Current views on the mechanism of catalytic cracking

Corma, Avelino; Orchillés, A. Vicent

doi:10.1016/s1387-1811(99)00205-x

Cited by 401 publications

(289 citation statements)

References 48 publications

Supporting

Mentioning

275

Contrasting

Unclassified

Order By: Relevance

“…As a result, the monomolecular and bimolecular cracking reactions [82][83][84][85][86][87] (Figure 12) occurred under the experimental conditions and the consecutive reaction of light olefins proceeded to form aromatics. Accordingly, the suppression of aromatic formation is indispensable to an increase in olefin yields, as for the ATO reaction discussed below.…”

Section: N-hexane Cracking Over Nano-sized Zeolitementioning

confidence: 99%

Size-Controlled Synthesis of Nano-Zeolites and Their Application to Light Olefin Synthesis

et al. 2012

View full text Add to dashboard Cite

For the application of zeolites as heterogeneous catalysts, low diffusion resistance for hydrocarbons within the micropore is essential for improving product selectivity and catalyst lifetime. This problem has been overcome by reducing the crystal size. This review introduces size-controlled preparation of nano-sized zeolites via hydrothermal synthesis in water/surfactant/organic solvent (emulsion method) and their application to heterogeneous catalysts. The ionicity of the hydrophilic group in surfactant molecules and the concentration of the Si source affected the crystallinity and morphology of zeolites prepared using the emulsion method. When using a non-ionic surfactant, mono-dispersed silicalite-1 nanocrystals approximately 60 nm in diameter were successfully prepared. Nano-and macro-ZSM-5 zeolites with crystal sizes of approximately 150-200 nm and 1.5 µm, respectively, were prepared and applied to n-hexane cracking and acetone-to-olefin reactions to investigate the effect of zeolite crystal size on catalytic stability and light olefin yield. Application of nano-zeolite to light olefin production was effective in achieving faster mass transfer of hydrocarbon molecules within the micropore, which led to improvements in olefin yields and catalyst lifetime.

show abstract

Section: N-hexane Cracking Over Nano-sized Zeolitementioning

confidence: 99%

Size-Controlled Synthesis of Nano-Zeolites and Their Application to Light Olefin Synthesis

et al. 2012

View full text Add to dashboard Cite

show abstract

“…[7][8][9] Zeolites have been identified as promising catalysts for the catalytic cracking of naphtha and many studies concerning the catalytic cracking of C6-8 paraffins over zeolite catalysts have been reported. [10][11][12][13][14][15][16] However, the pore sizes of zeolites are almost equal to the molecular sizes of the hydrocarbons found in naphtha, and so one impediment to naphtha cracking is the restricted diffusion of these hydrocarbons within the zeolite channels.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of the catalytic cracking of naphtha over ZSM-5 zeolite: effect of reduced crystal size on the reaction of naphthenes

Konno

Ohnaka

Nishimura

et al. 2014

Catal. Sci. Technol.

View full text Add to dashboard Cite

The catalytic cracking of model naphthenes (cyclohexane and methylcyclohexane) over ZSM-5 zeolites of different crystal sizes (macro and nanoZSM-5) was examined at reaction temperatures ranging from 748 to 923 K under atmospheric pressure, focusing on the associated reaction rate constants and activation energies. The catalytic cracking was found to follow first-order kinetics with respect to the naphthene concentrations and the activation energies for cyclohexane and methylcyclohexane cracking over nanoZSM-5 were determined to be 119 and 116 kJ/mol, respectively. In order to elucidate the rate-limiting step in the cracking process, the Thiele modulus and the effectiveness factor obtained from cracking over the two ZSM-5 zeolites were evaluated. Cracking with nanoZSM-5 proceeded under reaction-limiting conditions, whereas the reaction over macroZSM-5 at 923 K took place under transition conditions between reaction-and diffusion-limiting. The nanoZSM-5 was applied to the catalytic cracking of model naphtha and the results demonstrated that this catalyst was both effective and stable and generated a high yield of light olefins.

show abstract

“…Moreover, because this process consumes more than 30% of the total amount of energy required in petrochemical refinement, developing efficient processes for the production of light olefins is indispensable. In comparison with thermal cracking, because the catalytic cracking of naphtha over solid-acid catalysts can achieve a high propylene/ethylene ratio at low reaction temperatures via the carbenium ion/β-scission mechanism [6,7], using this process will reduce energy cost and provide selective production of propylene. Accordingly, the catalytic cracking of naphtha is expected to be an effective alternative to the thermal cracking process.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of n-hexane cracking over ZSM-5 zeolites – Effect of crystal size on effectiveness factor and catalyst lifetime

Konno

Okamura

Kawahara

et al. 2012

Chemical Engineering Journal

168

View full text Add to dashboard Cite

The catalytic cracking of n-hexane over ZSM-5 zeolite (MFI-type zeolite, Si/Al = 150 and 240) catalysts was examined at reaction temperatures ranging from 823 to 923 K under atmospheric pressure. The reaction rate constants and activation energies of n-hexane cracking over ZSM-5 zeolites with various crystal sizes and Si/Al ratios were evaluated. The catalytic cracking of n-hexane was first order with respect to the n-hexane concentration, and the activation energies of n-hexane cracking over ZSM-5 zeolites were found to be approximately 123-128 kJmol -1 . Compared with the macro-sized zeolite, the nano-sized zeolites exhibited high n-hexane conversion with stable activity for 50 h. This is because the cracking reaction with nano-sized zeolite proceeded under reaction-limiting conditions, whereas the reaction with macro-sized zeolite proceeded under transition conditions between reaction-and diffusion-limiting conditions. As a result, the application of nano-zeolite to the catalytic cracking of n-hexane was effective and gave light olefins with high yield and excellent stable activity.

show abstract

Current views on the mechanism of catalytic cracking

Cited by 401 publications

References 48 publications

Size-Controlled Synthesis of Nano-Zeolites and Their Application to Light Olefin Synthesis

Size-Controlled Synthesis of Nano-Zeolites and Their Application to Light Olefin Synthesis

Kinetics of the catalytic cracking of naphtha over ZSM-5 zeolite: effect of reduced crystal size on the reaction of naphthenes

Kinetics of n-hexane cracking over ZSM-5 zeolites – Effect of crystal size on effectiveness factor and catalyst lifetime

Contact Info

Product

Resources

About