A METHOD FOR NEUTRALIZATION AND STABILIZATION OF BIOMASS PYROLYSIS OILS

摘要

Biomass pyrolysis is the thermal decomposition of biomass that occurs in the absence of added oxygen. It results in solid, liquid, and gaseous products, proportions of which depend on the process temperature, pressure, and residence time of the liberated pyrolysis vapors. Fast pyrolysis that is carried out at moderate temperature (450-550°C), high heating rates (1000°C/s) and short residence times (1-2 s) generates high yield of a liquid product called bio-oil that contains up to 70% of the energy of the biomass feed [1, 2]. Fast- pyrolysis bio-oil currently produced in demonstration and semi- commercial plants has potential as a fuel for stationary power production [3]. However, it requires significant modification in order to become an acceptable transport fuel. Bio-oil is a very complex mixture comprised of many different molecules derived primarily from depolymerization and fragmentation reactions of original biomass building blocks. Therefore, the elemental composition of bio-oil resembles that of biomass rather than that of petroleum oils [4]. The presence of oxygen in many bio-oil components such as water, carboxylic acids, hydroxyaldehydes, hydroxyketones, and phenols is the primary reason for differences in the physical and chemical properties between hydrocarbon fuels and biomass pyrolysis oils. The main consequences are a low energy density (heating value 50% less than conventional fuel oils), a high acidity (pH 2.5), and chemical instability of bio-oil observed as an increase of viscosity and a decrease of volatility with time. Therefore, the efficient elimination of oxygen is necessary to transform bio-oil into a liquid transportation fuel that would be broadly accepted and economically attractive.