Synthesis of environment‐friendly, sustainable, and nontoxic bio‐lubricants: A critical review of advances and a path forward

Abstract

Carbon neutral biosources are sought for the protection of the environment and to meet the energy needs of the growing population. For instance, lubricants are required in huge quantities. Synthesis of environment-friendly, sustainable and non-toxic bio-lubricants from renewable and bio-degradable feedstocks such as vegetable oils and animal fats will be most desirable. The thermal stability and lower volatility of these triglycerides make them suitable as precursors for lubricants. This review briefly covers the chemical modifications required to transform plant-and animal-based triglycerides into efficient biolubricants. Chemical modifications are required to improve one or more physicochemical or tribological properties of bio-lubricants such as low-temperature flow properties or the oxidation stability of fatty acids/oils for different applications. The use of heterogeneous catalysts makes the processes clean. The relationship between their molecular structures, physicochemical properties and lubrication performance is reviewed. Additives such as antioxidants, sulfides, phosphates, metal and metal oxide nanoparticles, and ionic liquids are used to enhance the lubricant properties. With proper modifications in a base oil, support and additives, bio-lubricants can perform similar to or even better than conventional lubricants. A further advantage is that they can be easily adapted using existing infrastructure and lubricant formulations.

Synthesis of TMP esters as a biolubricant from canola oil via a two‐step transesterification–transesterification process

“…The reaction mixture was stirred at 1200 rpm and refluxed for the required reaction time. The effects of 4 reaction parameters were investigated by using the one-variable-at-a-time (OVAT) method: catalyst loading (0.25-1 wt.% of the vegetable oil mass), ethanolto-oil molar ratio (7)(8)(9)(10)(11)(12), reaction time (1.5-3.5 h), and reaction temperature (45-80 C).…”

“…[11] One of the most effective chemical modifications of vegetable oils, in order to produce complex esters, is the transesterification of vegetable oils (triglyceride) with methanol into methyl esters of fatty acids (FAMEs), followed by the transesterification of FAMEs with polyols such as trimethylolpropane (TMP), pentaerythritol (PET), and neopentyl glycol (NPG). [12][13][14][15] TMP is a colourless triol (three hydroxyl groups) with the formula of CH 3 CH 2 C(CH 2 OH) 3 , which is more economically attractive to produce complex esters on an industrial scale as it has a lower melting point than PET and NPG and is less expensive.…”

Recent advances in metal–organic frameworks for lubrication

“…Water, vegetable oils, animal fats, mineral oils, and synthetic oils (such as polyalphaolefin, referred to as PAO) are all used as lubricants in various contexts. [5][6][7] Lubricants reduce tribological problems in a variety of ways, such as overcoming sliding friction pair contact caused by severe or frequent metal-tometal interactions, forming low-shear and durable boundary friction optimized films at the interface, and so on. 8 Additives are an important part of lubricants.…”

The Enhancement of Overall Performance of Lubricating Grease by Adding Layered Double Hydroxides

“…Antioxidant is a key additive to protect lubricating oil from oxidative deterioration. At present, at least one antioxidant is added to industrial lubricating oil to improve its oxidation stability or enhance other properties, so as to meet the harsh requirements of lubricating oil in automotive, precision bearings, construction machinery, and other industrial fields [7,8]. Nowadays, countries around the world pay more and more attention to environmental protection and green development, and green chemical industry has become the trend in global chemical industry development.…”