Separation of o-xylene from the mixed xylenes

• Main Authors: Chiung Man Huang, 黃瓊滿
• Other Authors: L. D. Shiau
• Format: Others
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/49211666223948432449

碩士 === 長庚大學 === 化工與材料工程研究所 === 96 === Xylenes have very broad applications in chemical industries. The mixed xylenes mainly consist of p-xylene (PX), m-xylene (MX), o-xylene (OX) and ethylbenzene (EB). Due to the close boiling points among the mixed xylenes (e.g., MX = 139.12℃, PX = 138.37℃, OX = 144.41℃ and EB = 136.19℃), it is very difficult to separate and purify them. Distillative freezing (DF), is introduced in this work to purify OX from the mixed xylenes. Basically, 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 DF experiments show that OX can be purified from (Xox)0 = 0.90 ~ 0.95 to (Xox)f ≧ 0.99 with RE = 65 % or from (Xox)0 = 0.80 ~ 0.85 to (Xox)f ≧ 0.99 with RE = 45 %. Further study shows that, for (Xox)0 = 0.90 with a major impurity of MX or EB, DF results in (Xox)f = 0.99 with RE = 65 %. On the other hand, for (Xox)0 = 0.90 with a major impurity of PX, DF results in (Xox)f = 0.99 with RE = 35 % or (Xox)f = 0.98 with RE = 60 %.