Selective trimerization of ethylene using chromium catalysts complexed with tridentate ligands supported on titanium modified silica

Alpha-olefins like 1-hexene play a crucial role in petrochemical industries. This study investigates the development of chromium-based catalysts featuring tridentate ligands for selective 1-hexene production via ethylene trimerization under optimized conditions: 80 °C, 25 bar ethylene, 40 mL anhydrous toluene, and MMAO (Al/Cr = 700/1) as the co-catalyst. Both homogeneous catalysts (Cr-SNS-D and Cr-SNS-B) and heterogeneous catalysts supported on SBA-15, including titanium-modified SBA-15 (Ti-SBA-15), were examined. The homogeneous catalysts exhibited remarkable selectivity (99.9%) and high catalytic activity, reaching 60,772 and 53,344 g 1-C₆ g Cr⁻¹ h⁻¹, respectively. Upon immobilization onto SBA-15 supports, a slight reduction in activity was observed; however, the introduction of titanium into the SBA-15 framework led to a 1.5-fold enhancement in catalytic performance (35,115 g 1-C₆ g Cr⁻¹ h⁻¹) and a significant reduction in polyethylene by-product formation. This study highlights the critical influence of support modification on catalytic behavior, demonstrating how tailored electronic interactions between the active sites and the support can optimize performance. The findings provide a valuable framework for designing more efficient chromium-based catalysts, bridging the gap between homogeneous and heterogeneous systems for improved 1-hexene production.