An Infrared Study of the Adsorption of Butenes on Surfaces of Porous Vycor Glass

Abstract

The adsorption and reactions of the four butenes on porous Vycor glass a t room temperature have been studied by infrared spectroscopy. Initial adsorption was rapid and was found to perturb the surface hydroxyl groups of the glass. In the case of the n-butenes rapid isomerization took place a t room temperature. In addition to this the adsorbate spectra showed the occurrence of a slower reaction which led to an increase in saturated C-H groupings. Cs and higher con~pounds were shown to have formed; on outgassing a t room temperature small amounts of cracking products were collected. The polymerization of isobutene was particularly rapid. Experimeilts a t low coverage (0 -0.001-0.002) gave identical initial spectra for the n-butenes. These were discussed in terms of possible models for butene adsorption. A reduction in the alumina and zirconia content of the glass by acid leaching resulted in decreased rates of isomerization and polymerization, suggesting that one or both of these oxides are a t least partially responsible for the activity of the glass. A pure silica aerogel was almost completely inactive. Quantitative measurements of the spectra of several monoolefins in solutioil were made for comparison with the surface species, in particular with respect to their inolar intensities of absorption.

Infra-red studies of carbon monoxide and hydrocarbons adsorbed on silica-supported nickel

“…Later studies 10, 11 of ethylene on nickel/porous glass were also handicapped by poor transmission and complicated by catalytic activity of the porous glass support. 12 Additional infra-red study of adsorbed CO and hydrocarbons on nickel/silica seemed clearly warranted. Prospects for increased sensitivity and resolution in such study were improved by preparation of transparent plates of nickel/silica aerogel and by the availability of a new prism-grating spectrometer.…”

Infrared spectra of acetonitrile sorbed on porous glass

“…However, porous glass contains oxide impurities which markedly affect the reactivity of its surface. For example, Little, Klauser, and Amberg found isomerization, cracking, and polymerization reactions occurring on porous glass to be very dependent on the concentrations of alumina and zirconia impurities (2), and Cant and Little found evidence pointing to the binding of ammonia to electron-deficient surface boron atoms (3). More recently, the oxide impurities were found to affect the adsorption of NH, (4), HCN (5), pyridine (6), aniline (7), and trimethylamine (8).…”

Chemisorption sites on porous silica glass and on mixed-oxide catalysts

“…However, it is possible that Bronsted acid sites or other Lewis acid sites such as aluminium atoms exist on porous silica glass and are responsible for hydrocarbon reactions that have been observed (3). The number of these catalytically active sites may be small in relation to the total number of acid sites and the ammonia chernisorbed to them would be indistinguishable by infrared spectroscopy.…”