Synthesis of hydrophobic nanosized hierarchical titanosilicate-1 zeolites by an alkali-etching protocol and their enhanced performance in catalytic oxidative desulphurization of fuels

Abstract

Nanosized hierarchical titanosilicate-1 zeolites (nanoTS-1_D) with variable Ti doping content were synthesized by a simple and sequent two-step procedure consisting of microporous TS-1 nanocrystal synthesis through steam-assisted dry-gel conversion and post alkali-etching treatment for mesopore formation. Comprehensive characterizations, e.g. XRD, N2 sorption isotherms, DLS, UV-Vis, SEM, TEM and water-droplet contact angle, indicated that the resultant nanoTS-1_D materials not only possess abundant intracrystal mesopores and high surface area, but importantly maintain the intrinsic surface hydrophobicity as those of microporous TS-1 zeolites. Consequently, they showed the expected superior catalytic performance in both bulky cyclohexene/cyclooctene epoxidation and phenol hydroxylation probe reactions, contrast to the microporous TS-1 and amorphous Ti-MCM-41 mesoporous counterparts. In the oxidative desulfurization of fuels, they exhibited 100% removal ability for thiophene and its bulky derivatives and excellent recyclability. In addition, a new Ti-dopant directed alkali-etching mechanism has been proposed to illustrate the synthesis of high-specific-surface-area nanoTS-1_D.