Covalent Organic Framework-Supported Metallocene for Ethylene Polymerization.

The loading of homogeneous catalysts with support can dramatically improve their performance in olefin polymerization. However, the challenge lies in the development of supported catalysts with well-defined pore structures and good compatibility to achieve high catalytic activity and product performance. Herein, we report the use of an emergent class of porous material-covalent organic framework material (COF) as a carrier to support metallocene catalyst-Cp2 ZrCl2 for ethylene polymerization. The COF-supported catalyst demonstrates a higher catalytic activity of 31.1×106  g mol-1 h-1 at 140 °C, compared with 11.2×106  g mol-1 h-1 for the homogenous one. The resulting polyethylene (PE) products possess higher weight-average molecular weight (Mw ) and narrower molecular weight distribution (Ð) after COF supporting, that is, Mw increases from 160 to 308 kDa and Ð drops from 3.3 to 2.2. The melting point (Tm ) is also increased by up to 5.2 °C. Moreover, the PE product possesses a characteristic filamentous microstructure and demonstrates an increased tensile strength from 19.0 to 30.7 MPa and elongation at break from 350 to 1400 % after catalyst loading. We believe that the use of COF carriers will facilitate the future development of supported catalysts for highly efficient olefin polymerization and high-performance polyolefins.

Combination of an Asphalt Stabilizer and a Cellulose-Chitosan Composite Aerogel Used for the Separation of Oil-Water Mixtures Containing Asphalt.

In this paper, cellulose chitosan composite aerogels were prepared through sol-gel and freeze-drying processes. The porous morphology of the aerogels was controlled by adjusting the cellulose concentration. Within a certain range, as the concentration of cellulose increases, the pore diameter of the composite aerogel becomes smaller and the pore structure becomes denser. The cellulose-chitosan composite aerogel can successfully separate the oil-water mixture without asphalt and showed stable filtration performance. The filtration speed is basically unchanged after a slight decrease and can be maintained at about 90% of the initial filtration speed within 30 min. The filtration speed can reach up to 9315 kg·h-1·m-2. When filtering bituminous oil-water mixtures, the filtration rate decreased significantly, with a 50% drop in 30 min. After adding the asphalt stabilizer poly(styrene-alt-octadecyl maleimide) (SNODMI), which is made in our laboratory, the effect of aerogel filtering the asphalt-containing oil-water mixture is obviously improved, and the downward trend of filtration speed is obviously improved. The combination of SNODMI and cellulose-chitosan has great application potential in the field of asphalt-containing oil-water separation.