DEVELOPMENT OF LARGE PORE ZEOLITE FROM KAOLINITE CLAYS
DEVELOPMENT OF LARGE PORE ZEOLITE FROM KAOLINITE CLAYS
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Date
2012-08
Authors
AJAYI, OLUSEGUN AYOOLA
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Abstract
This thesis is focused on the synthesis of faujasite type NaY zeolite from both Kankara and
Elefun kaolinite clays. The raw kaolins were subjected to various treatments, for the purpose of
upgrading them and making them useable as an active monomer for zeolite synthesis. The
kaolins were beneficiated using wet method, calcined at various temperatures namely;
600,700,750, 800, 850, 900 and 950 degree Celsius. The silica and alumina in kaolin sourced
from Elefun was observed to attain it optimal activated state at 8500C, while that of Kankara
was at 9000C. Sulfuric acid was used to alter the silica-alumina ratio of the optimally calcined
metakaolin. A novel approach to dealumination, independent of external source of heating was
developed and employed in this work. Furthermore, the synthesis process took place without
using any structure directing agent, while parameters such as ageing, seeding, alkalinity (NaOH
and pH), dyeing (blanking) were investigated and a reproducibility corrective investigation was
done. The transformation stages involved in this work were monitored using X-Ray
Flourescence (XRF), X-Ray Diffractograph (XRD), Braunner-Emmett-Teller for surface area
analysis (BET), Scanning Electron Microscopy (SEM) and partially Fourier Trace Infrared
(FTIR). Faujasite type Y zeolite was synthesized from shelf soluble salts for control reason.
Zeolite Y was synthesis from red Kankara kaolin sample aged for 9 days having about 40%
NaX and 15% NaY aside other phases and an unnamed zeolite. Post-synthesis aging of this
product, for 95 days, established an insitu seeding and formation of more stable phase ZSM3, in
company of prominent persistent peak attributed to quartz. Irrespective of the type of kaolin
(Kankara or Elefun) 9 days of gel aging was observed to be sufficient for appearance of peak
attributeable to zeolite Y. The SEM for the resulting products from aging process indicated
increase in crystallinity with aging period, with presence of other highly siliceous phase.
Introduction of dye into the gel was observed to suppress nucleation of inherent impurities as
well as enhance rate of amorphosity, but with attendant indications that the same dye enveloped
the soluble ingredients from reacting, by increasing their degree of segregation. Both Elefun and
Kankara were observed to give zeolite NaY, though at different dye/metakaolin ratio. The gel
from Kankara and Elefun with Na2O/SiO2 ratio of 7 and 9, were observed to give NaY zeolite
peak. Increase in the alkalinity (NaOH and/or pH) gave increased crystallinity though not
favourably disposed to the synthesis of zeolite Y. Elefun gel seeded with 1, 1.5, 2.0 and 2.5wt%
commercial zeolite Y, were noticed to give zeolite Y with increased crystallinity. NaY zeolite
peak were noticed for samples from Kankara seeded with 1.5 and 2.5wt%, respectively. The
appearances of highly siliceous zeolite phases along with NaY were blamed either on the
inability of NaOH to depolymerise the silica, high level of sulfate salts in the gel and/or low
level of reconstitution reaction between the already dissociated silica and alumina. The
improvement studies conducted proved successful as highly crystalline NaY zeolite were
characterized using XRD analysis. Zeolites belonging to the SSZ, ITQ, ZSM families, were
synthesized without the use of templating agent, which gives an insight also of the useability of
Nigerian kaolin in an environmental friendly synthetic route.
Keywords: Kankara, Elefun, XRD, XRF, SEM, crystal violet, dealumination, nucleation
Description
A thesis submitted to the School of Post Graduate Studies, Ahmadu Bello University,
Zaria
In partial fulfillment of the requirements for the Award of Doctor of Philosophy in
Chemical Engineering, Faculty of Engineering, Ahmadu Bello University, Zaria. Kaduna
State, Nigeria.
August, 2012
Keywords
DEVELOPMENT,, LARGE,, PORE,, ZEOLITE,, KAOLINITE,, CLAYS.