利用反應性蒸餾系統經由轉酯反應生產乙酸丁酯之設計與控制

Design and Control of Reactive Distillation Processes for the Production of Butyl Acetate via Transesterification

陳俊宏(Jyun-Hong Chen)

指導教授 ： 余政靖

國立臺灣大學/工學院/化學工程學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.01178

摘要

聚乙烯醇為化學工業中用途廣泛的聚合物，但每製造1公噸聚乙烯醇會伴隨約1.6公噸的副產品乙酸甲酯，所以乙酸甲酯的再利用就顯得很重要。一般來說，乙酸甲酯有兩種化學路徑可以將其再利用。一為水解反應產生醋酸，另外一種為轉酯反應，本論文就針對後者的反應進行可行設計以及控制。我們所選擇的醇類為正丁醇，以進行MeOH + BuAc ↔ MeAc + BuOH的反應。在過去的文獻中，主要的設計有兩個架構，一為四根塔的架構，另一為三根塔的架構。在過去的架構中，為了打破正丁醇與乙酸丁酯共沸點，多花了不少的成本。在仔細的了解這些架構後，提出一個兩根蒸餾塔的架構。首先第一根是傳統蒸餾塔，其後接著一根反應蒸餾塔來打破共沸組成。由於平衡常數並不是非常的高，因此反應蒸餾塔中，過量的乙酸甲酯是必要的。一個有系統的最適化程序則用來取得最佳的板數以及進料位置。而結果也顯示出，本論文所提出的設計架構年總成本至少是過去文獻年總成本的三分之二。

最後，對這個回流架構提出幾個可行的動態設計。一個有系統的設計步驟從反應蒸餾塔開始然後設計回傳統蒸餾塔。三個可能動態架構:雙點溫控、一組成一溫度控制和雙組成控制都被模擬出來。其中雙點溫控的效果最好。而溫度控制所造成的濃度偏差，可用前饋控制得到令人滿意的結果。

關鍵字

反應蒸餾塔 ； 乙酸丁酯 ； 轉址

並列摘要

In the production of Polyvinyl Alcohol (PVA), a large amount of methyl acetate (MeAc) is produced as by-product, i.e., 1.6 kg MeAc/1 kg PVA. Since methyl acetate has relatively low economical value, efficient reuse of MeAc is an important issue in the PVA plants. Generally, two process alternatives exist. One is hydrolysis where acetate is converted back to acetic acid and the other is transesterification where MeAc is converted to a higher value acetate. The second chemical route is explored here and, in this work, methyl acetate transesterification using butanol is studied. The transeasterification reaction is MeOH + BuAc ↔ MeAc + BuOH. Two plantwide designs using reactive distillation (RD) can be found in the literature. One is a four column configuration and the other is a three-column design. In both examples, attempts have been made to break the azeotrope between BuOH and BuAc to achieve high purity product. Carefully examining the process, a new flowsheet is proposed. It includes one conventional distillation column followed by a reactive column in which the azeotrope is reacted away in the RD column. Because of relatively low chemical equilibrium constant, “excess” reactant (MeAc) design is considered. A systematic design procedure is used to optimize the flowsheet. The results show that the two-column design is capable of producing high-purity butyl acetate and methanol with a TAC only 2/3 of the three-column design. Finally, the control structure design for this recycle plant is addressed. A systematic procedure is proposed for the plantwide control system design which starts from the RD column and then back to the distillation column. Three possible quality control structures are considered: two-temperature scheme, one-temperature-one-composition control and two-composition control. Dynamic simulation results show that good control can be achieved using two-temperature control and, moreover, steady-state composition offset can be mitigated using feedforward compensation for temperature set points.

並列關鍵字

reactive distillation ； butyl acetate ； transesterification

參考文獻

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