Catalytic degradation of waste plastic into fuel range hydrocarbons

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Introduction
The huge amount of plastic waste that resulted
from the dramatic increase in polymer production
gives rise to serious environmental concerns, as
plastic does not degrade and remains in the
municipal refuse tips for decade [1]. According to
a nation wide survey conducted in the year 2003,
more than 10,000 MT of plastic waste is
generated daily in our country, and only 40 wt%
of the same is recycled, balance 60 wt% is not
possible to dispose off [2]. Plastic waste being
more voluminous than organic waste takes up a
lot of landfill space that is becoming a scare and
expensive. And India has been a favored
dumping ground for plastic waste mostly from
industrialized countries like Canada, Denmark,
Germany, U.K, the Netherlands, Japan, France
and the United States of America. According to
the govt. of India import data more than 59,000
tons and 61,000 tons of plastic waste have found
its way into India in the year 1999 and 2000
respectively [3-4].



Experimental
The model polymer feed was linear low density
polyethylene (LLDPE) in scrap form with an
average particle size in micrometer with a density
of .928gm/cm3 and average molecular mass of
117 gm/mole. The catalyst samples used were
two commercial cracking catalyst1 and cracking
catalyst2 containing 20% and 40% US-Y zeolite
respectively with average particle size in
micrometers. A thermocouple was used to
measure the temperature in the range of 250-800
K and a pressure gauge was also attached to
measure the pressure of the reactor.



Experimental calculation
The conversions to volatile products were
calculated as the fraction of initial mass of
polymer reacted to form the volatile products.
The yield of liquid product was calculated as the
mass of liquid collected divided by the mass of
the initial amount of polymer and represents the
fraction of original polymer converted to liquid
products. The selectivity to liquid products was
calculated as the mass of liquid collected divided
by the mass of reacted polymer.



Results and discussion
The overall conversion, liquid yield and coke
concentration obtained by cracking catalysts 1
and 2 are summarized in table II. Cracking
catalyst 1 could fully degrade the polymer
samples in all cases, even at low values of
overall content of active zeolite. No polymer
remnants were observed and coke formed on
catalyst was the only form of the polymer not
converted to volatile products. In terms of overall
liquid yield, a maximum was observed around a
ratio 4:1.