Pore Development During CO2 and Steam Activation of a Spent Tyre Pyrolysis Char

The activation of a spent tyre pyrolysis char using CO2 and steam was experimentally investigated, focusing on the pore development of the char during activation. The pyrolysis char, produced in an industrial scale retort process, was ground and sieved to a particle size fraction < 150 mu m, and activated in a fixed bed reactor under CO2 and steam, respectively. The effect of temperature (750 to 1050 degrees C), reaction time (0.5 to 4 h for steam activation, 1 to 6 h for CO2 activation) and activation agent concentration (33.3 to 66.7 vol% of CO2 or steam in N-2) on the carbon conversion and reaction rate was measured. The activated chars were characterised for the BET surface area, pore volume and average pore size of the activated chars using N-2 adsorption and morphology using SEM. Higher temperature and activation agent concentration, and longer reaction time led to higher carbon conversion. As the carbon conversion increased, the BET surface area initially increased linearly and then decreased, reaching a maximum surface area of 666.6 m(2) g(-1) (0.60 conversion) for steam and 434.5 m(2) g(-1) (0.52 conversion) for CO2. Micropores were created in the early stage of activation, increasing first until carbon conversion reaching ca. 0.30. Steam-activated chars showed higher BET surface areas than CO2-activated chars at the same carbon conversion. Steam was found to generate both greater microporosity and mesoporosity than CO2.

Automated summary

The experimental study focused on the activation of spent tyre pyrolysis char using CO2 and steam, with results showing that higher temperature, activation agent concentration, and longer reaction time can lead to higher carbon conversion and surface area. Micropores were created in the early stage of activation, with steam-activated chars exhibiting higher BET surface areas and more pores compared to CO2-activated chars.