Competition between reactive adsorption desulfurization and olefin hydrogenation over the NiO/ZnO–Al2O3–SiO2 adsorbent

The RADS process inhibits olefin hydrogenation by competitive adsorption, which is affected by temperature and Ni loading.

An Effective Hybrid Heterogeneous Catalyst to Desulfurize Diesel: Peroxotungstate@Metal-Organic Framework

A peroxotungstate composite comprising the chromium terephthalate metal–organic framework MIL-101(Cr) and the Venturello peroxotungstate [PO₄{WO(O₂)₂}₄]³⁻ (PW₄) has been prepared by the impregnation method. The PW₄@MIL-101(Cr) composite presents high catalytic efficiency for oxidative desulfurization of a multicomponent model diesel containing the most refractory sulfur compounds present in real fuels (2000 ppm of total S). The catalytic performance of this heterogeneous catalyst is similar to the corresponding homogeneous PW₄ active center. Desulfurization efficiency of 99.7% was achieved after only 40 min at 70 °C using H₂O₂ as an oxidant and an ionic liquid as an extraction solvent ([BMIM]PF₆, 2:1 model diesel/[BMIM]PF₆). High recycling and reusing capacity was also found for PW₄@MIL-101(Cr), maintaining its activity for consecutive oxidative desulfurization cycles. A comparison of the catalytic performance of this peroxotungstate composite with others previously reported tungstate@MIL-101(Cr) catalysts indicates that the presence of active oxygen atoms from the peroxo groups promotes a higher oxidative catalytic efficiency in a shorter reaction time.

New Approach to Synthesis of Tetralin via Naphthalene Hydrogenation in Supercritical Conditions Using Polymer-Stabilized Pt Nanoparticles

Supercritical (SC) fluid technologies are well-established methods in modern green chemical synthesis. Using SC fluids as solvents instead of traditional liquids gives benefits of higher diffusivity and lower viscosity, which allows mass transfer intensification and, thus, an increased production rate of chemical transformations. Therefore, a conjugation of heterogeneous catalysis with SC media is a large step toward a green chemistry. Tetralin (TL) is an important hydrogen donor solvent used for biomass liquefaction. In industry, TL is obtained via catalytic hydrogenation of naphthalene (NL). Herein, for the first time we have demonstrated the NL hydrogenation with close to 100% selectivity to TL at almost full conversion in the SC hexane. The observed transformation rates in SC hexane were much higher allowing process intensification. The downstream processes can be also facilitated since hexane after depressurisation can be easily separated from the reaction products via simple rectification. The TL synthesis was studied in a batch reactor at variation of reaction temperature and overall pressure. For the first time for this process, low Pt-loaded (1 wt.%) nanoparticles stabilized within hyper-cross-linked aromatic polymer (HAP) were applied. The Pt/HAP catalyst was stable under reaction conditions (250 °C, 6 MPa) allowing its recovery and reuse.

Effect of Pretreatment on the Adsorption Performance of Ni/ZnO Adsorbent for Dibenzothiophene Desulfurization

Ni/ZnO was prepared by co-precipitation and used as adsorbent for reactive adsorption desulfurization (RADS) of dibenzothiophene. The effect of calcination temperature, precipitate washing solvent, and reduction temperature on the adsorption performance of Ni/ZnO was investigated. It is observed that Ni/ZnO adsorbent calcined at 350 °C, washed with ethanol, and unreduced or reduced at low temperature performed best. By the characterization of BET, XRD, TPR, FTIR, and in situ XAFS, the optimal calcination temperature leads to the small crystallite of NiO and ZnO species. Washing with ethanol enhances the surface area of adsorbent and decreases its particle size. The influence of reduction temperature on the RADS performance is stronger than that of calcination temperature, which is ascribed to high-temperature reduction that makes the adsorbent easier to sinter and form a Ni-Zn alloy. The high RADS activity is a result of the adsorbent pretreatment conditions, which can form small Ni and ZnO particles, and the synergism between precursors.