Hydrotreated feeds, catalytic cracking

Hydrotreating Hydrogenation Catalytic Remove impnrities, satnrate HCs Residuals, cracked HCs Cracker feed, distillate, lube... 

Hydrotreating processes have two definite roles (1) desulfurization to supply low-sulfur fuel oils and (2) pretreatment of feed residua for residuum fluid catalytic cracking processes. The main goal is to remove sulfur, metal, and asphaltene contents from residua and other heavy feedstocks to a desired level. 

Feeds and Products, Barrels per Calendar Day Refinery Input High Severity Hydrotreating Catalytic Cracking Light Ends Recovery Catalytic Reforming Hydrogen Mf g. Recovery and Sulfur Plant Refinery Fuel Motor Gasoline By- Products... 

In the platforming process (Fig. 1), the feedstock is usually a straight-run, thermally cracked, catalytically cracked, or hydrocracked C6 to 200°C naphtha. The feed is first hydrotreated to remove sulfur, nitrogen, or oxygen compounds that would foul the catalyst, and also to remove olefins present in cracked naphthas. The hydrotreated feed is then mixed with recycled hydrogen and preheated to 495 to 525°C at pressures of 116 to 725 psi (0.8 to 5 MPa). Typical hydrogen charge ratios of 4000 to 8000 standard cubic feet per barrel (scf/bbl) of feed are necessary. 

Figure 4. Catalytic cracking yields from hydrotreated feeds. Shale oil arm Arabian Light vacuum gas oil at 975°F (O), shale oil containing 870 ppm N (0), shale oil containing 385 ppm N.

The feedstocks will t3 ically be low value refinery or petrochemical streams, such as steam cracker by-products rich in C4 s, which have poor propylene selectivity when recycled to the steam cracker. The feedstock can include raffinates, catalytic cracked naphtha, coker naphtha, steam cracker pyrolysis gasoline, as well as synthetic chemical streams containing sufficient amounts of C4-C7 olefins. Dienes, sulfur, nitrogen and oxygenates in the feeds are preferably selectively hydrotreated prior to the conversion process. However, feeds with low levels of dienes, sulfur, nitrogen, metal compounds and oxygenates can be processed directly from FCC units, cokers or steam crackers without any pretreatment. 

---