Synopsis by Wim Thielemans, Sep 15, 2011
Majano, G, E-P Ng, L Lakiss and S Mintova, 2011. Nanosized molecular sieves utilized as an environmentally friendly alternative to antioxidants for lubricant oils. Green Chemistry http://dx.doi.org/10.1039/c1gc15367f.
An environmentally-friendly, sieve-like nanomaterial can reduce the chemical fallout from the breakdown of lubricants better than the chemical additives now used.
Looking to solve an old problem in a new way, green chemists find that a special porous material can better reduce levels of dangerous breakdown byproducts in oil lubricants than the long-used but harmful chemicals now added. The team of researchers report their findings about the material – called zeolites – in a recent issue of Green Chemistry.
Lubricant oils reduce friction between moving parts in machines and motors in every part of society, including factory conveyor belts, cars and sewing machines. Synthetic mineral oils are used most often because they are more stable than other types. About 32 million tons of the lubricant oils leak and enter the environment every year.
To reduce human health impacts and meet new European regulatory standards, chemists are trying to find ways to make the oils both functional and environmentally benign.
One big problem with lubricants is they break down and form byproducts when exposed to oxygen – a process known as oxidation. Oxidation generates water, reactive alcohols and acids that increase corrosion and rust, thicken the lubricant, form sludge and sediment, break down the oil and create foam.
Chemical additives prevent or reduce the oxidative reactions. Unfortunately, most additives are dangerous and can impact human health and the environment. Some also affect the machine’s function, such as deactivating the catalyst converters in cars.
In this work, researchers from France, Belgium and Malaysia tested how a highly porous inorganic nanomaterial called zeolites absorb the initial oxidation products in an effort to reduce the harmful chemical byproducts that form. They did not try to stop oxidation like the current crop of chemical additives do. In theory, since oxidative reactions naturally speed up over time, removing the reaction products would reduce further oxidation, slow the process and create less harmful byproduct.
One of the three zeolites compared in the study worked surprisingly well. The researchers found the zeolite cleans up the process in two ways. First, it slowed the inherent oxidation reactions and reduced the amount of chemical byproduct produced. Second, it also absorbed the byproducts that formed. In the end, very little sludge was produced.
The zeolites used have no known adverse environmental effects and can even work together with existing oxidation-preventing chemical additives. The zeolites – when combined with perhaps a next generation of more benign additives – would then give added protection.
Future laboratory studies will need to test the performance of the numerous other zeolites available. From there, they must be tested and assessed in a real working environment. Even though this is not the final word on the technology, it looks to be very promising.
Read more science at Environmental Health News.