Researchers working with Chinese chemical supplier Naco recently reported progress in the development of low-viscosity polyalphaolefins, generated from coal, that could be used in the formulation of automotive engine oils.
Naco is one of several domestic companies that produce PAOs. According to process uses feedstock from a coal-to-liquids plant. Until now, the PAOs produced by all of these companies have been high-viscosity fluids, in the range of 25 to 100 centiStokes. Heavy PAOs are used mostly as viscosity-modifying additives in lubricant formulations.
During a presentation at the Annual Meeting and Exhibition of the Society of Tribologists and Lubrication Engineers in Las Vegas, Nevada, United States, in May, Jiushen Li, deputy director of the Advanced Lubricating Materials Laboratory at the Shanghai Advanced Research Institute said SARI, in cooperation with Luan Group, managed to produce low-vis PAOs by employing metallocene catalysts. Luan Group is one of Chinas largest coal producers and supplies the CTL feedstock used to make PAOs at Nacos plant in Shanxi province.
Li said researchers made three cuts of PAO - 4 cSt, 5.9 cSt and 8 cSt. He added that they showed favorable physical properties. Viscosity index ranged from 136 for the 4 cSt fluid to 159 for the 8 cSt fluid. Cold cranking simulator scores, measured at minus 35 degrees C, were 1,095 centiPoise for the 4 cSt fluid, 2,615 cP for the 6 cSt and 5,336 cP for the 8 cSt fluid. Noack volatility scores were 12.1 percent, 6.9 percent and 3.9 percent, respectively.
Li noted that these results for relatively high viscosity index and excellent low-temperature fluidity (CCS data) showed strong potential for commercial applications such as engine oils.
Li also compared performance test data for several 8 cSt mPAOs: two α-olefins obtained from coal and separated by distillation; one oligomerized from ethylene; and a commercial PAO. The three new PAOs had higher VI (157 to 159) than the commercial PAO (138); higher flash points (284 degrees to 286 degrees versus 262 degrees), lower Noack volatilities (3.03 percent to 3.69 percent compared to 3.89 percent), and comparable pour points (minus 53 to minus 54 compared to minus 56 degrees).
Li concluded that new mPAO8s synthesized from α-olefins derived from coal showed strong potential for providing China with a new, completely domestic source of Group IV base stocks for high-quality lubricants. He added that commercial production of mPAOs may disrupt global industry by providing an alternative to petroleum feedstocks as well as diverting market share from traditional suppliers of PAOs.
The most important [thing] about this projectis finding a novel way for the application of α-olefin produced by CTL industry, and as we know, it can improve the economic performancesobviously, Li said during an interview. During the research process of this project, [my] favorite part is the preparation and adjustment of the catalyst system, we can getmany kinds ofPAO withdifferent viscosities through this adjustment. He added, The yield ratio, about 85 percent, of PAO as the polymerization products of α-olefin is higher than we supposed before.