Edwards 149-1 Spec Sheet

[Katrine Freggiaro]

Thechemical composition and fuel properties of nine alternative jet fuels (named as AJF 1-9) and three commercial jet fuels (named as CJF 1, 2 and 3) are reported in this work. The fuels were characterized by GC/MS, SEP-GC/MS (for quantification of oxygenated molecules), viscosity, density, water content, water solubility at 0 C, carbonyl content, total acid number, elemental composition, calorific value, flash point, differential scanning calorimetry, and surface tension. The content of n-paraffins, iso-paraffins, olefins, naphthenes, and aromatics are reported. The fuel rich in aromatics (AJF 1) has the highest density (0.90 g/mL), C content (over 90 wt. %), and water solubility, lowest calorific value, and high surface tension. The fuels with high contents of light molecules have the lowest flash points (AJFs 1, 6, and 8). AJF 2 is the most viscous fuel due to the presence of a single relatively heavy molecule. The content of oxygenated compounds measured was in all the cases very low and comparable with the amount found in commercial jet fuels. Overall, these fuels comply with most of ASTM requirements and offer opportunities to develop specialized products.

The aviation industry is in fast expansion, with the number of passengers expected to increase from 2.4 billion in 2010 to approximately 16 billion in 2050 (IATA 2011). Nevertheless, the concern with increasing levels of carbon emissions, crude oil price volatility, and its impact on global warming is a serious concern for the aviation sector.

Therefore, in order to address this problem, the International Air Transportation Association (IATA) established a challenging goal of reducing the net CO2 production of the aviation industry by 50% by 2050, compared with 2005 levels (Hileman et al. 2013). One promising approach to achieve this goal is the use of alternative jet fuels derived from renewable resources (Popp et al. 2014).

In the United States, Jet A is the main commercial jet fuel. In Europe Jet A-1 is the main civil jet fuel used (Maurice et al. 2001; Lenz and Aicher 2005). These fuels have similar properties, but the limit value for freezing point of Jet A is higher (-40 C) than for Jet A-1 (-47 C) (Lenz and Aicher 2005). Jet fuel produced from petroleum refining typically comply with ASTM requirements and its production is very reliable.

Several papers have been published on properties of alternative jet fuels (Starck et al. 2016). Corporan et al. (2011) studied the chemical, thermal stability, seal swell, and emission of six alternative jet fuels (three from Fischer Tropsch and three from hydroprocessing). Zhang et al. (2016) have recently reviewed the recent studies on alternative jet fuel combustion of alternative jet fuels. Hui et al. (2012) reported experimental studies on the derived cetane number, autoignition response, laminar flame speed, and extinction stretch rate for premixed combustion of alternative jet fuels. Won et al. (2016)reported some correlations to predict the global combustion behaviorof petroleum derived and alternative jet fuels by simple fuel property measurements.

Most of the AJF pathways of interest to the Federal Aviation Administration (FAA), ASTM, CAAFI, and the industry rely on a final deoxygenation step through catalytic hydrotreatment (hydrogenation, hydrocracking, hydrodeoxygenation). Under certain circumstances (catalyst deactivation, changes in the composition of the feedstock, operational problems), the deoxygenation efficiency may decrease; this could cause some residual oxygenated compounds to remain in the fuel. There are several papers (Zabarnick 1994; Grinsted and Zabarnick 1999; Balster et al. 2006; Sobkowiak et al. 2009; Corporan et al. 2011; West 2011; Chuck and Donelly 2014b) on the presence of polar fractions in petroleum derived jet fuels. Balster et al. (2006) studied the role of polar molecules in the autoxidative deposit formation of jet fuels. The polar fraction of fuels they investigated were mainly composed of phenols and other oxygenated molecules, which demonstrated that they were related to surface deposit. West (2011) studied the effect of potential homogeneous catalytic sources on autoxidation chemistry of jet fuel. When naphthenic acids are added alone to fuel, there is little effect on the rate of hydroperoxide decomposition. The authors were not able to find any paper on the nature and the content of oxygenated compounds in alternative jet fuels.

Thus, the main goal of this paper is to report the chemical composition and fuel properties of alternative jet fuels derived from different feedstocks focusing on the content of residual oxygenated compounds.

The Alternative Jet Fuels (AJF) herein studied were produced by different processes: DSHC, HEFA, FT, Alcohol to Jet (ATJ), Catalytic Hydrothermolysis (CH), and Hydrotreated Depolymerized Cellulosic Jet (HDCJ). Description of these technologies can be found elsewhere (Staples et al. 2014; De Jong et al. 2015; Mawhood et al. 2016; Wang and Tao 2016). The fuels studied in this project were kindly provided by the US Air Force Research Laboratory. The commercial jet fuels (CJF) were obtained from Shell, Valero, and NuStar. The nomenclature used to designate each of the fuels studied is listed in Table 1.

Quantification and identification of individual compounds is important for understanding fuel composition and characteristics. Besides, the presence of aromatics and olefins must be known, as they can relate to problems in fuel properties and must be controlled.

The fuels studied were analyzed using an Agilent Technologies 7890A Gas Chromatograph linked to Agilent 5975C Mass Selective Detector with NIST 2.0 f Mass Spectral Search Program. GC was equipped with Restek Rtx-170 column with dimensions of 60m x 250m x 0.25m. 1 μL of sample was injected with split ratio 30:1. Front inlet parameters were set as: 250 oC, 9.5 psi, total flow He 21.6 mL/min, septum purge flow. Column flow (0.6 mL/min, 9.5 psi, 19.9 cm/s, 5.0 min hold time). Oven temperature was set at 45 oC for 10 min and then increased to 250 oC at the rate of 3 oC/min and final hold time was 5 min.

The internal standards method was used in this analysis (phenanthrene was used as internal standard). For the response factor calculation, solutions of internal standard, n-C7 to n-C18 compounds, xylene, toluene, naphthalene, and ethyl-benzene, all in a concentration of about 1 mg of compound per 1 g solvent (dichloromethane), were prepared. 1 g of each solution was then weighted and mixed. The sample mixture was then analyzed by GC-MS to calculate the response factors. Four different concentrations (0.1, 0.5, 1 and 5 mg/g) were prepared using HPLC grade methanol as solvent. The compounds quantified by each of the standards are listed on Table 2 below.

This method is important to quantify the content of individual elements from which the ratio C:H can be calculated. The analysis for carbon, hydrogen, and nitrogen was conducted in a 630-100-300 RFB TRUSPEC CHN, serial number 4299, software version 2.71. First 5 empty blank foils were analyzed, and the blank correction was assigned in the software. After that, 3 conditioned samples (approx. 0.1 g of EDTA) were run before the next step. 3 standards (approx. 0.15 g of EDTA) were then run, and the drift correction was made in the software. Finally, the samples were prepared using 0.15 g of the fuel and 0.15 g of the standard, placed in the Carousel and analyzed (ASTM D5291 (2010)). The hydrogen content data collected by the US Air Force Research Laboratory (AFRL, kindly provided by Dr. Tim Edwards) obtained by the ASTM D7171 (2005) and D3701 (2001) methods was compared with our data.

The presence of water is undesirable and needs to be quantified. According to ASTM D7566 (2017), the maximum allowed in AJF is 75 ppm. Water content in the jet fuel was measured using Karl Fischer titration with a Mettler Toledo C20 Compact Karl Fischer Coulometer that has a measurement range of 1 ppm to 5% of water in samples (ASTM D6304 (2007)). The data collected by AFRL was also obtained by this method, and it is described in ASTM D6304 (2007).

Fuel corrosion problems are associated with the presence of acids. According to ASTM D1655 (2004), the acid number of jet fuels should be less than 0.1 mg KOH/g. The method used at WSU to measure acid number is described elsewhere (Christensen et al. 2011; Wu et al. 2014; Shao and Agblevor 2015). Briefly, a Mettler Toledo T50 titrator with a Mettler Toledo Rondolino was used to test the samples. Acetone was used as solvent and 0.1 M KOH in DI water standardized with potassium hydrogen phthalate was used as titrant (Shao and Agblevor 2015). The data collected by the AFRL was obtained following the ASTM D3242 (2001) standard method.

The content of carbonyl groups was determined using a spectrophotometric technique (ASTM E411 (2012)). A series of standards using 2-butanone diluted in methanol was used for calibration. First a stock solution was prepared adding approximately 0.064 g of 2-butanone (Assay 99.8%) to a 100 mL glass stoppered volumetric flask and completing the volume to the mark with methanol. Then a sequence of 2, 4, 6, 8 and 10 mL aliquots of this stock solution was transferred to five 100 mL glass stoppered volumetric flasks and the volume completed with methanol, forming the standards. 2 mL aliquots of each standard were transferred to five 25 mL glass stoppered volumetric flasks.

An additional 2 mL sample of jet fuel was transferred to others 25 mL volumetric flasks to be analyzed and 2 mL of methanol were transferred to another 25 mL volumetric flask to serve as blank. To each flask, 2 mL of 2,4-dinitrophenylhydrazine was added and approximately 30 min were waited before completing the volume with a 100 g/L KOH solution and mixing well. After adding the KOH solution, a 12 min interval was allowed for color to develop and then, the absorbance was measured using a Shimadzu UV-2550PC UV/Vis Spectrophotometer at 480 nm, using a 1-cm cell.

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