Non-oxidative aromatization and ethylene formation over Ga/HZSM-5 catalysts using a mixed feed of methane and ethane

Lee, Byung Jin; Hur, Young Gul; Kim, Do Huei; Lee, Seong Ho; Lee, Kwan Young

doi:10.1016/j.fuel.2019.05.014

Cited by 42 publications

(18 citation statements)

References 59 publications

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“…Gallium oxide particles or clusters, located in the channels and/or external surface of the zeolite were usually produced by ion exchange or incipient wetness impregnation [ 50 , 103 , 104 , 105 , 106 ]. The potential existence of octahedral coordinated Ga 3+ or highly dispersed Ga 2 O 3 can be identified by the chemical shift in the range from −7 to 24 ppm on 71 Ga MAS NMR, and the appearance of reductive peaks in H 2 -TPR from 670 to 1170 K [ 45 , 50 , 58 , 70 , 103 , 107 , 108 ].…”

Section: Reactive Species In Ga-modified Zsm-5mentioning

confidence: 99%

“…The existence of cationic [GaO] + species in Ga-modified ZSM-5 can be identified by 71 Ga MAS NMR resonance signal at ~55 ppm [ 104 , 121 ]. The characteristic peaks of the reduction of extra-framework [GaO] + species in H 2 -TPR were observed in the range of 990 K to 1014 K [ 57 , 70 , 91 , 107 ]. The observed decrease of Ga coordination symmetry in Ga-modified ZSM-5 in 71 Ga quadrupolar Carr-Purcell-Meiboom-Gill NMR (QCPMG) spectra can also be ascribed to formation Ga species in the form of [GaO] + or hydrated cationic [GaO] + [ 122 , 123 ].…”

Section: Reactive Species In Ga-modified Zsm-5mentioning

confidence: 99%

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Recent Advances on Gallium-Modified ZSM-5 for Conversion of Light Hydrocarbons

et al. 2021

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Light olefins are key components of modern chemical industry and are feedstocks for the production of many commodity chemicals widely used in our daily life. It would be of great economic significance to convert light alkanes, produced during the refining of crude oil or extracted during the processing of natural gas selectively to value-added products, such as light alkenes, aromatic hydrocarbons, etc., through catalytic dehydrogenation. Among various catalysts developed, Ga-modified ZSM-5-based catalysts exhibit superior catalytic performance and stability in dehydrogenation of light alkanes. In this mini review, we summarize the progress on synthesis and application of Ga-modified ZSM-5 as catalysts in dehydrogenation of light alkanes to olefins, and the dehydroaromatization to aromatics in the past two decades, as well as the discussions on in-situ formation and evolution of reactive Ga species as catalytic centers and the reaction mechanisms.

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Section: Reactive Species In Ga-modified Zsm-5mentioning

confidence: 99%

Section: Reactive Species In Ga-modified Zsm-5mentioning

confidence: 99%

Recent Advances on Gallium-Modified ZSM-5 for Conversion of Light Hydrocarbons

et al. 2021

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“…The band at 1530 cm −1 identifies the formation of pyridinium ions (PyH + ) on the surface of the catalyst, associated with Brønsted acid sites. Finally, the low‐intensity band at 1490 cm −1 is due to the two contributions of both Brønsted and Lewis acid sites . We can clearly observe in Figure , that whilst Lewis acid sites are detected in the TiO 2 −P25, TiO 2 −NC and TiO 2 −NC−W materials, Brønsted acid sites are only apparent in the TiO 2 −NC sample, and they are clearly removed after additional washing.…”

Section: Resultsmentioning

confidence: 79%

Glycerol Selective Oxidation to Lactic Acid over AuPt Nanoparticles; Enhancing Reaction Selectivity and Understanding by Support Modification

et al. 2020

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A high surface area mesoporous TiO2 material (110 m2/g) was synthesised using a nanocasting methodology, utilizing SBA‐15 as a hard template. This material was subsequently used as a support to prepare a series of 1 wt.% AuPt/TiO2 catalysts, synthesised by conventional impregnation and sol‐immobilisation. Catalysts were tested for the oxidation of glycerol to lactic acid and their performance was compared with corresponding catalysts supported on TiO2−P25, TiO2‐anatase and TiO2‐rutile. Higher rates of reaction and higher selectivity to lactic acid were observed over nanocast TiO2 supported catalysts. The increased performance of these catalysts was attributed to the presence of Si on the surface of the support, which likely arose from inefficient etching of the SBA‐15 template. The presence of Si in these catalysts was confirmed by X‐ray photoelectron spectroscopy and electron energy loss spectroscopy. It was proposed that the residual Si present increases the Brønsted acidity of the TiO2 support, which can lead to the formation of Lewis acid sites under reaction conditions; both sites are known to catalyse the dehydration of a primary alcohol in glycerol. Typically, under alkaline conditions, lactic acid is formed by the nucleophilic abstraction of a hydrogen. Thus, we propose that the improved selectivity to lactic acid over the nanocast TiO2 supported catalyst is attributed to the co‐operation of heterogeneous and homogeneous dehydration reactions, as both compete directly with a direct oxidation pathway, which leads to the formation of oxidation products such as glyceric and tartronic acid.

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“…The relative proportion of the Brønsted and Lewis acid sites ( B/L ratio) was calculated from the intensity of the bands at 1540 cm −1 and 1444 cm −1 to quantify the Brønsted and Lewis acid sites of the mixed Mg−Yb oxides. Assuming that the adsorption sites of pyridine are identical to those of ammonia, the densities of Brønsted and Lewis acid sites were calculated by multiplying the total acid density (measured from NH 3 ‐TPD) by ( B/L )/( B/L +1) and 1/( B/L +1), respectively, as shown in Table …”

Section: Resultsmentioning

confidence: 99%

Catalytic Dehydration of 1,4‐Butanediol over Mg−Yb Binary Oxides and the Mechanism Study

et al. 2020

ChemCatChem

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In this study, MgÀ Yb binary oxides were synthesized using different MgO concentrations and investigated for the catalytic dehydration of 1,4-butanediol (BDO) into 3-buten-1-ol (BTO). The physicochemical properties of the catalysts were characterized by N 2 physisorption, X-ray diffraction, Raman spectroscopy, temperature-programmed techniques, and diffuse reflectance infrared Fourier transform spectroscopy. The MgÀ Yb binary oxides exhibited superior catalytic activity and better BTO selectivity compared with the pristine Yb 2 O 3 or MgO. Structures of MgÀ OÀ Yb were generated in the binary oxides via the interchange of Yb or Mg in the MgO or Yb 2 O 3 crystalline phases. Extra basic and acidic sites were formed over the MgÀ Yb binary oxides because of the formation of surface defects and the presence of MgÀ OÀ Yb structures, respectively. The acidic as well as basic sites were observed to influence the catalytic performance: BDO reactivity was enhanced by the more acidic sites, while BTO selectivity was favored by the basic sites. The highest BTO yield of 71.1 % was achieved over the Mg7Yb3 catalyst with 90.4 % BDO conversion and 78.6 % BTO selectivity at 350°C. The in situ DRIFTS results indicated that BDO was first adsorbed on the catalyst and then reacted with the acidic sites to generate butoxides. The β-H of the surface butoxides was abstracted by the basic oxygen anions to produce aldehyde species, which dissociated to form BTO.[a] R.

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Non-oxidative aromatization and ethylene formation over Ga/HZSM-5 catalysts using a mixed feed of methane and ethane

Cited by 42 publications

References 59 publications

Recent Advances on Gallium-Modified ZSM-5 for Conversion of Light Hydrocarbons

Recent Advances on Gallium-Modified ZSM-5 for Conversion of Light Hydrocarbons

Glycerol Selective Oxidation to Lactic Acid over AuPt Nanoparticles; Enhancing Reaction Selectivity and Understanding by Support Modification

Catalytic Dehydration of 1,4‐Butanediol over Mg−Yb Binary Oxides and the Mechanism Study

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