Sulfur fluid catalytic cracking

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. 

Hydrocarbon feedstocks for fluid catalytic cracking units (FCCU s) contain organo-sulfur compounds. The sulfur content of these feedstocks is about 0.3% to 3.0%, expressed as elemental sulfur. 

Advances in Fluid Catalytic Cracking The impact of feed sulfur to coke sulfur... 

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. 

Austenitic steels provide excellent corrosion, oxidation, and sulfidation resistance with high creep resistance, toughness, and strength at temperatures greater than 565 °C. Thus they are used in refineries for heater tubes, heater tube supports, and in amine, fluid catalytic cracking (FCC), catalytic hydro-desulfurization (CHD) sulfur, and hydrogen plants. 

An important example are alumina-supported Co—Mo and Ni—Mo sulfides, which constitute the active phases in catalysts for hydrotreating of middle distillates (403). It appears that in such catalysts, mostly pseudoboehmite-derived Y-AI2O3 is used as the support. According to fiter-ature data, catalysts for fluid catalytic cracking (FCC) gasoline desulfurization, which is performed at 260—340 °C and 5—30 atm, may contain 5—11 wt% molybdenum and 2-3 wt% cobalt supported on AI2O3 with a surface area of220—240 w (405). Catalysts for diesel fuel desulfurization to low-sulfur... 

Molecular mechanics has also been used to study skeletal isomerization of 1-butene to isobutene (80), olefin selectivity in fluid catalytic cracking using ZSM-5, zeolite Y, mordenite and P (81), carbon-sulfur bond cleavage over zeolite Y (82), and the location of naphthalene and 2-methylnaphthalene in HZSM-5 (83). In all cases, a methodology similar to those described earlier were adopted (75,77). 

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