Modelling of the hydrotreating process to produce renewable aviation fuel from micro-algae oil

Renewable jet fuel has been identified as the most promissory alternative to reduce CO2 emissions in the aviation sector, allowing its sustainable development. This renewable fuel, also known as biojet fuel, can be obtained from different types of biomass, which include lignocellulosic biomass, sugar, starchy and triglyceride feedstock. In particular, the conversion of triglyceride feedstock to biojet fuel is realized through the hydrotreating process, where hydrodeoxygenation, hydroisomerization and hydrocracking reactions are carried out; after that, the purification of the renewable hydrocarbons is realized through distillation columns. The modelling and intensification of the hydrotreating processes have been previously analyzed for castor oil and jatropha curcas oil, which are the non-edible crops with highest productive potential in Mexico. However, another raw material with high productive potential is micro-algae oil, since it can be cultivated in non-fertile lands, avoiding the competition with food crops for ground use. Therefore, in this work we propose the modelling of the hydrotreating process to produce biojet fuel, considering micro-algae oil as raw material. The reactive section is modelled with a multifunctional catalyst; thus, all the hydrotreating reactions are carried out in one vessel. The produced renewable hydrocarbons are purified by conventional distillation sequences: direct, indirect and combined. Thus, three conventional hydrotreating processes are defined and evaluated in terms of total annual costs, CO2 emissions and price of biojet fuel. It has been found that the hydrotreating process that includes the direct conventional sequence presents the lowest total annual costs. Also, in all scenarios the biojet fuel price is competitive with the fossil one. Considering the high productivity per hectare, microalgae oil is a very promissory raw material for sustainable production of renewable jet fuel with a competitive price.