Formation of dispersed carbon in the course of chlorination with CCl4 vapor of γ-Al2O3 surface

Abstract

The =Al-Сl surface groups of γ-Al 2 O 3 are known as more reactive towards the nucleophilic agents (water, alcohols) than the =Al-ОН groups [1,2]. The common method of generation of Cl groups on the inorganic matrix surface (for instance, silica) is reaction (1) with ССl 4 , vapor at 200-400°С in dry argon stream [3].=Al-OH + CCl 4 > =Al-Cl + HCl + COCl 2 .In the case of γ-Al 2 O 3 at 200-500°C, the chlorinetion of the surface according to reaction (2) was accompanied by condensation of the dispersed carbon particles on the matrix surface. Depending on the treatment duration and the process temperature, the samples containing 0.3 to 3 wt % of carbon were prepared. The presence of carbon was confirmed by energy-dispersive X-Ray microanalysis; the elemental analysis data and the surface mapping revealed that carbon was quite evenly distributed at the pellet chip surface. The highest carbon condensation level was observed at 500°С.Heterogeneous reactions were performed using the previously described gas phase installation [3], in the dry argon stream (residual moisture content 0.5-1 mg H 2 O/m 3 ). The surface of γ-Al 2 O 3 (70 m 2 /g, pores diameter 5.7 nm), was hydrated by boiling in distilled water. The content of OH groups was determined by differential thermal analysis using the DTA-500 device. The energy-dispersive X-Ray microanalysis was performed with Supra 40 VP X-ray emission microscope equipped with the INCA X-art attachment; Co was used as reference. ACKNOWLEDGMENTSThis work was financially supported by the Russian Foundation for Basic Research (project no. 11-03-00099-a). REFERENCES 1. Smirnov, V.M., Russ. J. Gen. Chem., 2002, vol. 72, no. 4, p. 590

Effect of Thermochemical Treatment on the Structure and Mechanical Properties of Materials Based on Aluminum Oxide

“…Unlike oxides, titanium nitrides have high thermodynamic strength, therefore, they do not significantly affect the change in mass during heat treatment and the parameters of the crystal lattice [14][15][16]. When planning the experiments, it was assumed that heat treatment in a nitrogen atmosphere would promote its adsorption on the surface of the grains, nitrogen diffusion and hardening of the particle surface [17][18][19][20][21].…”