N. S. Ovchinnikova’s research while affiliated with Russian Academy of Sciences and other places

The successive adsorption of some aliphatic amines and carboxylic acid on titanium dioxide (rutile modification) from their vapors and toluene solutions has been studied. It was found that the efficiency of double modification of TiO2 with different modifiers depends on the sequence of their adsorption. From adsorption measurements and mass-spectroscopic thermal analysis, it has been shown that when the rutile surface is modified with vapors of n-butylamine and acetic acid, it is possible for the two substances to interact in the surface layer. As a result, the order in which the amine and the acid are adsorbed affects the structure and properties of the resulting adsorbed layers. Both the displacement of the previously adsorbed substance and the formation of new surface compounds are observed. It has been established that the modifying amine layer on rutile with preadsorbed carboxylic acid is the densest. This layer consists of molecules of both the modifiers and the product of their surface reaction.

Using the method of mass-spectroscopic thermal analysis, it has been shown that when the surface of rutile is modified with n-butylamine and acetic acid, it is possible for the two substances to interact in the surface layer, with the result that the order in which the amine and the acid are adsorbed affects the structure of the resulting adsorbed layers. The chemisorbed layer on the surface of a sample of TiO2-AA-BA consists of molecules of both modifiers and the product of their surface reaction. Acetic acid adsorbed on TiO2-BA displaces the coordinatively bound amine molecules from the surfaces, leading to the formation of butylacetamide and the chemisorption of the acid molecules on unoccupied areas of the TiO2 surface.

The basic components (C3H6, NH3, H2O, C2H4, CH4, C2H2, and HCN) and temperature ranges of their separation in thermal decomposition of -aminopropanetriethoxysilane grafted on the surface of silica were determined with a mathematical program for processing mass spectra. The formation of these components was explained with well-known chemical reactions.

1. When silicas are modified with amines, not all surface silanol groups participate in the chemical reaction. 2. When amine-modified silica gels are heated, water is produced; the maximum rate of the formation of gas occurs at 625 and 750 K. Destruction of the modifying layer begins with the liberation of ammonia at T > 640 K. 3. Adsorption of SO2 and CO2 on aminated silicas is determined by the surface concentration of amino groups, by their nature, and by their mutual position.

The product of the reaction of isododecenylsuccinic anhydride with urea at 120–160°C is isododecenylsuccinimide.

1. Temperature intervals and kinetic parameters have been established for the evolution, from TiO2, of n-butylamine molecules forming surface hydrogen and coordination bonds with the adsorption centers; also, the temperature interval and kinetic parameters have been established for processes of thermolysis of surface amino compounds with a Ti-N σ-bond. 2. The character of adsorptive interaction of n-butylamine with TiO2 does not depend on the degree of hydroxylation of the surface. 3. When the amine-modified surface of rutile is exposed to light at −20°C, significant quantities of products of n-butylamine oxidation and autocondensation are formed. A decrease in the degree of hydroxylation of the TiO2 surface increases the photochemical stability of the adsorption system.

1. The technique of mass spectrometric thermal analysis has been used to establish that on heating rutile, modified by acetic acid, to 300°C, separation of physically adsorbed acetic acid, together with acetic acid formed by the thermal hydrolysis of surface acetates, takes place from the surface. Above 300°C, disruption of the surface acetates begins with the formation of acetone, ketene, water, and carbon dioxide. 2. Disruption of a methanol layer adsorbed on the surface of rutile begins at 200–300°C by loss of molecules of alcohol, both physically adsorbed and formed by thermal hydrolysis of surface esters, from the surface. At 300–400°C, the surface methanol compounds decompose with the separation of dimethyl ether, formaldehyde, and saturated and unsaturated hydrocarbons.

The mass spectra of perfluoroacyl derivatives of diethylamine, ethylenediatnine-1,2, propylenediamine-1, 2 and propylenediamine-1,3 have been obtained and the main routes identified for the fragmentation of these compounds under electron impact, depending on the structure of the amine and the size of the perfluoroacyl or fluoroalkyl substituent of the NH2 group.

1. The thermal decomposition of the solvate H6P2W18O62·3H2O·8C2H5OH is accompanied by dehydration of ethanol, which leads to diethyl ether and, at higher temperatures, to the formation of alkanes and olefins. 2. The major process in the thermal decomposition of the solvate H6P2W18O62·3H2O·9CH3OH is the catalytic dehydration of methanol which does not lead, however, to the formation of hydrocarbons. The oxidation of methanol is also observed above 400°C in addition to dehydration.

1. The nature of the catalytic transformation of acetone and methyl ethyl ketone upon the thermal decomposition of their solvates with dimeric 9-tungstenophosphoric acid is similar. Oxidation products consisting of acids and carbon dioxide are released initially followed by products of reduction and condensation (C3-C4 hydrocarbons and aromatic hydrocarbons). Then cracking products of the hydrocarbons formed, namely, methane, ethane, and water are detected. 2. Substitution of methyl for ethyl in the ketone causes a significant reduction in the velocity of the catalytic reaction.