## 1 Introduction  
In the search of green lubricant, vegetable oil and glycerol were considered as the replacement for traditional mineral oil. Vegetable oil and glycerol are both environmental friendly lubricants, however, the thermal stability and flow properties of glycerol are better than vegetable oil. Glycerol based oil has been used as industrial lubricant, for example, the lubricant branded biolube GLY produced by Molyub of Germany is used in food processing machinery. The glycerol product branded Glycerin of P&G Co. (Cincinnati, OH, USA) is also used as a lubricant in the manufacturing of paper. A glycerol based solution for use as a lubricant for plug valves was reported in March's [1] patent. In their invention, 78 wt %-89 wt % of glycerol was used as the base oil and has the effect of preventing the corrosion of underlying metal. [PERSON]'s invention [2] of glycerol triether compounds were excellent lubricants for dissolution in internal combustion engine fuels, especially spark ignition engine fuels. [PERSON] [3] formulated a lubricant that consists of glycerol, water, carboxymethyl cellulose, and sodium polyphosphate. The lubricant is used as a transport chain lubricant for the food industry, steel industry, and car industry. In recent years, researchers have pointed out the numerous advantages of adding nanoparticles to lubricant oil. With its miniscule size, nanoparticles can easily mix with the lubricant oil to enhance its lubricating properties. The nanoparticles added to the lubricant oil help in preventingcorrosion, reducing friction, and modifying the viscosity of the oil. Numerous articles have shown the effectiveness of adding nanoparticles to lubricants. [PERSON] et al. [4] compared the influence of two kinds of nanoparticles as additives on GL-4 fully-formulated oil and poly-alpha olefin 8 base oil. Their experimental results showed that CuO additives had better effects on tribological behavior than Al\({}_{2}\)O\({}_{3}\) nanoparticles in two types of synthetic oils. With 2 wt % CuO concentration dispersed in PAO 8, the wear scar diameter reduced by 14% and the coefficient of friction reduced by 18%. Research studies [5; 6] tested the tribological behavior of ZnO/Al\({}_{2}\)O\({}_{3}\) composite nanoparticles as additives to the lubricant. Their results showed that when added to lubricant the composite nanoparticles reduced friction and wear better than pure ZnO and Al\({}_{2}\)O\({}_{3}\). [PERSON] et al. [7] synthesized and modified the surface of TiO\({}_{2}\) nanoparticles with a double-coated agent. The concentration of nanoparticles ranged from 0.1 wt % to 1.6 wt % in a water-based medium. Their experimental results showed that the TiO\({}_{2}\)-modified nanoparticles could increase the applicable load, reduce the friction force, and increase the anti-wear capacity of pure water. [PERSON] et al. [8] added 25 nm TiO\({}_{2}\) nanoparticles into a base oil. Their experiments using lubricant with 0.01 wt % TiO\({}_{2}\) nanoparticle additives showed significant reduction in coefficient of friction (COF) and wear rate in comparison to using a pure base oil lubricant. [PERSON] et al. [9] investigated the tribology behavior of Pegasus 1005 oil with carbon nano-horns, TiO\({}_{2}\), and Cu nanoparticle additives. Their results showed that the friction reduction of engine oil containing Cu nanoparticles of 130 nm was more effective than the engine oil containing 50 nm nanoparticles. The COF of carbon nano-horns additives decreased by 12% when compared with raw oil, while the effect on the coefficient of friction with TiO\({}_{2}\) nanoparticles was negligible. [PERSON] et al. [10] synthesized copper nanoparticles and added them into paraffin oil to investigate their tribological performance. Their results showed that Cu nanoparticles of size 2-5 nm, when modified with oleic acid and oleylamine, reduced the COF of steel pair and displayed excellent thermal stability.