The ZnxZr1−xO2−y solid solution on m-ZrO2: Creating O vacancies and improving the m-ZrO2 redox properties

Silva-Calpa, Leydi del R.; Zonetti, Priscila C.; Rodrigues, Clarissa Perdomo; Alves, Odivaldo C.; Appel, Lucia G.; Avillez, Roberto R. de

doi:10.1016/j.molcata.2016.10.008

Cited by 53 publications

(34 citation statements)

References 24 publications

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“…Considering the EPR results ( Figure 3) and according to Silva-Calpa et al, [25] McFarland & Metiu [34] and Liu et al, [35] it can be suggested that Zn + 2 substitutes Zr + 4 in the t-ZrO 2 lattice generating oxygen vacancies and coordinatively unsaturated Zr 4 + ions (cus). The oxygen vacancies can be associated with strong basic sites [36] whereas the cus species with Lewis acid sites.…”

Section: The Mpv Model Reactionmentioning

confidence: 75%

“…A narrow signal is observed for t-ZrO 2 at approximately 3100 G, which shows a g-value of 2.20 and can be assigned to paramagnetic centers related to ZrO 2 isolated oxygen vacancies. [25][26][27][28] Both samples also exhibit paramagnetic signals around 3500 G with g-values of 2.02 and 1.98, which are attributed to the Zr 3 + species. Moreover, the samples show large signals at high field (around 2400 G) and low field (with maximum at 450 G).…”

Section: The Mpv Model Reactionmentioning

confidence: 99%

“…These signals are typical of ferromagnetic ordering and can be associated with oxygen vacancies aggregates. [25] The first one, at high field, can be assigned to small ferromagnetic aggregates whereas the second, at low field, is related to large ferromagnetic aggregates. [28][29] The area of each spectrum, which is proportional to the amount of magnetic material in each sample, was determined by deconvo- [a] The numbers in parentheses refers to the acid and basic densities.…”

Section: The Mpv Model Reactionmentioning

confidence: 99%

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The Role of the Oxygen Vacancies in the Synthesis of 1, 3‐Butadiene from Ethanol

et al. 2019

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The t‐ZrO2 doped with Zn catalyst and t‐ZrO2 as reference were employed in the butadiene synthesis from ethanol. Both catalysts were characterized by NH3‐TPD, CO2‐TPD, TPSR, the MPV model reaction, ICP, BET and EPR. Adding 0.2 wt% Zn to t‐ZrO2, the selectivity to butadiene increases three fold whereas the one to ethylene decreases. When ZrO2 is doped, the number of basic sites increases and the number of acid sites decreases. The TPSR spectra indicate that the acetaldehyde generation is the rate limiting step of the butadiene synthesis. The slowest step of the acetaldehyde generation is the H abstraction by a strong basic site. The EPR spectra show the replacement of Zr4+ by Zn2+ in the lattice of the t‐ZrO2 oxide. This phenomenon forms pairs of oxygen vacancies and coordinatively unsaturated Zr4+ ions (cus), which are strong basic sites and acid sites, respectively. Doping ZrO2 with Zn, the ethanol dehydrogenation and the butadiene synthesis are promoted not only due to the changes in the acidity and basicity of the catalyst but mainly because of the generation of oxygen vacancies and cus pairs during the reaction. These oxygen vacancies seem to behave as strong Brønsted basic sites.

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Section: The Mpv Model Reactionmentioning

confidence: 75%

Section: The Mpv Model Reactionmentioning

confidence: 99%

Section: The Mpv Model Reactionmentioning

confidence: 99%

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The Role of the Oxygen Vacancies in the Synthesis of 1, 3‐Butadiene from Ethanol

et al. 2019

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“…Under H 2 environment, MEK is converted to butenes via hydrogenation reaction that takes place due to the redox properties of Zn x Zr y O z catalysts . It is possible that the hydrogenation/ dehydration pathway under H 2 is kinetically faster than the condensation/decomposition pathway under N 2 .…”

Section: Effect Of the Feed Gas Composition (N2 Vs H2) On The Catalymentioning

confidence: 99%

Single‐step Conversion of Methyl Ethyl Ketone to Olefins over Zn_xZr_yO_z Catalysts in Water

Dagle

Kovařík

et al. 2019

ChemCatChem

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In this study we investigated the conversion of aqueous methyl‐ethyl‐ketone (MEK) to olefin fuel precursors over ZnxZryOz mixed oxide catalysts. Experiments were carried out in water as MEK is intended to be produced from the dehydration of 2,3‐butanediol in fermentation broth which is highly diluted in water. We demonstrated that ZnxZryOz catalysts are highly effective for converting aqueous MEK to C4−C5 olefins. High selectivity to olefins equal to 85 % was reached at 92 % per pass conversion when under H2 atmosphere. Catalyst stability was demonstrated for 60 hours’ time on stream, highlighting the potential for upgrading 2,3‐butanediol contained in fermentation broth without the need for energy‐intensive water separation. Increased concentration of MEK in the aqueous feed results in increased activity towards olefin production. However, water inhibits catalyst deactivation from coking. A mechanistic investigation revealed the impact of the reaction environment (inert or reducing atmosphere) on the reaction pathways. In an inert environment, the mechanism involves consecutive aldol condensation of MEK and 3‐pentanone intermediate. Under reducing conditions two reaction pathways compete with each other as MEK hydrogenation to butenes occurs concurrently with the aldol condensation/decomposition.

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“…Similarly, when Fe 2 O 3 is substituted by ZnO over the Fe 2 O 3 /Cr 2 O 3 catalyst, the corresponding ZnCr 2 O 4 phase is formed and thus becomes stable (Park et al, 2000). In the synthetic process of the ZnZrO x mixed oxide, the substitution of the Zr in the first layers of the m-ZrO 2 lattice with Zn causes the formation of a surface solution (Zn x Zr 1−x O 2−y ), which generates oxygen vacancies and improves its stability, reducibility, and oxygen mobility, thus increasing the CO 2 conversion in the RWGSR (Silva-Calpa et al, 2016).…”

Section: Oxide Catalystsmentioning

confidence: 99%

Recent Advances in Supported Metal Catalysts and Oxide Catalysts for the Reverse Water-Gas Shift Reaction

Chen

Song

et al. 2020

Front. Chem.

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The reverse water-gas shift reaction (RWGSR), a crucial stage in the conversion of abundant CO 2 into chemicals or hydrocarbon fuels, has attracted extensive attention as a renewable system to synthesize fuels by non-traditional routes. There have been persistent efforts to synthesize catalysts for industrial applications, with attention given to the catalytic activity, CO selectivity, and thermal stability. In this review, we describe the thermodynamics, kinetics, and atomic-level mechanisms of the RWGSR in relation to efficient RWGSR catalysts consisting of supported catalysts and oxide catalysts. In addition, we rationally classify, summarize, and analyze the effects of physicochemical properties, such as the morphologies, compositions, promoting abilities, and presence of strong metal-support interactions (SMSI), on the catalytic performance and CO selectivity in the RWGSR over supported catalysts. Regarding oxide catalysts (i.e., pure oxides, spinel, solid solution, and perovskite-type oxides), we emphasize the relationships among their surface structure, oxygen storage capacity (OSC), and catalytic performance in the RWGSR. Furthermore, the abilities of perovskite-type oxides to enhance the RWGSR with chemical looping cycles (RWGSR-CL) are systematically illustrated. These systematic introductions shed light on development of catalysts with high performance in RWGSR.

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The ZnxZr1−xO2−y solid solution on m-ZrO2: Creating O vacancies and improving the m-ZrO2 redox properties

Cited by 53 publications

References 24 publications

The Role of the Oxygen Vacancies in the Synthesis of 1, 3‐Butadiene from Ethanol

The Role of the Oxygen Vacancies in the Synthesis of 1, 3‐Butadiene from Ethanol

Single‐step Conversion of Methyl Ethyl Ketone to Olefins over Zn_xZr_yO_z Catalysts in Water

Recent Advances in Supported Metal Catalysts and Oxide Catalysts for the Reverse Water-Gas Shift Reaction

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The ZnxZr1−xO2−y solid solution on m-ZrO2: Creating O vacancies and improving the m-ZrO2 redox properties

Cited by 53 publications

References 24 publications

The Role of the Oxygen Vacancies in the Synthesis of 1, 3‐Butadiene from Ethanol

The Role of the Oxygen Vacancies in the Synthesis of 1, 3‐Butadiene from Ethanol

Single‐step Conversion of Methyl Ethyl Ketone to Olefins over ZnxZryOz Catalysts in Water

Recent Advances in Supported Metal Catalysts and Oxide Catalysts for the Reverse Water-Gas Shift Reaction

Contact Info

Product

Resources

About

Single‐step Conversion of Methyl Ethyl Ketone to Olefins over Zn_xZr_yO_z Catalysts in Water