Fluid cracking coking

Metal contaminants when deposited onto fluid cracking catalysis (FCC) have a serious detrimental effect on the catalysts physicochemical properties (1-21). Vanadium (at levels < 2,000 ppm) generally yield less hydrogen and coke than nickel contaminants in FCC s and its deleterious effects depend on its concentration and... 

The poisoning of fluid cracking catalysts (FCC) by vanadium is well known (7, 2). In general, vanadium is deposited on the cracking catalyst as coke by vanadyl porphyrins in the feed. During regeneration, the coke is burned off, and vanadium can be oxidized to the V+5 oxidation state. Woolery et al. (3) have shown that the oxidation state of the vanadium can alternate between +4 to +5 in... 

Chemical composition of waste plastic cracking products depends on shares of the individual polymers (PE, PP, PS) in the feed and process parameters. This fact decides the technological application of the final products. Important products of the cracking process, both petroleum fractions and waste plastics, are coke residues. Coke residue yield increases considerably, up to 10 wt%, in cracking of municipal and industrial waste plastics since they contain various inorganic impurities and additives. It can be applied as solid fuel, like brown coal. In the fluid cracking the solid residue is continuously removed from the process by combustion in a regenerator section. 

Combination processes (Table 2.10) link two light gaseous streams to form a larger higher valued fuel product. At least one of the gas streams used in the combination process is a reactive olefin hydrocarbon molecule produced via fluid catalytic cracking, coking or outside petrochemical operation. The major combination processes are alkylation, etherification and polymerization. 

Yen eta/ [1988] Fluid catalytic cracking Coke formation is kinetics control with fourth order reaction None considered (1) Complex - many parameters (2) Tested against actual coke data from both pilot and commercial fluid catalytic cracking units... 

FiaURE 8-8 Gasoline yield is primarily a (unction ot the Watson characterization factor for virgin vacuum gas oil. Coke yield held constant (adapted from the Davison Fluid Cracking Catalyst Handbook, p. 53). 

Catalytic Processes. A second group of refining operations which contribute to gas production are the catalytic cracking processes, such as fluid-bed catalytic cracking, and other variants, in which heavy gas oils are converted into gas, naphthas, fuel oil, and coke (5). 

The MTO process employs a turbulent fluid-bed reactor system and typical conversions exceed 99.9%. The coked catalyst is continuously withdrawn from the reactor and burned in a regenerator. Coke yield and catalyst circulation are an order of magnitude lower than in fluid catalytic cracking (FCC). The MTO process was first scaled up in a 0.64 m /d (4 bbl/d) pilot plant and a successfiil 15.9 m /d (100 bbl/d) demonstration plant was operated in Germany with U.S. and German government support. 

The catalyst is employed in bead, pellet, or microspherical form and can be used as a fixed bed, moving bed, or fluid bed. The fixed-bed process was the first process used commercially and employs a static bed of catalyst in several reactors, which allows a continuous flow of feedstock to be maintained. The cycle of operations consists of (/) the flow of feedstock through the catalyst bed (2) the discontinuance of feedstock flow and removal of coke from the catalyst by burning and (J) the insertion of the reactor back on-stream. The moving-bed process uses a reaction vessel, in which cracking takes place, and a kiln, in which the spent catalyst is regenerated and catalyst movement between the vessels is provided by various means. 

Refinery Production. Refinery propylene is formed as a by-product of fluid catalytic cracking of gas oils and, to a far lesser extent, of thermal processes, eg, coking. The total amount of propylene produced depends on the mix of these processes and the specific refinery product slate. For example, in the United States, refiners have maximized gasoline production. This results in a higher level of propylene production than in Europe, where proportionally more heating oil is produced. 

The most dominant catalytic process in the United States is the fluid catalytic cracking process. In this process, partially vaporized medium-cut petroleum fractions called gas oils are brought in contact with a hot, moving, freshly regenerated catalyst stream for a short period of time at process conditions noted above. Spent catalyst moves continuously into a regenerator where deposited coke on the catalyst is burnt off. The hot, freshly regenerated catalyst moves back to the reactor to contact the hot gas oil (see Catalysts, regeneration). 

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