【作者】 赖延清；

【导师】 刘业翔； 杨建红；

【作者基本信息】 中南大学 ， 有色金属冶金， 2001， 博士

【副题名】炭素阳极电化学活性与空气/CO_2反应活性的研究

【摘要】 本文针对铝电解工业中，电能消耗高和炭素阳极消耗大的突出问题，以铝电解节能、节炭、降低生产成本为主要目的，在“973”项目及我校与挪威科技大学国际合作项目的资助下，用改进的断电流技术，对炭素阳极的电化学活性和空气／CO₂反应活性进行了广泛深入的研究，研究了沥青含量、残极添加量、阳极焙烧温度、AlF₃掺杂、复合氧化物掺杂、电解质成分、炭渣、金属Al及CO等因素对阳极过电位的影响，在此基础上对铝电解阳极过程机理进行了初步探讨；采用等温热重法、TG和XRD，研究了多种含铝添加剂（Al、AlF₃、Al₄C₃和Al₂O₃）对炭素阳极空气／CO₂反应活性的影响和相关过程的物理化学变化等，从结构与化学两方面解释了含铝添加剂对炭素阳极空气／CO₂反应活性的影响机理。获得的主要结果如下： 1)改进了断电流技术。多次测量标准偏差仅有0.011V，可得到较前人更准确、可靠、重现的结果，为铝电解炭素阳极电化学活性的表征及其阳极过程的研究提供了可靠的试验研究手段， 也可广泛地应用于其它高温熔盐体系的电化学研究。该方法已成为国内外高温熔盐电极过程研究的重要手段，得到了国际上同行专家的肯定和采用，如国际著名的铝电解基础理论研究专家、拂威科技大学的Thonstad教授曾多次委托我方对他们制备的阳极试样进行阳极过电位测试。 2)发现了工业预焙阳极制备过程中若干降低阳极过电位的因素。残极的添加、沥青量的提高及高温焙烧时S的脱除均可降低阳极过电位。 3)发现多种阳极添加剂可降低阳极过电位。AlF₃、Al-Mg复合氧化物（浸渍法掺杂）均可降低炭素阳极过电位，且Al₂O₃／MgO配比越接近于MgAl₂O₄计量，越有利于降低炭素阳极过电位，提高焙烧温度对电催化活性不利；机械掺杂MgAl₂O₄也具有电催化活性，1A／cm²下，与空白阳极比较，970℃和1200℃下焙烧的MgAl₂O₄掺杂阳极过电位分别降低了63mV和28mV。 4)发现炭渣、金属Al和CO都会提高阳极过电位，MgAl₂O₄掺杂可提高阳极抗CO影响的能力。炭渣和金属Al与阳极气体CO₂反应后生成CO，CO易于吸附在阳极表面，阻止阳极反应的进行，提高阳极过电位。 5)发现炭素阳极过电位随电解质中CaF₂和AlF₃的添加而提高。其原因可能是CaF₂和AlF₃增大了电解质对炭素阳极的润湿角，提高了阳极真实电流密度，从而提高阳极过电位。 摘要－11－ 6)发现多种含铝添加剂可降低炭素阳极在450℃下的空气反应活性和 970℃下的CO。反应活性，且随着添加剂含量的变化出现最小活性值，但是 各种添加剂都提高了阳极在550℃下的空气反应活性。 7)发现含铝添加剂对炭素阳极空气汇。反应活性的影响是“结构因素” 与上化学因素”共同作用的结果。含铝添加剂可降低沥青热解过程的表观 活化能，催化其热解反应，提高了沥青的产焦率，有利于降低炭素阳极的 空气／CO；反应活性；在沥青的炭化过程中，通过A！4C3或A卜C中间化合物 的不断“化合－分解”，催化了沥穹豹炭化过程，提高了沥青焦的炭化程度， 有利于降低沥青结焦和炭素阳极艾生气汇0。反应活性：含铝添加剂经焙烧 后，产生了 a－A！。O。，残留干试样一，催化炭素材料的氧化反应，提高了 i))j 青结焦和炭素阳极的反应活性。更多还原

【Abstract】 Highly energy consumption and excessive carbon consumption are the prominent problems in aluminum electrolysis. Energy saving and carbon saving play an important role in aluminum production and are the primary object of this study. Based on the financially support by ?China National Key Fundamental Research Development Project" (U973"), the Norwegian Aluminum Industry and the Norwegian Research Council, the electrochemical reactivity and air/CO, reactivity of carbon anode are investigated widely and deeply. The following factors influencing the overvoltage of carbon anode are studied with a modified current interruption technique: pitch content and butt content in the raw material prescription of industrial prebaked anodes, anode additives (A1F3 and compound oxides), composition of electrolyte, carbon dust, aluminum addition and CO bubbling et al. On the basis, the mechanism of anode process in aluminum electrolysis is elementary discussed. The effect of aluminum-containing additives (A1F3, A14C3, Al and A12O3) on the air/CO2 reactivity of carbon anode is studied with Isothermal-gravimetric method. Additionally, some relevant physical and chemical reactions are investigated with TG and XRD, to study the function mechanism of the aluminum-containing additives on structural aspect and chemical aspect.The mainly conclusions and findings can be summarized as follows:The current interruption technique in aluminum electrolysis is modified. This technique can give more exact, reliable and reproducible overvoltage results than previous literature reported method, whose standard deviation is less than 0.01 IV. The improved current interruption technique is a reliable method to characterize the electrochemical reactivity of carbon anode and to study the anodicprocess mechanism in aluminum electrolysis. This method can also be used for electrode process in other molten salt systems. This technique has become an important method for investigation of electrode process in high temperature molten salt. It is adopted and consented by other craft brother experts, such as the famous aluminum electrolysis fundamental researcher in the Norwegian University of Technology, professor Thonstad, who relegated the measurement of his samples to us for several times. .Some factors in industrial prebaked anode production are found be able to lower the anodic overvoltage. These factors include pitch content increase, butt addition, and sulfur elimination during the high temperature baking.Some anode additives are found be able to lower the anodic overvoltage. A1F3 and Al-Mg compound Oxides (added by dipping) both can lower the anodic overvoltage, the anode baking temperature and the MgO/Al2O3 ratio has an effect on their electrocatalysis activity. Lowering the baking temperature can increase their electrocatalysis activity. The closer the ratio is to the spinel composition MgAl:O4, the more effective it is in decreasing the anodic overvoltage. Mechanical doped MgAl2O4 can also lower the anodic overvaltage of carbon anode, at lA/cm2 current density, compared with the identical undoped anode, the doped anode baked at 970癈 lower anodic overvoltage for 63 mV, the doped anode baked at 1200癈 lower anodic overvoltage for 28mV.Carbon dust, Al addition and CO bubbling are found be able to lower the anodic overvoltage of carbon anode, and MgAl2O4 is found be able to lower the negative effect of CO. The added Al and carbon dust react with the anode product CO, and form CO, CO is easy to adsorb on the surface of carbon anode. Consequently, the anode process is blocked and the anodic overvoltage increase.The anodic overvoltage is found to increase with increasing amount of A1F3 and CaF, in electrolyte. The reason may be that CaF2 and A1F3 increase the wetting angle of electrolyte on carbon anode, increase the real anodic current density, so increase the anodicovervoltage.The airburn reactivity at 450"C and carboxy reactivity at 970 of carbon anode are both found to decrease with Al-containing additives adding, an更多还原