Benzene removal over a fixed bed of wood char: The effect of pyrolysis temperature and activation with CO2 on the char reactivity

• Activation by CO2 at 800 °C doubled the microporous surface area of spruce wood char.
• Benzene adsorption was increased up to a factor 10 after char activation with CO2.
• Benzene cracking was increased by increasing char surface area above 700 m2/g.
• At 1050 °C the main mode of benzene conversion was homogeneous thermal decomposition.

Benzene removal using spruce wood char as catalyst was investigated. The influence of pyrolysis temperature and activation with CO2 on the char structure and reactivity for benzene adsorption and cracking was analyzed. The structural features of the char were examined by the CO2 adsorption technique and Fourier transform infrared spectroscopy (FTIR). The reactivity for benzene removal was investigated using a fixed bed quartz reactor.Surface analysis showed that the microporous char surface area was influenced by the pyrolysis temperature and was almost doubled by activation with CO2.The benzene adsorption capacity of the char decreased with increasing pyrolysis temperature. Activation with CO2 however, increased the fraction of adsorbed benzene by a factor of two and 10 for char produced at 500 and 800 °C, respectively. The total microporous surface above 700 m2/g was found to be a good indicator for the reactive char surface for benzene cracking at high temperatures. At 1050 °C the main mode of benzene conversion was homogeneous thermal decomposition.We confirmed that wood char has the potential to serve as an effective catalyst for benzene removal. However, benzene decomposed over the charcoal by carbon deposition which led to a fast deactivation of the wood char catalyst.