Sulfur and nitrogen removal

Kinetics studies of the hydrotreatment (and hydrocracking) of VR has led to the conclusion that most of the metals, sulfur and nitrogen removal takes place during the first 50% of the whole VR conversion [119-123], More than one reactor was needed for HDM and HDS of a Maya VR, when HDT is used as feed pretreatment [119,120], Although vanadium removal appears easier and faster than nickel removal, their kinetics results showed very similar values of the activation energy for the demetallization reactions [122],... 

Metals cause particular problems because they poison catalysts used for sulfur and nitrogen removal as well as other processes such as catalytic cracking (Chapter 5). Thus, serious attempts are being made to develop catalysts that can tolerate a high concentration of metals without serious loss of catalyst activity or catalyst life. 

These heavy gas oils were processed under conditions of 1300 psig, 3000 SCF Ha/bbl., 1 LHSV, and temperatures of 625°, 675°, and 725°F. In addition to sulfur and nitrogen removals, hydrogen consumption and aromatics saturation monitoring was attempted. 

A trickle-bed reactor 2.5 cm in diameter and 60 cm long was used by Baker to study sulfur and nitrogen removal from a heavy oil [37]. The catalyst in the form of 1.5-mm x 4.5-mm extrudates was diluted with an equal volume of 1.0-mm silicon carbide particles. Characteristics of the oil are given in Table 8.1. Test results are given in Table 8.2. 

Solvent extraction can also be achieved under milder conditions but the product may be a high-nitrogen solid or a heavy oil with only low yields of light oils and gases. The more severe conditions are more effective for sulfur and nitrogen removal to produce a lighter liquid product that is more amenable to downstream processing. 

Solutions of iron chelates can be used to remove hydrogen sulfide and oxides of sulfur and nitrogen in industrial gas scmbbing processes (41,50,51) before flue gases are released to the atmosphere. 

Fluid catalytic cracking units present formidable emission control problems. Contaminants are present in both reactor product gas and regenerator flue gas. The reactor product contains hydrogen sulfide, ammonia, and cyanides, plus combined sulfur and nitrogen in the liquid products. Hydrogen sulfide, ammonia and cyanides are handled as part of the overall refinery waste water cleanup. The combined sulfur and nitrogen may be removed by hydrotreating. 

Direct conversion of target compounds (sulfur and nitrogen compounds, hydrogen sulfide, polyaromatics, etc.) to an easily removable or desirable product. 

---