C&I Liquid Fuel


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C&I Liquid Fuel

  1. 1. Catalysis Liquid fuel revival Catalytic synthesis of liquid fuel from solids or gases is making a comeback both on decentralised small-scale and big refinery-sized plants. Michael Gross reports In the 20th century, synthetic fuel has often been SunDiesel the last resort used by countries cut off from global oil supplies for one reason or another. While gasoline was never quite expensive enough to make the synthetic alternative attractive in the global marketplace, isolated countries ranging from Germany to South Africa used synthesis on a massive scale. As soon as the Nazis seized power in Germany in 1933, they made the development of large-scale fuel synthesis from coal a national priority. It was a typical example of dual use science. Officially, the fuel was for the rapidly growing number of cars on the new Autobahn, which helped to pull the economy out of the crisis, but without it, Hitler’s wars would not have been possible either. To turn the country’s abundant coal into liquid fuel, there were two methods to choose from: •Catalytic hydration of coal at high pressure was based on the work of Friedrich Bergius, who won the Nobel prize for chemistry for his high pressure work in 1931. •The conversion of the coal feedstock into synthesis gas (CO + H2), which is then turned into liquid fuel at atmospheric or moderate pressure using a cobalt catalyst or at intermediate high pressures using an iron catalyst. This method, which can also start from gas feedstocks, was invented by Franz Fischer and Hans Tropsch in 1925. IG Farben boss Carl Bosch, having witnessed the spread of gasoline-fuelled cars in the US, was keen to In Brief • Germany and South Africa were among the first countries to promote the use of Fischer-Tropsch synthesis to make fuel from coal • Today, companies have revived the process mainly because of its use of renewable feedstocks such as biomass • Fischer-Tropsch fuel production currently amounts to 500,000bbl/day, just under 1% of crude oil production • Its versatility for carbon feedstocks including biomass means that it is likely to play a bigger role in the future Feedstock flexibility: new opportunities for Fischer-Tropsch synthesis from biomass Chemistry & Industry 23 November 2009 21
  2. 2. Catalysis make synthetic fuel his company’s next blockbuster product after the success of the nitrogen fertilisers from the Haber-Bosch process. From April 1927, IG’s plant at Leuna in Germany started producing fuel using the Bergius process. Shortly after that, however, the discovery of the Oklahoma oil fields eliminated all hopes of ever making the so called ‘Leunabenzin’ competitive in the market, and Leuna remained the only plant producing it. In December 1933, the Nazis, keen to make Germany independent of oil imports, made a contract or Benzin-Vertrag with IG Farben, guaranteeing the company a fixed price in exchange for a minimal production of 200t/year of fuel. Although a small amount today, this was 10% of Germany’s total fuel consumption at that time. This was just the first step. The following year, the government forced the companies mining lignite – brown coal – to invest in coal hydration plants, strategically located deep in the middle of the country. Three hydration plants and one Fischer- Tropsch plant took up production in 1936. By 1939, there were half a dozen of them. In 1943, in the middle of the war, Germany produced nearly 6.2m t of oil, half of it by catalytic hydration. Another 368,000t was produced using the Fischer-Tropsch synthesis. Only in May 1944 did the Allies start bombing these factories. After the war, the German Democratic Republic (GDR) continued to turn its abundant lignite supplies into fuel, using both the Bergius and the Fischer- Tropsch processes. In South Africa, the company Sasol used Fischer-Tropsch catalysis to convert both coal and gas into various petroleum products, opening its first coal-to-liquid plant in 1955. It became a global Harvesting coppice: feedstock for Choren's Beta plant at Freiberg, Germany ‘The FT microchannel petrochemical company after successfully expanding 1m t of dry wood matter annually, will be sourced reactor provides a its operations to Qatar, Iran, and Nigeria. from recycled and forest wood, and increasingly from woody crops. new way to make the Green revival Today, several companies have revived the Fischer- Another company adapting the Fischer-Tropsch technology is Oxford Catalysts, a spin-out from the production of next Tropsch process for entirely different reasons, mainly chemistry department at Oxford University. It has generation biofuels at to do with using new, climate-friendly feedstocks, such as biomass and ‘stranded’ gas. Choren Industries developed a new way of producing metal catalysts, the organic matrix combustion (OMX) method, a local scale workable – the name implies it uses C, H, O from RENewable sources – has built on engineering expertise from which ensures a narrower particle size range than conventional methods. This method is applicable and economically GDR times to adapt the Fischer-Tropsch method to to the production of metal catalysts for a range of the use of biomass as feedstock. Fuel expert Bodo different processes, including cobalt catalysts for feasible, while Wolf founded the company in 1990, building on Fischer-Tropsch synthesis. avoiding the need experience gained in the GDR’s research programme aimed at converting the abundant lignite into fuel. In the OMX method, the metal salt forms a complex with an organic component that serves to transport waste Shell helped to develop the process used to convert the synthesis gas into diesel fuel, by a variant of the to stabilise the metal. On rapid combustion, as the metal cores are separate from each other and don’t to large centralised established Fischer-Tropsch procedure using cobalt have time to sinter, nanocrystallites are produced production facilities catalysts. Currently, Choren is beginning production of with a tightly controlled size range and a terraced surface, both highly desirable features for catalysis. and reducing the synthesis gas at its Beta plant at Freiberg, Saxony, Germany. Fuel production, with an annual capacity The young company champions a decentralised approach with a larger number of facilities operating amount of waste of 15,000t of biomass-to-liquid (BTL), is scheduled on a much smaller scale. Its Fischer-Tropsch catalysts going to landfill’ to start in early 2010. Provided the necessary industrial policy legislation is in place, the Choren are to be used in special microchannel reactors developed by its subsidiary Velocys. Group is planning to build a large industrial-scale Microchannel reactors are made up of individual Derek Atkinson, BTL production plant in Schwedt in the state of modules, each just 0.6 x 0.6 x 0.6m in size and Oxford Catalysts Brandenburg. The feedstock for this plant, around capable of producing more than 25 barrels/day of 22 Chemistry & Industry 23 November 2009
  3. 3. Catalysis Choren Choren Control room: overseeing plant operations at Choren's Beta plant Emirate of Qatar, which hosts 14% of the world’s a way of regenerating their catalyst, bringing it known natural gas reserves, and a growing number back to almost 100% of its original activity. At a of Fischer-Tropsch plants. recent conference on catalyst deactivation in Delft, Sasol, which has been using Fischer-Tropsch to Netherlands, says Niemantsverdriet, ‘the stability convert coal to diesel fuel in South Africa since 1955, of Fischer-Tropsch catalysts was discussed in great set up a 34,000 bbl/day gas-to-liquid (GTL) plant at detail. It is a hot topic.’ Ras Laffan, Qatar, in 2007. Other multinational oil So far, Fischer-Tropsch production accounts for companies, including Shell, Exxon, and Syntroleum, 500,000bbl/day of fuel, less than 1% of the 80m bbl/ have also started to invest in Fischer-Tropsch plants day fuels generated from crude oil. But considering in Qatar. its potential to be adapted to all kinds of carbon The Sasol plant uses a catalyst consisting of sources, including biomass, it is likely to play a much cobalt nanocrystals supported on an Al2O3 matrix larger role in the future. It appears that, 85 years liquid fuel. In the modules the key process steps take and activated by traces of platinum. ‘The intrinsic after its invention, the ‘ersatz’ fuel of yesteryear could place in parallel arrays of microchannels, each with problem with the cobalt catalyst used in these plants become the fuel of choice for a more sustainable diameters ranging from 0.1 to 5mm. Plant size can is its limited stability,’ explains Hans Niemantsverdriet future. be increased by simply adding additional modules, from the Schuit Institute of Catalysis at the which greatly reduces both capital and operating Technical University of Eindhoven, Netherlands. Michael Gross is a science writer based in costs. In collaboration with Sasol, Niemantsverdriet has Oxford, UK. Derek Atkinson, business development director studied spent catalyst material from the Qatar plant at Oxford Catalysts explains: ‘The FT microchannel to work out what the problem was. Choren reactor provides a new way to make the production A popular hypothesis was that water – the of next generation biofuels at a local scale workable main by-product of the Fischer-Tropsch process, and economically feasible, while avoiding the need and thus not avoidable – oxidised the cobalt. At to transport waste to large centralised production the high temperatures of 230oC and moderate facilities and reducing the amount of waste going to pressures of 20 bar typical of the process, water landfill.’ With this approach, the large scale flaring of partial pressures reach 4 to 6 bar, which might ‘stranded’ natural gas, for example, at oil production conceivably corrode the metal. However, detailed sites, could also be abolished, as gas could be turned research of Niemantsverdriet’s group using materials into transportable liquids. from the Sasol plant showed that oxidation was not Oxford Catalysts plans to deploy a number of the problem, and that it could be easily avoided by commercial-scale demonstration units during 2009 choosing a suitable cobalt crystal size and adjusting and 2010, in preparation for full commercialisation the partial pressures of hydrogen and water. planned for 2011. Recently, the group identified an unexpected reaction that appears to play an important role in Scaling up catalyst deterioration, namely the accumulation of In recent years, the Fischer-Tropsch process has carbon species. Niemantsverdriet summarises the also experienced a renaissance on a large industrial results: ‘The catalyst deactivates due to a number scale, especially in places where supplies of natural of factors: sintering, poisons, and inactive carbon gas from oil fields exceeds local demand and cannot formation at a very slow rate.’ Quality counts: analysing fuel quality be transported economically. This is the case for the At the same time, researchers at Sasol discovered Chemistry & Industry 23 November 2009 23