Cross-polymerization between bio-oil and polyaniline: synergistic effects on pore development in subsequent activation and adsorption of phenol†

Abstract

Bio-oil is a major product from pyrolysis of biomass which serves as a carbon source to produce carbon material due to its high reactivity towards polymerization itself or cross-polymerization with other organic feedstocks. In this study, activation of polyaniline (PANI) mixed with wheat straw-derived bio-oil and K₂C₂O₄ at 800 °C was conducted, aiming to understand the effect of potential interactions of bio-oil with PANI on pore development of resulting activated carbon (AC). The results revealed cross-polymerization reactions between PANI and bio-oil during direct activation, which increased the yield of AC from 13.0% (calculated average) to 15.0%, the specific surface area from 1677.9 m² g⁻¹ (calculated average) to 1771.3 m² g⁻¹, and the percentage of micropores from 94.3% to 97.1%. In addition, pre-polymerization of PANI and bio-oil at 200 °C before activation was also conducted. Such pretreatment could increase the AC yield from 13.0% to 23.3%, but the specific surface area decreased to 1381.8 m² g⁻¹. The pre-polymerization formed the organics that were more resistant towards cracking/gasification, but introduced oxygen-rich functionalities. This made AC highly hydrophilic, rendering a much higher capability for adsorption of phenol despite the smaller specific surface area. Additionally, the AC with developed pore structures facilitated dispersion of nickel in Ni/AC and enhanced the catalytic activity for hydrogenation of o-chloronitrobenzene and vanillin.

Keywords: Polyaniline; Bio-oil; Activation; Activated carbon; Pre-polymerization; Adsorption.