It's almost impossible to think plastic without also thinking fossil fuels. Because plastic is made from oil, from which we extract, among other things, carbon—an essential ingredient in plastic. Around 5-6 per cent of all crude oil pumped up from the ground currently goes towards making various plastic products.
But it doesn't have to be that way in the future. With new technology, biomass can be used as an alternative to fossil raw materials for plastic production. By replacing crude oil with biomass, we can achieve significant reductions in the carbon emissions associated with the production of plastic.
Together with DTU, Danish company Topsoe, which supplies technology for the green transition of chemical and fuel production etc., is developing a biomass-based method for producing one of the components used in the production of PET plastic. It is one of the most widely used plastics, used for example to make bottles for soft drinks and other forms of food packaging as well as polyester fibres for clothing and blankets.
"The aim is to convert sugar into ethylene glycol, which is one of the building blocks for making PET plastic," explains Esben Taarning, R&D Director, Sustainable Chemicals, at Topsoe.
Two-step process
The idea of converting sugar into ethylene glycol is not new. However, the technology is not terribly efficient and cannot compete with production based on crude oil.
"With this method, you lose a lot of the carbon along the way. The aim of our project is to retain as much as possible of the carbon contained in the sugar and transfer it to the ethylene glycol molecule. In this way, we can increase the yield derived from the sugar," explains Esben Taarning.
The Topsoe-developed process involves two steps. First, an aqueous sugar solution is heated in a reactor. The heating from room temperature to 500-600 degrees results in sugar cracking—the decomposition of sugar molecules into smaller molecules. The main product resulting from sugar cracking is glycolaldehyde. During the second step of hydrogenation, hydrogen is added, leading to the formation of ethylene glycol, an important raw material in the production of plastic.
According to Esben Taarning, the first part of the process—the breaking-down of the sugar molecules into smaller parts—is the groundbreaking achievement. And this is precisely the process step DTU Chemical Engineering has participated in. Professor Anker Degn Jensen has been involved from the very beginning in 2017.
"Initially, DTU helped develop the technology to a scalable level. The goal was to progress from a laboratory-scale reactor to a reactor measuring one metre in diameter and with a capacity of several hundred thousand tonnes of sugar a year," says Anker Degn Jensen.
