MODIFIED NATURAL CLAY AS A POTENTIAL GREEN SOLID ACID CATALYST

ABSTRACT

The synthesis and employment of solid acid catalyst in various industrial processes for the production of chemicals is viewed as a green and sustainable alternative to the use of mineral acids. Of the solid acid catalyst employed in various industrial processes, zeolite has gained so much attention in the petrochemical industry because of the development of Zeolite Socony Mobil-5 (ZSM-5) by Mobil Oil Cooperation. A similar aluminosilicate material to zeolite is clay but has received less attention despite its abundance and cost-efficient nature. In this study, the natural clay samples were modified using certain concentrations of Hydrochloric acid and ammonium chloride and their acid strength and total acidity estimated. The clay was obtained from a site in Omialafara, Ifon, Ose Local Government Area Ondo state, Nigeria. The methodology includes weighing 5g of the calcined Natural clay and treating with 25% HCl and 10% NH4Cl respectively. After treatment of the natural clay, a pyridine FT-IR was done on both the treated and untreated clay sample. In the pyridine FT-IR of the untreated clay, and it was observed that the band at 3690.1cm-1 was a clear indication of the presence of OH stretching as well as a band at 913.2cm-1 indicates the presence of Al-OH-Al. For the 25% HCl treated clay, a band at 1453.5cm-1 shows the presence of Lewis acid site while the peak at 1551.2cm-1 indicates the presence of Bronsted-Lowry acid site. A little peak at 1539.4 shows the presence of a Bronsted-Lowry acid site in the 10% NH4Cl treated sample. A Hammett indicator test was also done on the clay samples using some selected indicators. (Crystal violet, Methyl red, and Neutral red) with the pKa of +0.8, +4.8, and +6.8 respectively. It was discovered that both the untreated and treated clay sample tested positive to Methyl red although the intensity of the colour observed in the treated clay was more compared to the untreated showing an increase in acid strength of the treated clay for both the 25%HCl and 10% NH4Cl respectively. xii A gravimetric pyridine analysis was also done on the treated and untreated but due to some unfortunate conditions, the result was not estimated. In conclusion, it was observed during this research, that there was a notable increase in the acidic properties of the treated clay samples and the comparative tests carried out shows that the modified clay is more effective than the unmodified clay although, more research should be carried out on this study with other acids to see if any more significant change can be observed.