Preparation And Application Of High Performance Rayon-based Activated Carbon Fibers

Activated carbon fiber (ACF) is a highly efficient carbonaceous adsorbent which was developed and industrialized gradually followed the powdery and granular activated carbon. Superior characteristics of activated carbon fiber are as followed:larger adsorption capacity, quick adsorption/desorption rate, rapid regeneration and so on. Rayon-based ACF is one of the activated carbon fiber used and researched widely because of its wide raw material sources, renewable and mature process. But its application is limited by the characteristics of low yield, small intensity.In the paper, the formula of dipping solution, the process conditions of carbonization and activation, the stretching rate, the pretreatment of rayon fibers and so on, which influenced yield coefficient and mechanical properties of rayon-based activated carbon fiber was investigated for the purpose of the low yield and small intensity with rayon fibers as raw materials. At the same time, testing rayon-based ACF adsorption performance and recycling capability to CH3Br gas with dynamic adsorption method in the25°C, pore structure of the activated carbon fiber were characterized. Moreover, the effect of activated carbon fiber pore structure, carrier gas flow rate, CH3Br concentration in the waste gas and recycling times on the adsorption capacity were systematically discussed. The results and achievements were summarized as follows:(1) Inorganic salt dipping solution significantly affect the pyrolysis mechanism of rayon fibers, promote reaction in the dehydration, reduce pyrolysis reaction temperature, inhibit the generation of tar, and improve the carbonized yield; Organic dipping agents can improve mechanical properties of activated carbon fiber,but can’t improve carbon yield. Organic/Inorganic salt complex dipping solution could give full play to advantages of different dipping agents. The optimum dipping solution formula of rayon fibers was as followed:mass concentration of5%organic impregnant+mass concentration of7%B/C=1:1inorganic salt compound of impregnant. The optimum carbonization process was as followed:the carbonization is900°C,the best pyrolysis heating rate is from room temperature to150°C at the rate of4°C/min, from150°C heating up to400°C at the rate of l°C/min, from400°C heating up to900°C at the rate of4°C/min, the best stretching rate is12%; The best activation technology:activation temperature is900°C, time has20min,Rayon-based fiber should be washed30min and dried2hour before the preparation of RACF.(2) Rayon-based ACF shows different adsorption ability, because they have different pore structures with specific surface area and pore sizes. Due to the greater specific surface area and the more developed microporous structure with the pore size of0.4nm to0.8nm, activated carbon fiber used in CH3Br adsorption ability is stronger, but the breakthrough and saturated adsorption time is shorter. With gas flow rate increasing, the adsorption capacity of CH3Br on ACF reduces obviously, while the adsorption quantity and capacity are reduced significantly. Activated carbon fiber has the outstanding recycled and reused performance. Disposing CH3Br waste gas is feasible, the adsorption quantity of activated carbon fiber is obviously reduced in recycling process. The breakthrough adsorption quantity of activated carbon fiber reaches the steady value as133.5mg/g and the initial adsorption of36.9%.