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Binder Effects in SiO2- and Al2O3-Bound Zeolite ZSM-5-Based Extrudates as Studied by Microspectroscopy.

Whiting GT, Meirer F, Mertens MM, Bons AJ, Weiss BM, Stevens PA, de Smit E, Weckhuysen BM - ChemCatChem (2015)

Bottom Line: It was found that aluminium migration occurs in ZSM-5-containing Al2O3-bound extrudates, forming additional Brønsted acid sites.Not only were the location and distribution of these oligomers visualised by 3 D analysis, it was also observed that more conjugated species appeared to grow off the surface of the zeolite ZSM-5 crystals (containing less conjugated species) into the surrounding binder material.Furthermore, a higher binder content resulted in an increasing overall reactivity owing to the greater number of stored thiophene monomers available per Brønsted acid site.

View Article: PubMed Central - PubMed

Affiliation: Inorganic Chemistry and Catalysis Group, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG, Utrecht (The Netherlands).

ABSTRACT

Microspectroscopic methods were explored to investigate binder effects occurring in ZSM-5-containing SiO2- and Al2O3-bound millimetre-sized extrudates. Using thiophene as a selective probe for Brønsted acidity, coupled with time-resolved in situ UV/Vis and confocal fluorescence microspectroscopy, variations in reactivity and selectivity between the two distinct binder types were established. It was found that aluminium migration occurs in ZSM-5-containing Al2O3-bound extrudates, forming additional Brønsted acid sites. These sites strongly influence the oligomer selectivity, favouring the formation of thiol-like species (i.e., ring-opened species) in contrast to higher oligomers, predominantly formed on SiO2-bound ZSM-5-containing extrudates. Not only were the location and distribution of these oligomers visualised by 3 D analysis, it was also observed that more conjugated species appeared to grow off the surface of the zeolite ZSM-5 crystals (containing less conjugated species) into the surrounding binder material. Furthermore, a higher binder content resulted in an increasing overall reactivity owing to the greater number of stored thiophene monomers available per Brønsted acid site.

No MeSH data available.


Related in: MedlinePlus

TPD profiles of NH3 for: a) a series of ZSM‐5‐containing SiO2‐bound extrudates and b) a series of ZSM‐5‐containing Al2O3‐bound extrudates.
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fig2: TPD profiles of NH3 for: a) a series of ZSM‐5‐containing SiO2‐bound extrudates and b) a series of ZSM‐5‐containing Al2O3‐bound extrudates.

Mentions: In Figure 2 the NH3‐temperature programmed desorption (TPD) profiles of both series of ZSM‐5‐based binder‐bound extrudates are shown, with Table S1 presenting the amounts of NH3 desorbed for each sample. As expected, ZSM‐5 crystals produce a broad band centred at 430 °C, attributed with NH3 desorbing from strong acid sites.46 A small peak at 270 °C is associated with physisorbed NH3. Owing to the lack of acid sites in SiO2, Z80‐Si experiences no significant change relative to that of ZSM‐5 (Figure 2 a), however, the large dilution of the active phase in Z20‐Si substantially decreases the amount of NH3 desorbed on the limited strong acid sites present. The NH3–TPD profile of Z80‐Al (Figure 2 b) is similar to that of Z80‐Si, however, the peak maximum, associated with strong acid sites is shifted slightly to higher temperatures. The dilution of the active phase in Z20‐Al produces a dramatic decrease in strong acid sites, with the peak maximum now shifted significantly to the left (340 °C). This behaviour corresponds well with the NH3‐TPD profile of pure Al2O3, which produces a broad band centred at 346 °C, showing that Al2O3, unlike SiO2, cannot be considered an “inert” binder, considering the high contribution towards the extrudates’ overall acidity.


Binder Effects in SiO2- and Al2O3-Bound Zeolite ZSM-5-Based Extrudates as Studied by Microspectroscopy.

Whiting GT, Meirer F, Mertens MM, Bons AJ, Weiss BM, Stevens PA, de Smit E, Weckhuysen BM - ChemCatChem (2015)

TPD profiles of NH3 for: a) a series of ZSM‐5‐containing SiO2‐bound extrudates and b) a series of ZSM‐5‐containing Al2O3‐bound extrudates.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4834610&req=5

fig2: TPD profiles of NH3 for: a) a series of ZSM‐5‐containing SiO2‐bound extrudates and b) a series of ZSM‐5‐containing Al2O3‐bound extrudates.
Mentions: In Figure 2 the NH3‐temperature programmed desorption (TPD) profiles of both series of ZSM‐5‐based binder‐bound extrudates are shown, with Table S1 presenting the amounts of NH3 desorbed for each sample. As expected, ZSM‐5 crystals produce a broad band centred at 430 °C, attributed with NH3 desorbing from strong acid sites.46 A small peak at 270 °C is associated with physisorbed NH3. Owing to the lack of acid sites in SiO2, Z80‐Si experiences no significant change relative to that of ZSM‐5 (Figure 2 a), however, the large dilution of the active phase in Z20‐Si substantially decreases the amount of NH3 desorbed on the limited strong acid sites present. The NH3–TPD profile of Z80‐Al (Figure 2 b) is similar to that of Z80‐Si, however, the peak maximum, associated with strong acid sites is shifted slightly to higher temperatures. The dilution of the active phase in Z20‐Al produces a dramatic decrease in strong acid sites, with the peak maximum now shifted significantly to the left (340 °C). This behaviour corresponds well with the NH3‐TPD profile of pure Al2O3, which produces a broad band centred at 346 °C, showing that Al2O3, unlike SiO2, cannot be considered an “inert” binder, considering the high contribution towards the extrudates’ overall acidity.

Bottom Line: It was found that aluminium migration occurs in ZSM-5-containing Al2O3-bound extrudates, forming additional Brønsted acid sites.Not only were the location and distribution of these oligomers visualised by 3 D analysis, it was also observed that more conjugated species appeared to grow off the surface of the zeolite ZSM-5 crystals (containing less conjugated species) into the surrounding binder material.Furthermore, a higher binder content resulted in an increasing overall reactivity owing to the greater number of stored thiophene monomers available per Brønsted acid site.

View Article: PubMed Central - PubMed

Affiliation: Inorganic Chemistry and Catalysis Group, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG, Utrecht (The Netherlands).

ABSTRACT

Microspectroscopic methods were explored to investigate binder effects occurring in ZSM-5-containing SiO2- and Al2O3-bound millimetre-sized extrudates. Using thiophene as a selective probe for Brønsted acidity, coupled with time-resolved in situ UV/Vis and confocal fluorescence microspectroscopy, variations in reactivity and selectivity between the two distinct binder types were established. It was found that aluminium migration occurs in ZSM-5-containing Al2O3-bound extrudates, forming additional Brønsted acid sites. These sites strongly influence the oligomer selectivity, favouring the formation of thiol-like species (i.e., ring-opened species) in contrast to higher oligomers, predominantly formed on SiO2-bound ZSM-5-containing extrudates. Not only were the location and distribution of these oligomers visualised by 3 D analysis, it was also observed that more conjugated species appeared to grow off the surface of the zeolite ZSM-5 crystals (containing less conjugated species) into the surrounding binder material. Furthermore, a higher binder content resulted in an increasing overall reactivity owing to the greater number of stored thiophene monomers available per Brønsted acid site.

No MeSH data available.


Related in: MedlinePlus