【作者】 王玮涵；

【导师】 李振花；

【作者基本信息】 天津大学 ， 化学工艺， 2013， 博士

【摘要】 以合成气为原料制备草酸酯并进一步加氢制乙二醇是一条具有良好发展前景的绿色化学新工艺。该工艺的核心步骤是CO气相催化偶联制备草酸酯，包括CO气相催化偶联反应和亚硝酸酯再生反应。以甲醇（或乙醇）为原料经亚硝酸甲酯（或亚硝酸乙酯）合成草酸二甲酯（或草酸二乙酯），均可实现乙二醇生产，但对同一催化剂上合成草酸二甲酯和草酸二乙酯两个过程的对比还未见报道。本论文在固定床反应器中对比了Pd-Fe/Al2O3催化剂上CO气相催化偶联制备草酸二甲酯和草酸二乙酯的反应性能。结果显示，与亚硝酸乙酯相比，亚硝酸甲酯具有更高的CO偶联反应活性。对亚硝酸酯的热分解反应以及在Pd-Fe/Al2O3催化剂上的催化分解反应进行了考察，并采用密度泛函理论（DFT）对亚硝酸酯的分解反应机理进行了研究。结果表明，催化剂对亚硝酸酯分解生成RCH2O·的过程有促进作用，并且亚硝酸酯分解反应和CO偶联合成草酸酯的反应为平行反应。DFT计算结果显示亚硝酸乙酯更易发生分解，这使得其在CO偶联反应中活性降低。另外，进一步对比研究了填料鼓泡塔反应器中亚硝酸酯再生反应，结果显示，相同反应条件下，亚硝酸甲酯再生反应的收率高于亚硝酸乙酯再生反应。因此，选择草酸二甲酯路线生产乙二醇更具有竞争力。基于此结论，本文进一步对亚硝酸甲酯再生反应动力学以及再生过程模拟进行了系统研究。亚硝酸甲酯再生反应是一个串联反应过程：第一步为NO的氧化反应，第二步为NO、NO2与甲醇的反应。中间产物NO2是再生反应过程的主要副产物。本文建立了适宜测定气液反应动力学的双搅拌气液反应器装置，并考察了各参数对于动力学测定的影响，在双搅拌气液反应器中对NO、NO2与甲醇反应生成亚硝酸甲酯这一过程的动力学进行了研究，并得到了亚硝酸甲酯再生反应动力学方程。基于得到的宏观动力学方程，并结合反应器内的流体力学特性，建立了描述填料鼓泡塔反应器中亚硝酸甲酯再生反应的数学模型，对填料鼓泡塔反应器中不同操作参数下亚硝酸甲酯再生反应过程进行了模拟计算。计算结果证明该模型能够较好地模拟不同工艺条件下的亚硝酸甲酯再生反应结果。计算结果和实验结果均表明，填料鼓泡塔反应器中亚硝酸甲酯再生反应适宜的工艺条件为：甲醇浓度不低于40wt.%，气相流量400~500mL/min，惰性组分氮气体积分数60~80%，NO/O2的摩尔比为5:1~6:1，反应温度30~40°C，反应器高径比8~10。另外，气相原料组成和气体流量是亚硝酸甲酯收率的敏感影响因素。在填料鼓泡塔反应器中进一步研究了系统压力和杂质气体对亚硝酸甲酯再生反应的影响。实验结果表明，适宜的反应压力0.2~0.3MPa。将一定比例的氮气分别以CO和CO2代替，在不同操作条件下考察了CO和CO2杂质气体对再生反应收率的影响。研究表明CO2存在时再生反应的转化率和收率显著下降，而CO对再生反应的影响很小。更多还原

【Abstract】 Ethylene glycol is an important organic compound. The hydrogenation of dialkyl oxalate from syngas to ethylene glycol is considered as a green chemical process with potential benefits in both environmental and economic consideration. The key step is the synthesis of dialkyl oxalate via CO gaseous phase coupling reaction, which involves two reactions: CO coupling reaction to produce dialkyl oxalate and the regeneration of alkyl nitrite. Either methanol or ethanol can be used in this process to produce dimethyl oxalate and diethyl oxalate respectively but the comparison of dimethyl oxalate and diethyl oxalate synthesis on same catalyst was not reported.In this paper, the synthesis of dimethyl oxalate and diethyl oxalate by CO coupling reaction in gaseous phase was investigated in a fixed bed reactor over a Pd/Fe-Al2O3catalyst. The results showed that the space time yield of dimethyl oxalate was higher than that of diethyl oxalate under same reaction conditions. The different performance of dimethyl oxalate and diethyl oxalate formation was attributed to the different decomposition performance of methyl nitrite and ethyl nitrite. Moreover, Density Functional Theory (DFT) was used to simulate the decomposition process of methyl nitrite and ethyl nitrite and the results indicated that ethyl nitrite can be decomposed more easily than methyl nitrite. Regeneration reaction of methyl nitrite and ethyl nitrite was further compared. The results showed that the yield of methyl nitrite was higher than that of ethyl nitrite under same reaction conditions. So the production of ethylene glycol through dimethyl oxalate was more competitive than the route through diethyl oxalate. The regeneration of methyl nitrite was studied in detail.A model-reactor system suitable for kinetics study of gas-liquid reaction was set up and the kinetics of methyl nitrite synthesis from NO, NO2and methanol was obtained in the consideration of NO2as the main by-product accompany with methyl nitrite regeneration. The methyl nitrite regeneration reaction was considered as a two-step irreversible series reaction: the first reaction was NO oxidation to form NO2; the second reaction was the reaction of NO, NO2with methanol to form methyl nitrite, whose kinetics was obtained at atmospheric pressure by using the model reactor in this work. Based on the kinetics equation and simplified plug flow model, a mathematical model depicting methyl nitrite regeneration reaction in a packed bubble column reactor was proposed to predict methyl nitrite yield at varied conditions. As a result, the calculated results by the model coincided well with the experimental data, which proved that the model was effective for guiding the scaling-up of methyl nitrite regeneration process. Using this model, the effect of reaction temperature, N2volume fraction, NO/O2molar ratio and superficial gas velocity on methyl nitrite yield was predicted and compared with the experimental data. The suitable operation conditions were determined to be as follows: methanol concentration of40~99.9wt.%, gas flow rate of400~500mL/min, NO/O2molar ratio of5:1~6:1and N2content of60~80%volume fraction, reaction temperature of30~40°C,. the ratio of height to diameter of8~10. The gaseous composition and gas flow rate are considered the most sensitive factors affecting on the yield.The effect of reaction pressure and other gases on the methyl nitrite regeneration was further discussed. It was found that the suitable pressure is0.2~0.3MPa. The effect of CO on methyl nitrite is not obvious, while the existence of CO2in the system will decrease the O2conversion and methyl nitrite yield.更多还原