution system on the gas chromatograph. Consistent injections were conducted regardless of sample source, temperatures, and pressure. Figure 1 illustrates the assembled valve system. Appendix Figure A1 illustrates the overall design of the GC-MS sampling system. An Agilent 6890 gas chromatograph was connected to the exhaust system through two extruded, stainless steel 1.6 mm (1/16 in.) tubes inserted inside a 9.5 mm (3/8 in.) stainless steel heated commercial heated sample line maintained at elevated temperatures. Sampling tubes were in contact with heated line (Unique Heated Product Inc., Part Number SII-C-6-300-S-E6-PRO-A-AK-D72-000, 300CMax). Temperatures were regulated by a proportional-integral-derivative (PID) controller. Two sampling temperatures were evaluated: 191[degrees]C (currently required for collection of regulated gaseous emissions) and 300[degrees]C (an elevated temperature expected to increase the heavy hydrocarbons transfer). 300 [degrees]C was maximum temperature for the commercial sampling line .
The chromatographic system used two detectors, a mass spectrometer (MS) to measure heavy hydrocarbon compounds and a thermal conductivity detector (TCD) to measure [H.sub.2], CO, oxygen ([O.sub.2]), and C[O.sub.2]. Different analytical columns were used for separation of the compounds of interest. The MS channel was used to detect the heavy hydrocarbon compounds. Initially, a 60m RTX-502.2 (Restek) column was used. Later, a 30m ZB-5MS (Phenomenex) column replaced to reduce the test time. Helium was used as the carrier gas. Since the hydrocarbon level was expected to be low, a 1 mL sample loop volume was used to inject the exhaust gas onto the MS analytical column.
The thermal conductivity detector was used to measure the [H.sub.2], CO, [O.sub.2], and C[O.sub.2] levels in the exhaust gas sample. The separation was performed using a 30m Poraplot-Q (Agilent) and a 2m ShinCarbon ST (Restek) column in series with nitrogen as the carrier gas. A 1mL sample loop was also used for this analysis in order to achieve a detection level of approximately 40 ppmv. Figure 2 illustrates a complete GC-MS system connected with an engine exhaust via heated line.
Linearity was measured by injection of the standards at different concentrations directly into the sample port of the GC-MS instrument. Figures 3 and 4 illustrate detectors responses for [H.sub.2], C[O.sub.2], CO, and [O.sub.2]. Repeat analysis of the hydrocarbons standards [C.sub.10-][C.sub.13] introduced at the instrument produced Relative Standard Deviation (%RSD) of 5%. These results fall within range for routinely acceptable GC-MS instrument performance. One goal of this project was to demonstrate that the system was able to detect hydrocarbons up to [C.sub.24]. Due to the high boiling point of [C.sub.24][H.sub.50] (tetracosane) at 391[degrees]C, there was no gaseous standard available for the program. A solution of tetracosane in carbon disulfide was injected into the instrument to determine if this compound could be sampled in the exhaust. Appendix Figure A2 illustrates that the method would detect this compound if it presents. Integrity of the entire sampling system was validated by comparison C[O.sub.2] results from TCD detector on GC-MS and a Non-Dispersive Infrared Detector installed in the Horiba MEXA7100DEGR bench during an engine tests. Based on the C[O.sub.2] results, both repeatability between triplicated tests from the on-line GC-MS and agreement between results from the on-line GC-MS and Horiba bench were sufficient to consider tests as valid tests and to confirm the integrity of the new sampling system. Table 1 includes C[O.sub.2] results from the triplicate engine tests from two analytical methods.
Hydrocarbon recovery and sample line temperature effects were measured by the injection of standards upstream of the sample line. Hydrocarbon standards (at 1 ppmC levels) were connected through the quick connect to the sampling port and injected upstream of the sample line maintained at 191[degrees]C and at 300[degrees]C, respectively; and responses were compared with those obtained via direct injection to the GC-MS. Experiments showed that the recovery of the higher molecular weight hydrocarbons was 15-20 percent higher for the sample line maintained at 300[degrees]C than at 191[degrees]C. This difference increased with carbon number. Table 2 includes results of the recovery studies with sample lines at two different temperatures. In addition when the sample line was maintained at 300[degrees]C, better repeatability of the hydrocarbon composition was also observed (both total and individual hydrocarbons). Table 3 illustrates repeatability of the several consecutive hydrocarbon injections upstream of the sample line. Based on recovery and repeatability of the results at 300[degrees]C, engine emission tests for the GC-MS system were conducted at this temperature rather than 191[degrees]C.
To validate the entire sampling system, the new method was applied to the exhaust characterization for a single mode emission characterization during three separate days. Major hydrocarbon classes and some of individual hydrocarbons were quantified. The identified hydrocarbon types included aromatics, polycyclic aromatic hydrocarbons (PAH), and various alkanes ranging from [C.sub.10] to [C.sub.20]. The heavy hydrocarbons were coarsely estimated at ppbv levels based on available standards. Table 4 includes the results of these tests. The concentration of the heaviest hydrocarbons increased from run to run either due to their accumulation in possible cold spots in the sampling system or due to insufficient timing for the chromatographic method. Based on these results, thermo isolation of the entire sampling system was improved and sample purging time was increased. The fully validated method was later applied to emission characterization from a second engine, a 2015 medium size heavy-duty diesel engine (Engine 2), for all thirteen modes of the RMC. Figure 5 illustrates the total speciated hydrocarbons for the [C.sub.10]-[C.sub.24] hydrocarbon range. Figure 6 includes detailed characterization distribution for the 25% load at intermediate rpm by carbon number, and Figure 7 shows the detailed polyaromatic hydrocarbon speciation on the range from [C.sub.10] through [C.sub.24] for the same mode. In addition, no hydrogen was detected above detection limits with either of the engines because both engines use traditional combustion strategies, and hydrogen in the exhaust was not expected.
PART 2 - SPECIATION OF HEAVY HYDROCARBONS UP TO C40+ VIA TWO DIMENSIONAL GAS CHROMATOGRAPHY
Emission generation was performed on a 2013 medium duty production engine (Engine 3). The emission testing sequence was performed after 125 hours of engine operation with the certification 2D diesel. Testing involved a transient cold- and hot-start test sequence with the aftertreatment system removed. The heavy-duty EPA transient Federal Test Procedure (FTP) is described by means of percent of maximum torque and percent of rated speed for each one-second interval over a test cycle of 1199 seconds duration. To generate a transient cycle, an engine's full load torque curve is obtained from an engine speed below curb idle speed to maximum no-load engine speed. Data from this "torque curve," or torque map, was used with the specified speed and load percentages to form a transient cycle. A graphic presentation of the speed and torque commands which constitute a transient cycle is given in Figure 8 for illustration purposes.
The sampling method for collection of particulate and semi-volatile (SVOC) hydrocarbons from dilute heavy-duty engine exhaust was described in detail in SAE Paper 2015-01-1062. For the collection of filter and XAD samples for chemical analysis, a large supplemental secondary dilution tunnel that permitted the use of an 203x254-mm (8x10-inch) Zefuor[TM] filter followed by four 10.2-cm (4-inch) diameter XAD traps that were sampled in parallel and downstream of the filter. Figure 9 illustrates the sample system for collecting the exhaust for semi-volatile compounds. The XAD traps contained 100 g of XAD-2 resin and were incorporated to improve the trapping efficiency for the lighter semi-volatile compounds. A cold-start sample was collected for the particulate and semi-volatile analyses. After test completion, the filters and XAD were extracted and analyzed separately. Media preparation and sample extraction were described in detail in the above referenced paper.
Extracts were analyzed by a comprehensive Two Dimensional Gas Chromatography (GCxGC) technique which is a relatively new technology (pioneered in the early 1990's).[6,7] GCxGC technology provided a significant improvement in the analytical performance relative to current GC techniques. The advantages of the GCxGC technique include enhanced resolution and increased peak capacity, up to an order of magnitude increase in component detectibility, visually elegant 3D display of the entire analyzed sample, and significant improvements over traditional one dimensional GC-MS especially for trace analysis in heavy matrices. In addition, this technique was more reliable in the identification of unknown species and their quantification. To achieve two orthogonal phases of separation, the typical analytical system included two columns connected in series with the second column located in a separate oven inside the primary oven. A modulation device between the columns continually sampled the effluent from the first column and re-injected this effluent into the second column. Resulting data was projected on a retention plane. Viewing the data on a retention plane (function of both separation dimensions) allowed easy peak identification and pattern recognition. Figure 10 illustrates typical GCxGC configuration. Figure 11 is an example of a three- dimensional chromatogram. GCxGC coupled with a time-of flight mass spectrometer (TOF MS or TOF) analysis was performed using an Agilent 7890 gas chromatograph coupled to a LECO PEGASUS 4DTOF (LECO, St. Joseph, MI). Figure 12 shows the analytical system, and Table 5 describes the columns and modular parameters used for the analysis.
The MS was operated using an electron ionization (EI) at 70eV. Spectra were collected from 40-600 m/z with a scan time of 100 spectra/sec. Sensitivity was checked by verifying a signal to noise (SN) of 10 with 2 pg of hexachlorobenzene on-column. A calibration curve was assayed using the 78 compounds from the detailed hydrocarbon analysis (DHA) Paraffins, Isoparaffins, Olefins, Naphthenes, and Aromatics (PIONA) standard (Restek Cat. no 30730, Bellefonte, PA) spiked with phytane and several additional n-alkanes providing a retention definition of carbon number up to [C.sub.40]. Data was processed using LECO's Chromatof software to integrate peaks and to quantify them against the curve or identify them based on National Institute of Standards and Technology (NIST) library searching (for compounds not in the calibration curve). Chromatof classification regions were used to define areas of the chromatogram where specific classes of compounds tend to elute. Appendix Figure A3 shows chromatogram for the external standard. Each dot represents a single hydrocarbon in the mixed standard. Dots marked as is/s represent internal standards that were artificially introduced to the XAD resin prior to the engine exhaust collection. These internal standards were used for the determination of extraction efficiency.
More than 870 individual compounds were identified in the XAD extract and more than 1740 hydrocarbons were extracted from the particular filter from the exhaust collected from the cold start. Appendix Figures A4 and A5 illustrates the raw chromatograms from both media, and Appendix Figures A6 and A7 shows processed chromatograms where each dot represents identified compound.
Results from the analyses were represented by either peak area percent distribution or by peak number distribution. Peak area percent distribution corresponded with the relative concentrations; peak number represented the relative amount of the individual compounds of different hydrocarbon classes. As expected, the composition of hydrocarbons collected on the filter and XAD differed significantly. The majority of the hydrocarbons on the filter represented long chain hydrocarbons with a dominance of [C.sub.21]-[C.sub.30] saturated hydrocarbons (normal and branched), [C.sub.21]-[C.sub.30] cyclic, PAH, multi-oxygenated compounds, and low boiling point iso-aromatics. These compounds matched those typical for unburned lubricated oil. Conversely, the majority of semi-volatile hydrocarbons collected on XAD resin represented alkane substituted benzenes such as 1,2,4-trimethyl benzene and 3-ethyl-1-methyl benzene, 3-ethyl-1-methyl benzene which are typical of unburned diesel fuel and oxygen containing benzenes representing partially burned fuel. Figure 13 compares the relative peak areas for semi-volatile and particulate hydrocarbons in the raw exhaust.
Figures 14 through 17 illustrate difference in distribution between peak areas related to concentration and the amount of each individual peaks identified for the specific hydrocarbon groups. For instance, while alkane substituted benzene for semi-volatile hydrocarbons (Figures 14 and 15) comprised almost 59 percent of the total concentration, the amount of the peaks related to the individual specific hydrocarbons from this group amounted to only 21 percent. On the contrary, PAH and multi-oxygenated PAH group had a sufficient amount of the individual compounds (9 percent of total peaks), but their total relative concentration was only 0.77 percent of total. Particulates on the filter (Figures 16 and 17 show an opposite trend: 14 percent of the PAH by peak number represented 55 percent by peak areas.
Chemical characterization of the raw exhaust from the heavy duty engines was extended beyond well established characterization of the light hydrocarbons up to [C.sub.12]. An automated sampling system incorporated with a GC-MS capable of collecting samples from raw engine exhaust without compromising the integrity of the exhaust components was designed and evaluated. The system was capable of analyzing hydrocarbon compounds up to [C.sub.24] and hydrogen. A second independent sampling and analytical method was developed to cover hydrocarbons beyond of [C.sub.24]. This system incorporated both a particulate filter and several XAD traps to capture the particulate and semi-volatile hydrocarbons in the exhaust, respectively. After extraction, the solutions were analyzed by GCxGC-MS. More than 2000 individual hydrocarbons were detected by this method. These hydrocarbons represented most of the known hydrocarbon classes. As a result, much of the existing gap between the results for total hydrocarbons and the current speciated hydrocarbons up to [C.sub.12] was filled. These new methods extended the capabilities in detailed engine exhaust characterization and provided valuable information in understanding combustion mechanisms to help aftertreatment developers respond to new challenges.
[1.] Siegl, W., Richert, J., Jensen, T., Schuetzle, D. et al., "Improved Emissions Speciation Methodology for Phase II of the Auto/Oil Air Quality Improvement Research Program - Hydrocarbons and Oxygenates," SAE Technical Paper 930142, 1993, doi:10.4271/930142.
[2.] Burns, V., Benson, J., Hochhauser, A., Koehi, W. et al., "Description of Auto/Oil Air Quality Improvement Research Program," SAE Technical Paper 912320, 1991, doi:10.4271/912320.
[3.] U.S. Code of Federal Regulations, Title 40 - Protection of Environment, Part 1065 - Engine-Testing Procedure.
[4.] Code of Federal Regulation (CFR) Title 40 - Protection of Environment, Part 86 - Control of Emissions from New and Inuse Highway Vehicles and Engines, Subpart F - Testing Requirements for Registration.
[5.] Fanick, E., Kroll, S., and Simescu, S., "Sampling System Investigation for the Determination of Semi-Volatile Organic Compounds (SVOC) Emissions From Engine Exhaust," SAE Technical Paper 2015-01-1062, 2015, doi:10.4271/2015-01-1062.
[6.] Gorecki, Tadeusz, Harynuk James, and Panic O.. "Comprehensive Two-dimensional Gas Chromatography (GCxGC)," New Horizons and Challenges in Environmental Analysis and Monitoring [Workshop], Gdansk, Poland. 2003.
[7.] Vendeuvre, C., Ruiz-Guerrero, R., Bertoncini, F., Duval, L., Thiebaut, D. and Hennion, M.C., "Characterisation of Middle-distillates by Comprehensive Two-dimensional Gas Chromatography (GCxGC): A Powerful Alternative for Performing Various Standard Analysis of Middle-distillates," Journal of Chromatography A, 1086(1), pp.21-28, 2005.
Southwest Research Institute 6220 Culebra Road San Antonio, Texas 78228
Southwest Research Institute 6220 Culebra Road San Antonio, Texas 78228
The information summarized in this paper was the result of work performed at Southwest Research Institute through an internal research program. The authors wish to thank the Internal Research and Development Advisory Committee for Research for providing the opportunity to perform this important work.
CFR - Code of Federal Regulations
CO - Carbon monoxide
C[O.sub.2] - Carbon dioxide
CRC - Coordinating Research Council
DHA - Detailed hydrocarbon analysis
EI - Electron ionization
FTP - Federal Test Procedure
GC-MS - Gas chromatography/mass spectrometry
GCxGC-MS - 2D gas chromatography/mass spectroscopy
[H.sub.2] - Hydrogen
IC - Internal combustion
IS - Internal standard
MS - Mass spectrometer
NIST - National Institute of Standards and Technology
[NO.sub.X] - Oxides of nitrogen
[O.sub.2] - Oxygen
PID - Proportional-integral-derivative
PAH - Polyaromatic hydrocarbons
PIONA - Paraffins, isopraffins, olefins, napthlenes, and aromatics
PVF - Polyvinyl fluoride
QC - Quality control
RMC - Ramped modal cycle
RSD - Relative standard deviation
TCD - Thermal conductivity detector
THC - Total hydrocarbons
TOF MS - Time-of-flight mass spectrometer
XAD - Porous polymer resin
E. Robert Fanick, Svitlana Kroll, and Kristin Favela Southwest Research Institute
Table 1. C[O.sub.2] Results C[O.sub.2]by % Difference C[O.sub.2] by GC- Horiba Between Two TEST MS (%) Bench (%) Methods Engine Sample 1 6.763 6.745 0.3% Engine Sample 2 6.773 6.744 0.4% Engine Sample 3 6.834 6.805 0.4% Average Three Tests 6.790 6.765 StDev 0.038 0.035 % RSD 0.6% 0.5% Table 2. GC-MS Recovery for Hydrocarbons at Different Sample Line Temperatures Standard Recovery Average Average Average Response Response Response Upstream at Recovery Upstream at on 300[degrees]C at 191[degrees]C Instrument Sample Line 300[degrees]C,% Sample Line C10 14557 12687 87 9650 C11 24087 17109 71 11826 C12 44104 26939 61 16007 C13 67139 48305 72 22389 Recovery at 191[degrees]C,% C10 66 C11 49 C12 36 C13 33 Table 3. GC-MS Response for Hydrocarbons at Different Sample Line Temperatures Injection Upstream of Sampling System ( Sampling Line Temperature 300[degrees]C) Std Response Factors Cone, Injection Injection Injection Injection ppb 1 2 3 4 C10 109 13626 12444 11632 13047 C11 100 18089 17545 15615 17189 C12 91 27142 28842 26462 25311 C13 77 44790 52423 47074 48934 % Avg STDEV RSD C10 12687 853 7% C11 17109 1063 6% C12 26939 1476 5% C13 48305 3226 7% Std Response Factors Cone, Injection Injection Injection Injection ppb 1 2 3 4 C10 109 11667 9504 9114 8314 C11 100 14747 11241 11174 10143 C12 91 20042 16541 14658 12787 C13 77 25650 26080 21118 16710 % Average STDEV RSD C10 9650 1433 15% C11 11826 2011 17% C12 16007 3096 19% C13 22389 4402 20% Table 4. Detailed Hydrocarbon Exhaust Composition (Sample Line at 300[degrees]) Components Engine Sample #1 Engine Sample #2 Area Cone Area Response (ppb) Response 1 -Ethyl-3-methylbenzene 1254736 47.8 1292026 1,2,3-Trimethylbenzene 382442 14.6 392096 Decane 69250 2.6 66393 Undecane 81077 3.1 92165 Naphthalene 1442721 54.9 1452793 Dodecane 107100 4.1 139064 Tridecane 109886 4.2 101340 2-Methylnaphthalene 948519 36.1 874866 1 -Methylnaphthalene 413557 15.7 368947 Tetradecane 155954 5.9 167921 Pentadecane 173291 6.6 216465 Eicosane 201240 7.7 255828 Alkanes C10-C11 249525 9.5 248238 Alkanes C11-C12 300845 11.5 276300 Alkanes C12-C13 422563 16.1 388113 Alkanes C13-C14 432547 16.5 529377 Alkanes C14-C15 465396 17.7 612695 Alkanes C15-C16 423826 16.1 472148 Alkanes C16-C17 - 341385 Alkanes C17+ - 573083 Components Engine Sample #3 Cone Area Cone (ppb) Response (ppb) 1-Ethyl-3-methylbenzene 49.2 1244768 47.4 (*) 1,2,3-Trimethylbenzene 14.9 370090 14.1 (*) Decane 2.5 65356 2.5 Undecane 3.5 82426 3.1 Naphthalene 55.3 1552174 59.1 (*) Dodecane 5.3 151227 5.8 Tridecane 3.9 129810 4.9 2-Methylnaphthalene 33.3 773604 29.5 (*) 1-Methylnaphthalene 14.1 386445 14.7 (*) Tetradecane 6.4 150415 5.7 Pentadecane 8.2 180553 6.9 Eicosane 9.7 238647 9.1 Alkanes C10-C11 9.5 210588 8.0 Alkanes C11-C12 10.5 235860 9.0 Alkanes C12-C13 14.8 381522 14.5 Alkanes C13-C14 20.2 567177 21.6 Alkanes C14-C15 23.3 601702 22.9 Alkanes C15-C16 18.0 569898 21.7 Alkanes C16-C17 13.0 629971 24.0 Alkanes C17+ 21.8 1222237 46.5 (*) Estimated based on Alkanes RF Table 5. GCxGC Parameters GC Parameter Injection volume 1.0 uL Inlet temperature 1.0 [micro]l Inlet mode 260[degrees]C Purge splitless Helium 1 min carrier flow GC Parameter Colum, Oven, and Modulator Set-Up Injection Primary volume RXi-lMS (30 m x 0.25 mm x volume (first dimension) 0.25 [mu]m Inlet Second column RXi-17SilMS, (1.5 m x 0.18 temperature (second dimension) mm x 0.18 [mu].m Held at 70[degrees]C for 5 minutes, ramped to 250[degrees]C at a rate Temperature of Inlet mode Profile for the First 4[degrees]C/min, ramped to Column 330[degrees]C at a rate of 6[degrees]C/min and held for 6 minutes Temperature Purge profile for the Offset by 5[degrees]C and 20[degrees]C, second column and respectively. modulator The modulation 7 seconds (1.75 s hot, 1.75 s Helium period cold with 2 cycles per carrier flow modulation period)
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|Author:||Fanick, E. Robert; Kroll, Svitlana; Favela, Kristin|
|Publication:||SAE International Journal of Engines|
|Date:||Dec 1, 2016|
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