Zeolites cracking process

Acid-treated clays were the first catalysts used in catalytic cracking processes, but have been replaced by synthetic amorphous silica-alumina, which is more active and stable.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. 

Houdry The first catalytic petroleum cracking process, based on an invention by E. J. Houdiy in 1927, which was developed and commercialized by the Houdry Process Corporation. The process was piloted by the Vacuum Oil Company, Paulsboro, NJ, in the early 1930s. The catalyst was contained in a fixed bed. The first successful catalyst was an aluminosilicate mineral. Subsequently, other related catalysts were developed by Houdry in the United States, by I. G. Farbenindustrie in Germany, and by Imperial Chemical Industries in England. After World War II, the clay-based catalysts were replaced by a variety of synthetic catalysts, many based on alumino-silicates. Later, these too were replaced by zeolites. U.S. Patents 1,837,963 1,957,648 1,957,649. 

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. 

Most of the commercial zeolite catalyzed processes occur either through acid catalysis fluid catalytic cracking (FCC), aromatic alkylation, methanol to olefins (MTO),... 

Olefin cracking has been developed as a process to produce propylene in a highly selective manner from butenes and pentenes. Zeolites used in processes such as UOP s Olefin Cracking Process are often MFI-based in order to avoid coke buildup during the reaction, leading to longer times between catalyst regeneration (Table 12.15). 

The synthesis of the open-framework zeolites improved the number of accessible active sites for catalysis dramatically. It is estimated that ZSM-5 has a turnover of more than 300 molecules per active site per minute during the cracking process, and that other... 

Acidic zeolite materials are the main catalysts in the cracking process, which is the most important process among industrial chemical processes. Broad studies of heterogeneous cracking catalysts, started in the 1950s, discovered that the basic nature of cracking catalysts is acidic, and generation of acidic sites on solids has been extensively studied. 

Hydrocarbon cracking catalysts comprising a USY zeolite and discrete particles of alumina dispersed in an inorganic oxide matrix are known. It has been investigated that catalytic cracking process utilizing catalysts comprising zeolites that have been pre-... 

Cerqueira and co-workers203 confirmed the appearance of the of the tetrahedral aluminium and phosphorus in AlPO-like crystalline structures both in beta (BEA) and in MOR zeolites treated with phosphoric acid. 31P MAS,27Al MAS and TQM AS NMR spectra permitted the species present in the samples to be assigned. Possibly, besides the the Altet-f species, other Al species are also taking part in the activity and selectivity of the catalysts. The formation of Alocl o P can also contribute to the increase in the activity by preventing further dealumination. Dual zeolite additives have no impact on the quality of naphtha when compared to MFI-based additives, which are used in the fluid catalytic cracking processes. 

Here we will describe the main aspects of the chemistry involved in selected zeolite-catalyzed processes in the field of oil refining and petrochemistry, such as short paraffin aromatization, skeletal isomerization of n-paraffins and n-olefins, isoparaffin/olefin alkylation, and catalytic cracking. 

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. 

D. L. Trimm in Fundamental Aspects of the Formation and Gasification of Coke in L. F. Albright, B. L. Crynes, W. H. Corcoran (eds.), Pyrolysis Theory and Industrial Practice , Academic Press, New York, 1983 L. F. Albright, B. L. Crynes, W. H. Corcoran (eds.), Pyrolysis Theory and Industrial Practice , Academic Press, New York, 1983 T. J. Ford, Ind. Eng. Chem. Fundam., 25, 240, 1986 Coastal Isobutane Cracking Process developed by Foster Wheeler P. B. Venuto and E. T. Habib, Fluid Catalytic Cracking with Zeolite Catalysts , Marcel Dekker, New York, 1979... 

In order to improve the olefin yield, zeolites which are more acidic than zeolite-Y are added to the matrix. These are mainly based on the smaller pored zeolite ZSM-5. This zeolite processes smaller molecules produced by the main cracking process and continues the cracking to smaller olefins and aromatics. 

Zeolites find major applications in catalysis. A form of the zeolite FAU is, for example, an active catalyst component in catalytic cracking of heavy hydrocarbons to produce motor gasoline and diesel. The catalyst activity arises from its Bronsted acidity, which in turn comes from the presence in the stmcture of protons attached to bridging oxygen atoms. Protons can be introduced by ion exchange of anunonium cations, followed by calcination to remove NH3 and generate the acid form of the zeolite. The process is more complex... 

A more recent development in fixed bed residue processing is the use of zeolitic cracking catalysts. These have been developed primarily in Japan, and are quite stable according to the literature (64). 

The book also explores the application of various acidic catalysts, such as silica-alumina, zeolites (HY, HZSM-5, mordenite) or alkaline compounds such as zinc oxide. However, the main problem with catalytic cracking is that in the course of the cracking process all catalysts deactivate very quickly. Expensive zeolite catalysts increase the cost of waste plastics cracking process to the point where it becomes economically unacceptable since the catalyst becomes contained in coke residue and therefore cannot be recovered and regenerated. 

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