间二甲苯生产技术
摘 要
本文概述了间二甲苯的用途，对国内外的生产现状进行了比较详细的描述，着重介绍了间二甲苯的各种生产技术，包括络合法、吸附分离法、磺化法、反应蒸馏法、共沸精馏法，并提及了间二甲苯的回收技术。对比了几种不同选择性硝化方法，实验结果发现，磷酸对硝化反应的选择性效果较好，乙酸酐的选择性不强，Sn改性皂土没有表现出很好的对位选择性，只有添加磷酸的方法可以提高4-硝基间二甲苯的相对含量，原料转化率也比较好。硝酸混酸的转化率最高。高浓度的磷酸在选择性上的表现和低浓度的相差不大，但在转化率上就表现得很突出，磷酸的效果较好。三酸的混合体系对反应没有很明显的效果，20℃时多聚磷酸—硝酸(1:l)体系反应大概要24h才能达到平衡，50℃体系反应大概在6h达到平衡，50℃多聚磷酸—硝酸(1:l)体系转换率和对位选择性要高于20℃时体系。通过国内外间二甲苯市场分析，对间二甲苯的市场前景进行了预测与展望。
关键词：间二甲苯；络合法；硝化反应；磷酸
The PRODUCTION TECHNOLOGY OF M-XYLENE
ABSTRACT
This article outlines the use of meta-xylene, compares the production status at home and abroad in detail, emphatically introduces all kinds of production technology of meta-xylene, including complex legal, adsorption separation, sulfonated method, reaction distillation, azeotropic distillation method, and the recovery technology of meta-xylene mentioned. Compared the different selective nitration method, the experimental results show that phosphoric acid for selective nitration effect is good, the selectivity of acetic anhydride is not strong, Sn modified bentonite has shown good para selectivity, only adding phosphoric acid method can improve the relative content of 4-nitro meta-xylene, raw material conversion rate is better. The highest conversion rate of sulfur nitrate mixed acid. A high concentration of phosphate on the selectivity and low concentration difference is not big, but performance is outstanding on the conversion rate, the effect of phosphate is better. Mixed system of three acid reaction is no obvious effect, reaction of polyphosphoric acid-nitric acid (1:l) system in 20℃ probably 24h to reach equilibrium, reaction of polyphosphoric acid-nitric acid (1:l) system in 50℃ probably 6h to reach equilibrium, the conversion rate and para selectivity of polyphosphoric acid-nitric acid (1:l) system higher than 20 ℃.By analyzing meta-xylene market at home and abroad, the market prospect of meta-xylene has carried on the forecast and prospect.
KEY WORDS: m-xylene; complex method; nitration; phosphoric acid
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