ABSTRACT
The efficacy of silica obtained from our local sand as a carrier in synthesis of Nickel-Silica catalyst was investigated. Six samples of soil were collected from two different sites (comprising five white coloured samples collected from Iva valley, lower part of Milliken hill, namely: pottery 2 (P2), down iva (DI), run-off iva (ROI), pottery rock (POR), white chalk (WTC) and one brown coloured sample (UdS) collected from Udi Siding) in Enugu, Nigeria. Prior to treatment by flotation method, some properties that could affect their catalytic use like organic matter content, texture, porosity and pH were assayed. (i) P2 (pH, 4.7; fine sand, 74.29 %; organic matter, 0.26 %), (ii) DI (pH, 4.7; fine sand, 72.72 %; organic matter, 0.26 %), (iii) ROI (pH, 7.4; fine sand, 87.42 %; organic matter, 0.19 %), (iv) POR (pH, 6.4; fine sand, 85.65 %; organic matter, 0.0%), (v) WTC (pH, 4.7; fine sand, 83.59 %; organic matter, 0.07 %) and (vi) UdS (pH, 4.4; fine sand, 32.79 %; organic matter, 0.19 %). Three of the samples with the best results ROI, POR, and WTC as can be seen above were selected. The pre-treated sand was purified by leaching process using 20 % HF, 20 % H2SO4, 10 % NaOH and distilled water. Comparison of the XRD results of the raw sand sample and silica extract showed complete removal of Al, Ca, and other oxide impurities from the raw sand. The silica was coupled with nickel employing two catalyst preparation methods. The Deposition method was used to couple silica with Ni(NO3)2 to prepare the catalyst named DPNN and NiCl2 to prepare the catalyst named DPNC. In the Co-precipitation method, silica was coupled with NiCl2 to prepare the catalyst named CPNC. The surface area, pore volume and particle size distributions of the catalyst samples were determined by N2 adsorption at 77 K using Trister II Plus BET analyzer. The elemental composition was obtained by XRF spectroscopy. Effect of using two different nickel precursors for coupling was investigated; the result showed that NiNO3 gave a higher degree of Ni dispersion and incorporation compared to NiCl2. Effect of using two different catalyst preparation methods was also investigated; Co-precipitation method allowed the highest degree of Ni incorporation and improved surface properties. The results showed that Ni-silica catalysts prepared using silica from the local soil has catalytic properties that are similar to the standard Ni-Silica catalyst, Euro Ni-1, and better catalytic properties than some previously synthesized ones reported by Unichema, C. B. V. (1990), Wang, W. et al (2006), and Hermida, L. et al (2012).
