Extremely Active Ethylene Tetramerization Catalyst Avoiding the Use of MAO
Extremely Active Ethylene Tetramerization Catalyst Avoiding the Use of MAO
- 주제(키워드) ethylene tetramerization , 1-octene production , chromium catalyst , PNP ligand derivative , tetrakis(pentafluorophenyl)borate
- 발행기관 아주대학교
- 지도교수 이분열
- 발행년도 2020
- 학위수여년월 2020. 2
- 학위명 석사
- 학과 및 전공 일반대학원 분자과학기술학과
- 실제URI http://www.dcollection.net/handler/ajou/000000029906
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Critical issues raised in the Sasol's original ethylene tetramerization catalyst composed of Cr(acac)3, iPrN(PPh2)2 and MMAO (modified-methylaluminoxane) are the use of expensive MMAO, low working temperature around 60 °C, and generation of PE side product. Generation of polyethylene, though its amount is small, also poses a critical problem that is often referred to as 'fouling' of the operation of the continuous commercial process. In this work, we disclosed an upgraded catalytic system that avoids the use of MAO solving the issues. In precedent trials to prepare the catalyst precursors, [(PNP)CrCl2]+[B(C6F5)4]–-type species, the main product isolated was inactive bis(PNP)-CrIII complex ([(PNP)2CrCl2]+[B(C6F5)4]–). The targeted mono(PNP)-CrIII complex was obtained from CrCl3(THF)3, [PhN(H)Me2]+[B(C6F5)4]–, and iPrN[P(C6H4-p-Si(nBu)3]2 (2). The bulky (nBu)3Si-substituents in 2 play a crucial role, preventing the formation of the inactive bis(PNP)-CrIII species and hindering the rotation around P-N bonds to block demetallation process. The prepared species [2-CrCl2]+[B(C6F5)4]– combined with iBu3Al was extremely active (> 6000 Kg/g-Cr/h), worked well at a high temperature up to 90 °C, and generated a negligible amount of PE (0.03 wt%). The extremely active [2-CrCl2]+[B(C6F5)4]– was also prepared by simply reacting 2 and [CrCl2(NCCH3)4]+[B(C6F5)4]–. Screening the performance with a series of iPrN[P(C6H4-p-SiR3]2 (R3Si- = (nBu)3Si-, iPr3Si-, Et3Si-, Me3Si-, Et2(iPr)Si-, Me2(iPr)Si-, and Me2(1-octyl)Si-) further supported that bulky R3Si-substiuents are crucial not only to gain the extremely high activities but also to minimize generation of the problematic side product PE even at a high temperature.
more목차
Abstract Ⅰ
1. Introduction 1
2. Results and Discussion 2
2.1 Preparation of [(PNP)CrCl2]+[B(C6F5)4]– 2
2.2 Preparation of the PNP ligand bearing various -SiR3 substituents 12
2.3 Oligomerization studies with [(PNP)CrCl2]+[B(C6F5)4]– 13
3. Conclusions 15
4. Experimental Section 16
4.1 General remarks 16
4.2 Synthesis of ligands and complexes 16
4.3 Ethylene oligomerization 24
4.4 X-Ray crystallography 24
5. Reference 25
6. Supporting information 29
