Hydrocarbon Fuels from Sequential Hydrothermal Liquefaction (HTL) of Lignite and Catalytic Upgrading of Crude Oil

Lignite from Belchatow in Poland was converted to hydrocarbon fuels, particularly in the kerosene and diesel ranges, through sequential hydrothermal liquefaction (HTL) and hydro-treatment (HDT) of the obtained crude oil. Different HDT temperatures were investigated (from 350 degrees C up to 390 degrees C). Despite the highly aromatic nature and high heteroatom content, the HTL lignite crude oil could undergo deep hydrodesulfurization (HDS = 99%) and hydrodeoxygenation (HDO = 98%) in a single HDT treatment stage, yielding a liquid product rich in aliphatic and aromatic, particularly monoaromatic, hydrocarbons. The hydro-treatment and hydrogenating capacity of the lignite crude oil was linked to the low concentration of compounds resistant to hydrotreatment in lignite and, consequently, lignite's crude oil, permitting the easy transformation of the crude oil into hydrocarbon fuel. Still, the significant concentration of aromatic compounds, particularly monoaromatic and diaromatic, in the liquid product (approximate to 45% of fuel range products) suggests that further upgrading, blending, or harsher HDT conditions might be necessary to improve the fuel quality. In addition to the crude oil, the HTL of lignite yielded a stream of char, which displayed a higher calorific value and lower heteroatom content than the original lignite feedstock, thus having a high potential for electricity production, which is the common use of lignite. Thus, introducing an HTL stage to extract crude oil before lignite use in electricity production could provide an alternative fuel source used as a strategy to increase multiple countries' energetic independence.