Synthesis of lower olefins from methanol and subsequent conversion of ethylene to higher olefins via oligomerisation

• Published in: Journal of molecular catalysis. A, Chemical Chemical, 2004-12, Vol.223 (1), p.231-235
• Main Authors: Dutta, P., Roy, S.C., Nandi, L.N., Samuel, P., Pillai, S. Muthukumaru, Bhat, B.D., Ravindranathan, M.
• Format: Article
• Language: English
• Subjects: Catalysis; Chemistry; Exact sciences and technology; General and physical chemistry; Heteropolyacids; Ion-exchange; Methanol; Olefins; Oligomerization; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Zeolites: preparations and properties; ZSM-5
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2003.11.043

Catalytic conversion of methanol to hydrocarbons with the special emphasis on lower olefins (ethylene and propylene) was carried out using 12-heteropoly acids of W and Mo and P or Si and salts of 12-heteropoly acids. Amongst the metal salts of tungstophosphoric acid, cesium salt exhibited better activity and selectivity for the formation of ethylene and propylene. The maximum selectivity for C 2–C 4 olefins was 60.7%. Physico-chemical characterization of the catalysts has been made by FTIR spectroscopy, XRD, DTA, acidity by n-butyl amine titration and surface area. Acidity and surface area of the catalysts influence the activity and selectivity for the olefins. Oligomerization of ethylene to higher olefins was carried out in liquid phase using TiCl 4–Et 3Al 2Cl 3, TiCl 4–Et 2AlCl, TiCl 4–Et 3Al and Ti(OBu) 4–Et 3Al 2Cl 3 catalyst systems. Among the catalysts tried, TiCl 4 and Ti(OBu) 4 based catalysts showed better activity and selectivity to alpha olefins in the range C 4–C 14. For vapour phase, HZSM-5, nickel salt supported on SAPO-5 molecular sieve, ZSM-5 and γ-alumina, heteropoly acid supported on ZSM-5 and potassium salt of tungstophosphoric acid were tested. The maximum selectivity of C 4–C 6 olefins was 10.0 wt.% with HZSM-5 catalyst with a Si/Al ratio of 100. The selectivity for higher olefins was less than that obtained by liquid phase oligomerization of ethylene. Tungstophosphoric acid and Cesium salt exhibit activity for conversion of methanol to lower olefins like ethylene and propylene. In liquid phase TiCl 4 and Ti(OBu) 4 based systems are good oligomerization catalysts of ethylene to give C 4–C 14 alpha olefins. On the other hand in vapour phase HZSM-5, Ni-SAPO-5 produce C 4–C 6 saturates and olefins from ethylene. ▪