Hydrotreated catalytic cracking

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... 

Derr, W. R., Holland, R. E., McGovern, S. J., and Nicoletti, M. P., (1990), Process for Hydrotreating Catalytic Cracking Feedstocks", AIChE Spring Meeting, Paper 44e Denver. 

Acid gases are mainly hydrogen sulfide (H2S) originating essentially from hydrotreating units off-gas. Smaller quantities are also produced in thermal and catalytic cracking units. 

Contaminated water comes from primary distillation (desalting), hydrotreating, thermal cracking and catalytic cracking units. 

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. 

Some invaluable isolated actions were taken from time to time in the last twenty to twenty five years that prevented air quality from declining at an even faster rate. For example, energy demand was met (electricity and refined oil products) by expanding capacity of plants located outside of the MCMA a metro was built the vehicular traffic system was reordered and new hydrotreating, reforming and catalytic cracking units reduced lead and sulfur in refined products. 

Nowadays, based on the amount of processed material, hydrotreating is the largest process in heterogeneous catalysis. On the basis of catalysts sold per year, hydro-treating ranks third after automotive exhaust and fluid catalytic cracking [R. Prins, V.H.J. de Beer and G.A. Somorjai, Catal. Rev.-Sci. Eng. 31 (1989) 1]. 

Sulfur is removed from a number of refinery process off-gas streams (sour gas) to meet the sulfur oxide emissions limits of the Clean Air Act and to recover salable elemental sulfur. Process off-gas streams, or sour gas, from the coker, catalytic cracking unit, hydrotreating units, and hydroprocessing units can contain high concentrations of hydrogen sulfide mixed with light refinery fuel gases. 

Catalytic Cracking of a Wilmington Vacuum Gas Oil and Selected Hydrotreated Products... 

Performance Analysis. In order to determine the effect of hydrotreating on catalytic cracking performance, the above feedstocks were evaluated at a low severity cracking condition (catalyst-to-oil ratio of 6.0 and reactor temperature of 910° F) and a high severity cracking condition (catalyst-to-oil of 8.0 and reactor temperature of 1010° F). The results from the catalytic cracking of these feedstocks (shown in Tables I and II) are shown in Tables III through V. The results presented in these tables are... 

Table IV. Catalytic cracking of lightly hydrotreated (511.5 scf/bbl) Wilmington 650° to 1000° F (WM-2-2R)...

Also shown in Tables III through V is the effect of hydrotreating on hydrogen transfer during catalytic cracking. This effect is shown by the ratio of saturated to olefinic C. In catalytic cracking, there are two mechanisms for the formation of saturates. These are the primary cracking reaction, such as... 

Figure 2. The effects of hydrotreating on catalytic cracking performance -- low cracking severity.

Figure 13. Effect of hydrotreating severity on catalytic cracking light gas composition -- low severity cracking.

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