Reading list: Nano-TiO2 on Dodecyl-Sulfated Silica: As an Efficient Heterogeneous  Lewis Acid−Surfactant-Combined Catalyst (HLASC) for Reaction in  Aqueous Media
ABSTRACT: A reusable Lewis acid−surfactant-combined catalyst (LASC),
using immobilization of nano-TiO2 on dodecyl-sulfated silica support
(NTDSS), has been developed. To obtain this catalyst system, sodium
dodecyl sulfate (SDS) was reacted with silica chloride (SC) to generate a
dodecyl-sulfated silica (DSS) substrate. Subsequently, the addition of TiCl4
to a water solution of DSS resulted in the immobilization of nano-TiO2 on
the surface of a DSS substrate. The NTDSS catalyst was characterized using
different techniques such as TEM, SEM, XRD, ICP, and FT-IR. The catalyst
was successfully used for the synthesis of coumarin derivatives via Pechmann
condensation in water as a green solvent. High catalytic activity of the
catalyst in water media can be a result of colloidal particle formation on the
surface of the NTDSS catalyst due to the grafted DS moieties on the surface
of silica, which act as a surfactant. It seems that the generation of emulsion
droplets containing nano-TiO2 on the surface of the catalyst would function as an effective reaction reactor to accelerate the rate of the reaction in water media.