Investigation of Kinetics of Hydroisomerization of C5/C6 and C6/C7 Alkanes and their Binary Mixtures

Abstract

Modern gasoline quality requirements globally became stricter. These specifications parallel with the applied developments of vehicle technologies contributing to the cleaner environment. Nowadays only the concentration of cyclo- and isoparaffins are not limited in gasoline, because they burn cleaner, have high octane number, lower sensibility and better combustion properties than aromatic or olefinic hydrocarbons. In the last decade because of the applied refinery investments both sulfur and aromatic content of gasolines decreased, but the octane mass of the gasoline pool significantly decreased against the increment of octane number requirement of spark ignition engines. Importance of isomerization of light paraffins has been publicized in many papers. However few of them investigated, studied and explained the individual hydrocarbons (C5/C6/C7) interaction with each other in multicomponent mixtures practically in similar to industrial hydrocarbon feedstocks. Binary and multicomponent hydrocarbon mixture investigations can contribute to the understanding the results of isomerization of real, feedstocks from multiple sources; which contain higher boiling point hydrocarbons (cycloparaffins, benzene, and heptanes). Further these results can help to operate with higher flexibility, safety and economically a light naphtha isomerization units. The hydroisomerization of n-pentane (n-C5), n-hexane (n-C6), cyclohexane (c-C6) and n-heptane (n-C7) and their binary mixture were studied on Pt/sulfated zirconia catalyst at temperature 150–170 °C, total pressure 20 bar, 1:1 H2-hydrocarbon molar ratio. The apparent activation energies of all individual components, further the reaction rates individually and in different composition binary mixtures were specified. Results of our experiments concluded that the rate of reaction of the higher carbon number hydrocarbon or in case of the same carbon number the cycloparaffins (lower volatility component) increased with increasing the concentration in the binary mixtures, while the rate of reaction of higher volatility component decreasing.