Cracking catalysts quinoline

Acid catalysts such as zeolites can be readily poisoned by basic organic compounds. One of the earlier studies of the deactivation of silica-alumina cracking catalysts by organic nitrogen compounds such as quinoline, quinaldine, pyrrole, piperidine, decylamine and aniline was done by Mills et al (6). The results of their partial poisoning studies showed an exponential dependence of the catalyst activity for cumene cracking reaction or... 

Physical properties, notably the specific surface areas, have been proposed by some authors as a measure for the activity of catalysts. This correlation is successful only when applied to catalysts which resemble one another in their composition and in their method of preparation. That surface area cannot be considered to be of exclusive importance to catalytic activity is demonstrated by the rather extreme examples given in Table VII. On the other hand, the fact that the capacity for quinoline chemisorption is quantitatively related to the activity of cracking catalysts is shown by Fig. 8 obtained with catalysts of various compositions, methods of preparation, and activities. The amount of quinoline chemisorbed thus measures a general property of this entire class of catalysts which is fundamentally related to their ability to act as catalysts. 

Fig. 3. Quinoline chemisorption at 315° as a function of activity for cracking light East Texas gas-oil (32). O, Si02-Al203 Houdry type S) , SiOj-1% Al203 , clay catalyst (fil-trol) O, SiOj-MgO V, Si02-Zr02. (Reprinted with permission of the American Chemical Society.)...

The work by Mills et al. (32) includes an early example of catalytic titration behavior. Figure 10 taken from their study shows that cumene cracking at 425°C drops sharply as nitrogen bases are chemisorbed in increasing amounts on silica-alumina catalyst. Base effectiveness decreases in the order quinaldine > quinoline > pyrrole > piperidine > decylamine > aniline. 

The adsorption of cumene and inhibitors on active cracking sites follows a Langmuir type of isotherm. This means that there is little or no interaction among the chemisorbed molecules on the surface. This might be expected to be the case as studies of the chemisorption of the inhibitor quinoline by similar catalyst (14) show that the surface is sparsely covered with active sites (<5% of internal surface area covered with chemisorbed quinoline at 315°C.). In addition, the active sites are homogeneous with respect to adsorption energies. 

The deactivation of a lanthanum exchanged zeolite Y catalyst for isopropyl benzene (cumene) cracking was studied using a thermobalance. The kinetics of the main reaction and the coking reaction were determined. The effects of catalyst coke content and poisoning by nitrogen compounds, quinoline, pyridine, and aniline, were evaluated. The Froment-Bischoff approach to modeling catalyst deactivation was used. 

The effect of quinoline and phenanthrene additions to a n-hexadecane feedstock has been determined for a model four-component FCC catalyst by means of a MAT reactor with analysis of all products and characterisation of the coke produced. Both additions lead to an overall loss in conversion quinoline is considered to act as a poison while phenanthrene participates strongly in coke formation and the resultant coke becomes more aromatic in nature. The cracking propensity and associated coke formation have been measured for a series of FCC catalysts with differing compositions. Increasing amounts of zeolite in a matrix lead to increasing extents of conversion but with little effect on the extent of coke production. However, a pure zeolite gave a very high coke content. 

The studies of Mills, Boedeker, and Oblad (2) on the chemisorption of the inhibition quinoline on similar catalysts can be used to place an upper limit on the value of Bo. Their data show that 1.27 X quinoline mole-cules/sq. m. are required to reduce the cumene cracking activity to essentially zero. 

A catalyst on which quinoline has been adsorbed at 427° has a pale-green translucent appearance, in marked contrast to the black appearance of a catalyst which has been inactivated by the deposition of a hydrocar-bonaceous residue during cracking. On boiling a quinoline-treated catalyst with aqueous hydrochloric acid solution, an extract was obtained which contained the major portion of the quinoline. These observations... 

Inactivation of a Cracking Catalgst by a Basic Nitrogen Compound Comparison of Quinoline Charged Before or With Cumene over Catalyst Catalyst (200 cc.) Houdry SiOj-AljOj of activity 32 (gasoline) (CAT-A) cracking conditions 427°, 1.5 liquid hourly space velocity, 10-minute test. 

Effects of partial poisoning were investigated by determining the influence on the cracking of cumene of a pretreatment of a given catalyst with various amoimts of quinoline and with various other organic nitrogen compounds. The data from this study are shown in Fig. 12. It... 

It is of interest to know the uniformity or lack of uniformity in terms of catalyst surface. For any given catalyst, the fraction of its total surface which is occupied by active sites can be estimated from the amount of basic nitrogenous molecules which are chemisorbed on its surface. The exact area covered by a quinoline molecule is uncertain depending upon whether or not it lies flat on the surface. However, taking 36 A. as the area of a flat-lying quinoline molecule bound to the surface, in the case of the catalyst in Table I, a simple calculation shows that only about four per cent of the surface is covered. Hence, the conclusion is that by far the major part of the surface does not contribute to the cracking activity of the catalyst. 

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