Biodiesel Production From Chinese Tallow Kernel Oil And Its Combustion, Emission Properties

Renewable alternative fuel sources are currently attracting wide attention aspetroleum resource is gradually depleted and oil price is spirally rising, at the same time,with the threat of greenhouse gas emission and air pollution, the global climate isdeteriorating. Biodiesel, as one of the alternative fuel resources, has become the researchhot spot because it’s renewable, nontoxic, biodegradable and compatible with existingdiesel engines. However, the development of biodiesel industry has been seriouslyhindered by the lack of feedstock. Edible oils can not be used as the main raw materialsfor biodiesel production because they must first meet the demand of food industry toensure food supply security, especially in China, the per capita cultivated land is very low.Therefore, the development of biodiesel industry should comply with the national energypolicy stated as “Without competition for food with people, without competition forfarmland with food”. It is the best choice to develop oil resources from woody plants.Chinese tallow is a subtropical deciduous tree native to China, with its seeds containing asmuch as45%of oil, making it suitable for biodiesel production. In addition, plantation ofChinese tallow does not occupy farmland resource. Thus, it is of great significance toexplore biodiesel preparation from Chinese tallow kernel oil. In this study, the enzymaticcatalyzed biodiesel production from Chinese tallow kernel oil were investigated, and thenits combustion and emission properties were priliminarily examined, in order to providetheoretical and technical support for developing biodiesel industry from Chinese tallowkernel oil. The main research contents and results are summarized as follows:1. The basic physical and chemical properties and fatty acid profiles of Chinesetallow kernel oil were first determined. The oil had very low acid value, moisture contentand relatively high iodine value, containing89.90%of unsaturated fatty acids, making itsuitable for enzymatic catalyzed biodiesel production. Most fatty acids had carbon chainswith16or18carbons. These properties indicated that Chinese tallow kernel oil could be asuitable raw material for biodiesel preparation.2. Biodiesel synthesis was investigated from the transesterification of Chinese tallowkernel oil and methanol catalyzed by Candida rugosa lipase in different organic solvents and ionic liquids, and the best yields were achieved in tert-butanol and [Hmim][PF6]systems. The reaction conditions in both media were optimized including enzyme loading,methanol/oil molar ratio, water content, temperature, solvent amount and reaction time.For [Hmim][PF6] medium, at the optimal conditions of catalyst dosage20wt%,methanol/oil molar ratio4:1, water content10wt%, temperature40°C,1.0mL/g[Hmim][PF6] based on oil weight and reaction period24h, a biodiesel conversion of94.4%was obtained. In tert-butanol, the optimized conditions were lipase loading30%,methonal/oil molar ratio4:1, water content15wt%,0.4mL/g of tert-butanol, reactiontemperature40°C. A biodiesel yield of65.8%at24h was achieved under these conditions.Then, response surface methodology was employed to further optimize conditions ofenzymatic catalyzed preparation in [Hmim][PF6] system. The obtained optimal parameterswere: methanol/oil molar ratio4.2:1, lipase loading22.7%, moisture content11%andtemperature40°C; and96.21%of biodiesel yield was achieved at24h.3. Basic fuel properties of the biodiesel were tested, revealing that the FAMEssynthesized nearly met the standards of EU and China. Four different biodiesel blends (B0,B20, B50and B100) were then directly used in a single cylinder diesel engine toinvestigate power performance and fuel economy of Chinese-tallow-kernel-oil biodiesel,and their emission properties including HC, CO, smoke, NOx and CO2emissions werefurther studied. The results revealed that those biodiesel blends could be directly used indiesel engine without any modification. Because the heating value of biodiesel was a littlelower than diesel fuel, the output power was found to be slightly reduced and fuelconsumption rates increased a bit, which indicated the fuel economy of biodiesel wassomewhat reduced. The HC, CO and smoke emissions were reduced prominently with theincrease of blending ratio of biodiesel, and the NOx emission increased slightly at thesame time. The CO2emission from biodiesel was also a little higher than diesel. As awhole, the combustion and emission properties of Chinese-tallow-kernel-oil biodieselwere much better than those of petroleum diesel. However, the formation mechanism andeffective reduction of NOx emission still required further investigation.