Mean penetration depth of metals in hydrodemetallation catalysts

Multilobed Magnetic Liposomes Enable Remotely Controlled Collection, Transport, and Delivery of Membrane-Soluble Cargos to Vesicles and Cells

“…Examples of multilobed structures in biological systems include the nuclei of neutrophiles, the brain, the garlic bulb, and the leaves of clover or those of the walnut tree. − In the physical world, multilobed structures can be found at length scales ranging from electron orbitals to the polar lakes of Titan . Multilobed structures have also inspired man-made objects in architecture, art, or industry. − In soft-matter colloidal materials, multilobed structures are not so common; the spherical shape is generally favored thermodynamically due to its minimization of interfacial free energy. − The present work reports one potentially useful anomaly, the so-called multilobed magnetic liposomes (MMLs), which possess some rather unique features owing to their specific shape and internal structure.…”

Engineering the Hierarchical Pore Structures and Geometries of Hydrodemetallization Catalyst Pellets

“…Catalytic hydrocracking of heavy oils to produce commercial-value and high-quality transportation fuels and other petrochemical products has received an increasing level of attention owing to energy demands and tighter environmental regulations. − Prior to this process, hydrodemetallization (HDM) is required to remove metal impurities in the feedstocks, , in which Ni- and V-porphyrin enriched in large asphaltene aggregates (>1 nm in size) are most abundant and problematic, causing detrimental impacts on the downstream catalysts. , Typically extruded alumina-supported catalyst pellets comprising Mo sulfide promoted by Co or Ni are employed for the HDM reaction in industrial plants. ,− However, the alumina-supported HDM catalysts generally undergo two-step deactivation, that is, a slow loss in the activity due to the active sites being covered by the metal deposition followed by a rapid deactivation attributed to the pore plugging arising from the accumulation of the metal sulfides and ultimate pore blockage. − This would lead to serious intraparticle diffusion limitations for the long-time HDM operation. , Hence, there is an urgent need to design appropriate pore structures and geometries of the catalyst pellet for a highly efficient HDM process.…”

“…A strategy to alleviate the intraparticle diffusion limitations by tailoring the pore structure has been proposed. − Two representative experimental studies showed that the alumina-supported catalyst with a bimodal pore size distribution of 9 and 100 nm shows higher HDM activity than the catalyst with purely a mesopore diameter of 8 nm, and the hierarchically structured HDM catalyst with the most probable macropore diameter of 120 nm exhibits better HDM performance than that with 200 nm . A large amount of theoretical studies based on mathematical modeling of the diffusion behavior and reaction in the HDM catalysts has been conducted for in-depth analysis of the effects of the pore structure parameters. ,,− Rao and Coppens optimized the broad pore network of a hierarchically structured HDM catalyst on the basis of the Random Spheres Model (RSM) with the optimization objective of the reaction rate of a single catalyst pellet at the pellet scale. It is noted that compared with commercial hydrotreating catalysts, the employment of rodlike alumina is favorable for the enhanced dispersion of active sites, − and the catalysts prepared by rodlike alumina show better HDM catalytic performance .…”