Streamlined physical activation of Pistacia terebinthus shells: carbonization and activation kinetic studies

Abstract

This study examines the physical activation of Pistacia terebinthus shells—an underutilized biomass—using CO₂ and H₂O, highlighting a single-reactor, energy-efficient process that eliminates intermediate cooling and reheating, reducing energy consumption by ∼30 %. Activation temperature (700–900 °C), carbonization temperature (300–500 °C), and activating agent concentration (volume ratio of activating gas to inert carrier, 1:4 to 4:1) were optimized for porosity and yield. Steam activation at 800 °C (H₂O:N₂ = 1:1) produced the highest surface area (1173 m²/g) and mesoporosity (70 %), outperforming CO₂ activation, which favored microporosity. Carbonization kinetics, modeled using the Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods, exhibited a two-phase activation energy trend over the conversion range of 0.10–0.45. Activation kinetics followed a zero-order model, with H₂O exhibiting a lower activation energy (64.8 kJ/mol) than CO₂ (117.2 kJ/mol), indicating higher reactivity.