| Because of its low emission of sulfur during combustion, non-toxic, low pollution, biodiesel has been considered as a new generation of green, environmentally friendly biomass fuel. Although some documents have been reported on biodiesel production, most researchers still choose edible vegetable oil and other raw materials as feedstock which is of high cost. However, as a populous country, China need large amount of edible oil and produce waste cooking oil. Therefore, we can select waste cooking oil to produce biodiesel, which make better use of resources. But when biodiesel at low temperature (about 0 ℃) used, the readily crystallized fatty acid methyl esters result in the engine clog, affecting normal operation of the engine. Therefore, improving cold flow properties is very important for the utilization of biodiesel.In this paper, waste cooking oil was selected as a feedstock for preparing biodiesel form waste oil biodiesel (BWCO), which was sequently improved on its cold flow properties. The specific content was shown as follows:(1) With traditional base-catalyzed transesterification, biodiesel was readily prepared from waste cooking oil. The biodiesel yield was 95.46 wt%. Most fuel properties of HM biodiesel satisfied ASTM D6751 and EN 14214 standards, with the exception of OS, which did not meet the EN 14214 requirement. The pour point (PP) and the cold filter plugging point (CFPP) of prepared biodiesel were-9 ℃ and 0 ℃ respectively. Overall, waste cooing oil is a potential low cost feedstock for biodiesel production.(2) Four kinds of commercial polymer-based diesel cold flow improvers were selected, namely:A-4, T-1804D, T803 and V-385, which respectively represent polymethyl methacrylate (PMA), ethylene-vinyl acetate vinyl acetate copolymer (EVAC), poly-a-olefin (PAO) and maleic anhydride and poly (HPMA), to figure out their effect on the cold flow properties of BWCO, including PP, CFPP, viscosity and viscosity index (VI). In addition, other important fuel properties were also determined, such as:thermogravimetry (TG), flash point (FB), the acid value (AV) and oxidation stability (OS) and so on. Finally, low-temperature polarized microscopy and differential scanning calorimetry were used to show the crystal structure and crystallization behavior for BWCO at low temperatures. PMA is the best choice of the four polymers ass cold flow improver for BWCO, which didn’t affect other important fuel properties. Add 0.04% PMA in cooking oil biodiesel, PP and CFPP were reduced by 8 ℃ and 6 ℃ respectively. PAO and HPMA almost showed on effect on the cold flow properties of biodiesel.(3) Ethyl acetoacetate (EA) was first used as a bio-based organic diluent for biodiesel. With the addition of 20 vol% EA, PP and CFPP of BWCO were both reduced by 4 ℃. At the same time, after adding EA, the oxidation stability of BWCO was improved significantly.(4) Complementary blending of BWCO with diesel from direct coal liquefaction (DDCL) was evaluated to improve fuel properties. The fuel properties of the biodiesel blends with the addition of 0%,2.5%,5%,10%, and 20% DDCL (vol) were determined. The deficiencies and superiorities of BWCO and DDCL were complemented through blending. DDCL can be used to significantly enhance the properties of biodiesel. In blending 20 vol% DDCL with BWCO, the fuel properties of the blends still met the specifications of EN 14214 and ASTM D6751 after storage for 100 days. Regardless of the blend ratio, the FP and KV of DDCL blended with BWCO were within the requirements stated in EN 14214 and ASTM D6751. The results indicate blending is a good way for full use of biodiesel and DDCL, which can alleviate the shortage of petroleum resources and promote the utilization of biodiesel in coal-rich country like China. |
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