In today’s increasingly eco-conscious world, there is a growing focus on sustainable manufacturing at every step of the process, from sourcing the raw materials to production, end use and eventual disposal. Consequently, companies worldwide are putting an emphasis on developing innovative green procedures, as they seek to establish more environmentally friendly, cleaner and safer industrial processes.
The epoxy propanol challenge
Epoxy propanol (EP), also known as glycidol, is an organic compound used in the manufacture of a range of products, such as detergents, industrial paints and coatings, and healthcare products. It is primarily manufactured in Japan and, to a much lesser degree, in the United States.
Traditionally, EP is produced by one of two methods: epoxidation of allyl alcohol with hydrogen peroxide, or the reaction of epichlorohydrin with a caustic agent. However, allyl alcohol is extremely toxic and epichlorohydrin is made from hydrocarbon feedstocks, such as propylene. Both methods generate toxic by-products, such as hydrochloric acid, requiring costly purification processes to prevent the acid residues entering the environment. Recognizing the need for a greener – but still economically viable – process, Green Lizard Technologies (GLT), a spin-out company from Queen's University Belfast, successfully developed a patented, safe and sustainable technology for the conversion of glycerol to EP and set up the first EP pilot production plant in Europe at the Wilton Centre in Redcar in 2018.
Glycerol is a waste product from the manufacture of biodiesel, a renewable fuel derived from natural vegetable oils and fats. The biodiesel industry has grown significantly as manufacturers strive to meet international biofuel targets; this has created a surplus of waste glycerol, which can require additional purification and result in the production of waste acids. The new method puts crude glycerol to good use as a biomass feedstock for EP production and has been successfully scaled up.
The patented production process involves the reaction of carbon dioxide with methanol to produce dimethyl carbonate (DMC), which can then be used in combination with glycerol to produce an important chemical intermediate of industrial interest – glycerol carbonate. This, in turn, is converted to EP. As the waste glycerol does not require any significant purification prior to combination with DMC, the economics are improved, and waste streams minimized.
The fast track to success
The development of this completely green route to glycerol carbonate and EP – from 5 g bench-scale production in the laboratory to pilot scale – took less than two years, enabling semi-commercial production of both compounds. Currently, the aim is to produce around 500 tonnes of EP per annum and move quickly to increase this capacity to 10,000 tonnes a year as additional customers are identified. With costs around 30 % less than traditional methods, the process is generating considerable interest from the manufacturing industry, which could pave the way for further investment in a full-scale production plant in the future. In addition, there is a market for the DMC intermediate produced during the process, which has demonstrated success as a diesel additive and marine diesel fuel. This is helping to eliminate the diesel soot particles identified as the cause of many of today’s health and environmental issues, without the need for engine modifications. The production cost is similar to conventional diesel at $60 per barrel.
From cooking oil to biodiesel and oleochemicals
EP production is just one area of interest in green manufacturing. Amid a growing need for non-fossil, environmentally friendly fuels, attention has turned to the conversion of waste cooking oils into low sulfur biodiesel, transferring technology developed on a small scale in the laboratory to pre-production operation. Waste cooking oil is rich in free fatty acids, which are difficult to remove and limit the potential for reuse. Displacing the fatty acids from the oil into an aqueous phase makes separation straightforward, enabling them to be isolated for further processing. Once removed, the oil phase can be converted into a feedstock for commercial use in the production of low sulfur biodiesel. Complementary to biodiesel, a range of oleochemicals – chemicals derived from plants or animal fats – and intermediates are co-produced, which are commonly used in surfactants, soaps, healthcare products and detergents. From initially treating 300 liters of waste cooking oil, the aim now is to scale up to a 10,000-liter capacity plant.
A greener future beckons
Sustainable manufacturing is ever-more important, with a global need to develop novel, greener processes that are more environmentally friendly, cleaner and safer than those currently in use. Since establishing the EP plant, the company has worked with industrial partners to scale up innovative green processes for the production of a variety of compounds – including surfactants, industrial paints and coatings, biodiesel and specialty chemicals – to help develop commercial ventures. By thinking outside the box, it has shown that it is possible for waste materials – such as glycerol and used cooking oils – to become a resource for other applications, rather than a problem to overcome.
Dr Martin Atkins is CEO of Green Lizard Technologies