11 Selective Hydrogenation of Aldehydes and Ketones
381
11.5.4 Pd on Oxides
Pd tetrahedrons (13 nm size) were deposited on MoO 3−x nanosheets (50–100 nm) in a
one-pot solvothermal method [93]. These materials were used for the selective hydrogenation of α,β-unsaturated aldehydes with high conversion (97%) and selectivity
(96%) to their saturated aldehydes. Thus 3-methylcrotonaldehyde was converted to
3-methylbutanal and a few % 3-methylbutanol (ethanol, 20 bar H 2 , 30 °C).
Five Pd catalysts on alumina were prepared from different precursors which led to
NP sizes from 1.2 to 8.5 nm [94]. In the gas-phase hydrogenation of crotonaldehyde
the primary product was in all cases butanal, which was converted into butanol at
a much lower in four cases (150 °C, 1.2 bar H 2 ). Butanal was obtained with the
NPs (2.5 nm) produced from PdCl 2 ; the second stage depends more severely on the
structure of the catalyst and it was proposed that this catalyst contained chlorides on
the edges.
Pd, Pd–Au and Au NPs (3.9 nm size) stabilized by tetraalkylammonium salts were
embedded in silica via a sol-gel method and used as catalysts in various hydrogenations [95]. In the case of CAL, the selectivity of pure Pd for COL was 18, HCAL 28,
HCOL 56%; for Au the numbers were 3, 33 and 58%, respectively. Interestingly, for
the alloyed catalysts the selectivities changed to 50, 20 and 30%, thus much higher
for COL. It was suggested that oxygen coordination to Au was the cause of this
effect.
Spherical Fe 3 O 4 @C core–shell composites with core diameter about 350 nm and
shell thickness about 10 nm were prepared by carbonization of glucose around Fe 3 O 4
microspheres [96]. By loading Pd onto the spherical Fe 3 O 4 @C core–shell composites via the ethylene glycol reduction method, Pd/Fe 3 O 4 @C catalysts with Pd NP
diameters ranging from 7.9 to 9.1 nm were prepared. The particles are magnetically
responsive and can be separated from the reaction medium this way. These catalysts were used in the CAL hydrogenation, where they gave only HCAL and HCOL
(resp. 72%, 28%) (80 °C, ethanol, water, 14 bar H 2 ).
Zhu, Fu and co-workers deposited Pd NPs and tungsten nitride (WN) on various
supports [97]. SBA-15 was found to ensure the best contact between the two types
of nanoparticles (sizes 13.6 nm for WN, and 16.8 nm for Pd). In the presence of WN
high selectivity to HCAL was reached (90%) at 70% conversion of CAL, whereas
conversion to HCOL was almost completely suppressed. In the absence of WN mostly
HCOL was obtained. Both catalysts show high TOF (400–700 h
−1 , isopropanol,
40 °C, 10 bar H 2 ).
11.5.5 Pd on Carbon
Xu, Pham-Huu, et al. prepared a structured catalyst of graphene felt and oxidized
graphene felt (OGF) on which Pd NPs were deposited (~3.8 nm size). They compared
the materials with commercial Pd/AC used as a powder in the hydrogenation of
381
11.5.4 Pd on Oxides
Pd tetrahedrons (13 nm size) were deposited on MoO 3−x nanosheets (50–100 nm) in a
one-pot solvothermal method [93]. These materials were used for the selective hydrogenation of α,β-unsaturated aldehydes with high conversion (97%) and selectivity
(96%) to their saturated aldehydes. Thus 3-methylcrotonaldehyde was converted to
3-methylbutanal and a few % 3-methylbutanol (ethanol, 20 bar H 2 , 30 °C).
Five Pd catalysts on alumina were prepared from different precursors which led to
NP sizes from 1.2 to 8.5 nm [94]. In the gas-phase hydrogenation of crotonaldehyde
the primary product was in all cases butanal, which was converted into butanol at
a much lower in four cases (150 °C, 1.2 bar H 2 ). Butanal was obtained with the
NPs (2.5 nm) produced from PdCl 2 ; the second stage depends more severely on the
structure of the catalyst and it was proposed that this catalyst contained chlorides on
the edges.
Pd, Pd–Au and Au NPs (3.9 nm size) stabilized by tetraalkylammonium salts were
embedded in silica via a sol-gel method and used as catalysts in various hydrogenations [95]. In the case of CAL, the selectivity of pure Pd for COL was 18, HCAL 28,
HCOL 56%; for Au the numbers were 3, 33 and 58%, respectively. Interestingly, for
the alloyed catalysts the selectivities changed to 50, 20 and 30%, thus much higher
for COL. It was suggested that oxygen coordination to Au was the cause of this
effect.
Spherical Fe 3 O 4 @C core–shell composites with core diameter about 350 nm and
shell thickness about 10 nm were prepared by carbonization of glucose around Fe 3 O 4
microspheres [96]. By loading Pd onto the spherical Fe 3 O 4 @C core–shell composites via the ethylene glycol reduction method, Pd/Fe 3 O 4 @C catalysts with Pd NP
diameters ranging from 7.9 to 9.1 nm were prepared. The particles are magnetically
responsive and can be separated from the reaction medium this way. These catalysts were used in the CAL hydrogenation, where they gave only HCAL and HCOL
(resp. 72%, 28%) (80 °C, ethanol, water, 14 bar H 2 ).
Zhu, Fu and co-workers deposited Pd NPs and tungsten nitride (WN) on various
supports [97]. SBA-15 was found to ensure the best contact between the two types
of nanoparticles (sizes 13.6 nm for WN, and 16.8 nm for Pd). In the presence of WN
high selectivity to HCAL was reached (90%) at 70% conversion of CAL, whereas
conversion to HCOL was almost completely suppressed. In the absence of WN mostly
HCOL was obtained. Both catalysts show high TOF (400–700 h
−1 , isopropanol,
40 °C, 10 bar H 2 ).
11.5.5 Pd on Carbon
Xu, Pham-Huu, et al. prepared a structured catalyst of graphene felt and oxidized
graphene felt (OGF) on which Pd NPs were deposited (~3.8 nm size). They compared
the materials with commercial Pd/AC used as a powder in the hydrogenation of