Fe catalysis for lignocellulosic biomass conversion to fuels and materials via thermochemical processes

Abstract

Recently, international research is aiming at developing gasification and pyrolysis processes for the cost-effective thermochemical conversion of non-food biomass to biofuels. Gasification produces a mixture of carbon monoxide and hydrogen, known as syngas. Pyrolysis produces a liquid bio-oil. Both syngas and bio-oil can be used directly or can be converted to clean fuels and other valuable chemicals. Catalysis is central to achieving this aim. This study presents results from lignocellulosic biomass pyrolysis, air and steam gasification in the presence of Fe. Noncatalytic and catalytic pyrolysis and gasification experiments were carried out at temperature range of T=500–760°C under an inert helium atmosphere for pyrolysis and at T=750–1050°C with air and steam as the gasification agents for gasification. The effect of temperature (°C), heating rate (°C/min), gasification medium (steam or air), air ratio (λ), steam to biomass ratio (S/B) as well as the catalytic effect of Fe naturally dispersed in the biomass char were studied. The influence of the iron traces originated from the native biomass and ending up in the char residue is mostly studied. Moreover, experiments were performed and results discussed of Fe residues utilization mixed with the bed material to act as catalyst for the conversion of biomass. The results of the performed study showed that olive kernel pyrolytic char is highly reactive comparing to cellulosic biomass char, due to its porous structure, increased surface area and ash content rich in metals. In combination, the presence of metals in olive kernel ash (especially Fe metal) can play an active catalytic role in tar cracking. Additional results have also shown that the addition of Fe residue as in bed catalyst for upgrading non edible residual biomass, favorises the production of H2 rich gas (syngas) due to Fe pronounced catalytic activity.