Extremely active mao-free catalytic system for Ethylene Tetramerization
Extremely active mao-free catalytic system for Ethylene Tetramerization
- 주제(키워드) 마오 미사용 , 크롬 촉매를 이용한 에틸렌 사량화
- 발행기관 아주대학교 중앙도서관
- 지도교수 이분열
- 발행년도 2019
- 학위수여년월 2019. 2
- 학위명 석사
- 학과 및 전공 일반대학원 분자과학기술학과
- 실제URI http://www.dcollection.net/handler/ajou/000000028842
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
The original Sasol catalytic system forethylene tetramerization is composed of a Cr source, a PNP ligand, and MAO (methylaluminoxane). The use of expensive MAO in excess has been a critical concern in commercial operation. Many efforts have been made to replace MAO with non-coordinating anions (e.g., [B(C6F5)4]-); however, most of such attempts were unsuccessful. Herein, an extremely active catalytic system that avoids the use of MAO is presented. The successive addition of two equivalent [H(OEt2)2]+[B(C6F5)4]- and one equivalent CrCl3(THF)3 to (acac)AlEt2 and subsequent treatment with a PNP ligand [CH3(CH2)16]2C(H)N(PPh2)2 (1) yielded a complex presumably formulated as [1-CrAl(acac)Cl3(THF)]2+[B(C6F5)4]-2, which exhibited high activity when combined with iBu3Al (1120 Kg/g-Cr/h; ~4 times that of the original Sasol systemcomposed of Cr(acac)3, iPrN(PPh2)2, and MAO). Via the introduction of bulky trialkylsilyl substituents such as –SiMe3, –Si(nBu)3, or –SiMe2(CH2)7CH3 at the para-position of phenyl groups in 1(i.e., by using [CH3(CH2)16]2C(H)N[P(C6H4-p-SiR3)2]2 instead of 1), the activities were dramatically improved, i.e., tripled (2960–3340 Kg/g-Cr/h; more than 10 times that of the original Sasol system). The generation of significantly less PE (<0.2 wt%) even at a high temperature is another advantage achieved by the introduction of bulky trialkylsilyl substituents. NMR studies and DFT calculations suggest that increase of the steric bulkiness on the alkyl-N and P-aryl moieties restrict the free rotation around (alkyl)N–P(aryl) bonds, which may cause the generation of more robust active species in higher proportion, leading to extremely high activity along with the generation of a smaller amount of PE.
more목차
Abstract....................................................................................................................I
1. Introduction ........................................................................................................1
2. Results and Discussion........................................................................................3
2.1Activity versus Catalyst Composition........................................................3
2.2Catalytic System of [1-CrAlCl4]2+[B(C6F5)4]-2/R3Al.................................5
2.3Catalytic System of [1-CrAlCl3X]2+[B(C6F5)4]-2/R3Al..............................9
2.4Derivatives of PNP Ligand........................................................................11
2.5NMR Studies and DFT Calculations........................................................16
3. Conclusions ....................................................................................................... 23
4. Experimental Section ....................................................................................... 24
4.1 General remarks.........................................................................................24
4.2Synthesis of ligands and complexes...........................................................25
4.3Ethylene oligomerization (entry 11 in Table 3)........................................28
5. Acknowledgements.............................................................................................29
6. Reference ............................................................................................................30
7. Supporting information .....................................................................................33
