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Preparation of physical activation of coconut shell -based activated carbon and its pore structure evolution

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Tutor: PengJinHui
School: Kunming University of Science and Technology
Course: Non-ferrous metallurgy
Keywords: Activated Carbon,Heating,Charring,Physical activation,Aperture control
CLC: TQ424.1
Type: PhD thesis
Year:  2010
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Abstract:
As the economy continues to develop, on the one hand is a resource, energy crisis have become increasingly prominent, the other is the deteriorating environment, these are restricting the sustainable development of society. Preparation of activated carbon present in the study mainly biomass and coal as raw materials such as activated carbon. The biomass resources with low cost, renewable characteristics, prepared through carbonization and activation with a well-developed pore structure of activated carbon products, improve its economic value is important. In this thesis, coconut shell activated carbon as raw material for the preparation of studies, examined two heating methods as well as different activators were prepared in both process routes coconut shell-based activated carbon, analyzes the heating mode and the activator type on the pore structure and surface chemistry of activated carbon properties. Realization of renewable biomass resource utilization to meet the energy, environmental protection, efficient social requirements. Using thermal gravimetric analyzer for coconut shell carbonization process is studied on the material at different heating rates pyrolysis characteristics and dynamics analysis, discusses the pyrolysis mechanism of pyrolysis kinetic parameters obtained. The results show that the heating rate on the rate of pyrolysis characteristics and have an impact: By using distributed activation energy model, the activation energy was coconut \law. Systematically investigated coconut shell charcoal carbonization temperature on the yield and properties of analyzed pore structure of carbonized material, microcrystalline structure and surface chemical properties of the material reveals the evolution of carbonization process. Studies show that, with carbonization temperature, the yield of carbonized material decreases, but the ratio of surface area, total pore volume, pore volume increases, the average pore size, pore size distribution moves to a smaller diameter. As the carbonization temperature, carbonization compound increase in the number of graphite crystallites, microcrystalline graphene layers stacked in the thickness Lc, crystallite size La, the graphite sheet layers increases, the average interlayer spacing d002 of graphite crystallites decreases, the its microcrystalline layer between the middle and the arrangement tends to be more structured and orderly. Oxygen-containing functional groups with carbonization temperature is reduced. . Using different heating methods and the activator was investigated activation temperature and activation time on the carbon yield and performance, analyze activated carbon pore structure and surface chemical properties, explores the different heating methods and pore structure of activated carbon under activator The formation mechanism. The results show that both the C02 was activated by steam or microwave heating can be reduced by about 50% of the activation time 100 ~ 150 ¡æ and lower activation temperature. The microwave heating of activated carbon has a higher surface area, total pore volume and micropore volume; in similar yield, the microwave heating of activated carbon has a higher specific surface area; similar surface area, the microwave heating of activated carbon a higher yield. To steam as activating gas, whether conventional heating or microwave heating, the activation process are a simultaneous opening and the reaming process; CO2 as activating agent, in the conventional heating conditions, the activation process for the first reaming the hole after the procedure; when the microwave heating conditions, the activation process is different from conventional heating, compared with an opening and hole processes occurring simultaneously. Microwave heating of the preparation of activated carbon containing functional groups decreased. One-step preparation of activated carbon research, analysis of the heating and activator of activated carbon products on pore structure and surface chemical properties. The results showed that microwave heating of the specific surface area of ??activated carbon than conventional high heat, CO2 activation of the specific surface area of ??activated carbon higher than that of water vapor. With the required activation step is shorter activation time, the activation temperature is lower, the advantages of higher yield. Through systematic study of different carbonization temperature carbonization material impact on the pore structure of activated carbon, high-temperature carbonization and activation process of microwave heating, preparation of high surface area activated carbon, reducing the activation time and improve the yield of activated carbon and pore structure of the samples analyzed and surface chemical properties. The results show that the carbonization temperature on the pore structure of activated carbon and its yield has a significant impact. As the activation time, the carbonized material different carbonization temperature of the activated carbon prepared surface area, total pore volume and micropore volume increased, and the yield are reduced. High-temperature carbonization of the carbonized material of activated carbon surface area, total pore volume and micropore volume lower than the carbonization temperature is high, and yield is low carbonization temperature is high. In the microwave heating, the use of water vapor, CO2 and mixed gas thereof as the activator, can be prepared having a specific surface area of ??2000m2 / g of high surface area activated carbon, activation time is greatly shortened, and higher yield. CO2 activation can be prepared having the largest surface area of ??the activated carbon, and have a more consistent pore size distribution. The activated carbon prepared surface functional groups independent of the type with an activating agent, and the nature of the carbonized material. In summary, this paper examines the heating mode and activator species in both process routes (two-step method and the one-step) prepared under the coconut shell-based activated carbon, analyzed different types of heating methods and the activator activated carbon pore structure and surface chemical properties affected. Through the carbonization temperature on the carbonized material impact on the systematic study and activated carbon by microwave heating, prepared with high specific surface area of ??activated carbon products, greatly reducing the activation time, improved product yield, to achieve energy saving, as Physical methods prepared in a short time high surface area activated carbon provides a new process route.
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