Characterization and Catalytic Performance of Niobic Acid Dispersed over Titanium Silicalite

Abstract

Niobic acid, Nb 2 O 5 ·nH 2 O, has been supported on the titanium silicalite by impregnation method. The obtained materials were characterized by X-ray diffraction, infrared, and ultra-violet-visible diffuse reflectance spectroscopy, temperature programmed reduction, pyridine adsorption, and field emission scanning electron microscopy techniques. It was demonstrated that the tetrahedral titanium species still retained after impregnation of niobic acid. The results revealed that niobium species interacted with hydroxyl groups on the surface of TS-1. The niobium species in the catalysts are predominantly polymerized niobium oxides species or bulk niobium oxide with the octahedral structure. All catalysts showed both Brønsted and Lewis acid sites. The catalysts have been tested for epoxidation of 1-octene with aqueous hydrogen peroxide. It was found that the presence of niobic acid in the catalysts enhanced the rate of the formation of epoxide at the initial reaction time. Diol as a side product was also observed due to the acidic properties of the catalysts.

Glass formation and structure of glasses in the WO3–ZnO–Nd2O3–Al2O3 system

“…The same figure displays also the spectrum of Al 2 (WO 4 ) 3 as a reference for the tetrahedrally coordinated W atoms against oxygen. Its UV-Vis spectrum contains only one maximum typical for the presence of isolated tetrahedra (WO 4 ) [52,63,64]. As it is seen from Fig.…”

Highly dispersed NbOPO4/SBA-15 as a versatile acid catalyst upon production of renewable jet-fuel from bio-based furanics via hydroxyalkylation-alkylation (HAA) and hydrodeoxygenation (HDO) reactions

“…Crystalline niobic acid and NbOPO4 possess very low surface areas (<12 m 2 /g) 22 and, also niobium is an expensive metal and its limited availability on earth limits its use in industrial applications. Several researchers attempted to increase its surface area in order to increase the number of available acid sites either by trying to make the material porous and amorphous or disperse it over porous carriers [23][24][25][26] . Zhang et al, prepared mesoporous NbOPO4 in the presence of cetyltrimethylammonium ammonium bromide (CTAB) with varying p H conditions and obtained porous amorphous material with maximum surface area of 290.1 m 2 /g 27 Mal et al, used a supramolecular templating mechanism and used different templates thus obtaining a porous niobium phosphate with a maximum surface area of 482m 2 /g [28][29] .…”

Application of La-ZSM-5 Coated Silicon Carbide Foam Catalyst for Toluene Methylation with Methanol

“…Barrows et al [6] found the effects of Nb on ZSM-5 where it was observed the change of structural property of HZSM-5 at different percentage of Nb impregnation. The characterization and catalytic performance of niobic acid dispersed over titanium silicate was investigated in 1-octene epoxidation [7]. Moreira et al [8] explained the nature and position of cerium in Ce-loaded Y zeolite and determined the catalytic performance in 2-propanol dehydration.…”