Researchers from Stellenbosch University, Western Cape, South Africa have developed a method of depolymerizing phenolic polymers to convert waste pulp into a new feedstock for the chemical industry. The researchers are Helen Pfukwa, Ndumiso Sibanda and Harald Pasch.
The technology converts lignin to low molar mass value-added compounds. It is mild and selective and produces functionalized aromatic compounds that are valuable building blocks in the chemical and polymer industries.
The chemical and polymer manufacturing industries rely heavily on the extraction of raw materials from non-renewable fossil fuels such as petroleum and coal. The use of these feedstocks is not sustainable because the supplies are dwindling and their extraction as well as conversion to desired functionalized chemicals has negative environmental effects.
Lignin, a constituent of lignocellulosic biomass, is an appealing alternative because it is the most abundant aromatic functionalized polymer, and more importantly, it is not in competition with societal needs.
Using suitable and selective technologies such as oxidative depolymerzation, lignin can be converted to useful chemicals which have aromatic functionality (the starting materials for a wide range of consumer products). Generally, polymers that have been synthesized from lignin-derived monomers and their derivatives have high Tg’s (glass transition temperatures) and thermal stabilities, as well as good mechanical properties, which make them appealing replacements for fossil-fuel derived styrene in the synthesis of high temperature-resistant plastics, advanced composites and resins.
The South African pulping industry produces millions of tonnes of waste lignin every year. A large portion of this lignin goes into the supply of energy. While the use of biofuel from waste lignin is extremely beneficial in reducing the pulping plant’s dependence on the national electrical grid, there are significant benefits that come with using waste lignin as a source of chemicals. With our society, facing challenges related to crude oil depletion and waste accumulation. It is important to investigate how waste that is being produced by various industries can be used as a potential replacement feedstock for crude oil.
The innovation is important for a green future as it presents a way of converting what would have been regarded as a waste product, to value added aromatic compounds that can be used in the chemical and/or polymer manufacturing industries. In essence, the value chain of lignin, which is produced as a waste product in one industry, is extended by using it as a feedstock for another. This promotes sustainable development.
We have filed for a patent in South Africa (2019/02602) and in the near future, plan to protect their technology internationally by filing an international patent application under the Patent Cooperation Treaty (PCT).
To encourage further research and innovation for economic benefit. Intellectual property (IP) protection offers and incentive to inventors and creators of innovative solutions to continuously innovate for societal impact. Improvements that make innovations look better or function better, help licensees and firms gain a competitive advantage in the market place by excluding those who are not authorized to commercially exploit the protected IP.
Lignin is a very complex macromolecule with a unique structure, which depends on the source and pre-treatment procedure. The β-ether linkage (β-O-4) constitutes about 40–60 percent of all linkages which means that most mild oxidative techniques that would target these bonds specifically and yield carbonyl or carboxyl functionalised compounds, does not lead to the complete conversion of lignin. It is also important, we have found, to effectively control the depolymerisation conditions to prevent over oxidation which may lead to structures that are even more complex than the starting lignin itself.
A green future in the chemical industry can be supported if governments make and enforce policies that encourage the chemical and material manufacturing industries to include sustainable development in their long-term plans. This will subsequently encourage industries to change their focus to providing the same quality of products in a way that is environmentally sustainable, including the efficient utilization of renewable feedstocks. New opportunities for collaborative research between industry and academia should be incorporated to enable this. Incentives mechanisms for consumers and industries that adopt these measures should be embedded in science, technology and innovation policies.
We are in the process of trying to commercialize the technology. We have approached a local (South African based) pulp and paper manufacturing company who want us to apply the technology to the waste lignin (lignosulphonate) they are producing. The aim of this project is to assess the method’s efficiency on their lignosulphonate in terms of the types of products that would be formed and their quantities.
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