Project report
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- Bu səhifədəki naviqasiya:
- CHAPTER 1 INTRODUCTION 1.1 Background Information
- 1.3 Objective of Research
- 1.5 Justification of the research
- CHAPTER 2 LITERATURE REVIEW 2.1 Kaolin
- 2.1.1 Properties of kaolin
- Locations of kaolin deposit in Nigeria
- 2.1.3 Processing of kaolin
- Raw Kaolin Hammer milling Higher speed bunger Spiral classified Vibratory screen Hydrocyclonse
- Pulverization Screening Bagging
                                           CHAPTER 1
INTRODUCTION 1.1 Background Information The name “kaolin” is derived from the word Kau-Ling, or high ridge, the name given to a hill near Jau-chau Fu, China, where kaolin was first mined (Sepulveda et al., 1983). Kaolin, commonly referred to as china clay, is clay that contains 10–95% of the mineral kaolinite and usually consists mainly of kaolinite (85–95%). In addition to kaolinite, kaolin usually contains quartz and mica and also, less frequently, feldspar, illite, montmorillonite, ilmenite, anastase, haematite, bauxite, zircon, rutile, kyanite, silliminate, graphite, attapulgite, and halloysite (Adamis, 2005). Zeolites are crystalline, microporous, hydrated aluminosilicates of alkaline or alkaline earth metals. The frameworks are composed of [SiO4]4- and [A1O4]5-tetrahedra, which corner-share to form different open structures. Nowadays 180 synthetic zeolites are known. Some of the earlier synthetic zeolites include zeolites A, X, Y, L, ZSM-5 and omega (Petrov and Michalev, 2012; Barrer, 1982). Most catalysts used in commercial catalytic cracking units today are either amorphous synthetic silica-alumina combinations or mixtures of amorphous synthetic silica-alumina and crystalline synthetic silica-alumina catalysts called zeolites or molecular sieves (Thomas, 1970). The advantages of the zeolite catalysts over the natural and synthetic amorphous catalysts are: higher activity, higher gasoline yields at a given conversion, production of gasoline containing a larger percentage of paraffinic and aromatic hydrocarbons, lower coke yield (and therefore usually a larger throughput at a given conversion level), increased isobutane production, and ability to go to higher conversions per pass without overcracking (Thomas, 1970; Gary, 2001). Automobiles run on gasoline fuels produced by fluid catalytic cracking (FCC) catalysts made from processed kaolin clay. Zeolites and molecular sieves synthesized from silica, alumina, and titania minerals are used commercially to produce chemicals like cumene or paraxylene that are processed further into plastics used in buildings, cars, and toys(Geoffrey et al., 2005). Zeolites have gained an irreplaceable role as catalysts in the refining industry. With a production capacity of 625million tones in 2004, the fluid catalytic cracking process (FCC) represents the second most important heterogeneously catalyzed process. As an active component, the catalyst of this process contains zeolite H-Y. Since a high-molecular feed is used, a detailed knowledge of the diffusion behavior of the feed molecules within the pores of zeolite Y is of interest (Berger et al., 2005). Catalytic cracking of gas oil fractions occurs over many types of materials such as acidified clay, alumina, silica, zeolites, and so on. However, relatively higher yields of desirable products are obtained with zeolites. In addition, zeolites are known to be stable to physical impact, loading and thermal shocks and withstand the action of carbon dioxide, air, nitrogen compounds and steam (Atta et al., 2007). Zeolites are widely used in adsorption, separation, catalysis, ion exchange and other processes. Some groups have already studied the preparation of various zeolites from kaolin or other ashes and have made great progress in synthesis of 4A, mordenite, X, Y zeolites, and so on (Liu et al., 2003). Nigeria as a country is endowed with natural clays, rich in Kaolinite principally required for Zeolite synthesis, thus it has become highly imperative that indigenous research on natural kaolin deposits be carried out, in order to maximize its utilization as it is much needed in the petroleum and chemical industries (Emofuriefa et al., 1992). This project therefore is carried out to contribute to the existing knowledge on the synthesis of zeolites from various kaolin deposits in Nigeria. In this case, kaolin deposit of Okpella is considered as it is of commercial quantity and relatively free of impurities. 1.2 Problem Statement The catalysts, example zeolite, used in oil industries and many other chemical industries in the nation are expensive and are mostly imported. The development of zeolite catalyst in Nigeria has been on a small scale or almost non-existent. Continuous research is being done to find out means of synthesizing such catalysts for these processes in the nation to reduce its price and empower the industry. This forms the reason for this project, the development of zeolite catalyst. 1.3 Objective of Research The objective of the project is to develop zeolite from Okpella kaolin clay. 1.4 Scope of Study The areas of study in the course of the project include:
1.5 Justification of the research This project, development of zeolite from Okpella kaolin clay is novel, as Okpella Kaolin has not been used to synthesize zeolite by any researcher. Okpella has kaolin in commercial quantity and relatively pure as it has limited oxides. From the past works done on kaolin clay from different parts of the country, we don’t have substantial conversion yet on zeolite Y from kaolin clay. In addition, the zeolite would be synthesized using kaolin which is a natural abundant material in Nigeria, thus making the local manufacturing process inexpensive. Synthesis of zeolite from kaolin would add to the value to the kaolin as a useful resource material in the country. Zeolites having extended applications in the chemical industry like in Fluidized Catalytic Cracking in the oil industry, particle separation, and molecular sieves and so on will provide Nigeria with an indigenous catalyst market.
The name “kaolin” is derived from the word Kau-Ling, or high ridge, the name given to a hill near Jau-chau Fu, China, where kaolin was first mined (Sepulveda et al., 1983). Occurrences in many parts of the world are well known today. Johnson and Blake in 1867 appear to have first clearly intended the name kaolinite for the mineral of kaolin. Ross and Kerr showed that the kaolin minerals cannot be assigned to a single species, i.e., clays of this character are not composed of a single mineral species, and minerals of that composition also are not all the same samples. They concluded that three distinct species are represented, namely, kaolinite, nacrite, and dickite (Grim, 1968). Kaolin, commonly referred to as china clay, is clay that contains 10–95% of the mineral kaolinite and usually consists mainly of kaolinite (85–95%). In addition to kaolinite, kaolin usually contains quartz and mica and also, less frequently, feldspar, illite, montmorillonite, ilmenite, anastase, haematite , bauxite, zircon, rutile, kyanite, silliminate, graphite, attapulgite, and halloysite (Adamis, 2005). Kaolin (hydrated aluminum silicate, Al2Si2O5(OH)4), is an important industrial clay for economic benefit. Properties of fine particle size, platy shape, inertness, non-toxicity, as well as high brightness and whiteness make it a more versatile mineral, with applications in a wide variety of industries. Commercial kaolin resources are found as sedimentary deposits and as weathering or hydrothermal alteration product of rocks containing a high proportion of alumino-silicate minerals (Badmus and Olatinsu, 2009). For most industrial applications kaolin must be refined and processed from the crude state to enhance its whiteness, purity and other important commercial characteristics. Common impurities in kaolin are quartz, micas, illate, montmorillonite, goethite, hematite, pyrite, anatase, rutile, ilmenite, and trace amounts of tourmaline, zircon and other heavy metals, most of which are removed by wet processing or beneficiation. Kaolinite is white or near white in colour which is another important attribute that relates to its chemical composition. One of the good properties that many kaolins exhibit is that they have good flow properties when present in large amounts of water (Murray, 1997). 
Figure 2.1: Kaolinite structure by Murray, 1997 2.1.1 Properties of kaolin The chemical composition and XRD pattern of kaolin are described in Table 2.1 and Fig. 2.2. The SEM image of kaolin is shown in Fig. 2.3. Table 2.1, Chemical composition of kaolin (Mu and Mya, 2008) 
Figure 2.2: XRD pattern of kaolin (Mu and Mya, 2008) 
Figure 2.3: SEM of kaolin (Mu and Mya, 2008) 2.1.2 Locations of kaolin deposit in Nigeria Kaolin deposits are wide spread throughout Nigeria. Almost every state in Nigeria has at least one known deposits of kaolin. In Anambra state, there is the Ozubulu deposit, Darazo deposit in Bauchi, Akpene-Obom deposit in Cross-River state, Kankara deposit in Kaduna state, just to mention a few (Badmus and Olatinsu, 2009). The bulk of the Kaolinitic clay deposits in the country are either sedimentary or residual in origin and are usually associated with granitic rocks. Occurrences of kaolin have been recorded in different parts of the country and specific abundant deposits have been identified in parts of Enugu, Anambra, Kaduna, Katsina, Plateau, Ondo, Ogun, Oyo, Bauchi, Sokoto, and Borno States. Of these reserves, about 800 million tones of probable/proven deposits have been quantified (Onwualu and Ibrahim, 2010). Table 2.2: Location of Kaolin deposits adapted from Non-metallic mineral endowments in Nigeria, (Onwualu and Ibrahim, 2010).
2.1.3 Processing of kaolin Mined kaolin is crushed and mixed with water into slurry. The slurry is pumped into degritting equipment and then stored in tanks for further processing. The slurry can be decolorized by a chemical leaching process, and by magnetically separating iron contaminants. The Kaolin particles are removed from suspension using press filters, rotary filters or continuous centrifuges. The filtered cake can be dried in apron dryers or sprayed-dried. It may be processed further to improve properties. The flow sheet diagram for the beneficiation of Kaolin is shown in fig. 2.4. The equipment require include blungers, hydrocyclones, serves, tanks, filter press, dryers, hammer mills, calciners, pumps conditioners, floatation machines and weighing/bagging machine(Onwualu and Ibrahim, 2010). Raw Kaolin Hammer milling Higher speed bunger Spiral classified Vibratory screen Hydrocyclonse Dewatering/thickener Refining tanks Settling/Storage Centrifuge Filter press Drying Pulverization Screening Bagging Figure 2.4: Flowsheet diagram for beneficiation of kaolin (Onwualu and Ibrahim, 2010) 2.1.4 Applications of kaolins Kaolin has many industrial uses as is shown in the table below The largest user of kaolin is the paper industry where it is used both as a filler in the sheet and as a coating on the surface of the sheet. Some properties that are important to the paper maker are dispersion, rheology (both low and high shear), brightness and whiteness, gloss and smoothness, adhesive demand, film strength, ink receptivity, and print quality (Murray, 1997). Another very large user of kaolins is the ceramics industry, particularly in whiteware, sanitaryware, insulators, pottery and refractories. Both primary and secondary kaolins can have excellent ceramic properties (Murray, 1986). Kaolin which does not have the physical and chemical properties for use in a paper-coating application can have excellent ceramic properties. Halloysite, one of the kaolin minerals, is used as an additive in high quality dinnerware to provide translucency and strength. The major source of halloysite is on the North Island of New Zealand (Murray et al., 1977). Table 2.3: Application of kaolin in the industries adapted from Murray, 1997.
Another area that deserves mention is the large industrial use of calcined kaolin. When kaolin is heated to approximately 1050 degrees it is converted to mullite, cristobalite, and/or a silica alumina spinel (Brindley and Nakahira, 1959). This calcined product is whiter and more abrasive than the original kaolin and the surface chemistry and physical properties are completely changed. The largest utilization of calcined kaolins is in paint, rubber, and plastics (Murray, 1997). Yüklə 357,43 Kb. Dostları ilə paylaş:
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