Latest Applications of Methanol – Development Status and Industrialization Prospects of Biodiesel

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I. Main properties of biodiesel Biodiesel is a clean renewable energy source. It is a liquid fuel produced from oilseeds such as soybeans and rapeseed, fruits of oil-bearing trees such as oil palms and carob trees, oil-producing aquatic plants such as engineered microalgae, as well as animal fats and waste cooking oil. It serves as an excellent substitute for petroleum diesel. Biodiesel is a typical \"green energy\" source. Vigorously developing biodiesel holds significant strategic importance for the sustainable economic development, the advancement of energy substitution, the reduction of environmental pressure, and the control of urban air pollution. As is well known, diesel molecules are composed of approximately 15 carbon chains, while studies have shown that plant oil molecules generally consist of 14–18 carbon chains, a number similar to that in diesel molecules. Therefore, biodiesel is a new type of fuel produced by processing renewable plant oils such as rapeseed oil. Based on chemical composition analysis, biodiesel fuel is a type of fatty acid methyl ester obtained through the decomposition of glycerides whose main component is the unsaturated oleic acid C18. Compared to conventional diesel, biodiesel possesses the following unparalleled advantages: 1. It has excellent environmental properties. This is mainly reflected in the low sulfur content in biodiesel, which results in low emissions of sulfur dioxide and sulfides – a reduction of about 30% (70% when a catalyst is used) ； Biodiesel does not contain aromatic alkanes that can pollute the environment, so the harm to human health caused by its exhaust fumes is less than that of diesel. Tests have shown that, compared to conventional diesel, the use of biodiesel can reduce air toxicity by 90% and the risk of cancer by 94% ； Due to its high oxygen content, biodiesel produces less smoke when burned, with carbon monoxide emissions reduced by about 10% compared to diesel (95% when a catalyst is used) ； Biodiesel has high biodegradability. 2. It has good low-temperature engine starting performance. The cold filter point without additives is -20°C. 3. It has good lubricating properties. It reduces the wear rate of the fuel injection pump, engine cylinder block, and connecting rods, thereby extending their service life. 4. It has good security performance. Due to its high flash point, biodiesel is not considered a hazardous material. Therefore, the safety in terms of transportation, storage, and use is obvious. 5. It has good fuel performance. Its high cetane number gives it better combustion properties compared to diesel, and its slightly acidic combustion residues extend the service life of catalysts and engine oils. 6. It has renewable properties. As a renewable resource, unlike oil reserves, its supply will not run out thanks to the efforts of agricultural and biological scientists. 7. No modifications to the diesel engine are required; it can be used directly, and no additional fueling equipment, storage facilities, or special technical training for personnel is needed. 8. When blended with petroleum diesel in a certain proportion, biodiesel can reduce fuel consumption, improve performance, and decrease exhaust pollution. The excellent properties of biodiesel ensure that the exhaust emission standards for engines using biodiesel not only meet the current European Standard II, but also satisfy the even stricter European Standard III, which is set to be implemented in Europe shortly. Furthermore, since the carbon dioxide emitted during the combustion of biodiesel is much lower than the amount absorbed by those plants during their growth, this helps to address global warming, a serious environmental problem that poses a threat to humanity due to carbon dioxide emissions. Therefore, biodiesel is a true green diesel. II. Production methods of biodiesel At present, biodiesel is mainly produced by chemical methods; that is, animal and vegetable oils are reacted with low-carbon alcohols such as methanol or ethanol in the presence of acidic or basic catalysts and at high temperatures (230–250°C) through a transesterification reaction to produce the corresponding fatty acid methyl esters or ethyl esters, which are then washed and dried to yield biodiesel. Methanol or ethanol can be reused in the production process; the production equipment is the same as that used in conventional oil production, and about 10% glycerin is produced as a by-product during this process. The main problem with biodiesel at present is its high cost. According to statistics, 75% of the production cost of biodiesel is the cost of raw materials. Therefore, using inexpensive raw materials and increasing conversion rates to reduce costs is key to the practical application of biodiesel. The United States has begun to study plants with high oil content using genetic engineering methods; Japan makes use of industrial waste oil and used frying oil, while Europe grows oil-rich crops on land unsuitable for growing food crops. However, the chemical synthesis of biodiesel has the following disadvantages: the process is complex, an excess of alcohol is required, and corresponding alcohol recovery systems are necessary in subsequent steps; it also has high energy consumption. Additionally, its color is dark, as the unsaturated fatty acids in fats tend to deteriorate at high temperatures ； Esterification products are difficult to recover and costly ； Waste alkaline solution is discharged during the production process. http://www.16ds.com/papers/49/topics/7147