Renewable Hydrogen Production from Bio-oil in an Aerosol Pyrolysis System

Abstract

Abundant bio-oil resulting from thermochemical conversion of biomass could potentially be an important source of renewable hydrogen (H2). Direct pyrolysis of hardwood bio-oil was carried out in an aerosol reaction system to evaluate temperature and catalytic effects on H2 production. The laboratory system achieved stable H2 output for hours without the need of steam or catalyst rejuvenation. Hydrogen yields (∼50%) are comparable to those from fixed-bed reactors under typical pyrolysis temperatures (700 – 900°C). Pure nickel catalyst enhanced hydrogen yield at lower temperatures (≤ 800°C) but suppressed it at higher temperatures, while an activated charcoal catalyst showed activities only above 800°C. Elemental balance calculations estimate an overall enthalpy of reaction of 2 – 3kJ/g bio-oil, less than 17% of the bio-oil heating value and lower than that of conventional steam-reforming processes. Advantages and future research needs of the aerosol approach for bio-oil/hydrogen conversion are discussed.