Catalysis/catalysts petroleum cracking

To satisfy the requirements of catalytic facilities in our refineries, catalyst production and sales have been thriving. Precise statistics for the catalyst industry are not available. But, in our evaluation, current sales of the main catalysts for cracking, reforming, and hydrogen pretreatment, are probably at an annual rate of 165 million dollars. Considering the future development of the apphcation of catalysis to the petroleum industry, sales may attain, by 1965, a level of 325 million dollars (see Table IV) (8). 

Fluid Cracking Catalysts, edited by Mario L. Occelli and Paul O Connor Catalysis of Organic Reactions, edited by Frank E. Herkes The Chemistry and Technology of Petroleum, Third Edition, Revised and Expanded, James G. Speight... 

Acids that have weakly nucleophilic anions, e.g. HS04e from dilute aqueous H2S04, are chosen as catalysts, so that their anions will offer little competition to H20 any R0S03H formed will in any case be hydrolysed to ROH under the conditions of the reaction. Rearrangement of the carbocationic intermediate may take place, and electrophilic addition of it to as yet unprotonated alkene is also known (p. 185). The reaction is used on the large scale to convert cracked petroleum alkene fractions to alcohols by vapour phase hydration with steam over heterogeneous acid catalysts. Also under acid catalysis, ROH may be added to alkenes to yield ethers, and RCOzH to yield esters. 

Since 1962 rare earths have been used to stabilize zeolite cracking catalysts for the petroleum industry (1, 2. Until recently this application to catalysis has been the only commercially significant one. Currently, however, a number of new applications of potential commercial significance are appearing. One of the most important of these is the use of cerium in catalysts for automobile exhaust emission control. We will emphasize this application in our review without neglecting other applications. 

In principle, all the kinetic concepts of intercalation introduced for layer-structured silicates hold for zeolites as well. Swelling, of course, is not found because of the rigidity of the three dimensional frame. The practical importance of zeolites as molecular sieves, cation exchangers, and catalysts (cracking and hydrocracking in petroleum industry) is enormous. Molecular shape-selective transport (large differences in diffusivities) and micro-environmental catalysis (in cages and channels)... 

Catalysis and reaction engineering became entwined in the late 1930s with the realization that the cracking of petroleum could be achieved most effectively using silica-alumina catalysts. With time, the connection between these two areas grew stronger as more and more catalytic processes were developed for the refining of petroleum, the production of petrochemicals, and the synthesis of polymers. 

There is good evidence now for believing that the poisoning of the silica-alumina gel catalysts used in cracking petroleum represents the neutralization of very strong active acids on the catalyst surface by bases (poisons) such as ion and amines. The acid sites may be H2O molecules bound to metal ions at the surface. See R. C. Hansford, Advances in Catalysis, vol. 4, chap. 1, Academic Press, Inc., New York, 1952. 

The early use and success of molecular sieve catalysis was spurred by the dramatic improvement in activity selectivity for catalytic cracking of vacuum gas oil achieved by using the faujasite based catalysts in comparison to the previously used amorphous SiOj/AUOj. These catalysts had a factor of about 10 -10 higher catalytic activity than the amorphous SiOj/AfrOj catalysts [42]. Paraffin, C4 to C8 isomerization [43] was one of the first successful non-petroleum processing applications using zeolite catalysts. The complexity of tailoring zeolite catalysts, however, is well illustrated by the fact that is only four years back that Shell has developed the first zeolite based process for isomerization of n-butene to isobutene [44]. 

From the standpoint of daily capacity, the greatest application of fluidized bed catalysis is to the cracking of petroleum fractions into the gasoline range. In this process the catalyst deactivates in a few minutes, so that advantage is taken of the mobihty of fluidized catalyst to transport it continuously between reaction and regeneration zones in order to maintain its activity some catalyst also must be bled off continuously to maintain permanent poisons such as heavy metal deposits at an acceptable level. 

The role of catalysis in the petroleum industry has been equally revolutionary. Meta I-supported systems (e.g. of Topsoe and Shell) for catalytic reforming, hydrodesulfurization and hydrodenitrification, alkylation catalysts and shape selective systems (e.g. zeolites and pillared clays) for catalytic cracking (FCC) and production of gasoline from methanol (Mobil MTG) all represent significant technical and commercial achievements. 

Heterogeneous catalysis is especially important in industry. Some of the major industrial processes that use solid catalysts include the synthesis of inorganic chemicals such as NH3, SO3 and NO, the various reactions used in the refining of crude petroleum such as cracking, isomerisation and reforming, and many of the major reactions of the petrochemical industry, such as the synthesis of methanol, the hydrogenation of aromatics and various controlled oxidations. Some of the major industrial processes to be catalysed by inorganic solids are shown in Table 1.3. 

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