Chemocatalytic upcycling of a post-consumer paper sludge via ex-situ catalytic pyrolysis using a commercial Pt/Al2O3 catalyst

Paper sludge (PS) is a solid waste generated during wastewater treatment in the papermaking industry. It contains lignocellulosic biomass and minerals, which can be recycled to produce bio-based chemicals and recover circular minerals. This study employed an ex-situ catalytic pyrolysis method, involving pyrolysis followed by catalytic upgrading of the pyrolysis vapor, using a newly developed staged free-fall reactor and a commercial Pt/Al₂O₃ catalyst for the chemocatalytic upcycling of PS. Five reaction-regeneration cycles were carried out to assess the catalytic performance, and particularly the catalyst reusability after regeneration. Morphology, proximate, ultimate, and biomass composition analyses of PS were conducted comprehensively. The qualification and quantification of the pyrolysis products were thoroughly analyzed using GC-TCD, GC-FID, GC×GC-FID, elemental analysis, Karl Fischer (KF) titration, total acid number (TAN), and gel permeation chromatography (GPC). Results show that the yields of hydrocarbons in the gas (C 1 -C 3 ) were increased from 0.8 wt% to 3.5 wt%, and the carbon yields of the oil phase ( e.g ., benzene, toluene, and xylenes, BTX) were significantly increased from 0.39 C.% to 1.84 C.% during the pyrolysis of PS after using the Pt/Al₂O₃ catalyst. Nevertheless, irreversible catalyst deactivation due to degraded catalyst characteristics ( e.g ., particle size, acidity, and surface area) occurred, resulting in a decreased BTX yield of 1.17 C.% after 5 reaction-regeneration cycles.