Synthesis, characterization and mechanism of formation of carbon aerogels incorporated with highly crystalline lanthanum oxychloride particles

Zhu, Xiurong; Yu, Yi; Yuan, Jüjun; Zhang, Xianke; Yu, Huajun; Zhang, Wen; Du, Ai; Zhou, Bin

doi:10.1039/c7ra05454h

Cited by 10 publications

(4 citation statements)

References 28 publications

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“… 33 Since LaOCl and EuOCl have the same space group, P 4/ nmm , and comparable ionic radii, 34 solid-state ion mixing of the two elements is expected to occur. 35 , 36 By deconvolution of the (110) XRD peaks of the as-synthesized LnOCl catalysts ( Figure 1 B–F) and applying Vegard’s law (see SI Section S1B for more details on the applied procedure), at least two mixed phases were distinguished with varying La 3+ /Eu 3+ ratios, referred to as phase 1 and phase 2 ( Table 1 ). Noticeable is that for every bimetallic La 3+ –Eu 3+ catalyst, we obtained one La 3+ -rich phase ( x > 70%, referred to as phase 1) and one phase with a larger distribution in the La 3+ –Eu 3+ ratio (phase 2).…”

Section: Resultsmentioning

confidence: 99%

Favoring the Methane Oxychlorination Reaction over EuOCl by Synergistic Effects with Lanthanum

Terlingen

Oord

Ahr³

et al. 2022

ACS Catal.

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The direct conversion of CH 4 into fuels and chemicals produces less waste, requires smaller capital investments, and has improved energy efficiency compared to multistep processes. While the methane oxychlorination (MOC) reaction has been given little attention, it offers the potential to achieve high CH 4 conversion levels at high selectivities. In a continuing effort to design commercially interesting MOC catalysts, we have improved the catalyst design of EuOCl by the partial replacement of Eu 3+ by La 3+ . A set of catalytic solid solutions of La 3+ and Eu 3+ (i.e., La x Eu 1– x OCl, where x = 0, 0.25, 0.50, 0.75, and 1) were synthesized and tested in the MOC reaction. The La 3+ –Eu 3+ catalysts exhibit an increased CH 3 Cl selectivity (i.e., 54–66 vs 41–52%), a lower CH 2 Cl 2 selectivity (i.e., 8–24 vs 18–34%), and a comparable CO selectivity (i.e., 11–28 vs 14–28%) compared to EuOCl under the same reaction conditions and varying HCl concentrations in the feed. The La 3+ –Eu 3+ catalysts possessed a higher CH 4 conversion rate than when the individual activities of LaOCl and EuOCl are summed with a similar La 3+ /Eu 3+ ratio (i.e., the linear combination). In the solid solution, La 3+ is readily chlorinated and acts as a chlorine buffer that can transfer chlorine to the active Eu 3+ phase, thereby enhancing the activity. The improved catalyst design enhances the CH 3 Cl yield and selectivity and reduces the catalyst cost and the separation cost of the unreacted HCl. These results showcase that, by matching intrinsic material properties, catalyst design can be altered to overcome reaction bottlenecks.

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Section: Resultsmentioning

confidence: 99%

Favoring the Methane Oxychlorination Reaction over EuOCl by Synergistic Effects with Lanthanum

Terlingen

Oord

Ahr³

et al. 2022

ACS Catal.

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“…In the case of La 3+ both a larger ionic radius (∼1.22 Å) and longer La-Cl bond length (∼2.4 Å) is observed 40 , 41 . However, both MgCl 2 and LaOCl are built up of successive layers of M x+ and Cl − anions (in the case of LaOCl, LaO + layers alternating with double Cl − layers), where primary particles of these compounds are platelets loosely bound together through ionic interactions 42 – 44 . After grafting the TiCl 4 active site precursor on the LaOCl spherical caps followed by the activation with a triethylaluminium (TEAL) co-catalyst and ethylene polymerization under mild conditions, e.g., 2 bar ethylene, slurry-phase at room temperature, the polyethylene-LaOCl composite spherical caps are studied in detail using a toolbox consisting of both surface-sensitive (micro)-spectroscopic and conventional micro-spectroscopic techniques.…”

Section: Resultsmentioning

confidence: 99%

A Ziegler-type spherical cap model reveals early stage ethylene polymerization growth versus catalyst fragmentation relationships

et al. 2022

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Polyolefin catalysts are characterized by their hierarchically complex nature, which complicates studies on the interplay between the catalyst and formed polymer phases. Here, the missing link in the morphology gap between planar model systems and industrially relevant spherical catalyst particles is introduced through the use of a spherical cap Ziegler-type catalyst model system for the polymerization of ethylene. More specifically, a moisture-stable LaOCl framework with enhanced imaging contrast has been designed to support the TiCl4 pre-active site, which could mimic the behaviour of the highly hygroscopic and industrially used MgCl2 framework. As a function of polymerization time, the fragmentation behaviour of the LaOCl framework changed from a mixture of the shrinking core (i.e., peeling off small polyethylene fragments at the surface) and continuous bisection (i.e., internal cleavage of the framework) into dominantly a continuous bisection model, which is linked to the evolution of the estimated polyethylene volume and the fraction of crystalline polyethylene formed. The combination of the spherical cap model system and the used advanced micro-spectroscopy toolbox, opens the route for high-throughput screening of catalyst functions with industrially relevant morphologies on the nano-scale.

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“…The appeared peaks at 1219 cm À1 and 1098 cm À1 correspond to C-O-C linkage stretching. 44,45 The peak at 1296 cm À1 is assigned to C-O.…”

Section: Resultsmentioning

confidence: 99%

Preparation and application of sunlight absorbing ultra-black carbon aerogel/graphene oxide membrane for solar steam generation systems

et al. 2020

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Synthesis, characterization and mechanism of formation of carbon aerogels incorporated with highly crystalline lanthanum oxychloride particles

Abstract: Low-density carbon aerogels incorporated with high crystallization LaOCl particles: (a) photograph, (b) SEM, (c) TEM and (d) XRD.

Cited by 10 publications

References 28 publications

Favoring the Methane Oxychlorination Reaction over EuOCl by Synergistic Effects with Lanthanum

Favoring the Methane Oxychlorination Reaction over EuOCl by Synergistic Effects with Lanthanum

A Ziegler-type spherical cap model reveals early stage ethylene polymerization growth versus catalyst fragmentation relationships

Preparation and application of sunlight absorbing ultra-black carbon aerogel/graphene oxide membrane for solar steam generation systems

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