NEW MOLECULAR-SIEVE PROCESS FOR LUBE DEWAXING BY WAX ISOMERIZATION

Ultra-high viscosity index (UHVI) lube oils can be prepared from waxy feedstocks by isomerization over an intermediate-pore silicoaluminophosphate (SAPO) molecular sieve catalyst. In a comparison of SAPO-11 with other dewaxing catalysts, results for pure paraffins and wax feeds are used to gain understanding of the process chemistry. Pt on SAPO-11 exhibits both a high isomerization selectivity at high conversion and a low selectivity for multiply branched isomers. Pt-SAPO-11 also has a low selectivity for cyclics formation, which may contribute to its high catalytic stability. With n-C-16 feed, the catalyst exhibits a low degree of secondary hydrocracking, giving little C4-by-product. For a - 57-degreesC pour point 4-cSt oil prepared from wax, C-13 nuclear magnetic resonance (NMR) shows an average of about three methyl branches per molecule.