Influence of adding a modified zeolite-Y onto the NiMo/Al2O3 catalyst utilized to produce a diesel fuel with highly reduced sulfur content

Abstract

In order to make a Na–Y zeolite with Si/Al ratio of 2.27 more acidic with a higher volume of mesopores, a combination of different and consecutive methods including; chemical (i.e.; utilizing different compounds, such as NH4F and EDTA) and thermal/hydrothermal (i.e.; implementing calcination/steaming) methods, were employed for modification and dealumination. The combination of acidic-hydrothermal dealumination method led to a further structural collapse compared to that of the acidic calcination. In comparison with the other dealumination methods, the fluorination strategy (i.e.; utilizing NH4F) resulted in a zeolite with higher crystallinity, acidity, and specific surface area. The modified and dealuminated zeolites were employed to prepare the catalyst support of FAU + Al2O3 for the HDS process. The sulfidation and performance evaluation of the prepared catalysts were carried out in a fixed bed microreactor. Then after, the effects of zeolite modification during the dealumination process, especially acidity and Si/Al ratio variations, upon the activity of NiMo/FAU + Al2O3 catalyst were understudied. Results indicated that, the enhanced performance of the catalysts containing the modified zeolites in removing of the sulfur containing aromatic compounds, as well as their longer observed lifetime in terms of lower coke deposition levels were obtained. The removal of the sulfur containing compounds increased with acidity so that the maximum removal (i.e.; of conversion = 93%) was determined using Cat-F-AT-Cal catalyst containing the zeolite modified by acid treatment-calcination together with fluorination. In addition, the highest performances in terms of removal of aromatic compounds and catalyst lifetime (i.e.; due to lower coke deposition) were shown by the Cat-AT-St and Cat-AT-Cal catalysts, respectively. These species contained the zeolite modified through the acid treatment-steaming and acid treatment-calcination methods, respectively.