Hydrotreatment of fast pyrolysis liquid over Cr and P-modified catalysts with high Ni content

Abstract

Hydrotreatment of birch wood pyrolysis liquid (PL) was carried out at 350 °C and 6.0 MPa initial hydrogen pressure (RT) for 4 h in a batch autoclave using promising high-loading Ni-based catalysts stabilized by SiO2. Different additives (Cu, Mo, Cr, P) were used to modify the catalysts. The products in liquid organic (OPh) and aqueous phases (AqPh) after PL hydrotreatment were characterized by different methods, such as gas chromatography-mass spectrometry (GC–MS), Fourier-transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), etc. Herein, the performance of the catalysts was evaluated by considering the yield and chemical composition of the products (gaseous phase, OPhs, AqPhs, and coke). For the MoCr-containing system, a higher yield of the aqueous phase with low O/C ratio was observed that could be explained by more effective hydrodeoxygenation of water-soluble compounds due to Ni-Mo-Cr solid solutions and coordinatively unsaturated Cry+ and Mox+ sites. P-modified NiCuMoP-SiO2 and NiCrP-SiO2 catalysts reveal more intense CO2 formation very likely due to decarboxylation over Ni3P particles, thus leading to the decrease in the oxygen content in organic phase to 14 wt.%. Fresh reduced catalysts were examined by CO chemisorption, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM) to provide insights into the structure and morphology. High resistance to coke formation was evidenced according to CHNS analysis of spent samples, besides, the stability of catalysts was additionally assessed by X-ray diffraction.