Fluid catalytic cracking powder catalyst

Example 9.7. Approximately 40% of the oil produced in the world is cracked catalytically to smaller molecules with zeolite catalysts—known as FCC (fluid catalytic cracking). The catalyst has an average diameter around 70 p,m and it becomes coarser with time as the fine fraction of the powder is lost in the cyclones. For a FCC unit containing 2001 of catalyst, what is the smallest sample size required to achieve a sampling error less than 5% if the coarsest size range is from 177 ttm to 210 tim. The particle density of FCC is 1200 kg m . ... 

The first cracking catalysts were acid-leached montmorillonite clays. The acid leach was to remove various metal impurities, principally iron, copper, and nickel, that could exert adverse effects on the cracking performance of a catalyst. The catalysts were first used in fixed- and moving-bed reactor systems in the form of shaped pellets. Later, with the development of the fluid catalytic cracking process, clay catalysts were made in the form of a ground, sized powder. Clay catalysts are relatively inexpensive and have been used extensively for many years. 

Fluidized catalytic processes, in which the finely powdered catalyst is handled as a fluid, have largely replaced the fixed-bed and moving-bed processes, which use a beaded or pelleted catalyst. A schematic flow diagram of fluid catalytic cracking (FCC) is shown in Fig. 4. 

Figure 4 Catalytic cracking (fluid catalytic cracking). Heavy fraction gas oils are cracked (broken down) into lower molecular weight fractions in the presence of finely powdered catalyst, handled as a fluid. (From Ref. 5.)...

The fluid-bed process differs from the fixed-bed and moving-bed processes, insofar as the powdered catalyst is circulated essentially as a fluid with the feedstock. The several fluid catalytic cracking processes in use differ primarily in mechanical design. Side-by-side reactor-regenerator construction along with unitary vessel construction (the reactor either above or below the regenerator) are the two main mechanical variations. 

Example 9.1. Three students measured the mass of three powders—sand, fluid catalytic cracking catalyst (FCC), and Cas (P04)2—10 times successively in a Scott Volumeter. The data is summarized in Table E9.1. Calculate the Scott density, uncertainty, and repeatability. The volume and uncertainty of the cylinder is 25.00 0.03 cm. ... 

The catalyst particles in the Houdry-type cracking processes, both fixed and moving bed, were initially granules, then pellets or beads of about 3 mm diameter. Later, fluid catalytic cracking used beds of catalyst in the form of fine powder, initially made by grinding and later by spray drying of microspheres, with 50 to 80 wt% of the particles in the size range of about 50 to 150 microns, with the remainder down to 20 or even 10 microns (That part was quickly lost from the unit, as fines.) ( 7),... 

The moving bed-type process that eventually won" was fluid catalytic cracking (FCC). The early developments for this process were accomplished by Standard (New Jersey). Work with fixed-bed reactors during the late 1930s convinced E. V. Murphree, vice-president in charge of development, to conclude that the only viable approach was to use circulating catalyst processing that would allow steady-state operations (4). He also made the decision to utilize a powdered catalyst (4). 

The early type of catalytic cracking units involved the use of a fixed-bed operation and this type of processing has been largely supplanted by the fluid- and moving-bed types of operation. The catalysts are used in the form of powder, microspheres, spheres, and other preformed shapes. The catalysts employed are either synthetic silica-alumina composites or natural aluminosilicates. Other catalysts, such as silica-magnesia, alumina-boria, silica-zirconia, and silica-alumina-zirconia have found limited commercial application and, at present, the synthetic silica-alumina and natural clay catalysts dominate the field. 

Catalytic cracking is a key process used to increase the quality and quantity of gasoline fractions. The most commonly used process is the fluid bed type, which uses a finely powdered zeolite catalyst that is kept in suspension in the reactor... 

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