Interaction with cracking catalysts

Two sets of experiments were made to show the effect of steaming temperature on stability. In the first set, steaming was done non-interactively. Cerium/alumina additive was steamed (100% steam, 1 atm) for 5 hours in a fixed bed from 1200 to 1450 F. SO2 removal ability was then measured on these steamed samples diluted with cracking catalyst. The data in Figure 14 show that, for steamings done separate from cracking catalyst, losses of SO2 removal ability are small but become more pronounced above 1350 F. 

All these difficulties arising from the interaction of cracking catalysts with an aqueous medium can be avoided by using the adsorption of gaseous substances of basic properties for the investigation of these catalysts. It is the authors belief that the only really valid demonstration and measurement of the acidity of cracking catalysts has to be based on the observation of chemisorption of basic substances from a... 

The Mobility of Silica in Steam. The reactivity of silica and silica-containing materials to steam has been assumed in the literature to explain several phenomena, a few of which are the sintering of silica (35), the aging of amorphous silica alumina cracking catalysts (36) and the formation of ultrastable molecular sieves (37). The basis of all these explanations is the interaction of siliceous materials with water to form mobile, low molecular weight silicon compounds by hydrolysis (38) such as ... 

Losses incurred in the non-interactive steamings, however, were lower than those found in the second set of experiments where the cerium/alumina additive was steamed together with a low alumina cracking catalyst at various temperatures. The results from this second set of experiments, shown in Figure 14, indicate that losses are important at temperatures above 1200 F. It should be noted that SO2 removal ability was measured under the same conditions in both sets of experiments. Also, these fixed bed steaming seem to be harsher than fluidized bed steamings because the losses incurred are greater. 

The interactions of the acid sites on clay cracking catalysts with water can be studied readily by immersional calorimetry even if chemisorption occurs and yields information concerning the type and energy distribution of these sites as we shall see in Sec. VII,A. 

Sect. 1.2, the surface of an oxide can change its structure quite easily. For example, cracking catalysts exchange oxygen with water almost instantaneously at higher temperatures [74,75] the interaction of water with such catalysts must therefore be a complex process, involving not only an adsorption in molecular form. 

Mechanism. The interaction of antimony with supported nickel particles was studied with X-ray diffraction (XRD) (10) These studies suggested that a high level of antimony is present on the surface of Ni-Sb alloys. Further studies of the Ni-Sb alloy, using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), confirmed the presence of an antimony enriched surface (.11) The surface enrichment of antimony on the Ni-Sb alloy would be expected to significantly alter the catalytic activity of nickel, as indeed occurs when antimony is added to nickel laden cracking catalysts. 

A study of the vanadium catalyzed dehydrogenation reaction showed antimony interacts with vanadium and decreases its dehydrogenation activity. Cracking catalyst was contaminated with vanadium in the laboratory, A portion of this contaminated catalyst was then treated with an antimony containing compound to passivate vanadium. The catalysts were evaluated by cracking gas oil. The yield of hydrogen for passivated catalyst averaged fifteen percent less than for the unpassivated catalyst. 

They find that Vanadium interacts with Nickel in a manner which inhibits the deactivation behaviour of Nickel. They therefore conclude that metals resistant cracking catalysts must be evaluated in the presence of both Nickel and Vanadium. We find that also the mobility of Vanadium is reduced by the presence of Nickel. 

For the production of gasoline and other fuels by catalytic cracking of oils, a fluid bed reactor is used. This is a hybrid of a fixed bed and slurry phase reactor. The catalyst is fluidized as it interacts with the feed to be processed. This application is so important it... 

Components of fluidized cracking catalysts (FCC), such as an aluminosilicate gel and a rare-earth (RE) exchanged zeolite Y, have been contaminated with vanadyl naphthenate and the V thus deposited passivated with organotin complexes. Luminescence, electron paramagnetic resonance (EPR) and Mossbauer spectroscopy have been used to monitor V-support interactions. Luminescence results have indicated that the naphthenate decomposes during calcination in air with generation of (V 0)+i ions. After steam-aging, V Og and REVO- formation occurred. In the presence of Sn, Tormation Of vanadium-tin oxide species enhance the zeolite stability in the presence of V-contaminants. 

Hershkowitz et al. (3,10,11) measured adsorption and coke deposition on zeolite catalysts as well as catalytic cracking activity of FCC catalysts in short-contact-time interactions with decane at 573 K. They used 5 pi liquid decane injections to the catalyst bed to simulate FCC reaction conditions. Hershkowitz et al. focused on the measurement of adsorption and coke formation during the flow of the pulses. 

Nickel and vanadium are contained within the crude oil as their respective porphyrins and napthenates (2). As these large molecules are cracked, the metals are deposited on the catalyst. Nickel which possesses a high intrinsic dehydrogenation and hydrogenolysis activity drastically increases the production of coke and dry gas (particularly H2) at the expense of gasoline. Vanadium on the other hand interacts with the zeolitic component of a cracking catalyst and leads to destruction of its crystallinity. This results in reduced activity as well as an increase in non-selective amorphous silica-alumina type cracking. Supported vanadium also has an intrinsic... 

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. 

In the case of Ni2P(001), the Ni—>P charge transfer is not large (<0.1 e) [15] and the surface has a substantial number of Ni atoms. Clusters of three Ni atoms are present (Fig. 6.8), and the separation between these clusters is not large enough to prevent effective bonding interactions with a relatively big molecule like thiophene. At 100 K molecular adsorption of C H S on Ni2P(001) occurs, but at temperatures above 200 K the surface is able to crack the C-S bonds of the adsorbate [15]. Similar results have been found for the interaction of thiophene with Ni P/SiOj catalysts [32]. 

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