The Impacts of Pd in BEA Zeolite on Decreasing Cold-Start NMOG Emission of an E85 Fuel Vehicle.
In 2025, fleet average emissions of non-methane organic gas (NMOG) plus nitrogen oxides (NOx) must be less than 30 mg/mile during the Federal Test Procedure (FTP-75) cycle to meet more stringent LEV III emission requirements . This is a 76% decrease over the LEV II standard of 125 mg/mile. When a vehicle starts from ambient temperature (cold start), the hot exhaust flow of the engine must heat the three-way catalyst (TWC) converter to an operating temperature over 250[degrees]C to enable effective conversion of engine out emissions [2, 3]. During this heating period, most of the engine's emissions exit the tailpipe unconverted. In a typical FTP cycles, these cold-start emissions can represent 80-90% of the overall test emissions . Moreover, when
E85 fuel is used rather than gasoline with a flex fuel vehicle, the tailpipe NMOG emissions at cold start could be doubled . The significant reduction of the cold-start emissions is a major challenge in meeting stringent LEV III emission standards for most of the vehicles, especially for a flex fuel vehicle running E85 fuel.
One way to reduce cold-start emissions is to use a catalytic hydrocarbon (HC) trap that can adsorb NMOG emissions when cold, and then later at operating temperature, the stored NMOG emissions are released and converted to C[O.sub.2] and water. A catalyzed HC trap-coated monolith has a bottom layer of molecular adsorbent material (aluminosilicate zeolite) for adsorbing HC emissions at ambient temperature and an overcoat of TWC to treat engine exhaust emissions when hot [6, 7, 8, 9, 10, 11, 12, 13]. A conventional HC trap contains these zeolites without any noted modifications [7, 8, 9, 10, 11]. The main challenge with conventional HC traps toward converting cold-start NMOG emissions is that the zeolite by itself releases stored NMOG at a temperature that is too low (<200[degrees]C) compared to the temperature required for efficient oxidation by the TWC overcoat ([greater than or equal to]250[degrees]C). The approach reported in this article is to modify conventional zeolite with active metal sites so that the adsorbing molecules are more strongly bound to the zeolite surface (chemisorption), resulting in a higher release temperature [12, 13, 14, 15].
The addition of active metals to zeolite also enables new reaction pathways with adsorbed ethanol (C[H.sub.3]C[H.sub.2]OH) [16, 17, 18]. Reaction 1 is a metal site ethanol dehydrogenation producing acetaldehyde (C[H.sub.3]CHO). Reactions 2 and 3 are metal site decomposition routes producing carbon monoxide (CO) and methane (C[H.sub.4]). In contrast, conventional HC trap zeolites typically exhibit different reactions [19, 20]. Reaction 4 is the Bronsted acid site dehydration of ethanol to produce ethene ([C.sub.2][H.sub.4]):
C[H.sub.3]C[H.sub.2]OH [right arrow] C[H.sub.3]CHO + [H.sub.2] Eq. (1)
C[H.sub.3]CHO [right arrow] CO + C[H.sub.4] Eq. (2)
C[H.sub.3]C[H.sub.2]OH [right arrow] CO + C[H.sub.4] + [H.sub.2] Eq. (3)
C[H.sub.3]C[H.sub.2]OH [right arrow] [C.sub.2][H.sub.4] + [H.sub.2]O Eq. (4)
Zeolite is known to be rapidly deteriorated from high-temperature steam exposure above 750[degrees]C . A new accelerated aging cycle was developed for HC trap useful life deterioration based on a more thermally protected far underbody location [4, 6, 21]. HC trap materials were investigated for improved treatment of E85 emissions that were designed for Pd to tolerate the new accelerated aging cycle. A flex fuel vehicle with E85 fuel showed that a HC trap with stabilized Pd-zeolite was much better at reducing NMOG emissions during the FTP-75 cycle cold start than a conventional HC trap.
Laboratory Powder Sample and Aging
Zeolite powder samples for laboratory reactor testing were made from Zeolyst product CP814E, a BEA zeolite with a Si[O.sub.2]/[Al.sub.2][O.sub.3] molar ratio of about 25/1 (BEA-25). BEA zeolite has large 12-member ring pores of about 0.7 nm diameter, which was shown to be effective for adsorbing gasoline HC species in other HC trap studies [7, 11, 12]. A Si[O.sub.2]/[Al.sub.2][O.sub.3] molar ratio of about 25/1 includes sufficient Brensted acid sites either for ethanol reaction  or ion exchange . A Pd(II) nitrate 10 wt% solution from Aldrich Chemical Co. was used to add Pd by incipient wetness method at 0.2 wt% of the zeolite. The samples were dried at 120[degrees]C and then calcined at 600[degrees]C for 2 hours to remove nitrates . TWC washcoat powder used was supplier proprietary washcoat (Pt/Pd/Rh, 2:47:1) with total platinum group metal (PGM) loadings of 25 and 50 g/[ft.sup.3]. All powder samples were sieved down to 40-60 mesh particles. Powder samples were then aged at 750[degrees]C for 25 hours in simulated four-mode engine exhaust as described in a separate manuscript . Mode 1 was at stoichiometry for 41 minutes with 2 vol% C[O.sub.2], 5 vol% [H.sub.2]O, and balance [N.sub.2]. Mode 2 was mild rich for 6 minutes with 1125 ppm CO, 375 ppm [H.sub.2], 2.0 vol% C[O.sub.2], 5 vol% [H.sub.2]O, and balance [N.sub.2]. Mode 3 was identical to Mode 1. Mode 4 was lean for 8 minutes with 2 vol% [O.sub.2], 2 vol% C[O.sub.2], 5 vol% [H.sub.2]O, and balance [N.sub.2].
Laboratory Reactor Testing
An MKS Fourier transform infrared (FTIR) analyzer was used to measure laboratory reaction gas species including ethanol. The FTIR method was specifically made for Ford HC trap work. The sample weight in laboratory powder testing is 0.5 gram. A flow rate of 1 liter per minute of the reaction gas mixture was used for powder reactor with an equivalent space velocity of 28,000/hour. Figure 1 shows a typical laboratory test protocol which includes both the adsorption and desorption steps. The gas mixture selection was based on the representative gas compositions during cold start in a vehicle test. The lab powder results shown in this report, unless specified, were all tested with adsorption gases of 450 ppm ethanol, 10 vol% [H.sub.2]O, and balance [N.sub.2] with 30-second exposure time, and desorption gases consisted of 10 vol% [H.sub.2]O vapor and balance [N.sub.2]. The flow reactor temperature programmed desorption (TPD) experiments heated the sample at a rate of 60[degrees]C/min. To prepare the sample for testing, it was heated to 650[degrees]C; then two possible pretreatment methods were used to set the oxidation state of Pd. The pre-lean treatment fed 2% [O.sub.2] for about 5 to 10 minutes to fully oxidize and disperse the Pd to available exchange sites and burn off carbon deposits. The oxidized sample was cooled down in the same pre-lean gas stream to 30[degrees]C. The pre-rich treatment first required the pre-lean treatment, but before the cool down, the 2% [O.sub.2] was turned off and 2000 ppm CO was turned on until the oxidation product C[O.sub.2] decayed to about 500 ppm, which removed most of the surface oxygen. The reduced sample was then cooled down in [N.sub.2] to 30[degrees]C.
Vehicle Emission Testing
The vehicle emission test cell had Horiba emission measurement benches and other instruments and is the same one used previously [4, 5, 6, 21, 22]. An MKS FTIR analyzer was used to measure NMOG emissions . Agilent 7890B gas chromatographs (GC) were used to determine the types of HC species ([C.sub.1]-[C.sub.12]) identified by a flame ionization detector (FID). Calculated concentrations (in ppm) were based on the response factor from propane which was analyzed daily using a representative mix of 23 HC during calibration. Detection limits for this technique were 0.01 mg/mi (0.0062 mg/km). Vehicle emission tests were performed in Ford Research and Innovation Center with the FTP-75 emission cycle followed by a US06 cycle. The bag method of data collection was used to calculate the test average emissions. Tailpipe emissions were gathered at each phase of the FTP-75 in separate bags, and weighted average emissions were calculated according to the method described elsewhere [4, 6].
A 2012 model year 2.0L gasoline direct injection (GDI) naturally aspirated Ford Focus with gasoline partial zero emission vehicle (PZEV)-certified aftertreatment was used as the test vehicle for this study over the FTP-75 test cycle to evaluate in-line HC trap performance with E85 fuel. All emission testing used the same close-coupled manifold catalyst assembly together with one of three underbody catalysts listed in Table 1. All samples in Table 1 used substrates with 62 cells/[cm.sup.2] (400 cells/[in..sup.2]). The TWC only and improved HC trap were each coated onto a cordierite monolith with a wall thickness of 0.15 mm (6.5 mil) and 0.11 mm (4.5 mil), respectively. The reference HC trap used an extruded substrate with large-pore acidic zeolite and binder materials with a 0.25 mm (10 mil) wall thickness similar to other works . The TWC-only sample was from the PZEV Focus underbody. The HC trap samples had a similar load of acidic large-pore zeolite relative to each other, but coated on top was a single TWC layer that contained about half as much TWC material as the Focus TWC-only sample. The three underbody catalysts were aged on the dynamometer to a simulated 150,000 miles. The TWC PGM column is stated in terms of PGM loading and ratio (Pt/Pd/Rh). The total content of Pd in Table 1 for the improved HC trap was distributed in the zeolite and TWC layers. The detailed information about catalysts, aging, and test conditions were described in a separate manuscript [4, 6, 22].
Lab BEA-25 and Pd-BEA-25 Zeolite Powder Samples
The ethanol adsorption efficiency for all samples tested in this work was close to 100%, and since our main interest was ethanol desorption, the results shown will be focused on the TPD only. Figures 2 and 3 show ethanol desorption (by TPD) for 0.5 gram pre-lean-treated BEA-25 powder samples in the fresh and aged state, respectively. For fresh BEA-25 (Figure 2), the peak release temperature of stored ethanol was about 220[degrees]C, and [C.sub.2][H.sub.4] desorption from Reaction 4 was observed at 260[degrees]C. The initially adsorbed ethanol in fresh BEA-25 was released as 42.2% ethanol and 46.1% [C.sub.2][H.sub.4]. For aged BEA-25 (Figure 3), the peak release temperature of stored ethanol was about 155[degrees]C, and [C.sub.2][H.sub.4] desorption was observed at 260[degrees]C. The initially adsorbed ethanol in aged BEA-25 was released as 96.7% ethanol and 3.6% [C.sub.2][H.sub.4]. The decreased ethanol release temperature, the increased ethanol release quantity, and the low [C.sub.2][H.sub.4] formation indicated that the aging removed most of the acid sites in the BEA-25 due to de-alumination; ethanol was primarily adsorbed by weak physisorption and ethanol dehydration was also minimized.
Figures 4 and 5 show lab-adsorbed ethanol desorption (TPD) for pre-lean-treated 0.5 gram BEA-25 + 0.2 wt% Pd powder sample in fresh and aged state, respectively. For fresh Pd-BEA-25 (Figure 4), the peak release temperature of ethanol was over 220[degrees]C and was accompanied by the low-temperature release of methane and C[H.sub.3]CHO at about 120[degrees]C. The initially adsorbed ethanol in fresh Pd-BEA-25 was released as 14.8% ethanol and 4.7% [C.sub.2][H.sub.4], with the balance as C[H.sub.4], CO, and C[O.sub.2]. For aged Pd-BEA-25 (Figure 5), the peak release temperature of ethanol was about 200[degrees]C. The initially adsorbed ethanol in aged Pd-BEA-25 was released as 32.7% ethanol and 0.1% [C.sub.2][H.sub.4], with the balance as C[H.sub.4], CO, and C[O.sub.2]. Thus, Pd in the aged Pd-BEA-25 significantly decreased the unconverted release of stored ethanol compared with aged pure BEA-25 from 96.7% (Figure 3) to 32.7% (Figure 5). It is thus apparent that the strong ethanol adsorption of Pd-modified BEA-25 does not appear to be associated with the formation and release of [C.sub.2][H.sub.4]. Instead, it promotes the ethanol dehydrogenation to form C[H.sub.3]CHO (Reaction 1) and methane (Reaction 2) at low temperature (about 100[degrees]C) [16, 17, 18]. However, the relatively high-temperature (about 200[degrees]C) ethanol release, which is very likely associated with stronger connection related to Pd in zeolite, demonstrated direct C[H.sub.3]C[H.sub.2]OH decomposition (Reaction 3) without releasing C[H.sub.3]CHO (Reaction 1). According to Reactions 1-3, both ethanol dehydrogenation and direct decomposition release equal amount of CO and methane. However, no CO release was observed at low temperature in this work, which could be the released CO adsorbed at Pd sites at low temperature (about 100[degrees]C) and released out at higher temperature (above 200[degrees]C) since more CO than methane released out above 175[degrees]C.
All the samples were also tested with pre-rich treatment, and the results (adsorption efficiencies, desorption products, and releasing temperatures) were very similar to those with pre-lean treatment. Figure 6 illustrates the percentage of adsorbed ethanol that was released unconverted (slip) during the TPD versus the Pd loading (wt%) in BEA-25 (lab aged). The adsorbed ethanol slip decreased with the increase of Pd loading and the benefit leveled off with Pd loading above 0.2 wt%. The tests included samples with both pre-lean and pre-rich treatments, which showed little difference.
Zeolite (BEA-25 and Pd-BEA-25) Plus TWC Powder Samples
Figure 7 shows the ethanol desorption (TPD) from an aged mixture of 0.5 g BEA-25 + 0.25 g TWC (50 g/[ft.sup.3] PGM) powder samples. The samples were first lab aged separately and then mixed together. The adsorbed ethanol was released during the TPD, and the components were identified as 49.3% unconverted ethanol, 9.2% C[H.sub.3]CHO, 7.3% C[H.sub.4], 0.4% CO, and 33.7% C[O.sub.2]. Comparing Figures 3 and 7, it is evident that adding 0.25 g TWC to BEA-25 decreased ethanol slip from 96.7% to 49.3% by the oxidation of ethanol and generated C[O.sub.2] (33.7%), C[H.sub.3]CHO (9.2%), and C[H.sub.4] (7.3%). However, in Figure 7, the ethanol released from BEA-25 at low temperature was converted in stages by the TWC during the temperature ramp, first to C[H.sub.3]CHO (mainly Reaction 1 below 140[degrees]C), then to C[H.sub.4] (when temperature above 140[degrees]C became Reactions 1 + 2 = Reaction 3), and then primarily to C[O.sub.2], as was observed in earlier work with conventional HC traps . The CO that would be expected to form along with C[H.sub.4] at 150[degrees]C by Reaction 2 or 3 may have been converted to C[O.sub.2] by the TWC layer. The comparison of Figures 4 and 7 indicates clearly that Pd in zeolite is active in catalyzing ethanol decomposition at lower temperature than Pd in TWC.
Figure 8 shows the laboratory ethanol desorption (TPD) from a lab-aged mixture of 0.5 g BEA-25 with 0.2 wt% Pd + 0.25 g TWC (PGM 25 g/[ft.sup.3]) powder samples. For a basis 180 g/L (3 g/[in..sup.3]) of washcoat, a 0.2 wt% Pd in zeolite load corresponds to 0.35 g/L (10 g/[ft.sup.3]). The samples were aged separately and then cooled down and mixed. The adsorbed ethanol was released during the TPD, and the components were identified as 15.5% unconverted ethanol, 22.5% C[H.sub.3]CHO, 20.6% C[H.sub.4], 2.9% CO, and 39.0% C[O.sub.2]. Comparing Figures 7 and 8, Pd in zeolite decreased ethanol slip over the entire ethanol release temperature range as the slip ethanol concentration was at most 25 ppm with Pd versus over 50 ppm without Pd. The most striking is the effect below 100[degrees]C where the TWC was not active as was observed in Figure 7, while Reactions 1-3 likely progressed with Pd-BEA-25 in Figure 8. The CO that would be expected to form along with C[H.sub.4] at 100[degrees]C by Reaction 2 or 3 may have been delayed by chemisorption on the Pd sites. Pd allocation was more effective at decreasing ethanol slip with 0.2 wt% (10 g/[ft.sup.3]) Pd in BEA-25 zeolite versus another 25 g/[ft.sup.3] Pd in the TWC powder. Thus, Pd in the zeolite plays a selective and different role in enhancing ethanol trapping as compared to Pd in the TWC catalyst. For a clear comparison, the adsorbed ethanol slipping out of BEA-25 catalyst and TWC catalyst is listed in Table 2.
Vehicle Test Results
The cold-start NMOG emissions of this vehicle end at 50 seconds after vehicle start . Figure 9 is a pie chart that shows the compositions of NMOG (E85 fuel) slipping out of close-coupled TWC with underbody TWC aftertreatment system during cold start (from 0 to 50 seconds measured by FTIR), which counts for 80-90% of the total NMOG emission over FTP-75. The three main components in the cold-start NMOG emissions are ethanol (54 wt%), [C.sub.2][H.sub.4]O (12 wt%), and [C.sub.2][H.sub.4] (11 wt%).
The vehicle test results with the three different underbody catalysts (Table 1) over FTP-75 are compared in Figure 10. Figure 10(a) shows the NMOG + NOx emissions over the entire FTP-75 cycle. The error bars are 95% confidence intervals on the mean of the test emissions and calculated as described elsewhere [4, 6]. The NMOG + NOx emissions over the FTP-75 cycle were reduced to 24 mg/mile with the reference HC trap (PGM loading 24 g/[ft.sup.3] with no Pd in zeolite) from 35 mg/mile with 24 g/[ft.sup.3] TWC only. It was further decreased to 19 mg/mile with the improved HC trap (total PGM loading 15 g/[ft.sup.3] with Pd in zeolite). Figure 10(b) shows the ethanol emissions with these three different underbody catalysts over Bag1 of the FTP-75 cycles, which included all the cold-start ethanol emissions. The ethanol emissions of TWC only, reference HC trap, and Pd-zeolite-based HC trap were 34.1, 4.6, and 0.3 mg/mile, respectively. The improved HC trap with Pd in the zeolite clearly demonstrated the benefit of enhancing the conversion of cold-start NMOG (ethanol) emissions, which is consistent with the lab powder catalyst test results.
FIGURE 9 The pie chart shows the compositions of NMOG (E85 fuel) slipping out of close-coupled TWC during cold start (from 0 to 50 seconds measured by FTIR). 2012MY 2.0L GDI Ford Focus PZEV, E85 fuel Ethanol 54% C2H40 12% C2H4 11% C5+ iso-alkanes 8% HCHO 4% C5+ n-alkanes 2% Aromatics 3% C2H6 4% C2H2 1% C3H6 1% Note: Table made from pie chart.
In the development of an improved HC trap for E85 fuel vehicle cold-start emission control , laboratory powder catalyst samples were formulated and investigated to give a direction for the improvement of fully formulated HC traps. Figure 9 shows that more than half (54%) of the cold-start NMOG in the E85 exhaust is ethanol, which is the main reason that this manuscript is focusing on increasing the adsorbed ethanol conversion to reduce cold-start NMOG emissions. The benefits of Pd-zeolite-based HC traps also decrease cold-start emissions of other adsorbed exhaust species and was reported in separate manuscripts [4, 21].
After aging, a conventional HC trap using H-zeolites as adsorbents without modification mainly relied upon the TWC top layer to oxidize the stored ethanol during desorption (as shown in Figure 7 with 49.3% unconverted ethanol slip). Our aging protocol de-aluminated and eliminated acid sites in the BEA-25 zeolite as the results showed in Figure 3. Pd-modified zeolite had improved conversion of stored ethanol even when aged (Figure 5) and Pd-zeolite HC trap (Pd-zeolite+TWC) significantly improved the stored ethanol conversion efficiency (as shown in Figure 8 with 15.5% unconverted ethanol slip). The total Pd loading in zeolite plus in TWC shown in Figure 8 (10 + 25 g/[ft.sup.3]) was lower than the Pd loading in the case of H-zeolite plus TWC shown in Figure 7 (50 g/[ft.sup.3]). Therefore, a small amount of Pd placed in the zeolite layer significantly improved the efficiency of a HC trap in reducing cold-start ethanol slip.
The benefits of Pd in zeolites as low-temperature NOx catalyst or cold-start NOx absorber catalyst (PNAs) in exhaust gas have already been published [24, 25, 26, 27]. It was also successfully applied in diesel (lean burn) exhaust gas for cold-start emission control . However, Pd in zeolite sinters when exposed to slightly rich conditions at high temperature , and the emission benefit over conventional zeolites is lost in gasoline aftertreatment applications . In our work, a base metal oxide [M.sup.n+] was added to the Pd-zeolite and successfully stabilized Pd during gasoline-type aging and preserved the benefit over conventional zeolites during vehicle emission tests with gasoline  and ethanol blended gasoline fuels [6, 21]. While not shown for proprietary reasons, the addition of the base metal [M.sup.n+] to BEA-25 zeolite powder was tested after laboratory four-mode aging at 750[degrees]C and showed no apparent impact to the cold-start HC adsorption process, while some ethanol desorption side products were observed at high temperature, similar in magnitude shown in Figure 3. The improved HC trap used in the vehicle tests contained [M.sup.n+]-zeolite to improve the durability of Pd sites during the four-mode catalyst aging.
* Fresh BEA-25 released about half of the stored ethanol as unconverted ethanol at low temperature (<200[degrees]C) and the rest as [C.sub.2][H.sub.4] via dehydration at higher temperature. After laboratory four-mode aging at 750[degrees]C, BEA-25 released nearly all of the stored ethanol as unconverted ethanol at low temperature (<200[degrees]C), and the ethanol dehydration reaction was insignificant.
* Pd added to BEA-25 significantly decreased ethanol slip and altered the zeolite reaction chemistry. The release of stored ethanol reaction began with ethanol dehydrogenation and C[H.sub.3]CHO decomposition reactions at low temperature, followed by ethanol decomposition reaction at higher temperature.
* Pd added into BEA zeolite powder was more effective for ethanol slip control than a higher Pd load in the TWC powder. Pd in zeolite is active in converting ethanol at lower temperature than Pd in TWC. However, Pd content higher than 0.2 wt% zeolite showed diminished improvement in the reduction of ethanol slip.
* Vehicle test results confirmed the benefits of Pd-zeolite in HC trap in improving cold-start NMOG conversion efficiencies of E85 exhaust gas. The improved HC trap (Pd-zeolite-based HC trap) reduced ethanol emissions of a flex fuel vehicle running E85 fuel down to near zero milligrams per mile.
Declarations of Interest
The author and publisher would like to acknowledge that this article is based on an oral-only presentation at CLEERS Workshop, Ann Arbor, Michigan, on October 3-5, 2017.
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Lifeng Xu, Jason Lupescu, Giovanni Cavataio, Kevin Guo, and Hungwen Jen, Research and Innovation Center, Ford Motor Co., USA
Pd catalyst, Zeolite,
Cold-start emissions, Cold-start catalyst, Ethanol emissions, HC trap, Flex fuel vehicle emission, Three-way catalyst (TWC)
Xu, L., Lupescu, J., Cavataio, G., Guo, K. et al., "The Impacts of Pd in BEA Zeolite on Decreasing Cold-Start NMOG Emission of an E85 Fuel Vehicle," SAE Int. J. Fuels Lubr. 11(3):239-246, 2018, doi:10.4271/04-11-03-0013.
Received: 09 May 2018
Revised: 03 Sep 2018
Accepted: 23 Sep 2018
e-Available: 25 Oct 2018
TABLE 1 TWC or HC traps used in vehicle tests. Catalyst Zeolite TWC TWC PGM load (Pt/Pd/Rh) TWC only None High 24 g/[ft.sup.3] (0:11:1) Reference HC trap No Pd in zeolite Low 24 g/[ft.sup.3] (0:11:1) Improved HC trap Pd and [M.sup.n+] (*) Low 15 g/[ft.sup.3] (2:47:1) in zeolite (*) [M.sup.n+] is a metal additive which helped to improve the Pd-zeolite durability during aging [4, 21]. TABLE 2 The percent of adsorbed ethanol slipping out of different catalysts with pre-lean treatment. Catalyst Ethanol slip (% of adsorbed ethanol) 0.5 g fresh BEA-25 42.2% 0.5 g aged BEA-25 96.7% 0.5 g fresh 0.2 wt% Pd-BEA-25 14.8% 0.5 g aged 0.2 wt% Pd-BEA-25 32.7% 0.5 g aged BEA-25 + 0.25 49.3% g aged TWC (50 g/[ft.sup.3]) 0.5 g aged 0.2 wt% Pd-BEA-25 + 0.25 g 15.5% aged TWC (25 g/[ft.sup.3])
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|Title Annotation:||Palldium, non-methane organic gas|
|Author:||Xu, Lifeng; Lupescu, Jason; Cavataio, Giovanni; Guo, Kevin; Jen, Hungwen|
|Publication:||SAE International Journal of Fuels and Lubricants|
|Article Type:||Technical report|
|Date:||Nov 1, 2018|
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