Depolymerization of Alcell lignin using Lewis acid catalysts NiCl2 or FeCl3 yielded gas, solid and liquid products including the formation of ether-soluble mono­mers under different reaction conditions. Both catalysts favor condensation reactions leading to insoluble resi­dues. The low yields of organic monomers were domi­nated by phenolics over ketones and aldehydes (Hepditch and Thring, 2000).

Pyrolysis

Pyrolysis of isolated lignins gives a different product distribution than pyrolysis of wood of other lignocellu — losic materials. Lignin pyrolysis occurs in a wider temperature range (e. g. 160—900 °C) compared to poly­saccharides (e. g. 220—400 °C) (Yang et al., 2007). Further­more, the amount of char from isolated lignins is significantly higher compared to whole biomass pyrolysis. Solid acid catalysts such as H-Zeolite Socony Mobil-5 can effectively shift the products toward more deoxygenated compounds. Different isolated lignins py — rolyzed at temperature ranges of 500—800 °C yielded bio-oil, gas and char of 16—70%, 3—39%, and 17—81%, respectively (Azadi et al., 2013). Several researchers showed that inorganic alkaline catalysts such as NaOH can facilitate depolymerization of lignin by pyrolysis and influence the product composition (Amen-Chen et al., 2001).

Recently, an international study of fast pyrolysis of lignin was undertaken with contribution from 14 labora­tories. Based on the results it was concluded that an impure lignin containing up to 50% carbohydrates behaves like whole biomass, while a purified lignin was difficult to process in the fast pyrolysis reactors and produced a much lower amount of a more enriched aromatic bio-oil. It was concluded that for highly pure lignin feedstocks new reactor designs will be required other than the typical fluidized bed fast pyrolysis sys­tems (Nowakowski et al., 2010).

Upgrading of lignin pyrolysis oil by catalytic hydro­deoxygenation (HDO) is often used as described by de Wild et al. (2009). More stable oil due to partial removal of oxygen is an important upgrading property. Bu et al.

(2012) made a review on the catalytic HDO upgrading of lignin-derived phenols from biomass pyrolysis. This study shows that further investigation of HDO is needed to improve catalysts and optimize operation conditions, further understanding of kinetics of complex bio-oils, and availability of sustainable and cost-effective hydrogen sources. Further HDO treatments are dis­cussed in the next session.

Anellotech (2010) has developed a technology plat­form using catalytic pyrolysis for the claimed inexpen­sive production of chemicals and transportation fuels from nonfood biomass. Vispute et al. (2010) claim that all chemical conversions can be performed in one reactor, using an inexpensive catalyst. Target green chemicals are BTX.