STATEMENT OF INVENTION:
The present invention discloses a simple method for the conversion of waste high density
polyethylene (HDPE) to liquid fuel. A stainless steel reactor is used to convert the waste
HDPE to liquid fuel in presence of an acid treated kaolin catalyst. This catalyst improves
the yield of oil and increases the rate of reaction. The physical properties analysis of the
oil obtained in the optimum condition shows that it is a mixture of different petroleum
fractions like gasoline, diesel and kerosene.
BACKGROUND OF INVENTION:
Plastic materials encompass a gradually increasing share of the municipal and industrial
waste going into landfill. Recycling of plastics has become a predominant subject in
today's plastics industry due to the huge amount of plastic wastes and environmental
pressures. Development of technologies for reducing plastic waste, which are acceptable
from the environmental standpoint and are cost-effective, has proven to be a difficult
challenge due to the complications innate in the reuse of polymers. Ascertaining most
advantageous processes for the recycling of plastic materials thus leftovers a worldwide
challenge in the new century. Plastic materials find applications in agriculture as well as
in plastic packaging, which is a high-volume market owing to the many advantages of
plastics over other traditional materials. High density polyethylene (HDPE) is the third
largest commodity plastic material in the world, after polyvinyl chloride and polyethylene
in terms of volume. The demand for HDPE is increasing day by day. The increased
demand and production of HDPE has led to accumulation of large amount of its waste
due to its low useful life. A thermal approach for dealing with waste plastics is the so-
called chemical feedstock or chemical recycling. The most attractive technique for the
chemical feed stock recycling is pyrolysis. A number of studies have been reported in
which a range of catalysts and reaction conditions have been employed to convert waste
plastics into the hydrocarbon liquid using pyrolysis during the past four decades. This is
also imitated by a number of pilot and commercial plants processing various types of
plastic wastes in the world.

Comprehensive patent search reveals that no patent has been filed in any country in this
trend using the waste high density polyethylene and acid treated kaolin clay as catalyst.
OBJECTIVE OF THE INVENTION:
The objective of the invention is to make a simple process for conversion of waste high
density polyethylene to liquid fuel. The basic purpose of this invention is to develop a
suitable acid treated kaolin catalyst for the degradation of waste HDPE.
SUMMARY OF INVENTION:
Waste high density polyethylene is subjected to thermal and catalytic pyrolysis. Pure
kaolin clay and different acid treated kaolin clays are used as the catalysts for conversion
of waste HDPE to liquid fuel. The reaction is carried out in a stainless steel reactor in the
temperature range of 400-550 °C with an objective to optimize the oil yield, optimize the
amount of catalyst. In the catalytic pyrolysis, a mixture of catalyst and the Waste HDPE
in different proportion were pyrolysed in the reactor at a desired temperature. The highest
yield of liquid product obtained is 51% by weight at 450 °C in thermal pyrolysis. Use of
kaolin as catalyst increased the yield of liquid fraction to 58.8%. Nitric acid (optimum
concentration 3M) treated kaolin clay further increased the oil yield to 79%. Study of
FTIR and GC-MS confirmed the presence of different hydrocarbons (mostly alkanes and
olefins) in the oil. The composition of the oil significantly narrowed in presence of kaolin
catalyst and also in acid treated kaoline as compared to thermal pyrolysis. The fuel
properties of the oil obtained by using 3M concentration nitric acid treated catalyst were
analyzed to find its suitability as a substitute of fossil fuel. Kaolin is a cheap clay material
and acid treatment technique is very simple process. The catalyst used can be regenerated
for further use. So this method is very simple and eco-friendly.
DRAWINGS (if any)

DETAILED DESCRIPTION
The present invention provides a process for the conversion of waste HDPE to liquid fuel
using suitable kaolin clay based catalyst. The different acid treated kaolin is prepared by
treating kaolin with four different acids (acetic acid, hydrochloric acid, nitric acid and
phosphoric acid) and one base (sodium hydroxide) of different concentrations, which is
used in the experiment.
The kaolin clay used in this experiment is procured commercially from Chemtex
Corporation, Kolkata, India. The modification of kaolin using four different acids and
one base of a concentration was carried out by adding 50g of the kaolin clay to 500ml of
acetic acid, hydrochloric acid, phosphoric acid, nitric acid and sodium hydroxide solution
of different concentrations and refluxing at 110 °C under the atmospheric pressure in a
round bottomed flask equipped with a reflux condenser for four hours. The resulting clay
suspension was then quickly quenched by adding 500ml ice cold water. The content was
then filtered, repeatedly washed with distilled water to remove any residual acid, dried in
an oven, calcined at 650 °C for four hours and ground in a mortar pastel to powder form.
The untreated sample is referred to as KC and acid treated samples after calcination at
650 °C are referred to as KC (HC1), KC (CH3COOH), KC (HNO3), KC (H3PO4) and KC
(NaOH). The clay samples were characterized by using XRD, XRF, TGA, SEM, BET
surface area analyzer, TPD (ammonia), FTIR to understand the effect of acid treatments.
The acid treatment of catalyst increases the Si/Al ratio, surface area and pore volume of
the kaolin clay sample. The composition and properties of the modified kaolin clay
samples are summarised in the Table 1.


The pyrolysis reaction is carried out in a stainless steel reactor set up. The waste HDPE is
pyrolysed in the reactor along with different clay catalyst samples using different catalyst
to feed ratio (1:4, 2:4, 3:4, 4:4) in the temperature range of 400-550 °C. The oil yield and
reaction time for the pyrolysis reaction carried out using different catalysts in optimum
condition (catalyst to feed ratio 1:4) is summarized in Table 2.
Table 2 The results of the pyrolysis (Temperature=450 °C, Catalyst: Feed=l:4) using
different types of catalysts of optimum concentration (3M concentration)

The properties of obtained liquid fuel are summarized in Table 3. The distillation report
of the oil infers that oil is in the boiling range of 58-376 °C, so it is a mixture of different
petroleum products like gasoline, kerosene and diesel.

Table 3 Physical properties of liquid fuel obtained by catalytic pyrolysis of waste HDPE
using nitric acid (3M concentration) treated kaolin clay

The present invention is further described in the following examples.
EXAMPLE 1
Waste HDPE when subjected to thermal pyrolysis at 450 °C yields 51% by weight of oil
in 175 minutes reaction time.
EXAMPLE 2
Waste HDPE when pyrolysed using kaolin catalyst with 1:4 catalyst to waste HDPE ratio
at 450 °C yields 58.8% by weight of oil in 157 minutes reaction time.

EXAMPLE 3
Waste HDPE when pyrolysed using 3M concentration hydrochloric acid treated kaolin
clay catalyst with 1:4 catalyst to waste HDPE ratio at 450 °C yields 69.2% by weight of
oil in 135 minutes reaction time.
EXAMPLE 4
Waste HDPE when pyrolysed using 3M concentration acetic acid treated kaolin clay
catalyst with 1:4 catalyst to waste HDPE ratio at 450 °C yields 59.8% by weight of oil in
148 minutes reaction time.
EXAMPLE 5
Waste HDPE when pyrolysed using 3M concentration nitric acid treated kaolin clay
catalyst with 1:4 catalyst to waste HDPE ratio at 450 °C yields 78.7% by weight of oil in
90 minutes reaction time.
EXAMPLE 6
Waste HDPE when pyrolysed using 3M concentration phosphoric acid treated kaolin clay
catalyst with 1:4 catalyst to waste HDPE ratio at 450 °C yields 62.9% by weight of oil in
145 minutes reaction time.
EXAMPLE 7
Waste HDPE when pyrolysed using 3M concentration sodium hydroxide treated kaolin
clay catalyst with 1:4 catalyst to waste HDPE ratio at 450 °C yields 59.4% by weight of
oil in 135 minutes reaction time.

We claim:
1. A process for conversion of waste High-density polyethylene (HDPE) to
liquid fuel using modified kaolin clay catalyst at 400-550 °C with 1:4 catalyst
to feed ratio.
2. A process according to claim 1, wherein the pyrolysis process is carried out in
a reactor made up of stainless steel.
3. A process according to claim 1, wherein the waste HDPE is pyrolysed using
nitric acid treated kaolin clay to obtain liquid fuel.
4. A process according to claim 1, wherein the reaction time decreased (rate of
reaction increased) in presence of acid treated kaolin catalyst.
5. A process according to claim 1, wherein the yield of oil was 79% by weight
using 3M concentration nitric acid treated kaolin clay catalyst at 450 °C with
1:4 catalyst to feed ratio.
6. A process according to claim 1, acid treated kaoline can be regenerated at 750
°C after use and reused with same efficiency.