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TOLEDO (SPAIN)CATALYTIC DECOMPOSITION OF NITROGEN-CONTAINING POLYMERS MIXEDWITH ZEOLITE CATALYSTS
J. Bozi1, and M. Blazsó1
1Institute of Materials and Environmental Chemistry, Chemical Research Center, Hungarian Academy of Sciences, H-1525

Budapest, P.O. Box 17, Hungary
e-mail: bozij@chemres.huAbstract
Thermal degradation of nitrogen-containing polymers may produce broad product range and environmentally hazardous
compounds; therefore catalytic pyrolysis was investigated as an alternative process solving these problems.
In this work nitrogen-containing polymers (polyamides and polyurethane) and acidic zeolite catalysts were mixed andthan pyrolysied at 500°C in a micro-pyrolyser on-line coupled with GC/MS.
The analysis of pyrolysis products revealed the nature of chemical reactions taking place in the presence of zeolites. The
experimental results show that most polymer segments cracked to gases and to compounds of gasoline volatility,
moreover aromatization takes place. However, there are distinctive differences in the decomposition paths of polymers
depending on the cation of zeolite.

Keywords: Polyamide-6,6, Polyamide-6, PUR, catalytic conversion, Pyrolysis–GC/MS

1. Introduction

2. Materials and Methods

Pyrolysis proved to be a suitable method for recycling
plastic waste at temperature range of 400–800°C [1].
Nevertheless, under thermal degradation of polymers
often a broad range of products are evolved, a highoperating temperature is required, and environmentallyhazardous compounds may be produced. Catalytic
pyrolysis proved to be an alternative process for avoiding
the above disadvantages. A suitable catalyst can bothcontrol the nature of the products and reduce thereaction temperature. Among various commercial orlaboratory prepared catalysts zeolite has been appliedoften [2–4].
Waste electronic and electric equipments (WEEE), andautomotive plastic shredder contain nitrogen-containing
polymers and various additives, therefore catalytic
pyrolysis may be an adequate way of recycling this kindof waste. There are two methods of catalytic conversion,
namely the catalytic upgrading of pyrolysis oils and thepyrolysis in the presence of catalyst.
The effect of zeolites on the thermal catalytic conversionof pyrolysis gases and oils of nitrogen-containing
polymers has been studied in our laboratory earlier [5,6].
The purpose of this work was to examine the pyrolysis
products derived from zeolite-polymer mixtures preparedin different ways and compositions in order to elucidate
the chemical reactions taking place under pyrolysis ofpolyamides and polyurethanes in the presence of acidic
zeolites.

2.1 Materials
2.1.1. Polymers
Polyamide-6,6 (PA-6,6), polyamide-6 (PA-6), polyamide12 (PA-12), polyester based polyurethane (PURest)
2.1.2. Catalysts
Zeolites used in this study were Y zeolites with averagepore diameter 0.74 nm, namely ultra stable hydrogenform of Si/Al = 2.49 (HUSY) and NH4NaY, Si/Al = 2.44(Grace Davison).
2.2 Pyrolysis-GC/MS
Pyrolysis–GC/MS experiments were performed at 500°C
for 20 s in a Pyroprobe 2000 pyrolyser (Chemical DataSystem, USA) equipped with a platinum coil and quartz
sample tube interfaced to a gas chromatograph (Agilent6890) coupled with a mass selective detector (Agilent5973). The polymers were mixed with the catalysts in theratios of 1:1, 1:3 and 1:5 and were placed into thesample holder quartz tube. Approximately 0.2 mg
polymer sample was pyrolysed. Helium carrier gas at aflow rate of 20mLmin−1 purged the pyrolysis chamber
held at 250°C that was split prior to be introduced into
the GC column. The GC separation was carried out on aHP-5MS capillary column (30m×0.25mm×0.25μm,Agilent Technologies, USA). After 1 min of isotherm
period at 50°C the oven temperature was programmed to300°C at 10°Cmin−1 heating rate and held at 300°C for 4min. The temperature of the transfer line of GC/MS andthe source of the mass spectrometer were 280 and230°C, respectively. The mass spectrometer wasinteriores libro.indd 75

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6th International Symposium on Feedstock Recycling of Polymeric Materials

operating in electron-impact mode (EI) at 70 eV. The
spectra were obtained over a mass range of 14–500 Da.

3. Results and Discussion
The acidic Y type zeolites (NH4NaY and HUSY) havesignificant effect on the degradation of polyamides (PA6,6, PA-6, PA-12) and polyurethane. Both have strong
catalytic cracking activity, however some characteristic
compounds of pyrolysis oils are different in the cases ofHUSY and NH4NaY.
3.1. Pyrolysis products of polyamides
Thermal decomposition of PA-6,6 and PA-12 leads to awide range of N-containing compounds. Amines, amides
and nitriles are found in these pyrolysates beside CO2,
unsaturated and cyclic hydrocarbons.
The structure and composition of these components arematching with the known thermal decomposition
mechanisms of cis-elimination and intramolecularrearrangements producing cyclic diamide and otheroligomeric cycles.
The most important thermal decomposition product ofPA-6 is H-caprolactam, however other N-containing andunsaturated hydrocarbons are also present.
Pyrolysis products of pure polyamides and polyamidezeolite mixtures are considerably different. Most of thepyrolysis products of polyamides either disappear or
notably diminish in the mixtures’ pyrolysates, while theamount of some originally negligible or undetectablecompounds increases significantly.
The cracking activity of zeolites is obvious. Heavy oil
components no longer present in the polymer-zeoilte
pyrolysates, but the amount of gases and compounds ofgasoline volatility became dominant. The intensity of lightunsaturated and cyclic hydrocarbons are prominent,
however several aromatic hydrocarbons (benzene,naphthalene, alkylbenzene and alkylnaphthalenecompounds) are present as well. No peaks occur after 15
minutes retention time.
The presence of NH4NaY has further consequences on
the decomposition mechanisms of polyamides and on
the oil composition. Not only the rearrangement of amide
linkages along the macromolecular chains is inhibited,
but this zeolite promotes the N-Calkyl bond cleavage
suppressing the homolytic cleavage of N-Ccarbonyl bonds.
Therefore hexanedinitrile, hex-5-enenitrile are still
determinant components in the pyrolysis oils of PA-6,6and PA-6 respectively.
This specific effect of NH4NaY may due to theammonolysis by means of the evolved NH3.
3.2. Pyrolysis products of aromatic polyester based
polyurethane
At 500°C the decomposition of polyester segmented
polyurethane leads to the formation of CO2, 1,3butadiene, tetrahydrofuran (THF), cyclopentanone, bis(4isocyanatophenyl)methane (MDI), and a number of ester
compounds.
Mixing the polyurethane sample with protonic Y zeolitesresults the alteration of MDI and the ester compounds ofinteriores libro.indd 76

high molecular mass into aromatic compounds whilemost of the gases and high volatility oil components areunchanged.
The pyrolysis oil composition of polyurethane mixed with
NH4NaY or HUSY is quite similar; however
tetrahydrofuran is completely eliminated from thepyrolysis oil of polyurethane-HUSY, while in the oil ofpolyurethane-NH4NaY it is still present.
Comparison of these present results with those ofpyrolysis oils were transformed over zeolit catalysts [5,6]has also been carried out.
It can be concluded that in both cases strong cracking
and aromatization were observed, but as for the mixtures
the zeolite influences the thermal decomposition
mechanisms as well. Therefore the product distributiondiffers and instead of extensive denitrogenation theformation of some nitrogen-containing pyrolysis products
is enhanced.

4. Conclusions
Pyrolysis studies of polyamide-protonic Y andpolyurethane-protonic Y zeolite mixtures revealed thatthese catalysts are directing the pyrolysis reactions
producing dominantly olefins and aromatics of low
molecular mass. Although both zeolites crack thepolymer chains there are characteristic differences in thecomposition of the pyrolysis oils.
Since the zeolites affect the decomposition reactions ofpolymers the pyrolysis oil compositions are differ fromthose of the pyrolysis oil products of polymers weretransformed over zeolite catalysts.

References[1] J. Scheirs,W. Kaminsky (Eds.), Feedstock Recycling
and Pyrolysis of Waste Plastics, Chichester, 2006. Wiley[2] J. Aguado, D. P. Serrano, G. San Miguel, J. M. Escolaand J. M. Rodrígues, Catalytic activity of zeolitic andmesostructured catalysts in the cracking of pure andwaste polyolefins, J. Anal. Appl. Pyrolysis 78 (2007) 153–161.
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