Oligomerization of Hex-1-ene over Acidic Aluminosilicate Zeolites, MCM-41, and Silica-Alumina Co-gel Catalysts: A Comparative Study

Hex-1-ene in octane solvent was oligomerized in a down-flow tubular reactor holding a fixed catalyst bed at temperatures of 80–300°C and a pressure of 5 MPa. Ultrastable Y (US-Y), hydrogen beta, and MCM-22 zeolites, MCM-41, silica–alumina and silica–magnesia co-gels, and γ-alumina were evaluated as catalysts. The reaction products obtained are composed of hexene dimers and trimers, cracked products, C6alkanes, and isohexenes. The catalytic activity of the mesoporous silica–alumina co-gels and MCM-41 is very similar to that of beta, MCM-22, and US-Y zeolites. The oligomerization process occurs in the mesopores and on the exterior surfaces of the zeolite crystals. In the micropores of zeolite beta and US-Y, the hexenes undergo dimerization-cracking reactions generating isohexenes and cracked products. In MCM-22, having narrower micropores, these cracking reactions are suppressed. MCM-22, MCM-41, and silica–alumina co-gels lacking microporosity are the most selective hexene dimerization catalysts.