Cracking catalysts preparation

Attrition- and Metal-Resistant Fluid Cracking Catalyst Prepared with Alumina Powder in the Matrix... 

At present, the aforementioned patent techniques have been industrialized for preparation of Si-rich zeolites. The industrial equipment based on the CHZ-3 residual oil cracking catalyst prepared using the corresponding zeolite as the active component has been in operation for heavy-oil catalytic cracking (RFCC). 

An important recent catalyst development is related to the nondestructive framework substitution of Si for A1 in the Y zeolite, described above. Using this recently disclosed mild aqueous chemistry, silicon-enriched forms of the Y zeolite structure (called LZ-210) have been synthesized, greatly improving the thermal and hydrothermal stability of the Y crystal. Cracking catalysts prepared from these silicon-rich zeolites show substantially increased cracking activity retention, following severe steaming pretreatments. In addition. 

Steam-aged pillared rectorites, at MAT conditions, have cracking activity similar to that of a commercial fluidized cracking catalyst (FCC) and can be regenerated with ease. However, their coke and light gas (h, CH.) selectivity will have to be drastically improved before these clays can compete with zeolites in cracking catalyst preparation. 

Volume 149 Fluid Catalytic Cracking VI Preparation and Characterization of Catalysts... 

Chromium zeolites are recognised to possess, at least at the laboratory scale, notable catalytic properties like in ethylene polymerization, oxidation of hydrocarbons, cracking of cumene, disproportionation of n-heptane, and thermolysis of H20 [ 1 ]. Several factors may have an effect on the catalytic activity of the chromium catalysts, such as the oxidation state, the structure (amorphous or crystalline, mono/di-chromate or polychromates, oxides, etc.) and the interaction of the chromium species with the support which depends essentially on the catalysts preparation method. They are ruled principally by several parameters such as the metal loading, the support characteristics, and the nature of the post-treatment (calcination, reduction, etc.). The nature of metal precursor is a parameter which can affect the predominance of chromium species in zeolite. In the case of solid-state exchange, the exchange process initially takes place at the solid- solid interface between the precursor salt and zeolite grains, and the success of the exchange depends on the type of interactions developed [2]. The aim of this work is to study the effect of the chromium precursor on the physicochemical properties of chromium loaded ZSM-5 catalysts and their catalytic performance in ethylene ammoxidation to acetonitrile. 

The most successful application of microwave energy in the preparation of heterogeneous solid catalysts has been the microwave synthesis and modification of zeolites [21, 22], For example, cracking catalysts in the form of uniformly sized Y zeolite crystallites were prepared by microwave irradiation in 10 min, whereas 10-50 h were required by conventional heating techniques. Similarly, ZSM-5 was synthesized in 30 min by use of this technique. The rapid internal heating induced by microwaves not only led to a shorter synthesis time, and high crystallinity, but also enhanced substitution and ion exchange [22]. 

The CVD catalyst exhibits good catalytic performance for the selective oxidation/ammoxida-tion of propene as shown in Table 8.5. Propene is converted selectively to acrolein (major) and acrylonitrile (minor) in the presence of NH3, whereas cracking to CxHy and complete oxidation to C02 proceeds under the propene+02 reaction conditions without NH3. The difference is obvious. HZ has no catalytic activity for the selective oxidation. A conventional impregnation Re/HZ catalyst and a physically mixed Re/HZ catalyst are not selective for the reaction (Table 8.5). Note that NH3 opened a reaction path to convert propene to acrolein. Catalysts prepared by impregnation and physical mixing methods also catalyzed the reaction but the selectivity was much lower than that for the CVD catalyst. Other zeolites are much less effective as supports for ReOx species in the selective oxidation because active Re clusters cannot be produced effectively in the pores of those zeolites, probably owing to its inappropriate pore structure and acidity. 

A cracking catalyst is subjected to two pretreatment steps. The first step effects vanadium removal the second, nickel removal, to prepare the metals on the catalyst for chemical conversion to compounds (chemical treatment step) that can... 

Different procedures can be used in practice to activate the zeolite, and the choice of a particular method will depend on the catalytic characteristics desired. If the main objective is to prepare a very active cracking catalyst, then a considerable percentage of the sodium is exchanged by rare earth cations. On the other hand, if the main purpose is to obtain gasoline with a high RON, ultrastable Y zeolites (USY) with very low Na content are prepared. Then a small amount of rare earth cations is exchanged, but a controlled steam deactivation step has to be introduced in the activation procedure to obtain a controlled dealumination of the zeolite. This procedure achieves a high thermal and hydrothermal stability of the zeolite, provided that silicon is inserted in the vacancies left by extraction of A1 from the framework (1). The commercial catalysts so obtained have framework Si/Al ratios in the... 

Catalyst Preparation. For most of the experiments conducted in this study, nickel or vanadium impregnated non-zeolitic particles were blended with metals-free high activity cracking component. This allowed us to examine the effects of the metals on the non-zeolitic component. The high activity zeolitic particles were prepared by in-situ zeolite synthesis on kaolin-based microspheres... 

At very low surface areas (about 5 m /g) and constant conversion (70%), the contaminant selectivities are dominated by the matrix composition (Table I). Rare earth and magnesium-containing microspheres were prepared to examine the effects of these metal oxides on catalyst selectivities in the presence of nickel and vanadium. These oxides were chosen because the literature (3,5,10-15) has shown them to be effective at reducing the deleterious effects of vanadium in cracking catalysts. 

When cracking catalysts are prepared with a silica or silica-alumina gel base, the pore volume and average pore... 

In response to recent federal and local environmental concerns (e.g., industrial emission controls and lead phase-out) and to the growing interest of refiners in cracking residual fuels, researchers have generated new families of cracking catalysts. There is now a need to review the merits of these newly developed materials. This volume contains contributions from researchers involved in the preparation and characterization of cracking catalysts. Other important aspects of fluid catalytic cracking, such as feedstocks and process hardware effects in refining, have been intentionally omitted because of time limitations and should be treated separately in future volumes. 

It follows from all the above considerations that the acidic character of the surface is necessary for the esterification reaction. This view is supported by the parallel found by some workers [405,406] between the rate of esterification and that of other typical acid-catalysed reactions. A linear correlation was established between the rate of acetic acid—ethanol esterification and that of deisopropylation of isopropylbenzene on a series of silica—alumina, alumina—boria and alumina catalysts [406] a similar relation was found between the rate coefficient of the same esterification reaction and the cracking activity of a series of silica—alumina catalysts prepared in a different way [405]. 

The major contaminating metals found on catalytic cracking catalyst are vanadium, nickel, copper, chromium, and iron. Small amounts of these metals are present in the crude petroleum and, except for some of the iron, all are in the form of metal-organic compounds. Some of these compounds are volatile and when the vacuum gas oil feed to the catalytic cracking units is prepared, they appear in the gas oil. A fraction of the iron, and probably chromium, found on the catalyst is the result of erosion and corrosion either in the lines or in the equipment. 

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