| Summary: | 碩士 === 長庚大學 === 化工與材料工程研究所 === 95 === Abstract
The mixed xylenes produced mainly consist of p-xylene (PX), m-xylene (MX), o-xylene (OX) and ethylbenzene (EB). Due to their similar molecular structures, these isomers have close boiling points (e.g.MX=139.12℃,PX=138.37℃,OX=144.41℃ and EB=136.19℃ ). It is very costly to separate and purify them.
A distillative crystallization technology, called distillative freezing (DF), is introduced to further purify OX from the mixed xylenes. Basically, DF is a distillative crystallization technology, which combines distillation and crystallization to produce pure crystals. DF is operated at triple point condition, in which the liquid mixture is simultaneously vaporized and solidified due to the three-phase equilibrium. A simulation method is proposed to provide essential information in operation of the DF process. The experiments show that OX can be purified by DF from 90% to 96% or from 95% to 99%+.
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