EVALUATION OF THE DEHYDROCHLORINATION
OF POLYVINYL CHLORIDE IN STEAM ATMOSPHERE
J.D. Fonseca, G. Grause, T. Kameda and T. Yoshioka*Graduate School of Environmental Studies, Tohoku University
e-mail:yoshioka@env.che.tohoku.ac.jp TEL/FAX: +81-22-795-7212

Abstract
The current research evaluates a process using steam for the acceleration of the thermal dehydrochlorination of polyvinyl
chloride (PVC) resin and flexible PVC. This process is aiming on waste streams such as medical equipment containing
PVC, which also requires a mandatory sterilization treatment. Thus, steam could act simultaneously as dechlorinationand sterilization agent.
Keywords: Dehydrochlorination; Atmospheric pressure; Medical waste

1. Introduction
Polyvinyl chloride (PVC) is a versatile material.
However the disposal of PVC-based waste isproblematic because of its high content ofchlorine. When incinerated, it is prone to
produce HCl which corrodes equipment, and isalso a precursor for dioxin formation. This
results in the release of hazrdous pollutants
into the atmosphere. Among the many
applications of PVC, medical tubing made fromflexible PVC is of interest for this research. A
process using steam that could beimplemented to fulfill both the need ofsterilization and dehydrochlorination of thiswaste was evaluated.

3. Results and Discussion
Steam assisted dehydrochlorination of PVC
resin: Results for PVC resin showed that asteam concentration of 50 vol% results in thehighest dehydrochlorination degree for all
temperatures (Fig.1a). It was observed that
there
wasa
sharp
increaseindehydrochlorination from 9.6 to 73.4% when
the temperature increased from 210 to 230 °C,
with no considerable rise afterward. Around
70% of the total dehydrochlorination occurred
between 15 and 60 minutes of reaction timeand only a further 10% was achieved for the2. Materials and Methods
0.5 g of either PVC resin or flexible PVC wereplaced on a ceramic boat inside a horizontal
glass-tube reactor. A total gas flow of 200 ml-1
min with varying compositions of 0, 25, 50
and 75 vol% steam was maintained. For eachsteam concentration, the reactor temperature
was set to values between 150 and 250 °C, forreaction time intervals ranging from 15 to 180
minutes. The amount of chlorine captured in
the iced water traps in the outlet of the reactor
was analyzed using ion chromatography andthe dehydrochlorination rate was calculated inrelation to the initial amount of chlorine present
in the sample mass: 57 wt% for PVC polymer
and 28 wt% for flexible PVC. Reaction kinetics
for steam dehydrochlorination of PVC resin
were obtainedusing thermogravimetricanalysis performed in helium and steam
atmosphere. The structure of the residue wasexamined by SEM and FT-IR.

Fig.1 Dehydrochlorination after 60 minutes atvariable steam fractions and temperatures forboth a) PVC resin and b) flexible PVC

7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013next 120 minutes of reaction time.
Steam assisted dehydrochlorination of flexible
PVC: It was also observed that steam had afavorable effect upon dehydrochlorination.
Both 50 vol% and 75 vol% contents of steam
had a similar effect upon the degree of
dehydrochlorination (Fig.1b). Dechlorination
increased with temperature, reaching amaximum of 68% at 250 °C with 50 vol%steam concentration in 60 minutes. Almost
complete dehydrochlorination was obtained
after 180 minutes under these conditions.
FT-IR (Fig. 2) showed a gradual increase of-1
the OH peak in the vicinity of 3400 cm and of-1
the C=C peak at 1680 cm that indicated not
only an effect of the temperature but also of
thesteamcontentupon
thedehydrochlorination. The decrease of the C=O-1
peak in 1700 cm at temperatures of morethan 210 °C indicated the decomposition of theplasticizer (Fig. 2a). It was also observed thatthe addition of steam increased the relative
occurrence of the substitution of Cl byOH-groups compared to results without steam.
(Fig. 2b).
Kinetics of dehydrochlorination using steam: It
is known that dehydrochlorination of PVC
initially proceeds as a zero order reaction, buta)b)

as dehydrochlorination progresses it tended to1)
follow a first order reaction model . This could
be observed for the steam assisted
dehydrochlorination as well. Activation energy-1
was calculated to be 120 kJ mol for bothreactions, with and without steam. This
activation energy values are consistent with1)
previously reported values for dry methods ,and are slightly lower in comparison to those ofother dehydrochlorination methods such as2)
NaOH/EG wet methods . Furthermore, thesimilar activation energies suggest that thereaction mechanisms are similar. However, thevalues of reaction rate constant k for the steam
assisted dehydrochlorination were 40-50%
higher compared to those of the reaction
without steam at 230 °C, 240 °C and 250 °C in
the first order reaction portion. Since thereaction mechanisms are similar in bothreactions, it can be assumed that the steam
improved the dehydrochlorination by acting asa heat and mass transfer medium.

4. Conclusions
The presence of steam in the processincreased the maximum dehydrochlorination
rate by about 15% for both PVC resin andflexible PVC. Furthermore, the reaction
kinetics study indicated that values of k wereobserved to be 40-50% faster when steam waspresent. According to these results, the use ofsteam dehydrochlorination as a pretreatment
for the recycling of PVC materials has benefits
over dry processing techniques such as
thermaldecomposition,
whileoffering
additional benefits for targeted waste streams
like flexible PVC used for medical purposes.
The higher degree of dehydrochlorination
provides a material better for posterior
recycling. The faster reaction allows a higher
volume of material to be processed in thesame amount of time. As for sterilization, eventhough the increased processing temperatures
alone can achieve this effect, the steam wasobserved to act as an effective heat and masstransport medium. This affects the heat
distribution in the waste positively, thus
assisting the effective sterilization of thematerial.

References[1] T. Yoshioka, N. Saitoh, A. Okuwaki, Chem.
Lett., 34, No.1 (2005) 70–71.
[2] T. Yoshioka, T. Kameda, S. Imai, A.
Okuwaki, Polym.Deg. and Stab., 93 (2008)
1138–1141.
Fig. 2 FT-IR spectra of flexible PVC at variousa) temperatures and b) steam contents at
250 °C. 60 minutes with 50 vol% steam.

7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013