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K WMumesthńge et al. / Furt Processing Technology 90 (2009) 1292 1299 1293

dimates than that from animal fat because SBO-biodiesel had morę unsaturated components| 19|. Also. palmoil (PO) based biodiesel with 70% saturated FAMĘ shows very poor eold flow properties though PO biodiesel shows very high oxidative stabilny and cetane number. Altering the degree of unsaturation of FAMĘ in order to improve some properties may aggravate another problem. Biodiesel produced from marinę fish oil which contain greater amount of polyunsaturated fatty acids and longchain fatty acid in the rangę between C20 and C22 than biodiesel produced from waste cooking oil appeared to havc higher acid number. kinematic viscosity. higher heating value and poor oxidation stabilny |20|. A reccnt paper by Knothe |21| reports a "Designer biodiesel composition for improved fuel properties. This paper described in details the properties of indwidual component of FAMĘ and their suitability as better fuel. Methyl palmitoleate (methyl (9Z)-hexadecenoate. C16:1) has been suggested as the ideał major component for biodiesel even though the abundance of palmitoleic acid in naturę is significantly less than that of oleić and.

The current commerdal approaches to improve the properties of biodiesel involve the use of antioxidants and cold flow additives (15.22.23). This approach raises the concern of effect of additives on other fuel properties and on after treatment devices.

The functional groups present in the fatty acid chain and the alcohol part of the ester can alter the properties of biodiesel. It was reported that castor oil based biodiesel has a higher lubridty. due to the presence of the hydroxyl group in the fatty aod chain |24J. Also. the kinematic viscosity of castor oil methyl esters is significantly higher than that allowed by ASTM D6751 as a result of higher riconoleic acid methyl ester content (methyl-12-hydroocy-9(Z)-orta-decanoate). A study by Knothe reported that the cetane number would generally increase as larger branched esters are produced from different alcohols of increasing chain length (251.

Several studies have reported Chemical modification of vegetable oil and biodiesel (26-29). Among these modifications. the most common strategy is hydrogenation of unsaturated double bonds in FAMEs (26.271. While uncontrolled or strong hydrogenation gives total saturation of double bonds. resulłing very poor cold flow properties. controlled or mild hydrogenation can be used to modify FAMEs to achieve improved properties. The FAMĘ structure has different Chemical functionalities such as double bonds. allylic carbons, saturated carbon-carbon bonds and ester groups. Among these functionalities the most a»active site of FAMĘ is the region with double bonds and triple bonds (if any) which can be easily trans-formed to different Chemical functionality. Several papersdescribe the genetic modification of oil producing seeds to obtain triglycerides with desired properties |28-30|. Mutational breeding approaches have been used to decrease the saturated fatty acid content of soybean oil (28|. Reducing the relative abundance of linoleic (CI8:2) and linolenic (08:3) acids has a profound impacton oxidative reactivity of the oil 130). In theory. genetic modifications should błock the pro-duction of polyunsaturated fatty acids. thus enhancing the mono-unsaturated fatty acid content at the expense of oxidatively reaaive polyunsaturated fatty acids. Genełically modified oil consistently displayed elevated oleić (08:1) acid content ranging from 84 to 88% across multiple environmental conditions (311. Recent works by Soriano et al. 118] and Diwani et al. |32| show tlvat biodiesel mixed with ozone treated vegetable oil shows bettercold flow properties and a lower flash point.

Guidotti et al. described a method to epoxidize unsaturated FAMEs usingTi grafted silica catalysts |33|. In this paper the influence of the naturę and the position of functional groups on the C-18 chain of the FAMEs obtained from several feedstocks were studied. Extensive work by Moser et al. describe a method of modifying pure oleić acid into branched diesters. which shows improved Iow temperaturę properties and oxidativestability |34.35|. It should l)e noted that most of the above studies were on triglycerides or pure fatty acids and did not address the properties of modified FAMĘ as described in ASTM D6751.

The objectives of this paper are to modify FAMEs using three different. single step Chemical transformations: catalytic hydrogenation. epoxidation. and hydroxylation and to evaluate the fuel properties of the modified FAMĘ. A detailed study of the structural and composition changes and the corresponding properties of hydro-genated. epoxidated and hydroxylated FAMĘ are presenłed.

2. Experimental

2.1. Materials

Biodiesel produced from poultry fat (PF) was obtained from Biodiesel Industries (Denton. Texas). This biodiesel was distilled under reduced pressure (3x 10^_3Torr) at about 130-150”C. Once distilled. they were stored at 4**C in dark. air tight bottles. The FAMĘ composition of this biodiesel is given in Table 1. A sample of synthetic jet fuel (S-8) produced by Syntroleum Corporation. (Tulsa. Oklahoma) was provided by National Automotwe Center. US Army (Warren. Michigan). S-8 was used to make FAMĘ biends for lubridty measurements.

22. Catalytic hydrogenation

The hydrogenation of FAMĘ was canried out in a high-pressure. high temperaturę laboratory-reactor model Panr 4575 (Parr Instaiment. Molme. IL). using a 4% Pd/C catalyst BI 13W from Sigma Aldrich. 400 mL (356 g) of distilled PF biodiesel and 14 g of P&C catalyst were placed in the reactor vessel and mixed thoroughly using a glass rod. Hydrogenation was carried out at 120 *C temperaturę and 4 atm pressure. 50 mL samples were taken every 30 min while the reaction was in progress. These samples were filtered using 5 pm hydrophobic fluoropore (FTIT) filter (Millex®-LS. Millipore. Bedford. MA) before analysis. 384 mL (341 7 g) of total FAMĘ (96%yield) were recovered after 2 h of hydroge na tion.

2.3. Epoxidation of biodiesel

The epoxidation reaction (36| was based on Swern epoxklation which has been modified for oleochemical use by Bunker and Wool |37|. First. 420.0 g (1.45 md) of PF based biodiesel was placed in a 1000 mL round-bottom fiask equipped with a magnetic słirier. Next. 15 g (0.3 mol) of formie arid was slowly added. forming a layered mixture. The reaction fiask was cooled in an ice bath. and 254 gof 30% aqueous hydrogen perooude (76.2 g of hydrogen peroxide. 2.2 mol) was added slowly over about 5 min while the temperaturę of the solution was maintained at or below 25 °C. The reaction was allowed to proceed at room temperaturę, and aliquots were taken and ana-lyzed by GC. The reaction was carried out for 5 h. The product was purified in a reaction fiask by stirring with 100 mL of hexane and discarding the aqueous/formic acid layer. Then. 110 mL of saturated sodium bicarbonate solution was stirred with the hexane layer and removed. This sodium bicarbonate washing was repeated. k*aving the solution slightly basie. The hexane layer was removed with vacuum evaporation. Samples were taken and analyzed after 5 h reaction time. The rccovered FAMĘ was 382 g (1.32 mol. 91% yield).

Tablet

FAMĘ composition of distilled and undistilled PF b»odr-sel.

FAMĘ	Dhtilled PF X	Un-di«illed PF X
ClłO	10	LI
CI6:0	21.9	22.1
C16:l	3.3	35
Ct8:0	63	60
C18:1	39.1	39.2
C18:2	268	266
08:3	1.6	14
iUFAME	70.7	70.7
łSFAME	29.3	29.3