己二腈 (Adiponitrile, ADN)是製造尼龍66的重要原料，可由丙烯腈 (Acrylonitrile, AN)透過電解二聚法 (Electrodimerization)獲得，此方法反應步驟簡單且生產成本低，是目前業界主流的生產方法。隨著全球生活用品需求大增及尼龍市場快速擴張，對其上游原料己二腈的需求也隨之增加。台灣目前仍透過進口方式取得己二腈，因為此生產技術被國際大廠壟斷，若他國刻意哄抬價格或切斷原料供應鏈，會嚴重影響本土輕重工業的生計，而台灣自行發展此技術就有其必要性了。
本研究是旋轉套管電極 (Rotating cylindrical electrode, RCE)第一次應用於己二腈電化學合成，操作簡單，易於擬合出高流速的生產條件，在陰極半徑為4 mm且轉速為3000 rpm時，電極表面流速即可達1.25 m/s，且在套管對電極的幫助下，更可提供劇烈的紊流 (Turbulence)以增加AN質傳效果，促使反應生成更多ADN。本研究在電解液加入個別四級銨鹽 (Quaternary ammonium salt, QAS)，Tetraethylammonium hydroxide (TEAH)、Tetrapropylammonium hydroxide (TPAH)、Tetrabutylammonium phosphate (TBAP)、Tetrapentylammonium bromide (TB)、Methyl tributylammonium phosphate (MBAP)、Benzyltributylammonium bromide (BB)和Hexadecyltrimethylammonium hydroxide (HH)，透過定電流合成法研究QAS對己二腈電解合成的影響。結果顯示，加入QAS可大幅提升ADN選擇率及電流效率，長碳鏈QAS更可促使聚合反應發生，抑制氫氣及Propionitrile (PN)生成。其中，若純粹要追求最高的產率，應選TBAP；若還要考慮低分離成本，則可選MBAP；若要追求最大比例的寡聚物 (oligomer)，應選BB；若要追求最高的主產物電流效率及AN利用效率 (AN utilization)，應選HH。
本研究也探討各種操作條件對己二腈電解合成的影響，如丙烯腈初始濃度、電流密度、反應時間、陰極轉速及電極幾何形狀對選擇率、電流效率、AN utilization、轉化率及產率的影響。透過凝膠滲透色譜儀得知，電解後的有機相溶液中含有六聚物及九聚物，水相溶液中含有分子量約650之十二聚物，代表反應能聚合出大分子，但透過氣相層析儀得知大分子的含量極少。另外透過感應耦合電漿光學發射光譜儀得知，工作電極和對電極會因操作電流過大而溶解出鉛及鐵元素，須加入螯合劑Ethylenediaminetetraacetic acid (EDTA)。也觀察到AN會在陽極氧化，降低AN利用效率，使用適當AN濃度、低電流密度、高陰極轉速及大面積之對電極可降低此問題。反應初期AN濃度較高，容易發生氧化，且消耗較多AN，傾向生成ADN及trimer；反應中後期由於AN降低，傾向生成PN。
AN反應為質傳控制，非產氫反應。高AN初始濃度及低電流密度有利於聚合反應；反之有利於質子化。高陰極轉速可使擴散層厚度變薄，降低阻力，提升AN質傳速率，有利聚合產生更多ADN及trimer，同時抑制氫氣及副反應；反之則無法有效質傳，傾向生成PN。
電極幾何形狀對己二腈電解合成的影響從大到小為陰極半徑，電極長度，電極間距。同時選用大陰極半徑、小陽極半徑及長電極長度，並操作在高陰極轉速，可達最劇烈的紊流狀態，具有最好的ADN選擇率及電流效率，同時抑制副反應及氫氣的生成。當陰極及陽極半徑分別為4及8 mm，兩者長度均為40 mm，dimensionless time為0.25且陰極轉速為3000 rpm時，產率為0.34 g/cm2⸱hr且ADN電流效率為84 %。

Adiponitrile (ADN) is an important raw material to produce nylon 66, which can be produced from Acrylonitrile (AN) through electrodimerization. A rotating cylindrical electrode (RCE) was used in the electrosynthesis of ADN for the first time. The RCE provides turbulence to promote mass transfer of AN for ADN formation. This study explored the influence of various variables on the electrosynthesis of ADN, such as Quaternary ammonium salt (QAS), initial concentration of AN, current density, reaction time, electrode rotation rate and electrode geometry on the conversion, selectivity, current efficiency, AN utilization and yield.
The results showed that adding QAS could greatly improve ADN performance. QAS with the long carbon chain could promote the polymerization and inhibit the generation of hydrogen and Propionitrile (PN). Among them, Tetrabutylammonium phosphate (TBAP) had the highest yield, Methyl tributylammonium phosphate (MBAP) had the low separation cost and high yield, Benzyltributylammonium bromide (BB) had the largest proportion of oligomers, Hexadecyltrimethylammonium hydroxide (HH) had the highest current efficiency and AN utilization of total. Higher AN concentration and lower current density were beneficial to the polymerization. On the contrary, it was suitable for protonation. Higher rotation rate could decrease the diffusion layer thickness and increase the mass transfer of AN, produce more ADN and trimer, and inhibit hydrogen and side reactions. Conversely, AN could not mass transfer well at low rotation rate, the reaction tended to generate PN. Total conversion of AN, including consumption of AN on the anode, was reduced at a high rotation rate and dimensionless time larger than 0.25 when the AN concentration was low. The effects of electrode geometry from large to small were cathode radius, electrode length and electrode spacing. Higher turbulence, due to a larger cathode radius, longer electrode length and smaller electrode spacing, produced ADN more efficiently. The highest yield among the results was 0.34 g/cm2⸱hr with the highest ADN current efficiency of 84 % at a dimensionless time of 0.25 and cathode rotation rate of 3000 rpm.

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