## 1 Introduction
Biodiesel can be made from vegetable oils, animal fats, or recycled restaurant greases (waste cooking oils). Both the original materials and the product of biodiesel are safe and can be degraded naturally. 2. It can reduce greenhouse gas emissions. A life cycle analysis of biodiesel showed that overall CO\({}_{2}\) emissions were reduced by 78% compared with petrodiesel fuel, which will contribute to domestic and international targets of greenhouse gas reductions. 3. It has a similar cetane number as compared to petrodiesel, so it can be used alone, or blended with petrodiesel in any proportions. 4. It is an oxygenated fuel without sulfur content, which can promote engine combustion and reduce emissions of HC, CO and PM, which helps to reduce the environmental pollution. 5. It has better lubricity, and unsaturated esters possess a slight advantage. So, there is no need to reconsider the lubricity of the engine fuel injection system when biodiesel is applied. 6. It is a mix of mono-alkyl esters of long chain fatty acids. It has a higher cloud and pour point (CP and PP) temperatures, density, and kinematic viscosity as well as the acid value compared to diesel, affecting the utility of the fuel, especially in cold conditions. 7. The calorific value of biodiesel is about 37.27 MJ/kg. There is 9% lower than regular petrodiesel. Fuel injection systems measure fuel by volume, and thus, engine output power may be affected under high ratio or pure application conditions. 8. It comprises of saturated and unsaturated esters. Saturated fatty esters are very stable, while unsaturated esters are likely to react with oxygen, therefore reduce oxidation stability. 9. And finally, because of its renewable feature, the use of biodiesel can reduce its dependence on foreign fossil fuels. Sustainable energy supply is necessary for the economic development of a country like China, whose petroleum depends much on import. For the application of biodiesel, cetane number is the most concerned parameter. The CN of most conventional biodiesel are around 50, which meet the requirement of CI engine, especially under low fraction blending application [21; 22; 23; 24; 25; 26]. However, the effects of reducing exhaust emissions are not so significant. There were studies showed that the improvement of CN may results in reduction of biodiesel engine emissions. Higher CN leads to lower NOx, higher oxygen content decreases CO, HC, PM emissions [27; 28; 29; 30]. So, instead of methanol, substances containing more oxygen should be adopted to increase CN and oxygen content for biodiesel. Conventional biodiesel is prepared through transesterification of vegetable oils or fatty oils with methanol. There are only two oxygen atoms existing in biodiesel molecule, hence the oxygen content in conventional biodiesel is not high. Although the conventional biodiesel has high cetane number (about 50) as petrodiesel, it has not evident competition superiority [21; 22; 23; 24; 26; 27; 31; 32]. The developed new model biodiesel is synthesized through transesterification reaction of vegetable oils and ethylene glycol ether derivatives. The ether group introduced into biodiesel molecule promotes its octane number and oxygen content to 70 and 17% approximately, which finally proves to have a better performance than conventional biodiesel in reducing engine emissions, especially smoke can be reduced 80% approximately. This review is to summarize our researches about the new model biodiesel. Transesterification processes were simply described and proved to be the same as FAME. The synthesized biodiesel itself, its fuel properties, engine test equipment and engine performance were reviewed respectively, which proves our research activity is interesting and progressive.