Abstract: A method to measure the quantity of olefin species in a complex hydrocarbon mixture by means of comprehensive multi-dimensional gas chromatography, involves passing a sample of a hydrocarbon mixture through a first capillary column comprising a dimethyl-polysiloxane stationary phase, subjecting the sample to a thermal modulation before entering a second column comprising a 50% phenyl, equivalent, polysilphenylene-siloxane stationary phase, wherein the introduction bandwidth into the second column is smaller than 20 milliseconds.

Abstract: Metallocene compounds having the general formula (I): R1 are hydrocarbon groups, R2 are hydrogen or hydrocarbon groups; M is a transition metal of group 3, 4, 5, 6 or to the lanthanide or actinide groups in the Periodic Table; M′ is a transition metal selected from those belonging to group 3 or to the lanthanide or actinide groups in the Periodic Table; X is a monoanionic ligand; p is an integer of from 0 to 3, being equal to the oxidation state of M minus two; q is an integer from 3 to 5; and n is an integer from 1 to 4, when the six-membered rings of formula (Ia) are not perhydrated, and is an integer of from 0 to 4, when the six-membered rings of formula (Ia) are perhydrated as well as in the compound of formula (Ib).