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Oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) was carried out over Ru/Al2O3 using O2 aqueous alkaline solutions in a trickle-bed reactor. HMF was completely converted at 140 °C, 30 bar O2, resulting in 98% FDCA selectivity (pH 11, GHSV = 900 h–1, WHSV = 1 h–1). At 140 °C, FDCA was the main product under all conditions. Alkali (nature and concentration) played a significant role in oxidation or degradation of HMF. The selectivity to oxidized compounds was favored using Na2CO3 by accelerating oxidation steps, principally to the aldehyde group maintaining an appropriate pH for the reaction. The estimated kinetic parameters obtained were statistically significant, suggesting an accurate representation of the system. The effects of parameters such as temperature, GHSV, WHSV, and oxygen pressure on product distribution and HMF conversion were evaluated. The catalyst showed high stability, retaining activity after 12 cycles, being reactivated by a simple hydrothermal treatment.

The effects of phosphorus content on competitive hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and hydrodenitrogenation (HDN) of quinoline (Q) over NiMo catalysts were evaluated. Reactions were carried out in a trickle-bed high-pressure flow microreactor. HDS of 4,6-DMDBT was strongly inhibited at Q concentrations of 90 ppmw N, mostly hydrogenation (HYD) route in HDS, suggesting that 4,6-DMDBT and Q compete for the same hydrogenation active sites, which was confirmed by the products’ distribution in HDN reactions. Morphology and nature of active sites promoted by phosphorus addition led to different activity performance on competitive HDS and HDN reactions, as evidenced by TOF values. At low concentrations of Q, promoted catalysts maintained activity for both HDS and HDN. High Q levels (above 90 ppmw N) decreased HDS and HDN activity due to stronger inhibition of catalysts. The addition of 1 wt % of phosphorus showed superior activity, attributed to a combination of better dispersed NiMoS active sites and Brønsted acidity.

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