Fluidized catalytic cracking

Cracking is an endothermic reaction, implying that the temperature must be rather high (500 °C), with the consequence that catalysts deactivate rapidly by carbon deposition. The fluidized catalytic cracking (FCC) process, developed by Standard Oil Company of New Jersey (1940) (better known as ESSO and nowadays EXXON), offers a solution for the short lifetime of the catalyst. Although cracking is 

Although cracking also occurs on chlorine-treated clays and amorphous silica-aluminas, the application of zeolites has resulted in a significant improvement in gasoline yield. The finite size of the zeolite micropores prohibits the formation of large condensed aromatic molecules. This beneficial shape-selectivity improves the carbon efficiency of the process and also the lifetime of the catalyst. 

The catalyst consists of about 20% zeolite Y and 80% matrix material or binder. 

FCC units, and in particular the catalyst regenerating section, may give rise to significant pollution. Sulfur in the coke oxidizes to SO2 and SO3, while the combustion also generates NOx compounds. In addition, the flue gas from the regenerator contains particulate matter from the catalyst. The FCC process is also the major source of sulfur in gasoline. Of all the sulfur in the feed, approximately 50% ends up as H2S in the light gas-LPG fraction, 43% in the liquid products and 7% in the coke on the spent catalysts. 

The reaction mechanism involves carbonium and carbenium ion intermediates. The first and difficult step is the generation of carbonium ions from alkanes  

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Other components in the feed gas may react with and degrade the amine solution. Many of these latter reactions can be reversed by appHcation of heat, as in a reclaimer. Some reaction products cannot be reclaimed, however. Thus to keep the concentration of these materials at an acceptable level, the solution must be purged and fresh amine added periodically. The principal sources of degradation products are the reactions with carbon dioxide, carbonyl sulfide, and carbon disulfide. In refineries, sour gas streams from vacuum distillation or from fluidized catalytic cracking (FCC) units can contain oxygen or sulfur dioxide which form heat-stable salts with the amine solution (see Fluidization Petroleum). 

Item Deep Catalytic Cracking (DCC) Fluidized Catalytic Cracking (FCC) Steam Cracking (SC)... 

Fluidized catalytic cracking (FCC) Heavy oils, Cig- - Fluidized catalyst particles None... 

Fuel industry is of increasing importance because of the rapidly growing energy needs worldwide. Many processes in fuel industry, e.g. fluidized catalytic cracking (FCC) [1], pyrolysis and hydrogenation of heavy oils [2], Fischer-Tropsch (FT) synthesis [3,4], methanol and dimethyl ether (DME) synthesis [5,6], are all carried out in multiphase reactors. The reactors for these processes are very large in scale. Unfortunately, they are complicated in design and their scale-up is very difflcult. Therefore, more and more attention has been paid to this field. The above mentioned chemical reactors, in which we are especially involved like deep catalytic pyrolysis and one-step synthesis of dimethyl ether, are focused on in this paper. 

Consider the example in Fig. 26 of determining if there is a problem with the feed injection system of a fluidized catalytic cracking unit (Ramesh et al., 1992). In this example, there is a set of rules that relate combinations of process observations to establish or reject this possibility. 

Fig. 26. A fluidized catalytic cracking unit example of combining numeric-symbolic and symbolic-symbolic interpretation (Ramesh et at., 1992).

Figure 26, shown earlier, is a simple form of input mapping called table lookup. A more complicated inference mechanism is illustrated in Fig. 30. Here we see a simple example from a fluidized catalytic cracking unit in which multiple product quality attributes can be explained by multiple operating parameters (Ramesh et al., 1992).

Cracking The evolution of fluidized catalytic cracking since the early 1940s has resulted in several fluidized-bed process configurations. 

In 1971, LDHs containing different metal cations (such as Mg, Zn, Ni, Cr, Co, Mn and Al) with carbonate as interlayer anions, calcined at 473-723 K and partially or completely chlorinated, were reported to be effective as supports for Ziegler catalysts in the polymerization of olefins [8], with the maximum catalytic activity of polyethylene production observed for Mg/Mn/Al - CO3 LDH calcined at 473 K. Even earher, calcined Mg/Al LDHs were used to support Ce02 for SO removal from the emissions from fluidized catalytic cracking units (FCCU) [9,10]. Some transition metal oxides have also been... 

Venuto, P.B. and HaWb, E.T. (1979) Fluidized Catalytic Cracking with Zeolite Catalysts, Marcel Dekker, New York. Magee, J.S. and Mitchell, M.M. (1993) Fluid cataytic cracking science and technology, in Studies in Surface Science and Technology, vol. 75, Elsevier. 

Fluidized catalytic cracking reactors, called cat crackers or FCC reactors, are one of society s most important large-scale reactors. On an average, each such... 

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