Diffusion effects in catalytic gas oil cracking

Best, D.A.; Pachovsky, Roman A.; Wojciechowski, B. W.

doi:10.1002/cjce.5450490617

Cited by 16 publications

(12 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The same phenomenon was observed by Best and Wojciechowski [9,16,19]. We report here data for ethyl toluene production for the first time.…”

Section: Discussion Of Resultssupporting

confidence: 85%

“…This result agrees with the observation of other workers [4,9] who have shown that an REY zeolite calcined at 480°C contains predominantly Bronsted-type active sites.…”

Section: Initial S E L E C T I V I T I E Ssupporting

confidence: 95%

“…At the same time in both HY and LaY catalysts, but far more prominently in LaY catalysts, Lewis sites are formed [4,9,19,20]. In all catalysts and at all levels of exchange it appears that the catalytically active Bronsted and Lewis sites are identical, as judged by the activation energies of the various primary reactions which occur on them and which are reported in Table IV and in [9]. However, as the exchange level of LaNaY is raised, or in going from HY to Lay, the relative proportion of BronstedLewis sites is changed.…”

Section: Discussionmentioning

confidence: 96%

“…Among the voluminous reports on cumene cracking is a cohesive set of works by Wojciechowski et a1 [9, who have systematically pursued the behavior of zeolite catalysts in various forms, using cumene cracking as a test reaction. To date, however, the kinetics of minor primary product formation in cumene cracking over a partially exchanged LaY zeolite have not been reported.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Kinetics of the formation of primary products of cumeme cracking over a partially exchanged LaY‐Zeolite

Corma

Farag

Wojciechowski

1981

Int J of Chemical Kinetics

Self Cite

View full text Add to dashboard Cite

The kinetics of formation of primary products from cumene cracking over a partially exchanged LaNaY catalyst have been studied a t 400,450, and 500°C. It has been found that in both the fully and the partially exchanged LaNaY zeolite catalysts the nature of active sites is the same. The higher activity of the fully exchanged catalyst is attributed to a higher concentration of the active sites. It has also been found that an increase in exchange level leads to an increase in the number of both Bronsted and Lewis active sites, but in somewhat different proportions. A comparatively slight increase in the decay rate constant is observed over the same increase in the level of exchange.

show abstract

“…The same phenomenon was observed by Best and Wojciechowski [9,16,19]. We report here data for ethyl toluene production for the first time.…”

Section: Discussion Of Resultssupporting

confidence: 85%

“…This result agrees with the observation of other workers [4,9] who have shown that an REY zeolite calcined at 480°C contains predominantly Bronsted-type active sites.…”

Section: Initial S E L E C T I V I T I E Ssupporting

confidence: 95%

Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Kinetics of the formation of primary products of cumeme cracking over a partially exchanged LaY‐Zeolite

Corma

Farag

Wojciechowski

1981

Int J of Chemical Kinetics

Self Cite

View full text Add to dashboard Cite

show abstract

“…In previous publications (Pachovsky, 1971;Best, 1971;Campbell, 1969) it has been proposed that gas oil cracking can be represented by the mechanism A…”

Section: Theorymentioning

confidence: 99%

Theoretical interpretation of gas oil selectivity data on X‐sieve catalyst

1973

View full text Add to dashboard Cite

A six-parameter multiresponse model based on the catalyst aging theory of Wojciechowski (1968) is applied to experimental selectivity data in gas oil cracking. Within the range of conditions studied, the model gave an adequate fit to the data. It was found that the selectivity curves at various cat/oil ratios were contained within optimum and minimum performance envelopes but that the relationships between these envelopes and the selectivity curves were not quite as simple as had previously been reported for a theoretical example (Campbell and Wojciechowski, 1969). The optimum time-on-stream for each of the cat/oil ratios was about one minute. Maximum gasoline production was 59 weight yo at 81 weight 7 ' total cumulative conversion, resulting in a gasoline efficiency of 72.8y0.

show abstract

Effects of diffusion resistance on gasoline selectivity in catalytic cracking

Pachovsky

Wojciechowski

1973

AIChE Journal

View full text Add to dashboard Cite

The time on stream theory of catalyst decay is applied to gas oil cracking selectivity data from a static bed reactor operating with a diffusion limited catalyst. It is found that intraparticle diffusion affects the reactions leading to the disappearance of gas oil to a much greater extent than the reaction leading to the recracking of gasoline and catalyst poisoning. Reasons for this behavior are postulated. It is also found that the overall kinetic order for the rate of disappearance of gas oil is decreased with the result that maximum selectivity occurs at a higher conversion value than for a corresponding diffusion-free catalyst. It is concluded that probably diffusion limitation is not a serious problem with respect to gasoline selectivity in commercial reactors. ROMAN SCOPEDiffusional limitations are generally to be avoided in catalytic systems. Various steps are therefore taken to ensure that reactions are not carried out under conditions involving diffusion limitations. Despite such precautions, in some cases it is impossible to avoid the use of a diffusion limited catalyst. One industrial example of this may be the moving bed reactor. Various physical factors conspire to make this reactor configuration a candidate for diffusion problems since they dictate the use of a hard bead catalyst which must be strong enough to withstand abrasion while at the same time large enough to allow proper transport and to forestall large pressure drops through the bed.The importance of diffusion within porous catalyst systems has long been recognized, and considerable work has been done both in predicting the effect of diffusion on reaction rates and on the selectivity of some simplified systems. One of the earliest such attempts was made by Wheeler (1951Wheeler ( , 1955 in which three basic types of selectivity behavior were defined and the effects of diffusion limitations under isothermal conditions on selectivity were described. Wheeler's theoretical analyses were extended and generalized by Carberry (1962) for a series reaction with various combinations of diffusion limitations in the bulk phase, in the pores, and i n the micro-macro pore structure. Unfortunately, predicting selectivity behavior under conditions involving diffusion for a complex system such as gas oil cracking is an even more complex task and is not likely to be treated successfully by the methods used by the above authors. For instance, Johnson et al. (1957) attempted to describe gas oil cracking as following Wheeler's type I11 selectivity. Subsequently, Campbell and Wojciechowski (1969) and Pachovsky and Wojciechowski (1971) showed that a more complex mechanism is required to describe gas oil cracking and postulated a more complex form of behavior.In an earlier work reported by Best et al. (1971) it was shown that the hyperbolic aging function (Wojciechowski, 1968) can be used to describe gas oil conversion in both diffusion limited and diffusion free systems. In this paper we will show that their treatment can be extended to describe the effects o...

show abstract

Diffusion effects in catalytic gas oil cracking

Cited by 16 publications

References 15 publications

Kinetics of the formation of primary products of cumeme cracking over a partially exchanged LaY‐Zeolite

Kinetics of the formation of primary products of cumeme cracking over a partially exchanged LaY‐Zeolite

Theoretical interpretation of gas oil selectivity data on X‐sieve catalyst

Effects of diffusion resistance on gasoline selectivity in catalytic cracking

Contact Info

Product

Resources

About