ABSTRACT
This research work was centred on mechanical properties of zeolite-Y and ZSM-5 catalysts synthesized from locally available clays such as Kaolin, Alumina, Gambe and Pindiga respectively. Pressure absorption capacities of the synthesised zeolite catalysts and that of the supportive clays were carried out with the aid of a bourdon gauge machine. Plastimeter machine alongside with a micro tensometer machine were equally used to determine the young’s modulus of the synthesized zeolite catalysts and flow characteristics of the clays. XRD analysis was carried out using Cu K α-radiation to find the textural properties. Results of the analysis indicated that synthesised ZSM-5 catalyst was denser, could absorbed more pressure as compared with synthesized Zeolite-Y catalyst. Though, in terms of flowability, synthesised Zeolite-Y is more effective than synthesise ZSM-5 catalyst. The young’s modulus of the synthesised catalysts was found to lie between 3.5 N/mm2 – 4.0 N/mm2. Among the clays analysed, alumina clay had proved a more superior support material for the synthesis of the zeolite catalysts in terms of flowability, porosity, and pore size. XRD analysis indicated that at point 2-theta (point where the highest peak occurred), the peak level of the synthesized zeolite catalysts and that of the referenced zeolite are, at the same level which indicated similarity in their performance ability.
TABLE OF CONTENTS
Title page —————————————————————————————————– i
Declaration —————————————————————————————————-ii
Certification ————————————————————————————————–iii
Acknowledgement ——————————————————————————————-iv
Abstract ——————————————————————————————————–v
Table of Contents ——————————————————————————————–vi
List of Tables ————————————————————————————————xi
List Figures ————————————————————————————————–xi
List of Plates ————————————————————————————————xii
CHAPTER ONE: INTRODUCTION——————————————————————1
1.1Background to the study —————————————————————————–1
1.2 Statement of the problem —————————————————————————4
1.3 The present research ———————————————————————————4
1.4 Aim and Objectives ———————————————————————————–5
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1.4.1 Aim ——————————————————————————————————5
1.4.2 Specific Objectives ————————————————————————————5
1.5 Significance of study ———————————————————————————–5
1.6 Justification ———————————————————————————————-6
1.7 Scope of study ——————————————————————————————-6
1.8 Limitation ————————————————————————————————6
CHAPTER TWO: LITERATURE REVIEW———————————————————7
2.1 Introduction ———————————————————————————————-7
2.2 Properties of Zeolite ————————————————————————————8
2.3 Catalysts ————————————————————————————————-10
2.4 Catalytic Cracking ————————————————————————————11
2.5 Uses of Zeolites —————————————————————————————–12
2.5.1 Commercial and domestic uses ———————————————————————12
2.5.2 Petrochemical industry ——————————————————————————12
2.5.3 Nuclear industry ————————————————————————————–13
2.5.4 Heating and Refrigeration —————————————————————————13
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2.5.5 Construction —————————————————————————————— 13
2.6 Review of past work ———————————————————————————-14
2.7 Catalyst support —————————————————————————————17
2.8 Supported catalyst ————————————————————————————18
2.9 Uses of kaolin clay ———————————————————————————–19
2.10 Compaction and Mechanical properties ——————————————————-21
CHAPTER THREE: MATERIALS AND METHODS——————————————-23
3.0 Materials, Equipment and Methods ————————————————————–23
3.1 Materials ————————————————————————————————23
3.2 Equipment ———————————————————————————————-24
3.3.0 Methods and experimental procedures ————————————————————24
3.3.1 Uniaxial compression test—————————————————————————24
3.3.2 Flow characteristics———————————————————————————-26
3.3.3Stress-Strain Analysis ——————————————————————————-27
3.3.4 X-ray diffractometer analysis ———————————————————————-27
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CHAPTER FOUR: RESULTS AND DISCUSSIONS——————————————–28
4.0 Results and Discussions —————————————————————————–28
4.1 Results—————————————————————————————————28
4.1.1 Compressive pressure absorption of Kaolin Zeolite-Y, ZSM-5 and Alumina clay———28
4.1.2 Stress / Strain Analysis on Gambe clay, Pindiga clay and Kaoli clay————————30
4.1.3 Stress / Strain Analysis on Sample A and Sample B——————————————–31
4.1.4Compression test on zeolite-Yn, gambe clay and pindiga clay———————————32
4.1.5 Analytical Comparison between CPD commercial Zeolite-Y, CPD pure chemical
ZSM-5 and CPD ZSM-5 ϓ alumina———————————————————————33
4.1.6 Comparison of compressive pressure against Load for Zeolite-Yn, Zeolite-Ys
and Compounded commercial Zeolite-Y—————————————————————–34
4.1.7 Pressure absorption comparison between Gambe clay, Pindiga clay, Kaolin
and Alumina clay——————————————————————————————–35
4.1.8 Pressure absorption capacity of Synthesized ZSM-5, pure chemical
ZSM-5 and Compounded ZSM-5 γ alumina————————————————————36
4.1.9 Stress / Strain Analysis on Zeolite-Yn————————————————————–37
4.1.10 X-ray diffractometer (XRD) analyses————————————————————38
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4.2 Discussion of Results———————————————————————————41
4.2.1 Discussion on compressive pressure absorption of kaolin clay, zeolite-Y,
ZSM-5 and alumina clay————————————————————————————41
4.2.2 Discussion on stress / strain analysis on gambe clay, pindiga clay and kaolin clay———42
4.2.3: Discussion on stress / strain analysis on sample A and sample B—————————–42
4.2.4 Discussion on compression test on zeolite-Yn, Gambe clay and Pindiga clay —————44
4.2.5 Discussion on Analytical Comparison between CPD commercial Zeolite-Y,
CPD pure chemical ZSM-5 and CPD ZSM-5 ϓ alumina———————————————-44
4.2.6 Discussion on Comparison of compressive pressure against Load for Zeolite-Yn
Zeolite-Ys and Compounded commercial Zeolite-Y—————————————————44
4.2.7: Discussion on Pressure absorption comparison between Gambe clay, Pindiga clay,
Kaolin and Alumina clay———————————————————————————–45
4.2.8 Discussion on Pressure absorption capacity of Synthesized ZSM-5, pure chemical
ZSM-5 and Compounded ZSM-5 γ alumina————————————————————45
4.2.9 Discussion on Stress / Strain Analysis on Zeolite-Yn——————————————–46
4.2.10 Discussion on X-ray diffractometer (XRD) analyses——————————————-46
CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS—————————48
5.0 Conclusions and Recommendations—————————————————————48
5.1 Conclusions———————————————————————————————-48
5.2 Recommendations for Further Research Work———————————————— 49
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5.3 Contribution to Knowledge————————————————————————–49
References—————————————————————————————————-50
CHAPTER ONE
INTRODUCTION
1.1 Background to The Study
Zeolites are micro-porous alumina-silicate minerals used for numerous commercial and domestic applications. These include applications in petroleum and petrochemical industries as catalysts, adsorbents and ion exchangers, nuclear industries for nuclear reprocessing, heating and refrigeration, detergents, construction as material additives, medicine, agriculture as a soil treatment, gemstones, as ion-exchange beds in domestic and commercial water purification and softening. The term Zeolite was originally coined in 1756 by Swedish mineralogist Axel Fredrik Cronstedt, who observed that upon rapidly heating the material stilbite, it produced large amounts of steam from water that has been adsorbed by the material. Base on this, he called the material zeolite, from the Greekzep, meaning “to boil” And lithos meaning “stone” (Cejka et al, 2007).
Today, Zeolite-Y is used commercially as catalyst in petroleum refinery because of its high concentration of active acid sites, its high thermal stability and high size selectivity. Zeolite-Y is a synthetic analog to the mineral faujasite and crystallizes with cubic symmetry. It has crystal sizes in the approximate range of 0.2-0.5μm and pore diameter of 7.4À. It thermally decomposes at 793oC (Htay et al, 2008).
The content of the zeolites themselves in zeolites-containing catalysts is not greater than 3-15%. In the preparation of catalyst, zeolites modified with metals (chromium, rhenium, platinum,
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palladium, etc.) are introduced into a matrix of inorganic oxides such as SiO2, Al2O3, Clays, etc. (Erikh et al, 1988).
In view of this, it is important to ascertain mechanical properties of these zeolite catalysts because, they are subjected to shear and compression forces when applied as fluidized catalytic cracking catalyst (FCC). Shear and compression stresses can lead not only to fracture of the crystals, but also to collapse of the micro-porous volume, loss of crystalline structure and a subsequent loss of catalytic properties (Zhongmin et al., 2002).
Moreover, energy is the vital basis of the development of human society, and is associated with several aspects of the social activities and daily life. With increasing world population and rising living standards, the demand for energy is steadily increasing in the world (energy information administration , 2007). Energy being an important resource, its cheapness and a stable supply is necessary to safeguard the economy and social development.
Developing countries face the double pressure of economic growth and environmental protection as they enter the 21st century. Petroleum became more and more important to the world’s economy, so important that today, without a steady flow of oil, most human activities on this planet would grind to a halt. The fuels that are derived from petroleum, supply more than half of the world’s total output of energy, such as gasoline, kerosene, and diesel oil provide fuel for automobiles, tractors, trucks, aircraft, and ships (energy information administration, 2007).
At the end of 2006, the world was consuming 84.8 million barrels of oil per day. Global petroleum demand is expected to rise by 1.5 million barrels per day in 2007, an increase of 0.7 million barrels per day above the 2006 growth (energy information administration, 2007).
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Majority of machines and equipment made at present are designed to run using liquid fuel. For these reasons, it is important to extract much useful products from crude oil (energy information administration, 2007). Zeolites have porous structures that can accommodate wide varieties of cations, such as Na+, K+, Ca2+, Mg2+. These positive ions are loosely held and can readily be exchanged for others in a contact solution. Some common mineral zeolites are analcime, chatazite, dingotilolite, heulandites, natrolite, phillipsite and stilbite. An example of mineral formula is Na2Al2Si3O10.2H20, for natrolite (Weitkamp, 1999).
Zeolite occurred naturally or it could be synthesized. Natural zeolites are formed where volcanic rocks and ash layers react with alkaline ground water or it could be crystallized in post-depositional environments over periods ranging from thousands to millions of years in shallow marine basin (Weitkamp, 1999).
Zeolite possess proton (H+) ion that make it active when it come in contact with carbon, it will donate that proton ions to carbon and accept electron from it and thereby weaking and breaking the long chain bond of the carbon. In doing that, the zeolite need to possess pore sizes that is not too large neither too small so that any particles that comes in will neither escape or unable to pass through.
Currently, the world’s annual production of natural zeolite is about 3 million tonnes. The major producers in 2010 were china (2 million tonnes, South Korea (210,000tonnes), Japan (150,000tonnes), Jordan (140,000tonnes), Turkey (100,000tonnes) Slovakia (85,000tonnes) and United States (59,000tonnes) (international zeolite administration, 2012).
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Synthetic zeolites are used as an additive in the production process of woven’s mix asphalt concrete. The development of the application started in Germany in the 1990s. It helps by decreasing the temperature level during manufacture and lying of asphalt concrete, resulting in lower consumption of fossil fuels, thus releasing less carbon dioxides, aerosols, and vapors to the atmosphere. Zeolite and related crystalline molecular sieves are widely used as catalyst in the industry since they possess catalytically active sites as well as uniform sized and shaped micro-pores that allow for their use as shape selective catalysts in oil refining, petro-chemistry and organic synthesis.
However, due to the pore size constraints, the unique catalytic properties of zeolites are limited to reactant molecules, having kinetics diameters below 10À (Maesen et al., 2004).
Zeolites have been successful when used as catalyst for cracking process because of their crystalline nature, high surface area, adsorption capacity, and uniform size distribution which enable shape selectivity (Weitkamp, 2000).
1.2 Statement of the Problem
Zeolite catalysts are subjected to wear, high temperature and compression stresses while in operations and thereby lose their catalytic properties with time. Hence it becomes necessary to investigate the mechanical properties of any zeolite catalyst especially those synthesised from locally available materials in order to estimate their possible period of life span before failure.
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1.3 The Present Reseacrh Work
The present research examines the ability of the synthesized zeolite catalysts to resist compressive stresses and the extents to which these compressive forces can act on them before deformation occur. The work also examines the morphology of supporting materials used in the synthesis of the zeolite catalysts. The stress and strain analysis of the developed zeolites would be carried out to determined the young’s modulus and compare with that of the reference zeolite. Wearing mode of each sample would be determined as a measure of its porosity.
1.4.0 Aim and Objectives
1.4.1 Aim
The aim of this research work is to investigate the mechanical properties of Zeolite-Y and ZSM-5 catalyst synthesised from locally available clays in order to establish its mechanical stability.
1.4.2 Specific Objectives
The specific objectives of the research work are:
i. To examine the morphology of the support materials used for the synthesis of the zeolite catalysts.
ii. To investigate mechanical properties (wear, compression pressure and young’s modulus) of the synthesized catalysts.
iii. To determine the resistance of synthesized zeolite catalysts to crushing in a packed-bed reactor.
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1.5 Significance of Study
Catalysts used for cracking operations are subjected to high compression stress, rubbing action between the particles and high temperature thereby losing their crystalline structure and micro-porous volume earlier than expected. Hence it becomes necessary to ascertain that any catalysts synthesized especially from local raw materials be characterized mechanically in order to ascertain its mechanical properties that will enable it function satisfactorily before losing its micro-porous volume and its crystalline structure when compared with the commercial zeolite catalysts in use.
1.6 Justification
Most works done on characterization of zeolite catalysts synthesized from local raw materials had not given much attention to their mechanical properties which is a major factor that determines the stability of the catalyst. In this work, necessary mechanical properties (Young modulus, Wear, Plasticity and porosity) had been examined.
1.7 Scope of Study
The scope of this work is to investigate mechanical properties of synthesized Zeolite-Y catalyst, ZSM-5 catalyst and support materials used in synthesis by determining their compression pressure absorption, examine the morphology of the support materials and to determine the Young’s Modulus.
1.8 Limitation
Listed below are some of the challenges encountered during the course of the experiment:
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i. The presence of substantial void fractions within the crystals allows for unusual mechanical and thermal properties.
ii. In availability of sensitive equipment that can be used for testing at the smallest scale.
iii. Difficulty of preparation of zeolite crystal that is large enough for measurement in standard mechanical testing machine
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