Limits...
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

3 D top‐view CFM images of a) Z80‐Si, b) Z80‐Al, c) Z50‐Si, d) Z50‐Al, e) Z20‐Si and f) Z20‐Al after thiophene oligomerisation and excited with 488 and 561 nm lasers simultaneously.
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4834610&req=5

fig4: 3 D top‐view CFM images of a) Z80‐Si, b) Z80‐Al, c) Z50‐Si, d) Z50‐Al, e) Z20‐Si and f) Z20‐Al after thiophene oligomerisation and excited with 488 and 561 nm lasers simultaneously.

Mentions: Upon termination of thiophene oligomerisation performed on ZSM‐5‐containing SiO2 and Al2O3‐bound extrudates, CFM was employed to visualise the distribution of various fluorescent carbocationic species present in two and three dimensions. Excitation of species that absorb light at approximately 485 and approximately 550 nm is possible by using 488 and 561 nm lasers simultaneously. The 3 D visualisation of pure ZSM‐5 crystals post‐reaction is given in Figure S4. All crystals/agglomerates within the field of view are fluorescent (green/yellow), with a select few intensely fluorescent (yellow). This heterogeneous distribution is attributed to the lower amount of Na present in these specific crystals/agglomerates, leading to a higher number of Brønsted acid sites (hence intensely fluorescent crystals).44 In Figure 4, the 3 D top‐view volumes of: Z80‐Al, Z80‐Si; Z50‐Al, Z50‐Si, Z20‐Al, and Z20‐Si extrudates are presented. The same heterogeneous distribution of fluorescent intensity can be observed for Z80‐Si (Figure 4 a) as for pure ZSM‐5. As observed in their optical spectra, both pure ZSM‐5 crystals (Figure 3 a) and Z80‐Si (Figure 3 b) exhibit a similar intensity of the 485 and 550 nm bands, which correlates with the similar fluorescent intensity/colour. In accordance with the optical spectra of the Z80‐Al extrudate (Figure 3 c), the orange fluorescence in the CFM image in Figure 4 b indicates a higher concentration of more conjugated species (which absorb light at 550 nm) than in the corresponding Z80‐Si sample (Figure 4 a).


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)

3 D top‐view CFM images of a) Z80‐Si, b) Z80‐Al, c) Z50‐Si, d) Z50‐Al, e) Z20‐Si and f) Z20‐Al after thiophene oligomerisation and excited with 488 and 561 nm lasers simultaneously.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig4: 3 D top‐view CFM images of a) Z80‐Si, b) Z80‐Al, c) Z50‐Si, d) Z50‐Al, e) Z20‐Si and f) Z20‐Al after thiophene oligomerisation and excited with 488 and 561 nm lasers simultaneously.
Mentions: Upon termination of thiophene oligomerisation performed on ZSM‐5‐containing SiO2 and Al2O3‐bound extrudates, CFM was employed to visualise the distribution of various fluorescent carbocationic species present in two and three dimensions. Excitation of species that absorb light at approximately 485 and approximately 550 nm is possible by using 488 and 561 nm lasers simultaneously. The 3 D visualisation of pure ZSM‐5 crystals post‐reaction is given in Figure S4. All crystals/agglomerates within the field of view are fluorescent (green/yellow), with a select few intensely fluorescent (yellow). This heterogeneous distribution is attributed to the lower amount of Na present in these specific crystals/agglomerates, leading to a higher number of Brønsted acid sites (hence intensely fluorescent crystals).44 In Figure 4, the 3 D top‐view volumes of: Z80‐Al, Z80‐Si; Z50‐Al, Z50‐Si, Z20‐Al, and Z20‐Si extrudates are presented. The same heterogeneous distribution of fluorescent intensity can be observed for Z80‐Si (Figure 4 a) as for pure ZSM‐5. As observed in their optical spectra, both pure ZSM‐5 crystals (Figure 3 a) and Z80‐Si (Figure 3 b) exhibit a similar intensity of the 485 and 550 nm bands, which correlates with the similar fluorescent intensity/colour. In accordance with the optical spectra of the Z80‐Al extrudate (Figure 3 c), the orange fluorescence in the CFM image in Figure 4 b indicates a higher concentration of more conjugated species (which absorb light at 550 nm) than in the corresponding Z80‐Si sample (Figure 4 a).

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