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The FT reaction is a key technology for producing second-generation biofuels from agricultural waste. Because it takes one tonne of biomass to produce one barrel of liquid fuel, small-scale Fischer-Tropsch reactors are being developed to convert the waste on a distributed basis locally rather than at large collection centres. Microchannel reactors are potentially the best candidates for this job because they enable more efficient and precise temperature control, leading to higher throughput and conversion. They are also able to dissipate the heat produced from the FT reaction more quickly than conventional systems. But to work efficiently, microchannel reactors require an FT catalyst with a high level of activity in order to boost the conversion rates to an economic level. The new FT catalyst developed by Oxford Catalysts fits this bill exactly. Following several thousands of hours of rigorous testing, Oxford Catalysts has signed a memorandum of understanding (MOU) with a leading developer of small scale FT microchannel reactors to deploy the new catalyst in small-scale FT applications, including the conversion of bio-waste or flare gas into liquid fuels. Derek Atkinson, Business Development Director, Oxford Catalysts says: "We have spent 12 months working on developing this particular catalyst, using our state-of-the-art equipment and our patented OMX method, and are very pleased with the results. The next stage will involve working closely with a catalyst producer to supply tonnage quantities for use in demonstration units. "
Background Information: Microchannel reactors Microchannel reactors are compact FT reactors that have channels with diameters in the millimetre range. The small diameter channels dissipate heat more quickly than conventional reactors with larger channel diameters in the 20-30 mm (i.e. inch) range so more active catalysts can be used. As a result microchannel reactors exhibit conversion efficiencies in the range of 70% per pass. Microchannel reactors are designed for economical production on a small scale. A single microchannel reactor block might produce up to 50 barrels (bbls) of liquid fuel/day. Conventional FT plants, in contrast, are designed to work at minimum capacities of 2,000 bbls/day, and function well and economically at capacities of 30,000 bbls/day or higher. They exhibit conversion efficiencies in the range of 50% or less per pass. The OMX method The level of catalyst activity is related to the surface area of the catalyst. This, in turn, is related to crystal size, so producing catalysts with the optimal crystal size for a given application is a key goal for catalyst developers. The big challenge lies in achieving the right balance between catalyst activity and stability. If the crystal size is too large, the catalyst activity – and hence, conversion rates – will be reduced. If too small, the catalyst becomes unstable. The aim is always to produce a catalyst crystal size that is not too big, not too small, but just right. Oxford Catalysts' patented OMX technology makes it possible to produce catalysts with higher metal loadings, which still maintaining small crystal sizes. The OMX method combines the metal salt and an organic component to make a complex that effectively stabilises the metal. On calcination, combustion occurs that fixes the crystallites at this very small size. Since the calcination is quick, the metal crystallites do not have time to grow, and hence remain in the ideal size for catalytic reactions. Compared to conventional catalyst production methods, such as Incipient Wetness Impregnation (IWI), OMX produces a narrower particle size distribution of crystallites in the 8-15 nanometre diameter range which exhibit terraced surfaces. These are both features that enhance catalyst activity. OMX also produces fewer very small crystallites that could sinter at an early stage of operation. This results in greater catalyst stability. Oxford Catalysts Oxford Catalysts Group PLC designs and develops specialty catalysts for the generation of clean fuels from both conventional fossil fuels and certain renewable sources such as biomass. Its patent-pending technology is the result of almost 20 years of research at the Wolfson Catalysis Centre at the University of Oxford, headed by Professor Malcolm Green. Oxford Catalysts was founded by Professor Green and Dr Tiancun Xiao in October 2004 and was admitted to trading on the AIM market of the London Stock Exchange on 26th April 2006, having raised £15m before expenses from a solid base of institutional investors. The company's strategy is to license its catalysts for commercial application by entering into co-development partnerships with leading manufacturers, producers and suppliers in the petroleum, petrochemicals, fuel cells, biogas, steam applications and catalysis markets. Oxford Catalysts has two key platform technologies. The first is based on a novel class of catalysts made from metal carbides. Aside from their lower cost, these catalysts offer a number of advantages. For example, in some reactions metal loadings can be reduced. In others, the need for precious metal promoters can be eliminated, while still retaining or even exceeding the benefits of traditional catalysts. Applications of these metal-carbide catalysts include hydroprocessing and the conversion of natural gas, biogas or coal into sulphur-free diesel. The second involves catalysts that can be used to produce steam at temperatures between 100ºC and 800ºC instantaneously starting from room temperature, from a liquid fuel containing dilute hydrogen peroxide and either an alcohol, sugar, glycerol, starch or formic acid. Such Instant Steam could have important applications in a broad range of markets, from cleaning and disinfecting, to green energy in the form of motive power or electricity.
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