Effects of crystal size and Si/Al ratio on the surface properties of H-ZSM-5 zeolites

Armaroli, Tiziana; Simon, Laurent; Digne, Mathieu; Montanari, Tania; Bevilacqua, Maria; Valtchev, Valentin; Patarin, Joël; Busca, Guido

doi:10.1016/j.apcata.2006.03.030

Cited by 179 publications

(99 citation statements)

References 29 publications

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“…The main factor allowing molecular sieving, and consequently, the shape selectivity is generally considered to be exclusively a steric effect, i.e., only molecules having a critical kinetic diameter lower than the channel diameter are allowed to enter the pores and to react on an active site, or to exit them and to be recovered as a product of the reaction [12]. Alternatively, transition state shape selectivity effects limit the formation of bulky transition state intermediates inside the pores and avoid the formation of some unwanted reaction products.…”

Section: B Effect Of Crystal Sizementioning

confidence: 99%

Maximizing propylene production via FCC technology

2015

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This review looks at the main processes available for the production of light olefins with a focus on maximizing the production of propylene. Maximization of propylene production has become the focus of most refineries because it is in high demand and there is a supply shortage from modern steam crackers, which now produce relatively less propylene. The flexibility of the fluid catalytic cracking (FCC) to various reaction conditions makes it possible as one of the means to close the gap between supply and demand. The appropriate modification of the FCC process is accomplished by the synergistic integration of the catalyst, temperature, reaction-residence time, coke make, and hydrocarbon partial pressure. The main constraints for maximum propylene yield are based on having a suitable catalyst, suitable reactor configuration and reaction conditions.

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Section: B Effect Of Crystal Sizementioning

confidence: 99%

Maximizing propylene production via FCC technology

2015

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“…However, only one study conducted by Armaroli et al 23 investigated this as a function of the SAR (37-137). Other studies did not probe the effect of the Al content in detail.…”

mentioning

confidence: 99%

“…As for terminal hydroxyl sites (terminal silanol sites), several IR studies [20][21][22][23]26,27 concluded that these sites are situated on the external ZSM-5 crystal surface independently of the total Al content and crystal size. However, only one study conducted by Armaroli et al 23 investigated this as a function of the SAR (37-137).…”

mentioning

confidence: 99%

Effect of Al content on number and location of hydroxyl acid species in zeolites: a DRIFTS quantitative protocol without the need for molar extinction coefficients

Bräuer

Situmorang

et al. 2017

RSC Adv.

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In this work, we have systematically investigated the effect of the Al content on the number and location of bridging hydroxyls (Brønsted acid sites) and terminal hydroxyls (terminal silanol sites) in ZSM-5 zeolites with varying silica-alumina ratio (SAR ¼ SiO 2 /Al 2 O 3 ) using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) without molar extinction coefficients. Two base probe molecules with different kinetic diameters, pyridine (5.7Å) and collidine (7.4Å), were used. The total content of Brønsted acid sites is obtained by elemental analysis of the proton form and sodium exchanged form of ZSM-5. To quantify the number of internal and external Brønsted acid sites the change in area of the Brønsted acid site peak in the O-H stretching region is then used; thus, the need for molar extinction coefficients to quantify Brønsted acid sites is thereby eliminated. The results reported here show that for ZSM-5 the number of external Brønsted sites, in absolute terms, increases with increasing total Al content, as evidenced by collidine adsorption. The number of terminal silanol acid sites was found to be proportional to the external surface area probed by argon sorption experiments. In summary, this work shows that the use of DRIFTS in conjunction with elemental analysis is a valid alternative to qualitatively and quantitatively probe the number and location of hydroxyl acid sites without the use of molar extinction coefficients and gives a comprehensive picture of the effect of Al content on number and location of hydroxyl acid species in ZSM-5 zeolites with varying SAR. The work contributes to advancing the range of characterisation protocols for solid acid catalysts.

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“…18. ábra: 10-tagú gyűrű az (100) irányból [122,123] 19. ábra: 10-tagú gyűrű a (010) irányból [122,123] A ZSM-5 zeolit jól meghatározott szerkezetéből adódóan alakszelektív, és kis alumínium-tartalmának köszönhetően nagy hőstabilitással rendelkezik. A szilikátvázon belüli alumínium Si-(OH)-Al egységeket alkot, melyek erős Brønsted-savasságot eredményeznek [124]. Ezek miatt, valamint ioncserélő tulajdonságának, pórusméretének, és szerkezetének köszönhetően széles körben használják mint alakszelektív adszorbenst és katalizátort a petrolkémiában [125−128].…”

Section: Zeolitokunclassified

“…Lewis-savas helyeket a külső felületen elhelyezkedő, gyengén savas szilanolcsoportok (SiOH) képezik [124]. Katalitikusan aktív helyek nemcsak a csatornákban, a külső felszínen és a pó-rusok bejáratánál is vannak.…”

Section: A Zsm-5 Szerkezete Tulajdonságai éS Alkalmazásaunclassified

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Effects of crystal size and Si/Al ratio on the surface properties of H-ZSM-5 zeolites

Cited by 179 publications

References 29 publications

Maximizing propylene production via FCC technology

Maximizing propylene production via FCC technology

Effect of Al content on number and location of hydroxyl acid species in zeolites: a DRIFTS quantitative protocol without the need for molar extinction coefficients

Mikro- és mezopórusos katalizátorok alkalmazása glicerin reaktív desztillációjában

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