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      https://www.ias.ac.in/article/fulltext/jcsc/127/11/1905-1917

    • Keywords

       

      Hydrophobicity; silylation; silica functionalized with silyated Ti-salicylaldimine complex; limonene oxidation; octadecyltrimethoxysilane.

    • Abstract

       

      This research work describes the effect of hydrophobicity in inducing the diffusion of alkene substrates to the catalytic active sites. The aim of this research is to improve the catalytic activity by tailoring the degree of hydrophobicity of the catalyst. Silica functionalized with solid non-silylated Ti-salicylaldimine complex was prepared at room temperature by mixing imine ligand and Ti(IV) sulphate solution. The amorphous, solid complex formed was further silylated with octadecyltrimethoxysilane (OTMS) to induce hydrophobicity. The composition of the resulting silica functionalized with silylated Ti-salicylaldimine complex was varied with Ti:OTMS molar ratio in the range of 1:1/4 to 1:4 at room temperature. The successful attachment of alkylsilyl groups to silica functionalized with Ti-salicylaldimine complex was proven by the FTIR and $_{}^{29}$Si solid state NMR spectra. The FTIR spectra showed increasing peak area for sp3 C-H stretching mode (ca. 2919 cm−1 and 2850 cm−1) and decreasing peak area for Si-OH band with increasing amount of OTMS. TGA showed less water content with higher amount of alkylsilyl groups in the catalyst. This is in agreement with the lower kinetic rate of water adsorption capacity for the hydrophobic catalysts prepared. It was observed that the hydrophobic, silica functionalized with silylated Ti-salicylaldimine complex exhibited higher substrate conversion and reusability compared to the non-silylated catalyst.

    • Author Affiliations

       

      Lai Sin Yuan1 Sheela Chandren1 Jon Efendi2 Chin Siong Ho3 Hadi Nur1 4

      1. Centre for Sustainable Nanomaterials, Ibnu Sina Institute for Scientific and Industrial Research, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia
      2. Department of Chemistry, Faculty of Mathematics and Science, Universitas Negeri Padang, Padang 25131, Indonesia
      3. Low Carbon Asia Research Center, Faculty of Built Environment, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia
      4. Department of Physics, Institut Sains dan Teknologi Nasional, Jl. Moh. Kahfi II, Jagakarsa, Jakarta Selatan 12640, Indonesia
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