Amorphous Ti species in titanium silicalite-1: Structural features, chemical properties, and inactivation with sulfosalt

The nature of the amorphous Ti species in titanium silicalite-1 (TS-1) was investigated by UV Raman spectroscopy (UV Raman), UV–vis diffuse reflectance spectroscopy (UVDRS), infrared spectroscopy (IR), and Hammett indicator titration methods. A new Raman feature at 700 cm−1, which is closely related to the UVDRS band at 260–280 nm, is first assigned to a totally symmetric vibration of hexacoordinated Ti–O–Ti linkages of the amorphous Ti species. The amorphous Ti species in TS-1 can be formed easily under the synthesis conditions in the presence of Na+ or after treatment in ammonia solution. The results reveal that the amorphous Ti species is the main factor in the enhanced acidity and H2O2 decomposition ability of TS-1. A sulfosalt impregnation method has been proved effective in reducing the adverse effect of the amorphous Ti species.

The structural features, chemical properties, and methods of inactivation of the amorphous Ti species in TS-1 are investigated. The formation of the amorphous Ti species, which is composed of fragments of Ti–O–Ti chains, is confirmed by the Raman band at 700 cm−1. The presence of the amorphous Ti species severely decreases the catalytic performance of TS-1 by causing byproduct formation and H2O2 decomposition. The sulfosalt impregnation method can easily reduce the adverse effects of the amorphous Ti species.Figure optionsDownload high-quality image (88 K)Download as PowerPoint slideHighlights
► New Raman feature at 700 cm−1 was assigned to the amorphous Ti species in TS-1.
► The amorphous Ti species compose by hexacoordinated Ti–O–Ti linkages.
► The amorphous Ti species enhancing the acidity and causing the H2O2 decomposition.
► The sulfosalt impregnation can reduce the adverse effect of the amorphous Ti species.