The Catalytic Cracking of Cumene

Corma, Avelino; Wojciechowski, B. W.

doi:10.1080/03602458208079649

Cited by 143 publications

(82 citation statements)

References 77 publications

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“…Regarding the various steps involved in the catalytic cracking of 1,3,5-TIPB, a network of three prevailing in-series reactions can be considered ( Figure 6 and condensation (Corma and Wojciechowski, 1982) that may affect gas phase product distribution and coke formation. The extent of these steps may depend on both temperature and catalyst properties (Tsai et al, 1999).…”

Section: -Experimental Results and Evaluation Of Model Parametersmentioning

confidence: 99%

Diffusion and catalytic cracking of 1,3,5 tri-iso-propyl-benzene in FCC catalysts

Al-Khattaf

Atias

Jarosch

et al. 2002

Chemical Engineering Science

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The present study describes catalytic cracking experiments developed in a novel CREC Riser Simulator using 1,3,5-Tri-iso-propyl-benzene and two FCC catalysts with different crystal sizes (0.4-μm and 0.9-μm diameter). The experiments are modeled using an unsteady state model for both gas and catalyst phases. It is found that a quasi-steady state approximation can be used for the catalyst and changes in the gas phase can be accounted, under the allowed model simplifications, with a relatively simple unsteady state equation. The model is completed using two catalytic decay models, with one of them involving a decay function based on "reactant converted". Experimental and modeling observations point towards an overall cracking reaction rate controlled by diffusion at 350°C -450°C with this rate shifting to one being controlled by the intrinsic cracking reaction at 500°C -550°C.(*) Author to whom correspondence may be addressed 2 1-IntroductionThe oil refining industry has experienced in recent years, a dramatic increase in the price and availability of crude oil. In this respect, new catalyst technology is needed to process heavier feedstocks and to produce more environmentally friendly products.The currently available 60-μm commercial FCC catalysts are manufactured with 1-2-μm Y-zeolite crystals dispersed in an amorphous silicaalumina matrix . The majority of the active sites are located within the zeolite pore structure. In order for the reaction to proceed, molecules have to diffuse through the large matrix pores into the zeolite crystals.As a result, only certain hydrocarbon species with a kinetic diameter smaller than 10.2 Å can penetrate the zeolite pores (Leiby, 1992). Hence the relationship between catalytic cracking reaction and diffusional processes can determine the extent of cracking and greatly influence the product selectivity. Such phenomena are complex and theoretical models to describe such systems are needed (Bidabehere and Sedran, 2000).Diffusion in catalysts belongs in many cases to the Knudsen regime.However, diffusion in zeolites falls more in a so-called "configurational regime", since the size of the hydrocarbon molecule is nearly the size of the zeolite inner channels (Karger and Ruthven, 1992; Gates et al,1979). As a result, diffusion of the hydrocarbon molecules is governed by an almost continuous interaction between the zeolite crystal and the diffusing molecules (Karger and Ruthven,1992;Gates et al,1979). In addition, there may be compounded effects 3 with larger hydrocarbon molecules hindering the diffusion of smaller molecules.As a result, lighter product molecules may be trapped or delayed in a zeolite pore network already filled with sorbed heavier molecules (Gates et al, 1979). The 1,3,5-TIPB is a relatively bulky molecule with a critical molecular diameter of about 9.5 Å (Bhatai, 1991). Due to its large size, it has been used to simulate the diffusional constrains expected in the catalytic cracking of gas oil (Aguiar et al, 1995). For instance, the cracking of 1,3,5-TIPB ...

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Section: -Experimental Results and Evaluation Of Model Parametersmentioning

confidence: 99%

Diffusion and catalytic cracking of 1,3,5 tri-iso-propyl-benzene in FCC catalysts

Al-Khattaf

Atias

Jarosch

et al. 2002

Chemical Engineering Science

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“…Using the procedures described above, initial selectivities in cumene cracking were determined at a variety of temperatures on various catalysts [56][57][58]2]. Table VI shows a set of selectivlties obtained on LaY and HY at three temperatures, together with product-type identification.…”

Section: The Reactions In Ciymene Crackingmentioning

confidence: 99%

“…Seen in another light, they represent the probabilities that the first feed molecule to react will form each of the primary products. In that case, being careful to avoid redundancy [2], the sum of all the initial sdectivities must be equal to one, confirming that all the initial products have been accounted for.…”

mentioning

confidence: 99%

Using kinetics to study intermediates in acid catalyzed reactions on solids

Wojciechowski

1987

Res Chem Intermed

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“…The reactor was cooled to the required temperature, the catalyst was transferred in the stream of dry air into a glass vial (5 cm 3 ) equipped with a screw closure and then the substrates (1 cm The investigated alumina did not possess any distinctive acid sites, especially of Brønsted type, nor redox properties. Cumene transformation products typical for the activity of the mentioned centers [11][12][13] i.e., benzene and a-methylstyrene (Fig. 1) appeared in very low quantities: 0.3 and 0.9 %.…”

Section: Acid Strength Measurementsmentioning

confidence: 99%

“…The acid and redox properties of the catalysts were studied using the test reaction method with cumene as a reactant at 753 K. The composition of products is indicative of the presence of specific active centers i.e., benzene and diisopropylbenzenes for Brønsted acid sites [11], ethyltoluene and ethylbenzene for Lewis acid centers [11] and a-methylstyrene for redox ones [12,13]. Transformation of amethylstyrene, styrene and tert-butylbenzene at 303 K was used for the evaluation of the strength of acid sites.…”

Section: Introductionmentioning

confidence: 99%

Decomposition of styrene dimers on Al2O3–Cr and Al2O3–SiO2–Cr catalysts of acid and redox nature

Marczewski

Kaminska

Marczewska

et al. 2013

Reac Kinet Mech Cat

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(allylic anion generation); c-Al 2 O 3 -Cr: Brønsted acid centers originating from chromium ions at high oxidation states (alkenyl chain protonation) and Cr 3? redox sites (allylic cation generation); SiO 2 -Al 2 O 3 (13 %)-Cr: Brønsted acid centers of silica-alumina (alkenyl chain and aromatic ring protonation) and Cr 3? redox sites (allylic cation generation). The protonation of styrene dimer at the alkenyl chain leads to b-cleavage to toluene and a-methylstyrene as well as to styrene and ethylbenzene. The allylic species formed react to the different styrene dimer isomers and through diphenylbutadiene intermediate to coke. The use of methylcyclohexane as solvent for the styrene dimers in the presence of chromium containing catalysts results in the aromatization reaction leading to toluene and hydrogen. The presence of the later reactant in the system causes styrene and a-methylstyrene hydrogenation to ethylbenzene and cumene.

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The Catalytic Cracking of Cumene

Cited by 143 publications

References 77 publications

Diffusion and catalytic cracking of 1,3,5 tri-iso-propyl-benzene in FCC catalysts

Diffusion and catalytic cracking of 1,3,5 tri-iso-propyl-benzene in FCC catalysts

Using kinetics to study intermediates in acid catalyzed reactions on solids

Decomposition of styrene dimers on Al2O3–Cr and Al2O3–SiO2–Cr catalysts of acid and redox nature

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