水熱碳化之蔗糖以氫氧化鉀活化製備活性碳及其性質 Hydrothermal carbonized sucrose as precursors for activated carbon; preparation and properties

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Title:	水熱碳化之蔗糖以氫氧化鉀活化製備活性碳及其性質 Hydrothermal carbonized sucrose as precursors for activated carbon;preparation and properties
Authors:	許嘉鴻;Chia-Hung Hsu
Contributors:	化學工程與材料工程研究所
Keywords:	比表面積;氫氧化鉀;活性碳;activated carbon;potassium hydroxide;specific surface
Date:	2009-07-24
Issue Date:	2009-09-21 12:31:44 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本研究以蔗糖為原料，採用了水熱碳化法(Hydrothermal carbonization, HTC)先製作出大小介於次微米到數十微米之含碳粒子或粒子團聚物，然後直接將水熱產物(或再經絕氧碳化後)用氫氧化鉀進行高溫化學活化，製作高比表面積的活性碳。研究目標以達到大於3000 m2/g的商業化高表面積活性碳水準(AX-21)，且孔徑分佈以微孔(<1 nm)及超微孔（1~2 nm）為主的活性碳。實驗探討於水熱時是否添加碳酸氫銨、是否需要將水熱產物絕氧碳化及碳化溫度、活化溫度、活化劑比例、活化劑浸泡方法等因素，並將不同條件製備之前驅物及活性碳產物進行分析。主要分析對象為活性碳產率(Yield)、表面官能基(FTIR)、結晶性(XRD)、表面形態(SEM)、比表面積及孔徑分佈(ASAP)、微量金屬元素(ICP-AES)、碘吸附等。經過上述研究，發現以添加碳酸氫銨、再以450 ℃絕氧碳化之產物進行活化，以氫氧化鉀/炭化物比例為4將炭化產物與氫氧化鉀溶液混合浸泡60分鐘後烘乾，然後進行800 ℃、60分鐘活化之條件所製作之產物相對較好。可獲得比表面積3280 m2/g、總孔洞體積、微孔體積1.34 cm3/g、微孔及超微孔佔孔體積比例88.4 %、平均孔徑1.85 nm的活性碳，產率為10.3 wt%。但是此產物仍含有約3.8 wt%之鉀元素，而且碘吸附量並沒有AX-21高。所以可能將活化時間延長或在活化升溫時在400 ℃持溫一段時間使氫氧化鉀能更均勻接觸反應面積，或許可以得到孔徑較均一且約1~2 nm的活性碳產物。 The objective of this research is to achieve a high specific surface area (>3000 m2/g) that was observed in some commercial activated carbons, and at the same time able to modify the distribution of micropores and super-micropores. The biomass-sucrose was chosen as the raw material for activated carbon in this research. The precursor was made by the hydrothermal carbonization of sucrose into sub-micron to tens of micron carbonaceous particles or their aggregates. The precursor was then directly chemically activated with KOH at high temperature in tubular furnace, or activated after further carbonization in dry nitrogen. Activated carbon powders with very high specific surface area were obtained. The following operation variables were also studied; (1) the benefit of adding ammonium bicarbonates during the hydrothermal carbonization step. (2) The necessity of dry carbonization after the hydrothermal step and the proper temperature for such step. (3) The activation temperature, the soaking method and the amount of KOH activator used. The products were analyzed with FTIR, SEM, XRD, ASAP, ICP-AES and iodine adsorption. We conclude that the proper process steps for producing high specific surface area activated carbon at high yield were (1) hydrothermal carbonization with the addition of ammonium bicarbonates, (2) dry carbonization at 450 °C, and (3) Chemical activation at 800 °C with KOH/C ratio of 4. The yield of our best activated carbon was 10.3 wt%, based on the amount of sucrose employed. The total pore volume was 1.517 cm3/g, and the specific surface area reached 3280 m2/g. 88.4% of the pore volume was contributed by micropores and the average pore size was 1.84 nm. The only problem was the incomplete removal of KOH, which amounted to 3.8 wt% of potassium in the final product. Therefore, although our product had a higher specific surface area than the commercial AX-21 sample, the iodine number was lower. We believe that by increasing the activation time or holding the activation temperature at 400 °C for 2 hours, such problems may be resolved.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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