Influence of the porosity and acidic properties of aluminosilicate catalysts on coke formation during the catalytic pyrolysis of lignin
Hanmin Yang, Tong Han, Weihong Yang, Linda Sandström, Pär G. Jönsson
Abstract
Five aluminosilicate catalysts with different textural and acidic properties are used to study the influence of their acidic and porous properties on the coke formation during the fast catalytic pyrolysis of lignin. The competition between coke formation and target product (hydrocarbons) formation in regard to different pore sizes and Si/Al ratios is classified via performing X-Ray Diffraction (XRD), nitrogen adsorption-desorption, pyrolysis–gas chromatography–mass spectrometry (Py-GCMS), kinetic calculations, and thermogravimetric (TG)/temperature programmed oxidation (TPO) measurements. The results indicated that a pore size consistent with the critical diameters of the pyrolysis products of lignin is a prerequisite for a catalyst to reach a high selectivity for the desired products with less coke formation. A relatively large pore size can cause severe coke formation; however, large pores are favorable for increasing the reaction rate by increasing the diffusion efficiency. A catalyst with sufficient acidity is also essential for high selectivity towards target products.