Silicated aluminas prepared from tetraethoxysilane: catalysts for skeletal isomerization of butenes

Abstract

Catalysts were prepared by the condensation reaction of tetraethoxysilane with the surface of alumina and characterized by X-ray photoelectron spectroscopy to determine surface compositions and by Infrared spectroscopy with adsorbed pyridine to determine surface acidity. Silicon-containing groups formed on the alumina surface at less than monolayer coverage, inducing strong acidity; both Bronsted and Lewis acid groups were detected. The catalytic activity for skeletal isomerization of 1-butene was determined In flow reactor experiments at atmospheric pressure and 450-525 °C. The reaction is first-order In the reactant; the activity increased with Increasing surface acidity, i.e., with increasing Si content of the surface and apparently with increasing Bronsted acidity. The surface is comparable in structure and catalytic activity to that of silica-alumina, and the catalytic sites are suggested to be Si-OH groups positioned next to coordinatively unsaturated Al3+ sites.

Acidity and Characterization of 12-Tungstophosphoric Acid Supported on Silica-Alumina

“…The characteristics of acid sites on amorphous silica-alumina have been debated for a long time in the literature. 17,[36][37][38] However, different reports using diffuse reflectance Fourier transformed infrared spectroscopy (DRIFTS), density functional theory (DFT) and their combination have clarified it. 17 It has been proposed that silica-alumina surface is formed by isolated silanols and/or hydrogen-bonded bridge silanols.…”

Revisiting carbenium chemistry on amorphous silica-alumina: Unraveling their milder acidity as compared to zeolites

“…Many experimental studies [19][20][21][22][23][24][25][26][27][28][29] groups [19][20][21][22], silanols in the vicinity of aluminum atoms [23][24][25], and water molecules adsorbed on aluminum atoms [26,27]. However, at a molecular scale, it remains crucial to understand the precise chemical behavior of the ASA Brønsted acid sites, how they catalyze cracking reactions and the reasons of their milder acidity of ASA as compared to zeolites.…”

Effect of acidity, hydrogenating phases and texture properties of catalysts on the evolution of asphaltenes structures during reside hydroconversion

“…To achieve this goal, NiMoP catalysts supported on mixed Al 2 O 3 -SiO 2 were prepared. Silica was introduced by using grafting procedures, described in literature [39][40][41][42][43]. After a brief description of the catalysts preparation, a detailed characterization of textures, acidity and hydrogenating active species is presented.…”