Research and selection of catalysts for the process of alkylation of oil fractions with catalytic cracking gases

The article presents the results of the study and use of modified zeolite-containing catalysts (ZSM-5) and natural alumosilicates (halloisite) in the process of alkylation of distillate fraction with catalytic cracking gases. Based on thermogravimetric analysis, it was determined that modification of halloisite with the Al+CCl4 system leads to the appearance of peaks indicating exo- and endo processes under the influence of temperature. When the oil fraction was alkylated at a temperature of 50 oC on Al+CCl4+halloisite catalyst with catalytic cracking gases containing olefins of 43.47 % the viscosity index was increased from 32 to 84. Based on NMR spectra, it was determined that alkylates differ from the original oil fraction by increased values isoparaffin index, the number of protons in aromatic structures and those furthes from the aromatic nucleus. These data confirm the improvement in the viscosity temperature characteristics of the oil fraction. Alkylation of an oil fraction with a viscosity index of 49.9 on ZSM-5 and ZSM-5-ZrO2 catalysts made it possible to obtain oils with a viscosity index of 80.7 and 137, respectively. Based on X-ray diffraction studies using rentgenographic method, it was shown that Zr is contained in the structure of ZSM-5 zeolite in the form of ZrO2. The introduction of Zr into the crystaline structure of the zeolite helps to increase the activity of the modified catalyst ZSM-5-ZrO2. Research has shown that the phase composition of samples of the modified ZSM-5-ZrO2 zeolite changes depending on the calcination temperature. An increase in temperature from 200 to 550 oC leads to the transition of the amorphous phase to the crystalline phase, and at a given calcination temperature a phase belonging to ZrO2 appears. The introduction of Zr into the catalyst composition leads to a change in the ratio of the Lewis and Brensted acid sites of the ZSM-5 catalyst. Namely, there is an increased Lewis and a decreased Brensted acid sites. Based on this it can be assumed that both Brensted and Lewis acid sites take part in the alkylation process.