This study describes the synthesis and characterization of a new supported bentonite catalyst prepared by the two-step modification of Na-bentonite. In the first step, Na-bentonite is modified with cetyl pyridinium bromide (CPB) to give a monolayer bentonite (CP-bentonite) in which surfactant ions are adsorbed by cation exchange with the counterions of bentonite. This gives a disordered liquid-like monolayer arrangement of alkyl chains within the gallery. This monolayer bentonite is then treated with the second generation of an amidoamine cascade known as 3,3′-(dodecylazanediyl)bis(N-(2-(2,3,3′-(dodecylazanediyl)bis(N-(2-(2-aminoethyl(2-hydroxybenzenimine))ethyl)propanamide) (DAEP), which has a long aliphatic tail (C12) and a hydrophilic head, to form a modified bilayer bentonite (Ben-DAEP-modified). The solid/liquid interface layer of this architecturally designed bentonite (Ben-DAEP-modified) was used as a pincer-type ligand for the synthesis of a new host–guest catalyst by immobilization of Co, Mn, or Co/Mn on it. The structure, specific surface area, and porosity of bentonite are significantly altered by the incorporation of nanoparticles. The resulting solid catalysts were characterized by UV–vis, Fourier transform infrared (FT-IR), inductively coupled plasma (ICP), scanning electron microscopy (SEM), N2 adsorption, and transmission electron microscopy (TEM) techniques. The oxidation of p-xylene produces five products: 4-methyl benzaldehyde, 4-methyl benzoic acid, 1,4-benzene dialdehyde, 4-carboxybenzaldehyde, and 1,4-benzenedioic acid. The reaction conditions for oxidation of p-xylene were optimized by varying the temperature, pressure, amount of catalyst, time, and catalyst-to-oxidant ratio. The optimum conditions for oxidation of p-xylene to 1,4-benzenedioic acid (terephthalic acid) were 0.15 g of Ben-DAEP-modified-Co/Mn (Co/Mn with a ratio of 10/1), 190 °C, 3% of Br– as promoter, 17 atm, and 3 h.

Solid ammine metal borohydrides [M­(BH4) m (NH3) n , AMBs] are promising materials for low temperature, high capacity hydrogen generation. Retention of metal halide co-products, arising from typical mechanochemical synthetic methods, is shown to have negative impacts on dehydrogenation properties of yttrium AMB. Halide-free yttrium and lanthanum AMBs, M­(BH4)3(NH3)4, have been synthesized directly by treatment of MCl3 with 3 equiv of NaBH4 in thf followed by filtration, cooling, and exposure to liquid ammonia. The peak dehydrogenation temperature of the Y analog decreased from previously reported 179 to 160 °C while the ammonia peak temperature increased from 86 to 165 °C. To enhance the dehydrogenation properties and increase the selectivity of gas formation from these AMBs, base-metal nanoparticle catalysts, M′NPs; M′ = Fe, Co, Ni, and Cu) were employed. Preparation of the M′NPs from M′Cl2 and liquid hexylamine–borane allowed for separation of the B–Cl byproducts by subsequent solvent washing. Sonification of the M′NPs in toluene followed by addition of the solid AMB afforded composite AMB–M′NP–BN solids. Thermolysis data indicated a threefold reduction in ammonia release from the Y–Co and fourfold for the La–Fe composite. The purity of the released hydrogen was estimated to be 97.9 mol % for Y–Co and 98.9 mol % for La–Fe.

Ammine metal borohydrides (AMBs) have recently commanded attention as low-temperature hydrogen sources. As an alternative to widely used mechanochemical synthesis that affords mixtures with salt co-products, we have been investigating solution synthesis routes to obtain pure AMBs. Here we show that reactions of MCln + nNaBH4 with ammonia in thf afford ammonia-borane (AB) via borane abstraction from M-coordinated borohydride. The amount of AB formed correlates roughly with the metal ion electronegativity and AMB thermal stability, except for reducible metals such as Ti, which affords nearly 3 equiv. of AB per Ti.

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