Fair Look at Coordination Oligomerization of Higher α-Olefins

Coordination catalysis is a highly efficient alternative to more traditional acid catalysis in the oligomerization of α-olefins. The distinct advantage of transition metal-based catalysts is the structural homogeneity of the oligomers. Given the great diversity of the catalysts and option of varying the reaction conditions, a wide spectrum of processes can be implemented. In recent years, both methylenealkanes (vinylidene dimers of α-olefins) and structurally uniform oligomers with the desired degrees of polymerization have become available for later use in the synthesis of amphiphilic organic compounds and polymers, high-quality oils or lubricants, and other prospective materials. In the present review, we discussed the selective dimerization and oligomerization of α-olefins, catalyzed by metallocene and post-metallocene complexes, and explored the prospects for the further applications of the coordination α-olefin dimers and oligomers.

Effect of kaolinite and Ca-montmorillonite on the alleviation of soil water repellency

The effects of adding 1–3% (weight) kaolinite or Ca-montmorillonite on the wettability of silica sand, made highly water repellent with stearic acid, was studied during wetting and prolonged drying phases at 50°C. The persistence of water repellency was estimated with the water drop penetration time (WDPT) test. After wetting water repellency disappeared in all the samples. During the drying phase, water repellency re-appeared in all samples (untreated and clay-treated) as the water content decreased below 1%. Repellency did, however, not reach pre-wetting levels. The effect of clay additions on water repellency differed strongly between the two clay types. Kaolinite reduced WDPT, while Ca-montmorillonite caused an increase in WDPT in the already highly repellent sand. Potential mechanisms for the alleviation effectiveness of kaolinite are proposed, with key factors being the high adhesion forces between water and clay mineral surfaces, and the ability kaolinite to disperse. In the case of Ca-montmorillonite, its lower affinity for water may lead to a displacement of water molecules at mineral surfaces by amphiphilic organic compounds, which may result in increased repellency. This phenomenon clearly requires further investigation.

Synthesis of Macroporous Polystyrene Validamycin a Amphiphilic Adsorbent Resin and its Adsorption Properties for Pueraia Isoflavones

A novel amphiphlic adsorbent resin of macroporous polystyrene Validamycin A was synthesizedviathe amination of chloromethylated macroporous crosslinked polystyrene resin using Validamycin A. Its chemical structure was characterized by Fourier transformation infrared spectra and elemental analysis. Its pore structure was determined by nitrogen adsorption-desorption measurements. Test results of swelling ratio in various solvents revealed that the aminated resin was amphiphilic. The resin showed excellent adsorption performance for the amphiphilic organic compounds of pueraia isoflavones in aqueous solution.