Synergetic Effect of Tetrabutylammonium Bromide and Polyethylene Glycol as Phase Transfer Catalysts in Third Liquid Phas
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Catalysis Letters Vol. 98, Nos. 2–3, November 2004 (Ó 2004)
Synergetic effect of tetrabutylammonium bromide and polyethylene glycol as phase transfer catalysts in third liquid phase for benzyl-n-butyl ether synthesis Gong Jin1, Cuifang Zhang2, Tadaatsu Ido,3 and Shigeo Goto3 1
The Dow Chemical Company (Shanghai), Suite 1101, Shui On Plaza, 333 Huai Hai Zhong Road, Shanghai 200021, China Japan Shin Shin Computer System (Shanghai), Co. Ltd., Building 61, 421 Plaza, Hong Cao Road, Shanghai 200233, China 3 Department of Chemical Engineering, Nagoya University, Chikusa, Nagoya 464-8603, Japan
2
Received 10 June 2004; accepted 27 July 2004
This study intends to clarify the forming characteristics of third liquid phase in phase transfer catalytic system in the presence of n-butanol and potassium hydroxide when tetrabutylammonium bromide, polyethylene glycol and their mixture serve as phase transfer catalyst, respectively. At 323 K, the three catalytic systems were applied to yield benzyl-n-butyl ether from benzyl chloride and n-butanol, and they performed distinct reaction activity. Among them, a combination of two kinds of catalyst results in a synergetic effect in reaction activity. KEY WORDS: chemical reaction; phase transfer catalyst; third liquid phase.
1. Introduction As the chemical industry strives to improve process efficiency, safety and reduce environmental impact, phase transfer catalysis (PTC) has found it way to be recognized as a strong weapon to achieve these goals. The PTC methodology involves a substrate (which is soluble in the organic bulk) and a reagent (which is dissolved in the aqueous bulk). The substrate and the regent are then brought together by a catalyst, which transports the regent into the organic phase where reaction can take place with the substrate. There are several advantages of the PTC system over single-phase systems, such as:an increased reaction rate, a lower reaction temperature, avoiding the need for expensive anhydrous or aprotic solvents, the use of water together with an organic solvent as reaction medium [1]. However, one of the primary drawbacks of a traditional liquid–liquid PTC is that the separation and recovery of the catalyst from the products and organic are hardly achieved [2]. One strategy to remove this obstacle is to build up a catalyst-rich third phase which could be attained under certain conditions. The third phase usually contains a high concentration of catalyst, accompanied by some water and organic solvent. This is not only improves the chances for recovery of the PTC but also, as a welcome consequence, owing to the high concentration of the catalyst and reactants in the third phase, the observed overall reaction rate increases dramatically once the third liquid is formed. [3–6]. *To whom correspondence should be addressed.
Normally, quaternary ammonium salts with their unique capability to dissolve in both aqueous and organic liquids are the catalysts of choice for most phase transfer applications. Other phase transfer catalysts include phosphonium salt
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