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Keywords:

  • biomass;
  • deactivation;
  • lignin;
  • pyrolysis;
  • zeolites

Abstract

Catalytic fast pyrolysis of alkaline lignin over H-USY zeolites uniquely yields a high fraction of aromatics but only very small amounts of tar and char. This study focused on the deactivation and regeneration of the H-USY zeolite. N2 physisorption, thermogravimetric analysis (TGA), temperature-programmed desorption of NH3, and 27Al MAS NMR analysis were used to determine coking, pore topology, and the number of acid sites of the deactivated and regenerated H-USY catalyst. Deactivation occurred mainly owing to coke deposition on the catalyst. Both pore blockage and active site poisoning were observed during deactivation. The coke was removed through calcination of the deactivated catalysts in air at high temperature. Calcination restored the high porosity and the acid sites to a large extent. Even better catalytic performance was obtained after the reintroduction of protons through an ion-exchange step. Recovery of catalytic properties was high but incomplete, because of structural changes in the catalyst during the reaction–regeneration process.