on poly(vinyl chloride) dehydrochlorination - Environmental Expert
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on poly(vinyl chloride) dehydrochlorination - Environmental Expert
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J Mater Cycles Waste Manag (2006) 8:116–121 © Springer 2006<br />
DOI 10.1007/s10163-006-0154-9<br />
SPECIAL FEATURE: ORIGINAL ARTICLE<br />
Krzysztof German · Kamil Kulesza · Miriam Florack<br />
3rd Internati<strong>on</strong>al Symposium <strong>on</strong> Feedstock Recycling of<br />
Plastics & Other Innovative Plastics Recycling Techniques<br />
(ISFR 2005)<br />
Influence of <strong>poly</strong>(bisphenol A carb<strong>on</strong>ate) and <strong>poly</strong>(ethylene terephthalate)<br />
<strong>on</strong> <strong>poly</strong>(<strong>vinyl</strong> <strong>chloride</strong>) dehydrochlorinati<strong>on</strong><br />
Received: December 29, 2005 / Accepted: May 22, 2006<br />
Abstract Recycling of <strong>poly</strong>(<strong>vinyl</strong> <strong>chloride</strong>) (PVC) waste is<br />
a serious problem because of its high chlorine c<strong>on</strong>tent.<br />
Dehydrochlorinati<strong>on</strong> of PVC-c<strong>on</strong>taining <strong>poly</strong>mer waste<br />
produces solid residue char, for which c<strong>on</strong>versi<strong>on</strong> to<br />
pyrolysis oil in a petrochemical plant seems to be an attractive<br />
way of recycling PVC waste. Unfortunately, some<br />
<strong>poly</strong>mer admixtures react with HCl and cause formati<strong>on</strong> of<br />
chloroorganic compounds in a char. This article describes<br />
the influence of <strong>poly</strong>carb<strong>on</strong>ates and <strong>poly</strong>(ethylene terephthalate)<br />
<strong>on</strong> thermal feedstock recycling of PVC wastes using<br />
a two-stage method. It was found that the presence of<br />
<strong>poly</strong>carb<strong>on</strong>ate causes the formati<strong>on</strong> of small amounts of<br />
benzyl <strong>chloride</strong> and other chloroaryl or chloroalkylaryl<br />
compounds. Poly(ethylene terephthalate) interacts with<br />
HCl forming significant amounts of various chlorocompounds<br />
– mainly chloroethyl esters of terephthalic and<br />
benzoic acids, but derivatives possessing chlorine directly<br />
c<strong>on</strong>nected to the aromatic ring are also formed.<br />
Key words PVC · BPA-based PC · PET · Recycling ·<br />
Pyrolysis<br />
Introducti<strong>on</strong><br />
K. German 1 (*) · M. Florack<br />
Department of Chemistry and Technology of Polymers, Cracow<br />
University of Technology, Kraków, Poland<br />
K. Kulesza<br />
Blachownia Institute of Heavy Organic Synthesis, Kędzierzyn-Koźle,<br />
Poland<br />
Present address:<br />
1 Politechnika Krakowska, Samodzielna Katedra Chemii i Technologii<br />
Tworzyw Sztucznych, ul. Warszawska 24, 31–155 Kraków, Poland<br />
Tel. +48-12-628-21-14; Fax +48-12-628-20-38<br />
e-mail: kfgerm@chemia.pk.edu.pl<br />
The disposal of plastic wastes will become an important part<br />
of the chemical industry because of the large quantities of<br />
plastics produced and their envir<strong>on</strong>mental impact.Chlorinec<strong>on</strong>taining<br />
<strong>poly</strong>mers cause problems during material or<br />
energetic recycling because of their decompositi<strong>on</strong> with the<br />
evoluti<strong>on</strong> of HCl. The most comm<strong>on</strong>ly used chlorinec<strong>on</strong>taining<br />
<strong>poly</strong>mer is <strong>poly</strong>(<strong>vinyl</strong> <strong>chloride</strong>) (PVC), the<br />
decompositi<strong>on</strong> of which c<strong>on</strong>siderably limits material<br />
recycling due to the deteriorati<strong>on</strong> of its properties:<br />
–CH 2 –CHCl– mers eliminate HCl under the influence of<br />
heat (or light) and the PVC becomes yellowish or even<br />
blackish and loses its plasticity. Such waste can be used as a<br />
raw material for pyrolysis or for gasificati<strong>on</strong>. The choice<br />
between these two methods depends <strong>on</strong> the amount of chlorine<br />
in the char residue derived from a mixture of plastics<br />
after HCl eliminati<strong>on</strong> from PVC. In this article we present<br />
gas chromatography (GC) results after the thermal treatment<br />
of pure PVC and of PVC mixtures with <strong>poly</strong>(ethylene<br />
terephthalate) (PET) and with <strong>poly</strong>carb<strong>on</strong>ate (PC).<br />
Two main, mostly n<strong>on</strong>overlapping, stages of mass loss are<br />
observed during the thermal analysis of PVC. 1,2 In <strong>on</strong>e<br />
series of experiments 0.5g samples of pure PVC underwent<br />
a dehydrochlorinati<strong>on</strong> (DHC) reacti<strong>on</strong> at temperatures of<br />
up to 400°C. DHC was dic<strong>on</strong>tinued when the char was free<br />
of chlorine (to the accuracy of c<strong>on</strong>ductometric analysis of<br />
eliminated HCl). DHC was followed by pyrolysis, which<br />
mainly formed aromatic hydrocarb<strong>on</strong>s – chloroorganic<br />
compounds were not found by gas chromatography coupled<br />
with mass detector (GC-MS) analysis. 2 In c<strong>on</strong>trast, Tromp<br />
et al. 3 found chlorobenzene and methylchlorobenzene<br />
after pyrolysis; however, it is not clear whether formati<strong>on</strong><br />
of these compounds resulted from admixtures present in the<br />
sample.<br />
Segregati<strong>on</strong> methods for plastic wastes that are acceptable<br />
from the ec<strong>on</strong>omical point of view do not guarantee<br />
100% selectivity. If density difference is applied as the segregati<strong>on</strong><br />
factor, PET remains in the PVC plastic fracti<strong>on</strong><br />
(Table 1). Other <strong>poly</strong>mers having a lower density will also<br />
be present in this fracti<strong>on</strong>; such <strong>poly</strong>mers are usually filled<br />
with inorganic additives (e.g., <strong>poly</strong>carb<strong>on</strong>ates). Both the<br />
<strong>poly</strong>mers PET and PC can react with HCl to form<br />
chloroderivatives, which then c<strong>on</strong>taminate the pyrolysis<br />
products of the char residue. The aim of our investigati<strong>on</strong>s<br />
is the identificati<strong>on</strong> of such compounds.
117<br />
Over the past decade, c<strong>on</strong>siderable progress has been<br />
reported in the development of methods of dechlorinati<strong>on</strong><br />
of pyrolysis oil, 4–13 but not all the problems have been<br />
solved as yet. Complete dechlorinati<strong>on</strong> is hard to realize if<br />
the dehydrochlorinated mixture also c<strong>on</strong>tains <strong>poly</strong>esters<br />
(e.g., PET). Some of the c<strong>on</strong>secutive HCl reacti<strong>on</strong>s that<br />
occur during the heating of these mixtures are yet to be elucidated.<br />
The goal of this work is to make progress in this<br />
area.<br />
The thermal degradati<strong>on</strong> of PVC has already been the<br />
subject of numerous investigati<strong>on</strong>s. Some attenti<strong>on</strong> has also<br />
been paid to the thermal degradati<strong>on</strong> of PET 14–16 and<br />
PC, 17–22 but the behavior of PVC–PET mixtures and especially<br />
the interacti<strong>on</strong> of PVC with PC have been less<br />
studied. The dehydrochlorinati<strong>on</strong> of PVC starts at temperatures<br />
of about 100°C lower than for PET and, if the <strong>poly</strong>mers<br />
are degraded separately, PVC is almost completely<br />
degraded before the temperature is reached at which PET<br />
starts to degrade (Fig. 1); however, the presence of HCl<br />
accelerates PET degradati<strong>on</strong> if the <strong>poly</strong>mers are mixed.<br />
The influence of PVC (mainly HCl from PVC) <strong>on</strong> the<br />
compositi<strong>on</strong> of the products of PET pyrolysis was discussed<br />
Table 1. Density of selected <strong>poly</strong>mers<br />
Polymer Abbreviati<strong>on</strong> Density (g/cm 3 )<br />
Polyolefines PE, PP 0.89–0.97<br />
Polystyrene PS 1.04–1.08<br />
Polyamide PA 1.03–1.15<br />
Polyurethane elastomers PU 1.10<br />
Poly(methyl methacrylate) PMMA 1.18<br />
Polycarb<strong>on</strong>ate PC 1.20<br />
(filled with glass fibers) 1.42<br />
Poly(<strong>vinyl</strong> <strong>chloride</strong>) PVC 1.38–1.55<br />
(plastificated) 1.19–1.38<br />
Poly(ethylene terephthalate) PET 1.38–1.41<br />
Polytetrafluorethylene PTFE 2.20<br />
in <strong>on</strong>e of our previous papers, 23 but our knowledge c<strong>on</strong>cerning<br />
this process has increased since that time.The interacti<strong>on</strong><br />
between PVC and PET was also taken into account<br />
in an article in which the pyrolysis of a selected mixture<br />
of plastics [intended to simulate municipal plastic waste<br />
(MPW)] was described 8 .The article describes the results of<br />
gas chromatography coupled with atomic emissi<strong>on</strong> detector<br />
(GC-AED) analysis, as well as showing C-NP grams based<br />
<strong>on</strong> gas chromatography coupled with flame i<strong>on</strong>izati<strong>on</strong><br />
detecter (GC-FID) results and selected results of the GC-<br />
MS analysis, which agree with the results of our model<br />
experiments. In the above work, 8 Bhaskar, with coworkers<br />
from the Sakata group, also reported the presence of some<br />
chloroalkyl esters; however, identificati<strong>on</strong> of the particular<br />
halogen compounds was not the goal of that work and<br />
detailed results were not given. Complex plastic mixtures,<br />
which also c<strong>on</strong>tain other halogen-c<strong>on</strong>taining <strong>poly</strong>mers,<br />
for example high impact <strong>poly</strong>styrene flame retarded with<br />
bromine compounds (HIPS-Br) or chlorinated PVC and<br />
<strong>poly</strong>(<strong>vinyl</strong>idene di<strong>chloride</strong>) (PVDC) have been intensively<br />
investigated (e.g., by Bhaskar et al. 9 and Jakab et al. 24 ). In<br />
our opini<strong>on</strong>, apart from the very important general experiments<br />
as described above, there is still a requirement for<br />
basic studies that seek for an explanati<strong>on</strong> of the formati<strong>on</strong><br />
pathways of halogen-c<strong>on</strong>taining compounds in more complex<br />
mixtures of plastic waste.<br />
Fast degradati<strong>on</strong> of PET starts at temperatures around<br />
350°C. No volatile products of thermal degradati<strong>on</strong> of<br />
bisphenol A-based <strong>poly</strong>carb<strong>on</strong>ate (BPA–PC) in an inert<br />
atmosphere were obtained up to 400°C. 17,18 It was found<br />
that product compositi<strong>on</strong> depended <strong>on</strong> the reacti<strong>on</strong><br />
medium – alkali media catalyze rearrangement reacti<strong>on</strong>s,<br />
whereas acids and other substances with active hydrogen<br />
atoms induce de<strong>poly</strong>merizati<strong>on</strong>. 19 Investigati<strong>on</strong>s of the<br />
pyrolysis of PVC–PC mixtures have not so far been<br />
reported. It is expected that the thermochemical de-<br />
0<br />
-1.6<br />
0<br />
0<br />
Mass loss of PVC sample<br />
-1<br />
-2<br />
-3<br />
-4<br />
TG - curve<br />
DTG - curve<br />
-1.8<br />
-2.0<br />
-2.2<br />
-2.4<br />
1 st derivative [mg/min]<br />
Mass loss of PET sample [mg]<br />
-1<br />
-2<br />
-3<br />
-4<br />
-5<br />
-6<br />
-7<br />
-8<br />
TG - curve<br />
DTG - curve<br />
-1<br />
-2<br />
-3<br />
-4<br />
-5<br />
1 st derivative [mg/min]<br />
-5<br />
0 100 200 300 400 500<br />
Temperature [°C]<br />
-2.6<br />
-9<br />
0 100 200 300 400 500<br />
Temperature [°C]<br />
-6<br />
Fig. 1. Thermogravimetric (TG) and derivative thermogravimetric (DTG) curves of <strong>poly</strong>(<strong>vinyl</strong> <strong>chloride</strong>) (PVC) and <strong>poly</strong>(ethylene terephthalate)<br />
(PET) degradati<strong>on</strong> in an inert atmosphere
118<br />
gradati<strong>on</strong> of BPA–PC should be observed in the presence<br />
of HCl.<br />
Experimental<br />
Materials<br />
Poly(<strong>vinyl</strong> <strong>chloride</strong>) (PVC S-70) was acquired from Anwil<br />
(Wl′ocl′awek, Poland), the BPA-based <strong>poly</strong>carb<strong>on</strong>ate<br />
LEXAN was provided as waste plastic by Telkom-<br />
Telos (Kraków, Poland), analytical grade carb<strong>on</strong> disulfide<br />
was from Riedel-de Haën (Seelze, Germany), HPLC-grade<br />
dichloromethane was from Aldrich (Steinheim, Germany),<br />
and active carb<strong>on</strong> samples from SKC (Dorset, UK).<br />
acid and biphenyl. Moreover, small amounts of other compounds<br />
were identified, as shown in Fig. 3. The retenti<strong>on</strong><br />
time of acetaldehyde was less than 14min.<br />
The product compositi<strong>on</strong> of the pyrolysis of PET<br />
changed radically in the presence of PVC (HCl), which<br />
caused the formati<strong>on</strong> of a great number of organic<br />
chloroderivatives. It is clear that the amount of these compounds<br />
produced depends <strong>on</strong> the proporti<strong>on</strong> of PVC to<br />
PET in the dehydrochlorinated and then pyrolyzed samples.<br />
High chlorine c<strong>on</strong>tent was the goal of our work because it<br />
makes for easier product identificati<strong>on</strong>, so we used 1:1<br />
(w/w) PVC–PET mixtures. In real-life waste mixtures there<br />
will be less PET than PVC.<br />
Table 2. Pyrolysis products of PVC char residue at 550°C<br />
Techniques<br />
Dehydrochlorinati<strong>on</strong> and pyrolysis were c<strong>on</strong>ducted in a<br />
purpose-built pyrolysis setup, as shown in Fig. 2. Samples<br />
weighed between 10 and 50g and the temperature was measured<br />
by a NiCr–NiAl thermocouple. Pyrolysis products<br />
were transported by nitrogen as a carrier gas into a glass<br />
c<strong>on</strong>denser system (air and water cooler) with an active<br />
carb<strong>on</strong> adsorber and water scrubber located at the<br />
<strong>poly</strong>propylene off-gas pipe. Dehydrochlorinati<strong>on</strong> was performed<br />
at 350°C for 90min and was followed by pyrolysis<br />
at 500°C for 90min.The pyrolysis of PC and PET separately<br />
was performed for comparis<strong>on</strong> under the same c<strong>on</strong>diti<strong>on</strong>s<br />
(90min at 350°C followed by 90min at 500°C). C<strong>on</strong>densed<br />
pyrolysis products were dissolved in CH 2 Cl 2 ; products<br />
adsorbed <strong>on</strong> active carb<strong>on</strong> were extracted by 4cm 3 of CS 2 .<br />
The soluti<strong>on</strong>s were analyzed by gas chromatography<br />
coupled with a quadruple mass detector (GC-MS, HP 8590<br />
Series 2 equipped with 30m HP-1 column) using helium as<br />
the carrier gas.<br />
Results and discussi<strong>on</strong><br />
Our early work <strong>on</strong> PVC dehydrochlorinati<strong>on</strong> and pyrolysis<br />
gave us much informati<strong>on</strong> about c<strong>on</strong>taminati<strong>on</strong>s of the<br />
derived oil (Table 2); however, when pure <strong>poly</strong>mer was<br />
used, we detected no chloroorganic compounds. The oil<br />
fracti<strong>on</strong> from the pyrolysis of PET c<strong>on</strong>tains mainly benzoic<br />
Pyrolysis product; R = H, alkyl Molar ratio C/H Peak area (%)<br />
R<br />
R<br />
R<br />
R<br />
R<br />
R<br />
R<br />
1 2<br />
1 3<br />
>1 1<br />
>1 to 1 11<br />
>1 2<br />
>1 4<br />
>1 2<br />
R<br />
R<br />
>1 2<br />
Unidentified 15<br />
Abundance<br />
TIC: MF6.D<br />
4000000<br />
3500000<br />
3000000<br />
COOH<br />
COOH<br />
O<br />
2500000<br />
2000000<br />
1500000<br />
1000000<br />
500000<br />
COOH<br />
Time--><br />
0<br />
14.00 16.00 18.00 20.00 22.00 24.00 26.00<br />
O<br />
CH<br />
o-terphenyl<br />
C 18 H 14<br />
C 14 H 10<br />
C 18 H 14<br />
Fig. 2. Experimental setup for pyrolysis<br />
Fig. 3. Result of GC-MS analysis of liquid products formed during<br />
PET pyrolysis
119<br />
Table 3. Chloroorganic products of PVC–PET 1 : 1 (w/w) mixture pyrolyzed at 450°C<br />
Chloroorganic compounds Peak area share (%)<br />
Chlorine in an aliphatic moiety<br />
Methane, bis(2-chloroethoxy) 0.8<br />
Chlorine in an aliphatic moiety of benzoic acid esters<br />
Benzoic acid, 2-chloroethyl ester 11.2<br />
4-Methyl and 4-formyl benzoic acid, 2-chloroethyl esters 8.5<br />
Chlorine in an aliphatic moiety of 1,4-benzenedicarboxylic acid esters<br />
1,4-Benzenedicarboxylic acid, m<strong>on</strong>o-2-chloroethyl esters 18.8<br />
1,4-Benzenedicarboxylic acid, bis-(2-chloroethyl ester) 30.6<br />
Chlorine in an aromatic ring<br />
3- and 4-Chlorobenzoic acid, ethyl ester 0.3<br />
Chlorine in an aromatic ring and in an aliphatic moiety<br />
4-Chlorobenzoic acid, 2-chloroethyl ester 0.4<br />
CH2CH2OOC<br />
COOCH2CH2OOC<br />
COOCH2CH2OH<br />
Abundance<br />
1.5e+07<br />
1.4e+07<br />
TIC: [BSB1]MF5.D<br />
1.3e+07<br />
1.2e+07<br />
HCl<br />
1.1e+07<br />
1e+07<br />
9000000<br />
8000000<br />
CH2CH2OOC COOH + ClCH2CH2OOC COOCH2CH2OH<br />
7000000<br />
6000000<br />
5000000<br />
4000000<br />
3000000<br />
HCl<br />
+HCl<br />
- H2O<br />
2000000<br />
1000000<br />
Time--><br />
0<br />
5.00 10.00 15.00 20.00 25.00 30.00<br />
CH2CH2Cl + HOOC<br />
COOH<br />
ClCH2CH2OOC<br />
COOCH2CH2Cl<br />
Fig. 5. Chromatogram of the products of <strong>poly</strong>carb<strong>on</strong>ate (PC)<br />
pyrolysis<br />
COOCH2CH2OOC<br />
COOCH2CH2Cl<br />
Abundance<br />
5500000<br />
5000000<br />
OH<br />
TIC: MF7.D<br />
OH<br />
HCl<br />
4500000<br />
4000000<br />
3500000<br />
O<br />
COOH<br />
+<br />
ClCH2CH2OOC<br />
COOCH2CH2Cl<br />
3000000<br />
2500000<br />
2000000<br />
Fig. 4. Formati<strong>on</strong> of chloroderivatives from PET in the presence of<br />
HCl<br />
1500000<br />
1000000<br />
500000<br />
0<br />
Time--><br />
5.00 10.00 15.00 20.00 25.00 30.00<br />
Fig. 6. GC-MS result of analysis of pyrolysis products of dehydrochlorinated<br />
PVC-PC (1:1 w/w) mixture<br />
Some of the chlorine compounds derived are specified in<br />
Table 3. Identificati<strong>on</strong> of these compounds was described<br />
in an earlier paper. 23 A possible formati<strong>on</strong> pathway of<br />
chloroderivatives from PET in reacti<strong>on</strong> with HCl is<br />
presented in Fig. 4. HCl attacks the ester b<strong>on</strong>d and a<br />
transesterificati<strong>on</strong> reacti<strong>on</strong> leads to formati<strong>on</strong> of the<br />
–COOC 2 H 4 Cl group. The atypical structure of<br />
–COOC 2 H 4 Cl and the relatively high probability of its formati<strong>on</strong><br />
are sources of the problems with dechlorinati<strong>on</strong> of<br />
pyrolysis oil derived from PVC-c<strong>on</strong>taining PET. It is noteworthy<br />
that chloroorganic derivatives (for example 3-<br />
chlorobenzoic acid and 4-chlorobenzoic acid) are formed<br />
not <strong>on</strong>ly in the transesterificati<strong>on</strong> reacti<strong>on</strong> of <strong>poly</strong>ester and<br />
HCl; compounds that include the formyl group, the alkyl<br />
group, or chlorine c<strong>on</strong>nected to an aromatic ring can be<br />
formed by c<strong>on</strong>secutive reacti<strong>on</strong>s after decarboxylati<strong>on</strong> of<br />
terephthalic acid m<strong>on</strong>o-2-chloroethyl ester.<br />
A chromatogram of the oil fracti<strong>on</strong> obtained during<br />
pyrolysis of PC is presented in Fig. 5. We did not find fluoren<strong>on</strong>e<br />
or xanth<strong>on</strong>e derivatives – in c<strong>on</strong>trast to the results<br />
described in other works 19,21 – and this fact can be explained<br />
by the absence of basic catalysts in the reacti<strong>on</strong> medium.<br />
A chromatogram of the oil fracti<strong>on</strong> produced by pyrolysis<br />
of a 1:1 (w/w) PC–PVC mixture is shown in Fig. 6.<br />
The main products of pyrolysis of a dehydrochlorinated<br />
PVC–PC mixture are phenol, 4-isopropylphenol, and 1-<br />
isopropyl-4-phenoxybenzene. Our results c<strong>on</strong>firm the findings<br />
regarding the influence of an acidic medium <strong>on</strong> the<br />
mechanism of thermal degradati<strong>on</strong> of PC.<br />
Am<strong>on</strong>g the pyrolysis products c<strong>on</strong>densed in oil fracti<strong>on</strong>s<br />
derived under the previously described DHC and pyrolysis<br />
c<strong>on</strong>diti<strong>on</strong>s, we did not find the chlorine derivatives<br />
predicted by the reacti<strong>on</strong> scheme shown in Fig. 7. We did<br />
find a number of these compounds am<strong>on</strong>g the products
120<br />
adsorbed <strong>on</strong> active carb<strong>on</strong>, but some of them were in<br />
isomerized form. A chromatogram of these products is presented<br />
in Fig. 8. The area of the peaks of all chlorocompounds<br />
that were identified by GC analysis is about 2%–3%<br />
H<br />
O<br />
O<br />
O<br />
C<br />
O<br />
HCl<br />
O<br />
O<br />
C<br />
+<br />
C<br />
HCl<br />
Cl<br />
O<br />
C<br />
H Cl +<br />
C<br />
HCl<br />
H<br />
H<br />
HCl<br />
O<br />
O<br />
HCl<br />
-CO2<br />
HCl<br />
Cl<br />
O H + CO2 +<br />
Fig. 7. Potential pathways for chloroderivative formati<strong>on</strong> during the<br />
interacti<strong>on</strong> of PC and HCl<br />
Abundance<br />
1.5e+07<br />
1.4e+07<br />
1.3e+07<br />
1.2e+07<br />
1.1e+07<br />
1e+07<br />
9000000<br />
8000000<br />
7000000<br />
6000000<br />
5000000<br />
4000000<br />
3000000<br />
2000000<br />
1000000<br />
0<br />
Time--><br />
Cl<br />
Cl<br />
Cl<br />
+<br />
Cl<br />
CH 2<br />
Cl<br />
+A<br />
5.00 10.00 15.00 20.00 25.00 30.00<br />
+<br />
TIC: MF9G1.D<br />
OH +<br />
Cl<br />
C<br />
Cl<br />
Cl<br />
+<br />
(treaces)<br />
Fig. 8. Chromatogram of products formed during pyrolysis of PVC–PC<br />
(1 : 1 w/w mixture) adsorbed <strong>on</strong> active carb<strong>on</strong><br />
Cl<br />
Cl<br />
Cl<br />
C<br />
C<br />
C<br />
HCl<br />
Cl<br />
+<br />
HCl<br />
A<br />
of the total area, but based <strong>on</strong> this it is not possible to say<br />
whether the ratio of chlorine in the oil fracti<strong>on</strong> from pyrolysis<br />
of PVC–PC mixtures exceeds the technological threshold<br />
of 10ppm, even though the amount of PC in waste<br />
mixtures is much lower than in our mixture. Identificati<strong>on</strong><br />
of chlorine derivatives by means of GC-MS requires<br />
close attenti<strong>on</strong> because of the masking effect of Cl-isotopes<br />
by signals resulting from other fragmentati<strong>on</strong> paths,<br />
especially when some compounds are not separated in the<br />
GC column. For example, it was not possible to detect<br />
the presence of 4-chlorophenol using <strong>on</strong>ly analytical standards<br />
because signals of this chloroderivative were masked<br />
by the signals of naphthalene. We did not separate<br />
these substances in our chromatograph column. Benzene<br />
di<strong>chloride</strong> and benzyl <strong>chloride</strong> were also not separated<br />
because of their similar vapor pressures, but they give<br />
characteristic signals at slightly different retenti<strong>on</strong> times<br />
(Fig. 9).<br />
Pyrolysis of PVC–PET–PC (1:1:1) mixtures did not<br />
reveal new chlorine-c<strong>on</strong>taining compounds, but the analysis<br />
has not yet been completed because of its complexity.<br />
C<strong>on</strong>clusi<strong>on</strong>s<br />
PET interacts with HCl forming large amounts of<br />
chloroderivatives, mainly chloroethyl esters of terephthalic<br />
acid and of benzoic acid but also compounds with chlorine<br />
in the benzene ring. Pyrolysis of BPA-based <strong>poly</strong>carb<strong>on</strong>ate<br />
produced 4-methylphenol, 4-ethylphenol, 4-isopropylphenol,<br />
4-(1-methyl-1-phenylethyl) phenol, 1-isopropyl-4-<br />
phenoxybenzene, BPA, and small amounts of other<br />
compounds. HCl evolved during the dehydrochlorinati<strong>on</strong> of<br />
PVC–PC mixtures changes the compositi<strong>on</strong> of PC degradati<strong>on</strong><br />
products – mainly phenol, isopropylphenol, and<br />
1-isopropyl-4-phenoxy-benzene are produced. Polyesters<br />
Fig. 9. Profile of characteristic<br />
fragmentati<strong>on</strong> signals of<br />
benzene di<strong>chloride</strong> and benzyl<br />
<strong>chloride</strong><br />
Abundance<br />
100000<br />
50000<br />
0<br />
Time--><br />
I<strong>on</strong> 146.00 (145.70 to 146.70): MF9G1.D<br />
10.30 10.40 10.50 10.60 10.70 10.80<br />
Abundance<br />
I<strong>on</strong> 148.00 (147.70 to 148.70): MF9G1.D<br />
100000<br />
50000<br />
0<br />
Time--><br />
10.30 10.40 10.50 10.60 10.70 10.80<br />
Abundance<br />
I<strong>on</strong> 126.00 (125.70 to 126.70): MF9G1.D<br />
100000<br />
50000<br />
0<br />
Time--><br />
10.30 10.40 10.50 10.60 10.70 10.80<br />
Abundance<br />
I<strong>on</strong> 128.00 (127.70 to 128.70): MF9G1.D<br />
100000<br />
50000<br />
0<br />
Time--><br />
10.30 10.40 10.50 10.60 10.70 10.80
121<br />
show interacti<strong>on</strong> with HCl at temperatures below 350°C.<br />
These sec<strong>on</strong>dary reacti<strong>on</strong>s during thermal degradati<strong>on</strong> of<br />
PVC–PC mixtures produce small amounts of halogen derivatives<br />
such as chlorobenzene, 1,4-dichlorobenzene, benzyl<br />
<strong>chloride</strong>, 4-chlorophenol, and isopropylchlorobenzene. The<br />
diversity of these substances proves that a universal method<br />
is necessary to eliminate the chlorine c<strong>on</strong>tent from char<br />
residue or from pyrolysis oil.<br />
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