Catalytic cracking catalyst case

The following examples reflect the main advantages of SIMS analysis the microanalysis of elements at trace level in the case of catalytic cracking catalysts (FCC). the sensitivity to light elements for the study of coke distribution and the possibility of providing composition profiles on zeolites modified by chemisorption of metals. 

Heterogeneous Catalysis, Selected Case Histories, Ed. by B. H. Davis and W. P Hettinger, (C. Plank, The Invention of Zeolite Catalytic Cracking Catalysts, p 253), ACS Symposium Series 222 (1983). 

In the case of the zeolite Y, the product distribution is intermediate. This could be explained, as this catalyst is less active, by a product distribution obtained by a contribution of the thermal and catalytic cracking. 

The modem gasolines are produced by blending products from cmde oil distillation, that is, fluid catalytic cracking, hydrocraking, reforming, coking, polymerization, isomerization, and alkylation.Two clear examples of the possible use of solid-acid catalysts in refining processes are the isomerization of lineal alkanes and the alkylation of isobutene with butanes. In both these cases, and due to the octane... 

Results, again, show net gain over the same cracking catalyst used previously for cerium/alumina case. Cerium, moreover, seems to act as a promotor for other rare earths as could be implied from the synergistic effect observed between cerium and lanthanum (27). Our conclusions about the catalytic effect of cerium have been confirmed recently by others (28). 

In some cases, as for example in catalytic cracking on silica-alumina, processes similar to those involved in sintering and recrystallisation can lead to a change in the texture of the catalyst. Surface areas are diminished and the pore-size distribution is changed. 

Hence, primary products may be obtained which is not the case in catalytic cracking over monofunctional catalysts where formation of carbenium ions occurs by hydride abstraction from the n-alkane rather than via n-alkenes. 

Several reactor types have been described [5, 7, 11, 12, 24-26]. They depend mainly on the type of reaction system that is investigated gas-solid (GS), liquid-solid (LS), gas-liquid-solid (GLS), liquid (L) and gas-liquid (GL) systems. The first three arc intended for solid or immobilized catalysts, whereas the last two refer to homogeneously catalyzed reactions. Unless unavoidable, the presence of two reaction phases (gas and liquid) should be avoided as far as possible for the case of data interpretation and experimentation. Premixing and saturation of the liquid phase with gas can be an alternative in this case. In homogenously catalyzed reactions continuous flow systems arc rarely encountered, since the catalyst also leaves the reactor with the product flow. So, fresh catalyst has to be fed in continuously, unless it has been immobilized somehow. One must be sure that in the analysis samples taken from the reactor contents or product stream that the catalyst docs not further affect the composition. Solid catalysts arc also to be fed continuously in rapidly deactivating systems, as in fluid catalytic cracking (FCC). 

Fluidised bed reactors are rarely suitable for catalytic studies because of their relatively large volume, the large quantity of catalyst to use and the difficulty to control bubble agglomeration and instabilities. However, it is still almost irreplaceable for the testing of fluid-bed cracking catalysts. On a laboratory scale a modification is applied in which an intensive mixing of particles is achieved by means of mechanical vibration. In this case, the gas flow rate can vary over a... 

In many ways, dehydrogenation is similar to catalytic cracking. In both cases, a catalyst lowers the activation energy, and both reactions use high temperatures to increase a favorable entropy term (—T AS) and overcome an unfavorable enthalpy term (A H). Unfortunately, dehydrogenation and catalytic cracking also share a tendency to produce mixtures of products, and neither reaction is well suited for the laboratory synthesis of alkenes. 

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