Synthesis and characterization of titanium silicalite TS-1 prepared using phosphonium ions

Abstract

Titanium silicalites with the MFI structure have been synthesized using binary mixtures of tetrabutylphosphonium hydroxide (TBPOH) and tetraethylphosphonium hydroxide (TEPOH). Whereas the MEL structure was obtained with pure TBPOH, addition of TEPOH led to a modification of the structure, and TS-1, with the MFI structure, was obtained. The crystals had a specific habit, similar to that of standard TS-1 crystals. Their size decreased with the Ti content in the zeolite. A maximum Ti incorporation of about 1.35 wt% could be achieved following this synthesis route. X-ray diffraction, u.v.-vis, and i.r. spectroscopies have shown that the zeolites thus obtained possessed all the structural characteristics of TS-1. 13C and 31P solid-state n.m.r. revealed that both TBP + and TEP + cations were introduced into the structure.