Selective removal of dibenzothiophene from commercial diesel using manganese dioxide-modified activated carbon: a kinetic study.

With a total concentration of 7055 mgS/kgfuel, the content of organosulphur compounds (OSCs) in local diesel is 20 times higher than the regulated value. Analysis revealed that 30% of OSC is originated from dibenzothiophene (DBT). It is known that DBT is a hardly removable compound and selective adsorbents are often needed for its removal with low affinity for other diesel components. In this work, a selective adsorbent based on surface modification of activated carbon (AC) by MnO2 is prepared for DBT removal from diesel. The porous nature of AC enabled carrying large amounts of MnO2 particles to end up with a selective adsorber for DBT. The best performance was observed at a surface loading of 26.8% of Mn and DBT is favourably removed over mono- and diaromatics hydrocarbons in diesel. Adsorption kinetics of DBT is studied under a high initial concentration of 835-11,890 mg/kg and at a ratio of 11 cm3/g (diesel:carbon). The results indicated a fast removal process after surface modification where 96% of the surface is occupied within 30 min of interaction. Kinetic data were best presented by reaction-based models with low prediction error sum of squares values 0.5-47.0, while, diffusion-based models showed limited application for modelling DBT adsorption. Accordingly, adsorption process is controlled by surface reactions and pore diffusion has a minor role in the overall process. The modified adsorbent is satisfactorily regenerated using n-hexane at 65°C.

Structural confirmation of the dihydrosphinganine and fatty acid constituents of the dental pathogen Porphyromonas gingivalis.

Porphyromonas gingivalis, a recognized periodontal pathogen, is a source of sphinganine bases, fatty acids, free ceramides as well as complex lipids that potentiate interleukin-1b-mediated secretory responses in gingival fibroblasts. The purpose of this study is the structural verification of the sphinganine bases and fatty acids that had been proposed as major components of the complex lipids found in P. gingivalis. The putative C17, C18, and C19 sphinganine bases were prepared from Garner's aldehyde (1) or from a protected serine Weinreb's amide (2). We confirmed that isobranched sphinganine bases are the major structural feature of the ceramides observed from P. gingivalis. We also prepared a C17 unsaturated fatty acid, along with an isobranched C17 3-hydroxy fatty acid, and determined that the major component of the active lipids was the latter.