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Along with oxidation of hydrogen-containing coke structures, we have observed oxidation of compact accumulations of hydrogen-free coke and as a result we can quantitatively differentiate between outer-surface and intraporous burned coke, and the intraporous coke in turn can be quantitatively distributed over the different elements of the zeolite structures.Coke formation is a very important reaction accompanying all carbonium-ion conversions of hydrocarbons. In this case, the coke plays a dual role. In small amounts, it promotes the occurrence of the major reaction [1], speeding up the movement of hydrogen, as a primary ingredient in carbonium ion conversions in all its forms [2]. But when accumulating on the surface of the catalyst, coke blocks the active sites, necessitating the process step of oxidative regeneration. Therefore information is needed about the chemical composition of coke and its localization within the crystal structure of the catalyst. Such information is complicated to obtain because of the indefinite composition of coke at a specific instant of time and also difficulties encountered in extracting this substance in unaltered form from the catalyst, as much as the at least equal difficulties involved in studying it without extraction [3,4].Earlier [5], in a study of the kinetics of regeneration of single grains of coked zeolite by the microbalance method in a stream of oxygen-containing gas in the temperature range 350-510°C, some variability (periods of slowdown and acceleration) in combustion over time was observed at 350, 360, and 375°C, which may indicate oxidation of coke of different elemental compositions or coke localized differently in the zeolite structure.The method of discontinuous sequential micro-oxidation of coke [6] was developed recently, which makes it possible to determine some characteristic features of coke composition and coke localization in the structure of acid zeolite catalysts for different purposes: alkylation of isoparaffins by olefins, isomerization of linear paraffins, disproportionation of monoalkyl aromatic hydrocarbons to form benzene and dimethyl-substituted aromatics.Each of these catalysts is prepared differently: by modification of the original forms by replacing the native sodium cations by other cations [7] or by reducing the latter (for example, nickel cations) to the zero-valence state [8]. Methods for such modification have been sufficiently developed.Considerably less attention has been focused on dealumination of the outer surface of zeolite crystals to avoid formation of outer-surface acid sites while grafting acidity into the modified samples. Moreover, these sites, as the most accessible to reactant molecules, may play a dominant role in the occurrence of the corresponding reactions, including coke 198 0040-5760/09/4503-0198

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