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Tetherball: A heterogeneous, mesoporous silica‐tethered iridium catalyst (Ir‐PN/SBA‐15) containing a bidentate iminophosphine ligand is synthesized for the hydrogenation of CO2 to formic acid in aqueous solution. This new recyclable catalyst exhibits high activities to formic acid production under mild conditions [60 °C, 4.0 MPa total pressure (H2/CO2=1:1)].

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We report the synthesis of a new multifunctional mesoporous zeolite catalyst with cerium incorporated within the framework. This catalyst shows a shift in selectivity from typical HZSM-5 products (benzene, toluene, and xylenes) to valuable oxygenated chemicals (furans, ketones, aldehydes) during the catalytic fast pyrolysis of lignocellulosic biomass. The cerium-incorporated hierarchical zeolite was synthesized using a dry-gel method followed by steam-assisted crystallization. The catalyst was characterized by X-ray diffraction (XRD), N 2 physisorption, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), NH 3 temperature-programmed desorption (NH 3 -TPD), diffuse reflectance FT-IR, and diffuse reflectance UV−Visible (UV−Vis) spectroscopy. The multifunctional catalyst was then studied in the catalytic fast pyrolysis of glucose (a carbohydrate model compound) at 600 °C. The new catalyst was compared with a mesoporous HZSM-5 catalyst with incipient wetness incorporated cerium and an ion exchanged commercial HZSM-5 catalyst. These catalysts behaved similarly to the parent materials, but the new catalyst with cerium incorporated into the zeolite framework exhibited selectivities greatly shifted from aromatics to oxygenated chemicals. Furthermore, this catalyst produced less coke (40 wt % or 11 mol % carbon) and increased CO production through decarbonylation reactions. These properties persisted after catalyst regeneration and recycle.

Mesoporous HZSM-5 was synthesized with a SiO2/Al2O3 ratio of 100 using a steam-assisted crystallization method. The resulting material was characterized by N2 physisorption, powder X-ray diffraction, focused ion beam-scanning electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectrometer (XPS) depth profiling, NH3-temperature programmed desorption (TPD), pyridine-TPD, and collidine-TPD. Crystallization time was varied to determine the effect on material physical properties, total acidity, accessible acid sites, and aluminum distribution within the zeolite particles. The Barrett, Joyner, and Halenda mesopore volumes, Brunauer, Emmett, and Teller surface areas, and total pore volumes decreased with longer crystallization times, while the mesopore sizes increased with time. At prolonged crystallization time, the material underwent dealumination via steam etching followed by reforming of material, thus blocking accessibility to the mesopores. The total acidity was optimized at 18 h of crystallization time. In addition to total acidity, the ratio of external and mesoporous acid sites to total acid sites decreased with increased crystallization time. Although a relatively uniform distribution of Al was observed across the center of the 18 h particles, XPS depth profiling showed an enrichment of aluminum on the outer shell of all HZSM-5 particles (“aluminum zoning”) with this steam-assisted crystallization method. Thus, crystallization time should be strongly monitored when using this dry-gel synthesis method with soft templates.