Advances in Ma terials Physics and Che mist ry, 2012, 2, 263-266
doi:10.4236/ampc.2012.24B067 Published Online December 2012 (htt p://www.SciRP.org/journal/ampc)
Catalytic Feedstock Recycling of Polymers
A Green Approach Towa r ds Sust ainable Environment
Raju Fr ancis1, Be e na Sethi2
1Department of chemistry, MahatamaGandhi University, Kottayam, Kerala, India
2Department of chemistry, K.L. Mehta Daya nan d College for Women, Faridabad, Haryana, India
Received 2012
ABSTRACT
This piece of study involves degradation of plastic waste in presence of two different catalysts. It was found in gas chromatography
(GC) analysis results that in presence of these catalysts more than 80% of polymer by weight was converted into either liquid or ga-
seous hydrocarbons. These can be utilized as fuel or can be transformed into other useful products. Thermo gravimetric analysis
(TGA) and different ial scann ing cal orimetric (DS C) anal ysis o f polymers su ggest th at pr esence of t hese catal ysts lo wers degrad ation
temperature and chan ge mechanism of degradatio n.
Keywords: Polymer De gradation; Catalyst ; Green Chemistryr; Feedstock Recyclin g; GC; TGA; DSC
1. Introduction
Polyolefins (polyethylene, polypropylene, polystyrene) are
plastic materials used extensively in containers and packing.
Polyethylene (PE) is the worldwide most produced polymer
with about 60 million tons per year and the main component of
plastic waste [1-3]. Other than PE polypropylene (PP), polyvi-
nyl chloride (PVC) and polystyrene are the main components of
solid waste [4-6]. They present approximate 60% of the total
solid plastic waste gen erated in urban so lid waste[1].
The current strategies to deal with solid plastic waste (around
62% of total available solid waste is collectable) are still based
on land filling and incineration without energy recovery [7].
Because of this huge plastic solid waste many municipal cities
are facing disposal problems such as emission of toxic sub-
stances (dioxins and furanes) on incineration and shortage of
landfill sites [8].
Plastic material has almost same composition to petroleum
and they are high yielding energy sources. For example one
liter of heating oil has a net calorific value of 10,200 Kcal,
whereas 1 Kg of plastic releases 11,000,Kcal worth of energy.
1Kg briquettes (blocks of pressed coal dust) have a net calorific
value of 4,800 Kcal only. So it can be recycled into petroleum
products safely with suitable technique without producing any
harmful gases [9-12]. At one side it will provide sustainable
alternative of energy recovery and material recovery and other
side society will get rid from the disposal problem of plastic
waste.
Polyethylene (PE) and polypropylene (PP) as typical
commodity plastics are better known as randomly degrading
polymers rather than depolymerizing polymers [13]. This is not
surprising because the heat of polymerization, an important
parameter for estimating the depolymerizability of polymers,
has larger negative values for ethylene and propylene, than for
styrene (St) and methyl methacrylate, indicating the difficulty
in depolymerising PE and PP [14]. However, cases in which the
zip length is controlled by chain-transfer reactions and in which
the activation energy value for a depolymerisation reaction,
such as β-scission, is higher than that of the chain-transfer
reactions, the monomer yield can be increased with increase in
temperature.
Many methods have been investigated by different research-
ers for feed stock recycling. These are broadly divided into two
categories as mechanical recycling and chemical recycling
methods. A promising method for the reprocessing of waste
plastic is feedstock recycling, or clean incineration of municipal
solid waste which allows the conversion of plastic residues into
raw chemicals, monomers of plastics and hydrocarbon feed-
stock It is a sustainable way for the recovery of the organic
content from polymeric waste and also to preserve petroleum
resources in addition to protecting environment [13-15].
In spite of many R&D projects over the three decades, it is
reported that recycling of waste plastic in oil production process
covers negligible amount in the total amount of waste plastic
generated all over the world. Moreover these methods are eco-
nomically not good due to technical problems such as low treat-
ment ability of techniques and high energy consumptions and
low quality of products obtained. The produced oils have lim-
ited uses and applications only in industrial boilers, burners and
power generators. And the fuel gas generated by plastic recy-
cling is two or three times more expensive than fuel oil [16].
So, it is correct time to develop more economic, safe, eco-
friendly and sustainable method for feedstock recycling of
waste polymer.
In this study, attempts are taken to obtain useful products and
virgin monomer by degradation of polymers in presence of
different catalysts without generation of any further hazard-
ous/poisonous chemicals at low temperature.
2. Materials and Methods
2.1. Linear Low Density Polyethylene (LLDPE)

R. FRAN CIS, B. SETHI
264
It was purchased B.R. Scientific and Chemicals Company,
Faridabad, Haryana. It was washed and dried in open air for
one day. After that it was used for practical purposes. It was
soaked in solvent for three days then warmed to get it liquid
state.
2.2. Toluene, Transition Metal Oxideand Nonmetal
Oxide
These enti re chemicals are also pur chased fro m B. R. Scien tific
and Chemicals Company, Faridabad, Haryana. These all were
used without further purification.
2.3. Preparation of Films of Polymers Samples
Films of polymer samples are prepared by dissolving polymer
into solvent in presence of weighed amount of desired catalyst
and dried in oven at 330 K.
2.4. TGA and DSC Anal ysis
TGA and DSC analysis of pure polymer and in presence of
catalyst was carried out at North Maharashtra University, Jal-
gaon, Maharashtra. All these analyses were carried out on Shi-
madzu DSC- 60 & Shimadzu TGA- 60 WS.
2.5. GC Analysis
The GC stu dies were carried out in a speci al GC-MS instrument
equipped with gas sample injector. This facility was kindly
provided by Mahatma Gandhi University, Kottayam.
3. Result and Discussion
We were interested to obtain useful products and virgin mono-
mer by degradation of polymers in presence of different cata-
lysts at low temperature. We observed certain catalysts de-
crease the degradation temperature of polymers. Further in
presence of these catalysts polymer degrades in more than one
step while in absence of these catalysts they show decomposi-
tion in one step at little higher temperature thus decrease the
reaction temperature. The quality of degradation products is
improved as well as percentage of dioxins and aromatic com-
pounds are decreased. These harmful products and aromatics
are generally produced at high temperature (above 6000C).
Prel iminary TGA data p resen ted in Fig ures 1 & 2 shows that
there is considerable increase in the thermal decomposition of
polymer sample when cracked in presence of catalyst A in
comparison to catalyst B. From the graph it can be seen that in
the former case the weight loss is 36% whereas in the latter
case it is only 20%. The amount of catalyst required for this
change is only 10% of the total polymer mass.. However the
onset of decomposition temperature remains the same in both
cases. Nevertheless the interesting point is the substantial
drop in the decomposition temperature to ~ 220oC, in the pres-
ence of catalyst (Figures 1 & 2). We also observed the possi-
bility of decreasing the catalyst amount and its reusability for
this cr acki ng experiment.
The DSC results showed a marked effect on the ability of
catalyst to effect the endothermic decomposition process. This
is can be clearly distinguished from the sluggish and sharp
changes in DSC profiles at the decomposition temperature in
absence and p r es ence of catalyst (Figures 3-5).
To get these t ests po lymer (LLD PE) was mixed with catal yst
physically in presence of solvent then a film was prepared for
analysis.
TGA and DS C were carried o ut each time prio r to GC analy-
sis. This gave information of number of steps involved in each
reaction and gave information of optimum and starting temper-
ature for each step of reaction.
To test obtained degradation products GC analysis of effluent
gases was carried out in absence and presence of catalysts.
Results obtained are given in Table 1. The GC studies were
carried out in a special GC-MS instrument equipped with gas
sample injector.
Figure 1. TGA of polymer in presence of catalyst A.
Figure 2. TGA of polymer in presence of catalyst B.
0.00
10.00
20.00
Time
[mi n]
0.00
5.00
10.00
mW
DSC
100.00
200.00
300.00
C
Temp
110.88
x
C
Onset
122.26
x
C
Endset
116.82
x
C
Peak
-153.31
x
mJ
-48.98
x
J/g
Heat
-3.04
x
mW
Height
5.00
mW
File Name:S1.tad
Detector: DSC60
Acquisition Date12/01/26
Acquisition Time11:03:19
Sample Name:S1
Sample Weight:3.130[mg]
Annotation:
[Temp Program]
Start Temp100. 0
Temp RateHold TempHold Time
[C/min ][ C ][ min ]
10.00 300.0 0
Thermal Analysis Result
S1.tad
S1.tad
Temp
DSC
Figure 3. DSC of polymer in absence Catalyst.

R. FRAN CIS, B. SETHI
265
0.00
10.00
20.00
Tim e
[min ]
0.00
10.00
mW
DSC
100.00
200.00
300.00
C
Temp
109.11
C
Onset
122.59
C
Endset
116.38
C
Peak
-272.10
x
mJ
-64.02
x
J/g
Heat
-4.14
x
mW
Height
10.00
x
mW
File Name:S2.tad
Detector: DSC60
Acquisition Date12/01/26
Acquisition Time11:35:47
Sample Name:S2
Sample Weight:4.250[mg]
Annotation:
[Temp Program]
Start Temp100.0
Temp RateHold TempHold Time
[C/min ][ C ][ min ]
10.00 300.0 0
Thermal Analysis R esult
S2.tad
S2.tad
Temp
DSC
Figure 4. DSC of polymer in presence Catalyst A.
0.00
10.00
20.00
Time
[min]
0.00
10.00
20.00
mW
DSC
100.00
200.00
300.00
C
Temp
113.33
C
Onset
123.13
C
Endset
116.84
C
Peak
-200.51
mJ
-59.85
x
J/g
Heat
-2.30
x
mW
Height
10.00
mW
File Name:S3.tad
Detector: DSC60
Acquisition Date12/01/26
Acquisition Time12:07:32
Sample Name:S3
Sample Weight:3.350[mg]
Annotation:
[Temp Program]
Start Temp100.0
Temp RateHold TempHold Time
[C/min ][ C ][ min ]
10.00 300.0 0
Thermal Analysis Result
S3.tad
S3.tad
Temp
DSC
Figure 5. DSC of polymer in presence Catalyst B.
Table 1. G C analysis of fragments obtained during catalytic
cracking of LLDPE.
Carbon
fragment
Sample
Polymer + cat
A
Polymer + cat
B
Polymer + cat
A+B Pure Polymer
C3/C4
(wt%) 7 2 .3 82.5 72.9 3 2 .4
C5/C6
(wt%) 0 1.5 7.2 1 2.0
C7
(wt%) 5 .5 14.5 1.7 1 .2
C8
(wt%) 9 .2 0 14 37
C9
(wt%) 0 0 0 16.4
C10
(wt%) 3 .0 1 .5 4.2 1.0
>C10
(wt%) 10 0 2 0
GC results of degraded products show that in presence of
catalyst A, B and in presence of both, percentage of C3- C4
hydrocarbons is very high while percentage of higher hydro-
carbons (above C10) is almost negligible.
It is found that on degradation of pure polymer results only
32% C3-C4 hydrocarbons while, in presence of catalyst A and
B percen tage of C3-C4 hydrocarbon was 72 and 82 respectively.
GC analysis of polymer in presence of both catalysts together
also gave high percentage of C3- C4 hydrocarbons and low
percentage of higher hydrocarbons.
To get good quality of products by varying dose of catalysts,
admixtures, temperature and rate of heating is still required.
Attempts will b e made to use n ano part icles of catalyst to ch eck
catalytic activity of catalyst in future.
Activity of catalyst and possibility of recyclization of cata-
lysts will also be tested by some methods. Attempts will be
made to get maximum fraction of monomer and gaseous frac-
tion.
All the above studies encouraged us and created lot of inter-
est to pursue further the degradation of polymer in presence of
catalysts.
4. Conclusion
From the experimental findings of the present work, the fol-
lowing conclusion can be drawn:
1. Pure polymer degrades at much higher temperatur e and it
involves single step in association of production of green house
and toxic gases like dioxin.
2. In presence of catalyst A and B, degradation temperature
lowers and degradation reaction involves more than one steps.
3. Degradation of pure polymer produces only 32% C3/C4
hydrocarbons and 12% C5/C6 hydrocarbons.
4. In presence of catalyst A and B degradation of polymer
produces 72% and 82% C3/C4 hydrocar bo ns re s pe c ti v e l y.
5. Adjusting dose of catalyst, use of nano particles and recy-
cling of catalyst can make this catalytic feedstock recycling
method a good tool to get sustainable environment.
This can help to get sustainable source of petroleum prod-
ucts.
5. Acknowledgements
Author sincerely thank to Dr. R.D. Kulkarni, Professor in Che-
mistry, Department of polymer science, N.M. University, Jal-
gaon, Maharashtra, giving facility of TGA and DSC analyzers
to carry out this study successfully.
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