A sulfur K-edge XANES study on the transfer of sulfur species in the reactive adsorption desulfurization of diesel oil over Ni/ZnO

Scale-up reactivation of spent S-Zorb adsorbents for gasoline desulfurization

Reactivating and recycling spent S-Zorb adsorbents reduce fresh adsorbents consumption and hazardous wastes emissions. Though the spent adsorbents have been successfully reactivated in the laboratory, a pilot-scale practice is indispensable before the industrial production. Herein, the reactivation of spent adsorbents was performed at laboratory (1.0 L), middle (10 L) and pilot (3000 L) scale, respectively. The inert Zn₂SiO₄ and ZnS over the spent adsorbents are recovered to active ZnO, and the NiS is transformed into NiO. There is almost no amplification effect in pore structure and acidity of the reactivated adsorbents, while NiO particle size reduces slightly with the reactivation scales. The computational fluid dynamic simulation indicates that enhanced contact between spent adsorbents and acid/alkaline reagents at larger scale account for the smaller NiO particle. It provides more hydrogenolysis centers for CS bonds breakage after reduction, increasing initial desulfurization activity. More importantly, the adsorbent reactivated at pilot scale exhibits comparable activity to the fresh one in gasoline desulfurization. The sulfur content in the outlet decreases to less than 10 μg g^-1 from 1 h of reaction. Thus, the reactivation of spent S-Zorb adsorbents is successfully scaled up to the pilot scale, accelerating industrial practice in recycling the spent adsorbents.

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.

Modulating Coordination Environment of Single-Atom Catalysts and Their Proximity to Photosensitive Units for Boosting MOF Photocatalysis

Well-organized photosensitive units and catalytic sites in proximity are crucial for improving charge separation efficiency and boosting photocatalysis. Herein, a general and facile strategy for the construction of high-loading (>4 wt %) single-atom catalysts (SACs) with a tunable coordination microenvironment has been developed on the basis of metal-organic frameworks (MOFs). The neighboring -O/OH_x groups from a Zr₆-oxo cluster in the MOFs provide lone-pair electrons and charge balance to immobilize the extraneous single metal atoms. The well-accessible and atomically dispersed metal sites possess close proximity to the photosensitive units (i.e., linkers), which greatly accelerates charge transfer and thereby promotes the redox reaction. The coordination environment of the representative single-atom Ni sites significantly modulates the electronic state and the proton activation barrier toward hydrogen production. As a result, the optimized Ni₁-S/MOF with a unique Ni(I) microenvironment presents excellent photocatalytic H₂ production activity, up to 270 fold of the pristine MOF and far surpassing the other Ni₁-X/MOF counterparts. This work unambiguously demonstrates the great advantage of MOFs in the fabrication of high-content SACs with variable microenvironments that are in close proximity to photosensitive linkers, thereby facilitating the electron transfer and promoting photocatalysis.

Density functional theory study of thiophene desulfurization and conversion of desulfurization products on the Ni(111) surface and Ni55 cluster: implication for the mechanism of reactive adsorption desulfurization over Ni/ZnO catalysts

Density functional theory calculations were performed to study thiophene desulfurization and conversion of desulfurization products on the Ni(111) surface and Ni₅₅ cluster.

Five-photon absorption upconversion lasing from on-chip whispering gallery mode

In the progress of ultrafast optics, nonlinear interactions between light and matter are very important in scientific and technical fields. In particular, the high-order nonlinear effect induced by multi-photon absorption (MPA) upconversion lasing has injected new impetus into the research on short-wavelength laser sources. Here, we report the realization of amplified spontaneous emission (ASE) by MPA simultaneously in an epitaxy thin film. In addition, by virtue of the excellent optical confinement of cylindrical microcavities with high Q (∼4 × 103) on-chip, we demonstrated, for the first time, low-threshold upconversion lasing of five-photon absorption enhanced by a microcavity at room temperature. The resonant whispering-gallery mode (WGM) distribution in cylindrical microcavities was simulated comprehensively by the finite difference time domain (FDTD) method. We found that the high-order nonlinear optical process could be significantly enhanced in the microcavity with an increase in the lifetime of radiation photons.

Reactive adsorption desulfurization of thiophene over NiMo/ZnO, a new adsorbent with high desulfurization performance and sulfur capacity at moderate temperature

3Ni7Mo/ZnO adsorbent was synthesized by a two-step impregnation method for reactive adsorption desulfurization (RADS) experiments.

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.

Reactive adsorption desulfurization of NiO and Ni0 over NiO/ZnO–Al2O3–SiO2 adsorbents: role of hydrogen pretreatment

Reactive adsorption desulfurization (RADS) of Fluidized Catalytically Cracked (FCC) gasoline on reduced and unreduced NiO/ZnO–Al₂O₃–SiO₂ adsorbents was studied. Various characterizations such as powder X-ray diffraction (XRD), H₂-temperature-programmed reduction (H₂-TPR), the H₂/O₂ pulse titration (HOPT), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are used to evaluate the effects of hydrogen pretreatment of the adsorbents. XRD and HOPT results indicate that NiO is hard to be reduced to Ni⁰ under the conditions of RADS. H₂-TPR shows that NiO might be reduced to Ni⁰ at the temperature of 598 °C, much higher than the temperature of RADS. The Ni 2p_3/2 spectrum of Ni⁰ is not observed for the reduced adsorbent, but the main peak of Ni 2p_3/2 of NiS is found for the spent adsorbent. The unreduced NiO/ZnO–Al₂O₃–SiO₂ adsorbent performs a better desulfurization than the reduced adsorbent at the beginning of desulfurization process. NiO and Ni⁰ are assumed as the main active components and present a good desulfurization ability in RADS. Finally, a change in the RADS mechanism is presented and discussed.

A possible reaction mechanism of desulfurization on NiO/ZnO–Al₂O₃–SiO₂ is discussed.