Determination of Lewis and Brönsted acid sites by gas flow-injection technique

Abstract

Gas flow-injection technique pyridine-FTIR was studied for determination of Lewis and Brönsted acid sites on the solid super acid catalysts. The system consists of stainless steel gas cell which can be heated up to 623 K, CaF2 windows, pyridine injection port and double liquid nitrogen trap for removal of moisture. Pure nitrogen gas and pyridine were used as a carrier and probe molecule. Pyridine was injected to the sysem at 423 K followed by flushing of N2 gas through double liquid nitrogen trap at 423 for 1 h and at 573 K for 30 min. All spectra were recorded at room temperature. This technique gave similar results to those of taken by vacuum system for HZSM-5, Pt/SO4 2--ZrO2, Al2O3 catalysts.

Electrochemical capacitor behavior of SO42-/MxOy (M-Fe, Ti, Zr, Sn)

“…The relative amount of Bronsted and Lewis acid sites could be estimated from the integrated area of the band at ca. 1540 cm À 1 and 1450 cm À 1 [47]. In Fig.…”

Vapor Phase Alkylation of Isomeric Cresols with Tert-Butyl Alcohol over Perlite Supported Sulfated Zirconia Catalyst

“…The absence of bands around 1540 and 1440 cm −1 reveals no sign of Bronsted and Lewis acidity in perlite and TAP [55]. The Bronsted acidic sites were obtained at 1545 cm −1 , whereas the Lewis acidic sites were obtained at 1445 cm −1 [56][57][58][59]. After an increase in sulfur content, the number of Lewis and Brønsted acid sites also increased [60].…”

Nonthermal Plasma Induced Fabrication of Solid Acid Catalysts for Glycerol Dehydration to Acrolein

“…Figure 4 shows the Py-FTIR spectra of HSiW-Al and HSiW-Si prepared via NTP-argon and NTP-air fabrication, in contrast to those of the regularly fabricated counterparts. The ratio of the signal intensity at 1545 cm −1 to that at 1445 cm −1 could be used as a measure of the relative amount of Brønsted acid sites to Lewis acid sites on a catalyst surface [36][37][38]. This ratio was calculated and marked as B/L in Figure 4.…”