Characterization of Sulfated SnO2-ZrO2 Catalysts and Their Catalytic Performance on the Tert-Butylation of Phenol

Understanding the catalytic behavior of sulfated metal oxides has been the topic of several research studies in the past few decades. Their apparent super-acidic behavior has been correlated with the molecular structure of the surface sulfate species. Herein, we couple FTIR and Raman spectroscopies to study the molecular structural evolution of surface sulfate species on mixed metal hydroxides as well as calcined oxides. We show that on the surface of hydroxides, monodentate and possibly bidentate species are dominant, while for SnO2-rich samples, clusters of polymeric sulfate species may also be present. After calcination, sulfate species bind strongly on the surface of mixed oxides, and different configurations can be seen with a range of S=O functionalities of varying strength. Through comparison of the catalytic performance of all sulfate oxides in the tert-butylation of phenol, it was found that SnO2-rich samples show high TBA conversion, with monoalkylated phenols as the primary product.

Evidence of Variations in Atomic Distribution in Disordered Mixed Metal Hydroxides

ABSTRACTNumerous fabrication protocols are known to yield transition metal oxides with structures related to layered double hydroxides, but the effect of fabrication protocol on the uniformity of mixed-metal compositions remain largely unexplored. We have analysed the apparent solubility limits and the structural implications of iron ions in nickel hydroxide lattices for materials prepared by four different fabrication protocols. Opposing shifts in the (100) and (001) reflection in powder X-ray diffraction results revealed a contraction of the nickel lattice upon successful incorporation of iron, with Ni-M distances exhibiting an apparently linear decrease with respect to iron content. This feature revealed the amount of iron incorporated into nickel-based materials to be dependent on fabrication protocol, varying from apparently negligible concentrations to over fifty atomic percent. The dependency of structure on fabrication protocols provides a handle to improve fundamental understanding of catalytically relevant coordination environments.

CHITOSAN-TEMPLATED LIGHTWEIGHT SPINEL CoAl2O4 NANOFIBRIL AEROGELS

We present lightweight macro-mesoporous spinel CoAl2O4 nanostructured aerogels derived from water-soluble aluminum-chitosan complexes. Chitosan nanofibrils interact with aluminum ions to swell into hydrogels. The aluminum-induced swelling is extended to dissolve the hydrogels in water to form a homogeneous aluminum-chitosan aqueous solution. The addition of cobalt ions in the aluminum-chitosan liquids which are solidified by lyophilization to generate cotton-like aerogel composites. Uniform incorporation of cobalt-aluminum hydroxide ions onto chitosan leads nanofibrils to serve as a hierarchical template to support mixed metal hydroxides in the aerogel composites. We investigated the thermal removal of chitosan template in the composites to obtain spinel CoAl2O4 aerogels that truly replicate spider web-like fibrillar networks of chitosan template. Enlarged porosity, high crystallinity, and lightweight make the CoAl2O4 aerogels useful as a colorful nano-pigment for magnetic ceramics.

Electrochemical route for accessing amorphous mixed-metal hydroxide nanospheres and magnetism

Amorphous mixed-metal hydroxides nanospheres with a homogeneous distribution of metals in compositions including binary Fe–Co, Fe–Ni and Co–Ni and ternary Ni–Co–Fe hydroxides were prepared via a simple, facile and green electrochemical technique.