Amine-containing adsorbents have been extensively investigated for post-combustion carbon dioxide capture due to their ability to chemisorb low-concentration carbon dioxide from a wet flue gas. However, earlier studies have focused primarily on the carbon dioxide uptake of adsorbents, and have not demonstrated effective adsorbent regeneration and long-term stability under such conditions. Here, we report the versatile and scalable synthesis of a functionalized-polyethyleneimine (PEI)/silica adsorbent which simultaneously exhibits a large working capacity (2.2 mmol g−1) and long-term stability in a practical temperature swing adsorption process (regeneration under 100% carbon dioxide at 120 °C), enabling the separation of concentrated carbon dioxide. We demonstrate that the functionalization of PEI with 1,2-epoxybutane reduces the heat of adsorption and facilitates carbon dioxide desorption (>99%) during regeneration compared with unmodified PEI (76%). Moreover, the functionalization significantly improves long-term adsorbent stability over repeated temperature swing adsorption cycles due to the suppression of urea formation and oxidative amine degradation.

SUMMARY:The molecular weight (MW) and the molecular weight distribution (MWD) of polyethylene (PE) prepared with various metallocene catalysts were investigated. The weight-average molecular weight (MW) of PE prepared with dicyclopentadienyltitanium dichloride/ aluminoxane (Cp,TiCl,/MAO) was about 4,O. lo', while that of PE obtained withPE of bimodal MWD was obtained with the mixed catalyst Cp,TiCl,/Cp,ZrCl,. Narrow MWD PE was obtained with the mixed catalyst Cp2ZrC1,/Et(ind),ZrC1,, because each catalyst produced an M, of 1,0 * lo5. However, the change of temperature during the polymerization with the mixture Cp,ZrC1,/Et(ind)2ZrClz produced PE with a bimodal MWD and a value of the ratio of weight-to number-average molecular weights of a w / M n = 4.

Et(ind)zZrClz (C2H,(indenyl)zZrC12) confined inside regular pores of molecular sieves MCM-41 and VPIJ were prepared and used to polymerize propene with high activity. Stereoregularity, melting point and molecular weight of polypropene obtained were increased and the polymerization behavior was quite different from that prepared with homogeneous Et(ind)zZrC12. The small, regular and cylindrical pores of MCM-4 1 and VPI-5 suppress the formation of inactive binuclear complexes between metallocene and metallocene, or between metallocene and methylaluminoxane, resulting in stable active sites and high activity in propene polymerization. ' )Present address: Polymer Technology Lab.,

No abstract

Metallocene catalysts entrapped inside the supercages of NaY zeolite were prepared by reacting NaY with methylaluminoxane (MAO) or trimethylaluminium (TMA) and then with Cp2ZrCI, (Cp: cyclopentadienyl) or Cp2TiCI2. NaY/MAO/Cp,ZrCl, and NaY/MAO/ Cp,TiCI, catalysts could polymerize ethylene. The amount of additional MA0 for the polymerization was lowered to a mole ratio of AVZr of 186. Molecular weights and melting points of polyethylene polymerized with Nay-supported catalysts were higher than those of polyethylene obtained with homogeneous metallocene catalysts. It could be confirmed by extraction experiments that the metallocene catalyst was confined securely inside the supercage of the NaY zeolite.