Membrane technology for removal of sulfur compounds from diesel fuel

Abstract

Removing sulfur compounds from diesel fuel is one of the most complicated problems in existing oil refining technologies. It is done with chemical and physicochemical methods. The chemical methods include treatment with sulfuric acid and hydrotreating, and the physicochemical methods include adsorption and absorption methods. I n s u l f u r i c a c i d t r e a t m e n t , t h e d i e s e l f u e l i s m i x e d w i t h a s m a l l a m o u n t o f s u l f u r i c a c i d of 90-93% concentration at normal temperature. As a result of chemical reactions, treated product and so-called acid tar with the undesirable contaminants that have migrated into it are obtained. The acid tar can be used for sulfuric acid production. This treatment method requires cumbersome equipment and a large amount of reagents.In the adsorption method, the petroleum product is placed in contact with adsorbents (bleaching clays or silica gel). Sulfur-, oxygen-, and nitrogen-containing compounds and gums are removed. A drawback of this method is partial regeneration of the adsorbents.Selective dissolution of the harmful components of the petroleum product takes place in the adsorption method of treatment. Nitrobenzene, furfural, liquid sulfur dioxide, dichloroethyl ether, etc., are used as selective solvents. The drawbacks of this method are losses of the solvents due to the impossibility of regenerating them.Hydrotreating is the most widely used method. This method consists of hydrogen acting on the treated product in the presence of aluminum -cobalt -molybdenum catalysts. In reacting with sulfur-, nitrogen-, and oxygen-containing compounds, hydrogen forms hydrogen sulfide, ammonia, and water. The drawbacks of this method are the high temperature (380-420°C) and pressure (up to 4 MPa) and the complicated implementation. The diesel fuel hydrotreating blocks are power consuming and cumbersome and can cost from $15 to $100-150 million as a function of the output and degree of treatment. In addition, a large technogenic load on the ecosystem is created due to important emissions of harmful substances into the atmosphere and wastewaters. Decontaminating the emissions requires additional capital and operating costs.