Cracking catalysts calcination

To promote the activity of steam deactivated PILC and to evaluate PILC as a matrix component in cracking catalysts, REY-PILC and REY-clay containing 10 wt % REY were deactivated by method D. The MAT conversions, using North Sea gas oil, and surface area after regeneration are compared with calcined PILC below. 

Table 2. Microactivity test results for several pillared clay catalysts after calcination in air at 400 C for lOh. The zeolitic cracking catalyst has been aoed for 5 hours at 760 C with 100% steam at 1 atm. ...

A different type of catalytic titration was carried out by Stright and Danforth (48), who added varying amounts of lithium or potassium hydroxide to aqueous suspensions of cracking catalysts. The products were dried, calcined, and tested for cetane cracking at 500°C by means of a flow reactor. Plots of cetane conversion versus amount of added lithium hydroxide were used to determine titers for a variety of cracking catalysts (Fig. 11). This type of catalytic titration is not recommended for quantitative studies because it given high acidity values. In aqueous media, alkali... 

Hopkins (161) found that a steady decrease in n-heptane cracking activity occurred over La- and Ca-exchanged Y zeolites as the catalyst calcination temperature was increased from 350° to 650°C. The lanthanum form was about twice as active as the calcium form. Reduction in activity with increasing activation temperature was attributed to removal of acidic framework hydroxyl sites as dehydration becomes more extensive. The greater activity of La—Y with respect to the calcium form was thought to result from the greater hydrolysis tendency of lanthanum ion, which would require more extensive dehydration to result in the same concentration of acidic OH groups as found on Ca—Y. 

In any case, if a USY cracking catalyst is prepared by steam-calcination followed by an (NH4)2SiF6 treatment to remove EFAL, the activity of the treated catalyst will be lower than that of the chemically untreated one. 

Transmission electron micrographs and XPS results have been used to show that a catalyst, with a high silica content in the matrix, prevents nickel dispersion (16,18). In fact, in a FCC with a Si-rich (Si/Al = 4.3) surface, XPS data has indicated that calcination and steaming cause nickel (and vanadium) migration to the cracking catalyst surface where nickel sinters. As a result, nickel crystallites 50... 

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. 

Feed and catalysts. A regular Kuwait vacuum gasoil was used as a feed. Its characteristics can be found in Table II. Three commercial cracking catalysts with an increasing rare earth and alumina content, viz. A, B, and C, were tested. All catalyst were presteamed and deactivated to an equilibrium level by its supplier. Larger catalyst particles were removed with a 150 pm sieve. This step is followed by either a calcination or regeneration. Fresh, but pre-steamed catalyst was calcined at 773 K for 1 h, while coked catalyst was regenerated at 873 K for 2 h. 

Increased severity of acid treatment continuously increases the surface area and porosity of the clay, but cracking activity shows a maximum at intermediate treating severity (223,325). Mild acid treatment removes a large part of the alkali and alkaline-earth metals. More-severe acid treatment removes increasing quantities of aluminum and iron, as well as other metals still remaining after mild treatment. It has been reported that treatment of clay with ammonium chloride solution, instead of acid, also results in an active cracking catalyst (70). The ammonium ion displaces some of the metal constituents of the clay by base exchange the treated clay is then calcined to drive out ammonia. 

Although 1 mole H+ per mole aluminum may be titrated in dilute aqueous systems, the acidity of the calcined catalyst represents only a portion of this value (17). A value of acidity of 0.3 to 0.5 meq. H+/g- of catalyst may be taken as reasonably representative for commercial cracking catalysts. 

Although protons may be present in calcined cracking catalysts (8) and some authors have considered these protons as responsible for catalyst activity (21,22), the present considerations indicate that the Lewis acid which has also been suggested (23, 24) is entirely responsible for catalyst activity. Thus, the proton acidity of different acids bears little or no necessary relationship to their activity as acid catalysts (26), and silica-magnesia cracking catalysts which are actually basic in their aqueous solutions and do not exchange protons with alkali metal ions are active cracking catalysts. In the catalyst chemistry to be discussed, a proton may or may not be present, but it does not contribute to the activity of the cata,lyst. The presence or absence of a proton is associated with the manner in which water functions as... 

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. 

The parent rectorite is essentially inactive. Table 2. However, after reacting with Chlorhydrol and calcination in air at 400°C/10h, a pillared product with cracking activity typical of zeolitic fluid cracking catalyst (FCC) and of similarly pillared montmorillonites is obtained. Tables 2,3. The mica-like particles have a bulk density that is less than 502 that of ACH-bentonite granules with similar size, Table 2. Thus, for a given cat/oil ratio longer oil-catalyst contact times are obtained when cracking gas oils at MAT... 

An accelerated test for the vanadium tolerance of cracking catalysts involves inpregnation with a vanadium ccmpound followed by air calcination euid steam deactivation. Examination of experimental catalysts after inpregnation with 0, 1000, 3000 and 5000 ppm vcinadium shows loss of micro and meso-pore surface areas, crystallinity and catalytic activity in direct preportion to the... 

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