Hydrothermal stability of different zeolites in supercritical water: Implication for synthesis of supported catalysts by supercritical water impregnation

Zhang, Yuechao; Li, Yingjie; Gu, Junjie; Tian, Senlin; Ning, Ping

doi:10.1007/s11814-018-0084-y

Cited by 9 publications

(8 citation statements)

References 56 publications

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“…The framework of nanoporous titanosilicates was reported to be stable upon exposure to aqueous H 2 O 2 solutions at temperatures below 343 K [ 102 ] and even to short exposure (10 min) to supercritical water (658 K at 22.5 MPa). [ 103 ] Some framework degradation (structure decomposition and titanium sintering) has been reported for Ti‐ BEA samples upon exposure to aqueous H 2 O 2 at room temperature and subsequent calcination at 723 K, [ 102c ] however, it was associated with: i) thermal instability of the BEA framework, as a similar loss of crystallinity in XRD analysis was also observed for purely siliceous BEA calcined at 823 K, and ii) reactivity of H 2 O 2 molecules, as exposure to pure liquid water did not result in the formation of extra‐framework titanium oligomers. In contrast, Ti‐ MFI samples were stable upon H 2 O 2 and thermal treatment.…”

Section: Reactive Interaction Of Water With Zeolitesmentioning

confidence: 99%

“…[ 102a,104 ] In supercritical water, though, titanium leaves the framework, as indicated by the complete disappearance of signals in ammonia temperature programmed desorption profiles and IR signals related to TiO 4 units. [ 103 ] Nevertheless, titanium containing zeolites appear to be hydrothermally more stable than their tin counterparts. This can be related to their increased hydrophobicity, which is comparable to purely siliceous frameworks (see Section 2.2).…”

Section: Reactive Interaction Of Water With Zeolitesmentioning

confidence: 99%

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Zeolite (In)Stability under Aqueous or Steaming Conditions

et al. 2020

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zeolites, modification of zeolite acidity for use as fluid catalytic cracking (FCC) catalysts or even for the preparation of novel zeolite frameworks. [1] Considering the significance of zeolite applications at the industrial level, a thorough understanding of zeolite (in)stability under aqueous conditions has been identified as a very important problem in catalysis and zeolite science. Zeolite (in)stability in water or under steaming conditions has been investigated by a number of experimental techniques, in particular magic angle spinning (MAS) NMR, IR, powder X-ray diffraction (PXRD), calorimetry and adsorption. Experimental studies have often been augmented by computational modeling and a large number of relevant theoretical papers can be found in the literature. While the main focus of this review is on reactive interactions of water with zeolites, it is also important to review the most important observations obtained for nonreactive water adsorption in zeolites. It is not surprising that all-silica zeolites, which exhibit negligible water uptake are stable even under conditions where Alcontaining zeolites lose crystallinity: the effective framework hydrolysis can only take place when sufficient water is present in the zeolite channel system. The amount of water inside the zeolite channels depends critically on the concentration of heteroatoms and/or framework defects, such as silanol nests, which show much higher affinity toward water than hydrophobic SiOSi bridges. Zeolite hydrophobicity increases with increasing Si/Al ratio and incomplete pore filling by water is commonly observed for zeolites with high Si/Al at standard pressure. It has been suggested already in the 1950s by Young that water can only adsorb on surface silanol groups, while the parts of the silica surfaces formed by SiOSi bridges are hydrophobic. [2] Both water adsorption in zeolites and zeolite (in)stability under aqueous conditions depend on the zeolite composition (Si/Al ratio, charge-compensating cations, and defect concentration in particular). Our primary goal is to review the most critical aspects of zeolite (in)stability for a broad range of temperature and partial water pressure (p 0), focusing on the framework zeolite composition (Si/Al ratio and presence of Ge, Sn, and Ti heteroatoms) and defect concentration. Zeolites (in)stability in water is discussed for increasing extent of framework degradation, starting from the nonreactive interaction with water, reversible hydrolysis of TO bonds, mild zeolite demetallation, mesopore formation, and total amorphization (Figure 1). Zeolites are among the most environmentally friendly materials produced industrially at the Megaton scale. They find numerous commercial applications, particularly in catalysis, adsorption, and separation. Under ambient conditions aluminosilicate zeolites are stable when exposed to water or water vapor. However, at extreme conditions as high temperature, high water vapor pressure or increased acidity/basicity, their crystalline framework can be destroyed....

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Section: Reactive Interaction Of Water With Zeolitesmentioning

confidence: 99%

Section: Reactive Interaction Of Water With Zeolitesmentioning

confidence: 99%

Zeolite (In)Stability under Aqueous or Steaming Conditions

et al. 2020

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“…In this work Cr-containing Beta zeolites were investigated as a catalysts for propane dehydrogenation in the presence of carbon dioxide. Beta zeolite was applied due to a three-dimensional structure, the pores larger than those of ZSM-5 with 12-membered ring openings (0.75 by 0.57 nm for linear and 0.65 by 0.56 nm for tortuous channels), a high thermal and acid stability and a large specific surface area needed for high chromium species dispersion [33][34][35]. We have shown that dealumination of Beta and subsequently chromium dispersion by simple impregnation procedure give excellent catalysts for CO 2 -PDH.…”

Section: Introductionmentioning

confidence: 99%

Effect of dealumination on the catalytic performance of Cr-containing Beta zeolite in carbon dioxide assisted propane dehydrogenation

Michorczyk

Zeńczak-Tomera

Michorczyk

et al. 2020

Journal of CO2 Utilization

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HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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“…However, the supports may be unstable in SCW. For example, γ-Al 2 O 3 was converted to α-Al 2 O 3 in a hydrothermal environment, and zeolites undergo structural collapse in SCW [38,39]. The phase transformation and structural collapse of the support can reduce catalytic activity.…”

Section: Metalsmentioning

confidence: 99%

Recent Advances in Supercritical Water Gasification of Pulping Black Liquor for Hydrogen Production

Chen¹,

Yu²,

Li³

et al. 2022

Clean Energy Technologies - Hydrogen and Gasification Processes

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Black liquor is the wastewater produced from paper-making-pulping industry, which has great threats to the environment and human health. Its pollution handling and resourcing attracted much attention, but conventional method showed several drawbacks, including low energy efficiency, emission of secondary pollutants, and safety and operating issues. Supercritical water gasification (SCWG) is a promising method for organic wastes, especially for those with high moisture content, so it has been widely investigated. A previous study showed that SCWG of pulping wastewater can realize pollution elimination and hydrogen production simultaneously. In this chapter, the recent development of this technology in past decade will be reviewed, including the gasification performance, the influence of the main operating parameter, the catalysts used in this process, the synergetic effect in co-gasification with other energy sources, and the evaluation of integrated system of SCWG of black liquor with pulping process. These progresses have been made will boost the industrial utilization of SCWG of black liquor in pulping industry.

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Hydrothermal stability of different zeolites in supercritical water: Implication for synthesis of supported catalysts by supercritical water impregnation

Cited by 9 publications

References 56 publications

Zeolite (In)Stability under Aqueous or Steaming Conditions

Zeolite (In)Stability under Aqueous or Steaming Conditions

Effect of dealumination on the catalytic performance of Cr-containing Beta zeolite in carbon dioxide assisted propane dehydrogenation

Recent Advances in Supercritical Water Gasification of Pulping Black Liquor for Hydrogen Production

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