Deactivation of Cu/ZnO/Al<sub>2</sub>O<sub>3</sub> Methanol Synthesis Catalyst by Sintering

Sun, James T.; Metcalfe, Ian S.; Sahibzada, M.

doi:10.1021/ie990078s

Cited by 173 publications

(118 citation statements)

References 15 publications

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“…It is clear that the Cu/ZnO/Al 2 O 3 suffers from rapid deactivation under these conditions. This deactivation is not surprising and caused by sintering of the Cu particles [16]. This is in stark contrast with the trend observed for the 8.8Pd/ZnO/Al 2 O 3 -0.38 catalyst.…”

Section: Scanning Transmission Electron Microscopy Analysiscontrasting

confidence: 69%

Single-Step Syngas-to-Distillates (S2D) Synthesis via Methanol and Dimethyl Ether Intermediates: Final Report

Dagle¹,

Lebarbier²,

Adarme³

et al. 2013

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Executive SummaryThe objective of the work was to enhance price-competitive, synthesis gas (syngas)-based production of transportation fuels that are directly compatible with the existing vehicle fleet (i.e., vehicles fueled by gasoline, diesel, jet fuel, etc.). To accomplish this, modifications to the traditional methanol-to-gasoline (MTG) process were investigated. Originally pioneered by Mobil, the MTG process was revolutionary; however, it proved to be uneconomical when initially developed. Because the chemistry is based on shape-selective catalysis, MTG has the potential to produce fuel streams that require very little downstream modification. The Fischer-Tropsch process, on the contrary, requires extensive catalytic modification and cracking to produce useful and proper fuel range products. Combining methanol synthesis and MTG in a single bed also has some potential to be economically advantageous. Implications for the temperature and pressure requirements in a combined system as compared to conventional methanol synthesis and MTG processes are shown in Figure Merging the two processes leads to the combined synthesis-to-distillates process that operates at high temperature and high pressure. Different catalyst functionalities also are required for both the methanol synthesis and MTG processes.In this study, we investigated direct conversion of syngas to distillates using methanol and dimethyl ether intermediates. For this application, a Pd/ZnO/Al 2 O 3 (PdZnAl) catalyst previously developed for methanol steam reforming was evaluated. The PdZnAl catalyst was shown to be far superior to a conventional copper-based methanol catalyst when operated at relatively high temperatures (i.e., >300°C), which is necessary for MTG-type applications. Catalytic performance was evaluated through parametric studies. Process conditions such as temperature, pressure, gas-hour-space velocity, and syngas feed ratio (i.e., hydrogen:carbon monoxide) were investigated. PdZnAl catalyst formulation also was optimized to maximize conversion and selectivity to methanol and dimethyl ether while suppressing methane formation. This was accomplished by adjusting the acid and base functionality of the catalyst. PdZn-metal sites are necessary for methanol synthesis. Alumina substrate not only plays the role of iv textural support but also offers acidic sites useful for the dehydration of methanol to dimethyl ether. Manipulation of the Pd:Zn molar ratio and total PdZn-metal loading were shown to greatly affect catalytic performance. Thus, a PdZn/Al 2 O 3 catalyst optimized for methanol and dimethyl ether formation was developed through combined catalytic material and process parameter exploration. However, even after compositional optimization, a significant amount of undesirable carbon dioxide was produced (formed via the water-gas-shift reaction), and some degree of methane formation could not be completely avoided.Pd/ZnO/Al 2 O 3 used in combination with ZSM-5 was investigated for direct syngas-to-distillates conversion. High conversion...

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Section: Scanning Transmission Electron Microscopy Analysiscontrasting

confidence: 69%

Single-Step Syngas-to-Distillates (S2D) Synthesis via Methanol and Dimethyl Ether Intermediates: Final Report

Dagle¹,

Lebarbier²,

Adarme³

et al. 2013

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“…Previous research of our group [14] showed that as active sites of methanol synthesis, Cu 0 -Cu + was more active than Cu 0 , and there needed some oxidative atmosphere in the system to complete the cycle. Likewise, Sun et al [15] also found that Cu 0 -Cu + in methanol synthesis depressed sintering of Cu crystalline significantly.…”

Section: Comparison Of Two Regeneration Mechanismsmentioning

confidence: 87%

In-situ regeneration mechanisms of hybrid catalysts in the one-step synthesis of dimethyl ether from syngas

Luan

Chong

et al. 2007

Catal Lett

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One-step synthesis of dimethyl ether (DME) from H 2 /CO has been studied in a fixed bed reactor over hybrid catalyst CuOZnOAl 2 O 3 /c-Al 2 O 3 -HZSM-5. The physicochemical properties of fresh and used catalysts were also studied by means of H 2 -TPR, XRD and N 2 O chemisorptions. The results showed that for deactivated catalysts by sintering, redox cycle was an effective method for in-situ regeneration. There were two different regeneration mechanisms according to various atmospheres: (i) For O 2 -syngas cycle, sintered Cu particles were re-dispersed and initial activity was restored mostly. The process was reversible, which was called reversible regeneration; (ii) for N 2 O (CO 2 )-syngas cycle, Cu particles could not be re-dispersed and catalytic activity was restored a little due to the regulation of surface state. On the other hand, this process could depress the deactivation velocity and was irreversible, which was called irreversible regeneration.

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“…Owing to an enhanced atom mobility, low melting point metals such as Cu, Au or Ag are particularly prone to grow. Cu-based catalysts, typically promoted by ZnO, are employed in industrial processes such as the water-gas shift reaction [18,19] and the synthesis of methanol from synthesis gas [20,21], for which Cu particle growth is a prominent deactivation mechanism [22,23,24].…”

Section: Introductionmentioning

confidence: 99%

Interplay between pore size and nanoparticle spatial distribution: Consequences for the stability of CuZn/SiO2 methanol synthesis catalysts

Prieto

Meeldijk

Jong

et al. 2013

Journal of Catalysis

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Particle growth is a major deactivation mechanism for supported metal catalysts. This study reveals that the impact of pore size on catalyst stability is very sensitive to the nanoscale metal distribution. A set of ex-nitrate CuZn/SiO 2 catalysts was synthesised using SiO 2 -gel supports (pore size 5-23 nm). The catalyst compositions were adjusted to attain series of catalysts with either constant pore volumetric (1.6 Cu nm -3 ) or surface (2.0 Cu nm -2 ) overall metal loading. The procedures of thermal decomposition of the metal nitrate precursors were adjusted to achieve < 10 nm Cu particles displaying markedly different nanospatial distributions, i.e either gathered in high-metaldensity domains with small interparticle spacings or evenly distributed over the support with maximum interparticle spacings. Under industrially relevant methanol synthesis conditions, a strong increase of the deactivation rate with the support pore size is observed for catalysts with high-density domains of Cu particles. For these samples the local, nanoscale Cu surface loading is determined by pore size rather than by the overall metal content, as ascertained by HAADF-STEM/EDX.Conversely, Cu nanoparticles evenly spaced on the surface of the SiO 2 carrier show improved stability, being the deactivation rate chiefly independent of the support pore size. The differences in catalyst stability are ascribed to the dominance of different particle growth mechanisms. Our study highlights the significance of local, nanoscale properties for rationalizing the relevance of structural parameters such as pore size for catalyst stability.

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Deactivation of Cu/ZnO/Al₂O₃ Methanol Synthesis Catalyst by Sintering

Cited by 173 publications

References 15 publications

Single-Step Syngas-to-Distillates (S2D) Synthesis via Methanol and Dimethyl Ether Intermediates: Final Report

Single-Step Syngas-to-Distillates (S2D) Synthesis via Methanol and Dimethyl Ether Intermediates: Final Report

In-situ regeneration mechanisms of hybrid catalysts in the one-step synthesis of dimethyl ether from syngas

Interplay between pore size and nanoparticle spatial distribution: Consequences for the stability of CuZn/SiO2 methanol synthesis catalysts

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Deactivation of Cu/ZnO/Al2O3 Methanol Synthesis Catalyst by Sintering

Cited by 173 publications

References 15 publications

Single-Step Syngas-to-Distillates (S2D) Synthesis via Methanol and Dimethyl Ether Intermediates: Final Report

Single-Step Syngas-to-Distillates (S2D) Synthesis via Methanol and Dimethyl Ether Intermediates: Final Report

In-situ regeneration mechanisms of hybrid catalysts in the one-step synthesis of dimethyl ether from syngas

Interplay between pore size and nanoparticle spatial distribution: Consequences for the stability of CuZn/SiO2 methanol synthesis catalysts

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Deactivation of Cu/ZnO/Al₂O₃ Methanol Synthesis Catalyst by Sintering