H2 effect in Chevron–Phillips ethylene trimerization catalytic system: an experimental and theoretical investigation

• DOI: 10.1007/s00289-017-2228-3
• Publication Date: 2017-11-08T00:18:17Z
• Authors: Naeimeh Bahri-Laleh; Majid Karimi; Zahra Kalantari; Mehrdad Fallah; Ahad Hanifpour; Mehdi Nekoomanesh...
• Keywords: 7. Clean energy; 01 natural sciences; 0104 chemical sciences

Effect of H2 amount on the activity and selectivity of Chevron–Phillips trimerization system, i.e., chromium(III) tris(2-ethylhexanoate)/2,5-dimethylpyrrole/triethylaluminum (TEA)/tetrachloroethane (TCE), was examined. In this regard, in addition to catalytic ingredients and ethylene monomer, 2.5 and 5 bar H2 were utilized in the oligomerization reactor and the reaction results were compared with those without H2. Results showed that addition of hydrogen has a remarkable effect on polymer formation and catalyst activity so that 147% decrease in polymer formation and 38% increase in activity were observed upon addition of 5 bar H2. However, its effect on 1-hexene selectivity was not pronounced. Then, molecular modeling with DFT method was employed to simulate oligomerization process in molecular level. Energy results revealed that formation of 1-hexene has less energy barrier than the formation of 1-butene and 1-octene which confirms higher selectivity of Chevron–Phillips system toward 1-hexene formation. Furthermore, interaction of hydrogen with catalytic active center was studied via hydrogenolysis of metalacycles. Energy results revealed that it is energetically a facile process so that the bigger the circle, the easier hydrogenolysis.