A series of α-amine ketoximesilanes were prepared and used as auto-catalyzed cross-linkers in one component room temperature vulcanized (RTV) silicone rubber.
A hyper cross-linked ionic polymer
(HCIP) PVimBCmBn was synthesized
through free radical polymerization of 1-vinylimidazole (Vim) and
quaternized cross-linking with 1,4-bis(chloromethyl) benzene (BCmBn).
Its composition, structure, morphology, specific area, porous structure
and thermal stability were characterized, and the desulfurization
performance was investigated. The results show that the HCIP prepared
with stoichiometric ratio of PVim and BCmBn are ultrafine powders
with specific area of 99.6 m2·g–1 and average pore size of 16.1 nm, being micro/mesoporous materials.
The S-removability of HCIP is superior to its precursor (ethyl imidazole)
and the imidazolium-based ionic liquids (ILs), which manifests the
importance of the available micropores for the accommodation of sulfur
molecules with less energy barrier. The adsorption isotherms of PVimBCmBn
follow the Langmuir equation with its saturated adsorbance being 7.0,
5.2, and 4.1 mgS·g–1, respectively, for dibenzothiophene,
benzothiophene, and thiophene in model oil at 293 K. However, its
adsorptive removal ability for DBT in diesel oil is quite low due
to its limited S-selectivity with respect to the abundant confused
ring aromatics wherein.
The past decade has seen some remarkable advances in the development of low‐coordinate and/or oxidation state aluminum chemistry. With efforts striving to find more economical and environmentally benign methods for bond activations and catalysis, aluminum presents itself as an ideal candidate owing to its low cost and high natural abundance. Concerning low‐valent aluminum chemistry, these complexes have been shown to act like transition‐metal mimics with Al(I) species undergoing facile oxidative addition with a series of strong σ bonds. This represents the first step in a redox‐active catalytic cycle, with the challenge still remaining to undergo reductive elimination from the stable Al(III) species. In this regard, efforts have focused on reversible bond activations as well as the development of alternate methodologies to enhance the reactive aluminum center. The ambiphilic nature of Al(I) chemistry has largely been dictated by the vacant p‐orbital and as such its electrophilicity. Recent advances have made it possible to amplify the nucleophilic character of Al(I), and as such the first examples highlighting aluminum's nucleophilic behavior have been reported. In addition, isolation of the first neutral aluminum multiple bond has also aided our understanding of the bonding properties of aluminum while also allowing for further advances in bond activations and catalysis. These recent advances in the chemistry of low‐valent aluminum are discussed in the following sections, along with the fundamental concepts that have aided the development of this field.
Despite the notable progress in aluminium chalcogenides, their sulfur congeners have rarely been isolated under mild conditions owing to limited synthetic precursors and methods. Herein, facile isolation of diverse molecular aluminium sulfides is achievable, by the reaction of N‐heterocyclic carbene‐stabilized terphenyl dihydridoaluminium (1) with various thiation reagents. Different to the known dihydridoaluminium 1Tipp, 1 features balanced stability and reactivity at the Al center. It is this balance that enables the first monomeric aluminium hydride hydrogensulfide 2, the six‐membered cyclic aluminium polysulfide 4 and the five‐membered cyclic aluminium polysulfide 6 to be isolated, by reaction with various equivalents of elemental sulfur. Moreover, a rare aluminium heterocyclic sulfide with Al−S−P five‐membered ring (7) was obtained in a controlled manner. All new compounds were fully characterized by multinuclear NMR spectroscopy and elemental analysis. Their structures were confirmed by single‐crystal X‐ray diffraction studies.
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