The Project File Details
- Name: RESEARCH ON COMPARATIVE STUDY ON THE CONVERSION OF WASTE PLASTIC MATERIALS TO LIQUID HYDROCARBONS THROUGH CATALYTIC PYROLYSIS
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- Length: [57] Pages
ABSTRACT
This research involves the application of pyrolysis has been viewed as an efficient means for the proper disposal of waste plastics in the environment amongst others. In this research, the influence of two catalysts namely; Zeolite and Titanium (IV) oxide are examined. Zeolite as a catalyst has obtained approval due to its ability to ensure the production of liquid hydrocarbons when applied in the pyrolysis of waste plastics. It has also been used a bench mark to determine the effectiveness of other catalyst in producing liquid hydrocarbons. Whereas, Titanium (IV) oxide which is known for its many applications in paints, pharmaceuticals and cosmetics is another catalyst which is used in catalytic pyrolysis of waste plastics for the first time. Titanium (IV) oxide has several appealing properties such as its mesoporous structure, mechanical resistance and high stability which are some of the reasons which prompted its use. This comparative study between this two catalysts were done at the same time in order to monitor the changes in temperature and other reaction conditions. The waste plastics used in this research were low density polyethylene and polypropylene. Positive results were gotten as the liquid hydrocarbons were formed. In the experimental phase, various ratios were used and all were to maximise catalyst consumption. Again, it was proved that Zeolite has a strong effect in the characteristics and distribution of pyrolysis products. Titanium (IV) oxide also produced good results but the better results are seen with its combination with polypropylene.
TABLE OF CONTENTS
CERTIFICATION OF STATEMENT ………………………………………………………………………………….. ii
ABTRACT ………………………………………………………………………………………………………………………….. iii
DEDICATION…………………………………………………………………………………………………………………….. iv
ACKNOWLEDGEMENT …………………………………………………………………………………………………….. v
1.0 CHAPTER ONE: INTRODUCTION ………………………………………………………………………………. 1
1.1 Some waste facts ……………………………………………………………………………………………………… 2
1.2 History of Pyrolysis ………………………………………………………………………………………………….. 3
1.3 Catalyst ………………………………………………………………………………………………………………….. 4
1.3.1 TiO2 ………………………………………………………………………………………………………………………. 5
1.3.2 Zeolite …………………………………………………………………………………………………………………… 6
1.4 Polymers: Polypropylene and LDPE (Low Density Polyethylene) ……………………………………….. 7
1.5 Problem Statement …………………………………………………………………………………………………… 9
1.6 Significance of Study ………………………………………………………………………………………………. 10
1.7 Aim of the Research ……………………………………………………………………………………………….. 10
1.8 Hypothesis …………………………………………………………………………………………………………….. 11
2.0 CHAPTER TWO: LITERATURE REVIEW …………………………………………………………………. 12
2.1 Overview ……………………………………………………………………………………………………………………. 12
2.2 Effect of Catalyst …………………………………………………………………………………………………………. 12
2.3 Effect of Catalyst contact mode …………………………………………………………………………………….. 13
2.4 Effect of Catalyst to Polymer ratio ………………………………………………………………………………… 13
2.5 Effect of Temperature ………………………………………………………………………………………………….. 14
2.6 Reactor performance …………………………………………………………………………………………………… 15
2.7 Cost of Catalyst …………………………………………………………………………………………………………… 15
3.0 CHAPTER THREE: MATERIALS AND METHODOLOGY ………………………………………… 16
3.1 Overview ……………………………………………………………………………………………………………………. 16
3.2 Materials Used ……………………………………………………………………………………………………………. 16
3.3 Chemicals and Reagents ………………………………………………………………………………………………. 17
3.4 Precautions ………………………………………………………………………………………………………………… 17
3.5 Preparation of feedstock for pyrolysis ……………………………………………………………………………. 18
3.5.1 Steps in the preparation of feedstock ……………………………………………………………………….. 18
3.6 Preparation of the pyrolysis set-up ………………………………………………………………………………… 19
3.6.1 Steps for catalytic pyrolysis ……………………………………………………………………………………. 20
3.7 Analysis of Hydrocarbon yields …………………………………………………………………………………….. 21
3.7.1 Fourier transform Infrared Spectroscopic analysis (FTIR) …………………………………………….. 21
3.7.1.1 Steps in the use of the FTIR machine for analysis …………………………………………………… 22
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3.7.2 Heat of combustion …………………………………………………………………………………………………… 23
3.7.2.1 Procedures in using the Bomb Calorimeter ……………………………………………………………. 24
3.7.3 Percentage Yield ………………………………………………………………………………………………………. 24
3.7.3.1 Procedure for determination of percent yield …………………………………………………………. 25
3.7.4 Specific gravity …………………………………………………………………………………………………………. 25
3.7.4.1 Steps in determining the specific gravity ……………………………………………………………….. 26
3.7.5 Viscosity ………………………………………………………………………………………………………………….. 26
3.7.5.1 Steps in determining the viscosity …………………………………………………………………………. 28
3.7.6 Gas Chromatography – Mass Spectrophotometry (GC-MS) ……………………………………………. 28
3.7.7 Cloud & Pour Point ………………………………………………………………………………………………….. 28
3.7.7.1 Steps in the determination of cloud and pour points ………………………………………………… 29
3.7.8 Flash Point ………………………………………………………………………………………………………………. 29
3.7.8.1 Steps in the determination of flash point ………………………………………………………………… 30
4.0 CHAPTER FOUR: RESULTS AND DISCUSSIONS ……………………………………………………… 31
4.1 Overview ……………………………………………………………………………………………………………………. 31
4.2 Fourier transform Infrared Spectroscopic analysis (FTIR)……………………………………………….. 31
4.3 Analysis of heat of combustion………………………………………………………………………………………. 32
4.3.1 The calorific results ………………………………………………………………………………………………. 33
4.4 Analysis – Percent Yield ……………………………………………………………………………………………….. 35
4.5 Analysis – Temperature change against Time …………………………………………………………………. 35
4.6 Analysis – Specific Gravity …………………………………………………………………………………………… 36
4.7 Analysis – Cloud and Pour Point …………………………………………………………………………………… 37
4.8 Analysis – Viscosity ……………………………………………………………………………………………………… 37
4.9 Analysis – Flash Point …………………………………………………………………………………………………. 39
4.10 Analysis – Gas Chromatography – Mass Spectrophotometer ………………………………………….. 39
5.0 CHAPTER 5: CONCLUSION AND RECOMMENDATIONS ……………………………………….. 42
5.1 CONCLUSIONS ………………………………………………………………………………………………………….. 42
5.2 RECOMMENDATIONS ……………………………………………………………………………………………….. 43
REFERENCES …………………………………………………………………………………………………………………… 44
CHAPTER ONE
INTRODUCTION
In our present-day society there has been a dynamic drive for new sources of energy possessing the qualities of commercial viability and environmental sustainability. In contrast, there has been an increased use in the consumption of materials involving plastics leading to an increased amount of waste plastics and thus the problem of disposal. The disposal of waste plastics has been a major contemporary issue all over the world today. The uses of plastics are broad and for that reason, they can be seen everywhere. The problem which has been encountered in the use of these plastics is in their disposal. Since the invention of plastic materials, there have not been discoveries related to the biodegradable waste plastic material. For that reason various suggestions have been proposed for the disposal of these waste plastics such as landfills, incineration and burying.1 These plastic materials which are used so regularly just occupy space in landfills; which would obviously one day get full. With the rise in demand for workable land, such practices should not be supported. Another means which has been proposed for the removal of these waste plastics is the process of incineration.1 Incineration involves the burning of waste substances. The problem with this is that it leads to the release of harmful and toxic gases into the environment such as CO2.1 A method of waste disposal also popularly used in rural areas is burying. The problem with this method lies in the fact that most plastics produced are non-biodegradable. So, these waste plastic materials which are buried just stay beneath the soil for hundreds and even thousands of years.1 All these methods of waste disposal affect the environment and we humans in different ways and in order to curb these problems pyrolysis was proposed.
Waste management is an important concept which had been developed in order to handle the
detriments which waste disposal poses to the environment. It involves the handling of discarded resources. The main objective of waste management systems is to keep people and the
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environment benign of the potentially harmful effects of waste which could occur. These waste materials are obtained from polymers such as low-density polyethylene (LDPE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC) and polystyrene.1, 2 Waste materials are not usually dangerous but over time and if certain conditions are kept in place such as intense heat and presence mixtures which could instigate chemical reactions, harmful substances could be produced. This project highlights the need for proper waste management by suggesting the conversion these waste plastics materials into useful resources through the process of pyrolysis.
1.1 Some waste facts
In the last 50 years, there has been a global increase in the production of plastic. According to some facts from the UN environmental program, around 22-43 % of plastic used are disposed in landfills.2 This fact stated simply highlights pure waste of possible resourceful materials and shows the possible effects which it poses to its surrounding communities to certain extents by providing unconducive environments. It was also suggested that plastics produced all around the world occupy a good 7% of the amount of crude oil produced yearly.2 This fact simply implies that plastic production is important and its management should also be handled similarly due to the fact that it possesses a variety of uses.
In that, the idea of pyrolysis comes in as a means for maximising waste plastic materials. Pyrolysis is the decomposition brought about by high temperatures. It is a chemical reaction which involves the molecular breakdown of large molecules into smaller molecules in the presence of heat and the absence of oxygen. In the pyrolysis process, the heavier gases are condensed to liquid oil while the lighter gases such as hydrogen and methane, which are gases at room temperature, are called “syngas”.2, 4 During the process of pyrolysis changing the temperature and duration of pyrolysis makes it possible to optimize for the production of more
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fractions. For example, slow pyrolysis under lower temperatures will produce more fuel gas whereas fast pyrolysis at higher temperatures will produce more bio-oil.2, 4 With fast pyrolysis, the syngas that is produced can be burned within the system to maintain the temperature, resulting in hydrocarbon formation as the sole products of pyrolysis.
The process of pyrolysis can occur in two different ways which are; catalytic pyrolysis and thermal pyrolysis.4 Thermal pyrolysis involves the use of intense heat to breakdown molecular chains in order to produce hydrocarbon yield. This process occurs at extremely high temperature conditions. The difficulty here lies in the fact that the product of this process has low liquid yield.4 This is partly due to the fact that intense heating condition would lead to the production of more gases. The other form of pyrolysis is the catalytic pyrolysis and this form of pyrolysis also involves heating too but at lower temperatures.4, 6 The key difference here is in the application of a catalyst and this helps reduce the reaction time and the reaction temperature. The advantage of this process is that high liquid yield is gotten and for that reason, catalytic pyrolysis is applied in this research.
1.2 History of Pyrolysis
Some thousands of years, the practise of pyrolysis was believed to have begun somewhere in the Amazon rainforest. The substances which were produced were bio char which was a charcoal like substance that was applied to improve and stabilize the nutrient poor rainforest soils.3 Individuals who lived in these areas started fires and when it became too hot, the fire was covered with earth materials to prevent oxygen from coming in contact with the fire. The intensity of the fire increased and temperature became higher so long as the source of the fire was present. The fuel was broken down in the absence of oxygen and bio char was produced rather than ash which turned out to be somewhat of a new innovation. An even more recent study suggested that pyrolysis was used with wood waste feedstock in World War 1 & 2 to
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produce transportation fuel when fossil fuels were unavailable.3 In 1945, vehicular machines such as trucks, buses and various agricultural machines were all powered by gasification. After an increase in the production of such fuels, it was estimated that there were nearly 9 million vehicles running on pyrolysis gas in many places around the world.3
Due to modernisation, the developments related to pyrolysis were made and the process emerged on a number of fronts in the 1950s. In 1958, a laboratory in the United States known as the Bell Laboratories alongside a number of universities, institutions and establishments around the world started the R&D programs to examine the usefulness of pyrolysis.3 The main focus of the program was to produce gas from waste materials found in the environment.
So initially, the first pyrolytic gasification systems were firebrick ovens which applied heat indirectly in a low oxygen environment. The early systems were batch processes: ovens were filled, sealed and then heat was applied. After each batch, the oven would be cleaned and readied for the next batch. It was quite a process.3 In the early 1970s, the first commercial The first commercial forms of pyrolysis batch systems for gasification were introduced in the health sector in hospitals but due to low volume capacity and issues with the mortar used in the kiln construction, little commercial success was observed. In the late 1970s and early 1980s the batch systems gave way to continuous feed systems with a cone design that made the evacuation of the gasses more efficient.3 The continuous feed cone design first showed up in England then the US, Germany, Japan, Canada and the Netherlands. The pyrolysis gradually became a major process for the production of fuels and prevention of waste was avoided.3
1.3 Catalyst
A catalyst is a substance which changes the way a reaction occurs by creating new pathways and thereby lowering its activation energy and speeding up the reaction. A catalyst can either be homogenous or heterogeneous in nature. 5 A homogeneous catalyst is one which exists in only one phase while a heterogeneous catalyst is one which exists in more than one phase. A concept which is usually discussed when catalysis is involved is activation energy. Activation energy is the minimum quantity of energy that the reactants must possess in order for a reaction to occur. A catalyst works by lowering activation energy for a reaction.5, 6 Catalysts lower activation energy by providing simple and less energy-intensive means for reactant molecules to break bonds and create new temporary pathways.
1.3.1 TiO2
Fig 1: Showing TiO2 sample
Titanium is the ninth most abundant metal found on earth. It was discovered by William Gregor in 1791. It occurs naturally in the environment. It is a group 4, period 4 of the periodic table. It is a d block transition element. It has its electronic configuration to be [Ar] 3d24s2.7 Titanium has low density and for that reason, it is applied in the creation of aircrafts and missiles. One of the largest uses of Titanium can be found in the form of titanium (IV) oxide. TiO2 exists in 3 crystalline forms which are; anastase, rutile and brookite.7 The rutile is the most thermally stable amongst the other forms. It has a molecular weight of 79.938 g/mol. TiO2 has no odour and has no taste. It is also insoluble in water.7
In the area of catalysis there has been the search for catalysts with high stability. During catalytic operations, various particles have the ability to enclose the active sites of the catalyst and thus causes instability. TiO2 as a catalyst possesses a high surface area and prevents that enclosure by particles because of its mesoporous structure.7, 8 In recent times, TiO2 metal
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catalysts have gotten added interest as a result of high activity nanoparticles for various reduction and oxidation in suitable conditions such as at low pressures and temperatures. TiO2 has gotten has gotten a lot of recognition in the field of science because of its high stability in acidic and basic media.7 The availability and mode of synthesis is an important factor to consider in the selection of a catalyst. Due to its non-toxicity, high effectiveness and long-term photo stability TiO2 has been applied in the mineralizing of non-biodegradable and toxic
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