Structure fluid catalytic cracking

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

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. 

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. 

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. 

Microporous and, more recently, mesoporous solids comprise a class of materials with great relevance to catalysis (cf. Chapters 2 and 4). Because of the well-defined porous systems active sites can now be built in with molecular precision. The most important catalysts derived from these materials are the acid zeolites. The acid site is defined by the crystalline structure and exhibits great chemical and steric selectivities for catalytic conversions, such as fluid catalytic cracking and alkane isomerization (cf. Chapter 2). In Section 9.5 we discuss the synthesis of zeolites and, briefly, of mesoporous solids. 

Cover Photo Photo courtesy of Irving Oil Ltd., Saint John, New Brunswick, Canada and Stone and Webster, Inc., A Shaw Group Company, Houston, Texas. The photo shows the Reactor-Regenerator Structure of the Converter Section of the RFCC (Resid Fluid Catalytic Cracking) Unit. This world class unit operates at the Irving Refinery Complex in Saint John, New Brunswick, Canada, and is a proprietary process of Stone and Webster. 

Section 2 introduces the idea of back-off and also presents a general linear framework for the back-off methodology while in section 3 the nonlinear back-off synthesis methodology is summarised. Section 4 presents a case study where the regulatory control structure of a fluid catalytic cracking model is investigated. The results of the linear and nonlinear back-off analysis are compared for first time and important conclusions are drawn in section 5. 

In this section a Fluid Catalytic Cracking (FCC) process case study is examined. The aim is to compare the alternative methodologies for regulatory control structure selection presented in sections 2 and 3. The FCC process is particularly suited for this purpose. The process d3mamics described by a low order but highly non-linear set of DAEs. The actual operation of the process is dominated by economics and a small number of disturbances that affect significantly its economics has been identified. Furthermore, the most appropriate control structure for this process is a matter of some controversy, with the conventional structure being criticized in a number of recent publications. 

When complex equipment (e.g., a converter and fractionator in a fluid catalytic cracking unit) is designed, a stair structure with a vertical pipe rack must be located between both vessels, as shown in Exhibit 12-26. Although elevators are often used, diem approval must be obtained before they are included. The optimum layout includes arranging the vessel platforms for easy access from the structure. Clearance between the vessel and structure platforms must accommodate die growth of the vessels, which should be calculated to satisfy safety concerns. This structure eliminates the... 

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