Nanotechnology could provide cleaner fuels

Scientists from the University of Aarhus, Denmark, have developed a technique that could improve the commercial processes used to remove environmentally harmful sulphur from fossil fuels. This is currently done using a catalyst, which binds the harmful sulphur molecules to it.

The Danish team have studied the chemical reactions that occur when the industrial catalyst combines with sulphur-based molecules in the oil. Until now these reactions have not been properly understood as they occur on an atomic scale. The researchers overcame this problem by making a model of the catalyst and observing these nanoscale reactions using a technique called scanning tunnelling microscopy (STM).

“Throughout the last century most catalysts have been developed by costly time-consuming trial-and-error methods,” says Dr Jeppe Lauritsen, a member of the research team. “Nanotechnology is about to change this, since we can now build and view matter directly on the nanoscale.”

The commercial catalysts used to remove sulphur contain tiny metal-sulphide nanoclusters. The particular metal-suphide complex used in the team?s nanocluster model is usually fairly non-reactive. However the nanoclusters are so small that the scientists found that at the edges, the clusters behaved unexpectedly. “Surprisingly, the nanocluster edges behave just like ordinary catalytically active metals,” says Lauritsen. “This metallic reactive behaviour is shown in the STM images as a bright brim extending around the cluster edges.” (see picture)

The team?s model shows how the first and most difficult step in the catalytic process, that removes sulphur from fossil fuels, occurs. They now plan to extend their model to provide information on the rest of the process. Through their collaboration with Danish catalyst company Haldor Tops?e, the team aims to provide the basis for the manufacture of better catalysts for the production of clean transport fuels.

The team explain that the chemical activity associated with sites on the metallic edge states may provide a route for the hydrogenation of aromatics, which is an integral part of hydrotreating catalysis. As the demands for cleaner transport fuels grow, it is of increasing importance to be able to hydrogenate averse aromatic compounds and the new atomistic insight may aid the design of the next-generation hydrotreating catalysts.

Generally, nanoparticles have inherently different electronic properties, and thus reactivity, to their macroscopic counterparts. So far, no general description of the reactivity of nanoclusters has been available, but the approach presented by the team should be applicable to inorganic nanoclusters on conducting substrates in general, and may therefore provide a breakthrough in the understanding of nanoscale reactivity.

The Polytechnic University of Spain has also being using nanotechnology to improve the catalysts used in the cracking process. They have redesigned the catalyst at the atomic scale, adjusting the size and connectivity of the microscopic tunnels within which the reactions occur. Their new material, which they have named zeolite, has larger internal cavities and larger openings than current catalysts, which leads to a greater surface area. The design also makes it easier for big chains of hydrocarbons to move into the catalyst and get broken down into smaller and more useful molecules.

This may be all good news for the high-end products resulting from the cracking process, but what about the residual fuels?

It may mean that current equipment installed onboard ships will no longer be able to cope with these new fuels. The current catalysts are sphere shaped but the new catalyst is crystal shaped, which could affect the degree of particle bonding within the residual fuel matrix.

Commercial fuels to international specifications rely on current machinery to separate water, sediments and in particular, abrasive elements, such as catalytic fines.

Catalyst fines are small particles of spent catalyst that remain in the by products from the catalytic cracking process in the refinery. If not reduced by suitable fuel treatment the abrasive nature of these fines causes increased wear in the engine, affecting the fuel pumps, injectors, piston rings and liners.

The purpose of the catalytic cracker in the refinery process is to increase the quantity of petrol from the crude processed. Nearly all catalysts contain aluminium silicate. Particles of the catalyst are in constant motion at relatively high velocities and collide with each other and the containment vessels. As a result of these collisions, break-up of the catalyst particles leads to the production of smaller catalyst fines.

The catalyst is expensive and refiners have developed various systems to minimise catalyst loss. However, these are not 100% efficient and some of the catalyst in the form of catalyst fines remains in the cycle oil streams which are a by-product of the catalytic cracker.

These streams form a useful component in the blending of residual fuel because their high aromaticity increases the available solvency of a fuel and reduces the likelihood of incompatibility problems. Catalyst fines are variable in size, with a range from sub micronic to approximately 30 microns and occasionally larger.

Currently, the limit for aluminium silicate is 80 ppm, which is based on typical purifier calorifier plant. However, if a centrifuge onboard can no longer clean the fuel, the quality of bunkers to the engine will be unknown.

Chemists will have done some research, but the quality of residual fuels won?t be known until production starts.

One grease for all

Grease only draws attention to itself when it fails to do the job, so if crew can be sure they?re using the right grease for the job it?s got to be a good thing ? especially when there?s a one-grease-suits-all formula for every purpose.

Castrol has improved its successful and innovative Shpeerol SX2 shipboard grease ? long used for general applications on deck ? to be suitable for engine room use. The result is that for most vessels, this single product will be the only grease required.

According to Castrol, SX2 provides “an excellent load-carrying, tenacious and resilient coating”, highly resistant to wash off, rub off or fling-off – all at temperatures ranging from -30oC to 175oC.

Medium speed lubricant

ExxonMobil Marine Lubricants has introduced a new medium-speed diesel lubricant for engines using residual fuels. The Mobilguard M Series oils feature additives designed to combat the effects of lower-quality residual fuels, higher fuel injection pressures and lower specific lub-oil consumption rates.

The oil is designed to deal with such problems as piston undercrown and ring-belt deposits, fuel contamination of the lub oil and crankcase sludge build up.

ExxonMobil describes M Series as “virtually eliminating” black deposits in the crankcase caused by poor lub-fuel compatibility. It also reduces deposits on pistons.

The lubricant has been accepted by major four-stroke makers MAN B&W, Wärtsilä, Pielstick and MaK.

l ExxonMobil Marine Fuels Singapore is moving offices. With effect from February 24, it will be located at 1 Harbour Front Place, # 06-00 Harbour Front Tower One, Singapore 098633. The office can be contacted by phone on +65 6885 8998 (Sales) and +65 6885 8999 (Customer Services), or by fax on +65 6885 8793.

Lubmarine acquires $2m cutting-edge test engine

Lubmarine, the worldwide maritime lubricants network of oil major TotalFinaElf, has installed a unique test engine at its research centre at Solaize, near Lyons, France. The $2m MAN B&W Innovator-4C test engine, which is being modified for Lubmarine, will come into service in May.

“To stay in the lead in the increasingly high-tech field of marine lubricants, you must have top R&D tools,” says Claude Ouvrier-Buffet, head of the Marine Technical Dept. “A test engine plays a key role in the development process, so having a proper marine engine specially adapted for research purposes gives us a big advantage.”

The new engine, based on an original MAN 5L 16/24 (160mm bore, 240mm stroke) unit, has undergone a redesign, specified by Lubmarine. Its five cylinders have been specially reconfigured into three separate lubrication circuits, two for testing and one for operational requirements. It has also been fitted with multiple high tech sensors and a comprehensive electronic control and information management system. It is equipped to analyse exhaust gas, in anticipation of future more stringent environmental controls on emissions of particles and oxides of sulphur and nitrogen.

The Innovator-4C will be used for validating both 2 stroke and 4 stroke engine oil formulations before proceeding to in-service trials, and for fundamental research including experiments with new additives, synthetic and biodegradable base stocks.

The Innovator-4C replaces the single-cylinder Elf-Optimizer test-bench (Pielstick PC2.6) first installed at Solaize 20 years ago and extensively modified in 1994 to cope with changing development needs.

“The cylinder configuration of the Innovator-4C lets us compare two formulations at the same time under precisely the same temperature and pressure conditions,” explains Denis Lancon, head of the Marine Lubricants team at Solaize. “And carrying out two tests at the same time means more tests are possible on a given formulation within a given time-frame. The very high safety margins of the MAN 5L 16/24 mean we can push lubricants much further in testing and also allows us to obtain meaningful results faster, more than doubling our previous testing productivity”.

ExxonMobil Marine Lubricants last year marked 10 years of testing cylinder oil on a Sulzer 6RTA 38, named Explorer, at its technology centre and refinery at Gravenchon, France.

Shell expands US services

Shell Marine Products has expanded is USA operations with the acquisition of the Equiva bunker business. The new operation greatly extends Shell?s presence on the east coast. The organisation can now supply fuels at Houston, Port Arthur, New Orleans, Philadelphia and New York.

With more than 60,000 international vessel calls in ports around its coast each year, the USA is the largest marine market in the world, accounting for more than 20 per cent of global demand.