Activated Carbon Preparation from Lignin by H₃PO₄ Activation and Its Application to Gas Separation

Abstract

Activated carbons were produced from corn straw lignin using H 3 PO 4 as activating agent. The optimal activation temperature for producing the largest BET specific surface area and pore volume of carbon was 500°C. The maximum BET specific surface area and pore volume of the resulting carbon were 820 m 2 g -1 and 0.8 cm 3 g -1, respectively. The adsorption isotherm model based on the Toth equation together with the Peng-Robinson equation of state for the determination of gas phase fugacity provide a satisfactory representation of high pressure CO 2 , CH 4 and N 2 adsorption. The kinetic adsorption results show that the breakthrough difference between CO 2 and CH 4 is not obvious, indicating that its kinetic separation performance is limited.

Controlling Synthesis of Polymer-Derived Carbon Molecular Sieve and Its Performance for CO2/CH4 Separation

“…In this work, the adsorption enthalpies of CH4 and CO2 on CMS-2 are in between 10 to 50 kJ mol -1 which are in agreement to the typical adsorptive behaviours of these gases on the porous adsorbent, such as activated carbons [24,29,30] and zeolites [2,34]. These values of heat of adsorption imply isosteric enthalpies of physic sorption and these low heat values featured by CMS-2 when adsorbing gases are helpful to prevent the reduction of adsorptive amount when performing an adiabatic operation.…”

“…Table 4 shows the obtained apparent diffusivity for CH4 and CO2 in the CMS-2 evaluated with the adsorption kinetics model. The ranges of values are 7-17×10 -7 and 1-2.75×10 -7 m 2 /s when using CH4 and CO2 as adsorbates, respectively at studied temperature between 293 and 323 K. These apparent diffusivity values are in the same order magnitude with the typical diffusivity constant obtained from literatures [24,29,35]. The higher temperature leads to more movable molecules, thus showing lower apparent diffusivity.…”

“…But these values are superior to those values of porous carbons based on natural carbonaceous matters which are typically ca. 1000 m 2 /g (see Table 2, for the specific surface area comparison) [28][29][30]. Hence, a high quality of porous carbons results by the carbonization of phenol and or para-tert-butyl phenol resin.…”

“…This concludes the molecular sieving characters of CMS-2 which are useful for the CO2/CH4 separation. Table 2 shows comparison of the uptake capacity of different molecular sieves such as natural polymer-derived activated carbon (activated carbon (AC) and microwave activated carbon (MAC)), synthetic polymer based carbon (ordered mesoporous carbon (OMC)] and Ajax commercial carbon [24,[27][28][29][30]. It can be clearly seen that CMS-2 features relatively high adsorption capacities of CO2 and CH4, thus high performance results.…”

Preparation of Different Carbon Materials by Thermochemical Conversion of Lignin

“…On the other hand, and being more related to the potential applications of these materials, Sun et al (2012) used an AC prepared from lignin by H 3 PO 4 activation, at 500°C and R = 2, as molecular sieve. However, despite the AC provided a satisfactory representation of high pressure CO 2 , CH 4 , and N 2 adsorption, the separation kinetic between CO 2 and CH 4 was quite limited.…”