The Adsorption Performance For Cellulosic Ethanol/Water Separation On Bamboo-based Carbon Materials

Biomass ethanol, a kind of clean and renewable energy, has become an important energy supplement in many countries. The "Fuel Ethanol" program is strongly being carried out in China, which gives a good opportunity for the development of bioethanol. However, bioethanol considered as directly application and the most important part of biomass energy system, has its drawbacks on low biomass conversion rate and high energy consumption in ethanol separation and purification process. Ehanol/water separation via adsorption technology, one of the non-phase separation technologies, is considered as an alternative process due to its low energy consumption.The preparation and application of adsorbent is the core of the adsorption separation technology. In this study, moso bamboos were selected as raw materials to synthesis a bamboo-based carbon materials for the purpose of application on ethanol/water separation process. The pore size and surface functional groups of the carbon materials were controlled through carbonization, activation and chemical vapor deposition ?CVD? technologies. The adsorption and separation performance toward ethanol/water mixtures on the prepared carbon materials were investigated. Moreover, a fixed-bed adsorption system was established to achieve the dynamic adsorption and separation of ethanol/water mixtures.Firstly, CO₂ was used as an activating agent, a bamboo-based activated carbon ?BAC? was prepared via optimized one-step carbonization-activation process. The result shows that the BET surface area and the micropore volume of the BAC850-80-300 obtained by CO₂ activation ?300 ml/min? at 850? for 80 min are 725.2 m2/g and 0.2967 cm3/g, respectively. The pore size distribution of the carbon material is mainly between 0.5?0.8 nm. The result of the batch adsorption experiment shows that the separation efficiency for ethanol/water solution on BAC850-80-300 is as high as 94.5%.Secondly, a porosity bamboo-based activated carbon was fabricated with ZnCl₂ activating. N2 adsorption-desorption experiment result shows that the BET surface area, total pore volume of the obtained activated carbons are 1596.3 m2/g and 0.7743 cm3/g, respectively. The pore size and pore distribution of zinc chloride-activated carbon was than tailored by chemical vapor deposition ?CVD? method, to obtained a bamboo-based carbon molecular sieve ?BCMS?, using methane as a carbon source.The result shows that the BET surface area, total pore volume of the BCMS800-70-30 obtained by CH4 deposition ?30 ml/min? at 800? for 70 min are of 736.1 m2/g and 0.3598 cm3/g, respectively. The pore size distribution of the BCMS800-70-30 is mainly between 0.4?0.6 nm. The result of the batch adsorption experiment shows that the separation efficiency for ethanol/water solution on BCMS800-70-30 is as high as 98.5%.Finally, a dynamic adsorption-desorption device for bio-ethanol/water mixtures separation was set up with the self-designed fixed-bed adsorption column to realize the on-line fermentation production and synchronous adsorption/desorption of bioethanol. The performance of the system was evaluated by the prepared bamboo-based carbon materials ?BCMS800-70-30?. The result shows that, on the designed device, the adsorption capacity of BCMS800-70-30 toward a 0.5 wt% ethanol solution is as high as 0.174 mg/g, indicating that the designed device is suitable for practical application in the separation and purification of bio-ethanol.