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Influence of Functionalization of Silica with Ionic Liquid on Ethylene Polymerization Behavior of Supported Metallocene

실리카의 이온성 액체 기능화가 메탈로센 담지촉매의 에틸렌 중합 거동에 미치는 영향

  • Lee, Jeong Suk (Department of Chemical Engineering, Kongju National University) ;
  • Lee, Chang Il (Department of Chemical Engineering, Kongju National University) ;
  • Ko, Young Soo (Department of Chemical Engineering, Kongju National University)
  • Received : 2015.12.25
  • Accepted : 2015.12.29
  • Published : 2016.02.10

Abstract

Three amorphous silicas and SBA-15 were employed as supports, which were capable of confining ionic liquid (IL) and metallocene in the nanopore. Ionic liquid functionalized silica was prepared by the interaction between the chloride anions of 1,3-bis(cyanomethyl)imidazolium chloride and the surface OH groups. Metallocene and methylaluminoxane (MAO) were subsequently immobilized on the ionic liquid functionalized silica for ethylene polymerization. The metallocene supported on ionic liquid functionalized XPO-2412 and XPO-2410 having a larger pore diameter compared to SBA-15 showed higher activity than that of using supported catalyst without ionic liquid functionalization. However, the activity of metallocene supported on SBA-15 decreased after ionic liquid functionalization, suggesting that the diffusion of ethylene monomer and cocatalyst to the active site of nanopore was restricted during ethylene polymerization. This could be resulted from significant reduction of the pore diameter due to the immobilization of ionic liquid and $(n-BuCp)_2ZrCl_2$ and MAO. The effect on polymerization activity in accordance with the concentration of hydroxyl groups on the surface was also investigated. The polymerization activity increased as the concentration of hydroxyl groups on amorphous silica increased. The polymerization activities of metallocene supported on silica showed the similar trend after ionic liquid functionalization.

Ionic liquid 기능화 및 메탈로센 촉매 담지를 위해 세 종류의 무정형 실리카와 SBA-15를 담체로 사용하였다. Ionic liquid가 표면 기능화된 실리카는 1,3-bis(cyanomethyl)imidazolium chloride의 염소 음이온과 실리카 표면의 OH 그룹 사이의 상호작용에 의해 합성되었다. 에틸렌 중합을 위해 ionic liquid가 기능화된 실리카에 메탈로센과 조촉매 methylaluminoxane(MAO)을 담지하였다. SBA-15와 비교하여 큰 기공 크기를 갖는 ionic liquid가 표면 기능화된 XPO-2412와 XPO-2410에 담지된 촉매는 기능화되지 않은 실리카에 담지된 촉매보다 높은 활성을 보였다. 그러나 SBA-15에 담지된 촉매는 ionic liquid의 표면 기능화 후에 활성이 감소하였다. 이는 ionic liquid와 메탈로센 촉매, 조촉매 MAO가 담지되면 기공의 크기가 크게 줄어들기 때문에 중합 시 에틸렌 모노머와 조촉매가 기공 내 촉매 활성점으로 확산하는데 제한을 받기 때문이다. 또한 실리카 표면의 OH 그룹의 농도 변화에 따른 촉매의 중합 활성에 대한 영향을 연구하였다. 무정형 실리카의 OH 그룹의 농도가 증가할수록 중합 활성도 증가하였으며 실리카에 담지된 촉매의 중합 활성은 ionic liquid 표면처리 후에도 유사한 경향을 보였다.

Keywords

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