【作者】 苏伟；

【导师】 周理；

【作者基本信息】 天津大学 ， 化学工程， 2003， 博士

【摘要】 椰壳具有优良的天然结构，是制备活性炭的好材料。本文研究以椰壳为原材料，制备微孔活性炭的有效方法。首先采用一种无活化剂方法制备微孔活性炭。在椰壳热解过程中，突然节流膨胀，依靠气流冲击作用改善椰壳组织结构、促进活性炭微孔的形成与发展。实验表明，选用适宜制备条件可以使活性炭比表面积达到500m2/g，并且孔径均一。在椰壳热解过程中，加入低浓度氧气氧化，同样可以促进活性炭微孔形成，活性炭比表面积可超过700m2/g，孔径分布很窄，平均孔径小于1nm。氧化时间、氧化温度和氧气浓度是影响活性炭性能的三个主要因素。以越南进口椰壳炭化料为原材料，分别采用KOH、水蒸气和一种复合型活化剂来制备活性炭。研究表明，以水蒸气为活化剂时，可以在一两个小时活化时间内，使活性炭比表面积达到1500m2/g，继续活化，比表面积则很难有进一步提高。采用KOH活化可以得到高比表面积活性炭，活化时间、活化温度、碱碳混合比例和碱碳混合方式是影响活性炭性能的主要因素。复合型活化制备工艺简单、无污染，与二氧化碳活化相比，其活化时间大大缩短。中试规模研究证实了这种方法的可行性。选用几种有代表性活性炭，利用吸附数据表征其比表面积和孔径分布。结果表明，BET法可以计算一些较大尺寸微孔活性炭的比表面积；DRK法也可以估算微孔活性炭比表面积，但是仍有较大局限性。提出了一种简单、有效的孔径分布计算方法。与D. Cazorla-Amoros计算孔径分布方法相比，该方法有了较大改进，主要表现在选取的局部等温线更为合理、准确；考虑了吸附相密度在孔内分布；能够计算出过剩吸附量，可以直接拟合实验数据。本研究中制备出的高比表面积活性炭对甲烷具有较强的吸附能力，而在常温下，对氢气的吸附量较低。活性炭对甲烷和氢气的吸附不仅受孔体积影响，还与其孔径分布密切相关。更多还原

【Abstract】 Coconut shell is suitable for preparing microporous activated carbons due to its excellent natural structure and low ash content. Various methods have been used to produce microporous activated carbon from it.A new method of preparing microporous activated carbon from coconut shell without using any activating agent was presented. In this method, the produced activated carbon has a very narrow pore size distribution, and the surface area is larger than 500m2/g.In another process of producing microporous activated carbon, coconut shell was oxygenated at 350~850℃ for several hours, then heated in inert environment to 850℃. By this procedure, activated carbons with surface area above 700m2/g are manufactured, and the average pore size of the carbon is smaller than 1nm. The effect of process variables such as oxygenation temperature, oxygenation time and oxygen concentration was studied in order to optimize those preparation parameters. A series of activated carbons were prepared from coconut shell by the activation with steam, KOH and a mixture of activating agents. It is difficult to get the carbon of high surface area with steam as an activation agent. Activated carbons with high surface area can be obtained with KOH as activation agent. Activation time, activation temperature and impregnation ratio are three important parameters that have significant effect on pore volume evolution. Under experimental circumstances, the optimum conditions in preparation carbons with high surface area are identified. Comparing with the activation by CO2, the activation time has been decreased effectively during the process activated by a mixture of activating agents, which also has been verified in a bench scale equipment.Adsorption of N2 at 77K and CO2 at 273.15K and pore size distribution have been studied for activated carbons made of different methods. The BET and DRK methods are used to calculate the surface area of carbon samples. A simple new method of calculating pore size distribution has been developed. In this method, local isotherms were calculated from the SLD theory, which can reasonably describe the adsorption mechanism in pores of different sizes. Comparing to the D. Cazorla-Amoros’ method, the method gives more reasonable result.Adsorption of CH4 and H2 at 298.15K has been measured in activated carbons <WP=4>of high surface area. It shows that the adsorption capacity of carbon is determined basically by its pore volume and pore size distribution.更多还原