Plasma enhanced anti-coking performance of Pd/CeO2 catalysts for conversion of methane

2021 ◽  
Author(s):  
Xiucui Hu ◽  
Yadi Liu ◽  
Liguang Dou ◽  
Cheng Zhang ◽  
Shuai Zhang ◽  
...  
Keyword(s):  
High Temperature ◽  
Carbon Deposition ◽  
Conversion Of Methane ◽  
Nonoxidative Conversion

The direct nonoxidative conversion of methane (CH4) to valuable chemicals has attracted increasing interests. However, the carbon deposition will inevitably occur due to CH4 decomposition at high temperature. Here, we...

Active Chemistry Control for Coolant Helium Applying High-Temperature Gas-Cooled Reactors

2008 ◽  
Author(s):  
Nariaki Sakaba ◽  
Shimpei Hamamoto ◽  
Yoichi Takeda
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Heat Exchanger ◽  
Chemical Composition ◽  
Structural Integrity ◽  
Carbon Deposition ◽  
Control Technology ◽  
Equilibrium Study ◽  
Intermediate Heat Exchanger ◽  
High Temperature Gas

Lifetime extension of high-temperature equipment such as the intermediate heat exchanger of high-temperature gas-cooled reactors (HTGRs) is important from the economical point of view. Since the replacing cost will cause the increasing of the running cost, it is important to reduce replacing times of the high-cost primary equipment during assumed reactor lifetime. In the past, helium chemistry has been controlled by the passive chemistry control technology in which chemical impurity in the coolant helium is removed as low concentration as possible, as does Japan’s HTTR. Although the lifetime of high-temperature equipment almost depends upon the chemistry conditions in the coolant helium, it is necessary to establish an active chemistry control technology to maintain adequate chemical conditions. In this study, carbon deposition which could occur at the surface of the heat transfer tubes of the intermediate heat exchanger and decarburization of the high-temperature material of Hastelloy XR used at the heat transfer tubes were evaluated by referring the actual chemistry data obtained by the HTTR. The chemical equilibrium study contributed to clarify the algorism of the chemistry behaviours to be controlled. The created algorism is planned to be added to the instrumentation system of the helium purification systems. In addition, the chemical composition to be maintained during the reactor operation was proposed by evaluating not only core graphite oxidation but also carbon deposition and decarburization. It was identified when the chemical composition could not keep adequately, injection of 10 ppm carbon monoxide could effectively control the chemical composition to the designated stable area where the high-temperature materials could keep their structural integrity beyond the assumed duration. The proposed active chemistry control technology is expected to contribute economically to the purification systems of the future very high-temperature reactors.

scholarly journals Catalytic molten metals for the direct conversion of methane to hydrogen and separable carbon

Science ◽  
2017 ◽  
Vol 358 (6365) ◽  
pp. 917-921 ◽  
Author(s):  
D. Chester Upham ◽  
Vishal Agarwal ◽  
Alexander Khechfe ◽  
Zachary R. Snodgrass ◽  
Michael J. Gordon ◽  
...  
Keyword(s):  
Carbon Deposition ◽  
Bubble Column ◽  
Alloy System ◽  
Direct Conversion ◽  
Pure Hydrogen ◽  
Molten Metals ◽  
Solid Catalysts ◽  
Conversion Of Methane ◽  
By Products ◽  
Alloy Catalysts

Metals that are active catalysts for methane (Ni, Pt, Pd), when dissolved in inactive low–melting temperature metals (In, Ga, Sn, Pb), produce stable molten metal alloy catalysts for pyrolysis of methane into hydrogen and carbon. All solid catalysts previously used for this reaction have been deactivated by carbon deposition. In the molten alloy system, the insoluble carbon floats to the surface where it can be skimmed off. A 27% Ni–73% Bi alloy achieved 95% methane conversion at 1065°C in a 1.1-meter bubble column and produced pure hydrogen without CO2 or other by-products. Calculations show that the active metals in the molten alloys are atomically dispersed and negatively charged. There is a correlation between the amount of charge on the atoms and their catalytic activity.

XPS AND FTIR STUDIES OF Mo/ZSM-5 CATALYSTS FOR NONOXIDATIVE CONVERSION OF METHANE TO AROMATICS

2001 ◽  
Vol 08 (06) ◽  
pp. 627-632 ◽  
Author(s):  
H. Y. CHEN ◽  
S. TANG ◽  
Z. Y. ZHONG ◽  
J. LIN ◽  
K. L. TAN
Keyword(s):  
Methane Conversion ◽  
Active Sites ◽  
Reaction Times ◽  
Initial Reaction ◽  
Oxygen Treatment ◽  
Conversion Of Methane ◽  
Xps Study ◽  
Nonoxidative Conversion ◽  
First Time

In this investigation, several Mo/ZSM-5 catalysts with various Mo loadings and various reaction times were prepared, and methane conversion to aromatics without the presence of oxygen was studied by microreactor evaluation, FTIR and XPS. It was found, for the first time, that oxygen treatment before the reaction could shorten the induction period of this reaction. In situ FTIR study indicated the formation of [Formula: see text] species ( 888 cm -1) and O–Al ( 670 cm -1) on the surface of the catalyst as a result of the oxygen treatment. The two IR bands shifted to 854 and 659 cm -1 respectively when 18 O 2 was used. These oxygen species may take part in the initial reaction and shorten the induction time. The XPS study revealed the coexistence of Mo 2 C and MoO 3 species on working catalyst surfaces, and a proper Mo 2 C/MoO 3 ratio (~0.38) was identified for the best aromatization Mo/ZSM-5 catalyst. The active sites for methane conversion to aromatics should include Mo oxide as well as Mo carbide.

Model Approach of Carbon Deposition Phenomenon in Steam and Dry Methane Reforming Process

2014 ◽  
Vol 59 (1) ◽  
pp. 145-148 ◽  
Author(s):  
R. Kaczmarczyk ◽  
S. Gurgul
Keyword(s):  
Carbon Deposition ◽  
Equilibrium Composition ◽  
Analytical Form ◽  
Methane Reforming ◽  
Basic Assumptions ◽  
Conversion Of Methane ◽  
Thermodynamic Conditions ◽  
Substrate Concentrations ◽  
Model Approach ◽  
Homogeneous Reactions

Abstract This paper presents thermodynamic conditions for carbon deposition in steam and dry methane reforming process. Ranges of substrate concentrations and temperatures for creating carbon deposition were specified in an analytical form. In the description of the conversion of methane CH4-H2O and CH4-CO2 parametric equations were used, which allowed to define equilibrium composition of the process. The article formulates the basic assumptions of parametric equations models and their use to describe the course of the homogeneous reactions. The results may provide a model basis for the description of properties of the mixed reforming process CH4-H2O-CO2.

Nonoxidative Conversion of Methane, Ethane, and Ethylene on Flat Ir(111) and Stepped Ir(211) Surfaces

2021 ◽  
Vol 125 (10) ◽  
pp. 5602-5615
Author(s):  
Chunli Liu ◽  
Xiaodong Wen ◽  
Yong Yang ◽  
Yong-Wang Li ◽  
Haijun Jiao
Keyword(s):  
Conversion Of Methane ◽  
Nonoxidative Conversion
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