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NEBULA: A catalyst for clean fuels

Plumes of black smoke spewing from the backs of cars and trucks have long been the bane of environmentalists.

Plumes of black smoke spewing from the backs of cars and trucks have long been the bane of environmentalists. But the cleaning of exhaust gases has been an ongoing effort over the last 15 years. It all started with replacing lead additives in gasoline and reducing the sulfur content of fuels, the latter being done to reduce the sulfur dioxide emissions that may lead to acid rain.
recent years, the focus was on further reduction of harmful emissions such as CO, NOx and particulates (soot), while at the same time making further improvements in CO2 emissions.

To achieve the very strict targets, car manufacturers have to apply the latest catalytic technology in exhaust cleaning and engine design. The car manufacturers have therefore proposed new fuel specifications targets whereby sulfur in particular needs to be reduced to unprecedented low levels. These proposals have been taken over by EU and U.S. governments, which now aim to introduce sulfur-free fuels over the next few years. Because the sulfur in crude petroleum is partly responsible for the black exhaust plume emitted from diesel-burning trucks, it is a highly visible pollutant. Sulfur also poisons a vehicle’s catalytic converter, a device designed to remove many particulates and polluting gases (such as CO and NOx) from the exhaust. Producing a cleaner diesel fuel means getting rid of the sulfur. Today, the sulfur level in diesel is typically reduced from 1% wt to 350 ppmwt in the EU and by 2005 this will be further lowered to 50 ppmwt.
At the same time, some EU countries have already promoted 50 ppm (parts per million) by means of tax incentives, with Germany going as far as 10 ppm by 2003. Later this decade, all diesel in the EU and U.S. will be at 10 and 15 ppm. “Many people think that the major problem with sulfur in diesel is that it contributes to acid rain,” said Frans Plantenga, Development Manager of Akzo Nobel’s Catalysts business unit.“
“Nowadays, the real problem is that sulfur poisons a vehicle’s catalytic converter. When this happens, the cleaning function of the catalytic converter is reduced and more particulates and polluting gases enter the environment.” That it is possible to remove all but a tiny percentage of sulfur-containing compounds from the diesel fraction of crude oil is due, in part, to recent developments in catalyst technology at Akzo Nobel Catalysts.
Thanks to the business unit’s innovative technology, the diesel fuel now available at many gas stations in the UK, Germany and the Netherlands already meets or exceeds the 2005 EU-imposed targets of 50 ppm of sulfur. Akzo Nobel Catalysts has for many years been the leader in this field. But thanks to its recent catalyst developments, such as the STARS technology, the BU has really benefited from the latest wave of environmental regulations.

AKZO Nobel Catalysts’ newest technology, dubbed NEBULA—an improvement on their earlier KF 848 and KF 757 STARS catalysts—makes it possible to remove the vast majority of sulfur compounds from crude oil feed stocks during the refining process. Although the basis for this technology has been around since the 1930s, very recent developments in catalyst preparation and design have resulted in massive improvements in getting rid of some of the more difficult-to-remove sulfur compounds. NEBULA catalyst is a joint development with ExxonMobil. The Akzo Nobel-ExxonMobil team started work on commercialization in 1997 and the resulting product was introduced successfully onto the market in 2001. Recently, the team was honored by ExxonMobil with the prestigious ExxonMobil Innovator of the Year 2002 Award. With NEBULA, the Catalysts BU’s research team succeeded in getting rid of the most difficult sulfur compounds in a much easier way. The result? Ultra-low diesel with a sulfur content below 15 ppm—that is 99.9 percent removal of the sulfur.

“You can remove sulfur using more drastic methods (such as increased pressures and temperatures) during the refining process, but that comes at considerable investment,” adds Plantenga.
“The R&D team has come up with a product which reduces the need for major new investments. It therefore makes it more economically attractive for the refineries to meet low-sulfur targets.”
The ability to remove sulfur at lower temperatures and commercial experience at two refineries in the Netherlands showed that they were able to produce 10-50 ppm sulfur-containing diesel fuel in units originally designed for 500 ppm fuel—all without revamping the equipment. Getting rid of the most difficult sulfur compounds still remains a challenge. But the road to nearly sulfur-free fuel is getting smoother.

(Released: January 2, 2002)

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