Influence of NH 3 /CO 2 Modification on the Characteristic of Biochar and the CO 2 Capture
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Influence of NH3/CO2 Modification on the Characteristic of Biochar and the CO2 Capture Zhang Xiong & Zhang Shihong & Yang Haiping & Shi Tao & Chen Yingquan & Chen Hanping
# Springer Science+Business Media New York 2013
Abstract This paper was aimed to study the influence of modification of biochar on the performance of CO2 adsorption. Biochar, obtained from cotton stalk pyrolysis in a fixed bed reactor, was modified with ammonia and CO2. The physicochemical properties of biochars were characterized by the Fourier transform infrared spectroscopy and automatic adsorption equipment (Micromeritics, ASAP 2020, USA). CO2 adsorption of biochar was performed in thermogravimetric analyzer. The results showed that the surface area of char was increased significantly by CO2 modification, while N-contained compound on char surface was enriched obviously by NH3 modification. CO2 adsorption of biochar increased greatly with CO2 and NH3 modification. CO2 adsorption was mainly attributed to physical adsorption at 20 °C, and the adsorption quantity (maximum = 99 mg/g) was proportional to the micropore volume of the char. However, at 120 °C, molecular thermal motion increase, chemical adsorption start to play a dominated role, and the adsorption was directly proportional to the N content of this char. Keywords Biomass char . CO2 activation . NH3 modification . CO2 adsorptions
Introduction Carbon dioxide is the main greenhouse gas; the average concentration of CO2 in the atmosphere is increasing at a Z. Xiong : Z. Shihong : Y. Haiping (*) : S. Tao : C. Yingquan : C. Hanping State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China e-mail: [email protected]
rate of 1.5 % per year [1]. Therefore, the reduction of CO2 emission has become a critical issue. CO2 capture and storage is a major technology to reduce CO2 emission [2–4]. Among various CO2 capture technologies, adsorption is a well-developed technology used in many industrial applications. However, respected to CO2 adsorption, it is necessary to produce easily regenerable and durable adsorbents with a high CO2 adsorption capacity [5–8]. Activated carbons attracted increasing concern as it is cheap, less sensitive to moisture, has high CO2 adsorption capacity at ambient pressure, and the last but not the least it is easy to regenerate [9, 10]. Cotton stalks are a low-cost, relatively abundant agricultural waste, which can be used as a feedstock for the production of activated carbons enriched with the micropore through carbonization followed by activation with CO2 [11, 12]. Some researchers believe that the micropore of the adsorbent plays an important role in CO2 adsorption [4, 5, 8]. However, the adsorption properties of the adsorbent are primarily determined by its micropore structure as well as surface chemistry [13, 14]. Moreover, in the case of high temperature adsorption, the acid gases adsorption of activated carbon is strongly influenced by the surface chemistry [4, 10, 15, 16]. Adib et al. and Bagreev et al. have re
