Role of Pt–Pd/γ-Al2O3 on the HDS of 4,6-DMBT: Kinetic modeling & contribution analysis

•Kinetic modeling and contribution analysis elucidate the role of Pt and/or Pd on HDS of a-DBTs.•Kinetic model is based on a Langmuir–Hinshelwood–Hougen–Watson mechanism.•Contribution analysis is based on predicted reaction rates.•Bimetallic catalyst with the highest contents of Pt leads to the highest conversion of 4,6-DMDBT.•Pt contents favor desulfurization reactions and Pd contents favor hydrogenation reactions.

The purpose of this study is to provide insights on the function of noble metals, namely Pt–Pd catalytic system, on the hydrodesulfurization (HDS) of alkyl-substituted dibenzothiophenes (a-DBTs) by means of kinetic modeling and contribution analyses. A series of Pt–Pd systems (1% wt. nominal loading) supported on γ-Al2O3 (0–100, 20–80, 50–50, 80–20 and 100–0; %mol Pt–%mol Pd) are synthesized and evaluated during the HDS of 4,6-dimethyldibenzothiophene (4,6-DMDBT) at operating conditions relevant for industry: 320 °C, 500 ppm of S and an H2 pressure of 5.5 MPa. A summary of their characterization is presented as reference herein. Kinetic model based on a Langmuir–Hinshelwood–Hougen–Watson (LHHW) mechanism and contribution analysis based on predicted reaction rates give rise to the following findings: the bimetallic catalyst 8Pt–2Pd/γ-Al2O3 (80–20; %mol Pt–%mol Pd) leads to the highest activity; in all Pt–Pd/γ-Al2O3 systems, Pt favors desulfurization reactions, i.e., 4,6-DMDBT to 3,3′-dimethylphenyl (3,3′-DMBP) and 4,6-dimethyltetrahydrodibenzothiophene (4,6-DM-th-DBT) to MCHT, whereas Pd favors hydrogenation of 4,6-DMDBT to 4,6-DM-th-DBT; and 4,6-DMDBT and methylcyclohexyltoluene (MCHT) are the hydrocarbons with the lowest and highest affinity to be adsorbed on the active sites from the studied Pt–Pd/γ-Al2O3 systems, respectively.

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