Environ. Sci. Technol. 2010, 44, 4361–4367
Reactive Extraction of Jatropha curcas L. Seed for Production of Biodiesel: Process Optimization Study SIEW HOONG SHUIT,† K E A T T E O N G L E E , * ,† AZLINA HARUN KAMARUDDIN,† AND SUZANA YUSUP‡ School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, Pulau Pinang, Malaysia, and Department of Chemical Engineering, Universiti Teknologi PETRONAS, 31750 Tronoh, Perak, Malaysia
Received September 8, 2009. Revised manuscript received April 20, 2010. Accepted April 27, 2010.
Biodiesel from Jatropha curcas L. seed is conventionally produced via a two-step method: extraction of oil and subsequent esterification/transesterification to fatty acid methyl esters (FAME), commonly known as biodiesel. Contrarily, in this study, a single step in situ extraction, esterification and transesterification (collectively known as reactive extraction) of J. curcas L. seed to biodiesel, was investigated and optimized. Design of experiments (DOE) was used to study the effect of various process parameters on the yield of FAME. The process parameters studied include reaction temperature (30-60 °C), methanol to seed ratio (5-20 mL/g), catalyst loading (5-30 wt %), and reaction time (1-24 h). The optimum reaction condition was then obtained by using response surface methodology (RSM) coupled with central composite design (CCD). Results showed that an optimum biodiesel yield of 98.1% can be obtained under the following reaction conditions: reaction temperature of 60 °C, methanol to seed ratio of 10.5 mL/g, 21.8 wt % of H2SO4, and reaction period of 10 h.
Introduction Owing to the world petroleum crisis, production of biodiesel in Malaysia has increased steadily for the past three years; from 325,000 tons in 2006 to 400,000 tons in 2007 and 420,000 tons in 2008 (1). This increase is in tandem with the world’s increasing biodiesel demand, especially in the European region. However, the practice of using edible oils, which is currently the most common feedstock for biodiesel production, has raised criticism from various sectors, especially nongovernmental organization (NGO), claiming that biodiesel is competing for resources with the food industry. Therefore, production of biodiesel from nonedible oils such as Jatropha curcas L. seeds (2), beef tallow (3), waste cooking oil (4), and Cerbera odollam (sea mango) (5) would be a * Corresponding author phone: +604-5996467; fax: +604-5941013; e-mail:
[email protected]. † School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, Pulau Pinang, Malaysia ‡ Department of Chemical Engineering, Universiti Teknologi PETRONAS, 31750 Tronoh, Perak, Malaysia 10.1021/es902608v
2010 American Chemical Society
Published on Web 05/10/2010
potential solution to this issue. Among these choices, J. curcas L. seed has recently been hailed as the promising feedstock for biodiesel production because it can be cultivated in dry and marginal lands (6), and thus it does not compete for arable land that would have otherwise being planted with food crops. Besides, its oil yield as shown in Table 1 is comparable to that of palm oil but much higher as compared to other edible oil crops such as rapeseed, sunflower, and soybean (7, 8). Therefore, even Malaysia, the world’s second largest palm oil producer, is now diversifying its biodiesel feedstock toward jatropha. The total jatropha plantation area in Malaysia, at the end of 2008, was estimated at 750,000 acres and is expected to increase to 1.5 million acres in 2009 and 2.5 million acres in 2010 (9). Conventional methods for producing biodiesel from jatropha and other types of oil seeds involve various stages: oil extraction, purification (degumming, dewaxing, deacidification, dephosphorization, dehydration, etc.), and subsequent esterification or transesterification. These multiple biodiesel processing stages constitute >70% of the total biodiesel production cost if refined oil is used as feedstock (10). Recently, in our previous study, it was shown that in situ extraction and esterification/transesterification, simply known as reactive extraction, is a feasible technology for the production of biodiesel using a single step that can cut the processing cost. In the reactive extraction process, extraction of oil and esterification/transesterification proceed in a single step in which the oil-bearing material contacts with alcohol directly instead of reacting with pre-extracted oil. In other words, alcohol acts both as an extraction solvent and as a transesterification reagent during reactive extraction, and therefore a higher amount of alcohol is required. However, reactive extraction eliminates the requirement of two separate processes, the costly hexane oil extraction process and the transesterification reaction process, thus reducing processing time, cost, and amount of solvent required (11). Furthermore, on the basis of a similar study reported in the literature (using soybeans), it was demonstrated that the reactive extraction process can be scaled up without encountering much problem in mass and heat transfer limitations (12). Nevertheless, in our previous study, the requirement of a 24 h reaction time to achieve a high fatty acid methyl esters (FAME) yield of 99.9% makes this process unattractive from an industrial perspective (11). Thus, the aim of this study is to optimize the process parameters of the acid-catalyzed reactive extraction process for the production of FAME from J. curcas L. seed.
Experimental Section Materials. J. curcas L. seed was purchased from Misi Bumi Alam Sdn Bhd, Malaysia. Methanol (99.9% purity) was purchased from J. T. Baker, Germany. The remaining chemicals used in this study, sulfuric acid (H2SO4, 95-97% purity), methyl heptadecanoate (internal standard), and pure methyl esters such as methyl palmitate, methyl stearate,
TABLE 1. Oil Yield of Jatropha curcas L. Seed and Other Major Oil Crops oil crop
oil yield (tons/ha/year)
J. curcas L. seed oil palm (mesocarp) rapeseed sunflower soybean
2.70 (7) 3.62 (8) 0.68 (8) 0.46 (8) 0.40 (8)
VOL. 44, NO. 11, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
4361
TABLE 2. Coded and Actual Values of Process Parameters in Central Composite Design level variable
code
unit
-2 (-r)
-1
0
+1
+2 (+r)
reaction time reaction temperature methanol to seed ratio H2SO4 loading
A B C D
h °C g/mL wt %
1 30 5 5
7 38 8.75 11.25
13 45 12.5 17.5
18 53 16.25 23.75
24 60 20 30
methyl oleate, and methyl linoleate, were purchased from Fluka Chemie, Germany. Pretreatment of J. curcas L. Seed and Oil Content. Initially, fresh J. curcas L. seed was blended and sieved to a size of F” of >0.05), multiple regression analysis gives the following quadratic model equation (in coded factors) that correlates the yield of FAME to the various process parameters: yield (wt %) ) 58.6 + 10.2A + 16.8B + 9.11C + 18.5D 5.34A2 - 4.28D2 + 5.63BD (2) As shown in Table 4, the F test (Fisher) on eq 2 gives an F value of 21.8 and a “prob > F” value of F
TABLE 4. ANOVA for Response Surface Quadratic Model for the Yield of FAME source
sum of squares
DF
mean square
model 21688.99 14 1549.21 21.84 A 2504.31 1 2504.31 35.30 B 6758.98 1 6758.98 95.27 C 1994.00 1 1994.00 28.11 D 8242.14 1 8242.14 116.18 A2 788.11 1 788.11 11.01 B2 0.35 1 0.35 0.004984 2 C 4.5 1 4.5 0.063 D2 502.2 1 502.2 7.08 AB 183.06 1 183.06 2.58 AC 81.09 1 81.09 1.14 AD 219.93 1 219.93 3.10 BC 9.09 1 9.09 0.13 BD 507.6 1 507.6 7.15 CD 0.002025 1 0.002025 0.00002854 residual 1064.19 15 70.95 R2 ) 0.9532; adjusted R2 ) 0.9096; predicted R2 ) 0.7394; standard deviation ) 8.42; mean ) 50.69 a
Significant at 95% confident interval.
b
