CHARACTERIZATION BY C-13 NMR-SPECTROSCOPY OF BASE OILS PRODUCED BY DIFFERENT PROCESSES

The hydrocarbon composition of base oils produced by different process es - hydrotreatment (hydrocracking and wax isomerization), solvent ref ining plus hydrofinishing, and severe hydrofinishing - were determined by C-13 n.m.r. spectroscopy. Structural parameters such as normal and iso-paraffin contents, average chain length and number of branching s ites were estimated by new equations derived after complete assignment of signals in the 5-21 ppm C-13 n.m.r. region. Quantitative differenc es in various types of branched structures among different categories of base oils were established. Relations between specific iso-paraffin ic structures responsible for very high viscosity index and low pour p oint are discussed in terms of mobility behaviour and spin-lattice rel axation time measurements. (C) 1997 Elsevier Science Ltd.