以拉曼光譜偵測生質材料的碳化反應

Monitoring the carbonization of biomass using Raman spectroscopy

林瑋庭(WEI-TING LIN)

指導教授 ： 李世琛

中原大學/理學院/化學系/碩士(2022年)

https://doi.org/10.6840/cycu202201276

摘要

本篇研究探討在氮氣環境中利用高溫爐碳化生質材料—纖維素、甲基纖維素、乙基纖維素、支鏈澱粉的過程，我們也在碳化過程中添加硝酸鐵作為催化劑，試圖增加碳化產物的石墨含量。我們以拉曼光譜分析碳化溫度、時間、催化劑對於D band、G band、G' band的強度比值(ID/IG、IG'/I¬G)、位置和線寬的影響。了解生質材料經由高溫處理後的結構變化之外，我們特別分析IG'/I¬G強度比值，因為此比值不但與石墨烯層的堆疊順序有關，也是碳材石墨化的指標。因為ID/IG強度比值與碳質顆粒的石墨化程度成反比，我們根據四種生質材料碳化的溫度所對應之ID/IG比值找到最佳碳化溫度(即ID/IG最小值)，碳化時間設定在1小時，分別為纖維素900 ℃、甲基纖維素900℃、乙基纖維素1000 ℃和支鏈澱粉1000℃。除了改變溫度外，我們還改變碳化時間(1到3小時，每間格0.5小時做一次實驗)以探討四種生質材料碳化的活化能，溫度改變範圍從600℃到1000℃，依不同生質材料而有所調整。以Arrhenius equation計算得到四種生質材料碳化反應的活化能均為負值，因為生質材料的碳化繁瑣，涉及多道反應速率以及平衡係數不同的反應，包含脫水、產生CO及CO2以及C-H、C-C、C=C鍵重組等，即使每步反應的活化能都是正值，但是多道反應的過渡狀態彼此之間的能量高低落差可能使整體反應的活化能為負值，詳細之結果將於論文中討論。

關鍵字

拉曼光譜 ； 生質材料 ； 碳化反應

並列摘要

The carbonization process of biomass materials (cellulose, methyl cellulose, ethyl cellulose and amylopectin) in a tubular furnace under nitrogen flow is discussed in this study. During carbonization, ferric nitrate was added as a catalyst to increase the graphitic content in the carbonization product. The effects of carbonization temperature, time and catalyst on intensity ratios (ID/IG, IG'/IG), positions and linewidths of D band, G band and G' band were analyzed on the basis of Raman spectra. In addition to the structural changes of biomass materials after high temperature treatment, the IG'/IG intensity ratio, which is not only related to the stacking order of graphene layers but also an indicator of the degree of graphitization of carbon materials, was investigated in particular. Since the ID/IG intensity ratio is inversely proportional to the graphitization degree of carbonaceous particles, the optimized temperature was determined based on the ID/IG intensity ratio (i.e., minimum ID/IG) corresponding to the carbonization temperatures of four different biomass materials (cellulose = 900℃, methyl cellulose = 900℃, ethyl cellulose = 1000℃ and amylopectin = 1000℃). The carbonization time was set to be 1 h. Besides the temperature, carbonization time was tuned (1-3 h, a test was executed at an interval of 0.5 h) to investigate the activation energy of four different biomass materials. The temperature range was 600-1000℃, depending on the specific biomass material. According to Arrhenius equation, the activation energies calculated from the carbonization reactions of all the four biomass materials were negative. This can be attributed to the fact that carbonization of biomass materials is a complicated process involving multiple reactions with different reaction rates and equilibrium coefficients, including dehydration, generation of CO and CO2 (decarboxylation) and rearrangement of C-H, C-C, C=C. Even if the activation energy of each reaction is positive, the activation energy of transition state may lead to negative activation energy of the overall reaction. Detailed results will be discussed in this thesis.

並列關鍵字

Raman spectroscopy ； biomass ； carbonization

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