What is the connection between a Christmas tree, chewing gum, used frying oil and 14 flashlight batteries? Answer: together with some other commonly used items, this incongruous recipe can be turned into a liter of automotive-quality engine oil—not formally analyzed for a specification but approximating to an SAE 0w20 by Nexcel, a BP innovation business.

Sharply focused on recycling used oil via its self-contained, sealed-cell system, the company has completed a technology demonstrator program (not for production but it is understood the results are expected to contribute to improved molecular efficiency in production) to show what can be achieved by using some unlikely ingredients to create a lubricant from recycled resources. 

The aim is to highlight the value in items considered to be waste that can be linked to deliver useful raw materials, said Marc Payne, Nexcel’s formulation manager, who got the idea when he was redecorating a home bathroom.

“I was using a commercially-available product containing acidic organophosphates to depolymerize and remove silicone sealant in my shower, when I noticed that the resultant action gave an oily residue. This oily substance was a silicone oil similar to those used as anti-foam agents in lubricants.” This discovery triggered thoughts about other materials and inspired the preparation of a “recipe” to create oil from wholly recycled common-use materials. But one item in particular was proving a problem: identifying a suitable source of recycled materials to yield an anti-oxidant—essential because oxidation in engine oil increases viscosity, produces unwanted acids and results in corrosion of metal parts and sludge in the sump. 

The difficult one 
“This was the difficult one,” admitted Payne. “I needed hindered phenols or aromatic amines as an anti-oxidant and consulted specialists at the knowledge-based business Concept Life Sciences (CLS) who said that spruce trees were a good source of phenolic compounds. The month was December, when spruce Christmas trees were on sale and plentiful, so CLS chipped up one, extracted some phenolics and converted them to aromatic amines for use as anti-oxidants.”

The project then could proceed with all the necessary ingredients mustered—and so began a “cooking time” of about four months.  

This is Payne’s detailed ingredients’ list and chemistry lesson: 

• Viscosity modifier: extracted from used engine oil via preparatory dialysis. 
• Anti-foam: derived from discarded cured silicone sealant broken down via acid hydrolysis to a silicone oil. 
• Pour-point depressant: derived from used cooking oil fatty acids grafted onto a methacrylate and polymerized. 
• Detergent: derived from used cooking oil converted to a phenate detergent and then over-based (CaO + CO2) to produce a calcium based detergent system. 
• Anti-wear: zinc oxide extracted from used alkaline batteries and converted to ZDDP (zinc dialkyldithiophosphates) via the standard synthetic route. 
• Dispersant: derived from used chewing gum (180 pellets); PIB (polyisobutyleme) gum base radically cracked to about the correct chain length, reacted with maleic anhydride then subsequently reacted with a polyamine. 
• Anti-oxidant: derived from phenols extracted from discarded Christmas trees (spruce) and converted to an aminic anti-oxidant. 
• Base oil: derived from a distilled and hydro-treated used engine oil. 

Zero-waste goal 
John-Ward-Zinski, Nexcel sustainability director, said of the result: “The project shows the sustainability of waste. This was a hugely demanding project, particularly regarding yielding of phenols and catechols for antioxidants—and one which we hope will open the public’s eyes to the importance of recycling and sustainability.” 

The project team worked to a zero-waste goal, with trial-and-error a necessity as they moved into experimental territory. 

Ward-Zinski said re-refinement of used oil can create a high-quality product when blended with new additives, but added that bulk feedstocks made up of many different types of used oils can complicate the process and reduce the process yield.

“Nexcel’s oil management system avoids this by segregating used engine oil, keeping it in the cell during collection,” said. “For this particular project we wanted to make the entire oil from waste materials and the challenge lay in the creation of the chemical additives. However, with creative utilization of modern technology, there is huge potential in recycling.”