Zeolites catalytic cracking

Catalytic cracking Zeolite in Si02 A1203 matrix plus other ingredients (transport reactor)... 

Refinery catalysts Catalytic cracking Zeolites, silica-alumina... 

Catalytic cracking Zeolites 500-600 C 1-3 bar 10 (coke formation reversible deactivation.) 0.1 (ineversible deactivation)... 

P. B. Venuto and E. T. Habib, Jr., Eluid Catalytic Cracking with Zeolite Catalysts, Marcel Dekker, Inc., New York, 1979. 

Zeolites and Catalytic Cracking. The best-understood metal oxide catalysts are zeoHtes, ie, crystalline aluminosihcates (77—79). The zeoHtes are well understood because they have much more nearly uniform compositions and stmctures than amorphous metal oxides such as siUca and alumina. Here the usage of amorphous refers to results of x-ray diffraction experiments the crystaUites of a metal oxide such as y-Al202 that constitute the microparticles are usually so small that sharp x-ray diffraction patterns are not measured consequendy the soHds are said to be x-ray amorphous or simply amorphous. 

Acid-treated clays were the first catalysts used in catalytic cracking processes, but have been replaced by synthetic amorphous silica-alumina, which is more active and stable. Incorporating zeolites (crystalline alumina-silica) with the silica/alumina catalyst improves selectivity towards aromatics. These catalysts have both Fewis and Bronsted acid sites that promote carbonium ion formation. An important structural feature of zeolites is the presence of holes in the crystal lattice, which are formed by the silica-alumina tetrahedra. Each tetrahedron is made of four oxygen anions with either an aluminum or a silicon cation in the center. Each oxygen anion with a -2 oxidation state is shared between either two silicon, two aluminum, or an aluminum and a silicon cation. 

Comparison of Yield Structure for Fluid Catalytic Cracking of Waxy Gas Oil over Commercial Equilibrium Zeolite and Amorphous Catalysts... 

Catalytic cracking Conversion of vacuum gas oil into Zeolite Y... 

The most important undesired metallic impurities are nickel and vanadium, present in porphyrinic structures that originate from plants and are predominantly found in the heavy residues. In addition, iron may be present due to corrosion in storage tanks. These metals deposit on catalysts and give rise to enhanced carbon deposition (nickel in particular). Vanadium has a deleterious effect on the lattice structure of zeolites used in fluid catalytic cracking. A host of other elements may also be present. Hydrodemetallization is strictly speaking not a catalytic process, because the metallic elements remain in the form of sulfides on the catalyst. Decomposition of the porphyrinic structures is a relatively rapid reaction and as a result it occurs mainly in the front end of the catalyst bed, and at the outside of the catalyst particles. 

Table 9.5. Approximate product distributions of fluid catalytic cracking for amorphous silica-alumina and zeolite catalysts.

Catalytic cracking with faujasite zeolites X and y zeolites... 

The aim of this work is to compare the thermal and catalytic cracking under representative conditions. To make things easier, the zeolites are used as powder in the catalytic test. 

In the case of the zeolite Y, the product distribution is intermediate. This could be explained, as this catalyst is less active, by a product distribution obtained by a contribution of the thermal and catalytic cracking. 

R2R A catalytic cracking process using an ultrastable zeolite catalyst with two-stage regeneration. Developed by Institut Frangais du Petrole and used at Idemitsu Kosan s refineries at Aichi and Hokaido. In 1994, 13 existing plants had been converted to this process. 

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