Nonlinear optical refraction characteristics of rapidly grown K(DxH1−x)2PO4crystals

Wang, Duanliang; Li, Tingbin; Wang, Shenglai; Wang, Jing; Shen, Chuanying; Ding, Jianxiu; Li, Weidong; Huang, Pingping; Liu, Hui

doi:10.7567/apex.10.052601

Cited by 12 publications

(23 citation statements)

References 31 publications

(45 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[139,140] In addition to conventional hierarchically porous zeolites, in recent years, several novel hollow zeolite structures have been synthesized, used as MDA catalysts and displayed significant deactivation stability and high extent of crystal utilization. [141][142][143] The promising performance of hollow zeolite catalysts is likely related to a combination of shortened diffusion pathway within the micropores and limited external surface area. Further systematic studies are necessary to determine the optimal (hierarchical and/or hollow) porous structure and identification of textural descriptors similar to the hierarchy factor [144] will likely be useful in this regard.…”

Section: Catalyst Engineeringmentioning

confidence: 99%

Reactivity, Selectivity, and Stability of Zeolite‐Based Catalysts for Methane Dehydroaromatization

2020

View full text Add to dashboard Cite

strong C-H bonds complicates the selective conversion of methane to higher hydrocarbons and oxygenates. Currently, the main industrial method to use methane as a material feedstock involves the transformation to syngas by steam reforming, followed by processes such as methanol synthesis and Fischer-Tropsch synthesis to obtain liquid fuels and other useful chemicals. A disadvantage of this indirect technology is the high capital cost of reforming plants, making it only economically attractive at a very large scale. An efficient direct process for the conversion of methane to higher hydrocarbons or oxygenates remains one of the "holy grails" of chemistry. [6,7] The approaches to directly convert methane can be categorized into oxidative and non-oxidative methods. Oxidative processes are often met with low product selectivity because of the higher reactivity of targeted products as compared to methane itself, resulting in overoxidation to CO 2. Non-oxidative methods are generally more atom-efficient, because, in addition to valuable hydrocarbon products, pure CO xfree hydrogen gas (H 2) is obtained, which can be used for instance in fuel cells. [8] Among several alternatives, including non-oxidative coupling of methane to ethylene and deep methane dehydrogenation to solid carbon and hydrogen, [9-12] methane dehydroaromatization (MDA) remains one of the most promising non-oxidative reactions for the direct valorization of natural gas. MDA involves the selective conversion of methane to a mixture of easily transportable aromatics, that is, benzene (predominantly), naphthalene, and toluene. As all other non-oxidative methane conversion reactions, MDA is a highly endothermic process: 6CH C H 9H 532 kJ mol Non-oxidative dehydroaromatization is arguably the most promising process for the direct upgrading of cheap and abundant methane to liquid hydrocarbons. This reaction has not been commercialized yet because of the suboptimal activity and swift deactivation of benchmark Mo-zeolite catalysts. This progress report represents an elaboration on the recent developments in understanding of zeolite-based catalytic materials for high-temperature non-oxidative dehydroaromatization of methane. It is specifically focused on recent studies, relevant to the materials chemistry and elucidating i) the structure of active species in working catalysts; ii) the complex molecular pathways underlying the mechanism of selective conversion of methane to benzene; iii) structure, evolution and role of coke species; and iv) process intensification strategies to improve the deactivation resistance and overall performance of the catalysts. Finally, unsolved challenges in this field of research are outlined and an outlook is provided on promising directions toward improving the activity, stability, and selectivity of methane dehydroaromatization catalysts.

show abstract

Section: Catalyst Engineeringmentioning

confidence: 99%

Reactivity, Selectivity, and Stability of Zeolite‐Based Catalysts for Methane Dehydroaromatization

2020

View full text Add to dashboard Cite

show abstract

“…[ 31,39 ] Moreover, no peaks at 2 θ = 12.9° and 27.3° that are related to the (011) and (121) phases, respectively, for α‐MoO 3 were noticed in the case of both Mo/HZSM‐5 and CZO‐Mo/HZSM‐5 samples, which might specify the homogeneous dispersion of Mo oxide species bound to the zeolitic surface or possessing the size of Mo crystallite, which is below the detection limit in XRD. [ 9,22 ] Further, as described in the previous studies, the higher distribution of Mo oxide species and their suitable binding with the zeolitic surface acid sites is one of the prerequisites for the enhanced catalytic activity of Mo‐modified HZSM‐5 catalyst. [ 22,40 ]…”

Section: Resultsmentioning

confidence: 97%

“…To date, catalyst deactivation due to extensive coking, low single‐pass methane conversion, and aromatic yields (<10%) are the two bottleneck problems that need to be addressed for the industrial viability of the MDA process. [ 3,12,13,20–22 ]…”

Section: Introductionmentioning

confidence: 99%

Catalytic conversion of methane into benzene over ceria–zirconia‐promoted molybdenum‐supported zeolite for methane dehydroaromatization

Mishra

Modak

Pant

et al. 2023

Applied Organom Chemis

View full text Add to dashboard Cite

The promotional effect of mixed ceria–zirconia oxides (CZO) over the Mo/HZSM‐5 catalyst for methane dehydroaromatization (MDA) reaction was studied. The surface and structural properties of the synthesized catalyst were thoroughly exemplified using various microscopic and spectroscopic tools, and the correlation between catalytic properties and its performance for MDA reaction is discussed. The impregnation of CZO solid solution on Mo/HZSM‐5 was monitored to give an excellent catalytic performance and improved benzene production rate (4.5 μmol/gcat.s) related to the conventionally prepared Mo/HZSM‐5 (3.1 μmol/gcat.s) catalyst. In addition, a significant reduction in coke formation was examined in the CZO‐modified Mo/HZSM‐5 catalyst. The prevailing comprehension for higher catalytic activity could be because of the redox properties of CZO‐deposited Mo/HZSM‐5, which acts as a selective oxygen supplier and performs hydrogen combustion during the reaction, which is indirectly probed by residual gas analysis‐mass spectroscopy, oxygen‐temperature programmed desorption, and hydrogen‐temperature programmed reduction analysis. The selective hydrogen combustion prevents the over‐oxidation of aromatic species formed during the reaction, whereas the generated steam helps in reducing the coke content deposition in the MDA reaction. Thus, the advantage of CZO‐incorporated Mo/HZSM‐5 is manifested as it promotes the reaction equilibrium to shift towards the formation of benzene which is favourable for MDA reaction.

show abstract

“…The spent ZSM‐5@MoO 3 contained the less hard coke than ZSM‐5/MoO 3 . This is caused by the fact that ZSM‐5@MoO 3 had a lower Brønsted acid amount and the micro‐mesoporous system, which promoted the outward diffusion of products, inhibiting the formation of polynuclear aromatic species [36] . Thus, the core‐shell ZSM‐5@MoO 3 catalyst effectively suppressed the generation of the carbon deposits [36] …”

Section: Resultsmentioning

confidence: 99%

A Convenient Synthesis of Core‐shell ZSM‐5@MoO₃ Catalyst for Enhanced Catalytic Properties in Methane Aromatization

Zhu

2022

ChemistrySelect

View full text Add to dashboard Cite

A novel core‐shell ZSM‐5@MoO3 catalyst was successfully synthesized by the hydrothermal coating strategy, and its physicochemical properties and catalytic properties in methane aromatization were investigated using a physically‐blended ZSM‐5/MoO3 catalyst as a comparison. Multitechniques including XRD, SEM, TEM, EDS, N2 adsorption, ICP, IR and IG were employed to investigate the characteristics of methane aromatization reaction and the deactivation of carbon deposits. At the reaction temperature of 700 °C and a space velocity of 2400 mL g−1 h−1, methane conversion and aromatics selectivity of the core‐shell ZSM‐5@MoO3 catalyst were 11.3 % and 88.1 %, respectively, which were higher than those of the physically‐blended ZSM‐5/MoO3 catalyst by 3.1 % and 14.8 %, respectively. The special reaction pathway of core (ZSM‐5, acid sites)‐shell (MoO3, Mo sites) and the relatively close proximity between MoO3 and ZSM‐5 were mainly responsible for the excellent properties in the methane aromatization reaction. At the same time, the formation of the micro‐mesoporous property accelerated the mass‐transfer rate and inhibited the formation of carbonaceous deposition, greatly improving the stability of methane aromatization. Thanks to its core‐shell structure, ZSM‐5@MoO3 catalyst showed the excellent properties in methane aromatization.

show abstract

Nonlinear optical refraction characteristics of rapidly grown K(D_xH₁₋_x)₂PO₄crystals

Cited by 12 publications

References 31 publications

Reactivity, Selectivity, and Stability of Zeolite‐Based Catalysts for Methane Dehydroaromatization

Reactivity, Selectivity, and Stability of Zeolite‐Based Catalysts for Methane Dehydroaromatization

Catalytic conversion of methane into benzene over ceria–zirconia‐promoted molybdenum‐supported zeolite for methane dehydroaromatization

A Convenient Synthesis of Core‐shell ZSM‐5@MoO₃ Catalyst for Enhanced Catalytic Properties in Methane Aromatization

Contact Info

Product

Resources

About

Nonlinear optical refraction characteristics of rapidly grown K(DxH1−x)2PO4crystals

Cited by 12 publications

References 31 publications

Reactivity, Selectivity, and Stability of Zeolite‐Based Catalysts for Methane Dehydroaromatization

Reactivity, Selectivity, and Stability of Zeolite‐Based Catalysts for Methane Dehydroaromatization

Catalytic conversion of methane into benzene over ceria–zirconia‐promoted molybdenum‐supported zeolite for methane dehydroaromatization

A Convenient Synthesis of Core‐shell ZSM‐5@MoO3 Catalyst for Enhanced Catalytic Properties in Methane Aromatization

Contact Info

Product

Resources

About

Nonlinear optical refraction characteristics of rapidly grown K(D_xH₁₋_x)₂PO₄crystals

A Convenient Synthesis of Core‐shell ZSM‐5@MoO₃ Catalyst for Enhanced Catalytic Properties in Methane Aromatization