(635g) Total Acid Number Reduction of Renewable Thermal Deoxygenation (TDO) Oil for Coprocessing in Refineries

Co-processing biocrude in existing petroleum refineries is an efficient way to produce renewable transportation fuels. It also provides biofuel tax incentives and a potential method for competitive production prices of biofuels. Currently, the major obstacles in the co-processing of biocrude with petroleum crude are high acidity, high oxygen content, and miscibility of biocrude with petroleum crude. The acidity of crude, measured by Total Acid Number (TAN) is an indication of the potential for corrosion problems in a refinery. The presence of oxygen compounds in crude oil has a deleterious effect on the lifetime of hydrotreating catalysts. Typical refinery prefers crude oil with less than 0.5mg KOH/g of TAN and free of oxygen compounds.

In this work, different chemical and catalytic processes are investigated to evaluate the potential of crude Thermal DeOxygenation (TDO) oil for co-processing in a petroleum refinery. TDO oil is a type of synthetic crude produced by a non-catalytic thermochemical conversion of neutralized biomass acid hydrolysate. TDO oil is fully miscible with petroleum products and typically has a low TAN (1.9 mg KOH/g) and low oxygen content (< 5wt%) compared to pyrolysis oil. The presence of naphthols, phenols, and ketones contributes to the acidity and oxygen content of the biocrude.

TDO oils used in these experiments are produced using a mixture of levulinate and formate salts in a pilot-scale continuous flow reactor at 450 °C and atmospheric pressure. Hydrodeoxygenation, neutralization, and ionic liquid extraction methods are used to reduce the TAN below 0.5mg KOH/g and remove oxygen compounds in the crude TDO oil. Hydrodeoxygenation reactions are carried out using catalysts (e.g., Ni/SiO₂-Al₂O₃) in a bench-scale continuous flow reactor at different reaction temperatures and weight hourly space velocities. Neutralization of crude TDO oil is performed with a dilute caustic wash using alkali metals (e.g., Na⁺, K⁺, Ca²⁺) at different concentrations. Ionic liquid (IL) extractions are carried out using Imidazolium-based ILs at different ILs/oil ratios. TDO oils are characterized by GC-MS and FTIR to determine the differences in chemical composition. TAN and oxygen content of oils are measured according to standard ASTM methods (ASTM D664 and ASTM D5291 respectively).