Hydrotreating lipids for aviation biofuels derived from extraction of wet and dry algae

Abstract

Upgrading is a critical step for producing hydrocarbon biofuels. Recently, upgrading algae lipids had attracted a lot of attention, but the attention to aviation biofuel was not enough. Meanwhile, the research of upgrading wet algae lipids was very limited. The hydrogenation characteristics were investigated for lipids derived from extraction of dry and wet algae. Hydrotreating parameters including temperature (270–350 °C) and catalyst loading (10–30%) were investigated and two-stage hydrogenation was conducted at the optimal reaction condition. Two-stage biofuels resulted in lower heteroatoms including O and N both for dry and wet algae lipids. The elemental contents of N were below 0.007% and the O contents were below 0.3%. The heating values were about 46.2 MJ/kg. Both of dry and wet algae lipids can be hydrotreated to aviation biofuel by the two-stage hydrogenation, even though the wet algae lipids contained more carboxylic acid, sterol, and vitamin E than dry algae lipids, which contains more alcohols and esters. The compound of 5-Methyl-3-phenylcyclopent-2-en-1-one is difficult to be upgraded. The content of aromatics and cyclo-paraffins shows a rising trend and some of the aromatics could be upgraded to cyclo-paraffins in the hydrogenation process. In addition, the yield of high-quality biofuel from dry algae lipids is 73.02%, and that is 76.47% for wet algae lipids, which indicated that the wet route hydrogenation might have an advantage over the dry route. The hydrotreating results of model compound cholesterol indicated that much amounts of aromatics was generated.