Fluoroalkyl ether chemistry on alumina: a transmission infrared study of the adsorption and thermal decomposition of difluoromethyl ether on alumina

Abstract

Transmission infrared spectroscopy has been utilized to study the adsorption and thermal decomposition of (CF2H)20 on A1203. At 150 K the fluoro ether is adsorbed molecularly and reversibly via hydrogen bonding to isolated surface hydroxyl groups. The monolayer capacity was estimated to be ~3 X 10u molecules/cm1 2 judged by saturation effects in the IR spectra and correlation to an adsorption isotherm. The characteristic shape of the isotherm is indicative of associative interactions within the adlayer. The (CF2H)20 adsorbed at 150 K desorbs molecularly at higher temperatures, with the majority of the molecules desorbing by 250 K. As desorption progresses the isolated OH groups are regenerated on the surface; the original IR intensity of the isolated OH groups is regained only after heating to 500 K. Concomitant with the desorption process CA. P.B. is grateful for a supported educational leave from Alcoa.

Electron stimulated decomposition of fluorocarbons on amorphous hydrogenated carbon (a-CHx) overcoats used in data storage media

“…The roles of temperature and free electrons in the decomposition of small fluorinated ethers on metal and metal-oxide surfaces such as Ru [21], ZrO 2 [22], and Al 2 O 3 [23,24], have been studied. It is noteworthy that 300 eV electrons have a high cross section for decomposition of (CF 2 H) 2 O on Al 2 O 3 [11,24].…”

Surface chemistry of fluoroethanols

“…Previous studies of our group [9][10][11][12][13] as well as Basu et al [14] and Chen et al [15], on the interaction of partially and fully fluorinated ethers with high-surface-area alumina oxide have shown that surface hydroxyl groups and Lewis acid sites play a significant role in the process of catalyzing thermal decomposition of these compounds on alumina surfaces.…”

“…New peaks appeared at 1618 and 1680 cm À1 at 400 K, and their intensities increased significantly by 500 K. The band at 1457 cm À1 decreased until 350 K and then increased at 450-500 K. These features are assigned to the symmetric and asymmetric stretching modes of surface fluorinated carboxylates. The assignments are made based on published assignments of fluorinated carboxylates on alumina Table 1 The observed vibrational frequencies of physisorbed and gas phase difluoroethanol, in wavenumbers (cm À1 ), at different temperatures [3,[9][10][11]14,16,22,23]. Assignment of the observed vibrational modes of the reaction products are summarized in Table 2.…”

Surface chemistry of fluoroethanols II. A FTIR study of the reaction of 2,2,2-trifluoroethanol on Al2O3 surface

“…[8]; (2) the gas phase IR absorption spectra of CF 3 -CH 2 -OH measured at 100 K, 150 K, and 300 K in our laboratory; (3) recognition of vibrational features that change intensity concomitantly as temperature changes in IR spectra reported in this study; (4) comparison with published IR spectra assignments of fluorinated ethers, fluorinated acetates, and fluorinated formates on Al 2 O 3 surfaces obtained in similar conditions in our laboratory earlier [3,4,7 and references within]; (5) the assignment of IR absorption features of carboxylic acids and salts published in Refs. [9][10][11][12][13][14][15][16]. An extensive collection of published vibrational frequencies of alkyl and fluorinated acetates and formates can be found in Table I in Ref.…”

“…1 and 2 show the difference spectra between the two, the bands appear very small. Surprisingly, [3,10,[9][10][11][12][13][14][15][16] Notes: s = shoulder; parenthesis indicates low intensity. in the 2900-3900 cm À1 region of the spectra on Fig.…”