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研究生:劉柏宏
研究生(外文):Po-Hong Liu
論文名稱:以雙重阻力模式探討晶體成長的動力學
論文名稱(外文):Studies of crystal growth kinetics using the two-step model
指導教授:蕭立鼎
指導教授(外文):Lie-Ding Shiau
學位類別:碩士
校院名稱:長庚大學
系所名稱:化學工程研究所
學門:工程學門
學類:化學工程學類
論文種類:學術論文
論文出版年:2001
畢業學年度:89
語文別:中文
論文頁數:80
中文關鍵詞:雙重阻力模式接觸成核蔗糖晶體
外文關鍵詞:two-step modelcontact nucleationsucrose crystal
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本實驗將進行流動式顯微照相實驗,以顯微照相的方式來觀察溶液流動時蔗糖晶體的成長。實驗中將改變晶體的過飽和度、溫度、流速、雜質的加入,採取接觸成核(contact nucleation)的方式,使其產生許多細小的晶種,然後再觀察其成長,並以雙重阻力晶體成長模式(two-step model)為理論基礎,來求出該程序溶液中的質傳係數(kd),晶面整合反應係數(Kr)等參數並分析其成長機制。
從實驗中可以發現,當活化能Ea達到40 Kcal/mole,迴歸值(R-square)已經能達到0.91,所以我們保守的推斷,晶體成長時所需的反應活化能(Ea),應在40 Kcal/mole以上。另外,由Table 5-7和5-9可以看出表面反應係數(Kr),隨著溫度的增加有明顯上昇的趨勢;但是質傳擴散係數(Kd)並無明顯的變化。若以活化能 為40 Kcal/mole為例,當溫度在30~40℃間時,每上昇5℃,Kr 增加了約3倍,但是Kd只有增加1.01倍。因此,當溫度增加時,表面反應的速率會增快許多,使得質傳擴散速率成為主要控制反應速率的步驟;換句話說,晶體的成長速率在高溫時,是受到質傳擴散速率的控制(diffusion controlled),在低溫較可能是是受到表面整合速率的控制(integration controlled)。
最後,由雜質對成長速率影響的實驗結果可以發現,因蔗糖和氯化鈣的分子結構差異很大,所以當蔗糖溶液加入氯化鈣(CaCl2)時,雜質會吸附在蔗糖晶核的表面,影響溶液中蔗糖分子群集排入晶格中,而抑制晶體成長;而棉子糖有些和蔗糖結構相似(含有一分子的果糖和葡萄糖)的部分會排入蔗糖晶體的表面,但另一部份和蔗糖相差很多的部分(屬於半乳糖(galactose)的分子結構)會阻礙蔗糖分子進一步的排入晶格中,而抑制了晶體的成長。另一方面,因蔗糖的分子結構為一分子的果糖和葡萄糖所構成,當加入果糖時,可能因果糖吸附於蔗糖晶體表面而形成新的成長基,使晶體的成長速率加快。

In this research, the growth rates of sucrose crystals formed by contact nucleation were studied in a flow cell system using a photomicroscopic technique. The effects of supersaturation and temperature on the growth rates were investigated in the experiments to recover the mass transfer coefficient (Kd) and the surface reaction constant (Kr) using the two-step model.
The growth rate data were analyzed based on the two-step model. Then, different values of activation energy (Ea) were chosen to obtain the corresponding values of Kd and Kr . It was shown that the correlation coefficient in the regression analysis reaches up to 0.91 at Ea=40 kcal/mole and remains nearly unchanged for Ea>40 kcal/mole. Therefor, we were unable to determine the exact values of Ea using this procedure. However, it is reasonable to assume that Ea should be greater than 40 kcal/mole. The experiment results also show that, for example, for Ea=40 kcal/mole, kr approximately increases 3-fold when temperature rises 5℃ within the temperature range from 30℃ to 40℃. On the other hand, Kd only increases 1.01-flod when temperature rises 5℃ within the same temperature range. Therefore, it can be concluded that growth rate of sucrose crystals tends to become diffusion controlled at high temperature and surface integration controlled at low temperature.
Finally, the effects of the presence of various impurities on the growth rates were also investigated. As the structures of calcium chloride differ very much from that of sucrose, the adsorption of calcium chloride might cause the inhibition of further incorporation of sucrose into the lattice of sucrose crystal, resulting in the slower growth rate on the sucrose surface. While raffinose molecules consists of one fructose, one galactose and one glucose, the adsorption of raffinose on the sucrose surface might inhibit the further adsorption of sucrose due to the presence of galactose on the crystal surface, resulting in the slower growth rate. On the other hand, as sucrose molecule consists of one fructose and one glucose, the adsorption of fructose on the sucrose surface might cause the formation of new growth sites, resulting in the faster growth rate on the sucrose surface.

指導教授推薦書…………………………………………………………………
口試委員會審定書………………………………………………………………
授權書…………………………………………………………………….iii
簽署人須知……………………………………………………………….iv
中文摘要………………………………………………………………….xi
英文摘要………………………………………………………………….xiii
誌謝…………………………………………………….………………. xv
第一章 序論……………………………………………………………1
第二章 文獻回顧………………………………………………… … 4
2.1 蔗糖簡介:……………………………………….……………….4
2.1.1蔗糖的物理性質………………………………………… 4
2.2 結晶理論:………………………………………………………..6
2.2.1過飽和度(supersaturation)產生……….…………… 6
2.2.2成核現象…………………………………………………….. 8
2.2.3晶體成長………………………………………………….... 11
2.3 蔗糖晶體的成長:…………………….………………………. .14
2.4 雜質對晶體結晶速率的影響:……….……………………...16
2.4.1雜質對晶體成長速率的影響…………………………….... 16
2.4.2雜質對成核速率的影響……………………………………….18
2.4.3雜質進入晶體的機構………………………………………….19
第三章 原理……………….………………………………………. 35
3.1雙重阻力模式……………………………………………… 35
3.2成長速率之整體經驗方程式……….…………………... 37
3.3流體化床中的質傳式…………….………………………. 38
3.4雙重阻力中的質傳係數與表面整合係數之探討….…... 41
3.5流速的影響………………………………………………… 44
第四章 實驗裝置……………………….…………………………. 47
4.1實驗藥品………………………………….……………... 48
4.2分析儀器…………………………………….…………... 48
第五章 結果與討論…………………………………………………. 53
5.1晶體大小和成長速率的關係…….……………………... 53
5.2成長速率之整體經驗方程式分析……….……………... 54
5.3雙重阻力模式…………………………….…………….… 54
5.4雙重阻力模式雙重阻力中的質傳係數
和表面整合係數的探討……………….………………..54
5.5流速的影響……………………………………………………56
5.6雜質的影響……………………………………………………57
第六章 結論…………………………………….…………………. 75
參考文獻………………………………………….……………….… 77

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