The 5th ISFR (October 11-14, 2009, Chengdu, China)

DEHYDROCHLORINATION OF POLYVINYL CHLORIDE
IN BASIC IONIC LIQUIDS
Tao Zhao, Qian Zhou*, Xian-Hong Jiang, An-Ke Du, Yu-Zhong Wang
Center for Degradable and Flame-Retardant Polymeric Materials (ERCEPM-MoE), Collegeof Chemistry, State Key Laboratory of Polymer Materials Engineering, Sichuan University,Chengdu 610064, China;
Tel: +86-28-85410755;Fax: +86-28-85410755;
E-mail:qzhou@scu.edu.cn
1. Introduction
PVC can be dehydrochlorinated through various methods, such as catalytic
dechlorination using metal oxides or composite oxides, mechanochemical dechlorination, andchemical method in an alkaline solution[1]. For dehydrochlorination in an alkaline solution,
however, volatile and toxic solvents were adopted using this method. Although the methodsof hydrothermal and supercritical dechlorination have been developed to increase thedechlorination efficiency, they have high requirements for the equipments[2]. Therefore, thedevelopment of environment-friendly methods for highly efficient dehydrochlorination ofPVC is an area of considerable importance.
Poly(ethylene glycol) (PEG) has been used as an environment-friendly reaction medium
to enhance the dehydrochlorination of PVC in our previous work [3]. Recently, ionic liquids(ILs), i.e., organic salts that melt at or below 100 oC, have been used in various reactions dueto the advantages such as: easy to operate, less energy demanding, and environmentallyfriendly due to chemical and thermal stability, low vapor pressure and ease of recycling [4]. It
had been reported that the stability of PVC would be reduced when blending with ionicliquids [5]. In this paper, 1-Butyl-3-methylimidazolium Hydroxide ([Bmim]OH), a kind ofbasic ionic liquids, has been adopted for dechlorination of PVC at atmospheric pressure,which is expected to be a promising environmental friendly reactive solvent for highly
efficient dehydrochlorination of PVC.
2. Experimental
PVC (SG-1) was obtained from Xi’an Chemical Co., China. The chlorine content of thePVC is 51.5 %. All other chemical materials were of analytical grade. [Bmim]OH has been
prepared according to reference [6].
Dechlorination of PVC was carried out in a 100 ml three-neck flask. In a typical reaction,
5 ml [Bmim]OH and 0.15 g PVC were added into the flask, and then the mixture was reacted- 260 -PARTⅤ SOLVOLYSISat 100 ◦C for 1 h with stirring. The product as black powder was separated by filtration, andwashed with deionized water times, then extracted in a Soxhlet extractor with distilled waterfor 48 h. The dechlorinated PVC (DPVC) was dried under vacuum at 60 ◦C for 24 h before
characterization. The chlorine contents in DPVC were measured by theoxygen–combustion–chlorine selective electrode method.

Dechlorination Degree(%)

3. Results and Discussion
The effect of ionic liquids on the dechlorination of PVC has been shown in Fig.1. As canbe seen, the dechlorination of PVC at 100 ◦C for 1 h only gives a low dechlorination degree(DD) of 13.53 %, while using ionic liquids, the DD increases. Especially, the basic ionicliquid [Bmim]OH shows the highest dechlorination ability (DD: 24.10%).
20151050none[Bmim]BF4 [Bmim]PF6 [Bmim]Cl [Bmim]OHFig. 1 Effects of ionic liquid on the dechlorination degree of PVC (100 ◦C, 1 h).
Moreover, it can be seen from Fig.2 that the dechlorination degree increases with theincrease of reaction time that the dechloriantion degree reaches 55.57% after reaction for 8 h.
Dechlorination Degree(%)

55504540353025200246810R eaction T im e(h)Fig.2 Effects of reaction time on the dechlorination degreeof PVC using [Bmim]OH at 100 ◦C.

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4. Conclusions
Highly efficient dehydrochlorination of PVC has been achieved under mild reactionconditions using [Bmim]OH as an environment-friendly reaction medium. Especially, no basecatalysts have been adopted, which did not generate toxic waste byproducts such as KCl.
Preliminary results show that the dechlorination degree increases with the increase of reaction
time and the DD reaches 55.57% after reaction for 8 h.
Acknowledgements
The authors thank the financial support of the 863 program (Contract No:2007AA06Z325) and the National Science Fund for Distinguished Young Scholars(50525309).
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[2] Y. Sueoka, W. Matsubara, N. Ishihaara, W. Kawamura, T. Moritani, M. J. Giho
1999,34(3),146.
[3] Y. H. Wu, Q. Zhou, T. Zhao, M. L. Deng, J. Zhang, Y. Z. Wang Hazardous Materials,2009, 163(2~3),1408-1411.
[4] M. B. Shiflett, A. Yokozeki. Science Direct ,2007, 259, 210-217.
[5] M. Rahman, C. S. Brazel. Polymer Degradation and Stability 2006, 91, 3371-3382.
[6] B. C. Ranu, S. Banerjee. Organic Letters 2005, 7(14), 3049-3052.

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