Transesterified biodiesel

Transesterified biodiesel presents some drawbacks, such as high corrosion problems, oxidation instabihty, methane toxicity, high viscosity, and high cost compared to conventional diesel (Muthukmnaran et al., 2015). Therefore, alternative methods of fuel production from vegetable oils will also be discussed in this section. 

Demirbas, A. 2003. Biodiesel fuels from vegetable oils via catalytie and non-eatalytie supereritieal aleohol transesterifieations and other methods a survey. Energy Convers Manage 44 2093-2109. 

Much work has been done on the incorporation of castor oil into polyurethane formulations, including flexible foams [64], rigid foams [65], and elastomers [66]. Castor oil derivatives have also been investigated, by the isolation of methyl ricinoleate from castor oil, in a fashion similar to that used for the preparation of biodiesel. The methyl ricinoleate is then transesterified to a synthetic triol, and the chain simultaneously extended by homo-polymerization to provide polyols of 1,000, 000 molecular weight. Polyurethane elastomers were then prepared by reaction with MDl. It was determined that lower hardness and tensile/elongation properties could be related to the formation of cyclization products that are common to polyester polyols, or could be due to monomer dehydration, which is a known side reaction of ricinoleic acid [67]. Both side reactions limit the growth of polyol molecular weight. 

The most important challenge in enzymatic biodiesel production is the high cost of the lipase. Therefore, immobilization was considered in order to reduce overall biodiesel production costs. Lu et al. (2007) transesterified lard using immobilized Candida sp. 99-125 and found that the enzyme was reusable over seven repeated cycles (for 180 hours) with no significant decrease in activity. Also the production yield was higher than 80%. Modi et al. (2007) found a similar stability when ethyl acetate was used instead of alcohol they used Novozym 435. The immobilized enzyme was reused for 12 cycles without any loss in the activity. On the other hand, Shimada et al. (1999) reported more than 95% conversion even after 50 cycles (100 days) of the reaction. Table 6.7 shows a sununary of different lipases tested with different feedstocks, conditions and immobilization methods. 

Sinha, S., A. K. Agarwal, and S. Garg. 2008. Biodiesel Development from Riee Bran Oil Transesterifieation Process Optimization and Fuel Characterization. Energy Conversion and Management 49 (5) 1248-1257... 

Acid Catalysis Add catalysis transesterification includes the combination of three reversible reactions (Fig. 22.4). The high conversion of the acid catalyzed transesterification procedure is due to the capacity to transesterify fatty acids and fatty acid salts present in the system. The acids employed are HCl, H SO, BFj, and sulfonic acids [15, 22-24]. Generally, acid catdysis is many times slower than basic catalysis. The rate of the biodiesel production reaction... 

Biorefineries can be considered to belong to three types. Type 1 biorefineries focus on the conversion of one feedstock, using one process and targeting one product. A biodiesel production plant would be a good example rapeseed or sunflower is used for oil extraction, which is subsequently transesterified to produce fatty acid methyl esters or biodiesel using methanol and a catalyst. 

Biodiesel production from com oil can also be carried out in enzymatic catalysis. In a study using immobilized lipase enzyme (Novozym 435) as a catalyst, it was reported that 81.3% fattj acid methyl ester content was obtained at 15% enzyme load, 60°C temperatures and 10 MPa pressure in 4 horns (Ciftci Temelli 2013). Com oil was also transesterified with methanol by injecting it into a supercritical carbon dioxide stream in the presence of immobilized lipase enzyme. Fatty acid methyl ester yield was observed as greater than 98% (Meher et al., 2006). 

Nanopowder calcium oxide (Nano CaO) is another form of CaO, whieh has been tested for biodiesel production. Transesterifieation of soybean oil wifii methanol under microwave conditions was foimd to be more efficient than eon-ventional heating for Nano CaO catalyzed biodiesel production [19] with conversion rates of over 96% with properties within the limits of standard biodiesel. 

The reported order of activity of alkaline earth oxide catalysts was observed to be BaO>SrO>CaO>MgO. Among them, MgO was more active than CaO in the transesterifieation of rapeseed oil, but was also responsible for soap formation. In the transesterifieation of Camelina sativa oil, BaO and SrO were found to be effective catalysts for the synthesis of biodiesel at 100° C compared to CaO and MgO [20]. The authors suggested that SrO can be preferred over BaO due to the noxious nature of BaO. Similar results were also observed for the transesterifieation of palm oil using CaO, SrO and BaO as heterogeneous base catalyst imder ultra sonic assisted preparation of biodiesel. BaO and SrO were found to be efficient catalysts than CaO for production biodiesel with a yield of 95%. With BaO, there was a drop in catalytic activity due to the dissolution of BaO catalyst in methanol [21]. 

BaO is reported to be harmful/poisonous eatalyst and cannot be used as heterogeneous eatalyst as it ean be solubilized in methanol. Whereas, SrO on the other hand has stronger basie sites and it is insoluble in methanol. [22]. Transesterifieation of soybean oil using SrO (3%) as solid base eatalyst at 65° C resulted in more than 95% of biodiesel in less than 30 min. It was observed that SrO had longer lifetime and activity was retained even after 10 cycles of biodiesel production [22]. In another study, transesterifieation of canola oil with MgO, CaO, SrO and BaO for biodiesel preparation, it was observed that BaO (1 mol%) showed >95% conversion in 1 h at 50° C [23]. 

Ba/CaO solid base catalyst was prepared from construction site marble waste and was employed in the transesterifieation of waste cooking oil to produce biodiesel. With 1 9 molar ratio of oil to methanol and 3% catalyst at 65° C, conversion of 88% was observed in 3 h reaction time. It was shown that the catalyst can be reused for over three cycles and the method is uses less energy and provides value addition to both waste cooking oil and construction waste [24]. Table 12.1 provides a brief description of the single metal oxides as base catalysts for the production of biodiesel. 

Mg-Co-Al-La layered double hydroxide was examined for the transesteri-fieation of canola with ethanol, fith 1 16 ratio of oil to ethanol and 2% of eatalyst and at a temperature of 200° C or 473K in a reaetor was observed to produce 97% of biodiesel in 4 h [69]. Caleined Li-Al, Mg-Al and Mg-Fe layered double hydroxides for the transesterifieation of both glyceryl tributyrate and soybean oil with methanol. With 1-3% of catalyst and oil to methanol ratio of 1 15 and at reflux temperature resulted in about 83% biodiesel yield [70]. 

KF/Ca-Al hydrotalcite solid base catalyst was used for the transesterifieation of palm oil with methanol. With oil to methanol ratio of 1 12 and temperature of 65° C with 5% eatalyst produced biodiesel in 97.9% in 5 h. It was observed that loading of Ca-Al oxide with KF improved the activity of the catalyst [71]. KF/hydrotalcite solid base catalyst was tested for transesterifieation of palm oil with methanol to produce biodiesel. The optimmn conditions were oil to methanol ratio of 1 12 at 338K temperature with 3% catalyst. The authors reported that 85% FAME yield was obtained at 3 h and the yield increased to 92% when the reaction time was increased to 5 h [72]. 

Magnesia-rich magnesiiun aluminate spinel (MgO MgAl O ) were tested as solid base catalysts for the transesterifieation of soybean oil with methanol. With oil to MeOH ratio of 1 25 and 3% catalyst at 65° C, biodiesel with 60% yield was obtained in 10 h. The enhanced catalytic activity of the catalyst... 

Kouzu, M., Nakagaito, A., Hidaka, J., 2011. Pre-esterification of FFA in plant oil transesterified into biodiesel with the help of solid acid catalysis of sulfonated cation-exchange resin. AppUed Catalysis A General 405 (1—2), 36—44. Available at http //www.sciencedirect. com/science/article/pii/S0926860Xl 1004182 (accessed 09.06.14.). 

The complete transesterification of 1 mol of TAG requires 3 mol of alcohol, producing 1 mol of glycerol and 3 mol of fatty esters (Fig. 22.8). As the reaction is reversible, alcohol is commonly added in excess in industrial processes to ensure the direction of fatty acyl esters. A number of alcohols can be used as the substrates, eg, methanol, ethanol, propanol, butanol, and amyl alcohol. Methanol is the most preferable one because of its low cost. The most abundant composition of microalgal oil transesterified with methanol is C19H36O2, which has been demonstrated to meet the standard of biodiesel (Xu et al., 2006). 

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