Activated Carbons Derived from High-Temperature Pyrolysis of Lignocellulosic Biomass

Abstract

Biomass pyrolysis to produce biofuel and hydrogen yields large amounts of charred byproducts with low commercial value. A study was conducted to evaluate their potential for being converted into higher value activated carbons by a low-cost process. Six chars derived from various lignocellulosic precursors were activated in CO2 at 800 °C to 30–35% weight loss, and their surface area and porosity were characterized by nitrogen adsorption at 77 K. It was found that, in similar activation conditions, the surface area of the activated carbons correlates with the activation energy of the oxidation reaction by CO2, which in turn varies inversely with the carbon yield after thermolysis in nitrogen at 1000 °C. Since lignin is the most thermally-stable component of lignocellulosic biomass, these results demonstrate, indirectly, that robust, lignin-rich vegetal precursors are to be preferred to produce higher quality activated carbons. The chars derived from white pine (pinus strobus) and chestnut oak (quercus prinus) were converted to activated carbons with the highest surface area (900–1100 m2/g) and largest mesopores volume (0.85–1.06 cm3/g). These activated carbons have properties similar to those of commercially-available activated carbons used successfully for removal of pollutants from aqueous solutions.

Comparative Study of Toluene and Hexane Adsorption on Activated Carbons From Gas and Liquid Phase. Enthalpy and Isotherms

“…It can be seen that the immersion enthalpies increased with basicity and decrease with the total acidity of the samples, this occurred because according to other investigations the electron density of the adsorbent depended on its type of surface chemistry: electron withdrawing groups (like oxygen surface groups) reduced the adsorptive potential of the material whereas donating functional groups favored the electron density and then the adsorptive potential of the carbonaceous solid Montes-Morán et al, 2012;Rubahamya et al, 2019). This is why enthalpies for CS were lower than for CST, since CS contained higher concentration of acidic oxygen groups, which reduced the electron density and the potential adsorptive of activated carbon, as well as the adsorption affinity by ππ interactions (Goto et al, 2015), generating less adsorbate-adsorbent interaction, mainly with toluene; the opposite occurred with CST since when it was subjected to high temperature, electron withdrawing groups were removed and at the same time the concentration of aromatic rings in the solid structure was intensified (Contescu et al, 2018), increasing its electron density and therefore, the intensity of the interaction adsorbent-adsorbate was higher.…”

Chestnut-Derived Activated Carbon as a Prospective Material for Energy Storage

“…For chemical activation, the biochar sample was mixed with solid KOH with a mass ratio of 1:3 and ground by mortar. The amount of an activating agent was selected based on literature reports [ 44 , 45 ] where the dependence of the KOH amount on the surface area of activated carbon was described. The activation process took place in a quartz tube inside the horizontal ceramic furnace, under controlled nitrogen flow (flow rate of 50 mL min −1 ) and temperature (800 °C for 1 h, the heating rate of 10 °C min −1 ).…”

Sustainable Carbon as Efficient Support for Metal-Based Nanocatalyst: Applications in Energy Harvesting and Storage

“…These methods give rise to low-cost carbon-based materials, require lower operation temperatures, and in addition, these processes are more environmentally friendly than those previously reported. Furthermore, precursors employed are from natural origin without the need of toxic chemical compounds [ 8 , 9 , 10 ].…”