Depolymerization of acetosolv lignin through in-situ catalytic fast pyrolysis

CARRIER, M.; MULLER, N.; GRANDON, H.; SEGURA, C.; WILKOMIRSKY, I.; BERG, A.:
Revista de la Facultad de Ciencias Químicas de la Universidad de Cuenca, Ecuador, 10, 61-66, diciembre (2014).

Abstract

The valorisation of secondary streams such as Acetosolv lignin is a key issue in the development of lignocellulosic biorefineries. Fast pyrolysis, a thermochemical process that converts biomass into a liquid product, is currently of particular interest for chemicalproduction. However, conventionalfast pyrolysisof lignin presents feeding problems, due to their low fusion point, bed agglomeration and low yield of highly oxygenated liquids. In this work, we investigated the catalytic effect of co-feeding CaO and the use of olivine as bed material to overcome these hurdles.

A laboratory fast pyrolysis system with a feed capacity of 0.1 kg/h was used to depolymerize pine sawdust and its Acetosolv lignin at 540 ºC. An in-depth characterization of the tarry phase using solid and liquid- state nuclear magnetic resonance provided a more detailed structural information of the pyrolytic liquid products over conventional characterization techniques. Main results showed that the addition of CaO improved the feeding of lignin into the pyrolytic reactor, while an increase in liquid yield was observed in the presence of olivine. The combined use of CaO and olivine appeared to be the most beneficial, as it displayed the highest liquid yield, despite of the lack of reproducibility. Compared to quartz sand, the use of olivine alone decreased the liquid yield and increased the total amount of aliphatics in the tarry phase at the expense of aromatics. By displaying a high aliphatic content, the composition of liquid product revealed the efficient depolymerization of lignin. It is also important to note that the presence of olivine promoted the deoxygenation of the overall liquid. The catalytic activity of olivine was attributed to the presence of iron, known as a tar destruction agent in gasification.

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