Effects of nickel-deactivations on zeolites-Y of different SiO2/Al2O3 ratios in catalytic cracking of hydrocarbons

Abstract

Effects of nickel deactivation on catalytic activities of three types of zeolites-Y (Y-5.1, USY-5.2, and VUSY-12) with varying SiO2/Al2O3 ratios were studied in cracking of hydrocarbons. Physicochemical characteristics such as crystalline phases, Ni oxidation states, morphology, acidity, surface area, and thermal stability of the samples were analysed. XRD revealed the absence of observable nickel compounds below 5 wt%, with NiO phase emerging at higher concentrations. Surface areas decreased from 826 to 615 m2/g (Y-5.1), 786–686 m2/g (USY-5.2), and 762–571 m2/g (VUSY-12) at 30 wt% Ni. The total acid sites also reduced from 17.247 to 9.826 µmol/g (Y-5.1), 15.464–8.854 µmol/g (USY-5.2), and 7.094–4.876 µmol/g (VUSY-12). XPS confirmed Ni2+ states. Catalytic cracking tests using n-Heptane demonstrated increases in C5-C6 alkanes, olefins, hydrogen, and methane yields as nickel concentration increased, with respective values of 64 %, 28 %, 79 % and 68 % for Y-5.1; 62 %, 28 %, 76 %, and 62 % for USY-5.2; and 58 %, 21 %, 75 %, and 60 % for VUSY-12. A corresponding decrease in heavier components were observed. The study demonstrates that nickel modification significantly impacts the physicochemical properties and catalytic performance of zeolite-Y and these depend strongly on the SiO2/Al2O3 ratios. The study gives further insights into the structural and catalytic modifications induced by nickel doping in zeolites, highlighting the potential of nickel-modified zeolites in promoting undesirable hydrogen and gas.