484
D. Zhang et al. / Catalysis Today 175 (2011) 477–484
in gas oil. The BS-supported NiMo catalyst showed the highest
about 1.6 times as much as that over the Al2O3-supported cata-
all weight times, although it had larger surface area and pore vol-
ume (Table 1). This is probably due to the relatively weak acidity
NiMo catalyst exhibited the lowest conversion although it had
the most acid sites (Table 2). Although Al-SBA-15-supported NiMo
catalysts showed a little higher DBT conversion than SBA-15 sup-
one (Fig. 15).
The catalytic testing results revealed that NiMo/BS had the high-
est DBT HDS activity among all the studied catalysts, and the DBT
conversion on NiMo/BS was about 1.6 times as much as that on
NiMo/Al2O3 at weight time of 0.75 g min mol−1. The high activity
of BS-supported catalyst might be attributed to the combination of
open mesoporous structure and the large amounts of acid sites.
Acknowledgements
The authors acknowledge the financial supports from National
Natural Science Foundation of China (no. 20876173, 21073235 and
20833011), Ministry of Education key project of China (no. 31).
The acid properties of catalysts had a large effect on the cat-
alytic performances of the HDS catalysts. Supports or catalysts
with proper acid distributions can improve the conversions of DBT
and/or 4,6-DMDBT [10,11]. One of explanations was that acidity
helped to improve the reaction rates of dealkylation and isomer-
ization of alkyl substituents, which might favor the transformation
of the refractory components into more reactive species and thus
promote the catalytic activity by the creation of a second hydro-
genation pathway through spillover of hydrogen atoms from the
metal particles to the aromatic sulfur-containing molecules that
were adsorbed on acid sites in the vicinity of the metal active sites
[32]. In this paper, however, NiMo/Beta catalyst exhibited the low-
est activity although it had the highest amounts of acid sites, which
indicated that the pore size also played an important role in DBT
HDS reaction. Mesoporous materials with large pores can eliminate
the diffusion resistance and enhance the accessibility of the active
sites to reactant molecules. So mesoporous materials MCM-41 and
SBA-15 have been employed as catalyst supports for the HDS of
DBT or 4,6-DMDBT and exhibited good catalytic performances [3,9].
However, pure silica mesoporous materials possessed electroni-
cally neutral frameworks and were devoid of Brönsted and Lewis
acid sites. Micro-mesoporous material BS not only combined the
superiorities of pore structure (as the mesoporous materials) but
also possessed large amounts of acid sites (like zeolite), those prop-
erties made BS to be a good catalyst support for DBT HDS reaction.
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In this study, micro-mesoporous composite material BS was
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