Enhanced product quality through hydrodesulfurization of pyrolysis gasoline over a mixed metal oxide catalyst: An experimental and DFT study

Abstract

Manipulating electronic properties of the hydrodesulfurization (HDS) catalysts can greatly impact the resulting product distribution. To address such effect decently in theoretical and experimental approaches, high-performance cobalt-molybdenum-supported alumina-titania (CoMo/Al2O3-TiO2) with different TiO2 loadings of 10–28 wt% were synthesized. The characterization of the catalysts was implemented by FE-SEM, TEM, XRD, BET/BJH (based on N2 adsorption–desorption), Fourier transform infrared spectroscopy (FTIR), H2-Temperature programmed reduction (H2-TPR), NH3-Temperature programmed desorption (NH3-TPD), and Thermal gravimetric analysis (TGA). The synthesized catalysts were evaluated through HDS of an industrial feedstock– pyrolysis gasoline (Pygas) in a pilot plant tubular fixed bed reactor. It was found that the modification of the electronic properties by titania could also increase the surface acidity while improving the reductive behavior of the tetrahedral and octahedral molybdenum species. In addition, the CoMo/Al2O3-TiO2 with 10 wt% titania content could excellently remove over 96% of sulfur-containing molecules in Pygas. Besides, the developed CoMo catalyst showed an increase in the aromatic compounds, resulting in improved product quality and value through the HDS process. Furthermore, the contribution of TiO2 to the synthesized catalyst was theoretically interpreted through the density functional theory (DFT) method. It was found that lower adsorption energy levels were estimated for the adsorption of the sulfur-bearing molecules on the CoMo/Al2O3-TiO2 than the CoMo/Al2O3 catalyst.