Tuning Zeolite Properties for a Highly Efficient Synthesis of Propylene from Methanol

Palčić, Ana; Ordomsky, Vitaly V.; Qin, Zhengxing; Georgieva, Veselina; Valtchev, Valentin

doi:10.1002/chem.201803136

Cited by 39 publications

(29 citation statements)

References 70 publications

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“…The zeolite topology, e.g., structure, 1-, 2-, 3-dimention, shape, cage size, and channel system, affect the nature of the retained hydrocarbon pool that formed during MTO reaction, and, accordingly, the olefin product selectivity [8,9]. In addition to the effort of forming high selectivity towards propylene, Palčić et al [10] studied the effect of crystallization temperature (170, 150, 120, and 100 • C) on the ZSM-5 properties. They observed that the decrease in the crystallization temperature 100 • C led to significant changes in zeolite properties exhibiting many framework defects with decrease in acid-site density, decrease in their strength, and larger external surface area.…”

Section: Introductionmentioning

confidence: 99%

H-ZSM-5 Materials Embedded in an Amorphous Silica Matrix: Highly Selective Catalysts for Propylene in Methanol-to-Olefin Process

et al. 2019

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H-ZSM-5 materials embedded in an amorphous silica were successfully synthesized with three different Si/Al ratios (i.e., 40, 45, and 50). The presence of the MFI structure in the synthesized samples was confirmed by X-ray diffraction (XRD), Fourier transform infra-red (FT-IR), and solid state-nuclear magnetic resonance (SSNMR) techniques. The morphology and textural properties of the samples were investigated by scanning electron microscopy (SEM), TEM, and N2-physisorption measurements. Furthermore, acidic properties of the synthesized catalysts have been studied by NH3-TPD and FT-IR spectroscopy of CO adsorption studies. Variation of the Si/Al ratio affected the crystal morphology, porosity, and particle size, as well as the strength and distribution of acid sites. The synthesized zeolite materials possessed low acid-site density and exhibited high catalytic activity in the methanol-to-olefin (MTO) reaction. To study the intermediate species responsible for catalyst deactivation, the MTO reaction was carried out at high temperature (500 °C) to accelerate catalyst deactivation. Interestingly, the synthesized catalysts offered high selectivity towards the formation of propylene (C3=), in comparison to a commercial microporous crystalline H-ZSM-5 with Si/Al = 40, under the same reaction conditions. The synthesized H-ZSM-5 materials offered a selectivity ratio of C3=/C2= 12, while it is around 2 for the commercial H-ZSM-5 sample. The formation of hydrocarbon species during MTO reaction over zeolite samples has been systematically studied with operando UV-vis spectroscopy and online gas chromatography. It is proposed that the strength and type of acid sites of catalyst play a role in propylene selectivity as well as the fast growing of active intermediate species. The effective conversion of methanol into propylene in the case of synthesized H-ZSM-5 materials was observed due to possession of weak acid sites. This effect is more pronounced in H-ZSM-5 sample with a Si/Al ratio of 45.

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Section: Introductionmentioning

confidence: 99%

H-ZSM-5 Materials Embedded in an Amorphous Silica Matrix: Highly Selective Catalysts for Propylene in Methanol-to-Olefin Process

et al. 2019

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“…In addition to Al-atoms, the exchangeable copper cations can also bond coordinatively ammonia molecules providing a contribution to the total density of Lewis acid sites detected with this probe. As above, an increase in the concentration of Lewis sites is easily explained by the higher Cu content for Cu-SSZ-13(2) than Cu-SSZ-13(1) (4.9 versus 4.4 wt.%, respectively, Figure 3 shows the 27 Al NMR spectra for the H-SSZ-13 samples. The majority of Al is tetrahedrally coordinated and fully incorporated in the framework, as indicated by the peak at 59 ppm for Cu-SSZ-13(1) and 60 ppm for Cu-SSZ-13(2-4).…”

Section: N(si)/n(al); N(cu)/n(al)mentioning

confidence: 62%

“…Those Al 4+ in Si(OH)Al units can provide Brønsted acidity. Only a small amount of extra-framework octahedral Al at 0 ppm is noticeable [27], indicating that extra-framework Al species are marginally populated at the same time, suggesting that enhanced Lewis acidity that was observed in the IR spectra stems from Cu species. synthesized in the presence of solely TMAdaOH, were found to contain only isolated framework Al [22].…”

Section: N(si)/n(al); N(cu)/n(al)mentioning

confidence: 99%

“…Those Al 4+ in Si(OH)Al units can provide Brønsted acidity. Only a small amount of extraframework octahedral Al at 0 ppm is noticeable [27], indicating that extra-framework Al species are marginally populated at the same time, suggesting that enhanced Lewis acidity that was observed in the IR spectra stems from Cu species. According to the IUPAC classification [28], all isotherms of the samples exhibit a mixed Type I and Type IVa isotherm with an H1 type hysteresis loop in the range of p p 0 −1 > 0.9, indicating the presence of the inter-crystalline meso-/macroporosity.…”

Section: N(si)/n(al); N(cu)/n(al)mentioning

confidence: 99%

“…Finally, in Cu-SSZ-13(3,4) the co-existence of ion-exchange copper cations and small oligomeric or bulky CuO species is assumed. Figure 3 shows the 27 Al NMR spectra for the H-SSZ-13 samples. The majority of Al is tetrahedrally coordinated and fully incorporated in the framework, as indicated by the peak at 59 ppm for Cu-SSZ-13(1) and 60 ppm for Cu-SSZ-13(2-4).…”

Section: N(si)/n(al); N(cu)/n(al)mentioning

confidence: 99%

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Nanosized Cu-SSZ-13 and Its Application in NH3-SCR

et al. 2020

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Nanosized SSZ-13 was synthesized hydrothermally by applying N,N,N-trimethyl-1-adamantammonium hydroxide (TMAdaOH) as a structure-directing agent. In the next step, the quantity of TMAdaOH in the initial synthesis mixture of SSZ-13 was reduced by half. Furthermore, we varied the sodium hydroxide concentration. After ion-exchange with copper ions (Cu2+ and Cu+), the Cu-SSZ-13 catalysts were characterized to explore their framework composition (XRD, solid-state NMR, ICP-OES), texture (N2-sorption, SEM) and acid/redox properties (FT-IR, TPR-H2, DR UV-Vis, EPR). Finally, the materials were tested in the selective catalytic reduction of NOx with ammonia (NH3-SCR). The main difference between the Cu-SSZ-13 catalysts was the number of Cu2+ in the double six-membered ring (6MRs). Such copper species contribute to a high NH3-SCR activity. Nevertheless, all materials show comparable activity in NH3-SCR up to 350 °C. Above 350 °C, NO conversion decreased for Cu-SSZ-13(2–4) due to side reaction of NH3 oxidation.

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Influence of Framework n(Si)/n(Al) Ratio on the Nature of Cu Species in Cu‐ZSM‐5 for NH₃‐SCR‐DeNO_x

et al. 2022

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Nanosized Cu-containing ZSM-5 catalysts with different n(Si)/ n(Al) ratio of 18.9-50.5 were prepared by ion-exchange. The physico-chemical characterization clearly shows that the molar ratio of framework T atoms influences the nature and distribution of copper species. According to DR UV-Vis, TPR-H 2 , EPR, or FT-IR spectroscopy analyses, the amount of aggregated copper species increases with increasing the framework n(Si)/n(Al) ratio. Thus, the activity of the Cu-containing ZSM-5 with n(Si)/n(Al) ratio of 47.0-50.5 in the selective catalytic NO reduction with NH 3 (NH 3 -SCR-DeNO x ) significantly decreases compared to the other materials (n(Si)/n(Al) ratio of 18.9-19.6). The reaction mechanism has been discussed in light of the results of 2D COS (two-dimensional correlation spectroscopy) analysis of IR spectra and catalytic properties of the zeolites. The results make evident that enhanced activity of Cu-containing ZSM-5 in NH 3 -SCR-DeNO x is correlated with the formation of different NO x À under the experimental conditions.

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Tuning Zeolite Properties for a Highly Efficient Synthesis of Propylene from Methanol

Cited by 39 publications

References 70 publications

H-ZSM-5 Materials Embedded in an Amorphous Silica Matrix: Highly Selective Catalysts for Propylene in Methanol-to-Olefin Process

H-ZSM-5 Materials Embedded in an Amorphous Silica Matrix: Highly Selective Catalysts for Propylene in Methanol-to-Olefin Process

Nanosized Cu-SSZ-13 and Its Application in NH3-SCR

Influence of Framework n(Si)/n(Al) Ratio on the Nature of Cu Species in Cu‐ZSM‐5 for NH₃‐SCR‐DeNO_x

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Tuning Zeolite Properties for a Highly Efficient Synthesis of Propylene from Methanol

Cited by 39 publications

References 70 publications

H-ZSM-5 Materials Embedded in an Amorphous Silica Matrix: Highly Selective Catalysts for Propylene in Methanol-to-Olefin Process

H-ZSM-5 Materials Embedded in an Amorphous Silica Matrix: Highly Selective Catalysts for Propylene in Methanol-to-Olefin Process

Nanosized Cu-SSZ-13 and Its Application in NH3-SCR

Influence of Framework n(Si)/n(Al) Ratio on the Nature of Cu Species in Cu‐ZSM‐5 for NH3‐SCR‐DeNOx

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Product

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Influence of Framework n(Si)/n(Al) Ratio on the Nature of Cu Species in Cu‐ZSM‐5 for NH₃‐SCR‐DeNO_x