0023-1584/02/4301- $27.00 © 2002 MAIK “Nauka /Interperiodica” 0139 Kinetics and Catalysis, Vol. 43, No. 1, 2002, pp. 139–145. Translated from Kinetika i Kataliz, Vol. 43, No. 1, 2002, pp. 150–156. Original Russian Text Copyright © 2002 by Ivanova, Fedotov, Litvak, Trukhan, Ivanov. INTRODUCTION Sol–gel synthesis in the presence of surfactants is a possible method for controlling a particle size in hydrox- ide and oxide systems [1]. This is due to the fact that the addition of a surfactant is accompanied by a significant change in the properties of supersaturated solutions. For instance, the surface tension of an intermicellar liquid may change and affect the size, morphology, and the spa- tial orientation of prepared crystals. The goal of this work was to study the effect of surfac- tants and their fractions on the phase composition, disper- sion, and pore structure of the iron–zirconium system. EXPERIMENTAL The Fe–Zr–O system with a molar ratio [Fe 3+ ]/[Zr 4+ ] of 0.123 was chosen for the study. Sam- ples were prepared by the addition of a base (2 mol/l KOH) to a solution containing iron and zirconyl nitrates and a certain amount of the surfactant. Then, the sus- pension was allowed to stay at 20°C and an elevated temperature for different times (τ). The suspensions were filtered, and the precipitates were washed with distilled water until the nitrates in the filtrate disap- peared. The samples were dried in air and then in a dry box at 110°C for 12 h and calcined in a dry air flow at 400–700°C for 4 h. The solutions of glycerol, polyvinyl alcohol, carboxymethylcellulose, sodium salt of ethyl- enediaminetetraacetic acid (NaEDTA), and stearic acid were used as surfactants. The concentrations of main components in the sam- ples were determined by atomic absorption spectros- copy [2]. The state of the components in the liquid phase was studied by NMR on different nuclei as described in [3]. In solutions containing paramagnetic (Fe 3+ ) ions, the concentration of the mononuclear spe- cies Fe 3+ + (FeOH) 2+ can be estimated from the 2 D NMR line width of water. The effect of polynuclear paramagnetic species on the line width is not strong because of a decrease in the effective magnetic moment due to spin–spin interaction. The formation of colloidal particles causes a sharp broadening of the lines in the 14 N NMR spectra. This makes it possible to estimate the presence of colloidal particles in a solution. Thermal analysis was carried out using a Derivato- graph-Q-1500 D at 20–1000°C in air at a heating rate of 10°/min. A sample loading was 0.2 g, and the accuracy in the determination of weight loss was ± 0.5%. Studies by secondary ion mass spectrometry were performed using an MS-7201 secondary ion mass spectrometer automated by a PC and KAMAK interface. The spec- tral region with masses from 45 to 135 was periodically scanned during recording the secondary emission spec- tra. The recording period for each cycle was 150 s. Samples were previously deposited on a support cov- ered with indium of high purity to avoid their charging. The Ar + ions with an energy of 4 keV were used as a primary beam. The density of current was 20 μA/cm 2 . The textural characteristics of the samples were calcu- lated from the isotherms of low-temperature (–196°C) nitrogen adsorption measured using an ASAP-2400 Micromeritics setup according to a standard procedure [4] with the use of the desorption branch. The Role of Surfactants in the Formation of Highly Dispersed Iron–Zirconium Oxide Composites with Uniform Pores A. S. Ivanova, M. A. Fedotov, G. S. Litvak, S. N. Trukhan, and V. P. Ivanov Boreskov Institute of Catalysis, Siberian Division, Russian Academy of Sciences, Novosibirsk, 630090 Russia Received May 12, 2000 Abstract—The effects of the nature and concentration of surfactants and the preparation conditions on the gen- esis of iron–zirconium composites with a [Fe 3+ ]/[Zr 4+ ] ratio of 0.123 were studied. The effect of surfactants on the physicochemical properties of precipitates is determined by the conditions of synthesis. The amount of sur- factants retained by the precipitate at pH ~3 is about an order of magnitude greater than at pH ~9. The thermol- ysis of samples synthesized at acidic pH is accompanied by the dehydration and dehydroxylation of iron–zir- conium composites as well as by the decomposition and destruction of surfactants. In the latter processes, com- pounds or their fragments capable of reducing some phases are removed in a stepped-up manner. The specific surface area of oxide systems formed in this way is at most 100–150 m 2 /g. In the pH range corresponding to the complete precipitation of the components, highly dispersed single-phase and uniformly porous composites are formed. The choice of a surfactant, its fraction, and preparation conditions enables the preparation of oxides with specific surface areas of 100–400 m 2 /g. The average pore diameter of the samples ranges from 3.0 to 27.0 nm, and the total pore volume ranges from 0.20 to 0.38 cm 3 /g.