Hydrodeoxygenation of pyrolysis oils derived from kraft lignin using Ru-based catalysts in a continuous flow reactor

The hydrodeoxygenation (HDO) of pyrolysis oils derived from lignin is considered to be the most effective method for improving the quality of oil by selectively removing oxygen functionalities [1]. Although the effectiveness of noble metal-based catalysts such as Ru/C and RuRe/C for the HDO of lignin model compounds (e.g., phenol, guaiacol) are demonstrated, HDO studies with real pyrolysis oil are relatively unexplored [2-3]. Due to its complex composition and mineral impurities such as sulfur, the activity and stability of the catalysts for the HDO of pyrolysis oil would be significantly different from those for the model compounds. In this work, the HDO of pyrolysis-oils derived from kraft lignin using ruthenium-based catalysts (i.e., bimetallic RuRe/C) was studied in a continuous flow trickle bed reactor system. The effects of reaction temperature and space velocity were investigated, and a detailed analysis of the reaction products were performed to understand the fundamental reaction chemistry. The spent RuRe/C catalysts were also characterized by using X-ray photoelectron spectroscopy, high-resolution TEM, chemisorption, and ICP analyses to elucidate the main cause of catalyst deactivation.