Organic syntheses catalyzed by superacidic metal oxides: sulfated zirconia and related compounds

Surface structural-chemical characterization of a single-site d 0 heterogeneous arene hydrogenation catalyst having 100% active sites

“…The long Zr + ···O AlS − distances indicate loose, nondirectional ion pairing, as might be expected from the conjugate base of an extremely strong solid Brønsted acid in which the negative charge is highly dispersed (15,16), and finds surprisingly close analogy to homogeneous ion-paired early-transition metal polymerization catalysts in which the nature of the ion pairing between the cationic catalyst and the charge-dispersed, electrostatically bound, and easily displaceable counteranion strongly modulates the barrier to olefin activation and enchainment (44)(45)(46)(47). Indeed, this description is closely analogous to Fig.…”

One‐Step Preparation of Efficient and Reusable SO42−/ZrO2‐Based Hybrid Solid Catalysts Functionalized by Alkyl‐Bridged Organosilica Moieties for Biodiesel Production

“…[9] However, the current heterogeneous acid-catalyzed biodiesel production system is not a popular choice for commercial applications because more severe reaction conditions, such as high reaction temperature and high molar ratio of alcohol to oil, are required. [10] In the search for efficient, stable, separable, and reusable solid acid catalysts for the purpose of providing a promising, environmentally benign, biodiesel production process from less-expensive feedstock, a series of mesoporous sulfated zirconia-based hybrid catalysts functionalized by alkyl-bridged organosilica moieties (SO 4 2À /ZrO 2 ÀSiO 2 (R) with R = CH 2 CH 2 or C 6 H 4 ) were developed by using a one-step, co-condensation technique combined with hydrothermal treatment in the presence of a triblock copolymer surfactant, P123.…”

“…Sulfated metal oxides, in particular, sulfated zirconia (SO 4 2À /ZrO 2 ), possess potential economic and green benefits for a wide variety of reactions, including alkane isomerization, Friedel-Crafts acylation, esterification, and transesterification. [9,[11][12][13][14] However, conventional preparation of SO 4 2À /ZrO 2 is through a postsynthetic grafting method followed by calcination at relatively high temperatures (600-650 8C). Accordingly, the porosity of the sulfated metal oxides is poor; more importantly, despite the high acidity of the sulfated metal oxides, significant deactivation during the process of liquid-solid-phase reactions was observed, possibly due to a combination of sulfate-group leaching and blocking of the active sites by reactants and/or products.…”

Supported Single-Site Organometallic Catalysts for the Synthesis of High-Performance Polyolefins

“…Thus, comparing the key aspects of the adsorbate-oxide surface interaction with the relevant features in well-characterized solution-phase analogues offers an opportunity to better understand the distinctive aspects of the surface organometallic chemistry. This review focuses primarily on recent research at Northwestern in which organo-groups 4 and 5, and organoactinide complexes are supported on dehydroxylated c-alumina [86,87] and sulfated metal oxides [88][89][90]. The combined application of solid-state NMR spectroscopy, periodic DFT calculations, and metal X-ray absorption spectroscopy indicates formation of organometallic cations having a largely electrostatic L n -M ?…”