Synthesis of phosphorus-modified small-pore zeolites utilizing tetraalkyl phosphonium cations as both structure-directing and phosphorous modification agents

Yamasaki, Yoshitaka; Tsunoji, Nao; Takamitsu, Yasuyuki; Sadakane, Masahiro; Sano, Tsuneji

doi:10.1016/j.micromeso.2015.10.038

Cited by 56 publications

(35 citation statements)

References 53 publications

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“…CHA zeolite (Si/Al=14) was prepared according to the previous report . Sodium hydroxide, dealuminated FAU zeolite, N , N , N ‐trimethyl‐1‐adamantammonium hydroxide (TMAda, 25 wt%, Sachem Asia Co., Ltd., Japan), and distilled water were mixed to obtain a gel with the composition 1 : 0.0625 : 0.3 : 0.1 : 7.5 of Si/Al/TMAda/NaOH/H 2 O.…”

Section: Methodsmentioning

confidence: 99%

In Situ Spectroscopic Studies on the Redox Cycle of NH₃−SCR over Cu−CHA Zeolites

et al. 2020

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The selective catalytic reduction of NO with ammonia (NH3−SCR) catalyzed by Cu−CHA zeolites is thoroughly investigated using in situ spectroscopic experiments combined with on‐line mass spectroscopy (MS) under steady‐state NH3−SCR conditions and transient conditions for Cu(II)/Cu(I) redox cycles. Quantitative analysis of the in situ XANES spectra of Cu−CHA under steady‐state conditions of NH3−SCR show that NH3‐coordinated Cu(II) species is the dominant Cu species at low temperatures (100–150 °C). At higher temperatures, Cu(II) species and [Cu(NH3)2]+ complex coexist, possibly because the rate of the Cu(II)→Cu(I) reduction step is comparable to that of the Cu(I)→Cu(II) oxidation step. In situ XANES, IR/MS, and UV‐vis/MS experiments on the reduction half cycle demonstrate that the reduction of Cu(II) species occurs via the reaction of NH3‐liganded Cu(II) with NO to yield N2 and H2O. For the oxidation half cycle, in situ XANES experiments of Cu(I) oxidation in 10 % O2 at 200 °C indicate that an increased density in CHA zeolite exhibits a higher oxidation rate. In situ UV‐vis experiments of Cu(I) reoxidation using different mixtures of oxidant feed gas demonstrate the key role of O2 in the oxidation cycle. It is suggested that the reoxidation of Cu(I) to Cu(II) species occurs with only O2 as the oxidant, and a high Cu density in CHA zeolite promotes SCR activity by enhancing the oxidative activation of Cu(I) to Cu(II) during the catalytic cycle.

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Section: Methodsmentioning

confidence: 99%

In Situ Spectroscopic Studies on the Redox Cycle of NH₃−SCR over Cu−CHA Zeolites

et al. 2020

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“…In addition to differences in the size, morphology, and number of mesopores inside the crystals, the SH and MH catalysts also differ in the nature of mineralizing agent that was used to create the porosity. MH crystals were obtained in the presence of phosphonium cations, which are known to contaminate zeolites with phosphorus‐containing species upon calcination . Phosphorous‐based compounds are also known as poisons for nickel catalysts …”

Section: Resultsmentioning

confidence: 99%

Highly Dispersed Nickel Particles Encapsulated in Multi‐hollow Silicalite‐1 Single Crystal Nanoboxes: Effects of Siliceous Deposits and Phosphorous Species on the Catalytic Performances

et al. 2017

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Multi‐hollow silicalite‐1 single crystals (MH) were prepared for the first time by an original synthesis pathway by using tetrabutylphosphonium hydroxide (TBPOH) as a mild desilicating agent. This new generation of hierarchical zeolite allowed the encapsulation of nanoparticles (NPs) featuring an enhanced confinement of the metallic guest and a thin wall thickness. The MH catalyst exhibited a better stability for methane steam reforming at 700 °C than a single‐hollow counterpart (SH). Ni average particle size could be kept lower than 4 nm after 20 h on stream for the MH sample. However, a detailed analysis of kinetic data of the structure‐insensitive CO methanation used as a model reaction revealed that the sample activity was adversely affected by two main factors deriving from the preparation steps. First, a siliceous over‐layer derived from the decomposition of intermediate Ni phyllosilicates, which partly covered the resulting Ni nanoparticles. Second, phosphorus from the templates remained in the samples, probably forming a Ni–P compound upon reduction. The overall catalytic activities observed here were therefore a complex interplay of improved dispersion and poisonous effects.

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“…More recent efforts in zeolite transformation utilize various organic templates for synthesizing targeted zeolites, either in the presence or absence of targeted zeolite seeds . New advances in the seed‐directed OSDA‐free synthesis of zeolites stimulated more research activities on interzeolite transformation with the goal of providing unique strategies to synthesize zeolites without OSDAs.…”

Section: Organotemplate‐free Interzeolite Transformationmentioning

confidence: 99%

Understanding Commonalities and Interplay Between Organotemplate‐Free Zeolite Synthesis, Hierarchical Structure Creation, and Interzeolite Transformation

2018

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are crystalline microporous materials that have been widely used in many applications related to industrial catalysis, ion-exchange, and adsorption. In recent years, there has been a growing emphasis on the development of green chemistry toward more sustainable zeolite synthesis routes. Considerable efforts have been devoted to identifying alternative approaches in order to reduce the negative impacts of organic templates. This review will focus on the significant progress achieved during the past decade on the development of novel organotemplate-free strategies through three distinctive topics, i. e. zeolite synthesis, hierarchical zeolite synthesis, and interzeolite transformation. The progress of each topic will be documented, followed by a summary of the intriguing commonalities and interplay among these approaches. The insights into the mechanism and interplay leading to different zeolite materials will enable us to understand the requirements for designing novel zeolite catalysts and catalyst supports in an organotemplate-free environment that are likely to further enhance the industrial impact of these materials in the future. We conclude this article with a perspective and outlook focusing on current trends and future directions in this area.[a] Dr.

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Synthesis of phosphorus-modified small-pore zeolites utilizing tetraalkyl phosphonium cations as both structure-directing and phosphorous modification agents

Cited by 56 publications

References 53 publications

In Situ Spectroscopic Studies on the Redox Cycle of NH₃−SCR over Cu−CHA Zeolites

In Situ Spectroscopic Studies on the Redox Cycle of NH₃−SCR over Cu−CHA Zeolites

Highly Dispersed Nickel Particles Encapsulated in Multi‐hollow Silicalite‐1 Single Crystal Nanoboxes: Effects of Siliceous Deposits and Phosphorous Species on the Catalytic Performances

Understanding Commonalities and Interplay Between Organotemplate‐Free Zeolite Synthesis, Hierarchical Structure Creation, and Interzeolite Transformation

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Synthesis of phosphorus-modified small-pore zeolites utilizing tetraalkyl phosphonium cations as both structure-directing and phosphorous modification agents

Cited by 56 publications

References 53 publications

In Situ Spectroscopic Studies on the Redox Cycle of NH3−SCR over Cu−CHA Zeolites

In Situ Spectroscopic Studies on the Redox Cycle of NH3−SCR over Cu−CHA Zeolites

Highly Dispersed Nickel Particles Encapsulated in Multi‐hollow Silicalite‐1 Single Crystal Nanoboxes: Effects of Siliceous Deposits and Phosphorous Species on the Catalytic Performances

Understanding Commonalities and Interplay Between Organotemplate‐Free Zeolite Synthesis, Hierarchical Structure Creation, and Interzeolite Transformation

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In Situ Spectroscopic Studies on the Redox Cycle of NH₃−SCR over Cu−CHA Zeolites

In Situ Spectroscopic Studies on the Redox Cycle of NH₃−SCR over Cu−CHA Zeolites