Fuel from biorenewable polyols: A new catalytic route

Limited fossil fuel resources, an expanding global population and a desire for improved living standards will require ever more efficient and environmentally friendly routes to our chemical feedstocks. The chemical industry faces the challenge of moving towards more benign reagents, eliminating toxic by-products and increasing efficiency from an ever decreasing set of natural resources, while also exploring renewable ones. One way to address all of these concerns is to develop efficient catalytic processes that convert low value waste streams into more useful and valuable chemical products.

An example of a process using a bio-renewable feedstock to partially replace a fossil source is biodiesel manufacture. This takes triglycerides and other fatty materials, derived from plant or animal sources, and reacts them with methanol. The methanol used is derived from nonsustainable fossil fuel resources. The process produces high quality biodiesel, together with glycerol as a waste product. Typically on a mass basis 10 tons of biodiesel produces 1 ton of glycerol as an undesired by-product. Waste glycerol is highly contaminated with sodium hydroxide and unconverted fats. Hence, presently the waste glycerol stream only has use as an inefficient low grade fuel, and represents a major environmental problem that keeps a brake on the future expansion of biodiesel production. There has been much research dedicated to finding commercially viable uses for waste glycerol, with a simple and efficient process for conversion to useful chemicals and fuels offering significant potential to deliver economic, environmental and societal impact.

This works seeks to build on one of our recent discoveries. We have identified that simple metal oxide catalysts (MgO and CeO2) are very effective for the synthesis of methanol and other industrially important intermediates from bio-renewable glycerol. This new green technology represents a potential paradigm shift in the manufacture of methanol. At present methanol is produced by a two-step process requiring large scale to achieve the necessary efficiency. Methanol is a major commodity chemical, and today over 50 Mt pa are produced globally. There is considerable potential in the development of a new one step process using green environmentally sound reaction conditions. Aqueous glycerol conversion into methanol and other chemicals, using mild reaction conditions, can be achieved, but a step change is required to broaden the scope of this chemistry and improve product yield. Importantly additional hydrogen is not required as water acts as a hydrogen transfer reagent. Furthermore, the process can operate using a crude glycerol stream directly from a biodiesel source, and the requirement for expensive purification circumvented.

We will combine experimental and theoretical studies in an integrated approach, to develop a detailed fundamental understanding of the new catalytic chemistry we have recently discovered. Theory has the potential to guide experimental studies and also deliver fundamental understanding of new catalysts and processes, but this approach is most effective when theory is embedded within an experimental programme with both strands working closely together. Achieving a detailed fundamental understanding of the chemistry will support development of improved catalysts and technology. The experimental approach will build on our experience and expertise of catalyst design. It will use a combination of steady-state and transient studies to evaluate catalyst performance and elucidate key steps in the reaction mechanism. Detailed catalyst characterisation, both ex situ and in situ, will provide essential information on catalyst structure and chemical properties. Once structure activity relationships are established, improved catalysts will be designed making use of our expertise in preparing catalysts with controlled composition, morphology and structure.

General Impact to society and industry
The efficient use of resources, as well as more environmentally friendly routes to our chemical feedstocks, is of great importance if society is to maintain living standards with ever increasing pressure on resources. Just as importantly, new processes must be environmentally friendly, with reduced ecological footprints. Catalytic processes deliver these aims, and do so with lower energy costs and reduced waste production when compared to noncatalytic processes. The chemistry proposed in this project offers further potential to achieve these aims, as it will convert a major waste stream from a bio-renewable source, into chemical products that can be used to substitute those derived from fossil fuels, creating clear economic impact. The project is supported by Greenergy, the UKs largest producer of biodiesel and fuel distributor, and the catalytic chemistry is of direct relevance to Greenergy's business, thus offering a potential partner for exploitation.

Further economic impact can be created as the catalysis business has an annual turnover of ~$16B and UK companies are major players in this market. Generation of new catalysts and processes, and enhanced fundamental understanding, will create a competitive advantage for companies looking to exploit these aspects. Critically, around 35-40% of the global GDP depends on catalytic processes, and hence the economic influence of a catalyst extends across a very wide range of business sectors. This can be exemplified, as it is estimated that for each USD spent on a catalyst it returns around 800 USD in products. Accordingly, new heterogeneous catalysts will create significant economic benefits to society at many levels.

The use of a biorenewable waste source to create useful chemicals and fuels has environmental impact. It removes the requirements for disposal of the waste stream by converting it into valuable compounds and also reduces the reliance on fossil fuel resources by introducing a closed carbon cycle that will support reduction of carbon dioxide emissions and associated global warming.

Impact is also expected through public engagement. Catalysis forms the basis of our extensive outreach activities, and the development of new green processes using a biorenewable source is an excellent topic to engage with the public. We regularly deliver outreach by interacting with schools and the wider public at exhibitions and events. Specific aspects of the modelling component of the project will target outreach activities to support structure and bonding in the school curriculum.