scholarly journals Acidic and Catalytic Properties of Mo-Containing Zeolite Catalysts for Non-Oxidative Methane Conversion

2017 ◽  
Vol 6 (3) ◽  
pp. 201 ◽  
Author(s):  
A.V. Vosmerikov ◽  
G.V. Echevsky ◽  
L.L. Korobitsyna ◽  
N.V. Arbuzova ◽  
L.M. Velichkina ◽  
...  
Keyword(s):  
Induction Period ◽  
Methane Conversion ◽  
Space Velocity ◽  
Zeolite Catalysts ◽  
Mechanical Mixing ◽  
Ammonium Heptamolybdate ◽  
Methane Dehydroaromatization ◽  
Conversion Of Methane ◽  
Benzene Toluene ◽  
The Stability

<p>The conversion of methane into benzene, toluene and naphthalene at the reaction temperature of 750 °C and gas hourly space velocity (GHSV) of 500-1500 h<sup>-1</sup> over zeolites modified via impregnation with ammonium heptamolybdate and mechanical mixing with Mo oxide and nanopowder is studied under non-oxidative conditions. It has been established that the highest methane conversion per one run and maximal yield of aromatic hydrocarbons are reached for the sample containing 4.0 mass.% the Mo nanopowder. The stability of Mo-containing zeolite catalysts in the process of methane dehydroaromatization at different GHSV has been studied and a characteristic presence of the induction period caused by the formation of active Mo forms both on the external surface and into the zeolite channels has been established. Both the duration of induction period and stable catalyst operation are decreasing with increasing of GHSV. It was demonstrated that acidic properties of a Mo-containing zeolite catalyst depend on the Mo concentration and method of its introduction.</p>

scholarly journals Deactivation and Regeneration of Mo/ZSM-5 Catalysts for Methane Dehydroaromatization

2009 ◽  
Vol 12 (1) ◽  
pp. 1 ◽  
Author(s):  
E.V. Matus ◽  
O.B. Sukhova ◽  
I.Z. Ismagilov ◽  
V.I. Zaikovskii ◽  
M.A. Kerzhentsev ◽  
...  
Keyword(s):  
Reaction Time ◽  
Reaction Temperature ◽  
Methane Conversion ◽  
Formation Rate ◽  
Space Velocity ◽  
Molybdenum Content ◽  
Stable Operation ◽  
Carbonaceous Deposits ◽  
Methane Dehydroaromatization ◽  
The Stability

The methane dehydroaromatization (DHA) was studied over a series of impregnated Mo/ZSM-5 catalysts with different molybdenum contents (1-10 wt.%). It was shown that total methane conversion was decreased by 30% during 12 h of DHA reaction. The benzene formation rate was increased from 0.5 to 13.9 mol C<sub>6</sub>H<sub>6</sub>/(g<sub>Mo</sub>·s) when the molybdenum content in the catalyst was lowered from 10 to 1 wt.%. The deactivated Mo/ZSM-5 catalysts were studied by a group of methods: N<sub>2</sub> adsorption, XRD, TGDTA, HRTEM and XPS. The content and condensation degree (C/H ratio) of the carbonaceous deposits was found to increase with an increase of either of the following parameters: molybdenum content (1-10 wt.%), reaction temperature (720-780 °C), space velocity (405-1620 h<sup>-1</sup>), reaction time (0.5-20 h). The stability of Mo/ZSM-5 catalysts in reaction-regeneration cycles was better when the time on stream was shorter. The regeneration conditions of deactivated Mo/ZSM-5 catalysts providing their stable operation under multiple reaction-regeneration cycles have been selected.

The Conversion of Light Naphtha Into Aromatics by Using Promoted Zeolite Catalysts

1989 ◽  
Vol 42 (12) ◽  
pp. 2095 ◽  
Author(s):  
G Berti ◽  
JE Moore ◽  
L Salusinszky ◽  
D Seddon
Keyword(s):  
Liquid Product ◽  
Space Velocity ◽  
Zeolite Catalysts ◽  
Weight Hourly Space Velocity ◽  
Liquid Products ◽  
Lower Severity ◽  
Benzene Toluene ◽  
Rich Liquid ◽  
Liquid Yield ◽  
Benzene Content

Zeolites of the ZSM-5 family are poor for converting liquid paraffins into aromatics, but commercially available H-ZSM-5 can be effectively promoted with zinc or gallium. A gallium-promoted zeolite was used for the conversion of pentane and a natural-gas condensate into aromatic-rich liquid products. Optimum performance was obtained at temperatures of 475�C and weight-hourly space velocity of 1 h-1. The aromatic products were principally benzene, toluene and xylene, with the benzene content increasing with increasing conversion temperature. Operation of the catalyst at high severity (high temperature, low space velocity) produced a liquid product containing over 90% of aromatics. Lower severity produced less aromatics but higher overall liquid yield.

Performance of Ag-HZSM-5 Zeolite Catalysts in n-heptane Conversion

2017 ◽  
Vol 68 (1) ◽  
pp. 116-120
Author(s):  
Iuliean Vasile Asaftei ◽  
Neculai Catalin Lungu ◽  
Lucian Mihail Birsa ◽  
Ioan Gabriel Sandu ◽  
Laura Gabriela Sarbu ◽  
...  
Keyword(s):  
Aromatic Hydrocarbons ◽  
Metal Content ◽  
Pulse Method ◽  
Acid Strength ◽  
Strength Distribution ◽  
Zeolite Catalysts ◽  
Benzene Toluene ◽  
Acid Strength Distribution ◽  
Silver Cations ◽  
Heptane Conversion

The conversion of n-heptanes into aromatic hydrocarbons benzene, toluene and xylenes (BTX), by the chromatographic pulse method in the temperature range of 673 - 823K was performed over the HZSM-5 and Ag-HZSM-5 zeolites modified by ion exchange with AgNO3 aqueous solutions. The catalysts, HZSM-5 (SiO2/Al2O3 = 33.9), and Ag-HZSM-5 (Ag1-HZSM-5 wt. % Ag1.02, Ag2-HZSM-5 wt. % Ag 1.62; and Ag3-HZSM-5 wt. % Ag 2.05 having different acid strength distribution exhibit a conversion and a yield of aromatics depending on temperature and metal content. The yield of aromatic hydrocarbons BTX appreciably increased by incorporating silver cations Ag+ into HZSM-5.

Active Sites and Induction Period of Fe/ZSM-5 Catalyst in Methane Dehydroaromatization

ACS Catalysis ◽  
2021 ◽  
pp. 6771-6786
Author(s):  
Yu Gu ◽  
Pingping Chen ◽  
Xiaohui Wang ◽  
Yuchao Lyu ◽  
Wanrong Liu ◽  
...  
Keyword(s):  
Induction Period ◽  
Active Sites ◽  
Methane Dehydroaromatization

Unprecedentedly high efficiency for photocatalytic conversion of methane to methanol over Au–Pd/TiO2 – what is the role of each component in the system?

2021 ◽  
Author(s):  
Xiaojiao Cai ◽  
Siyuan Fang ◽  
Yun Hang Hu
Keyword(s):  
Methane Conversion ◽  
High Efficiency ◽  
Mild Conditions ◽  
Highly Efficient ◽  
System P ◽  
Conversion Of Methane

Direct and highly efficient methane conversion to methanol under mild conditions is achieved via photocatalysis over Au–Pd/TiO2.

Pyrolysis of Methane to Higher Hydrocarbons: A Thermodynamic Study

1989 ◽  
Vol 42 (10) ◽  
pp. 1655 ◽  
Author(s):  
FP Larkins ◽  
AZ Khan
Keyword(s):  
Gas Phase ◽  
Pressure Range ◽  
Solid Carbon ◽  
Free Energies ◽  
Oxidation Of Methane ◽  
Conversion Of Methane ◽  
Equilibrium Conversion ◽  
Benzene Toluene ◽  
Higher Hydrocarbons ◽  
The Individual

Some basic thermodynamic parameters such as Gibbs free energies, enthalpies of reactions and equilibrium compositions of products from the pyrolysis and partial oxidation of methane to higher hydrocarbons in the gas phase have been determined within a consistent framework for the temperature range 800-1500 K and the pressure range 0.1-3 MPa , by using the CSIRO-SGTE THERMODATA system. It has been established that the pyrolysis of methane to higher hydrocarbons, e.g. acetylene, ethylene, ethane, prop-1-ene, propane, benzene, toluene, naphthalene, 1-methylnaphthalene and 2-methylnaphthalene, considered as separate reactions, is a highly endothermic reaction with the Gibbs free energies for the individual reactions being positive until 1300 K. The aromatics are thermodynamically most favoured with the equilibrium yields increasing with temperature. Addition of O2 lowers the heats of synthesis and the free energies for methane conversion but no enhancement in the equilibrium yields of hydrocarbons is observed. When solid carbon is allowed, it is the dominant product in all cases with the equilibrium yields for all hydrocarbons becoming negligible. Increasing the pressure at a particular temperature has more effect on the lowering of the equilibrium conversion of methane than on the suppression of solid carbon. Such data are valuable for understanding the conversion limits for methane into higher hydrocarbons.

Catalytic conversion of methane to methanol on Cu-SSZ-13 using N2O as oxidant

2016 ◽  
Vol 52 (91) ◽  
pp. 13401-13404 ◽  
Author(s):  
B. Ipek ◽  
R. F. Lobo
Keyword(s):  
Catalytic Conversion ◽  
Zeolite Catalysts ◽  
Methanol Production ◽  
Conversion Of Methane

Direct catalytic methanol production from methane is achieved on Cu-SSZ-13 zeolite catalysts using N2O as the oxidant.

scholarly journals On the Mechanism of Methane Conversion in the Nonсatalytic Processes of Its Thermal Pyrolysis and Steam and Carbon Dioxide Reforming

2021 ◽  
Author(s):  
E. Busillo ◽  
V. I. Savchenko ◽  
V. S. Arutyunov
Keyword(s):  
Carbon Dioxide ◽  
Methane Conversion ◽  
Carbon Dioxide Reforming ◽  
Temperature Range ◽  
Thermal Pyrolysis ◽  
First Order Kinetics ◽  
Initial Stage ◽  
Conversion Of Methane ◽  
Exponential Factors ◽  
Kinetics Of

Abstract A detailed kinetic modeling of the noncatalytic processes of thermal pyrolysis and steam and carbon dioxide reforming of methane revealed almost completely identical kinetics of the methane conversion in these processes. This suggests that, in the temperature range 1400–1800 K, the initial stage of conversion of methane in all these processes is its thermal pyrolysis. The modeling results agree well with the experimental data on methane pyrolysis. For the temperature range examined, the Arrhenius expressions (pre-exponential factors and activation energy) were obtained in the first-order kinetics approximation for the rate of methane conversion in the processes studied. The expressions derived may be useful for making preliminary estimates and carrying out engineering calculations.

scholarly journals Stabilitas Zeolit HY Hidrofobik terhadap Uji Hot Liquid Water (HLW)

2021 ◽  
Vol 10 (2) ◽  
pp. 58-62
Author(s):  
Yuni Susanti ◽  
Yeni Variyana
Keyword(s):  
Liquid Water ◽  
Raw Materials ◽  
Sodium Aluminate ◽  
Zeolite Catalysts ◽  
Wave Number ◽  
Physical Test ◽  
Hy Zeolite ◽  
Ftir Spectrometer ◽  
Two Phases ◽  
The Stability

Initially, zeolite catalysts cannot be used for reactions involving hot liquid water, so it is necessary to modify the zeolite to be stable under these conditions. The synthesis of HY and hydrophobic zeolites aimed to determine the stability of zeolite in hot liquid water (HLW). The stability of zeolite in HLW is related to zeolite hydrophobicity. In this study, the main raw materials for the synthesis of HY zeolite were sodium aluminate (NaAlO2) and Ludox HS-40 by calcining the product at 350 oC for 1 hour. Furthermore, increasing the hydrophobicity of HY zeolite was carried out by modifying the external zeolite surface using organosilanes (aminopropyltriethoxysilane). The stability of two zeolites in HLW was set at 200 oC. Zeolite analysis used physical test and Fourier Transform-Infra Red (FTIR) Spectrometer. The results of the zeolite distribution in two phases confirmed that HY zeolite was completely dispersed in the water phase, while the zeolite one was dispersed in the organic phase. Moreover, the IR spectra of HY zeolite showed that the wide peak detection at wave number 720 cm-1 for beginning to disappear. This means that the HLW condition could be damaged to the d6r unit. Another result was shown by hydrophobic zeolite spectra with a stable peak for 72 hours. This indicates that the hydrophobic zeolite has thermal stability in HLW so that it can be used in chemical reaction catalytic applications that use on phase.

Lyapunov and marginal instability in Hamiltonian systems

1999 ◽  
Vol 77 (8) ◽  
pp. 603-633 ◽  
Author(s):  
J Grindlay
Keyword(s):  
Lyapunov Exponents ◽  
Nonlinear Oscillator ◽  
Linear Chain ◽  
Mathieu Equation ◽  
Singular Values ◽  
Space Velocity ◽  
Singular Value ◽  
The Stability ◽  
Value Decomposition ◽  
Simple Systems

The variational equations and the evolution matrix are introduced and used to discuss the stability of a bound Hamiltonian trajectory. Singular-value decomposition is applied to the evolution matrix. Singular values and Lyapunov exponents are defined and their properties described. The singular-value expansion of the phase-space velocity is derived. Singular values and Lyapunov exponents are used to characterize the stability behaviour of five simple systems, namely, the nonlinear oscillator with cubic anharmonicity, the quasi-periodic Mathieu equation, the Hénon-Heilesmodel, the 4+2 linear chain with cubic anharmonicity, and an integrable system of arbitrary order.PACS Nos.: 03.20, 05.20

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