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CNT‐Supported Mo x C Catalysts: Effect of Loading and Carburization Parameters
Author(s) -
Frank Benjamin,
Friedel Klaus,
Girgsdies Frank,
Huang Xing,
Schlögl Robert,
Trunschke Annette
Publication year - 2013
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201300010
Subject(s) - catalysis , molybdenum , physisorption , materials science , selectivity , crystallite , chemical engineering , desorption , inorganic chemistry , adsorption , chemistry , metallurgy , organic chemistry , engineering
Mo x C/CNT catalysts were prepared through carburization of an oxidic molybdenum precursor impregnated on multiwalled carbon nanotubes (CNTs). The effects of different carburization atmospheres, heating rates, and molybdenum loadings were tested. The catalysts were characterized by using CO temperature‐programmed desorption, XRD, N 2 physisorption, SEM, and TEM. The catalytic performance in the steam reforming of methanol was used as a sensitive probe to indicate changes in the catalyst surface during the catalytic action. Contrary to the bulk Mo x C catalysts, the heating rate during carburization has no effect on the catalysts. Instead, molybdenum loading and carburization atmosphere are the key factors for catalyst structure and performance. The molybdenum‐based activity decreases at loadings >10 wt % at a constant product selectivity. The CO 2 /CH 4 product ratio indicates changes in the catalyst properties at the loadings <20 wt %, at which the activity is constant. Carburization in 20 % CH 4 /H 2 yields 2 nm sized crystallites of cubic α‐MoC. Carburization in pure H 2 and He yields hexagonal β‐Mo 2 C with a larger particle size. Both phases show different catalytic performances in terms of activity and CO 2 /CH 4 selectivity. Thus, a multiparameter toolbox for fine‐tuning of catalyst properties is presented.