|导师||高志贤 ; 吾满江.艾力|
|关键词||甲醇 甲醛 二甲氧基甲烷 催化精馏 萃取精馏|
二甲氧基甲烷具有优良的理化性能，在化妆品、药品、油漆等产品中广泛用作溶剂，还是很有潜力的油品添加剂。为了获得高纯度的甲缩醛，本论文的工作主要从以下方面展开： （1）获得连续实验基础数据 通过实验建立一套完整的分析方法。通过间歇实验，系统研究了甲醇和甲醛缩合制备二甲氧基甲烷的反应及其逆反应，筛选了合适的催化剂，研究了温度、水含量和催化剂用量等与反应效果之间的关系，为连续合成二甲氧基甲烷的实验做好准备工作。 （2）连续萃取催化精馏实验 设计、搭建连续萃取催化精馏装置，通过实验研究了连续萃取催化精馏合成二甲氧基甲烷的进料量、回流比和塔釜温度等工艺参数的影响。对比不同的萃取剂发现，以水为萃取剂时效果较好，在进料速度为100 mL/h，回流比为5，萃取剂与进料的体积比为1.0-1.4，再沸器温度为98.6℃的情况下，二甲氧基甲烷纯度和甲醛转化率分别可达到98.7%wt和98.0%。证明了使用该工艺合成高纯度二甲氧基甲烷的可行性。 （3）二甲氧基甲烷催化氧化制备高浓度甲醛初探 初步研究了二甲氧基甲烷空气氧化制备高浓度甲醛的催化剂，考察了不同组分、反应温度等因素的影响。选择Fe-Mo二组分催化剂为本反应的催化剂，该催化剂有较高的二甲氧基甲烷转化率，甲醛选择性可达到82.9%。
Methylal is an excellent industrial solvent, frequently used in household and industrial sprays, as a blowing agent for polyurethane foams and ion-exchange resins production. Because of its high oxygen content (42%) and high cetane number, methylal has been proposed as an extraordinarily promising additive to diesel oil. In conventional processes, methylal is synthesized from formalin and methanol in the presence of catalyst in a catalytic distillation column, in which both reaction and separation take place simultaneously in a single operation unit, but an azeotrope (92.2 % methylal and 7.8 % methanol) boiling at 41.9°C is formed on the top of the distillation column. In this work, in accordance with the problems of synthesis of high-purity methylal and the methods of purifying methylal from azeotropic system, the extractive catalytic distillation, which combines catalytic distillation and extractive distillation in one column, was proposed. The extractive catalytic distillation is investigated for the synthesis of high-purity methylal from methanol and formalin in the presence of a cation-exchange resin catalyst. The main research contents are as follows: (1) Basic experimenal study of methylal synthesis Through a series of experiments, a method for detecting different reactants was developed. Both the reaction for methylal synthesis and the reverse reaction were investigated by batch tests. We studied the performances of solid acid catalysts for producing methylal from methanol and formalin, and found that polystyrene based macroporous cation exchange resin (D-001) was the best catalyst. The effects of reaction temperature, molar ratio of methanol to formaldehyde, loading of catalyst and water were investigated. The reverse reaction was studies in a homogeneous reactor. Thus the valuable data will be provided for the continuous synthesis of methylal. (2) Synthesis of high-purity methylal via extractive catalytic distillation A laboratory-scale glass column was designed and built. A feed with 2:1 molar ratio of methanol to formaldehyde was chosen to investigate the effects of operating parameters such as extractant feeding position, ratio of the extractant to feed, reflux ratio, and the temperature of reboiler on the continuous synthesis of methylal. Under the optimum operating conditions, using water as extractant, the extractive catalytic distillation process operated continuously, producing methylal purity of 98.7% with formaldehyde conversion of 98.0%. Therefore, the feasibility of the synthesis of high-purity methylal via extractive catalytic distillation was proved. (3)Preliminary study on synthesis of concentrated formaldehyde via oxidation of methylal The method of prepare iron–molybdenum mixed oxide catalysts was studied. And the effects of different additives, temperature of reaction and the molar ratio of reactants were investigated. Under the optimum operating conditions, the conversion of methylal is 90% and the formaldehyde selectivity is 82.9%.
|刘洪忠. 连续催化合成二甲氧基甲烷研究[D]. 北京. 中国科学院研究生院,2012.|
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