Liquid 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. 

MSCC [Millisecond catalytic cracking] A fluid catalytic cracking process which uses an ultra-short contact time reaction system. It is claimed that less capital investment and higher liquid yields can be achieved using this process, compared with conventional FCC units. Developed by Bar-Co and now offered by UOP it has been operating since 1994. 

Deep Catalytic Cracking. This process is a variation of fluid catalytic cracking. It uses heavy petroleum fractions, such as heavy vacuum gas oil, to produce propylene- and butylene-rich gaseous products and an aromatic-rich liquid product. The liquid product contains predominandy benzene, toluene, and xylene (see BTX processing). This process is being developed by SINOPEC in China (42,73). SINOPEC is currendy converting one of its fluid catalytic units into a demonstration unit with a capacity of 60,000 t/yr of vacuum gas oil feedstock. 

Riser the part of the bubble-plate assembly which channels the vapor and causes it to flow downward to escape through the liquid also the vertical pipe where fluid catalytic cracking reactions occur. 

Several reactor types have been described [5, 7, 11, 12, 24-26]. They depend mainly on the type of reaction system that is investigated gas-solid (GS), liquid-solid (LS), gas-liquid-solid (GLS), liquid (L) and gas-liquid (GL) systems. The first three arc intended for solid or immobilized catalysts, whereas the last two refer to homogeneously catalyzed reactions. Unless unavoidable, the presence of two reaction phases (gas and liquid) should be avoided as far as possible for the case of data interpretation and experimentation. Premixing and saturation of the liquid phase with gas can be an alternative in this case. In homogenously catalyzed reactions continuous flow systems arc rarely encountered, since the catalyst also leaves the reactor with the product flow. So, fresh catalyst has to be fed in continuously, unless it has been immobilized somehow. One must be sure that in the analysis samples taken from the reactor contents or product stream that the catalyst docs not further affect the composition. Solid catalysts arc also to be fed continuously in rapidly deactivating systems, as in fluid catalytic cracking (FCC). 

In petrochemical and oil refining operations, the zeolite is primarily responsible for the catalyst s activity, selectivity and stability (catalytic, thermal and hydrothermal). The fluid catalytic cracking process (FCC) is the most widely used of the oil refining process and is characterized by the use of a finely divided catalyst, which is moved through the processing unit. The catalyst particles are of such a size (about 70 pm) that when aerated with air or hydrocarbon vapor, the catalyst behaves like a liquid and can be moved easily through pipes. 

Fluid catalytic cracking, fluid cat-cracking or FCC, is a common oil refinery process. The duty of an FCC unit is to take a heavy low value gas oil or fuel oil and convert this to higher valued liquid products, particularly gasoline blend-stock. The process also produces diesel fuel blend-stock and a gas by-product stream. The gaseous by-products are rich in olefins and in particular propylene and isobutene. Ethylene is a minor component. 

One particular advantage of the CDTECH process is the ability of the alkylation reactor to accept a dilute ethylene feed. Because the alkylator operates in a mixed vapor-liquid phase, it is capable of utilizing dilute ethylene feeds, for example, offgas from a fluid catalytic cracking plant or dilute ethylene from a steam... 

Fluidization. Once the solids are in the bed, fluid is injected into the bed at a high velocity through a distributor, which is commonly either a grid or a porous plate at the bottom of the bed. The fluid can be both in liquid or gas form, as defined in physics. Very often, superheated steam is used or, in the case of fluid catalytic cracking, evaporated hydrocarbon molecule chains. 

Europe and Asia obtain propylene mainly from steam cracking of liquid petroleum feedstocks such as naphtha or from FCC units (fluid catalytic cracking). Also, propylene can be obtained from cracking of gas oil from refineries. Propylene can also be produced from cracking of propane and butane, to a lesser extent. This latter process is more feasible if the cost of propane is relatively low. 

Lappas, A.A., Papapetrou, M., Vasalos, I.A., 2007. Catalytic cracking to liquids (BTL) fuels with novel cracking catalysts. In Occelli, M.L. (Ed.), Fluid Catalytic Cracking VII Materials, Methods Ad Process Innovations, Studies in Surface Sciences and Catalysis, 166. Elsevier, Amsterdam. 

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