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Extension of analytical methods for detailed characterization of advanced combustion engine emissions.

ABSTRACT

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.

INTRODUCTION

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].[1]

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]

Method Development

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.[3] 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).[4] 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]

* [H.sub.2]

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 .

GC-MS Configuration

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.

Method Validation

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.[5] 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.[5]

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.

Results

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.

CONCLUSIONS

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.

REFERENCES

[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.

CONTACT INFORMATION

Robert Fanick

Southwest Research Institute 6220 Culebra Road San Antonio, Texas 78228

Telephone: 210-522-2653

FAX: 210-522-3950

rfanick@swri.org

Svitlana Kroll

Southwest Research Institute 6220 Culebra Road San Antonio, Texas 78228

Telephone: 210-522-5145

FAX: 210-522-3950

skroll@swri.org

ACKNOWLEDGMENTS

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.

DEFINITIONS/ABBREVIATIONS

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

APPENDIX

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
Article Type:Report
Date:Dec 1, 2016
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