Cracking catalysts chemical properties

Various catalysts used in the two processes have been described as follows zeolite, alumina, silica-alumina, FCC catalyst, reforming catalyst, and others. The most common catalysts used in the cracking of heavy hydrocarbons are acidic catalysts alumina and silica-alumina with mesopores, and also zeolite with micropores, etc. They are typically used in the commercial petroleum process. For the chemical properties of catalyst, the... 

Four types of REY zeolite (Si/Al = 4.8) with different crystal sizes and acidic properties were used. The physical and chemical properties of the fresh zeolites are given in Table 6.4. Polyethylene plastics-derived heavy oil, shown in Table 6.2, was used as the feed oil. The cracking reaction was conducted in a tubular reactor filled with catalyst particles under the following conditions time factor W/F = 0.2-3.0 kg-catkg oil h and reaction temperature = 300-450°C. The lumping of reaction products were gas (carbon number 1-4), gasoline (5-11), heavy oil (above 12), and a carbonaceous residue referred to as coke. The index of the gasoline quality used was the research octane number (RON), which was calculated from Equation 6.1 [31]. 

The use of CeOs-based materials in catalysis has attracted considerable attention in recent years, particularly in applications like environmental catalysis, where ceria has shown great potential. This book critically reviews the most recent advances in the field, with the focus on both fundamental and applied issues. The first few chapters cover structural and chemical properties of ceria and related materials, i.e. phase stability, reduction behaviour, synthesis, interaction with probe molecules (CO. O2, NO), and metal-support interaction — all presented from the viewpoint of catalytic applications. The use of computational techniques and ceria surfaces and films for model catalytic studies are also reviewed. The second part of the book provides a critical evaluation of the role of ceria in the most important catalytic processes three-way catalysis, catalytic wet oxidation and fluid catalytic cracking. Other topics include oxidation-combustion catalysts, electrocatalysis and the use of cerium catalysts/additives in diesel soot abatement technology. 

These results confirm that, because of their structure and physico-chemical properties, the HM and HZSM-5 zeolites are not suitable catalysts to produce the main reaction products with high selectivity values, because the side reactions of oligomerization, cracking, realkylation and coking are prevailing. 

Thus, it has been demonstrated by chemical tests that cracking catalysts display acid properties. This is true even after those materials have been calcined prior to their use as catalysts. The acidity, in terms of acidic sites per unit of surface area is small. The acid is strong in terms of effective hydrogen ion activity. There is more than sufficient hydrt en present in these catalysts to account for all the apparent acidity, assuming such acids to be Brpnsted acids. 

Zeolites first made their appearance as cracking catalysts in the petroleum refining industry and were then quickly taken up by the petrochemicals industry. Chen et al. (1989) and Corma (1991) give excellent reviews of these applications. The extraordinary shape-selective properties of zeolites have since been exploited by many sectors of the chemical industry. The properties of zeolites are so much in tune with the selectivity demands of industry and the environmental regulations of society that one can enthusiastically agree with the statement that zeolite ca talysis and technology will (almost) certainly be the future cornerstone of a clean, environmentally friendly organic chemicals industry (Hoelderich and van Bekkum, 1991). The factual basis for such optimism will be reviewed in this section. 

Catalytic Cracking Catalysts, Chemistry, and Kinetics, Bohdan W. Wojciechowski and Avelino Corma Chemical Reaction and Reactor Engineering, edited by J. J. Carberry and A. Varma Filtration Principles and Practices Second Edition, edited by Michael J. Matteson and Clyde Orr Corrosion Mechanisms, edited by Florian Mansfeld Catalysis and Surface Properties of Liquid Metals andAlloys,Yoshisada Ogino... 

If one examines the evolution of new zeolite structures over the past decade the most interesting discoveries have been made with high silica compositions. Many of these phases can be prepared in essentially all silica forms. Purists would prefer to classify such molecular sieves as organosilicates or porosils (1), in part because the physical properties differ from more classical low Si/Al ratio zeolites. In particular, the high silica zeolites tend to be more thermally stable and chemically robust. Additionally, the higher the Si/Al ratio the more hydrophobic the zeolite. These features are desirable for catalysts that may be used in catalytic processes such as cracking (3). 

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