Study of Thermochemical Transformations of Bast of Birch Bark, Structure and Properties of the Produced Porous Carbon Materials

Abstract

The porous structure and sorption properties of carbon materials produced by thermochemical activation of the bast of birch bark with potassium hydroxide at 800°C have been studied. The effect of the amount of introduced KOH on the specific surface area of carbon materials obtained from bast was established. The selection of the optimal conditions for the preliminary carbonization of the bast was carried out, providing after thermal activation with KOH the formation of porous carbon materials with a specific surface of up to 2469 m2 g–1, a total pore volume of up to 1.085 cm3 g–1, a micropore volume of up to 0.84 cm3 g–1, and an average size pores less than 2.0 nm. It is shown that preliminary carbonization of bast at 500–580°С and subsequent activation with KOH at 800°С shifts the pore distribution in the resulting carbon materials towards smaller sizes (0.5–1.0 nm). It was found that carbon materials produced from heat-treated birch bast have a sorption activity for benzene, which exceeds the performance of foreign industrial carbon sorbents by 2.4 times and domestic active carbons of SKT-3 and SKT-10 grades by 3.4 times. Pre-carbonization of birch bast increases the yield of porous carbon materials by a factor of 3–4 compared to their yield when using untreated bast.