Abstract
In this study the catalytic activity of Na-rich and MO-containing natural clinoptilolite (MO – nanoparticles of NiO, ZnO, or Cu2O) was studied in the pyrolysis of hardwood lignin. The clinoptilolite samples exhibit different catalytic activities which depend mainly on the type of the nano-oxide. The presence of nano-oxides did not affect the porosity of the clinoptilolite framework but influenced its acidity. However, it seems that acidity of the lattice did not influence the catalytic activity of the clinoptilolite in the pyrolisis of hardwood lignin. The number of Lewis acid sites increased significantly for the ZnO- and Cu2O-containing clinoptilolite whereas for the NiO-sample it did not change appreciably in comparison to the parent zeolite. The amount of phenols in the as-produced bio-oil varies from 39% for ZnO-clinoptilolite, 43% for Na-rich clinoptilolite, to 50 and 54% for Cu2O- and NiO-containing samples, respectively. The highest yield of phenols obtained in the presence of NiO-containing clinoptilolite is ascribed to a synergetic interaction of the clinoptilolite lattice and nano-NiO particles.