Hydrodechlorination of polyvinyl chloride in sub-critical water

• Main Author: Gong, ShiYi, 1970-
• Format: Others
• Language: en
• Published: McGill University 2005
• Subjects: Polyvinyl chloride > Deterioration.; Polyvinyl chloride > Environmental aspects.
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=98711

Polyvinyl Chloride (PVC), a plastic polymer composed of ∼43% hydrocarbon by weight and ~57% chlorine has become extensively used in our daily lives. However, the disposal of waste PVC plastics presents serious problems. The increased awareness of these problems requires the development of a reliable technique to dispose of these wastes in a safe and environmentally benign way that is devoid of the formation/release of organo-chlorine compounds. Chemical degradation of PVC is a technology that transforms PVC waste into completely new chemical products that don't contain chlorine. Sub-critical water (SCW) treatment is one of the most reliable technologies since SCW as a chemical reaction medium having adjustable physico-chemical properties. Hydrodechlorination (HDC), a reaction that replaces organically bound chlorine by hydrogen, can be accelerated by the presence of metal oxide catalysts (alumina supported palladium, Pd0/Al2O3) or raney nickel. When combined with SCW treatment, HDC offers a disposal process that is free from unwanted by-products. The rate of borohydride decomposition is accelerated by raney nickel. The HDC efficiency of virgin and formulated PVC in SCW under various reaction conditions of time and temperature was evaluated systematically. The time of reaction was varied from 1 to 4.5 hours and the temperature was varied from 150 to 280°C in the presence of palladium on alumina (Pd/Al2O3) or raney nickel. The efficiency of HDC varied from ~3% up to a completed dechlorination. Thus, organically bound chlorine in PVC in a water phase can be converted, virtually quantitatively, to chloride ion. === Response surface methodology (RSM) was used for experimental design and data analysis. The computer output from the Design-Expert software was used to optimize a model for the dechlorination as a function of time and temperature. A subsequent analysis of variance associated with the fitted model indicated a good fit between observed and predicted HDC efficiencies.