Preparation, Characterization And Catalytic Performance Of Hydrophobic Solid Acid Catalyst Of Sba-15

The mesoporous molecular sieve SBA-15 was reported to have many advantages as follows: very high surface area, periodic hexagonal channels, tailoring of pore dimension, high thermal stability and easily polished interior-exterior surface. It has very wide potential applications in the catalytic chemistry and the adsorption-separation field. Design and preparation of a highly effective catalyst can be optimized through the organic-functional modification of mesoporous molecular sieve SBA-15. It plays an important role in developing novel catalysts for heterogeneous catalysis. In this paper the synthesis of modified SBA-15 samples with different hydrophobic properties and adjusted acid sites by grafting method and direct synthesis method and catalytic properties of the modified SBA-15 samples in the esterification of acetic acid and n - butanol were mainly investigated.Firstly, after the synthesis of SBA-15, incorporation of different hydrophobic groups on the external of SBA-15 was carried and then the templates were wiped off. Subsequently sulfonic groups were attached on the internal surface of SBA-15. So modified SBA-15 samples were attained by grafting method. XRD spectra showed the modified SBA-15 samples reserved periodic hexagonal channels. The results of IR, contact angle and titration measurements showed the organic groups had been successfully incorporated on both internal and external surfaces. The results of TGA also showed the organic groups had high thermal stability.Secondly, the modified SBA-15 catalysts were prepared by direct synthesis method through simultaneous reaction of condensable inorganic silica species and silylated organic compounds in the acidic condition while PEO₂₀-PPO₇₀-PEO₂₀ was used as surfactant. XRD spectra showed the modified SBA-15 samples also had periodic hexagonal channels except the samples in which the proportion of organic groups reached 26.42%. The results of IR, contact angle and titration measurements showed the organic groups had been successfully incorporated on the surface and had better effects than which incorporated by grafting method. Moreover, the wetting contact angle of the sample named d-C₁₆H₃₃-SBA-15-SO₃H (α= 0.111) reached 91.90⁰ and its acid content was 0.98mmolH⁺/g. The results of TGA also showed the organic groups had high thermal stability.Thirdly, the catalytic properties of organic modified SBA-15 for the esterification of acetic acid and n-butanol were studied. The results indicated that the sample named d-C₁₆H₃₃-SBA-15-SO₃H (α= 0.111) had excellent activity and stability. Under the conditions as follows: catalyst ratio to acetic acid: 10%, reaction time: 6 hours, the yield of n-butyl acetate reached 83.2%. The catalyst could be reused.