A new Fischer-Tropsch microreactor could convert agricultural waste into biofuel at small local plants

A new Fischer-Tropsch catalyst could offer the potential for agricultural waste to be turned into biofuel at small local plants, avoiding high transport costs to large waste collection centres. The cobalt hydride catalyst, developed by Oxford Catalysts, UK, is designed for use in small-scale Fischer-Tropsch (FT) microchannel reactors, which convert syngas - carbon monoxide and hydrogen - into biofuel.

Second generation biofuel production is seen as a sustainable alternative to growing fuel crops, but has the drawback that it takes one tonne of waste to produce one barrel of liquid fuel, explains Derek Atkinson, business development director, Oxford Catalysts. This means that biomass plants can’t compete for scale with gas-to-liquid plants such as Shell’s FT plant in Qatar, which produces 140 000 tonnes of liquid fuel per day from natural gas.

’To make biomass-to-liquid conversion more attractive needs more active and process intensified technology,’ he adds. Microchannel reactors could be the answer - their millimetre-wide channels rapidly dissipate the large amounts of heat produced by the FT reaction so that very active catalysts can be used.

New kind of reactor

’The microchannel reactor is a new kind of reactor never applied before in industry,’ says Giuseppe Bellussi, a catalysis expert at Italian energy firm Eni. ’In principle it should allow a better heat transfer and catalyst efficiency, because of the small particle size. But the fluid dynamics could be unfavourable, including through partial pore blocking.’ Bulk carbide catalysts have never before been used in industry, adds Bellussi.

The new FT catalyst is manufactured using Oxford Catalyst’s patented organic matrix combustion (OMX) technology, which the company claims gives high metal loadings and small catalyst crystal sizes. OMX combines the metal salt with an organic component to make a complex that stabilises the metal. The complex is heated to high temperatures until combustion takes over and fixes the very small crystals. The heating stage is so rapid that the metal crystallites do not have time to grow. 

Oxford Catalysts has tested the catalyst’s performance over a period of months, but doesn’t yet know its ultimate lifetime. ’Performance dropped only slightly in our tests - a decay of fractions of one per cent,’ reveals Atkinson. Replacing catalysts in the microchannel reactors would be extremely expensive.

Oxford Catalysts has signed a memorandum of understanding with a company that develops FT microchannel reactors to use the new catalyst in small-scale FT applications, including the conversion of biowaste into liquid fuel. It is also working with a catalyst manufacturer to scale up production. 

Oxford Catalysts is also looking to broaden the appeal of FT and has a concept for an integrated approach to treating municipal solid waste, which links together waste treatment processes and incorporates a small-scale FT plant. The company is trying to build a consortium to work on its concept and is seeking EU funding. 

Emma Davies

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