| Popis: |
The catalysis of the polymerisation and/or isomerisation of C 4 , C 5 , and C 6 α-methyl mono-olefins on some commercial carbon blacks has been studied. Catalysis was observed only after the blacks had been heated at 100 to 115°C in vacuum for 20 to 40 hr. When 2. l g of an oxidised channel black (Black Pearls 2) was held at 120°C in an atmosphere of isobutene, 5.2 g of clear liquid oligomers collected in a cooled side arm in about 4 days. The predominant oligomers were dimers, and more than 90 per cent of the dimeric fraction was 2,4,4,-trimethyl-1-pentene. Under similar conditions 2-methyl--butene produced a dimeric fraction containing at least eleven C 10 isomers; however, the isomerisation to 2-methyl-2-butene was more rapid than the polymerisation. At lower temperatures (40–60°C) the rate of polymerisation of 2-methyl-1-pentene in a slurry with carbon blacks is negligible compared to the rate of isomerisation to 2-methyl-2-pentene. Reversible first order kinetics, with respect to olefin, were found for this isomerisation. The rate constants at 52.5°C for four carbon blacks have been compared for slurries having the same ratio of olefin to black by weight. For these blacks the rate constants increase with the acidities. A thermochemical titration apparatus, designed for non-aqueous solvents, was built and used for the determination of acidities. |
