Combination of precipitation and ultrasound irradiation methods for preparation of lanthanum-modified Y zeolite nano-catalysts used in catalytic cracking of bulky hydrocarbons

Abstract

Abstract In the present study, lanthanum-containing HY nano-catalysts were prepared using three different techniques including wet impregnation, precipitation, and new precipitation-ultrasonic methods for the sake of catalysts performance promotion through improvement of rare earth dispersion on zeolite. The synthesized nano-catalysts were characterized by means of XRD, N2 adsorption-desorption, TEM, NH3-TPD, FE-SEM and EDX dot-Mapping techniques. Furthermore, amount and type of deposited coke over the spent nano-catalysts were investigated using TGA and FT-IR analyses, respectively. N2 adsorption-desorption analysis showed that the textural properties of zeolite were acceptably preserved in the prepared nano-catalyst with precipitation-ultrasonic method. TEM and EDX dot-Mapping analyses indicated that using ultrasonic irradiation led to synthesis well-dispersed and smaller size lanthanum species over the Y zeolite. Obtained results from the catalytic performance of nano-catalysts revealed that compared with impregnation and precipitation methods, using precipitation-ultrasonic technique not only led to achievement of significantly higher gasoline yield (increase 41% in comparison to parent catalyst), but also efficient decrease in density, viscosity and molecular weight of liquid product were obtained. In addition, application of precipitation-ultrasonic method moderated the acidity strength of zeolite. It led to increased nano-catalyst life time and less coke formation.