Study on the pyrolysis products of two different hardwood lignins in the presence of NiO contained-zeolites

Several NiO contained-zeolites (NiO/H-ZSM-5, NiO/H-BETA and NiO/H-Y) prepared by a mechanochemical dry milling (MCDM) were tested in the pyrolysis of two hardwood lignins: Eucalyptus (EUC) and a mixture of birch and aspen woods (BA). All prepared catalysts increased the yield of aromatics and decreased the yield of oxygenates as compared to non-catalytic experiment. The catalytic activity depends on the lignin type and zeolite structural features. The highest liquid and gas yields and lowest coke yield was obtained with NiO/H-Y which also increased the amounts of desirable and decreased undesirable pyrolysis products, giving a high concentration of hydrogen in the gaseous phase. The highest yield of aromatics and the lowest yield of oxygenates was obtained with NiO/H-ZSM-5. The obtained results showed that BA is a more suitable feedstock, producing higher yields of liquids and aromatics and lower yields of coke and oxygenates.