SELECTIVE HYDROISOMERIZATION OF LONG-CHAIN NORMAL-PARAFFINS

The removal of long chain normal paraffins from lubricating oils is essential to produce an oil with acceptable cold flow properties. Conventional lubricant dewaxing processes remove these normal paraffins by selective cracking or crystallization mechanisms, resulting in a yield loss directly proportional to the concentration of the normal paraffins in the oil. More recent lubricant dewaxing processes attempt to isomerize the normal paraffins to isoparaffins, allowing them to remain in the oil and produce a higher quality oil in higher yield. The work reported here is a study of the effect of zeolite type and acidity on the selective isomerization of the long chain normal paraffins typically found in lubricating oils. Catalysts containing beta, USY, SDUSY, mordenite, ZSM-5 and SAPO-11 are tested for their ability to isomerize neat hexadecane and a 50:50 mixture of hexadecane and tetramethylpentadecane. Beta, SAPO-11 and ZSM-5 are also tested with a refined wax distillate lubricating oil which contains 15% normal paraffins. In summary, these results show that SAPO-11 was the only catalyst tested which was capable of isomerizing normal paraffins in the presence of isoparaffins without large yield losses due to unwanted cracking.