No abstract

When a mixture of light gas oil (LGO) and light cycle oil is fed into an oil refinery’s hydrodesulfurization (HDS) unit to produce diesel fuel, the catalyst in the HDS unit is rapidly deactivated. By contrast, when the feed is LGO mixed with residue desulfurization gas oil, the catalyst is deactivated slowly. Hoping to understand why, the authors focused on the coke formed on the catalysts during the HDS reaction. The result of a comprehensive analysis of the coke suggested that the ways coke formed and grew on the catalysts may differ depending on the feeds used, which in turn could affect the deactivation behaviors of the catalysts.

The effect of nitrilotriacetic acid (NTA) as a complexing agent on the sulfidation mechanisms of Co-Mo catalysts supported on activated carbon and alumina was examined by the XAFS technique. The XAFS results revealed that NTA interacted with Co atoms and formed the Co-NTA interaction, while it showed almost no influence on the local structures around Mo atoms. The Co-NTA interaction suppressed the aggregation of cobalt atoms and the interaction between cobalt and alumina during sulfiding, and consequently promoted the formation of the Co-Mo-S phase.

The fuel-saving performance of automotive lubricants greatly depends on the composition and structure of the reaction films that form on metal surfaces through chemical reactions between the additives in the lubricant and the metals. In this study, we prepared reaction films on metal surfaces using two lubricants formulated with different base oils of different degrees of polarity and an anti-wear additive commonly used in automotive engine oils, and examined the chemical state of the films using HAXPES. It was observed that polyphosphates found in the reaction film formed with the lubricant formulated with the polar base oil had shorter chains than those in the reaction film formed with the lubricant formulated with the non-polar base oil. In the latter reaction film, polyphosphates with longer chains may concentrate near the film surface. By contrast, in the former reaction film the polyphosphates may have chains of mostly the same length.

No abstract