Theoretical interpretation of gas oil conversion data on an x‐sieve catalyst

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

doi:10.1002/cjce.5450490311

Cited by 46 publications

(14 citation statements)

References 6 publications

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“…VGO is cracked to gasoline, gas and coke. The rate of consumption of reactant j per unit catalyst volume can be expressed as (Pachovsky and Wojciechowski, 1971):…”

Section: Cracking Reactionsmentioning

confidence: 99%

Modeling of vaporization and cracking of liquid oil injected in a gas–solid riser

Nayak

Joshi

Ranade

2005

Chemical Engineering Science

107

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“…VGO is cracked to gasoline, gas and coke. The rate of consumption of reactant j per unit catalyst volume can be expressed as (Pachovsky and Wojciechowski, 1971):…”

Section: Cracking Reactionsmentioning

confidence: 99%

Modeling of vaporization and cracking of liquid oil injected in a gas–solid riser

Nayak

Joshi

Ranade

2005

Chemical Engineering Science

107

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“…From Table 3 it is readily apparent that for both the 4/10 mesh and 30/60 mesh data the selectivity model adequately describes the data at the 95% confidence level. In previous publications (Pachovsky and Wojciechowski, 1971; Best et al, 1971), it has been shown that the conversion model also adequately describes the conversion data at the 95% confidence level for both the 4/10 mesh and 30/60 mesh catalysts.…”

Section: Discussionmentioning

confidence: 79%

“…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.…”

Section: Scopementioning

confidence: 98%

Effects of diffusion resistance on gasoline selectivity in catalytic cracking

Pachovsky

Wojciechowski

1973

AIChE Journal

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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...

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“…The value of n is assumed to be one for the 21 VGO cracking reactions and zero for all other cracking reactions. M a n u s c r i p t There are two other types of rate equations are available in the literature, which can be written as: 1 (for 3-lump model of Pachovsky and Wojciechowski, 1971) eq. (99) 2…”

Section: Coupling Between Gas-solid Flow Model and Cracking Kinetic Mmentioning

confidence: 99%