Perturbation of adsorbed CO by amine derivatives coadsorbed on the gamma-Al2O3 surface: FTIR and first principles studies

The coadsorption of CO and triethylenediamine (TEDA) (also called 1,4-diazabicyclo[2.2.2]octane, DABCO) on a high-area gamma-Al2O3 surface has been investigated with use of transmission FTIR spectroscopy. It has been found that TEDA binds more strongly to both Lewis acid sites and to Br?nsted Al-OH sites than does CO. Competition experiments indicate that TEDA displaces CO to less strong binding sites. Evidence for weak CO...TEDA interactions is found in which small nu(CO) redshifts are produced. Comparison between different amines such as triethylenemonoamine (TEMA) (also called 1-azabicyclo[2.2.2]octane, ABCO), trimethylamine (TMA), and ammonia indicates that the nu(CO) redshift increases with increasing amine polarizability, indicating that the redshift is mainly due to dipole image damping effects on the CO oscillator frequency. The direct bonding between the exposed N lone pair electrons of the TEDA molecule and CO does not occur. First principles theoretical studies have characterized the bonding of CO with gamma-Al2O3 Lewis acid sites of various types as well as TEDA bonding to both Lewis acid sites and to Al-OH groups. The theoretical studies also indicate that strong bonding of adsorbed CO with TEDA molecules does not occur, and that the observed decrease in the binding energy of CO when coadsorbed with TEDA on gamma-Al2O3 is expected.     

Solitary wave solutions to nonlinear evolution equations in mathematical physics

This paper obtains solitons as well as other solutions to a few nonlinear evolution equations that appear in various areas of mathematical physics. The two analytical integrators that are applied to extract solutions are tan–cot method and functional variable approaches. The soliton solutions can be used in the further study of shallow water waves in (1+1) as well as (2+1) dimensions.     

Changes in structure and catalytic properties of V2O5 caused by mechanochemical treatment

By means of x-ray phase analysis and tunneling microscopy, it has been shown that when vanadium(V) oxide in an ethanol medium is subjected to mechanochemical treatment in a planetary mill, it undergoes not only size reduction with an increase of surface area, but also a change of structure. Extension of the processing time increases the relative content of the vanadyl plane (010) by a factor of more than 5. It has been established by means of x-ray photoelectron spectroscopy that some of the surface vanadyl ions are reduced. Modification of the structure and composition of the surface of the vanadium oxide leads to changes in its catalytic properties in n-butane and benzene oxidation reactions. The approximately twofold increase of hydrocarbon conversion may be related to the increase of surface area of the specimen; this view is supported by the constancy of the specific rate of n-butane oxidation. The sharp increases that are observed in the selectivity of maleic anhydride formation (sixfold in the oxidation of n-butane, threefold in the oxidation of benzene) are related to the increased content of the vanadyl plane and the surface formation of groupings of vanadium differing in valence. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 3, pp. 180–183, May–June, 1998.     

Adsorption of triethylenediamine on Al2O3-III: Bonding to Lewis acid Al3+ sites

The adsorption of triethylenediamine (TEDA) on Lewis acid (Al(3+)) sites of the highly dehydroxylated Al(2)O(3) surface has been observed by FT-IR spectroscopy. This was done by monitoring the competitive adsorption of TEDA and CO on the Al(3+) sites. A stoichiometric replacement of Al(3+)-CO species was observed as Al(3+)-TEDA surface species were formed.