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Investigation of Y/SBA Composite Molecular Sieves Morphology Control and Catalytic Performance for n-Pentane Aromatization.

Shi CW, Wu WY, Li S, Bian X, Zhao SL, Pei MY - Sci Rep (2016)

Bottom Line: The catalysis performances of the composite molecular sieves were investigated in the aromatization reaction of n-pentane.The results indicated that the desired core-shell composite molecular sieves were obtained when the crystallization conditions were 36 hours, 100 °C and secondary crystallization.The aromatization results showed that core-shell composite molecular sieves had better selectivity for producing high application value xylenes compared to mixed-crystal composite molecular sieves.

View Article: PubMed Central - PubMed

Affiliation: College of Chemistry, Chemical Engineering and Environmental Engineering, Liaoning Shihua University, Funshun Liaoning 113001, China.

ABSTRACT
Using Y molecular sieve as the core, Y/SBA-15 composite molecular sieves were prepared by different crystallization methods in the paper. The growth process and morphologies of the composite molecular sieves were controlled by adjusting the synthesis factors. The structures and acidity of two kinds of composite molecular sieves were characterized by X-ray diffraction (XRD), N2 adsorption/desorption, transmission electron microscopy (TEM), and NH3-TPD. The catalysis performances of the composite molecular sieves were investigated in the aromatization reaction of n-pentane. The results indicated that the desired core-shell composite molecular sieves were obtained when the crystallization conditions were 36 hours, 100 °C and secondary crystallization. The aromatization results showed that core-shell composite molecular sieves had better selectivity for producing high application value xylenes compared to mixed-crystal composite molecular sieves.

No MeSH data available.


Related in: MedlinePlus

Crystallization curves of the core phase and the shell phase of Y/S-Dcomposite molecular sieves.
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f7: Crystallization curves of the core phase and the shell phase of Y/S-Dcomposite molecular sieves.

Mentions: Figure 7 shows the crystallization curves of each phase of the composite molecular sieves prepared by secondary crystallization method. It can be seen from Fig. 7 that at the low temperature stage, the relative crystallinity of the SBA-15 phase increased slowly. This is due to the relatively high supersaturation degree of the initial gel, which promotes the nucleation and initial growth of the shell phase SBA-15 on the outer surface of the core phase Y. In addition, low temperature treatment favored the contact between the SBA-15 primary building units and Y, thus increasing the interaction and possibility of combination between the two phases. The high temperature stage provided a good platform for the crystal growth of the shell phase molecular sieves, leading to a more uniform crystal growth on the primary building units formed at the low temperature stage17. In the case of single crystallization treatment, complex crystals of the composite molecular sieves were formed in large amounts. This is likely due to the fact that at high temperature, the SBA-15 initial gel would rapidly go through the nucleation and crystal growth processes, leading to unstable contact of the formed nucleus and Y molecular sieve surface or monotonic growth orientation. Thus, the composite molecular sieve crystals prepared by single crystallization method were irregular.


Investigation of Y/SBA Composite Molecular Sieves Morphology Control and Catalytic Performance for n-Pentane Aromatization.

Shi CW, Wu WY, Li S, Bian X, Zhao SL, Pei MY - Sci Rep (2016)

Crystallization curves of the core phase and the shell phase of Y/S-Dcomposite molecular sieves.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4814903&req=5

f7: Crystallization curves of the core phase and the shell phase of Y/S-Dcomposite molecular sieves.
Mentions: Figure 7 shows the crystallization curves of each phase of the composite molecular sieves prepared by secondary crystallization method. It can be seen from Fig. 7 that at the low temperature stage, the relative crystallinity of the SBA-15 phase increased slowly. This is due to the relatively high supersaturation degree of the initial gel, which promotes the nucleation and initial growth of the shell phase SBA-15 on the outer surface of the core phase Y. In addition, low temperature treatment favored the contact between the SBA-15 primary building units and Y, thus increasing the interaction and possibility of combination between the two phases. The high temperature stage provided a good platform for the crystal growth of the shell phase molecular sieves, leading to a more uniform crystal growth on the primary building units formed at the low temperature stage17. In the case of single crystallization treatment, complex crystals of the composite molecular sieves were formed in large amounts. This is likely due to the fact that at high temperature, the SBA-15 initial gel would rapidly go through the nucleation and crystal growth processes, leading to unstable contact of the formed nucleus and Y molecular sieve surface or monotonic growth orientation. Thus, the composite molecular sieve crystals prepared by single crystallization method were irregular.

Bottom Line: The catalysis performances of the composite molecular sieves were investigated in the aromatization reaction of n-pentane.The results indicated that the desired core-shell composite molecular sieves were obtained when the crystallization conditions were 36 hours, 100 °C and secondary crystallization.The aromatization results showed that core-shell composite molecular sieves had better selectivity for producing high application value xylenes compared to mixed-crystal composite molecular sieves.

View Article: PubMed Central - PubMed

Affiliation: College of Chemistry, Chemical Engineering and Environmental Engineering, Liaoning Shihua University, Funshun Liaoning 113001, China.

ABSTRACT
Using Y molecular sieve as the core, Y/SBA-15 composite molecular sieves were prepared by different crystallization methods in the paper. The growth process and morphologies of the composite molecular sieves were controlled by adjusting the synthesis factors. The structures and acidity of two kinds of composite molecular sieves were characterized by X-ray diffraction (XRD), N2 adsorption/desorption, transmission electron microscopy (TEM), and NH3-TPD. The catalysis performances of the composite molecular sieves were investigated in the aromatization reaction of n-pentane. The results indicated that the desired core-shell composite molecular sieves were obtained when the crystallization conditions were 36 hours, 100 °C and secondary crystallization. The aromatization results showed that core-shell composite molecular sieves had better selectivity for producing high application value xylenes compared to mixed-crystal composite molecular sieves.

No MeSH data available.


Related in: MedlinePlus