Chemistry Reference
In-Depth Information
Excessive catalyst deactivation was happening due to the presence of
water, absence of sulfur, and pore blocking by char formation
Product consisted of several phases (gas, liquids, char)
The High Heating Value (HHV) was about twice that of the crude
pyrolysis oil
3.2 Carbides, Nitrides and Phosphides
Carbides. Zhang et al.
85
have studied bimetallic NiMo carbide sup-
ported on SiO
2
, prepared by temperature programmed reaction, for HDO
of ethyl benzoate, acetone and also acetaldehyde, all rather stable but
also very reactive (with H
2
) components. Characterization by TPO indi-
cated a successful formation of the carbide phase. Comparison with
Mo
2
C and CoMoS was performed, and it was concluded that the bi-
metallic system was the most stable. Deactivation by oxygen accumu-
lation and carbon formation was observed. Figure 6 shows the time on
stream behavior of the total conversion of ethyl benzoate over the three
systems, Mo carbide, NiMo carbide, and CoMo sulfide. All catalysts are
subject to strong deactivation, but the carbides show the longest life-
times in these tests. It was claimed that the bimetallic system was highly
active and also stable for conversion of acetone and acetaldehyde.
Dhandapani et al.
27
studied the simultaneous HDS, HDO and hydro-
genation of model compounds over a b-Mo
2
C (hcp) catalyst. Minimal
deactivation was observed for up to 30 ppm S, 2000 ppm O and 5 wt%
cumene for more than 80 h on stream. Two types of active sites were
proposed: one molybdenum carbide site active for hydrogenation and
Fig. 6 Total conversion of ethyl benzoate over the (a) Mo carbide, (b) NiMo carbide, and
(c) CoMo sulphide. Reprinted with permission from ref. 85: W. Zhang, Y. Zhang, L. Zhao,
W. Wei, Energy & Fuels, 2010, 24, 2052. Copyright (2010) American Chemical Society.
