臺灣博碩士論文加值系統

間二甲苯(m-xylene，簡稱MX)是重要化工原料，可用於生產間苯二甲酸(isophthalic acid，簡稱IPA)。而IPA近年來日益增加用於生產PET塑膠瓶時，當作添加的共聚物。二甲苯含有MX、對二甲苯(p-xylene，簡稱PX)、鄰二甲苯(o-xylene，簡稱OX)以及乙苯(ethylbenzene，簡稱EB)。彼此具有相似的分子結構而表現出非常相似的性質(如沸點：MX=139.12℃、PX=138.37℃、OX= 144.41℃、EB=136.19℃)，也因為它們的沸點非常接近，所以很困難將它們彼此間加以分離。

本研究主要從MX、PX、OX與EB混合液中分離純化MX。分為兩階段進行，第一階段為熔融結晶法之直接接觸技術是以二氧化碳為冷媒直接與四成份MX混合物接觸，混合液溫度降低產生MX晶體。實驗結果顯示，進料組成(XMX)0=0.700混合物經實驗後所得之MX結晶，直接過濾不經過洗晶，可純化至(XMX)f=0.780。

第二階段再以蒸餾固化法(distillative freezing process，簡稱DF法)將MX繼續純化。此法是一種結合蒸餾及結晶操作的新式分離方法，實驗結果顯示當進料組成由(XMX)0=0.700~0.980時，最終操作條件至共晶點或以下，實驗純度與理論值相當符合。進料為(XMX)0=0.960時，當主要不純物為PX時，DF僅可純化至(XMX)f=0.975；而當主要不純物為OX或EB時，DF可純化至(XMX)f=0.990~0.991。進料為(XMX)0=0.980時，當主要不純物為PX時，DF僅可純化至(XMX)f=0.990；而當主要不純物為OX或EB時，DF可純化至(XMX)f=0.993~0.994。整體而言，實驗回收率亦相當接近理論回收率。

The demand for m-xylene is rising worldwide, because this compound is consumed primarily for the production of isophthalic acid (IPA), which is used increasingly as a copolymer in the manufacture of polyethylene terephthalate (PET) plastic bottles. 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 extremely difficult to separate MX economically.

This research is focused on the separation of MX from the mixed xylenes. The study is divided into two parts. Firstly, direct-contact melt crystallization is applied to produce MX crystals from the mixed xylenes. The high pressure carbon dioxide is used as the coolant. The experiments show that the mixed xylenes can be purified from (XMX)0 = 0.700 to (XMX)f = 0.780 by direct-contact melt crystallization when the produced MX crystals are filtered without crystal washing.

Secondly, a distillative crystallization technology, called distillative freezing (DF), is introduced to further purify MX 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 DF experiments show that, for (XMX)0 = 0.700~0.960, (XMX)f is close to (XMX)S while, for (XMX)0 = 0.980, (XMX)f is lower than (XMX)S. Further study shows that, for (XMX)0 = 0.960 with a major impurity of PX, DF results in (XMX)f =0.975. For (XMX)0 = 0.960 with a major impurity of OX or EB, DF results in (XMX)f =0.990~0.991. On the other hand, for (XMX)0 = 0.980 with a major impurity of PX, DF results in (XMX)f =0.990. For (XMX)0 = 0.980 with a major impurity of OX or EB, DF results in (XMX)f =0.993~0.994. Thus, it is more difficult to purify a feed of (XMX)0 = 0.960~0.980 with a major impurity of PX than a feed of (XMX)0 = 0.960~0.980 with a major impurity of OX or EB. In general, the experimental recovery rate of MX is close to the simulated recovery rate of MX.

指導教授推薦書..........................................i
口試委員會審定書........................................ii
授權書................................................iii
誌謝...................................................iv
中文摘要................................................v
英文摘要................................................vi
目錄..................................................viii
圖表目錄................................................xi
第一章 緒論.............................................1
1.1 研究動機..........................................1
1.2 研究目標..........................................3
第二章 文獻回顧..........................................4
2.1 二甲苯介紹........................................4
2.2 MX的製程與純化技術.................................6
2.3 熔融結晶法........................................8
2.4 DF法純化技術......................................9
第三章 結晶法純化之原理..................................21
3.1 熔融結晶法之直接接觸技術...........................21
3.1.1 MX之過冷度.......................................21
3.1.2 二氧化碳相變化....................................21
3.2 DF法.............................................23
3.2.1 二成份相圖........................................23
3.2.2 三成份共晶線......................................28
3.2.3 四成分共晶線與共晶面...............................30
3.2.4 程序分析..........................................31
第四章 實驗設備與方法.....................................51
4.1 熔融結晶法之直接接觸技術............................51
4.1.1 實驗設備..........................................51
4.1.2 實驗器材..........................................53
4.1.3 實驗藥品..........................................54
4.1.4 實驗步驟..........................................54
4.2 DF法.............................................55
4.2.1 實驗設備..........................................55
4.2.2 實驗器材..........................................59
4.2.3 實驗藥品..........................................59
4.2.4 實驗步驟..........................................59
4.3 氣相層析儀..........................................60
第五章 結果與討論..........................................71
5.1 熔融結晶法之直接接觸技術..............................71
5.2 DF法...............................................71
5.2.1 兩成份系統實驗分析...................................71
5.2.2 三成份系統實驗分析...................................72
5.2.3 四成份系統實驗分析...................................73
5.3 DF法與結晶法比較.....................................76
第六章 結論與建議..........................................109
6.1 技術可行性..........................................109
6.2 應用範圍............................................110
參考文獻....................................................111
附錄一......................................................114
附錄二......................................................115
附錄三......................................................116
附錄四......................................................127
附錄五......................................................129
附錄六......................................................131

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