Energy Fuels 2010, 24, 3189–3194 Published on Web 04/26/2010
: DOI:10.1021/ef9012455
Preparation of Biofuel Using Acetylatation of Jojoba Fatty Alcohols and Assessment as a Blend Component in Ultralow Sulfur Diesel Fuel† Shailesh N. Shah,‡ Brajendra K. Sharma,‡,§ and Bryan R. Moser*,‡ ‡
United States Department of Agriculture, Agricultural Research Service, National Center for Agricultural Utilization Research, 1815 N University St, Peoria, Illinois 61604, and §Pennsylvania State University, Department of Chemical Engineering, University Park, Pennsylvania 16802. Received October 30, 2009. Revised Manuscript Received March 4, 2010
The majority of biodiesel fuels are produced from vegetable oils or animal fats by transesterification of oil with alcohol in the presence of a catalyst. In this study, a new class of biofuel is explored by acetylation of fatty alcohols from Jojoba oil. Jojobyl methyl acetate (JMA) was produced using direct acetylation of purified jojobyl alcohol obtained during preparation of Jojobyl methyl esters (JME). Important fuel properties of JMA, such as kinematic viscosity, cloud point (CP), pour point (PP), cold filter plugging point (CFPP), acid value, oxidative stability, gross heat of combustion, and lubricity were evaluated using standard methods. A comparison was made with previously reported JME and relevant biodiesel fuel standards, such as ASTM D6751 and EN 14214. The CP, CFPP, and PP values of JMA were 2, -10, and -16 °C, respectively. These results were comparable to JME with the exception of a higher CP in the case of JMA. The kinematic viscosity (40 °C) of JMA was 7.64 mm2/s, which was higher than that observed for JME. Blends (B5 and B20) of JMA in ultralow sulfur diesel fuel (ULSD) were also evaluated for the aforementioned fuel properties and compared to an analogous set of blends of JME in ULSD and relevant petrodiesel fuel standards such as ASTM D975 and D7467. Blends of JMA in ULSD displayed similar low temperature properties to neat ULSD and blends of JME in ULSD. This research demonstrates utilization of a byproduct as feedstock for biofuel preparation and establishes a new innovative class of biofuel, which can be prepared via the acetylation of fatty alcohols.
component.2 Currently, many uses of jojoba oil (JO) have been reported, such as use in hair care products and cosmetics, as well as in lubricant and additive applications, as a result of the higher viscosity index of JO than that of petroleum oil.4-7 In addition, further uses of jojoba include polishing, gardening, and pharmaceutical applications.8 Recently, the effect of aging on JO quality has been investigated.9,10 Biodiesel is normally produced from vegetable oils or animal fats via transesterification with alcohol in the presence of a catalyst at elevated temperature.11 In this study, a new class of biodiesel is explored by acetylation of fatty alcohols. Recently, we have reported preparation of Jojoba oil methyl esters (JME) as biodiesel from transesterification of jojoba oil with methanol using sodium methoxide as catalyst to produce JME, along with jojobyl alcohol as byproduct.12 In this study, Jojobyl methyl acetate (JMA) was produced using direct
1. Introduction As per the American Society for Testing and Materials (ASTM),1 biodiesel (BD), which is an alternative fuel composed of monoalkyl esters of long-chain fatty acids prepared from renewable vegetable oils or animal fats, has attracted significant attention as an alternative fuel or blend component for conventional petroleum diesel fuel (petrodiesel). Jojoba (Simmondsia chinensis) is a permanent shrub belonging to the Simmondsiaceae family that is native to the Mojave and Sonoran deserts of Mexico, California, and Arizona. The jojoba plant produces seeds that contain 45-55 wt % inedible long-chain esters of fatty acids and alcohols (wax esters), as opposed to triacylglycerols (TAG) encountered in other vegetable oils and animal fats.2,3 The fatty alcohol component of jojoba wax esters primarily consists of cis-11-eicosen-1-ol and cis-13-docosen-1-ol, with eicosenoic, erucic, and oleic acids composing the acid
(4) Sivasankarn, G. A.; Bisht, R. P. S.; Jain, V. K.; Gupta, M. Tribol. Int. 1998, 21, 327–333. (5) Bhatia, V. K.; Chaudhary, A.; Masohan, A.; Sivasankarn, G. A.; Bisht, R. P. S. J. Am. Oil Chem. Soc. 1988, 65, 1502–1507. (6) Bhatia, V. K.; Chaudhary, A.; Sivasankarn, G. A.; Bisht, R. P. S.; Kashyap, M. J. Am. Oil Chem. Soc. 1990, 67, 1–7. (7) Bisht, R. P. S.; Sivasankarn, G. A.; Bhatia, V. K. Wear 1993, 161, 193–197. (8) Shani, A. CHEMTECH 1995, 25, 49–54. (9) Savita, K.; Goyal, H. B.; Bhatnagar, A. K.; Gupta, A. K. Ind. Crops Prod. 2009, 29, 102–107. (10) Le Dreau, Y.; Dupuy, N.; Gaydou, V.; Joachim, J.; Kister, J. Anal. Chim. Acta 2009, 642 (1-2), 163-170. (DOI:10.1016/j. aca.2008.12.001). (11) Moser, B. R. In Vitro Cell. Dev. Biol.: Plant 2009, 45, 229–266. (12) Shah, S. N.; Sharma, B. K.; Moser, B. R.; Erhan, S. Z. Bioenergy Res., in press. (DOI: 10.1007/s12155-009-9053-y).
† Disclaimer: Product names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable. *To whom correspondence should be addressed. Tel.: þ1-309-6816511. Fax: þ1-309-681-6524. E-mail:
[email protected]. (1) Standard specification for biodiesel fuel blend stock (B100) for middle distillate fuels, ASTM D6751-08. In 2008 ASTM Annual Book of Standards; American Society for Testing and Materials: West Conshohocken, PA, 2008. (2) Canoira, L.; Alcantara, R.; Garcia-Martinez, M. J.; Carrasco, J. Biomass Bioenergy 2006, 30, 76–81. (3) Bouaid, A.; Bajo, L.; Martinez, M.; Aracil, J. Process Saf. Environ. 2007, 85, 378–382.
This article not subject to U.S. Copyright. Published 2010 by the American Chemical Society
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: DOI:10.1021/ef9012455
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2.4. Fuel Properties of Jojobyl Methyl Acetate. CP and PP determinations (°C) were made following ASTM standards D577314 and D5949,15 respectively, using a Model PSA-70S phase technology analyzer (Richmond, B.C., Canada). CP and PP values were rounded to the nearest whole degree (°C). For a greater degree of accuracy, PP measurements were done with a resolution of 1 °C instead of the specified 3 °C increment. CFPP (°C) was measured in accordance to ASTM standard D6371,16 utilizing a model FPP 5Gs ISL automatic CFPP analyzer provided by PAC, L.P. (Houston, TX). All experiments were run in triplicate, and mean values are reported (see Tables 2-4). Kinematic viscosity (υ, mm2/s) was measured with a Cannon-Fenske viscometer (Cannon Instrument Co., State College, PA) following ASTM standard D445 (Tables 2-4).17 AV (mg KOH/g) was measured (in triplicate, with means reported in Tables 2-4) as described in AOCS official method Cd 3d-6318 using a Metrohm Model 836 Titrando (Westbury, NY) autotitrator equipped with a Model 801 stirrer and a Solvotrode electrode. The official method was modified for scale to use 2 g of sample and 0.02 M KOH. The titration end point was automatically determined and visually verified using a phenolphthalein indicator. Lubricity (in duplicate, with means reported in Tables 2-4) was measured at 60 °C ((1 °C), according to ASTM standard D607919 using a high-frequency reciprocating rig (HFRR) lubricity tester (PCS Instruments, London, England) via Lazar Scientific (Granger, IN). Reported wear scars (μm) were the result of measuring the maximum lengths of the x- and y-axes of each wear scar using a Prior Scientific (Rockland, MA) Epimat Model M4000 microscope, followed by calculating the average of these maximum values. Oxidative stability (induction period, IP, h) was determined (measured in triplicate, with means reported in Tables 2-4) at 110 °C with a correction factor of 1.5 °C utilizing a Model 743 Rancimat instrument (Metrohm USA, Inc., Riverview, FL), according to the EN 14112 specification.20 Pressurized differential scanning calorimetry (PDSC) experiments were performed using a personal computer (PC)controlled DSC Q10 thermal analyzer from TA Instruments (New Castle, IN). The instrument has a maximum sensitivity of 5 mV/cm and a temperature sensitivity of 0.2 mV/cm.
Figure 1. Synthetic route of jojobyl methyl acetate (JMA) from jojobyl alcohol (JA).
acetylation of purified jojobyl alcohol (Figure 1) obtained during preparation of JME. JMA and its blend with ultralow sulfur diesel fuel (ULSD) were evaluated for important fuel properties, like kinematic viscosity, cloud point (CP), pour point (PP), cold filter plugging point (CFPP), acid value (AV), oxidative stability, and lubricity using standard methods. A comparison was made with previously reported JME and relevant biodiesel fuel standards such as ASTM D6751 and EN 14214. 2. Experimental Section 2.1. Materials. PNJ Golden jojoba oil (JO) without commercial additives was purchased from Purcell Jojoba International (Lake Havasu City, AZ) and used as received. ULSD, described as fungible by the manufacturer, was donated by a major petrochemical company that wishes to remain anonymous. Conductivity and corrosion inhibitor additives were added by the manufacturer to the ULSD, but no drag-reducing, lubricity, low-temperature, or antioxidant additives were present. All other chemicals and reagents were obtained from either Fisher Scientific or Sigma-Aldrich Corp (St. Louis, MO) and used as received. 2.2. Acetylation of Jojobyl Alcohol (JA). The acetylation of JA (Figure 1) was performed using a previously reported method.13 Jojobyl methyl acetate (JMA) was obtained by reacting jojobyl alcohol (54.0 g, 0.183 mol) with acetic anhydride (Fisher Scientific, 97.2%), (36.7 g, 0.36 mol) in triethylamine (Aldrich, 99%) at room temperature. The reaction mixture was dissolved in dichloromethane (Sigma-Aldrich, 99.8%), washed with a saturated solution of NaHCO3 (3 times), water, and finally with brine (3 times) and dried over anhydrous sodium sulfate. The solvent was evaporated in a rotary evaporator. Traces of water and acetic acid were eliminated from the mixture by vacuum distillation. The amount of product collected was 54.9 g (92.7 wt %). 2.3. NMR and FT-IR Spectroscopy. 1H and 13C NMR data were recorded using a Bruker Model AV-500 spectrometer (Billerica, MA) operating at 500 MHz (125 MHz in the case of 13C NMR), using a 5-mm broadband inverse Z-gradient probe in CDCl3 (Cambridge Isotope Laboratories, Andover, MA) as the solvent. FT-IR spectra were obtained on a Thermo-Nicolet Nexus 470 FTIR spectrometer (Madison, WI) with a Smart ARK accessory containing a 45 ZeSe trough in a scanning range of 650-4000 cm-1 for 64 scans at a spectral resolution of 4 cm-1.
(14) Standard test method for cloud point of petroleum products (constant cooling rate method), ASTM D5773-07. In 2007 ASTM Annual Book of Standards; American Society for Testing and Materials: West Conshohocken, PA, 2007. (15) Standard test method for pour point of petroleum products (automatic pressure pulsing method), ASTM D5949-01. In 2001 ASTM Annual Book of Standards; American Society for Testing and Materials: West Conshohocken, PA, 2001. (16) Standard test method for cold filter plugging point of diesel and heating fuels, ASTM D6371-05. In 2005 ASTM Annual Book of Standards; American Society for Testing and Materials: West Conshohocken, PA, 2005. (17) Standard test method for kinematic viscosity of transparent and opaque liquids (and calculation of dynamic viscosity), ASTM D445-06. In 2006 ASTM Annual Book of Standards; American Society for Testing and Materials: West Conshohocken, PA, 2006. (18) Official Methods and Recommended Practices of the American Oil Chemists’ Society (Method AOCS Cd 3d-63), 5th ed.; Firestone, D., Ed.; American Oil Chemists’ Society: Champaign, IL, 1999. (19) Standard test method for evaluating lubricity of diesel fuels by high frequency reciprocating rig (HFRR), ASTM D6079-04. In 2004 ASTM Annual Book of Standards; American Society for Testing and Materials: West Conshohocken, PA, 2004. (20) European Committee for Standardization (CEN). Fat and oil derivatives. Fatty acid methyl esters (FAME). Determination of oxidative stability (accelerated oxidation test), EN 14112:2009. European Committee for Standardization (CEN): Brussels, Belgium, 2009.
(13) Garcı´ a, E.; Laca, M.; Perez, E.; Garrido, A.; Peinado, J. Energy Fuels 2008, 22, 4274–4280.
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Shah et al. Table 1. Fatty Alcohol Composition (wt %) of Jojobyl Alcohola
A 1.5-2.0 mg sample was placed in a hermetically sealed type of aluminum pan with a pinhole lid for interaction of the sample with the reactant gas (dry air). The controlled diffusion of the gas through the hole greatly restricts the volatilization of the oil while still allowing for saturation of the liquid phase with air. A film thickness of 24 0.02 198 213
-15 -24 -15 273 2.49 17 0.12 196 216
-15 -25 -16 320 2.45 21 0.02 194 211
520 max 1.9-4.1
See ref 12.
Table 4. Physical Properties of Jojoba Methyl Acetate (JMA) and Jojoba Oil Methyl Esters (JME) at 20 vol % with Ultralow Sulfur Diesel Fuel (ULSD) and Their Comparison with Fuel Specification ASTM D975 for 20% BD Value property cloud point, CP (°C) pour point, PP (°C) cold filter plugging point, CFPP (°C) induction period (110 °C), IP (h) lubricity (60 °C) (μm) kinematic viscosity (40 °C), υ (mm2/s) acid value, AV (mg KOH/g) onset temperature, OT, °C signal maximum temperature, SMT (°C) a
ASTM D7467
ULSD
JMA
JMEa
report
-18 -23 -16 >24 493 2.34 0.02 198 213
-15 -22 -21 15 189 2.92 1.64 186 212
-16 -21 -16 17 222 2.96 0.16 188 208
6.0 min 520 max 1.9-4.1 0.30 max
See ref 12.
-20, -35, and -57 °C, respectively.24 The low-temperature properties of JMA blended at 5 and 20 vol % with ULSD (see Tables 3 and 4) were compared to the corresponding JME blends with ULSD. Both the 5 and 20 vol % blends of JMA in ULSD had negligible impact on CP, PP, and CFPP of ULSD. This result showed that JMA can be blended with ULSD without any significant impact on the low-temperature characteristics. JME also showed similar trends for the low-temperature characteristics (see Tables 3 and 4). The oxidative stabilities of JA and JMA were 0.5 h, which was similar to JME (0.4 h), as measured by the Rancimat method (IP, EN 14112, Table 2). Except for JO, none of the others (JA, JMA, and JME) met the ASTM D6751 (>3.0 h) or EN 14214 (>6.0 h) specifications. The addition of antioxidants or blending with more oxidatively stable feedstocks would be necessary to satisfy the oxidative stability
-16, and -10 °C, respectively. The better low temperature operability of both JMA and JME is attributed to the relatively high level of unsaturated components in JA (98.6 wt %; Table 1) and in JME (97.8, wt %).12 Soybean oil methyl esters have CP, PP, and CFPP values of 0, -3, and -4 °C, respectively.12 In addition, unsaturated FAME (in the case of JME) and fatty alcohol chains (in case of JMA) have noticeably lower melting point (mp) values than the analogous saturated species. For example, the melting points of methyl gondoate and erucate are -45 and -34 °C.24,25 In addition, the melting points of methyl esters of stearic (C18:0), oleic, linoleic, and linolenic acids are 39, (24) Dictionary Section. In The Lipid Handbook, 3rd ed.: Gunstone, F. D., Harwood, J. L., Dijkstra, A. J. (Eds.) ; CRC Press: Boca Raton, FL; pp 444-445. (25) Chang, S. P.; Rothfus, J. A. J. Am. Oil Chem. Soc. 1996, 73, 403–410.
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requirements in the ASTM D6751 and EN 14214 standards. Tables 3 and 4 also reveal that the oxidative stability of ULSD decreases as the percentage of biodiesel (JMA and JME) was increased from 0 vol % to 20 vol %. Despite the very low IP value (0.5 h) of JMA, the IP values of 5% and 20% blends are considerably good (17 and 15 h, respectively). Table 4 shows that the 20 vol % blend of JMA in ULSD satisfied the ASTM D7467 (IP > 6 h) specification. This observation is consistent with previously reported results for a 20 vol % JME blend in ULSD. The petrodiesel standard—ASTM D975 (up to 5 vol % biodiesel)—does not contain an oxidative stability specification. Both ASTM D6751 and EN 14214 restrict the AV to a maximum value of 0.50 mg KOH/g. The AV values of JMA and JME were 1.22 and 1.37 mg KOH/g, respectively, which was not within the specified limit of 0.50 mg KOH/g (Table 2). The high AV of JMA was probably a result of the presence of free fatty acids in JA, which itself had an AV of 0.57 mg KOH/g. Moreover, during the acetylation of JA, more acetic acid may have been generated from acetic anhydride and might not have been completely removed during the purification process. Blends of JMA in ULSD showed higher AVs than the corresponding JME blends (see Tables 3 and 4). For instance, 20 vol % JMA and JME correspondingly showed AVs of 1.64 and 0.16 mg KOH/g. Thus, the JMA blend does not meet the ASTM D7467 specification (
