(580f) Hydrotreating Kinetics of Nitrogen-, Oxygen- and Sulfur-Containing Model Compounds for Co-Processing Biocrude Oils with Vacuum Gas Oil

Co-processing of HTL bio-crude oils with petroleum crude oils is a practically feasible way to produce green transportation fuels and dramatically reduce the capital cost. Researchers have performed extensive studies on the hydrotreating kinetics of heteroatoms (N, O, S) removal. However, there is very limited information on the simultaneous hydrodenitrogenation (HDN) and hydrodeoxygenation (HDO) of fatty acid amides which are the major nitrogen content in the biocrudes. It is necessary to develop detailed kinetic model and investigate the impact of co-processing on the hydrotreating chemistry. First of all, we evaluated the activity and product selectivity of a single molecule model compound, N,N-diethyldodecanamide (DEDAD), using a bench-scale fixed-bed, continuous, downflow hydrotreater over a commercial NiMo/Al₂O₃ sulfide catalyst. Especially, we revealed the reaction mechanism of simultaneous HDN and HDO of DEDAD, which was dominated by directly deoxygenation (DO pathway) to produce amine intermediate, instead of C-N bond cleavage through denitrogenation (DN pathway) to yield a nitrogen-containing compound and an oxygen-containing species. In addition, to study the influence of sulfur on simultaneous HDN and HDO, H₂S was added to the DEDAD test, which showed significant inhibition effect on the DO path. Moreover, we have studied the effect of substitution of the amide group on the HDN and HDO chemistry of alkylamides. N-methyldodecanamide (MDAD) was selected as secondary amide which reacted slower compared with tertiary amide DEDAD under the same reaction conditions. Besides, we have also successfully determined the kinetics with respect to HDO of dodecanoic acid (DA) and 4-propylphenol (PP), HDS of dibenzothiophene (DBT), as well as HDN of quinoline (Q) and amines. The commercial NiMo sulfide catalyst showed better HDO and HDS performance than HDN with the highest overall rate constant for hydrotreating of fatty acid.