In-Depth Analysis of Raw Bio-Oil and Its Hydrodeoxygenated Products for a Comprehensive Catalyst Performance Evaluation

Biomass pyrolysis liquids (bio-oils) unavoidably require catalytic hydrodeoxygenation (HDO) for their upgrading and stabilization for commercial usage. The complex composition of bio-oil constrains the fundamental kinetic understanding of HDO. Here, we propose a multitechnique methodology to compositionally assess the complete spectrum of the HDO reactants and products and then use it to pre-evaluate different catalysts in the HDO of a raw bio-oil obtained from black poplar. The used techniques are: micro (gas) chromatography (GC), GC with mass spectrometry (GC/MS), bidimensional GC × GC/MS, elemental analysis (EA), gel permeation chromatography (GPC), Karl Fischer, thermogravimetric analysis (TGA), as well as Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS) using different ionization sources (electrospray ionization (ESI) and atmospheric pressure photoionization (APPI)). FT-ICR/MS allows for the assessment of the heaviest and most refractory oxygenates in bio-oil, which have a pivotal role in HDO catalyst performance. Three activated carbon-supported catalysts based on PtPd, NiW, and CoMo mixed with a commercial HZSM-5 zeolite were used. We have been able to evaluate the multiple facets of catalyst performance: production of gases, catalytic coke, thermal lignin, and, most importantly, the aqueous and organic product fractions (hydrodeoxygenation of heavy species and production of light aromatics). The results of the detailed analytical methodology highlight their potential for understanding the HDO mechanism and for a detailed catalyst screening.