In-situ decreasing of contaminants in products of agricultural plastic waste
pyrolysis
N. Miskolczi*, N. Borsodi, L. Bartha
MOL Department of Hydrocarbon and Coal Processing, University of Pannonia, 10 Egyetem u., 8200, Veszprém, Hungary
e-mail: mnorbert@almos.uni-pannon.hu, tel: +36 88 624 000, fax: +36 88 624720

Abstract
This paper discloses the possibility of in-situ contaminant decreasing during pyrolysis of contaminated polyethylene wastefrom agricultural sector using different metal containing catalysts. Pyrolysis was carried out at 450 and 600°C. For
modification of product yield, composition and contaminant quantity Co-Mo catalyst, Ni-Mo catalyst, MoO3, CaO, Fe2O3,TiO2 have been applied. Both gas and pyrolysis oil yield could be increased by catalysts; Ni-Mo catalyst was the mostefficient in gas yield increasing, while Co-Mo in pyrolysis oil yields increasing. Mainly C2, C3 and C4 hydrocarbons wereinvolved in gaseous products and they were contaminated by nitrogen, sulphur, chorine, and phosphorous. Pyrolysis oils
could be characterized as hydrocarbon mixtures from C5 to C26 and they consisted of S, N, P, Cl, K and Ca ascontaminants. Catalysts could increase the branched and aromatic hydrocarbon content of pyrolysis oils, while decrease
their contaminant level. Especially Ni-Mo catalyst showed advanced behaviour in contaminant decreasing.

Keywords: pyrolysis, contaminants, EDXRFS, pyrolysis oil

1. Introduction
Pyrolysis is one of the possible ways for waste
plastic/polymer recycling. Many papers give excellent
summary about the effect of pyrolysis parameters(temperature, raw materials, reactor construction,catalysts, etc.) to the product yield and composition, but
the decreasing of contaminants in pyrolysis product is a
big challenge yet. Especially S, N and Cl are the mostproblematic contaminants, because they are reversible
and irreversible catalyst poisonings in further utilization
process of pyrolysis products [1-5].
The aim of our work was to investigate the possibility ofin-situ contaminant decreasing in pyrolysis using different
metal containing catalysts.

2. Materials and Methods
Waste polyethylene from agricultural sector was used as
raw material. Based on ICP-OES analysis it consisted ofS, N, P, Cl, K and Ca as contaminants. FTIR analysis
has resulted that raw material consisted of 73.1% LDPE,
19.3% HDPE, 5.1% PP, and 2.5% PS. For modificationof product yield, hydrocarbon composition andcontaminant quantity Co-Mo catalyst, Ni-Mo catalyst,
MoO3, CaO, Fe2O3 and TiO2 have been applied.
Pyrolysis was carried out at 450ºC and 600°C.
Temperature has been controlled by PID controller andmeasured with thermocouple. Gaseous pyrolysis
products were driven in a water cooler, and thecondensable fraction transformed into liquid at 20ºC.
Heavy fractions had been removed from separation unit
and the heavy oil separated from char by hightemperature pressure filtration. Gases and pyrolysis oils
were analyzed by GC, FTIR, EDXRFS methods, while
heavy oils by SEC, too.

3. Results and Discussion
The yields of both gaseous products and pyrolysis oils
were higher at higher temperature, or using catalysts. NiMo catalyst was the most efficient in gas yield increasing,while Co-Mo in pyrolysis oil yields increasing. Higher
yields of volatile products were found using catalysts withhigher Si/Al ratio and pore surface areas.
Gaseous products contained dominantly C2, C3 and C4hydrocarbons. The branched content in gases could beincreased by catalysts, especially by Ni-Mo catalyst.
Regarding contaminants, S, Cl and P were measured ingases. Their level could be significantly decreased byCaO catalyst, while increasing in S, Cl and P levels were
found using TiO2, Ni-Mo, Co-Mo and MoO3 catalysts.
Pyrolysis oils could be characterized as hydrocarbon
mixtures from C5 to C26; n-olefin, n-paraffin, branchedhydrocarbons, aromatics and naphthenic were involvedin pyrolysis oils. Based on GC analysis catalyst
application could increase the aromatic and branchedhydrocarbon content, which was the consequence of themore intensive isomerization and aromatization
reactions. Ni-Mo and Co-Mo catalysts have shown highefficiency in isomerization reactions. Pyrolysis oils
consisted of S, N, P, Cl, K and Ca as contaminants.
Especially Ni-Mo catalyst showed advanced behaviour incontaminant decreasing. The positive effects of catalysts

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

to the product properties were more significant at higher
temperature using MoO3, CaO, Fe2O3 and TiO2.
C25+ hydrocarbons were in heavy oils, with averagemolecular weight of 940-1310g/mol. The averagemolecular weight of heavy oils and their S, N, P, Cl, K
and Ca content could be decreased in thermo-catalytic
pyrolysis.
The morphology of solid char was investigated by SEM
method. SEM micrograph well demonstrated that
contaminants were accumulated on the surface
especially in case of MoO3, CaO, Fe2O3 and TiO2
catalysts.

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