Mechanistic Considerations in Acid-Catalyzed Cracking of Olefins

Buchanan, J. Scott; Santiesteban, J.G.; Haag, Werner O.

doi:10.1006/jcat.1996.0027

Cited by 254 publications

(231 citation statements)

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“…SAPO-34 zeolite frameworks and crystal shape depend upon AlO 4 -, PO 4 + , SiO 4 composition and its appropriate elemental mixing ratio. SAPO-34 has Si based acid sites and structure, while both Y and ZSM-5 have Al based acid sites and structures (Buchanan et al, 1996). The comparison of these zeolite catalyst characterization results is tabulated in Table 1.…”

Section: Catalyst Characterizationmentioning

confidence: 99%

“…These zeolite materials are crystalline and contain micro-pores of different sizes. Y-zeolite is too acidic and promotes both cracking and hydrogen transfer reactions violently (Buchanan et al, 1996). On the other hand, ZSM-5 zeolite has the macromolecular shape-selective effect, while light hydrocarbon does not follow shape-selectivity (Buchanan et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

“…Y-zeolite is too acidic and promotes both cracking and hydrogen transfer reactions violently (Buchanan et al, 1996). On the other hand, ZSM-5 zeolite has the macromolecular shape-selective effect, while light hydrocarbon does not follow shape-selectivity (Buchanan et al, 1996). The strong Brønsted acid sites of ZSM-5 promote surface reactions and somehow take part in further propylene cracking.…”

Section: Introductionmentioning

confidence: 99%

“…The appreciable trend of a continuous increase in propylene yield with conversion was obtained over SAPO-34. The reaction was explained by a β-scission carbenium ion mechanism and possible routes are shown in Scheme II (Buchanan et al, 1996 andHuaqun et al, 2008). The chance of polymerization has been ruled out, as no C 7 and higher hydrocarbons were obtained under the designated operating conditions using 30% SAPO-34.…”

Section: -Hexene Cracking Reactionsmentioning

confidence: 99%

“…The chance of polymerization has been ruled out, as no C 7 and higher hydrocarbons were obtained under the designated operating conditions using 30% SAPO-34. Scheme II: 1-hexene carbenium ion models of β-scission (Buchanan et al, 1996) The alkane OPE indicates that methane, ethane, propane, butane and pentane are stable secondary products. Figure 10 indicates that paraffins increased with the conversion rate due to hydrogen transfer reaction activation.…”

Section: -Hexene Cracking Reactionsmentioning

confidence: 99%

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Hexene catalytic cracking over 30% sapo-34 catalyst for propylene maximization: influence of reaction conditions and reaction pathway exploration

Nawaz

Tang

Wei

2009

Braz. J. Chem. Eng.

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-Higher olefins are produced as a by product in a number of refinery processes and are one of the potential raw materials to produce propylene. In the present study, FCC model feed compound was considered to explore the olefin cracking features and options to enhance propylene using 30% SAPO-34 zeolite as catalyst in a micro-reactor. The superior selectivity of propylene (73 wt%) and higher total olefin selectivity was obtained over 30% SAPO-34 catalyst than over Y or ZSM-5 zeolite catalysts. The thermodynamical constraints were found to be relatively less serious in the case of 1-hexene conversion. Most of the 1-hexene follows a direct cracking pathway to give two propylene molecules, due to weak acid sites and better diffusion opportunities. The higher temperature and short residence time could also suppress the hydrogen transfer reactions. From OPE (olefins performance envelop) the products were classified as primary, secondary, or both. Iso-hexene (2-methyl-2-pentene) cracking was also analyzed in order to justify a shape selective effect of the SAPO-34 catalyst. A detailed integrated reaction network together with an associated mechanism was proposed and discussed in detail for their fundamental importance in understanding the olefin cracking processes over

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Section: Catalyst Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: -Hexene Cracking Reactionsmentioning

confidence: 99%

Section: -Hexene Cracking Reactionsmentioning

confidence: 99%

See 3 more Smart Citations

Hexene catalytic cracking over 30% sapo-34 catalyst for propylene maximization: influence of reaction conditions and reaction pathway exploration

Nawaz

Tang

Wei

2009

Braz. J. Chem. Eng.

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Catalysis by Solid Acids

Gates

2002

Encyclopedia of Catalysis

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This article is an introduction to catalysis by solid acids, with an emphasis on principles and a selection of industrially important examples chosen to illustrate them. Acid catalysts often provide a proton to a reactant to initiate a catalytic cycle, but often the chemistry is more complex. Brønsted acid sites (usually surface OH groups) and Lewis acid sites (such as Al 3+ ions at a surface) are often important, and other groups, such as metals and redox groups on the catalyst surface, may also play a role, for example, in initiation of catalysis. Subtleties in the catalytic chemistry are associated with various acid–base interactions, such as adsorption of a basic product on the proton donors that are catalytic sites. The best‐understood solid acid catalysts are those with the simplest structures, crystalline solids such as zeolites. Methods are available for counting the proton‐donor sites in them. In one example of catalysis by an acidic zeolite, catalytic cracking of an alkane, there is a clear linear dependence of the catalytic activity on the number of proton‐donor groups in the zeolite. Theory is beginning to have an impact on the understanding of the simplest catalytic reactions catalyzed by solid acids. Mass transfer effects may be important, as in shape‐selective catalysis by some zeolites, and other phenomena related to the catalyst pore structure may be important, as in restricted transition state shape‐selective catalysis of alkane cracking in some zeolites.

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Fluid Catalytic Cracking (FCC): Catalysts and Additives

Bryden

Singh

Berg

et al. 2015

Kirk-Othmer Encyclopedia of Chemical Technology

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The fluid catalytic cracking (FCC) unit is the primary hydrocarbon conversion unit in the modern petroleum refinery. It uses heat and catalyst to convert a variety of high molecular weight feed types (eg, gas oils, cracked gas oils, deasphalted gas oils, and atmospheric/vacuum resids) into lighter, more valuable products such as gasoline, light fuel oil, and petrochemical feedstocks such as propylene and butylene. This article reviews the role of catalyst in the fluid catalytic cracking process. The design of catalyst, catalyst poisons, and the effect of catalyst on product yields and selectivity are covered. Also, the role of catalytic additives in maximizing light olefins and in controlling emissions is discussed. In addition, the importance of catalyst testing is covered, along with unconventional feedstocks and processes that are extending the role of FCC catalyst to areas beyond the original FCC process scope of converting heavy petroleum feedstocks into transportation fuels.

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Mechanistic Considerations in Acid-Catalyzed Cracking of Olefins

Cited by 254 publications

References 0 publications

Hexene catalytic cracking over 30% sapo-34 catalyst for propylene maximization: influence of reaction conditions and reaction pathway exploration

Hexene catalytic cracking over 30% sapo-34 catalyst for propylene maximization: influence of reaction conditions and reaction pathway exploration

Catalysis by Solid Acids

Fluid Catalytic Cracking (FCC): Catalysts and Additives

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