Development and characterization of activated carbon derived from bacterial cellulose (Year 2)

Abstract

Bacterial cellulose (BC) was investigated as a novel material for preparing activated carbons. BC was dried by heating and it was carbonized with a chemical activation process using phosphoric acid (H₃PO₄) as an activating agent at different temperatures (400, 500 and 600 °C). The properties of the activated carbons were characterized such as chemical property, structure, pore size, thermal property by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), N₂ -physisorption (BET), scanning electron microscopy (SEM) , thermal gravimetric (TGA). The obtained BC activated carbons at carbonization temperature of 500 °C (BC-AC500) showed maximum BET surface area (1,734 m²/g) with mesoporous structure (2.33 nm) and large pore volume (1.01 cm³/g). The adsorption capacity was evaluated by using as adsorbent for the adsorption of methylene blue (MB). The equilibrium adsorption data were analyzed by the Langmuir, Freundlich, and Redlich-Peterson isotherm models. The results showed that the Redlich-Peterson model was found to be most fitted to the equilibrium data with correlation coefficient (R2) value of 1.000. The maximum adsorption capacity (qm) was 505.8 mg/g. The experimental results indicated that the BC activated carbon has the potential to be used as an effective adsorbent. A novel catalyst of Al/BC was developed by soaking purified BC hydrogel in aluminum nitrate aqueous solution, dehydration and calcination. The high yield of diethyl ether at ~ 42 % can be produced from ethanol at 200 °C with the selectivity of almost 100% by using Al/BC as catalyst in ethanol dehydration. On the other hand, BC activated carbon, BC-AC500 is modified with various loading of H₃PO₄ and applied as acid catalyst in the ethanol dehydration reaction at the temperature from 200-400 °C. An increase in the H₃PO₄ loading from 5% to 40% increased the number of weak acid sites on the catalyst surface, which consequently enhanced ethanol conversion. At a reaction temperature of 400 °C, the modified BC-AC500 with 30-40% H₃PO₄ loading (P/BC-AC) gave ethanol conversion at 100%, with ethylene selectivity of 100%, whereas high selectivity for DEE at 66%-68%, at ethanol conversion of 49%-51% was obtained at 200 °C. Stability tests with a time-on-stream of 12 h, at reaction temperatures of 200 and 400 °C showed that the P/BC-AC catalyst had high thermal stability and stable catalytic activity. Therefore, P/BC-AC was found to be very effective as an inexpensive and environmentally friendly catalyst for ethylene production from ethanol dehydration.