ИСТИНА

Decyclization of gasoline and diesel fuel is one of the most important problems of modern oil refining. The presence of cyclic hydrocarbons in the fuel leads to a decrease in its resistance to ignition, as well as to the formation of undesirable products during the combustion of the fuel, for example, the formation of soot in the engine exhaust gases in the case of diesel fuel. One of the possible ways to solve the problem is the hydrogenation of aromatic compounds present in fuels, with the transition of the latter to naphthenes, with the further formation of saturated hydrocarbons. In the case of diesel fuel, decyclization that occurs without skeletal isomerization can also lead to an increase in cetane number, while ring opening of C6-C9 gasoline cyclic components can be useful for increasing the octane number of motor fuels. To consider the decyclization process, cyclohexane is considered as a suitable model compound. The ring-opening reaction of cyclohexane with the formation of n-hexane under certain conditions proceeds on oxide catalysts containing Rh, Ru, or Pt. Interestingly to estimate the influence of the nature and acidity of carriers on the activity of the catalyst and the selectivity for target products. It is assumed that the combination of a sufficiently strong acidic function (zeolites, solid superacids) and electron-deficient metal particles formed during the interaction of an uncharged metal particle with an acid center and the transfer of electron density from the metal to the acid center favors nice for ring opening of cycles. This is often associated with an increased activity of electron-deficient metal particles in the hydrogenolysis of C–C bonds in comparison with uncharged or electron-rich particles, for which high activity in hydrogenation is more typical [1]. The aim of this work is to synthesize a series of catalysts containing 1 wt.% Rh by impregnating supports based on Al2O3, SiO2, CaO+MgO+Al2O3, Na2O+Al2O3+SiO2 with a solution of (NH4)3[RhCl6]; studying of carriers and obtained samples of catalysts by physico-chemical methods of analysis to determine the conditions for the synthesis of catalysts, as well as to determine the qualitative and quantitative composition of the obtained catalysts, carrying out the reduction reaction of cyclohexane on the obtained catalysts and studying the effect of the carrier on the catalytic activity of the catalyst. The synthesis of catalysts included impregnation of carriers with (NH4)3[RhCl6] solution; drying of samples with stirring, calcination in an oven, reduction in a stream of hydrogen at 450 °С. The catalysts were examined by SEM-EDX, XRD, TGA, TPR-H2. The prepared samples of rhodium-containing catalysts were investigated in the catalytic reduction reaction of cyclohexane. For each catalyst, the selectivity to n-hexane and the conversion of cyclohexane were determined at temperatures of 275–325°C and a pressure of 40 atm. At the same time, the predominant reaction products with increasing temperature are the cracking products of cyclohexane with composition C1 - C5. A high conversion of cyclohexane was achieved when using a catalyst on an Al2O3 + CaO + MgO carrier at a temperature of 325 °C - 60.2%. Greater selectivity to n-hexane was achieved using the same catalyst at a temperature of 275 °C - 70.8%.