TEM evidence for factors affecting the genesis of carbon species on bare and K-promoted Ni/MgO catalysts during the dry reforming of methane

被引:83
作者
Frusteri, F
Spadaro, L
Arena, F
Chuvilin, A
机构
[1] CNR, Ist TAE, I-98126 Messina, Italy
[2] Univ Messina, Dipartimento Chim Ind & Ingn Mat, I-98166 Messina, Italy
[3] Boreskov Inst Catalysis, Novosibirsk 630090, Russia
关键词
catalytically grown carbon; catalyst support; doping; transmission electron microscopy;
D O I
10.1016/S0008-6223(01)00243-3
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The structure and morphology of carbon species generated under dry reforming of methane (DRM) at 650 and 800degreesC on 'bare' and 'K-doped' Ni/MgO catalysts have been comparatively investigated by Transmission Electron Microscopy (TEM) analyses of 'used' samples. K-addition (K-at/Ni-at, 0.125) strongly improves the resistance of the Ni/MgO catalyst to coking and sintering phenomena at any temperature. At 650degreesC, an extensive formation of filamentous (whisker carbon) carbon species on bare Ni/MgO catalyst causes the detachment of a large number of Ni particles from the support with a consequent destruction of the structure and remarkable sintering phenomena of the active phase. Considerably lower amounts of carbon deposits with a shell-like (encapsulating carbon) morphology, forming at 800degreesC on both catalysts, point to the Bouduard reaction as the main route of carbon deposition on Ni-based catalysts during DRM. The electronic effect induced by potassium on the active phase of the Ni/MgO system, timely monitored by a rise in E-app of DRM from 50 to 70 kJ/mol, markedly hinders the rate of coking also affecting the morphology of carbon whiskers, by inhibiting the processes of C diffusion and nucleation across Ni particles under steady-state conditions. (C) 2002 Elsevier Science Ltd. All rights reserved.
引用
收藏
页码:1063 / 1070
页数:8
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