Synthesis and characterization of Pd-MCM-22 and Pt-SAPO-11 catalysts for transformation of n-butane to aromatic hydrocarbons

Pd-Na-MCM-22, Pd-H-MCM-22 and Pt-SAPO-11 catalysts were synthesized and characterized using techniques of X-ray powder diffraction, scanning electron microscopy, FTIR, nitrogen adsorption and X-ray fluorescency. The FTIR spectra of Pd and Pt modified MCM-22 and SAPO-11 exhibited lower amounts of Brønsted (B) and Lewis (L) acid sites than the unmodified MCM-22 and SAPO-11. The catalysts were tested in the transformation of n-butane to aromatic hydrocarbons. Aluminosilicate type of zeolite catalysts Pd-Na-MCM-22 and Pd-H-MCM-22 exhibited higher selectivity to aromatics than aluminophosphate Pt-SAPO-11. The pretreatment of the catalysts with oxygen and hydrogen was found to influence the n-butane conversion and selectivity to aromatic hydrocarbons. The hydrogen pretreated Pt-SAPO-11 exhibited higher n-butane conversion than the oxygen pretreated. The catalysts exhibited deactivation with time on stream due to coke formation and pore blocking. The specific surface areas of the Pt-SAPO-11, Pd-Na-MCM-22 and Pd-H-MCM-22 deactivated catalysts were found to be lower than the fresh because of coke deposits inside the pores.