Sulfur content diesel fuel

Lepperhof, G., Stommel, P, Luers, B. and Searles, RA. (2000). Vehicle study on the impact of diesel fuel sulfur content on the performance of DeNox catalysts and the influence of DeNox catalysts on particle size and number. Soc. Automot. Eng. Tech. Pap. Ser., SAE 2000-01-1877. 

Figure 6 Effect of platinum content (g ft ) in diesel oxidation catalysts on tailpipe emissions in the ECE R49 test carbon monoxide (a), hydrocarbon (b), soluble organic fraction (c), sulfur trioxide (d), and particulates (e). The fuel sulfur content was 500 ppm.

The NOx concentration was measured with an Eco Physics chemiluminescence NOx analyser. Ammonia was measured with a Siemens MIPAN (Microwave Process ANalyser). In case of dry model gases the disappearance of SO2 was measured with a Siemens Ultramat 5E NDIR (Non- Dispersive Infi a-Red) analyser. In case of diesel gases SO3 was measured with a Severn Science Instruments automatic titration unit and the SO2 concentration was calculated on basis of the fuel sulfur content. 

More recently, the EPA has announced plan to reduce non-road diesel fuel sulfur from the current average of 3400 ppm to 500 ppm by 2007 and further to 15 ppm by 2010 . The U.S. Clean Air Act Amendments of 1990 and related new fuel regulations by the U.S. EPA and government regulations in many countries call for the production and use of more environmentally friendly transportation fuels with lower contents of sulfur and aromatics. 

With respect to fuels utilized as heating fuels for industrial furnaces, or as motor fuels for large diesel engines such as those in ships or power generation sets, the characteristics of primary importance are viscosity, sulfur content and the content of extremely heavy materials (asphaltenes) whose combustion can cause high emissions of particulates which are incompatible with antipollution legislation. 

The gas oil cut from catalytic cracking called Light Cycle Oil (LCO), is characterized by a very low cetane number (about 20), high contents in aromatics, sulfur and nitrogen, all of which strongly limit its addition to the diesel fuel pool to a maximum of 5 to 10%. 

Hydrocracking makes very good quality diesel fuels concerning the cetane number, cold behavior, stability, and sulfur content. However this type of stock is only available in limited quantities since the process is still not widely used owing essentially to its high cost. 

Following 1 October 1996, diesel fuel should be desulfurized to a level of 0.05% while the maximum sulfur content of home-heating oils will stay provisionally at 0.2 %. 

We have previously stated that the sulfur content of diesel fuel will be limited in Europe to 0.2% as of 1 October 1994 and to 0.05% as of 1 October 1996. 

The main justification for diesel fuel desulfurization is related to particulate emissions which are subject to very strict rules. Part of the sulfur is transformed first into SO3, then into hydrated sulfuric acid on the filter designed to collect the particulates. Figure 5.21 gives an estimate of the variation of the particulate weights as a function of sulfur content of diesel fuel for heavy vehicles. The effect is greater when the test cycle contains more high temperature operating phases which favor the transformation of SO2 to SO3. This is particularly noticeable in the standard cycle used in Europe (ECE R49). 

Desulfurization will become mandatory when oxidizing catalysts are installed on the exhaust systems of diesel engines. At high temperatures this catalyst accelerates the oxidation of SO2 to SO3 and causes an increase in the weight of particulate emissions if the diesel fuel has not been desulfurized. As an illustrative example, Figure 5.22 shows that starting from a catalyst temperature of 400°C, the quantity of particulates increases very rapidly with the sulfur content. 

Influence of the sulfur content in diesel fuel on particulate emissions as a, function of the catalytic converter inlet temperature. 

For example, in the case of light Arabian crude (Table 8.16), the sulfur content of the heavy gasoline, a potential feedstock for a catalytic reforming unit, is of 0.036 weight per cent while the maximum permissible sulfur content for maintaining catalyst service life is 1 ppm. It is therefore necessary to plan for a desulfurization pretreatment unit. Likewise, the sulfur content of the gas oil cut is 1.39% while the finished diesel motor fuel specification has been set for a maximum limit of 0.2% and 0.05% in 1996 (French specifications). 

Heavy residue conversion is linked to the demand for high quality diesel motor fuel (aromatics content 10%, cetane number 55) as well as to the demand for production of light fuel-oil having very low sulfur, nitrogen and metal contents. 

Diesel Fuel. Eederal diesel specifications were changed to specify a maximum of 0.05% sulfur and a minimum cetane index of 40 or a maximum aromatics content of 35 vol % for on-road diesel. Eor off-road diesel, higher sulfur is allowed. CARB specifications require 0.05% sulfur on or off road and 10% aromatics maximum or passage of a qualification test. Process technologies chosen to meet these specifications include hydrotreating, hydrocracking, and aromatics saturation. 

Control of diesel-powered vehicles is parhally accomplished by fuel modification to obtain reduced sulfur content and cleaner burning and by proper tuning of the engine using restricted fuel settings to prevent overfueling. 

In summaiy, diesel fuel with veiy low to no sulfur content is now possible with chemical and technological advances. Along with catalytic converters, electronic fuel systems, and sensors, the diesel engine for the new millennium will he capable of complying with ever more stringent EPA exliaust emissions. The diesel engine will continue to sei"ve as the main global workliorse for all of the many thousands of different applications of its power cycle. 

Effective October 1993, highway diesel fuel was limited to a maximum sulfur content of 0.05 wt% (500 ppm) and a minimum cetane rating of 40. 

Usually, only three categories are generally referred, light, medium, and heavy, and each of them are also subdivided in terms of the sulfur content, as low-S and high-S. Similarly, as the market is demanding an increasing proportion of diesel fuels, it is also... 

Mukai, Y., and Mizutani, Y., Survey of Petroleum Refining Technology for High-quality (Ultra-low Sulfur Content) Diesel Fuel. Petroleum Energy Center. 01 Survey 4-3, 2001. 

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