11/23/2023 0 Comments Renewable diesel production process![]() In addition, water produced during the reaction could deactivate the catalyst. The HDO route is preferable from the point of view of atom economy because it produces H 2O as a by-product, though it consumes more hydrogen. Reaction selectivity can be driven by varying operating parameters, such as temperature and pressure, but also by varying the nature of the metal catalysts and the supporting material. The free fatty acids can then follow three different reaction pathways according to the selectivity of the process: (a) a hydrodeoxygenation reaction (HDO), which forms an alkane with the same number of carbon atoms as the starting fatty acid and water (b) decarbonylation (DCO) (c) decarboxylation (DCO 2) reactions in which an alkane with a carbon atom less than the starting fatty acid is formed and the oxygen is released as CO and H 2O (DCO) or CO 2 (DCO 2). The third step of hydrogenation and β-elimination leads to the release of the third fatty acid and a propane molecule. The diglyceride needs to be re-hydrogenated before undergoing further β-elimination to release a second fatty acid molecule. The most common mechanism of triglyceride cleavage is a β-elimination reaction in which the triglyceride is converted into a free fatty acid and an unsaturated diglyceride. Then, the triglycerides are broken down to obtain free fatty acids. Catalytic Deoxygenation (DO) ProcessĪs suggested by Kubicka et al., the first step of DO involves the hydrogenation of the double bonds of unsaturated fatty acids. Green diesel, on the other hand, being chemically similar to petrol diesel, can completely replace conventional diesel. ![]() In fact, it can be used pure only after the adaptation of the engine. Furthermore, the different chemical composition between biodiesel and petrol diesel implies that the former can only be used in a mixture with conventional diesel. On the other hand, green diesel has high oxidation stability, storage stability, and when properly treated by a hydroisomerization reaction (a reaction in which the n-alkanes of green diesel are partially converted into the corresponding branched isomers) it also has excellent cold properties. In contrast, it has poorer oxidation stability, storage, and also poor cold flow properties. Compared to green diesel, biodiesel has better properties as a lubricant, and it also has a higher flash point. observed a reduction of greenhouse gas emissions of 41–63% in the case of jet biofuels produced by catalytic deoxygenation. CO 2 emissions are also significantly reduced. Both biodiesel and green diesel have low sulfur emissions, but unlike green diesel, biodiesel has higher nitrogen emissions. In contrast, green diesel is chemically similar to petrol diesel and more suitable than biodiesel as its substitute. In fact, it has a high oxygen content and as a result a lower calorific value, energy density, and energy content. Biodiesel is chemically different from petrol diesel. īoth green diesel and biodiesel have a higher cetane number than conventional petrol diesel (higher for green diesel). The differences between biodiesel, green diesel, and petrol diesel can be seen in Table 1. This treatment produces a biofuel mainly consisting of n-alkanes, which is therefore chemically similar to mineral diesel, making it completely compatible and miscible in every proportion. A DO commercial process was patented by Neste Oil. DO is a thermal process, typically conducted in a hydrogen atmosphere and with a heterogeneous metal catalyst, in which vegetable oils are converted into hydrocarbons. A valuable alternative to biodiesel is green diesel, which is obtained by the catalytic deoxygenation (DO) of vegetable oils. However, several drawbacks, such as high oxygen content, high corrosivity, storage instability, and limited miscibility with conventional fossil fuels, make biodiesel an unsuitable substitute for petrol diesel. Moreover, the production process leads to high yields and requires mild operating conditions. The main advantages of biodiesel relay to the use of renewable materials and to the reduction of polluting gas emissions.
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