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of hydrogen. Glycerol is converted to polyols, alcohols via hydrogenolysis over the
temperature range of 373–523 K and at 200 bar using monometallic catalysts. The
selectivity and yield of hydrogenolysis can be greatly improved over bimetallic
catalysts. Hydrogenolysis is sometimes referred to as hydrodeoxygenation (HDO)
when used for the removal of oxygen. For example, the ethylene glycol was produced over Ni/Al 2 O 3 , but the selectivity was improved when palladium/iridium/
rhodium was added to Ni/Al 2 O 3 as the second metal. Glycerol can be oxidized in
two ways: (1) oxidation of secondary alcohol to give dihydroxyacetone and
hydroxypiruvic acid and (2) oxidation of primary alcohol to give glyceraldehydes
and glyceric acid. The most commonly used bimetallic catalyst for glycerol oxidation was AuPd in basic medium and PtBi in acidic medium [6]. The summary of the
bimetallic catalysts used for the conversion of biomass- derived chemicals is given
in Table 3.
Table 3 Summary of bimetallic catalysts used for the conversion of biomass-derived chemicals
Feedstock Reaction
Catalysts Conv. Selectivity
P,
bar
T,
K Remark
Ref
Ethylene
glycol
Aqueous-phase
reforming
Pt/Al 2 O 3 >90% 88% (H 2 ),
8%
(alkane)
56 338 90% activity
lost in
2 days. No
restoration of
activity
[92]
Sorbitol
Aqueous-phase
reforming
RANEY
®
Ni 14 Sn
>90% 46% (H 2 ),
31%
(alkane)
51 538 Consistent
activity for
H 2
production
for 340 h
without
regeneration
[92]
Glycerol Hydrogenolysis
Ru-Co/
ZrO 2
56.2% 70.3%
(1,2
PDO),
18.0%
(EG)
50 453 A synergetic
effect
between Ru
and Co
observed
[93]
Glycerol Hydrogenolysis
CuAg/
Al 2 O 3
27% 96% (1,2
PDO)
15 473 The catalyst
showed
higher
activity than
commercial
chromite
catalyst
[94]
Guaiacol
(lignin)
Deoxygenation
PtSn/
Inconel
>80% –
1 673 Higher rate
of catalyst
deactivation
[95]
o-Cresol
(lignin)
Hydrodeoxygenation CoMO/
Al 2 O 3
23% 65%
(C 6 H 6 )
50 573 Activity of
the catalyst is
low
[96]
Sustainability of the Catalytic Process for Biomass Conversion: Recent Trends and…