Development of a green process for poly-alpha-olefin based lubricants

Poly-alpha-olefin ( PAO) based lubricants have a large share of the synlubes market and these are produced in two stages-oligomerisation of alpha-olefins and hydrogenation. The current industrial processes use AlCl(3) and BF(3) as catalysts for oligomerisation, which are polluting, hazardous and give a very wide molecular weight distribution. This study reports a green synthesis of a PAO synlube by using 1-decene as the starting material with a variety of solid acidic catalysts, mainly based on clays. The activities for oligomerisation were found to be in the following order: K10 montmorillonite clay > 20% w/w ZnCl(2)/K10 > 5% w/ w (dodecatungstophosphoric acid, DTP)/ K10 > 20% DTP/ K10 > 10% AlCl(3) + 10% FeCl(3)/K10 > S-ZrO(2) > Al-pillared clay > DTP > 20% DTP/carbon. K10 clay gave a conversion of 1-decene of 73% but the selectivities towards the dimer and trimer were 88 and 12%, respectively. 20% ZnCl(2)/K10 led to a conversion of 68% with 100% dimer formation. The kinetics of reaction were established by using both K-10 and 20% ZnCl(2)/K10. Oligomerisation is controlled by intrinsic kinetics. The catalysts are reusable. Other olefins such as 1-octene and 1-dodecene were also oligomerized in the presence of 20% ZnCl(2)/K10. 1-Decene dimer was isolated and then in the next step hydrogenated by employing 20% w/ w Ni/SiO(2), 20% w/ w Ni-Cu (50: 50)/SiO(2) and a clay anchored bipyridine - montmorillonite-PdCl(2) complex as catalysts. Amongst these 20% w/ w Ni/SiO(2) was found to be the most active catalyst at 50 atm and 150 degreesC, whereas the anchored catalyst BM-Pd(II) was active at atmospheric pressure and 30 degreesC. Effects of various parameters were studied to arrive at a kinetic model with both the catalysts. The reactions are intrinsically kinetically controlled showing zero order in dimer concentration and first order in hydrogen partial pressure. 1-Decene based PAO with a viscosity of about 2 cSt has great many applications The hydrogenated product had a viscosity of 2.22 cSt which was found to be comparable with commercially available sample. High-speed spindle oil used in textile industry was also prepared and its performance tested.