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对二甲苯是化学合成常用的原料,但普通的二甲苯大都由对、间、邻二甲苯等同分异构体所组成。由于它们的沸点极其相近,用一般的分镏法是很难得到纯的对二甲苯。但依据它们之间熔点的不同(对二甲苯:13℃、间二甲苯:-47℃、邻二甲苯:-25℃),采用分步结晶的方法,可很易得到纯对二甲苯。我们并借助纸外光谱的方法,对所得分离物进行了鉴定,还由此找到了分离纯对二甲苯的最好制备条件。
Paraxylene is a commonly used raw material for chemical synthesis, but the common xylene mostly consists of isomers, meta, xylene and other isomers. Due to their very similar boiling points, it is difficult to obtain pure paraxylene with the usual method of fractionation. However, pure paraxylene can be easily obtained by fractional crystallization according to the difference in melting point between them (p-xylene: 13 ° C, m-xylene: -47 ° C, o-xylene: -25 ° C) We also used the method of extra-paper spectrum to identify the obtained isolates, and also found the best conditions for the separation of pure para-xylene.