Refining straight-run gasoline using MFI zeolite synthesised with two templates
L. M. VELICHKINA1, L. N. VOSMERIKOVA1, V. G. BONDALETOV2, A. V. VOSMERIKOV1
1Institute of Petroleum Chemistry, Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia
2National Research Tomsk Polytechnic University, Tomsk, Russia
Keywords: zeolite, template, hexamethylenediamine, polyaniline, catalyst, gasoline
Abstract
A method of hydrothermal synthesis of pentasyl type zeolites (MFI or ZSM-5) with the silicate modulus of 40 is proposed, which consists in adding, along with hexamethylenediamine as a structure-forming agent (template), the second structure former - polyaniline, to alkaline alumosilicon gel. Polyaniline used in the work was also synthesised according to the authors’ method. It has been determined using IR spectroscopy and X-ray diffraction analysis that the synthesised zeolites belong to the pentasyl family, and their degree of crystallinity is close to 100 %. The acid characteristics of the obtained zeolite samples were studied by temperature-programmed desorption of ammonia, and a decrease in the strength and concentration of weak acidic centres in comparison with zeolite synthesised without the use of polyaniline was shown. On the contrary, the number of high-temperature acidic centres of zeolites obtained using polyaniline has somewhat increased. A correlation between the acidic properties of zeolites and the concentration of polyaniline added to the reaction mixture during synthesis has been established. The catalytic activity of the obtained zeolite catalysts was determined during the refining of the straight-run gasoline fraction of oil. An increase in the aromatising activity of the catalysts and the octane numbers of the resulting gasolines has been shown when using zeolites synthesised using two templates - hexamethylenediamine and polyaniline. The optimal temperature range for refining straight-run gasoline has been determined, which makes it possible to obtain high-octane gasoline, meeting the modern requirements for automotive gasoline in terms of hydrocarbon composition and octane number, on all the studied zeolite catalysts. The fractional composition of the gasoline produced (except for the final boiling point) corresponds to the summer grade of gasoline.
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