工业生产中存在大量气体产物气氛中的气固反应,如水泥烧制、高温烟气脱硫等涉及的碳酸钙分解。常用的热重（TGA）法存在传质传热速率低、温度分布不均匀、气体扩散阻力大等问题,测得的动力学严重偏离实际,尤其是在反应产物气氛中发生的反应,但此现象未引起足够重视。微型流化床反应分析仪（MFBRA）由于最小化气体外扩散和返混影响被证明为获得近本征动力学的有效方法。然而,针对气氛与气体产物存在相同组分的气固反应,MFBRA无法鉴别其来源从而难以求解动力学。
针对上述问题,本文以菱镁矿在含二氧化碳（CO2）分解为例,在内外扩散对反应最小化影响的条件下,首先利用传统的热重法研究了不同浓度CO2（CO2和氩气的体积比为0%、10%、30%、50%、100%）气氛中菱镁矿初始分解温度、最大分解反应速率对应温度与分解反应动力学参数的变化规律,并建立了相关的经验方程式。其次,利用MFBRA通过在反应气氛中的CO2标记同位素(13CO2)研究了不同浓度13CO2(13CO2和氩气的体积比为0%、10%、30%、50%)气氛中菱镁矿分解的反应速率、转化率与动力学参数的变化,并与热重法获得的结果进行了对比,建立了适用于研究反应气氛中气固反应的微型流化床同位素标记法,其成功应用可推动反应测试、反应研究的科学方法的进步和发展,具有重要的意义。研究结果如下:
（1）TGA中,随着反应气氛中CO2浓度的增加,菱镁矿分解受到的抑制作用显著增强最大反应速率对应温度呈指数型增加,初始分解温度呈对数型增加;在0%CO2（Ar）气氛中菱镁矿分解的活化能为196 k J/mol,而在100%CO2气氛中活化能高达537 k J/mol,且菱镁矿分解的活化能随CO2浓度的增加呈对数型增加,表明CO2的存在严重抑制菱镁矿的分解。在含不同浓度的CO2气氛中菱镁矿分解均遵循成核与生长控制模型:G（x）=-ln（1-x）。
（2）MFBRA中,CO2浓度的增加使最大反应速率对应的转化率逐渐变小;在0%CO2（Ar）气氛中获得的菱镁矿分解的活化能为117 k J/mol,50%CO2气氛中活化能为182 k J/mol,活化能随CO2浓度的变化趋势与TGA相同,均呈指数型增加。不同浓度13CO2气氛中菱镁矿分解遵循的机理模型不同,随着反应气氛中CO2浓度的增加,其机理模型由相边界控制变为成核与生长控制模型。
（3）MFBRA获得的活化能和指前因子均低于TGA测得的值;在Ar气氛中TGA与MFBRA获得的活化能之比(ETGA/EMFBRA)只有1.7,随着CO2浓度的增加,ETGA/EMFBRA逐渐增大,充分表明了随着CO2浓度的增加,在TGA中从样品扩散到周围气氛中的气体产物受到的抑制作用越来越严重;MFBRA中的反应速率明显高于TGA,反应速率增加很快,之后缓慢下降,而在TGA中,反应速率变化平缓,最大反应速率对应的转化率在0.7左右,表明TGA可能会揭示出错误的反应机理,尤其是在含气体产物的气氛中进行的反应。
Biological processes have intricate designs by nature. The main purpose of this work is to decode some of these designs. Many areas in biology including studies on microbial communities and cellular bioch...
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Biological processes have intricate designs by nature. The main purpose of this work is to decode some of these designs. Many areas in biology including studies on microbial communities and cellular biochemistry still largely remain unexplored due primarily to the lack of appropriate tools. In this thesis, we present the applications of Raman micro-spectroscopy and imaging to gain fundamental and otherwise unobtainable biological information on complex structured communities of bacteria known as biofilms and on the metabolic dynamics in single yeast cells. To demonstrate the power of Raman spectroscopy for complex biological systems, model Escherichia coli biofilms were studied. A variety of biomolecules have been shown to play a unique role as signals and/or regulators in biofilm formation. By using Raman imaging,we investigated model Escherichia coli biofilms and detected high levels of he amino acid leucine accumulation during the early stage of the E. coli biofilm formation, which may have resulted from physiological environment-specific metabolic adaptation. Our results demonstrates that our label-free Raman imaging method provides a useful platform for directly identifying still unknown natural products produced in biofilms as well as for visualizing heterogeneous distributions of biofilm constituents in situ. To elucidate the dynamics of intracellular proteins and lipids at the single cell level, the Raman method was coupled with a very powerful strategy, namely, stable isotope labelling. Here, we present in vivo time lapse Raman imaging, coupled with stable-isotope (13C) labelling, of single living Schizosaccharomyces pombe cells. Lipid droplets have been hypothesized to be intimately associated with intracellular proteins. However, there is little direct evidence for both spatiotemporal and functional relations between lipid droplets and proteins provided by molecular-lev
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