- Fuel dyes
Fuel dyes are dyes added to fuels, as in some countries it is required by law to dye a low-tax fuel to deter its use in applications intended for higher-taxed ones. Untaxed fuels are referred to as "dyed", while taxed ones are called "clear" or "white".
The dyes used have to be soluble in the fuels they are added to and therefore in hydrocarbon-based nonpolar solvents ("solvent dyes"). Red dyes are often various diazo dyes, e.g. Solvent Red 19, Solvent Red 24, and Solvent Red 26. Anthraquinone dyes are used for green and blue shades, e.g. Solvent Green 33, Solvent Blue 35 and Solvent Blue 26.
It is advantageous to mix a liquid with a liquid instead of handling powdered dyes into a liquid.
The pure dyes found in modern liquid petroleum dyes are essentially longer alkyl side chain forms of traditional dyes and normally multiple chain length variations of the chromophore are found within a typical commercial liquid petroleum dye. For instance, Sudan Red 462 is essentially Solvent Red 19, with the ethyl side chain replaced by either a 2-ethylhexyl or a tridecyl side chain. The longer branched side chains improve solubility dramatically, but in some cases the high solubility prevents the dye being isolated as a crystal, except at very low temperatures. The high solubility liquid dyes originated with Morton International and BASF (ACNA Italy) as the primary inventors. For instance, Morton created Solvent Blue 98 as a high solubility form of Solvent Blue 35. BASF created Solvent Blue 79 as its high solubility form of Solvent Blue 35. In some cases it is possible, with normal solvents - e.g. xylene - to prepare stable (to -20C) solutions at 65% "solids" content. The original powder dye form of the chromophore would not be soluble beyond 2% in xylene.
Only a few refineries worldwide still use powder dyes for colouring fuels, as ultimately they are still lower cost per active molecule of dye chromphore than the modified forms. They have significant handling issues and health and safety issues that inherently arise from the handling of azo dyes (reds/yellows/green mixes).
Aviation gasoline is dyed, both for tax reasons (avgas is typically taxed to support aviation infrastructure) as well as safety—there being obvious and disastrous consequences of fueling an aircraft with the wrong kind of fuel.
Fuel dye in the European Union
After August 2002, all European Union countries became obliged to add about 6 mg/L of Solvent Yellow 124, a dye with structure similar to Solvent Yellow 56, to all motor diesel fuel. This dye can be easily hydrolyzed with acids, splitting off the acetal group responsible for its solubility in nonpolar solvents, and yielding a water-soluble form. Like a similar methyl orange dye, it changes color to red in acidic pH. It can be easily detected in the fuel at levels as low as 0.3 ppm by extraction to a diluted hydrochloric acid, allowing detection of the red diesel added into motor diesel in amounts as low as 2-3%.
In the United Kingdom, "red diesel" is dyed gas oil for registered agricultural or construction vehicles such as tractors, excavators, cranes and some other non-road applications such as boats. Red diesel carries a significantly reduced tax levy than un-dyed diesel fuel used in ordinary road vehicles. As red diesel is widely available in the UK, the authorities regularly carry out roadside checks, highly unlikely in a metropolitan area but much more likely in a rural area. Unauthorized use incurs heavy fines but despite this spot checks have occasionally found as many as one in five motorists using red diesel. Red diesel can also be used in road vehicles which are registered as SORN with the DVLA provided they are only used on private land. There is also no need to tax a vehicle that is not used on a public road.
Fuel dye in North America
In United States of America, the Environmental Protection Agency mandates use of a red dye to identify high-sulfur fuels for off-road use. Solvent Red 26 is used in the United States as a standard, though it is often replaced with Solvent Red 164, which is similar to Solvent Red 26 but with longer alkyl chains. The Internal Revenue Service mandates use of the same red dyes, in fivefold concentration, for tax-exempt diesel fuels such as heating oil; their argument for the higher dye content is to allow detection even when diluted with "legal" fuel. Detection of red-dyed fuel in the fuel system of an on-road vehicle will incur substantial penalties.
Blue dyes are used for diesel designated for governmental and institutional vehicles, to detect theft.
Processing fuel to remove the dye so it may be illicitly sold to motorists is a recognized criminal activity in the United Kingdom. In Northern Ireland, it has been a means of fund raising by illegal paramilitary organizations. In 2004, Northern Irish police discovered an illegal facility capable of removing the dye from 12 million litres of fuel per year . In 2009, customs officials shut down a plant capable of removing the dye from 6.5 million litres of fuel per year . In 2011, a plant capable of processing 30m litres was discovered.
Some dyes required in some countries are listed here:
Country Fuel Dye Australia Regular Unleaded Petrol Purple (or Bronze) Premium Unleaded Petrol Yellow Austria Heating oil any red dye Canada Agricultural Fuel red/purple dye Heating oil any red dye Finland Heating oil Furfural and Solvent Yellow 124 Diesel for construction and agriculture Furfural and Solvent Yellow 124 France Gas oil Solvent Red 24 Marine diesel Solvent Blue 35 Estonia Heating oil Automate Red NR or similar + Solvent Yellow 124 Agricultural diesel Automate Blue 8 GHF or similar + Solvent Yellow 124 Germany Heating oil Solvent Yellow 124 and similar Greece Heating oil any red dye Marine diesel any black dye Ireland Gas oil green dye Kerosene Solvent Red 19 and similar Italy Heating oil Solvent Red 161 Gas oil Solvent Green 32 or 33 Netherlands Agricultural diesel any red dye and the additive Furfural Norway Agricultural diesel any green dye Portugal Agricultural diesel Solvent Blue 35 Heating oil Solvent Red 19 and similar Spain Agricultural diesel any red dye Heating oil any blue dye Sweden Heating oil Solvent Blue 35, Solvent Blue 79, Solvent Blue 98 Thailand Gasoline 95 yellow dye Gasoline 91 red dye United Kingdom Gas oil ("Red Diesel") Solvent Red 24, quinizarin Rebated kerosene Coumarin Europe many rebated Solvent Yellow 124 ("Euromarker") United States low-tax fuels, high-sulfur fuels Solvent Red 26, Solvent Red 164 Worldwide Aviation gasoline 80/87 red dye Aviation gasoline 82UL purple dye Aviation gasoline 100LL blue dye Aviation gasoline 100/130 green dye
- ^ "Thousands using illegal car fuel". BBC News. 2007-11-03. http://news.bbc.co.uk/1/hi/uk/7076799.stm. Retrieved 2008-04-16.
- ^ "Blackmarket Britain: Fake Fuel". BBC News. 2004-06-09. http://news.bbc.co.uk/1/hi/business/3086941.stm. Retrieved 2008-04-16.
- ^ "Illegal fuel plant largest in NI". BBC News. 2009-12-01. http://news.bbc.co.uk/1/hi/northern_ireland/8389523.stm. Retrieved 2009-12-01.
- ^ "UK's biggest fuel laundering plant found in Crossmaglen". BBC News. 2011-03-16. http://www.bbc.co.uk/news/uk-northern-ireland-12757309. Retrieved 2011-03-17.
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