Winterization studies of different vegetable oil biodiesel

Accepted Manuscript Winterization studies of different vegetable oil biodiesel

Sandhya K. Vijayan, Mary NaveenaVictor, Abinandan Sudharsanam, Velappan Kandukalpatti Chinnaraj, Nagarajan Vedaraman PII: DOI: Reference:

S2589-014X(18)30012-4 doi:10.1016/j.biteb.2018.02.005 BITEB 13

To appear in: Received date: Revised date: Accepted date:

6 January 2018 21 February 2018 22 February 2018

Please cite this article as: Sandhya K. Vijayan, Mary NaveenaVictor, Abinandan Sudharsanam, Velappan Kandukalpatti Chinnaraj, Nagarajan Vedaraman , Winterization studies of different vegetable oil biodiesel. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Biteb(2017), doi:10.1016/j.biteb.2018.02.005

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ACCEPTED MANUSCRIPT Winterization studies of different vegetable oil biodiesel Sandhya K.Vijayan, Mary NaveenaVictor, Abinandan Sudharsanam, Velappan Kandukalpatti Chinnaraj, Nagarajan Vedaraman* Chemical Engineering Division, Central Leather Research Institute, Adyar, Chennai-600

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020, India. Corresponding author: [email protected] Tel: 00 91 9444907898

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Orcid Id: https://orcid.org/0000-0002-8981-4865

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ACCEPTED MANUSCRIPT ABSTRACT

At low temperature, the presence of oleaginous compound with fatty acids bound to crystallize and cause operability problems with compression engines. In this present investigation, seven different fatty acid methyl esters (FAMEs) biodiesel from vegetable oils

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(such as sunflower, coconut, jatropha, rice bran, palm, neem and mahua) were prepared by transesterification and were analyzed by gas chromatography (GC). Winterization of these

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synthesized biodiesel were carried out to find their usability at low temperatures (0ºC—20ºC)

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and the crystals formed were separated. Further, the differential scanning colorimetry (DSC) were employed to identify the onset of melting point of the biodiesel from vegetable oils. The

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results showed that crystal formation was observed for various biodiesel except sunflower oil

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that recorded no crystal formation with minimum temperature of 0ºC. These findings suggest that biodiesel synthesized from sunflower can be used as such at low temperatures compared

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to the other synthesized biodiesel from vegetable oil.

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Keywords: Biodiesel, Temperature effects, Differential Scanning Calorimetry, FAME,

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1. Introduction

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Winterization.

Overwhelming response towards clean energy utilization has provoked the interest towards the use of biodiesel among the world. Biodiesel (derived from plant or animal bio resources) is alternative fuel that can be blended with conventional fuels to use in compression ignition engines (McCormick et al., 2006). Furthermore, biodiesel is highly advantageous compare to conventional diesel that includes: high cetane characteristics, condensed emanation of NOx, SOx, carbon monoxide, hydrocarbons and particulate matter, respectively (Kulkarni & Dalai, 2

ACCEPTED MANUSCRIPT 2006). Additionally, emissions of biodiesel contain less pollutants, such as poly-aromatic hydrocarbons compare to conventional fuel (Graboski et al., 2003; Karavalakis et al., 2009). The preparation of biodiesel is usually carried out by transesterification with alcohol as a catalyst and the reaction is shown in Figure 1. Meanwhile, the blending of biodiesel (B5-B20 (v/v)) with conventional fuels is the most commonly in practice and are highly recommended

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for good engine performance and better exhaust emissions (Moser & Vaughn, 2010).

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However, it is observed that use of biodiesel (B100) despite of blending, resulted in

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substantial reduction of carbon monoxide and hydrocarbon emissions (Vedaraman et al., 2011). Despite these advantageous mentioned above, the major setback of biodiesel is the

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cold flow properties that hinders the practical application (Bhale et al., 2009; Lee et al., 1996; Soriano et al., 2006). The occurrence of saturated fatty acid in biodiesel is crucial for

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temperature explicit parameters. So, at low temperature the fatty acids tends to form cloud (cloud point -CP), semi solid fractions (pour point-PP) and forms crystals (cold filter

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plugging point -CFPP) thereby clogging and blocking the flow of biodiesel to engines

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(Rasimoglu & Temur, 2014). Hence, several methods such as winterization, anti-gel additives and blending have been used to prevent the formation of crystals (Kreulen, 1976; Nainwal et

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al., 2015; Ooi et al., 2005). Among the methods, winterization is the economical and simple, which is carried by keeping the biodiesel under refrigeration for specific temperature and

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decanting the liquid after crystal formation (Smith et al., 2010). Further, the crystallization process reduces the overall onset temperature which tends to use the biodiesel at lower temperature without clogging (Gómez et al., 2002). The use of branched chain alcohol to produce biodiesel has reduced the crystallization onset temperature (Tco) (Lee et al., 1995). Various researchers have reported to reduce the saturated fatty acids in biodiesel using blending and addition of agents. For instance, the saturated fatty acids have been eliminated using three stages of winterization and achieved reduction in CFPP to −8 °C and exhibited 9 3

ACCEPTED MANUSCRIPT % loss of peanut biodiesel (Karavalakis et al., 2009; Pérez et al., 2010). However, the saturated fatty acid content in biodiesel obtained from beef tallow post winterization was 73.38% compared to the initial value of 86.91% yielded at temp 16.3°C (Doğan & Temur, 2013). Similarly, winterization based on micro heat exchangers of biodiesel from waste cooking oil (BWCO) exhibited reduction of CFPP up to -7°C and saturated fatty acids from

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21.3% to 9.6% (Kerschbaum et al., 2008). Meanwhile, the use of additives in winterization of

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BWCO resulted in CFPP reduction from −10 °C to −16 °C (Cheong et al., 1998; Wang et al.,

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2014). The process of winterization with additives has significantly enhanced the biodiesel properties (Chastek, 2011; Joshi et al., 2011; Wang et al., 2014; Wang et al., 2011).

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However, in the use of additive (ethylene vinyl acetate copolymer) with blending (20%) of BWCO the CP, CFPP and PP reduced by -12°C, -16°C and -18°C with respect to the pre

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winterization (Cao et al., 2014). Despite these significance, the additives may also possess the ability to induce more toxicity to the emission from the biodiesel. It is very imperative, the

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biodiesel produced by winterization without additive is more efficient economically and

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environmentally. Furthermore, not much extensive studies have been recorded to identify the crystallization under various temperature of winterization of biodiesel from vegetable oil.

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Hence, this study investigated the temperature effect on crystallization of transesterification biodiesel of seven different vegetable oils (sunflower, coconut, jatropha, rice bran, palm,

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neem, and mahua) respectively. Further, the loss of biodiesel during winterization was identified and reported along with solid fraction of saturated fatty acids. The properties of biodiesel viz., density (ρ), viscosity (υ), PP, CP, flash point (FLP) and fire point (FRP) were evaluated as per the standard procedures. Furthermore, the fatty acid composition of different biodiesel and crystallization onset temperature (TCO) was analyzed by gas chromatography (GC) and differential scanning colorimetry (DSC).

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ACCEPTED MANUSCRIPT 2.Experimental

2.1.Materials

Commercial refined vegetable oil from coconut, sunflower, rice bran, palm and unrefined oil derived from jatropha, neem and mahua purchased from local market (Chennai, Tamilnadu,

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India). All the chemicals used in experiment were of analytical grade (S.D fine Chemicals,

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India).

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2.2.Transesterification process

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Biodiesel usually referred as (FAMEs) from refined vegetable oils were prepared by transesterifying with NaOH 0.5% (w/w) with respect to oil dissolved in CH3OH

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(oil/methanol ratio of 1:9 on a molar basis) at 67°C to 70 °C for a period of 2 hours. Unrefined oils, were transesterified with acid catalysis using 0.5 % Conc. H2SO4 by weight

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with respect to oil and 30 % by weight of methanol along with un-refined oils at a

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temperature of 65-72°C for a period of 16 hours (Canoira et al., 2006; Van Gerpen, 2005). After transesterification, the upper methyl ester layer was separated and washed with water to

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eliminate the residuals from biodiesel (Demirbas, 2007). The transesterification process took place in round bottom flasks (two necked) Liebig condenser in a heating mantle with

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magnetic stirrer. Then the biodiesel was dried in oven at 105 °C (378 K) for 3 h to remove traces of moisture. The product yield (Eqn 1) was calculated on a mass basis and are expressed below

𝑃𝑟𝑜𝑑𝑢𝑐𝑡 𝑦𝑖𝑒𝑙𝑑 (%) =

𝑊𝑡 𝑜𝑓 𝑏𝑖𝑜𝑑𝑖𝑒𝑠𝑒𝑙 𝑊𝑡 𝑜𝑓 𝑜𝑖𝑙

𝑋 100

(1)

2.3. Winterization

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ACCEPTED MANUSCRIPT Winterization experiment was carried out on all the different biodiesel at samples at 20±1°C, 15±1°C, 10 ±1°C, 5±1°C, and 0±1°C, correspondingly for a minimum period of 12 hours slightly modified from literature (Lee et al., 1996). It was done using a low temperature chamber (ROSS FLEXER TER62 STM141F). Different biodiesel samples were weighed and poured into flasks and kept inside the chilling unit (Sub Zero Cooling Instruments, Chennai,

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India). Subsequently, the samples were transferred to the erlenmeyer flask using a dried filter

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paper and funnel. The filter paper and the crystals separated out with it were weighed for all

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biodiesel samples and the liquid separated out was also weighed (Eqn 2 & Eqn 3). This procedure was repeated thrice and average value is taken for all the temperatures for each of

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the seven biodiesel.

𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑖𝑙𝑑 𝑎𝑓𝑡𝑒𝑟 𝑤𝑖𝑛𝑡𝑒𝑟𝑖𝑧𝑎𝑡𝑖𝑜𝑛

𝑋 100

(2)

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𝑇𝑜𝑡𝑎𝑙 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑖𝑛 𝑤𝑖𝑛𝑡𝑒𝑟𝑖𝑧𝑎𝑡𝑖𝑜𝑛

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𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑖𝑑 𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛 (𝐶𝑟𝑦𝑠𝑡𝑎𝑙 𝑤𝑡. (%)) =

𝐿𝑖𝑞𝑢𝑖𝑑 𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛 (𝐵𝑖𝑜𝑑𝑖𝑒𝑠𝑒𝑙 𝑤𝑡. (%)) = 100 − 𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑖𝑙𝑑 𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛

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3.1.GC Analysis

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3.Analytical methods

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Biodiesel (FAME) produced from vegetable oils were analyzed using gas chromatography (GC) AGILENT 6850 Series GC System. HP-1, with capillary column (DB-23 fused silica Column - 202 × 200 × 105 mm (HWD)), Detector – Flame Ionization Detector, Split 1:50 and N2 Flow – 1 ml/min. Temperature programming in oven was maintained primarily at 160°C for 2 minutes at 6°C/min, 180°C for 2 minutes at 6°C/minutes and finally increased to 230°C for 10 minutes at 4°C/minute with injector and detector temperature maintained at 230 6

ACCEPTED MANUSCRIPT °C and 270°C. The standard was used Supelco 37 FAME mix (Sigma Aldrich) along with samples.

3.2. Fuel property analysis

After each transesterification experiments, the biodiesel was analyzed for various fuel

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characteristics such as density, kinematic viscosity, FLP, FRP, PP, CP (ASTM- D4052, D

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445, D 93, D 92, D97, D2500) was measured for all biodiesel as per the standard methods of

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biodiesel.

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3.3. DSC Thermograms

The thermograms of the resulted biodiesel was analyzed using differential scanning

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calorimetry (DSC Q200 V24. 10 Build 122) (Pérez et al., 2010). Briefly, the samples were first heated to 100°C for 2 mins and then brought to 60°C and cooled at 1°C/min, 5°C /min

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and 10°C /min. After comparing the various heating rates, 5°C/min was selected for this

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study experiment. TCO (maximum temperature for crystallization Onset) was located from the transition in the graph plotting Temperature (°C) and Heat Flow (mW) gives the exact

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temperature at which the biodiesel sample starts to have a transition from liquid to solid.

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4. Results & discussion

The physicochemical characteristics of vegetable oil and biodiesel synthesized are shown in Table 1 and Table 2. Undoubtfully, transesterification process resulted in maximum yield of biodiesel from various vegetable oils, especially for jatropha and coconut oil resulting in 96.5% yield compared to other sources of biodiesel. The fact that the byproduct of glycerol accumulation in from transesterification process might have resulted in not obtaining 100% yield. Moreover, high viscosity diesel enables larger droplets upon injection that results in 7

ACCEPTED MANUSCRIPT poor combustion and increased emissions (Knothe & Dunn, 2009). It can be noted from Table 1, oil from mahua, neem, rice bran and jatropha exhibited higher densities varied from 920-925 Kgm-3 compared to other vegetable oils. However, the density was found to lower in the synthesized biodiesel which is due to the transesterification process and is consistent with literature report (Esteban et al., 2012). Similarly, the viscosity was higher in neem, jatropha

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and mahua resulted in 45.8 mm2s-1, 44.3 mm2s-1 and 41.6 mm2s-1. However, the density and

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viscosity values were decreased upon transesterification process and are shown in Table 2. It

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can be observed that the viscosity of the vegetable oil is approximately 10-20 fold lesser than that of the synthesized biodiesel and is well in agreement with the reported literature (Nabi et

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al., 2009).The density and the viscosity of the biodiesel obtained from jatropha oil is very high with 888 kg m-3 and 5.6 mm-2s-1 compared to another biodiesel. Furthermore, the density

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and the viscosity of the values are within the limits prescribed EN14214:2003 and IS15607:2005 well accepted biodiesel standards. Flash point is lowermost temperature at

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which the biodiesel will ignite with absence of vapor at a rate to sustain the fire. The fire

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point of biodiesel may be defined as the temperature at which aids in burning for at least 5 seconds’ post ignition by an open flame. For all biodiesel, the flash point was within the

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range of 152 °C – 182°C and fire point between the range of 175 °C – 195 °C which is higher when compared to the EN1414:2003 and IS15607:2005 standard. This indicates that all

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biodiesel has a higher flash point and fire point they are safe for handling and transportation (Gumus, 2010). Similarly, the composition of FAMEs from vegetable oil is shown in Table 3. It can be noted that presence of unsaturated outlays the saturated fatty acid in all the biodiesel obtained. The maximum percentage (%) of the total unsaturated fatty acid (C 18:1 and C18:2) was found higher in sunflower oil, jatropha oil and neem oil in the range of 88.20%, 77.58% and 73.92 respectively. Similarly, the maximum percentage (%) of total saturated fatty acid was found higher in coconut oil, palm oil and mahua oil and were in the range of 58.87%, 8

ACCEPTED MANUSCRIPT 40.68% and 38.65% respectively. This results follow the same trend of the saturated fatty acid composition in literature reported (Liu, 2015). Furthermore, the melting temperature of each saturated and unsaturated compound has a direct impact on the overall melting temperature of the oil and biodiesel called as a eutectic mixture (Lee et al., 1995). From the Table 4, it can be perceived that, sunflower oil, jatropha oil and mahua oil exhibited onset

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crystallization temperature of -3.81°C, 1.20°C and 1.42°C respectively. This is due to higher

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existence of unsaturated fatty acid point can have the dominating impact on the overall

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melting temperature (Knothe & Dunn, 2009).

The effect of various temperatures on liquid fraction yield of winterized biodiesel from

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vegetable oil is shown in Table 5. During the winterization process, most of the high melting

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(FAMEs) separates out leading to formation of turbidity or precipitation. As pure biodiesel is preferred over biodiesel-diesel blends, to have better exhaust emissions, and to avoid addition

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of the second substance such as fuel additives, the use of pure biodiesel after winterization is

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the safer and easier option. Based on this study, it can be concluded that by winterizing sunflower biodiesel up to 0°C as no solid fraction is obtained and can be used directly without any winterization up to 0°C. Similarly, coconut biodiesel resulted in 3.34 % of solid upon

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winterization up to 5°C and hence can be used > 5°C. Similarly, jatropha and rice bran

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biodiesel can be winterized at 10°C with solid fraction removal of 3.5 %. Palm and Mahua biodiesel can be used only at temperatures above 15°C and the solid fraction removal was about 0-6.24 %. Furthermore, neem biodiesel can be used only above 20°C. Based on our initial screening process, we observed 5°C /min exhibited TG profile of the samples were better. Yet, this profile varies with respect to samples as castor oil exhibited 10°C /min compared to higher heating rates (Conceição et al., 2007). Tan & Man (2002) showed that low heating rate (5°C /min) favors for thermal equilibrium of vegetable oils when compared to other heating rates indicating our observation is very consistent. Further, the DSC cooling 9

ACCEPTED MANUSCRIPT thermograms were obtained at the proportion of 5°C /min and are shown in Figure 2 for various biodiesel. The biodiesel from coconut oil and palm oil exhibited four melting points of 3.59°C, - 2.21°C, - 8.47°C, – 14.27°C and 13.48°C, 10.41°C, 7.22°C and –33.38°C respectively. Similarly, biodiesel from neem oil, rice bran oil and mahua oil resulted in three melting points of 8.89°C, 5.8°C and 3.06°C; 1.20°C, - 4.15°C and – 14.27°C, 7.78°C, 5.01°C

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and 3.55°C respectively. Furthermore, the biodiesel from sunflower biodiesel showed two

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melting temperatures at 1.42°C and – 6.99°C and the biodiesel from jatropha oil showed only

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one temperature of -3.81°C. The Rice bran oil showed two distinct peaks which may be due to the equal distribution of linoleic and oleic acid content are in consistent with the literature

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(Ajithkumar et al., 2009). Interestingly, these disparities in different melting point amongst vegetable oil are due to the presence of the mixed unsaturated and saturated fatty acids in the

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biodiesel (Dunn, 1999). Comparing the above results, we find the order of increasing crystallization temperature for different vegetable oil biodiesel were jatropha> sunflower>

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rice bran> coconut> mahua> neem > palm.

5.Conclusions

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Biodiesel was produced from seven different vegetable oils – sunflower, coconut, rice bran, palm, jatropha, mahua and neem oil by acid or alkali transesterification process. The yield by

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transesterification was 92 – 97 % and coconut oil yield higher quantity of biodiesel. Different fuel properties were measured for all the biodiesel and they meet biodiesel specifications. The GC analysis shows that all the oils vary significantly in their fatty acid compositions. Based on winterization studies, jatropha biodiesel exhibits no solid fraction is obtained up to 0oC and can be a promising biodiesel. Similarly, the coconut biodiesel resulted solid fraction upon winterization up to 5°C followed by jatropha and rice bran biodiesel at 10°C. The palm and mahua biodiesel can be used only at temperatures above 15°C. Since, neem biodiesel 10

ACCEPTED MANUSCRIPT possesses poor cold flow properties and it can be used only above 20°C because solid fraction formation at 15°C is nearly 38.5 %.

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Acknowledgement

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We thank Dr. Gildhyal, ONGC, Chennai for helping us in fuel properties analysis.

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Figure Captions

Figure 1. Transesterification reaction 15

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AC

CE

PT E

D

MA

NU

SC

RI

PT

Figure 2. DSC Cooling thermograms for various biodiesel

16

ACCEPTED MANUSCRIPT Table 1. Vegetable oil - Physical Properties Oil

Sunflower

Coconut

Palm

Rice

Jatropha

Mahua

Neem

920

925

922

41.6

45.8

Bran Density

918

919

910

921

28.3

30.6

32.7

33.2

Viscosity

PT

(Kg/m3) 44.3

RI

At 40oC

AC

CE

PT E

D

MA

NU

SC

(mm2s-1)

17

ACCEPTED MANUSCRIPT Table 2. Physicochemical Comparison of Biodiesel yield from different vegetable oil and their fuel properties with standards Biodiesel

Yield %

Density

Viscosity

Flash

Fire

Cloud

Pour

(Kgm-3)

at 40oC

Point (oC)

Point (oC)

Point

Point

(oC)

(oC)

94.2 %

866

2.6

169

193

-2

-6

Coconut

96.5 %

868

3.3

152

188

+4

-1

Palm

95.4%

846

3.5

192

+10

+8

Rice Bran

92.1 %

856

4.7

176

183

+4

0

Jatropha

96.5 %

888

5.6

170

176

+3

-6

Mahua

92.7 %

881

5.3

174

185

+ 12

4

Neem

93.3 %

880

5.5

180

195

+12

+8

EN14214:2003

N.A

860-900

3.5-5

>120

-

-

-

IS15607:2005

N.A

860-900

2.5-6.0

120

-

-

-

Diesel

N.A

1.9-3.8

70

74

-

-

SC

182

NU

D

PT E

RI

Sunflower

MA

PT

(mm2s-1)

AC

CE

840-860

18

ACCEPTED MANUSCRIPT Table 3. Composition of vegetable oil fatty acid methyl ester and their corresponding melting point Biodiesel

C8:0

C10:0

C12:0

C14:0

C16:0

C18:0

C18:1

C18:2

C18:3

C20:0

Methyl

Methyl

Methyl

Methyl

Methyl

Methyl

Methyl

Methyl

Methyl

of FAME

Caprylate

Caproate

Laurate

Myristate

Palmitate

Stearate

Oleate

Linoleate

Linolenate

Arachidic

Melting

- 34

- 18

5

18.5

30.55

39.1

- 20

- 35

-52

C24:0

Total

Total

Sat.FA

Unsat.FA

(%)

(%)

Methyl

Methyl

behenate

Lingnocerate

46.6

54

58

-

-

0.803

0.298

11.511

88.22

-

-

58.875

42.722

A

of FAME (oC)

Methyl

C S

U N

T P

I R

Name

Point

C22:0

D E

[28,

29] Sunflower

-

-

-

0.071

Coconut

0.424

1.301

22.018

15.179

Palm

0.067

-

0.288

Rice Bran

-

-

-

Jatropha

-

-

Mahua

-

-

T P

6.288

M

3.770

33.545

54.675

0.035

0.246

17.343

2.610

29.435

13.287

-

-

0.749

36.766

-

46.482

13.745

0.524

0.123

0.072

0.063

38.652

60.227

0.527

19.515

2.953

38.109

34.297

0.638

1.984

-

-

25.617

72.406

-

0.178

13.297

7.082

41.787

35.801

0.341

0.275

-

-

21.173

77.588

-

1.045

17.838

21.798

48.016

9.276

-

-

-

-

40.681

57.292

E C

C A

19

ACCEPTED MANUSCRIPT Neem

-

-

-

2.387

12.913

11.396

35.492

38.435

-

-

-

T P

I R

C S

A

U N

D E

M

T P

E C

C A

20

0.348

27.044

73.927

ACCEPTED MANUSCRIPT

Table 4. Crystallization Onset Temperature from DSC for different biodiesel Sunflower Coconut

Palm

Rice

Jatropha Mahua

PT

Biodiesel

1.42

3.59

13.48

1.20

SC

Crystallization

RI

Bran

AC

CE

PT E

D

MA

NU

Onset (oC)

21

-3.81

7.78

Neem

8.89

ACCEPTED MANUSCRIPT

Table 5. Amount of liquid fraction in winterized biodiesel at different temperature

Biodiesel Liquid Fraction %

PT

Temperature 0C Sunflower Coconut Mahua Rice Bran Palm Jatropha Neem 100

100

93.76

99.64

61.54

96.5

12.61

97.73

19.76

34.48

0

81.82

0

0

77.41

0

100

100

100

100

15

100

100

100

100

10

100

100

62.75

5

100

96.66

0

0

100

64.88

SC

NU

AC

CE

PT E

D

MA

0

22

100

RI

20

0

ACCEPTED MANUSCRIPT Highlights

Biodiesel was prepared using seven different vegetable oil.



Temperature effect on winterization of biodiesel was investigated



DSC was used to estimate the crystallization onset temperature



Sunflower biodiesel recorded no crystal formation with minimum temperature of 0ºC.

PT



AC

CE

PT E

D

MA

NU

SC

RI

.

23

Figure 1

Figure 2r1

Figure 2r2