Production of renewable hydrocarbons through hydrodeoxygenation of crude oil from microalgae Scenedesmus sp. with “in-situ” hydrogen production

Abstract

Abstract Fatty materials hydroprocessing is one of the most promising routes for renewable hydrocarbons production in the range of aviation bio-kerosene and green diesel. This study investigated the feasibility of producing renewable hydrocarbons from crude oil of the microalgae Scenedesmus sp. Two technological routes were explored: Route 1 - hydrodeoxygenation (HDO) of the microalgae crude oil with external hydrogen addition, and Route 2 - HDO of the microalgae crude oil with "in-situ" hydrogen production through glycerol reforming. Both routes employ the commercial catalyst NiMoS2/Al2O3, commonly used in removing contaminants in aviation kerosene and diesel refineries. Catalytic tests were conducted using a Design of Experiments (DOE) to evaluate the production of renewable hydrocarbons from the crude oil of microalgae Scenedesmus sp. Parameters such as temperature, glycerol amount, H2 partial pressure, and reaction time were varied to analyze the conversion of microalgae crude oil and the selectivity towards liquid hydrocarbons. Statistical analysis using ANOVA and response surface methodology demonstrated the possibility of producing renewable hydrocarbons from the crude oil of microalgae Scenedesmus sp. The proposed catalyst showed efficiency in converting triglycerides and fatty acids. Optimal conditions were identified for each route, resulting in positive conversion rates (≈100%) and high selectivity towards hydrocarbons, Route 1: 95.44% and Route 2: 94.37%. Most of the generated hydrocarbons were classified as renewable diesel, while the remaining portion belonged to the synthetic paraffinic kerosene (SPK) range. Route 2 demonstrated greater economic appeal as it enabled "in-situ" hydrogen production through glycerol reforming, eliminating the need for external hydrogen addition. Moreover, Route 2 achieved a higher hydrocarbon content in the aviation bio-kerosene range (72%) compared to Route 1, without the need for additional hydrocracking steps, along with 23% in the renewable diesel fraction up to 400 °C.