Biodiesel Conversion via Thermal Assisted in-Situ Transesterification

Subscriber access provided by CORNELL UNIVERSITY LIBRARY

Article

Biodiesel conversion via thermal assisted in-situ transesterification of bovine fat using dimethyl carbonate as an acyl acceptor Jong-Min Jung, Jechan Lee, Ki-Hyun Kim, Sang Ryong Lee, Hocheol Song, and Eilhann E. Kwon ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b01456 • Publication Date (Web): 01 Sep 2016 Downloaded from http://pubs.acs.org on September 5, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Sustainable Chemistry & Engineering is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 17

1 2 3 1 4 5 6 2 7 8 9 3 10 11 12 4 13 14 5 15 16 6 17 18 19 7 20 21 8 22 23 9 24 25 26 10 27 28 11 29 30 31 12 32 33 13 34 35 14 36 37 38 15 39 40 16 41 42 17 43 44 45 18 46 47 19 48 49 20 50 51 52 21 53 54 22 55 56 57 58 59 60

ACS Sustainable Chemistry & Engineering

Biodiesel conversion via thermal assisted in-situ transesterification of bovine fat using dimethyl carbonate as an acyl acceptor

Jong-Min Jung,1 Jechan Lee,1 Ki-Hyun Kim,2 Sang Ryong Lee,3 Hocheol Song,1 and Eilhann E. Kwon1,*

1

Department of Environment and Energy, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, Korea; 2Department of Civil and Environmental Engineering, Hanyang University, 222

Wangsimni-ro, Seongdong-gu, Seoul 04763, Korea; 3Livestock Air Quality Lab, Animal Environment Division, National Institute of Animal Science, 1500 Kongjwipatjwi-ro, Iseo-myeon, Wanju-gun, Jeollabuk-do, 55365, Korea

ABSTRACT This study experimentally evidenced that bovine fat could be directly converted into fatty acid methyl esters (FAMEs) without lipid extraction step via thermally assisted in-situ transesterification on a porous material such as SiO2 since providing thermal energy from an external heating source drove pseudocatalytic mechanisms caused by mobility difference between lipid in bovine fat and acyl acceptor. In particular, this study employed dimethyl carbonate (DMC) as an acyl acceptor due to its non-toxicity and economic viability. In order to validate thermal assisted in-situ transesterification, thermal degradation of bovine fat was characterized, which revealed that thermal behavior of lipid in bovine fat was nearly identical to refined lipid. The results also evidenced that bovine fat contains 12.51 wt.% impurities. Fatty acid profiles were identical under different transesterification conditions, which evidences that the thermal assisted in-situ transesterification should be technically feasible. In order to find an optimal reaction *

Corresponding author: Prof. Eilhann E. Kwon, E-mail: [email protected], Phone: 82-2-3408-4166, Fax: 82-2-3408-4320 1 ACS Paragon Plus Environment


1 2 23 3 4 5 24 6 7 25 8 9 26 10 11 12 27 13 14 28 15 16 29 17 18 19 30 20 21 31 22 23 32 24 25 26 33 27 28 34 29 30 31 35 32 33 36 34 35 37 36 37 38 38 39 40 39 41 42 40 43 44 45 41 46 47 42 48 49 43 50 51 52 44 53 54 45 55 56 57 46 58 59 60

Page 2 of 17

condition, in-situ transesterification of bovine fat was tested between 340 to 390 ˚C; the maximum conversion of bovine fat was achieved at 380 ˚C. This study reported optimal condition for thermal assisted in-situ transesterification of bovine fat and 96.1% FAME yield from bovine fat was achieved at 380 ˚C.

KEYWORDS: bovine fat; dimethyl carbonate; fatty acid methyl esters; in-situ transesterification; silica; biodiesel

INTRODUCTION Total worldwide energy consumption has been increased from 6.1 billion TOE (e.g., ton of energy) in 1973 to 13.541 billion TOE in 2013 and more than 80% of energy has been obtained from various types of fossil fuel.1 Our heavy dependence on fossil fuels has caused energy security issues in most developed countries due to the limited reserves and uneven distribution of fossil fuels in line with the political uncertainties. Furthermore, combusting fossil fuels for electricity generation and transportation emit a tremendous amount of CO2 into the atmosphere, which causes severe global environmental issues such as global warming.2 In this respect, it is highly desirable to replace fossil fuels with renewable energies to mitigate global environmental issues triggered by anthropogenic carbon input. Biofuels have been considered as a promising substitute for fossil fuels. Amongst biofuels, biodiesel has drawn a great deal of public attention due to its high compatibility with the current fuel distribution network and current diesel engine without any modifications; thus, the first generation of biodiesel (i.e., biodiesel produced from edible oil-bearing crop) has been commercialized.3-4 Moreover, the use of biodiesel as transportation fuel resulted in the substantial reduction of greenhouse gases (GHGs) emission, carbon monoxide (CO), polycyclic aromatic hydrocarbons (PAHs), particulate matter (PM) and sulfuric dioxide (SO2).4-7 In spite of numerous benefits of 1st generation of biodiesel, there have been problems 2 ACS Paragon Plus Environment

Page 3 of 17

1 2 47 3 4 5 48 6 7 49 8 9 50 10 11 12 51 13 14 52 15 16 53 17 18 19 54 20 21 55 22 23 56 24 25 26 57 27 28 58 29 30 31 59 32 33 60 34 35 61 36 37 38 62 39 40 63 41 42 64 43 44 45 65 46 47 66 48 49 67 50 51 52 68 53 54 69 55 56 57 70 58 59 60


associated with increasing crop cost (e.g., soybean and corn) and have brought forth ethical dilemma.8 Thus, a great deal of researches has been initiated to produce biodiesel from inedible oil such as waste animal fat, jatropha oil and microalgal lipid (i.e., 2nd and 3rd generations of biodiesel).9-10 In general, production of biodiesel involves lipid extraction from oil-bearing biomass and transesterification of lipid.11-14 Various lipid extraction methods such as solvent extraction, supercritical extraction, hydrothermal liquefaction and melting have been developed.15-18 However, a large amount of solvent is required for lipid extraction, which is not environmentally friendly and increases process cost.1920

The conventional transesterification process for biodiesel production is conducted in the presence of a

homogeneous base and/or acid catalyst (e.g., KOH, NaOH and H2SO4).21-23 Homogeneous base catalysts are known to have a faster reaction rate than other catalysts, but its practical implication is very limited to the refined lipid feedstock for biodiesel production due to the high sensitivity of free fatty acids (FFAs); saponification reaction (i.e., soap formation) can occur through a reaction between FFAs and base catalysts. The formation of soap not only consumes catalyst itself thereby inhibiting glycerol separation from lipids but also causes a formation of emulsion in washing step.24 Homogeneous acid catalysts show much slower reaction rate than base catalysts.23 Both acid and base catalysts generate toxic and dangerous chemicals and extra separation steps are required after catalytic transesterification. Heterogeneous catalysts (e.g., zeolite, sulfated zirconia, supported metal catalysts, etc.) have also been used for biodiesel production to resolve these issues triggered by homogeneous catalysts. However, the cost and stability of the heterogeneous catalysts under transesterification conditions has been recognized as critical challenges for the commercialization. The production cost of biodiesel is highly dependent on feed materials and processing cost.9 For example, initial feedstocks take 75% of total production cost and conversion processing takes 25% of total production cost.8 Therefore, a great deal of researches associated with a new class of biodiesel feedstock has been actively initiated. In parallel, researches for achieving the efficient transformation of biodiesel 3 ACS Paragon Plus Environment


1 2 71 3 4 5 72 6 7 73 8 9 74 10 11 12 75 13 14 76 15 16 77 17 18 19 78 20 21 79 22 23 80 24 25 26 81 27 28 82 29 30 31 83 32 33 84 34 35 85 36 37 38 86 39 40 87 41 42 88 43 44 45 89 46 47 90 48 49 91 50 51 52 92 53 54 55 56 57 58 59 60

Page 4 of 17

have been conducted actively.25 For example, transesterification under supercritical conditions without using catalyst has widely been suggested and conducted.26-28 Another effort making biodiesel production more environmentally friendly and economically viable was to replace typical acyl acceptor for transesterification (e.g., methanol) with dimethyl carbonate (DMC). DMC is an inexpensive, safe (i.e., non-toxic and non-corrosive) and environmentally friendly solvent.29-30 Also, transesterification of lipid with DMC produces glycerol carbonate that is a versatile chemical used as surfactants, chemical intermediate and building block of polymers.31-32 Thus, producing valuable byproducts potentially boosts the economic viability of biodiesel. Thus, it is highly desirable to develop an effective biodiesel conversion process with cheap oil-bearing biomass such as animal fat with eco-friendly chemical agent like DMC. More preferably, in-situ transesterification of animal fat without an oil extraction step will be very desirable in economic aspects. Moreover, the biodiesel production method shown in this study does not require high pressure required for supercritical transesterification, making in-situ transesterification more cost-effective. In order to achieve this, this study placed great emphasis on thermal assisted in-situ transesterification of bovine fat as a case study. Thermal assisted in-situ transesterification on SiO2 was systematically investigated at the fundamental levels in this study. First, the thermal degradation of bovine fat was characterized via a series of thermo-gravimetric analysis (TGA) tests. And then, the technical feasibility of thermal assisted in-situ transesterification of bovine fat was experimentally validated via comparing fatty acid profiles established in different transesterification conditions. Finally, the optimal conditions for thermal assisted in-situ transesterification of bovine fat were experimentally established.

EXPERIMENTAL

4 ACS Paragon Plus Environment

Page 5 of 17

1 2 93 3 4 5 94 6 7 95 8 9 96 10 11 12 97 13 14 98 15 16 99 17 18 19100 20 21101 22 23 102 24 25 26103 27 28104 29 30 31105 32 33106 34 35107 36 37 38108 39 40109 41 42 110 43 44 45111 46 47112 48 49 113 50 51 52114 53 54115 55 56 57116 58 59 60


Chemical Reagents and Sample Preparation. Dichloromethane, methanol (MeOH), DMC and SiO2 were purchased from Sigma-Aldrich (St. Louis, USA). Sodium hydroxide (NaOH) was purchased from Daejung Chemical. Bovine fat was obtained from national institute of animal science (Jeonju, Korea).

Triglycerides Extraction from Bovine Fat. Ten g of bovine fat was extracted with dichloromethane of 200 mL using a Soxhlet device (WHM 12293, DAIHAN Science, Korea) equipped with a reflux condenser. An extraction temperature was set to 60 ˚C during 72 h. After extraction, dichloromethane was recovered using a rotary evaporator (WEV-1001V, DAIHAN Science).

Thermo-Gravimetric Analysis of Bovine Fat. To characterize the thermolysis of bovine fat, the thermogravimetric analysis (TGA) test of bovine fat was performed using a Mettler Toledo TGA/DSC star system (Mettler, Switzerland). The TGA test was conducted at a heating rate of 20 ˚C min-1 from 30 to 900 ˚C and a flow rate of purge gas (e.g., N2) was set as 40 mL min-1.

Conventional (catalytic) Transesterification of Bovine Fat. Prior to conventional transesterification, each reagent is prepared: 7.5 mL of extracted lipid from bovine fat and 1.79 mL of MeOH (molar ratio of oil to MeOH = 1 : 6), 0.082 g of NaOH (weight ratio of oil to NaOH = 1 : 0.011). Premixed MeOH with NaOH in ambient temperature for 5 min is reacted with extracted lipid in 20 mL vial. The 9.29 mL of the mixture was placed in a flask connected to the reflux condenser with water circulation and was heated at 60 ± 2 ˚C for 2 h with stirring at 500 rpm. Also, to confirm conventional transesterification of bovine fat, 3.2 g of bovine fat, 6.2 g of MeOH and 0.032 g of NaOH were reacted by same experimental method.

Thermal Assisted in-situ Transesterification of Bovine Fat. Bulkhead union (2507-400-61, Swagelok, USA) was used as batch reactor. One side of the bulkhead was sealed with a Swagelok stopper (SS-400-P, 5 ACS Paragon Plus Environment


1 2 117 3 4 5 118 6 7 119 8 9 120 10 11 12121 13 14122 15 16123 17 18 19124 20 21125 22 23 126 24 25 26127 27 28128 29 30 31129 32 33130 34 35131 36 37 38132 39 40133 41 42 134 43 44 45135 46 47136 48 49 137 50 51 52138 53 54139 55 56 57140 58 59 60

Page 6 of 17

Swagelok, USA). A half of the sealed bulkhead was filled with silica. After that, 1) 20 µL of extracted bovine fat oil and 180 µL of DMC were loaded in the bulkhead; 2) About 10mg of bovine fat and 180 µL of DMC was loaded in the bulkhead. Next, remaining half of the bulkhead was filled with silica and sealed with Swagelok stopper. The sealed bulkhead was placed in a muffle furnace and was heated to a desired temperature. The reacted bulkhead was quenched with water (4 ˚C). Each experiment was conducted in triplicates.

Chemical Analysis. A sample was diluted 15 times by dichloromethane. A GC-FID (Varian 450) equipped with DB-Wax column (Agilent J&W GC column, 30 m × 0.25 mm × 0.25 µm) was utilized to quantify FAMEs. GC calibration was conducted with a FAME standard mixture (CRM47885, SigmaAldrich). Nitrogen (UHP) was used as a carrier gas with a column flow rate of 29 mL min-1. Hydrogen (UHP) and air (zero grades) flow rates were 30 and 300 mL min-1, respectively. All detailed information on GC-FID operation parameters and calibration of FAMEs is summarized in Tables S1 and S2.

RESULTS AND DISCUSSION Characterization of Thermal Degradation of Bovine Fat. In order to characterize the thermal degradation of bovine fat, a series of TGA tests was conducted at a heating rate of 20 ˚C min-1 from 30 to 900 ˚C and mass decay of bovine fat varied on temperature changes was illustrated in Figure 1 (a). As evidence in Figure 1 (a), there are two distinctive thermal degradation zones, which can be easily identified by the thermal degradation rate of bovine fat (i.e., DTG curve). The first thermal degradation occurring from 100 to 120 ˚C is likely attributed to moisture and non-lipid components in bovine fat, which mass portion reaches up to 12.51 wt.% of the total mass of bovine fat. The second thermal degradation initiated at 380 ˚C is likely attributed to the thermolysis (i.e., bond dissociation of fatty acid from triglyceride backbone) of lipid in bovine fat, which is well consistent with the previous study done 6 ACS Paragon Plus Environment

Page 7 of 17

1 2 141 3 4 5 142 6 7 143 8 9 144 10 11 12145 13 14146 15 16147 17 18 19148 20 21149 22 23 150 24 25 26151 27 28152 29 30 31153 32 33154 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57155 58 59 60


by the authors. In order to justify the second thermal degradation attributed to the thermolysis of lipid in bovine fat, the thermal degradation of refined sesame oil and bovine fat was compared in Figure 1 (b). As illustrated in Figure 1 (b), the thermolysis of sesame oil occurs from 380 to 510 ˚C. One interesting observation is the onset and end temperature of the thermolysis of sesame oil are very similar to the second thermal degradation zone in bovine fat. This observation implies that the thermal degradation behaviors of lipid in bovine fat are nearly identical to that of refine sesame oil. Furthermore, the influences from moisture, non-lipid component and pyrolytic products are nearly negligible. Thus, the lipid content of bovine fat through the TGA tests in Figure 1 can be estimated as 84.25 wt.%. The lipid content of bovine fat measured by solvent extraction described in Sec. of material and methods is nearly good agreement with the TGA tests in Figure 1 and their deviations are less than 0.3% (e.g., 85.25 ± 0.25 wt.%). FESEM images of bovine fat before and after lipid extraction were compared in Figure 2. As evidenced in Figure 2 (d), 0.87 wt.% of scaffold (i.e., protein) was remained after lipid extraction, which is well consistent with the previous discussions associated with non-lipid components in Figure 1 (a).



1 2 156 3 4 5 157 6 7 158 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25159 26 27 160 28 29 30161 31 32162 33 34 35 163 36 37 38164 39 40165 41 42 43166 44 45167 46 47168 48 49 50169 51 52170 53 54 171 55 56 57172 58 59 60

Page 8 of 17

Figure 1. (a) Mass decay and DTG curve of bovine fat in N2, (b) comparison of thermolysis of bovine fat and refined sesame oil in N2

Figure 2. (a) Image of bovine fat before lipid extraction, (b) FESEM image of bovine fat before lipid extraction, (c) Image of scaffold after lipid extraction and (d) FESEM image of scaffold after lipid extraction

Thermal Assisted in-situ Transesterification of Bovine Fat. In the previous section of 3.1, all experimental findings significantly provide two key factors in thermal assisted in-situ transesterification of bovine fat. First, thermal assisted in-situ transesterification should have high tolerance against impurities such as water since 12.5 wt.% of non-lipid components in bovine fat was identified. Second, the thermolysis of lipid in bovine fat via the simultaneous thermal cracking and direct bond dissociation of fatty acids (FAs) from the triglyceride backbone was observed at temperatures from 390 to 510 ˚C. This thermolysis pattern provides a key aspect for thermal assisted in-situ transesterification of bovine fat since the bond dissociation of FAs from the backbone of triglycerides is the first initiation step for transesterification. In this respect, providing energy from an external heating source possibly initiates 8 ACS Paragon Plus Environment

Page 9 of 17

1 2 173 3 4 5 174 6 7 175 8 9 176 10 11 12177 13 14178 15 16179 17 18 19180 20 21181 22 23 182 24 25 26183 27 28184 29 30 31185 32 33186 34 35187 36 37 38188 39 40189 41 42 190 43 44 45191 46 47192 48 49 193 50 51 52194 53 54195 55 56 57196 58 59 60


thermal assisted in-situ transesterification in the absence of catalyst. Furthermore, Figure 1 (b) experimentally suggests that the thermolysis of lipid with/without impurities follows the very similar thermal degradation patterns: the thermal degradation behavior of refined lipid (e.g., sesame oil) and lipid in bovine fat is quite identical. Therefore, it can be hypothesized that conversion of lipid into FAMEs through thermal assisted in-situ transesterification of bovine fat is possible at the temperature regime, where the thermal dissociation of FAs from the backbone of triglycerides. For instance, the thermolysis phenomenon identified in Figure 1 (a) significantly implies that the heterogeneous reaction (i.e., reaction between gaseous phase of DMC and liquid phase of triglycerides) occurs at temperatures higher than 90 ˚C since to the boiling point of DMC is 90 ˚C. The phase differences allow the relative mobility differences of reactants, which significantly increase the probability of collision between DMC and triglycerides. However, the short contact time between the gaseous phase of DMC and liquid phase of triglyceride is problematic in the heterogeneous reaction (i.e., thermodynamically favorable, but kinetically not favorable). Thus, finding a feasible way to increase the contact time between two different phase reactants is a key factor to initiate thermal assisted in-situ transesterification of bovine fat. Thus, our choice for increasing the contact time between two different phase reactants (i.e., DMC and triglyceride) is to use porous material since using a porous material like silica for thermal assisted in-situ transesterification of bovine fat provides numerous confined spaces, where the collision frequency of the two reactants will be significantly enhanced due to the mobility differences. These behaviors are very similar with the catalytic reaction since the gaseous phase of DMC and liquid phase of triglyceride acts like the stationary and mobile phase. Thus, thermal assisted in-situ transesterification was referred to as pseudo-catalytic transesterification. In order to validate the technical feasibility of pseudo-catalytic transesterification (i.e., thermal assisted in-situ transesterification), all FAMEs components obtained from conventional protocol must be identical to those from conventional transesterification (i.e., alkali-catalyzed transesterification of 9 ACS Paragon Plus Environment


1 2 197 3 4 5 198 6 7 199 8 9 200 10 11 12201 13 14202 15 16203 17 18 19204 20 21205 22 23 206 24 25 26207 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45208 46 47209 48 49210 50 51 211 52 53 54 55212 56 57 58 59 60

Page 10 of 17

extracted lipid from bovine fat). Thus, the representative chromatogram depicting each individual peak of FAMEs derived from various transesterification conditions were compared in Figure S1, which provides qualitative information on FAMEs. As evidenced in Figure S1, the profiles of FAME obtained from various transesterification conditions are nearly identical. For example, the major FAME peaks were quantified as myristic acid (4.40%), palmitic acid (29.68%), palmitoleic acid (4.58%), stearic acid (16.89%), oleic acid (39.83%), linoleic acid (1.49%) and other fatty acid (3.13%). Difference between pseudo-catalytic (i.e., thermal assisted in-situ transesterification) and conventional transesterification is within 3% deviation error range. This result suggests that pseudo-catalytic transesterification of bovine fat can be successfully achieved without lipid extraction and technically feasible.

3.3. Optimal reaction temperature for thermal assisted in-situ transesterification

Figure 3. (a) FAME recovery from pseudo-catalytic transesterification of bovine fat, (b) Amount of each FAME for pseudo-catalytic transesterification of bovine fat, (c) Ratio of FAME amount normalized on C16:0 amount


Page 11 of 17

1 2 213 3 4 5 214 6 7 215 8 9 216 10 11 12217 13 14218 15 16219 17 18 19220 20 21221 22 23 222 24 25 26223 27 28224 29 30 31225 32 33226 34 35227 36 37 38228 39 40229 41 42 230 43 44 45231 46 47232 48 49 233 50 51 52234 53 54235 55 56 57236 58 59 60


The section of 3.1 and 3.2 experimentally justifies that thermal assisted in-situ transesterification of bovine fat is possible in the presence of silica, thus, the optimal temperature conditions was sought. For example, to chase the optimal temperature for thermal assisted in-situ transesterification of bovine fat, the profiles of FAME recovery were established in Figure 3 (a). Considering the previous observations associated with 12.51 wt.% of non-lipid content in bovine fat, the FAME yield with/without correction was shown together in Figure 3 (a). Figure 3 (a) also indicates that the FAME yield increased from ~62 to 96.1 % as reaction temperature increased from 340 to 380 ˚C. Moreover, the FAME yield reaches the plateau at temperatures higher than 380 ˚C since the maximum achievable conversion is already reached. Therefore, 380 ˚C can be the optimal temperature for thermal assisted in-situ transesterification of bovine fat on silica. Figure 3 (a) significantly suggests that the yield of FAMEs derived from bovine fat is highly sensitive to temperature change. Considering a batch-type reactor, heat transfer from the external heating source to the reactor can explain the reaction time of 11 min. In this respect, the reaction time of in-situ transesterification is substantially shorter than 11 min. Also, as evidenced in Figure 3 (b), the composition of FAMEs is proportional to the reaction temperature. Figure 3 (c) shows the relative ratio of FAME to C16:0 is almost constant as a function of reaction temperature. This significantly suggests that the thermal cracking is avoided at our optimal temperatures at 380 ˚C, which is also very consistent the experimental finding in Figure 1. Under the optimal temperature, the FAME components derived from thermal assisted in-situ transesterification of bovine fat were quantified and summarized in Table 1. Table 1 shows that the amount of each FAME from thermal assisted in-situ transesterification of bovine fat on silica composed of methyl palmitate (C16:0), methyl stearate (C18:0), methyl oleate (C18:1) and methyl linoleate (C18:2) were main products from the transesterification reaction. Scheme 1 describes the conversion of triglyceride in bovine fat with DMC into corresponding FAMEs (i.e., methyl palmitate, methyl stearate and methyl oleate).



1 2 237 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27238 28 29239 30 31 32 33 34 35 36 37 38 39 40 41240 42 43241 44 45242 46 47 48243 49 50244 51 52245 53 54 55246 56 57247 58 59 60

Page 12 of 17

Table 1. Amount of each FAME based on bovine fat converted with DMC Chemical name Fatty acid formula Amount (mg mgbovine fat-1) Methyl Myristate C14:0 0.0402 Myristoleic Acid Methyl Ester C14:1 0.0092 Methyl Pentadecanoate C15:0 0.0025 Methyl pamitate C16:0 0.2607 Methyl Palmitoleate C16:1 0.0421 Methyl Heptadecanoate C17:0 0.0068 Cis-10-Heptadecanoic Acid Methyl Ester C17:1 0.0036 Methyl Stearate C18:0 0.1499 Methyl oleate C18:1 0.3480 Methyl Linoleate C18:2 0.0140 Methyl Linolenate C18:3 0.0010 Methyl Arachidate C20:0 0.0007 Methyl cis-11-Eicosanoate C20:1 0.0012 Cis-11,14-Eicosadienoic Acid Methyl Ester C20:2 0.0003 C20:3 0.0004 Cis-8,11,14-Eicosatrienoic acid Methyl Ester Methyl Behenate C22:0 0.0000 Methyl Erucate C22:1 0.0001 Cis-13,16-Docosadienoic Acid Methyl Ester C22:2 0.0002

Scheme 1. Conversion of lipid in bovine fat into FAMEs

Figure 4 compares the final FAME recovery from four different transesterification reactions. Conventional transesterification of extracted lipid from bovine fat on NaOH produced 81.7% of FAMEs (Figure 4 (a)). However, conventional transesterification of bovine fat on NaOH produced only 4.5% of FAMEs (Figure 4 (b)). This is due to conventional transesterification needing more time to extract lipid from bovine fat during transesterification. Thermal assisted transesterification of extracted lipid from 12 ACS Paragon Plus Environment

Page 13 of 17

1 2 248 3 4 5 249 6 7 250 8 9 251 10 11 12252 13 14253 15 16254 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46255 47 48256 49 50 257 51 52 53258 54 55259 56 57 58260 59 60


bovine fat with DMC produced more FAMEs (97%) than conventional transesterification of bovine oil with DMC (81.7%) (Figure 4 (a) and (c)) in spite of mush shorter reaction time of thermal assisted transesterification (~10 min) than conventional transesterification (2 h). This indicates that thermal assisted transesterification is more effective than conventional transesterification. Lastly, the FAME recovery from thermal assisted in-situ transesterification of bovine fat without oil extraction (96.1%) is almost same as the FAME recovery from pseudo-catalytic transesterification of bovine oil (97%) (Figure 4 (c) and (d)).

Figure 4. Comparison of FAME recovery from (a) conventional transesterification of extracted bovine oil with NaOH, (b) conventional transesterification of bovine fat with NaOH, (c) pseudo-catalytic transesterification of extracted bovine oil on SiO2 and (d) pseudo-catalytic transesterification of bovine fat on SiO2



1 2 261 3 4 5 262 6 7 263 8 9 264 10 11 12265 13 14266 15 16267 17 18 19268 20 21269 22 23 270 24 25 26271 27 28272 29 30 31273 32 33274 34 35275 36 37 38276 39 40277 41 42 278 43 44 45279 46 47280 48 49 281 50 51 52282 53 54283 55 56 57284 58 59 60

Page 14 of 17

This study systematically investigated thermal assisted in-situ transesterification of bovine fat for biodiesel production. The technical feasibility of thermal assisted in-situ transesterification was experimentally justified since all FAME components generated from thermal assisted in-situ transesterification of bovine fat was exactly the same as those from the conventional transesterification condition of extracted lipid from bovine fat. In particular, DMC was used as an acyl acceptor in this study. A range of reaction temperature (340~390 °C) was also tested for in-situ transesterification of bovine fat; 380 °C was found to be an optimal temperature where maximum conversion was achieved. In addition, this study experimentally optimized the operation parameters of thermal assisted in-situ transesterification of bovine fat and the maximum achievable FAME yield from bovine fat reached up to 96.1 % at 380 ˚C. The process shown in this work has a great potential for applications to other scientific fields such as lipid analysis of biology and biodiesel production from other feedstocks such as biomass and microalgae.

ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. GC operation conditions, FAME calibration information, and GC chromatograms of FAMEs

ACKNOWLEDGEMENTS This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MSIP) (No. 2014RA1A004893). The second author (J. Lee) was supported by a National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MSIP) (No. NRF-2015H1D3A1066513).

REFERENCES 14 ACS Paragon Plus Environment

Page 15 of 17

1 2 285 3 4 286 5 287 6 7 8 288 9 289 10 11290 12291 13 14292 15 16293 17294 18295 19 20296 21 297 22 23 24298 25299 26 27300 28301 29 30 302 31 32303 33304 34305 35 36306 37 307 38 39 40308 41 42309 43310 44311 45 46 312 47 313 48 49 50314 51315 52 53316 54 317 55 56 57318 58319 59 60

1.


IEA 2015 Key World Energy Statistics; International Energy Agency: 2015.

2. Jacobson, M. Z., Control of fossil-fuel particulate black carbon and organic matter, possibly the most effective method of slowing global warming. J. Geophys. Res. 2002, 107 (D19). 3. Fukuda, H.; Kondo, A.; Noda, H., Biodiesel fuel production by transesterification of oils. J. Biosci. Bioeng. 2001, 92 (5), 405-416. 4. Atabani, A. E.; Silitonga, A. S.; Badruddin, I. A.; Mahlia, T. M. I.; Masjuki, H. H.; Mekhilef, S., A comprehensive review on biodiesel as an alternative energy resource and its characteristics. Renew. Sust. Energ. Rev. 2012, 16 (4), 2070-2093. 5. Tsai, J.-H.; Chen, S.-J.; Huang, K.-L.; Lin, Y.-C.; Lee, W.-J.; Lin, C.-C.; Lin, W.-Y., PM, carbon, and PAH emissions from a diesel generator fuelled with soy-biodiesel blends. J. Hazard. Mater. 2010, 179 (1), 237-243. 6. Vicente, G.; Martınez, M.; Aracil, J., Integrated biodiesel production: a comparison of different homogeneous catalysts systems. Bioresour. Technol. 2004, 92 (3), 297-305. 7. Dorado, M.; Ballesteros, E.; Arnal, J.; Gomez, J.; Lopez, F., Exhaust emissions from a Diesel engine fueled with transesterified waste olive oil. Fuel 2003, 82 (11), 1311-1315. 8. Mata, T. M.; Martins, A. A.; Caetano, N. S., Microalgae for biodiesel production and other applications: a review. Renew. Sust. Energ. Rev. 2010, 14 (1), 217-232. 9. Atabani, A. E.; Silitonga, A. S.; Ong, H. C.; Mahlia, T. M. I.; Masjuki, H. H.; Badruddin, I. A.; Fayaz, H., Non-edible vegetable oils: a critical evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production. Renew. Sust. Energ. Rev. 2013, 18, 211-245. 10. Gui, M. M.; Lee, K.; Bhatia, S., Feasibility of edible oil vs. non-edible oil vs. waste edible oil as biodiesel feedstock. Energy 2008, 33 (11), 1646-1653. 11.

Zubr, J., Oil-seed crop: Camelina sativa. Ind. Crop. Prod. 1997, 6 (2), 113-119.

12. Pinzi, S.; Garcia, I.; Lopez-Gimenez, F.; Luque de Castro, M.; Dorado, G.; Dorado, M., The ideal vegetable oil-based biodiesel composition: a review of social, economical and technical implications. Energy Fuels 2009, 23 (5), 2325-2341. 13. Durrett, T. P.; Benning, C.; Ohlrogge, J., Plant triacylglycerols as feedstocks for the production of biofuels. Plant J. 2008, 54 (4), 593-607. 14. Jung, J.-M.; Lee, J.; Kim, J.; Kim, K.-H.; Kwon, E. E., Pyrogenic transformation of oil-bearing biomass into biodiesel without lipid extraction. Energy Conv. Manag. 2016, 123, 317-323. 15. Saka, S.; Kusdiana, D., Biodiesel fuel from rapeseed oil as prepared in supercritical methanol. Fuel 2001, 80 (2), 225-231. 16. Abbaszaadeh, A.; Ghobadian, B.; Omidkhah, M. R.; Najafi, G., Current biodiesel production technologies: a comparative review. Energy Conv. Manag. 2012, 63, 138-148. 15 ACS Paragon Plus Environment


1 2 320 3 321 4 5 6 322 7 323 8 9 324 10325 11 12326 13 14327 15 16328 17329 18 19330 20331 21 22 23332 24333 25 26334 27335 28 29336 30 337 31 32 33338 34339 35 36340 37341 38 39 342 40 41343 42 43344 44345 45 46346 47 347 48 49 50348 51349 52 53350 54351 55 352 56 57353 58 59 60

Page 16 of 17

17. Yusuf, N.; Kamarudin, S. K.; Yaakub, Z., Overview on the current trends in biodiesel production. Energy Conv. Manag. 2011, 52 (7), 2741-2751. 18. Carrapiso, A. I.; García, C., Development in lipid analysis: some new extraction techniques and in situ transesterification. Lipids 2000, 35 (11), 1167-1177. 19. Halim, R.; Gladman, B.; Danquah, M. K.; Webley, P. A., Oil extraction from microalgae for biodiesel production. Bioresour. Technol. 2011, 102 (1), 178-185. 20. Halim, R.; Danquah, M. K.; Webley, P. A., Extraction of oil from microalgae for biodiesel production: A review. Biotechnol. Adv. 2012, 30 (3), 709-732. 21. Meher, L.; Sagar, D. V.; Naik, S., Technical aspects of biodiesel production by transesterification—a review. Renew. Sust. Energ. Rev. 2006, 10 (3), 248-268. 22. Lopez, D. E.; Goodwin, J. G.; Bruce, D. A.; Lotero, E., Transesterification of triacetin with methanol on solid acid and base catalysts. Appl. Catal. A-Gen. 2005, 295 (2), 97-105. 23. Leung, D. Y. C.; Wu, X.; Leung, M. K. H., A review on biodiesel production using catalyzed transesterification. Appl. Energy 2010, 87 (4), 1083-1095. 24. Atadashi, I.; Aroua, M.; Aziz, A. A., Biodiesel separation and purification: a review. Renew. Energy 2011, 36 (2), 437-443. 25. Jung, J.-M.; Cho, J.; Kim, K.-H.; Kwon, E. E., Pseudo catalytic transformation of volatile fatty acids into fatty acid methyl esters. Bioresour. Technol. 2016, 203, 26-31. 26. Demirbas, A., Biodiesel from waste cooking oil via base-catalytic and supercritical methanol transesterification. Energy Conv. Manag. 2009, 50 (4), 923-927. 27. Deshpande, A.; Anitescu, G.; Rice, P.; Tavlarides, L., Supercritical biodiesel production and power cogeneration: technical and economic feasibilities. Bioresour. Technol. 2010, 101 (6), 1834-1843. 28. Marchetti, J.; Errazu, A., Technoeconomic study of supercritical biodiesel production plant. Energy Conv. Manag. 2008, 49 (8), 2160-2164. 29. Ilham, Z.; Saka, S., Dimethyl carbonate as potential reactant in non-catalytic biodiesel production by supercritical method. Bioresour. Technol. 2009, 100 (5), 1793-1796. 30. Fuming, M.; Zhi, P.; Guangxing, L., The transesterification of dimethyl carbonate with phenol over Mg-Al-hydrotalcite catalyst. Org. Process Res. Dev. 2004, 8 (3), 372-375. 31. Rokicki, G.; Rakoczy, P.; Parzuchowski, P.; Sobiecki, M., Hyperbranched aliphatic polyethers obtained from environmentally benign monomer: glycerol carbonate. Green Chem. 2005, 7 (7), 529-539. 32. Seong, P.-J.; Jeon, B. W.; Lee, M.; Cho, D. H.; Kim, D.-K.; Jung, K. S.; Kim, S. W.; Han, S. O.; Kim, Y. H.; Park, C., Enzymatic coproduction of biodiesel and glycerol carbonate from soybean oil and dimethyl carbonate. Enzyme Microb. Technol. 2011, 48 (6), 505-509.


Page 17 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


This study introduces the biodiesel conversion methodology via thermal assisted in-situ transesterification of bovine fat using dimethyl carbonate as an acyl acceptor. 348x188mm (72 x 72 DPI)

ACS Paragon Plus Environment

Biodiesel Conversion via Thermal Assisted in-Situ Transesterification

Recommend Documents